• IEMEK Journal of Embedded Systems and Applications
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• v.14 no.4
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• pp.165-175
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• 2019

Networks use relatively slow heartbeat mechanisms, usually in routing protocols, to detect failures when there is no hardware signaling to help out. The time to detect failures available in the existing protocols is no better than a second, which is far too long for some applications and represents a great deal of lost data at 10 Gigabit rates. We compare the convergence time of routing protocol applying Bidirectional Forwarding Detection (BFD) protocol in wired mesh network topology. This paper suggests the combinations of protocols improving fail-over performance. Through the performance analysis, we contribute to reduce convergence time when system is fail-over.

• Journal of Auto-vehicle Safety Association
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• v.12 no.1
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• pp.15-25
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• 2020

This paper presents a longitudinal control algorithm for ensuring takeover time of autonomous vehicle using V2V communication. In the autonomous driving of more than level 3, autonomous systems should control the vehicles by itself partially. However if the driver's intervention is required for functional safety, the driver should take over the control reasonably. Autonomous driving system has to be designed so that drivers can take over the control from autonomous vehicle reasonably for driving safety. In this study, control algorithm considering takeover time has been developed based on computation method of takeover time. Takeover time is analysed by conditions of longitudinal velocity of preceding vehicle in time-velocity plane. In addition, desired clearance is derived based on takeover time. The performance evaluation of the proposed algorithm in this study was conducted using 3D vehicle model with actual driving data in Matlab/Simulink environment. The results of the performance evaluation show that the longitudinal control algorithm can control while securing takeover time reasonably.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.12
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• pp.4909-4926
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• 2020

Cyberattacks penetrate the server and perform various malicious acts such as stealing confidential information, destroying systems, and exposing personal information. To achieve this, attackers perform various malicious actions by infecting endpoints and accessing the internal network. However, the current countermeasures are only anti-viruses that operate in a signature or pattern manner, allowing initial unknown attacks. Endpoint Detection and Response (EDR) technology is focused on providing visibility, and strong countermeasures are lacking. If you fail to respond to the initial attack, it is difficult to respond additionally because malicious behavior like Advanced Persistent Threat (APT) attack does not occur immediately, but occurs over a long period of time. In this paper, we propose a technique that detects an unknown attack using an event log without prior knowledge, although the initial response failed with anti-virus. The proposed technology uses a combination of AutoEncoder and 1D CNN (1-Dimention Convolutional Neural Network) based on semi-supervised learning. The experiment trained a dataset collected over a month in a real-world commercial endpoint environment, and tested the data collected over the next month. As a result of the experiment, 37 unknown attacks were detected in the event log collected for one month in the actual commercial endpoint environment, and 26 of them were verified as malicious through VirusTotal (VT). In the future, it is expected that the proposed model will be applied to EDR technology to form a secure endpoint environment and reduce time and labor costs to effectively detect unknown attacks.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.12
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• pp.54-59
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• 2011

LED lightings typically do not fail catastrophically during use. However, over time the light output will gradually depreciate. Even if there are same LED lighting, they are so different at all. because of dissimilar the use and environment of each LED lighting. In this paper, we make a description of reliability analysis procedures for the degradation data using collected field data. Reliability analysis procedures are consisted of estimating degradation models and failure time, verification of distribution and parameters of the distribution, and reliability measures estimation. At some point in time, the light emitted from an LED lightings depreciates to a level where it is no longer considered adequate for a specific application.

• Proceedings of the KIEE Conference
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• 1997.07a
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• pp.346-348
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• 1997

This paper presents microprocessor-based real-time speed and position detection by inductive radio loop in new transportation system, such as magnetically levitated train system, rubber tyred train, and linear-motor car. The constant elapsed time method is used in this study for high accurate detection over a wide speed range. And for reliability and safety of the system, it is duplicated and data-bus level comparison is performed by fail-safe comparator.

• Journal of Applied Reliability
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• v.15 no.4
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• pp.233-240
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• 2015

We analyse reliability of multi-state UH-60 helicopter hydraulic pump system with a multi-functional standby component using Markov analysis method. The system consists of seven components: 2 main pumps, 1 standby pump, 2 primary servos, and 2 tail rotor servos. The standby pump can take over when one more than components fail. Therefore the standby pump is multi-functional standby component. The system has four states: good, deteriorated, dangerous, and failed. The components have 2 states: working and failed. We assume the system is unrepairable when the components fail. We estimate failure distributions and rates using collected failure time data in field. And we classify multi-state of the system according to emergency procedure of UH-60A student handout. We obtain the reliabilities of multi-state system using Visual Basic program because the differential equations is extremely complicated and tedious to solve.

• Geomechanics and Engineering
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• v.11 no.4
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• pp.531-552
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• 2016

The greenschist in the Jinping II Hydropower Station in southwest China exhibits continuous creep behaviour because of the geological conditions in the region. This phenomenon illustrates the time-dependent deformation and progressive damage that occurs after excavation. In this study, the responses of greenschist to stress over time were determined in a series of laboratory tests on samples collected from the access tunnel walls at the construction site. The results showed that the greenschist presented time-dependent behaviour under long-term loading. The samples generally experienced two stages: transient creep and steady creep, but no accelerating creep. The periods of transient creep and steady creep increased with increasing stress levels. The long-term strength of the greenschist was identified based on the variation of creep strain and creep rate. The ratio of long-term strength to conventional strength was around 80% and did not vary much with confining pressures. A quantitative method for predicting the failure period of greenschist, based on analysis of the stress-strain curve, is presented and implemented. At a confining pressure of 40 MPa, greenschist was predicted to fail in 5000 days under a stress of 290 MPa and to fail in 85 days under the stress of 320 MPa, indicating that the long-term strength identified by the creep rate and creep strain is a reliable estimate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1162-1169
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• 2012

One of the important operational requirements for mission critical Ethernet networked system is having the fault tolerant capability. Such capability can be obtained by equipping multiport Network Interface Card (NIC) in each node in the system. Conventional NIC uses two or more Media Access Controls (MACs) and a co-processor for the MAC switching whenever an active port fails. Since firmware is needed for the co-processor, longer fail-over switching and degraded throughput can be generally expected. Furthermore the system upgrading requiring the firmware revision in each tactical node demands high cost. In this paper we propose a novel single MAC based NIC that does not use a co-processor, but just use general discrete building blocks such as MAC chip and switching chip, which results in better performances than conventional method. Experimental results validate our scheme.

• The Journal of Industrial Distribution & Business
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• v.12 no.1
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• pp.7-13
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• 2021

Purpose: Unemployment in its general form is a result stemming from the decisions of workers to search for a new and better paying job. In this study, the view that unemployed workers were not simply desiring any job, but one that would maximize their expected future outcome, was examined. Research design, data, and methodology: In order for collection of data and analysis, the panel dates of individual applications for job openings on job search websites were utilized to examine search effort and period for individuals. Results: It was found that the number of applications sent by a job seeker declined over their period of job searching, and that job seekers over a long duration of time tend to send relatively more applications per week throughout their entire search period. The latter finding contradicts the implications of the standard labor search effort models. Conclusions: It can be observed that these job search models fail to capture several key elements in search efforts, and that the search time for an offer is not entirely predetermined by the labor market conditions and socio-economic (individual) characteristics of the searcher. It can be shortened as he or she intensifies their job search efforts.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.79-85
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• 2016

A concrete silo plays an important role in subsurface low- and intermediate-level waste facilities (LILW) by limiting the release of radionuclides from the silo geosphere. However, due to several physical and chemical processes the performance of the concrete structure decreases over time and consequently the concrete loses its effectiveness as a barrier against groundwater inflow and the release of radionuclides. Although a number of processes are responsible for degradation of the silo concrete, it is determined that the main cause is corrosion of the reinforcing steel. Therefore, the time it takes for the silo concrete to fail is calculated based on two factors: the initiation time of corrosion, defined as the time it takes for chloride ions to penetrate through the concrete cover, and the propagation time of corrosion. This paper aims to estimate the time taken for concrete to fail in a LILW disposal facility. Based on the United States Department of Energy (DOE) approach, which indicates that concrete fails completely once 50% of the volume of the reinforcing steel corrodes, the corrosion propagation time is calculated to be 640 years, which is the time it takes for corrosion to penetrate 0.640 cm into the reinforcing steel. In addition to the corrosion propagation time, a diffusion equation is used to calculate the initiation time of corrosion, yielding a time of 1284 years, which post-dates the closure time of the LILW disposal facility if we also consider the 640 years of corrosion propagation. The electrochemical conditions of the passive rebar surface were modified using an acceleration method. This is a useful approach because it can reduce the test time significantly by accelerating the transport of chlorides. Using instrumental analysis, the physicochemical properties of corrosion products were determined, thereby confirming that corrosion occurred, although we did not observe significant cracks in, or expansion of, the concrete. These results are consistent with those of Smartet al., 2006 who reported that corrosion products are easily compressed, meaning that cracks cannot be discerned by eye. Therefore, it is worth noting that rebar corrosion does not strongly influence the hydraulic conductivity of the concrete.