Determination Of Gas Concentrations Research Articles

Combined Seebeck and resistive SnO2 gas sensors, a new selective device

Simultaneous measurements of electrical resistance R and Seebeck e.m.f. Vs of thick film SnO2 gas sensors were performed in air containing different concentrations pi of reducing gas (ethanol vapours, CO, CH4, C2H6 were successively used). The graphical representations of the Vs versus ln h values both for the identification of the reducing gas (selectivity) and for the determination of gas concentration.

High-precision neural pre-processing for signal analysis of a sensor array

An array of semiconducting thin-film sensors is used for high-accuracy determination of gas concentrations in a binary mixture of H2S and NO2. For this purpose we developed a newly conceived pre-processing method for data feeding of a standard neural network. Pre-processing exploits dimension compaction of the vectorial signal of the sensor array. This operation is being accomplished by an auxiliary auto-associative network, separately trained from the main one. Our results present unprecedented accuracy even when applied to a validation-data set and appear to be of widespread application.

Dissolved gas concentration determination

Dissolved gas concentration determination

The use of partial least squares (PLS) in quantitative FTIR: Determination of gas concentrations in smoke gases of burning textiles

AbstractFourier transform infrared spectroscopy ca be used for on‐line smoke gas analysis of burning textile materials for several gases simultaneously. The technique is sensitive enough for the determination of the concentrations of compounds like H2O, CO2, Co, NO, NO2, SO2, C3H4O, HCI, HBr, HCN and HF. Quantitative analysis is, however, sometimes difficult to perform due to spectral interferences of two or more components. Simple mathematical techniques based on the direct relation between concentration and peak height or peak height or peak area then becomes impossible since they cannot be completely assigned to one component. Spectral subtraction can then be used but the results are sometimes unsatisfactory. Alternative techniques, like Partial Least Squares (PLS), Provide excellent possibilities to overcome the problems due to overlapping spectral features, without making use of spectral concentrations of different compounds in smoke gases. The use of PLS as a tool to overcome the problem of interfering of different compounds in smoke gases. The use of PLS as a tool to overcome the problem of interfering components is demonstrated by application to the overlapping spectral bands of H2O/CO2 and of H2O/NO. PLS calibration curves for other interfering components can be constructed in an analogous way.

Physical aspects of clinical measurement

Summary This chapter deals with the underlying concepts of physics and physicalchemistry as applied to anaesthesia research in the context of the associated techniques of physical measurement. The accuracy and performance characteristics, such as the response times of an instrument, are defined. The methods of measurement of flow rates include rotameters, flow controllers and pneumotachographs. The measurement of pressure under both static and dynamic conditions is discussed. The concepts of partial pressure underly the determination of gas concentration. The methods of gas analyses are divided into the underlying physical principles which affect both the inherent specificity and the limitations of the alternative techniques. These include those based on bulk properties of the gas (refractivity), spectroscopy (infra-red, ultra-violet and Raman), gas chromatography and mass spectrometry.

Planar imaging of a turbulent methane jet

Introduction I N this Note, concentration measurements are reported for a round methane jet discharging into air at moderate Reynolds number. The primary objective of this study was to compare concentrations determined by two independent methods, planar digital imaging and gas sampling (physical probe). Since elastic light scattering from small seed particles was used in the optical determination of gas concentration (i.e., marker nephelometry), the experiment also provided information on the adequacy of marker nephelometry at a relatively low Reynolds number.

Determination of gas concentrations and temperature in the exhaust of a power plant with a cw chemical HF laser

A cw chemical hydrogen fluoride laser system was used to investigate the exhaust of a gas and garbage burning power plant for the period of three months. The concentration of water vapor and carbon dioxide as well as the temperature in the exhaust was measured online with a time resolution as small as 5 ms. The temperature could be determined with a relative accuracy of better than 0.1 K over an averaging time of 9 s. This high accuracy together with the fast response make the system well suited not only for industrial combustion control but also for remote and precise measurement of temperature profiles.

A pulsed ultrasound transducer system for two component flow

There are industrial requirements for instrumentation of two and three component flows. The authors present an investigation into an ultrasound transducer suitable for determining gas concentration. A pair of ultrasound transducers are positioned opposite to each other, one on either side of the flow pipe. The transmitter is excited by pulses of power and pulsed ultrasound beams pass through the acoustic cavity between transmitter and receiver. The beam is randomly modulated in both amplitude and phase by either turbulent eddies in single phase fluids or suspended particles in two phases flows (e.g. sand in solid/liquid mixture, air bubbles in air/water mixture). The peak values of the output signal from the receiver are measured by a peak detector and, after time averaging, are functionally related to the concentration of the discontinuous phase. The main advantage of pulsed ultrasound sensors compared with the continuous wave (CW) ultrasound sensors is the avoidance of the deleterious effect of standing waves which occur in the acoustic cavity between transducers when CW is used. Therefore simpler and more reliable measurement systems can be built.

Gas concentration determination in fermentors with quadrupole mass spectrometer

In the pharmaceutical production it has a vital importance to determine and control the concentrations of gases involved in the fermentation process. Conventional methods are specific or difficult to handle and a quadrupole mass spectrometer with a sampling unit devised for this purpose proved to be the optimum means for measuring the concentrations of both the exit gases and the gases dissolved in the fermentation broth. The measuring system and examples of mass spectrometric monitoring of fermentation gases are presented.

Rare gases in the Lost City and Suchy Dul meteorites

Lost City /Oklahoma/ and Suchy Dul /Czechoslovakia/ bronzite chondrites stable rare gas concentration determination

Form and Function in the Human Lung

This small volume contains a wealth of valuable information concerning the structure and physiology of the normal and abnormal lung. Its contributors include most of the outstanding workers in the field. Many of the concepts presented are quite new, stimulating, and, indeed, occasionally controversial. The volume is divided into five sections based on the five sessions of the symposium: (1) the structure of the lung and the changes induced by disease, (2) factors determining gas concentration in the alveoli and the role of regional and stratified inhomogeneity, (3) factors determining blood flow in the pulmonary circulation, (4) the development of pulmonary hypertension and its relation to structural changes, and (5) the diagnosis of emphysema during life. Each section in turn is composed of two to four well-written and welledited chapters. There is little or no overlap between sections and chapters, a fault commonly encountered in multiauthored symposia. The discussion which

Molecular Correlation Spectrometry

The method of spectrometric determination of gas concentration by use of a mask is examined and described. Calibration curves for four gases, NH(3), C(6)H(5)CH(3), NO(2), and SO(2), are reported in detail, and results are included for C(6)H(6), NO, and SiF(4). The calibration curves are shown to be linear in a log-log plot over ranges of practical interest. The slopes are reproducible. The technique used in making masks is described. The proposed manner of making measurements involves the use of a small reference cell containing a sample of the gas being measured. When such a method of measurement is used, several gases of practical importance are concluded to be determined as to concentration to a few parts per billion with a precision of 10% or less, if path lengths of the order of several hundred meters are used. The results appear to be independent of the presence of unknown absorbing gases under many circumstances.

Factors affecting efficiency in fumigation with hydrocyanic acid

does not appear. First page follows. Introduction In most of the previous efforts to determine gas concentration, rate of diffusion, leakage, etc., in fumigation with hydrocyanic acid the results have been expressed in terms of insect kill. This method is not entirely adequate inasmuch as it fails to provide any data as to the actual concentration of gas present under the tent at any given time during the exposure, the rate of leakage through the tent, or the effect of temperature. In an effort to gain a more complete understanding of what actually occurs during fumigation the writer has attacked the problem from both the chemical and the entomological standpoint, with the following aims: (1) To ascertain the actual gas concentration necessary to kill coccinellid beetles (Hippodamia convergens Guer.) and red scale (Chrysomphalus aurantii Mask.); (2) to establish a standard of measurement by which the relative efficiency of different methods of fumigation might be determined; and (3) to apply the results thus obtained to the study of certain factors affecting killing efficiency under the conditions of orchard fumigation.