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Статті в журналах з теми "Size reduction of materials – Computer simulation":
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Tang, L. Q., K. Pochiraju, C. Chassapis, and S. Manoochehri. "A Computer-Aided Optimization Approach for the Design of Injection Mold Cooling Systems." Journal of Mechanical Design 120, no. 2 (June 1, 1998): 165–74. http://dx.doi.org/10.1115/1.2826955.
Анотація:
A methodology is presented for the design of optimal cooling systems for injection mold tooling which models the mold cooling as a nonlinear constrained optimization problem. The design constraints and objective function are evaluated using Finite Element Analysis (FEA). The objective function for the constrained optimization problem is stated as minimization of both a function related to part average temperature and temperature gradients throughout the polymeric part. The goal of this minimization problem is to achieve reduction of undesired defects as sink marks, differential shrinkage, thermal residual stress built-up, and part warpage primarily due to non-uniform temperature distribution in the part. The cooling channel size, locations, and coolant flow rate are chosen as the design variables. The constrained optimal design problem is solved using Powell’s conjugate direction method using penalty function. The cooling cycle time and temperature gradients are evaluated using transient heat conduction simulation. A matrix-free algorithm of the Galerkin Finite Element Method (FEM) with the Jacobi Conjugate Gradient (JCG) scheme is utilized to perform the cooling simulation. The optimal design methodology is illustrated using a case study.
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Mauromicale, Giuseppe, Alessandro Sitta, Michele Calabretta, Salvatore Massimo Oliveri, and Gaetano Sequenzia. "Integrated Electromagnetic-Thermal Approach to Simulate a GaN-Based Monolithic Half-Bridge for Automotive DC-DC Converter." Applied Sciences 11, no. 18 (September 7, 2021): 8302. http://dx.doi.org/10.3390/app11188302.
Анотація:
New technological and packaging solutions are more and more being employed for power semiconductor switches in an automotive environment, especially the SiC- and GaN-based ones. In this framework, new front-end and back-end solutions have been developed, and many more are in the design stage. New and more integrated power devices are useful to guarantee the performances in electric vehicles, in terms of thermal management, size reduction, and low power losses. In this paper, a GaN-based system in package solution is simulated to assess the structure temperature submitted to a Joule heating power loss. The monolithic package solution involves a half-bridge topology, as well as a driver logic. A novel integrated electromagnetic and thermal method, based on finite element simulations, is proposed in this work. More specifically, dynamic electric power losses of the copper interconnections are computed in the first simulation stage, by an electromagnetic model. In the second stage, the obtained losses’ geometrical map is imported in the finite element thermal simulation, and it is considered as the input. Hence, the temperature distribution of the package’s copper traces is computed. The simulation model verifies the proper design of copper traces. The obtained temperature swing avoids any thermal-related reliability bottleneck.
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Masoud, Ziyad N., Ali H. Nayfeh, and Nader A. Nayfeh. "Sway Reduction on Quay-side Container Cranes Using Delayed Feedback Controller: Simulations and Experiments." Journal of Vibration and Control 11, no. 8 (August 2005): 1103–22. http://dx.doi.org/10.1177/1077546305056300.
Анотація:
Traditionally, a container crane is modeled as a simple pendulum with either a flexible or a rigid hoisting cable, and a lumped mass at the end of the cable. However, in the case of quay-side container cranes, the actual configuration of the hoisting mechanism is significantly different; it consists typically of a set of four hoisting cables. The cables are hoisted from four different points on a trolley and are attached on the load side to four points on a spreader bar used to lift containers. A controller design based on the actual model will most likely result in a response superior to those based on simple pendulum models. In this paper, we develop a mathematical model of the actual quay-side container crane. A simplified model is then used to obtain the gain and time delay for a delayed feedback controller, which will be used for the control of payload sway oscillation. Performance of the controller is simulated on a 1/10th scale computer model of a 65 ton container crane using the full model. Simulation results are verified experimentally on a 1/10th scale model of the same container crane.
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Andreotti, Mirco, Dario Bottino-Leone, Marta Calzolari, Pietromaria Davoli, Luisa Dias Pereira, Elena Lucchi, and Alexandra Troi. "Applied Research of the Hygrothermal Behaviour of an Internally Insulated Historic Wall without Vapour Barrier: In Situ Measurements and Dynamic Simulations." Energies 13, no. 13 (July 1, 2020): 3362. http://dx.doi.org/10.3390/en13133362.
Анотація:
The hygrothermal behaviour of an internally insulated historic wall is still hard to predict, mainly because the physical characteristics of the materials composing the historic wall are unknown. In this study, the hygrothermal assessment of an internally thermal insulated masonry wall of an historic palace located in Ferrara, in Italy, is shown. In situ non-destructive monitoring method is combined with a hygrothermal simulation tool, aiming to better analyse and discuss future refurbishment scenarios. In this context, the original U-value of the wall (not refurbished) is decreased from 1.44 W/m2K to 0.26 W/m2K (10 cm stone wool). Under the site specific conditions of this wall, not reached by the sun or rain, it was verified that even in the absence of vapour barrier, no frost damage is likely to occur and the condensation risk is very limited. Authors proposed further discussion based on simulation. The results showed that the introduction of a second gypsum board to the studied technology compensated such absence, while the reduction of the insulation material thickness provides a reduction of RH peaks in the interstitial area by 1%; this second solution proved to be more efficient, providing a 3% RH reduction and the avoidance of further thermal losses.
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Popov, Oleg, Irina Talovina, Holger Lieberwirth, and Asiia Duriagina. "Quantitative Microstructural Analysis and X-ray Computed Tomography of Ores and Rocks—Comparison of Results." Minerals 10, no. 2 (January 31, 2020): 129. http://dx.doi.org/10.3390/min10020129.
Анотація:
Profound knowledge of the structure and texture of rocks and ores as well as the behavior of the materials under external loads is essential to further improvements in size reduction processes, particularly in terms of liberation size. New analytical methods such as computer tomography (CT) were adopted to improve the understanding of material characteristics in rocks and ores relevant to mineral processing, particular the crushing and grinding and the modelling/simulation thereof. Results obtained on the texture and structure of identical samples of rather different rocks and ores (copper ore, granodiorite, kimberlite) are compared by CT with quantitative results from traditional optical microscopy obtained by quantitative microstructural analysis (QMA). While the two approaches show a good agreement of the results in many areas, the measurements with the two different methods also exhibit remarkable differences in other areas, which are discussed further. In conclusion, both methods have their specific advantages starting from sample preparation to the accuracy of information obtained concerning certain parameters of mode and fabric. While sample preparation is faster with CT and information on special distribution of metal minerals is more reliable, the information on mode, grain size and clustering seem to be more precise with QMA. Based on the results, it can be concluded that both methods are comparable in many areas, but in in the field of spatial distribution, they are merely complementary.
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Zhang, Shang, Seyedmehdi Karimi, Shahaboddin Shamshirband, and Amir Mosavi. "Optimization Algorithm for Reduction the Size of Dixon Resultant Matrix: A Case Study on Mechanical Application." Computers, Materials & Continua 58, no. 2 (2019): 567–83. http://dx.doi.org/10.32604/cmc.2019.02795.
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Nguyen, L. T., S. A. Gee, and W. F. v. d. Bogert. "Effects of Configuration on Plastic Package Stresses." Journal of Electronic Packaging 113, no. 4 (December 1, 1991): 397–404. http://dx.doi.org/10.1115/1.2905426.
Анотація:
This paper examines the effects of device and leadframe configurations on the stresses encountered in typical Dual-in-Line plastic packages. The parameters studied include the die size, the die pad size, the location of the die with respect to the die pad center, and the die coating configuration. Special piezoresistive strain gages deposited on dies of varying sizes are used to map the stress profile across the die surfaces after molding. Finite element simulation of these effects is also conducted. Results indicate that the compressive stresses from the molding compounds are governed with diminishing influence by the size of the die. Furthermore, rather high compressive stresses are observed in the vicinity of the edges of large dies. More subtle effects are found for the influence of the die pad size, the aspect ratio of the die, and the extent of the die offsetting with respect to the die pad center. Finally, by surrounding the die with a thin trail of silicone gel to provide for lateral cushioning, stress reduction is slightly more effective than in the standard “glob-top” coating.
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Grujicic, M., R. Yavari, J. S. Snipes, and S. Ramaswami. "Design optimization of a mine-blast-venting solution for protection of light-tactical-vehicle subjected to shallow-buried underbody mine detonation." Multidiscipline Modeling in Materials and Structures 12, no. 1 (June 13, 2016): 2–32. http://dx.doi.org/10.1108/mmms-11-2014-0058.
Анотація:
Purpose – The purpose of this paper is computer-aided engineering analysis of the recently proposed side-vent-channel concept for mitigation of the blast-loads resulting from a shallow-buried mine detonated underneath a light tactical vehicle. The concept involves the use of side-vent-channels attached to the V-shaped vehicle underbody, and was motivated by the concepts and principles of operation of the so-called “pulse detonation” rocket engines. By proper shaping of the V-hull and side-vent-channels, venting of supersonically expanding gaseous detonation products is promoted in order to generate a downward thrust on the targeted vehicle. Design/methodology/approach – The utility and the blast-mitigation capacity of this concept were examined in the prior work using computational methods and tools which suffered from some deficiencies related to the proper representation of the mine, soil, and vehicle materials, as well as air/gaseous detonation products. In the present work, an attempt is made to remove some of these deficiencies, and to carry out a bi-objective engineering-optimization analysis of the V-hull and side-vent-channel shape and size for maximum reduction of the momentum transferred to and the maximum acceleration acquired by the targeted vehicle. Findings – Due to the conflicting nature of the two objectives, a set of the Pareto designs was identified, which provide the optimal levels of the trade-off between the two objectives. Originality/value – To the authors’ knowledge, the present work is the first public-domain report of the side-vent-channel blast-mitigation concept.
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Lluesma-Rodríguez, Federico, Temoatzin González, and Sergio Hoyas. "CFD Simulation of a Hyperloop Capsule Inside a Low-Pressure Environment Using an Aerodynamic Compressor as Propulsion and Drag Reduction Method." Applied Sciences 11, no. 9 (April 27, 2021): 3934. http://dx.doi.org/10.3390/app11093934.
Анотація:
One of the most restrictive conditions in ground transportation at high speeds is aerodynamic drag. This is even more problematic when running inside a tunnel, where compressible phenomena such as wave propagation, shock waves, or flow blocking can happen. Considering Evacuated-Tube Trains (ETTs) or hyperloops, these effects appear during the whole route, as they always operate in a closed environment. Then, one of the concerns is the size of the tunnel, as it directly affects the cost of the infrastructure. When the tube size decreases with a constant section of the vehicle, the power consumption increases exponentially, as the Kantrowitz limit is surpassed. This can be mitigated when adding a compressor to the vehicle as a means of propulsion. The turbomachinery increases the pressure of part of the air faced by the vehicle, thus delaying the critical conditions on surrounding flow. With tunnels using a blockage ratio of 0.5 or higher, the reported reduction in the power consumption is 70%. Additionally, the induced pressure in front of the capsule became a negligible effect. The analysis of the flow shows that the compressor can remove the shock waves downstream and thus allows operation above the Kantrowitz limit. Actually, for a vehicle speed of 700 km/h, the case without a compressor reaches critical conditions at a blockage ratio of 0.18, which is a tunnel even smaller than those used for High-Speed Rails (0.23). When aerodynamic propulsion is used, sonic Mach numbers are reached above a blockage ratio of 0.5. A direct effect is that cases with turbomachinery can operate in tunnels with blockage ratios even 2.8 times higher than the non-compressor cases, enabling a considerable reduction in the size of the tunnel without affecting the performance. This work, after conducting bibliographic research, presents the geometry, mesh, and setup. Later, results for the flow without compressor are shown. Finally, it is discussed how the addition of the compressor improves the flow behavior and power consumption of the case.
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Bottarelli, Michele, and Francisco Javier González Gallero. "Energy Analysis of a Dual-Source Heat Pump Coupled with Phase Change Materials." Energies 13, no. 11 (June 8, 2020): 2933. http://dx.doi.org/10.3390/en13112933.
Анотація:
Installation costs of ground heat exchangers (GHEs) make the technology based on ground-coupled heat pumps (GCHPs) less competitive than air source heat pumps for space heating and cooling in mild climates. A smart solution is the dual source heat pump (DSHP) which switches between the air and ground to reduce frosting issues and save the system against extreme temperatures affecting air-mode. This work analyses the coupling of DSHP with a flat-panel (FP) horizontal GHE (HGHE) and a mixture of sand and phase change materials (PCMs). From numerical simulations and considering the energy demand of a real building in Northern Italy, different combinations of heat pumps (HPs) and trench backfill material were compared. The results show that PCMs always improve the performance of the systems, allowing a further reduction of the size of the geothermal facility. Annual average heat flux at FP is four times higher when coupled with the DSHP system, due to the lower exploitation. Furthermore, the enhanced dual systems are able to perform well during extreme weather conditions for which a sole air source heat pump (ASHP) system would be unable either to work or perform efficiently. Thus, the DSHP and HGHE with PCMs are robust and resilient alternatives for air conditioning.
Дисертації з теми "Size reduction of materials – Computer simulation":
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Sridhar, H. K. "Influence of Lot Sizing on Lead Time Error Costs in M.R.P. Systems- a Computer Simulation Study." Thesis, Indian Institute of Science, 1988. http://hdl.handle.net/2005/85.
Анотація:
Timing of ordering of inventory items is of very great importance in Materials Requirement Planning. Uncertainties in timing can have an adverse effect on the system performance. Most often the lead time variation contribute to timing uncertainties; and their effects are reflected in added costs.
Lead time error effects are investigated in this thesis. The study attempts to estimate the effects through some relevant costs, and their variations across the lot sizing rules.
The hypotheses for this study are 1) Between any two lot sizing rules, there will be a significant difference in error coats due to combined effect of purchased lead time error and manufacturing lead time errors; 2) Relative cost performance of lot sizing rules in MRP is influenced by the lead time errors; 3) There will be a difference in error cost between lot for l o t rule and least total cost rule even with single source of lead time variation.
To carry out the study a MRP programme was developed, in FORTRAN 77 with provisions to include the lot sizing rules while exploding the structure. The lot sizing rules used in the study are Lot for Lot, Silver and Meal heuristics, Wagner-Whitin algorithm, Least total cost, Least unit cost and Part Period balancing.
A simulation model is developed using GPSS/PC, to test the hypotheses. An hypothetical production situation with three end items, each with a different product structure is designed. In addition, a master production schedule and a job shop are also structured. Appropriate distributions are assumed for both manufacturing lead times and purchase lead times. These provide the stochastic variables in the simulation experiments.
A series of experiments were carried out with the model to investigate into the variations of costs amongst lot sizing rules. Results of the simulation experiments prove that there are costs associated with lead time errors in MRP. These error costs vary significantly with different lot sizing rules.
It is also found that the resultant error costs vary significantly even with a single source of lead time variation. Least unit cost rule gives the beat performance having least error costs. Lot for Lot rule has shown the worst performance amongst the lot sizing rules considered. Other interesting results have emerged out of the study.
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Thage, Rorisang Gomolemo. "A theoretical analysis of the implications of comminution practices on open pit mine planning." Diss., 2020. http://hdl.handle.net/10500/27517.
Анотація:
The implications of comminution practices on the planning of a typical open pit mine was investigated in this study by means of computer simulation. The objective was to assess the effects of mining costs as well as processing costs on the production plan of a typical open pit mine.
For the purpose of the research, MineLib, an open library of ore body models was consulted. This led to the selection of a copper-gold ore body named “Newman1” for use in the strategic mine optimisation. Various scenarios were considered in order to highlight the contribution of comminution costs to the mine plan. In all the simulated scenarios, the objective function was to maximise the Net Present Value (NPV). And in terms of simulation setup, the comminution costs and cut-off grades were systematically varied from 70 % to 140 %. It was hence possible to investigate their effects on the NPV of the Newman1 ore body using SimSched, a freeware for mine optimisation and planning.
Results showed that there is a great opportunity to increase the NPV of the Newman1 block model by adjusting the contribution of processing costs in general and comminution costs in particular. This can be achieved for instance by controlling the policy of cut-off grades, lowering production costs, and increasing throughput.Civil and Chemical Engineering
M. Tech. (Chemical Engineering)
Частини книг з теми "Size reduction of materials – Computer simulation":
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WEI, C., R. G. QIAN, S. LIN, and J. M. XIAO. "COMPUTER SIMULATION OF THE EFFECT OF GRAIN SIZE ON THE PROPERTIES OF POLYCRYSTALLINE SPECIMENS BY FINITE ELEMENT METHOD." In Mechanical Behaviour of Materials VI, 153–58. Elsevier, 1992. http://dx.doi.org/10.1016/b978-0-08-037890-9.50032-6.
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Hamidi, H., and K. Mohammadi. "Modeling Fault Tolerant and Secure Mobile Agent Execution in Distributed Systems." In Mobile Computing, 2739–51. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-054-7.ch207.
Анотація:
A mobile agent is a software program which migrates from a site to another site to perform tasks assigned by a user. For the mobile agent system to support agents in various application areas, the issues regarding reliable agent execution, as well as compatibility between two different agent systems or secure agent migration, have been considered. Some of the proposed schemes are either replicating the agents (Hamidi & Mohammadi, 2005) or check-pointing the agents (Park, Byun, Kim, & Yeom, 2002; Pleisch & Schiper, 2001;) For a single agent environment without considering inter-agent communication, the performance of the replication scheme and the check-pointing scheme is compared in Park et al. (2002) and Silva, Batista, and Silva (2000). In the area of mobile agents, only few works can be found relating to fault tolerance. Most of them refer to special agent systems or cover only some special aspects relating to mobile agents, such as the communication subsystem. Nevertheless, most people working with mobile agents consider fault tolerance to be an important issue (Izatt, Chan, & Brecht, 1999; Shiraishi, Enokido, & Takzawa, 2003). Mobile agents are becoming a major trend for designing distributed systems and applications in the last few years and foreseeable future. It can bring benefits such as reduced network load and overcoming of network latency (Chan, Won, & Lyu, 1993). Nevertheless, security is one of the limiting factors of the development of these systems. The main unsolved security problem lies in the possible existence of malicious hosts that can manipulate the execution and data of agents (Defago, Schiper, & Sergent, 1998). Most distributed applications we see today are deploying the client/server paradigm. There are certain problems with the client/server paradigm, such as the requirement of a high network bandwidth, and continuous user-computer interactivity. In view of the deficiencies of the client/server paradigm, the mobile code paradigm has been developed as an alternative approach for distributed application design. In the client/server paradigm, programs cannot move across different machines and must run on the machines they reside on. The mobile code paradigm, on the other hand, allows programs to be transferred among and executed on different computers. By allowing code to move between hosts, programs can interact on the same computer instead of over the network. Therefore, communication cost can be reduced. Besides, mobile agent (Fischer, Lynch, & Paterson, 1983) programs can be designed to work on behalf of users autonomously. This autonomy allows users to delegate their tasks to the mobile agents, and not to stay continuously in front of the computer terminal. The promises of the mobile code paradigm bring about active research in its realization. Most researchers, however, agree that security concerns are a hurdle (Greenberg, Byington, & Harper, 1998). In this article, we investigate these concerns. First, we review some of the foundation materials of the mobile code paradigm. We elaborate Ghezzi and Vigna’s classification of mobile code paradigms (Ghezzi & Vigna, 1997), which is a collection of the remote evaluation, code on demand, and mobile agent approaches. In the next section, we address the current status of mobile code security. The following section presents the model for fault-tolerant mobile agent. In the next section, security issues of the mobile agent are discussed, and we discuss security modeling and evaluation for the mobile agent in the section after. In the following section, simulation results and influence of the size of agent are discussed. We then conclude the article.
Тези доповідей конференцій з теми "Size reduction of materials – Computer simulation":
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Tamura, Masato, Masahiro Uchida, Emi Oono, Yoshiaki Matsuzawa, Takahiro Kozaki, and He Li. "Computationally Predicted Performance of Pulverised Coal Fired Boilers and Study of Ash Deposition Phenomenon." In ASME 2011 Power Conference collocated with JSME ICOPE 2011. ASMEDC, 2011. http://dx.doi.org/10.1115/power2011-55370.
Анотація:
Understanding of pulverised coal combustion performance including ash behaviour is very important to design optimum boiler furnaces. In the last decades, remarkable advance of computers and computational fluid dynamics (CFD) codes have been realised and plenty of numerical modelling has been applied. However total performance of pulverised coal fired boilers including burner geometries and ash deposition behaviours is still difficult to predict. There are the limitation of computer performance and unknown phenomenon of ash deposition. Therefore, the new method of modelling to perform the full size furnace simulation has been developed to materialise both reduction of calculation load and improvement in prediction accuracy. It is confirmed that this new technique can express the difference between varied burner conditions. Detailed coal ash deposition behaviours and heat absorption rate are currently unknown and were measured and analysed experimentally by using the horizontal cylindrical furnace with water cooled probes. The experiments gave the better understandings of ash deposition and inhibition of heat absorption and heat absorption model is proposed. Boiler furnace heat absorption with ash deposition will be calculated and ash deposition behaviour will be modelled.
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Med, Michael, and Andreas Krall. "Instruction Set Encoding Optimization for Code Size Reduction." In 2007 International Conference on Embedded Computer Systems: Architectures, Modeling and Simulation. IEEE, 2007. http://dx.doi.org/10.1109/icsamos.2007.4285728.
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Nijhawan, Sunil, and YongMann Song. "Simulation of Severe Accident Progression Using ROSHNI: A New Integrated Simulation Code for PHWR Severe Accidents." In 2020 International Conference on Nuclear Engineering collocated with the ASME 2020 Power Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/icone2020-16633.
Анотація:
Abstract As analysts still grapple with understanding core damage accident progression at Three Mile Island and Fukushima that caught the nuclear industry off-guard once too many times, one notices the very limited detail with which the large reactor cores of these subject reactors have been modelled in their severe accident simulation code packages. At the same time, modelling of CANDU severe accidents have largely borrowed from and suffered from the limitations of the same LWR codes (see IAEA TECDOC 1727) whose applications to PHWRs have poorly caught critical PHWR design specifics and vulnerabilities. As a result, accident management measures that have been instituted at CANDU PHWRs, while meeting the important industry objective of publically seeming to be doing something about lessons learnt from say Fukushima and showing that the reactor designs are oh so close to perfect and the off-site consequences of severe accidents happily benign. Integrated PHWR severe accident progression and consequence assessment code ROSHNI can make a significant contribution to actual, practical understanding of severe accident progression in CANDU PHWRs, improving significantly on the other PHWR specific computer codes developed three decades ago when modeling decisions were constrained by limited computing power and poor understanding of and interest in severe core damage accidents. These codes force gross simplifications in reactor core modelling and do not adequately represent all the right CANDU core details, materials, fluids, vessels or phenomena. But they produce results that are familiar and palatable. They do, however to their credit, also excel in their computational speed, largely because they model and compute so little and with such un-necessary simplifications. ROSHNI sheds most previous modelling simplifications and represents each of the 380 channels, 4560 bundle, 37 elements in four concentric ring, Zircaloy clad fuel geometry, materials and fluids more faithfully in a 2000 MW(Th) CANDU6 reactor. It can be used easily for other PHWRs with different number of fuel channels and bundles per each channel. Each of horizontal PHWR reactor channels with all their bundles, fuel rings, sheaths, appendages, end fittings and feeders are modelled and in detail that reflects large across core differences. While other codes model at best a few hundred core fuel entities, thermo-chemical transient behaviour of about 73,000 different fuel channel entities within the core is considered by ROSHNI simultaneously along with other 15,000 or so other flow path segments. At each location all known thermo-chemical and hydraulic phenomena are computed. With such detail, ROSHNI is able to provide information on their progressive and parallel thermo-chemical contribution to accident progression and a more realistic fission product release source term that would belie the miniscule one (100 TBq of Cs-137 or 0.15% of core inventory) used by EMOs now in Canada on recommendation of our national regulator CNSC. ROSHNI has an advanced, more CANDU specific consideration of each bundle transitioning to a solid debris behaviour in the Calandria vessel without reverting to a simplified molten corium formulation that happily ignores interaction of debris with vessel welds, further vessel failures and energetic interactions. The code is able to follow behaviour of each fuel bundle following its disassembly from the fuel channel and thus demonstrate that the gross assumption of a core collapse made in some analyses is wrong and misleading. It is able to thus demonstrate that PHWR core disassembly is not only gradual, it will be also be incomplete with a large number of low power, peripheral fuel channels never disassembling under most credible scenarios. The code is designed to grow into and use its voluminous results in a severe accident simulator for operator training. It’s phenomenological models are able to examine design inadequacies / issues that affect accident progression and several simple to implement design improvements that have a profound effect on results. For example, an early pressure boundary failure due to inadequacy of heat sinks in a station blackout scenario can be examined along with the effect of improved and adequate over pressure protection. A best effort code such as ROSHNI can be instrumental in identifying the risk reduction benefits of undertaking certain design, operational and accidental management improvements for PHWRs, with some of the multi-unit ones handicapped by poor pressurizer placement and leaky containments with vulnerable materials, poor overpressure protection, ad-hoc mitigation measures and limited instrumentation common to all CANDUs. Case in point is the PSA supported design and installed number of Hydrogen recombiners that are neither for the right gas (designed mysteriously for H2 instead of D2) or its potential release quantity (they are sparse and will cause explosions). The paper presents ROSHNI results of simulations of a postulated station blackout scenario and sheds a light on the challenges ahead in minimizing risk from operation of these otherwise unique power reactors.
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Mauder, Tomas, Lubomir Klimes, Pavel Charvat, and Josef Stetina. "Robustness Analysis of Various Approaches to Modeling of the Phase Change Front Propagation." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-71372.
Анотація:
Latent heat thermal energy storage (LHTES) has recently evolved into a promising approach for energy savings and pollution reduction. Phase change materials (PCMs) and the latent heat accompanying the phase change can be utilized to accumulate, store, are release the thermal energy when needed. The latent heat of the phase change allows for a storage of a relatively large amount of heat in a narrow temperature interval. The solid-liquid phase transition is widely utilized in such LHTES applications. Computer simulation tools are usually applied in the optimal design and real-time control of LHTES devices as the simulations are fast, relatively easy to perform and not expensive. Different numerical methods exist for modeling of heat transfer problems with phase changes. The methods can be assessed in several ways — accuracy, mathematical and programming complexity, demands for computational time and hardware, robustness etc. The well-known enthalpy method, the effective heat capacity method and the temperature recovery method are widely utilized as they are simple and easy to implement. These so-called domain or front capturing methods suffer from a low accuracy in the vicinity of the phase interface and they are quite sensitive to the size of the time step. On the other hand, front tracking methods allow for very precise results near the phase interface, but they are more complex and computationally quite demanding. An important point is also the sensitivity and robustness of a method in relation to the thermal conditions and properties. In particular, the large heat flux at the boundary and the high thermal conductivity often cause numerical difficulties and instabilities. In practice, computer models have to be precise enough and sufficiently fast, especially in real-time applications. However, these two objectives are related in an opposite direction. The paper presents a robustness and sensitivity analysis of the above mentioned methods. The responses and numerical behavior of the methods are investigated and analyzed. The test problems with distinct grid spacing, sizes of time steps and thermophysical properties of phase change materials. The results show that the front tracking method can achieve higher accuracy for coarse mesh sizes than other tested methods. This characteristic compensates for higher computational demands of the front tracking method.
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Guan, Linyu, Bo Jiao, Chengdong Huang, Bo Li, Fei Huang, and Yinglong Liu. "Network simulation and evaluation for the size reduction of a given topology." In 2016 5th International Conference on Computer Science and Network Technology (ICCSNT). IEEE, 2016. http://dx.doi.org/10.1109/iccsnt.2016.8070202.
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An, Jian, and A. H. Soni. "A Critical Review of Tube and Sheet Metal Hydroforming Technology." In ASME 1996 Design Engineering Technical Conferences and Computers in Engineering Conference. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-detc/fas-1368.
Анотація:
Abstract The hydroforming technology, which is rapidly gaining popularity in the sheet metal and tube forming industry is reviewed. The features and the characteristics of the hydroforming process are described. The uniformly distributed fluid pressure covers the back side of the sheet as a die generates many advantages in the technical point of view as improving the part surface quality, reducing the forming severity and smoothing the thickness distribution. The benefits of using hydroforming technology are examined and analyzed in a technical level. The better part quality, less cost of tooling, materials saving and part weight reduction can be achieved using the hydroforming technology. The design methodologies for the hydroforming process parameters are reviewed and discussed in a certain detail. Computer-aided-engineering such as finite element simulation is suggested for such process parameter design.
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Melanz, Dan, Martin Tupy, Bryce Smith, Kevin Turner, and Dan Negrut. "On the Validation of a Differential Variational Inequality Approach for the Dynamics of Granular Material." In ASME 2010 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/detc2010-28804.
Анотація:
The validation of a DVI approach for the dynamics of granular material focuses on comparing the experimental and simulation results of granular flow for two tests in the Chrono::Engine simulation environment. A macro scale validation was previously carried out through examination of granular flow in PBR reactors [1]. For this work, an aluminum rig was designed and fabricated to measure the flow rate of a given amount of micro scale granular material flowing due to gravity through a slit. The flow was initiated by using a Newport UMR8.25 translational stage and Newport LTA-HL precision linear actuator to open and close the slit steadily. Once the slit was open, the weight of the granular material was transmitted to the processor via a router connected to a Cooper LFS242 Tension/Compression Cell (Serial No. 286284) and graphed over time. A model of the flow meter was created in Chrono::Engine and the results were matched to experimental runs by changing the friction coefficient between particles. After the friction coefficient of the particles was determined to be 0.15, several experimental runs with differing slit sizes were run. These flow rates were compared to the weight versus time data that Chrono::Engine output for the corresponding slit size. Runs for gap sizes of 1.5mm, 2.0mm, 2.5mm and 3.0mm were performed with 0.0624 N of granular material, which amounted to approximately 39,000 spheres with 500μm in diameter. These gap sizes corresponded to an experimental flow rate of 1.41E-2 N/s, 2.59E-2 N/s, 4.00E-2 N/s, and 4.44E-2 N/s, and a simulated flow rate of 1.40E-2 N/s, 2.62E-2 N/s, 4.05E-2 N/s, and 4.48E-2 N/s, respectively. Based on this experiment, Chrono::Engine had less than a 2% error in calculating the flow rate of the granular material through a slit. In addition to comparing flow rates, the pile repose angle from the experimental runs was compared to the simulation results. A description of the GPU execution model along with its memory spaces is provided to illustrate its potential for parallel scientific computing. The equations of motion associated with the dynamics of many rigid bodies are introduced and a solution method is presented. The solution method is designed to map well on the parallel hardware, which is demonstrated by an order of magnitude reductions in simulation time for large systems that concern the dynamics of granular material.
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Enright, Michael P., R. Craig McClung, James C. Sobotka, Jonathan P. Moody, John McFarland, Yi-Der Lee, Irving Gray, and Joe Gray. "Influences of Non-Destructive Inspection Simulation on Fracture Risk Assessment of Additively Manufactured Turbine Engine Components." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-77058.
Анотація:
Additive manufacturing processes produce components that may introduce material anomalies at any location within a component. NDE inspection can be used to find and remove anomalies that could grow to failure during the service life, but two key inputs are required for an effective inspection: (1) the critical locations to search for anomalies, and (2) the minimum sizes of the anomalies that must be found. A new methodology is presented for probabilistic damage tolerance assessment of additively manufactured components. It consists of a new link between the DARWIN® probabilistic damage tolerance software and the XRSim X-ray NDE simulation software. DARWIN computes fracture risk and critical initial crack sizes throughout a component, providing the two key inputs that are necessary for effective NDE inspections. XRSim computes location-specific POD curves everywhere in a component, providing the key information needed to assess the influence of inspection on fracture risk reduction. The methodology is illustrated for a representative gas turbine engine component manufactured via the direct metal laser sintering process. The results can be used to optimize the effectiveness of NDE inspection of additively manufactured components.
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Zhang, Jenmy Zimi, Conner Sharpe, and Carolyn Conner Seepersad. "Stress-Constrained Design of Functionally Graded Lattice Structures With Spline-Based Dimensionality Reduction." In ASME 2019 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/detc2019-97905.
Анотація:
Abstract This paper presents a computationally tractable approach for designing lattice structures for stiffness and strength. Yielding in the mesostructure is determined by a worst-case stress analysis of the homogenization simulation data. This provides a physically meaningful, generalizable, and conservative way to estimate structural failure in three-dimensional functionally graded lattice structures composed of any unit cell architectures. Computational efficiency of the design framework is ensured by developing surrogate models for the unit cell stiffness and strength as a function of density. The surrogate models are then used in the coarse-scale analysis and synthesis. The proposed methodology further uses a compact representation of the material distribution via B-splines, which reduces the size of the design parameter space while ensuring a smooth density variation that is desirable for manufacturing. The proposed method is demonstrated in compliance minimization studies using two types of unit cells with distinct mechanical properties. The effects of B-spline mesh refinement and the presence of a stress constraint on the optimization results are also investigated.
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Kumano, Yutaka, Tetsuyoshi Ogura, and Toru Yamada. "High Accuracy Thermal Analysis Methodology for Semiconductor Junction Temperatures Considering Line Patterns of Multilayered Circuit Boards." In ASME 2007 InterPACK Conference collocated with the ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ipack2007-33372.
Анотація:
As multilayered circuit boards in which semiconductors are embedded have been well reported, thermal management is becoming quite an important issue. In order to predict the junction temperature of an embedded semiconductor precisely, it is necessary that line patterns should be taken into consideration for thermal fluid analysis. However modeling all the patterns correctly is unacceptable because of far too long calculation time. Thus only the ratio of a pattern area to a gross board area was considered, which caused up to 30% calculation error compared to the experimental results. We have developed a novel method to predict semiconductor junction temperatures precisely without modeling patterns themselves. Firstly boards are divided into multiple regions in order to express how much dense or coarse the patterns are. Since the size of each region is much larger than L/S (line and space) specification of the boards, the number of meshes for calculation does not increase explosively and the simulation can be finished within appropriate time. Secondly equivalent anisotropic thermal conductivity of each region is assigned as follows. All the regions are once divided into smaller subregions whose sizes are approximately L/S specification. Then thermal conductivity of each subregion is defined by the property of the material at the centered subregion. After that a thermal network composed of all the subregions is generated and anisotropic thermal conductivities of each divided region are computed by solving this thermal network matrix. This procedure should be executed in an electrical CAD (E-CAD) where line pattern data are stored. A new interface format using which we can transfer board data from E-CAD to thermal fluid simulator was prepared. This format can have not only layouts and sizes but also anisotropic thermal conductivities of all divided regions. There is no need either to prepare model geometries or to input attributes of a great number of divided regions on thermal fluid simulator. By way of this format, analytical models are imported in thermal fluid simulator and semiconductor junction temperatures are computed. It was confirmed that semiconductor junction temperatures calculated by this method were precisely coincident with the experimental results. We can predict semiconductor temperatures without making preproduction samples. This analysis methodology will highly contribute to the reduction of designing time and cost.