• Title/Summary/Keyword: 5자유도 오차

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Development of the Spherical Flange Used in a Cryogenic High Pressure Pipe (극저온 고압 배관용 구형 플랜지 개발)

  • Moon, Il-Yoon;Moon, In-Sang;Yoo, Jae-Han;Lee, Soo-Young
    • Journal of the Korean Society of Propulsion Engineers
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    • v.15 no.3
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    • pp.64-69
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    • 2011
  • The spherical flange was designed to apply to a cryogenic high pressure pipe of a liquid rocket engine. It is designed that the spherical flange is able to be assembled and kept airtight up to $2.5^{\circ}$ of the axial misalignment between the combined components. It increases the degree of freedom of the engine assembly. The spherical flange is composed of a ball and socket joint, a metal seal, spherical type bolts and washers. The prototype was verified by leak test at the room temperature and the cryogenic temperature. Additionally the strength test and the destructive test were performed at the room temperature.

Determination of Free Acid in U(VI)-Al(III) Solutions by Gran Plot Titration (Gran Plot 적정법을 이용한 U(VI)-AI(III) 용액의 자유산 농도 측정)

  • Suh, Moo-Yul;Lee, Chang-Heon;Sohn, Se-Chul;Kim, Jung-Suk;Kim, Won-Ho;Eom, Tae-Yoon
    • Analytical Science and Technology
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    • v.12 no.3
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    • pp.177-183
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    • 1999
  • The determination method of free acid in spent U-Al nuclear fuel solutions by Gran plot titration was described. Effect of U(VI) and Al(III) on the alkalimetric titration of nitric acid was investigated in oxalate complexing media as well as in noncomplexing media. Positive biases were observed in both titration media when the end-point was estimated by the Gran plot method. It was found that the cause of the bias was U(VI) in the oxalate complexing media, but Al(III) in the noncomplexing media. The relative error was less than 1% in the titration of 0.1 M $HNO_3$ at a U(VI) : Al(III) : $H^+$ mole ratio of up to 2:12:1 as long as the pH of the oxalate titration media was sustained to be below 5.0 at the beginning of titration. The method was successfully applied to the determination of nitric acid in a solution of HANARO reactor fuel with U:Al mole ratio of 1:6.

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A Successive Region Setting Algorithm Using Signal Strength Ranking from Anchor Nodes for Indoor Localization in the Wireless Sensor Networks (실내 무선 센서 네트워크에서의 측위를 위하여 고정 노드 신호들의 크기 순위를 사용한 순차적 구역 설정 알고리즘)

  • Han, Jun-Sang;Kim, Myoung-Jin
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.48 no.6
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    • pp.51-60
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    • 2011
  • Researches on indoor localization using the wireless sensor network have been actively carried out to be used for indoor area where GPS signal is not received. Computationally efficient WCL(Weighted Centroid Localization) algorithm is shown to perform relatively well. However, to get the best performance for WCL all the anchor nodes must send signal with power to cover 96% of the network. The fact that outside the transmission range of the fixed nodes drastic localization error occurs results in large mean error and deviation. Due to these problems the WCL algorithm is not easily applied for use in the real indoor environment. In this paper we propose SRS(Succesive Region Setting) algorithm which sequentially reduces the estimated location area using the signal strength from the anchor nodes. The proposed algorithm does not show significant performance degradation corresponding to transmission range of the anchor nodes. Simulation results show that the proposed SRS algorithm has mean localization error 5 times lower than that of the WCL under free space propagation environment.

Direct Control of Displacement Using Displacement and Resistance Force Contribution Factor (변위 및 내력기여도계수를 이용한 정량적 변위 제어)

  • Kim, Young-Min;Kim, Chee-Kyeong
    • Journal of Korean Association for Spatial Structures
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    • v.5 no.3 s.17
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    • pp.91-100
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    • 2005
  • The paper presents a direct method for the diplacement control and stiffness redesign using displacement and response force contribution factors. At first, these two kinds of factors are derived and the relationship between them is examined. An equation to evaluate the change of displacement according to the change of each member stiffness is proposed. For the statically determinate structures, the proposed equation gives the exact solution with no approximation. But it has some error in case of statically indeterminate structures because the redistribution of response forces is neglected in the equation. However, the equation may be very useful even for statically indeterminate structures because it provides the relationship between the member stiffness and the global displacement. The proposed method is expected to be useful for the displacement control of large space or hi-rise building structures where the stiffness design governs the design result.

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Influence of Fluid Height and Structure width ratio on the Dynamic Behavior of Fluid in a Rectangular Structure (사각형 구조물에 저장된 유체의 동적거동에 유체높이와 구조물 폭의 비가 미치는 영향)

  • Park, Gun;Yoon, Hyungchul;Hong, Ki Nam
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.5
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    • pp.126-134
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    • 2020
  • In the case of an earthquake, the fluid storage structure generates hydraulic pressure due to the fluctuation of the fluid. At this time, the hydraulic pressure of the fluid changes not only the peaked acceleration of the earthquake but also the sloshing height of the fluid free water surface. Factors influencing this change in load include the shape of the seismic wave, the maximum seismic strength, the size of the fluid storage structure, the width of the structure, and the height of the fluid. In this study, the effect of the ratio between the height of the fluid and the width of the structure was investigated on the fluctuation characteristics of the fluid. 200mm and 140mm of fluid were placed in a water storage tank with a width of 500mm, and a real seismic wave was applied to measure the shape of the fluctuation of the fluid free water surface. The similarity between the experiment and the analysis was verified through the S.P.H(Smoothed Particle Hydrodynamic) technique, one of the numerical analysis techniques. It was confirmed that the free water surface of the fluid showed a similar shape, through comparison of experiment and analysis. And based on this results, SPH technique was applied to analyze the fluctuation shape of the fluid free water surface while varying the ratio between the fluid height and the structure width. An equation to predict the maximum and minimum heights of the fluid free water surface during an earthquake was proposed, and it was confirmed that the error between the maximum and minimum heights of the fluid free water surface predicted by the proposed equation was within a maximum of 3%.

Quasi-breath-hold (QBH) Biofeedback in Gated 3D Thoracic MRI: Feasibility Study (게이트 흉부자기 공명 영상법과 함께 사용할 수 있는 의사호흡정지(QBH) 바이오 피드백)

  • Kim, Taeho;Pooley, Robert;Lee, Danny;Keall, Paul;Lee, Rena;Kim, Siyong
    • Progress in Medical Physics
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    • v.25 no.2
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    • pp.72-78
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    • 2014
  • The aim of the study is to test a hypothesis that quasi-breath-hold (QBH) biofeedback improves the residual respiratory motion management in gated 3D thoracic MR imaging, reducing respiratory motion artifacts with insignificant acquisition time alteration. To test the hypothesis five healthy human subjects underwent two gated MR imaging studies based on a T2 weighted SPACE MR pulse sequence using a respiratory navigator of a 3T Siemens MRI: one under free breathing and the other under QBH biofeedback breathing. The QBH biofeedback system utilized the external marker position on the abdomen obtained with an RPM system (Real-time Position Management, Varian) to audio-visually guide a human subject for 2s breath-hold at 90% exhalation position in each respiratory cycle. The improvement in the upper liver breath-hold motion reproducibility within the gating window using the QBH biofeedback system has been assessed for a group of volunteers. We assessed the residual respiratory motion management within the gating window and respiratory motion artifacts in 3D thoracic MRI both with/without QBH biofeedback. In addition, the RMSE (root mean square error) of abdominal displacement has been investigated. The QBH biofeedback reduced the residual upper liver motion within the gating window during MR acquisitions (~6 minutes) compared to that for free breathing, resulting in the reduction of respiratory motion artifacts in lung and liver of gated 3D thoracic MR images. The abdominal motion reduction in the gated window was consistent with the residual motion reduction of the diaphragm with QBH biofeedback. Consequently, average RMSE (root mean square error) of abdominal displacement obtained from the RPM has been also reduced from 2.0 mm of free breathing to 0.7 mm of QBH biofeedback breathing over the entire cycle (67% reduction, p-value=0.02) and from 1.7 mm of free breathing to 0.7 mm of QBH biofeedback breathing in the gated window (58% reduction, p-value=0.14). The average baseline drift obtained using a linear fit was reduced from 5.5 mm/min with free breathing to 0.6 mm/min (89% reduction, p-value=0.017) with QBH biofeedback. The study demonstrated that the QBH biofeedback improved the upper liver breath-hold motion reproducibility during the gated 3D thoracic MR imaging. This system can provide clinically applicable motion management of the internal anatomy for gated medical imaging as well as gated radiotherapy.

Experimental Study on Establishment of Downstream Critical Depth in Round-Crested Weir (보 하류부 임계수심 설정에 관한 실험적 연구)

  • Yeo Hong Gu;Kang Joon Gu;Cheong Sang Hwa;Yoon Byeong Mo
    • Proceedings of the Korea Water Resources Association Conference
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    • 2005.05b
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    • pp.1113-1117
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    • 2005
  • 보 상류의 유속 및 수심과 같은 흐름 조건은 보, 하천 형상, 그리고 하류 흐름 특성에 의해 좌우된다. 본 연구에서는 하류 조건에 따라 보 상류의 흐름 특성에 미치는 영향을 검토하였다. 이를 위해 구형단면의 수로에 하천설계지침(2002)에 따라 보를 제작하여 설치하였으며 보에서의 임계수심 및 이에 따른 유량의 변화를 파악하였으며 실험결과를 기존 문헌과 비교$\cdot$분석하였다. 또한 자유 월류로 빠른 유속을 지닌 흐름이 수로의 마찰저항과 하류 배수효과에 의해 에너지 소멸로 나타나는 도수현상을 관측하여 발생특성을 파악하였다. 도수의 발생조건은 Posey와 Hsing(1938)에 제시한 결과와 유사한 결과를 보였으며 하류영향에 따른 도수 발생 위치는 하류단 수위와 일정한 관계를 갖고 있으나 유량과는 선형적인 관계를 보이지 않는 것을 알 수 있었다. 또한 임계수심 설정에 대해 Knap(1960)이 제시한 산정식과 비교한 결과 유량이 작은 경우 거의 일치하는 결과를 보였으나 유량이 증가할수록 오차가 커졌다. 임계수심 전$\cdot$후의 유량계수를 살펴본 결과 하류 조건에 의해 임계수심을 넘으면 유량계수가 자유 월류 시보다 약 $2\%\~6.5\%의 감소를 나타냈으며 공급유량이 $0.05m^3/s$ 일 경우 유량계수의 차이가 가장 큰 것을 알 수 있다.

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Modeling of Wheeled-Mobile Robots and Path-Tracking using Time-Scaling Method (구륜이동로봇의 모델링과 Time-Scaling 기법을 이용한 경로추적)

  • Kim, Choung-Soo
    • Journal of the Korea Computer Industry Society
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    • v.5 no.9
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    • pp.993-1004
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    • 2004
  • We propose the method for kinematic and dynamic modeling and Path-tracking of four-wheeled mobile robots with 2 d.o.f having the limited drive-torques. Controllability of wheeled-mobile robots is revealed by using the kinematic model. Instantaneously coincident coordinate system, force/torque propagation and Newton's equilibrium law are used to induce the dynamic model. When drive-torques generated by inverse dynamics exceed the limitation, we make wheeled-mobile robots follow the reference path by modifying the planned reference trajectory with time-scaling. The controller is introduced to compensate for error owing to modeling uncertainty and measurement noise. And simulation results prove that the method proposed by this paper is efficient.

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Design of Upper-limb Rehabilitation Device with Power-assist Function for Stroke Survivals (뇌졸중 환자용 동력보조형 상지재활훈련기의 설계)

  • Bae, J.H.;Moon, I.
    • Journal of rehabilitation welfare engineering & assistive technology
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    • v.5 no.1
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    • pp.79-85
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    • 2011
  • In this paper, we proposed a design of upper-limb rehabilitation device with power-assist function for stroke survivals. The designed upper-limb rehabilitation device has three degrees of freedom; it is possible to perform flexion and extension motions of wrist, index finger and the other fingers except the thumb independently. The power-assist for wrist motion is performed by a pneumatic double-acting cylinder, but the fingers are actuated by electrical linear actuators to assist motions. A prototype upper-limb rehabilitation device and its controller were implemented. The position controller showed 0.8 mm errors in the steady-state. Experimental results showed that the proposed upper-limb rehabilitation device with power-assist function is feasible.

Application of Tuned Mass Damper to Suppress Man-Induced Vibrations of Cable Stayed Foot-bridge (사장교형식 보도교의 보행진동제어를 위한 TMD 적용)

  • Kim, Yun-Seok;Lee, Seung-Woo;Kim, Jae-Min;Chang, Seong-Kyu
    • 한국방재학회:학술대회논문집
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    • 2011.02a
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    • pp.74-74
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    • 2011
  • 본 연구에서는 중앙경간 54m, 교폭 4m의 사장교형식의 보도교로 측경간은 계단으로 이루어진 1경간 케이블교량을 대상으로 보행하중에 의한 수직진동을 제어하기 위해 제진장치(TMD)를 적용하기로 하고 실물 TMD의 설계 및 제작 그리고 설치 및 제어성능실험을 수행하였다. 우선 사장교형식의 교량. 그리고 1경간 교량이라는 점에서 상대적으로 감쇠율이 낮을 것으로 예측되었고 또한 54m의 경간장이 보행자가 가진 주파수에 근접한 고유진동수를 나타낼 것으로 사료되어 Eurocode 2 part 2(EC5-2)의 규준에 따라 1인 및 다수 보행하중에 의한 보도교의 발생가속도를 산출하였다. 이 경우 최대가속도는 다수의 보행자가 연속적으로 진행할 때 발생하였으며, 수직방향의 가속도가 사용성기준을 초과하는 것으로 나타났다. 또한 구조해석프로그램에 의한 고유치 해석결과, 보행하중의 주파수대역내에 진동모드가 존재하는 것으로 나타났다. 따라서 본 교량의 설계단계에 있어서 보행진동을 제어하기 위하여 유지관리가 용이한 수동형의 동조질량감쇠장치(Tuned Mass Damper)를 적용하기로 하였으며 TMD의 설계에서는 TMD의 제어목표를 만족시킬 수 있는 TMD의 가동질량(moving mass)을 우선적으로 결정하였고, 이로부터 Den Hartog의 제안식에 따라 TMD의 고유진동수비, 유효감쇠비를 산정하였다. 산정된 변수들을 이용하여 설계된 TMD는 현장설치 및 튜닝의 편의성을 고려하여 수평 외팔보형식으로 설계, 제작되었으며 제작된 TMD의 경우 회전축에 대해 질량, 스프링, 댐퍼의 중심거리를 조정함으로써 TMD의 진동수, 강성, 감쇠력을 상대적으로 매우 용이하게 조절할 수 있으며, 조정범위 또한 광범위하여 일반 TMD에 비해 현장설치시 대상구조물에 동조시키기가 용이하며, 작동시 마찰감쇠가 거의 없다는 장점이 있다. 현장설치전에 제작된 TMD를 대상으로 자유진동 시험을 통하여 질량의 중심거리, 스프링 크기 그리고 댐퍼의 설치유무를 각각 변화시키며 TMD의 자유진동 데이터를 취득하였다. 각각의 시험에서 얻어진 데이터로부터 스펙트럼해석을 통하여 고유진동수를 구하였고, 자유진동 파형으로 부터 감쇠비를 구하였다. TMD는 일반적으로 제어모드의 변형형상이 가장 큰 곳에 설치되었을 때 최대의 제진효과를 발휘할 수 있다. 그러나 현장여건상 설치가 불가능하거나 미관을 해치는 경우에는 가능한 범위 내에서 TMD 제어효율이 가장 크게 발휘할 수 있는 곳을 선택하여야 한다. 본 보도교의 경우, 중앙경간 중심부에서 가장 큰 모드변형형상을 나타내지만, 보도교의 상판 연결부 등에 따른 TMD 시공문제로 인하여 TMD 설치위치는 교량 중앙에서 양 방향으로 1.25m 떨어진 곳에 대칭으로 총 2기를 설치하기로 하였다. 일반적으로 TMD의 모든 설계변수는 구조물의 설계단계에서 수행된 구조해석결과에 근거하여 설정하므로 완공된 구조물, 즉 실제보도교의 동적특성을 계측하여 정확하게 진동수를 튜닝하여야 한다. 구조해석에 의한 보도교의 수직방향(TMD 작동방향) 고유진동수는 1.5225 Hz이며, 감쇠비는 규준에 의하여 0.6 %로 가정하였다. 그러나 이 값들은 구조해석모델 및 재료적 특성과 시공상의 오차에 의하여 실제와 다를 수 있으므로 현장계측에 의한 확인이 요구된다. 또한 TMD의 제진효율이 설계시의 목표대로 확보되었는지도 확인해야 하므로 현장튜닝 및 성능시험을 실시하였다. 보도교의 가진은 사전에 실시한 상시 미진동계측결과를 토대로 2Hz를 목표로 하여 인력가진실험을 수행하였고, 탁월진동 주파수는 1.9896Hz로 나타나 구조해석결과와 오차가 있음을 알 수 있다. 가진실험결과를 토대로 TMD의 진동수를 최적진동수비로 튜닝하고 인력가진 실험을 다시 실시하여 TMD의 진동제어성능을 검토하였다. TMD 튜닝 전, 후의 보도교 감쇠비를 비교한 결과, TMD를 설치함으로써 약 4.218%의 감쇠비 증가가 있음을 알 수 있다.

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