Teses / dissertações sobre o tema "Perturbation-Based methods"
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Khabir, Mohmed Hassan Mohmed. "Numerical singular perturbation approaches based on spline approximation methods for solving problems in computational finance". Thesis, University of the Western Cape, 2011. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_7416_1320395978.
Texto completo da fonteFukasaku, Kotaro. "Explorative study for stochastic failure analysis of a roughened bi-material interface: implementation of the size sensitivity based perturbation method". Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41114.
Texto completo da fonteGraf, Daniel [Verfasser], e Christian [Akademischer Betreuer] Ochsenfeld. "Development of efficient electronic-structure methods based on the adiabatic-connection fluctuation-dissipation theorem and Møller–Plesset perturbation theory / Daniel Graf ; Betreuer: Christian Ochsenfeld". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2021. http://d-nb.info/123217629X/34.
Texto completo da fonteJue, Stephen Gregory. "Characterizing Neurotransmitter Receptor Activation with a Perturbation Based Decomposition Method". DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1631.
Texto completo da fonteBen, Gamra Siwar. "Contribution à la mise en place de réseaux profonds pour l'étude de tableaux par le biais de l'explicabilité : Application au style Tenebrisme ("clair-obscur")". Electronic Thesis or Diss., Littoral, 2023. http://www.theses.fr/2023DUNK0695.
Texto completo da fonteFace detection from Tenebrism paintings is of growing interest to art historians and researchers in order to estimate the illuminant location, and thereby answer several technical questions. Deep learning is gaining increasing interest due to is high performance capabilities. An optimization of Faster Region based Convolutional Neural Network has demonstrated its ability to effectively address challenges and deliver promising face detection results from Tenebrism paintings. However, deep neural networks are often characterized as "black box" because of the inherent complexity and non-linearity of their architectures. To tackle these issues, eXplainable Artificial Intelligence (XAI) is becoming an active researcj area to understand deep models. So, we propose a novel iterative XAI method based on guided perturbations to explain model's application
Al, Hosani Mohamed. "Transient and Distributed Algorithms to Improve Islanding Detection Capability of Inverter Based Distributed Generation". Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6235.
Texto completo da fontePh.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
Dixit, Akash. "Damage modeling and damage detection for structures using a perturbation method". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43575.
Texto completo da fonteWang, Yiwei. "Développement de stratégies de maintenance structurales prédictives pour aéronefs utilisant le pronostic à base de modèles". Thesis, Toulouse, INSA, 2017. http://www.theses.fr/2017ISAT0005/document.
Texto completo da fonteAircraft maintenance represents a major economic cost for the aviation industry. Traditionally, the aircraft maintenance is highly regulated based on fixed schedules (thus called scheduled maintenance) in order to ensure safety. The frequency of scheduled maintenance is designed to be very conservative to maintain a desirable level of reliability. Developing efficient maintenance can be an important way for airlines to allow a new profit growth. With the development of sensor technology, structural health monitoring (SHM) system, which employ a sensor network sealing inside aircraft structures to monitor the damage state, are gradually being introduced in the aviation industry. Once it is possible to monitor the structure damage state automatically and continuously by SHM systems, it enables to plan the maintenance activities according to the actual or predicted health state of the aircraft rather than a fixed schedule. This work focus on the fatigue crack propagation in the fuselage panels. The SHM system is assumed to be employed. A model-based prognostics method is developed, which enables to filter the noise of SHM data to estimate the crack size, and to predict the future health state of the panels. This predictive information is integrated into the maintenance decision-making and two types of predictive maintenance are developed. The numerical study shows that the predictive maintenance significantly reduces the maintenance cost by reducing the number of maintenance stop and the repaired panels
Abid, Fatma. "Contribution à la robustesse et à l'optimisation fiabiliste des structures Uncertainty of shape memory alloy micro-actuator using generalized polynomial chaos methodUncertainty of shape memory alloy micro-actuator using generalized polynomial chaos method Numerical modeling of shape memory alloy problem in presence of perturbation : application to Cu-Al-Zn-Mn specimen An approach for the reliability-based design optimization of shape memory alloy structure Surrogate models for uncertainty analysis of micro-actuator". Thesis, Normandie, 2019. http://www.theses.fr/2019NORMIR24.
Texto completo da fonteThe design of economic system leads to many advances in the fields of modeling and optimization, allowing the analysis of structures more and more complex. However, optimized designs can suffer from uncertain parameters that may not meet certain reliability criteria. To ensure the proper functioning of the structure, it is important to consider uncertainty study is called the reliability analysis. The integration of reliability analysis in optimization problems is a new discipline introducing reliability criteria in the search for the optimal configuration of structures, this is the domain of reliability optimization (RBDO). This RBDO methodology aims to consider the propagation of uncertainties in the mechanical performance by relying on a probabilistic modeling of input parameter fluctuations. In this context, this thesis focuses on a robust analysis and a reliability optimization of complex mechanical problems. It is important to consider the uncertain parameters of the system to ensure a robust design. The objective of the RBDO method is to design a structure in order to establish a good compromise between the cost and the reliability assurance. As a result, several methods, such as the hybrid method and the optimum safety factor method, have been developed to achieve this goal. To address the complexity of complex mechanical problems with uncertain parameters, methodologies specific to this issue, such as meta-modeling methods, have been developed to build a mechanical substitution model, which at the same time satisfies the efficiency and the precision of the model
Wu, Chia-Pin, e 吳佳斌. "Using Singular Perturbation Methods in Observer-based Controller Design". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/88637893484414157491.
Texto completo da fonte國立臺灣科技大學
電機工程系
100
The thesis is mainly to design the controller by applying the theory of singular perturbation. First of all, using the singular perturbation technique to design the output feedback controller of mechanic systems, it is similar to the design of a proportional-derivative control law. We can precede the speed control by only measuring the displacement. The controller algorithm is the rule of low-order dynamic output feedback control. It is simple and easily accomplished. Besides, when the mechanical system contains uncertain items, this thesis presents robust stability of the closed-loop system. It also offers the analysis of Lyapunov theory by solving a Riccati algebra equation and a linear matrix inequality. Furthermore, for the mismatched parameter uncertainties and matched nonlinear perturbations in a linear MIMO system, the thesis proposes a disturbance-observer based controller in which the input disturbance can be effectively estimated by using a high-gain integration observer. Finally, it is verified the practicability by numerical examples.
ZHAO, SHU-GUANG, e 趙樹光. "Study and comparison of stochastic optimization methods based on perturbation analysis and finite difference estimate". Thesis, 1991. http://ndltd.ncl.edu.tw/handle/40875244403720092384.
Texto completo da fonteAnnam, Chandrakanth. "Advanced Guidance Laws for Field-of-View and Impact Angle Constrained Engagements". Thesis, 2020. https://etd.iisc.ac.in/handle/2005/4820.
Texto completo da fonteWei, Chia-Hua, e 韋嘉驊. "A Perturbation Method for Quantization Adjustment based on TMN8 Rate Control Model". Thesis, 2002. http://ndltd.ncl.edu.tw/handle/96933009989636497564.
Texto completo da fonte國立交通大學
電信工程系
90
The research is based on TMN8 rate control method in H.263. We know that, theoretically, the bit allocation by TMN8 for each macroblock is proportional to the product of the deviation value and the distortion weighting . The way to find the optimized quantization value Q is to predict two parameters, K and C. Although the approach to find K and C in TMN8 results in constant frame rate, the bit allocation in each macroblock usually is not the same as the theoretical value for some reasons. Now we want to find a new approach to get K and C. By the new K and C, we will get a new optimized quantization value Q that can be used to encode the macroblock and will make the bit allocation close to the theoretical value. The parameter C is called overhead rate. In H.263 syntax, some header fields are known before rate control. We can get a new C value by finding these known fields and predicting the others. As mentioned before, the theoretical bit allocated value is usually not the same as the actual bit rate. We find the difference between the theoretical bit allocated value and the actual bit rate. According to the difference value, we update the parameter K by some algorithms. By the simulation results, we can see that the new approach to update K and C will let the actual bit rate closer to the theoretical bit allocated value. Because the new approach is still based on TMN8, we still can have constant frame rate. The benefits are getting greater PSNR and reducing skip blocks in a frame.
Huang, Chien-Chia, e 黃建嘉. "VIF-based Iterative Matrix Perturbation Method for Linear Models Having Collinearity Problems". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/82087871716756616864.
Texto completo da fonte國立交通大學
運輸與物流管理學系
103
Regression modeling has been one of the most useful and important tools for statistical research. Of all the clans in regression modeling, \emph{linear regression} refers to building a linear relationship between a set of \emph{explanatory} variables and a \emph{response} variable, enabling the researchers to examine how those explantory interact with each other and affect the responses. For instance, in econometrics, by having all other factors fixed, one can perform the \emph{ceteris peribus} analysis to examine how a unit change in a given factor affects the outcome by simply looking at the coefficient associated. Others such as biology, physics, environmental science and the likes are the related applicable fields. Thence, its wide applicability renders regression modeling an important tool for scientific studies. Linear regression is favorable in the sense that the estimation can be done by using the ordinary least squares (OLS). The theorey of OLS is so well-founded that it provides a systematic way for researchers to obtain an estimate almost automatically. In the meanwhile, supported by a rich body of statistical inference, OLS has become the core of the regression analysis. Whereas theoretically explanatory variables are assumed independent implicitly in most, if not all, linear models, the analysis proceeds with data given exogenously in practice. Usually, data are collected from a vast unknown population, encompassing certain degree of stochasticity and unpredictability, and thus problems result. For instance, an erroneous input of a data point may likely yield a completely different result for the estimates; missing data points due to certain reasons can be an obstacle for the subsequently analysis; or high similarity (dependency) in the collected data may lead to unsatisfactory results and so like. Problems of this sort are referred to as the \emph{data problems}. Of all data problems in linear regression, we are more concerned about the nearly linear dependency among several factors assumed independent implicitly in the model specification. Numerically, high dependency results directly in rank-deficiency problem in the OLS estimation. The resultant problems, such as high variance, low statistical significance, and even incorrect signs, can frustrate the researchers aiming to model a problem using the regression. Biased regression has been one of the approaches devised in the literature for solving data collinearity problems in linear regression. The most dominant method is this particular category is the ridge regression. Ridge regression has won its fame by its simplicity in implementation in practice and by producing good results. Yet, ridge regression has certain problems. First of all, by definition, the collinearity stems from the dependency between at least two different covariates in the data matrix. Instead of tackling the problem from the root, the ridge method tackles the problem by breaking the intrinsic structure of the correlation matrix, under the assumption that the data matrix is normalized. Second, the breaking the intrinsic structure leads to plausibly good results. In particular, from the persepective of VIF, the results are even infeasible, rendering also the hypothesis testings infeasible, which in turn renders the future inferences infeasible. Third, the ridge method requires a one-dimensional parameter. To find a good parameter for the ridge method, one potentially has to deal with hard optimization problem which is NP-hard in nature. Thence, to even find a local optimal, the computational effort will be quite unfriendly, let alone looking for the global oiptimality. Moreover, a simply local optimal cannot guarantee the performance of the resulting ridge estimate. Motivated by such frustrations, we aim to develope a alternative and useful method, based on the reliable diagnostic tool, to solve the commonly seen problem in the context of linear regression. The developed method is useful becasue our method inherits the merit from matrix theory and mitigates the data collinearity problem by improving not only the values of the underlying diagnostic but also the very intrinsic eigenstructure of the correlation matrix. The close connection between the diagnostic used and the correlation matrix leads to the success of our method in dealing with the problem. We carry out both the real-world applications (when they are accessible) and random instance experiments (when they are inaccessible) to validate the developed method. The success in real-world applications reveals that our method is capable of addressing realistic datasets troubled by the existence of data collinearity. Moreover, from the results of the random instance experiments, we learn that our method has more capability in dealing with arbitrarily generated (with some variabilities well controlled) datasets.
Li, Min-Chi, e 黎旻其. "An Improved Perturbation and Observation method –Based MPPT Controller for Photovoltaic Power System". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/04159949392680073671.
Texto completo da fonte明新科技大學
電機工程研究所
101
Photovoltaic (PV) power system becomes an important alternative due to its merits such as freely available, environment friendly, and less maintenance cost. Hence, the demand of PV power system has increased. Tracking of the maximum power point (MPP) is an important and essential function of most of the PV power system. Every maximum power point tracking (MPPT) technique has its own merits and demerits, but the perturbation and observation (P&O)method is widely used because of its low cost and easy implementation. The P&O method may fail to track the exact MPP when atmospheric conditions change rapidly or the P&O method is not correctly implemented. Many improved P&O methods have been published, but most of these published techniques focus on the adjustment of the perturbation magnitude. The discussions to the effect of sampling time are seldom to be found in the corresponding literatures. Basically, the contributions of the thesis can be summarized as follows. First, a new voltage-boost dc-dc converter for PV power system is proposed, and the corresponding improved P&O method is also proposed to enhance the performance of MPPT when the solar cell module is locally operated on short circuit or open circuit. Secondly, to speed up the convergent time of the P&O method, an index is adopted to judge the steady-state operation mode. Third, a DSP-based PV power system prototype is constructed. And some experimental results are given to demonstrate the performance of the proposed improved P&O method. Finally, a LCL filter-tied grid connected PV system is simulated, and the simulated results can verify the validity.
Liang, Wen-fan, e 梁文凡. "Permittivity and Permeability Iron-based Studies of Nanocrystalline Composite Materials by the Cavity Perturbation Method". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/49472337934415582048.
Texto completo da fonte逢甲大學
航太與系統工程所
96
Resonant cavity perturbation method is a technique to obtain the complex permittivity and permeability of bulk materials or thin films at microwave frequencies. This method uses a microwave resonant circuit to measure the shift of resonant frequency and the change of quality factor in a closed rectangular or circular waveguide. In this study, the accuracy of the resonant cavity perturbation is evaluated by changing the samples sizes and lengths of Teflon and RT/duroid. To verify the formulae used in the calculation of the complex permittivity and permeability, a numerical simulation is also carried out by using Ansoft HFSS to analyze the electromagnetic disturbance in a rectangular waveguide with an open slot for the test samples. Microwave absorbing composites are fabricated by mixing epoxy resin with carbonyl iron, nano-Fe3O4, and conductive carbon black for different weight ratios and then molded in rod shapes. Using the resonant perturbation method, these microwave absorbing composites are measured in X-band and compared with the transmission/reflection method by using a coaxial line. The results show either complex permittivity or permeability of these two methods are rather consistent. The discrepancy becomes large for high permittivity materials. This research provides a simple and reliable method to measure the electromagnetic properties of materials in the microwave frequency range and may benefit the development of new microwave materials and microwave devices.
Zeng, Jin-Yu, e 曾金玉. "Enhanced Maximum Power Point Tracking control Based on Perturbation and observation Method for PV Systems". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/16803803488922117515.
Texto completo da fonte國立雲林科技大學
電子與光電工程研究所碩士班
100
This thesis presents a novel algorithm for tracking maximum power points (MPPs) for a photovoltaic (PV) system. The algorithm which combines a lookup table (LUT) method and a perturbation and observation (P&O) method can quickly and accurately track the MPPs. The LUT method makes the operating points close to MPPs by the linear relationship between the current at the MPPs and the short circuit current. And then the P&O method is adopted to obtain the MPPs. The data of LUT will be updated from the MPPs obtained by the P&O method. Therefore, the proposed method which does not require additional sensor can solve the problems when the system gets old or the data of lookup table has errors. The novel algorithm which is easy to implement does not require the knowledge or specification of PV arrays, and it can work on stand-alone systems or grid-connected systems. The proposed maximum power point tracking controller has been verified with a boost converter by using a digital signal processor (TMS320LF2812).
Xing, X. Q., e Murali Damodaran. "Aerodynamic Shape Design of Nozzles Using a Hybrid Optimization Method". 2003. http://hdl.handle.net/1721.1/3875.
Texto completo da fonteSingapore-MIT Alliance (SMA)