• 한국환경생태학회지
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• 제5권1호
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• pp.91-103
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• 1991

지리산국립공원의 등산로 및 야영장의 훼손과 등산로 주연부의 식생구조 변화에 대한 이용영향을 파악하기 위해 1991년에 조사를 실시하였다. 등산로폭, 나지노출폭 및 최대 깊이는 이용강도에 따른 차이가 인정되었고 총 32km의 132개 조사지정에서, 관찰된 훼손형태는 다양하였으며 훼손된 지점의 등산로상태 중 해발고, 등산로폭 및 최대깊이는 건전한 지점의 상태와 유의한 차이를 보였다. 능선부 등산로에서는 훼손이 심화되고 있었으며 인위적인 복구공법이 필요한 환경피해도 4등급 이상인 면적이 약 34,000$m^2$에 달하고, 야영장에서도 이용압력과 훼손현상은 증가되고 있었다. 등산로 주연부의 상층수관에 있어서 우점수종은 해발이 높아짐에 따라 화엄사등산로에서는 개서어나무$\longrightarrow$졸참나무, 서어나무$\longrightarrow$신갈나무, 서어나무로, 피아골등산로에서 졸참나무$\longrightarrow$신갈나무로 바뀌고 있었으며 조록싸리, 노린재나무, 바위말발도리, 병꽃나무가 화엄사등산로에서, 조록싸리, 노린재나무, 국수나무, 철쭉이 피아골등산로에서 높은 상대우점치를 나타내었다.

• 한국주조공학회지
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• 제21권1호
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• pp.7-14
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• 2001

The research on new DRA(discontinuous reinforced alloy) and CRA(continous reinforced alloy) composites has been carried out to improve the properties of ceramic fiber and particle reinforced metal matrix composites(MMCs). Effects of alloying elements and aging conditions on the microstructures and aging behavior of Al-Si-Cu-Mg-(Ni)-SiCp composite have been examined. The specimens used in this study were manufactured by duplex process. The first squeeze casting is the process to make precomposite and the second squeeze casting is the process to make final composite. The hardening behavior was accelerated with decreasing the size of SiCp particle in the composites. It is considered that the dislocation density increased with increasing SiCp size, due to the different thermal deformation between Al matrix and SiCp during quenching after the solution treatment. Peak aging time to obtain the maximum hardness in 3 ${\mu}m$ SiCp reinforced Al composite was reduced than that in large size(5, 10 ${\mu}m$) of SiCp because of difference in dislocation density. Aging hardening responce(${\Delta}H$ = $H_{Max}.-H_{S.T}$) of composites was greater than that of unreinforced Al alloy because of higher density of second phases in matrix.

• 한국재료학회지
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• 제27권10호
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• pp.524-529
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• 2017

The effect of strain aging on the tensile properties of API X70 linepipe steel was investigated in this study. The API X70 linepipe steel was fabricated by controlled rolling and accelerated cooling processes, and the microstructure was analyzed using optical and scanning electron microscopes and electron backscatter diffraction. Strain aging tests consisting of 1 % pre-strain and thermal aging at $200^{\circ}C$ and $250^{\circ}C$ were conducted to simulate U-forming, O-forming, Expansion(UOE) pipe forming and anti-corrosion coating processes. The API X70 linepipe steel was composed of polygonal ferrite, acicular ferrite, granular bainite, and bainitic ferrite whose volume fraction was dependent on the chemical composition and process conditions. As the thermal aging temperature increased, the steel specimens showed more clearly discontinuous type yielding behavior in the tensile stress-strain curve due to the formation of a Cottrell atmosphere. After pre-strain and thermal aging, the yield and tensile strengths increased and the yield-to-tensile strength ratio decreased because yielding and aging behaviors significantly affected work hardening. On the other hand, uniform and total elongations decreased after pre-strain and thermal aging since dislocation gliding was restricted by increased dislocation density after a 1 % pre-strain.

• 한국수산과학회지
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• 제36권2호
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• pp.69-73
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• 2003

To improve the sensory quality of sliced raw fish, the effect of cold brine temperature on the texture properties was investigated. Fishes were immersed in cold brine by various condition and killed instantly by spiking at the head. The onset of rigor-mortis was accelerated by decrease of immersion temperature. Also, the time reaching full rigor was shortened remarkably too. However, the rigor index of samples immersed in the cold brine decreased more than that of samples killed instantly. Rigor index was the highest in samples killed instantly, followed by $0^{\circ}C,\;-5^{\circ}C,\;-10^{\circ}C,\;-12.5^{\circ}C,\;-15^{\circ}C\;and\;-20^{\circ}C$ in that order. The breaking strength of samples immersed in the cold brine increased slowly but did not increase through all the conditions in the samples. Breaking strength of all samples immersed in the cold brine decreased significantly after reaching the maximum values (p<0.05). The lactate content of muscle was increased by the decreased brine temperature, however ATP content decreased. Minimum lactate and maximum ATP content in fish muscle showed at $-12.5^{\circ}C$. Those results demonstrate that optimal temperature for improvement of sliced raw fish quality by cold brine was $-12.5^{\circ}C.$

• The Korean Journal of Physiology and Pharmacology
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• 제14권5호
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• pp.273-278
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• 2010

Tropical inhabitants are able to tolerate heat through permanent residence in hot and often humid tropical climates. The goal of this study was to clarify the peripheral mechanisms involved in thermal sweating pre and post exposure (heat-acclimatization over 10 days) by studying the sweating responses to acetylcholine (ACh), a primary neurotransmitter of sudomotor activity, in healthy subjects (n=12). Ten percent ACh was administered on the inner forearm skin for iontophoresis. Quantitative sudomotor axon reflex testing, after iontophoresis (2 mA for 5 min) with ACH, was performed to determine directly activated (DIR) and axon reflex-mediated (AXR) sweating during ACh iontophoresis. The sweat rate, activated sweat gland density, sweat gland output per single gland activated, as well as oral and skin temperature changes were measured. The post exposure activity had a short onset time (p<0.01), higher active sweat rate [(AXR (p<0.001) and DIR (p<0.001)], higher sweat output per gland (p<0.001) and higher transepidermal water loss (p<0.001) compared to the pre-exposure measurements. The activated sweat rate in the sudomotor activity increased the output for post-exposure compared to the pre-exposure measurements. The results suggested that post-exposure activity showed a higher active sweat gland output due to the combination of a higher AXR (DIR) sweat rate and a shorter onset time. Therefore, higher sudomotor responses to ACh receptors indicate accelerated sympathetic nerve responsiveness to ACh sensitivity by exposure to environmental conditions.

• 대한기계학회논문집B
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• 제29권7호
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• pp.878-885
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• 2005

The water jet impingement cooling is one of the techniques to remove the heat from high heat flux equipments. Local heat transfer of the confined water impinging jet and the effect of nozzle collar to enhance the heat transfer are investigated in the fee surface jet and submerged jet. Boiling is initiated from the farthest downstream and increase of the wall temperature is reduced with developing boiling, forming the flat temperature distributions. The reduction in the nozzle-to-surface distance fur H/W$\le$1 causes significant increases and distribution changes of heat transfer. Developed boiling reduces the differences of heat transfer for various conditions. The nozzle collar is employed at the nozzle exit. The distances from heated surface to nozzle collar, Hc are 0.25W, 0.5W and 1.0W. The liquid film thickness is reduced and the velocity of wall jet increases as decreased spacing of collar to heated surface. Heat transfer is enhanced fur region from the stagnation to x/W$\~$8 in the free surface jet and to x/W$\~$5 in the submerged jet. For nucleate boiling region of further downstream, the heat transfer by the nozzle collar is decreased in submerged jet comparing with higher velocity condition. It is because the increased velocity by collar is de-accelerated downstream.

• Journal of Plant Biotechnology
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• 제7권3호
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• pp.161-167
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• 2005

Brassinosteroids are steroidal plant hormones and are known to modulate physiological and cellular response in a wide range of plant species. Considerable insights has been achieved of the physiological role of brassinosteroid in Brassica species in the past few years, but their effect on direct organogenesis has not been extensively studied. In this sense, under optimal basal media and growth conditions we tested the cellular and organogenic response of 24-epibrassinolide (EBL) in a variable concentration (0.1 to $5.0\;{\mu}M$) and Zeatin (Z) (1.0 to $100\;{\mu}M$) and their synergic effect on hypocotyl explants of cauliflower and broccoli. The isolated EBL accelerated cell elongation and promotes direct organogenesis. One micromolar EBL + $10\;{\mu}M$ of Z was the most efficient combination for cell elongation, cell differentiation as well as for organogenesis. A suppressing effect on root induction was confirmed for all the tested hormone levels. The general results indicate a synergic effect of EBL-Z and EBL potentates Zeatin activity, at least in certain tissues. Besides de genetic factors, we can speculate that the natural hormone concentration in the explants might affect the responses by application of exogenous growth regulators. Experiments with new plant growth regulators, like brassinolide, are important aiming to maximize or accelerate plant regeneration for in vitro multiplication or for genetic transformation.

• 한국잡초학회지
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• 제18권3호
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• pp.257-261
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• 1998

실내 실험을 통하여 토양중 napropamide의 흡착 및 분해성에 대하여 연구 검토하였다. 3 토양중 napropamide의 흡착 분배 계수 값(kd)은 5.38 - 11.39이었으며 유기물 함량이 많은 토양에서 Kd값이 높았다. 토양중 napropamide는 일정 기간의 lag time 후에 분해가 진행되었다. 처리량의 50%가 소실되는 기간은 $10^{\circ}C$에서 약 65 일, $20^{\circ}C$에서 약 45일, $30^{\circ}C$에서 30일 정도 이었으며, 90%까지 분해 소실되는 되는 $10^{\circ}C$에서 약 90일 $20^{\circ}C$ 에서 약 60일 $30^{\circ}C$에서 약 45일정도 소요되었다. Napropamide를 처리한 전력이 있는 토양중 napropamide의 분해는 lag period가 없이 진행되었으며 분해속도도 매우 빨라졌다. 이는 napropamide의 반복처리에 의하여 그 분해속도가 촉진됨을 입증해주는 결과라 하겠다.

• 상하수도학회지
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• 제30권1호
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• pp.19-31
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• 2016

The Saemangeum watershed is required to manage water pollution effectively but the effect of liquid manure (LM) on soil and water quality in the basin is not clearly identified as yet. This study aims at assessing the effect on soil of a rice field and water quality of water bodies near the rice field during rice-crop time period to find out the effect of LM, the effect of rainfall, and the effect of rice-crop environment on soil and water quality by analyzing data of nitrogen components. As a result of the LM distribution, $NO_3-N$ was much higher than other N components in the entire soil layers and it was accelerated by rainfall right after the LM distribution. Compared to chemical fertilizer (CF), LM was slightly affected but still influenced on the surface water quality. During weak rainfall, low nitrogen concentration in topsoil was resulted as NH3-N decreased and Org-N and $NO_3-N$ increased. $NO_3-N$ concentration in the water of irrigation canals increased with time. During intensive rainfall, $NO_3-N$ and Org-N of the soil were measured highly in the submerged condition, while the water quality of the rice field was lower due to flooding into the irrigation canal as well as the growth of the rice plants. Also, total nitrogen was increased more than 7 times and it showed serious water quality deterioration due to LM and excessive fertilizer distribution, and rainfall during all rice-crop processes. The effect of LM on water quality should be studied consistently to provide critical data while considering weather condition, cropping conditions, soil characteristics, and so on.

• 상하수도학회지
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• 제31권5호
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• pp.389-395
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• 2017

In this paper, we investigate the characteristics of membrane fouling caused by water temperature in the Membrane bioreactor(MBR) process and try to derive the membrane fouling control by chemical enhanced backwashing(CEB). The extracellular polymeric substances(EPS) concentration was analyzed according to the water temperature in the MBR, and the membrane fouling characteristics were investigated according to the conditions, with sludge & without sludge, through a lab-scale reactor. As shown in the existing literature the fouling resistance rate was increased within sludge with the water temperature was lowered. However, in the lab-scale test using the synthetic wastewater, the fouling resistance increased with the water temperature. This is because that the protein of the EPS was more easily adsorbed on the membrane surface due to the increase of entropy due to the structural rearrangement of the protein inside the protein as the water temperature increases. In order to control membrane fouling, we tried to derive the cleaning characteristics of CEB by using sodium hypochlorite(NaOCl). We selected the condition with the chemicals and the retention time, and the higher the water temperature and the chemical concentration are the higher the efficiencies. It is considered that the increasing temperature accelerated the chemical reaction such as protein peptide binding and hydrolysis, so that the attached proteinaceous structure was dissolved and the frequency of the reaction collision with the protein with the chemical agent becomes higher. These results suggest that the MBRs operation focus on the fouling control of cake layer on membrane surface in low temperatures. On the other hand, the higher the water temperature is the more the operation strategies of fouling control by soluble EPS adsorption are needed.