• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.19 no.8
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• pp.585-592
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• 2007

Good cold start characteristics are essential for satisfactory operation of fuel cell vehicles. In this study, the melting process has been numerically investigated for a water tank used in fuel cell vehicles. The 2-D model of the tank containing ice and plate heaters was assumed and the unsteady melting process of the ice was calculated. The enthalpy method was used for the description of the melting process, and a FVM code was used to solve the problem. The feasibility study compared with other experiment showed that the developed program was able to describe the melting process well. From the numerical analysis carried out for different wall temperatures of the pate heaters, some important design factors could be found such as local overheating and pressurization in the tank.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.09a
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• pp.603-607
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• 2003

The judgment of forged passports plays an important role in the immigration control system, for which the automatic and accurate processing is required because of the rapid increase of travelers. So, as the preprocessing phase for the judgment of forged passports, this paper proposed the novel method for the recognition of passport based on the fuzzy binarization and the fuzzy RBF neural network newly proposed. first, for the extraction of individual codes being recognized, the paper extracts code sequence blocks including individual codes by applying the Sobel masking, the horizontal smearing and the contour tracking algorithm in turn to the passport image, binarizes the extracted blocks by using the fuzzy binarization based on the membership function of trapezoid type, and, as the last step, recovers and extracts individual codes from the binarized areas by applying the CDM masking and the vertical smearing. Next, the paper proposed the enhanced fuzzy RBF neural network that adapts the enhanced fuzzy ART network to the middle layer and applied to the recognition of individual codes. The results of the experiment for performance evaluation on the real passport images showed that the proposed method in the paper has the improved performance in the recognition of passport.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.7
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• pp.730-735
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• 2004

This paper describes what brings about DC offset and the impact or the DC offset on the performance or direct-conversion mobile receiver in WCDMA system. The performance degradation of $E_{b}/N_{o}$ due to the DC offset is presented through simulation result. Direct-conversion RF Transceiver which has the function of DC offset control is implemented and then applied to the WCDMA test-bed for the performance evaluation. The receiver performance degradation of $E_{c}/I_{o}$ is evaluated and analyzed by varying DC offset value. The practical test showed the minimum requirement of DC offset value to meet system performance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.3
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• pp.497-504
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• 2002

The purpose of this study is to analyze thermal cycles and to investigate microstructures of heat affected zones for a low alloy carbon steel pipe under a multipass weld. The commercial finite element code SYSWELD is used to compute thermal cycles during multipass weld. The numerical results such as thermal cycles and size of heat affected zone are compared with those of the experiment and the two results show a good agreement. In addition, the microstructure and hardness are investigated from the weldment in detail. The weakest location is founded at intercritical region near the base metal.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.2
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• pp.190-199
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• 2011

Unsteady flow simulations of complete helicopter configurations were conducted, and the flow fields and the aerodynamic interferences between the main rotor, fuselage, and tail rotor were investigated. For these simulations, a three-dimensional flow solver based on unstructured meshes was used, coupled with an overset mesh technique to handle relative motion among those components. To validate the flow solver, calculations were made for a UH-60A complete helicopter configuration at high-speed and low-speed forward flight conditions, and the unsteady airloads on the main rotor blade were compared to available flight test data and other calculated results. The results showed that the fuselage changed the rotor inflow distribution in the main rotor blade airloads. Such unsteady vibratory airloads were produced on the fuselage, which were nearly in-phase with the blade passage over the fuselage. The flow solver was then applied to the simulation of a generic complete helicopter configuration at various flight conditions, and the results were compared with those of the CAMRAD-II comprehensive analysis code. It was found that the main rotor blades strongly interact with a pair of disk-vortices at the outer edge of the rotor disk plane, which leads to high pulse airloads on the blade, and these airloads behave differently depending on the specific flight condition.

• New & Renewable Energy
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• v.2 no.2 s.6
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• pp.28-36
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• 2006

Numerical analysis of wind turbine scale effect was performed by using commercial CFD code, Fluent. For the numerical analysis of wind turbine, the three dimensional Navier-Stokes solver with various turbulence models was tested. As a turbulence mode, the realizable k-e turbulence model was selected for the simulation of wind turbines. To validate the present method, performance of NREL (National Renewable Energy Laboratory) Phase VI wind turbine model was analyzed and compared with its wind tunnel test and blind test data. Using the present method, numerical simulations for various size of wind tunnel models were carried out and characteristics were analyzed in detail. For wind tunnel test model, the size of nacelle may not be scaled down precisely because of available motor. The effect of nacelle size was also computed and analyzed though CFD simulation. The present results showed the good correlations in pre-stall region but much to be improved in post-stall region. In 2006 and 2007, the performance and the scale effect of standard wind turbine model will be tested in KARI(Korea Aerospace Research Institute) LSWT(Low Speed Wind Tunnel) and the present results will be validated with the wind tunnel data.

• Korean Management Science Review
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• v.15 no.2
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• pp.109-124
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• 1998

Recently, as the importance placed on the design phase of system development has increased, the use of diagrams to design the overall system before implementing the actual program code has seen a proportionate increase. This study focuses on the diverse diagrams depicting organizational processes when integrating multiple processes of individual organizations to form an Inter-Organizational System(IOS). In this study, we attempt to identify the critical representation features of process diagrams that enable the effective integration of Inter-Organizational processes. In particular, the effect of the mapping relationship between the representation features of different diagrams to be integrated was tested empirically in a laboratory setting. The experimental task consisted of integrating the processes of two organization based upon the given process diagrams. Actual business processes were selected from real world cases and process diagrams were formulated based upon existing object-oriented notation. An analysis of the errors committed by the subjects during the integration process indicated that the mapping relationship between the diagram features representing the respective organizational processes had a significant impact upon the final integration outcome. Based upon these results, the present study provides a guideline for process diagrams that are crucial to effective Inter-Organizational process implementation and maintenance.

• The KIPS Transactions:PartD
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• v.15D no.3
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• pp.327-336
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• 2008

Many XML-compliant UIDLs(User Interface Description Languages) have been developed to specify user interfaces. Although previous UIDLs are helpful to describe user interfaces of web and desktop applications, they are not available of developing UI of mobile applications. In this paper, in order to effectively specify user interfaces of MIDlet which is application model on J2ME(Java Platform, Micro Edition), we propose MIML(Midlet Interface Markup Language) and present transformation rules to generate source codes from MIML. Further, we enhance the usability of MIML through J2MERenderer which is a tool using presented rules. The proposed method can specify user interfaces of mobile applications and allow developers to keep productivity and consistency in development phase.

• Korean Management Science Review
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• v.19 no.2
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• pp.191-204
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• 2002

As the portion of information systems (IS) budget to the total government budget becomes greater, the cost estimation of IS development and maintenance projects is recognized as one of the most important problems to be resolved for scientific and efficient management of IS budget. Since IS budget makes much effect on the delivery time, quality and productivity of IS projects, the exact cost estimation is also necessary for the successful accomplishment of IS projects. The primary concern in the cost estimation of IS projects is software cost estimation, which requires the measurement of the size of softwares. There are two methods for sizing software : line-of-code approach, function point model. In this paper, we propose a function-point-based model for estimating software cost. The proposed model is derived by collecting about fifty domestic IT projects in public sector and analyzing their relationship between cost drivers and development effort. Since the proposed model is developed by simplifying the function point model that can be used only when detailed user requirements are specified, it can be also applied at project planning and budgeting phase.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.5
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• pp.74-80
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• 2006

GPS, which has been opened to the public since the 1980's, uses the C/A code time of arrival to estimate the position, and measures the carrier doppler frequency to estimate the velocity. In development from the 1990's, DGPS has improved position accuracy by eliminating common errors and CDGPS has achieved cm-level position accuracy using carrier phase. In this paper, a modified LSAST ambiguity resolution method for CDGPS is proposed to improve reliability and computational efficiency. Also the test results of cm level relative positioning of a moving vehicle using single frequency GPS receivers are compared to INS position. This research result can be widely used for the development of high precision INS, unmanned autonomous driving, survey and mapping, etc.