• Korea-Australia Rheology Journal
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• v.19 no.4
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• pp.201-209
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• 2007

The present paper is concerned with non-isothermal spherical Couette flow of Oldroyd-B fluid in the annular region between two concentric spheres. The inner sphere rotates with a uniform angular velocity while the outer sphere is kept at rest. Moreover, the two spherical boundaries are maintained at fixed temperature values. Hence, the fluid is effect by two heat sources; namely, the viscous heating and the temperature gradient between the two spheres. The viscoelasticity of the fluid is assumed to dominate the inertia such that the latter can be neglected. An approximate analytical solution of the energy and momentum equations is obtained through the expansion of the dynamical fields in power series of Nahme number. The analysis show that, the temperature variation due to the external source appears in the zero order solution and its effect extends to the fluid velocity distribution up to present second order. Viscous heating contributes in the first and second order solutions. In contrast to isothermal case, a first order axial velocity and a second order stream function fields has been appeared. Moreover, at higher orders the temperature distribution depends on the gap width between the two spheres. Finally, there exist a thermal distribution of positive and negative values depend on their positions in the domain region between the two spheres.

• Earthquakes and Structures
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• v.12 no.2
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• pp.153-163
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• 2017

The underlying goal of the present paper is to investigate soil and structural uncertainties on impedance functions and structural response of soil-shallow foundation-structure (SSFS) system using Monte Carlo simulations. The impedance functions of a rigid massless circular foundation resting on the surface of a random soil layer underlain by a homogeneous half-space are obtained using 1-D wave propagation in cones with reflection and refraction occurring at the layer-basement interface and free surface. Firstly, two distribution functions (lognormal and gamma) were used to generate random numbers of soil parameters (layer's thickness and shear wave velocity) for both horizontal and rocking modes of vibration with coefficients of variation ranging between 5 and 20%, for each distribution and each parameter. Secondly, the influence of uncertainties of soil parameters (layer's thickness, and shear wave velocity), as well as structural parameters (height of the superstructure, and radius of the foundation) on the response of the coupled system using lognormal distribution was investigated. This study illustrated that uncertainties on soil and structure properties, especially shear wave velocity and thickness of the layer, height of the structure and the foundation radius significantly affect the impedance functions, and in same time the response of the coupled system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.2
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• pp.31-37
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• 2008

In this paper, we analyzed the dynamic behavior of magnetic fluid in a circular pipe with multiple permanent magnets. Magnetic fluid react on magnetic field against the normal fluid. In other words, magnetic fluid flow has the electromagnetism and fluid mechanics. So magnetic fluids has studied about the fluids properties and experiment. In this paper we studied the magnetic fluids velocity and pressure distribution for the novel type actuator. Because the velocity and pressure distribution is the important element of the magnetic fluids flow. First, we analyzed the Maxwell equation for the multiple permanent magnet and then concluded the governing equations for the magnetic fluid flow using the equation of Navier-Stokes. And, we simulated the dynamic behavior of magnetic fluid flow using the FEM(Finite Element Method). And we illustrated the relation between magnetic field and dynamic behavior of magnetic fluid flow.

• Journal of Oral Medicine and Pain
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• v.9 no.1
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• pp.93-101
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• 1984

The author has studied mandibular opening and closing movement patterns using mandibular kinesiograph in order to make basic data that is necessary to diagnose the mandibular movement function. The 83 normal subjects, who were students of the school of dentistry. Kyunpook National University and Daegu Junior Health College, were selected according to sampling criteria. The results were as follow : In the sagittal plan, crossover pattern had the highest incidence in male (72.7%) and female(76.8%). There was no significant defference of distribution of habitual closing movement patterns between male and female.(p>0.05). There were difference between each patterns.(p<0.01) In the frontal plane, there was no difference of distribution of male's opening and closing movement patterns between habitual and maximum velocity (p<0.05),but difference between each subjects. (p<0.05) In the frontal plane, there was no difference of distribution of habitual opening and closing movement patterns between male and female.(p<0.05) In the frontal plane, the average number of habitual opening and closing pathways cross the midline was greater than that of maximum velocity.(p<0.05) The average of the maximum mandibular movemet velocity of male was greater than female in opening and contact(p<0.01) and there was no difference between male and female in closing.(p>0.05)

• Journal of the korean society of oceanography
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• v.37 no.3
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• pp.178-186
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• 2002

The mud deposit located to the south of Cheju Island, the East China Sea, is characterized by an upwelling system or, on occasions, a combined upwelling-downwelling system. The water mass here is associated with relatively high suspended matter concentrations. In the present study, a vertical I-D model is used to undertake numerical experiments for evaluating the upwelling and downwelling effects on the suspended particulate matter distribution patterns within the water column. The results show that: (1) because the upwelling or downwelling velocity tends to be of the same order of magnitude as the settling velocity of suspended particles, a number of different patterns of suspended matter concentration distribution are possible, depending on the relative importance of the velocities; (2) the presence of upwelling can enhance the suspended particulate matter concentration; and (3) in an upwelling-downwelling system, maximum concentrations may or may not lie in the middle of the water column, depending on, once again, the interrelationships between the opwelling/downwelling velocities and the settling velocity. Hence, the physical processes associated with upwelling/downwelling appear to be relevant to the suspended material distribution over shelf mud areas.

• Journal of ILASS-Korea
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• v.4 no.3
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• pp.32-41
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• 1999

In this research, internal-mixing twin-fluid atomizer using sonic energy is designed and manufactured. We are trying to intimate high efficiency twin-fluid atomizer to obtain good liquid atomization in the low pressure region. Define of geometric form of atomizer, characteristics of spray is influenced by position, depth and height variation of cavity resonator, variation of sound intensity and resonant sound frequency with liquid flow rate. The liquid atomization is promoted by multi-stage disintegration of mixing flow of gas with liquid and the optimum condition of position and depth of cavity resonator according to sonic energy is obtained from the condition at a=2.5mm and L=2mm. The velocity distribution of droplets shows negative value due to recirculation region at the center of axial, and as the radial direction distance is far, the velocity distribution of droplets decrease slowly after having a maximum value. However velocity and SMD show nearly uniform distribution at the down stream and as result compared to Nukiyama and Tanasawa's equation. atomization of mixing flow with air and liquid dispersing from the outlet of the nozzle is promoted by the effect of collision at the cavity resonator.

• Journal of Korean Society on Water Environment
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• v.22 no.1
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• pp.150-158
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• 2006

Over the past few years, many studies have been conducted on the flow, sediment movement, pollution transportation and scour etc. However, very few attempts have been made at the hydraulic studies reflecting upon the ecological function. The objective of this study is to examine the structures of the flow and turbulence in an open circular channel and their relationship to distribution of the organisms and chironomids. Under different flow conditions, the organic matter and some chironomids were injected into the channel. Using the obtained velocity data, the flow mechanisms and the turbulent shear stresses were analyzed. Organic matters and chironomids were distributed on the region that the velocity was slower and the turbulent shear stresses were smaller. Some habitat moved even though chironomids were inhabited. This phenomenon has relationship with the flow mechanism. Some chironomids have distributed around the habitat structure of a hemisphere. The secondary flow has affected the deposition of the organic matters and the distribution of chironomids.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.3
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• pp.371-380
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• 2015

Particulate matters in a water distribution system are main causes of turbidity and discoloration of tap water. They could be removed by conventional or uni-directional flushing in a water distribution system. The behaviors and required flow velocity of particles are not well known for their flushing. A model water main and hydrant were made from transparent acrylic pipe of 30mm and 16mm in diameter, respectively. We analyzed the effect of flushing velocity, particle density, and particle diameter. We found that the existence of break-though velocities at which particles begin to be removed, and which are affected by their physical properties. The removal efficiencies seemed to be influenced by resuspension capabilities related to their upward movement from the bottom. Heavy particles like scale were hard to remove through upflow hydrant because the falling velocity, calculated using Stokes' law, was higher. Particle removal efficiencies of upward hydrant and downward drain showed minor differences. Additionally, the length between hydrant and control valve affected flushing efficiency because the particulate matters were trapped in this space by inertia and recirculating flow.

• Journal of Astronomy and Space Sciences
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• v.14 no.1
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• pp.24-32
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• 1997

We have calculated the velocity distribution of wind driven by Alfven waves. The assumed initial number density of wind can affect the line profiles because it produces the change in the velocity distribution under the mass conservation. Initial density $N_O=5.5{\times}10^{12}/cm^3$ is chosen for a proper initial density from the observation by Schroder(1986). The wind models for $N_O=10^9,10^{10},10^{11},5.5{\times}10^{12}/cm^3$ are calculated at ${phi}$=0.06 and ${phi}$=0.78. The line profiles for lower initial density show the strong emissions and narrow absorptions because of their steeper velocity gradients.

• Journal of ILASS-Korea
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• v.10 no.4
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• pp.47-53
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• 2005

This paper presents the effects of ambient pressure on atomization characteristics of high-Pressure injector in a direct injection gasoline engine both experimentally and numerically. The atomization characteristics such as mean droplet size, mean velocity, and velocity distribution were measured by phase Doppler particle analyzer. The spray development, spray penetration, and global spray structure were visualized using a shadowgraph technique. In order to investigate the atomization process numerically, the LISA-DDB hybrid model was utilized. This breakup model assumes that the primary breakup occurs when the amplitude of the unstable waves is equal to the radius of the ligament of liquid sheet near the nozzle and the droplet deformation induces the secondary breakup. The results provide the effect of ambient pressure on the macroscopic and microscopic behaviors such as spray development, spray penetration, mean droplet size, and mean velocity distribution. It is also revealed that the accuracy of prediction of LISA-DDB hybrid model is pretty good in terms of spray developing process, spray tip penetration, and SMD distribution.