• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6D
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• pp.917-926
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• 2006

Transportation Economies of scale are the essential properties of hub networks. One critical property of the hub network design problem is to quantify cost savings which stem from economies of scale, the costs of operating hub facilities and opportunity costs associated with delays stemming from consolidation of traffic flows. Due to the NP-complete property of the hub location problem, however, most previous researchers have focused on the development of heuristic algorithms for approximate solutions. The purpose of this paper is to develop a hub network design model considering transportation economies of scale from the consolidation of traffic flows. The model is designed to consider the uniqueness of hub networks and to determine several cost components. The heuristic algorithms for the developed model are suggested and the results of the model are compared with recently published studies using real data. Results of the analysis show that the proposed model reflects transportation economies of scale due to consolidation of flows. This study can form not only the theoretical basis of an effective and rational hub network design but contribute to the assessment of existing and planned logistics systems.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.01a
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• pp.241-242
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• 2023

본 논문에서는 딥러닝 소리 인식을 이용하여 실내에서 발생할 수 있는 다양한 소리를 시각적인 정보로 제공해주는 스마트허브 시스템을 제안한다. 인공지능 모델은 2D-CNN 구조를 활용하여 학습을 진행하였고, 스마트허브 하드웨어는 라즈베리파이를 이용하여 구현하였다. 제안된 시스템은 청각장애인을 위해 설계된 다양한 청각 정보를 시각 정보로 전달하는 다양한 제품을 하나로 대체할 수 있을 뿐만 아니라, 설치 및 운반이 간편하여 누구나 사용하기 쉬워서 활용도가 높을 것으로 기대된다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.7
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• pp.634-641
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• 2009

In this work, the behavior of vibratory hub loads induced due to the uncertainties of composite material properties for each of the participating rotor blades is investigated. The random material properties of composites available from the existing experimental data are processed by using the Monte-Carlo simulation technique to obtain the stochastic distribution of sectional stiffnesses of composite blades. The coefficients of variation (standard deviation divided by the mean) obtained from the sectional stiffness constants are used as an input to the comprehensive aeroelastic analysis code that can evaluate the hub loads of a rotor system. It is found that the uncertainty effects of composite material properties inevitably bring a dissimilarity to the rotor system. The influence of hub vibration response with respect to the individual stiffness (flatwise bending, chordwise bending and torsion) changes is also identified.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.612-615
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• 2013

Hub BLDC(Brushless Direct Current) motor, called wheel-in motor is a outer rotor type high efficient direct driving motor which have a multi-pole permanent magnet type rotor as a driving wheel. This study shows a hub BLDC motor speed controller design methode using PIC micro controller to drive 2 wheels or 3 wheels driving body having hub motor driving shaft. The motor driver unit consists of six discrete MOSFET switching devices and the gate driving module is directly designed for high economy.

• Journal of Korean Society of Transportation
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• v.27 no.1
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• pp.129-141
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• 2009

Intermodal freight transportation is defined as the movement of freight from origins to destinations by two or more transportation modes. When implemented in hub networks, it could enhance the efficiency of the networks because consolidated flows are transported by more suitable modes and technologies. In spite of this advantage, the intermodal hub network design problem has received limited attention in the literature partly because of the complex nature of the problem. This paper aims to develop an optimization model for designing intermodal hub networks with sin91e allocation strategy. The model takes into account various cost components of intermodal hub networks including transportation, stationary inventory, and service delay costs. Moreover, using transport frequency variables, it is capable of endogenously determining the transportation economies of scale achieved by consolidation of flows. As such, the model is able to realistically represent the characteristics of intermodal hub networks in practice. Since the model Is a complicated nonlinear integer programming problem, we perform model simplification based on the analytical study of the model, which could facilitate the development of solution algorithms in the future. We expect that this study contributes to the design of intermodal hub networks as well as to the assessment of existing logistics systems.

• Aerospace Engineering and Technology
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• v.13 no.1
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• pp.10-19
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• 2014

We designed bearingless rotor hub system which replace mechanical hinge/bearing with composite beam component and conducted fatigue analysis for flexbeam and torque tube. Extension/bending/torsional stiffness was calculated from 2D section analysis using VABS and 2D section structure analysis was applied for strain calculation. S-N curve of each composite material was generated using Wohler equation and fatigue analysis was conducted on weakness section which was decided from static structure analysis. CAMRAD II was used for load analysis and load analysis result was applied HELIX/FELIX standard load spectrum to generate bearingless rotor system load spectrum which was used fatigue safe life analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.7
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• pp.561-568
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• 2013

After we designed Bearingless rotor hub system for 7,000lb class helicopter, flexbeam fatigue analysis was conducted for validation of requirement life time 8,000 hours. sectional structural analysis method applying elastic beam model was used. Fatigue analysis for two sections of flexbeam which were expected to weak to fatigue damage from result of static analysis was conducted. Extension, bending and torsion stiffness of flexbeam section shape was calculated using VABS for structure analysis. S-N curve of two composite material which composed flexbeam was generated using wohler equation. Load analysis of bearingless rotor system was conducted using CAMRAD II and load analysis result was applied HELIX/FELIX standard load spectrum to generate bearingless rotor system load spectrum which was used flexbeam fatigue safe life analysis.

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.2
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• pp.206-218
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• 2002

In this paper, we design and implement a system that presents a method for selecting and providing personalized services independently without unifying the existing system platform with shopping malls joined in the hub site. This system provides a mechanism for gathering information left behind by many clients visiting Web sites for analysis of customers property, vector model for selecting personalized services, and mechanism for providing them to customers who visited in a shopping mall joined to the hub site. In a position of shopping mall site, this kind of personalization system can provide target advertisement, point marketing, and point share service etc. without changing existing shopping mall's environment through wrapper web server. Hub site customers can get personalized services from many shopping mall sites with only once registration for the hub site.

• Composites Research
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• v.16 no.5
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• pp.7-14
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• 2003

Modeling of thick composite structures for finite element analysis is relatively complicated. 2-D plane elements may cause inaccurate result since the plane stress condition cannot be applicable in these structures. Therefore a 3-D modeling should be used. However, the difficulty to model all the layers with different material properties and ply orientation arise in this case. In this paper, an equivalent modeling is proposed and numerically tested for analysis of thick composite structures. By grouping layers with same material and ply orientation, number of elements through the thickness is remarkably reduced and still the result is close enough to the one from a detail finite element model. MSC/NASTRAN and PATRAN are used for the analysis. The proposed modeling technique has been applied for analysis of composite rotor hub system designed by Korea Aerospace Research Institute(KARI). Using the proposed equivalent modeling technique, we could conduct stress analysis for the hub system and check the safety factor of each part.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.196-198
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• 2003

최근 인터넷상에서 B2B 전자상거래는 상당히 급성장 하고 있다. 그러나 기존의 전자상거래 시스템들은 각기 다른 전자상거래 플랫폼과 시스템을 구축하여 사용했기 때문에 전자상거래 시스템간의 상호 호환 및 운영에 많은 어려움이 있다. 분산 환경 시스템들로 구성되는 다수의 인터넷 쇼핑몰들의 통합 정보 검색 시스템으로 허브 사이트들이 등장하여 고객들이 구매하고자 하는 상품에 대한 정보를 보다 쉽게 검색을 할 수 있도록 각종 쇼핑몰 사이트를 연결하여 통합하는 과정이 진행 중이다. 그러나 분산 환경의 시스템을 통합하는 것이 데이터 통합이 아닌 링크 해주는 정도로 그치고 있는 게 현재 실정이다. 이에 본 논문에서는 분산 환경에서의 통합 정보 검색을 위한 허브 사이트를 효율적으로 관리하는 XML Hub System을 이용한 DIIS(Distributed Information Integration System)를 설계 제안한다.