• 한국ITS학회:학술대회논문집
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• 2004.11a
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• pp.125-132
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• 2004

• Journal of Korean Society of Transportation
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• v.23 no.4 s.82
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• pp.17-28
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• 2005

About 91.1% of Railway-Highway Crossings (RHC) in Korea use a Constant Distance Warning System(CDWS), while about 8.9% use a Constant Warning Time System(CWTS). The CDWS does not recognize speed differences of approaching trains and provides only waiting times to vehicles and pedestrians based on the highest speed of approaching trains. Under the CDWS, therefore, low speed trains provide unnecessary waiting times at crossings which often generates complains to vehicle drivers and pedestrians and may cause wrong decisions to pass the crossings. The objective of this research is to improve the safety of the RHC by developing accurate a CWTS. In this research a train speed and location detection system was developed with ultra sonic detectors. Locations of the detectors was decided based on the highest speed and the minimum warning time of Saemaul of 160 km/h. To validate the algorithms of the newly developed systems the lab tests were conducted. The results show that the train detection system provides accurate locations of trains and the maximum error between real speeds of trains and those of the system was 0.07m/s.

• The Journal of the Korea Contents Association
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• v.21 no.12
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• pp.107-118
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• 2021

One of the debates regarding the college admission systems is about which admissions screening works as a mechanism for social mobility, between early and regular admissions. This study attempted to contribute to related discussions by analyzing the income level of college admissions students according to the admissions screening (early vs. regular admissions) using data from the third year survey of the Korean Education & Employment Panel II (KEEP II). Analyzing the dataset, we found that parental income was almost the same between students admitted from early and regular admissions. To be specific, average monthly parental income was 586.4 million Korean Won for students admitted from early admission while it was 585.4 million Korean Won for those admitted from regular admission, which means that the difference between the two was neither practically nor statistically significant. Applying the chi-square test, we tested whether the relationship between parental income and types of college admissions and found no statistical significance. Finally, categorizing colleges where students are admitted by ranking, we compared parental incomes among students. We found that parental income was higher for top-ranked universities, and that parental income was higher for students admitted from early admission. We concluded that early admission can possibly be an admission system for "well-offs" between the two, and that early admission may not be working as a pathway to facilitate social mobility compared to the regular admissions.

• Journal of Korean Society of Transportation
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• v.27 no.6
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• pp.119-127
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• 2009

It has been known that bus route and company related characteristics have influences on punctuality, but fewer research have been conducted. Independent variables used in this study were selected using correlation analysis, and OLS(Ordinary Least Square) and HLM(Hierarchical Linear Model) were employed to identify factors affecting bus punctuality(headway deviation). The results showed that ICC(intraclass Correlation Coefficient) is 0.10, indicating that hierarchical linear models are more adequate for these data because there is effective variation in the subjects between companies. Punctuality was found to be negatively associated with the number of vehicles, the number of persons per vehicle, and total travel time. On the other hand, average headway and company size have a positive relationship with punctuality. Therefore, the number of vehicles per route, average headway, and the number of vehicles managed by a company should be considered for more accurately evaluating the management of piunctuality.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.2646-2648
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• 2005

열차는 타 교통수단에 비하여 정시성과 안전성이 우수하다는 장점을 가지고 있다. 이러한 열차의 정시성을 유지하는데 있어서 열차 경합에 대한 대응은 매우 중요한 용소이다. 열차 경합은 열차와 열차간의 충돌로 정의된다. 이러한 열차의 경합은 두 열차의 각 역에서의 도착 및 출발시각을 변경함으로써 해결할 수 있다. 본 논문에서는 전문가 시스템 및 제약조건 만족 기법을 이용하여 열차 경합을 해소하는 알고리즘을 제시한다.

• Journal of the Korean Society for Railway
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• v.15 no.1
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• pp.80-87
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• 2012

This study analyzed the quality of a commuter rail service of Incheon line 1 with respect to two service measures such as occupancy (crowdedness) and punctuality based on transit smart card data collected in 2009. In order to analyze the metro services by individual fleet, we aggregated the personal level card data into the fleet operated in each planned schedule. The results show a low level of service for both crowdedness and punctuality during peak hours at the line segment from 'Gyeyang' to 'International business district'. Further, a close relationship between vehicle occupancy and punctuality is found, which illustrates high passenger demand causes successive metro delay.

• Journal of the Korean Society for Railway
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• v.8 no.2
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• pp.145-154
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• 2005

Traffic accidents at highway-rail crossing result in larger social and economic damages than the accidents at the typical highway intersections. The traditional control and warning systems of the highway-rail crossing have limitations in that 1) they do not recognize the differences of the trains' arrival times because they rely on the distance-based control system, rather than the time-based one, and 2) thereby they usually cause longer delays of vehicles and pedestrians at the highway-rail crossings. The objective of this study is to develop a time-based railroad crossing control system which takes into account the speed and expected arrival time of trains. using the spot speeds and acceleration rates of trains measured at three points, the developed system was found to be able to accurately estimate the arrival time of train. VISSIM simulation package was utilized to compare system effect of the developed time-based railroad crossing control system with that of the conventional distance-based one. It was found that the developed time-based railroad crossing control system reduced the average travel time, maximum delay length, average delay time, and average number of stop-experienced vehicles as much as 7.0$\%$, 75.6$\%$, 12.7$\%$, and 60.0$\%$, respectively, compared with those from the conventional distance-based one.

• Journal of Korean Ophthalmic Optics Society
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• v.21 no.2
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• pp.119-126
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• 2016

Purpose: To analyze the effect of accommodative control and change values between subjective refraction (SR) and auto-refraction (AR) according to application of fogging after accommodative stimulation depending on ametropia type. Methods: Myopic ametropia 76 eyes and hyperopic ametropia 52 eyes participated for this study. SR and AR values measured by three test conditions (Before accommodative stimulation; Before AS, After accommodative stimulation; After AS, and After application of fogging; After AF) were compared, respectively. Results: In myopic eyes, (-)spherical power by SR and AR in After AS test was significantly increased as compared to Before AS test, (-)spherical power in After AF test was decreased to the level of Before AS test. The differences of spherical power between SR and AR were highly measured by SR in After AS test, and highly measured by AR in After AF test, respectively. In hyperopic eyes, (+)spherical power of SR significantly decreased in After AS test compared to Before AS test, more (+)spherical power was detected in After AF test compared to Before AS test. (+)spherical power of AR have no significant difference between Before AS and After AS test, but more (+)spherical power was detected in After AF test compared to Before AS test. The differences of (+)spherical power between SR and AR were significant in all test conditions. Among 52 eyes which were measured as hyperopic ametropia, 7 eyes were measured as myopia by SR in After AS test. In case of AR, 25 eyes among 52 eyes were mismeasured as myopia of ranges from -0.25 D to -1.25 D in Before AS test, 26 eyes in After AS test, and 19 eyes in After AF test were mismeasured as myopia of ranges from -0.25 D to -1.25 D. Conclusions: Regardless of ametropia type, accommodative control by After AF test was effective on both refraction process. However, in auto-refraction for hyperopic eyes, the misdetermined proportion of refractive error's type was high due to consistent accommodative intervention in all test condition. Therefore, in order to obtain an accurate value of refractive errors, full correction should be determined by subjective refraction process after fogging method.

• Journal of Korean Ophthalmic Optics Society
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• v.13 no.1
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• pp.77-81
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• 2008

Purpose: This study was to investigate the refractive state of an asian population (male: 39, female: 53) from 21 to 30 years old who visited the A optical shop at jongnogu in seoul. Methods: The visual acuity test was performed by the object and subject method. Results: Among the 184 eyes, myopia is 83.16% and emmetropia is 16.84%, respectively. As for the equivalent spheric power of myopic abnormal refractive eyes, the -m0.5Dt < spheric equivalent ${\leq}$ -2.00Dt was 40.53%, the -2.00Dt < spheric equivalent ${\leq}$ -6.00Dt was 51.63% and anything over the -6.00Dt was 7.85%. The percentages of with-the-rule, against-the-rule and oblique astigmatism among people with astigmatism were 46.67%, 35.56% and 7.77%, respectively. The average of pupillary distance in male (64.5${\pm}$2.9 mm) was greater than that in female (61.9${\pm}$2.3 mm). Conclusions: Korean opticians were provided some useful information about making up a prescription by this research.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10c
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• pp.143-145
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• 1999

정시 서비스를 제공하는 실시간 시스템을 설계할 때 일반성을 지니도록 하기 위하여 실시간 객체인 TMO(Time-triggered Message-triggered Object) 모델이 연구되었으며 이러한 객체를 수행하기 위한 객체 모델 수행 플렛폼이 다양한 환경에서 개발되었다. 본 논문에서는 최근 들어 많은 주목을 받고 있는 리눅스 환경에서 설계 및 구현된 미들웨어 형태의 실시간 객체 모델 수행 플렛폼 LTMOS(Linux TMO System)에 대해 기술한다. 응용 프로그램 개발자가 실시간 시스템을 TMO 모델로 디자인하면 LTMOS는 TMO의 메쏘드를 리눅스의 쓰레드로 매핑하여 리눅스 커널의 실시간 스케쥴링을 받도록 한다.