64 Slice MDCT에서 HR Variation이 Image Quality에 미치는 영향에 대한 고찰

김주현(Joo Hyun Kim),김상현(Sang Hyun Kim),여상근(Sang Geun Yeo),대창민(Chang Min Dae),민관홍(Kwan Hong Min),김성룡(Sung Ryong Kim) 대한CT영상기술학회 2007 대한CT영상기술학회지 Vol.9 No.1

Purpose 16 slice MDCT is Widely used for coronary CT angiography, however it is well known that image quality is more affected the variation of heart rate than heart rates. Recently, 64 slice MDCT has been introduced, it has the merit of faster scan time. Therefore, it might be improve image quality for minimizing the variation of heart rate during scan time. The purpose of this study is, (a) to analyze the variation of heart rate according to time-course during CT scanning (b) to evaluate how to impact to the image quality by the differences of heart rate variation. Materials and Methods Total 200 patients were enrolled in this study. 100 patients who underwent cardiac CT With 16 MDCT from Jan 2004 to Jul 2004(74 men, 26 women; mean age 55.15±12.75 years), 100 patients who underwent cardiac CT With 64 MDCT from Jun 8, 2006 to Jun 30, 2006(68 men, 32 women; mean age 58.4±11.56 years). Mean heart rate is no significant difference between two groups(16 MDCT 71.04±3.52bpm, 64 MDCT 69.31±4.71bpm). Equipments were used 16 MDCT(Mx8000 IDT, Philips) and 64 MDCT(Brilliance 64, Philips) which are the same rotation times(420msec, i.e. temporal resolution is same as 53msec). We recorded the variation of HR during pre and post scan as well as scanning period. We evaluated the image quality by dividing several groups according to the variation of HR ; Group I(0-5bpm), Group II(11-15bpm), Group III(11-5bpm), Group IV(16-20bpm), Group V(above 20bpm). The results are also compared for the evaluation of quality between 16 MDCT and 64 MDCT. For the qualitative analysis of image quality, we used 4 grade scoring system(Excellent : 4 points, Good : 3 points, Fair : 2 points, Bad : 1 point). For the quantitative analysis, we analyzed the presence and frequency of banding artifacts including stair-step artifact and acceleration artifact. Results The result of mean HR variation on 64 MDCT was significantly diminished comparing With 16 MDCT(5.48±4.20 bpm vs 10.31±5.90, P<0.05). For the qualitative analysis of image quality. The overall score of 64 MDCT is statistically larger than that of 16 MDCT(3.41±0.7 VS 2.84±0.9, P<0.05). For the quantitative analysis the frequency of stairstep artifacts is markedly occurred on 16 MDCT(64 MDCT: 0.5±1.04, 16 MDCT: 2.4±3.2, P<0.05). Furthermore, acceleration artifact was extremely rare on 64 MDCT (64 MDCT: 1, 16 MDCT : 11, P<0.05). Conclusion In this study, we suggest that 64 MDCT have the merit to improve image quality by reducing scan time and minimizing the variation of heart rate comparing With 16 MDCT. We conclude that 64 MDCT will be play an important role for the evaluation of ischemic heart disease due to markedly eliminating acceleration artifact which is frequently occurred in patients who could not sufficient breath-hold.

생활시간조사 자료를 활용한 통행시간예산 연구

장수은 한국교통연구원 2018 交通硏究 Vol.25 No.3

The hypothesis entitled “travel time budgets” represents that personal daily travel time expenditure is stable. This paper empirically explored the theory analyzing the Korean time use survey data. Five research questions were raised and examined. First, Korean travel time budgets were 100 and 110minutes for total people and travelers only, respectively. Second, the cross-sectional stability of travel time use was not confirmed while the time-series stability of the spending was verified. Third, there were little connections between travel time budgets and day-of-week variations of travel time use. Fourth, travel time budgets of trip purposes for commuting and business and those for social interaction and leisure were found. In contrast, travel time budgets of the other trip purposes could not be examined mainly because their travel times consumed were too short. Fifth, inter-group average travel time use was different while intra-group average travel time expenditure showed time-series stability. The concluding remarks stressed the need for theoretical structure that can address the hypothesis itself and also can reestablish the relationship between existing transport theory and the stability of travel time use. 사람들이 하루 24시간 중 이동에 사용하는 평균 통행시간이 일정하다는 학설이 있다. 이를 통행시간예산이라고 한다. 본 연구는 통계청의 생활시간조사 마이크로 자료를 분석하여 이 가설을 실증적으로 검증하였다. 본 연구의 분석결과를 정리하면 다음과 같다. 첫째, 우리나라 교통체계의 통행시간예산은 모집단을 전국민으로 설정했을 경우 약 100분, 모집단을 통행자 집단으로 국한했을 경우 약 110분으로 나타났다. 둘째, 통행시간의 시계열적 안정성과 달리 횡단면적 안정성은 확인할 수 없었다. 셋째, 통행시간예산과 요일 변동 사이에는 큰 연관이 없었다. 넷째, “출퇴근 및 업무”와 “교제 및 여가” 목적의 통행시간예산은 나타났으나 그 외 나머지 통행목적의 평균 통행시간은 절댓값이 작아 통행시간예산 여부를 판단할 수 없었다. 다섯째, 사회집단 간 평균 통행시간 사이에는 일정 부분 차이가 있었으나 각 집단별 평균 통행시간은 시계열적 안정성을 보였다. 향후 연구과제로는 통행시간예산을 설명할 수 있는 이론체계, 특히 이 가설과 통행행태 이론 등 기존 교통학 이론체계와의 관계정립 문제가 강조되었다.

동적통행배정모형의 실시간 교통상황 반영

신성일,최기주,오영태 대한교통학회 2002 대한교통학회지 Vol.20 No.4

The basic assumption of analytical Dynamic Traffic Assignment models is that traffic demand and network conditions are known as a priori and unchanging during the whole planning horizon. This assumption may not be realistic in the practical traffic situation because traffic demand and network conditions may vary from time to time. The rolling horizon implementation recognizes a fact: The prediction of origin-destination(OD) matrices and network conditions is usually more accurate in a short period of time, while further into the whole horizon there exists a substantial uncertainty. In the rolling horizon implementation, therefore, rather than assuming time-dependent OD matrices and network conditions are known at the beginning of the horizon, it is assumed that the deterministic information of OD and traffic conditions for a short period are possessed, whereas information beyond this short period will not be available until the time rolls forward. This paper introduces rolling horizon implemen- tation to enable a multi-class analytical DTA model to respond operationally to dynamic variations of both traffic demand and network conditions. In the paper, implementation procedure is discussed in detail, and practical solutions for some raised issues of 1) unfinished trips and 2) rerouting strategy of these trips, are proposed. Compu- tational examples and results are presented and analyzed. 기 제안된 수리적 동적통행배정모형은 전체 시뮬레이션 기간동안 시간종속적 교통수요와 교통망의 교통상황이 이미 안정되어 있고 장래에도 예측가능 하다는 가정을 전제로 개발되었다. 이러한 가정은 실제 시시각각으로 변화하는 교통수요와 교통상황의 예측 불가능함 고려할 때 비현실적이라고 할 수 있다. 한편, Rolling Horizon Implementation(RHI)은 기종점간의 수요행렬(trip matrix)과 교통상황(traffic condition)이 단기간의 예측시간동안 현재의 예측정보를 기반으로 신뢰성 있게 모니터링 될 수 있고, 그 시점에서 보다 미래로 연장된 시간으로는 불확실성(uncertainty)의 증가를 고려한다는 가정을 전제로 제안되었다. 따라서, RHI개념과 부합되는 수리적 동적통행배정모형은 시뮬레이션 출발시점에 수요와 교통상황에 대한 확정적 정보가 이미 획득되어 있고, 그 기간이후의 정보에 대해서는 시간이 흐름에 따른 정보의 유용성을 근거로 각 운전자 그룹이 인지(perceived)하는 가로망의 통행비용(travel cost)을 최소화되도록 차량을 배정하는 것으로, 실시간적으로 인지된 교통수요와 교통망에 대한 정보를 통행배정초기에 입력변수로 사용하여 실시간 교통정보모형으로서 운영가능 하다는 장점을 제공한다.본 연구는 수리적 동적통행배정모형이 RHI개념과 부합되어 교통상황과 수요변화를 실시간적으로 반영하여 운영되도록 모형의 기능을 확장하는 데 있다. 이를 위해, 다계층 이용자(multiple user classes) 동적통행배정모형을 변동등식(variational equality)이론에 근거한 모형식을 기반으로, 실시간 통행배정에서 발생하는 종점에 도착하지 못한 차량 (unfinished trips)과 이들의 재배정(rerouting strategy) 문제를 인식하고, 이 차량들을 링크상의 교통량 전파조건(flow propagation constraint)을 토대로 다음 통행배정 시간대의 실시간 수요로서 반영할 수 있는 방안을 제시한다.

동적통행배정모형의 실시간 적용을 위한 변동등식의 응용

신성일,Ran, Bin,최대순,백남철 대한교통학회 2002 大韓交通學會誌 Vol.20 No.3

This paper presents a variational equality for- mulation by providing new dynamic route choice condition for a link-based dynamic traffic assignment model. The concepts of used paths, used links, used departure times are employed to derive a new link-based dynamic route choice condition. The route choice condition is formulated as a time-dependent variational equality problem and necessity and sufficiency conditions are provided to prove equivalence of the variational equality model. A solution algorithm is proposed based on physical network approach and diagonalization technique. An asymmetric network computational study shows that ideal dynamic-user optimal route condition is satisfied when the length of each time interval is shortened. The I-394 corridor study shows that more than 93% of computational speed improved compared to conventional variational inequality approach, and furthermore as the larger network size, the more computational performance can be expected. This paper concludes that the variational equality could be a promising approach for real-time application of a dynamic traffic assign- ment model based on fast computational performance. 본 연구에서 변동등식에 근거한 동적경로선택조건을 도출하여 동적통행배정모형을 제안한다. 동적경로선택조건은 운전자에 의해 이용된 경로, 링크 그리고 출발지의 출발시간을 고려하여 도출되며 이 조건을 동적통행배정모형으로 전환하는 과정에서 모형의 변동등식문제로 압축된다. 등식이론에 근거한 모델의 이론적 배경을 입증하기 위해 제안된 동적통행배정모형이 필요충분조건을 만족함이 증명되었다. 해법으로서 기존의 제안된 네트워크의 시간과 공간확장기법을 채택하지 않고 물리적 네트워크가 직접 알고리즘에 반영되도록 하기위해 각 링크의 시간대별 통행량과 방출통행량을 링크진입통행으로 표현하여 시간종속 통행시간함수를 단일변수로 처리하여 대각화알고리즘에 반영하였다. 소규모 비대칭 네트워크 적용결과 사용자 동적최적경로선택조건이 만족됨을 입증하였는데 단위시간간격이 적을수록 개선된 효과를 보여준다. I-394네트워크 실험결과로서 기존의 변동부등식에 근거한 알고리즘에 비해 제안된 알고리즘이 최소한93%이상의 컴퓨터연산 속도의 개선효과를 가져왔다. 등식이론에 근거한 모델개발의 장점으로서는 제안된 모델의 최적해의 계산시간이 전체시간의 증가에 전혀 영향을 받지 않는 다는 것으로 이는 동적통행배정모형에 적용될 네트워크의 규모가 커질수록 제안된 알고리즘의 계산 효율성은 더욱 증가하는 것을 의미한다. 따라서 제안된 동적통행배정모형은 대규모 시간종속적 교통망에서 교통상황의 변화에 민감하게 반응할 수 있는 실시간첨단교통제어의 핵심기능으로서 역할수행이 기대된다.

딸기 조직배양 시 BA (benzyladenine) 처리에 따른 변이 발생 및 변이 연속성 검정

김혜진,최미자,이종남,서종택,김기덕,김율호,홍수영,김수정,손황배,남정환,Kim, Hye Jin,Choi, Mi Ja,Lee, Jong Nam,Suh, Jong Taek,Kim, Ki Deog,Kim, Yul Ho,Hong, Su Young,Kim, Su Jeong,Sohn, Hwang Bae,Nam, Jeong Hwan 한국식물생명공학회 2020 식물생명공학회지 Vol.47 No.1

본 실험은 딸기 조직배양 시 BA 처리에 따른 변이 발생 및 변이 연속성을 확인하고자 실시하였다. 본 실험에 사용된 공시 품종은 '고하'이며, 본 실험에 사용한 BA 농도는 0.0, 0.5, 1.0, 2.0 mg·L^-1로 처리하였다. 변이는 형태적, 유전적 검정을 실시하였으며, 변이 연속성 검정은 3년간 실시하였다. BA 처리 시 형태적 변이는 10.5 ~ 20.0%로 매우 높게 나타났으나, 유전적 변이는 재배 1년차에 7.0 ~ 15.0%, 재배 2년차에는 1.8 ~ 10.0%, 재배 3년차에는 5.0%로 재배연수가 길어짐에 따라 유전적 변이 발생율이 낮아졌다. 뿐만 아니라 재배1년차와 2년차에는 BA 1.0 mg·L^-1과 BA 2.0 mg·L^-1에서 유전적 변이가 발생한 반면, 재배 3년차에는 BA 2.0 mg·L^-1에서만 유전적 변이가 발생하였다. 따라서 딸기 조직배양묘의 증식을 위해서 BA는 1.0 mg·L^-1미만으로 처리하고, 반드시 변이 검정 후 보급하는 것이 바람직하다고 판단되었다. This experiment study aimed to identify the continuous genetic variation caused by benzyladenine (BA) treatment in strawberry tissue culture. The 'Goha' cultivar was used and treated with different concentrations of BA (0.0, 0.5, 1.0, 2.0 mg·L^-1). Morphological and genetic variation tests were performed, and genetic continuity tests were performed for three years. The morphological variation induced by BA was distinctively high (10.5 ~ 20.0%) and the genetic variation was 7.0 ~ 15.0%, 1.8 ~ 10.0%, and 5.0% in the first, second, and third year of cultivation, respectively. The rate of genetic variation decreased with increasing cultivation years. In addition, genetic variation caused by BA 1.0 mg·L^-1 and BA 2.0 mg·L^-1 occurred in the first and second years of cultivation, whereas only BA 2.0 mg·L^-1 caused genetic variation in the third year of cultivation. Therefore, a concentration of less than 1.0 mg·L^-1 BA was used for the propagation of strawberry tissue culture plants, and it was necessary to identify their variation.

생산현장에서 발생하는 불확실성을 고려한 생산통제기법들의 유용성 분석 : Shop Floor Control 측면을 중심으로

이장한,박진우 한국경영과학회 1993 한국경영과학회 학술대회논문집 Vol.- No.2

In this paper, we investigate the effect of production uncertainty - especially demand fluctuation and activity time variation, to production control policies. First, we examine three famous production control policies, namely, MRP, JIT, OPT, from shop floor control perspective and analyze the difference among them. Based on these, simulation studies are performed to draw out the effects of demand fluctuations which are classified into demand lumpiness and demand irregularity, and, the effects of activity time variations which are classified into standard time variation and non-standard time variation. Experimental investigation shows that, in term of demand fluctuations, MRP is affected by demand lumpiness. but JIT by demand irregularity. And we also see that both MRP and JIT are influenced by standard time variation with respect to activity time variations.

상장기업 부채비율의 안정성에 관한 연구

김병기 한국금융공학회 2018 금융공학연구 Vol.17 No.1

Recently, several studies on capital structure have begun to focus on the stability of leverage. The studies indicate that the explanatory power of the previously identified determinants of capital structure is low and the effects of these determinants on leverage varies with time. As an extension of the studies on variation in capital structure, this study sheds some light on the stability of Korean listed firms' leverage in the period of 2000-2016. The main results are as follows. First, firm fixed effects explain much more leverage variation than the determinants of capital structure identified in previous studies. Second, cross-sectional variation is more important than time-series variation. This implies that between-firm variation is greater than within-firm variation. Third, the initial debt ratio, if included as a determinant, plays a more important role than any other determinants in the panel model. This implies that firms intend to maintain its leverage stable fairly long time. Fourth, the effects of leverage determinants change according to the range of leverage. 최근 부채비율이 얼마나 안정적인가에 대한 연구가 활기를 띠고 있다. 특히 부채비율의 변동성을 횡단면적 변동성과 시계열적 변동성으로 구분하여 양자의 상대적 중요성을 알아보려고 한다. 이는 부채비율의 변동성에 대한 기존 자본구조 결정모형의 전반적인 설명력이 낮고 또한 결정요인이 부채비율에 미치는 영향이 시기에 따라 달라지기 때문이다. 본 연구도 이러한 노력의 일환으로 2000년부터 2016년까지 17년간 국내 기업의 부채비율의 안정성을 패널모형을 적용해 분석하였다. 주요 분석결과는 다음과 같다. 첫째, 기업고정효과가 기존연구에서 밝힌 자본구조 결정요인보다 부채비율의 변동성을 훨씬 더 잘 설명하고 있다. 고정효과모형에서는 기업고정효과가 중요한 역할을 한 반면에 시간고정효과 및 산업고정효과는 그렇지 못했다. 둘째, 횡단면적 변동성이 시계열적 변동성보다 더 중요했다. 이는 기업간 변동성이 기업내 변동성보다 더 크다는 것을 의미한다. 셋째, 초기 부채비율이 결정요인으로 포함되면 이 요인이 부채비율에 강한 정(+)의 영향을 끼쳐 기업이 안정성을 유지하려는 것을 알 수 있다. 넷째, 표본기간 동안 부채비율의 범위의 크기에 따라 기업을 분류하여 패널모형을 실행한 결과 부채비율의 변동성에 따라 결정요인의 유의성이 달라졌다. 분석결과를 종합하면 부채비율의 변동성을 설명하는데는 시간불변적인 기업고정효과가 가장 중요하며, 기업내 변동성보다는 기업간 변동성이 더 중요하다. 또한 결정요인의 부채비율의 변동성을 설명하는데 있어 기존 결정요인의 설명력은 낮게 나타나고 있어 설명력 개선을 위해서는 시간가변적인 결정요인의 추가적 투입이 요구된다. 끝으로 본 연구는 표본기간의 확장, 패널모형에서의 상호작용 검증, 표본의 세분화 등을 추후연구과제로 제시하고 있다.

Comparison of TDC Circuit Design Method to Constant Delay Time

Choi, Jin-Ho The Korea Institute of Information and Commucation 2010 Journal of information and communication convergen Vol.8 No.4

This paper describes the design method of Time-to-Digital Converter(TDC) to obtain the constant delay time and good reliability. The reliability property is described with delay elements. In TDC the time signal is converted to digital value which is based on delay elements for the time interpolation. To obtain the constant delay time, the first and the last delay elements have different structure compared to the middle delay elements. In the first and the last delay elements, the driving ability could be controlled for the different delay time. The delay element can be designed by analog and digital devices. The delay time of the element using analog devices is not sensitive to process parameters than that of the element using digital devices. And the TDC circuit by the elements using analog devices shows better reliability than that by the elements using digital devices also.

Time series analysis of patients seeking orthodontic treatment at Seoul National University Dental Hospital over the past decade

Hyun-Woo Lim,Ji-Hoon Park,Hyun-Hee Park,Shin-Jae Lee 대한치과교정학회 2017 대한치과교정학회지 Vol.47 No.5

Objective: This paper describes changes in the characteristics of patients seeking orthodontic treatment over the past decade and the treatment they received, to identify any seasonal variations or trends. Methods: This singlecenter retrospective cohort study included all patients who presented to Seoul National University Dental Hospital for orthodontic diagnosis and treatment between January 1, 2005 and December 31, 2015. The study analyzed a set of heterogeneous variables grouped into the following categories: demographic (age, gender, and address), clinical (Angle Classification, anomaly, mode of orthodontic treatment, removable appliances for Phase 1 treatment, fixed appliances for Phase 2 treatment, orthognathic surgery, extraction, mini-plate, mini-implant, and patient transfer) and time-related variables (date of first visit and orthodontic treatment time). Time series analysis was applied to each variable. Results: The sample included 14,510 patients with a median age of 19.5 years. The number of patients and their ages demonstrated a clear seasonal variation, which peaked in the summer and winter. Increasing trends were observed for the proportion of male patients, use of non-extraction treatment modality, use of ceramic brackets, patients from provinces outside the Seoul region at large, patients transferred from private practitioners, and patients who underwent orthognathic surgery performed by university surgeons. Decreasing trends included the use of metal brackets and orthodontic treatment time. Conclusions: Time series analysis revealed a seasonal variation in some characteristics, and several variables showed changing trends over the past decade.

대도시 토지피복의 변화와 기온 상승의 관계에 대한 시계열적 연구

정환도,송승근,조현주,이재근,이소라,이은재,이야마요시노부 충북연구원 2014 지역정책연구 Vol.25 No.1

The average temperatures had been increased by 0.74 degrees in around the world and 1.7 degrees in korea during the last hundred years. Especially, Changed the land cover and energy consumption by urbanization. It was attributed to a urban temperatures rise. These urban temperature rise an important factor cause tropical night, Increase citizens' health damage as well as cooling energy consumption. Thus to grasp caused of urban temperature rise and prepare a countermeasure. In this study, To investigate an the spatial variation in land cover and temperature rise of the time-series variation due to urbanization. Especially, propose to improvement direction for reduce rise in temperature of Daejeon. -