基于模型修正的空间变异边坡可靠度分析方法

空间变异边坡可靠度计算需要进行多次重复性边坡稳定性分析,常用的边坡稳定性分析极限平衡方法（LEM）计算效率较高而有限元方法（FEM）可捕捉真实的边坡失效机制,边坡可靠度评价中如能充分利用这两者的优势将具有重要的工程价值。该文在发展考虑参数空间变异性边坡可靠度分析的一阶可靠度方法（FORM）基础上,提出基于模型修正的空间变异边坡可靠度分析方法,引入一修正系数将基于LEM的简化极限状态面逐渐修正为基于FEM的准确极限状态面,最后基于修正系数和LEM安全系数计算公式采用线抽样法计算边坡失效概率。通过一个考虑参数空间变异性的摩擦/粘性土坡算例验证提出方法的有效性,并探讨土体参数空间变异性和黏聚力与内摩擦角之间互相关性对边坡可靠度的影响。结果表明：提出方法的边坡可靠度计算精度与基于FEM子集模拟方法一致,但是计算效率远远大于后者,尤其对于低概率水平边坡可靠度问题,从而为解决考虑土体参数空间变异性的低概率水平边坡可靠度问题提供一条新的途径。     

Analysis of the reliability of the local effect model for the use in carbon ion treatment planning systems

In radiotherapy with carbon ions, biological effects of treatments have to be predicted. For this purpose, one of the most used models is the local effect model (LEM) developed at the Gesellschaft für Schwerionenforschung (GSI), Germany. At the Istituto Nazionale di Fisica Nucleare, Italy, the reliability of the last published version of LEM (LEM III) in reproducing radiobiological data has been checked under both monoenergetic and spread-out Bragg peak (SOBP) carbon-ion irradiation. The reproduction of the monoenergetic measurements with the LEM was rather successful for some cell lines, while it failed for the less-radioresistant ones. The SOBP experimental trend was predicted by the LEM, but a large shift between model curves and measured points was observed.     

Improvement of the local effect model (LEM)--implications of clustered DNA damage

An improvement of the Local Effect Model (LEM) is presented which takes clustered DNA damage into account. Single strand breaks (SSBs) and double strand breaks (DSBs) are distributed stochastically onto the DNA molecule and additional DSBs are recorded. Consideration of this additional damage leads to a modification of the underlying photon survival curve at high doses. As a consequence of the new approach, the ratio of maximum relative biological effectiveness (RBE) values to minimum RBEs is increased. This can be understood in terms of a higher radiation effect resulting from the cluster damage at high local doses. We find that the extended LEM including cluster effects reproduces experimental data for V79 cells significantly better than the original LEM.     

乳化液膜技术分离提取Cu2+的应用研究进展

乳化液膜技术是一种新型的分离提取技术．综述了乳化液膜技术在含铜废水处理、从铜矿石堆浸液中回收铜、湿法冶金中除铜以及痕量铜的富集与测定中的应用研究进展．目前，乳化液膜技术分离提取Cu^2 仍处于试验研究阶段，但近年来的应用研究表明，该项技术在分离提取Cu^2 方面具有广阔的应用前景．     

The application of amorphous track models to study cell survival in heavy ions beams

In a study of amorphous track models, in the local effect model (LEM), the Kellerer algorithm was used, which folds radial dose distributions from different ion tracks. In representative set of 10 experimental cell survival curves of normal human skin fibroblast cells irradiated with carbon ions, the method that applies the Kellerer algorithm was found to be more accurate and 10(4) times faster than the usual Monte Carlo summation method based on a regular grid.     

Line element-less method (LEM) for beam torsion solution (truly no-mesh method)

Summary In this paper a new numerical method for finding approximate solutions of the torsion problem is proposed. The method takes full advantage of the theory of analytic complex functions. A new potential function directly in terms of shear stresses is proposed and expanded in the double-ended Laurent series involving harmonic polynomials. A novel element-free weak form procedure, labeled line element-less method (LEM), has been developed imposing that the square of the net flux across the border is minimal with respect to coefficients expansion. Numerical implementation of the LEM results in systems of linear algebraic equations involving symmetric and positive-definite matrices without resorting to any discretization neither in the domain nor in the boundary. Some numerical applications are reported to demonstrate the efficiency and accuracy of the method. Dedicated to Professor Franz Ziegler on the occasion of his 70th birthday     

Comparison among three boundary element methods for torsion problems: CPM,CVBEM, LEM

This paper provides solutions for De Saint-Venant torsion problem on a beam with arbitrary and uniform cross-section. In particular three methods framed into complex analysis have been considered: Complex Polynomial Method (CPM), Complex Variable Boundary Element Method (CVBEM) and Line Element-less Method (LEM), recently proposed. CPM involves the expansion of a complex potential in Taylor series, computing the unknown coefficients by means of collocation points on the boundary. CVBEM takes advantage of Cauchy's integral formula that returns the solution of Laplace equation when mixed boundary conditions on both real and imaginary parts of the complex potential are known. LEM introduces the expansion in the double-ended Laurent series involving harmonic polynomials, proposing an element-free weak form procedure, by imposing that the square of the net flux of the shear stress across the border is minimized with respect to the series coefficients. These methods have been compared with respect to numerical efficiency and accuracy. Numerical results have been correlated with analytical and approximate solutions that can be already found in literature.     

De Saint-Venant flexure-torsion problem handled by Line Element-less Method (LEM)

In this paper, the De Saint-Venant flexure-torsion problem is developed via a technique by means of a novel complex potential function analytic in all the domain whose real and imaginary parts are related to the shear stresses. The latter feature makes the complex analysis enforceable for the shear problem. Taking full advantage of the double-ended Laurent series involving harmonic polynomials, a novel element-free weak form procedure, labelled Line Element-less Method (LEM), is introduced, imposing that the square of the net flux across the border is minimized with respect to expansion coefficients. Numerical implementation of the LEM results in systems of linear algebraic equations involving positive-definite and symmetric matrices solving only contour integrals. Some numerical applications are reported to assess not only the efficiency and accuracy of the method to handle shear stress problems but also the robustness in the sense that exact solutions when available are captured straight away.     

Analysis of HBM ESD testers and specifications using a fourth-order lumped element model

This paper presents the general and analytical solution of a fourth-order lumped element model (LEM) to describe human body model (HBM) electrostatic discharge (ESD) testers including the main tester parasitic elements. The analytical fitting to the LEM of experimentally obtained HBM pulse data is a new scientifically justified tool to determine HBM tester parasitic elements. The impact of the test board capacitance on HBM testing is demonstrated and explained. Furthermore, the MIL 883C/3015.7¹ and EOS/ESD S5.1-1991² Standards on HBM testers are evaluated upon their selectivity to the test board capacitance. Finally, recommendations to improve HBM tester specifications regarding their selectivity to the parasitic test board capacitance are formulated     

乳状液膜法提取赖氨酸

研究了用乳状液膜法提取赖氨酸的液膜配方及一些重要操作参数 ,初步得出了既能相对减少溶胀 ,又能保持较高分离效率的膜组成及最佳工艺条件 .赖氨酸提取的液膜组成为 :载体二 - (2 -乙基己基 )磷酸脂 7% (质量分数 ) ,表面活性剂 (Span - 80 ) 5 % (质量分数 ) ,膜溶剂 5 0 % (体积分数 )液体石蜡和 5 0 %煤油 .内相选用 0 .5mol/L的HCl溶液 ,处理比为 3.75 ,提取率可达 72 .6 %     

高效无机CsPbI2Br钙钛矿太阳能电池表面钝化的简便方法

近年来,基于CsPbI2Br的钙钛矿太阳能电池(PVSC)由于能在效率和稳定性之间获得良好平衡而受到越来越多的关注.通过溶液法制备的CsPbI2Br钙钛矿薄膜通常包含各种缺陷,为了获得具有高性能和良好稳定性的钙钛矿太阳能电池,这些缺陷需要被钝化.针对此问题,本文报道了一种简便的缺陷钝化策略,即通过在CsPbI2Br钙钛矿表面旋涂KF溶液来对其进行缺陷钝化.结果表明,沉积的KF大部分位于钙钛矿表面的晶界处,而钙钛矿膜的降解通常始于晶界,因此钝化后的PVSC具有更高的稳定性.稳态和时间分辨光致发光光谱均表明钙钛矿的缺陷被KF显著钝化了.最终,基于KF处理的CsPbI2Br的电池器件能量转换效率(PCE)提高到了15.01%,同时具有较大的开路电压(VOC,1.26 V).与之相比,基于CsPbI2Br的对照器件的PCE仅为14.14%,VOC只有1.18 V.     

Superficial Plastic Response Determination of Hard Isotropic Materials Using Ball Indentations and a FEM Optimization Technique

This article introduces a novel method for determining the superficial relation between stresses and elastoplastic strains for hard and commonly brittle isotropic materials. An experimental-computational procedure is developed based on a finite element method simulation of successive ball indentations with increasing loads onto machine elements, which are in their final geometry and heat treatment. The imprint profiles, measured by means of profilometry, are used as input data to a finite element method-supported optimization algorithm. The goal of the optimization procedure is to determine the constitutive stress strain curve, expressed as a multilinear hardening law. The proposed method yields superficial plastic properties accurately, extending forward already existing models that determine bulk-flow material data using ball indentations. The developed procedure is demonstrated with the aid of 100Cr6 through hardened bearing steel, annealed at different temperatures.     

低轮廓不饱和聚酯树脂的中低温固化形态

研究了加有低轮廓添加剂的不饱和聚酯树脂在中低温固化时的形态,结果表明:温度对加入聚醋酸乙烯酯类LPA试样的固化形态影响不大,而加入聚苯乙烯类LPA对试样的固化形态则有较大的影响.在固化过程中极性较大的LPA更有利于从UPR相中分离出来,形成有利于补偿收缩的两相交互连续的相态结构,而玻璃转化温度与UPR的差别大并且低于固化温度的LPA,使得固化试样形成微孔有更多的时间和更高的效率对于加入聚醋酸乙烯酯类LPA的试样,试样的固化形态随着LPA含量的增加发生两次明显的转变.对于具有较高分子量的LPA,只需要加入较低的含量就能使试样形成相互连续的两相结构,而加入聚苯乙烯类LPA的试样,固化的形态随着LPA含量的增加没有明显的改变.     

高温退火对V30Ti33Cr27Fe10贮氢合金性能与结构的影响

研究了高温退火处理对V30Ti33Cr27Fe10贮氢合金性能与结构的影响。结果表明高温退火使放氢平台变平，平台压降低，减小了合金吸放氢后的体胀，改变了合金晶粒的形态，改善了合金基体的组织均匀性。随保温时间延长，合金晶粒长大，晶胞体积减小，吸放氢量降低，BCC主相中析出越来越多的富Ti相，富Ti相中Fe含量随保温时间延长而减少。1523K保温30min的合金具有最大的室温吸放氢量，分别为3．679，5和2．14%（质量分数）；保温3h的合金具有最好的室温吸氢动力学性能，5min内就能达到其饱和吸氢量的80％。     

Effect of reheat temperature on continuous cooling bainite transformation behavior in low carbon microalloyed steel

The effect of reheat temperature on continuous cooling bainite transformation in a low carbon microalloyed steel was investigated using a dilatometer based on welding thermal simulation process. The variation of microstructure was analyzed in detail by means of optical microscope and transmission electron microscope (TEM). The results showed that the morphology of the main microstructure changes from polygonal ferrite to granular bainite with increasing reheat temperature at a given lower cooling rate. For the higher cooling rate, the microstructure is predominantly lath bainite irrespective of the reheat temperature. The specimens with the relatively fine austenite grain size have the lowest bainite start and finish temperatures among the simulated sub-zones of heat affected zone, which is consistent with the result of the bainite lath width size observed using the TEM. Meanwhile, although the prevailing type of impingement mode of transformation is anisotropic growth impingement for all heat treatment processes, the reheat temperature has some influence on the maximum transformation rate and effective activation energy of bainite transformation.     

Thermally induced structural and mechanical variations in ternary Al–Si based alloys

The effect of heat treatment on the variations in the structural and mechanical characteristics of Al–Si based ternary alloys was studied for samples prepared from elements of purity 99.99% and aged at 673 K for 2 h through tensile tests in the temperature range (413–493 K). Softening behaviour was observed with increasing the working temperature. The mechanical results were discussed in relation to the structure analysis of TEM micrographs obtained at room temperature for samples aged at 673 K. Sn addition improved the mechanical properties of the samples but this was not achieved with Ag addition which improved softening and ductility under the same testing conditions.     

Study of plasma-solid interaction in electronegative gas mixtures at higher pressures

Surface treatment at higher pressures has become an important issue of plasma science and technology. The analysis of processes in such plasmas is now often based on computer modelling; however, the main problem of simulation in medium and higher pressures is the increasing number of collisions among plasma particles and because of this, decreasing efficiency of simulations. A combination of experimental and computational approaches was used for the study of this problem in the present work. The measurements were performed in the positive column of a DC glow discharge in oxygen, both pure and in mixtures with rare gases, at medium pressures. These experiments were completed by computer simulations, where an attempt was made to extend the particle simulation technique to higher pressures. It was shown that the standard Particle-In-Cell/Monte Carlo simulation technique loses its applicability at higher pressures and must be replaced by more sophisticated computational methods. In the present work new algorithms for particle treatment in plasma at higher pressures were suggested and successfully tested.     

P91钢高温热损伤的二次谐波评价

P91钢是重要的核电承压钢结构材料,对其进行早期损伤评价具有重要意义。基于非线性超声理论,对P91钢不同温度的热损伤试样进行了非线性超声检测试验,逐级加大激励电压,基波幅度平方和二次谐波幅度呈现出良好线性关系,对基波和二次谐波进行频谱分析得到非线性系数,结果显示随着热处理温度的升高,非线性系数逐渐增大,可用于对这类材料热损伤进行有效评价。     

A comparison of the effect of hot stretching on microstructures and properties of polyacrylonitrile and rayon-based carbon fibers

The effect of a different stretching stress at different heat treatment temperatures (HTT) on the structure and the mechanical properties of polyacrylonitrile (PAN)- and rayon-based carbon fibers was studied. The tensile strength increases first and then decreases with increasing stretching stress, whereas the Young’s modulus of the fibers continuously increases. The behavior of PAN- and rayon-based carbon fibers is similar with increasing stretching stress, but the tensile strength of PAN fiber decreased while that of rayon fiber increased with increasing HTT, what is more, the latter have a considerable lower tensile strength and modulus for equivalent processing conditions. The structure of the fibers was investigated with X-ray diffraction. A continuous change toward a nanostructure with a higher order was observed, which explains the increase in the Young’s modulus. For more complex dependence of the tensile strength on the processing conditions, a quantitative model to describe the effect of stretching stress at different HTT on preferred orientation degree and shear modulus is proposed. From the critical stress fracture of carbon fiber analysis, we can understand the different changes of tensile strength of both type fibers with stretching stress at different HTT.     

Increasing the working range of coherent optical time-domain reflectometer

A new method for increasing the working range of a coherent optical time-domain reflectometer (COTDR) has been theoretically justified and experimentally demonstrated. The proposed method is based on the use of several types of optic fibers with different backscatter coefficients, in which the fiber with a higher backscatter coefficient is connected to the end of a fiber with the minimum absorption coefficient at the working wavelength, the length of which is the maximum possible in order to ensure a preset sensitivity level. It is shown that, using this approach, the COTDR working range can be increased up to 50 km.