• New Physics: Sae Mulli
• /
• v.68 no.11
• /
• pp.1167-1172
• /
• 2018

Carbon nanotubes (CNTs) are structures of carbon atoms bonded together in hexagonal honeycomb shapes, with multi-walled CNTs having a very high thermal conductivity of $3000W/m{\cdot}K$ and single-walled CNTs having a conductivity of $6000W/m{\cdot}K$. In this work, the transmittance and the thermal diffusivity of a multi-walled carbon nanotube dispersion with a concentration of 1.5 M were measured using a single beam method, a dual beam method, and the thermal lens effect. The nonlinear optical coefficients were obtained by using the z-scan method, which moved the sample in the direction of propagation of the single laser beam, propagation and the thermal diffusivity was measured using a double laser beam. As a pump beam, a diode-pumped solid state (DPSS) laser with a wavelength of 532 nm and an intensity of 100 mW was used. As the probe beam, a He-Ne laser having a wavelength of 633 nm and an intensity of 5 mW was used. The experimental result shows that when the concentrations of the sample were 9.99, 11.10, 16.65, and 19.98 mM, the nonlinear absorption coefficients were 0.046, 0.051, 0.136 and 0.169 m/W, respectively. Also, the nonlinear refractive indices were 0.20, 0.51, 1.25 and $1.32{\times}10^{-11}m^2/W$, respectively, and the average thermal diffusivity was $1.33{\times}10^{-6}m^2/s$.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.3
• /
• pp.51-57
• /
• 2021

The seawater cooling system of naval ships is installed to remove the toxic substances generated by CBR (Chemical, Biological, and Radiological) warfare and reduce the infrared signature of naval ships from outside the hull. The dispersion range of the nozzle is determined according to the injection pressure of seawater and the nozzle type. Therefore, it is necessary to select the appropriate injection pressure and design the optimal nozzles to increase the seawater dispersion area and maximize the efficiency of the cooling system. In this study, the applying feasibility of 3D printing technology to produce an injection nozzle for the seawater cooling system was examined. To this end, the extruded plastic specimens were fabricated by 3D printing, and the physical properties of the specimens were estimated through tensile testing. After this, the strain and stress of the nozzle as a function of the pressure were simulated by applying the estimated results to the finite element analysis. The finite element analysis results showed that the nozzle remained within the elastic range at the optimal pressure. The nozzle was estimated to be structurally stable, and the possibility of this study was confirmed.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.24 no.5
• /
• pp.395-409
• /
• 2022

To overcome the limitation of conventional rock excavation methods, the excavation with abrasive waterjet has been actively developed. The abrasive waterjet excavation method has the effect of reducing blasting vibration and enhancing the excavation efficiency by forming a continuous free surface on the rock. However, the waterjet cutting performance varies with rock fracturing characteristics. Thus, it is necessary to analyze the cutting performance for various rocks in order to effectively utilize the waterjet excavation. In this study, cutting experiments with the high pressure waterjet system were performed for basalt and granite specimens. Water pressure, standoff distance, and traverse speed were determined as effective parameters for the abrasive waterjet cutting. The cutting depth and width of basalt specimens were analyzed to compare with granite results. The averaged cutting depth of basalt was shown in 41% deeper than granite; in addition, the averaged cutting width of basalt was formed by 18.5% narrower than granite. The results of this study are expected to be useful basic data for applying rock excavation site with low strength and high porosity such as basalt.

• Journal of the Korean Institute of Gas
• /
• v.27 no.2
• /
• pp.7-15
• /
• 2023

The electric submersible pump (ESP) has been operating in production wells around the world because of its high applicability and operational efficiency among artificial lift techniques. When operating an ESP in a reservoir, variables such as temperature, pressure, gas/oil ratio, and flow rate are factors that affect ESP performance. In particular, free gas in the production fluid is a major factor that reduces the life and operational efficiency of ESP. This study presents the flow loop system which can implement the performance and damage tests of ESP considering field operating conditions to quantitatively analyze the variables that affect ESP performance. The developed apparatus in an integrated system that can diagnose the failure and causes of ESP, and detect leak of tubing by linking ESP and tubing as one system. In this study, the flow conditions for stable operation of ESP were identified through single phase and two phase flow experiments related to evaluation for the performance of ESP. The results provide the basic data to develop the failure prediction and diagnosis program of ESP, and are expected to be used for real-time monitoring for optimal operating conditions and failure diagnosis for ESP operation.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2020.06a
• /
• pp.67-67
• /
• 2020

일반적으로 농업용수 이용량은 기후, 토양, 지역별 재배 특성 등에 따라 다양하게 나타날 수 있으며, 용수공급 계획을 위해 수요량 추정방법을 이용하고 있다. 농업용수 수요량은 논과 밭 등에서 작물 재배에 필요한 용수량이라 정의할 수 있으며, 구체적으로는 작물 재배에 소요되는 전체 용수량에서 강우에 의해 공급되는 양을 제외한 수량으로 볼 수 있다. 현재 농업용수 수요량의 추정 방법은 현장에서 직접 실측하는 방법, 대표 작물을 대상으로 계측한 후 일반화 하는 방법, 증발산 이론에 의하여 추정하는 방법 등으로 구분 되며, 최근 광역적인 분석으로 증발산 이론에 의한 추정 방법을 주로 사용하고 있다. 농업용 지하수 이용은 국내 지하수 이용량의 51%를 차지하고 있어 보다 적확한 농업용 지하수 사용량조사는 지하수의 효율적 정책 추진을 위하여 중요하다. 본 연구의 목적은 현장조사로 수집한 자료를 이용해 각 조사지역의 사용량을 추정하고 월별사용량 및 단위면적당 사용량을 분석하는 것이다. 조사지역은 창녕함안보(오천리, 성산리), 합천창녕보(율지리), 달성보(좌학리, 위천리), 구미보(궁기리)이고, 지하수사용량을 분석하기 위해 유량계(계량기) 검침, 전력사용량 검침, 수중모터펌프 가동시간을 이용하였으며, 조사기간은 2018년 12월 부터 2020년 02월 까지 이다. 농업용관정 조사시 실제 지하수를 사용하는 면적(ha)도 같이 조사해, 월별 지하수사용량에 실제사용면적(ha)을 나누어 면적당 지하수사용량으로 분석하였다. 조사결과 창녕함안보 오천리는 20,956㎥/mon/ha, 창녕함안보 성산리는 19,911㎥/mon/ha, 합천창녕보 율지리는 3,648㎥/mon/ha, 달성보 좌학리는 2,417㎥/mon/ha, 달성보 위천리는 3,546㎥/mon/ha, 구미보 궁기리는 619㎥/mon/ha로 분석되었다. 수막재배가 많은 창녕함안보가 지하수사용량이 가장 많았으며, 구미보의 경우 지하수사용량이 가장 적은 것으로 분석되었다. 월별 지하수 사용량을 살펴보면 2019년 01월 ~ 02월 보다 2020년 01월 ~ 02월의 평균 지하수 사용량이 793㎥/mon/ha 적게 분석되었고, 평균기온은 2019년 01월에 0.3℃, 2020년 1월은 2.6℃로 2.3℃ 높다. 이는 겨울철 지하수 사용량에 영향을 주었다고 판단된다. 겨울철 지하수 사용량차이는 재배작물과 겨울철 기온차이가 원인으로 판단되며, 다년간 지하수사용량과 기온을 조사할 필요가 있다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.1B
• /
• pp.79-88
• /
• 2006

In this study, a methodology is developed for flood runoff analysis considering the interaction between interior floodplain and channel. Riparian lowland is modeled as storage areas by HEC-RAS and is connected with main channel through gravity drainage structure and pumping stations. As a result, we were able to compute the difference between runoff into the interior floodplain and delayed runoff to main channel from interior floodplain. This allowed us to compute the storage change in the interior floodplain and corresponding inundation areas. Furthermore, the levee is modeled as a lateral structure and the flood from the main channel to interior floodplain is modeled by installing a weir on top of it. In addition, levee breach is also modeled so that flooding from main channel to interior floodplain can be considered. Computed flooding depth in the storage areas are compared with elevation to identify the inundated areas and flood maps can then be produced for a desired time or for the extent of flooding given a flooding depth. Output from this modeling effort can provide many useful information for flood planning such as flow depth in main channel, flooding depth and area in interior floodplain. The method was applied to Sapgyo river basin and the comparison with observed flood events showed that it can reproduce the observation fairly well, hence proving the utility of the method.

• Applied Biological Chemistry
• /
• v.42 no.2
• /
• pp.116-122
• /
• 1999

In order to characterize the property of $Ca^{2+}$ transport in plant cell, microsomes were prepared from the roots of tomato and microsomal $^{45}Ca^{2+}$ uptake was measured. When 1 mM vanadate, a selective inhibitor of P-type ATPases, 50 mM $NO_3^-$, a specific inhibitor of vacuolar $H^{+}-ATPase$, and both of these inhibitors were treated, the microsomal $^{45}Ca^{2+}$ uptakes were inhibited by 20, 33 and 47%, respectively. The inhibitory effects of these two inhibitors were investigated by using a protonophore, gramicidin. When the chemical gradient of $H^{+}$ was relieved by gramicidin, the uptake was decreased by 30%, implying the presence of $Ca^{2+}/H^+$ antiporter in the microsomal membrane. In the $^{45}Ca^{2+}$ uptake experiment, the effect of gramicidin was independent of vanadate-induced inhibition. However, when the activity of vacuolar $H^{+}-ATPase$ was inhibited by $NO_3^-$, the effect of gramicidin was severely decreased. Meanwhile, thapsigargin, a specific antagonist of ER/SR-type $Ca^{2+}-ATPase$, inhibited the microsomal $^{45}Ca^{2+}$ uptake and the maximum inhibitory effect was obtained at $10\;{\mu}M$. The effect of thapsigargin was blocked by $NO_3^-$ and gramicidin, but not by vanadate. These results imply that vanadate directly inhibits the activity of $Ca^{2+}-ATPase$; however, $NO_3^-$ and thapsigargin block the activity of $Ca^{2+}/H^+$ antiporter by inhibiting the vacuolar $H^{+}-ATPase$. In conclusion, the microsomal $^{45}Ca^{2+}$ uptakes are mediated by two major enzymes, $Ca^{2+}-ATPase$ and $Ca^{2+}/H^+$ antiporter in tomato root tissue.

• Journal of Aquaculture
• /
• v.13 no.3
• /
• pp.267-275
• /
• 2000

To evaluate the characteristics and efficiency of oxygen transfer rate of a polystyrene foam bead as media in a packed column aerator was tested. This media has more surface area and cheaper than other ordinary plastic media. The polystyrene foam media was a sphere-shaped bead with 2.5 mm in diameter and specific surface area was 1,350 $m^2$/$m^3$. Oxygen transfer rate and standard aeration efficiency were tested under different hydraulic loading rates, depths of the media and temperatures. Experiment 1 was performed using a small packed column aerator with 10 cm in diameter and 1 m in length. The aerator filled with 0, 4.5, 9.0 and 18.0 cm of the media was tested under hydraulic loading rates of 2.0, 4.0 and 5.6 $m^3$/$m^2$/min at temperatures of 20, 25 and 3$0^{\circ}C$, respectively. In this experiment, standard oxygen transfer rate (SOTR) increased with the hydraulic loading rate and depth of the media increased. The maximum SOTR was reached at 5.6 $m^3$/$m^2$/min of hydraulic loading rate with 9 cm in depth of the media. However, standard aeration efficiency (SAE) decreased with the hydraulic loading rate increased because electricity consumed by pump increased as hydraulic loading rate increased. The highest SAE was reached at hydraulic loading rate of 2.0 $m^3$/$m^2$/min with 9.0 cm in depth of the media. Therefore, the highest SOTR and SAE were achieved at 9.0 cm in depth of the media regardless of the hydraulic loading rate. The maximum SAE was about 1.8 kg $O_2$/kW-hr with the hydraulic loading .ate of $m^3$/$m^2$/min at temperature of 20 $^{\circ}C$.Experiment 2 was performed using a larger aerator, 20 cm in diameter with 2 m in height. The aerator filled with 0, 9, 18, 27 and 36 cm of the media was operated under hydraulic loading rate of 2.0, 4.0 and 5.6 $m^3$/$m^2$/min at temperature of 27 $^{\circ}C$. The SAE reached to the highest efficiency (1.9 kg $O_2$/kW-hr) at 2.0 $m^3$/$m^2$/min of hydraulic loading rate and 36 cm in depth of the media. According to the above results, the polystyrene foam bead as a media in a packed column aerator was effective to increase oxygen transfer rate.

• Korean Journal of Microbiology
• /
• v.40 no.4
• /
• pp.342-347
• /
• 2004

A bacterial strain YC4963 with antifungal activity against Colletotrichum orbiculare, a causal organism of cucumber anthracnose was isolated from the rhizosphere soil of Siegesbeckia pubescens Makino in Korea. Based on physiological and biochemical characteristics and 16S ribosomal DNA sequence analysis, the bac­terial strain was identified as Pseudomonas aurantiaca. The bacteria also inhibited mycelial growth of several plant fungal pathogens such as Botrytis cinerea, Fusarium oxysporum and Rhizoctonia solani on PDA and 0.1 TSA media. The antifungal activity was found from the culture filtrate of this isolate and the active compound was quantitatively bound to XAD adsorption resin. The antibiotic compound was purified and identified as phenazine-l-carboxylic acid on the basis of combined spectral and chemical analyses data. This is the first report on the production of phenazine-l-carboxylic acid by Pseudomonas aurantiaca.

• Applied Biological Chemistry
• /
• v.41 no.2
• /
• pp.130-136
• /
• 1998

Microsomes of tomato roots were prepared and the activities of microsomal ATPases were measured in order to understand the molecular mechanisms of various ion transports. The activities of plasma membrane $H^+-ATPase$ and vacuolar $H^+-ATPase$ were evaluated to ${\sim}30%$ and ${\sim}38%$ of total microsomal ATPase activity by using their specific inhibitor, vanadate and nitrate $(NO^-_3)$, respectively. The inhibitory effects of vanadate and $NO^-_3$ were additive and the simultaneous additions of these two inhibitors decreased the total activity up to $50{\sim}70%$. The microsomal ATPase activity was regulated key pH and the maximal activity was obtained at pH 7.4. The activity of microsomal ATPase was increased by $K^+$ up to ${\sim}30%$ at the concentration of $K^+$ above 10 mM. However, the $K^+-induced$ increase in the activity was completely inhibited by the simultaneous addition of $Na^+$. To identify the ATPase activity regulated by $K^+$, the effects of specific inhibitors were measured. Vanadate and $NO^-_3$ inhibited total ATPase activity by 27% and 32% in the absence, of $K^+$ and by 27% and 40% in the presence of 120 mM $K^+$, respectively. These results suggest that $K^+$ increases the activity of $NO^-_3-sensitive$ vacuolar $H^+-ATPase$ but not that of vanadate-sensitive plasma membrane $H^+-ATPase$ since vanadate has no effect on $K^+-induced$ increase in ATPase activity. The microsomal ATPase activity was also decreased by increasing $Ca^{2+}$ concentration. Interestingly, $NO^-_3$ blocked the $Ca^{2+}-induced$ inhibition of microsomal ATPase activity; however, vanadate had no effect. These results imply that vacuolar $H^+-ATPase$ is activated by $K^+$ and inhibited by $Ca^{2+}$.