• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.03a
• /
• pp.84-88
• /
• 2008

The UAV propulsion system that will be operated for long time at more than 40,000ft altitude should have not only fuel flow minimization but also high reliability and durability. If this UAV propulsion system may have faults, it is not easy to recover the system from the abnormal, and hence an accurate diagnostic technology must be needed to keep the operational reliability. For this purpose, the development of the health monitoring system which can monitor remotely the engine condition should be required. In this study, a fuzzy trend monitoring method for detecting the engine faults including mechanical faults was proposed through analyzing performance trends of measurement data. The trend monitoring is an engine conditioning method which can find engine faults by monitoring important measuring parameters such as fuel flow, exhaust gas temperatures, rotational speeds, vibration and etc. Using engine condition database as an input to be generated by linear regression analysis of real engine instrument data, an application of the fuzzy logic in diagnostics estimated the cause of fault in each component. According to study results, it was confirmed that the proposed trend monitoring method can improve reliability and durability of the propulsion system for a long endurance UAV to be operated at medium altitude.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.17 no.1
• /
• pp.25-34
• /
• 2021

Availability is one of the important factor for developing weapon system, because it indicates the mission capability and sustainable life cycle management of weapon system. Recently, as weapon system becomes more advanced and more complex, availability estimation becomes more important to reduce the life cycle cost of weapon system. Modeling and simulation(M&S) is useful method to describe the availability of complex weapon system applying operational environment and maintenance plan. Especially agent based model(ABM) has the strength to describe interactions between agents and environments in complex system. Therefore, this paper presents the availability estimation of weapon system using agent based model. The sample data of part list and reliability analysis is applied to build availability estimation model. User agent and mechanic agent are developed to illustrate the behavior of operation and maintenance using formal specification. Storage reliability is applied to describe failure of each parts. The experimental result shows that this model is quite useful to estimate availability of weapon system. This model may estimate more reasonable availability, if full scale data of weapon system and real field data of operation is provided.

• Journal of the Korea Safety Management & Science
• /
• v.26 no.1
• /
• pp.63-74
• /
• 2024

The objectives of this study is to classify evacuation types, derive the characteristics of 4 types, develop and discover evacuation routes within the performance hall space, and present the statistical classification results of the evacuation classification model by classification type. To achieve this purpose, the characteristics of each evacuation type's four types are applied through a network reliability analysis method and utilized for institutional improvement and policy. This study applies for the building law, evacuation and relief safety standards when establishing a performance hall safety management plan, and reflects it in safety-related laws, safety standards, and policy systems. Statistical data by evacuation type were analyzed, and measurement characteristics were compared and analyzed by evacuation types. Evaluate the morphological similarity and reliability of evacuation types according to door width and passage length and propose the install position of evacuation guidance sign boards. The results of this study are expected to be used as basic data to provide operation strategies for safety facility evacuation information sign boards according to evacuation route classification types when taking a safety management plan. The operation strategy for the evacuation sign boards installation that integrates employee guidance and safety training is applied to the performance hall safety management plan. It will contribute to establishing an operational strategy for performance space safety when constructing performance facilities in the future.

• Journal of the Korean Society for Railway
• /
• v.20 no.5
• /
• pp.569-576
• /
• 2017

The electromagnetic valve of pneumatic doors of EMUs has a high failure rate due to air leakage because it supplies air on and off to operate the doors repeatedly. The electromagnetic valve is a very important safety component for which a very high reliability is required because failure makes it impossible to operate the passenger cars. However, domestic urban railway operators maintain electronic valves of the EMU door under a fixed cycle with a spare period according to the full overhaul cycle of the EMU. An improvement of the current maintenance cycle was suggested based on the reliability function and mission reliability. Using the statistical program MINITAB for the operational data of EMU line 6, we analyzed the characteristics of the fault distribution and derived the shape and scale parameters of the reliability function. If we limit the specific reliability probability to under a certain failure rate and calculate its statistical parameters, we can calculate the allowable inspection period with mission reliability. Through this study, we suggested a maintenance period based on RCM (reliability centered-maintenance) to improve the reliability of electromagnetic valves from 68% to 95%.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.26 no.6
• /
• pp.43-52
• /
• 2022

Operational reliability of the single-use turbo engine for guided weapons must be guaranteed even after long-term storage. Rolling element bearings have a great influence on the operational reliability of the turbo engine, however changes in micro dimensions of bearings by an oxide layers on rolling elements and raceways may cause failures after long-term storage. In this study, changes in dimensions of bearings were measured and roughness of rolling elements was used for estimating the storage life. Storage life estimation was performed via two kinds of methods, Weibayes method and random sample generation method. The results of two methods were compared and their characteristics were analyzed. This study will contribute to establish an efficient maintenance schedule for the single-use turbo engine.

• Journal of the Korean earth science society
• /
• v.24 no.3
• /
• pp.150-159
• /
• 2003

This study suggests methods of assessing scientific creativity and developing items, which can be achieved when both earth science knowledge and general creativity are applied at the same time. According to the results of this study, the cognitive ability gaps between creativity and scientific creativity were clearly defined by the terms' operational definition. Four factors in the Subcategory Of Scientific Creativity-fluency, flexibility, elaboration, and originality-were selected, and the possibility of developing items out of these factors was discovered. The operational definitions of the four factors were given and the criteria for assessment and scoring were set. The validity, reliability, discrimination, and difficulty, which were the conditions required for the assessment instruments, were verified through three field trials of inputting the assessment instruments for scientific creativity. The assessment instruments were composed of 8 items with 2items for each factor. The average item fitness index obtained was 0.99, Cronbach , the item inter-consistency was 0.79,the inter-rater reliability of each item was 0.78, the inter-rater reliability of each factor was 0.75, the item discrimination power was 0.19, and the item difficulty was 0.00. Because the results were within the permitted limit of the conditions required for assessment instruments, the assessment instruments developed for scientific creativity in this study can be said to be very favorable.

• Journal of Oriental Neuropsychiatry
• /
• v.25 no.1
• /
• pp.109-122
• /
• 2014

Objectives: The aim of this study is to investigate the core emotion assessment instrument based on the Chiljeong. Methods: We searched for a literature review of oriental medicine and established the operational definition. Based on the existing psychological scale measurement, we selected the items and analyzed the reliability through a two-step preliminary study. Results: 1) Through the analysis of reliability after the two-step preliminary study (first: 170 items, n=63, second: 152 items, n=42), we had excellent internal consistency (Cronbach's alpha > 0.70) as well as good test-retest reliability (>0.70). Thus, we demonstrated that this scale had reliability. 2) Analyzing the correlation of each emotion, we had a comparatively strong positive-correlation (>0.6), except for Hui, and found a particularly high correlation of Sa, U and Bi. Conclusions: We developed the final 141 items of the core emotion assessment instrument through the two-time preliminary study. In the future, the main study on the clinical and non clinical groups of various ages should be continued.

• Journal of IKEEE
• /
• v.25 no.3
• /
• pp.578-583
• /
• 2021

This paper describes acceleration tests for reliability of semiconductors. It also describes AEC-Q100, international test standard for reliability of automotive semiconductors. Semiconductors can be used for dozens of years. So acceleration tests are essential to test potential problems over whole period of product where test time is minimized by applying intensive stresses. AEC-Q100 is a typical acceleration test in automotive semiconductors, and it is designed to find various failures in semiconductors and to analyze their causes of occurance. So it finds many problems in design and fabrication as well as it predicts lifetime and reliability of semiconductors. AEC-Q100 consists of 7 test groups such as accelerated environmental stress tests, accelerated lifetime simulation tests, package assembly integrity tests, die fabrication reliability tests, electrical verification tests, defect screening tests, and cavity package integrity tests. It has 4 grades from grade 0 to grade 3 based on operational temperature. AEC-Q101, Q102, Q103, Q104, and Q200 are applied to discrete semiconductors, optoelectronic semiconductors, sensors, multichip modules, and passive components, respectively.

• Aerospace Engineering and Technology
• /
• v.6 no.1
• /
• pp.222-229
• /
• 2007

Environmental tests should be carried out to show that design performance is in an operational condition in an actual operational environment to assure maintainability and reliability. Aero-products electromagnetic compatibility tests are performed mainly for the individual parts and Specifications MIL-STD-461E and RTCA DO-160E are developed for the military and commercial parts tests respectively. The MIL-STD-461E which is a military environmental test standard is targeting all munitions and that user can apply by selecting applicable requirements from this specification. On the other hand, requirements are applied exclusively for the Avionics Equipments in commercial test standard.

• Journal of Korean Institute of Industrial Engineers
• /
• v.16 no.2
• /
• pp.135-147
• /
• 1990

A nuclear power plant can be viewed as a large complex man-machine system where high system reliability is obtained by ensuring that sub-systems are designed to operate at a very high level of performance. The chance of severe accident involving at least partial core-melt is very low but once it happens the consequence is very catastrophic. The prediction of risk in low probability, high-risk incidents must be examined in the contest of general engineering knowledge and operational experience. Engineering knowledge forms part of the prior information that must be quantified and then updated by statistical evidence gathered from operational experience. Recently, Bayesian procedures have been used to estimate rate of accident and to predict future risks. The Bayesian procedure has advantages in that it efficiently incorporates experts opinions and, if properly applied, it adaptively updates the model parameters such as the rate or probability of accidents. But at the same time it has the disadvantages of computational complexity. The predictive distribution for the time to next incident can not always be expected to end up with a nice closed form even with conjugate priors. Thus we often encounter a numerical integration problem with high dimensions to obtain a predictive distribution, which is practically unsolvable for a model that involves many parameters. In order to circumvent this difficulty, we propose a method of approximation that essentially breaks down a problem involving many integrations into several repetitive steps so that each step involves only a small number of integrations.