• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.11
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• pp.4573-4594
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• 2020

Announcement protocol in Internet of Vehicles (IoV) is an intelligent application to enhance public safety, alleviate traffic jams and improve transportation quality. It requires communication between vehicles, roadside units and pedestrian to disseminate safety-related messages. However, as vehicles connected to internet, it makes them accessible globally to a potential adversary. Safety-related application requires a message to be reliable, however it may intrude the privacy of a vehicle. Contrarily, if some misbehaviour emerges, the malicious vehicles must be able to traceable and revoke from the network. This is a contradiction between privacy and accountability since the privacy of a user should be preserved. For a secure communication among intelligent entities, we propose a novel announcement protocol in IoV using group signature. To the best of our knowledge, our work is the first comprehensive construction of an announcement protocol in IoV that deploys group signature. We show that our protocol efficiently solves these conflicting security requirements of message reliability, privacy and accountability using 5G communication channel. The performance analysis and simulation results signify our work achieves performance efficiency in IoV communication.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.9
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• pp.3104-3123
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• 2022

The development of Vehicular Ad hoc Network (VANET) has greatly improved the efficiency and safety of social transportation, and the routing strategy for VANET has also received high attention from both academia and industry. However, studies on dynamic matching of routing policies with the message types of VANET are in short supply, which affects the operational efficiency and security of VANET to a certain extent. This paper studies the message types in VANET and fully considers the urgency and reliability requirements of message forwarding under various types. Based on the diversified types of messages to be transmitted, and taking the diversified message forwarding strategies suitable for VANET scenarios as behavioral candidates, an adaptive routing method for the VANET message types based on reinforcement learning (RL) is proposed. The key parameters of the method, such as state, action and reward, are reasonably designed. Simulation and analysis show that the proposed method could converge quickly, and the comprehensive performance of the proposed method is obviously better than the comparison methods in terms of timeliness and reliability.

• Progress in Superconductivity and Cryogenics
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• v.11 no.3
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• pp.55-59
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• 2009

In attempts to closely study the effect of high efficiency, friendly environment HTS(High Temperature Superconducting) cable and SFCL(Superconducting Fault Current Limiters) on power system, several projects were carried out around the world. Promising results have been achieved in terms of cable capacity and reliability. commercial HTS cable and SFCL, however, must not only be only be feasible, but meet practical requirements as well. To facilitate the transition of HTS cable technology from the Lab. to the Real Grid, a New project for applying 22.9kV HTS cables and SFCL to the commercial Power Grid supported by Government has just started in KEPCO. Target of this project is to operate two 22.9kV, 50MVA, 150MVA HTS cables and two 22.9kV 630A, 3000A SFCL in a KEPCO Grid in order to demonstrate its reliability and stable operation. This paper will present the technology for selecting appropriate site and its plan for installation & operating of 22.9kV HTS cables & SFCL in KEPCO Grid.

• Composites Research
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• v.20 no.4
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• pp.25-30
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• 2007

The advanced fiber-reinforced laminated composites are widely used in a variety of engineering applications such as aerospace, marine, mechanical and civil engineering for weight savings because of their high specific strength and stiffness. The material properties of ply is known to have larger variations than that of conventional materials and very sensitive to the loading direction. Therefore, it is important to consider the variations on designing the laminated composite. This paper demonstrates the importance of considering uncertainties through examining the effect of material properties variations on various design requirements such as tip deflection, natural frequency and buckling stress using COMSOL-MATLAB interface.

• Journal of the Korean Society for Railway
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• v.20 no.4
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• pp.458-465
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• 2017

The railway signaling system, which controls the course of trains and the distance between trains, is a safety critical system of the railway system because derailment or collision of trains can occur if unsafe failure is generated by any fault. The international standards of reliability, availability, maintainability, and safety of railway applications require that the safety of functions be guaranteed in safety critical systems; system reliability and safety are quantitatively estimated and demonstrated by the failure rates of devices. The development of technology has accelerated the development of railway signaling systems. Existing devices, which have already been verified as to their safety, are applied with special user requirements to reflect the new operation scenario. It is found that the reliability and safety of the devices are different depending on individual application. Therefore, the reliability of the railway signaling system must be considered while complying with the international standards; this requires that the initial failure rate be estimated and demonstrated using fault data gathered over several years. This paper shows a method for demonstrating the initial estimated failure rate and suggests a fault data collection method and an overall process that is based on probability.

• Journal of the Korean Society of Safety
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• v.32 no.4
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• pp.7-15
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• 2017

International standards such as IEC-61508 and IEC-61511 require Safety Integrity Levels (SILs) for Safety Instrumented Functions (SIFs) in process industries. SIL verification is one of the methods for process safety description. Results of the SIL verification in some cases indicated that several Safety Instrumented Functions (SIFs) do not satisfy the required SIL. This results in some problems in terms of cost and risks to the industries. This study has been performed to improve the reliability of a safety instrumented function (SIF) installed in hydrodesulfurization reactor heater using Partial Stroke Testing (PST). Emergency shutdown system was chosen as an SIF in this study. SIL verification has been performed for cases chosen through the layer of protection analysis method. The probability of failure on demands (PFDs) for SIFs in fault tree analysis was $4.82{\times}10^{-3}$. As a result, the SIFs were unsuitable for the needed RRF, although they were capable of satisfying their target SIL 2. So, different PST intervals from 1 to 4 years were applied to the SIFs. It was found that the PFD of SIFs was $2.13{\times}10^{-3}$ and the RRF was 469 at the PST interval of one year, and this satisfies the RRF requirements in this case. It was also found that shorter interval of PST caused higher reliability of the SIF.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.947-952
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• 2010

Components such as pressure vessel, hydraulic hose assembly, accumulator, hydraulic cylinder, hydraulic valve, pipe, etc., are tested under the impulse-pressure conditions prescribed in ISO and SAE standards. The impulse pressure test machine needs to have a high pressure, a precise control system and a long life. It should satisfy the requirements for fabrication of the impulse tester to generate ultra high pressure in the hydraulic system. In the impulse tester, a servo-valve control system is adopted; although the control application is convenient, it is expensive owing to the cost of developing the system. The type of the control system determines the pressure wave, which affects the components that are tested. In this study, the manufacturing process and the intensifier system design related to the flow, pressure, and the increasing rate of pressure are investigated. The results indicate the ultra high pressure waves in the system.

• Journal of KIISE:Software and Applications
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• v.36 no.1
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• pp.1-9
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• 2009

In heterogeneous and distributed computing environments, with an increasing number of Web services providing similar functionalities, the reliability of Web services is a critical decision factor. To fulfill the open business model such as cooperation among enterprises, several Web services can be composed into the upper level business transaction. In Web services composition, the reliability of services is more and more critical. Though each unit Web service can be reliable, the reliability of the composed service is not guaranteed. Thus a way to efficiently assess and select composed Web services is needed. In this paper, we define new metrics for measuring the trust value of Web services, and propose an evaluation method to predict the trustworthy degree of the composed services based on the metrics. We also define a conceptual framework to support optimal Web services selection based on the proposed trust evaluation method. By selecting using the quantitative measurement rather than intuitive selection of the service user, it allows the service users to select the high reliable service meeting their quality requirements well.

• Journal of the Korea Safety Management & Science
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• v.22 no.1
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• pp.33-44
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• 2020

This study analyzed how the installation of a pressure gauge in the indoor fire hydrant of an apartment building affected identifying pressurized water in the pipe, making it easier to conduct internal inspection on the fire suppression system, and ensuring reliability of fire suppression. The following are the study's results: First, identifying pressurized water in the indoor firefighting pipe had a positive effect on the installation of a pressure gauge in the indoor fire hydrant. This implies that a higher level of identification of pressurized water in the indoor firefighting pipe had a positive impact on improving the installation and use of a pressure gauge in the indoor fire hydrant. Second, making it easier for the fire safety officer to inspect the fire suppression system had a positive effect on the installation of a pressure gauge in the indoor fire hydrant. This suggests that if it becomes easier for the apartment building's stakeholder to conduct internal inspection or the firefighting facility manager to carry out inspection on the fire suppression system, it would have a positive effect on the installation of a pressure gauge in the indoor fire hydrant. Finally, ensuring reliability in fire suppression had a positive effect on the installation of a pressure gauge in the indoor fire hydrant. This implies that if it becomes easier to identify pressurized water in the indoor firefighting pipe, for the fire safety officer to conduct internal inspection, or for the firefighting facility manager to carry out inspection in accordance with the fire suppression system's internal inspection requirements, it would increase reliability in fire suppression, making it more necessary to install a pressure gauge in the indoor fire hydrant.

• Journal of Digital Convergence
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• v.15 no.2
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• pp.199-206
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• 2017

Embedded control system is widely spreaded and used in various fields including military defence, aviation, medical, etc. due to extended use of smart phones, connected car, IoT. Increasing examples are introduced where embedded control system that perform their unique role such as smart phone and network system organically configure to create new system. According to this trend, organic interface and reliability of each embedded control system are becoming important evaluation factors. The purpose of this paper is to develop quality evaluation criteria method for automobile embedded system, among the fields that use embedded control systems. In order to satisfy high quality level requirements of automobile embedded control system, we surveyed latest trend of automobile embedded control system, analyzed structure and application technology of embedded control system, to establish quality evaluation criteria and method for automobile embedded control system by referring international standard for software (ISO/IEC 9126), and international standard for electric & electronic products (ISO 26262).