• Wind and Structures
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• v.30 no.5
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• pp.533-546
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• 2020

Large Eddy Simulation (LES) is used to study the effects of steady slot suction on the aerodynamic forces of and flow around a wall-mounted finite-length square cylinder. The aspect ratio H/d of the tested cylinder is 5, where H and d are the cylinder height and width, respectively. The Reynolds number based on free-stream oncoming flow velocity U_∞ and d is 2.78×10⁴. The suction slot locates near the leading edge of the free end, with a width of 0.025d and a length of 0.9d. The suction coefficient Q (= U_s/U_∞) is varied as Q = 0, 1 and 3, where U_s is the velocity at the entrance of the suction slot. It is found that the free-end steady slot suction can effectively suppress the aerodynamic forces of the model. The maximum reduction of aerodynamic forces occurs at Q = 1, with the time-mean drag, fluctuating drag, and fluctuating lift reduced by 3.75%, 19.08%, 40.91%, respectively. For Q = 3, all aerodynamic forces are still smaller than those for Q = 0 (uncontrolled case), but obviously higher than those for Q = 1. The involved control mechanism is successfully revealed, based on the comparison of the flow around cylinder free end and the near wake for the three tested Q values.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.636-644
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• 1999

Experimental and simulation results are presented on the Aperture-Coupled microstrip patch antennal with U-shaped slot. Experiment and simulation results include impedance bandwidth, copolar and crosspolar-pattern characteristics and gain measurements. Simulation results show the advantages of U-slotted patch antenna comparing with the normal patch antenna. More than 35% impedance bandwidth is obtained with reasonably restricted cross-polar radiation pattern. The U-slotted radiation element fed by aperture-coupling method can be more easily extended to array structure, compared with that fed by coaxial cable.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.194-198
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• 2005

A novel ultra wideband microstrip-fed circular patch antenna having band stop characteristic in UNII band is presented. The band stop characteristic is realized by inverted-U shaped slot. The range of stop bandwidth can be adjusted by changing the length of the slot. The measured impedance bandwidth of the proposed antenna is from 2.9 GHz to 12.1 GHz with the stop band from 4.9 GHz to 6 GHz for VSWR<2. This antenna shows a monopole-like radiation pattern and flat gain characteristic throughout the operating frequency band.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.3-6
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• 2008

In this paper, we propose the folded PIFA with its made an alteration to a factor of resonance for L-slot PIFA. Proposed antenna maintain diminished size patch and improve each bandwidth of GSM(0.88$\sim$-0.96 GHz) and W-CDMA(1.92$\sim$2,17 GHz) for miniaturized repeater. The non-slot step folded PIFA's structure that design of essence was general L-slot PIFA for dual-band. It has no U-slot, multi band and the another slot. The parameters of proposed antenna were optimized for dual-band and compact size by folded singleness patch. Proposed antenna by using folded singleness patch take satisfaction main point, bandwidth of GSM and W-CDMA, compact patch size($39{\times}21{\times}13mm^3$). The antenna was designed by FDTD simulation tool and it was made from result of simulation. Measured data shown that the proposed non-slot step folded PIFA was strong possibility.

• Journal of electromagnetic engineering and science
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• v.17 no.2
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• pp.57-64
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• 2017

In this paper, an asymmetric compact multiband slot antenna is proposed for global positioning system (GPS), worldwide interoperability for microwave access (WiMAX), and wireless area network (WLAN) applications. The top plane, a ground is composed of a rectangular slot with a trapezoidal-like stub, an inverted U-shaped slot at the right side of the rectangular slot, an inverted L-shaped slot at the left side of the rectangular slot, and three stubs. The proposed antenna is fed by an asymmetric cross-parasitic strip on the bottom plane. By properly designing the slots and stubs, four resonant frequency bands are achieved with -10 dB reflection coefficient bandwidths of 50 MHz, 400 MHz, 390 MHz, and 830 MHz in the 1.57 GHz GPS band, 2.4 GHz WLAN band, 3.5 GHz WiMAX band, and 5.5 GHz WLAN bands, respectively. The antenna has a total compact size of $13mm{\times}32mm{\times}0.8mm$. Simulated and measured results indicate that the proposed antenna has sufficient bandwidth and good radiation performance in each band.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.3
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• pp.291-297
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• 2006

In this study, the equivalent physical properties of the shielded slot plate having a lot of very tiny bridge shape structures on its plane were determined by tensile tests and structural analyses. With those results, numerical analyses for the deflection profile by gravity effect were carried out to compare with experimental results. The two results were shown coincident very well so that the estimated equivalent physical properties were verified enough for further studies such as curvature reduction for the shielded slot plate.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.219-222
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• 2006

In this paper, we have designed 800MHz band broadband antenna which is improves of microstrip antenna narrow bandwidth problem including the CDMA band and be able to integrated the GSM and TRS band will design. It used the duplex resonance effect it had the L-Shaped feeding structure which adds the u-slot. It was measured that the frequency bandwidth of the designed antenna which is planed $897MHz\sim1013MHz$ with 215MHz(23.8%). And the antenna gain is 9.3dBi, 3dB beam width $60^{\circ}$ in both the E-plane and H-plane.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.6
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• pp.998-1002
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• 2006

In this paper, we have designed 800MHz band broadband antenna which is improves of microstrip antenna narrow bandwidth problem including the CDMA band and be able to integrated the GSM and TRS band will design. It used the duplex resonance effect it had the L-Shaped feeding structure which adds the u-slot. It was measured that the frequency bandwidth of the designed antenna which is planed $897MHz\sim1013MHz$ with 215MHz(23.8%). And the antenna gain is 9.3dBi, 3dB beam width $60^{\circ}$ in both the E-plane and H-plane.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.8
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• pp.754-760
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• 2011

Reconfigurable beam steering using microstrippatch antenna with U-slot is proposed for wearable fabric applications. The proposed antenna is manufactured on a fabric substrate, and designed to steer the beam directions at the operation frequency of 6.0 GHz. The U-shaped slot and the indirect feeding-techniques are utilized in designing the proposed antenna. By the configuration of two artificial switches($S_0$, $S_1$, $S_2$) in between the indirect feed and the antenna patch, the antenna has three beam directions. The maximum beam directions are steerable in the yz-plane(${\theta}=0^{\circ}$, $30^{\circ}$, $331^{\circ}$), and the overall HPBW is $115^{\circ}$. The measured peak gains are 6.11~6.69 dBi.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.9
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• pp.5796-5800
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• 2014

This paper presents reconfigurable beam steering patch antenna with high gain for a wireless headset. Because existing antenna for wireless communication in headsets has an omni-directional radiation pattern, it has a deleterious effect in the vicinity of the human head. To reduce this effect, this paper proposed an antenna comprised of a U-slot and manufactured on a FR-4 substrate. The antenna operating at the 2.37-2.5 GHz band used a tapered matching method to match the impedance between the feed part and patch part. To implement the beam steering capability, the antenna used two PIN diodes. Using PIN diodes, the antenna presented three states ($S_0$, $S_1$ and $S_2$) in the maximum beam directions of the YZ-plane ($0^{\circ}$, $30^{\circ}$ and $330^{\circ}$, respectively). The peak gains of the antenna in the headset were 4.22-5.15 dBi. The fabricated antenna could communicate efficiently with a wireless headset.