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Design Options (design + option)
Selected AbstractsPost-earthquake bridge repair cost and repair time estimation methodologyEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2010Kevin R. Mackie Abstract While structural engineers have traditionally focused on individual components (bridges, for example) of transportation networks for design, retrofit, and analysis, it has become increasingly apparent that the economic costs to society after extreme earthquake events are caused at least as much from indirect costs as direct costs due to individual structures. This paper describes an improved methodology for developing probabilistic estimates of repair costs and repair times that can be used for evaluating the performance of new bridge design options and existing bridges in preparation for the next major earthquake. The proposed approach in this paper is an improvement on previous bridge loss modeling studies,it is based on the local linearization of the dependence between repair quantities and damage states so that the resulting model follows a linear relationship between damage states and repair points. The methodology uses the concept of performance groups (PGs) that account for damage and repair of individual bridge components and subassemblies. The method is validated using two simple examples that compare the proposed method to simulation and previous methods based on loss models using a power,law relationship between repair quantities and damage. In addition, an illustration of the method is provided for a complete study on the performance of a common five-span overpass bridge structure in California. Intensity-dependent repair cost ratios (RCRs) and repair times are calculated using the proposed approach, as well as plots that show the disaggregation of repair cost by repair quantity and by PG. This provides the decision maker with a higher fidelity of data when evaluating the contribution of different bridge components to the performance of the bridge system, where performance is evaluated in terms of repair costs and repair times rather than traditional engineering quantities such as displacements and stresses. Copyright © 2009 John Wiley & Sons, Ltd. [source] Fuel Cell Vehicle Simulation , Part 1: Benchmarking Available Fuel Cell Vehicle Simulation ToolsFUEL CELLS, Issue 3 2003K.H. Hauer Abstract Fuel cell vehicle simulation is one method for systematic and fast investigation of the different vehicle options (fuel choice, hybridization, reformer technologies). However, a sufficient modeling program, capable of modeling the different design options, is not available today. Modern simulation programs should be capable of serving as tools for analysis as well as development. Shortfalls of the existing programs, initially developed for internal combustion engine hybrid vehicles, are: (i)Insufficient modeling of transient characteristics; (ii) Insufficient modeling of the fuel cells system; (iii) Insufficient modeling of advanced hybrid systems; (iv) Employment of a non-causal (backwards looking) structure; (v) Significant shortcomings in the area of controls. In the area of analysis, a modeling tool for fuel cell vehicles needs to address the transient dynamic interaction between the electric drive train and the fuel cell system. Especially for vehicles with slow responding on-board fuel processor, this interaction is very different from the interaction between a battery (as power source) and an electric drive train in an electric vehicle design. Non-transient modeling leads to inaccurate predictions of vehicle performance and fuel consumption. When applied in the area of development, the existing programs do not support the employment of newer techniques, such as rapid prototyping. This is because the program structure merges control algorithms and component models, or different control algorithms (from different components) are lumped together in one single control block and not assigned to individual components as they are in real vehicles. In both cases, the transfer of control algorithms from the model into existing hardware is not possible. This paper is the first part of a three part series and benchmarks the "state of the art" of existing programs. The second paper introduces a new simulation program, which tries to overcome existing barriers. Specifically it explicitly recognizes the dynamic interaction between fuel cell system, drive train and optional additional energy storage. [source] An evolutionary optimization of diffuser shapes based on CFD simulationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10 2010S. Ghosh Abstract An efficient and robust algorithm is presented for the optimum design of plane symmetric diffusers handling incompressible turbulent flow. The indigenously developed algorithm uses the CFD software: Fluent for the hydrodynamic analysis and employs a genetic algorithm (GA) for optimization. For a prescribed inlet velocity and outlet pressure, pressure recovery coefficient C (the objective function) is estimated computationally for various design options. The CFD software and the GA have been combined in a monolithic platform for a fully automated operation using some special control commands. Based on the developed algorithm, an extensive exercise has been made to optimize the diffuser shape. Different methodologies have been adopted to create a large number of design options. Interestingly, not much difference has been noted in the optimum C values obtained through different approaches. However, in all the approaches, a better design has been obtained through a proper selection of the number of design variables. Finally, the effect of diffuser length on the optimum shape has also been studied. Copyright © 2009 John Wiley & Sons, Ltd. [source] Up-to-date cancer survival: Period analysis and beyondINTERNATIONAL JOURNAL OF CANCER, Issue 6 2009Hermann Brenner Abstract Since its introduction in 1996, period analysis has been shown to be useful for deriving more up-to-date cancer survival estimates, and the method is now increasingly used for that purpose in national and international cancer survival studies. However, period analysis, like other commonly employed methods, is just a special case from a broad class of design options in the analysis of cancer survival data. Here, we explore a broader range of design options, including 2 model-based approaches, for deriving up-to-date estimates of 5- and 10-year relative survival for patients diagnosed in the most recent 5-year interval for which data are available. The performance of the various designs is evaluated empirically for 20 common forms of cancer using more than 50-year long time series of data from the Finnish Cancer Registry. Period analysis as well as the 2 model-based approaches, one using a "cohort-type model" and another using a "period-type model", all performed better than traditional cohort or complete analysis. Compared with "standard period analysis", the cohort-type model further increased up-to-dateness of survival estimates, whereas the period-type model increased their precision. While our analysis confirms advantages of period analysis over traditional methods in terms of up-to-dateness of cancer survival data, further improvements are possible by flexible use of model-based approaches. © 2008 Wiley-Liss, Inc. [source] Evaluating the power of monitoring plot designs for detecting long-term trends in the numbers of common guillemotsJOURNAL OF APPLIED ECOLOGY, Issue 3 2006MICHELLE SIMS Summary 1In recent years concerns have been raised regarding the status of the common guillemot Uria aalge in the UK. Numbers have declined in several regions, highlighting the need for continued monitoring of this internationally important population. However, the extent to which the current monitoring scheme is capable of detecting declines and options for improving efficiency has received little attention. 2We investigated the power of different monitoring design options for detecting long-term trends in abundance at a colony of guillemots. The ability to detect trends in abundance was reduced by the large temporal and spatial variability in colony attendance. Taking a linear mixed model approach, we obtained details on the sources and sizes of the variance components using count data collected from monitoring plots on the Isle of May, Scotland, and assessed how best to allocate sampling effort in the light of the count variability structure. 3Our results indicated that trend detection will be improved by counting birds in more plots rather than by increasing the number of counts at existing plots. 4The revisit pattern of counts at the monitoring plots during the seasonal counting period had little effect on trend detection power. However, given the practical issues associated with counting guillemots, alternative revisit patterns to the current approach are preferred. 5For a fixed number of visits per plot, power is strongly influenced by the choice of revisit design if the day-to-day variation in colony attendance is increased. 6Synthesis and applications. Aspects of the UK seabird monitoring scheme can be improved. Changes to the allocation of sampling effort and the plot-revisit pattern will improve both the statistical power to detect long-term trends and the efficiency of conducting the survey. We stress the importance of considering the structure and magnitude of the count variation in a power analysis because judicious design decisions depend on the relative magnitude of these variance components. [source] PDF simulations of ethylene decomposition in tubular LDPE reactorsAICHE JOURNAL, Issue 2 2005Nitin H. Kolhapure Abstract The present study deals with turbulent reacting flow simulation inside low-density polyethylene (LDPE) tubular reactors, based on a detailed computational fluid dynamics (CFD) technique,transported probability density function (PDF) methods. The ability of the PDF methods to provide an exact representation of chemical source terms is ideally suited for coupling complex LDPE chemistry with small-scale fluid dynamic fluctuations in turbulent flow. LDPE chemistry with a total of 16 scalars provides an ideal test case for illustrating the applicability of an efficient chemistry algorithm based on in-situ adaptive tabulation. A particle-based Monte Carlo algorithm is used to solve the joint-composition PDF equation, whereas a finite-volume code is used to obtain hydrodynamic fields from the standard k,, turbulence model. The influence of feed temperature, initiator concentration, and degree of premixing is investigated to gain detailed knowledge of micromixing effects on steady-state reactor performance. The computational approach provides a low-cost alternative to experimental and pilot-plant tests for exploring a variety of design options when making important design and operational decisions, or for investigating unstable reactor operating conditions. The ability of a simplified, but otherwise equivalent multi-environment-presumed PDF model to predict turbulence,chemistry interactions close to physical reality is validated using the detailed transported PDF simulations. The transported PDF method is shown to be an excellent tool for obtaining fundamental information on turbulent reacting flows, as well as for deriving simplified models for faster and easier interpretation of these flows when developing safe and efficient chemical processes. © 2005 American Institute of Chemical Engineers AIChE J, 51: 585,606, 2005 [source] Nonlinear refractive index of ceramic laser media and perspectives of their usage in a high-power laser-driverLASER PHYSICS LETTERS, Issue 10 2004Yu. Senatsky Abstract At the recent years a technology of ceramic laser media on the base of crystals with a cubic symmetry has been developed. The perspective of the usage of ceramic materials in many different applications including high - power short pulse lasers stimulates the work on the systematic study of the properties of these new laser media. A nonlinear refractive index, n2 was studied for several garnet and sesquioxide laser ceramics using Z-scan method. n2 indices in the range of (2 , 6) × 10,13 were measured for YAG, Y2O3, Lu2O3, and Sc2O3 ceramic samples. These data together with the other laser and spectroscopic parameters of several Nd3+ and Yb3+ doped crystals of a cubic symmetry were used to estimate the properties of laser ceramics for the application in a high-power pulsed-repetitive laser - driver for inertial confinement fusion (ICF) program. A high heat conductivity of ceramic materials is a profitable characteristic for this application as compared to glasses, which are used now for experiments in ICF at single shots regime. Compared to single crystals, ceramic elements provide laser designers with a variety of new design options for the projects of laser-drivers. (© 2004 by ASTRO, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Evaluation of available indices for inherently safer design optionsPROCESS SAFETY PROGRESS, Issue 2 2003Faisal I. Khan Inherent safety is a proactive approach for loss prevention during process plant design. It has been proven that, considering the lifetime costs of a process and its operation, an inherent safety approach can lead to a cost-optimal option. Application of inherent safety at the early stages of process design yields the best results with respect to process selection, conceptual design, and engineering design. However, in spite of being an attractive and cost-effective approach to loss prevention, it is not widely used. Reasons have been suggested for this lack of widespread use, but the lack of systematic tools to apply inherent safety principles is perhaps the most important one. A detailed study was conducted to analyze the performance of available hazard indices with reference to various inherent safety principles (guidewords). The performance of four main indices (Dow, Mond, Inherent Safety, and Safety Weighted Hazard [SweHI] indices) was studied for five inherent safety guidewords. None of the indexing procedures can capture all of the inherent safety guidewords, although the SWeHI and Dow Index were found to be robust on many accounts. It is recommended that a new specific index be developed for inherently safer design evaluation. The SWeHI and Dow indexing procedures may be a good basis on which to build. [source] A project invitation: What do students think of educational design options?BRITISH JOURNAL OF EDUCATIONAL TECHNOLOGY, Issue 1 2008Gordon Burt No abstract is available for this article. [source] | |||||||||||||