螺栓连接大变形梁非线性振动特性的实验研究

柔性机械臂、大型可展开天线等机械结构的动作精度受运动过程中大变形几何非线性和连接处接触非线性的影响十分显著。以含螺栓连接结构的大变形梁作为研究对象，针对动力学建模和振动特性开展了实验研究，通过数值计算验证了实验发现的非线性振动特性。搭建了含螺栓连接柔性大变形梁的实验台架，开展了敲击和正弦激振的实验测试。实验结果表明，螺栓连接的柔性梁较连续梁的（无螺栓连接）模态频率降低，阻尼增加，反映出随着激励能量增大，模态频率降低的非线性模态特征。改变螺栓连接位置会显著影响结构的模态频率，其变化规律可由求解线性矩阵特征值定性反映。     

Optimization of Transducer Location for Novel Non-Intrusive Methodologies of Diagnosis in Diesel Engines

The health monitoring has been studied to ensure integrity of design of engine structure by detection, quantification, and prediction of damages. Early detection of faults may allow the downtime of maintenance to be rescheduled, thus preventing sudden shutdown of machines. In cylinder pressure developed, vibrations and noise emissions data provide a rich source of information about condition of engines. Monitoring of vibrations and noise emissions are novel non-intrusive methodologies for which positioning of various transducers are important issue. The presented work shows applicability of these diagnosis methodologies adopted in case of diesel engines. The effects of changing various fuel injection parameters was analyzed. Scope of using non-intrusive technique has been analyzed by changing locations of microphone. Novelty of this worklies in exploring signal processing methods for various locations around the engine test set up. Various frequency ranges of contributing noise and vibration sources were identified. Time-Frequency analysis showed the onset of various cyclic. Based on the identification of various frequency bands, it is possible to device suitable filters in order to extract more information.     

2017—2019 年北京地区实验动物质量抽检结果分析

摘要:目的 比对分析 2017—2019 年北京地区实验动物微生物及遗传质量监测结果,为实验动物产业发展提供参考。 方法 按照国家和地方现行实验动物检测标准,对北京地区实验动物生产单位进行抽检,并发布检测报告。按照报告数据,对此阶段小鼠、大鼠、豚鼠、地鼠、兔、犬、猴和小型猪共 8 个品种的实验动物按照品种、等级、单位等进行分类,分析质量问题,并与 2014—2016 年同期实验动物质量比对,分析变化趋势。 结果 2017—2019 年分别抽检动物 144、131 和 135 批次,检出不合格批次分别为 30、15 和 17 批。 不合格主要因素为兔、犬及猪免疫不达标(20 批) ,病原感染 20 批,未发现遗传变异。 与 2014—2016 年同期相比,未检出遗传问题相同,免疫不达标状况好转,但病原感染出现上升。 结论 通过质量分析比对,能够为实验动物产业健康发展提供数据支持。     

轧制道次间插入冷却对特厚钢板组织与性能的影响

使用实验轧机旁冷却装置配合轧机进行轧制实验，研究轧制道次间不同冷却工艺对特厚钢板组织和性能的影响规律.研究结果表明:采用道次间冷却工艺可以在全厚度方向获得组织细化及强韧性提高效果，采用强冷道次间冷却实验钢1/4处晶粒尺寸可细化至10μm，强度为376MPa，-40℃冲击功为169J;心部晶粒尺寸可细化至15μm，强度为360MPa，-40℃冲击功为123J.本工艺可形成470μm厚表层细晶层，晶粒尺寸可细化至5μm;粗轧道次间插入冷却工艺轧制钢板强度和冲击韧性优于中间坯冷却工艺;随冷却强度增加，钢板内部组织明显细化且强度大幅提高.     

Formation of low-temperature deformation-induced segregations of nickel in Fe–Ni-based austenitic alloys

ABSTRACT

The authors present the results of an investigation in Fe–Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography – APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe–13Cr–30Ni and Fe–37Ni–3Ti.     

ZnO nanowire lines and bundles: Template-deformation-guided alignment for patterned field-electron emitters

One-dimensional ZnO materials have been promising for field-emission (FE) application, but how to facially control the alignment of ZnO emitters is still a great challenge especially for patterned display application. Here, we report the fabrication of novel ZnO nanowire (NW) line and bundle arrays for patterned field-electron emitters. The effects of PS template size and heating time on the resulted ZnO nanoarrays were systematically studied. The deformation degree of PS templates was controlled and hence utilized to adjust the alignment of electrochemically deposited ZnO arrays. It was found that the length of NW lines and the density of NW bundles can effectively tuned by the PS template heating time. The optimal FE performance with turn-on electric field as low as of 4.4 V μm⁻¹ and the field-enhancement factor as high as of 1450 were achieved through decreasing the screening effect among the patterned field-electron emitters.     

Current air quality analytics and monitoring: A review

This review summarizes the different tools and concepts that are commonly applied in air quality monitoring. The monitoring of atmosphere is extremely important as the air quality is an important problem for large communities. Main requirements for analytical devices used for monitoring include a long period of autonomic operation and portability. These instruments, however, are often characterized by poor analytical performance. Monitoring networks are the most common tools used for monitoring, so large-scale monitoring programmes are summarized here. Biomonitoring, as a cheap and convenient alternative to traditional sample collection, is becoming more and more popular, although its main drawback is the lack of standard procedures. Telemonitoring is another approach to air monitoring, which offers some interesting opportunities, such as ease of coverage of large or remote areas, constituting a complementary approach to traditional strategies; however, it requires huge costs.     

Recent trends in capillary and micro-chip electrophoretic instrumentation for field-analysis

Technical advances in the development of field-deployable capillary and microchip electrophoretic instruments and reports of their deployment between 2013 and 2017 were reviewed. Strategies and considerations in the design of the injection, separation and detection hardware, chemistry and associated infrastructure were discussed from an in-field perspective, with portability, robustness and automation/“ease of use” featuring as key requirements. Integration of functionality is important for adequate in-field performance. Progress was made towards the use of multiple channel devices for increased throughput and/or resolving power, mixing devices for on-line/in-line sample derivatization, battery operation and temperature control. The strengths and weaknesses of the various approaches described in the literature are discussed from the perspective of in-field operation. An overview of the applications of the field electrophoretic instruments is provided, including environmental science and planetary investigation.     

尾水管水力振动的监测与故障判断

从模型及真机试验结果出发，叙述混流式水轮机一般的水力故障形式，研究了尾水管的水力振动特点及振动随运行工况而变化的情况，介绍了以压力脉动频率及幅值作为特征参量对尾水管进行振动监测及故障判断的方法。     

空气自动站监测与传统监测方法测定值的对比分析

为保证不同监测方法下监测数据的连续性、可比性以及正确判断环境空气变化规律，通过自动监测与传统的连续监测、五日法监测方法进行实验对比分析，找出传统方法与自动监测定值之间的偏差，探讨产生偏差的原因。