• Journal of Korea Trade
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• 제27권2호
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• pp.22-46
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• 2023

Purpose - study aims to investigate the relationships between global value chain (GVC)- and transportation-related determinants and economic performance. Also, moderating effects of COVID-19 on the relationships are theoretically and empirically discussed. A limitation of previous studies includes their over-reliance on the opportunities of GVC participation and larger transportation. This study represents the challenges associated with them. Also, it shows how GVC and logistics can be difficult in case of a market fluctuation such as COVID-19. Design/methodology - The sample for this study includes 828 observations from 138 countries. A semi-panel data set has been used. Six observations for each country are used to empirically test the hypotheses and a Two-way cluster model is conducted. Findings - It is confirmed that GVC forward participation contributes more than the backward participation to enhance performance. Transportation infrastructure is critical, but large scales of marine and air transportations are not positive in terms of economic performance. Stricter government response to COVID-19 negatively moderates economic performance by GVC backward participation and transportation infrastructure. Originality/value - The spread of COVID-19 is causing a severe collapse of GVC and transportation. This study empirically verifies the moderating effects of the government stringency on GVC and transportation. Previous studies usually discuss a positive impact of GVC and transportation size on economic performance. However, this study aims to show various challenges behind GVC participation and large scale transportation.

• 제어로봇시스템학회논문지
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• 제6권9호
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• pp.836-843
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• 2000

A sequence planning method is proposed to reduce the assembly time of gantey-type chip mounters with single head. The overall path of the chip mounter is divided into forward and backward path, and formulate the optimization problem is formulated as an transpoetation problem and an Euler's tour problem. The transportation alforithm is applied to find optimal backward path, and Euler's tour algorithm used to generate an assembly sequence. Simulation results are presented to verify the usefulness of the proposed method.

• 융복합기술연구소 논문집
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• 제4권1호
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• pp.33-35
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• 2014

Investigation of flow characteristics behind a edged backward facing step is important for selecting appropriate positions of building constructions in the desert area. In the present study, the effect of edge angles on the flow characteristics is investigated using a commercial software CFD-ACE+. When the edge angle is less than 30 degree, reattachment length decreases, whereas when the edge angle is larger than 30 degrees, reattachment angle increases. It can be concluded that the flow patterns behind an edged backward facing step is classified as the two, streamlined and bluffed bodies. Appropriate edge angles have an effect of increasing the momentum toward the wall, which can reduce the reattachment length. It can be said that present results can be utilized for diverse industrial applications that includes the backward facing step.

• 유통과학연구
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• 제14권2호
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• pp.41-45
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• 2016

Purpose - Finding an optimal path is an essential component for the design and operation of smart transportation or logistics network. Many applications in navigation system assume that travel time of each link is fixed and same. However, in practice, the travel time of each link changes over time. In this paper, we introduce a new transportation problem to find a latest departing time and delivery path between the two nodes, while not violating the appointed time at the destination node. Research design, data, and methodology - To solve the problem, we suggest a mathematical model based on network optimization theory and a backward search method to find an optimal solution. Results - First, we introduce a dynamic transportation problem which is different with traditional shortest path or minimum cost path. Second, we propose an algorithm solution based on backward search to solve the problem in a large-sized network. Conclusions - We proposed a new transportation problem which is different with traditional shortest path or minimum cost path. We analyzed the problem under the conditions that travel time is changing, and proposed an algorithm to solve them. Extending our models for visiting two or more destinations is one of the further research topics.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.343-348
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• 2002

We are going to build a direct railway line between Europe and Asia by connecting North-South line. It can reduce a transportation distance by above 10,000km. But problems of TSR which is most important line have been exposed such as backward facilities and operations. In this paper we find out problems of TSR in detail and show those improvements.

• 한국항만경제학회지
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• 제22권2호
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• pp.35-60
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• 2006

This paper uses input-output techniques to analyze the impacts of the coastal and inland water transportation (CIWT) upon the Korean economy between 1990 and 2000. The impacts were identified by means of backward and forward linkages effects, production inducing and import-inducing effects, and commodity prices repercussion effects of the coastal and inland water transportation. The data of this study come from The Bank of Korea databases for Input-Output Structure of the Korean economy. The major findings in this study can, among others, be summarized: that the power of dispersion(=backward linkage effect) and the degree of sensitivity (=forward linkage effect) of CIWT are higher than those of the deep sea transportation sector and that it has higher production-inducing effect than the average of total industries, while it has lower import-inducing effect than the average of total industries.

• 로봇학회논문지
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• 제5권4호
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• pp.286-293
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• 2010

The trailer system offers efficiency of transportation capability. However, it is difficult to control the backward motion. It is an open loop unstable problem. To solve this problem, we are proposed the driver assistance system. Driver assistance system assists a driver to control the backward motion of trailer system as if forward motion. A driver only secure the rear view of last passive trailer, and select the control input to drive the last passive trailer. The driver assistance system converts the control input of the driver into velocity and steering angle of the vehicle using the inverse kinematics. It is possible by electronic control input devices and the rear view camera. Effectiveness of driving assistance system is verified by the simulation and the experiments.

• 대한물리치료과학회지
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• 제26권3호
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• pp.70-75
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• 2019

Purpose: The purpose of this study was to investigate the changes of static and dynamic balance control ability according to the stability of shoes in elderly woman and female university student. Design: Cross-sectional study. Methods: Six elderly women and seven female university students were recruited for this study. The subject's static and dynamic balance were evaluated while wearing two different types of shoes (comfortable running shoe and masai walking shoe). The BT4 system was used to measure the static (postural sway area and velocity) and dynamic balance (limit of stability on forward, backward and left and right side). The measurement of static and dynamic balance control ability was performed in standing posture wearing comfortable running shoes and masai walking shoes. Results: In the static balance control ability, both female university students and elderly women showed significant increase in postural sway area and velocity when wearing unstable shoes (p<0.05) In addition, in the dynamic balance control ability, both female university students and elderly women showed significant decrease in limit of stability on forward and backward when wearing unstable shoes (p<0.05). Conclusion: In selecting shoes for the elderly, the stability of shoe should be considered for prevention of falls.

• Physical Therapy Rehabilitation Science
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• 제8권1호
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• pp.40-44
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• 2019

Objective: The purpose of this study was to examine the changes in postural stability according to ankle fixation in healthy university students. Design: Cross-sectional study. Methods: Thirty healthy subjects (15 males and 15 females, 20.13 years, 167.49 cm, 65.87 kg) were recruited on a voluntary basis. The BT4 system (HUR Laps Oy, Tampere, Finland) was used to measure the static (standing posture with eyes open and eyes closed) and dynamic (external perturbation and limits of stability (LOS) in the forward, backward, left, and right side) balance abilities. External perturbation was measured by the subject's postural sway velocity and area for 20 seconds after being impacted by a gym ball. Static and dynamic stabilities were measured with ankle joint fixation and non-fixation conditions. Ankle fixation was provided using Mueller tape on both ankle joints. Results: For static stability under the standing posture, there was no significant difference between standing with ankle joint fixation and non-fixation conditions. However, dynamic stability (external perturbation and LOS in the forward, backward, left, and right side) was significantly higher in the standing with the non-fixation condition compared to the standing with ankle joint fixation condition (p<0.05). Conclusions: Our results reveal that ankle joint fixation can influence dynamic stability during standing. Thus, we believe that this result provides basic information for making improvements in postural control and may be useful in balance training for fall prevention.

• 대한물리의학회지
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• 제12권2호
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• pp.21-31
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• 2017

PURPOSE: The purpose of this study was to identify whether backward walking exercise was more effective than conventional physical therapy for balance and gait in hemiplegic stroke patients. METHODS: Eighteen patients with chronic stroke were randomly assigned to the experimental (n=9) or control (n=9) group. The experimental and control group performed backward walking exercise and conventional physical therapy, respectively, for 8 weeks. Stability Index (SI) and Weight Distribution Index (WDI) during standing were assessed using the Tetrax Balance System. The Timed Up and Go (TUG) test and Korean version of the Berg Balance Scale (K-BBS) were used to evaluate balance and fall risk. Walking speed, stride length, and step length on the affected side were measured using the 10-Meter Walk and ink foot printing tests. Wilcoxon signed-rank and Mann-Whitney U tests were used for within- and between- group comparisons, respectively. RESULTS: The experimental group showed significantly higher changes in SI (p<.01), WDI (p<.01), TUG (p<.001), and BBS score (p<.001) following intervention compared with the control group. The experimental group also showed significantly greater improvements in walking speed (p<.01), stride length (p<.001), and step length on the affected side (p<.001) after intervention compared with the control group. CONCLUSION: Backward walking exercise is an effective intervention to improve balance and gait in hemiplegic stroke patients.