• Computers and Concrete
• /
• 제21권5호
• /
• pp.593-605
• /
• 2018

A nonlinear finite element modeling approach is developed to assess the behavior of a dowel bar embedded on a single concrete block substrate, subjected to monotonic loading. In this approach, a discrete representation of the steel reinforcing bar is considered, using beam finite elements with nonlinear material behavior. The bar is connected to the concrete embedment through nonlinear Winkler spring elements. This modeling approach can only be used if a new constitutive model is developed for the spring elements, to simulate the deformability and strength of the concrete substrate. To define this constitutive model, an extensive literature review was conducted, as well as 3 experimental tests, in order to select the experimental data which can be used in the calibration of the model. Based on this data, an empirical model was established to predict the global dowel response, for a wide range of bar diameters and concrete strengths. This empirical model provided the information needed for calibration of the nonlinear Winkler spring model, valid for dowel displacements up to 4 mm. This new constitutive model is composed by 5 stages, in order to reproduce the concrete substrate response.

• 디지털융복합연구
• /
• 제10권4호
• /
• pp.79-93
• /
• 2012

경영자와 연구자들은 경영성과에 대해 관심도 높고 이에 대해 인식하고 있지만, 성숙도나 하부조직 같은 기업정보시스템의 특징이 조직의 경영성과에 어떻게 그리고 어떤 요인들이 영향을 미치는지에 대한 연구는 아직 미비한 실정이다. 그래서 본 연구는 정보화수준, 경영환경, 정보시스템의 성숙도와 하부구조가 경영성과(재무적 경영성과와 비재무적 경영성과)에 어떤 영향을 미치는지를 알아보고자 대만의 136개 기업을 대상으로 실증분석을 실시하였다. 설문지 표본의 응답자들은 각각의 기업 경영성과업무와 관련된 부서에 근무하고 있는 사람들을 대상으로 하였다. 본 연구에는 구조방정식모델을 사용하여 연구 가설들을 검증하였다.

• 한국시뮬레이션학회논문지
• /
• 제18권1호
• /
• pp.53-62
• /
• 2009

실 기동 훈련을 기반으로 획득한 데이터는 전투 또는 워게임 모델링 및 시뮬레이션에 중요한 역할을 지니게 된다. 특히 이들 데이터는 무기체계 분석을 위한 중요한 입력자료로 활용하게 된다. 현존하는 분석모델들은 사격시간간격의 평균값을 상수로 지정하여 적용하여 왔으나 사격시간간격은 기존 확률분포 또는 경험분포로 적합하여 사용함이 보다 현실적이라고 할 수 있다. 실제 전장의 데이터를 획득하기 어려운 여건이므로 실기동 훈련으로 획득된 경험 데이터를 활용할 수 있는 방법을 제시한다. 본 연구는 확률과정을 따르는 전투상황을 보다 근접하게 모의할 수 있는 새로운 접근방법 및 기법을 연구하고 비교한다. 이 연구는 다양한 혼합 무기체계, 적정 전투의 규모, 그리고 전술적 측면 등을 포함하는 향후 연구과제의 필요성을 제기하면서 이를 위한 첫 번째 단계에 해당하는 기초연구이다.

• Bulletin of the Korean Chemical Society
• /
• 제23권1호
• /
• pp.48-52
• /
• 2002

Using several molecular modeling programs we have performed computer simulations to investigate the complexation behaviors of an ester derivative of p-tert-butylcalix[5]arene (1e) toward a variety of butylammonium ions. Semi-empirical AM1 method was used for calculating the binding energies and the formation enthalpies. MM and CVFF forcefields for molecular mechanics calculations were adapted to express the complexation energies of the host. Molecular dynamics were performed to the calculated complex systems to simulate the ionophoric behavior of the host-guest complexes. The absolute Gibbs free energies of the host (1e) complexed with four kinds of butylammonium ions have been calculated using the Finite Difference Thermodynamic Integration (FDTI) method in Discover. Calculation results show that the trend in complex formation is n-$BuNH_3^+$ > iso-$BuNH_3^+$ >> sec-$BuNH_3^+$ > tert-$BuNH_3^+$, which is in good agreement with the experimental results.

• 제어로봇시스템학회논문지
• /
• 제13권4호
• /
• pp.358-364
• /
• 2007

Intelligent walking modeling of humanoid robot using learning based neuro-fuzzy system is presented in this paper. Walking pattern, trajectory of the zero moment point (ZMP) in a humanoid robot is used as an important criterion for the balance of the walking robots but its complex dynamics makes robot control difficult. In addition, it is difficult to generate stable and natural walking motion for a robot. To handle these difficulties and explain empirical laws of the humanoid robot, we are modeling practical humanoid robot using neuro-fuzzy system based on the two types of natural motions which are walking trajectories on a t1at floor and on an ascent. Learning based neuro-fuzzy system employed has good learning capability and computational performance. The results from neuro-fuzzy system are compared with previous approach.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
• /
• pp.453-457
• /
• 1998

The sorption of UO$_2$$^{2+}$showed ionic strength independece for goethite and dependence for kaolinite. In the presence of carbonate, the sorption decreased in the weakly alkaline pH range becase of the formation of aqueous U(VI)-carbonate complexes. The sorption of UO$_2$$^{2+}$onto goethite and kaolinite under various experimental conditions was successfully interpreted using a surface complexation modeling, named triple layer model (TLM). The best fit to the experimental data was obtained by the FITEQL program, and then evaluated with available spectroscopic data. The results showed the versatility of surface complexation modeling over empirical one to predict UO$_2$$^{2+}$ sorption behavior.avior.

• 항공우주시스템공학회지
• /
• 제8권4호
• /
• pp.18-23
• /
• 2014

In preliminary design phase, the wing geometry of the civil aircraft was determined using the empirical equation and historical data. To make wing geometry more aerodynamically efficient, an aerodynamic shape optimization was conducted. For this purpose the parametric modeling, high fidelity CFD analysis and metamodel-based optimal design technique were adopted. The parametric modeling got the design process to achieve the improvement by generating the configuration outputs easily for the major design variables. The optimal design equations were formularized as the type of the multi-objective functions considering low/high speed and lift/drag coefficient. The optimal solution was explored with the help of the kriging metamodel and the desirability function, therefore the optimal wing planform was sought to be excellent at both low and high speed region. Additionally the optimal wing planform was validated that it was excellent not only at the specific AOA, but also all over the range of AOA.

• Clinical and Experimental Pediatrics
• /
• 제64권7호
• /
• pp.322-327
• /
• 2021

School closures during the coronavirus disease 2019 (COVID-19) pandemic have been outlined in studies from different disciplines, including economics, sociology, mathematical modeling, epidemiology, and public health. In this review, we discuss the implications of school closures in the context of the current COVID-19 pandemic. Modeling studies of the effects of school closures, largely derived from the pandemic influenza model, on severe acute respiratory syndrome coronavirus 2 produced conflicting results. Earlier studies assessed the risk of school reopening by modeling transmission across schools and communities; however, it remains unclear whether the risk is due to increased transmission in adults or children. The empirical findings of the impact of school closures on COVID-19 outbreaks suggest no clear effect, likely because of heterogeneity in community infection pressure, differences in school closure strategies, or the use of multiple interventions. The benefits of school closings are unclear and not readily quantifiable; however, they must be weighed against the potential high social costs, which can also negatively affect the health of this generation.

• Communications for Statistical Applications and Methods
• /
• 제25권6호
• /
• pp.605-618
• /
• 2018

Risk management has been a crucial part of the daily operations of the financial industry over the past two decades. Value at Risk (VaR), a quantitative measure introduced by JP Morgan in 1995, is the most popular and simplest quantitative measure of risk. VaR has been widely applied to the risk evaluation over all types of financial activities, including portfolio management and asset allocation. This paper uses the implementations of multivariate GARCH models and copula methods to illustrate the performance of a one-day-ahead VaR prediction modeling process for high-dimensional portfolios. Many factors, such as the interaction among included assets, are included in the modeling process. Additionally, empirical data analyses and backtesting results are demonstrated through a rolling analysis, which help capture the instability of parameter estimates. We find that our way of modeling is relatively robust and flexible.

• 한국정밀공학회지
• /
• 제13권12호
• /
• pp.54-62
• /
• 1996

To get the time response characteristics of the hydrostatic transmission, seaborne winch is modelde by using bond graphs. After modeling of its basic elements, it is represented as power flow, and the determination of variable causality. The state equations are derived by using CAMP. As dynamic stabilites and solutions are investigated by perturbation method and direct integration, winch system is stable. Simulations are performed under the conditions of low speed, high speed, and maximum tension. The pressure and flow rate of the hydrostatic transmission have a big overshoot. But when it is comparaed to the empirical data with simulation results, it is similar to each other. When a lead compensator is applied to improve response characteristics of the hydrostatic transmission, rise time and overshoot of the system are improved.