Stiffness Degradation of Undisturbed Saturated Soft Clay in the Yangtze Estuary Under Complex Stress Conditions

Stiffness degradation will occur due to the generation of accumulated pore pressure in saturated soft clays under cyclic loading. The soil static-dynamic multi-purpose triaxial and torsional shear apparatus in Dalian University of Technology was employed to perform different types of test on the saturated soft marine clay in the Yangtze Estuary. Undisturbed samples of the clay were subjected to undrained cyclic vertical and torsional coupling shear and cyclic torsional shear after three-directional anisotropic consolidation with different initial consolidation parameters. Investigated were the effects of the initial orientation angle of the major principal stress, initial ratio of deviatoric stress, initial coefficient of intermediate principal stress and continuous rotation of principal stress axes on the stiffness degradation. It is found that the degradation index decreases （or degradation degree increases） significantly with increasing initial orientation angle of the major principal stress and initial ratio of deviatoric stress. Compared with the effects of the initial orientation angle of the major principal stress and initial ratio of deviatoric stress, the effect of initial coefficient of intermediate principal stress is less evident and this trend is more clearly reflected by the results of the cyclic torsional shear tests than those of the cyclic coupling shear tests. At the same cycle number, the degradation index obtained from the cyclic torsional shear test is higher than that from the cyclic coupling shear test. The main reason is that the continuous rotation in principal stress directions during cyclic coupling shear damages the original structure of the soil more than the cyclic torsional shear does.Based on a series of experiments, a mathematical model for stiffness degradation is proposed and the relevant parameters are determined.

Expression Analysis of Proline Metabolism-related Genes From Halophyte Arabis stelleri under Osmotic Stress Conditions

Arabis stelleri var. japonica evidenced stronger osmotic stress tolerance than Arabidopsis thaliana. Using an A. thaliana microarray chip, we determined changes in the expression of approximately 2 800 genes between A. stelleri plants treated with 0.2 M mannitol versus mock-treated plants. The most significant changes in the gene expression patterns were in genes defining cellular components or in genes associated with the endomembrane system, stimulus response, stress response, chemical stimulus response, and defense response. The expression patterns of three de novo proline biosynthesis enzymes were evaluated in A. stelleri var. japonica seedlings treated with 0.2 M mannitol, 0.2 M sorbitol, and 0.2 M NaCI. The expression of At-pyrroline-5-carboxylate synthetase was not affected by NaCI stress but was similarly induced by mannitol and sorbitol. The proline dehydrogenase gene, which is known to be repressed by dehydration stress and induced by free L-proline, was induced at an early stage by mannitol treatment, but the level of proline dehydrogenase was increased later by treatment with both mannitol and NaCI. The level of free L-proline accumulation increased progressively in response to treatments with mannitol, sorbitol, and NaCI. Mannitol induced L-proline accumulation more rapidly than NaCI or sorbitol. These findings demonstrate that the osmotic tolerance of the novel halophyte, Arabis stelleri, is associated with the accumulation of L-proline.

Thermal characteristics investigation of high voltage grounded gate-LDMOS under ESD stress conditions

The thermal characteristics of high voltage gg-LDMOS under ESD stress conditions are investigated in detail based on the Sentaurus process and device simulators.The total heat and lattice temperature distributions along the Si–SiO2 interface under different stress conditions are presented and the physical mechanisms are discussed in detail.The influence of structure parameters on peak lattice temperature is also discussed,which is useful for designers to optimize the parameters of LDMSO for better ESD performance.

The Effects of Nonuniform Thermal Boundary Condition on Thermal Stress Calculation of Water-Cooled W/Cu Divertors

The thermal boundary condition has very important effects on the accuracy of thermal stress calculation of a water-cooled W/Cu divertor. In this paper, phase-change heat transfer was simulated based on the Euler homogeneous phase model, and local differences of liquid physical properties were considered under one-sided high heating conditions. The steady-state temperature field and thermal stress field under nonuniform thermal boundary conditions were obtained through numerical calculation. By comparison with the case of traditional uniform thermal boundary conditions, the results show that the distribution of thermal stress under nonuniform thermal boundary conditions exhibits tbe same trend as that under uniform thermal boundary conditions, but is larger in value. The maximum difference of maximum von Mises stress is up to 42% under the highest heating conditions. These results provide a valuable reference for the thermal stress caleulat.ion of water-cooled W/Cu divertors.

Development and applications of the quasi‐dynamic triaxial apparatus for deep rocks

The mechanical behaviors of deep rocks have always posed a challenge for the implementation and safe operation of major underground engineering projects.To this end,this study modified the existing mainstream rock mechanics instruments equipped with a dynamic disturbance loading system and developed a second‐generation TFD‐2000/D triaxial instrument.The first‐generation device is equipped with an independent disturbance system and an advanced EDC‐580 all‐digital servo controller,which can apply disturbing load independently,implement the function of cyclic disturbance,and combine dynamic and static disturbances.The instrument was found to be reliable for use in analyzing the damage process of rocks in the disturbance test of marbles.The second‐generation instrument tackles three limitations of the first‐generation instrument:(i)it upgrades the strain measurement system and uses extensometers with linear variable differential transformers to accurately measure deformation;(ii)it uses the self‐balanced chamber to replace the Hoek–Franklin triaxial cell and auto‐balancing triaxial pressure chamber;and(iii)the loading rod is independently equipped with an EDC‐580 all‐digital servo controller,which measures precise loads.The experimental findings confirmed that the second‐generation instrument can be used for rock mechanics testing under cyclic disturbance loading,the disturbance–stress relaxation cycle,and the creep–fatigue cycle.In this sense,the second‐generation instrument can be a useful addition to deep rock mechanical instruments and provide a valuable reference.

Effect of CO_(2)on coal P-wave velocity under triaxial stress

As P-wave velocity is sensitive to the variations in coal reservoir parameters,it is possible to monitor the injected CO_(2)through P-wave velocity during CO_(2)sequestration in coal.However,the effects of CO_(2)on the coal P-wave velocity under triaxial stress are not clearly discerned.In the present study,different boundary conditions and gases were utilised to investigate the factors affecting the P-wave velocity after the interaction of coal with CO_(2).Experiments with helium indicated that the pore pressure primarily affected the P-wave velocity by altering the effective stress.Experiments with CH4 and CO_(2)indicated that matrix swelling induced-cleats porosity decline significantly promoted P-wave velocity.Moreover,CO_(2)caused a wider scale and severe weakening of coal matrix than CH4,thereby significantly decreasing the P-wave velocity,and the decline in P-wave velocity increases with vitrinite content.Furthermore,experiments under different boundary conditions showed that with the boundary condition having more constraints,the decrement of pore pressure on P-wave velocity is more weaken,whereas the improvement of matrix swelling on P-wave velocity is more evident.This study contributes to understanding the mechanism of effect of CO_(2)on P-wave velocity under triaxial stress condition and provides guidance for monitoring CO_(2)sequestration in coal.

The Plane Stress Crack-Tip Field for an Incompressible Rubber Material

The crack-tip field under plane stress condition for an incompressible rubbermaterial￣[1] is investigated by. the use of the fully nonlinear equilibrium theory. It isfound thai the crack-tip field is composed of two shrink sectors and one expansion se-ctor. At the crack-tip, stress and strain possess the singularity of R￣(-1) and R￣(-1n), respec-tively, (R is the distance to the crack-tip before deformation, n is the material const-ant). When the crack-tip is approached, the thickness of the sheet shrinks to zerowith the order of R￣(1.4n). The results obtained in this paper are consistent with that ob-tained in [8] when s→∞ .

The stress release model and results from modelling features of some seismic regions in China

The stress release model is a stochastic point process model developed from the theory of elastic rebound. It can be used to analyse, simulate or predict the seismicity in a certain seismic region. This paper first gives a brief representation of the theory of the stress release model and the method of how to use it to analyse earthquake data, then this model is to fit the earthquake data in North China, Southwest China and Taiwan. The results show that the stress release model fits to the data better than the Poisson model. The different features of stress accumulation and release in these regions imply that the seismic activity is essentially different among these regions.

Rock mass response for lined rock caverns subjected to high internal gas pressure

The storage of hydrogen gas in underground lined rock caverns(LRCs)enables the implementation of the first fossil-free steelmaking process to meet the large demand for crude steel.Predicting the response of rock mass is important to ensure that gas leakage due to rupture of the steel lining does not occur.Analytical and numerical models can be used to estimate the rock mass response to high internal pressure;however,the fitness of these models under different in situ stress conditions and cavern shapes has not been studied.In this paper,the suitability of analytical and numerical models to estimate the maximum cavern wall tangential strain under high internal pressure is studied.The analytical model is derived in detail and finite element(FE)models considering both two-dimensional(2D)and three-dimensional(3D)geometries are presented.These models are verified with field measurements from the LRC in Skallen,southwestern Sweden.The analytical model is inexpensive to implement and gives good results for isotropic in situ stress conditions and large cavern heights.For the case of anisotropic horizontal in situ stresses,as the conditions in Skallen,the 3D FE model is the best approach.

基于弯管机工艺约束的空调管路优化及应用

某空调器进行可靠性性能测试时,运行至500h,冷凝器进气管支管出现泄露,晶相分析结果显示为管路在大应力作用下,出现低周疲劳,开裂的原因是空调器频繁启停时热应力导致。引入管路加工的工艺约束,对冷凝器进气管支管的管路进行优化后,管路的热应力由原管路102.4MPa降低至48.3MPa,低于管路疲劳极限70MPa,满足弯管生产的工艺要求及可靠性要求,且未出现管路断裂。

空调器压缩机启停瞬间管路应变分析及结构优化

某型定速单冷窗机压缩机停机时管路应变超标,本文通过模态分析和启停瞬态分析相结合的方法,利用仿真数据对优化方案进行可行性预判,并进行试验验证,结果表明,同一位置仿真应变值与实测应变值差异在4%左右,仿真结果在偏差范围内。可见,应用瞬态分析技术对空调器压缩机停机时管路应变进行辅助分析能够提高空调器的开发效率。

分体落地式房间空调器导风板失效分析及改进

某分体落地式房间空调器在长期运转试验中容易出现导风板开裂问题,利用有限元分析软件(ANSYS)及模流分析软件(MoldFlow)分析导致导风板开裂的原因,并与实际开裂位置进行对比,验证仿真分析的有效性。在此基础上提出改进方案,并进行有限元分析评估,确定改进方案。

一种土壤调理剂对玉米幼苗抗旱性的影响

为研究新型高效土壤调理剂M3T对作物抗旱性的影响,开展水分胁迫下不同浓度M3T对盆栽玉米幼苗的抗旱性影响的试验。结果表明：添加M3T可增强土壤保水能力;M3T处理延长玉米幼苗的存活时间3～11天,增加玉米幼苗的株高和生物量;玉米幼苗体内叶绿素、丙二醛、脯氨酸、可溶性蛋白含量及过氧化物酶和超氧化歧化酶活性的动态测定结果表明,未加M3T的处理玉米幼苗最早感受到水分胁迫而产生生理生化反应,M3T处理的玉米幼苗出现水分胁迫反应延迟。干旱胁迫下,0.01%～0.03%M3T处理有利于玉米幼苗生长,0.04%～0.05%M3T处理增强了玉米幼苗抗旱性,其存活时间更长;0.02%～0.03%M3T处理下农作物在干旱胁迫下可正常生长发育,且具有较好的抗旱性,为较佳处理。

Quantitative analysis with plastic strain indicators to estimate damage induced by fault-slip

In the present study, methodologies to evaluate damage around an underground opening due to seismic waves arising from mining-induced fault-slip are examined. First, expressions for an associated flow rule with a failure criterion are developed for biaxial stress conditions, which are implemented into FLAC3D code. A three-dimensional(3D) mine model encompassing a fault running parallel to a steeply dipping orebody is constructed, whereby static and dynamic analyses are performed to extract stopes and simulate fault-slip in dynamic condition, respectively. In the analysis, the developed biaxial model is applied to the stope wall. The fault-slip simulation is performed, considering shearing of fault surface asperities and resultant stress drop driving the fault-slip. Two methodologies to evaluate damage caused by seismic waves arising from the simulated fault-slip are examined:(i) the ratio of dynamic plastic strain increment to elastic strain limit and(ii) plastic strain energy density. For the former one, two types of strain increments are tested, namely effective shear strain increment and volumetric strain increment.The results indicate that volumetric strain increment is a suitable index for detecting damage near the stope wall, while effective shear strain increment is appropriate for evaluating damage in backfill. The evaluation method with plastic strain energy density is found to be capable of assessing damage accumulated in an extensive area caused by rock mass oscillation due to seismic wave propagation. Possible damage to mine developments in the proximity of a stope is clearly described with the index. The comparison of the two methods clarifies that the former one assesses "instantaneous" damage, which is found to be different from "accumulated" damage calculated using plastic strain energy density, in terms of damage area and its location. It is thus concluded that the combination of the two methodologies leads to more accurate damage assessment as a proper measure against rockburst.

冷拉铜管材应力腐蚀倾向研究

本文对直接拉制的低残余应力铜管和去应力退火铜管的应力腐蚀行为进行了对比试验,所取得的结果和数据对于指导空调铜管的生产和使用有重要意义。

施用改良剂对重度镉胁迫下甜高粱重金属吸收和转运的调控效应

【目的】本文探明施用改良剂对重度镉胁迫下甜高粱重金属吸收和转运的调控效应。【方法】采用盆栽试验,研究了凹凸棒、腐殖酸、有机硅3种土壤改良剂对重度镉胁迫下的甜高粱生物性状和对重金属吸收、转运的影响。【结果】重度镉胁迫对甜高粱的生长有很强的抑制作用,各改良剂处理均能增加甜高粱生物量,但无显著影响;甜高粱能促进Cd吸收,但施用改良剂对甜高粱不同部位的Cd含量没有显著影响;凹凸棒降低了甜高粱根、茎、叶部的Cd含量,腐殖酸、有机硅降低了甜高粱根部的Cd含量,提高了茎、叶中的Cd含量。重度镉胁迫均显著降低了Cu、Cd、Pb、As、Hg 5种重金属的吸收量,有机硅、腐殖酸处理能促进重度镉胁迫下Cd、Cu、As等重金属向地上部转移。【结论】3种有机改良剂均能提高总Cd积累量,分别较对照增加了8.3%、15.5%、4.16%;综合改良作用效果为腐殖酸>凹凸棒>有机硅,甜高粱对Hg和Cu的富集能力和转移能力强。

土壤改良剂对干旱胁迫下青稞幼苗形态及生理特性的影响

采用盆栽试验研究了施用菌剂(2 g/kg土)、腐植酸钾(2 g/kg土)对干旱胁迫下青稞幼苗形态及生理特性的影响。结果表明,腐植酸钾和菌剂均能有效促进干旱胁迫下青稞幼苗的生长,其中腐植酸钾效果更好,不仅能提高青稞幼苗株高、鲜重、干重、根冠比、根平均直径、茎粗和叶面积、根的投影面积、表面积、体积及分支数等形态指标,也提高了根系活力、叶绿素含量、过氧化物酶、超氧化物歧化酶、过氧化氢酶活性,降低丙二醛含量。

空调用电子膨胀阀应力腐蚀外漏原因分析

空调用电子膨胀阀在售后频繁出现外漏失效。采用扫描电镜、能谱分析、断口金相检验等分析方法,发现泄漏以阀体内侧为源,断面呈现沿晶脆性断裂及冰糖状腐蚀特征,析出大量氯化物,在阀体外表形成垂直于焊缝的多处近平行裂纹。金相组织评定显示晶间腐蚀倾向弱,为活化环境下的应力腐蚀失效。追溯制程发现清洗剂变质试验分解出Cl-,将电子膨胀阀浸入可再现售后失效。结合失效机理,制定辅料试验、残留标准,并进行外壳深冲、激光焊接约束拉应力控制,可有效防止故障发生。

扁塑藤素增强顺铂对条件性重编程原代肺癌细胞敏感性的机制

目的 探究扁塑藤素是否能增强顺铂的抗肺癌作用及其作用机制。方法 利用条件性重编程技术建立患者肿瘤组织来源的肺癌细胞;用MTS检测细胞的增殖活力;用Calcein-AM/PI双染法检测细胞的状态;用Transwell实验检测细胞的迁移和侵袭能力;用Annexin V-APC流式细胞凋亡实验检测细胞的凋亡情况;用DCFH-DA检测细胞内ROS的水平;用JC-1和DiOC6染色定性和定量检测细胞的线粒体膜电位;用qRT-PCR检测mRNA的水平;用Western Blot检测细胞蛋白表达水平。结果 与单一药物处理相比,扁塑藤素联合顺铂能显著抑制细胞活力(P <0.01);增强顺铂诱导的细胞迁移和侵袭抑制能力(P <0.01);提高细胞内ROS的水平(P <0.01);降低细胞线粒体膜电位(P<0.01);抑制NRF2和HO-1的表达,增加细胞凋亡(P <0.01)。结论 扁塑藤素可协同增强顺铂的抗肺癌能力,其机制可能与调控KEAP1-NRF2/HO-1信号通路蛋白表达有关。

有限元技术在空调应力应变中的应用分析

本文以ANSYS有限元分析软件为工具,对空调管路系统进行模态分析,并结合实验得出解决应力超标的方案,体现了有限元技术在空调应力应变分析中的重要性。