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The main source rocks, hydrocarbon generative subbasins, hydrocarbon generation periods, resource potential, and the relationship between the trap evolution history and hydrocarbon generation history are important problems associated with oil and gas exploration. In this study, we develop a three-dimensional geological model with respect to the Mesozoic and Cenozoic strata of the northern margin of the Qaidam Basin based on the most recent geological data. Using this model, the burial depth, temperature, maturity, and gas generation history of the source rock, the plane diagram of the source-rock current maturity, the gas generation intensity map, and the amount of gas generation during each geological period and within different subbasins can be obtained. Based on the obtained maps, we can state that the maturity of the source rock controls the distribution of natural gas (i.e., natural gas is located within and in the vicinity of mature and highly mature source rocks). We also observed the following: (1) the Lower Jurassic section is the main gas source rock; (2) the Yibei subbasin is the main hydrocarbon generative subbasin, followed by the Kunteyi, Pingdong, and Lenghu subbasins; (3) the main gas generation period is after the upper member of the lower Ganchaigou Formation deposition, with maximum gas generation occurring during the upper Ganchaigou Formation deposition and gradually decreasing thereafter—the majority of the structures in the inner basin are formed after lower Youshashan Formation deposition, demonstrating the tectonic activity coincided with periods of natural gas formation; and (4) the amount of natural gas resource becomes 1.23 trillion cubic meters. From these analyses, we can demonstrate that the late tectonic belts formed in the four gas-generating subbasins exhibit considerable promise for exploration.

In recent years, gas reservoirs containing high levels of hydrogen sulfide have been found in salinized lacustrine carbonate rocks in the upper member of the Lower Ganchaigou Formation (E32) in the Yingxiongling area of the western Qaidam Basin. This poses great safety risks to drilling and development. To clarify the genetic mechanisms of hydrogen sulfide, we have analyzed the geochemical characteristics and sulfur isotopes of natural gas and predicted the distribution of hydrogen sulfide. The results show that (1) natural gas in the Yingxiongling area is dominated by wet gas, with relatively high nonhydrocarbon content. The gas is E32oil-type gas in a mature stage. (2) Hydrogen sulfide in natural gas reservoirs is less likely to originate from biological and volcanic geneses, and it is primarily a product of thermochemical sulfate reduction. The high-quality Oligocene source rocks distributed across a large area, the saline-deposit formations widely distributed in the western Qaidam Basin, and the high geothermal gradients and large numbers of developed pore-type reservoirs, all combine to provide favorable conditions for the formation of hydrogen sulfide reservoirs. (3) During the E32 deposition period, rock salt developed in the center of the lake basin, the sealing conditions for oil and gas were favorable, and the formation temperature was high during the reservoir formation period. Development of subsalt porous reservoirs is conducive to enrichment of hydrogen sulfide, and comprehensive prediction indicates that the subsalt formation in the Central Yingxiongling-Ganchaigou area is an enrichment zone for hydrogen sulfide. The research results are of considerable significance for the exploration and deployment, and the production safety, of hydrogen sulfide-containing reservoirs.

Breakthroughs have been made for the natural gas exploration of the Middle Devonian and the Middle Permian formations in the Sichuan Basin in recent years. Nevertheless, its natural gas source is still not clear, which then affects the next exploration deployment decision. A comprehensive study is conducted on the geochemical characteristics of the Middle Devonian and the Middle Permian natural gas, the biomarkers of reservoir bitumen, and the source rocks. The results show that these natural gases are secondary cracking dry gas that includes more than 86% of methane content, a small amount of ethane, propane, and a non-hydrocarbon gas (e.g., nitrogen, carbon dioxide, and hydrogen sulfide). The natural gas maturity varies slightly in different regions. The carbon and hydrogen isotope values of natural gas are as follows: δ13C1 ranges from −35.7‰ to −27.3‰, δ13C2 ranges from −38.7‰ to −26.6‰, δ13C3 ranges from −37‰ to −26.5‰, δ2HCH4 ranges from −141‰ to −138‰, and δ2HC2H6 ranges from −164‰ to −112‰. The isotope values indicate that the genetic type of natural gas is the sapropelic type and the mixture type is dominated by sapropelic type. The difference between natural gas values of δ13C1, δ13C2, and δ2HCH4 in different regions is related to the contribution ratio of source rocks from different ages. The gases of the Middle Devonian and the Middle Permian of the Shuangyushi structure in Northwestern Sichuan, the Middle Permian of Southwestern Sichuan, and the Middle Permian of Paleo-uplift in Central Sichuan are mainly derived from the Cambrian Qiongzhusi Formation and the Middle-Lower Permian source rocks. The Middle-Upper Permian natural gases of the volcanic reservoir in Southwestern Sichuan is mainly from the Qiongzhusi source rock. The Middle Permian natural gases of the Hewanchang structure in Northwestern Sichuan, Eastern Sichuan, and Southern Sichuan are mainly derived from the Silurian Longmaxi source rock. The research results have important guiding significance for developing exploration and deployment solutions for natural gas of the Middle Devonian and the Middle Permian formation in the Sichuan Basin.

Natural gas resources in the Qaidam Basin are abundant and of various types. On the basis of the natural gas carbon isotope distribution characteristics, the western Qaidam Basin mainly comprises o...

To study the influence of oblique flow on propeller fluctuation pressure characteristics of a four-screw vessel, the wake field and self-propulsion performance are calculated and analyzed utilizing computational fluid dynamics simulations. The characteristics of the wake field and propeller fluctuation pressure under different drift angle consisting of 0°, ±10°, and ±20° are compared and discussed in detail. The results show that negative drift angle affected the wake field of inside propeller more severely due to the generation of bilge vortex. The mean values of inside propeller fluctuation pressure are about 30% larger than those of the outside one, while the amplitudes of fluctuation pressure are reversed. The mean values of propeller fluctuation pressure experience a gradual decrease from β = −20° to 20° with an exception of inside propeller at β = −20° condition. The fluctuation amplitude of outside propeller is more affected by oblique flow due to the influence of oblique flow on flow separation point.

By direct numerical simulations, non-isothermal effects on turbulence anisotropy and growth rate are investigated in three-dimensional spatially developing supersonic mixing layers with high convective Mach numbers ( Mc > 0.6). Hot air is blown into the high-speed stream, and cold air is added on the low-speed side. Two non-isothermal simulations with different temperature gradients are conducted and compared with the isothermal mixing layer. The Reynolds stress transport is analyzed to reveal the underlying modulation mechanisms by temperature gradients. The supersonic mixing layer is significantly anisotropic, and the streamwise turbulent intensity is larger than the transverse and spanwise turbulent intensities. The non-isothermal effects enhance the energy transfer from the streamwise Reynolds stress to transverse and spanwise Reynolds stresses in the initial shear layer, and the mixing layer anisotropy is intensely attenuated, which is attributed to the increment of the flow instability. Thus, the shear layer growth is initially accelerated, and the supersonic mixing layer is destabilized. However, the fluid viscosity and the viscous dissipation are enhanced, and the Reynolds stresses decay more strongly in the fully developed region. The transverse and spanwise turbulent intensities decrease more than the streamwise turbulent intensity due to the attenuation of the correlation between pressure and dilatation fluctuations. Consequently, the shear layer turbulence anisotropy is augmented with stronger three-dimensionality. As the Reynolds shear stress is reduced and the entrainment of irrotational fluid from the free streams into the shear layer is attenuated, the mixing layer growth rate is decreased in the self-similar turbulence.

The heterogeneous characteristics and their influencing factors of organic matter are still the research focuses of saline lacustrine hydrocarbon source rocks. This paper examined the heterogeneous characteristics of organic matter richness and type. The effects of tectonic activities, sedimentary facies, climate, biological sources, and preservation conditions on organic matter richness and type were examined in the Yiliping Depression, Qaidam Basin, northwestern China. Organic matter enrichment models for the Yiliping Depression were developed. Total organic carbon (TOC) content, extractable organic matter (EOM) content, and free hydrocarbon and kerogen thermal cracking hydrocarbon yield of mudstones are higher than 0.5%, 0.05% and 0.5 mg/g in the condensed sections and the early stage of high stand systems tracts while lower in other intervals. The heterogeneity of organic matter richness and type in the Pliocene is displayed. With the uplift of the A-erh-chin mountains, influenced by the Himalayan tectonic movement during the Neogene, the sedimentary facies were mainly saline lakes with braided river deltas, and their depocenters gradually migrated eastward. Climatic conditions changed from humid in the lower Pliocene to dry in the middle and upper Pliocene. Multiple water transgressive and regressive cycles formed multiple condensed sections and high stand systems tracts, where enough accommodation space, organic matter supply, favorable preservation conditions resulting from relatively deep and quiet water brought more organic matter accumulation. Mixed input of aquatic algae and terrestrial plants formed type II2 and type III kerogen in the depression, and there are more type II1 and type I hydrocarbon source rocks around lacustrine centers. The saline lacustrine evolution and organic matter accumulation models were developed, showing that the peak saline lacustrine period in the middle Pliocene was the most favorable for organic matter enrichment. The results indicate that there are active hydrocarbon source rocks (TOC content more than 0.4% and reflectance of vitrinite more than 0.5%) from the Neogene around the Jianshishan and Hongsanhan structures, and the Yikeyawuru and Taijinaier structures in the Yiliping Depression.

In order to study the influence of the head cone angle and velocity of truncated cone-shaped projectiles on the cavitation and trajectory characteristics under the condition of low-speed oblique entry into water, based on the high-speed camera method, the comparative experiments of different truncated cone-shaped projectiles at low-speed oblique entry into water were carried out, and the effects of the head cone angle and velocity of truncated cone-shaped projectiles on the entry cavitation, movement speed and pitch angle were obtained. The experimental results show that the smaller the cone angle of the truncated cone projectile's head, the earlier the tail collides with the lower wall of the bubble. The smaller the head cone angle is, the faster the initial velocity is, and the later the time of deep closure of the cavitation is. The cavitation of the projectile increases with the decrease of the head cone angle and the increase of the velocity. Velocity and head cone angle have influence on the stability of water inflow. When the velocity of projectile is lower than the critical value, it tends to increase, and when it is higher than the critical value, it tends to decrease.

Based on the volume of fluid (VOF) multiphase flow equations, the k-e turbulent model and sliding mesh technique, the low speed vertical water-entry of a hollow cylinder was investigated numerically. The numerical results have a good agreement with corresponding experimental results and finer mesh independence. The results show that a jet flow induced by the through-hole provides a new connection between the inner and outer flow at the pinch-off time underwater. Furthermore, a little bubble on the top of the through-hole jet is created by the collision of the edge surface of the water column inside the cylinder. The initial water-entry speed has a significant influence on the inner cavity formation, the pinch-off depth, the through-hole jet ejection and the motion parameter during the vertical water-entry process.

During the Paleogene–Neogene, the Qaidam Basin was a saline lacustrine basin so the biomarkers of hydrocarbon source rocks exhibited unique characteristics under the salinization conditions. Saturated hydrocarbons extracted from a large number of source-rock samples were analyzed using gas chromatography and mass spectrometry. The results showed that n-alkanes in the source rocks were evenly distributed between even and odd carbon numbers, isoprenoid alkenes were predominantly phytanes, and ratios of pristane to phytane (Pr/Ph) were low, mostly in the range from 0.2 to 0.8. Terpanes typically showed high contents of C35 homohopane and gammacerane. Overall, the ratios of gammacerane to C30 hopane (gammacerane/C30 hopane) and C35–C34 homohopane (C35/C34 homohopane) exhibited a positive correlation. Differing concentrations of oleanane were detected. The relative content of C27 and C29 steranes in the hydrocarbon source rocks varied from 25 to 75%, and the relative content of C28 sterane in a considerable number of samples was higher than 30%. C27–C29 steranes generally showed an asymmetric V-shaped distribution, and the distribution of sterane/hopane and Pr/Ph ratios showed negative correlations. The salinity and reducibility indexes of the southern area of the Western Qaidam Basin were significantly higher than those of the northern area of the basin during the Oligocene–Miocene. Source rocks in the northern area were formed in a low-salinity and weakly reductive environment with type II2–III kerogen, whereas the hydrocarbon source rocks in the southern area formed in a high salinity and strongly reductive environment. The sedimentary water salinity and reducibility of the different areas were reduced in the following order: Hongliuquan, Yuejin, Shizigou, and Wunan–Lvcaotan. The best source rocks in this basin were developed in the Hongliuquan, Yuejin, and Shizigou areas with type II1–II2 kerogen. This study lays a foundation for further understanding the geochemical distribution of the hydrocarbon source rocks and crude oil in addition to the characteristics of the oil source in Paleogene and Neogene.

Based on large eddy simulation (LES), combined with high order tuned centered-difference (TCD) scheme, the initial flow characteristics of the unsteady subsonic elliptic jet was investigated numerically. The numerical results illustrate the formation, variation and development of the subsonic elliptic jets’ initial flow structures. Moreover, the self-induced deformation of the noncircular vortex loops and the distribution of the streamwise vorticity field have been completely clear using the three-dimensional (3D) view. The vorticity field of the results qualitatively shows that the self-induced Biot-Savart deformation of primary vortex loop (PVL) leads to the streamwise vortices generation in the flow, and the streamwise vortex pairs enlarge along the primary vortex core and augment the deformation of PVL. These two mechanisms govern the phenomenon of axis switching. Subsequently, the coherent structures present in the major and minor axis planes of the elliptic vortex loop and jet shear layer are identified with proper orthogonal decomposition (POD) method. Moreover, the mechanisms of vortex dynamics and the entrainment features of various noncircular jets have also been described in detail.

The northern margin of the Qaidam Basin is an important area for natural gas exploration that includes the recently discovered Dongping and Niudong gas fields. However, the origins of the natural gas and the primary factors controlling gas accumulation in the region are unclear, particularly in the piedmont zone. Planning and exploration strategies are limited by a lack of knowledge about natural gas accumulation mechanisms. In this study, various comprehensive geochemical, geophysical and geological techniques were applied to investigate the origin and distribution of natural gas in this area, as well as the main factors controlling gas accumulation. The results demonstrate that the gas deposits are dominated by gaseous hydrocarbons with C1/C1–5 ratios in the range 0.76–0.99. The natural gases are characterized by wide variations in δ13C1 values (−19.1‰ to −36.1‰) and relatively heavy δ13C2 values (−19.82% to −25.42%). The oil and gas in the investigated area exhibit a zonal spatial distribution and have features typical of coal-generated gases. The locations of major hydrocarbon-generating depressions and source rock maturity exert primary control on the distribution of oil and gas reservoirs. Paleo-uplifts and paleo-slopes controlled the direction of hydrocarbon migration and accumulation, while faults and conducting systems connected to the hydrocarbon source rocks constituted channel systems that controlled the transport of oil and gas. Suggestions for future exploration have been put forward, which will provide significant guidance for gas exploration in the area. Future promising areas for exploration include the paleo-uplifts in the east of the Altun Mountains and the west of the Qilian Mountains front and the Eboliang-Lenghu structural belt in the northern margin of the Qaidam Basin. These results will also provide guidance to natural gas exploration and research efforts in other basins with similar geological settings.

The initial flow fields of the supersonic underexpanded square jets with different nozzle pressure ratios were investigated numerically. The governing equations of large eddy simulation (LES) for compressible flow have been employed and solved numerically with the combination of high-order hybrid schemes. The numerical result provides the 3D shock wave structures embedded in the underexpanded square jet. Moreover, the effect of nozzle pressure ratio on the 3D characteristic behavior of near-nozzle shock wave and the jet boundary are discussed, it is found that the near-nozzle shock wave structure suppresses the jet boundary at the corner position expansion along the diagonal direction, and accelerates the jet boundary near the sidewall position to move in normal direction to the nozzle side, finally resulting in a remarkable cross-shaped jet cross section at the downstream. Besides, the 3D behavior of streamwise vortices during the self-induced deformation of primary vortex loop is identified using the iso-vorticity field, and their role in the axis-switching behavior of supersonic square vortex loop is analyzed in detail.

In case of a four-screw ship, the propellers show different hydrodynamics performance due to the asymmetric distribution of the wake. And the particularity of the scale effect on wake field for this type of ship would make a more complicated characteristics on propeller bearing force. In this paper, a numerical simulation study of scale effect on propeller unsteady bearing force of a four-screw ship was performed by employing RANS method. The load variation of the single-blade is analyzed to understand the fluid mechanism of the interaction between the propeller blade and wake flow. The larger wake field difference between inside and outside propeller disk aggravates the unbalanced load distribution for the full-scale ship. The results of propeller bearing force highlight that the fluctuation values of full-scale ship are smaller than those of model one. Moreover, the scale effect of outside propeller is strong with respect to the inside one. The above findings can provide theoretical guidance for load balancing and vibration reduction of the four-screw ships.

The Songliao Basin is a large-scale petroliferous basin in China. With a gradual decline in conventional oil production, the exploration and development of replacement resources in the basin is becoming increasingly important. Previous studies have shown that the Cretaceous Qingshankou Formation (K2qn) has favorable geological conditions for the formation of shale oil. Thus, shale oil in the Qingshankou Formation represents a promising and practical replacement resource for conventional oil. In this study, geological field surveys, core observation, sample tests, and the analysis of well logs were applied to study the geochemical and reservoir characteristics of shales, identify shale oil beds, build shale oil enrichment models, and classify favorable exploration areas of shale oil from the Cretaceous Qingshankou Formation. The organic matter content is high in shales from the first member of the Cretaceous Qingshankou Formation (K2qn1), with average total organic carbon (TOC) content exceeding 2%. The organic matter is mainly derived from lower aquatic organisms in a reducing brackish to fresh water environment, resulting in mostly type I kerogen. The vitrinite reflectance (Ro) and the temperature at which the maximum is release of hydrocarbons from cracking of kerogen occurred during pyrolysis (Tmax) respectively range from 0.5% to 1.1% and from 430 °C to 450 °C, indicating that the K2qn1 shales are in the low-mature to mature stage (Ro ranges from 0.5% to 1.2%) and currently generating a large amount of oil. The favorable depth for oil generation and expulsion is 1800–2200 m and 1900–2500 m, respectively as determined by basin modeling. The reserving space of the K2qn1 shale oil includes micropores and mircofractures. The micropore reservoirs are developed in shales interbedded with siltstones exhibiting high gamma ray (GR), high resistivity (Rt), low density (DEN), and slightly abnormal spontaneous potential (SP) in the well-logging curves. The microfracture reservoirs are mainly thick shales with high Rt, high AC (acoustic transit time), high GR, low DEN, and abnormal SP. Based on the shale distribution, geochemical characteristics, reservoir types, fracture development, and the process of shale oil generation and enrichment, the southern Taikang and northern Da'an are classified as two favorable shale oil exploration areas in the Songliao Basin.

During the Pleistocene, the western Qaidam Basin has largely experienced strong structural reconstruction and strong erosion. First, the eroded thickness of Neogene strata was restored approximately by the stratigraphic profile comparison method and plane trend surface restoring method; then, accurate calculation of erosion was recovered using vitrinite reflectance, and the erosion that was restored by the trend surface restoring method was corrected; finally, a distribution map of cumulative erosion was produced. This study marks an important achievement in that one of the most important parameters of basin tectonic evolution, sedimentary evolution, and oil and gas accumulation history has been obtained, and that a basic geological problem has been solved in the Qaidam Basin. The areas with high erosion and low erosion are shown in the map and a close relation between the distribution of oil and gas fields and erosion was recognized. Large and medium oil and gas fields are mainly distributed in areas with medium and low erosion. It is difficult to form large-scale oil and gas accumulation in areas in which erosion is more than 2000 m. The mechanism of the relation between oil and gas distribution and erosion is explained. This study will be of use in predicting the distribution of oil and gas.

With the rapid development of mobile applications and online social networks, users often encounter a frustrating challenge to set privacy and security policies (i.e., permission requests) of various applications correctly. For instance, in an Android system, it is hard for users, even programmers, to identify malicious permission requests (policies) when they install a third-party application. To simplify the task of policy management, in this paper, we propose a novel policy administration method where the policy settings from users' friends will be used as a key recommendation to guide policy administration, and the security of friends' privacy will be protected. We propose to let a user invite his or her friends to help with policy setting in applications, and we call such a method socialized policy administration (SPA for short). We designed two types of SPA: basic SPA and composite SPA. Both types of SPA are equipped with a privacy preserving mechanism that enables users' friends to help users without leaking the friends' preferences. In our prototype based on Telegram, i.e., one of the most popular instant messaging applications, we utilize partially homomorphic encryption cryptosystems to implement our framework. Based on the performance evaluation, SPA is able to configure almost all types of policies of current popular Android applications with a modest performance overhead.

Deep natural gas in the northern margin of the Qaidam Basin is characterized by low exploration degree and large resource potential, but the genesis of deep gas reservoirs is complex. In particular, Jurassic source rocks do not develop in west of Altun foreland. The mechanism of deep accumulation is unknown, which restricts the exploration of deep gas reservoirs. Using gas components, isotopes and other data, combined with the geological characteristics of the Altun foreland, this study analyzes the genesis and source of deep gas in this area, and establishes the accumulation procesess of the deep gas reservoirs. Analysis shows that the gas in the Altun foreland is dominated by coal-type gas with the characteristics of oil cracking gas in deep reservoirs. The Jurassic source rocks in the Qaidam Basin are mainly lacustrine mudstones, with black mudstones and oil shale developed, which have the material basis for forming large oil reservoirs. The deep reservoir has experienced the process of long-term deep burial and high-temperature cracking, and has the conditions to form oil cracked gas. Accumulation in deep bedrock gas reservoirs is characterized by early oil filling, later high-temperature cracking into gas, and late adjustment. Reservoirs formed in early stage can be deeply cracked into gas reservoir under high temperature in the process of deep burial. The ancient uplifts along the basin margin and large anticline traps in the late tectonic zone are favorable exploration areas for deep gas. The exploration area for natural gas in the Qaidam Basin has been expanded by the discovery of deep oil cracking gas in the Altun foreland, which has crucial significance for guiding and intensifying deep gas exploration in the Qaidam Basin.

The vertical water-entry processes of a hollow cylinder with three different velocities are investigated both numerically and experimentally. Three different closure patterns and flow characteristics of the air-entraining cavities induced by water-entry processes are discovered and discussed. Our results show that three different closure patterns appear with the increase of entry velocity, the deep-closure, the surface closure on the through-hole jet and on the geometry wall. Three high-speed regions also appear during the water entry process and their characteristics are different with various closure patterns. Besides, with the increase of water entry velocity, the velocity variation will vary from increase to decrease, but their water depths all increase linearly due to the short time and small variations of velocities.

On the basis of salinity and organic geochemical analyses of mudstones, this paper analyzed the relationship between salinity and sedimentary facies of different strata; studied influences of salinity on organic matter richness, types, and thermal maturities of source rocks; and built the organic enrichment accumulation model for the Paleogene and Neogene saline lakes of the western Qaidam Basin. In the western Qaidam Basin, saline lake depocenters and high salinity areas migrated eastward, and chloride ion (Cl–) concentration of source rocks showed an increasing trend from the Paleocene to Pliocene. The relationship between organic matter content and salinity of the Paleocene and Pliocene source rocks shows a three-interval model: both TOC (total organic carbon) content and chloroform bitumen content have low values at the low salinity stage, first increase to the peak and then decrease to the lowest values at the medium salinity stage, and sustain the lowest values at the super saline stage because of t...

The Western Qaidam Basin (WQB) is situated at the northeastern margin of the Tibetan Plateau. It is adjacent to the Altyn Tagh Range to the west and is bordered at the south and north by the Eastern Kunlun Range and Southern Qilian Range, respectively. Sporadic Jurassic outcrops are exposed along the Altyn Tagh Range. Although subsurface data have revealed that the Jurassic rocks also developed in the basin interior, little is known about their distribution and depositional characteristics. Hydrocarbon exploration has revealed that the Lower–Middle Jurassic strata are important source rocks and reservoirs in the WQB. However, due to post-depositional uplifting, exhumation or deep burial, the sediments provenance, paleogeography and the basin properties during the Early–Middle Jurassic in the whole WQB remain less understood. In this study, we examine the sedimentary records combined with detrital zircon U–Pb geochronology based on an analysis of post-depositional modification, to reveal the source-to-sink relationship between the WQB and surrounding potential source areas, and to further reconstruct the Early–Middle Jurassic paleogeography of the WQB. During the Early Jurassic, there were a series of small-scale, separated rift basins which were characterized by proximal sedimentation and rapid facies shift in the WQB. Specifically, the Lower Jurassic sediments in the southern WQB mainly originated from the Eastern Kunlun Range with minor supply from the Paleozoic intrusions that might have been exposed in the hinterland of the Qaidam Block; the provenance in the northern WQB was dominated by the uplift area to the west. There was a broader depression basin in the southern WQB. The Eastern Kunlun Range and the ancestral Altyn Mountains, served as the two dominant source areas for the clastic material of the southern WQB during the Middle Jurassic. Integrated analysis on sedimentology and provenance reveals that the southeastern Tarim Basin and the WQB were likely to have been interconnected or adjacent during Middle Jurassic period. We thus infer that no large-scale strike-slip displacement along the Altyn Tagh Fault occurred during that period. Combining regional tectonic settings, we tentatively suggest that the extensional setting following the orogenic movement in the eastern part of the Paleo–Tethys Ocean could have been responsible for the formation of the Early Jurassic rift basins. By the early Middle Jurassic, the Bangonghu–Nujiang Tethys Ocean and the Mongol–Okhotsk Ocean were subducted northward beneath the Qiangtang terrane and Siberian continent, respectively. These led to the presence of an extensional stress field and the formation of a broader depression basin in the southern WQB during the Middle Jurassic. Paleogeography reconstruction results indicate that the northern WQB should have much potential for hydrocarbon exploration.

The current challenge in the development of high-performance lithium-sulfur (Li-S) batteries is to facilitate the redox kinetics of sulfur species as well as to suppress the shuttle effect of polysulfides, especially at high current rates. Herein, aiming the application of Li-S at high current rates, we coupled a sp2 carbon configuration consisting of 3D carbon nanotubes/graphene prepared by ultrahigh temperature treatment (2850 °C) with S (2850CNTs-Gra-S) for application in Li-S batteries. The 2850CNTs-Gra as the host material exhibits a nearly perfect sp2 hybridized structure because ultrahigh temperature treatment not only repairs the raw defects in CNTs and graphene, but it also forms new sp2 C-C bonds between them. The 3D sp2 carbon network ensures ultrafast ion/electron transfer and efficient heat dissipation to protect the integrity of the separator when the Li-S battery is running at an ultrahigh rate. Based on these unique advantages, the 2850CNTs-Gra-S cathode shows a high current rate performance. Critically, it still delivers a considerable specific capacity after 1500 cycles even at a current rate of 15C and exhibits an extremely low capacity degradation rate of 0.0087% per cycle.

Lithium–sulfur batteries suffer from poor cycling stability at high areal sulfur loadings (ASLs) mainly because of the infamous shuttle problem and the increasing diffusion distance for ions to diffuse along the vertical direction of the cathode plane. Here, a carbon nanotube (CNT)/graphene (Gra)‐S‐Al3Ni2 cathode with 3D network structure is designed and prepared. The 3D network configuration and the Al in the Al3Ni2 provide an efficient channel for fast electron and ion transfer in the three dimensions, especially along the vertical direction of the cathode. The introduction of Ni in the Al3Ni2 is able to suppress the shuttle effect via accelerating reaction kinetics of lithium polysulfide species conversion reactions. The CNT/Gra‐S‐Al3Ni2 cathode exhibits ultrahigh cycle‐ability at 1 C over 800 cycles, with a capacity degradation rate of 0.055% per cycle. Additionally, having high ASLs of 3.3 mg cm−2, the electrode delivers a high reversible areal capacity of 2.05 mA h cm−2 (622 mA h g−1) over 200 cycles at a higher current density of 2.76 mA cm−2 with high capacity retention of 85.9%. The outstanding discharge performance indicates that the design offers a promising avenue to develop long‐life cycle and high‐sulfur‐loading Li–S batteries.

Based on large eddy simulation (LES) combined with the high-order hybrid schemes, the flow characteristics of both supersonic circular and square jets were investigated numerically for Ma = 1.4 . Our results illustrate the three-dimensional (3D) structures and their evolutions of both circular and square jets, as well as the shock structures of both jets. Moreover, the phenomena of 45° axis switching and stream-wise vortices enhancing the entrainment and mixing process of the square jet were also identified and discussed in detail.

The Paleogene and Neogene oil and gas in the western Qaidam basin have a regular distribution in three concentric zones from the edge to the center of the basin. Natural gas mainly occurs in the inner zone, and the gas-oil ratio of the northern area of the basin is significantly higher than that of the southern area. Large amounts of carbon isotope data of natural gas, plotted in X-shaped and comprehensive identification diagrams for the southern area and northern area, respectively, were used to identify the types of natural gas. The large-scale distribution of natural gas is highly consistent with the Ro values of major source rocks, but is poorly correlated with the type of organic matter. This indicates that the main controlling factor of natural gas distribution is organic matter maturity, and the kerogen types act as the basis for the formation of different types of natural gas. Paleouplifts and squeezed anticlines near hydrocarbon generation depression centers, which are major natural gas-rich regions, control the migration directions of natural gas, while hydrocarbon migration pathways and fault systems connecting gas sources are the most important factors for natural gas reservoir formation in the inner basin. Therefore, favorable zones for natural gas distribution can be predicted on the basis of the distribution of thermal evolution and the gas generation intensity of major source rocks as well as the structural map. The Shizigou-Youshashan-Yingdong-Dawusi, Youquanzi –Kaitemilike – Youdunzi, and Xiaoliangshan – Nanyishan – Dafengshan structural belts are favorable zones for natural gas accumulation. This study has important theoretical and practical significance for future natural gas exploration.

The vertical water-entry of a low-speed hollow cylinder is studied numerically and experimentally in this work. The special flow characteristics of the hollow cylinder during the water entry have been revealed and discussed. Different from water entry of typical solid bodies, a through-hole jet with a bubble attached at the top forms at the impact stage, and the deep closure occurs around the circumference of the through-hole jet, and the secondary jet generated during the pinch-off has the shape of a hollow thin cylinder. Moreover, its head cavity includes both external and internal parts, and the internal cavity is more complicated and instable. The reasons for above differences have also been explained and discussed. Furthermore, the numerical results agree well with corresponding experimental data.

Based on magnetohydrodynamics(MHD), the evolution of the Richtmyer-Meshkov instability in different magnetic field configurations are studied. To ensure the zero magnetic divergence, an unsplit integration algorithm is adopted by combining corner transport upwind and constrained transport (CTU+CT) algorithm. The second order Godunov flux is obtained by using piecewise parabolic method(PPM) to construct conserved variables. The numerical results show that the evolution of complex wave patterns is not affected by magnetic fields, but the interface instability is compressed by magnetic field, especially in the case of transverse magnetic fields. Specifically, whether there exists magnetic field or not, irregular reflections occur outside the cylinder. Meanwhile, the central part of incident shock wave interacts with the density interface and generates the transmitted shock wave. Subsequently, the transmitted shock wave oscillates back and forth inside the cylinder, forming a transmission-reflection structure multiple times. Besides, in the absence of magnetic field, the density interface rolls up with a series of vortex sequences and an SF6 jet surrounded by vortex pairs appears. Then the SF6 jet passes through the downstream interface. In a longitudinal magnetic field, although density interface is smooth, a few vortex sequences still exist in the downstream interface and SF6 jet can still pass through downstream interface. However, in the case of transverse magnetic field, the interface is much smoother than in the other cases and the SF6 jet cannot pass through the downstream interface. The quantitative study also indicate that the increase of characteristic sizes is suppressed by the magnetic field. In addition, because of the influence of Richtmyer-Meshkov instability, magnetic lines are distorted near density interfaces. More distortions can be observed in the upstream interfaces, resulting in strong Lorentz forces in that area, which leads to the long distance between two vortex sheets distributed along two sides of the interface. In the downstream interfaces Lorentz forces are rather small, but the forces are even smaller in the longitudinal magnetic field, as a result vortex sheets interact with each other in that area. Furthermore, the dynamic mode decomposition(DMD) is primarily used in this paper and the results illustrate that even controlled by magnetic fields, vortex sequences can still exist, especially in the case of longitudinal magnetic field. For all cases, the first DMD modes all illustrate that a stable mode is the dominated feature of fluid field, and the following second to fourth mode show that the strength of vortex sequences decreases while their frequencies increase continually. Besides, for the same modes, the frequency of vortex sequences is reduced by magnetic fields, especially by the transverse magnetic field.