水库水有机污染物遗传毒性的研究简

为研究水库水经国内常规给水处理工艺的各阶段出水中有机提取物对细胞DNA损伤的情况,于8月和1月取水库水作为原水,设定采集4个水样：原水（A）、经混凝沉淀后的沉后水（B）、滤后水（C）和经氯消毒的出水（D）。提取水样中的有机物配成不同浓度溶液,喂食小白鼠,取小白鼠脾脏细胞做彗星实验。结果无论在枯水期还是丰水期,水处理工艺各阶段出水对DNA都有不同程度的损伤,损伤程度顺序：A〉B〉D〉C;丰水期水样对DNA损伤程度高于枯水期水样对DNA的损伤。结果表明,水库水中的有机物污染物具有一定的遗传毒性,常规给水处理工艺对遗传毒性有削减作用,但不能消除。加氯消毒增加了水库水的遗传毒性。     

An iterative HAM approach for nonlinear boundary value problems in a semi-infinite domain

In this paper, we propose an iterative approach to increase the computation efficiency of the homotopy analysis method (HAM), a analytic technique for highly nonlinear problems. By means of the Schmidt–Gram process (Arfken et al., 1985)  [15], we approximate the right-hand side terms of high-order linear sub-equations by a finite set of orthonormal bases. Based on this truncation technique, we introduce the M$M$th-order iterative HAM by using each M$M$th-order approximation as a new initial guess. It is found that the iterative HAM is much more efficient than the standard HAM without truncation, as illustrated by three nonlinear differential equations defined in an infinite domain as examples. This work might greatly improve the computational efficiency of the HAM and also the Mathematica package BVPh for nonlinear BVPs.     

A hybrid differential evolution augmented Lagrangian method for constrained numerical and engineering optimization

We present a new hybrid method for solving constrained numerical and engineering optimization problems in this paper. The proposed hybrid method takes advantage of the differential evolution (DE) ability to find global optimum in problems with complex design spaces while directly enforcing feasibility of constraints using a modified augmented Lagrangian multiplier method. The basic steps of the proposed method are comprised of an outer iteration, in which the Lagrangian multipliers and various penalty parameters are updated using a first-order update scheme, and an inner iteration, in which a nonlinear optimization of the modified augmented Lagrangian function with simple bound constraints is implemented by a modified differential evolution algorithm. Experimental results based on several well-known constrained numerical and engineering optimization problems demonstrate that the proposed method shows better performance in comparison to the state-of-the-art algorithms.     

Interface diffusion-induced creep and stress relaxation in unidirectional metal matrix composites under biaxial loading

Analytical solutions are developed for interface diffusion-induced creep and stress relaxation in unidirectional metal matrix composites under biaxial transverse loading. The driving force for the interface diffusion is the normal stress acting on the interface, which is obtained from rigorous Eshelby inclusion theory. The solutions are a function of the applied stress, volume fraction and radius of the reinforced-fiber, the modulus ratio between the fiber and the matrix, specially, exhibit a strong dependence of creep rate and stress relaxation behavior on the biaxial stress ratio. Moreover, the solution for the interface stress presented in this study also gives some insight into the relationship between the interface diffusion and interface slip. For the application of the solutions in the realistic composites, the scale effect is taken into account by detailed finite element analysis based on a unit cell model.     

Experimental investigation on the thermal volumetric behavior of highly compacted GMZ01 Bent

Gaomiaozi (GMZ) Bent has been recognized as the potential buffer/backfill material for construction of Chinese deep geological repository for disposal of high-level radioactive waste (HLW). For investigation of pressure and suction effects on the thermal volumetric behavior of the highly compacted GMZ01 Bent, a new suction-temperature controlled oedometer was developed. Several suction and pressure controlled cyclic heating and cooling tests have been performed on highly compacted GMZ01 Bent. Suctions ranging from 4 to 110 MPa, temperatures from 25 to 80 °C and vertical loads from 0.1 to 5 MPa were applied. Results show that heating at constant suction and pressure induces either swelling or contraction. At high pressure and low suction, heating tends to induce contraction, while at low pressure and high suction, heating induces expansion. Thermal volumetric strain of GMZ01 Bent tested strongly depends on the overconsolidation ratio (OCR). Two opposite mechanisms are considered to explain the observed phenomena, that is, the volume increase induced by the thermal expansion of the mineralogical components and the adsorbed water and the double-layer thickness at the microstructure level, as well as the volume reduction caused by the macrostructural rearrangements.     

Magnetothermostress Wave Propagation and Perturbation of Magnetic Field Vector in an Orthotropic Laminated Hollow Cylinder

An analytical method is developed to determine the transient response of magneto-thermostress and perturbation of the magnetic field vector produced in orthotropic laminated hollow cylinders subjected to thermal shock, and permeated by a primarily uniform magnetic field. A magnetothermostress equation for each separate hollow cylinder is found by making use of a series of simply mathematical transform. Then, by using the interface continuity conditions between layers and the boundary conditions at the internal and external surfaces of the orthotropic laminated hollow cylinders, the unknown constants involved are determined. Thus, an exact expression for the magnetothermostress wave propagation and the perturbation response of magnetic field vector in the orthotropic laminated hollow cylinders are obtained. From sample numerical calculations, some characters of magnetothermodynamic stresses and perturbation of magnetic field vector in orthotropic laminated hollow cylinders are revealed and discussed.     

德尔菲法在超高层建筑项目风险评估中的应用

本文以造型独特的厦门地标性建筑———212m的厦门会展北片区监管大厦工程为背景,运用德尔菲法对项目施工过程的风险进行识别和分析,找出项目潜在的风险因素,制定出风险应对措施,使项目实施过程中的风险得到有效控制,如期实现项目目标。     

Response modification factor for steel moment-resisting frames by different pushover analysis methods

The earthquake loads imposed to the structures are generally much more than what they are designed for. This reduction of design loads by seismic codes is through the application of response modification factor (R-factor). During moderate to severe earthquakes, structures usually behave inelastically, and therefore inelastic analysis is required for design. Inelastic dynamic analysis is time consuming and interpretation of its results demands high level of expertise. Pushover analysis, recently commonly used, is however, a simple way of estimating inelastic response of structures. Despite its capabilities, conventional pushover analysis (CPA) does not account for higher mode effects and member stiffness changes. Adaptive pushover analysis (APA) method however, overcomes these drawbacks. This research deals with derivation and comparison of some seismic demand parameters such as ductility based reduction factor, R_μ, overstrength factor, Ω, and in particular, response modification factor, R, from capacity curves obtained from different methods of APA and CPA. Three steel moment-resisting frames of 3, 9 and 20 stories adopted from SAC steel project are analyzed. In pushover analyses for each frame, eight different constant as well as adaptive lateral load patterns are used. Among the main conclusions drawn is that the maximum relative difference for response modification factors was about 16% obtained by the methods of conventional and adaptive pushover analyses.     

Effects of sustained axial load and cooling phase on post-fire behaviour of reinforced concrete stub columns

In this paper is presented an experimental investigation of the effects of preload and cooling phase on the residual strength, stiffness and ductility of reinforced concrete stub columns which were heated and cooled down to room temperature under sustained axial load. Reinforced concrete stub columns were axially loaded and heated to designed temperatures in a specially built electrical furnace. After the specimens cooled down to ambient temperature with the axial loads kept constant, the stub columns were loaded to failure. The sustained preload led to significant residual deformations of reinforced concrete stub columns during the cooling phase. The test results showed that the mechanical behaviour of the fire-damaged reinforced concrete stub columns with preload was remarkably different from those without preload. The sustained axial loads resulted in obviously increased strength and stiffness during the loading phase, but reduced stiffness and deteriorated ductility in the unloading phase. Based on the test results, it is recommended that the effects of sustained axial loads during the fire and cooling phase should be taken into consideration in assessing the fire-damaged reinforced concrete columns.     

Self sensing carbon nanotube (CNT) and nanofiber (CNF) cementitious composites for real time damage assessment in smart structures

The self sensing properties of cementitious composites reinforced with well dispersed carbon nanotubes and carbon nanofibers were investigated. The electrical resistance of cementitious nanocomposites with w/c = 0.3 reinforced with well dispersed carbon nanotubes (CNTs) and nanofibers (CNFs) at an amount of 0.1 wt% and 0.3 wt% of cement was experimentally determined and compared with resistivity results of nanocomposites fabricated with “as received” nanoscale fibers at the same loading. Results indicate that conductivity measurements, besides being a valuable tool in evaluating the smart properties of the nanocomposites, may provide a good correlation between the resistivity values measured and the degree of dispersion of the material in the matrix. The addition of CNTs and CNFs at different loadings was proven to induce a decrease in electrical resistance, with the nanocomposites containing 0.1 wt% CNTs yielding better electrical properties. Furthermore, conductivity measurements under cyclic compressive loading provided an insight in the piezoresistive properties of selected nanocomposites. Results confirm that nanocomposites, reinforced with 0.1 wt% CNTs and CNFs, exhibited an increased change in resistivity, which is indicative of the amplified sensitivity of the material in strain sensing.