• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.18 no.1
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• pp.91-102
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• 2019

Autonomous vehicles can be exposed to severe danger when failure occurs in any of its components. For this reason many countries are making efforts on the legislative issue how to objectively evaluate failure safety of an autonomous vehicle when such a vehicle is commercially available to a customer in the near future. In level-3 automation, a driver must take over the control of his vehicle when failure occurs, and the driver's controllability must be secured for escape from the imminent danger. In this paper, quantitative methods have been developed for evaluating failure safety of the level-3 autonomous vehicle, and they were validated by simulation. And also, we confirmed that the proposed evaluation method can quantitatively evaluate the failure safety.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.4
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• pp.311-320
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• 2021

A study is performed for the real time fault diagnosis during operation and health estimation relating to performance deterioration in a turbojet engine used for an unmanned air vehicle. For this study the real time dynamic model is derived from the transient thermodynamic gas path analysis. For real fault conditions which are manipulated for the simulation, the detection techniques are applied such as Kalman filter and probabilistic decision-making approach based on statistical hypothesis test. Thereby the effectiveness is verified by showing good fault detection and isolation performances. For the health estimation with measurement parameters, it shows using an assumed performance degradation that the method by adaptive Kalman filter is feasible in practice for a condition based diagnosis and maintenance.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.767-770
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• 2009

In this paper, I studied the "Establishment of Fault Tolerant System" as well as the sensor and cylinder that are general components being used in automation equipments. I design a system that when the sensor breaks down on free flow conveyor, it will be converted to virtual sensor system mode by simulation, also I design IPC(Internal Pressure Cylinder), a basis of various applicable fault tolerant system by analyzing the changing of analog data according to the load of operation. With IPC and the increasing ability of developer, the Fault Tolerant System will be widely applied in the increasment of service time of cylinder, grease pouring time expection, fault recognition of cylinder and etc.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1340-1343
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• 2009

본 논문에서는 센서 노드의 고장에도 신뢰성있는 데이터 전송을 위해 위치 기반 k-독립경로 라우팅 알고리즘을 제안한다. 제안 라우팅 알고리즘은 센서 노드의 랜덤 고장률을 고려하여 독립경로의 수(k)를 결정하고, 구역고장으로 인한 데이터 전달률의 저하를 최소화하기 위해 노드의 위치를 바탕으로 k-독립경로를 지리적으로 분산하여 생성한다. 데이터 변동률을 이용하여 중요이벤트의 발생유무를 판단하고, 중요이벤트 발생시에는 k-독립경로를 통해 메시지를 전송함으로써 데이터 전달률을 높이고, 보통 이벤트일 때는 단일경로로 메시지를 전송함으로써 에너지 소모를 줄인다. 성능평가를 통해 제안하는 위치기반의 k-독립경올 라우팅 알고리즘은 에너지 효율이 높고, 중요이벤트의 데이터 전달률이 높음을 알 수 있었다. 특히, 구역 고장에 대해 다른 라우팅 알고리즘에 비해 훨씬 높은 견고함을 보였다.

• Journal of Korean Society of Steel Construction
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• v.28 no.2
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• pp.121-128
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• 2016

In order to suggest a reasonable design for the circular concrete filled tube steel column-foundation connection applying high-tension bolts, Overall structural behavior and characteristics according to various variables of column-foundation connection are numerically analyzed using a commercial FE analysis program, ABAQUS. To that goal, finite element analysis is conducted on the basis of the previous study replacing anchor bolts to high-tension bolts, and the analytical results are validated by comparison with experimental results. Also, the various variables(embedded depth and grade of anchor, and height and thickness of rib) involved in behavior of the column-foundation connection are selected through analyzing the current design criteria, and the characteristics of the column-foundation connection are compared and analyzed according to the various variables. In case of the anchor bolts, Applying the high-tension bolts is more advantage and securing the embedded depth beyond 0.5D is recommendable. In case of the rib, a minimum of 0.5D for rib's height and $0.4t_b$ for rib's thickness should be secured to develop the structural performance.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.6
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• pp.566-572
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• 2016

Software Reliability implemented in software development is one of the most important issues. In finite failure NHPP software reliability models for software failure analysis, the hazard function that means a failure rate may have constant independently for failure time, non-increasing or non-decreasing pattern. In this study, software development cost analysis considering the variable shape parameter of Erlang distribution as the failure life distribution in the software product testing process was studied. The software failure model was applied finite failure Non-Homogeneous Poisson Procedure and the parameters approximation using maximum likelihood estimation was accompanied. Thus, this paper was presented comparative analysis by applying a software failure time data to the software, considering the shape parameter of Erlang distribution for development cost model analysis. When compared to the cost curve in accordance with the shape parameter, the model of smaller shape can be seen that the optimal software release time delay and more cost. Through this study, it is thought that it can serve as a preliminary information which can basically help the software developers to search for development cost according to software shape parameters.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.78-84
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• 2017

Consistent efforts have been made to reduce the weight of automotive parts by using lightweight materials. This has resulted in the replacement of conventional steels in car body structures with high-strength steels, and the current usage rate has reached 50%. This study examines the structural stiffness and energy absorption capability of bumper beams made of high-strength steels. New types of bumper beam cross sections are proposed.The structural stiffness and maximum bending force were computed via finite element analysis as about 25tons and 7.5tons/mm, and there were no significant differences among the proposedcross sections. Dynamic analysis was also carried out to investigate the energy absorption capabilities of the bumper beams, and the effects of materials and thickness reduction were analyzed. High-strength steel can be used to achieve weight reduction with comparable structural performance to conventional bumper beams.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.432-436
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• 2016

The cooler, which is the main part in a Thermal Observation Device (TOD), makes the TOD function by reducing the temperature. As the cooler is imported, overseas enterprises presented 20,000 hours as the operation time and the military have used the cooler as presented. However, failures have occurred occasionally after mass production stage. Therefore, we need to analyze the MTBF of the TOD cooler. So, military and defense industry companies collected the failure data of the TOD cooler. We analyze the MTBF of the TOD cooler using survival probability function and failure data. We find the optimal distribution by applying parametric method and estimate parameters. We determine that the Log-logistic distribution is the most appropriate for this data. Also, we analyze the reliability per hour of the TOD cooler. The result of MTBF of the TOD cooler was higher than that of presented by oversee enterprises.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1351-1358
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• 2011

To approximate the threshold of the fault detection and diagnosis (FDD) system, validation of the measurements is mandatory. Naturally, the system shows uncertainties due to measuring sensors - mostly thermocouples or RTDs - and due to repeatability. The uncertainty of a thermocouple comes from natural variation or a drift of the thermocouple measurement. Considering the natural variation behaves like zero-mean white noise, its natural variation can be characterized closely by the steady-state standard deviation. However, residuals between measurements and no-fault references in FDD systems show a statistical distribution with various uncertainties. In this paper, steady-state variations of measurement residuals were investigated by utilizing built-in temperature sensors in a heat pump for the model development and the final application.

• Journal of Satellite, Information and Communications
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• v.9 no.4
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• pp.97-103
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• 2014

In order to verify normal operation of satellite OBC(On Board Computer), it is essential that processor monitoring and debugging. So we are using the GRMON of Aeroflex Gaisler. It provides a lot of features for debugging of LEON processor but we can't use that features on the NGSCB(Next Generation Spacecraft Computer Board) except a few things. So the cost-effectiveness is very low. And for hardware fault injection, we are using a method of modify satellite flight software, because we can't modify GRMON. This method can not guarantee normal operation of the satellite flight software. So in this paper we were developed the processor monitoring and fault injection tool for NGSCB.