粗颗粒煤水混合物的稠度和流变特性的研究

燃煤增压流化床的燃料制备与输送系统往往需采用气力输送方法送入加压罐后再送入炉内，系统复杂．采用煤水混合燃料泵送技术则可解决上述困难．提出了用塌落度测定方法判断０～６ｍｍ粗颗粒煤水混合物的可泵性，并选择适于泵送的较佳颗粒级配．建立了泵送与管道输送试验台进行粗颗粒徐州煤水混合物的流变特性试验，所得的泵送流变试验数据处理后的模型，可用于商用粗颗粒煤水混合物输送系统的设计计算．     

An Area Optimization Method for Digital Filter Design

In this paper, we propose an efficient design method for area optimization in a digital filter. The conventional methods to reduce the number of adders in a filter have the problem of a long critical path delay caused by the deep logic depth of the filter due to adder sharing. Furthermore, there is such a disadvantage that they use the transposed direct form (TDF) filter which needs more registers than those of the direct form (DF) filter. In this paper, we present a hybrid structure of a TDF and DF based on the flattened coefficients method so that it can reduce the number of flip‐flops and full‐adders without additional critical path delay. We also propose a resource sharing method and sharing‐pattern searching algorithm to reduce the number of adders without deepening the logic depth. Simulation results show that the proposed structure can save the number of adders and registers by 22 and 26%, respectively, compared to the best one used in the past.     

Fine‐Grained FSMD Power Gating Considering Power Overhead

As a fine‐grained power gating method for achieving greater power savings, our approach takes advantage of the finite state machine with a datapath (FSMD) characteristic which shows sequential idleness among subcircuits. In an FSMD‐based power gating, while only an active subcircuit is expected to be turned on, more subcircuits should be activated due to the power overhead. To reduce the number of missed opportunities for power savings, we deactivated some of the turned‐on subcircuits by slowing the FSMD down and predicting its behavior. Our microprocessor experiments showed that the power savings are close to the upper bound.     

Content-based image retrieval using block-constrained fractalcoding and nona-tree decomposition

Fractal coding has been proved useful for image compression. In fractal coding, an image is represented by a number of self-transformations (fractal code) by which an approximation of the original image can be reconstructed. The authors present a block-constrained fractal coding scheme and a nona-tree decomposition based matching strategy for content-based image retrieval. In the coding scheme, an image is partitioned into non-overlapped blocks with a size close to that of a query iconic image. The fractal code is generated for each block independently. In the similarity measure of the fractal code, an improved nona-tree decomposition scheme is adopted to avoid matching the fractal code globally in order to reduce computational complexity. The experimental results show that the authors' coding scheme and matching strategy are useful for image retrieval, and compare favourably with two other methods tested in terms of storage usage and computing time     

多维多阶调制格式产生方案的比较研究

随着带宽需求的不断增长,多维多阶调制格式成为目前研究的热点.文章对8PSK(3阶相移键控)、8QAM(3阶正交调幅)和16QAM(4阶正交调幅)的实现方式从原理和拓扑结构上进行了综合性的比较研究.使用已商用的调制器件,通过串行或串并混合的结构配置,可以得到8PSK、8QAM和16QAM的调制光信号;而使用并行结构的配置...     

加气混凝土蒸汽渗透系数的变物性取值方法

通过静态称重法和干湿杯法测得了加气混凝土在15、25和35℃下的等温吸放湿曲线和蒸汽渗透系数,讨论了蒸汽渗透系数的变物性取值方法,并与《民用建筑热工设计规范》（GB 50176-93）中的取值进行了对比。结果表明,加气混凝土的等温吸放湿曲线和蒸汽渗透系数在实验温度范围内受温度影响不大。该取值方法能针对吸湿过程,在中等相对湿度（60%~80%）或者整个典型建筑环境相对湿度（40%~95%）范围内计算得到与规范规定值基本相同的平均蒸汽渗透系数。此外,该方法能推广到各种多孔材料,针对吸湿或放湿过程,在各相对湿度范围内得到准确的蒸汽渗透系数。     

Low conversion-loss fourth subharmonic mixers incorporating CMRC for millimeter-wave applications

Low conversion-loss millimeter-wave fourth subharmonic (SH) mixer designs are proposed in this paper. A millimeter-wave (35 GHz) fourth SH mixer with four open/shorted stubs is designed and measured. The conversion loss is less than 15 dB within a 2.4-GHz bandwidth. The minimum loss is 11.5 dB at the center frequency. By replacing two of the shunt stubs with a dual-frequency in-line stub consisting of newly developed compact microstrip resonating cells (CMRCs), the performance of the SH mixer is improved significantly. At 35 GHz, the conversion loss of this new fourth SH mixer is as low as 6.1 dB with a 3-dB bandwidth of 6 GHz. The conversion loss in the whole Ka-band (26.5-40 GHz) is less than 16 dB. The proposed fourth SH mixer incorporating with CMRCs provides a low-cost high-performance solution for RF subsystem design.     

Analysis of fade margins for soft and hard handoffs in cellular CDMA systems

The effect of handoff techniques on fade margin is investigated. We provide an accurate comparison for soft and hard handoffs in a two-cell system. An upper bound on the fade margin for hard-handoff systems is derived and an approximation formula is obtained empirically. Simulation results show that this approximation is very accurate over reasonable ranges of system parameters. Extension of our analysis to multiple-cell systems are illustrated using a three-cell system as an example.     

Al_2O_3高k栅介质的可靠性

利用反应溅射方法制备了等效氧化层厚度为3 45nm的Al2 O3栅介质MOS电容,研究了Al2 O3作为栅介质的瞬时击穿和恒压应力下的时变击穿等可靠性特征.击穿实验显示,样品的Al2 O3栅介质的等效击穿场强大小为1 2 8MV/cm .在时变击穿的实验中,Al2 O3栅介质表现出类似于SiO2 的软击穿现象.不同栅压应力作用的测试结果表明,介质中注入电荷的积累效应是引起软击穿的主要因素,其对应的介质击穿电荷QBD约为30～60C/cm2 .     

ZnO压敏防雷芯片工频耐受与通流能力的相关性

为了研究ZnO压敏防雷芯片的工频过电压耐受特性和8/20μs通流能力的相关性,在生产线上抽取同批次产品进行工频过电压耐受试验和8/20μs通流能力试验。研究结果表明:工频过电压老化后会使压敏电阻的通流能力下降,但经过8/20μs雷电流峰值20 kA冲击后,压敏电阻的工频过电压耐受能力会增强,在冲击15次左右时达到最大值,随着冲击次数的增多,工频过电压耐受能力会降低。