• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.24 no.5
• /
• pp.531-542
• /
• 2011

The time-dependent temperature distribution across the section in bridges is determined on the basis of the three-dimensional finite element analyses and numerical time integration in this study. The material properties which change with time and thermal stress of concrete are taken into account to effectively trace the early-age structural responses. Since the temperature distribution is nonlinear and depends upon many material constants such as the thermal conductivity, specific heat, hydration heat of concrete, heat transfer coefficients and solar radiation, three representative influencing factors of the construction season, wind velocity and bridge pavement are considered at the parametric studies. The validity of the introduced numerical model is established by comparing the analytical predictions with results from previous analytical studies. On the basis of parametric studies for four different bridge sections, it is found that the creep deformation in concrete bridges must be considered to reach more reasonable design results and the temperature distribution proposed in the Korean bridge design specification need to be improved.

• Journal of Energy Engineering
• /
• v.24 no.1
• /
• pp.17-23
• /
• 2015

Electrical door system is one of the most essential items for the successful commercial operation of the railway vehicles. Nowadays, reliability values of electrical door system have a tendency to be included in technical requirements for design and manufacturing of rolling stocks. Manufacturer shall meet the reliability target values of electrical door system which is proposed by railway operator in procurement contract book. Railway operator shall approve the supplier's the reliability target values based on maintenance operation data. Railway operators are in the transition stage from the framework of maintenance interval based on time to the framework of maintenance interval based on distance. In this study, failure rates of the electrical door system currently used in railway vehicles are collected from maintenance field data. Failure rates are analyzed by using Minitab. Several kinds of plan for improving reliability are also suggested. It is necessary to keep studying on reliability prediction methodology, applying it in the field and implementing on improvement of reliability through feedback as well. Further, it will be useful for determining new maintenance policies or changing maintenance intervals for existing railway vehicles.

• Proceedings of the Korean Institute Of Construction Engineering and Management
• /
• 2008.11a
• /
• pp.885-890
• /
• 2008

Until now, the domestic construction market has been formed focusing on new construction and reconstruction in the apartment industry. Recently, however, the remodeling market for old structures have shown a tendency towards land shortage and land price increases in the major cities: the reinforcement of regulations regarding reconstruction; expenditure reduction and the solving of environmental problems by regarding old structures is pursuing low costs and maximum efficiency. The interest in remodeling is increasing, however, remodeling has not been successfully initiated in the apartment division for a reasonable period of time. Consequently to acquire mutual agreement for remodeling from the residential occupants. In order to evaluate profitability, it is necessary to set priorities and reasonable criteria for remodelling and to this end, it is also required to assess each fact of remodelling in view of both customers and supplied. Thus, a sample apartment housing complex was analyzed for geographic location, surrounding environment floor area ratio, site area, number of households, number of stories and unit area and thereupon, its remodelling profitability was analyzed to select an effective remodeling method as an alternative case for apartment house owners and remodelling.

• Explosives and Blasting
• /
• v.22 no.1
• /
• pp.57-65
• /
• 2004

Explosive blasting in tunnel excavation produces ground vibration and air blast as its side effects, which may cause complaints from nearby residents. This study was intended to investigate the propagation characteristics of ground vibration induced by tunnel blasting and to evaluate its effects on the residential structures near the site. We have conducted field measurements for 6 blasts and acquired vibration data from 70 measuring points, some of which on positioned inside the tunnel for comparative reason. Various documentation was reviewed to determine an allowable level of peak particle velocity for the residential structures in the area and the allowable limit was set to 0.5 cm/sec. Propagation equations for peak particle velocities were derived from regression analyses using the data acquired at both the surface and the underground tunnel. Finally we proposed appropriate predictive equations for the two areas and a safe blasting criterion.

• Journal of Energy Engineering
• /
• v.26 no.2
• /
• pp.1-11
• /
• 2017

While they are becoming more viable, synthetic natural gas (SNG) plants, with their high temperatures and pressures, are still heavily dependent on advancements in the state-of-the-art technologies. However, most of the current work in the literature is focused on optimizing chemical processes and process variables, with little work being done on relevant mechanical damage and maintenance engineering. In this study, a combination of pipe system stress analysis and detailed local stress analysis was implemented to prioritize the inspection locations for main pipes of SNG plant in accordance to ASME B31.3. A pipe system stress analysis was conducted for pre-selecting critical locations by considering design condition and actual operating conditions such as heat-up and cool-down. Identified critical locations were further analyzed using a finite element method to locate specific high-stress points. Resultant stress values met ASME B31.3 code standards for the gasification reactor and lower transition piece (bend Y in Fig.1); however, it is recommended that the vertical displacement of bend Y be restricted more. The results presented here provide valuable information for future risk based maintenance inspection and further safe operation considerations.

• Journal of Intelligence and Information Systems
• /
• v.4 no.2
• /
• pp.45-59
• /
• 1998

다양한 산업영역에서 수행되는 스케줄링 문제를 해결하기 위하여 AI분야에서는 지식을 기반으로한 방법이 적용되어 왔다. 그러나 최근 CSP(Constraints Satisfaction Problem) 개념이 소개되어 그 효율성이 입증되고 있으며 스케줄링 응용 문제들이 CSP로 정형화되면서부터 지식 기반 기법과 제약만족 기법의 적용이 공존하고 있다. 지식을 기반으로 한 방법은 도메인 전문가(domain expert)의 지식을 습득하여 시스템에 반영하는데 이러한 지식은 문제해결에 중심적 역할을 수행하게 된다. 제약조건을 기반으로 한 방법은 문제를 CSP로 정형화 한 후 제약조건에 따른 일관성 유지 및 휴리스틱 탐색 방법을 적용하여 문제의 해를 효율적으로 구하게 된다. 본 연구에서는 스케줄링 문제를 해결하기 위한 지식기반 기법과 제약만족 기법을 주기장 할당 문제에 적용하여 실제 항공사의 운항 데이터를 바탕으로 실험하고 분석 및 비교를 통해 제약 만족 기법이 시스템의 유지 및 보수 측면에서 효율적이며 근사해가 아닌 최적해를 통한 문제 해결이 가능함을 보였다.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.29 no.2
• /
• pp.109-120
• /
• 2017

A discounted cost model for preventive maintenance of armor units of rubble-mound breakwaters is mathematically derived by combining the deterioration model based on a discrete-time stochastic process of shock occurrence with the cost model of renewal process together. The discounted cost model of condition-based maintenance proposed in this paper can take into account the nonlinearity of cumulative damage process as well as the discounting effect of cost. By comparing the present results with the previous other results, the verification is carried out satisfactorily. In addition, it is known from the sensitivity analysis on variables related to the model that the more often preventive maintenance should be implemented, the more crucial the level of importance of system is. However, the tendency is shown in reverse as the interest rate is increased. Meanwhile, the present model has been applied to the armor units of rubble-mound breakwaters. The parameters of damage intensity function have been estimated through the time-dependent prediction of the expected cumulative damage level obtained from the sample path method. In particular, it is confirmed that the shock occurrences can be considered to be a discrete-time stochastic process by investigating the effects of uncertainty of the shock occurrences on the expected cumulative damage level with homogeneous Poisson process and doubly stochastic Poisson process that are the continuous-time stochastic processes. It can be also seen that the stochastic process of cumulative damage would depend directly on the design conditions, thus the preventive maintenance would be varied due to those. Finally, the optimal periods and scale for the preventive maintenance of armor units of rubble-mound breakwaters can be quantitatively determined with the failure limits, the levels of importance of structure, and the interest rates.

• Korean journal of food and cookery science
• /
• v.10 no.4
• /
• pp.394-404
• /
• 1994

본 실험은 1.5Kg 무게의 고기를 3가지 다른 내부온도(60$^{\circ}C$-rare, 70$^{\circ}C$-medium, 80$^{\circ}C$-well done)에 이르도록 3가지 다른 출력의 전자파(40%, 60%, 100%)로 조리시에 나타나는 고기의 조리조건(조리시간, 대기시간 및 대기시 상승온도)과 고거의 물리 화학적인 변화(수분, 단백질, 지방, vit $B_1$의 함량, 콜라겐의 용해도, 보수력, texture)를 관찰하였다. 각 처리구 간에 Kg당 조리시간은 유의적인 차이를 나타내었으나 대기시간은 유의적인 차이를 나타내지 않았다. 그러나 고기의 내부용도가 낮은 처리구일수록 긴 대기 시간이 요구되었다. 대기시 상승온도도 각 처리구 간에 유의적인 차이를 나타내지 않았으나 거의 모든 처리구에서 10도 이상의 상승온도가 관찰되었다. 고기의 내부온도가 상승할수록 조리시 중량손실도 증가되었고, 수분함량, 수분: 단백질의 비, 보수력, 비타민 $B_1$의 함량도 감소되었다. Texture를 측정한 항목들에서는 각 처리구간의 유의척인 차이를 나타내지 않았다. 콜라겐의 용해도는 각 처리구간에 유의적인 차이를 나타내지 않았으나 내부온도 60$^{\circ}C$와 70$^{\circ}C$ 처리구 사이의 용해도는 뚜렷한 증가가 관찰되었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2010.10a
• /
• pp.115-118
• /
• 2010

최근 RFID (Radio Frequency Identification)기술은 다양한 분야에서 관심을 받고 사용되고 있으며 RFID 리더의 종류도 매우 다양하다. 이러한 RFID 리더들을 지원하기 위해 RFID 미들웨어는 리더에서 지속적으로 발생하는 데이터를 수집, 제어, 관리하는 기능을 가지고 있으며 다양한 형태의 RFID 리더 인터페이스를 지원하여 이기종 RFID 리더와의 연동을 용이하게 한다. 현재 표준 규약에 따른 RFID 미들웨어들이 개발되고 있으며 RFID 표준 단체인 EPCglobal에서는 EPC (Electronic Product Code) 처리 시스템에서 RFID 태그를 인식한 리더가 애플리케이션 계층으로 데이터를 전달하는 역할을 하는 ALE (Application Level Events)라는 RFID 미들웨어를 제시하였다. 그러나 표준을 따르는 RFID 미들웨어는 그 자체가 복잡하고 부피가 크며 가격이 높기 때문에 이를 기반으로 한 시스템은 개발 속도가 늦어지고, 유지보수가 힘들어진다. 따라서 한 기업 내에서 사용되는 애플리케이션의 크기가 소규모 또는 중규모인 경우를 위해 보다 가벼운 RFID 미들웨어가 필요하다. 본 논문에서는 다양한 RFID 리더를 처리하기 위한 리더 매니저와 애플리케이션의 목적에 맞는 이벤트를 생성하는 쿼리 매니저를 가진 경량의 RFID 미들웨어를 개발하고자 한다. 리더 매니저는 RFID 리더를 관리하기 위한 추상 어댑터를 제공하고 리더 구성 XML 파일을 이용하여 RFID 리더를 관리한다. 쿼리 매니저는 질의 조건을 주기적으로 체크하는 스케줄러를 통해 RFID 이벤트를 관리한다. 본 경량적 RFID 미들웨어는 하드웨어의 투명성을 지원하며, 유지보수가 용이하고 유연성과 확장성을 제공하는 RFID 애플리케이션을 개발할 수 있도록 해준다.

• Korean journal of food and cookery science
• /
• v.10 no.2
• /
• pp.111-120
• /
• 1994

본 실험은 4가지의 다른 무게를 가진 고기(0.1kg,0.5kg, 1kg, 1.5kg)를, 3가지의 다른 출력의 전자파(40%, 60%, 100%)로 조리시 나타나는 조리조건(오븐의 효율성, 대기시간, 대기시 상승온도)과 물리 화학적인변화(수분, 단백질, 지방, vit B$_1$,의 함량, 콜라겐의 용해도, 보수력, texture)를 관찰하였다. 고기의 무게가 증가할수록 전자렌지의 효율성은 낮아졌으며, 단위 무게당 조리시간은 고기의 무게가 증가할수록 길어졌다. 화학적 성분들에 있어서는 지방과 콜라겐의 용해도를 제외하고는 처리구간에 유의적인 차이를 보이지 않았다. 지방과 콜라겐의 용해도는 전자파의 출력차이에 의한 유의적인 차이는 나타나지 않았으나, 고기 무게가 증가할수록 지방의 함량의 증가와 콜라겐의 용해도는 증가하였다. Texture를 측정한 항목들에 대해서는 고기의 무게에 따른 유의적인 차이는 나타나지 않았으나 전자파의 출력에 의한 차이를 나타내었다.