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2기 전력계통의 동적 안정도 해석을 위한 단순화된 모델
장성환,안태천,이중빈 원광대학교 공업기술개발연구소 1981 工業技術開發硏究誌 Vol.1 No.-
Dynamic stability analysis of a large interconnected power system may even exceed the storage capacity of modern fast computers because of the high order of the matrix. In this paper two methods hav teen introduced to obtain simplified models of the systems bared on the magnitude of the variables or the eigenvalves. The difference between the eigenvalves of the reduced models and that of the original models was within 0.53% and the difference of the rerponse during the transient time in negligible. This method can be used to calculate the eigenvalues and analyze the dynamic stability of systems of high order matrix.
셀룰라 이동통신 제어 시스템에서 색채화 문제에 의한 채널할당
장성환,라상동 한국통신학회 1994 韓國通信學會論文誌 Vol.19 No.9
셀룰라 이동통신 제어 시스템에서 고도의 스펙트럼 효과를 도출해 내기 위해 셀에서 호에 대한 채널을 할당하는 것은 한정된 주파수 대역폭내에서 중요한 문제이다. 이동통신 제어 시스템에 있어서는 스펙트럼 효과를 그래프 이론의 색채화 문제로 연관 시킬 수 있다. 본 논문에서는 셀룰라 이동통신 제어시스템의 그래프 이론을 이용하여 채널 오프셋 구조를 제안하고, 그래프 색채화 문제와 관련된 채널 오프셋 구조의 색체화 대역폭을 수식화 하였다. 수식화 된 채널할당 문제로부터 채널 구성에 따른 셀 설계와 보다 효율적인 주파수 스펙트럼의 최적 채널 오프셋을 연구하여 전체 스펙트럼 대역폭에 대한 상한치와 하한치를 부여 한다. In a cellular mobile communication control system, assignment channel for a call in a cell so as to achieve high spectral efficience is an important problem within limited frequence bandwidth. The spectral efficiency is related to the coloring problem of graph theory in a cellular mobile communication control system. In this paper, we propose channel offset scheme using a graph theory of cellular mobile communication control system and formulate chromatic bandwidth of channel offset system which is related graph coloring problem. From formulated channel assignment problem, we investgate an optimal channel offset scheme of more efficent frequence spectrum and cell design according to channel constitution and give and upper and lower bound for overall srectral bandwidth.
장성환,고대식,전계석,Jang, Seong-Hwan,Go, Dae-Sik,Jeon, Gye-Seok 한국음향학회 1989 韓國音響學會誌 Vol.8 No.4
In this paper, the construction of ultrasonic hologram and the image reconstruction using computer have been studied, and it has been compared with optical reconstruction. The ultrasonic hologram has been constructed using c-scanning method$(128\times128 step)$and the image of the object has been reconstructed by computer using Rayleigh -Sommerfeld formula and DFT algorithm. In this experiment, the holography system has been builted with the transducer of 5MHz center frequency and 5cm focal length, and the mechanical c-scanning system. It has been shown that the reconstructed image using computer for aluminum plane with the 'S' shaped defect has been displayed image of high quality. 본 논문에서는 컴퓨터에 의한 초음파 홀로그램의 구성과 영상 재생방법을 연구하였으며 이를 광학적 재생방법과 비교 분석하였다. 초음파 홀로그램은 초음파 변환자를 기계적으로 c-scan $(128\times128 step)$하여 구성하였고 물체에 대한 영상은 Rayleigh-Sommerfeld 식과 DFT 알고리즘을 이용하여 컴퓨터 재생하였다. 본 실험에서 는 중심주파수가 5MHz이고 촛점 거리가 5cm 인 초음파 변환자와 기계적인 c-scanning 시스템을 사용하여 음향 홀로그래피 시스템을 구성하였고 알루미늄 판에 S자 형태를 새긴 샘플을 제작하여 실험하였다. 실험결과 컴퓨터에 의해 재생된 영상은 실체와 동일한 고질의 영상임을 확인하였다.
장성환,이정학 한국청각언어재활학회 2016 Audiology and Speech Research Vol.12 No.2
Purpose: The purpose of this study was to develop a list of sentences for auditory training, especially speech tracking for hearing impaired adults. Methods: A total of 1,000 sentences which were collected from five popular novels, were recorded on a compact disk. Seventy-five hundred basic sentences were selected based on the validity test and 750 noise sentences were made by synthesizing basic sentences with 4-talker babble noise. Participants were 20 young and 20 elder people who spoke Korean as their first language. Results: Results showed that all 750 basic sentences scored greater than 90% of correct response rate. However, 138 noise sentences scored lower than 90% of correct response rate. In 750 noise sentences, there were significant differences in correct response rate with respect to the number of words in each sentence, age, and speaker. Conclusion: These results recommend that newly developed 750 basic sentences are appropriate in speech tracking for adult auditory training. For noise sentences, however, 618 sentences are recommended for speech tracking.