• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.5
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• pp.102-109
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• 2008

In this paper, the robust hybrid modulation type classifier which use both HOS and WT key features and can recognize 10 digitally modulated signals without a priori information in multipath fading channel conditions is proposed. The proposed classifier developed using data taken field measurements in various propagation model (i,e., rural area, small town and urban area) for real world scenarios. The 9 channel data are used for supervised training and the 6 channel data are used for testing among total 15 channel data(i.e., holdout-like method). The Proposed classifier is based on HOS key features because they are relatively robust to signal distortion in AWGN and multipath environments, and combined WT key features for classifying MQAM(M=16, 64, 256) signals which are difficult to classify without equalization scheme such as AMA(Alphabet Matched Algorithm) or MMA(Multi-modulus Algorithm. To investigate the performance of proposed classifier, these selected key features are applied in SVM(Support Vector Machine) which is known to having good capability of classifying because of mapping input space to hyperspace for margin maximization. The Pcc(Probability of correct classification) of the proposed classifier shows higher than those of classifiers using only HOS or WT key features in both training channels and testing channels. Especially, the Pccs of MQAM 3re almost perfect in various SNR levels.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.1
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• pp.51-56
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• 2019

This paper related with the performance comparison of CCA and RMMA blind adaptive equalization in order to reduce the intersymbol interference which is occurred in channel when transmitting the 16-QAM signal, high spectrum efficiencies of nonconstant modulus characteristic. The CCA possible to improve the misadustment and initial convergence by compacting the every signal constellation of 16 by using the sliced symbol of the decision device output, namely statistical symbol, but incresing the computational cost. The RMMA possible to minimize the fast convergence speed and misadjustment and channel tracking capability without increasing the computational cost by obtain the error signal after transform to 4 constant modulus signal based on the region of signal constellation located. In this paper, these algorithm were implemented in the same channel, and the blind adaptive equalization performance were compared using the equalizer output signal constellation, residual isi, MSE, SER. As a result of simulation, the RMMA has better performance in output signal constellation, residual isi and MSE compared to the CCA, but has slow convergence speed about 1.3 times. And the SER performance presenting the robustness to the noise signal, the CCA has more beeter in less SNR, but the RMMA has better in greater than 6dB in SNR.

• Corrosion Science and Technology
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• v.8 no.5
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• pp.197-202
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• 2009

The high toxicity of wax, oil, varnish and volatile corrosion inhibitor(VCI) corrosion inhibitors lead to an increasing interest in using non-toxic alternatives such as anti-corrosive film. This study aims to investigate the possibility to use acryl based anti-corrosive film as a substitution of toxic corrosion inhibitors. Acryl emulsions were polymerized by several acryl monomers(acrylonitrile(AN), n-butyl acrylate(nBA), methylmethacrylate(MMA) and glycycyl methacrylate(GMA)), non-toxic corrosion inhibitor, crosslinking agents(diethylene glycol dimethacrylate(DEGDA)) and various additives in order to apply substrate of anti-corrosive film. Acryl emulsion for anti-corrosive film(AeACF) as a substrate of corrosion inhibitor film has excellent removal characteristic at above $25^{\circ}C$. The crosslinked by DEGDA in a range of above 4 wt% content anti-corrosive film can easily remove from the metal surface by using hands because it kept a balance of cohesion and adhesion strength. Anti - corrosive performance of AeACF is better than anti-corrosive oil by corrosion rate test, which was measured $54.3mg/dm^2$ day(MDD) and $142.9mg/dm^2$ day, respectively. Anti-corrosive film consisting of acryl monomers and inorganic anti-corrosive ingredients did not emit any toxic pollutants by gas chromatography. Thus it is estimated that acryl based anti-corrosion film can substitute toxic corrosion inhibitors.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.94.2-94.2
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• 2011

In this work, multi-functional groups, i.e., nitrogen and oxygen, contained microporous carbons (MF-MCs) were prepared by the one step carbonization of the poly(vinylidene chloride-co-acrylonitrile-co-methyl methacryalte) (PVDC-AN-MMA) without activation. The electrochemical performance of MF-MCs was investigated as a function of carbonization temperature. It was found that MF-MCs had a high specific surface area over $800m^2/g$ without additional activation, resulting from the micropore's formation by the release of chlorine groups. In addition, although functional groups decreased, specific surface area was increased with increasing carbonization temperature, leading to the enhanced electrochemical performance. The pore size of the carbon distributed mainly in small micropore of 1.5 to 2 nm, which was idal for aqueous electrolyte. Indeed, the unique microstructure features, i.e. high specific surface area and optimized pore size provided high energy storage capability of MF-MCs. These results indicated that the microporous features of MF-MCs lead to feasible electron transfer during charge/discharge duration and the presence of nitrogen and oxygen groups on the MF-MCs electrode led to a pseudocapacitive reaction.

• Journal of the Korean Society of Safety
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• v.16 no.3
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• pp.68-75
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• 2001

Photopolymerization, the utilization of electromagnetic radiation(or light) as the energy source for polymerization of functional monomers, oligomers is the basis of important commercial processes with broad applicability, including photoimaging and RV curing of coatings and inks. The objective of this study is to investigate the characteristics of environmental fraternitive photopolymerization of methyl methacrylate(MMA). This work is the first step to continue further research about alkyl methacrylate. The experiment was done in aqueous solution under the influence of photo-initiator concentration(0.05-0.25mol/l), light intensity (5000-9000 ${\mu}J/cm^2$) and monomer concentration(2-6mol/l). Methyl methacrylate was polymerized to high conversion ratio using hydrogen peroxide($H_2O_2$) and the kinetics model we have obtained is as follows. $R_p=k_p[S]^{0.41}[M]^{0.62}[L]^{2.45} exp(53.64/RT$). The differential method of thermogravimetric analysis(Friedman method) was used to obtain value of activation energy on decomposition reaction. The average value of it res 45.4Kca1/mol.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.5
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• pp.697-702
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• 2011

In this paper, We have fabricated PMMA thin films by plasma polymerization method for organic thin film transistor's insulator layer. In the electrical characteristic results with deposition pressures and substrate RF bias power in thin film deposition process, we have got dielectric constant of 3.4, high deposition rate of 8.6 [nm/min] and high insulation characteristics in condition of RF100 [W], Ar20 [sccm], 5 [mtorr], RF bias 20 [W]. Therefore, the fabricated thin films are possible as insulation layer of OTFT and organic memory.

• Journal of Adhesion and Interface
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• v.3 no.1
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• pp.13-19
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• 2002

We have studied on the surface and adhesion properties for acrylic terpolymers, having both hydrophobic and hydrophilic side chains, synthesized via solution polymerization. In order to develop a waterborne material. we tried to synthesize these terpolymers via emulsion polymerization. The polymeric emulsion synthesized was mainly composed of methyl methacrylate (MMA), methoxy-polyethyleneglycol methacrylate (MPEGMA) having hydrophilic side chains and methoxypolypropyleneglycol methacrylate (MPEGMA) having hydrophobic side chains. The viscosities of this series increased with an increase in the content of the co-monomer such as MPEGMA and (MPEGMA). This behavior resulted in the increase in the diameter and heterogeneity of the emulsion particle via AFM observation. Furthermore. the tensile adhesion strength and 90-degree peel strength of the adhesive of these polymeric emulsions were measured. In the case of polymeric emulsion composed of the same content of both hydrophilic and hydrophobic component, the adhesion property showed the highest value. However, since the adhesion properties as a practical applicable adhesive were poor, some improvements were required. When the composition above was modified with butyl acrylate (BA), the improvement effect on adhesion strength was accepted. In particular, 90-degree peel strength increased up to a maximum of 400% of the original value.

• Journal of Adhesion and Interface
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• v.11 no.3
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• pp.112-119
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• 2010

Poly(methyl methacrylate)/poly(butyl acrylate) PMMA/PBA core-shell composite particles were prepared by the emulsion polymerization of MMA and BA in the presence of different concentration of sodium dodecyl benzene sulfonate (SDBS). The following conclusions are drawn from the measured conversion and particle size distribution, morphology, average molecular weight distribution, observation of film formation and particle formation, glass transition temperature and physical properties of polymerized core-shell composition particles for using adhesive binder. When the concentration of 0.03 wt% surfactant, the conversions of PMMA and PBA core polymerization are excellent as 95.8% for PMMA core and 92.3% for PBA core. Core-shell composite particles are obtained 90.0% for PMMA/PBA core-shell composite particles and 89.0% for PMMA/PBA core-shell composite particles. It is considered that the core and shell particles are polymerized to be confirmed FT-IR spectra and average molecular weight measured with a GPC, formation of the composite particles is confirmed by the film formation from normal temperature, and composition of inside and outside of the composite particle is confirmed by TEM photograph. The synthesized polymer has two glass transition temperatures, suggesting that the polymer is composed of core polymer and shell polymer unlike general copolymers. It is considered that each core-shell composite particle can be used as a high functionality adhesion binder by the measurement of tensile strength and elongation.

• Clinical and Experimental Pediatrics
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• v.49 no.11
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• pp.1125-1139
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• 2006

In 1991, the Ministry of Health & Social affairs adopted a nationwide service program for neonatal screening of phenylketonuria, galactosemia, maple syrup urine disease, homocystinuria, histidinemia & congenital hypothyroidism for newborns delivered from low class pregnant women registered in health centers. Government decreased the test items from six to two, PKU & congenital hypothyroidism to increase test numbers with same budget from 1995. Government decided to test PKU & hypothyroidism for all newborns from 1997. 78 laboratories wanted to participate for neonatal screening test in 1999. Government didn't decide laboratory center for a certain district and placed responsibility on free competition. Government are planning to test 573,000 newborns from 1998, Government decided to screen 6 items PKU, congenital hypothyroidism, maple syrup urine disese, homocystinuria, galactosemia and congenital adrenal hyperplasia from 2006. 17 laboratores are participating now. The cost of screening test is supported by both the federal government and local government on a 40-60 basis. In case a patient with an inherited metabolic disease is diagnosed by screening of government program, special milk is provided at government's expense. Interlaboratory quality control was started 6 times a year from 1994. According to the government project, 3,707,773 newborns were screened. 86 PKU, 718 congenital hypothyroidism were detected. So incidence of PKU is 1/43,114 and congenital hypothyroidism is 1/4,612. Maeil dairy company produced new special formula for PKU, MMA and PA, MSUD, urea cycle disorder, homocystinuria, isovaleric acidemia from Oct. 1999. The cost benefit of performing screening procedures coupled with treatment has been estimated to be as high as 1.77 times in PKU, 11.11 times in congenital hypothyroidism than cost without screening. We are trying to increase the budget to test all newborns for Tandem mass sereening & Wilson disease from 2008. Now it is a very important problem to decrease laboratory numbers of neonatal screening in Korea. So we are considering 4-5 central laboratories which cover all newborns and are equipped with tandem mass spectrometer & enzyme immunoassay for TSH, 17OHP & enzyme colorimetric assay for galactose.

• The Journal of the Korean dental association
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• v.53 no.1
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• pp.47-56
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• 2015

Obstructive sleep apnea (OSA), most common respiratory disorder of sleep, is characterized by intermittent partial or complete occlusions of the upper airway due to loss of upper airway dilating muscle activity during sleep superimposed on a narrow upper airway. Termination of these events usually requires arousal from sleep and results in sleep fragmentation and hypoxemia, which leads to poor quality of sleep, excessive daytime sleepiness, reduced quality of life and numerous other serious health consequences Untreated OSAS can cause various problems such as hypertension, diabetes, stroke, cardiac disease, daytime sleepiness. Various treatments are available, including non-surgical treatment such as medication or modification of life style, surgical treatment, continuous positive airway pressure (CPAP) and oral appliance (OA). Oral appliance is known to be effective in mild to moderate OSA, also genioglossus muscle advancement (GA) or maxillomandibluar advancement (MMA) is a good option for OSA patients with muscular or skeletal problems. Although the prevalence of OSA is increasing, the proportion of the patient treated by dentist is still very law. Dentists need to understand the mechanism of OSA and develop abilities to treat OSA patients with dental problems. The purpose of this paper is to give a brief overview about OSA and the dentist's role in OSA patients.