• The Korean Journal of Ecology
• /
• v.25 no.2
• /
• pp.119-125
• /
• 2002

In order to elucidate the budget and cycling of Nitrogen and Sulfur, esential elements and principal constituents of acid rain, their input through precipitation, and their output by streamflow were quantified in coniferous and deciduous forested watersheds, using combination of nutrient concentration and hydrological analysis, in Kwangnung Experimental Forest from July 1991 to Decmeber 1993. Amount of annual mean precipitation was 12.916 ton·ha/sup -1/·yr/sup -1/, annual mean runoff 5,094 ton·ha/sup -1/·yr/sup -1/(39%), 7,647 ton·ha/sup -1/·yr/sup -1/(59%) in coniferous and deciduous forest watersheds, respectively. Amounts of annual input of N(NO₃/sup -/+NH₄/sup +/) and SO/sup 2-/₄ through preciptation were 12.5, 81.7 kg·ha/sup -1/·yr/sup -1/, respectively. Annual output via runoff of N(NO₃/sup -/+NH₄/sup +/) and SO/sup 2-/₄were 0.06, 39.23 ton·ha/sup -1/·yr/sup -1/ in the coniferous forest watershed ecosystem, and 0.15, 55.46 ton·ha/sup -1/·yr/sup -1/ in the deciduous one, respectively. On the basis of annual nutrient input and output, the annual budget of N(NO₃/sup -/+NH₄/sup +/) and SO/sup 2-/₄were +12.46, +42.49 ton·ha/sup -1/·yr/sup -1/ in the coniferous forest watershed, and +11.35, +26.26 ton·ha/sup -1/·yr/sup -1/ in the deciduous one. Thus N(NO₃/sup -/+NH₄/sup +/) and SO/sup 2-/₄were accumulated in both forested watershed ecosystems.

• Journal of Korean Society of Forest Science
• /
• v.88 no.2
• /
• pp.249-254
• /
• 1999

The effects of various levels of Al concentration on growth, nutrient status and net photosynthetic rate of 2-year-old Pinus densiflora Sieb. et Zucc. seedlings grown in a nutrient culture solution were investigated. Al concentrations were added as aluminum chloride($AlCl_3$) at 0(control), 10, 30 and 60ppm to the nutrient culture solution. The nutrient culture solution was maintained at pH 4.0 by adding HCl or NaOH solution. The seedlings were transplanted into the nutrient culture solution and grown in a greenhouse for 90 days from May 8 to August 6, 1996. The treatment above 10ppm of Al concentrations induced a significant reduction on the dry weight growth of the seedlings. The relative growth rate(RGR), net assimilation rate(NAR) and net photosynthetic rate of the seedlings were reduced with increasing of Al concentrations in the nutrient culture solutions. This result suggests that reductions in the RGR and NAR of the seedlings were mainly due to the inhibition of net photosynthesis. In addition, the increase of Al concentrations in a nutrient culture solution decreased the concentration of essential mineral elements such as Ca and Mg in the needle of the seedlings. However, the concentrations of Al of each plant organ increased in the treatment above 10ppm of Al concentrations in the nutrient culture solutions. This result suggests that the increased Al concentration in the belowground part resulted from the decreased concentration of essential mineral elements in the aboveground part of the seedlings.

• Journal of Korean Society of Forest Science
• /
• v.97 no.3
• /
• pp.266-273
• /
• 2008

The effects of soil acidification on the seedling growth and nutrition of Pinus densiflora and Quercus acutissima were investigated. The relationship between the seedling growth and molar (Ca+Mg+K)/Al ratio of in soil solution was examined. The results suggested that growth inhibition of seedling Pinus densiflora and Quercus acutissima was due to the low pH of soil solution, which was followed by leach of Al into soil solution, and decrease of essential elements, such as Ca in aerial pant of the seeding caused by the increase of Al concentration in subterranean pant of the seedlings. The level of growth inhibition was determined not only by Al concentration, but also by the balance of inorganic elements, Al, Ca, Mg and K. The growths of two species in total dry weight were clearly inhibited when molar (Ca+Mg+K)/Al ratio of the soil was lower than 6.0. The growth in dry weight, in the condition of the molar ratio was 0.8, was decreased 60% or 50% for the seedling of Pinus densiflora or Quercus acutissima respectively. It was concluded that the molar (Ca+Mg+K)/ Al ratio could be an important index for evaluation of the effects of soil acidification, due to acid deposition such as acid rain, on growth of trees and nutrition. And it might be a more useful indicator for evaluation of critical load of acid deposition on forest ecosystems.

• Journal of Korean Society of Forest Science
• /
• v.87 no.4
• /
• pp.611-619
• /
• 1998

This study was carried out to examine the effects of soil acidification on growth and nutrient status of 2 - year - old Pious densiflora Sieb. et Zucc. seedlings grown for 120 days in brown forest soils acidified with $H_2SO_4$ solution with or without leaching rations from the soil. The concentrations of A1 in the acidified soils increased with increasing amount of $H^+$ added to the soil. The total dry weight of the seedlings was decreased by the addition of the $H_2SO_4$ solution. The increase of Al concentration in the belowground part resulted from the decreased concentration of essential mineral elements such as Ca and Mg in the aboveground part. In addition, a strong positive correlation(r=0.96, p<0.001) was observed between the dry weight of the seedlings and the molar (Ca+Mg+K)/A1 ratio of the soil solution. When the molar (Ca+Mg+K)/Al ratio was approximately 7.0, the dry weight of the seedlings began to decrease compared with that of the seedlings in the control treatment. The seedlings with the molar (Ca+Mg+K)/Al ratio of 1.0 resulted from approximately 40% growth reduction compared with the control value. The results suggest that the molar (Ca+Mg+K)/Al ratio of the soil solution may be a useful indicator for assessing the critical load of acid deposition.

• Resources Recycling
• /
• v.24 no.4
• /
• pp.32-37
• /
• 2015

Cobalt is abundant only in some countries including Democratic Republic of the Congo. It would be necessary to secure overseas Co ores and Co extraction technology. Two kinds of matte varying the sulfur content were manufactured by smelting reduction of Co concentrate containing ~8 wt% Co, ~19 wt% Cu, and ~3 wt% Fe. The amount of Co, Cu and Fe was concentrated to 19~21 wt%, 39~41 wt%, and 7~9 wt% respectively in the resulting matte. High-pressure leaching of matte was performed in an autoclave with considering the effect of oxidizing agent, $H_2SO_4$ concentration as a lixiviant, and the amount of sulfur added to the matte. An oxidizing agent (oxygen) is necessary to improve Co leaching efficiency enabling usage of a dilute $H_2SO_4$ leaching agent. An increase in $H_2SO_4$ concentration prevents selective leaching of Co, and the sulfur content in matte has a minor influence on the Co leaching efficiency.

• Journal of the Korean Magnetics Society
• /
• v.22 no.2
• /
• pp.58-65
• /
• 2012

Since Nd-Fe-B magnet was first synthesized in 1983, many new applications have emerged in the past two decades. With regard to motor market, it will expand because of strong energy saving requirements from the automobile and electric application markets. Especially, permanent magnet motors for hybrid and electric vehicles are drawing great attention and the usage of Nd-Fe-B magnets will increase all the more hereafter. There is, however, a serious problem as motors in such eco-friendly cars are said to operate in high temperatures of about $200^{\circ}C$. Nd-Fe-B magnet has a drawback of dramatically decreasing coercive force with the rise of temperature. In order to improve this aspect. the best way is to add dysprosium (Dy) into the magnet. So, Dy has become an essential element for Nd-Fe-B high-performance magnet as it helps to maintain coercive force even at high temperatures. On the other hand, the rare earth resources in the earth crust are eccentrically-located and its majority is produced in China. There is a need to reduce its usage as, especially compared to light rare earth elements as neodymium (Nd) and samarium (Sm), heavy rare earth elements including Dy are unevenly distributed to a dramatic degree, their output low, and their prices are about 10 times that of Nd. The present article includes a summary of the trend in research and development of motors and permanent magnets to solve rare-earth resources problem.

• Korean Journal of Soil Science and Fertilizer
• /
• v.4 no.1
• /
• pp.1-11
• /
• 1971

1. Rice plant grown with silica had more elect leaves and heading was one week earlier with silica than without silica grown in both water culture and Akiochi soil. 2. Silica content of rice plant was apparently increased by silica application and the increase insilica was more increased by bassal application of silica than top dressing. The content of other eements in plant decreased with silica application and the trend was most noticeable in iron. 3. Rice plant low in silica were more susceptible to reaf blast, Helminthosporium, mites and smaller brown plant hopper. 4. There was no significant effect of silica on increasing the dry matter production of rice plant grown on water culture, but silica remarkerbly increased the dry matter production of rice plant grown on Akiochi soil. The increasing effect of silica on rice grown on Akiochi fields was more noticeable than that of grown on Pots. 5. In rice plant grown on Akiochi soil, number of spikelets and percentage of ripened grains were increased by application of silica. The silica effects can be increased by application of well balanced nitrogen and potassium ratio. 6. From these results, it can be concluded that silica seems to have no direct effect on rice growth, but application of silica to Akiochi soil associated with low silica supply may be critical for healthy growth of rice plant, and silica directly related to rice agronomy.

• Journal of Space Technology and Applications
• /
• v.3 no.1
• /
• pp.86-99
• /
• 2023

The mass spectrometer, being an essential scientific instrument for uncovering the origin of the solar system and life, has been used since the early 1970s on board spacecraft to obtain information of neutral and ionized elements in the atmosphere and surface of the moon, planets, asteroids, and comets. According to the 4th Basic Plan for the Promotion of Space Development (2023-2027), Korea plans to conduct lunar landing in 2032 and Mars landing in 2045 as the core goals of the plan and focuses on developing the technologies required for unmanned robotic exploration missions. In this regard, it is crucial to develop the technology of a mass spectrometer, which is the most fundamental payload for space exploration for maximized scientific achievements, however never tried before in any domestic space missions. We describe in this paper the principle of a domestically developed quadrupole mass spectrometer, its prototype model, and the test results of its performance. We conclude this paper with intended future improvements.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2016.02a
• /
• pp.117-117
• /
• 2016

일반적인 박막 성장용 CVD는 막 성장 시간이 짧게는 수분에서 수시간 정도 소요하기 때문에 장비에 문제가 발생 할 시 조치를 취하고 다음 현상을 개선하기에 용이 하였다. 그리고 대분분의 장비가 국산화되어 있을 만큼 많은 경험치가 축척되어 있다. 그러나 2, 4 족 화합물 성장용 CVD는 고아학 렌즈 생산용 장비로 국내에서는 아직 생소하고 공정 경험이 없는 새로운 장비이다. 2,4 족 화합물의 특징은 다음과 같다. 2,4 족 화합물은 M, N 이라는 두가 물질이 결합하여 형성한다. 2,4 족 화합물은 높은 융점과 낮은 증기압을 갖니다. 이런 물질들은 고온에서 아래와 같이 평형적으로 반응한다. $$nMN_{(s)}=nM_{(g)}+Nn_{(g)}$$ 화합물인 $MN_{(g)}$의 상태로 존재할 수 있으나 일바적으로 n=2인 4족 원소의 2원자 분자로된 기체가 지배적이다. 증기상을 이용한 성장 공정에서는 구성 원자나 분자를 만들어내는 단계, 이들을 공급원에서 기판까지 수송하는 단계, 기판 위에 흡착하는 단계, 핵의 생성과 단결정을 생성하는 단계, 필요치 않는 구성물을 제거하는 단계를 거쳐 공정이 진행 된다. 각 공정은 성장 물질에 충분한 자유도를 주어야하고 자유도를 주기 위해서는 많은 열에너지가 공급 되어야 한다. 따라서 기존의 박막 성장 공정 보다 성장 속도가 느리고 증착하는 양보다는 버리는 양이 많으며 버려지는 성장물질들은 급격한 온도 변화가 생기는 곳에서 급격히 증착하기 시작한다. 본 성장 공정이 진행되는 압력은 30 torr 부근이며 공정 온도는 $1000^{\circ}C$ 부근이다. 30 torr 영역에서는 열전달이 대기압과 같은 속도로 진행되기 때문에 지속적으로 온도에의해 손상을 받는 부위가 있을 수 있다. 높은 공정 온도와 높은 공정 압력은 내부 구조물로 발생된 열을 빠르게 장비 표면으로 수송하게 되고 그 결과 장비의 연결 부분에 장착된 오링에 손상을 주게 된다. 오링 손상을 방지 하기위해 냉각수 라인을 형성하여 오링을 보호하게 되면 열역학적 기울기가 급격히 발생하는 부분이므로 CVD의 반응 부산물들이 빠른 시간동안 증착하게 되고 막히는 현상이 발생하게 된다. 목표한 두게까지 박막을 성장시키기 위해서는 장시간 공정이 필수이며 장시간 공정을 안정적으로 가져가지 위해서는 배기 라인의 막힘 현상을 해결하여야 한다. 본 논문에서는 막힘 현상의 진행을 시간에 따라 해석하였으며 장시간 공정을 진행하기위해 필요한 요소와 기구적으로 조치가 가능한 방법에 대해 작성하였다.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2017.04a
• /
• pp.120-120
• /
• 2017

최근 국내 소비자들의 안전한 음식과 환경문제에 대한 관심이 높아지면서 재배작물과 경작지 토양의 물리 화학적 특성 등에 맞추어 적정 시비 및 재배관리를 적용하는 정밀농업이 시도되고 있다. 정밀농업은 농약 및 비료 등의 양을 적절하게 사용하여 생산 비용을 절감할 수 있으며, 과다사용을 막아 환경오염을 줄일 수 있다. 현재 토양의 수분, EC, pH등과 같은 항목은 신속하고 간단하게 분석이 가능하지만 토양의 필수 원소인 N, P, K 성분을 분석하는 제품은 상용화 되지 않았거나 가격이 비싸 일반 농가에서는 사용이 어렵다. 특히, 토양의 인을 현장에서 분석하기 위한 연구가 많이 수행되고 있으나 실제로 현장에서 사용되는 경우 또한 없는 상황이다. 일반적으로 토양에 포함되어 있는 인을 측정하기 위해서 많은 실험실에서는 이화학적 분석법을 사용하고 있다. 하지만 이 분석법은 오랜 시간과 전문적인 인력이 필요하며 주변 환경변화에 민감하여 실시간으로 분석하기에는 어렵다고 한다. 따라서 본 연구에서는 현장에서 실시간으로 토양의 인을 분석하기 위해 반자동 분석시스템을 제작하고 이를 검증하고자 하였다. 이전 연구에서 현장 토양을 이용한 신속측정법의 가능성($R^2>0.7$)을 확인하여 이 분석법을 바탕으로 반자동 분석시스템을 제작하였고 표준결과 값의 약 70% 이상의 수준을 목표로 하였다. 진주 지역의 현장 토양 20개 샘플과 반자동 침출 장치, 여과 장치, 발색 장치 그리고 통합 반자동 시스템을 이용하여 분석한 후 표준 분석 결과와 비교하였을 때 $R^2$ 값이 각각 0.985, 0.817, 0.893, 0.837로 약 70% 이상의 수준을 달성하였다. 추후, 반자동 토양 인 신속측정시스템을 완전 자동화 시스템으로 개발하고 주행 장치를 부착시켜 현장에서 실시간으로 원하는 위치의 인을 측정 할 수 있을 것으로 판단된다.