Chebyshev Polynomials for Boxing and Intersections of Parametric Curves and Surfaces

Parametric curves and surfaces are powerful and popular modelling tools in Computer Graphics and Computer Aided Design. Ray-tracing is a versatile and popular rendering technique. There is therefore a strong incentive in developing fast, accurate and reliable algorithms to intersect rays and parametric curves and surfaces. We propose and demonstrate the use of Chebyshev basis functions to speed up the computation of the intersections between rays and parametric curves or surfaces. The properties of Chebyshev polynomials result in the computation of better and tighter enclosing boxes. For surfaces they provide a better termination criterion to decide on the limits of subdivision, and allow the use of bilinear surfaces for the computation of the intersection when needed. The efficiency of the techniques used depends on the relative magnitude of the coefficients of the Chebyshev basis functions. We show from a statistical analysis of the characteristics of several thousands surfaces of different origin that these techniques will result most of the time in significant improvement in speed and accuracy over other other boxing and subdivision techniques.     

Integrated quantum well intersub-band photodetector and lightemitting diode

The authors propose and demonstrate the integration of a quantum well intersub-band photodetector (QWIP) and a light emitting diode (LED) for making large two-dimensional focal plane arrays for thermal imaging applications. The newly developed QWIP technology is combined with the well established LED technology both based on GaAs and related epitaxially grown alloys, such as AlGaAs and InGaAs     

Cardiopulmonary bypass pumps and thrombin generation: what goes around comes around

Thrombin generation and subsequent fibrin deposition occur during cardiopulmonary bypass (CPB) using roller pumps (RPs) despite the administration of high dose heparin. The authors attempted to determine if less thrombin is generated and less fibrin is deposited during CPB using a centrifugal pump (CP). In Part 1 of the experiment, 12 pigs receiving 400 U/kg heparin underwent CPB, including hypothermia, cardioplegia, and aortic cross-clamping, using a CP or RP. Blood samples were collected throughout CPB to measure thrombin generation. At the end of CPB, the amount of fibrin deposited onto each filter was assessed spectrophotometrically. In Part 2, blood samples and arterial in-line filters were obtained from 20 patients undergoing CPB, using either RP or CP, and studied as described previously. The Part 1 results showed that thrombin generation and fibrin deposition in CP pigs were <50% of those seen in the RP pigs (p < 0.01 and p < 0.01, respectively). In Part 2, thrombin generation was significantly attenuated both during and after CPB in the CP patients (p < 0.01 and p < 0.01, respectively). However, there was no significant difference in fibrin deposition between the two types of pumps after their use in the patients undergoing cardiopulmonary bypass. It is concluded that there is less thrombin generation and subsequent fibrin deposition during CPB when using a CP instead of RP in a defined experimental in vivo situation, suggesting that there is less hypercoagulability during CPB when using a CP instead of an RP. However, a large study in more patients undergoing CPB for longer pump runs is required to determine the relevance of these observations on subsequent clinical endpoints.     

Investigating the Social Dimensions of Transport Disadvantage—I. Towards New Concepts and Methods

This article is the first of two papers that engage critically and productively with the relationship between the socio-economic transformations of cities, the differentiation of vulnerable groups within urban space and the distribution of transport services. This article undertakes a comprehensive review of the major conceptual and methodological approaches by which scholars and policy researchers have sought to address the connection between social disadvantage and access to transport. The article critically assesses the relative merits of various spatial analytical methodologies in illuminating social-transport links. The study finds that there is a need for greater sophistication in the use of analytical methods in transport research as well as an imperative for greater sensitivity to social differentiation within urban areas and relative to infrastructure and services. The article concludes by developing a method for combining spatial social and transport service data that is then deployed in the empirical case study reported in the second paper.     

Experimental 0.1 μm p-channel MOSFET withp+-polysilicon gate on 35 Å gate oxide

Very-high-transconductance 0.1 μm surface-channel pMOSFET devices are fabricated with p⁺-poly gate on 35 Å-thick gate oxide. A 600 Å-deep p⁺ source-drain extension is used with self-aligned TiSi₂ to achieve low series resistance. The saturation transconductances, 400 mS/mm at 300 K and 500 mS/mm at 77 K, are the highest reported to date for pMOSFET devices     

Thermal-imaging technologies for detecting damage during high-cycle fatigue

A high-speed and high-sensitivity thermographic-infrared (IR) imaging system has been used for nondestructive evaluation of specimen-temperature evolutions during high-cycle fatigue experiments. The relationship among the temperature, stress-strain state, and fatigue behavior is discussed. Both thermodynamics and heat-transfer theories are applied to model and quantify the observed temperature variations during fatigue. The predicted and measured temperature evolutions and inelastic strains during fatigue were found to be in good agreement. During fatigue experiments, in-situ observations as well as qualitative and quantitative analyses of Lüders-band evolutions, crack propagation, plastic zones, and final fracture have been performed by thermography, which can open up wide applications of thermography in detecting the in-situ heat-related processes, including mechanical damages and phase transformations, of materials and structural components.     

Congestive heart failure in elderly patients. The treatment goal is improved quality, not quantity, of life

Primary care physicians who see elderly patients are likely to see cases of congestive heart failure, since this condition is typically the result of long-standing hypertension or coronary artery disease. Recognizing the condition in elderly patients may not be easy, though, because clinical signs can be distorted by accompanying symptoms. In this article, the authors discuss pathophysiologic, diagnostic, and pharmacokinetic issues. They also describe therapy with diuretics, angiotensin-converting enzyme inhibitors, and digoxin and outline special considerations in the elderly.