• International Journal of Control, Automation, and Systems
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• v.5 no.6
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• pp.674-680
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• 2007

The probabilistic roadmap (PRM) method, which is a popular path planning scheme, for a manipulator, can find a collision-free path by connecting the start and goal poses through a roadmap constructed by drawing random nodes in the free configuration space. PRM exhibits robust performance for static environments, but its performance is poor for dynamic environments. On the other hand, reinforcement learning, a behavior-based control technique, can deal with uncertainties in the environment. The reinforcement learning agent can establish a policy that maximizes the sum of rewards by selecting the optimal actions in any state through iterative interactions with the environment. In this paper, we propose efficient real-time path planning by combining PRM and reinforcement learning to deal with uncertain dynamic environments and similar environments. A series of experiments demonstrate that the proposed hybrid path planner can generate a collision-free path even for dynamic environments in which objects block the pre-planned global path. It is also shown that the hybrid path planner can adapt to the similar, previously learned environments without significant additional learning.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.2
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• pp.159-165
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• 1999

Three-phase AC-DC flyback converter with high power factor correction and tight regulation is presented in this p paper. The advantage of the proposed converter does not require expensive high voltage and high cun‘ent devices that a are normally needed in popular boost type 3-phase converter. In this paper the detailed small signal analysis of the m modular 3-phase AC-DC flyback converter is provided for control purposes and also experimental results are included t to confirm the validity of the analysis.

• Journal of Korean Foot and Ankle Society
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• v.1 no.1
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• pp.65-73
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• 1997

Hallux valgus deformity has been slowly getting popular in Korea. Many surgical procedures are available for treating the hallux valgus, but it is still controversial for the best treatment. We operated 25 feet(15 patients) of hallux valgus between May. 88 and December. 94. The clinical results were as follow ; 1. Age distribution was 25 to 82, and all female. 10 patients have bilateral hallux valgus. 2. 19 feet were treated by soft tissue procedures only and 6 feet by combined soft tissue and bony procedures. 3. Bunion deformity was recurred in 2 feet (1 Patient) which were treated with modified McBride Method. 4. Lateral sesamoidectomies were performed in 7 feet without development of hallux varus. 5. The cosmetic and functional results were good in 6 cases treated by proximal metatarsal osteotomy. 6. 9 feet had other digits deformities, which need surgical correction. 7. Tightening repair of medial capsule seems to be important for prevention of recurrence of bunion.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.137-140
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• 2005

Resin transfer molding (RTM) is one of the most popular processes for producing fiber reinforced polymer composites. In the manufacture of complex thick composite structures, analysis on flow front advancement on the resin impregnating the multi-layered fiber preform is helpful for the optimization of the process. In this study, three-dimensional mold filling simulation of RTM is carried out by using CVFEM (Control Volume Finite Element Method). On the assumption of isothermal flow of Newtonian fluid, Darcy’s law and continuity equation are used as governing equations. Different permeability tensors employed in each layer are obtained by experiments. Numerically predicted flow front is compared with experimental one in order to validate the numerical results. Flow simulations are conducted in the two mold geometries, rectangular plate and hollow cylinder. Permeability tensor of each layer preform in Cartesian coordinate system is transformed to cylinder coordinates system so that the flow within the multi-layered preforms of the hollow cylinder can be calculated exactly. Our emphasis is on the three dimensional flow analysis for circular three-dimensional braided preform, which shows outstanding mechanical properties such as high impact strength and toughness compared with other conventional two-dimensional laminar-structured preforms.

• The Korean Journal of Food And Nutrition
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• v.25 no.4
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• pp.980-989
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• 2012

This study examined 389 customers visiting restaurants located in the Guemo mountain resort who filled out self-administered questionnaires. The results showed that 60% of the participants dined out monthly. The 30 to 40-year-old age group did so the most frequently, dining out one to two times weekly. For men, the favorite menu item was the sanchejeongsik along side traditional liquor and for women was the samgaetang. By age, the 20, 30, and 60-year-olds selected samgaetang as their favorite, the 40-year-olds selected traditional liquor, and the 50-year-olds selected the sanchejungsik. The reasons for selecting the dishes were because participants previously enjoyed them or considered the dishes healthy, regardless of sex or age. Participants suggested that the sanchejeongsik and samgaetang be promoted for tourism, without significant differences between gender. The current findings suggest that the quality of certain local menu such as sanchejungsik and samgaetang could be improved to become more nutritious for future customers. Also, traditional Korean liquor may become even more popular with visitors to the Guemo mountain resort if paired with simple menu items such as jeon or muk.

• The Korean Journal of Pain
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• v.10 no.1
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• pp.73-76
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• 1997

Background : Epidural anesthesia is now accepted as a popular technique for pain relief and anesthesia. However, accidental dural puncture may occur during placement of the epidural needle. This study was undertaken to evaluate difference of the epidural depth between parturients and non-parturients. Method : Eighty non-parturients receiving epidural anesthesia were assigned to group I, and eighty parturients whose body weight had not yet increased over 15 kg from pregnancy were assigned to group II. With patients in lateral decubitus position, 18 guage Tuohy needle was punctured by approaching at $L_{3-4}$ interspace. Epidural space was identified using loss-of-resistance to air technique. Result : Epidural depth was 4.18 cm and 4.25 cm in group I and group II respectively. There was no significant statistical difference in body mass index(BMI) and ponderal index(PI) (p<0.05), nor in epidural depth between the two groups. Conclusion : Epidural needle need not be placed deeper in parturients than in nonparturients.

• Journal of Mechanical Science and Technology
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• v.19 no.3
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• pp.768-777
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• 2005

This paper shows that the performance of a nonlinear fluid engine mount can be improved by an optimal design process. The property of a hydraulic mount with inertia track and decoupler differs according to the disturbance frequency range. Since the excitation amplitude is large at low excitation frequency range and is small at high excitation frequency range, mathematical model of the mount can be divided into two linear models. One is a low frequency model and the other is a high frequency model. The combination of the two models is very useful in the analysis of the mount and is used for the first time in the optimization of an engine mount in this paper. Normally, the design of a fluid mount is based on a trial and error approach in industry because there are many design parameters. In this study, a nonlinear mount was optimized to minimize the transmissibilities of the mount at the notch and the resonance frequencies for low and high-frequency models by a popular optimization technique of sequential quadratic programming (SQP) supported by $MATLAB^{(R)}$subroutine. The results show that the performance of the mount can be greatly improved for the low and high frequencies ranges by the optimization method.

• Journal of Biosystems Engineering
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• v.18 no.3
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• pp.262-269
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• 1993

Stress relaxation behaviors of the cucumber under bending moment were tested with UTM at three levels of loading rate and initial deflection ratio. Sample cucumber was selected from three cultivars of cucumber, Cheongjangmadi, Baekdadagi, and Gyeousalicheongjang, because these cultivars are the most popular grown cultivars in Korea. When the bending moment was applied to the cucumber sample, the effective span between simple supports was held a constant value of 116mm with consideration of the selected sample length. The objectives of this study were to develop the rheological models such as linear and nonlinear models of the stress relaxation for the cucumber samples, and to investigate the effects of loading rate and initial deflection ratio on the stress relaxation behavior of the cucumber. The results of this study may be summarized as follows : 1. Stress relaxation behavior of the cucumber could be well described by the generalized Maxwell model for each level of deflection ratio. But the stress relaxation behavior of the sample was found to be initial deflection ratio and time dependent, and it was represented the nonlinear viscoelastic model as a function of initial deflection ratio and time. 2. Stress relaxation behavior of the cucumber samples was very highly affected by the loading rate and the initial deflection ratio. The more loading rate and initial deflection ratio resulted in the more initial bending stress and after stress relaxation progressed more rapidly. 3. At the same test conditions, it was found that the stress relaxation rate of Cheongjangmadi was faster than that of other cultivars.

• The Journal of Industrial Distribution & Business
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• v.9 no.5
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• pp.25-35
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• 2018

Purpose - The purpose of this paper is to partition a last-mile delivery network into zones and to determine locations of last mile delivery centers (LMDCs) in Bangkok, Thailand. Research design, data, and methodology - As online shopping has become popular, parcel companies need to improve their delivery services as fast as possible. A network partition has been applied to evaluate suitable service areas by using METIS algorithm to solve this scenario and a facility location problem is used to address LMDC in a partitioned area. Research design, data, and methodology - Clustering and mixed integer programming algorithms are applied to partition the network and to locate facilities in the network. Results - Network partition improves last mile delivery service. METIS algorithm divided the area into 25 partitions by minimizing the inter-network links. To serve short-haul deliveries, this paper located 96 LMDCs in compact partitioning to satisfy customer demands. Conclusions -The computational results from the case study showed that the proposed two-phase algorithm with network partitioning and facility location can efficiently design a last-mile delivery network. It improves parcel delivery services when sending parcels to customers and reduces the overall delivery time. It is expected that the proposed two-phase approach can help parcel delivery companies minimize investment while providing faster delivery services.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2018.05a
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• pp.287-288
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• 2018

Developing games is a popular work in itself and a field of commercial development. It also occupies an important position in the design field as well. Because the game has a high commercial value and a design role in the game. This study examines the interface in terms of usability evaluation to see how to design the interface that corresponds to the appearance of the game. For this purpose, the previous research is examined and the interface elements derived from the survey are used as questionnaire items. The results of this study are expected to help guide the design of game interface design.