• Structural Engineering and Mechanics
• /
• 제61권3호
• /
• pp.335-345
• /
• 2017

Free vibration analysis for continuous bridge under any number of vehicles is conducted in this paper. Calculation strategy for natural frequency and mode shape is proposed based on Euler-Bernoulli beam theory and numerical assembly method. Firstly, a half-car planar model is adopted; equations of motion and displacement functions for bridge and vehicle are established, respectively. Secondly, the undermined coefficient matrices for wheels, vehicles, intermediate support, left-end support and right-end support are derived. Then, the numerical assembly technique for conventional finite element method is adopted to construct the overall matrix of coefficients for whole system. Finally, natural frequencies and corresponding mode shapes are determined based on iterative method and overall matrix solution. Numerical simulation is presented to verify the effectiveness of the proposed method. The results reveal that the solutions of present method are exact ones. Natural frequencies and associate modal shapes of continuous bridge under different conditions of vehicles are investigated. The influences of vehicle parameters on natural frequencies are also demonstrated.

• Nuclear Engineering and Technology
• /
• 제54권9호
• /
• pp.3347-3352
• /
• 2022

In 2013, the International Atomic Energy Agency (IAEA) changed the recommended maximum range of the Emergency Planning Zone (EPZ) to 30 km, and the Kori Nuclear Power Plant in Republic of Korea has also expanded the EPZ to 30 km, following the recommendation. As a result, metropolitan cities with a high population density are contained within the EPZ, and evacuating millions of people should be considered if the 30 km range of evacuation is to take place. This study proposes an evacuation plan using buses (public transportation) to transport people outside of the EPZ, quickly and efficiently. To verify the appropriate mode share ratio of buses that can guarantee the right of vulnerable road users and reduce traffic congestion, a model was built simulating the Kori Nuclear Power Plant in Ulsan Metropolitan City. The scenarios were established by changing the mode share ratio of buses and passenger cars by 10%. Considering a large-scale network analysis at the city level, a cell transmission model was applied to calculate the evacuation time in each scenario. The result shows that the optimal mode share ratio of buses is 40%, with a total evacuation time of 132 min, considering feasible bus fleets in Ulsan Metropolitan City.

• 전력전자학회논문지
• /
• 제28권1호
• /
• pp.22-29
• /
• 2023

A grid-connected inverter can be used in grid-connected or stand-alone modes. Generally, a grid-connected inverter operates in a grid-connected mode, but the inverter operates in stand-alone mode if grid faults occur. In the stand-alone mode, the grid-connected inverter must supply electric power to a critical load that needs to receive stable power even though grid faults occur. Generally, three-phase loads are used as critical loads, but a single phase is configured in some cases. In these conditions, the critical load is required to unbalance the load power consumption, which makes the three-phase load voltage unbalancd. This unbalanced voltage problem can cause fatal problems to the three-phase critical loads, and thus must be addressed. Hence, this paper proposes an algorithm to solve this unbalanced voltage problem by the individual phase current control. The proposed method is verified using Psim simulation and experiments.

• 대한교통학회지
• /
• 제26권3호
• /
• pp.97-108
• /
• 2008

본 연구에서는 통행목적별 교통수단을 선택하는 데에 영향을 미치는 요인들이 다를 것이라고 판단하고, 교통수단을 결정하는 과정을 단계별로 구분하여 그 요인들의 영향을 찾아보았다. 변수들로는 개인의 사회경제적 속성과 목적지와 거주지에서 대중교통수단 결절점 접근성, 그리고 승용차 이용여건 등으로 설정하였다. 분석결과 통행자는 통행목적과 상관없이 교통수단을 선택하는 데에 통행시간을 크게 고려하고 있어서, 통행시간이 길수록 대중교통수단을 선택하고, 환승을 감수하며, 버스보다는 지하철을 선택한다. 승용차 여부를 선택 시에는 차량이용 여건과 목적지의 주차용이성을 고려하며, 대중교통수단 선택이후에는 대중교통 결절점 접근성의 영향을 받는 것으로 나타났다. 통행목적간 비교에서는 통근통행에서는 목적지에서의 주차와 차량이용 여건이 좋을수록 승용차를, 쇼핑 및 여가통행에서는 주거지에서의 버스 및 지하철의 접근성에 따라서 대중교통수단을 선택할 확률이 높게 나타났다.

• 대한교통학회지
• /
• 제19권6호
• /
• pp.260-261
• /
• 2001

• 대한교통학회지
• /
• 제1권1호
• /
• pp.28-42
• /
• 1983

In recent years, significant advances have been made enabling travel demand analysis and network design methods to be used as increasingly realistic evaluation tools. What has been lacking is the integration of travel demand analysis with network design models. This paper reviews some of advanced (integrated) modeling approaches and presents future research directions of integrated modeling system. To design urban transportation networks, it is argued that the travelers' free choice of mode, destination and route should be introduced into transportation network design procedure instead of assuming that trips from a zone to a workplace are fixed or deriving them in a normative procedure to achieve hypothetical system optima.

• 한국재난정보학회 논문집
• /
• 제20권2호
• /
• pp.257-269
• /
• 2024

Purpose: The purpose of this study is to explain the pivotal role of the travel forecasting process in urban transportation planning. This study emphasizes the use of travel forecasting models to anticipate future traffic. Method: This study examines the methodology used in urban travel demand modeling within transportation planning, specifically focusing on the Urban Transportation Modeling System (UTMS). UTMS is designed to predict various aspects of urban transportation, including quantities, temporal patterns, origin-destination pairs, modal preferences, and optimal routes in metropolitan areas. By analyzing UTMS and its operational framework, this research aims to enhance an understanding of contemporary urban travel demand modeling practices and their implications for transportation planning and urban mobility management. Result: The result of this study provides a nuanced understanding of travel dynamics, emphasizing the influence of variables such as average income, household size, and vehicle ownership on travel patterns. Furthermore, the attraction model highlights specific areas of significance, elucidating the role of retail locations, non-retail areas, and other locales in shaping the observed dynamics of transportation. Conclusion: The study methodically addressed urban travel dynamics in a four-ward area, employing a comprehensive modeling approach involving trip generation, attraction, distribution, modal split, and assignment. The findings, such as the prevalence of motorbikes as the primary mode of transportation and the impact of adjusted traffic patterns on reduced travel times, offer valuable insights for urban planners and policymakers in optimizing transportation networks. These insights can inform strategic decisions to enhance efficiency and sustainability in urban mobility planning.

• 대한교통학회지
• /
• 제23권8호
• /
• pp.7-17
• /
• 2005

교통은 개인의 이동(mobility)에 기원을 둔다. 교통환경에서 이 같은 개인의 이동을 특정 값으로 제시하려는 이동성연구는 여러 각도에서 시행되어 왔으며, 그 결과로 통행자의 통행 서비스수준을 정량적으로 평가할 수 있는 다양한 방안이 제안되어왔다. 그러나 복합대중교통에 대한, 특히 지역적 범위에서 평가할 수 있는, 이동성연구는 많지 않았다. 본 연구는 복합대중교통망에 대한 이동성지표를 지점 대 지점에서 지역간 범위로 확대하여, 대중교통 승객의 접근시간, 주행시간, 환승시간을 고려한 대중교통 이동성지표를 제안한다. 복합대중교통의 이동성 (mobility) 평가를 위하여 대중교통 이동성을 도보수단까지 포함하였으며, 비교 대안수단은 대중교통의 경쟁수단인 개인교통수단으로 설정하였다. 본 연구에서 제안한 대중교통 이동성 분석지표는 지역간 대중교통시설이 개인교통수단에 비해 어느 정도의 경쟁력을 가지는지 (지표1), 도보수단을 포함하여, 출발지역에서 도착지역까지 개인교통수단에 비해 얼마나 편리한지 (지표 2), 이용자의 지역간 통행을 지원할 수 있도록 얼마나 많은 경쟁력 있는 다양한 경로가 제공되는지 (지표 3)를 평가할 수 있도록 설정하였다.

• 한국대기환경학회지
• /
• 제24권3호
• /
• pp.275-283
• /
• 2008

Since mobile source is a major source of VOCs, quantifying emissions from motor vehicles is an important factor to control VOCs in atmosphere. In this study, in order to evaluate tailpipe VOCs emissions from motor vehicles, mass emissions of non-methane volatile organic compounds from 45 vehicles were determined. Measurements were made on a chassis dynamometer using CVS-75 mode and speed specific drive modes. Target VOCs are 53 compounds determined as the volatile ozone precursors. The individual VOCs composition of vehicle emission and emission rates were also determined. In case of gasoline vehicles, VOCs emission from over 80,000 km vehicles were about 46% larger than less 80,000 km vehicles. The difference in benzene and toluene according to driving mileage was 44% and 26% respectively. The composition of VOCs were different by fuel type. The order of VOCs composition was paraffins>aromatics>olefins in gasoline vehicle emissions, paraffins>olefins>aromatics in light duty diesel vehicle emissions. The VOCs emissions were decreased as vehicle speed increasing. These results will be used to calculate total VOCs emissions from automobiles in the future.

• 농촌계획
• /
• 제10권1호
• /
• pp.41-55
• /
• 2004

The purpose of this study is to investigate a causal relationship between the mode of production and change of rural society. While dominant theories of social change have stressed variation of contingencies and periodical contexts, this theoretical paper drives a new insight paralleling diverse theoretical arguments of each mode of production with rural and urban changes. Investigating the drifts of intellectual ideologies of the mode of production, we get through diverse paradigm shifts of the production accumulation and its trigger effects on rural change. More specifically, the present study investigates change of rural society by way of investigating such fluctuations of societal changes as ancient society, slavery society, feudal society, industrial society, post-industrial society, and information society. We find that transportation and communication technologies have had a key role in the changes, however, the effects of the technologies on social changes have been different between rural- and urban-society. While we take it for granted that flexible accumulation in post-industrial society and time-space compression and informatization in information society will reduce developmental gap between rural- and urban-society, we also found that there have been big differences of actual application of the technologies between theory and reality in each era of mode of production.