• Polymer(Korea)
• /
• v.39 no.1
• /
• pp.78-87
• /
• 2015

With aiming to prepare microcapsules having a particle size of $30-50{\mu}m$, thermally expandable capsules with relatively uniform particle sizes consisting of a n-octane/poly(acrylonitrile-co-methyl methacrylate) core/shell structure were synthesized using SPG membrane emulsification and suspension polymerization. Four steric stabilizers and five crosslinking agents were employed. When poly(vinyl alcohol) as a stabilizer was used, the prepared capsules showed a smooth and regular morphology and the liquid hydrocarbon (n-octane) was well encapsulated in the core. When 1,4-butnaediol methacrylate (BDDMA) was used as a crosslinker, the uniform capsules with the average diameter of $36.8{\mu}m$ were synthesized. The capsules prepared with 0.05 mol% BDDMA showed the best encapsulation efficiency.

• Journal of the Institute of Electronics Engineers of Korea SD
• /
• v.46 no.9
• /
• pp.74-80
• /
• 2009

This paper describes a $2{\sim}6GHz$ CMOS frequency synthesizer that employs only one LC-tank voltage controlled oscillator (VCO). For wide-band operation, optimized LO signal generator is used. The LC-tank VCO oscillating in $6{\sim}8GHz$ provides the required LO frequency by dividing and mixing the VCO output clocks appropriately. The frequency synthesizer is based on a fractional-N phase locked loop (PLL) employing third-order 1-1-1 MASH type sigma-delta modulator. Implemented in a $0.18{\mu}m$ CMOS technology, the frequency synthesizer occupies the area of $0.92mm^2$ with of-chip loop filter and consumes 36mW from a 1.8V supply. The PLL is completed in less than $8{\mu}s$. The phase noise is -110dBC/Hz at 1MHz offset from the carrier.

• Applied Chemistry for Engineering
• /
• v.2 no.2
• /
• pp.97-107
• /
• 1991

Highly-siliceous dealuminated zeolite, silicalite(end member of ZSM-5) was synthesized from a batch composition of 2.55 $Na_2O-5.0$ TPABr-$100SiO_2-2800H_2O $ at $180^{\circ}C$ and at times ranging from one to seven days of reaction time. Autoclaves containing the synthesis mixture were centrifuged within the specially-equipped convection oven to provide an elevated gravitational force field like 30 and 50 G. Tests were also conducted at normal gravity. For synthesis performed under elevated gravities, average and maximum crystal sizes were substantially greater than those synthesized under normal gravity and product yields were also found to be affected by elevated gravity ; that is, product yields were substantially enhanced under elevated gravity from 4 % to 55 % with respect to normal gravity. The average crystal sizes of silicalite synthesized at normal gravity were 50 to $70{\mu}m$ over an entire range of reaction time, one to seven days while the average crystal sizes synthsized under elevated gravities, 30 and 50 G, were 160 to $190{\mu}m$ respectively. For the elevated gravity, in particular, two separate nucleations and growths were observed. For examples, at 50G, large crystals of $200{\mu}m$ were produced through the second growing stage after 5 days of reaction following the rapid first growing stage where fairly large crystals of $135{\mu}m$ were produced only in 2 days of reaction. The maximum crystal sizes obtained through the above two growing stages were 190 and $300{\mu}m$, respectively. A discussion of how elevated gravity affects nucleation, growth, yield and crystal size of silicalite is presented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.07b
• /
• pp.1037-1041
• /
• 2004

공액계 유기가교로서 butadiene을 사용한 이핵 유기금속착체를 합성하였고, 합성된 유기금속착체 화합물에 대한 구조적 특징과 두 금속간의 전기화학적 특성에 관한 연구를 수행하였다. $[Cp*Fe(CO)_2]_2-({\mu}-CH=CH-CH=CH)$ 착체는 $Cp*(CO)_2$FeK와 cis-3,4-dichlorocyclobutene과의 반응으로 합성하였고, 이 착체에 결합된 CO기는 UV 광반응하에서 $PPh_3$로 치환시켜 $[Cp*Fe(CO(PPh)_3]_2-({\mu}-CH=CH-CH=CH)$를 합성하였다. 합성된 착체에 대한 전기화학적 특성을 파악하기 위해 CV 실험결과, 전위차 ${\Delta}E^{\circ}=0.575{\sim}0.605$ V이고 $K_c$값은 $109{\sim}1010$으로 매우 큰 값을 얻음으로서 두 금속간의 상호작용이 탄화수소사슬을 통해 활발하게 이루어지고 있음을 알수가 있었다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2001.05a
• /
• pp.197-200
• /
• 2001

Recently, Switching time is the principal factor in a design of frerquency synthesizer for Spread-Spectrum Communications. fast switching frequency synthesizer is important to improve the channel efficiency in a Frequency Hopping Spread Spectrum (FH-SS) tranceiver. In this paper, we design the frequency synthesizer with fast switching time as fast as 1${\mu}\textrm{s}$. In frequency synthesizer design, we use the interpolated PLL method inserted memory Look-up table of DDS to reduce switching time, and have result of improved channel efficiency about 20% by applying to FH-SS Transceiver.

• Journal of the Korean Society for Precision Engineering
• /
• v.16 no.3 s.96
• /
• pp.180-188
• /
• 1999

${\mu}$-synthesis is applied to design a robust controller for a seeker scan loop system which has model uncertainty and is subject to a external disturbance due to abrupt missile maneuver. The issue of modelling a real-valued parametric uncertainty of a physical seeker scan loop system is discussed. The two-degree-of-frame control structure is employed to obtain better performance. It is shown that ${\mu}$-synthesis provides a superior framework for the robust control design of a seeker scan loop system which exhibits robust performance. The proposed robust control system satisfies design requirements, and especially shows good scanning performances for conical and rosette scan patterns despite parametric uncertainty in real system model.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.6 no.6
• /
• pp.41-48
• /
• 2002

This study is on the structural control experiment for a small scale three-story building structure employing on active mass damper subjected to earthquake loading. $\mu$-synthesis controllers, which belong to robust control strategies, were designed and their performance were experimentally verified. Frequency-dependent weighting functions corresponding to disturbance input and controlled output were defined and combined to produce optimal $\mu$-synthesis controllers. The experiment result shows 60-70% reduction in RMS responses under the band-limited white noise excitation and 30-45% reduction in peak responses under the scaled earthquake excitations. Good agreement was obtained between the simulations based on the identified mathematical model and experimental results. And the simulations for the system with uncertainties show that the designed controllers are robust within a specified range of uncertainties.

• Korean Journal of Environmental Agriculture
• /
• v.12 no.2
• /
• pp.144-152
• /
• 1993

A bacterium which degrades efficiently synthetic detergents was isolated from the polluted waters, activated sludge of wastewater treatment plants or polluted soil. This bacterium showed considerably higher growth rate in the agar plate containing $2,000{\mu}g/ml$ of synthetic detergents than any other isolated strains, was identified as a Pseudomonas fluorescens or strains similar to it. The strain was named as a Pseudomonas fluorescens S1. Optimum pH and temperature for the growth of the Pseudomonas fluorescens S1 were pH 7.0 and $30^{\circ}C$, respectively. The strain was resistant to streptomycin and gentamycin, but sensitive to kanamycin. The strain was greatly resistant to zinc chloride, lead nitrate and copper sulfate, but unable to grow in the presence of relatively low concentrations of mercury chloride and silver nitrate. This strain utilized benzene, catechol, cyclohexane and xylene as a sole carbon source. The strain was well grown in the medium containing ABS 10,000${\mu}g$/ml. Degradation of ABS was 55% and 60% at 20${\mu}g$/ml and 100${\mu}g$/ml of ABS, respectively. Benzene ring was degraded 45% in 100${\mu}g$/ml of ABS. During the incubation of the strain in the medium containing ABS 100${\mu}g$/ml and COD 10,000${\mu}g$/ml for 4 days, degradation of ABS and COD were reduced to 40${\mu}g$/ml and 3,200${\mu}g$/ml, respectively. Total amino acid content of the Pseudomonas fluorescens S1 grown with 1,000${\mu}g$/ml of ABS was 115mg/g cell, whereas its content was decreased in the bacterium grown without synthetic detergent by 9.4%.

• Resources Recycling
• /
• v.5 no.3
• /
• pp.65-72
• /
• 1996

Colloidal calcium wrbonate(diametcr 0.02-0 09 m~wja s developed to maintain the mamenl of pnriide formatio~>w ~lhoutsurlace trealment. The control factors of particle size and optimum condiliuna for compound fam*tition has not bccn studiedyet. This shldy war aimed at developing a method fur compounding colloidal calcium carbonfcte to cnl~hol cubic calciumcarbonate, and then compounding the b-o types oI precipitated calcium wrbonatc under optimum wndilrans Calc~umhydroxide was calcinated at 1, lWC far two hours, md then hydrated for 30 minutes at t i i O rprn and ambiznt temperahlle.Two-liter suspension was subjected to the contact with carbon dioxide at l5"C, 600 ipxn and C0= injection in the rate of 1 Umin Two types of dcium carbonate(cuhic calcium carbonatc(0 24.9 pm) md collnidd calcium mhnnate (0.02-0 09 pm))were compounded by "wing the concentrations of calcium oxide and ihe suspension were compounded. It was found that theoptimum concentrations of each suspensions were 5 wt % and 2.5 \I*.% respectively. ' h c key control factor af thc parlicle slzcdislribution was the concenkation al the suspension. The size of compounded particles was measured by a Zcla S k r 'fieaverage particle size of the cubic calcium carbonate aas 223.4 nm(0.223 pm), and that of thc colloidal a~lciumc arbonate was93.6 nm (0.093 km). Ihe particle sizc was evenly cantlolled on a stdblc basis in an H, O reaction system.asis in an H, O reaction system.

• Journal of IKEEE
• /
• v.17 no.1
• /
• pp.16-21
• /
• 2013

Recently, frequency synthesizers are being designed in two ways narrow-band loop or dual-loop for wide-band to reduce the phase noise. However, dual-loop has the disadvantage of center frequency mismatch and requiring an extra loop. In this paper, we propose a new structure that supports a range of 800Mhz ~ 3Ghz with multiple control of the single-loop frequency synthesizer without another loop. The control voltage of the VCO(coarse, fine) will be fixed, and finally the VCO will have a low Kvco. The frequency synthesizer is simulated using UMC $0.11{\mu}m$ process, proposed frequency synthesizer can be used in a variety of applications in the future.