• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.14 no.12
• /
• pp.1233-1238
• /
• 2003

In this paper, radially corrugated circular-type microstrip patch antenna was devised and manufactured for GPS (center frequency: 1.575 GHz). Radially corrugated circular-type microstrip patch antenna having radiational corrugation-patch contributed to add size reduction ratio by lowering the resonant frequency because the edge current also has the extended and perpendicular path. As a result, radially corrugated circular-type microstrip patch antenna has 28 % area reduction than planer circular-type patch antenna for linear polarization and 27.7 % area reduction than planer circular-type patch antenna for circular polarization. Radially corrugated circular-type microstrip patch antenna is suitable for miniaturized receive antenna for GPS which has the characteristic of gain 2.1 dBd, axiai ratio 1.3 dB, 2 dB axial bandwidth 15 MHz(0.9 %).

• Journal of Embryo Transfer
• /
• v.24 no.3
• /
• pp.159-167
• /
• 2009

Ultrasonographic examination was performed to observe the ultrasonographic image of Korean native cows' normal uterus in condition of in vitro and in vivo. The experiment was done 28 slaughtered cows' uterus using immersed in water in vitro, and 41 healthy breeding cows taken rectal ultrasonography in vivo. Ultrasonographic examination of uterine was taken on the reference of cross section of intercornual ligaments' cranial. Each uterus on the experiments was compared by estrous cycle and ultrasonographic frequency. The uterine structure using ultrasonography was 5 layers of uterine horn in vivo as well as in vitro. Uterine horn was observed to be distinguished from inside to outside as endometrium to inner echogenic layer, circular muscle layer to slightly echogenic elliptical layer, stratum vasculare to central echogenic layer, longitudinal muscle layer to slightly echogenic arched layer, and perimetrium to outer echogenic layer, respectively. According to the observation of uterus related to estrous cycle and ultrasonographic examination, uterine endometrium in vitro was constantly founded irrespective of estrous cycle and ultrasonographic frequency. On the low frequency, endometrium and circular muscle layer in estrus were prone to distinguished than in diestrus. On the high frequency, endometrium and circular muscle layer were always distinguished regardless of estrous cycle. In vivo, uterine endometrium and circular muscle layer were observed regardless of estrus and ultrasonographic frequency. On the low frequency, stratum vasculare and longitudinal muscle layer were not likely to be distinguished in diestrus, but estrus. On the high frequency, stratum vasculare and longitudinal muscle layer were observed regardless of estrous cycle. Also, every uterine structure was easily distinguished on high frequency than low frequency owing to precision of distinction in layers. The difference of results followed by the experiments conditions between in vitro and in vivo was that uterine endometrium and circular muscle layer in diestrus in vitro were difficult to be distinguished and uterine lumen was observed during whole estrous cycle. In vivo, It was founded that the distinction of stratum vasculare and logitudinal muscle layer in diestrus was complicated and uterine lumen was observed during only estrus. In view of the result so far achieved, normal uterine structure divided in 5 layers on ultrasonography was accorded with microscopic organization, uterine structure was likely to be observed during estrus than diestrus, high frequency checkup than low frequency, and uterine endometrium, circular muscle, stratum vasculare was easily observed regardless of estrous cycle and ultrasonographic frequency.

• Proceedings of KOSOMES biannual meeting
• /
• 2007.11a
• /
• pp.177-183
• /
• 2007

Flow characteristics of the cylinder wake controlled with a small control cylinder were experimentally investigated by the PN (Particle Image Velocimetry) technique. Flow visualization of the flow around a circular cylinder was conducted in the Circulating Water Channel. The control cylinder having diameter of d=5mm, 10mm and 20mm was installed behind a circular cylinder of D=50mm. And the Reynolds number were $Re=4.9{\times}10^3,\;Re=9.9{times}10^3$ and $Re=1.9{\times}10^4$. In this study, the frequency characteristics of the controlled wake were analyzed by using spectral analysis of the measured wake velocity signals. As a result, the controlled wake had smaller vortex shedding frequency than that of circular cylinder wake by the effect of the control cylinder. Governing parameters of the flow control were d/D, and Reynolds number and they largely influenced the frequency characteristics of the cylinder wake. And vortex shedding frequency appeared most lowly at d=0.2D

• Coupled systems mechanics
• /
• v.5 no.3
• /
• pp.255-267
• /
• 2016

To investigate the surface effects on vibration of embedded circular curved nanosize beams, nonlocal elasticity model is used in combination with surface properties including surface elasticity, surface tension and surface density for modeling the nano scale effect. The governing equations are determined via the energy method. Analytically Navier method is utilized to solve the governing equations for simply supported at both ends. Solving these equations enables us to estimate the natural frequency for circular curved nanobeam including Winkler and Pasternak elastic foundations. The results determined are verified by comparing the results by available ones in literature. The effects of various parameters such as nonlocal parameter, surface properties, Winkler and Pasternak elastic foundations and opening angle of circular curved nanobeam on the natural frequency are successfully studied. The results reveal that the natural frequency of circular curved nanobeam is significantly influenced by these effects.

• Structural Engineering and Mechanics
• /
• v.22 no.6
• /
• pp.719-739
• /
• 2006

An analytical method for the free vibration of two circular plates coupled with an inviscid and compressible fluid is developed by the Rayleigh-Ritz method. The fluid is bounded by a rigid cylindrical vessel and two circular plates with an unequal thickness and diameter. It was found that the theoretical results could predict well the fluid-coupled natural frequencies with an excellent accuracy when compared with the finite element analysis results. As the fluid thickness increases or the plate thickness difference increases, an abrupt curve veering in the natural frequency loci of the neighboring modes and drastic changes in the corresponding mode shapes are observed. The mode localization frequently appears in the higher modes and in the wide gap between the plates because of a decrease in the fluid coupling owing to the fluid dispersion effect.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.11 no.4
• /
• pp.43-51
• /
• 2001

An experimental modal analysis is the process to identify structure's dynamic characteristics such as resonant frequencies, damping values and mode shapes. An experimental model was made of stainless steel in the shape of a circular cylindrical shell and installed on the test bed with jigs. For investigating vibrational characteristics of the continuous circular cylindrical shell with intermediate supports, modal testing is performed by using impact hammer, accelerometer and 8-channel FFT analyzer. The frequency response function(FRF) measurements are also made on the experimental model within the frequency range from 0 to 4kHz. Modal parameters are identified from resonant peaks in the FRF's and animated deformation patterns associated with each of the resonances are shown on a computer screen. The experimental results are compared with analytical and FEA results.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.26 no.12
• /
• pp.1934-1939
• /
• 1989

The circular microstrip resonator which can be exactly performed with theoretical resonant frequency using the conception of dynamic effective relative dielectric constants is analyzed in this paper. The formula of exact resonant frequency of resonator, in this study, is estabilished by effective resonator dimension and dynamic relative dielectric constant. The measurement of transmission type circular resonator which fabricated by AL2O3 and Epsilam-10 is to prove that the experimental results are more agreed a well with the simulated values by this new method than the simple resonator model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1997.04a
• /
• pp.551-556
• /
• 1997

Based on the experiment for the frequency characteristics and the feedback theory of the impinging-tones, the unstable characteristics of the symmetric mode is analyzed among the various unstable modes of circular impinging jets. There are two different symmetric modes; one is the low-frequency mode S1 due to the vortex at the outside of the jet and the high-frequency mode S2 due to the inside vortex. Each mode has its own characterictics of convection speed decreasing with frequency.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.21 no.6
• /
• pp.570-579
• /
• 2011

This paper deals with free vibrations of the circular curved beams with constant volume, whose cross sectional shapes are the circular solid cross-sections. Volumes of the objective beam are always held in constant regardless shape functions of the cross-sectional radius. The shape functions are chosen as the linear, parabolic and sinusoidal ones. Ordinary differential equations governing free vibrations of such beam are derived and solved numerically for determining the natural frequencies. In numerical examples, the hinged-hinged, hinged-clamped and clamped-clamped end constraints are considered. As the numerical results, relationships between frequency parameters and various beam parameters such as rise ratio, section ratio, elasticity ratio, volume ratio, slenderness ratio and taper type are reported in tables and figures.

• Journal of the Society of Naval Architects of Korea
• /
• v.50 no.4
• /
• pp.224-231
• /
• 2013

The concept of the natural frequency is useful for understanding the characters of oscillating systems. However, when a circular cylinder floating horizontally on the water surface is heaving, due to the hydrodynamic forces, the system is not governed by the equation like that of the harmonic one. In this paper, in order to shed some lights on the more correct use of the concept of the natural frequency, a problem of the heaving circular cylinder is analyzed in the time domain. The equation of motion, an integro-differential equation, was derived following the fashion of Cummins (1962), and its coefficients including the retardation function were obtained using the numerical solution of Lee (2012). The equation was solved numerically, and the experiment was also carried out in the CNU flume. Using our numerical and experimental results, the natural frequency was defined as its average value given by the motion data excluding those of the initial stage. Our results were then compared with those of the existing investigations such as Maskell and Ursell (1970), Ito (1977) and Yeung (1982) as well as the newly obtained results of Lee (2012). Comparison showed that the natural frequency obtained here agrees well with that of Lee (2012), which was found through the frequency domain analysis. It was also shown that the approximation of heaving motion by a damped harmonic oscillation, which was regarded as suitable by most previous investigators, is not physically suitable for the reason that can be clearly shown through comparing the shape of MCFRs(Modulus of Complex Frequency Response). Furthermore, we found that although the previous approximations yield the damping ratio significantly different from our result the magnitude of natural frequency is not much different from our result.