汽轮发电机轴系扭振的机理研究

导出了多质块轴系的扭振模式解耦等效二阶模型，用复数力矩系数法分析了串补电容引起的轴系扭振机理和直流输电系统引起的轴系扭振机理，揭示了上述两种情况下轴系发生扭振的条件，为复杂系统的轴系扭振问题的计算机分析研究奠定了基础。     

关于汽轮发电机组轴系扭振的研究工作

本文对在我国开展汽轮发电机组轴系扭振的研究工作就以下几个方面提出若干建议: 关于扭振研究工作的重点, 关于数学模型的建立和数据采集, 关于扭振暂态的计算分析, 关于扭振的监测和分析装置, 关于减少扭振危害的对策。认为围绕电力系统中急剧扰动引起的扭振开展研究刻不容缓.     

用非接触式扭振仪测量柴油机扭振及结果分析

用非接触式扭振仪测量柴油机扭振是一种较为先进的测量方法。本文介绍了在扭振实测中所选用的记录与分析仪器及应注意的事项;对扭振测量结果进行了分析,采用从合成振幅中扣除滚振部分的分析方法,对于获得正确的扭振结果有实际意义。     

考虑连续质量的扭振系统的传递矩阵分析

为准确地分析主轴尺寸和质量相对较大的轴盘扭振系统的扭振特性，将连续质量模型引入扭振系统，推导出了考虑连续质量的扭振系统的传递矩阵，即用考虑连续质量的轴段传递矩阵替代轴盘扭振系统中的场传递矩阵。实例分析表明，该方法符合实际要求。     

汽车传动系扭转振动建模与仿真分析

文章根据汽车传动系扭振动力学方程,建立了传动系扭振仿真模型,在此基础上进行仿真分析,并通过实车试验加以验证,通过仿真运算,观察到传动系中存在较明显的扭振成分;对仿真模型中的参数进行灵敏度分析,得出对扭振影响较大的参数,通过对相应参数的修改,使得扭振降低,该方法为解决车辆传动系扭振提供了参考依据。     

罗拉扭振及其测试

罗拉扭振是严重影响纺纱质量的一个机械因素.本文建立了罗拉系统的数学模型,进行了振动分析,并通过在罗拉扭振测试台上的测定,阐明罗拉扭振的机理,为消除罗拉扭振指明方向.     

考虑扭转速度预估的大型风电机组传动链扭振抑制方法

大型风电机组传动链转动惯量大，在随机风速作用下低频扭振风险高，而传统基于确定扭转速度控制目标的传动链扭振控制方法未考虑因测量设备引起的随机测量噪声对扭转速度的影响，可能导致控制性能下降。针对扭转速度测量不确定性，提出了大型风电机组传动链扭振自抗扰控制方法，设计了KF-ADRC扭振控制器，通过卡尔曼滤波动态估计传动链扭转速度，并以扭转速度为零作为ADRC控制目标，控制发电机电磁转矩，抑制传动链低频扭振。研究结果表明：当常规的扭振控制器输入信号存在随机测量噪声时，会显著降低其对传动链低频扭振的抑制性能，而KFADRC扭振控制器在输入信号存在测量噪声时可有效预估传动链扭转速度，较好地实现了传动链低频扭振抑制效果。     

船用主机轴系扭振计算的一些问题

我俩在赴厂实践中曾对某远洋万吨级货论的轴系扭振进行了新算分析和随船实测,并对正在设计的十艘油轮的轴系进行了不同排列的扭振计算,计算是在电子计算机上进行的。 这里,介绍了某实船的扭振计算和实测情况; 并且对在实践中碰到的一些问题,例如,化计算问题,飞轮在扭振中所起的作用问题进行了分析和讨论; 另外,对扭振计算,从数学力学的角度,对矩阵计算作一个简单的综合分析和介绍。 由于接触面的局限和篇幅所限不拟对扭振问题作全面的分析和论述,在这方面已经有了比较完整的著作[1][2] 一、为什么要计算扭振 当船用主机的转速和轴系自振频率…     

电力传动中的扭振及振动抑制

传动系统中的机械扭振会引起控制系统控制的振荡,从而加大机械传动装置的磨损,成为制约机械动态性能提高的主要原因.通过并联谐振电路理论分析机械扭振发生的机理和扭振时的能量传递过程,利用品质因数评估扭振的危害程度,定量计算引发扭振的谐波转矩含量.指出在大惯量负载时,扭振危害程度更大,较小的转矩谐波即可激发几十倍的扭矩.最后,引入扭矩反馈抑制扭振,给出了扭矩观测器的有限带宽设计方法,指出基于扭矩观测器的反馈控制能增大谐振频率,并对关键的系统参数进行了敏感性分析.分析和仿真结果表明,该方法可以很好地抑制谐振.     

扭振测量在煤岩界面识别中的应用研究

为了更有效地进行煤岩界面识别,利用扭振信号来进行煤岩界面识别研究。首先从理论上分析了扭振信号与滚筒截割力的关系;应用小波包和模糊神经网络技术进行信息特征提取和数据融合,论证了扭振信号的有效性与可靠性,并与直线振动信号进行了对比。识别结果表明,扭振信号数据比较稳定,识别正确率达到92%;而直线振动信号的正确识别率为63%,理论分析与试验验证是一致的。通过滚筒轴扭振信号来监测采煤机运行状态是一有效手段。     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

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