基于步进式电子变阻器的直流电机调速技术

介绍了多级电子分档调速技术。采用步进式电子变阻器和晶闸管研制成的新型直流电机调速电路能使速度逐级平缓地变化。电路设计闭环控制形式，能自动用多种条件完成对直流电动机的控制，并减少功耗。该技术已用在电瓶叉车上，能保证其起步平稳，有效地防止因速度跳变而对机械传动装置所产生的极大冲击力。失控保护电路，既保证安全运行，又能实现联锁及安全自保。该电路在电机控制技术中有较广阔的发展空间。     

湖北省高校科技成果产业化环境分析

高校科技成果的产业化是科教兴国战略的重要组成部分,环境因素发挥着重要作用.本文就发展科技成果产业化的政策法律环境,建设科技胚胎企业的孵化环境,发展风险投资、构筑科技成果产业化的资金环境及相关的信息服务环境等方面进行了探讨.     

粘弹材料复弹性模量的全频段表征与测量

1引言 声学上常用的吸声材料多为高阻尼的有机材料,这类材料在力学性能上表现为恒应力加载下的蠕变行为和恒应变加载下的应力松弛行为,在声学性能上表现为材料响应比激励明显滞后,即损耗角较大,并且材料的性质强烈依赖于激励频率.     

单质铝水解机理研究(Ⅲ)——单质铝水解结晶过程研究

为了了解单质铝在水解过程中产物物相的变化规律,对单质铝水解过程进行了全过程监测,在反应的不同时段取样并对其进行XRD、SEM分析。以XRD分析结果为依据,对单质铝水解结晶过程中产物物相的变化进行了深入研究,彻底弄清了水解产物的生成顺序。以SEM分析为依据,对影响水解产物形貌、粒度及粒度分布的因素进行了研究。分析认为,团聚、二次成核、搅拌等因素对结晶过程中水解产物的形貌、粒度有显著影响。     

大断面结构参数计算机模拟研究

为了解决弓长岭井下在矿体倾角较大、下盘围岩不稳固的情况下矿石回收率低的问题,本文从弓长岭铁矿的实际应用出发,深入研究了放矿口对散体移动规律的影响,在分析模拟系统的设计要求及功能的基础上,对D.Jolley模型进行建模.采用C#开发了计算机模拟系统,模拟实现了大断面出矿的一系列过程。该系统能够对多种方案进行模拟,并对模拟结果进行选优。仿真结果表明大断面进路出矿对提高矿石回收率的正确性及有效性。     

Explicit local buckling analysis and design of fiber–reinforced plastic composite structural shapes

Pultruded fiber–reinforced plastic (FRP) composite structural shapes (beams and columns) are thin-walled open or closed sections consisting of assemblies of flat plates and commonly made of E-glass fiber and either polyester or vinylester resins. Due to high strength-to-stiffness ratio of composites and thin-walled sectional geometry of FRP shapes, buckling is the most likely mode of failure before material failure. In this paper, explicit analyses of local buckling of rectangular orthotropic composite plates with various unloaded edge boundary conditions (i.e., (1) rotationally restrained along both unloaded edges (RR), and (2) one rotationally restrained and the other free along the unloaded edges (RF)) and subjected to uniform in-plane axial action at simply-supported loaded edges are first presented. A variational formulation of the Ritz method is used to establish an eigenvalue problem, and explicit solutions of plate local buckling coefficients in term of the rotational restraint stiffness (k) are obtained. The two cases of rotationally restrained plates (i.e., the RR and RF plates) are further treated as discrete plates of closed and open sections, and by considering the effect of elastic restraints at the joint connections of flanges and webs, the local buckling of different FRP shapes under uniform axial compression is studied. The approximate expressions of the rotational restraint stiffness (k) for various common FRP sections are provided, and their application to sectional local buckling predictions is illustrated. The explicit local buckling formulas of rotationally restrained plates are validated with the exact transcendental solutions. The analytical predictions for local buckling of various FRP profiles based on the present discrete plate analysis and considering the elastic restraints of the flange–web connections are in excellent agreements with available experimental results and finite element eigenvalue analyses. A design guideline for local buckling prediction and related performance improvement is proposed. The present explicit formulation can be applied effectively to determine the local buckling capacities of composite plates with elastic restraints along the unloaded edges and can be further used to predict the local buckling strength of FRP shapes.     

C语言中嵌套选择语句的逻辑关系浅析

本文介绍了如何用分析嵌套选择语句的逻辑关系，主要方法是借助分裂图画出N-S图，最后再根据IF…ELSE…语句配对原理分析出各子句的关系。     

浅论在重视数学认知教育的同时亦应重视情感教育

本阐述在数学教学过程中，应注重优化学生的心理品质，注重学生各种素质的发展，在重视认知教育的同时，亦重视情感教育。     

低压省煤器在电站锅炉中的应用

针对排烟损失大的问题，某些电厂在电除尘器出口加装低压省煤器，用来加热凝结水或热网补水，从而吸收烟气热量，实际测试结果表明，对于节能降耗和保证安全运行均起到了重要作用。     

四波长分光光度法测定四组分的研究

利用四波长分光先度法测定混合四组分中的任一组分，在任意的测量波长组合下，使共存的三种干扰组分的吸先光度为零，从而消除干扰，即△A=Aλ1 K2Aλ2 K3Aλ K4Aλ4只与待测组分的浓度成正比，可以直接测定混合组分中的任一组分或四组分，不必进行分离及繁杂的计算，以相对误差为标准，用计算机来选择最佳测定波长组合，获得较好的准确度和精密度。通过对对硝基酚(PNP)，对氨基酚(PAP)，对乙酰氨基酚(APAP)，醋酸混合组分的合成样品分析，其相对误差均小于5％，具有一定的应用价值。