• International Journal of Automotive Technology
• /
• v.6 no.5
• /
• pp.483-489
• /
• 2005

Based on a two-degree of freedom vehicle model, this paper investigates ride comfort for a heavy off-road vehicle mounted a nonlinear hydropneumatic spring, which is influenced by nonlinear stiffness and damping characteristics of the hydropneumatic spring. Especially, the damping force is derived by applying H. Blasius formula in modeling process according to the real physical structure of the hydropneumatic spring, and the established model of nonlinear stiffness characteristics have been validated by experiments. Furthermore, the effects of parameter variations of the hydropneumatic spring, such as initial charge pressure and damping coefficient, on body acceleration, suspension deflection and dynamic tire deflection are also investigated.

• Journal of the Korean Society of Industry Convergence
• /
• v.5 no.4
• /
• pp.313-320
• /
• 2002

A 2-dimensional $k-{\varepsilon}$ numerical model was developed to explore the effects of vehicle movement, jet fan and wind speed for the ventilation of road tunnels. To consider the temperature distribution in the tunnel, the energy equation was solved with a source term of the energy exhausted from vehicles. Although the tunnel ventilation can be made by the piston effect of vehicle movement, an additional ventilation is necessary when a head wind is existing. Jet fans may assist the air flow in the tunnel. However, more efficient ventilation system should be necessary, because the exhaust gas from vehicles flow along the road surface and it cannot be diffused in the longitudinal tunnel.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.21 no.1
• /
• pp.273-286
• /
• 2022

An HD map is essential in the automated driving of level 4 and above to generate the vehicle's global path since it contains road information and each road's lane information. Therefore, all the road elements in the HD map must be correctly defined to construct the correct road network necessary to generate the global path. But unfortunately, it is not difficult to find various errors even in the most recent HD maps. Hence, a preprocessing algorithm has been developed to detect and correct errors in the HD map. This error detection and correction result in constructing the correct road network for use in global path planning. Furthermore, the algorithm was tested on real roads' HD maps, demonstrating its validity.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.6 no.4
• /
• pp.74-84
• /
• 2003

This study focuses on the technology to reduce destruction and damages of an ecosystem in the process of road construction. The authors investigated the ecological conservation activities and restoration technology which were applied to the construction of 2 bridges in Japan. The key results are as following : First, the most important thing in constructing eco-road was the linear design. Second, we need to adopt the environmental construction forms and materials to the design of structure. Finally, we have to use environment-friendly methods for the sake of the ecosystem at the real construction stage. Adopting those technologies has at least a few merits. First, we can achieve out goals : conservation and restoration in the local habitat. Second, we can save money instead of building a eco-bridge. There is a further advantage which makes it possible to develop environment-friendly technologies than before by drawing developers' attention.

• Korea Trade Review
• /
• v.47 no.6
• /
• pp.307-333
• /
• 2022

In recent years, the outward foreign direct investment (oFDI) in the Belt and Road Initiative (BRI) by Chinese companies has significantly increased in size and changed in content. However, changes in the oFDI patterns between the pre- and post-BRI periods have not received sufficient attention from academia despite their theoretical and strategic significance. This paper reviewed existing research to establish seven hypotheses on changes in the oFDI patterns of Chinese companies investing in BRI countries and conducted empirical analyses to test the hypotheses using secondary data. The results showed that after the BRI agreement, Chinese oFDI in BRI countries was more active in less economically and less institutionally developed countries, that the oFDI by privately-owned enterprises (POEs) increased more than that of state-owned enterprises (SOEs), and that SOEs were more active in the social overhead capital (SOC) area while POEs were more active in the non-SOC area. The paper concludes with a summary, implications, and future research directions.

• Journal of Forest and Environmental Science
• /
• v.12 no.1
• /
• pp.26-36
• /
• 1996

In our country, nation-wide forest road works are being carried out as one of the efforts to bolster the international competitiveness of agriculture, however such environmental problems as sediment discharge and water quality degradation accompany such efforts more often than not. Hence, in this research report, we compile and analyze the Japanese sources dealing with the "research direction of the forest road construction", "environmental impact assessment upon the watershed of the forest road construction", "environmentally-sound forest road construction and its research method" in consideration of the fact that natural environment of Japan is similar to that of our country and Japanese forest road works has a long history. We hope that this report be useful to the reasonable watershed management and the environmentally-sound forest road works.

• International conference on construction engineering and project management
• /
• 2024.07a
• /
• pp.1112-1119
• /
• 2024

Addis Ababa, the capital of Ethiopia, has been lacking an adequate road network to ensure community access to social, political, and economic resources and to facilitate economic development. The road network coverage was about 22.5% in 2022, which is below the minimum international standard of 25%. To improve accessibility and mobility, the Addis Ababa City Roads Authority(AACRA) has engaged its own force crew (contractor), as well as local and foreign road contractors, in the construction of urban roads. However, these road construction projects are rarely completed within the estimated time and cost, along with a variety of other issues that also need to be addressed. This study aims to explore the application of lean construction for improving the performance of urban road construction projects in Addis Ababa City. A survey of road construction stakeholders was carried out to evaluate their perspectives on the importance of project performance indicators, with the goal of identifying key factors affecting road construction project performance. First, a list of performance indicators was prepared based on a review of lean construction literature, and a total of 38 identified factors were grouped into six performance indicator categories. Cross-tabulation analysis of the stakeholder perspectives was then carried out, and it was found that the indicators that affect the performance of urban road infrastructure projects (in descending order of importance) were: time, quality, cost, risk, safety, and sustainability. Through this analysis it was concluded that right-of-way issues, delay to finish, inflation, contractor capacity, and scope change with change order are also major factors that affect the performance of urban roads construction projects. Clarification of these factors will provide AACRA with useful information on what aspects of lean construction should be prioritized when evaluating future construction projects.

• Journal of Korean Society of Transportation
• /
• v.33 no.3
• /
• pp.237-246
• /
• 2015

Operation and Maintenance in road infrastructure is repetitive carbon emissions activities to preserve the road in its originally constructed condition. In the view of road planning and construction, operation, and maintenance of life cycle, operation and maintenance stage quantification of carbon emissions is very important because it is easily accessible activities to reduce carbon emissions in road infrastructure that existing and new road. However, carbon emissions estimation in operation and maintenance stage is yet to do, because data collection is so hard and carbon emissions estimation methodology is very complicated. In this study, a basic unit of carbon emission in the operation and maintenance stage of the road infrastructure was developed in order to get the quantitative determination of carbon that occurring. Carbon emissions of the Expressway and Common state road was calculated by using the basic unit of carbon emission and application plan of basic unit of carbon emission are presented.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.41 no.4
• /
• pp.238-247
• /
• 2018

This paper considers the problem of scheduling loading and unloading operations of a crane in a railway terminal motivated from rail-road container transshipment operations at Uiwang Inland Container Depot (ICD). Unlike previous studies only considering the total handling time of containers, this paper considers a bi-criteria objective of minimizing the weighted sum of the total handling time and tenant service time. The tenant service time is an important criterion in terms of terminal tenants who are private logistics companies in charge of moving containers from/to the terminal using their trucks. In the rail-road container shipment yard, the tenant service time of a tenant can be defined by a time difference between beginning and finishing loading and unloading operations of a crane. Thus, finding a set of sequences and time of the crane operations becomes a crucial decision issue in the problem. The problem is formulated as a nonlinear program which is improved by linearizing a nonlinear constraint in the model. This paper develops a genetic algorithm to solve the problem and performs a case study on the Uiwang ICD terminal. Computational experiment results show that the genetic algorithm shows better performance than commercial optimization solvers. Operational implications in terms of tenants are drawn through sensitivity analyses.

• International Journal of Highway Engineering
• /
• v.19 no.3
• /
• pp.65-70
• /
• 2017

PURPOSES : Pavement Management System contains the data that describe the condition of the road. Under limited budget, the data can be utilized for efficient plans. The objective of this research is to develop a mixed integer program model that maximizes remaining durable years (or Lane-Kilometer-Years) in road maintenance planning. METHODS : An optimization model based on a mixed integer program is developed. The model selects a cluster of sectors that are adjacent to each other according to the road condition. The model also considers constraints required by the Seoul Metropolitan Facilities Management Corporation. They select two lanes at most not to block the traffic and limit the number of sectors for one-time construction to finish the work in given time. We incorporate variable cost constraints. As the model selects more sectors, the unit cost of the construction becomes smaller. The optimal choice of the number of sectors is implemented using piecewise linear constraints. RESULTS : Data (SPI) collected from Pavement Management System managed by Seoul Metropolitan City are fed into the model. Based on the data and the model, the optimal maintenance plans are established. Some of the optimal plans cannot be generated directly in existing heuristic approach or by human intuition. CONCLUSIONS:The mathematical model using actual data generates the optimal maintenance plans.