• Journal of the Korean Institute of Telematics and Electronics C
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• v.34C no.7
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• pp.18-27
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• 1997

A CMOS 950 MHz frequency synthesizer is designed and fabricated in a 0.8.mu.m standard CMOS process for IS-95-A CDMA mobile communication transceivers To utilize a CMOS ring VCO in a CDMA wireless communication receisver, we employed a QDC (quasi-direct conversion) receiver architecture for CDMA applications. Realized RF frequency synthesizer used as the RF local oscillator for a QDC receiver exhibits a phase noise of -92 dBc/Hz at 885kHz offset from the 950.4 MHz carrier, which complies with IS-95-A CDMA specification. It has a rms jitter of 23.7 ps, and draws 30mA from a 5V supply. Measured I/Q phase error of the 950.4 output signals is 0.7 degree.

• Journal of Korea Ship Safrty Technology Authority
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• s.32
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• pp.46-56
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• 2012

해양사고 예방 또는 해양사고 시 2차 피해 감소를 위한 관점에서 안전수역, 안전항구 및 최적 수리장소의 제공 또는 제공되는 장소까지 안전한 수로의 안내는 해양선진국으로 갖추어야 할 핵심 해사안전 서비스의 하나로 볼 수 있다. Erika호 해양사고와 같은 중대사고로 큰 손해를 겪은 국제사회는 피난처의 중요성을 깨닫고 여러 해를 거친 검토 끝에 피난처의 제공목적, 선장과 구조자의 책임지침 등을 담은 IMO Res. A.949(23) 및 A.950(23)과 같은 피난처 관련 지침을 제정하게 되었다. 이 지침을 바탕으로 덴마크, 미국, 캐나다, 남아프리카에서는 MAS 체제, 잠재적 피난처(PPOR, Potential Places of Refuge), 국가비상계획 포함 등의 방법으로 피난처를 지정하여 활용하고 있었다. 위의 요소들을 고려할 때, 우리나라 연안을 통항하는 선박들에 대한 최적의 피난처를 지정하기 위해서 연안해역 및 항만의 자연환경, 해상 및 기상조건, 과거 해양사고통계 및 분석자료, 항적도 및 교통량 등 해상교통환경의 평가를 위한 기초자료가 수집되어야 한다.

• Journal of Welding and Joining
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• v.34 no.6
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• pp.55-61
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• 2016

Recently developed ferritic heat resistance steel, T24 was used to evaluate microstructure characteristics of simulated heat affected zone. Also, correlation between the prior austenite grain size and amount of $M_{23}C_6$ carbide dissolution was discussed. With the increasing of peak temperature, Grain size steadily increased up to $1050^{\circ}C$ and then rapidly increased at $1150^{\circ}C$. Of the peak temperature $950{\sim}1050^{\circ}C$, amounts of $M_{23}C_6$carbide dissolution are low. But Most of $M_{23}C_6$ carbide that is inhibited grain growth were dissolved above $1050^{\circ}C$ and decreased volume fraction of carbide. This indicates that grain growth may be achieved through dissolution of carbide in the base material. As of welding, due to very rapid heating rate, $M_{23}C_6$ carbide exists above equilibrium solution temperature that is $800^{\circ}C$, even at $1050^{\circ}C$. So, It was confirmed that close correlation between carbide dissolution in the base material and grain growth. Calculated grain size has a linear relationship with peak temperature, on the other hand, measured grain size discontinuously increased between $950{\sim}1050^{\circ}C$ and above $1050^{\circ}C$. Grain size of heat affected zone at $1350^{\circ}C$ peak temperature showed maximum 67um and minimum 4um. Also, The number of side showed 3 to 10.

• Journal of the Korean institute of surface engineering
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• v.30 no.1
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• pp.23-32
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• 1997

The electrolytic boronizing on carbon steels in the mixture of $Na_2B_4O_7$ and NaCl was conducted at 750~$950^{\circ}C$ for 1~6 hours under 0.5A/$\textrm{cm}^2$ current density. The micorostructrure and microheredness of boronized layer was also studien. The effect of the additive such as $CaCl_2$ or NaOH on the formation of boronized layer was also investigated. The boronized layer were composed of two sublayers, i.e., FeB and $Fe_2B$ , which have tooth structure. the average layer thinknesses of the low carbon steel and SM45C boronized at $900^{\circ}C$ for 4hours were 153 and 138 $\mu\textrm{m}$, respectively. The thickness of the twosublayers was significantly increased with increasing boronizing temperature. To obtain a single $Fe_2B$ layer without FeB sublayer, the boronized materials ware homegenized at $950^{\circ}C$ for 4 hours. It was fount that the single layer with a microhardness Hv$\thickapprox$ 1120 -1250 was formed. The calculated activation energies for formation of boronized layer on the low carbon steel and SM45C were 18.7 and 12.6 Kcal/mol, respectively.

• Journal of Biosystems Engineering
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• v.23 no.5
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• pp.445-456
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• 1998

This study was carried out to evaluate the performance of a medium scale rice polisher of 2.5 t/h and to improve its performance for producing the clean rice with high quality. The maximum internal pressure, broken rice ratio. whiteness in the rice polisher were investigated, and the effects of outlet resistance, water spraying rate, shaft revolution speed and rice moisture content on the polishing performance were analyzed to find out proper operating conditions. The conclusions of this study were as follows: 1. In the performance evaluation of the polisher, the broken rice ratio increment of 0.1%, the max. internal pressure of about 11 N/${cm}^2$, and whiteness increment of 2.2~3.7 resulted at the conditions of 20 PS driving power, 950 rpm, 150 cc/min water spraying rate, 44.1 Nㆍcm outlet resistance and about 15% rice moisture content. 2. Though max. internal pressure and whiteness at the 17% rice moisture content were higher than those at the 15% moisture content under the same operating conditions of the polisher, but the broken rice rate at the 17% moisture content was absolutely low compared with that at 15% moisture content. The water spraying effect to reduce broken rice and to increase whiteness was much significant at the 15% moisture content not significant at 17% moisture content. 3. The main parameter of the performance was outlet resistance, and low resistance of about 44.1 Nㆍcm was recommended at the polisher. 4. The proper water spraying rate in the polisher was about 150 cc/min. 5. As the shaft revolution speed decreased from 950 rpm and 800 rpm to 650 rpm, the broken rice ratio increased and whiteness decreased. 6. As the driving power of the polisher increased from 20 PS to 30 PS, the max. internal pressure decreased by about 1~2.5 N/${cm}^2$ and whiteness increased by about 1~2, but the broken rice rate was not changed. 7. The proper operating conditions of the polisher seemed to be the revolution speed of 800-950 rpm, the water spraying rate of about 150 cc/min, the oulet resistance of about 44.1 N.cm and 30 PS driving power.

• Applied Science and Convergence Technology
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• v.23 no.6
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• pp.371-375
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• 2014

Diffusion coefficient of Fe in polycrystalline host ZnSe as a mid-IR gain medium has been measured in the annealing temperature ranges of 850 to $950^{\circ}C$. The synthesis of the samples was carried out in quartz ampoule in which the Fe thin film deposited by physical vapor evaporation method on the ZnSe. One can realize that the diffusion coefficient strongly depends on the surface active surfactants through the cleaning process and the substrate temperature during the thin film deposition leading to $2.04{\times}10^{-9}cm^2/s$ for $Fe^{2+}:ZnSe$. The Annealing temperature dependence of the Fe ions diffusion in ZnSe was used to evaluate the activation energy, $E_a$=1.39 eV for diffusion and the pre-exponential factor $D_0$ of $13.5cm^2/s$.

• Korean Journal of Poultry Science
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• v.36 no.1
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• pp.23-28
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• 2009

The experiment were protein and metabolizable energy level in performance and carcass rate in cross bred chicks. One day old, 720 male and female cross bred chick were used for the experiments, and 20 chicks were placed at each pen. The energy level of feed was maintained about 2,950, 3,000, 3,050 kcal/kg, and protein content was adjusted about 19, 20, 21% from 0 to 5 weeks and energy level was maintained about 3,100, 3,150, 3,200 kcal/kg, and protein content was adjusted about 17, 18, 19% from the 6 to 10 weeks old of the experiment. At the whole time, ME 3,100 (2,950), 3,150 (3,000) and 3,200 (3,050) kcal/kg treatment groups was not significant difference in weight gain, feed intake, but 3,150 (3,000), 3,200 (3,050) kcal/kg treated groups revealed to show improved feed conversion rate than the group treated with ME 3,100 (2,950) kcal (P<0.05). And CP 17 (19), 18 (20), 19 (21)% treatment groups did not significant difference weight gain and feed intake but CP 19 (21)% treated group wan significant difference feed conversion rate than the CP 17 (19)% treated group (P<0.05). ME level of 3,100 (2,950), 3,150 (3,000), 3,200 (3,050) kcal/kg treatment groups in carcass rate and abdominal fat rate was not signficant difference and protein of 17 (19), 18 (20), 19 (21)% treatment groups after end of experiment. Between ME and CP of dietary was significant appeared to interact at 6~10 weeks (P<0.05).

• Resources Recycling
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• v.23 no.5
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• pp.3-11
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• 2014

Calcium ferrite is more effective binder for making sintered ore and flux for steel making because of it's low melting temperature. In this Study, calcium ferrite was made by calcinating method in the cement manufacturing process in order to reduce manufacturing costs and increase productivity. Limestone and calcination sludge were used as CaO source, steelmaking sludge, blast furnace dust and iron ore were used as Fe-bearing raw materials. The sintering temperature of specimens is in the range of $950{\sim}1170^{\circ}C$. For Calcium ferrite can be used 'binder for making sintered ore' or 'flux for converter/electric furnace' with a low melting point properties, the raw material characteristics and sintering properties were investigated.

• Bulletin of the Korean Chemical Society
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• v.23 no.12
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• pp.1801-1805
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• 2002

The graphite intercalation compounds(GIC) were prepared by a dry process that led to the intercalation from the direct reaction of gaseous $SO_3$ with flake type graphite. The basal spacing of the GIC was increased from 8.3 ${\AA}$ to 12 in the gallery height. The ejection of interlayer $SO_3$ molecules by the heating for 1 minute at $950^{\circ}C$ resulted in an exfoliated graphite (EG) with surprisingly high expansion in the direction of c-axis. The expansion ratios of the exfoliated graphites were increased greatly between 220 times and 400 times compared to the original graphite particles, and the bulk density was range of 0.0053 to 0.01 $g/cm^3$, depending on reaction time. The pore size distribution of exfoliated graphite was in the range of $10-170{\mu}m$, which exhibites both mesoporosity and macroporosities. This result indicates that the direct reaction of graphite paricles with gaseous $SO_3$ can be proposed as an another route for the exfoliated graphite having excellent physical properties.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.6
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• pp.950-956
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• 1986

In this paper, a direct addressing mode of a microprocessor is introduced to save memory capacity, and also a dedicated digital filter is constructed to speed up the filter processing and to enable an easy selection of the impulse response types. A theoretical analysis has been conducted on the errors caused by the finite word klength, rounding-off and multiplication procedures. The digital filter designed by the proposed method is made into a module which can function as a 7th-order recursive or a 14-order nonrecursive type with a simples witch operation. The proposed filter is implemented on a printed-circuit board. The frequency characteristics of this filter can be controlled by the multiplication values stored in ROMs. A low-pass, a high-pass and a band-pass filter have been designed and their frequency characteristics are verified by actual measurements. For a order higher filer, two filter modules have been cascaded into an integrated filter of 23rd-order non-recursive low-pass type and a 12th-order recursive multiband type. Their frequency characteirstics have been found to agree with the theory.