浮空器膜材循环拉伸力学性能及弹性常数研究

对全新飞艇蒙皮膜材Uretek3216L进行了单轴循环拉伸试验,采用自主研发的多功能薄膜双轴拉伸试验机进行5种应力比例下的拉伸试验.探讨了单双轴循环试验的应力应变关系及弹性模量随循环次数的变化规律,对双轴耦合弹性模量的理论公式进行了推导,分析了纬经向应力比对耦合弹性模量的影响规律.结果表明,单轴循环的第15次和第1次循环相比,经纬向弹性模量分别增大了20.7%和39.1%,其中第2次循环增大幅度最大,经纬向均占总增量的60%以上.对于双轴试验,随纬经向应力比R的增大,经向耦合弹性模量增大而纬向减小.确定了膜材的单、双轴应力下的弹性模量和3D应力应变响应曲面.     

ETFE薄膜单轴和双轴拉伸试验与分析

采用乙烯-四氟乙烯共聚物(ETFE)薄膜哑铃形试件,进行单轴拉伸试验,得到了工程中常用的ETFE薄膜的力学参数(屈服强度、屈服应变、切线模量和割线模量);在考虑ETFE薄膜粘弹塑性效应特征的前提下,应用应变能等效的方法计算ETFE薄膜等效弹性模量,结果表明计算得到的等效弹性模量介于切线模量和割线弹性模量之间.研制了一种专用于ETFE薄膜双轴拉伸试验的装置,并进行了系列试验;基于正交异性薄膜理论推导出薄膜双向解耦的独立弹性常数计算列式.根据ETFE薄膜双轴拉伸应力-应变曲线,求得厚度为250μm的ETFE薄膜在双边应力比为1:1的工况下的耦合模量为1163 MPa;由正交异性理论计算得该薄膜的解耦模量为814.2 MPa,与单轴拉伸试验得到的等效弹性模量相近.     

建筑PVC膜材双轴正交拉伸循环试验

通过对PVC膜材进行7种应力比下的双轴正交拉伸循环试验,经纬向应力比值分别为0∶1,1∶5,1∶2,1∶1,2∶1,5∶1和1∶0,对膜材在双轴拉伸作用下的拉伸特性进行了研究.试验表明,经过3次循环作用后,膜材的力学试验性能更接近工程实际情况,且材料具有非线性和正交各向异性.在循环荷载作用下,初次循环后残余应变较大.随着循环次数的增加（一般3次后）,残余应变趋于常数,滞回曲线形状趋于稳定.采用双轴拉伸试验方法测定了PVC膜材的广义泊松比,验证了广义泊松比的非线性特征.试验证明,当经纬向应力比C≥1时,经向应变为正值;当C≥0.5时,广义泊松比变为负值;当应力比C为1∶0或0∶1时,双轴变成单轴试验,广义泊松比测定变成常规泊松比试验.理论和试验均证明当C1时,膜材的经向和纬向同时具有最大的弹性模量.     

PVDF涂层织物拉伸力学性能试验研究

为获得膜材的本构关系规律,以SH-1050P膜材为试验对象,采用纱线与拉伸方向夹角α为参数进行单轴拉伸破坏试验;然后进行多比例位移加载下的双轴拉伸试验,得到完整的单、双轴试验结果.假设膜片应变均匀且铺层与纱线无滑移,对单轴下膜片弹性模量与夹角α的关系进行了理论推导,并获得膜材力学参数与方向角α的解析公式.同时,假设膜片在双轴加载下为正交弹性双向材料,求解出不同比例加载下的双轴弹性模量与泊松比.结果表明,单轴下膜片弹性模量可按2%的应变划分为弹性与塑性2个阶段,其值与2倍夹角的正弦成线性关系.而双轴试验情况下,在1∶1等量加载时,双轴弹性模量与单轴相同;在非等量加载时,双向加载力离散越大,双轴弹性模量离散性也越大.     

大骨料混凝土动态双轴拉压强度试验研究

为了研究不同应变速率下混凝土双轴动态受力状态的力学性能,在大型静、动态三轴试验机上,对大骨料混凝土和湿筛混凝土试件进行了不同应变速率和应力比下的双轴动态拉压试验,系统研究了应变速率和应力比对混凝土双轴拉压强度的影响.试验结果表明:两种混凝土双轴拉压强度均低于单轴拉伸或单轴压缩强度,其变化规律不但与应力比有着密切的联系,还随应变速率的增大而增大.在主应力空间建立了考虑应变速率和应力比的混凝土双轴拉压破坏准则,为水工结构物的非线性分析提供了试验依据.     

耦合振动对钻柱疲劳的影响

从钻柱在耦合振动时各截面的应力变化规律出发，运用金属非比例循环概念及特性，讨论了双轴非比例循环对钻柱疲劳的影响．结果表明，金属耦合振动引起双轴非比例循环的应力明显高于单轴振动及比例循环的应力；振幅是影响非比例循环损伤的重要因素之一。     

冷锻模具材料高速基体钢应变控制室温疲劳性能

对冷锻模具材料高速基体钢进行了室温下的单轴静态拉伸试验和应变控制单轴对称拉压低周疲劳试验,获得了静态拉伸力学性能和低周疲劳性能参数.通过对试验数据进行拟合,得到了高速基体钢材料在室温下静态单调拉伸应力-应变关系、循环应力-应变关系以及循环应变-寿命曲线.试验结果表明,该模具材料在本试验控制的循环应变幅范围内发生了循环软化,疲劳断裂之前未观察到明显的应力饱和现象.以控制应变幅为1.5%的试样为例,对材料的低周疲劳行为特性进行了分析.材料的循环应力响应分为明显软化,软化效应减弱和瞬时断裂3个阶段.     

耦合振动对钻柱疲劳的影响

从钻柱上在耦合振动时各截面的应力变化规律出发，运用金属非比例循环概念及特性，讨论了双轴非比例循环对钻柱疲劳的影响。结果表明，金属耦合振动引起双轴非比例循环的应力明显高于单轴振动及比例循环的压力；振幅是影响非比例循环损伤的重要因素之一。     

乙烯-四氟乙烯共聚物薄膜单向拉伸性能及黏塑性本构模型

对厚度为250μm的长条形ETFE(乙烯-四氟乙烯共聚物)薄膜试样进行了8种定速(拉伸速度由极慢的1mm/min到极快的500mm/min)单向拉伸试验,得到了相应的应力应变曲线、屈服强度、弹性模量等参数随拉伸速率的变化规律.结果表明:ETFE薄膜的屈服强度和屈服应变随拉伸速率的增加而增加;ETFE薄膜的切线、割线弹性模量,以及基于应变能和应变余能的等效弹性模量随拉伸速率的增加而增大,3种弹性模量之间的差值也随拉伸速率的增加而增大.对上述应力应变曲线进行分析,提出了ETFE膜材的黏塑性本构模型(Peirce模型),并在有限元分析软件ANSYS中进行了数值模拟,其结果与试验得出的应力应变曲线吻合较好.     

Kapton薄膜高温单轴循环拉伸的力学性能

以25μm厚充气可展结构膜材Kapton(聚酰亚胺膜)为研究对象，选取6种温度工况(20,50,80,110,140,170℃)对其进行高温下单轴循环拉伸试验.通过分析不同循环次数和温度下的应力-应变数据，阐释了高温循环荷载作用下材料的受力机理与性能表征，分别建立了循环弹性模量与循环次数和温度的关系式，并获得了对棘轮应变以及滞回环面积等力学性能参数的影响规律.试验和分析结果表明：随着循环次数的增加，弹性模量逐步增大，滞回环面积减小；高温使得弹性模量显著降低，而滞回环面积增大；以最后一次循环加载后的结果来看，温度对TD(垂直膜材长度方向)的棘轮应变影响更大.研究所得结论可为极端温度场下的充气可展结构设计及在轨交变高低温测试提供参考.     

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