Earticle

본 연구에서는 Sn-3.0Ag-0.5Cu 솔더를 이용한 자동차 전장부품의 다양한 chip을 선정하여, 장기신뢰성 평가 시험 방법 중 열충격 시험 전후 기계적 접합강도 특성을 검토하였다. 장기 신뢰성 평가 시험 후 기계적 접합강도의 값은 감소하는 결과를 나타내었다. 열충격 시험 후 각 시편의 기계적 접합강도가 평균 4.3 N이 감소하였으며, 열수명 시험 후 기계적 접합 강도의 감소는 평균 5.3N, 고온고습 시험 후 기계적 접합강도의 감소는 평균 3.8 N이었다. 시편의 최대 평균 감소율은 22.6 %로 C1 chip의 열수명 시험에서 나타났으며, 최소 평균 감소율은 3.5 %로 R1 chip의 고온고습 시험 후 나타났다. 상대적으로 시편이 큰 chip에서는 고온고습 시험이 작은 chip에서는 열수명 시험이 기계적 접합강도에 가장 크게 영향을 미치는 것으로 나타났다. 향후 보다 미세한 부품을 대상으로 공정조건 및 기계적 신뢰성 평가 기법을 확립하여야 할 것으로 사료된다.

In this study, the mechanical bonding strength were analyzed according to before and after long-term reliability evaluation test for various chips of automotive application component using Sn-3.0Ag-0.5Cu solder. In the after long-term reliability evaluation test, the mechanical bonding strengths tended to decrease. After thermal shock test, each specimen's mechanical bonding strengths decreased average 4.3N, in the case of after thermal life test, that of specimens decreased average 5.3N. After high-temperature & humidity test, mechanical bonding strengths decreased average 3.8N. The maximum average decreasing rate of specimens were 22.6% at thermal life test of Ci chip, and the minimum average decreasing rate of specimens were 3.5% at high-temperature & humidity test of R1 chip. In the case of large chip specimen, high-temperature & humidity test has a decisive effect on the mechanical bonding strengths. Inversely, in the small chip specimen, thermal life test has a decisive effect on the mechanical bonding strengths. For the reliability management, the process conditions and the mechanical reliability evaluation techniques should be established for the more fine component.

Improving the reliability or long-term dependability of a system requires a different approach from the previous emphasis on short-term concerns. The purpose of this paper is to present a reliability evaluation method for an oil cooler intended for high-precision machining centers. The oil cooler system in question is a cooling device that minimizes the deformation caused from the heat generated by driving devices. This system is used for machine tools and semiconductor equipment. We predicted the reliability of the system based on the failure rate database and conducted the reliability test using a test-bed to evaluate the life of the oil cooler. The results provided an indication of the reliability of the system in terms of the failure rate and the MTBF of the oil cooler system and its components, as well as a distribution of the failure mode. These results will help increase the reliability of oil cooler systems. The evaluation method can also be used to determine the reliability of other machinery products.

This study has the aim of developing an evaluation index that can help evaluate the reliability of the information resources of institutions retaining humanities assets for the purposes of laying out the foundation for providing one-stop portal service for humanities assets. To this end, the evaluation index was derived through the analysis of previous research, case studies, and interviews with experts, the derived evaluation index was then applied to the humanities assets retaining institutions to verify the utility. The institutional information resources' reliability evaluation index consisted of the two dimensions of the institutions' own reliability evaluation index. The institution provided a service and system evaluation index. The institutions' own reliability evaluation index consisted of 25 points for institutional authority, 25 points for data collection and construction, 30 points for data provision, and 20 points for appropriateness of data, for a total of 100 points, respectively. The institution provided service and system evaluation indexes consisting of 25 points for information quality, 15 points for appropriateness (decency), 15 points for accessibility, 20 points for tangibility, 15 points for form, and 10 points for cooperation, for the total of 100 points, respectively. The derived evaluation index was used to evaluate the utility of 6 institutions representing humanities assets through application. Consequently, the reliability of the information resources retained by the Research Information Service System (RISS) of the Korea Education & Research Information Service (KERIS) turned out to be the highest.

Over the past twenty years, the maintenance system developed, and its importance increased. For the effective maintenance, the maintenance system has been developed by introducing the concept of RCM (Reliability Centered Maintenance). This research is to develop an effective maintenance system for urban transit based on the concept of RCM. RCM is a systematic approach to develop a cost-effective maintenance strategy based on the various components' reliability of the subject system. The final process of RCM determines appropriate failure maintenance strategies. For realization of RCM, reliability evaluation framework has been studied to compute the reliability index for urban transit. The framework requires the following processes: BOM (Bill of Materials), RBD (Reliability Block Diagram) based on FBD (Function Block Diagram), and failure code classification. The goal of this paper is to define the maintenance procedure for the subject system since successful maintenance system depends on an automated maintenance plan. This plan can be scheduled effectively by collecting and analyzing data from maintenance experience. For doing this, this paper proposes the web-based maintenance system for collecting data and the computing of MTBF (Mean Time between Failures) at the maintenance stage for analyzing data.

Objective To replace camera-based three-dimensional motion analyzers which are widely used to analyze body movements and gait but are also costly and require a large dedicated space, this study evaluates the validity and reliability of inertial measurement unit (IMU)-based systems by analyzing their spatio-temporal and kinematic measurement parameters. Methods The investigation was conducted in three separate hospitals with three healthy participants. IMUs were attached to the abdomen as well as the thigh, shank, and foot of both legs of each participant. Each participant then completed a 10-m gait course 10 times. During each gait cycle, the hips, knees, and ankle joints were observed from the sagittal, frontal, and transverse planes. The experiments were conducted with both a camerabased system and an IMU-based system. The measured gait analysis data were evaluated for validity and reliability using root mean square error (RMSE) and intraclass correlation coefficient (ICC) analyses. Results The differences between the RMSE values of the two systems determined through kinematic parameters ranged from a minimum of 1.83 to a maximum of 3.98 with a tolerance close to 1%. The results of this study also confirmed the reliability of the IMU-based system, and all of the variables showed a statistically high ICC. Conclusion These results confirmed that IMU-based systems can reliably replace camera-based systems for clinical body motion and gait analyses.

Objective: The aim of this study was to evaluate the validity and reliability of using static surface electromyography (sEMG) on persons with neck pain and in healthy adults. Design: Cross-sectional study. Methods: Twenty-two female participants with neck pain and thirty healthy adults in the age group of 20-65 years were recruited in this study. To evaluate the validity and reliability of sEMG in subjects with neck pain, the subjects'characteristics were recorded and the Visual Analog Scale (VAS) and Neck Disability Index (NDI) were examined in addition to sEMG and algometer tests being carried out on the subjects. The site for using the sEMG and algometer was the upper trapezius. sEMG test-retest reliability was measured by intraclass correlation coefficients (ICCs). Independent t-tests were used to analyze the differences in the dependent variables between subjects with neck pain and healthy adults. The Pearson correlation coefficient was used to examine the linear relationship between measured variables. Results: sEMG and algometer tests were reliable according to the test-retest reliability results in subjects with neck pain and healthy adults (ICC=0.815-0.979). The results of this study showed that there were significant differences in respect to age, VAS, sEMG and algometer tests between persons with neck pain and healthy adults (p<0.05). The VAS and NDI were statistically correlated with sEMG and algometer results (p<0.05). Conclusions: In this study, we investigated the clinical usefulness of the static sEMG test in evaluating the pain scale of persons with neck pain with high reliability and validity.

Objective To establish the reliability and validity the Korean version of the Stroke Impact Scale (K-SIS) 3.0.Methods A total of 70 post-stroke patients were enrolled. All subjects were evaluated for general characteristics, Mini-Mental State Examination (MMSE), the National Institutes of Health Stroke Scale (NIHSS), Modified Barthel Index, Hospital Anxiety and Depression Scale (HADS). The SF-36 and K-SIS 3.0 assessed their health-related quality of life. Statistical analysis after evaluation, determined the reliability and validity of the K-SIS 3.0.Results A total of 70 patients (mean age, 54.97 years) participated in this study. Internal consistency of the SIS 3.0 (Cronbach’s alpha) was obtained, and all domains had good co-efficiency, with threshold above 0.70. Test-retest reliability of SIS 3.0 required correlation (Spearman’s rho) of the same domain scores obtained on the first and second assessments. Results were above 0.5, with the exception of social participation and mobility. Concurrent validity of K-SIS 3.0 was assessed using the SF-36, and other scales with the same or similar domains. Each domain of K-SIS 3.0 had a positive correlation with corresponding similar domain of SF-36 and other scales (HADS, MMSE, and NIHSS).Conclusion The newly developed K-SIS 3.0 showed high inter-intra reliability and test-retest reliabilities, together with high concurrent validity with the original and various other scales, for patients with stroke. K-SIS 3.0 can therefore be used for stroke patients, to assess their health-related quality of life and treatment efficacy.

Objective To systematically translate the Fugl-Meyer Assessment (FMA) into a Korean version of the FMA (K-FMA). Methods We translated the original FMA into the Korean version with three translators and a translation committee, which included physiatrists, physical therapists, and occupational therapists. Based on a test-retest method, each of 31 patients with stroke was assessed by two evaluators twice, once on recruitment, and again after a week. Analysis of intra- and inter-rater reliabilities was performed using the intra-class correlation coefficient, whereas validity was analysed using Pearson correlation test along with the Motricity Index (MI), Motor Assessment Scale (MAS), and Berg Balance Scale (BBS). Results The intra- and inter-rater reliabilities were significant for the total score, and good to excellent reliability was noted in all domains except for the joint range of motion of the lower extremity domain of the K-FMA. The MI and MAS scores were significantly correlated with all domains, all with p<0.01. The results for the MI ranged from r=0.639 to r=0.891 and those for the MAS from r=0.339 to r=0.555. However, the BBS was not significantly correlated with any domain, as the K-FMA lacks balance evaluation items. Conclusion The K-FMA was found to have high reliability and validity. Additionally, the newly developed manual for the K-FMA may help minimise errors that can occur during evaluation and improve the reliability of motor function evaluation.

Objective To translate the Stroke Rehabilitation Motivation Scale (SRMS), developed to evaluate the motivation level of stroke patients during rehabilitation, into the Korean language and to verify the reliability and validity of the Korean version of SRMS (K-SRMS). Methods The K-SRMS was developed following a structured process that included translation, verification, compromise assessment, reverse translation, feedback, and final correction. K-SRMS reliability was evaluated by performing internal consistency and test?retest analyses. The reliability test was conducted in 50 stroke patients. Its validity was assessed by comparing the K-SRMS with the scale and performing exploratory factor analysis. The validity test was conducted in 102 stroke patients. Results The test?retest analysis showed good reliability, and the internal consistency of the K-SRMS was similar to that of the original version for all, except 4, items. Thus, these 4 items were excluded, and then the validity test was conducted. Pearson correlation analysis demonstrated that the K-SRMS score was significantly correlated with the BAS total score (Pearson r=0.207, p<0.05). In the exploratory factor analysis, K-SRMS items were categorized into 7 groups (factors), and factors 1 and 4 showed mutual concordance with K-SRMS subscales, including intrinsic motivation factors and amotivation, respectively. Conclusion The newly developed K-SRMS showed good reliability and validity. It could also be used as a tool to objectify the degree of motivation for rehabilitation among stroke patients in clinical care and research.

Background: As social problems due to the acceleration of the aging era and the increase in the elderly population are becoming serious, virtual reality (VR)-based healthcare is emerging as an approach for preventing and managing health issues. Objects: This study used validity and reliability analyses to examine the clinical efficacy that is, the clinical value and usability of a novel VR cognitive evaluation system index that we developed. Methods: We developed a VR cognitive evaluation system based on motion recognition analysis evaluation for individuals aged 65 to 85. After conducting the Korean version of the Mini-Mental State Exam (K-MMSE) cognitive evaluation, the evaluation score was verified through correlation analysis in the VR cognitive evaluation system. To verify the construct validity of the two groups, the Global Deterioration Scale (GDS) grades were categorized into a normal cognitive group (GDS grade 1) and a cognitive impairment group (GDS grades 2 and 3). The data were measured twice to determine the reliability between the two measurements and assess the stability and clinical value of the evaluation system. Results: Our evaluation system had a high correlation of 0.85 with the widely used K-MMSE cognitive evaluation. The system had strong criterion-related validity at the 95% confidence interval. Compared to the average score of GDS grade 1 in the VR cognitive evaluation system, the average score of GDS grades 2 and 3 in the VR cognitive evaluation system was statistically significantly lower while also having strong construct validity at the 95% confidence interval. To measure the reliability of the VR cognitive evaluation system, tests-retests were conducted using the intraclass correlation coefficient (3,1), which equaled 0.923 and was statistically significant. Conclusion: The VR cognitive evaluation system we developed is a valid and reliable clinical tool to distinguish between normal cognitive status and mild cognitive impairment.

The purposes of this study were to examine the reliability and validity of Korean translation of Pediatric Evaluation of Disability Inventory (PEDI-K) in school-aged children with cerebral palsy (CP). The PEDI-K, Functional Independence Measure for Children (WeeFIM) and Gross Motor Function Classification System (GMIFCS) were completed in 104 school-aged children with CP by therapists. The internal consistency of the PEDI-K was calculated by Cronbach's alpha (${\alpha}$) for assessing reliability. Concurrent validity was evaluated by correlation with the subsets of WeeFIM. Discriminant validity was assessed by comparing GMFCS levels with tests of the PEDI-K. The results showed that internal consistency was good (Cronbach's ${\alpha}$ ranged from .97~.98). Concurrent validity was demonstrated. The correlation with WeeFIM was high in the Functional Skills (self-care, r=.74~.94; mobility, r=.59~.91; social function, r=.65~.93) and in the Caregiver Assistance (self-care, r=.75~.94; mobility, r=.63~.90; social function, r=.78~.96). Discriminant validity was demonstrated on significant decreases in domain scores with increasing GMFCS levels. Reliability and validity have been demonstrated on the PEDI-K. This study extends usage of PEDI-K in clinical activities and research.

Objective To investigate the reliability and validity of a new method for isometric back extensor strength measurement using a portable dynamometer.Methods A chair equipped with a small portable dynamometer was designed (Power Track II Commander Muscle Tester). A total of 15 men (mean age, 34.8±7.5 years) and 15 women (mean age, 33.1±5.5 years) with no current back problems or previous history of back surgery were recruited. Subjects were asked to push the back of the chair while seated, and their isometric back extensor strength was measured by the portable dynamometer. Test-retest reliability was assessed with intraclass correlation coefficient (ICC). For the validity assessment, isometric back extensor strength of all subjects was measured by a widely used physical performance evaluation instrument, BTE PrimusRS system. The limit of agreement (LoA) from the Bland-Altman plot was evaluated between two methods.Results The test-retest reliability was excellent (ICC=0.82; 95% confidence interval, 0.65?0.91). The Bland-Altman plots demonstrated acceptable agreement between the two methods: the lower 95% LoA was ?63.1 N and the upper 95% LoA was 61.1 N.Conclusion This study shows that isometric back extensor strength measurement using a portable dynamometer has good reliability and validity.

기후변화, 이상기후 등 환경 변화로 인한 댐 붕괴 위험성이 높아지고 있다. 이에 따라 국내외 대형 수공구조물의 노후화에 대한 관심이 증가하고 있다. 국제 댐 안전관리 규제 방향과 구조물 의 잠재 위험도를 추정하기 위한 안정성 해석방법론의 필요성이 대두되고 있으며, 이에 본 연구 에서는 Bayesian 기법을 활용한 확률론적 안전성 평가 모형을 제시하였다. 노후화 평가 방법으로 는 정상성(stationarity) 및 비정상성(nonstationarity)에 따른 이항분포(binomial distribution)와 포아 송 분포(Poisson distribution)를 기반의 해석 방법을 개발하였다. 또한, 자료 변동성을 반영한 사전 정보를 활용하여 위험확률을 산정하는 모형(population variability model)으로 확장하여 분석 을 수행하였다. 본 노후화 평가 모형은 댐의 노후도를 정량화함으로써 잔여 수명과 최적 보수 시기 등을 판단할 수 있는 근거를 제공할 수 있을 것으로 기대된다.

The risk of dam failure is increasing due to environmental changes such as climate change and extreme weather events. As a result, there is growing interest in the aging of large hydraulic structures both domestically and internationally. The need for stability analysis methodologies to estimate the potential risks of these structures, along with international regulatory directions on dam safety management, has become evident. This study proposes a probabilistic safety evaluation model using Bayesian techniques. Analytical methods based on the binomial distribution and Poisson distribution were developed for aging assessment under both stationarity and nonstationarity conditions. Furthermore, the analysis was extended to include a population variability model that incorporates prior information reflecting data variability to calculate risk probabilities. The proposed aging evaluation model is expected to provide a basis for quantifying the aging of dams, thereby enabling the determination of remaining service life and the optimal timing for maintenance and repair.

This study presents a comprehensive procedure for the low cycle fatigue test of ultrasonically welded (UW) coated conductor (CC) lap-joints. The entire process is examined in detail, from the robust fabrication of the UW REBCO CC joints to the reliability testing under a low number of repeated cycle fatigue conditions. A continuous Ic measurement system enables real-time monitoring of Ic variations throughout the fatigue tests. The study aims to provide a step-by-step procedure that involves joint fabrication, electromechanical property (EMP) tests under uniaxial tension for stress level determination, and subsequent low-cycle fatigue tests. The joints are fabricated using a hybrid method that combines UW with adding In-Sn soldering, achieving a flux-free hybrid welding approach (UW-HW flux-free). The selected conditions for the low cycle fatigue tests include a stress ratio of R=0.1 and a frequency of 0.02 Hz. The results reveal some insights into the fatigue behavior, irreversible changes, and cumulative damage in the CC joints.

본 연구는 신경망 알고리즘 및 반응표면법을 이용하여 부품의 최적화 설계 치수를 예측하고, 예측된 데이터의 신뢰성을 상호 검증하는 하는 데 있다. 부하가 변할 때, 부품의 치수를 변화시켜 가며 응력 및 변형량의 변화를 해석 데이터로 수집하여 반응표면법 및 신경망학습에 이용하였다. 이를 위해 임의의 조건에서 반응표면법으로 최적화 설계를 수행하고, 동일한 조건에서 신경망 알고리즘의 예측결과와 비교하였다. 그 결과 최대 3.0%의 치수 오차를 보이는 것으로 나타났다. 또한 검증을 위해 반대로 동일한 하중 및 치수 조건에서 유한요소해석을 통해 응력 및 처짐량을 구해 반응표면법 및 신경망학습의 결과를 비교하였으며, 이때 4.2%의 오차를 보였다. 이는 부품의 사양 변경 시 최적화 설계를 위해 반응표면법 및 신경망을 이용할 수 있으며 신뢰성이 있음을 알 수 있었다. 특히 신경망 학습을 통해 보다 효과적으로 최적화 설계가 가능함을 확인할 수 있었다.

본 연구는 도로 하부에 설치된 노후 철근콘크리트(RC) 암거를 대상으로 코어 압축강도 기반 비파괴시험(NDT) 보정기법을 적용하여 구조성능 평가의 신뢰성을 검토하였다. 현장 조사 결과 비파괴시험 추정강도가 코어 압축강도 대비 다소 높은 값으로 나타났으며, 보정계수를 적용함으로써 추정값과 실측값 간의 차이를 감소시켜 구조성능 평가의 신뢰성을 향상시킬 수 있음을 확인하였다. 구조물의 전반적인 내구성 상태는 양호하나 일부 특정 구간에서 균열, 누수, 이음부 변형 등의 국부적 손상이 관찰되었으며, 이는 철근콘크리트 암거의 재료 열화보다 지반의 부등침하와 밀접한 관련이 있는 것으로 분석되었다. 향후 연구에서는 다양한 형식의 암거 구조물을 대상으로 장기 모니터링 자료와 지반 거동 분석을 함께 적용하여 비파괴시험 보정기법의 일반화 가능성을 검증할 필요가 있으며, 지반침하에 따른 구조물의 물리적 변화와 구조적 거동 간의 정량적 관계를 고려한 통합 평가 모델이 개발될 경우, 지하시설물의 유지관리 효율성 향상에 기여할 수 있을 것으로 기대된다.

This study evaluates the reliability of structural performance assessment for an aged reinforced concrete (RC) culvert installed beneath a roadway by applying a core compressive strength–based calibration method to nondestructive testing (NDT). Field investigation results showed that the strength estimated from nondestructive testing was slightly higher than the measured core compressive strength. By applying a calibration coefficient, the discrepancy between the estimated and measured strengths was reduced, thereby improving the reliability of the structural performance assessment. Although the overall durability condition of the structure was generally sound, localized defects such as cracks, leakage, and joint displacement were observed in certain sections. These defects were found to be more closely related to differential ground settlement than to the material deterioration of the RC culvert. The development of an integrated assessment model that considers the quantitative relationship between ground settlement and structural behavior is expected to improve the maintenance efficiency of underground infrastructure.

This study aims to develop and commercialize a soundproof wall capable of planting at the urban ecological. The vegetative soundproof wall developed in the study showed highly superb structural test results for sound absorption coefficients and met the quality standards in the sound-absorbing performance test. Its structure is systemized to supply water to soils and plant roots inside the planting basis with rainwater running down the inclined planes near the planting basis in the front of the vegetation panel. It allows for sporadic water supply for about 30 days of drought. The test results show that the plants continued favorable growth and development in leaves, stems, and roots, making the vegetative soundproof plate a product capable of reacting to climate environment changes.

Recently, the reliability evaluation and analysis are applied far many industrial products which are required to guarantee in quality and efficiency. The purpose of this paper is to present some of reliability evaluation methodologies that are applicable to machine tools. Especially ATC (Automatic Tool Changer), which is a core component of line center, was chosen as the target of the reliability evaluation and analysis. The scope of research is reliability prediction, reliability test and evaluates their results. The results of reliability evaluation have shown the failure rates, MTBF (Mean Time Between Failure), reliability for those components of ATC and real tests reliability through the constructed reliability test-bed. It is expected that proposed methodologies would increase reliability for a high-speed line center.

Hot Plate is the major unit that it used to remove damp of wafer surface, to strength adhesion of photoresist (PR) and to bake coated PR in FAB process of semiconductor. The badness of Hot Plate (HP) has directly influence upon the performance of wafer, it is necessary to guarantee the performance of HP. In this study, a reliability evaluation system has been designed and developed, which is to measure and to estimate thermal uniformity and flatness of HP in range of temperature 0~$250^\circC$. This system has included the techniques which measures and analyzes thermal uniformity using infrared thermal vision, and which compensates measuring error of flatness using laser displacement sensor For measuring flatness, a measurement stage of 3 axes are developed which adapts the precision encoder. The allowable error of this system in respect of thermal uniformity is less $than\pm0.1^\circC$ and in respect of flatness is less $than\pm$1mm . It is expected that the developed system can measure from $\Phi200mm\;(wafer 8＂)\;to\;\Phi300mm$ (wafer 12＂) and also can be used in performance test of the Cool Plate and industrial heater, etc.