• Korean Chemical Engineering Research
• /
• 제53권6호
• /
• pp.723-729
• /
• 2015

고성능액체크로마토그래피(high-performance liquid chromatography, HPLC)에서 C18(octadecyl silica, ODS) 칼럼에서 고리형 아데노신 일인산(cyclic adenosine monophosphate, cAMP)의 크로마토그램을 얻은 후, 모멘트 분석을 수행하였다. 일반속도 모델(general rate model, GR model)을 기반으로 first absolute moment와 second central moment를 계산하였다. 모멘트 분석의 중요한 세 가지 계수인 분자확산계수(molecular diffusivity, $D_m$), 외부물질전달계수(external mass transfer coefficient, $k_f$), 입자내부확산계수(intra-particle diffusivity, $D_e$)는 각각 Wilke-Chang 식, Wilson-Geankoplis 식을 이용하고 이론단수(theoretical plate number) 식과 van Deemter 식을 비교하여 계산하였다. 실험은 각각 세 가지의 이동상 조성, 용질 농도, 유량 조건에서 수행하였다. Van Deemter 그래프를 그려 모멘트 분석결과를 정성적으로 정리했으며, 이론단 상당높이(height equivalent to a theoretical plate, HETP, $H_{total}$)에 $H_{ax}$, $H_f$, $H_d$가 미치는 영향을 알아보기 위해 van Deemter coefficient를 비교했다. HETP에 가장 큰 영향을 주는 요인은 입자내부확산($H_d$)이었으며 외부물질 전달($H_f$)는 그 영향이 매우 작았다.

• Tribology and Lubricants
• /
• 제14권3호
• /
• pp.94-99
• /
• 1998

Generally not only the radial load but also the moment may be applied to the ball bearings for a shaft system. However it has been difficult to determine the static equivalent load because there is the radial static equivalent equation only for the axial and radial force on the bearings. In this paper, the same static equivalent radial load which makes the maximum contact force at the interface between the ball and groove as the applied radial force and moment generate is calculated under the condition that the radial force and the moment are applied to the bearings simultaneously. The relation between the static equivalent load and applied force is studied. Therefore the simple and effective equation for the static equivalent radial load of the radial load and moment is proposed for the deep groove ball bearings.

• 한국농공학회지
• /
• 제42권2호
• /
• pp.78-85
• /
• 2000

The moment equations of the concentration distribution for the multi-region model are derived using the method of moment. The method originally devised by Aris is to obtain the concentration moments satisfying a given PDE (Partial Differential Equation. The method of moment is used to obtain the first five moments (0th to 4to) that satisfy the model PDE. Each moment of the concentration distribution for the model equation is plotted for the dimensionless time and gave similar results except the skewness and the kurtosis. The results of the analysis show the physical meaning of each moment. The comparisons with the number of regions or the global interaction coefficient give a possibility to determine the parameters of the multi-region model with the analytical concepts.

• Computers and Concrete
• /
• 제9권4호
• /
• pp.275-291
• /
• 2012

The service loads are often decisive in the design of concrete structures. The evaluation of the cracking moment, $M_{cr}$, is an important issue to predict the performance of the structure, such as, the deflections of the reinforced concrete beams and slabs. To neglect the steel bars of the section is a simplification that is normally used in the computation of the cracking moment. Such simplification leads to small errors in the value of this moment (typically less than 20%). However, these small errors can conduce to significant errors when the values of deflections need to be computed from $M_{cr}$. The article shows that an error of 10% on the evaluation of $M_{cr}$ can lead to errors over 100% in the deformation values. When the deformation of the structure is the decisive design parameter, the exact computing of the cracking moment is obviously very important. Such rigorous computing might lead to important savings in the cost of the structure. With this article the authors wish to draw the attention of the technical community to this fact. A simple equation to evaluate the cracking moment, $M_{cr}$, is proposed for a rectangular cross-section. This equation leads to cracking moments higher than those obtained by neglecting the reinforcement bars and is a simple rule that can be included in Eurocode 2. To verify the accuracy of the developed model, the results of the proposed equation was compared with a rigorous computational procedure. The proposed equation corresponds to a good agreement when compared with the previous approach and, therefore, this model can be used as a practical aid for calculating an accurate value of the cracking moment.

• Smart Structures and Systems
• /
• 제23권6호
• /
• pp.641-651
• /
• 2019

The stochastic stability control of the parameter-excited vibration of an inclined stay cable with multiple modes coupling under random and periodic combined support disturbances is studied by using the direct eigenvalue analysis approach based on the response moment stability, Floquet theorem, Fourier series and matrix eigenvalue analysis. The differential equation with time-varying parameters for the transverse vibration of the inclined cable with control under random and deterministic support disturbances is derived and converted into the randomly and deterministically parameter-excited multi-degree-of-freedom vibration equations. As the stochastic stability of the parameter-excited vibration is mainly determined by the characteristics of perturbation moment, the differential equation with only deterministic parameters for the perturbation second moment is derived based on the $It{\hat{o}}$ stochastic differential rule. The stochastically and deterministically parameter-excited vibration stability is then determined by the deterministic parameter-varying response moment stability. Based on the Floquet theorem, expanding the periodic parameters of the perturbation moment equation and the periodic component of the characteristic perturbation moment expression into the Fourier series yields the eigenvalue equation which determines the perturbation moment behavior. Thus the stochastic stability of the parameter-excited cable vibration under the random and periodic combined support disturbances is determined directly by the matrix eigenvalues. The direct eigenvalue analysis approach is applicable to the stochastic stability of the control cable with multiple modes coupling under various periodic and/or random support disturbances. Numerical results illustrate that the multiple cable modes need to be considered for the stochastic stability of the parameter-excited cable vibration under the random and periodic support disturbances, and the increase of the control damping rather than control stiffness can greatly enhance the stochastic stability of the parameter-excited cable vibration including the frequency width increase of the periodic disturbance and the critical value increase of the random disturbance amplitude.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
• /
• pp.477-482
• /
• 2001

This paper is to study the effect of longitudinal reinforcement ratios and axial deformation on the frame analysis in reinforced concrete(RC) columns and to investigate the effect of confined concrete core, the length-width ratio and longitudinal steel ratios on frame analysis in Concrete-Filled steel Tubular(CFT) columns. An equation if derived to evaluate the modulus of elasticity for core concrete. The 34 reference data have been collected for the purpose and are processed by the mean of a multiple regression analysis technique. The equation and longitudinal reinforcement ratios was applied to RC columns for structural analysis. Then, the difference of beam moment was identified. In general, the results of analysis was indicated reasonable differences in beam moment, in case of longitudinal reinforcement ratios applied to RC columns when compared with the plain concrete columns. In CFT columns the equation was also applied in order to the effect of confined concrete core on structural analysis. Beam moment was increased as volumetric ratio of lateral steel was decreased. The effect of longitudinal steel ratios was investigated in CFT columns and was confirmed beam moment variety. The result was appeared reasonable difference in beam moment as longitudinal steel was increased.

• 한국구조물진단유지관리공학회 논문집
• /
• 제18권2호
• /
• pp.1-8
• /
• 2014

본 연구의 목적은 경계요소를 갖는 철근콘크리트 전단벽의 잠재소성힌지길이를 합리적으로 평가할 수 있는 단순모델의 제시이다. 전단벽의 높이에 따른 이상화된 곡률분포로부터, 기본방정식은 항복모멘트와 최대모멘트 그리고 사인장균열에 의한 부가모멘트의 함수로 일반화되었다. 전단벽의 항복모멘트와 최대모멘트는 변형률 적합조건과 힘의 평형조건을 기반하여 산정하였다. 사인장균열 발생의 여부는 ACI 318-11에서 제시된 콘크리트의 전단력으로부터 검토되었으며, 부가모멘트는 Park and Paulay에 의해 제시된 트러스기구를 이용하여 산정하였다. 이들 모멘트식들은 다양한 변수범위에서 변수연구를 수행하였다. 결과적으로 등가소성힌지길이는 주철근 및 수직철근지수와 축력지수의 함수로 제시될 수 있었다. 제시된 등가소성힌지길이의 모델은 실험결과의 비교에서 평균 및 표준편차가 각각 1.019와 0.102로 실험 결과를 정확하게 예측하였다.

• 대한기계학회논문집
• /
• 제14권6호
• /
• pp.1509-1514
• /
• 1990

본 연구에서는 비압축성 유체가 온도의 영향을 받아 변화하는 경우에 대한 시 일링 간극내에서의 압력분포를 유한차분법을 이용하여 해석하였다. 여러기서 얻어진 결과를 이용하여 시일의 축력과 모멘트를 해석함으로써 시일의 동적 불안정성에 대하 여 논하였다. 이 때 기계평면시일의 형상은 코닝이 있고, 시일의 중심축이 경사진 경우를 고려하였다.

• 한국조사연구학회:학술대회논문집
• /
• 한국조사연구학회 2007년도 추계학술대회 발표논문집
• /
• pp.55-65
• /
• 2007

연구에서는 공분산구조분석을 실시하기 위해 주로 사용하고 있는 AMOS 소프트웨어에 대하여 알아보려고 한다. 응용소프트웨어에서 활용된 수학적인 모형을 알지 못하면, 구조방정식에 대한 충분한 이해를 할 수 없으며, 구조방정식에 대한 8가지 가정이 어떻게 구현되는지 알 수 가 없다. 따라서 본 연구에서는 구조방정식모형 연구에서 주로 활용되었던 LISREL 프로그램으로 RAM과 MOSAN을 구현하였고 AMOS 결과와 비교분석하였다. 연구 결과에 따르면 AMOS프로그램은 8가지의 모든 가정을 따르지 않는 것으로 나타났다. AMOS 프로그램이 MOSAN보다는 RAM으로 구현되고 있음을 본 연구를 통해 알 수 있다. AMOS 소프트웨어 프로그램은 잠재변수(F)와 측정오차(e)간의 상관값을 산출할 때 충분히 추정을 하지 못하고 부분적으로만 추정하여 값을 산출하고 있음을 알 수 있었다.

• 소음진동
• /
• 제9권3호
• /
• pp.502-508
• /
• 1999

Newly developed control methodology applied to dynamic system under random disturbance is investigated and its performance is verified experimentall. Flexible cantilever beam sticked with piezofilm sensor and piezoceramic actuator is modelled in physical domain. Dynamic moment equation for the system is derived via Ito's stochastic differential equation and F-P-K equation. Also system's characteristics in stochastic domain is analyzed simultaneously. LQG controller is designed and used in physical and stochastic domain as wall. It is shown experimentally that randomly excited beam on the base is controlled effectively by designed LQG controller in physical domain. By comparing the result with that of LQG controller designed in stochastic domain, it is shown that new control method, what we called $\ulcorner$Heo-stochastic controller design technique$\lrcorner$, has better performance than conventional ones as a controller.