• Geomechanics and Engineering
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• 제17권4호
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• pp.385-392
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• 2019

The present fractional-order plasticity models for granular soil are mainly established under the triaxial compression condition, due to its difficult in analytically solving the fractional differentiation of the third stress invariant, e.g., Lode's angle. To solve this problem, a three dimensional fractional-order elastoplastic model based on the transformed stress method, which does not rely on the analytical solution of the Lode's angle, is proposed. A nonassociated plastic flow rule is derived by conducting the fractional derivative of the yielding function with respect to the stress tensor in the transformed stress space. All the model parameters can be easily determined by using laboratory test. The performance of this 3D model is then verified by simulating multi series of true triaxial test results of rockfill.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권12호
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• pp.4763-4775
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• 2020

This research aims to develop a deep learning-based method that automatically detects and segments the defects on railroad surfaces to reduce the cost of visual inspection of the railroad. We developed our segmentation model by modifying a fully convolutional network model [1], a well-known segmentation model used for machine learning, to detect and segment railroad surface defects. The data used in this research are images of the railroad surface with one or more defect regions. Railroad images were cropped to a suitable size, considering the long height and relatively narrow width of the images. They were also normalized based on the variance and mean of the data images. Using these images, the suggested model was trained to segment the defect regions. The proposed method showed promising results in the segmentation of defects. We consider that the proposed method can facilitate decision-making about railroad maintenance, and potentially be applied for other analyses.

• 대한교통학회지
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• 제30권1호
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• pp.45-58
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• 2012

기존의 전통적 4단계 수요추정기법은 화물의 물류특성(Logistics Characteristics)을 반영하지 못하는 한계가 있다. 이로 인해 물류시설의 신설 개선에 따른 수요 및 편익변화를 제대로 추정을 하지 못한다. 따라서 화물수요추정 과정의 신뢰도 및 활용도 제고를 위해 물류특성을 고려한 화물수요추정방법의 개발이 요구된다. 화물수요추정방법의 개선을 위해 1990년대 후반부터 유럽을 중심으로 물류행태 반영방법에 대한 연구가 시작되었다. 이에 반해 우리나라는 이러한 분야에 대한 연구가 미흡한 편이다. 본 연구는 물류행태 반영방법 및 대규모 화물조사에 대한 국내외 학술대회 발표논문, 학술지 게재논문 및 연구보고서 등을 바탕으로 1) 화물 품목구분, 2) P/C(Production- Consumption) 구축, 3) 물류 네트워크 구축, 4) 물류체인모형(logistics chain model) 구축, 5) 대규모 화물조사 분야에 대한 국내외 사례 및 최근 연구동향을 조사 분석하고 시사점을 도출하였다. 또한 화물수요추정방법 개선을 위한 발전방향을 제시하였다.

• 대한산업공학회지
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• 제24권1호
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• pp.157-165
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• 1998

This paper considers the single-product production and transportation problem with discrete time, dynamic demand and finite time horizon, an extension of classical dynamic lot-sizing model. In the model, multiple freight container types are allowed as the transportation mode and each order (product) placed in a period is shipped immediately by containers in the period. Moreover, each container has type-dependent carrying capacity restriction and at most one container type is allowed in each shipping period. The unit freight cost for each container type depends on the size of its carrying capacity. The total freight cost is proportional to the number of each container type employed. Such a freight cost is considered as another set-up cost. Also, it is assumed in the model that production and inventory cost functions are dynamically concave and backlogging is not allowed. The objective of this study is to determine the optimal production policy and the optimal transportation policy simultaneously that minimizes the total system cost (including production cost, inventory holding cost, and freight cost) to satisfy dynamic demands over a finite time horizon. In the analysis, the optimal solution properties are characterized, based on which a dynamic programming algorithm is derived. The solution algorithm is then illustrated with a numerical example.

• 대한교통학회지
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• 제7권1호
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• pp.19-34
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• 1989

In general, Shopping centers are located in the center of transportation, which induce more traffic concentration than other facilities. As a result, it becomes to one of the aggravating factors of urban ＆ transportation problem such as traffic conjestion, parking problems. Thus, in planning shopping-center, it is desirable that consumer\`s trip pattern is should lie more carefully analyzed in order to alleviate the above problems. This study is aimed at finding the characteristics of shopping tripes and analyzing the choice behavior of shopping center and mode-to-shop. This study has developed a nested logit model in which consumers choose shopping center and mode-to-shop with a sequential structure. The model was estimated using household data from the 1989 May, Seoul metropolitan area and the 18 alternatives of shopping center and 5 mode alternatives. The estimated model have been evaluated and it may be concluded that this model for shopping trips is effective and fesible. The conclusion of this study are as fellows. 1. Out-of-vehicle travel time is more important factor affecting behavior of mode choice than in-vehicle travel time. 2. All of direct-elasticities for mode with respect to the travel time is more elastic than travel cost. 3. Accessibility to shop is more important factor affecting the choice of shopping center than parking space. 4. The value of out-of-vehicle travel time exceeds the value of in-vesicle travel time by 1.64 times.

• 한국BIM학회 논문집
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• 제8권3호
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• pp.12-19
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• 2018

The research aims to find implications of machine learning and urban big data as a way to construct the flexible transportation network system of smart city by responding the urban context changes. This research deals with a problem that existing a bus headway model is difficult to respond urban situations in real-time. Therefore, utilizing the urban big data and machine learning prototyping tool in weathers, traffics, and bus statues, this research presents a flexible headway model to predict bus delay and analyze the result. The prototyping model is composed by real-time data of buses. The data is gathered through public data portals and real time Application Program Interface (API) by the government. These data are fundamental resources to organize interval pattern models of bus operations as traffic environment factors (road speeds, station conditions, weathers, and bus information of operating in real-time). The prototyping model is implemented by the machine learning tool (RapidMiner Studio) and conducted several tests for bus delays prediction according to specific circumstances. As a result, possibilities of transportation system are discussed for promoting the urban efficiency and the citizens' convenience by responding to urban conditions.

• 도시과학
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• 제7권2호
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• pp.1-9
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• 2018

In this study, Analysis of DRT model and contribustion based on the case of local governments adopting the Demand Responsive Transit(DRT) in order to provide transportation in public transportation service weak area. Based on the case of Yeoju Area, the contribution of the DRT was analyzed. The DRT model was established as a fixed and call type model with taxi and bus transportation. Based on the results of the happy taxi service in Yeoju Area in 2016, the contribution of DRT was analyzed. According to the happy taxi performance of Yeoju city, it was introduced to 27 villages, and operated 4,188 times. And 9,111 people used it and Yeoju Area supported about 53 million Won. The contribution of local governments was analyzed in terms of local government, users, and social aspects. On local government aspects, we analyzed the budget cuts and complaints resolution. On the user aspects, we analyzed waiting time reduction, walking time reduction, travel time reduction, comfort, punctuality, and stability. On social aspects, we analyzed taxi and regional economy activation, and convenience of mobility.

• Wind and Structures
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• 제29권3호
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• pp.149-161
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• 2019

When a railway vehicle runs in crosswinds, the unsteady aerodynamic forces acting on the train induced by the vehicle speed, crosswind velocity and local landforms are a common problem. To investigate the dynamic performance of a railway vehicle due to the influence of unsteady aerodynamic forces caused by local landforms, a vehicle aerodynamic model and vehicle dynamic model were established. Then, a wind-loaded vehicle system model was presented and validated. Based on the wind-loaded vehicle system model, the dynamic response performance of the vehicle, including safety indexes and vibration characteristics, was examined in detail. Finally, the effects of the crosswind velocity and vehicle speed on the dynamic response performance of the vehicle system were analyzed and compared.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1615-1622
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• 2010

Recently, there has been an increase in interest from the aspects of transshipment and connection between the means of transportation. Not only for passengers but also for freight transportation as the need for transportation efficiency is growing while the importance of logistic railway transportation is emerging. The domestic freight transportation is carried out by roads, railroads, ships, and port. However, as other means of transportation, except road, is impossible for Door to Door Service, multimodal transportation accompanied by road transportation is carried out. Here, even though 'transshipment' occurs, because of the lack of basic data regarding this, it is difficult to reflect it in the demand forecasting. With respect to the Korean freight O-D, it was very difficult to have equivalent comparison on the competitiveness and availability of transportation services between the point of departure and the final destination. Taking into account the study of implementation of logit model considering the time and cost of transshipment of multimodal transportation and the transshipment resistance value upon selecting means of freight transportation on multimodal transportation was comparatively insufficient. This study consisted of questionnaire targeting shippers, and based on this, transshipment resistance value was calculated by deriving utility function. By doing so, I intend to examine the effect 'transshipment' has on selecting the means of transportation occurring from freight transportation.

• 대한교통학회지
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• 제36권2호
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• pp.141-154
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• 2018

지속적으로 증가하는 국제선 항공수요에 대웅하기 위해 지방 광역권에도 새로운 공항 건설 및 기존 공항 확장 계획이 이루어지고 있다. 그러나 기존 항공수요예측은 우리나라 전체 항공수요 또는 주요 도시 간의 항공수요에 대해서 수행되어 왔으며, 지방의 고유 특성을 고려한 지역별 항공수요예측은 많이 이루어지지 않았다. 본 연구에서는 영남권 국제선 항공수요를 대상으로 하였고, 현실적으로 관측하기 어려운 지방 광역권의 고유 특성을 반영할 수 있는 패널 자료를 활용한 fixed-effects model을 최적 모형으로 제안하였다. 모형 검증결과를 살펴보면 패널 자료 분석은 시계열 특성을 가지는 몇 개의 거시 사회경제지표만을 사용한 모형에서 다루기 어려운 허구적 회귀와 미관찰 이질성을 효과적으로 처리하고 있음을 알 수 있다. 다양한 통계적 검증과 적합성 평가를 통해서 본 연구에서 제안한 fixed-effects model이 다른 계량경제 모형들에 비해서 영남권 국제선 수요예측에 있어서 우수함을 증명하였다.