Reliability of Hip Migration Index in Children with Cerebral Palsy: The Classic and Modifi ed Methods

Sun Mi Kim,박은숙,Eun Geol Sim,Seong Gyu Lim 대한재활의학회 2012 Annals of Rehabilitation Medicine Vol.36 No.1

Objective To determine reliability and clinical use of two methods of migration index (MI) in CP patients with or without hip dysplasia. Method The materials included radiographs of 200 hips of children with cerebral palsy. Conventional anteroposterior radiographs of the pelvis were taken with the child in the supine position with standardized methods. Two rehabilitation doctors measured the migration index using two methods. In the classic method,the lateral margin of the acetabular roof was used as a landmark and in the modifi ed method the lateral margin of the sourcil was used as a landmark. Each rater measured the migration index at three separate times with a time interval of at least one week. Intraclass correlation (ICC) was used to test the inter- and intra-rater reliability. Results MI shows excellent intra-rater reliability in both the classic and modified methods, but the inter-rater reliability was higher in the classic method than in the modified method. When categorized according to the sourcil classifi cation, inter-rater reliability was higher in the normal sourcil type and lower in the dysplastic sourcil types. Conclusion Generally, the classic method showed higher reliability than the modifi ed method, even though the reliability of the MI measurement was relatively high with both methods. Objective To determine reliability and clinical use of two methods of migration index (MI) in CP patients with or without hip dysplasia. Method The materials included radiographs of 200 hips of children with cerebral palsy. Conventional anteroposterior radiographs of the pelvis were taken with the child in the supine position with standardized methods. Two rehabilitation doctors measured the migration index using two methods. In the classic method,the lateral margin of the acetabular roof was used as a landmark and in the modifi ed method the lateral margin of the sourcil was used as a landmark. Each rater measured the migration index at three separate times with a time interval of at least one week. Intraclass correlation (ICC) was used to test the inter- and intra-rater reliability. Results MI shows excellent intra-rater reliability in both the classic and modified methods, but the inter-rater reliability was higher in the classic method than in the modified method. When categorized according to the sourcil classifi cation, inter-rater reliability was higher in the normal sourcil type and lower in the dysplastic sourcil types. Conclusion Generally, the classic method showed higher reliability than the modifi ed method, even though the reliability of the MI measurement was relatively high with both methods.

L.E.O. Satellite Power Subsystem Reliability Analysis

M. Zahran,S. Tawfik,Gennady Dyakov 전력전자학회 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.2

Satellites have provided the impetus for the orderly development of reliability engineering research and analysis because they tend to have complex systems and hence acute problems. They were instrumental in developing mathematical models for reliability, as well as design techniques to permit quantitative specification, prediction and measurement of reliability. Reliability engineering is based on implementing measures which insure an item will perform its mission successfully. The discipline of reliability engineering consists of two fundamental aspects; (1<SUP>st</SUP>) paying attention to details, and (2<SUP>nd</SUP>) handling uncertainties. This paper uses some of the basic concepts, formulas and examples of reliability theory in application.<br/> This paper emphasizes the practical reliability analysis of a Low Earth Orbit (LEO) Micro-satellite power subsystem. Approaches for specifying and allocating the reliability of each element of the power system so as to meet the overall power system reliability requirements, as well as to give detailed modeling and predicting of equipment/system reliability are introduced. The results are handled and analyzed to form the final reliability results for the satellite power system. The results show that the Electric Power Subsystem (EPS) reliability meets the requirements with quad microcontrollers (MC), two boards working as main and cold redundant while each board contains two MCs in a hot redundant.

Reliability Evaluation of Power System Operations Considering Time-Varying Features of Components

Bo Hu,Ying Zheng,Hejun Yang,Yun Xia 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.4

The reliability of power system components can be affected by a numbers of factors such as the health level of components, external environment and operation environment of power systems. These factors also affect the electrical parameters of power system components for example the thermal capacity of a transmission element. The relationship of component reliability and power system is, therefore, a complex nonlinear function related to the above-mentioned factors. Traditional approaches for reliability assessment of power systems do not take the influence of these factors into account. The assessment results could not, therefore, reflect the short-term trend of the system reliability performance considering the influence of the key factors and provide the system dispatchers with enough information to make decent operational decisions. This paper discusses some of these important operational issues from the perspective of power system reliability. The discussions include operational reliability of power systems, reliability influence models for main performance parameters of components, time-varying reliability models of components, and a reliability assessment algorithm for power system operations considering the time-varying characteristic of various parameters. The significance of these discussions and applications of the proposed techniques are illustrated by case study results using the IEEE-RTS.

A Study on Maintenance Reliability Allocation of Urban Transit Brake System Using Hybrid Neuro-Genetic Technique

Chul-Ho Bae,Yul Chu,Hyun-Jun Kim,Jung-Hwan Lee,Myung-Won Suh 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.1

For reasonable establishing of maintenance strategies, safety security and cost limitation must be considered at the same time. In this paper, the concept of system reliability introduces and optimizes as the key of reasonable maintenance strategies. This study aims at optimizing component’s reliability that satisfies the target reliability of brake system in the urban transit. First of all, constructed reliability evaluation system is used to predict and analyze reliability. This data is used for the optimization. To identify component reliability in a system, a method is presented in this paper which uses hybrid neuro-genetic technique. Feed-forward multi-layer neural networks trained by back propagation are used to find out the relationship between component reliability (input) and system reliability (output) of a structural system. The inverse problem can be formulated by using neural network. Genetic algorithm is used to find the minimum square error. Finally, this paper presents reasonable maintenance cycle of urban transit brake system by using optimal system reliability.

RELIABILITY-BASED SENSITIVITY ANALYSIS OF VEHICLE COMPONENTS WITH NON-NORMAL DISTRIBUTION PARAMETERS

Y. M. ZHANG,Z. YANG 한국자동차공학회 2009 International journal of automotive technology Vol.10 No.2

Techniques from the perturbation method, fourth moment method, reliability based design theory, and sensitivity analysis approach are employed to present a practical and efficient method for testing the reliability sensitivity of vehicle components with non-normal distribution parameters. With the condition that the first four moments of original random variables are known, the reliability sensitivity theory and cases are researched using the presented numerical method. The variation regularities of reliability sensitivity are obtained and the effects of design parameters on reliability of the vehicle components are studied. The sophisticated formulation provided in this paper is easily amenable to computational procedures. The respective program can be used to obtain the reliability sensitivity of vehicle components with non-normal distribution parameters accurately and quickly. The results obtained are perfect and the solutions compared very well with those from Monte Carlo simulation. The method presents a theoretic basis for the reliability design of the vehicle components. Techniques from the perturbation method, fourth moment method, reliability based design theory, and sensitivity analysis approach are employed to present a practical and efficient method for testing the reliability sensitivity of vehicle components with non-normal distribution parameters. With the condition that the first four moments of original random variables are known, the reliability sensitivity theory and cases are researched using the presented numerical method. The variation regularities of reliability sensitivity are obtained and the effects of design parameters on reliability of the vehicle components are studied. The sophisticated formulation provided in this paper is easily amenable to computational procedures. The respective program can be used to obtain the reliability sensitivity of vehicle components with non-normal distribution parameters accurately and quickly. The results obtained are perfect and the solutions compared very well with those from Monte Carlo simulation. The method presents a theoretic basis for the reliability design of the vehicle components.

신뢰도 예측 기반 신뢰도 성장 관리 : 감시체계 사례

김상부,박우재,유재우,이자경,용화영 한국품질경영학회 2019 품질경영학회지 Vol.47 No.1

Purpose: In this study, a reliability prediction based reliability growth management is suggested especially for the early development phase of a system and the case study of surveillance system is given. Methods: The proposed reliability prediction based reliability growth management procedures consists of 7 Steps. In Step 1, the stages for reliability growth management are classified according to the major design changes. From Step 2 to Step 5, system reliability is predicted based on reliability structures and the predicted reliabilities of subsystems (Level 2) and modules (Level 3). At each stage, by comparing the predicted system reliability with that of the previous stage, the reliability growth of the system is checked in Step 6. In Step 7, when the predicted value of sustem reliability does not satisfy the reliability goal, some design alternatives are considered and suggested to improve the system reliability. Results: The proposed reliability prediction based reliability growth management can be an efficient alternative for managing reliability growth of a system in its early development phase. The case study shows that it is applicable to weapon system such as a surveillance system. Conclusion: In this study, the procedures for a reliability prediction based reliability growth management are proposed to satisfy the reliability goal of the system efficiently. And it is expected that the use of the proposed procedures would reduce, in the test and evaluation phase, the number of corrective actions and its cost as well.

L.E.O. Satellite Power Subsystem Reliability Analysis

Zahran M.,Tawfik S.,Dyakov Gennady The Korean Institute of Power Electronics 2006 JOURNAL OF POWER ELECTRONICS Vol.6 No.2

Satellites have provided the impetus for the orderly development of reliability engineering research and analysis because they tend to have complex systems and hence acute problems. They were instrumental in developing mathematical models for reliability, as well as design techniques to permit quantitative specification, prediction and measurement of reliability. Reliability engineering is based on implementing measures which insure an item will perform its mission successfully. The discipline of reliability engineering consists of two fundamental aspects; $(1^{st})$ paying attention to details, and $(2^{nd})$ handling uncertainties. This paper uses some of the basic concepts, formulas and examples of reliability theory in application. This paper emphasizes the practical reliability analysis of a Low Earth Orbit (LEO) Micro-satellite power subsystem. Approaches for specifying and allocating the reliability of each element of the power system so as to meet the overall power system reliability requirements, as well as to give detailed modeling and predicting of equipment/system reliability are introduced. The results are handled and analyzed to form the final reliability results for the satellite power system. The results show that the Electric Power Subsystem (EPS) reliability meets the requirements with quad microcontrollers (MC), two boards working as main and cold redundant while each board contains two MCs in a hot redundant.

발목관절 복합체의 가동범위 측정을 위한 중립위치와 측정방법의 신뢰도

홍완성,김기원,Hong, Wan-Sung,Kim, Gi-Won 대한물리치료학회 2011 대한물리치료학회지 Vol.23 No.4

Purpose: To determine the correct measurement methods of the ankle joint complex range of motion for measuring the neutral position and evaluate the rater reliability. In addition, the impact of training on the rater reliability was also assessed. Methods: The subjects were eleven healthy women, who were evaluated by two physical therapists and one physical therapist recorded the results of the study. Standard goniometer was used as the measurement tool. The ankle and subtalar joint neutral position and the active range of motion of the ankle and subtalar joint were measured. Intra-rater reliability and inter-rater reliability measures were analyzed with intraclass correlation coefficients. Results: Intra-rater reliability and inter-rater reliability ranged from high to medium for the neutral position of the ankle joint complex. Intra-rater reliability for dorsiflexion and plantarflexion measurements was medium, while the inter-rater reliability was high. The range of motion of the subtalar joint was measured, and the intra-rater reliability and inter-rater reliability were low and medium, respectively Also, the intra-rater reliability was increased with formal training of the measurement techniques. Intra-rater reliability was reduced in case the raters had not undertaken the training. Conclusion: In summary, the results obtained with the measurement tools and joint measurement of position, indicate the consistency of repeated measurements made by the same observers. Under the same circumstances along with repetition of the same measurement technique during training caused an increase in the rater reliability of formally trained raters.

Reliability-Based Design for Market Systems (RBDMS) : Case Study on Electric Vehicle Design

Ungki Lee(이웅기),Namwoo Kang(강남우),Ikjin Lee(이익진) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11

When designing a product, both engineering uncertainty and market heterogeneity should be considered to reduce the risk of failure in the market. Reliability-based design optimization (RBDO) approach allows decision makers to achieve target confidence in product performance under engineering uncertainty. On the other hand, design for market systems (DMS) approach helps decision makers to find profit-maximized product design under market heterogeneity. This paper proposes a reliability-based design for market systems (RBDMS) framework for electric vehicle (EV) design by integrating RBDO and DMS approaches. In RBDO, the product quality is controlled based on arbitrarily defined reliability. However, from the viewpoint of the company, it is necessary to set the appropriate reliability since the increased reliability increases both consumer satisfaction and manufacturing cost. Therefore, by modeling how reliability affects the customer choice, the optimum reliability which maximizes the profit can be derived. The “reliability” in the framework is used as follows: (1) a decision variable; (2) an attribute that directly influences the customer preference; (3) standards to determine advertised performance; and (4) reliability constraints in engineering model. We optimized and compared four scenarios depending on whether engineering systems are deterministic or probabilistic, and whether a market is homogeneous or heterogeneous. The results show that designing an entry EV model with low reliability is recommended under engineering uncertainty and market heterogeneity, while designing a premium EV model with high reliability is recommended to ensure the robustness of the profit.

신뢰도 경로의 고장열거를 이용한 시스템 신뢰도 계산방법 연구

이장일(Jang-Il Lee),박기준(Kee-Jun Park),천환규(Hwan-Kyu Chun),정충민(Choong-Min Jeong),신동준(Dong-Jun Shin),서명원(Myung-Won Suh) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.6

항공기, 철도, 선박과 같은 대형 시스템들은 전기, 기계적으로 매우 복잡한 구조를 가졌으며 부품의 수명만을 고려한 기존의 유지보수에서 탈피하여, 고장분석의 시스템화를 통해 장치의 고유수명과는 관계없이 발생 가능한 우발고장도 대처할 수 있는 신뢰성 기반의 유지보수체계를 연구하여야 한다. 본 연구에서는 선행연구로 필요한 복합 시스템의 신뢰도 계산방법에 관한 연구이다. 복합 시스템의 신뢰도를 효과적으로 계산하기 위해 시스템의 RBD(Reliability Block Diagram)를 구성하고 인접행렬을 사용하여 RBD(Reliability Block Diagram)를 행렬로 표현한다. 또한 RBD(Reliability Block Diagram)행렬을 통하여 신뢰도 경로행렬과 고장열거 행렬을 구성하여 시스템의 신뢰도를 계산한다. 본 연구에서 제안한 알고리즘은 자동화, 시스템화가 가능하며 현재 개발하고 있는 신뢰도 정보관리 시스템 및 신뢰성 기반 유지보수 시스템에서 활용될 것이다. Recently, systems such as aircraft, trains and ships have become larger more complex. Therefore, the reliability calculation of these systems is more difficult. This paper presents a reliability calculation algorithm for a complex system with a solution that is difficult to analyze. When the system has a very complex structure, it is very difficult to find an analytical solution. In this case, we can assess system reliability using the failure enumeration method of the reliability path. In this research, we represent the reliability block diagram by an adjacent matrix and define the reliability path. We can find any system status by the failure enumeration of the reliability path, and thus we can calculate any kind of system reliability through this process. This result can be applied to RCM (Reliability-Centered Maintenance) and reliability information-management systems, in which the system reliability is composed of the reliabilities of individual parts.