임상연구 : 신선가스유량의 변화가 흡입마취제의 흡기가스농도에 대한 호기가스농도 비율에 미치는 영향

신원정 ( Won Jung Shin ),최규택 ( Kyu Taek Choi ) 대한마취과학회 2006 Korean Journal of Anesthesiology Vol.50 No.6

Background: One way to make rapid increase in alveolar anesthetic concentration includes using high fresh gas flow rates. Fresh gas flow rates should be increased to compensate the amount of uptake either. This study was performed to elucidate optimal fresh gas flow rates for rapid induction by comparison of changes of ratio of expired to inspired concentration. Methods: The study population was composed of 107 patients undergoing thyroidectomy. Patients were randomly allocated to one of three groups who received desflurane or sevoflurane or isoflurane. Each group was randomly subdivided into three groups who received one of the fresh gas flow rate: 2, 5 or 10 L/min. Inspired anesthetic concentration (Fi) and expiratory anesthetic concentration (Fe), delivered concentration (FD) were recorded. Results: With same fresh gas flow rates, there were significant differences between Fe/Fi of desflurane, sevoflurane, isoflurane. With same anesthetics, Fe/Fi of desflurane and sevoflurane were not influenced by fresh gas flow rates. But Fe/Fi of isoflurane at 2 L/min was significantly lower than 5 L/min and 10 L/min. Fi/FD of desflurane at 10 L/min did not differ from sevoflurane. At 2 L/min and 5 L/min, Fi/FD of desflurane was highest and then sevofluane, isoflurane in that order. Conclusions: Because rates of Fe/Fi of desflurane and sevoflurane were not influenced by fresh gas flow rates, 2 L/min of fresh gas flow rates could be selected. However, considering the wash-in time in circuit, optimal choice of fresh gas flow rate for desflurane and sevoflurane could be 5 L/min, that of isoflurane be 10 L/min. (Korean J Anesthesiol 2006; 50: 629~36)

불균일 농도 LPG의 폭발 특성에 관한 연구

오규형 한국화재소방학회 2003 한국화재소방학회논문지 Vol.17 No.4

가로, 세로, 높이가 각각 100cm, 60cm, 45cm로 내용적이 <TEX>$270\ell$</TEX>인 폭발 용기를 이용하여 불균일 농도 상태의 LPG-공기 혼합가스의 폭발특성을 측정하였다. 폭발은 vented-explosion과 closed explosion의 조건에서 실시하였다. 실험의 변수로는 점화원의 위치, 노즐직경 및 유속으로, 시료가스를 주입하는 노즐의 직경과 유속을 변화시키면서 용기 내에서의 불균일 혼합정도를 조절하였다. 폭발압력은 strain형 압력센사를 사용하여 측정하였고 폭발화염의 거동은 비디오카메라로 측정하여 분석하였다. 실험결과 유속과 가스 주입 시간이 용기 내 가스 혼합에 중요한 요소임을 알 수 있었으며, 불균일 정도가 심화될 수록 폭발압력과 압력상승속도가 감소하였으나 용기 내 폭발화염의 체류시간은 크게 증가하였으며 이로 인하여 가스 폭발 후 화재로의 전이 위험성이 증가함을 알 수 있었다. LPG explosion characteristics in non-uniform concentration was investigated with a 270 liter explosion vessel of which the scale is 100 cm<TEX>${\times}$</TEX>60 cm<TEX>${\times}$</TEX>45 cm. Vented explosion and closed explosion system were used. Experimental parameter were position of ignition source, nozzle diameter and flow rate of gas. Non uniform concentration was controlled by the nozzle diameter and flow rate. Explosion pressure were measured with strain type pressure sensor and the flame behavior was pictured with the video camera. Based on this experimental result, it was found that the flow rate of gas and the duration of gas injection are important factor for mixing the gas in the vessel. And as the increase the non-uniformity of gas concentration, explosion pressure and pressure rise rate Is decrease but the flame resident time in the vessel is increase. Therefore gas explosion to fire transition possibility will increase in non-uniform concentration gas explosion.

열처리에 따른 MWCNT/ZnO 복합체 필름 가스센서의NOX 가스 검출 특성

김현수,장경욱 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.7

In particular, gas sensors require characteristics such as high speed, sensitivity, and selectivity. In this study,we fabricated a NOX gas sensor by using a multi-walled carbon nanotube (MWCNT)/zinc oxide (ZnO) composite film. The fabricated MWCNT/ZnO gas sensor was then treated by a 450℃ temperature process to increase its detectionsensitivity for NOx gas. We compared the detection characteristics of a ZnO film gas sensor, MWCNT film gas sensor,and the MWCNT/ZnO composited film gas sensor with and without the heat-treatment process. The fabricated gassensors were used to detect NOX gas at different concentrations. The gas sensor absorbed NOX gas molecules, exhibitingincreased sensitivity. The sensitivity of the gas sensor was increased by increasing the gas concentration. Additionally,while changing the temperature inside the chamber for the MWCNT/ZnO composite film gas sensor, we obtained itssensitivity for detecting NOX gas. Compared with ZnO, the MWCNT film gas sensor is excellent for detecting NOX gas. From the experimental results, we confirmed the enhanced gas sensor sensing mechanism. The increased effect byelectronic interaction between the MWCNT and ZnO films contributes to the improved sensor performance.

열처리에 따른 MWCNT/ZnO 복합체 필름 가스센서의 NO_X 가스 검출 특성

김현수,장경욱,Kim, Hyun-Soo,Jang, Kyung-Uk 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.7

In particular, gas sensors require characteristics such as high speed, sensitivity, and selectivity. In this study, we fabricated a $NO_X$ gas sensor by using a multi-walled carbon nanotube (MWCNT)/zinc oxide (ZnO) composite film. The fabricated MWCNT/ZnO gas sensor was then treated by a $450^{\circ}C$ temperature process to increase its detection sensitivity for NOx gas. We compared the detection characteristics of a ZnO film gas sensor, MWCNT film gas sensor, and the MWCNT/ZnO composited film gas sensor with and without the heat-treatment process. The fabricated gas sensors were used to detect $NO_X$ gas at different concentrations. The gas sensor absorbed $NO_X$ gas molecules, exhibiting increased sensitivity. The sensitivity of the gas sensor was increased by increasing the gas concentration. Additionally, while changing the temperature inside the chamber for the MWCNT/ZnO composite film gas sensor, we obtained its sensitivity for detecting $NO_X$ gas. Compared with ZnO, the MWCNT film gas sensor is excellent for detecting $NO_X$ gas. From the experimental results, we confirmed the enhanced gas sensor sensing mechanism. The increased effect by electronic interaction between the MWCNT and ZnO films contributes to the improved sensor performance.

MOS-FET 구조의 MWCNT 가스센서를 이용한 초희박 NOx 가스 검출 특성

김현수,이승훈,장경욱,Kim, Hyun-Soo,Lee, Seung-Hun,Jang, Kyung-Uk 한국전기전자재료학회 2013 전기전자재료학회논문지 Vol.26 No.9

Carbon nanotubes(CNT) has strength and chemical stability, greatly conductivity characteristics. In particular, MWCNT (multi-walled carbon nanotubes) show rapidly resistance sensitive for changes in the ambient gas, and therefore they are ideal materials to gas sensor. So, we fabricated NOx gas sensors structured MOS-FET using MWCNT (multi-walled carbon nanotubes) material. We investigate the change resistance of NOx gas sensors based on MOS-FET with ultra lean NOx gas concentrations absorption. And NOx gas sensors show sensitivity on the change of gate-source voltage ($V_{gs}=0[V]$ or $V_{gs}=3.5[V]$). The gas sensors show the increase of sensitivity with increasing the temperature (largest value at $40^{\circ}C$). On the other hand, the sensitivity of sensors decreased with increasing of NOx gas concentration. In addition, We obtained the adsorption energy($U_a$), $U_a$ = 0.06714[eV] at the NOx gas concentration of 8[ppm], $U_a$ = 0.06769[eV] at 16[ppm], $U_a$ = 0.06847[eV] at 24[ppm] and $U_a$ = 0.06842[eV] at 32[ppm], of NOx gas molecules concentration on the MWCNT gas sensors surface with using the Arrhenius plots. As a result, the saturation phenomena is occurred by NOx gas injection of concentration for 32[ppm].

Numerical modeling of two‐phase bubbly flow mixing with mass transport in an effective microorganism odor removing system

Ali, Haider,Cheema, Taqi Ahmad,Park, Cheol Woo John WileySons, Ltd 2016 Journal of chemical technology and biotechnology Vol.91 No.4

<P>BACKGROUNDIndustrial odor removers are two-phase flow systems that use effective microorganisms to capture malodor-producing gases from the surroundings. The potency of such systems depends on the interaction of gas with the microorganisms. Therefore, the flow and mass transport properties are key to defining the phenomenon more clearly. RESULTSAn efficient mechanism for mixing the two-phase flow is required to enhance the interaction between the gas and microorganisms. Gas flow must also be controlled to obtain a large residence time in the water basin and facilitate the microorganisms to maximize the usage of malodor-producing gases. One method of improving the gas residence time is by installing baffles in the water basin. However, the installation of baffles also limits the gas concentration distribution in the water basin. Placing a rotating drum in addition to the baffles may overcome the limitations on gas distribution in the water basin. Gas volume fractions, interfacial area per volume, and gas concentration are evaluated to observe the mixing and gas dissolution phenomenon. CONCLUSIONBefore practical implementation, a numerical study on the subject is required for various designs to investigate their effectiveness. Therefore, the present study uses the Euler-Euler numerical scheme to model the gas-liquid flow with mass transport for various designs of water basin. Results show that gas concentration is the most critical parameter in the case of two-phase bubbly flow. (c) 2015 Society of Chemical Industry</P>

A Rapid Preconcentration Method Using Modified GP-MSE for Sensitive Determination of Trace Semivolatile Organic Pollutants in the Gas Phase of Ambient Air

Miao He,Qingjuan Xu,Cui Yang,Xiangfan Piao,Narayanan Kannan,Donghao Li 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.10

A sensitive concentration method utilising modified gas-purge microsyringe extraction (GP-MSE) was developed. Concentration (reduction in volume) to a microlitre volume was achieved. PAHs were utilised as semivolatile analytes to optimise the various parameters that affect the concentration efficiency. The injection rate and temperature were the key factors that affected the concentration efficiency. An efficient concentration (75.0−96.1%) of PAHs was obtained under the optimised conditions. The method exhibited good reproducibility (RSD values that ranged from 1.5 to 9.0%). The GP-MSE concentration method enhances the volume reduction (concentration factor), leading to a low method detection limit (0.5−15 ng L–1). Furthermore, this method offers the advantage of small-volume sampling, enabling even the detection of diurnal hourly changes in the concentration of PAHs in ambient air. Utilising this method in combination with GC−MS, the diurnal hourly flux of PAHs from the gas phase of ambient air was measured. Indeed, the proposed technique is a simple, fast, low-cost and environmentally friendly.

Effect of various gas compositions on gas interchangeability and combustion characteristics for domestic appliances

Kee-Man Lee,김종민,유병훈,이창언,이승로 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.4

In this study, an investigation into the gas interchangeability and combustion characteristics of various gas compositions for domestic appliances was performed. In order to suggest the appropriateness of gas interchangeability using the specific gravity (SG) and the Wobbe index (WI) values, combustion characteristics included incomplete combustion and flame lifting were measured and observed for the upper and lower limits using the gas-oven as a domestic partial–premixed type appliance and the condensing boiler as a domestic premixed type appliance. The flame was stable, and the CO and NOx concentrations increased when the WI and SG values increased. Specifically, the behavior of the flame lifting changed between WI values of 52.0 MJ/Nm3 and 53.0 MJ/Nm3. The CO and NOx concentrations of the reference gas were approximately 173 ppm and 74 ppm for the gas-oven and 175 ppm and 35 ppm for the boiler, respectively. Consequently, a WI value of 53.0 MJ/Nm3 can be considered the flame lifting limit as the lower limit for gas interchangeability. For the upper limit of gas interchangeability, the CO and NOx concentrations varied significantly with the type of burner.

Role of critical concentration of PEI in NMP solutions on gas permeation characteristics of PEI gas separation membranes

Ahmad Arabi Shamsabadi,Masoud Bahrami Babaheidari,Ali Kargari,Saeed Laki,Hadi Ajami 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.2

In preparation of polymeric gas separation membranes by phase inversion method, polymer concentration is one of the most important variables which can change membrane morphology and behavior. In this research, critical concentration of the polyetherimide (PEI) solutions in N-methyl-2-pyrrolidone (NMP) as a solvent was determined by viscometric method. The influence of temperature on critical concentration was studied. Three asymmetric PDMS/PEI membranes with different concentrations of PEI were prepared and characterized for H2/CH4 separation. The results showed that the membranes with higher concentrations than critical concentration were more suitable for gas separation. In addition, the viscosity data were fitted by appropriate equations and the densities were satisfactorily correlated by a simple first-order polynomial with respect to temperature and the PEI mass fraction. The prepared membrane showed the selectivity of 26 for H2/CH4 separation at 1 bar and 25 8C for pure gas and 24.8 for mixed gas. The influence of the pressure on the H2 and CH4 permeance and the selectivity for a mixed binary gas showed that the permeance of both gases declined by pressure enhancement and the selectivity increased.

Development of a Gas Mixing System for Controlled Atmosphere(CA) Chambers

Yun, Hong Sun,Lee, Won Ock,Chung, Hun,Cho, Kwang Hwan 한국농업기계학회 2001 Agricultural and Biosystems Engineering Vol.2 No.1

Based on the viscous flow characteristics of gas through capillary tube, a simple and cheap gas mixing system was developed for controlling gas compositions in CA chambers. The gas flow rate through capillary tube had a linear relationship with pressure, (length)^(-1) and (radius)^(4) of capillary tube, which agreed well with Hagen-Poiseuille's law. The relationship between flow rate and combined parameters was described as Q = 0.000209724(π r^(4)P / μL) and the coefficient of determination was 0.9984. The developed system could control gas concentrations in CA chambers within ±0.3% deviation compared to the preset concentrations. It was possible to predict the required time and required gas flow rate for exchanging the gas in CA chamber to a certain concentration of gas by using the mathematical model developed in this study.