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Several Case Studies (several + case_studies)
Selected AbstractsFatigue of cantilevered pipe fittings subjected to vibrationFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 8 2003M. HAMBLIN ABSTRACT Vibration fatigue failures in piping systems often occur at cantilevered small-bore fittings (SBF) such as pressure tappings and drain valves. Piping vibration has often been assessed by measuring vibration displacement or velocity. However, in the case of straight cantilevered fittings with a concentrated mass, a better method exists. This paper presents a simple robust method of calculating vibration induced stress for cantilevered fittings at both the fitting branch neck and the main pipe. The method is based on measurement of acceleration at the concentrated mass (e.g., valve) and simple mechanics calculations. Extensive laboratory and field verification of the technique is presented. The choices of a fatigue strength criterion, such as ASME BPVC VIII Div. 2, BS7608, or a fracture mechanics approach such as BSI PD6493, are discussed. Several case studies are presented as well as simple ,good engineering practice' rules-of-thumb for SBF design. These ,rules-of-thumb' are now incorporated in the piping specifications of the author's company. [source] A node-based agglomeration AMG solver for linear elasticity in thin bodiesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 3 2009Prasad S. Sumant Abstract This paper describes the development of an efficient and accurate algebraic multigrid finite element solver for analysis of linear elasticity problems in two-dimensional thin body elasticity. Such problems are commonly encountered during the analysis of thin film devices in micro-electro-mechanical systems. An algebraic multigrid based on element interpolation is adopted and streamlined for the development of the proposed solver. A new node-based agglomeration scheme is proposed for computationally efficient, aggressive and yet effective generation of coarse grids. It is demonstrated that the use of appropriate finite element discretization along with the proposed algebraic multigrid process preserves the rigid body modes that are essential for good convergence of the multigrid solution. Several case studies are taken up to validate the approach. The proposed node-based agglomeration scheme is shown to lead to development of sparse and efficient intergrid transfer operators making the overall multigrid solution process very efficient. The proposed solver is found to work very well even for Poisson's ratio >0.4. Finally, an application of the proposed solver is demonstrated through a simulation of a micro-electro-mechanical switch. Copyright © 2008 John Wiley & Sons, Ltd. [source] Simulation and validation of resin flow during manufacturing of composite panels containing embedded impermeable inserts with the VARTM processPOLYMER COMPOSITES, Issue 4 2007Jeffrey M. Lawrence Modern composite materials are becoming more and more advanced as engineers are better able to take advantage of their properties. In addition to their lighter weight and net-shape manufacturing, current interest is to make these materials multifunctional. This may require one to insert various objects into the composite to achieve a variety of different goals. It is important to understand how these embedded objects will affect both the manufacturing and the structural integrity of the component. In this work, the effects of impermeable embedded inserts on the infusion stage of vacuum-assisted resin transfer molding (VARTM) will be explored. In VARTM, one places a distribution media on top of the preform to aid the filling as the resin will first fill the face of the preform in contact with the distribution media and will then infuse the preform in the thickness direction. However, if one has an embedded impermeable insert in the thickness direction, it will obstruct the flow in the region below the embedded object. Several case studies are conducted to understand the effect of the geometry and placement of the embedded insert and the distribution media lay out and properties on the impregnation of the resin into the fiber preform. Finally, an approach is outlined to modify the layout of the distribution media in order to ensure a complete saturation of the preform under all but the most extreme conditions. The approach is validated with experiments. POLYM. COMPOS., 28:442,450, 2007. © 2007 Society of Plastics Engineers [source] Ground motion duration effects on nonlinear seismic responseEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 1 2006Iunio Iervolino Abstract The study presented in this paper addresses the question of which nonlinear demand measures are sensitive to ground motion duration by statistical analyses of several case studies. A number of single degree of freedom (SDOF) structures were selected considering: (1) four oscillation periods; (2) three evolutionary and non-evolutionary hysteretic behaviours; (3) two target ductility levels. Effects of duration are investigated, by nonlinear dynamic analysis, with respect to six different demand indices ranging from displacement ductility ratio to equivalent number of cycles. Input is made of six real accelerogram sets representing three specific duration scenarios (small, moderate and large duration). For all considered demand quantities time-history results are formally compared by statistical hypothesis test to asses the difference, if any, in the demand concerning different scenarios. Incremental dynamic analysis curves are used to evaluate duration effect as function of ground motion intensity (e.g. spectral acceleration corresponding to the SDOF's oscillation period). Duration impact on structural failure probability is evaluated by fragility curves. The results lead to the conclusion that duration content of ground motion is statistically insignificant to displacement ductility and cyclic ductility demand. The conclusions hold regardless of SDOF's period and hysteretic relationship investigated. Copyright © 2005 John Wiley & Sons, Ltd. [source] The Cocoon of Power: Democratic Implications of Interinstitutional AgreementsEUROPEAN LAW JOURNAL, Issue 1 2007Sonja Puntscher Riekmann It starts from the premise that democratic rules as developed in the national context may be used as a yardstick for supranational governance as well. Thus, parliamentarisation of the Union is defined as an increase in democracy, although relating problems such as weak European party systems, low turnouts, and remoteness are not to be neglected. The article evaluates several case studies on IIAs in this vein and asks whether they strengthen the European Parliament or not, and why. It arrives at conclusions that allow for differentiation: empowerment of the European Parliament occurs in particular when authorisation to conclude an IIA stems from the Treaty or from the power that the European Parliament has in crucial fields such as the budget and is willing to use for this purpose. Success is, however, not guaranteed in every case, and is sometimes more symbolic than real. However, a democratic critique must also stress negative consequences of IIAs in terms of responsivity, accountability, and transparency. [source] Eliciting information about organizational culture via ladderingINFORMATION SYSTEMS JOURNAL, Issue 3 2002Gordon Rugg Abstract. Eliciting information about organizational culture is an important part of system analysis and design. However, eliciting knowledge of this sort is difficult. Laddering is an established technique that is particularly suitable for eliciting information about goals and for eliciting explanations, which are important issues when investigating organizational culture. This paper describes the method, its strengths and limitations, its use in several case studies and its relation to other elicitation techniques. Recommendations for further work are given. [source] Harmonic Balance, Melnikov method and nonlinear oscillators under resonant perturbationINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 3 2008Michele Bonnin Abstract The subharmonic Melnikov's method is a classical tool for the analysis of subharmonic orbits in weakly perturbed nonlinear oscillators, but its application requires the availability of an analytical expression for the periodic trajectories of the unperturbed system. On the other hand, spectral techniques, like the Harmonic Balance, have been widely applied to the analysis and design of nonlinear oscillators. In this manuscript, we show that bifurcations of subharmonic orbits in perturbed systems can be easily detected computing the Melnikov's integral over the Harmonic Balance approximation of the unperturbed orbits. The proposed method significantly extends the applicability of the Melnikov's method since the orbits of any nonlinear oscillator can be easily detected by the Harmonic Balance technique, and the integrability of the unperturbed equations is not required anymore. As examples, several case studies are presented, the results obtained are confirmed by extensive numerical experiments. Copyright © 2007 John Wiley & Sons, Ltd. [source] Male,male combats in a polymorphic lizard: residency and size, but not color, affect fighting rules and contest outcomeAGGRESSIVE BEHAVIOR, Issue 3 2009Roberto Sacchi Abstract Theoretical models predict that the outcome of dyadic agonistic encounters between males is influenced by resource-holding potential, resource value, and intrinsic aggressiveness of contestants. Moreover, in territorial disputes residents enjoy a further obvious competitive advantage from the residency itself, owing to the intimate familiarity with their territory. Costs of physical combats are, however, dramatically high in many instances. Thus, signals reliably reflecting fighting ability of the opponents could easily evolve in order to reduce these costs. For example, variation in color morph in polymorphic species has been associated with dominance in several case studies. In this study, we staged asymmetric resident-intruder encounters in males of the common wall lizard Podarcis muralis, a species showing three discrete morphs (white, yellow, and red) to investigate the effects of asymmetries in color morph, residency, and size between contestants on the outcome of territorial contests. We collected aggression data by presenting each resident male with three intruders of different color morph, in three consecutive tests conducted in different days, and videotaping their interactions. The results showed that simple rules such as residency and body size differences could determine the outcome of agonistic interactions: residents were more aggressive than intruders, and larger males were competitively superior to smaller males. However, we did not find any effect of color on male aggression or fighting success, suggesting that color polymorphism in this species is not a signal of status or fighting ability in intermale conflicts. Aggr. Behav. 35:274,283, 2009. © 2009 Wiley-Liss, Inc. [source] Phosphodiesterase 5 (PDE 5) inhibitors for the treatment of male erectile disorder: Attaining selectivity versus PDE6MEDICINAL RESEARCH REVIEWS, Issue 3 2006Dmitri Pissarnitski Abstract The role of phosphodiesterase type 5 (PDE5) in the mechanism of male erection has been well understood, and several drugs inhibiting this enzyme are being used for the treatment of erectile dysfunction (ED). Discovery of inhibitors with improved selectivity versus other PDE isozymes could lead to drugs with improved safety profile. Achievement of selectivity versus PDE6, co-inhibition of which results in disturbances of color perception, remains the most challenging aspect of current drug discovery programs. The present review describes several case studies, where significant (>100 fold) selectivity versus PDE6 has been attained via investigation of structure,activity relationships (SAR). Special attention is given to the chemical routes leading to novel chemotypes and allowing efficient exploration of their SAR's. Strategies for attaining inhibitor selectivity discussed below may be applicable for other drug discovery programs. © 2005 Wiley Periodicals, Inc. Med Res Rev [source] Biotechnology, the Environment, and SustainabilityNUTRITION REVIEWS, Issue 2003Dr. Harry Kuiper This article reviews the environmental impact of genetically modified crops through discussion of environmental risk assessment and includes several case studies. Influence of European regulatory and political issues is considered. [source] Adoption and evaluation issues of automatic and computer aided indexing systemsPROCEEDINGS OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE & TECHNOLOGY (ELECTRONIC), Issue 1 2008Miguel E. Ruiz organizer This panel will present an overview of the state-of-the-art in automatic and computer aided indexing systems, and focus on discussion of the factors that influence the success of the implementation of these system as well as the criteria for evaluation. We also will present several case studies of operational systems such as the Indexing Initiative at the National Library of Medicine, the American Water Works Association, the IEEE and ASIS&T Digital Library. Final recommendations and "best practices" will be presented and discussed among panel members and the audience. [source] Sustainable governance of natural resources and institutional change,an analytical frameworkPUBLIC ADMINISTRATION & DEVELOPMENT, Issue 2 2007Anke Fischer Abstract This article presents a conceptual framework for analysing the governance of natural resource use, as governance is often the primary issue when natural resources are overexploited and degraded. It addresses both spontaneous and active governance, including institutional change induced by development co-operation. Drawing on existing frameworks of institutional analysis, fundamental modifications are presented to adapt the concept to the context of international co-operation, and to include dynamic aspects of institutional change as well as multiple actor interactions. Tested in several case studies, the framework was found suitable and relevant for use in project planning and evaluation, as well as for comparing governance issues across cases in a conceptually rigorous way. Copyright © 2007 John Wiley & Sons, Ltd. [source] Drug disposition of chiral and achiral drug substrates metabolized by cytochrome P450 2D6 isozyme: case studies, analytical perspectives and developmental implicationsBIOMEDICAL CHROMATOGRAPHY, Issue 6-7 2006Nuggehally R. Srinivas Abstract The concepts of drug development have evolved over the last few decades. Although number of novel chemical entitities belonging to varied classes have made it to the market, the process of drug development is challenging, intertwined as it is with complexities and uncertainities. The intention of this article is to provide a comprehensive review of novel chemical entities (NCEs) that are substrates to cytochrome P450 (CYP) 2D6 isozyme. Topics covered in this review aim: (1) to provide a framework of the importance of CYP2D6 isozyme in the biotransformation of NCEs as stand-alones and/or in conjunction with other CYP isozymes; (2) to provide several case studies of drug disposition of important drug substrates, (3) to cover key analytical perspectives and key assay considerations to assess the role and involvement of CYP2D6, and (4) to elaborate some important considerations from the development point of view. Additionally, wherever applicable, special emphasis is provided on chiral drug substrates in the various subsections of the review. Copyright © 2006 John Wiley & Sons, Ltd. [source] Industrial biotechnology: Tools and applicationsBIOTECHNOLOGY JOURNAL, Issue 12 2009Weng Lin Tang Abstract Industrial biotechnology involves the use of enzymes and microorganisms to produce value-added chemicals from renewable sources. Because of its association with reduced energy consumption, greenhouse gas emissions, and waste generation, industrial biotechnology is a rapidly growing field. Here we highlight a variety of important tools for industrial biotechnology, including protein engineering, metabolic engineering, synthetic biology, systems biology, and downstream processing. In addition, we show how these tools have been successfully applied in several case studies, including the production of 1, 3-propanediol, lactic acid, and biofuels. It is expected that industrial biotechnology will be increasingly adopted by chemical, pharmaceutical, food, and agricultural industries. [source] | |||||||||||||||||||