切入磨削砂轮堵塞的试验研究

本文阐述了运用正交设计的方法,对切入磨削中砂轮进给速度、工件转速、修整速度及深度给予砂轮堵塞的影响进行了实验研究,初步探讨了砂轮堵塞的机理。     

一种新型高速动态液压加载装置

介绍了一种自行设计的用于高速齿轮试验台的新型液压加载装置,阐明了该装置的结构及工作原理．对影响加载装置的转矩和效率的几个主要参数进行了公式推导和分析．     

连续潮流与最优潮流相结合的电力市场双侧竞价交易计划研究

电力市场双侧竟价交易中发电商和用户报价变化所导致的竟价电量波动将会引起电力系统中潮流重新分布，对安全运行产生影响。该文结合双边合同与双侧竞价并计及静态电压稳定裕度约束建立了交易模型，提出将连续潮流和最优潮流相结合，识别双方特定报价水平下网络中存在的薄弱环节，制定出既能实现社会效益最大化，又能保证系统安全运行的交易计划。IEEE30节点系统算例结果表明该文模型和方法的正确性与有效性。     

纵向磨削砂轮堵塞的试验研究

本文研究了纵向外圆磨削中,工件转速,修速速度,走刀量,磨削厚度及冷却液对硝轮堵塞深度和而积的影响。初步探讨了纵磨时,砂轮堵塞的基本规律。     

冲击载荷下脆性岩板损伤断裂演化的实验模拟研究

在矿山运输系统中,井壁围岩冲击损伤破坏对经济和安全效益的影响是至关重要的,因为动态冲击载荷对井壁围岩和支护结构会产生严重的削弱破坏作用,室内研究表明,岩石样品如岩板在动态载荷的冲击作用下会失效。为研究在低速冲击载荷作用下,脆性岩石损伤断裂的演化过程,利用分离式霍普金森压杆(SHPB)装置中压缩气体发射球体子弹对脆性岩板进行变角度冲击损伤实验,岩板受到冲击后,边缘出现凹坑,表面裂纹从撞击凹坑直达岩板边缘,实验中样品的表面裂纹能有效代表试样内部的开裂状况,能有效反映冲击能量的耗散、破裂区面积与裂纹表面积随入射能量呈非线性增长趋势,同时与入射角度相关,但当破裂区面积急剧下降时,裂纹表面积反而急剧上升,表明裂纹的发生发展有明显的孕育期,在入射能量达到临界值前,主要表现为裂纹孕育增长,在达到临界值后,发生宏观断裂破坏,裂纹面积呈负增长,破裂区面积增大。实验结果分析表明在实际工程中,围岩和支护结构的抗冲击的最优化设计角度范围在15°～30°。     

数据集市技术浅析

数据集市是当前数据仓库建设的重要环节,本文通过对目前某电信的数据现状进行分析,给出了两种数据集市的建设方案,并分别对两种方案特点进行了描述。解决了电信所遇到的数据问题。     

装载机动臂结构通用前后置处理系统

本文在ＡＵＴＯＣＡＤ图形环境下，结合装载机动臂的结构特点，采用自动化分单元网格技术，设计了一个适用于微机、操作简单、自动化程度高的有限元前后处理程序，该程序与微机有限元计算软件相结合形成了适于工程人员使用的动臂结构通用有限元分析系统，为有限元技术在轮式装载机动臂设计工作中的广泛应用提供了一个有力工具，并给出了具体的应用实例     

一种电阻加载的L型谐振器及其在微带均衡器中的应用研究

文章提出了一种薄膜电阻加载的L型谐振器,设计了一种小尺寸的微带均衡器子结构电路,并对薄膜电阻的加载位置进行了研究。分析表明这种电阻加载的L型谐振器不仅能够进行中心频率调节、曲线衰减幅度调节,而且能够对谐振回路的品质因数进行调节,适合在微带均衡器中应用。为微带均衡器的设计提供了一种新的设计途径。     

Comparison of OWAS,RULA and REBA for assessing potential work-related musculoskeletal disorders

This study compared three representative observational methods for assessing musculoskeletal loadings: Ovako Working Posture Analysis System (OWAS), Rapid Upper Limb Assessment (RULA), and Rapid Entire Body Assessment (REBA). The comparison was based on 209 cases of upper-body musculoskeletal disorders (MSDs) diagnosed by medical doctors. The most awkward/stressful posture in each participant's tasks was assessed using these techniques. Postural loadings were rated more highly by the RULA than by the OWAS and REBA (p < 0.01). The chi-square test and logistic regression analysis showed that only RULA grand score and action level, and REBA action level were associated with MSD work-relatedness (p < 0.01, p < 0.05, and p < 0.05, respectively). The percentage concordant values of the logistic model for the RULA grand score and action level were 52.4% and 44.8%, respectively, while the percentage concordant value for the REBA action level was 22.1%. Therefore, the RULA may be the best system for estimating the postural loads and work-relatedness of MSDs.Relevance to industryWork-related musculoskeletal disorders are the leading cause of workplace disability in the developed countries. For preventing the disorders, quantification of musculoskeletal loads is required.     

Influence of tyre pressure and vertical load on coefficient of rolling resistance and simulated cycling performance

The coefficient of rolling resistance (C _r) for pneumatic tyres is dependent on hysteresis loss from tyre deformation which is affected by the vertical force applied to the tyres (F _v) and the tyre inflation pressure (P _r). The purpose of this paper was to determine the relative influence of five different levels of P _r and four different levels of F _v on C _r and to examine the relationships of C _r with P _r and F _v during cycling locomotion. F _v was modified through carriage of additional mass by the subject. C _r was determined with the coasting deceleration method from measurements performed in a level hallway. Iterations minimizing the sum of the squared difference between the actual deceleration distance and a predicted deceleration distance were used to determine C _r. This latter distance was computed from a derivation based on Newton's second law applied to the forces opposing motion. C _r was described by a hyperbolic function of P _r (C _r = 0.1071 P _r ^?0.477, r ² = 0.99, p &lt; 0.05), decreasing 62.4% from 150 kPa (C_r= 0.0101) to 1200 kPa (C_r = 0.0038). F _v was related to C _r by a polynomial function (C _r = 1.92.10^?8 F _v ² ?2.86.10^?5 F _v + 0.0142, r ² = 0.99, p = 0.084), with an added mass of 15 kg (C _r = 0.0040) resulting in an 11.4% increase in C _r compared with no added mass (C _r = 0.0035). From this study, it is concluded that the relationships of P _r and F _v with C _r for cycling are non-linear. Furthermore, a simulation model shows that changes in P _r and F _v of the magnitude examined here have an important effect on competitive cycling performance.