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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
201

A Study of Post-Weld-Shift Measurement Technology in Cylindrical-Type Laser Diode Module Packages

He, Yue-Lin 12 July 2004 (has links)
The objective of this study is to investigate the technique of the PWS (Post-Weld-Shift) measurement in cylindrical-type laser diode module packaging processes. Including measure the shift in focus plane and the run-out between the axis of laser diode and optical fiber. The objective of this technique is to quantify the PWS in packaging processes. This technique can improve the efficient of the laser hammering technique. The measurement technique developed in this study employs a laser displacement meter (Keyence LC-2430) to measure the profile and position the upper housing of laser diode module. Using the concepts of ellipse and symmetric figure, the Ellipse Fitting Method (EFM) and the Symmetric Center Method (SCM) are developed. A simulation program is coded for discussing the relationship between the measurement error and the roundness of the optical fiber housing. Finally, these measuring technique are applied on the laser diode module packaging system (Newport-LW4000) to measure the PWS. The experimental measuring data of PWS is 3.5£gm, which is reasonable in compare to the estimate alignment offset (2.9£gm to 5.9£gm) by the coupling efficiency method. Therefore it is believed that the technique developed in this study is feasible and practical.
202

Optimum Designs for Model Discrimination and Estimation in Binary Response Models

Hsieh, Wei-shan 29 June 2005 (has links)
This paper is concerned with the problem of finding an experimental design for discrimination between two rival models and for model robustness that minimizing the maximum bias simultaneously in binary response experiments. The criterion for model discrimination is based on the $T$-optimality criterion proposed in Atkinson and Fedorov (1975), which maximizes the sum of squares of deviations between the two rival models while the criterion for model robustness is based on minimizing the maximum probability bias of the two rival models. In this paper we obtain the optimum designs satisfy the above two criteria for some commonly used rival models in binary response experiments such as the probit and logit models etc.
203

Optimization of Code-Constellation for M-ary CDMA Systems

Chen, Yang-Wen 02 September 2006 (has links)
In this thesis, we propose and evaluate quasi-optimal algorithms for solving the code-constellation optimization problem in M-ary CDMA system. The M-ary CDMA system is a new CDMA architecture. The more spreading codes used in each user, and the higher bandwidth efficiency can achieve with more bits packed in each symbol. We use a code, which we refer to as ¡§mapping code¡¨, to help form a multidimensional spherical code-constellation. The M codewords of the mapping code correspond one-to-one to the M points on the code-constellation. Thus, the code-constellation optimization problem is a combinatorial optimization problem. We present that an exhaustive search (ES) algorithm would have compute and check all possible subset, and then this problem becomes a NP-hard. Based on the exhaustive search algorithm, we propose symmetric points search (SPS) algorithm to reduce computation complexity, but it is not optimal algorithm. In addition, we propose a quasi-optimal algorithm, namely Manhattan distance search (MDS) algorithm. Numerical results and comparisons are provided to illustrate that the computation complexity of the Manhattan distance search algorithm increases linearly with dimension of code-constellation and its performance is better than others.
204

Novel Studies On The Chemoenzymatic Synthesis Of Polychlorinated Bicyclic Systems And The Synthesis Of C2 And C3 Symmetric Chiral Ligands

Turkmen, Yunus Emre 01 July 2006 (has links) (PDF)
Optically active polychlorinated bicyclic systems are important starting materials for the synthesis of complex target molecules. In the first part of the study, the syntheses of several racemic and meso hexachloronorbornene derivatives were executed successfully, starting from hexachlorocyclopentadiene. The enantio-enriched acetoxymethyl derivative (-)-2 and the hemiester (-)-6 were synthesized in high e.e. values by using several hydrolase type enzymes. The absolute configuration of (-)-2 was determined by transforming it to the corresponding norbornene derivative (-)-7 with known absolute configuration. In the second part of the study, C2 symmetric chiral ligand (-)-11 and C3 symmetric chiral triamide derivative (-)-12 were synthesized in high chemical yields starting from L-proline. In connection to these studies, the syntheses of the monoamide derivative (-)-14 and the C2 symmetric diamide derivative (-)-15 were achieved by using appropriate amounts of L-proline.
205

Pairwise Multiple Comparisons Under Short-tailed Symmetric Distribution

Balci, Sibel 01 May 2007 (has links) (PDF)
In this thesis, pairwise multiple comparisons and multiple comparisons with a control are studied when the observations have short-tailed symmetric distributions. Under non-normality, the testing procedure is given and Huber estimators, trimmed mean with winsorized standard deviation, modified maximum likelihood estimators and ordinary sample mean and sample variance used in this procedure are reviewed. Finally, robustness properties of the stated estimators are compared with each other and it is shown that the test based on the modified maximum likelihood estimators has better robustness properties under short-tailed symmetric distribution.
206

Time Memory Trade Off Attack On Symmetric Ciphers

Saran, Nurdan A. 01 February 2009 (has links) (PDF)
Time Memory Trade O (TMTO) is a cryptanalytic method that aims to develop an attack which has a lower memory complexity than lookup table and a lower online time complexity than exhaustive search. TMTO methods are widely studied in the literature and used for inverting various cryptosystems. We focus on the design and the analysis of TMTO on symmetric ciphers in this thesis. Firstly, the summary of the random mapping statistics from the view point of TMTO is presented. We also recalculate some expected values with a simpler approach than the existing proofs. Then, we propose some variant constructions and also present three new distinguishers based on random mappings. Next, we provide a detailed analysis of the success rate of two main improvements of the attack / Distinguished Point Method and Rainbow Method. Finally, we discuss the adjustment of the parameters to achieve a high success rate. To support our theoretical framework, we also present empirical results of our analysis to actual ciphers.
207

Robust Estimation And Hypothesis Testing In Microarray Analysis

Ulgen, Burcin Emre 01 August 2010 (has links) (PDF)
Microarray technology allows the simultaneous measurement of thousands of gene expressions simultaneously. As a result of this, many statistical methods emerged for identifying differentially expressed genes. Kerr et al. (2001) proposed analysis of variance (ANOVA) procedure for the analysis of gene expression data. Their estimators are based on the assumption of normality, however the parameter estimates and residuals from this analysis are notably heavier-tailed than normal as they commented. Since non-normality complicates the data analysis and results in inefficient estimators, it is very important to develop statistical procedures which are efficient and robust. For this reason, in this work, we use Modified Maximum Likelihood (MML) and Adaptive Maximum Likelihood estimation method (Tiku and Suresh, 1992) and show that MML and AMML estimators are more efficient and robust. In our study we compared MML and AMML method with widely used statistical analysis methods via simulations and real microarray data sets.
208

Effect Of Symmetry On Recognition Of Unfamiliar Faces

Yildirim, Gulsen 01 December 2010 (has links) (PDF)
In the literature, there exist several studies on recognition memory performance for faces and related facial characteristics such as distinctiveness, typicality, attractiveness. In our study, we examined the relationship between symmetry and human face recognition for the first time. In order to have symmetry as the only manipulated factor in our stimuli, we constructed a unique face database, METUFaceTwo, which contains standardized symmetric and asymmetric face images without facial textures. In our study, we assumed that faces and related features such as symmetry are perceived holistically, and defined facial symmetry with two different measures: entropy calculations and perceived symmetry values. Our fundamental finding is that symmetry increases recognition performance. This increase seems to be due to the additional study time or additional effort spent for symmetric face images during the recall period rather than the encoding period. More studies need to be performed in order to isolate the causes of this surprising finding.
209

The design and implementation of security and networking co-processors for high performance SoC applications

Chung, Kuo-huang 23 January 2003 (has links)
With the development of Internet, there are more and more applications around us are connected tightly with it. Security of network is important. This thesis will follow OSI 7-layers architecture, which defined by ISO, to propose several hardware improvement approaches of network security. In data-link layer, we improve performance of CRC calculation with parallel CRC calculation, such that a 32-bit data can be finished using CRC calculation in one cycle. In network layer and transport layer, bit-oriented instruction set has good performance for processing packet header. In application, we implement DES and AES algorithm in hardware. We integrate all hardware module with ARM7TDMI coprocessor¡¦s interface. Finally, we download integrated circuit into Xilinx XCV2000E chip to observe its demo to verify it.
210

Robust D-optimal designs for mixture experiments in Scheffe models

Hsu, Hsiang-Ling 10 July 2003 (has links)
A mixture experiment is an experiment in which the q-ingredients {xi,i=1,...,q} are nonnegative and subject to the simplex restriction sum_{i=1}^q x_i=1 on the (q-1)-dimensional probability simplex S^{q-1}. In this work, we investigate the robust D-optimal designs for mixture experiments with consideration on uncertainties in the Scheffe's linear, quadratic and cubic model without 3-way effects. The D-optimal designs for each of the Scheffe's models are used to find the robust D-optimal designs. With uncertianties on the Scheffe's linear and quadratic models, the optimal convex combination of the two model's D-optimal designs can be proved to be a robust D-optimal design. For the case of the Scheffe's linear and cubic model without 3-way effects, we have some numerical results about the robust D-optimal designs, as well as that for Scheffe's linear, quadratic and cubic model without 3-way effects. Ultimately, we discuss the efficiency of a maxmin type criterion D_r under given the robust D-optimal designs for the Scheffe's linear and quadratic models.

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