MPGA-Based Indoor Localization for Non Steady-State Gas Source

Qiuming Li,Zhigang Liu,Jinkuan Wang,Kai Cheng 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.11

Traditional gas source localization algorithms are usually based on gas steady-state diffusion model which ignores the factor of the time, it is difficult to meet the practical application conditions. In order to solve this problem, we propose an effective gas source localization method based multiple population genetic algorithm(MPGA) to estimate the location of gas-leakage source via wireless sensor network. In this paper, we first build a gas unsteady-state diffusion model without wind based on the gas diffusion theory, and then we transfer the gas source location problem into a global optimization problem with the measured information of sensor nodes. Finally, we use MPGA to solve the optimization problem and obtain the location of the gas source. The simulation results show that the proposed method can quickly obtain the location of the gas source, and has the higher positioning accuracy as compared with tradition localization algorithms.

Hydrogen Sensing of Graphene-based Chemoresistive Gas Sensor Enabled by Surface Decoration

엄태훈,김태훈,장호원 한국센서학회 2020 센서학회지 Vol.29 No.6

Hydrogen (H2) is considered as a new clean energy resource for replacing petroleum because it produces only H2O after the combustion process. However, owing to its explosive nature, it is extremely important to detect H2 gas in the ambient atmosphere. This has triggered the development of H2 gas sensors. 2-dimensional (2D) graphene has emerged as one of the most promising candidates for chemical sensors in various industries. In particular, graphene exhibits outstanding potential in chemoresistive gas sensors for the detection of diverse harmful gases and the control of indoor air quality. Graphene-based chemoresistive gas sensors have attracted tremendous attention owing to their promising properties such as room temperature operation, effective gas adsorption, and high flexibility and transparency. Pristine graphene exhibits good sensitivity to NO2 gas at room temperature and relatively low sensitivity to H2 gas. Thus, research to control the selectivity of graphene gas sensors and improve the sensitivity to H2 gas has been performed. Noble metal decoration and metal oxide decoration on the surface of graphene are the most favored approaches for effectively controlling the selectivity of graphene gas sensors. Herein, we introduce several strategies that enhance the sensitivity of graphene gas sensors to H2 gas.

가스하이드레이트 제조성능 향상을 위한 영향인자 검토 연구

신창훈(Chang Hoon Shin),김유나(Yu Na Kim),권옥배(Ok Bae Kwon),박승수(Seung Su Park),한정민(Jeong Min Han),이정환(Jeong Hwan Lee) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

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.

1.4L 급 터보 CNG 엔진에서 흡기압력 상승에 따른 출력 증대 효과에 관한 연구

이정우,박철웅,배종원,김창기,이선엽,김용래 한국가스학회 2019 한국가스학회지 Vol.23 No.6

셰일가스의 채굴량 확장과 러시아를 통한 PNG (Pipeline Natural Gas)의 도입은 천연가스가 유력한 대체 연료임을 시사해주고 있다. 따라서 향후 증대될 천연가스의 공급에 맞추어 해당 연료의 수요처 증대가 필수적인 상황이다. 이와 같은 상황에서 수송분야는 저탄소 기체 연료인 천연가스를 적용하기 적합한 분야이며, 이를 통해 이산화탄소와 입자상 물질 등의 유해 배기물질을 저감하는 데 큰 역할을 할 것으로 기대된다. 천연가스는 자발화 특성이 낮고, 내노킹(Anti-knocking)성이 우수하기 때문에 전기점화 방식에 적합하다. 최근가솔린 엔진은 연비 개선을 위해 연소실에 직접 분사하는 방식을 주로 채택하고 있으나,연소실 내로 액상 직분사를하는 반면 천연가스의 경우 액상분사 혹은 고압 분사가 어렵다. 따라서 포트에 분사하는 방식을 사용하므로 동등흡기압력에서 연료의 분율이 흡입공기의 체적을 대체하여 가솔린 직분 방식에 비해 출력이 저하되는 현상을 피할수 없게 된다. 이에 본 연구에서는 터보차저를 천연가스 포트 분사 엔진에 적용하여 흡기 압력 상향을 통한 출력 보상을 도모하고자 하였다.그 결과 천연가스 적용 시 흡기압력을 기존 가솔린 대비 5-27 % 상향 시 가솔린 직분사 엔진과 동등 출력을 확보함과 동시에 향상된 제동 열효율을 확인 할 수 있었다. Natural gas has been regarded as one of major alternative fuels, because of the increment of mining shale gas and supplying PNG(Pipeline Natural Gas) from Russia. Thus, it needs to broaden the usage of natural gas as the increasing its supplement. In this situation, application of natural gas on the transport area is a good suggestion to reduce exhaust emissions such as CO2(carbon dioxides) and soot from vehicles. For this reason, natural gas can be applied to SI(spark ignition) engines due to its anti-knocking and low auto-ignitibility characteristics. Recently, since turbocharged SI engine has been widely used, it needs to apply natural gas on the turbocharged SI engine. However, there is a major challenge for using natural gas on turbocharged SI engine, because it is hard to make natural gas direct injection in the cylinder, while gasoline is possible. As a result, there is a loss of fresh air when natural gas is injected by MPI (multi-point injection) method under the same intake pressure with gasoline-fueled condition. It brings the power reduction. Therefore, in this research, intake pressure was increased by controling the turbocharger system under natural gas-fueled condition to improve power output. The goal of improved power is the same level with that of gasoline-fueled condition under the maximum torque condition of each engine speed. As a result, the maximum power levels, which are the same with those of gasoline-fueled conditions, with improved brake thermal efficiency could be achieved for each engine speed (from 2,000 to 6,000 rpm) by increasing intake pressure 5-27 % compared to those of gasoline-fueled conditions.

Gas sensing characteristics of the FET-type gas sensor having inkjet-printed WS₂ sensing layer

Jeong, Yujeong,Shin, Jongmin,Hong, Yoonki,Wu, Meile,Hong, Seongbin,Kwon, Ki Chang,Choi, Seokhoon,Lee, Taehyung,Jang, Ho Won,Lee, Jong-Ho Elsevier 2019 Solid-State Electronics Vol.153 No.-

<P><B>Abstract</B></P> <P>This paper investigates the gas sensing characteristics of the MOSFET-type sensor having an inkjet-printed WS<SUB>2</SUB> sensing layer. The drain current of the gas sensor increases when NO<SUB>2</SUB> gas is injected into the test chamber since NO<SUB>2</SUB> gas is an oxidizing gas that extracts electrons from the sensing layer. On the contrary, the drain current decreases when H<SUB>2</SUB>S gas is injected into the test chamber since H<SUB>2</SUB>S gas is a reducing gas that donates electrons to the sensing layer. In both cases, the change of the drain current increases as the gas concentration increases. However, for other gases (NH<SUB>3</SUB> and CO<SUB>2</SUB>), the gas sensor has a small change of the drain current. The responses of the gas sensor to 10 ppm NO<SUB>2</SUB>, H<SUB>2</SUB>S, NH<SUB>3</SUB>, and CO<SUB>2</SUB> gases are 15.20%, 7.18%, 1.66%, and 3.02%, respectively. Therefore, the WS<SUB>2</SUB> sensor has a high selectivity for NO<SUB>2</SUB> gas among the four target gases.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The drain current of the WS<SUB>2</SUB> gas sensor increases when NO<SUB>2</SUB> gas is injected, but decreases when H<SUB>2</SUB>S gas is injected. </LI> <LI> However, for other gases, the gas sensor has a small change of the drain current. </LI> <LI> As a result, the sensor has a high selectivity for NO<SUB>2</SUB> gas. </LI> </UL> </P>

Optimization of water-saturated superabsorbent polymers for hydrate-based gas storage

김민경,한금비,김현진,유지희,이영기,송택용,박진모,김요한,안윤호 한국화학공학회 2023 Korean Journal of Chemical Engineering Vol.40 No.5

Gas hydrates are an environmentally benign and cost-effective gas storage media that can store gas molecules in a lattice formed by hydrogen bonds between water molecules. To utilize gas hydrates on an industrial scale, the formation rate of gas hydrates must be improved. In this study, superabsorbent polymer (SAP) having a three-dimensional porous polymeric network was used to promote the formation of natural gas hydrates. SAP can absorb water efficiently and improve the kinetics of natural gas hydrates without mechanical agitation by expanding the gas-water interfacial area. The promotion effect of SAP is affected by various factors: the formation rate of natural gas hydrate and its reproducibility are determined by how water is dispersed over the SAP powders. Moreover, as the SAP is less crosslinked, the natural gas hydrate formation occurs more rapidly. The amount of saturated water is also a critical factor in determining the formation rate and yield of natural gas hydrates. Through this study, we provide engineering data to design hydrate-based gas storage media in a quiescent system for a large-scale application.

Gas Hydrates: A Cleaner Source of Energy and Opportunity for Innovative Technologies (Review)

Peter Englezos,Ju Dong Lee 한국화학공학회 2005 Korean Journal of Chemical Engineering Vol.22 No.5

The global energy system is characterized by a gradual de-carbonization and move to cleaner burning tech-is desired. Gas hydrate found in the earth’s crust is considered a source of natural gas that is essentially 100% methane(CH4) gas. Natural gas hydrate estimates worldwide range from 10,000 to 40,000 trillion cubic meters (TCM). Effortsare underway to exploit this resource. These methane hydrates in the earth’s crust also have the potential to be a signif-icant factor in global climate change. Moreover, gas hydrates ofer opportunities for the development of innovativetechnologies (separation of CO2 from CO2/N2 and CO2/H2 mixtures, CO2storage and H2 storage). In this work we assess the progress towards exploitation of gas hydrates as a resource for meth-ane (cleaner energy) and sumarize the state of the art with respect to the role of gas hydrates in the development of innovative technologies.

국내 가스사고와 기상자료의 데이터마이닝을 이용한 가스사고 예측모델 연구

허영택(Young-taeg Hur),신동일(Dongil Shin),이수경(Su-Kyung Lee) 한국가스학회 2012 한국가스학회지 Vol.16 No.1

본 연구에서는 국내 가스사고의 발생 환경을 분석하여 가스사고의 재발을 방지하고자 가스 사고를 유형별로 분석하였다. 가스사고는 지속적으로 발생하고 있고, 사고의 내용에서도 시기별, 날씨 등에 따라 가스사용 형태가 변하고 있어서 가스의 사용환경과 가스사고는 밀접한 관계가 있는 것으로 나타났다. 가스사고를 평균기온, 최고기온, 최저기온, 상대습도, 운량, 강수량 및 풍속의 7가지 기상요소별로 분석해 본 결과, 기온과 상대습도 등에 따라 영향을 받고 있은 것으로 나타났으며, 맑은 날, 풍속은 낮을 때 가스사고 발생빈도가 많았다. 가스사고 예측을 위하여 제시된 모델식을 활용하여 기상청의 일기예보 시스템과 연계하여 가스사고 발생 가능성을 실시간으로 제공하고, 회사의 업무시스템과 연계시켜 실시간으로 확인이 가능하도록 하여 가스사고 예방활동에 적극 활용할 수 있을 것으로 사료된다. Analysis on gas accidents by types occurred has been made to prevent the recurrence of accidents, through analysis of past history of gas accident occurring environment. The number of gas accidents has been decreasing, but still accidents are occurring steadily. Gas-using environment and gas accidents are estimated to be closely connected since gas-using types are changing by time period, weather, etc. in terms of accident contents. As a result of analysing gas accidents by 7 meteorological elements, such as the mean temperature, the highest temperature, the lowest temperature, relative humidity, the amount of clouds, precipitation and wind velocity, it has been found out that gas accidents are influenced by temperature or relative humidity, and accident occurs more frequently when the sky is clean and wind velocity is slow. Possibility of gas accidents can be provided in real time, using the proposed model made to predict gas accidents in connection with the weather forecast service. Possibility and number of gas accidents will be checked real time by connecting to the business system of Korea Gas Safety Corp., and it is considered that it would be positively used for preventing gas accidents.

이종접합 필름 가스 센서의 유해 가스 검출 및 민감도 특성 분석

김현수 대한설비관리학회 2023 대한설비관리학회지 Vol.28 No.4

In this study, we fabricated a NOx gas sensor using a multi-walled carbon nanotube (MWCNT)/zinc oxide (ZnO) composite film. The fabricated MWCNT/ZnO gas sensor was temperature processes at 450℃ and 710℃, resulting in an enhancement of detection sensitivity for NOx gas, as confirmed through the detection characteristics of NOx gas. Additionally, we compared the detection characteristics of MWCNT film gas sensors and MWCNT/ZnO composite film gas sensors. The fabricated gas sensor was used to detect NOX gas at different concentrations. The gas sensor absorbed NOx gas molecules with an associated increase in the sensitivity. The sensitivity of the gas sensor increased with increasing gas concentration. Furthermore, by varying the temperature inside the chamber for the MWCNT/ZnO composite film gas sensor, we observed high detection characteristics for NOx gas. As a result, the MWCNT/ZnO film gas sensor demonstrated superior performance in detecting NOx gas compared to the MWCNT gas sensor.

Prediction of Gas Flow Directions in Gas Assisted Injection Molding When Cavities and Runners Are Involved

Lim, Kwang-Hee,Lee, Eun Ju 한국화학공학회 2003 Korean Journal of Chemical Engineering Vol.20 No.3

In the prediction of gas flow-direction for gas-assisted injection molding (GAIM), the statement "Gas goes to the direction of the last area to fill with resin" has been accepted as a correct one. When there exists more than one area to fill with resin, a mold design engineer for GAIM technologies has to determine to which direction gas goes that commercial software for GAIM (e.g., Moldflow) may be utilized for its mold design. However commercial software is generally expensive and is sometimes hard to become familiar with. As a rule of thumb, it is suggested that the resistance to the initial velocity of melt polymer at the nearest geometry to a gas injection point should be used as its criterion since gas goes in the direction of least resistance to initial resin-velocity. Neither the flow rate nor the resistance to flow rate can be a criterion in the prediction. Thus the statement "Gas goes to the direction of the least resistance to flow rates" should be corrected to "More flow rate goes to the direction of the least resistance to flow rates. "The rule of thumb suggested in this paper was verified by using commercial software, Moldflow, in the prediction of gas flow directions in GAIM under geometries where cavities and runners were involved. When the ratio of initial resin-velocity is so close to unity it is proposed as the adapted rule of thumb to calculate new emerging resinvelocities and resistances to resinvelocity at the first coming change of diameters in series of pipes and to compare those for upper and lower sides each other to predict the gas direction. Thus the judgment as to which point is the point where gas starts to choose a preferred direction is very important in the prediction.