• 제어로봇시스템학회논문지
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• 제5권5호
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• pp.614-621
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• 1999

In this paper, the analytical appproaches are presented for jointly determining the profit-miximizing configuration of the fault-tolerance real time modular cell manufacturing system. The transient(time-dependent) analysis of Markovian models is firstly applied to modular cell manufacturing system from a performability viewpoint whose modeling advantage lies in its ability to express the performance that truly matters - the user's perception of it - as well as various performance measures compositely in the context of application. The modular cells are modeled with hybrid decomposition method and then availability measures such as instantaneous availability, interval availability, expected cumulative operational time are evaluated as special cases of performability. In addition to this evaluation, sensitivity analysis of the entire manufacturing system as well as each machining cell is performed, from which the time of a major repair policy and the optimal configuration among the alternative configurations of the system can be determined. Secondly, the recovery policies from the machine failures by computing the minimal number of redundant machines and also from the task failures by computing the minimum number of tasks equipped with detection schemes of task failure and reworked upon failure detection, to meet the timing requirements are optimized. Some numerical examples are presented to demonstrate the effectiveness of the work.

• 정보처리학회논문지A
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• 제13A권5호
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• pp.421-428
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• 2006

본 논문에서는 복잡해져 가는 제어 컴퓨터의 높은 신뢰성 확보를 위해 시간 여분(time redundancy)의 일종인 재실행과 rollback 기법을 TMR 구조에 적절하게 혼용하는 방법을 제안한다 재실행과 rollback 기법은 약간의 추가 시간만으로 재구성(reconfiguration) 없이도 일시적인 결함(fault)에 의해 발생한 TMR 고장(failure)의 회복을 위해 상호 보완적으로 사용될 수 있다. 이를 위해 고장 검출시 가능한 모든 시스템의 고장상태 확률을 추정하였으며, 이를 바탕으로 전체 작업의 평균 실행시간이 최소가 되는 최적의 재실행과 rollback 횟수를 유도하였다. 또한 제안된 방법과 다른 고장회복 기법을 적용했을 때의 평균 실행 시간을 정량적으로 비교하여 그 우수성을 검증하였다.

• Korea-Australia Rheology Journal
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• 제20권1호
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• pp.27-34
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• 2008

Clay suspensions in liquid polymers exhibit a time-dependent behaviour that includes viscoelastic as well as thixotropic features. Because of the presence of interacting clay platelets, particulate networks can develop, which are broken down during flow and rebuild upon cessation of the flow. Here, the use of thixotropic techniques in probing flow-induced structures in nanocomposites is explored with data on a hectorite-poly(isobutylene) model system. By means of fast stress jump measurements the hydrodynamic contributions to the steady state stresses are determined as well as those caused by the stretching of the clay floes. Flow reversal measurements do not provide a clear indication of flow-induced anisotropy in the present case. The recovery of the clay microstructure upon cessation of flow is followed by means of overshoot and dynamic measurements. The development of a particulate network is detected by the appearance and growth of a low frequency plateau of the storage moduli. The modulus-frequency curves after various rest times collapse onto universal master curves, regardless of the pre-shear history or temperature. The scaling factors for this master curve are the crossover parameters. The crossover moduli are nearly a linear function of the crossover frequency, the relation being identical for recovery after shearing at different shear rates. This function depends, however, on temperature.

• 한국정밀공학회지
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• 제22권7호
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• pp.62-70
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• 2005

The nanoindenter and AFM have been used for nanofabrication, such as nanolithography, nanowriting, and nanopatterning, as well as measurement of mechanical properties and surface topology. Nanoscale indents can be used as cells for molecular electronics and drug delivery, slots for integration into nanodevices, and defects for tailoring the structure and properties. Therefore, it is very important to make indents of desired morphology (shape, size and depth). Indents of different shapes can be obtained by using indenters of different geometries such as a cube comer and conical and spherical tips. The depth and size of indents can be controlled by making indentations at different indentation loads. However, in case of viscoplastic viscoelastic materials such as polymethylmethacrylate (PMMA) the time dependent deformation (TDD) should also be considered. In this study, the effect of process parameters such as loading rate and hold-time at peak load on the indent morphology (maximum penetration depth, elastic recovery, transient creep recovery, residual depth pile-up height) of PMMA were studied for hyperfine pattern fabrication.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.1066-1069
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• 2002

Dynamic postural control varies with the environmental context, specific task and intentions of the subject. In this paper, dynamic postural control against forward-backward perturbations of a platform was estimated using tri-axial accelerometers and a force plate. Ten young healthy volunteers stood upright in comfortable condition on the perturbation system which was controlled by an AC servo motor. With anterior-posterior perturbations, movements of ankle, knee and hip Joints were obtained by tri-axial accelerometers. and ground reaction forces with corresponding displacements of the center of pressure(CoP) by the force plate. The result showed that the ankle moved first and the trunk forward, which implies that the mechanism of the dynamic postural control in forward-backward perturbations, occurred in the procedure of the ankle, the knee and the hip. Knee flexion and hip extension in the period of acceleration, constant velocity and deceleration phase is very important fur the balance recovery. These responses depends on the magnitude and timing of the perturbation. From the present study the accelerometry-system appears to be a promising tool for understanding kinematic accelerative In response to a transient platform perturbation. A more through understanding of balance recovery mechanism may aid in designing methods for reducing falls and the resulting injuries.

• 대한전자공학회논문지TC
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• 제44권7호통권361호
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• pp.112-121
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• 2007

본 논문에서는 중복 구조 시스템을 이용하여 각 프로세서에서의 출력을 비교하여 효율적으로 고장을 탐지하고, 체크포인팅 기법을 적용하여 과도 고장뿐 아니라 영구적 고장을 극복하기 위한 방법을 제안한다. 매 체크포인터에서는 각 프로세서로부터의 출력과 과거 체크포인터에 저장된 데이터를 불러와 서로 비교한 후 과거 체크포인터로 회귀할지 태스크의 수행을 계속 수행할지 결정한다. 과도 고장과 영구 고장이 발생할 수 있는 상황에서 제안된 체크포인팅 기법을 탑재한 중복 구조 시스템을 마코프 모델을 이용하여 모델링한다. 마코프 모델로부터 실시간 태스크가 데드라인 이내에서 성공적으로 수행을 끝낼 확률을 계산하고, 이 확률식을 이용하여 중복구조 시스템에 탑재할 체크포인터 구간을 최적화한다. 최적화된 체크포인터 구간은 태스크의 성공적 수행 확율을 최대화 하도록 선정하였다.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.291-296
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• 2009

This paper investigates the energy saving potentials of a dedicated outdoor air system (DOAS) applied to a highrise apartment building. As for a typical $132-m^2$ apartment unit, two different HVAC systems; centralized DOAS-Ceiling Radiant Cooling Panel and decentralized Energy Recovery Ventilator-Packaged Air Conditioner were installed. Transient behavior and control characteristics of each system were modeled numerically using a commercial equation solver program, and annual cooling coil load and heating load reduction potentials were compared. The research shows that DOAS-Ceiling Radiant Cooling Panel system can reduce the cooling coil load over 21% annually compared with the current Energy Recovery Ventilator-Packaged Air Conditioner pair. In addition, over 40% of annual ventilation heating load can be reduced by use of DOAS.

• The Korean Journal of Physiology
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• 제11권2호
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• pp.23-31
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• 1977

It is Proposed in the Present study to investigate the effects of TTX intravenously or intrahypothalamically administered on the arterial blood pressure and respiration and also to explorc effect of intrahypothalamically administered TTX on the pressor responses to electrical stimulation in the hypothalamus. The results obtained are as follows; 1) The pressor responses to electrical stimulation in the hypothalamus were markedly reduced after administration of TTX. In the $0.01\;{\mu}g/kg$ of TTX administered group, the pressor responses were almost abolished in 6 minutes and there was no tendency toward recovery throughout the experiment. 2) In $0.01\;{\mu}g/kg$ of TTX administered group, the mean arterial blood pressure and heart rate-were gradually reduced while there was a transient increase in respiratory rate followed by slow recovery thereafter. On the other hand no changes in arterial blood pressure, heart rate an4 respiration were observed in $0.005\;{\mu}g/kg$ TTX administered group. 3) Following intravenous administration of $1\;{\mu}g/kg$ TTX, the arterial blood pressure and heart rate were slowly reduced by 60 minutes while no marked changes were found in respiration. From the results of present study it is strongly suggested that TTX exerts its depressant effect not only on peripheral nerves but also on central nervous system.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제10권2호
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• pp.173-178
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• 2007

목 적: 한국인 소아에서 양성 일과성 고인산분해효소 혈증(Benign transient hyperphosphatasemia, BTH)의 임상적 특징 및 자연 경과를 살펴보고자 하였다. 방 법: 2006년 6월부터 2007년 7월까지 분당서울대학교병원 소아과를 내원한 환아 중 Kraut 등의 진단기준에 따라 BTH로 진단된 17명의 의무기록과 검사결과를 후향적으로 분석하였다. 결 과: 총 17명의 환아 중 남아가 6명, 여아가 11명이었으며, 연령은 평균 26.9${\pm}$13.8개월(범위: 9~49개월)이었다. 동반된 질환으로는 감염성 질환이 52.9%로 가장 많았고, 계절적으로 9월에서 12월 사이에 더 높은 발생률을 보였다. 첫 내원 시 측정한 혈청 ALP는 평균 2500.2${\pm}$1165.1 U/L이었고, 모든 환아에서 7주 내에 혈청 ALP가 정상 또는 정상 상한치의 두 배 이내로 감소하였다. ALP isoenzyme 검사를 시행한 7명의 환아 중 3명에서 간 분획과 골 분획의 증가가 있었고, 4명은 골분획의 증가만을 보였다. 결 론: 한국인 소아에서 BTH의 임상적 특징 및 경과를 이해함으로써 ALP 상승 소견을 보이는 영유아에서 불필요한 진단적 검사들을 지양하며 임상 경과의 관찰을 통해 ALP 활성도의 정상화 여부를 확인하도록 하여야 한다.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제18권3호
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• pp.160-167
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• 2015

Purpose: We aimed to analyze the effectiveness and safety of low-dose midazolam and ketamine combination for upper gastrointestinal endoscopy (UGIE) in children. Methods: The study included the children (n=425, $10.78{\pm}3.81years$) who underwent UGIE for diagnostic purpose during 1 year period. All children were sedated with low dose midazolam (0.1 mg/kg) and ketamine (0.5 mg/kg) intravenously. Effectiveness of the sedation and complications during the procedure and recovery period were recorded. Results: Endoscopic procedure was successfully completed in 414 patients (97.4%; 95% confidence interval, 95.8-98.9). $Mean{\pm}standard$ deviation (SD) duration of procedure was $6.36{\pm}1.64minutes$ (median, 6.0 minutes; range, 4-12 minutes). Minor complications occurred during the procedure in 39.2% of the patients. The most common complication was increased oral secretion (33.1%). No major complications were observed in any patient. Age and Ramsay sedation scores of patients with complications during the procedure were lower than the others ($9.49{\pm}4.05years$ vs. $11.61{\pm}3.43years$, p=0.002 and $2.10{\pm}1.46$ vs. $4.37{\pm}1.16$, p=0.001). Mean recovery time was 22 minutes (range, 10-90 minutes; $mean{\pm}SD$, $25{\pm}12.32minutes$). Minor complications developed during recovery in 60.1% of the patients. The most common complication was transient double vision (n=127, 30.7%). Emergence reaction was observed in 5 patients (1.2%). Conclusion: The procedure was completed with high level of success without any major complication in our study. Combination of low-dose midazolam and ketamine is a suitable sedation protocol for pediatric endoscopists in UGIE.