• 한국정보과학회논문지:정보통신
• /
• 제30권5호
• /
• pp.641-648
• /
• 2003

본 논문은 가변 패킷을 사용하는 일반적인 망에서 실시간 세션이 이종의 여러 스케줄러들을 통과할 때 네트워크가 보장하는 지연의 한계를 추출하는 범용 도구를 제안한다. 이 도구는 이질적인 각 스케줄러를 동질적인 서비스 곡선 서버로 특성화한다. 우리는 서비스 곡선 서버가 LR 서버보다 엄격히 큰 범주의 스케줄러들을 특성화할 수 있음을 보인다 즉, 모든 LR 서버는 서비스 곡선 서버로 특성화할 수 있고, 또한 RC-EDF와 SC 알고리즘조차도 서비스 곡선 서버로 정확히 특성화할 수 있음을 보인다. 이와 같이 서비스 곡선 서버는 LR 서버에 비해서 범용성 관점에서 큰 장점이 있으면서도 분석 결과가 정확하다. 우리는 LR 서버들로 분석할 수 있는 네트워크의 경우도 서비스 곡선 서버로 분석했을 때, 두 경우 모두 동일한 지연의 한계를 추출함을 수학적으로 증명한다.

• 한국정보과학회논문지:정보통신
• /
• 제30권4호
• /
• pp.535-544
• /
• 2003

통합 서비스망은 실시간 응용들에게 고품질의 서비스를 제공하기 위해서 종단간 지연의 한계를 보장해야 한다. 이러한 보장 서비스는 라우터의 출력 포트에 설치되는 실시간 스케줄러에 의해서 제공된다. 그러나 현재까지 연구된 스케줄링 알고리즘들은 네트워크 유용도 혹은 확장성(scalability)에 문제점을 갖고 있다. 여기서 네트워크 유용도는 얼마나 많은 실시간 세션들을 승인할 수 있는 지를 의미한다. 본 논문은 서비스 곡선 알고리즘에서 높은 네트러크 유용도와 확장성 양쪽을 모두 성취할 수 있는 서비스 곡선 할당 방식을 제안한다. 서비스 곡선 알고리즘의 가장 큰 특징은 서비스 곡선 할당 방식에 따라서 네트워크 유용도와 확장성 모두가 결정된다는 점이다. 일상적인 믿음과 반대로, 데드라인을 계산할 때 전체 서비스 곡선이 아닌 일부만이 사용됨을 증명한다. 이 사실로부터 우리는 데드라인을 계산하는 비용이 상수 시간인 서비스 곡선 할당 방식을 제안한다. 또한, 수치결과를 통해서 제안하는 방식이 mutirate 알고리즘을 포함한 GPS 알고리즘들보다 더 높은 네트워크 유용도를 성취함을 보인다. 우리가 아는 한, 서비스 곡선 알고리즘이 제안하는 서비스 곡선 할당 방식을 채용하면 동일한 확장성을 갖는 스케줄링 알고리즘들 중에 가장 놀은 네트워크 유용도를 성취한다.

• 대한화학회지
• /
• 제59권6호
• /
• pp.508-519
• /
• 2015

본 연구에서는 개념 질문지를 사용하여 퍼텐셜 에너지 곡선에 대한 예비 화학 교사들의 이해 정도를 조사하였다. 조사 대상은 화학교육을 전공하는 사범대학 3학년 학생 24명, 4학년 학생 26명으로 총 50명이었다. 개념 질문지는 구슬 두 개의 거리에 따른 퍼텐셜 에너지 변화 곡선을 주고 상상실험을 하는 것으로 구성하였다. 질문지의 응답을 분석한 결과 예비 화학 교사들은 퍼텐셜 에너지나 전체 역학적 에너지가 음의 값을 가지는 것을 받아들이기 어려워하였다. 또한 역학적 에너지 보존은 대부분 알고 있었으나 이를 상상실험의 조건에 제대로 적용하지 못하는 것으로 나타났다. 그리고 구슬에 작용하는 힘의 방향은 대체로 알고 있었으나, 초기 위치에서 구슬이 이동하여 퍼텐셜 에너지가 가장 낮은 우물 바닥에서 정지할 것이라는 응답이 상당히 많았다. 또한 퍼텐셜 에너지 곡선과 관련지어 화학 결합, 기체의 액화, 분자의 진동 운동에 대한 이해도가 매우 낮은 것으로 드러났다.

• 한국통신학회논문지
• /
• 제39B권8호
• /
• pp.518-527
• /
• 2014

본 연구는 유선통신 서비스 상품별 고객 불만(Voice of Customer) 감소에 따른 학습곡선을 추정 하고자 한다. 학습곡선모형 중 가장 일반적인 지수감소모형(Exponential decay model)을 사용하여 시간에 따라 고객 불만(VOC)이 감소하는지를 검증하였다. 그리고 통신사들의 서비스 상품의 인력투입, 소프트웨어 적용, 투자 등의 노력에 따른 고객 불만(VOC) 변화효과를 추가로 검증하였다. 서비스 상품별 실증 분석의 결과는 다음과 같다. 첫째, 학습곡선대로 시간에 따라 고객 불만(VOC)이 감소하였다. 둘째, 초고속 인터넷, 전화, IPTV 등은 인력투입, Network 장애, 계절요인으로 인해 고객 불만(VOC)을 증가 시키거나 감소 시켰다. 셋째, 서비스 상품별 다양한 변수는 고객의 체감 품질을 높이고 있지만, 오히려 지속적으로 감소하지 않는 서비스 패러독스(Service Paradox)현상이 발생하는 것을 알 수 있었다.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2008년도 추계학술대회 논문집
• /
• pp.897-904
• /
• 2008

The major objective of this study is to investigate the effective improvement plan for the curve sections in the conventional lines which the tilting train runs on. In order to the speed-up of conventional lines that have many curve lines, there needs a improvement construction of substructure such as the straight or double track work and so on. But in this case, it needs to have a plenty of the cost and the period. Therefore, the tilting train which provides the high-speed service effectively in curve tracks and is operating at abroad, was been studying to be suited to natural features. So, in this paper we investigate the improvement method at the sections only where need the extension of the transition curves, and the present status of them for the effective tiling train service using results which were examined on the preceding study which was the development of track system innovation technology for speed-up of them. And we look forward to playing a decisive role as reference material for the decision of the linear fitness in order to operate effectively on the conventional lines for the commercial service of the tilting train, on the basis of checking out the sufficient condition concerned in the track alignment and the velocity which are required in the railway construction rules and the design criteria.

• 산업경영시스템학회지
• /
• 제46권1호
• /
• pp.84-90
• /
• 2023

ASL estimation of public building is based on how appropriate the maximum age of the asset is derived based on the age record of the asset in the statistical data owned by public institutions. This is because we get a 'constrained' ASL by that number. And it is especially true because other studies have assumed that the building is an Iowa curve R3. Also, in this study, the survival rate is 1% as the threshold value at which the survival curve and the predictable life curve almost coincide. Rather than a theoretical basis, in the national statistical survey, the value of residual assets was recognized from the net value of 10% of the acquisition value when the average service life has elapsed, and 1% when doubling the average service life has elapsed. It is based on the setting mentioned above. The biggest constraint in fitting statistical data to the Iowa curve is that the maximum ASL is selected at R3 150%, and the 'constrained' ASL is calculated by the proportional expression on the assumption that the Iowa curve is followed. In like manner constraints were considered. First, the R3 disposal curve for the RCC(reinforced cement concrete) building was prepared according to the discarding method in the 2000 work, and it was jointly worked on with the National Statistical Office to secure the maximum amount of vintage data, but the lacking of sample size must be acknowledged. Even after that, the National Statistical Office and the Bank of Korea have been working on estimating the Iowa curve for each asset class in the I-O table. Another limitation is that the asset classification uses the broad classification of buildings as a subcategory. Second, if there were such assets with a lifespan of 115 years that were acquired in 1905 and disposed of in 2020, these discarded data would be omitted from this ASL calculation. Third, it is difficult to estimate the correct Iowa curve based on the stub-curve even if there is disposal data because Korea has a relatively shorter construction history, accumulated economic wealth since the 1980's. In other words, "constrained" ASL is an under-estimation of its ASL. Considering the fact that Korea was an economically developing country in the past and during rapid economic development, environmental factors such as asset accumulation and economic ability should be considered. Korea has a short period of accumulation of economic wealth, and the history of 'proper' architectures faithful to building regulations and principles is short and as a result, buildings 'not built properly' and 'proper' architectures are mixed. In this study, ASL of RCC public building was estimated at 70 years.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2000년도 춘계학술대회논문집A
• /
• pp.7-12
• /
• 2000

The automatic turbine startup system provides turbine control based on thermal stress. During the startup, control system monitors and evaluates main components of turbine using damage mechanism and life assessment. In case of valve chest, the temperature of inner/outer wall is measured by thermo-couples and the safety of these values are evaluated by using allowable ${\Delta}T$ limit curve during the startup. Because allowable ${\Delta}T$ limit curve includes life assessment, it is possible to apply this curve to turbine control system. In this paper, low cycle fatigue damage and combined rupture and low cycle fatigue damage criterion proposed for yielding the allowable ${\Delta}T$ limit curve of CV(control valve) chest. To calculate low cycle fatigue damage, the stress analysis of valve chest has peformed using FEM. Automatic turbine startup to assure service life of CV was achieved using allowable ${\Delta}T$ limit curve.

• Nuclear Engineering and Technology
• /
• 제56권1호
• /
• pp.1-8
• /
• 2024

In this study, the influence of thermal aging on structural integrity is investigated for Gr. 91 steel. A commercial grade Gr. 91 steel is used for the virgin material, and service-exposed Gr. 91 steel is sampled from a steam pipe of a super critical plant. Time versus creep strain curves are obtained through creep tests with various stress levels at 600 ℃ for the virgin and service-exposed Gr. 91 steels, respectively. Based on the creep test results, the improved Omega model is characterized for describing the total creep strain curve for both Gr. 91 steels. The proposed parameters for creep deformation model are used for predicting the steady-state creep strain rate, creep rupture curve, and stress relaxation. Creep-fatigue damage is evaluated for the intermediate heat exchanger (IHX) in a large-scale sodium test facility of STELLA-2 by using creep deformation model with proposed creep parameters and creep rupture curve for both Gr. 91 steels. Based on the comparison results of creep fatigue damage for the virgin and service-exposed Gr. 91 steels, the thermal aging effect has been shown to be significant.

• 대한기계학회논문집A
• /
• 제26권1호
• /
• pp.1-6
• /
• 2002

The automatic turbine startup system provides turbine control based on thermal stress. During the startup, control system monitors and evaluates main components of turbine using damage mechanism and life assessment. In case of valve chest, the temperature of inner/outer wall is measured by thermo-couples and the safety of these values are evaluated by using allowable △T limit currie during the startup. Because allowable ΔT limit curve includes life assessment, it is possible to apply this curve to turbine control system. In this paper, low cycle fatigue damage, combined rupture and low cycle fatigue damage criterion were proposed for yielding the allowable ΔTf limit curve of CV(control valve) chest. To calculate low cycle fatigue damage, the stress analysis of valve chest has been performed using FEM. Automatic turbine startup to assure service life of CV was achieved using allowable ΔT limit curve.

• Steel and Composite Structures
• /
• 제50권3호
• /
• pp.363-374
• /
• 2024

The fatigue life of steel wire is affected not only by fatigue load, but also by corrosion environment in service period. Specially, the corrosion pit will lead to stress concentration on the surface of steel wire inducing the formation of fatigue cracks, and the fatigue cracks will accelerate the corrosion process. Therefore, the corrosion fatigue of steel wire is a coupling effect. In this study, the corrosion-fatigue coupling life curve is derived with considering corrosion-fatigue pitting stage, corrosion-fatigue short crack stage and corrosion-fatigue long crack stage. In addition, the stress concentration factors of different corrosion pits are calculated by COMSOL software. Furthermore, the effect of corrosion environment factors, that is, corrosion rate, corrosion pit morphology, frequency and action factor of fatigue load, on fatigue life of steel wire is analyzed. And then, the corrosion-fatigue coupling life curve is compared with the fatigue life curve and fatigue life curve with pre-corrosion. The result showed that the anti-fatigue performance of the steel wire with considering corrosion-fatigue coupling is 68.08% and 41.79% lower than fatigue life curve and fatigue life curve with pre-corrosion. Therefore, the corrosion-fatigue coupling effect should be considered in the design of steel wire.