• Journal of Electrical Engineering and Technology
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• v.6 no.1
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• pp.25-31
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• 2011

The purpose of power system maintenance is to prevent equipment failure. The maintenance strategy should be designed to balance costs and benefits because frequent maintenance increases cost while infrequent maintenance can also be costly due to electricity outages. This paper proposes maintenance modeling of a power distribution system using reliability centered maintenance (RCM). The proposed method includes comprehensive equipment modeling and impact analysis to evaluate the effect of equipment faults. The problem of finding the optimum maintenance strategy is formulated in terms of dynamic programming. The applied power system is based on the RBTS Bus 2 model, and the results demonstrate the potential for designing a maintenance strategy using the proposed model.

• Transactions of the Society of Information Storage Systems
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• v.9 no.2
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• pp.56-61
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• 2013

The recent increased use of mobile phone has resulted in a technical focusing on reliability issues related to drop performance. Since mobile phone may be dropped several times during their use, it is required to survive common drop accidents. The plastic injection parts such as base stopper and carrier in the encoder type actuator can be broken easily in the actual reliability test of 1.5m free drop. So, we analyzed the shock resistance characteristics of auto focus actuator with variables in the material properties using finite element method. By applying the new resin materials, we can decrease the breakage of plastic injection parts and improve the reliability of mobile phone.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.4
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• pp.267-273
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• 2020

The research examines the impacts of empowering leadership on teamwork performance of the employees in sales departments at commercial banks in Vietnam. Based on the data from the sample survey of 406 employees in sales departments of commercial banks in Vietnam, the paper uses various types of statistical methods and assesses the reliability of scales with Cronbach's Alpha, Confirmatory Factor Analysis as well as Structural Equation Modeling for analysis. The results show that the Empowering Leadership factor has a directly positive impact on Knowledge Sharing and Teamwork Performance, which means when the Empowering Leadership is positive, the Knowledge Sharing and Teamwork Performance will increase. In addition, Empowering Leadership also has an indirect impact on Teamwork Performance through Knowledge Sharing factor, which means when the Empowering Leadership is positive, the Teamwork Performance will increase. Moreover, Knowledge Sharing factor has a directly positive impact on Teamwork Performance, which means when the Knowledge Sharing factor is positive, the Teamwork Performance will increase. The findings suggest that Empowering Leadership has both directly and indirectly positive influence on Teamwork Performance. Moreover, Empowering leadership has a directly positive impact on Knowledge-sharing while Knowledge-sharing has a directly positive impact on Teamwork Performance of sales departments of commercial banks in Vietnam.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.10
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• pp.1499-1507
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• 2017

This paper presents an impact-based piezoelectric vibration energy harvester using a freely movable metal sphere and a piezoceramic fiber-based MFC (Macro Fiber Composite) as piezoelectric cantilever. The free motion of the metal sphere, which impacts both ends of the cavity in an aluminum housing, generates power across a cantilever-type MFC beam in response to low frequency vibration such as human-body-induced motion. Impacting force of the spherical proof mass is transformed into the vibration of the piezoelectric cantilever indirectly via the aluminum housing. A proof-of-concept energy harvesting device has been fabricated and tested. Effect of the indirect impact-based system has been tested and compared with the direct impact-based counterpart. Maximum peak-to-peak open circuit voltage of 39.8V and average power of $598.9{\mu}W$ have been obtained at 3g acceleration at 18Hz. Long-term reliability of the fabricated device has been verified by cyclic testing. For the improvement of output performance and reliability, various devices have been tested and compared. Using device fabricated with anodized aluminum housing, maximum peak-to-peak open-circuit voltage of 34.4V and average power of $372.8{\mu}W$ have been obtained at 3g excitation at 20Hz. In terms of reliability, housing with 0.5mm-thick steel plate and anodized aluminum gave improved results with reduced power reduction during initial phase of the cyclic testing.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.3
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• pp.11-17
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• 2009

The drop impact reliability comes to be important for evaluation of the life time of mobile electronic products such as cellular phone. The drop impact reliability of solder joint is generally affected by the kinds of pad and reflow number, therefore, the reliability evaluation is needed. Drop impact test proposed by JEDEC has been used as a standard method, however, which requires high cost and long time. The drop impact reliability can be indirectly evaluated by using high speed shear test of solder joints. Solder joints formed on 3 kinds of surface finishes OSP (Organic Solderability Preservation), ENIG (Electroless Nickel Immersion Gold) and ENEPIG (Electroless Nickel Electroless Palladium Immersion Gold) was investigated. The shear strength was analysed with the morphology change of intermetallic compound (IMC) layer according to reflow number. The layer thickness of IMC was increased with the increase of reflow number, which resulted in the decrease of the high speed shear strength and impact energy. The order of the high speed shear strength and impact energy was ENEPIG > ENIG > OSP after the 1st reflow, and ENEPIG > OSP > ENIG after 8th reflow.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.918-923
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• 2018

The main function of a fuel tank is to store fuel. On the other hand, the structural soundness of the fuel tank is related directly to the survival of the crew in an emergency situation, such as an aircraft crash, and the relevant performance is demonstrated by a crash impact test. Because crash impact tests have a high risk of failure due to the high impact loads, various efforts have been made to minimize the possibility of trial and error in the actual test at the beginning of the design. Numerical analysis performed before the actual test is a part of such efforts. For the results of numerical analysis to be reflected in the design, however, the reliability of numerical analysis needs to be ensured. In this study, the results of numerical analysis and actual test data were compared to ensure the reliability of numerical analysis for the crash impact test of a rotorcraft fuel tank. For the numerical analysis of a crash impact test, LS-DYNA, crash analysis software, was used and the ALE (arbitrary Lagrangian Eulerian) technique was applied as the analysis method. To obtain actual test data, strain gages were installed on the metal fittings of the fuel tank and linked to the data acquisition equipment. The strain and stress of the fuel tank fitting were calculated by numerical analysis. The reliability of the numerical analysis was enhanced by assessing the error between the strain measurement of the upper fitting obtained from an actual fuel tank and the strain calculated from numerical analysis.

• KIEE International Transactions on Power Engineering
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• v.4A no.3
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• pp.122-128
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• 2004

With the advent of distributed generation, power systems are fundamentally impacted in regards to stability and power quality. Distributed generation has a positive impact on system restoration following a fault, higher reliability, and mitigation of effect due to voltage sag. However, distributed generation also has a negative impact on decrease of reliability such as changes of protective device setting and mal-operation. Because bulk power systems consist of various sources and loads, it becomes complicated to analyze a power system with distributed generation. The types of distributed generation are usually classified by both rotating machinery and the inverter-based system. In this paper, distributed generation is designed by rotating machinery, and the distributed system having a model of the distributed generation is simulated using EMTP. In addition, this paper presents the simulation results according to the types of distributed generation.

• Korean Journal of Organic Agriculture
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• v.16 no.3
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• pp.275-286
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• 2008

This paper examines the impact of reliability on consumers' demand for environmentally friendly agricultural products using ordered logit model. We survey 100 housewives living in the capital region and five metropolitian cities cross sectional data in 2007. This paper especially estimates the impact of instrumental factor, such as history tracking system, provision of information, safety assurance and labelling of brands on the consumers' demand. The main results show that provision of information and safety assurance affect consumers' demand more confident than others. In order to motivate consumers to buy more environmentally friendly agricultural products, the safety should be assured and more information on production and marketing channel should be labelled.

• Journal of Applied Reliability
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• v.12 no.2
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• pp.91-103
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• 2012

Tubular markers for road safety facilities are used to lead the driver's sight line and separate the lanes on the road. Such tubular markers are usually installed on the road and frequently hit by vehicles, they are accordingly requested to assure the product durability. The traditional evaluation method of tubular markers include only quality tests of the material properties. However, most of consuming agencies in charge of road management at fields have proposed problems on long-term performance of the products hit by vehicles under various weather conditions. Therefore, the objectives of this study are to develop the reliability test methods and equipments to simulate the product failures of tubular markers due to vehicle collision and wheel compression and the delamination and discoloration of reflection sheets attached on the surface of the products under high and low temperatures.

• Journal of the Korean Operations Research and Management Science Society
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• v.18 no.2
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• pp.157-173
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• 1993

Reliability growth modeling can be a requirement when bidding on large military hardware systems. Under current reliability warranty legislature, the reliability growth model can be later translated into necessary reliability performance which must be demonstrated over an extended period of usage. In this paper the modeling situation is concerned with determining the number of spares needed to support a projected reliability growth both at the fightine and in a depot inventory. The model differs from existing models for logistics planning in that we allow for the phenomena of reliability growth. The model can also be used to determine central depot staffing requirements based upon a specified system utilization.