• Composites Research
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• v.33 no.6
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• pp.346-352
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• 2020

In mobility industries, the use of thermoplastic composites increased dynamically. In this study, the mechanical and impregnation properties of continuous glass fiber (GF)/polypropylene (PP) composite were evaluated with different GF contents. The GF/PP commingled fiber was manufactured with different GF contents and continuous GF/PP composite was manufactured using continuous compression molding process. Tensile, flexural, and impact test of specimens were evaluated with different GF contents. The fracture behavior of specimens was proved using field emission-scanning electron microscope images of fracture area and impregnation property was evaluated using dynamic mechanical analyzer and interlaminar shear strength. Finally, the GF/PP composite was the optimized mechanical and impregnation properties using 50 wt.% GF/PP commingled fiber.

• The Journal of the Korea Contents Association
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• v.21 no.12
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• pp.287-295
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• 2021

This study examines the performance of program providers(PP) considering various factors. This study employs the panel regression models with the dataset from 2014 to 2019. This study analyzes how various market structural factors and behavioral factors have impact on the performance. The results show that the high proportion of retransmission fees to broadcasting revenue is negatively associated with total media revenue and operating income while advertising revenue is positively associated with these factors. The results imply PPs that have heavily depended on the fees have not showed a superior performance. Current PP markets are evaluated to have low average revenue per users and thus the size of retransmission fees cannot be enlarged. Under such market conditions, PPs focusing on raising advertising revenue show better performance. This study also suggests that PPs that own diverse channel assets have improved their performances.

• Korean Journal of Veterinary Research
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• v.40 no.3
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• pp.421-430
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• 2000

The regional distribution and relative frequency of the pancreatic polypeptide (PP)-immunoreactive cells in the pancreas of the Korean native goat (Capra hircus) were studied by immunohistochemical methods (PAP methods) using specific antisera against to PP during developmental stage, fetus, neonate, 1-month-old, 6-month-old and adult. The different regional distribution and relative frequency of PP-immunoreactive cells in the pancreas of Korean native goat were observed during development. In the exocrine portions, they were detected in the all ages and distributed in the interacinar regions. PP-immunoreactive cells were increased from neonate to 1-month-old but thereafter decreased with developmental stage. In the pancreatic duct, PP-immunoreactive cells were demonstrated from 1-month-old but they were decreased with developmental stages in these regions. These cells were observed in the subepithelial connective tissue of the pancreatic duct with a few frequencies in 1-and 6-month-old. However, they were located in the interepithelial cells of the pancreatic duct in the adult with rare frequency. In the endocrine portion (pancreatic islets), PP-immunoreactive cells were observed from neonate, and the regional distribution of PP-immunoreactive cells from 1-month-old was divided into two patterns : dispersed 1) in the marginal regions of the pancreatic islets with moderate or a few frequencies, and 2) in the whole pancreatic islets (in a case of 1-month-old) or in the central cores (in a case of 6-month-old and adult) with numerous frequency. In conclusion, the different regional distribution and relative frequency of PP-immunoreactive cells in the pancreas of the Korean native goat were observed during development. It is suggested that the changing of feeding habits and physiological conditions during different developmental stages may cause these differences.

• 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.

• Polymer(Korea)
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• v.27 no.5
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• pp.458-463
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• 2003

The effect of ozone surface treatment of montmorillonite (MMT) was investigated in thermal stabilities of polypropylene (PP) nanocomposites. Sodium montmorillonite (Na$\^$+/-MMT) was organically modified with dodecylammonium chloride. The surface properties of MMT, including the specific surface area (S$\_$BET/), equilibrium spreading pressure ($\pi$$\_$e/), and London dispersive component (${\gamma}$s$\^$L/), were studied by the BET method with $N_2$ adsorption. Also, the thermal stabilities of the nanocomposites were investigated in DSC and TGA. As experimental results, $\pi$$\_$e/ and ${\gamma}$s$\^$L/ of the ozonized dodecylammonium chloride (DA-MK ( $O_3$)) were increased in about 1.7 and 3.5 mJ/ $m^2$, resulting from the increasing of the micropores. From the DSC results, it was found that the melting temperature and crystallization temperature of PP/DA-MK and PP/DA-MK ( $O_3$) were higher that those of pure PP. These results were explained that dodecylammonium chloride of nano-scale led to a nucleation effect for PP crystallization. Also, it was found that E$\_$t/ of the PP/DA-MK ( $O_3$) nanocomposies was increased within about 64 kJ/mol. These results were probably explained by the improvement of dispersivity of DA-MK ( $O_3$) in a PP matrix.

• Applied Microscopy
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• v.26 no.1
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• pp.67-77
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• 1996

Pancreases obtained from native Korean goats were used, and examined by immunoelectron microscopy using several antisera. Five types cells, glucagon (A), insulin (B), somatostatin (D), and pancreatic polypeptide (PP-I and PP-II) cells, were identified in the pancreatic islets. The morphologies of A, B, and D cells corresponded to the typical charateristics described in previous reports on other mammals. Serotonin immunoreactivity was observed in the D cells on the basis of the granular profiles. Two types of PP cells could be distinguished on the basis of the granular profile: the first type was formed by round, homogeneous secretory granules ($220{\sim}400nm$) having a narrow halo between the dense core and limiting membrane, while the other type consisted of cells whose secretory granules ($240{\sim}440\;nm$ in the major axis, $150{\sim}200nm$ in the minor axis) were pleomorphic, having a dense core and a closely fitting limiting membrane. From these results, we suggest that the pancreatic islets of the native Korean goat consist of five types of endocrine cells, A, B, D, PP-I and PP-II cells. Among these, PP-I type cells may correspond to the classical PP of other mammalian pancreases, while PP-II type cells may correspond to the enterochromaffin cells in other species.

• Korean Journal of Environmental Agriculture
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• v.38 no.2
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• pp.83-88
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• 2019

BACKGROUND: In recent years, studies on microplastics have focused on their decomposition in the ocean. However, no studies have been reported on the interaction between microplastics and metal ions in aqueous solutions. Therefore, this study was conducted to evaluate the adsorption capacity of cadmium(Cd) by polypropylene (PP) in aqueous solution. METHODS AND RESULTS: Cadmium adsorption characteristics of PP in aqueous solution were evaluated through various conditions including initial Cd concentration(1.25-25 mg/L), contact time(0.5-24 h), initial pH(2-6) and temperature($20-50^{\circ}C$). Cadmium adsorption fit on PP was well described by Freundlich isotherm model with adsorption capacity(K) of 0.028. The adsorption amount of Cd by PP increased with increasing contact time, indicating that adsorption of PP by Cd was dominantly influenced by contact time. Especially, the removal efficiency of Cd by PP was highest at high temperature. However, the surface functional groups of PP before and after adsorption of Cd were similar, suggesting that adsorption of Cd by PP is not related to surface functional groups. CONCLUSION: Our study suggests that PP affects the behavior of Cd in aqueous solution. However, in order to clarify the specific relationship between microplastics and metal ions, mechanism research should be carried out.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.679-684
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• 2011

Branched polypropylenes (LCB-PP) with a long chain branch were prepared by the solid-state and molt-state reaction. Divinylbenzene (DVB), 1,4-benzenediol (RES), and furfuryl sulphide (FS) were used as branching agents of fabricate LCB-PP/silicate composites. Chemical structures, thermal properties, and rheological properties of the LCB-PP were determined by FT-IR, DSC, TGA, and dynamic rheometer (ARES). The chemical structure of the LCB-PP was confirmed by the existence of =C-H stretching peak of the branching agent at $3100cm^{-1}$. From DSC and TGA results, the melting reaction was more effective than the solid state reaction in the manufacture of LCB-PP, which was additionally certified by rheological properties. Based on rheological properties, FS was the best for branching efficiency of PP. Compared to PP, LCB-PPs indicated an increase of complex viscosity in the low frequency and shear thinning tendency, and G'-G" plot represented an increase in elasticity and the heterogeneousness in a melt state. Rheological properties of LCB-PP/silicate composites were observed with the silicate content. When 5 wt% silicate was added in LCB-PP, distinct changes in the shear thinning and the slope of G'-G" plots were observed.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.469-479
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• 2021

As a material for preventing spalling of concrete, the effectiveness of PP fiber has already been confirmed. However, it is necessary to consider the maximum temperature that occurs during a fire, and to solve the mixing problem and the strength reduction problem that occur depending on the mixing amount. In this study, the fire resistance performance of tunnel segment linings according to the PP fiber content and air volume under the RABT fire scenario was investigated. As a result, no spalling or cross-sectional loss occurred in all test specimens, and when the PP fiber content was small, the maximum temperature was relatively high and the maximum temperature arrival time was also fast. On the other hand, no trend was found for the maximum temperature and arrival time according to the difference in air volume. In the internal temperature distribution results for the PP fiber mixing amount of 0.75, 1.0, 1.5, and 2.0 kg/m³, the results of 0.75 and 1.0 kg/m³ showed similar temperature distribution, and the results of 1.5 and 2.0 kg/m³ were similar. It was confirmed that the internal temperature distribution tends to decrease at the same depth when the amount of PP fiber mixed is large, and it was confirmed that a remarkable difference occurred from the results of 1.0 kg/m³ and 1.5 kg/m³ of PP fiber mixed amounts.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.6
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• pp.151-158
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• 2012

This study will not only prove experimental dynamic properties which are classified to slump, compressed strength, bending strength and toughness index blast-furnace cement concrete with polypropylene (PP) fiber that refer properties and volume of it, but also establish a basic data in order to use PP fiber reinforced blast-furnace cement concrete. The slump didn't changed by PP fiber volume $5kgf/m^3$ because of flexibility of fiber in despite of loose mixing. The reason why the slump decreased steadily by PP fiber volume $3kgf/m^3$ was rising contact surface of water. The compressed strength indicated a range of 19.49~26.32 MPa. The tensile strength indicated a range of 2.10~2.44 MPa. The bending strength was stronger about 3~16 % in case of mixing with PP fiber volume than normal concrete. The flexure strength indicated a range of 4.30~4.83 MPa. The toughness indicated a range of $0{\sim}19.88N{\cdot}mm$ and was stronger about 6.7 times in case of PP fiber volume $9kg/m^3$ than PP fiber volume $1kg/m^3$. The pavement with PP fiber volume over such a fixed quantity in the roads of a respectable amount load can have a effect to prevent not only resistance against clack but also rip off failures.