Dissertations / Theses on the topic 'Synthetic loading'

Energy is lost when a rope transfers from a slack state to a taut state. This transfer is called a snap load and can be very violent. It is proposed to use synthetic fiber ropes as a type of passive control device in new or existing structures to mitigate seismic response. Experimental static and snap load (dynamic) tests were conducted on various synthetic fiber ropes. An eleven-foot-tall drop tower was built in the Virginia Tech Structures and Materials Laboratory in order to conduct these tests. Force and acceleration of the drop plate, which slides vertically within the drop tower, were measured with respect to time for all dynamic tests. Acceleration data was integrated using the trapezoidal or midpoint rule to obtain velocity and displacement values. Plots were made for each test in order to give a better representation of the results. These plots include representations of force and acceleration vs. time, force vs. absolute displacement, force vs. velocity, and force, acceleration, velocity, and displacement vs. time (during the initial taut phase only). Test results show that energy was dissipated in all of the dynamic drop tests, which was expected. Also, the displacement of each rope did not return to zero at the same time that the force returned to zero after the initial snap load. This proves that the ropes undergo some permanent elongation under load. The stiffness of each rope increased with continuous testing. As more tests are conducted on each rope, the strands are pulled tighter into the braided configuration, which causes the rope to become stiffer.
Master of Science

This thesis investigates the application of the synthetic loading technique for efficiency evaluation, of permanent magnet (PM) synchronous machines. The standard tests require specialist test facilities, additional machines, and for large machines, linear machines, or vertical mounted machine and floor space. Therefore, an efficiency test method that avoids the need for an external mechanical load is desirable. Synthetic loading can determine machine losses and eliminates the need for a mechanical load connected to the test machine. The synthetic loading technique forces the machine under test to accelerate and decelerate thereby alternating between motor-generator action. If configured correctly the machine, on average over each synthetic loading cycle, operates at rated rms current, rated rms voltage and rated speed, thus producing rated copper loss, iron loss and friction and windage loss. The thesis considers how to properly configure synthetic loading for PM synchronous machines. A derivation of the mathematical models of the synthetic loading technique applied to the permanent magnet synchronous machines is provided in the thesis. The model is based on the direct and quadrature axis equivalent circuits. From the mathematical model, a quadrature axis current algorithm is proposed which is used to develop the speed equation and the stator direct and quadrature axis voltage and current equations. The thesis also establishes a generalised mathematical model of the synthetic loading technique for permanent magnet synchronous machines. Using the derived equations, the effects of synthetic loading frequency on the dc link voltage and the inverter phase-leg volt-ampere rating are analysed. This shows that the synthetic loading technique requires an increased dc link voltage and inverter volt-ampere rating compared to the standard efficiency test technique. A test rig is constructed and used to assess synthetic loading for fractional hp machines. The research verifies the synthetic loading technique experimentally for three permanent magnet synchronous machine types: the surface-mount PM synchronous machine, the interior PM synchronous machine and the linear PM synchronous machine. Simulation and experimental results from synthetic loading are compared with the standard efficiency test. The simulation and the experimental results show that the synthetic loading technique is capable of evaluating the efficiency of the permanent magnet synchronous machines. The key contributions of this work concerns the mathematical model of PM synchronous machines under synthetic loading, the hardware and software implementation and validation of synthetic loading as a technique for efficiency evaluation of PM synchronous machines.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 45-46).
According to the Munch mechanism, vascular plants rely on osmotic pressure gradients to export sugars from regions of synthesis (mature leaves) to sugar sinks (roots, fruits). A crucial step in this process is the loading of sugars from photosynthetic cells to the export conduit (the phloem). In this thesis, we developed a synthetic microfluidic osmotic pump mimicking the mechanism of passive phloem loading, where sugars are transported by diffusion from a sugar reservoir to the phloem. This design allows the development of steady flow over several hours. We show that in our system, phloem concentration is set by a relative balance between loading by diffusion from the source and export by convection through the phloem, via a single nondimensional system-scale Peclet number that we call the flushing number. For large flushing numbers, export is limited by diffusion from the source, and flow rates scale weakly with transport resistance. For low flushing numbers, export is limited by convection through the phloem and phloem concentration is close to that of the source, leading to efficient export of water and sugars. In plants, passive phloem loading is used predominantly by trees. We show that the hydrostatic pressures developed in our synthetic system can reach up to ten bars and are thus compatible with the pressures expected to drive long-distance transport in large trees. Moreover, we show that the regime of efficient export in passive loaders is more accessible to plants with large transport resistances, providing a rational for the use of the passive loading mechanism by most tree species.
by Jean Comtet.
S.M.

This thesis describes new methods of evaluating the efficiency of three-phase induction machines using synthetic loading. Synthetic loading causes the induction machine to draw full-load current without the need to connect a mechanical load to the machine's drive shaft. The synthetic loading methods cause the machine to periodically accelerate and decelerate, producing an alternating motor-generator action. This action causes the machine, on average over each synthetic loading cycle, to operate at rated rms current, rated rms voltage and full-load speed, thereby producing rated copper losses, iron loss and friction and windage loss. The excitation voltages are supplied from a PWM inverter with a large capacity DC bus capable of supplying rated rms voltage. The synthetic loading methods of efficiency evaluation are verified in terms of the individual losses in the machine by using a new dynamic model that accounts for iron loss and all parameter variations. The losses are compared with the steady-state loss distribution determined using very accurate induction machine parameters. The parameters were identified using a run-up-to-speed test at rated voltage and the locked rotor and synchronous speed tests conducted with a variable voltage supply. The latter tests were used to synthesise the variations in stator leakage reactance, magnetising reactance and the equivalent iron loss resistance over the induction machine's speed range. The run-up-to-speed test was used to determine the rotor resistance and leakage reactance variations over the same speed range. The test method results showed for the first time that the rotor leakage reactance varied in the same manner as the stator leakage and magnetising reactances with respect to current. When all parameter variations are taken into account there is good agreement between theoretical and measured results for the synthetic loading methods. The synthetic loading methods are applied to three-phase induction machines with both single- and double-cage rotors to assess the effect of rotor parameter variations in the method. Various excitation waveforms for each method were used and the measured and modelled efficiencies compared to conventional efficiency test results. The results verify that it is possible to accurately evaluate the efficiency of three-phase induction machines using synthetic loading.

In summary, it has been shown during this study that bimetallic Fe and Mn containing catalysts can be prepared by wet impregnation and not by ion exchange because of the competition between two different metals at different oxidation number. Only a single metallic phase catalyst could be prepared successfully by using ion exchange.

Bacterial infections are becoming progressively more difficult to treat due to antibiotic resistance and the decreasing rate at which new antibiotics are brought to market. The Turos laboratory has attempted to tackle this problem for the last 15 years with the discovery of N-thiolated β-lactams leading to the design of polyacrylate nanoparticles to deliver these and other drugs. Chapter 1 discusses many reported instances of utilizing different types of polymeric nanoparticles to deliver antibiotics. Poly(lactic-co-glycolic acid) (PLGA), poly(alkyl cyanoacrylate) (PACA), poly(styrene-co-butylacrylate), and chitosan are the main polymers used to make nanoparticles. Chapter 2 describes the synthesis, antibacterial activity, and mechanism of action of N-acyl ciprofloxacins, which have demonstrated in vitro bioactivity against Staphyloccocus aureus, methicillin-resistant Staphylococcus aureus, Bacillus anthracis, Enterococcus faecalis, Bartonella, and E. coli. Antimicrobial activity was found to diminish with increasingly lipophilic acyl groups of the derivatives. The N-acyl ciprofloxacins were found to utilize the same mechanism of action as the parent drug, ciprofloxacin, however, several exhibited lower mutation frequencies. Chapter 3 discusses the use of the N-acyl ciprofloxacins as probes for experimentation on the poly(vinyl benzoate) nanoparticles. These compounds were incorporated into poly(vinyl benzoate) nanoparticles, also designed in the Turos laboratory, to determine the effects of the lipophilic acyl groups on drug loading and drug release. N-acyl ciprofloxacins with higher lipophilicities (predicted logP values) experienced higher drug loading than the less lipophilic counterparts. However, the nanoparticles were unable to release large amounts of entrapped drug. N-acyl ciprofloxacins with increased hydrophilicity were found to either not be incorporated at all, or in incredibly small amounts. Drug release studies of these drugs indicate that possible the hydrophobic compounds that were associated with the nanoparticles were done so via adsorption onto the surface resulting in a burst release of drug. The work is concluded in Chapter 4, followed by experimental procedures and spectral data in Chapters 5 and 6.

The benefits of fibre reinforced concrete (FRC) have been thoroughly investigated. Much of this work has focussed on steel FRC subjected to monotonic loads. Data on the structural behaviour of macro-synthetic FRC or FRC under cyclic loads is scarce. A pilot investigation on the shear behaviour of macro-synthetic FRC and on the behaviour of FRC under reversed cyclic in-plane shear loading was carried out. Five in-plane shear panel tests were performed. The parameters under study were the fibre material type (steel or macrosynthetic) and loading protocol. Additionally, a number of compression, direct tension, and flexural tests were performed to determine the material properties of the concretes for comparison. The material response of 2.0% by volume of macro-synthetic FRC matched closely with 1.0% steel FRC. Finally, building upon an existing steel FRC model, a model for macro-synthetic FRC in tension was proposed and a short verification study was undertaken.

Indiana University-Purdue University Indianapolis (IUPUI)
Microspectrophotometry is a quick, accurate, and reproducible method to compare colored fibers for forensic purposes. The use of chemometric techniques applied to spectroscopic data can provide valuable discriminatory information especially when looking at a complex dataset. Differentiating a group of samples by employing chemometric analysis increases the evidential value of fiber comparisons by decreasing the probability of false association. The aims of this research were to (1) evaluate the chemometric procedure on a data set consisting of blue acrylic fibers and (2) accurately discriminate between yellow polyester fibers with the same dye composition but different dye loadings along with introducing a multivariate calibration approach to determine the dye concentration of fibers. In the first study, background subtracted and normalized visible spectra from eleven blue acrylic exemplars dyed with varying compositions of dyes were discriminated from one another using agglomerative hierarchical clustering (AHC), principal component analysis (PCA), and discriminant analysis (DA). AHC and PCA results agreed showing similar spectra clustering close to one another. DA analysis indicated a total classification accuracy of approximately 93% with only two of the eleven exemplars confused with one another. This was expected because two exemplars consisted of the same dye compositions. An external validation of the data set was performed and showed consistent results, which validated the model produced from the training set. In the second study, background subtracted and normalized visible spectra from ten yellow polyester exemplars dyed with different concentrations of the same dye ranging from 0.1-3.5% (w/w), were analyzed by the same techniques. Three classes of fibers with a classification accuracy of approximately 96% were found representing low, medium, and high dye loadings. Exemplars with similar dye loadings were able to be readily discriminated in some cases based on a classification accuracy of 90% or higher and a receiver operating characteristic area under the curve score of 0.9 or greater. Calibration curves based upon a proximity matrix of dye loadings between 0.1-0.75% (w/w) were developed that provided better accuracy and precision to that of a traditional approach.

近半个世纪来，大量精力致力于研究针对满足不同需求的滤波器综合设计理论。对基于解析方法的滤波器综合设计理论的需求，源源不断的推动着这个课题的研究与发展。传统滤波器综合理论假设滤波器网络两端口终端阻抗相同并且均为不随频率变化的纯实阻抗，该假设等效于认为滤波器两端匹配到具有相同特征阻抗的无耗传输线。但对于一些实际应用，例如多工器中信道滤波器的设计，滤波器的其中一个端口需要匹配到随频率变换的复阻抗 。本篇论文提出了一种适用于广义切比雪夫带通滤波器复阻抗匹配的解析综合方法用于设计一端匹配负载为频率变换的复阻抗而另一端匹配负载为常数实阻抗的滤波器。该方法以功率波再归一化理论为依据并假设：（1） 指定的传输零点不变 （2）反射零点始终纯虚数轴上。本论文通过端口参考阻抗的再归一化，推导出定义滤波器在不同参考阻抗的散射参数的特征多项式之间的三个关系并证在保证网络可实现性的前提下该关系只能通过一个理想的滤波器电路加上一段适合长度的位于滤波器与复阻抗之间的传输线来满足。设计匹配复阻抗的滤波器网络的关键在于保证电路的可实现性的前提下最大程度满足匹配条件。 本篇论文证明了为满足上述要求，引入一段最优长度的传输线的必要性。从在一定频率范围内最大限度匹配复阻抗的角度考虑，引入的传输线长度能够最优确定。论文中所提出的解析且灵活的设计方法可应用于多工器或双工器中信道滤波器的设计。通过具体的设计实例与全波软件的仿真，该方法的可行性得到了验证。
A great deal of effort has been devoted to the synthesis of microwave filters with required characteristic over the past half century. The driving force to this subject is the demand of analytical solution that facilitates various filter design requirements. Conventional filter synthesis approach assumes the termination impedance of a filter network at both ports is a real constant matched load, which is equivalent to a matched transmission line with same characteristic impedance. But for practical applications such as designing a channel filter of a multiplexer, the filter is required to match a frequency variant complex load at one port. This thesis presents an analytical approach to the synthesis of a general Chebyshev filter that matches to a frequency variant complex load at one port and a real constant load at the other port based on power wave renormalization theory under two practical assumptions: (1) the prescribed transmission zeros are stationary; and (2) the reflection zeros are located along imaginary axis. Three necessary conditions that stipulate the characteristic polynomials associated to the filter are derived through renormalization of the load reference impedances. It has been shown that these three conditions can only be satisfied by an ideal filter circuit model separated by a piece of transmission line from the complex load. The key issues in the synthesis approach are to enforce the realizability conditions of a filter network and to match the complex load with a best effort. For this purpose, it is proved that a section of transmission line with an optimal length must be inserted between the filter network and the complex load. The length of the transmission line will be optimally designed in the sense that the designed filter will best match to the complex load over a given frequency range. The proposed method offers a deterministic yet flexible way for optimally designing a diplexer or a multiplexer with a realistic loading effect. The effectiveness of the method is demonstrated by a number of design examples.
Detailed summary in vernacular field only.
Meng, Huan.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references (leaves 114-116).
Abstracts also in Chinese.
ABSTRACT --- p.i
ACKNOWLEDGEMENTS --- p.v
Table of contents --- p.iv
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Overview of Microwave Filters --- p.1
Chapter 1.2 --- Introduction to Filter Synthesis --- p.3
Chapter 1.3 --- Contributions of this Thesis --- p.6
Chapter 1.4 --- Organization of this Thesis --- p.7
Chapter Chapter 2 --- Review of Direct Filter Synthesis Theory --- p.8
Chapter 2.1 --- Basic Properties of Characteristic Polynomials --- p.8
Chapter 2.2 --- Derivation of General Chebyshev Polynomial --- p.15
Chapter 2.3 --- Analysis of Cross Coupled Resonator Circuit --- p.27
Chapter 2.4 --- Synthesis of N+2 Transversal Coupling Matrix --- p.35
Chapter 2.5 --- Reconfiguration of coupling topology --- p.44
Chapter 2.6 --- Summary --- p.50
Chapter Chapter 3 --- Direct Synthesis of Microwave Bandpass Filters with A General Loading Effect --- p.51
Chapter 3.1 --- Introduction --- p.51
Chapter 3.2 --- Renormalization of Reference Impedance --- p.56
Chapter 3.3 --- The Direct Synthesis Approach --- p.65
Chapter 3.4 --- Examples --- p.72
Chapter 3.4.1 --- Example 1: synthesis with frequency invariant complex load --- p.73
Chapter 3.4.2 --- Example 2: synthesis with frequency variant complex load --- p.74
Chapter 3.4.3 --- Example 3: synthesis with a highly reactive complex load --- p.77
Chapter 3.5 --- Future work --- p.80
Chapter 3.6 --- Summary --- p.81
Chapter Chapter 4 --- Design Examples of RF/Microwave Diplexers --- p.82
Chapter 4.1 --- Introduction --- p.82
Chapter 4.2 --- Non-contiguous band diplexer design --- p.85
Chapter 4.2.1 --- Example 1: Diplexer Design Using an H-plane T-Junction --- p.85
Chapter 4.2.2 --- Example 2: Diplexer Design with a wired Y-junction --- p.92
Chapter 4.3 --- Discussion on designing a contiguous diplexer --- p.96
Chapter 4.4 --- Future work --- p.101
Chapter 4.5 --- Summary --- p.102
Conclusion --- p.103
Chapter Appendix I --- : Power Wave Renormalization Theory --- p.104
Chapter Appendix II --- : Necessary and Sufficient condition of Power Conservation for Objective S --- p.109
Proof of Sufficiency --- p.109
Proof of Necessarity --- p.111
References --- p.114
Publication --- p.117

I compared and contrasted nitrogen and phosphorus concentrations and land use differences in two oligotrophic lakes (Sooke and Shawnigan) and two meso-eutrophic lakes (St. Mary and Elk) in order to evaluate nutrient concentrations over time, and evaluate the relationship between in-lake nutrients and land use in the surrounding watershed. I used MapShed© nutrient transport modeling software to estimate the mass load of phosphorus and nitrogen to each lake, and evaluated the feasibility of land use modifications for reducing in-lake nutrients. In comparing nitrogen and phosphorus data in Sooke and Shawnigan Lakes, I determined that natural watershed characteristics (i.e., precipitation, topography, and soils) did not account for the elevated nutrient concentrations in Shawnigan verses Sooke Lake. Natural watershed characteristics indicated that external loads into Shawnigan Lake would be lesser-than or equal to those into Sooke Lake if both watersheds were completely forested. I evaluated trends of in-lake nutrient concentrations for Sooke and Shawnigan Lakes, as well as two eutrophic lakes, St. Mary and Elk. Ten to 30-year trends indicate that nitrogen and phosphorus levels in these lakes have not changed significantly over time. Time-segmented data showed that nutrient trends are mostly in decline or are maintaining a steady-state. Most nutrient concentration data are not precipitation-dependent, and this, coupled with significant correlations to water temperature and dissolved oxygen, indicate that in-lake processes are the primary influence on lake nutrient concentrations -- not external loading. External loading was estimated using, MapShed©, a GIS-based watershed loading software program. Model validation results indicate that MapShed© could be used to determine the effect of external loading on lake water quality if accurate outflow volumes are available. Based on various land-cover scenarios, some reduction in external loading may be achieved through land-based restoration (e.g., reforestation), but the feasibility of restoration activities are limited by private property. Given that most of the causal loads were determined to be due to in-lake processes, land-based restoration may not be the most effective solution for reducing in-lake nitrogen and phosphorus concentrations.
Graduate