• Journal of the Society of Naval Architects of Korea
• /
• v.41 no.1
• /
• pp.23-30
• /
• 2004

In the Lagrangian vortex particle method based on the vorticity-velocity formulation for solving the incompressible Navier-Stokes equations, a numerical scheme for calculating pressure fields is presented. Implementation of the numerical method is directly connected with the well-established surface panel methods, just by dealing with the dynamic coupling among vorticity field. Assuming the vorticity and the velocity fields are to be calculated in time domain analysis, the pressure calculation for a complete set of solution at present time step is performed in a similar way to the one used in the Eulerian description. For a validation of the present method, we illustrate the early development of the viscous flow about an impulsive started circular cylinder for Reynolds number 550. The comparative study with the Eulerian finite Volume method provides an extensive understanding and application of the mesh-free Lagrangian vortex methods for numerical simulation of viscous flows around arbitrary bodies of general shape.

• Journal of electromagnetic engineering and science
• /
• v.11 no.3
• /
• pp.227-233
• /
• 2011

This paper describes the development of a broadband quasi-Yagi antenna using a folded dipole driver. The antenna is designed on a low-permittivity substrate to reduce the surface wave effect, and hence the gain can be enhanced easily by adding directors. The folded dipole driver is connected to a 50-${\Omega}$ microstripline via a simple broadband microstrip-to-coplanar stripline transition with a quarter radial stub. The key motivation for the use of a folded dipole is to increase the input impedance at the driver, allowing a smaller mismatch loss between the antenna driver and the coplanar stripline feed. The proposed antenna has a measured bandwidth of 4.67~6.26 GHz for the -10 dB reflection coefficient, and a flat gain of 4.86~5.15 dB within the bandwidth.

• Journal of the Korean Society of Safety
• /
• v.5 no.3
• /
• pp.8-26
• /
• 1990

It is important to have exact information about the contact pressure distribution in the design of connected parts of machines and structures. In previous works, stress analyses on a two body contact problem have been carried out in large numbers. Besides, the measurement of contact stress is important to confirm the adequateness of the theoretical analysis, to verify appropriateness of Hertzian contact theory and to know the practical pressure distribution, but an excellent measuring method con't be found at present. Therefore, a quantitative measurement of contact pressure by means of ultrasonic waves using a normal probe and an angle has been proposed to measure the contact pressure distribution between two rough flat surfaces. At first, in a new proposed calibration method, the relation between mean contact pressure and sound pressure of reflected waves is obtained by using calibration blocks with various surface roughnesses made of the same material as the rectangular section beams And then, this experimental results are compared with the analytical ones, and the utility of this method is discussed.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.57 no.2
• /
• pp.181-185
• /
• 2008

In this paper, we investigates accident actual conditions of electric outlet for low voltage that is used into interior and clear hazardous factor. Electric outlet for general can know that melting of socket-outlet and carbonization of support occur if a contaminant becomes burnout because is flowed in. Existent outlet consists of structure that special quality is good but inflow of a contaminant is easy when is dry. But, waterproof outlet passes silicon layer and have connected structure plug. As developed outlet covers whole surface and back side, interval was shut. Safety pin of developed outlet was established to operate to vertical direction. Therefore, we estimate that contribute on prevention of electrical disaster if use developed outlet to a restaurant, a laundry, a laboratory etc.

• The KIPS Transactions:PartA
• /
• v.8A no.1
• /
• pp.42-47
• /
• 2001

In this paper, we present a curve fitting algorithm using a ball curve. Our algorithm is recursive method for fitting, which is not a traditional ball function but a continuous ball function. This algorithm consists of two steps. The first step, it is classified the composite corner points to joint points until selected from the given data set. The second step is the curve fitting. The basis function for curve fitting is use to ball function. Also, the weighted least square method, to insert knot, is an efficient method for piecewise ball curve and ball curve segments will be smoothly connected at all composit points. The proposed algorithm will be applied to represent image representation, like fonts, digital image and GIS.

• Journal of Magnetics
• /
• v.22 no.1
• /
• pp.78-84
• /
• 2017

This paper investigates the influence of mechanical energy storage on the interior permanent magnet synchronous machine (IPMSM) when it is operated in the generating mode. An IPMSM with six-poles and nine-slots employing concentrated coil winding type is considered as the analysis model, and a surface-mounted permanent magnet synchronous motor directly connected to a heavy wheel is applied as the mechanical energy storage system by using the moment of inertia. Based on the constructed experimental set-up with manufactured machines and power converters, the generated electrical energy is converted into the mechanical energy, and the electromagnetic filed characteristics of IPMSM are subsequently investigated by applying the measured phase current of IPMSM based on finite element method. Compared to the characteristics in a no-load condition, it is confirmed that the magnetic behavior, radial force, and power loss characteristics are highly influenced by the harmonics of the phase current due to the mechanical energy storage system.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.3
• /
• pp.515-520
• /
• 2009

In this paper, the monitoring system was developed measuring the light signal emitted from the plasma in aluminum laser welding. Spectrum of plasma was measured using a spectrometer, and the photodiode was selected based on the spectrum analysis. The sensor signals for various welding conditions could be obtained, the characteristic of signal was closely related to the intensity and stability of plasma through mean value of signal and FFT analysis. The reason of signal fluctuation was behavior of plasma and keyhole and it was also connected with the surface bead shape of weld.

• Bulletin of the Korean Mathematical Society
• /
• v.26 no.1
• /
• pp.1-9
• /
• 1989

In 1980 and 1983, it was proved that P $D^{2}$-groups are surface groups ([2], [3]). Since then, topologists have been positively studying about P $D^{n}$ -groups (or $D^{n}$ -groups). For example, let a topological space X have a right .pi.-action, where .pi. is a multiplicative group. If each x.memX has an open neighborhood U such that for each u.mem..pi., u.neq.1, U.cap. $U_{u}$ =.phi., this right .pi.-action is said to be proper. In this case, if X/.pi. is compact then (1) .pi.$_{1}$(X/.pi).iden..pi.(X:connected, .pi.$_{1}$: fundamental group) ([4]), (2) if X is a differentiable orientable manifold with demension n and .rho.X (the boundary of X)=.phi. then $H^{k}$ (X;Z).iden. $H_{n-k}$(X;Z), ([6]), where Z is the set of all integers.s.

• Corrosion Science and Technology
• /
• v.18 no.4
• /
• pp.117-120
• /
• 2019

Considering the tendency of development of electrification vehicles, development and verification of new evaluation technology is needed because of new technology applications. Recently, as the battery package is set outdoors of an electric vehicle, such vehicles are exposed to corrosive environments. Among major components connected to the battery package, rust prevention of high-voltage cables and connectors is considered the most important issue. For example, if corrosion of high voltage cable connectors occurs, the corrosion durability assessment of using an electric vehicle will be different from general environmental corrosion phenomena. The purpose of this study is to investigate the corrosion mechanism of high voltage cable connectors of an electric vehicle under various driving environments (road surface vibration, corrosion environment, current conduction by stray current, etc.) and develop an optimal rust prevention solution. To improve our parts test method, we have proposed a realistic test method to reproduce actual electric vehicle corrosion issues based on the principle test.

• Bulletin of the Korean Mathematical Society
• /
• v.59 no.1
• /
• pp.27-43
• /
• 2022

The one-sided fattenings (called semi-ribbon graph in this paper) of the graph embedded in the real projective plane ℝℙ² are completely classified up to topological equivalence. A planar graph (i.e., embedded in the plane), admitting the one-sided fattening, is known to be a cactus boundary. For the graphs embedded in ℝℙ² admitting the one-sided fattening, unlike the planar graphs, a new building block appears: a bracelet along the Möbius band, which is not a connected summand of the oriented surfaces.