Computational models of a nano probe tip for static behaviors

It is difficult to predict the measurement bias arising from the compliance of the atomic force microscope (AFM) probe. The issue becomes particularly important in this situation where nanometer uncertainties are sought for measurements with dimensional probes composed of flexible carbon nanotubes mounted on AFM cantilevers. We have developed a finite element model for simulating the mechanical behavior of AFM cantilevers with carbon nanotubes attached. Spring constants of both the nanotube and cantilever in two directions are calculated using the finite element method with known Young's moduli of both silicon and multiwall nanotube as input data. Compliance of the nanotube-attached AFM probe tip may be calculated from the set of spring constants. This paper presents static models that together provide a basis to estimate uncertainties in linewidth measurement using nanotubes. In particular, the interaction between a multiwall nanotube tip and a silicon sample is modeled using the Lennard-Jones theory. Snap-in and snap-out of the probe tip in a scanning mode are calculated by integrating the compliance of the probe and the sample-tip interacting force model. Cantilever and probe tip deflections and points of contact are derived for both horizontal scanning of a plateau and vertically scanning of a wall. The finite element method and the Lennard-Jones model provide a means to analyze the interaction of the probe and sample and measurement uncertainty, including actual deflection and the gap between the probe tip and the measured sample surface.     

Germline stem cell lineage tracing by free-floating immunofluorescent assay of mouse seminiferous tubule

Whole-mount immunohistochemistry (whole-mount IH) of the seminiferous tubule is widely used to investigate the self-renewal and differentiation of spermatogonial stem cells (SSCs). Examination of the length of spermatogonial cysts is critical for tracing SSCs lineage by using Whole-mount IH. However, it is difficult for antibody molecules to penetrate into the depth of seminiferous epithelium because its thickness and the tight peritubular myoid and basement membrane outside. Here, we developed a free-floating immunofluorescent procedure of mouse seminiferous tubules using regular incubation time and normal antibody concentration. Microscopic results showed that undifferentiated spermatogonia were positively labeled by promyelocytic leukemia zinc finger protein, E-cadherin, and glial cell line-derived neurotrophic factor family receptor alpha 1, respectively. Spermatogonial cysts in varied length were revealed clearly and spermatogonia subpopulations including A(single) (A(s)), A(paired) (A(pr)), and A(aligned) (A(al)) were distinguished in lower background images. This method provides us an alternate simple way to trace the lineage of individual SSCs and show their three-dimensional locations and distributions within their niches anatomically in next step.     

钢骨高强混凝土柱的非线性分析

目的 进一步研究钢骨高强混凝土柱的工作性能．方法 以有限元理论为基础，运用分析软件(ANSYS)对钢骨高强混凝土柱在单调载荷作用下由混凝土开裂、型钢屈服直至构件破坏的整个受力过程进行数值模拟．结果 计算得到的荷载一位移曲线与试验曲线比较一致，当水平荷载达到极限荷载50％左右时，混凝土开裂；水平荷载达到极限荷载的60％左右时，跨中钢骨下翼缘开始屈服．结论 采用ANSYS程序中的SOLID65单元、SOLID45单元、LINK8杆单元建立钢骨高强混凝土柱有限元模型并进行计算是可行的．     

鞍钢无料钟布料数学模型研制与应用

阐述了鞍钢无料钟布料模型的开发与应用,重点分析了模型对料流阀开口度、料面形状和矿／焦比分布应用的结果。选择料流阀开口度采用三种方法,一是理论计算方法;二是利用实际测量数据对理论模型进行修正后,采用体积流速计算方法;三是利用实际测量数据对理论模型进行修正后,采用重量流速计算方法。通过对比三种方法结果,认为采用体积流速计算方法最能够保证布料过程料层均匀,无料钟布料模型可以实现对各种布料制度、料面形状的计算。     

电子束选区熔化成形Nb521合金微观组织与性能分析

采用电子束选区熔化技术制备Nb521合金,研究其致密化成形工艺。通过对成形试样的组织、物相、显微硬度、室温拉伸性能的检测与分析,探讨了电子束选区熔化成形Nb521合金的机理。结果表明,电子束选区熔化成形过程中,电子束熔化电流及速度的合理匹配,是得到表面质量及内部质量优异的成形样品的基础;电子束能量密度为340 J/mm3时,样品的密度达到8.78～8.79 g/cm3; Nb521合金显微组织沿沉积方向呈柱状晶,晶粒沿(200)晶面有较强的择优生长取向;成形样品中除Nb基体相外,还存在少量的Nb2C与Zr C碳化物析出;样品室温抗拉强度达到384 MPa,屈服强度为307 MPa,断后延伸率为16.5%;显微硬度处于1 500～1 700 MPa之间,无各向异性。     

良好设施 科学规范化管理的必要性

江西省药物研究所于2008年建立了实验动物屏障设施,同年八月取得《实验动物使用许可证》,现已正常运行两年,由于我们严格按照屏障系统设施标准操作规范进行管理,实验动物屏障设施启用后,一直比较稳定。通过对实验动物屏障设施空调净化系统两年多的运行管理,深深体会到良好设施科学规范管理是非常必要的。     

NKChemSQL——针对MySQL的化学信息学扩展

化学数据库是进行化学信息学研究的重要资源,分子属性与指纹计算、分子结构格式转换、分子相似度匹配、精确匹配和子结构匹配以及分子结构图片导出等,都是必需的基本服务内容。应用广泛的数据库系统MySQL却缺乏这些功能,难以满足化学信息处理、网站开发等开发的需求。NKChemSQL是自行编制的MySQL扩展库,通过对开源软件OpenBabel的功能进行包装,以SQL语言的格式完成相应操作。NKChemSQL具有良好的运行表现,经过对含26万余条分子结构信息的NCI数据库进行的测试,全结构匹配只需不到1秒而子结构匹配达300个结构/秒,相似度匹配则达1万个结构/秒。NKChemSQL为开发化学信息学软件和网站提供了非常便利的新方式。     

大口径枪械质心测量系统及其误差评定

本文介绍了一种大口径枪械质心测量系统,并对该系统进行了误差分析.大口径枪械质心测量系统,基于力矩平衡法原理,利用测量传感器,拾取测量信号,工控计算机进行数据分析,实现了智能化、自动化测量.为保证测量的可信度,本文从测量不确定度方面进行了误差分析,并针对测量系统的测量数据,根据GUM导则中对测量不确定度的分类,进行了测量不确定度的评定,给出了测量报告.报告结论该系统测量结果的质量较高,有很好的使用价值.     

鞍钢铜冷却壁高炉操作炉型管理模型开发与应用

对鞍钢铜冷却壁高炉操作管理模型的建立方法进行了阐述,并对在2号高炉上的实践进行了总结.根据经验知识和实验室热态模拟实验结果,利用传热模型反推计算,建立铜冷却壁高炉操作炉型管理模型,可对铜冷却壁热面渣皮厚度进行实时计算,实现操作炉型管理.鞍钢2号高炉应用结果表明,铜冷却壁操作管理模型可对渣皮脱落部位、炉腰和炉身下部铜冷却壁热面温度和渣皮厚度变化趋势进行判断,提示操作人员及时采取措施,控制渣皮厚度适宜并保持稳定,减少铜冷却壁区域热损失,并保证高炉操作炉型合理.