• 품질경영학회지
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• 제35권4호
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• pp.61-66
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• 2007

The performance of a building material degrades as time goes by and the failure of the material is often defined as the point at which the performance of the material reaches a pre-specified degraded level. Based on a stochastic deterioration model, a performance based service life prediction method for building materials and components is developed. As a stochastic degradation model, a gamma process is considered and lifetime distribution and service life of a material are predicted using the degradation model. A numerical example is provided to illustrate the use of the proposed service life prediction method.

• 보건의료산업학회지
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• 제5권2호
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• pp.77-89
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• 2011

This study conducted a secondary analysis by using original data of performed by Korea Institute for Health and Social Affairs to know factors affecting determinants of health using Lalonde model for the adults aged over 19 years living in Korea. The survey was conducted in 2009 and it evaluated finally 5,867 cases by excluding cases with no answer or a wrong answer. This study model adopted two categories of instrument measure health were objective (Average remaining lifetime) and subjective(EQ-5D) health status. The health determinants included in this study could be divided in to four categories, which were human biology, environment, lifestyle, and health care organization. The results were as follows. In the factors affecting average remaining lifetime, human biology were sex, ages, BMI, showed statistically significant difference, environment category were merry status, education showed statistically significant difference, lifestyle category were exercise, drunks showed statistically significant difference and health care organization category were vaccination, health screening showed statistically significant difference. In the factors affecting EQ-5D, human biology category and health care organization category showed with same average remaining lifetime, environment category were merry status, education, income showed statistically significant difference and lifestyle category were exercise, drunks, stress showed statistically significant difference. The results demonstrated that the best powerful factor was life style category and environment category, the least factor was health care organization category. So lifestyle style and environment category should be considered for the future health plan, budget allocation and the priority in the health care.

• Industrial Engineering and Management Systems
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• 제8권4호
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• pp.221-227
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• 2009

There are customer services jointly provided by two facilities so that each customer will complete the course made up of both facilities' sub-services. The two facilities are assumed invested respectively by an infrastructure owner and one subordinate facility owner, whose partnership is built on their capital investments. This paper presents a mathematical model of Stackelberg competition between the two facility owners to derive their optimal Nash equilibrium. In this study, each facility owner's profit is consisted of fixed revenue fractions of sold services, operating costs (including depreciation cost) and maintenance costs of her facility. The maintenance costs of one facility are incurred both by failures and deterioration due to usage. Moreover, for both facilities, failures are rectified immediately by minimal repairs and preventive maintenance is carried out at a fixed time epoch. Additional assumptions are also employed to develop the model such as customer arrivals are manipulated to follow a Poisson process, and each facility's lifetime is independently Weibull-distributed. The Stackelberg game proceeds as follows. At the first stage of decision making process, the infrastructure owner (acting as a leader) decides the allocation of revenue shares based on her self-interest. After observing the allocation of revenue shares, the subordinate facility owner determines her own optimal price of services. This paper investigates actions and reactions of the two partners in the system. Then analytical conditions are proposed to achieve a unique optimal Nash equilibrium. Finally, some suggestions for further research are discussed.

• International Journal of Internet, Broadcasting and Communication
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• 제8권1호
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• pp.7-18
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• 2016

Several authentication methods have been developed to make use of tokens in the mobile networks and smart payment systems. Token used in smart payment system is genearated in place of Primary Account Number. The use of token in each payment transaction is advantageous because the token authentication prevents enemy from intercepting credit card number over the network. Existing token authentication methods work together with the cryptogram, which is computed using the shared key that is provisioned by the token service provider. Long lifetime and repeated use of shared key cause potential brawback related to its vulnerability against the brute-force attack. This paper proposes a per-transaction shared key mechanism, where the per-transaction key is agreed between the mobile device and token service provider for each smart payment transaction. From server viewpoint, per-transaction key list is easy to handle because the per-transaction key has short lifetime below a couple of seconds and the server does not need to maintain the state for the mobile device. We analyze the optimum size of the per-transaction shared key which satisfy the requirements for transaction latency and security strength for secure payment transactions.

• Carbon letters
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• 제28권
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• pp.9-15
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• 2018

In the aerospace field, Carbon/Cork composites have been used for rocket propulsion systems as a light weight structural component with a high bending stiffness and high thermal insulation properties. For the fabrication of a carbon composite with a heat insulation cork part, the bonding properties between them are very important to determine the service life of the Carbon/Cork composite structure. In this study, the changes in the interfacial adhesion and mechanical properties of Carbon/Cork composites under accelerated aging conditions were investigated. The accelerated aging experiments were performed with different temperatures and humidity conditions. The properties of the aged Carbon/Cork composites were evaluated mainly with the interfacial strength. Finally, the lifetime prediction of the Carbon/Cork composites was performed with the long-term property data under accelerated conditions.

• Journal of Information Processing Systems
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• 제15권4호
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• pp.833-852
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• 2019

In real time applications, due to their effective cost and small size, wireless networks play an important role in receiving particular data and transmitting it to a base station for analysis, a process that can be easily deployed. Due to various internal and external factors, networks can change dynamically, which impacts the localisation of nodes, delays, routing mechanisms, geographical coverage, cross-layer design, the quality of links, fault detection, and quality of service, among others. Conventional methods were programmed, for static networks which made it difficult for networks to respond dynamically. Here, machine learning strategies can be applied for dynamic networks effecting self-learning and developing tools to react quickly and efficiently, with less human intervention and reprogramming. In this paper, we present a wireless networks survey based on different machine learning algorithms and network lifetime parameters, and include the advantages and drawbacks of such a system. Furthermore, we present learning algorithms and techniques for congestion, synchronisation, energy harvesting, and for scheduling mobile sinks. Finally, we present a statistical evaluation of the survey, the motive for choosing specific techniques to deal with wireless network problems, and a brief discussion on the challenges inherent in this area of research.

• International Journal of Human Ecology
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• 제13권1호
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• pp.1-16
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• 2012

Information about the characteristics of street-living versus shelter-residing youth is vital for tailoring prevention and intervention efforts to the unique needs of runaway and homeless youth. The present study compared two samples of youth [street-living (n=73) versus shelter-residing (n=205)], between the ages of 14 to 17 years, on behavioral and emotional factors and service use. Based on the different characteristics of the two groups, the predictors explaining the living status of the runaways and homeless youth were explored. In general, street-living youth reported more severe substance use, depressive symptoms, and risky sexual behavior, but less lifetime service involvement compared to shelter-residing youth. The factors that predicted shelter-residing status were related to younger age, prior service care experience, more knowledge about HIV, and engaging in less delinquent and risky behavior. Given the little overlap among youth in service involvement and the greater severity faced by street-living youth, the conclusions highlight the need for increased funding and attention towards facilitating the ability of street-living youth to find and enter mental health and reintegration services.

• 한국건강관리협회지
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• 제2권3호
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• pp.97-116
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• 2004

Lifetime Health Maintenance Program(LHMP) for Koreans is the Korean guide to clinical preventive services which include screening for chronic diseases, counseling and immunization. The Korean Task Force on the LHMP vigorously reviews evidence for interventions to prevent over 50 different illnesses and conditions which are important in Korea. The problems addressed in this program are common ones seen every day by primary care physicians in Korea: cardiovascular, infectious diseases, gastrointestinal and endocrine diseases, cancers, alcohol and smoking, and many others. Primary care clinicians have a key role in screening for many of these problems and immunizing against others. Of equal importance, however, is the clinician's role in counseling patients to change unhealthful behaviors related to diet, smoking, exercise, injuries, and sexually transmitted diseases. The recommendations are grouped by age, sex, and other risk factors.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.7-12
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• 2004

A lifetime prediction of holddown spring screw in nuclear fuel assembly was performed using fracture mechanics approach. The spring screw was designed such that it was capable of sustaining the loads imposed by the initial tensile preload and operational loads. In order to investigate the cause of failure and to predict the stress corrosion cracking life of the screw, a stress analysis of the top nozzle spring assembly was done using finite element analysis. The elastic-plastic finite element analysis showed that the local stresses at the critical regions of head-shank fillet and thread root significantly exceeded than the yield strength of the screw material, resulting in local plastic deformation. Normalized stress intensity factors for PWSCC life prediction was proposed. Primary water stress corrosion cracking life of the Inconel 600 screw was predicted by using integration of the Scott model and resulted in 1.78 years, which was fairly close to the actual service life of the holddown spring screw.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2003년도 학술발표논문집
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• pp.359-362
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• 2003

This research deriving the lifetime distribution function of embank as one of main components in reservoir was carried out by mining the data of precise safety diagnosis in 1995 to 2001 as one of researches that were performed for determining the propriety for making item at design for planning and considering optimal maintenance strategy for service life through acquiring the system function of reservoir as main resource for irrigation and analyzing the life cycle cost of it.