• Journal of the Korean Geographical Society
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• v.41 no.2 s.113
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• pp.227-243
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• 2006

This paper reviews how electronic media technologies involve and produce time-space dimensions in geometrical spaces, focusing on four theoretical perspectives: van Dijk's dual structure of networks as scale extension and reduction; Latour's actor-networks as fluid and hybrid networks; Virilio's dromospherical time as global media vectors; and Castells' timeless time as non-sequential flows. In these four theoretical perspectives, we can see that electronic media technologies involve different and multiple time-space dimensions in geometrical media spaces: from the two-dimensional spaces (surfaces) of concentric circles, through the one-dimensional spaces (lines) of actor-networks to the zero-dimensional spaces (points) of dromospherical time and finally to the multi-dimensional spaces (hypertexts) of timeless time. The paper concludes by suggesting that we need to explain electronic media spaces not only in terms of geometrical media spaces but also in terms of geographical media spaces in order to understand the ways in which electronic media spaces are dis/embedded in geographical spaces.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5D
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• pp.467-476
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• 2010

Travel delay (TD) denotes a time difference between the running time of vehicle with a normal speed and the travel time of vehicle with a reduced speed for traversing the same segment of roadway, and is sometimes used as a measure of time delayed in the junction or bottleneck areas of roadway. Urban freeways in the foreign countries are often suffering from traffic delay within the entrance and exit ramp junction influence areas, as a freeway with the speed limit of 80 km/h or higher only during the rush hours, but those in our country are especially experiencing severe traffic delay on the mainline segments as well as within the entrance and exit ramp junction influence areas, as a freeway with the speed limit of 80 km/h or less regardless of the rush hours. So, the purpose in this study is to develop the models that could predict the travel delay within the ramp junction influence areas of urban freeway having the geographical features which differ from the expressway, and also examine the validity of the travel delay predictive models developed.

• Journal of Korean Society of Transportation
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• v.17 no.5
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• pp.137-149
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• 1999

For decades, many traffic flow studies on the analysis and determination of level of service (LOS) for the weaving sections have been made to Provide several regression equations. Weaving and non-weaving speeds were dependent variables for the equations, with independent variables being weaving length, number of lanes, and weaving ratios. One of the difficulties in developing the equations was that the weaving areas were rare in Korea, so the statistical analyses for calibrating the equation parameter could not be performed in a desirable manner. In this regard, a new and stochastic methodology for predicting the weaving and non-weaving speeds within the weaving sections was required. In this study the following design variables were developed; influence area of the weaving section. headway distribution within the weaving section, maximum weaving volume of the weaving section, length of the ideal weaving section, and speed estimations for the weaving and non-weaving flows. The evaluation of the new model was made comparing the delay in the weaving section with the one in the freeway basic section.

• 전기의세계
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• v.11
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• pp.1-7
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• 1963

직류분권 전동기에 있어서 정상운전시에 계자회로를 개방하면 회전자의 속도가 매우 상승하는 경향이 있다. 여기에서는 이러한 이상현상 자체를 수학적으로 해석해서 개방후의 회전자의 속도변화와 전기자전류의 변화를 시간의 함수로써 구하였다. 그리고 회전자의 속도 및 전기자전류, 잔류자기와 회전자 최종속도와의 관계, 부하 torque를 생각했을 경우의 회전자속도강하조건, 및 speed-torque curve도 구해보았다. Speed-torque curve의 경우에는 수학적으로는 복잡함으로 간단히 하기 위하여 과도기간을 편의상 subtransient와 transient의 두가지 period로 나눈 다음 물리적 현상을 고려하여 sub-transient를 무시해서 생각하였다. 본 실험에서 detector로는 Diehl tachometer-generator를, tachometer입력으로는 Hewlett-Packard사제 Model 200CD형 oscillator에 의한 20cps signal을 사용하였다. 그리고 회전 속도와 전기자전류를 Duel Channel Sanborn-150 recorder로 기록하였다.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.52-53
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• 2003

세슘 원자 주파수 표준기에서 사용되는 램지 방법은 세슘 원자 빔을 U-자형 마이크로파 공진기로 지나게 하여 마이크로파와 시간 간격을 두고 두 번 상호작용하게 함으로써 간섭형 원자 공진 신호를 얻는 방법이다(그림 1). 이 방법을 사용하면 그림 2와 같은 공진 신호를 얻는데 이를 램지 신호라 한다. 원자 주파수 표준기의 정확도 평가를 위해서는 사용된 세슘 원자 빔의 속도 분포를 알아야 하는데, 이 램지 신호를 이용하여 속도 분포를 구할 수 있다. (중략)

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4D
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• pp.469-476
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• 2008

Recently, TOD gains popularity as a traffic solution measure of high density urban regeneration projects. The purpose of this study is to investigate traffic impacts of high density TOD projects, and to identify the issues to be resolved. For a case study, it chooses Gangnamgucheong station in Gangnam area served by two subway lines, and designates 400m radius from the station as a site for high-density development. The MOEs chosen for this study is traffic volume, time, distance, speed, and mode share. The SECOM model is adopted for traffic simulation. The analysis results show that high-density TOD is an effective tool for traffic improvement even with only one station area being implemented. It is found that the traffic volume increases near the station in nature where high-density development occurs, but it declines overall in the rest of Gangam area. The total travel time and distance of passenger vehicles decline, meaning that the traffic condition becomes better than before. With regulation on parking supply, the improvement becomes more vivid. In terms of the changes of traffic speed, both alternatives show 4.1% increase in speed, but the difference between alternatives is not quite noticeable because of the induced vehicle demand driven to the streets with improved traffic condition. The mode share changes occur for the benefit of subway ridership, because the study station is equipped with two subway line services. When mixed with parking supply restriction, the impact becomes clearer.

• Physical Therapy Korea
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• v.5 no.4
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• pp.30-40
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• 1998

이 연구의 목적은 젊은 아시아인과 코카시아 여성의 보행패턴 중 보폭시간(step time) 과 보폭 (step length)을 비교하고 두 집단의 골반넓이와 보폭과 상관관계가 있는지 알아보는 것이다. 연구대상자는 15명의 아시아인과 15명의 코카시아 여성이었으며 나이는 23세에서 35세 범위에 있었다. 보행분석을 위해서는 GAITRite System을 사용하였으며 분석방법으로는 인종(아시아인대 코카시아인)과 신체부위(좌측, 우측)를 요인으로 하여 반복측정에 의한 분산분석을 하였다. 아시아인 여성보다 코카시아인 여성의 보폭, 다리길이, 골반 넓이가 통계학적으로 유의하게 높았고 왼쪽 다리의 걸음과 오른쪽 다리의 걸음에 있어서는 통계학적으로 유의한 차이가 없었다. 그리고 보폭시간, 속도, 걸음수(cadence)에 있어서도 두 여성 인종간에 통계학적으로 유의한 차이가 없었다. 이러한 결과는 보행변수 중에서 걸음수나 속도와 같은 시간변수에 았어서는 아시아인 여성과 코카시아인 여성간에 차이가 없음을 의미한다.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.6
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• pp.23-35
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• 2009

This study proposes a methodology for estimating representative section travel times using individual vehicle travel information under the ubiquitous transportation environment (UTE). A novel approach is to substantialize a concept of dynamic node-links in processing trajectory data. Also, grouping vehicles was conducted to obtain more reliable travel times representing characteristics of individual vehicle travels. Since the UTE allows us to obtain higher accuracy of vehicle positions, travel times for each lane can be estimated based on the proposed methodology. Evaluation results show that less than 10% of mean absolute percentage error was achievable with 20% of probe vehicle rate. It is expected that outcome of this study is useful for providing more accurate and reliable traffic information services.

• Journal of Cadastre & Land InformatiX
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• v.51 no.1
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• pp.97-110
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• 2021

This study estimated the delay factor, which is the ratio of travel time at the speed limit and travel time at the actual speed using real-time traffic information in Seoul. The actual travel speed on the road was lower than the maximum speed of the road and the travel speed was the slowest during the rush hour. As a result of accessibility analysis based on travel speed during the rush hour, the travel time at the actual speed was 37.49 minutes on average. However, the travel time at the speed limit was 15.70 minutes on average. This result indicated that the travel time at the actual speed is 2.4 times longer than that at the speed limit. In addition, this study proposedly defined the delay factor as the ratio of accessibility by the speed limit and accessibility to actual travel speed. As a result of delay factor analysis, the delay factor of Seoul was 2.44. The results by the administrative district showed that the delay factor in the north part areas of the Han River is higher than her south part areas. Analysis results after applying the relationship between road density and traffic volume showed that as the traffic volume with road density increased, the delay factor decreased. These results indicated that it could not be said that heavy traffic caused longer travel time. Therefore, follow-up research is needed based on more detailed information such as road system shape, road width, and signal system for finding the exact cause of increased travel time.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.107-107
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• 2003

GPS Receiver는 위성에 위치 정보와 시간 정보등을 제공하고 navigation을 관리하며 이에 관련된 signal을 processing하는 역할을 한다. 2005년에 발사 예정인 KOMPSAT-2 위성에는 Alcatel에서 제작된 Topstar 3000이 사용된다. Topstar 3000은 RF 부분과 digital 처리부분으로 구성된 GPS core부분과 MLD-STD_1553, DC-DC converter, 그리고 Ovened-controlled Oscillator(OCXO)부분으로 구성되는 option module 부분으로 구성되어 있다. 본 논문에서는 GPS Signal Simulator로 KOMPSAT-2의 실제 궤도를 구현해서 Sun-Point Mode와 Earth-Point Mode 등 여러가지 Mode 에서 GPS Receiver의 시간, 위치, 속도 정보의 정확성에 대한 성능이 분석된다.