• 한국토양비료학회지
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• 제48권6호
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• pp.705-711
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• 2015

Management of soil water and fertilization is known to primarily affect physiological properties and yield in plant. The effect of soil water potential and nitrogen application on characteristics of photosynthesis and chlorophyll fluorescence in Schisandra chinensis Baillon was investigated on a sandy loam soil. Net photosyntheis rate and transpiration rate increased as a photon flux density and was highest at -50kPa of soil water potential. Light compensation point ($1.5{\mu}molm^{-1}s^{-1}$) and dark respiration ($0.13{\mu}molCO_2m^{-1}s^{-1}$) was lowest at -50 kPa but maximum photosynthesis rate ($13.10{\mu}molCO_2m^{-1}s^{-1}$) and net apparent quantum yield ($0.083{\mu}molCO_2m^{-1}s^{-1}$) was highest at -50 kPa. As results of chlorophyll fluorescence by OJIP analysis, maximum quantum yield (Fv/Fm) of photosystem II (PSII) and PIabs was higher in treatments of -50 kPa and -60 kPa respectively, which reflects the relative reduction state of PSII. But the relative activities per reaction center such as ABS/RC and DIo/RC were low with decreasing soil water potential. Net photosyntheis rate and transpiration rate were highest at treatment of soil testing 1.0 times ($92kgha^{-1}$). Application of nitrogen resulted in high Fv/Fm, $PI_{abs}$ and low ABS/RC, DIo/RC. This result implies that -50 kPa of soil water potential and nitrogen fertilizer may improve the efficiency of photosynthesis through controlling a photosystem in Schisandra chinensis Baillon.

• Nuclear Engineering and Technology
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• 제52권3호
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• pp.633-646
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• 2020

Imaging and scattering techniques using thermal neutrons allow to analyze complex specimens in scientific and industrial researches. Owing to this advantage, there have been a considerable demand for neutron facilities in the industrial sector. Among neutron sources, an accelerator driven compact neutron source is the only one that can satisfy the various requirements-construction budget, facility size, and required neutron flux-of industrial applications. In this paper, a target, moderator, and reflector (TMR) system for low-energy proton-accelerator driven compact thermal neutron source was designed via Monte Carlo simulations. For 10-30 MeV proton beams, the optimal conditions of the beryllium target were determined by considering the neutron yield and the blistering of the target. For a non-borated polyethylene moderator, the neutronic properties were verified based on its thickness. For a reflector, three candidates-light water, beryllium, and graphite-were considered as reflector materials, and the optimal conditions were identified. The results verified that the neutronic intensity varied in the order beryllium > light water > graphite, the compacter size in the order light water < beryllium < graphite and the shorter emission time in the order graphite < light water < beryllium. The performance of the designed TMR system was compared with that of existing facilities and were laid between performance of existing facilities.

• Nuclear Engineering and Technology
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• 제47권4호
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• pp.472-478
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• 2015

The patient dose incurred from diagnostic procedures during advanced radiotherapy has become an important issue. Many researchers in medical physics are using computational simulations to calculate complex parameters in experiments. However, extended computation times make it difficult for personal computers to run the conventional Monte Carlo method to simulate radiological images with high-flux photons such as images produced by computed tomography (CT). To minimize the computation time without degrading imaging quality, we applied a deterministic adaptation to the Monte Carlo calculation and verified its effectiveness by simulating CT image reconstruction for an image evaluation phantom (Catphan; Phantom Laboratory, New York NY, USA) and a human-like voxel phantom (KTMAN-2) (Los Alamos National Laboratory, Los Alamos, NM, USA). For the deterministic adaptation, the relationship between iteration numbers and the simulations was estimated and the option to simulate scattered radiation was evaluated. The processing times of simulations using the adaptive method were at least 500 times faster than those using a conventional statistical process. In addition, compared with the conventional statistical method, the adaptive method provided images that were more similar to the experimental images, which proved that the adaptive method was highly effective for a simulation that requires a large number of iterations-assuming no radiation scattering in the vicinity of detectors minimized artifacts in the reconstructed image.

• Journal of Magnetics
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• 제21권2호
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• pp.183-186
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• 2016

In this study, we report on an investigation of proton radiation resistance of 410 martensitic stainless steels under 3 MeV proton with the doses ranging from $1.0{\times}10^{15}$ to $1.0{\times}10^{17}p/cm^2$ at the temperature 623 K. Vibrating sample magnetometer (VSM) and X-ray diffractometer (XRD) were used to study the variation of magnetic properties and structural damages by virtue of proton irradiation, respectively. VSM and XRD analysis revealed that the 410 martensitic stainless steels showed proton radiation resistance up to $10^{17}p/cm^2$. Proton energy degradation and flux attenuations in 410 stainless steels as a function of penetration depth were calculated by using Stopping and Range of Ions in Matter (SRIM) code. It suggested that the 410 stainless steels have the radiation resistance up to $5.2{\times}10^{-3}$ dpa which corresponds to neutron irradiation of $3.5{\times}10^{18}n/cm^2$. These results could be used to predict the maintenance period of SUS410 stainless steels in fission power plants.

• Nuclear Engineering and Technology
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• 제52권1호
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• pp.37-50
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• 2020

A passive containment cooling system (PCCS) has been developed as advanced safety feature for innovative power reactor (iPOWER). Passive systems are inherently less stable than active systems and the PCCS encountered the flashing-induced instability previously identified. The objective of this study is to develop stability maps for flashing-induced instability using MARS (Multi-dimensional Analysis of Reactor Safety) code. Firstly, we conducted a series of sensitivity analysis to see the effects of time step size, nodalization, and alternative MARS user options on the onset of flashing-induced instability. The riser nodalization strongly affects the prediction of flashing in a long riser of the PCCS, while time step size and alternative user options do not. Based on the sensitivity analysis, a standard input and an analysis methodology were set up to develop the stability maps of PCCS. We found out that the calculated equilibrium quality at the exit of the riser as a stability boundary above 5 kW/㎡ was approximately 1.2%, which was in good agreement with Furuya's results. However, in case of a very low heat flux condition, the onset of instability occurred at the lower equilibrium quality. In addition, it was confirmed that inlet throttling reduces the unstable region.

• 한국산학기술학회논문지
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• 제21권11호
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• pp.788-794
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• 2020

본 연구는 전자산업 해당공정 작업자가 노출될 수 있는 천식유발물질인 Abietic acid가 플라스마 처리로 인해 제거되는 효과를 확인하고자 2019년 1월부터 11월 까지 측정 분석하였다. 솔더 와이어와 천연 Rosin을 사용을 사용하여 250℃, 300℃, 350℃ 온도에서 발생하는 공기를 2ℓ/min 유속으로 10분간 에어샘플러로 유리섬유여과지로 포집하였다. 포집한 시료의 분석은 메틸알코올로 전처리 후 HPLC로 Abietic acid를 정량 분석하였다. 그 결과 천연 Rosin, 솔더 와이어에서 모두 Abietic acid의 발생을 확인하였으며, 열처리 온도가 상승함에 따라 모두 Abietic acid 발생량 또한 증가함을 확인하였다. 천연 Rosin과 솔더 와이어 중에 천연 Rosin에서 Abietic acid의 발생량이 더 많았다. 플라스마 처리 결과 천연 Rosin에서 약 92% 이상의 제거효율을 확인하였고, 솔더 와이어에서는 Abietic acid의 Peak가 검출되지 않아 100%의 제거효율을 확인하였다. 본 연구를 통해 솔더 와이어와 천연 Rosin에서 천식 유발물질인 Abietic acid가 발생하는 것을 확인 하였으며, 플라스마 처리로 Abietic acid가 제거되는 효과를 확인 할 수 있었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.342-343
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• 2013

AlSb is a promising material for optical devices, particularly for high-frequency and nonlinear-optical applications. And AlSb offers significant potential for devices such as quantum-well lasers, laser diodes, and heterojunction bipolar transistors. In this work we study molecular beam epitaxy (MBE) growth of an unstrained AISb film on a GaAs substrate and identify the real-time monitoring capabilities of in situ spectroscopic ellipsometry (SE). The samples were fabricated on semi-insulating (0 0 1) GaAs substrates using MBE system. A rotating sample stage ensured uniform film growth. The substrate was first heated to $620^{\circ}C$ under As2 to remove surface oxides. A GaAs buffer layer approximately 200 nm- thick was then grown at $580^{\circ}C$. During the temperature changing process from $580^{\circ}C$ to $530^{\circ}C$, As2 flux is maintained with the shutter for Ga being closed and the reflection high-energy electron diffraction (RHEED) pattern remaining at ($2{\times}4$). Upon reaching the preset temperature of $530^{\circ}C$, As shutter was promptly closed with Sb shutter open, resulting in the change of RHEED pattern from ($2{\times}4$) to ($1{\times}3$). This was followed by the growth of AlSb while using a rotating-compensator SE with a charge-coupled-device (CCD) detector to obtain real-time SE spectra from 0.74 to 6.48 eV. Fig. 1 shows the real time measured SE spectra of AlSb on GaAs in growth process. In the Fig. 1 (a), a change of ellipsometric parameter ${\Delta}$ is observed. The ${\Delta}$ is the parameter which contains thickness information of the sample, and it changes in a periodic from 0 to 180o with growth. The significant change of ${\Delta}$ at~0.4 min means that the growth of AlSb on GaAs has been started. Fig. 1b shows the changes of dielectric function with time over the range 0.74~6.48 eV. These changes mean phase transition from pseudodielectric function of GaAs to AlSb at~0.44 min. Fig. 2 shows the observed RHEED patterns in the growth process. The observed RHEED pattern of GaAs is ($2{\times}4$), and the pattern changes into ($1{\times}3$) with starting the growth of AlSb. This means that the RHEED pattern is in agreement with the result of SE measurements. These data show the importance and sensitivity of SE for real-time monitoring for materials growth by MBE. We performed the real-time monitoring of AlSb growth by using SE measurements, and it is good agreement with the results of RHEED pattern. This fact proves the importance and the sensitivity of SE technique for the real-time monitoring of film growth by using ellipsometry. We believe that these results will be useful in a number of contexts including more accurate optical properties for high speed device engineering.

• 한국약용작물학회지
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• 제28권1호
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• pp.1-8
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• 2020

Background: This study was conducted to investigate the effects of NaCl concentration on the photosynthetic parameters, chlorophyll fluorescence and growth characteristics of Crepidiastrum sonchifolium. Methods and Results: As treatments, we subjected C. sonchifolium plants to four different concentrations of NaCl (0, 50, 100 and 200 mM). We found that the photosynthetic parameters maximum photosynthesis rate (P_{N max}), net apparent quantum yield (Φ), maximum carboxylation rate (V_cmax), and maximum electron transport rate (J_max) were significantly reduced at an NaCl concentration greater than 100 mM. In contrast, there was an increase in water-use efficiency with increasing NaCl concentration, although in terms of growth performances, leaf dry weight, root dry weight, stem length, and total dry weight all decreased with increasing NaCl concentration. Furthermore, leakage of electrolytes, as a consequence of cell membrane damage, clearly increased in response to an increase in NaCl concentration. Analysis of the polyphasic elevation of chlorophyll a fluorescence transients (OKJIP) revealed marked decrease in flux ratios (Φ_PO, Ψ_O and Φ_EO) and the PI_abs, performance index in response to treatment with 200 mM NaCl, thereby reflectings the relatively reduced state of photosystem II. This increase in fluorescence could be due to a reduction in electron transport beyond Q^-_A. We thus found that the photosynthetic parameters, chlorophyll fluorescence and growth characteristics of C. sonchifolium significantly increased in response to treatment with 200 mM NaCl. Conclusions: Collectively, the findings of this study indicate that C. sonchifolium shows relatively low sensitivity to NaCl stress, although photosynthetic activity was markedly reduced in plants exposed to 200 mM NaCl.

• 한국해양학회지:바다
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• 제23권1호
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• pp.32-48
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• 2018

대기 중 메탄의 해양 흡수와 방출 메커니즘은 생지화학 순환이 갖는 복잡성과 해양-대기 경계면에서 지역 규모 혹은 기작 단위에서의 관측 연구 부족으로 잘 알려져 있지 못하다. 그러나 다양한 시 공간적 규모에서 탄소 수지와 순환을 조절하는 해양 메커니즘에 대한 완전한 이해 없이는, 해양의 탄소 변동과 전 지구적 지역적 기후 변화에 미치는 영향을 예측하기란 불가능하다. 표층해양 및 해양대기에서 용존 메탄의 탄소동위원소 조성에 대한 정밀한 연속 관측은 해양-대기 경계면에서의 유 출입 및 생산 소모 과정에 대한 추가적인 정보를 제공한다. 본 연구는 최근 급격히 발전한 광학기반 동위원소 분석 기기들을 개괄적으로 소개하고, 표층 양 내 용존 메탄과 해양대기 메탄의 탄소동위원소 실시간 연속 측정으로의 적용을 위해, 현재 이들 기기들의 기술 및 활용 현황을 논의한다. 이어 레이저 광원의 흡수분광기 중 하나로, 사용이 최근 급증하고 있는 광공동 링다운분광기(CRDS, Cavity Ring Down Spectroscopy)기반 동위원소 분석기기를 예시로 하여 연속 관측 시스템의 운용, 최적화 조건, 보정법을 제안하며, 기체 시료로부터 실시간 관측된 메탄 농도 및 메탄 탄소동위원소의 관측 예를 소개하고자 한다. 이러한 가능성 검토를 통해 향후 해양 환경에서의 실시간 메탄 탄소동위원소 분석 연구의 방향을 제안하고자 한다.

• 한국산림과학회지
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• 제106권3호
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• pp.288-299
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• 2017

이 연구는 건조스트레스가 수리취의 생리적 반응에 미치는 영향을 알아보고자 수행하였으며, 건조스트레스는 25일 간의 단수처리를 통해 유도하였다. 건조스트레스가 진행됨에 따라 새벽 녘 수분포텐셜(${\Psi}_{pd}$)과 정오의 수분포텐셜(${\Psi}_{mid}$)이 모두 감소하였으며, 수분불포화도(WSD)는 약 7배 증가하였다. 특히 일중 수분포텐셜차(${\Psi}_{pd}-{\Psi}_{mid}$)는 처리 후 10일까지 0.22~0.18 MPa 범위로 큰 차이를 나타냈으나 이후에는 차이가 크게 줄어드는 경향을 보였다. 수리취는 건조스트레스 처리 후 15일부터 기공전도도와 기공증산속도의 감소가 두드러졌고, 처리 20일 이후에는 최대광합성 속도와 순양자수율 역시 큰 폭으로 감소한 반면 수분이용효율은 반대의 경향을 보였다. 이것은 기공을 통한 $CO_2$와 수분의 조절이 원활하지 못해 광합성량의 감소가 일어난 것을 의미한다. JIP 분석을 통해 단수처리 15일 이후에 기능지수($PI_{ABS}$) 및 에너지전달 효율의 감소가 두드러진 것으로 나타났으며, 광계 2의 활성이 감소한 것을 보여준다. 엽의 원형질 분리시 삼투포텐셜 ${\Psi}_o{^{tlp}}$은 -0.4 MPa, 최대포수시의 삼투포텐셜 ${\Psi}_o{^{sat}}$은 -0.35 MPa의 삼투적 적응 반응을 나타냈으며, 최대탄성계수($E_{max}$)의 탄성적 적응은 9.4 MPa로 나타나 수리취는 건조스트레스에 따라 삼투적 적응과 탄성적 적응이 모두 나타나는 것을 알 수 있었다. Vo/DW, Vt/DW와 같은 수분특성인자는 건조스트레스에 따라 증가되는 것으로 나타났다. 결과적으로 수리취는 새벽녘 엽수분포텐셜이 -0.93 MPa 이하로 저하되면 광합성 활성의 감소가 크게 나타나고, 건조스트레스에 따라 삼투적 적응과 탄성적 적응이 나타나 이것이 이 식물의 중요한 적응방법임을 알 수 있었다.