• Title, Summary, Keyword: computational model

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Analysis for the Stability of a Haptic System with the Computational Time-varying Delay (가변적인 계산시간지연에 의한 햅틱 시스템에서의 안정성 영향 분석)

  • Lee, Kyungno
    • Journal of Institute of Convergence Technology
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    • v.5 no.2
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    • pp.37-42
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    • 2015
  • This paper presents the effects of the computational time-varying delay on the stability of the haptic system that includes a virtual wall and a first-order-hold method. The model of a haptic system includes a haptic device model with a mass and a damper, a virtual wall model, a first-order-hold model and a computational time-varying delay model. In this paper, the maximum of the computational time-varying delay is assumed to be as much as the sampling time. Using the simulation, it is analyzed how the sample-hold methods and the computational time-varying delay affect the maximum available stiffness. As the maximum of computational time-varying delay increases, the maximal available stiffness of a virtual wall model is reduced.

Comparison of Vibration Characteristics of a Multi-leaf Spring and a Tapered Leaf Spring of a Heavy Truck (대형트럭 다판 스프링과 테이퍼 판스프링의 진동특성 비교)

  • Oh Chae-Youn;Moon Il-Dong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.2
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    • pp.270-276
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    • 2005
  • This paper develops the flexible computational model of a heavy truck by interfacing the frame modeled as a flexible body to the heavy truck's computational model composed of rigid bodies. The frame is modeled by the finite element method. Three torsional modes and three bending modes of the frame are considered for the interface of the heavy truck's computational model. The actual vehicle test is conducted off road with a velocity of 20km/h. The vertical accelerations at the cab and front axle are measured in the test. For the verification of the developed computational model, the measured vertical acceleration profiles are compared with the simulation results of the heavy truck's flexible computational model. E grade irregular road profile of ISO is used as an excitation input in the simulation. The verified flexible computational model is used to compare the vibration characteristics of a front suspension system having a multi-leaf spring and that having a tapered leaf spring. The comparison results show that the front suspension having a tapered leaf spring has a higher vertical acceleration at the front axle but a lower vertical acceleration at the cab than the suspension system having a multi-leaf spring.

Model Order Reduction for Mid-Frequency Response Analysis (중주파수 응답해석을 위한 축소 기법)

  • Ko, Jin-Hwan
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.135-138
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    • 2009
  • Most of the studies use model order reduction for low frequency (LF) response analysis due to their high computational efficiency. In LF response analysis, one of model order reduction, algebraic substructuring (AS) retains all LF modes when using the modal superposition. However, in mid-frequency (MF) response analysis, the LF modes make very little contribution and also increase the number of retained modes, which leads to loss of computational efficiency. Therefore, MF response analysis should consider low truncated modes to improve the computational efficiency. The current work is focused on improving the computational efficiency using a AS and a frequency sweep algorithm. Finite element simulation for a MEMS resonator array showed that the performance of the presented method is superior to a conventional method.

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Service Prediction-Based Job Scheduling Model for Computational Grid (계산 그리드를 위한 서비스 예측 기반의 작업 스케쥴링 모델)

  • Jang Sung-Ho;Lee Jong-Sik
    • Proceedings of the Korea Society for Simulation Conference
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    • pp.29-33
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    • 2005
  • Grid computing is widely applicable to various fields of industry including process control and manufacturing, military command and control, transportation management, and so on. In a viewpoint of application area, grid computing can be classified to three aspects that are computational grid, data grid and access grid. This paper focuses on computational grid which handles complex and large-scale computing problems. Computational grid is characterized by system dynamics which handles a variety of processors and jobs on continuous time. To solve problems of system complexity and reliability due to complex system dynamics, computational grid needs scheduling policies that allocate various jobs to proper processors and decide processing orders of allocated jobs. This paper proposes the service prediction-based job scheduling model and present its algorithm that is applicable for computational grid. The service prediction-based job scheduling model can minimize overall system execution time since the model predicts a processing time of each processing component and distributes a job to processing component with minimum processing time. This paper implements the job scheduling model on the DEVSJAVA modeling and simulation environment and simulates with a case study to evaluate its efficiency and reliability Empirical results, which are compared to the conventional scheduling policies such as the random scheduling and the round-robin scheduling, show the usefulness of service prediction-based job scheduling.

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Service Prediction-Based Job Scheduling Model for Computational Grid (계산 그리드를 위한 서비스 예측 기반의 작업 스케줄링 모델)

  • Jang Sung-Ho;Lee Jong-Sik
    • Journal of the Korea Society for Simulation
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    • v.14 no.3
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    • pp.91-100
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    • 2005
  • Grid computing is widely applicable to various fields of industry including process control and manufacturing, military command and control, transportation management, and so on. In a viewpoint of application area, grid computing can be classified to three aspects that are computational grid, data grid and access grid. This paper focuses on computational grid which handles complex and large-scale computing problems. Computational grid is characterized by system dynamics which handles a variety of processors and jobs on continuous time. To solve problems of system complexity and reliability due to complex system dynamics, computational grid needs scheduling policies that allocate various jobs to proper processors and decide processing orders of allocated jobs. This paper proposes a service prediction-based job scheduling model and present its scheduling algorithm that is applicable for computational grid. The service prediction-based job scheduling model can minimize overall system execution time since the model predicts the next processing time of each processing component and distributes a job to a processing component with minimum processing time. This paper implements the job scheduling model on the DEVS modeling and simulation environment and evaluates its efficiency and reliability. Empirical results, which are compared to conventional scheduling policies, show the usefulness of service prediction-based job scheduling.

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Computational analysis of vortex breakup in arrhythmias (심장 부정맥 시 vortex breakup 현상에 대한 수치적 연구)

  • Shim, Eun-Bo;Kwon, Soon-Sung;Choi, Seung-Yoon
    • 한국전산유체공학회:학술대회논문집
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    • pp.496-497
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    • 2008
  • In this study, we present the computational analysis of cardiac arrhythmias that is the major cause of human sudden cardiac death. First, electric excitation and condution in one dimensional cardiac tissue model is solved and the results on condution block are represented. In two dimensional model, vortex daynamics in cardiac tissue is analyzed to delineate the breakup phenomenon inducing ventricular fibrillation. We also simulated a three dimenional heart model to see the vortex breakup and explained the mechanism in physiological aspect.

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A Study on the Development of Air Pollution Model Applicable to the Complex Terrain (복잡지형에서의 대기순환모델에 관한 연구)

  • Yoon J. Y.;Yi S. C.;Hong M. S.
    • Journal of computational fluids engineering
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    • v.2 no.1
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    • pp.109-116
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    • 1997
  • The objective of this paper is to develop a computational model for the prediction of the pollutant spread from a mass source over a complex terrain. The model comprises a two-dimensional, steady state flow model and a concentration model which employs the results of the computed flow field. The computational model is applied to predict the spread of pollutants for Sanbon city, and the two cases have been compard with the results of SF/sub 6/ trace experiments.

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Topomer-CoMFA Study of Tricyclic Azepine Derivatives-EGFR Inhibitors

  • Chung, Jae-Yoon;Pasha, F.A.;Chung, Hwan-Won;Yang, Beom-Seok;Lee, Cheol-Ju;Oh, Jung-Soo;Moon, Myoung-Woon;Cho, Seung-Joo;Cho, Art E.
    • Molecular & Cellular Toxicology
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    • v.4 no.1
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    • pp.78-84
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    • 2008
  • EGFR has been intensively investigated as a target to block the signal transduction pathway which stimulates cancer growth and metastasis. Studies about structure-activity relationship for tricyclic azepine derivatives were performed with topomer-CoMFA. The derived topomer-CoMFA model with steric and electrostatic field parameters based on fragment units gave reasonable statistics ($q^2$=0.561, $r^2$=0.679). The model explains why a halogen atom at the meta position of aniline is important to increases inhibitory activity. This comes from an electrostatically negative groups are favored near this region. The model also shows that there are sterically favored regions around methoxy group extended from oxazepine derivatives. The findings about steric and electrostatic effects can be utilized for designing new inhibitors.

Reduced Quasi-Dimensional Combustion Model of the Direct Injection Diesel Engine for Performance and Emissions Predictions

  • Jung, Dohoy;Assanis, Dennis N.
    • Journal of Mechanical Science and Technology
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    • v.18 no.5
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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.

Transient response analysis by model order reduction of a Mokpo-Jeju submerged floating tunnel under seismic excitations

  • Han, Jeong Sam;Won, Boreum;Park, Woo-Sun;Ko, Jin Hwan
    • Structural Engineering and Mechanics
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    • v.57 no.5
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    • pp.921-936
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    • 2016
  • In this study, a model order reduction technique is applied to solve the transient responses of submerged floating tunnel (SFT) from Mokpo to Jeju under seismic excitations. Because the SFT is a very long structure as well as a transient response analysis requires large amount of computational resources, the model order reduction is mandatory in the design stage of the SFT. Thus, we apply a model order reduction based on Krylov subspace to the simplified finite element model of the SFT. The responses of the reduced order model are compared with those of the full order model and also are verified by referring a previous work. In conclusion, the computational resources are dramatically reduced with an acceptable accuracy by using the model order reduction, which eventually is useful for designing the full-scale model of SFTs.