共查询到20条相似文献,搜索用时 812 毫秒
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Nurcin Celik 《国际生产研究杂志》2013,51(3):843-865
In a simulation-based planning and control framework, timely monitoring, analysis, and control is important not to disrupt a dynamically changing system. To meet this temporal requirement, a dynamic-data-driven adaptive multi-scale simulation (DDDAMS) paradigm was proposed earlier, where the fidelity of a complex simulation model adapts to available computational resources by incorporating dynamic data into the executing model, which then steers the measurement process for selective data update. In this work, a sequential Monte Carlo method (sequential Bayesian inference technique) is proposed and embedded into the simulation to enable its ideal fidelity selection given massive datasets under the DDDAMS framework. As dynamic information becomes available, the proposed method makes efficient inferences to determine the sources of abnormality in the system (a shop floor in this paper). A parallelisation framework is also discussed to further reduce the number of data accesses while maintaining the accuracy of parameter estimates. A prototype DDDAMS involving the proposed algorithm has been implemented successfully for preventive maintenance scheduling and part routing scheduling in a semiconductor manufacturing supply chain, reducing the average waiting time of batches and increasing the machine utilisation significantly. 相似文献
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Feyzi Inanc 《Journal of Nondestructive Evaluation》2007,26(2-4):33-46
Backscatter radiography has become a well known inspection technique for the cases where the inspection is to be carried out
only for one sided configurations. Compared to the conventional projection radiography, the backscatter radiography has more
parameters to be adjusted for a well implemented inspection procedure. The interrogating beam and detector collimation, beam
and detector orientation and the distance to the target surface are among those parameters that need to be adjusted. The adjustment
of these parameters is not straightforward. A simulation based approach can provide good insight into adjusting the parameters.
In this article, we show how simulations can be used for understanding the impact of various parameters. In doing that, we
also document how the deterministic methods can prove to be very beneficial since the computations can be done only once and
the scattered flux can be computed for various detector configurations without going back to transport computations. Some
computational results are provided. 相似文献
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The formation of atom-doped fullerenes has been investigated by using several types of radionuclides produced by nuclear reactions. From the trace of the radioactivities after a high performance liquid chromatography, it was found that formation of endohedral fullerenes (or heterofullerenes) of small atoms (Be, Li), noble-gas atoms (Kr, Xe) and 4B–6B elements (Ge, As, Se, Sb, Te, etc.) is possible by a recoil process following the nuclear reaction. In order to show the possibility of creating endohedral fullerenes with a suitably high kinetic energy of foreign atoms, we have carried out large-scale ab initio molecular dynamics simulations on the basis of the all-electron mixed-basis approach with atomic orbitals and plane waves for several atoms. 相似文献
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The formation of atom-doped fullerenes has been investigated by using several types of radionuclides produced by nuclear reactions. From the trace of the radioactivities after a high performance liquid chromatography, it was found that formation of endohedral fullerenes (or heterofullerenes) of small atoms (Be, Li), noble-gas atoms (Kr, Xe) and 4B–6B elements (Ge, As, Se, Sb, Te, etc.) is possible by a recoil process following the nuclear reaction. In order to show the possibility of creating endohedral fullerenes with a suitably high kinetic energy of foreign atoms, we have carried out large-scale ab initio molecular dynamics simulations on the basis of the all-electron mixed-basis approach with atomic orbitals and plane waves for several atoms. 相似文献
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We present a new simulation technique that allows accurate and very efficient determination of free energies as a function
of temperature using a single constant temperature molecular dynamics or Monte Carlo simulation. The method is based on the
dynamical reversible scaling of the potential energy function of the system of interest and is implemented using the adiabatic
switching method. Application to the calculation of the free energy of crystalline silicon using a semi-empirical interatomic
potential demonstrates that the reversible-scaling method provides an accurate and very efficient tool for the calculation
of free energies over a wide temperature interval.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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In the paper a discrete system of particles carried by fluid is considered in a planar motion. The volumetric density of
particles is assumed to be small enough such that they can be treated within the framework of a molecular dynamics model.
The fluid is then considered as a carrier of particles. The Landau-Lifshitz concept of turbulence is used to describe the
fluctuating part of fluid velocity. This approach is applied to simulate different regimes (laminar and turbulent) and various
states of particle motion (moving bed, heterogeneous flow, and homogeneous flow) using only two parameters, which have to
be determined experimentally. These two parameters, found for a particular pipe and for a particular velocity from a simple
experiment, then can be used for other pipe diameters and different velocities. The computer simulations performed for the
flow of particles in pipes at different flow velocities and different pipe diameters agree favorably with experimental observations
of the type of flow and critical velocities identifying transitions from one type to another.
Received: 8 January 1999 相似文献
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The present paper deals with the interfacial debonding processes in Al/SiC metal matrix composites, by using 3D finite element calculations on representative cells. The reinforcements are considered as elastic, while the behaviour of the matrix is described by an elastoviscoplastic law. The debonding of the reinforcement is allowed for by using a non-linear elastic dependence between the stress vector and the separation vector at the interface. The results obtained show that the macroscopic behaviour of the composite depends to a large extent on the ratio between the the normal and tangential strength of the interface and the characteristic lengths defining the geometry of the reinforcements. 相似文献
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R. Reifarth M. Heil F. Kppeler R. Plag 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2009,608(1):139-143
The 7Li(p,n) reaction in combination with a 3.7 MV Van de Graaff accelerator was routinely used at FZK to perform activation as well as time-of-flight measurements with neutrons in the keV-region. Planned new setups with much higher proton currents like SARAF and FRANZ and the availability of liquid-lithium target technology will trigger a renaissance of this method. A detailed understanding of the neutron spectrum is not only important during the planning phase of an experiment, but also for the analysis of activation experiments. Therefore, the Monte-Carlo based program PINO (Protons In Neutrons Out) was developed, which allows the simulation of neutron spectra considering the geometry of the setup and the proton-energy distribution. 相似文献
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Jin-Yoo Suh Young-Su LeeJae-Hyeok Shim Hoon Mo Park 《Computational Materials Science》2012,51(1):365-371
A methodology is proposed for predicting the elastic properties of precipitation-hardened alloys by combining different modeling techniques: the CALPHAD method, first-principles calculation, and elasticity models. The proposed procedure was applied to conventional aluminum cast alloys to predict their elastic moduli. The predicted Young’s moduli are in reasonable agreement with values reported in the literature, which verifies the potential applicability of the methodology to the development of high-stiffness aluminum cast alloys. 相似文献
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This paper reports the results of a study into the impact of computer simulations on the understanding of fluid mechanics by engineering students. A “lesson study” approach was taken, using constructivist educational theory combined with the variation theory of learning from phenomenography to inform the design of learning activities and to assess their impact. Student difficulties with fluid mechanics concepts were assessed using questions from the Fluid Mechanics Concept Inventory (FMCI). Students had the greatest difficulties with pressure measurement, fluid flow through pipes with changing diameter, and velocity profiles for fluid between flat plates. We developed a set of three simulations to address these difficulties. The impact of the simulations was gauged by a second administration of the FMCI. Most of the students in the sophomore fluid mechanics class participated in the whole of this exercise. Students showed significant improvement in two of the three areas of difficulty. Student feedback on this as an additional learning exercise was very positive. 相似文献
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Sputter deposition process of a multicomponent Zr-Ti-Cu-Ni-Be metallic alloy has been studied experimentally and by numerical simulations. Monte-Carlo simulations were performed using a model based on thermalization and diffusion of sputtered atoms. Incident energy and angle of sputtered atoms on substrate were obtained from simulations. The incident angular distribution was observed to be a normal distribution at all sputtering pressures. Average incident kinetic energy of the condensing atoms on the substrate was observed to be 0.2-0.3 eV indicating most of them are thermalized. Simulations were extended to predict compositional variations in films prepared at various process conditions. These results were compared with composition of films determined experimentally using Rutherford Backscattering Spectrometry (RBS). Contents of Zr, Ti, Cu and Ni quantified using RBS were in moderate agreement with the simulated composition. Be could not be quantified accurately by RBS largely due to very low energy peak of Be in the spectrum. These studies are shown to be useful in understanding the complexities in multicomponent sputtering. 相似文献
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Vijay Venkatesh Niharika Swain G. Srinivas Praveen Kumar 《Materials and Manufacturing Processes》2017,32(3):235-262
The concept of miniaturizing machine tools has received a strong interest in the research community due to their ability to fabricate intricate components. Lower power consumption, higher productivity rate, and smaller sizes of work stations have enabled microscale machining operations to acquire an edge over other fabrication techniques in various applications such as aerospace, instrumentation, automotive, biomedical, etc. The literature is filled with works done by researchers working in this domain. A significant contribution comes from the works which have been published during the period 1998–2014. The focus of these studies has primarily been on conventional and nonconventional micromachining techniques. Since nonconventional machining operations such as microelectrical discharge machining, laser machining, etc., are not compatible with traditional workpiece materials, conventional micromachining techniques such as micromilling and microdrilling are generally used. However, as of today, there has been no revision on the state of the-art in this field to serve as a reference for the experienced researcher and as a handbook for the newcomer. In this review, we have attempted to summarize the current state of understanding on this topic. A variety of issues which are representative of micromachining operations are critically analyzed and presented. Conventional micromachining operations have been compared with their nonconventional counterparts with respect to performance characteristics such as burr formation, surface integrity, etc., and their advantages and shortcomings have been listed. Meticulous efforts have been taken to address the key challenges faced in typical micromachining operations. Taking the convenience of the reader into consideration, we have presented a bird's-eye view of the various micromachining operations and simulation studies as performed in the last decade. In the last few years, diamond turning operations have gained more importance and are particularly used for machining composite materials and superalloys. This paper gives an insight into these operations apart from providing an outlook for future growth and development of micromachining technology. 相似文献
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