Mcmc- Based Optimization And Application

In the thesis, we study the theory of Markov Chain Monte Carlo (MCMC) and its application in statistical optimization. The MCMC method is a class of evolutionary algorithms for generating samples from given probability distributions. In the thesis, we first focus on the methods of slice sampling and simulated annealing. While slice sampling has a merit to generate samples based on the underlying distribution with adjustable step size, simulated annealing can facilitate samples to jump out of local optima and converge quickly to the global optimum. With this MCMC method, we then solve two practical optimization problems. The first problem is image transmission over varying channels. Existing work in media transmission generally assumes that channel condition is stationary. However, communication channels are often varying with time in practice. Adaptive design needs frequent feedback for channel updates, which is often impractical due to the complexity and delay. In this application, we design an unequal error protection scheme for image transmission over noisy varying channels based on MCMC. First, the problem cost function is mapped into a multi-variable probability distribution. Then, with the “detailed balance , MCMC is used to generate samples from the mapped stationary distribution so that the optimal solution is the one that gives the lowest data distortion. We also show that the final rate allocation designed with this method works better than a conventional design that considers the mean value of the channel. In the second application, we consider a terminal-location-planning problem for intermodal transportation systems. With a given number of potential locations, it needs to find the most appropriate number of terminals and their locations to provide the economically most efficient operation when multiple service pairs exist simultaneously. The problem also has an inherent issue that for a particular planning, the optimal route paths must be determined for the co-existing service pairs. To solve this NP-hard problem, we design a MCMC-based two-layer method. The lower-layer is an optimal routing design for all service pairs given a particular planning that considers both efficiency and fairness. The upper-layer is finding the optimal planning based on MCMC with the stationary distribution that is mapped from the cost function. The effectiveness of this method is demonstrated through computer simulations and comparison with one state-of-the-art method. The work of this thesis has shown that a MCMC-method, consisting of both slice sampling and simulated annealing, can be successfully applied to solving practical optimization problems. Particularly, the method has advantages in dealing with high-dimensional problems with large searching spaces

Research and developments of distributed video coding

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.The recent developed Distributed Video Coding (DVC) is typically suitable for the applications such as wireless/wired video sensor network, mobile camera etc. where the traditional video coding standard is not feasible due to the constrained computation at the encoder. With DVC, the computational burden is moved from encoder to decoder. The compression efficiency is achieved via joint decoding at the decoder. The practical application of DVC is referred to Wyner-Ziv video coding (WZ) where the side information is available at the decoder to perform joint decoding. This join decoding inevitably causes a very complex decoder. In current WZ video coding issues, many of them emphasise how to improve the system coding performance but neglect the huge complexity caused at the decoder. The complexity of the decoder has direct influence to the system output. The beginning period of this research targets to optimise the decoder in pixel domain WZ video coding (PDWZ), while still achieves similar compression performance. More specifically, four issues are raised to optimise the input block size, the side information generation, the side information refinement process and the feedback channel respectively. The transform domain WZ video coding (TDWZ) has distinct superior performance to the normal PDWZ due to the exploitation in spatial direction during the encoding. However, since there is no motion estimation at the encoder in WZ video coding, the temporal correlation is not exploited at all at the encoder in all current WZ video coding issues. In the middle period of this research, the 3D DCT is adopted in the TDWZ to remove redundancy in both spatial and temporal direction thus to provide even higher coding performance. In the next step of this research, the performance of transform domain Distributed Multiview Video Coding (DMVC) is also investigated. Particularly, three types transform domain DMVC frameworks which are transform domain DMVC using TDWZ based 2D DCT, transform domain DMVC using TDWZ based on 3D DCT and transform domain residual DMVC using TDWZ based on 3D DCT are investigated respectively. One of the important applications of WZ coding principle is error-resilience. There have been several attempts to apply WZ error-resilient coding for current video coding standard e.g. H.264/AVC or MEPG 2. The final stage of this research is the design of WZ error-resilient scheme for wavelet based video codec. To balance the trade-off between error resilience ability and bandwidth consumption, the proposed scheme emphasises the protection of the Region of Interest (ROI) area. The efficiency of bandwidth utilisation is achieved by mutual efforts of WZ coding and sacrificing the quality of unimportant area. In summary, this research work contributed to achieves several advances in WZ video coding. First of all, it is targeting to build an efficient PDWZ with optimised decoder. Secondly, it aims to build an advanced TDWZ based on 3D DCT, which then is applied into multiview video coding to realise advanced transform domain DMVC. Finally, it aims to design an efficient error-resilient scheme for wavelet video codec, with which the trade-off between bandwidth consumption and error-resilience can be better balanced

Optimal Progressive Image Transmission Over Rayleigh Fading Channels

A fixed-packet optimal joint source channel coding scheme for transmission of progressive images over Rayleigh channels is proposed. A first order Markov model is used in rate allocation problem to concern channel temporal variations during image transmission. Also, introducing a modification on the used progressive coding scheme, the requirement for the immediate decoding termination upon the observation of an erroneous packet is relatively relaxed. A rate allocation mechanism for this modified version of progressive codes is also proposed

Implementation of Self-Consolidating Concrete for Bridge Applications

Self-Consolidating Concrete (SCC) typically refers to a highly-flowable classification of high-performance concrete. Unlike traditional concrete, SCC has the potential ability to flow into and completely fill complex forms under its own weight. A well-designed SCC mix does not need to be vibrated for compaction, unlike a traditional vibrated concrete (TVC) mix. This gives the use of SCC the potential advantages of reduced placement costs and a more worker-friendly construction environment due to the elimination of construction noise and the added ease of placement. The primary objective of this study was to work with contractors, WVDOT officials in order to safely utilize SCC technology on the Stalnaker Run Bridge Replacement, which would be the first WVDOT bridge construction project to utilize SCC. SCC was incorporated for cast-in-place caissons as well as precast/prestressed beam components.;Prior to use of a 4,500 psi mix for the caisson applications, deemed SCC-1, a novel test procedure was developed to assess the uniformity of SCC within a model caisson member. Instead of allowing the entire mock section of SCC to harden prior to dissecting it for core samples, fresh core tubes were used to sample the SCC while it was still green. After hardening, the wet cores revealed non-uniformities in the aggregate distribution and hardened properties of the mix as placed within the trial caisson. Despite the non-homogeneity, tests did not indicate a relationship between the absence of aggregates and detrimental effects on the hardened properties of the SCC-1.;SCC-1 was used for the construction of the caissons of Abutment 1, while a traditional caisson mix was used for Abutment 2. Samples taken during casting of the caissons revealed that both caisson mixes exceeded the minimum strength requirement, and specimens of both types exhibited approximately the same modulus of elasticity, around 4,400 ksi. The SCC-1 mix exhibited low Rapid Chloride Permeability and was deemed freeze-thaw durable based on ASTM C 666 testing.;Three precast/prestressed box beams for the Stalnaker Run Bridge were fabricated using a traditional vibrated concrete and two were cast using SCC-2, both of which required a strength of 8,000 psi. Additionally, one extra beam was fabricated and shipped to WVU facilities for testing. All beams were instrumented with a barrage of gages prior to casting. After casting, the SCC-2 mix required 2 nights of steam curing prior to detensioning, while the TVC needed only one. Temperature data collected during curing of the beams indicated maximum temperatures of around 160°F to 170°F, which fall below the PCI-prescribed threshold of 180°F. Specimens collected during construction of the Stalnaker Run Bridge showed some major differences in the hardened behaviors of SCC-2 and TVC. The TVC has a higher modulus of elasticity than the SCC-2 concrete, both at detensioning (19% higher) and at 28 days (21.0% higher). Durability testing of SCC-2 specimens indicate that the SCC-2 concrete from production may not be freeze-thaw durable, and not all specimens exhibited the required durability factor of 80% per project specifications. Results of RCPT testing of both types of concrete would classify SCC-2 as having predominately moderate permeability, while the TVC would be classified as having high permeability.;The laboratory beam underwent both destructive and non-destructive testing. The effective prestress in the beam calculated using the observed decompression behavior of the beam (Pe = 707.5 kips or fpe = 159.7 ksi), was within 1.5% of a direct measurement of the residual strain based on strand strain readings, which were taken directly from the strand strain gage readings. The test beam exhibited higher deflection and lower capacity at cracking than the theoretical behavior using PCI design values. Adjustments of the material properties to measured values for SCC-2 gave a good correlation between theoretical and observed load-deflection behaviors. The results of the non-destructive modal analysis did not correlate well with the damage state of the prestressed beam.;Strain data from the Stalnaker Run Bridge data collection station is being collected incrementally. Over a four month period, the magnitudes of measured strain change in the prestressing strand gages ranged from 200 microstrain to 400 microstrain, and 200 microstrain to 500 microstrain for the SCC-2 and TVC beams, respectively. The rate of change in the strain readings for the beams has since decreased drastically

A Study on the Usage of Cross-Layer Power Control and Forward Error Correction for Embedded Video Transmission over Wireless Links

Cross-layering is a design paradigm for overcoming the limitations deriving from the ISO/OSI layering principle, thus improving the performance of communications in specific scenarios, such as wireless multimedia communications. However, most available solutions are based on empirical considerations, and do not provide a theoretical background supporting such approaches. The paper aims at providing an analytical framework for the study of single-hop video delivery over a wireless link, enabling cross-layer interactions for performance optimization using power control and FEC and providing a useful tool to determine the potential gain deriving from the employment of such design paradigm. The analysis is performed using rate-distortion information of an embedded video bitstream jointly with a Lagrangian power minimization approach. Simulation results underline that cross-layering can provide relevant improvement in specific environments and that the proposed approach is able to capitalize on the advantage deriving from its deployment

Short term sensory and vascular responses to physical agent modalities and exercise in healthy volunteers and patients with distal radius fracture.

Currently, there is weak evidence on the effectiveness of different rehabilitation regimens following distal radius fracture (DRF). This thesis evaluated sensory and vascular effects of exercise, thermal and ultrasound interventions that can be used in the mobilization phase (cast removal) after DRF. Methods This thesis includes 3 studies. The first study compared responses to Immersion in Cold water Evaluation (ICE) in the DRF and uninjured hands. Skin blood flow (Sbf), skin temperature (temp.) and sensory perception thresholds (sPT) at 2000Hz for A –beta fibres and at 5 Hz for C fibres were obtained before, immediately after ICE and 10 min later. The second study assessed Sbf, temp., and sPT before and after 3 conditions: control, 1 MHz continuous and 3 MHz pulsed US in healthy subjects. The third study assessed Sbf and sPT before and after 3 conditions: control, 5 min of high intensity and low intensity hand exercises in healthy subjects. Differences in these were analyzed using General Linear Models. Results In the DRF hand, Sbf increased (Mean Difference (MD) = -42.2 A.U.) immediately, at 1 min (MD= -35 A.U.), and 10 min after ICE (MD= -1 A.U.). There was a decrease in temp. for the index and little fingers immediately after ICE (MD=9. 9 & 9.1 o C) and these did not return to baseline by 10 min (MD= 4.4 & 4 o C). ICE had no effect on sPT at 5 Hz (p\u3e0.05). There was no difference between the DRF and uninjured hand on all measures(p\u3e0.05) except for the sPT at 2000Hz, which remained high on the DRF side for up to 10 min( MD= -1.8 m. A.). Both pulsed and continuous US caused small to moderate reductions in Sbf (MD= 2.8 A.U. & 3.9 A.U.), temp. (MD = 2.5 0 C & 1.1 0 C) and sPT at 5 Hz (MD=1.3 m. A. & 1 m. A.). US had no effect on sPT at 2000Hz (p\u3e0.05). Both type of exercises were insufficient to alter Sbf and sPT at 2000Hz and 5 Hz (p\u3e0.05). Conclusions Normal thermo-physiological responses were observed after ICE in both hands. A-beta fibres on the DRF side became less sensitive after ICE. Minor changes can occur in Sbf, temp., and sPT at 5 Hz following 3 to 5 min exposure to US in healthy subjects. Hand grip exercises had minimal impact on Sbf or sPT in healthy subjects. The changes seen with ICE and US are presumed to help with tissue healing and pain modulation which needs further investigation

REGION-BASED ADAPTIVE DISTRIBUTED VIDEO CODING CODEC

The recently developed Distributed Video Coding (DVC) is typically suitable for the applications where the conventional video coding is not feasible because of its inherent high-complexity encoding. Examples include video surveillance usmg wireless/wired video sensor network and applications using mobile cameras etc. With DVC, the complexity is shifted from the encoder to the decoder. The practical application of DVC is referred to as Wyner-Ziv video coding (WZ) where an estimate of the original frame called "side information" is generated using motion compensation at the decoder. The compression is achieved by sending only that extra information that is needed to correct this estimation. An error-correcting code is used with the assumption that the estimate is a noisy version of the original frame and the rate needed is certain amount of the parity bits. The side information is assumed to have become available at the decoder through a virtual channel. Due to the limitation of compensation method, the predicted frame, or the side information, is expected to have varying degrees of success. These limitations stem from locationspecific non-stationary estimation noise. In order to avoid these, the conventional video coders, like MPEG, make use of frame partitioning to allocate optimum coder for each partition and hence achieve better rate-distortion performance. The same, however, has not been used in DVC as it increases the encoder complexity. This work proposes partitioning the considered frame into many coding units (region) where each unit is encoded differently. This partitioning is, however, done at the decoder while generating the side-information and the region map is sent over to encoder at very little rate penalty. The partitioning allows allocation of appropriate DVC coding parameters (virtual channel, rate, and quantizer) to each region. The resulting regions map is compressed by employing quadtree algorithm and communicated to the encoder via the feedback channel. The rate control in DVC is performed by channel coding techniques (turbo codes, LDPC, etc.). The performance of the channel code depends heavily on the accuracy of virtual channel model that models estimation error for each region. In this work, a turbo code has been used and an adaptive WZ DVC is designed both in transform domain and in pixel domain. The transform domain WZ video coding (TDWZ) has distinct superior performance as compared to the normal Pixel Domain Wyner-Ziv (PDWZ), since it exploits the ' spatial redundancy during the encoding. The performance evaluations show that the proposed system is superior to the existing distributed video coding solutions. Although the, proposed system requires extra bits representing the "regions map" to be transmitted, fuut still the rate gain is noticeable and it outperforms the state-of-the-art frame based DVC by 0.6-1.9 dB. The feedback channel (FC) has the role to adapt the bit rate to the changing ' statistics between the side infonmation and the frame to be encoded. In the unidirectional scenario, the encoder must perform the rate control. To correctly estimate the rate, the encoder must calculate typical side information. However, the rate cannot be exactly calculated at the encoder, instead it can only be estimated. This work also prbposes a feedback-free region-based adaptive DVC solution in pixel domain based on machine learning approach to estimate the side information. Although the performance evaluations show rate-penalty but it is acceptable considering the simplicity of the proposed algorithm. vii