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This study aims to present the optimum technological parameters of the hot forging process of aerospace bolts. Deformation-related parameters were determined according to the relevant conditions for commercial production of bolts. Deformation behavior and evolution of the microstructure of Waspaloy were systematically studied at temperature in the range of 1000–1120 °C and strain rate in the range of 0.01–10 s−1. The obtained results revealed the sensitivity of the flow stresses to the deformation parameters and stresses increased when deformed at lower temperatures or higher strain rates. At the high strain rates of 5–10 s−1, the flow curves exhibited a pronounced flow softening. The curves demonstrated a dynamic equilibrium at the low strain rates of 0.01–0.1 s−1. A constituent model of Waspaloy was established to describe the flow characteristic of Waspaloy. The microstructures showed that the grain refinement of DRX at low temperature (1000–1040 °C) was the main mechanism for microstructural evolution, while the grain growth kinetic was the dominant mechanism at high temperature (1080–1120 °C). The DRX kinetic model of this superalloy was established. Also, the constitutive and dynamic recrystallization models were used in the Deform-3D software for validation. The obtained results revealed that the simulation results matched well with the experimental results of grain sizes at different regions of the bolt specimens. The study can provide guidance to optimize technological parameters and predict the microstructure for commercial bolt forging.

To achieve an accurate and comprehensive characterization of the multiscale pore–fracture characteristics of Permian coal in the Jingbian Block, Ordos Basin, a combination of scanning electron microscopy (SEM), X-ray computed tomography (CT), and nuclear magnetic resonance (NMR) techniques was utilized. With these experiments, the mineral composition, pore size distribution (PSD), porosity, and connectivity of pores in coal samples were characterized through qualitative and quantitative methods. The results show that the SEM experiments enabled qualitative identification of pores and mineral types. The coal samples primarily contained gas pores, cell pores, intercrystalline pores, and moldic pores, and clay minerals were the predominant fracture fillings. The 3D reconstruction of the CT experiments shows that the pores and fractures generally expand horizontally, while the minerals show obvious bedding expansion characteristics. Moreover, the estimation of full-size porosity in coal samples can be achieved by combining CT and NMR experiments. The full-size porosity of samples G11-5-1, G11-5-6, G11-5-9, and G11-5-11 was 8.93%, 9.11%, 10.45%, and 11.63%, respectively. The connectivity differences are primarily determined by the throat development degree and the connected pore–fracture count. Samples with more connected pores and larger throat radii exhibit excellent connectivity.

Introduction Coronavirus disease-2019 (COVID-19) spreads worldwide. The study aimed to understand the clinical characteristics of young COVID-19 patients. Material and methods Ninety patients with severe COVID-19 infection in western Chongqing were collected from 21 January to 14 March 2020. They were divided into 4 groups based on age: youth ( 60 years). The clinical symptoms, laboratory findings, imaging findings, and treatment effects were compared among the groups. Results There were 22, 27, 19, and 22 cases in the youth, middle-aged, middle-elderly, and elderly groups, respectively. There were no significant differences with respect to gender or smoking status among the four groups. The clinical indicators of severe disease in the youth group were significantly different from the other three groups, and included the lymphocyte count (p < 0.001), C-reactive protein level (p = 0.03), interleukin-6 level (p = 0.01), chest computed tomography (CT) findings (p < 0.001), number of mild cases (p = 0.02), education level (p < 0.001), and CD4 + T lymphocyte level (p = 0.02) at the time of admission, and the pneumonia severity index (PSI) at the time of discharge (p < 0.001). The complications (p < 0.001) among the youth group were also significantly different from the other groups. Conclusions Young patients have milder clinical manifestations, which may be related to higher education level, higher awareness and higher acceptance of the prevention and control of the COVID-19 epidemic, as well as their good immune function.

Coal measure gas resources, including coalbed methane (CBM), shale gas, and tight gas are abundant in the Daning–Jixian Block. The complexity of the source–reservoir–cap relationship in the coal measure strata leads to unclear symbiotic characteristics and gas accumulation, which in turn, restrict the exploration and exploitation of the coal measure gas. In this study, the enrichment and accumulation of coal measure gas are discussed and summarized in detail. The results show that there are eight lithofacies and six reservoir combinations in the superposed strata of the coal measures in the study area. Controlled by the tidal flat-lagoon facies, the “sand-mud-coal” type mainly distributes in P1s2 and P1t, showing a good gas indication. Based on the variation of the total hydrocarbon content, key strata, and pressure coefficient of the coal measure gas reservoir, four superposed gas-bearing systems are identified in the vertical direction. According to the relationship between the gas-bearing system and gas reservoir, the enrichment of coal measure gas in the study area can be divided into three modes, including an intra-source enrichment mode, a near-source migration enrichment mode, and a far-source migration enrichment mode. The symbiotic accumulation of a coal measure gas model is further proposed, that is, an “Adjacent to co-source reservoir” type superimposed coalbed methane and shale gas reservoir model, a “Three gas symbiosis” superimposed reservoir model in the local gas-bearing system, and a “Co-source far reservoir” tight sandstone gas reservoir model. Clarifying the symbiotic relationship of coal measure gas reservoirs is beneficial to the exploration and further production of unconventional gas in the study area.

Coal-measure gas is the natural gas generated by coal, carbonaceous shale, and dark shale in coal-measure strata. It includes resources of continuous-type coalbed methane (CBM), shale gas and tight gas reservoirs, and trap-type coal-bearing gas reservoirs. Huge in resources, it is an important gas source in the natural gas industry. The formation and distribution characteristics of coal-measure gas in San Juan, Surat, West Siberia and Ordos basins are introduced in this paper. By reviewing the progress of exploration and development of coal-measure gas around the world, the coal-measure gas is confirmed as an important strategic option for gas supply. This understanding is mainly manifested in three aspects. First, globally, the Eurasian east-west coal-accumulation belt and North American north-south coal-accumulation belt are two major coal-accumulation areas in the world, and the Late Carboniferous–Permian, Jurassic and end of Late Cretaceous–Neogene are 3 main coal-accumulation periods. Second, continuous-type and trap-type are two main accumulation modes of coal-measure gas; it is proposed that the area with gas generation intensity of greater than 10×108 m3/km2 is essential for the formation of large coal-measure gas field, and the CBM generated by medium- to high-rank coal is usually enriched in syncline, while CBM generated by low-rank coal is likely to accumulate when the source rock and caprock are in good configuration. Third, it is predicted that coal-measure gas around the world has huge remaining resources, coal-measure gas outside source is concentrated in Central Asia-Russia, the United States, Canada and other countries/regions, while CBM inside source is largely concentrated in 12 countries. The production of coal-measure gas in China is expected to exceed 1000×108 m3 by 2030, including (500–550)×108 m3 conventional coal-measure gas, (400–450)×108 m3 coal-measure tight gas, and (150–200)×108 m3 CBM. Key words: coal-measure gas (CMG), coalbed methane (CBM), tight gas, continuous-type, trap-type, gas generation intensity, resource potential, coal-accumulation period, coal-accumulation area

Negative absorption of an inverse V type which rises first and then drops is often observed in the adsorption test of low adsorption samples. In view of this, a gravimetric isotherm rig with a large sample size was introduced. Its testing principles and operation processes were analyzed based on the previous research results. Then, the volumetric method, magnetic-levitation gravimetric method and large sample size gravimetric method were compared in terms of their advantages and disadvantages. Accordingly, this gravimetric isotherm rig with a large sample size was adopted to perform isotherm adsorption experiments on the low-rank coal samples taken from Well Jimei 2 in the Jiergalangtu sag, Erlian Basin, Inner Mongolia, and shale samples from the Lower Silurian Longmaxi Fm in the southern Sichuan Basin, so as to explore the essential reason for the “negative adsorption” after the effect of a systematical cumulative error is eliminated. And the following research results were obtained. First, when the large sample size gravimetric method is adopted, the phenomenon of “negative adsorption” doesn't occur and the test results of low-rank coal and shale samples are reliable with a high fitting degree (R2 > 0.99). Second, an electronic sensor error (e.g. electronic balance and P&T sensors), a system cumulative error and an adsorbed phase density error are not the factors leading to the reversal of negative adsorption curves. Third, the void volume error of a sample cell is the essential reason for the negative adsorption. In conclusion, the test accuracy can be improved by introducing the volume correction factor into the isotherm adsorption interpretation algorithm. Keywords: Low-adsorption, Coal, Shale, Isotherm adsorption experiment, Negative adsorption, Volumetric method, Gravimetric method, Sample cell, Void volume error, Adsorbed phase density

Coal measure gas is broadly defined as all natural gas occurring in coal measure strata while narrowly defined as the coalbed methane (CBM) in coal beds and the natural gas in the adjacent tight sandstone reservoirs. In this paper, the accumulation characteristics and control factors of narrowly defined coal measure gas in China were analyzed from the aspects of source rock distribution, coal–sandstone combination type, sedimentary facies and closed system to improve CBM development benefit. And the following research results were obtained. First, there are various coal–sandstone combination relationships in coal measure strata of coal bearing basins in China. Second, the widely-distributed source rocks provide sufficient gas sources for the enrichment of coal measure gas. Third, sedimentary facies dominate the combination relationships of source–reservoir–caprock assemblages of coal measure gas, so the inborn material base of coal measure gas accumulation is formed. The sedimentary systems of fluvial facies and delta facies are the most favorable sedimentary facies for the paragenesis and accumulation of coal measure gas for their coal beds and sandstones are developed. Fourth, the closed system controls the whole process of generation, enrichment and accumulation of CBM (coal measure gas). Three types of coal measure gas reservoirs are identified: self-source and self-reservoir CBM reservoirs, paragenetic CBM–sandstone gas reservoirs, coal-derived sandstone gas reservoirs, among which the first type is currently the main target of CBM exploration and development. Finally, the next exploration direction of coal measure gas was pointed out as follows. First, the exploration and evaluation of coal measure gas shall be focused on the giant basins with abundant coal measure gas, such as Qinshui, Ordos, Junggar, Hailar and Jixi. Second, coal measure gas reservoirs shall be explored specifically based on different types. It is necessary to carry out CBM exploration in the self-source and self-reservoir CBM enriched zones in the shallow layers, integrated exploration of CBM and sandstone gas in the paragenetic CBM–sandstone gas reservoirs in the deep layers, and sandstone gas exploration in coal-derived sandstone gas reservoirs. Keywords: China, Coal measure gas, Coalbed methane (CBM), Tight sandstone gas, Accumulation characteristic, Control factor, Closed system, Integrated exploration and development

The Baode block on the eastern margin of the Ordos Basin is a key area for the development of low-rank coalbed methane (CBM) in China. In order to find out the genesis of CBM and its storage and seepage space in Baode block, the isotopic testing of gas samples was carried out to reveal the origin of CH4 and CO2, as well, mercury intrusion porosimetry, low temperature nitrogen adsorption, and X-ray CT tests were performed to characterize the pores and fractures in No. 4 + 5 and No. 8 + 9 coal seams. The results showed that the average volume fraction of CH4, N2, and CO2 is 88.31%, 4.73%, and 6.36%, respectively. No. 4 + 5 and No. 8 + 9 coal seams both have biogenic gas and thermogenic methane. Meanwhile, No. 4 + 5 and No. 8 + 9 coal seams both contain CO2 generated by coal pyrolysis, which belongs to organic genetic gas, while shallow CO2 is greatly affected by the action of microorganisms and belongs to biogenic gas. The average proportion of micropores, transition pores, mesopores, and macropores is 56.61%, 28.22%, 5.10%, and 10.07%, respectively. Samples collected from No. 4 + 5 coal seams have developed more sorption pores. Meanwhile, samples collected from No. 8 + 9 coal seams exhibited a relatively low degree of hysteresis (Hg retention), suggesting good pore connectivity and relatively high seepage ability, which is conducive to gas migration. The connected porosity of coal samples varies greatly, mainly depending on the relative mineral content and the proportion of connected pores.

It is of great significance to study the controlling effect of sealing systems on CBM enrichment in coalbed methane (CBM) exploration and development. In this paper, the relationships between CBM enrichment and geological elements were analyzed. The geological elements include sealing layers (e.g. regional cap rock, regional floor, and immediate roof and floor), later structural adjustment and strata production status. It is shown that CBM tends to enrich in the areas where regional mudstone cap rocks and floors are distributed stably, structures are uplifted and inversed slightly after the hydrocarbon accumulation period and the strata is gentle in a balanced state. Then, the concept of sealing system was put forward based on the worldwide CBM exploration and development practices over the years. A sealing system refers to a geological unit composed of a lateral stable zone and cap rock which prevents gas from migrating upward and downward. In a sealing system, CBM can get enriched and coal-measure gas can also be accumulated. Finally, three gas reservoir types (i.e., sandwich-type CBM reservoir, associated CBM-sandstone gas reservoir and coal-derived sandstone gas reservoir) were identified based on the configuration relationships between elements of the CBM (or coal-measure gas) sealing system. It is recommended to change the exploration ideas from simple CBM exploration to 3D CBM and coal-measure gas exploration. In addition, an evaluation index system of CBM (or coal-measure gas) geological selection was established. It is pointed out that good application effects may be realized if the stereoscopic CBM and coal-measure gas exploration is applied in the Junggar Basin and the eastern margin of the Ordos Basin.

The Wuwei Basin is located in the Gansu Corridor, which has abundant coalbed methane resources of 2.75 × 10 11 m 3 . However, a low degree of coalbed methane exploration exists, and only a few wells have been drilled in local regions due to insufficient understanding of coalbed methane enrichment and its main controlling factors. This study analyzed the controlling factors of coalbed methane enrichment, including coal reservoir characteristics, hydrogeological conditions, and the original sedimentary environment of the coal-bearing strata. The results showed that the main coal seams were developed in the Taiyuan Formation, and were mostly concentrated in the Yingpan Sag in the south and the Ermahu Sag in the north of the study area. The macrolithotype of the coals in this basin was mainly semi-bright coal with a medium to high rank. Coal macerals were mainly vitrinite, ranging between 65.1% and 91.6% (averaged 81.70%), followed by liptinite, ranging between 1.9% and 29.5% (averaged 8.82%), and inertinite, ranging between 0.2% and 16.5% (averaged 3.66%). Mineral contents varied from 2.5% to 15.1% (averaged 6.16%). The macrolithotype and microlithotype of the Taiyuan Formation coals were favorable for coalbed methane formation. Through comparative analysis of moisture content, ash yield, gas content, and coal-forming sedimentary environments, it was found that the coal formed in the lagoon environment had a higher gas content and lower ash yield than that of the coal formed in the tidal flat environment. The high contents of total dissolved solids in aquifers around coal seams (1.75–16.70 g/L) reflected the closed hydrodynamic environment and were favorable for the preservation of coalbed methane in the Yingpan Sag. Considering various controlling factors (i.e., structure, sedimentation and hydrogeology), three coalbed methane enrichment models were proposed. The model of coalbed methane enrichment in the synclinorium was the most favorable for the enrichment of coalbed methane in the Yingpan Sag.

In situ synthesized TiB whiskers (TiBw) reinforced Ti-15Mo-3Al-2.7Nb-0.2Si alloys were successfully manufactured by pre-sintering and canned hot extrusion via adding TiB2 powders. During pre-sintering, most TiB2 were reacted with Ti atoms to produce TiB. During extrusion, the continuous dynamic recrystallization (CDRX) of β grains was promoted with the rotation of TiBw, and CDRXed grains were strongly inhibited by TiBw with hindering dislocation motion. Eventually, the grain sizes of composites decreased obviously. Furthermore, the stress transmitted from the matrix to TiBw for strengthening in a tensile test, besides grain refinement. Meanwhile, the fractured TiBw and microcracks around them contributed to fracturing.

Introduction: Coronavirus disease-2019 (COVID-19) has spread worldwide. The study aimed to understand the clinical characteristics of young COVID-19 patients.Material and methods: Ninety patients with severe COVID-19 infection in western Chongqing were collected from 21 January to 14 March 2020. They were divided into 4 groups based on age: youth (< 39 years), middle-aged (39-48 years), middle-elderly aged (49-60 years), and elderly (> 60 years). The clinical symptoms, laboratory findings, imaging findings, and treatment effects were compared among the groups.Results: There were 22, 27, 19, and 22 cases in the youth, middle-aged, middle-elderly, and elderly groups, respectively. There were no significant differences with respect to gender or smoking status among the four groups. The clinical indicators of severe disease in the youth group were significantly different from the other three groups, and included the lymphocyte count (p < 0.001), C-reactive protein level (p = 0.03), interleukin-6 level (p = 0.01), chest computed tomography (CT) findings (p < 0.001), number of mild cases (p = 0.02), education level (p < 0.001), and CD4 + T lymphocyte level (p = 0.02) at the time of admission, and the pneumonia severity index (PSI) at the time of discharge (p < 0.001). The complications (p < 0.001) among the youth group were also significantly different from the other groups.Conclusions: Young patients have milder clinical manifestations, which may be related to higher education level, higher awareness and higher acceptance of the prevention and control of the COVID-19 epidemic, as well as their good immune function. [ABSTRACT FROM AUTHOR]