Dissertations / Theses on the topic 'Load sharing'
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1
Afzal, Tahir Mahmood. "Load sharing in distributed computer systems." Thesis, University of Newcastle Upon Tyne, 1987. http://hdl.handle.net/10443/2066.
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In this thesis the problem of load sharing in distributed computer systems is investigated. Fundamental issues that need to be resolved in order to implement a load sharing scheme in a distributed system are identified and possible solutions suggested. A load sharing scheme has been designed and implemented on an existing Unix United system. The performance of this load sharing scheme is then measured for different types of programs. It is demonstrated that a load sharing scheme can be implemented on the Unix United systems using the existing mechanisms provided by the Newcastle Connection, and without making any significant changes to the existing software. It is concluded that under some circumstances a substantial improvement in the system performance can be obtained by the load sharing scheme.
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Al-Jarrah, Omar M. "Arm-Manipulator Coordination For Load Sharing /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu148793324553837.
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Massey, Keith James. "Neuromuscular activation and the load sharing concept." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0001/MQ32182.pdf.
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Cripton, Peter Alec. "Load-sharing in the human cervical spine." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0016/NQ45264.pdf.
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Overvåg, Thomas Ferstad. "Centrifugal Compressor Load Sharing with the use of MPC." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for teknisk kybernetikk, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20687.
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The work presented in this thesis examines the possibilities of having compressors running in an optimal manner which can result in energy savings. This research looks at how a compressor operates and the problems which can occur when connecting several machines, both in series and parallel. It is mainly focused on using Model Predictive Control (MPC), as a setup for controlling each compressor to a fixed operating point on the characteristic with relation to mass flow and pressure. Constraints are set on the controller outputs to help minimize the area of operation. Several types of efficiency are investigated in detail and this has helped to create a continuous efficiency island definition. These continuous curves are assumed to be equal to the characteristic plotted from tests and measurements in the lab. The continuous efficiency definition enables the possibility of calculating an operating point for each compressor. This is done using a Quadric Programming setup, which is calculated explicitly beforehand. Together with this and the implementation of MPC, the result is a load sharing scheme used here on two compressors connected in parallel. The control inputs to the plant being the impeller rotational speeds and the outflow from the throttle valve, while the measurements are in the form of plenum pressure and mass flow from each machine.
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Arcand, Simon Carleton University Dissertation Engineering Systems and Computer. "Load sharing in an integrated satellite - terrestrial cellular network." Ottawa, 1995.
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Sanderson, Brian T. "Reducing Seed Load in the BitTorrent File Sharing System." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2439.pdf.
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Adams, Daniel Alan. "Optimal Load Balancing in a Beowulf Cluster." Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-050205-135758/.
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Moore, Jonathan E. "Frequency-based load sharing in current-mode-controlled buck converters." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA362884.
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Thesis (M.S. in Electrical Engineering) Naval Postgraduate School, March 1999."March 1999". Thesis advisor(s): John G. Ciezki, Robert W. Ashton. Includes bibliographical references (p. 103-105). Also available online.
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Rydén, Patrik. "Statistical analysis and simulation methods related to load-sharing models." Doctoral thesis, Umeå universitet, Matematisk statistik, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-46772.
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We consider the problem of estimating the reliability of bundles constructed of several fibres, given a particular kind of censored data. The bundles consist of several fibres which have their own independent identically dis-tributed failure stresses (i.e.the forces that destroy the fibres). The force applied to a bundle is distributed between the fibres in the bundle, accord-ing to a load-sharing model. A bundle with these properties is an example of a load-sharing system. Ropes constructed of twisted threads, compos-ite materials constructed of parallel carbon fibres, and suspension cables constructed of steel wires are all examples of load-sharing systems. In par-ticular, we consider bundles where load-sharing is described by either the Equal load-sharing model or the more general Local load-sharing model. In order to estimate the cumulative distribution function of failure stresses of bundles, we need some observed data. This data is obtained either by testing bundles or by testing individual fibres. In this thesis, we develop several theoretical testing methods for both fibres and bundles, and related methods of statistical inference. Non-parametric and parametric estimators of the cumulative distribu-tion functions of failure stresses of fibres and bundles are obtained from different kinds of observed data. It is proved that most of these estimators are consistent, and that some are strongly consistent estimators. We show that resampling, in this case random sampling with replacement from sta-tistically independent portions of data, can be used to assess the accuracy of these estimators. Several numerical examples illustrate the behavior of the obtained estimators. These examples suggest that the obtained estimators usually perform well when the number of observations is moderate.
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Othman, Mazliza. "Load sharing as a power management strategy for mobile computers." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325034.
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Leslie, Robert. "An evaluation of load sharing algorithms for heterogeneous distributed systems." Thesis, University of Greenwich, 1997. http://gala.gre.ac.uk/6224/.
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Distributed systems offer the ability to execute a job at other nodes than the originating one. Load sharing algorithms use this ability to distribute work around the system in order to achieve greater efficiency. This is reflected in substantially reduced response times. In the majority of studies the systems on which load sharing has been evaluated have been homogeneous in nature. This thesis considers load sharing in heterogeneous systems, in which the heterogeneity is exhibited in the processing power of the constituent nodes. Existing algorithms are evaluated and improved ones proposed. Most of the performance analysis is done through simulation. A model of diskless workstations communicating and transferring jobs by Remote Procedure Call is used. All assumptions about the overheads of inter-node communication are based upon measurements made on the university networks. The comparison of algorithms identifies those characteristics that offer improved performance in heterogeneous systems. The level of system information required for transfer is investigated and an optimum found. Judicious use of the collected information via algorithm design is shown to account for much of the improvement. However detailed examination of algorithm behaviour compared with that of a 'optimum' load sharing scenario reveals that there are occasions when full use of all the information available is not beneficial. Investigations are carried out on the most promising algorithms to assess their adaptability, scalability and stability under a variety of differing conditions. The standard definitions of load balancing and load sharing are shown not to apply when considering heterogeneous systems. To validate the assumptions in the simulation model a load sharing scenario was implemented on a network of Sun workstations at the University. While the scope of the implementation was somewhat limited by lack of resources, it does demonstrate the relative ease with which the algorithms can be implemented without alteration of the operating system code or modification at the kernel level.
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Lo, Kwok Cheong Michael Carleton University Dissertation Computer Science. "Performance of load sharing policies in homogeneous and heterogeneous systems." Ottawa, 1996.
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Anthony, Richard John. "Load sharing in loosely-coupled distributed systems : a rich-information approach." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326771.
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Leque, Nicholas. "Development of Load Sharing Models for Double-Helical Epicyclic Gear Sets." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1422570590.
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Bø, Torstein Ingebrigtsen. "Dynamic Model Predictive Control for Load Sharing in Electric Power Plants for Ships." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18749.
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The main contribution of this thesis is an investigation of model predictive control(MPC) for marine diesel electric power plants. Recommendations and new ideasfor further development are emphasized.The motivation of the thesis is to develop a controller for diesel electric power plantsthat can control the plant in a more efficient way. This includes reducing wear andtear, fuel consumption, and emissions. However, the safety aspect is always themost important factor and must be handled with care.The case plant to be studied is a diesel electrical power plant consisting of severaldiesel driven generators (genset). These gensets produce electrical power to servethe electrical demands on a marine vessel. The consumers can be propulsion units,heave compensators, drilling equipment, and hotel loads. These highly dynamicconsumers are large compared with the producers. This gives unwanted fluctuationof frequency. In some vessels this effect is so large that more gensets are requiredfor transients than for peak demands. This can be avoided with better controlstrategies.The controller developed in this thesis adjusts the local controllers on the dieselengines. The objective is to keep the genset at a given load sharing, while keepingthe frequency within rules and regulations. In addition is the plant controlled to astate where a single point failure does not lead to blackout.Blackout is prevented by calculating a failure case in addition to the normal case.The failure case may be a disconnection of the largest genset on the power bussegment. The case is calculated in the controller to make sure that if the caseoccurs the plant is able to handle the failure without a blackout. A normal case,where everything goes as normal, is calculated to optimize the current operation.The controller is verified by simulation done in MATLAB/Simulink. Theimplemented controller performs well during all of the simulated cases. However,the predictions made by the controller are in some cases conservative. This is dueto the choice of the fuel rate constraints. Lastly, suggestions for how to improvethe performance of the controller are included. The most important suggestionsare to include a model of the turbocharger in the control plant model and toinclude more failure cases.
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Kelley, Stephen Hume. "Load sharing in anti-air warfare coordination : criteria and a simulation test plan." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26613.
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Rydén, Patrik. "Estimation of the reliability of systems described by the Daniels Load-Sharing Model." Licentiate thesis, Umeå universitet, Matematisk statistik, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-46724.
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We consider the problem of estimating the failure stresses of bundles (i.e. the tensile forces that destroy the bundles), constructed of several statisti-cally similar fibres, given a particular kind of censored data. Each bundle consists of several fibres which have their own independent identically dis-tributed failure stresses, and where the force applied on a bundle at any moment is distributed equally between the unbroken fibres in the bundle. A bundle with these properties is an example of an equal load-sharing sys-tem, often referred to as the Daniels failure model. The testing of several bundles generates a special kind of censored data, which is complexly struc-tured. Strongly consistent non-parametric estimators of the distribution laws of bundles are obtained by applying the theory of martingales, and by using the observed data. It is proved that random sampling, with replace-ment from the statistical data related to each tested bundle, can be used to obtain asymptotically correct estimators for the distribution functions of deviations of non-parametric estimators from true values. In the case when the failure stresses of the fibres are described by a Weibull distribution, we obtain strongly consistent parametric maximum likelihood estimators of the distribution functions of failure stresses of bundles, by using the complexly structured data. Numerical examples illustrate the behavior of the obtained estimators.
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Zhang, Jie. "Impact of disk access on the performance of load sharing policies in distributed systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq36882.pdf.
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Iyer, Jaishankar. "Load sharing schemes in multiple induction motor drive applications using volts per hertz control." Thesis, University of British Columbia, 2011. http://hdl.handle.net/2429/39837.
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Multi induction-motor (IM) drives are commonly used to share a mechanical load in a wide range of industrial applications. In many existing auxiliary applications, the traditional low-cost Volts-per-Hertz (V/F) drives are typically used in speed control mode to simultaneously operate several IMs.
In multi-machine load-sharing applications, it is preferred to have number of identical IMs to share the load equally. Under ideal conditions, the identical IMs would operate with equal loading. However, in practice deviations of the load sharing among the IMs is possible due to many factors including variations in internal or external parameters and operating conditions of each individual IM. Such deviations may result in disproportionate sharing of the mechanical load and even overloading one or several machines while some machines may be under-loaded. The basic low-cost variable frequency drives (VFDs) with traditional open-loop V/F control scheme fail to share the load under such conditions.
In this Thesis, two new methods are proposed to address the load sharing problems under an internal disturbances (such as rotor resistance variations) and external disturbances (such as wheel slippage due to snow/water/oil etc.). The new methods are shown to be effective in sharing the load under disturbances. Moreover, the proposed methodologies may be readily extended to an arbitrary number of motors driving a common mechanical load, and are easy to implement with traditional/existing low-cost VFDs, which may be advantageous for many existing or legacy applications.
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Chan, Kristen Y. "MULTIPLE INPUT SINGLE OUTPUT CONVERTER WITH UNEVEN LOAD SHARING CONTROL FOR IMPROVED SYSTEM EFFICIENCY." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2139.
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This paper presents the development and study of multiple-input single-output converter (MISO) for the DC House project that utilizes a controller to maximize the overall converter’s efficiency. The premise of this thesis is to create uneven load current sharing between the converters at different loading conditions in order to maximize the efficiency of the overall MISO converter. The goal is to find a proper ratio of current from each converter to the total load current of the MISO system to achieve the greatest efficiency. The Arduino microcontroller is implemented to achieve this goal. The design and operation of the MISO converter with the proposed controller will be explained in this paper. The design and operation of the converter was tested and verified through simulation in LTSpice in addition to hardware implementation. Different ratios of current from each converter were used to fully test the MISO converter. For the 5A and 6A load current, the maximum efficiencies were reached with the 70% / 30% ratio case, with efficiencies of 94.91% and 95.07%, respectively. For 7A load current, the maximum efficiency was reached with the 60% / 40% ratio case, with an efficiency of 94.59%. The results were then compared with those obtained from the equal current sharing cases. For the cases tested, the efficiency of the unequal current sharing outperforms that obtained from the equal current sharing method.
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Pradhan, Rahul. "Adaptive multimedia content delivery for scalable web servers." Link to electronic thesis, 2001. http://www.wpi.edu/Pubs/ETD/Available/etd-0502101-112152.
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Lenton, Gavin. "The Use of Kinematic and Kinetic Analysis Measurement to Identify the Critical Factors in Optimising Dismounted Combatant Load Sharing Systems." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/371906.
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Armed forces throughout the world value maintaining effective and capable soldiers. That means having soldiers who can perform their job unhindered and without sustaining injury. Exposure to the physical demands of military service, including heavy load carriage, directly threatens soldier capability by impeding performance and increasing the risk of musculoskeletal injuries (MSI). Soldier attrition due to MSI has increased globally in the last 10 years, leading to reduced workforce capability and incurring substantial costs. Additionally, wearing heavy loads affects performance sustainability by increasing metabolic energy expenditure and decreasing time to fatigue compared to wearing lighter loads. To reduce the physical burden of load carriage, industry manufacturers have developed load sharing systems that re-distribute load from the shoulders to the hips via a hip belt, and claim that these systems decrease shoulder pressure and discomfort. However, these claims made by industry have not yet been substantiated by rigorous and impartial testing. Additionally, other potential effects of using these systems (e.g., altered walking patterns) have not been investigated. Changing the distribution of load may affect soldier performance in the field, or alter lower-limb joint loading in a manner that increases MSI risk. Therefore, the general purpose of this thesis was to comprehensively investigate biomechanical changes that occur when soldiers wear different load sharing systems compared to standard issue military armour, with implications for reducing MSI risk and/or improving soldier performance discussed throughout. The first study developed and evaluated performance of a new marker set to track trunk and pelvis motion during load carriage. This was essential as existing marker sets were validated for skin-surface placement or for use in obese populations, but not when using torso-borne load carriage systems. Two torso-borne load carriage armour conditions were examined by comparing joint angles measured from eight participants using a new marker set against those obtained using markers placed on the skin surface (i.e., without armour), and markers placed on body armour. Bland Altman analyses showed strong agreement between joint angles from the new marker set and markers placed directly on the skin. The agreement worsened with markers placed on top of body armour. Additionally, inter-protocol coefficient of multiple correlations (CMCs) comparing markers on body armour to the new marker set were poor to compared to CMCs between the skin-mounted markers and new marker set. Intra- and inter-session repeatability were high for the new marker set compared to placing marker over-top body armour. Given these positive results, the new marker set provides a viable alternative for researchers to reliably measure trunk and pelvis motion when equipment, such as body armour, obscures marker placement. The paper describing the new marker set was published as Lenton, G. K., Doyle, T. L. A., Saxby, D. J., & Lloyd, D. G., An alternative whole-body marker set to accurately and reliably quantify joint kinematics during load carriage. Gait and Posture, 54, 318-324, 2017. The second study evaluated the veracity of manufacturer claims of load sharing systems reducing shoulder pressure and discomfort. Twenty soldiers each wore twelve body armour variations: six armour types (one standard-issue armour, TBAS, and five prototype designs, cARM1-2, pARM1-3) and two carried loads (15 and 30kg) while walking on an instrumented treadmill at moderate (1.53 m⋅s-1) and fast (1.81 m⋅s-1) speeds for 10 minutes at each speed. Walking with hip belt compared to no hip belt armour resulted in decreased mean and maximum shoulder contact pressures, and 30% fewer participants experiencing shoulder discomfort in best performing hip belt designs. Additionally, regression analyses showed laterally concentrated shoulder pressure was associated with 1.34-times greater likelihood of experiencing shoulder discomfort (p=0.026). These results suggest body armour and backpack designs should integrate a hip belt and distribute load closer to the shoulder midline to reduce load carriage discomfort and, potentially, injury risk. The paper describing these results was submitted as Lenton G. K., Doyle T. L. A., Saxby D. J., Higgs J, Billing D, Lloyd D. G. Integrating a hip belt with body armour reduces the magnitude and changes the location of shoulder pressure and perceived discomfort in soldiers, Ergonomics. The purpose of study three was to determine the effects of load distribution, load magnitude, and walking speed on biomechanical surrogates of MSI. Whole-body marker kinematics and ground reaction forces were collected during the protocol outlined in study two. Subsequently, a scaled anatomic model was used in OpenSim’s inverse kinematic and inverse dynamic procedures to determine whole-body joint angles and lower-limb net joint moments, respectively. It was found that lower-limb joint moments increased when participants carried greater load and/or walked faster, while combined effects of carried load and movement speed were mostly additive. Peak plantarflexion moment was reduced by 16% when wearing cARM1 compared to the standard issue TBAS system while carrying 30kg and walking fast. This suggests there are positive benefits of load sharing at higher demands. Importantly, shoulder-to-hip load transfer resulted in soldiers walking with a more upright posture, and did not negatively alter joint kinetics. A manuscript has been submitted as Lenton, G. K., Saxby, D. J., Lloyd, D. G., Billing, D., & Doyle, T. L. A., Carried load configuration, mass, and movement speed alter biomechanical risk factors for musculoskeletal injuries in soldiers, Medicine and Science in Sports and Exercise. The fourth study examined how lower-limb joint work and power magnitudes, surrogates of performance longevity, as well as relative contributions of lower-limb joints to total average positive power were modulated in different load configurations and movement speeds during gait. The joint angle and joint moment data from study three were used to determine hip, knee, and ankle joint work and powers using standard computational methods. While total average power was largely dictated by task demands (i.e., carried load and gait speed), different armour systems and carried loads resulted in different lower-limb joint powers. Carrying 30 kg with cARM1 armour caused significantly greater contributions of hip powers to total positive power, while knee and ankle powers decreased insignificantly compared to carrying 15 kg with cARM1. Additionally, as gait speed and carried load increased, hip powers increased, and knee and ankle powers decreased, possibly as a control strategy to balance load while maintaining forward progression. These results suggest physical training programs and assistive devices should be designed based upon physical requirements of a particular armour type and/or carried load to maximise soldier in-field sustainability. A manuscript has been submitted as Lenton, G. K., Doyle, T. L. A., Lloyd, D. G., Billing, D., & Saxby, D. J., Lower-limb joint work and power are modulated during load carriage based on load configuration and movement speed, Journal of Biomechanics. In conclusion, load sharing systems should improve soldier capability immediately by reducing shoulder pressure and associated discomfort compared to current-issued armour, and long-term by enhancing performance longevity and reducing lower-limb MSI risk. The hip-dominant joint power profiles suggest that physical training programs and device design should target hip extensor muscles and provide assistance to the hip respectively. However, design-specific recommendations should maximise benefits as different design elicited slightly different joint power profiles. An optimal load carriage design building upon best features of existing designs may provide greater benefit than any single design we tested.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School Allied Health Sciences
Griffith Health
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AFSHARIPOUR, BABAK. "Estimation of load sharing among muscles acting on the same joint and Applications of surface electromyography." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2535698.
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The force produced by a specific muscle cannot be measured and what is measured is the total force provided by all the active muscles acting on a joint, including agonists and antagonists. The first part of this work (chapter 3) addresses the issue of load sharing by proposing two possible approaches and testing them. The second part (chapter 4 and 5) addresses two applications of surface EMG focusing on the study of a) muscle relaxation associated to Yoga sessions and b) the activation of muscle of the back and shoulder of musicians playing string instruments (violin, viola and cello).
In both parts the element of innovation is the use of two dimensional electrode arrays and of techniques based on EMG Imaging. The objectives of this work are presented and explained in chapter 1 while the basic concepts of surface EMG are summarized in chapter 2. Different EMG-based muscle force models found in the literature are explained and discussed.
Two renowned amplitude indicators in surface EMG (sEMG) studies are the average rectified value (ARV) and the root mean square (RMS). These two amplitude indicators are computed over a defined time window of the recorded signals to represent the muscle activity. The advantages and disadvantages of RMS and ARV are compared and discussed for a simple sinusoid as well as for more complex signals (simulated motor unit action potential detected by high density electrode grid). The results show that RMS is more robust to the sampling frequency than ARV.
In this thesis, starting from the simulation of a single fiber and of a group of fibers (motor unit), it is shown that inter electrode distance (IED) greater than10 mm causes aliasing. Aliasing is a source of error in sEMG map interpretation or decisions that are made by automatic algorithms such as those providing image segmentation for the identifications of regions of interest.
Chapter 2 discusses three segmentation algorithms (K-means, h-dome, watershed) and compares them in order to find the most suitable method. Results reveal that among the three mentioned algorithms, watershed provides most accurate segmentation for the simulated ARV maps.
Chapter 3 presents a mathematical model that is associated to the monotonic Force-EMG relation. A possible non-linear relationship between the EMG and force or torque is presented.
A system of "M" equations is obtained by performing "M" measurements at "M" different force levels in isometric conditions. The solutions of such system of equations are the values for each muscles. Two different approaches were investigated for finding the solutions of the system, which are: a) Analytical-Graphical Approach (AGA) and b) Numerical Approach (NA) consisting of error minimization (between the total estimated and measured force) applying optimization algorithms.
The AGA was used to find the model parameters of each muscle contributing to the force production on a joint by finding the intersection of those surfaces that can be obtained from sequential substitutions of the model parameters in the equations corresponding to each contraction level. In simulation studies, the AGA graphically shows that there is more than one solution to the load sharing problem even for the simplest theoretical case (i.e. a joint spanned by only two muscles). The second approach, based on minimization of the mean square error between the measured and the total estimated force or torque (with "N" muscles involved) provides an estimate of the model parameters that in turn provides the force contributions of the individual muscles. The optimization algorithms can find the solutions of our system made of non-linear equations (see chapter 3). Starting from different point (initial conditions), different solutions can be found, as predicted by the AGA approach for the two-muscle case. The main conclusion of this study is that the load sharing strategy is not unique.
Chapter 4 discusses the application of surface electromyography to a single case study of Yoga relaxation to show the feasibility of measurements. The effect of yoga relaxation on muscle activity (sEMG amplitude), as well as on mean and median frequencies and muscle fiber's conduction Velocity, is discussed in this chapter. No changes in the sEMG activity pattern distribution were found for the same task performed before and after applying yoga relaxation technique. However, myoelectric manifestations of fatigue were smaller after relaxation and returned to the normal pattern after the recovery phase from relaxation. Further studies are justified.
Chapter 5 describes results and discusses the spatial distribution of muscle activity over the Trapezius and Erector Spinae muscles of musicians playing string instruments. In chapter 5, the effect of backrest support in sitting position during playing cello, viola, and violin on the muscle activity index of upper and lower Trapezius muscle of the bowing arm, upper Trapezius muscle of non-bowing arm, left and right Erector Spinae muscles is investigated. Two professional players (one cello and one viola) and five student players (one cello, three violin and one viola) participated in this study. The muscle activity index (MAI) was defined as the spatial average of RMS values of the muscle active region detected by watershed segmentation for Trapezius muscles (left and right), and thresholding technique (70% of the maximum value) for left and right Erector Spinae muscles. It was found that the MAI is string (note) dependent. Statistical difference (p < 0:05) between the MAIs of left Erector Spinae muscle during playing with and without backrest support was observed in four (out of five) student players. No statistical differences were observed on the muscle activity of Trapezius (bowing and no-bowing arms) during playing with and without backrest support in different types of bowing for all musicians.
In conclusion, this work addresses a) the issue of spatial sampling and segmentation of sEMG using 2D electrode arrays, b) two possible approaches to the load-sharing issue, c) a single-case study of Yoga relaxation and d) the distribution of muscle activity above the Trapezius and Erector Spinae muscles of musicians playing string instruments. Previously unavailable knowledge has been achieved in all these four studies.
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Foster, Glenn C. "Tensile and Flexure Strength of Unidirectional Fiber-Reinforced Composites: Direct Numerical Simulations and Analytic Models." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36688.
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A Local Load Sharing (LLS) model recently developed by Curtin
and co-workers for the numerical simulation of tensile
stress-strain behavior in fiber-reinforced composites is used
to predict the tensile strength of metal matrix composites
consisting of a Titanium matrix and unidirectionally aligned
SiC fibers.
This model is extended to include the effects of free
boundary conditions and non-constant load gradients and then
used to predict the strength of a Ti-6Al-4V matrix reinforced
with Sigma SiC fibers under 4-point flexure testing.
The predicted tensile and flexure strengths agree very well
with the values measured by Gundel and Wawner and Ramamurty
et al.
The composite strength of disordered spatial fiber
distributions is investigated and is shown to have a
distribution similar to the corresponding ordered composite,
but with a mean strength that decreases (as compared to the
ordered composite) with increasing Weibull modulus.
A modified Batdorf-type analytic model is developed and
similarly extended to the case of non-uniform loading to
predict the strength of composites under tension and flexure. The
flexure model is found to be inappropriate for application
to the experimental materials, but the tensile model yields
predictions similar to the Local Load Sharing models for the
experimental materials.
The ideas and predictions of the Batdorf-type model, which
is essentially an approximation to the simulation model, are
then compared in more detail to a simulation-based model
developed by Ibnabdeljalil and Curtin to more generally
assess the accuracy of the Batdorf model in predicting
tensile strength and notch strength versus composite size
and fiber Weibull modulus.
The study shows the Batdorf model to be accurate for tensile
strength at high Weibull moduli and to capture general trends
well, but it is not quantitatively accurate over the full
range of material parameters encountered in various fiber
composite systems.Master of Science
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Broberg, James Andrew, and james@broberg com au. "Effective task assignment strategies for distributed systems under highly variable workloads." RMIT University. Computer Science and Information Technology, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080130.150130.
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Heavy-tailed workload distributions are commonly experienced in many areas of distributed computing. Such workloads are highly variable, where a small number of very large tasks make up a large proportion of the workload, making the load very hard to distribute effectively. Traditional task assignment policies are ineffective under these conditions as they were formulated based on the assumption of an exponentially distributed workload. Size-based task assignment policies have been proposed to handle heavy-tailed workloads, but their applications are limited by their static nature and assumption of prior knowledge of a task's service requirement. This thesis analyses existing approaches to load distribution under heavy-tailed workloads, and presents a new generalised task assignment policy that significantly improves performance for many distributed applications, by intelligently addressing the negative effects on performance that highly variable workloads cause. Many problems associated with the modelling and optimisations of systems under highly variable workloads were then addressed by a novel technique that approximated these workloads with simpler mathematical representations, without losing any of their pertinent original properties. Finally, we obtain advance queuing metrics (such as the variance of key measurements like waiting time and slowdown that are difficult to obtain analytically) through rigorous simulation.
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Song, Yongle. "Optimum design and 3D CAD/CAE simulation of spiroid and worm gears." Thesis, Nottingham Trent University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369311.
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Bharadwaj, V. "Distributed Computation With Communication Delays: Design And Analysis Of Load Distribution Strategies." Thesis, Indian Institute of Science, 1994. http://hdl.handle.net/2005/161.
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Load distribution problems in distributed computing networks have attracted much attention in the literature. A major objective in these studies is to distribute the processing load so as to minimize the time of processing of the entire load. In general, the processing load can be indivisible or divisible. An indivisible load has to be processed in its entirety on a single processor. On the other hand, a divisible load can be partitioned and processed on more than one processor. Divisible loads are either modularly divisible or arbitrarily divisible. Modularly divisible loads can be divided into pre-defined modules and cannot be further sub-divided. Further, precedence relations between modules may exist. Arbitrarily divisible loads can be divided into several fractions of arbitrary lengths which usually do not have any precedence relations. Such type of loads are characterized by their large volume and the property that each data element requires an identical and independent processing. One of the important problems here is to obtain an optimal load distribution, which minimizes the processing time when the distribution is subject to communication delays in the interconnecting links. A specific application in which such loads are encountered is in edge-detection of images. Here the given image frame can be arbitrarily divided into many sub-frames and each of these can be independently processed. Other applications include processing of massive experimental data. The problems associated with the distribution of such arbitrarily divisible loads are usually analysed in the framework of what is known as divisible job theory.
The research work reported in this thesis is a contribution in the area of distributing arbitrarily divisible loads in distributed computing systems subject to communication delays. The main objective in this work is to design and analyseload distribution strategies to minimize the processing time of the entire load in a given network. Two types of networks are considered, namely (i) single-level tree (or star) network and (ii) linear network. In both the networks we assume that there is a non-zero delay associated with load transfer. Further, the processors in the network may or may not be equipped with front-ends (Le., communication co-processors). The main contributions in this thesis are summarized below.
First, a mathematical formulation of the load distribution problem in single-level tree and linear networks is presented. In both the networks, it is assumed that there are (m +1) processors and m communication links. In the case of single-level tree networks, the load to be processed is assumed to originate at the root processor, which divides the load into (m +1) fractions, keeps its own share of the load for processing, and distributes the rest to the child processors one at a time and in a fixed sequence. In all the earlier studies in the literature, it had been assumed that for a load distribution to be optimal, it should be such that all the processors must stop computing at the same time. In this thesis, it is shown that this assumption is in general not true, and holds only for a restricted class of single-level tree networks which satisfy a certain condition. The concept of an equivalent network is introduced to obtain a precise formulation of this condition in terms of the processor and link speed parameters. It is shown that this condition can be used to identify processor-link pairs which can be eliminated from a given network (i.e., these processors need not be given any computational load) without degrading its time performance. It is proved that the resultant reduced network (a network from which these inefficient processor-link pairs have been removed) gives the optimal time performance if and only if the load distribution is such that all the processors stop computing at the same time instant. These results are first proved for the case when the root processor is equipped with a front-end and then extended to the case when it is not. In the latter case, an additional condition, between the speed of the root processor and the speed of each of the links, to be satisfied by the network is specified. An optimal sequence for applying these conditions is also obtained. In the case of linear networks the processing load is assumed to originate at the processor situated at one end of the network. Each processor in the network keeps its own load fraction for computing and transmits the rest to its successor. Here too, in all the earlier studies in the literature, it has been assumed that for the processing time to be a minimum, the load distribution must be such that all the processors must stop computing at the same instant in time. Though this condition has been proved by others to be both necessary and sufficient, a different and more rigorous proof, similar to the case of single-level tree network, is presented here. Finally, the effect of inaccurate modelling on the processing time and on the above conditions are discussed through an illustrative example and it is shown that the model adopted in this thesis gives reasonably accurate results.
In the case of single-level tree networks, so far it has been assumed that the root processor distributes the processing load in a fixed sequence. However, since there are m child processors, a total of m! different sequences of load distribution are possible. Using the closed-form derived for the processing time, it is proved here that the optimal sequence of load distribution follows the decreasing order of link speeds. Further, if physical rearrangement of processors and links is allowed, then it is shown that the optimal arrangement follows a decreasing order of link and processor speeds with the fastest processor at the root. The entire analysis is first done for the case when the root processor is equipped with a front-end, and then extended to the case when it is not. In the without front-end case, it is shown that the same optimal sequencing result holds. However, in an optimal arrangement, the root processor need not be the fastest. In this case an algorithm has been proposed for obtaining optimal arrangement. Illustrative examples are given for all the cases considered.
Next, a new strategy of load distribution is proposed by which the processing time obtained in earlier studies can be further minimized. Here the load is distributed by the root processor to a child processor in more than one installment (instead of in a single installment) such that the processing time is further minimized. First; the case in which all the processors are equipped :tn front-ends is considered. Recursive equations are obtained for a heterogeneous network and these are solved for the special case of a homogeneous network (having identical processors and identical links). Using this closed-form solution, the ultimate limits of performance are explored through an asymptotic analysis with respect to the number of installments and number of processors in the network. Trade-off relationships between the number of installments and the number of processors in the network are also presented. These results are then extended to the case when the processors are not equipped with front-ends. Finally, the efficiency of this new strategy of load distribution is demonstrated by comparing it with the existing single-installment strategy in the literature.
The multi-installment strategy explained above is then applied to linear net-As. Here, .the processing load is assumed to originate at one extreme end of the network, First the case when all the processors are equipped with front-ends is considered. Recursive equations for a heterogeneous network are obtained and these are solved for the special case of a homogeneous network. Using this closed form solution, an asymptotic analysis is performed with respect to the number of installments. However, the asymptotic results with respect to the number of processors was obtained computationally since analytical results could not be obtained. It is found that for a given network, once the number of installments is fixed, there is an optimum number of processors to be used in the network, beyond which the time performance degrades. Trade-off relationships between the number of installments and the number of processors is obtained. These results are then extended to the case when the processors are not equipped with front-ends. Comparisions with the existing single-installment strategy is also done.
The single-installment strategy discussed in the literature has the disadvantage that the front-ends of the processors are not utilized efficiently in a linear network. This is due to the fact that a processor starts computing its own load fraction only after the entire load to be communicated through its front-end has been received. In this thesis, a new strategy is proposed in which a processor starts computing as soon as it receives its load fraction, simultaneously allowing its front-end to receive and transmit load to its successors. Recursive equations are developed and solved for the special case of a heterogeneous network in which the processors and links are arranged in the decreasing order of speeds. Further, it is shown that in this strategy, if the processing load originates in the interior of the network, the sequence of load distribution should- be such that the load should be first distributed to the side with a lesser number of processors. An expression for the optimal load origination point in the network is derived. A comparative study of this strategy with an earlier strategy is also presented. Finally, it is shown that even though the analysis is carried out for a special case of a heterogeneous network, this load distribution strategy can also be applied to a linear network in which the processors and links are arbitrarily arranged and still obtain a significant improvement in the time performance.
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Roberson, Jason Roscoe. "Use of compliant interbody force sensing grafts to compare load sharing properties of unidirectional and bidirectional multilevel dynamic translational anterior cervical plates." View the abstract Download the full-text PDF version, 2008. http://etd.utmem.edu/ABSTRACTS/2008-051-Roberson-index.htm.
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Thesis (M.S.)--University of Tennessee Health Science Center, 2008.Title from title page screen (viewed on February 9, 2009). Research advisor: Denis J DiAngelo, Ph.D. Document formatted into pages (x, 62 p. : ill.). Vita. Abstract. Includes bibliographical references (p. 35-36).
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Keski-Säntti, J. (Jarmo). "Neural networks in the production optimization of a kraft pulp bleach plant." Doctoral thesis, University of Oulu, 2007. http://urn.fi/urn:isbn:9789514285691.
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Abstract
Bleaching is an essential process in chemical pulp production for better pulp brightness and longer life expectancy. However, it causes costs such as chemicals, energy, equipment, and loss of yield. Non-linear reactions and several process variables, with interactions, make large plants complicated to model and optimize. As an expensive process bleaching has been a natural target of optimization, but there is still the need to either improve these methods or consider the optimization problem from a new point of view.
The aim of this thesis was to develop production optimization methods for pulp bleaching, so that they are practical, usable on-line, easy to tune, and transferable. According to our assumption, neural networks could provide a practical optimization method by combining analytical knowledge with real data. In this kind of problem, the load sharing concept, recognizing interactions in chemical usage and the serial multi-stage nature of the process can simplify the task.
The related work in bleaching optimization was studied as well as multi-stage serial process solving in principle, related optimization methods and especially neural networks in optimization. The data were collected during normal mill operation and modeled using neural networks. Optimization was performed based on visualizing the neural network models.
The results showed that backpropagation neural networks are capable of modeling parts of the bleach plant and also the entire bleaching operation to such an extent that they are useful in the optimization. The modeling and the tuning can be performed without a profound knowledge of the system, but the process is slower and less reliable. Moving a trained neural network to another mill is inadvisable. It is more reasonable just to transfer the knowledge of variables and network structure. The important factor in on-line production optimization is the stabilization of the disturbances and a well-controlled operation towards a more economical state. Generally, more than half of the total chemicals should be used in the first bleaching stage D0 and the remaining load should be divided so that the dosage at the D1 is about 30% higher than in the D2 stage.
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Tariq, Usama. "Robotic Grasping of Large Objects for Collaborative Manipulation." Thesis, Luleå tekniska universitet, Rymdteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65866.
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In near future, robots are envisioned to work alongside humans in professional anddomestic environments without significant restructuring of workspace. Roboticsystems in such setups must be adept at observation, analysis and rational de-cision making. To coexist in an environment, humans and robots will need tointeract and cooperate for multiple tasks. A fundamental such task is the manip-ulation of large objects in work environments which requires cooperation betweenmultiple manipulating agents for load sharing. Collaborative manipulation hasbeen studied in the literature with the focus on multi-agent planning and controlstrategies. However, for a collaborative manipulation task, grasp planning alsoplays a pivotal role in cooperation and task completion.In this work, a novel approach is proposed for collaborative grasping and manipu-lation of large unknown objects. The manipulation task was defined as a sequenceof poses and expected external wrench acting on the target object. In a two-agentmanipulation task, the proposed approach selects a grasp for the second agentafter observing the grasp location of the first agent. The solution is computed ina way that it minimizes the grasp wrenches by load sharing between both agents.To verify the proposed methodology, an online system for human-robot manipu-lation of unknown objects was developed. The system utilized depth informationfrom a fixed Kinect sensor for perception and decision making for a human-robotcollaborative lift-up. Experiments with multiple objects substantiated that theproposed method results in an optimal load sharing despite limited informationand partial observability.
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McBagonluri-Nuuri, David Fred. "Simulation of Fatigue Performance & Creep Rupture of Glass-Reinforced Polymeric Composites for Infrastructure Applications." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36924.
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A simulation model which incorporates the statistical- and numerical-based Lattice Green Function Local Load Sharing Model and a Fracture Mechanics-based Residual Strength Model has been developed. The model simulates creep rupture by imposing a fixed load of constant stress on the composite over the simulation duration. Simulation of the fatigue of glass fiber-reinforced composites is achieved by replacing the constant stress parameter in the model with a sinusoidal wave function. Results from the creep rupture model using fused silica fiber parameters, compare well with S-2 glass/epoxy systems. Results using Mandell's postulate that fatigue failure in glass fiber-reinforced polymeric composites is a fiber-dominated mechanism, with a characteristic slope of 10 %UTS/decade are consistent with available experimental data. The slopes of fatigue curves for simulated composites for three frequencies namely: 2, 5 and 10 Hz are within 12-14 %UTS/decade compared with that of 10.6-13.0%UTS/decade for unidirectionl glass reinforced composites (epoxy and vinyl ester) obtained from Demers' [40] data.Master of Science
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Chen, Fang. "Control of DC Power Distribution Systems and Low-Voltage Grid-Interface Converter Design." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77532.
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DC power distribution has gained popularity in sustainable buildings, renewable energy utilization, transportation electrification and high-efficiency data centers. This dissertation focuses on two aspects of facilitating the application of dc systems: (a) system-level control to improve load sharing, voltage regulation and efficiency; (b) design of a high-efficiency interface converter to connect dc microgrids with the existing low-voltage ac distributions, with a special focus on common-mode (CM) voltage attenuation.
Droop control has been used in dc microgrids to share loads among multiple sources. However, line resistance and sensor discrepancy deteriorate the performance. The quantitative relation between the droop voltage range and the load sharing accuracy is derived to help create droop design guidelines. DC system designers can use the guidelines to choose the minimum droop voltage range and guarantee that the sharing error is within a defined range even under the worst cases.
A nonlinear droop method is proposed to improve the performance of droop control. The droop resistance is a function of the output current and increases when the output current increases. Experiments demonstrate that the nonlinear droop achieves better load sharing under heavy load and tighter bus voltage regulation. The control needs only local information, so the advantages of droop control are preserved. The output impedances of the droop-controlled power converters are also modeled and measured for the system stability analysis.
Communication-based control is developed to further improve the performance of dc microgrids. A generic dc microgrid is modeled and the static power flow is solved. A secondary control system is presented to achieve the benefits of restored bus voltage, enhanced load sharing and high system efficiency. The considered method only needs the information from its adjacent node; hence system expendability is guaranteed.
A high-efficiency two-stage single-phase ac-dc converter is designed to connect a 380 V bipolar dc microgrid with a 240 V split-phase single-phase ac system. The converter efficiencies using different two-level and three-level topologies with state-of-the-art semiconductor devices are compared, based on which a two-level interleaved topology using silicon carbide (SiC) MOSFETs is chosen. The volt-second applied on each inductive component is analyzed and the interleaving angles are optimized. A 10 kW converter prototype is built and achieves an efficiency higher than 97% for the first time.
An active CM duty cycle injection method is proposed to control the dc and low-frequency CM voltage for grounded systems interconnected with power converters. Experiments with resistive and constant power loads in rectification and regeneration modes validate the performance and stability of the control method. The dc bus voltages are rendered symmetric with respect to ground, and the leakage current is reduced. The control method is generalized to three-phase ac-dc converters for larger power systems.Ph. D.
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Raghami, Alireza. "A novel Thevenin-based voltage droop control improving reactive power sharing with structures to identify Thevenin parameters." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/130620/9/Alireza%20Raghami%20Thesis.pdf.
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In this research project, a low-cost local voltage compensation strategy is proposed that evenly utilises the capability of the customers’ inverters spreading over a branched suburban utility network. The improved utilisation is based on a straightforward two-element equivalent of the network locally seen by each inverter. The network is simultaneously probed by all inverters, each one tries to identify its two-element perspective. Receiving an appropriate local response is challenged by the interference created by simultaneous probing and demand variation and also inverters’ compensating nature. Identification structures are designed to suppress all challenges while probing remains effectively invisible to the customers.
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Gaihre, Nirajan. "ANALYTICAL AND NUMERICAL MODELING OF FOUNDATIONS FOR TALL WIND TURBINE IN VARIOUS SOILS." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2650.
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Wind farm construction is increasing progressively, to cope-up with the current global energy scenario. The advantage of clean energy and sustainability helps wind turbine construction to flourish rapidly. Location of wind turbines is independent of foundation soil condition but depends on the wind speeds and socio-environment issues. Hence, a construction sites may not be favorable in terms of geotechnical demands. The taller wind towers facilitate the generation of high energy production, which will increase loads on the foundation, and eventually increase the dimension of the foundation. Hence, the choice of a suitable foundation system is necessary for geotechnical engineer to design tall wind towers. This study aims to analyze different foundation types e.g., raft/mat foundation, pile group foundation, and piled raft/mat foundation using analytical calculation verified with numerical models using PLAXIS 3D software. The foundation for steel wind turbine towers 100 m high was designed for different types of soils e.g., soft clayey soil, medium-stiff clayey soil, stiff clayey soil, and sandy soil. The design wind speed was taken from the ASCE 7-10 (2010) standard for Occupancy Category III and IV Buildings and Other Structures, as the Illinois region falls in that category. The parametric study was performed by varying the diameter of raft/mat, wind speed, number of piles, and soil types to evaluate the settlement in any type of foundation with load sharing proportion in piled raft/mat foundation. First, the raft/mat foundation design was carried out manually by changing the diameter of 15 m, 20 m, 25 m, 30 m, and 35 m, and changing load by considering different wind speed. Then the foundation was modeled using PLAXIS 3D software with a raft/mat diameter of 25 m, 30 m, and 35 m only, by considering the eccentricity and factor of safety criteria. With the increase in wind speed, the differential settlement on the raft/mat foundation was found to be increased. However, the increase in diameter of raft/mat caused the reduction in differential settlement. Soft clayey soil was found to be more sensitive than other soils used in the present study. For the same diameter of raft/mat, applied the same wind load, the differential settlement of foundation in soft clayey soil was found to be 6-10 times higher than the sandy soil.The position of piles was fixed based on the spacing criteria in the pile group foundation. The number of piles used in this study were 23, 32, and 46. Settlement was found to be varied with the number of piles in all soils used in this study. The lateral deflection for soft clayey soil decreased to half, when number of piles increased from 23 to 46. The differential settlement was found to be increased with the increase in wind speed in pile group foundation. Raft/mat foundation settlement was found to be 4 to 6 times higher than the settlement in pile group foundation in any soils, used in this study, for a given wind speed.The result of piled raft/mat foundation showed that the majority of the total load is shared by the piles (i.e., 60% to 94%) and remaining load is shared by the raft/mat (i.e., 6% to 40%), based on the stiffness of raft/mat and piles as well as pile-soil-pile interaction. The increase in wind speed in the wind turbines increased the differential settlement of piled raft/mat foundation in all soils. Similarly, the lateral deflection also increased with the increase in wind speed in pile raft/mat foundation in all soils. The PLAXIS 3D analysis revealed that the differential settlement in soft clayey soil was 1.5 to 2.0 times higher than the settlement in sandy soil.The validation of numerical modeling was carried out by the raft/mat foundation using Boussinesq’s theory and calculating settlement for single pile and group pile foundation. The current study showed that the soft clayey soil and medium-stiff clayey soil favor deep foundation, like pile group and piled raft/mat rather than shallow foundation, like raft/mat foundation. The results obtained from both analytical calculation and numerical modeling was found to be approximately matching. This study will help local construction company and geotechnical engineer to guide a proper foundation design of tall onshore wind turbine.
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Mohd, Daut Mohamad Hazwan. "Pico-grid : multiple multitype energy harvesting system." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289426.
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This thesis focuses on the development of a low power energy harvesting system specifically targeted for wireless sensor nodes (WSN) and wireless body area network (WBAN) applications. The idea for the system is derived from the operation of a micro-grid and therefore is termed as a pico-grid and it is capable of simultaneously delivering power from multiple and multitype energy harvesters to the load at the same time, through the proposed parallel load sharing mechanism achieved by a voltage droop control method. Solar panels and thermoelectric generator (TEG) are demonstrated as the main energy harvesters for the system. Since the magnitude of the output power of the harvesters is time-varying, the droop gain in the droop feedback circuitry should be designed to be dynamic and self-adjusted according to this variation. This ensures that the maximum power is capable to be delivered to the load at all times. To achieve this, the droop gain is integrated with a light dependent resistor (LDR) and thermistor whose resistance varies with the magnitude of the source of energy for the solar panel and TEG, respectively. The experimental results demonstrate a successful variation droop mechanism and all connected sources are able to share equal load demands between them, with a maximum load sharing error of 5 %. The same mechanism is also demonstrated to work for maximum power point tracking (MPPT) functionality. This concept can potentially be extended to any other types of energy harvester. The integration of energy storage elements becomes a necessity in the pico-grid, in order to support the intermittent and sporadic nature of the output power for the harvesters. A rechargeable battery and supercapacitor are integrated in the system, and each is accurately designed to be charged when the loading in the system is low and discharged when the loading in the system is high. The dc bus voltage which indicates the magnitude of the loading in the system is utilised as the signal for the desired mode of operation. The constructed system demonstrates a successful operation of charging and discharging at specific levels of loading in the system. The system is then integrated and the first wearable prototype of the pico-grid is built and tested. A successful operation of the prototype is demonstrated and the load demand is shared equally between the source converters and energy storage. Furthermore, the pico-grid is shown to possess an inherent plug-and-play capability for the source and load converters. Few recommendations are presented in order to further improve the feasibility and reliability of the prototype for real world applications. Next, due to the opportunity of working with a new semiconductor compound and accessibility to the fabrication facilities, a ZnON thin film diode is fabricated and intended to be implemented as a flexible rectifier circuit. The fabrication process can be done at low temperature, hence opening up the possibility of depositing the device on a flexible substrate. From the temperature dependent I-V measurements, a novel method of extracting important parameters such as ideality factor, barrier height, and series resistance of the diode based on a curve fitting method is proposed. It is determined that the ideality factor of the fabricated diode is high (> 2 at RT), due to the existence of other transport mechanism apart from thermionic emission that dominates the conduction process at lower temperature. It is concluded that the high series resistance of the fabricated diode (3.8 kΩ at RT) would mainly hinder the performance of the diode in a rectifier circuit.
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Boguski, Brian C. "An Experimental Investigation of the System-Level Behavior of Planetary Gear Sets." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1291009879.
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Song, Sukho. "Soft Robotic Grippers Using Gecko-Inspired Fibrillar Adhesives for Three-Dimensional Surface Grasping." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/936.
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Researches on biological adhesive systems in nature have changed a perspective view on adhesion that it is not only the area of surface chemistry, but also mechanics of interfacial geometry which can significantly effect on fracture strength and load distribution on the contact interface. Various synthetic fibrillar adhesives in previous works have shown enhanced interfacial bond strength with the capacity of adhesion control by exploiting mechanical deformation of the elastomeric fibrillar structures inspired by geckos. However, control of the interfacial load distribution has been focused on the size of micro-contact with single or a few of micro-/nano-fibers on planar surface, and not for a large contact area on complex three-dimensional (3D) surfaces. This thesis work aims at investigating principles of the interfacial load distribution control in multi-scale, ranging from micro-contact with single micro-fiber to a centimeter-scale contact with a membrane-backed micro-fiber array on non-planar 3D surfaces. The findings are also applied for developing a soft robotic gripper capable of grasping a wide range of complex objects in size, shape, and number, expanding the area of practical applications for bio-inspired adhesives in transfer printing, robotic manipulators, and mobile robots. This paper comprises three main works. First, we investigate the effect of tip-shapes on the interfacial load sharing of mushroom-shaped micro-fibrillar adhesives with precisely defined tipgeometries using high resolution 3D nano-fabrication technique. For a large area of non-planar contact interface, we fabricate fibrillar adhesives on a membrane (FAM) by integrating micro-fibers with a soft backing, which enables robust and controllable adhesion on 3D surfaces. Picking and releasing mechanism for the maximal controllability in adhesion are discussed. Finally, we propose a soft robotic architecture which can control the interfacial load distribution for the FAM on 3D surfaces, solving an inherit dilemma between conformability and high fracture strength with the equal load sharing on complex non-planar 3D surfaces.
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野田, 利弘, Toshihiro NODA, むつみ 田代, Mutsumi TASHIRO, 敏浩 高稲, Toshihiro TAKAINE, 顕. 浅岡, and Akira ASAOKA. "沈下低減と荷重分担に着目したパイルドラフト敷設地盤の変形解析." 土木学会, 2005. http://hdl.handle.net/2237/8610.
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Prueter, Phillip Edward. "A Study of the Mechanical Design and Gear Tooth Root Strains in Flexible Pin, Multi-Stage, Planetary Wind Turbine Gear Trains Using Three Dimensional Finite Element/Contact Mechanics Models and Experiments." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313372765.
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Glad, Andreas, and Mattias Forsman. "Automated Live Migration of Virtual Machines." Thesis, Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-5443.
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This thesis studies the area of virtualization. The focus is on the sub-area live migration, a technique that allows a seamless migration of a virtual machine from one physical machine to another physical machine. Virtualization is an attractive technique, utilized in large computer systems, for example data centers. By using live migration, data center administrators can migrate virtual machines, seamlessly, without the users of the virtual machines taking notice about the migrations. Manually initiated migrations can become cumbersome, with an ever-increasing number of physical machines. The number of physical and virtual machines is not the only problem, deciding when to migrate and where to migrate are other problems that needs to be solved. Manually initiated migrations can also be inaccurate and untimely. Two different strategies for automated live migration have been developed in this thesis. The Push and the Pull strategies. The Push strategy tries to get rid of virtual machines and the Pull strategy tries to steal virtual machines. Both of these strategies, their design and implementation, are presented in the thesis. The strategies utilizes Shannon's Information Entropy to measure the balance in the system. The strategies further utilizes a cost model to predict the time a migration would require. This is used together with the Information Entropy to decide which virtual machine to migrate if and when a hotspot occurs. The implementation was done with the help of OMNeT++, an open-source simulation tool. The strategies are evaluated with the help of a set of simulations. These simulations include a variety of scenarios with different workloads. Our results shows that the developed strategies can re-balance a system of computers, after a large amount of virtual machines has been added or removed, in only 4-5 minutes. The results further shows that our strategies are able to keep the system balanced when the system load is at medium. This while virtual machines are continuously added or removed from the system. The contribution this thesis brings to the field is a model for how automated live migration of virtual machines can be done to improve the performance of a computer system, for example a data center.
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Ye, Zhihong. "Modeling and Control of Parallel Three-Phase PWM Converters." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29476.
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This dissertation studies modeling and control issues of parallel three-phase pulse-width modulated (PWM) converters. The converters include three-phase boost rectifiers, voltage source inverters, buck rectifiers and current source inverters.
The averaging of the parallel converters is performed based on a generic functional switching unit, which is called a phase leg in boost rectifiers and voltage source inverters, and a rail arm in buck rectifiers and current source inverters. Based on phase-leg and rail-arm averaging, the developed models are not only equivalent to the conventional three-phase converter models that are based on phase-to-phase averaging, but they also preserve common-mode information, which is critical in the analysis of the parallel converters. The models reveal such parallel dynamics as reactive power circulation and small-signal interaction.
A unique feature of the parallel three-phase converters is a zero-sequence circulating current. This work proposes a novel zero-sequence control concept that uses variable zero-vectors in the space-vector modulation (SVM) of the converters. The control can be implemented within an individual converter and is independent from the other control loops for the converter. Therefore, it greatly facilitates the design and expansion of a parallel system.
Proper operation of the parallel converters requires an explicit load-sharing mechanism. In order to have a modular design, a droop method is recommended. Traditionally, however, a droop method has to compromise between voltage regulation and load sharing. After parametric analysis, a novel droop method using a gain-scheduling technique is proposed. The numeric analysis shows that the proposed droop method can achieve both good voltage regulation and good load sharing.
An interleaving technique is often used in parallel converter systems in order to reduce current ripples. Because of its symmetrical circuit structure, the parallel three-phase converter system can reduce both differential-mode and common-mode noise with a center-aligned symmetrical SVM.
Based on the concept that a symmetrical circuit can reduce common-mode dv/dt noise, a conventional three-phase, four-leg inverter is modified so that its fourth leg is symmetrical to the other three legs. The common-mode dv/dt noise can be practically eliminated with a new modulation strategy. Meanwhile, with a modified control design, the new four-leg inverter still can handle low-frequency common-mode components that occur due to unbalanced and nonlinear load.Ph. D.
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Klintrot, Oskar, and Daniel Forsström. "Lastfördelning och effektmätning med Arduino och PLC." Thesis, Linnéuniversitetet, Sjöfartshögskolan (SJÖ), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-34236.
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Detta arbete var beställt av Sjöfartshögskolan i Kalmar. Skolan ville ha en enhet som kunde mäta aktiv-, reaktiv- och skenbar effekt, ström, spänning, frekvens och cosϕ på en generator och som kommunicerade vidare dessa värden till en PLC. Detta för att kunna lastfördela lasten mellan ett antal generatorer i kursen Tillämpad elteknik 15 hp där studenterna bygger en generatorinstallation med tre generatorer. Ett funktionsblock för lastfördelning skulle också programmeras. Prototypen som konstruerades baserades på en Arduino Ethernet och kommunikationen löstes med Modbus TCP/IP över Ethernet. Ett lastfördelningsprogram programmerades i form av ett funktionsblock som studenterna kunde importera till CoDeSys v2.3 och använda i sina installationer. Prototypen kunde läsa av värdena med ungefär samma noggrannhet som ett kommersiellt instrument som använder sig av samma mätteknik som prototypen. Uppdateringsfrekvensen var dock lägre än hos ett kommersiellt instrument. Kommunikationen med PLC:n fungerade utan problem. Då ingen undervisning hölls i arbetets slutskede kunde inte lastfördelningen testas på en fullskalig anläggning. Lastfördelningsprogrammet klarade dock av att hålla rätt frekvens på en ensam generator och fungerade som tänkt när programmet testades i en simulator. Prototypen gav fel mätvärden vid kapacitiv last. Vid jämförelse med en kommersiell tångamperemeter visade sig mätfelet bero på mätmetoden då båda gav liknande resultat. Som referens användes en professionell elkvalitetsanalysator. Alla uppdragsgivarens krav blev uppfyllda och arbetet kommer att kunna användas i undervisningen.This thesis was ordered by Kalmar Maritime Academy. The request was for a device that could measure active, reactive and apparent power, as well as frequency, voltage, current and cosϕ on a generator. The measured values would be communicated to a PLC for use in a load sharing program between a number of generators in the course Tillämpad elteknik, 15 ECTS. In that course the students constructs a three-generator electric power grid. Included in the request was also to program a load sharing program. The prototype being constructed was based on the Arduino Ethernet, and the communication was enabled by means of the Modbus TCP/IP protocol over Ethernet. A load sharing program was created in the form of a function block which the student could import into the CoDeSys for use in the generator systems. The prototype could measure values with close to the same accuracy as a commercial available instrument that were using the same technique for measuring. The refresh rate was however lower than the commercial available instrument. Communication with the PLC worked without any issues. No full-scale testing could be done since no course was held during the final stages of the thesis, however the load sharing program could keep frequency on a single generator alone and worked in a simulated soft environment. Measuring errors occurred when measuring a capacitive load. When comparing to a commercial available clamp meter, the same errors occurred. As a reference a professional power and energy quality analyser was used. All the requests were fulfilled and the result of this thesis will be used in the educational programme at the Academy.
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Davis, Lloyd Eric. "Heavy vehicle suspensions : testing and analysis." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/34499/1/Lloyd_Davis_Thesis.pdf.
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Transport regulators consider that, with respect to pavement damage, heavy vehicles (HVs) are the riskiest vehicles on the road network. That HV suspension design contributes to road and bridge damage has been recognised for some decades. This thesis deals with some aspects of HV suspension characteristics, particularly (but not exclusively) air suspensions. This is in the areas of developing low-cost in-service heavy vehicle (HV) suspension testing, the effects of larger-than-industry-standard longitudinal air lines and the characteristics of on-board mass (OBM) systems for HVs. All these areas, whilst seemingly disparate, seek to inform the management of HVs, reduce of their impact on the network asset and/or provide a measurement mechanism for worn HV suspensions. A number of project management groups at the State and National level in Australia have been, and will be, presented with the results of the project that resulted in this thesis. This should serve to inform their activities applicable to this research. A number of HVs were tested for various characteristics. These tests were used to form a number of conclusions about HV suspension behaviours. Wheel forces from road test data were analysed. A “novel roughness” measure was developed and applied to the road test data to determine dynamic load sharing, amongst other research outcomes. Further, it was proposed that this approach could inform future development of pavement models incorporating roughness and peak wheel forces. Left/right variations in wheel forces and wheel force variations for different speeds were also presented. This led on to some conclusions regarding suspension and wheel force frequencies, their transmission to the pavement and repetitive wheel loads in the spatial domain. An improved method of determining dynamic load sharing was developed and presented. It used the correlation coefficient between two elements of a HV to determine dynamic load sharing. This was validated against a mature dynamic loadsharing metric, the dynamic load sharing coefficient (de Pont, 1997). This was the first time that the technique of measuring correlation between elements on a HV has been used for a test case vs. a control case for two different sized air lines. That dynamic load sharing was improved at the air springs was shown for the test case of the large longitudinal air lines. The statistically significant improvement in dynamic load sharing at the air springs from larger longitudinal air lines varied from approximately 30 percent to 80 percent. Dynamic load sharing at the wheels was improved only for low air line flow events for the test case of larger longitudinal air lines. Statistically significant improvements to some suspension metrics across the range of test speeds and “novel roughness” values were evident from the use of larger longitudinal air lines, but these were not uniform. Of note were improvements to suspension metrics involving peak dynamic forces ranging from below the error margin to approximately 24 percent. Abstract models of HV suspensions were developed from the results of some of the tests. Those models were used to propose further development of, and future directions of research into, further gains in HV dynamic load sharing. This was from alterations to currently available damping characteristics combined with implementation of large longitudinal air lines. In-service testing of HV suspensions was found to be possible within a documented range from below the error margin to an error of approximately 16 percent. These results were in comparison with either the manufacturer’s certified data or test results replicating the Australian standard for “road-friendly” HV suspensions, Vehicle Standards Bulletin 11. OBM accuracy testing and development of tamper evidence from OBM data were detailed for over 2000 individual data points across twelve test and control OBM systems from eight suppliers installed on eleven HVs. The results indicated that 95 percent of contemporary OBM systems available in Australia are accurate to +/- 500 kg. The total variation in OBM linearity, after three outliers in the data were removed, was 0.5 percent. A tamper indicator and other OBM metrics that could be used by jurisdictions to determine tamper events were developed and documented. That OBM systems could be used as one vector for in-service testing of HV suspensions was one of a number of synergies between the seemingly disparate streams of this project.
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Cathelin, Julien. "Modélisation du comportement mécanique des engrenages en plastique renforcé." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0029/document.
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Les engrenages en matériau polymère présentent de nombreux avantages par rapport aux aciers. Ils sont plus légers, résistants à la corrosion, fonctionne sans lubrifiant et leurs coûts de revient est moindre grâce au moulage par injection. Ils sont de plus en plus utilisés dans des domaines variés, mais se limitent à la transmission de mouvement. L’ajout de fibre de verre courte permet d’augmenter leur tenue mécanique et de diversifier leur domaine d’utilisation à des transmissions de petite à moyenne puissance. Le polyamide (Nylon) renforcé de fibres de verre est le composite le plus couramment utilisé dans le domaine des engrenages. Néanmoins, son comportement viscoélastique ainsi que la présence de fibres introduit une difficulté supplémentaire dans la modélisation. En outre, le comportement viscoélastique dépend de la température et pour le Polyamide, de l’humidité. Par conséquent, la viscoélasticité impacte directement la répartition des charges, l’erreur de transmission sous charge, la raideur d’engrènement. Dans cette thèse, une méthode numérique originale modélisant le comportement mécanique des engrenages en Polyamide 6 renforcé de fibre de verre est proposée. L’approche utilise le modèle rhéologique linéaire de Kelvin généralisé pour simuler le comportement viscoélastique du matériau et prendre en compte la température, l’humidité ainsi que le taux de fibre et leur anisotropie. Ensuite ce modèle rhéologique est intégré dans le modèle quasi-statique du partage des charges développé par le LaMCoS. Ce processus de calcul permet d’obtenir les résultats essentiels pour les engrenages (répartition des charges, pressions de contact, erreur de transmission sous charge, raideur d’engrènement) avec un temps de calcul assez court. Afin de de valider les modèles numériques développés, un banc d’essai a été mis en place, permettant la mesure de l'erreur de transmission et la visualisation de la température de l’engrenage pendant son fonctionnementPolymer gears present several advantages: they can be used without lubricant, their meshing is silencer, resistance to corrosion is better, weight is reduced. However they have a poor heat resistance and are limited to rotation transmission. In order to improve the gears performance, glass fibre reinforcement is being increasingly used, where their lower cost and higher strength, compared to unreinforced polyamide, offer a potential increase in gear performance. Mechanical behaviour of polymers materials is very complex; it depends on time, history of displacement, temperature and for several polymers, on humidity. Moreover, an addition of fibres can make the material properties heterogeneous and anisotropic. The particular case of Polyamide 6 + 30% glass fibres which is the most common fibre reinforced plastic is studied in this work. In the first part of this work, a mould was developed to better control the material choice and moulding conditions. Using tomographic observations, investigations were done to better understand the relation between moulding conditions, gears geometry and fibres orientation. Based on these observations and with the help of mechanical characterisation, a linear rheological generalized-Kelvin model was developed to simulate the viscoelastic behavior of the polymer material. In a second part, this model taking into account temperature, humidity and rotation speed is integrated in quasi-static load sharing computation developed by the LaMCoS laboratory. In the load sharing calculus, the displacements are obtained on a large meshing covering the entire surface of the tooth. This relation integrates the viscoelastic displacement, the fibre orientation and the geometrical influence coefficients. The method permits to obtain results such as the loaded transmission error, the instantaneous meshing stiffness, the load sharing and the root tooth stress at different temperature, humidity and rotation speeds within a reasonable computation time. Investigation have shown interesting results regarding the historic of displacements which represents up to 15% of the total displacement at the tip radius, the localization of the maximal tooth root stress, which is the same than metal gears, or the influence of the thermal expansion toward transmission error. On another hand, we have highlighted the low difference between a realistic description of the fibre orientation and an homogeneous anisotropic one. The last step concerns the validation of the numerical. The measurements are carried out on a test bench developed at the LaMCoS laboratory. It provides two experimental results: the temperature of the gear during operation, and the load transmission error using optical encoders to measure the angular positions of the pinion and the gear. This one is global enough to validate the three steps of the model: geometry, kinematics and load sharing
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Burnett, David Clint. "Psalm 110:1 in Confessional Material in Corpus Paulinum: Cultural and Religious Context." Thesis, Boston College, 2018. http://hdl.handle.net/2345/bc-ir:107709.
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Thesis advisor: Pheme PerkinsPsalm 110:1 was not a Second Temple messianic proof-text. Yet, it became the early Christian text par excellence for articulating exaltation Christology: Jesus was exalted to God’s right hand (Acts 2:33, 34-35; 5:31; 7:55-56; Rom 8:34; Col 3:1; Eph 1:20; 1 Pet 3:22; Heb 1:3, 13; 8:1; 10:12; 12:2) and κύριος of the cosmos (Phil 2:9-11). Therefore, this unprecedented and singular use of Ps 110:1 by early Christians requires an explanation. This dissertation argues that the unparalleled Christian use of Ps 110:1 is indebted to a Greco-Roman royal ideological concept: rulers as sharers of divine/sacred space, which consisted of three elements: temple sharing, throne sharing, and joint temples of imperials and gods. Greek cities and Roman period provinces made autocrats sharers of sacred space to show appreciation for concrete royal benefactions and to acknowledge the piety of monarchs and divine approval of their regimes. Early Christians adopted two of these practices—temple sharing and throne sharing—for similar purposes, creating a unique variant of the Greco-Roman royal practice and using scripture to justify it (Ps 110:1). Consequently, early Christian use of Ps 110:1, exaltation Christology, and Jesus’s Lordship are indebted to royal messianism
Thesis (PhD) — Boston College, 2018
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Theology
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Leutenegger, Anne-Louise B. "Estimation of random genome sharing : consequences for linkage detection." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/9574.
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Armstrong, E. Price 1985. "Bike Sharing: A Randomized Study Evaluating the University of Oregon Bike Loan Program." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/10619.
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x, 61 p. A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.Around the world, active transportation is looked at as one solution to problems presented by climate change, epidemic obesity, rising fuel prices, and crippling traffic congestion. In 2008, the University of Oregon launched the Bike Loan Program as an effort to address these issues. Because those interested in participating in the Bike Loan Program were randomly selected based on bicycle size availability, those who were not chosen acted as a perfect control group. This study evaluates the impacts of the Bike Loan Program on participants vis-a.-vis non-participants, and seeks to determine if those participating do ride bikes more often than non-participants. This study will also show what modes of transportation are being replaced by bike trips when a person participates in the Bike Loan Program. Finally, this study also shows if there are changes in attitudes or perceptions about transportation resulting from participation in the program.
Committee in Charge: Dr. Neil Bania; Dr. Marc Schlossberg; David Roth
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Morrison, Heather. "The dramatic growth of open access : implications and opportunities for resource sharing." Haworth Press, 2006. http://hdl.handle.net/2429/953.
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The Open Access movement seeks to make scholarly, peer-reviewed journal articles freely available to anyone, anywhere over the World Wide Web. There were some very significant developments in the area of Open Access (OA) in 2004, including statements by major funders in support of Open Access. There are now so many Open Access scholarly journal articles freely available, that, in the author’s opinion, being aware of, and using, the resources and related tools is now essential for libraries. Libraries can provide more resources faster for users by supplementing paid resources with ones that are Open Access.
Library resources, such as link resolvers, are beginning to incorporate Open Access materials and web searches for Open Access materials. For example, the reSearcher software suite includes Open Access collections along with subscription-based resources in the CUFTS journals knowledgebase, and a web search for an Open Access copy of an article in the GODOT link resolver. SFX also incorporates Open Access journals. After exhausting more traditional resources, interlibrary loans staff are beginning to include Google searching in their workflow.
This article will discuss what Open Access is, the dramatic growth of Open Access, and major collections, resources and tools. Implications, issues, and leadership opportunities for resource sharing specialists will be explored.
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Alsafran, Ahmed Sulaiman. "Consensus Control for Power Sharing in an Islanded Microgrid Using an Adaptive Virtual Impedance Approach." University of Dayton / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1607607802396011.
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