• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.5
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• pp.24-29
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• 1993

The national standards of microwave power in X-band and Ku-band were established using the waveguide microcalorimeters and have been disseminated to the related industries to contribute to industrial development. Through the comparisons and analysis of the measured effective efficiencies for waveguide thermistor mounts in the recent years, the accuracy for maintenance of power standards was confirmed.

• Bulletin of the Korean Chemical Society
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• v.17 no.8
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• pp.686-688
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• 1996

We have produced nanophase iron clusters inside a gas cell by decomposing iron pentacarbonyls from the mixture of ~20 Torr Fe(CO)5/~3 Torr SF6 with a pulsed CO2 laser. The product displayed a black tint. Its composition was identified to be mostly iron from an inductively coupled plasma (ICP) atomic emission spectrum. The X-ray diffraction (XRD) pattern indicates a body-centered cubic structure for the cluster. A transmission electron micrograph proves that their diameter ranges between 50 and 70 Å and their average diameter is 60 Å.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.12
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• pp.6-13
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• 2009

For X-band phased array systems, a power amplifier, a 6-bit phase shifter, a 6-bit digital attenuator, and a SPDT transmit/receive (T/R) switch are fabricated and measured. All circuits are demonstrated by using CMOS 0.18 um technology. The power amplifier has 2-stage differential and cascade structures. It provides 1-dB gain-compressed output power ($P_{1dB}$) of 20 dBm and power-added-efficiency (PAE) of 19 % at 8-11 GHz frequencies. The 6-bit phase shifter utilizes embedded switched filter structure which consists of nMOS transistors as a switch and meandered microstrip lines for desired inductances. It has $360^{\circ}$ phase-control range and $5.6^{\circ}$ phase resolution. At 8-11 GHz frequencies, it has RMS phase and amplitude errors are below $5^{\circ}$ and 0.8 dB, and insertion loss of $-15.7\;{\pm}\;1,1\;dB$. The 6-bit digital attenuator is comprised of embedded switched Pi-and T-type attenuators resistive networks and nMOS switches and employes compensation circuits for low insertion phase variation. It has max. attenuation of 31.5 dB and 0.5 dB amplitude resolution. Its RMS amplitude and phase errors are below 0.4 dB and $2^{\circ}$ at 8-11 GHz frequencies, and insertion loss is $-10.5\;{\pm}\;0.8\;dB$. The SPDT T/R switch has series and shunt transistor pairs on transmit and receive path, and only one inductance to reduce chip area. It shows insertion loss of -1.5 dB, return loss below -15 dB, and isolation about -30 dB. The fabricated chip areas are $1.28\;mm^2$, $1.9mm^2$, $0.34\;mm^2$, $0.02mm^2$, respectively.

• Journal of the Korean Society of Safety
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• v.31 no.5
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• pp.22-27
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• 2016

The Electrostatic Charge Prevention Technology is a core factor that highly influences the yield of Ultra High Resolution Flat Panel Display and high-integrated semiconductor manufacturing processes. The corona or x-ray ionizations are commonly used in order to eliminate static charges during manufacturing processes. To develop such a revolutionary x-ray ionizer that is free of x-ray radiation and has function to control the volume of ion formation simultaneously is a goal of this research and it absolutely overcomes the current risks of x-ray ionization. Under the International Commission on Radiological Protection, it must have a leakage radiation level that should be lower than a recommended level that is $1{\mu}Sv/hour$. In this research, the new generation of x-ray ionizer can easily control both the volume of ion formation and the leakage radiation level at the same time. In the research, the test constraints were set and the descriptions are as below; First, In order not to leak x-ray radiation while testing, the shielding box was fully installed around the test equipment area. Second, Implement the metallic Ring Electrode along a tube window and applied zero to ${\pm}8kV$ with respect to manage the positive and negative ions formation. Lastly, the ion duty ratio was able to be controlled in different test set-ups along with a free x-ray leakage through the metallic Ring Electrode. In the result of experiment, the maximum x-ray radiation leakage was $0.2{\mu}Sv/h$. These outcome is lower than the ICRP 103 recommended value, which is $1{\mu}Sv/h$. When applying voltage to the metallic ring electrode, the positive decay time was 2.18s at the distance of 300 mm and its slope was 0.272. In addition, the negative decay time was 2.1s at the distance of 300 mm and its slope was 0.262. At the distance of 200 mm, the positive decay time was 2.29s and its slope was 0.286. The negative decay time was 2.35s and its slope was 0.293. At the distance of 100 mm, the positive decay time was 2.71s and its slope was 0.338. The negative decay time was 3.07s and its slope was 0.383. According to these research, the observation was shown that these new concept of ionizer is able to minimize the leakage radiation level and to control the positive and negative ion duty ratio while ionization.

• Korean Journal of Remote Sensing
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• v.36 no.2_2
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• pp.325-335
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• 2020

Forest canopy height can be used for estimate of above-ground forest biomass (AGB) by means of the allometric equation. The remote locations and harsh conditions of mangrove forests limit the number of field inventory data stations needed for large-scale modeling of carbon and biomass dynamics. Although active and passive spaceborne sensors have proven successful in mapping mangroves globally, the sensors generally have coarse spatial resolution and overlook small-scale features. Here we generate a 12 m spatial resolution mangrove canopy height map from TanDEM-X data acquired over the world largest intact mangrove forest located in the Sundarbans. With single-pol. TanDEM-X data from 2011 to 2013, the proposed technique makes use of the fact that the double-bounce scattering that occurs between the water and mangrove trees yields water surface level elevation over mangrove forest areas, thus allowing us to estimate forest height with the assumption of an underlying flat topography. Our observations have led to a large-scale mangrove canopy height map over the entire Sundarbans region at a 12 m spatial resolution. Our canopy height estimates were validated with ground measurements acquired in 2015, a correlation coefficient of 0.83 and a RMSE of 0.84 m. With globally available TanDEM-X data, the technique described here will potentially provide accurate global maps of mangrove canopy height at 12 m spatial resolution and provide crucial information for understanding biomass and carbon dynamics in the mangrove ecosystems.

• Journal of Pharmaceutical Investigation
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• v.40 no.5
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• pp.313-319
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• 2010

The objectives of this study were to evaluate the effect of formulation ingredients on the drug release and to optimize the novel sustained release matrix tablet formulations of bupropion hydrochloride. A three factor, three-level Box-Behnken design was used for the optimization procedure, with the amounts of PEO ($X_1$), citric acid ($X_2$) and Compritol 888 ATO ($X_3$) as the independent variables. The selected dependent variables were the cumulative percentage values of bupropion hydrochloride that had dissolved after 1, 4 and 8 hr. Various dissolution profiles of the drug from sustained release matrix tablets were obtained. Optimization was performed for $X_1$, $X_2$ and $X_3$ using the following target ranges; $30%{\leq}Y_1{\leq}45%$; $70{\leq}Y_2{\leq}85%$; $85%{\leq}Y_3{\leq}100%$. The optimized formulation for bupropion hydrochloride was achieved with 12.5% PEO ($X_1$), 2.5% citric acid ($X_2$) and 10% Compritol 888 ATO ($X_3$). The sustained release matrix tablets with the optimized formulation provided a release profile that was close to predicted values. In addition, the dissolution profiles of the sustained release matrix tablet with the optimized formulation were similar to those of the commercial product Wellbutrin$^{(R)}$ SR tablets ($f_2$=79.83).

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.1-11
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• 2014

The aim of this study is to investigate the effect of SCR reactor on the exhaust emissions characteristics in order to develop a urea-SCR aftertreatment system for reducing $NO_x$ emissions. The experiments are conducted by using a flue tube LPG steam boiler with the urea-SCR aftertreatment system. The urea-SCR aftertreatment system utilizes the ammonia converted from 17% aqueous urea solution injected in front of SCR catalyst as a reducing agent for reducing $NO_x$ emissions. The equivalence ratio, urea injection amount, ammonia slip and $NO_x$ conversion efficiency relative to boiler load are applied to discuss the experimental results. In this experiment, the average equivalence ratio is calculated by changing only the fuel consumption rate while the intake air amount is constantly fixed at $25,957.11cm^3/sec$. The average equivalence ratios are 1.38, 1.11, 0.81 and 0.57 when boiler loads are 100, 80, 60 and 40%. The $NO_x$ conversion efficiency is raised with increasing urea injection amount, and $NH_3$ slip is also boosted at the same time. Consequently, the $NO_x$ conversion efficiency relative to boiler load should be examined in combination with urea injection amount and $NH_3$ slip. The results are calculated by 89, 85, 77 and 79% for the boiler loads of 100, 80, 60 and 40%. The appropriate amount of urea injection for the respective boiler load can be not discussed by only $NO_x$ emissions, and should be determined by considering the $NO_x$ conversion efficiency, $NH_3$ slip and reactive activation temperature simultaneously. In this study, the urea amounts of 230, 235, 233 and 231 mg/min are injected at the boiler loads of 100, 80, 60 and 40%, and the final $NH_3$ slips are measured by 8.48, 5.58, 11.97 and 11.34 ppm at the same conditions. THC emission is affected by the SCR reactor under other experimental conditions except 100% engine load, and CO emission at only 40% engine load. The rest of exhaust emissions are not affected by the SCR reactor under all experimental conditions.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06b
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• pp.311-352
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• 1996

Peltier 효과를 이용한 열전소자는 열응담 감도가 좋고 선택적 냉각이 가능하며 무소음, 무진동 및 소형화의 장점으로 각종 전자부품의 국부냉각소자로 응용되고 있다. 또한 최근 냉매의 사용없이 냉각이 가능한 열전재료를 이용한 자동차나 가정용 에어컨 및 냉장고 등의 각종 냉방시스템의 개발도 크게 주목을 받고 있다. 기존의 Bi2Te3계 단결정 열전재료는 성능지수는 우수하나, 기계적 취약성에 기인하여 소자가공시 수율 저하가 가장 큰 문제점으로 지적되고 있다. 이와 같은 문제점을 해결하기 위해 최근 단결정에 비해 기계적 강도가 우수한 다결정 열전재료의 제조공정에 관한 연구가 활발히 이루어지고 있으며, 그 일환으로 기계적 합금화법을 이용한 열전재료의 제조공정이 연구되고 있다. 원료금속이 고 에너지 볼-밀 내에서의 연쇄적인 파괴와 압접에 의해 합금분말로 변화되는 기계적 합금화 공정은 상온공정으로 이를 사용하여 다결정 열전재료를 제조시 기존의 다결정 열전재료의 제조공정인 "용해 및 분쇄법'과 비교하여 제조단가를 낮출 수 있는 장점이 있다. 본 연구에서는 전자냉각소자용 열전재료로서 상온부근에서 성능지수가 가장 우수한 p형 (Bi,Sb)2Te3 및 n형 Bi2(Te,Se)3 합금분말을 기계적 합금화 공정으로 제조하여 분말 특성을 분석하였으며, 가압소결 후 열전특성의 변화거동을 연구하였다. 순도 99.99% 이상인 Bi, Sb, Te, Se granule을 (Bi1-xSbx)2Te3 및 Bi2(Te1-ySey)3 조성에 맞게 칭량하여 불과 분말의 무게비 5:1로 강구와 함께 공구강 vial에 장입 후, Spex mixer/mill을 이용하여 기계적 합금화 하였다. 기계적 합금화 공정으로 제조한 분말에 대한 X-선 회절분석과 시차 열분석으로 합금화 정도를 분석하였다. (Bi1-xSbx)2Te3 및 Bi2(Te1-ySey)3 합금분말을 10-5 torr의 진공중에서 300℃∼550℃의 온도로 30분간 가압소결하였다. 가압소결체의 파단면에서의 미세구조를 주사전자현미경으로 관찰하였으며, 상온에서 가압소결체의 열전특성을 측정하였다. (Bi1-xSbx)2Te3의 기계적 합금화에 요구되는 공정시간은 Sb2Te3 함량에 따라 증가하여 x=0.5 조성에서는 4 시간 45분, x=0.75 조성에서는 5 시간, x=1 조성에서는 6 시간 45분의 vibro 밀링이 요구되었다. n형 Bi2(Te1-ySey)3 합금분말의 제조에 요구되는 밀링시간 역시 Bi2Se3 함량 증가에 따라 증가하였으며 Bi2(Te0.95Se0.05)3 합금분말의 제조에는 2시간, Bi2(Te0.9Se0.1)3 및 Bi2(Te0.85Se0.15)3 합금분말의 형성에는 3시간의 bivro 밀링이 요구되었다. 기계적 합금화로 제조한 p형 (Bi0.2Sb0.8)2Te3 및 n형 Bi2(Te0.9Se0.1)3 가압 소결체는 각기 2.9x10-3/K 및 2.1x10-3/K 의 우수한 성능지수를 나타내었다.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.55 no.6
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• pp.817-826
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• 2022

This study was conducted to determinean optimal soaking solution for inhibiting the texture softening of shrimp Litopenaeus vannamei pressured at high temperature (S-P/HT) in a retort, and also to optimize concentrations of 0.5% calcium chloride (CC) and 5.0% potato starch (PS) for preparation of a mixed solution (MS) and soaking time (ST) in the MS. On the basis of the results of expressible drip (4.6%), water holding capacity (95.1%), hardness (18.4 N/cm²) and sensory texture (7.2 score), the MS was found to be the optimal soaking solution for inhibition of texture softening under S-P/HT conditions, The concentrations of CC (X₁, %), PS (X₂, %), and ST (X₃, min) were selected as independent variables, and hardness (Y₁), springiness (Y₂) and sensory texture (Y₃) were selected as dependent variables. The optimal conditions of X₁, X₂, and X₃ were 0.51%, 6.34%, and 364 min, respectively. Under the optimal conditions, the experimental values of Y₁, Y₂ and Y₃ were 18.3±0.8 N/cm², 4.4±0.3 mm and 7.7±0.2, respectively, which did not diffr significantly from the predicted values (P>0.05). In conclusion, the optimized models of X₁, X₂, and X₃ for the preparation of S-P/HT using CC-PS were suitably fitted.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.294-302
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• 2023

Ni-Mn-Zn ferrite, Ni_0.5-xMn_xZn_0.5Fe₂O₄ (0 ≤ x ≤ 0.5), was synthesized using the sol-gel method to investigate the crystal structure, microstructure, magnetic properties, high-frequency characteristics, and electromagnetic (EM) wave absorption characteristics as a function of Mn substitution. As the Mn content increased, a continuous decrease in saturation magnetization (M_S) was observed with little change in coercivity (H_C). Samples for each composition (x) exhibited strong EM wave absorption performance with first and second strong EM wave absorption regions satisfying minimum reflection loss, RL_min < -40 dB in the 1.5~2.5, 6~11 GHz range, respectively. The EM wave absorption in Ni-Mn-Zn ferrite depends on magnetic loss, and adjusting µ' and µ'' spectra by Mn substitution or H field allows control of the EM wave absorption frequency.