Modeling of thermal mass transfer in porous media with applications to the organic phase transition in landfills

In order to describe the thermomechanical behavior of landfills, a constitutive model based on the macromechanical Theory of Porous Media (TPM) for a saturated thermoelastic porous body has been developed. The body under investigation consists of an organic and inorganic solid phase and a gas phase. All interaction relations between the constituents such as mass transfers, interaction forces and energy supplies are taken into consideration. Based on a consistent thermomechanical treatment the governing equations are obtained as a set of equations which consists of the balance equations of momentum and mass for each individual constituent, the balance equation of energy for the mixture and the physical constrained conditions. In this set of macroscopic equations, several parameters are contained. They are interrelated by constitutive relationships in order to complete the system of equations. This procedure renders the set of equations solvable. Thus, we obtain a mathematical concept to describe the motion of the solid phase, the pressure of the gas phase, the temperature of the mixture and the biodegradation of organic material into a gas mixture of methane and carbon dioxide produced by bacterial decomposition during stable methane fermentation (biogas).     

Parallel Krylov methods and the application to 3-d simulations of a triphasic porous media model in soil mechanics

We introduce a general parallel model for solving coupled nonlinear and time-dependent problems in soil mechanics, where we employ general purpose linear solvers with specially adjusted preconditioners. In particular, we present a parallel realization of the GMRES method applied to a triphasic porous media model in soil mechanics, where we compute the deformation of unsaturated soil together with the pore-fluid flow of water and air in the soil. Therefore, we propose a pointwise preconditioner coupling all unknowns at the nodal points. In two large-scale numerical experiments we finally present an extended evaluation of our parallel model for demanding configurations of the triphasic model.     

Applicability of the method of fundamental solutions to interaction of fully nonlinear water waves with a semi-infinite floating ice plate

In this research effort, a meshless numerical model was developed to study the hydroelastic interaction of an incident wave with a semi-infinite horizontal floating plate. It is assumed that the fluid is homogenous, inviscid and incompressible. Fundamental solution of the governing Laplace equation is considered to be radial basis functions. In this method, only a few boundary points are located on the boundary. Moreover, there are a few source points that are located outside the computational domain. Two additional source points are introduced to deal with the plate's edge conditions. The problem is solved using collocations at only a few boundary points. When density and thickness of the plate are reduced to zero, good agreements with other numerical works are observed.     

The threshold value of group similarity in the formation of cellular manufacturing systems

Cellular manufacturing is an effective alternative to batch-type production systems where different products are intermittently produced in small lot sizes with frequent setups, large in-process storage quantities, long production lead times, decreasing throughputs, and complex planning and control functions. An effective approach to forming manufacturing cells and introducing families of similar parts, consequently increasing production volumes and machine utilisation, is the use of similarity coefficients in conjunction with clustering procedures. In a similarity coefficients-based approach, the results of the clustering analysis depend on the minimum admissible level of similarity adopted for the generic group of clustered items. This is the so-called threshold value of group similarity. The aim of this paper is to identify effective values of the threshold value of group similarity to help practitioners and managers of manufacturing systems form machine groups and related part families. The proposed threshold values for a given similarity coefficient are based on calculation of the percentile of aggregations generated by the adopted clustering algorithm. The importance of the proposed measure of group similarity has been demonstrated by experimental analysis conducted on a large set of significant instances of the cell formation problem in the literature. This analysis can also support the best determination of this percentile-based cut value especially when the number of manufacturing cells is not known in advance.     

Finite element analysis of chip formation and residual stresses induced by sequential cutting in side milling with microns to submicron uncut chip thickness and finite cutting edge radius

In this paper,the effect of four sequential cuts in side milling of Ti6Al4 V on chip formation and residual stresses(RS) are investigated using finite element method(FEM).While the open literature is limited mainly to the studies of orthogonal sequential cutting with the constant uncut chip thickness greater than 0.01 mm,it is suggested herein to investigate not only the variable uncut chip thickness which characterises the down milling process,but also the uncut chip thickness in the sub-micron range using a finite cutting edge radius.For the resulting ductile machining regime,the characteristics of the chip morphology,the force profiles,the plastic deformation and temperature distributions have been analyzed.Furthermore,this study revealed that the RS should be extracted toward the area where the insert exits the workpiece in the FE simulation of the down-milling process.The simulation of a number of sequential cuts due to the consecutive engagements of the insert is required in order to capture the gradual accumulation of the RS before reaching an asymptotic convergence of the RS profile.The predicted RS are in reasonable agreement with the experimental results.     

On the growth morphous of capillaries and tissue in porous silk fibroin films

In this study, the porous silk fibroin film (PSFF) is implanted into the body of a rat. Ten days later, the growing state of the capillaries in the material was observed, and the growing law of the capillaries in porous material is discussed to better understand the growing state of the peripheral tissue and cells around the material. The fact that the PSFF creates a beneficial environment for the growth of the capillaries in the tissue is confirmed, and the good growing states of the new skeleton muscle and the hypodermal tissue are also observed. This provides basic experimental results for the design of the PSFFs, which is a new medical biomaterial.     

Collaborative tool for solving human factors problems in the manufacturing environment: the Theory of Inventive Problem Solving Technique (TRIZ) method

In this study an analysis is made regarding the Theory of Inventive Problem Solving Technique (TRIZ), which emerged in Russia in 1946 and has been commonly used in the USA and Europe in the past few last decades. TRIZ is a method that is used successfully to solve the problems arising during the process of product development. Within this study this method is evaluated from the human factors point of view for the first time. In addition, two applications of the adaptation of TRIZ into human factors problems and works on this goal are presented. The benefits of TRIZ when solving such kind problems are also revealed.     

Density of capillaries and the oxygen diffusion model in the porous silk fibroin film

In order to obtain porous silk fibroin films (PSFFs) fit for the repair of different tissues and organs and design the configuration of the PSFFs more rationally, a model of the oxygen diffusing system of the capillary was built, and also the equations of the model were solved. Moreover, the relationships between the distribution of the oxygen concentration and each affecting factors were discussed, a method was developed to estimate the density of the capillaries in the tissue, and hereby discussed the characteristics of the oxygen diffusion in the tissues around the open capillaries.     

Size effect in the micro- and nanoindentation and its compensation with regard for the specific features of initial contact

The diagram of penetration recorded in the course indentation is represented in the form of a quadratic function with the origin of coordinates shifted to the left along the abscissa. This models the smooth character of penetration of an indenter in its initial contact with the surface. The recorded depth of penetration increases by the length of the shift. The application of the quadratic function and the corrected depth of penetration guarantees that the values of hardness are constant under various loads. Translated from Problemy Prochnosti, No. 2, pp. 43–54, March–April, 2009.     

高掺杂氧化镝的BSA玻璃的制备稳定性研究

为了研究高掺杂稀土情况下B2O3-SiO2-Al2O3体系玻璃的成玻璃性能,玻璃受到不同的化学溶液侵蚀时的抗腐蚀能力,及其腐蚀的机理与规律.通过采用扩张选点方法,探讨了的玻璃的形成区域图;采用UV3101-PC型分光光度仪,DTA和粉末失重法等测试手段研究了玻璃的化学稳定性.通过比较不同的H 浓度,不同场强的稀土离子,以及玻璃表面覆盖层等影响因素对玻璃化学腐蚀速率的影响规律,结果表明,BSA玻璃具有较好的玻璃形成能力;化学侵蚀过程中由于稀土离子的氢氧化物扩散与H 离子交换作用会影响玻璃化学侵蚀程度,因此玻璃耐酸性最差,耐碱性最好;稀土离子的场强越大,玻璃的抗腐蚀能力越强,化学稳定性越好;随着时间的延长由于玻璃表面产生了覆盖层,从而使得玻璃的溶解速率减缓.     

Effects of stacking thickness on the damage behavior in CFRP composite cylinders subjected to out-of-plane loading

The purpose of this study is to evaluate effects of stacking thickness on the microscopic damage behavior in a filament wound carbon fiber reinforced plastics (FW-CFRPs) composite cylinder subjected to impact or quasi-static out-of-plane loading. From both tests, thicker CFRP improved the stiffness of the cylinder and decreased the resultant plastic deformation due to indentation. From the cross-sectional observation, it is clarified that fiber breakages were localized for the specimens with impact tests more than 10-layers and specimens with quasi-static tests more than 15-layers. In order to discuss the relation between the damage and the absorbed energy, damage depth ratio was defined as fiber damage depth per unit CFRP thickness. To normalize the effect of thickness, absorbed energy ratio was also defined as absorbed energy per unit CFRP thickness. Absorbed energy ratio as a function of absorbed energy ratio was expressed as one master curve regardless of loading conditions.     

Effect of curing conditions and concrete mix design on the expansion generated by delayed ettringite formation

Many studies have shown the effect of different parameters on the expansion induced by delayed ettringite formation (DEF), but there is not yet a general agreement on their relative effects due to discrepancies on experimental results generally attributed to different experimental conditions. The aim of this study is to assess the coupling effects between some of the main parameters of this reaction using the experimental design method. The main interactions concern two factors: temperature and duration of heating during curing. Each interaction has been subjected to statistical tests in order to be validated. The resulting empirical models can reflect the experimental fields and therefore provide useful information about the risk of expansion related to␣DEF, knowing the temperature and the duration of curing, the alkali content of the concrete, the aggregate nature and the water to cement ratio.

---

Résumé De nombreuses études ont montré l’influence de différents paramètres sur les expansions induites par la formation différée de l’ettringite (DEF). En raison des divergences de résultats attribuées à des conditions expérimentales différentes, il n’existe pas d’accord unanime sur l’effet de ces paramètres. L’objectif de cette étude consiste à étudier les couplages entre certains des principaux paramètres de cette réaction par la méthode des plans d’expériences. Les principales interactions concernent la température et la durée de l’échauffement. Chaque interaction a subi un test statistique afin d’être validée. Les modèles empiriques déterminés peuvent reproduire le champ expérimental étudié et ainsi fournir des informations pertinentes sur les risques d’expansion attribuée à la DEF, à partir de la connaissance de la température et de la durée de l’échauffement, la teneur en alcalins du béton, la nature des granulats et le rapport E/C.

     

A quasi-static indentation test to elucidate the sequence of damage events in low velocity impacts on composite laminates

Any attempt to achieve composite laminates with improved damage tolerance to low velocity impacts must depart from the understanding of the sequence of damage mechanisms taking place. To this purpose, a series of quasi-static indentation experiments was conducted on AS4D/TC350 carbon/epoxy specimens. The induced damage at different indenter displacements was characterized using electron microscopy and C-scan, while the residual indentation profiles were captured with a 3D surface roughness machine. The indentation depth was shown to have relaxed after the test, reaching a steady value after 14 days. For the conditions explored, the relaxation was not dependent on the damage extent. The results showed that matrix cracking is in fact the crucial damage mechanism as it is responsible for the first sudden loss of load capacity and triggers the progressive growth of delaminations.     

利用EXCEL实现对标准铂电阻温度计正温段分度表的计算

本文以常用的正温段(0~419.527)℃为例,介绍了1990国际温标对该温度段参考函数的计算方法,并推导出了对SPRT分度表的计算方法以及计算公式。同时以(0~419.527)℃温度段为例,介绍了利用EXCEL的功能实现对标准铂电阻温度计正温段分度表的计算。该方法简单易行,对于不熟悉编程的客户也能够很快掌握。对于工厂广大的计量人员来讲,拿到证书,即使没有分度表,也能很快的把分度表计算出来。     

Catching-up with supermajors: the technology factor in building the competitive power of national oil companies from developing economies

Abstract

The paper investigates the role of technology in the growing competitive potential of state-controlled national oil companies (NOCs) from developing countries. The technological development of NOCs is analyzed in the context of their increasing rivalry with supermajors, which have dominated the global oil and gas industry for decades. The author reveals the main features of NOCs’ catch-up development amid the dynamic changes in the competitive landscape of the global oil industry. These trends were analyzed against the background of the current phase of the oil industry’s technological evolution. The paper concludes that although rapid technological growth did become a key strategic priority of many NOCs, only very small group of them managed to achieve equal footing with traditional industry leaders. For the majority of the remaining NOCs, the existing limitations related to the policy of their home state did not allow them to narrow the technological gap with global supermajors.     

p‐version of the generalized FEM using mesh‐based handbooks with applications to multiscale problems

In this paper, we analyse the p‐convergence of a new version of the generalized finite element method (generalized FEM or GFEM) which employs mesh‐based handbook functions which are solutions of boundary value problems in domains extracted from vertex patches of the employed mesh and are pasted into the global approximation by the partition of unity method (PUM). We show that the p‐version of our GFEM is capable of achieving very high accuracy for multiscale problems which may be impossible to solve using the standard FEM. We analyse the effect of the main factors affecting the accuracy of the method namely: (a) The data and the buffer included in the handbook domains, and (b) The accuracy of the numerical construction of the handbook functions. We illustrate the robustness of the method by employing as model problem the Laplacian in a domain with a large number of closely spaced voids. Similar robustness can be expected for problems of heat‐conduction and elasticity set in domains with a large number of closely spaced voids, cracks, inclusions, etc. Copyright © 2004 John Wiley & Sons, Ltd.     

Effects of the feeling of invulnerability and the feeling of control on motivation to participate in experience-based analysis,by type of risk

Experience-based analysis (EBA) refers to a set of safety-management practices consisting of detecting, analyzing, and correcting the individual, material, and organizational causal factors of accidents in order to prevent their reoccurrence. Unfortunately, these practices do not always garner the adherence of employees. This article presents a study that examines the impact of risk perceptions on agents’ motivation to participate in EBA in various production sectors. The study was conducted at two sites, a chemical factory and a nuclear power plant, by means of a questionnaire administered to 302 employees. The results indicated that the feeling of control was not only positively linked to the feeling of invulnerability, but that these two factors were negatively linked to risk perception. In addition, the actors in both production sectors were more motivated to participate in EBA of accidents linked to the core processes of their industry (which were more accurately perceived) than in EBA of ordinary accidents (accidents not specific to chemical or nuclear processes). Moreover, the agents’ feeling of invulnerability and feeling of control both reduced EBA motivation for ordinary accidents to a greater extent than for chemical and radiation-related accidents. Recommendations are made in view of encouraging agents to get more involved in EBA.     

Reducing the domain in the mechanical analysis of periodic structures, with application to woven composites

A theoretical framework is developed leading to a sound derivation of Periodic Boundary Conditions (PBCs) for the analysis of domains smaller then the Unit Cells (UCs), named reduced Unit Cells (rUCs), by exploiting non-orthogonal translations and symmetries. A particular type of UCs, Offset-reduced Unit Cells (OrUCs) are highlighted. These enable the reduction of the analysis domain of the traditionally defined UCs without any loading restriction. The relevance of the framework and its application is illustrated through practical examples: 2D woven laminates and 3D woven composites.The framework proposed is used to develop an algorithm that automatically: (i) selects the smallest rUC for a given loading, (ii) determines and (iii) applies the appropriate periodic boundary conditions to the Finite Element Model (FEM). Coupled with a modelling/meshing tool, it provides a strategy for the efficient automatic numerical modelling and analysis of periodic structures. The algorithm is applied and validated for 2D woven orthogonal weaves. The results suggest the relevance of the proposed algorithm towards the efficient multiscale modelling of this class of materials.     

AEYFI 05实验‘温度-声简正波传播时间'起伏特性研究

处理分析AEYFI 05声学实验温度链和声传播数据,研究温度时-空间统计、相关特性及其声传播时间统计特性。分析表明1号声简正波的传播时间起伏的功率谱与温跃层附近温度时间序列的功率谱存在明显的相似：在高频区域f〉30cpd呈ω-β（β≌1.7-1.8）的幂次衰减,包含相干结构。应用简正波传播时间与声速起伏的对应关系式,给出了上述对应关系的理论解释。     

工程车辆FOPS受冲击板壳动态响应研究

工程车辆FOPS在受落锤冲击时产生塑性流变 ,响应为非线性 ,本文建立了FOPS板壳弹性变形、塑性变形和流动变形的各极限速度的数学模型 ;研究了薄板的撞击动态响应 ,建立了撞击中心的最大位移量的数学模型。为设计合理的FOPS结构奠定了理论基础。