Alzheimer＇s disease （AD） is the most frequent cause of dementia in the western world. In clinical terms, AD is characterized by progres- sive cognitive decline that usually begins with memory impairment. As the dis...Alzheimer＇s disease （AD） is the most frequent cause of dementia in the western world. In clinical terms, AD is characterized by progres- sive cognitive decline that usually begins with memory impairment. As the disease progresses, AD inevitably affects all intellectual functions including executive functions, leading to complete dependence for basic activities of daily life and premature death.展开更多
Implementing the flyby to Near-Earth Asteroids (NEAs) with the potential impact risks to the Earth allows for obtaining detailed physical parameters, thereby supporting the high-precision orbit prediction and planetar...Implementing the flyby to Near-Earth Asteroids (NEAs) with the potential impact risks to the Earth allows for obtaining detailed physical parameters, thereby supporting the high-precision orbit prediction and planetary defense strategy. Different from those conducted asteroid flyby missions, in the 12th China Trajectory Optimization Competition (CTOC-12), a NEAs flyby trajectory design problem using reusable probes that depart from a Lunar Distant Retrograde Orbit (DRO) station in the cislunar space was released. The objective was flyby to as many NEAs as possible using up to 20 probes within a total of 10 years. The ∑ team proposed a solution that can explore 47 NEAs using 11 probes, ranking the first in the competition. In this paper, the methods and results from the winning team are introduced, including mission analysis and preliminary design, and low-energy transfer trajectory optimization. In particular, a round-trip trajectory is divided into three phases: deep space transfer, indirect transfer between the Earth to DRO, and DRO phasing and rendezvous. With the combination of global optimization and local optimization algorithms, the required velocity increments to change the orbital planes are effectively reduced, thus increasing the number of the explored NEAs. The final solution of our team is presented and the results are compared with those of the top three teams. The competition demonstrates that the regularization of flyby missions from the cislunar space to explore NEAs with the potential impact risks to the Earth is the feasible and promising.展开更多
Cu2O@Cu2O core-shell nanoparticles (NPs) were prepared by using solution phase strategy. It was found that Cu2O@Cu2O NPs were easily converted to Cu2O@Cu NPs with the help of polyvinylpyrrolidine (PVP) and excessive a...Cu2O@Cu2O core-shell nanoparticles (NPs) were prepared by using solution phase strategy. It was found that Cu2O@Cu2O NPs were easily converted to Cu2O@Cu NPs with the help of polyvinylpyrrolidine (PVP) and excessive ascorbic acid (AA) in air at room temperature, which was an interesting phenomenon. The features of the two kinds of NPs were characterized by XRD, TEM and extinction spectra. Cu2O@Cu NPs with different shell thicknesses showed wide tunable optical properties for the localized surface plasmon (LSP) in metallic Cu. But Cu2O@Cu2O NPs did not indicate this feature. FTIR results reveal that Cu+ ions on the surface of Cu2O shell coordinate with N and O atoms in PVP and are further reduced to metallic Cu by excessive AA and then form a nucleation site on the surface of Cu2O nanocrystalline. PVP binds onto different sites to proceed with the reduction utill all the Cu sources in Cu2O shell are completely assumed.展开更多
High-performance microprocessors have rapidlyevolved and become ubiquitous in modern society.However,their power supply has become a significant factor limiting their overall performance.A power delivery module,known ...High-performance microprocessors have rapidlyevolved and become ubiquitous in modern society.However,their power supply has become a significant factor limiting their overall performance.A power delivery module,known as a voltage regulator module(VRM),is required to provide high voltage,low current,and a fast transient response to meet microprocessor demands.An interleaved parallel-buck converter is suitable for VRM applications.Selecting an appropriate control strategy for the interleaved converter can help achieve high precision and fast response,thereby optimizing performance.First,the operating principles of interleaved parallel converters are analyzed.The relationship between the number of phases and conversion efficiency is also examined.Subsequently,commonly employed control techniques for interleaved converters are reviewed,discussing their respective advantages and limitations,along with an analysis of their suitabilityfor phase-shedding strategies.A phase-shedding technique for interleaved converters is then introduced.Finally,the shortcomings of current control approaches for interleaved buck converters are outlined,and potential future research directions are suggested.These insights aim to enhance control performance and advance practical engineering applications.展开更多
Intermediate spoofing can impact most off-the-shelf Global Navigation Satellite Systems （GNSS） receivers, therefore low cost detection of such spoofing is very important to protect the reliability of the GNSS receiv...Intermediate spoofing can impact most off-the-shelf Global Navigation Satellite Systems （GNSS） receivers, therefore low cost detection of such spoofing is very important to protect the reliability of the GNSS receivers used in critical safety and financial applications. This paper presents two strategies to analyze attacks by intermediate spoofing attackers to identify the weaknesses of such attacks. The analyses lead to a code and carrier phase consistency detection method with simulation results showing that this method can indicate the receiver when spoofing has occurred. The method can be used by most receivers, is inexpensive, and requires only a small software upgrade.展开更多
High-fidelity aerodynamic optimization of compressors is afflicted by the"curse of dimensionality",which limits its engineering applications.This paper proposes a new multi-degrees-of-freedom(MDOF)surface pa...High-fidelity aerodynamic optimization of compressors is afflicted by the"curse of dimensionality",which limits its engineering applications.This paper proposes a new multi-degrees-of-freedom(MDOF)surface parameterization method that combines the characteristics of conventional surface parameterization methods,low-dimensionality and surface smoothness,with the advantages of design flexibility and ease of construction.The proposed method is applied to the high-fidelity aerodynamic optimization of Rotor37.An optimized solution is obtained within 111 h by combining a phased optimization strategy based on the idea of modal optimization.To explore a better way of setting the control variables of the blade body,two methods of varying the control points of the suction and pressure surfaces,independent change and synchronous change,are compared.Synchronous change has better flexibility,and under the condition of satisfying the constraints,it increases the efficiency at the design point by 2.2%and the surge margin by 0.5%.This demonstrates the effectiveness of the proposed method in the high-fidelity aerodynamic optimization of compressors.It also provides technical support to solve the"curse of dimensionality"problem.展开更多
Since the 21st century,increasing environmental protection and human health concern have been the driving force to develop lead-free piezoelectric materials with enhanced performances,and phase en-gineering strategy h...Since the 21st century,increasing environmental protection and human health concern have been the driving force to develop lead-free piezoelectric materials with enhanced performances,and phase en-gineering strategy has been validated to be a viable method in numerous methodologies.Here,we gained a superb d_(33)~(637±30)pC/N in lead-free(1-x)(Ba_(0.93)Ca_(0.07))(Sn_(0.08)Ti_(0.92))O_(3-x)(Sb_(0.5)Li_(0.5))TiO_(3)[abbreviated as(1-x)BCST-xSLT,0≤x≤0.4%(in mole)]piezoelectrics utilizing chemical doping.To illustrate the relationship among composition-structure-performance,microstructure characterization,electrical properties measurement,first-principles calculation,and phase-field simulations were per-formed.Atomic-resolved polarization mapping of z-contrast imaging manifests the ferroelectric three phases(ReOeT)coexist at the nanoscale with nanoscale polarization switching among them.Theoretical calculations and simulations confirm that the high-density nano-domain boundary bridges the poly-phase coexisting nano-domains,which makes the polarization reversal easy,thus significantly reducing the energy barrier and polarization anisotropy among different phases.展开更多
文摘Alzheimer＇s disease （AD） is the most frequent cause of dementia in the western world. In clinical terms, AD is characterized by progres- sive cognitive decline that usually begins with memory impairment. As the disease progresses, AD inevitably affects all intellectual functions including executive functions, leading to complete dependence for basic activities of daily life and premature death.
基金supported by the Special Funding Project for Space Debris and Near-Earth Asteroids Defense Research, China (No. KJSP2023020303)Beijing Municipal Science and Technology Commission, China (No. Z181100002918004)the Youth Innovation Promotion Association, Chinese Academy of Sciences (No. 2022146)
文摘Implementing the flyby to Near-Earth Asteroids (NEAs) with the potential impact risks to the Earth allows for obtaining detailed physical parameters, thereby supporting the high-precision orbit prediction and planetary defense strategy. Different from those conducted asteroid flyby missions, in the 12th China Trajectory Optimization Competition (CTOC-12), a NEAs flyby trajectory design problem using reusable probes that depart from a Lunar Distant Retrograde Orbit (DRO) station in the cislunar space was released. The objective was flyby to as many NEAs as possible using up to 20 probes within a total of 10 years. The ∑ team proposed a solution that can explore 47 NEAs using 11 probes, ranking the first in the competition. In this paper, the methods and results from the winning team are introduced, including mission analysis and preliminary design, and low-energy transfer trajectory optimization. In particular, a round-trip trajectory is divided into three phases: deep space transfer, indirect transfer between the Earth to DRO, and DRO phasing and rendezvous. With the combination of global optimization and local optimization algorithms, the required velocity increments to change the orbital planes are effectively reduced, thus increasing the number of the explored NEAs. The final solution of our team is presented and the results are compared with those of the top three teams. The competition demonstrates that the regularization of flyby missions from the cislunar space to explore NEAs with the potential impact risks to the Earth is the feasible and promising.
基金Projects(41172110,61107090)supported by the National Natural Science Foundation of China
文摘Cu2O@Cu2O core-shell nanoparticles (NPs) were prepared by using solution phase strategy. It was found that Cu2O@Cu2O NPs were easily converted to Cu2O@Cu NPs with the help of polyvinylpyrrolidine (PVP) and excessive ascorbic acid (AA) in air at room temperature, which was an interesting phenomenon. The features of the two kinds of NPs were characterized by XRD, TEM and extinction spectra. Cu2O@Cu NPs with different shell thicknesses showed wide tunable optical properties for the localized surface plasmon (LSP) in metallic Cu. But Cu2O@Cu2O NPs did not indicate this feature. FTIR results reveal that Cu+ ions on the surface of Cu2O shell coordinate with N and O atoms in PVP and are further reduced to metallic Cu by excessive AA and then form a nucleation site on the surface of Cu2O nanocrystalline. PVP binds onto different sites to proceed with the reduction utill all the Cu sources in Cu2O shell are completely assumed.
基金Supported by Guangdong Basic and Applied Basic Research Foundation(2023A1515240033)Basic and Applied Basic Research Foundation of Guangzhou(2024A04J6540)Guangdong Science Fund for Distinguished Young Scholars(2022B1515020002).
文摘High-performance microprocessors have rapidlyevolved and become ubiquitous in modern society.However,their power supply has become a significant factor limiting their overall performance.A power delivery module,known as a voltage regulator module(VRM),is required to provide high voltage,low current,and a fast transient response to meet microprocessor demands.An interleaved parallel-buck converter is suitable for VRM applications.Selecting an appropriate control strategy for the interleaved converter can help achieve high precision and fast response,thereby optimizing performance.First,the operating principles of interleaved parallel converters are analyzed.The relationship between the number of phases and conversion efficiency is also examined.Subsequently,commonly employed control techniques for interleaved converters are reviewed,discussing their respective advantages and limitations,along with an analysis of their suitabilityfor phase-shedding strategies.A phase-shedding technique for interleaved converters is then introduced.Finally,the shortcomings of current control approaches for interleaved buck converters are outlined,and potential future research directions are suggested.These insights aim to enhance control performance and advance practical engineering applications.
基金National Natural Science Foundation of China(No.61101070)
文摘Intermediate spoofing can impact most off-the-shelf Global Navigation Satellite Systems （GNSS） receivers, therefore low cost detection of such spoofing is very important to protect the reliability of the GNSS receivers used in critical safety and financial applications. This paper presents two strategies to analyze attacks by intermediate spoofing attackers to identify the weaknesses of such attacks. The analyses lead to a code and carrier phase consistency detection method with simulation results showing that this method can indicate the receiver when spoofing has occurred. The method can be used by most receivers, is inexpensive, and requires only a small software upgrade.
基金financially supported by Civil Aircraft Special Project(Grant No.MJZ-2017-D-32(Y81H061A41)).
文摘High-fidelity aerodynamic optimization of compressors is afflicted by the"curse of dimensionality",which limits its engineering applications.This paper proposes a new multi-degrees-of-freedom(MDOF)surface parameterization method that combines the characteristics of conventional surface parameterization methods,low-dimensionality and surface smoothness,with the advantages of design flexibility and ease of construction.The proposed method is applied to the high-fidelity aerodynamic optimization of Rotor37.An optimized solution is obtained within 111 h by combining a phased optimization strategy based on the idea of modal optimization.To explore a better way of setting the control variables of the blade body,two methods of varying the control points of the suction and pressure surfaces,independent change and synchronous change,are compared.Synchronous change has better flexibility,and under the condition of satisfying the constraints,it increases the efficiency at the design point by 2.2%and the surge margin by 0.5%.This demonstrates the effectiveness of the proposed method in the high-fidelity aerodynamic optimization of compressors.It also provides technical support to solve the"curse of dimensionality"problem.
基金supported by High-level Innovative Talents Plan of Guizhou Province(Grant No.(2015)4009)National Natural Science Foundation of China(Grant No.51602066).
文摘Since the 21st century,increasing environmental protection and human health concern have been the driving force to develop lead-free piezoelectric materials with enhanced performances,and phase en-gineering strategy has been validated to be a viable method in numerous methodologies.Here,we gained a superb d_(33)~(637±30)pC/N in lead-free(1-x)(Ba_(0.93)Ca_(0.07))(Sn_(0.08)Ti_(0.92))O_(3-x)(Sb_(0.5)Li_(0.5))TiO_(3)[abbreviated as(1-x)BCST-xSLT,0≤x≤0.4%(in mole)]piezoelectrics utilizing chemical doping.To illustrate the relationship among composition-structure-performance,microstructure characterization,electrical properties measurement,first-principles calculation,and phase-field simulations were per-formed.Atomic-resolved polarization mapping of z-contrast imaging manifests the ferroelectric three phases(ReOeT)coexist at the nanoscale with nanoscale polarization switching among them.Theoretical calculations and simulations confirm that the high-density nano-domain boundary bridges the poly-phase coexisting nano-domains,which makes the polarization reversal easy,thus significantly reducing the energy barrier and polarization anisotropy among different phases.
