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Михайленко, Ігор Всеволодович. "Напівпровідникові перетворювачі механічних величин з використанням поперечних тензоефектів." Thesis, КПІ ім. Ігоря Сікорського, 2019. https://ela.kpi.ua/handle/123456789/30025.
Full textAbstract:
Дисертація присвячена розробленню фізико-технологічних засад створення та дослідженню перетворювачів механічних величин на основі поперечних ефектів в анізотропних напівпровідниках.
Розроблені фізичні основи побудови перетворювачів механічних величин з використанням поперечних ефектів і проведено їх дослідження на експериментальних зразках. Продемонстрована перспективність використання перетворювачів на основі ефекту тензо-е.р.с. як в дискретному, так і в інтегральному виконанні для створення датчиків сили і тиску, які працюють в діапазоні температур 233-373 K. Виявлений ряд концентраційних ефектів у германії і запропоновані перетворювачі оригінальних конструкцій, таких як диференціальний тензотранзистор, безконтактний лінійний датчик переміщень на основі магнітоконцентраційного ефекту, порогові датчики кута повороту і сили на основі осцилісторного ефекту з можливістю управління порогом переключення. Дослідження, що проведені, підтверджують перспективність практичного використання поперечних ефектів у багатодолинних напівпровідниках для створення перетворювачів механічних величин.The purpose of the work is to develop a physical basis for transducers of mechanical values design and technology using transverse tenso-effects. The object of the research - characteristics of transverse effects caused by induced anisotropy in Si and Ge. The subject of research are transducers of mechanical values based on the transverse tenso-effects in Si and Ge. The result of the research is the development of both MEMS integrated pressure transducers and the industrial device for measuring the pressure of liquid media. The introduction substantiates the relevance of the topic, shows the relationship with scientific programs and plans, formulates purpose and objectives of scientific research, outlines the novelty and practical significance of the results obtained, indicates the personal contribution of the applicant, provides data on the validation of the results The First chapter analyzes phenomena leading to transverse effects. Consideration given in terms of anisotropy of conductivity, which is interpreted as the non-collinearity of the vectors of electric field and current. It allows using similar formal apparatus in the analysis of various effects. In particular, the cases of anisotropy induced by deformation and magnetic field have been examined. The Second chapter is devoted to the study of discrete tenso-emf transducers. In the proposed tenso-emf transducers, problems of matching the temperature dependencies of the sensitivity and impedances of individual strain gages are virtually eliminated. The dynamic range of the non-fixed tenso-emf transducer was about 120 dB. The Third chapter contains the results of the design and study of transducers using concentration effects in Ge in combination with other physical effects. New types of mechanical transducers proposed, such as differential tenso-transistor, non-contact linear displacement sensor, threshold angle sensors, and oscillistor-effect based force sensor. The Fourth chapter is devoted to the development of an integrated pressure transducer using MEMS technology. Problems of the physical principle of sensing element operation, optimization of the elastic element topology and design of the converter as a whole, as well as a choice of optimal manufacturing technology processes, are solved here. The sensitivity of the integrated transducer with a membrane thickness of 100 μm was 0.02 1/MPa at a nominal conversion range of 1 MPa and a 100% strength margin. Tests of the manufactured series of MEMS integrated transducer showed that the additive component of the error and its change in the range 233-373 K are, respectively, 1% and 1% ... 2% of the nominal signal, which is at least an order of magnitude smaller than the corresponding parameters of a strain gauge Wheatstone bridge. The Fifth chapter describes the design and test results of devices developed on the basis of tenso-emf transducers research. Such devices, introduced for industrial use, are remote manometer transducers PDM-2 and PDMT-1. These devices are designed to measure oil and bitumen wells pressure in the range 0 ... 2.5 MPa, with a nominal output signal of 100 mV. In addition, PDMT-1 transmits information about temperature. The PDM-2 device has passed the State Testing and was recommended for serial production. The conducted studies confirm the high potential of the practical application of transverse effects in multi-valley semiconductors for the development of mechanical values sensors.
Диссертация посвящена разработке физико-технологических принципов создания и исследованию преобразователей механических величин на основе поперечных эффектов в анизотропних полупроводниках. Разработаны физические основы построения преобразователей механических величин с использованием поперечных эффектов и проведено их исследование на экспериментальных образцах. Продемонстрирована перспективность использования преобразователей на основе эффекта тензо-э.д.с. как в дискретном, так и в интегральном исполнении для создания датчиков силы и давления, работающих в диапазоне температур 233-373K. Обнаружен ряд концентрационных эффектов в германии и предложены преобразователи оригинальных конструкций, таких как дифференциальный тензотранзистор, бесконтактный линейный датчик перемещений на основе магнитоконцентрационного эффекта, пороговые датчики угла поворота и силы на основе осциллисторного эффекта с возможностью управления порогом переключения. Проведенные исследования подтверждают перспективность практического использования поперечных эффектов в многодолинных полупроводниках для создания преобразователей механических величин.
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Михайленко, Ігор Всеволодович. "Напівпровідникові перетворювачі механічних величин з використанням поперечних тензоефектів." Doctoral thesis, Київ, 2019. https://ela.kpi.ua/handle/123456789/30024.
Full textAbstract:
Дисертація присвячена розробленню фізико-технологічних засад створення та дослідженню перетворювачів механічних величин на основі поперечних ефектів в анізотропних напівпровідниках.
Розроблені фізичні основи побудови перетворювачів механічних величин з використанням поперечних ефектів і проведено їх дослідження на експериментальних зразках. Продемонстрована перспективність використання перетворювачів на основі ефекту тензо-е.р.с. як в дискретному, так і в інтегральному виконанні для створення датчиків сили і тиску, які працюють в діапазоні температур 233-373 K. Виявлений ряд концентраційних ефектів у германії і запропоновані перетворювачі оригінальних конструкцій, таких як диференціальний тензотранзистор, безконтактний лінійний датчик переміщень на основі магнітоконцентраційного ефекту, порогові датчики кута повороту і сили на основі осцилісторного ефекту з можливістю управління порогом переключення. Дослідження, що проведені, підтверджують перспективність практичного використання поперечних ефектів у багатодолинних напівпровідниках для створення перетворювачів механічних величин.
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Smyth, Katherine Marie. "Piezoelectric micro-machined ultrasonic transducers for medical imaging." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108938.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 175-184).
Next generation medical imaging technology hinges on the development of cost effective and array compatible transducers making piezoelectric micro-machined ultrasonic transducers (pMUTs) an attractive alternative to the current bulk piezoelectric technology. This thesis aims to realize pMUT potential starting with the development of an effective single cell model that is further scaled to optimize multi-cell elements in a 1D array. In the first half of this work, a transverse mode, lead zirconate titanate (PZT) pMUT plate cell is fabricated using common micro-fabrication techniques and a PZT sol-gel deposition process. Through derivation using a novel Greens function solution technique, an equivalent circuit model with explicitly defined lumped parameters is presented and validated through electrical impedance measurements of fabricated devices and finite element modeling. The equivalent circuit is a crucial design tool as transducer performance metrics, including experimentally validated acoustic domain values, are shown to be defined directly from the lumped parameters. In the second half, figures of merit are identified from these performance metrics and an expanded multi-cell model is employed to strategically target improvements in both bandwidth and coupling while maintaining high pressure output. The resulting, optimized multicell elements in a 1D array are fabricated via a commercially viable, wafer-scale manufacturing process including a novel PZT dry etch. A top-down fabrication approach facilitates achievement of the largest active area of a multi-cell pMUT to date consisting of over 1000 cells in a 200pm x 4mm element footprint, and more substantially, results in the highest electromechanical coupling recorded for a pMUT to date measured at 9 ± 1.4% per element.
by Katherine Marie Smyth.
Ph. D.
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Cullinan, Michael A. (Michael Arthur). "Design and fabrication of precision carbon nanotube-based flexural transducers." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/65166.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 179-197).
As mechanical devices move towards the nanoscale, smaller and more sensitive force and displacement sensors need to be developed. Currently, many biological, materials science, and nanomanufacturing applications could benefit from multi-axis micro- and nanoscale sensors with fine force and displacement resolutions. Unfortunately, such systems do not yet exist due to the limitations of traditional sensing techniques and fabrication procedures. Carbon nanotube-based (CNT) piezoresistive transducers offer the potential to overcome many of these limitations. Previous research has shown the potential for the use of CNTs in high resolution micro- and nanoscale sensing devices due to the high gauge factor and inherent size of CNTs. However, a better understanding of CNT-based piezoresistive sensors is needed in order to be able to design and engineer CNT-based sensor systems to take advantage of this potential. The purpose of this thesis is to take CNT-based strain sensors from the single element test structures that have been fabricated and turn them into precision sensor systems that can be used in micro- and nanoscale force and displacement transducers. In order to achieve this purpose and engineer high resolution CNT-based sensor systems, the design and manufacturing methods used to create CNT-based piezoresistive sensors were investigated. At the system level, a noise model was developed in order to be able to optimize the design of the sensor system. At the element level, a link was established between the structure of the CNT and its gauge factor using a theoretical model developed from quantum mechanics. This model was confirmed experimentally using CNT-based piezoresistive sensors integrated into a microfabricated test structure. At the device level, noise mitigation techniques including annealing and the use of a protective ceramic coating were investigated in order to reduce the noise in the sensor. From these investigations, best practices for the design and manufacturing of CNT-based piezoresistive sensors were established. Using these best practices, it is possible to increase the performance of CNT-based piezoresistive sensor systems by more than three orders of magnitude. These best practices were implemented in the design and fabrication of a multi-axis force sensor used to measure the adhesion force of an array of cells to the different material's surfaces for the development of biomedical implants. This force sensor is capable of measuring forces in the z-axis as well as torques in the [theta]x and [theta]y axis. The range and resolution of the force sensor were determined to be 84 [mu]N and 5.6 nN, respectively. This corresponds to a dynamic range of 83 dB, which closely matches the dynamic range predicted by the system noise model used to design the sensor. The accuracy of the force sensor is better than 1% over the device's full range.
by Michael A. Cullinan.
Ph.D.
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Feeney, Andrew. "Nitinol cymbal transducers for tuneable ultrasonic devices." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5805/.
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In recent years, there has been notable interest in the integration of smart and active materials, such as shape memory alloys, in the design of tuneable and multiple frequency devices. There is a growing desire to be able to tune transducers for a range of applications. As an example, surgical procedures could be enhanced by using an ultrasonic device whose performance could be tailored to penetrate more than one material, such as bone and soft tissue. Research conducted on cymbal transducers, a type of Class V flextensional transducer developed at Pennsylvania State University in the early 1990s, has been largely limited to low power applications, such as for hydrophone systems, and their performance in high power applications has only recently been studied. As such, the integration of smart materials to expand the useful applications of this type of transducer has not been fully explored. In this investigation, a shape memory alloy (SMA) called nickel-titanium, or Nitinol, has been adopted in two forms, one being superelastic and the other shape memory, as the end-cap material in the classical cymbal transducer configuration. The resonant frequencies of these transducers can be tuned by changes to the temperature of the Nitinol, which alters the microstructure, and the modulus, of the material. The microstructure of Nitinol can also be controlled by changes in applied stress. The phases present in the Nitinol microstructure are relatively hard cubic austenite and comparably soft monoclinic martensite. An intermediate phase, called the R-phase, can also appear. This is a rhombohedral distortion of austenite, and has been known to be a source of inconvenience for those who wish to avoid multiple stage transformations. An advantage of using Nitinol end-caps in the classical cymbal transducer configuration is that they are very small, hence minimal thermal energy is required to generate a phase transformation. Also, cymbal transducers are very simple and inexpensive to fabricate. The first part of this research focuses on the development of a dual resonance cymbal transducer using steel and titanium as the end-cap materials. Dynamic analysis techniques comprising electrical impedance measurements, experimental modal analysis (EMA) and vibration resonance response characterisation (VRRC) using laser Doppler vibrometry are introduced and form the dynamic characterisation process. The experimental data is supported in part by finite element analysis (FEA). It is demonstrated that a major problem in cymbal transducer fabrication is the difficulty in controlling the deposition of epoxy resin which is used to create the mechanical coupling in the transducer. This means that the bond layers in a transducer will likely be dissimilar, thereby introducing asymmetry into the transducer. This asymmetry can contribute to the dual resonance in a cymbal transducer. The cymbal transducer is designed to be actively tuneable by the incorporation of Nitinol end-caps in the transducer assembly. The characterisation of Nitinol transducers is performed using the dynamic characterisation methods in conjunction with differential scanning calorimetry (DSC). This is a thermoanalytical technique which has been adopted to estimate the transformation temperatures of Nitinol, and hence the temperatures at which each transducer must be driven to generate the desired operating frequencies. It is demonstrated that in certain cases, particularly with respect to superelastic Nitinol, the estimations of the transformation temperatures from the DSC analysis of Nitinol can be misinterpreted. The dynamic performance of Nitinol vibrating at ultrasonic frequencies has not before been the subject of detailed investigation, including the influence of superelasticity on the vibration response of an ultrasonic transducer. Superelasticity occurs in the austenite phase of Nitinol, where austenite reorients to martensite after a characteristic stress threshold is passed, thereby accommodating very large strains. The results show that whilst Nitinol can be used to fabricate cymbal transducers with tuneable resonant frequencies, there is no evidence that superelasticity contributes to the vibration response of the transducers. The incorporation of shape memory Nitinol in a simple prototype actuator device is also considered, where it appears that the transformation of the shape memory Nitinol is affected by the affixed cylinders used to create the device.
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Cepni, Kerim. "A Methodology For Designing Tonpilz-type Transducers." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613526/index.pdf.
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Tonpilz-type transducers are the most commonly used projectors in underwater acoustic applications. However, no complete design approach is available in the literature for such transducers. The present study aims to fill this gap in the literature by providing a systematic design approach for the Tonpilz-type transducers. The proposed methodology involves the use of different analytical models and a finite element model of such transducers. Each model provides a different level of accuracy that is tightly correlated with the models complexity and computational cost. By using these models sequentially starting with the simplest and fastest model to yield an initial design and concluding with the most detailed and accurate model to yield an optimized final design the overall design time is reduced and greater flexibility is given to the designer. An overview of each of these four models is given. The constructed models are benchmarked against published experimental data. The overall design methodology is demonstrated by systematically applying the four models to design a Tonpilz-type transducer. Possible improvements to the proposed methodology are discussed.
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Sutliff, Robert William. "The Effects of Loading on Equivalent Electric Circuit Models for Piezoelectric Transducers." Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami1533304929347075.
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Pulitzer, Seward Webb 1974. "Feasibility assessment and design of micro hydraulic solid-state transducers." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9064.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998.Includes bibliographical references (p. 179-184).
The performance of a number of mechanical applications could be greatly improved by the introduction of transducers that are capable of exploiting the inherent power densities of piezoelectric materials. The ability of these solid-state materials to exert large forces at high frequencies engenders them with specific power levels (mass normalized) that are often several orders of magnitude greater than conventional transducers, but their utility is offset by their small achievable strains. A novel concept for a device capable of improved solid-state transduction, Micro Hydraulic Solid-State Transducers (MHSTs), is introduced and explored in this thesis. The concept is comprised of two core principles: ( 1) utilization of a hydraulic system consisting of a pump, valves, and a working fluid to rectify the high frequency reciprocations of a piezoelectric drive element into unidirectional motion, and (2) performance enhancement through miniaturization. The goal is a transducer possessing high power densities that is useful in conventional applications. Feasibility of the MHST concept is evaluated by designing, modeling, and simulating a prototype mechanism. The effects of miniattariza~ion on device performance are investigated and an optimal scale is determined. Concept feasibility is based on predicted system performance, existing issues, and manufacturing constraints. It is concluded that the concept is feasible and warrants further development.
by Seward Webb Pulitzer, III.
S.M.
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Wang, Tao. "Optimization and Characterization of Integrated Microfluidic Surface Acoustic Wave Sensors and Transducers." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6153.
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Surface acoustic waves (SAWs) have a large number of applications and the majority of them are in the sensor and actuator fields targeted to satisfy market needs. Recently, researchers have focused on optimizing and improving device functions, sensitivity, power consumption, etc. However, SAW actuators and sensors still cannot replace their conventional counterparts in some mechanical and biomedical areas, such as actuators for liquid pumping under microfluidic channels and sensors for real-time cell culture monitoring. The two objectives of this dissertation are to explore the potential of piezoelectric materials and surface acoustic waves for research on actuators and sensors in the mechanical pump and biosensor areas.
Manipulation of liquids in microfluidic channels is important for many mechanical, chemical and biomedical applications. In this dissertation, we first introduced a novel integrated surface acoustic wave based pump for liquid delivery and precise manipulation within a microchannel. The device employed a hydrophobic surface coating (Cytop) in the device design to decrease the friction force and increase the bonding. Contrary to previous surface acoustic wave based pumps which were mostly based on the filling and sucking process, we demonstrated long distance media delivery (up to 8mm) and a high pumping velocity, which increased the device’s application space and mass production potential. Additionally, the device design didn’t need precise layers of water and glass between substrate and channel, which simplified the design significantly. In this study, we conducted extensive parametric studies to quantify the effects of the liquid volume pumped, microchannel size, and input applied power as well as the existence of hydrophobic surface coating on the pumping velocity and pump performance. Our results indicated that the pumping velocity for a constant liquid volume with the same applied input power could be increased by over 130% (2.31 mm/min vs 0.99 mm/min) by employing a hydrophobic surface coating (Cytop) in a thinner microchannel (250 µm vs 500 µm) design. This device could be used in circulation, dosing, metering and drug delivery applications which necessitated small-scale precise liquid control and delivery.
This dissertation also introduced a novel SAW-based sensor designed and employed for detecting changes in cell concentration. Before conducting cell concentration experiments, preliminary experiments were conducted on weight concentration differentiation of microfluidic particles based on a polydimethylsiloxane (PDMS) channel and surface acoustic wave resonator design. The results confirmed that our device exerted an ultra-stable status to detect liquid properties by monitoring continuous fluids. An improved design was carried out by depositing a 200 nm ZnO layer on top of the lithium tantalate substrate surface increased the sensitivity and enabled cell concentration detection in a microfluidic system.
Comprehensive studies on cell viability were carried out to investigate the effect of shear horizontal (SH) SAWs on both a cancerous (A549 lung adenocarcinoma) and a non-cancerous (RAW264.7 macrophage) cell line. Two pairs of resonators consisting of interdigital transducers (IDTs) and reflecting fingers were used to quantify mass loading by the cells in suspension media as well as within a 3-dimensional cell culture model. In order to predict the characteristics and optimize the design of the SH-SAW biosensor, a 3D COMSOL model was built to simulate the mass loading response of the cell suspensions. These results were compared to experimental data generated by pipetting cell concentrations of 3.125K, 6.25K 12.5K, 25K and 50K cells per 100µL into the PDMS well and measuring to obtain the relative frequency shift from the two oscillatory circuit systems (one of which functioned as a control). Frequency shift measurements were also collected from A549 cells cultured on a 3D nanofiber scaffold produced by electrospinning to evaluate the device’s ability to detect changes in cell density as the cells proliferated in culture over the course of eight days. The device’s ability to detect changes in cell density over time in a 3D model along with its biocompatibility reveal great potential for this device to be incorporated into 3D in vitro cancer research applications.
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Smith, Emily (Emily C. ). "Fabrication of a picoliter microreactor with multilayer elastomer values." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32916.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.Includes bibliographical references (leaves 45-46).
Microfluidics has the ability to greatly reduce the time needed to do many biological tests. The development of polymers has brought about substrates with elastomeric properties that can be used to the advantage of microfluidic device design. Elastomeric polymers can be used to create small scale passive valve systems. These valves can compartmentalize reactions in devices. Current microreactors only allow researchers to do one test at a time. Devices with the capability to compartmentalize reactions using valves could perform multiple reactions simultaneously. This thesis details the fabrication and design of a microreactor that can maintain cells in the device after a reaction. The fabrication of the device was done without a clean room and using no specialized equipment. Creation of the device and using it for testing requires little training and takes less time than performing the test using conventional methods. The device could readily be made and used by researchers using equipment already in their lab and is cheaper than current devices on the market.
by Emily Smith.
S.B.
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HARIHARAN, PRASANNA. "Free field characterization of High Intensity Focused Ultrasound (HIFU) transducers using acoustic streaming." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1204570105.
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Jain, Lakshya. "Characterization of the exhaust gas condensate pH values of gasoline engines." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/106780.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 55-56).
Exhaust Gas Recirculation has been used in gasoline engines to reduce NOx formation and part-load throttle loss for many years. More recently, there is a trend towards down-sizing and turbocharging engines as the strategy helps to improve fuel economy. Cooled low pressure EGR complements down-sizing-turbocharging in direct injection gasoline engines and has the potential to further improve efficiency. When exhaust gas gets cooled down below its dew point in an EGR cooler, the contained water vapor condenses on the cooler walls and dissolves some of the exhaust gases, which may make the condensate corrosive. For this reason, the extraction point for EGR is usually located downstream of the catalyst, where the gas that condenses with water has substantial amount of ammonia, making the condensate slightly basic but not corrosive. Following a recent study which showed potential fuel economy benefits of locating the EGR extraction point upstream of the catalyst, an understanding of the chemistry of pre-catalyst condensate is required. The feed gas to the catalyst contains NO, and other gases, which dissolve in the condensate to form acids. This study attempts to quantify the contribution of NOx, SOx and CO2 in the exhaust towards acid formation, in order to identify the cause of the acidity under different engine operating conditions. Theoretical calculations were done to predict the condensate pH for different air-fuel ratios and combustion phasing, for each gas separately and then together, assuming equilibrium between exhaust gas and condensate. Condensate pH was also measured experimentally for these running conditions to attempt to verify the calculations. Calculations show that the pH varies in the range 2 to 4. Contribution from SO, is the determining factor during rich operation; that from NO, is more important at stoichiometric and lean conditions. Actual pH values are generally less acidic than the calculated values and vary between 3 and 6. This discrepancy indicates that the dissolving of these gases into the condensate does not reach equilibrium. However, the calculated values may serve as useful bounds on the condensate pH.
by Lakshya Jain.
S.M.
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Turner, Kevin Thomas 1977. "An evaluation of critical issues for microhydraulic transducers : silicon wafer bonding, strength of silicon on insulator membranes and gold-tin solder bonding." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/8552.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.Includes bibliographical references (p. 121-127).
Microhydraulics transducers (MHT) are a class of microelectromechanical systems (MEMS) currently being developed to produce bi-directional transducers with high power densities (500-1000 W/kg). The development of these devices, which combine microfabrication technology and piezoelectric materials, requires the use of variety of materials and fabrication technologies that are not fully developed. Three materials and structures issues, which are essential to the development of MHT devices, are silicon wafer bonding, strength of silicon-on- insulator (SOI) membranes, and gold-tin bonding. Each of these topics was addressed independently. The mechanical integrity of silicon fusion bonds as a function of processing parameters was examined using a four-point bend delamination specimen. The study showed that the specimen was effective for characterizing low toughness bonds and that certain processing conditions can have a profound impact on bond toughness. Bond toughness increased with anneal time and temperature, but, initial contacting conditions, such as time and clamping pressure, proved to have little effect on final bond toughness. The fracture strength of membranes fabricated from SOI wafers using deep reactive ion etching was experimentally measured. Results showed that the strengths of these membranes was less than that of structures etched from bulk silicon and that the strength was dependent on SOI manufacturer. Finally, a thin film gold-tin solder bond was developed to bond bulk piezoelectric material to silicon structures. The process, which uses a sputtered gold-tin eutectic alloy (80wt%Au-20wt%Sn), was refined to produce void-free bonds. Preliminary tensile tests indicated failure was likely to occur in the piezoelectric material itself or along the solder-piezoelectric material interface. The results of these three studies provide information that is essential to the development of MHT devices as well as a wide range of MEMS devices.
by Kevin Thomas Turner.
S.M.
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Jiang, Yanxia. "MEASUREMENT OF J-INTEGRAL VALUES OF DENTAL CERAMICS BY DIGITAL IMAGE CORRELATION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1453880114.
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Hammad, Bashar Khalil. "Modeling, Simulation, and Analysis of Micromechanical Filters Coupled with Capacitive Transducers." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/27744.
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The first objective of this Dissertation is to present a methodology to calculate analytically the mode shapes and corresponding natural frequencies and determine critical buckling loads of mechanically coupled microbeam resonators with a focus on micromechanical filters. The second objective is to adopt a nonlinear approach to build a reduced-order model and obtain closed-form expressions for the response of the filter to a primary resonance. The third objective is to investigate the feasibility of employing subharmonic excitation to build bandpass filters consisting of either two sets of two beams coupled mechanically or two sets of clamped-clamped beams. Throughout this Dissertation, we treat filters as distributed-parameter systems.
In the first part of the Dissertation, we demonstrate the methodology by considering a mechanical filter composed of two beams coupled by a weak beam. We solve a boundary-value problem (BVP) composed of five equations and twenty boundary conditions for the natural frequencies and mode shapes. We reduce the problem to a set of three linear homogeneous algebraic equations for three constants and the frequencies in order to obtain a deeper insight into the relation between the design parameters and the performance metrics. In an approach similar to the vibration problem, we solve the buckling problem to study the effect of the residual stress on the static stability of the structure.
To achieve the second objective, we develop a reduced-order model for the filter by writing the Lagrangian and applying the Galerkin procedure using its analytically calculated linear global mode shapes as basis functions. The resulting model accounts for the geometric and electric nonlinearities and the coupling between them. Using the method of multiple scales, we obtain closed-form expressions for the deflection and the electric current in the case of one-to-one internal and primary resonances. The closed-form solution shows that there are three possible operating ranges, depending on the DC voltage. For low DC voltages, the effective nonlinearity is positive and the filter behavior is hardening, whereas for large DC voltages, the effective nonlinearity is negative and the filter behavior is softening. We found that, when mismatched DC voltages are applied to the primary resonators, the first mode is localized in the softer resonator and the second mode is localized in the stiffer resonator. We note that the excitation amplitude can be increased without worrying about the appearance of multivaluedness when operating the filter in the near-linear range. The upper bound in this case is the occurrence of the dynamic pull-in instability. In the softening and hardening operating ranges, the adverse effects of the multi-valued response, such as hysteresis and jumps, limit the range of the input signal.
To achieve the third objective, we propose a filtration technique based on subharmonic resonance excitation to attain bandpass filters with ideal stopband rejection and sharp rolloff. The filtration mechanism depends on tuning two oscillators such that one operates in the softening range and the other operates in the hardening range. Hardware and logic schemes are necessary to realize the proposed filter. We derive a reduced-order model using a methodology similar to that used in the primary excitation case, but with all necessary changes to account for the subharmonic resonance of order one-half. We observe that some manipulations are essential for a structure of two beams coupled by a weak spring to be suitable for filtration. To avoid these complications, we use a pair of single clamped-clamped beams to achieve our goal. Using a model derived by attacking directly the distributed-parameters problem, we suggest design guidelines to select beams that are potential candidates for building a bandpass filter. We demonstrate the proposed mechanism using an example.Ph. D.
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Yeh, Shochi. "Theoretical and experimental evaluation of radiation patterns generated by phased array ultrasound transducers with mechanical and electronic focussing /." Zürich, 1986. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=7962.
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Evans, Phillip G. "Nonlinear Magnetomechanical Modeling and Characterization of Galfenol and System-Level Modeling of Galfenol-Based Transducers." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1259680723.
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Xiping, Huo. "Design, analysis and characterization of a miniature second-order directional microphone." Diss., Online access via UMI:, 2009.
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Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2009.Includes bibliographical references.
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Chakrabarti, Suryarghya. "Modeling of 3D Magnetostrictive Systems with Application to Galfenol and Terfenol-D Transducers." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1322635954.
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Ceridon, Kimi Malia 1975. "Remote cooling using cold electromagnetic values to drive an external flow loop on a G-M cryocooler." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/88879.
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Hudson, Tyler Blake. "Real-time Cure Monitoring of Composites Using a Guided wave-based System with High Temperature Piezoelectric Transducers, Fiber Bragg Gratings, and Phase-shifted Fiber Bragg Gratings." Thesis, North Carolina State University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10758821.
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An in-process, in-situ cure monitoring technique utilizing a guided wave-based concept for carbon fiber reinforced polymer (CFRP) composites was investigated. Two automated cure monitoring systems using guided-wave ultrasonics were developed for characterizing the state of the cure. In the first system, surface mounted high-temperature piezoelectric transducer arrays were employed for actuation and sensing. The second system motivated by the success of the first system includes a single piezoelectric disc, bonded onto the surface of the composite for excitation; fiber Bragg gratings (FBGs) and/or phase-shifted fiber Bragg gratings (PSFBGs) were embedded in the composite for distributed cure sensing.
Composite material properties (viscosity and degree of cure) evolved during cure of the panels fabricated from Hexcel® IM7/8552 prepreg correlated well to the amplitude, time of arrival, and group velocity of the guided wave-based measurements during the cure cycle. In addition, key phase transitions (gelation and vitrification) were clearly identified from the experimental data during the same cure cycle. The material properties and phase transitions were validated using cure process modeling software (e.g., RAVEN®).
The high-temperature piezoelectric transducer array system demonstrated the feasibility of a guided wave-based, in-process, cure monitoring and provided the framework for defect detection during cure. Ultimately, this system could provide a traceable data stream for non-compliance investigations during serial production and perform closed-loop process control to maximize composite panel quality and consistency. In addition, this system could be deployed as a “smart” caul/tool plate to existing production lines without changing the design of the aircraft/structure.
With the second system, strain in low frequency (quasi-static) and the guided wavebased signals in several hundred kilohertz range were measured almost simultaneously using the same FBG or PS-FBG throughout the cure cycle. Also, the residual strain can be readily determined at the end of the cure. This system demonstrated a real-time, in-situ, cure monitoring system using embedded multiplexed FBG/PS-FBG sensors to record both guided wave-based signals and strain. The distinct advantages of a fiber optic-based system include multiplexing, small size, embedding, utilization in harsh environments, electrically passive operation, and electromagnetic interference (EMI) immunity. The embedded multiplexed FBG/PS-FBG fiber optic sensor can monitor the entire life-cycle of the composite structure from curing, post-cure/assembly, and in-service for creating “smart structures”.
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Hahnlen, Ryan M. "Development and Characterization of NiTi Joining Methods and Metal Matrix Composite Transducers with Embedded NiTi by Ultrasonic Consolidation." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243886351.
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Wandler, Jeff. "Calculating Cardiovascular Lumped-Parameter Model Values by Injecting Small Volume Perturbations in an Isovolumic Heart." Thesis, North Dakota State University, 2011. https://hdl.handle.net/10365/28884.
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Diagnosing cardiac patient problems contains many uncertainties, and to fully diagnose the patient's condition usually requires a lengthy drug regimen to see what works and what does not. Compounding this problem is that even after the correct drug regimen has been discovered, the underlying cause for the problem may remain a mystery. Thus, the uncertainty and the length of time required to provide an accurate and adequate solution makes it very difficult to provide quality care to the patient. Templeton and others have shown that lumped cardiac muscle parameters can be extracted from an isolated heart by injecting small volumes at high frequencies relative to the heart rate and measuring the pressure response to this volume change. Using the Hill muscle model of two springs and a dash pot to portray the different elements of the cardiac muscle, the pressure and volume relationship makes it possible to calculate these muscle parameters using frequency response analysis techniques. The hypothesis to be tested is "Is it possible to develop a method to test cardiac muscle for stiffness, resistance, and contractile force from measuring ventricular pressure and injected flow?" To test this hypothesis, an isovolumic heart model is developed and allowed to develop pressure, along with a small volume injected to create a pressure response. Analysis of the pressure and flow waveforms produces a measured value of the cardiac model parameter values to compare to the model values. Results from injecting small volume changes into a mathematical heart model show that it is possible to extract the muscle model parameters of non-linear resistance, inertia of the fluid and muscle, and stiffness of the muscle while filling and contracting. The injected frequency and volume were varied to find usable conditions, both with regard to the calculations and the practical limits. Analyzing the error between the measured and model values for a large number of different combinations of model parameters shows an average error of less than 1%.Iron Range Engineering
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OVERLY, TIMOTHY G. S. "DEVELOPMENT AND INTEGRATION OF HARDWARE AND SOFTWARE FOR ACTIVE-SENSORS IN STRUCTURAL HEALTH MONITORING." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1178813386.
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Zarro, Sarah E. "Steady state and transient measurements within a compressor rotor during steam-induced stall at transonic operational speeds." Thesis, Monterey, California. Naval Postgraduate School, 2006. http://hdl.handle.net/10945/2528.
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Approved for public release, distribution unlimitedSteam leakage from an aircraft carrier catapult is sometimes ingested into the aircraft engines upon launch which may induce compressor stall. Investigation of this phenomenon is of particular interest to the Navy with its new F35C, the aircraft carrier variant of the joint strike fighter. The single engine configuration of the F-35C makes this aircraft particularly vunerable to steam-induced stall. The present study examined both throttle-induced stall and steam-induced stall in a compressor at 90% and 95% speed through the use of 9 Kulite and 2 hot-film pressure transducers. The use of Fast Fourier Transform waterfall plots of the transient data before and during stall proved invaluable in determining stall precursors as well as the mode of rotor stall. In addition, a new computational fluid dynamic model was designed using CFX-5 software to represent a single blade passage of the compressor rotor, in order to predict compressor performance. The computed results were compared to experimental results gathered at various throttle settings. An accurate model will enable researchers to predict compressor performance for various and multiple gases.
Outstanding Thesis
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Alrobaian, Abdulrahman Abdullah. "Multi-Spectral Remote Thermal Imaging for Surface Emissivity and Estimation of Roof R-Values Using Physics-Based and Data Mining Models." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton148898993590168.
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Abbas, Syed Farhat. "Development of a low cost shock pressure sensor." Ohio : Ohio University, 1988. http://www.ohiolink.edu/etd/view.cgi?ohiou1182538469.
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Quevedo, Henrique Müller de. "Determination of normative values for mechanical quantitative sensory tests in the orofacial regionDeterminação de valores normativos para testes quantitativos sensoriais mecânicos na região orofacial." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/25/25146/tde-13092016-102731/.
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Modern concepts for the treatment of pain patients are based on the hypothesis that different clinical signs and symptoms reflect different underlying pathophysiological mechanisms of pain generation. To analyze these mechanisms, in 2006, the DFNS (German Research Network on Neuropathic Pain) developed a standardized protocol of quantitative sensory testing (QST) for a quantitative evaluation of pain generating mechanisms, creating reference values for hand, foot and face (masseter muscle) sites. However, there is a lack of orofacial reference values for the temporalis muscle and maxillary gingiva. This study aimed to determine reference values for QST protocol in the orofacial region and evaluate the effectiveness of two test stimuli during conditioned pain modulation (CPM) test. Sixty participants (30 men/30 women) were examined through the tests of mechanical detection (MDT), mechanical pain (MPT), wind-up ratio (WUR), pressure pain threshold (PPT) and conditioned pain modulation (CPM), to determine reference values in healthy subjects. Individuals were examined in a single session by a trained examiner under the protocol developed by the DFNS (2006). The CPM statistical evaluation was done by a multi-way analysis of variance (ANOVA) within the factors site (2 levels), time (2 levels), and sex (2 levels); comparing the absolute values of MPT and PPT. QST reference values comparison was made by a multi-way withinsubjects ANOVA performed considering the factors site (3 levels), side (2 levels) and sex (2 levels) (α=5%). MDT and MPT showed main effects of site (p<0.001), where the maxillary gingiva presented the highest thresholds for MDT and lowest MPT thresholds. In addition, PPT values of the anterior temporalis were lower than the hand (p<0.001). PPT (p<0.001) showed main effects of sex, where men presented higher thresholds. WUR did not show any main effects of sex, site or side. Both CPM test-stimulus (PPT and MPT) were capable of producing significantly higher thresholds during conditioning stimulus when compared to baseline thresholds (p<0.001). Temporalis CPM respondents were significantly higher (p=0.002) than hand respondents for both QSTs. The study concluded that orofacial QST profile of healthy participants could be influenced by the test site and sex. The CPM does not differ considering PPT and MPT as test stimuli, but the test site can influence its effects.Um novo conceito de tratamento de síndromes dolorosas baseada em mecanismos de dor é baseado na hipótese de que diferentes sinais clínicos refletem alterações em diversos mecanismos de geração de dor. Para analisar estes mecanismos, em 2006, o DFNS (German Research Network on Neuropathic Pain) criou um protocolo padronizado de testes quantitativos sensoriais (QST) para uma avaliação quantitativa de mecanismos de geração de dor, criando valores de referência para mão, pé e face (músculo masseter). No entanto, ainda há falta de valores de referência para alguns testes quantitativos em diversas importantes regiões orofaciais como o músculo temporal anterior e a mucosa oral. Este estudo buscou determinar valores normativos dos QSTs nessas regiões e avaliou a eficácia de um estímulo condicionante (CPM) na percepção da dor por meio de dois estímulos teste (PPT e MPT). 60 sujeitos saudáveis (30 homens/30 mulheres) foram examinados com os testes de sensibilidade tátil (MDT), limiar de dor mecânico (MPT), somação temporal (WUR), limiar de dor à pressão (PPT) e condicionamento modulatório da dor (CPM), afim de determinar valores normativos na população. Os pacientes foram examinados em sessão única por um único examinador treinado sob o protocolo desenvolvido pelo DFNS. Para avaliação estatística dos dados da CPM uma análise de variância (ANOVA) foi utilizada comparando os fatores sítio (2 níveis), tempo (2 níveis) e sexo (2 níveis) entre os dois estímulos teste (MPT e PPT). Os valores de referência para QST foram comparados por uma ANOVA multi-vias considerando os fatores sítio (3 níveis), lado (2 níveis), e sexo (2 níveis) (α=5%). MDT e MPT mostraram efeitos principais de sítio (p<0,001), em que a mucosa apresentou os maiores limiares para MDT e menos limiares para MPT, quando comparada à mão e temporal anterior. PPT demonstrou efeitos principais de sítio e sexo. Limiares de dor à pressão do músculo temporal foram menores comparados com a mão (p<0,001) e homens apresentaram maiores limiares que as mulheres em todos os sítios. O teste WUR não apresentou nenhum efeito de sexo, sítio ou lado examinado. Os dois estímulos teste da CPM (MPT e PPT) foram capazes de produzir maiores limiares quando comparados aos estímulos não condicionados (p<0,001). Um maior número significativo de sujeitos respondeu positivamente a estimulação CPM no músculo temporal (p=0,002) para ambos estímulos teste. O estudo concluiu que o perfil sensorial avaliados por meio de QSTs pode ser influenciado pela região de exame e sexo. O efeito da CPM foi igualmente positivo para ambos estímulos teste. No entanto, seu grau de resposta depende da região avaliada.
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Kiyono, César Yukishigue. "Projeto de transdutores piezocompósitos de casca multi-camada utilizando o método de otimização topológica." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3152/tde-30072013-210104/.
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Transdutores baseados em cascas piezocompósitas têm uma vasta aplicação no campo de estruturas inteligentes, principalmente como atuadores, sensores e coletores de energia. Essas estruturas piezocompósitas são geralmente compostas por dois ou mais tipos de materiais, como por exemplo materiais piezelétricos, ortotrópicos elásticos (possuem fibras de reforçamento) e isotrópicos (materiais homogêneos). Vários fatores devem ser considerados no projeto de transdutores baseados em cascas piezocompósitas, como o tamanho, a forma, a localização e a polarização do material piezelétrico, bem como a orientação das fibras do material ortotrópico. O projeto desses transdutores é complexo e trabalhos anteriores envolvendo esses tipos de materiais sugerem utilizar Método de Otimização Topológica (MOT) para aprimorar o desempenho dos transdutores distribuindo o material piezelétrico sobre substratos fixos de materiais isotrópicos e ortotrópicos, ou otimizar a orientação das fibras dos materiais ortotrópicos com material piezelétrico com tamanho, forma e localização previamente estabelecidos. Assim, nesta tese, propõe-se o desenvolvimento de uma metodologia baseada no MOT para projetar transdutores piezocompósitos de casca considerando, simultaneamente, a otimização da distribuição e do sentido de polarização do material piezelétrico, e também a otimização da orientação das fibras de materiais ortotrópicos, que é livre para assumir valores diferentes ao longo da mesma camada compósita. Utilizando essa metodologia, são obtidos resultados numéricos para atuadores e sensores em regime estático e para coletores de energia com circuito elétrico acoplado, em regime dinâmico amortecido. Para os casos dos sensores e dos coletores de energia, também são consideradas as tensões mecânicas na estrutura, as quais devem obedecer os critérios de von Mises (para materiais isotrópicos) e de Tsai-Wu (para materiais ortotrópicos) para que não haja falhas na estrutura, que está sujeita a esforços mecânicos.Transducers based on laminated piezocomposite shell structures have a wide application in the field of smart structures, especially as actuators, sensors and energy harvesting devices. These piezocomposite structures are generally composed by two or more kinds of materials, such as piezoelectric, isotropic, and elastic orthotropic (fiber reinforcement) materials. Several factors must be considered in the design of piezocomposite transducers, such as size, shape, location and polarization of the piezoelectric material and the fiber orientation of the orthotropic material. The design of these transducers is complex and previous studies involving these types of materials suggest using \"Topology Optimization Method\" (TOM) to enhance the performance of piezoelectric transducers by distributing piezoelectric material over fixed isotropic and orthotropic substrate or to optimize the fiber orientation of orthotropic materials with piezoelectric patches previously established. Thus, this thesis proposes the development of a methodology based on the TOM to design laminated piezocomposite shell transducers by considering simultaneously the optimization of distribution and the polarization direction of the piezoelectric material, and also the optimization of the fiber orientation orthotropic material, which is free to assume different values along the same composite layer. By using this methodology, numerical results are obtained for actuators and sensors under static response, and energy harvesting devices with an electrical circuit coupled, in dynamic damped analysis. In the case of sensors and energy harvesting devices, which are subjected to mechanical loads, the mechanical stresses in the structure are also considered, which must satisfy two stress criteria to prevent failure: von Mises for isotropic materials and Tsai-Wu for orthotropic materials.
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Khatiwada, Dilip. "Assessing the sustainability of bioethanol production in Nepal." Licentiate thesis, KTH, Energi och klimatstudier, ECS, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-25336.
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Access to modern energy services derived from renewable sources is a prerequisite, not only for economic growth, rural development and sustainable development, but also for energy security and climate change mitigation. The least developed countries (LDCs) primarily use traditional biomass and have little access to commercial energy sources. They are more vulnerable to problems relating to energy security, air pollution, and the need for hard-cash currency to import fossil fuels. This thesis evaluates sugarcane-molasses bioethanol, a renewable energy source with the potential to be used as a transport fuel in Nepal. Sustainability aspects of molasses-based ethanol have been analyzed. Two important indicators for sustainability, viz. net energy and greenhouse gas (GHG) balances have been used to assess the appropriateness of bioethanol in the life cycle assessment (LCA) framework. This thesis has found that the production of bioethanol is energy-efficient in terms of the fossil fuel inputs required to produce it. Life cycle greenhouse gas (GHG) emissions from production and combustion are also lower than those of gasoline. The impacts of important physical and market parameters, such as sugar cane productivity, the use of fertilizers, energy consumption in different processes, and price have been observed in evaluating the sustainability aspects of bioethanol production. The production potential of bioethanol has been assessed. Concerns relating to the fuel vs. food debate, energy security, and air pollution have also been discussed. The thesis concludes that the major sustainability indicators for molasses ethanol in Nepal are in line with the goals of sustainable development. Thus, Nepal could be a good example for other LDCs when favorable governmental policy, institutional set-ups, and developmental cooperation from donor partners are in place to strengthen the development of renewable energy technologies.QC 20101029
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Liu, Qiang. "Microstructure Evaluation and Wear-Resistant Properties of Ti-alloyed Hypereutectic High Chromium Cast Iron." Doctoral thesis, KTH, Tillämpad processmetallurgi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-128532.
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High chromium cast iron (HCCI) is considered as one of the most useful wear resistance materials and their usage are widely spread in industry. The mechanical properties of HCCI mainly depend on type, size, number, morphology of hard carbides and the matrix structure (γ or α). The hypereutectic HCCI with large volume fractions of hard carbides is preferred to apply in wear applications. However, the coarser and larger primary M7C3 carbides will be precipitated during the solidification of the hypereutectic alloy and these will have a negative influence on the wear resistance. In this thesis, the Ti-alloyed hypereutectic HCCI with a main composition of Fe-17mass%Cr-4mass%C is studied based on the experimental results and calculation results. The type, size distribution, composition and morphology of hard carbides and martensite units are discussed quantitatively. For a as-cast condition, a 11.2μm border size is suggested to classify the primary M7C3 carbides and eutectic M7C3 carbides. Thereafter, the change of the solidification structure and especially the refinement of carbides (M7C3 and TiC) size by changing the cooling rates and Ti addition is determined and discussed. Furthermore, the mechanical properties of hypereutectic HCCI related to the solidification structure are discussed. Mechanical properties of HCCI can normally be improved by a heat treatment process. The size distribution and the volume fraction of carbides (M7C3 and TiC) as well as the matrix structure (martensite) were examined by means of scanning electron microscopy (SEM), in-situ observation by using Confocal Laser Scanning Microscope (CLSM), Transmission electron microscopy (TEM) and electron backscattered diffraction (EBSD). Especially for the matrix structure and secondary M7C3 carbides, EBSD and CLSM are useful tools to classify the fcc (γ) and bcc (α) phases and to study the dynamic behavior of secondary M7C3 carbides. In conclusion, low holding temperatures close to the eutectic temperature and long holding times are the best heat treatment strategies in order to improve wear resistance and hardness of Ti-alloyed hypereutectic HCCI. Finally, the maximum carbides size is estimated by using statistics of extreme values (SEV) method in order to complete the size distribution results. Meanwhile, the characteristic of different carbides types will be summarized and classified based on the shape factor.QC 20130913
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Nanjappa, Jagdish. "Web-based dynamic material modeling." Ohio University / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1174918633.
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Leschka, Stephan. "Entwurfsmethoden und Leistungsgrenzen elektromechanischer Schallquellen für Ultraschallanwendungen in Gasen im Frequenzbereich um 100 kHz." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1134573918125-13603.
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Air-borne ultrasonic transducers are optimised to achieve a maximal sound pressure in a frequency range around 100 kHz. Moreover, the radiation of a high acoustic power is desired, which requires a large transducer area. Within this dissertation the ultrasonic transducers are, therefore, optimised to operate in the resonance mode. Using this operating point the maximal force is fed into the transducer while it is charged with the lowest loss possible. Many applications of air-borne ultrasound need a sufficient bandwidth in addition to a high sound pressure, that s why the swinging mass of the transducer has to be minimised. For these reasons, air-borne capacitive and piezoelectric film transducers take centre stage of these examinations. New network models of the stripe membrane and the pre-stressed stripe plate are derived to optimise these ultrasonic transducers. Besides its mechanical tension and its bending stiffness, the new network model of the pre-stressed and pressure loaded stripe plate takes also the stiffness caused by the shape of the plate into account. The examined transducers achive a maximal piston velocity around 1 m/sUltraschallwandler für Anwendungen in Luft werden zur Bereitstellung eines maximalen Schalldrucks im Frequenzbereich um 100 kHz optimiert. Sie sollen außerdem die Abstrahlung einer großen Schallleistung zulassen, was eine große Wandlerfläche voraussetzt. Deshalb werden in dieser Arbeit die Ultraschallsender für den Resonanzbetrieb optimiert, wo man die maximale Krafteinspeisung bei minimalen Verlusten einstellt. Viele Anwendungen von Ultraschall in Luft benötigen neben einem hohen Schalldruckpegel auch eine ausreichende Bandbreite, wozu die schwingende Masse der Wandler zu minimieren ist. Deshalb stehen kapazitive und piezoelektrische Folienwandler im Resonanzbetrieb im Vordergrund der Untersuchungen. Zur Optimierung dieser Ultraschallsender werden die Netzwerkmodelle der Streifenmembran und der gespannten Streifenplatte abgeleitet. Neben der mechanischen Spannung und der Biegesteifigkeit berücksichtigt das Netzwerkmodell der gespannten und statisch druckbelasteten Streifenplatte die Formversteifung. Die untersuchten Wandler erreichen eine maximale Kolbenschnelle um 1 m/s
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Leschka, Stephan. "Entwurfsmethoden und Leistungsgrenzen elektromechanischer Schallquellen für Ultraschallanwendungen in Gasen im Frequenzbereich um 100 kHz." Doctoral thesis, Technische Universität Dresden, 2003. https://tud.qucosa.de/id/qucosa%3A24606.
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Air-borne ultrasonic transducers are optimised to achieve a maximal sound pressure in a frequency range around 100 kHz. Moreover, the radiation of a high acoustic power is desired, which requires a large transducer area. Within this dissertation the ultrasonic transducers are, therefore, optimised to operate in the resonance mode. Using this operating point the maximal force is fed into the transducer while it is charged with the lowest loss possible. Many applications of air-borne ultrasound need a sufficient bandwidth in addition to a high sound pressure, that s why the swinging mass of the transducer has to be minimised. For these reasons, air-borne capacitive and piezoelectric film transducers take centre stage of these examinations. New network models of the stripe membrane and the pre-stressed stripe plate are derived to optimise these ultrasonic transducers. Besides its mechanical tension and its bending stiffness, the new network model of the pre-stressed and pressure loaded stripe plate takes also the stiffness caused by the shape of the plate into account. The examined transducers achive a maximal piston velocity around 1 m/s.Ultraschallwandler für Anwendungen in Luft werden zur Bereitstellung eines maximalen Schalldrucks im Frequenzbereich um 100 kHz optimiert. Sie sollen außerdem die Abstrahlung einer großen Schallleistung zulassen, was eine große Wandlerfläche voraussetzt. Deshalb werden in dieser Arbeit die Ultraschallsender für den Resonanzbetrieb optimiert, wo man die maximale Krafteinspeisung bei minimalen Verlusten einstellt. Viele Anwendungen von Ultraschall in Luft benötigen neben einem hohen Schalldruckpegel auch eine ausreichende Bandbreite, wozu die schwingende Masse der Wandler zu minimieren ist. Deshalb stehen kapazitive und piezoelektrische Folienwandler im Resonanzbetrieb im Vordergrund der Untersuchungen. Zur Optimierung dieser Ultraschallsender werden die Netzwerkmodelle der Streifenmembran und der gespannten Streifenplatte abgeleitet. Neben der mechanischen Spannung und der Biegesteifigkeit berücksichtigt das Netzwerkmodell der gespannten und statisch druckbelasteten Streifenplatte die Formversteifung. Die untersuchten Wandler erreichen eine maximale Kolbenschnelle um 1 m/s.
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Chvatík, Štěpán. "Asynchronní motor s vnějším rotorem." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377075.
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Hurst, Adam. "Advanced Transducers." Thesis, 2015. https://doi.org/10.7916/D83N22QH.
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Sensing the world around us is fundamental to modern life. Since the advent of micro-scale, batch-fabricated sensors, we now interact with sensors in an array of consumer electronics, such as smart phones, watches and other wearables, and we rely on sensors for control and monitoring of complex systems, such as cars, jet engines, fossil fuel and renewable power generation as well as industrial processes. Sensors enable the internet-of-things; they are defining what we can measure within our data driven society. As the number of sensors produced increases, we seek to further innovate and scale sensor technologies with the key economic drivers being improved sensor performance and functionality, better system integration and characterization, reduced sensor size and power consumption, improved manufacturability and reduced cost.
This thesis presents a brief history and overview of state-of-the-art microelectromechanical systems (MEMS) strain, pressure and acceleration sensors followed by new advancements in dynamic pressure measurements and the characterization of dynamic pressure transducers. Accurate dynamic pressure measurement is vital to proper system design and operation, such as active control and system health monitoring of gas turbines. This work presents several dynamic pressure characterization techniques in gases and liquids. Applying these characterization methodologies, the frequency response of pressure transducers and pressure measurement systems are experimentally determined. These tools along with several analytical modeling techniques are further employed in the development of static pressure compensation for differential pressure transducers, low-pass filtering to prevent aliasing and real-time, analog active frequency response correction for aerodynamically-driven resonances in pressure transducers.
In addition to these advancements, this work explores nano-scale strain, pressure and acceleration sensors employing 2D materials. The 2D materials used within these innovative transducers include graphene and molybdenum disulfide (MoS2). Detailed electrical and mechanical characterization of both materials are presented with unique test methodologies. This work provides the design, modeling and fabrication processes for these 2D material-based sensors. Application specific packaging and test methodologies are included. This thesis further compares commercially available MEMS sensors and 2D material-based sensors.
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Giorgio, Ivan. "Multimode Collocated Vibration Control with Multiple Piezoelectric Transducers." Phd thesis, 2008. http://tel.archives-ouvertes.fr/tel-00798635.
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Dangi, Ajay. "Piezoelectric Micromachined Ultrasound Transducers : From Design to Applications." Thesis, 2016. http://etd.iisc.ernet.in/2005/3737.
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Ultrasonic sensors are well known for various applications such as NDT, ultrasound imaging, and proximity sensing. Conventional ultrasound transducers are bulky, work at notoriously high voltages, and consume significant power. Microfabrication techniques are leading to a paradigm shift in the field of ultrasonics by enabling development of low power - small footprint ultrasound transducers.
This work focuses on the development of piezoelectric type flexural mode micromachined ultrasound transducer also known as PMUTs. We start by establishing a system level analytical model of a PMUT and use it to offer insights into scaling of the performance of the transducer with respect to various design parameters. In this analysis we give special attention to residual stresses thus establishing a contrast between membrane type and plate type PMUTs. After going through various steps of material development and microfabrication, we obtain arrays of PMUTs with different designs. PZT thin films deposited by sol-gel method are used as the piezoelectric layer in the multilayer stack. Further, we present a thorough characterization of fabricated PMUTs which includes measurement of the piezoelectric properties of the embedded PZT thin film, electrical impedance of the electromechanical transducer, its vibrational charac-teristics and acoustic radiation from a single PMUT cell. We also develop a pre-amplifier circuit for a PMUT receiver and present its working as a simple proximity sensor. After establishing the repeatability and predictability of our PMUT sensors we delve into application development beyond ultrasound imaging. Experiments and analysis of PMUTs submerged in water show strong structural-acoustic coupling between the PMUT membrane and the surrounding fluid. We hypothesize the applicability of this feature to sense changes in the acoustic environment of a PMUT. To this end, we integrate an array of PMUTs with a micro-fluidic chip and study the changes in the vibrational behaviour of the PMUT in response to change in the air-water ratio in a closed cell around a PMUT membrane. We also present our preliminary results on presence of micro-bubbles in the closed cell around the PMUT.
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Ahmad, Babar. "Design and Development of Capacitive Micromachined Ultrasonic Transducers." Thesis, 2012. http://hdl.handle.net/2005/3164.
Full textAbstract:
This thesis presents the design and analysis for development of a Capacitive Micromachined Ultrasonic Transducer (CMUT), a novel sensor and actuator, aimed at replacing the conventional piezoelectric transducers for air-coupled ultrasonic imaging applications. These CMUTs are fabricated using the silicon micromachining technology wherein all fabrication is done on the surface of a silicon wafer by means of thin-film depositions, patterning with photolithography and etching. The main emphasis of this study is on developing analytical models that serve as effective design tools for the development of these devices. A desirable goal of such study is to create reasonable mathematical models, obtain analytical solutions, wherever possible, for various measures of transducer performance and provide design aids.
A logical start is the lumped parameter modeling wherein the explicit dependence of the physical parameters on the spatial extent of the device is ignored. The system lumped parameters, such as the equivalent stiffness, the equivalent mass, and the equivalent damping are extracted from reasonable analytical or numerical models and subsequently used in the static and dynamic analysis of the device. Useful predictions are made with regard to the key transducer parameters, such as, the pull-in voltage, the static deflection, the dynamic response and the acoustic field produced. The modeling work presented embodies two main objectives: (i) it serves to provide direction in the design phase, and, (ii) it serves to aid in the extraction of critical parameters which affect the device behavior. Comparison of the results with the more rigorous FEM simulations as well as with those present in the existing literature assure that the developed models are accurate enough to serve as useful design tools.
The distributed parameter modeling is presented next. Analysis of MEMS devices which rely on electrostatic actuation is complicated due to the fact that the structural deformations alter the electrostatic forces, which redistribute and modify the applied loads. Hence, it becomes imperative to consider the electro-elastic coupling aspect in the design of these devices. An approximate analytical solution for the static deflection of a thin, clamped circular plate caused by electrostatic forces which are inherently nonlinear, is presented. The model is based on the Kirchhoff-Love assumptions that the plate is thin and the deflections and slopes are small. The classical thin-plate theory is adequate when the ratio of the diameter to thickness of the plate is very large, a situation commonly prevalent in many MEMS devices, especially the CMUTs. This theory is used to determine the static deflection of the CMUT membrane due to a DC bias voltage. The thin-plate electro-elastic equation is solved using the Galerkin weighted residual technique under the assumption that the deflections are small in comparison to the thickness of the plate. The results obtained are compared to those obtained from ANSYS simulations and an excellent agreement is observed between the two. The pull-in voltage predicted by our model is close to the value predicted by ANSYS simulations. A simple analytical formula, which gives fairly accurate results (to within 3% of the value predicted by ANSYS simulations) for determination of the pull-in voltage, is also presented. As stated, this formula accounts for the elastic deflection of the membrane due to the coupled interaction with the electrostatic field.
The effect of vacuum sealing the backside cavity of a CMUT is investigated in some detail. The presence or absence of air inside the cavity has a marked effect upon the system parameters, such as the natural frequency and the pull-in voltage. The possibility of using sealed CMUT cavities with air inside at ambient pressure is explored. In order to estimate the transducer loss due to the presence of air in the sealed cavity, the squeeze film forces resulting from the compression of the trapped air film are evaluated. Towards this end, the linearized Reynolds equation is solved in conjunction with the appropriate boundary conditions, taking the flexure of the membrane into account. From this analysis, it is concluded that, for a sealed CMUT cavity, the presence of air does not cause any squeeze film damping even when the flexure of the membrane is taken into account (the case of a rigid plate is already known).
Although the emphasis of the study undertaken here is not on the physical realization of a working CMUT, a single cell as well as a linear array based on the design presented here, were fabricated (in a foundry elsewhere) in order to verify some of the most fundamental device parameters from experimental measurements. The fabricated devices have been characterized for their resonant frequency, quality factor, and structural integrity. These tests were conducted using the laser Doppler vibrometer and the Focused Ion Beam milling.
Having investigated thoroughly the behavior of a single cell, we proceed to demonstrate how these cells can be arranged optimally in the form of an array to provide a comprehensive ultrasonic imaging system. A thorough analysis of the requirements for the array architecture is undertaken to determine the optimal configuration. The design constraints that need to be taken into account for CMUT arrays, especially for NDE applications, are presented. The main issue of designing an array consisting of a large number of CMUT cells required for producing a pressure wave of sufficient strength which is detectable upon reflection from the desired location even after suffering severe attenuation resulting from propagation in various media is addressed. A scalable annular array architecture of CMUT cells is recommended based on the analysis carried out.
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"Measuring Dynamic Membrane Mechanical Properties Using a Combined Microfabricated Magnetic Force Transducer-Microaspiration System." Thesis, 2012. http://hdl.handle.net/1911/70451.
Full textAbstract:
This thesis examines the dynamics of the formation of tethers, which are tubes of lipids 20 - 200 nm in diameter. In particular, this work investigates how the loading rate affects the observed threshold force at which a tether forms from a vesicle membrane. Tether dynamics are important to a myriad of biological processes such as signaling when white blood cells adhere to the walls of healthy and diseased blood vessels, or in the transport of intracellular material between neighboring cells. To understand the dynamics of tether formation in such systems more fully, the studies presented in this thesis focus on the dependence of the force needed to create a tether on the rate of force change. To conduct these experiments, I combined, for the first time, a microfabricated magnetic force transducer, or a microscale device that generates well-controlled and localized magnetic fields, and microaspiration, a technique to apply known tension to a lipid membrane. Using the combined global and local mechanical control of the joint system, I discovered a strong correlation between the threshold force of tether formation and the applied force ramp. An energy model, based upon that used to describe membrane rupture, characterized the observed dependencies and provided a mechanism to examine physically relevant quantities within the system. The usefulness of this combined approach was further substantiated by determining the influence of membrane modulators, including cholesterol, tension, adhesion site concentration, and phosphatidylserine, on the dependence seen between force threshold and force rates. Additionally, application of the experimental technique developed in this thesis led to the calculation of the inter-layer drag coefficient between membrane leaflets and to the first measurements of the thermal expansivity in aspirated 1-stearoy1-2-oleoyl- sn -glycero-3-phosphatidylcholine vesicles. This new tool for dynamic studies of membrane mechanics may further be extended to study how tethers form off of flowing cells or how phase regimes, induced by the presence of cholesterol, influence membrane dynamics.
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Costa, João Nuno da Silva Pedro Castanheira da. "Analysis of a Typical Offshore Tubular KT-Joint to Evaluate the SCF and SIF Values." Dissertação, 2019. https://hdl.handle.net/10216/123215.
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Costa, João Nuno da Silva Pedro Castanheira da. "Analysis of a Typical Offshore Tubular KT-Joint to Evaluate the SCF and SIF Values." Master's thesis, 2019. https://hdl.handle.net/10216/123215.
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Sablak, Mukaddes Selviboy Kazakia Jacob Y. Oztekin Alparslan Smith Charles R. Salathe Eric P. Ozturk Murat. "Multilayer flow of Giesekus fluids in pressure driven two-dimensional channel at small values of the mobility parameters." 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3373087.
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Olivier, Allan Andre. "Mechanical shock values applied in condition monitoring of bearings operating under variable speed and load conditions." Thesis, 2014. http://hdl.handle.net/10352/299.
Full textAbstract:
M. Tech. (Mechanical Engineering) Vaal University of TechnologyMonitoring the condition of equipment in industry is very important to prevent unplanned breakdowns and to prolong their life. This is necessary, since it is not always economically viable to stop equipment at regular intervals to do maintenance. Failure on machines can lead to high repair costs and production losses. It is thus of paramount importance that early failure symptoms be identified by means of condition monitoring. This study in the field of condition monitoring is performed to determine if the mechanical shock values induced in defect bearings could be used to measure the condition of a bearing while operating under variable speed and variable load. Variable speed and variable load is becoming more popular in industry because variable speed drives applications ensure effective process control. Variable speed application, cause fault frequencies to fluctuate and therefore vibration applications for constant speed applications, which are speed-dependent, can no longer apply. Vibration-monitoring techniques that have applied for many years have now become obsolete in these variable speed applications. Methods such as Short Time Fourier Transformation (STFT), time scale like wavelet transform, and Order tracking has been applied in variable speed applications with some success. These methods analyses the vibration phases on the signal buy compensating for the speed changes. In this thesis, the Shock pulse method is selected as the analyses tool to measure the mechanical shock. Shock pulse monitoring does not focus on the vibration phases but measures in a small-time window when mechanical shocks are induced in the bearing material before the vibration phase. There is very little documented research in the field of mechanical shock pulse monitoring for conditions of variable speed and variable loads, and therefore this research focuses on recording these mechanical shock values by empirical tests. The tests were performed on a bearing with an induced defect on the outer race. The rolling element of the bearing strikes the defect and the mechanical shock value (dBsv) is measured. The mechanical shock is measured with the Shock pulse method in a small-time window before vibration occurs. In this time window, the dBsv is recorded over time to provide diagnostic information of the bearing during acceleration, deceleration and various loading conditions. These mechanical shocks are elastic waves that mirror the impact-contact-force's time function and the Shock pulse monitoring accelerometer, which is tuned to 32 kHz, will respond to the elastic wave fronts with transient amplitudes proportional to the square of the impact velocities. The mechanical shock values were analysed and reoccurring fault levels were identified on each empirical test. These recurring events from the empirical tests were used as primary data for analysis in this research. These tests were performed on a bearing with an induced failure and it was found that the dBsv measured over time could not be used to monitor the condition of the bearing under variable speed applications. This was because the dBsv changed as the speed increased. To overcome this problem Sohoel’s theory was applied and the initial mechanical shock value (dBi) was calculated for the bearing. The dbi value was subtracted from the dBsv and a value called the maximum mechanical shock value (dBm) was obtained. The dBm values stayed constant for the duration of the test and this allowed the condition of the bearing to be measured under variable speed and variable load conditions with some exception. The exception to the findings was that the dBm values stayed constant during acceleration phases, but during the deceleration phases the values were erratic and scattered. At speed below 200rpm the dBm values did not stay constant and therefore it was concluded that the dBm value recorded the best results only when thrust on the bearing was maximum. The other exception was under no-load conditions. The values were erratic and scattered, and therefore the results were not a true reflection of the bearing condition. The third exception was that the results on bearings with various loads remained constant during increased load changes unless the loading was erratic. During erratic load changes, the results were affected. The results also indicated that the larger the defect on the bearing raceway, the higher the dBm values were. Multipil defects on the bearing race ways were not part of this thesis and this gives an opertunity for futher research. The Shock pulse monitoring technique was 100% successful in monitoring the bearing condition only while the speed of the bearing was increasing. The results obtained in this work demonstrated that the condition of bearings can be monitored in applications of variable speed and variable load if the exception are eliminated and to obtain conclusive results the mechanical shock pulses should be measured over time and not be used as once-off value.
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Usha, Devi Amma C. "Ultrasound Assisted Optical Elastography For Measurement Of Mechanical Properties Of Soft Tissue Mimicking Phantoms." Thesis, 2006. http://hdl.handle.net/2005/394.
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This work describes the development of an optical probe for measuring movement of tissue particles deep inside which are loaded by an ultrasound remote palpation device. The principle of the method is that ultrasound force which can be applied inside the tissue makes the tissue particles vibrate and this vibration phase-modulates the light intercepting the insoniified region which results in a modulated speckle intensity on detection outside the object. This speckle intensity modulation detected through the measured intensity autocorrelation is a measure of the vibration amplitude. Since the vibration amplitude is related to the local elastic properties of the medium, the measured modulation depth in intensity autocorrelation can be used to map the elastic property in the insonified region. In this work, first the ultrasound induced force is calculated for both plane and focused ultrasound beams, and converted to amplitude of vibration and refractive index modulation, solving the forward elastography equation. Light propagation inside an insonified object is modelled using Monte Carlo simulation and the amplitude and intensity correlations are computed. The modulation depth on the autocorrelation is estimated and shown that it is inversely correlated to the local elastic modulus and optical absorption coefficient. It is further shown that whereas the variation in modulation depth is linear with respect to absorption coefficient, the same variation with elastic property is nonlinear. These results are verified experimentally in a tissue mimicking phantom. The phantom was constructed out of poly vinyl alcohol(PVA) whose optical, mechanical and acoustic properties are independently controlled. It is also shown that for loading with focused ultrasound beam the displacement is almost along the ultrasound transducer axis and therefore the contribution from refractive index modulation alone can be ascertained by probing the insonified perpendicular to the transducer axis. This helps one to find the contribution to the modulation depth from the ultrasound-induced vibration, which can be used to compute a quantitative estimate of the elastic modulus from the modulation depth.
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陳俊宏. "The Study of Relationship between Learning Satisfactions and Work Values of Rotary Co-operative Education Program Students of Mechanical Engineering Departments in Vocational High Schools." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/21771462120876069109.
Full textAbstract:
碩士國立彰化師範大學
工業教育與技術學系
98
The purpose of this study was to explore the relationship between the learning satisfactions and work values. The data was collected with a questionnaire. The target population of research was limited to students of Rotary Co-operative Education Program of mechanical engineering department in vocational high school. There were 571 questionnaires sent out. The valid questionnaires remained 403 with the return rate 70.6%. According to statistical analysis results, conclusions of this study were as follows: 1.The Rotary Co-operative Education Program students of Mechanical Engineering Department in Vocational High School come from the low social family. 2.The working condition of student in co-operative organization was normal, but most work were operational on the scene. 3.The student intensely wants to enter a higher school. 4.The situation is serious that students were unable normally to practice in the original co-operative organization, because economy was depressive. 5.The student’s work values and learning satisfactions of the school and the co-operative organization were high-intermediately level. 6.The differences in the learning satisfactions of school resulted from the grade and plan of future. 7.The differences in the learning satisfactions of co-operative organization resulted from the rotary method, in-service training and plan of future. 8.The differences in the work values resulted from the parent’s education level and plan of future. 9.There were significant correllations between learning satisfactions of school and learning satisfactions of co-operative organization. 10.There were significant correllations between learning satisfactions of school and work values. 11.There were significant correllations between learning satisfactions of co-operative organization and work values.
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Chandran, Sriram R. "Ultrasound-Assisted Diffuse Correlation Spectroscopy : Recovery of Local Dynamics and Mechanical Properties in Soft Condensed Matter Materials." Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2753.
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This thesis describes the development and applications of an extension of DWS which enables the recovery of ‘localized’ mechanical properties, in a specified region of a complex jelly-like object which is inhomogeneous, marked out by the focal volume of an ultrasound transducer, also called the region-of-interest (ROI). Introduction of the sinusoidal forcing creates a sinusoidal phase variation in the detected light in a DWS experiment which modulates the measured intensity autocorrelation, g2 (τ ). Decay in the modulation depth with τ is used to recover the visco-elastic spectrum of the material in the ROI. En route to this, growth of the mean-squared dis- placement (MSD) with time is extracted from the modulation depth decay, which was verified first by the usual DWS experimental data from an homogeneous object with properties matching those in the ROI of the inhomogeneous object and then those obtained by solving the generalized Langevin equation (GLE) modelling the dynamics of a typical scattering centre in the ROI. A region-specific visco-elastic spectral map was obtained by scanning the inhomogeneous object by the ultrasound focal volume. Further, the resonant modes of the vibrating ROI were measured by locating the peaks of the modulation depth variation in g2(τ ) with respect to the ultrasound frequency. These resonant modes were made use of to recover elasticity of the material of the object in the ROI. Using a similar strategy, it was also shown that flow in pipe can be detected and flow rate computed by ‘tagging’ the photons passing through the pipe with a focussed ultrasound beam. It is demonstrated, both through experiments and simulations that the ultrasound-assisted technique devel- oped is better suited to both detect and quantitatively assess flow in a background of Brownian dynamics than the usual DWS. In particular, the MSD of particles in the flow, which shows forth a super-diffusive dynamics with MSD growing following τ α with α < 2, is captured over larger intervals of τ than was possible using existing methods. On the theoretical front, the main contribution is the derivation of the GLE, with multiplicative noise modulating the interaction ‘spring constant’. The noise is derived as an average effect of the micropolar rotations suffered by the
‘bath’ particles on the ‘system’ particle modelled. It has been shown that the ‘local’ dynamics of the system particle is nontrivially influenced by the dynamics, both translation and rotation, of ‘nonlocal’ bath particles.
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Soon, Chin Fhong, Mansour Youseffi, Rebecca F. Berends, Nicholas Blagden, and Morgan C. T. Denyer. "Development of a novel liquid crystal based cell traction force transducer system." 2013. http://hdl.handle.net/10454/6199.
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Keratinocyte traction forces play a crucial role in wound healing. The aim of this study was to develop a novel cell traction force (CTF) transducer system based on cholesteryl ester liquid crystals (LC). Keratinocytes cultured on LC induced linear and isolated deformation lines in the LC surface. As suggested by the fluorescence staining, the deformation lines appeared to correlate with the forces generated by the contraction of circumferential actin filaments which were transmitted to the LC surface via the focal adhesions. Due to the linear viscoelastic behavior of the LC, Hooke's equation was used to quantify the CTFs by associating Young's modulus of LC to the cell induced stresses and biaxial strain in forming the LC deformation. Young's modulus of the LC was profiled by using spherical indentation and determined at approximately 87.1+/-17.2kPa. A new technique involving cytochalasin-B treatment was used to disrupt the intracellular force generating actin fibers, and consequently the biaxial strain in the LC induced by the cells was determined. Due to the improved sensitivity and spatial resolution ( approximately 1mum) of the LC based CTF transducer, a wide range of CTFs was determined (10-120nN). These were found to be linearly proportional to the length of the deformations. The linear relationship of CTF-deformations was then applied in a bespoke CTF mapping software to estimate CTFs and to map CTF fields. The generated CTF map highlighted distinct distributions and different magnitude of CTFs were revealed for polarized and non-polarized keratinocytes.
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Wu, Gang-Long, and 吳岡隆. "A Study of the Influence in learning Effectiveness of Students of Mechanical Engineering Department at Senior High Schools by The Teaching Strategies of Theory of Consumption Values into Team-Games Tournaments (TGT) – A Case of the Basic Electricity." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/mqbgjv.
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碩士國立彰化師範大學
工業教育與技術學系
105
The study aimed at integrating the Theory of Consumption Values which influences consumer purchase behaviors into designs of assignments sheets and game-based competitions. By applying the instructional strategies of game-based group competitions to courses of basic electricity of the electrical machine department of senior high school, the study discussed the reason that learning effectiveness being different for students. By employing quasi-experiment research methods, the study took first-grade students from the electrical machine department as its subjects. One class, with 36 students, was classified as the experimental group which integrating the Theory of Consumption Values into instructional strategies of game-based group competitions. Another class, with 38 students, was regarded as the control group which representing traditional instructional strategies. The study used the Cognitive Test Paper and Learning Motivation Scale to discuss learning effectiveness of cognitive domains and learning motivations. The followings are research results: First, Post-test scores regarding learning effectiveness of cognitive domains in the experimental group were higher than its pre-test scores and achieved significant ifferences. Second, Post-test scores regarding learning effectiveness of cognitive domains in the control group were higher than its pre-test scores and achieved significant differences. Third, Post-test scores of learning motivations of the experimental group were higher than its pre-test scores but achieved no significant difference. Fourth, Post-test scores of learning motivations of the control group were higher than its pre-test scores but achieved no significant difference. Fifth, After excluding costate variables, learning effectiveness of cognitive domains in the experimental group were superior to that of the control group. Nevertheless, no significant difference was achieved here. Sixth, After excluding costate variables, learning motivations of the experimental group were superior to that of the control group. Nevertheless, no significant difference was achieved here.
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Malhi, Charanjeet Kaur. "Studies on the Design of Novel MEMS Microphones." Thesis, 2014. http://hdl.handle.net/2005/3125.
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MEMS microphones have been a research topic for the last two and half decades. The state-of-the-art comprises surface mount MEMS microphones in laptops, mobile phones and tablets, etc. The popularity and the commercial success of MEMS microphones is largely due to the steep cost reduction in manufacturing afforded by the mass scale production with microfabrication technology. The current MEMS microphones are de-signed along the lines of traditional microphones that use capacitive transduction with or without permanent charge (electret type microphones use permanent charge of their sensor element). These microphones offer high sensitivity, stability and reasonably at frequency response while reducing the overall size and energy consumption by exploiting MEMS technology.
Conceptually, microphones are simple transducers that use a membrane or diaphragm as a mechanical structure which deflects elastically in response to the incident acoustic pressure. This dynamic deflection is converted into an electrical signal using an appropriate transduction technique. The most popular transduction technique used for this application is capacitive, where an elastic diaphragm forms one of the two parallel plates of a capacitor, the fixed substrate or the base plate being the other one. Thus, there are basically two main elements in a microphone { the elastic membrane as a mechanical element, and the transduction technique as the electrical element. In this thesis, we propose and study novel design for both these elements. In the mechanical element, we propose a simple topological change by introducing slits in the membrane along its periphery to enhance the mechanical sensitivity. This simple change, however, has significant impact on the microphone design, performance and its eventual cost. Introduction of slits in the membrane makes the geometry of the structural element non-trivial for response analysis. We devote considerable effort in devising appropriate modeling techniques for deriving lumped parameters that are then used for simulating the system response. For transduction, we propose and study an FET (Field Effect Transistor) coupled micro-phone design where the elastic diaphragm is used as the moving (suspended) gate of an FET and the gate deflection modulated drain current is used in the subthreshold regime of operation as the output signal of the microphone. This design is explored in detail with respect to various design parameters in order to enhance the electrical sensitivity. Both proposed changes in the microphone design are motivated by the possibilities that the microfabrication technology offers. In fact, the design proposed here requires further developments in MEMS technology for reliably creating gaps of 50-100 nm between the substrate and a large 2D structure of the order of a few hundred microns in diameter.
In the First part of the thesis, we present detailed simulations of acoustic and squeeze lm domain to understand the effect slits could bring upon the behaviour of the device as a microphone. Since the geometry is nontrivial, we resort to Finite element simulations using commercial packages such as COMSOL Multiphysics and ANSYS in the structural, acoustic and Fluid-structure domains to analyze the behaviour of a microphone which has top plate with nontrivial geometry. On the simulated Finite element data, we conduct low and high frequency limit analysis to extract expressions for the lumped parameters. This technique is well known in acoustics. We borrow this technique of curve Fitting from the acoustics domain and apply it in modified form into the squeeze lm domain. The dynamic behaviour of the entire device is then simulated using the extracted parameters. This helps to simulate the microphone behaviour either as a receiver or as a transmitter.
The designed device is fabricated using MEMSCAP PolyMUMPS process (a foundry Polysilicon surface micromachining process). We conduct vibrometer (electrostatic ex-citation) and acoustic characterization. We also study the feasibility of a microphone with slits and the issues involved. The effect of the two dissipation modes (acoustic and squeeze lm ) are quantified with the experimentally determined quality factor. The experimentally measured values are: Resonance is 488 kHz (experimentally determined), low frequency roll-off is 796 Hz (theoretical value) and is 780 Hz as obtained by electrical characterization.
The first part of this thesis focusses on developing a comprehensive understanding
of the effect of slits on the performance of a MEMS microphone. The presence of slits near the circumference of the clamped plate cause reduction in its rigidity. This leads to an increase in the sensitivity of the device. Slits also cause pressure equalization between the top and bottom of the diaphragm if the incoming sound is at relatively low frequencies. At this frequency, also known as the lower cutoff frequency, the microphone's response starts dropping. The presence of slits also changes the radiation impedance of the plate as well as the squeeze lm damping below the plate. The useful bandwidth of the microphone changes as a consequence. The cavity formed between the top plate and the bottom fixed substrate increases the stiffness of the device significantly due to compression of the trapped air. This effect is more pronounced here because unlike the existing capacitive MEMS microphones, there is no backchamber in the device fabricated here.
In the second part of the thesis, we present a novel subthreshold biased FET based MEMS microphone. This biasing of the transistor in the subthreshold region (also called as the OFF-region) offers higher sensitivity as compared to the above threshold region (also called as the ON-region) biasing. This is due to the exponentially varying current with change in the bias voltage in the OFF-region as compared to the quadratic variation in the ON-region. Detailed simulations are done to predict the behaviour of the device. A lumped parameter model of the mechanical domain is coupled with the drain current equations to predict the device behaviour in response to the deflection of the moving gate. From the simulations, we predict that the proposed biasing offers a device sensitive to even sub-nanometer deflection of the flexible gate. As a proof of concept, we fabricate fixed-fixed beams which utilize CMOS-MEMS fabrication. The process involves six lithography steps which involve two CMOS and the remaining MEMS fabrication. The fabricated beams are mechanically characterized for resonance. Further, we carry out electrical characterization for I-V (current-voltage) characteristics.
The second part of the thesis focusses on a novel biasing method which circumvents the need of signal conditioning circuitry needed in a capacitive based transduction due to inbuilt amplification. Extensive simulations with equivalent circuit has been carried out to determine the increased sensitivity and the role of various design variables.