• 한국경영과학회지
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• 제41권1호
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• pp.41-53
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• 2016

Static repositioning is a well-known and commonly used strategy to maximize customer satisfaction in public bike-sharing systems. Repositioning is performed by trucks at night when no customers are in the system. In models that represent the static repositioning problem, the decision variables are truck routes and the number of bikes to pick up and deliver at each rental station. To simplify the problem, the decision on the number of bikes to pick up and deliver is implicitly included in the truck routes. Two relocation-based local search algorithms (1-relocate and 2-relocate) with the best-accept strategy are incorporated into a variable neighborhood search (VNS) to obtain high-quality solutions for the problem. The performances of the VNS algorithm with the effect of local search algorithms and shaking strength are evaluated with data on Tashu public bike-sharing system operating in Daejeon, Korea. Experiments show that VNS based on the sequential execution of two local search algorithms generates good, reliable solutions.

• 산업경영시스템학회지
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• 제44권2호
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• pp.36-42
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• 2021

This paper deals with a vehicle routing problem with resource repositioning (VRPRR) which is a variation of well-known vehicle routing problem with pickup and delivery (VRPPD). VRPRR in which static repositioning of public bikes is a representative case, can be defined as a multi-objective optimization problem aiming at minimizing both transportation cost and the amount of unmet demand. To obtain Pareto sets for the problem, famous multi-objective optimization algorithms such as Strength Pareto Evolutionary Algorithm 2 (SPEA2) can be applied. In addition, a linear combination of two objective functions with weights can be exploited to generate Pareto sets. By varying weight values in the combined single objective function, a set of solutions is created. Experiments accomplished with a standard benchmark problem sets show that Variable Neighborhood Search (VNS) applied to solve a number of single objective function outperforms SPEA2. All generated solutions from SPEA2 are completely dominated by a set of VNS solutions. It seems that local optimization technique inherent in VNS makes it possible to generate near optimal solutions for the single objective function. Also, it shows that trade-off between the number of solutions in Pareto set and the computation time should be considered to obtain good solutions effectively in case of linearly combined single objective function.

• 한국산학기술학회논문지
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• 제14권2호
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• pp.737-743
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• 2013

본 연구는 시각 통제를 이용한 다중감각 훈련이 아급성 뇌졸중 환자의 균형 및 체간위치감각에 미치는 영향을 알아보고자 시행하였다. 뇌졸중 환자 30명을 대상으로, 다중감각 훈련군은 시각통제 후 훈련을 실시하였고, 대조군은 안대로 눈을 가린 것을 제외하고는 실험군과 동일한 훈련을 실행 하였다. 두 군 모두 훈련 과정은 4주간 주 5회 60분 동안 실시하였다. 대상자들은 사전, 사후 평가로 정적 균형, 동적 균형 및 체간위치감각을 검사하였다. 본 연구의 결과는 다중감각 훈련군에서 훈련 전, 후를 비교한 결과 정적 균형, 동적 균형, 체간위치감각에서 유의한 향상이 나타났고(p<.05), 두 그룹 사이에서는 동적 균형, 체간위치감각에서 유의한 차이가 나타났다(p<.05). 본 연구의 결과를 통하여 다중감각 훈련은 동적 균형 및 체간위치감각을 향상시키는데 효과적인 훈련방법으로 제시 할 수 있다.

• 대한물리의학회지
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• 제16권4호
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• pp.125-137
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• 2021

PURPOSE: The growing number of people exposed to a static sitting posture has resulted in an increase in people with a poor posture out of the optimally aligned posture because of the low awareness of a correct sitting posture. Learning the correct sitting posture by applying sensory feedback is essential because a poor posture has negative consequences for the spine. Therefore, this study examined the effects of the sensory feedback types on learning correct sitting posture. METHODS: Thirty-six healthy adult males were assigned to a visual feedback group, a tactile feedback group, and a visuotactile feedback group to learn the correct sitting posture by applying sensory feedback. The spine angle, muscle activity, and muscle thickness were measured in the sitting position using retro-reflexive markers, electromyography, and ultrasound immediately after, five minutes, and 10 minutes after intervention. RESULTS: The intervention time was significantly shorter in the visuotactile feedback group than the visual feedback group (p < .05). Compared to the pre-intervention, the repositioning error angles of the thoracic and lumbar vertebrae of all groups were reduced significantly immediately after intervention and after five minutes. After 10 minutes, there was a significant difference in the thoracic and lumbar repositioning error angles of the tactile feedback group and the visuotactile feedback group (p < .05). No significant difference was noted at any time compared to the pre-intervention in all groups (p > .05). CONCLUSION: The use of tactile and visuotactile feedback in intervention to correct the sitting posture is proposed.