• Journal of Communications and Networks
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• 제18권3호
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• pp.502-512
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• 2016

The wireless carrier sense multiple access with collision detection (WCSMA/CD) and carrier sense multiple access with collision resolution (CSMA/CR) protocols are considered representative distributed collision detection protocols for fully connected dense wireless local area networks. These protocols identify collisions through additional short-sensing within a collision detection (CD) period after the start of data transmission. In this study, we analyze their throughput numerically and show that the throughput has a trade-off that accords with the length of the CD period. Consequently, we obtain the optimal length of the CD period that maximizes the throughput as a closed-form solution. Analysis and simulation results show that the throughput of distributed collision detection protocols is considerably improved when the optimal CD period is allocated according to the number of stations and the length of the transmitted packet.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1487-1493
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• 2008

Railway vehicle is very important to implement the effective maintenance in proper to prevent any failure during operation period. Many railway authorities are making efforts to maintain the railway vehicle through scientific and systematic procedure. To achieve this, Reliability Centered Maintenance(RCM) is partially applied. The efficiency of RCM has proven and its terminology was familiar with nuclear power, military and chemical plant etc. since the commercial aircraft's industries has introduced the maintenance program based on the target of reliability. The application of RCM on railway vehicle can be utilized with systematic analysis method to select the best effective maintenance period and action to prevent the failures by selecting the equipment affecting the its safety and reliability. This paper is presented that the procedure of adequate and effective maintenance for railway vehicle by comparing among the related standards in example IEC60300-3,11, MIL-STD-2173, and technical documents or papers. In accordance with above result, RCM procedure is proposed to apply effectively for maintenance of railway vehicle. That is, (1) Analysis of data and Calculation of criticality per equipment (2) Selection of equipment to analyze (3) Analysis of failure mode and effect (4) Evaluation of maintenance method and period (5) Optimization of maintenance program through renewal of maintenance method and period.

• 한국콘텐츠학회논문지
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• 제16권11호
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• pp.83-90
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• 2016

본 논문에서는 저전력 통신 기술인 IEEE 802.15.4 MAC (Media Access Control) 프로토콜에서 지원하는 Collision Free Period(CFP)에서의 전송 성능 분석을 수행한다. 분석을 위해 CFP의 서비스 타겟인 주기적 트래픽을 고려하고 Quality of Service 요구사항에 따라 MAC 계층에 전달되는 패킷전달 형태를 batch와 non-batch로 구분하여 throughput, delay, energy 측면에서 성능을 분석한다. 도출된 분석 결과를 토대로 Pedometer, ECG, EMG와 같이 주기적인 트래픽을 생성하는 헬스케어 애플리케이션에 대해 Collision Avoidance Period(CAP)에서의 전송과 성능 비교를 수행한다. 성능 평가를 통해 헬스케어와 같이 주기적이며 time-critical 트래픽을 생성하는 애플리케이션은 CFP 전송이 에너지 효율적이며 대역폭 요구 사항이 큰 애플리케이션에서는 CAP 대비 최대 46%의 에너지가 절감됨을 확인하였다.

• Asian Pacific Journal of Cancer Prevention
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• 제16권9호
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• pp.3951-3955
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• 2015

Background: Colorectal cancer mortality has started to decrease in several developed countries in Asia. The current study aimed to present the long-term trends in colorectal cancer mortality in Korea using joinpoint analysis and age-period-cohort modeling. Materials and Methods: The number of colorectal cancer deaths and the population for each 5-year age group were obtained from Statistics Korea for the period 1984-2013 for adults 30 years and older. Joinpoint regression analysis was conducted to determine changes in trends in age-standardized mortality rates, and age-period-cohort analysis was performed to describe trends in colorectal cancer mortality using the intrinsic estimator method. Results: In men, the age-standardized mortality rate for colorectal cancer increased from 1984 to 2003, and the mortality rates stabilized thereafter, whereas the mortality rate of colorectal cancer in women has decreased since 2004. The age-specific mortality rate of colorectal cancer increased in both men and women over time, whereas decreases in the age-specific mortality rate in younger cohorts were observed. In the age-period-cohort analysis, old age and recent period were associated with higher mortality for both men and women. The birth cohort born after 1919 showed reduced colorectal cancer mortality in both men and women. Conclusions: Our study showed a recent decreasing trend in colorectal cancer mortality in women and a stable trend in men after 2003-2004. These changes in colorectal cancer mortality may be attributed to birth cohort effects.

• 한국콘텐츠학회논문지
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• 제16권7호
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• pp.484-491
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• 2016

본 연구는 육아지원기관 이용기간과 아동의 언어 인지 발달 정도에 어떠한 상관관계가 있는지 연구하고, 이를 통해 아동 발달을 긍정적인 측면으로 이끄는데 그 목적이 있다. 이를 위하여 육아정책연구소 한국아동패널의 5차년도(2012) 자료를 사용하였으며, 조사에 응답한 1703가구 중 대상을 제외한 총 913가구를 대상으로 하였다. IBM SPSS Statistics SPSS 23 프로그램을 이용하여 빈도분석, t검정, 분산분석, 다중 선형회귀분석(multiple linear regression analysis) 등을 통하여 결과를 도출하였다. 분석 결과, 육아지원기관 이용 기간과 아동의 언어 인지발달 사이에 유의한 상관관계가 있었으며, 육아지원기관 이용기간이 길수록 아동의 언어 인지 발달이 높다는 것을 알 수 있었다. 이를 보건 정책에 적용하여 무상보육정책을 확대한다면, 아동의 언어와 인지 발달 정도에 긍정적인 영향을 미칠 것이라 예상된다.

• 융합정보논문지
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• 제10권3호
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• pp.67-75
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• 2020

본 연구에서는 주식시장과 채권시장간의 정보 이전효과(information flow effect)를 살펴보기 위해 우리나라 KOSPI의 일일지수와 초단기 채권형 펀드(money market fund : MMF) 수익률 자료를 이용하여 분석하였다. 전체 분석대상 기간은 1997년 5월 2일부터 2019년 8월 30일까지 이다. 1997년 5월 2일부터 2008년 12월 30일 글로벌금융위기전 기간, 2008년 12월 30일부터 2019년 8월 30일까지 글로벌금융위기 후 기간과 전체기간으로 세분하여 실증분석을 하였다. 분석결과 비대칭적 변동성을 고려한 EGARCH 모형이 적합한 것으로 나타났다. 주식시장과 채권시장 간에는 가격이전효과와 변동성 이전효과가 양방향으로 존재하는 것으로 나타났으며, 가격이전효과는 두 시장 간에 글로벌금융위기전 기간이 후보다 더 크게 나타났다. 주식시장과 채권시장간의 정보에 대한 비대칭적 변동성이 두 시장에 존재하는 것으로 나타났다.

• 정보관리학회지
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• 제35권2호
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• pp.89-114
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• 2018

학문 분야의 연구 동향 변화에 대한 연구는 해당 분야의 세부 연구주제와 구조에 대한 파악뿐만 아니라 시간 흐름에 따른 변화 모습을 관찰할 수 있는 방법이다. 이에 본 연구에서는 국내 문헌정보학 분야의 연구 동향을 살펴보기 위하여 2003년부터 2017년까지 한국학술지인용색인(KCI)에 등재된 문헌정보학 분야 학술지 중 인용지수가 가장 높은 3종에 개제된 논문의 한국어 저자키워드를 대상으로 동시출현단어 분석을 수행하였다. 시계열 분석을 위해 15년의 연구 기간을 5년 단위로 누적하여 2003년~2007년, 2003년~2012년, 2003년~2017년으로 구분하였고, 기간별로 출현빈도 10회 이상의 저자키워드를 선정하여 분석하고 이를 시각화하였다. 분석 결과, 2003년~2007년 기간의 지적구조는 총 25개의 키워드로 구성된 8개의 영역이 확인되었으며, 2003년~2012년 기간의 지적구조에서는 총 76개의 키워드로 구성된 3영역 17 군집이 확인되었다. 또한, 2003년~2017년 기간의 지적구조는 총 132개의 키워드로 구성된 6영역 32군집으로 나타났다. 누적 기간별 종합 분석 결과, 한국의 문헌정보학 분야는 지난 15년간 기간별로 새로운 키워드가 포괄적으로 추가되었으며, 세부 주제 역시 세분화 되어 점차 세분화되고 확장되고 있음을 확인하였다.

• Earthquakes and Structures
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• 제4권4호
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• pp.397-428
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• 2013

This paper examines whether the "effective period" of bilinear isolation systems, as defined invariably in most current design codes, expresses in reality the period of vibration that appears in the horizontal axis of the design response spectrum. Starting with the free vibration response, the study proceeds with a comprehensive parametric analysis of the forced vibration response of a wide collection of bilinear isolation systems subjected to pulse and seismic excitations. The study employs Fourier and Wavelet analysis together with a powerful time domain identification method for linear systems known as the Prediction Error Method. When the response history of the bilinear system exhibits a coherent oscillatory trace with a narrow frequency band as in the case of free vibration or forced vibration response from most pulselike excitations, the paper shows that the "effective period" = $T_{eff}$ of the bilinear isolation system is a dependable estimate of its vibration period; nevertheless, the period associated with the second slope of the bilinear system = $T_2$ is an even better approximation regardless the value of the dimensionless strength,$Q/(K_2u_y)=1/{\alpha}-1$, of the system. As the frequency content of the excitation widens and the intensity of the acceleration response history fluctuates more randomly, the paper reveals that the computed vibration period of the systems exhibits appreciably scattering from the computed mean value. This suggests that for several earthquake excitations the mild nonlinearities of the bilinear isolation system dominate the response and the expectation of the design codes to identify a "linear" vibration period has a marginal engineering merit.

• 대한방사선기술학회지:방사선기술과학
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• 제23권1호
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• pp.39-47
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• 2000

In this study, we showed a comparison and analysis making use of DWI(diffusion weighted image) using early diagnosis of cerebral Infarction and with the classified T2 weighted image, FLAIR images signal intensity for brain infarction period. period of cerebral infarction after the condition of a disease by ischemic stroke. To compare 3 types of image, we performed polynomial warping and affined transform for image matching. Using proposed algorithm, calculated signal intensity difference between T2WI, DWI, FLAIR and DWI. The quantification values between hand made and calculated data are almost the same. We quantified the each period and performed pseudo color mapping by comparing signal intensity each other according to previously obtained hand made data, and compared the result of this paper according to obtained quantified data to that of doctors decision. The examined mean and standard deviation for each brain infarction stage are as follows ; the means and standard deviations of signal intensity difference between DWI and T2WI for each period are $197.7{\pm}6.9$ in hyperacute, $110.2{\pm}5.4$ in acute, and $67.8{\pm}7.2$ in subacute. And the means and standard deviations of signal intensity difference between DWI and FLAIR for each period are $199.8{\pm}7.5$ in hyperacute, $115.3{\pm}8.0$ in acute, and $70.9{\pm}5.8$ in subacute. We can quantificate and decide cerebral infarction period objectively. According to this study, DWI is very exact for early diagnosis. We classified the period of infarction occurrence to analyze the region of disease and normal region in DW, T2WI, FLAIR images.

• 한국병원경영학회지
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• 제4권1호
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• pp.147-170
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• 1999

This study was performed to assess the financial performance of medical institutions and examine the affecting factors in Taegu metropolitan and Kyungpook province. The major results are as follows ; The liability to total assets was significantly different according to the ownership type of medical institution. It was the highest in the case of juridical person having a special status. The total assets turnover and value added to total assets were significantly different according to the type of medical institution, period of establishment, and ownership type of medical institution. They were higher in the tertiary medical institution, in private hospital and university hospital, and they were increased with establishment period of medical institution. The growth rate of patient revenues were significantly different according to the type of medical institution, period of establishment, and the growth rate of adjusted inpatient days were significantly different by period of establishment. The return on assets and net profit to gross revenues were the highest in private hospital. Private hospital went into the black, but other hospitals went into the red figures. According to the multiple regression analysis for the net profit to gross revenues, ownership type, period of establishment, and management strategy of medical institution were significant It was higher in private hospital and medical institution with prospector management strategy, and it was increased with establishment period of medical institution. In multiple logistic regression analysis for the status of financial performance in medical institution, period of establishment, management strategy of medical institution were significant It was better in medical institution with prospector management strategy and longer period of establishment.