To mitigate the sand burial of highways in sandy regions,a separated subgrade design was widely adopted in the embankments of high-grade highways,but the problem of sand deposition on subgrade slopes and pavements sti...To mitigate the sand burial of highways in sandy regions,a separated subgrade design was widely adopted in the embankments of high-grade highways,but the problem of sand deposition on subgrade slopes and pavements still happens frequently.Based on the theory of wind-sand two-phase flow,this paper constructed a three-dimensional model of the separated subgrade,the wind-sand flow transport law around the subgrade with varying median strip widths and concave depths was simulated by Fluent software.After comparison and analysis of seven subgrade models,the flow field distribution,wind speed horizontal variation,and erosion-deposition characteristics were investigated.The findings are as follows:(1)The width of the median strip in the separated subgrade had significant influences on the wind-sand flow.The smooth passage of wind-sand flow over the road surface was facilitated with the increase of the median strip width.However,sand deposition in the median strip happened.It can lead to secondary sand damage of downwind subgrade and increase the work load of road sand removal for subsequent maintenance.(2)The obstruction to airflow and sand accumulation was aggravated with greater concave depth of the median strip.Therefore,it is advisable to minimize the concave depth of the median strip in case of more sand damage.(3)A median strip width exceeding 12 m(possibly without guardrails)for an integral embankment without enough road land is recommended.Conversely,median strip width of over 40 m for separate subgrade with unrestricted land is suggested.(4)In the case of sand deposition in the existing separated subgrade,the median strip can be filled by sand deposition or other materials,then was covered with gravel to form a flat ground like Gobi smooth surface,which can let the wind-blown sand flow pass through the subgrade section without sand deposition.展开更多
The rapid advancement of artificial intelligence(AI),recognized with Nobel Prizes in both Physics and Chemistry in 2024,has been revolutionizing countless aspects of modern life,driving innovations across diverse fiel...The rapid advancement of artificial intelligence(AI),recognized with Nobel Prizes in both Physics and Chemistry in 2024,has been revolutionizing countless aspects of modern life,driving innovations across diverse fields and reshaping how people interact with technology.Despite its great advances,the computing of AI systems is now approaching the limit of traditional computing based on the von Neumann architecture,which is characterized by separated memory and process units-a challenge known as the"von Neumann bottleneck".展开更多
With the acceleration of urbanization,prefabricated bridges have become a significant choice for transportation infrastructure construction due to their environmental friendliness,efficiency,and reliable quality.Howev...With the acceleration of urbanization,prefabricated bridges have become a significant choice for transportation infrastructure construction due to their environmental friendliness,efficiency,and reliable quality.However,existing connection technologies still face shortcomings in construction efficiency,seismic performance,and cost control.This paper summarizes the process characteristics of commonly used connection technologies such as socket connections,grouted sleeve connections and corrugated pipe connections,and analyzes their seismic capacity and mechanical performance.In response to existing issues,two new technologies—separated steel connection and multi-chamber steel tube concrete connection—are proposed,and their comprehensive performance and economic efficiency are analyzed.The new connection technologies outperform traditional methods in construction efficiency,economic efficiency,and structural stability,with more reasonable force distribution,clearer load transfer paths,and significantly reduced overall costs.Existing technologies,such as socket connections,perform well in seismic performance but are complex to construct;grouted sleeve connections are mature in technology,but the quality of grouting is difficult to inspect.The separated steel connection and multi-chamber steel tube concrete connection technologies offer significant advantages.With the increasing demands for energy conservation and emission reduction,coupled with the rising labor costs,prefabricated bridge piers are undoubtedly poised to become one of the preferred technologies for bridge construction in China in the future.Therefore,in light of the current research landscape,this paper concludes by offering a forward-looking perspective on the development directions of connection methods for prefabricated bridge piers and identifying key areas for future research.展开更多
To address the challenges associated with existing separated zone oil production technologies,such as incompatibility with pump inspection operations,short effective working life,and poor communication reliability,an ...To address the challenges associated with existing separated zone oil production technologies,such as incompatibility with pump inspection operations,short effective working life,and poor communication reliability,an innovative electromagnetic coupling intelligent zonal oil production technology has been proposed.The core and accessory tools have been developed and applied in field tests.This technology employs a pipe string structure incorporation a release sub,which separates the production and allocation pipe strings.When the two strings are docked downhole,electromagnetic coupling enables close-range wireless transmission of electrical power and signals between the strings,powering multiple downhole intelligent production allocators(IPAs)and enabling two-way communication.Core tools adapted to the complex working conditions downhole were developed,including downhole electricity&signal transmission equipment based on electromagnetic coupling(EST),IPAs,and ground communication controllers(GCCs).Accessory tools,including large-diameter release sub anchor and cable-crossing packers,have also been technically finalized.Field tests conducted on ten wells in Daqing Oilfield demonstrated that the downhole docking of the two strings was convenient and reliable,and the EST worked stably.Real-time monitoring of flow rate,pressure and temperature in separate layers and regulation of zonal fluid production were also achieved.This technology has enhanced reservoir understanding and achieved practical production results of increased oil output with reduced water cut.展开更多
Herein,a new type of two-dimensional(2D)/2D Ti_(3)C_(2)/TiO_(2) heterojunction was developed for efficient photocatalytic nitrogen reduction reaction(NRR),in which TiO_(2) nanosheets(TiO_(2) Ns)were designed as the ma...Herein,a new type of two-dimensional(2D)/2D Ti_(3)C_(2)/TiO_(2) heterojunction was developed for efficient photocatalytic nitrogen reduction reaction(NRR),in which TiO_(2) nanosheets(TiO_(2) Ns)were designed as the main catalyst,while Ti_(3)C_(2) MXene served as the co-catalyst.Experimental and theoretical results revealed that Ti_(3)C_(2) MXene introduced electron-rich unsaturated Ti sites,serving as highly active sites for both the adsorption and activation of N_(2) on the Ti_(3)C_(2)/TiO_(2) heterojunction.Furthermore,the 2D/2D Ti_(3)C_(2)/TiO_(2) heterostructure greatly promoted the directional separation and transfer of charge carriers,facilitated by the internal electric field.This structural feature enabled the spatial separation of the N_(2) reduction and H2 O oxidation half-reactions on the distinct surfaces of Ti_(3)C_(2)(001)and TiO_(2)(001),con-sequently reducing the reaction energy barrier for each respective process.The synergistic effects arising from the interface and surface interactions within the heterojunction conspicuously improved the photo-catalytic NRR activity.As a result,the optimized Ti_(3)C_(2)/TiO_(2) heterojunction exhibited a high NH_(3) produc-tion rate of 24.4μmol g−1 h−1 in the absence of sacrificial agents,representing a remarkable 12.8-fold increase compared to individual TiO_(2) Ns.This work provides new insights into rational design of high-performance heterogeneous photocatalysts and offers a deeper understanding of the mechanism under-lying surface active sites in the photocatalytic NRR process.展开更多
Metal-free organic emitters,characterized by their thermally activated delayed fluorescence(TADF)properties,offer considerable promise for the creation of highly efficient organic light-emitting diodes(OLEDs).Recently...Metal-free organic emitters,characterized by their thermally activated delayed fluorescence(TADF)properties,offer considerable promise for the creation of highly efficient organic light-emitting diodes(OLEDs).Recently,Shao et al.presented a novel excited state intramolecular proton transfer(ESIPT)system BrA-HBI,demonstrating an emission quantum yield of up to 50%[Adv.Funct.Mater.32,2201256(2022)].However,many open issues cannot be answered solely by experimental means only and require detailed theoretical investigations.For instance,what causes the activation of TADF from the Keto^(*) tautomer and leads to fluorescence quenching in the Enol^(*)form?Herein,we provide a theoretical investigation on the TADF mechanism of the BrA-HBI molecule by optimally tuned range-separated functionals.Our findings reveal that ESIPT occurs in the BrA-HBI molecule.Moreover,we have disclosed the reason for the fluorescence quenching of the Enol^(*)form and determined that the T_(2)state plays a dominant role in the TADF phenomenon.In addition,double hybrid density functionals method was utilized to verify the reliability of optimally tuned range separation functionals on the calculation of the TADF mechanism in BrA-HBI.These findings not only provide a theoretical reference for development of highly efficient organic light-emitting diodes,but also demonstrate the effectiveness of the optimally tuned range-separated functionals in predicting the luminescence properties of TADF molecules.展开更多
Based on the waterflooding development in carbonate reservoirs in the Middle East,in order to solve the problem of the poor development effects caused by commingled injection and production,taking the thick bioclastic...Based on the waterflooding development in carbonate reservoirs in the Middle East,in order to solve the problem of the poor development effects caused by commingled injection and production,taking the thick bioclastic limestone reservoirs of Cretaceous in Iran-Iraq as an example,this paper proposes a balanced waterflooding development technology for thick and complex carbonate reservoirs.This technology includes the fine division of development units by concealed baffles and barriers,the combination of multi well type and multi well pattern,and the construction of balanced water injection and recovery system.Thick carbonate reservoirs in Iran-Iraq are characterized by extremely vertical heterogeneity,development of multi-genesis ultra-high permeability zones,and highly concealed baffles and barriers.Based on the technologies of identification,characterization,and sealing evaluation for concealed baffles and barriers,the balanced waterflooding development technology is proposed,and three types of balanced waterflooding development modes/techniques are formed,namely,conventional stratigraphic framework,fine stratigraphic framework,and deepened stratigraphic framework.Numerical simulations show that this technology is able to realize a fine and efficient waterflooding development to recover,in a balanced manner,the reserves of thick and complex carbonate reservoirs in Iran and Iraq.The proposed technology provides a reference for the development optimization of similar reservoirs.展开更多
[Objectives]To investigate the effect and mechanism of Dachengqi Decoction and separated decoction on incomplete intestinal obstruction in rats.[Methods]80 healthy SD rats were selected to establish incomplete intesti...[Objectives]To investigate the effect and mechanism of Dachengqi Decoction and separated decoction on incomplete intestinal obstruction in rats.[Methods]80 healthy SD rats were selected to establish incomplete intestinal obstruction model by silk ligation.The dosage was 20 mL/kg for 3 d,and the damage index of ileocecal mucosa was analyzed;the morphology of ileocecal mucosa was observed by HE staining;the serum levels of IL-1α,IL-1β,IL-6,IL-18,Ach,NO,ET,IL-1,TNF-αand ultra-micro Na+-K+-ATPase were detected by ELISA.[Results]Compared with the model group,the mucosal damage index of Dachengqi Decoction and each separated decoction group decreased significantly(P<0.05);compared with the normal group and sham operation group,the serum level of IL-1,IL-6,TNF-αand other factors in the model group increased significantly(P<0.05);compared with the model group,the serum IL-1,IL-6 and TNF-αsecretion levels of rats in Dachengqi Decoction group and separated decoction group decreased(P<0.01).[Conclusions]Dachengqi Decoction and each separated decoction can effectively improve intestinal tissue pathological damage in the incomplete intestinal obstruction model rats,and reduce the inflammatory reaction in the rat body.展开更多
Finned-tube heat exchanger(FTHE)is often used as an evaporator in commercial products of separated heat pipe(SHP).The working conditions of FTHE in gravity-assisted SHP are significantly different from those working i...Finned-tube heat exchanger(FTHE)is often used as an evaporator in commercial products of separated heat pipe(SHP).The working conditions of FTHE in gravity-assisted SHP are significantly different from those working in refrigerators and air conditioners.Although FTHE is widely used in commercial products of SHP,previous research on its characteristics is very limited.In this paper,a mathematical model for a SHP with FTHE as the evaporator and plate heat exchanger as the condenser is established and verified with experiments.Parametric analyses are carried out to investigate the influences of evaporator design parameters:air inlet velocity,number of tube rows,tube diameter,and fin pitch.With the increasing of air velocity,number of tube rows and tube diameter,and the decreasing of fin pitch,the heat transfer rate increases,while the energy efficiency ratio(EER)decreases monotonically.Using the total cost of the ten-year life cycle as the performance index,the structure parameters of the evaporator with a given heat transfer rate are optimized by the method of orthogonal experimental design.It is found that the total cost can differ as large as nearly ten times between groups.Among the three factors investigated,the number of tube rows has a significant impact on the total cost of the evaporator.With more tube rows,the total cost will be less.The impacts of fin pitch and tube diameter are insignificant.These results are of practical importance for the engineering design of FTHE in gravity-assisted SHP.展开更多
An afforestation project transforms a desert prefecture in Xinjiang into an oasis.YUSUPJAN Alim would win any reality show like Survivor hands down.The 36-year-old forest ranger started his career planting trees in th...An afforestation project transforms a desert prefecture in Xinjiang into an oasis.YUSUPJAN Alim would win any reality show like Survivor hands down.The 36-year-old forest ranger started his career planting trees in the bleak and blazing Gobi Desert in 2004 in circumstances entirely different from today’s.At that time,there were no mobile phones,no GPS or transportation.The team would drive deep into the desert in a truck,carrying naans,the flatbread of Xinjiang that keeps for days.It was their staple,if not only,food.“We lived on Xinjiang naans and water for 15-20 days while working in the desert,”Yusupjan said.“We would dip the naan into water to make it soft.”When they worked,they tied their food in a bundle around their body so that if they got separated or even lost in the hostile desert,they would still have food.Every time they went in,Yusupjan would note the way carefully so that even if he got separated from his co-workers,he could still walk out of the desert alive.展开更多
On May 3,a Long March 5 rocket carrying the Chang’e 6 probe blasted off from its launchpad at the Wenchang Space Launch Site at 17:27.The probe separated from the rocket and entered its planned transfer orbit shortly...On May 3,a Long March 5 rocket carrying the Chang’e 6 probe blasted off from its launchpad at the Wenchang Space Launch Site at 17:27.The probe separated from the rocket and entered its planned transfer orbit shortly thereafter,demonstrating a completely successful launch.With the world’s attention,the Chang’e 6 probe will retrieve samples from the far side of the moon in a historic first.展开更多
Private garden is one of the three major garden styles in China,the artistic achievements of which have devoted remarkable contributions to the development of global landscape architecture.Through studying the spatial...Private garden is one of the three major garden styles in China,the artistic achievements of which have devoted remarkable contributions to the development of global landscape architecture.Through studying the spatial layout of private gardens,the authors further analyzed three ways of landscape layouts,specifically,separated scenery,winding scenery and borrowed scenery.Concrete examples were taken to demonstrate the connotations and application skills of such three layouts,in order to benefit the inheritance and development of traditional Chinese garden art.展开更多
In this paper we shall offer a separation axiom for frames inspired by the Hausdorff separation axiom for topological spaces. We call it separated condition. This is a condition on topology OX equivalent to the ...In this paper we shall offer a separation axiom for frames inspired by the Hausdorff separation axiom for topological spaces. We call it separated condition. This is a condition on topology OX equivalent to the T O space X being Hausdorff. The class of separated frames includes that of strong Hausdorff frames and that of S frames. We shall show that the class of separated frames is a class closed under the formation of coproducts and subspaces, and the space Fil( L ) is Hausdorff for any separated frame L . Therefore there is a contravariant adjunction between the category TOP 2 of Hausdorff topological spaces and the category FRAM 2 of separated frames.展开更多
Natural ice accretion on the lifting surface of an aircraft is detrimental to its aerodynamic performance, as it changes the effective streamlined body. The main focus of this work considers the optimization design of...Natural ice accretion on the lifting surface of an aircraft is detrimental to its aerodynamic performance, as it changes the effective streamlined body. The main focus of this work considers the optimization design of airfoils under atmospheric icing conditions for the Unmanned Aerial Vehicle(UAV). The ice formation process is simulated by the Eulerian approach and the three-dimensional Myers model. A three-equation turbulence model is implemented to accurately predict the stall performance of the iced airfoil. In recognition of the real atmospheric variability in the icing parameters, the medium volume diameter of supercooled water droplets is treated as an uncertainty with an assumed probability density function. A technique of polynomial chaos expansion is used to propagate the input uncertainty through the deterministic system. The numerical results show that the multipoint/multiobjective optimization strategy can efficiently improve both the ice tolerance and the cruise performance of an airfoil. The reason for the focus on robust optimization is that the ice angle of the optimized airfoil becomes less critical to the incoming flow.The optimized airfoils are applied to a UAV platform, in which the performance improvement and the relevant key flow feature are both preserved.展开更多
Suppression of photogenerated charge recombination is crucial for efficient photocatalytic hydrogen production.Homojunctions have garnered more attention than heterojunctions due to their superior crystal binding and ...Suppression of photogenerated charge recombination is crucial for efficient photocatalytic hydrogen production.Homojunctions have garnered more attention than heterojunctions due to their superior crystal binding and band structure matching.However,most homojunctions suffer from redox interference caused by continuous oxidizing and reducing phases that impede the ability to improve photocatalytic activity.Consequently,the preparation of homojunction photocatalysts with completely spatial separation of both in charge and redox phases remains challenging.Here,the preparation of a two-dimensional(2D)homojunction CeO_(2) with a back-to-back geometry and fully separated oxidizing and reducing phases is reported.The prepared CeO_(2) is composed of nanosheets with twocontrasting smooth and rough surfaces.Experimental and theoretical results indicate that the rough surface contains more highly reducing CeO_(2){220}and strongly visiblelight-absorbing CeO_(2){200}facets than the smooth surface.The 2D homojunction CeO_(2) produces three-times more hydrogen than normal CeO_(2) nanosheets,and even more than that of CeO_(2) nanosheets loaded with gold nanoparticles.This work presents a new homojunction photocatalyst model with completely spatial separation of both in charge and redox phases that is expected to inspire further research into homojunction photocatalysts.展开更多
In transonic flow,buffet is a phenomenon of flow instability caused by shock wave/boundary layer interaction and flow separation.The phenomenon is common in transonic flow,and it has serious impact on the structural s...In transonic flow,buffet is a phenomenon of flow instability caused by shock wave/boundary layer interaction and flow separation.The phenomenon is common in transonic flow,and it has serious impact on the structural strength and fatigue life of aircraft.In this paper,three typical airfoils:the supercritical OAT15A,the high-speed symmetrical NACA64A010,and the thin,transonic/supersonic NACA64A204 are selected as the research objects.The flow fields of these airfoils under pre-buffet and buffet onset conditions are simulated by Unsteady Reynolds Averaged Navier-Stokes (URANS) method,and the mode analysis of numerical results is carried out by Dynamic Mode Decomposition (DMD).Qualitative and quantitative analysis of the shock wave motion,shock wave intensity,shock foot bubble and trailing edge separation,and pressure coefficient fluctuation were performed to attain deep insight of transonic buffet flow features of different airfoils near buffet onset conditions.The results of DMD analysis show that the energy proportion of the steady mode of these airfoils decreases dramatically when approaching the buffet onset angle of attack,while the growth rate of the primary mode increases inversely.It was found that at the onset of buffet,there exist different degrees of merging behavior between shock foot bubble and trailing edge separation during one buffet cycle,and the instability of shock wave and separation induced shear layer are closely related to the merging behavior.展开更多
Numerical studies of the flow past a circular cylinder at Reynolds number 1.4 × 105 and NACA0021 airfoil at the angle of attack 60° have been carried out by scale-adaptive simulation （SAS） and detached edd...Numerical studies of the flow past a circular cylinder at Reynolds number 1.4 × 105 and NACA0021 airfoil at the angle of attack 60° have been carried out by scale-adaptive simulation （SAS） and detached eddy simu- lation （DES）, in comparison with the existing experimental data. The new version of the model developed by Egorov and Menter is assessed, and advantages and disadvantages of the SAS simulation are analyzed in detail to provide guidance for industrial application in the future. Moreover, the mechanism of the scale-adaptive characteristics in separated regions is discussed, which is obscure in previous analyses. It is con- cluded that： the mean flow properties satisfactorily agree with the experimental results for the SAS simulation, although the prediction of the second order turbulent statistics in the near wake region is just reasonable. The SAS model can produce a larger magnitude of the turbulent kinetic energy in the recir- culation bubble, and, consequently, a smaller recirculation region and a more rapid recovery of the mean velocity out- side the recirculation region than the DES approach with the same grid resolution. The vortex shedding is slightly less irregular with the SAS model than with the DES approach, probably due to the higher dissipation of the SAS simulation under the condition of the coarse mesh.展开更多
This article outlines the development of downhole monitoring and data transmission technology for separated zone water injection in China.According to the development stages,the principles,operation processes,adaptabi...This article outlines the development of downhole monitoring and data transmission technology for separated zone water injection in China.According to the development stages,the principles,operation processes,adaptability and application status of traditional downhole data acquisition method,cable communications and testing technology,cable-controlled downhole parameter real-time monitoring communication method and downhole wireless communication technology are introduced in detail.Problems and challenges of existing technologies in downhole monitoring and data transmission technology are pointed out.According to the production requirement,the future development direction of the downhole monitoring and data transmission technology for separated zone water injection is proposed.For the large number of wells adopting cable measuring and adjustment technology,the key is to realize the digitalization of downhole plug.For the key monitoring wells,cable-controlled communication technology needs to be improved,and downhole monitoring and data transmission technology based on composite coiled tubing needs to be developed to make the operation more convenient and reliable.For large-scale application in oil fields,downhole wireless communication technology should be developed to realize automation of measurement and adjustment.In line with ground mobile communication network,a digital communication network covering the control center,water distribution station and oil reservoir should be built quickly to provide technical support for the digitization of reservoir development.展开更多
Acryloyl terminated Poly (ethyleneoxide)macromonomers (PEO-A) with different PEO chain lengths have been prepared by deactivation of PEO alkoxide with acryloyl chloride. A new kind of amphiphilic polystyrene-g-poly (e...Acryloyl terminated Poly (ethyleneoxide)macromonomers (PEO-A) with different PEO chain lengths have been prepared by deactivation of PEO alkoxide with acryloyl chloride. A new kind of amphiphilic polystyrene-g-poly (ethylene oxide)graft copolymer containing both microphase separated and PEO side chain structures has been synthesized from radical copolymerization of PEO-A macromonomer with styrene. After careful purification by a newly-developed method called 'selective dissolution', the well-defined structure of the purified copolymers was confirmed by IR, ~1H-NMR and GPC. Various experimental parameters controlling the copolymerization were studied in detail. The results indicated that the feed ratio of styrene to macromonomer(S/M) was the most important determining factor for the composition of the copolymers. A detailed 'comb- model' was proposed to describe the molecular structure of the graft copolymers. Finally, this amphiphilic graft copolymers may readily form microphase separated structures as clearly indicated by transmission electron microscopy.展开更多
基金supported by the Third Xinjiang Scientific Expedition and Research Program-Investigation and Risk Assessment of Drought and Aeolian Disasters in Tarim River Basin(No.2021xjkk0300)the National Natural Science Foundation of China(No.62466056)the subject of'the technical scheme and application demonstration of sand disaster prevention and control of Xinjiang expressway to engineering practice,Xinjiang Transportation Investment(Group)Co.,Ltd.(No.XJJTZKX-FWCG-202401-0043).
文摘To mitigate the sand burial of highways in sandy regions,a separated subgrade design was widely adopted in the embankments of high-grade highways,but the problem of sand deposition on subgrade slopes and pavements still happens frequently.Based on the theory of wind-sand two-phase flow,this paper constructed a three-dimensional model of the separated subgrade,the wind-sand flow transport law around the subgrade with varying median strip widths and concave depths was simulated by Fluent software.After comparison and analysis of seven subgrade models,the flow field distribution,wind speed horizontal variation,and erosion-deposition characteristics were investigated.The findings are as follows:(1)The width of the median strip in the separated subgrade had significant influences on the wind-sand flow.The smooth passage of wind-sand flow over the road surface was facilitated with the increase of the median strip width.However,sand deposition in the median strip happened.It can lead to secondary sand damage of downwind subgrade and increase the work load of road sand removal for subsequent maintenance.(2)The obstruction to airflow and sand accumulation was aggravated with greater concave depth of the median strip.Therefore,it is advisable to minimize the concave depth of the median strip in case of more sand damage.(3)A median strip width exceeding 12 m(possibly without guardrails)for an integral embankment without enough road land is recommended.Conversely,median strip width of over 40 m for separate subgrade with unrestricted land is suggested.(4)In the case of sand deposition in the existing separated subgrade,the median strip can be filled by sand deposition or other materials,then was covered with gravel to form a flat ground like Gobi smooth surface,which can let the wind-blown sand flow pass through the subgrade section without sand deposition.
文摘The rapid advancement of artificial intelligence(AI),recognized with Nobel Prizes in both Physics and Chemistry in 2024,has been revolutionizing countless aspects of modern life,driving innovations across diverse fields and reshaping how people interact with technology.Despite its great advances,the computing of AI systems is now approaching the limit of traditional computing based on the von Neumann architecture,which is characterized by separated memory and process units-a challenge known as the"von Neumann bottleneck".
基金supported by Prevention the Fundamental Research Funds for the Central Universities“Study on the general joint of prefabricated high-pier columns”(ZY20230218)Science and Technology Innovation Program for Postgraduate students in IDP subsidized by Fundamental Research Funds for the Central Universities“Research on seismic performance of prefabricated bridge piers with embedded separated steel connections”(ZY20250316).
文摘With the acceleration of urbanization,prefabricated bridges have become a significant choice for transportation infrastructure construction due to their environmental friendliness,efficiency,and reliable quality.However,existing connection technologies still face shortcomings in construction efficiency,seismic performance,and cost control.This paper summarizes the process characteristics of commonly used connection technologies such as socket connections,grouted sleeve connections and corrugated pipe connections,and analyzes their seismic capacity and mechanical performance.In response to existing issues,two new technologies—separated steel connection and multi-chamber steel tube concrete connection—are proposed,and their comprehensive performance and economic efficiency are analyzed.The new connection technologies outperform traditional methods in construction efficiency,economic efficiency,and structural stability,with more reasonable force distribution,clearer load transfer paths,and significantly reduced overall costs.Existing technologies,such as socket connections,perform well in seismic performance but are complex to construct;grouted sleeve connections are mature in technology,but the quality of grouting is difficult to inspect.The separated steel connection and multi-chamber steel tube concrete connection technologies offer significant advantages.With the increasing demands for energy conservation and emission reduction,coupled with the rising labor costs,prefabricated bridge piers are undoubtedly poised to become one of the preferred technologies for bridge construction in China in the future.Therefore,in light of the current research landscape,this paper concludes by offering a forward-looking perspective on the development directions of connection methods for prefabricated bridge piers and identifying key areas for future research.
基金Supported by the National Natural Science Foundation of China(52374067)PetroChina Scientific Research and Technology Development Project(2021ZG12)PetroChina Technology Project(2023ZZ09).
文摘To address the challenges associated with existing separated zone oil production technologies,such as incompatibility with pump inspection operations,short effective working life,and poor communication reliability,an innovative electromagnetic coupling intelligent zonal oil production technology has been proposed.The core and accessory tools have been developed and applied in field tests.This technology employs a pipe string structure incorporation a release sub,which separates the production and allocation pipe strings.When the two strings are docked downhole,electromagnetic coupling enables close-range wireless transmission of electrical power and signals between the strings,powering multiple downhole intelligent production allocators(IPAs)and enabling two-way communication.Core tools adapted to the complex working conditions downhole were developed,including downhole electricity&signal transmission equipment based on electromagnetic coupling(EST),IPAs,and ground communication controllers(GCCs).Accessory tools,including large-diameter release sub anchor and cable-crossing packers,have also been technically finalized.Field tests conducted on ten wells in Daqing Oilfield demonstrated that the downhole docking of the two strings was convenient and reliable,and the EST worked stably.Real-time monitoring of flow rate,pressure and temperature in separate layers and regulation of zonal fluid production were also achieved.This technology has enhanced reservoir understanding and achieved practical production results of increased oil output with reduced water cut.
基金supported by the National Natural Science Foundation of China(No.21773089)the Henan Center for Outstanding Overseas Scientist(No.GZS2024004).
文摘Herein,a new type of two-dimensional(2D)/2D Ti_(3)C_(2)/TiO_(2) heterojunction was developed for efficient photocatalytic nitrogen reduction reaction(NRR),in which TiO_(2) nanosheets(TiO_(2) Ns)were designed as the main catalyst,while Ti_(3)C_(2) MXene served as the co-catalyst.Experimental and theoretical results revealed that Ti_(3)C_(2) MXene introduced electron-rich unsaturated Ti sites,serving as highly active sites for both the adsorption and activation of N_(2) on the Ti_(3)C_(2)/TiO_(2) heterojunction.Furthermore,the 2D/2D Ti_(3)C_(2)/TiO_(2) heterostructure greatly promoted the directional separation and transfer of charge carriers,facilitated by the internal electric field.This structural feature enabled the spatial separation of the N_(2) reduction and H2 O oxidation half-reactions on the distinct surfaces of Ti_(3)C_(2)(001)and TiO_(2)(001),con-sequently reducing the reaction energy barrier for each respective process.The synergistic effects arising from the interface and surface interactions within the heterojunction conspicuously improved the photo-catalytic NRR activity.As a result,the optimized Ti_(3)C_(2)/TiO_(2) heterojunction exhibited a high NH_(3) produc-tion rate of 24.4μmol g−1 h−1 in the absence of sacrificial agents,representing a remarkable 12.8-fold increase compared to individual TiO_(2) Ns.This work provides new insights into rational design of high-performance heterogeneous photocatalysts and offers a deeper understanding of the mechanism under-lying surface active sites in the photocatalytic NRR process.
基金supported by the National Natural Science Foundation of China(Grant No.12174149)。
文摘Metal-free organic emitters,characterized by their thermally activated delayed fluorescence(TADF)properties,offer considerable promise for the creation of highly efficient organic light-emitting diodes(OLEDs).Recently,Shao et al.presented a novel excited state intramolecular proton transfer(ESIPT)system BrA-HBI,demonstrating an emission quantum yield of up to 50%[Adv.Funct.Mater.32,2201256(2022)].However,many open issues cannot be answered solely by experimental means only and require detailed theoretical investigations.For instance,what causes the activation of TADF from the Keto^(*) tautomer and leads to fluorescence quenching in the Enol^(*)form?Herein,we provide a theoretical investigation on the TADF mechanism of the BrA-HBI molecule by optimally tuned range-separated functionals.Our findings reveal that ESIPT occurs in the BrA-HBI molecule.Moreover,we have disclosed the reason for the fluorescence quenching of the Enol^(*)form and determined that the T_(2)state plays a dominant role in the TADF phenomenon.In addition,double hybrid density functionals method was utilized to verify the reliability of optimally tuned range separation functionals on the calculation of the TADF mechanism in BrA-HBI.These findings not only provide a theoretical reference for development of highly efficient organic light-emitting diodes,but also demonstrate the effectiveness of the optimally tuned range-separated functionals in predicting the luminescence properties of TADF molecules.
基金Supported by the Major Science and Technology Project of CNPC(2023ZZ19-01).
文摘Based on the waterflooding development in carbonate reservoirs in the Middle East,in order to solve the problem of the poor development effects caused by commingled injection and production,taking the thick bioclastic limestone reservoirs of Cretaceous in Iran-Iraq as an example,this paper proposes a balanced waterflooding development technology for thick and complex carbonate reservoirs.This technology includes the fine division of development units by concealed baffles and barriers,the combination of multi well type and multi well pattern,and the construction of balanced water injection and recovery system.Thick carbonate reservoirs in Iran-Iraq are characterized by extremely vertical heterogeneity,development of multi-genesis ultra-high permeability zones,and highly concealed baffles and barriers.Based on the technologies of identification,characterization,and sealing evaluation for concealed baffles and barriers,the balanced waterflooding development technology is proposed,and three types of balanced waterflooding development modes/techniques are formed,namely,conventional stratigraphic framework,fine stratigraphic framework,and deepened stratigraphic framework.Numerical simulations show that this technology is able to realize a fine and efficient waterflooding development to recover,in a balanced manner,the reserves of thick and complex carbonate reservoirs in Iran and Iraq.The proposed technology provides a reference for the development optimization of similar reservoirs.
基金2023 Young and Middle-aged University Teachers Basic Scientific Research Ability Improvement Project in Guangxi(2023KY0299)High-level Key Discipline Construction Project of Traditional Chinese Medicine of National Administration of Traditional Chinese Medicine(zyyzdxk-2023165)+3 种基金Talent Training Project of Guangxi International Zhuang Medicine Hospital—"Young Seedling Project"(2022001)Guangxi Traditional Chinese Medicine Multidisciplinary and Interdisciplinary Innovation Team Project(GZKJ2309)High-level Talent Cultivation Innovation Team Funding Project of Guangxi University of Chinese Medicine(2022A008)2023 Three-Year Action Plan Project for High-Level Talent Team Construction of Guangxi International Zhuang Medicine Hospital(GZCX20231203,GZCX20231202).
文摘[Objectives]To investigate the effect and mechanism of Dachengqi Decoction and separated decoction on incomplete intestinal obstruction in rats.[Methods]80 healthy SD rats were selected to establish incomplete intestinal obstruction model by silk ligation.The dosage was 20 mL/kg for 3 d,and the damage index of ileocecal mucosa was analyzed;the morphology of ileocecal mucosa was observed by HE staining;the serum levels of IL-1α,IL-1β,IL-6,IL-18,Ach,NO,ET,IL-1,TNF-αand ultra-micro Na+-K+-ATPase were detected by ELISA.[Results]Compared with the model group,the mucosal damage index of Dachengqi Decoction and each separated decoction group decreased significantly(P<0.05);compared with the normal group and sham operation group,the serum level of IL-1,IL-6,TNF-αand other factors in the model group increased significantly(P<0.05);compared with the model group,the serum IL-1,IL-6 and TNF-αsecretion levels of rats in Dachengqi Decoction group and separated decoction group decreased(P<0.01).[Conclusions]Dachengqi Decoction and each separated decoction can effectively improve intestinal tissue pathological damage in the incomplete intestinal obstruction model rats,and reduce the inflammatory reaction in the rat body.
基金supported by Archaeological Artifact Protection Technology Project of Zhejiang Province(NO2021013).
文摘Finned-tube heat exchanger(FTHE)is often used as an evaporator in commercial products of separated heat pipe(SHP).The working conditions of FTHE in gravity-assisted SHP are significantly different from those working in refrigerators and air conditioners.Although FTHE is widely used in commercial products of SHP,previous research on its characteristics is very limited.In this paper,a mathematical model for a SHP with FTHE as the evaporator and plate heat exchanger as the condenser is established and verified with experiments.Parametric analyses are carried out to investigate the influences of evaporator design parameters:air inlet velocity,number of tube rows,tube diameter,and fin pitch.With the increasing of air velocity,number of tube rows and tube diameter,and the decreasing of fin pitch,the heat transfer rate increases,while the energy efficiency ratio(EER)decreases monotonically.Using the total cost of the ten-year life cycle as the performance index,the structure parameters of the evaporator with a given heat transfer rate are optimized by the method of orthogonal experimental design.It is found that the total cost can differ as large as nearly ten times between groups.Among the three factors investigated,the number of tube rows has a significant impact on the total cost of the evaporator.With more tube rows,the total cost will be less.The impacts of fin pitch and tube diameter are insignificant.These results are of practical importance for the engineering design of FTHE in gravity-assisted SHP.
文摘An afforestation project transforms a desert prefecture in Xinjiang into an oasis.YUSUPJAN Alim would win any reality show like Survivor hands down.The 36-year-old forest ranger started his career planting trees in the bleak and blazing Gobi Desert in 2004 in circumstances entirely different from today’s.At that time,there were no mobile phones,no GPS or transportation.The team would drive deep into the desert in a truck,carrying naans,the flatbread of Xinjiang that keeps for days.It was their staple,if not only,food.“We lived on Xinjiang naans and water for 15-20 days while working in the desert,”Yusupjan said.“We would dip the naan into water to make it soft.”When they worked,they tied their food in a bundle around their body so that if they got separated or even lost in the hostile desert,they would still have food.Every time they went in,Yusupjan would note the way carefully so that even if he got separated from his co-workers,he could still walk out of the desert alive.
文摘On May 3,a Long March 5 rocket carrying the Chang’e 6 probe blasted off from its launchpad at the Wenchang Space Launch Site at 17:27.The probe separated from the rocket and entered its planned transfer orbit shortly thereafter,demonstrating a completely successful launch.With the world’s attention,the Chang’e 6 probe will retrieve samples from the far side of the moon in a historic first.
文摘Private garden is one of the three major garden styles in China,the artistic achievements of which have devoted remarkable contributions to the development of global landscape architecture.Through studying the spatial layout of private gardens,the authors further analyzed three ways of landscape layouts,specifically,separated scenery,winding scenery and borrowed scenery.Concrete examples were taken to demonstrate the connotations and application skills of such three layouts,in order to benefit the inheritance and development of traditional Chinese garden art.
文摘In this paper we shall offer a separation axiom for frames inspired by the Hausdorff separation axiom for topological spaces. We call it separated condition. This is a condition on topology OX equivalent to the T O space X being Hausdorff. The class of separated frames includes that of strong Hausdorff frames and that of S frames. We shall show that the class of separated frames is a class closed under the formation of coproducts and subspaces, and the space Fil( L ) is Hausdorff for any separated frame L . Therefore there is a contravariant adjunction between the category TOP 2 of Hausdorff topological spaces and the category FRAM 2 of separated frames.
基金supported by the National Key Project of China(No.GJXM92579)the National Natural Science Foundation of China(Nos.92052203 and 11872230 and 91852108)。
文摘Natural ice accretion on the lifting surface of an aircraft is detrimental to its aerodynamic performance, as it changes the effective streamlined body. The main focus of this work considers the optimization design of airfoils under atmospheric icing conditions for the Unmanned Aerial Vehicle(UAV). The ice formation process is simulated by the Eulerian approach and the three-dimensional Myers model. A three-equation turbulence model is implemented to accurately predict the stall performance of the iced airfoil. In recognition of the real atmospheric variability in the icing parameters, the medium volume diameter of supercooled water droplets is treated as an uncertainty with an assumed probability density function. A technique of polynomial chaos expansion is used to propagate the input uncertainty through the deterministic system. The numerical results show that the multipoint/multiobjective optimization strategy can efficiently improve both the ice tolerance and the cruise performance of an airfoil. The reason for the focus on robust optimization is that the ice angle of the optimized airfoil becomes less critical to the incoming flow.The optimized airfoils are applied to a UAV platform, in which the performance improvement and the relevant key flow feature are both preserved.
基金financially supported by the National Natural Science Foundation of China (Nos.22205084 and21805191)the Start-Up Funding of Jiangsu University of Science and Technology (No.1112932203)+2 种基金Guangdong Basic and Applied Basic Research Foundation (No.2020A1515010982)Shenzhen Stable Support Project (No.20200812122947002)Shenzhen Peacock Plan (No.20210802524B)。
文摘Suppression of photogenerated charge recombination is crucial for efficient photocatalytic hydrogen production.Homojunctions have garnered more attention than heterojunctions due to their superior crystal binding and band structure matching.However,most homojunctions suffer from redox interference caused by continuous oxidizing and reducing phases that impede the ability to improve photocatalytic activity.Consequently,the preparation of homojunction photocatalysts with completely spatial separation of both in charge and redox phases remains challenging.Here,the preparation of a two-dimensional(2D)homojunction CeO_(2) with a back-to-back geometry and fully separated oxidizing and reducing phases is reported.The prepared CeO_(2) is composed of nanosheets with twocontrasting smooth and rough surfaces.Experimental and theoretical results indicate that the rough surface contains more highly reducing CeO_(2){220}and strongly visiblelight-absorbing CeO_(2){200}facets than the smooth surface.The 2D homojunction CeO_(2) produces three-times more hydrogen than normal CeO_(2) nanosheets,and even more than that of CeO_(2) nanosheets loaded with gold nanoparticles.This work presents a new homojunction photocatalyst model with completely spatial separation of both in charge and redox phases that is expected to inspire further research into homojunction photocatalysts.
基金supported by the National Natural Science Foundation of China (No. 11802009)
文摘In transonic flow,buffet is a phenomenon of flow instability caused by shock wave/boundary layer interaction and flow separation.The phenomenon is common in transonic flow,and it has serious impact on the structural strength and fatigue life of aircraft.In this paper,three typical airfoils:the supercritical OAT15A,the high-speed symmetrical NACA64A010,and the thin,transonic/supersonic NACA64A204 are selected as the research objects.The flow fields of these airfoils under pre-buffet and buffet onset conditions are simulated by Unsteady Reynolds Averaged Navier-Stokes (URANS) method,and the mode analysis of numerical results is carried out by Dynamic Mode Decomposition (DMD).Qualitative and quantitative analysis of the shock wave motion,shock wave intensity,shock foot bubble and trailing edge separation,and pressure coefficient fluctuation were performed to attain deep insight of transonic buffet flow features of different airfoils near buffet onset conditions.The results of DMD analysis show that the energy proportion of the steady mode of these airfoils decreases dramatically when approaching the buffet onset angle of attack,while the growth rate of the primary mode increases inversely.It was found that at the onset of buffet,there exist different degrees of merging behavior between shock foot bubble and trailing edge separation during one buffet cycle,and the instability of shock wave and separation induced shear layer are closely related to the merging behavior.
基金the National Basic Research Program of China ("973" Project) (Grant No. 2009CB724104)
文摘Numerical studies of the flow past a circular cylinder at Reynolds number 1.4 × 105 and NACA0021 airfoil at the angle of attack 60° have been carried out by scale-adaptive simulation （SAS） and detached eddy simu- lation （DES）, in comparison with the existing experimental data. The new version of the model developed by Egorov and Menter is assessed, and advantages and disadvantages of the SAS simulation are analyzed in detail to provide guidance for industrial application in the future. Moreover, the mechanism of the scale-adaptive characteristics in separated regions is discussed, which is obscure in previous analyses. It is con- cluded that： the mean flow properties satisfactorily agree with the experimental results for the SAS simulation, although the prediction of the second order turbulent statistics in the near wake region is just reasonable. The SAS model can produce a larger magnitude of the turbulent kinetic energy in the recir- culation bubble, and, consequently, a smaller recirculation region and a more rapid recovery of the mean velocity out- side the recirculation region than the DES approach with the same grid resolution. The vortex shedding is slightly less irregular with the SAS model than with the DES approach, probably due to the higher dissipation of the SAS simulation under the condition of the coarse mesh.
基金Supported by the National Natural Science Foundation Science Center Project/Basic Science Center Project(72088101)PetroChina Scientific Research and Technology Development Project(2020B-4119,2021ZG12).
文摘This article outlines the development of downhole monitoring and data transmission technology for separated zone water injection in China.According to the development stages,the principles,operation processes,adaptability and application status of traditional downhole data acquisition method,cable communications and testing technology,cable-controlled downhole parameter real-time monitoring communication method and downhole wireless communication technology are introduced in detail.Problems and challenges of existing technologies in downhole monitoring and data transmission technology are pointed out.According to the production requirement,the future development direction of the downhole monitoring and data transmission technology for separated zone water injection is proposed.For the large number of wells adopting cable measuring and adjustment technology,the key is to realize the digitalization of downhole plug.For the key monitoring wells,cable-controlled communication technology needs to be improved,and downhole monitoring and data transmission technology based on composite coiled tubing needs to be developed to make the operation more convenient and reliable.For large-scale application in oil fields,downhole wireless communication technology should be developed to realize automation of measurement and adjustment.In line with ground mobile communication network,a digital communication network covering the control center,water distribution station and oil reservoir should be built quickly to provide technical support for the digitization of reservoir development.
基金Supported by the National Natural Science Foundation of China and the State Education Committee of China
文摘Acryloyl terminated Poly (ethyleneoxide)macromonomers (PEO-A) with different PEO chain lengths have been prepared by deactivation of PEO alkoxide with acryloyl chloride. A new kind of amphiphilic polystyrene-g-poly (ethylene oxide)graft copolymer containing both microphase separated and PEO side chain structures has been synthesized from radical copolymerization of PEO-A macromonomer with styrene. After careful purification by a newly-developed method called 'selective dissolution', the well-defined structure of the purified copolymers was confirmed by IR, ~1H-NMR and GPC. Various experimental parameters controlling the copolymerization were studied in detail. The results indicated that the feed ratio of styrene to macromonomer(S/M) was the most important determining factor for the composition of the copolymers. A detailed 'comb- model' was proposed to describe the molecular structure of the graft copolymers. Finally, this amphiphilic graft copolymers may readily form microphase separated structures as clearly indicated by transmission electron microscopy.
