• Biomaterials and Biomechanics in Bioengineering
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• 제1권2호
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• pp.63-71
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• 2014

This study aimed to develop a novel bioactive hybrid xerogel consisting of silk fibroin /$SiO_2-CaO-P_2O_5$ by sol-gel process at room temperature. Scanning electron microscopy (SEM), FT-IR Spectroscopy, pore measurement, mechanical property testing, in vitro bioactivity test and cytotoxicity assay were performed to characterize the xerogel for bone tissue engineering application. We have found that the xerogel possessed excellent pore structures and mechanical property. Once immersed in a simulated fluid (SBF), the xerogel exhibited profound bioactivity by inducing hydroxyapatite layers on its surfaces. The cell toxicity study also demonstrated that there was little toxic to MC3T3-E1 cells. These results indicate that silk fibroin /$SiO_2-CaO-P_2O_5$ hybrid xerogel potentially could be used as a bone tissue engineering material.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.791-794
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• 2008

MRE(Magneto-rheological Elastomer) is a material which shows reversible and various modulus in magnetic field. Comparing to conventional rubber vibration isolator, MREs are able to absorb broader frequency range of vibration. These characteristic phenomena result from the orientation of magnetic particle (i.e., chain-like formation) in rubber matrix. In this study, NR was used as a matrix in order to manufacture MREs. Magnetic reactive powder(MRP), having rapid magnetic reaction, was selected as a magnetic particle to give magnetic field reactive modulus. The mechanical properties of manufactured MREs were measured without the application of magnetic field. The results showed that the tensile property and resilience were decreased while the hardness was increased with the addition of CIP. The analysis of MR effect was carried out by FFT analyzer with various magnetic flux. As the addition of MRP and magnetic flux increased, increment of MR effect was observed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권5호
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• pp.968-988
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• 2010

Anonymous hierarchical identity based encryption (HIBE) is an extension of identity based encryption (IBE) that can use an arbitrary string like an e-mail address for a public key, and it additionally provide the anonymity of identity in ciphertexts. Using the anonymous HIBE schemes, it is possible to construct anonymous communication systems and public key encryption with keyword search. This paper presents an anonymous HIBE scheme with constant size ciphertexts under prime order symmetric bilinear groups, and shows that it is secure under the selective security model. Previous anonymous HIBE schemes were constructed to have linear size ciphertexts, to use composite order bilinear groups, or to use asymmetric bilinear groups that is a special type of bilinear groups. Our construction is the first efficient anonymous HIBE scheme that has constant size ciphertexts and that uses prime order symmetric bilinear groups. Compared to the previous scheme of composite order bilinear groups, ours is ten times faster. To achieve our construction, we first devise a novel cancelable random blinding technique. The random blinding property of our technique provides the anonymity of our construction, and the cancellation property of our technique enables decryption.

• The Journal of Asian Finance, Economics and Business
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• 제8권3호
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• pp.469-477
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• 2021

In this paper, the relationship between the profitability level of an enterprise and the credit policy adopted by an enterprise was measured. A sample of industrial firms listed on the stock exchanges of Iraq, Jordan, and Kuwait was analyzed. Five industrial firms were randomly selected from each exchange with a condition of having at least 5 year-activity. The total sample size was 15 industrial firms. The study financial data was imported from the sample firms' websites. The financial data was for the financial year 2017. The Regression Analysis was adopted to measure the impact of trade credit on the profitability of an enterprise using the SPSS software. It was found that the receivable accounts have a proportional relationship with the turnover property rights rate. Similarly, the statistical results showed that the turnover property rights rate increased with an increase in the turnover receivable accounts rate and the percentage of investment in receivable accounts. The influence of trade credit on the enterprise profitability percentage in the Iraq stock exchange, Amman stock exchange, and Boursa Kuwait were 0.938, 0.200, and 0.089, respectively. The results showed that the three secondary assumptions were incorrect, while the zeroth assumption, i.e., trade credit has no influence on profitability, was correct.

• 전기학회논문지P
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• 제58권4호
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• pp.451-454
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• 2009

The $\beta-In_2Te_3$ single crystal was grown by vertical Bridgman method. The $\beta-In_2Te_3$ single crystal had a face centered cubic(fcc) structure. The lattice constants were found to be $a\;=\;0.617\;{\AA}$. The direct optical energy gap ($E_g$) was found to be 1.11 ev at 300 K. Raman spectra peak of $\beta-In_2Te_3$ single crystal showed the low $E_{LO}$ mode at $105\;cm^{-1}$. The electrical conduction type was measured by the thermal method and was p-type. The electrical conductivity was found to be $1.8\;{\times}\;10^{-2}\;{\Omega}^{-1}cm^{-1}$ at 300 K. The activation energy was found to be 0.51 eV.

• 한국세라믹학회지
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• 제40권10호
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• pp.936-942
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• 2003

In order to develop glass formulations for vitrifying Low-and Intermediate-Level radioactive Wastes (LILW) from nuclear power plants of Korea Hydro & Nuclear Power (KHNP) Co., Ltd., promising glass formulations were selected based on glass property model predictions for viscosity, electrical conductivity and leach resistance. Laboratory measurements were conducted to verify the model predictions. Based on the results, the models for electrical conductivity, US DOE 7-day Product Consistency Test (PCT) elemental release, and pH of PCT leachate are accurate for the LILW glass formulations. However, the model for viscosity was able to provide only qualitative results. A leachate conductivity test was conducted on several samples to estimate glass leach resistance. Test results from the leachate conductivity test were useful for comparison before PCT elemental release results were available. A glass formulation K11A meets all the KHNP glass property constraints, and use of this glass formulation on the pilot scale is recommended. Glass formulations K12A, K12B, and K12E meet nearly all of the processing constraints and may be suitable for additional testing. Based on the comparison between the measured and predicted glass properties, existing glass property models may be used to assist with the LILW glass formulation development.

• 한국터널지하공간학회 논문집
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• 제17권5호
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• pp.533-551
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• 2015

암석은 인공적인 재료(금속, 유리)에 비해 불균질하고 이방성을 가지고 있기 때문에 워터젯 절삭시 매우 복잡하게 파쇄되는 특성을 가진다. 워터젯 절삭시 암석특성에 따라 절삭성능이 결정되므로 물성에 대한 영향을 파악하는 것은 매우 중요하다. 워터젯 절삭효율에 영향을 미치는 물성은 선행문헌의 실험조건(수압, 연마재 투입량, 이격거리 등) 및 암종에 따라 다양하게 제시되고 있다. 본 연구에서는 워터젯 시스템을 이용한 암석절삭에 있어서 물성영향에 대해 문헌연구를 실시하고 중요 물성을 분석하였다. 선행문헌 연구를 통해 암석의 공극율, 일축압축강도, 경도가 워터젯 암석 절삭에 있어서 중요한 물성으로 도출되었다. 분석결과는 향후 워터젯 절삭 기술을 이용한 터널공사시, 암반특성에 따른 굴착효율을 예측하기 위한 기초지식을 제공할 수 있을 것이다.

• 한국응용과학기술학회지
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• 제33권1호
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• pp.23-29
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• 2016

육방정계 우르자이츠형의 산화아연은 n형 반도체로써 3.37 eV의 넓은 밴드갭 에너지와 60 meV의 큰 엑시톤 바인딩 에너지를 가진 물질이다. 가스센서, 발광 다이오드, 염료 감응 태양 전지, 염료오염의 분해 등의 넓은 범위에서 활용이 가능하다. 합성 시 마이크로파 수열합성법을 사용하게 되면 높은 수율, 빠른 반응속도, 에너지 절약의 장점이 있다. 아민첨가제는 수산이온 생성 및 킬레이트 효과로 인해 산화아연 입자 형상을 조정하는 역할을 한다. 본 논문에서는 전구체로는 질산아연육수화물을 사용하였고, 형상조정제로는 에탄올아민, 에틸렌디아민, 디에틸렌트리아민, 헥사메틸렌테트라민을 사용하였다. 수산화소듐을 사용하여 용액을 pH 11로 조정하였다. 합성된 산화아연은 별모양, 막대형, 꽃모양, 원추형의 다양한 형상을 확인할 수 있었다. 아민첨가제에 의한 물리 화학적 특성과 광학적 특성을 분석하기 위해 XRD, SEM, EDS, FT-IR, UV-vis 스펙트럼, PL 스펙트럼을 사용하였다.

• 한국산학기술학회논문지
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• 제16권2호
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• pp.1555-1562
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• 2015

금속 산화물 반도체는 독특한 전기 광학적 특성, 높은 표면적 등으로 인해 태양전지, 센서, 광소자 및 디스플레이 등 여러 분야에 걸쳐 응용되고 있다. 금속 산화물 가운데 우수한 물리 화학적 특성을 가지는 산화아연은 3.37 eV의 넓은 밴드갭 에너지와 60 meV의 큰 엑시톤 결합에너지를 갖는 n-형 반도체로서 산화아연에 양이온을 도핑하여 전기 광학적 특성을 보완하는 연구가 진행되고 있다. 본 연구는 알루미늄이 도핑 된 산화아연을 마이크로파 수열합성법으로 합성하였다. 전구체의 종류와 몰 비 등의 반응 변수를 조절하여 최적의 결정형상과 광학적 특성을 갖는 산화아연을 합성하였으며, 알루미늄을 도핑하여 광학적 특성 변화를 시도하였다. 합성된 입자는 SEM, XRD, PL, UV-Vis 분광기 및 EDS 등의 기기분석을 통해 광학적, 물리 화학적 특성을 확인하였다.

• 대한본초학회지
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• 제24권2호
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• pp.39-48
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• 2009

Objectives : To clarify the possible effect of JS (Juglans sinensis), PCF (Psoralea corylifolia L.), and J+P(JS+PCF), we examined their influence on the development of pulmonary eosinophilic inflammation in the asthmatic murine model. Methods : All mice were immunized on two different days (21 days and 7 days before inhalational exposure) by intraperitonial injections of 0.2 ml alum-precipitated Ag containing 100 ${\mu}$g of OVA bound to 4 mg of aluminum hydroxide in PBS. Seven days after the second sensitization, mice were exposed to aerosolized ovalbumin for 30 minutes/day on 3 days/week for 8 weeks (at a flow rate of 250 L/min, 2.5% ovalbumin in normal saline) and, JS, PCF and J+P (200 mg/kg, 400 mg/kg) were orally administered 3 times per week for 8 weeks. Results : The suppressive effects of JS, PCF, and J+P were demonstrated by the accumulation of eosinophils into airways, with the reduction of eosinophils and lung leukocytes. These were correlated with the marked reduction of IL-4, IL-5, IL-13 levels in the BALF and serum. OVA-specific IgE levels were also decreased in serum and BAL from these mice. And also JS, PCF, and J+P decreased eosinophilic CCR3 and CD11b expression in lung tissue. Conclusions : These results indicate that JS, PCF, and J+P have deep inhibitory effects on airway inflammation and hyper-responsiveness in the asthmatic murine model. The suppression of IL-5, IgE, and eosinophilils and the increase of IFN-${\gamma}$ production in BALF seem to contribute to these effects. Specially, esosinophils and TNF-a in J+P combination group were significantly reduced in BALF and lung tissue. Hence, the results indicated that JS, PCF, and J+P could act as an immuno-modulator which possesses anti-inflammatory and anti-asthmatic property by modulating the imbalance between Th1 and Th2 cytokines.