低噪声、低失真、16位、1Msps SAR ADC的驱动课程设计要点477

引言 设计一种能够提供不打任何性能折扣的ADC驱动拓扑结构是颇具挑战性,特别是在围绕一款诸如1Msps LTC(R)2393-16等超低噪声SAR ADC进行设计的时候.     

Spectrum mobility management in cognitive two‐tier networks

Recently, new type of small Base Station known as “femtocell” has emerged. Femtocells are deployed by customers with minimal or no radio frequency planning in arbitrary locations. Thus, operators must use new approaches rather than the classic network planning and optimization. Self‐organization techniques will allow femtocells to integrate themselves into the network, learn about their environment, and adjust their parameters (power, frequency) accordingly. In this paper, a new spectrum mobility management algorithm is proposed. It allows intelligent use of the spectrum by secondary user (femtocell guest user) accessing spectrum holes unoccupied by primary users (subscriber user) and handing over to new channels or femtocells when primary user appears. Our solution aims to have more adaptive and aware communication system, which can make better use of available natural resources.     

Flow investigation of phase change material (PCM) slurry as a heat transfer fluid in a closed loop system

Aqueous phase change material (PCM) particles are dispersed in an organic phase to constitute a slurry for using as a cold heat transfer medium for district cooling in refrigeration and air conditioning industry. The PCM contains 90% of water stabilized by a three‐dimensional network of polymer. The flow behaviour of the slurry is investigated in a small‐scale loop circuit with transparent pipes to allow observation of flow patterns. Data show that pressure drop increases with velocity and decreases with temperature, which can be explained by heterogeneities in flow for temperature higher than 0°C and for Reynolds number (based on the properties of the liquid phase) lower than 7000. A homogeneous particle field is observed for Reynolds number up to 7000, which guarantees a safe operation of the system without the occurrence of clogging in ducts. For this range of flow, the flow rate and the pump consumption for the PCM slurry decrease notably for the same heat transportation quantity compared with chilled water. Copyright © 2008 John Wiley & Sons, Ltd.     

Polysaccharides as excipients for colon-specific coatings. Permeability and swelling properties of casted films

Oligosaccharides such as inulin (In) and polysaccharides such as galactomannans, combined with polymethacrylates on isolated films for film coatings, were obtained from aqueous-based solvents and investigated as potential vehicles for colonic drug delivery. These compositions, which are susceptible to fermentation by colonic microflora, constitute promising excipients for the development of new colon-specific therapeutic systems. The characteristics of several compositions have been demonstrated in permeability and swelling studies on isolated films composed of a polymethacrylate associated with In or galactomannans of mesquite seed gum (MSG). Results reported prove a dependency of the properties of mixed films on the polymethacrylate-polysaccharide concentration ratio and on the composition of the dissolution media. An increase in permeability through the mixed films was observed in a simulated colonic environment for the following compositions: Eudragit®RS30D-MSG 70 : 30 w/w; Eudragit® RS30D-In 90 : 10 w/w; Eudragit®RS30D-In 76 : 24 w/w.     

Detection of hydrogen peroxide at mesoporous platinum microelectrodes

Mesoporous (H(I)-ePt) platinum microelectrodes electrodeposited from the hexagonal (H(I)) lyotropic liquid crystalline phase are shown to be excellent amperometric sensors for the detection of hydrogen peroxide over a wide range of concentrations. Good reproducibility, high precision, and accuracy of measurements are demonstrated. Mesoporous microelectrodes retain the high rates of mass transport typical of conventional microelectrodes, and their high real surface area greatly enhances their catalytic activity. This unique combination of properties overcomes the limitations of previous amperometric hydrogen peroxide sensors and yields outstanding qualitative and quantitative results.     

The Data Locality of Work Stealing

This paper studies the data locality of the work-stealing scheduling algorithm on hardware-controlled shared-memory machines, where movement of data to and from the cache is solely controlled by the hardware. We present lower and upper bounds on the number of cache misses when using work stealing, and introduce a locality-guided work-stealing algorithm and its experimental validation. {As a lower bound, we show that a work-stealing application that exhibits good data locality on a uniprocessor may exhibit poor data locality on a multiprocessor. In particular, we show a family of multithreaded computations G _n whose members perform Θ(n) operations (work) and incur a constant number of cache misses on a uniprocessor, while even on two processors the total number of cache misses soars to Ω(n) . On the other hand, we show a tight upper bound on the number of cache misses that nested-parallel computations, a large, important class of computations, incur due to multiprocessing. In particular, for nested-parallel computations, we show that on P processors a multiprocessor execution incurs an expected

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B-spline image model for energy minimization-based optical flow estimation.

Robust estimation of the optical flow is addressed through a multiresolution energy minimization. It involves repeated evaluation of spatial and temporal gradients of image intensity which rely usually on bilinear interpolation and image filtering. We propose to base both computations on a single pyramidal cubic B-spline model of image intensity. We show empirically improvements in convergence speed and estimation error and validate the resulting algorithm on real test sequences.     

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Left ventricular radial tagging acquisition using gradient-recalled-echo techniques: sequence optimization

Myocardial tagging with magnetic resonance (MR) imaging offers unique possibilities for noninvasive left ventricular (LV) strain analysis. True three-dimensional strain analysis can be achieved with tags implemented in cardiac short axis and long axis images. Spin-echo (SE) techniques have been used for these studies. However, this approach is time-consuming: images at different phases of the cardiac cycle have to be obtained in successive measurements and hence the total number of measurements equals the number of time frames. Moreover, the images are often degraded by flow and motion artifacts. The purpose of this study was to optimize a faster and more robust MR tagging sequence for use on a clinical whole-body 1 T MR system with optimal persistence of the tags during the entire cardiac cycle. The tagging pulses were implemented in gradient-recalled-echo (GRE) sequences and compared to SE-based acquisitions. The effects of the use of flow-compensating gradients, the excitation angles, and the angles of the saturation pulses have been studied with MR signal simulations and in comparative measurements in volunteers. GRE acquisitions with flow-compensating gradients are robust techniques for myocardial tagging acquisitions. Use of optimized flip angles and saturation pulses can significantly improve delineation of the tag and can be used up to at least 700 ms after the R-wave. Therefore, LV tagging with GRE acquisitions using optimized MR parameters is a robust and promising technique.