Developing the Accurate Method of Test Data Assessment with Changing Reliability Growth Rate and the Effect Evaluation for Complex and Repairable Products

So, Young-Kug,Ryu, Byeong-Jin The Korean Reliability Society 2015 신뢰성응용연구 Vol.15 No.2

Reliability growth rate (or reliability growth curve slope) have the two cases of trend as a constant or changing one during the reliability growth testing. The changing case is very common situation. The reasons of reliability growth rate changing are that the failures to follow the NHPP (None-Homogeneous Poisson Process), and the solutions implemented during test to break out other problems or not to take out all of the root cause permanently. If the changing were big, the "Goodness of Fit (GOF)" of reliability growth curve to test data would be very low and then reduce the accuracy of assessing result with test data. In this research, we are using Duane model and AMSAA model for assessing test data and projecting the reliability level of complex and repairable system as like construction equipment and vehicle. In case of no changing in reliability growth rate, it is reasonable for reliability engineer to implement the original Duane model (1964) and Crow-AMSAA model (1975) for the assessment and projection activity. However, in case of reliability growth rate changing, it is necessary to find the method to increase the "GOF" of reliability growth curves to test data. To increase GOF of reliability growth curves, it is necessary to find the proper parameter calculation method of interesting reliability growth models that are applicable to the situation of reliability growth rate changing. Since the Duane and AMSAA models have a characteristic to get more strong influence from the initial test (or failure) data than the latest one, the both models have a limitation to contain the latest test data information that is more important and better to assess test data in view of accuracy, especially when the reliability growth rate changing. The main objective of this research is to find the parameter calculation method to reflect the latest test data in the case of reliability growth rate changing. According to my experience in vehicle and construction equipment developments over 18 years, over the 90% in the total development cases are with such changing during the developing test. The objective of this research was to develop the newly assessing method and the process for GOF level increasing in case of reliability growth rate changing that would contribute to achieve more accurate assessing and projecting result. We also developed the new evaluation method for GOF that are applicable to the both models as Duane and AMSAA, so it is possible to compare it between models and check the effectiveness of new parameter calculation methods in any interesting situation. These research results can reduce the decision error for development process and business control with the accurately assessing and projecting result.

Developing the Accurate Method of Test Data Assessment with Changing Reliability Growth Rate and the Effect Evaluation for Complex and Repairable Products

Young-Kug So,Byeong-Jin Ryu 한국신뢰성학회 2015 신뢰성응용연구 Vol.15 No.2

Reliability growth rate (or reliability growth curve slope) have the two cases of trend as a constant or changing one during the reliability growth testing. The changing case is very common situation. The reasons of reliability growth rate changing are that the failures to follow the NHPP (None-Homogeneous Poisson Process), and the solutions implemented during test to break out other problems or not to take out all of the root cause permanently. If the changing were big, the “Goodness of Fit (GOF)” of reliability growth curve to test data would be very low and then reduce the accuracy of assessing result with test data. In this research, we are using Duane model and AMSAA model for assessing test data and projecting the reliability level of complex and repairable system as like construction equipment and vehicle. In case of no changing in reliability growth rate, it is reasonable for reliability engineer to implement the original Duane model (1964) and Crow-AMSAA model (1975) for the assessment and projection activity. However, in case of reliability growth rate changing, it is necessary to find the method to increase the “GOF” of reliability growth curves to test data. To increase GOF of reliability growth curves, it is necessary to find the proper parameter calculation method of interesting reliability growth models that are applicable to the situation of reliability growth rate changing. Since the Duane and AMSAA models have a characteristic to get more strong influence from the initial test (or failure) data than the latest one, the both models have a limitation to contain the latest test data information that is more important and better to assess test data in view of accuracy, especially when the reliability growth rate changing. The main objective of this research is to find the parameter calculation method to reflect the latest test data in the case of reliability growth rate changing. According to my experience in vehicle and construction equipment developments over 18 years, over the 90% in the total development cases are with such changing during the developing test. The objective of this research was to develop the newly assessing method and the process for GOF level increasing in case of reliability growth rate changing that would contribute to achieve more accurate assessing and projecting result. We also developed the new evaluation method for GOF that are applicable to the both models as Duane and AMSAA, so it is possible to compare it between models and check the effectiveness of new parameter calculation methods in any interesting situation. These research results can reduce the decision error for development process and business control with the accurately assessing and projecting result.

원샷 시스템의 신뢰성 성장 시험 설계 방안

서양우(Yang-Woo Seo),김희욱(Hee-Wook Kim),김소정(So-Jung Kim),김용근(Yong-Geun Kim) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.12

본 논문은 원샷 시스템의 신뢰성 성장 시험 설계 방안을 제시하였다. 우선 원샷 시스템의 신뢰성 성장 시험 설계절차를 제시한 후 각각의 세부 활동을 제안하였다. 제안한 절차에 따라 OOO 원샷 시스템에 대하여 신뢰성 성장 시험 사례분석을 수행하였다. 신뢰성 성장 시험 데이터가 고장모드가 동일한 형태가 있기 때문에 데이터 유형은 이산형 데이터 중의 고장모드를 포함하는 순차적 데이터 유형으로 선정하였다. 이 때, 신뢰성 성장 모델은 시험-수정조치-시험을 수행하는 가장 일반적으로 적용되는 Standard Gompertz 모델을 선정하였다. 발사시험 13발에 대한 신뢰성 성장 시험분석 결과는 신뢰성 86.23 %로 목표 값에 미충족되는 결과이었다. 따라서, 추가 발사시험을 통해 신뢰성 목표 값을 만족시키기 위해 대안분석을 수행하였다. 13발 이후의 추가 발사시험이 성공되는 경우는 추가로 2발 발사시험이 필요하며, 신뢰성 값은 91.16 %이었다. 추가 발사시험을 수행하면서 1발이 실패하는 경우는 추가로 5발 발사시험이 필요하며, 신뢰성 값은 90.83 %이었다. 추가 발사시험을 수행하면서 2발이 실패하는 경우는 추가로 7발 발사시험이 필요하며, 신뢰성 값은 90.28 %이었다. 본 연구의 결과는 원샷 시스템의 신뢰성 성장 시험 설계 시 자원 재할당을 하는데 유용하게 활용할 수 있다. 또한, 모든 원샷 시스템의 신뢰성 성장 시험 설계 수립 시에 활용 가능하다. In this article, we propose a method of reliability growth test design for one-shot systems. First, the procedure for the reliability growth test design for the one-shot system was presented. Then, the detailed activities in each step in the procedure were proposed. A case analysis of the reliability growth test was performed on the OOO one-shot system in accordance with the proposed procedure. Since the reliability growth test data has the same failure mode, the data type was selected to be sequential with the mode data containing failure mode among the discrete data. At this time, the reliability growth model used the most commonly used Standard Gompertz model to perform the test-fix-test. The results of the reliability growth test for 13 launch tests showed 86.23% reliability which did not meet the reliability target. So, an alternative analysis was performed to achieve the reliability target through additional launch tests. If additional launch tests after the 13 launch tests do not fail, additional two launch tests were required for the alternative analysis, and the reliability value for this case was 91.16%. If they fail once, additional five launch tests were required, and the reliability value for this case was 90.83%. Furthermore, if additional launch tests fail twice, additional seven launch tests were required, and the corresponding reliability value was 90.28%. The results of this study can be useful in resource reallocation when designing reliability growth tests for a one-shot system. Also, it can be used when establishing the design of reliability growth tests for all one-shot systems.

Developing the Accurate Method of Test Data Assessment with Changing Reliability Growth Rate and the Effect Evaluation for Complex and Repairable Products

소영국,류병진 한국신뢰성학회 2015 신뢰성응용연구 Vol.15 No.2

Reliability growth rate (or reliability growth curve slope) have the two cases of trend as a constant or changing one during the reliability growth testing. The changing case is very common situation. The reasons of reliability growth rate changing are that the failures to follow the NHPP (None-Homogeneous Poisson Process), and the solutions implemented during test to break out other problems or not to take out all of the root cause permanently. If the changing were big, the “Goodness of Fit (GOF)” of reliability growth curve to test data would be very low and then reduce the accuracy of assessing result with test data. In this research, we are using Duane model and AMSAA model for assessing test data and projecting the reliability level of complex and repairable system as like construction equipment and vehicle. In case of no changing in reliability growth rate, it is reasonable for reliability engineer to implement the original Duane model (1964) and Crow-AMSAA model (1975) for the assessment and projection activity. However, in case of reliability growth rate changing, it is necessary to find the method to increase the “GOF” of reliability growth curves to test data. To increase GOF of reliability growth curves, it is necessary to find the proper parameter calculation method of interesting reliability growth models that are applicable to the situation of reliability growth rate changing. Since the Duane and AMSAA models have a characteristic to get more strong influence from the initial test (or failure) data than the latest one, the both models have a limitation to contain the latest test data information that is more important and better to assess test data in view of accuracy, especially when the reliability growth rate changing. The main objective of this research is to find the parameter calculation method to reflect the latest test data in the case of reliability growth rate changing. According to my experience in vehicle and construction equipment developments over 18 years, over the 90% in the total development cases are with such changing during the developing test. The objective of this research was to develop the newly assessing method and the process for GOF level increasing in case of reliability growth rate changing that would contribute to achieve more accurate assessing and projecting result. We also developed the new evaluation method for GOF that are applicable to the both models as Duane and AMSAA, so it is possible to compare it between models and check the effectiveness of new parameter calculation methods in any interesting situation. These research results can reduce the decision error for development process and business control with the accurately assessing and projecting result.

복수장비의 고장 데이터를 활용한 신뢰성 성장 시험 적용 방안

서양우,오영일,임성준,엄천섭 한국산학기술학회 2022 한국산학기술학회논문지 Vol.23 No.6

In this paper, we proposed a method for reliability growth testing in multiple systems. First, the reliability growth test procedure for multiple systems was presented, and then the case analysis of the reliability growth test was performed on the A system. Since the test time and failure event for the same system can be known, the reliability growth data was set as a known operating times data type. The total test time was 8,000 hours, and the number of failures was 16. Accordingly, the demonstrated mean time between failures was calculated as 628.241399 hours. In addition, a test alternative analysis was performed to determine the end time of the reliability growth test. It was confirmed that the reliability target value was satisfied at 1,770 individual test times. In this case, the demonstrated mean time between failure was 501.934460 hours, and the total test time of 920 hours may be shortened. That is, it is possible to reduce the test time and related costs. Therefore, since most weapon systems tests use multiple equipment types rather than a single type of equipment, a reliability growth test can be performed in accordance with the proposed reliability growth test procedure. Also, it can be used as an alternative to reducing the test period and business risk through the alternative analysis of the reliability growth test. 본 논문은 복수장비의 고장 데이터를 활용한 신뢰성 성장 시험 적용 방안을 제시하였다. 우선 복수장비의 신뢰성 성장 시험 절차를 제시한 후 제안한 절차에 따라 A System에 대하여 신뢰성 성장 시험 사례분석을 수행하였다. 동일한 시스템에 대한 시험 시간 및 고장 이벤트를 알 수 있기 때문에 신뢰성 성장 데이터는 알려진 운용시간 데이터 유형으로 설정하였다. 총 시험시간은 8,000시간을 수행하였으며, 시험 종료 시점까지 고장발생 건수는 16번이었다. 이에 따라, 입증된 고장 간 평균 시간은 628.241399시간의 결과 값이 산출되었다. 또한, 신뢰성 성장 시험 종료 시점을 결정할 수 있는 시험 대안 분석을 수행하였다. 개별 시험 시간 1,770시점에서 신뢰도 목표 값이 만족되어 신뢰성 성장 시험 종료가 가능함을 확인하였다. 이 때, 입증된 고장 간 평균 시간 값은 501.934460시간으로 충족되었으며, 총 시험시간 920시간을 단축시킬 수 있다. 즉, 시험기간 및 관련된 비용을 줄일 수 있는 효과를 기대할 수 있다. 따라서, 대부분 무기체계는 시험 시제 수량을 단일장비가 아닌 복수장비로써 시험을 수행하기 때문에 제안한 신뢰성 성장 시험 절차에 따라 신뢰성 성장 시험을 수행할 수 있다. 또한, 신뢰성 성장 시험 대안 분석을 통하여 시험 기간 및 사업 리스크를 제거하는 대안으로 활용가능하다.

Intra-Rater Test-Retest Reliability of Ely`s Test Using Smartphone in Patients With Lumbar Extension-Rotation Syndrome

( Kyue Nam Park ),( Sung Min Ha ),( Sung Dae Chung ),( Si Hyun Kim ),( Jun Hyeok Jang ) 한국전문물리치료학회 2012 한국전문물리치료학회지 Vol.19 No.4

Ely`s test is commonly used to assess rectus femoris muscle flexibility, however, a reliability limit of this test was demonstrated by a previous study. In this study, we present an alternative method using an application for a digital horizontal level in a smartphone (DHLS) to complement the reliability limit of Ely`s test. The aim of this study was to examine the reliability of Ely`s test using DHLS on the pelvis, compared to using visual observation (VO) of pelvic and hip motions. Nineteen patients with lumbar extension-rotation syndrome were recruited for this study. An examiner examined the rectus femoris flexibility (both pass/fail and goniometer scoring) through Ely`s test using both DHLS and VO. A retest session was completed two hours later for within-day reliability and seven days later for between-day intra-rater test-retest reliability. Results showed higher Kappa values for pass/fail scoring and higher intraclass correlation coefficient values for goniometer scoring in Ely`s test using DHLS, compared to using VO. Measurement error and Bland and Altman plots further demonstrated the degree of intra-rater variance during Ely`s test using DHLS in a clinical setting, compared to using VO. These results demonstrated that Ely`s test using DHLS showed acceptable reliability compared to using VO. Ely`s test using DHLS could be widely used for measuring the rectus femoris muscle flexibility in patients with lumbar extension-rotation syndrome, although the inter-rater reliability needs to be established first.

고연령층 청력 선별검사로서 귓속말 검사의 유용성 및 신뢰도

박시내,정연훈,정원호,오승하,박용문,이준호,박헌이,최성준,여상원,이원철,박기현 대한이비인후과학회 2008 대한이비인후과학회지 두경부외과학 Vol.51 No.7

The purpose of this study is to evaluate the validity and reliability of the whispered voice test, which has been suggested as a screening test tool for hearing in the elderly group. Subjects and Method:A prospective multicenter trial has been designed. One hundred and seventy two elderly subjects from four university hospitals were included in this study. A whispered voice test using a number list and number/word list was performed by two testers for each elderly subject. To evaluate their test-retest reliability, a second whispered voice test was done 1-2 weeks later. The result of the whispered voice test was analyzed with the criteria of 26 dB and 40 dB hearing level, checked by pure tone audiometry. Sensitivity, specificity, and cut-off point of whispered voice test at each gold standard, inter-observer reliability and test-retest reliability have been investigated. Results:There were significant differences with respect to correctly answered numbers in the whispered voice test between the normal and impaired hearing group at both criteria of 26 dBHL and 40 dBHL. With the 26 dB criteria of hearing level which showed higher inter-observer reliability of the number/word list, the whispered voice test has 86.0% sensitivity and 58.9% specificity with the cut-off point of 3 out of six on the number set. The test-retest reliability of whispered voice test using the number list was as high as 0.9 of correlation coefficient. However, the inter-observer reliability of whispered voice test was less than 0.6 (Cohen’s kappa value). Conclusion:As a screening test for hearing in the elderly group, the whispered voice test has quite high sensitivity and test-retest reliability. The environmental sound level and test method for each tester, however, should be monitored to get better specificity and inter-observer reliability. (Korean J Otorhinolaryngol-Head Neck Surg 2008;51:609-16)

Developing Eye Movement Test Available in Clinical Practice (Pilot Study)

Ki-Seok Lee 대한시과학회 2021 대한시과학회지 Vol.23 No.4

목적 : 기존의 안구운동 검사에서 몇 가지 개선을 통해 임상에서 활용 가능한 안구운동 검사를 제안하고자 한다. 방법 : NSCUO 검사를 기반으로 검사가 가진 단점을 간단한 하드 및 소프트웨어를 적용하여 개선하였다. 하드 웨어로는 노트북, 모니터, 웹캠, 투명 격자 용지와 소프트웨어로는 MS office를 이용한 타깃, 검사 과정 녹화에 필요한 BandicamⓇ, 그리고 검사자가 관찰하는 모니터 화면을 분할하기 위한 WinSplit Revolution 9.02Ⓡ 이다. 개선된 안구운동 검사로서의 객관성과 신뢰성을 위하여 정상 성인 12명을 대상으로 검사의 반복성 및 신뢰도를 위해 검사자 한 명이 저장된 안구운동 결과 영상을 2주 후 재검사한 검사-재검사 신뢰도, 두 검사자가 하나의 검사 결과 영상을 평가한 결과를 비교한 검사자 간 신뢰도를 확인하였다. 결과 : 기존의 NSUCO 검사에서 추가된 하드 및 소프트웨어를 이용하여 개선된 검사로서 검사-재검사와 검사자 간 신뢰도를 비교하였다. 두 검사 비교 모두 유의한 차이를 보이지 않았으며(p<0.050), NSUCO 검사와의 신뢰도 비교에서도 높은 신뢰도를 보였다. 결론 : 개선된 안구운동 검사는 기존 NSUCO 검사 환경을 객관화하여 검사-재검사와 검사자간의 신뢰도를 높여 임상에서 활용 가능한 검사로 확인되었다. Purpose : The aim of this study is to propose an eye movement test that can be used in clinical practice through several improvements in the existing eye movement tests. Methods : Based on the NSUCO test, the shortcomings of the test were improved by applying simple hardware and software. For hardware, it is a laptop, monitor, webcap and transparent grid paper, and as software, a target using MS office, Bandicam® for recording the observation process, and WinSplit Revolution 9.02® for dividing the monitor screen observed by a tester. For the objectivity and reliability of the improved eye movement test, one tester retested the stored eye movement result images after 2 weeks for the repeatability and reliability of the test with 12 normal adults. Reliability between two testers who compared the results of image evaluation was confirmed. Results : Test-retest and inter-test reliability were compared as an improved test using hardware and software added to the existing NSUCO test. Both tests did not show a significant difference (p<0.050), and the reliability comparison with the NSUCO test showed high reliability. Conclusion : The improved eye movement test has been confirmed as a test that can be used in clinical practice by increasing the reliability between test-retest and tester by objectifying the existing NSUCO test environment.

기동장비 신뢰도 성장 관리 연구 : 발사대 체계 사례

이용준 ( Lee Yj ),배공명 ( Bae Gb ),허영무 ( Heo Ym ),서재현 ( Seo Jh ),김상부 ( Kim Sb ),최재경 ( Choi Jk ),박우재 ( Park Wj ) 한국품질경영학회 2017 품질경영학회지 Vol.45 No.4

Purpose: In this study, the reliability growth management procedures for armed vehicle is suggested and an illustrative case study of launcher system is given. Methods: Crow-AMSAA model is adopted to manage reliability growth of armed vehicle using failure data acquired from development test phase to field operation phase. Between the development test phase and the production phase, the suggested reliability growth procedures for armed vehicle entails accelerated life test of the selected module whose design is changed to improve its reliability for assuring the target system reliability. And it can be verified through estimating the system reliability based on the failure data of field operation phase. Results: It is shown that the proposed reliability growth management procedures are effective for armed vehicle based on the case study of launcher system. After estimating the reliability of launcher system at every development test, some items are selected to change their designs for improving reliability. Accelerated life test is performed to prove the reliability improvement and finally it is verified through the field operation. Conclusion: The reliability growth management procedures for armed vehicle is suggested and the case study of launcher system shows it can be effective for managing the reliability growth of the armed vehicle.

Reliability of the Active Knee Extension Test With a Pressure Biofeedback Unit

Chang-ho Kim,Gyeong-tae Gwak,Oh-yun Kwon 한국전문물리치료학회 2017 한국전문물리치료학회지 Vol.24 No.3

Background: The active knee extension (AKE) test commonly used to assess the flexibility of the hamstring muscles. Many researchers have tested the reliability of the AKE test; however, no published studies have examined the intrarater and interrater reliability of the AKE test using a PBU. Objects: The purpose of this study was to determine the intrarater and interrater reliability of the AKE test performed with a pressure biofeedback unit (PBU) on healthy subjects. Methods: Sixteen healthy male participants volunteered and gave informed consent to participate in this study. Two raters conducted AKE tests independently with a PBU. Each knee was measured twice, and the AKE testing was repeated one week after the first round of testing. Results: The interrater reliability’s intraclass correlation coefficients (ICC 2,1 ) were .887∼.986 for the right knees and .915∼.988 for the left knees. In addition, the intrarater (test-retest) reliability (ICC 3,1 ) values ranged between .820∼.915 and .820∼.884 for Raters 1 and 2, respectively. The values for the standard error of mesurement were low for all tests (.81∼2.97˚); the calculated minimum detectable change was 2.24∼8.21˚. Conclusion: These findings suggest that the AKE test performed with a PBU had excellent interrater and intrarater reliability for assessing hamstring flexibility in healthy young males.