• Journal of computational fluids engineering
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• v.19 no.1
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• pp.27-33
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• 2014

A new and efficient implicit scheme is proposed to obtain a steady-state solution in time integration and the comparison of characteristics with the approximation ways for the implicit method to solve the incompressible Navier-Stokes equations is provided. The conservative, finite-volume cell-vertex upwind scheme and artificial compressibility method using dual time stepping for time accuracy is applied in this paper. The numerical results obtained indicate that the direct application of Jacobian matrix to the Lower and upper sweeps of implicit LU-SGS leads to better performance as well as convergence regardless of CFL number and true time step than explicit scheme and approximation of Jacobian matrix. The flow simulation around box in uniform flow with unstructured meshes is demonstrated to check the validity of the current formulation.

• Journal of the Korea Institute of Building Construction
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• v.4 no.1
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• pp.105-110
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• 2004

Resource procurement is an important management area because cost of resource covers 40％ of total construction project cost and resource delivery has direct relationship with project performance. Integration of cost provides various potentials for effective and efficient project control. This study investigates the usefulness of time in resource procurement management focused on materials. These days, construction projects have characterized manufacture because of industrialization and component. Therefore, application of systematic resource planning has been requested in the construction. There are many companies conducting procurement of resource on the web by applying MRP, ERP etc. in the construction. However, in applying them in the construction yet, there is obstruction. MRP has the character doing its function under accurate cost prediction of resource. But prediction of resource is difficult in industry mechanism of the construction. If accurate cost prediction of resource is possible in the construction, it will be expected to reduce cost of procurement of resource substantially by applying successful resource planning model in the manufacture. On the basis of recent current, the purpose of study is to present procurement of resource system that period observance of construction and minimization of stock is possible by reflecting accurate lead-time to apply proactive thought to be able to cope with alteration of construction schedule efficiently in analyzing resource planning of the construction site.

• 한국전산유체공학회:학술대회논문집
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• 2001.10a
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• pp.84-90
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• 2001

Secondary instability of flow past a circular cylinder is examined using direct numerical simulation at Reynolds number 220 and 250. The higher-order finite difference scheme is employed for the spatial distributions along with the second order Adams-Bashforth and the first order backward-Euler time integration. In x-y plane, the convection term is applied by the 5th order upwind scheme, and the pressure and viscosity terms are applied by the 4th order central difference. In spanwise, Navier-Stokes equation is distributed using Spectral Method. The critical Reynolds number for this instability is found to be about Re=190. The secondary instability leads re three-dimensionality with a spanwise wavelength about 4 cylinder diameters at onset (A-mode). Results of three-dimensional effect in wake of a circular cylinder are represented with spanwise and streamwise vorticity contours as Reynolds numbers.

• Progress in Superconductivity and Cryogenics
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• v.25 no.4
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• pp.54-59
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• 2023

In this paper, we analyze experimental results by applying the PHILS model to a lab-scale superconducting current limiter system for its actual application in medium-voltage direct current (MVDC) systems. Superconducting current limiters exhibit effective current-limiting performance in circuit breaker operations, particularly in limiting large fault currents within a short period, addressing the challenges posed by the increasing use of renewable energy and the integration of DC medium-voltage distribution systems. The development of such superconducting current limiters faces various technical and cost disadvantages, especially when applying a medium-voltage 35kV level system, which is intended for future introduction. The proven lab-scale superconducting current limiter system and the PHILS model are combined and integrated into the actual system. Our plan involves analyzing the limiter's performance, assessing its impact on the system, and preparing for its application in future medium-voltage systems. Utilizing RTDS, a simulation was conducted by connecting actual scaled-down equipment and systems, with the analysis results presented.

• Journal of Agricultural Extension & Community Development
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• v.6 no.2
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• pp.119-139
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• 1999

While many factors could be mentioned to the rapid development of Israel for the last 50 years, it could not be overemphasized the critical role of large scale influx of Jewish immigrants not only in the process of achieving national independence but to the development of modernization. It is well known that mass influx of people in a relatively short period of time may cause serious social problems in various areas such as housing shortage, increasing crime rate, etc. Nontheless, Israel is avidly recognized as a country that successfully overcome such problems by means of creating systematic social integration systems and practicing various adaptation assistance programs for new immigrants. This study was concerned with such a successful social adaptation-assistance programs of Israel for large scale immigrants those who came from all over the world with different socio-economic background. In order to answer the research questions, following two areas of topics were researcher`s main concern. First, organizational structure and functions of the Ministry of Immigrant Absorption of Israel and Jewish Agency that are primarily responsible for the economic, occupational, social, and cultural integration of immigrants during their first three years (five years for housing-aid) in Israel. Second practical adaptation assistance programs such as direct absorption basket, Ulpan, Aliyah 2000, special projects of Keren Hayesod and two of Aliyah Absorption Centers are examined. And lastly some of implications and suggestions are provided in the conclusion section in relation with social adaptation-assistance and integration of reunified Korea, especially from the point of North Koreans.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.4
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• pp.458-467
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• 2012

In this study, the linear viscoelastic response of a rectangular laminated plate is investigated. The viscoelastic properties, expressed by two basic spring-dashpot models, that is Kelvin and Maxwell models, is assumed in the range to investigate the influence of viscoelastic coefficients to mechanical behavior. In the present study, viscoelastic responses are performed for two popular equivalent single-layered theories, such as the first-order shear deformation theory (FSDT) and third-order shear deformation theory (TSDT). Compliance and relaxation modulus of time-dependent viscoelastic behavior are approximately determined by Prony series. The constitutive equation for linear viscoelastic material as the Boltzmann superposition integral equation is simplified by the convolution theorem of Laplace transformation to avoid direct time integration as well as to improve both accuracy and computational efficiency. The viscoelastic responses of composite laminates in the real time domain are obtained by applying the inverse Laplace transformation. The numerical results of viscoelastic phenomena such as creep, cyclic creep and recovery creep are presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.5
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• pp.16-25
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• 1996

In the present work a rigid-plastic finite element formulation using dynamic explicit time integration scheme is proposed for numerical analysis of auto-body panel stamping processes. The rigid-plastic finite element method based on membrane elements has long been employed as a useful numerical technique for the analysis of sheet metal forming because of its time effectiveness. A damping scheme is proposed in order to achieve a stable solution procedure in dynamic sheet forming problems. In order to improve the drawbacks of the conventional membrane elements, BEAM(abbreviated from Bending Energy Augmented Membrane) elements are employed. Rotational damping and spring about the drilling direction are introduced to prevent a zero energy mode. The lumping scheme is employed for the diagonal mass matrix and linearizing dynamic formulation. A contact scheme is developed by combining the skew boundary condition and the direct trial-and-error method. Computations are carried out for analysis of complicated auto-body panel stamping processes such as forming of an oilpan, a fuel tank and a front fender. The numerical results of explicit analysis are compared with the implicit results with good agreements and it is shown that the explicit scheme requires much shorter computational time, especially when the problem becomes more complicated. It is thus shown that the proposed dynamic explicit rigid-plastic finite element method enables an effective computation for complicated autobody panel stamping processes.

• Structural Engineering and Mechanics
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• v.42 no.2
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• pp.211-228
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• 2012

Present study deals with the development of finite element based solution methodology to investigate active control of dynamic response of delaminated composite shells with piezoelectric sensors and actuators. The formulation is based on first order shear deformation theory and an eight-noded isoparametric element is used. A coupled piezoelectric-mechanical formulation is used in the development of the constitutive equations. For modeling the delamination, multipoint constraint algorithm is incorporated in the finite element code. A simple negative feedback control algorithm coupling the direct and converse piezoelectric effects is used to actively control the dynamic response of delaminated composite shells in a closed loop employing Newmark's time integration scheme. The validity of the numerical model is demonstrated by comparing the present results with those available in the literature. A number of parametric studies such as the locations of sensor/actuator patches, delamination size and its location, radius of curvature to width ratio, shell types and loading conditions are carried out to understand their effect on the transient response of piezoceramic delaminated composite shells.

• Coupled systems mechanics
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• v.2 no.2
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• pp.159-174
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• 2013

The present work aims at investigating the nonlinear dynamics, bifurcations, and stability of an axially accelerating beam with an intermediate spring-support. The problem of a parametrically excited system is addressed for the gyroscopic system. A geometric nonlinearity due to mid-plane stretching is considered and Hamilton's principle is employed to derive the nonlinear equation of motion. The equation is then reduced into a set of nonlinear ordinary differential equations with coupled terms via Galerkin's method. For the system in the sub-critical speed regime, the pseudo-arclength continuation technique is employed to plot the frequency-response curves. The results are presented for the system with and without a three-to-one internal resonance between the first two transverse modes. Also, the global dynamics of the system is investigated using direct time integration of the discretized equations. The mean axial speed and the amplitude of speed variations are varied as the bifurcation parameters and the bifurcation diagrams of Poincare maps are constructed.

• Tribology and Lubricants
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• v.12 no.1
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• pp.42-46
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• 1996

This paper deals with a numerical study of the dynamic response of rubber oil seals for rotating shaft when interference as well as static and dynamic eccentricities are present. In loss of contact conditions the dynamic curve of oil seals is numerically simulated using the FEM package MSC/NASTRAN. The direct integration method is selected to analyze the time domain response of the seal lip-shaft contact. The computed results based on the experimental data indicate that the increased rotating speed may produce the gap separation between lip edge of rubber seals and shaft. These results will be very useful in predicting the dynamic leakage due to contact behaviors of rubber oil seals under dynamic conditions.