The statistics from the US Department of Energy show that about one-third of the total consumption of electricity in the households and industries is due to the Air Conditioning and Refrigeration (AC & R) systems. This wide usage has prompted many researchers to develop models for each of the components of the vapor compression systems. However, there has been very little information on developing simulation models that have been validated for the conditions of start-up/shutdown operations as well as vapor compression system faults. This thesis addresses these concerns and enhances the existing modeling library to capture the transients related to the above mentioned conditions. In this thesis, the various faults occurring in a vapor compressor cycle (VCC) have been identified along with the parameters affecting them. The transients of the refrigerant have also been studied with respect to the start-up/shutdown of a vapor compression system. All the simulations related to the faults and start-up/shutdown have been performed using the vapor compression system models developed in MATLAB/Simulink environment and validated against the 3-ton air conditioning unit present in the Thermo-Fluids Control Laboratory at Texas A & M University. The simulation and validation results presented in this thesis can be used to lay out certain rules of thumb to identify a particular fault depending on the unusual behavior of the system thus helping in creating certain fault diagnostic algorithms and emphasize the importance of the study of start-up/shutdown transient characteristics from the point of actual energy efficiency of the systems. Also, these results prove the capability and validity of the finite control volume models to describe VCC system faults and start-up/shutdown transients.

For digital media, the risk of piracy is aggravated by the ease to copy and distribute the content. Watermarking has become the technology of choice for discouraging people from creating illegal copies of digital content. Watermarking is the practice of imperceptibly altering the media content by embedding a message, which can be used to identify the owner of that content. A watermark message can also be a set of instructions for the display equipment, providing information about the content’s usage restrictions. Several applications are considered and three watermarking solutions are provided. First, applications such as owner identification, proof of ownership, and digital fingerprinting are considered and a fast content-dependent image watermarking method is proposed. The scheme offers a high degree of robustness against distortions, mainly additive noise, scaling, low-pass filtering, and lossy compression. This method also requires a small amount of computations. The method generates a set of evenly distributed codewords that are constructed via an iterative algorithm. Every message bit is represented by one of these codewords and is then embedded in one of the image’s 8 × 8 pixel blocks. The information in that particular block is used in the embedding so as to ensure robustness and image fidelity. Two watermarking schemes designed to prevent theatre camcorder piracy are also presented. In these methods, the video is watermarked so that its display is not permitted if a compliant video player detects the watermark. A watermark that is robust to geometric distortions (rotation, scaling, cropping) and lossy compression is required in order to block access to media content that has been recorded with a camera inside a movie theatre. The proposed algorithms take advantage of the properties of the dual-tree complex wavelet transform (DT CWT). This transform offers the advantages of both the regular and the complex wavelets (perfect reconstruction, approximate shift invariance and good directional selectivity). Our methods use these characteristics to create watermarks that are robust to geometric distortions and lossy compression. The proposed schemes are simple to implement and outperform comparable methods when tested against geometric distortions.

In order to validate the appropriate functional characteristics of cartilage, we need to systematically study and understand what constitutes normality and degradation in cartilage. This thesis provides an important step in this direction. To understand the mechanical repercussions of disruption to the matrix properties, cartilage is often artificially degraded using common enzymes. Although the process of artificial degradation does not provide an accurate representation of osteoarthritis, it can provide insight into the biomechanical properties of single matrix components by examining the behaviour of the tissue following its removal. Through histological analysis utilising the optical absorbance measurements of Safranin O stain, this work has demonstrated that for a given time and enzyme concentration, the action of Trypsin on proteoglycans is highly variable and is dependent on: * The initial distribution and concentration of proteoglycans at different depths * The intrinsic sample depth * The location in the joint space, and * The medium type. These findings provide initial data towards a mathematical model which researchers can use to optimise Trypsin treatment of articular cartilage, and therefore model degeneration in vitro with a better degree of certainty. The variability noted in the distribution and concentration of proteoglycans, and most likely the collagen network, creates a large variation in the compressive and tensile stiffness of all samples, and total failure strain energy. The average values for each of these tests indicate that a loss of proteoglycan through Trypsin treatment results in decreased compressive stiffness, increased tensile stiffness, and little change to the failure strains or total failure strain energy. Conversely, disruption to the collagen network shows increased compressive and tensile stiffness, as well as failure strain and total failure strain energy. Due to the large variation in the results for each treatment group, the average values for the treated samples fall within the range of results for normal cartilage. These values cannot therefore be used as dependable parameters to benchmark cartilage, since the parameters for artificially degraded cartilage are within the normal levels. The Yeoh and Polynomial hyperelastic laws were found to best represent the material characteristics of cartilage across the range of tested samples, regardless of differences in health and strength. The results presented here provide important insight into the biomechanical outcomes of artificial degradation and provide direction for future research in this area.

The use of cold-formed steel structures is increasing rapidly around the world due to the many advances in construction and manufacturing technologies and relevant standards. However, the structural behaviour of these thin-walled steel structures is characterised by a range of buckling modes such as local buckling, distortional buckling or flexural torsional buckling. These buckling problems generally lead to severe reduction and complicated calculations of their member strengths. Therefore it is important to eliminate or delay these buckling problems and simplify the strength calculations of cold-formed steel members. The Hollow Flange Beam with two triangular hollow flanges, developed by Palmer Tube Mills Pty Ltd in the mid-1990s, has an innovative section that can delay the above buckling problems efficiently. This structural member is considered to combine the advantages of hot-rolled I-sections and conventional cold-formed sections such as C- and Z-sections (Dempsey, 1990). However, this structural product was discontinued in 1997 due to the complicated manufacturing process and the expensive electric resistance welding method associated with severe residual stresses (Doan and Mahendran, 1996). In this thesis, new fastening methods using spot-weld, screw fastener and self-pierced rivet were considered for the triangular Hollow Flange Beams (HFBs) and the new rectangular hollow flange beams (RHFBs). The structural behaviour of these types of members in axial compression was focused in this research project. The objective of this research was to develop suitable design models for the members with triangular and rectangular hollow flanges using new fastening methods so that their behaviour and ultimate strength can be predicted accurately under axial compression. In the first stage of this research a large number of finite element analyses (FEA) was conducted to study the behaviour of the electric resistance welded, triangular HFBs (ERW-HFBs) under axial compression. Experimental results from previous researchers were used to verify the finite element model and its results. Appropriate design rules based on the current design codes were recommended. Further, a series of finite element models was developed to simulate the corresponding HFBs fastened using lap-welds (called LW-HFBs) and screw fasteners or spot-welds or self-piercing rivets (called S-HFBs). Since the test specimens of LW-HFBs and S-HFBs were unavailable, the finite element results were verified by comparison with the experimental results of ERW-HFB with reasonable agreement. In the second stage of this research, a total of 51 members with rectangular hollow flanges including the RHFBs made from a single plate and 3PRHFBs made from three plates fastened with spot-welds and screws was tested under axial compression. The finite element models based on the tests were then developed that included the new fasteners, contact simulations, geometric imperfections and residual stresses. The improved finite element models were able to simulate local buckling, yielding, global buckling and local/global buckling interaction failure associated with gap opening as agreed well with the corresponding full-scale experimental results. Extensive parametric studies for the RHFBs made from a single plate and the 3PRHFBs made from three plates were undertaken using finite element analyses. The analytical results were compared with the predictions using the current design rules based on AS 4100, AS/NZS 4600 and the new direct strength method. Appropriate design formulae based on the direct strength method for RHFBs and 3PRHFBs were developed. This thesis has thus enabled the accurate prediction of the behaviour and strength of the new compression members with hollow flanges and paved the way for economical and efficient use of these members in the industry.

Articular cartilage disorders are a leading cause of human disability in many countries around the world. In this work, new techniques and strategies were developed to improve the quality of cartilage produced in vitro by methods of tissue engineering. Chondrocytes were isolated from the hip and knee joints of aborted human foetuses. The cells were expanded and seeded into scaffolds and the seeded scaffolds were cultured in perfusion bioreactors. The quality of the final cartilage constructs was assessed biochemically by measuring their content of glycosaminoglycan (GAG), total collagen and collagen type II and histologically by staining cross-sections of the constructs for GAG, collagen type I and collagen type II. The amount of proteoglycan released in the culture medium was also measured at regular intervals. Proteoglycans from tissue-engineered cartilage and spent culture medium were compared and analysed for degradation and capability of aggregation. During monolayer expansion, the chondrocyte differentiation indices decreased, the cell size increased and the percentage of cells present in G2/S??M phase decreased with the greatest changes occurring during the first passage. Expanding chondrocytes in PGA or PGA??alginate scaffolds produced cells with a higher level of differentiation than monolayer-expanded cells. However, PGA and PGA??alginate could not be justified as suitable systems for the routine expansion of chondrocytes mainly because of the relatively low cell proliferation obtained. Two new methods for seeding of cells into scaffolds were investigated using PGA and PGA??alginate as scaffold materials. Both methods produced high seeding efficiencies and homogeneous distribution of cells. When seeded PGA??alginate scaffolds were cultured in perfusion bioreactors, they produced good quality constructs with higher concentrations of extracellular matrix (ECM) components compared with previously described methods. However, when seeded PGA scaffolds were cultured in perfusion bioreactors, they produced small constructs of poor quality. Investigation of the effect of medium flow rate on the PGA scaffolds showed that a low flow rate was needed at the beginning of the culture to enable the cells to form a framework onto which other synthesised elements could deposit. Applying a gradual increase in medium flow rate to PGA scaffolds cultured in perfusion bioreactors solved the shrinkage problem and produced constructs with quality similar to those produced using PGA??alginate scaffolds. A novel compression bioreactor that mimicked the physiological stimulation of cartilage by joint movement was constructed. Using this bioreactor, compressed constructs showed significantly higher wet weight and higher concentrations of GAG, total collagen and collagen type II compared with non-compressed constructs.

Compression and information retrieval are two areas of document management that exist separately due to the conflicting methods of achieving their goals. This research examines a mechanism which provides lossless compression and phrase-based browsing and searching of large document collections. The framework for the investigation is an existing off-line dictionary-based compression algorithm. (For complete abstract open document)

Pinus radiata is by far the dominant species grown in New Zealand plantations as a renewable source of wood. Several wood quality issues have been identified in the material produced, including the high incidence of compression wood, which is undesirable for end users. At present our understanding of the complex array of developmental processes involved in wood formation (which has a direct bearing on wood quality) is limited. Hence, the forest industry is interested in attaining a better understanding of the processes involved. Towards this goal, and for reasons of biological curiosity, the experiments described in this thesis were carried out to investigate several aspects of xylem cell development. In an in arbor study, changes in the orientation of cortical microtubules and cellulose microfibrils were observed in developing tracheids. Results obtained provide evidence that cortical microtubules act to guide cellulose synthase complexes during secondary wall formation in tracheids. The mechanisms involved in controlling cell wall deposition in wood cells are poorly understood, and are difficult to study, especially in arbor. A major part of this thesis involved the development of an in vitro method for culturing radiata pine wood in which hormone levels, nutrients, sugars and other factors, could be controlled without confounding influences from other parts of the tree. The method developed was used in subsequent parts of this thesis to study compression wood development, and the influence of the hormone gibberellin on cellulose microfibril organisation in the cell wall. Results from the in vitro compression wood experiments suggested that: 1. when a tree is growing at a lean, the developing cell wall was able to perceive compressive forces generated by the weight of the rest of the tree, rather than perceive the lean per se. 2. ethylene, rather than auxin, was involved in the induction of compression wood. Culture of stem explants with gibberellin resulted in wider cells, with steeper cortical microtubules, and correspondingly steeper cellulose microfibrils in the S2 layer of developing wood cells. This observation provides further evidence that the orientation of microtubules guides the orientation of cellulose microfibrils. Overall, the work described in this thesis furthers our knowledge in the field of xylem cell development. The stem culture protocol developed will undoubtedly provide a valuable tool for future studies to be carried out.

Articular cartilage disorders are a leading cause of human disability in many countries around the world. In this work, new techniques and strategies were developed to improve the quality of cartilage produced in vitro by methods of tissue engineering. Chondrocytes were isolated from the hip and knee joints of aborted human foetuses. The cells were expanded and seeded into scaffolds and the seeded scaffolds were cultured in perfusion bioreactors. The quality of the final cartilage constructs was assessed biochemically by measuring their content of glycosaminoglycan (GAG), total collagen and collagen type II and histologically by staining cross-sections of the constructs for GAG, collagen type I and collagen type II. The amount of proteoglycan released in the culture medium was also measured at regular intervals. Proteoglycans from tissue-engineered cartilage and spent culture medium were compared and analysed for degradation and capability of aggregation. During monolayer expansion, the chondrocyte differentiation indices decreased, the cell size increased and the percentage of cells present in G2/S??M phase decreased with the greatest changes occurring during the first passage. Expanding chondrocytes in PGA or PGA??alginate scaffolds produced cells with a higher level of differentiation than monolayer-expanded cells. However, PGA and PGA??alginate could not be justified as suitable systems for the routine expansion of chondrocytes mainly because of the relatively low cell proliferation obtained. Two new methods for seeding of cells into scaffolds were investigated using PGA and PGA??alginate as scaffold materials. Both methods produced high seeding efficiencies and homogeneous distribution of cells. When seeded PGA??alginate scaffolds were cultured in perfusion bioreactors, they produced good quality constructs with higher concentrations of extracellular matrix (ECM) components compared with previously described methods. However, when seeded PGA scaffolds were cultured in perfusion bioreactors, they produced small constructs of poor quality. Investigation of the effect of medium flow rate on the PGA scaffolds showed that a low flow rate was needed at the beginning of the culture to enable the cells to form a framework onto which other synthesised elements could deposit. Applying a gradual increase in medium flow rate to PGA scaffolds cultured in perfusion bioreactors solved the shrinkage problem and produced constructs with quality similar to those produced using PGA??alginate scaffolds. A novel compression bioreactor that mimicked the physiological stimulation of cartilage by joint movement was constructed. Using this bioreactor, compressed constructs showed significantly higher wet weight and higher concentrations of GAG, total collagen and collagen type II compared with non-compressed constructs.

Thesis (Ph.D.)--University of Melbourne, Dept. of Computer Science and Software Engineering, 2004. / Typescript (photocopy). Includes bibliographical references (leaves 247-263).

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 33-34). Also available on the World Wide Web.