• Journal of Mechanical Science and Technology
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• 제14권9호
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• pp.985-996
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• 2000

The issue of quench is related to safety operation of large-scale superconducting magnet system fabricated by cable-in-conduit conductor. A numerical method is presented to simulate the thermal hydraulic quench characteristics in the superconducting Tokamak magnet system, One-dimensional fluid dynamic equations for supercritical helium and the equation of heat conduction for the conduit are used to describe the thermal hydraulic characteristics in the cable-in-conduit conductor. The high heat transfer approximation between supercritical helium and superconducting strands is taken into account due to strong heating induced flow of supercritical helium. The fully implicit time integration of upwind scheme for finite volume method is utilized to discretize the equations on the staggered mesh. The scheme of a new adaptive mesh is proposed for the moving boundary problem and the time term is discretized by the-implicit scheme. It remarkably reduces the CPU time by local linearization of coefficient and the compressible storage of the large sparse matrix of discretized equations. The discretized equations are solved by the IMSL. The numerical implement is discussed in detail. The validation of this method is demonstrated by comparison of the numerical results with those of the SARUMAN and the QUENCHER and experimental measurements.

• 한국의류학회지
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• 제24권6호
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• pp.895-906
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• 2000

The study planned to testify the accuracy of the 3D scanner through analyzing the human body measurement method and the evaluation of flare skirt with 3D scanner. The results obtained from this study were as follows; First, the results of measurement for the dress form and human body by 3D scanner were more accurate than one or two dimensional measurement method. Second, from the results of the scan for the flare skirts as worn the human body, we could obtain very accurate horizontal section map. Third, in the clothing ergonomics viewpoint, the accuracy of the 3D scanner was very excellent and its utility was higher than that of the moir photography method. Therefore, the 3D scanner is very useful for the human body measurement and the wearing evaluation. In a nutshell, this study illustrates that we have to develop a program of automatic human body measurement system which will enhance the application of the 3D scanner.

• 한국치위생학회지
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• 제19권6호
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• pp.1089-1097
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• 2019

Objectives: The purpose of this study is to assess the accuracy of provisional restorative resins fabricated using dental three-dimensional (3D) printers. Methods: Provisional restorative resins were fabricated using the first molar of the right mandibular. Three groups comprising a total of 24 samples of such resins were fabricated. The prepared abutment was scanned initially and then designed using a computer-aided design (CAD) software. The conventional subtractive manufacturing system was employed to fabricate the first group of resins, while the second and third groups were fabricated using a digital light processing (DLP) 3D printer and a stereolithography (SLA) 3D printer, respectively. The internal surfaces of the resins were scanned and 3D measurements of the resins were taken to confirm their accuracy. Results: The root-mean-square deviation (RMS±SD) of the accuracy of the resins fabricated using the conventional subtractive manufacturing system, DLP 3D printer, and SLA 3D printer were 68.83±2.22 ㎛, 74.63±6.23 ㎛, and 61.74±4.09 ㎛, respectively. A one-way analysis of variance (ANOVA) test showed significant differences between the three groups (p < 0.05). Conclusions: Provisional restorative resins fabricated using DLP and SLA 3D printers demonstrated clinically-acceptable results.

• 한국수산과학회지
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• 제15권2호
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• pp.154-160
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• 1982

1) 수-단백질-지질의 3성분계 식품으로서 '두부'를 선택하여 일차원 비정상 열전도에 관한 실험을 행하였다. 두부는 불균질계 물질이지란 '유효'한 개념을 도입하여 유효열확산율을 측정함으로써 수학적으로 균질계 물질로 취급이 가능했다. 2) 저자가 고안 제작한 장치의 성능(performance)및 정도를 검토하기 위하여 표준물질로서 toluene은 물론 얼음(빙)의 열확산율을 측정한 결과, $-5\sim-25^{\circ}C$의 온도역에서 문헌치와 비교하여 재현성 $\pm1.5\%$, 오차 $-2\%$ 정도로 그 신뢰도는 매우 높았다. 3) 경계조건이 경시적으로 변화하는 경우라 찰지라도 Crank-Nicolson's implicit method를 이용하여 열확산율을 구할 수 있는 computer program을 개발했다. 4) 성분조성이 각각 상이한 3종류의 두부의 열확산율을 측정한 결과, 그 양들은 수분, 단백질 및 지질의 각 성분 함량의 분율에 정확하게 의존하고 있음을 보여 주었다.

• Journal of Mechanical Science and Technology
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• 제16권9호
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• pp.1147-1155
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• 2002

Discharge flows from a centrifugal pump impeller with a specific speed of 150 [rpm, m$^3$/min, m] were experimentally investigated. A large axisymmetric collector instead of a volute casing was installed to obtain circumferentially uniform flow, i.e. without interaction of the impeller and the volute. The unsteady flow was measured at the impeller exit and vaneless diffuser using a hot film probe and a pressure transducer. The flow at impeller exit showed pronounced jet-wake flow patterns. The wake, which was on the suction/hub side at high flow rate, became enlarged pitchwisely on both the hub and the shroud side as the flow rate decreases. The pitchwise non-uniformity of the flow rapidly decreased along the downstream and the non-uniformity almost disappeared at radius ratio of 1.18 for medium flow rate. The mean vaneless diffuser flow was reasonably predicted using a one dimensional analysis when an empirical constant was used to specify the skin friction coefficient. The data can be used for a centrifugal pump impeller design and validation of CFD codes and flow modeling.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2007년도 추계 종합학술대회 논문집
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• pp.30-34
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• 2007

레이저는 단시간에 높은 정밀도로 다량의 측정을 행할 수 있는 장점을 지니며, 이의 구체적인 실현이 지상 LiDAR라고도 불리는 지상레이저 스캐너이다. 본 논문에서는 Z-F 레이저시스템을 사용하여 대상물의 3차원 레이저 측정, Point 데이터의 생성, Registration & Merging, Polygon 데이터의 생성, Surface 데이터 생성의 과정을 거쳐 수행된 고건축물의 3차원 모델링 결과에 대하여 기술한다. 문화재의 보존 및 복원을 위한 자료 기록 및 측정에 있어서 지상 레이저스캐너를 사용한 고건축물의 데이터베이스 구축기술은 문화유산의 복원 및 관련분야에 커다란 영향력으로 자리매김할 수 있을 것으로 사료된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.185-188
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• 2002

The objective of present paper is to apply a stereoscopic PIV(Particle Image Velocimetry) techiique for measuring the 3 dimensional flow structure of turbulent wake behind a marine propeller with 5 blades. It is essential to measure 3-components velocity fields for the investigation of complicated near-wake behind the propeller. The out-of-plane velocity component was measured using the particle images captured by two CCD cameras in the angular displacement configuration.400 instantaneous velocity fields were measured for each of few different blade phases of $0^{\circ},\;18^{\circ},\;36^{\circ}\;and\;54^{\circ}$. They were ensemble averaged to investigate the spatial evolution of the propeller wake in the region ranged from the trailing edge to the region of one propeller diameter(D) downstream. The phase-averaged velocity fields show the viscous wake formed by the boundary layers developed along the blade surfaces. Tip vortices were formed periodically and the slipstream contraction occurs in the near-wake region. The out-of-plane velocity component has large values at the tip and trailing votices. With going downstream, the axial turbulence intensity and the strength of tip vortices were decreased due to the visous dissipation, turbulence diffusion and blade-to-blade interaction. The blade wake traveling at higher speed with respect to the tip vortex overtakes and interacts with tip vortices formed from the previous blade. Tip vortices are separated from the wake and show oscillating trajectory

• 대한기계학회논문집B
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• 제30권4호
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• pp.287-297
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• 2006

The Holographic Particle Velocimetry system can be a promising optical tool for the measurements of three dimensional particle velocities. One of inherent limitations of particle holography is the very long depth of field of particle images, which causes considerable difficulty in the determination of particle positions in the optical axis. In this study, we introduced three auto-focusing parameters corresponding to the size of particles, namely, Correlation Coefficient, Sharpness Index, and Depth Intensity to determine the focal plane of a particle along the optical axis. To investigate the suitability of the above parameters, the plane image of dot array screens containing different size of dots was recorded by diffused illumination holography and the positions of each dot in the optical axis were evaluated. In addition, the effect of particle position from the holographic film was examined by changing the distance of the screen from the holographic film. All measurement results verified that the evaluated positions using suggested auto-focusing parameters remain within acceptable range of errors. These research results may provide fundamental information for the development of the holographic velocimetry system based on the automatic image processing.

• 대한치과의사협회지
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• 제17권9호통권124호
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• pp.701-708
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• 1979

A series of combined impressions, alginate impressions and rubber base impression made of the lower left quadrant of one subject having a cast gold crown with six reference marks on lower let 1st molar. the combined impressions of hydrocolloid were removed from the mouth at 2.5min, after the insertion of the tray. The alginate impressions were removed from the mouth at 2min, after the insertion of the tray. The rubber base impressions were removed from the mouth at 10min. The effect on the accuracy of the combined impressions, alginate impressions and rubber base impressions was obtained following results by comparing the distances between the reference marks in indirect stone cast with the standard measurements of the cast gold crown prior to cementation. The findings through this study could be summarized as follows; 1. The accuracy of combined impression was superior to that of alginate impression, but it was inferior to that of rubber base impressions. 2. Combined impressions produced a little distortion of the mesio-distal length, alginate impressions produced the largest distortion, ut rubber base impressions produced the least distortion.

• 대한기계학회논문집B
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• 제27권6호
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• pp.685-692
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• 2003

A numerical simulation of flame propagation in a micro combustor was carried out. Combustor has a sub -millimeter depth cylindrical internal volume and axisymmetric one-dimensional was used to simplify the geometry. Semi-empirical heat transfer model was used to account for the heat loss to the walls during the flame propagation. A detailed chemical kinetics model of $H_2/Air$ with 10 species and 16 reaction steps was used to calculate the combustion. An operator-splitting PISO scheme that is non-iterative, time-dependent, and implicit was used to solve the system of transport equations. The computation was validated for adiabatic flame propagation and showed good agreement with existing results of adiabatic flame propagation. A full simulation including the heat loss model was carried out and results were compared with measurements made at corresponding test conditions. The heat loss that adds its significance at smaller value of combust or height obviously affected the flame propagation speed as final temperature of the burnt gas inside the combustor. Also, the distribution of gas properties such as temperature and species concentration showed wide variation inside the combustor, which affected the evaluation of total work available of the gases.