• Journal of the Korean Institute of Telematics and Electronics
• /
• v.16 no.1
• /
• pp.9-13
• /
• 1979

Multimode characteristics of a dielectrically loaded rectangular cavity are analyzed by a graphical method. Coupled transcendental equations for multimode frequencies may be solved graphlially. This shows that the resonant frequencies of the partially flued cavity with a dielectic are shifted toward lower frequencies compared to those of the empty cavity. It is shown that a perturbational scheme can not be employed to calculate multimode frequencies because of relatively large frequency shrift. Existence of the surface wave modes In the dielectric and their resonant frequencies are early predicted from this graphical method.

• ETRI Journal
• /
• v.36 no.6
• /
• pp.1062-1065
• /
• 2014

A novel substrate-integrated waveguide (SIW) cavity-backed slot antenna is proposed in this study to achieve enhanced-gain performance. The peak gain is remarkably improved with the use of an SIW cavity and metallic superstrate. The superstrate comprises a single rectangular slot window and two half-wavelength patches. The gain can be enhanced by combining the in-phase radiating fields. Further, the 10 dB bandwidth of the proposed antenna ranges from 2.32 GHz to 2.49 GHz, which covers the wireless local area network band. The measured peak gain is 9.44 dBi at 2.42 GHz.

• Solar Energy
• /
• v.9 no.2
• /
• pp.51-57
• /
• 1989

A two-dimensional velocity map of natural convection in a rectangular cavity is determined using laser speckle photography. Isovelocity contour drawn by spatial filtering and local velocity by pointwise method are obtained. These results are compared with those of numerical analysis.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.3009-3014
• /
• 2007

The effectiveness of passive control techniques for alleviating the pressure oscillation generated in a supersonic cavity flow was investigated numerically and experimentally, respectively. The control device includes a sub-cavity installed near the leading edge of a rectangular cavity. Time-dependent supersonic cavity flow characteristics with turbulent features were examined by using the three-dimensional, mass-averaged Navier-Stokes computation based on a finite volume scheme and large eddy simulation. The results show that the pressure oscillation near the trailing edge dominates overall time-dependent cavity pressure variations. Such an oscillation can be attenuated more significantly in the presence of the sub-cavity compared with the cavity without sub-cavity, and a larger sub-cavity leads to better control performance.

• Journal of the Korean Institute of Telematics and Electronics D
• /
• v.34D no.12
• /
• pp.8-13
• /
• 1997

In this paper, the input impedance and efficiency of rectangulr microstip patch antenna located inside a rectangular wavegudie is calculated by using the cavity model and the mode excited by te patch antenna which is modeled as an equivanlent surface magnetic current on the conducting plate. Measured return losses of a rectangular microstrip patch antenna tuned at 5.93 GHz in the free space and inside the retangular waveguide are compared and found to be in good agreement with calculated results.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.5 no.4
• /
• pp.822-828
• /
• 2001

In this paper, a high gain microstrip antenna with rectangular cavity backed is designed. A single microstrip patch is basically a low gain radiator As a ga in enhancement method, superstrate loading techniques are applied to the $2\times2$ microstrip array antenna with cavity backed. In antenna design, although the broadside gain increases as the cavity is enlarged, a cavity size of $3\times3$ wavelength is sufficient. The distance between the radiating elements is chosen as 1.5 free-space wavelength. The antenna radiation characteristics are calculated by IE3D software and compared with the experimental results. Experimental results show that the maximum gain is 18.6dBi at the frequency of 9.16GHz, which is good agreement with the calculations.

• Transactions of the Korean hydrogen and new energy society
• /
• v.33 no.5
• /
• pp.598-606
• /
• 2022

With the advancement of industry, the use of various sustainable energy sources and solutions to problems affecting the environment are being actively requested. From this point of view, it is intended to directly burn unused biogas to use it as energy and to solve environmental problems such as greenhouse gases. In this study, a new type of cavity matrix combustor capable of low-emission complete combustion without complex facilities such as separation or purification of biogas produced in small and medium-sized facilities was proposed, and CFD numerical calculation was performed to understand the performance characteristics of this combustor. The cavity matrix combustor consists of a burner with a rectangular porous microwave receptor at the center inside a 3D cavity that maintains a rectangular parallelepiped shape composed of a porous plate that can store heat in the combustor chamber. As a result of numerical calculation, the biogas supplied to the inlet of the combustor is converted to CO and H₂, which are intermediate products, on the surface of the 3D matrix porous burner. And then the optimal combustion process was achieved through complete combustion into CO₂ and H₂O due to increased combustibility by receiving heat energy from the microwave heating receptor.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.27 no.11
• /
• pp.25-31
• /
• 1990

We analyze the spherical-rectangular patch microstrip resonator with conformal surface by the cavity model and derive the formulas to calculate resonant frequency in the consideration of effective dielectric constant in order to minimize the errors of resonant frequency due to the fringing fields. A transmission type spherical-rectangular patch microstrip resonator operating at 3GHz, for example, is designed and fabricated on Epsilam-10 substate. Measuring data of resonant frequency and return loss are 2.985 GHz and -44.4dB respectively. Those well agreed with theoretical values.

• Geomechanics and Engineering
• /
• v.6 no.5
• /
• pp.503-515
• /
• 2014

On the basis of Hoek-Brown failure criterion, a numerical solution for the shape of collapsing block in the rectangular cavity subjected to seepage forces is obtained by upper bound theorem of limit analysis. The seepage forces obtained from the gradient of excess pore pressure distribution are taken as external loadings in the limit analysis, and the pore pressure is easily calculated with pore pressure coefficient. Thus the seepage force is incorporated into the upper bound analysis as a work rate of external force. The upper solution of the shape of collapsing block is derived by virtue of variational calculation. In order to verify the validity of the method proposed in the paper, the result when the pore pressure coefficient equals zero, and only hydrostatic pressure is taken into consideration, is compared with that of previous work. The results show good effectiveness in calculating the collapsing block shape subjected to seepage forces. The influence of parameters on the failure mechanisms is investigated.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.10
• /
• pp.1666-1673
• /
• 1997

In order to investigate the characteristics of sound-structure interaction plate having a cut-out, we modeled a rectangular cavity and the flexible plate of the cavity. Because the particle velocity of air is the same as that of plate on the plate, we could easily redefine vibration equation using the velocity potential. We calculated the natural frequencies of plate using orthogonal polynomial functions which satisfy the boundary conditions in the Rayleigh-Ritz method. For the change of vibration characteristics, the effect of sound-structure interaction is more dominant than that of cut-out size.