IMPACCT: Methodology and Tools for Power-Aware Embedded Systems

Power-aware systems are those that must exploit a widerange of power/performance trade-offs in order to adapt to the power availabilityand application requirements. They require the integration of many novel powermanagement techniques, ranging from voltage scaling to subsystem shutdown.However, those techniques do not always compose synergistically with eachother; in fact, they can combine subtractively and often yield counterintuitive,and sometimes incorrect, results in the context of a complete system. Thiscan become a serious problem as more of these power aware systems are beingdeployed in mission critical applications.To address the problem of technique integration for power-aware embedded systems, we propose a new design tool framework called IMPACCT and the associated design methodology. The system modeling methodology includes application model for capturing timing/powerconstraints and mode dependencies at the system level. The tool performs power-awarescheduling and mode selection to ensure that all timing/power constraintsare satisfied and that all overhead is taken into account. IMPACCT then synthesizesthe implementation targeting a symmetric multiprocessor platform. Experimentalresults show that the increased dynamic range of power/performance settingsenabled a Mars rover to achieve significant acceleration while using lessenergy. More importantly, our tool correctly combines the state-of-the-arttechniques at the system level, thereby saving even experienced designersfrom many pitfalls of system-level power management.     

The effect of mischmetal addition on the structure and mechanical properties of a cast Al-7Si-0.3Mg alloy containing excess iron (up to 0.6 Pct)

The effect of Fe content (0.2 to 0.6 pct) on the microstructure and mechanical properties of a cast Al-7Si-0.3Mg (LM 25/356) alloy has been investigated. Further, 1 pct mischmetal (MM) additions (a mixture of rare-earth (RE) elements) were made to these alloys, and their mechanical properties at room and at elevated temperatures (up to 200 °C) were evaluated. A structure-property correlation on this alloy was attempted using optical microstructure analysis, fractographs, X-ray diffraction, energy-dispersive analysis of X-rays (EDX), and quantitative metallography by image analysis. An increase in Fe content increased the volume percentage of Fe-bearing intermetallic compounds (β and π phases), contributing to the loweryield strength (YS), ultimate tensile strength (UTS), percentage elongation, and higher hardness. An addition of 1 pct MM to the alloys containing 0.2 and 0.6 pct Fe was found to refine the microstructure; modify the eutectic silicon and La, Ce, and Nd present in the MM; form different intermetallic compounds with Al, Si, Fe, and Mg; and improve the mechanical properties of the alloys both at room and elevated temperatures.     

Pedestrian detection and tracking at crossroads

This paper presents a system that can perform pedestrian detection and tracking using vision-based techniques. A very important issue in the field of intelligent transportation system is to prevent pedestrians from being hit by vehicles. Recently, a great number of vision-based techniques have been proposed for this purpose. In this paper, we propose a vision-based method, which combines the use of a pedestrian model as well as the walking rhythm of pedestrians to detect and track walking pedestrians. Through integrating some spatial and temporal information grabbed by a vision system, we are able to develop a reliable system that can be used to prevent traffic accidents happened at crossroads. In addition, the proposed system can deal with the occlusion problem. Experimental results obtained by executing some real world cases have demonstrated that the proposed system is indeed superb.     

The investigation of 32P wire for catheter-based endovascular irradiation

The dose distribution from a 32P source has been measured and calculated in order to evaluate its application in endovascular irradiation. The source dimension was 27 mm in length and 0.3 mm in diameter and was embedded in the end of a Ni-Ti wire. Dose measurements were performed using radiochromic film in several specially designed tissue equivalent phantoms. Loevinger's point dose kernel was used for the calculation. The approximate dose rate at a radial distance of 1.5 mm from the center of the source was found to be 6.75 cGy/s per GBq (0.25 cGy/s per mCi), which allows the delivery of a therapeutic dose in a short time interval with a satisfactory homogeneity without stepping the source. However, the dose rate falls off almost exponentially along the radial distance. Therefore it may not be suitable for treating large diameter vessel from a centrally located source. The effect of a curved 32P wire source on the radial dose distribution was also investigated. The results showed that for a maximum bend of 180 degrees the dose rate was increased by as much as 20% along the inner radial distance but decreased by as much as 20% along the outer radial distance compared to the dose along a straight wire. However, for curvatures normally encountered in a clinical situation, the dose rate was changed less than 5%.     

Challenges in computer architecture evaluation

We focus on problems suited to the current evaluation infrastructure. The current limitation and trends in evaluation techniques are troublesome and could noticeably slow the rate of computer system innovation. New research has been recommended to help and make quantitative evaluations of computer systems manageable. We support research in the areas of simulation frameworks, benchmarking methodologies, analytic methods, and validation techniques.     

Parametric study of the electrical to thermal power conversion in an inductively coupledrf plasma torch

An inductively coupled (ic) radio-frequency (rf) stabilized argon plasma was generated in a quartz tube using a 7 MHzrf generator. The electrical and thermal powers were measured and the efficiency of energy conversion was computed. The results indicate that for a constant power input, there is an optimum argon flow rate for which maximum energy conversion efficiency occurs.     

Copper coating on carbon fibres and their composites with aluminium matrix

A uniform and continuous coating of copper was given to carbon fibres by cementation or electroless techniques. In both cases, when coating thicknesses were less than 0.2 m, copper deposition was discontinuous over the fibres, and above 0.2 m, coatings were continuous. In electroless coating, about 75% of the continuously coated fibres had a coating thickness range 0.2–0.5 m and above this showed isolated dendrite deposits of copper. In the cementation process, about 75% of the continuously coated fibres had a coating thickness range 0.2–0.6 m, and above this thickness, fine crystallite-type copper deposition was found over smoothly coated copper. The ultimate tensile strength of continuously electroless-coated fibres were nearer to the uncoated fibres, suggesting defect-free coating, while fibres coated by the cementation process exhibited lower ultimate tensile strength values. The tensile fracture of both electroless- and cementation-coated fibres showed delamination of the coating, suggesting poor bonding between coating and the fibre. In composites, prepared by dispersing the coated chopped fibres in a pure aluminium matrix, uniform and random distribution of the fibres were observed without appreciable fibre-metal interaction. The CuAl₂ intermetallics were largely found in the matrix and only very small amounts were observed at fibre/matrix interfaces. Additions of about 2 wt% Mg to the matrix prior to the fibre dispersion did not appreciably change the distribution pattern of the fibres, but in addition to CuAl₂ phase, Mg₂Si phases were observed in the matrix as well as at the interface.     

石墨防爆片静态变形及应力分析

本文旨在通过对石墨防爆片的变形、应力分布及爆破压力的试验研究,探讨以石墨电极为原材料加工石墨防爆片的可行性。文中运用有限单元法及薄板理论对该防爆破片的应力分布做了初步分析,并以电测和爆破试验验证了以薄板理论为基础的爆破压力计算公式,可供进一步研究时参考。