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Search Results: 1 - 10 of 203175 matches for " 周伟军 "
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遥观南枢纽泵站工程水泵机组选型研究?
 丁
南水北调与水利科技 , 2014,
Abstract: 遥观南枢纽泵站工程是新沟河延伸拓浚工程的干河枢纽工程之一,其主要任务是抽排武进港地区的水入京杭大运河,兼顾排涝。该泵站设计净扬程仅为0.7m,属超低扬程泵站。根据已建泵站工程模型泵装置试验成果,从水力性能、工程投资、施工和运行管理等方面进行综合比较,选用了已在溧阳新村枢纽成功应用的贯流泵水力模型。考虑到该泵站的最大扬程接近设计扬程的3倍,还对电机定速和调速方案进行了投资及运行成本比较,发现调速方案机泵投资较大,但运行成本的降低并不显著,因此最终采用定速方案。
利用小孢子胚离体筛选抗除草剂油菜的研究
许玲,,
农业生物技术学报 , 2005,
Abstract:
黑暗条件下逆境胁迫诱导油菜籽次生休眠
,KRISTIANSSON,Bo
浙江大学学报(农业与生命科学版) , 2000,
Abstract: Oilseed rape seeds (Brassica napus L.) harvested from mature plants require only imbibition of water and a suitable temperature. Despite this absence of primary dormancy, there is evidence that rapeseeds, due to the induction of secondary dormancy, are able to persist in the field for up to 10 years, and thus can emerge as volunteer plants in later crops. In addition, volunteers originate from seeds shed before and during harvest. The level of seed losses is influenced by the timing and technique of harvest, and can reach several thousand seeds per m2. As a consequence of both these effects, problems from volunteer rape occur frequently in subsequent crops.   Volunteer rape has been particularly troublesome in broad-leaved crops. It is a highly competitive weed and due to its prolonged period of emergence, timing of herbicide application is sometimes a problem. Volunteer rape can contaminate the sown crop resulting in heterogenous mixtures of seeds. This not only affects breeding and the production of seed crops, but can also affect growers when they switch from one type or quality of rape to another, or if they grow different rape qualities in one rotation, e.g., rapeseed for human consumption in the normal rotation and rapeseed for industrial use on set-aside land. The problem will not disappear with the introduction of herbicide resistant oilseed rape, as there are no indications that seeds of these cultivars will not have the potential to persist. The ability of rapeseed to persist in the soil for a long time and at high percentages also has to be taken into account in risk assessment of genetically manipulated rape, as rape can escape in space by pollen transfer or in time via the soil seedbank. Although hybridization between oilseed rape and wild crucifers is infrequent, it does occur. Traits, such as herbicide resistance or pest and disease resistance, if transferred into wild plants have the potential to alter the agro-ecosystem significantly.……
导管螺旋桨不同桨叶的叶梢泄露涡分析
,王大政
哈尔滨工业大学学报 , 2014, DOI: 10.11918/j.issn.0367-6234.2014.07.003
Abstract: 为了深入探讨叶梢泄露涡的流动机理,研究了导管螺旋桨中桨叶螺距比与盘面比对叶梢泄露涡的影响,以及不同桨叶中叶梢泄露涡、叶梢负荷与叶梢泄露流三者之间的关联.采用数值方法对不同桨叶的导管螺旋桨流场进行了模拟分析.结果表明:当螺距比增大,叶梢泄露涡逐渐远离桨叶吸力面,涡核空化数降低;当盘面比增大,叶梢泄露涡的轨迹基本不变化,涡核空化数提高;叶梢泄露流通过与叶梢泄露涡之间的流动剪切作用影响叶梢泄露涡的发展;叶梢泄露流流速受到叶梢负荷的影响,负荷越高的位置,叶梢泄露流的速度也越高.
基于完全式公钥的叛徒追踪方案的密码分析

计算机科学 , 2007,
Abstract: 由于广播加密容易受到串谋攻击,叛徒追踪方案已成为版权保护的一个重要工具。利用中国剩余定理让用户自己生成私钥,lyuu和wu提出了面向无状态接收者的e1gamal类广播加密算法及黑盒可追踪方案。本文首先从群编码和参数配置的角度考察对该方案的几种安全威胁。接着,利用解密预言机发起一种适应性选择密文攻击。最后,针对其密钥管理与追踪算法的特点提出一种串谋攻击方法,使其不能追踪出所有的叛徒和真正的盗版者,表明在实际应用中完全式公钥方法存在冤枉无辜用户的安全风险。
转子叶尖引射式射流的数值研究
,侯安平,
力学学报 , 2011, DOI: 10.6052/0459-1879-2011-1-lxxb2009-603
Abstract: 转子叶尖射流能够有效地提高压气机的稳定工作裕度,但是现有的各种射流器结构复杂,并使发动机的重量增加.研究目的在于探索一种新型的射流方式,以方便在压气机中的实现,并且不增加发动机的重量.采用对转子叶尖前缘位置机匣进行局部修型的方法,提高了转子叶尖前缘附近流场的轴向速度,从而产生类似转子叶尖射流的效果.在Rotor37上的数值分析发现,该方法能够提高转子的失速裕度约6.7%,并能使转子的效率与压比有较小的提升.对比不同机匣修型方案发现,修型位置对压气机裕度的影响最为明显.对转子叶尖流场的分析表明,该方法能够提高转子叶尖前缘的轴向速度,并将叶尖泄露涡向下游推移,减小了转子叶尖的流动堵塞,从而拓宽了转子的失速裕度.
钛合金β→α相变的变体选择
Variant Selection of β→α Phase Transformation in Titanium Alloys
 [PDF]

杨义, 卢亚锋, 葛鹏, 冯亮, 屈磊, , 黄爱
Material Sciences (MS) , 2014, DOI: 10.12677/MS.2014.45028
Abstract:
β→α转变是钛合金中最基本和最重要的一种相变,两相之间存在严格的Burgers取向关系,即(0001)α//{110}β和<1120>α//<111>β,这种关系决定了在一个β晶粒内可能会出现12个α相变体。在各种类型的钛合金中,均会出现在一个β晶粒内只有少数几个取向的α相能够存在的现象,即发生变体选择,其对强度、塑性、疲劳等力学性能的负面影响逐步被关注,抑制其发生将是进一步提高钛合金性能的潜在方法之一。本文结合作者的研究工作,介绍了钛合金中β→α转变时发生变体选择的本质、成因以及对合金力学性能的影响等方面的研究现状,并分析了该研究方向目前存在的问题和今后的研究重点。
β→α transformation is the most essential phase transition in titanium alloys. The α phase formed in the β matrix is oriented according to the so-called Burgers orientation relationship, viz. (0001)α//{110}β and <1120>α//<111>β. Because of the symmetry of the two crystals, 12 α va-riants can form in a β grain theoretically. Variant selection can take place in almost all kinds of ti-tanium alloys and decline the strength, plasticity and fatigue resistance, which have been attended by the researchers gradually. To control the occurrence of variant selection will be one of the po-tential methods to improve the properties of titanium alloys. In this paper, by integrating our re-search work, the progress in research of variant selection of β→α phase transformation in titanium alloys is briefly reviewed from aspects of the substance and the reason of variant selection, and its influence on the mechanical properties. The problems at present study and the research directions in the future are also analyzed.
基于可变逻辑门限的HEV多目标优化仿真
,云山,
公路交通科技 , 2012,
Abstract: 为实现混合动力汽车的动力性、燃油经济性以及模式切换平顺性,以基于CVT的插电式混合动力汽车为研究对象,针对混合动力汽车的多目标优化问题,提出一种可变逻辑门限控制策略。整车控制过程中根据功率需求进行模式切换,其中行驶需求功率根据车速和节气门开度计算得到,切换门限根据整车参数实时计算。以发动机和电机的输出特性、电池的SOC为主要依据计算工作模式切换的可变逻辑门限值。通过电机助力保证整车具有较好的动力性能,通过不同模式下驱动功率的一致性实现模式切换平顺,通过小功率需求时仅可能多用纯电动来提高燃油经济性。在MATLAB/Simulink平台下建立混合动力汽车前向仿真模型,并在NEDC工况下进行仿真。仿真结果表明整车动力性能得到了提高,实现了模式切换平顺性,节油40%。
新疆北疆地区葡萄霜霉病发病规律研究及综合防治技术
,贺建华,
北方园艺 , 2014,
Abstract:
轻钢龙骨房屋足尺模型低周反复试验
,马庆平,
地震工程与工程振动 , 2011,
Abstract: 对一个具有完整边界条件的轻钢龙骨体系房屋足尺模型进行了低周反复试验。试验主要考虑转角墙对轻钢龙骨体系房屋抗震性能的影响,以及龙骨壁厚对复合承载墙体破坏模式的影响,研究房屋在低周反复荷载作用下的变形过程、破坏特征和滞回性能等。试验结果表明轻钢龙骨房屋的抗震性能与自攻螺钉连接性能密切相关。自攻螺钉的连接性能决定了轻钢龙骨房屋的耗能机制、耗能能力以及破坏形态。由于螺钉在该结构中分布广泛,使得结构的侧向变形能力和耗能能力较好,同时,试验验证了轻钢龙骨复合墙体抗剪承载力计算时关于自攻螺钉连接受力方向的假设和受力大小分析结果的正确性。
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