A Two-network thermomechanical model of a shape memory polymer

The aim of this work is to demonstrate a Helmholtz potential based approach for the development of the constitutive equations for a shape memory polymer undergoing a thermomechanical cycle. The model is able to simulate the response of the material during heating and cooling cycles and the sensitive dependence of the response on thermal expansion. We notice that the yield-stress of the material controls the gross features of the response of the model, and suggests that the material yields differently depending on not just the current value of the temperature but also on whether the temperature of the material dropped or increased from the previous time-step somewhat similar to the Bauschinger effect in plasticity, except that here the controlling parameter is the rate of temperature change rather than rate of plastic strain. The results of the simulation are in qualitative and quantitative agreement with experiments performed on two different shape memory polymer samples: polyurethane and epoxy resin. We find that modeling the hysteresis of the yield stress of the material during temperature changes is the key to the results.     

An efficient preconditioning scheme for plane-wave-based electronic structure calculations

We propose a preconditioning scheme for diagonalizing large Hamiltonian matrices arising in first-principles plane-wave pseudopotential calculations. The new scheme is based on the Neumann expansion for the inverse, shifted Hamiltonian from which only a nonlocal part is omitted. The preconditioner is applied to a gradient vector using the fast Fourier transformation technique. In the framework of the Davidson-type diagonalization algorithm, we have found the present preconditioning scheme to be more efficient than widely accepted diagonal scaling methods.     

神木钢管拱桥钢结构制作技术

介绍神木钢管拱桥的结构特点和制作方法。为保证产品质量要求，神木钢管拱桥严格执行TB10212—98《铁路钢桥制造规范》，依据焊接评定工艺确定合理的焊接坡口及焊接方法；其次，设计并制造符合结构特点的工装设备，以及严格地执行检测方法，是钢管拱桥制造成功的必要措施。     

Probability of failure sensitivity analysis using polynomial expansion

Probability of failure sensitivity analysis is a subject of major interest in uncertainty based optimization. However, the computational effort required to obtain accurate results is frequently very high. In this work we present a novel strategy for probability of failure sensitivity analysis, that is based on polynomial expansions of both the performance function and its derivatives. Sensitivity analysis is then made using the obtained polynomial expansions together with standard expressions. Since the simulation step requires only evaluation of closed form polynomials, very large samples can be used to obtain accurate results with small computational effort. The proposed approach is expected to be efficient when polynomial expansion methods are suitable. Four numerical examples are presented in order to show the effectiveness of the proposed approach.     

Effect of co-dopant addition on properties of gadolinia-doped ceria electrolyte

Various trivalent oxides were added as co-dopants to gadolinia-doped ceria (GDC) electrolyte used for solid oxide fuel cells at up to 5 mol%. An examination was made on how they affect the electrical conductivity of the electrolyte and, eventually, the open-circuit voltage (OCV) of a unit cell. Through a comparison of the thermal expansion coefficients (TEC), it was investigated whether or not the co-doped electrolytes are thermomechanically compatible with other cell components. The addition of co-dopants generally improve the electrical properties of the electrolyte by yielding greater OCV values and not changing the TEC significantly (5% at most), except in the case of Pr. Among the electrolytes examined, the one co-doped with Sm (3 mol%) shows the best improvement in performance.     

21世纪我国钾肥工业的发展与展望

概述了当前我国钾肥工业的发展现状及存在问题。21世纪我国钾肥工业将乘“西部大开发战略”之东风，在国家产业政策的支持下，通过加强宏观管理，增大投入，加大科研与综合利用，实现规模化，效益化，将取得重大进展，到2010年，国产钾肥可满足国内需求量的20％。     

轧辊的热膨胀对辊型的影响

本文以1300 mm热轧机为研究对象,对其生产过程辊形随温度的变化进行实测,分析研究轧辊的热膨胀对板形的影响.     

对井涌关井气体升移的探讨

对文献[1]、[2]中井涌关井后气柱在上升至井口过程中体积和压力不变的说法进行了分析，提出其中存在的问题，并利用相关理论进行了论证。指出，井涌（或井喷）关井后，气体在上升过程中，其压力和体积都是在不断变化的，甚至在深井中，井底不可能形成气柱，侵入井眼的气体以液态形式存在。     

Thermal Expansion Behavior of Amorphous Fe-Si-B Alloys

 To study the thermal expansion of amorphous Fe Si B alloys, the amorphous Fe78Si9B13 and Fe735Nb3 Cu1Si135B9 and their crystallized alloys were detected using thermal dilatometer. The results indicate that at the same temperature, the relative length change (ΔL/L0) values of the two Fe based amorphous alloys decrease with increasing heating rate, but those of their crystallized alloys show an opposite trend. It is concluded that the effect of heating rate on the ΔL/L0 of amorphous and crystallized alloys is related to free volume and defects, respectively.     

Molex原料煤油加氢装置扩容改造

介绍了金陵石化烷基苯厂的加氢－分子筛装置90kt/a扩容改造中，Molex原料煤油加氢装置的扩容改造开工情况。改造后的煤油加氢装置在低、高空速下运行状况良好，产出合格的精制煤油，实现了煤油加氢催化剂的国产化。