• 한국군사과학기술학회지
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• 제14권6호
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• pp.1171-1177
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• 2011

A high power laser beam focused on a small area accelerates a thin material that flies and hits other target material in which a shock wave may be induced. This laser induced shock experimental method is more repeatable and cheaper but worse than other experimental method using gas gun or other apparatus. An optical system including a phase zone plate reduces the interference and also makes the focused-beam-intensity distribution uniform. We wrote a computer code that calculates light ray traces. Using the code we designed and fabricated an optical system including a phase zone plate and improved the laser-beam uniformity. We introduce preliminary experimental results of laser induced shock of the samples such as aluminum and other materials.

• Journal of Information Processing Systems
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• 제13권1호
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• pp.114-127
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• 2017

This paper proposes a color image coding algorithm based on shape-adaptive all phase biorthogonal transform (SA-APBT). This algorithm is implemented through four procedures: color space conversion, image segmentation, shape coding, and texture coding. Region-of-interest (ROI) and background area are obtained by image segmentation. Shape coding uses chain code. The texture coding of the ROI is prior to the background area. SA-APBT and uniform quantization are adopted in texture coding. Compared with the color image coding algorithm based on shape-adaptive discrete cosine transform (SA-DCT) at the same bit rates, experimental results on test color images reveal that the objective quality and subjective effects of the reconstructed images using the proposed algorithm are better, especially at low bit rates. Moreover, the complexity of the proposed algorithm is reduced because of uniform quantization.

• 한국가시화정보학회지
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• 제15권3호
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• pp.20-26
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• 2017

The two-fluid equations are widely used to simulate two-phase flows in a nuclear reactor. For the two-fluid momentum equation, the wall and interfacial drag terms play an important role in predicting a two-phase flow behavior. Since the bubble density is much smaller than the water density, the bubble accelerates faster than the liquid in a nozzle. As a result, the bubble phase becomes faster than the liquid phase in the nozzle. In contrast, the opposite phenomena occur in the diffuser. The purpose of our study is to experimentally show these behaviors in an area-varying channel such as nozzle and diffuser. Experiments were made of turbulent bubbly flows in an area-varying horizontal channel. The velocities of the bubble and liquid phases were measured by the PIV technique. It was shown that the two-phase velocities were no longer close to each other in the area-varying regions. The bubble was faster than the liquid in the nozzle; in contrast, the bubble was slower than the liquid in the diffuser. Code simulations were also performed using the MARS code. By replacing the original wall drag model in the MARS code with Kim (1)'s wall drag partition model, we obtained the simulation results being consistent with experimental observations.

• Nuclear Engineering and Technology
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• 제31권3호
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• pp.314-327
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• 1999

A subchannel analysis code MATRA applicable to PWRs and ALWRs has been developed to be run on an IBM PC or HP WS based on the existing CDC CYBER mainframe version of COBRA-Rf-1. This MATRA code is a thermal-hydraulic analysis code based on the subchannel approach for calculating the enthalpy and How distribution in fuel assemblies and reactor cores for both steady-state and transient conditions. HATRA has been provided with an improved structure, various functions, and models to give more convenient user environment and to enhance the code accuracy. Among them, the pressure drop model has been improved to be applied to non-square-lattice rod arrays, and the models for the lateral transport between adjacent subchannels have been improved to enhance the accuracy in predicting two-phase flow phenomena. The predictions of MATRA were compared with the experimental data on the flow and enthalpy distribution in some sample rod-bundle cases to evaluate the performance of MATRA. All the results revealed that the predictions of MATRA were better than those of COBRA-IV-I.

• Journal of Positioning, Navigation, and Timing
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• 제7권1호
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• pp.1-14
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• 2018

The Global Positioning System (GPS) provides more accurate positioning estimation performance by processing L1 and L2 signals simultaneously through dual frequency signal processing technology at the L-band rather than using only L1 signal. However, if anti-spoofing (AS) mode is run at the GPS, the precision (P) code in L2 signal is encrypted to Y code (or P(Y) code). Thus, dual frequency signal processing can be done only when the effect of P(Y) code is eliminated through the L2 signal processing technology. To do this, a codeless technique or semi-codeless technique that can acquire phase measurement information of L2 signal without information about W code should be employed. In this regard, this paper implements L2 signal processing technology where two typical codeless techniques and four typical semi-codeless techniques of previous studies are applied and compares their performances to discuss the optimal technique selection according to implementation environments and constraints.

• 한국통신학회논문지
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• 제22권3호
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• pp.506-514
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• 1997

In this paper, we implement digital circuit of despreading delay lock loop for GPS receiver. The designed system consists of Epoch signal generator, two 13bit correlators which correlates the received C/A code and the locally generated C/A code in the receiver, the C/A code generator which generates C/A code of selected satellite, and the direct digital clock synthesizer which generates the clock of the C/A code generator to control the phase and clock rate, the clock controller, and the clock divider. The designed circuit has the function of the acquisition and tracking by the autocorrelation characteristics of Gold code. The controller generates each other control signals according to the correlation value. The designed circuit is simulated to verify the logic functional performance. By using the simulator STR-2770 that generates the virtual GPS signal, the deigned FPGA chip is verified the circuit performance.

• 한국통신학회논문지
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• 제32권9C호
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• pp.820-825
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• 2007

초직교 시공간 격자 부호(Super-Orthogonal Space-Time Trellis Codes; SOSTTC)는 직교 행렬의 집합을 확장하여 부호율의 손실 없이 부호 이득과 다이버시티 이득을 동시에 얻는 방법이다. SOSTTC에서 신호 집합 확장은 부호 행렬의 첫째 열을 회전시킴으로써 이루어진다. 기존에 사용된 회전각은 성능 개선보다 신호 성좌의 확장을 피하기 위한 목적으로 선택되었다. 본 논문에서는 고속 레일리 페이딩 채널에서 SOSTTC의 성능을 개선하기 위해 적당한 회전각을 선택하기 위한 설계 요건을 만들었다. 또한, 적당한 회전각을 사용하여 개선된 SOSTTC를 설계하였다. 그리고 모의실험을 통하여 본 논문에서 설계된 SOSTTC가 기존의 SOSTTC 보다 BER 성능 면에서 더 뛰어남을 입증하였다.

• 한국통신학회논문지
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• 제32권11C호
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• pp.1059-1065
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• 2007

이 논문에서는, 일반 홀상관 (general odd correlation) 성질이 비동기 (asynchronous) M진 위상 신호 (M-ary phase signal) 방식에 알맞은 다상 (polyphase) 서명 수열 (signature sequence) 집합을 제안하고 상관 성질을 분석한다. 또한, 제안한 수열과 짝상관 (even correlation) 성질이 좋은 기존 다상 수열인 FZC (Frank-Zadoff-Chu) 수열, 짝상관과 홀상관이 같은 EOE (equivalent odd and even correlation) 수열을 최대 절대 상관값을 (the maximum magnitude of correlations) 사용하여 상관 성질을 견주어 본다. M진 위상 신호 방식을 사용한 직접수열 부호분할 다중접속 (direct sequence code division multiple access: DS/CDMA) 시스템에서 제안한 수열과 FZC 수열을 사용할 때를 모의 실험한 결과, 다중 경로 성분이 존재할 때 제안한 수열을 쓴 시스템 성능이 FZC 수열을 쓸 때보다 더 나음을 보인다.

• 한국전산유체공학회지
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• 제14권4호
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• pp.13-22
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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.

• 전기전자학회논문지
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• 제19권2호
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• pp.186-192
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• 2015

본 논문에서는 소프트웨어 개발 과정에서 소프트웨어의 품질향상에 필요한 소스코드의 API를 기반으로 테스트 케이스를 자동으로 생성할 수 있는 기법을 제안한다. 제안된 기법은 Doxygen 오픈소스 툴을 이용한 소스코드 분석 과정, 분석된 결과를 이용한 API 사양 정의 과정, 테스트 디자인 생성 과정, Pairwise Test 기법을 적용한 테스트 케이스 생성 과정 등의 4가지 과정으로 구성된다. Doxygen 오픈소스 툴을 이용한 소스코드 분석 과정은 소스코드의 API 정보인 API 명, 입력 파라미터, 리턴 파라미터 정보 등을 추출하는 단계이다. 분석된 결과를 이용한 API 사양 정의 과정은 추출한 API 정보를 바탕으로 SQLite 데이터베이스를 이용하여 테스트 케이스 생성에 필요한 API 정보들을 데이터베이스화하여 정의하는 단계이다. 테스트 디자인 생성 과정은 정의된 API를 기반으로 입력 파라미터, 리턴 파라미터의 임계치 설정, 제약사항 설정 등을 통해 시나리오를 디자인하여 데이터베이스로 구성하는 단계이다. Pairwise Test 기법을 적용한 테스트 케이스 생성 과정은 테스트 디자인 정보를 바탕으로 Pairwise 조합 기법을 적용하여 실제 테스트 케이스를 생성하여 데이터베이스로 구성하는 단계이다. 제안된 기법의 효율성을 평가하기 위하여 기존의 명세서 기반의 테스트 케이스 생성 방법과 비교한 결과 비슷한 시간 내에 훨씬 더 많은 테스트 케이스가 생성되며, 명세 기반 기법으로는 불가능한 소스코드에 대한 기능 검증도 가능하여 소스코드내 결함 위치도 확인할 수 있다. 따라서 사람의 인력을 통한 수작업에 의존적으로 진행하였던 소프트웨어 개발 품질 향상 과정을 소스코드의 API를 기반으로 자동으로 테스트 케이스를 생성함으로써, 노동력 절감 및 제품 개발 시간 등을 단축 할 수 있으리라 기대된다.