• Title/Summary/Keyword: acceleration test

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A SIMPLIFIED TREATMENT OF GRAVITATIONAL INTERACTION ON GALACTIC SCALES

  • Trippe, Sascha
    • Journal of The Korean Astronomical Society
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    • 제46권1호
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    • pp.41-47
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    • 2013
  • I present a simple scheme for the treatment of gravitational interactions on galactic scales. In anal- ogy with known mechanisms of quantum field theory, I assume ad hoc that gravitation is mediated by virtual exchange particles-gravitons-with very small but non-zero masses. The resulting den- sity and mass profiles are proportional to the mass of the gravitating body. The mass profile scales with the centripetal acceleration experienced by a test particle orbiting the central mass, but this comes at the cost of postulating a universal characteristic acceleration $a_0{\approx}4.3{\times}10^{-12}msec^{-2}$ (or $8{\pi}a_0{\approx}1.1{\times}10^{-10}msec^{-2}$). The scheme predicts the asymptotic flattening of galactic rotation curves, the Tully-Fisher/Faber-Jackson relations, the mass discrepancy-acceleration relation of galaxies, the surface brightness-acceleration relation of galaxies, the kinematics of galaxy clusters, and "Renzo's rule" correctly; additional (dark) mass components are not required. Given that it is based on various ad-hoc assumptions and given further limitations, the scheme I present is not yet a consistent theory of gravitation; rather, it is a "toy model" providing a convenient scaling law that simplifies the description of gravity on galactic scales.

Vibration Characteristics of Cantilever Beam with a Crack (단일 크랙을 갖는 외팔보의 진동특성)

  • Kim, Jong-Do;Jo, Ji-Yun;Yoon, Moon-Chul
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • 제23권3호
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    • pp.223-229
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    • 2014
  • In this paper, the natural frequency and damping ratio are analyzed with the acceleration signal of an Euler-Bernoulli beam using the impact hammer test. The results are presented according to crack depth and position using the recursive least squares method. The results are compared and investigated with FEM analysis of CATIA. Both methods agree well with each other regarding the natural mode characteristics. The captured acceleration can be used for the calculation of the natural frequency and damping ratio using time series methods that are based on the measured acceleration. Using these data, a recursive time series model with the acceleration signal was configured and the behaviors of the natural frequency and damping ratio were investigated and analyzed. Finally, the results can be used for the prediction of crack position and depth under different crack conditions for an Euler-Bernoulli beam.

A study on Improvement for distorted images of the Digital X-ray Scanner System based on Fuzzy Correction Algorithm

  • Baek, Jae-Ho;Kim, Kyung-Jung;Park, Mi-Gnon
    • Proceedings of the Korea Society of Information Technology Applications Conference
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    • 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
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    • pp.173-176
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    • 2005
  • This paper proposes a fuzzy correction algorithm that can correct the distorted medical image caused by the scanning nonlinear velocity of the Digital X-ray Scanner System (DX-Scanner) using the Multichannel Ionization Chamber (MIC). In the DX-Scanner, the scanned medical image is distorted for reasons of unsuitable integration time at the nonlinear acceleration period of the AC servo motor during the inspection of patients. The proposed algorithm finds the nonlinear motor velocity modeling through fuzzy system by clustering and reconstructs the normal medical image lines by calculating the suitable moving distance with the velocity of the motor using the modeling, acceleration time and integration time. In addition, several image processing is included in the algorithm. This algorithm analyzes exact pixel lines by comparing the distance of the acceleration period with the distance of the uniform velocity period in every integration time and is able to compensate for the velocity of the acceleration period. By applying the proposed algorithm to the test pattern for checking the image resolution, the effectiveness of this algorithm is verified. The corrected image obtained from distorted image is similar to the normal and better image for a doctor's diagnosis.

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A Study on Balanced-Type Oscillating Mole Drainer (II) (Model Test For Vibration) (평형식진동탄환암거천공기의 연구(II) -모수실험 : 진동에 대하여-)

  • 김용환
    • Magazine of the Korean Society of Agricultural Engineers
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    • 제17권4호
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    • pp.3962-3969
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    • 1975
  • 1. When the frame of the experimental apparatus was directly fixed on the platform, result from the spectrum density analysis showed that the generated vibration frequecy of the system was nearly-same as the system's own characteristic vibration frequency, 80Hz, in the case of the forcing vibration frequency was 7.5 to 22.5Hz. The reduction ratio of acceleration by balanced type model compare to non-balanced type one was 26.66 percent. 2. When the frame of experimental apparatus was fixed on the platform with putting a shock absorbing rubber between the frame and the platform, the generated vibration frequency of the system was same as forcing vibration frequency. When either frequency or the amplitude of the forcing vibration was increased, the acceleration ratio was increased too. The average reduction ratio was resulted 44.77 per cent. It was concluded that this method of acceleration measurement(the method using a shock absorbing rubber) was a reaonable method, because actual machine will work under such condition. As the vibration frequency and aptitude were increased, the absolute magnitude of acceleration was increased. 3. unbalanced rotating parts, and unbalanced moment of inertia of links were supposed to be causing factors of residual vibration in spite of using the balanced type oscillating mole drainer. This fact suggested that the attachment of the counter weight on the rotating parts which satisfy the condition mw$.$rw=m0e, was necessary. And also, it was expected that the shock absorbing effect could be improved by putting the shock absorbing materials between the moving parts and their supports.

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A Study on the Accelerometer for the Acceleration and Inclination Estimation of Structures using Double-FBG Optical Sensors (이중 FBG 광섬유센서를 이용한 구조물 가속도 및 기울기 측정 장치에 관한 연구)

  • Lee, Geum-Suk;Ahn, Soo-Hong;Shon, Su-Deok;Lee, Seung-Jae
    • Journal of Korean Association for Spatial Structures
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    • 제16권1호
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    • pp.85-94
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    • 2016
  • In this study, an acceleration sensor that has optical fibers to measure the inclination and acceleration of a structure through contradictory changes in two-component FBG sensors was examined. The proposed method was to ensure precise measurement through the unification of the deformation rate sensor and the angular displacement sensor. A high sensitivity three-axis accelerometer was designed and prepared using this method. To verify the accuracy of the accelerometer, the change in wavelength according to temperature and tension was tested. Then, the change in wavelength of the prepared accelerometer according to the sensor angle, and that of the sensor according to the change in ambient temperature were measured. According to the test results on the FBG-based vibration sensor that was developed using a high-speed vibrator, the range in measurement was 0.7 g or more, wavelength sensitivity, 2150 pm/g or more, and the change in wavelength change, $9.5pm/^{\circ}C$.

A Study on the Solution of Excessive Accelerations on the Bridge for Gyeongbu High-speed Railway (경부고속철도 교량의 과도한 가속도의 저감방안에 대한 연구)

  • Kwark, Jong-Won;Chin, Won-Jong;Choi, Eun-Suk;Cho, Jeong-Rae;Lee, Jung-Woo
    • Proceedings of the KSR Conference
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    • 한국철도학회 2007년도 춘계학술대회 논문집
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    • pp.477-485
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    • 2007
  • When Korean High Speed Train (KTX) runs over a high-speed railway bridge, the high-speed railway bridge gives quite large acceleration response. Local vibration at the large cross section, the impact from equally spaced sleepers, the vibration due to elastomeric bearings, and the vibration from the train itself are the causes of this acceleration response. Maximum peaks of the accelerations measured at the bridges are sometimes going over the limit value. Although it is smaller than 0.35G, the limit from the Korean Bridge Design Manual(BRDM), this acceleration response should be reduced for the safety of running trains with high speed. In this paper, to reduce the acceleration response by controlling excessive local vibration at the large cross section, vibration reduction method is studied. The result shows that the effect of elastomeric bearings on the vibration of the bridge is very large and that the vibration reduction device is effective against wing mode local vibration PSC box girder bridge for the high-speed railway, which usually has very large cross section, although it has little effect on global vibration modes such as flexural and twisting modes. The test of the vibration reduction device on the bridge in service has been performed in this study.

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Assessment for Amount Increment of Dredged Soil using infiltrated consolidation method (침투압밀공법을 이용한 준설투기용량 산정)

  • Kwak, No-Kyung;Lee, Mu-Cheol;Lee, Song
    • Proceedings of the Korean Geotechical Society Conference
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    • 한국지반공학회 2009년도 춘계 학술발표회
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    • pp.1198-1209
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    • 2009
  • In this study, an experimental research on the acceleration effect of dredged soil's self weight consolidation with seepage consolidation and PBD was conducted. The middle-sized consolidation equipment had been manufactured in order to investigate the acceleration of sedimentation and self-weight consolidation by PBD and a lower drainage. Seepage pressure was applied to the PBD installed in the center of the test equipment and a drainage by seepage pressure was allowed. The comparison between cases with and without PBD and seepage pressure reveals that the quantity of drained water and the amount of settlement was nearly 1.2 times to 3.68 times greater in the case with PBD and seepage. Early consolidation completion and the use of reclaimed site are expected due to the acceleration of settlement and increase of the quantity of reclamation if PBD is installed while being reclaiming using the result of the research.

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A Study on the Development of a Rapid Safety Assessment System for Buildings Using Seismic Accelerometers (지진가속도 계측기를 이용한 건축물의 긴급 안전성 평가 알고리즘 개발에 대한 연구)

  • Jeong, Seong-Hoon;Jang, Won-Seok;Park, Byung-Chul
    • Journal of the Korea institute for structural maintenance and inspection
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    • 제24권6호
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    • pp.161-170
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    • 2020
  • In this study, develop the seismic acceleration measurement data conversion and signal processing algorithms for improve the operational efficiency of the seismic acceleration measurement system installed for public facilities. Through the analysis of the seismic acceleration time history data, the evaluation methods and criteria and evaluating the safety of buildings were proposed. The system was applied to the test bed building to verify its operation and usability. It is expected to be used as a decision making support data and determining the direction and priority of disaster response in the event of an earthquake.

A Study on the Acceleration Response Amplification Ratio of Buildings and Non-structural Components Considering Long-Period Ground Motions (장주기 지진동을 고려한 건축물 및 비구조요소의 가속도 응답 증폭비)

  • Oh, Sang Hoon;Kim, Ju Chan
    • Journal of the Earthquake Engineering Society of Korea
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    • 제27권1호
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    • pp.1-12
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    • 2023
  • Structures of high-rise buildings are less prone to earthquake damage. This is because the response acceleration of high-rise buildings appears to be small by generally occurring short-period ground motions. However, due to the increased construction volume of high-rise buildings and concerns about large earthquakes, long-period ground motions have begun to be recognized as a risk factor for high-rise buildings. Ground motion observed on each floor of the building is affected by the eigenmode of the building because the ground motion input to the building is amplified in the frequency range corresponding to the building's natural frequency. In addition, long-period components of ground motion are more easily transmitted to the floor or attached components of the building than short-period components. As such, high-rise buildings and non-structural components pose concerns about long-period ground motion. However, the criteria (ASCE 7-22) underestimate the acceleration response of buildings and non-structural components caused by long-period ground motion. Therefore, the characteristics of buildings' acceleration response amplification ratio and non-structural components were reviewed in this study through shake table tests considering long-period ground motions.

A Model for Diffusive Shock Acceleration of Protons in Intracluster Shocks and Gamma-ray and Neutrino Emissions from Clusters of Galaxies

  • Ha, Ji-Hoon;Ryu, Dongsu;Kang, Hyesung
    • The Bulletin of The Korean Astronomical Society
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    • 제44권2호
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    • pp.54.3-54.3
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    • 2019
  • During the formation of large-scale structures in the universe, shocks with the sonic Mach number Ms <~ 5 are naturally induced by supersonic flow motions of baryonic matter in the intracluster medium (ICM). Cosmic rays (CRs) are expected to be accelerated via diffusive shock acceleration (DSA) at these ICM shocks, although the existence of CR protons in the ICM remains to be confirmed through gamma-ray observations. Based on the results obtained from kinetic plasma simulations, we build an analytic DSA model for weak, quasi-parallel shocks in the test-particle regime. With our DSA model, the CR acceleration efficiency ranges ~ 0.001 - 0.02 in supercritical quasi-parallel shocks with sonic Mach number Ms ~ 2.25 - 5, and the acceleration would be negligible in subcritical shocks wth Ms <~ 2.25. Adopting our DSA model, we estimate gamma-ray and neutrino emissions from clusters of galaxies by performing cosmological hydrodynamic simulations. The estimated gamma-ray flux is below the Fermi-LAT upper limit. In addition, the possible neutrino emission due to the decay of charged pions in galaxy clusters would be about <~ 1% of the atmospheric neutrino intensity in the energy range of <~ 100 GeV. In this talk, we will discuss the implication of our results.

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