• Journal of Korea Society of Industrial Information Systems
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• v.15 no.5
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• pp.149-158
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• 2010

A messenger program in this paper was designed and implemented using Use Case Diagram, Class Diagram, Activity Diagram, and Sequence Diagram. We selected total 7 major functionalities such as PC server, login, friends management, chatting, file transfer, account management, etc. The followings are various implementation results from this paper. First, developers could easily understand the desired product and programming flow from using UML Diagrams. Second, PDA users could communicate with developers for a long time without time constraints. Third, there was high usability of UML Diagram in the phase of objected-oriented analysis. Forth, it was easy to update and maintain a program.

• Nuclear Engineering and Technology
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• v.55 no.9
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• pp.3367-3382
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• 2023

Smoothed Particle Hydrodynamics (SPH) is a Lagrangian computational fluid dynamics method that has been widely used in the analysis of physical phenomena characterized by large deformation or multi-phase flow analysis, including free surface. Despite the recent implementation of eddy-viscosity models in SPH methodology, sophisticated turbulent analysis using Lagrangian methodology has been limited due to the lack of computational performance and numerical consistency. In this study, we implement the standard and dynamic Smagorinsky model and dynamic Vreman model as sub-particle scale models based on a weakly compressible SPH solver. The large eddy simulation method is numerically identical to the spatial discretization method of smoothed particle dynamics, enabling the intuitive implementation of the turbulence model. Furthermore, there is no additional filtering process required for physical variables since the sub-grid scale filtering is inherently processed in the kernel interpolation. We simulate lid-driven flow under transition and turbulent conditions as a benchmark. The simulation results show that the dynamic Vreman model produces consistent results with experimental and numerical research regarding Reynolds averaged physical quantities and flow structure. Spectral analysis also confirms that it is possible to analyze turbulent eddies with a smaller length scale using the dynamic Vreman model with the same particle size.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.46 no.3
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• pp.221-230
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• 2023

Under increased complexity and uncertainty of overseas construction projects, it is important for construction companies to improve their own project risk management capabilities instead of risk-taking strategies to secure competitiveness in the overseas construction market. Although most of the risks occur in project execution stage, many previous studies focused on planning stage including risk identification and analysis among PRM process. Therefore, this study aims to verify the effectiveness of whole PRM process during project execution stage through empirical study on participants of overseas construction projects. As the result it was found that first, the factor directly affects the project success is the execution process of PRM. It implies that appropriate actions such as appointing charged manager for risks, timely implementation of responding plan, continuous risk monitoring and updating established plan are the key for contribution to the project success. Second, the importance of communication in PRM is also found, which is not conducted at a specific but throughout the entire PRM process and need to be managed as essential factor for successful PRM..

• 한국전산유체공학회:학술대회논문집
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• 2009.04a
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• pp.290-297
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• 2009

A two-phase (gas and liquid) flow analysis solver, named CUPID, has been developed for a realistic simulation of transient two-phase flows in light water nuclear reactor components. In the CUPID solver, a two-fluid three-field model is adopted and the governing equations are solved on unstructured grids for flow analyses in complicated geometries. For the numerical solution scheme, the semi-implicit method of the RELAP5 code, which has been proved to be very stable and accurate for most practical applications of nuclear thermal hydraulics, was used with some modifications for an application to unstructured non-staggered grids. This paper is concerned with the effects of interpolation schemes on the simulation of two-phase flows. In order to stabilize a numerical solution and assure a high numerical accuracy, the second-order upwind scheme is implemented into the CUPID code in the present paper. Some numerical tests have been performed with the implemented scheme and the comparison results between the second-order and first-order upwind schemes are introduced in the present paper. The comparison results among the two interpolation schemes and either the exact solutions or the mesh convergence studies showed the reduced numerical diffusion with the second order scheme.

• Korean Journal of Community Nutrition
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• v.10 no.6
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• pp.905-919
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• 2005

This study raised the necessity of developing performance indicators for measuring the management efficiency and effectiveness of school food service, and as a means of helping its implementation, a balanced score card (BSC) approach developed by Norton and Kaplan was adopted. This study established BSC in seven phases through literature: Phase 1 Defining a school food service and the scope of working activities, Phase 2 Establishing the vision of a school food service, Phase 3 Setting strategic goals, Phase 4 Identifying critical success factors (CSFs), Phase 5 Developing Key Performance Indicators (KPIs), Phase 6 Extracting cause and effect relationship, and Phase 7 Completing a preliminary BSC. The preliminary BSC was fumed into a survey, which was administered to food service related people working at the Office of Education and School Food Service including 16 offices,209 dietitians, 48 school administrators both from self-operated and contract-managed, and 9 experts in areas related to school food service. They were asked questions about strategies from 4 different perspectives,12 CSFs, 39 KPls, and the cause and effect relationships among them. As a result, among the CSFs based on 4 different perspectives, all factors other than ' zero sum on profit/loss ' from the financial perspective turned out to be valid. In terms of KPIs, manufacturing cost percentages, casualty loss count/reduction rates, school foodervice participation rates, and sales goal achievement rates were found to be valid from the financial perspective, while student satisfaction index, faculty satisfaction index, leftover ratio, nutrition educational performance count, index of evaluating nutrition education, customer claim count/reduction rate, handling customer claim count/reduction rate, and parent satisfaction index were found to be valid from the customers' perspective. Besides, nutritional requirement sufficient ratio, nutritional management score, food poisoning outbreak count, employee safety accident count, sanitary inspection assessment index, meals per labor hour (productivity index), computerization ratio, operational management index, and purchase management assessment index were also found to be valid from the perspective of internal business processes. From the perspective of innovation and learning, employee turnover ratio/rate of absenteeism, annual education and training count, employee satisfaction index, human resource management assessment index, annual menu-related customer feedback, food service information index for employees and parents/schools were also found to be valid. The significance of this study is to present indices for measuring overall performance of school lunch food service operations without putting any limitation on types of school food service management, and to help correctly assess the contribution of the current types of school food service management to schools and students. (Korean J Community Nutrition 10(6) : $905\∼919$, 2005)

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.8A
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• pp.801-809
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• 2010

Limitation of optical phase conjugation for implementation of wideband and long-haul WDM transmission system is symmetric distribution of optical power and local dispersion with respect to optical phase conjugator (OPC). This limitation forces OPC to place at midway of total transmission length. This paper shows that the limitation of optical phase conjugation is overcame by applying optimal net residual dispersion (NRD) into transmission links based in inline dispersion management (DM). Optimal NRD related with OPC position is decided by combination of precompensation and postcompensation. It is confirmed that optimal NRD depends on launch power of WDM channels and system performance criterion as well as OPC position. That is, in case of 1 dB eye opening penaty (EOP) as a performance criterion for WDM channels with 0 dBm launch power, it is confirmed that OPC is allowed to place at anywhere of 1000 km by applying best NRD related with exact OPC position into transmission links. And, it is confirmed that, under 3 dB EOP criterioin for WDM channels with 3 dBm launch power, OPC is allowed to place at 350~700 km by applying NRD between 100 ps/nm and 200 ps/nm into transmission links, though that NRD value is not best combination of precompensation and postcompensation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1112-1119
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• 2006

In this paper, mutually coupled oscillator is employed to improve phase noise. Mutually coupled structure oscillator couples two oscillator's phase shifted output signals, that is fabricated using teflon board which has dielectric constant of 2.5 and Surface Mount Gallium Arsenide FET devices. And this paper proposed the structure to bias adjustment for the phase condition of mutually couples. When one oscillator has bias point of 4.4 V and 37 mA, it's output signal has phase noise characteristic of -96.37 dBc(@9305 MHz, offset frequency 100 KHz), -73.46 dBc(10 kHz). and After it's output signal mutually coupled the other's output signal that has bias point of 8.1 V and 69 mA, it has superior phase noise characteristic of -106.7 dBc(@9305 MHz, offset frequency 100 kHz), -81 dBc(10 kHz).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.547-555
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• 2008

This parer proposed the path mismatch detection and compensation algorithm with closed form for linear amplification with non-linear components(LINC) system implementation. The LINC system has a merit of using the high efficient amplifier by transferring the non-constant envelop signal which is high peak to average signal ratio into constant envelop signal. However, the performance degradation is very sensitive to the path mismatch such as an amplitude mismatch and a phase mismatch. In order to improve the path mismatch, the error detection and compensation method is introduced by the use of four test signals. Since the presented method has the closed form solution, the efficient and fast detection is available. The digital-IF structure of LINC system applied by the proposed error detection and compensation algorithm was implemented. The performance was evaluated with the IEEE 802.16 WiMAX baseband sinal which has 7 MHz channel bandwidth and 16-QAM. The Error Vector Magnitude(EVM) of -37.37 dB was obtained through performance test, which meets performance requirement of -24 dB EVM. As a result, the introduced error detection and compensation method was verified to improve the LINC system performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.777-784
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• 2004

In this paper, a new filter structure to improve frequency response characteristics in decimation filter using CIC(Cascaded Integrator-Comb) filters and half band filters is proposed. Conventional filters improve only passband characteristics, but we propose a new filter which can improve stop band and pass band characteristics simultaneously. Since proposed filter needs only two multiplication, additional implementation cost is not much. And overall linear phase characteristics are maintained since the proposed filter is also linear phase. Finally, filter coefficients quantization effects ate discussed after Verilog-HDL coding.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.8 no.4
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• pp.38-45
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• 1994

It is very imprtant and necessary to predict luminous enviroment in an interior space. This paper has de scribed about energy saving and evaluated interior visual environment in a office building having on/off turning control lighting system utilizing daylight. In order to predict the interior varior illumination distribution, the scale model w a m~a de and examined under various conditions, such ad difference of window glass, and color pattern of wall, floor, and also ceiling lighting system type. Ths paper suggests that basic fundamental data of lighting design ~rformancein the concept and schematic stages of design.