二氧化碳焊接弧压智能控制器

研制了基于短路过渡过程评价的二氧化碳弧焊电弧电压自寻优微机智能控制器,该智能控制器根据焊接电流的设定值对电弧电压进行自寻优调节,使焊接参数达到最佳配合,该控制器主要由弧压模糊控制模块与一元化推荐表组成,弧压模糊控制模块以二氧化碳弧焊过程中的熔滴短路过渡频率、燃弧时间与短路时间的比值,以及短路周期标准差等特征参数的综合值作为判据进行弧压寻优,实验表明,此智能控制器能显著改善二氧化碳焊机的性能,同时也降低了焊接飞溅。     

高频逆变式弧焊机电源的研制初探

弧焊机电源是电弧焊机的重要组成部分,它是对焊接电弧供给电能的装置,它应满足电弧焊所要求的电气特性。弧焊机电源电气性能的优劣,在很大程度上决定了电弧焊机焊接过程的稳定性。没有先进的弧焊机电源,要实现先进的焊接工艺和焊接过程自动化也是难以办到的。弧焊机电源具有较大的短路电流和较高的空栽电压等特点。高频逆变式弧焊机电源是近年来世界焊接电源界研究的新技术。它具有控制性能优异、动特性好、焊接工艺性优良、重量轻、效率高、功率因数高、引弧性能好、焊接速度快等优点,是当前国际上焊接电源设备发展的主流和方向。这种电源除了能够用于弧焊机外,还可以用作喷涂等需要大电流,低电压的设备的电源。     

弧焊过程的动态电阻波形分析

利用自行研制的焊接动态电弧小波分析仪对两台CO2焊机的焊接过程进行了分析测试.结果表明,动态电阻能综合反映焊接电源的电气特性.起弧时动态电阻值应迅速上升到稳定值,以保证引弧顺利.在焊接过程中应减少动态电阻纹波干扰,其峰值维持一段时间有利于熔滴平稳过渡.收弧时动态电阻值应在一个过渡周期内,由峰值平稳上升至无穷大,避免尖峰.分析结果可为改进焊接工艺和波形控制方法提供依据.     

新型脉冲钨极氩弧焊机初步试制成功

在光辉的《毛泽东选集》第五卷出版发行的大喜日子里,在全国工业学大庆会议胜利召开的大好形势下,我校机械系于“五一”节前夕,初步试制成功了一种新型焊机——感容稳弧型交流钨极氩弧焊机。新焊机的稳弧不采用常规的脉冲稳弧系统,其原理是在电流过零点时,电弧发生瞬时熄     

关于交焊机手弧焊过渡过程的探讨——交流弧焊机节约用电之四

交焊机的作用是使电弧燃烧稳定,焊接电流和焊接电压稳定,焊接电流能在40～300安范围内调节(指手弧焊机而言);焊接消耗电能少。交焊机还应该重量轻、体积小、成本低;安全可靠、维护容易等。这是因为金属焊件的大小,板的厚薄、金属的性质和工艺条件等的不同,故使用的焊条规格就不同,因而要求焊接电弧的功率、焊接电弧的稳定性、焊接电弧的弹性也不同。由于工业发展、钢种增多、节能呼声更大,因此对交焊机的要求就提高了。     

水蒸气保护焊短路过渡动态过程研究

在测定了水蒸气作为保护气体时的电弧物理特性参数的基础上,对水蒸气保护焊下短路过渡的动态过程进行了模拟．模拟结果与实验结果相吻令,随着电源电压与电感值的升高,短路过渡形式由燃弧──熄弧—短路—燃弧,向燃弧──短路──燃弧过渡。研究了电源电压、电感和送丝速度等焊接参数对短路过渡动态过程的影响．把电弧过程呈燃弧—熄弧—短路－燃弧交替进行,并且熄弧时间最短,短路频率最高作为研究目标,找出此条件下具体的电源电压与电感值及其关系,为制定焊接规范提供依据．     

交流弧焊机电弧稳定性的初步研究——交流弧焊机节约用电之三

用提高功率因素的方法来使交流弧焊机省电不一定能被人们接受,原因可能是:一、提高功率因素会使电弧不稳定;二、提高功率因素会使焊机短路电流太大;三、提高功率因素会使焊机焊接电流的调节范围变窄;四、电抗线圈几乎不耗电。     

气压对分断电弧两相转变过程的影响研究

研究了不同气压条件下小功率直流继电器触点电弧的分断过程,发现气压的变化对分断电弧的燃弧过程有较大影响.近似真空下燃弧过程只有金属相;1.01×105Pa时两相转变过程明显;2.01×105Pa时的两相持续时间比较长.讨论了金属相、气体相持续时间与分断电流的关系,重点研究了电压平台的变化规律.发现电压平台是燃弧过程的一个固有特征,并验证了多级电压平台的存在.这些工作对电弧的机理研究是较好的补充和发展.     

水蒸气保护下电弧堆焊工艺特点

通过分析不同焊接规范下的焊接电压和电流的波形 .研究了水蒸气保护下电弧及熔滴过渡的特点 ,发现其电弧过程行为有“燃弧—熄弧—短路”和“燃弧—短路”两种形式 .在焊丝直径和送丝速度一定的情况下 ,通过调节焊接回路中的电感量和电源电压 ,可以改变电弧的过程行为形式 .若电弧过程呈“燃弧—熄弧—短路”交替进行 ,并且熄弧时间最短时 ,短路过渡频率最高 ,在这种情况下 ,飞溅小 ,焊道成型好 ,焊接过程稳定 .     

脉冲旁路耦合电弧GMAW焊接过程的稳定性控制

脉冲旁路耦合电弧GMAW(Pulsed DE-GMAW)是一种低热输入的新型焊接方法,可以应用于铝钢异种金属的焊接.针对其在开环条件下耦合电弧抗干扰能力较弱、焊接过程不稳定、焊缝成形较差等影响焊接质量的关键问题,提出通过调节主路弧长控制耦合电弧稳定性的方案,并利用Matlab/Simulink软件和xPC-target快速原型控制平台,进行耦合电弧弧长稳定性控制实验.结果表明:通过控制主路弧长可以有效解决Pulsed DE-GMAW焊接过程中耦合电弧稳定性问题,保证Pulsed DE-GMAW焊接质量,获得成形良好的焊缝形貌.     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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