• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.421-422
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• 2008

In this paper, CMOS RF front-end circuits for an L1/L5 dual-band global positioning system (GPS)/Galileo receiver are designed in $0.13\;{\mu}m$ CMOS technology. The RF front-end circuits are composed of an RF single-to-differential low noise amplifier, an RF polyphase filter, two down-conversion mixers, two transimpedance amplifiers, a IF polyphase filter, four de-coupling capacitors. The CMOS RF front-end circuits provide gains of 43 dB and 44 dB, noise figures of 4 dB and 3 dB and consume 3.6 mW and 4.8 mW from 1.2 V supply voltage for L1 and L5, respectively.

• Nuclear Engineering and Technology
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• v.31 no.6
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• pp.561-571
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• 1999

Microstructure and mechanical properties of five Cr-Mo steels for nuclear industry applications have been investigated. Transmission electron microscopy, energy dispersive spectrometer, differential scanning calorimeter, hardness, tensile, and impact test were used to evaluate the Cr and W effect on the microstructure and mechanical properties. Microstructures of Cr-Mo steels after tempering are classified into three types : bainitic 2.25Cr-lMo steel, martensitic Mod.9Cr-lMo, HT9M, and HT9W steels, and dual phase HT9 steel. The majority of the precipitates were found to be M$_{23}$C$_{6}$ carbides. As minor phases, fine needle-like V(C,N), spherical NbC, fine needle-like Cr-rich Cr$_2$N, and Cr-rich M$_{7}$C$_3$were also found. Addition of 2wt.% W in Cr-Mo steels retarded the formation of subgrain and dissolution of Cr$_2$N precipitates. Hardness and ultimate tensile strength increased with increasing Cr content. Though Cr content of HT9W steel was lower than that of HT9 steel, the hardness of HT9W was higher due to the higher W content. W added HT9W steel had the highest ultimate tensile strength above $600^{\circ}C$. But impact toughness of W added steel (HT9W) and high Cr steel (HT9) was low.w.w.

• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.2801-2808
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• 2022

The synergistic effect of ZrC nanoparticle pining and Re solution in W matrix on the thermal stability of tungsten was studied by investigating the evolution of the microstructure, hardness and tensile properties after annealing in a temperature range of 1000-1700 ℃. The results of metallography, electron backscatter diffraction pattern and Vickers micro-hardness indicate that the rolled W-1wt%Re-0.5 wt% ZrC alloy has a higher recrystallization temperature (1600 ℃-1700 ℃) than that of the rolled pure W (1200 ℃), W-0.5 wt%ZrC (1300 ℃), W-0.5 wt%HfC (1400-1500 ℃) and W-K-3wt%Re alloy fabricated by the same technology. The molecular dynamics simulation results indicated that solution Re atoms in W matrix can slow down the self-diffusion of W atoms and form dragging effect to delay the growth of W grain, moreover, the diffusion coefficient decrease with increasing Re content. In addition, the ZrC nanoparticles can pin the grain boundaries and dislocations effectively, preventing the recrystallization. Therefore, synergistic effect of solid solution Re element and dispersed ZrC nanoparticles significantly increase recrystallization temperature.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.6
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• pp.419-427
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• 2009

To test applicability for continuous flow treatment of ultrasound technology, sonolysis of TCE aqueous solution using 584 kHz multi irradiation reactor was performed under batch and continuous flow conditions. Under batch condition (3 and 4 sides irradiation, 600 W), first order degradation rate constant of TCE was higher under 4 sides than 3 sides irradiation conditions, while the generation of $H_2O_2$ and chloride was similar under both irradiation conditions. Under continuous flow condition with 4 sides irradiation, removal efficiencies of TCE in steady-state were decreased from 83 to 48% with increasing flow rate from 67 to 300 mL/min at 600 W, and were increased from 14 to 75% with increasing acoustic power from 100 to 600 W at 100 mL/min. Removal efficiency of TCE in groundwater was decreased 10% compared to in distilled water at 100 mL/min and 600 W.

• Journal of Oral Medicine and Pain
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• v.30 no.4
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• pp.447-455
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• 2005

The purpose of this study was to examine the effect of Nd:YAG laser irradiation for sensory nerve conduction change. Nd:YAG laser was irradiated to mental region for 5 minutes with the parameters that 10 Hz and 20 Hz of 100 mJ/pulse. Target size of irradiation was 30 mm diameter of circle and target-tip distance was about 10 mm. Therefore, the power density were 212 $mW/cm^2$ and 424 $mW/cm^2$. Sensory nerve conduction was evaluated with $Neurometer^{\circled}$ CPT/C before and after Nd:YAG laser irradiation. As an outcomes, the current perception threshold(CPT) and pain tolerance threshold(PTT) were obtained. We made a comparison of these two values and the results were as follows. 1. There was no significant difference in CPT at 1W, 10 Hz and 2 W, 20 Hz Nd:YAG laser irradiation. 2. There was no significant difference in PTT at 10 Hz, 20 Hz of 100 mJ/pulse Nd:YAG laser. 3. There were no significant differences in CPT and PTT between 1 W, 10 Hz group and 2 W, 20 Hz group. Therefore, We can make a conclusion that Nd:YAG laser irradiation to mental region have no effect on mental nerve conduction in our study model.

• Journal of Nutrition and Health
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• v.24 no.5
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• pp.399-407
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• 1991

The purpose of this study was to estimate the intake of individual fatty acid and eventually to contribute to the establishment of dietary guidelines and recommendations of fatty acids for the Koreans. The subjects consisted of female college students aged 20 to 29 years old. Their dietary intake was assessed twice. in summer and in winter, by means of a 24-hour dietary recall method. Food models and other measuring tools were also used. Concentrations of serm total triglyceride, total cholesterol and HDL-& LDL-cholesterol were measured. The subjects consumed 12.3g of polyunsaturated fatty acids, 14.3g of monounsaturated fatty acids and 14.99g of saturated fatty acids per day The ratios of polyunsaturated/saturated fatty acids( P/S) and polyunsaturatedimonounsaturatedi saturated fatty acids (P/M/S) taken by the subjects were 0.8/1.0 and 0.8/l.0/l.0, respectively. The ratio of w61w3 fatty acids was found to be 8.3/l.0. All of these values seem to fall in the desirable range. The percentages of total calorie from carbohydrate. fat and protein were 59.4%, 23.4% and 17.2%, respectively. The concentrations of serum total triglyceride, total cholesterol. HDL-cholesterol and LDL-cholesterol were 59.3ms/dl, 192.7mg/dl, and 59.0mg/dl, and 121.9mg/dl., respectively.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.4
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• pp.65-70
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• 2015

A study on thermal properties for a single-layer metal and two-layer composites was investigated for the heat-sink application. For the single-layer metal, an aluminum alloy (Al6061) was selected. A screen printed aluminum nitride (AlN) layer on the Al6061 substrate was chosen for the two-layer composites. The thermal conductivity of the sample was determined from the thermal diffusivity measured by the light flash analysis (LFA), specific heat and density. Measured thermal property values were compared to calculated values using the data from the references. The thermal conductivity of composites with screen printed AlN layer on the Al6061 substrate decreased linearly with increasing the thickness of AlN layer. Measured values of the thermal conductivity for composites with $53{\mu}m$ and $163{\mu}m$ thick AlN layers were $114.1W/m{\cdot}K$ and $72.3W/m{\cdot}K$, respectively. In particular, the thermal conductivity of the screen-printed AlN layer was demonstrated by appling the rule of mixture in view point of thermal resistivity. Measured values of the thermal conductivity for AlN layers with the thickness of $53{\mu}m$ and $163{\mu}m$ showed $9.35W/m{\cdot}K$ and $12.40W/m{\cdot}K$, respectively.

• Journal of the Korea Organic Resources Recycling Association
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• v.19 no.1
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• pp.109-114
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• 2011

This study was conducted to investigate the effect of hydraulic retention time(HRT) on the power density in a horizontal flow microbial fuel cell(MFC) reactor. When HRTs were 15min, 30min, 60min and 180min, maximum power densities were $24.7mW/m^2$, $27.3mW/m^2$, $22.8mW/m^2$ and $17.2mW/m^2$, respectively. The highest power density was obtained at HRT of 30min. It was 59% improvement when compared to the power density at an HRT of 180min. When HRT was increased, COD removal rate increased whereas the coulombic efficiency remained constant. The result shows that the optimal performance of the horizontal flow MFC reactor could be achieved at HRT of 30min.

• Korean Journal of Animal Reproduction
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• v.24 no.1
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• pp.35-40
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• 2000

This experiment was conducted to investigate how restricted-lactation and regulation of weaning-time influence the levels of insulin-like growth factor-I (IGF-I) in primiparous rats during the suckling period. All the rats were raised in the individual cage from a few days before parturition through the whole suckling period. The restrictedlactation (RL) and weaned (W) groups were subdivided into 5 subgroups as RL0, RL5, RL10, RL15 and RL20 as well as W0, W5, Wl0, W15, and W20 according to the day of onset of suckling only 4 pups in restriction lactation and of suckling no pups in weaned group, respectively, in contrast to suckling 8 pups per litter in normal lactation (NL) group. The results obtained were summarized as follows: 1. The serum IGF- I concentration of NL rats was 750.59$\pm$3.52ng/$m\ell$ on Day 0, which was not changed until Day 15, and then it was increased through the subsequent suckling period to 1690.20$\pm$4.42ng/$m\ell$ on Day 25. 2. The IGF-I concentrations of early restricted lactation (RL0, RL5) were 1395.90$\pm$3.45ng/$m\ell$ and 1351$\pm$3.23ng/$m\ell$ on Day 10, respeotively. It was significantly higher (P＜0.05) than NL group (745.96$\pm$2.24ng/$m\ell$), and then was not different between group from day 15 of lactation. 3. The IGF- I concentration of W-group in the early lactation was higher (P＜0.05) than NL group during the first week of lactation. But it was decreased to the similar concentration as NL group on Day 10. These data show that lactation stimulus may regulate the IGF-I concentration.

• Korean Journal of Materials Research
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• v.10 no.2
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• pp.144-147
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• 2000

10%C-5%Mo-5%W-10%Cr 및 10%C-5%Mo-5%W-10%V 백주철의 응고거동을 열분석을 통하여 연구하였다. 15Kg 용량의 고주파 유도옹해로에 선철, 고철, Fe-Mo, Fe-W, Fe-Cr, Fe-V 등을 장입시켜 용해시킨 후 슬래그를 제거시키고 $1550^{\circ}C$에서 Y블럭의 펩 주형에 주입하였다. 응고거동을 조사하기 위하여 50g을 Y블럭에서 채취한 뒤 알루미나 도가니에 넣어 재용해시킨 후 1$0^{\circ}C$/min의 냉각속도로 냉각시키면서 여섯 종류의 다른 온도에서 도중에 급냉시켜 응고조직을 광학현미경으로 관찰하였다. 10%C-5%Mo-5%W-10%Cr 백주철의 경우 초정 오스테나이트, 오스테나이트와 M(sub)7C(sob)3의 공정, 오스테나이트와 M(sub)6C의 공정으로, 10%C-5%Mo-5%W-10%V 백주철의 경우 초정 MC, 오스테나이트와 MC의 공정, 오스테나이트와 M(sub)2C의 공정으로 각각 순차적으로 정출하였다. 정출하였다.