• Elastomers and Composites
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• v.39 no.2
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• pp.131-141
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• 2004

The recycling of waste XLPE(crosslinked polyethylene), which is a major source of scraps from high voltage power transmission cables, has been discussed. The waste XLPE scraps were ground into fine powder with various sizes from less than $100{\mu}m$ up to about $1000{\mu}m$ using two types of tailor-made pulverizers. The compounds were prepared in a modular intermeshing co-rotating twin screw extruder at various conditions such as different compositions, types and powder sizes of waste XLPE, screw configurations and various polymer matrices (LDPE, HDPE, PP, PS). The mechanical and rheological properties and the fracture surface or the compounds were investigated. It was found that an improved impact strength was obtained from the compound with white XLPE powder pulverized from the scraps without outer/inner semi-conductive layers. Generally, the impact strength increases with the content of XLPE but decreases with the size of XLPE. Especially for LDPE, the extrusion was possible up to 80 wt% loading of XLPE. Also, the impact strength increases with the number of kneading disc blocks in the given screw configurations. The melt viscosity of the compounds increases with increasing XLPE loading. However, the higher shear thinning behavior of the compounds at common shear rates implies proper processibility of the compounds. In addition, the impact strength for other polymer matrices used increases with XLPE and it is noticeable that the impact strength of PS/XLPE (80/20 wt%) compound was improved twice that of pure PS.

• The korean journal of orthodontics
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• v.27 no.1
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• pp.35-44
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• 1997

mastication is basically regulated by central pattern regulalor(CPG) of brain system, target organ output from CPG is modulated by oral sensory feedback, anterior cross bite pattern infuluence the feedback mechanism and change muscle activity and jaw movement. The purpose of this study was to investigate differnce anterior cross bite group from normal group, the selected sample groups were 30 normal patient, 30 anterior cross bite patient. EMG and EGN of Biopak system were used for this study The following results were obtained 1 In resting slate of mandible, anterior cross-bite showed the higher muscle activities in all the muscle.(exception:left digastric muscle) than normal group. 2. In clenching state, No significant difference in muscle activities of normal group and anterior cross bite group was noticed 3. In swallowing state Normal group showed the higher muscle activities in left and right masseter muscle, right posterior temporal muscle. 4. In maximum opening and closing velocity, normal group showed the higher value than anterior cross-bite. 5. In the mean value of the maximum opening,the maximum anterior posterior movemenl from centric-occlusion, the lateral deviation from centric occclusion, normal group showed the higher value than anterior cross-bite group.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.5
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• pp.192-200
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• 2008

Multimodal biometrics is a method for personal authentication and verification using more than two types of biometrics data. RBF based score-level fusion uses pattern recognition algorithm for multimodal biometrics, seeking the optimal decision boundary to classify score feature vectors each of which consists of matching scores obtained from several unimodal biometrics system for each sample. In this case, all matching scores are assumed to have the same reliability. However, in recent research it is reported that the quality of input sample affects the result of biometrics. Currently the matching scores having low reliability caused by low quality of samples are not currently considered for pattern recognition modelling in multimodal biometrics. To solve this problem, in this paper, we proposed the RBF based score-level fusion approach which employs quality information of input biometrics data to adjust decision boundary. As a result the proposed method with Qualify information showed better recognition performance than both the unimodal biometrics and the usual RBF based score-level fusion without using quality information.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.3
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• pp.50-62
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• 2015

Recently, Subway Line No. 9, described as a 'hell-like' subway for its recorded load factor of max. 240% due to the opening of the 2nd phase extension section, has been causing problems of recurrent congestion in a subway station building. A recurrent congestion in the station building becomes a factor to offend rail users and to reduce the efficiency of railway management. This study aims to establish the methodology for effect evaluation of information provided to rail users, and conducts a gate metering case study considering the congested conditions at a platform among the methodologies for effect evaluation. The metering effect evaluation by load factor was conducted through selecting the micro simulation and pedestrian simulation tool grafting a gate metering. As a result, it was confirmed that, if gate metering is performed, the service level and pedestrian density of a platform by load factor would improve. In other words, if metering is conducted at a platform, it is possible to control the load factor in the waiting space of a platform. Therefore, it was judged through this study that it is possible to set up the index for effect evaluation of information provided to manage congestion of rail users, and establish the methodology for effect evaluation of information provided to rail users through a program.

• Journal of The Korean Association For Science Education
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• v.37 no.5
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• pp.891-909
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• 2017

This study analyzed some of the discrepancies in quantitative and qualitative data focusing on cognitive and affective achievement in science education. Academic and affective achievement score of 308 high school students were collected as quantitative data, and 33 students were interviewed for qualitative data. We examined the causes and types of discrepancies in terms of testing tools. As a result from quantitative data, there were a large number of students with a big difference between subjects in cognitive achievement, and constructs in affective achievement. More than 20% of the students did not match tendency between achievements in two areas. Through interviews, some examples such as intentional control of science learning for future study and careers, different responses by differences in perception between school science and science, appeared. A comparison of quantitative data by testing tool between qualitative ones and interviews showed conflicting result, where most students evaluated themselves differently from their own quantitative data. That is due to the students' interaction with the testing tools. Two types of discrepancy related to testing tool are found. One is 'the concept difference between the item developer and students,' the other is 'the difference between students' exposed response and their real mindset.' These are related to the ambiguity of the terms used in the tool and response bias due to various causes. Based on this study, an effort is required to elaborate the testing item that matches students' actual perception and to apply students' science learning experience to testing items.

• Polymer(Korea)
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• v.36 no.2
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• pp.216-222
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• 2012

We synthesized microcapsule absorbent with crosslinked poly(styrene-$alt$-maleic anhydride) (PSMA) as a core and PSMA as a shell by a precipitation polymerization method for the delayed absorption of excess water in cement mortar. cPSMA-PSMAs with core-shell structure were synthesized with ratios of 1/1, 1/2 and 1/3 as core monomer mass to shell monomer mass to control shell thickness. We observed the hydrolysis of PSMA in cement-saturated aqueous solution by a FTIR spectrometer. We observed good core-shell structure microcapsules for 1/2(cPSMA #3), but observed incomplete core-shell structure for 1/1(cPSMA #2) and 1/3(cPSMA #4) of core/shell monomer ratios. The swelling ratio of cPSMA #3 in cement-saturated aqueous solution was increased until 20 min. After that it was decreased until 2 hrs swelling time, and they started to increase again. The viscosities of cement paste with cPSMA #3 microcapsules were very slowly increased until 1 hr and increased fast after 1.5 hrs. Cement mortar with 0.5 wt% cPSMA #1 having only core part showed about 5% increase in compressive strength compared to that of plain cement mortar. cPSMA #3 added cement mortar showed the highest compressive strength with 7% increase.

• Polymer(Korea)
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• v.36 no.4
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• pp.542-548
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• 2012

Morphological characteristics and formation of symmetric polystyrene-block-poly(1,4-butadiene) copolymer (PS-b-PBD) in thin films upon solvent-annealing were investigated by using atomic force microscopy (AFM). The thin films solvent-annealed in cyclohexane revealed the perforated lamellae of poly(1,4-butadiene) in the matrix of polystyrene while those solvent-annealed in n-hexane exhibited highly disordered patterns. Interestingly, when the thin films of PS-b-PBD were solvent-annealed with binary mixtures of cyclohexane and n-hexane, the morphological transition from the perforated lameallae to the perpendicularly-oriented lamellae of poly(1,4-butadiene) could be induced by changing the mixing ratio of both solvents. We also demonstrated that after microdomians of poly(1,4-butadiene) were successfully degraded by UV-$O_3$, linear poly(dimethyl siloxane) chains were back-filled into the etched regions of the thin film and then converted to silica nano-objects by oxygen plasma treatments.

• Polymer(Korea)
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• v.36 no.2
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• pp.177-181
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• 2012

This study presents the preparation of double emulsions in a poly(dimethylsiloxane) (PDMS)-based microfluidic device. To improve the wettability of hydrophilic continuous phase onto a hydrophobic PDMS microchannel, the surface was modified with 3-(trimethoxysilyl) propyl methacrylate (TPM) and then sequentially reacted with acrylic acid monomer solution, which produced selective covalent bonding between acrylic acids and methacrylate groups. For the proof of selective surface modification, tolonium chloride solution was used to identify the modified region and we confirmed that the approach was successfully performed. When water containing 0.5% w/w sodium dodecyl sulfate and 1% w/w Span80 with hexadecane were loaded into the selectively modified microfluidic channels, we can produce stable double emulsion. Based on the spreading coefficients, we predict the morphology of double emulsions. Our proposed method efficiently produces monodisperse double emulsions having 48.5 ${\mu}m$(CV:1.6%) core and 65.1 ${\mu}m$ (CV:1.6%) shell. Furthermore, the multiple emulsions having different numbers of core were easily prepared by simple control of flow rates.

• Polymer(Korea)
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• v.36 no.4
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• pp.531-535
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• 2012

Conductive polyaniline (PANI) nanofibers in UV-curable resin were used for a transparent conductive film. The emeraldine-salt PANI (ES-PANI) nanofibers were prepared by chemical oxidation polymerization of aniline, which could be changed into emeraldine-base PANI by dedoping. EB-PANI nanofibers as a precursor for conductive fillers were thereby transformed into re-dpoed PANI (rES-PANI) by dodecylbenzenesulfonic acid in the UV-curable resin solution. rES-PANI nanofibers have high conductivity and long-term stability in the solution without a defect of nanostructure. The resulting conductive resin solution was proved to be highly stable where no precipitation of rES-PANI fillers was observed over a period of 3 months. The transparent film was spin-casted on a poly(methyl methacrylate) sheet of thickness ca. $5{\mu}m$. A surface resistance of $6.5{\times}10^8{\Omega}/sq$ and transmittance at 550 nm of 91.1% were obtained for the film prepared with a concentration of 1.4 wt% rES-PANI nanofibers in the solution. This transformation process of rES-PANI from ES-PANI by dedoping-redoping can be an alternative method for the preparation of an antistatic protection film with controllable surface resistance and optical transparencies with the PANI concentration in UV-curable solution.

• Polymer(Korea)
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• v.38 no.6
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• pp.774-781
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• 2014

Acetylenic or phenylethynyl end-capped polyisoimide oligomers ($M_w$ 2500 g/mol, 5000 g/mol) based upon 4,4'-diamino diphenyl ether (4,4'-ODA)/4,4'-oxydiphthalic anhydride (ODPA) and 4,4'-ODA/3,3',4,4'-benzophenone tetracarboxylic acid dianhydride (BTDA) were synthesized by using 4-ethynylaniline (4-EA) or 4-phenylethynyl phthalic anhydride (4-PEPA) as an end capper. The incorporation of ethynyl groups were confirmed by FTIR spectroscopy. The isomerization temperature was influenced by molecular weight as well as the backbone structure of polyisoimides oligomers. Thus, polyisoimide oligomers with molecular weight of 2500 g/mol was found to be imidized at temperature $10^{\circ}C$ lower than that for the oligomers with molecular weight of 5000 g/mol. The crosslinking reaction of ethynyl groups occurred at a higher temperature than that for the isoimide/imide isomerization reaction. These two reactions were totally or partially overlapped on the DSC thermograms for the polyisoimide oligomer end-capped with 4-EA. Kinetics of thermal imidization and crosslinking reactions for the 4,4'-ODA/ODPA polyisoimide oligomers end-capped with 4-PEPA were investigated by performing dynamic DSC experiments at heating rate of $10^{\circ}C/min$. The activation energy and pre-exponential factors were 141 kJ/mol and $1.45{\times}10^{13}min^{-1}$ for the imidization reaction and 177 kJ/mol and $2.90{\times}10^{13}min^{-1}$ for the crosslinking reaction, respectively.