W-35%Cu液相活化烧结工艺研究

本文从钨铜两相迁移机制和固溶扩散的角度 ,实验研究了钨铜复合粉的活化和常规烧结 ,分析了钨铜复合粉液相活化烧结过程中球磨时间、烧结温度、保温时间和升温速度对材料致密度的影响。结果表明 ,短时间球磨的钨铜复合粉具有良好的烧结性能 ,烧结温度和保温时间对材料致密度影响很大 ,活化烧结能有效降低烧结温度 ,提高烧结致密度     

Effect of Different Surface Treatment Methods on the Friction and Wear Behavior of AISI 4140 Steel

In this study,the effects of various surface treatments on the friction and wear behavior of AISI 4140 steel have been evaluated.Sample surfaces of AISI 4140 steel were treated by quenching,carburizing,boronizing and plasma transferred arc (PTA) modification.The microstructural characteristics of surface treated steel samples were examined by optical microscopy and scanning electron microscopy (SEM).The mechanical properties of the samples including the surface roughness,microhardness,and abrasive and adhesive wear characteristics were also evaluated.Wear tests were applied by using a block-on-disc configuration under dry sliding conditions.The wear behavior and friction characteristics of the samples were determined as a function of sliding distance.Each sample group was compared with the other sample groups,and it was observed that the carburized samples demonstrated the lowest weight losses;however,PTA-treated samples demonstrated the lowest coefficient of friction in comparison to the other sample groups at the same sliding distance.     

硫钝化对Fe/GaAs(100)界面电子结构和磁性质的影响

利用同步辐射和铁磁共振研究了使用 CH3CSNH2 硫钝化的 Ga As( 1 0 0 )表面铁超薄膜的电子结构和磁性 .实验结果表明 ,硫钝化能阻止 As向铁薄膜层的扩散 ,减弱 As和 Fe的相互作用并增强了在 Ga As( 1 0 0 )表面生长的铁超薄膜的磁性 .     

国内外钻探用金刚石复合片性能的研究

主要介绍国内外金刚石复合片性能及采用四高复合片钻探硬岩的初试,为快速钻探提供一个新的途径.     

辛酰丙氨酸镁（Ⅱ）、钙（Ⅱ）及锌（Ⅱ）配合物的溶解性及其聚集行为

采用镁、钙和锌的氢氧化合物分别与辛酰丙氨酸配体[CH3(CH2)6CONHCH(CH3)COOH]反应,合成了辛酰丙氨酸镁、钙和锌表面活性剂配合物。通过配合物的纯溶媒及水/有机溶媒系的溶解性测试发现,镁和钙的配合物均在大部分有机纯溶媒和水/有机溶媒系里有极高的溶解性,而锌的配合物在大部分有机纯溶媒系里有很低的溶解性。此外,通过核磁共振(NMR)光谱、电导、蒸汽压降下(VPO)和FTIR方法研究了溶液中镁、钙和锌表面活性剂配合物的聚集行为。Mg(oct-ala)2、Ca(oct-ala)2和Zn(oct-ala)2配合物在有机溶媒系里吸附水易发生聚集行为,并有形成逆胶束体的倾向。     

Mechanically activated disproportionation of NdFeB alloy by ball milling in hydrogen

1　INTRODUCTIONSincethediscoveryoftheuniaxialNd2 Fe14 Bcompoundin 1983[1,2 ] ,theNdFeBalloyshavebeenwidelyusedforpermanentmagnetapplicationsowingtotheirexcellentmagneticproperties ,suchashighcoercivity ,high energy products[3,4 ] .Intheserareearthpermanentmagnets ,afurtherexcitingrecentdevelopmentisthesuggestionofnano compositeex changemagnetscombiningthelargecoercivitiesinhardmagnetswithlargeinductionsfoundinsoftertransitionmetalmagnets[5,6 ] .Indeed ,thenano com positemagnetshavebeent…     

刚性桩复合地基承载及变形特性试验研究

通过现场试验 ,测出了刚性桩复合地基各土层的变形、桩体的上下刺入量、桩身轴力、侧摩阻力 ,并由此得到桩土荷载分担比、应力比 .试验表明 :垫层起到了使桩土共同参与工作的作用 ,使土能够较充分发挥其承载能力 ;单桩复合地基中加固层压缩是产生沉降的主要原因 ,下卧层的压缩量很小 ,垫层压缩量占沉降的比例随荷载而变化 ;单桩复合地基首先是桩周土承担较大荷载 ,使其从局部剪切破坏开始 ,逐步向整体剪切破坏发展 ,而后随着桩承担荷载的加大 ,桩承载力达到极限而破坏 ,进而复合地基发生破坏     

植被作用下的弯曲复式河槽漫滩水流2维解析解

研究植被作用下的弯曲复式河槽流速分布对于确定其过流能力、泥沙输移、河床变形、滩岸保护有着十分重要的作用。作者研究了有植被的弯曲复式河槽中的垂线平均流速横向分布问题,在动量方程中加入滩地植被引起的拖曳力项,并考虑弯曲主槽和二次流的影响,采用3种不同的紊流扩散项积分方法,得到了3种计算模型。运用英国FCF弯曲复式河槽试验资料对模型进行验证,结果表明,在不同区域选取合适的二次流系数K比仅考虑主槽中的K值能更好地预测流速分布;滩地种植植物后,主槽中的K值明显增大;3种模型的预测结果在滩地上基本相同,主要差别出现在主槽区和掺混区。通过比较分析不同模型的计算误差,得到了计算结果最优的模型。     

能源动力类专业基础课参与式教学设计与实践

以教学实践为基础,结合能源动力类专业基础课课程的教学特点,深入探讨创新型人才培养背景下参与式教学在《热工理论基础》系列课程中应用的设计理念、实施策略、实践过程及其结果,结果表明参与式教学对于提高学生学习兴趣、自主能力和创新能力起着积极地作用,探索出了行之有效的工科专业基础课参与式教学模式。     

Selective Covalent Protein Modification by 4‐Halopyridines through Catalysis

We have investigated 4‐halopyridines as selective, tunable, and switchable covalent protein modifiers for use in the development of chemical probes. Nonenzymatic reactivity of 4‐chloropyridine with amino acids and thiols was ranked with respect to common covalent protein‐modifying reagents and found to have reactivity similar to that of acrylamide, but could be switched to a reactivity similar to that of iodoacetamide upon stabilization of the positively charged pyridinium. Diverse, fragment‐sized 4‐halopyridines inactivated human dimethylarginine dimethylaminohydrolase‐1 (DDAH1) through covalent modification of the active site cysteine, acting as quiescent affinity labels that required off‐pathway catalysis through stabilization of the protonated pyridinium by a neighboring aspartate residue. A series of 2‐fluoromethyl‐substituted 4‐chloropyridines demonstrated that the pK_a and k_inact/K_I values could be predictably varied over several orders of magnitude. Covalent labeling of proteins in an Escherichia coli lysate was shown to require folded proteins, indicating that alternative proteins can be targeted, and modification is likely to be catalysisdependent. 4‐Halopyridines, and quiescent affinity labels in general, represent an attractive strategy to develop reagents with switchable electrophilicity as selective covalent protein modifiers.