• 한국환경과학회지
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• 제11권10호
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• pp.1133-1140
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• 2002

The growth and extent of the local pressure field at any point is of primary importance as it supplies the driving force for the local wind circulation which causes a medium-range transport of air pollutants. The local pressure field is produced by the variation of temperature in the lower layers of the atmosphere, and is called the thermal wave. The thermal wave is influenced by the difference in the diurnal variations between two regions with different surface condition, for example land and sea. This difference produces the land- and sea-breeze phenomenon, and brings corresponding variations in the form of the thermal wave. Daytime temperature over the inland area (Daegu) was higher than that of the coastal area (Busan). The temperature difference reached about 5~6$^{\circ}C$ in the late afternoon(30-31 May 1999). The low pressure system of Daegu was most fully developed at the time. In this study, we investigated the possibility of thermal low onset around Daegu in summer with an analytical model. The topography effect was neglected in the model. We could predict a thermal low-pressure of about 3.4hPa at Daegu with wide flat land surface, when the inland area is about 6K warmer than the coastal area temperature. The pressure decrease is somewhat less than the observed value(4~5 hPa).

• Journal of Microbiology and Biotechnology
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• 제15권1호
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• pp.125-130
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• 2005

The growth and phosphatase (phosphomonoesterase) activity of Chroococcidiopsis culture isolated from the cryptoendoliths of the Antarctic were compared with a similar isolate from the Arizona hot desert. Such cyanobacteria living inside rocks share several features with the immobilized cells produced in the laboratory. This study has relevance because the availability of phosphorus is a key factor influencing the growth of these cyanobacteria in nature, in such unique ecological niches as the hot and cold deserts. Phosphatase activity therefore is of particular importance for these organisms if they are to survive without any other source of phosphorus availability. Also, there is paucity of knowledge regarding this aspect of study in cyanobacterial cultures from these extreme environments. The salient feature of this study shows the importance of specific pH and temperatures for growth and phosphatase activity of both cultures, although there were marked differences between the two isolates. The pH and temperature optima for growth and phosphatase activity (PMEase) of Chroococcidiopsis 1 and 2 were 9.5, $240^{\circ}C$ and 8.5, $40^{\circ}C$ respectively. The $K_m and V_max$ values of cultured Chroococcidiopsis 1 showed lower affinity of PMEase for the substrate compared to the enzyme affinity of the same organism when found within the rocks; Chroococcidiopsis 2 and Arizona rocks containing the same alga however showed similar affinity of PMEase for the substrate. An interesting observation was the similarity in response of immobilized Chroococcidiopsis 1 culture and the same organism in the Antarctic rocks to low light and low temperature stimulation of PMEase. This thermal response seems to be related to the ability of the immobilized Antarctic isolate and the rocks to either cryoprotect the PMEase or undergo a change to save the enzyme from becoming nonfunctional under low temperatures. The free cells of Chroococcidiopsis 1 culture however did not show such responses.

• 한국세라믹학회지
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• 제34권3호
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• pp.289-295
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• 1997

저손실 Mn-Zn 페라이트의 제조공정과 첨가제가 코아의 미세구조와 전기적 특성에 미치는 영향을 조사하였다. C\ulcorner와 SiO2를 원료분체혼합시에 첨가하는 경우보다 하소분체의 재분쇄시에 첨가할 때가 작고 균일한 소결체를 얻을 수 있었다. 산소분압(Po2)이 높아짐에 따라 미세구조가 불균일해졌고 DF(disaccomodation fac-색)가 증가하였다. 또한 하소온도가 높고 분쇄시간이 짧은 소결체의 경우 치밀한 속도가 감소하여, 130$0^{\circ}C$까지 정상입성장거동을 보였고, 따라서 높은 소결온도에서도 비교적 저손실 Mn-Zn 페라이트를 얻을 수 있었다. 장시간 분쇄하거나 하소온도가 낮은 시편의 경우는 치밀화속도의 증가에 기인하여 120$0^{\circ}C$이하의 저온 소결시 미립자의 저손실 Mn-Zn 페라이트를 얻을 수 있었으나 소결온도 125$0^{\circ}C$이상에서는 비정상 입성장을 유발시켰다.

• 한국재료학회지
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• 제31권3호
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• pp.139-149
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• 2021

In this study, three kinds of bainitic steels are fabricated by controlling the contents of vanadium and boron. High vanadium steel has a lot of carbides and nitrides, and so, during the cooling process, acicular ferrite is well formed. Carbides and nitrides develop fine grains by inhibiting grain growth. As a result, the low temperature Charpy absorbed energy of high vanadium steel is higher than that of low vanadium steel. In boron added steel, boron segregates at the prior austenite grain boundary, so that acicular ferrite formation occurs well during the cooling process. However, the granular bainite packet size of the boron added steel is larger than that of high vanadium steel because boron cannot effectively suppress grain growth. Therefore, the low temperature Charpy absorbed energy of the boron added steel is lower than that of the low vanadium steel. HAZ (heat affected zone) microstructure formation affects not only vanadium and boron but also the prior austenite grain size. In the HAZ specimen having large prior austenite grain size, acicular ferrite is formed inside the austenite, and granular bainite, bainitic ferrite, and martensite are also formed in a complex, resulting in a mixed acicular ferrite region with a high volume fraction. On the other hand, in the HAZ specimen having small prior austenite grain size, the volume fraction of the mixed acicular ferrite region is low because granular bainite and bainitic ferrite are coarse due to the large number of prior austenite grain boundaries.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.9-9
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• 2009

1 wt % Ga-dope ZnO (ZnO:Ga) thin films with n-type semiconducting behavior were grown on c-sapphire substrates by radio frequency magnetron sputtering at various growth temperatures. The room temperature grown ZnO:Ga film showed the faint preferred orientation behavior along the c-axis with small domain size and high density of stacking faults, despite limited surface diffusion of the deposited atoms. The increase in the growth temperature in the range between $300\sim550^{\circ}C$ led to the granular shape of epitaxial ZnO:Ga films due to not enough thermal energy and large lattice mismatch. The growth temperature above $550^{\circ}C$ induced the quite flat surface and the simultaneous improvement of electrical carrier concentration and carrier mobility, $6.3\;\times\;10^{18}/cm^3$ and $27\;cm^2/Vs$, respectively. In addition, the increase in the grain size and the decrease in the dislocation density were observed in the high temperature grown films. The low-temperature photoluminescence of the ZnO:Ga films grown below $450^{\circ}C$ showed the redshift of deep-level emission, which was due to the transition from $Zn_j$ to $O_i$ level.

• Journal of Microbiology and Biotechnology
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• 제31권9호
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• pp.1218-1230
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• 2021

Cold-adapted plant growth-promoting bacteria (PGPB) with multiple functions are an important resource for microbial fertilizers with low-temperature application. In this study, culturable cold-adapted PGPB strains with nitrogen fixation and phosphorus solubilization abilities were isolated. They were screened from root and rhizosphere of four dominant grass species in nondegraded alpine grasslands of the Qilian Mountains, China. Their other growth-promoting characteristics, including secretion of indole-3-acetic acid (IAA), production of siderophores and ACC deaminase, and antifungal activity, were further studied by qualitative and quantitative methods. In addition, whether the PGPB strains could still exert plant growth-promoting activity at 4℃ was verified. The results showed that 67 isolates could maintain one or more growth-promoting traits at 4℃, and these isolates were defined as cold-adapted PGPB. They were divided into 8 genera by 16S rRNA gene sequencing and phylogenetic analysis, of which Pseudomonas (64.2%) and Serratia (13.4%) were the common dominant genera, and a few specific genera varied among the plant species. A test-tube culture showed that inoculation of Elymus nutans seedlings with cold-adapted PGPB possessing different functional characteristics had a significant growth-promoting effect under controlled low-temperature conditions, including the development of the roots and aboveground parts. Pearson correlation analysis revealed that different growth-promoting characteristics made different contributions to the development of the roots and aboveground parts. These cold-adapted PGPB can be used as excellent strain resources suitable for the near-natural restoration of degraded alpine grasslands or agriculture stock production in cold areas.

• 한국결정성장학회지
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• 제17권1호
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• pp.1-5
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• 2007

본 연구에서는 HVPE(hydride vapor phase epitaxy) 방법으로 r-plane 사파이어 기판 위에 무극성의 (11-20) a-plane GaN을 성장하여 구조적인 특성을 관찰하였다. HVPE 방법으로 저온($500/550/600/660^{\circ}C$)에서 성장한 AIN 버퍼층이 고온의 a-GaN에 미치는 영향을 확인하였다. 또한, AIN 버퍼층과의 비교를 위하여 저온에서 성장한 GaN 버퍼층과 InGaN 버퍼층 같은 다양한 버퍼층을 이용하여 a-plane GaN의 성장도 실시하였다. 고온에서 성장된 a-GaN의 구조적 형상은 저온버퍼층의 성장 조건에 크게 영향을 받음을 알 수 있었다. $GaCl_3$ 전 처리를 실시하고 $820^{\circ}C$에서 성장한 경우에 가장 평탄한 표면을 가지는 a-GaN을 얻을 수 있었다.

• Fisheries and Aquatic Sciences
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• 제22권10호
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• pp.23.1-23.10
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• 2019

Background: Taurine is a conditional essential amino acid for fish. A study was conducted to investigate the compensating effect of supplemental taurine in diets for red seabream (Pagrus major) on impaired growth performance by fish meal (FM) replacement with soybean meal (SM) at low water temperature (14.15 ± 1.95 ℃). Methods: A FM-based diet was considered as a high FM diet and three other experimental diets were formulated to replace FM with SM by 20, 35, or 50% (HFM, SM20, SM35, or SM50, respectively) without taurine and other four diets were formulated by adding 1% taurine to the diets (HFM-T, SM20-T, SM35-T, or SM50-T, respectively). Triplicate groups of fish (108.9 ± 1.58 g/fish) were distributed into 24 polyvinyl circular tanks (215 L) with 20 fish per tank and fed one of the diets to satiation for 20 weeks. Results: Growth performance and feed utilization of red seabream were significantly improved by the dietary taurine supplementation. SM20-T and SM35-T diets increased fish growth that are comparable to HFM diet. Feed intake, feed conversion ratio, and protein efficiency ratio of fish fed SM20-T and SM35-T diets were not significantly different from those of HFM group. Dietary taurine supplementation in each FM replaced group numerically increased innate immunity of the fish. Lysozyme and superoxide dismutase activities were significantly decreased in fish fed SM35, SM50, and SM50-T diets compared to those of fish fed HFM diet while they were not significantly lower in SM20, SM20-T, SM35, and SM35-T groups. Glutathione peroxidase activity was significantly lower in fish group fed SM50 diet while SM50-T group did not significantly lower compared to that of HFM group. The relative expression level of hepatic IGF-1 mRNA was improved in fish fed taurine-supplemented diets compared to their respective SM diets. Conclusions: Growth performance and feed utilization of red seabream can be accelerated or restored by 1% taurine supplementation when they are fed high level of SM up to 35% in diets during low water temperature season.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2002년도 춘계 학술발표강연 및 논문개요집
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• pp.146-146
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• 2002

• 한국재료학회:학술대회논문집
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• 한국재료학회 2007년도 추계학술발표대회 및
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• pp.11.1-11.1
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• 2007