• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.52-61
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• 2003

$SrBi_2Ta_2O_9(SBT)$and$ZrO_2$thin films for MFIS structure(Metal-Ferroelectric-Insulator-Semiconductor) were deposited by RF magnetron sputtering method. In order to investigate the effect of heat treatment of insulator layers and MFIS structure, the insulator layers were heat treated from $550^{circ}C;to; 850^{\circ}C$in conventional furnace or RTA furnace under$O_2$and Ar ambient, respectively. After then, C-V characteristics and leakage current were measured. The capacitor with 20 nm thick $ZrO_2$layer treated at RTA$750^{circ}C;in;O_2$ atmosphere had the largest memory window. The C-V and leakage current characteristics of the$Pt/SBT(260nm)/ZrO_2(20nm)/Si$structure were better than those of$Pt/SBT(260nm)/Si$ structure. These results showed that$ZrO_2$films took a role of buffer layer effectively.

• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.291-298
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• 2020

ZITO/Ag/ZITO multilayer transparent electrodes at room temperature on glass substrates were prepared using RF/DC magnetron sputtering. Transparent conductive films with a sheet resistance of 9.4 Ω/㎡ and a transmittance of 83.2% at 550 nm were obtained for the multilayer structure comprising ZITO/Ag/ZITO (100/8/42 nm). The sheet resistance and transmittance of ZITO/Ag/ZITO multilayer films meant that they would be highly applicable for use in polymer-dispersed liquid crystal (PDLC)-based smart windows due to the ability to effectively block infrared rays (heat rays) and thereby act as an energy-saving smart glass. Effects of the thickness of the PDLC layer and the intensity of ultraviolet light (UV) on electro-optical properties, photopolymerization kinetics, and morphologies of difunctional urethane acrylate-based PDLC systems were investigated using new transparent conducting electrodes. A PDLC cell photo-cured using UV at an intensity of 2.0 mW/c㎡ with a 15 ㎛-thick PDLC layer showed outstanding off-state opacity, good on-state transmittance, and favorable driving voltage. Also, the PDLC-based smart window optimized in this study formed liquid crystal droplets with a favorable microstructure, having an average size range of 2~5 ㎛ for scattering light efficiently, which could contribute to its superior final performance.

• Journal of Biomedical Engineering Research
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• v.23 no.1
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• pp.61-72
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• 2002

In this parer, a new harmonic imaging technique is Proposed and evaluated experimentally. In the Proposed method. a weighted chirp signal with a hanning window is transmitted. The RF samples obtained on each array element are individually compressed by correlating with the reference signal defined as the 2nd harmonic component($2f_0$) of a transmitted chirp signal generated in a square-law system. The correlator output will then consist of the compressed version of the $2f_0$ component generated in tissue and the crosscorrelation sequence of the fundamental($f_0$) and 2f$_{0}$components. The Proposed method uses the compressed $2f_0$ component to form an image. for which the crosscorrelation term should be suppressed below at least -50dB. The Proposed method has two process, 2f$_{0}$-correlation and $2f_0$-correlation(PI) . $2f_0$-correlation can successfully eliminate the $f_0$ component with a single transmit-receive events and therefore is more efficient than the conventional Pulse inversion method in terms of the frame rate. 2i)-correlation(Pl) Performs pulse compression after applying pulse inversion method for the 2nd harmonic image with high resolution and SNR. Another advantage of the proposed method is that the SNR of 2nd harmonic imaging can be improved without limitation by increasing the duration of the chirp signal. The proposed method was verified through both the computer simulations and actual experiments .ts .

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.3
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• pp.34-39
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• 1999

Electron temperature and electron density were rreasured in a radio-frequency inductively coupled plasma (RFICP) using a Langmuir probe method. Measurerrent was conducted in an argon discharge for pressures from 10 mTorr to 40 mTorr and input rf rnwer from 100 W to 600 W. Spatial distribution electroo temperature and electron density were rreasured for discharge with satre aspect ratio (R/L=2). Electron temperature and electron density were discovered depending on both pressure and power. Electron density was increased with iocreasing input power, but saturated at 450 W. Electron density was iocreased with iocreasing pressure. Radial distribution of the electron density was peaked at the rnsition which was a little rmved from center toward quartz window. Normal distribution of the electron density was peaked in the center between quartz plate and substrate. The above results could contribute to understand the Mechanism of Radio-Frequency Inductively Discharge Plasma.Plasma.

• Journal of Chest Surgery
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• v.8 no.2
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• pp.101-108
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• 1975

Since 1959 the authors experienced 43 cases of chronic constrictive pericarditis treated surgically at the Department of Thoracic & Cardiovascular Surgery, the National Medical Center in Seonl. Of 43 cases, detailed patients' records could be obtainable in 36 cases, and most of our studies. were made on the basis of these 36 available cases. About 84 per cent of the cases were male with several pediatric cases, and duration of symptoms ranged between 2 months and 10 years. The diagnosis of this condition is not difficult, however, about half of our cases were previously treated under the impression rf various other conditions such as liver cirrhosis or nephrotic syndrome at other hospitals and clinics. Many of our cases showed hepatic functional disturbances and about 89 per cent of the cases showed reversed A/G ratio, and we are sure that some of them had so-called protein losing enteropathy. Three of 36 cases showed normal electrocardiogram, and most peculiar electrocardiographic findings were ST or T changes and low amplitude of QRS complexes. Seven cases showed auricular fibrillation and five had first degree A-V block. Mean preoperative peripheral venous pressure at the antecubital fossa and arm-to-tongue circulation time were 273 mm $H_2O$and 20.2 seconds, respectively, and they were markedly reduced postoperatively to 152 mm $H_2O$ and 13 seconds, respectively. Several different approaches were made with various extents of pericardial decortication according to patients' condition and probably surgeon's preference. In 12 cases we met cardiovascular injuries during decortication and one of them died of massive bleeding through the torn right atrium, and we experienced excellent postoperative result in a grave case operated on just a small pericardial window. Eleven of 35 cases were tuberculous pericarditis and others were non-specific pericarditis histopathologically, and 6 of total 43 cases operated on passed away by various ways with the mortality rate of 13.9 per cent.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.108-111
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• 2002

CIGS film has been fabricated on soda-lime glass, which is coated with Mo film. by multi-source evaporation process. The films has been prepared with thickness of 1.0 ${\mu}m$, 1.75${\mu}m$, 2.0${\mu}m$, 2.3${\mu}m$, and 3.0${\mu}m$. X-ray diffraction analysis with film thickness shows that CIGS films exhibit a strong (112) preferred orientation. Furthermore. CIGS films exhibited distinctly decreasing the full width of half-maximum and (112) preferred peak with film thickness. Also, The film's microstructure, such as the preferred orientation, the full width at half-maximum(FWHM), and the interplanar spacing were examined by X-ray diffraction. The preparation condition and the characteristics of the unit layers were as followings ; Mo back contact DC sputter, CIGS absorber layer : three-stage coevaporation, CdS buffer layer : chemical bath deposition, ZnO window layer : RF sputtering, $MgF_2$ antireflectance : E-gun evaporation

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10A
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• pp.965-973
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• 2007

We analyzed that the loss of data in TCP protocol based wireless networks caused by overlapped responses in bi-directional nodes that were resulted in out of the data sequence. This loss can be prevented by using revised TCP rate control algorithm and the performance of throughput can also be improved. The rate control algorithm is applied when the congestion happens between nodes while traffic packets are retransmitting in TCP bandwidth. In addition to applying the rate control algorithm, we determine the number of system clients in bandwidth and the average of pausing time between transmitting serial files to produce a competitive level so that an efficient performance of rapid retransmitting for the loss of multi-packets. This paper discusses the improvement of congestion control in that the decrease of the loss, firstly, as ensuring an efficient connection rate and, secondly, as using sliding window flow control.

• Investigative Magnetic Resonance Imaging
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• v.26 no.2
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• pp.125-134
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• 2022

Purpose: The aim of this study was to investigate the change in signal sensitivity over different acquisition start times and optimize the scanning window to provide the maximal signal sensitivity of [1-¹³C]pyruvate and its metabolic products, lactate and alanine, using spatially localized hyperpolarized 3D ¹³C magnetic resonance spectroscopic imaging (MRSI). Materials and Methods: We acquired 3D ¹³C MRSI data from the brain (n = 3), kidney (n = 3), and liver (n = 3) of rats using a 3T clinical scanner and a custom RF coil after the injection of hyperpolarized [1-¹³C]pyruvate. For each organ, we obtained three consecutive 3D ¹³C MRSI datasets with different acquisition start times per animal from a total of three animals. The mean signal-to-noise ratios (SNRs) of pyruvate, lactate, and alanine were calculated and compared between different acquisition start times. Based on the SNRs of lactate and alanine, we identified the optimal acquisition start timing for each organ. Results: For the brain, the acquisition start time of 18 s provided the highest mean SNR of lactate. At 18 s, however, the lactate signal predominantly originated from not the brain, but the blood vessels; therefore, the acquisition start time of 22 s was recommended for 3D ¹³C MRSI of the rat brain. For the kidney, all three metabolites demonstrated the highest mean SNR at the acquisition start time of 32 s. Similarly, the acquisition start time of 22 s provided the highest SNRs for all three metabolites in the liver. Conclusion: In this study, the acquisition start timing was optimized in an attempt to maximize metabolic signals in hyperpolarized 3D ¹³C MRSI examination with [1-¹³C] pyruvate as a substrate. We investigated the changes in metabolic signal sensitivity in the brain, kidney, and liver of rats to establish the optimal acquisition start time for each organ. We expect the results from this study to be of help in future studies.

• Journal of the Korean institute of surface engineering
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• v.56 no.6
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• pp.451-456
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• 2023

Transparent conducting films having a three layered structure of ZnO/Cu/ZnO (ZCZ) were deposited onto the glass substrates by using RF and DC magnetron sputtering at room temperature. The emissivity and opto-electrical properties of the films were investigated with a varying thickness(5, 10, 15 nm) of the Cu interlayer. With increasing the Cu thickness to 15 nm, the films showed a enhanced electrical properties. Although ZnO 30/Cu 15/ZnO 30 nm film shows a lower resistivity of 5.2×10^-5 Ωcm, it's visible transmittance is deteriorated by increased optical absorbtion of the films. In addition, X-ray diffraction patterns indicated that the insertion of Cu interlayer improve the grain size of ZnO films, which is favor for the electrical and optical properties of transparent conducting films. From the observed low emissivity of the films, it is concluded that the ZCZ thin films with optimal thickness of Cu interlayer can be applied effectively for the car's window coating materials.

• Journal of the Korean Vacuum Society
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• v.21 no.1
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• pp.29-35
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• 2012

The Hydrogenated silicon nitride (SiNx:H) using plasma enhanced chemical vapor deposition is widely used in photovoltaic industry as an antireflection coating and passivation layer. In the high temperature firing process, the $SiN_x:H$ film should not change the properties for its use as high quality surface layer in crystalline silicon solar cells. Initially PECVD-$SiN_x:H$ film trends were investigated by varying the deposition parameters (temperature, electrode gap, RF power, gas flow rate etc.) to optimize the process parameter conditions. Then by varying gas ratios ($NH_3/SiH_4$), the hydrogenated silicon nitride films were analyzed for its optical, electrical, chemical and surface passivation properties. The $SiN_x:H$ films of refractive indices 1.90~2.20 were obtained. The film deposited with the gas ratio of 3.6 (Refractive index=1.98) showed the best properties in after firing process condition. The single crystalline silicon solar cells fabricated according to optimized gas ratio (R=3.6) condition on large area substrate of size $156{\times}156mm$ (Pseudo square) was found to have the conversion efficiency as high as 17.2%. Optimized hydrogenated silicon nitride surface layer and high efficiency crystalline silicon solar cells fabrication sequence has also been explained in this study.