• Title, Summary, Keyword: NR

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Properties and Crosslink Density of the NR/HNBR Blends Influenced by Carbon Black Loading (카본블랙의 충전량에 따른 NR/HNBR블렌드의 물성과 가교밀도에 관한 연구)

  • Hong, Suk-Pyo;Choi, Sang-Goo;Yu, Kil-Sang;Lee, Bum-Chul
    • Elastomers and Composites
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    • v.27 no.3
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    • pp.183-193
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    • 1992
  • Compared with NR and HNBR compounds, the blend properties of NR/HNBR were studied. The heat, oil and ozone resistance of NR compounds were improved by blending HNBR, and these effects were more clearly revealed with elevating temperatures. For the overall stabilities of the compounds, it was resonable to use the carbon black under the 60phr. In the EV systems, high-saturated NR/HNBR and HNBR compounds showed similar total crosslink density in comparison with NR compounds. Interaction parameters calculated by stress-strain method showed widely varied value.

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Effect of Precured EPDM on the Property of Magneto-rheological Elastomer Based on NR/EPDM Blend

  • Na, Bokgyun;Chung, Kyungho
    • Elastomers and Composites
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    • v.53 no.2
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    • pp.67-74
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    • 2018
  • Magneto-rheological elastomers (MREs) are smart materials in which the inherent stiffness and damping properties can be changed by the influence of an external magnetic field. The magneto-rheological (MR) effect depends on the orientation characteristics of the dispersed magneto-responsible particles (MRPs) in the matrix. In this study, natural rubber (NR) and ethylene propylene diene rubber (EPDM) were blended and used as a matrix of an MRE. EPDM was pre-cured before blending with NR. The Mooney viscosity, curing characteristics, and mechanical properties were analyzed with various pre-curing conditions of EPDM and the NR/EPDM blend. The results show that excellent mechanical properties of the NR/EPDM blend-based MRE were obtained when the pre-curing time of EPDM was 60 min. The aging property of the NR-based MRE was improved by the introduction of pre-cured EPDM. Also, the anisotropic MRE showed a higher MR effect than that of the isotropic MRE.

천연고무 및 합성시스-1,4- 포리이소프렌의 무우니이점도와 완화탄성률의 관계

  • GyeonSa Ung-Il;ChimGan Ho
    • The tire
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    • pp.16-19
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    • 1975
  • 무우니이점도 30에서 70까지의 천연고무(이하 NR이라고 약)와 합성 시스-1,4-포리이소프렌(이하 IR이라고 약)의 완화탄성률에 대해서 검토했다. 완화탄성률은 -50℃로부터 90℃이며 시간 3초로부터 3,000초에 긍해서 측정했다. 동일한 무우니이점도로서 어느 온도에 있어서도 IR의 완화탄성률은 NR에 비하면 작으며 따라서 IR은 부드럽게 촉감된다고 생각된다. NR과 IR의 각종온도에서의 완화탄성률과 시간의 관계는 같은 환산계수를 사용해서 중합이 가능했었다. 얻어진 합성곡선에 대해서 특히 종단역에 있어서 NR의 완화탄성률이 IR에 비해서 크다. 이것은 같은 무우니이점도로서 NR쪽이 IR에 비하여 높은 평균분자량과 넓은 분자량분포를 가지기 때문이라고 생각된다.

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Involvement of Serine Phosphorylation of Spinal Cord NR-2B Subunit of the N-methyl-D-aspartate Receptor Following Electroacupuncture Stimulation (전침자극이 척수 N-methy1-D-aspartate receptor외 NR-2B Subunit 인산화에 미치는 영향)

  • Kang, Byeol-Rim;Choi, Byung-Tae;Yoon, Hyun-Min;Min, Young-Kwang;Ahn, Chang-Beohn
    • Journal of Acupuncture Research
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    • v.24 no.2
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    • pp.63-71
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    • 2007
  • 목적 : 저주파에 해당하는 2Hz 전침 자극이 척수 N-methyl-D-aspartate receptor (NMDAR)의 NR-2B subunit의 발현 및 인산화에 미치는 영향을 조사하였다. 방법 : Sprague-Dawley계 흰쥐를 Storkson등의 방법에 의해 척수막의 지주막하강에 catheter를 삽입하는 수술을 행한 후 마비등의 척수 손상을 나타내지 않는 개체를 대상으로 하였다. N-methyl-D-aspartate (NMDA) antagonist인 D-2-amino-5- phosphonopentanoic acid (AP-5)를 투여한 후 족삼리와 삼음교에 해당하는 부위에 30분간 전침 자극하였다. 무통각 여부는 hot plate test를 시행하였으며 NMDAR NR-2 subunit 발현과 인산화 여부는 Western blot과 면역조직화학적으로 살펴보았다. 결과 : 전침 무통각은 전침 자극 후 180분 후까지 지속되었으며 NMDA antagonist인 AP-5를 투여하였을 때 전침 무통각이 저하되었으나 유의성은 나타내지 않았다. Western blot 분석으로 보아 NMDAR NR-2B 및 인산화 NR-2B의 발현은 전침자극에 의해 미약한 증가를 보이나 AP-5투여에 의해 현저한 저해를 보였다. 면역조직화학에 의한 척수배각 구역별 발현을 보면 NMDAR NR-2B 및 인산화 NR-2B는 전 배각에 걸쳐 관찰되나 경부(층판 V-VI)에서 약한 반응을 보였다. 전침 자극에 의한 각 군별 NR-2B 발현은 유의한 차이를 보여 주지 않았으나 인산화 NR-2B는 천층(층판I-II) 및 고유핵 층판(III-IV)에서 유의성 있는 증가를 보였다. 전침 자극시 AP-5 투여는 유의성은 보이지 않았으나 인산화 NR-2B 발현을 저해하였다. 결론: 저주파 2Hz 전침에 의한 무통각은 NMDA antagonist인 AP-5 투여에 의해 저해될 뿐 아니라 NMDAR NR-2B subunit의 인산화를 저해하는 것으로 보아 전침 무통각의 과정에 NMDAR 및 NMDAR NR-2B의 인산화가 관여함을 알 수 있다.

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A Study on the Effects of Herbal-acupuncture with Notopterygii Radix solution at ST36 on CIA in Mice (족삼리(足三里) 강활약침(羌活藥鍼)이 생쥐의 Collagen-induced arthritis에 미치는 영향)

  • Park, Hyeun-Sun;Yim, Yun-Kyoung;Lee, Byung-Ryul
    • Korean Journal of Acupuncture
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    • v.22 no.2
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    • pp.89-105
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    • 2005
  • Objective & Methods : This study is performed to observe the effect of Herbal-acupuncture with Notopterygii Radix Herbal-Acupuncture Solution(NR-HAS) at Joksamni(ST36) on Collagen II-induced arthritis (CIA) in DBA/1J mice. Result : 1. The highest survival rate of mice lung fibroblasts were measured in the 1% NR-HAS, and the expression of $TNF-{\alpha}$ in synovial cells were significantly decreased in the 1% and 10% NR-HAS. 2. The incidence of arthritis and the spleen weight were significantly decreased by Notopterygii Radix Herbal-acupuncture(NR-HA) at ST36. 3. The levels of IL-6, $INF-{\gamma},\;TNF-{\alpha}$, IgG, IgM, anti-collagen II in serum of CIA mice were significantly decreased by NR-HA at ST36. 4. In histology, the cartilage destruction and synovial cell proliferation were decreased by NR-HA at ST36, and the collagen fiber expressions in the NR-HA I II groups were similar with that of the normal group. 5. In lymph node, the expression ratios of $CD3e^+\;to\;CD19^+$ cell and $CD4^+\;to\;CD8^+$ cell in the NR-HA I II groups were similarly maintained as those in the normal group. 6. In lymph node, $CD69^+/CD3e^+$ cells and $CD11a^+/CD19^+$ cells were decreased by NR-HA at ST36. 7. In the articular joint, $CD11b^+/Gr-1^+$ cells were decreased by NR-HA at ST36. 8. NR-HA at ST36 did not make a considerable difference in DBA/1J mice without CIA 9. Throughout the overall experimental result, NR-HA I group showed more predominant effect than the NR-HA II group. Conclusion : These results suggest that NR-HA at ST36 has an effect to control synovial cell proliferation and cartilage destruction in rheumatoid arthritis, as well as prophylaxis is important to treat rheumatoid arthritis in clinic.

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Nutrient requirements in Hanwoo cows with artificial insemination: effects on blood metabolites and embryo recovery rate

  • Kang, Sung-Sik;Kim, Ui-Hyung;Han, Man-Hye;Cho, Sang-Rae
    • Journal of Animal Science and Technology
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    • v.62 no.4
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    • pp.449-459
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    • 2020
  • Here, we investigated the effects of different nutrient requirements (NR) on blood metabolites, transferable embryo number after multiple superovulations with artificial insemination (AI), body condition score (BCS), and estrus cycle in Hanwoo cow. Nineteen Hanwoo cows were randomly divided into three groups (80%, 100%, and 120% NR, containing 6, 8, and 5 individuals, respectively) and fed based on the NR. In experiment 1, glucose, total cholesterol, triglyceride, blood urea nitrogen (BUN), aspartate aminotransferase (AST), alanine aminotransferase (ALT), non-esterified fatty acids (NEFA), albumin (ALB), and total protein (TP) were analyzed. In experiment 2, total number of recovered embryos and transferable embryos was examined after embryo recovery and multiple superovulations with AI. In experiment 3, body weight, BCS, and estrus cycle were examined. In experiment 1, total cholesterol was significantly different among the 80%, 100%, and 120% NR groups (126.5 ± 3.3, 152.6 ± 2.4, and 177.4 ± 1.8 mg/dL, respectively, p < 0.05). The triglyceride and BUN levels in the 120% NR group were significantly higher than those in the 80% and 100% groups (p < 0.05). The NEFA levels were significantly different among the 80%, 100%, and 120% NR groups (440.5 ± 18.2, 318.5 ± 23.1, and 195.1 ± 8.5 ЧEq/L, respectively, p < 0.05). The AST and TP levels in the 80% NR group were significantly lower than those in the 100% and 120% NR groups (p < 0.05). In experiment 2, the 120% NR group showed a higher percentage of transferable embryos than the 80% and 100% groups (p < 0.01). The mean body weight and BCS among the 80%, 100%, and 120% NR groups were significantly different (p < 0.05). The estrus cycle in the 80% NR group was delayed compared with the 100% and 120% NR groups (20.8 ± 0.2 and 21.2 ± 0.5 days, respectively). In conclusion, the blood metabolic tests proved that Hanwoo cows with 120% NR can produce a large number of transferable embryos. Thus, 120% NR is the appropriate feeding level for this type of cows as it results in the production of a large number of transferable embryos by multiple superovulations with AI.

A Study on the Iterative Solution Procedures for the Elasto-Plastic Large Deflection Analysis of Plates (판부재의 탄소성대변형 유한요소 해석문제에서의 수렴기법에 관한 고찰)

  • 백점기;김창렬;이정권
    • Computational Structural Engineering
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    • v.2 no.3
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    • pp.97-103
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    • 1989
  • In this study, a usefulness of the iterative solution procedures is reviewed for the elasto-plastic large deflection analysis of imperfect plates by finite element method. Three typical solution techniques such as simple incremental(SI) method, Newton-Raphson(NR) method and modified Newton-Raphson (mNR) method are compared. It is concluded that for thin plates which are given rise to the large deflection, iteration for the convergence of the unbalance force should be performed and in this case mNR method is more useful than NR method since the computing time of the former becomes to be a half of the latter, in which the accuracy of the result remains same. For thick plates or thin plates with large initial deflection, however, the use of SI method is quite better since the unbalance force may be negligible.

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Cure Characteristics of Carbon Block-Filled Rubber Compounds Composed of NR, SBR, and BR (NR, SBR, BR로 이루어진 고무배합물의 고무조성비에 따른 가황 특성)

  • Choi, Sung-Seen
    • Elastomers and Composites
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    • v.35 no.3
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    • pp.215-226
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    • 2000
  • Cure characteristics of carbon black-filled rubber compounds with different rubber composition were studied using a rheometer. The carbon black-filled rubber compounds with single, binary, and ternary rubber compositions of natural rubber (NR), styrene-butadiene rubber (SBR), and butadiene rubber (BR) were used. Delta-torques of the NR/BR- and SBR/BR-based compounds with a high BR content were higher than those of the single rubber-based compounds. For ternary rubber-based compounds, the delta-torques of the compounds were lower when the difference in the rubber content ratios was small than when it was big. Scorch and optimum cure times of the rubber compounds became shorter by increasing the content of NR in the compounds while those became longer by increasing the SBR content. Cure rates of the rubber compounds increased with a decrease of the SBR content in the rubber compounds. Reversion ratios decreased with an increase of the SBR content in the rubber compounds.

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A New Species of Hyphomycetes, Aspergillus coreanus sp.nov.,Isolated from Traditional Korean Nuruk

  • Yu, Tae-Shick;Yeo, Soo-Hwan;Kim, Hyun-Soo
    • Journal of Microbiology and Biotechnology
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    • v.14 no.1
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    • pp.182-187
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    • 2004
  • Strain NR $15-1^T$ isolated from traditional Korean Nuruk is described as a new species and named as Aspergillus coreanus NR $15-1^T$ sp. novo Strain NR $15-1^T$ grew rapidly to form yellow-green colonies whose surfaces were velvety on Czapek solution agar. Conidial heads were yellow to light and elliptical, whereas the conidiophore was colorless and typically long. In addition, vesicles were from flask-shaped to globose, and sterigmata are uniseriate. Conidia were spherical and deep yellow-green, and their surfaces were lightly roughened. The G+C content of strain NR $15-1^T$ was 51 mol% and strain NR $15-1^T$contained a dihydrogenated ubiquinone with Q9 (94.9%) as a major quinone. The nucleotide sequences of strain NR $15-1^T$ in the two Internal Transcribed Spacers (ITS 1 and 2) and 5.8S rDNA showed highest similarity when compared with that of A. tubingensis and A. phoenicis NRRL $365^T$. However, based on morphological and chemotaxonomic characteristics, this strain was different from A. tubingensis and A. phoenicis NRRL $365^T$. On the basis of the data presented, it is proposed that strain NR $15-1^T$ should be placed in the genus Aspergillus as a new species, Aspergillus coreanus sp. novo Therefore, the type strain of the new species is strain NR $15-1^T$ (=KCTC 18075P^T,=KCCM 80006^T$.

Optimal Conditions of Protoplast Formation of Aspergillus coreanus NR 15-1 and Aspergilus oryzae NR 2-5 (Aspergillus coreanus NR 15-1 과 Aspergillus oryzae NR 2-5의 원형질체 형성의 최적조건)

  • 정혁준;유대식
    • Microbiology and Biotechnology Letters
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    • v.29 no.1
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    • pp.12-17
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    • 2001
  • Aspergil-lus coreanus NR-15 and Aspergilus oryzae NR-2-5 from traditional Korean Nuruk were selected as parental strains producing starch hydrolysis enzyme. Xll(Arginine-) mutant from A. coreanus NR 15-1 showed high glu-doamylase activity and total acid productivity. Z6(Adenine-) mutant from A. oryzae NR2-5 showed the highest $\alpha$-amylase activity. Therefore, both XII and Z6 mutants were selected and investigated for the optimal conditions of protoplast formation for protoplast fusion. Mixture of equal amount of cellulase and driselase(10mg/ml each) was the most effective as lytic enzymes. The optimal pH and temperature for protoplast formation were 5.0 and $30^{\circ}C$, respectively. The most effective reaction for protoplast formation time was 4 hours. The maximum of protoplst for- mation of Xll mutant and Z6 mutant were $6.54$\times$10^{7}$ protoplasts/ ml and $3.04$\times$10^{ 7}$ protoplasts/ml, and the regen-eration frequencies of the protoplasts were 11.3% and 11.6%, respectively. The size of the protoplasts from X11 and Z6 mutants were 3~6 $\mu\textrm{m}$ and 4~9$\mu\textrm{m}$, respectively.

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