多室式钢管混凝土T形柱压弯性能分析

对几种新型多室式钢管混凝土T形柱形式,通过有限元方法研究其典型压弯受力性能,考虑多室式布置方式、轴压比、混凝土强度等因素的影响。有限元分析结果与试验结果基本符合,其中将腹板钢材延伸到翼缘内,并在最为薄弱的腹板尖端加厚钢板的多室式布置最为合理。研究发现,随轴压比增大,曲线延性下降,构件正向和负向承载力差距变大。混凝土强度下降时,承载力有小幅下降,构件的延性位移有所增加。     

基于功率谱密度的风电功率特性分析

风电有功功率波动特性的分析,对指导发电和电网运行非常重要。根据内蒙古赤峰东山风电场运行的实测数据,运用功率谱密度分析的方法,对风电有功功率的波动特性进行了分析。结果表明,风电功率的功率谱密度在超过4个数量级频域范围内符合Kolmogorov谱分布理论,且装机容量的增加,对风电功率的汇聚效应具有明显的影响。     

排包小议

１排包与混棉混棉是清棉工序主要任务之一，各种原棉成分的充分混和，对黄白纱的产生及单强ＣＶ％的改善，都有密切的关系。抓棉机既抓棉同时又肩负着混棉的作用，圆盘式抓棉机每转一周，即完成一个混棉成分，或称混棉单元，而往复式抓棉机若棉包排列得当，一个单程即可完...     

GB/T20887.2-2010汽车用高强度热连轧高扩孔钢(英文)

With the increasing requirements for reducing the weight and emission of automobiles,the automobile manufacturers turn to use the high strength steel.Car chassis as an important component has complex shape and is difficult to form.As the strength of design steel strength increases from     

法律法规对钢铁产品中有毒有害物质的限制和钢厂应对策略

介绍了国内外法律法规对钢铁产品中有毒有害物质的限制规定，宝钢在针对这些法律法规的规定进行识别的同时，还研究了用户采购技术规范中的相应规定，确定合适的检化验方法，以验证宝铜的铜铁产品是否符合相关法律法规的规定。根据宝钢的经验，确保钢铁产品符合相关法律法规规定的关键，是对钢铁产品制造过程所使用的原材料进行限制和控制。     

PXI数字I/O数据传输的实现

虚拟仪器技术将仪器功能分为输入、输出和数据处理3个模块,通过PXI(compact PCI bus extensions for instrumentation)等总线平台来建立系统.因此,理论上在虚拟仪器平台上借助I/O模块和程序支持就能完成信号输入、输出和处理的全部软硬件设计.文中基于PXI总线平台和LabWindows/CVI软件开发环境,以PXI-6533数据传输的向量模式为例,探讨数字I/O在虚拟仪器系统中对数字信号传输的控制问题,以及基准频率、占空比和数据传输宽度的设定和程序实现.     

发电电动机励磁绕组匝间短路故障在线监测

通用的励磁绕组匝间短路故障在线监测方法未加分辨地采用定子中性点不平衡电流中的所有分数次谐波分量构成监测量及相应的报警值,可能因报警值较高而对小匝数故障不够灵敏。以江苏宜兴抽水蓄能电站发电电动机为例,计算小匝数励磁绕组匝间短路故障引起的定子中性点不平衡电流并实测正常工况下固有不平衡电流,在此基础上提出了一种改进的在线监测方案,提取由匝间短路引起的不平衡电流中含量较高的3/8次和5/8次谐波电流构成报警值。仿真计算结果表明,对于江苏宜兴抽水蓄能电站发电电动机,改进的在线监测方案能对3%及以上匝比的励磁绕组匝间短路故障发出警报,灵敏性优于通用监测方案。基于所提改进方案的在线监测装置已经成功投运于江苏宜兴抽水蓄能电站4号发电电动机。     

Alzheimer’s Disease—A Panorama Glimpse

The single-mutation of genes associated with Alzheimer’s disease (AD) increases the production of Aβ peptides. An elevated concentration of Aβ peptides is prone to aggregation into oligomers and further deposition as plaque. Aβ plaques and neurofibrillary tangles are two hallmarks of AD. In this review, we provide a broad overview of the diverses sources that could lead to AD, which include genetic origins, Aβ peptides and tau protein. We shall discuss on tau protein and tau accumulation, which result in neurofibrillary tangles. We detail the mechanisms of Aβ aggregation, fibril formation and its polymorphism. We then show the possible links between Aβ and tau pathology. Furthermore, we summarize the structural data of Aβ and its precursor protein obtained via Nuclear Magnetic Resonance (NMR) or X-ray crystallography. At the end, we go through the C-terminal and N-terminal truncated Aβ variants. We wish to draw reader’s attention to two predominant and toxic Aβ species, namely Aβ₄₋₄₂/ and pyroglutamate amyloid-beta peptides, which have been neglected for more than a decade and may be crucial in Aβ pathogenesis due to their dominant presence in the AD brain.     

In Situ Electrochemical Synthesis and Deposition of Discotic Hexa‐peri‐hexabenzocoronene Molecules on Electrodes: Self‐Assembled Structure,Redox Properties,and Application for Supercapacitor

Discotic hexa‐peri‐hexabenzocoronene (HBC) molecules are synthesized by electrochemical cyclodehydrogenation reaction and in situ self‐assembled to π‐electronic, discrete nanofibular objects with an average diameter about 70 nm, which are deposited directly onto the electrode. The nanofibers consist of columnar arrays of the π‐stacked HBC molecules and the intercolumnar distance is determined to be 1.19 nm by X‐ray diffraction, which corresponds well to the distance of 1.1 nm observed by high‐resolution transmitting electron microscopy. The diameter of the molecular columns matches the size of the discotic HBC molecule indicating face‐to‐face π‐stacking of HBC units in the column. The HBC nanofibers on electrode are redox active, and the nanosized columnar structures provide a huge surface area, which is a great benefit for the charging/discharging process, delivering excellent capacitance of 155 F g^?1. The described electrochemical deposition method shows great advantage for self‐assembling the family of insoluble and structurally designable graphene‐like nano materials, which constitutes an important step toward molecular electronics.     

基于有限元法的周期拱形结构振动特性

设计一种新型低频隔振系统,该系统利用拱形的结构特点,将拱形结构重组设计后沿竖直方向周期化排列,形成周期拱形结构。运用有限元法结合Bloch定理对周期拱形结构的振动传播特性进行理论推导,并讨论尺寸和材料参数对振动带隙的影响规律。讨论发现,拱形高度对隔振频率范围没有影响,这能够很好解决工程实际中在某一方向有空间尺寸限制的问题,实现此方向小尺寸隔振的目的;隔振频率的降低可以通过增加结构长度、减小材料厚度、降低材料弹性模量和密度来实现。通过有限元分析软件和试验测试证实了周期拱形结构带隙算法的有效性。分析和测试结果证明,周期拱形结构具有小尺寸抑制该方向低频振动的能力,这对工程实际中的低频隔振技术具有参考价值。