• Clean Technology
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• v.4 no.2
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• pp.32-40
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• 1998

The polymeric porous materials which consist of polypropylene(PP) and polyethylene(PE) powder were prepared to apply to the air purification systems by extrusion sintering method. SEM analysis showed that a composite polymeric porous structure made up of PP and PE was obtained, where PE was melted and adhered to PP because the melting temperature of PE was lower than that of PP. The filtration characteristics and mechanical properties of polymeric porous materials were investigated by varying the head die temperature of the extruder, extrusion velocity, and the melt index and quantity of PE. The filtration efficiency was proportional to the quantity of PE but inversely proportional to the melt index of PE. The polymeric porous materials composed of PP and PE, which was made by extrusion sintering method, was found to be suitable for the filter element of the air purification system.

• Applied Chemistry for Engineering
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• v.29 no.2
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• pp.168-175
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• 2018

In order to investigate the effect of the chemical treatment of bamboo fiber on physical properties of polypropylene (PP)/bamboo fiber (BF) composites, silane coupling agents such as ${\gamma}$-aminopropyltriethoxysilane (APS), ${\gamma}$-glycidoxypropyl-trimethoxysilane (GPS) and ${\gamma}$-mercaptopropyltrimethoxysilane (MRPS) were applied to BF and alkaline treated BF. Morphological properties of the chemically treated BF were confirmed by optical microscope and SEM measurements, and chemical structure changes were confirmed by FT-IR and EDS. TGA results showed that the thermal stability of silane treated BF increased. Based on the analysis of a universal testing machine and an Izod impact test, the flexural and impact properties of PP/silane treated BF composites showed higher values than those of PP/BF composites. The enhancement of interfacial adhesion properties of the PP/BF composite was checked from SEM images of the fracture of specimens after the tensile test.

• Korean Journal of Animal Reproduction
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• v.21 no.3
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• pp.255-264
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• 1997

The purpose of this study was attempted to investigate the number changes of the growing and mature follicles in ovary following repeats of pregnant mare serum gonadotropin(PMSG) treatments for superovulation in nulliparous rats. Thirty two rats(Sprague-Dawely, about 200~250 gm) were randomized into 4 groups. Control group rats were sacrified at estrus phase confirmed by vaginal smear. PMSG-treated group 1 rats, PMSG-treated group 2 rats and PMSG-treated group 3 rats were sacrified at 48 hrs after injection once with PMSG 25 IU, after 2 repeated injection by a week interval, and 3 repeated injection, respectively. The uteri and ovaries of rats were removed and weighed and then were observed grossly and serial sections of all ovaries and some sections of uteri by paraffin embedding were stained with H-E. Number of ovarian follicles about 3 grades of small, middle and large follicles from seondary and follicles were investigated by LM photographies of ovary preparations. The criteria of the small, middle, and large follicles were based as small follicle with preantral follicles with 2~4 layers of granulosa cells surrounding the oocyte, as secondary follicles with more than 5 layers of granulosa cells and early signs of antral cavity or with small clefts on either side of the oocytes, and as tirtiary follicles with a single medium sized antral cavity or large well-formed antral cavity, respectively. In gross findings, the wall of the uteri in control group were thin, and those in 3 PMS-treated group were markedly thickened and some uterine lumen of those filled with fluid. In histological findings, the walls of the uteri from 3 PMSG-treated groups were hypertrophied and their blood and lymph vessels were dilated than those of control group. The ovaries fo 3 PMSG-treated groups were more increased in size and the cortexes were more developed and increased in width but there are no difference of development and changes in 3 PMSG-treated groups. The weight of the uteri and ovaries per rat in PMSG -treated group 1, 2 and 3 were a, pp.ared to be significantly increased 171.4$\pm$47.6%, 162.3$\pm$43.9%, 206.9$\pm$30.4%, respectively than those of control groups. The mean number of follicle per ovary in control group were a, pp.ared to be 17.1$\pm$3.5, 46.2$\pm$14.5, and 74.3$\pm$22.7 at large, middle and small follicles, respectively and total number of these 3 grade follicles per ovary were a, pp.ared to be 137.7$\pm$31.7. The mean number of follicle per ovary in PMSG-treated group 1 were a, pp.ared to be 25.6$\pm$7.3, 78.1$\pm$29.9, and 83.2$\pm$34.0, at large, middle and small follicles, respectively and total number of these 3 grade follicles were a, pp.ared to be 187.5$\pm$58.8. The mean number of follicle per ovary in PMS-treated group 2 were a, pp.ared to be 21.9$\pm$5.2, 67.8$\pm$16.8, and 68.0$\pm$14.9 at large, middle and small follicles, respectively and total number of these 3 grade follicles were a, pp.ared to be 157.7$\pm$26.2. The mean number of follicle per ovary in PMS-treated group 3 were a, pp.ared to be 21.7$\pm$4.8, 61.5$\pm$17.0, and 59.7$\pm$16.2 at large, middle and small follicles, respectively and total number of these 3 grade follicles were a, pp.ared to be 143.5$\pm$29.6. The number of follicles in PMSG-treated group 1 a, pp.ared to be more number than other 2 PMSG-treated gruops and tended to be decreased by frequency of PMSG-treatment.

• Proceedings of the Korean Vacuum Society Conference
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• 1994.02a
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• pp.50-50
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• 1994

Half-metallic Heusler alloys (NiMnSb, ppdMnSb, pptMnSb) have attracted much attention due to their unique electronic and magnetic structures. Sppin-ppolarized band structure calculation ppredicts metallic behavior for the majority sppin states and semiconductor behavior for the minority sppin states. We have studied the electronic structures of these half-metallic Heusler alloys by core-level pphotoemission sppectroscoppy of Mn 2pp and 3s XppS sppectra. We found large intensities of Mn 2pp satellites and 3s exchange spplitting comppared with other metal Mn-alloys. These satellite structure can be understood by applying Anderson imppurity model. This fact supports the calculated sppin pprojected ppartial density of states which suggests that the valence electrons be highly sppin ppolarized near Fermi level and that the electrons involved with charge-transfer be mainly minority sppin ones which have semiconducting band structure. The trend of charge transfer energies Δ from ligands (Sb 5pp) to Mn 3d, obtained from our model fitting, is consistent with that calculated from sppin pprojected ppartial density of state. Also the trend of d-d electron correlation energies U calculated from Mn Auger line L3 VV by Mg $K\alpha$ source is comppatible with that resulted from our model fitting. We fitted the Mn 3s curve in the same way as for insulating Mn comppounds by using the same pparameters calculated from Mn 2pp curve fitting exceppt for the Coulomb interaction energy Q between core hole and d-electrons. The 3s sppectra were analyzed by combing the charge transfer model and a simpple model taking into account the configuration mixing effect due to the intra-shell correlation. We found that the exchange interaction between 3s hole and 3d electrons is mainly respponsible for the satellite of Mn 3s sppectra. This is consistent with the neutron scattering data, which suggests local 3d magnetic moment. We find that the XppS analysis results of Mn 2pp and 3s satellite structures of half-metallic Heusler alloys are very similar to those of insulating transition metal comppounds.

• Ocean and Polar Research
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• v.45 no.3
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• pp.125-140
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• 2023

We investigated meiofaunal biofouling (40-1,000 ㎛) on stranded marine plastic debris (hereafter MPD) collected from 8 coastal areas highly affected by plastic pollution located in the southern part of Korea during June, 2021, in order to analyze the abundance and composition of MPD associated organisms. A total of eight shapes of MPD was collected and classified into four types of plastics (LDPE, PET, PP and EPS) based on Resin Identification Coding System. Meiofounal biofouling was identified into 35 taxa belonging to 11 phylum, 10 classes and 12 order, and were numerically dominated by harpacticoids (EPS: 21.6%, PP: 27.1%), nematodes (LDPE: 23.2%) and foraminiferans (PET: 29.6%). Surface area of MPD was negatively correlated with abundances of organisms on the plastic debris (r = -0.487, p < 0.05, n = 24), indicating that abundances (avg. 3,225 inds. 0.1 m^-2) on the smallest area of PP debris (avg. 0.0208 m² ) were higher than those (avg. 50 inds. 0.1 m^-2) on the largest area of LDPE debris (avg. 0.4029 m^-2). Whereas, there was no correlation between surface area of MPD and the number of taxa on the debris (r = 0.147, p = 0.49, n = 24). These results showed that higher abundances of meiofaunal biofouling were observed on the PP material debris than those on the other debris collected from eight hot spots of the southern coastal waters in Korea, associated with not only polymer type and surface area of the PP debris, but also possibly surface microstructure of the PP debris.

• Carbon letters
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• v.15 no.2
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• pp.117-124
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• 2014

Conductive polymer composites (CPCs) consist of a polymeric matrix and a conductive filler, for example, carbon black, carbon fibers, graphite or carbon nanotubes (CNTs). The critical amount of the electrically conductive filler necessary to build up a continuous conductive network, and accordingly, to make the material conductive; is referred to as the percolation threshold. From technical and economical viewpoints, it is desirable to decrease the conductive-filler percolation-threshold as much as possible. In this study, we investigated the effect of polymer/conductive-filler interactions, as well as the processing and morphological development of low-percolation-threshold (${\Phi}c$) conductive-polymer composites. The aim of the study was to produce conductive composites containing less multi-walled CNTs (MWCNTs) than required for pure polypropylene (PP) through two approaches: one using various mixing methods and the other using immiscible polymer blends. Variants of the conductive PP composite filled with MWCNT was prepared by dry mixing, melt mixing, mechanofusion, and compression molding. The percolation threshold (${\Phi}c$) of the MWCNT-PP composites was most successfully lowered using the mechanofusion process than with any other mixing method (2-5 wt%). The mechanofusion process was found to enhance formation of a percolation network structure, and to ensure a more uniform state of dispersion in the CPCs. The immiscible-polymer blends were prepared by melt mixing (internal mixer) poly(vinylidene fluoride) (PVDF, PP/PVDF, volume ratio 1:1) filled with MWCNT.

• Journal of Microbiology
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• v.44 no.5
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• pp.473-479
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• 2006

A well characterized naphthalene-degrading strain, Pseudomonas putida PpG7 was observed to utilize limonin, a highly-oxygenated triterpenoid compound as a sole source of carbon and energy. Limonin concentrations evidenced a 64% reduction over 48 h of growth in batch cultures. Attempts were made to acquire a plasmid-less derivative via various methods (viz. Ethidium Bromide, SDS, elevated temperature & mitomycin C), among which the method involving mitomycin C ($20{\mu}g/ml$) proved successful. Concomitant with the loss of plasmid in P. putida PpG7 strain, the cured derivative was identified as a $lim^-$ phenotype. The $lim^+$ phenotype could be conjugally transferred to the cured derivative. Based on the results of curing with mitomycin C, conjugation studies and presence of ndo gene encoding naphthalene 1,2 dioxygenase, it was demonstrated that genes for the limonin utilization were encoded on an 83 kb indigenous transmissible Inc. P9 NAH plasmid in Pseudomonas putida PpG7 strain.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.1C
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• pp.59-64
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• 2004

We propose a new RLL(run length limited) (2,7) PP(parity preserving) code with 4 RMTR(repeated minimum transition run) for optical recording. The proposed code has better characteristics in terms of density ratio, RMTR, DC(direct current) component suppression, BER(bit error rate) and system complexity than (2,1O) code that currently applied in storage systems and (1,7) PP code that highly recommended as the next generation optical recording system. Some characteristics of the code are described with several simulations. And the proposed code's superiorites in performance is illustrated as compared with the other codes.

• FLOWER RESEARCH JOURNAL
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• v.19 no.1
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• pp.15-21
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• 2011

This study investigated the effect of soil mulching materials and methods on weed occurring for the growth and flowering characteristics in Gypsophila plants cultivation. For mulching materials were used black polyethylene (PE) film, black polypropylene (PP), and green polypropylene, and these were mulched in both ridge and furrow (BRF) or only furrow, respectively. The weed was occurred total $146.2g/m^2/yr$ as dry weight in non-mulching, but $4.1{\sim}4.2g/m^2/yr$ in BRF mulching by black or green PP. Also weed control were yearly required 27.9 persons/10a in non-mulching, whereas 2.4 persons/10a in BRF mulching by black or green PP. Flower budding and blooming were roughly delayed in non-mulching and furrow mulching. Flowering characteristics such as flower stalk length, primary branches number, and stem firmness were remarkably improved in BRF mulching of black or green PP. Cut flower yield was increased on black BRF mulching or green PP in summer cultivation, while green PP BRF mulching showed better yield in in autumn cultivation. Mortality rate of Gypsophila plants after summer season was lowest as 12.4% in furrow mulching with black PP, followed by about 19.0% in green PP mulching, but highest as 39.0% in BRF mulching with black PE film. Rosette formation rate was lower in furrow than BRF mulching, and was lowest as 13.1% in BRF mulching with green PP, followed by 15.2~15.8% in BRF mulching with black PE film or black PP. So it was thought that BRF mulching with green PP was highly effective in weed control and improvement of yield and cut flower quality in Gypsophila plants cultivation.

• Proceedings of the Korean Vacuum Society Conference
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• 1997.02a
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• pp.144-145
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• 1997