Multi-factor sensitivity analysis on the stability of submarine hydrate-bearing slope

There are many factors affecting the instability of the submarine hydrate-bearing slope (SHBS),and the interaction with hydrate is very complicated.In this paper,the mechanical mechanism of the static liquefaction and instability of submarine slope caused by the dissociation of natural gas hydrate (NGH) resulting in the rapid increase of pore pressure of gas hydrate-bearing sediments (GHBS) and the decrease of effective stress are analyzed based on the time series and type of SHBS.Then,taking the typical submarine slope in the northern South China Sea as an example,four important factors affecting the stability of SHBS are selected,such as the degree of hydrate dissociation,the depth of hydrate burial,the thickness of hydrate,and the depth of seawater.According to the principle of orthogonal method,25 orthogonal test schemes with 4 factors and 5 levels are designed and the safety factors of submarine slope stability of each scheme are calculated by using the strength reduction finite element method.By means of the orthogonal design range analysis and the variance analysis,sensitivity of influential factors on stability of SHBS are obtained.The results show that the degree of hydrate dissociation is the most sensitive,followed by hydrate burial depth,the thickness of hydrate and the depth of seawater.Finally,the concept of gas hydrate critical burial depth is put forward according to the influence law of gas hydrate burial depth,and the numerical simulation for specific submarine slope is carried out,which indicates the existence of critical burial depth.

Sensitivity Analysis of Petrophysical Parameters for Estimating Hydrate Saturation in the Shenhu Area

Acoustic and electrical methods are commonly used to evaluate hydrate saturation based on P-wave velocity(Vp)and resistivity,respectively.We evaluate hydrate saturation using petrophysical parameters directly related to the presence of hydrates.Five petrophysical parameters sensitive to hydrate saturation were first analyzed using the equivalent medium rock physical model,logging intersection plots,and petrophysical parameter inversion.The simulated annealing global optimization method was then used to estimate the hydrate saturation profile in the Shenhu Area,China.The petrophysical parameters Vp,λρ,andλμ,which are associated with the rock elastic and shear moduli,are highly sensitive to hydrate saturation for an estimated saturation range of 0.1-0.44.This range is consistent with that obtained from the original well diameter curves.However,the parameters Vs andμρ,which are only related to the rock shear modulus,yield high hydrate saturation estimates of 0.22-0.43 and exhibit some deviations from the real-time data.Owing to its sensitivity,the Poisson’s ratio is least desired for hydrate evaluation among the studied parameters.The sensitivity of hydrate saturation depends on the petrophysical model used for studying hydrate physical properties and storage analysis.

Catalytic property and gas sensitivity of α-Fe_2O_3 based nanometer materials

Being a good gas sensitive material α-Fe2O3 has been developed in a variety ofapplications. On the other hand, the perovskite-type complex oxide （ABO3 B, Mn, Fe,or Co） has also been regarded as an excellent catalyst. However, there has been noattempt to get a comprehensive understanding of the relationship between the gas sensi-tivity and catalytic property of nanometer-sized α-Fe2O3. In our study coprecipitation

PREPARATION OF CAPACITIVE-TYPE CO_2 GASSENSITIVE ELEMENT USING NANOMETER POWDERS

ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｃｅｎｔｌｙ，ａｇｒｅａｔａｔｅｎｔｉｏｎｈａｓｂｅｅｎｐａｉｄｔｏｔｈｅｄｅｖｅｌｏｐｍｅｎｔａｎｄａｐｐｌｉｃａｔｉｏｎｏｆｅｎｖｉｒｏｎｍｅｎｔａｌｇａｓｓｅｎｓｏｒｓ［１－３］．Ｔｈｅｒｅｓｅａｒｃｈｅｓｏｎｓｏ...

Experimental research on reservoir sensitivity to stress and impacts on productivity in Kela 2 Gas Field

Kela 2 Gas Field, with high formation pressure (74.35MPa), high pressure coeffi-cient (2.022) and difficulty of potential test and evaluation, is the largest integrated proved dry gas reservoir in China so far and the principal source for West-East Gas Development Project. In order to correctly evaluate the elastic-plastic deformation of rocks caused by the pressure decline during production, some researches, as the experiment on reservoir sensitivity to stress of gas filed with abnormal high pressure, are made. By testing the rock mechanic properties, porosities and permeabilities at different temperature and pressure of 342 core samples from 5 wells in this area, the variations of petro-physical properties at changing pressure are analyzed, and the ap-plicable inspection relationship is concluded. The average productivity curve with the reservoir sensitivity to stress is plotted on the basis of the research, integrated with the field-wide produc-tivity equation. The knowledge lays a foundation for the gas well productivity evaluation in the field and the gas field development plan, and provides effective techniques and measures for basic research on the development of similar gas fields.

Preparation and Gas Sensitive Properties of Nanometer-Sized SnO_(2)

Nanometer sized SnO 2 particles were prepared by a sol gel method using inorganic salt as a precursor material. Its crystallization was investigated by means of TG DTA,IR absorption spectra, X ray diffractometry and TEM as well as its resistivity change and the gas sensitivity varied with temperature were measured in various reducing gas. The results indicate that well crystallized nano sized SnO 2 with size around 15nm can be obtained at annealing temperature 600℃. The activation energy for the growth of nano SnO 2 was calculated to be 26.55kJ.mol 1 when the annealing temperature was higher than 500℃. The measurements also show that there is a peculiar resistance change varied with temperature for nano SnO 2.It has relevance to the increase in surface adsorbed oxygen. The selective detectivities to C 4H 10 and petrol can be increased when ruthenium ion was doped in nano SnO 2 as a catalyst and so do the gas sensitivity to CO,CH 4,H 2 etc. when rhodium ion was doped in.The detection to the several reducing gas can be realized when the temperature ranged from 260℃ to 400℃.

Element Analysis of Instrumented Sharp Indentations into Pressure-sensitive Materials

Finite element analysis was carried out to investigate the conical indentation response of elastic-plastic solids within the framework of the hydrostatic pressure dependence and the power law strain hardening. A large number of 40 difierent combinations of elasto-plastic properties with n ranging from 0 to 0.5 and σy/E ranging from 0.0014 to 0.03 were used in the computations. The loading curvature C and the average contact pressure Pave were considered within the concept of representative strains and the dimensional analysis.Dimensionless functions associated with these two parameters were formulated for each studied value of the pressure sensitivity. The results for pressure sensitive materials lie between those for Von Mises materials and the elastic model.

锂离子电池用PET-Cu复合集流体拉伸性能研究

随着锂离子电池技术的不断发展,复合集流体因其具有显著提升电池能量密度和安全性高等优势而引起了产业界的广泛关注。而复合集流体的力学性能可靠性是保证其安全服役的前提,为此,本文针对商业用聚对苯二甲酸乙二醇酯-铜(PET-Cu)复合集流体的拉伸性能开展了系统性的研究。利用扫描电镜、激光共聚焦显微镜、X射线衍射等技术手段对复合集流体材料的表面形貌、微观结构及拉伸断裂行为进行了表征与分析。借助有限元模拟分析了不同几何形状试样在拉伸过程中的应力分布状态;通过数字图像相关技术辅助的拉伸实验研究了取样方向、应变速率及试样几何尺寸对PET-Cu复合集流体拉伸性能的影响规律,并对其应变测量进行了校正。结果表明,采用狗骨状试样并进行应变校正可以更准确地评估复合集流体的拉伸性能;PET-Cu复合集流体的拉伸性能表现出试样取样方向相关性和应变速率敏感性。此外,PET-Cu复合集流体的断裂伸长率表现出明显的试样几何尺寸效应,通过引入几何尺寸系数K可以对不同尺寸的试样拉伸性能进行合理的预测。本研究为聚合物复合集流体实际应用提供了理论依据与可靠性的论证,也为相关试验标准的建立提供了参考,有望推动高性能锂离子电池的开发。

Thin Film Nanocomposites for Gas Sensors

Nanocomposites on the base of thin films SnO_2 with additives of metal oxides such as SiO_2,ZrO_2,MnO_2 and others,were prepared by reactive ion-beam sputtering of metal target in the ambient of O_2+At,and then thermal treated at 500℃.Atomic composition and morphology of thin film nanocomposites were investigated.Electrical properties and gas sensitivity of nanocomposites were studied.It Was determined that the grain size of polycrystals depends on the film composition and can run down to 10 nm.It was found that temperature of maximal gas sensitivity of the films depends on their composition as well and it can be decreased by 100℃～150℃lower than temperature of maximal sensitivity of undoped films SnO_2.

基于Morris方法的微波消融肺组织温度场参数敏感度分析

为了获取微波消融肺组织温度场中组织特性敏感度,采用有限元方法建立微波消融肺组织计算模型,进行电磁场-温度场的耦合,基于Morris方法获取组织电导率(σ)、相对介电常数(ε)、导热率(k)、密度(ρ)、比热容(Cp)和血液灌注率(ωb)的敏感度,建立二维有限元模型.肺组织的σ、ε、k、ρ、Cp、ωb六个参数各设置4个水平,分别获取在50 W、300 s时的微波消融肺组织的消融面积和中心温度,并采用Morris方法,分析各参数对消融面积和消融形状的影响程度.结果表明,血液灌注率、相对介电常数、电导率是对微波消融肺组织的消融区域和消融形状影响较大的参数.

掺杂对γ－Fe_2O_3气敏元件灵敏度及其它特性的影响

本文着重研究了稀土氧化物及其它某些化合物对γ－Ｆｅ＿２Ｏ＿３气敏元件灵敏度、选择性、工作温度和使用寿命的影响，并对加粘土在γ－Ｆｅ＿２Ｏ＿３气敏元件中的作用做了详细研究，为制备优异的γ－Ｆｅ＿２Ｏ＿３气敏元件提供了实验依据。

基于人工材料的结构拓扑渐进优化设计

首先,提出了一种在结构边界和孔洞周围附加人工材料的思路。在此基础上,结合ESO方法和应力灵敏度,建立了结构有限单元增、删的准则, 给出了一种新的拓扑优化算法。算例表明该方法能采用固定有限元网格中不同的初始优化结构就可获得优化拓扑。由于其概念上的简洁性和应用上的有效性,该方法具有一定的工程应用价值。

敏感环境条件下深基坑工程的设计方法

随着沿海软土地区城市建设的快速发展,市区的深基坑工程周围通常存在建(构)筑物、地铁隧道和地下管线等复杂敏感环境条件,基坑工程的开挖受到更严格的环境制约。结合上海地区大量深基坑工程设计和施工的实践,探讨了敏感环境下深基坑工程的设计方法。建议根据不同敏感环境的附加变形控制要求,结合深基坑工程的特点,采用针对性的设计对策。包括周边环境附加变形的预估、"时空效应"设计方法、主体工程与支护结构相结合、预加固措施、基坑分区施工和动态施工控制等方法,并结合实际工程对不同的设计方法进行了说明。

大跨V形刚构桥标高控制动态可靠性及灵敏度研究

提出基于响应面法进行大跨V形刚构桥标高控制动态可靠性及灵敏度分析的方法,该方法包括试验设计、有限元分析、响应面函数拟合、标高控制动态可靠性评估和灵敏度分析.以镇大公路运河大桥为例,在考虑有关参数变异的情况下,对施工过程中的标高控制动态可靠性及可靠性灵敏度进行评估,定量分析了各结构参数对标高控制动态可靠性的影响.研究结果表明:大跨混凝土V形刚构桥施工监控过程中随着悬臂长度的增加,标高控制动态可靠性和可靠性敏感性绝对值变化较大,应根据动态可靠性分析结果确定施工过程中的挠度变化允许最大误差.

溶胶-凝胶法制备SnO_2薄膜气敏特性的实验研究

本文介绍了,以SnCl_2·2H_2O为原材料,用sol-gel技术制备La_2O_3掺杂的SnO_2薄膜气敏材料。研究掺杂量、工艺条件、衬底材料对气敏特性的影响。实验表明La_2O_3掺杂的SnO_2薄膜气敏材料对CO_2有很好的响应特性,即有高的灵敏度和快的响应时间。随镧含量的增加〔(3～10)％mol〕,灵敏度增加,工作温度向低温方向移动。在低氧分压下热处理,能形成精细的晶粒与孔洞,灵敏度大幅度增加。

Electrical Conductivity and Sensitive Characteristics of Ag-Added BaTiO_3-CuO Mixed Oxide for CO_2 Gas Sensing

Carbon dioxide gas sensors based on BaTiO3-CuO composite with different concentrations of Ag addition（1,1.5 and 2 wt%） have been prepared by stander ceramic method and sintered at 500 and 700℃ for 5 h.Electrical conductivity and gas sensing properties of the prepared samples were investigated.Electrical conductivity measurement was used to characterize the obtained sintered sensor pellets.It was found that electrical conductivity and the sensitivity to CO2 were improved with Ag addition and sintering.The correlation between Ag content at different sintering temperature and sensing characteristics towards CO2 is discussed.

稀土元素掺杂对ZnO纳米线气敏性能的影响

为解决ZnO基气体传感器在实际应用中存在着灵敏度低、选择性差、响应时间长等问题,以采用物理热蒸发法制备的纯ZnO纳米线和稀土元素（Y2O3、CeO2、La2O3）掺杂的ZnO纳米线为气敏基料,制备成旁热式气敏元件,用静态配气法对浓度均为100 ppm的无水乙醇蒸汽、氨气、甲烷及一氧化碳四种气体进行气敏性能测试.结果表明,稀土元素掺杂后,ZnO纳米线对四种气体灵敏度的最高值都有明显的提高,响应时间和恢复时间分别为4 s和3 s.

Data-Driven Prediction of Mechanical Properties in Support of Rapid Certification of Additively Manufactured Alloys

Predicting the mechanical properties of additively manufactured parts is often a tedious process,requiring the integration of multiple stand-alone and expensive simulations.Furthermore,as properties are highly location-dependent due to repeated heating and cooling cycles,the properties prediction models must be run for multiple locations before the part-level performance can be analyzed for certification,compounding the computational expense.This work has proposed a rapid prediction framework that replaces the physics-based mechanistic models with Gaussian process metamodels,a type of machine learning model for statistical inference with limited data.The metamodels can predict the varying properties within an entire part in a fraction of the time while providing uncertainty quantification.The framework was demonstrated with the prediction of the tensile yield strength of Ferrium?PH48S maraging stainless steel fabricated by additive manufacturing.Impressive agreement was found between the metamodels and the mechanistic models,and the computation was dramatically decreased from hours of physics-based simulations to less than a second with metamodels.This method can be extended to predict various materials properties in different alloy systems whose processstructure-property-performance interrelationships are linked by mechanistic models.It is powerful for rapidly identifying the spatial properties of a part with compositional and processing parameter variations,and can support part certification by providing a fast interface between materials models and part-level thermal and performance simulations.

基于数值计算的某新型生态挡土墙力学特性分析

城市化发展日益表现出对城市建设与生态环境协调关系的重视。作为挡土墙的重要类型之一,生态挡土墙逐渐成为城市挡土墙建设的重要部分。本文提出并设计出了一种新型装配式生态挡土墙,经工程实践,该挡土墙可有效建立两侧水力联系,体现出较好的生态价值。为论证该生态挡土墙的力学稳定性,采用ANSYS数值模拟的方法,对新型生态挡土墙进行了变形与应力分布规律的研究,计算结果与相关规范要求对比表明该生态挡土墙在稳定性方面均满足要求。最后运用层次分析法对挡土墙土压力的主要影响因素进行了敏感性分析,结果表明挡土墙结构的选型以及结构材料这两个指标的权重最高。研究成果可为实际工程安全控制提供有效依据。

拉伸与扭转载荷作用下LNG低温复合软管的力学性能研究

LNG低温复合软管结构复杂,且在运行时受风、浪、流等多种载荷联合作用,其在超低温环境下的力学性能直接关系到其能否安全运行。首先参考江苏某软管公司生产的4英寸LNG低温复合软管,建立软管精细化有限元模型,接着对软管在拉伸、扭转两种轴对称载荷作用下的力学性能进行研究,最后就软管结构尺寸对其力学性能的影响展开分析。结果表明:在拉伸及扭转载荷作用下,不同层芳纶布以及同层芳纶布不同材料主方向在对应波峰、波谷处的受力情况不同。芳纶布铺设角度、芳纶布铺设层数、钢丝螺距以及钢丝直径对复合软管力学性能影响显著,分析相应的灵敏度规律从而对结构尺寸做出调整。研究成果可以为LNG低温复合软管的结构设计提供参考。