• Journal of information and communication convergence engineering
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• 제21권4호
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• pp.261-267
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• 2023

Public research, which requires large computational resources, utilizes the supercomputers of the National Supercomputing Center in the Republic of Korea. The average utilization rate of resources over the past three years reached 80%. Therefore, to ensure the operational stability of this national infrastructure, specialized centers have been established to distribute the computational demand concentrated in the national centers. It is necessary to predict the computational demand accurately to build an appropriate resource scale. Therefore, it is important to estimate the inflow and outflow of computational demand between the national and specialized centers to size the resources required to construct specialized centers. We conducted a logit model analysis using the probabilistic utility theory to derive the preferences of individual users for future supercomputer resources. This analysis shows that the computational demand share of specialized centers is 59.5%, which exceeds the resource utilization plan of existing specialized centers.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2013년도 제46회 KOSCO SYMPOSIUM 초록집
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• pp.91-94
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• 2013

Commercial computational fluid dynamics (CFD) codes traditionally rely on the computational efficiency of the simplified single-film apparent char kinetic model to predict char particle temperatures and char conversion rates in pulverized coal boilers. The aim of this study is to evaluate the reliability of the single-film apparent kinetic model and to suggest the importance of proper use of this model. For this, a parametric study was conducted with a consideration of main parameters such as Stefan flow, product species, particle evolution, and kinetic parameters.

• Journal of Mechanical Science and Technology
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• 제18권5호
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• pp.865-876
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• 2004

A new concept of reduced quasi-dimensional combustion model for a direct injection diesel engine is developed based on the previously developed quasi-dimensional multi-zone model to improve the computational efficiency. In the reduced model, spray penetration and air entrainment are calculated for a number of zones within the spray while three zones with aggregated spray zone concept are used for the calculation of spray combustion and emission formation processes. It is also assumed that liquid phase fuel appears only near the nozzle exit during the breakup period and that spray vaporization is immediate in order to reduce the computational time. Validation of the reduced model with experimental data demonstrated that the new model can predict engine performance and NO and soot emissions reasonably well compared to the original model. With the new concept of reduced model, computational efficiency is significantly improved as much as 200 times compared to the original model.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.760-765
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• 2000

The study deals with the development of a computational procedure for evaluating the temperature rise in dry and lubricated multi-layered contacts of head/disk interface. A transient computational model with a transformed rectangular computational domain is utilized. A model and a computational method for micro-contact with sub-lubricated zone, including friction heat generation, have been presented. The model was applied, taking full account of the changes in contact area and contact load due to frictional heating. The computational distribution of temperature is obtained with the analytical findings for various composition and contact conditions. Especially, a rapid rise ($220^{\circ}C$ or above) in read head temperature lese to a saturation in the influence of a thermal spike on signal performance. This general class of problems can be treated provided that heat generation distribution and layer properties are known.

• Nuclear Engineering and Technology
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• 제43권6호
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• pp.547-556
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• 2011

Two computational methods for determining equilibrium states for the Mark-IV electrorefiner (ER) have been assessed to improve the current computational electrorefiner model developed at University of Idaho. Both methods were validated against measured data to better understand their effects on the calculation of the equilibrium compositions in the ER. In addition, a sensitivity study was performed on the effect of specific unknown activity coefficients-including sodium in molten cadmium, zirconium in molten cadmium, and sodium chloride in molten LiCl-KCl. Both computational methods produced identical results, which stayed within the 95% confidence interval of the experimental data. Furthermore, sensitivity to unavailable activity coefficients was found to be low (a change in concentration of less than 3 ppm).

• 인터넷정보학회논문지
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• 제20권3호
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• pp.93-100
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• 2019

The interest in the Fourth Industrial Revolution along with the development of ICT makes the software get the attention of the world. This phenomenon naturally leads to the concern for software education. Learning software coding is not easy for students whose major is in humanities or social sciences. This paper is a study of how cognition on software education affects to education of computational thinking. For research method, moderator variables were adopted on the proposed research model to prove that positive cognition can derive good influence on improvement of computational thinking. To find out moderator variables of the research model, we have conducted the questionnaire over three years for total of 928 students who took the software coding courses. As the result of the study, we proved that the positive cognition on software education can make the better improvement of computational thinking within proper moderator variables.

• 한국정보통신학회논문지
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• 제15권7호
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• pp.1598-1603
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• 2011

본 논문에서는 컴퓨터 픽업 모델에 대한 개선 방법을 제안한다. 기존의 컴퓨터 픽업은 레이 추적 모델에 입각한 핀홀 모델 방법을 사용한다. 비록 기존 방법이 매우 유용한 방법이지만 원거리에 위치한 물체를 픽업시 화질 열화가 발생한다. 이 문제를 해결하기 위해서 본 논문에서는 보다 정교한 픽업 방법을 제안한다. 제안된 픽업 모델은 실제 센서가 화소를 만들 때 입사하는 레이들을 누적하는 과정을 첨가함으로써 얻어지고, 구조적으로 에이리어싱 현상에 더 강인하다. 제안된 방법을 입증하기 위해서 컴퓨터 실험을 진행했고 그 결과는 제안된 방법이 기존 방법보다 우수함을 입증했다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.347-349
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• 2014

Model verification and validation (V&V) is a current research topic to build computational models with high predictive capability by addressing the general concepts, processes and statistical techniques. The hypothesis test for validity check is one of the model validation techniques and gives a guideline to evaluate the validity of a computational model when limited experimental data only exist due to restricted test resources (e.g., time and budget). The hypothesis test for validity check mainly employ Type I error, the risk of rejecting the valid computational model, for the validity evaluation since quantification of Type II error is not feasible for model validation. However, Type II error, the risk of accepting invalid computational model, should be importantly considered for an engineered products having high risk on predicted results. This paper proposes a technique named as the response-adaptive experimental design to reduce Type II error by adaptively designing experimental conditions for the validation experiment. A tire tread block problem and a numerical example are employed to show the effectiveness of the response-adaptive experimental design for the validity evaluation.

• ETRI Journal
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• 제28권4호
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• pp.521-524
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• 2006

In this letter, we propose a novel computational integral imaging reconstruction technique based on a lenslet array model. The proposed technique provides improvement of viewing images by extracting multiple pixels from elemental images according to ray tracing based on the lenslet array model. To show the feasibility of the proposed technique, we analyze it according to ray optics and present the experimental results.

• Journal of Ship and Ocean Technology
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• 제11권4호
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• pp.55-71
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• 2007

The primary objective of this work is to develop methodologies for virtual model basin and to demonstrate the capabilities for generic multi-hull ship geometry. A computational fluid dynamics approach is used to simulate various model basin tests for steady resistance, maneuvering and seakeeping. For a catamaran hull configuration, the methodologies are used for solving these problems and the results are discussed. Computational results are compared with the results of a benchmarked potential flow theory method for calm water resistance.