高频超声空化场喷射枪

根据高频超声及其空化场的力、热效应,以及空化场聚束管和液-固界面的增强作用原理,提出、设计和制作了一种小型的高频超声空化场喷射枪。试验表明,它用于水下破解冰冻物品、高分子板材焊接和瓶装液体除气方面是可行的。     

电子在相互垂直的均匀电场和磁场中的运动

本文应用四元数形式的相对论性波动方程,对电子在相互垂直的均匀电场和磁场中的运动进行了分析,并求出了在忽略算符EQEuCi的近以条件下的能量本征值和本征函数。     

社会资本视角下科学共同体中的马太效应

从社会资本的视角探讨了马太效应所体现的不公平性和排他性,有助于处理现代科技管理中公平和效率之间的矛盾。     

In vitro corrosion of Mg–1.21Li –1.12Ca –1Y alloy

The influence of the microstructure on mechanical properties and corrosion behavior of the Mg–1.21Li–1.12Ca–1Y alloy was investigated using OM, SEM, XRD, EPMA, EDS, tensile tests and corrosion measurements. The results demonstrated that the microstructure of the Mg–1.21Li–1.12Ca–1Y alloy was characterized by α-Mg substrate and intermetallic compounds Mg2 Ca and Mg24Y5. Most of the fine Mg2 Ca particles for the as-cast alloy were distributed along the grain boundaries, while for the as-extruded along the extrusion direction. The Mg24Y5 particles with a larger size than the Mg2 Ca particles were positioned inside the grains. The mechanical properties of Mg–1.21Li–1.12Ca–1Y alloy were improved by the grain refinement and dispersion strengthening. Corrosion pits initiated at the α-Mg matrix neighboring the Mg2 Ca particles and subsequently the alloy exhibited general corrosion and filiform corrosion as the corrosion product layer of Mg(OH)2and Mg CO3 became compact and thick.     

Tubular pure copper grain refining by tube cyclic extrusion–compression (TCEC) as a severe plastic deformation technique

Tube Cyclic Extrusion–Compression(TCEC) method is a novel severe plastic deformation technique developed for grain refining of cylindrical tubes to ultrafine grained(UFG)/nanostructured ones. In this method, tubes are fully constrained and deformed between chamber and mandrel with a small neck zone. The principle of TCEC technique which was adopted to impose severe plastic strains to the tubular materials was explained. Also, the deformation and grain fragmentation mechanism during TCEC was analyzed. The material deformation characteristics during TCEC were numerically simulated by FE code of ABAQUS/Explicit. The FEM results demonstrated that TCEC technique was able to impose extremely high plastic strains. The TCEC method was successfully applied to a commercially pure copper(99.99%) and significant grain refinement was achieved. TEM observation demonstrated the refinement of grains from the initial size of 45 μm to 200–350 nm after four processing cycles of TCEC. Microhardness measurements were carried out across the thickness of the initial and processed tubes. The results show good homogeneity of hardness distribution and an increase to 102 Hv from initial value of 55 Hv after four TCEC cycles. Mechanical properties of the specimens were extracted from tensile tests. The obtained results documented notable increase in the yield and ultimate strengths, whereas the uniform and total elongations decreased. Fracture surfaces after tensile tests were investigated by scanning electron microscopy(SEM), and the observed morphology indicates ductile fracture mode after four cycles of TCEC.     

Enhancement of the thermo-mechanical properties and efficacy of mixing technique in the preparation of graphene/PVC nanocomposites compared to carbon nanotubes/PVC

Thin films of poly vinyl chloride(PVC)/multiwalled carbon nanotubes(MWCNT) and PVC/graphene(GN) nanocomposites were prepared by mixing in the presence of different quantities of nanoparticles. Film casting was performed using tetrahydrofuran as a solvent. The as-prepared PVC/MWCNT and PVC/GN nanocomposites were characterized by scanning electron microscopy, Raman spectroscopy, X-ray diffraction,thermogravimetric analysis, differential scanning calorimetry, dynamic mechanical analysis, and diffused reflectance spectroscopy. Only the PVC/GN nanocomposite films were evaluated further for detailed mechanical analysis because of the poor dispersion of MWCNTs in PVC. The PVC/GN nanocomposite films were thermo-mechanically more stable than the PVC films. These nanocomposites have potential as a replacement material for PVC and PVC/MWCNT owing to their better dispersion and high stability.     

Leep刀治疗慢性宫颈炎及宫颈不典型增生100例临床报告

目的探讨Leep刀治疗慢性宫颈炎的临床效果.方法将检查确诊为慢性宫颈炎的患者200例,随机分成Leep刀治疗组及激光对照组,分析比较两组的术中出血量、手术时间及治疗效果.结果Leep刀治疗组与激光对照组的术中出血量,手术时间及治疗效果差异有显著性意义.结论Leep刀治疗慢性宫颈炎具有手术时间短、出血少、治愈率高的特点.     

陇西县中学体育教学改革现状调查分析

通过对甘肃省陇西县部分中学体育教师进行问卷调查和走访,对体育教学现状进行了分析。结果表明,陇西县体育教学各环节仍旧存在很大问题,体育教师对体育教学各环节改革认识不深,同时受当地现实条件的约束,体育教学的进行仍旧维持在副科的位置,目前很难有进一步的发展,针对这些情况,本文对所发现问题进行分析并提出相应的建议。     

刀型截齿截割煤岩的实验研究

采用煤岩截割综合实验系统对刀型割煤岩的截割过程进行了实验研究，得到了刀型齿截割过程有关参数的变化规律曲线，这对于提高刀型齿截割效率，对于有效地提高采掘机械的效益具有十分重要的作用。     

浅谈生物安全柜辐射抗扰度的整改

文中主要介绍了电磁兼容干扰形成途径,干扰分类,针对生物安全柜辐射抗扰度测试过程中出现的问题,运用电磁兼容原理进行整改。