Thèses : « Harvesting methods »

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JANA, SOURAV KANTI. « Light harvesting methods in photovoltaic devices with superficial treatments ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2012. http://hdl.handle.net/10281/28621.

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Photovoltaics is fast emerging as an attractive renewable energy technology due to concerns of global warming, pollution and scarcity of fossil fuels supplies. However to compete in the global energy market, solar cells need to be cheaper and more energy efficient. Silicon is the favourite semiconductor used in solar photovoltaic cells because of its abandoned in nature, well established technology and non toxicity. But due to its indirect band gap, silicon is poor absorber of light and theoretical limiting efficiency of single junction wafer based silicon solar cells is ~31% which is called Shockley Queisser limit. But up to now the maximum achievable efficiency in laboratory for single crystal single junction silicon solar cells is ~ 24.7%. So far the cost of the wafer based silicon photovoltaics is high. Also thin film cells play an important role in low cost photvoltaics, but efficiency of the cost reduced cells is lower compared to wafer based cells. So light trapping into photovoltaic cells is a great issue inorder to increase the carrier generation inside the active layer of both bulk as well as thin film cells with out disturbing their fabrication technology. There many light harvesting methods; among them Surface Plasmon method using metal nanoparticles and spectrum downshifting method using nanocrystals are discussed here. Metal nanoparticles support surface plamson when light is incident on them, which cause the scatter light into the underlying substrate. This process is realized on standard silicon solar cells. The feasible light scattering related enhancement was examined using spectral response and I-V measurements. Relative increases of the total delivered power under simulated solar irradiation were observed for cells both with and without antireflection coating using both silver and gold nanoparticles. The relative enhancement of External Quantum Efficiency derived from the spectral response measurements was observed for both the silicon cells. The better results obtained from both spectral response and I-V measurements were ascribed in the case of cells without antireflection coating. The results from I-V measurements under Air Mass 1.5 irradiation on the cells (without antireflection coating) correspond to a clear increase of the short circuit current due to both silver (relative increase of 7.5%) and gold (relative increase of 6.1%) nanoparticles. Also there is a relative enhancement (1.5%) of short circuit current was ascribed in the cells (with antireflection coating). Further realization of this method on copper indium gallium selenide based thin film solar cells attributed the enhancement of external quantum efficiency in the red wavelength region where these cells have already a poor spectral response. Spectral downshifting method by the nanocrystals was investigated on the silicon based solar cells. Down shifting of photons on the silicon solar cells is realized by the absorption and emission property of the manganese doped zinc sulfide nanocrystals. The variation of band gap and photoluminescence intensity of different nanocrystals due to different doping concentration was observed. Relative enhancement of External Quantum Efficiency has been attributed in UV region (where silicon solar cells have poor spectral response) due to lower concentration of nanocrystals. A strong concentration quenching effect which causes decrease of external quantum efficiency in both UV and visible region has been observed.

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Cerney, Dawna Lynn. « Two methods of harvesting native grass community seed ». Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0015/MQ48244.pdf.

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Blanchard, Jonathan Peter. « Rainwater Harvesting Storage Methods and Self Supply in Uganda ». Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/3979.

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Self supply is an emerging approach to water supply which focuses on fostering household investment in incremental improvements to their water sources. When successful, it can lower costs and increase sustainability by offering users a larger share of ownership in their own supply, and harnessing the already existing strengths of a community rather than trying to impose an external perspective. In addition to well upgrading and source protection, one of the key self supply areas is rainwater harvesting. Uganda has a diverse selection of rainwater storage options, but many of them are scattered and disparate. The objective of this study was to create a comprehensive collection of well-established Ugandan rainwater storage options, and to demonstrate the geographical disparities in availability, particularly for Rakai District, where the author lived and worked as a Water and Sanitation Engineer for two years. Data was gathered by interviewing key stakeholders in rainwater harvesting at the national, regional, and district level in order to gather their collective knowledge in rainwater harvesting storage techniques. In order to understand the availability and pricing of manufactured products, a survey of Rakai District hardware stores determined the prices and range of volumes at which different manufactured products were available. The study found 11 distinct technologies widely used for rainwater storage: three informal or traditional, three manufactured, and five built-in-place by skilled artisans. The traditional/informal technologies consisted of clay pots, pots and basins, and brick mortar tanks. The manufactured products were plastic tanks ranging from 60 to 24,000 liters, corrugated iron tanks, and 55-gallon metal drums. The built-in-place tank technologies were mortar jars, tarpaulin tanks, ferrocement tanks, partially below ground ferrocement tanks, and interlocking stabilized soil brick tanks. The study also found that while the manufactured products are well distributed, built-in-place options have not spread beyond where they were originally introduced by NGO's trying to promote certain technologies. With regard to costs, tanks with storage volume less than 1,000 liters had costs that ranged from 182 to 724 UGX/liter, with small plastic tanks being least expensive. For volumes between 1,000 and 10,000 liters, costs ranged between 42 and 350 UGX/liter, with tarpaulin tanks providing the largest storage per unit cost. Above 10,000 liters of storage, tanks ranged from 35 to 341 UGX/liter, with tarpaulin tanks again ranking first by cost per unit volume. In order for self supply to flourish, these technologies need to be implemented in such a way that fosters a thriving private sector and independent uptake of rainwater harvesting. This research provides a starting point by laying out the technologies, costs, and volumes available.

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Lenhard, Allison N. « Review of energy harvesting methods for twin screw extruders ». Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127922.

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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, May, 2020
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 44-48).
Energy harvesting is the process of accumulating and storing energy from residual sources for use in powering electronic devices. Low-power energy harvesting technologies typically utilize either mechanical, thermal, radiation, flow-based, or bio-chemical energy sources. Research in low-power energy harvesting technologies is motivated by an increased interest in the Internet of Things and the need to create isolated electronic systems, such as wireless sensor networks for system monitoring. Twin screw extruders are a type of extrusion processing machinery and could benefit from a condition monitoring system. Implementing a condition monitoring system for a twin screw extruder can prevent wasting materials, producing unusable products, and working extensively on machine maintenance. However, it becomes difficult to integrate a condition monitoring system into the machinery because of the lack of accessibility. Condition monitoring would have to occur in the process section of the twin screw extruder, but the nature of the process section makes it difficult to implement a traditionally wired and powered condition monitoring system. A condition monitoring system powered by energy harvesting techniques would be ideal for a twin screw extruder. The shaft mechanical vibrations, high temperature thermal dissipation, and polymer fluid dynamics present in a twin screw extruder can potentially be used in an energy harvesting system. After a literature review, mechanical vibrations and temperature gradients were regarded as the best potential energy harvesting drivers. Based on preliminary analysis of the system, vibrational energy harvesting is predicted to produce between 3.35-16.75 mW of power, while thermally driven energy harvesting is expected to produce between 8-15 mW of power. The estimated power output would be significant enough to power a low-power consumption strain sensor and has the potential to power other sensors as well.
by Allison N. Lenhard.
S.B.
S.B. Massachusetts Institute of Technology, Department of Mechanical Engineering

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Grozdanovski, Tatjana, et Tatjana grozdanovski@rmit edu au. « Multi-scaling methods applied to population models ». RMIT University. Mathematical and Geospatial Sciences, 2009. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20091130.102832.

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This dissertation presents several applications of the multi-scaling (multi-timing) technique to the analysis of both single and two species population models where the defining parameters vary slowly with time. Although exact solutions in such cases would be preferred, they are almost always impossible to obtain when slow variation is involved. Numerical solutions can be obtained in these cases, however they are often time consuming and offer limited insight into what is causing the behaviour we see in the solution. Here an approximation method is chosen as it gives an explicit analytic approximate expression for the solutions of such population models. The multi-scaling method was chosen because the defining parameters are varying slowly compared to the response of the system. This technique is well-established in the physical and engineering sciences literature; however, it has rarely been applied in the area of population modelling. All single species differential equation population models incorporate parameters which define the model - for example, the growth rate r and the carrying capacity k, for the Logistic model. For constant parameter values an exact solution may be found, giving the population as a function of time. However, for arbitrary time-varying parameters, exact solutions are rarely possible, and numerical solution techniques must be employed. Here we will demonstrate that for a Logistic model where the growth rate and carrying capacity both vary slowly with time, an analysis with multiple time scales leads to approximate closed form solutions that are explicit. These solutions prove to be valid for a range of parameter values and compare favourably with numerically generated ones.

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Eriksson, Jesper, et Shwana Piroti. « Review of Methods for Energy Harvesting from a Vehicle Suspension System ». Thesis, KTH, Skolan för teknikvetenskap (SCI), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-223215.

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With the increasing population the energy consumption has increased which makes the requirement for clean energy important, now more than ever. The transport sector is one of the biggest contributors to this consumption and should therefore be taken into consideration when looking for environmentally friendly solutions. The majority of fuel energy in road-bound vehicles of today is dissipated and is therefore never utilized. For a passenger car traveling at 13.4 m/s it is found that 200 W worth of energy is lost in the vehicles suspension system. The purpose of this work is to analyze and evaluate existing methods for energy regeneration from vehicle suspension systems in order to identify the most optimal solution. To end with, the report will propose mathematical models for simulations of the chosen system. This report examines electrostatic, piezoelectric and electromagnetic methods of energy regenera- tion and it is concluded that electromagnetic generators are the most viable when applied to vehicles. Furthermore, already existing ideas for regenerative suspension systems using electromagnetic generators are explained and compared. It is concluded that a suspension system using an electromagnetic generator coupled with a magneto-rheological (MR) damper is the most optimal when looking at e-ciency, cost, robustness and environmental impact. It can generate up to 90 W and is shown to be the most robust system because of its few moving parts. The working principle of the regenerative electromagnetic MR damper is explained and mathematical models describing the characteristics of the MR damper and the electromagnetic generator, based on previous work, are proposed. A simulation model using a quarter-car model is also proposed where dierent methods of road prole generation are suggested. The environmental aspects of the regenerative MR damper is conclusively discussed and evaluated so that the overall environmental performance of the system can be decided.

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Thiffault, Évelyne. « Biogeochemistry of forest harvesting methods in the boreal zone of Quebec ». Thesis, Université Laval, 2006. http://www.theses.ulaval.ca/2006/24124/24124.pdf.

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Singh, Raymond Charan. « Modeling Energy Harvesting From Membrane Vibrations using Multi-physics Modeling ». Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/76793.

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Given the ever-growing need for device autonomy and renewable sources of energy, energy harvesting has become an increasingly popular field of research. This research focuses on energy harvesting using the piezoelectric effect, from vibrating membrane structures by converting mechanical energy into electric energy. Specific applications of this research include powering components of bio-inspired micro air vehicles (MAVs), which require long range with as little regular maintenance as possible, and powering sensors for structural health monitoring on otherwise inaccessible locations (the roof of the Denver Int'l Airport is a good example). Coming up with an efficient, high-fidelity model of these systems allows for design optimization without the extensive use of experimental testing, as well as a deeper understanding of the physics involved. These are the twin goals of this research. This work describes a modeling algorithm using COMSOL, a multi-physics software, to predict the structural mechanics of and subsequent power harvested from a piezoelectric patch placed on a prestressed membrane structure. The model is verified by an FE comparison of the modeled system's dynamic response. For a 0.5 x 0.5 x 0.001 m nylon membrane with a 0.1 x 0.1 x 0.001 m piezoelectric patch placed on its corner, a maximum power output of ~10 microwatts was achieved, using a resistance of 100 Ohms and exciting the system around resonance. When the patch was placed on the side of the membrane, the power output was ~100 milliwatts. The ultimate goal is to estimate the energy harvested by a network of these piezoelectric patches and optimize the harvesting system based on the size, shape and location of the patches.
Master of Science

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Wang, Yafang [Verfasser], et Gerhard [Akademischer Betreuer] Weikum. « Methods and tools for temporal knowledge harvesting / Yafang Wang. Betreuer : Gerhard Weikum ». Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2013. http://d-nb.info/1052779883/34.

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Griffin, S. Michael. « Islet tissue autotransplantation - harvesting methods and long-term assessment of graft function ». Thesis, University of Newcastle Upon Tyne, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329157.

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Reed, Ryan Tyler. « Wireless Information and Power Transfer Methods for IoT Applications ». Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104146.

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As Internet of Things (IoT) technology continues to become more commonplace, demand for self-sustainable and low-power networking schemes has increased. Future IoT devices will require a ubiquitous energy source and will need to be capable of low power communication. RF energy can be harvested through ambient or dedicated RF sources to satisfy this energy demand. In addition, these RF signals can be modified to convey information. This thesis surveys a variety of RF energy harvesting methods. A new low complexity energy harvesting system (circuit and antenna) is proposed. Low power communication schemes are examined, and low complexity and efficient transmitter designs are developed that utilize RF backscattering, harmonics, and intermodulation products. These communication schemes operate with minimal power consumption and can be powered solely from harvested RF energy. The RF energy harvester and RF-powered transmitters designs are validated through simulation, prototyping, and measurements. The results are compared to the performance of state-of-the-art devices described in the literature.
Master of Science
Future devices are expected to feature high levels of interconnectivity and have long lifetimes. RF energy from dedicated power beacons or ambient sources, such as Wi-Fi, cellular, DTV, or radio stations can be used to power these devices allowing them to be battery-less. These devices that harvest the RF energy can use that energy to transmit information. This thesis develops various methods to harvest RF energy and use this energy to transmit information as efficiently as possible. The designs are verified through simulation and experimental results.

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Bell, Robert D. « Influences of varying stand harvest methods on timber harvesting costs in southwestern Virginia hardwoods ». Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/43079.

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A method was developed for estimating costs of harvesting operations in the hardwood stands of the Appalachian region of southwestern Virginia. The method was then tested on one logging operation to estimate the cost of harvesting a group selection tract as compared to a clearcut. Eight loggers were contacted and interviewed to obtain data on their costs of logging. The mean, median, and standard deviation of the responses were calculated to develop a profile. Mean crew size was three men, including the owner operator. Mechanized equipment consisted of a cable skidder from 75 to 120 hp. and a small to medium size loader. Average skidder age was 4.8 years. Loggers produced 144 cords per week, of which 54.6% was pulpwood and 42.4% sawtimber with 3% firewood. Products were hauled an average of 33 miles one way. Labor costs, including wages and all benefits averaged $411 per man per week. Total harvesting costs had a mean of $2252 per week. Mean hauling cost was $1289 per week. Annual production averaged 6778 cords. Cords per man hour was 0.99. Total cost per cord including hauling averaged $26. The information taken from the interviews was incorporated along with data from current literature into the Harvesting Analysis Technique (HAT), a main frame harvesting simulator, to model group selection harvests against clearcut harvests. A twenty-seven acre group selection cut was compared to a 160-acre clearcut. Clearcut area was based on the access estimated possible by the group selection skid road network. Results showed group selection harvested at a 21% slower rate than clearcutting. Harvest cost per cord was 25.8% greater. Variation in cost was caused mainly by the increased average skid distances present in the groups. Every 100 foot increase in skid distance resulted in a $0.68 increase in cost per cord for skidding in group selection harvests compared to a $0.33 increase for clearcutting.
Master of Science

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Björk, Gabriella. « Evaluation of system design strategies and supervised classification methods for fruit recognition in harvesting robots ». Thesis, KTH, Skolan för industriell teknik och management (ITM), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217859.

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This master thesis project is carried out by one student at the Royal Institute of Technology in collaboration with Cybercom Group. The aim was to evaluate and compare system design strategies for fruit recognition in harvesting robots and the performance of supervised machine learning classification methods when applied to this specific task. The thesis covers the basics of these systems; to which parameters, constraints, requirements, and design decisions have been investigated. The framework is used as a foundation for the implementation of both sensing system, and processing and classification algorithms. A plastic tomato plant with fruit of varying maturity was used as a basis for training and testing, and a Kinect v2 for Windows including sensors for high resolution color-, depth, and IR data was used for image acquisition. The obtained data were processed and features of objects of interest extracted using MATLAB and a SDK for Kinect provided by Microsoft. Multiple views of the plant were acquired by having the plant rotate on a platform controlled by a stepper motor and an Ardunio Uno. The algorithms tested were binary classifiers, including Support Vector Machine, Decision Tree, and k-Nearest Neighbor. The models were trained and validated using a five fold cross validation in MATLABs Classification Learner application. Peformance metrics such as precision, recall, and the F1-score, used for accuracy comparison, were calculated. The statistical models k-NN and SVM achieved the best scores. The method considered most promising for fruit recognition purposes was the SVM.
Det här masterexamensarbetet har utförts av en student från Kungliga Tekniska Högskolan i samarbete med Cybercom Group. Målet var att utvärdera och jämföra designstrategier för igenkänning av frukt i en skörderobot och prestandan av klassificerande maskininlärningsalgoritmer när de appliceras på det specifika problemet. Arbetet omfattar grunderna av dessa system; till vilket parametrar, begränsningar, krav och designbeslut har undersökts. Ramverket användes sedan som grund för implementationen av sensorsystemet, processerings- och klassifikationsalgoritmerna. En tomatplanta i pplast med frukter av varierande mognasgrad användes som bas för träning och validering av systemet, och en Kinect för Windows v2 utrustad med sensorer för högupplöst färg, djup, och infraröd data anvöndes för att erhålla bilder. Datan processerades i MATLAB med hjälp av mjukvaruutvecklingskit för Kinect tillhandahållandet av Windows, i syfte att extrahera egenskaper ifrån objekt på bilderna. Multipla vyer erhölls genom att låta tomatplantan rotera på en plattform, driven av en stegmotor Arduino Uno. De binära klassifikationsalgoritmer som testades var Support Vector MAchine, Decision Tree och k-Nearest Neighbor. Modellerna tränades och valideras med hjälp av en five fold cross validation i MATLABs Classification Learner applikation. Prestationsindikatorer som precision, återkallelse och F1- poäng beräknades för de olika modellerna. Resultatet visade bland annat att statiska modeller som k-NN och SVM presterade bättre för det givna problemet, och att den sistnömnda är mest lovande för framtida applikationer.

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Hodges, Amelia Lynn. « Investigation of antennas and energy harvesting methods for use with a UHF microtransceiver in a biosensor network ». Thesis, Kansas State University, 2013. http://hdl.handle.net/2097/16218.

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Master of Science
Department of Electrical and Computer Engineering
William B. Kuhn
This work was a part of NASA EPSCoR Project NNX11AM05A: Biosensor Networks and Telecommunication Subsystems for Long Duration Missions, EVA Suits, and Robotic Precursor Scout Missions. The project’s main goal is the development of a wireless sensor network inside an astronaut’s spacesuit. Antennas are essential components in a wireless network. Since this antenna will be used inside the spacesuit it is important to consider both the physical size limitations and the desired antenna polarization. After exploring the WWVB radio station antenna which provides the preferred vertical polarization and has a suitable aspect ratio, the top hat antenna seemed promising for intrasuit communication. The design of a top hat antenna is outlined. Then, the antennas were tested using 433 MHz radios in a full scale model spacesuit. This spacesuit was designed specifically to model the behavior of aluminized mylar in the real suit. Test results support the feasibility of an intrasuit wireless network. If a gateway radio is placed on the chest or back, a sensor could be placed anywhere on the body and provide an adequate signal. These initial tests did not include a matching network, but the additional link-margin afforded by a matching network, even an imperfect match, is considered. Energy harvesting is explored as an alternative to batteries powering the intrasuit radio. In the oxygen rich environment of a spacesuit, even the smallest spark can be catastrophic. A variety of energy harvesting options are explored with a focus on thermal energy harvesting. The temperature difference between the human skin and the astronaut’s Liquid Cooling and Ventilation Garment can be used to produce a small voltage. To increase the voltage a step-up converter is implemented. Final integration of the two systems with a biosensor is left for on-going work in the three year NASA project.

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Still, Gwilym T. « Methods for reducing the cost of cementitious building components in developing countries, with particular reference to rainwater harvesting ». Thesis, University of Warwick, 2007. http://wrap.warwick.ac.uk/2342/.

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Cementitious building components, although widely used in low-income countries, are too expensive for many applications related to low-income housing. This thesis explores three options for reducing component cost: 1. Use of local fine aggregates, often with clay contamination, instead of low-fines sands transported from a distance. 2. Improved designs, to achieve better material economy. 3. Change of production environment, from on-site to component prefabrication followed by transport to site. Water storage tanks for rainwater harvesting were used as the example for component design, and as a case-study for considering the effect of changing the production environment. The work showed that: In some cases, use of local aggregates will give a cost saving of around 10%. Improved design can give significant reduction in materials usage, of up to 40%. Off-site prefabrication of components, followed by on-site assembly to produce the desired product, does not seem preferable to the prevelant practice of entirely on-site production from raw materials. However, factory-based manufacture of complete products, followed by transport to site, has a number of attractions over entirely on-site production. Out of the three options examined, improved component design offers the greatest benefits for the case study considered.

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Rodriguez, Henry. « A Comparison of Rainwater Harvesting Tank Sizing Methods : Optimizing to Reduce Greenhouse Gas Emissions versus Maximizing System Reliability ». University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo151577155419202.

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Ramaswamy, Maya. « Assessing occupational health among transitional agricultural workforces : a mixed methods study among U.S. beginning farmers and South Indian tea harvesting workers ». Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6251.

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Agriculture is a hazardous industry worldwide, and certain groups of agricultural workers are at increased risk of experiencing adverse health outcomes. Agricultural workforces are becoming increasingly transitional, as established and experienced workers exit the industry and new workers take their place. Limited occupational health surveillance exists among certain transitional agricultural workforces. In the US, beginning farmers, i.e., agricultural workers with 10 years or less experience operating a farm, may differ from established farmers in terms of their demographics, length of experience within the agricultural industry, and occupational exposures and health outcomes. Separately, South Indian tea harvesting workers are exposed to occupational physical demands that are risk factors for musculoskeletal health outcomes. However, few studies have examined associations between occupational demands and musculoskeletal pain among these workers. Furthermore, no studies have identified additional occupational health issues within the tea harvesting process. To address the lack of available knowledge on beginning farmers and tea harvesting workers, the goals of this mixed method study were to estimate the associations between musculoskeletal symptoms and occupational physical demands and occupational psychosocial stress among beginning farmers in the US and tea harvesting workers in South India. An additional goal was to identify occupational health issues within the tea harvesting process and to determine how tea harvesting workers conceptualize and prioritize these issues. An online survey was conducted among beginning farmers across the U.S. Participants answered questions about their demographics, personal health and farm characteristics, occupational physical demands, occupational psychosocial stress, and musculoskeletal symptoms of the low back, neck/shoulder, and elbow/wrist/hand. An interviewer-based survey was conducted among South Indian tea harvesting workers. Participants answered questions about their demographics, personal health, occupational physical demands, occupational psychosocial stress, and musculoskeletal symptoms of the neck/upper back, lower back, upper extremity region, and lower extremity region. A qualitative study was conducted using focus groups among South Indian tea harvesting workers and semi-structured interviews and structured interviews among South Indian tea harvesting workers and supervisors. Results from the cross sectional online survey concluded that musculoskeletal symptoms were common among beginning farmers. In addition, occupational physical demands were associated with musculoskeletal pain, particularly low back pain was associated with working in awkward and cramped positions, bending or twisting the back, and carrying, lifting, or moving heavy material by hand. Results from the cross sectional interviewer-based survey concluded that musculoskeletal symptoms were also common among South Indian tea harvesting workers. Musculoskeletal pain was associated with exposure to forceful exertions, awkward posture, and repetition. Finally, results from the qualitative study identified additional occupational health issues within tea harvesting, including the presence of animals and pelvic organ prolapse. The study further identified important influential stakeholders within the tea harvesting process. Findings from these three studies may be used to inform future health interventions among these transitional workforces.

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Lindemuth, Robert M. « A Field Trial Comparison of Sampling Methods for Estimating Basal Area and Volume in Partially Harvested Stands in Maine ». Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/LindemuthRM2007.pdf.

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Dhayal, Vandana Sultan Singh. « Exploring Simscape™ Modeling for Piezoelectric Sensor Based Energy Harvester ». Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc984261/.

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This work presents an investigation of a piezoelectric sensor based energy harvesting system, which collects energy from the surrounding environment. Increasing costs and scarcity of fossil fuels is a great concern today for supplying power to electronic devices. Furthermore, generating electricity by ordinary methods is a complicated process. Disposal of chemical batteries and cables is polluting the nature every day. Due to these reasons, research on energy harvesting from renewable resources has become mandatory in order to achieve improved methods and strategies of generating and storing electricity. Many low power devices being used in everyday life can be powered by harvesting energy from natural energy resources. Power overhead and power energy efficiency is of prime concern in electronic circuits. In this work, an energy harvester is modeled and simulated in Simscape™ for the functional analysis and comparison of achieved outcomes with previous work. Results demonstrate that the harvester produces power in the 0 μW to 100 μW range, which is an adequate amount to provide supply to low power devices. Power efficiency calculations also demonstrate that the implemented harvester is capable of generating and storing power for low power pervasive applications.

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Drummond, Hazel. « Distribution and biomass of epiphytic seaweeds on the kelp Ecklonia maxima (Osbeck) Papenfuss, and the potential effects of two kelp-harvesting methods in the Western Cape ». Bachelor's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/25563.

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The demand for freshly harvested kelp, Ecklonia maxima, in the Western Cape, has greatly increased due to the need for fodder to supply the growing abalone industry. There is evidence suggesting that the present demand may exceed the amount of E. maxima available, if the traditional method of harvesting continues (cutting the whole kelp plant off, just above the holdfast). There is also evidence that, although the kelp beds recover in 2 - 3 years, and are ready for the next harvesting event, the epiphytic seaweed populations have not recovered even 5 years after harvesting. A new method of harvesting has been proposed, where the secondary blades of the E. maxima are cut 30cm from the primary blade. This method would increase the amount of kelp that can be harvested sustainably. This study investigated whether this new method of harvesting would have less impact on the epiphytic seaweed populations, particularly the three obligate epiphyte species; Carpoblepharis flaccida, Polysiphonia virgata and Suhria vittata, and whether there is pattern of distribution of epiphyte populations around the Cape Peninsula. The distribution of the epiphytes on the different portions (stipe; primary blade and first 30cm of secondary blades; rest of the secondary blades) of kelp was investigated. E.maxima was sampled at five sites around the Cape Peninsula, and the epiphytes on each portion were identified and weighed. All the epiphytes except Carpoblepharis flaccida were found predominantly on the portion of kelp that would be left after the new method of harvesting, and would therefore be unaffected. It was found that the mass of C.flaccida removed in the new method was not significantly different from the mass remaining; therefore a large proportion is left untouched. There was no geographic pattern of distribution of C.flaccida in relation to water temperature around the Cape Peninsula. The results suggest that this new method of harvesting would have little impact on the epiphyte populations, which is an added incentive for changing the method of harvesting.

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Xu, Sheng. « Oxide nanowire arrays for energy sciences ». Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42876.

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Oxide nanowire arrays are playing an important role in energy sciences nowadays, including energy harvesting, energy storage, and power management. By utilizing a wet chemical growth method, we demonstrated the capabilities of synthesizing density controlled vertical ZnO nanowire arrays on a general substrate, optimizing the aspect ratio of the vertical ZnO nanowire arrays guided by a statistical method, epitaxially growing patterned vertical ZnO nanowire arrays on inorganic substrates, epitaxially growing patterned horizontal ZnO nanowire arrays on non-polar ZnO substrates, and the lift-off of the horizontal ZnO nanowire arrays onto general flexible substrates. In addition, single crystalline PbZrxTi1-xO3 (PZT) nanowire arrays were epitaxially grown on conductive and nonconductive substrates by hydrothermal decomposition. Beyond that, based on the as-synthesized ZnO nanowire arrays, we demonstrated multilayered three dimensionally integrated direct current and alternating current nanogenerators. By integrating a ZnO nanowire based nanogenerator with a ZnO nanowire based nanosensor, we demonstrated solely ZnO nanowire based self-powered nanosystems. Also, utilizing a commercial full-wave bridge rectifier, we rectified the alternating output charges of the nanogenerator based on PZT nanowire arrays, and the rectified charges were stored into capacitors, which were later discharged to light up a laser diode (LD). In addition, blue/near-ultraviolet (UV) light emitting diodes (LED) composed of ordered ZnO nanowire arrays on p-GaN wafers were presented.

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Meesala, Vamsi Chandra. « Modeling and Analysis of a Cantilever Beam Tip Mass System ». Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/83378.

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We model the nonlinear dynamics of a cantilever beam with tip mass system subjected to different excitation and exploit the nonlinear behavior to perform sensitivity analysis and propose a parameter identification scheme for nonlinear piezoelectric coefficients. First, the distributed parameter governing equations taking into consideration the nonlinear boundary conditions of a cantilever beam with a tip mass subjected to principal parametric excitation are developed using generalized Hamilton's principle. Using a Galerkin's discretization scheme, the discretized equation for the first mode is developed for simpler representation assuming linear and nonlinear boundary conditions. We solve the distributed parameter and discretized equations separately using the method of multiple scales. We determine that the cantilever beam tip mass system subjected to parametric excitation is highly sensitive to the detuning. Finally, we show that assuming linearized boundary conditions yields the wrong type of bifurcation. Noting the highly sensitive nature of a cantilever beam with tip mass system subjected to parametric excitation to detuning, we perform sensitivity of the response to small variations in elasticity (stiffness), and the tip mass. The governing equation of the first mode is derived, and the method of multiple scales is used to determine the approximate solution based on the order of the expected variations. We demonstrate that the system can be designed so that small variations in either stiffness or tip mass can alter the type of bifurcation. Notably, we show that the response of a system designed for a supercritical bifurcation can change to yield a subcritical bifurcation with small variations in the parameters. Although such a trend is usually undesired, we argue that it can be used to detect small variations induced by fatigue or small mass depositions in sensing applications. Finally, we consider a cantilever beam with tip mass and piezoelectric layer and propose a parameter identification scheme that exploits the vibration response to estimate the nonlinear piezoelectric coefficients. We develop the governing equations of a cantilever beam with tip mass and piezoelectric layer by considering an enthalpy that accounts for quadratic and cubic material nonlinearities. We then use the method of multiple scales to determine the approximate solution of the response to direct excitation. We show that approximate solution and amplitude and phase modulation equations obtained from the method of multiple scales analysis can be matched with numerical simulation of the response to estimate the nonlinear piezoelectric coefficients.
Master of Science

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Fofana, Alpha, et Carl Mossberg. « Energy harvesting from ambient WiFi energy : A method of harvesting and measuring ambient WiFi energy ». Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-257860.

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The aim of this thesis was to investigate the question of how to harvest RF energy and if we can harvest enough RF energy for it to be useful in an application. It is aimed towards sensor node applications, commonly used in a typical office environment. The WiFi band was chosen since it is omnipresent in the same environment. With the current development within wireless technology and the IoT domain the demand for low power electronic applications has increased and one of the challenges is to find efficient and sustainable ways of powering these types of devices.The best possible theoretical power content was initially calculated followed by measurements in an office. A circuit was designed containing an impedance matching network and rectifier. A measurement application was constructed using a microcontroller. Measurements were made in an office environment and the maximum harvested energy over 24 hours was 350 mJ. The energy was stored in a supercapacitor and is estimated to be enough to power a low energy sensor for about 30 seconds. A large part of the thesis is devoted to impedance matching involving calculating, simulating and experimenting to get a good result.
Med den nuvarande utvecklingen inom trådlös teknik och IoT-domänen har efterfrågan på elektroniska applikationer med låg effekt ökat och en av utmaningarna är att hitta effektiva och hållbara sätt att driva dessa typer av enheter. Syftet med detta projekt var att undersöka frågan hur vi skördar radiovågsenergi och kan vi skörda tillräckligt mycket med energi för att den ska vara användbar i en applikation. I ett typiskt kontor finns fler källor till radiovågor, däribland WiFi som antas ha en hög nyttjandegrad. Projektet valde att inrikta sig på WiFi bandet och undersöka om det går att utvinna tillräckligt med energi där.Projektet strävade efter att leverera en färdig produkt med alla ingående delar, en antenn, en likriktare, en lagringsenhet och ett matchningsnätverk för att anpassa antenn och likriktare till varandra. För att undersöka hur mycket energi som finns att skörda gjordes först beräkningar och sedan mätningar i bland annat ett typiskt kontor. Det konstaterades att det rör sig om väldigt låga nivåer och betonas att de apparater som använder WiFi klarar av att känna av signaler som är långt mycket lägre än de som krävs för att kunna utvinna energi. Detta innebär alltså att apparaterna kan kommunicera felfritt samtidigt som energiinnehållet är så lågt att det inte går att utvinna någon energi.Projektet ägnar stor del åt att optimera den impedansmatchning som måste ske mellan antenn och likriktare för att största möjliga effektutbyte ska kunna ske. Basen är ett kretskort med ett typiskt impedansnätverk och genom beräkningar, simuleringar och experiment tas en prototyp fram. För att kunna analysera resultaten används en mikrokontroller som tar de analoga värdena, omvandlar dem till digitala och skickar dem till en PC för analys.Mätningar gjordes i en kontorsmiljö och den maximala mängden energi som gick att utvinna var 350 mJ på 24 timmar. Energin lagrades i en superkondensator och bedöms vara tillräcklig för att driva en lågenergisensor i ca 30 sekunder.

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Quadros, Carlos Schmidt. « Rainwater harvesting case study : FCT/UNL campus ». Master's thesis, Faculdade de Ciências e Tecnologia, 2010. http://hdl.handle.net/10362/4799.

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Dissertação apresentada para a obtenção do grau de Mestre em Engenharia do Ambiente, Perfil Engenharia Sanitária
With increasing pressure on the environment, particularly on water resources, due to outside forces such as climate change and population growth, water is nowadays a scarce and a valuable resource. With the need to find new alternatives, rainwater harvesting should be seen as an important strategy for better management of water resources, once it constitutes a free source of potable water. Rainwater harvesting systems, which already have a global implementation, are a recognised way for urban buildings to reduce their reliance on the public mains supply. Its applications are predominantly non-potable, namely toilet flushing and gardening. The aim of this report is to produce a comprehensive assessment of rainwater harvesting and its potential use all over the world, as well as the potential economical and environmental benefits. It is provided a description of all the rainwater harvesting system components, as well as water quality requirements according to the water final purpose. A case study is presented, which main object is to evaluate the feasibility of rainwater harvesting for gardening, applied to the University Campus of the Faculty of Sciences and Technology of Universidade Nova, Lisbon (FCT/UNL). A detailed characterization of the existing irrigation system on campus is provided, as well as its potential ability to collect rainwater. According to the supply and demand balance, several scenarios are presented in order to provide the necessary information for the decision-makers to evaluate the best solution for the desired application. For such, all the available information was analyzed, in order to determine the environmental, technical and economical viability of the project.

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Brandeau, Erich John. « An in-situ interdiffusion method for harvesting energy from an aluminum-water reaction ». Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74424.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 57-58).
Autonomous underwater vehicles (AUVs) are indispensable for countless underwater tasks but are currently limited in their range and endurance by the energy density of their battery packs. Aluminum is an ideal energy source for AUVs because it exothermically reacts with water and is two orders of magnitude more energy dense than current lithium-ion batteries. An in-situ interdiffusion method for reacting aluminum in water was conceived in which elemental aluminum is able to overcome the passivating aluminum oxide layer by diffusing into liquid gallium. The aluminum atoms in solution with the gallium react to produce heat and hydrogen gas when they reach the interface of the liquid gallium and water. This thesis attempts to quantify the diffusion of aluminum into liquid gallium as well as to quantify the reaction of the aluminum-gallium solution in water. Experiments are conducted to measure the diffusion and reaction rate constants, and the data is fit to the Arrhenius equation to predict the diffusion and reaction rates at elevated system temperatures. With the predicted diffusion and reaction rates, it was found how the size and temperature effect the power output of an in-situ inderdiffusion aluminum-water reactor.
by Erich John Brandeau.
S.B.

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Triplett, Angela Lynn. « Vibration-Based Energy Harvesting with Essential Non-Linearities ». University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1322493879.

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Rafique, Sajid. « Piezoelectric vibration energy harvesting and its application to vibration control ». Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/piezoelectric-vibration-energy-harvesting-and-its-application-to-vibration-control(d9edcedf-054e-4921-9ba3-5e015b9bbd8f).html.

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Vibration-based energy harvesting using piezoelectric materials have been investigated by several research groups with the aim of harvesting maximum energy and providing power to low-powered wireless electronic systems for their entire operational life. The electromechanical coupling effect introduced by the piezoelectric vibration energy harvesting (PVEH) mechanism presents modelling challenges. For this reason, there has been a continuous effort to develop different modelling techniques to describe the PVEH mechanism and its effects on the dynamics of the system. The overall aims of this thesis are twofold: (1) a thorough theoretical and experimental analysis of a PVEH beam or assembly of beams; (2) an in-depth analytical and experimental investigation of the novel concept of a dual function piezoelectric vibration energy harvester beam/tuned vibration absorber (PVEH/TVA) or 'electromechanical TVA' and its potential application to vibration control. The salient novel contributions of this thesis can be summarised as follows: (i) An in-depth experimental validation of a PVEH beam model based on the analytical modal analysis method (AMAM), with the investigations conducted over a wider frequency range than previously tested. (ii) The precise identification of the electrical loads that harvest maximum power and that induce maximum electrical damping. (iii) A thorough investigation of the influence of mechanical damping on PVEH beams. (iv) A procedure for the exact modelling of PVEH beams, and assemblies of such beams, using the dynamic stiffness matrix (DSM) method. (v) A procedure to enhance the power output from a PVEH beam through the application of a tip rotational restraint and the use of segmented electrodes. (vi) The theoretical basis for the novel concept of a dual function PVEH beam/TVA, and its realisation and experimental validation for a prototype device. A thorough experimental validation of a cantilever piezoelectric bimorph energy harvester without a tip mass is presented under random excitation. The study provided a deep insight into the effect of PVEH on the dynamics of the system for variations in electrical load. An alternative modelling technique to AMAM, based on the DSM, is introduced for PVEH beams. Unlike AMAM, the DSM is exact, since it is based on the exact solution to the bending wave equation. It also readily lends itself to the modelling of beams with different boundary conditions or assemblies of beams of different crosssections. AMAM is shown to converge to DSM if a sufficiency of modes is used. Finally, an in-depth theoretical and experimental investigation of a prototype PVEHbeam/TVA device is presented. This device comprises a pair of bimorphs shunted by R-L-C circuitry and can be used as a tuned mass damper (TMD) to attenuate a vibration mode of a generic structure. The optimal damping required by this TMD is generated by the PVEH effect of the bimorphs. Such a device combines the advantages of conventional mechanical and electrical TVAs, overcoming their relative disadvantages. The results demonstrate that the ideal degree of attenuation can be achieved by the proposed device through appropriate tuning of the circuitry, thereby presenting the prospect of a novel class of 'electromechanical' tuned vibration absorbers.

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Kim, Woon Kyung. « Design and Analysis of Switching Circuits for Energy Harvesting in Piezostrutures ». Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28646.

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This study deals with a general method for the analysis of a semi-active control technique for a fast-shunt switching system. The benefit of the semi-active system is the reduction in power consumption, which is a significant disadvantage of a fully active system compared with a passive system. A semi-active system under consideration is a semi-actively shunted piezoelectric system, which converts the strain energy into electrical energy through strong electromechanical coupling achieved though the piezoelectric phenomenon. Our proposed semi-active approach combines a PZT-based energy harvesting with a fast switching system driven by a Pulse-Width Modulated (PWM) signal. The fast switching system enables continuous adaptation of vibration energy control/harvesting by varying the PWM duty cycle. This contrasts with a conventional capacitance switching system that can only change the capacitance at discrete values. The analysis of the current piezoelectric system combined with a fast-switching system poses a considerable challenge as it contains both continuous and discrete characteristics. The study proposes an enhanced averaging method for analyzing the piecewise linear system. The simulation of the averaged system is much faster than that of the time-varying system. Moreover, the analysis derives error bounds that characterize convergence in the time domain of the averaged system to the original system. The dissertation begins with the derivation of the equations governing the physics of a piezostructure combined with an electrical switching shunt network. The results of the averaging analysis and numerical simulation are presented in order to provide a basis for estimating the structural responses that range between open- and short-circuit conditions which constitutes two limiting conditions. An experimental study demonstrates that the capacitive shunt bimorph piezostructure coupled with a single switch can be adjusted continuously by varying the PWM duty cycle. And the behavior of such hybrid system can be well predicted by the averaging analysis.
Ph. D.

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Hassan, Mahmoud Wifag. « Water Harvesting for Integrated Water Resources Management and Sustainable Development in Khartoum State ». Doctoral thesis, Universitätsbibliothek Leipzig, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-125079.

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Khartoum State in Sudan is subject to the erratic and intense rainfall during the short rainy season and dryness and heat throughout the rest of the year. High intensity rainstorms with a short duration have become more frequent in the area during the last two decades resulting in cities inundation and flash floods in the rural parts. On the other hand, the dry season means hot weather in the urban parts and water shortage in the rural part. Rural areas are dependent on the runoff water brought about by the seasonal streams as a source of water. For this study, Khartoum City Center and Seleit area were taken to investigate the application of water harvesting in the urban and rural areas, respectively. Accordingly, the hydrological characteristics and the specification of the potential water harvesting sites and systems were examined. For Khartoum City Center, characteristics of the drainage system were examined using ArcGIS platform. It is found that the drainage system covers 42% of the area with total capacity of 24000 m3. Daily rainfall data for urban meteorological station were used to calculate the probability and the return period of the rainfall, as well as the potential runoff. Rainfall probability of occurrence was calculated applying Gumbel distribution method for extreme events that were arranged according to the Peak-over-Threshold method. The potential runoff that could be generated from a certain rainfall was calculated using the Natural Resources Conservation Services method provided by the United States Department of Agriculture (US-NRCS). Accordingly, the curve number was calculated depending on the land use/land cover and the hydrological soil group. Consequently, the weighted curve number is found to be 94%, indicating dominant imperviousness. 13.1 mm rainfall depth produces runoff volume equal to the drainage system capacity with return period of one year; whereas more than four folds the drainage system capacity is produced by 30 mm rainfall depth that is considered the threshold for raising flood hazard. Six potential sites for roof rainwater harvesting were selected. Accordingly, it is found that, the application of roof water harvesting in 18% and 72% of the commercial and business district buildings can accommodate the runoff resulting from the 13.1 and 30 mm rainfall depth, respectively. Hence, impounding rainstorm water would help managing the urban runoff water, and consequently, the stored water could be used for making more green areas that will enhance the urban environment. Three watersheds of ephemeral streams (wadi), namely Wadi El Kangar, Wadi El Seleit, and Wadi El Kabbashi make up Seleit area. Distinct maps were prepared in ArcMap for the calculation of the potential runoff and the specification of the appropriate water harvesting sites and systems. The Wadis watersheds areas are found to be 540, 344 and 42 km2 for Wadi El Kangar, Wadi El Seleit and Wadi El Kabbashi, respectively. Daily rainfall data of rural meteorological station were classified into three groups representing the soil dry (AMCI), moderate (AMCII), and wet (AMCIII) moisture conditions; the respective CNI, CNII, and CNIII values were calculated accordingly. The weighted CN values indicate high runoff potential within the three soil moisture conditions. Accordingly, the rainfall thresholds for runoff generation for AMCI, AMCII and AMCIII conditions are found to be respectively 18.3 mm, 9.1 mm and 4.4 mm for Wadi El Kabbashi and 22 mm, 11 mm and 5 mm for both Wadi El Seleit and Wadi El Kangar. El Kangar dam subwatershed was used for calibrating the potential runoff calculated by the NRCS method. Since the Wadis are ungauged, Google Earth and GIS platforms were used to calculate geometrically the volume of the dam reservoir water for three years. This volume was compared to the annual runoff calculated by the NRCS method. Consideration to different factors was made to locate the potential water harvesting sites. Accordingly, water harvesting systems for fodder and crop plantation; sand storage surface or subsurface dams; or groundwater recharge, were specified. The socio-economic study revealed that the financial capacity, if any, of the villagers is very limited. Thus, the financial source for the construction of the suggested potential water harvesting or the rehabilitation of the existing ones is questionable. Hence, other potential financial sources are needed to help executing water harvesting projects in the region, e.g. Khartoum State Government. Applying water harvesting in Seleit area is found to be promising. Improving the livelihood of the villagers by applying runoff water harvesting could assure better water accessibility, better income generation from farms production, and allocation of time for other activities, e.g. education. This would be reflected in reduced migration to nearby cities and stabilized market supply of agricultural and animal products. Therefore, the development of the rural part is of great benefit to the development of Khartoum State, as long as the interdependency and mutual benefit between the rural and urban areas, represented by the local food and labor market, remain exist.

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OLIVIERI, STEFANO. « Elastically-bounded flapping plates for flow-induced energy harvesting ». Doctoral thesis, Università degli studi di Genova, 2020. http://hdl.handle.net/11567/999997.

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This work concerns a novel concept for energy harvesting (EH) from fluid flows, based on the aeroelastic flutter of elastically-bounded plates immersed in laminar flow. The resulting flapping motions are investigated in order to support the development of centimetric-size EH devices exploiting low wind velocities, with potential application in the autonomous powering of low-power wireless sensor networks used, e.g., for remote environmental monitoring. The problem is studied combining three-dimensional direct numerical simulations exploiting a state-of-the-art immersed boundary method, wind-tunnel experiments on prototypal EH devices, and a reduced-order phenomenological model based on a set of ordinary differential equations. Three key features of the aeroelastic system are investigated: (i) we identify the critical condition for self-sustained flapping using a simple balance between characteristic timescales involved in the problem; (ii) we explore postcritical regimes characterized by regular limit-cycle oscillations, highlighting how to maximize their amplitude and/or frequency and in turns the potential energy extraction; (iii) we consider arrays of multiple devices, revealing for certain arrangements a constructive interference effect that leads to significant performance improvements. These findings lead to an improved characterization of the system and can be useful for the optimal design of EH devices. Moreover, we outline future research directions with the ultimate goal of realizing high-performance networks of numerous harvesters in real-world environmental conditions.

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Wang, Junjie. « Energy Harvesting Circuit for Indoor Light based on the FOCV Method with an Adaptive Fraction Approach ». Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/94319.

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The proposed energy harvesting circuit system is designed for indoor solar environment especially for factories where the light energy is abundant and stable. The designed circuits are intended to power wireless sensor nodes (WSNs) or other computing unit such as microcontrollers or DSPs to provide a power solution for Internet of Things (IoTs). The proposed circuit can extract maximum power from the PV panel by utilizing the maximum power point tracking (MPPT) technique. The power stage is a synchronous dual-input dual-output non-inverting buck-boost converter operating in discontinuous conduction mode (DCM) and constant on-time pulse skipping modulation (COT-PSM) to achieve voltage regulation and maximum power delivery to the load. Battery is used as secondary input also as secondary output to achieve a longer lifecycle, a fast load response time and support higher load conditions. The proposed MPPT technique doesn't require any current sensor or computing units. Fully digitalized simple circuits are used to achieve sampling, store, and comparing tasks to save power. The whole circuits including power stage and control circuits are designed and will fabricate in TSMC BCDMOS 180 nm process. The circuits are verified through schematic level simulations and post-layout simulations. The results are validated to prove the proposed circuit and control scheme work in a manner.
Master of Science
With the growing energy demands, the efficient energy conversion systems caught great attentions. Especially, in the era of Internet of Things, powering those wireless devices can be extremely difficult. Nowadays, lots of devices such as consumer electronics, wireless sensor nodes, computing and mission system etc. are still powered by the batteries. Regular changing the batteries of those devices can be inconvenient or expensive. Energy harvesting provides a good solution to this issue because there are lots of ambient energy source is available. To design an energy efficient energy harvesting circuit system can help extend the device lifecycle per charging cycle. Even with some specific energy source which power scale is high enough, meanwhile the load doesn’t require too much power, the devices can be power-independent or standalone. In this work, the proposed circuit targets for indoor solar energy harvesting via solar panel. The target powering devices are wireless sensor nodes (WSNs). Meanwhile, WSNs can monitor the temperature, humidity, pressure, noise level etc. The proposed circuit design combines the power stage and control circuit on an integrated chip (IC), only few components are off-chip. It provides a very compact, endurable, and economical solution to the current IoT powering issue.

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Adamou, Djibrilla Incha. « Réseaux de collecte de données pour les zones blanches étendues ». Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS457/document.

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Les zones blanches étendues sont de vastes espaces géographiques (forêts, déserts), sans ou ayant très peu d’infrastructures telles que les routes, les réseaux électriques ou de télécommunication. Cependant, très souvent, dans ces zones se développent de nombreuses activités économiques ou environnementales telles que le monitoring de l’environnement, la surveillance d’une frontière ou d’une installation de pipeline, ou encore la prévention des feux de forêt. Grâce aux techniques de télédétection et de communication, une fonction clé de ces activités repose sur la collecte d’informations issues de capteurs qui sont transmises à un centre d’analyse distant. Nous proposons des solutions réseau afin d’effectuer la collecte de ces données dans les zones blanches étendues grâce à des technologies de communication longue distance et faible énergie, de type LoRaWAN. Pour le problème du déploiement du réseau de capteurs sans fil dans ces zones difficiles, nous avons proposé une heuristique inspirée de la croissance biologique d’un champignon, le physarum. Le physarum est capable de créer un corps complexe de liens pour trouver de la nourriture nécessaire à sa survie tout en optimisant ses propres ressources corporelles lors des périodes de disette. Ce principe d’optimisation a été adapté au domaine des réseaux pour déployer un réseau tolérant aux fautes, tout en minimisant le nombre de ressources ou relais à placer sur la zone d’intérêt. Nous nous sommes ensuite intéressés à la collecte opportuniste de données dans les zones blanches afin de pouvoir collecter l’information des nœuds trop éloignés d’une station relais. Nous avons développé une méthode de collecte basée sur les avions de ligne qui survole le territoire. Durant une fenêtre de communication, l’avion est à portée d’un capteur et peut ainsi collecter les données stockées qui seront livrées au serveur à l’atterrissage de l’avion. Notre dernière contribution utilise conjointement les deux méthodes précédentes, pour permettre à la fois le déploiement du réseau et la collecte des capteurs isolés
Although wide white areas are not equipped or sparsely equipped with any infrastructure (energy, roads ...), strategic human activities are being carried out such as mines, forest, pipeline... To tackle the problem of deploying sensor networks in a very large area where few infrastructures are available, we propose a network deployment algorithm which aims at efficiently linking sparse points of interest in a very wide white area. The originality of the proposed method is that it mimics the evolution of a type of mold called physarum. Secondly, we aim at overcoming the deployment problem in wide white areas by using long range communication between an aircraft and earth. The new data collection scheme he proposes is based on the use of commercial flights to collect data while they cross over an area of interest. It investigates the feasibility of such a scheme by determining the collection capacity of commercial aircraft in different locations of the desert. Finally, we mixed both solutions do repatriate data from sensors not covered by any flight to a covered data sink that relays data to the aircraft

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Masghouni, Nejib. « Hybrid Carbon Fiber/ZnO Nanowires Polymeric Composite for Stuctural and Energy Harvesting Applications ». Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/64354.

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Despite the many attractive features of carbon fiber reinforced polymers (FRPs) composites, they are prone to failure due to delamination. The ability to tailor the fiber/matrix interface FRPs is crucial to the development of composite materials with enhanced structural performance. In this dissertation, ZnO nanowires (NWs) were grown on the surface of carbon fibers utilizing low temperature hydrothermal synthesis technique prior to the hybrid composite fabrication. The scanning electron microscopy revealed that the ZnO nanowires were grown uniformly on the surface of the carbon fabric. The surface grown ZnO NWs functionally-graded the composite material properties and ensured effective load transfer across the interface. To assess the influence of the ZnO NWs growth, reference samples were also prepared by exposing the carbon fabric to the hydrothermal conditions. The damping properties of the hybrid ZnO NWs-CFRP composite were examined using the dynamic mechanical analysis (DMA) technique. The results showed enhanced energy dissipation within the hybrid composite. Quasi-static tensile testing revealed that the in-plane and out-of-plane strengths and moduli of the hybrid FRP composite were also boosted. The interlaminar shear strength (ILSS) measurements suggested the improvement in the mechanical properties of the composite to the enhanced adhesion between the ZnO nanowires and the other constituents (carbon fiber and epoxy). It was necessary thus, to utilize the molecular dynamics simulations (MD) to investigate the adhesion within the CFRP structure upon growing the ZnO nanowires on the surface of the carbon fibers. Molecular models of the carbon fibers, the epoxy matrix and the ZnO nanowires were built. The resulting molecular structures were minimized and placed within a simulation box with periodic boundary conditions. The MD simulations were performed using the force field COMPASS to account for the empirical energy interactions between the different toms in the simulation box. Proper statistical thermodynamics were employed to relate the dynamics of the molecular model to the macroscale thermodynamic states (pressure, temperature and volume). Per the computed potential energies of the different components of the composite, it was found that the polar surfaces in the ZnO structures facilitates good adhesion properties in the graphite-epoxy composite. Besides the attractive mechanical properties of the ZnO nanowires, their piezoelectric and semiconductor properties were sought to design an energy harvesting device. To ensure sufficient charges collection from the mechanically stressed individual ZnO nanowires, a copper layer was sputtered on top of the ZnO nanowires which introduced also a Schottky effect. The mechanical excitation was provided by exposing the device to different vibration environment. The output voltage and currents were measured at the conditions (in terms of frequency and resistive load). It was demonstrated that the electrical output could be enhanced by stacking up similar devices in series or in parallel. Finally, in an attempt to exploit the reversibility of the electromechanical coupling of the energy harvesting device, the constitutive properties of the hybrid ZnO nanowires-CFRP composite were estimated using the Mori-Tanaka approach. This approach was validated by a finite element model (FEM). The FEM simulations were performed on a representative volume element (RVE) to reduce the computational time. The results demonstrated that the mechanical properties of the hybrid ZnO NWs-CFRP composite were better than those for the baseline CFRP composite with identical carbon fiber volume fraction (but with no ZnO NWs) which confirmed the experimental findings. Furthermore, the electro-elastic properties of the hybrid composite were determined by applying proper boundary conditions to the FE RVE. The work outlined in this dissertation will enable significant advancement in the next generation of hybrid composites with improved structural and energy harvesting multifunctionalties.
Ph. D.

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Zhao, Xiaofei. « Harvesting Microalgae-Development of a Short Residence Time Method Using Rapid-response Temperature-sensitive Semi-IPN Hydrogels ». University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1434501731.

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Sadeghi, Saviz. « Multi-criteria Spatial Evaluation and Modelling of Farm Dam Site Suitability for Water Harvesting and Conservation ». Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/16261.

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This study presents a conceptual model designed to identify and rank potential areas for siting farm dams in a section of the Hawkesbury-Nepean catchment in western Sydney, Australia. The method takes into account environmental site assessment criteria using a decision-making method known as the Analytic Hierarchy Process (AHP). Spatial data is processed by applying GIS and potential sites are ranked by a multi-criteria evaluation based on meteorologic, hydrologic, topographic, agronomic and pedologic criteria. Particular to this study is the application of the SCS-CN method using curve numbers (CN) slightly modified for Australian conditions (CNMAC) for estimating runoff along with the original NCRS-CN values for comparative purposes. The use in this research of CNMAC has indicated modified CNs could be applied successfully in Australia especially in areas with limited physical data. Spatially-explicit sensitivity analysis was used to examine the model’s robustness to the sensitivity of criteria weights resulting from AHP pair-wise comparisons. Application of the One-At-a-Time (OAT) method (Chen et al.’s (2010, 2013)) demonstrated runoff has the highest impact on the evaluation results. Most of the study catchment showed a relatively stable suitability class; therefore, the model (SSMFD) was relatively robust and flexible in identifying suitable sites. The study then focussed on climate change impacts through annual rainfall patterns and their influence on the hydrology of the catchment and the model. Investigating 130 years of rainfall pattern indicated model low sensitivity to annual rainfall amount. In addition, changing the input data resolution used in SSMFD indicated that detailed outcomes were influenced by the resolution of input datasets. According to the SCS-CN method, results indicated the most decisive factor is CN values, consequently, soil and land cover are two crucial parameters and have the greatest impact on the model performance.

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Turner, Kate. « Assessing wild plant vulnerability to over-harvesting : refinement of the "rapid vulnerability assessment" method and its application in Huitzilac, Mexico ». Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18450.

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Many concerns have been voiced about the impacts of non-timber forest product harvesting on forest ecosystems, prompting the development of tools for assessing harvest sustainability. The "rapid vulnerability assessment" (RVA) is one method that predicts vulnerability of plants to over-harvesting. However, there is little consensus on how to perform an RVA or interpret the results. The objective of my research is to analyze and refine the RVA method to enhance its utility. I examine factors affecting plant vulnerability used in various versions of the RVA to create a "short list" of important factors. I then use this short list of factors to perform an RVA for selected wild plant species in Huitzilac, Mexico, to further refine the RVA method. Information for this assessment comes from literature, interviews, observation, plant sampling and a town survey. Based upon these I re-conceptualize the RVA method, placing increased value on several critical factors which directly affect the availability and the rate of loss of the target species. I also suggest a method to aid in interpreting the results. Results from the case study, presented in this re-conceptualized format, indicate that none of the selected species is highly vulnerable to over-harvesting.
Plusieurs critiques ont été formulées concernant l'impacts de la collecte des produits forestiers non ligneux (PFLN) sur les écosystèmes forestiers, ce qui a mené au développement d'outils afin d'évaluer la durabilité de la sous dite collecte. L'évaluation rapide de vulnérabilité (ERV) est une méthode afin de prédire la vulnérabilité de plantes à la sur collecte. Cependant, il y a peu de consensus sur la manière optimale d'effectuer une ERV ou d'interpréter les résultats obtenus. L'objectif de ma recherche est d'analyser et de raffiner la méthode ERV afin d'augmenter son utilité pratique. J'examine des facteurs influençant la vulnérabilité des plantes utilisées dans différentes versions de l'ERV afin de créer une liste abrégée de facteurs-clés. J'utilise ensuite cette liste abrégée afin d'effectuer une ERV sur une série de plantes sauvages sélectionnées à Huitzilac, au Mexique; dans le but d'améliorer la méthode ERV. L'information pour cette ERV provient de la littérature scientifique, des entrevues, des observations directes, l'échantillonnage de plantes et une évaluation d'utilisation en ville. Basée sur ces informations, je re-conceptualise la méthode ERV plaçant plus de valeur sur plusieurs facteurs critiques qui affectent directement l'existence et le taux de perte d'espèces sélectionnées. Je suggère également une méthode afin de faciliter l'interprétation de résultats. Les résultats de l'étude de cas, présentée de forme re-conceptualisée, indiquent qu'aucune des espèces sélectionnées n'est extrêmement vulnérable à la sur-collecte.

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Perju, Dragos-Stefan. « Applying Memoization as an Approximate Computing Method for Transiently Powered Systems ». Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-256065.

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Internet of Things (IoT) is becoming a more and more prevailing technology, as it not only makes the routine of our life easier, but it also helps industry and enteprise become more eﬀicient. The high potential of IoT can also help support our own population on Earth, through precision agriculture, smart transportation, smart city and so on. It is therefore important that IoT is made scalable in a sustainable manner, in order to secure our own future as well.The current work is concerning transiently powered systems (TPS), which are embedded systems that use energy harvesting as their only power source. In their basic form, TPS suffer frequent reboots due to unreliable availability of energy from the environment. Initially, the throughput of such systems are therefore lower than their battery-enabled counterparts. To improve this, TPS involve checkpointing of RAM and processor state to non-volatile memory, as to keep computation progress saved throughout power loss intervals.The aim of this project is to lower the number of checkpoints necessary during an application run on a TPS in the generic case, by using approximate computing. The energy need of TPS is lowered using approximations, meaning more results are coming through when the system is working between power loss periods. For this study, the memoization technique is implemented in the form of a hash table. The Kalman filter is taken as the testing application of choice, to run on the Microchip SAM-L11 embedded platform.The memoization technique manages to yield an improvement for the Kalman application considered, versus the initial baseline version of the program. A user is allowed to ”balance” between more energy savings but more inaccurate results or the opposite, by adjusting a ”quality knob” variable epsilon ϵ.For example, for an epsilon ϵ = 0.7, the improvement is of 32% fewer checkpoints needed than for the baseline version, with the output deviating by 42% on average and 71% at its maximum point.The proof of concept has been made, being that approximate computing can indeed improve the throughput of TPS and make them more feasiable. It is pointed out however that only one single application type was tested, with a certain input trace. The hash table method implemented can behave differently depending on what application and/or data it is working with. It is therefore suggested that a pre-analysis of the specific dataset and application can be done at design time, in order to check feasiability of applying approximations for the certain case considered.
Internet of Things (IoT) håller på att bli en mer och mer utbredd teknik, eftersom det inte bara underlättar rutiner i vårt liv, utan det hjälper också industrin och företag att bli effektivare. Den höga potentialen med IoT kan också hjälpa till att ge stöd åt vår egen befolkning på jorden, genom precisionslantbruk, smart transport, smarta städer och mer. Det är därför viktigt att IoT görs skalbart på ett hållbart sätt för att säkra vår egen framtid.Det nuvarande arbetet handlar om transientdrivna system (TPS), vilket är inbäddade system som använder energiskörning som sin enda kraftkälla. I sin grundform har TPS ofta återställningar på grund av opålitlig tillgång till energi från miljön. Ursprungligen är därför sådana systems genomströmning lägre än deras batteriaktiverade motsvarigheter. För att förbättra detta använder TPS kontrollpunkter i RAM och processortillstånd till icke-flyktigt minne, för att hålla beräkningsförloppet sparat under strömförlustintervaller.Syftet med detta projekt är att sänka antalet kontrollpunkter som krävs under en applikationskörning på en TPS i ett generiskt fall, genom att använda ungefärlig datorberäkning. Energibehovet för TPS sänks med ungefärliga belopp, vilket innebär att fler resultat kommer när systemet arbetar mellan strömförlustperioder. För denna studie implementeras memoiseringstekniken i form av en hashtabell. Kalman-filtret tas som testapplikation för att köra på Microchip SAM-L11 inbäddad plattform.Memoization-tekniken lyckas ge en förbättring för Kalman-applikationen som beaktades, jämfört med den ursprungliga baslinjeversionen av programmet. En användare får ”balansera” mellan mer energibesparingar men mer felaktiga resultat eller motsatsen genom att justera en ”kvalitetsrat”-variabel epsilon ϵ. Till exempel, för en epsilon ϵ = 0.7, är förbättringen 32% färre kontrollpunkter som behövs än för baslinjeversionen, med en utdata avvikelse med 42% i genomsnitt och 71% vid sin högsta punkt.Beviset på konceptet har gjorts, att ungefärlig databeräkning verkligen kan förbättra genomströmning av TPS och göra dem mer genomförbara. Det påpekas dock att endast en enda applikationstyp testades, med ett visst inmatningsspår. Den implementerade hashtabellmetoden kan bete sig annorlunda beroende på vilken applikation och/eller data den arbetar med. Det föreslås därför att en föranalys av det specifika datasättet och applikationen kan göras vid designtidpunkten för att kontrollera genomförbarheten av att tillämpa ungefärliga belopp för det aktuella fallet.

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Gisselman, Fredrik. « Economic assessment of harvesting and removing macro algae and reed as an eutrophication mitigation method : A cost-benefit analysis using an ecosystem service approach applied on Burgsviken Gotland ». Thesis, Umeå universitet, Nationalekonomi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-99663.

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Odhiambo, Benedict O. « The use of time study, method study and GPS tracking in improving operational harvest planning in terms of system productivity and costs ». Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/5333.

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Thesis (MScFor (Dept. of Forest and Wood Science)--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: This study aims to quantify the benefits of implementing an operational harvesting plan in forest harvesting operations. This is to be achieved by comparing productivity and costs from unplanned and planned harvesting operations. The study was conducted on a Pinus radiata plantation owned by Mountain to Ocean Forestry Company (Pty) Ltd (MTO) located near the town of Grabouw in the Western Cape Province of South Africa. MTO conducts harvesting operations using semi-mechanised tree-length harvesting systems. A wheeled H67 Clark Ranger cable skidder is used to extract tree-lengths from infield to the landing. Data was obtained both manually (work study) and from GPS tracking. Choking and dechoking data was obtained through time and method studies. GPS tracking was used to measure travel loaded and travel empty times, as well as travel distances and travel speeds. The aim of using both manual techniques and GPS tracking was to obtain detailed and spatially accurate information about the operation. The operating costs were estimated using South African Harvesting and Transport Costing Model. Productivity of the newly introduced tagline system (45.97 m³/pmh) exceeded that of mainline system (37.85 m³/pmhh) by 26%. The unit production cost of using tagline system (R20.21/m³) was 10% lower than the unit production cost of using mainline system (R22.54/³3). There were no benefits to be gained from improving the level of skid trail construction by removal of logging residue or cutting down stumps to as near the ground level as possible. A combination of manual (time and method studies) data collection and GPS tracking provided more detailed and accurate information on the semi-mechanised harvesting system.
AFRKAANSE OPSOMMING: Hierdie studie beoog om die voordele van die uitvoering van 'n operasionele inoestingsplan te kwantifiseer. Dit word bereik deur produktiwiteit en kostes van beplande en onbeplande inoestingswerksaamhede te vergelyk. Die studie is gedoen in Pinus radiata opstande van Mountain to Ocean Forestry Company (Pty) Ltd (MTO) naby Grabouw in die Wes-Kaap provinsie van Suid Afrika. MTO gebruik semi-gemeganiseerde boomlengte inoestingstelsels in hul inoestingswerksaamhede. . H67 Clark Ranger wielsleeptrekker met kabel en wenas is gebruik om boomlengtes van die veld na die pad te sleep. Data is versamel deur van beide hand (werkstudie) en GPS-opsporing gebruik te maak. Afhaak en aanhaak data is verkry deur van tyd- en metodestudies gebruik te maak. Gelaaide en ongelaaide tyd, spoed en afstande is met behulp van die GPS gemeet. Deur van beide hand en GPS versamelingsmetodes gebruik te maak, kon omvattende sowel as ruimtelik akkurate inligting oor die werksaamhede verkry word. Die bedryfskostes is verkry van die South African Harvesting and Transport Costing Model. Produktiwiteit van die nuut ingestelde verbindingslynstelsel (45.97 m³/pmh) het die hooflynstelsel (37.85 m³/pmh) met 26% oorskry. Die eenheidsproduksiekoste van die verbindingslynstelsel (R20.21/m³) was 10% laer as die eenheidsproduksiekoste van die hooflynstelsel (R22.54/m³). Daar was geen voordeel in die verbetering van die sleeppad konstruksie deur afval te verwyder of stompe nader aan die grondvlak af te sny nie. 'n Kombinasie van hand (tyd- en metodestudies) dataversameling en GPS-opsporing het meer akkurate en omvattende inligting oor die semi-gemeganiseerde inoestingstelsel verskaf.

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Yan, Zhimiao. « Modeling of Nonlinear Unsteady Aerodynamics, Dynamics and Fluid Structure Interactions ». Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/71824.

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We model different nonlinear systems, analyze their nonlinear aspects and discuss their applications. First, we present a semi-analytical, geometrically-exact, unsteady potential flow model is developed for airfoils undergoing large amplitude maneuvers. Towards this objective, the classical unsteady theory of Theodorsen is revisited by relaxing some of the major assumptions such as (1) flat wake, (2) small angle of attack, (3) small disturbances to the mean flow components, and (4) time-invariant free-stream. The kinematics of the wake vortices is simulated numerically while the wake and bound circulation distribution and, consequently, the associated pressure distribution are determined analytically. The steady and unsteady behaviors of the developed model are validated against experimental and computational results. The model is then used to determine the lift frequency response at different mean angles of attack. Second, we investigate the nonlinear characteristics of an autoparametric vibration system. This system consists of a base structure and a cantilever beam with a tip mass. The dynamic equations for the system are derived using the extended Hamilton's principle. The method of multiple scales is then used to analytically determine the stability and bifurcation of the system. The effects of the amplitude and frequency of the external force, the damping coefficient and frequency of the attached cantilever beam and the tip mass on the nonlinear responses of the system are determined. As an application, the concept of energy harvesting based on the autoparametric vibration system consisting of a base structure subjected to the external force and a cantilever beam with a tip mass is evaluated. Piezoelectric sheets are attached to the cantilever beam to convert the vibrations of the base structure into electrical energy. The coupled nonlinear distributed-parameter model is developed and analyzed. The effects of the electrical load resistance on the global frequency and damping ratio of the cantilever beam are analyzed by linearizion of the governing equations and perturbation method. Nonlinear analysis is performed to investigate the impacts of external force and load resistance on the response of the harvester. Finally, the concept of harvesting energy from ambient and galloping vibrations of a bluff body is investigated. A piezoelectric transducer is attached to the transverse degree of freedom of the body in order to convert the vibration energy to electrical power. A coupled nonlinear distributed-parameter model is developed that takes into consideration the galloping force and moment nonlinearities and the base excitation effects. The aerodynamic loads are modeled using the quasi-steady approximation. Linear analysis is performed to determine the effects of the electrical load resistance and wind speed on the global damping and frequency of the harvester as well as on the onset of instability. Then, nonlinear analysis is performed to investigate the impact of the base acceleration, wind speed, and electrical load resistance on the performance of the harvester and the associated nonlinear phenomena. Short- and open-circuit configurations for different wind speeds and base accelerations are assessed
Ph. D.

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Topal, Emre Tan. « A Mems Thermoelectric Energy Harvester For Energy Generation In Mobile Systems ». Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613636/index.pdf.

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In this thesis design, optimization, fabrication and performance characterization of MEMS thermoelectric (TE) energy harvesters for harnessing waste heat in mobile systems are presented. As a proof of concept, chromium and nickel are used as the thermoelectric material in the proposed design. The feasibility of the state of the art thermoelectric materials is also discussed. MEMS TE energy harvesters proposed in this study are designed to generate power at relatively lower &Delta
T values. The performance of the MEMS TE energy harvesters was optimized using analytical and 3-D finite element models. An analytical code was used for profiling the electrical power output with varying geometry. The design points with maximum generated power were selected, and the microfabricated thermoelectric energy harvesters were designed accordingly. The fabricated devices are formed on a silicon wafer and composed of Nickel and Chromium thermocouples on SiO2/Si3N4 diaphragms, and Titanium heater and monitor resistors for testing purposes. Microfabrication was followed by the performance characterization of MEMS TE energy harvesters with the conducted tests. For 10 °
C temperature difference between the hot and cold junctions (a heat source at 35 °
C), the proposed TE energy harvesters are capable of providing 1.1 µ
W/cm2 power density and 1.71 V voltage. The performance of the thermoelectric generators in general is limited by Carnot cycle efficiency. Nevertheless, the validated practical performance of MEMS TE energy harvesters proposed in this thesis is comparable to other examples in literature. It is anticipated by the calculations that this design will be able to provide the highest thermoelectric efficiency factor (4.04 µ
W/K2cm2) among the lateral TE energy harvesters if thermoelectric materials having high Seebeck coefficient values (such as p-Si, n-Si, polysilicon, Bi2Te3 etc.) are used. According to the performance results, the MEMS TE energy harvesters can be implemented in mobile systems to convert waste heat into electricity. The fabrication process can be adapted to CMOS with some modifications if needed. The lateral MEMS thermoelectric energy harvesters can also be combined with vibration energy harvesters to realize multi-mode energy scavenging. For prospective study, vertical thermoelectric generator configurations are also discussed in order to further increase the power density generated. The finite element simulations for proposed vertical configurations with air and water convection were completed. The vertical TE generators proposed can supply up to 4.2 mW/cm2 with a heat source at a temperature of 310 K.

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Sijková, Simona. « Návrh testovacího přípravku piezoelektrických vlastností PVDF vrstvy ». Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417737.

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The diploma thesis deals with a design of a tester device, a selection and verification of a suitable method for comparing the piezoelectric properties of tested PVDF samples. In the introduction, a basic overview of the theory is important to understand the issue and the various branches of use of PVDF in the field of energy harvesting. The tester device includes a unimorph piezoelectric cantilever beam with tip mass, whose properties are described by three models: a model with N degrees of freedom reduced to one degree of freedom (NDOF), a single degree of freedom model (SDOF), both created in Matlab and a model for verifying results in FEM ANSYS Workbench program. The voltage time response and the voltage frequency response of the models is compared with each other. For two different PVDF samples, the voltage response to harmonic excitation is measured using a tester device, and the piezoelectric properties of one of them are determined using the NDOF and SDOF models.

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Deng, Jie. « Vibroacoustic modeling of acoustic blackhole applications in flat, curved andcomplex mechanical structures ». Doctoral thesis, Universitat Ramon Llull, 2020. http://hdl.handle.net/10803/670666.

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Els forats negres acústics en mecànica (coneguts per les sigles ABHs, de l’anglès Acoustic Black Holes) solen estar formats per osques en bigues i plaques, el gruix de les quals decau segons una llei potencial. L’efecte de l’ABH és el d’alentir les velocitats de fase i de grup de les ones de flexió incidents de tal manera que, en teoria, faria falta un temps infinit perquè les ones arribessin al centre de l’ABH, si el gruix d’aquest últim fos exactament zero. Tanmateix, a la pràctica això no és possible tot i que es pot aconseguir una forta dissipació col·locant una capa de material esmorteïdor al centre de l’ABH, on es concentra la major part de l’energia de les ones. En els darrers anys, els ABHs no només s’han explotat com a mètode passiu per reduir vibracions estructurals i l’emissió corresponent de soroll, sinó que també s’ha explorat el seu potencial per altres aplicacions com la manipulació d’ones o la captació d’energia. Aquesta tesi té tres objectius principals. Així, doncs, després d'una introducció general als ABHs, el treball s’ha dividit en tres grans seccions. La primera aborda aplicacions dels ABHs en bigues rectes i plaques planes. Per començar, es proposa i s’analitza un voladís piezoelèctric amb un acabament d’ABH per capturar energia. A continuació es presenten ABHs en forma d’anell per tal d’aïllar punts d’excitació externs en plaques planes i així evitar la transmissió de vibracions. Finalment, es contemplen configuracions periòdiques de matrius d’ABHs per tal de col·limar feixos d'ones de flexió i concentrar la seva energia en zones predeterminades d’una placa. La segona part de la tesi proposa nous dissenys d’ABHs per a estructures amb curvatura. Aquestes són molt habituals en els sectors naval, aeronàutic i industrial, de manera que val la pena investigar si els ABH poden resultar alguns casos. La secció comença analitzant la inclusió d’ABHs en bigues circulars i es veu com això dona peu a l’aparició de fenòmens típics en sistemes periòdics. Acte seguit es proposa un ABH anular per reduir les vibracions en conductes cilíndrics. En concret, es tracten els casos d’un conducte simplement suportat amb un ABH anular, i el d’un conducte amb ABH, suports periòdics i rigidificadors. Per finalitzar la secció, s’investiguen els efectes dels ABH anulars en la radiació acústica del conducte tenint en compte el nivell de potència acústica, l’eficiència de radiació i la intensitat supersònica. La tercera part de la tesi és més curta que les anteriors i simula l’aïllament d'una placa amb múltiples ABHs, en el rang de mitja i alta freqüència. A tal efecte s’empra el mètode de l’anàlisi estadística de distribució modal d'energia (SmEdA: statistical modal energy distribution analysis). En aquesta secció, l’estructura amb ABHs ja no s’analitza com un element individual sinó que s’acobla a dues cavitats d’aire, formant part d’un sistema mecànic més complex. Al llarg de la tesi s’utilitza repetidament el mètode d’expansió gaussiana (GEM: Gaussian expansion method). Pel GEM entenem prendre funcions gaussianes com a base per resoldre equacions diferencials en derivades parcials en el marc del mètode de Rayleigh-Ritz. El GEM s’assembla molt als enfocaments d’ondetes, però ofereix alguns avantatges en el cas de condicions de contorn periòdiques. Al principi de la tesi s’exposa un breu repàs del GEM i, quan és necessari, s’aborda la seva reformulació per a un problema particular en el capítol corresponent.
Los agujeros negros acústicos en mecánica (conocidos por las siglas ABHs, del inglés Acoustic Black Holes) suelen estar formados por muescas en vigas y placas, el grueso de las cuales decae según una ley potencial. El efecto del ABH es el de ralentizar las velocidades de fase y de grupo de las ondas de flexión incidentes de tal modo que, en teoría, haría falta un tiempo infinito para que las ondas alcanzaran el centro del ABH, si el grueso de este último fuera exactamente cero. Sin embargo, en la práctica esto no es posible, aunque se puede conseguir una fuerte disipación colocando una capa de material amortiguador en el centro del ABH, donde se concentra la mayor parte de la energía de las ondas. En los últimos años, los ABHs no sólo se han explotado como método pasivo para reducir vibraciones estructurales y la consecuente emisión de ruido, sino que también se ha explorado su potencial para otras aplicaciones como la manipulación de ondas o la captación de energía. Esta tesis tiene tres objetivos principales. Así pues, tras una introducción general a los ABHs, el trabajo se ha dividido en tres grandes secciones. La primera aborda aplicaciones de los ABHs en vigas rectas y placas planas. Para empezar, se propone y analiza un voladizo piezoeléctrico con un acabado de ABH para capturar energía. A continuación, se presentan ABHs en forma de anillo para aislar puntos de excitación externos en placas planas y así evitar la transmisión de vibraciones. Finalmente, se contemplan configuraciones periódicas de matrices de ABHs para colimar haces de ondas de flexión y concentrar su energía en zonas predeterminadas de una placa. La segunda parte de la tesis propone nuevos diseños de ABHs para estructuras con curvatura. Estas son muy habituales en los sectores naval, aeronáutico e industrial, por lo que merece la pena investigar si los ABH pueden dar buenos resultados en algunos casos. La sección comienza analizando la inclusión de ABHs en vigas circulares y se ve como estos dan pie a la aparición de fenómenos típicos de sistemas periódicos. Seguidamente se propone un ABH anular para reducir las vibraciones en conductos cilíndricos. En concreto, se tratan los casos de un conducto simplemente soportado con un ABH anular, y el de un conducto con ABH, soportes periódicos y rigidificadores. Para finalizar la sección, se investigan los efectos de los ABH anulares en la radiación acústica del conducto teniendo en cuenta el nivel de potencia acústica, la eficiencia de radiación y la intensidad supersónica. La tercera parte de la tesis es más corta que las anteriores y simula el aislamiento de una placa con múltiples ABHs, en el rango de media y alta frecuencia. A tal efecto se emplea el método del análisis estadístico de distribución modal de energía (SmEdA: statistical modal energy distribution analysis). En esta sección, la estructura con ABHs ya no se analiza como un elemento individual, sino que se acopla a dos cavidades de aire formando parte de un sistema mecánico más complejo. A lo largo de la tesis se utiliza repetidamente el método de expansión gaussiana (GEM: Gaussian expansión method). Por GEM entendemos tomar funciones gaussianas como base para resolver ecuaciones diferenciales en derivadas parciales en el marco del método de Rayleigh-Ritz. El GEM se parece mucho a los enfoques de ondículas, pero ofrece algunas ventajas en el caso de condiciones de contorno periódicas. Al principio de la tesis se expone un breve repaso del GEM y, cuando es necesario, se aborda su reformulación para un problema particular en el capítulo correspondiente.
Acoustic black holes (ABHs) in mechanics usually consist of geometrical indentations on beams and plates having a power-law decreasing thickness profile. An ABH slows down the phase and group velocity of incident flexural waves in such a way that, ideally, it would take an infinite amount of time for them to reach the ABH center, if the latter had an exact zero thickness. Though this is not possible in practice, strong wave dissipation can be achieved by placing a damping layer at the central region of the ABH, where most vibration energy concentrates. In recent years, ABHs have been not only exploited as a passive means for structural vibration and noise reduction, but its potential for other applications like wave manipulation or energy harvesting have been also explored. The objective of this thesis is threefold. Therefore, after an initial overview the work is divided into three main parts. The first one deals with ABH applications on straight beams and flat plates. To start with, an ABH piezoelectric bimorph cantilever for energy harvesting is proposed and analyzed. Then, ring-shaped ABH indentations are suggested as a means of isolating external excitation points in flat plates and prevent vibration transmission. Finally, periodic ABH array configurations are contemplated to collimate flexural wave beams and focus energy at desired plate locations. The second part of the thesis proposes new ABH designs for curved structures. The latter are very common in the naval, aeronautical and industrial sectors so it is worth investigating if ABHs could function for them. The section starts analyzing the embedding of ABHs on circular beams and how this results in the appearance of typical phenomena of periodic systems. After that, an annular ABH is proposed to reduce vibrations in cylindrical shells. The cases of a simply supported shell with an annular ABH indentation and of a periodic simply supported ABH shell with stiffeners are considered. To finish the section, the effects of annular ABHs on sound radiation are investigated in terms of sound power level, radiation efficiency and supersonic intensity. The third part of the thesis is shorter than the previous ones and is devoted to analyzing the transmission loss of a plate with multiple ABH indentations, in the mid-high frequency range. Statistical modal energy distribution analysis is used for that purpose. Here, the ABH plate is not taken as an individual structure but coupled to two air cavities, thus being part of a more complex mechanical system. Throughout the thesis repeated use is made of the Gaussian expansion method (GEM). The GEM refers to taking Gaussian functions as the basis for solving partial differential equations in the framework of the Rayleigh-Ritz method. The GEM closely resembles wavelet approaches but offers some advantages in the case of periodic boundary conditions. A brief overview of the GEM is exposed at the beginning of the thesis and, when necessary, its reformulation for a particular problem is tackled in its corresponding chapter.

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Hoang, Thien. « Dispositif de récupération d'énergie piézoélectrique : modélisation, fabrication et caractérisation ». Thesis, Tours, 2019. http://www.theses.fr/2019TOUR4023.

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Cette thèse s’inscrit dans le cadre du projet Lab-TMEMS, une collaboration entre le laboratoire GREMAN et l’entreprise VERMON. Le but de ce projet est de réaliser des générateurs piézoélectriques miniaturisés convertissant l’énergie de vibrations basses fréquences, pour alimenter des composants électroniques utilisés notamment dans des applications biomédicales. L’objectif de cette thèse est donc de proposer une stratégie de conception et d’optimisation de tels dispositifs. Afin d’atteindre cet objectif, nous avons développé une démarche originale de modélisation par la méthode des éléments finis en tridimensionnel, pour modéliser l’ensemble de la structure du générateur. Après avoir été validé expérimentalement, notre outil de conception est utilisé pour optimiser le générateur piézoélectrique selon un cahier des charges spécifique. Cet outil de conception s’appuie sur des études paramétriques géométriques, en considérant un régime de fonctionnement linéaire. Grâce à cette méthode, nous avons conçu, fabriqué et caractérisé un générateur piézoélectrique optimisé et l’avons ensuite intégré dans un capteur communicant utilisé pour la maintenance préventive d’une machine tournante industrielle. Nous avons ainsi démontré que la puissance fournie par le générateur puis convertie par un circuit électronique dédié est suffisante pour alimenter le capteur et le rendre ainsi autonome
This thesis is part of the Lab-TMEMS project, a collaboration between the GREMAN laboratory and the VERMON Company. The goal of this project is to realize miniaturized piezoelectric devices harvesting energy from low frequency vibrations in order to supply devices used in biomedical applications, for example. Thus, the objective of this thesis is to propose a strategy for the design and optimization of such devices. In order to achieve this objective, we have developed an original approach of modeling by finite element method in three-dimensional space in order to model the whole structure of the harvester. After being validated experimentally, our design tool is used to optimize the piezoelectric harvester according to given specifications. This design tool for linear piezoelectric harvesters design was developed based on geometrical parametric studies in linear domain. By using this tool, we have designed, fabricated and characterized the optimized piezoelectric harvester. Then we integrated it into an autonomous wireless sensor used for the preventive maintenance of an industrial rotating machine. The power recovered from the harvester, coupled with its power management circuit, is sufficient to power the sensor, making it autonomous

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Brites, Alice Dantas. « Monitoramento dos efeitos ecológicos e socioeconômicos da comercialização de produtos florestais não madereiros ». Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/90/90131/tde-24032011-215203/.

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A comercialização de produtos florestais não madeireiros (PFNMs) popularizou-se como atividade promotora do desenvolvimento socioeconômico de comunidades florestais com baixo impacto ambiental. Há evidências, contudo, de que a exploração possa produzir efeitos ecológicos e socioeconômicos negativos, sugerindo que é necessário monitorar tais iniciativas. A comercialização frequentemente ocorre em áreas remotas e em contextos de pobreza, como é o caso de muitas daquelas da Amazônia brasileira. Desta forma, é necessário que o monitoramento restrinja-se a avaliar os efeitos evidenciados como mais comuns em estudos anteriores. Este estudo revisa e sintetiza as evidências científicas dos efeitos da exploração de PFNMs sobre parâmetros ecológicos e socioeconômicos e, a partir daí, indica aqueles mais relevantes ao monitoramento. O estudo também levanta até que ponto o monitoramento é implementado no contexto da Amazônia brasileira e avalia quais os parâmetros importantes e viáveis de monitoramento neste caso específico. Para isso, foram realizadas revisões sistemáticas da literatura e a consulta a profissionais da área através do método Delphi. Os resultados indicam que efeitos ecológicos negativos são frequentes, principalmente quando se coletam folhas ou cascas. Alterações em órgãos ou processos fisiológicos e a taxa de sobrevivência dos espécimes explorados são parâmetros que devem ser monitorados, em particular quando se coletam frutos e partes vegetativas. Para todos os tipos de PFNMs, o tamanho e a estrutura populacional são parâmetros prioritários ao monitoramento. A riqueza de espécies da comunidade explorada merece atenção, principalmente quando se coletam frutos. Para os aspectos socioeconômicos, efeitos positivos foram mais frequentes que negativos. A contribuição da renda monetária obtida com o comércio na renda total, a regularidade de ingresso desta renda e o papel dos PFNMs como recursos de salvaguarda são parâmetros do capital financeiro prioritários ao monitoramento. Para o capital social, o empoderamento feminino, a coesão de grupo e o acesso aos benefícios gerados pela comercialização devem ser monitorados. Na Amazônia brasileira são poucas as iniciativas de implementação do monitoramento da comercialização de PFNMs. Embora este seja considerado importante, existem dificuldades que derivam principalmente da falta de apoio institucional, políticas de incentivo e de recursos financeiros. Os profissionais participantes do Delphi consideram que os parâmetros ecológicos mais importantes a monitorar neste contexto são o tamanho e a estrutura populacional do recurso explorado, o aumento da taxa de mortalidade, a quantidade total de recurso extraída e a técnica de coleta utilizada. Para os parâmetros econômicos, aspectos do mercado, como o preço pago ao coletor, a demanda e a qualidade do produto, bem como a renda monetária obtida pelos indivíduos são os parâmetros considerados mais importantes. Por fim, para os aspectos sociais, os efeitos na cultura, na qualidade de vida e na organização interna da comunidade foram priorizados. Os profissionais indicam que é viável estabelecer o monitoramento dos parâmetros levantados.
Amazon, non-timber forest products, ecological effects, socioeconomic effects, monitoring.

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Elliott, Robert Bailey. « Quantitative Comparison of Mechanical Harvesting Methods and Conventional Harvesting Methods of Burley Tobacco in the Southeast ». 2008. http://trace.tennessee.edu/utk_gradthes/374.

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The purpose of this study is to examine burley tobacco growers decision making processes as they pertain to labor usage during the harvest of their crop and adoption rates of mechanical harvesting technology in order to create a laudable document that could be used by those who disseminate knowledge in agricultural communities. This study sought to compare current conventional harvesting methods to mechanical harvesting methods to determine efficiency and affordability of each of the two methods for the tobacco grower. This study incorporated both survey data and focus group data in order to develop the findings herein. Survey data were used to examine burley tobacco growing regions in order to effectively site focus groups and to collect descriptive statistics on burley tobacco growers. Focus groups were conducted in Kentucky and Tennessee, the two major burley tobacco producing states in the southeast. There were 41 growers who participated in the focus groups with burley acreages ranging from 9 – 350 acres and years experience of tobacco production ranging from 3 – 60 years. The study revealed overall that growers were very satisfied with their conventional labor practices. The growers were reluctant to invest in mechanical harvesting technology due to uncertainty about the future of the burley tobacco market, inefficiency of the machines, cost of the harvesters and the availability of migrant labor. Survey data that were collected directly correlate with focus group findings, and recommendations for further study are provided in this thesis.

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Kim, Hyeoungwoo. « Impedance adaptation methods of the piezoelectric energy harvesting ». 2006. http://www.etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-1258/index.html.

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« Biogeochemistry of forest harvesting methods in the boreal zone of Quebec ». Thesis, Université Laval, 2006. http://www.theses.ulaval.ca/2006/24124/24124.pdf.

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Hamann, Mark Thomas. « Impact of Cotton Harvesting and Storage Methods on Seed and Fiber Quality ». Thesis, 2011. http://hdl.handle.net/1969.1/ETD-TAMU-2011-12-10230.

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There are currently two main types of machinery used for harvesting cotton in the United States, cotton pickers and cotton strippers with or without field cleaners. These different machine types package seed cotton with varying amounts of burrs, sticks, and leaves. Harvested cotton is placed in modules for storage prior to ginning. Recent developments in the industry include on-board module builders that package seed cotton as they harvest. This leads to three methods of storage: 1) traditional seed cotton modules, 2) half-modules, and 3) round modules utilized by harvesters with on-board module builders; all of these have different levels of packaging density. Cotton is harvested under widely varying conditions throughout the country and the moisture content of seed cotton at the point of containerization can be an important factor in the final quality of the crop. Seed cotton is being stored for increasing periods of time before being processed by cotton gins. The number of cotton gins in the U.S. has decreased while the production of cotton has increased. All cotton is harvested as it matures and the harvesting rate greatly exceeds the ginning rate. As a consequence of fewer gins, increased harvesting rates and increased quantities of cotton, the storage time of seed cotton prior to ginning has increased. It is hypothesized that the impact of varying densities, varying trash contents, and increased storage times prior to ginning is impacting the quality of the cotton lint and seed. The goal of this research is to quantify the impacts of these factors. The purpose of this research is to evaluate the effects of packaging seed cotton from any of the three different harvesting methods into varying types of storage as a function of differing moisture content and increased storage time. Results are indicated in terms of quality of both the fiber and the seed of ginned samples, as well as how the quality changes affect the value of the processed cotton. Samples of seed cotton are sealed in plastic containers for up to three months at varying levels of moisture, density, and trash content. Temperature and oxygen levels are monitored during storage. Samples are ginned and cottonseed and fiber are analyzed. The results of this research indicate that density does not affect the final quality of the lint and seed harvested. Increased moisture contents have a negative effect on both the quality and the value of the seed cotton, and this effect becomes more pronounced as the length of storage increases.

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Fontes, Tomás Miguel Guedes. « Methods of adipose tissue harvesting and preparation for autologous grafting in reconstructive surgery ». Master's thesis, 2017. https://hdl.handle.net/10216/105207.

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