• 자원리싸이클링
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• 제14권6호
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• pp.37-43
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• 2005

페리튬이온전지로부터 회수된 코발트와 리튬 침출액으로부터 화염분부열분해법에 의하여 $LiCoO_{2}$ 나노분말을 제조하였다. 리튬 및 코발트 성분을 함유하는 전극물질은 열처리 및 기계적 처리에 의해 그 농도를 증가 시켰다. 리튬이온전지 양극물질을 질산으로 용해한 다음 침출액중 Li과 Co의 당량비가 1.0 되도록 $LiNO_{3}$로 조절하여 화염분무열분해용 전구체를 제조하었다. 화염분무열분해법에 의해 제조된 $LiCoO_{2}$ 분말의 평균입자크기는 전구체의 몰 농도가 증가하면서 증가되었으며, 화염온도 역시 입자의 크기를 증가시켰다. 변수실험 결과 $11{\~}35nm$ 크기의 결정형 $LiCoO_{2}$ 나노분말을 제조할 수 있었다 또한 나노 $LiCoO_{2}$의 전극재료로서의 가능성을 확인하기 위하여 충방전 특성 평가와 같은 전기화학적 분석을 수행하였다.

• Journal of Biosystems Engineering
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• 제30권5호
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• pp.261-267
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• 2005

In order to save labor and cost, direct seeding has been considered as an important alternative to the machine transplanting in rice cultivation. As current seeders for direct seeding of rice seeds drill irregular amount of seeds under various operating conditions, conventional drilling should be turned to precision planting which enables accurate placement of proper amount of rice seeds at equal intervals within rows. In this study, design, construction and performance evaluation of a precision seed metering device for planting of rice seeds were carried out. As prototype, the conventional roller type seed metering device was modified for planting: increasing diameter of metering roller, setting 2 or 4 seed cells on metering roller, adding seed discharging lid and its driving cam mechanism. Through performance tests for prototype and the current seed metering device, number of seeds in a hill, planting space and its error ratio, coefficient of variation of planting space (planting accuracy), and seeding length of $90\%$ of seeds in a hill divided by planting space (planting precision) at setting planting spaces of 15, and 20cm, seeding heights of 10, and 20cm, and seeding speeds of 0.1, 0.2, and 0.5m/s were investigated. Prototype showed better seed planting performance than the current seed metering devices. When setting planting space of 15 cm and seeding height of 10cm, prototype with 2 seed cells showed that variations of planting space and seeding lengths of $90\%$ of seeds in a hill at up to seeding speed of 0.5m/s were within 0.9cm, and 3.6cm, respectively.

• 폴리머
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• 제26권5호
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• pp.607-614
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• 2002

폴리우레탄 (ITPU) 실란트의 내후성 및 변색성 개선을 위하여 polyorganosiloxane변성 폴리우레탄 (UMPS)을 합성하고 이들의 유변 특성을 고찰하였다. 폴리우레탄에 도입되는 polyorgano-siloxane block (HBPS)의 함량을 증가시키면 주사슬의 HBPS 부분의 segregation에 의하여 ITPU//HBPS의 비가 70/30에서 점도가 가장 높음을 알 수 있으나 HBPS의 함량을 더 증가시키면 HHPS 주사슬의 유연성에 의하여 점도가 다시 감소함을 확인할 수 있었다. 또한 UMPS는 기존의 폴리우레탄에 비하여 전단속도, 온도, 습도 및 경화 온도의 점도 의존성이 높음을 알 수 있었다. 아울러 MPS에 커플링제를 첨가할 경우 말단 Si(O$CH_3$)$_3$의 도입으로 경화가 촉진되나 이들의 함량이 0.5 wt% 이상 되면 말단 NCO기의 감소에 따라 경화가 늦어지며 그 결과, 전도가 급격히 감소함을 알수 있었다.

• 대한핵의학회지
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• 제21권2호
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• pp.155-165
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• 1987

The noninvasive nature of the radionuclide angiocardiography provided a useful approach for the evaluation of left-to-right cardiac shunts (LRCS). While the qualitative information can be obtained by inspection of serial radionuclide angiocardiograms, the quantitative information of radionuclide angiocardiography can be obtained by the analysis-of time-activity curves using advanced computer system. The count ratios method and pulmonary-to-systemic flow ratio (QP/QS) by gamma variate fit method were used to evaluate the accuracy of detection and localization of LRCS. One hundred and ten time-activity curves were analyzed. There were 46 LRCS (atrial septal defects 11, ventricular septal defects 22, patent ductus arteriosus 13) and 64 normal subjects. By computer analysis of time-activity curves of the right atrium, ventricle and the lungs separately, the count ratios modified by adding the mean cardiac transit time were calculated in each anatomic site. In normal subjects the mean count ratios in the right atrium, ventricle and lungs were 0.24 on average. In atrial septal defects, the count ratios were high in the right atrium, ventricle and lungs, whereas in ventricular septal defects the count ratios were higher only in the right ventricle and lungs. Patent ductus arteriosus showed normal count ratios in the heart but high count ratios were obtained in the lungs. Thus, this count ratios method could be separated normal from those with intra cardiac or extracardiac shunts, and moreover, with this method the localization of the shunt level was possible in LRCS. Another method that could differentiate the intracardiac shunts from extracardiac shunts was measuring QP/QS in the left and right lungs. In patent ductus arteriosus, the left lung QP/QS was higher than those of the right lung, whereas in atrial septal defects and ventricular septal defects QP/QS ratios were equal in both lungs. From this study, it was found that by measuring QP/QS separately in the lungs, intracardiac shunt could be differenciated from extracardiac shunts.

• 한국화재소방학회논문지
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• 제20권4호
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• pp.72-76
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• 2006

고분자/점토의 nanocomposite는 고분자에 소량의 점토를 첨가해도 물리적, 기계적, 열적 특성이 증가하기 때문에 최근 이에 관련된 연구가 증가되고 있다. 특히 montmorillonite(MMT)와 같은 smectite 계열의 점토는 높은 종횡비, 판형의 층상구조, 경제성 때문에 산업적으로 이용가치가 많다고 할 수 있다. 본 연구에서는 PE/MMT nanocomposite는 고분자를 용융시킨 후 점토를 삽입하여 시편을 제조하였다. 나노입자의 구조는 XRD 및 TEM을 이용하여 확인하였고, 난연성은 LOI, 탄화층 생성량, 연기중량농도의 측정을 통하여 검토하였다. 또한 PE/MMT nanocomposite의 열적 안정성은 DTG-DTA 분석을 통하여 검토하였다. 그 결과 종래의 화합물보다 그 특성이 보강되었다. 난연성은 연소시 탄화층 형성에 의하여 증가 되었음을 확인할 수 있었다.

• 한국식품영양학회지
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• 제30권5호
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• pp.860-866
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• 2017

This study was conducted to assess effects of addition of walnuts on soy sauce quality. The pH was significantly increased by adding more than 4 percent of walnuts. As the addition of walnuts increased, Hunter's color values and brown color increased. Total solid of soy sauce did not change significantly with the addition of walnuts. Crude fat content increased by two times in the 2 percent added walnuts group compared to the control group, but it was not dependent on the addition of walnuts. DPPH radical scavenging activity was significantly increased with the addition of walnuts. The addition of walnuts decrease saturated fatty acids and increased unsaturated fatty acids. Composition ratio of linoleic acid was highest in the control group and all the additions. These results revealed that soy sauce made with walnuts have a positive effect on functionality and preference.

• 한국멀티미디어학회논문지
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• 제9권5호
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• pp.606-614
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• 2006

기존에 이동 Ad Hoc On-demand 방식의 대표적인 DSR과 AODV 프로토콜 라우팅 알고리즘은 단지 경로의 손실이 발생할 경우에만 경로 발견을 시작하며, 단절된 경로를 발견하고 새로운 경로 확립하는데 막대한 경비와 시간이 소요된다. 본 논문에서는 기존의 대표적인 DSR과 AODV 프로토콜 라우팅 알고리즘에서 제안하는 견고한 On-demand 방식의 사전 활성화 경로 선택과 관리유지 알고리즘의 추가시키는 측면을 연구한다. 본 연구의 핵심 아이디어는 수신되는 패킷의 신호파워 세기가 손실되기 전의 최적 임계치 신호파워 세기까지 근접하게 되면 경로는 손실될 경향이 높다고 간주하는 것과 수신되는 패킷의 신호파워 세기가 최적 임계치 이하로 떨어졌을 경우, 사전경고 패킷을 발생하는 것이다. 사전경고 패킷을 발생 후에, 송신 노드는 계속적으로 패킷이 전송하는 동안 사전에 경로 발견을 시작하기 때문에, 모든 경로의 단절에 대한 잠재적인 가능성을 피할 수 있다. 성능평가 결과에 의하면, 제안하는 견고한 On-demand 방식의 사전 활성화 경로 선택과 관리유지 알고리즘은 기존의 DSR과 AODV 프로토콜보다 패킷 전달율과 평균 지연시간 그리고 오버헤드 측면에서 성능이 우수한 경향을 나타낸다.

• Archives of Pharmacal Research
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• 제27권7호
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• pp.720-726
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• 2004

Two Spectrophotometric procedures are presented for the determination of two commonly used H2-receptor antagonists, nizatidine (I) and ranitidine hydrochloride (II). The methods are based mainly on charge transfer complexation reaction of these drugs with either ${\rho}-chloranilic$ acid (${\rho}-CA$) or 2, 3 dichloro-5, 6-dicyanoquinone (DDQ). The produced colored products are quantified spectrophotometrically at 515 and 467 nm in chloranilic acid and 000 methods, respectively. The molar ratios for the reaction products and the optimum assay conditions were studied. The methods determine the cited drugs in concentration ranges of 20-200 and $20-160\;\mu\textrm{g}/mL$ for nizatidine and ranges of 20-240 and $20-140\;\mu\textrm{g}/mL$ for ranitidine with chloranilic acid and DDQ methods, respectively. A more detailed investigation of the complexes formed was made with respect to their composition, association constant, molar absorptivity and free energy change. The proposed procedures were successfully utilized in the determination of the drugs in pharmaceutical preparations. The standard addition method was applied by adding nizatidine and ranitidine to the previously analyzed tablets or capsules. The recovery of each drug was calculated by comparing the concentration obtained from the spiked mixtures with those of the pure drug. The results of analysis of commercial tablets and the recovery study (standard addition method) of the cited drugs suggested that there is no interference from any excipients, which are present in tablets or capsules. Statistical comparison of the results was performed with regard to accuracy and precision using student's t-test and F-ratio at 95％ confidence level. There is no significant difference between the reported and proposed methods with regard to accuracy and precision.

• 대한조선학회논문집
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• 제55권6호
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• pp.514-520
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• 2018

Polyurethane foam has excellent mechanical strength and insulation performance, and has been adopted as an insulation material for $-163^{\circ}C$ liquefied natural gas carrier. In this study, Kevlar Polyurethane Foams(K-PUF) were synthesized by adding Kevlar pulp with excellent mechanical strength for the purpose of improving the performance of existing polyurethane foam. Since polyurethane foam has mechanical performance depending on the proportions of Kevlar pulp added, the mechanical strength of the K-PUF with ratios of fiber0.2wt.%, 0.4wt.%, 0.6wt.%, 0.8wt.% and 1.0wt.%) was evaluated. The compression tests were performed on the 4 different temperatures($20^{\circ}C$, $-50^{\circ}C$, $-110^{\circ}C$ and $-163^{\circ}C$) in consideration of the environmental characteristics as a cryogenic insulation used in LNG carrier. Besides, the effects of the fiber addition on polyurethane foam with closed cell structure were evaluated in a phenomenological approach through SEM analysis. All the results were compared to Neat-polyurethane foam. As a results, 0.8wt.% K-PUF showed the improved mechanical strength, and the addition of Kevlar pulp in a certain ratio improves the mechanical performance by enhancing the compression resistance.

• Steel and Composite Structures
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• 제30권3호
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• pp.281-292
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• 2019

In this paper, analysis of critical fluid velocity and heat transfer in the nanocomposite pipes conveying nanofluid is presented. The pipe is reinforced by carbon nanotubes (CNTs) and the fluid is mixed by $AL_2O_3$ nanoparticles. The material properties of the nanocomposite pipe and nanofluid are considered temperature-dependent and the structure is subjected to magnetic field. The forces of fluid viscosity and turbulent pressure are obtained using momentum equations of fluid. Based on energy balance, the convection of inner and outer fluids, conduction of pipe and heat generation are considered. For mathematical modeling of the nanocomposite pipes, the first order shear deformation theory (FSDT) and energy method are used. Utilizing the Lagrange method, the coupled pipe-nanofluid motion equations are derived. Applying a semi-analytical method, the motion equations are solved for obtaining the critical fluid velocity and critical Reynolds and Nusselt numbers. The effects of CNTs volume percent, $AL_2O_3$ nanoparticles volume percent, length to radius ratio of the pipe and shell surface roughness were shown on the critical fluid velocity, critical Reynolds and Nusselt numbers. The results are validated with other published work which shows the accuracy of obtained results of this work. Numerical results indicate that for heat generation of $Q=10MW/m^3$, adding 6% $AL_2O_3$ nanoparticles to the fluid increases 20% the critical fluid velocity and 15% the Nusselt number which can be useful for heat exchangers.