• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 추계학술발표대회
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• pp.33.1-33.1
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• 2009

To date, nanostructured tungsten oxides with a variety of stoichiometries, such as WO3, WO2.9, W18O49, and WO2, have been prepared, because they are promising candidates for applications such as gas sensors, photocatalysts, electrochromic devices, and field emission devices. Among them, W18O49 and WO2 have been widely studied due to their outstanding chemical sensing, catalytic, and electron emissive properties. Here we report, for the first time, a one-pot solution-phase route to synthesizing a novel composite hierarchical hollow structure without adding catalysts, surfactants, or templates. The products, consisting of a WO2 hollow core sphere surrounded by a W18O49 nanorod shell (yielding a sea urchin-like structure), were generated as discrete structures via Ostwald ripening. To our knowledge, this type of composite hierarchical core/shell structure has not been reported previously. The morphological evolution and the detailed growth mechanism were carefully studied. We also demonstrate that the size of the hollow urchins is readily tunable by controlling the reactant concentrations.Interestingly, although bulk tungsten oxides are weakly paramagnetic or diamagnetic, the as-prepared products show unusual ferromagnetic behavior atroom temperature. The urchin structures also show a very high Brunauer-Emmet-Teller (BET) surface area, suggesting that they may potentially be applied to chemical sensor or effective catalyst technologies.

• Journal of Communications and Networks
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• 제13권4호
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• pp.408-417
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• 2011

The stringent performance requirement for the high efficiency of routing protocols on the Internet can be satisfied by exploiting the threaded border gateway protocol (TBGP) on multi-cores, but the state-of-the-art TBGP performance is restricted by a mass of contentions when racing to access the routing table. To this end, the highly-efficient parallel access approach appears to be a promising solution to achieve ultra-high route processing speed. This study proposes a general routing table structure consisting of two-level tries for fast parallel access, and it presents a heuristic-based divide-and-recombine algorithm to solve a mass of contentions, thereby accelerating the parallel route updates of multi-threading and boosting the TBGP performance. As a projected TBGP, this study also modifies the table operations such as insert and lookup, and validates their correctness according to the behaviors of the traditional routing table. Our evaluations on a dual quad-core Xeon server show that the parallel access contentions decrease sharply by 92.5% versus the traditional routing table, and the maximal update time of a thread is reduced by 56.8 % on average with little overhead. The convergence time of update messages are improved by 49.7%.

• 방송공학회논문지
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• 제22권5호
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• pp.548-559
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• 2017

최근 들어, UHDTV같은 고품질 AV서비스가 증가하면서 방송 기술도 진화하게 되었으며, 방송 표준 또한 새롭게 정의하게 되었다. 현재 한국에서는 지상파 UHD 방송을 위해 북미 지상파 디지털 TV 방송 규격 표준화 기구인 ATSC(Advanced Television Systems Committee)에서 제정한 ATSC3.0 규격 기반으로 국내 표준을 제정하였다. 지상파 UHDTV 표준에는 다양한 방송 표준 중에서 대표적인 전송표준으로는 DASH/ROUTE와 MMTP이 있다. DASH/ROUTE와 MMTP는 현재 한국에서 지상파 UHD 방송을 시작하면서 전송표준으로 DASH/ROUTE와 MMTP를 채택하였다. DASH segment와 MPU는 각기 DASH/ROUTE 및 MMTP를 통하여 전송하는 미디어 데이터를 포함한 segment 단위이다. 본 논문에서는 DASH segment와 MPU의 구조를 분석하고, DASH segment를 MPU로 변환하여 MMTP를 통하여 전달할 수 있는 검증 시스템을 제안한다.

• 대한금속재료학회지
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• 제50권12호
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• pp.931-937
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• 2012

The microstructure of Cu-15 wt%Ag composites fabricated by equal channel angular pressing (ECAP) with intermediate heat treatment at $320^{\circ}C$ was investigated by transmission electron microscopy (TEM) observations. Ag precipitates with a thickness of 20-40 nm were observed in the eutectic region of the Cu-15 wt%Ag composite solution treated at $700^{\circ}C$ before ECAP. The Cu matrix and Ag precipitates had a cube on cube orientation relationship. ECAPed composites exhibited ultrafine-grained microstructures with the shape and distribution dependent on the processing routes. For route A in which the sample was pressed without rotation between each pass, the Cu and Ag grains were elongated along the shear direction and many micro-twins were observed in elongated Cu grains as well as in Ag filaments. The steps were observed on coherent twin boundaries in Cu grains. For route Bc in which the sample was rotated by 90 degrees after each pass, a subgrain structure with misorientation of 2-4 degree by fragmentation of the large Cu grains were observed. For route C in which the sample was rotated by 180 degrees after each pass, the microstructure was similar to that of the route A sample. However, the thickness of the elongated grains along the shear direction was wider than that of the route A sample and the twin density was lower than the route A sample. It was found that more microtwins were formed in ECAPed Cu-15 wt%Ag than in the drawn sample. Grain boundaries were observed in relatively thick and long Ag filaments in Cu-15 wt%Ag ECAPed by route C, indicating the multi-crystalline nature of Ag filaments.

• 대한교통학회지
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• 제26권5호
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• pp.227-235
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• 2008

본 연구에서는 간선-지선 노선체계인 가지형과 지선형 노선체계의 이용자 비용과 운영자 비용을 비교하여 각 노선체계의 효율성을 분석하였다. 기본적으로 지선형 노선체계의 간선구간 시스템이 지선 시스템과 동일할 경우에는 이용자 측면에서 가지형 노선체계가 보다 효율적이다. 간선구간의 시스템이 지선구간의 시스템보다 상위 위계의 시스템일 경우에는 지선형 노선체계의 간선운행 시스템을 통한 통행비용 절감이 그에 따라 추가적으로 발생하는 환승과 대기비용보다 클 경우에 지선형 노선체계가 기지형 노선체계보다 효율적이다. 이는 격자형 대중교통 노선망에 대해 위계구조 노선망의 효율성을 분석한 박준식 외(2007c)의 연구결과와 일치하는 결과이다. 각 기종점간 통행수요가 적을 경우에는 지선형 노선체계에서 각 지점의 통행수요에 맞추어 운행간격을 증가시켜 차량의 승객 탑승률 또는 운행효율을 높이는 방안을 모색할 수 있다. 이 경우 차량 운행비용계수 노선길이, 그리고 종점 수가 증가할수록 지선형 노선체계가 효율적일 상황이 증가하고, 환승비용과 통행자의 대기시간 비용환산계수가 증가할수록 지선형 노선체계가 효율적일 상황이 감소한다. 간선구간의 중간에 도시 중심지가 위치하여 승하차 통행수요가 발생하는 경우, 간선의 중간에 위치하는 도시 중심지로의 통행량이 많을수록 지선형 노선체계가 가지형 노선체계보다 효율적일 상황이 증가한다. 따라서 승하차 수요가 집중되는 도시 중심부와 수요가 분산되어 있는 외곽부의 노선체계를 이원화시킬 경우 하나의 노선체계로 운영하는 경우보다 효율적이라 결론내릴 수 있다. 원활한 환승체계를 갖추어 환승비용을 감소시킬 경우 더욱 효과적이라 하겠다.

• 경영과학
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• 제28권3호
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• pp.1-13
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• 2011

Hub-and-spoke transportation network is a powerful and useful network structure that takes full advantage of economies of scale on routes between hubs. In recent studies, the network structure is extended to hybrid hub-andspoke that allows direct transportation between spokes. In this study, we considered more extended network structure which is called hybrid multiple hub-and-spoke that has multiple hubs and allows direct transportation between spokes. We developed a mathematical optimization model for automotive service parts transportation planning under hybrid multiple hub-and-spoke network structure. The model suggests a long-term transportation route planning and a short-term vehicle assignment planning. The model is verified by simulation and validated in real world application to Hyundai Mobis automotive service parts transportation planning. From the simulation result, the model reduced the transportation cost about 24.7%, the total distance about 6.8% and the CO2 emissions about 8.8%. In real world application for 6 months from July to December 2010, the model reduced the transportation cost about 9.1% by changing the long-term transportation route without daily vehicle assignment planning.

• 한국유기농업학회지
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• 제15권2호
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• pp.151-169
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• 2007

By the environment-friendly(hereafter EF) agricultural policy and toward the safety food of consumers, there is much glowing supply and demand fur EF agricultural products, in Korea. But, in general, EF agricultural products are blown as unique, unreasonable and high price system. This study aims to make clare the main bodies and competition structure in EF agricultural products and the different from the agricultural products. The mail results of this study are summarized as follows. Firstly, farmers and consumers directly participate in the distribution, and the major distributors participate in the market of EF agricultural products after the certification system is got ready. Because EF agricultural products is not dealt and the price system is not built up in agricultural wholesale market. Secondly, the distribution route of EF agricultural products is organized the unified organization by the main bodies such as farmers, consumers co-op, and special distributors. In any step of distribution, the main body of distribution surely deals with the contracted farmers, consumers co-op, and special distributors. Accordingly, it is said that EF agricultural products has the competition structure between the distribution route organized the unified organization rather than between main bodies in the each steps of distribution.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2004년도 추계학술대회 및 정기총회
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• pp.389-392
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• 2004

The column generation process for the set-partitioning model of the vehicle routing problem requires repeated solutions of column generation subproblems which has a combinatorial structure similar to that of the traveling salesman problem. This limits the size of the problem that can be addressed. We introduce a new modeling approach, termed route-splitting, which splits each vehicle route into segments, and results in more tractable subproblems. A lower bounding scheme that yields an updated bound at each iteration of the column generation process is developed. Implementation issues, including a technique of controlling columns in the master problem, are explored. Lower bounds are computed on standard benchmark problems with up to 199 customers.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 춘계학술대회 논문집
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• pp.165-175
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• 2003

Railway route maps including subways is a guide map which offers transport information as well as cartographic diagrams and is not only a way of communication, but it should give also concrete image and pleasing form. The elements of route map should meet satisfaction requirement condition and design attributes with aesthetic principles. To guide passengers by giving geographic information effectively, we need to understanding the following concepts and its application of basic elements such as expressing its structure and value. Therefore it should appear as a diagram with typography, form, symbols and colour. This means the aim of a good visualization should be done by a method that is concrete and a synthesis of well composed elements.

• 한국철도학회논문집
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• 제7권3호
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• pp.215-222
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• 2004

Optimal route selection of railway should take consideration of the function of the railway, topography, practicability of construction and management as well as the cost. This study performed the surveys for experts and surrounding industries and the review for the bid guidelines in order to develop the quality model with the AHP method and establish the weight for each factor. Six quality models were developed for such as the efficiency of railway operation, structure design and practicability, economic feasibility, correspondence with other plans, civil appeal and environmental sustainability, and correspondence with system. The detailed evaluation elements were also derived by each factors.