电子汽车衡常见故障与预防

本文主要以举例的方式介绍电子汽车衡常见故障及排除方法,再从实际工作出发如何去预防故障的发生。     

基于模糊方法的磨矿分级自动控制

基于模糊方法的磨矿分级自动控制能够很好地克服球磨机非线性、时变等因素的干扰影响,能有效地避免球磨机发生涨磨或是空磨现象。系统运行可靠,抗干扰能力强,能较好地实现球磨机恒功率自动控制,提高了设备的生产率和自动化水平,具有较好的推广应用价值。     

预应力管桩水平承载力试桩结果分析

通过天津地区30根预应力管桩的水平静载荷试桩结果,分析了天津地区预应力管桩水平承载力特征值和对应的水平位移值,并对JGJ 94-2008建筑桩基技术规范提供的预应力管桩水平承载力估算公式中桩顶允许水平位移值在天津地区的取值进行了总结,以供参考。     

The cognitive impact of interactive design features for learning complex materials in medical education

To identify the most effective way for medical students to interact with a browser-based learning module on the symptoms and neurological underpinnings of stroke syndromes, this study manipulated the way in which subjects interacted with a graphical model of the brain and examined the impact of functional changes on learning outcomes. It was hypothesized that behavioral interactions that were behaviorally more engaging and which required deeper consideration of the model would result in heightened cognitive interaction and better learning than those whose manipulation required less deliberate behavioral and cognitive processing. One hundred forty four students were randomly assigned to four conditions whose model controls incorporated features that required different levels of behavioral and cognitive interaction: Movie (low behavioral/low cognitive, n = 40), Slider (high behavioral/low cognitive, n = 36), Click (low behavioral/high cognitive, n = 30), and Drag (high behavioral/high cognitive, n = 38). Analysis of Covariates (ANCOVA) showed that students who received the treatments associated with lower cognitive interactivity (Movie and Slider) performed better on a transfer task than those receiving the module associated with high cognitive interactivity (Click and Drag, partial eta squared = .03). In addition, the students in the high cognitive interactivity conditions spent significantly more time on the stroke locator activity than other conditions (partial eta squared = .36). The results suggest that interaction with controls that were tightly coupled with the model and whose manipulation required deliberate consideration of the model's features may have overtaxed subjects' cognitive resources. Cognitive effort that facilitated manipulation of content, though directed at the model, may have resulted in extraneous cognitive load, impeding subjects in recognizing the deeper, global relationships in the materials. Instructional designers must, therefore, keep in mind that the way in which functional affordances are integrated with the content can shape both behavioral and cognitive processing, and has significant cognitive load implications.     

复杂岩性储层压裂改造技术在歧口凹陷的应用

为解决大港油田歧口凹陷沙一下储层物性差、水敏性强、裂缝发育情况复杂和压裂施工成功率低等难题,研究出与储层配伍性较好的低伤害、高黏度压裂液。该压裂液残渣含量低、防膨性能好,并相应配套了加砂时机优选技术、前置液多级支撑剂段塞技术和压裂液流变性优选技术。该技术现场应用9井次,施工成功率由60%提高到100%,平均增产倍数由1.5倍提高到10.8倍,压裂效果明显。     

基于美国规范的桥梁下部结构计算

分析了美国公路桥梁设计规范(AASHTO),采用MIDAS软件,对某项目桥梁下部结构设计进行了介绍,并针对美国规范和中国规范进行了比较,为公路桥梁设计者了解美国规范提供参考。     

Crack propagation prediction of CFRP retrofitted steel plates with different degrees of damage using BEM

Although carbon fibre reinforced polymer (CFRP) materials have proven effective in strengthening steel structures especially when used to improve fatigue behaviour, further study is required to investigate their effectiveness when applied at different stages of crack propagation in steel elements. This paper presents a numerical study on CFRP retrofitted steel plates with different degrees of damage using the boundary element method (BEM). The numerical results compared well with the experimental data, which demonstrated that the BEM is reliable for crack propagation analysis of CFRP laminate retrofitted steel plates. Finally, a parametric analysis was conducted to investigate the influence of bond length, bond width, CFRP stiffness and adhesive shear modulus on stress intensity factor (SIF) values.     

DNA Comet Giemsa Staining for Conventional Bright-Field Microscopy

This study was undertaken to evaluate the compatibility of Giemsa staining protocol with the comet assay. We showed, for the first time, that DNA comets can be visualized and analyzed using Giemsa staining. We generated DNA damage dose response curves for human peripheral blood lymphocytes exposed to X-ray radiation using the comet assay with either SybrGreen I or Giemsa stain. The dose response curves were fitted by linear regressions (R² > 0.977). The SybrGreen I results showed only ~1.2-fold higher slope coefficient (method sensitivity) compared to the Giemsa results. The unexpectedly high sensitivity of Giemsa staining for the comet assay is due to the Romanowsky-Giemsa effect, the stain photo-stability and the higher resolution of bright-field imaging compared to fluorescence imaging. Our results demonstrate that Giemsa staining can effectively be used for measuring DNA damage by the comet assay. The low cost and availability of Giemsa stain makes this method affordable for any low budget research and will facilitate new applications of the comet assay in biology and medicine.     

Investigation of the effect of chamfer size on the behaviour of hybrid joints made by adhesive bonding and riveting

The paper reports the results of a numerical study performed on: (a) purely adhesive joints and (b) new hybrid single lap joints with a variable adherend thickness in the lap region. The variable thickness creates chamfer defined by a geometric parameter ch which has a very positive influence on the mechanical response of the joint. The novelty in this paper is the investigation of the effect of chamfer size on the behaviour of hybrid joints made by 2 simple techniques: adhesive bonding and riveting. In particular, 10 types of chamfer geometries are considered, each causing a different stiffness of the adherends being joined. As a result, the strength of the connection is increased and its weight reduced, which is of vital importance in aircraft constructions.The adherends and rivets are assumed to be made of aluminium, i.e., an elastic-plastic material, and subjected to gradual degradation due to tension. The adhesive layer is modelled as a semi-brittle material with progressive degradation using cohesive elements. Following the creation of 3D finite element models, the samples are subjected to quasi-static uniaxial deformation (nonlinear analysis with ABAQUS/Explicit).The numerical results lead to the conclusion that the variable geometry, i.e., chamfering, has a very positive effect. At the maximum chamfer length equal to 10 mm, the increase in the maximum force was about 32.8% compared to the model without chamfer.     

Realization of direct flow control with load pressure compensation on a load control valve applied in overrunning load hydraulic systems

This paper presents the realization of direct proportional flow control with load pressure compensation feature on a LCV (load control valve). Proportional flow control performance means the flow through the LCV is proportional to the pilot pressure in the control stroke. Proportional flow control decides the overrunning load lowering speed control performance of the whole system. The load pressure compensation feature means when the load pressure is too high, the flow of the LCV can be restricted about the maximum rated flow. The load pressure compensation feature is important to the safety of the system. That is because large flow means undesired fast lowering speed, which will cause accident in applications, especially those large mass overrunning load systems. In this paper, the flow control performance was simulated and the parameter relationship of the orifices was derived, which is the base for the optimizing of the compensation orifice. In addition, load pressure compensation feature was simulated and the compensation orifice size was optimized. Finally, an LCV built according to above methods was tested on a test rig. Experiment data validates the methods presented and the realization of direct flow control with load pressure compensation feature gives guidance for the direct flow control performance development of other valves.