大口径管道供水系统水锤模拟与防护

根据对泵站供水系统因事故停泵引发停泵水锤问题的模拟分析,采用Hammer软件,以某电厂厂外大口径管道供水系统为例,对该泵站供水系统检修时停泵水锤压力变化加以分析,基于无防护措施停泵水锤模拟结果,提出了空气阀+泵端蝶阀防护、调压塔+泵端蝶阀防护、调压塔+泵端泄压阀3种防护措施。模拟结果显示,调压塔+泵端蝶阀防护和调压塔+泵端泄压阀防护可以达到水锤防护的目的;采用调压塔+泵端蝶阀联合防护,对两根大口径管道供水检修时单管供水流量倍增情况下的停泵水锤正压降低及负压提高的效果最佳。     

长距离超高扬程输水系统水锤防护模拟研究

为研究长距离、超高扬程、一次加压提升的长距离输水系统水锤防护问题,结合我国西北地区某工程实例,针对超高扬程达370 m、一次加压提升的长距离输水系统建立了水锤防护设备模型.以特征线法对其进行求解,分别以两阶段控制阀、单向调压塔、气压罐为水锤防护设备方案,建立水锤防护设备模型,分别模拟分析事故停泵管线水锤防护效果,最终通过综合对比技术性能和经济性能来确定最优的水锤防护方案.结果表明,对于超高扬程、一次加压提升的长距离输水系统,在水泵出口处设置气压罐进行水锤防护,能够有效缓解过高和过低的水锤压力,水锤防护效果好.针对不同长距离输水工程特点,建立各种水锤防护设备模型,以特征线法进行求解,其求解结果有效指导水锤防护方案的优选.     

电厂用水管线事故停泵水锤分析

应用水锤基本理论,针对长距离供水系统的特点,拟定单向调压水箱和空气阀的设置位置、数量及结构尺寸,进行系统试算和比较,对系统事故停泵水锤进行了计算分析,最终确定设置六只单向调压水箱和十个空气阀的方案,以确保供水系统的安全运行。     

长距离压力管道的水锤防护

本文针对长距离压力管道出现的水锤问题,论述了水锤的各种防护措施和计算方法,并对其进行了比较、分析,提出对于复杂管道出现的水锤问题要采用多种防护措施才能有效地缓解管道压力,保证管道系统的正常运作。     

大口径泵压输水管道系统停泵水锤防护方案分析研究

结合事故停泵,首先介绍了停泵水锤可供选择的水锤防护措施,然后建立了泵压输水管道系统水锤数值计算的数学模型及边界条件。再以盐环定扬黄工程梯级提水泵站系统设计为模型,利用特征线法,进行了大口径泵压输水管道系统的水锤模拟计算及分析,并拟定水锤防护方案。该研究为类似大口径泵压输水管道系统的停泵水锤防护方案选择提供了经验与参考。     

浅谈停泵水锤的危害及防护

介绍了水锤现象的分类及其危害,提出了水锤防护措施以及在选择停泵水锤的防护措施时要注意的事项。     

怀柔应急备用水源工程水力过渡过程分析

针对怀柔应急备用水源工程具有的多水源、长距离等特点,在阐述工程特点的基础上,通过对水力过渡过程进行正确的计算与分析,应用水锤计算的基本理论,并用特征线法及各种边界条件方程进行了数值模拟,得出了一些基本规律.在此基础上,提出的水锤防护技术措施,不仅很好地解决了该工程的水锤防护问题,同时也给长距离输水系统的水锤计算与防护提供了技术借鉴.     

长距离加压供水工程水锤防护及试运行注意事项

分析了长距离供水工程中水锤产生的原因与类型,提出了水锤常见防护措施,指出了工程试运行时的注意事项。     

水轮机组用脉冲式安全阀—爆破膜装置作调节保证措施的研究

以机械设备代替调压塔(井),是目前国内外水电建设中共同关注的课题。作者提出用脉冲式安全阀——爆破膜装置代替调压塔的设计,在1970年建成的灵正渠水电站安装使用,效果良好。该装置当机组甩负荷急速关机时,利用水压升高开启脉冲式安全阀,泄放一定流量,保证机组和引水系统的安全;并在压力引水管上装有金属薄膜片(爆破膜),作为后备措施。由于直接根据引水系统的水压升高而动作,免去了一套复杂的液压系统,不需对定型的调速器作任何改动,制造和使用都比较简单。安全阀采用脉冲式,既保证了动作灵敏,又避免了水锤作用下的开度频跳。以该装置取代调压塔(井),经济效益明显,水电站和扬水站都可采用,已建工程增设也较方便。灵正渠水电站多年运用情况和甩负荷试验电测记录都表明,用该装置作调节保证措施是成功的,它能有效地对机组和引水系统起到保护作用,压力上升和速率上升都能控制在要求范围之内。本文论述了水轮机组引水系统用该装置调压的原理,动态过程及计算方法,介绍了这一新技术的设计研究成果。     

工程中空气阀防护停泵水锤的应用

以北方某工程为例,介绍了复合型空气阀在停泵水锤防护方面的应用,并在工程中对空气阀口径和安装位置的选择作了详细的计算,根据计算结果进行停泵水锤模拟分析,得出应用复合型空气阀防护停泵水锤可以有效控制负压和防止断流弥合水锤的发生.     

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