Rapid and sensitive detection of dissolved gases in seawater is quite essential for the investigation of the global carbon cycle.Large quantities of in situ optical detection techniques showed restricted measurement e...Rapid and sensitive detection of dissolved gases in seawater is quite essential for the investigation of the global carbon cycle.Large quantities of in situ optical detection techniques showed restricted measurement efficiency,owing to the single gas sensor without the identification ability of multiple gases.In this work,a novel gas-liquid Raman detection method of monitoring the multi-component dissolved gases was proposed based on a continuous gas-liquid separator under a large difference of partial pressure.The limit of detection(LOD)of the gas Raman spectrometer could arrive at about 14 μl·L^(-1)for N_(2)gas.Moreover,based on the continuous gas-liquid separation process,the detection time of the dissolved gases could be largely decreased to about 200 s compared with that of the traditional detection method(30 min).Effect of equilibrium time on gas-liquid separation process indicated that the extracted efficiency and decay time of these dissolved gases was CO_(2)>O_(2)>N_(2).In addition,the analysis of the relationship between equilibrium time and flow speed indicated that the decay time decreased with the increase of the flow speed.The validation and application of the developed system presented its great potential for studying the components and spatiotemporal distribution of dissolved gases in seawater.展开更多
Current gas well decline analysis under boundary-dominated flow(BDF)is largely based on the Arps'empirical hyperbolic decline model and the analytical type curve tools associated with pseudo-functions.Due to the n...Current gas well decline analysis under boundary-dominated flow(BDF)is largely based on the Arps'empirical hyperbolic decline model and the analytical type curve tools associated with pseudo-functions.Due to the nonlinear flow behavior of natural gas,these analysis methods generally require iterative calculations.In this study,the dimensionless gas rate(qg/qgi)is introduced,and an explicit method to determine the average reservoir pressure and the original gas in place(OGIP)for a volumetric gas reservoir is proposed.We show that the dimensionless gas rate in the BDF is only the function of the gas PVT parameters and reservoir pressure.Step-by-step analysis procedures are presented that enable explicit and straightforward estimation of average reservoir pressure and OGIP by straight-line analysis.Compared with current techniques,this methodology avoids the iterative calculation of pseudo-time and pseudo-pressure functions,lowers the multiplicity of type curve analysis,and is applicable in different production situations(constant/variable gas flow rate,constant/variable bottom-hole pressure)with a broad range of applications and ease of use.Reservoir numerical simulation and field examples are thoroughly discussed to highlight the capabilities of the proposed approach.展开更多
Shale gas, as a clean, low-carbon, and abundant unconventional natural gas resource, plays a crucial role in achieving clean energy transformation and carbon neutrality. The Fuling shale gas reservoir in Sichuan Basin...Shale gas, as a clean, low-carbon, and abundant unconventional natural gas resource, plays a crucial role in achieving clean energy transformation and carbon neutrality. The Fuling shale gas reservoir in Sichuan Basin stands out as China's most promising area for shale gas exploration and recovery. However, the continuous recovery of shale gas in the southern Sichuan Basin has led to well interference events in hundreds of wells, with the furthest well distance reaching over 2000 m. This study introduces a multi-scale approach for transient analysis of a multi-well horizontal pad with well interference in shale gas reservoirs. The approach utilizes Laplace transform technology, boundary element theory, and the finite difference method to address the complexities of the system. Well interference is managed using the pressure superposition principle. To validate the proposed multi-scale method, a commercial numerical simulator is employed. The comprehensive pressure behavior of a multi-well horizontal pad in a shale gas reservoir is analyzed, encompassing wellbore storage effect, skin effect, bilinear flow, linear flow, pseudo-radial flow of primary fractures, well interference period, dual-porosity flow, pseudo-radial flow of the total system, and boundary-dominated flow. A case study is conducted on the typical well, the well with the longest production history in the Fuling shale gas reservoir. The rate transient analysis is conducted to integrate up to 229 days of shale gas production daily data and wellhead pressure data, enabling the generation of pressure behavior under unit flow rate. The results indicate that the linear flow, transitional flow, and boundary-dominated flow are more likely to be observed in the actual data. Secondary fractures are considered to be the primary pathways for fluid migration during well interference events. The evaluated formation permeability is 2.58 × 10^(-2) mD, the well spacing is 227.8 m, the diffusion coefficient is 1.49 × 10^(-4), and the skin factor is 0.09.展开更多
Transitions within the boundary layer significantly affect the aerodynamic and aerothermodynamic dynamics of hypersonic vehicles.Accurately predicting these transitions poses a significant challenge in vehicle design....Transitions within the boundary layer significantly affect the aerodynamic and aerothermodynamic dynamics of hypersonic vehicles.Accurately predicting these transitions poses a significant challenge in vehicle design.At high speeds and altitudes,thermochemical processes within the hypersonic boundary layer lead to real gas effects that alter flow stability and further complicate transition prediction.Direct numerical simulation and linear stability theory are used to investigate the effects of chemical reaction-induced terms on the second and cross-flow modes,and to identify the main sources of species disturbances.Efficient stability analysis method for real gas is developed by applying multilevel assumptions to the linear stability equation.The results indicate that at lower wall temperatures,species disturbances primarily arise from convective terms,and there is a continuous contribution from chemical reaction source terms.The contributions of the diffusion and chemical source terms to species disturbances increase with the intensity of chemical reactions.When the nitrogen within the boundary layer is not dissociated or is only weakly dissociated,the assumption of complete freezing of the species disturbances can be employed to enhance the computational efficiency of the linear stability analysis.Chemical non-equilibrium linear stability theory based on the freezing assumption is suitable for most experimental and flight conditions,significantly reducing the computational time for real gas transition predictions,making it comparable to that for perfect gas.展开更多
In the present study, a method for the quantitative analysis of multi-components by single marker(QAMS) has been developed and validated for the simultaneous determination of echinacoside(ECH), tubuloside A, acteoside...In the present study, a method for the quantitative analysis of multi-components by single marker(QAMS) has been developed and validated for the simultaneous determination of echinacoside(ECH), tubuloside A, acteoside, isoacteoside, and2’-acetylacteoside in Cistanches Herba. ECH was used as the internal standard(IS) to obtain the relative correction factors(RCFs) of the other four phenylethanoid glycosides(PhGs);meanwhile, various influencing factors on RCFs were investigated under different conditions. The content of each component was calculated with RCF. The results were compared with those obtained by the external standard method(ESM) to verify the feasibility and accuracy of the established QAMS method. No significant difference was found in the quantitative results of 10 batches of Cistanches Herba between QAMS and ESM. The proposed QAMS method for simultaneous determination of PhGs in Cistanches Herba is accurate and feasible, providing an efficient and economical approach for the quality control of Cistanches Herba.展开更多
Multi-component mooring systems become widely used in deep water position-keeping of drilling and production platforms. However, versatile materials make it difficult to design appropriate mooring lines made of severa...Multi-component mooring systems become widely used in deep water position-keeping of drilling and production platforms. However, versatile materials make it difficult to design appropriate mooring lines made of several segments. Based on catenary equations of a multi-component mooring line at a specific water depth, this paper establishes a minimum model for designing this kind of lines. The model is solved by Genetic Algorithm and Multi-Objective Planning respectively. The model is verified by its application to a practical mooring design assignment—a quasi-static analysis for a large semi-submersible. The optimal result is finally obtained with the aid of design graphs.展开更多
The Hirota equation can be used to describe the wave propagation of an ultrashort optical field.In this paper,the multi-component Hirota(alias n-Hirota,i.e.n-component third-order nonlinear Schrodinger)equations with ...The Hirota equation can be used to describe the wave propagation of an ultrashort optical field.In this paper,the multi-component Hirota(alias n-Hirota,i.e.n-component third-order nonlinear Schrodinger)equations with mixed non-zero and zero boundary conditions are explored.We employ the multiple roots of the characteristic polynomial related to the Lax pair and modified Darboux transform to find vector semi-rational rogon-soliton solutions(i.e.nonlinear combinations of rogon and soliton solutions).The semi-rational rogon-soliton features can be modulated by the polynomial degree.For the larger solution parameters,the first m(m<n)components with non-zero backgrounds can be decomposed into rational rogons and grey-like solitons,and the last n-m components with zero backgrounds can approach bright-like solitons.Moreover,we analyze the accelerations and curvatures of the quasi-characteristic curves,as well as the variations of accelerations with the distances to judge the interaction intensities between rogons and grey-like solitons.We also find the semi-rational rogon-soliton solutions with ultrahigh amplitudes.In particular,we can also deduce vector semi-rational solitons of the ncomponent complex mKdV equation.These results will be useful to further study the related nonlinear wave phenomena of multi-component physical models with mixed background,and even design the related physical experiments.展开更多
During the past decade, coal dust and gas explosions have been the most two serious types of disasters in China, threatening the lives of miners and causing significant losses in terms of national property. In this pa...During the past decade, coal dust and gas explosions have been the most two serious types of disasters in China, threatening the lives of miners and causing significant losses in terms of national property. In this paper, an evaluation model of coal dust and gas explosions was constructed based on a fuzzy fault tree by taking the Xingli Coal Mine as a research site to identify the risk factors of coal dust and gas explosions.Furthermore, the hazards associated with such explosions were evaluated for this particular coal mine.After completing an on-site investigation, the fuzzy probabilities of basic events were obtained through expert scoring, and these expert opinions were then aggregated as trapezoidal fuzzy numbers to calculate the degrees of importance of all basic events. Finally, these degrees of importance were sorted. According to the resulting order, the basic events with higher probabilities were determined to identify key hazards in the daily safety management of this particular coal mine. Moreover, effective measures for preventing gas and coal dust explosions were derived. The fuzzy fault tree analysis method is of high significance in the analysis of accidental coal mine explosions and provides theoretical guidance for improving the efficiency of coal mine safety management in a scientific and feasible manner.展开更多
BACKGROUND:Emergency patients with sepsis or septic shock are at high risk of death.Despite increasing attention to microhemodynamics,the clinical use of advanced microcirculatory assessment is limited due to its shor...BACKGROUND:Emergency patients with sepsis or septic shock are at high risk of death.Despite increasing attention to microhemodynamics,the clinical use of advanced microcirculatory assessment is limited due to its shortcomings.Since blood gas analysis is a widely used technique reflecting global oxygen supply and consumption,it may serve as a surrogate for microcirculation monitoring in septic treatment.METHODS:We performed a search using PubMed,Web of Science,and Google scholar.The studies and reviews that were most relevant to septic microcirculatory dysfunctions and blood gas parameters were identified and included.RESULTS:Based on the pathophysiology of oxygen metabolism,the included articles provided a general overview of employing blood gas analysis and its derived set of indicators for microhemodynamic monitoring in septic care.Notwithstanding flaws,several parameters are linked to changes in the microcirculation.A comprehensive interpretation of blood gas parameters can be used in order to achieve hemodynamic optimization in septic patients.CONCLUSION:Blood gas analysis in combination with clinical performance is a reliable alternative for microcirculatory assessments.A deep understanding of oxygen metabolism in septic settings may help emergency physicians to better use blood gas analysis in the evaluation and treatment of sepsis and septic shock.展开更多
In order to suppress the harm of gas explosion,the current study researched on the body of vacuum chamber.The previous studies verifed that it could obviously lower the explosion overpressure by reasonably arranging v...In order to suppress the harm of gas explosion,the current study researched on the body of vacuum chamber.The previous studies verifed that it could obviously lower the explosion overpressure by reasonably arranging vacuum chamber on pipe.That is to say,the vacuum chamber has the effect of absorbing wave and energy.To further deeply analyze the vacuum chamber suppressing gas explosion,this research designed the L-type pipe of gas explosion,and compared the experimental results of gas explosion with vacuum chamber and without vacuum chamber.Besides,using the gas chromatograph,this study also investigated the gas compositions in the pipe before and after explosion.The results show that:(1)without vacuum chamber,the maximum value of explosion overpressure is 0.22 MPa,with60 ms duration,and after explosion,the concentration of oxygen drops to 12.07%,but the concentration of carbon monoxide increases to 4392.3 10à6,and the concentration of carbon dioxide goes up to7.848%,which can make the persons in danger suffocate and die;(2)with vacuum chamber,explosion overpressure drops to 0.18 MPa,with 20 ms duration or less,and after explosion,the concentration of oxygen still remains 12.07%,but the concentration of methane is 7.83%,however the concentration of carbon monoxide is only 727.24 10à6,and the concentration of carbon dioxide is only 1.219%,at the this moment the concentration ratio of toxic gas drops by more than 83%in comparison to be that without vacuum chamber.Consequently,the vacuum chamber can guarantee that most methane does not take part in chemical reaction,and timely quenches the deflagration reaction of gas and oxygen.Because of the two points mentioned above,it reduces the explosion energy,and lowers that the overpressure of blast wave impacts and damages on the persons and facilities,and also decreases the consumption of oxygen and the production of the toxic gas.Therefore,it is safe to conclude that the vacuum chamber not only absorbs wave and energy,but also prevents and suppresses explosion.展开更多
This paper presents a method for analysis of stress and strain of gas pipelines under the effect of horizontal catastrophic landslides. A soil spring model was used to analyze the nonlinear characteristics concerning ...This paper presents a method for analysis of stress and strain of gas pipelines under the effect of horizontal catastrophic landslides. A soil spring model was used to analyze the nonlinear characteristics concerning the mutual effects between the pipeline and the soil. The Ramberg–Osgood model was used to describe the constitutive relations of pipeline materials. This paper also constructed a finite element analysis model using ABAQUS finite element software and studied the distribution of the maximum stress and strain of the pipeline and the axial stress and strain along the pipeline by referencing some typical accident cases. The calculation results indicated that the maximum stress and strain increased gradually with the displacement of landslide.The limit values of pipeline axial stress strain appeared at the junction of the landslide area and non-landslide area. The stress failure criterion was relatively more conservative than the strain failure criterion. The research results of this paper may be used as a technical reference concerning the design and safety management of large-diameter gas pipelines under the effects of catastrophic landslides.展开更多
This article presents an acetylene production process by partial oxidation/combustion of natural gas. The thermodynamic performance and exergy analysis in the process are investigated using the flow-sheeting program A...This article presents an acetylene production process by partial oxidation/combustion of natural gas. The thermodynamic performance and exergy analysis in the process are investigated using the flow-sheeting program Aspen Plus. The results indicate that the most important destruction of exergy is found to occur in the reactor and water quenching scrubber, amounting to 8.23% and 10.39%, respectively, of the entire system. Based on the results of thermodynamic and exergy analysis, the acetylene reactor has been retrofitted. The improvement ratios of molar 02 to CH4 and molar CO to CN4 are 0.65 and 0.20, respectively. An improvement of the acetylene production system is proposed. Adopting the improvement operation conditions and using oil to realize the reaction heat recovery, the feedstock of natural gas is reduced by 9.88% and the exergy loss in the retrofitting process is decreased by 19.71% compared to the original process.展开更多
As longwall caving mining method prevails rapidly in China coal mines, amount of gas emission from longwall faces and goaf area increased significantly. Using traditional gas drainage methods, such as drilling upward ...As longwall caving mining method prevails rapidly in China coal mines, amount of gas emission from longwall faces and goaf area increased significantly. Using traditional gas drainage methods, such as drilling upward holes to roof strata in tailgate or drilling inseam and cross-measure boreholes, could not meet methane drainage requirements in a gassy mine. The alternative is to drill boreholes from surface down to the Iongwall goaf area to drain the gas out. As soon as a coal seam is extracted out, the upper rock strata above the goaf start to collapse or become fractured depending upon the rock characteristics and the height above the coal seam. During overlying rock strata being fractured, boreholes in the area may be damaged due to ground movement after the passage of the Iongwall face. The sudden damage of a borehole may cause a Iongwall production halt or even a serious mine accident. A theoretical calculation of the stability of surface boreholes in mining affected area is introduced along with an example of determination of borehole and casing diameters is given for demonstration. By using this method for the drilling design, the damage of surface boreholes caused by excessive mining induced displacement can be effectively reduced if not totally avoided. Borehole and casing diameters as well as characteristics of filling materials can be determined using the proposed method by calculating the horizontal movement and vertical stain at different borehole depths.展开更多
Based on the principle of Bayesian discriminant analysis, we established a model of Bayesian discriminant analysis for predicting coal and gas outbursts. We selected five major indices which affect outbursts, i.e., in...Based on the principle of Bayesian discriminant analysis, we established a model of Bayesian discriminant analysis for predicting coal and gas outbursts. We selected five major indices which affect outbursts, i.e., initial speed of methane diffusion, a consistent coal coefficient, gas pressure, destructive style of coal and mining depth, as discriminating factors of the model. In our model, we divided the type of coal and gas outbursts into four grades regarded as four normal populations. We then obtained the corresponding discriminant functions through training a set of data from engineering examples as learning samples and evaluated their criteria by a back substitution method to verify the optimal properties of the model. Finally, we applied the model to the prediction of coal and gas outbursts in the Yunnan Enhong Mine. Our results coincided completely with the actual situation. These results show that a model of Bayesian discriminant analysis has excellent recognition performance, high prediction accuracy and a low error rate and is an effective method to predict coal and gas outbursts.展开更多
Tokamak exhaust is an important part of the deuterium-tritium fuel cycle system in fusion reactions.In this work,we present a laser-induced breakdown spectroscopy(LIBS)-based method to monitor the gas compositions fro...Tokamak exhaust is an important part of the deuterium-tritium fuel cycle system in fusion reactions.In this work,we present a laser-induced breakdown spectroscopy(LIBS)-based method to monitor the gas compositions from the exhaust system in the tokamak device.Helium(He),a main impurity in the exhaust gas,was mixed with hydrogen(H_(2))in different ratios through a self-designed gas distribution system,and sealed into a measurement chamber as a standard specimen.A 532 nm wavelength laser pulse with an output power of 100 mJ was used for plasma excitation.The time-resolved LIBS is used to study the time evolution characteristics of the signal strength,signal-to-background ratio(SBR),signal-to-noise ratio(SNR)and relative standard deviation(RSD)of the helium and hydrogen characteristic lines.The Boltzmann twoline method was employed to estimate the plasma temperature of laser-induced plasma(LIP).The Stark-broadened profile of He I 587.56 nm was exploited to measure the electron density.From these studies,an appropriate time was determined in which the low RSD%was consistent with the high signal-to-noise ratio.The He I 587.56 nm and Hαemission lines with good signalto-noise ratio were extracted from the spectrum and used in the external standard method and internal standard method for quantitative analysis.The test results for mixed gas showed that the average relative error of prediction was less than 11.15%,demonstrating the great potential of LIBS in detecting impurities in plasma exhaust gas.展开更多
Urban natural gas is becoming the main sector driving China’s natural gas consumption growth in recent years.This study explores the impacts of urban natural gas price,wage,socioeconomic determinants,and meteorologic...Urban natural gas is becoming the main sector driving China’s natural gas consumption growth in recent years.This study explores the impacts of urban natural gas price,wage,socioeconomic determinants,and meteorological conditions on urban natural gas demand in China over 2006-2017.Furthermore,this study also analyzes the potential regional heterogeneity and asymmetry in the impacts of gas price and income on China’s urban gas demand.Empirical results reveal that:(1)The increased gas price can significantly reduce the urban gas demand,and the average income level may effectively promote the gas demand,also,a strong switching effect exists between electricity and natural gas in urban China;(2)these impacts are heterogeneous in regions among China,urban natural gas demand is largely affected by the gas price in regions with high-gas-price and by income in regions with low-gas-price;and(3)the impact of gas price on urban gas consumption is consistent in regions with different urban natural gas consumption,while the impact of income is asymmetric.This study further provides several policy implications for improving the urban natural gas industry in China.展开更多
Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is...Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is essential.In this work,a risk analysis and maintenance decision-making model for natural gas pipelines with external corrosion is proposed based on a Bayesian network.A fault tree model is first employed to identify the causes of external corrosion.The Bayesian network for risk analysis is determined accordingly.The maintenance strategies are then inserted into the Bayesian network to show a reduction of the risk.The costs of maintenance strategies and the reduced risk after maintenance are combined in an optimization function to build a decision-making model.Because of the limitations of historical data,some of the parameters in the Bayesian network are obtained from a probabilistic estimation model,which combines expert experience and fuzzy set theory.Finally,a case study is carried out to verify the feasibility of the maintenance decision model.This indicates that the method proposed in this work can be used to provide effective maintenance schemes for different pipeline external corrosion scenarios and to reduce the possible losses caused by external corrosion.展开更多
The present study is aimed to compare the microstructure characteristics and mechanical properties of AA6082 in T6 condition of tubular joints fabricated by tungsten inert gas welding （TIG） and metal inert gas weldi...The present study is aimed to compare the microstructure characteristics and mechanical properties of AA6082 in T6 condition of tubular joints fabricated by tungsten inert gas welding （TIG） and metal inert gas welding （MIG） processes. The effect of welding processes was analysed based on optical microscopy image, tensile testing, and Vickers micro-hardness measurements. The results showed that the tensile strengths of the TIG-welded joints were better than those of the MIG-welded joints, due to the contribution of fine equiaxed grains formation with narrower spacing arms. In terms of joint efficiency, the TIG process produced more reliable strength, which was about 25% higher compared to the MIG-joint. A significant decay of hardness was recorded in the adjacent of the weld bead zone, shown in both joints, related to phase transformation, induced by high temperatures experienced by material. A very low hardness, which was about 1.08 GPa, was recorded in the MIG-weldcd specimens. The extent of the heat-affected-zone （HAZ） in the MIG-welded joints was slightly wider than those of the TIG-welded specimens, which corresponded with a higher heat input per unit length.展开更多
The increasing intensity and frequency of sand-dust storms in China has led to greater prominence of associated environmentaland health issues. Many studies have focused on the health effects of air particulate contam...The increasing intensity and frequency of sand-dust storms in China has led to greater prominence of associated environmentaland health issues. Many studies have focused on the health effects of air particulate contaminants, but fewformal investigations have studied the effects of sand-dust storms on human and animal health. The aim of this study wasto investigate the effects of dust storms on rat lung by using high resolution computed tomography （HRCT） and blood gasanalysis through a wind tunnel simulating. We found that the rat lung damage effects can be detected by the HRCT imagingafter exposure to sand-dust storm environments, but had no obvious result through blood gas analysis. Exposure durationspositively correlated with the damage degree to lung tissue. These will provide some evidence for clinical diagnosis ofnon-occupational pneumoconiosis.展开更多
The tight-fractured gas reservoir of the Upper Triassic Xujiahe Formation in the Western Sichuan Depression has low porosity and permeability. This study presents a DNN-based method for identifying gas-bearing strata ...The tight-fractured gas reservoir of the Upper Triassic Xujiahe Formation in the Western Sichuan Depression has low porosity and permeability. This study presents a DNN-based method for identifying gas-bearing strata in tight sandstone. First, multi-component composite seismic attributes are obtained.The strong nonlinear relationships between multi-component composite attributes and gas-bearing reservoirs can be constrained through a DNN. Therefore, we identify and predict the gas-bearing strata using a DNN. Then, sample data are fed into the DNN for training and testing. After optimized network parameters are determined by the performance curves and empirical formulas, the best deep learning gas-bearing prediction model is determined. The composite seismic attributes can then be fed into the model to extrapolate the hydrocarbon-bearing characteristics from known drilling areas to the entire region for predicting the gas reservoir distribution. Finally, we assess the proposed method in terms of the structure and fracture characteristics and predict favorable exploration areas for identifying gas reservoirs.展开更多
基金the National Natural Science Foundation of China(52304236)the Natural Science Foundation of Shandong Province(ZR2021QE076)for the financial support to this research extracted from the project.
文摘Rapid and sensitive detection of dissolved gases in seawater is quite essential for the investigation of the global carbon cycle.Large quantities of in situ optical detection techniques showed restricted measurement efficiency,owing to the single gas sensor without the identification ability of multiple gases.In this work,a novel gas-liquid Raman detection method of monitoring the multi-component dissolved gases was proposed based on a continuous gas-liquid separator under a large difference of partial pressure.The limit of detection(LOD)of the gas Raman spectrometer could arrive at about 14 μl·L^(-1)for N_(2)gas.Moreover,based on the continuous gas-liquid separation process,the detection time of the dissolved gases could be largely decreased to about 200 s compared with that of the traditional detection method(30 min).Effect of equilibrium time on gas-liquid separation process indicated that the extracted efficiency and decay time of these dissolved gases was CO_(2)>O_(2)>N_(2).In addition,the analysis of the relationship between equilibrium time and flow speed indicated that the decay time decreased with the increase of the flow speed.The validation and application of the developed system presented its great potential for studying the components and spatiotemporal distribution of dissolved gases in seawater.
基金supported by the Young Elite Scientist Sponsorship Program by Beijing Association for Science and Technology,China(No.BYESS2023262)the Science Foundation of China University of Petroleum(Beijing),China(No.2462022BJRC004).
文摘Current gas well decline analysis under boundary-dominated flow(BDF)is largely based on the Arps'empirical hyperbolic decline model and the analytical type curve tools associated with pseudo-functions.Due to the nonlinear flow behavior of natural gas,these analysis methods generally require iterative calculations.In this study,the dimensionless gas rate(qg/qgi)is introduced,and an explicit method to determine the average reservoir pressure and the original gas in place(OGIP)for a volumetric gas reservoir is proposed.We show that the dimensionless gas rate in the BDF is only the function of the gas PVT parameters and reservoir pressure.Step-by-step analysis procedures are presented that enable explicit and straightforward estimation of average reservoir pressure and OGIP by straight-line analysis.Compared with current techniques,this methodology avoids the iterative calculation of pseudo-time and pseudo-pressure functions,lowers the multiplicity of type curve analysis,and is applicable in different production situations(constant/variable gas flow rate,constant/variable bottom-hole pressure)with a broad range of applications and ease of use.Reservoir numerical simulation and field examples are thoroughly discussed to highlight the capabilities of the proposed approach.
基金support from the National Natural Science Foundation of China(12202042)the Fundamental Research Funds for the Central Universities(QNXM20220011,FRF-TP-22-119A1,FRF-IDRY-22-001)+2 种基金the Open Fund Project of Sinopec State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development(33550000-22-ZC0613-0269)China Postdoctoral Science Foundations(2021M700391)High-end Foreign Expert Introduction Program(G2023105006L).
文摘Shale gas, as a clean, low-carbon, and abundant unconventional natural gas resource, plays a crucial role in achieving clean energy transformation and carbon neutrality. The Fuling shale gas reservoir in Sichuan Basin stands out as China's most promising area for shale gas exploration and recovery. However, the continuous recovery of shale gas in the southern Sichuan Basin has led to well interference events in hundreds of wells, with the furthest well distance reaching over 2000 m. This study introduces a multi-scale approach for transient analysis of a multi-well horizontal pad with well interference in shale gas reservoirs. The approach utilizes Laplace transform technology, boundary element theory, and the finite difference method to address the complexities of the system. Well interference is managed using the pressure superposition principle. To validate the proposed multi-scale method, a commercial numerical simulator is employed. The comprehensive pressure behavior of a multi-well horizontal pad in a shale gas reservoir is analyzed, encompassing wellbore storage effect, skin effect, bilinear flow, linear flow, pseudo-radial flow of primary fractures, well interference period, dual-porosity flow, pseudo-radial flow of the total system, and boundary-dominated flow. A case study is conducted on the typical well, the well with the longest production history in the Fuling shale gas reservoir. The rate transient analysis is conducted to integrate up to 229 days of shale gas production daily data and wellhead pressure data, enabling the generation of pressure behavior under unit flow rate. The results indicate that the linear flow, transitional flow, and boundary-dominated flow are more likely to be observed in the actual data. Secondary fractures are considered to be the primary pathways for fluid migration during well interference events. The evaluated formation permeability is 2.58 × 10^(-2) mD, the well spacing is 227.8 m, the diffusion coefficient is 1.49 × 10^(-4), and the skin factor is 0.09.
基金supported by the National Natural Science Foundation of China(No.92271102).
文摘Transitions within the boundary layer significantly affect the aerodynamic and aerothermodynamic dynamics of hypersonic vehicles.Accurately predicting these transitions poses a significant challenge in vehicle design.At high speeds and altitudes,thermochemical processes within the hypersonic boundary layer lead to real gas effects that alter flow stability and further complicate transition prediction.Direct numerical simulation and linear stability theory are used to investigate the effects of chemical reaction-induced terms on the second and cross-flow modes,and to identify the main sources of species disturbances.Efficient stability analysis method for real gas is developed by applying multilevel assumptions to the linear stability equation.The results indicate that at lower wall temperatures,species disturbances primarily arise from convective terms,and there is a continuous contribution from chemical reaction source terms.The contributions of the diffusion and chemical source terms to species disturbances increase with the intensity of chemical reactions.When the nitrogen within the boundary layer is not dissociated or is only weakly dissociated,the assumption of complete freezing of the species disturbances can be employed to enhance the computational efficiency of the linear stability analysis.Chemical non-equilibrium linear stability theory based on the freezing assumption is suitable for most experimental and flight conditions,significantly reducing the computational time for real gas transition predictions,making it comparable to that for perfect gas.
基金National Key R&D Program of China(Grant Nos.2017YFC1702400,2018YFC1707300 and 2018YFC1707904)
文摘In the present study, a method for the quantitative analysis of multi-components by single marker(QAMS) has been developed and validated for the simultaneous determination of echinacoside(ECH), tubuloside A, acteoside, isoacteoside, and2’-acetylacteoside in Cistanches Herba. ECH was used as the internal standard(IS) to obtain the relative correction factors(RCFs) of the other four phenylethanoid glycosides(PhGs);meanwhile, various influencing factors on RCFs were investigated under different conditions. The content of each component was calculated with RCF. The results were compared with those obtained by the external standard method(ESM) to verify the feasibility and accuracy of the established QAMS method. No significant difference was found in the quantitative results of 10 batches of Cistanches Herba between QAMS and ESM. The proposed QAMS method for simultaneous determination of PhGs in Cistanches Herba is accurate and feasible, providing an efficient and economical approach for the quality control of Cistanches Herba.
文摘Multi-component mooring systems become widely used in deep water position-keeping of drilling and production platforms. However, versatile materials make it difficult to design appropriate mooring lines made of several segments. Based on catenary equations of a multi-component mooring line at a specific water depth, this paper establishes a minimum model for designing this kind of lines. The model is solved by Genetic Algorithm and Multi-Objective Planning respectively. The model is verified by its application to a practical mooring design assignment—a quasi-static analysis for a large semi-submersible. The optimal result is finally obtained with the aid of design graphs.
基金supported by the National Natural Science Foundation of China(Nos.11925108 and 11731014)
文摘The Hirota equation can be used to describe the wave propagation of an ultrashort optical field.In this paper,the multi-component Hirota(alias n-Hirota,i.e.n-component third-order nonlinear Schrodinger)equations with mixed non-zero and zero boundary conditions are explored.We employ the multiple roots of the characteristic polynomial related to the Lax pair and modified Darboux transform to find vector semi-rational rogon-soliton solutions(i.e.nonlinear combinations of rogon and soliton solutions).The semi-rational rogon-soliton features can be modulated by the polynomial degree.For the larger solution parameters,the first m(m<n)components with non-zero backgrounds can be decomposed into rational rogons and grey-like solitons,and the last n-m components with zero backgrounds can approach bright-like solitons.Moreover,we analyze the accelerations and curvatures of the quasi-characteristic curves,as well as the variations of accelerations with the distances to judge the interaction intensities between rogons and grey-like solitons.We also find the semi-rational rogon-soliton solutions with ultrahigh amplitudes.In particular,we can also deduce vector semi-rational solitons of the ncomponent complex mKdV equation.These results will be useful to further study the related nonlinear wave phenomena of multi-component physical models with mixed background,and even design the related physical experiments.
基金supported by the National Natural Science Foundation of China (Nos.51504008,71371014,and 51774012)the Natural Science Foundation of Anhui Higher Education Institutions of China (No.KJ2015A068)+3 种基金the Anhui Provincial Natural Science Foundation (No.1608085QE115)the China Postdoctoral Science Foundation funded project (Nos.2015M571913 and 2018T110612)the Postdoctoral Fund of Anhui Province (No.2017B212)the Scientific Research Foundation for Introduction of Talent of Anhui University of Science & Technology (No.ZY530)
文摘During the past decade, coal dust and gas explosions have been the most two serious types of disasters in China, threatening the lives of miners and causing significant losses in terms of national property. In this paper, an evaluation model of coal dust and gas explosions was constructed based on a fuzzy fault tree by taking the Xingli Coal Mine as a research site to identify the risk factors of coal dust and gas explosions.Furthermore, the hazards associated with such explosions were evaluated for this particular coal mine.After completing an on-site investigation, the fuzzy probabilities of basic events were obtained through expert scoring, and these expert opinions were then aggregated as trapezoidal fuzzy numbers to calculate the degrees of importance of all basic events. Finally, these degrees of importance were sorted. According to the resulting order, the basic events with higher probabilities were determined to identify key hazards in the daily safety management of this particular coal mine. Moreover, effective measures for preventing gas and coal dust explosions were derived. The fuzzy fault tree analysis method is of high significance in the analysis of accidental coal mine explosions and provides theoretical guidance for improving the efficiency of coal mine safety management in a scientific and feasible manner.
基金supported by the grants from Innovation Fund for Medical Sciences (CIFMS) from Chinese Academy of Medical Sciences (No.2021-I2M-1-062)National Key R&D Program of China from Ministry of Science and Technology of the People’s Republic of China (No.2022YFC2304601,2021YFC2500801)+1 种基金National High Level Hospital Clinical Research Funding (2022-PUMCH-D-005,2022-PUMCH-D-111,2022-PUMCH-B-126)National key clinical specialty construction projects from National Health Commission。
文摘BACKGROUND:Emergency patients with sepsis or septic shock are at high risk of death.Despite increasing attention to microhemodynamics,the clinical use of advanced microcirculatory assessment is limited due to its shortcomings.Since blood gas analysis is a widely used technique reflecting global oxygen supply and consumption,it may serve as a surrogate for microcirculation monitoring in septic treatment.METHODS:We performed a search using PubMed,Web of Science,and Google scholar.The studies and reviews that were most relevant to septic microcirculatory dysfunctions and blood gas parameters were identified and included.RESULTS:Based on the pathophysiology of oxygen metabolism,the included articles provided a general overview of employing blood gas analysis and its derived set of indicators for microhemodynamic monitoring in septic care.Notwithstanding flaws,several parameters are linked to changes in the microcirculation.A comprehensive interpretation of blood gas parameters can be used in order to achieve hemodynamic optimization in septic patients.CONCLUSION:Blood gas analysis in combination with clinical performance is a reliable alternative for microcirculatory assessments.A deep understanding of oxygen metabolism in septic settings may help emergency physicians to better use blood gas analysis in the evaluation and treatment of sepsis and septic shock.
基金Financial support from the State Key Laboratory Cultivation Base for Gas Geology and Gas Control of Henan Polytechnic University of China(No.WS2012A04)
文摘In order to suppress the harm of gas explosion,the current study researched on the body of vacuum chamber.The previous studies verifed that it could obviously lower the explosion overpressure by reasonably arranging vacuum chamber on pipe.That is to say,the vacuum chamber has the effect of absorbing wave and energy.To further deeply analyze the vacuum chamber suppressing gas explosion,this research designed the L-type pipe of gas explosion,and compared the experimental results of gas explosion with vacuum chamber and without vacuum chamber.Besides,using the gas chromatograph,this study also investigated the gas compositions in the pipe before and after explosion.The results show that:(1)without vacuum chamber,the maximum value of explosion overpressure is 0.22 MPa,with60 ms duration,and after explosion,the concentration of oxygen drops to 12.07%,but the concentration of carbon monoxide increases to 4392.3 10à6,and the concentration of carbon dioxide goes up to7.848%,which can make the persons in danger suffocate and die;(2)with vacuum chamber,explosion overpressure drops to 0.18 MPa,with 20 ms duration or less,and after explosion,the concentration of oxygen still remains 12.07%,but the concentration of methane is 7.83%,however the concentration of carbon monoxide is only 727.24 10à6,and the concentration of carbon dioxide is only 1.219%,at the this moment the concentration ratio of toxic gas drops by more than 83%in comparison to be that without vacuum chamber.Consequently,the vacuum chamber can guarantee that most methane does not take part in chemical reaction,and timely quenches the deflagration reaction of gas and oxygen.Because of the two points mentioned above,it reduces the explosion energy,and lowers that the overpressure of blast wave impacts and damages on the persons and facilities,and also decreases the consumption of oxygen and the production of the toxic gas.Therefore,it is safe to conclude that the vacuum chamber not only absorbs wave and energy,but also prevents and suppresses explosion.
基金funded by the National Science and Technology Support Program (2015BAK16B02 and 2015BAK16B01)the Fundamental Research Funds of China Academy of Safety Science and Technology
文摘This paper presents a method for analysis of stress and strain of gas pipelines under the effect of horizontal catastrophic landslides. A soil spring model was used to analyze the nonlinear characteristics concerning the mutual effects between the pipeline and the soil. The Ramberg–Osgood model was used to describe the constitutive relations of pipeline materials. This paper also constructed a finite element analysis model using ABAQUS finite element software and studied the distribution of the maximum stress and strain of the pipeline and the axial stress and strain along the pipeline by referencing some typical accident cases. The calculation results indicated that the maximum stress and strain increased gradually with the displacement of landslide.The limit values of pipeline axial stress strain appeared at the junction of the landslide area and non-landslide area. The stress failure criterion was relatively more conservative than the strain failure criterion. The research results of this paper may be used as a technical reference concerning the design and safety management of large-diameter gas pipelines under the effects of catastrophic landslides.
基金Supported by the National Natural Science Foundation of China （90210032, 50576001）.
文摘This article presents an acetylene production process by partial oxidation/combustion of natural gas. The thermodynamic performance and exergy analysis in the process are investigated using the flow-sheeting program Aspen Plus. The results indicate that the most important destruction of exergy is found to occur in the reactor and water quenching scrubber, amounting to 8.23% and 10.39%, respectively, of the entire system. Based on the results of thermodynamic and exergy analysis, the acetylene reactor has been retrofitted. The improvement ratios of molar 02 to CH4 and molar CO to CN4 are 0.65 and 0.20, respectively. An improvement of the acetylene production system is proposed. Adopting the improvement operation conditions and using oil to realize the reaction heat recovery, the feedstock of natural gas is reduced by 9.88% and the exergy loss in the retrofitting process is decreased by 19.71% compared to the original process.
文摘As longwall caving mining method prevails rapidly in China coal mines, amount of gas emission from longwall faces and goaf area increased significantly. Using traditional gas drainage methods, such as drilling upward holes to roof strata in tailgate or drilling inseam and cross-measure boreholes, could not meet methane drainage requirements in a gassy mine. The alternative is to drill boreholes from surface down to the Iongwall goaf area to drain the gas out. As soon as a coal seam is extracted out, the upper rock strata above the goaf start to collapse or become fractured depending upon the rock characteristics and the height above the coal seam. During overlying rock strata being fractured, boreholes in the area may be damaged due to ground movement after the passage of the Iongwall face. The sudden damage of a borehole may cause a Iongwall production halt or even a serious mine accident. A theoretical calculation of the stability of surface boreholes in mining affected area is introduced along with an example of determination of borehole and casing diameters is given for demonstration. By using this method for the drilling design, the damage of surface boreholes caused by excessive mining induced displacement can be effectively reduced if not totally avoided. Borehole and casing diameters as well as characteristics of filling materials can be determined using the proposed method by calculating the horizontal movement and vertical stain at different borehole depths.
基金supported by the National Hi-tech Research and Development Program of China (No.2006BAK03B02-04) the New Century Excellent Talent Support Plan of Ministry of Education of China (No.NCET-06-0477)
文摘Based on the principle of Bayesian discriminant analysis, we established a model of Bayesian discriminant analysis for predicting coal and gas outbursts. We selected five major indices which affect outbursts, i.e., initial speed of methane diffusion, a consistent coal coefficient, gas pressure, destructive style of coal and mining depth, as discriminating factors of the model. In our model, we divided the type of coal and gas outbursts into four grades regarded as four normal populations. We then obtained the corresponding discriminant functions through training a set of data from engineering examples as learning samples and evaluated their criteria by a back substitution method to verify the optimal properties of the model. Finally, we applied the model to the prediction of coal and gas outbursts in the Yunnan Enhong Mine. Our results coincided completely with the actual situation. These results show that a model of Bayesian discriminant analysis has excellent recognition performance, high prediction accuracy and a low error rate and is an effective method to predict coal and gas outbursts.
基金supported by the National Key R&D Program of China(Nos.2017YFE0301506 and 2017YFE0301306)。
文摘Tokamak exhaust is an important part of the deuterium-tritium fuel cycle system in fusion reactions.In this work,we present a laser-induced breakdown spectroscopy(LIBS)-based method to monitor the gas compositions from the exhaust system in the tokamak device.Helium(He),a main impurity in the exhaust gas,was mixed with hydrogen(H_(2))in different ratios through a self-designed gas distribution system,and sealed into a measurement chamber as a standard specimen.A 532 nm wavelength laser pulse with an output power of 100 mJ was used for plasma excitation.The time-resolved LIBS is used to study the time evolution characteristics of the signal strength,signal-to-background ratio(SBR),signal-to-noise ratio(SNR)and relative standard deviation(RSD)of the helium and hydrogen characteristic lines.The Boltzmann twoline method was employed to estimate the plasma temperature of laser-induced plasma(LIP).The Stark-broadened profile of He I 587.56 nm was exploited to measure the electron density.From these studies,an appropriate time was determined in which the low RSD%was consistent with the high signal-to-noise ratio.The He I 587.56 nm and Hαemission lines with good signalto-noise ratio were extracted from the spectrum and used in the external standard method and internal standard method for quantitative analysis.The test results for mixed gas showed that the average relative error of prediction was less than 11.15%,demonstrating the great potential of LIBS in detecting impurities in plasma exhaust gas.
基金supported by the National Social Science Foundation of China(Grant No.20VGQ003)。
文摘Urban natural gas is becoming the main sector driving China’s natural gas consumption growth in recent years.This study explores the impacts of urban natural gas price,wage,socioeconomic determinants,and meteorological conditions on urban natural gas demand in China over 2006-2017.Furthermore,this study also analyzes the potential regional heterogeneity and asymmetry in the impacts of gas price and income on China’s urban gas demand.Empirical results reveal that:(1)The increased gas price can significantly reduce the urban gas demand,and the average income level may effectively promote the gas demand,also,a strong switching effect exists between electricity and natural gas in urban China;(2)these impacts are heterogeneous in regions among China,urban natural gas demand is largely affected by the gas price in regions with high-gas-price and by income in regions with low-gas-price;and(3)the impact of gas price on urban gas consumption is consistent in regions with different urban natural gas consumption,while the impact of income is asymmetric.This study further provides several policy implications for improving the urban natural gas industry in China.
基金supported by the National Key R&D Program of China(Grant No.2018YFC0809300)the National Natural Science Foundation of China(Grant No.51806247)+2 种基金the Key Technology Project of Petro China Co Ltd.(Grant No.ZLZX2020-05)the Foundation of Sinopec(Grant No.320034)the Science Foundation of China University of Petroleum,Beijing(Grant No.2462020YXZZ052)
文摘Buried natural gas pipelines are vulnerable to external corrosion because they are encased in a soil environment for a long time.Identifying the causes of external corrosion and taking specific maintenance measures is essential.In this work,a risk analysis and maintenance decision-making model for natural gas pipelines with external corrosion is proposed based on a Bayesian network.A fault tree model is first employed to identify the causes of external corrosion.The Bayesian network for risk analysis is determined accordingly.The maintenance strategies are then inserted into the Bayesian network to show a reduction of the risk.The costs of maintenance strategies and the reduced risk after maintenance are combined in an optimization function to build a decision-making model.Because of the limitations of historical data,some of the parameters in the Bayesian network are obtained from a probabilistic estimation model,which combines expert experience and fuzzy set theory.Finally,a case study is carried out to verify the feasibility of the maintenance decision model.This indicates that the method proposed in this work can be used to provide effective maintenance schemes for different pipeline external corrosion scenarios and to reduce the possible losses caused by external corrosion.
基金University Science Malaysia (USM) and Malaysia Ministry of Education (MoE) for their technical and financial support
文摘The present study is aimed to compare the microstructure characteristics and mechanical properties of AA6082 in T6 condition of tubular joints fabricated by tungsten inert gas welding （TIG） and metal inert gas welding （MIG） processes. The effect of welding processes was analysed based on optical microscopy image, tensile testing, and Vickers micro-hardness measurements. The results showed that the tensile strengths of the TIG-welded joints were better than those of the MIG-welded joints, due to the contribution of fine equiaxed grains formation with narrower spacing arms. In terms of joint efficiency, the TIG process produced more reliable strength, which was about 25% higher compared to the MIG-joint. A significant decay of hardness was recorded in the adjacent of the weld bead zone, shown in both joints, related to phase transformation, induced by high temperatures experienced by material. A very low hardness, which was about 1.08 GPa, was recorded in the MIG-weldcd specimens. The extent of the heat-affected-zone （HAZ） in the MIG-welded joints was slightly wider than those of the TIG-welded specimens, which corresponded with a higher heat input per unit length.
基金supported by the National Natural Science Foundation of China (41161019, 41461020)
文摘The increasing intensity and frequency of sand-dust storms in China has led to greater prominence of associated environmentaland health issues. Many studies have focused on the health effects of air particulate contaminants, but fewformal investigations have studied the effects of sand-dust storms on human and animal health. The aim of this study wasto investigate the effects of dust storms on rat lung by using high resolution computed tomography （HRCT） and blood gasanalysis through a wind tunnel simulating. We found that the rat lung damage effects can be detected by the HRCT imagingafter exposure to sand-dust storm environments, but had no obvious result through blood gas analysis. Exposure durationspositively correlated with the damage degree to lung tissue. These will provide some evidence for clinical diagnosis ofnon-occupational pneumoconiosis.
基金funded by the Natural Science Foundation of Shandong Province (ZR202103050722)National Natural Science Foundation of China (41174098)。
文摘The tight-fractured gas reservoir of the Upper Triassic Xujiahe Formation in the Western Sichuan Depression has low porosity and permeability. This study presents a DNN-based method for identifying gas-bearing strata in tight sandstone. First, multi-component composite seismic attributes are obtained.The strong nonlinear relationships between multi-component composite attributes and gas-bearing reservoirs can be constrained through a DNN. Therefore, we identify and predict the gas-bearing strata using a DNN. Then, sample data are fed into the DNN for training and testing. After optimized network parameters are determined by the performance curves and empirical formulas, the best deep learning gas-bearing prediction model is determined. The composite seismic attributes can then be fed into the model to extrapolate the hydrocarbon-bearing characteristics from known drilling areas to the entire region for predicting the gas reservoir distribution. Finally, we assess the proposed method in terms of the structure and fracture characteristics and predict favorable exploration areas for identifying gas reservoirs.
