行走马达溢流阀高温溢流压力特性研究

全液压挖掘机行走马达的性能对挖掘机的整体性能有重要影响,其中行走马达上集成的溢流阀对马达起缓冲保护作用,挖掘机工作时油液温度较高,若高温时溢流阀溢流压力偏低则会造成行走无力。着重对行走马达上集成的溢流阀高温溢流压力特性进行研究,建立溢流阀的数学模型,分析影响因素,对其中最重要的阀芯阀套间隙进行动态仿真分析,并根据仿真结果进行相应的试验验证。试验结果表明,阀芯阀套间隙是影响高温溢流压力的决定性因素。     

导叶闭合状态下立面间隙的接触分析

本文基于三维带摩擦的接触分析理论，建立了水轮机导叶在闭紧状态下的力学模型、导叶立面接触力及接触间隙的分析方程、确定了计算方法、开发了专用软件。使水轮机导叶立面的研究水平得到明显提高。     

基于斜刃浮动凹模、阶梯快换凸模的车架复合冲裁模研究

根据企业加工设备条件。研制了拖拉机车架切边冲孔复合模具。该模具在结构上采用斜刃冲、阶梯冲相结合来降低冲裁力。运用外置式弹压卸料及变间隙冲裁提高了模具的可靠性。主要工作零件结构设计采用浮动、快换、镶拼等。大大方便了模具制造和维修。经实际生产验证。具有较好的经济性和实用性。     

基于扩展Canetti-Krawczyk模型的认证密钥交换协议的模块化设计与分析

提出一种模块化的扩展Canetti-Krawczyk模型(简称meCK模型)以摆脱认证密钥交换协议对随机预言机的依赖.首先将认证密钥交换协议划分为秘密交换模块和密钥派生模块,并分别形式化定义其攻击者的能力与安全属性;然后综合上述模块得到认证密钥交换协议的模块化安全模型,并证明所提出的安全定义蕴涵原始的扩展Canetti-Krawczyk安全.借助协议模块化分析的思想,设计了一种高效且在标准模型下可证明安全的认证密钥交换协议(简称UPS协议).在meCK模型下,UPS协议的安全性可有效归约到伪随机函数簇、目标抗碰撞Hash函数簇和GapDiffie-Hellman等标准密码学假设上.与其他标准模型下可证明安全的协议相比,UPS协议所需的密码学假设更弱、更标准,且指数运算次数降低了50%～67%.最后,UPS协议的构造与安全性验证了所提出的模块化方法的合理性和有效性,并解决了ProvSec09上的一个公开问题.     

混流泵效率特性的预测与实测特性的比较

Ａ·ＤＥ·ＫＯＶＡＴＳ方法是预测泵特性的传统方法,本文对其加以改进,用叶片尖端间隙数值解析法预测其中的容积效率。通过对一个系列四个不同比转速导叶式混流泵效率特性的预测,并与实测结果的比较,表明在设计点和最高效率点附近,两者达到了良好的一致。说明这种方法可提高Ａ·ＤＥ·ＫＯＶＡＴＳ方法的预测精度,简单实用,可以用来预测性能,修改设计。     

预制夹心混凝土墙板热工性能研究

通过研究不同种类及厚度的夹心保温材料、拉结件布置数量及保温板缝隙宽度,分析了其对预制夹心混凝土墙板传热系数的影响。结果表明:夹心层保温材料导热系数越小、夹心层越厚,预制夹心混凝土墙板传热系数越小;非金属拉结件对夹心墙板传热系数的影响约为1.3%～3.2%,夹心层厚度越厚,墙板传热系数越小,拉结件影响越大;夹心层保温板采用定制式保温板可有效降低保温板缝隙对预制墙板传热系数的影响,计算结果可为预制夹心墙板的热工设计提供依据。     

The Ambivalence of Connexin43 Gap Peptides in Cardioprotection of the Isolated Heart against Ischemic Injury

The present study investigates infarct-reducing effects of blocking ischemia-induced opening of connexin43 hemichannels using peptides Gap19, Gap26 or Gap27. Cardioprotection by ischemic preconditioning (IPC) and Gap peptides was compared, and combined treatment was tested in isolated, perfused male rat hearts using function and infarct size after global ischemia, high-resolution respirometry of isolated mitochondrial and peptide binding kinetics as endpoints. The Gap peptides reduced infarct size significantly when given prior to ischemia plus at reperfusion (Gap19 76.2 ± 2.7, Gap26 72.9 ± 5.8 and Gap27 71.9 ± 5.8% of untreated control infarcts, mean ± SEM). Cardioprotection was lost when Gap26, but not Gap27 or Gap19, was combined with triggering IPC (IPC 73.4 ± 5.5, Gap19-IPC 60.9 ± 5.1, Gap26-IPC 109.6 ± 7.8, Gap27-IPC 56.3 ± 8.0% of untreated control infarct). Binding stability of peptide Gap26 to its specific extracellular loop sequence (EL2) of connexin43 was stronger than Gap27 to its corresponding loop EL1 (dissociation rate constant K_d 0.061 ± 0.004 vs. 0.0043 ± 0.0001 s⁻¹, mean ± SD). Mitochondria from IPC hearts showed slightly but significantly reduced respiratory control ratio (RCR). In vitro addition of Gap peptides did not significantly alter respiration. If transient hemichannel activity is part of the IPC triggering event, inhibition of IPC triggering stimuli might limit the use of cardioprotective Gap peptides.     

Direct measurements of particle flux along gap sides in castellated plasma facing component in COMPASS

In this paper, we report results of a dedicated experiment that gives the plasma penetration profiles inside a gap of a tokamak castellated plasma-facing component. A specially designed probe that recreates a gap between two tiles has been built for the purpose of this study. It allows to measure ion saturation profiles along the 2 sides and at the bottom of the gap for both poloidal and toroidal orientations. The novelty of such experiment is the real time measurement of the plasma flux inside the gap during a tokamak D-shaped discharge compared to previous experimental studies which were mainly post-mortem. This experiment was performed in the COMPASS tokamak and results are compared with particle-in-cell simulations. The plasma deposition is found to be asymmetric in both orientations with a stronger effect in poloidal gaps. The Larmor radius of the incoming ions plays a role in the plasma penetration only in poloidal gaps but seems to have little impact in toroidal gaps. Profiles are qualitatively well reproduced by simulations. Ion current is recorded at the bottom of a toroidal gap under certain conditions.     

刚挠印制板的一种开盖流程实验

主要讨论一种刚挠印制板的开盖流程,以实验的方式确定其关键制程的设置并对实验过程中遇到的一些问题进行讨论。     

The construction of research questions in project management

This article examines how opportunities for contributions are created in project research. In the article the arguments that underlie research question constructions are analyzed and their role in theory construction is reflected upon. The analysis is based upon a review of 61 papers published between 2007 and 2011 in the four major project management outlets. The results show that questions identify gaps and extend literature rather than challenge the theoretical assumptions. It is argued that the dominance of “gap spotting” hampers the development of the project field by producing theories that do not challenge long-held, sometimes possibly false, assumptions. Researchers are therefore urged to become bolder in their claims, some suggestions on how to achieve this are offered.