Clean up of Petroleum-Hydrocarbon Contaminated Soils Using Enhanced Bioremediation System: Laboratory Feasibility Study

The objective of this study was to assess the potential of applying enhanced bioremediation on the treatment of petroleum-hydrocarbon contaminated soils. Microcosm experiments were conducted to determine the optimal biodegradation conditions. The control factors included oxygen content, nutrient addition, addition of commercially available mixed microbial inocula, addition of wood chip and rice husk mixtures (volume ratio = 1:1) as bulking agents, and addition of organic amendments (chicken manures). Results indicate that the supplement of microbial inocula or chicken manures could significantly increase the microbial populations in soils, and thus enhance the efficiency of total petroleum hydrocarbon (TPH) removal (initial TPH = 5,500?mg/kg). The highest first-order TPH decay rate and removal ratio were approximately 0.015?day?1 and 85%, respectively, observed in microcosms containing microbial inocula (mass ratio of soil to inocula = 50:1), nutrient, and bulking agent (volume ratio of soil to bulking agent = 10 to 1) during 155 days of incubation. Results indicate that the first-order TPH decay rates of 0.015 and 0.0142?day?1 can be obtained with the addition of microbial inocula and chicken manures, respectively, compared with the decay rate of 0.0069?day?1 under intrinsic conditions. Thus, chicken manures have the potential to be used as substitutes of commercial microbial inocula. The decay rate and removal ratio can be further enhanced to 0.0196?day?1 and 87%, respectively, with frequent soil shaking and air replacement. Results will be useful in designing an ex situ soil bioremediation systems (e.g., biopile and land farming) for practical application.     

In situ Sea Ice Experiments in McMurdo Sound: Cyclic Loading, Fracture, and Acoustic Emissions

The breakup of first-year sea ice plays an important role in the dynamics and thermodynamics of polar ice covers. A recent research program has studied the in situ mechanical properties of the annual ice in Antarctica to support the development of physically based models of the breakup process. As part of this effort, two field trips were conducted to McMurdo Sound, and the present paper describes the experimental work and presents selected results. The in situ experiments investigated the constitutive and fracture behavior of edge-notched, square plate specimens of first-year ice and involved a detailed characterization of the physical properties and thermal state of the ice. Acoustic emissions, which are generated by microcracking, were monitored in the crack tip vicinity and provide insight regarding the size of the process zone. The paper describes the physical properties and microstructure of the sheet, the cyclic-loading response, and the acoustic emissions activity from an extensive series of experiments conducted on one of the in situ specimens. Varying the cyclic-loading frequency and amplitude provided a means to examine rate effects on the anelastic and viscous components of strain and the extent of microcracking near the crack tip. The viscous deformation rate estimated from the experiments exhibited an increasing power-law exponent with values between one and three. Acoustic emissions monitoring indicated that microcracking occurred in a process zone near the crack tip, and the size of the process zone increased with decreasing cyclic loading frequency. Practical aspects of the experiments are considered, and the results are put into context with the overall modeling goals of the project.     

Influence of Osmotic Suction on the Soil-Water Characteristic Curves of Compacted Expansive Clay

Unsaturated clays are subject to osmotic suction gradients in geoenvironmental engineering applications and it therefore becomes important to understand the effect of these chemical concentration gradients on soil-water characteristic curves (SWCCs). This paper brings out the influence of induced osmotic suction gradient on the wetting SWCCs of compacted clay specimens inundated with sodium chloride solutions/distilled water at vertical stress of 6.25 kPa in oedometer cells. The experimental results illustrate that variations in initial osmotic suction difference induce different magnitudes of osmotic induced consolidation and osmotic consolidation strains thereby impacting the wetting SWCCs and equilibrium water contents of identically compacted clay specimens. Osmotic suction induced by chemical concentration gradients between reservoir salt solution and soil-water can be treated as an equivalent net stress component, (pπ) that decreases the swelling strains of unsaturated specimens from reduction in microstructural and macrostructural swelling components. The direction of osmotic flow affects the matric SWCCs. Unsaturated specimens experiencing osmotic induced consolidation and osmotic consolidation develop lower equilibrium water content than specimens experiencing osmotic swelling during the wetting path. The findings of the study illustrate the need to incorporate the influence of osmotic suction in determination of the matric SWCCs.     

MIG Brazing of Galvanized Thin Sheet Joints for Automotive Industry

MIG welding of zinc-coated thin plates in the automotive industry leads to major issues, mainly zinc evaporation followed by a decrease of corrosion resistance, as well as residual strains and stresses difficult to minimize. The use of a lower heat input technique for joining galvanized steels would bring significant benefit, if the final overall mechanical properties of the joints are adequate for the application. The use of MIG brazing (MIGB) with the recently commercialized alloyed copper-based filler metal is an alternative worth considering. The present paper addresses the MIGB processes, describing the influence of the different shielding gases and the process parameters on the mechanical, corrosion, and metallurgical properties of the joint, when lower heat input procedures are targeted. The paper describes the influence of the gases on the mechanical properties of the brazed joint, both in normal conditions after joining and after corrosion in a salt water environment. Microstructural features of the different zones are discussed. Results of corrosion and tensile tests are presented and interpreted.     

Efficient and accurate multilayer solid‐shell element: non‐linear materials at finite strain

We present in this paper an efficient and accurate low‐order solid‐shell element formulation for analyses of large deformable multilayer shell structures with non‐linear materials. The element has only displacement degrees of freedom (dofs), and an optimal number of enhancing assumed strain (EAS) parameters to pass the patch tests (both membrane and out‐of‐plane bending) and to remedy volumetric locking. Based on the mixed Fraeijs de Veubeke‐Hu‐Washizu (FHW) variational principle, the in‐plane and out‐of‐plane bending behaviours are improved and the locking associated with (nearly) incompressible materials is avoided via a new efficient enhancement of strain tensor. Shear locking and curvature thickness locking are resolved effectively by using the assumed natural strain (ANS) method. Two non‐linear 3‐D constitutive models (Mooney–Rivlin material and hyperelastoplastic material at finite strain) are applied directly without requiring the enforcement of the plane‐stress assumption. In particular, we give a simple derivation for the hyperelastoplastic model using spectral representations. In addition, the present element has a well‐defined lumped mass matrix, and provides double‐side contact surfaces for shell contact problems. With the dynamics referred to a fixed inertial frame, the present element can be used to analyse multilayer shell structures undergoing large overall motion. Numerical examples involving static analyses and implicit/explicit dynamic analyses of multilayer shell structures with both material and geometric non‐linearities are presented, and compared with existing results obtained from other shell elements and from a meshless method. It is shown that elements that did not pass the out‐of‐plane bending patch test could not provide accurate results, as compared to the present element formulation, which passed the out‐of‐plane bending patch test. The present element proves to be versatile and efficient in the modelling and analyses of general non‐linear composite multilayer shell structures. Copyright © 2005 John Wiley & Sons, Ltd.     

CYCLIC FATIGUE OF Al2O3 AND Al2O3-Al2TiO5 COMPOSITES IN DIRECT PUSH-PULL

Abstract— A reaction sintering route is developed to produce, "in situ", composites of alumina-aluminium titanate using alumina and titania as starting powders. Aluminium titanate, can be formed by a solid state reaction between Al₂O₃ and TiO₂ at temperatures above the eutectoid temperature of 1280°C. These composites have different grain sizes of alumina matrix and a different quantity and distribution of aluminium titanate according to the heating cycle used.
In the present work direct push-pull tests under cyclic loads have been carried out with both monolithic alumina and alumina-aluminium titanate composites. It has been found that all the samples show a decrease in tensile strength with the number of applied cycles of loading when plotted in graphical form but the slopes of these graphs for both Al₂O₃-Al₂TiO₅ composites are lower than for the alumina specimens. The role of aluminium titanate and the alumina matrix grain size in fatigue crack growth resistance has been studied during push-pull tests, where failure occurs by catastrophic propagation of small surface cracks after a very short regime of subcritical crack growth. These results have been compared with measurements of slow stable fatigue crack growth rates in Al₂O3-Al₂TiO₅ composites carried out elsewhere with pre-notched specimens of the compact tension type. These latter tests provide information about the behaviour of significantly long cracks, i.e. cracks that are several millimetres long.     

蒸发冷却空调与风光互补发电结合使用的可行性分析

夏季,为给户外场所降温并节约电能使用,提出利用蒸发冷却空调与风光互补发电相结合的方式。本文分别介绍了这两项技术的发展现状、原理及特点,并通过风洞模拟自然界风力带动风车发电,再与光伏板进行互补发电实验,得出其互补发电功率为166.4W,能够带动一台额定功率为170W的蒸发式冷风扇平稳运转。这两项技术的有效结合是一种绿色、低碳、环保的降温和能源利用方式。     

Effect of Temperature on the Tensile Strength and Failure Modes of Angle Ply Aramid Fibre (KRP) Tubes Under Hoop Loading

A comprehensive study was undertaken to characterise Kevlar reinforced plastic (KRP) angle ply filament wound tubes at different temperatures. Quasi-static burst tests were performed on tubes of 25°, 55° and 75° winding angle. The tubes were burst under internal radial pressure with minimum end constraints. An experimental rig and two conditioning tanks were designed and built to test the specimens at three temperatures; –46°C (low temperature) and +20°C (room temperature) and +70°C (high temperature). For each test the internal pressure and the strains in both circumferential and longitudinal directions were recorded on suitable digital processing equipment.For a particular batch of tubes tested at three different temperatures, an increase in ultimate hoop strain and a decrease in hoop modulus of the 55° tubes with increasing temperatures was recorded; the temperature effect was less pronounced on the corresponding properties of 25° and 75° tubes. The use of a non-structural thin liner during the tests led to a higher ultimate strength of 55° tubes but had negligible effect on the behaviour of 25° and 75° tubes. The 75° tubes failed in a catastrophic fibre fracture under all test conditions. The mode of failure of 55° changed from weeping at 70°C to fibre fracture at –46°C. The 25° tubes failed by weeping with matrix cracking. The matrix cracking was particularly severe when a liner was used.     

带有调整系统的远铰解耦挂架风洞试验研究

进行了带有调整系统的远铰解耦挂架抑制机翼/外挂颤振的低速风洞试验研究.试验是在大展弦比机翼颤振模型上进行的.试验结果表明:当外挂俯仰频率落在柔性区范围时,机翼/远铰解耦挂架/外挂的颤振速度比机翼/常规挂架/外挂的颤振速度有显著提高;且其颤振速度对外挂惯性特性的变化不敏感.试验结果还表明;调整系统可将外挂与机翼的相对静偏移修正到很小的设计角度内.文中还进行了单铰和远铰两种解耦挂架方案颤振抑制效果的比较,试验结果表明:远铰方案中外挂俯仰振动加速度响应比单铰时明显减小;且调整电机启动频率也比单铰时为低.文中还讨论了远铰挂架四连杆机构参数对外挂俯仰频率的影响.     

一种混沌流密码算法设计与实现

提出了一种基于Logistic混沌映射的流密码算法,该算法利用混沌本身所具有的随机特性,提出了一种新的对混沌系统扰动的方法。通过编码算法以及在混沌随机序列数字化的基础上引入一种新的非线性变换算法,以抵抗对混沌流密码系统的各种攻击。经统计测试和相关分析,密钥序列具有较高的线性复杂度和良好的密码学特性。整个加密系统的周期性大、灵活性好,加密模型还可以推广到其他混沌系统。