Finite Element Analysis for In-Plane Crushing Behaviour of Aluminium Honeycombs

A number of finite element simulations were performed to analyze the in-plane crushing behaviour of aluminium honeycombs and the results are presented and discussed. The simulations include both X1 and X2 cases. All the analyses are quasi-static, and can be divided into three groups, which are designed to investigate the effects of cell size, foil thickness and yield stress of the foil material, respectively, on the structural response of honeycombs. The result indicates that these factors can significantly affect the plateau stresses of honeycomb cellular structures in both directions, and the plateau stresses in X2 direction are slightly smaller than those in X1 direction. The simulation results were further compared with published theoretical predictions and show higher values. The difference was then analyzed and a new expression for the plateau stress of honeycombs was suggested.     

Cu2＋胁迫对凤眼莲根系活力及Cu2＋-ATPase 活性的影响

通过水培法研究了不同Cu2＋浓度（0．5,1．0,2．5,5．0,10．0 mg/L）对水生植物凤眼莲[Eichhornia crassipes]蛋白质含量、根系活力及Cu2＋-ATP酶活性的影响．结果表明,Cu2＋胁迫对凤眼莲蛋白质含量、根系活力及Cu2＋-ATP酶活性的影响与 Cu2＋胁迫浓度及胁迫时间均有关,在 Cu2＋胁迫时间为1,3,10 d 时,各Cu2＋胁迫浓度下均有利于凤眼莲叶片蛋白质含量的积累．一定浓度和时间的 Cu2＋胁迫使凤眼莲体内蛋白质含量应激积累增多．在Cu2＋胁迫时间为1 d时,随着Cu2＋浓度的增加,凤眼莲根系活力逐渐增大;当胁迫时间达10 d时,根系活力在Cu2＋浓度为1．0 mg/L Cu2＋时达最大,以后逐渐降低．试验表明,随着 Cu2＋浓度的增加,叶片Cu2＋-ATP酶活性在0．5 mg/L时达最大,之后逐渐降低;随Cu2＋浓度的增加根系Cu2＋-ATP酶活性的变化趋势与叶片Cu2＋-ATP酶活性的变化趋势相似．     

大骨料混凝土在双轴压应力状态下的变形和强度试验研究

利用大连理工大学自行研制改造的液压伺服静、动态三轴试验系统对不同骨料级配和尺寸的混凝土试件在双向压荷载作用下的变形和强度特性进行了试验研究.试验所用试件有3种:采用大坝原级配最大骨料粒径为80 mm的立方体试件以及相应的湿筛混凝土试件,尺寸分别为250mm×250mm×250 mm,150 mm×150 mm×150 mm和100 mm×100 mm×100 mm.试验过程中,测得了所有试件两个加载方向的应力和应变,以及未加载方向上的侧向变形,并根据试验结果,系统地探讨了不同级配混凝土的双轴抗压强度、极限变形、应力-应变曲线以及破坏形态的变化规律,发现大骨料混凝土在双轴压作用下的极限强度和变形能力要比相应的湿筛小骨料混凝土提高的更多,最后分别在主应力空间和主应变空间建立了不同级配混凝土的破坏准则,这为水工大体积混凝土按多轴强度理论进行设计提供了试验依据.     

Mechanical analysis and reasonable design for Ti-Al alloy liner wound with carbon fiber resin composite high pressure vessel

To consider the internal pressure loaded by both the cylindrical Ti-Al alloy liner and the carbon fiber resin composite （CFRC） wound layers, two models are built. The first one is a cylinder loaded with the internal pressure in the hoop direction only. In this model, the total hoop direction load is distributed over all layers under the internal pressure. The second one is a cylinder loaded with the internal pressure in the axial direction only. In this model, the total axial load is distributed over all cylinders under the internal pressure. Taking the boundary conditions of the continuous displacement between layers into account, a group of equations are built. From these equations, we get the solutions of stresses in both hoop direction and axial direction loaded by every layer under internal pressures. After the stresses are obtained, a reasonable design can be done. An example is given in the final section of this study.     

NiTi薄膜残余应力测试方法的探讨

介绍了适用薄膜残余应力测量的弯曲法和X射线掠射法,重点介绍了一种新型测量薄膜残余应力的方法—纳米压痕法,并采用非球形压头纳米压痕法测量了NiTi薄膜的残余应力,对薄膜残余应力的测量进行了有益的探讨和尝试,结果表明纳米压痕技术可作为定性测量薄膜残余应力的有效手段。     

现实的幻影与人性的聚光--论徐訏小说的人物塑造

徐訏骨小说的主要笔力集中于人性的反思，他淡化小说中人物的社会性，而主要表现其作为社会人的生物性、自然性等共性，而其中最主要的又是“性”意识；现实背景只作为人性表现的衬托幻影而存在。徐骨小说具有“寓言小说”的意味。     

通过珩磨附加拉应力提高脆性陶瓷材料的去除率(英文)

根据珩磨加工特性和脆性陶瓷材料力学性能,应用断裂力学理论,分析加工表面裂纹尖端的应力强度因子及应力状态．珩磨附加拉应力增大陶瓷材料加工表面裂纹尖端的应力强度因子,降低陶瓷材料的临界磨削力,使陶瓷材料的去除容易进行．研究表明,珩磨可作为脆性陶瓷材料的一种高效加工方式．     

Experimental study on surface integrity of Ti-6Al-4V in high speed side milling

Aiming at the surface integrity of titanium alloy Ti-6Al-4V in high speed side milling, a series of side mill- ing tests were carried out with uncoated carbide milling cutter at various milling speeds. Surface roughness, residual stress, subsurface microstructure and microhardness variations were investigated. The surface roughness measurement results present that the milling speed from 80 to 120 m/min fails to produce better and more stable roughness values compared with the result obtained from 320 to 380 m/min. The residual stresses in the feed direction and axial depth of cut direction are in similar trends for the two milling speed levels mentioned above. Moreover, the residual stress pro- duced at 320 to 380 m/min is lower and more stable than that at 80 to 120 m/min. The microstructure analysis shows that the volume of β phase in the near surface becomes smaller and the deformation of β phase in the near surface be- comes obvious with the increase of the milling speed. Subsurface microhardness variation was observed down to 200 μm below the machined surface at 80 to 120 m/min and down to 160 μm at 320 to 380 m/min. It is concluded that better surface integrity and higher material removal rate can be obtained at 320 to 380 m/min than at 80 to 120 m/min.     

祁东煤矿地应力测量成果分析

采用应力解除法在祁东矿-408、-500和-600三个水平进行了原岩应力测试及计算，确定了祁东井田主应力的大小和方向以及三个主应力随深度的变化关系：祁东煤矿的地应力场以水平构造应力为主，最大主应力方向为北东向到近于东西向；中间主应力为垂直应力，垂直应力接近于上覆岩层的重量；最大主应力梯度值为0．029MPa／m，垂直应力梯度值为0．026MPa／m，最小主应力梯度值为0．023MPa，／m；地应力测量结果为研究祁东矿区域内各点的应力状态及应力场分布提供了理论依据。     

Numerical simulation of residual stress field induced by laser shock processing with square spot

Laser shock processing (LSP), also known as laser peening, is a novel surface treatment technique in the past few years. Compressive residual stresses which imparted by LSP are very important for improving fatigue, corrosion and wear resistance of metals. Finite element analysis (FEA) simulation using ABAQUS software has been applied to predict residual stresses induced by LSP on Ti-6Al-4V titanium alloy with laser pulse duration 30 ns and water confined ablation mode. The residual stress field generated by different shape laser spots was studied, and the square laser spot is shown the most suitability for avoiding stress lack phenomenon and overlapping LSP. Surface residual stresses and plastically affected depth within single square spot both increased with the increase of laser intensity and laser shock times. Furthermore, compared with circle and ellipse spot, the residual stress distribution in overlapping square spots is very uniform only with small overlapping ratio. LSP with square spot can process advantageous residual stress field, and this technique will be used widely.     

氮化物硬质薄膜残余应力的研究进展

文章讨论了几种薄膜残余应力测试方法的优缺点,介绍了氮化物薄膜应力沿层深分布趋势的最新研究,偏压和N2分压工艺对薄膜应力的影响及几种调节薄膜残余应力的有效方法．脉冲偏压增大,薄膜残余应力显著增加：N2分压增大,薄膜残余应力显著增加．采用独立变化脉冲偏压或变化N2分压工艺制备的薄膜,其残余应力沿层深分布趋势明显均匀,薄膜残余应力可得到有效调整．     

Application of 2-D Position Sensitive Detector in Spatial Straightness Measurement of Guide Rails

A laser collimating system based on 2-D position sensitive detector (PSD) is presented in this paper. The working principle of PSD is depicted in detail. A calibration device was developed to check the nonlinearity errors of PSD and a multilayer feedforward neural network based on error back-propagation algorithm was used to compensate errors. With the aid of computer-based data acquisition system, an automatic dynamic measuring process was realized. A series of experiments, including comparison tests with laser interferometer, were done to evaluate the performance of the measuring system. The experimental results show that the spatial straightness errors of guide rails can be measured with high accuracy. The maximum differences between the device and laser interferometer are 0. 027 mm in Y direction, and 0. 053 mm in X direction in the measuring distance of 6 m.     

谈《史记》人物传记的衬托艺术

司马迁的《史记》在塑造人物时,大量地运用衬托这一艺术手法,并且灵活多变：或让人物两相对照,相互衬托;或虚实参用,以实托虚;或以宾衬主,对人物进行侧面烘托;或引用歌诗,渲染气氛,烘托人物;或大衬托下包含多层小衬托。他之所以如此不吝笔墨大肆运用衬托手法传写人物,是有着极为复杂的主客观方面的原因的。由于善于吸取前代成功经验并加以发展,衬托艺术经他而迈上了一个新台阶。     

Time- and stress-dependent model for predicting moisture retention capacity of high-food-waste-content municipal solid waste: based on experimental evidence

Moisture retention capacity (MRC) is a key parameter for the prediction of leachate production of a municipal solid waste (MSW) pile. In this paper, five sets of laboratory tests were conducted in compression cells to characterize the variation of MRC with degradation time and overburden stress. Set A was conducted on the fresh high-food-waste-content (HFWC)-MSW under different degradation conditions and a sustained stress; Set B was on the fresh HFWC-MSW by alternation of degradation time and incremental stresses; Sets C, D, and E were on fresh HFWC-MSW, zero-food-waste-content (NFWC)-MSW, and decomposed MSW, respectively, being subjected to incremental stresses. The following findings were obtained from the test results: (1) The MRC of fresh HFWC-MSW decreased exponentially with degradation time under a sustained stress. The higher waste temperature or oxygen introduction would result in a faster declining of MRC. (2) The MRCs decreased linearly with a logarithmic increase of stress for all the MSW samples with different food waste contents. The MRC of HFWC-MSW was higher than that of NFWC-MSW under a given stress, and the decomposed MSW took the second place. (3) The variation of MRC appeared to be independent of stress path in terms of stress and degradation time. Based on the test results, the dependencies of the MRC of HFWC-MSW on degradation and stress were interpreted. Then, a time- and stress-dependent model was proposed for predicting the MRC of HFWC-MSW. The model was relatively simple and convenient for design purposes, and was verified by the measured data of leachate production at the pretreatment container of Laogang Incineration Plant. Finally, the model was developed to evaluate the dewatering effect of the HFWC-MSW pile. The strategy of combining the degradationenhancing measures with stress-increasing measures is recommended in a rapid dewatering project.     

厚壁球形封头的弹性应力分析

厚壁球形封头在内压力作用下处于三向应力状态 ,可以按类似于拉美公式的分析方法对其三向应力作近似分析。基于这种认识 ,在厚壁球形封头上取一微元体 ,通过分析其受力、位移、变形协调及应力应变关系 ,找出了求解应力的微分方程 ,并根据边界条件得出了厚壁球形封头三向应力的计算公式 ,即径向应力为 pK3 - 1(1- R30r3 ) ,环向应力和经向应力相等 ,其值为 pK3 - 1(1+ R302r3 )。     

等离子喷涂NiCrAl/Cr2O3-8%TiO2涂层残余应力模拟分析

建立了模拟涂层残余应力的数学模型,对等离子喷涂不同厚度NiCrAl/Cr2O3-8%TiO2涂层的残余应力进行了模拟,模拟结果表明:由于涂层与基体的热膨胀系数不匹配等原因,在界面等区域存在严重的应力集中,涂层内部的残余应力水平,随涂层厚度增加而增加,涂层中的径向、轴向、切向应力均为压应力,径向应力是最主要的应力。     

Undrained anisotropy and non-coaxial behavior of clayey soil under principal stress rotation

In this study, a series of undrained tests were conducted on both intact and reconstituted clay using an automatic hollow cylinder apparatus. Monotonic shearing tests with fixed principal stress directions were carried out, pure and cyclic prin- cipal stress rotation tests were also performed. The non-coaxiality, defined as the non-coincidence of the principal plastic strain increment direction and the corresponding principal stress direction, of clayey soil was studied experimentally. The effects of the intermediate principal stress, shear stress level, and inherent anisotropy were highlighted. Clear non-coaxiality was observed during pure principal stress rotation, in both intact and reconstituted clay. The influence of the intermediate principal stress pa- rameter, shear stress level, and inherent anisotropy on the non-coaxial behavior of the clayey soil was found to be insignificant when compared with the sand. The non-coaxial behavior of the clayey soil depended more on the stress paths. Under undrained conditions, the contribution of elastic strain to the direction of the total principal strain increment cannot be ignored.     

Interaction of salinity and cadmium stresses on mineral nutrients,sodium, and cadmium accumulation in four barley genotypes

Interaction of salinity （NaCI） and cadmium （Cd） on growth, mineral nutrients, Na and Cd accumulation in four barley genotypes differing in salt tolerance was studied in a hydroponic experiment. Cd, NaCI and their combined stresses reduced Ca and Mg concentrations in roots and shoots, K concentration in shoots, increased K and Cu concentrations in roots relative to control, but had non-significant effect on micronutrients Cu, Fe and Mn concentrations in shoot. The three stresses reduced accumulation of most tested nutrients in both roots and shoots, except NaCI and NaCl＋Cd stresses for root K and shoot Cu accumulation in salt tolerant genotypes. The salt tolerant genotypes did not have higher nutrient concentration and accumulation than the sensitive ones when exposed to Cd and NaCI stresses. In conclusion, the affecting mechanism of Cd stress on nutrients was to some extent different from salinity stress, and the NaCl＋Cd stress was not equal to additional Cd and NaCI stresses, probably due to the different valence and competitive site of Na^＋ and Cd^2＋. NaCI addition in the Cd-containing medium caused remarkable reductions in both Cd concentration and accumulation, with the extent of reduction being also dependent on genotypes. The salt-tolerant genotypes had lower Na concentration than sensitive ones.     

人白血病细胞系KG1a中P2X7受体的表达和功能研究

用半定量RT-PCR和流式细胞术，研究了白血病细胞系KG1a中P2X7受体在基因和蛋白水平的表达。用荧光分光光度计，测定了用激动剂三磷酸腺苷（ATP）和苯甲酰苯甲酸ATP（BzATP）刺激前后细胞内钙离子浓度的变化，证明P2X7受体的功能。结果表明：KG1a细胞表达P2X7受体，且在激动剂的刺激下能引起KG1a细胞通过P2X7受体的胞外钙内流；去除胞外钙离子时，激动剂不能引起胞内钙浓度的升高；提示KG1a细胞表达P2X7受体的基因和功能蛋白，激活该受体引起胞外钙离子的内流。     

Students' stress

The major objective of the present research was to identify stresses perceived by undergraduate students to characterize their university-related life sphere. Graduate students (n = 16) served as the researcher's confederates. Each confederate solicited highly frequent and important stress conditions from a group of up to ten undergraduates, (total n = 108) using the nominal group technique.Each group provided a rank order of the ten most relevant stresses. Fifteen stresses were identified as appearing in most groups. For each of the fifteen stresses, its mean rank order was calculated across the relevant groups. The highest mean rankings were given to the group of stresses classified as examination related, followed by those which had to do with meeting class assignments and by those related to the teaching process. The results were interpreted as providing strong support to the conceptualization of stress as a condition appraised by the individual to pose threat or danger to himself or herself.