Breaking Symmetries and Constraints: Transitions from 2D to 3D in Passive Walkers

The inherent dynamics of bipedal, passive mechanisms are studiedto investigate the relation between motions constrained to two-dimensional (2D)planes and those free to move in a three-dimensional (3D) environment. Inparticular, we develop numerical and analytical techniques usingdynamical-systems methodology to address the persistence and stabilitychanges of periodic, gait-like motions due to the relaxation ofconfiguration constraints and the breaking of problem symmetries. Theresults indicate the limitations of a 2D analysis to predictthe dynamics in the 3D environment. For example, it is shownhow the loss of constraints may introduce characteristically non-2Dinstability mechanisms, and how small symmetry-breaking terms may result inthe termination of solution branches.     

Low-frequency quadrature mode birdcage resonator

The birdcage resonator is frequently used in conventional MRI because of its excellent attributes. Its use in low-field MRI is restricted to field strengths higher than, for example, 0.1 T, dependent on the size of the coil. This is because of the intrinsically low inductance value of the birdcage coils. Furthermore, the sensitivity of the birdcage at low field strengths is significantly lower when compared to, for example, the solenoid. Both problems can be overcome with the multiturn technique and a novel wound birdcage coil. The quadrature mode wound birdcage coil presented in this paper can be used at frequencies as low as 100 kHz. Its sensitivity is also increased when compared to the conventional strip-ring birdcage. Homogeneity effective volume, and methods to increase the resonator bandwidth to match the signal bandwidth are left intact. The latter is a typical low-field problem.     

用于去除单张图像高光的光照约束补色

在计算机视觉研究领域,如何检测和消除图像中的高光(specular)一直是个热点问题,有关的研究结果对于提高计算机视觉算法性能有着重要的影响.针对这一问题,提出了一种检测和消除高光的方法.首先,通过比较高光和漫反射光(diffuse)的色度特性的不同,给出了一种交互检测单色物体表面高光区域的方法;然后,引入补色(inpainting)方法并结合光照约束条件,设计了一种去除单张图像中高光并还原出漫反射分量的新的补色算法.与一般补色方法不同,该算法充分利用了高光区域含有的信息来指导补色过程.通过综合利用观测到的像素值、光源的色度分析(illumination chromaticity analysis)、光源颜色的平滑性等来约束补色过程,保证了算法能够克服一般的补色方法无法保持物体表面细微明暗变化的缺点.实验结果表明,与以往的去除单张图像高光的方法相比,该算法能够提供更好的光源色度估计,从而得到更准确的结果.     

Information Exchange in Virtual Communities: A Comparative Study

As more and more consumers spend more money on the Internet, traditional retailers and manufacturers as well as entrepreneurial dot-coms are jousting to explore and shape this new business opportunity. Their long-term survival and profitability may be determined by how well the Web site helps form and sustain positive attitudes toward the site and, eventually, toward the product or the company. The purpose of this study is two-fold: (1) to examine if and how attitude toward the Web site (A_st) affects consumer brand choice; and (2) to examine the association between A_st and consumers' confidence in choice, and the moderating effect of consumer product knowledge in its relationship. The study asked participants to choose a laptop brand after visiting three laptop manufacturer Web sites for a total of 30 minutes. Their product knowledge and attitude toward the three Web sites were also measured. The study found that attitude toward the Web site is a good predictor of consumer brand choice. In addition, confidence in choice seemed to be affected by A_st, depending on product knowledge. For a group with low product knowledge (novices), A_st was likely to influence confidence in choice. For a group with high product knowledge (experts), however, A_st did not seem to affect confidence in choice.     

Particle Swarm Optimisation for Protein Motif Discovery

In this paper, a modified particle swarm optimisation algorithm is proposed for protein sequence motif discovery. Protein sequences are represented as a chain of symbols and a protein sequence motif is a short sequence that exists in most of the protein sequence families. Protein sequence symbols are converted into numbers using a one to one amino acid translation table. The simulation uses EGF protein and C2H2 Zinc Finger protein families obtained from the PROSITE database. Simulation results show that the modified particle swarm optimisation algorithm is effective in obtaining global optimum sequence patterns, achieving 96.9 and 99.5 classification accuracy respectively in EGF and C2H2 Zinc Finger protein families. A better true positive hit result is achieved when compared to the motifs published in PROSITE database.     

Recent progress on commercialization of castrip® direct strip casting technology at Nucor Crawfordsville

The world’s first commercial installation for direct casting of low-carbon steel sheet utilizing CASTRIP® technology is undergoing production ramp-up at Nucor Steel’s plant in Crawfordsville, Indiana. Construction of the plant was initiated in February 2001 and the first ladle was delivered to the caster in May 2002. Since that time, Nucor Steel has been working with technology partners BlueScope Steel (formerly BHP Steel) and IHI (Ishikawajima-Harima Heavy Industries) to fully commercialize this exciting new technology for the direct production of steel sheet less than 2 mm in thickness.     

Computerized transcutaneous monitoring incorporating laser Doppler velocimetry

Measurements of transcutaneous oxygen tension, transcutaneous carbon dioxide tension, transcutaneous heater power, transcutaneous electrode temperature, and peripheral perfusion at the gas measurement site (assessed by laser Doppler velocimetry) are monitored by a microprocessor-based data acquisition system. Arterial blood pressure, central venous pressure, pulmonary artery pressure, respiration rate, and heart rate may be simultaneously captured with the system unattended for 12-hour intervals. This computerized monitoring system is mobile and easily applied by medical technologists to adult or neonatal intensive care patients. Simultaneous collection of the measurement data has facilitated research on the interrelationships of the measured parameters. It should be helpful in assessing optimal therapeutic interventions as well as the changing physiology of acutely ill patients.     

Mathematical analysis of oxygen transfer through polydimethylsiloxane membrane between double layers of cell culture channel and gas chamber in microfluidic oxygenator

For successful cell culture in microfluidic devices, precise control of the microenvironment, including gas transfer between the cells and the surrounding medium, is exceptionally important. The work is motivated by a polydimethylsiloxane (PDMS) microfluidic oxygenator chip for mammalian cell culture suggesting that the speed of the oxygen transfer may vary depending on the thickness of a PDMS membrane or the height of a fluid channel. In this paper, a model is presented to describe the oxygen transfer dynamics in the PDMS microfluidic oxygenator chip for mammalian cell culture. Theoretical studies were carried out to evaluate the oxygen profile within the multilayer device, consisting of a gas reservoir, a PDMS membrane, a fluid channel containing growth media, and a cell culture layer. The corresponding semi-analytical solution was derived to evaluate dissolved oxygen concentration within the heterogeneous materials, and was found to be in good agreement with the numerical solution. In addition, a separate analytical solution was obtained to investigate the oxygen pressure drop (OPD) along the cell layer due to oxygen uptake of cells, with experimental validation of the OPD model carried out using human umbilical vein endothelial cells cultured in a PDMS microfluidic oxygenator. Within the theoretical framework, the effects of several microfluidic oxygenator design parameters were studied, including cell type and critical device dimensions.     

Fully distributed robust synchronization of networked Lur’e systems with incremental nonlinearities

This paper deals with robust synchronization problems for uncertain dynamical networks of diffusively interconnected identical Lur’e systems subject to incrementally passive nonlinearities and incrementally sector bounded nonlinearities, respectively, in a fully distributed fashion. Whereas in stabilization of one single Lur’e system the conditions of passivity and sector boundedness for the uncertain nonlinear function in the negative feedback loop are commonly assumed, in our context of networked Lur’e systems we adopt the stronger assumptions of incremental passivity and incremental sector boundedness. Throughout this paper the interconnection topologies among these Lur’e agents are assumed to be undirected and connected. We design robustly synchronizing protocols and subsequently implement these protocols in a fully distributed way by means of an adaptive control law that adjusts the coupling weights between neighboring agents. Both for the cases of incrementally passive as well as incrementally sector bounded nonlinearities we obtain sufficient conditions for the existence of fully distributed robustly synchronizing protocols. The state feedback matrices are computed by solving LMIs in terms of the matrices defining the individual agent dynamics. Numerical simulation examples illustrate our theoretical results.