• Journal of the Korean Society of Safety
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• v.26 no.4
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• pp.47-58
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• 2011

Halogen free intumescent flame retardants(IFRS), such as the mixture of melamine phosphate(MP) and char forming agents(pentaerythritol(PER), di-pentaerythritol(DiPER), tris(2-hydroxyethyl) isocyanurate(THEIC)), were prepared and characterized. Polypropylene(PP)/$IFR_S$ composites were also prepared in the presence of ethylene diamine phosphate(EDAP) as a synergist and used into flame retardant PP powder coatings. Thermoplastic PP powder coatings at 20 wt% flame retardant loading were manufactured by extruded and then mechanical cryogenic crushed to bring them in fine powder form. These intumescent flame retardant powder coatings($IFRPC_S$) were applied on mild steel surface for the purpose of protection and decorative. It is a process in which a $IFRPC_S$ particles coming in contact with the preheated mild steel surface melt and form a thin coating layer. The obtained MP flame retardant was analyzed by utilizing FTIR, solid-state $^{31}P$ NMR, ICP, EA and PSA. The mechanical properties as tensile strength, melt flow index(MFI) and the thermal property as TGA/DTA and the fire safety characteristics as limiting oxygen index(LOI), UL94 test, SEM were used to investigate the effect of $IFRPC_S$. The experimental results show that the presence of $IFR_S$ considerably enhanced the fire retardant performances as evidenced by the increase of LOI values 17.3 vol% and 32.6 vol% for original PP and $IFRPC_S$-3(PP/MP-DiPER/EDAP), respectively, and a reduction in total flaming combustion time(under 15 sec) in UL94 test of $IFRPC_S$. The prepared $IFRPC_S$-3 have good comprehensive properties with fire retardancy 3.2 mm UL94 V-0 level, LOI value 32.6%, tensile strength $247.3kg/cm^2$, surface roughness Ra $0.78{\mu}m$, showing a better application prospect. Through $IFRPC_S$-2(PP/MP-PER/EDAP) and $IFRPC_S$-3 a better flame retardancy than that of the $IFRPC_S$-1(PP/MP/EDAP) was investigated which was responsible for the formed more dense and compact char layer, improved synergy effect of MP and PER/DiPER.

• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.553-557
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• 2014

Sulfonated polypropylene (S-PP) is prepared by sulfuric acid-acetone aldol condensation reaction of polypropylene (PP) separator to yield hydrophilic separator surface with a moderate amount of $-SO_3H$ groups. Activated carbon supercapacitor is also fabricated adopting the S-PP separator coated with potassium polyacrylate (PAAK) hydrogel polymer electrolyte. As a result, the hydrophilic surface of S-PP separator involves better physical and electrochemical properties such as decrease in contact angle, improvements of wettability, electrolyte uptake, and ionic conductivity to give higher specific capacitance and long cycle-life.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.6
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• pp.13-21
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• 2010

A energy efficient $V_{pp}$ generator using a variable pumping frequency for mobile DRAM is presented in this paper. The proposed $V_{pp}$ generator exploits 3 stages of a cross-coupled charge pump for energy efficiency. Instead of using a fixed pumping frequency in the conventional $V_{pp}$ generator, our proposed $V_{pp}$ generator adopts a voltage-controlled oscillator and uses variable frequencies to reduce the ramp-up time. As a result, our $V_{pp}$ generator generates 3.0 V output voltage with 24.0-${\mu}s$ ramp-up time at 2 mA current load and 1 nF capacitor load with 1.2 V supply voltage. Experimental results show that the proposed $V_{pp}$ generator consumes around 26% less energy (1573 nJ $\rightarrow$ 1162 nJ) and reduces 29% less ramp-up time (33.7-${\mu}s$ $\rightarrow$ 24.0-${\mu}s$) compared to the conventional approach.

• The Journal of the Korea Contents Association
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• v.11 no.1
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• pp.357-370
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• 2011

Using strategy group theory, this thesis reviewed the status of program providers analysis and the performances it has made so far, and sought measures to improve its limitations. The constraint of program providers analysis based on existing concept of strategy group is that the strategy group was derived from the statistics, and therefore only applied the characteristics of program provider's channels to the analysis, on account of which a systematic and sophisticated classification as well as generalization of strategy or strategy group were hard to obtain. Moreover, the PP strategy variables used to be selected at the firm level and business level, and in relation with resource and competition scope. In future, more appropriate procedure should be followed to obtain objectivity in selecting variables to avoid controversy over intentionality. The measures in this thesis to improve the study of PP strategy group can be summarized as follows: firstly analysis of variables for strategy group classification should be made to single out key variables which are to be classification criteria. Secondly, variables are to be cross-checked by industry experts to increase generalizability. Thirdly, proxy variables should be sublated, and strategy group model which enables the reflection of subsistent properties of PP industry, and the cognitive perception of the executives(CEO) needs to be established. Fourthly, the concepts of mobility barrier and isolating mechanism should be applied to the classification criteria of strategy group to reveal the gap of performance between different strategy groups. Lastly, chronicle study on PP strategy group should be done to perceive the dynamic changes of PP strategy group.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.830-833
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• 2004

Voltage step-down characteristics of Ring/Dot type piezoelectric transformer were examined with increasing input voltage from $10\;V_{pp}$ to $140V_{pp}$. Then the output load resistance was fixed to $125\;\Omega$. The voltage gain showed constant value till the input voltage of $70\;V_{pp}$. And then it linearly decreased till the input voltage of $140V_{pp}$. The output voltage of fabricated piezoelectric transformer increased with increasing input voltage. And driving frequencies when the output voltage was maximum value were changed according to input voltage. Frequency shifts and temperature rise of fabricated sample showed 2 kHz, $13^{\circ}C$, respectively when input voltage was changed from $10\;V_{pp}$ to $140V_{pp}$. Because of the temperature rise of fabricated piezoelectric transformer, the step-down characteristics of it was deteriorated above the input voltage of $70\;V_{pp}$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.2
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• pp.155-163
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• 2007

High Strength Concrete (HSC) has weakness that in a fire, it is spalled and brittles. The phenomenon of spalling is made by water vapor's (resulting from evaporation in the material at over $100{^{\circ}C}$)' being confined in watertight concrete. As the concrete strength increases, the degree of damage caused by the spalling becomes more serious because of the permeability. It is reported that the polypropylene(PP) fiber has an important role in protecting concrete from spalling and the optimum dosage of PP fiber is 0.2%. This study was conducted on the nonreinforced concrete specimens. The high-temperature behavior of high-strength reinforced concrete columns with various concrete strength and various dosage of PP fibers was investigated in this study. The results show that the ratio of unstressed residual strength of columns increases as the concrete strength increases and the ratio of unstressed residual strength of columns increases as the dosage of PP fiber increases from 0% to 0.2%, however, the effect of fiber dosage on residual strength of column barely changes above 0.2%.

• Convergence Security Journal
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• v.3 no.1
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• pp.1-6
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• 2003

Virtual Private Network (VPN) is the technology that can reduce the cost revolutionary and maintain the security like an private line, and the demand is increased more and more. Two kinds of current VPN Protection Profiles(PP) for the national organ are used on development, but it is considered by being several problems. In this paper we consider the VPN's PP problems that has been used currently, and describe to an improvement direction.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.3
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• pp.432-437
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• 2002

Immunosuppressive potential of 65 kDa buffalo placental protein (bPP65) on B-cell proliferation in vitro and antibody response in vivo was evaluated. B-cell proliferation was estimated by measuring incorporation of tritiated thymidine in buffalo lymphocytes while primary antibody responses against phytohaemagglutinin (PHA) or keyhole limpet haemocyanin (KLH) were evaluated in mice. bPP65 suppressed proliferation of lipopolysaccharide (a B-cell specific mitogen)-stimulated buffalo lymphocytes in vitro indicating suppression of B-cells. This suppression was dose dependent over the protein concentration range $25-100 {\mu}g/ml$. Primary antibody responses in mice against PHA and KLH in presence of bPP65 were lower as compared to in its absence but these were not statistically significant. Amino acid composition data of bPP65 and BSA suggested that bPP65 is different from BSA.

• International Journal of Advanced Culture Technology
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• v.3 no.1
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• pp.52-60
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• 2015

The present study aims to the use of carboxymenthyl cellulose (CMC) improving the ability of fiber in the dyeing process. Cellulose was extracted from banana leaves by NaOH and then modified by reacting with chloroacetic acid to obtain the carboxymenthyl cellulose. The effect of carboxymenthyl cellulose contents on the mechanical properties and dye absorption were also investigated. Then, CMC were blend with polypropylene (grade 561R) at 1%, 3% and 5% by weight ratio. The fibers were obtained from single screw extruder. The results show that the mechanical properties of the product decreased when increased the amount of CMC in the fiber product. After dyeing, the dye however were absorbed by the CMC-PP fibers more than the original PP fibers. The absorption of dye on the CMC-PP fibers increased significantly with the CMC ratio.

• Proceedings of the Korean Vacuum Society Conference
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• 1995.06a
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• pp.141-141
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• 1995