Optimum Magnetic Circuit Configurations for Permanent Magnet Aerospace Generators

In the design of high-speed low-power electrical generators for unmanned aircraft and spacecraft, maximization of specific output (power/weight) is of prime importance. Several magnetic circuit configurations (radial-field, axial-field, flux-squeezing, homopolar) have been proposed, and in this paper the relative merits of these configurations are subjected to a quantitative investigation over the speed range 10 000–100000 rev/min and power range 250 W-10 kW. The advantages of incorporating new high energy-density magnetic materials are described. Part I deals with establishing an equivalent circuit for permanent-magnet generators. For each configuration the equivalent circuit parameters are related to the physical dimensions of the generator components and an optimization procedure produces a minimum volume design at discrete output powers and operating speeds. The technique is illustrated by a quantitative comparison of the specific outputs of conventional radial-field generators with samarium cobalt and alnico magnets. In Part II the specific outputs of conventional, flux-squeezing, and claw-rotor magnetic circuit configurations are compared. The flux-squeezing configuration is shown to produce the highest specific output for small sizes whereas the conventional configuration is best at large sizes. For all sizes the claw-rotor configuration is significantly inferior. In Part III the power densities available from axial-field and flux-switching magnetic circuit configurations are maximized, over the power range 0.25-10 kW and speed range 10 000–100000 rpm, and compared to the results of Parts I & II. For the axial-field configuration the power density is always less than that of the conventional and flux-squeezing radial-field configurations. For the flux-switching generator, which is able to withstand relatively high mechanical forces in the rotor, the power density is again inferior to the radial-field types, but the difference is less apparent for small (low power, high speed) generator sizes. From the combined results it can be concluded that the flux-squeezing and conventional radial-field magnetic circuit configurations yield designs with minimum volume over the power and speed ranges considered. © 1985, IEEE. All rights reserved.

Laboratory measurement of strength mobilisation in kaolin: Link to stress history

This letter presents data from triaxial tests conducted as part of a research programme into the stress-strain behaviour of clays and silts at Cambridge University. To support findings from earlier research using databases of soil tests, eighteen CIU triaxial tests on speswhite kaolin were performed to confirm an assumed link between mobilisation strain (γ M=2) and overconsolidation ratio (OCR). In the moderate shear stress range (0.2c u to 0.8c u) the test data are essentially linear on log-log plots. Both the slopes and intercepts of these lines are simple functions of OCR.

武汉市郊农田土壤中有机氯农药的残留分析

通过采集武汉市郊农田表层土壤,用GC-ECD法分析了土壤中HCH(六六六)、DDT(滴滴涕)及其代谢物的残留情况.结果表明:HCH残留低于DDT,∑HCHs介于0.18~18.90 ng.g-1,平均值为1.97 ng.g-1,∑DDTs介于1.82~165.34 ng.g-1,平均值为31.41 ng.g-1;残留水平较高的是p,p′-DDE、p,p′-DDD和p,p′-DDT.部分表层土壤中的∑DDTs超出了中国土壤环境质量标准的自然背景值.初步分析结果表明武汉市郊土壤中HCH及DDT的含量处于低浓度

基于光合色素的化学分类法在淡水藻类研究中的应用

采用反相高效液相色谱技术(RP-HPLC)系统研究了我国主要淡水藻类———蓝藻、绿藻、硅藻、甲藻、金藻、裸藻和隐藻等的光合色素,在8种纯培养藻类中共确定类胡萝卜素、叶绿素及其衍生物19种。分离到的主要标志性色素按洗脱时间分别为脱植基叶绿素a、19′-丁酰氧岩藻黄素、叶绿素c、脱镁叶绿素a、多甲藻素、甲基脱植基叶绿素a、岩藻黄素、新黄质、紫黄质、蓝藻叶黄素、硅甲藻黄素、硅藻黄质、叶黄素、玉米黄素、叶绿素b异构体、叶绿素b、叶绿素a异构体、叶绿素a和β-胡萝卜素;其中在纯培养的铜绿微囊藻中首次鉴定到19′-丁

阳光紫外辐射对室内水培发状念珠藻生理特性的影响

发状念珠藻(Nostoc flagelli forme Bornet & Flahault)是一种重要的陆生经济蓝藻,室内培育出的原植体如何适应阳光辐射的问题尚需探讨。为此,作者将室内水培发菜置于阳光下培养,测定了其生长、有效光化学效率(ΔF/F′m)和色素的变化。结果表明,较高的可见光(PAR,395—700nm)和紫外辐射(UVR,280—395nm)均导致水培发菜的ΔF/F′m下降。第1天中午,PAR和UVR分别使ΔF/F′m下降了54%和13%;傍晚,ΔF/F′m有部分恢复。UVR对发菜适应阳光2

两种东方鲀的GH基因单核苷酸多态性分析

根据红鳍东方鲀生长激素基因全序列,设计13对引物,结合单链构象多态性(SSCP)技术和克隆测序技术对野生红鳍东方鲀、养殖红鳍东方鲀和养殖暗纹东方鲀群体进行了遗传多样性分析。结果表明:东方鲀整个生长激素基因的6个外显子中没有多态性,在其内含子2、内含子5以及3′侧翼区发现有多处序列变异位点,包括碱基的缺失、插入和一些单核苷酸突变。这些遗传多态性的存在为从分子水平上对东方鲀的鉴定提供了一定的依据。群体遗传结构分析结果表明,红鳍东方鲀养殖群体的一些等位基因丧失,造成其遗传多样性显著下降,应及早加强对其种质的保护

草鱼免疫球蛋白M重链基因的克隆及表达

用RACE-PCR方法扩增出草鱼免疫球蛋白M(immunoglobulin M,IgM)分泌型的重链全长cDNA。其cDNA全长为1 940nt,包含5′非编码区20nt,3′非编码区189nt,开放阅读框1 731nt,编码576个氨基酸。序列比对分析表明草鱼IgM与鲤的相似性高达68%,与斑马鱼、斑点叉尾鱼回、鳜以及大西洋鳕的相似性分别为61%、43%、33%和30%。ClustalX比对结果显示:草鱼IgM中存在半胱氨酸和色氨酸的保守位点。进化分析表明,草鱼IgM与斑马鱼的IgM聚为一枝。荧光定量P

不同纬度螅状独缩虫耐热能力及Hsp70 mRNA表达水平的比较

本文以游泳体的形成作为虫体对热激响应的指征,比较了不同纬度(西安:东经108°98′,北纬34°25′;武汉:东经114°34′,北纬30°57′)两地螅状独缩虫(Carchesium polypinum)的耐热能力,发现武汉地区螅状独缩虫(WH株)形成游泳体的热激温度(36℃)高于西安地区(XA株)的33℃,说明前者的耐热能力较强;进一步利用实时PCR技术分析不同热激温度下两地螅状独缩虫热休克蛋白Hsp70mRNA的表达变化发现,XA株Hsp70mRNA热激后高表达水平的阈值温度为28℃,而WH株的为3

基于S6K1基因部分序列的鲤科鱼类系统发育关系及内含子1Indel位点分析

鲤科鱼类在东亚分布广泛且数量丰富,在物种演化上具有重要的系统发育地位.本研究基于S6K1基因5′端功能调控序列,通过PCR扩增、克隆和测序,共获得30种鱼类S6K1前端部分DNA序列(外显子1,外显子2及内含子1),对序列变异进行分析,并采用邻接法(NJ)、最大简约法(MP)、最大似然法(ML)和贝叶斯法(Bayesian)重建鲤科鱼类系统发育关系.亚口鱼科的胭脂鱼(Myxocyprinus asiaticus)作为外类群,通过4种方法所得系统发育分支图大致相同,均以较高的节点支持率支持雅罗鱼系和鲃系的划

黄颡鱼属两种鱼类的线粒体ND4基因序列变异性分析

以东亚特有种光泽黄颡鱼(Pelteobagrus nitidus)和长须黄颡鱼(Pelteobagrus eupogon)为研究对象,采用PCR技术获得了这两种鱼类的部分线粒体DNA DN4基因及其3′端的tRNA基因碱基共约772个,用MEGA2.1软件分析了此片段序列,采用Kimura双参数模型计算遗传距离,以科属的大鳍(Hemibagrus macropterus)为外类群,用邻接法构建不同水系的光泽黄颡鱼和长须黄颡鱼的分子系统树。不同水系的光泽黄颡鱼的遗传距离在0.000—0.012之间,长须黄颡

淋巴囊肿病毒中国株TNFR类似物的原核表达与结构分析

肿瘤坏死因子受体(TNFR)是细胞因子受体家族中的一员,在大DNA病毒的免疫逃避中起着重要的作用。 淋巴囊肿病毒中国株(LCDV-C)是一种大DNA病毒,属于虹彩病毒科。参照已知虹彩病毒TNFR基因设计引物: P1,5′GGATCCAAAACTATGATTAAAATAAAGA 3′;P2:5′ATTACTCGAGAATGTTAAAAATTAAGCTT 3′。以LCDV-C基因组DNA为模板,PCR扩增得到一个834bp的DNA片段,并对该片段进行测序。构建原核表 达重组质粒后,在大肠杆菌DE3中诱导表达,

鳜IL-1β基因的克隆及原核表达

用RACE PCR获得了鳜白介素-1β(IL-1β)的全长cDNA.鳜IL-1β的cDNA全长为1298 nt(核苷酸),其5′非编码区包含UTR 93 nt;3′非编码区包含452 nt;其开放阅读框内包含753 nt,翻译成251个氨基酸.将鳜IL-1β克隆到原核表达载体pET-32a上,在大肠杆菌Rosetta- gami(DE3)内以包涵体形式得以高效表达.

Graphics processing unit cooling solutions: Acoustic characteristics

The change in acoustic characteristics in personal computers to console gaming and home entertainment systems with the change in the Graphics Processing Unit (GPU), is presented. The tests are carried out using identical configurations of the software and system hardware. The prime components of the hardware used in the project are central processing unit, motherboard, hard disc drive, memory, power supply, optical drive, and additional cooling system. The results from the measurements taken for each GPU tested are analyzed and compared. The test results are obtained using a photo tachometer and reflective tape adhered to one particular fan blade. The test shows that loudness is a psychoacoustic metric developed by Zwicker and Fastal that aims to quantify how loud a sound is perceived as compared to a standard sound. The acoustic experiment reveals that the inherent noise generation mechanism increases with the increase of the complexity of the cooling solution.

PFU微型生物群落采样法研究有机氯污染物在水中相间分布

运用PFU微型生物群落采样法在武汉东湖取样研究了六六六、滴滴涕、六氯苯等有机氯污染物在水中相间分布。将PFU(Polyurethanefoamunit)取样得到的挤出液 ,经细胞固定、超声、消解及分步萃取等不同的预处理步骤后 ,用GC ECD测定了各部分提取物中α HCH、β HCH、γ HCH、δ HCH、HCB、pp′ DDE等有机氯污染物的浓度。并用四膜虫模拟试验检验了细胞固定化、消解过程对微型生物的作用效果。结果分析表明 ,以上有机物主要以微型生物富集或颗粒物强吸附形式存在于水中 ,颗粒物弱吸附形

香港米浦基围塘中有机氯农药和多氯联苯在微型生物群落中的积累

分别在 2 0 0 1年和 2 0 0 2年用国家标准《水质 -微型生物群落监测 -PFU法》在香港米浦自然保护区的基围塘和红树林中监测水质 .在 3个基围塘中共鉴定出 91种原生动物 ,为香港地区的首次记录 .同时在群落级水平上分析了4种生态结构参数和 5种功能参数 .用化学的方法成功地监测出在此 3个基围塘的PFU挤出液中 pp′-DDE和PCB的浓度 ,并且获得两年一致性的结果 .本文化学和生物学结合的研究结果为测定水中超痕量持久性有机污染物 (POPs)的环境暴露与生态毒性提供了一种新的尝试 .图