• The Korean Journal of Ecology
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• 제25권4호
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• pp.261-265
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• 2002

In order to elucidate the characteristics of standing crop biomass, production and nutrient content of dead bole in mature ecosystem, we surveyed the dynamics of decaying bole of old-aged deciduous forest in 1993 and 2002 in Kwangnung Experimetal Forest Station. In addition, we and estimated annual bole production, water content, wood density and nutrient content and compared the results with that of temperate ecosystem. Total dead wood biomass was estimated to be 5.6ton/ha in 1993 and 17.6 ton/ha in 2002. Standing dead tree accounted for a total of 1.1 ton/ha in 1993 and 4.8 ton/ha in 2002, which was 20% and 27$\%$ of the sum of dead bole mass in 1993 and 2002, respectively. Annual production of bole biomass was 1.3 ton/ha/yr. These values fall into the low range of dead wood biomass for the mature temperate ecosystems. Tree species composing standing bole was mainly Quercus and Carpinus trees. This bole species composition resembles alive species composition of this forest. Water content of bole increased as positive logarithmically, but wood density of bole decreased as negative exponentially along with the progress of decay. N, P, Ca and Mg concentrations in decaying boles generally increased with decay, except for K. Annual nutrient input via dead bole is 1.6 kg/ha/yr for N, 0.04 kg/ha/yr for P, 1.0 kg/ha/yr for K, 1.7 kg/ha/yr for Ca and 0.3 kg/ha/yr for Mg, respectively.

• 한국광학회지
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• 제3권3호
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• pp.183-190
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• 1992

$Al_x/Ga_{1-x}$ /As/AlAs GaAs 계로 이루어진 비대칭 이중 양자우물 구조의 광학적 특성을 photoluminescence, photoluminescence excitation, time-resolved photoluminescence를 통하여 조사하였다. 양자장벽 AlAs의 두께에 따른 특성 변화를 조사하기 위하여 두께를 15$\AA$., 150$\AA$로 제작하였다. 양자장벽이 15$\AA$인 경우 매우 빠른 전자의 관통 현상을 보여 주었으며, 이로 인해 $Al_x/Ga_{1-x}$As의 여기자 재결합에 해당하는 피크가 관찰되지 않았다. AlAs 양자장벽이 150$\AA$인 경우에는 $Al_x/Ga_{1-x}$As양자우물에서 여기자 재결합에 의한 피크가 50ps 이하로 빠른 decay시간을 보여 주었으며 이것은 양자장벽과의 $\Gamma$-X전이에 의한 것으로 사료되었다. GaAs양자우물에서의 luminescence decay는 두 시료 모두 1ns정도 이었으나, 15$\AA$인 경우에는 약 100ps의 rise시간이 존재하였으며 이것은 정공의 관통에 의한 시간으로 판명되었다.

• Journal of Advanced Marine Engineering and Technology
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• 제40권3호
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• pp.235-239
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• 2016

복원력을 잃고 선박이 전복될 때의 횡경사 속도는 선체가 사고 상황에 대해 외부로 표현하는 고유 응답의 하나가 된다. 자유 횡요 시 횡운동은 횡관성모멘트와 GM 및 횡감쇠계수와 같은 선체계수에 의해 나타낼 수 있으나 선체가 저속으로 진행되는 전복의 경우에는 각가속 성분이 특히 작아지므로 특성 해석은 보다 용이해진다. 따라서 빠르게 진행되는 전복사고에 비해 저속 전복 사고는 선체 거동의 예측이 적절히 가능할 뿐 아니라 선박구조에 필요한 시간의 확보가 수월해지므로 선박의 구조전략 측면에서 저속 전복사고는 별도로 분류하여 대응할 필요가 있다. 이를 위해 본 연구에서는 선체의 자유 횡운동에 대한 선형미분방정식을 토대로 저속 전복 시 선체계수들이 전복속도에 미치는 영향을 관련된 함수들로 나타내었으며 횡운동 진폭감쇠비를 기준으로 횡감쇠계수 크기와 선체 특성을 분석하였다. 또한, 여기에서의 수식적 관계를 실제 선박의 제원에 적용함으로써 얻어지는 결과들을 통해 제시된 저속 전복 선박의 일반적 특성이 도시적으로 설명될 수 있음을 확인하였다.

• 한국환경과학회지
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• 제24권10호
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• pp.1273-1283
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• 2015

In present study, the temporal characteristics of nine selected volatile organic compounds (VOCs), including four alcohol, 2 aldehyde, and 3 ketone compounds, in high-stories urban apartments over a 2-y period were investigated. The indoor VOC concentrations had generally a decreasing trend over the 2-y follow-up period. For examples, the 2E1H indoor concentration decreased from $10.8{\mu}g/m^3$ for the first two months to $5.1{\mu}g/m^3$ for the last two months. In addition, the DCA and ACT indoor concentrations decreased from 5.0 and $14{\mu}g/m^3$ for the first two months to 2.2 and $6.4{\mu}g/m^3$, respectively, for the last two months. The indoor-to outdoor concentration ratios over the 2-y period were much greater than 1, indicating that indoor VOC concentrations were higher than the outdoor VOC concentrations. Similar to those of the individual VOCs, the indoor-to-outdoor concentration ratios of all three VOC groups were higher than 1 over the 2-y follow-up period, suggesting higher indoor concentrations of the three VOC groups than outdoor concentrations. In consistence with the results of VOC indoor concentrations, the VOC emission rates decreased gradually as time passed, due to the decreased VOC emission strengths of indoor sources. Finally, there was an initial sharp decrease in the indoor VOC concentrations followed by a slower decrease, indicating a multi-exponential decay model for the target VOCs, which was demonstrated by comparison of the residuals and the adjusted coefficient of determination associated with the one and two-exponential fits of each data set.

• 식물병연구
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• 제8권2호
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• pp.107-112
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• 2002

수확 후 피해를 주는 Penicillium속의 병원체를 분리 동정하기 위하여 여러 특성을 조사하였다. 저장 중 배에서 분리한 198균주는 상처 접종과 무상 접종에서 병반을 형성하여 병원성이 있었으며, 균총 크기와 형태, 색, 배지뒷면 색소와 포자형태 등의 특성에 따라 15개 그룹으로 나눌 수 있었다. 분리한 균주들은 배양·형태적·생리적 특성에 따라 P. expansum, P. solitum, P. crustosum 등 3종으로 동정되었다. 분리된 균주들의 병원성 검정 결과 저온에서 상처접종이 무상접종 보다 병원성이 강하게 나타났으며 P. expansum이 저장 배 과실에 대해 가장 병원성이 강하였고, P. solitum과 P. crustosum은 약한 편이었다.

• Journal of the Korean Wood Science and Technology
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• 제41권6호
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• pp.576-582
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• 2013

구리계 보존제 처리에 대한 기초 자료를 얻기 위하여 Douglas fir 변재와 ACQ-2 보존제를 사용하여 목재 내 침투 및 부후 특성을 조사하였다. 약제의 주입이 어려운 Douglas fir 수종에 대하여 약제의 주입이 잘된 곳과 안된 곳의 시료를 채취하여 약제 이동을 방해하는 인자를 구명하고자 방사조직 높이, 방사조직 밀도, 가도관의 길이를 실체현미경, 광학현미경, 그리고 전자현미경으로 측정 및 관찰하였다. 그 결과 방사조직의 높이와 밀도 그리고 가도관길이는 약제의 주입이 용이했던 부분과 주입이 안된 부분에서 차이를 보이지 않았지만, 목재 구성 세포들의 벽공에서는 차이가 나타났음을 전자현미경을 통해 관찰할 수 있었다. 약제의 주입이 안된 곳에서는 폐색된 벽공이 많이 관찰되었다. 그리고 여러 농도의 ACQ로 처리한 목재 시편을 갈색부후균으로 부후시킨 후 광학 현미경으로 부후 특성을 관찰하였다. 그 결과 무처리 시편의 가도관, 방사조직, 수지구 등의 조직이 부후되어 파괴된 것을 볼 수 있었으며, 약제 처리 농도가 낮으면 부후가 진행되므로 일정 농도 이상으로 처리해야함을 알 수 있었다.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2005년도 International Meeting on Information Displayvol.II
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• pp.1262-1265
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• 2005

The picture quality of a plasma display panel is very sensitive to the phosphor characteristics such as decay time, surface state, and even longevity of phosphor material in itself. In this work, material characteristics of $Zn_2SiO_4:Mn$, $Y_2O_3-coated$ $Zn_2SiO_4:Mn$, and $YBO_3:Tb$, which are dominant in commercial application, were examined for investigating the aging characteristics of green PDP phosphors. It was found that $Y_2O_3-coated$ $Zn_2SiO_4:Mn$ are easily degraded at high temperature. However, all the samples were very weak after vacuum annealing. The luminescence intensity was decreased by order of one magnitude.

• 전자공학회논문지D
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• 제35D권4호
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• pp.53-60
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• 1998

The purpose of this paper is to meausre the electrophotographic characteristics of double-layered organic photoreceptor and to evaluate an application for the laser beam printer drum. The characte carrier generation layer(CGL) of double-layered photoreceptor was fabricated with .tau.-H$_{2}$Pc which has high photosensitivity in the near-infrareed region(thickness is about 0.3.mu.m), and Oxadiazole derivative was chosen as a charge carrier transport layer(CTL) because of its high hole mobility. To observe the electrophotographic characteristics of the photoreceptor, we measured the charge acceptance, dark-decay ratio, residual potential after light irradiation. From the result of this study, proper thickness of CTL was about 10.mu.m. Also it's realized that electrophotographic characteristics of the photoreceptor were depend on the thickness of the CTL and the initial surface potential.

• Nuclear Engineering and Technology
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• 제39권2호
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• pp.143-148
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• 2007

Spent nuclear fuel generated at nuclear power plants must be safely stored during interim storage periods. A dry storage cask to safely store the spent nuclear fuel should be able to adequately emit the decay heat from the spent nuclear fuel. Therefore, heat removal tests using a half scale dry storage cask have been performed to estimate the heat transfer characteristics of a dry storage cask under normal, off-normal, and accident conditions. In the normal condition, the heat transfer rate to an ambient atmosphere by convective air through a passive heat removal system reached 83%. Accordingly, the passive heat removal system is designed well and works adequately. In the off-normal condition, the influence of a half blockage in the inlet on the temperature appears minimal. In the accident condition, the temperature rose for 12 hours after the accident, but the temperature rise steadied after 36 hours.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 C
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• pp.1682-1684
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• 2004

In this study, the surface properties of PET film were analyzed after plasma surface treatment. After plasma treatment of surface roughness and XPS were evaluated to analyze the chemical property, while the surface potential decay and surface resistivity was measured to analyze the electrical characteristic. When plasma discharge treatment was conducted for less than 10 minutes, the electrical insulating property was found to be improved through evaporation of low molecular weight materials and cleaning of surface. However, when the treatment was conducted for more than 10 minutes, the insulating property was decreased due to excessive discharge energy. Analysis of chemical characteristics showed that 10-minute treatment resulted in increase of C-O and O=C-O. However, when treated for more than 10 minutes, they were relatively decreased.