• 한국정밀공학회지
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• 제13권2호
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• pp.62-66
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• 1996

Since 1980, Korea Research Institute of Standards and Science (KRISS) have performed 8 round robin tests in gauge block measurement in order to evaluate the measurement capability and the state of environment control of National Calibration and Test Institutions. Two sets of five gauge blocks (nominal size : 1, 3, 10, 25, 100 mm) having different thermal expansion coefficients for each set were circulated for the measurement, and the measurement results were collected and analyzed to evaluate the traceability to the standard of KRISS. The method and results of the test are presented.

• 센서학회지
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• 제4권1호
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• pp.43-50
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• 1995

고온에서 교정용 표준기로 사용되는 S형 열전대를 사용하여, 국내의 9개 고온분야 교정검사기관의 고온측정 능력을 순회교정을 통하여 평가하여 고온의 소급성 오차를 측정하였다. 참여기관 중 3개교정검사기관만이 열전대의 교정불확도인 ${\pm}0.5^{\circ}C$이내에서 한국표준과학연구원의 측정값과 일치하였으며, 나머지 6개 기관의 측정값은 규정된 불확도를 벗어났다. 각 측정값의 차이는 온도가 높아질수록 증가하여 비교측정점 중 가장 높은 온도인 금점에서 가장 큰 차이가 $2^{\circ}C$로 교정 불확도를 크게 벗어났다. 이 연구에서 측정된 국내 고온분야 교정검사기관의 소급성 오차는 $2.0^{\circ}C$ 이내였다.

• Structural Engineering and Mechanics
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• 제71권1호
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• pp.77-87
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• 2019

In this paper, the interaction between two neighboring tunnel has been investigated using PFC2D. For this purpose, firstly calibration of PFC was performed using Brazilian experimental test. Secondly, various configuration of two neighboring tunnel was prepared and tested by biaxial test. The maximum and minimum principle stresses were 0.2 and 30 MPa respectively. The modeling results show that in most cases, the tensile cracks are dominant mode of cracks that occurred in the model. With increasing the diameter of internal circle, number of cracks decreases in rock pillar also number of total cracks decreases in the model. The rock pillar was heavily broken when its width was too small. In fixed quarter size of tunnel, the crack initiation stress decreases with increasing the central tunnel diameter. In fixed central tunnel size, the crack initiation stress decreases with increasing the quarter size of tunnel.

• Smart Structures and Systems
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• 제25권4호
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• pp.433-446
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• 2020

In this paper the effect of confining pressure and tunnel depth on the ground vertical settlement has been investigated using particle flow code (PFC2D). For this perpuse firstly calibration of PFC2D was performed using both of tensile test and triaxial test. Then a model with dimention of 100 m × 100 m was built. A circular tunnel with diameter of 20 m was drillled in the middle of the model. Also, a rectangular tunnel with wide of 10 m and length of 20 m was drilled in the model. The center of tunnel was situated 15 m, 20 m, 25 m, 30 m, 35 m, 40 m, 45 m, 50 m, 55 m and 60 m below the ground surface. these models are under confining pressure of 0.001 GPa, 0.005 GPa, 0.01 GPa, 0.03 GPa, 0.05 GPa and 0.07 GPa. The results show that the volume of colapce zone is constant by increasing the distance between ground surface and tunnel position. Also, the volume of colapce zone was increased by decreasing of confining pressure. The maximum of settlement occurs at the top of the tunnel roof. The maximum of settlement occurs when center of tunnel was situated 15 m below the ground surface. The settlement decreases by increasing the distance between tunnel center line and measuring circles in the ground surface. The minimum of settlement occurs when center of circular tunnel was situated 60 m below the surface ground. Its to be note that the settlement increase by decreasing the confining pressure.

• Journal of Preventive Medicine and Public Health
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• 제46권2호
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• pp.74-81
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• 2013

Objectives: The objective of this study was to evaluate the performance of risk-adjusted mortality models for colorectal cancer surgery. Methods: We investigated patients (n=652) who had undergone colorectal cancer surgery (colectomy, colectomy of the rectum and sigmoid colon, total colectomy, total proctectomy) at five teaching hospitals during 2008. Mortality was defined as 30-day or in-hospital surgical mortality. Risk-adjusted mortality models were constructed using claims data (basic model) with the addition of TNM staging (TNM model), physiological data (physiological model), surgical data (surgical model), or all clinical data (composite model). Multiple logistic regression analysis was performed to develop the risk-adjustment models. To compare the performance of the models, both c-statistics using Hanley-McNeil pair-wise testing and the ratio of the observed to the expected mortality within quartiles of mortality risk were evaluated to assess the abilities of discrimination and calibration. Results: The physiological model (c=0.92), surgical model (c=0.92), and composite model (c=0.93) displayed a similar improvement in discrimination, whereas the TNM model (c=0.87) displayed little improvement over the basic model (c=0.86). The discriminatory power of the models did not differ by the Hanley-McNeil test (p>0.05). Within each quartile of mortality, the composite and surgical models displayed an expected mortality ratio close to 1. Conclusions: The addition of clinical data to claims data efficiently enhances the performance of the risk-adjusted postoperative mortality models in colorectal cancer surgery. We recommended that the performance of models should be evaluated through both discrimination and calibration.

• 한국항공우주학회지
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• 제36권12호
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• pp.1222-1228
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• 2008

㈜쎄트렉아이는 UAE의 EIAST와 함께 2008년 발사를 목표로 SI-200 표준버스시스템을 기반으로 하는 DubaiSat-1 비행모델을 개발하였다. DubaiSat-1 비행모델의 열제어계는 전력 소비의 최소화를 위해 수동 열제어를 기반으로 하되, 주요 부품에는 히터를 이용한 능동 열제어가 이뤄지도록 설계되었다. 또한 열해석 모델을 작성하여 DubaiSat-1의 임무궤도에 대해 열해석을 수행하였으며, 해석 결과를 토대로 모든 구성품이 설계 요구조건을 만족시킬 수 있도록 설계 보정 작업을 진행하였다. 또한 우주환경을 모사한 열진공시험을 수행하여 DubaiSat-1 비행모델의 열제어 성능에 대해 검토하였으며, 시험 결과와 해석 결과의 비교를 통한 열해석 모델의 보정 작업을 완료하였다.