• International Journal of Fluid Machinery and Systems
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• v.3 no.4
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• pp.386-395
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• 2010

The article is focused in three areas. In the first part there are analyzed the adhesion forces at the liquid and solid surface interface. There are shown the measured values of surface energy for different types of surfaces. The value of surface energy is decisive for determining the extent of the surface wettability by the liquid. The second part points to the possible negative effects of partly wettable surfaces, showing susceptibility to cavitation. The third section describes the practical aspects of surface wettability by the liquid. Under the new boundary conditions bases, expressing the effect of adhesion forces, there are determined the centrifugal pump characteristics.

• International Journal of Human Ecology
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• v.10 no.2
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• pp.1-12
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• 2009

The purpose of this study was to explore the dynamics of stepfamilies and the adjustment difficulties such families may experience. The study describes some sociodemographic characteristics of a sample of 117 stepfamilies. The independent variables were stresses due to adjustment difficulties, which were defined as "role strains". Sociodemographic variables included gender, family income level, length of time since remarriage, type of stepfamily, and the existence of any children born to the new marriage. The dependent variable was the extent of stepfamily adjustment, expressed as a scale. The factors influencing family adjustment included stepparent gender, family income level, type of stepfamily, and various role strain variables (family boundary ambiguity, role conflict, etc.). Practical recommendations for social work are made and possibilities for future research in this area are discussed based on the results of this study.

• Journal of Ocean Engineering and Technology
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• v.19 no.5 s.66
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• pp.78-82
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• 2005

The motion response results of a submerged submarine section in waves are presented. The numerical method is based on Cauchy's integral and 3 degrees-of-freedom motions of submarine sections are calculated in two dimensions, in regular waves. The fully nonlinear free surface and body boundary conditions are applied to the present problem, and the viscous effects on the submarine are modeled by Morison's formulas. The motions of submarine sections in beam sea are directly simulated and the effects of wave frequency, snorkel depth, and bridge are discussed.

• Journal of Ocean Engineering and Technology
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• v.8 no.2
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• pp.31-37
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• 1994

3-Dimensional panel method is now developed to the level that one can calculate the lift of a three dimensional body with the same accuracy of wind tunnel test and some current codes can consider the boundary layer effects due to the viscosity and unsteady motion in the calculation of lift. This paper is also aimed to develop these kinds of computing programs, and as a beginning, the authors restricted the problems to the steady potential flow cases. The calculation of 3-Dimensional body, wing and tandem wing carried out, using source panel and vortex ring panel. Finally, the interactions between 3-Dimension symmetric body and a wing are also calculated.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.231-239
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• 2003

A Digital Wave Tank simulation technique based on a finite-difference method and a modified marker-and-cell (MAC) algorithm is applied to investigate the characteristics of nonlinear Tsunami propagations and their interactions with a 2D sloping beach and Ohkushiri island, and to predict maximum wave run-up around the island. The Navier-Stokes (NS) and continuity equation are governed in the computational domain and the boundary values updated at each time step by a finite-difference time-marching scheme in the frame of rectangular coordinate system. The fully nonlinear kinematic free-surface condition is satisfied by the modified marker-density function technique. The Nearshore Tsunami is assumed to be a solitary wave and generated from the numerical wavemaker in the developed Digital Wave Tank. The simulation results are compared with the experiments and other numerical methods based on the shallow-water wave theory.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.12 s.255
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• pp.1581-1587
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• 2006

An optimization formulation is proposed to minimize sound pressures in a two-dimensional cavity by controlling the attachment area of viscoelastic unconstrained damping materials. For the analysis of structural- acoustic systems, a hybrid approach that uses finite elements for structures and boundary elements for cavity is adopted. Four-parameter fractional derivative model is used to accurately represent dynamic characteristics of the viscoelastic materials with respect to frequency and temperature. Optimal layouts of the unconstrained damping layer on structural wall of cavity are identified according to temperatures and the amount of damping material by using a numerical search algorithm.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.1011-1018
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• 1992

A series of experiment has been performed on the spray characteristics in a cylindrical confined space with the injection pressure taken as a parameter. By using a single-hole patternator and the Malvern particle sizer, the spray mass flux, drop size and volume concentration distributions along the radial and axial directions were obtained ; the line-of- sight data by Malvern particle sizer have been converted to the ring-of-sight data by using the tomographical transformation techniqe. The experimental results show that, due to the restriction on the ambient gas entrainment by the wall boundary, the effective spray angle is increasing. The spray drops were measured to be smaller in the confined space because of a large number of floating small drops by recirculation of the gas phase and the breakup of large drops by the wall collision. Also the details on the flow behavior of the confined spray are discussed.

• Journal of the Korean Society of Safety
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• v.11 no.2
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• pp.116-121
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• 1996

On the stability of Timoshenko cantilever beam subjected to a follower force, the influence of the characteristics of elastic constraints at the free end Is studied. The equations of motion and boundary conditions of this nonconservative elastic system are estabilished by using the Hamilton's principle. Upon evaluation of the stability of this system, the effect of shear deformation and rotatory inertia is considered in calculation. Using cowper's formulae Timoshenko's shear coefficient K'are determined. From this imvestigation it is found that the constrain parameter have an appreciable stabilizing effect in this nonconservative system. Moreover, it is obvious that the small values of K'decrease the flutter load of this system.

• 한국기계연구소 소보
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• s.20
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• pp.27-32
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• 1990

A counter balance valve is used as one part of hydraulic motor brake system. The function of this valve is to protect over-run or free falling of inertia load. But occasionally the brake system with counter balance valve makes some undesirable problems such as pressure surges or vibrations. In this study, for the purpose of easy estimation about dynamic chrcteristics of hydraulic system including counter balance valve, precise formulation describing fluid dynamics and valve dynamics under various boundary conditions were made. dynamic caracteristics were analysed by numerical intergration using Runge-Kutta method, because the equations in this circuit with counter balance valve contain various nonlinear terms. So the analyzing method developed in this study enabled very easy estimating the relation between the performance of counter balance valve and various physical parameters related to the valve.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.59-65
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• 2000

This paper describes the characteristics of a one dimensional narrow-wall slotted waveguide array with a single-layer linear-to-circular polarization converter consisting of a dipole array. An external boundary value Problem of one slot and three dipoles, which approximates the mutual coupling between the dipole array and an edge slot extending over three faces of a rectangular waveguide, is formulated and analyzed by the method of moments; design of polarization conversion is conducted for this model as a unit element. If every unit element has perfect circular polarization, grating lobes appear in the array pattern due to the alternating slot angle: these are suppressed in this paper by changing the dipole angle and degrading the axial ratio of the unit element. The validity of the design is confirmed by the measurements. The dipole array has negligible effects upon slot impedance; the polarization conversion for existing narrow-wall slotted arrays is realized by add-on dipole array.