• 시스템엔지니어링학술지
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• 제11권2호
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• pp.125-135
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• 2015

Various methods have been used for safety and reliability as it becomes more difficult to ensure safety owing to the increasing complexity and scale of systems. This study aims at making it easier and more efficient to discuss risks and countermeasures for completeness, review, and knowledge transfer by improving methods to create fault tree analyses which focus on the GSN [1], which are among the methods used to describe assurance cases. More specifically, the purpose of this study is to incorporate strategy and context, GSN concepts, along with reason, which is a new concept, into FTA; the study focuses on three points. One point is support for the safety designer to draw a mutually exclusive and collectively exhaustive (MECE) FTA. The second is to make it easier to understand diagrams and meanings of FTA compared with the usual methods. The third is to make creating an FTA more efficient and to pass on existing know-how. Eventually, FTA can achieve completeness, review, and knowledge transfer. An introduction is provided in the first section. Next, the methodology covered in this paper is explained in the second section. The third section describes the proposed notation method based on two proposals made in this paper. In the fourth and fifth sections, results and discussion are provided, respectively. Finally, in the sixth section, conclusions are described.

• 한국주조공학회지
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• 제18권3호
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• pp.246-253
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• 1998

Precision metal mold casting process is a casting method manufacturing mechanical elements with high precision, having heavy/light alloys as casting materials and using permanent mold. To improve dimensional accuracy and the final mechanical properties of the castings, the solidification speed and the cooling rate of the casting should be controlled with the optimum mold cooling system, and moreover, to obtain more accurate control of the whole process interfacial heat transfer characteristic at the mold/casting interface must be studied in advance. In the present study, aluminum alloy casting system with metal mold equipped with electrical heating elements and water cooling system was designed and the temperature histories at points inside the metal mold were measured during the casting process. The heat transfer phenomena at the mold/casting interface was characterized by the heat flux between solidifying casting metal and metal mold, and the heat flux history was obtained using inverse heat conduction method. The effect of mold cooling condition upon the heat flux profile was examined, and the analysis shows that the heat flux value has its maximum at the beginning of the process.

• Journal of Advanced Marine Engineering and Technology
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• 제11권1호
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• pp.72-79
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• 1987

When the wall temperature is very high, a stable vapor film covers the heat transfer surface. The vapor film creates a strong thermal resistance when heat is transferred to the liquid though it. This phenomenon, called "film boiling" is very important in the heat treatment of metals, the design of cryogenic heat exchangers, and the emergency cooling of nuclear reactors. In the practical engineering problems of the transient cooling process of a high temperature wall, the wall temperature history, the variation of the heat transfer coefficients, and the wall superheat at the rewetting points, are the main areas of concern. These three areas are influenced in a complex fashion such factors as the initial wall temperature, the physical properties of both the wall and the coolant, the fluid temperature, and the flow state. Therefore many kinds of specialized experiments are necessary in the creation of precise thermal design. The object of this study is to investigate the heat transfer characteristics in the transient cooling process of a high temperature wall. The slow transient cooling experiment was carried out with a copper block of high thermal capacity. The block was 240 mm high and 79 mm O.D.. The coolant flowed throuogh the center of a 10 mm diameter channel in the copper block. In the copper block, three sheathed thermocouples were placed in a line perpendicular to the flow. These thermocouples were used to take measurements of the temperature histories of the copper block.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.764-769
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• 2001

Brake-induced vibrations of a vehicle such as brake judder are determined by the excitation of brake torque variations and by their transfer to the driver's contact points via suspension, body and steering system. The formation of brake torque variation is mainly determined by static and dynamic disk thickness variations. The vibration transfer from the excitation by brake torque variation to the perception by the driver depends on the kinematic and dynamic behaviour of the components in the transfer path. Optimization of the judder performance can be achieved either by minimizing the excitation or by reduction of the judder sensitivity of the vehicle. In this paper, the optimization process of a front rotor is suggested to reduce brake judder considering the cooling performance of the rotor, the judder sensitivity of the vehicle and durability of the rotor.

• 융합보안논문지
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• 제13권4호
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• pp.109-115
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• 2013

인터넷망을 이용한 정보 전달의 대표적인 수단인 이메일 서비스 등을 통한 보안위협이 급증하고 있다. 이러한 보안위협의 공격 경로는 첨부된 문서파일에 악성코드를 삽입하고, 해당 응용프로그램의 취약점을 이용하여 사용자의 시스템을 감염시키게 된다. 따라서 본 연구에서는 파일 전송과정에서 위장악성코드의 감염을 차단하기 위해, 논리적 망 분리인 FTS(File Transfer System)를 이용한 무결성 검증 및 행위기반 탐지 시스템을 제안하고, 기존의 보안기법과의 비교 및 검증하고자 한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권7호
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• pp.3511-3532
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• 2019

Coverage-guided fuzzing is an efficient solution that has been widely used in software testing. By guiding fuzzers through the coverage information, seeds that generate new paths will be retained to continually increase the coverage. However, we observed that most samples follow the same few high-frequency paths. The seeds that exercise a high-frequency path are saved for the subsequent mutation process until the user terminates the test process, which directly affects the efficiency with which the low-frequency paths are tested. In this paper, we propose a fuzzing solution, ER-Fuzz, that truncates the recording of a high-frequency path to influence coverage. It utilizes a deep learning-based classifier to locate the high and low-frequency path transfer points; then, it instruments at the transfer position to promote the probability low-frequency transfer paths while eliminating subsequent variations of the high-frequency path seeds. We implemented a prototype of ER-Fuzz based on the popular fuzzer AFL and evaluated it on several applications. The experimental results show that ER-Fuzz improves the coverage of the original AFL method to different degrees. In terms of the number of crash discoveries, in the best case, ER-Fuzz found 115% more unique crashes than did AFL. In total, seven new bugs were found and new CVEs were assigned.

• Nuclear Engineering and Technology
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• 제54권8호
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• pp.3140-3153
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• 2022

A numerical feasibility study was conducted to investigate the thermal-hydraulic characteristics of a steam generator with corrugated plates for a small modular reactor. Accordingly, a one-dimensional thermal-hydraulic analysis code was developed based on the existing state-of-the-art thermal-hydraulic models and correlations for corrugated plate heat exchangers. Subsequently, the pressure loss, heat transfer, and instability characteristics of the steam generator with corrugated plates were investigated according to the chevron angle and mass flux. Additionally, the characteristics of rectangular and disk-type corrugated plate steam generators with equivalent heat transfer areas were analyzed. The steam generator with disk-type corrugated plates exhibited better performance in terms of pressure loss and heat transfer rate than the rectangular type. In addition, when the mass flux decreased from the onset of boiling points, reverse gradients of the total pressure change were observed in both types. Thus, it was confirmed that Ledinegg instability could occur in the steam generator with corrugated plates. However, it was dependent on the chevron angle, and the optimal chevron angle to minimize instability was 45° under the conditions of the present analysis.

• Wind and Structures
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• 제37권5호
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• pp.383-397
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• 2023

In the Structural Health Monitoring (SHM) system of civil engineering, data missing inevitably occurs during the data acquisition and transmission process, which brings great difficulties to data analysis and poses challenges to structural health monitoring. In this paper, Convolution Neural Network (CNN) is used to recover the nonstationary wind speed data missing randomly at sampling points. Given the technical constraints and financial implications, field monitoring data samples are often insufficient to train a deep learning model for the task at hand. Thus, simulation combined transfer learning strategy is proposed to address issues of overfitting and instability of the deep learning model caused by the paucity of training samples. According to a portion of target data samples, a substantial quantity of simulated data consistent with the characteristics of target data can be obtained by nonstationary wind-field simulation and are subsequently deployed for training an auxiliary CNN model. Afterwards, parameters of the pretrained auxiliary model are transferred to the target model as initial parameters, greatly enhancing training efficiency for the target task. Simulation synergy strategy effectively promotes the accuracy and stability of the target model to a great extent. Finally, the structural dynamic response analysis verifies the efficiency of the simulation synergy strategy.

• 기술혁신학회지
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• 제17권3호
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• pp.490-518
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• 2014

본 연구는 전자부품연구원과 반도체 테스트용 프로브카드 회사간 기술이전 사례를 중심으로 기술이전이 사업화 성과까지 연계되기 위해 필요한 요인들을 분석하였다. 이러한 연구를 통해 실제 현장에서 가장 영향력 있는 기술이전의 성공요인을 살펴보고 정부정책과 기업전략 측면에서 기술이전과 기술사업화 성과를 창출하는 것을 주요 목적으로 한다. 국내외 선행연구 분석, 프레임워크 설정, 사례분석의 과정을 거쳐 기술 수요자, 기술 공급자, 이전 기술, 기술이전 과정 특성의 4가지 측면에서 시사점을 도출하였다. 연구결과 기술 수요자 특성은 신기술 이전획득전략 및 추진의지/보완 자산과 흡수 능력, 기술 공급자 특성은 기술이전 및 사업화 경험/기술이전과 연계한 사업화 지원의지/풍부한 이전 대상 기술군, 이전 기술 특성은 연구개발단계 및 기술분야/기존 기술과의 연계성, 기술이전 과정 특성은 기술이전 전담조직의 지원활동/기술 이전과정의 적극적 참여 등이 성공요인으로 도출되었다.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제6권11호
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• pp.71-78
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• 2000

This study indicates bed-transfer as the significant behavior of a ward and points out architecture that cannot meet the patient's need. It is examined that inpatient's behavior depends on visibility, psychological security, privacy & communication, control, support and this study applies them to analyze the selected cases. This study also emphasizes the supportive role of hospital architecture so that the function of a ward as a healing environment may be maintained.