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Carbon dioxide (CO 2 ) and methane (CH 4 ) are natural and anthropogenic products that play a central role in the global carbon cycle and regulating Earth's climate. Applications utilizing laser absorption spectroscopy, which continuously measure concentrations and stable isotope ratios of these greenhouse gases, are routinely employed to measure the source and magnitude of atmospheric inputs. We developed a discrete sample introduction module (DSIM) to enable measurements of methane and CO 2 concentrations and δ 13 C values from limited volume (5-100 mL) gas samples when interfaced with a commercially available cavity ring-down spectroscopy (CRDS) analyzer. The analysis has a dynamic range that spans six orders of magnitude from 100% analyte to the lower limit of instrument detection (2 ppm). We demonstrate system performance for methane by comparing concentrations and δ 13 C results from the DSIM-CRDS system and traditional methods for a variety of sample types, including low concentration (nanomolar CH 4 ) seawater and high concentration (>90% CH 4 ) natural gas. The expansive concentration range of the field-portable DSIM-CRDS system can measure enhances analytical performance for investigating methane and CO 2 dynamics and, potentially, other gases measured by laser absorption spectroscopy.

Postmortem imaging consists in the non-invasive examination of bodies using medical imaging techniques. However, gas volume quantification and the interpretation of the gas collection results from cadavers remain difficult. We used whole-body postmortem multi-detector computed tomography (MDCT) followed by a full autopsy or external examination to detect the gaseous volumes in bodies. Gases were sampled from cardiac cavities, and the sample compositions were analyzed by headspace gas chromatography-mass spectrometry/thermal conductivity detection (HS-GC-MS/TCD). Three categories were defined according to the presumed origin of the gas: alteration/putrefaction, high-magnitude vital gas embolism (e.g., from scuba diving accident) and gas embolism of lower magnitude (e.g., following a traumatic injury). Cadaveric alteration gas was diagnosed even if only one gas from among hydrogen, hydrogen sulfide or methane was detected. In alteration cases, the carbon dioxide/nitrogen ratio was often >0.2, except in the case of advanced alteration, when methane presence was the best indicator. In the gas embolism cases (vital or not), hydrogen, hydrogen sulfide and methane were absent. Moreover, with high-magnitude vital gas embolisms, carbon dioxide content was >20%, and the carbon dioxide/nitrogen ratio was >0.2. With gas embolisms of lower magnitude (gas presence consecutive to a traumatic injury), carbon dioxide content was <20% and the carbon dioxide/nitrogen ratio was often <0.2. We found that gas analysis provided useful assistance to the postmortem imaging diagnosis of causes of death. Based on the quantifications of gaseous cardiac samples, reliable indicators were determined to document causes of death. MDCT examination of the body must be performed as quickly as possible, as does gas sampling, to avoid generating any artifactual alteration gases. Because of cardiac gas composition analysis, it is possible to distinguish alteration gases and gas embolisms of different magnitudes., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

The response of a flame ionisation detector (FID) on a gas chromatograph to methane, ethane, propane, i-butane and n-butane in a series of multi-component refinery gas standards was investigated to assess the matrix sensitivity of the instrument. High-accuracy synthetic gas standards, traceable to the International System of Units, were used to minimise uncertainties. The instrument response exhibited a small dependence on the component amount fraction: this behaviour, consistent with that of another FID, was thoroughly characterised over a wide range of component amount fractions and was shown to introduce a negligible bias in the analysis of refinery gas samples, provided a suitable reference standard is employed. No significant effects of the molar volume, density and viscosity of the gas mixtures on the instrument response were observed, indicating that the FID is suitable for the analysis of refinery gas mixtures over a wide range of component amount fractions provided that appropriate drift-correction procedures are employed., (Copyright © 2015 Elsevier B.V. All rights reserved.)

This article employs fluid equations to analyze muon beams in gases subject to crossed electric and magnetic fields, focusing, in particular, on a scheme proposed by Taqqu [Phys. Rev. Lett. 97, 194801 (2006)], whereby transverse compression of the beam is achieved by creating a density gradient in the gas. A general criterion for maximizing beam compression, derived from first principles, is then applied to determine optimal experimental conditions for μ+ in helium gas. Although the calculations require the input of transport data for (μ+, He), which are generally unavailable, this issue is circumvented by "aliasing" (μ+, He) with (H+, He), for which transport coefficient data are available. [ABSTRACT FROM AUTHOR]

There are many methods to diagnose transformer faults, including dissolved gas analysis (DGA), done in two conventional and smart ways. This paper presents a new method based on fuzzy logic and 5 DGA methods (key gas method, Durenberg's ratio method, Rogerˊs ratio method, IEC method, and Duval triangle method) to evaluate the condition of power transformers. At first, it is determined whether the transformer is healthy or defective. This step is performed based on key gas methods and Durenberg's ratio method with a fuzzy logic approach. Then, if it is detected that the transformer is defective, the type of error is detected using Rogers and IEC methods. If the error detection by these two methods reaches the same result, the error type detection is terminated and if the result is not the same, the Duval triangle method with fuzzy logic approach is used to detect the error type. The presented algorithm has been tested on 30 transformer devices and the results confirm its high accuracy (96.7%) in fault detection. In this article, in addition to detecting the type of fault, the location of the fault has been investigated and diagnosed using the CO2/CO ratio and the key gas method with a fuzzy logic approach. [ABSTRACT FROM AUTHOR]

Lithium iron phosphate (LFP) batteries are widely utilized in energy storage systems due to their numerous advantages. However, their further development is impeded by the issue of thermal runaway. This paper offers a comparative analysis of gas generation in thermal runaway incidents resulting from two abuse scenarios: thermal abuse and electrical abuse. The study initially focuses on 13-Ah lithium iron phosphate single-cell batteries. Experiments were conducted to induce thermal runaway through both forms of abuse, analyzing the production and dispersion of H2 and CO gases in each case. It was observed that thermal abuse–induced thermal runaway resulted in higher gas concentrations and more pronounced fluctuations, whereas electrical abuse–induced thermal runaway exhibited lower gas concentrations and lower fluctuations. Subsequently, key materials and temperature variations at the positive and negative electrodes were investigated under both types of thermal runaway, revealing distinct differences that are identified as the primary reasons for the significant disparities in H2 and CO gas generation during the two thermal runaway conditions. The conclusions drawn in this paper advance the understanding of the mechanisms underlying H2 and CO gas concentration generation in thermal runaway scenarios. [ABSTRACT FROM AUTHOR]

The emergence of dry gas seals has revolutionized the form of fluid sealing. The traditional research and analysis of dry gas seals is carried out by considering the lubricating medium gas as an ideal gas, but at this stage, the sealing application environment is complicated, so it is necessary to consider the real gas effect of the lubricating medium gas to expand and break through the design system of dry gas seals. We choose seven common lubricating media in dry gas seal applications and screen the optimal density expression of the real gas using different real gas equations of state. Then, we study the extent to which the compression factors of different lubricating gases deviate from the ideal gas and analyze the errors of different real gas equations of state. These results can provide an optimal expression to clarify the mechanism by which the real gas effect affects the dry gas seal performance, which helps to grasp the nature of dry gas seals, predict the dry gas seal behavior, and guide the dry gas seal application. [ABSTRACT FROM AUTHOR]

Power transformers are the most important and expensive assets in high-voltage power systems. To ensure an adequate level of reliability throughout the transformer's lifetime, its maintenance strategy must be well defined. When an incipient fault occurs in the transformer insulation, a gas concentration pattern, representative of the type of fault, is generated. Fault-identification methods use gas concentrations and their ratios to identify the type of fault. None of the traditional or new fault-identification methods attempt to detect transformer oil contamination from on-load tap changer (OLTC) gases. In this study, from dissolved gas analysis (DGA) samples of transformers identified as contaminated in a previous study, fault-identification methods based on graphical representations were used to observe the patterns of results. From such patterns, Duval's triangle and pentagon methods were modified to include a new zone indicating oil contamination (OC) from OLTC gases. Finally, the proposed modifications were validated using 75 DGA samples extracted from previous studies that were identified as D1 or D2 faults or contaminated from OLTC. This validation showed that only 14.7% and 13.3% of the DGA samples fell within the new OC zone of the proposed triangle and pentagon, respectively. [ABSTRACT FROM AUTHOR]

Air‐insulated switchgear plays an important role in distribution network and partial discharge (PD) is one of the common faults in its operation. The method of gas component analysis, which is to detect chemical gas products, is a novel one to discover PD. In order to study the feasibility of the method, the monitoring experiment of characteristic gases, comprising carbon monoxide (CO), nitrogen dioxide (NO2), and ozone (O3), of metal protrusion PD is carried out. This paper conducts the comparative experiments on three main factors affecting PD: voltage, air humidity and degree of protrusion, as well as studies how they affect the formation of characteristic gases. According to the experimental result, higher applied voltage promotes the formation of characteristic gases in the same conditions. In addition, with the increase of humidity from 40% to 75%, the generation of gases is inhibited. Furthermore, when the needle–plate distance is 30 mm, the gas concentration has almost no change within 6 h, which is different from that of 10 mm. In conclusion, the difference in gases concentration reveals the influence of three main factors on the generation of characteristic gases and provides an analytical basis for PD detection by gas composition analysis. [ABSTRACT FROM AUTHOR]

Lithium batteries are being utilized more widely, increasing the focus on their thermal safety, which is primarily brought on by their thermal runaway. This paper's focus is the energy storage power station's 50 Ah lithium iron phosphate battery. An in situ eruption study was conducted in an inert environment, while a thermal runaway experiment was conducted utilizing sealed pressure containers and an external heating triggering mechanism. Both the amount of gas release and the battery's maximum temperature were discovered. Using gas chromatography, the gas emission from the battery was examined. Its principal constituents included CO, H2, CO2, CH4, C2H4, and so on. Moreover, the experiment discovered a second eruption of lithium iron phosphate, and the stage of its eruption was separated by the pressure signal of the sealed experimental chamber, giving a theoretical foundation and technological backing for the thermal catastrophe safety of lithium batteries. [ABSTRACT FROM AUTHOR]

The force equilibrium and moment equilibrium play a significant role on the sealing performance of gas split floating ring seals. A small deflection angle may generate seriously wear on sealing surface and cause seal failure. Therefore, the thermo-hydrodynamic lubrication analysis of gas split floating ring seal with Rayleigh grooves is investigated considering the deflection angle and frictional heat of surface contact, which is beneficial to grasp the hydrodynamic characteristics and rules under high-temperature and high-speed conditions. Pressure and temperature distributions of sealing rings are numerically calculated for the cases with different deflection angle, rational speed, seal pressure and ambient temperature. Then, the hydrodynamic effect and sealing performance are analyzed. The obtained results show that, the surface Rayleigh step grooves do not present obvious hydrodynamic effect when split seal ring has no deflection. While, a significant hydrodynamic effect can be obtained when the split seal ring presents a deflection angle about dozens of micro radians. Here, a 10% increase of opening force is achieved when the deflection angle reaches 80 μrad in the case of speed 30,000 r/min and seal pressure 0.2 MPa. Moreover, the hydrodynamic effect becomes obvious with increasing deflection angle as well as rotational speed. Meanwhile, the growth of rotational speed results in an obvious increase of film temperature. The increase of ambient temperature has a significant influence on the decrease of leakage rate. When the ambient temperature increases from 340 K to 540 K, the leakage rate reduces exceeding 50%, however, it does not present obvious effect on the opening force. The proposed model has the potential to provide the theoretical basis and design guidance for surface grooves of gas split floating ring seal in the future. [ABSTRACT FROM AUTHOR]

In pouch cell modules, the sealing edges of the aluminum-plastic film are often installed facing either downward or up upward. The different sealing edge directions could lead to varying results of thermal runaway. The thermal runaway difference of different sealing edge install directions needs to be studied to help improve module safety. This paper proposes a novel experimental method for conducting thermal runaway tests on pouch cells with different sealing edge directions. The differences in heat generation and gas production of the cells are evaluated through Constant Volume Reactor and Gas Chromatograph analysis. The results indicate that the hazard is higher when the sealing edge is facing down compared to facing up. When thermal runaway is triggered in a 60 mm*60 mm heating area, the sealing edge facing downward delays the internal thermal runaway propagation time by 22.59 % compared to when it faces upward. The mass loss, peak venting pressure, and gas volume are respectively higher by 7.26 %, 14.52 %, and 1.78 %. Gas chromatograph analysis indicated minimal impact of sealing edge orientation on gas composition. This work provides guidance for the design of pouch cell modules, clarifying the optimal installation direction of sealing edges. • Thermal runaway venting behaviour of pouch cell. • The direction of sealing edge affects the thermal runaway. • The sealing edge facing downward poses a greater hazard of thermal runaway. [ABSTRACT FROM AUTHOR]

Operating experience has shown that characteristic gases can be found in oil‐immersed power transformers and high‐voltage reactors under strong vibration without discharge or thermal faults occurring. This will cause misdiagnosis of Dissolved Gases Analysis (DGA). In this study, generation characteristics and mechanism of characteristic gases in transformer oil dependent on vibration are investigated. The results show that there is a vibration pressure threshold that makes characteristic gases such as hydrogen (H2), methane (CH4), ethylene (C2H4), ethane (C2H6), and acetylene (C2H2) appear in transformer oil. The concentration of each characteristic gas increases with the increase of vibration pressure. Furthermore, misdiagnosis of insulation status which may be caused by vibration is illustrated based on Duval triangles method. Besides, vibration bubbling phenomenon in the experiment is observed. The generation mechanism of characteristic gases is analyzed with bubble dynamics under vibration. Higher vibration pressure induces cavitation processes and creates local thermal effects, which is the main reason for the generation of characteristic gases. A method based on combination of Duval triangle 1 and assistant triangle is proposed to distinguish characteristic gases generated by vibration from those generated by discharge and thermal faults. The results may provide theoretical support for fault identification and insulation state assessment of oil‐immersed power transformers and high‐voltage reactors. [ABSTRACT FROM AUTHOR]

The influence of impellers system, baffles system and type of liquid on gas hold-up in a vessel has been presented in this paper. The analysis of gas hold-up was conducted on the basis of the data obtained in the vessel. The vessel used in the study was of inner diameter D = 0.288 m, and it was filled with liquid up to a height of H = 0.576 m. The vessel used in the study was equipped in four planar standard baffles or 24 vertical tubular baffles located on the circuit. A high-speed impellers system, consisting of two impellers located on the shaft, was used to agitate the liquid. The six gas–liquid systems were tested. The gas used in the study was air. The liquids were distilled water, aqueous solutions of NaCl (concentration c = 0.4 kmol/m3 or 0.8 kmol/m3), aqueous solution of sucrose (concentration c = 2.5% mass., 5% mass.), 5% mass. aqueous solution of sucrose and yeast suspension concentration ys = 1% mass. The obtained set of over 1600 experimental points allowed to derive the equations describing the effect of gas flow number Kg, Weber number We and parameter Y (for air–water and air–aqueous solution of NaCl) and Kg, We, c and ys (for air–water, air–aqueous solution of sucrose and air–yeast suspension–aqueous solution of sucrose) on gas hold-up. These equations do not have equivalents in the literature. [ABSTRACT FROM AUTHOR]

Semiconductor manufacturing is performed through unit processes that use various chemicals and facilities. In particular, flammable gases, such as H2, NH3, and CH4, are used, and there is a risk of explosion when such gases leak. In this study, computational fluid dynamics (CFD) simulation and a "tracer gas test" according to the SEMI (Semiconductor Equipment and Materials International) S6 Environmental, Health, and Safety Guideline for Exhaust Ventilation of Semiconductor Manufacturing Equipment specification were performed during the leakage of hydrogen, a highly flammable gas used in the etching process of a gas box in the semiconductor industry. The CFD simulation was conducted to investigate the safety of semiconductor production facilities in relation to the explosion risk. Flow analysis was performed for the interior of a gas box used in the etching process. A steady-state analysis was performed to predict the concentration range of the explosion limit in the case of continuous hydrogen gas leakage. The interior of the gas box used in the simulation was modeled, and the ventilation flow rate, which has a significant impact on the leakage gas concentration distribution, obtained from experiments was used. The lower flammability limit (LFL) value of the leaked gas was 4% based on H2, and LFL/4 (25% of the LFL) was analyzed as the explosion limit concentration according to the acceptance criteria of the SEMI S6 tracer gas test. To validate the CFD simulation, a tracer gas test was performed according to SEMI S6. A mixture of hydrogen (5%) and nitrogen (95%) was used as the tracer gas. The flow rate was controlled by a gas regulator valve and measured using an Aalborg mass flow meter. The measured concentration of the tracer gas was calculated using the equivalent release concentration, which was calculated when 100% of the hydrogen was released, and the risk was assessed by comparing it with the LFL/4 of H2. [ABSTRACT FROM AUTHOR]

An oil-filled transformer should be able to operate for a long time with proper maintenance. One of the best diagnostic methods for oil-immersed transformer condition is dissolved gas analysis (DGA). However, there are times where the produce of stray gassing event might lead to fault indication in the transformer. Machine learning algorithms are used to classify the DGA data into normal condition and corresponding faults based on IEEE limits and Duval pentagon method. The algorithms that will be used include boosted trees, RUS boosted trees and subspace KNN, which belongs to the same ensemble group. Data resampling technique (SMOTETomek) is applied and shows further improvement on the accuracy of predictions by machine learning algorithms when deal with imbalance data. The algorithms are able to achieve the accuracy of 82.6% (boosted trees), 81.2% (RUS boosted trees) and 72.5% (subspace KNN), respectively, when validated with actual transformer condition. [ABSTRACT FROM AUTHOR]

The prediction of dynamic gas emission is of important significance for the prevention of gas accidents. Currently, multifield coupling theory has been applied to gas drainage, but the physical model of gas emission calculation is underused. In our research, a thermo-hydro-mechanical coupled gas emission (THMGE) model was constructed and verified with the results of gas emission in three driven headings. Through calculation, the effects of temperature, time, gas pressure, and tunneling speed on gas emission were analyzed. The research results show that gas emission is controlled by the coupling of the gas migration field, coal stress field, and coal gas temperature field. It is calculated that when the starting temperature is 298–318 K, the average gas emission increases by 3.51–6.13% as the temperature increases by 5 K. For exposure times of 10, 50, and 100 h, the gas emission is 0.47, 0.31, and 0.25 times the starting value, respectively. When the gas pressure is 1.5 and 2.0 MPa, the gas emission is 1.62 and 2.24 times the gas pressure of 1.0 MPa. The correlation coefficient between the model and experimental data is 0.912–0.961 and is successfully applied in the project, which provides a theoretical basis for the control of gas accidents. [ABSTRACT FROM AUTHOR]

The use of solubility coefficients for the measurement and evaluation of gas-in-oil analysis is critically discussed. A procedure for the relative calibration of headspace equipment for non-mineral insulating liquids, based on a known mineral oil calibration, is proposed. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to study the gas film stiffness of the spiral groove dry gas seal. Design/methodology/approach: The present study represents the first attempt to calculate gas film stiffness in consideration of the slipping effect by using the new test technology for dry gas seals. First, a theoretical model of modified generalized Reynolds equation is derived with slipping effect of a micro gap for spiral groove gas seal. Second, the test technology examines micro-scale gas film vibration and stationary ring vibration to determine gas film stiffness by establishing a dynamic test system. Findings: An optimum value of the spiral angle and groove depth for improved gas film stiffness is clearly seen: the spiral angle is 1.34 rad (76.8º) and the groove depth is 1 × 10–5 m. Moreover, it can be observed that optimal structural parameters can obtain higher gas film stiffness in the experiment. The average error between experiment and theory is less than 20%. Originality/value: The present study represents the first attempt to calculate gas film stiffness in consideration of the slipping effect by using the new test technology for dry gas seals. [ABSTRACT FROM AUTHOR]

We validated a procedure for the determination of indicator congeners (ICs) of polychlorinated biphenyls (PCBs) (IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) in water at an ultratrace concentration level in the range from 0.02 to 0.90 ng/L. The procedure includes collecting 1-L samples, extraction of PCBs with n-hexane, preconcentration of the extracts (kconc = 104), and the direct analysis of the preconcentrates by gas chromatography–tandem mass spectrometry. The chromatographic separation of the preconcentrates in columns with a carborane stationary phase (HT-8, 30 m), the detection of analytical peaks in the selected reaction monitoring mode, and the use of ICs labeled with 13C as surrogate internal standards ensured the high reliability of peak identification and the accuracy of quantitative determination with a total error (±δ, P = 0.95) of 35%. The procedure was tested in monitoring PCBs in the aquatic ecosystem of Lake Baikal, and the concentrations of ICs were determined in the upper water layer of the pelagic zone and the lake's tributaries. [ABSTRACT FROM AUTHOR]

Algae cultivation in open raceway ponds is considered the most economical method for photosynthetically producing biomass for biofuels, chemical feedstocks, and other high-value products. One of the primary challenges for open ponds is diminished biomass yields due to attack by grazers, competitors, and infectious organisms. Higher-frequency observations are needed for detection of grazer infections, which can rapidly reduce biomass levels. In this study, real-time measurements were performed using chemical ionization mass spectrometry (CIMS) to monitor the impact of grazer infections on cyanobacterial cultures. Numerous volatile gases were produced during healthy growth periods from freshwater Synechococcus elongatus Pasteur Culture Collection (PCC) 7942, with 6-methyl-5-hepten-2-one serving as a unique metabolic indicator of exponential growth. Following the introduction of a Tetrahymena ciliate grazer, the concentrations of multiple volatile species were observed to change after a latent period as short as 18 h. Nitrogenous gases, including ammonia and pyrroline, were found to be reliable indicators of grazing. Detection of grazing by CIMS showed indicators of infections much sooner than traditional methods, microscopy, and continuous fluorescence, which did not detect changes until 37 to 76 h after CIMS detection. CIMS analysis of gases produced by PCC 7942 further shows a complex temporal array of biomass-dependent volatile gas production, which demonstrates the potential for using volatile gas analysis as a diagnostic for grazer infections. Overall, these results show promise for the use of continuous volatile metabolite monitoring for the detection of grazing in algal monocultures, potentially reducing current grazing-induced biomass losses, which could save hundreds of millions of dollars. [ABSTRACT FROM AUTHOR]

Adopting yellow mud as barrier layer materials, coal and gas delay outburst experiments under conditions of geostress and gas accumulation disturbance were carried out by using self-developed simulation system, to find out roles of geostress and gas pressure played in the process of the delay outburst and ways to predict it, through analysis of variations of gas pressure, and AE characteristics during the process. The results show that after the geostress increased by 0.11 MPa from 1.80 MPa, an outburst occurs, while in gas accumulation situations, the gas pressure increase of 0.27 MPa from 0.67 MPa induces an outburst; hence, geostress is one of the dominant factors impacting an outburst occurrence. The lasting time of the outburst triggering under geostress disturbance is shorter than that under gas accumulation disturbance, while the duration of the outburst development under gas accumulation conditions is longer than that under geostress conditions. Coal seam breakage by geostress is the precondition for an outburst risk, and gas expansion energy is the dominant parameter influencing the duration of the outburst development. The AE signals show distinctive features in different stages of the outburst under geostress disturbance. At the preparation stage of the outburst, the AE signals increase sharply but have a low intensity and then drop to a lower balance level. At the triggering stage, the AE signals become active and increasing until up to the peak where the outburst occurs, and the intensity is highest. [ABSTRACT FROM AUTHOR]

The influence of the parameters (laser linewidths and profiles) of the CO2 laser based on the main molecular isotope on the absorption coefficient of a gaseous compound is analyzed using ammonia as an example. Results of application of the CO2 laser for the determination of the gaseous ammonia content are considered and possible errors in calculating the gas concentration caused by the neglect of the specific spectral linewidth of the CO2 laser are analyzed. [ABSTRACT FROM AUTHOR]

In this paper, a series of laboratory experiments are conducted to investigate the effect of momentary small variations in the transformer operating temperature on the dissolved gas analysis (DGA) measurement. With the increased penetration level of renewable energy sources of intermittent characteristics into electricity grids, operating power transformers are expected to experience frequent temperature variations. Sampling transformer oil during such temperature variation leads to inaccurate diagnosis. Experimental results reveal that gas evolution in transformer oil is greatly affected by the small variations in the operating temperature. Such small variation can be a result of the intermittent generation characteristics of renewable energy sources. Hence, false analysis may be reported if oil is sampled during generation or load fluctuation events. Experimental results are explained through chemical equilibrium constant theory, which indicates that dissolved gases reflect the change in aging rate of the transformer oil-paper insulation system. These results suggest a new paradigm for DGA process through correlating measurements with the transformer operating temperature through the generation and load profiles at the instant of oil sampling. [ABSTRACT FROM AUTHOR]

This work addresses the gas formation mechanisms for paraffinic-type mineral oil and soybean-based natural ester with a predominantly linoleic fatty acid under thermal faults. Based on a literature review, possible decomposition paths due to pyrolysis are proposed. A case study of hot spots of different temperatures is presented and its results are compared and analyzed with the gas profiles of the IEEE C57.155-2014 guide. The results obtained for both cases are consistent with the proposed mechanisms. For the same thermal fault, the gas profiles are different. The natural ester presents significant proportions of ethane and carbon dioxide concerning mineral oil. For temperature faults above 700 °C, the behavior of the chemical structures of the natural ester is similar to the carbon structures of the mineral oil and is subject to similar reactions. Therefore, the major differences in the gases generated for thermal faults are at low temperatures. [ABSTRACT FROM AUTHOR]

The investigation of technologically critical elements (TCEs) as emerging pollutants is a constantly growing field of environmental research and societal concern. Nevertheless, existing data for most TCEs are still unsatisfactory for an accurate assessment of their potential (eco)toxicological effects on humans and the environment. The limited availability of data mainly results from the technically challenging analysis of selected TCEs. Low concentrations of TCEs in environmental matrices (μg kg−1 or lower) and the associated complex and time-consuming sample preparation pose the greatest challenges. This work aims at developing a new ICP-MS/MS-based multi-elemental approach targeting the analysis of all major TCEs (Sc, Ga, Ge, Nb, In, Te, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Yb, Lu, and Ta) in sediment, which represents one of the most important matrices for environmental research. N2O is applied as a reaction gas to overcome possible spectral interferences during ICP-MS/MS analysis. The use of N2O as a reaction gas for ICP-MS/MS analysis enabled higher oxide-product ion yields for many TCEs in comparison to the frequently used O2 cell gas. Hence, the selectivity and sensitivity of the method were improved. The presented multi-element method using N2O as a reaction gas achieved LODs between 0.00023 μg L−1 (Eu) and 0.13 μg L−1 (Te) for all analyzed TCEs. Likewise, for all analyzed elements, except for Te, recoveries between 80% and 112% were obtained for at least one of the analyzed reference materials (GBW 07313, GBW 07311, and BCR-2). [ABSTRACT FROM AUTHOR]

To combat the increased emission rate and energy waste, a business case for an online optimizer was established to examine the energy-saving and emission reduction figures. Prior to embarking on this study, there is a need to understand the performance of oil and gas companies in managing the continuous flared gas. From the data gathered, it was quite evident that oil and gas operators do not significantly invest in optimizing gas flaring. The survey has included 706 participants from more than 59 different countries and indicated that there is a lack of awareness where regular monitoring of flared gas is overlooked. The survey shows about 17.6% of the participants never analyzed flared gas compositions, while only 36.6% of participants do this on monthly basis. More importantly, the survey indicated that most participants don't update their process operating conditions in response to day and night or yearly seasons thermal conditions. The optimization study is primarily focusing on having an online flared gas controller technique to continually monitor and analyze flared gas compositions with an intention to automatically manipulate separator operating conditions to increase the flared gas recovery. This approach was tested using a dynamic model developed for three real offshore and onshore oil and gas fields in Egypt and Saudi Arabia. In the three cases of study, this approach was able to adjust the operating conditions of the separator based on the flared gas analysis and the objective function identified to largely recover heavy hydrocarbons and control flared gas. [ABSTRACT FROM AUTHOR]

Objective. A rapidly growing home healthcare market has resulted in the development of many portable or wearable products. Most of these products measure, estimate, or calculate physiologic signals or parameters, such as step counts, blood pressure, or electrocardiogram. One of the most important applications in home healthcare is monitoring one's metabolic state since the change of metabolic state could reveal minor or major changes in one's health condition. A simple and noninvasive way to measure metabolism is through breath monitoring. With breath monitoring by breath gas analysis, two important indicators like the respiratory quotient (RQ) and resting energy exposure (REE) can be calculated. Therefore, we developed a portable respiratory gas analyzer for breath monitoring to monitor metabolic state, and the performance of the developed device was tested in a clinical trial. Approach. The subjects consisted of 40 healthy men and women. Subjects begin to measure exhalation gas using Vmax 29 for 15 minutes. After that, subjects begin to measure exhalation gas via the developed respiratory gas analyzer. Finally, the recorded data on the volume of oxygen (VO2), volume of carbon dioxide (VCO2), RQ, and REE were used to validate correlations between Vmax 29 and the developed respiratory gas analyzer. Results. The results showed that the root-mean-square errors (RMSE) values of VCO2, VO2, RQ, and REE are 0.0315, 0.0417, 0.504, and 0.127. Bland-Altman plots showed that most of the VCO2, VO2, RQ, and REE values are within 95% of the significance level. Conclusions. We have successfully developed and tested a portable respiratory gas analyzer for home healthcare. However, there are limitations of the clinical trial; the number of subjects is small in size, and the age and race of subjects are confined. The developed portable respiratory gas analyzer is a cost-efficient method for measuring metabolic state and a new application of home healthcare. [ABSTRACT FROM AUTHOR]

Analyses of the composition of exhaled gases are among important areas of non-invasive medicine. Diagnostics based on the analysis of exhaled gases offers several advantages over traditional laboratory methods. An analysis of a gas mixture is safe for the staff, because it does not involve chemical and biological fluids. The analysis is relatively inexpensive, takes little time, and ensures the detection of volatile components in the exhaled gas at the trace level of substances in real time. This paper discusses algorithms for the processing of mass spectra of exhaled gases obtained on an MC7-200 quadrupole mass spectrometer with electron ionization and the direct capillary injection of a sample. A comparative evaluation of algorithms for the detection of spectral lines in mass spectra based on data convolution with a model of response function or its derivatives is given. The Hermite function, the Gaussian function, and its even-order derivatives are considered as convolution kernels. The results of evaluation of the potential for increasing the signal-to-noise ratio by algorithms of convolution with these functions are presented. [ABSTRACT FROM AUTHOR]

Advancements in sensor devices have resulted in increased use of gas detection and concentration estimation in various fields. An electronic nose (E-nose) is an intelligent sensing device that mimics the human olfactory system and has been applied in gas analysis. We propose a multi-task learning–long short-term memory (MLSTM) recurrent network for simultaneous gas detection and concentration estimation, in which the two tasks share underlying features. The network utilizes the synergy between both two tasks, thereby enhancing the individual performances. Particle swarm optimization (PSO) proved a good method for optimizing the hyper-parameters used in the framework. The effectiveness of the framework and the parameter optimization method were verified by comparing the performances of the MLSTM model with those of eight models (two multi-task models, three classification models, and three regression models) using three datasets (two publicly available datasets and one dataset from the E-nose). The results showed that the proposed MLSTM model exhibited the best performance for simultaneous gas detection and concentration estimation because it was able to capture both global and local information. [ABSTRACT FROM AUTHOR]

This article investigates the effect of voltage sag propagation through the transformer due to various symmetrical and asymmetrical faults in a chronological manner. A unique and precise explanation has been presented for the propagation of voltage sag through different transformer connections. The effect of voltage sag has been studied in determining the healthiness of the transformer by analyzing the parameters of insulating oil obtained through dissolved gas analysis. For this purpose, different transformer winding connections have been considered, and the analysis has been performed considering the occurrence of all major faults. In order to justify and strengthen the proposal, a real-time case study has been deliberated for depicting the correlation of propagation of fault and its effect on transformer remaining in-service period through dissolved gas analysis. The study presented in this article will help utilities to understand the voltage sag propagation along with realizing its effect on transformer healthiness, thereby ensuring total system reliability and better economical service. [ABSTRACT FROM AUTHOR]

It is generally recognized that dissolved gas analysis (DGA) is a powerful tool in the diagnosis of insulating liquid filled power equipment. There exist numerous evaluating schemes for the mineral oil filled equipment, nevertheless, the experiences show that a fine tuning and revision of the schemes is required for equipment filled with synthetic esters. [ABSTRACT FROM AUTHOR]

This paper presents a fault tree analysis (FTA) method for the unavailability of supply of gas networks. The method is based on the automatic generation of fault trees, which estimate the probability of disruption of the gas delivery from terminals/storages to the demand nodes. Moreover, it allows probabilistic analyses of the availability of gas supply to individual demand nodes and to the overall gas network. To assess the importance of each network component, the risk achievement worth and the risk reduction worth importance measures are utilized. The developed method can identify weakness in the gas network and can guide expansion planning and maintenance scheduling activities. Furthermore, the developed framework is enriched by steady-state analysis of the gas network operations performed using a physical flow/pressure model. The impact of a component failure on the gas supply interruption at different demand nodes is assessed by the physical model in retrospective to the FTA results. The framework is exemplified with reference to the reduced gas network of Great Britain. The results provide insights to support a robust reliability assessment of the gas network. Moreover, the probability mapping of the most important components in the gas network informs optimal strategies for maintenance scheduling as well for prioritizing improvements of the gas network aimed at significant risk reduction. Remarkably, the failure of components identified as most important according to the FTA importance measures may not have significant effects on the gas supply. A discussion on the range of applicability and limitations of the two methodologies is provided. [ABSTRACT FROM AUTHOR]

The CO2 is regarded to be an excellent solvent for miscible flooding. However, it is still facing a main problem which is the high mobility. Microbubbles with their unique characters offer some advantages for CO2 EOR application. Different pore throat size filters were used to generate different dominant sizes of microbubbles that were injected into sandpacks under tertiary condition. Microscopic analysis was carried out to visualize the presence, stability and behavior of microbubbles inside the solution and porous media. The microbubbles with a dominant size of 10–50 µm showed additional 26.38% of oil recovery, showing their advantages over a larger dominant size of microbubbles up to 5.28% of oil recovery. The injection with larger microbubbles with a dominant size of 70–150 µm showed 27.5% of higher injection pressure than with a smaller dominant size of microbubbles, showing their advantage in gas blocking ability. In the heterogeneous porous media experiment, the recovery volume ratio between low- and high-permeability sandpacks was increased from 1:57 during water flooding to 1:4 during the CO2 microbubble injection with 74.65% of additional recovery from a low-permeability zone, showing the microbubble gas blocking capability to change the flow pattern inside heterogeneous porous media. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effects of C 2 + and H 2 S on the ν 1 (CH 4) peak position in CH 4 -dominated gas. • New Raman quantification factors for determining the composition of wet gas. • Application to wet gas inclusion analysis in the Sichuan Basin, South China. • Previous estimate of the trapping depth for wet gas inclusion was overestimated. Carbonaceous fluid within mineral-hosted inclusions provides important information for carbon cycle in deep Earth. In addition to CH 4 and CO 2 , heavy hydrocarbons (e.g., C 2 H 6 and C 3 H 8) are frequently observed in carbonaceous fluid inclusions (i.e, wet gas inclusions with C 1 /∑C i < 0.95). However, determination of the composition of such complex volatiles is difficult based on traditional microthermometric measurements. Here we carried out experimental calibrations on Raman spectroscopic measurements of the pressure (P) and composition of the CH 4 ± C 2 H 6 ± C 3 H 8 ± H 2 S system at room temperature and 0.1–130 MPa. We confirmed that the C–H symmetric stretching vibration band of CH 4 [ν 1 (CH 4), ∼2917 cm−1] shifted to lower wavenumber with rising pressure, thus the P -ν 1 (CH 4) relationship could be applied to calculate the pressure of wet gas. It should be noted that the presence of C 2 + and/or H 2 S will shift the [ν 1 (CH 4)] to lower wavenumber at constant pressure (with the order of C 3 H 8 ≥ H 2 S > C 2 H 6). Obviously, the P -ν 1 (CH 4) relationship derived from pure CH 4 system could not be simply applied to wet gas inclusion, otherwise the pressure would be overestimated. To avoid the overlap of the C–H vibrations of CH 4 , C 2 H 6 and C 3 H 8 , the peak areas and peak heights of the overtone vibration of CH 4 [2ν 4 (CH 4), ∼2580 cm−1], C–C symmetric stretching vibrations of C 2 H 6 [ν 3 (C 2 H 6), ∼995 cm−1] and C 3 H 8 [ν 8 (C 3 H 8), ∼868 cm−1], and S–H symmetric stretching vibration of H 2 S [ν 1 (H 2 S), ∼2612 cm−1] were fitted using Gaussian + Lorentz functions. The obtained peak areas and peak heights were then used to calculate the Raman quantification factors (F factor and G factor, respectively) of C 2 H 6 , C 3 H 8 and H 2 S relative to CH 4 , respectively. Both the F factor and G factor increased with rising pressure, whereas the F C 2 H 6 , F C 3 H 8 and G H 2 S kept nearly constant at ∼5.69, 6.39 and 153.8, respectively in high pressure gas mixtures (e.g., >30 MPa). Therefore, for inclusions with higher internal pressure, the molar ratio of CH 4 , C 2 H 6 , C 3 H 8 and H 2 S could be determined by the aforementioned F and G factors. This method was applied to the calcite-hosted single-phase gas inclusions in the Upper Permian Changxing Formation carbonate reservoir from the eastern Sichuan Basin (South China). Our results indicated that the trapping pressure would be obviously overestimated if the presence of heavy hydrocarbons was not taken into account. [ABSTRACT FROM AUTHOR]

Dissolved gases analysis (DGA) provides widely recognized practice for oil-immersed power transformers, and it is mainly interpreted for fault diagnosis. In order to accurately estimate the health index state of power transformers and predict the incipient operation failure, a dynamic fault prediction technique based on hidden Markov model (HMM) of DGA is proposed in this paper. Gaussian mixture model, as a soft clustering method, is used to extract the static features of different health states from a DGA dataset of 65 in-service power transformers with 1600 days operation. Especially, a sub-health state is introduced to enrich the health index and aging stages of power transformers. The static features between health states and concentrations of dissolved gases are built, and the effectiveness of clustering is cross validated. Furthermore, taking time sequence into consideration, transition probability of power transformer between different health states based on the HMM model is calculated and analyzed. The effectiveness of dynamic early warning and incipient fault prediction in sub-health status of in-service power transformers has been proved. Moreover, the dynamic fault prediction is able to provide decision-making basis for practical condition-based operation and maintenances. [ABSTRACT FROM AUTHOR]

An intelligent transformer fault diagnostic model is the urgent need of reliable power system. To achieve this goal, a diagnostic system using a dissolved gas analysis (DGA)-based fault interpretation matrix (FIM) is proposed. FIM overcomes the issues of contradictory decisions of independent methods and provides low-complexity solution in comparison with the previous literature for transformer fault diagnosis. The developed system has accuracy enhancement and decision-making stages. In the first stage, fuzzy augmentation of three important DGA methods, namely Rogers', IEC and Duval triangle, is carried out followed by the FIM stage and an intermediate normalisation stage. The output of fuzzy models serves as input to the matrix which smartly interprets the fault along with its criticality by exploiting the advantages of individual methods in diagnosing particular fault. This matrix integrates fuzzy augmented methods as per priorities assigned to their outputs. The rules of integration are constructed based on performance assessing factors of individual fuzzy models, and overall decision is made on sensitivity of method for the particular fault type. The performance evaluation of FIM shows its improved diagnostic ability which is intended to improve reliability of DGA-based condition monitoring. [ABSTRACT FROM AUTHOR]

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Abstract A gas tank is an important storage facility in chemical enterprises. When an explosion occurs, it can easily cause mass injury and death. This paper takes a 50,000 m3 gas tank as an example to analyze the consequences of an accident. First, a TNT-equivalent explosion model, quantitative risk analysis and FLACS software are used to quantitatively analyze the explosion consequences. The range of casualties caused by the vapor cloud explosion is obtained. The simulation results are then compared with the actual damage range of a gas tank explosion, and the accuracy of the simulation results is verified. Next, the personal and social risks of a gas tank are identified according to China's national standards, and it is concluded that the individual risk can be tolerated, the social risk is within the tolerable range and its area has been reduced as far as possible, and it is necessary to minimize the overall risk as much as possible. Finally, a qualitative analysis of the gas tank explosion accident is carried out and the causes of the accident are analyzed. These analyses can be used to guide practices and effectively prevent the occurrence of similar accidents. Graphical abstract Unlabelled Image Highlights • Obtain the range of casualties caused by the vapor cloud explosion. • The actual damage range is verified by simulation results for the first time. • Personal and social risks of a gas tank explosion are identified. • Guide practices and effectively prevent the occurrence of similar accidents. [ABSTRACT FROM AUTHOR]

Abstract 40Ar/39Ar stepwise crushing technique has become more important for dating hydrothermal fluids trapped in mineral-hosted fluid inclusions. However, understanding the gas release patterns and interpreting the 40Ar/39Ar dating results have remained challenging. Here we use 40Ar/39Ar analyses coupled with quadrupole mass spectrometer (QMS) analyses of gases released by stepwise crushing to reconstruct the hydrothermal activities recorded by fluid inclusions hosted by wolframite, cassiterite, and quartz from the Yaogangxian tungsten deposit in South China. Microscopic observations and laser Raman spectroscopic studies reveal two main groups of fluid inclusions hosted in hydrothermal minerals: small, isolated and CH 4 -rich primary fluid inclusions (PFIs), and larger, mostly CO 2 -rich secondary fluid inclusions (SFIs) that distribute along micro-cracks. Formamide and alkane in the vapor phases of large aqueous SFIs are also found. The QMS analyses reveal systematic compositional features for gases released during different crushing stages: (1) gases from the initial crushing stage are H 2 O-poor, CO 2 -rich with CO 2 /CH 4 > 1, likely dominated by gases from large vapor-rich SFIs; (2) gases from the final crushing stage are CH 4 -dominated gas mixtures with CO 2 /CH 4 < 1, likely dominated by gases from small PFIs; while (3) gases from the intermediate stage are rich in H 2 O, formamide, and ethane, which resemble gases from large liquid-rich SFIs. Combined results from microscopic observations, and Raman and QMS analyses suggest that stepwise crushing extracts gases progressively from large vapor-rich SFIs, large aqueous SFIs to small PFIs. Similarly, gases released during each crushing stage have distinct 40Ar/39Ar compositions and corresponding ages. Gases released during the initial crushing stage show high and correlated 40Ar* and 38Ar Cl signals with abnormally old 40Ar/39Ar ages, which could be related to the vapor-rich SFIs. Gases released during the final crushing stage yield 40Ar/39Ar ages of 159–154 Ma, which agree well with stepwise heating 40Ar/39Ar age (156 ± 0.9 Ma) of intergrown muscovite and published ore-forming ages. We propose that the 40Ar/39Ar ages of gases released during the final crushing stage are reasonable age estimates for the PFIs. Gases released during the intermediate stage yield 40Ar/39Ar ages of 128–127 Ma, which agree well with stepwise heating 40Ar/39Ar age (129 ± 2.1 Ma) of the cross-cutting K-feldspar vein. This result likely suggests that intermediate stage gases mainly derived from aqueous SFIs that formed during late-stage hydrothermal events. In this study, we demonstrate that gas release patterns revealed by 40Ar/39Ar stepwise crushing are consistent with those revealed by Raman and QMS analyses. Therefore, combining these techniques provides a better picture of the timing and nature of hydrothermal geofluids in general. [ABSTRACT FROM AUTHOR]

Spontaneous combustion of coal is one of the major hazards threatening production safety during longwall mining. Mining-induced voids, which provide passages for air leakage, are the key factor triggering spontaneous combustion of coal in longwall goafs. In this study, a comprehensive method, which combined pressure balance, grouting injection, and filling fissures, was proposed to prevent spontaneous combustion of coal in longwall goafs with complex air leakage. Field engineering practice was carried out in Sitai Coal Mine in China. The results demonstrated that with the application of the proposed method, in the working face, the concentration of CO was decreased from 31ppm to 0 and the air leakage quantity was decreased from 261 to below 80 m3min-1. The gas samples analysis from the gob areas also indicated that concentrations of O2 and CO were successively decreased, indicating that the risk of spontaneous combustion of coal in goafs was eliminated. The above mentioned analysis indicates that, the method proposed in this study is useful and efficient. Successful application of this technology could provide reference for the treatment of other coal mines. [ABSTRACT FROM AUTHOR]