• Tunnel and Underground Space
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• v.17 no.1 s.66
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• pp.17-25
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• 2007

Research and development for disposal of contaminants including radioactive wastes in deep underground have been carried out from laboratory works. However, validation and reliability of the data from the laboratory are arguing issues because they are not obtained from real disposal situations. Underground research laboratory (URL) is not only a solution to overcome such limitations, but also a valuable facility for performance assessment as an engineering scale. However, it requires much budget, and environmental issues can give rise to social conflicts easily. Such considering points related to URL are discussed as well as current status of worldwide URLs are introduced. Furthermore study plans for solute transport in a small-scale underground research tunnel (KURT), which was authorized recently as an non-radioactive facility in Korea, also described.

• Smart Structures and Systems
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• v.26 no.4
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• pp.451-468
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• 2020

Although model updating has been widely applied using a specific optimization algorithm with a single objective function using frequencies, mode shapes or frequency response functions, there are few studies that investigate hybrid optimization algorithms for real structures. Many of them did not take into account the sensitivity of the updating parameters to the model outputs. Therefore, in this paper, optimization algorithms and sensitivity analysis are applied for model updating of a real cable-stayed bridge, i.e., the Kien bridge in Vietnam, based on experimental data. First, a global sensitivity analysis using Morris method is employed to find out the most sensitive parameters among twenty surveyed parameters based on the outputs of a Finite Element (FE) model. Then, an objective function related to the differences between frequencies, and mode shapes by means of MAC, COMAC and eCOMAC indices, is introduced. Three metaheuristic algorithms, namely Gravitational Search Algorithm (GSA), Particle Swarm Optimization algorithm (PSO) and hybrid PSOGSA algorithm, are applied to minimize the difference between simulation and experimental results. A laboratory pipe and Kien bridge are used to validate the proposed approach. Efficiency and reliability of the proposed algorithms are investigated by comparing their convergence rate, computational time, errors in frequencies and mode shapes with experimental data. From the results, PSO and PSOGSA show good performance and are suitable for complex and time-consuming analysis such as model updating of a real cable-stayed bridge. Meanwhile, GSA shows a slow convergence for the same number of population and iterations as PSO and PSOGSA.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.59-73
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• 2016

The demand for subsurface transport is increasing. The users and the operators of road tunnels are exposed to risks with different causes. One main cause, however, is the traffic situation in the event of accidents. The importance of a Quantified Risk Assessment is increasing to quantify the safety of road tunnels and to balance the requirements (capacity, reliability, availability, maintainability and safety) of various stakeholders. Although there are classical methods for risk assessments, such as ETA and FTA. These methods are used for relatively simple cases because it could not relevantly reflect the diversity and relationship of the parameters. Therefore, a quantitative risk assessment based on Bayesian Probabilistic Networks considering interdependence between the parameters of a complex underground system as a double deck tunnel is provided.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3B
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• pp.485-492
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• 2010

Intelligent Transport System(ITS) has been studied in various systems, such as road environment information offering, vehicle short-range wireless/wire communication, vehicle collision preventing and pedestrian safety offering systems. Related to this, the USN technology based on the sensing accuracy for motorists and pedestrians safety, the information reliability, the maintenance and convenience for Sensor Network is highlighted. This study uses various sensors to construct USN to the road, and connect it to the developed RSU so it collects the real-time road environment information and offers it to OBU and Traffic Control Surveillance Center with Road Weather Information System. RSU collects roadside information for driver's safety and analyzes it to offer IP and beacon service according to the service priority to OBU & upper layer terminal. In the upper layer terminal it is developed the IP based Settop Box application program to offer the urban traffic information & road environment, and environment sensor error, etc. Finally, RWIS develops the real-time collection of roadside information to complement the driver's safety to the intelligent traffic system, and presents various service modes with technology convergence.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.79-88
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• 2015

In this paper, we examine Ethernet based vehicle network which is recently emerging technology. Current MOST for entertainment will be soon replaced with the emerging Ethernet based vehicle network. Although legacy standard Ethernet has several advantages it is not suitable for vehicle backbone network without any modification. As a result, many researches are happening on extending and modification of the Ethernet function for realtime and reliability. Time-triggered Ethernet, one of many trials known as AS6802, is investigated on the architecture and functionalities. We design the traffic model on Time-triggered Ethernet and analyse the latency of the network. We also consider the QoS requirement and environment of operating configuration for vehicle network.

• JSTS:Journal of Semiconductor Technology and Science
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• v.14 no.4
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• pp.495-502
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• 2014

Fast recovery diodes (FRDs) were developed using the $p^{{+}{+}}/n^-/n^{{+}{+}}$ epitaxial layers grown by low temperature epitaxy technology. We investigated the effect of electrostatic discharge (ESD) stresses on their electrical and switching properties using current-voltage (I-V) and reverse recovery time analyses. The FRDs presented a high breakdown voltage, >450 V, and a low reverse leakage current, < $10^{-9}$ A. From the temperature dependence of thermal activation energy, the reverse leakage current was dominated by thermal generation-recombination and diffusion, respectively, at low and high temperature regions. By virtue of the abrupt junction and the Pt drive-in for the controlling of carrier lifetime, the soft reverse recovery behavior could be obtained along with a well-controlled reverse recovery time of 21.12 ns. The FRDs exhibited excellent ESD robustness with negligible degradations in the I-V and the reverse recovery characteristics up to ${\pm}5.5$ kV of HBM and ${\pm}3.5$ kV of IEC61000-4-2 shocks. Likewise, transmission line pulse (TLP) analysis reveals that the FRDs can handle the maximum peak pulse current, $I_{pp,max}$, up to 30 A in the forward mode and down to - 24 A in the reverse mode. The robust ESD property can improve the long term reliability of various power applications such as automobile and switching mode power supply.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.12
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• pp.1857-1863
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• 2012

The VDS(Vehicle Detection System) collects and transfers information about traffic situations in real time, therefore it makes the traffic management effective. Recently, the VDSs have provided good stability and accuracy in regard to system reliability and functions but they also have showed problems such as raising costs and consuming times when a new system is installed and/or the environmental requirements for the system are set up. The reason of the problems is that up to now the collection of the data and information about the traffic situations has been achieved by the 1:1 information exchange between the traffic control surveillance center and the each traffic field, between equipments and centers, and among data processing equipments and also centers. The communication systems used in the VDS are generally composed of 1 : 1 connection of the lines because the communication protocols are different in the most of the cases mentioned above. Consequently, this makes the number of communication lines become larger and causes the cost for the whole traffic information systems to increase. In this paper, a development of a controller to unify the communication protocols for the VDS is peformed to solve the problems which were mentioned above. Specially, the controller developed in this paper was applied to a radar vehicle detector and tested to show its usefulness. In addition to that, the developed controller was also designed to include functions to transfer the information about weather conditions on the roads.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.896-897
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• 2013

In recent years, logistics tracking Device using GSM & WCDMA to improve logistics efficiency are being extensively researched. The purpose of this paper is to examine the performance development antenna usable cargo container security transport. Antenna developed by study were optimized to match logistics environment apply to GSM & WCDMA dual frequency for monitering system. The measure of antenna have confirmation VSWR is 3:1 measured in return loss -10dB. Reliability of this antenna has been verified about GSM & WCDMA through test-operation between the south korea and Russia.

• Tribology and Lubricants
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• v.31 no.2
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• pp.42-49
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• 2015

Because of the growing need for high-speed transport options such as trains and aircraft, there is increasing demand for technology related to high-speed trains. Among them, braking systems are important in high-speed trains in terms of reliability. Especially, the disk brake system, in use in most high-speed trains, transforms kinetic energy into thermal energy and noise. Therefore, the material properties of both the friction materials and disks are expected to influence the tribological characteristics. In this paper, the tribological characteristics depend on the hardness of the brake disks between the Cu-based sintered metallic friction material and the heat-treated heat-resisting steel disks. A lab-scale dynamometer used to perform braking tests at a variety of braking speeds using dry conditions. The test results revealed that the hardness of the disks affects the friction coefficients, friction stabilities, and wear rates. Thus, the brake system using the heat-resisting steel disk requires proper heat-treatment. These differences are considered to be caused by the change in tribological mechanisms and the generation of an oxide layer on the friction surfaces. The oxide layers on the friction surfaces are confirmed to Fe₂O₃ by x-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectroscopy (SEM-EDS) analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.2
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• pp.143-148
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• 2011

Corrosion at the top of a distillation column is a common problem in refineries and chemical plants. In particular, severe damage has been inflicted in refineries by corrosive materials such as hydrogen sulfide and chlorine. Therefore, the mechanism of the corrosion occurring at the top of a distillation column has been analyzed, and a model for forecasting the corrosion rate has been developed. Four major materials were selected for modeling: $H_2S$, $CO_2$, $H^+$ and $Cl^-$. These were selected by taking into consideration their effect on the corrosion rate. Studies on the transport phenomenon and reaction engineering for this model were carried out, and the reliability of the model was verified on the basis of the data measured at a real refinery.