• Journal of Biosystems Engineering
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• v.12 no.4
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• pp.9-15
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• 1987

The vibrational characteristics of a radial-ply (155SR13 4PR) and a biased-ply tire (6.15-134PR) were investigated for examining the effects of tires with different structure on the ride characteristics of the vehicle. The natural frequencies at the tread band, mode shapes, and damping factors of two tires at the state of plane vibration were determined experimentally. The test work was performed at four levels of the inflation pressure, ranging from 171.7 kPa to 245.2 kPa, and three levels of the vertical load, deviating by 10% from the standard load designated by the Department of Transportation of the United States of America. The following results were drawn by the analysis of the test results: 1. The first-order natural frequencies of the radial-ply and the biased-ply tires at the tread band were 112 Hz and 159 Hz, respectively, at the state o f the free vibration when the inflation pressure of 196.2 kPa was applied. It was known that the biased-ply tire has higher resonant frequency than the radial-ply tire and the natural frequencies of the both tires move to the high frequency range as t he inflation pressure is increased. 2. The vibration modes of both tires were quite different. No big difference in mode shapes was examined as the inflation pressure was increased. But the natural frequencies of two tires were changed. For the radial-ply tire, no difference in mode shape was found whether the vertical load was applied or not. But a significant difference in mode shape was examined for the biased-ply tire. 3. Any difference was not found in damping factor as the different inflation pressures were applied. 4. When no vertical load was applied, damping factors of the radial-ply and biased-ply tire at the state of the natural vibration ranged from 2.6 to 5.9%, and from 4.1 to 7.8%, respectively. It was estimated that the radial-ply tire would have better cushioning than the biased-ply tire since the vertical spring rate of the radial-ply tire was much less than that of the biased-ply tire, even though the damping effect of the radial-ply tire was smaller than that of the biased-ply tire.

• Journal of the Korean Geographical Society
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• v.44 no.6
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• pp.723-744
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• 2009

The purpose of this paper is to clarify the prospects and problems in the study of geography related to the concept of commodity, transport, and supply chains. The geography studies related to commodity chains are expanded to each field of industry focusing on the subjects and economic difference which lead the commodity chain in core and periphery regions. These vertical connection are studied with the political economy approach that gives attention to geographical pattern of agricultural products and foods. But in viewpoint of commodity circuit and commodity network, the culture or subjects of micro regions and interaction are also studied. The contents of these study are to clarify the importance of cultural turn and local. And the study of chain standpoint appears that the series of transport process by transportation modes can be understood by transport chains and the physical distribution process of sea freight is to be grasped by supply chains.

• Journal of the Korean Society for Railway
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• v.16 no.2
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• pp.122-128
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• 2013

As a result of investment in railway safety focusing on passenger safety, the train accident rate has been reduced by half domestically and we have reached a high level of safety compared to other countries and other transportation modes. However, accidents related to staff are still at a high ratio compared to other countries. There have been few studies on staff safety and no relevant systematic safety measures have been implemented. More than 90% of staff fatalities occurred from rolling stock in motion and electrification, which are representative railway accidents. In this study, causes of accidents, and current safety measures for staff are analyzed focusing on trains in motion. The results can be utilized for developing new safety measures.

• Journal of the Society of Disaster Information
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• v.8 no.2
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• pp.188-196
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• 2012

Dynamic parameters such as natural frequencies can provide global stiffness information of a structure, and thus be utilized in monitoring structural integrity of large structures such as a containment. To identify the dynamic parameters without interrupting normal operation, a modal analysis method based on ambient vibration measurements should be applied. In this study, dynamic parameters of the containment of Wolsong Unit 2 are identified using ambient vibration measurement data. The feasibility of the study is verified using a numerical model for the containment. From the modal analysis, dynamic parameters of the containment with acceptable correlation to analytical modes can be estimated.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.4
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• pp.491-496
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• 2017

The hydrogen($H_2$) is promising energy carrier of renewable energy in the microgrid system such as small village and military base due to its high energy density, pure emission and convenient transportation. $H_2$ can be generated by photocatalytic water splitting, gasification of biomass and water electrolysis driven by solar cell or wind turbine. Solid oxide electrolysis cells(SOECs) are the most efficient way to mass production due to high operating temperature improving the electrode kinetics and reducing the electrolyte resistance. The SOECs are consist of nickel-yttria stabilized zirconia(NiO-YSZ) fuel electrode / YSZ electrolyte / lanthanum strontium manganite-YSZ(LSM-YSZ) air electrode due to similarity to Solid Oxide Fuel Cells(SOFCs). The Ni-YSZ most widely used fuel electrode shows several problems at SOEC mode such as degradation of the fuel electrode because of Ni particle's redox reaction and agglomeration. Therefore Ni-YSZ need to be replaced to an alternative fuel electrode material. In this study, We studied on the Double perovskite $PrBrMnO_{5+{\delta}}$(PBMO) due to its high electric conductivity, catalytic activity and electrochemical stability. PBMO was impregnated into the scaffold electrolyte $La_{0.8}Sr_{0.2}Ga_{0.85}Mg_{0.15}O_{3-{\delta}}$(LSGM) to be synthesized at low temperature for avoiding secondary phase generated when it exposed to high temperature. The Half cell test was conducted at SOECs and SOFCs modes.

• Journal of Navigation and Port Research
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• v.36 no.8
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• pp.683-689
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• 2012

The logistics industry is growing rapidly with China's economic development in recent years. Particularly, the intermodal freight system is becoming the main issue to reduce the logistic costs under the situation that the quantity of cargo transported between Korea and China is continuously increasing. Shift from road transportation to eco-friendly modes such as rail and coastwise shipping is also increasing. The present study suggests technical aspects related to the implementation of intermodal transport system centered on train ferries between two countries with already employed Chinese infrastructure into consideration. Technical assessment of intermodal train ferry system entails not only the vessels but supporting facilities and technologies as well. Port and rail facilities and operating skills for efficient modal shifting, and their standardization is indispensible to the realization of an intermodal train ferry system between the two countries.

• International Journal of Highway Engineering
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• v.18 no.1
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• pp.57-62
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• 2016

PURPOSES : Reflection cracking has been one of the major causes of distress when asphalt pavement is laid on top of concrete pavement. This study evaluated the reflection cracking resistance of asphalt mixtures reinforced with asphalt embedded glass fiber and carbon fiber using a Texas Transportation Institute (TTI) overlay tester. METHODS : Different asphalt mixtures such as polymer-modified mastic asphalt (PSMA) and a dense graded asphalt mixture were reinforced with asphalt-embedded carbon fiber and glass fiber. For comparison purposes, two PSMA asphalt mixtures and one dense graded asphalt mixture were evaluated without fiber reinforcement. Two different overlay test modes, the repeated overlay test (R-OT) and monotonic overlay test (M-OT), were used to evaluate the reflection cracking resistance of asphalt mixtures at $0^{\circ}C$. In the R-OT test, the number of repeated load when the specimen failed was obtained. In the M-OT test, the tensile strength at the peak load and tensile strain were obtained. RESULTS : As expected, the fiber-reinforced asphalt mixture showed a higher reflection cracking resistance than the conventional nonreinforced asphalt mixtures based on the R-OT test and M-OT test. The dense graded asphalt mixture showed the least reflection cracking resistance and less resistance than the PSMA. CONCLUSIONS : The TTI overlay tester could be used to differentiate the reflection cracking resistance values of asphalt mixtures. Based on the R-OT and M-OT results, the carbon-fiber-reinforced asphalt mixture showed the highest reflection cracking resistance among the nonreinforced asphalt mixtures and glass-fiber-reinforced asphalt mixture.

• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.262-267
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• 2006

For growing need for the multimedia application in the vehicles, the MOST protocol has been focused on. The MOST protocol supports three kinds of communication modes; short control message, asynchronous packets, and reserved synchronous stream data. Because of a variety of transportation, the MOST is suitable for various applications in vehicle environment. In this paper, we implemented embedded system which is MOST-enabled AMS platform and tested the network communication operation through the control port and the synchronous channel of the source port. We implemented the prototype platforms which communicate each other on the MOST's POF network. Moreover we implemented the DivX decoder attached AMS platform and verified the operation by transferring the video stream and the control messages through the MOST network.

• Journal of Environmental Health Sciences
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• v.45 no.2
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• pp.186-191
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• 2019

Objectives: Subway is one of the most common transportation modes in Seoul, Korea. The objectives of this study were to determine characteristics of in-cabin $PM_{2.5}$ concentration in Seoul Metro Line Number 2 and to identify factors of the $PM_{2.5}$ concentration. Methods: In-cabin $PM_{2.5}$ concentrations in Seoul Metro Line Number 2 were measured using real-time monitors and the factors affecting $PM_{2.5}$ concentration in cabin were observed. Linear regression analysis of in-cabin $PM_{2.5}$ concentration and indoor/outdoor (I/O) ratio were performed. Results: In-cabin $PM_{2.5}$ concentration was associated with the in-cabin $PM_{2.5}$ concentration in previous station. In-cabin $PM_{2.5}$ concentration was correlated with ambient $PM_{2.5}$ concentration and associated with underground station with control of the in-cabin $PM_{2.5}$ concentration in previous station. I/O ratio increased as the number of passengers increased and when passing through the underground station with control of I/O ratio in previous station. Conclusion: In-cabin $PM_{2.5}$ concentration was affected by ambient $PM_{2.5}$ concentration. Therefore, management of in-cabin $PM_{2.5}$ concentrations should be based on outdoor air quality.

• Geomechanics and Engineering
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• v.18 no.4
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• pp.353-362
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• 2019

Soil-rock mixture (S-RM) is an inhomogeneous geomaterial that is widely encountered in nature. The mechanical and physical properties of S-RM are important factors contributing towards different deformation characteristics and unstable modes of the talus slope. In this paper, the equivalent substitution method was employed for the preparation of S-RM test samples, and large-scale triaxial laboratory tests were conducted to investigate their mechanical parameters by varying the water content and confining pressure. Additionally, a simplified geological model based on the finite element method was established to compare the stability of talus slopes with different strength parameters and in different excavation and support processes. The results showed that the S-RM samples exhibit slight strain softening and strain hardening under low and high water content, respectively. The water content of S-RM also had an effect on decreasing strength parameters, with the decrease in magnitude of the cohesive force and internal friction angle being mainly influenced by the low and high water content, respectively. The stability of talus slope decreased with a decrease in the cohesion force and internal friction angle, thereby creating a new shallow slip surface. Since the excavation of toe of the slope for road construction can easily cause a landslide, anti-slide piles can be used to effectively improve the slope stability, especially for shallow excavations. But the efficacy of anti-slide piles gradually decreases with increasing water content. This paper can act as a reference for the selection of strength parameters of S-RM and provide an analysis of the instability of the talus slope.