• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.9
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• pp.9-17
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• 1999

In this paper, we present a mathematical modeling and perform a performance analysis of double-dwell serial search algorithm, which has a search window concept, for pilot channel in DS-CDMA(Direct Sequence Code Division Multiple Access). We derive a code detection function, a false alarm function, a code miss function, and a mean code acquisition time for the performance analysis. We calculate the mean code acquisition time of the mathematical model in IS-95 forward link and compare it with that of the conventional search methods. The performance of the code acquisition system is also evaluated to investigate the effect of dwell times and search window size. The JTC channel model, which is a PCS channel model in North America, is used for the analysis. The numerical result shows that the mean code acquisition time of the double-dwell serial search algorithm with a search window is reduced by about 17%~25% than those of the conventional ones.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.7
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• pp.730-738
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• 1992

This paper alms to analyse the performance of frequency hopping /spread spectrum multiple access system by employing the channel with mixture of AWGN, partial band Jamming, fading and user interference. The performance analysis of FH /SSMA system, taking account of frequency 'hit'(user Interference ) which occurs in the presence of multiple user, produces the following numerical results by computing error probability and throughput of each code in two cases whether the side Information about channel is used or not. The numerical results are as follows : When composite interferences coexist In channel, RS code Is significantly superior to convolutional code in terms of performance. Concatenated code provides the same performance as RS code. The above results show that RS code is pertinent as error-correction code.

• Nuclear Engineering and Technology
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• v.54 no.3
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• pp.888-895
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• 2022

Lately, ocean nuclear power plants have attracted attention as one of diverse uses of nuclear power plants. Because ocean nuclear power plants are movable or transportable, it is necessary to analyze the thermal hydraulics in a moving frame of reference, and computer codes have been developed to predict thermal hydraulics in large moving systems. The purpose of this study is to incorporate a three dimensional dynamic motion model into the SPACE code (Safety and Performance Analysis CodE) so that the code is able to analyze thermal hydraulics in an ocean nuclear power plant. A rotation system that describes three-dimensional rotations about an arbitrary axis was implemented, and modifications were made to the one-dimensional momentum equations to reflect the rectilinear and rotational acceleration effects. To demonstrate the code's ability to solve a problem utilizing a rotational frame of reference, code calculations were conducted on various conceptual problems in the two-dimensional and three-dimensional pipeline loops. In particular, the code results for the three-dimensional pipeline loop with a tilted rotation axis agreed well with the multi-dimensional CFD results.

• Nuclear Engineering and Technology
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• v.53 no.2
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• pp.455-465
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• 2021

The Molten Salt Reactor (MSR), one of the six advanced reactor types of the 4th generation nuclear energy systems, has many impressive features including economic advantages, inherent safety and nuclear non-proliferation. This paper introduces a system analysis code named TREND, which is developed and used for the steady and transient simulation of MSRs. The TREND code calculates the distributions of pressure, velocity and temperature of single-phase flows by solving the conservation equations of mass, momentum and energy, along with a fluid state equation. Heat structures coupled with the fluid dynamics model is sufficient to meet the demands of modeling MSR system-level thermal-hydraulics. The core power is based on the point reactor neutron kinetics model calculated by the typical Runge-Kutta method. An incremental PID controller is inserted to adjust the operation behaviors. The verification and validation of the TREND code have been carried out in two aspects: detailed code-to-code comparison with established thermal-hydraulic system codes such as RELAP5, and validation with the experimental data from MSRE and the CIET facility (the University of California, Berkeley's Compact Integral Effects Test facility).The results indicate that TREND can be used in analyzing the transient behaviors of MSRs and will be improved by validating with more experimental results with the support of SINAP.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.14 no.3
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• pp.7-15
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• 2006

Aerodynamic analysis of an airfoil in the transonic region was automated in order to enable parametric study by using the journal file of the commercial analysis code FLUENT, pre/post process Gambit and computational mathematics code MATLAB. The automated capability was illustrated via NACA 0012 and RAE 2822 airfoils. This analysis was carried out at Mach numbers ranged from 0.70 to 0.80, angles of attack; 1$^{\circ}$, 2$^{\circ}$ and 4$^{\circ}$, Reynolds numbers; 4.0${\times}$106, 6.5${\times}$106. The analysis results of a pressure coefficient were verified by comparing with the experimental data which were measured in terms of chord length because the pressure coefficient of an airfoil surface is a good estimator of flow characteristics. The results of two airfoils show that this analysis code is useful enough to be used in the design optimization of airfoil.

• Journal of the Korean Society of Marine Environment & Safety
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• v.9 no.1
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• pp.25-31
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• 2003

In 1994, the International Maritime Organization (IMO) adopted the International Safety Management Code (ISM Code) as SOLAS convention to ensure the safe operation of ships and to protect marine environment from pollution In December 2002, the IMO adopted the International Ship and Port Facility Security Code (ISPS Code) in the Chapter XI-1 of SOLAS to ensure the security of ships, crew, cargo and port facility. With 1 July 2004 being the coming into effective date of ISPS Code, there is a sense of urgency among the shipping companies and port authorities to accomodate the ISPS Code. Although both the ISM Code and the ISPS Code are based on the management system concept introduced in the ISO 9001, two Codes pursue different objective. Accordingly, it is meaningful to compare and analyze the requirements of three standards. In this article, the backgrounds, principles and requirements of three standards are analyzed and presented to offer several suggestions on the establishment and implementation of security measures in compliance with the ISPS Code to the shipping industry in time.

• Korean Journal of Human Ecology
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• v.22 no.5
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• pp.477-490
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• 2013

This study explores critical and success factor of benefits and risks for predicting the acceptance of QR code virtual fashion stores. As an exploratory approach, this study conducted focus group interviews(FGI) with 21 panels who had experience with selected QR virtual stores (e.g., Home plus, 11th Street, Pin & Fit). Content analysis was used to generate 184 excerpts and classify into benefits and risks related to QR code virtual stores. With respect to benefits, content analysis identified four factors: Affective appeal, perceived usefulness, ubiquity, and brand promotion. Also, contents regarding perceived risks were classified into four factors: Complexity, lack of information, lack of technology infrastructure, and perceived cost. A managerial implication was discussed for predicting consumer technology acceptance of a QR code virtual store in the fashion retailing market.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.3 no.2
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• pp.161-171
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• 1999

Aerodynamic sensitivity analysis codes are developed via the hand-differentiation using a direct differentiation method and an adjoint method respectively from discrete two-dimensional compressible Navier-Stokes equations. Unlike previous other researches, Baldwin-Lomax algebraic turbulence model is also differentiated by hand to obtain design sensitivities with respect to design variables of interest in turbulent flows. Discrete direct sensitivity equations and adjoint equations are efficiently solved by the same time integration scheme adopted in the flow solver routine. The required memory for the adjoint sensitivity code is greatly reduced at the cost of the computational time by allowing the large banded flux jacobian matrix unassembled. Direct sensitivity code results are found to be exactly coincident with sensitivity derivatives obtained by the finite difference. Adjoint code results of a turbulent flow case show slight deviations from the exact results due to the limitation of the algebraic turbulence model in implementing the adjoint formulation. However, current adjoint sensitivity code yields much more accurate sensitivity derivatives than the adjoint code with the turbulence eddy viscosity being kept constant, which is a usual assumption for the prior researches.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.28A no.11
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• pp.855-865
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• 1991

A simple method for analysis of serial search burst-format direct-sequence spread-spectrum (DS-SS) code acquisition system had been recently proposed, and therein, the effect of the code autocorrelation sidelobes on the performance of DS-SS code acquisition system has been assessed [4],[5]. In this paper, a new hybrid scheme which combines the serial search with maximum likelihood search is proposed to eliminate the deleterious effect of code autocorrelation sidelobes, and the performance is analyzed for the additive withe Gaussian noise (AWGN) channels. To analyze the performance of this system, we have generalized the method used in [4],[5] to arbitrary burst-format DS-SS acquisition schemes. The results show that a new hybrid scheme has good immunity against the effect of code autocorrelation sidelobes. Thevalidity of the presented approach has been confirmed form the results of simulation.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.771-776
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• 2010

Since the importance of seismic design is greater, dynamic analysis is more widely using than past. The input motion is one of the most important factors of dynamic analysis. However, in Korea input motions are selected from U.S. and Japan those are captured from large magnitude earthquakes without considering seismic environment or generated in frequency domain. In this research, the methodology for generating input motions those are considered seismic environment and design code is proposed. The seismic environment compatibility is considered by performing deaggregation and the design code compatibility is considered by time-domain artificial time history accelration generation method. The results shows that seismic environment and design code compatible input motions are successfully generated.