A 22-kHz multibit switched-capacitor sigma-delta D/A converter with92 dB dynamic range

A time- and capacitor-multiplexing technique for use in a highly linear switched-capacitor multibit DAC in sigma-delta data converters is presented. The technique uses subintervals in the sample clock to deliver multiple charge packets to holding capacitors. It avoids distortion effects caused by mismatched capacitors and finite opamp gain. A five-level switched-capacitor DAC using the proposed technique was designed as part of an audio-band multibit sigma-delta D/A converter that achieved a dynamic range of 92 dB and a THD of -93 dB with a low oversampling ratio of 32. No trimming, calibration, or dynamic matching scheme was required. The five-level SC DAC has been fabricated in a 2-μm CMOS process, and testing confirmed the anticipated theoretical results     

Flow patterns and thermal drag in a one-dimensional inviscid channel with heating or cooling

In this paper investigations on the flow patterns and the thermal drag phenomenon in one-dimensional inviscid channel flow with heating or cooling are described and discussed; expressions of flow rate ratio and thermal drag coefficient for different flow patterns and its physical mechanism are presented.     

Grain Growth Kinetics and Debye Temperature of Nanometer TiO_2 Powders Prepared by a Sol-gel Process

The development of microstructure of nanometer TiO2 powders prepared by a sol-gel process was systematically studied. Grain growth was mon itored using X-ray diffraction (XRD) and transmission electron microscopy (TEM). and the Debye temperature of anatase crystallites was determined. It was found that the grain size of the powders increased slowly with annealing temperature up to 773 K. but grew rapidly in the temperature range of 773-1273K. The activation energies (Ea) for the growth of anatase crystallites in the two temperature regions were calculated to be 16 and 90 kJ / mol, respectively. The Debye temperatures of nanocrystalline anatase powders were all lower than that of microcrystalline anatase. which implies that the bonding force between Ti and O atoms in nanocrystalline TiO2 shourd be smaller than that in microcrystalline state. However. it was noted that the Debye temperature of nanocrystalline anatase increased with the decrease of grain size. This may be attributed to the enhancement in atomic bonding force due to the existence of high surface tension in nanocrystalline powders     

Operating experience of desalination units in Schevchenko

The paper discusses the main disign and process features of desalination units of three types built at the largest in the USSR system in Schevchenko and operated at the atomic thermoelectric fast reactor plant. Data are also presented on the experience gained in operation of natural and forced circulation evaporators, adjustment of specially designed circulation pumps and initial sea water cleaeration, impronement of non-condensing gas removal system and method of preventing scale from depositing in regeneration heaters through carbon dioxide stabilization of sea water and in evaporators through the introduction of chalk.     

Representational specificity of within-category phonetic variation in the long-term mental lexicon.

This study examines the potential encoding in long-term memory of subphonemic, within-category variation in voice onset time (VOT) and the degree to which this encoding of subtle variation is mediated by lexical competition. In 4 long-term repetition-priming experiments, magnitude of priming was examined as a function of variation in VOT in words with voiced counterparts (cape-gape) and without (cow-*gow) and words whose counterparts were high frequency (pest-best) or low frequency (pile-bile). The results showed that within-category variation was indeed encoded in memory and could have demonstrable effects on priming. However, there were also robust effects of prototypical representations on priming. Encoding of within-category variation was also affected by the presence of lexical counterparts and by the frequency of counterparts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

一种有机/金属肖特基二极管的实验研究

提出了一种简单有效的有机/金属肖特基二极管的制备方法:通过简单的真空气相沉积工艺,依次将有机材料PTCDA(C24H8O6)薄膜和金属电极Au蒸镀在透明导电玻璃ITO上.通过在室温条件下对该二极管的电流-电压(I-V)特性的测试发现,其整流系数可达104.根据标准肖特基理论以及实验所得电容-频率(C-f)和电容-电压(C-V)的测试结果,得到该有机肖特基势垒高度在0.2～0.3eV范围内.     

交联大分子的合成与表征

设计了含有分子内反应和分子间反应的聚合体系，这是一对竞争反应，竞争的结果可达到一定的平衡，使无法控制的凝胶化过程得以控制，从而合成了具有交联结构的大分子。通过分子尺寸的测定还发现了交联大分子在溶液中的特殊行为，这种特殊行为恰好验证了所合成的大分子具有交联结构。     

样条函数在补偿中子算法中的应用

本文从对补偿中子测井实验刻度点的讨论出发,提出用样条插值方法而不是通常回归拟合方法来构造补偿中子响应方程。样条函数采用分段的多项式。文中指出,四点三次样条插值是其较为实用的形式,这时插值多项式参数计算的解析式容易导出,实时处理中求视孔隙度的计算量完全可为一般采用软件作数值运算的微处理机系统所接受;并提出补偿中子测井的刻度方法,这种算法极大地简化了井下仪的调校;对水点取值也进行了讨论。附录中给出求解参数的具体计算公式,可以此作为上机编程的依据。     

Color analysis of natural colorant‐dyed fabrics

Colors from naturally dyed fabrics recently have attracted both consumers and manufacturers in fashion markets. Even though color attributes of the fabrics have been partially observed in some literature, a data base of colors for natural colorants in fabrics needs to be established and the colors to be characterized according to systematic color notations and tones in order to relate the traditional natural colors to contemporary color communication systems. Therefore, a study was performed to investigate color characteristics for a given large set of natural colorants‐dyed fabrics based on the Munsell color notations, to analyze their tones with relation to the notation such as hue, value, and chroma, and finally to identify the effects of mordanting, an important coloring auxiliary, on the colorimetric properties of the fabrics. As a result, the dominant hue for a total of 350 naturally dyed fabrics was yellowish families followed by reddish and purplish ones in the Munsell notation owing to the use of leaves and plant as usual natural dyestuff, which confirms the limit of color hues of the fabrics. Color value for most of naturally dyed fabrics was generally higher whereas the chroma was lower, which means that most of colors for naturally dyed fabrics tended to be bright and weak shaded. Grayish, light grayish, and soft tones were the main tones of natural colorant‐dyed fabrics. All of hue, value, and chroma were found as being influenced by mordanting in that more particularly; iron mordanting was likely to cause the decrease of both value and chroma for most of naturally dyed fabrics. These results could provide a systematic color data for naturally dyed fashion fabrics and suggest a future direction of color development for them. © 2008 Wiley Periodicals, Inc. Col Res Appl, 33, 148–157, 2008