一种宽带贴片天线的设计与仿真

介绍了微带贴片天线的特点、原理和设计方法，针对孔径耦合的馈电方式，运用以有限元法为原理的软件对设计的贴片天线进行仿真，并对天线参数进行优化，结果表明孔径耦合微带贴片天线结构简单，可以达到21％的相对带宽（VSWR〈2），和较高的增益。同时对影响天线性能的主要参数进行仿真对比，得出了实用性的结论，对方便有效地改进电子对抗装备性能有一定的意义。     

双门选超声波收发模拟电路的设计

针对现有模拟板中存在冗余的电容导致建波信号拖尾较长,致使超声信号经模拟板处理后分辨率低的问题,提出了一种以差分接收、双门选回波处理硬件电路设计。在检波放大之前设计一个门选电路,直接从全波信号中选取缺陷信号,避免了界面波经过检波放大电路后,形成拖尾淹没缺陷信号,提高了接收电路信号的可靠性。文中从硬件方面介绍了接收电路的调整。实验表明,电路性能稳定、精度高、成本低,并具有良好的应用前景。     

毛霉蛋白酶提取方法的研究

研究了不同浓度的ＮａＣｌ溶液、不同温度条件及不同取方法对腐乳生产菌和睦我霉的蛋白酶的提取效果。４０℃、０．３ｍｏｌ／Ｌ的ＮａＣｌ溶液分次提取可得最大酶活力。     

黑色保健粥配方及工艺的研究

以黑米和黑木耳为原料,根据老年人的营养需求,运用计算机设计了黑色保健粥的配方,对其工艺进行了探讨,该产品具有营养和食疗的双重作用。     

浅谈近红外NIR分析仪在制粉行业中的应用

介绍了近红外ＮＩＲ 分析仪的原理、优点、可测定的物质成分及其在制粉工业从原粮接收到生产加工到产出成品的质量控制中的应用。     

克鲁维酵母突变株UV-G-40-3菊粉酶性质的研究

研究了克鲁维酵母突变株（Ｋｌｕｙｖｅｒｏｍｙｃｅｓ－ＵＶ－Ｇ－４０－３）所产菊粉酶的分布为胞外酶∶胞壁酶∶胞内酶比是５．７∶１．６∶１。该酶Ｓ／Ｉ为５．３,最适温度为５０℃,最适ｐＨ为４．５,在５０℃以下、ｐＨ４．５～８的范围内比较稳定,４℃贮存稳定性好,１４ｄ后仍保持７６％活力,为外切型菊粉酶,酶解粗菊糖（洋姜提取液）活性为纯菊糖的４倍。     

The design and optimization of high-performance, double-polyself-aligned p-n-p technology

The device design and performance of double-poly self-aligned p-n-p technology, featuring a low-resistivity p⁺ subcollector, thin p-epi, and boron-doped poly-emitter are described. Device isolation is provided by deep and shallow trenches which reduce the collector-to-substrate capacitance while maintaining a high breakdown voltage (⩾40 V). By utilizing a shallow emitter process in conjunction with an optimized arsenic-base implant, devices with emitter-base junction depths as shallow as 20 nm and base widths of less than 100 nm were obtained. Cutoff frequencies of up to 27 GHz were obtained, and the AC performance was demonstrated by an NTL-gate delay of 36 ps and an active-pull-down (APD) ECL-gate delay of 20 ps. This high-performance p-n-p technology was developed to be compatible with existing double-poly n-p-n technologies. The matching speed of p-n-p devices opens up new opportunities for high-performance complementary bipolar circuits     

激光预脉冲对双层靶LPX辐射特性的影响

以激光产生的等离子体作为短波激光的激活介质,是目前实现X射线激光最有希望的方案之一,早在1985年,美国利弗莫尔国家实验室(LLNL)的D.L.Matthaws等人首次观察到了硒等离子体介质中类氖离子的20.9nm和20.6nm跃迁的短波激光输出,这给许多实验室X射线激光研究带来了新的生机。继后许多实验报道了他们利用各种机制所取得的结果,目前认为最有希望的泵浦机制是电子碰撞激发和碰撞复合,相应地它们对激光条件和靶的结构要求是不同的。为此,我们在文献[3]中已较系统地研究了激光与高、中和低Z元素靶相互作用的辐射特性,在文献[4]中研究了激光产生的等离子体基本参数和分布特性,在文献[1]中研究了不同结构靶对短波域粒子数反转的影响。本文是在上述工作的基础上,进一步深入地研     

Broadband dual-frequency operation of circular patch antennas and arrays with a pair of L-shaped slots

By embedding properly arranged L-shaped slots in a circular patch, a novel broadband dual-frequency design is proposed and experimentally studied. With the use of an L-strip microstrip line for feeding the proposed antenna, the impedance bandwidths, determined from 10 dB return loss, of two operating bands can reach about 7.0% to 12.5% for the lower band and 18.9% to 21.5% for the higher band. Operating frequencies across the obtained lower and higher bands are of the same polarization planes, and have a tunable frequency ratio between the center frequencies of the two operating bands ranging from about 1.31-1.61. The application of the proposed antenna to the design of a 2 /spl times/ 2 broadband dual-frequency patch antenna array is also demonstrated. Details of the proposed broadband dual-frequency design are described, and experimental results of the constructed prototypes are presented and discussed.     

The impact of multihop wireless channel on TCP performance

This paper studies TCP performance in a stationary multihop wireless network using IEEE 802.11 for channel access control. We first show that, given a specific network topology and flow patterns, there exists an optimal window size W* at which TCP achieves the highest throughput via maximum spatial reuse of the shared wireless channel. However, TCP grows its window size much larger than W* leading to throughput reduction. We then explain the TCP throughput decrease using our observations and analysis of the packet loss in an overloaded multihop wireless network. We find out that the network overload is typically first signified by packet drops due to wireless link-layer contention, rather than buffer overflow-induced losses observed in the wired Internet. As the offered load increases, the probability of packet drops due to link contention also increases, and eventually saturates. Unfortunately the link-layer drop probability is insufficient to keep the TCP window size around W'*. We model and analyze the link contention behavior, based on which we propose link RED that fine-tunes the link-layer packet dropping probability to stabilize the TCP window size around W*. We further devise adaptive pacing to better coordinate channel access along the packet forwarding path. Our simulations demonstrate 5 to 30 percent improvement of TCP throughput using the proposed two techniques.