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Analytical Investigations (analytical + investigation)
Selected AbstractsAn Analytical Investigation of the Bullwhip EffectPRODUCTION AND OPERATIONS MANAGEMENT, Issue 2 2004Roger D. H. Warburton The Bullwhip Effect is problematic: order variability increases as orders propagate along the supply chain. The fundamental differential delay equations for a retailer's inventory reacting to a surge in demand are solved exactly. Much of the rich and complex inventory behavior is determined by the replenishment delay. The analytical solutions agree with numerical integrations and previous control theory results. Managerially useful ordering strategies are proposed. Exact expressions are derived for the retailer's orders to the manufacturer, and the Bullwhip Effect arises naturally. The approach is quite general and applicable to a wide variety of supply chain problems. [source] Analytical investigation of styrax and benzoin balsams by HPLC- PAD-fluorimetry and GC-MSPHYTOCHEMICAL ANALYSIS, Issue 4 2008Michael Hovaneissian Abstract An HPLC and GC study has been conducted on the aromatic oleoresins styrax and benzoin produced by several American, Mediterranean and East-Asian trees, and widely used in ancient civilisations for their therapeutic and odoriferous properties. Initial experiments were performed by HPLC-PAD-fluorimetry for the analysis of several aromatic components, and then completed by GC-MS for the characterisation of both aromatic and triterpenic derivatives. In this work, it was crucial to isolate from fresh natural exudates, and to characterise by two-dimensional NMR, some of the major constituents in order to extend the standard molecular pool prior to chromatographic identifications. This study reveals coniferyl benzoate as an excellent distinctive fluorescent biomarker of Siam benzoin substrate. It also confirms that fluorimetric-coupled detection is a powerful analytical tool for the identification of compounds in Hamamelidaceae extracts that are almost undetectable by UV. GC-MS was successfully applied to the determination of the botanical origin of Sumatra benzoin, and to the identification of lupeol [3, -lup-20(29)-en-3-ol] for the first time in such balsam-type materials. Copyright © 2007 John Wiley & Sons, Ltd. [source] Prediction of crack growth direction under plane stress for mixed-mode I and II loadingFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2000Wasiluk The estimation of the plastic zone geometry ahead of a crack is fundamental to the evaluation of crack growth. Presented here is an analytical investigation for predicting crack growth direction for mixed-mode I and II loading under plane stress conditions. It is proposed that under complex loading the crack will extend in the direction where the radius of the plastic zone attains a minimum value. There is good agreement between the predicted results which are computed on the basis of this criterion and experimental data published in the literature. [source] Analysis of flow and heat transfer in evaporator porous wicking structure of a flat heat pipeHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 2 2009Congxiang Hu Abstract With a specified pressure distribution, an analytical investigation was conducted to explore the flow and heat transfer characteristics in an evaporator porous wicking structure of a flat heat pipe. The boundary effect on the flow rate is more significant than the inertia, and both the boundary and inertia effects exert very little influence on fluid layer thickness and velocity distribution. The bottom of the porous layer is at a quite uniform temperature, and the heat flux is almost normal to the solid boundary. © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20237 [source] An extended finite element method with analytical enrichment for cohesive crack modelingINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2009James V. CoxArticle first published online: 28 NOV 200 Abstract A recent approach to fracture modeling has combined the extended finite element method (XFEM) with cohesive zone models. Most studies have used simplified enrichment functions to represent the strong discontinuity but have lacked an analytical basis to represent the displacement gradients in the vicinity of the cohesive crack. In this study enrichment functions based upon an existing analytical investigation of the cohesive crack problem are proposed. These functions have the potential of representing displacement gradients in the vicinity of the cohesive crack and allow the crack to incrementally advance across each element. Key aspects of the corresponding numerical formulation and enrichment functions are discussed. A parameter study for a simple mode I model problem is presented to evaluate if quasi-static crack propagation can be accurately followed with the proposed formulation. The effects of mesh refinement and mesh orientation are considered. Propagation of the cohesive zone tip and crack tip, time variation of the cohesive zone length, and crack profiles are examined. The analysis results indicate that the analytically based enrichment functions can accurately track the cohesive crack propagation of a mode I crack independent of mesh orientation. A mixed mode example further demonstrates the potential of the formulation. Copyright © 2008 John Wiley & Sons, Ltd. [source] Murder by poisoning: successful analytical investigations of spectacular cases in AustriaDRUG TESTING AND ANALYSIS, Issue 4 2009Walter Vycudilik Abstract To prove murder by poisoning requires the application of analytical toxicology to detect the fatal substance and clear up the cause of death. Improvements in the development of mass spectrometry in combination with high-resolution chromatographic methods are steadily enhancing detection and identification power but making use of these advances relies on proper sample preparation as well as on knowledge about the chemical nature of the substances and their bio-transformation products. This review gives examples of case reports with successful analytical investigations of murder by poisoning in spectacular Austrian cases involving low molecular weight. Copyright © 2009 John Wiley & Sons, Ltd. [source] Adulteration of Chinese herbal medicines with synthetic drugs: a systematic reviewJOURNAL OF INTERNAL MEDICINE, Issue 2 2002E. Ernst Abstract.,Ernst E. (University of Exeter, Exeter, UK). Adulteration of Chinese herbal medicines with synthetic drugs: a systematic review (Review Article). J Intern Med 2002; 252: 107,113. The popularity of Chinese herbal medicines (CHMs) demands a critical analysis of safety issues. The aim of this systematic review is to summarize data regarding adulterations of CHMs with conventional drugs. Literature searches were carried out in six databases. Articles containing original data on adulterations were considered without language restrictions. Eighteen case reports, two case series and four analytical investigations were identified. The list of adulterants contains drugs associated with serious adverse effects like corticosteroids. In several instances, patients were seriously harmed. One report from Taiwan suggests that 24% of all samples were contaminated with at least one conventional pharmacological compound. It is concluded that adulteration of CHMs with synthetic drugs is a potentially serious problem which needs to be addressed by adequate regulatory measures. [source] Model of inelastic impact of unit loadsPACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2009Tomasz Piatkowski Abstract In this study, the authors present a model of the inelastic impact of bodies that takes place during handling of unit loads (cubiform parcels). A modified non-linear Kelvin model is proposed, in which the relationships between object strains and elastic and damping forces of the impact are represented by power functions. The results of analytical investigations on the proposed model were confirmed by experiments consisting in tests of free fall of the load on rigid ground and on elastic beam. The developed model allows the assessment of the influence of mechanical properties of loads and conveyor-line deflection mechanisms as well as impact velocity, on the dynamic forces exerted on the manipulated objects during the impact. Copyright © 2008 John Wiley & Sons, Ltd. [source] Prevention of Stick-Slip Vibrations by Passive Normal Force ControlPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003Martin Rudolph The classical stick-slip oscillator is extended by an additional degree of freedom which couples the slipping motion to the normal force. Using this, the effective friction force can be altered without changing the friction-velocity characteristic. The paper deals with the optimization problem of finding parameters of the additional system that prevent stick-slip motion or minimize the amplitude of the residual limit cycle. Another goal is to increase the decay rate of vibration. Results were achieved by numerical integration based on analytical investigations. 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