• 전자공학회논문지 IE
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• v.45 no.4
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• pp.54-59
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• 2008

In this paper, circularly polarized patch antenna with 2-stage LNA for the reception of S-DMB is presented. It used teflon didelectric substrate of ${\in}_r$=2.2 and the size is $40{\times}40{\times}15\;[mm]$. Experimental results of fabricated antenna show that bandwidths of input return loss and axial ratio are about 22 [MHz] and 25 [MHz]. Input return loss, output return loss, gain, and noise figure of the fabricated 2-stage LNA are $S_{11}$=-14 [dB], $S_{22}$=-18 [dB], $S_{21}$=26.8 [dB], and NF=1.14 [dB] respectively. The fabricated active type antenna has total gain of 30.4 [dB] at 2.642 [GHz].

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2359-2366
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• 2014

In this paper, the characteristics of a inset fed rectangular microstrip patch antenna for S-band applications is studied. The variations of return loss along inset length and inset width are investigated on the inset fed rectangular microstrip patch antenna. From the investigated results, the optimized inset fed antenna is designed. At the resonant frequency 2.3 GHz, the optimized dimension of the patch is $45.0mm{\times}40.9mm$. The inset length and width are 14 mm and 1 mm, respectively. The designed antenna is fabricated on the substrate which has a dielectric constant and thickness with 2.5 and 0.787 mm. Simulation results are obtained by a 3D EM(Electromagnetic) solver. The resonant frequency and return loss are measured 2.3025 GHz and -21.11 dB, respectively. The measured and simulated results of the fabricated antenna are in good agreement.

• The Journal of Advanced Prosthodontics
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• v.13 no.3
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• pp.144-151
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• 2021

PURPOSE. The purpose of this in vitro study was to investigate the wear resistance and surface roughness of three interim resin materials, which were subjected to chewing simulation. MATERIALS AND METHODS. Three interim resin materials were evaluated: (1) three-dimensional (3D) printed (digital light processing type), (2) computer-aided design and computer-aided manufacturing (CAD/CAM) milled, and (3) conventional polymethyl methacrylate interim resin materials. A total of 48 substrate specimens were prepared. The specimens were divided into two subgroups and subjected to 30,000 or 60,000 cycles of chewing simulation (n = 8). The wear volume loss and surface roughness of the materials were compared. Statistical analysis was performed using one-way analysis of variance and Tukey's post-hoc test (α=.05). RESULTS. The mean ± standard deviation values of wear volume loss (in mm³) against the metal abrader after 60,000 cycles were 0.10 ± 0.01 for the 3D printed resin, 0.21 ± 0.02 for the milled resin, and 0.44 ± 0.01 for the conventional resin. Statistically significant differences among volume losses were found in the order of 3D printed, milled, and conventional interim materials (P<.001). After 60,000 cycles of simulated chewing, the mean surface roughness (Ra; ㎛) values for 3D printed, milled, and conventional materials were 0.59 ± 0.06, 1.27 ± 0.49, and 1.64 ± 0.44, respectively. A significant difference was found in the Ra value between 3D printed and conventional materials (P=.01). CONCLUSION. The interim restorative materials for additive and subtractive manufacturing digital technologies exhibited less wear volume loss than the conventional interim resin. The 3D printed interim restorative material showed a smoother surface than the conventional interim material after simulated chewing.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.6
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• pp.1047-1055
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• 2006

We patterned nano-width lines on a super hard bulk diamond substrate by varying the ion beam current and ion beam sources with a dual beam field ion beam (FIB). In addition, we successfully fabricated two-dimensional nano patterns and three-dimensional nano plate modules. We prepared nano lines on a diamond and a silicon substrate at the beam condition of 30 kV, 10 pA $\sim$ 5 nA with $Ga^+$ ion and $H_2O$ assisted ion sources. We measured each of the line-width, line-depth, etched line profiles, etch rate, and aspect ratio, and then compared them. We confirmed that nano patterning was possible on both a bulk diamond and a silicon substrate. The etch rate of $H_2O$ source can be enhanced about two times than that of Ga source. The width of patterns on a diamond was smaller than that on a silicon substrate at the same ion beam power The sub-100 nm patterns on a diamond were made under the charge neutralization mode to prevent charge accumulation. We successfully made a two-dimensional, 240 nm-width text of the 300-lettered Lord's Prayer on a gem diamond with 30 kV-30 pA FIB. The patterned text image was readable with a scanning electron microscope. Moreover, three dimensional nano-thick plate module fabrication was made successfully with an FIB and a platinum deposition, and electron energy loss spectrum (EELS) analysis was easily performed with the prepared nano plate module.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.2
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• pp.251-258
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• 2023

In this paper, we propose DLP(Dual Linear Polarization) stack antenna for private network. The proposed antenna has general stack structure and design airgap between two substrate to obtain the maximum gain. Also, to improve cross polarization isolation, two feeding port is designed to separate for each substrate. The size of each patch antenna is 17.80 mm(W1)×16.70 mm(L1) for lower patch and 18.56 mm(W2)×18.73 mm(L2) for upper patch, which is designed on the FR-4 substrate which thickness (h) is 1.6 mm, and the dielectric constant is 4.3, and which is 40.0 mm(W)×40.0 mm(L) for total size of substrate. From the fabrication and measurement results, bandwidths of 100 MHz (4.74 to 4.84 GHz) for feeding port 1, and 150 MHz (4.67 to 4.82 GHz) for feeding port 2 are obtained on the basis of -10 dB return loss and transmission coefficient S21 is got under the -20 dB. Also, cross polarization isolation between each feeding port obtained

• Journal of Microbiology and Biotechnology
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• v.17 no.8
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• pp.1249-1253
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• 2007

A hyperthermostable endoglucanase from Pyrococcus horikoshii with the capability of hydrolyzing crystalline cellulose was analyzed. A protein engineering study was carried out to obtain a reduced-size mutant. Five amino acid residues at both the N- and C-terminus were found to be removable without any loss of activity or thermal stability. Site-directed mutagenesis was also performed on R102, N200, E201, H297, Y299, E342, and W377, residues possibly involved in the active center or in the recognition and binding of a cellulose substrate. The activity of the resulting mutants was considerably decreased, confirming that the mutated residues were all important for activity. A reduced-size enzyme, as active as the wild-type endoglucanase, was successfully obtained, plus the residues critical for its activity and specificity were confirmed. Consequently, an engineered enzyme with a reduced size was obtained, and the amino acids essential for activity were confirmed by site-directed mutagenesis and comparison with a known three-dimensional structure.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.4
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• pp.165-169
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• 2004

This paper reports a miniaturized conductor-backed CPW (CBCPW) bandpass filter based on a thin film polyimide layer coated on CMOS-grade silicon. With a 20 ${\mu}{\textrm}{m}$-thick polyimide interface layer and back metallization on the CMOS-grade silicon, the interaction of electromagnetic fields with the lossy silicon substrate has been isolated, and as a result a low-loss and low-dispersive CBCPW line has been obtained. Measured attenuation constant at 20 GHz is below 1.2 ㏈/cm, which is compatible with the CPW on GaAs. In addition, by using the proposed CBCPW geometry, miniaturized BPF for Ku band application is designed and its measured frequency response shows excellent agreement with the predicted value with validating the performances of the proposed CBCPW geometry for RFIC interconnects and filter applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.6 no.1
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• pp.51-57
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• 1981

Carriers moving in a semiconductor can impart gain or loss to an acousic wave traveling through Piezo-electric materials. In this paper, surface a coustic wave amplifiers, which employ the interaction between carriers drifting in a semiconduct or film and electic fields accompanying a Rayleigh wave propagating on a Piezoelectric substrate, are described. The effect of various electromagnetic boundary condition on th propagation of surface waves in Piezoelectrics is considered. An expression for the dependence of surface wave velocity on electic boundary conditions is derived. Calculations show that, for properly prepared material, significant amplification is expected up to the microwave frequencies. At high frequencies, gain is reduced because electro diffusion smooths out the electron bucning necessary for amplification.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1618-1620
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• 2004

The $Pb(Zr_{0.4}Ti_{0.6})O_3/Pb(Zr_{0.6}Ti_{0.4})O_3$ [PZT(4060)/(6040)] multilayered thin films were deposited by RF Sputtering method on the Pt/Ti/$SiO_2$/Si substrate. This procedure was repeated several times to form PZT(4060)/(6040) heterolayerd thin films. The effects on the structural and dielectric properties of PZT multilayered thin films were investigated. The MFM(Metal Ferroelectric Metal) type capacitors were made using the PZT(4060)/(6040) multilayered thin films deposited with optimum deposition condition. An enhanced dielectric property was observed in the PZT(4060)/(6040) multilayered thin films. The relative dielectric constant and dielectric loss at 100Hz of the PZT(4060)/(6040)-5 multilayered thin films were about 1106 and 0.016, respectively.

• Journal of Information Technology Services
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• v.13 no.1
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• pp.135-146
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• 2014

In this paper, an antenna has been proposed for the operation of mobile devices such as Zigbee. The presented rectenna operates at ISM (Industrial Scientific Medical) band of 2.45 GHz and consists of $2{\times}2$ array patch antenna and Villard voltage double rectifier circuit for high conversion efficiency. $2{\times}2$ array patch antenna is fabricated in FR4 substrate having thickness of 1.6mm and dielectric constant of 4.7. The proposed $2{\times}2$ array patch antenna resonates at 2.56GHz with return loss of 38.36dB, VSWR of 1.0244, and its impedance is matched to $50{\Omega}$. The fabricated rectenna has maximum conversion efficiency of 59.8% at an input power lever of 15dBm and load resistance of $500{\Omega}$.