• 제목/요약/키워드: mass formula

검색결과 265건 처리시간 0.021초

An approximate formula to calculate the fundamental period of a fixed-free mass-spring system with varying mass and stiffness

  • Kim, Juwhan;CoIIins, Kevin R.;Lim, Yun Mook
    • Structural Engineering and Mechanics
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    • 제25권6호
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    • pp.717-732
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    • 2007
  • A formula to approximate the fundamental period of a fixed-free mass-spring system with varying mass and varying stiffness is formulated. The formula is derived mainly by taking the dominant parts from the general form of the characteristic polynomial, and adjusting the initial approximation by a coefficient derived from the exact solution of a uniform case. The formula is tested for a large number of randomly generated structures, and the results show that the approximated fundamental periods are within the error range of 4% with 90% of confidence. Also, the error is shown to be normally distributed with zero mean, and the width of the distribution (as measured by the standard deviation) tends to decrease as the total number of discretized elements in the system increases. Other possible extensions of the formula are discussed, including an extension to a continuous cantilever structure with distributed mass and stiffness. The suggested formula provides an efficient way to estimate the fundamental period of building structures and other systems that can be modeled as mass-spring systems.

파동반사와 도플러 효과를 고려한 전차선의 속도향상 설계 (Speed-up Design for Overhead-line Considering Contact Force Fluctuations by a Wave Reflection and a Doppler Effect)

  • 조용현;이기원;권삼영;김도원
    • 한국철도학회:학술대회논문집
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    • 한국철도학회 2004년도 추계학술대회 논문집
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    • pp.1353-1359
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    • 2004
  • There are many massive components added on the railway overhead-line. These components cause larger fluctuations of contact forces, which are due to wave reflections and Doppler effects when a high-speed train passes those. In this paper, mathematical formula are derived for the relation between the added mass and contact force fluctuations. Using the derived formula, we calculate a added mass on the overhead-line which cause amplification factor to become 2.5. German design practice requires that amplification factor due to the wave reflection should be less than 2.5 to obtain good current collection performance. To show the validity of the formula, simulation results are compared with the calculation results. Simulation results showed that contact force fluctuations grow rapidly when an added mass is larger than the calculation result. Therefore, the simple form of formula can be used for estimating maximum added mass not to cause large fluctuations of contact forces in early design phase.

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Survey of Inositol in Infant Formula

  • Patel, A.;Ditiatkovski, M.;Kennedy, L.;Oglobline, A.;Choi, N.;Richardson, G.
    • Mass Spectrometry Letters
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    • 제7권1호
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    • pp.12-15
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    • 2016
  • Results of free and bound myo-inositol in infant formula (IF) are presented. Inositol was analyzed by HILIC ultra-performance liquid chromatography coupled with mass spectrometer. The levels of free myo-inositol in 27 Australian and 4 EU originated IF samples were 300-600 mg/kg of powder or 1.6-3.1 mg/100 kJ. The amount of bound inositol in lipid fraction of IF was, on average, 10% of free myo-inositol.

상하동요하는 2차원 원주의 고유진동수 (Natural Frequency of 2-dimensional Heaving Circular Cylinder)

  • 이승준
    • 대한조선학회논문집
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    • 제45권4호
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    • pp.389-395
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    • 2008
  • It is very well known that the natural frequency of an oscillating body on the free surface is determinable only after the added mass is given. However, it is hard to find analytical investigations in which actually the natural frequency is obtained. Difficulties arise from the fact that in order to determine the natural frequency we need to compute the added mass at least for a range of frequencies, and to solve an equation where the frequency is a variable. In this study, first, a formula is obtained for the added mass, and then an equation for finding the natural frequency is defined and solved by Newton's iteration. It is confirmed that the formula shows a good agreement with the results given by Ursell(1949), and the value of natural frequency is reduced by 21.5% compared to the pre-natural frequency, which is obtained without considering the effect of added mass.

Simplified formulas of heave added mass coefficients at high frequency for various two-dimensional bodies in a finite water depth

  • Koo, Weoncheol;Kim, Jun-Dong
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제7권1호
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    • pp.115-127
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    • 2015
  • The aim of this study is to develop a simplified formula for added mass coefficients of a two-dimensional floating body moving vertically in a finite water depth. Floating bodies with various sectional areas may represent simplified structure sections transformed by Lewis form, and can be used for floating body motion analysis using strip theory or another relevant method. Since the added mass of a floating body varies with wave frequency and water depth, a correction factor is developed to take these effects into account. Using a developed two-dimensional numerical wave tank technique, the reference added masses are calculated for various water depths at high frequency, and used them as basis values to formulate the correction factors. To verify the effectiveness of the developed formulas, the predicted heave added mass coefficients for various wetted body sections and wave frequencies are compared with numerical results from the Numerical Wave Tank (NWT) technique.

방제의 본초 중량비를 활용한 방제 비교 방안에 관한 연구 (A Study on the Comparative Method of Prescription Using Herb Weight Ratio)

  • 박대식;이부균;이병욱
    • 대한한의학방제학회지
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    • 제21권2호
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    • pp.121-132
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    • 2013
  • Objectives : The objectives of this study is to establish data-base to find out similar herbal formulas with a particular herbal formula by comparing composition ratio of configuring herbs. And this thesis is to analyze differences of prescriptions and find out similar prescriptions by utilizing galenical mass ratio, which is directly related to effectiveness of galenical. Methods : This study was proceeded by using Access 2007 with Window 7(MS) and 2,787 prescriptions of which herbal configuration could be indicated by weight unit were analysed from Donguibogam. We standardize all units of the prescription and input the mass ratio data when entered galenical data. Results : We could confirm a degree of similarity between compared prescriptions and a particular prescription according to the sum of differences of herb weight ratio and similarity ratio. Conclusions : A most similar herbal formula could be searched through comparing multi prescriptions by multi prescriptions of herbal configuration from established herbal formula data-base where herb weight ratio of prescriptions is to be input.

바닥경계 가까이 있는 원형실린더의 부가질량계수의 재유도 (Re-derivation of Added Mass Coefficient of Circular Cylinder near Bottom Boundary)

  • 편종근;박창근
    • 한국해안해양공학회지
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    • 제6권3호
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    • pp.275-280
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    • 1994
  • 바닥영향을 받는 수평원형 실린더에 작용하는 힘에 대한 해석해를 복소포텐셜을 이용하여 재유도하였다. 본 연구에서 해석해를 재유도한 이유는 Yamamoto 등(1974)이 유도한 해석해는 부가질량제수가 거동하는 경향을 정확하게 설명하지 못하고있기 때문이다. 재유도한 부가질량계수 CM은 Yamamoto 등(1974)의 $C_{M}$ 과 다르며, 또한 부가질랑계수가 거동하는 경향을 만족하게 설명하고 있음을 알 수 있었다.

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