This paper chronicles the evolution of load-sharing parameter estimation methodologies, with a particular focus on the significant contributions made by Kim and Kvam (2004) and Park (2012). Kim and Kvam's pioneering work underscored the inherent challenges in deriving closed-form solutions for load-share parameters, which necessitated the use of sophisticated numerical optimization techniques. Park's research, on the other hand, provided groundbreaking closed-form solutions and extended the theoretical framework to accommodate more general distributions of component lifetimes. This was achieved by incorporating EM-type methods for maximum likelihood estimation, which represented a significant advancement in the field. Unlike previous efforts, this paper zeroes in on the specific characteristics and advantages of closed-form solutions for load-share parameters within reliability systems. Much like the basic Economic Order Quantity (EOQ) model enhances the understanding of real-life inventory systems dynamics, our analysis aims to thoroughly explore the conditions under which these closed-form solutions are valid. We investigate their stability, robustness, and applicability to various types of systems. Through this comprehensive study, we aspire to provide a deep understanding of the practical implications and potential benefits of these solutions. Building on previous advancements, our research further examines the robustness of these solutions in diverse reliability contexts, aiming to shed light on their practical relevance and utility in real-world applications.

Recently, due to the expansion of the logistics industry, demand for logistics automation equipment is increasing. The modern logistics industry is a high-tech industry that combines various technologies. In general, as various technologies are grafted, the complexity of the system increases, and the occurrence rate of defects and failures also increases. As such, it is time for a predictive maintenance model specialized for logistics automation equipment. In this paper, in order to secure the operational safety and reliability of the parcel loading system, a predictive maintenance platform was implemented based on the Naive Bayes-LSTM(Long Short Term Memory) model. The predictive maintenance platform presented in this paper works by collecting data and receiving data based on a RabbitMQ, loading data in an InMemory method using a Redis, and managing snapshot DB in real time. Also, in this paper, as a verification of the Naive Bayes-LSTM predictive maintenance platform, the function of measuring the time for data collection/storage/processing and determining outliers/normal values was confirmed. The predictive maintenance platform can contribute to securing reliability and safety by identifying potential failures and defects that may occur in the operation of the parcel loading system in the future.

In the semiconductor manufacturing clean room, contamination that directly affects process yield is managed through the operation of a monitoring system that measures molecular contamination in the air. In this study, I presented the component inspection method, test conditions, and judgment criteria through the life test of the solenoid valve that will be applied to the sampling module of the AMC Monitoring System.

In modern society, the delivery service market has grown explosively due to rapid changes in social structure and the recent COVID-19 pandemic. Therefore, various problems such as injury to workers and an increase in human accidents are occurring due to the loading and unloading of parcels. In order to solve this problem, domestic company n is developing a “robot-based cargo loading and unloading system”. In developing a new technology system, quantitative reliability targets should be set for efficient operation and development. In this paper, reliability analysis was conducted through field data for the pneumatic gripper of the “robot-based cargo loading system”. The reliability of the failure data was analyzed to estimate the distribution parameters and MTTF. Random data was derived for the probability of occurrence of a failure with the estimated value. By repeating the simulation to predict the number and year of failures according to the estimated parameters of the probability distribution, it was proposed as a method that reflects realistic probabilities rather than calculating with simple arithmetic using the average MTTF previously used in the field.

본 연구에서는 운전 시뮬레이션을 이용하여 적응형 정속 주행(adaptive cruise control: ACC) 시스템에 대한 운전자의 신뢰 및 도로 혼잡도가 운전자의 작업부하와 상황인식에 미치는 효과를 알아보았다. ACC 시스템에 대한 운전자의 신뢰는 ACC 시스템이 정상 작동하는 조건과 시스템이 오작동하는 조건을 통해 신뢰상승 집단과 신뢰감소 집단으로 구분하였다. 도로 혼잡도는 운전자 차량 주변의 차량 수로 수준을 조작하였다. ACC 시스템에 대한 신뢰와 도로 혼잡도를 달리한 네 가지의 실험 조건 각각에 대해 운전자들의 작업부하와 상황인식을 측정하였다. 본 연구의 결과를 요약하면 다음과 같다. 먼저 ACC 시스템에 대한 신뢰감소 집단은 신뢰상승 집단에 비해 이 시스템의 사용으로 인한 운전부담 경감이나 안전운전 확보 등을 포함한 측정 항목 모두에서 시스템에 대한 신뢰 점수가 유의하게 더 낮았다. 둘째, ACC 시스템에 대한 신뢰감소 집단은 신뢰상승 집단에 비해 이차과제에서 더 느린 반응시간을 보였고, 시스템 사용에서의 주관적인 작업부하 수준도 더 높게 평정하였다. 셋째, 이와는 대조적으로 운전자들의 운전상황에 대한 상황인식은 ACC 시스템 신뢰감소 집단이 신뢰상승 집단보다 유의하게 더 우수하였다. 본 연구의 결과들은 ACC 시스템에 대한 신뢰가 운전 중에 수행하는 다양한 정보처리에 영향을 미칠 수 있음을 보였는데, 이것은 자동화된 운전보조 시스템의 설계에서 사용자의 시스템에 대한 신뢰가 중요한 변인으로 고려되어야 한다는 것을 시사한다.

A one-shot system (device) refers to a system that is stored for a long period of time and is then disposed of after a single mission because it is accompanied by a chemical reaction or physical destruction when it operates, such as shells, munitions in a defense weapon system and automobile airbags. Because these systems are primarily related with safety and life, it is required to maintain a high level of storage reliability. Storage reliability is the probability that the system will operate at a particular point in time after storage. Since the stored one-shot system can be confirmed only through inspection, periodic inspection and maintenance should be performed to maintain a high level of storage reliability. Since the one-shot system is characterized by a large loss in the event of a failure, it is necessary to determine an appropriate inspection period to maintain the storage reliability above the reliability goal. In this study, we propose an optimal inspection policy that minimizes the total cost while exceeding the reliability goal that the storage reliability is set in advance for the one-shot system in which periodic inspections are performed. We assume that the failure time is the Weibull distribution. And the cost model is presented considering the existing storage reliability model by Martinez and Kim et al. The cost components to be included in the cost model are the cost of inspection c1, the cost of loss per unit time between failure and detection c2, the cost of minimum repair of the detected breakdown of units c3, and the overhaul cost c4 of  ≤ . And in this paper, we will determine the optimal inspection policy to find the inspection period and number of tests that minimize the expected cost per unit time from the finite lifetime to the overhaul. Compare them through numerical examples.

As the functions and structure of the system are complicated and elaborated, various types of structures are emerging to increase reliability in order to cope with a system requiring higher reliability. Among these, standby systems with standby components for each major component are mainly used in aircraft or power plants requiring high reliability. In this study, we consider a standby system with a multi-functional standby component in which one standby component simultaneously performs the functions of several major components. The structure of a parallel system with multifunctional standby components can also be seen in real aircraft hydraulic pump systems and is very efficient in terms of weight, space, and cost as compared to a basic standby system. All components of the system have complete operation, complete failure, only two states, and the system has multiple states depending on the state of the component. At this time, the multi-functional standby component is assumed to be in a non-operating standby state (Cold Standby) when the main component fails. In addition, the failure rate of each part follows the Weibull distribution which can be expressed as increasing type, constant type, and decreasing type according to the shape parameter. If the Weibull distribution is used, it can be applied to various environments in a realistic manner compared to the exponential distribution that can be reflected only when the failure rate is constant. In this paper, Markov chain analysis method is applied to evaluate the reliability of multi-functional multi-state standby system. In order to verify the validity of the reliability, a graph was generated by applying arbitrary shape parameters and scale parameter values through Excel. In order to analyze the effect of multi-functional multi-state standby system using Weibull distribution, we compared the reliability based on the most basic parallel system and the standby system.

본 연구에서는 보다 넓은 범위에서 영상기반 변위계측 시스템의 동특성 추정 신뢰성을 확보하기 위해 Shaking Table을 이용해 넓은 대역의 진동수와 진동수별 다양한 진폭에 대한 Sine Wave 동적실험을 실시하였다. 영상기반 변위계측을 위해 DDVS(Dynamic Displacement Vision System) 기법을 활용하였으며, DDVS 기법을 통해 구한 동적변위는 기존의 접촉·비접촉식 센서인 LVDT(Wire Type, Pole Type)과 LDS의 변위계측 결과와 비교하여 그 오차를 분석하였다. 구해진 동적변위를 FFT하여 진동수 영역에서의 정확도 비교도 함께 수행하였다. 4가지 타입의 계측센서 모두 동적변위계측 결과 최대 변위 도달 및 주기 운동 계측에 있어 대체적으로 유사한 결과를 나타냈으며, 특히 영상기반의 DDVS 기법과 LDS를 통한 계측 결과는 높은 상호 일치성을 보였다. LDS와의 비교를 통한 오차분석 결과, DDVS 기법에 의한 동적변위 계측의 정확도는 계측 대상의 진동수에 영향을 받는다고 판단되었다. 동일 가진 진동수 내에서 가해준 변위 변화에 의한 오차는 미미하였으나, 동일 발생 변위에서는 가진 진동수가 커질수록 오차 값이 증가하였다. 기존 센서인 LVDT 경우, 발생 변위가 작을 때 상대적으로 큰 오차를 나타냈으며, 이를 통해 진동계측과 같은 작은 동적변위의 계측에 한계가 존재한다고 판단된다.

As a preparation of a design standard regarding road facilities, such as cantilever columns for traffic lights, optimum design and risk assessment for foundation of street lights on highways are proposed. The preliminary evaluation of optimization with reliability assessment resultantly makes it possible to reduce not only the duration of construction but the cost of construction as well. Ultimate limit states and constraints functions are selected for the sliding, overturning and settlement of the foundation under external loads from super and sub-structures itself. An example foundation under the super structure of height 12m, is optimized as 30% decreased embedded depth of foundation, in which as increasing the depth of embedded connection parts, the necessary depth of foundation is deceased. However, the optimum depths and the reliability indices are sensitively dependent with earth properties and dimensions of foundation.

Due to advancements in technology and manufacturing capability, it is not uncommon that life tests yield no or few failures at low stress levels. In these situations it is difficult to analyse lifetime data and make meaningful inferences about product or system reliability. For some products or systems whose performance characteristics degrade over time, a failure is said to have occurred when a performance characteristic crosses a critical threshold. The measurements of the degradation characteristic contain much useful and credible information about product or system reliability. Degradation measurements of the performance characteristics of an unfailed unit at different times can directly relate reliability measures to physical characteristics. Reliability prediction based on physical performance measures can be an efficient and alternative method to estimate for some highly reliable parts or systems. If the degradation process and the distance between the last measurement and a specified threshold can be established, the remaining useful life is predicted in advance. In turn, this prediction leads to just in time maintenance decision to protect systems. In this paper, we describe techniques for mapping product or system which has degrading performance parameter to the associated classical reliability measures in the performance domain. This paper described a general modeling and analysis procedure for reliability prediction based on one dominant degradation performance characteristic considering pseudo degradation performance life trend model. This pseudo degradation trend model is based on probability modeling of a failure mechanism degradation trend and comparison of a projected distribution to pre-defined critical soft failure point in time or cycle.

To evaluate system reliability of a composite structure consisting of more than two structural members, it is necessary to identify that the members are connected to each others in parallel or in serial. Especially for parallel composite system, it is also necessary to confirm that mechanical properties of materials for the members are brittle or ductile. For parallel system of brittle materials, if one part fails, that part cannot resist load anymore and the whole load transfers to the other part. However, for parallel system of perfectly plastic materials, if one part fails, that part can maintain the amount of its maximum load capacity and the remaining load transfers to the other part. In this study, a methodology to determine reliability index for composite structures consisting of quasi-brittle materials. By assuming quasi-brittle materials as brittle or perfectly plastic materials, the upper and lower bounds of the reliability index can be determined. The reliability index for parallel system of quasi-brittle materials is then determined by interpolating the upper and lower bounds indices using ductility number extracted from stress-strain curves of quasi-brittle materials.

This paper is a case study of reliability assessment with field warranty data of Clutch Master Cylinder (CMC) in hydraulic clutch system. We estimate lifetime distribution using field warranty data which contain much useful information for understanding reliability of the system in the real-world environments. However, the estimated parameters are far from existing reference values, which seems to be caused right censored field warranty data. To modify the parameters, we use the information of the durability test which is performed to verify that the lifetime of the item meets the required level. After that, we can observe that the modified parameters are closer to the existing reference values. This case study shows a possible idea to supplement lack of right censored field warranty data and its applicability.

In recent years, anti-PID (Potential Induced Degradation) technologies have been studied and developed at various stages through- out the solar value chain from solar cells to systems in an effort to enhance long-term reliability of the photovoltaics (PV) system. Such technologies and applications must bring in profits economically for both manufacturers of solar cell/module and investors of PV systems, simultaneously for the development of the PV industry. In this study two selected anti-PID technologies, ES (modification of emitter structure) and ARC (modification of anti-reflective coating) were compared based on the economic features of both a cell maker with 60MW production capacity and an investor of 1MW PV power plant. As a result of this study, it is shown that ARC anti-PID technology can ensure more profits over ES technology for both the cell manufacturer and the investor of PV power plant.

In recent years, there has been developed anti-PID technologies(Potential Induced Degradation) in various levels from solar cell to module and to system to enhance of the long life reliability of photovoltaics(PV) system. Such technologies must economically ensure profits for both manufacturers of solar cells and investors of PV system simultaneously for PV industry development. This paper describes a comparison between and selection from two anti-PID technologies in the solar cell level, ES(modification of emitter structure) and ARC(modification of anti-reflective coating) based on the economic features of anti-PID solar cell production system with 60MW capacity for a solar cell maker and a 1MW PV power plant installed with PV modules using anti-PID solar cells. From the comparison between ES and ARC, it is shown that ARC anti-PID technology can make more profit for both a solar cell maker and a PV power plant investor.

This paper is a case study of reliability assessment with field warranty data of Clutch Master Cylinder(CMC) in hydraulic clutch system. We estimate lifetime distribution using field warranty data which contain much useful information for understanding reliability of the system in the real-world environments. However, the estimated parameters are far from existing reference values, which seems to be caused right censored field warranty data. To modify the parameters, we use the information of the durability test which is performed to verify that the lifetime of the item meets the required level. After that, we can observe that the modified parameters are closer to the existing reference values. This case study shows a possible idea to supplement lack of right censored field warranty data and its applicability