• 전기학회논문지
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• 제66권12호
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• pp.1689-1696
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• 2017

In this paper, the voltage measurement-based coordinated Voltage/VAR control (VMCVVC) algorithm for conservation voltage reduction(CVR) is proposed. The proposed algorithm has the purpose of enhancing the CVR effect through coordinated control of the voltage control devices such as the distributed energy resources and the load tap changer(LTC) transformers. It calculates the references of the voltage control devices such that the bus voltages are maintained at as close to the lower operation limit as possible. For this purpose, firstly, the distribution system is divided into LTC transformer control zones through topological search. Secondly, the reactive power references of the reactive power control devices are determined such that the voltage profile of the section is flattened. Finally, the tap references of the LTC transformers are calculated to lower the voltage profile. The effectiveness of the proposed algorithm is demonstrated through case studies using IEEE test network.

• 비파괴검사학회지
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• 제30권3호
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• pp.225-235
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• 2010

There are many types of the geometric transitions such as dent, bulge, protrusion, expansion, etc, on the inner and outer surfaces of heat exchanger tubes, steam generator tubes, and condenser tubes of nuclear power plants. Such geometric transition causes a local residual stress in heat exchanger tubes and acts as a structural factor accelerating the evolution of defects, in particular stress corrosion cracks. In the conventional eddy current test methods, the bobbin coil profilometry can provide 2-dimensional geometric information on the variation of the average inner diameter along the tube length, but the 3-dimensional distribution and the quantitative size of a local geometric transition existing in the tube cannot be measured. In this paper, a new eddy current probe, developed for the 3-dimensional profile measurement, is introduced and its superior performance is compared with that from the conventional bobbin coil profilometry for the various types of geometric transition. Also, the accuracy of the probe for the quantitative profile measurement is verified by comparing the results with that from the laser profilometry. It is expected that the new eddy current probe and techniques can be effectively used for an optimization of the tube expansion process, and the management of tubes with geometric transitions in service.

• Journal of Astronomy and Space Sciences
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• 제23권3호
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• pp.237-244
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• 2006

한국천문연구원에서 운영중인 9개의 GPS(Global Positioning System) 상시관측소 데이터를 이용하여 한반도 상공의 고도에 따른 전리층 내의 전자밀도 분포를 산출하였다. 전리층의 전자 밀도를 정밀하게 추정하기 위해 이중주파수(L1,L2) 데이터가 사용되었고, 2차원 총전자수(Total Electron Contents, TEC)값을 기반으로 정밀한 전자 밀도 분포를 얻을 수 있었다. 그리고 토모그래피 모델개발에 널리 사용되고 있는 Inversion 기법 중의 하나인 ART(Algebraic Reconstruction Technique) 알고리즘을 적용하였다. 본 연구에서는 지역적 GPS 관측망을 활용하여 시간에 따른 한반도 상공의 전자밀도 분포 유형을 제시하였고, GPS에 의한 전리층 재구성으로 얻어진 전자밀도 유형을 경험적 모델인 IRI-2001에 의해 계산된 값과 관측으로부터 얻어진 Ionosonde 관측값을 서로 비교하였다. 그 결과 GPS 재구성에 의한 전자밀도 분포 유형이 Ionosonde에 의한 관측값과 잘 일치하는 경향을 보였다.

• 대한원격탐사학회지
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• 제26권5호
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• pp.527-536
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• 2010

본 논문에서는 영상의 품질 지표인 GRD(Ground Resolved Distance) 측정에 있어서 인공표적만을 이용하던 기존의 측정방식과는 다르게 지표상에 분포하고 있는 자연표적만을 이용하여 신뢰성 있는 GRD 산출이 가능하도록 새로운 방식의 GRD 측정가법을 고안하였다. 자연표적에서 활용 가능한 Edge Profile 추출기법을 개발하여 추출 정확도 및 안정성을 분석하였으며 그 결과, 자연표적을 이용할 경우 본 논문의 추출방식이 가장 적합한 방식임을 확인 할 수 있었다. 이를 적용한 GRD 측정기법의 정확도와 자연 표적에서의 활용 가능성을 평가하기 위해 육안분석결과를 보유하고 있는 인공표적영상과 인공표적이 된 인공위성영상을 이용하여 GRD 측정 실험을 수행하였다. 인공표적영상에서의 GRD 측정결과는 육안분석 결과와 매우 유사하여 높은 정확도를 보여주었으며 인공위성영상에서의 GRD 측정결과, 자연표적과 인공표적에서의 GRD 측정값이 유사하게 나타났다. 이는 제안한 GRD 측정기법을 이용하여 자연표적만으로도 신뢰성 있는 GRD 측정이 가능함을 보여준다.

• 한국의학물리학회지:의학물리
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• 제31권4호
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• pp.163-171
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• 2020

Purpose: In this study, the accuracies of electron Monte Carlo (eMC) calculation algorithms were evaluated to determine whether electron beams were modeled by optional air profiles (APs) designed for each applicator size. Methods: Electron beams with the energies of 6, 9, 12, and 16 MeV for VitalBeam (Varian Medical System, Palo Alto, CA, USA) and 6, 9, 12, 16, and 20 MeV for Clinac iX (Varian Medical System) were used. Optional APs were measured at the source-to-detector distance of 95 cm with jaw openings appropriate for each machine, electron beam energy, and applicator size. The measured optional APs were postprocessed and converted into the w2CAD format. Then, the electron beams were modeled and calculated with and without optional APs. Measured profiles, percentage depth doses, penumbras with respect to each machine, and energy were compared to calculated dose distributions. Results: For VitalBeam, the profile differences between the measurement and calculation were reduced by 0.35%, 0.15%, 0.14%, and 0.38% at 6, 9, 12, and 16 MeV, respectively, when the beams were modeled with APs. For Clinac iX, the differences were decreased by 0.16%, -0.31%, 0.94%, 0.42%, and 0.74%, at 6, 9, 12, 16, and 20 MeV, respectively, with the insertion of APs. Of note, no significant improvements in penumbra and percentage depth dose were observed, although the beam models were configured with APs. Conclusions: The accuracy of the eMC calculation can be improved in profiles when electron beams are modeled with optional APs.

• Investigative Magnetic Resonance Imaging
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• 제16권1호
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• pp.6-15
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• 2012

목적: 이 연구의 목적은 excitation pulse profile을 이용하여 불균일 자장에 의하여 발생하는 배경 경사 자장에 의한 영향을 보상하여 2차원 다중 단면 경사에코 간 영상에서의 정확한 지방 및 $T_2{^*}$ 측정을 하는 데에 있다. 대상과 방법: 2차원 경사에코영상에서 불균일 자장에 의한 배경경사자장으로 인하여 유도되는 신호의 감소는 excitation pulse profile weighting으로 나타난다. 이에 의한 영향을 최소화 하기 위하여 $B_0$ field map을 통하여 단면선택방향으로의 선형 경사자장의 정도를 추정한 후, 획득한 신호를 excitation pulse profile을 이용하여 보정하였다. $T_2{^*}$ 및 지방은 보정된 신호로부터 측정되었으며 보정방법은 3.0T 임상용 장비에서 팬텀 및 in vivo 실험을 통하여 이루어 졌다. 결과: 팬텀 실험 결과는 보정 후 측정된 $T_2{^*}$ 및 지방의 양이 자장이 균일한 경우에 가까워 진 것을 보여 주었다. In vivo 실험에서는 간에서 배경경사자장의 크기가 약 120 ${\mu}T/m$ 정도 까지로 나타났으며 보정하기 전에 비하여 측정된 $T_2{^*}$ 및 지방의 정도의 균일도가 높아지는 것을 확인할 수 있었다. 결론: Excitation pulse profile을 이용한 배경경사자장 보정 방법은 경사 에코 신호에서의 거시적인 불균일 자장에 의한 영향을 줄여 주며 2차원 간 영상에서의 적용을 통하여 보다 정확한 지방 및 $T_2{^*}$의 측정에 도움이 될 수 있다.

• 대한기계학회논문집A
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• 제26권3호
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• pp.537-543
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• 2002

This paper examines a new in-process measurement system for the measurement of micro-defects on the surfaces of brittle materials by using the AFM (Atomic Force Microscopy). A new AFM scanning stage that can also perform nano-scale bending of the sample was developed by adding a bending unit to a commercially available AFM scanner. The bending unit consists of a PZT actuator and sample holder, and can perform static and cyclic three-point bending. The true bending displacement of the bending unit is approximately 1.8mm when 80 volts are applied to the PZT actuator. The frequency response of the bending unit and the stress on the sample were also analyzed, both theoretically and experimentally. Potential surface defects of the sample were successfully detected by this measurement system. It was confirmed that the number of micro-defects on a scratched surface increases when the surface is subjected to a cyclic bending load.

• 한국유체기계학회 논문집
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• 제2권2호
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• pp.19-26
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• 1999

Thermal output in a nuclear power plant is verified with calorimetric heat balance on the secondary plant. The calorimetry involves the precise measurement of the feedwater flow rate. However, the correct indication of feedwater flow rate obtained by a pressure-difference measurement across a venturi can be affected by instrument errors, fouling or a poorly developed velocity profile. This can result in an inaccurate mass flow rate and consequently an inaccurate estimate of power. The purpose of this study is to develop verification methods with accuracy better than $0.5\%$ for high precision flow measurement to be used for measuring feedwater flow rate. This chemical tracer method is a testing process that uses tracers which can be applied to quantify losses in electrical output due to the incorrect measurements of feedwater flow rate. And this system has good response to the variation of the flow rate. Accuracy of better than 0.5 percent can be expected for feedwater flow measurement, providing that the system can be stabilized during the test. This methodology is applicable to other flow systems well.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제14권1_2호
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• pp.54-64
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• 1992

The balance of facial sop tissue is important factor for the treatment of maxillofacial deformity patients. There are many cephalometric analysis of facial bone but a few soft tissue analysis of face for the orthognathic surgery, especially in the oriental people. This study aimed at examining the mean value of the soft tissue measurement of 120 Korean adult women with the linear and angular measurement and comparing with Caucasian. The results ere as follows. 1. In the frontal linear measurement, Korean women have larger interocular distant and width of nose, but the width of mouth appeared less than Caucasian. 2. In the frontal angular measurement, Korean women have larger inclination of the eye than Caucasian. 3. In the lateral linear measurement, Korean women have more prominent upper and lower lip position than Caucasian and have longer upper facial height comparing with lower facial height than Caucasian. 4. In the lateral angular measurement, Korean women have more convex facial profile and less nasolabial and geniolabial angle. 5. In the lateral facial ratio, Korean women have larger proportion in the lower department below the stomion.

• 한국자동차공학회논문집
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• 제24권2호
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• pp.242-254
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• 2016

This paper is the forth investigation on the evaluation methods of flow characteristics in a steady flow bench. In the previous works, it was concluded that the assumption of the solid rotation might cause serious problems and both of the eccentricity and the velocity profile distort the flow characteristics when using the ISM at 1.75B plane. Also particle image velocimetry (PIV) measurement at this position showed that the real velocity profile was far from the assumption of ISM evaluation. In this paper, the planar velocity profiles were measure from 1.75B to 6.00B position by PIV and the characteristics were examined according to the valve angles and lifts for further investigations about the effect of the position on the velocity profile. The results show that $26^{\circ}$ valve angle is always an unique exceptional case in all aspects. If the valve angle is $21^{\circ}$ and below, the planar velocity profiles according to the lift and the position are similar to each other, however, the tangential velocity curves along with the radial direction have common tendencies up to $16^{\circ}$ angle. Also the well arranged swirl behaviors are generally observed at the position above 3.00B and the velocity contour lines come closer to the concentric circle as the valve lift increases. In addition, the gradient of tangential velocity along with the radial direction from the swirl center becomes stable and constant as the position goes downstream. Concurrently the velocity gradient is larger to the eccentric direction of the center. In the meantime the tangential velocity curves along with the radial direction are irregular and various at 1.75B, however, they become regular and reach higher level as the evaluation position goes downstream. At this time the curves of 4.50B are the best fitted to the ideal one. On the other hand in an exceptional case, $26^{\circ}$, the velocity contours are very complicated over 6mm valve lift regardless the position and the gradient increases to the opposite direction of the eccentric center. Also, 6.00B is a best fitting position in the geometrical cylinder center base. With respect to the swirl center, the distribution range of centers for 1.75B is different to that for the other positions and the eccentricities of this plane are larger regardless the valve angle. After 1.75B, there is no certain tendency in the center position change according to the valve angle and lift. Additionally, the eccentricities are not sufficiently small to neglecting the effect on ISM measurement.