Continued to decline According to statistics from China Association of Automobile Manufacturers(CAAM),while Chinas auto production and sale continue to increase,automobile export has declined.Statistics show that the ...Continued to decline According to statistics from China Association of Automobile Manufacturers(CAAM),while Chinas auto production and sale continue to increase,automobile export has declined.Statistics show that the number of China’s automobile export declined in2013 with overall export of 977,300。展开更多
Three-dimensional(3D)Stokes flow of an incompressible fluid in a curved channel is analyzed.The flow field and characteristics under the influence of 3D surface bumps are studied.A mathematical model describing the 3D...Three-dimensional(3D)Stokes flow of an incompressible fluid in a curved channel is analyzed.The flow field and characteristics under the influence of 3D surface bumps are studied.A mathematical model describing the 3D complex flow in the curvilinear geometry is formulated and validated.The solution of the coupled system of quasilinear partial differential equations associated with the model is obtained analytically.The behavior of the velocity distribution as the fluid moves through the undulating passage of the bumpy curved channel is examined and explained for each velocity component.The analysis of this flow problem indicates that the velocity vector of the flow is significantly altered by the presence of the structures on the bounding bumpy surfaces,depending on the alignment of the bumps.Furthermore,it is found that the difference between the flow rate in the bumpy curved channel and that in a smooth curved channel is essentially a function of the geometric characteristics of the surface bumps and the curved channel.Notably,the flow in a bumpy straight channel is a limiting case of that in the bumpy curved channel,but the overall effect of the bumps is more significant for a bumpy curved channel.展开更多
Bump mapping is a texture-based rendering approach for simulating surface details to make its illumination results have three-dimensional effects. The bumpy properties of an object are determined by height maps. But i...Bump mapping is a texture-based rendering approach for simulating surface details to make its illumination results have three-dimensional effects. The bumpy properties of an object are determined by height maps. But in the process of generating height maps, a problem arises, i.e. to get a correct value of the pixel height, empirical data should be calculated repeatedly, which proves very complicated, and meanwhile the realistic rendering effect is reduced, because the bumpy property is exaggerated in the height map. Therefore, in this paper, we present a method for describing the details of the bumpy texture, where a new concept ＂bumpy map＂ is introduced to replace the height map. Experimental results demonstrate that the bumpy details produced by the ＂bumpy map＂ are more consistent with the original bumpy texture than by the method of height map.展开更多
The world economy crawls ahead amid risk and uncertainty The world economic situation has been extremely complicated in 2010. This year saw fluctuating market confidence,changing commodity prices, imbalanced economic ...The world economy crawls ahead amid risk and uncertainty The world economic situation has been extremely complicated in 2010. This year saw fluctuating market confidence,changing commodity prices, imbalanced economic recovery, diverse economic policies, lingering trade protectionism, and fierce currency battles.展开更多
Theoretical and experimental studies associated with electric field effectson the stability and transport are briefly surveyed. The effects of radial electric field on thesuppression and/or enhancement of various micr...Theoretical and experimental studies associated with electric field effectson the stability and transport are briefly surveyed. The effects of radial electric field on thesuppression and/or enhancement of various microinstabilities such as drift waves, flute mode andtemperature gradient modes are discussed. The suppression of flow shear on the electron temperaturegradient mode in plasmas with slightly hollow density profiles is investigated by solving thegyrokinetic integral eigenvalue equation. Comparison between theoretical predictions andexperimental observations based on the HIBP measurements with high temporal and spatial resolutionsis made in bumpy tori and heliotron (CHS) devices.展开更多
CONSPECTUS:Nanocatalysts have shown remarkable potential for various catalytic reactions due to their high specific surface area.But the inherently high surface energy of these nanocatalysts promotes spontaneous growt...CONSPECTUS:Nanocatalysts have shown remarkable potential for various catalytic reactions due to their high specific surface area.But the inherently high surface energy of these nanocatalysts promotes spontaneous growth,leading to their instability under harsh catalytic conditions.Additionally,high-temperature treatment is an important way to prepare nanocatalysts because it can enhance atomic diffusion and generate a wide range of nanocatalysts.Unfortunately,many nanocatalysts suffer from inevitable aggregation and fusion during the high-temperature treatment procedure and thus face challenges in controlling their sizes and morphologies.In recent decades,significant progress has been achieved in synthesizing silica with a controllable thickness and mesoporous structures.The construction of silica on nanocatalysts as a protective shell,including core@shell,yolk@shell,or reverse bubble-ball structures,proves to be an effective strategy to prevent aggregation under harsh catalytic conditions.Furthermore,the subsequent etching of the silica shell,similar to protection/deprotection procedures in organic synthesis,enables the successful synthesis of nanocatalysts with controllable size and morphology under high-temperature conditions.In this Account,we provide an overview of the key role of silica in protecting and controllably synthesizing nanocatalysts,focusing on the optimization of their sizes,phases,and morphologies for improved catalytic performance and broader applications.First,we highlight the design principles of yolk@shell and reverse-bumpy-ball nanoreactors.These nanoreactors incorporate single or multiple nanoparticles effectively and impart enhanced properties to the synthesized nanocatalysts.Furthermore,we discuss recent advancements in silica encapsulation strategies that facilitate the fabrication of diverse nanocatalysts with tunable sizes and superior catalytic capabilities even under high-temperature conditions.The materials synthesized by these strategies include noble metalbased alloys and intermetallic compounds,non-noble-metal-based interstitial compounds,sulfides,oxides,and carbon-based materials.By examining the protective effects of silica and underscoring its critical role,we shed light on the potential as well as the challenges associated with employing silica encapsulation techniques in the design of high-performance nanocatalysts.We hope that this Account serves as an informative resource for researchers interested in the controllable synthesis of nanocatalysts;meanwhile,it can inspire the development of novel nanocatalysts through the utilization of encapsulation strategies.展开更多
If all prime closed geodesics on(S^n, F) with an irreversible Finsler metric F are irrationally elliptic,there exist either exactly 2 [(n+1)/2] or infinitely many distinct closed geodesics. As an application, we show ...If all prime closed geodesics on(S^n, F) with an irreversible Finsler metric F are irrationally elliptic,there exist either exactly 2 [(n+1)/2] or infinitely many distinct closed geodesics. As an application, we show the existence of three distinct closed geodesics on bumpy Finsler(S^3, F) if any prime closed geodesic has non-zero Morse index.展开更多
文摘Continued to decline According to statistics from China Association of Automobile Manufacturers(CAAM),while Chinas auto production and sale continue to increase,automobile export has declined.Statistics show that the number of China’s automobile export declined in2013 with overall export of 977,300。
文摘Three-dimensional(3D)Stokes flow of an incompressible fluid in a curved channel is analyzed.The flow field and characteristics under the influence of 3D surface bumps are studied.A mathematical model describing the 3D complex flow in the curvilinear geometry is formulated and validated.The solution of the coupled system of quasilinear partial differential equations associated with the model is obtained analytically.The behavior of the velocity distribution as the fluid moves through the undulating passage of the bumpy curved channel is examined and explained for each velocity component.The analysis of this flow problem indicates that the velocity vector of the flow is significantly altered by the presence of the structures on the bounding bumpy surfaces,depending on the alignment of the bumps.Furthermore,it is found that the difference between the flow rate in the bumpy curved channel and that in a smooth curved channel is essentially a function of the geometric characteristics of the surface bumps and the curved channel.Notably,the flow in a bumpy straight channel is a limiting case of that in the bumpy curved channel,but the overall effect of the bumps is more significant for a bumpy curved channel.
基金Supported partially by the National Natural Science Foundation of China (Grant Nos. 60533030, 60825203, 60572104)National High-Tech Re-search & Development Program of China (Grant No.2006AA01Z317)Science and Technology Development Program of Education Commission in Beijing (Grant No. KM200710005017)
文摘Bump mapping is a texture-based rendering approach for simulating surface details to make its illumination results have three-dimensional effects. The bumpy properties of an object are determined by height maps. But in the process of generating height maps, a problem arises, i.e. to get a correct value of the pixel height, empirical data should be calculated repeatedly, which proves very complicated, and meanwhile the realistic rendering effect is reduced, because the bumpy property is exaggerated in the height map. Therefore, in this paper, we present a method for describing the details of the bumpy texture, where a new concept ＂bumpy map＂ is introduced to replace the height map. Experimental results demonstrate that the bumpy details produced by the ＂bumpy map＂ are more consistent with the original bumpy texture than by the method of height map.
文摘The world economy crawls ahead amid risk and uncertainty The world economic situation has been extremely complicated in 2010. This year saw fluctuating market confidence,changing commodity prices, imbalanced economic recovery, diverse economic policies, lingering trade protectionism, and fierce currency battles.
文摘Theoretical and experimental studies associated with electric field effectson the stability and transport are briefly surveyed. The effects of radial electric field on thesuppression and/or enhancement of various microinstabilities such as drift waves, flute mode andtemperature gradient modes are discussed. The suppression of flow shear on the electron temperaturegradient mode in plasmas with slightly hollow density profiles is investigated by solving thegyrokinetic integral eigenvalue equation. Comparison between theoretical predictions andexperimental observations based on the HIBP measurements with high temporal and spatial resolutionsis made in bumpy tori and heliotron (CHS) devices.
基金financial support from the National Key R&D Program of China(2021YFF0500402)the National Natural Science Foundation of China(51825205,2120105002,22088102,22279150)+1 种基金the Beijing Natural Science Foundation(2222080)the Youth Innovation Promotion Association of the CAS(Y2021011).
文摘CONSPECTUS:Nanocatalysts have shown remarkable potential for various catalytic reactions due to their high specific surface area.But the inherently high surface energy of these nanocatalysts promotes spontaneous growth,leading to their instability under harsh catalytic conditions.Additionally,high-temperature treatment is an important way to prepare nanocatalysts because it can enhance atomic diffusion and generate a wide range of nanocatalysts.Unfortunately,many nanocatalysts suffer from inevitable aggregation and fusion during the high-temperature treatment procedure and thus face challenges in controlling their sizes and morphologies.In recent decades,significant progress has been achieved in synthesizing silica with a controllable thickness and mesoporous structures.The construction of silica on nanocatalysts as a protective shell,including core@shell,yolk@shell,or reverse bubble-ball structures,proves to be an effective strategy to prevent aggregation under harsh catalytic conditions.Furthermore,the subsequent etching of the silica shell,similar to protection/deprotection procedures in organic synthesis,enables the successful synthesis of nanocatalysts with controllable size and morphology under high-temperature conditions.In this Account,we provide an overview of the key role of silica in protecting and controllably synthesizing nanocatalysts,focusing on the optimization of their sizes,phases,and morphologies for improved catalytic performance and broader applications.First,we highlight the design principles of yolk@shell and reverse-bumpy-ball nanoreactors.These nanoreactors incorporate single or multiple nanoparticles effectively and impart enhanced properties to the synthesized nanocatalysts.Furthermore,we discuss recent advancements in silica encapsulation strategies that facilitate the fabrication of diverse nanocatalysts with tunable sizes and superior catalytic capabilities even under high-temperature conditions.The materials synthesized by these strategies include noble metalbased alloys and intermetallic compounds,non-noble-metal-based interstitial compounds,sulfides,oxides,and carbon-based materials.By examining the protective effects of silica and underscoring its critical role,we shed light on the potential as well as the challenges associated with employing silica encapsulation techniques in the design of high-performance nanocatalysts.We hope that this Account serves as an informative resource for researchers interested in the controllable synthesis of nanocatalysts;meanwhile,it can inspire the development of novel nanocatalysts through the utilization of encapsulation strategies.
基金National Natural Science Foundation of China (Grant Nos. 11131004, 11471169 and 11401555)the Key Laboratory of Pure Mathematics and Combinatorics of Ministry of Education of China and Nankai University, China Postdoctoral Science Foundation (Grant No. 2014T70589)Chinese Universities Scientific Fund (Grant No. WK0010000037)
文摘If all prime closed geodesics on(S^n, F) with an irreversible Finsler metric F are irrationally elliptic,there exist either exactly 2 [(n+1)/2] or infinitely many distinct closed geodesics. As an application, we show the existence of three distinct closed geodesics on bumpy Finsler(S^3, F) if any prime closed geodesic has non-zero Morse index.
