An analytical model for describing the charged-particle transport in a wall-confined laser-induced decaying plasma is established under an external electrostatic field,focusing on the effects of the initial plasma-ele...An analytical model for describing the charged-particle transport in a wall-confined laser-induced decaying plasma is established under an external electrostatic field,focusing on the effects of the initial plasma-electrode gap(IPEG)that exists in applications such as laser isotope separation.This newly developed analytical model is validated by particle-in-cell simulations and the experimental scaling relation,and can also be reduced to its previously published counterpart that did not consider IPEGs.Based on this analytical model,the influences of different IPEG spacings on the characteristics of the whole ion extraction process are studied.The results show that the ion extraction ratios at the endpoints of the first and second stages both decrease with increasing IPEG spacing,while the corresponding time durations for the first two stages show a non-monotonous variation trend.The specific ion extraction time,defined as the ion extraction time per unit mass to comprehensively characterize the ion extraction efficiency,increases generally with the increase of IPEG spacing.This study not only provides further insight into the fundamental physical processes in a wall-bounded decaying plasma under an externally applied electrostatic field,but also offers useful theoretical guidance for optimal designs of geometrical and operating parameters in laser isotope separation processes.展开更多
The theoretical analysis of springback in rotary stretch bending process of L-section extrusion was studied. The models for characterizing the springback angle after unloading were established based on the stress and ...The theoretical analysis of springback in rotary stretch bending process of L-section extrusion was studied. The models for characterizing the springback angle after unloading were established based on the stress and strain distributions in the cross-section of the part. With the proposed model, analysis of the effect of pre-stretch force and post-stretch force on springback angle shows that springback decreases as the pre-stretch force or post-stretch force increases. Comparative study with experiments clearly demonstrates that the prediction of springback can resort to the current model without the loss of accuracy.展开更多
Mega-urban agglomerations are strategic core areas for national economic development and the main regions of new urbanization. They also have important roles in shifting the global economic center of gravity to China....Mega-urban agglomerations are strategic core areas for national economic development and the main regions of new urbanization. They also have important roles in shifting the global economic center of gravity to China. However, the development of mega-urban agglomerations has triggered the interactive coercion between resources and the eco-envi- ronment. The interactive coupled effects between urbanization and the eco-environment in mega-urban agglomerations represent frontier and high-priority research topics in the field of Earth system science over the next decade. In this paper, we carried out systematic theo- retical analysis of the interactive coupling mechanisms and coercing effects between ur- banization and the eco-environment in mega-urban agglomerations. In detail, we analyzed the nonlinear-coupled relationships and the coupling characteristics between natural and human elements in mega-urban agglomerations. We also investigated the interactive coercion intensities between internal and external elements, and the mechanisms and patterns of local couplings and telecouplings in mega-urban agglomeration systems, which are affected by key internal and external control elements. In addition, we proposed the interactive coupling theory on urbanization and the eco-environment in mega-urban agglomerations. Furthermore we established a spatiotemporal dynamic coupling model with multi-element, multi-scale, multi-scenario, multi-module and multi-agent integrations, which can be used to develop an intelligent decision support system for sustainable development of mega-urban agglomera- tions. In general, our research may provide theoretical guidance and method support to solve problems related to mega-urban agglomerations and maintain their sustainable development.展开更多
Cathode activity plays an important role in the improvement of the microbial fuel cells on ocean floor （BMFCs）. A comparison study between Rayon-based （CF-R） and PAN-based carbon fiber （CF-P） cathodes is conduct...Cathode activity plays an important role in the improvement of the microbial fuel cells on ocean floor （BMFCs）. A comparison study between Rayon-based （CF-R） and PAN-based carbon fiber （CF-P） cathodes is conducted in the paper. The two carbon fibers were heat treated to improve cell performance （CF-R-H ＆ CF-P-H）, and were used to build a new BMFCs structure with a foamy carbon anode. The maximum power density was 112.4mWm-2 for CF-R-H, followed by 66.6mWm-2 for CF-R, 49.7 mWm-2 for CF-P-H and 21.6mWm-2 for CF-P respectively. The higher specific area and deep groove make CF-R have a better power output than with CF-P. Meanwhile, heat treatment of carbon fiber can improve cell power, nearly two-fold higher than heat treatment of plain fiber. This improvement may be due to the quinones group formation to accelerate the reduction of oxygen and electron transfer on the fiber surface in the three phase boundary after heat treatment. Compared to PAN-based carbon fiber, Rayon-based carbon fiber would be preferentially selected as cathode in novel BMFCs design due to its high surface area, low cost and higher power. The comparison research is significant for cathode material selection and cell design.展开更多
The aim of this paper is to propose a theoretical approach for performing the nonprobabilistic reliability analysis of structure.Due to a great deal of uncertainties and limited measured data in engineering practice,t...The aim of this paper is to propose a theoretical approach for performing the nonprobabilistic reliability analysis of structure.Due to a great deal of uncertainties and limited measured data in engineering practice,the structural uncertain parameters were described as interval variables.The theoretical analysis model was developed by starting from the 2-D plane and 3-D space.In order to avoid the loss of probable failure points,the 2-D plane and 3-D space were respectively divided into two parts and three parts for further analysis.The study pointed out that the probable failure points only existed among extreme points and root points of the limit state function.Furthermore,the low-dimensional analytical scheme was extended to the high-dimensional case.Using the proposed approach,it is easy to find the most probable failure point and to acquire the reliability index through simple comparison directly.A number of equations used for calculating the extreme points and root points were also evaluated.This result was useful to avoid the loss of probable failure points and meaningful for optimizing searches in the research field.Finally,two kinds of examples were presented and compared with the existing computation.The good agreements show that the proposed theoretical analysis approach in the paper is correct.The efforts were conducted to improve the optimization method,to indicate the search direction and path,and to avoid only searching the local optimal solution which would result in missed probable failure points.展开更多
In this paper, the principle to determine the atmospheric columnar Mie optical depth from downward total solar radiative flux is theoretically studied, and the effect on Mie optical depth solution of the errors in sur...In this paper, the principle to determine the atmospheric columnar Mie optical depth from downward total solar radiative flux is theoretically studied, and the effect on Mie optical depth solution of the errors in surface albedo, sin-gle scattering albedo, asymmetrical factor of scattering phase function, instrumental constant and the approximate expression of diffusion flux is analy/ed, and then a method for determining surface albedo in shorter wavelength range is presented.展开更多
It is identified that barely passing electrons are the drive of the e-fishbones, rather than the barely trapped electrons at low frequency. The frequency jump in e-fishbone experiments is reproduced and analyzed. It i...It is identified that barely passing electrons are the drive of the e-fishbones, rather than the barely trapped electrons at low frequency. The frequency jump in e-fishbone experiments is reproduced and analyzed. It is found that the e-fishbone frequency increases with the hot electron energy, which is consistent with the experiments. The growth rate of the mode （m= 2, n = 2） is greater than that of the mode （m = 1, n = 1）.展开更多
The kind of micro-/nano-meter precision actuator in cludes a piezoelectric one, an electric deformation one, a magnetic deformation one, a mechanical one, and a mechanical and electrical one. This paper puts forw ard ...The kind of micro-/nano-meter precision actuator in cludes a piezoelectric one, an electric deformation one, a magnetic deformation one, a mechanical one, and a mechanical and electrical one. This paper puts forw ard a mechanical and electrical step actuator of nanometer precision, which cons ists of a step motor of large fine-dividing number of step angle, shaft couplin gs, a decelerator of large decelerating ratio, a screw mechanism and a pole of U shape, and has the minimum step displacement of 10 nm, the step displac ement precision of 1 nm, the step frequency of 4 kHz, the maximum loadability of 20 kg. In order to achieve the nano displacement of nano precision by this actu ator, the theoretical analysis of stress and strain must be made on the transmit ting course of nano displacement of the actuator, and their numerical simulation is done by computer. The paper establishes the constitutive equation of 3-D stress and the strain co ordinate equation of the composing system of the nanometer precision actuator. A s a result, the theoretical relation among stress and strain and displacement is set up. The torque of the step motor produces a thrust to transmit the displace ment of the above system of the parts and assemblies to output the needed nano d isplacement. In the case of concrete analysis and calculating, the comparing met hod of film-roof is applied to analyze and calculate the motor axis, decelerato r axes, the screw pole and the nut. The analysis method of plane stress and stra in is used to analyze and calculate the shaft couplings and gears. The analysis method of beam stress and strain is used to do the pole of U shape. These calcul ation is belong to the physical non-linear problem. Under the condition of smal l deformation, the analysis way of the finite element can be combined with the a bove analyses and calculations. The elementary analysis results show that the na nometer precision actuator can be applied in STM nanofabrication.展开更多
The theoretical calculation of LaNi4Co, in which Co substituted for Ni at various sites, was performed by adopting the method of total energy based on the Density Functional Theory. The augmented plane wave function w...The theoretical calculation of LaNi4Co, in which Co substituted for Ni at various sites, was performed by adopting the method of total energy based on the Density Functional Theory. The augmented plane wave function was selected as a basis set in combination with Ultra-soft Pseudopotential technology. The geometry of LaNi5 was optimized and the parameters and properties of the structure were given. The theoretical results accord well with experiments. This method provides a theoretical approach for the structure prediction of such alloy. The calculations of total energy, electronic density of states and Mulliken population of LaNi4Co were carried out. The electronic structure of LaNi4Co and the change of the electronic structure due to the Co-substitution in LaNi5 alloy were analyzed from the calculated results. The stability of the alloy in which Ni was partially substituted by Co at various sites was compared and the factors controlling stability were discussed. The theoretical value of formation heat was calculated.展开更多
As conducting an impact hammer testing during experimental modal analysis,the multiple impact phenomenon must be avoided.It is generally recognized that the multiple impact phenomenon is induced by the tester’s impro...As conducting an impact hammer testing during experimental modal analysis,the multiple impact phenomenon must be avoided.It is generally recognized that the multiple impact phenomenon is induced by the tester’s improper operation and can be avoided through more careful operation.This study theoretically and numerically investigates the whole process of the dynamical interaction between the hammer tip and the impacted structure and discovers the intrinsically physical mechanism of the multiple impact phenomenon.The determination of the interacting process comes down to solve two sets of governing differential equations alternately,and the effectiveness of the theoretical analysis is validated by numerical simulations.Four dimensionless parameters governing the interacting process are recognized in the theoretical framework.The critical stiffness ratio for a given impacted location and the critical impacted location for a given stiffness ratio are analytically determined.These results can guide impact hammer testing to avoid the occurrence of multiple impact by suggesting the hammer tip and impacted locations.展开更多
We calculate the Rydberg and autoionization Rydberg spectra of antimony （Sb） from first principles by relativistic multichannel theory within the framework of multichannel quantum defect theory. Our calculation can ...We calculate the Rydberg and autoionization Rydberg spectra of antimony （Sb） from first principles by relativistic multichannel theory within the framework of multichannel quantum defect theory. Our calculation can be used to classify and assign the atomic states described in recently reported three Rydberg series and four autoionizing states. The perturbation effects on line intensity, variation and line profile are discussed. Assignments of the perturber states and autoionizing states are presented.展开更多
Cryo-electron microscopy(cryo-EM) provides a powerful tool to resolve the structure of biological macromolecules in natural state. One advantage of cryo-EM technology is that different conformation states of a protein...Cryo-electron microscopy(cryo-EM) provides a powerful tool to resolve the structure of biological macromolecules in natural state. One advantage of cryo-EM technology is that different conformation states of a protein complex structure can be simultaneously built, and the distribution of different states can be measured. This provides a tool to push cryo-EM technology beyond just to resolve protein structures, but to obtain the thermodynamic properties of protein machines. Here, we used a deep manifold learning framework to get the conformational landscape of Kai C proteins, and further obtained the thermodynamic properties of this central oscillator component in the circadian clock by means of statistical physics.展开更多
In the present paper, the author sums up and analyzes descriptions about needle-insertion depth in Chinese classical medical book Huang Di Nei Jing (《黄帝内经》The Yellow Emperor’s Internal Classic). In many chapter...In the present paper, the author sums up and analyzes descriptions about needle-insertion depth in Chinese classical medical book Huang Di Nei Jing (《黄帝内经》The Yellow Emperor’s Internal Classic). In many chapters of Nei Jing, the needle-insertion depth is stressed to be various according to 1) the deficiency or excess of syndromes, 2) the patients’ constitution, 3) the severity of disease, 4) the duration of disease, 5) the location of disease, 6) the patient’s age, 7) the location of the needled acupoint, 8) the season, 9) the patient’s temperament, 10) the pulse condition, 11) the state of “Deqi”, and 12) the location of the running course of meridians. In addition, different kinds of diseases and different stages of diseases also need different depths of needle insertion, different manipulating skills and different stimulating quantity.展开更多
The kinetics of electron transmission at solid/solid interface system are investigation and studied using a simple model that derives depending on the quantum consideration. A two quantum state for donor state ｜αn ...The kinetics of electron transmission at solid/solid interface system are investigation and studied using a simple model that derives depending on the quantum consideration. A two quantum state for donor state ｜αn 〉 and acceptor state ｜αA 〉 are supposed. Marcus-Hush semi classical continuum levels theory adapted to evaluated the energies for orientation before transfer. The probability of transmission of electron is calculated to investigation the kinetics of transfer. Our result for calculation of rate constant of electron transfer shows a good agreement with experiment data.展开更多
As the world becomes more interconnected, learning a foreign language in the associated cultural context proves to be more efficient and effective. EFL （English as a Foreign Language） Teachers are sparing no efforts...As the world becomes more interconnected, learning a foreign language in the associated cultural context proves to be more efficient and effective. EFL （English as a Foreign Language） Teachers are sparing no efforts to raise students＇ awareness and understanding of the culture and to help students become interculturally competent. On the basis of thorough literature review on cultural study, this paper probes into theoretical analysis and strategic approaches of cultural learning in EFL classes. The extensive strategies are discussed and presented in the paper so as for more confidence and capabilities from practitioners incorporating sufficient cultural knowledge and understanding into successful EFL classroom.展开更多
The double-sided lapping process is extensively employed in the manufacturing of wafers,optical windows,and seal rings due to its high efficiency and ability to achieve precise flatness.However,limited research has ex...The double-sided lapping process is extensively employed in the manufacturing of wafers,optical windows,and seal rings due to its high efficiency and ability to achieve precise flatness.However,limited research has explored the thickness uniformity among different workpieces after double-sided lapping,and the underlying mechanism remains unclear.To address the demand for higher precision,this paper first analyzed the relative kinematic model between the workpiece and the lapping plate to clarify the causes of thickness variations among workpieces after double-sided lapping.Subsequently,a finite element method(FEM)model was developed to account for the pressure distribution on the workpiece surfaces at the initial stage of the process.The results indicate that the number of workpieces influences the final thickness variation.Then,various sets of thin copper plates with different thicknesses were lapped,and the findings revealed that five copper plates processed simultaneously exhibited more uniform thickness compared to the three plates.The experimental results align well with the theoretical analysis.Ultimately,a thickness variation of less than 6μm was achieved on five copper plates measuringΦ100×2.9 mm.This study presents a comprehensive analysis of the mechanisms influencing thickness uniformity in the double-sided lapping process and provides practical guidelines for optimizing the process to achieve stringent precision standards in industrial applications.展开更多
Hydraulic fracture growth is significantly influenced by the minimum horizontal principal stress gradient and the fracturing fluid pressure gradient.However,these gradients are often neglected in scaled physical model...Hydraulic fracture growth is significantly influenced by the minimum horizontal principal stress gradient and the fracturing fluid pressure gradient.However,these gradients are often neglected in scaled physical modeling experiments due to difficulties in reproducing them.This study uses centrifugal hypergravity to simulate both gradients and investigate their effects on fracture propagation.Artificial mortar specimens(ϕ200 mm×400 mm)are fractured under 1g(normal gravity),50g,and 100g.Results show that compared to 1g,fractures under 50g and 100g exhibit increasingly uneven propagation,with higher g-values leading to greater asymmetry.To interpret this,a theoretical analysis based on fracture mechanics is conducted.When the fluid pressure gradient exceeds the stress gradient,a positive net gradient is generated,increasing net pressure at the lower fracture tip.This raises the stress intensity factor at the lower tip,promoting downward growth.As g increases,the disparity becomes more significant,resulting in greater fracture deviation.In conclusion,this study,for the first time,has verified and explained that the net gradient can change the propagation of hydraulic fractures,providing important guidance for wellbore placement under stress gradients.展开更多
The effects of boundary layer bleed on the scramjet thrust are studied in the present paper.A theoretical model is developed to evaluate the thrust increment and influencing factors.The thrust increment resulting from...The effects of boundary layer bleed on the scramjet thrust are studied in the present paper.A theoretical model is developed to evaluate the thrust increment and influencing factors.The thrust increment resulting from the bleed is dominated by the rise in total pressure recovery and bleed mass flow rate.The bleed mass flow rate exerts stronger impact on the engine thrust than the total pressure.According to current bleed design,it is a severe challenge for the engine to enhance its total pressure to maintain the original thrust when there is no bleeding.Furthermore,the initial total pressure recovery,fuel mass addition,combustion efficiency and area ratio of engine exit to entrance can affect the contributions of the bleeding to the thrust increment.The scramjet needs a higher rise in total pressure recovery to counteract the negative effect of bleed mass loss at higher initial total pressure recovery or larger area ratio of engine exit/entrance.More heat release results in a little lower demand on the rise in total pressure recovery for maintaining the scramjet thrust.These results will aid in understanding the fundamental mechanism of bleeding on engine thrust.展开更多
With the growing economy and technology,disease prevention and individual health are becoming more and more important.It is highly urgent to develop a non-toxic,self-powered,and safe high-voltage power source to preve...With the growing economy and technology,disease prevention and individual health are becoming more and more important.It is highly urgent to develop a non-toxic,self-powered,and safe high-voltage power source to prevent diseases spread by mosquitoes,especially in isolated or remote areas.Herein,we reported a high-performance rotary triboelectric nanogenerator(R-TENG)based on customized theoretical simulations and a ferroelectric nanocomposite intermediate layer.The customized theoretical simulations based on gradient electrode gaps were established to optimize gap angles and segment numbers of the electrodes,which could prevent air breakdown and enhance the R-TENG output energy by at least 1.5 times.Meanwhile,the electrical output performance of the TENG was further enhanced with a highly oriented BaTiO3(BTO)nanoparticles intermediate layer by about 2.5 times.The open-circuit voltage of R-TENG reached more than 6 kV and could continuously light 3420 light-emitting devices(LEDs)or 4 serially connected 36 W household fluorescent lamps.Therefore,a self-powered high-voltage disease prevention system is developed based on the high-performance R-TENG to reduce the risk of disease transmission.This work provides a prospective strategy for the further development of TENGs and expands practical applications of self-powered and high-voltage systems.展开更多
基金supported by the National Key Laboratory of Particle Transport and Separation Technology(Grant No.WZKF-2024-2).
文摘An analytical model for describing the charged-particle transport in a wall-confined laser-induced decaying plasma is established under an external electrostatic field,focusing on the effects of the initial plasma-electrode gap(IPEG)that exists in applications such as laser isotope separation.This newly developed analytical model is validated by particle-in-cell simulations and the experimental scaling relation,and can also be reduced to its previously published counterpart that did not consider IPEGs.Based on this analytical model,the influences of different IPEG spacings on the characteristics of the whole ion extraction process are studied.The results show that the ion extraction ratios at the endpoints of the first and second stages both decrease with increasing IPEG spacing,while the corresponding time durations for the first two stages show a non-monotonous variation trend.The specific ion extraction time,defined as the ion extraction time per unit mass to comprehensively characterize the ion extraction efficiency,increases generally with the increase of IPEG spacing.This study not only provides further insight into the fundamental physical processes in a wall-bounded decaying plasma under an externally applied electrostatic field,but also offers useful theoretical guidance for optimal designs of geometrical and operating parameters in laser isotope separation processes.
基金Project (20090450276) supported by the China Postdoctoral Science FoundationProject (50905008) supported by the National Natural Science Foundation of China
文摘The theoretical analysis of springback in rotary stretch bending process of L-section extrusion was studied. The models for characterizing the springback angle after unloading were established based on the stress and strain distributions in the cross-section of the part. With the proposed model, analysis of the effect of pre-stretch force and post-stretch force on springback angle shows that springback decreases as the pre-stretch force or post-stretch force increases. Comparative study with experiments clearly demonstrates that the prediction of springback can resort to the current model without the loss of accuracy.
基金The Major Program of National Natural Science Foundation of China, No.41590840, No.41590842
文摘Mega-urban agglomerations are strategic core areas for national economic development and the main regions of new urbanization. They also have important roles in shifting the global economic center of gravity to China. However, the development of mega-urban agglomerations has triggered the interactive coercion between resources and the eco-envi- ronment. The interactive coupled effects between urbanization and the eco-environment in mega-urban agglomerations represent frontier and high-priority research topics in the field of Earth system science over the next decade. In this paper, we carried out systematic theo- retical analysis of the interactive coupling mechanisms and coercing effects between ur- banization and the eco-environment in mega-urban agglomerations. In detail, we analyzed the nonlinear-coupled relationships and the coupling characteristics between natural and human elements in mega-urban agglomerations. We also investigated the interactive coercion intensities between internal and external elements, and the mechanisms and patterns of local couplings and telecouplings in mega-urban agglomeration systems, which are affected by key internal and external control elements. In addition, we proposed the interactive coupling theory on urbanization and the eco-environment in mega-urban agglomerations. Furthermore we established a spatiotemporal dynamic coupling model with multi-element, multi-scale, multi-scenario, multi-module and multi-agent integrations, which can be used to develop an intelligent decision support system for sustainable development of mega-urban agglomera- tions. In general, our research may provide theoretical guidance and method support to solve problems related to mega-urban agglomerations and maintain their sustainable development.
基金support by the Key Project of Nature Science Fund of Shandong Province, China (ZR2011B Z008)the Special Fund of Marine Renewable Energy from China’s State Oceanic Administration (GHME 2011GD04)
文摘Cathode activity plays an important role in the improvement of the microbial fuel cells on ocean floor （BMFCs）. A comparison study between Rayon-based （CF-R） and PAN-based carbon fiber （CF-P） cathodes is conducted in the paper. The two carbon fibers were heat treated to improve cell performance （CF-R-H ＆ CF-P-H）, and were used to build a new BMFCs structure with a foamy carbon anode. The maximum power density was 112.4mWm-2 for CF-R-H, followed by 66.6mWm-2 for CF-R, 49.7 mWm-2 for CF-P-H and 21.6mWm-2 for CF-P respectively. The higher specific area and deep groove make CF-R have a better power output than with CF-P. Meanwhile, heat treatment of carbon fiber can improve cell power, nearly two-fold higher than heat treatment of plain fiber. This improvement may be due to the quinones group formation to accelerate the reduction of oxygen and electron transfer on the fiber surface in the three phase boundary after heat treatment. Compared to PAN-based carbon fiber, Rayon-based carbon fiber would be preferentially selected as cathode in novel BMFCs design due to its high surface area, low cost and higher power. The comparison research is significant for cathode material selection and cell design.
基金the National Natural Science Foundation of China (51408444, 51708428)
文摘The aim of this paper is to propose a theoretical approach for performing the nonprobabilistic reliability analysis of structure.Due to a great deal of uncertainties and limited measured data in engineering practice,the structural uncertain parameters were described as interval variables.The theoretical analysis model was developed by starting from the 2-D plane and 3-D space.In order to avoid the loss of probable failure points,the 2-D plane and 3-D space were respectively divided into two parts and three parts for further analysis.The study pointed out that the probable failure points only existed among extreme points and root points of the limit state function.Furthermore,the low-dimensional analytical scheme was extended to the high-dimensional case.Using the proposed approach,it is easy to find the most probable failure point and to acquire the reliability index through simple comparison directly.A number of equations used for calculating the extreme points and root points were also evaluated.This result was useful to avoid the loss of probable failure points and meaningful for optimizing searches in the research field.Finally,two kinds of examples were presented and compared with the existing computation.The good agreements show that the proposed theoretical analysis approach in the paper is correct.The efforts were conducted to improve the optimization method,to indicate the search direction and path,and to avoid only searching the local optimal solution which would result in missed probable failure points.
文摘In this paper, the principle to determine the atmospheric columnar Mie optical depth from downward total solar radiative flux is theoretically studied, and the effect on Mie optical depth solution of the errors in surface albedo, sin-gle scattering albedo, asymmetrical factor of scattering phase function, instrumental constant and the approximate expression of diffusion flux is analy/ed, and then a method for determining surface albedo in shorter wavelength range is presented.
基金Supported by the Funds of the Youth Innovation Team of Science and Technology in Sichuan Province of China under Grant No2014TD0023the National Natural Science Foundation of China under Grant Nos 11447228,11261140327,11005035 and 11205053the Project-the Plasma Confinement in the Advanced Magnetic Mirror under Grant No WX-2015-01-01
文摘It is identified that barely passing electrons are the drive of the e-fishbones, rather than the barely trapped electrons at low frequency. The frequency jump in e-fishbone experiments is reproduced and analyzed. It is found that the e-fishbone frequency increases with the hot electron energy, which is consistent with the experiments. The growth rate of the mode （m= 2, n = 2） is greater than that of the mode （m = 1, n = 1）.
文摘The kind of micro-/nano-meter precision actuator in cludes a piezoelectric one, an electric deformation one, a magnetic deformation one, a mechanical one, and a mechanical and electrical one. This paper puts forw ard a mechanical and electrical step actuator of nanometer precision, which cons ists of a step motor of large fine-dividing number of step angle, shaft couplin gs, a decelerator of large decelerating ratio, a screw mechanism and a pole of U shape, and has the minimum step displacement of 10 nm, the step displac ement precision of 1 nm, the step frequency of 4 kHz, the maximum loadability of 20 kg. In order to achieve the nano displacement of nano precision by this actu ator, the theoretical analysis of stress and strain must be made on the transmit ting course of nano displacement of the actuator, and their numerical simulation is done by computer. The paper establishes the constitutive equation of 3-D stress and the strain co ordinate equation of the composing system of the nanometer precision actuator. A s a result, the theoretical relation among stress and strain and displacement is set up. The torque of the step motor produces a thrust to transmit the displace ment of the above system of the parts and assemblies to output the needed nano d isplacement. In the case of concrete analysis and calculating, the comparing met hod of film-roof is applied to analyze and calculate the motor axis, decelerato r axes, the screw pole and the nut. The analysis method of plane stress and stra in is used to analyze and calculate the shaft couplings and gears. The analysis method of beam stress and strain is used to do the pole of U shape. These calcul ation is belong to the physical non-linear problem. Under the condition of smal l deformation, the analysis way of the finite element can be combined with the a bove analyses and calculations. The elementary analysis results show that the na nometer precision actuator can be applied in STM nanofabrication.
文摘The theoretical calculation of LaNi4Co, in which Co substituted for Ni at various sites, was performed by adopting the method of total energy based on the Density Functional Theory. The augmented plane wave function was selected as a basis set in combination with Ultra-soft Pseudopotential technology. The geometry of LaNi5 was optimized and the parameters and properties of the structure were given. The theoretical results accord well with experiments. This method provides a theoretical approach for the structure prediction of such alloy. The calculations of total energy, electronic density of states and Mulliken population of LaNi4Co were carried out. The electronic structure of LaNi4Co and the change of the electronic structure due to the Co-substitution in LaNi5 alloy were analyzed from the calculated results. The stability of the alloy in which Ni was partially substituted by Co at various sites was compared and the factors controlling stability were discussed. The theoretical value of formation heat was calculated.
基金the National Natural Science Foundation of China under Grant Nos.11872328,11532011,and 11621062.
文摘As conducting an impact hammer testing during experimental modal analysis,the multiple impact phenomenon must be avoided.It is generally recognized that the multiple impact phenomenon is induced by the tester’s improper operation and can be avoided through more careful operation.This study theoretically and numerically investigates the whole process of the dynamical interaction between the hammer tip and the impacted structure and discovers the intrinsically physical mechanism of the multiple impact phenomenon.The determination of the interacting process comes down to solve two sets of governing differential equations alternately,and the effectiveness of the theoretical analysis is validated by numerical simulations.Four dimensionless parameters governing the interacting process are recognized in the theoretical framework.The critical stiffness ratio for a given impacted location and the critical impacted location for a given stiffness ratio are analytically determined.These results can guide impact hammer testing to avoid the occurrence of multiple impact by suggesting the hammer tip and impacted locations.
基金Supported by the Beijing Natural Science Foundation under Grant No 1164016the National Natural Science Foundation of China under Grant No 11604334the Funding from TRIUMF which receives Federal Funding via a Contribution Agreement with the National Research Council of Canada and through a Natural Sciences and Engineering Research Council of Canada under Grant No 386343-2011
文摘We calculate the Rydberg and autoionization Rydberg spectra of antimony （Sb） from first principles by relativistic multichannel theory within the framework of multichannel quantum defect theory. Our calculation can be used to classify and assign the atomic states described in recently reported three Rydberg series and four autoionizing states. The perturbation effects on line intensity, variation and line profile are discussed. Assignments of the perturber states and autoionizing states are presented.
基金supported by the National Natural Science Foundation of China (Grant No. 12090054)。
文摘Cryo-electron microscopy(cryo-EM) provides a powerful tool to resolve the structure of biological macromolecules in natural state. One advantage of cryo-EM technology is that different conformation states of a protein complex structure can be simultaneously built, and the distribution of different states can be measured. This provides a tool to push cryo-EM technology beyond just to resolve protein structures, but to obtain the thermodynamic properties of protein machines. Here, we used a deep manifold learning framework to get the conformational landscape of Kai C proteins, and further obtained the thermodynamic properties of this central oscillator component in the circadian clock by means of statistical physics.
文摘In the present paper, the author sums up and analyzes descriptions about needle-insertion depth in Chinese classical medical book Huang Di Nei Jing (《黄帝内经》The Yellow Emperor’s Internal Classic). In many chapters of Nei Jing, the needle-insertion depth is stressed to be various according to 1) the deficiency or excess of syndromes, 2) the patients’ constitution, 3) the severity of disease, 4) the duration of disease, 5) the location of disease, 6) the patient’s age, 7) the location of the needled acupoint, 8) the season, 9) the patient’s temperament, 10) the pulse condition, 11) the state of “Deqi”, and 12) the location of the running course of meridians. In addition, different kinds of diseases and different stages of diseases also need different depths of needle insertion, different manipulating skills and different stimulating quantity.
文摘The kinetics of electron transmission at solid/solid interface system are investigation and studied using a simple model that derives depending on the quantum consideration. A two quantum state for donor state ｜αn 〉 and acceptor state ｜αA 〉 are supposed. Marcus-Hush semi classical continuum levels theory adapted to evaluated the energies for orientation before transfer. The probability of transmission of electron is calculated to investigation the kinetics of transfer. Our result for calculation of rate constant of electron transfer shows a good agreement with experiment data.
文摘As the world becomes more interconnected, learning a foreign language in the associated cultural context proves to be more efficient and effective. EFL （English as a Foreign Language） Teachers are sparing no efforts to raise students＇ awareness and understanding of the culture and to help students become interculturally competent. On the basis of thorough literature review on cultural study, this paper probes into theoretical analysis and strategic approaches of cultural learning in EFL classes. The extensive strategies are discussed and presented in the paper so as for more confidence and capabilities from practitioners incorporating sufficient cultural knowledge and understanding into successful EFL classroom.
文摘Microscopic imaging based on second-harmonic generation has been proving to be a powerful tool for biomedical studies, especially in that tissues with
基金Supported by the Liaoning Provincial Natural Science Foundation(Grant No.2023-MSBA-008)Unveiling and Commanding Program of Liaoning Province(Grant No.2022JH1/10800080)the Fundamental Research Funds for the Central Universities(Grant No.DUT24MS008).
文摘The double-sided lapping process is extensively employed in the manufacturing of wafers,optical windows,and seal rings due to its high efficiency and ability to achieve precise flatness.However,limited research has explored the thickness uniformity among different workpieces after double-sided lapping,and the underlying mechanism remains unclear.To address the demand for higher precision,this paper first analyzed the relative kinematic model between the workpiece and the lapping plate to clarify the causes of thickness variations among workpieces after double-sided lapping.Subsequently,a finite element method(FEM)model was developed to account for the pressure distribution on the workpiece surfaces at the initial stage of the process.The results indicate that the number of workpieces influences the final thickness variation.Then,various sets of thin copper plates with different thicknesses were lapped,and the findings revealed that five copper plates processed simultaneously exhibited more uniform thickness compared to the three plates.The experimental results align well with the theoretical analysis.Ultimately,a thickness variation of less than 6μm was achieved on five copper plates measuringΦ100×2.9 mm.This study presents a comprehensive analysis of the mechanisms influencing thickness uniformity in the double-sided lapping process and provides practical guidelines for optimizing the process to achieve stringent precision standards in industrial applications.
基金supports of Basic Science Center Program for Multiphase Evolution in Hyper-gravity of the National Natural Science Foundation of China(No.51988101)National Natural Science Foundation of China(Nos.52109138 and 52122403)Young Elite Scientists Sponsorship Program by CAST(No.2023QNRC001).
文摘Hydraulic fracture growth is significantly influenced by the minimum horizontal principal stress gradient and the fracturing fluid pressure gradient.However,these gradients are often neglected in scaled physical modeling experiments due to difficulties in reproducing them.This study uses centrifugal hypergravity to simulate both gradients and investigate their effects on fracture propagation.Artificial mortar specimens(ϕ200 mm×400 mm)are fractured under 1g(normal gravity),50g,and 100g.Results show that compared to 1g,fractures under 50g and 100g exhibit increasingly uneven propagation,with higher g-values leading to greater asymmetry.To interpret this,a theoretical analysis based on fracture mechanics is conducted.When the fluid pressure gradient exceeds the stress gradient,a positive net gradient is generated,increasing net pressure at the lower fracture tip.This raises the stress intensity factor at the lower tip,promoting downward growth.As g increases,the disparity becomes more significant,resulting in greater fracture deviation.In conclusion,this study,for the first time,has verified and explained that the net gradient can change the propagation of hydraulic fractures,providing important guidance for wellbore placement under stress gradients.
基金supported by the National Natural Science Foundation of China(Grant Nos.90716014 and 91216115)
文摘The effects of boundary layer bleed on the scramjet thrust are studied in the present paper.A theoretical model is developed to evaluate the thrust increment and influencing factors.The thrust increment resulting from the bleed is dominated by the rise in total pressure recovery and bleed mass flow rate.The bleed mass flow rate exerts stronger impact on the engine thrust than the total pressure.According to current bleed design,it is a severe challenge for the engine to enhance its total pressure to maintain the original thrust when there is no bleeding.Furthermore,the initial total pressure recovery,fuel mass addition,combustion efficiency and area ratio of engine exit to entrance can affect the contributions of the bleeding to the thrust increment.The scramjet needs a higher rise in total pressure recovery to counteract the negative effect of bleed mass loss at higher initial total pressure recovery or larger area ratio of engine exit/entrance.More heat release results in a little lower demand on the rise in total pressure recovery for maintaining the scramjet thrust.These results will aid in understanding the fundamental mechanism of bleeding on engine thrust.
基金The research is supported by the National Natural Science Foundation of China(Nos.52101390,52125205,U20A20166,61805015,and 61804011)Natural Science Foundation of Shandong Province,China(No.ZR2021QE043)+3 种基金Fundamental Research Funds for the Central Universities,China(No.202112011)Open Project of Key Lab of Special Functional Materials of Ministry of Education,Henan University(No.KFKT-2022-11)Natural Science Foundation of Beijing Municipality(No.Z180011)Joint Funds of National Natural Science Foundation of China(No.U2106216).
文摘With the growing economy and technology,disease prevention and individual health are becoming more and more important.It is highly urgent to develop a non-toxic,self-powered,and safe high-voltage power source to prevent diseases spread by mosquitoes,especially in isolated or remote areas.Herein,we reported a high-performance rotary triboelectric nanogenerator(R-TENG)based on customized theoretical simulations and a ferroelectric nanocomposite intermediate layer.The customized theoretical simulations based on gradient electrode gaps were established to optimize gap angles and segment numbers of the electrodes,which could prevent air breakdown and enhance the R-TENG output energy by at least 1.5 times.Meanwhile,the electrical output performance of the TENG was further enhanced with a highly oriented BaTiO3(BTO)nanoparticles intermediate layer by about 2.5 times.The open-circuit voltage of R-TENG reached more than 6 kV and could continuously light 3420 light-emitting devices(LEDs)or 4 serially connected 36 W household fluorescent lamps.Therefore,a self-powered high-voltage disease prevention system is developed based on the high-performance R-TENG to reduce the risk of disease transmission.This work provides a prospective strategy for the further development of TENGs and expands practical applications of self-powered and high-voltage systems.
