• 한국치위생학회지
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• 제13권5호
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• pp.713-726
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• 2013

Objectives : The purpose of this study is to develop a job performance assessment tool for dental hygienists. Methods : The development consisted of three steps. The first step was to construct the contents of the assessment tool and a pretest questionnaire. In the second step, validity and reliability tests were done and modified for the pretest questionnaires and an assessment tool was made. The third step was verification of the assessment tool. A total of 678 data from the dental hygienists were analyzed to verify the validity and reliability. The assessment tool consisted of two areas such as job performance and competency/attitude: the job performance area covered four sub-areas including oral health education, preventive dental care, assistance for dental treatment, and administrative management. Results : The number of questions and reliability test result for each sub-area were as follows. Reliability coefficient for oral health education (10 questions) was 0.899, preventive dental care (8 questions) was 0.861, assistance for dental treatment (18 questions) was 0.915, administrative management (8 questions) was 0.919, competency of dental hygienists (11 questions) was 0.947, and attitude of dental hygienists (15 questions) was 0.955. Cronbach ${\alpha}$ coefficient for reliability of total 70 questions of the assessment tool was 0.980. Conclusions : The validity of the assessment tool was verified by three steps and the reliability proved to be significant. Consequently the assessment tool was found to be useful as an objective and valid job performance assessment tool for the dental hygienists.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권4호
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• pp.263-271
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• 2016

Purpose: A slurry pump for flue gas desulfurization system performs a role that discharges the slurry of a plaster shape in a thermal power plant. Since a slurry pump transfers the slurry by the centrifugal force, it has the friction wear in the impeller and liner because of the slurry. Methods: In this study, failure analysis and test evaluation on the slurry pump have been proposed and the process that reliability of the product improves through design improvement has been presented. And failure cause of typical failure case has been investigated and improvement design has been presented. Results: Reliability improvement is established by analysis of the test results of before and after acceleration test. Conclusion: This study can be provided to improve the product reliability through failure analysis of a slurry pump.

• Tribology and Lubricants
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• 제31권2호
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• pp.35-41
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• 2015

A water-pump located in the cooling area of a car circulates cooling water. A particular bearing element, known as a water-pump bearing, installed in the rotating part carries the entire load. The failure of this water-pump bearing has a direct impact on the failure of the automobile engine, and so securing its reliability is crucial. Several researchers have examined the design principles of the water-pump bearing, but there are no reports on the life characteristic of the bearing yet. Herein, we report the construction of test equipment to reproduce the spalling of the roller contact, which is the main failure mode of the chosen water-pump bearing. We chose the radial load as an accelerated stress factor and validated the failure mode by monitoring the surface defects. We conducted the accelerated life test after determining the accelerated stress level through a combination of finite element analysis and a preliminary test. In the life tests, we used an accelerometer to perform failure diagnosis. In the last stage of this study, we present a statistical reliability analysis. Thus, we fully estimated the shape parameter of the water-pump bearing, accelerating level on the load , and the lifetime (MTTF and B₁₀ life) under real use conditions, and finally proposed an interval estimation value considering the uncertainty of the estimated value.

• Physical Therapy Rehabilitation Science
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• 제8권3호
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• pp.146-151
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• 2019

Objective: The purpose of this study was to investigate the test-retest reliability and concurrent validity of the joint angle of the lower extremities during sit-to-stand movements with wearable sensors based on a portable gait analysis system (PGAS), and the results were compared with a analysis system (MAS) to predict the clinical potential of it. Design: Cross-sectional study. Methods: Sixteen persons with stroke (9 males, 7 females) participated in this study. All subjects had the MAS and designed PGS applied simultaneously and eight sensor units of designed PGAS were placed in a position to avoid overlap with the reflexive markers from MAS. The initial position of the subjects was 90º of hip, knee, and ankle joint flexion while sitting on a chair that was armless and backless. The height of the chair was adjusted to each individual. After each trial, the test administrator checked the quality of data from both systems that measured sit-to-stand for test-retest reliability and concurrent validity. Results: As a result, wearable sensor based designed PGAS and MAS demonstrated reasonable test-retest reliability for the assessment of joint angle in the lower extremities during sit-to-stand performance. The intra-class correlation coefficients (ICCs) for wearable sensor based designed PGAS showed an acceptable test-retest reliability, with ICCs ranging from 0.759 to 0.959. In contrast, the MAS showed good to excellent test-retest reliability, with ICCS ranging from 0.811 to 0.950. In concurrent validity, a significant positive relationship was observed between PGAS and MAS for variation of joint angle during sit-to-stand movements (p<0.01). A moderate to high relationship was found in the affected hip (r=0.665), unaffected hip (r=0.767), affected knee (r=0.876), unaffected knee (r=0.886), affected ankle (r=0.943) and unaffected ankle (r=0.823) respectively. Conclusions: The results of this study indicated that wearable sensor based designed PGAS showed acceptable test-retest reliability and concurrent validity in persons with stroke for sit-to-stand movements and wearable sensors based on developed PGAS may be a useful tool for clinical assessment of functional movement.

• 대한기계학회논문집A
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• 제38권12호
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• pp.1379-1385
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• 2014

제품의 수명시험 전에 소요될 시험시간을 대강이라도 예측할 수 있으면 비용을 측정하여 시험을 어떻게 진행할지 판단하는데 도움이 된다. 기계부품의 경우의 신뢰도예측은 시스템의 고장 혹은 열화 메커니즘이 복잡하고 보편적인 데이터베이스가 존재하지 않기 때문에 수행이 난해하다. 본 연구는 유압 액추에이터와 공압 액추에이터에 각각 설치되는 탄성 U 형 씰을 대상으로 수명예측을 NSWC에서 제안하는 고장물리를 고려한 고장률 모형과 현장 데이터베이스를 활용하여 수행하였다. 그 결과들을 검증하기 위해 예측된 수명과 시험된 수명데이터들을 비교하였다. 본 연구는 고장률 모형에 포함된 각종 계수 값들을 결정하는 과정과 씰의 수명에 영향을 주는 인자들의 개별 민감도를 분석하고 그 미비점을 고찰하였다.

• 대한전기학회논문지:전력기술부문A
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• 제52권1호
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• pp.9-16
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• 2003

In this paper, we propose a reliability evaluation method considering the momentary interruptions of power distribution systems. The results of research are concentrated on two parts. One is the analytic and probabilistic reliability evaluation of power distribution system considering the momentary interruptions and the other is the reliability cost evaluation that unifies the cost of sustained and momentary interruptions. This proposed reliability cost evaluation methodology is also divided into the analytic and probabilistic approach and the time sequential Monte Carlo method is used for the probabilistic method. The proposed methods are tested using the modified RBTS (Roy Billinton Test System) form and historical reliability data of KEPCO (Korea Electric Power Corporation) system. Through the case studies, it is verified that the proposed reliability evaluation and its cost/worth assessment methodologies can be applied to the actual reliability studies.

• 한국신뢰성학회지:신뢰성응용연구
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• 제14권1호
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• pp.59-70
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• 2014

The requirements of reliability verification for new products and technology are increasing more and more in accordance with the trend of climate change prevention and GHG reduction technology, functional skills. SCA(Swirl Control Actuator) is the important part of a car intake manifold system. This device generates swirl that is mixing the fuel and air into the engine combustion chamber. This is to improve output for engine and reduce the emission for exhaust. In this article reliability assessment criteria for swirl control actuator for automobiles are established in terms of basic HALT and life time test.

• 한국신뢰성학회지:신뢰성응용연구
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• 제14권4호
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• pp.236-242
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• 2014

Since permanent magnet coupling transfers power by magnetic force without contact, it has little shock, vibration, noise. In case of overload, it protects a pump or a motor which is relatively important by slipping internally. In this study, failure analysis and test evaluation on the permanent magnet coupling have been proposed and the process that reliability of the product improves through design improvement has been presented. And failure cause of typical failure case has been investigated and improvement plan has been presented. Finally, reliability improvement is established by analysis of the test results of before and after acceleration test.

• 공학기술논문지
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• 제6권2호
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• pp.121-124
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• 2013

This paper proposed a new concept of estimating method for LED(light-emitting diode) delamination with high accuracy. Usually, The LED is composed several materials which are LED chips, gold wire, phosphor, epoxy resin, adhesive, reflector and lead frame. These different materials are usually delaminated in a trouble conditions which are huge temperature difference, hot and humid or mechanical shocked. When the components are delaminated, a luminance will be lost, moisture be absorbed easily and a thermal resistance be increased attendantly. As a conventional method to estimate a delamination of LEDs, a solution immersing method is usually used in a field of LED manufacturing companies or researching institutes. This method has an advantage of simplicity but it is only shown that the existence of delamination or not. In this paper, we have proposed an estimating method for LEDs delamination using the polishing and the electron microscope. New proposed method has shown the result of confirming delamination without destruction and enabled quantitative analysis for LED delamination.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.1450-1451
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• 2008

To investigate the reliability of the conductive lines patterned by ink-jet printing, we evaluated the reliability of the ink-jet printed silver (Ag) patterns according to the guide lines built up as assessments methods in the production of conventional rigid printed circuit boards. The assessment methods include the uniformity of line width and space, adhesive strength, dielectric withstand, solder float, thermal shock test and pressure cooker test (PCT). To prepare assesment vehicles, different regular test patterns were created by Ag ink-jet printing on the same polyimide substrate for each of assessment methods.