• Structural Engineering and Mechanics
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• 제35권6호
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• pp.759-772
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• 2010

Seismic isolation is a well-known method to mitigate the earthquake effects on structures by increasing their fundamental natural periods at the expense of larger displacements in the structural system. In this paper, the seismic response of isolated and fixed base vertical, cylindrical, liquid storage tanks is investigated using a Finite Element Model (FEM), taking into account fluid-structure interaction effects. Three vertical, cylindrical tanks with different ratios of height to radius (H/R = 2.6, 1.0 and 0.3) are numerically analyzed and the results of response-history analysis, including base shear, overturning moment and free surface displacement are reported for isolated and non-isolated tanks. Isolated tanks equipped by lead rubber bearings isolators and the bearing are modeled by using a non-linear spring in FEM model. It is observed that the seismic isolation of liquid storage tanks is quite effective and the response of isolated tanks is significantly influenced by the system parameters such as their fundamental frequencies and the aspect ratio of the tanks. However, the base isolation does not significantly affect the surface wave height and even it can causes adverse effects on the free surface sloshing motion.

• International Journal of Aeronautical and Space Sciences
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• 제13권2호
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• pp.188-198
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• 2012

An improvement to the k-${\varepsilon}$ turbulence model is presented and is shown to lead to better agreement with data regarding supersonic base flows. The improvement was achieved by imposing a grid-independent realizability constraint in the Launder-Sharma k-${\varepsilon}$ model. The effects of compressibility were also examined. The numerical results show that the modified Launder-Sharma model leads to some improvement in the prediction of the velocity and turbulent kinetic energy profiles. Compressibility corrections also lead to better agreement in both the turbulent kinetic energy and the Reynolds stress profiles with the experimental data.

• Journal of applied mathematics & informatics
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• 제22권1_2호
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• pp.67-82
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• 2006

In this paper, we present a finite difference method for the implementation of the rotation of a circular cylinder in the incompressible flow field by solving the two-dimensional unsteady Navier-Stokes equations. The approach is to use staggered grid method so that the accuracy and order of convergence of the associated algorithms can be maintained. The proposed method is easy to be implemented and is effective. A set of simulations for the flow dynamics is provided to show the computational results.

• 약학회지
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• 제31권5호
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• pp.286-295
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• 1987

The relationship between in vitro release and in vivo bioavailability of acetaminophen from suppositories was investigated. Effect of glycyrrhizin on the drug release and rectal absorption in rats was also examined. Suppositories containing 25mg of acetaminophen were prepared with Wecobee FS (fatty base) or PEG (water-soluble base) bases. The release from the suppositories were determined with USP rotating basket dissolution apparatus and with the suppository release tester. The temperature of the dissolution medium was very critical for the dissolution of acetaminophen from Wecobee FS suppositories. The bioavailability of acetaminophen was calculated from the plasma concentration-time curve after rectal administration of the suppositories to the rats. There were no significant differences in AUC following rectal administration of Wecobee FS and PEG suppositories, but the release and absorption from the Wecobee FS suppositories were faster than those from PEG suppositories. The dissolution rate obtained by the suppository release tester was better correlated with in vivo absorption rate constant than that by the USP dissolution apparatus. It suggests that the partitioning between rectal fluid and suppository base is the rate-limiting step in the rectal absorption of acetaminophen from suppositories. Glycyrrhizin was found not to affect in vitro dissolution and rectal absorption of acetaminophen.

• 수산해양기술연구
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• 제30권4호
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• pp.312-319
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• 1994

Recently, with the rapid development in the industries such as an iron mill and chemical plants, there is enlarged by the use of the piping. Sepecially, the piping connected with a fluid, if it is increase the speed of running fluid, ought to generate cavitation phenomenon with unbalanced pressure. So, the cavitation phenomenon cause serious damage of the piping, because it generate erosion and corrosion in the piping. In this study, the steel pipe piping water (SPPW) and SPPW on weldment were tested by using of cavitation-erosion test apparatus with nozzle and were investigated under the marine environment of liquid. (specific resistance : 25 $Omega$. cm) The main results obtained are as follows : 1) The total weight loss and weight loss rate of affected zone of weldment by corrosion-erosion in the sea water are more increased than that of base metal. 2) The electrode potential by corrosion-erosion in the sea water becomes less noble than that of base metal, and current density is more increased. 3) As time goes by, the total weight loss and weight loss rate by cavitation erosion-corrosion in air-liquid 2 phase flow become more increased then those in only liquid solution. but these values turn to be decreased.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.128-135
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• 2006

This paper presents a finite element method to analyze the free vibration of a flexible HDD composed of the spinning disk-spindle system with fluid dynamic bearings(FDBs), the head-suspension-actuator with pivot bearings, and the base plate with complicated geometry. Experimental modal testing shows that the proposed method well predicts tue vibration characteristics of a HDD. This research also shows that even the vibration motion of the spinning disk corresponding to half-speed whirl and the pure disk mode are transferred to a head-suspension-actuator and base plate through the air bearing and the pivot bearing consecutively. The proposed method can be effectively extended to investigate the forced vibration of a HDD and to design a robust HDD against shock.

• Advances in nano research
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• 제2권2호
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• pp.99-109
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• 2014

Experiments are performed to investigate the single-phase flow heat transfer augmentation of MWCNT/HT-B Oil in both smooth and micro-fin helical tubes with constant wall temperature. The tests in laminar regime were carried out in helical tubes with three curvature ratios of 2R/d=22.1, 26.3 and 30.4. Flow Reynolds number varied from 170 to 1800 resulting in laminar flow regime. The effect of some parameters such as the nanoparticles concentration, the dimensionless curvature radius (2R/d) and the Reynolds number on heat transfer was investigated for the laminar flow regime. The weight fraction of nanoparticles in base fluid was less than 0.4%. Within the applied range of Reynolds number, results indicated that for smooth helical tube the addition of nanoparticles to the base fluid enhanced heat transfer remarkably. However, compared to the smooth helical tube, the average heat transfer augmentation ratio for finned tube was small and about 17%. Also, by increasing the weight fraction of nanoparticles in micro-fin helical tubes, no substantial changes were observed in the rate of heat transfer enhancement.

• 한국소음진동공학회논문집
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• 제17권1호
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• pp.24-32
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• 2007

This paper presents a finite element method to analyze the free vibration of a flexible HDD composed of the spinning disk-spindle system with fluid dynamic bearings(FDBs), the head-suspension-actuator with pivot bearings, and the base plate with complicated geometry. Experimental modal testing shows that the proposed method well predicts the vibration characteristics of a HDD. This research also shows that even the vibration motion of the spinning disk corresponding to half-speed whirl and the pure disk mode are transferred to a head-suspension-actuator and base plate through the air bearing and the pivot bearing consecutively. The proposed method can be effectively extended to investigate the forced vibration of a HDD and to design a robust HDD against shock.

• Journal of Advanced Marine Engineering and Technology
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• 제25권4호
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• pp.797-808
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• 2001

Three-dimensional trajectory of fluid particle is simulated by a particle motion, which is able to examine the influences of changes in the several parameters. To calculate the trajectory of a particle, the Runge-Kutta method was utilized. The use of a projectile of particles for the trajectory of liquid jet has been shown to be useful to estimate the influence of different operating parameters such as best particle diameter, density of liquid body, initial take-off velocity, wind velocity, cross wind velocity, take-off angle, and base angle for a released flow from the nozzle. The results give the trajectories of various types of particle of body and at different elevations, base angles, wind velocities and densities of liquid body. The trajectories in a vacuum show that air resistances decreases both the distance and the maximum height of a projectile, and also explain that the termination time is also reduced in air. In addition, the maximum distance in the x direction was obtained with take-off angles from 30 degrees to 45 degrees in still air and the projectile of particles was highly effected by wind and cross wind. Clearly, a particle has to be so positioned as to take the optimum possible advantage of the wind if the maximum distances is requested. The wind astern increased the maximum distances of x direction compared with the wind ahead. Finally, it is possible to optimize the design of pump by using these results.

• Advances in Computational Design
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• 제6권1호
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• pp.31-42
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• 2021

This research aims to demonstrate the optimal geometrical design of splayed multiple cross-sectional pin fin heat sinks (SMCSPFHS), which are a type of side-inlet-side-outlet heat sink (SISOHS). The optimiser strength Pareto evolutionary algorithm2 (SPEA2)is employed to explore a set of Pareto optimalsolutions. Objective functions are the fan pumping power and junction temperature. Function evaluations can be accomplished using computational fluid dynamics(CFD) analysis. Design variablesinclude pin cross-sectional areas, the number of fins, fin pitch, thickness of heatsink base, inlet air speed, fin heights, and fin orientations with respect to the base. Design constraints are defined in such a way as to make a heat sink usable and easy to manufacture. The optimum results obtained from SPEA2 are compared with the straight pin fin design results obtained from hybrid population-based incremental learning and differential evolution (PBIL-DE), SPEA2, and an unrestricted population size evolutionary multiobjective optimisation algorithm (UPSEMOA). The results indicate that the splayed pin-fin design using SPEA2 issuperiorto those reported in the literature.