Thermo-hydraulic characteristics of Hybrid mixing vanes in a 17×17 nuclear rod bundle

The lateral flow in the sub-channel of a nuclear rod bundle increase turbulent mixing and enhance heat transfer rate and safety. Various types of mixing vanes have been investigated to produce more lateral flow. In this study, the thermal-hydraulic characteristics of Hybrid mixing vane in a 17×17 rod bundle were calculated. Hybrid mixing vane has bended root part and split stem part. The computation was performed using a supercomputer due to the high number of grid meshes. The characteristics of Hybrid mixing vane were compared to Split mixing vane. The Hybrid mixing vane showed higher values of secondary intensity, cross-sectional turbulence intensity and Nu number and lower values of maximum temperature and standard deviation of temperature. Meanwhile, The Hybrid mixing vane has higher invariance because small vortexes travel, stretch and are connected with main stream.     

Structural analysis of planar jointed mechanisms: Current state and problems

On the basis of study of the history of development of structural synthesis of planar jointed mechanisms, as well as Assur structural groups, Baranov statically determinate trusses, and Grubler closed kinematic chains, a picture of the current state of research in this field is provided.     

Study of event mixing and its application to the extraction of resonance signals

The features of the invariant mass distribution obtained from combinations of particles from different events, i.e. event mixing, is studied in detail. It is shown that special care is needed in order to reproduce the shape of the uncorrelated invariant mass distribution. A way to determine the number of resonances and its statistical error using an event mixing technique is described.     

Peculiarities of equilibrium state bifurcations in transcritical mechanisms

Mechanisms with one degree of freedom whose position space is characterized by self-intersection at a specified value of a coupling parameter in the field of action of a potential force are considered. Bifurcations of equilibrium positions of transcritical mechanisms and their dependence on the properties of the potential energy in the vicinity of a singular point are studied. The results obtained are illustrated by the example of a crank-and-slot mechanism.     

High voltage electron microscopy of cellular changes in the wet state

Red blood cells and bacteria have been viewed under the high voltage transmission electron microscope, using a controlled environment chamber. Red cell changes on introduction of an agglutinating serum into the environment and bacterial changes on addition of an antibiotic, were observed. The results are compared with those obtained by phase contrast light microscopy and the potentialities of the system discussed.     

谈混凝土搅拌站(楼)之配料秤的动静态检定

混凝土搅拌站（楼）广泛使用在建筑施工、隧道桥梁、基础设施等重点项目上,其配料秤的准确与否直接关系到工程的质量安全。因此,非常有必要对配料秤进行检定,以保证混凝土配料的准确无误。     

Study of cylindrical grinding using ball and cone centers: static and dynamic characteristics of cone and ball center systems

In cylindrical grinding, it is known that using balls in place of conventional cone machine centers (CMCs), makes it possible to grind a workpiece without the influences of the misalignments and the geometric deviations of the workpiece center holes and machine centers. This study determines the characteristics of these ball machine centers (BMCs) and CMCs. In this paper, the stiffness and the damping capacity of CMC and BMC systems are measured to investigate the potential of chatter in stability of BMCs compared to conventional 60° CMCs. The main results obtained are as follows: 1) The stiffness difference between BMCs and CMCs was small or negligible, because the stiffness of the taper connection of our machine center shank was remarkably low; 2) the damping ratio of the BMCs was slightly larger than that of the CMCs; 3) the misalignments of the workpiece and CMC reduced the stiffness, while the stiffness of the BMCs was inherently independent of any misalignment; 4) using BMCs, a lubricant with a center hole diameter appropriate to the workpiece size can be used because the balls run-in to the center holes rapidly; 5) using CMCs, the stiffness depends on the center hole diameter; and 6) using BMCs, the waviness of the socket center hole containing the steel ball influences the stiffness. The ball diameter, moreover, affects the damping. Furthermore, it is unnecessary to worry about a more frequent occurrence of chatter when using BMCs, because the dynamic characteristics of BMCs are almost the same as those of CMCs.     

基于时频特征融合与 GWO-ELM 的棒控电源早期故障状态辨识方法

针对核电棒控系统电源(PWE)早期故障状态辨识问题,提出一种基于融合时域与时频域的故障特征和灰狼优化算法(GWO)的极限学习机(ELM)辨识方法。首先,根据棒控电源PWE工作原理和控制棒驱动机构的驱动电流,利用电流上升时间分析了早期波形形态与早期故障模式。然后,构建融合电流上升时间、均方根-差分和和小波包奇异熵的故障时频特征,分析了特征的可区分性。进而,采用GWO算法进行ELM分类器参数择优,建立GWO-ELM模型实现PWE早期故障状态的辨识,以提高辨识精度。最后,通过开展不同特征组合和辨识模型比对试验,结果表明所提方法能有效实现棒控电源早期故障识别诊断,且平均辨识准确度可达98.86%。     

Neurotrophins and development of the rod pathway: an elementary deduction

The rodent retina is a particularly attractive model for the study of neuronal developmental processes since considerable neurogenesis, cellular migration, phenotypic differentiation of retinal cell types and synaptogenesis occurs postnatally. In addition, the retina is readily accessible to surgical intervention, pharmacological manipulation, and local suppression of gene expression-tools that can be utilized to study mechanisms underlying the development of retinal neurons and their interconnections that form distinct functional circuits. Here, I review our studies describing the ontogeny of a specific retinal interneuron, the AII amacrine cell, an integral element in the rod (scotopic) pathway. Specifically, we used a number of approaches to examine the potential role of neurotrophic factors on the morphological and neurochemical differentiation of the AII.     

发动机连杆新材料的发展与研究

连杆是汽车发动机中的重要零件,其强度、刚度和质量对提高发动机的动力性和可靠性至关重要。为了保证发动机的可靠性,要求连杆材料具有良好的综合性能。介绍了汽车发动机连杆材料的发展特点及其应用现状,研究指出了金属基复合材料的巨大优势和发展应用前景,并结合粉末冶金工艺研究指出了金属基复合连杆材料的制备工艺思路。     

圆形混匀料场刮板堆取料机结构形式及物料混匀工艺

用于某水泥厂露天圆形混匀料场的刮板堆取料机由堆料臂、刮板取料桥和中间柱三大部分组成。堆料臂按大人字形逐层往返堆料,刮板取料桥沿料堆断面的底部刮取物料,同时,取料桥上的料耙在取料断面往返移动耙及物料,从而实现物料混匀。     

Effect of ion-beam nitriding on structure, phase state, and tribological behavior of efficient thermal spray coatings deposited from various classes of rod steels

Thermal spray coatings produced by the hypersonic spraying of ferritic (Sv-08G2S), martensitic (40Kh13), and austenitic (06Kh19N9T) rod steels and treated by intensive nitrogen ion flows were studied. Metallographic and X-ray diffraction structural analyses of modified coatings were carried out, as well as their microhardness and tribological characteristics were determined. It has been shown that ion-beam treatment leads to an increase in the wear resistance of coatings from the ferritic steel by 2–80 times, those from the martensitic steel by 2–13 times, and those from the austenitic steel by 10–35 times. Based on the results obtained, temperature conditions for ion-beam nitriding that ensure the best tribological characteristics of the coatings deposited from various classes of rod steels have been selected.     

Computer-aided design of mechanisms: 1984 and beyond

This special issue on computer-aided design of mechanisms has the objective of representing the state-of-the-art in computer-assisted mechanism analysis and synthesis. The events of the past 25 years are reviewed in this article. The brief look at today and the potential future of this fast-growing area are meant to set the stage for this special issue of Mechanism and Machine Theory.     

High velocity oblique impact and ricochet mainly of long rod projectiles: An overview

A review of the literature on high velocity oblique impact and the ricochet of projectiles of various shapes is given, with emphasis on long rod projectiles. Aspects of cratering and penetration in oblique impact are highlighted and the mechanics of ricochet off solid, fluid and granular media are also discussed.     

激光棒干涉测量中单双通法的对比

由于激光棒具有细长的特殊形貌特征,传统的双通测试方法虽然灵敏度较高,但是往往存在明显的衍射效应和多重成像导致的边缘黑环,这会导致有效测量面积的缩减,对于小口径光学元件的测量尤为不利。为了克服这一缺陷,采用单通法测量激光棒的波前畸变,使用直角棱镜作为反射件,使得测试光仅通过激光棒一次,从而减少光路中的等效圆孔数和成像次数,抑制衍射和边缘重叠。利用展开的多小孔模型讨论了衍射效应的影响,并且从成像角度讨论边缘重叠的成因,从而得出单通法的优势。另外,为使参考光与测试光的匹配,需要将直角棱镜旋转至少5.40°偏摆角以提高干涉条纹的对比度。最终测得激光棒波前畸变的峰谷值为0.068λ,均方根值为0.012λ。     

Combined rod and tube extrusion: Numerical solution of axi-symmetric slip-line fields and associated velocity fields

Numerical method of construction of axi-symmetric slip-line fields and associated velocity fields in the form of computographic plots of axial and radial velocity components, earlier given by the authors for rod extrusion and tube extrusion, was extended to the solution of two types of combined rod and tube extrusions: (i) where the rod and tube are extruded in opposite direction to each other and (ii) where, both the rod and tube move in the same axial direction as the punch movement during the extrusion process. Computographic plots of slip-line fields and associated velocity fields in the (r, z) plane are given and the deficiencies noticed in the solutions are highlighted. The results of specific punch pressures are observed to compare well with those estimated, using simple upper bound analysis and the experimental work of the authors.     

An investigation of tube and rod electrode wear in micro EDM drilling

This paper studies the influence of various factors contributing to micro electrode wear during electrical discharge machining (EDM) drilling with micro rod and micro tube electrodes. In this paper, a simple method for calculating volumetric wear ratios is proposed based only on geometrical information obtained from the process. The objective of the research is to investigate the wear behaviour of electrodes and the suitability of electrode wear compensation methods. Electrode shape deformation and random variation of the volumetric wear are studied as the main factors affecting the applicability of wear compensation methods and as an indicator of the accuracy achievable with the micro EDM process.     

光锥在光电探测仪器中的应用和设计方法

光锥可以弥补场镜、光纤在光电探测仪器中光线传输汇聚的弊端,光锥传输光线不但损失小,而且可以把光阑后面的光线根据需求分开传输。通过光锥的应用,使光电探测器的灵敏度大幅增强。叙述了光锥的传输特性和设计方法。     

Simulation of the mixing of components in lubricant and coolant fluids

Simulation of the mixing of lubricant and coolant fluids using equipment with a rotary vibrational drive is considered. Such simulation provides information regarding numerous physical effects.