• Elastomers and Composites
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• v.33 no.3
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• pp.193-200
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• 1998

It is well known that EPDM(ethylene propylene diene monomer) rubber has inherently excellent resistance to the weathering, ozone, heat, cold and moisture, whereas crosslinked IIR (isobutylene isoprene divlnyl benzene terpolymer) shows proper resistance to the water and gas permeation. Various characteristics of EPDM blend with crosslinked IIR such as curing characteristics, mechanical properties, dispersion of minor component and gas impermeability were explored. The optimum curing time $(t_{90})$ examined with peroxide was decreased by adding small amount of crosslinked IIR to the EPDM rubber. Mechanical properties of blends such as tensile strength, hardness and elongation at break were enhanced by increasing EPDM content. These results might be explained with the affinity of carbon black to the EPDM rubber. On the other hand, the physical properties were not changed significantly after aging, and the increase of crosslinked IIR fraction caused the decrease of compression set to small rate. EPDM rubber shows different behavior with crosslinked IIR in oxygen permeability. By adding 30wt.% crosslinked IIR to the EPDM rubber, the resistance to the oxygen permeation was improved up to three times than that of pure EPDM rubber. Conclusively, EPDM blend containing 30wt.% crosslinked IIR might be commercially applied to the o-ring and electric parts because of its proper resistance to the weathering, ozone and oxygen permeability.

• Polymer(Korea)
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• v.29 no.4
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• pp.399-402
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• 2005

In this study, ethyl cellulose (EC)/montmorilloniote(MMT) nanocomposite films plasticized with environmental-friendly plasticizer (BET, EBN, ESO) were prepared by melt process using Hakke mixer. The $T_g$ of plasticized EC films decreased from 122 to $71^{circ}C$ with the increase in the BET content up to 30 $wt\%$. The addition of 10 $wt\%$ epoxidized soybean oil (ESO) as the second plasticizer cause the further drop of $T_g$ from 81 to $61^{circ}C$. The plasticizer-effect of BET was better than that of EBN. When the plasticizer was added into the EC films, the mechanical properties of EC films was decreased, however the addition of monotmorillonite (MMT) into the EC films or the ring opening reaction of ESO plasticizer cause enhancement of mechanical properties.

• Journal of Veterinary Clinics
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• v.22 no.3
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• pp.220-227
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• 2005

Although ketamine has been used in the field of anesthetic medicine for its safety and favourable respiratory effects, the cardiovascular effects of ketamine is still controversial. To clarify the action and mechanism of ketamine upon cardiovascular system, arterial blood pressure, tension of aortic ring, left ventricular developed pressure and heart rate were measured in rats, Ketamine produced two types of effects on arterial blood pressure in anesthetized rats; monophasic effect (blood pressure lowering) and biphasic effect (initial transient blood pressure increasing following sustained lowering), The ketamine-induced lowering of aterial blood pressure showed a concentration-dependent manner, inhibited by the pretreament of $MgCl_2$ and potentiated by the pretreatment of $CaCl_2$. The ketamine-induced lowering of aterial blood pressure was suppressed by the pretreatment of nifedipine, verapamil or lidocaine. In phenylephrine-precontracted endothelium intact (+E) aortic rings, ketamine sometimes caused a small enhancement of contraction ($112.5{\pm}3.6{\%}$). However, in many experiments, ketamine produced a concentration-dependent relaxation in +E aortic rings precontracted with either phenylephrine or KCl. Ketamine-induced relaxation was significantly greater in KCl-precontracted strips than phenylephrine-precontracted strips. In phenylephrine-precontracted +E aortic rings, the ketamine-induced vasorelaxation was not suppressed by endothelium removal or by the pretreatment of a nitric oxide synthase inhibitors, L-$N^G$-nitro-arginine and a guanylate cyclase inhibitors, methylene blue, suggesting that the ketamine-induced vasorelaxation is not dependent on the endothelial function. In addition, ketamine elicited an increase in left ventricular developed pressure in perfused hearts accompanied by decrease in heart rate. These results suggest that ketamine could evoke a hypotension due to vasorelaxation and decrease in heart rate in rats. The inhibitory effect of cardiovascular system might be associated with modulation of $Ca^{2+}$ homeostasis.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.258-261
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• 2003

The optimal design and combustion analysis of the gas generator for Liquid Rocket Engine (LRE) were performed. A fuel-rich gas generator in open cycle turbopump system was designed for 101on1 in thrust with RP-1/LOx combination. The optimal design was done for maximizing specific impulse of main combustion chamber with constraints of combustion temperature and power matching in turbopump system. Results of optimal design show the dimension of length, diameter, and contraction ratio of gas generator. The configuration of the gas generator and the condition for performance which can maximize the objective function were determined and found to meet the design constraints. Also, the combustion analysis was conducted to evaluate the performance of designed chamber and injector of gas generator. And the effect of the turbulence ring was investigated on the mixing enhancement in the chamber.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.12
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• pp.139-145
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• 2008

In this paper, a microstrip surface wave antenna(SWA) with a frequency selective surface structure(FSS) is designed and measured. A microstrip SWA has many advantages such as low profile, low weight, easy fabrication, and compatibility with monolithic microwave integrated circuits(MMIC). In addition, it has demonstrated monopole like beam patterns. The microstrip SWA consists of two parts : a center-fed modified microstrip patch to excite surface wave, and a periodic patches to support the propagation of the surface waves. To obtain wide bandwidth, the ring type parasitic element is inserted and the circular patch is selected for the unit element in FSS structure. Experimental results show that the microstrip SWA has monopole like beam patterns at 5.9GHz. Impedance bandwidth and gain is 12% and 5.6dBi.

• Current Applied Physics
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• v.18 no.11
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• pp.1458-1464
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• 2018

An improved method for the preparation of g-$C_3N_4$ is described. Currently, heating (> $400^{\circ}C$) of urea is the common method used for preparing the g-$C_3N_4$. We have found that sonication of melamine in $HNO_3$ solution, followed by washing with anhydrous ethanol, not only reduce the crystallite size of g-$C_3N_4$ but also facilitate intriguing electronic structure and photoluminescence (PL) properties. Moreover, loading of metal (Pt and Ag) nanoparticles, by applying the borohydride reduction method, has resulted in multicolor-emission from g-$C_3N_4$. With the help of PL spectra and local electronic structure study, at C K-edge, N K-edge, Pt L-edge and Ag K-edge by X-ray absorption spectroscopy (XAS), a precise mechanism of tunable luminescence is established. The PL mechanism ascribes the amendments in the transitions, via defect and/or metal states assimilation, between the ${\pi}^*$ states of tris-triazine ring of g-$C_3N_4$ and lone pair states of nitride. It is evidenced that interaction between the C/N 2p and metal 4d/5d orbitals of Ag/Pt has manifested a net detraction in the ${\delta}^*{\rightarrow}LP$ transitions and enhancement in the ${\pi}^*{\rightarrow}LP$ and ${\pi}^*{\rightarrow}{\pi}$ transitions, leading to broad PL spectra from g-$C_3N_4$ organic semiconductor compound.

• Journal of Veterinary Clinics
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• v.26 no.4
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• pp.367-370
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• 2009

A 5-year-old, intact female Shih-Tzu dog was presented with 1 year history of icterus, ascites and anorexia. The serum biochemistry revealed elevated liver enzyme levels. Microhepatica and decreased serosal detail were detected in abdominal radiography. Abdominal ultrasonographic findings included irregular liver margins, multifocal hypoechoic nodules in the liver parenchyma, and ascites. Computed tomography (CT) showed multifocal hypodense nodules with ring-like contrast enhancement. Cytologic and histopathologic examination by liver core biopsy revealed fibrosis. Cirrhosis was diagnosed based on above results. This report focuses on the imaging characteristics of ultrasonography and CT for liver cirrhosis in a dog.

• The Korean Journal of Pain
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• v.23 no.1
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• pp.1-10
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• 2010

Background: Recent studies indicate that reactive oxygen species (ROS) are involved in persistent pain, including neuropathic and inflammatory pain. Since the data suggest that ROS are involved in central sensitization, the present study examines the levels of activated N-methyl-D-aspartate (NMDA) receptors in the dorsal horn after an exogenous supply of three antioxidants in rats with chronic post-ischemia pain (CPIP). This serves as an animal model of complex regional pain syndrome type-I induced by hindpaw ischemia/reperfusion injury. Methods: The application of tight-fitting O-rings for a period of three hours produced CPIP in male Sprague-Dawley rats. Allopurinol 4 mg/kg, allopurinol 40 mg/kg, superoxide dismutase (SOD) 4,000 U/kg, N-nitro-L-arginine methyl ester (L-NAME) 10 mg/kg and SOD 4,000 U/kg plus L-NAME 10 mg/kg were administered intraperitoneally just after O-ring application and on the first and second days after reperfusion. Mechanical allodynia was measured, and activation of the NMDA receptor subunit 1 (pNR1) of the lumbar spinal cord (L4-L6) was analyzed by the Western blot three days after reperfusion. Results: Allopurinol reduced mechanical allodynia and attenuated the enhancement of spinal pNR1 expression in CPIP rats. SOD and L-NAME also blocked spinal pNR1 in accordance with the reduced mechanical allodynia in rats with CPIP. Conclusions: The present data suggest the contribution of superoxide, produced via xanthine oxidase, and the participation of superoxide and nitric oxide as a precursor of peroxynitrite in NMDA mediated central sensitization. Finally, the findings support a therapeutic potential for the manipulation of superoxide and nitric oxide in ischemia/reperfusion related pain conditions.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.8
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• pp.3333-3338
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• 2015

Background: This study was conducted to analyze positron emission tomography (PET) / computed tomography (CT) and magnetic resonance imaging (MRI) performance with oropharyngeal non-Hodgkin's lymphoma (ONHL).Materials and Methods: The complete image data of 30 ONHL cases were analyzed, all patients were performed PET / CT and MRI examination before the treatment, with the time interval of these two inspections not exceeding 14 days. The distribution, morphology, MRI signal characteristics, enhancement feature, standardized uptake value (SUV) max value and lymph node metastasis way of the lesions were analyzed. Results: Among the 30 cases, 23 cases were derived from the B-cell (76.7%), 5 cases were derived from the peripheral T cells (16.7%) and 2 cases were derived from the NK/T cells (6.7%). 19 cases exhibited the palatine tonsil involvement (63.3%). As for the lesion appearance, 10 cases appeared as mass, 8 cases were the diffused type and 12 cases were the mixed type. 25 cases exhibited the SUVmax value of PET / CT primary lesions as 11 or more (83.3%). MRI showed that all patients exhibited various degrees of parapharyngeal side-compressed narrowing, but MRI still exhibited the high-signal fat, and the oropharyngeal mucosa was intact. 25 cases were associated with the neck lymph node metastasis, among who 22 cases had no necrosis in the metastatic lymph nodes, while the rest 3 cases exhibited the central necrosis in the metastatic lymph nodes. Conclusions: PET / CT and MRI have important value in diagnosing and determining the lesion extent of ONHL.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.5
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• pp.332-339
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• 2011

Effects of powdered activated carbon impregnated by iron oxide nano particle (Impregnated PAC) on the microfiltration (MF) membrane system performance in NOM removal from water were investigated in this study. A fluidized bed column was employed as a pretreatment of MF membrane process. The Impregnated PAC bed was stably maintained at an upflow rate of 63 m/d without leakage of the Impregnated PAC particles, which provided a contact time of 29 minutes. A magnetic ring at the upper part of the column could effectively hold the overflowing discrete particles. The Impregnated PAC column demonstrated a significant enhancement in the MF membrane performance in terms of fouling prevention and natural organic matter (NOM) removal. Trans-membrane pressure of the MF membrane increased to 41 kPa in 98 hours of operation, while it could be maintained at 12 kPa with the Impregnated PAC pretreatment. Removal of NOM determined by dissolved organic carbon and UV254 was also enhanced from 46% and 51% to 75% and 84%, respectively, by the pretreatment. It was found that the Impregnated PAC effectively removed a wide range of different molecular-sized organic compounds from size exclusion analysis.