• Journal of Korea Society of Digital Industry and Information Management
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• v.15 no.4
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• pp.19-29
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• 2019

Recently, with the rise of environmental issues and the change of government policy (Renewable Energy 3020 Implementation Plan), a large amount of renewable energy such as solar and wind power is connected to the power system, and most of the renewable energy is concentrated in the power distribution network. This causes many problems with the voltage management and the protection coordination of the grid due to the its intermittent power generation. In order to effectively operate the distribution network, it is necessary to deploy more intelligent terminal devices in the field to measure the status of the distribution network and develop various operation functions such as visualization and big data analysis to support the power distribution system operators. In addition, the failover technology must be supported for the non-stop operation of the power distribution system. This paper proposes the system architecture of new power distribution management system to cope with high penetration of renewable energy. To verify the proposed system architecture, the functional unit test and performance measurement were performed.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.04a
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• pp.27-34
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• 2001

The BGA Package has been the area array package of choice for several rears. Recently, the transition has been to finer pitch configuration called Chip Scale Packages (CSP). Several of these package types are available at 0.5 mm pitch, requiring surface mount assemblers to evaluate and optimize various elements of the assembly process. This presentation describes the issues associated with making the transition from BGA to CSP assembly. Areas addressed will include the accuracy of pick and piece equipment, printed wiring board lines and spaces, PWB vias, in-circuit test issues, solder paste printing, moisture related factors, rework and reliability. The transition to 0.5 mm pitch requires careful evaluation of the board design, solder paste selection, stencil design and component placement accuracy. At this pitch, ball and board pad diameters can be as small as 0.25 mm and 0.20 mm respectively. Drilled interstitial vias are no longer possible and higher ball count packages require micro-via board technology. The transition to CSP requires careful evaluation of these issues. Normal paste registration and BGA component tolerances can no longer achieve the required process levels and higher accuracy pick and place machines need to be implemented. This presentation will examine the optimization of these critical assembly operations, contrast the challenges at 0.5 mm and also look at the continuation of the process to incorporate smaller pitch flip chip devices.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.3
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• pp.31-36
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• 2002

The 2nd level solder joint reliability of 153 FC-BGA for high-speed SRAM (Static Random Access Memory) with the large chip on laminate substrate comparing to PBGA(Plastic Ball Grid Array) was studied in this paper. This work has been done to understand an influence as the mounting with single side or double sides, structure of package, properties of underfill, properties and thickness of substrate and size of solder ball on the thermal cycling test. It was confirmed that thickness of BT(bismaleimide tiazine) substrate increased from 0.95 mm to 1.20 mm and solder joint fatigue life improved about 30% in the underfill with the low young's modulus. And resistance against the solder ball crack became twice with an increase of the solder ball size from 0.76 mm to 0.89 mm in solder joints.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.2
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• pp.327-334
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• 2020

In this paper, an automatic cruise system of unmanned boat was developed for surveying water depth in reservoir using accurate location information. Using global satellite navigation system(GNSS) data in real time, this unmanned system, combined with an echo sounder, can simultaneously collect location information and depth information on the reservoir. This automatic navigation system allows the automatic route generation program to automatically generate a cruise route according to the input conditions for grid sizes of 5m, 10m and 20m, and automatically controls the cruise route with high positional accuracy. The developed system was tested to verify the applicability of the selected Yonggok(Geoncheon) reservoir as a test reservoir located in Suncheon, Jeollanam-do.

• International Journal of Fluid Machinery and Systems
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• v.4 no.1
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• pp.199-208
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• 2011

This work presents numerical results, using OpenFOAM, of the flow in the swirl flow generator test rig developed at Politehnica University of Timisoara, Romania. The work shows results computed by solving the unsteady Reynolds Averaged Navier Stokes equations. The unsteady method couples the rotating and stationary parts using a sliding grid interface based on a GGI formulation. Turbulence is modeled using the standard k-${\varepsilon}$ model, and block structured wall function ICEM-Hexa meshes are used. The numerical results are validated against experimental LDV results, and against design velocity profiles. The investigation shows that OpenFOAM gives results that are comparable to the experimental and design profiles. The unsteady pressure fluctuations at four different positions in the draft tube is recorded. A Fourier analysis of the numerical results is compared whit that of the experimental values. The amplitude and frequency predicted by the numerical simulation are comparable to those given by the experimental results, though slightly over estimated.

• Journal of information and communication convergence engineering
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• v.8 no.4
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• pp.349-354
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• 2010

Moving pixel displacement detection algorithm using correlation functions for making panorama image on the continuous images is presented in this paper. The input images get from a CMOS image sensor (CIS). The camera is maintained by constant brightness and uniform sensing area in test input pattern. For simple navigation and capture image has to 70% overlapped region. A correlation rate in two image data is evaluated by using reference image with first captures, and compare image with next captures. The displacement of the two images are expressed to second order function of x, y and solved with finding the coefficient in second order function. That results in the change in the peak correlation displacement from the reference to the compare image, is moving to pixel length. The navigating error is reduced by varying the path because the error is shown in the difference of the positioning vector between the true pixel position and the navigated pixel position. The algorithm performance is evaluated to be different from the error vector to vary the navigating path grid.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.3
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• pp.82-89
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• 2009

The purpose of this study is to investigate the actual field application of the linear piston pump for the solid transferring driven by the hydraulic power unit. In this paper, the numerical analysis and performance evaluating experiments were performed. CFX program has been used to obtain the solutions for the problems of three-dimensional, turbulent water flow in the linear piston pump. The velocity and the pressure distributions are obtained using the turbulent $k-\varepsilon$ model. To evaluate the performance of the linear piston pump, the performance test stand and data acquisition system were manufactured. The numerical predictions agree favorably with experimental results within 7% error. Speed of the piston which is satisfied the flow rate 3,000l/min which considers from basic design became 0.33m/s. This paper could be applied to the design of the linear piston pump for the fish transferring.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.5
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• pp.385-393
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• 2018

In this study, the analysis of 2DOF (2 Degree Of Freedom) motion and added resistance of a ship in regular head waves is carried out using RANS (Reynolds Averaged Navier-Stokes) approach. In order to improve the accuracy for large amplitude motions, the dynamic overset scheme is adopted. One of the dynamic overset schemes, Suggar++ is applied to WAVIS which is the in-house RANS code of KRISO (Korea Research Institute of Ships and Ocean Engineering). The grid convergence test is carried out using the present scheme before the analysis. The target hull form is KRISO VLCC tanker (KVLCC2) and 13 wave length conditions are applied. The present scheme shows the improved results comparing with the results of WAVIS2 in the non-inertial reference frame. The dynamic overset scheme is confirmed to give the comparatively better results for the large amplitude motion cases than the non-inertial frame based scheme.

• Journal of Korean Association for Spatial Structures
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• v.8 no.3
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• pp.91-99
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• 2008

As number of the buildings increases, it shows new trends such as twisted, tilted, taperer shape. As a structural solution for the new trend buildings, diagonal grid (Diagrid) structure was developed. Though a few buildings was built using diagird system, the structural performance of the corresponding node was not clearly identified. Therefore, experimental evaluation is needed to apply diagrid for higher buildings. In this study, the node was tested depending on the amounts of welding materials. As a result, the partial welding can provide enough strength for the node as required in the full penetration welding under monotonin compressive loadings.

• Water for future
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• v.22 no.3
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• pp.315-322
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• 1989

The effects of open boundary conditions including the radiation condition are compared by utilizing the $L^{2_}$-norm and RMS error in the numerical modeling of ocean problem. In numerical tests of $M_2$ tide, grid size and bed roughness are considered and analyzed. For the $M_2$ tide test in a simplified bay where the analytical solutions are available, it is found that improved radiating boundary condition(IMPSOM) may increase the reliability of computed results by 40% of $L^{2_}$-norm and 96% of RMS error than the open boundary condition without radiation effect. In case of using the half-size grids, better results are obtained. It is also found that the IMPSOM is applicable with satisfaction when the bottom friction is included.