• Kyungpook Mathematical Journal
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• 제52권2호
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• pp.201-208
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• 2012

By the works of Kondo and Sakai, it is known that Alexander polynomials of knots which are transformed into the trivial knot by a single crossing change are characterized. In this note, we will characterize Alexander polynomials of knots which are transformed into the trefoil knot (and into the figure-eight knot) by a single crossing change.

• The Journal of Korean Physical Therapy
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• 제19권5호
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• pp.1-10
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• 2007

Purpose: Leg-crossing sitting is very common for men and woman. No solid evidence exists for either a beneficial or a detrimental effect of this posture. This study investigated the change of activities of trunk muscles between the normal group and the low back pain group during various leg-crossing positions. Methods: The subjects were consisted of 10 subjects who don't have low back pain and 10 subjects who have low back pain. In this study, we used electromyography(EMG) to evaluate the activities of both the trunk muscles (rectus abdominis, external oblique, internal oblique, and multifidus) during various leg-crossing positions (up-right, leg-crossing, tailor-crossing, and ankle-crossing). We analyzed the data by using repeated one way ANOVA. Results: In normal group, there were increased in EMG activities of trunk muscles, but no significant differences during leg-crossing positions. In back pain group, there were increased in EMG activities of right external oblique, left. internal oblique, and both multifidus muscles in leg-crossing and tailor-crossing position, but no significant differences during leg-crossing positions. There was no significant difference of muscle activity of trunk muscles between the back pain group and the normal group. Conclusion: We suggest that low back pain people who have weak muscles of rectus abdominis, external and internal oblique are often experienced in leg-crossing posture than normal. To compensate this unstability of trunk, leg-crossing posture is substituted passive structure for activities of active muscle.

• 한국안전학회지
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• 제37권1호
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• pp.12-19
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• 2022

Circuit breakers are a crucial factor in ensuring the safety of a Direct Current (DC) grid. One type of DC circuit breaker, the Z-source DC circuit breaker (ZCB), uses a thyristor, which is a type of semiconductor switch. In the event of a fault in the circuit, the ZCB isolates the fault by generating a zero crossing current in the thyristor. The thyristor quickly and actively isolates the fault while generating a zero crossing current, but thyristor switch cannot control turn-off and the allowable current is lower than the current of the mechanical switch. Therefore, it is best to use a mechanical switch with a high allowable current capacity that is capable of on/off control. Due to the slow reaction time of mechanical switches, they may not isolate the fault during the zero crossing current time interval created by the existing circuit. In this case, the zero crossing current time can be increased by using the property that hinders the rapid change in the current of the inductor. This paper will explore whether adding system inductance to increase the zero crossing current time interval is a solution to this problem. The simulation of changing inductor and capacitor (LC) of the circuit is repeated to find an optimal change in the zero crossing current time according to the LC change and provides an inductor and capacitor range optimized for a specific load. The inductor and capacitor range are expected to provide optimization information in the form LC values for future applications of ZCB's using a mechanical switch.

• Kyungpook Mathematical Journal
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• 제47권3호
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• pp.329-334
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• 2007

By the works of Levine [2] and Rolfsen [5], [6], it is known that a local move called a crossing-change is strongly related to the Alexander invariant. In this note, we will consider to what degree the relationship is strong. Let K be a knot, and $K^{\times}$ the set of knots obtained from a knot K by a single crossing-change. Let MK be the Alexander invariant of a knot K, and MK the set of the Alexander invariants $\{MK\}_{K{\in}\mathcal{K}}$ for a set of knots $\mathcal{K}$. Our main result is the following: If both $K_1$ and $K_2$ are knots with unknotting number one, then $MK_1=MK_2$ implies $MK_1^{\times}=MK_2^{\times}$. On the other hand, there exists a pair of knots $K_1$ and $K_2$ such that $MK_1=MK_2$ and $MK_1^{\times}{\neq}MK_2^{\times}$. In other words, the Gordian complex is not homogeneous with respect to Alexander invariants.

• 한국철도학회논문집
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• 제9권2호
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• pp.174-179
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• 2006

Recently, the crossing tunnel has been constructed frequently to connect the separated area by highway and railroad. The construction of crossing tunnel must be progressed while maintaining the existing traffic of the highway as well as railroad. There are many cross funnelling methods such as NTR, TRCM, Messer Shield, Front Jacking, and Pipe Roof Method. The advantages of adopting RPS(Roof Panel Shield) method in crossing tunnel construction with comparing other existing cross funnelling methods are needed a little volume of concrete and easy to change the direction of cutting shoe during the construction of pipe roof, The 3-dimensional numerical analysis of RPS to consider the arching effect was performed for the application in the crossing tunnel under railroad. The earth pressure distribution and settlement were predicted when the RPS method was applied during the excavation for crossing railroad tunnel construction.

• 한국ITS학회 논문지
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• 제7권5호
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• pp.77-89
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• 2008

자전거도로가 설치된 교차로 빛 횡단도로에서 자전거, 차량 및 보행자 간에 상충이 발생하게 된다. 이와 같이 자전거 도로와 여타 교통류가 교차되는 구간에서 자전거와 자동차, 자전거와 보행자와의 상충을 분리해주어야 하는데, 이런 방법 중 하나가 자전거전용신호라고 할 수 있다 자전거도로 시설 및 이용자 특성조사에 따르면 자전거도로가 횡단보도와 연 계하여 설치되어 있고, 자전거이용자 대부분이 횡단보도신호를 이용하고 있으며, 횡단보도시간 내에 횡단을 종료하는 것으로 조사되었다. 따라서 횡단보도와 자전거도로가 인접된 자전거횡단도로에서는 보행신호등과 연계한 운영방안 즉, 영국의 TOUCAN Crossing 형태의 적용이 제안된다. 이와 같은 자전거전용신호 운영체계는 현재 자전거횡단도로의 위치가 횡단보도와 인접하여 설치되어 있고, 대부분의 자전거이용자들이 보행신호에 따라 도로를 횡단하고 있으며, 보행선호시간동안 횡단할 수 있기 때문이다. 반면에 자전거횡단도로가 보행도로와 이격되어 설치된 경우 및 자전거의 통행속도 등을 고려하여 전용도로 형태로 자전거도로가 설치된 경우에는 차량신호와 연계한 자전거신호등 형태 (3색 등화체계)가 제안된다. 이와 같은 자전거신호등의 운영형태는 기존 자전거도로 시설과 자전거이용자의 도로횡단특성을 수용하고, 교통 신호제어기의 기능변경 없이 신호시간의 조정만으로 적용이 가능한 이점이 있다.

• Geomechanics and Engineering
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• 제20권2호
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• pp.103-112
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• 2020

The dynamic response of crossing tunnels under heavy-haul train loads is still not fully understood. In this study, based on the case of a high-speed tunnel underneath an existing heavy-haul railway tunnel, a model experiment was performed to research the dynamic response characteristics of crossing tunnels. It is found that the under-crossing changes the dynamic response of the existing tunnel and surrounding rock. The acceleration response of the existing tunnel enhances, and the dynamic stress of rock mass between crossing tunnels decreases after the excavation. Both tunneling and the excitation of heavy-haul train loads stretch the tunnel base, and the maximum tensile strain is 18.35 µε in this model test. Then, the measured results were validated by numerical simulation. Also, a parametric study was performed to discuss the influence of the relative position between crossing tunnels and the advanced support on the dynamic behavior of the existing tunnel, where an amplifying coefficient of tunnel vibration was introduced to describe the change in acceleration due to tunneling. These results reveal the dynamic amplifying phenomenon of the existing tunnel during the new tunnel construction, which can be referred in the dynamic design of crossing tunnels.

• Kyungpook Mathematical Journal
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• 제56권4호
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• pp.1247-1257
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• 2016

In this paper, we discuss the crossing change operation along exchangeable double curves of a surface-knot diagram. We show that under certain condition, a finite sequence of Roseman moves preserves the property of those exchangeable double curves. As an application for this result, we also define a numerical invariant for a set of surface-knots called du-exchangeable set.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.655-660
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• 2005

Recently, the crossing tunnel has been constructed to maintain the operation highway as well as railroad. The advantages of adopting RPS method in crossing tunnel construction are needed a little space and easy to change the direction of cutting shoe during the construction of pipe roof. The numerical analysis of RPS was performed for the application in the crossing tunnel under railroad. The earth pressure distribution and settlement were predicted when the RPS method was applied during the excavation for crossing tunnel construction.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 추계학술대회 논문집 학회본부
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• pp.225-227
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• 1995

An object detection algorithm using a modified IDM(Image Differential Method) is proposed for detecting an object in a level crossing area. The conventional object detection method using LASER light has the deadzone that it cannot detect small objects, while the object detection method using image data in a level crossing area can detect such small objects. But the image data in a level crossing area can be changeable easily because the data is outdoor and sensitive to such surrounding environments as the change of the sun beam, the shadow of cars, and so on. So we resolve these problems by adding the normalization and the process for shadow of the image data in a level crossing area to the basic IDM(Image Differential Method).