Amorphous alloys,also known as metallic glasses,are solid metallic materials having long-range disordered atomic structures.Compared to crystalline alloys,amorphous alloys not only have metallic characters,but also po...Amorphous alloys,also known as metallic glasses,are solid metallic materials having long-range disordered atomic structures.Compared to crystalline alloys,amorphous alloys not only have metallic characters,but also possess several distinct properties associated to the amorphous structure,such as isotropy,composition flexibility,unsaturated surface,etc.As a result,amorphous alloys offer a class of highly promising materials for catalyzing electrochemical reactions.In this minireview,the preparation,characterization and electrocatalytic performances of a variety of metallic amorphous alloy materials are summarized.The influences of the amorphous alloy structure on different electrochemical reactions are discussed.Finally,a summary on the advantages and challenges of amorphous alloys in electrocatalysis is provided,along with some perspectives about the future research directions.展开更多
Harmonic analysis, the traditional tidal forecasting method, cannot take into account the impact of noncyclical factors, and is also based on the BP neural network tidal prediction model which is easily limited by the...Harmonic analysis, the traditional tidal forecasting method, cannot take into account the impact of noncyclical factors, and is also based on the BP neural network tidal prediction model which is easily limited by the amount of data. According to the movement of celestial bodies, and considering the insufficient tidal characteristics of historical data which are impacted by the nonperiodic weather, a tidal prediction method is designed based on support vector machine （SVM） to carry out the simulation experiment by using tidal data from Xiamen Tide Gauge, Luchaogang Tide Gauge and Weifang Tide Gauge individually. And the results show that the model satisfactorily carries out the tide prediction which is influenced by noncyclical factors. At the same time, it also proves that the proposed prediction method, which when compared with harmonic analysis method and the BP neural network method, has faster modeling speed, higher prediction precision and stronger generalization ability.展开更多
The predator-prey model for three species in which the right-hand sides are nonperiodic functions in time were considered, It's proved that the model is persistent under appropriate conditions.
Stepped frequency chirp signal obtains high-resolution radar images by synthesizing multiple narrowband chirp pulses.It has been one of the most commonly used wideband radar waveforms due to its lower demand for radar...Stepped frequency chirp signal obtains high-resolution radar images by synthesizing multiple narrowband chirp pulses.It has been one of the most commonly used wideband radar waveforms due to its lower demand for radar instant bandwidth.In this paper,we propose a radar jamming method using two-dimensional nonperiodic phase modulation against stepped frequency chirp signal imaging radar.Using the unique property of nonperiodic phase modulation,the proposed method can generate high-level sidelobes that perform as a special blanket jamming along both the range and azimuth directions and make the target unrecognizable.Then,the influence of different modulation parameters,such as the code width and duty ratio,are further discussed.Based on this,the corresponding parameter design principles are presented.Finally,the validity of the proposed method is demonstrated by the Yake-42 plane data simulation and measured unmanned aerial vehicle data experiment.展开更多
The fabrication and characterization of p-i-n photodiodes integrated with wide spectrum focusing reflectors using nonperiodic strip and concentric-circular subwavelength gratings are presented. The experimental result...The fabrication and characterization of p-i-n photodiodes integrated with wide spectrum focusing reflectors using nonperiodic strip and concentric-circular subwavelength gratings are presented. The experimental results show that the gratings can reflect and focus the incident light on the absorber of the photodiode, and thus can simultaneously achieve high speed and high efficiency. For the gratings’ integrated photodiodes, the responsivity is improved over a wide spectral range, and when the absorber was 600 nm and the mesa diameter was40 μm, a responsivity of 0.46 A/W at a wavelength of 1.55 μm and a 3 dB bandwidth of 21.6 GHz under a reverse bias of 3 V were simultaneously obtained.展开更多
In order to obtain large broadband, a novel travelling-wave modulator with nonperiodic domain inversions and ridge structure is proposed. The composite structure is designed to achieve velocity matching between the op...In order to obtain large broadband, a novel travelling-wave modulator with nonperiodic domain inversions and ridge structure is proposed. The composite structure is designed to achieve velocity matching between the optical wave and the microwave, to get a 50 characteristic impedance and to reduce the loss of the microwave electrodes with finite element method (FEM). The calculation results show that the frequency response of the new device is flat up to 350 GHz with interaction length of 1 cm, characteristic impedance of 49 , and microwave refractive index of 2.5.展开更多
Malaria infection continues to be a major problem in many parts of the world including Africa.Environmental variables are known to significantly affect the population dynamics and abundance of insects,major catalysts ...Malaria infection continues to be a major problem in many parts of the world including Africa.Environmental variables are known to significantly affect the population dynamics and abundance of insects,major catalysts of vector-borne diseases,but the exact extent and consequences of this sensitivity are not yet well established.To assess the impact of the variability in temperature and rainfall on the transmission dynamics of malaria in a population,we propose a model consisting of a system of non-autonomous deterministic equations that incorporate the effect of both temperature and rainfall to the dispersion and mortality rate of adult mosquitoes.The model has been validated using epidemiological data collected from the western region of Ethiopia by considering the trends for the cases of malaria and the climate variation in the region.Further,a mathematical analysis is performed to assess the impact of temperature and rainfall change on the transmission dynamics of the model.The periodic variation of seasonal variables as well as the non-periodic variation due to the long-term climate variation have been incorporated and analyzed.In both periodic and non-periodic cases,it has been shown that the disease-free solution of the model is globally asymptotically stable when the basic reproduction ratio is less than unity in the periodic system and when the threshold function is less than unity in the non-periodic system.The disease is uniformly persistent when the basic reproduction ratio is greater than unity in the periodic system and when the threshold function is greater than unity in the non-periodic system.展开更多
In this paper, we investigate standing waves in discrete nonlinear Schr?dinger equations with nonperiodic bounded potentials. By using the critical point theory and the spectral theory of self-adjoint operators, we pr...In this paper, we investigate standing waves in discrete nonlinear Schr?dinger equations with nonperiodic bounded potentials. By using the critical point theory and the spectral theory of self-adjoint operators, we prove the existence and infinitely many sign-changing solutions of the equation. The results on the exponential decay of standing waves are also provided.展开更多
基金supported by the Ministry of Education of Singapore under Tier 1 RG115/18 and RG4/20,and Tier 2 T2EP10120-0009.
文摘Amorphous alloys,also known as metallic glasses,are solid metallic materials having long-range disordered atomic structures.Compared to crystalline alloys,amorphous alloys not only have metallic characters,but also possess several distinct properties associated to the amorphous structure,such as isotropy,composition flexibility,unsaturated surface,etc.As a result,amorphous alloys offer a class of highly promising materials for catalyzing electrochemical reactions.In this minireview,the preparation,characterization and electrocatalytic performances of a variety of metallic amorphous alloy materials are summarized.The influences of the amorphous alloy structure on different electrochemical reactions are discussed.Finally,a summary on the advantages and challenges of amorphous alloys in electrocatalysis is provided,along with some perspectives about the future research directions.
基金The Shanghai Committee of Science and Technology of China under contract No. 10510502800the Graduate Student Education Innovation Program Foundation of Shanghai Municipal Education Commission of Chinathe National Key Science Foundation Research "973" Project of the Ministry of Science and Technology of China under contract No. 2012CB316200
文摘Harmonic analysis, the traditional tidal forecasting method, cannot take into account the impact of noncyclical factors, and is also based on the BP neural network tidal prediction model which is easily limited by the amount of data. According to the movement of celestial bodies, and considering the insufficient tidal characteristics of historical data which are impacted by the nonperiodic weather, a tidal prediction method is designed based on support vector machine （SVM） to carry out the simulation experiment by using tidal data from Xiamen Tide Gauge, Luchaogang Tide Gauge and Weifang Tide Gauge individually. And the results show that the model satisfactorily carries out the tide prediction which is influenced by noncyclical factors. At the same time, it also proves that the proposed prediction method, which when compared with harmonic analysis method and the BP neural network method, has faster modeling speed, higher prediction precision and stronger generalization ability.
文摘The predator-prey model for three species in which the right-hand sides are nonperiodic functions in time were considered, It's proved that the model is persistent under appropriate conditions.
基金Project supported by the Natural Science Foundation of Hunan Province,China(No.2022JJ40561)the Scientific Research Program of National University of Defense Technology,China(No.ZK22-46)the National Natural Science Foundation of China(Nos.61890542,62001481,and 62071475)。
文摘Stepped frequency chirp signal obtains high-resolution radar images by synthesizing multiple narrowband chirp pulses.It has been one of the most commonly used wideband radar waveforms due to its lower demand for radar instant bandwidth.In this paper,we propose a radar jamming method using two-dimensional nonperiodic phase modulation against stepped frequency chirp signal imaging radar.Using the unique property of nonperiodic phase modulation,the proposed method can generate high-level sidelobes that perform as a special blanket jamming along both the range and azimuth directions and make the target unrecognizable.Then,the influence of different modulation parameters,such as the code width and duty ratio,are further discussed.Based on this,the corresponding parameter design principles are presented.Finally,the validity of the proposed method is demonstrated by the Yake-42 plane data simulation and measured unmanned aerial vehicle data experiment.
基金funded by the National Natural Science Foundation of China(NSFC)(Nos.61574019,61674020,and 61274044)the 111 Project(No.B07005)+2 种基金the Beijing Municipality Natural Science Foundation(No.4132069)the Program for Changjiang ScholarsInnovative Research Team in University through the Ministry of Education of China(No.IRT0609)
文摘The fabrication and characterization of p-i-n photodiodes integrated with wide spectrum focusing reflectors using nonperiodic strip and concentric-circular subwavelength gratings are presented. The experimental results show that the gratings can reflect and focus the incident light on the absorber of the photodiode, and thus can simultaneously achieve high speed and high efficiency. For the gratings’ integrated photodiodes, the responsivity is improved over a wide spectral range, and when the absorber was 600 nm and the mesa diameter was40 μm, a responsivity of 0.46 A/W at a wavelength of 1.55 μm and a 3 dB bandwidth of 21.6 GHz under a reverse bias of 3 V were simultaneously obtained.
基金This work was supported by the National Natural Science Foundation of China(No.60077030)
文摘In order to obtain large broadband, a novel travelling-wave modulator with nonperiodic domain inversions and ridge structure is proposed. The composite structure is designed to achieve velocity matching between the optical wave and the microwave, to get a 50 characteristic impedance and to reduce the loss of the microwave electrodes with finite element method (FEM). The calculation results show that the frequency response of the new device is flat up to 350 GHz with interaction length of 1 cm, characteristic impedance of 49 , and microwave refractive index of 2.5.
文摘Malaria infection continues to be a major problem in many parts of the world including Africa.Environmental variables are known to significantly affect the population dynamics and abundance of insects,major catalysts of vector-borne diseases,but the exact extent and consequences of this sensitivity are not yet well established.To assess the impact of the variability in temperature and rainfall on the transmission dynamics of malaria in a population,we propose a model consisting of a system of non-autonomous deterministic equations that incorporate the effect of both temperature and rainfall to the dispersion and mortality rate of adult mosquitoes.The model has been validated using epidemiological data collected from the western region of Ethiopia by considering the trends for the cases of malaria and the climate variation in the region.Further,a mathematical analysis is performed to assess the impact of temperature and rainfall change on the transmission dynamics of the model.The periodic variation of seasonal variables as well as the non-periodic variation due to the long-term climate variation have been incorporated and analyzed.In both periodic and non-periodic cases,it has been shown that the disease-free solution of the model is globally asymptotically stable when the basic reproduction ratio is less than unity in the periodic system and when the threshold function is less than unity in the non-periodic system.The disease is uniformly persistent when the basic reproduction ratio is greater than unity in the periodic system and when the threshold function is greater than unity in the non-periodic system.
基金Supported by Science and technology plan foundation of Guangzhou(No.201607010218)by Public Research&Capacity-Building Project of Guangdong(No.2015A070704059).
文摘In this paper, we investigate standing waves in discrete nonlinear Schr?dinger equations with nonperiodic bounded potentials. By using the critical point theory and the spectral theory of self-adjoint operators, we prove the existence and infinitely many sign-changing solutions of the equation. The results on the exponential decay of standing waves are also provided.
