• The Journal of the Acoustical Society of Korea
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• v.36 no.1
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• pp.39-48
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• 2017

CDMA (Code Division Multiple Access) is promising medium access control schemes for underwater acoustic sensor networks because of its robustness against frequency-selective fading and high frequency-reuse efficiency. In this paper, we design diversity schemes of underwater CDMA transceiver for the forward and reverse links. User data are multiplexed by Walsh code and a pseudo random noise code acquisition process is added for phase error correction before decoding the user data at the receiver. Then, the diversity reception using equal gain combining and maximal ratio combining is performed in order to minimize performance degradation caused by rich multipath fading of underwater acoustic channel. We evaluated the performance of diversity transceiver through lake experiment, which was performed at Lake Kyungcheon, Mungyeong city using two transmitters and two receivers placed 460 m apart at an average depth of 40 m. The lake experiment results show that user data are recovered with error-free in both of the forward and reverse links.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.08a
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• pp.128-132
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• 2008

본 논문에서는 현재 자가용 차량 번호판으로 사용되고 있는 4종류의 번호판인, 구형 녹색 번호판 두 종류와 유럽식 신형 흰색 번호판 두 종류에 대해 개별 코드를 효과적으로 추출하기 위한 개선된 퍼지 이진화 방법을 제안한다. 차량 영상에서 수직 에지와 반복 이진화 기법, 그리고 Grassfire 알고리즘을 적용하여 번호판의 후보 영역을 추출하고, 번호판의 형태학적 특징을 이용해 잡음을 제거한 후, 최종 번호판 영역을 추출한다 추출된 번호판 영역에서 개선된 퍼지 이진화 기법을 적용하여 개별 코드를 추출한다. 본 논문에서 제안하는 개선된 퍼지 이진화 방법은 추출한 번호판 영역을 그레이 레벨로 변환한 후에 번호판의 명도를 2구간으로 나누고 각각의 구간에 퍼지 소속 함수를 적용하여 번호판 영역을 이진화한 후, 퍼지 소속 함수에 의해 이진화 된 2개의 번호판 영역 중에서 가장 최적화된 번호판 영역을 선택하여 개별 코드를 추출한다. 본 논문에서 제안한 기법을 4종류의 번호판이 부착된 327장(구형녹색 50장, 신형녹색 157장, 짧은 흰색 60장, 긴 흰색 60장)을 대상으로 실험한 결과, 번호판 영역 추출은 327장의 영상중 97%가 추출되었고 개별 코드 추출은 번호판 영역이 추출된 324장의 영상에서 97%가 추출된 결과를 보였다.

• KIPS Transactions on Software and Data Engineering
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• v.12 no.10
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• pp.431-436
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• 2023

Recently the incorporation of artificial intelligence approaches in the field of software engineering has been one of the big topics. In the world, there are actively studying in two directions: 1) software engineering for artificial intelligence and 2) artificial intelligence for software engineering. We attempt to apply artificial intelligence to software engineering to identify and refactor bad code module areas. To learn the patterns of bad code elements well, we must have many datasets with bad code elements labeled correctly for artificial intelligence in this task. The current problems have insufficient datasets for learning and can not guarantee the accuracy of the datasets that we collected. To solve this problem, when collecting code data, bad code data is collected only for code module areas with high-complexity, not the entire code. We propose a method for exploring common weakness enumeration by learning the collected dataset based on transfer learning of the CodeBERT model. The CodeBERT model learns the corresponding dataset more about common weakness patterns in code. With this approach, we expect to identify common weakness patterns more accurately better than one in traditional software engineering.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10A
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• pp.980-989
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• 2002

In this paper, we have proposed the sectorization method of the adaptive sector antenna and the new receiver structure for the CDMA wireless multi-media communication which uses multi-code and single-code. The sectorization and average BER performance of the adaptive sector antenna, which employs the proposed sectorization method, are obtained through simulation. The simulation results have shown that the sizes of sectors are properly controlled according to the distribution of the load and that the BER performance of the adaptive sector antenna is enhanced much more than that of the fixed sector antenna. Also, we have proposed two receivers, which are different from the positions to detect multi-code signals, for the multi-media communication. Each receiver has a simple cancellation scheme and two adaptive sector antennas, which are called the 1st adaptive sector antenna and the 2nd adaptive sector antenna, respectively. In this paper, the average BER performances of the receivers are compared through simulation. As the results of the simulation, we have recognized that all user' BER performances are greatly dependent on the positions to detect the multi-code signals. When we consider both system complexity and terget BERs of signals, we have concluded that the receiver, which detect multi-code signals in the 1st and the 2nd adaptive sector antenna, is appropriate for the CDMA wireless multi-media communication systems.

• The KIPS Transactions:PartA
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• v.16A no.6
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• pp.453-462
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• 2009

Studies on software plagiarism detection, prevention and judgement have become widespread due to the growing of interest and importance for the protection and authentication of software intellectual property. Many previous studies focused on comparing all pairs of submitted codes by using attribute counting, token pattern, program parse tree, and similarity measuring algorithm. It is important to provide a clear-cut model for distinguishing plagiarism and collaboration. This paper proposes a source code clustering algorithm using a probability model on extreme value distribution. First, we propose an asymmetric distance measure pdist($P_a$, $P_b$) to measure the similarity of $P_a$ and $P_b$ Then, we construct the Plagiarism Direction Graph (PDG) for a given program set using pdist($P_a$, $P_b$) as edge weights. And, we transform the PDG into a Gumbel Distance Graph (GDG) model, since we found that the pdist($P_a$, $P_b$) score distribution is similar to a well-known Gumbel distribution. Second, we newly define pseudo-plagiarism which is a sort of virtual plagiarism forced by a very strong functional requirement in the specification. We conducted experiments with 18 groups of programs (more than 700 source codes) collected from the ICPC (International Collegiate Programming Contest) and KOI (Korean Olympiad for Informatics) programming contests. The experiments showed that most plagiarized codes could be detected with high sensitivity and that our algorithm successfully separated real plagiarism from pseudo plagiarism.

• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.4
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• pp.228-236
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• 1995

In this paper the method to evaluate shielding deficiency by gamma scanning test was presented and verified theoretically by Monte Carlo code which is one of the best effective method for radiation shielding calculation. The cylindrical shielding model was selected to evaluate shielding deficiency by gamma scanning test. First, the reference shielding according to the design requirement of cask was fabricated specially and reference values were measured with Co-60 source and scintillation detector. As a result with which calculated the reference values, it is shown that maximum deficiency thickness for lead of true cylindrical shielding model was 12mm. To verify this, thickness of lead was calculated by MCNP code and maximum deficiency thickness was 11.6mm. The experimental result obtained by the use of reference shielding was in good agreement with the theoretical result within 4.1%. So, this method can be applied to inspect the shielding ability for great shielding or cask which the radioactive material is used. To perform measurement more exactly, the further work on the development of measuring equipment to display the results on the screen will be required.

• Proceeding of EDISON Challenge
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• 2013.04a
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• pp.377-381
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• 2013

익형의 형상이 대칭인 NACA00xx 시리즈의 두께 비 변화에 따른 익형의 공력 특성을 조사하였다. 익형주위의 유동을 2D-압축성 유동으로 가정하여 비선형 유동방정식인 2D-Comp-2.0 solver를 사용하여 수치해석을 수행하였다. 주어진 두께 비에 대한 mesh study를 수행하고 수치해석의 결과는 Fluent 6.3의 수치해석 결과와 비교 분석하였다. 또한 선택 된 최적의 mesh size를 이용하여 익형의 두께비에 따른 양력계수와 항력계수를 비교 분석 하였다. 수치해석 결과로부터 익형의 두께비가 증가할수록 양력계수와 항력계수는 증가하였으며, 또한 받음각의 크기에 따른 익형의 공력특성은 받음각이 증가할수록 양력계수와 항력계수는 증가하였다. 일반적으로 익형의 두께비가 증가하면 shock wave의 강도는 증가하고, shock wave의 위치는 익형의 끝단으로 이동한다. 본 연구에서는 NACA00xx 시리즈의 공력특성에 대한 이해뿐만 아니라 Edison CFD 코드를 이용하여 얼마나 우리가 정확하게 공력해석을 수행할 수 있는지에 중점을 두었다.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06c
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• pp.521-526
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• 2007

내장형 자바의 성능 향상을 위해 바이트코드를 기계어 코드로 미리 번역하여 내장형 시스템에 설치하는 Ahead-of-Time Compile(AOTC)가 많이 사용되고 있으나 수행 중에 동적으로 다운로드 되는 바이트코드를 수행하기 위해서는 기존의 해석기도 함께 사용되어야 한다. 이 경우 일부 자바 메소드는 AOTC에 의해 처리되고 일부 메소드는 해석기에 의해 수행되는 하이브리드 수행 환경이 된다. 이러한 환경에서 해석기 메소드가 AOTC 메소드를 호출하거나 AOTC 메소드가 해석기 메소드를 호출하는 경우 호출 오버헤드가 커서 성능을 저하시킬 수 가 있다. 본 연구에서는 AOTC에서 사용 가능한 두 가지 호출 인터페이스인 Java Native Interface(JNI)와 Compiled Native Interface(CNI)에 대해 하이브리드 수행 환경에서의 호출 오버헤드와 성능을 평가하고 각각의 장단점에 대해 논의한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.18 no.4
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• pp.313-320
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• 1998

To record and evaluate the flaws which were found during pre-service/in-service inspection performance of nuclear power plants in Korea, the center line beam method described in ASME code and 6 dB drop method stated in CSA code were used. The measured through wall dimensions and lengths by these methods were compared and analyzed in this report. With the measured data analysis, the ekact understanding and use of these methods improves the reliability of flaw sizing and assures the integrity of nuclear power plant components.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.11a
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• pp.281-283
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• 2009

본 논문에서는 군집 소실 채널 상에서 동작할 수 있는 짧은 길이의 인터리빙 된 코드들의 성능을 분석한다. 먼저 좋은 성능을 갖는 짧은 길이의 그래프 부호와 해밍부호를 설계한다. 이 후 군집 소실에 잘 대응하기 위하여 인터리빙 기능을 채널 부호화 방법에 적용한다. 생성된 짧은 코드에 적용한 인터리빙 부호를 군집 소실에 최적의 성능을 보이는 Reed-Solomon (RS) 부호와 성능을 비교한다. 짧은 길이의 부호이므로, ML(Maximum Likelihood)방법과 BP(Belief propagation)의 두 가지 복호 방법들을 이용한 경우 성능의 차이 또한 비교해 본다.