基于ADAMS的发动机新型动力输出机构的仿真

目的研究基于曲柄摆杆机构的发动机动力输出机构,改善传统发动机活塞与气缸的受力状况,提高动力传递效率.方法利用Pro/E三维建模软件构建曲柄摆杆机构发动机的三维实体模型,将其导入到动力学分析软件ADAMS中进行运动学及动力学仿真分析,得到主轴扭矩、连杆摆角、活塞对气缸的侧压力等参数并与传统曲柄连杆发动机对应参数相比较.结果完成了ADAMS的仿真分析,获得了一些仿真数据.结果表明发动机采用曲柄摆杆机构具有可行性,其摆杆摆角在0~0.97°范围内,远小于传统曲轴连杆发动机的相应值.同等燃气压力条件下其气缸侧压力约为传统发动机相应值的1/20.结论通过仿真分析验证,曲柄摆杆作为动力输出机构能够满足发动机工作循环要求,活塞与气缸受力状况比传统发动机有显著的改善,对延长活塞和气缸的工作期限及简化发动机结构均有重要意义.     

一种回转式活塞压缩机的产品化设计及实验

提出了一种新型双环结构的回转式活塞压缩机,将常规往复式活塞改为新型回转式活塞,同时活塞的往复运动转变为回转运动.在保持了往复式活塞压缩机压缩比范围广、制造工艺简单等特点的同时借鉴一些回转式压缩机的优点,消除了常规活塞式压缩机的活塞惯性力,取消了常规活塞式压缩机的吸、排气阀,提升了活塞式压缩机的应用优势.设计了首款产品样机并进行了实验,实验结果证实了回转式活塞压缩机工作原理的可行性,排气压力达到了设计指标,实际排气量则达到理论排气量的一半以上.     

活塞式压缩机常见故障及处理措施

本文从曲柄销轴瓦的偏磨、曲柄销轴颈的损坏、十字头销的处理、活塞杆尾部的连接、活塞及活塞杆的损坏、活塞杆跳动的异常处理六个方面简要介绍了往复活塞式压缩机的故障诊断及处置措施,对于往复活塞式压缩机的使用与维护有一定的借鉴意义。     

柱塞式高速气缸试验研究(摘要)

气缸是气动机械的主要执行元件,提高执行元件的工作速度,是提高各种机械生产效率的重要因素。普通气缸活塞的平均运动速度,取决于工作压力、缸径及负荷。缸径100毫米的气缸,工作压力5巴,空载时活塞平均速度约1米/秒,70％负荷时约为0.45米/秒,因流量饱和及排气背压的影响,提高工作压力并不能进一步提高工作速度,因此空载时的工作速度,是普通气缸所能达到的运动速度的上限。要想进一步提高气动执行元件的工作速度,只有从根本上改变工作原理,采用新型结构。我们对这一课题作了初步的试验研究,参考压紧活塞式冲击气缸的工作原理,把普通气缸的活     

同步回转式制冷压缩机的运动分析

为了解决目前小型全封闭制冷压缩机由于运动部件之间相对运动速度较高而引起的摩擦磨损严重和零部件使用寿命短的问题,开发研制了一种新型的全封闭同步回转式制冷压缩机.介绍了同步回转式制冷压缩机的工作原理和结构特点,对关键零部件的运动规律以及相互之间的运动关系进行了分析推导,并对一台同步回转式制冷压缩机样机进行了数值计算.结果表明:样机的转子与气缸之间的平均相对运动速度为2.62 m/s,比同规格的滚动活塞式压缩机和滑片式压缩机的分别降低了79.16%和76.83%;样机的滑板与转子之间的平均相对运动速度只有0.80 m/s,比同规格滚动活塞式压缩机的降低了92.93%,比滑片式压缩机的滑片与气缸之间的平均相对运动速度降低了93.64%;同步回转式制冷压缩机转子与气缸以及滑板与转子之间的相对运动速度非常小,可以大大降低相互之间的摩擦磨损,提高压缩机的性能及零部件的使用寿命.     

便携式双气缸气钉枪研制及试验

针对传统气钉枪需要携带空气压缩机长线作业的缺点,提出一种便携式双气缸气钉枪,即采用偏心布置大小气缸,由大活塞压缩气体蓄能,通过电子元件触发小活塞将气体能量瞬间释放,达到打钉的目的。通过试验得到气钉枪工作时所需的冲击功,分析其撞针组件运动过程,建立计算模型。分析得到双气缸气钉枪的各个参数,包括大小气缸的布局及尺寸参数、曲柄滑块机构参数和2Z-X(A)型三级微型行星齿轮减速器参数。研制了该便携式双气缸气钉枪实物样机,打钉试验表明该气钉枪的力度较大,与电磁铁直接推动撞针工作的电动射钉枪比较,冒钉现象减少了13.3%。     

Ⅴ型双缸往复活塞式无油空气压缩机惯性力的行为特性及消减方法

以某款车用直联式Ⅴ型双缸无油空气压缩机为研究对象,探讨其惯性力的行为特性及消减方法.通过建立能反映并解析惯性力规律特征的动力学模型,对平衡块的离心惯性力与活塞组件的往复惯性力的融合表现进行了研究,借助工程分析软件MATLAB对不同平衡配重的配置参数进行了数值模拟计算,获得了最优的平衡配重方案.研究结果表明,Ⅴ型双缸无油空气压缩机的往复惯性力依然可以采用过量平衡法来消减,但与传统单缸机型相比,其配重在质量占比及相位布局方面均存在较大的差异,通过优化包括质量半径积和相位设置在内的过量配重参数,仍然可以显著转移一级往复惯性力的大小及方向,从而能够选择出满足压缩机在特定敏感方向振动强度限制要求的最优平衡控制方案.     

局部投影降噪在往复压缩机故障诊断中的应用

往复压缩机的振动信号为典型的非线性、非平稳信号.提出利用局部投影法对振动信号降噪,提取关联维数,并与热力参数相结合诊断往复压缩机故障的方法.首先利用基于定量递归分析的局部投影降噪算法滤除振动信号中的噪声,然后提取关联维数,再根据热力参数计算气缸的压缩比,最后结合关联维数和压缩比,诊断压缩机的故障.结果表明:应用局部投影法降噪后振动信号的局部标度指数曲线存在明显的平台区,关联维数易收敛;在降噪后时域指标无明显变化的情况下,关联维数变化明显,基于局部投影法降噪后的关联维数更能有效地反映设备的故障状态变化.实例中诊断出的往复压缩机活塞磨损故障验证了这种方法的有效性.     

旋转气缸压缩机缸体的静动态特性

利用流体动力润滑理论,建立了旋转气缸压缩机缸体的静、动态特性计算模型,以1台XG-0.36／7型旋转气缸空气压缩机为例,求解了机器缸体的轴心轨迹等动态特性以及缸体的摩擦功耗等静态特性,并对计算结果与有关实验进行了对比。     

基于混沌理论的往复式压缩机故障诊断

实测某往复压缩机气缸在正常、活塞体松动及拉缸工况下的振动信号,计算信号的关联维数、Kolmogorov熵及最大Lyapunov指数,并证明信号具有非线性。用奇异值分解(SVD)降噪法对信号进行降噪,通过奇异熵增量曲线选择降噪阶次,用互信息法求最佳延时,并用假近邻域法求最佳嵌入维数,同时用G-P算法、小数据量法求出关联维数、Kolmogorov熵及最大Lyapunov指数。计算结果表明,3种工况下的往复压缩机气缸振动信号均为非线性混沌信号,故障越严重,信号表现出的混沌特性越明显,可依据混沌指标对往复压缩机气缸的状态进行监测。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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