Gas Concentration Monitoring Research Articles

Non-invasive cardiac output evaluation in postoperative cardiac surgery patients, using a new prolonged expiration-based technique

The gold standard methods to measure cardiac output (CO) are invasive and expose the patient to high risks of various complications. The aim of this study is to assess an innovative non-invasive method for CO monitoring in mechanically ventilated patients after cardiac surgery and its agreement with values obtained by thermodilution technique. Continuous monitoring of respiratory gas concentrations and airflow allows the estimation of CO through a newly developed algorithm derived from a modified version of the Fick equation. It consists of two phases: the first involves measurements during steady breathing state, and the second starts when a sudden perturbation into the carbon dioxide elimination process is introduced by a prolonged expiration. This prospective clinical study involved thirty-five adult patients, undergone cardiac surgery. The measurements were performed in curarized and haemodynamically stable patients, during the post-surgery recovery in intensive care unit. The study protocol, which lasted 1h for each patient, consisted of 20 measurements obtained by prolonged expiration-based method and 10 by thermodilution. The estimation of CO using the proposed method (COK) agreed with the thermodilution (COT) as demonstrated by: a low mean bias between COK and COT considering all patients (i.e., -0.11Lmin(-1)); a best fitting line having slope=0.98, r=0.81, p<0.0001; the lower and upper limits of agreement were -0.77 and +0.54Lmin(-1), respectively. COK shows a mean percentage error of 34%. In stable mechanically ventilated patients, undergone cardiac surgery, the proposed method is reliable if compared to the thermodilution. Considering the non-invasivity of the technique, further evaluations of its performances are encouraged.

Dry deposition of nitrogen compounds (NO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, HNO&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;, NH&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;), sulfur dioxide and ozone in west and central African ecosystems using the inferential method

Abstract. This work is part of the IDAF program (IGAC-DEBITS-AFRICA) and is based on the long-term monitoring of gas concentrations (1998–2007) established at seven remote sites representative of major African ecosystems. Dry deposition fluxes were estimated by the inferential method using on the one hand surface measurements of gas concentrations (NO2, HNO3, NH3, SO2 and O3) and on the other hand modeled exchange rates. Dry deposition velocities (Vd) were calculated using the big-leaf model of Zhang et al. (2003b). The bidirectional approach is used for NH3 surface–atmosphere exchange (Zhang et al., 2010). Surface and meteorological conditions specific to IDAF sites have been used in the models of deposition. The seasonal and annual mean variations of gaseous dry deposition fluxes (NO2, HNO3, NH3, O3 and SO2) are analyzed. Along the latitudinal transect of ecosystems, the annual mean dry deposition fluxes of nitrogen compounds range from −0.4 to −0.8 kg N ha−1 yr−1 for NO2, from −0.7 to −1.0 kg N ha−1 yr−1 for HNO3 and from −0.7 to −8.3 kg N ha−1 yr−1 for NH3 over the study period (1998–2007). The total nitrogen dry deposition flux (NO2+HNO3+NH3) is more important in forests (−10 kg N ha−1 yr−1) than in wet and dry savannas (−1.6 to −3.9 kg N ha−1 yr−1). The annual mean dry deposition fluxes of ozone range between −11 and −19 kg ha−1 yr−1 in dry and wet savannas, and −11 and −13 kg ha−1 yr−1 in forests. Lowest O3 dry deposition fluxes in forests are correlated to low measured O3 concentrations, lower by a factor of 2–3, compared to other ecosystems. Along the ecosystem transect, the annual mean of SO2 dry deposition fluxes presents low values and a small variability (−0.5 to −1 kg S ha−1 yr−1). No specific trend in the interannual variability of these gaseous dry deposition fluxes is observed over the study period.

Nitrous Oxide as a Tracer Gas in the ASHRAE 110-1995 Standard

ANSI/ASHRAE Standard 110 provides a quantitative method for testing the performance of laboratory fume hoods. Through release of a known quantity (4.0 Lpm) of a tracer gas, and subsequent monitoring of the tracer gas concentration in the “breathing zone” of a mannequin positioned in front of the hood, this method allows for evaluation of laboratory hood performance. Standard 110 specifies sulfur hexafluoride (SF6) as the tracer gas; however, suitable alternatives are allowed. Through three series of performance tests, this analysis serves to investigate the use of nitrous oxide (N2O) as an alternate tracer gas for hood performance testing. Single gas tests were performed according to ASHRAE Standard 110-1995 with each tracer gas individually. These tests showed identical results using an acceptance criterion of AU 0.1 with the sash half open, nominal 18 inches (0.46m) high, and the face velocity at a nominal 60 fpm (0.3 m/s). Most data collected in these single gas tests, for both tracer gases, were below the minimum detection limit, thus two dual gas tests were developed for simultaneous sampling of both tracer gases. Dual gas dual ejector tests were performed with both tracer gases released simultaneously through two ejectors, and the concentration measured with two detectors using a common sampling probe. Dual gas single ejector tests were performed with both tracer gases released though a single ejector, and the concentration measured in the same manner as the dual gas dual ejector tests. The dual gas dual ejector tests showed excellent correlation, with R typically greater than 0.9. Variance was observed in the resulting regression line for each hood, likely due to non-symmetry between the two challenges caused by variables beyond the control of the investigators. Dual gas single ejector tests resulted in exceptional correlation, with R>0.99 typically for the consolidated data, with a slope of 1.0. These data indicate equivalent results for ASHRAE 110 performance testing using either SF6 or N2O, indicating N2O as an applicable alternate tracer gas.

Design and Research on the Gas Monitoring System Based on LabVIEW

Gas detection alarm system plays a more and more important role in People's Daily life and every field. This paper proposes semiconductor gas sensors and SCM as the core, which could achieves the gas concentration monitoring and alarm functions. The gas monitoring system includes host computer that consists of LabVIEW operating interface and slave computer that constructed with AT89C51 microcomputer and MQ-2 gas sensor.It achieves remote monitoring and controlling housing environment in real-time and has a certain practical value in society.

Research on the Mine Safety Monitoring System Based on Wireless Sensor Network Technology

The development of computers wireless network monitoring system mainly includes steps such as the selection of transmission protocol, the calls of database program, data display and automation implementation and so on. The transmission speed of protocol TD-SCDMA is faster. In addition, it also can transmit voice and pure data files. Thus, this article selects TD-SCDMA protocol as transport protocol of wireless sensor networks. On the basis of the software OLEDB, this paper has developed ActiveX Data Object program, and has implemented the safety supervision automation process of wireless sensor network technology. Finally, this paper uses VC++ software to make a numerical simulation experiment on computer programs by taking an example of coal mine gas monitoring. At the same time, through the display on the window, it is the gas concentration monitoring curve that is obtained when the mine safety is abnormal, which provides the safeguard for mine personnel safety and normal work.

Sensors for the ultra-fast monitoring of explosive gas concentrations

The target of this paper is answering the question about the minimum response time of metal oxide semiconductor gas sensors. This question is very important at the monitoring of sudden explosive emission of high concentrations of combustible gases in mines, chemical and oil refinery factories, nuclear power stations, etc. To reach this target, we eliminated the influence of internal and external diffusion to the sensor response time by the optimization of the thickness of sensing layer, deposition conditions, material, and working temperature of the sensor. As a result, it was possible to fabricate the sensor with very short response time ∼ 160ms (hexane) in a concentration range up to 12vol%. The response time of the sensor was compared with the response time of IR optic sensor based on LED (λ=3.4μm) using testing gas mixing installation equipped with ultra-fast valves. The effect of sensing layer thickness and the conditions necessary to exclude the influence of reagent and product diffusion through the sensing layer to the response time were studied in detail. It was shown that, if the thickness of thin film sensing layer exceeds 200nm, the sensor response rate is diffusion limited, the diffusion coefficient corresponding to inter-grain diffusion at 550°C was estimated as (1.5±0.5)·10−10cm2/s. The results were proven in field experiment with spike emission of petrol aerosol.

Gas Concentration Monitoring System Based on Soft Redundancy and ZigBee

The scheme based on soft redundancy and ZigBee is introduced due to the inadequacy of existing mine gas concentration monitoring system. The system is divided into underground and aerial parts. The gas concentration of mine working site can be tested automatically by underground part, which can transmit the data to the ground using ZigBee wireless communications technology. Two sets of identically configured PLC control system constitute the aerial part, which can meet redundancy requirements by procedures and directives. The solid technical support in mine safe operation can be provided based on the system, which improves the stability and reliability of the gas concentration monitoring.

Tunable multi-mode diode laser absorption spectroscopy for methane detection

Tunable multi-mode diode laser absorption spectroscopy for methane detection was demonstrated. The exclusive dependence of the 1318nm laser modes distribution on the input current and temperature was justified. Stable absorption signals related to the methane concentrations were obtained based on second-harmonic detection technique. A real-time data recording and analyzing software program was developed to realize the on-line gas concentration monitoring. A measurement sensitivity of 25ppmm and an accuracy of 0.27% of this system were achieved.

An optical ammonia (NH3) gas sensing by means of Pd/CuPc interferometric nanostructures based on white light interferometry

The monitoring of ammonia gas concentrations by means of an optoelectronic gas sensor is described in this paper. An optoelectronic gas sensor based on interferometric, gasochromic nanostructures contains Cu-phthalocyanine (CuPc) thin films and palladium (Pd) thin film. The optical changes (interferometric colour changes) that occur Pd/CuPc or CuPc are due to being exposed to different relative humidites (RH) or various ammonia concentrations (at 70°C). The CuPc films were deposited by thermal evaporation. Additionally, to enhance the sensing performance of these CuPc thin films, the surfaces of CuPc were coated with an ultra-thin film of palladium. This metallic Pd film can act as catalyst that increasing the efficiency of dissociation of the molecular ammonia gas to its more reactive atomic form in order to enhance the surface reaction during the gas sensing. The thin films of Pd were obtained also by means of the vacuum-thermal method.When a physical–chemical interaction between the sensing structure and ammonia gas is taking place (on the sensing window of the measuring channel), the interferential colour of the sensing element (nanostructure) changes and colour coordinates the measuring optical signal will also change. The colour sensor TCS230 detecting the intensity and change of the colour coordinates RGB of the optical signal resulting from the exposure sensing structure to ammonia gas. An optical ammonia gas sensor displays a very fast response time and a fast regeneration time at low temperature (70°C) in a dry and humid gaseous environment.

Inhaled Anesthetic Agent-Vaporizer Mismatch

Agent-specific vaporizers minimize opportunities for error and evidence our specialty's commitment to patient safety as a general principle. End-tidal anesthetic gas concentration monitoring is a useful adjunct whenever inhaled anesthetics are used in operating rooms. Due to their expense and required maintenance, end-tidal anesthetic gas monitors are not commonly used in developing nations. Unfortunately, in resource-constrained environments, situations may arise in which inhaled anesthetic agent-vaporizer mismatch may be necessary in the absence of end-tidal anesthetic gas monitoring. Rather than merely censure such practice as a threat to safety, we believe that certain anesthetic agent-vaporizer mismatch situations can be safely managed providing patients with predictable inspired anesthetic gas concentrations while minimizing errors. We present an approach based on mathematical models and tested in an artificial lung model. Mismatching of inhaled agent and vaporizer is a dangerous practice and should not be performed unless it is absolutely necessary. Such situations may arise in remote locations where neither end-tidal anesthetic gas monitoring nor vaporizer-specific agent is available. We hope our article provides guidance in such situations.

ZigBee技术无线瓦斯报警系统的设计与实现

瓦斯泄露的检测与报警是煤矿开采安全生产中的重点监控对象。本文使用ZigBee无线通信模块组网技术和MQ-5的瓦斯浓度探测传感器与温湿度传感器设计并实现了无线瓦斯浓度报警系统。本无线瓦斯报警器系统，能够起到多节点瓦斯浓度采集、自动组网、远距离报警的作用。与传统的单点矿井瓦斯报警器相比，本报警系统使用电池供电具有布置灵活、低功耗、测量采集精度高、容灾性高等特点，可应用于煤炭井下开采的瓦斯浓度监控，可大大降低煤矿瓦斯爆炸的安全隐患。 The gas leak detection and alarm is the most important coal mining safety production supervision and control object. This article uses the ZigBee wireless networking technology of communication module and MQ-5 gas concentration detection sensor with temperature and humidity sensors, designs and implements the wireless gas concentration alarm system. The wireless gas concentration alarm system can play multi-node capture, automatic networking and remote alarm roles. Compared with the traditional single-point mine gas alarm, the alarm system has the characteristics such as flexible layout, low power consumption, high accuracy measurement acquisition, disaster tolerance and so on. It can be applied to the gas concentration monitoring in the coal mine and can greatly reduce the gas explosion.

Study on the temperature modified method for monitoring gas concentrations with tunable diode laser absorption spectroscopy

Tunable diode laser absorption spectroscopy (TDLAS) is often used to detect gas concentrations in many fields. But because of the variation of ambient temperature, the measured harmonic signal amplitudes are affected and may lead to the monitoring errors. The impact of temperature on the measurement as well as the temperature compensation method is emphasized. So in order to modify the inversion results and adapt industrial measurement, combustion diagnostics, the numerical fitting empirical modified equation and theoretical modified equation from HITRAN database are discussed and compared in this paper. In experiment, the 21% oxygen as the safety monitoring gas and absorption wavelength at 760.77 nm are employed. Meanwhile, the first harmonic signals are also used to decrease the laser intensity fluctuations. We thus obtained the unmodified and modified results with the tube furnace in the temperature range 300–900 K (interval 50 K). Experimental results show that these two modified methods have some effective influence on the temperature changes and can be applied to gas monitoring correction to improve the accuracy and feasibility of the TDLAS technology. In addition, the methods also provide evidence for the real-time gas monitoring in the application of combustion diagnosis.

Nutrient Fate and Transport in the Vadose Zone below an At-Grade Wastewater Distribution System in a Cold Climate

AbstractAt-grade distribution systems for wastewater treatment represent potential sources of nutrient input to the environment. The efficacy of nutrient treatment in the vadose zone below an at-grade distribution system receiving secondary treated municipal wastewater effluent was studied on silt loam soil at a site in Calgary, Alberta, Canada, where there are large seasonal temperature fluctuations and cold winter conditions. In addition to wastewater effluent characterization, field monitoring of pore water chemistry, soil temperature, and interstitial soil gas concentrations was conducted at five different depths (up to 150 cm below surface) over the 47-week effluent dosing period. Results showed that ammonium-N from the applied effluent was effectively nitrified in the top 30 cm of the soil profile. While there was evidence for subsequent nitrate removal by denitrification in this same zone, it was limited to the warm summer months and did not appear to result in significant nitrogen mass removal (5–...

A review of continuous soil gas monitoring related to CCS – Technical advances and lessons learned

One of the most vigorously discussed issues related to Carbon Capture and Storage (CCS) in the public and scientific community is the development of adequate monitoring strategies. Geological monitoring is mostly related to large scale migration of the injected CO2 in the storage formations. However, public interest (or fear as that) is more related to massive CO2 discharge at the surface and possible affects on human health and the environment. Public acceptance of CO2 sequestration will only be achieved if secure and comprehensible monitoring methods for the natural habitat exist. For this reason the compulsory directive 2009/31/EG of the European Union as well as other international regulations demand a monitoring strategy for CO2 at the surface. The variation of CO2 emissions of different soil types and vegetation is extremely large. Hence, reliable statements on actual CO2 emissions can only be made using continuous long-term gas-concentration measurements. Here the lessons learned from the (to the authors’ knowledge) first world-wide continuous gas concentration monitoring program applied on a selected site in the Altmark area (Germany), are described.This paper focuses on the authors’ technical experiences and recommendations for further extensive monitoring programs related to CCS. Although many of the individual statements and suggestions have been addressed in the literature, a comprehensive overview is presented of the main technical and scientific issues. The most important topics are the reliability of the single stations as well as range of the measured parameters. Each selected site needs a thorough pre-investigation with respect to the depth of the biologically active zone and potential free water level. For the site installation and interface the application of small drill holes is recommended for quantifying the soil gas by means of a closed circuit design. This configuration allows for the effective drying of the soil gas and avoids pressure disturbance in the soil gas. Standard soil parameters (humidity, temperature) as well as local weather data are crucial for site specific interpretation of the data. The complexity, time and effort to handle a dozen (or even more) single stations in a large case study should not be underestimated. Management and control of data, automatic data handling and presentation must be considered right from the beginning of the monitoring. Quality control is a pre-condition for reproducible measurements, correct interpretation and subsequently for public acceptance. From the experience with the recent monitoring program it is strongly recommended that baseline measurements should start at least 3 a before any gas injection to the reservoir.

Mid-infrared virtually imaged phased array spectrometer for rapid and broadband trace gas detection

We present and characterize a two-dimensional (2D) imaging spectrometer based on a virtually imaged phased array (VIPA) disperser for rapid, high-resolution molecular detection using mid-infrared (MIR) frequency combs at 3.1 and 3.8 μm. We demonstrate detection of CH4 at 3.1 μm with >3750 resolution elements spanning >80 nm with ~600 MHz resolution in a <10 μs acquisition time. In addition to broadband detection, we also demonstrate rapid, time-resolved single-image detection by capturing dynamic concentration changes of CH4 at a rate of ~375 frames per second. Changes in absorption above the noise floor of 5×10(-4) are readily detected on the millisecond time scale, leading to important future applications such as real-time monitoring of trace gas concentrations and detection of reactive intermediates.

Hardware Design of Coal Mine Safety Monitoring System Based on WSN

In the safety production of coal mine, monitoring exact and real-time mine parameter is very important and key problem. The monitoring system of mine environment with wireless is designed, which is based on the structure of wireless sensor network (WSN).The system includes sensor node, Sink node and monitoring center. In the paper, the function structure and hardware design of sensor are introduced for the monitoring of temperature, humidity and gas concentration, and the function structure and hardware design of sink node is designed. The system has low power, rapid real-timing, stable running. Etc. This can satisfy with the requirement of WSN and suit the monitoring of bad environments. It will have wide application prospect.

Design of Colliery Gas Monitoring Alarm System Based on DSP

A monitoring and alarm system of colliery gas has been designed with DSP technology. It has been simulated with CCS. The simulation results have shown that this system can realize the real-time on-line monitoring of the colliery gas concentration and auto-alarm when the concentration overruns.

Measuring System for Longtime Monitoring and Visualization of Temperature and Toxic Gases Concentration

The contribution describes a developed measuring system intended for long-term monitoring of temperatures and hazardous gas concentrations within old mining dumps affected by thermal processes. It includes a short introduction describing the creation of thermal processes, including related hazards and impact on the environment. Furthermore, the contribution provides a detailed analysis of sensors for measuring CO and CH4 gas concentrations. It provides the advantages and disadvantages of the individual sensors, including the experience with their use. The conclusion contains a description of the complex measuring chain, including the data transfer technology and visualization at the dispatching station. Ill. 5, bibl. 7 (in English; abstracts in English and Lithuanian).DOI: http://dx.doi.org/10.5755/j01.eee.122.6.1838

Fiber Optic Temperature and Gas Concentration Sensor for Mine Goaf Area Inner Detecting

Spontaneous combustion in coal goaf area is one of major disasters in coal mines. Detection technology based on signature Gas and Temperature is the primary means of spontaneous combustion forecasting of coal goaf area. A real-time remote fire detection system is proposed based on tunable diode laser absorption spectroscopy technology and FBG temperature sensing technology, to achieve valid detect of gas concentration and temperature. The System include fiber mathen concentration sensor and fiber temperature sensor based FBG. The system achieved remote on-line monitoring of gas concentration and temperature in mine goaf, meet the fire forecast need for Coal goaf area. There are obvious advantages Compared with the existing beam tube monitoring system in coal mine.

Mine Gas Wireless Monitoring and Forecasting Network Based on Support Vector Machine

Gas monitoring is considered as the most important mean in the safe production of coalmine. Time delay inevitably exists in the current gas monitoring technology widely used today. This research uses Support vector machine to forecast gas concentration. ZigBee wireless network protocol is adopted so that a wireless gas monitoring network with concentration predicting function is obtained. In this way the present time delay in Gas concentration monitoring will be improved and the scope of monitoring will be expanded at the same time