• Journal of the Korean Society of Systems Engineering
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• v.1 no.1
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• pp.14-19
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• 2005

High temperature vacuum furnaces or high standard electric furnaces demand high technology level and high production cost. Therefore, an iterative design process and the optimization approach under integrated computing environment are required to reduce the development risk. Moreover, it also required to develop an integrated design software that can manage the centralized database system between factory and design department, and the automated furnace design and analysis. The developed software is dedicated to the development of the vacuum (electric) furnaces. Based on the distribute middleware system, the GUI module, the CAD module, the thermal analysis module and the optimization module are integrated. For the DBMS, Microsoft Access is employed, the GUI is developed using Visual Basic language, and AutoCAD is utilized for the configuration design. By investigating the analysis code interface, the analysis and optimization process, and the data communication method, the overall system architecture, the method to integrate the optimizer and ana lysis codes, and the method to manage the data flow are proposed and verified through the optimal furnace design.

• Journal of Astronomy and Space Sciences
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• v.6 no.1
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• pp.1-15
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• 1989

Magnetospheic substorm in the magnetotail region is studied numerically by means of a three dimensional MHD code. The analytic solution for the quiet magnetotail is employed as an initial configuration. The localized solar wind is modeled to enter the simulation domain through the boundaries located in the magnetotail lobe region. As a result of the interaction between the solar wind and the magnetosphere, the magnetic field lines are stretched, and the plasma sheet becomes thinner and thinner. When the current driven resistivity is generated, magnetic reconnection is triggered by this resistivity. The resulting plasma jetting is found to be super-magnetosonic. Although the plasmoid formation and its tailward motion is not quite clear as in the two dimensional simulation, which is mainly because of the numerical model chosen for the present simulation, the rarification of the plasmas near the x-point is observed. Field aligned currents are observed in the late expansive stage of the magnetospheric substorm. These field aligned currents flow from the tail toward the ionosphere on the dawn side from the ionosphere to ward the tail on the dusk side, namely in the same sense of the region 1 current. As the field aligned currents develop, it is found that the cross tail current in the earth side midnight section of the magnetic x-point is reduced.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.8
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• pp.714-721
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• 2005

The water jet impingement cooling with boiling is one of the techniques to remove heat from high heat flux equipments. The configuration of surface roughness is one obvious condition of affecting the performance on heat transfer in nucleate boiling, The present study investigates the water jet impinging single-phase convection and nucleate boiling heat transfer for the effect of surface roughness to enhance the heat transfer in free surface and submerged jet. The distributions of the averaged wall temperature as well as the boiling curves are discussed. Jet velocities are varied from 0.65 to 1.7 m/s. Surface roughness by sand blast and sand paper varies from 0.3 to 2.51 ${\mu}m$ and cavity shapes on surface are semi-circle and v-shape, respectively The results showed that higher velocity of the jet caused the boiling incipience to be delayed more. The incipient boiling and heat transfer increase with increasing surface roughness due to a large number of cavities of uniform size.

• The KSFM Journal of Fluid Machinery
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• v.9 no.1 s.34
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• pp.32-39
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• 2006

Recently, according to the trend of small size in scale and high speed in rotation of turbomachinery, very low specific speed centrifugal pump is taking a growing interest because the pump is characterized by high head and low flow rate with convenience of manufacturing and maintenance compared with conventional positive displacement pump. However, the efficiency of the very low specific speed centrifugal pump drops rapidly with the decrease of specific speed. The purpose of this study is nor only to examine the influence of casing type on the performance of centrifugal pump in the range of very low specific speed but also to determine the proper casing type for the improvement of pump performance. The results show that circular casing is suitable for the centrifugal pump in the range of very low specific speed and the influence of impeller configuration on the pump performance is very small. Radial thrust in the circular and volute casings is considerably small in the range of very low specific speed.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.5
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• pp.638-644
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• 2016

In this research, theoretical study on empirical analysis method to estimate waterdrop's deformation by shock wave is presented. Flow field is calculated using theoretical and empirical relations. Waterdrop's deformation including movement, size, mass, and orientation is modeled using empirical relations derived from existing experimental data. Developed method is applied to specific flight examples with arbitrary flight speed and vehicle's configuration. The flight speed is assumed to Mach number of 2 and 4. The diameter of waterdrop is varied from 1 to 5 mm. Waterdrops along the stagnation line in front of hemispherical nose with the radius of 50 mm and around a cone-shaped side wall with the half angle of 20 degree are considered. It is found that the maximum diameter of the waterdrop is increased up to 2.77 times the initial diameter. The mass is conserved more than 66.7 %. In the case of a cone-shaped side wall, waterdrop's orientation angles defined from the flight direction when the Mach number is 2 and 4 are calculated as 33.0 and 25.6 degree, respectively.

• Industrial Engineering and Management Systems
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• v.15 no.4
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• pp.374-384
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• 2016

The efficiency of a supply chain can be extremely affected by its design which includes determining the flow pattern of material from suppliers to costumers, selecting the suppliers, and defining the opened facilities in network. In this paper, a multi-objective multi-echelon multi-product supply chain design model is proposed in which several suppliers, several manufacturers, several distribution centers as different stages of supply chain cooperate with each other to satisfy various costumers' demands. The multi-objectives of this model which considered simultaneously are 1-minimize the total cost of supply chain including production cost, transportation cost, shortage cost, and costs of opening a facility, 2-minimize the transportation time from suppliers to costumers, and 3-maximize the service level of the system by minimizing the maximum level of shortages. To configure this model a graph theoretic approach is used by considering channels among each two facilities as links and each facility as the nodes in this configuration. Based on complexity of the proposed model a multi-objective Pareto-based vibration damping optimization (VDO) algorithm is applied to solve the model and finally non-dominated sorting genetic algorithm (NSGA-II) is also applied to evaluate the performance of MOVDO. The results indicated the effectiveness of the proposed MOVDO to solve the model.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.10
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• pp.2047-2053
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• 2015

Our research proposese an IoT Broker (gateway) platform which considers the both sides of a service developer and a user. The platform associates the devices around us with virtual-entities and infers the owner of the devices through the ontology scheme. These functionalities can make the service developer easily design a new service. For the user, the service can be automatically installed and deployed under this platform. We also make it possible for the IoT broker to be plugged-in by integrating various communication platforms and protocols into that platform. Our expreriment with the AllJoyn plug-in on Node-RED substantiated that various service flows can be easily deployed and work on our platform.

• Geomechanics and Engineering
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• v.5 no.6
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• pp.595-611
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• 2013

This paper presents a three-dimensional (3D) integrated numerical model where the wave-induced pore pressures in a porous seabed around breakwater heads were investigated. Unlike previous research, the Navier-Stokes equation is solved with internal wave generation for the flow model, while Biot's dynamic seabed behaviour is considered in the seabed model. With the present model, a parametric study was conducted to examine the effects of wave and soil characteristics and breakwater configuration on the wave-induced pore pressure around breakwater heads. Based on numerical examples, it was found that the wave-induced pore pressures at breakwater heads are greater than that beneath a breakwater. The wave-induced seabed response around breakwater heads become more important with: (i) a longer wave period; (ii) a seabed with higher permeability and degree of saturation; and (iii) larger angle between the incident waves and breakwater. Furthermore, the relative difference of wave-induced pore pressure between fully-dynamic and quasi-static solutions are larger at breakwater heads than that beneath a breakwater.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.3
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• pp.397-404
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• 2001

The behavior of unsteady wake vortices for the two-dimensional flat plate is simulated by a discrete vortex method. The flat plates and their wakes are represented by vortex sheets. The vortex sheets are replaced with discrete vortices. The freely deforming wake sheets are computed as a part of solution and the ground effect is included by a image method. In order to predict wake shapes accurately and to model closely coupled aerodynamic interference, a vortex core model and a vortex core addition scheme are used. The simulated wake shapes convecting behind the plates in unsteady motion are compared to a flow visualization result and other numerical results. The present results agree well with them. The present method is also applied to the aerodynamic analysis of flat plates in tandem configuration in ground effect.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.9
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• pp.704-711
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• 2008

Integrated gasification combined cycle (IGCC) is an environment friendly method of using coal. Several commercial IGCC plants have been built worldwide during the past decade, and a domestic development project has also been launched recently. Operation and performance characteristics of a gas turbine in the IGCC plant deviates from those of original gas turbines due to several factors such as increased amount of fuel supply and integration with other components. In this study, performance of a gas turbine in the IGCC plant is analyzed considering its integration with the air separation unit (ASU). Influence of the degree of integration (split of air supplies to ASU from the auxiliary compressor and the gas turbine compressor) on the system performance is investigated. In addition, effect of modulating nitrogen return flow from the gasifier to the gas turbine on the operating characteristics of the gas turbine is examined.