• Title/Summary/Keyword: Radiation efficiency

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Effect of Coating Technique on the Characteristics of ZnS(Ag) Scintillation Composite for Alpha-ray Detection (알파선 측정용 ZnS(Ag) 섬광 복합체의 특성에 있어 도포방법이 미치는 영향)

  • Jung, Yeon-Hee;Park, So-Jin;Seo, Bum-Kyoung;Lee, Kune Woo;Han, Myeong-Jin
    • Applied Chemistry for Engineering
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    • v.17 no.6
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    • pp.604-608
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    • 2006
  • Polymer composites for measuring the radioactive contamination are prepared by coating ZnS(Ag) powders as a scintillator on polysulfone base layer. The composites consist of the active layer for a scintillation reaction with radioactive wastes and the transparent support layer for transmittance of light photons emitted by scintillation in the active layer. The binding of the active layer, including ZnS(Ag), on the support layer is proceeded via coating with polysulfone as a binder, without any extra adhesive. The coating was obtained by either casting via a Doctor Blade as applicator or screen printing. The prepared composites feature a monolithic structure, resulting in the complete adhesion between two layers. The composite prepared by the casting technique using an applicator holds a good detection efficiency in measuring the alpha radionuclide, but its structure becomes fragile because of warping in morphology. On the contrary, the composite prepared by the screen printing shows a good detection capacity as well as a good stability in a mechanical shape.

Evaluation of Photochemical Reflectance Index (PRI) Response to Soybean Drought stress under Climate Change Conditions (기후변화 조건에서 콩 한발스트레스에 대한 광화학 반사 지수 반응 평가)

  • Sang, Wan-Gyu;Kim, Jun-Hwan;Shin, Pyeong;Baek, Jae-Kyeong;Lee, Yun-Ho;Cho, Jung-Il;Seo, Myung-Chul
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.21 no.4
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    • pp.261-268
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    • 2019
  • Climate change and drought stress are having profound impacts on crop growth and development by altering crop physiological processes including photosynthetic activity. But finding a rapid, efficient, and non-destructive method for estimating environmental stress responses in the leaf and canopy is still a difficult issue for remote sensing research. We compared the relationships between photochemical reflectance index(PRI) and various optical and experimental indices on soybean drought stress under climate change conditions. Canopy photosynthesis trait, biomass change, chlorophyll fluorescence(Fv/Fm), stomatal conductance showed significant correlations with midday PRI value across the drought stress period under various climate conditions. In high temperature treatment, PRI were more sensitive to enhanced drought stress, demonstrating the negative effect of the high temperature on the drought stress. But high CO2 concentration alleviated the midday depression of both photosynthesis and PRI. Although air temperature and CO2 concentration could affect PRI interpretation and assessment of canopy radiation use efficiency(RUE), PRI was significantly correlated with canopy RUE both under climate change and drought stress conditions, indicating the applicability of PRI for tracking the drought stress responses in soybean. However, it is necessary to develop an integrated model for stress diagnosis using PRI at canopy level by minimizing the influence of physical and physiological factors on PRI and incorporating the effects of other vegetation indices.

Numerical Analysis on Heat Gain of Liquid from Ambient Air with Various Fin Heights and Pitches of Fin-and-Tube Heat Exchanger in Hybrid Solar Collector (핀-튜브 열교환 구조를 갖는 복합집열기에서 핀 높이 및 간격에 따른 공기열 이용 액체 가열 성능에 관한 수치해석 연구)

  • Choi, Hwi-Ung;Fatkhur, Rokhman;Lyu, Nam-Jin;Yoon, Jung-In;Son, Chang-Hyo;Choi, Kwang-Hwan
    • Journal of the Korean Solar Energy Society
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    • v.36 no.3
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    • pp.53-61
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    • 2016
  • Solar assisted heat pump system uses solar thermal energy as a heat source of evaporator of heat pump. So, COP can be enhanced as well as collector efficiency. For improving performance of this system, some research about hybrid solar collector that has fin-and-tube heat exchanger has been conducted. This collector can get a thermal energy from ambient air for liquid heating, so heated liquid can be used as a heat source of evaporator in heat pump even the solar radiation is not enough. In this study, numerical analysis was conducted for confirming heat gain of liquid according to fin height and pitch of fin-and-tube heat exchanger in collector. As a result, higher heat gain was obtained on lower fin height and narrow fin pitch, but the pressure drop also increased with increment of heat gain. Thus the JF factor considering both heat transfer enhancement and pressure drop was investigated and the maximum value was shown when the fin height and pitch were 40mm and 45mm. So it is considered that this installation condition has a highest heat transfer improvement when comparing with pressure drop. However heat gain of liquid at this condition was less than the other installation conditions of fin pitch on same height. Then, after establishing a proper minimum heat gain of liquid, actual production and experiment of collector will be conducted with fin height and pitch showing maximum JF factor and satisfying selected minimum heat gain of liquid on the basis of results of this study.

A Study on the Enhancement of Isolation of the MIMO Antenna for LTE/DCS1800/USPCS1900 Handset (LTE/DCS1800/USPCS1900 단말기용 MIMO 안테나의 격리도 개선에 관한 연구)

  • Cho, Dong-Ki;Son, Ho-Cheol;Lee, Jin-Woo;Lee, Sang-Woon;Lee, Mun-Soo
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.47 no.10
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    • pp.80-85
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    • 2010
  • In this paper, a MIMO antenna is proposed for LTE/DCSl800/USPCSl900 handset applications. The proposed antenna is based on the IFA and its wide bandwidth is obtained by using a stagger tuning technique. To improve the isolation, a suspended line is connected to the shorting points in two antennas, and capacitors and inductors are added to the connected suspended line. Two identical antennas of which dimension is 2.8cc($40{\times}10{\times}7mm$) are mounted on the two end lines of the system ground plane($40{\times}60mm$). Analysis of the antenna performance and optimization is performed using CST Microwave Studio. The bandwidths are satisfied for LTE band class 13(746-787MHz), class 14(758-798MHz) and DCSl800/USPCSl900 band (1710-1990MHz). The isolations between two antennas are about -12dB for LTE band and -10dB for DCSl800/USPCSl900 band. And the radiation efficiency of each antenna is about for LTE band 33% and 45% for DCSl800/USPCSl900 band respectively.

-1 Mode Circularly Polarized Patch Antenna Using CRLH Transmission Line (CRLH 전송 선로 구조를 이용한 -1 모드 원형 편파 패치 안테나)

  • Ko, Seung-Tae;Park, Byung-Chul;Lee, Jeong-Hae
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.23 no.9
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    • pp.1034-1041
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    • 2012
  • In this paper, a compact circularly polarized metamaterial patch antenna using the -1 mode that is induced by the composit right-left handed(CRLH) transmission line is proposed. Basically, since the -1 mode is the same properties with the +1 mode of the conventional patch antenna, the circular polarization(CP) is realized. If two orthogonal -1 modes are excited with $90^{\circ}$ phase difference, the CP property can be obtained. In order to obtain two orthogonal modes and $90^{\circ}$ phase difference, 4 mushroom structures having the shape of triangle are employed and the inter-digital gaps are optimized, respectively. The fabricated antenna is based on RT/duroid5880 substrate and the total area of the 4 mushrooms is $0.161{\lambda}_0{\times}0.161{\lambda}_0$. It is confirmed that the center frequency of the proposed antenna is measured as 2.845 GHz and it operates from 2.830 GHz to 2.850 GHz. In addition, the antenna maintains the CP property from 2.842 GHz to 2.847 GHz at the peak gain and the measured radiation efficiency is 46 %.

Design and Implementation of Plannar S-DMB Antenna with Omni-Directional Radiation Pattern Using Metamaterial Technique (메타 물질 기법을 이용한 전방향성 복사 패턴을 갖는 평면형 S-DMB 안테나 설계 및 구현)

  • An, Chan-Kyu;Yu, Ju-Bong;Jeon, Jun-Ho;Kim, Woo-Chan;Yang, Woon-Geun;Nah, Byung-Ku;Lee, Jae-Ho
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.21 no.12
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    • pp.1343-1351
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    • 2010
  • In this paper, a novel patch antenna based on the metamaterial CRLH(Composite Right- and Left-Handed) structure is designed, implemented, and measured. Contrary to the standard microstrip patch's fundamental resonance mode of half-wavelength or its positive multiple, the proposed antenna shows the in-phase electric field over the entire antenna. The proposed antenna has a desired omni-directional field pattern which is typical characteristic of $\lambda/4$ monopole antenna, and also shows the merit of low profile. HFSS(High Frequency Structure Simulator) of Ansoft which is based on the FEM(Finite Element Method) is used to simulate the proposed antenna. FR-4 substrate of thickness 1.6 mm and relative permitivity 4.4 is used for the proposed antenna implementation. The implemented antenna showed VSWR (Voltage Standarding Wave Ratio)$\leq$2 for the frequency band from 2.63 GHz to 2.655 GHz which is used for S-DMB (Satellite-Digital Multimedia Broadcasting) service. And measured peak gain and efficiency are 2.65 dBi and 81.14 %, respectively.

Design of Compact and Broadband Quasi-Yagi Antenna Using Balance Analysis of the Balun (발룬의 평형도 해석을 이용한 소형화된 광대역 Quasi-Yagi 안테나 설계)

  • Woo, Dong Sik;Kim, In-Bok;Kim, Young-Gon;Kim, Kang Wook
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.24 no.1
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    • pp.27-35
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    • 2013
  • In this paper, a compact, broadband quasi-Yagi antenna utilizing balance analysis of the ultra-wideband microstrip-to-coplanar stripline(MS-to-CPS) balun is proposed. The antenna size was reduced by removing the reflector on bottom layer and ground plane is used as a reflector. A planar balun that transforms from microstrip(MS) to balanced coplanar stripline(CPS) is characterized in the amplitude and phase imbalances at CPS output ports are investigated and discussed. As compared with the conventional balun, the proposed MS-to-CPS balun demonstrated very wideband performance from 7 to over 20 GHz. From the simulation study, amplitude and phase imbalances are within 1 dB and ${\pm}5^{\circ}$, respectively. The implemented antenna provides very wide bandwidth from 6.9 to 15.1 GHz(74.5 %). The gain of the antenna is from 3.7 to 5.5 dBi, the front-to-back ratio is more than 10 dB, and the nominal radiation efficiency is about 94 %.

Growth Characteristics and Physiological Adaptation of Pinus densiflora Seedling in the Canopy Gap (소나무 묘목(苗木)의 Gap내 생장(生長) 및 생리적(生理的) 적응과정(適應過程))

  • Jin, Yonghuan;Lee, Don Koo
    • Journal of Korean Society of Forest Science
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    • v.89 no.3
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    • pp.452-460
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    • 2000
  • This study was to investigate the growth characteristics, physiological adaptation of Pinus densiflora(Japanese Red Pine) seedlings at the artificial canopy gap in the Quercus acutissima plantation and to analyze its natural regeneration mechanism. Photosynthetic and transpiration rates were analyzed by different levels of photosynthetically active radiation and by seedling growth. Comparing to seedlings at the open area, those at the canopy gap showed more growth in height than in diameter with different levels of light quality and low light intensity, and the increase rate of dry weight was higher in the aboveground than in the underground, maintaining relatively high T/R rate. The C/F(the ratio of non-photosynthetic organs to photosynthetic organs in dry weight) of the aboveground at the canopy gap was higher than that at the open area by 0.1~0.2, while light saturation and light compensation points at the canopy gap were lower than that at the open area by $300{\mu}mol\;m^{-2}s^{-1}$ and 40%, respectively. The seedlings appeared to have shade tolerance to a certain extent at the young growth stage despite Pinus densiflora is typically classified shade-intolerant species. With light intensity lower than $400{\sim}450{\mu}mol\;m^{-2}s^{-1}$, photosynthetic rate and water use efficiency relatively increased by effective use of light energy.

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Cavity-Backed Slot Array Antenna for a Repeater System of a Satellite Digital Multimedia Broadcasting (위성 DMB 중계기용 Cavity-Backed슬롯 배열 안테나)

  • Jung Hee-Chul;Lee Hak-Yong;Jung Byungwoon;Kang Gi-Cho;Park Myun-Joo;Lee Byungje
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.16 no.4 s.95
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    • pp.366-372
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    • 2005
  • This paper presents analysis of a slot array antenna having a low side lobe level and high front-to-back ratio for a repeater system of a satellite DMB(Digital Multimedia Broadcasting) service. Antennas for this repeater system require a high gain and enough isolation to reduce interferences between signals in system. Therefore, it is necessary to suppress a side lobe level and to increase front-to-back ratio. Unlike a structure 134 by lossy microstrip lines, in this work a single cavity-backed slot antenna array using a single waveguide feed is proposed to obtain the reliability for high power handling and high radiation efficiency. The side lobe level and front-to-back ratio are enhanced with tapered array technique and an optimized vertical reflector. The measured side lobe levels in H- and E-plane are under $-33.24\;\cal{dB}$ and $-35.78\;\cal{dB}$, respectively. The front-to-back ratio over $37.84\;\cal{dB}$, and the peak gain of over $17\;\cal{dBi}$ are measured.

Generation of Chemically Active Species in Hybrid Gas-Liquid Discharges (기체-액체 혼합 방전에 의한 화학적 활성종 생성 특성)

  • Chung, Jae-Woo;Locke, Bruce R.
    • Journal of Korean Society of Environmental Engineers
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    • v.29 no.5
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    • pp.556-563
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    • 2007
  • We carried out a laboratory scale experiment about the characteristics of chemically active species produced in hybrid gas-liquid discharges. The electrode configuration which had high voltage electrode in the gas phase and ground electrode in the liquid was utilized while high voltage electrode has been typically positioned in the liquid in other studies. Our electrode was configured in such a way as to increase the energy efficiency of chemical reactions by creating a higher electrical field strength and a narrower pulse width than the typical electrode configuration. The highest ozone concentration was obtained at 45 kV which was the medium value in operating voltages. The decrease of solution conductivity increased the resistance of liquid phase and the electric field strength through the gas phase, so ozone gene-ration rate was enhanced. The increase of voltage promoted the production rate of hydrogen peroxide by increasing the electric field strength. In a lower voltage, the increase of solution conductivity increased the degradation rate of $H_2O_2$, so the $H_2O_2$ generation rate decreased. On the other hand, the effects of UV radiation, shock waves etc. increased the $H_2O_2$ generation rate as the solution conductivity increased. A higher rate of $H_2O_2$ generation can be achieved by mixing argon to oxygen which generates a stronger and more stable discharges.