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A Study on the Current Measurement Using birefringence Fiber (복굴절 광섬유를 이용한 전류측정에 관한 연구)

  • Jang Nam-Young;Choi Pyung-Suk;Eun Jae-Jeong
    • Journal of the Institute of Convergence Signal Processing
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    • v.6 no.2
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    • pp.59-66
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    • 2005
  • Accuracy of current measurement in fiber optic current sensor(FOCS), especially, unidirectional polarimetric fiber optic current sensor(PFOCS) is affected by the environment perturbations such as acoustic vibrations changes to the sensing fiber, and intrinsic perturbations such as the bending fiber that the sensing fiber wound around a current carrying wire. The perturbations affect the birefringence properties of sensing fiber in sensor head and cause false current readings. Thus, using compensation technique, reciprocal PFOCS, for unidirectional PFOCS the perturbations are suppressed. In this paper, we carried out the numerical analysis of performance in reciprocal PFOCS including the degree of polarization error, and false current of environmental and intrinsic perturbations on the sensing fiber. Also, we compared the effect of mirror with the faraday rotation mirror(FRM) in reciprocal PFOCS configuration. And the different optical source's wavelengths, 633nm and 1300nm is used. In the results, at 633nm, using mirror and FRM, the degree of polarization error is calculated to $2.3\%$ and $0.0196\%$, respectively. At $1300{\cal}nm$ using mirror and FRM the degree of polarization error is calculated to $9.97\%$ and $0.0196\%$, respectively. Also, compared with false current, the results is calculated to $9.82{\times}10^{-9}A$ and $1.4{\times}10^{-17}A$, respectively, and show that the reciprocal PFOCS is more robust configuration than unidiretionnal PFOCS for environmental and intrinsic perturbations.

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The Validity of Head Posture Aligner in Posteroanterior Cephalometry (정모 두부 방사선 사진 촬영시 Head Posture Aligner의 유용성에 관한 연구)

  • Kim, Eun-Hee;Hwang, Hyeon-Shik
    • The korean journal of orthodontics
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    • v.30 no.5 s.82
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    • pp.543-552
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    • 2000
  • The purposes of this study were to evaluate the reproducibility of posteroanterior(PA) cephalograms obtained by two methods, the Head Posture Aligner(HPA) method in natural head posture and the conventional method(operator-guided method), and to compare the vertical rotational differences of the head Posture between lateral and PA cephalograms according to the method. The sample was consisted of 30 adults. At first day, a PA cephalogram and a lateral cephalogram were obtained from each subject by two methods to investigate the difference of vertical rotational posture between lateral and PA cephalograms. Two weeks later, another PA cephalogram was obtained using each method to evaluate the reproducibility of head posture. Five height measurements and nine width measurements were used in the paired t-test to compare the reproducibility of the PA cephalometric measurements between two methods. The differences of vertical rotational posture between lateral and PA cephalograms were calculated from a computer program and compared according to the method used, and following results were obtained. 1. Height measurements obtained by operator-guided method showed significant differences according to the time interval and revealed low reproducibility. 2. Height measurements obtained by HPA method did not show significant differences according to the time interval and presented high reproducibility. 3. In the comparison of width measurement, two methods did not show distinct differences in reproducibility. 4. The difference of vertical rotational posture between lateral and PA cephalograms showed $0.8^{\circ}$ in the HPA method, more less than $2.5^{\circ}$ in the operator-guided method. The results of the present study suggest that the HPA may be helpful in the PA cephalometric radiography in terms of reproducibility.

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The Relationship Between Knowledge of Oral Health and Actual Condition on Oral Health Care of Diabetic Patients (당뇨병 환자의 구강건강지식 정도와 구강관리실태의 관련성)

  • Kim, Ki-Eun;Han, Ji-Hyoung
    • Journal of dental hygiene science
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    • v.9 no.3
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    • pp.345-351
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    • 2009
  • The aim of this study is understanding the relationship between degree of knowledge and actual condition on oral health care to raise people's attention on oral health care and to develop a oral health care program and respondents are 121 diabetes patients. The conclusion of this study is as follows; 1. In terms of degree of Knowledge, women have better knowledge on dental healthcare than men. People aged between 20 and 50 have relatively good knowledge and the longer patients fight against diabetes the more they know about oral healthcare. 2. In actual oral healthcare condition, only 21.5% of patients use rolling method. Patients who have good knowledge have relatively high frequency of dental treatment. Most patients see dentists for their oral healthcare consultation. 3. All the respondent group hesitate to have dental treatment because of expensive cost. Surprisingly. most patients with good knowledge answers that diabetes has nothing to do with dental disease. 4. In terms of degree of knowledge and having oral healthcare program, diabetes patients who are having programs has better knowledge. 5. Respondent group which has middle level of knowledge in oral healthcare give high marks on oral healthcare but does not show statistical significance.

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Hand-Eye Laser Range Finder based Welding Plane Recognition Method for Autonomous Robotic Welding (자동 로봇 용접을 위한 Hand-Eye 레이저 거리 측정기 기반 용접 평면 인식 기법)

  • Park, Jae Byung;Lee, Sung Min
    • Journal of the Institute of Electronics and Information Engineers
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    • v.49 no.9
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    • pp.307-313
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    • 2012
  • This paper proposes a hand-eye laser range finder (LRF) based welding plane recognition method for autonomous robotic welding. The robot welding is the process of joining a metal piece and the welding plane along the welding path predefined by the shape of the metal piece. Thus, for successful robotic welding, the position and direction of the welding plane should be exactly detected. If the detected position and direction of the plane is not accurate, the autonomous robotic welding should fail. For precise recognition of the welding plane, a line on the plane is detected by the LRF. For obtaining the line on the plane, the Hough transform is applied to the obtained data from the LRF. Since the Hough transform is based on the voting method, the sensor noise can be reduced. Two lines on the plane are obtained before and after rotation of the robot joint, and then the direction of the plane is calculated by the cross product of two direction vectors of two lines. For verifying the feasibility of the proposed method, the simulation with the robot simulator, RoboticsLab developed by Simlab Co. Ltd., is carried out.

Disk harrow structure analysis of non-motorized composite implement of tractor (무동력 트랙터 복합작업기의 디스크 구조해석)

  • Lee, Choong Ho;Jang, Ji Un;Lee, In Beom;Kim, Hyun Gyung
    • Proceedings of the Korean Society for Agricultural Machinery Conference
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    • 2017.04a
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    • pp.85-85
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    • 2017
  • 무동력 복합작업기는 치즐쟁기와 디스크의 배열에 따라 작업성능이 좌우된다. 프레임과 디스크, 치즐쟁기에 가해지는 기본적인 힘의 상태를 확인하기 위한 정적 구조해석을 수행하였다. 복합작업기는 디스크는 $18^{\circ}$가 경사진 형태로 전면9개 후면9로 총 18개, 치즐쟁기(Chiselplow)는 4개로, 디스크는 모두 18개이다. 정적인 상태에서 끄는 견인력은 100마력, 150마력, 200마력으로 하였으며 Inventor의 해석 시스템은 힘을 N으로 사용하기 때문에 각 마력에 부가되는 하중을 N으로 치환하여 사용하였다. 구속조건은 frame과, disc, chisel plow에 맞닿는 면을 구속하고, 힘의 방향은 프레임과 트랙터의 연결면, 디스크 날과 땅의 접촉면에 적용했다. front /rear 디스크는 이론상으로는 양 디스크가 쌍으로 마주하고 있어서 스캔데이타를 중심으로 모델링한 결과를 바탕으로, 전후면 디스크해로우의 해석을 수행하였다. 조립 또는 사용상의 문제점이나 자연적인 유격에 의해 어느 정도 대칭이 되지 않을수 있으나 그 정도에 따라 진동과 내구성에 문제가 될 수도 있기에 한쌍에 대해 모델링을 통한 해석을 수행하였다. 해석결과에 따르면 디스크에 작용하는 폰미세스 응력은 극한강도에 미치지 않은 것으로 나타났으며 Frame의 최대 폰 미세스 응력을 제외하면, 대부분의 응력은 항복강도에 현저히 미치지 못하는 수치이고, 프레임의 경우는 150마력, 200마력으로 힘을 가할 때 항복강도는 넘는 수치이지만 극한인장강도에는 미치지 못하는 수치인 것을 알 수 있었다. 100마력에 폰 미세스 응력의 최대값은 0.161918 MPa이고 프레임 강의 항복강도인 207MPa와 디스크의 항복강도인 250MPa에 못 미치는 수치이다. 150마력과 200마력의 힘으로 회전할 때의 폰 미세스 응력의 최대값은 0.286425MPa과 0.381921 MPa로 항복강도인 250MPa에 크게 못 미치는 수치이다. 그 이유는 디스크해로우 방식의 복합작업기는 견인저항력이 작게 설계되고 작업속도를 개선하기 위한 목적으로 사용되기 때문으로 사료된다. 벤치마킹 기대의 Rear 디스크도 마찬가지로 각도는 $18^{\circ}$이며, 동일한 구속조건을 적용하여 시뮬레이션을 수행하였으며 해석결과는 모두 항복강도 이내로 예측 되었다. 디스크에 최대로 응력이 미치는 부분은 디스크와 프레임이 연결되는 허브 부분이다. 각도가 커짐에 따라 응력이 증가하므로 이를 감안한 설계인자 도출이 가능하다. 마력과 각도가 증가함에 따라 디스크 해로우에 작용하는 폰미세스 응력과, 접촉압력이 증가하므로 이에 대한 검토와 동적하중인 로드프로파일을 적용한 해석을 수행하여 내구수명 특성에 대한 연구를 수행할 계획이다.

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The Comparison of Motion Correction Methods in Myocardial Perfusion SPECT (심근관류 SPECT에서 움직임 보정 방법들의 비교)

  • Park, Jang-Won;Nam, Ki-Pyo;Lee, Hoon-Dong;Kim, Sung-Hwan
    • The Korean Journal of Nuclear Medicine Technology
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    • v.18 no.2
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    • pp.28-32
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    • 2014
  • Purpose Patient motion during myocardial perfusion SPECT can produce images that show visual artifacts and perfusion defects. This artifacts and defects remain a significant source of unsatisfactory myocardial perfusion SPECT. Motion correction has been developed as a way to correct and detect the patient motion for reducing artifacts and defects, and each motion correction uses different algorithm. We corrected simulated motion patterns with several motion correction methods and compared those images. Materials and Methods Phantom study was performed. The anthropomorphic torso phantom was made with equal counts from patient's body and simulated defect was added in myocardium phantom for to observe the change in defect. Vertical motion was intentionally generated by moving phantom downward in a returning pattern and in a non-returning pattern throughout the acquisition. In addition, Lateral motion was generated by moving phantom upward in a returning pattern and in a non-returning pattern. The simulated motion patterns were detected and corrected similarly to no-motion pattern image and QPS score, after Motion Detection and Correction Method (MDC), stasis, Hopkins method were applied. Results In phantom study, Changes of perfusion defect were shown in the anterior wall by the simulated phantom motions, and inferior wall's defect was found in some situations. The changes derived from motion were corrected by motion correction methods, but Hopkins and Stasis method showed visual artifact, and this visual artifact did not affect to perfusion score. Conclusion It was confirmed that motion correction method is possible to reduce the motion artifact and artifactual perfusion defect, through the apply on the phantom tests. Motion Detection and Correction Method (MDC) performed better than other method with polar map image and perfusion score result.

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FeO, $TiH_2$, Carbon 원료분말을 이용한 Fe-TiC 나노 복합분말 제조 및 소결

  • An, Gi-Bong;Kim, Ji-Sun
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2011.10a
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    • pp.26-26
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    • 2011
  • Fe계 TiC 합금은 미량의 합금원소를 첨가시켜 경화능, 내식성, 내마모성 성질을 개선한 특수 공구용 재료로서 현재 절삭, 내마모성, 광산, 금형재료 등의 분야에 널리 사용되고 있다. 금속과 세라믹의 복합재료인 초경합금은 비열처리용 공구강으로 WC, TiC 등의 4, 5, 6족 금속탄화물에 Co, Ni, Fe등의 철족이 결합금속으로 소결한 복합재료로 WC-Co계 초경합금이 주종을 이루고 있으나, 전략 소재로서 고가인 Co 원료를 대체하기 위한 재료로서 초경재료의 고경도와 공구강의 경제성 및 가공성의 장점을 이용한 Fe-TiC계 초경합금의 연구가 다양하게 진행되고 있다. 본 연구에서는 Fe기지에 서브마이크론 크기의 미세한 TiC 입자가 균일하게 분산된 Fe-TiC 복합분말을 경제적으로 제조하기 위해 순수한 Fe, Ti 원료분말에 비해 단가가 낮고 미세 분쇄가 용이한 FeO, $TiH_2$ 분말을 고에너지 밀링 후 반응 열처리 시키는 유사 기계화학적 공정을 시도하였다. 조성비 Fe-30wt%TiC 복합분말을 제조하기위해 마이크론(micron) 크기의 FeO, $TiH_2$, C 분말을 사용하였고, 1단계로 FeO와 C을 고에너지 밀링으로 혼합 후 반응시켜 환원시키는 공정과 2단계로 이렇게 환원된 분말과 TiH2를 고에너지 밀링으로 다시 혼합, 분쇄한 후 반응열처리 하는 두 단계 공정을 사용하였다. FeO의 환원 단계에서는 $700{\sim}1,000^{\circ}C$ 온도 범위에서 1시간 유지하였고, 고에너지 밀링 시 밀링시간, 회전속도를 변수로 두고 실험하였다. 환원된 분말은 수평관상로를 이용해 아르곤분위기에서 $1,000{\sim}1300^{\circ}C$까지 1시간 유지하여 반응열처리시켜 Fe-TiC 복합분말을 제조하였다. 준비된 복합분말을 XRD와 FE-SEM, EDS, 입도분석기 (LPSA) 등을 이용해 분말의 형태와 특성, 상, 조성, 입도, 분산도 등을 조사하였다. 제조된 Fe-TiC 나노복합분말을 방전플라즈마소결(SPS) 과 상압소결 실험을 진행하였다. Fe-TiC 복합분말 제조공정의 첫 번째 단계인 FeO의 환원반응은 $800^{\circ}C$이상의 온도에서 Fe로 환원이 진행됨을 확인하였다. 두 번째 단계인 반응열처리공정에서는 $1,000^{\circ}C$ 이상에서 TiC가 형성됨을 XRD 상분석을 통해 확인할 수 있었고, $1,100^{\circ}C$ 이상의 온도에서 반응열처리를 했을 때 XRD 분석결과와 산소 조성 분석 결과로부터 반응의 완결성과 순도에서 최적 온도 조건임을 확인하였다. 온도를 $1,300^{\circ}C$로 증가시킬 경우 반응의 완결성에 큰 변화가 없는 반면 분말입자간의 목형성이 일어나 가소결 되는 것을 FE-SEM을 통해 관찰하였다. 또한 최적조건으로 제조된 Fe-TiC 복합분말의 입도분석과 FE-SEM/EDS 관찰/분석을 시행한 결과 평균 입도 0.6 ${\mu}m$의 미세한 Fe-TiC 복합분말 내에 Fe분말 주변과 내부에 나노크기의 TiC입자가 균일하게 분산되어 존재하는 것을 확인하였다.

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Numerical Analysis of Heat Transfer in the Ribbed Channel Inserted with Tape (테이퍼가 설치된 리브(rib)이 있는 채널의 열전달에 대한 수치해석)

  • Kang, Ho-Keun;Ahn, Soo-Whan
    • Journal of Advanced Marine Engineering and Technology
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    • v.34 no.5
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    • pp.638-644
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    • 2010
  • Numerical predictions of a fully developed turbulent flow through a square duct ($30mm{\times}30mm$) with twisted tape inserts and with twisted tape plus interrupted ribs are respectively conducted to investigate regionally averaged heat transfer and flow patterns. A rib height-to-channel hydraulic diameter(e/$D_h$) of 0.067 and a lengthto-hydraulic diameter(L/$D_h$) of 30 are considered at Reynolds number ranging 8,900 to 29,000. The interrupted ribs are axially arranged on the bottom wall. The twisted tape is 0.1 mm thick carbon steel sheet with diameter of 28 mm, length of 900 mm, and 2.5 turns. Each wall of the square channel is composed of isolated aluminum sections. Two heating conditions are investigated for test channels with twisted tape inserts and rib turbulators: (1) electric heat uniformly applied to four side walls of the square duct, and (2) electric heat uniformly applied to two opposite walls of the square channel. The results show that uneven surface heating enhances the heat transfer coefficient over uniform heating conditions, and significant improvements can be achieved with twisted tape inserts plus interrupted ribs.

A Design Method of Three-phase IPMSM and Clamping Force Control of EMB for High-speed Train (고속철도차량의 EMB 적용을 위한 3상 IPMSM의 설계 및 제동압부력 제어)

  • Baek, Seung-Koo;Oh, Hyuck-Keun;Kwak, Min-ho;Kim, Seog-Won
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.4
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    • pp.578-585
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    • 2018
  • This paper proposes a design method for a 3-phase interior permanent magnet synchronous motor (IPMSM) and clamping force control method for an electro-mechanical brake (EMB) using co-simulation for a high-speed train (HST). A traditional pneumatic brake system needs much space for the compressor, brake reservoir, and air pipe. However, an EMB system uses up to 50% less space due to the use of a motor and electric wires for controlling the brake caliper. In addition, it can reduce the latency time for brake control because of the fast response and precise control. A train that has many brakes is advantageous for safety because of the control by sharing the braking force. In this paper, a driving method for a cam-shaft-type EMB is modeled. It is different from the ball-screw-type brakes that are widely used in automobiles. In addition, a co-simulation method is proposed using JMAG and Matlab/Simulink. The IPMSM was designed and analyzed with the JMAG tool, and the control system was simulated using Matlab/Simulink. The effectiveness of the co-simulation results of the mechanical clamping force and braking force was verified by comparison with the clamping force specifications of a HEMU-430X HST.

Detection of Thermal Ratcheting Deformation for Cylindrical Shells by Ultrasonic Guided Wave (유도초음파를 이용한 원통형 쉘의 열 라체팅 변형 탐지)

  • Joo, Young-Sang;Lee, Hyeong-Yeon;Kim, Jong-Bum;Park, Chang-Gyu;Lee, Jae-Han
    • Journal of the Korean Society for Nondestructive Testing
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    • v.26 no.5
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    • pp.297-305
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    • 2006
  • The thermal ratcheting deformation at the reactor baffle and upper internal structure of the liquid metal reactor (LMR) can occur due to movement of the hot sodium free surface. In in-service inspection of reactor internals of LMR, a new inspection technique should be developed for the detection of the thermal ratcheting damage. In this study, an inspection technique using ultrasonic guided wave is proposed for the detection of the thermal ratcheting damage of cylindrical vessels. A 316L stainless steel cylindrical shell specimen has been prepared. The thermal ratchet structural tests were cyclically performed by heat-up up to $550^{\circ}C$ with steep temperature gradients along the axial direction after cool-down by cooling water. Ultrasonic guided wave propagation has been characterized by analysis of dispersion curve of the stainless steel plate. The zero-order antisymmetric $A_0$ guided wave has been selected as the optimal mode for detection of the ratcheting deformation. It is confirmed that the thermal ratcheting deformation can be detected by the measurement of transit time difference of circumferentially propagated $A_0$ guided waves.