• 한국세라믹학회지
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• 제53권4호
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• pp.456-462
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• 2016

$NaCaGd(MoO_4)_3:Ho^{3+}/Yb^{3+}$ ternary molybdates were successfully synthesized by microwave sol-gel method for the first time. Well-crystallized particles formed after heat-treatment at $900^{\circ}C$ for 16 h showed a fine and homogeneous morphology with particle sizes of $3-5{\mu}m$. Under excitation at 980 nm, the UC intensities of the doped samples exhibited strong yellow emissions based on the combination of strong emission bands at the 520-nm and 630-nm emission bands in the green and red spectral regions, respectively. The strong 520-nm emission band in the green region corresponds to the $^5S_2/^5F_4{\rightarrow}^5I_8$ transition of $Ho^{3+}$ ions, while the strong 630-nm emission band in the red region appears to be due to the $^5F_5{\rightarrow}^5I_8$ transition of the $Ho^{3+}$ ions. The optimal $Yb^{3+}:Ho^{3+}$ ratio was found at 9:1, as indicated by the composition-dependent quenching effect of $Ho^{3+}$ ions. The pump power dependence of the upconversion emission intensity and the Commission Internationale de L'Eclairage chromaticity coordinates of the phosphors were evaluated in detail.

• 한국기계가공학회지
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• 제13권4호
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• pp.121-129
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• 2014

This study was carried out to develop an efficient plant growth system that can be controlled by altering the wavelength and illumination using a LED module. If it is possible to develop a system that can be controlled in this manner, utilizing different characteristics in the meaningful wavelength band depending on the growth time or type of plant, the plant growth conditions can be optimized. In order to this, red, green, blue and white LEDs are arrayed in a rectangle, consisting of LED modules which can be combined with each other. Consequently, the array can be used to select the optimal light conditions with monochromatic red, green, blue and white LEDs, or mixed LEDs, for plant growth. Experiments on the characteristics of the wavelengths to evaluate the efficiency of the plant growth system were performed. The usefulness of the system was demonstrated through a cultivation test involving several special plants.

• 설비공학논문집
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• 제24권2호
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• pp.183-189
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• 2012

Most of the domestic residential buildings have used the traditional radiant heating system, circulating hot water through the cross-linked polyethylene(PE-X) pipe buried in the floor panel of the heating space. New type of the heating panel was recently developed using heat pipes with double wicks. Some experiments were carried out in this study to verify the thermal characteristics of this heating system at the unit heating space which surrounded by outer space whose temperature of air be maintained scheduled value with time. Through the various experiments with several parameters, such as flow rate, inlet and outlet temperatures of hot water and the heating duration and so on, we found that the floor heating system with heat pipes was able to reduce the pumping power for hot water circulation by 4~31% compared with the conventional panel heating system using PE-X pipe. These results could be used for optimal design and efficient operation of the heating system as well as improvement of thermal comfort.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.734-745
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• 2021

In order to achieve a good and competitive FPSO design, the building cost and the motion performances are the two most critical and conflicting KPIs to be considered. In this study, the author's previous work (Lee, et al., 2021) on the optimization of an FPSO's hull dimensions with 1800 MBBLs storage capacity at Brazil field was extended using a multi-objective parametric optimization with the hull steel weight and the operability which are closely related to the building cost and the operational cost during the lifetime, respectively. For the purpose of more realistic and practical FPSO design, the constraints related to crew comfort and the safe helicopter take-off and landing operation were newly added. Also, the green water on deck was calculated accurately to check the suitability of the designed freeboard height using a newly developed real-time calculation module for the relative wave elevations. With aids of this updated optimization formulation, we presented multiple optimal FPSO dimensions expressed as a Pareto set which aids FPSO designers to conveniently select the practical and competitive dimensions. The excellence of the developed approach was verified by comparing the optimization results with those of FPSOs dimensioned for operation at West Africa and Brazil field.

• KSBB Journal
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• 제19권3호
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• pp.236-240
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• 2004

Batch experiment에서 다양한 질소 농도에서 구해진 질소제거 속도와 비 생장속도 등의 데이터를 토대로 4.6일의 체류시간을 갖는 2단 처리 장치를 설계하였다. 그리고 continuous experiments에서는 3.5일의 체류시간을 갖는 2단의 처리 장치를 설계하였다. 두 가지 값에 차이는 있지만 실제 현장에서 폐수 처리 장치를 설계할 때 충분한 자료가 되리라고 판단한다. 따라서 위의 결과를 토대로 기존 시스템에 미세조류 시스템을 부가한다면 기존공정의 단점인 잉여질소 제거 장치로서 충분히 역할을 수행해 배출 기준치를 만족시키는 안전한 폐수처리장치가 되리라고 판단한다.

• 미생물학회지
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• 제45권4호
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• pp.385-390
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• 2009

광합성 담수 녹조류인 Chlorella pyrenoidosa의 최적 생장 조건을 알기 위해 배양 온도, 시간, 영양물질의 영향 및 조도 등을 조사하였다. Growth chamber를 사용하여 알아본 가장 적절한 조건은 온도 $28^{\circ}C$에서 4일간 배양했을 때이며 배지에 첨가된 타 영양물질의 농도가 높을수록 활발한 광합성을 하면서 생장하였고 조도(Lux)가 크면 클 수록 잘 자랐다. 또한 동일 균주로부터 acetaldehyde를 분해하는 효소의 활성을 살펴보았는데 이 효소는 $\beta$-$NAD^+$를 조효소로 하는 탈수소효소였으며, ODS-Hypersil column과 50%(v/v) acetonitrile을 이동상으로 한 HPLC로 분석한 결과 pH 9.0, 온도 $40^{\circ}C$ 부근에서 최대 효소 활성을 보여주었다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권6호
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• pp.2709-2734
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• 2020

The growing demand to make wireless data services 5G compatible has necessitated the development of an energy-efficient approach for an effective new wireless environment. In this paper, we first propose a cognitive sensor node (CSN) based game theory for deriving energy via a primary user-transmitted radio frequency signal. Cognitive users' time was segmented into three phases based on a time switching protocol: energy harvest, spectrum sensing and data transmission. The proposed model chooses the optimal energy-harvesting phase as the effected factor. We further propose a distributed energy-harvesting model as a utility function via pricing techniques. The model is a non-cooperative game where players can increase their net benefit in a selfish manner. Here, the price is described as a function pertaining to transmit power, which proves that the proposed energy harvest game includes Nash Equilibrium and is also unique. The best response algorithm is used to achieve the green connection between players. As a result, the results obtained from the proposed model and algorithm show the advantages as well as the effectiveness of the proposed study. Moreover, energy consumption was reduced significantly (12%) compared to the benchmark algorithm because the proposed algorithm succeeded in delivering energy in micro which is much better compared to previous studies. Considering the reduction and improvement in power consumption, we could say the proposed model is suitable for the next wireless environment represented in 5G.

• 대한약침학회지
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• 제21권2호
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• pp.48-60
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• 2018

Objective: The aim of this study is to optimize the extraction of beneficial substance from Cudrania tricuspidata leaves grown at Jirisan Mountain in South Korea by three different solvents depending on extraction time and at different temperature. Methods: The total phenolic contents were determined by the method reported by $S{\acute{a}}nchez$-Moreno et al. The total flavonoid contents were analyzed by Slinkard and Singleton. The DPPH radical scavenging activity was determined according to the method reported by Blois Results: The extraction yield for each solvent is 9.05-14.1%, 2.17-5.67%, and 2.3-3.9% for D.W., ethanol, and hexane, respectively. The overall results were maximized for the extract obtained with D.W. for 5 min at $100^{\circ}C$. The average phenol contents were 77.11, 45.64, and 0.343 mg/g at $100^{\circ}C$ in water, $78^{\circ}C$ in ethanol, and $68^{\circ}C$ in hexane, respectively. The flavonoid contents were the highest in the materials extracted with D.W., and were increased with increasing temperature, regardless of the extraction solvents, whether water (green), polar organic ethanol, or nonpolar organic hexane. In the ethanol extract, the flavonoid contents are increased gradually from 5.66 mg/g to 7.73 mg/g. The total flavonoid contents were proportional to the concentrations of the water extracts, ranging from 4.14 mg/g to 48.89 mg/g. The antioxidative activities of the water-extracted compounds are generally increased with increasing temperature from 42.5% to 85.5%. Those of the hexane extracts are increased slowly from 3.79% to 8.8%, while those of ethanol extracts are increased from 29.8% to 47.4%. Conclusion: The extraction yields were dependent upon solvents for extraction as well as extraction time and the temperature. The optimal extraction time was 5 min and the extraction yields were increased with increasing temperature excepted hexane. Of the three tested extraction solvents, the greenest solvent of water shows excellent results, suggesting that water is among the most effective solvents for natural sample extractions for general medicinal, pharmaceutical, and food applications.

• 한국재료학회지
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• 제33권7호
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• pp.315-322
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• 2023

In the present work, we address the new route for the green synthesis of manganese dioxide (MnO₂) by an innovative method named the solution plasma process (SPP). The reaction mechanism of both colloidal and nanostructured MnO₂ was investigated. Firstly, colloidal MnO₂ was synthesized by plasma discharging in KMnO₄ aqueous solution without any additives such as reducing agents, acids, or base chemicals. As a function of the discharge time, the purple color solution of MnO₄^- (oxidation state +7) was changed to the brown color of MnO₂ (oxidation state +4) and then light yellow of Mn²⁺ (oxidation state +2). Based on the UV-vis analysis we found the optimal discharging time for the synthesis of stable colloidal MnO₂ and also reaction mechanism was verified by optical emission spectroscopy (OES) analysis. Secondly, MnO₂ nanoparticles were synthesized by SPP with a small amount of reducing sugar. The precipitation of brown color was observed after 8 min of plasma discharge and then completely separated into colorless solution and precipitation. It was confirmed layered type of nanoporous birnessite-MnO₂ by X-ray powder diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), and electron microscopes. The most important merits of this approach are environmentally friendly process within a short time compared to the conventional method. Moreover, the morphology and the microstructure could be controllable by discharge conditions for the appropriate potential applications, such as secondary batteries, supercapacitors, adsorbents, and catalysts.

• 아시안잔디학회지
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• 제19권2호
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• pp.103-113
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• 2005

본 연구는 한국잔디 및 한지형 잔디로 조성되어 있는 경기장의 이용 효율을 높이기 위해 잔디의 초봄 그린업(green up) 촉진 기술을 개발하고자 하였다. 실험기간은 2000년과 2001년 2월부터 4월까지 광엽형 한국잔디 및 한지형 잔디로 조성된 건국대 포장에서 실험하였다. 한국잔디의 초봄 그린업 촉진을 위해 대조구, 비닐, 검정 차광망, 녹색 차광망, 검정 차광망+비닐, 녹색 차광망+비닐, 비닐+검정 차광망, 비닐+녹색 차광망 등과 낮은 잔디깎기 높이 및 잔디 태우기를 처리하였다. 피복 시기에 관한 실험은 한국잔디 및 한지형 잔디에 장수 비닐(두께 0.06mm)을 2월 22일, 2월 28일, 3월 7일, 3월 14일 등 시기를 달리하여 피복하였다. 또한 한지형 잔디의 경우 무공비닐과 유공비닐이 초봄 그린업에 미치는 영향을 구명하고자 하였다. 실험구의 크기는 $2\times$2m이며 3반복 완전임의 배치로 배치하였다. 실험 결과를 요약하면 다음과 같다. 1. 한국잔디의 초봄 그린업은 비닐, 녹색 차광망+비닐 및 비닐+녹색 차광망 처리구가 다른 처리구에 비해 그린업이 촉진되었다. 비닐피복 시기에 따른 한국잔디의 그린업은 2월 22일 처리구가 다른 처리구에 비하여 빨랐다. 그러나 비닐피복 약 50일 후에는 피복시기에 상관없이 양호한 진녹색을 나타내었다. 또한 그린업 시기는 피복시기가 빠를수록 그린업이 촉진되는 경향이었다. 2. 낮은 잔디깎기(1.5$\sim$2cm)와 잔디 태우기 방법도 한국잔디의 그린업을 대조구보다 5 $\sim$ 7일정도 촉진하였다. 3. 한지형 잔디의 초봄 그린업은 무공비닐 피복 처리구가 대조구보다 2$\sim$3주 빨랐다. 비닐 종류에 따른 그린업은 무공비닐 처리구가 대조구 및 유공비닐 처리구보다 5$\sim$7일정도 촉진하는 것으로 나타났다. 또한 피복시기에 따른 한지형 잔디의 그린업은 피복시기가 빠를수록 그린업은 촉진되었으나 3월 8일과 3월 15일 피복처리구의 그린업이 가장 효과적이었다. 한국잔디 및 한지형 잔디의 비닐 피복으로 인한 초봄 그린업 촉진시 유의할 점은 충분한 수분 유지를 위해 비닐 피복전에 관수를 하거나 비온 후에 비닐 피복하는 것이 좋으며, 비닐 제거시 잔디의 일소현상의 피해를 줄이기 위해 흐린날 비닐을 제거하는 것이 좋을 것으로 판단되었다.