Fraction Of Carbon Dioxide Research Articles

Preservation of Natural Phase Balance in Multi-pass and Wire Arc Additive Manufacturing-Made Duplex Stainless Steel Structures

This work investigates the effects of Ar-based shielding gases on the microstructure and phase balance of duplex stainless steel (DSS) depositions. The results are then used for fabrication of DSS walls using wire arc additive manufacturing (WAAM), and the microstructural characteristics and mechanical performance of the products are assessed. WAAM currently poses as one of the most interesting methods of manufacturing by enabling joining of materials to fabricate structures layer by layer. However, the extreme conditions imposed by the process, such as high heat inputs and re-melt and solidification of the deposited layers, could compromise the performance of the products. A detailed microstructural analysis is conducted on single layer and double layer depositions of DSS to assess the effects of different shielding gases on the ferrite/austenite phase balance in the specimens. The results show that the depositions shielded with a small fraction of carbon dioxide (CO2) present better microstructural features in comparison to depositions shielded with the other selected gases. A mixture of 98%Ar + 2%CO2 was employed for fabrication of a 60-layer DSS WAAM-made wall and some mechanical characteristics were studied. The mechanical examinations demonstrate that the properties of the parts fabricated using WAAM are comparable with their wrought counterparts.

Urban-focused satellite CO2 observations from the Orbiting Carbon Observatory-3: A first look at the Los Angeles megacity

NASA's Orbiting Carbon Observatory-3 (OCO-3) was designed to support the quantification and monitoring of anthropogenic CO2 emissions. Its Snapshot Area Map (SAM) and target mode measurements provide an innovative dataset for carbon studies on sub-city scales. Unlike any other current space-based instrument, OCO-3 has the ability to scan large contiguous areas of emission hot spots like cities, power plants, and volcanoes. These measurements result in dense, fine-scale spatial maps of column averaged dry-air mole fractions of carbon dioxide (XCO2). For the first time, we present and analyze XCO2 distributions over the Los Angeles megacity (LA) derived from OCO-3 SAM and target mode observations. Urban XCO2 enhancements range from 0 − 6 ppm (median enhancements ≃ 2 ppm) relative to a clean background and show excellent agreement with nearby ground-based TCCON measurements of XCO2. OCO-3's dense observations reveal intra-urban variations of XCO2 over the city that have never been observed from space before. The spatial variations are mainly driven by the complex fossil fuel emission patterns and meteorological conditions in the LA Basin and are in good agreement with those from co-located TROPOMI measurements of co-emitted NO2. Differences between measured and simulated XCO2 enhancements from two models (WRF-Chem and X-STILT) are typically below 1 ppm with larger differences for some sub regions. Both models capture the observed intra-urban XCO2 gradients. Further, OCO-3's multi-swath measurements capture about three times as much of the city emissions compared to single-swath overpasses. OCO-3's frequent target and SAM mode observations will pave the way to constrain urban emissions at finer, sub-city scales.

Shipborne measurements of XCO<sub>2</sub>, XCH<sub>4</sub>, and XCO above the Pacific Ocean and comparison to CAMS atmospheric analyses and S5P/TROPOMI

Abstract. Measurements of atmospheric column-averaged dry-air mole fractions of carbon dioxide (XCO2), methane (XCH4), and carbon monoxide (XCO) have been collected across the Pacific Ocean during the Measuring Ocean REferences 2 (MORE-2) campaign in June 2019. We deployed a shipborne variant of the EM27/SUN Fourier transform spectrometer (FTS) on board the German R/V Sonne which, during MORE-2, crossed the Pacific Ocean from Vancouver, Canada, to Singapore. Equipped with a specially manufactured fast solar tracker, the FTS operated in direct-sun viewing geometry during the ship cruise reliably delivering solar absorption spectra in the shortwave infrared spectral range (4000 to 11000 cm−1). After filtering and bias correcting the dataset, we report on XCO2, XCH4, and XCO measurements for 22 d along a trajectory that largely aligns with 30∘ N of latitude between 140∘ W and 120∘ E of longitude. The dataset has been scaled to the Total Carbon Column Observing Network (TCCON) station in Karlsruhe, Germany, before and after the MORE-2 campaign through side-by-side measurements. The 1σ repeatability of hourly means of XCO2, XCH4, and XCO is found to be 0.24 ppm, 1.1 ppb, and 0.75 ppb, respectively. The Copernicus Atmosphere Monitoring Service (CAMS) models gridded concentration fields of the atmospheric composition using assimilated satellite observations, which show excellent agreement of 0.52±0.31 ppm for XCO2, 0.9±4.1 ppb for XCH4, and 3.2±3.4 ppb for XCO (mean difference ± SD, standard deviation, of differences for entire record) with our observations. Likewise, we find excellent agreement to within 2.2±6.6 ppb with the XCO observations of the TROPOspheric MOnitoring Instrument (TROPOMI) on the Sentinel-5 Precursor satellite (S5P). The shipborne measurements are accessible at https://doi.org/10.1594/PANGAEA.917240 (Knapp et al., 2020).

Oil Extraction from Rice Bran Using Expanded Liquid Hexane with CO2

Bio-oil is often extracted from biomass using liquid solvent or supercritical carbon dioxide. However, extraction using these methods has several disadvantages. In this study, expanded hexane with carbon dioxide is examined as a new extraction solvent. The objective of this study is to develop a new technique for the extraction of bio-oil from biomass using expanded hexane with carbon dioxide; rice bran is used as the raw biomass. The extraction was carried out at 25— 27°C, 5.0—5.3 MPa, and 0.78—0.94 mole fraction of carbon dioxide in expanded hexane. At 26°C, 5.1 MPa, 0.87 of mole fraction of carbon dioxide, the oil yield was 1.6 times greater than that with normal liquid hexane because of the low viscosity and high permeability of expanded hexane. Furthermore, the phosphorus concentration in the extracted oil was 9.5 ppm. This was very low, compared with that in rice bran,in which it is approximately 350 ppm. This was because the solvent power of expanded hexane to extract neutral lipid decreased slightly while that to extract polar components decreased significantly. As a result, expanded hexane with carbon dioxide could extract the phosphorus-free bio-oil in high yield under mild conditions.

Effect of Carbon Dioxide Fractional Laser on the Levels of Regulated Upon Activation Normal T-Cell Expressed and Secretedserum Chemokines and Vitiligo Clinical Scoring in Stable Non-Segmental Vitiligo: A Case-Control Study

Effect of Carbon Dioxide Fractional Laser on the Levels of Regulated Upon Activation Normal T-Cell Expressed and Secretedserum Chemokines and Vitiligo Clinical Scoring in Stable Non-Segmental Vitiligo: A Case-Control Study

The Roman amphitheatre in Mérida, Spain ˗Augustan or Flavian? Radiocarbon dating results on mortar carbonate

Abstract Four lime mortar samples from the Mérida amphitheatre in Spain were dated in 2001 and re-dated in 2019 with refined dating methods and focus on carbon dioxide that was released in late CO2 fractions when dissolved in phosphoric acid. The samples were difficult to date because they contained highly soluble, young carbonate contamination that dominated the carbon dioxide from the early stages of the reaction with the acid in the hydrolysis process. They were also rather hydraulic and rich in magnesium, which could have caused delayed hardening. However, there was very little dead carbon contamination so that late carbon dioxide fraction gave uniform 14C ages, pointing to a late 1st c. AD Flavian, or later age of the amphitheatre.

Effects of carbon dioxide addition to fuel on flame radiation fraction in propane diffusion flames

The flame radiation fraction of the turbulent jet diffusion flame of propane and carbon dioxide mixed gas was studied under the ambient temperature of 300 K and the pressure of 1 bar. The diameters of the nozzle were 2, 3, and 4 mm. Different flow rates of propane and carbon dioxide were controlled to obtain different concentration ratios. The results showed that for a given heat release rate, the flame heat radiation fraction decreases with increasing the concentration of carbon dioxide in the gas mixture. Theories of soot formation and laminar flame speed were used to explain the evolution of the radiation fraction under different volume fractions of carbon dioxide. A correlation model about the relationship among the radiation fraction, heat release rate, and fuel equivalent ratio was proposed.

Local Anomalies in the Column-Averaged Dry Air Mole Fractions of Carbon Dioxide Across the Globe During the First Months of the Coronavirus Recession.

We use a global transport model and satellite retrievals of the carbon dioxide (CO2) column average to explore the impact of CO2 emissions reductions that occurred during the economic downturn at the start of the Covid‐19 pandemic. The changes in the column averages are substantial in a few places of the model global grid, but the induced gradients are most often less than the random errors of the retrievals. The current necessity to restrict the quality‐assured column retrievals to almost cloud‐free areas appears to be a major obstacle in identifying changes in CO2 emissions. Indeed, large changes have occurred in the presence of clouds, and in places that were cloud free in 2020, the comparison with previous years is hampered by different cloud conditions during these years. We therefore recommend to favor all‐weather CO2 monitoring systems, at least in situ, to support international efforts to reduce emissions.

The Significance of Fast Radiative Transfer for Hyperspectral SWIR XCO2 Retrievals

Fast radiative transfer (RT) methods are commonplace in most algorithms which retrieve the column-averaged dry-mole fraction of carbon dioxide (XCO2) in the Earth’s atmosphere. These methods are required to keep the computational effort at a manageable level and to allow for operational processing of tens of thousands of measurements per day. Without utilizing any fast RT method, the involved computation times would be one to two orders of magnitude larger. In this study, we investigate three established methods within the same retrieval algorithm, and for the first time, analyze the impact of the fast RT method while keeping every other aspect of the algorithm the same. We perform XCO2 retrievals on measurements from the OCO-2 instrument and apply quality filters and parametric bias correction. We find that the central 50% of scene-by-scene differences in XCO2 between retrieval sets, after threshold filtering and bias correction, that use different fast RT methods, are less than 0.40 ppm for land scenes, and less than 0.11 ppm for ocean scenes. Significant regional differences larger than 0.3 ppm are observed and further studies with larger samples and regional-scale subsets need to be undertaken to fully understand the impact on applications that utilize space-based XCO2.

Indirect calorimetry: best results with close monitoring of the carbon dioxide fraction in exhaled air

This study describes methods to improve resting energy expenditure (REE) estimated by the indirect calorimetry by evaluating predictors for the achievement of steady-state conditions (SSC). Cross-sectional study carried out with 20 women (30.2 ± 4.1 years; 27.8 ± 6.7 kg/m2). Indirect calorimetry was performed with the Quark RMR® calorimeter, during a 15-min period. VO2 consumption and VCO2 production were measured and data was collected every 5 s. Specific spreadsheet was used to compute the values of Steady REE and Software REE (deltaREE). Bias and concordance between values were assessed by the Bland-Altman plot and Lin’s correlation coefficient. There is an almost perfect concordance between Software REE and Steady REE (p = 0.001). Steady% was important for predicting deltaREE while variation of carbon dioxide exhaled (CVFECO2) was significant to predict Steady%. Also, CVFECO2 was strongly and significantly correlated with the CV of VO2 (r = 0.83, p = 0001) and with the CV of VCO2 (r = 0.9, p = 0001). FECO2 should be sustained without huge variations to ensure SSC when using a calorimeter based on the canopy dilution technique with spontaneous breathing patients of similar characteristics. Also, these results suggest that since SSC occurs at least one time in the test, the Software REE may be considered reliable.

Numerical simulation of bread baking in a convection oven

The paper reports on a numerical study conducted to simulate the bread baking process in an industrial convection oven. This involves predicting the unsteady multiphase flow and heat and mass transfer fields within the oven while accounting for changes in bread properties and volume. The clean air and combustion gases circulate inside the oven in two separate compartments. In the clean section, the rotational motion of the blower needed to move air around is modeled following a rotating reference frame approach, while the increase in bread volume is accounted for by a dynamic mesh. Moreover, to predict the motion of the grid, a general model for loaf expansion is developed based on the changes in the volume of the bread’s water and carbon dioxide content during baking. In addition, the bread is modeled as a porous material and therefore generated solutions account for the loaf porosity, volume expansion, water evaporation and condensation, starch gelatinization, and release of carbon dioxide. The numerical solution is validated by demonstrating, for one bread, that predictions are in good agreement with experimental measurements. Finally, numerical results for the full setup are reported in the form of hydrodynamic and thermal fields in the oven, contour plots of temperature and volume fraction of water and carbon dioxide along cross-sections of the baking chamber and the bread, bread deformation, and transient profiles of average quantities. It is found that generated results are in agreement with work reported in the literature demonstrating that the developed model can be used to optimize the performance of the oven and the bread baking process.

Optimal Sizing of Stand Alone Hybrid Renewable Energy System with Load Shifting

ABSTRACT In the present study, a model is proposed for the sizing optimization of a hybrid renewable energy system (HRES) based on local resource assessment and demand side management (DSM). It involves resource estimation for both micro hydro and solar photovoltaic systems. The sizing optimization of the HRES with or without load shifting based DSM is carried out using PSO (particle swarm optimization) and BBO (biogeography-based optimization) techniques. The purpose of DSM is to reduce the peak hourly power consumption. The cycle charging dispatch strategy has been used for sizing optimization of HRES. A comparative analysis has been made for PSO and BBO algorithms, by keeping energy index ratio at 1. Based on demand side management, the cost of energy, net present cost, renewable fraction, and emissions of carbon dioxide from diesel generators are also calculated. The results show that HRES with diesel generator (DG) of (10 kW), solar photovoltaic system (SPV) of (0.3 kW), and batteries of (300 Ah) each are most cost effective in the present scenario. This HRES combination consists of 4 units of DGs, 184 units SPV, and 44 units battery possesses 95.31% of renewable fraction during load shifting process with BBO algorithm. Finally, the proposed, model is validated with HOMER.

Validation of XCO<sub>2</sub> and XCH<sub>4</sub> retrieved from a portable Fourier transform spectrometer with those from in situ profiles from aircraft-borne instruments

Abstract. Column-averaged dry-air mole fractions of carbon dioxide (XCO2) and methane (XCH4) measured by a solar viewing portable Fourier transform spectrometer (FTS, EM27/SUN) have been characterized and validated by comparison using in situ profile measurements made during the transfer flights of two aircraft campaigns: Korea-United States Air Quality Study (KORUS-AQ) and Effect of Megacities on the Transport and Transformation of Pollutants at Regional and Global Scales (EMeRGe). The aircraft flew over two Total Carbon Column Observing Network (TCCON) sites: Rikubetsu, Japan (43.46∘ N, 143.77∘ E), for the KORUS-AQ campaign and Burgos, Philippines (18.53∘ N, 120.65∘ E), for the EMeRGe campaign. The EM27/SUN was deployed at the corresponding TCCON sites during the overflights. The mole fraction profiles obtained by the aircraft over Rikubetsu differed between the ascending and the descending flights above approximately 8 km for both CO2 and CH4. Because the spatial pattern of tropopause heights based on potential vorticity values from the ERA5 reanalysis shows that the tropopause height over the Rikubetsu site was consistent with the descending profile, we used only the descending profile to compare with the EM27/SUN data. Both the XCO2 and XCH4 derived from the descending profiles over Burgos were lower than those from the ascending profiles. Output from the Weather Research and Forecasting Model indicates that higher CO2 for the ascending profile originated in central Luzon, an industrialized and densely populated region about 400 km south of the Burgos TCCON site. Air masses observed with the EM27/SUN overlap better with those from the descending aircraft profiles than those from the ascending aircraft profiles with respect to their properties such as origin and atmospheric residence times. Consequently, the descending aircraft profiles were used for the comparison with the EM27/SUN data. The EM27/SUN XCO2 and XCH4 data were derived by using the GGG2014 software without applying air-mass-independent correction factors (AICFs). The comparison of the EM27/SUN observations with the aircraft data revealed that, on average, the EM27/SUN XCO2 data were biased low by 1.22 % and the EM27/SUN XCH4 data were biased low by 1.71 %. The resulting AICFs of 0.9878 for XCO2 and 0.9829 for XCH4 were obtained for the EM27/SUN. Applying AICFs being utilized for the TCCON data (0.9898 for XCO2 and 0.9765 for XCH4) to the EM27/SUN data induces an underestimate for XCO2 and an overestimate for XCH4.

Retrieval and Validation of XCO2 from TanSat Target Mode Observations in Beijing

Satellite observation is one of the main methods used to monitor the global distribution and variation of atmospheric carbon dioxide (CO2). Several CO2 monitoring satellites have been successfully launched, including Japan’s Greenhouse Gases Observing SATellite (GOSAT), the USA’s Orbiting Carbon Observatory-2 (OCO-2), and China’s Carbon Dioxide Observation Satellite Mission (TanSat). Satellite observation targeting the ground-based Fourier transform spectrometer (FTS) station is the most effective technique for validating satellite CO2 measurement precision. In this study, the coincident observations from TanSat and ground-based FTS were performed numerous times in Beijing under a clear sky. The column-averaged dry-air mole fraction of carbon dioxide (XCO2) obtained from TanSat was retrieved by the Department for Eco-Environmental Informatics (DEEI) of China’s State Key Laboratory of Resources and Environmental Information System based on a full physical model. The comparison and validation of the TanSat target mode observations revealed that the average of the XCO2 bias between TanSat retrievals and ground-based FTS measurements was 2.62 ppm, with a standard deviation (SD) of the mean difference of 1.41 ppm, which met the accuracy standard of 1% required by the mission tasks. With bias correction, the mean absolute error (MAE) improved to 1.11 ppm and the SD of the mean difference fell to 1.35 ppm. We compared simultaneous observations from GOSAT and OCO-2 Level 2 (L2) bias-corrected products within a ±1° latitude and longitude box centered at the ground-based FTS station in Beijing. The results indicated that measurements from GOSAT and OCO-2 were 1.8 ppm and 1.76 ppm higher than the FTS measurements on 20 June 2018, on which the daily observation bias of the TanSat XOC2 results was 1.87 ppm. These validation efforts have proven that TanSat can measure XCO2 effectively. In addition, the DEEI-retrieved XCO2 results agreed well with measurements from GOSAT, OCO-2, and the Beijing ground-based FTS.

Intercomparison of atmospheric CO<sub>2</sub> and CH<sub>4</sub> abundances on regional scales in boreal areas using Copernicus Atmosphere Monitoring Service (CAMS) analysis, COllaborative Carbon Column Observing Network (COCCON) spectrometers, and Sentinel-5 Precursor satellite observations

Abstract. We compare the atmospheric column-averaged dry-air mole fractions of carbon dioxide (XCO2) and methane (XCH4) measured with a pair of COllaborative Carbon Column Observing Network (COCCON) spectrometers at Kiruna and Sodankylä (boreal areas). We compare model data provided by the Copernicus Atmosphere Monitoring Service (CAMS) between 2017 and 2019 with XCH4 data from the recently launched Sentinel-5 Precursor (S5P) satellite between 2018 and 2019. In addition, measured and modeled gradients of XCO2 and XCH4 (ΔXCO2 and ΔXCH4) on regional scales are investigated. Both sites show a similar and very good correlation between COCCON retrievals and the modeled CAMS XCO2 data, while CAMS data are biased high with respect to COCCON by 3.72 ppm (±1.80 ppm) in Kiruna and 3.46 ppm (±1.73 ppm) in Sodankylä on average. For XCH4, CAMS values are higher than the COCCON observations by 0.33 ppb (±11.93 ppb) in Kiruna and 7.39 ppb (±10.92 ppb) in Sodankylä. In contrast, the S5P satellite generally measures lower atmospheric XCH4 than the COCCON spectrometers, with a mean difference of 9.69 ppb (±20.51 ppb) in Kiruna and 3.36 ppb (±17.05 ppb) in Sodankylä. We compare the gradients of XCO2 and XCH4 (ΔXCO2 and ΔXCH4) between Kiruna and Sodankylä derived from CAMS analysis and COCCON and S5P measurements to study the capability of detecting sources and sinks on regional scales. The correlations in ΔXCO2 and ΔXCH4 between the different datasets are generally smaller than the correlations in XCO2 and XCH4 between the datasets at either site. The ΔXCO2 values predicted by CAMS are generally higher than those observed with COCCON with a slope of 0.51. The ΔXCH4 values predicted by CAMS are mostly higher than those observed with COCCON with a slope of 0.65, covering a larger dataset than the comparison between S5P and COCCON. When comparing CAMS ΔXCH4 with COCCON ΔXCH4 only in S5P overpass days (slope = 0.53), the correlation is close to that between S5P and COCCON (slope = 0.51). CAMS, COCCON, and S5P predict gradients in reasonable agreement. However, the small number of observations coinciding with S5P limits our ability to verify the performance of this spaceborne sensor. We detect no significant impact of ground albedo and viewing zenith angle on the S5P results. Both sites show similar situations with the average ratios of XCH4 (S5P/COCCON) of 0.9949±0.0118 in Kiruna and 0.9953±0.0089 in Sodankylä. Overall, the results indicate that the COCCON instruments have the capability of measuring greenhouse gas (GHG) gradients on regional scales, and observations performed with the portable spectrometers can contribute to inferring sources and sinks and to validating spaceborne greenhouse gas sensors. To our knowledge, this is the first published study using COCCON spectrometers for the validation of XCH4 measurements collected by S5P.

Investigation of the Effects of Steam Injection on Equilibrium Products and Thermodynamic Properties of Diesel and Biodiesel Fuels

The effects of steam injection on combustion products and thermodynamic properties of diesel fuel, soybean oil-based biodiesel (NBD), and waste cooking oil biodiesel (WCOB) are examined in this study by considering the chemical equilibrium. The model gives equilibrium mole fractions, specific heat of the exhaust mixtures of 10 combustion products, and adiabatic flame temperatures. The results show that the mole fractions of carbon monoxide (CO) and carbon dioxide (CO2) decrease with the steam injection ratios. Nitric oxide (NO) mole fractions decrease with the steam injections ratios for lean mixtures. The specific heat of combustion products increases with the steam injection ratios. The equilibrium combustion products obtained can be used to calculate the nonequilibrium values of NO in the exhaust gases using some existing correlations of NO kinetics.

RESULTS OF RESEARCH FOR THE USE OF THE BIOGAS AND METHANE MIXTURE IN A GAS POWER PLANT ENGINE

The analysis of scientific publications over the past ten years in the line of creating gas ICEs in Ukraine, operating on natural gas, biogas or similar low-calorie fuels has been carried out. The objectives of the work are to summarize the results of studies on the use of model gas in a gas internal combustion engine operating as a power plant drive, to develop recommendations on biogas additives to natural gas depending on the power plant load, and to develop a fuel supply control algorithm. It is possible to simplify labor intensity of experimental work with the help of model gas - a mixture of natural and carbon dioxide. The article provides recommendations on setting up the power system and automatic regulation of a gas engine running on a mixture of natural gas (methane) and biogas. To solve the tasks, research was carried out on a gas-electric plant with a rated capacity of 30 kW. The unit was originally equipped with a spark-ignited 8-cylinder petrol engine and an electric generator. The base ICE was converted to pure gas engine with a compression ratio of 8.5. In the physical modeling of biogas to natural gas additives in the model gas, the volume fraction of carbon dioxide was increased to 30 % depending on the external load. By calculation, we determined a similar ratio of compressed natural gas and biogas additives. For the calculation, it was assumed that compressed natural gas contains 90...95 % of methane, and biogas 60 % of methane and 40% of carbon dioxide. The possibility of using biogas with 60 % methane as an additive to natural gas in piston ICEs with spark ignition has been confirmed. It was found that with a decrease in load, the share of biogas can increase and replace up to 85% of natural gas. When working on biogas additives, the values of the concentrations of hydrocarbons and residual oxygen in the exhaust gases were determined to control the setting of the gas equipment of the internal combustion engine. Under operating conditions, three test modes have been selected for the power plant: idle, 50 % load, rated mode. The research results can serve as the basis for creating a control algorithm for the supply of biogas additives to natural gas, depending on load changes.

Study on Prediction Model About Water Content in High-Temperature and High-Pressure Water-Soluble Gas Reservoirs

Abstract Because of a large amount of natural gas dissolved in the formation water of high-temperature and high-pressure (HTHP) water-soluble gas reservoirs, the water vapor content in water-soluble gas reservoirs is generally maintained under a supersaturated state; meanwhile, natural gas has a high carbon dioxide fraction, which significantly affects the water vapor content. Application of the conventional method to calculate the water content of HTHP water-soluble gas reservoirs leads to errors. In this work, the water content of HTHP water-soluble gas reservoirs was studied through laboratory experiments and theoretical research, and the main factors affecting water content were studied. Results show that the water content of water-soluble gas reservoirs decreases as pressure increases. The water content decreases faster in the low-pressure stage, while the decease of water content in the high-pressure stage is relatively steady. The water content of gas reservoirs increases with increasing temperature. When the temperature is lower than 100 °C, the change is slow; when the temperature is higher than 100 °C, the change is fast. The water content of gas reservoirs is affected by temperature during the low-pressure stage. The water content in the high-temperature stage is obviously affected by pressure; the water content of the gas reservoir is also affected by the carbon dioxide content of the natural gas component and the salinity of the formation water. Higher carbon dioxide content and lower formation water salinity yield higher water content. Furthermore, error analysis of the conventional water content prediction method and the measurement shows inconsistency in measurement and calculation. The error between the two methods is large, with an average of 54.88%. Based on the experiment, a mathematical model for calculating the water content of HTHP water-soluble gas reservoirs was established considering pressure, temperature, salinity, and natural gas composition. The predicted water vapor content of natural gas is close to the experimental value with a high precision. The average relative error between the measured and model calculated value is about 8.72%.

Carbon Dioxide Retrieval from TanSat Observations and Validation with TCCON Measurements

In this study we present the retrieval of the column-averaged dry air mole fraction of carbon dioxide (XCO2) from the TanSat observations using the ACOS (Atmospheric CO2 Observations from Space) algorithm. The XCO2 product has been validated with collocated ground-based measurements from the Total Carbon Column Observing Network (TCCON) for 2 years of TanSat data from 2017 to 2018. Based on the correlation of the XCO2 error over land with goodness of fit in three spectral bands at 0.76, 1.61 and 2.06 μm, we applied an a posteriori bias correction to TanSat retrievals. For overpass averaged results, XCO2 retrievals show a standard deviation (SD) of ~2.45 ppm and a positive bias of ~0.27 ppm compared to collocated TCCON sites. The validation also shows a relatively higher positive bias and variance against TCCON over high-latitude regions. Three cases to evaluate TanSat target mode retrievals are investigated, including one field campaign at Dunhuang with measurements by a greenhouse gas analyzer deployed on an unmanned aerial vehicle and two cases with measurements by a ground-based Fourier-transform spectrometer in Beijing. The results show the retrievals of all footprints, except footprint-6, have relatively low bias (within ~2 ppm). In addition, the orbital XCO2 distributions over Australia and Northeast China between TanSat and the second Orbiting Carbon Observatory (OCO-2) on 20 April 2017 are compared. It shows that the mean XCO2 from TanSat is slightly lower than that of OCO-2 with an average difference of ~0.85 ppm. A reasonable agreement in XCO2 distribution is found over Australia and Northeast China between TanSat and OCO-2.

Modifying a Full-Face Snorkel Mask to Meet N95 Respirator Standards for Use With Coronavirus Disease 2019 Patients.

We evaluated a full-face snorkel mask with an airway circuit filter to protect health care providers against airborne pathogens. First, a quantified N95 fit test was performed using aerosolized saline. Second, cardiorespiratory variables (heart rate, peripheral oxygen saturation, end-tidal carbon dioxide tension, and inspired fraction of carbon dioxide) were measured at rest and during moderate exercise. The modified mask passed the United States Occupational Safety and Health Administration (OSHA) N95 respirator (N95) fit test requirements with a fit factor of 142. Neither hypercapnia nor hypoxemia occurred. This modified mask has the potential to protect providers who care for patients with coronavirus disease 2019 (COVID-19).