• 자동차안전학회지
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• 제12권2호
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• pp.47-55
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• 2020

In this case study, the brake line failure of air over hydraulic(AOH) brake system is described. AOH brake system is applied to commercial vehicles between 5 to 8 tons. It consists of a hydraulic system using compressed air and operates the air master to form hydraulic pressure to transfer braking power to the wheels. When the brake lines of the system applied to vehicles with high load capacity are damaged, the braking force of one shaft is lost, and the braking distance increases rapidly, leading to a big accident. Failure of the brake line occurs due to various causes such as road surface fragmentation, corrosion of the line, and aged deterioration of air brake hose. The braking force could be decreased even when a very small break in the form of a pin-hole occurs. However, it is difficult to find a part where the thickness of the line is thin due to stone pecking or corrosion generated in the pin-hole formed on the brake line located under the lower part of the vehicle by the sensory evaluation or the conventional braking force test. Accordingly, it is necessary to analyze the condition and cause of the failure of the brake line more precisely when the accident investigation of the heavy vehicles, and also to examine the necessity of the advanced test for the aged brake line.

• Nuclear Engineering and Technology
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• 제41권3호
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• pp.287-294
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• 2009

Due to thermal hydraulics phenomena, such as thermal stratification, various events occur to the parts of a nuclear power plant during their lifetimes: e.g. cracked and dislocated pipes and thermally fatigued, bent, and damaged supports. Due to the operational characteristics of the parts of the steam generator feedwater inlet horizontal pipe, thermal stratification takes place particularly frequently. However, the thermal stress due to thermal stratification at the steam generator feedwater inlet horizontal pipe was not reflected in the design stage of old plants(Kori Unit No.1, 2, 3 and 4, Yeonggwang Unit No. 1 and 2, and Uljin Unit No. 1 and 2; referred to as old-style power plants hereinafter). Accordingly, a verification experiment was performed for thermal stratification in the horizontal inlet nozzle steam generator of old-style plants. If thermal stratification occurred in the horizontal pipe of an old-style power plant, numerical analysis of the temperature distribution of the pipes and fluids was conducted. The temperature distributions were compared at the curved part of the pipe and the horizontal pipe before and after the installation of the improved thermal sleeves designed to alleviate thermal stress due to thermal stratification. The thermal stress reduction measure was proven effective at the steam generator inlet horizontal pipe and the curved part of the pipe.

• 복식문화연구
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• 제10권6호
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• pp.718-734
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• 2002

The purpose of this study is to provide basic data f3r improvement in Working Uniform in both scientific and efficient ways. The study were enforced by questionnaire and personal interview. The subject of the survey were the workers of 264 in mechanic industry in Seoul. The results obtained from the researches by methods above are as follows. 1. In general, Working Uniform could be classified types of two. One is loose-fitting one-piece garment covering the body and legs, the other is two-piece garment. The latter is a jacket with either sports collar or soutein collar, fastened with either buttons or a zipper and its sleeve is finished by cuffs and tapes. Regarding to color. inkblue, dark navy, khaky, dark beige are favourable ones. 2. In regard to the necessity of uniform that workers suppose, most of them were aware of it and agreed wearing uniform could play an important part. The reason why are on the basis of safety-first and work efficiency and also to protect a body from harmful or toxic dirt specially in machinery workplace. 3. The purpose of wearing an uniform according to statistics of population make some difference in age, gender. categories of industry, and the scale of factory. 4. In regard to care of uniform, front hem, edge of sleeve in a jacket, and knee, hip part in pants were most vulnerable spots for dirt. The parts damaged easily are edge of sleeve in a jacket and a zipper in pants. On the average, laundry have been done by water and was once a week frequency.

• International Journal of Concrete Structures and Materials
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• 제2권2호
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• pp.123-136
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• 2008

A new plastic-damage constitutive model applicable to lightweight concrete (LWC) and normal weight concrete (NWC) is proposed in this paper based on both continuum damage mechanics and plasticity theories. Two damage variables are used to represent tensile and compressive damage independently. The effective stress is computed in the Drucker-Prager multi-surface plasticity framework. The stress is then computed by multiplication of the damaged part and the effective part. The proposed model is coded as a user material subroutine and incorporated in a finite element analysis software. The constitutive integration algorithm is implemented by adopting the operator split involving elastic predictor, plastic corrector and damage corrector. The numerical study shows that the algorithm is efficient and robust in the finite element analysis. Experimental investigation is conducted to verify the proposed model involving both static and dynamic tests. The very good agreement between the numerical results and experimental results demonstrates the capability of the proposed model to capture the behaviors of LWC and NWC structures for static and impact loading.

• 한국통신학회논문지
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• 제17권1호
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• pp.47-57
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• 1992

전동기 회전시 발생되는 소음이 전동기 구조상의 소손부분 및 정도에 따라 서로 다른 소음의 특징을 갖는다는 점을 고려하여 신경회로망을 이용한 시그널(소음)인식 시스템으로써 전동기의 고장부분 탐지에 적용하였다. 적용된 신경회로망은 역전파(back-propagation)알고리즘을 써서 학습하였고 2개의 은역층을 갖는 4단 신경회로망으로 구성 되었다. 실혐 결과 전동기의 구조와 출력이 거의 일치하는 경우에는 고정 부분에 대한 항상 바른 판정을 내릴 수 있었으나 출력은 유사하더라도 전동기의 구조가 상이한 경우나 전동기 제작회사가 다른 경우에는 부정확한 판정으로 나타난다.

• Structural Engineering and Mechanics
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• 제53권2호
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• pp.325-336
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• 2015

This paper presents a study based on the damage due to the fatigue life of thrust ball bearings using vibratory analysis. The main contribution of this work lies in establishing a relation between modal damping and the rolling contact fatigue damage of the thrust ball bearing. Time domain signals and frequency spectra are extracted from both static and dynamic experiments. The first part of this research consists in measuring the damping of damaged thrust ball bearings using impact hammer characterization tests. In a second part, indented components representing spalled bearings are studied to determine the evolution of damping values in real-time vibration spectra using the random decrement method. Dynamic results, in good agreement with static tests, show that damping varies depending on the component's damage state. Therefore, the method detailed in this work will offer a possible technique to estimate the thrust ball bearing fatigue damage variation in presence of spalling.

• 한국자동차공학회논문집
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• 제14권6호
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• pp.95-103
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• 2006

Wheel treads of E.M.U. are usually under a heavy thermal load by brake frictional heat between wheel and brake shoe and damaged by repeated thermal and mechanical loads. To examine the cause of wheel tread damage of E.M.U.'s in service running, a systematic approach has been used. This study is composed of three parts. Frictional heat analysis was conducted in the first part by finite element method. Two kinds of brake shoes in service were considered. In the second part, experimental study was carried out on a brake dynamometer. Temperatures were measured for the two brake shoes. And experimental study in service running E.M.U.'s was performed. Wheel and brake shoe temperatures were measured by using thermocouples and temperature indicating strips. Finally metallurgical characteristics were examined by a SEM/EDS and the cause of the wheel damage was analyzed. It seems that aggregated ferrous component is a main cause of the wheel tread damage.

• Journal of Korean Dental Science
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• 제2권2호
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• pp.24-30
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• 2009

Two component orthodontic C-implants have been introduced as intermaxillary fixation (IMF) screws in cases of periodontal problems with bone loss, severely damaged teeth, or short roots. This retrospective research sought to investigate the complications and risk factors associated with the failure of two-part C-implants for IMF cases and to show the possible indications compared to one-component mini-implants. The study sample consisted of 46 randomly selected patients who had a total of 203 implants. Pearson chi-square tests of independence were used to test for associations among categorical variables. At least 19 of the total 203 implants failed (9.3%). There was no significant difference in implant failure due to gender, oral hygiene, and placement, although a significant difference due to soft tissue characteristics and root contact was observed. The two-component design of the mini-implant is reliable for difficult IMF cases. Note, however, that the factors influencing implant failure were found to be age, root damage, and condition of soft tissues.

• 전자공학회논문지CI
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• 제47권4호
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• pp.88-95
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• 2010

IT 기술이 발전하면서 반드시 유지해야하는 중요한 데이터들 또한 스토리지에 저장되기 시작했다. 이러한 현상은 저장된 데이터를 보호하기 위한 백업 작업의 중요성을 증가시켰으며 데이터의 양이 증가하면서 백업 작업의 수행 시간 또한 중요한 문제로 대두되었다. 스냅샷은 데이터 일관성을 유지하기 위한 서비스 중단 시간을 최소화하면서 데이터 백업을 수행할 수 있는 방식 중 하나이다. 본 논문에서는 디스크 기반 파일 시스템 스냅샷과 네트워크 기반 파일 시스템의 스냅샷에 대해서 연구한다. 디스크 기반 파일 시스템 스냅샷 연구에서는 Ext2, Ext3, XFS와 같이 스냅샷 기능을 제공하지 않는 리눅스 파일 시스템에서 사용 가능한 스냅샷 라이브러리인 PSnap을 제안하다. 또한 네트워크 기반 파일 시스템 스냅샷 연구에서는 ETRI에서 개발한 대용량 분산 파일 시스템인 GloryFS에 적용할 수 있는 GlorySnap를 제안한다.

• 전자공학회논문지 IE
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• 제44권1호
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• pp.15-19
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• 2007

본 연구는 전송 오차의 이미지 복원에 관한 방법으로 정지영상 또는 내부프레임 정정을 위한 모서리 방향 보간법에 기초한 오차 복원 기술의 개선을 목표로 한다. 여기서 제안된 방법은 블록의 모서리 방향 검출 방법은 스웨터의 손상된 부분을 남아 있는 부분과 맞추어가는 모서리 방향을 이용하는 것에 근거한다 처리 후 데이터 정보에 남은 에러 픽셀을 마지막 단계로 비선형 미디안 필터를 사용하여 보간 하였다. 실험 결과는 제안된 방법의 높은 회복 성향과 낮은 계산 시간은 실시간 영상 처리의 실현 가능성을 나타낸다.