An extended finite element library

This paper presents and exercises a general structure for an object‐oriented‐enriched finite element code. The programming environment provides a robust tool for extended finite element (XFEM) computations and a modular and extensible system. The programme structure has been designed to meet all natural requirements for modularity, extensibility, and robustness. To facilitate mesh–geometry interactions with hundreds of enrichment items, a mesh generator and mesh database are included. The salient features of the programme are: flexibility in the integration schemes (subtriangles, subquadrilaterals, independent near‐tip, and discontinuous quadrature rules); domain integral methods for homogeneous and bi‐material interface cracks arbitrarily oriented with respect to the mesh; geometry is described and updated by level sets, vector level sets or a standard method; standard and enriched approximations are independent; enrichment detection schemes: topological, geometrical, narrow‐band, etc.; multi‐material problem with an arbitrary number of interfaces and slip‐interfaces; non‐linear material models such as J2 plasticity with linear, isotropic and kinematic hardening. To illustrate the possible applications of our paradigm, we present 2D linear elastic fracture mechanics for hundreds of cracks with local near‐tip refinement, and crack propagation in two dimensions as well as complex 3D industrial problems. Copyright © 2007 John Wiley & Sons, Ltd.     

A heuristic technique for inventory replenishment policy with increasing demand pattern and shortage allowance

In the growth stage of a product life cycle, the demand rate is usually unstable and follows an increasing pattern. The traditional inventory policies, which have been developed for stationary demand pattern, are not appropriate to this situation. Although there exist some researches in the past dealing with inventory policy for the case of increasing demand pattern, most of them focused on the inventory systems in which shortages are not allowed. In reality, the presence of shortages is sometimes economically preferable when holding cost is significant as compared with shortage cost. The aim of the research presented in this paper is, therefore, to develop a replenishment policy for inventory systems with nonlinear increasing demand pattern and shortage allowance in such a way that the total demand during a predefined planning horizon can be exactly met. A heuristic technique to help determine the operational parameters for the inventory policy is then developed. In the proposed heuristic technique, the consecutive improvement method developed by Wang (Comput Oper Res, 29:1819–1825, 2002) will first be used to help determine replenishment times. And then, a new concept of reduction cost, which is defined as the difference between the holding cost when shortage is allowed and the incurred shortage cost, is introduced and applied to help find the optimal shortage starting point in each replenishment cycle. Numerical experiments are also conducted to illustrate the applicability of the proposed technique.     

Examination of general health following Typhoon Xangsane: A pre–postanalysis.

An individual's health status immediately following a disaster may predict long-term morbidity and mortality. However, relative to the growing literature on postdisaster mental health, less is known about physical health outcomes, particularly in developing countries. Unlike most studies, the current investigation obtained physical health data both before and after Typhoon Xangsane, which struck the Da Nang province of Vietnam in 2006, and related these predisaster data to postdisaster health functioning, among other factors. Specifically, a sample of 795 randomly selected adults was interviewed both prior to, and after the typhoon. Results indicated that participants with symptoms of major depressive disorder and panic disorder, older participants, and participants who reported high distress during the actual typhoon were most at-risk for lower self-rated health postdisaster compared to those without these risk factors. Given that Vietnam is still designated a developing country, the present study enhances the literature on postdisaster physical health correlates in developing nations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

In situ fabrication of platinum/graphene composite shell on polymer microspheres through reactive self-assembly and in situ reduction

We present a simple method to fabricate a uniform-sized graphene–metal–polymer composite microsphere of core–shell structure. On the surface of amine-functionalized polymer microsphere, graphene oxide (GO) sheets were affixed to give a core–shell structure by self-assembly process followed by the immobilization of platinum (Pt) ions to the assembled GO shell. Subsequently, they were chemically reduced in situ converting both GO and Pt ions to reduced GO (RGO) and Pt nanoparticles (NPs), respectively. As a result, a robust RGO-Pt composite shell, composed of RGO sheets and well-distributed Pt NPs, was fabricated on the microsphere surface. Meanwhile, the insulative GO shell was converted to the conductive RGO-Pt shell giving 24.0 S m^?1 of electrical conductivity. We demonstrated that the electrical property of the shell was significantly improved by the incorporation of Pt NPs.     

深圳能源集团总部大厦结构体系研究

深圳能源集团总部大厦项目,由南、北塔楼及连接南北塔楼的连桥组成,北塔楼主体结构高208.5m,南塔楼主体结构高100m,南北塔楼在2～9层通过连桥连接,属于复杂高层建筑。由于Y向高宽比为6.8,尤其核心筒高宽比约为17,远大于规范建议值12,造成结构Y向刚度偏弱。针对上述结构特性,结合建筑布置,设置腰桁架和伸臂桁架,以探求伸臂桁架和腰桁架的最优布置。北塔楼结构体系采用框架体系+核心筒+加强层架的抗侧体系。整体结构及构件融入了性能化设计思想,对主要抗侧力构件,如加强层、连桥区域提高抗震等级和性能目标。动力弹塑性时程分析进一步验证结构在大震下的整体性能要优于不倒塌要求。分析结果表明,塔楼结构设计可满足所提出的抗震性能目标,各项性能指标均符合国家相关规范的要求。     

An eco-friendly and efficient route of lignin extraction from black liquor and a lignin-based copolyester synthesis

Traditional method for extraction of lignin from black liquor in chemical pulping processes requires a huge amount of toxic inorganic acids like sulfuric acid which are potentially harmful to our environment and life. Furthermore, the traditional method always contains multiple steps, and thus it is time-consuming process. With a purpose to eliminate all these above disadvantages, in this study, we successfully developed an efficient process for the extraction of lignin from black liquor using a non-toxic aluminum potassium sulfate dodecahydrate (AlK(SO₄)₂·12H₂O). The developed process is simple, efficient, and short-time, which obviously have more advantages over the traditional extraction method. Furthermore, the lignin extracted in this study was used to synthesize a copolyester through polyesterification between lignin and sebacoyl chloride. The copolymer possesses a molecular weight of 31,800, corresponding to four to five repeating units of lignin macromonomers. Notably, it showed a good thermal stability up to 200 °C in TGA analysis. It was also possible to shape the copolymer using solvent casting. We believe that this newly developed method of lignin extraction may exploit new applications for eco-friendly sustainable materials in various fields.     

LaAlO<Subscript>3</Subscript>/SrTiO<Subscript>3</Subscript> Epitaxial Heterostructures by Atomic Layer Deposition

Thin films of LaAlO₃ were deposited on TiO₂-terminated (100) SrTiO₃ crystals by atomic layer deposition (ALD), using tris(iso-propylcyclopentadienyl)lanthanum and trimethyl aluminum precursors. Water was used as the oxidizer. The film composition was shown to be controlled by the ratio of La/Al precursor pulses during ALD, with near-stoichiometric LaAlO₃ resulting at precursor pulse ratios of 4/1 to 5/1. Films near the stoichiometric LaAlO₃ composition were shown to crystallize on subsequent annealing to form epitaxial LaAlO₃/SrTiO₃ heterostructures. Electrical characterization of these structures was done by two-terminal direct-current (DC) current–voltage scans at room temperature and under high-vacuum conditions. The results show electrical conductivity for the ALD-deposited epitaxial LaAlO₃/SrTiO₃ heterostructures, which turns on for thickness above four unit cells for the LaAlO₃ film.     

Development of Biogenic Amines in Yellowfin Tuna (Thunnus albacares): Effect of Storage and Correlation with Decarboxylase-Positive Bacterial Flora

ABSTRACT: The effects of storage at 0,4,10, and 22°C for 0,1,3,5, and 9 d on the quality of yellowfin tuna fillets as determined by microbiological assessment, development of some biogenic amines, and sensory analysis were studied. Tuna fillets stored at 22 °C for 3 d, 10 °C for 5 d, and 4 °C for 9 d were rated unacceptable for consumption. Those stored at 22 °C for 3 d had total aerobic bacterial count of > 8 log₁₀ CFU/g, a histamine-producing bacterial population of 7 log₁₀ CFU/g, and 832 ppm of histamine, 35.8 ppm of putrescine, and 147 ppm of cadaverine. A comparison of the capillary electrophoresis, AOAC fluorometric method, and gas chromatography showed a very good correlation (r² > 0.99) among these 3 methods for histamine quantitation in tuna samples. Morganella morganii, Enterobacter agglomerans, Enterobacter intermedium, Pseudomonas fluorescens, Proteins vulgaris , and Serratia liquefaciens were the decarboxylase-positive bacterial species isolated by using the Niven's medium and identified during storage, which were responsible for histamine production in test tuna fillets.     

Effects of Lactobacillus casei and Alterations in Fermentation Conditions on Biosynthesis of Glucuronic Acid by a Dekkera bruxellensis-Gluconacetobacter intermedius Kombucha Symbiosis Model System

A combination of Dekkera bruxellensis and Gluconacetobacter intermedius is used as a model system to emulate the microbial symbiosis between yeast and acetic acid bacteria in kombucha, and to study glucuronic acid (GlcUA) production in this system. In the current study, the addition of Lactobacillus casei and variations in the fermentative conditions, such as sucrose concentration, temperature and duration, were examined to evaluate their effects on GlcUA formation. Results showed that L. casei acts as a supporter species and stimulated GlcUA production in the kombucha symbiosis model to levels 54.1% greater than in the control. Varying the fermentation parameters also affected GlcUA production. Therefore, the range of each factor value was screened and restricted to achieve a higher amount of target acid, as it was 5–15%, 25–31°C, 3–7 days, and 5–7 units in sucrose concentration, temperature, fermentation time and initial pH value, respectively. These findings are an important step for optimizing GlcUA production by this model system.