A fast 600-V Tandem PiN Schottky (TPS) rectifier with ultra-low on-state voltage

The Tandem PiN Schottky (TPS) rectifier features lowly-doped p-layers in both active and termination regions, and is applied in 600-V rating for the first time. In the active region, the Schottky contact is in series connection with a transparent p-layer, leading to a superior forward performance than the conventional diodes. In addition, due to the benefit of moderate hole injection from the p-layer, the TPS offers a better trade-off between the on-state voltage and the switching speed. The active p-layer also helps to stabilise the Schottky contact, and hence the electrical data distributions are more concentrated. Regarding the floating p-layer in the termination region, its purpose is to reduce the peak electric fields, and the TPS demonstrates a high breakdown voltage with a compact termination width, less than 70% of the state-of-the-art devices on the market. Experimental results have shown that the 600-V TPS rectifier has an ultra-low on-state voltage of 0.98 V at 250 A/cm 2, a fast turn-off time of 75 ns by the standard RG1 test (I F=0.5A, I R=1A, and I RR=0.25A) and a breakdown voltage over 720 V. It is noteworthy that the p-layers in the active and termination regions can be formed at no extra cost for the use of self-alignment process. © 2012 IEEE.

Simultaneous colour search renders other object properties less salient

A common approach to visualise multidimensional data sets is to map every data dimension to a separate visual feature. It is generally assumed that such visual features can be judged independently from each other. However, we have recently shown that interactions between features do exist [Hannus et al. 2004; van den Berg et al. 2005]. In those studies, we first determined individual colour and size contrast or colour and orientation contrast necessary to achieve a fixed level of discrimination performance in single feature search tasks. These contrasts were then used in a conjunction search task in which the target was defined by a combination of a colour and a size or a colour and an orientation. We found that in conjunction search, despite the matched feature discriminability, subjects significantly more often chose an item with the correct colour than one with correct size or orientation. This finding may have consequences for visualisation: the saliency of information coded by objects' size or orientation may change when there is a need to simultaneously search for colour that codes another aspect of the information. In the present experiment, we studied whether a colour bias can also be found in a more complex and continuous task, Subjects had to search for a target in a node-link diagram consisting of SO nodes, while their eye movements were being tracked, Each node was assigned a random colour and size (from a range of 10 possible values with fixed perceptual distances). We found that when we base the distances on the mean threshold contrasts that were determined in our previous experiments, the fixated nodes tend to resemble the target colour more than the target size (Figure 1a). This indicates that despite the perceptual matching, colour is judged with greater precision than size during conjunction search. We also found that when we double the size contrast (i.e. the distances between the 10 possible node sizes), this effect disappears (Figure 1b). Our findings confirm that the previously found decrease in salience of other features during colour conjunction search is also present in more complex (more 'visualisation- realistic') visual search tasks. The asymmetry in visual search behaviour can be compensated for by manipulating step sizes (perceptual distances) within feature dimensions. Our results therefore also imply that feature hierarchies are not completely fixed and may be adapted to the requirements of a particular visualisation. Copyright © 2005 by the Association for Computing Machinery, Inc.

椭圆背角无齿蚌对重金属元素的积累作用

检测了滇池水饲养 1a的椭圆背角无齿蚌 (Anodontawoodianaelliptica)体内重金属等元素含量 ,结果显示椭圆背角无齿蚌体内锌含量为 7.0 8× 1 0 2 mg/kg ,铅为 3 5 .6 8mg/kg ,铜为 9.0 4mg/kg ,铁为 4 .74× 1 0 3mg/kg ,砷为 6 2 .0 9mg/kg ,磷为 4 .4 4× 1 0 4mg/kg .与滇池水中锌 0 .0 2 0 5 μg/L ,铅 0 .4 1 2 μg/L ,铜 3 .1 98μg/L相比较 ,表明椭

鲫耳石年轮的观察及其确证

对耳石边缘年轮形成周期进行了分析。结果表明 ,鲫耳石上 1a形成 1个年轮 ,年轮形成时期洪湖种群主要在 4～ 6月 ,洞庭湖种群主要在 3～ 5月。星耳石和微耳石一样 ,可用于鲫年龄鉴定 ,而且不经磨片即可直接读取年轮 ,完整星耳石和微耳石与微耳石磨片上的年轮读数的吻合率均在 80 %以上 ,误差不超过 1龄。但相对而言 ,微耳石上年轮更易观察。文中对耳石形态和年轮特征作了描述

葡萄藻三个品系脂类物质含量的比较研究

<正> 葡萄藻作为一种新的再生性能源的研究,已引起了不少学者的重视。其中较为关键的是对葡萄藻所含脂类物质的研究。过去通常采用重量法及各类色谱法测定植物中的脂类物质。这些方法不但繁琐,而且均需一个较长时间的提取过程。近年来国外采用一种新型染料——尼罗

A miniature insertion element transposable in Microcystis sp FACHB 854

A 186-bp sequence with imperfect terminal inverted repeats and target direct repeats but without any transposase-encoding capacity was found to be transposable in an isolate derived from Microcystis sp. FACHB 854. This miniature insertion element, designated as ISM854-1, and with its homologues present at least 10 copies in the genome of Microcystis FACHB 854, is inserted into the 8-bp long and AT-rich target sequences, but none or few in other Microcystis strains. A variant of ISM854-1, denoted ISM854-1A, has perfect inverted repeat sequences and may transpose in pairs in a structure like a composite transposon. This is the first report of non-autonomous transposition of a mini-IS in a cyanobacterium.

Photochromic diarylethene for polarization holographic optical recording

Photochromic diarylethene, 1,2-bis[2-methyl-5-(3-fluorophenyl)-3-thienyl] perfluorocyleopentene (1a), was synthesized. The compound showed good photochromic reactions both in solution and in PMMA matrix by photo-irradiation. Using the diarylethene lb/PMMA film as recording medium and a He-Ne laser for recording and readout, four types of polarization holographic optical recording were accomplished for the first time. The results show that the orthogonal circular polarization recording is the best method for holographic optical recording when the target photochromic diarylethene is used as recording material. (c) 2006 Published by Elsevier B.V.

Polarization multiplexing holographic optical recording of a new photochromic diarylethene

A new unsymmetrical photochromic diarylethene 1a is synthesized, and the photochromic properties of it are also investigated. The compound exhibits good photochromism with UV/ visible light irradiation. Compound 1a in polymethyl methacrylate ( PMMA ) film changes color upon 313- nm light irradiation from colorless to blue, in which the absorption maximum is observed at 587 nm. Photon- mode polarization multiplexing holographic optical recording is performed successfully using this compound as a recording medium. In the diarylethene 1b/ PMMA film, polarization multiplexing hologram recording and retrieval, and a combination with the angular multiplexing scheme, are demonstrated systematically. The results indicate that recording capacity can be significantly improved with the combined method of polarization and angular multiplexing holographic recording. (C) 2008 Society of Photo- Optical Instrumentation Engineers.

黄土丘陵区退耕撂荒地土壤微生物量演变过程

土壤微生物量是表征土壤生态系统中物质和能量流动的重要参数,研究黄土丘陵区坡耕地撂荒后微生物量及其活性的变化过程对认识该地区生态恢复过程中土壤质量的演变及其效果评价具有重要意义。【方法】采用时空互代法,以典型侵蚀环境纸坊沟流域生态恢复过程中不同年限的撂荒地为研究对象,选取坡耕地和天然侧柏林为参照,通过室内测试分析,并运用统计和相关分析等方法,研究坡耕地撂荒后土壤微生物量、呼吸强度、代谢商(qCO2)及土壤理化性质的演变特征。【结果】侵蚀环境下的坡耕地土壤微生物量含量偏低,土壤理化性质较差,撂荒后理化性质得到显著改善,微生物量碳(Cmic)在撂荒1a后显著增大,前7a较为剧烈,增幅较大,随后呈波动式上升,50a达到最大值;微生物量氮(Nmic)在撂荒初期增长缓慢,40a时才达到显著水平,微生物量磷(Pmic)在撂荒初期显著降低,5～7a达到最低值,随后逐渐上升,20～25a时和坡耕地没有显著差异,50a时达到最大值。撂荒50a时土壤Cmic、Nmic和Pmic分别较坡耕地增加166%、146%和52%,但仅为侧柏林的43.42%、45.06%和51.47%。呼吸强度在撂荒初期迅速增加,随后趋于稳定,与侧柏...

枣芽象甲的综合防治

近年来红枣发展迅速,陕西、山西黄河沿岸红枣栽培面积达30万hm2。随着红枣栽培面积扩大,枣芽象甲(Scythropus yasumatsui)在陕西省佳县和山西省柳林县、稷山县等地危害严重。枣芽象甲属鞘翅目象甲科,又名食芽象甲、枣飞象、枣月象、小灰象甲等,分布于陕西、山西、河南、河北、山东、辽宁等地,危害红枣、苹果、核桃等多种果树。枣芽象甲成虫早春上树危害嫩芽、幼叶,严重时可将枣树嫩芽吃光,造成二次萌芽,削弱树势,推迟生育,严重降低红枣产量和品质。1形态特征枣芽象甲一生经过卵、幼虫、蛹、成虫四种形态。成虫:雄虫体长4.5~5.5mm,深灰色。雌虫体长约4.3~5.5mm,土灰色。头管粗短,末端宽,背面两复眼之间凹陷,前胸背面中间色较深,呈棕灰色。鞘翅弧形,每侧各有细纵沟10条,两沟之间有黑色鳞毛,鞘翅背面有模糊的褐色晕斑。腹面银灰色。卵:长椭圆形,堆生,初产时乳白色,后变棕色。幼虫:乳白色,体长5mm,略弯曲,无足。蛹:4.0~5.0mm,纺锤形,初乳白色,近羽化时红褐色。2生活习性1a(年)发生1代,以幼虫在土壤中越冬。春季3月下旬至4月上旬化蛹,蛹期12~15d(天)。4月中下旬当枣树萌芽时成虫出土,群集...

一维结构发光体的研制及发光特性的研究

论文从证实一种新的发光机制入手，首先详细地研究了具有一维结构的发光体Sr_2CeO_4的发光特性，对这一类发光体的发光机制有了较深入的认识。简单地说，Sr_2CeO_4的发光机制可表述如下，在Sr_2CeO_4中存在由CeO_6八面体通过公用边形成一维链状结构，在其链状结构中，存在两种Ce－O键：Ce－O－Ce和Ce-O, 后者比前者短0.1A，这种较短的 Ce-O键使电荷迁移成为可能，即O的一个外层电子吸收外界能量迁移至 Ce的空的f轨道形成电荷迁移态，然后该电子跃迁至基态辐射出光子。结合这种机制，我们总结了其他低维结构发光的规律和特征。具体为：1 一般在一维结构中存在不对称结构导致较短大M-O键时，才可能发生电荷迁移发光现象。2 一般在高价态的可变价元素且其低价具有发光性质中才可能产生电荷迁移发光。3 一维结构中电荷迁移发光大光谱一般为宽带激发和发射。我们相信这种发光机制里具有普遍性，因此以此为指导探索新的具有一维结构发光体的合成，并终于得到可一种新的发光体 Sr_2ZrO_4，研究发现，Sr_2ZrO_4的发光特性与Sr_2CeO_4极其相似。通过对两者X－射线衍射谱的比较和分析，以及文献的数据，我们认为在 Sr_2ZrO_4中也存在着由ZrO_6形成的一维链状结构。但遗憾的是，无论是Sr_2CeO_4还是Sr_2ZrO_4都未能发现同族的Ba、Ca化合物具有在室温下发光的现象。进一步，我们探索了Sr_2CeO_4和Sr_2ZrO_4作为发光基质的可能性。并发现，由于二者的宽带吸收和发射，它们都适于作发光基质。其中，Eu~(3+)，Er~(3+)等与基质有非常好的能量传递效率。

高性能综合电化学系统的研制与开发

现代分析化学正经历着一场新的重大变革。随着各门学科的相互交叉、高新技术的不断引进和分析对象的复杂多样化向传统分析仪器提出了严峻挑战。单纯采用一种分析方法和简单的数据处理技术，已无法揭示分析体系的特异性、复杂性和多样性。本文基于上述考虑，研制出高性能综合电化学系统，并力求将其设计为系统化、开放式与柔性化的多功能工作平台。通过对综合电化学系统的任意波形发生器、数据采集系统和恒电位仪的核心等进行细致研究和设计，我们在高速和高精度波形输出（分辨率为0.1mV时的扫速达600V/s，满度电压3V时可达25μV）、高达500KHz的数据采样速率、校宽的采样范围(1A～0.1pA)与高转换精度(16位)，高达10~(13)Ω的参比电极输入阻抗，0.1pA的微电流检测等技术指标上接近国外同类产品，并在输入阻抗、输入漏电流和采样速率等关键指标上更加优越。软件编程采用C++语言，集系统管理、实验控制和数据处理等多项功能于一体，人机界面友好。高性能综合电化学系统的多功能和模块化为新兴的电化学发光技术的引入和自动化的pH测试与聚合物场效应晶体管的性能测试等提供了可行性。只需设计专用测量与控制电路，并以总线方式与综合电化学系统相连接，便可赋予综合电化学系统的新的测试功能。这些工作进一步体现了我们所研制的综合电化学系统所具有的极好的适应性和极其灵活的开发能力。

联萘基手性联吡啶的合成及其应用

本论文以手性联萘酚为手性源，合成一系列联蔡基手性联毗陡及其衍生物，歼探讨了部分手性配体在不对称催化氢转移等反应中的应用。同时，通过部分配体与金属离子配位合成了旋光纯手性金属配合物，并对其溶液性质进行了深入研究。主要工作和结论如下：利用Krohnke方法，从（R）-6-乙酞基-2，2'-二甲氧基-1，1'-联萘简洁地合成了6-[6-((R)-2,2'-二甲氧基-1，1'-联萘基）]-2，2'-联吡啶及其衍生物（R)-1a-e。在相似条件下，合成了6，6'-二［6-（2，2'-联吡啶基）］-1，1'-联萘衍生物（R）-27-b。利用Suztlki偶联反应，对化合物（R）-1e进一步进行修饰得到了高产率的6-芳基-6'-[6-((R)-2,2'-二甲氧基-1,1'-联萘基）〕-2，2'-联吡啶(R)-1f-i。通过（R）3-（4，4，5：5-四甲基-1，3，2-二唑硼烷基）2，2'-乙氧基-1,1'-联萘与6-溴-2，2'-联吡啶及其衍生物的Suzuki偶联合成了四种手性6-［3-（（R）-2，2'-乙氧基-1，1'-联萘基）］-2，2'-联吡啶衍生物（R）-3a-d。将（R）-27b与AgSO3CF3进行配位合成Ag（I）配位聚合物35。固态下，35具有M构型的无限单股螺旋结构，且每个Ag（I）中心的手性受到配体，扫联蔡基的控制，其构型为Λ。在用MS、CD、UV及NMR对配合物35的溶液性质进行深入研究时发现，在溶液中配合物35离解为剂聚体，同时齐聚体之间存在快速平衡，且平衡随浓度、温度等条件的不同而发生改变，配体的平衡构象也相应被调整。另外，合成了Ag（I）与(R)-1d的单核配合物34，其洛液表现出与配台物35相似的性质。探讨了1a-i在苯乙酮氢转移还原、苯乙烯环丙烷化等不对称催化反应中的应用。在这些反应中，大部分配体表现出很好的反应活性，但立体选择性比较差。以(S)3，3'-二（4，4，5．5-四甲基-1，3，2-唑硼烷基于-2，2'-二（甲氧亚甲氧基）-1,1'-联萘为原料与2-溴吡啶及其衍生物先进行Stlzuki偶联，再经水解反应较高产率地合成了C2-对称性新型（S）-3，3'-二吡啶丛联茶酚衍生物（S）-38a-d。

不含桥基的茂金属烯烃聚合催化剂的合成及催化

本论文探讨了烯烃聚合催化剂的合成及其用于聚合的研究，合成的催化剂是不含桥基的IVB族的茂金属化合物。共合成了十九个茂金属化合物：（~tBuC_5H_4)CpMCl_2[M=Ti(1a)，Zr(1b)]； Me_3SiC_5H_4CpMCl_2[M=Ti(2a)， Zr(2b)]；~tBu_2C_5H_3CpMCl_2[M=Ti(3a)，Zr(3b)]；C_5H_9IndCpMCl_2[M=Ti(4a)，Zr(4b)]；PhCH_2IndCpMCl_2[M=Ti(5a)，Zr(5b)]；(~tBu_2C_5H_3)_2MCl~2[M=Ti(6a)，Zr(6b)，Hf(6c)]；(C_5H_9Ind)_2MCl_2[M=Ti(7a)，Zr(7b)，Hf(7c)]；(PhCH_2C_6H_5)_2MCl_2[M=Ti(8a)，Zr(8b)，Hf(8c)]。这十九个化合物分别通过EI-MS，~1H-NMR，IR 和元素分析进行了表征。用所合成的十九种茂金属化合物与甲基铝氧烷作为催化体系，在常温常压下，研究了乙烯聚合反应。得到的主要结论如下：（1）1a，2a， 5b 8b 催化活性最好。（2）1a 在铝钛比等于 1167 时聚合效率最高，2a 在铝钛比等于 1500 时聚合效率最高， 5b 在铝锆比大于 2955 时聚合效率最高，8b 在铝锆比等于 1667 时聚合效率最高。（3）相同的聚合条件下，催化效率是 1a＜2a，8b＜5b。（4）由聚合物的DSC表征中可见，所得聚合物的结晶度是 1a＜2a，5b＞8b。（5）由聚合物的分子量的测定可知，所得聚合物的分子量是 1a＞2a ，5b＜8b，由 8b 催化得到的聚合物的分子量最大。

60瓦半导体激光器光纤耦合器件

应用光纤列阵耦合方式，对大功率半导体激光器线列阵输出光束的快轴方向用一根柱透镜准直，准直后的光速耦合到光纤列阵中，实现出纤功率为60瓦的大功率半导体激光二极管线列阵光纤耦合效率大于80％，光纤的数值孔径NA为0.11。