• 센서학회지
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• 제29권1호
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• pp.1-6
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• 2020

Gas sensors that operate at room temperature have been extensively studied because of sensor stability, lift time, and power consumption. To design effective room-temperature gas sensors, various nanostructures, such as nanoparticles, nanotubes, nanodomes, or nanofibers, are utilized because of their large-surface-to-volume ratio and unique surface properties. In addition, two-dimensional materials, including MoS₂, SnS₂, WS₂, and MoSe, and ultraviolet-activated methods have been studied to develop ideal room-temperature gas sensors. Herein, a brief overview of state-of-the-art research on room-temperature gas sensors and their sensing properties, including nanostructured materials, two-dimensional materials, the ultraviolet-activated method, and ionic-activated gas sensors, is provided.

• Structural Engineering and Mechanics
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• 제83권1호
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• pp.31-43
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• 2022

A nonlinear gas-spring tuned mass damper is proposed to mitigate the seismic responses of the multi-degree-of-freedom (MDOF) structure, in which the nine-story benchmark model is selected as the controlled object. The nonlinear mechanical properties of the gas-spring are investigated through theoretical analysis and experiments, and the damper's control parameters are designed. The control performance and damping mechanism of the proposed damper attached to the MDOF structure are systematically studied, and its reliability is also explored by parameter sensitivity analysis. The results illustrate that the nonlinear gas-spring TMD can transfer the primary structure's vibration energy from the lower to the higher modes, and consume energy through its own relative movement. The proposed damper has excellent "Reconciling Control Performance", which not only has a comparable control effect as the linear TMD, but also has certain advantages in working stroke. Furthermore, the control parameters of the gas-spring TMD can be determined according to the external excitation amplitude and the gas-spring's initial volume.

• 한국초전도ㆍ저온공학회논문지
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• 제8권2호
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• pp.37-42
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• 2006

A research on several characteristics such as volume breakdown and surface discharge of insulators for a termination of power transmission class HTS cable was performed. We investigated the surface discharge of glass fiber reinforced plastic (GFRP) under air, cryogenic nitrogen gas and nitrogen gas media. The breakdown characteristics of these media were studied. Experimental results revealed that flashover voltage greatly depends on pressure, temperature, the kinds of insulating media and voltages, but it is slightly affected by shape and material of electrode. The breakdown voltage of liquid nitrogen, cryogenic nitrogen gas and nitrogen gas deeply depends on the shape and dimension of electrode, kinds of voltages and pressure. Moreover, the breakdown voltage of cryogenic nitrogen gas and flashover voltage of GFRP in the cryogenic nitrogen gas is also influenced by temperature and vapour-mist density of the gas.

• 자원환경지질
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• 제36권3호
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• pp.149-157
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• 2003

울릉분지 남서부 심해저 퇴적층에 분포하는 천부 가스의 특성을 파악하기 위해서 피스톤 코아시료를 채취하고 공기층 가스 기법으로 퇴적물 내에 함유된 가스를 포집하여 탄화수소 가스의 함량, 성분 및 탄소 동위원소 분석을 실시하였다. 또한 가스의 함량과 시추 코아 퇴적물의 연관성 및 특성을 파악하기 위해서 가스를 함유하는 퇴적물에 대해서 유기 지화학 분석을 실시하였다. 그리고 가스를 함유하는 퇴적물의 탄성파 특성을 살펴보았다. 퇴적물에서는 탄화수소 가스가 0.01%에서 11.25%까지 검출되었다. 단위 퇴적물내의 탄화수소 가스의 양을 젖은 퇴적물의 부피를 기준으로 정량적으로 계산하면 0.1에서 87.4ml/L wet sediment를 나타냈다. 분석된 탄화수소 가스의 성분은 주로 메탄으로 분석 시료에서 2개 시료를 제외하고는 메탄의 함유비가 98%이상을 나타냈으며 32개 분석 시료 중에서 15개 구간에서는 메탄만이 검출되었다. 채취된 시료의 메탄 가스의 탄소 동위원소 비$(\delta^{13}c)$는 -94.31$extperthousand$에서 -55.50$\textperthousand$까지의 범위를 나타내서 분석된 가스의 기원은 메탄 생성 박테리아에 의한 생물 기원 가스인 것으로 판명된다. 연구 지역의 퇴적물내의 탄화수소 가스의 함량은 지역에 따라서 차이를 보인다. 퇴적물내의 가스의 함량은 퇴적물의 지화학적 특성과 퇴적물의 입도와는 뚜렷한 상관 관계를 보이지 않았다. 단지 탄성파 단면상에서 이상대를 나타내는 곳에서는 가스의 함량이 많은 것으로 나타났다. 탄성파 단면상에 보이는 이상대는 현장의 온도 압력 조건에서 공극수에 탄화수소 가스가 과포화 된 곳으로 다른 조건이 만족된다면 가스 하이드레이트를 형성하기에 적합한 것으로 해석한다.

• 멤브레인
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• 제29권1호
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• pp.51-60
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• 2019

분리막 소재의 투과도와 선택도 사이의 trade-off 관계로 인해 여전히 많은 연구가 필요하다. 특히 고분자 분리막에 무기물 나노입자가 들어가 있을 때, 기체투과 거동의 학문적 이해는 여전히 부족하다. 따라서 본 연구에서는 분리막 소재로 가장 많이 사용되는 PDMS에 2~5 nm의 기공을 가지고 있으며 직경이 약 5 nm 크기의 aluminosilicate hollow nanoparticles인 allophane을 이용하여 복합매질 분리막을 제조하여 기체투과특성을 연구하였다. 대표적인 분리막 소재인 PDMS에 친수성 allophane, 그리고 나노입자에 undecylenic acid로 표면을 개질한 allophane을 막 내부에 고르게 분산시켜 함량 별로 복합매질 분리막을 제조하였다. 나노입자가 분산된 혼합매질 분리막 내에서 기체의 투과 특성을 파악하고, 이에 따른 기체투과 거동과 나노입자가 가지고 있는 기공의 역할을 평가하고자 하였다. 표면개질된 allophane을 첨가함에 따라 기체 투과도와 산소/질소 그리고 이산화탄소/메탄의 선택도가 동시에 점진적으로 향상되는 결과를 얻었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2989-2994
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• 2007

Gas hydrates are ice-like crystalline compounds that form under low temperature and elevated pressure conditions. Although hydrate formation can pose serious flow-assurance problems in the gas pipelines or facilities, gas hydrates present a novel means for natural gas storage and transportation with potential applications in a wide variety of areas. An important property of hydrates that makes them attractive for use in gas storage and transportation is their very high gas-to-solid ratio. In addition to the high gas content, gas hydrates are remarkably stable. The main barrier to development of gas hydrate technology is the lack of an effective method to mass produce gas hydrate in solid form. The first objective of this study is investigating the characteristics of gas hydrate formation related to several factors such as pressure, temperature, water-to-storage volume ratio, concentration of SDS, heat transfer and whether stirred or not respectively. And the second objective is clarifying the relation between the formation efficiency and each factor in order to find the proper way or direction to improve the formation performance.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.662-669
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• 2000

Based on the viscous flow characteristics of gas through capillary tube, a simple and low cost system was developed for controlling gas concentration for use in C.A experiments. 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 developed system could control the gas concentration in storage chamber within ${\pm}0.3%$ deviation compared to the preset concentration. The required time for producing target gas concentration in storage chamber was exactly predicted by the model used in this study, and it required much longer time than the calculated time which divided the volume of chamber by flow rate. Therefore, for producing target gas concentration as quickly as possible, it needs to supply higher flow rate of gas during the initial stage of experiment when gas concentration in storage chamber has not reached at target value. It appeared that the developed system was very useful for C.A experiments. Because one could decide a desired flow rate by the prediction model, control flow rate freely and easily by changing pressure in the pressure-regulating chamber and the accuracy was high.

• 신재생에너지
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• 제2권2호
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• pp.94-101
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• 2006

[ $1m^3$ ] solid hydrate contains up to $200m^3$ of natural gas, depending on pressure and temperature. Such large volume of natural gas hydrate can be utilized to store and transport large quantity of natural gas in a stable condition. So, in the present investigation, experiments carried out for the formation of natural gas hydrate governed by pressure, temperature, and gas compositions, etc.. The results show that the equilibrium pressure of structure II natural gas hydrate) is approximately 65% lower and the solubility is approximately three times higher than structure I methane hydrate). Also, the subcooling conditions of the structure I and II must be above 9K and 11K in order to form hydrate rapidly regardless of gas components, but the pressure increase is more advantageous than the temperature decrease in order to increase the gas consumption. And utilizing nozzles for spraying water in the form of droplets into the natural gas dramatically reduces the hydrate formation time and increases its solubility at the same time.

• 한국진공학회지
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• 제15권5호
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• pp.465-474
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• 2006

기체저장용기, 단순 개폐밸브 및 기체 공급 관으로 구성된 기체연료 주입계는 가장 간단하게 사전에 기체 도입유형을 정할 수 있다는 장점이 있다. 장치의 동작특성을 알아보기 위해 기체 흐름에 관한 일차원 동특성 방정식을 세우고 수치적으로 풀었다. 이 계산의 목적은 저장기체 압력, 저장용기 체적, 공급관의 굵기, 길이 따위의 기계적 요소들과 최대유량까지의 지연시간, 최대유량 값, 기체 펄스폭 따위의 기체 흐름의 유형을 결정하는 인자들 사이의 관계를 정립하려는 것이다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.227-230
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• 2006

The method of mass flow rate measurement using a critical nozzle is well established in the flow satisfying ideal gas law. However, in the case of measuring high-pressure gas flow, the current method shows invalid discharge coefficient because the flow does not follow ideal gas law. Therefore an appropriate equation of state considering real gas effects should be applied into the method. The present computational study has been performed to give an understanding of the physics of a critical nozzle flow for high-pressure hydrogen gas and find a way for the exact mass flow prediction. The two-dimensional, axisymmetric, compressible Navier-Stokes equations are computed using a fully implicit finite volume method. The real gas effects are considered in the calculation of discharge coefficient as well as in the computation. The computational results are compared with the previous experimental data and predict well the measured mass flow rates. It has been found that the discharge coefficient for high-pressure hydrogen gas can be corrected properly adopting the real gas effects.