作者：
Watson, W. R.Jones, M. G.NASA
Langley Res Ctr Res & Technol Directorate Computat Aerosci BranchLiner Phys Grp Hampton VA 23681 USA NASA
Langley Res Ctr Res & Technol Directorate Struct Acoust BranchHead Liner Phys Grp Hampton VA 23681 USA
A new impedance eduction method is presented and validated against a benchmark method, and the effects of measurement uncertainty errors on the impedances educed with this new method are assessed. Unique features of t...
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A new impedance eduction method is presented and validated against a benchmark method, and the effects of measurement uncertainty errors on the impedances educed with this new method are assessed. Unique features of the new method include the following: 1) the upstream and downstream boundary conditions contain higher-order duct modes, 2) the impedance spectra of unique nonuniform test liners on opposite walls may be educed simultaneously, and 3) the measured data for the impedance eduction are acquired only at the source and duct termination planes. The validation exercise is performed with a rigid-wall insert and a conventional liner over a range of frequencies and flow Mach numbers in the NASA Langley Research Center's grazing flow impedance tube. The primary conclusions of the study are that the impedance spectra of the rigid-wall insert and the conventional liner that were educed from the new method are in very good agreement with those that were educed by using the benchmark method. However, the effects of measurement uncertainty on the educed impedance are greater at the lower frequencies and the higher Mach numbers for the new method. All indications are that this occurs because the new method 1) uses significantly less data to perform the impedance eduction than the benchmark and 2) is currently based on a rather crude approximation to the measured pressure gradient, which is more sensitive to the refractive effects of the boundary layer than the measured lower-wall pressure that is required in the benchmark method.
This paper presents the evaluation of the performance, in terms of uncertainty, of a tool designed to estimate the main parameters of a model of a photovoltaic panel (PVP) under real and/or simulated working condition...
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This paper presents the evaluation of the performance, in terms of uncertainty, of a tool designed to estimate the main parameters of a model of a photovoltaic panel (PVP) under real and/or simulated working conditions. The presented tool permits the characterization of the panel, and it is useful to predict its behavior in whatever working condition;in this way, it is possible to compare the actual and expected performance to prevent any decrease in the output power, so permitting the replacement of the monitored module before it goes out of order or its efficiency falls under a given threshold. The well-known two-diode model is used to estimate the parameters of the electrical equivalent circuit of the PVP and to simulate the I-V and P-V characteristic curves in any given environmental condition of irradiance and/or temperature. The model and the estimation algorithm are implemented with MATLAB functions, whereas data acquisition and result presentation are managed by a LabVIEW graphics user interface. The presented tool has been validated against an experimentally characterized PVP. The environmental parameters of the model such as irradiance and temperature have been set (with their respective uncertainties) during simulations or directly measured during the outdoor tests, whereas the others parameters have been evaluated using a best-fit algorithm on the measured data. The estimation is based on the minimization of a new objective function and on a modified expression of the model resistances, which differ from those mentioned in the available literature. After a review of the state of the art, this paper provides the description of the estimation technique and its validation by means of simulations and experiments. Some results are also provided to illustrate the performance of the proposed test method.
A nonlinear hybrid dynamical system is established to describe the batch culture of glycerol to 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae (K. pneumoniae), in which glycerol is assumed to pass the cell membrane...
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A nonlinear hybrid dynamical system is established to describe the batch culture of glycerol to 1,3-propanediol (1,3-PD) by Klebsiella pneumoniae (K. pneumoniae), in which glycerol is assumed to pass the cell membrane by passive diffusion coupled with facilitated transport and transport mechanism of 1,3-PD is assumed to be uncertain. The existence, uniqueness and continuity of solutions are also discussed. To infer the most reasonable transport mechanism of 1,3-PD, a system identification model consisting of both discrete and continuous variables is proposed. Additionally, we construct a two-phase optimization algorithm on the basis of modified complex method together with very fast simulated annealing technology. Numerical results show that it is most reasonable for 1,3-PD to pass the cell membrane by passive diffusion coupled with facilitated transport and that the optimization algorithm is valid. (C) 2011 Elsevier Ltd. All rights reserved.
Programming with parallel tasks leads to task graphs with dependencies representing a parallel program. Scheduling algorithms are employed to find an efficient execution order of the parallel tasks. A large variety of...
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Programming with parallel tasks leads to task graphs with dependencies representing a parallel program. Scheduling algorithms are employed to find an efficient execution order of the parallel tasks. A large variety of scheduling algorithms exist, including layer-based scheduling algorithms for homogeneous target platforms that build consecutive layers of independent parallel tasks and schedule each layer separately. Although these scheduling algorithms provide good results in terms of scheduling algorithm runtime and schedule execution time, the resulting schedules leave room for optimization. This article proposes an optimization for arbitrary layer-based scheduling algorithms, which is called Move-blocks algorithm. Given a layer-based schedule of the parallel tasks, this algorithm moves blocks of parallel tasks into preceding layers in order to reduce the overall execution time of a task-based application. Suitable blocks of parallel tasks are identified by the algorithm Find-blocks, which is employed together with the Move-blocks algorithm. The algorithm Move-blocks is applied to four well-known scheduling algorithms. A detailed evaluation for a wide range of test cases is given. Copyright (C) 2010 John Wiley & Sons, Ltd.
The identification of the parameters of a nonlinear constitutive model of soil mass is based on an inverse analysis procedure, which consists of minimizing the objective function representing the difference between th...
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The identification of the parameters of a nonlinear constitutive model of soil mass is based on an inverse analysis procedure, which consists of minimizing the objective function representing the difference between the experimental data and the calculated data of the mechanical model. A gradient-based optimization algorithm is developed for estimating model parameters of soils in earth pressure balance (EPB) shield tunneling. The parameter values of the nonlinear constitutive model are searched for by using the Levenberg-Marquardt approximation which can provide fast convergence. The parameter identification results illustrate that the proposed parameter inversion procedure has not only higher computing efficiency but also better identification accuracy. The results from the model are compared with simulated observations. The models are found to have good predictive ability and are expected to be very useful for estimating model parameters for soils in EPB shield tunneling. (C) 2010 Elsevier Ltd. All rights reserved.
The deconvolution of temperature-dependent rate coefficients to energy-dependent cross sections is accomplished by using a nonlinear optimization technique. The suggested method is successfully applied to atom-molecul...
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The deconvolution of temperature-dependent rate coefficients to energy-dependent cross sections is accomplished by using a nonlinear optimization technique. The suggested method is successfully applied to atom-molecule and molecule-molecule dissociation processes in hydrogen.
Receding horizon control is a kind of optimal feedback control, in which the control performance over a finite future is optimized. The control of fluid dynamics is a challenging problem that arises in many fields. Th...
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ISBN:
(纸本)9781467322591
Receding horizon control is a kind of optimal feedback control, in which the control performance over a finite future is optimized. The control of fluid dynamics is a challenging problem that arises in many fields. The objective of this study is to provide a novel framework of designing a receding horizon controller for thermal fluid systems. The method proposed here is advantageous for its applicability to a wide class of optimization problem of thermal fluid systems. The effectiveness of the proposed method is verified by numerical simulation.
A numerical approach to select an optimized turboprop engine configuration that matches with the power requirement of a class of propeller-driven aircraft, was reported. Biobjective optimizations of the propulsion cyc...
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A numerical approach to select an optimized turboprop engine configuration that matches with the power requirement of a class of propeller-driven aircraft, was reported. Biobjective optimizations of the propulsion cycles' parameters for three variants of turboprops were carried out based on an efficient repulsive particle swarm algorithm (RPSO). On each Pareto front, three distinguishable design points were selected. A cycle optimization was performed considering a basic technology level to determine the optimum turbine inlet temperature (TIT), overall pressure ratio (OPR), and turbine temperature expansion rate (TTR) and the subsequent performance for the three configurations of turboprops. The optimizations carried out for the three turboprops' configurations at the same cruising conditions showed that for a basic technology level the two-shaft fixed-turbine turboprop is preferred, owing to better performance for the same OPR range, but needs more LP turbine stages as compared with the free-turbine version.
As buildings become taller and larger, the lifting plan safety review has become more important in construction project management. However, the cost and safety aspects of the lifting plan are contradictory to each ot...
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As buildings become taller and larger, the lifting plan safety review has become more important in construction project management. However, the cost and safety aspects of the lifting plan are contradictory to each other. Therefore, an optimization algorithm needs to be devised as a solution to this problem. In many cases at construction sites, the selection and stability review of the tower cranes are assigned to the equipment suppliers or the field managers, which causes problems for the safety and cost of a project. To prove this aspect of the current situation, this study examines an automatic optimization algorithm for designing the foundation of tower cranes. This algorithm can be implemented by a computerized system and easily and promptly utilized by field managers without the need for substantial knowledge. (C) 2010 Elsevier B.V. All rights reserved.
In order to solve the problems of optimization algorithm used to identify the physical parameters of structures, a new method based on a series of equivalent single degree systems is proposed in this paper. The key id...
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ISBN:
(纸本)9780878492503
In order to solve the problems of optimization algorithm used to identify the physical parameters of structures, a new method based on a series of equivalent single degree systems is proposed in this paper. The key idea of the method is that a multi-degree system can be represented by a series of single degree systems that can be identified one by one to perform the identification of the whole system. This method can not only decrease the dimensions of optimization algorithm, but also reduce the amount of estimation work in searching for the bound of parameters, and at the same time improve the identification results when parameters might suddenly change. In the numerical simulation of the physical parameter identification of a multi-degree system, Differential evolution is one of the optimization algorithm methods which are used to identify a series of equivalent single degree systems instead of the multi-degree system they represent, and the identification results prove that the method proposed in this paper is valid.
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