• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.99-102
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• 2002

The present study describes a numerical analysis for simulation of the sloshing of flows with free-surface which contained in a rectangular tank The SOLA-VOF (Volume of fluid) method uses a fixed mesh for calculating the motion of flow and the free-surface. This Eulerian approach enables the VOF method to use only a small amount of computer memory for simulating sloshing problems with complicated free-surface contours. The VOF function, representing the volume fraction of a cell occupied by the fluid, is calculated for each cells, which gives the locating of the free-surface filling any some fraction of cells with fluid. Using SOLA-VOF method, the study describes visualization about simulation of the sloshing of flows and damping effect by baffle. Translation and pitching motion of the forms have been investigated The time-dependent changes of free-surface height are used for visualization subject to several conditions such as fluid height horizontal acceleration, sinusoidal motion, and viscosity. The free-surface heights were used for comparing wall-force, which is caused by sloshing of flows. Baffle was Installed to reduce the force on the wall by sloshing of flows. Damping effects was extensively expressed under the conditions such as baffle shape and position.

• 한국소음진동공학회논문집
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• 제16권1호
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• pp.12-18
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• 2006

This research investigates the electromechanical characteristics of a spindle motor in a free-falling mobile hard disk drive before unexpected shock. Electromechanical simulation includes a time-stepping finite element analysis of the magnetic field in a speed controlled brushless DC motor and dynamic analysis of the stationary and rotating part linked by the fluid dynamic bearing under the free-falling condition. Analysis results show that the dynamic characteristics of the rotating spindle system during free-falling state have an effect on the relative motion between the stationary and rotating part of HDD. It results from the variation of reaction force in the bearing area due to the gravity force exerted on the rotating part of HDD, and the free-falling condition can be detected by observing the signal of the spindle motor and disk-head interface without using an accelerometer.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.324-329
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• 2005

This research investigates the electromechanical characteristics of a spindle motor in a free-falling mobile hard disk drive before unexpected shock. Electromechanical simulation includes a time-stepping finite element analysis of the magnetic field in a speed controlled brushless DC motor and dynamic analysis of the stationary and rotating part linked by fluid dynamic bearing under the free-failing condition. Analysis results show that the dynamic characteristics of the rotating spindle system during free-falling state have an effect on the relative motion between the stationary and rotating part of HDD. It results from the variation of reaction force in the bearing area due to the gravely force exerted on the rotating part of HDD, and the free-failing condition can be detected by observing the signal of the spindle motor and disk-head interface without using the accelerometer.

• Structural Engineering and Mechanics
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• 제31권4호
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• pp.453-475
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• 2009

The literature regarding the free vibration analysis of Bernoulli-Euler and Timoshenko beams on elastic soil is plenty, but the free vibration analysis of Reddy-Bickford beams on elastic soil with/without axial force effect using the Differential Transform Method (DTM) has not been investigated by any of the studies in open literature so far. In this study, the free vibration analysis of axially loaded Reddy-Bickford beam on elastic soil is carried out by using DTM. The model has six degrees of freedom at the two ends, one transverse displacement and two rotations, and the end forces are a shear force and two end moments in this study. The governing differential equations of motion of the rectangular beam in free vibration are derived using Hamilton's principle and considering rotatory inertia. Parameters for the relative stiffness, stiffness ratio and nondimensionalized multiplication factor for the axial compressive force are incorporated into the equations of motion in order to investigate their effects on the natural frequencies. At first, the terms are found directly from the analytical solutions of the differential equations that describe the deformations of the cross-section according to the high-order theory. After the analytical solution, an efficient and easy mathematical technique called DTM is used to solve the governing differential equations of the motion. The calculated natural frequencies of one end fixed and the other end simply supported Reddy-Bickford beam on elastic soil using DTM are tabulated in several tables and figures and are compared with the results of the analytical solution where a very good agreement is observed and the mode shapes are presented in graphs.

• 대한약리학회지
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• 제31권1호
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• pp.53-61
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• 1995

Lidocaine의 심근 수축력 억제 기전이 적출 심장에서 내인성 기질의 사용과 관련이 있는가를 규명하기 위하여, 심장의 phosphofructokinase (PFK)에 대한 강력한 억제 작용을 나타내는 citracte와 bicarbonate-free medium을 이용하여 쥐의 적출 심방 수축성에 대한 lidocaine의 영향을 연구하여 다음과 같은 실험 결과를 얻었다. Citrate와 bicarbonate-free medium은 쥐의 적출 심방의 수축력을 현저히 저하시켰다. Pyruvate나 acetate는 citracte와 bicarbonate-free medium에서 저하된 심방 수축력을 현저히 증가시키는 반면, fructose는 수축력을 증가시키지 못했다. 이 결과는 citrate와 bicarbonate-free medium이 Embden-Meyerhof pathway의 일부, 즉 PFK step을 억제함을 시사한다. 외인성 기질이 없을때 citrate와 bicarbonate-free medium은 기질 제거 용액에서 심방 수축력을 현저히 감소시키며, acetate에 의해 수축력이 회복되었다. 이는 PFK step 이전 단계의 내인성 기질 (glycogen)이 citrated에 의해 억제됨을 시사한다. Lidocaine은 citrate에 의해 억제된 수축력을 더욱 감소시켰다. 이 결과는 lidocaine에 의한 심방 수축력 억제가 PFK step 이후 단계의 내인성 기질 억제에 의한 것임을 시사한다. 이상의 결과로 보아 lidocaine의 적출 심방에 대한 수축력 억제 작용은 두가지 (또는 그 이상)의 기전에 의한 것으로 사료된다: 하나는 PFK step 전단계의 해당과정의 억제기전이고 또 다른 기전은 PFK step 이후의 내인성 기질(들)의 억제인 것으로 사료된다.

• 한국해양공학회지
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• 제29권3호
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• pp.270-282
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• 2015

A submerged body moving near the free surface needs to maintain its attitude and position to accomplish missions. It is necessary to validate the performance of a designed controller before a sea trial. The hydrodynamic coefficients of maneuvering are generally obtained by experiments or computational fluid dynamics, but these coefficients have uncertainty. Environmental loads such as the wave exciting force and suction force act on the submerged body when it moves near the free surface. Thus, a controller for the submerged body should be robust to parameter uncertainty and environmental loads. In this paper, the six-degree-of-freedom equations of motions for the submerged body are constructed. The suction force is calculated using the double Rankine body method. An adaptive control method based on an artificial neural network and proportional-integral-derivative control are used for the depth controller. Simulations are performed under various depth and speed conditions, and the results show the effectiveness of the designed controller.

• 한국공간구조학회논문집
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• 제17권1호
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• pp.77-84
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• 2017

Vortex-induced vibration and instability vibration of tall buildings are very important fluid-structure interaction phenomenon, and many fundamental questions concerning the influence of body movement on the unsteady aerodynamic force remain unanswered. For tall buildings, there are two experimental methods to investigate the characteristics of unsteady aerodynamic forces, one is forced vibration method and the other is free vibration method. In the present paper, a free vibration method was used to investigate the unsteady aerodynamic force on tall building whose aspect ratio is 9 under boundary layer simulating city area. Wind pressures on surfaces and tip displacements were measured simultaneously, and the characteristics of tip displacements and generalized forces were discussed. It was found that variation of across-wind displacements showed different trend between the case when wind speed increases and wind speed decreases, and the fluctuating generalize forces in across-wind direction of vibrating model are larger than that of static model near the resonant wind speed and approach to the static value. And for higher wind speed range, there were two peaks in across-wind power spectra of generalize forces of vibrating model, which means that two frequency components are predominant in unsteady aerodynamic forces.

• 한국식품영양과학회지
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• 제28권3호
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• pp.511-519
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• 1999

To prevent the denaturation of ficin(EC 3.4.22.3) that is a proteolytic enzyme in fig(Ficus carica L.), fig conserve was heated to 55oC. The fig conserve was added as a tenderizer to native Korean cattle beef(KCB), dairy cattle beef(DCB), castrated dairy cattle beef(CDCB), and imported beef(IB). The composition of free amino acids, hydroxyproline content, shear force, cooking loss, morphological changes and sensory evaluation were then investigated to observe the effect of tenderizing beef with fig conserve. Free amino acids and cooking loss of treated beef were higher than those of control, whereas hydroxyproline and shear force were lower. Glutamine in treated beef decreased relatively but asparagine increased. Hydroxyproline was found, in increasing order of abundance, in DCB, CDCB, IB and KCB. By portion, loin was higher than tenderloin in free amino acids, hydroxyproline and shear force but was lower in cooking loss. Observation with a light microgram revealed a surprising loss of muscle fiber in treated beef. In sensory evaluation of uncooked beef, the control was redder than the treated beef(p<0.01~p<0.05). Treatment with fig conserve increased the juiciness of both cooked CDCB and IB(p<0.001) and decreased their hardness(p<0.01~p<0.001).

• KEPCO Journal on Electric Power and Energy
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• 제8권1호
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• pp.31-36
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• 2022

This paper presents the measuring process of dynamic properties of offshore wind power foundation and provides consideration of each step. This Guideline enables to maintain consistent measuring procedure and therefore increase the reliability of test results. Small scaled suction bucket foundation was fabricated to represent the commercial support structure installation mechanism and two cases(free-free, free-fixed) of dynamic tests were performed at workshop. From the tests, the importance of dynamic properties of connection part between suction bucket and tower was figured out. More over, types and configuration of measuring devices are recommended which can help find the natural frequency of wind turbine foundation correctly. In field test, it was found that the natural frequency of suction bucket foundation was increased linearly with the penetration depth due to the confining effect of ambient soil. Meanwhile, it was not easy to get an enough excitation force with normal impact hammer because the N.F of suction bucket model was in the lower range of 0 Hz ~ 5 Hz. Therefore, new excitation method which has enough force and can excite lower frequency range was devised. This study will help develop safety check procedure of suction bucket foundation in field at each installation stage using the N.F measurement.

• 한국전산유체공학회지
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• 제22권1호
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• pp.81-87
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• 2017

The characteristics of flow past a square cylinder submerged under the free surface have been numerically studied. An immersed boundary method was adopted for implementation of the cylinder cross-section in a Cartesian grid system. Also, a level-set method was used to capture the interface of the two fluids. The case for Reynolds number 150 was examined. At the specific Reynolds number, by varying the gap ratio(0.25, 0.40, 0.55, 0.70, 1.00, 1.50, 2.50, 5.00) the effects of the free surface on the force coefficients and Strouhal number of vortex shedding were identified. The presence of the free surface very close to the cylinder significantly affects the shedding pattern, resulting in considerable deviation of the force coefficients and Strouhal number from those of the single-phase flow. In addition, the influence of Froude number was considered in this study. By increasing Froude number(0.2-0.4), flow topology change was identified at the specific gap ratios(0.40, 0.70, 1.50, 5.00).