• Title/Summary/Keyword: numerical Model

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Isogeometric Analysis of Mindlin Plate Structures Using Commercial CAD Codes (상용 CAD와 연계한 후판 구조의 아이소-지오메트릭 해석)

  • Lee, Seung-Wook;Koo, Bon-Yong;Yoon, Min-Ho;Lee, Jae-Ok;Cho, Seon-Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.3
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    • pp.329-335
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    • 2011
  • The finite element method (FEM) has been used for various fields like mathematics and engineering. However, the FEM has a difficulty in describing the geometric shape exactly due to its property of piecewise linear discretization. Recently, however, a so-called isogeometric analysis method that uses the non-uniform rational B-spline(NURBS) basis function has been developed. The NURBS can be used to describe the geometry exactly and play a role of basis functions for the response analysis. Nevertheless, constructing the NURBS basis functions in analysis is as costly as a meshing process in the FEM. Since the isogeometric method shares geometric data with CAD, it is possible to intactly import the model data from commercial CAD tools. In this paper, we use the Rhinoceros 3D software to create CAD models and export in the form of STEP file. The information of knot vectors and control points in the NURBS is utilized in the isogeometric analysis. Through some numerical examples, the accuracy of isogeometric method is compared with that of FEM. Also, the efficiency of the isogeometric method that includes the CAD and CAE in a unified framework is verified.

A financial projection model on defined benefit pension plan (우리나라 퇴직연금의 재정추계모형과 장기전망 - 확정급여형 가정 중심으로 -)

  • Han, Jeonglim;Lee, Hangsuck
    • Journal of the Korean Data and Information Science Society
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    • v.25 no.1
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    • pp.131-153
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    • 2014
  • The Korean market of pension plans has recently increased and pension plans will be expected to play an important role in the retirement system as complement of the national pension system in the future. However, there are a few of research papers on actuarial projections of pension plans. This paper will discuss a long-term financial projection on defined pension plans using data based on the national pension workplace participants. Previous researches focused on company-based financial projection of pension plan. But, this paper concerns on total Korean pension participants and suggests a method to calculate future financial projection of total pension plans. Finally, this research will suggest several numerical results of normal costs, benefits, numbers of workers, etc.

Thermal Behavior of Energy Pile Considering Ground Thermal Conductivity and Thermal Interference Between Piles (주변 지반의 열전도도를 고려한 PHC 에너지파일의 열 거동 및 파일 간 열 간섭 현상에 대한 수치해석 연구)

  • Go, Gyu Hyun;Yoon, Seok;Park, Do Won;Lee, Seung-Rae
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.6
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    • pp.2381-2391
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    • 2013
  • In general, ground's thermal properties, types of heat exchanger, operational method, thermal interference between piles can be considered as key factors which affect the thermal performance of energy pile. This study focused on the effect of these factors on the performance by a numerical model reflecting a real ground condition. Depending on the degree of saturation of ground, pile's heat transfer rate showed a maximum difference of three times, and the thermal resistance of pile made a maximum difference of 8.7%. As for the type of heat exchanger effects on thermal performance, thermal efficiency of 3U type energy pile had a higher value than those of W and U types. The periodic operation (8 hours operation, 16 hours pause) can preserve about 20% of heat efficiency compared to continuous operation, and hence it has an advantage of preventing the thermal accumulation phenomenon. Thermal interference effect in group piles may vary depending on the ground condition because the extent decreases as the ground condition varies from saturated to dry. The optimal separation distance that maintains the decreasing rate of heat efficiency less than 1% was suggested as 3.2D in U type, 3.6D in W type, and 3.7D in 3U type in a general ground condition.

Validation of Equivalent Shear Beam Container Using Dynamic Centrifuge Tests (동적 원심모형실험을 이용한 등가전단보 토조의 성능 검증)

  • Kim, Yoon-Ah;Lee, Hae-In;Ko, Kil-Wan;Kim, Dong-Soo
    • Journal of the Korean Geotechnical Society
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    • v.36 no.11
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    • pp.61-70
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    • 2020
  • In dynamic centrifuge tests, equivalent shear beam (ESB) container minimizes the boundary effect between the soil model and the wall of the container so as to effectively simulate the boundary conditions of real field state. The ESB container at KAIST was evaluated to be performing properly by Lee et al. (2013). However, it is necessary to re-evaluate the performance of ESB container since the ESB container may have deteriorated over time. Thus, the performance of eight-year-old ESB container was re-evaluated through dynamic centrifuge tests. Firstly, the natural period of the empty ESB container was compared with the results of Lee et al. (2013). Then the boundary effect of sand-filled ESB container was evaluated. Results show that the dynamic behavior of the sand-filled ESB container was similar to that of the ground, despite a decrease in the natural period of the empty ESB container over time. In addition, the dynamic response of the ground built in the ESB container and the same ground simulated through numerical analysis with free-field boundary conditions were similar. Therefore, it was found that the boundary effect of the ESB container due to the decrease in the natural period was not significant.

Isogeometric Shape Design Optimization of Structures Subjected to Design-dependent Loads (설계 의존형 하중 조건을 갖는 구조물의 아이소-지오메트릭 형상 최적설계)

  • Yoon, Min-Ho;Koo, Bon-Yong;Ha, Seung-Hyun;Cho, Seon-Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.24 no.1
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    • pp.1-7
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    • 2011
  • In this paper, based on an isogeometric approach, we have developed a shape design optimization method for plane elasticity problems subjected to design-dependent loads. The conventional shape optimization using the finite element method has some difficulties in the parameterization of geometry. In an isogeometric analysis, however, the geometric properties are already embedded in the B-spline basis functions and control points so that it has potential capability to overcome the aforementioned difficulties. The solution space for the response analysis can be represented in terms of the same NURBS basis functions to represent the geometry, which yields a precise analysis model that exactly represents the normal and curvature depending on the applied loads. A continuum-based isogeometric adjoint sensitivity is extensively derived for the plane elasticity problems under the design-dependent loads. Through some numerical examples, the developed isogeometric sensitivity analysis method is verified to show excellent agreement with finite difference sensitivity.

An Enhanced Fast Handover Scheme for Proxy Mobile IPv6 (Proxy Mobile IPv6를 위한 개선된 신속한 핸드오버 방안)

  • Kang, Ju-Eun;Kum, Dong-Won;Cho, You-Ze
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.46 no.6
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    • pp.1-10
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    • 2009
  • In a network-based approach such as Proxy Mobile IPv6 (PMIPv6), the serving network controls the mobility management on behalf of a Mobile Node (MN), thereby eliminating a MN from any mobility-related signaling. Although PMIPv6 is being standardized by the IETF NetLMM WG, PMIPv6 still suffers from a lengthy handover latency and the on-the-fly packet loss during a handover. Therefore, this paper presents an enhanced fast handover scheme for PMIPv6. The proposed handover scheme uses the Neighbor Discovery message of IPv6 to reduce the handover latency and packet buffering at the Mobile Access Gateway (MAG) to avoid the on-the-fly packet loss during a handover. In addition, it uses an additional packet buffering at the Local Mobility Anchor (LMA) to solve the packet ordering problem. We evaluate the performance of the proposed handover scheme using both analytical model and simulation. The numerical analysis shows that the proposed scheme has a relatively shorter handover latency. Simulation results demonstrate that the proposed scheme could avoid the on-the-fly packet loss and ensure the packet sequence.

Development of high performance and low noise axial-flow fan for cooling machine room of refrigerator using airfoil-cascade analysis and surface ridge shape (익렬 분석 및 표면 돌기 형상을 이용한 냉장고 기계실 냉각용 고성능/저소음 축류팬 개발)

  • Choi, Jinho;Ryu, Seo-Yoon;Cheong, Cheolung;Kim, Tae-hoon;Koo, Junhyo
    • The Journal of the Acoustical Society of Korea
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    • v.39 no.6
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    • pp.515-523
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    • 2020
  • This study aims to improve the flow and noise performances of an axial-flow fan for cooling the machine room in a refrigerator by using airfoil-cascade analysis and surface ridge shape. First, the experimental evaluations using a fan performance tester and an anechoic chamber are performed to analyze the flow and noise performances of the existing fan system. Then, the corresponding flow and noise performances are numerically assessed using the Computational Fluid Dynamics (CFD) techniques and the Ffowcs-Williams and Hawkings (FW-H) equation, and the validity of numerical results are confirmed through their comparisons with the experimental results. The analysis for the flow of a cascade of airfoils constructed from the existing fan blades is performed, and the pitch angles for the maximum lift-to-drag ratio are determined. The improved flow performance of the new fan applied with the optimum pitch angles is confirmed. Then, the fan blades with surface ridges on their pressure sides are devised, and the reduction of aerodynamic noise of the ridged fan is numerically confirmed. Finally, the prototype of the final fan model is manufactured, and improvements in the flow and noise performances of the prototype are experimentally confirmed.

A Study on the Lunar Ground Temperature Profile for Investigation of Possible Condition of the Ice Layer Existence in Sub-surface of the Moon (달 지하 얼음 층 존재 가능조건 검토를 위한 달 지반 온도 프로파일 산정 연구)

  • Go, Gyu-Hyun;Lee, Jangguen;Shin, Hyu-Soung
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.39 no.6
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    • pp.801-809
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    • 2019
  • NASA's lunar polar exploration mission in 2009 confirmed the presence of ice-layer in the permanently shadowed regions (PSR) of the moon. Since then, studies have been actively conducted to evaluate the ground characteristics for exploring the ice-layer in the polar regions of the Moon. In this study, transient heat transfer analysis for the lunar ground was conducted to predict the ground's temperature that varies with the time and location. As a result of the numerical analysis, it was confirmed that the temperature under the lunar ground converged to below the ice sublimation reference temperature (≒112 K) at above 86° latitude. This model enabled us to identify the regions where there is a high possibility of ice being buried. Besides, we found that the ice-layer in the shallow region, where the temperature deviation is significant, makes ground temperature distribution heterogeneous. Lastly, this study suggested the maximum allowable frictional heat of a drill bit that can preserve the phase of buried ice.

Multiple Regression Analysis to Estimate the Unit Price of Hanwoo (Bos taurus coreanae) Beef

  • Eum, Seung-Hoon;Park, Hu-Rak;Seo, Jakyeom;Cho, Seong-Keun;Hur, Sun-Jin;Kim, Byeong-Woo
    • Food Science of Animal Resources
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    • v.37 no.5
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    • pp.663-669
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    • 2017
  • This study were estimated the contribution of carcass traits to unit price, to analyze the marbling score as a categorical variable rather than a numerical variable, and to develop an optimal model that also includes the holiday effect and the raising period. The data for this study were acquired from the Quality Evaluation of the Korea Institute for Animal Products, and consisted of the trading records of 1,613,699 heads at 12 wholesale markets from 2010 to 2014. The unit price of a cow was estimated from the following parameters: -52.50 Won/mm, 8.93Won/cm28.93Won/cm2, 7.20 Won/kg, and -1.04 Won/day for backfat thickness, eye muscle area, carcass weight, and raising period, respectively. Parameters for the dummy variables of marbling scores varied from 0 to 8328.74 Won/kg, which means that each marbling score grade had a different price value. The unit price of a steer was estimated from the following parameters: - 92.12 Won/mm, 20.22Won/cm2, 1.30 Won/kg, and -1.72 Won/day for backfat thickness, eye muscle area, carcass weights, and raising period, respectively. Parameters for dummy variables of marbling scores varied from 0 to 7338.80 Won/kg, which means that the grades of each marbling score had different price values. The unit price of sales during traditional holidays was significantly higher (827.71 Won/kg for cows, and 645.15 Won/kg for steers) than during non-holidays.We conclude that the use of categorical values for marbling scores would be needed to evaluate the price of Hanwoo beef using multiple regression analysis based on carcass traits and environmental factors.

The Study of Sediment Volume Concentration in Liquefied-Layer of Debris Flow (토석류 유동층에서 토사체적 농도 특성에 관한 연구)

  • Kim, Sungduk
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.12
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    • pp.109-115
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    • 2014
  • The purpose of this study is to estimate the sediment volume concentration of the liquified-solid mixture which is included fine sediment fractions, according to the variance of the channel slope and the water supply. The numerical model was performed by using the Finite Differential Element Method (FDM) based on the equation for the mass conservation, momentum conservation and the equation of coarse sediment an fine sediment. In comparison of varying the channel slope, the deeper the channel slope, the inflection point of the sediment concentration was occurred rapidly. In comparison of variance of the water supply, as the water supply increases fluctuation with high sediment concentration. In this situation, debris flow changes to the turbulent flow and the sediment becomes to be floated. In comparison varying the length paved saturated sediment, the longer the length, the high concentration of sediment occurred, for the safety of the slope it is needed to check the possibility of the erosion in the slope by debris flow. The results of this study will provide useful information in predicting of the disaster by the liquified-solid mixture and in prevention of the debris flow with various the slope in the mountain side.