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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.
51

Optimisation of Iterative Multi-user Receivers using Analytical Tools

Shepherd, David Peter, RSISE [sic] January 2008 (has links)
The objective of this thesis is to develop tools for the analysis and optimization of an iterative receiver. These tools can be applied to most soft-in soft-out (SISO) receiver components. For illustration purposes we consider a multi-user DS-CDMA system with forward error correction that employs iterative multi-user detection based on soft interference cancellation and single user decoding. Optimized power levels combined with adaptive scheduling allows for efficient utilization of receiver resources for heavily loaded systems.¶ Metric transfer analysis has been shown to be an accurate method of predicting the convergence behavior of iterative receivers. EXtrinsic Information (EXIT), fidelity (FT) and variance (VT) transfer analysis are well-known methods, however the relationship between the different approaches has not been explored in detail. We compare the metrics numerically and analytically and derive functions to closely approximate the relationship between them. The result allows for easy translation between EXIT, FT and VT methods. Furthermore, we extend the $J$ function, which describes mutual information as a function of variance, to fidelity and symbol error variance, the Rayleigh fading channel model and a channel estimate. These $J$ functions allow the \textit{a priori} inputs to the channel estimator, interference canceller and decoder to be accurately modeled. We also derive the effective EXIT charts which can be used for the convergence analysis and performance predictions of unequal power CDMA systems.¶ The optimization of the coded DS-CDMA system is done in two parts; firstly the received power levels are optimized to minimize the power used in the terminal transmitters, then the decoder activation schedule is optimized such that the multi-user receiver complexity is minimized. The uplink received power levels are optimized for the system load using a constrained nonlinear optimization approach. EXIT charts are used to optimize the power allocation in a multi-user turbo-coded DS-CDMA system. We show through simulation that the optimized power levels allow for successful decoding of heavily loaded systems with a large reduction in the convergence SNR.¶ We utilize EXIT chart analysis and a Viterbi search algorithm to derive the optimal decoding schedule for a multi component receiver/decoder. We show through simulations that decoding delay and complexity can be significantly reduced while maintaining BER performance through optimization of the decoding schedule.
52

數據相關之二階製程管制 / Two-step Process Control for Autocorrelated data

陳維倫, Chen, Wei-Lun Unknown Date (has links)
Most products are produced by several process steps and have more than one interested quality characteristics. If each step of the process is independent, and the observations taken from the process are also independent then we may use Shewhart control chart at each step. However, in many processes, most production steps are dependent and the observations taken from the process are correlated. In this research, we consider the process has two dependent steps and the observations taken from the process are correlated over time. We construct the individual residual control chart to monitor the previous process and the cause-selecting control chart to monitor the current process. Then simulate all the states occur in the process and present the individual residual control chart and the cause-selecting control chart of the simulations. Furthermore compare the proposed control charts with the Hotelling T2 control chart. At last, we give an example to illustrate how to construct the proposed control From the proposed control charts, we can determine which step of the process is out of control easily. If there is a signal in the individual residual control chart, it means the previous process is out of control. If there is a signal in the cause-selecting control chart, it means the current process is out of control. The Hotelling T2 control chart only indicate the process is out of control but does not detect which step of the process is out of control.
53

Application of Tidal Model for Tide Correction in Hydrographic Survey

Lee, Meng-lin 24 August 2007 (has links)
It is necessary to subtracting the tidal height from the observed depth to derived real depth while conduct hydrographic survey. The tidal data can be collected by conventional tide gauge or by using real time kinematics (RTK) GPS survey in the near shore region. However, when setting up tidal instruments in the offshore areas, many restricts still remained due to many factors such as topography, weather, and sea state. On contrary, the RTK GPS survey method has the limitation on the radio transmitting range. Therefore, the tidal zone method integrates the tidal station data to calculate the offshore tide data which can solve these problems. Generally, the tidal zone is constructed by using real tidal station data around the narrow channel. But the tide data is not possible to integrate on both side of the Taiwan Strait due to the vertical datum is not identical due to current political separation. To overcome this problem, this study proposed tidal zone method based on the tidal height derived from a tide numerical model. The tidal zone method is consequently applied to improve the accuracy of the offshore hydrographic survey. After processing the tide data derived from the model output and performing harmonic analysis, this study utilized the analysis result to draw a co-tidal chart to demonstrate the tidal characteristics for the purpose of establishing the tidal zone of the Taiwan Strait. This study also accomplished correspondent tidal zones for all the tide stations of Taiwan west coast within 12 miles territorial waters. This study further proposed a virtual station method for offshore hydrographic survey tide correction which applied the analysis result of each numerical model grid point as a virtual tidal station to derive the offshore tide correction values with spatial continuous characteristics. This study selected three experiment areas based on the multi-beam echo sounder survey data acquired offshore Ma-Liuo tide station. The direct tide station correction, tidal zone correction, and virtual station correction methods are applied to the hydrographic survey data to evaluate the performance of the tidal zone and virtual station correction methods. According to the experiment results, the tidal zone and virtual station correction method improve 20 and 16 cm respectively over the direct tide station correction method in the offshore area with the distance 25 km to the Ma-Liuo tide station. It indicates that the feasibility of the tidal zone method and it can improve the hydrographic survey results significant while the tide characteristics are different. Tidal zone can provide the required information to decide a proper reference tide station according to the tidal characteristics for the hydrographic survey data post-processing.
54

Low-complexity iterative receivers for multiuser space-time block coding systems

Yang, Yajun 31 October 2006
Iterative processing has been shown to be very effective in multiuser space-time block coding (STBC) systems. The complexity and efficiency of an iterative receiver depend heavily on how the log-likelihood ratios (LLRs) of the coded bits are computed and exchanged at the receiver among its three major components, namely the multiuser detector, the maximum a posterior probability (MAP) demodulators and the MAP channel decoders. This thesis first presents a method to quantitatively measure the system complexities with floating-point operations (FLOPS) and a technique to evaluate the iterative receiver's convergence property based on mutual information and extrinsic information transfer (EXIT) charts.<p>Then, an integrated iterative receiver is developed by applying the sigma mappings for M-ary quadrature amplitude modulation (M-QAM) constellations. Due to the linear relationship between the coded bits and the transmitted channel symbol, the multiuser detector can work on the bit-level and hence improves the convergence property of the iterative receiver. It is shown that the integrated iterative receiver is an attractive candidate to replace the conventional receiver when a few receive antennas and a high-order M-QAM constellation are employed.<p> Finally, a more general two-loop iterative receiver is proposed by introducing an inner iteration loop between the MAP demodulators and the MAP convolutional decoders besides the outer iteration loop that involves the multiuser detection (MUD) as in the conventional iterative receiver. The proposed two-loop iterative receiver greatly improves the iteration efficiency. It is demonstrated that the proposed two-loop iterative receiver can achieve the same asymptotic performance as that of the conventional iterative receiver, but with much less outer-loop iterations.
55

Characterization of stress-deformation behaviour of municipal solid waste

Singh, Manoj Kumar 05 September 2008
Several catastrophic failures have occurred during the past two decades, both in engineered as well as non-engineered landfills. In addition, there are numerous instances of significant deformations, although not failure in the sense of significant and rapid downslope mass movement, which may cause sufficient damage to buried gas and leachate collection infrastructure. One such instance was observed in 1999 near the toe of a 75 m high 4H:1V slope at the Brock West Landfill in Ontario, Canada. Significant distortion of gas collection laterals was observed at this site. The present research is an in-depth study intended to examine deformation in landfills based on a detailed study of the mechanical properties of municipal solid waste. Four research objectives were defined based on identified shortcomings and knowledge gaps in the existing literature pertaining to mechanical properties of MSW viz; (a) to develop a method for obtaining intact samples of MSW and to examine the significance of using intact and recompacted samples in characterizing the stress-deformation behaviour of MSW; (b) to characterize MSW shear strength and Youngs modulus of elasticity from interpretation of triaxial test results and to determine the parameters of a non-linear elastic constitutive model as applied to MSW; (c) to measure the evolution of compressibility behaviour of MSW with degradation and verify the mechanism of secondary compression in waste; (d) to develop a simple design chart for predicting lateral deformations in landfills. A comprehensive research program was carried out to address various research objectives - field monitoring of deformations at the Brock West site; triaxial compression tests on large intact and recompacted samples of waste; simulating waste degradation in a large laboratory compression cell; analyzing stress-strain data from various published studies and a numerical modelling study. Interpretation of the effective stress paths followed during shearing in triaxial compression tests suggested that while recompacted samples may be sufficient to characterize shear strength parameters for use in stability analysis of landfill slopes, there might be a benefit in obtaining intact samples to evaluate the deformation characteristics of MSW. A hyperbolic model is proposed to describe the stress-deformation response of waste. The required parameters for this model were determined from evaluation of the results of numerous triaxial tests, both from this study and from the published literature. Observations from the long-term degradation test suggested that degradation has a significant effect on the compressibility of waste and further verifies the mechanism of secondary compression in waste. The coefficient of at-rest lateral pressure was observed to maintain an essentially constant value during combined compression and degradation.<p>The results obtained from the experimental work were combined with the findings of a stochastic numerical modelling study and a statistical evaluation of published data and used to propose a simple design chart for estimating the maximum lateral displacement in a landfill slope. The design chart was developed using results of a finite element parametric study in which the behaviour of the municipal solid waste was modeled using a non-linear elastic hyperbolic model. The design chart incorporates nonlinear variation in unit weight as well as Youngs modulus with depth. The predictions from the design chart were compared with the results of field monitoring of lateral displacement in the instrumented slope at the Brock West landfill and were found to be in good agreement.
56

Low-complexity iterative receivers for multiuser space-time block coding systems

Yang, Yajun 31 October 2006 (has links)
Iterative processing has been shown to be very effective in multiuser space-time block coding (STBC) systems. The complexity and efficiency of an iterative receiver depend heavily on how the log-likelihood ratios (LLRs) of the coded bits are computed and exchanged at the receiver among its three major components, namely the multiuser detector, the maximum a posterior probability (MAP) demodulators and the MAP channel decoders. This thesis first presents a method to quantitatively measure the system complexities with floating-point operations (FLOPS) and a technique to evaluate the iterative receiver's convergence property based on mutual information and extrinsic information transfer (EXIT) charts.<p>Then, an integrated iterative receiver is developed by applying the sigma mappings for M-ary quadrature amplitude modulation (M-QAM) constellations. Due to the linear relationship between the coded bits and the transmitted channel symbol, the multiuser detector can work on the bit-level and hence improves the convergence property of the iterative receiver. It is shown that the integrated iterative receiver is an attractive candidate to replace the conventional receiver when a few receive antennas and a high-order M-QAM constellation are employed.<p> Finally, a more general two-loop iterative receiver is proposed by introducing an inner iteration loop between the MAP demodulators and the MAP convolutional decoders besides the outer iteration loop that involves the multiuser detection (MUD) as in the conventional iterative receiver. The proposed two-loop iterative receiver greatly improves the iteration efficiency. It is demonstrated that the proposed two-loop iterative receiver can achieve the same asymptotic performance as that of the conventional iterative receiver, but with much less outer-loop iterations.
57

Characterization of stress-deformation behaviour of municipal solid waste

Singh, Manoj Kumar 05 September 2008 (has links)
Several catastrophic failures have occurred during the past two decades, both in engineered as well as non-engineered landfills. In addition, there are numerous instances of significant deformations, although not failure in the sense of significant and rapid downslope mass movement, which may cause sufficient damage to buried gas and leachate collection infrastructure. One such instance was observed in 1999 near the toe of a 75 m high 4H:1V slope at the Brock West Landfill in Ontario, Canada. Significant distortion of gas collection laterals was observed at this site. The present research is an in-depth study intended to examine deformation in landfills based on a detailed study of the mechanical properties of municipal solid waste. Four research objectives were defined based on identified shortcomings and knowledge gaps in the existing literature pertaining to mechanical properties of MSW viz; (a) to develop a method for obtaining intact samples of MSW and to examine the significance of using intact and recompacted samples in characterizing the stress-deformation behaviour of MSW; (b) to characterize MSW shear strength and Youngs modulus of elasticity from interpretation of triaxial test results and to determine the parameters of a non-linear elastic constitutive model as applied to MSW; (c) to measure the evolution of compressibility behaviour of MSW with degradation and verify the mechanism of secondary compression in waste; (d) to develop a simple design chart for predicting lateral deformations in landfills. A comprehensive research program was carried out to address various research objectives - field monitoring of deformations at the Brock West site; triaxial compression tests on large intact and recompacted samples of waste; simulating waste degradation in a large laboratory compression cell; analyzing stress-strain data from various published studies and a numerical modelling study. Interpretation of the effective stress paths followed during shearing in triaxial compression tests suggested that while recompacted samples may be sufficient to characterize shear strength parameters for use in stability analysis of landfill slopes, there might be a benefit in obtaining intact samples to evaluate the deformation characteristics of MSW. A hyperbolic model is proposed to describe the stress-deformation response of waste. The required parameters for this model were determined from evaluation of the results of numerous triaxial tests, both from this study and from the published literature. Observations from the long-term degradation test suggested that degradation has a significant effect on the compressibility of waste and further verifies the mechanism of secondary compression in waste. The coefficient of at-rest lateral pressure was observed to maintain an essentially constant value during combined compression and degradation.<p>The results obtained from the experimental work were combined with the findings of a stochastic numerical modelling study and a statistical evaluation of published data and used to propose a simple design chart for estimating the maximum lateral displacement in a landfill slope. The design chart was developed using results of a finite element parametric study in which the behaviour of the municipal solid waste was modeled using a non-linear elastic hyperbolic model. The design chart incorporates nonlinear variation in unit weight as well as Youngs modulus with depth. The predictions from the design chart were compared with the results of field monitoring of lateral displacement in the instrumented slope at the Brock West landfill and were found to be in good agreement.
58

Design of the Opening/Closing Door Mechanism System in the Elevator

Liao, Shu-Mao 30 August 2003 (has links)
The elevator is a common vertical transportation in our life. The elevator door system includes a door driven system, a door coupling, a door safety, and two door locks. The purpose of this work is to develop a systematic methodology for the design of the elevator door system. First, basic characteristics of the elevator door system are deduced, and all possible variants of function structures are synthesized by functional analysis method. Next, a system of kinematic notation is used to generate the principle solutions of each function in the function structure. Finally, all design concept variant can be created by using morphological chart method. Several design concept can be created for new elevator door system.
59

Constructing Service Pathways Model of Hemodialysis Center

Huang, Hong-bin 26 December 2005 (has links)
Introduction The number of the people who needs dialysis escalates rapidly year each. The rising cost of dialysis is relative. Because Bureau National Health Insurance endures the co-payment of hemodialysis, patients have freedom of choice. Two critical factors that influence patient¡¦s decision in medical care are access and quality. Facing pressure from competition, many hemodialysis service providers believe that high quality service will retain patients to return as well as maintain a healthy physician-patient relationship. Therefore, they apply many quality management tools, which also include service pathways. There are few investigations that discuss service pathways. Thus, this research constructs a model to analyze the effect of service pathways in hemodialysis service providers. Method From Nov. 1, 2003 to Dec. 31, 2004, the researcher interviewed hemodialysis nurses to develop flow chart, customer encounter, and check list for hemodialysis. We also collected the check list records of the hemodialysis patients to examine the effect. Conclusion First, the construction of total service pathways comprised three critical interlocking phases: flow chart, customer encounter, and check list. After that we shall evaluate and correct them continuously. Secondly, the researcher found that most patients are routine members, and come from long-term care center and respiratory care ward (RCW). Thirdly, the indicators influencing hemodialysis results and error incidents were steady. Finally, in the value-added services dimensions, the indicators of nurses¡¦ performance on greeting and asking patients if they want to have a meal were significant, but the indicators of telephone and inpatient interview were unfavorable.
60

Reconstructing Data Flow Diagrams from Structure Charts Based on the Input and Output Relationship

YAMAMOTO, Shuichiro 20 September 1995 (has links)
No description available.

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