In Tian Qin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic pro...In Tian Qin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic properties. Here we present a single frequency modulation method based on a torsion pendulum to measure the remanent magnetic moment mr of 1.1 kg dummy copper test mass, and the measurement result is(6.45 ± 0.04(stat) ± 0.07(syst)) × 10^(-8)A · m^(2). The measurement precision of the mr is about 0.9 n A · m^(2), well below the present measurement requirement of Tian Qin. The method is particularly useful for measuring extremely low magnetic properties of the materials for use in the construction of space-borne gravitational wave detection and other precision scientific apparatus.展开更多
A simple and fast route for the synthesis of metal-organic framework（MOF） particles was presented.Cu 3（BTC） 2（HKUST-1,BTC=1,3,5-benzenetricarboxylate）,one of the most well-known MOFs,was synthesized at room temp...A simple and fast route for the synthesis of metal-organic framework（MOF） particles was presented.Cu 3（BTC） 2（HKUST-1,BTC=1,3,5-benzenetricarboxylate）,one of the most well-known MOFs,was synthesized at room temperature via coordination modulation method.By adding different modulators（monocarboxylic acids） into the reaction system,the morphologies of HKUST-1 crystals were tuned from nano spheres to micro octahedrons at room temperature without any complex equipment.X-Ray diffractions and gas sorption measurements revealed highly crystalline particles with large Brunauer-Emmett-Teller（BET） surface areas（1116―1273 m^ 2 /g） and total pore volumes（0.62―0.73 cm^ 3 /g）.The significantly small particle sizes and high capacity of gas sorption are considered advantageous for envisaged application in practical industrial process.展开更多
As the family of magnetic materials is rapidly growing,two-dimensional(2D)van der Waals(vdW)magnets have attracted increasing attention as a platform to explore fundamental physical problems of magnetism and their pot...As the family of magnetic materials is rapidly growing,two-dimensional(2D)van der Waals(vdW)magnets have attracted increasing attention as a platform to explore fundamental physical problems of magnetism and their potential applications.This paper reviews the recent progress on emergent vd W magnetic compounds and their potential applications in devices.First,we summarize the current vd W magnetic materials and their synthetic methods.Then,we focus on their structure and the modulation of magnetic properties by analyzing the representative vd W magnetic materials with different magnetic structures.In addition,we pay attention to the heterostructures of vd W magnetic materials,which are expected to produce revolutionary applications of magnetism-related devices.To motivate the researchers in this area,we finally provide the challenges and outlook on 2D vd W magnetism.展开更多
Based on the Longuet-Higgins wave model theory, the previews studies have shown that freak waves can be generated in finite space and time successfully. However, as to generating high nonlinear freak waves, the simula...Based on the Longuet-Higgins wave model theory, the previews studies have shown that freak waves can be generated in finite space and time successfully. However, as to generating high nonlinear freak waves, the simulation results will be unrealistic. Therefore, a modified phase modulation method for simulating high nonlinear freak waves was developed. The surface elevations of some wave components at certain time and place are positive by modulating the corresponding random initial phases, then the total surface elevation at the focused point is enhanced and furthermore a freak wave event is generated. The new method can not only make the freak wave occur at certain time and place, but also make the simulated wave surface time series satisfy statistical properties of the realistic sea state and keep identical with the target wave spectrum. This numerical approach is of good precision and high efficiency by the comparisons of the simulated freak waves and the recorded freak waves.展开更多
In order to charge batteries and supply all the electrical devices like wheel-motors used in a heavy-duty hybrid electric vehicle, a solution consists in using an assembly permanent magnet generator driven by a diesel...In order to charge batteries and supply all the electrical devices like wheel-motors used in a heavy-duty hybrid electric vehicle, a solution consists in using an assembly permanent magnet generator driven by a diesel engine and a three-phase insulated gate bipolar transistor/diodes bridge controlled rectifier connected to the battery. In this work, hysteresis current control strategies combined with a judicious current sensing mode for the assembly permanent magnet synchronous machine-controlled rectifier are investigated. Main issues first concern the different kinds of transistors switching modes allowed by the proposed current sensing mode when the machine operates either as a generator or as a motor. Second, the modulated hysteresis method is presented, which merges the performances of robustness and dynamic of the classical hysteresis method and imposes the switching frequency alike pulsewidth modulation techniques. A test bench at reduced power permits to test the switching modes as well as classical and modulated hysteresis methods for both motor and generator operating modes and to validate the simulation predictions. The digital signal processor algorithm elaborated for the control strategy is flexible and adaptable to all kinds of transistor switchings and machine operating modes.展开更多
We propose a simple iterative algorithm based on a temporally movable phase modulation process to retrieve the weak temporal phase of laser pulses. This unambiguous method can be used to achieve a high accuracy and to...We propose a simple iterative algorithm based on a temporally movable phase modulation process to retrieve the weak temporal phase of laser pulses. This unambiguous method can be used to achieve a high accuracy and to simultaneously measure the weak temporal phase and temporal profile of pulses, which are almost transform- limited. A detailed analysis shows that this iterative method has valuable potential applications in the charac- terization of pulses with weak temporal phase.展开更多
Seismic method is usually used for elastic parametric estimation. This is why this method presents dynamic parameters of Earth. Frequency seismic range changes greatly from geodynamic modelling time. Now we have oppor...Seismic method is usually used for elastic parametric estimation. This is why this method presents dynamic parameters of Earth. Frequency seismic range changes greatly from geodynamic modelling time. Now we have opportunity to use geodesy result for some years for elastic parameters estimation. Static solution from elastic theory may be used for the interpretation of long term results. It presents static elastic parameter. The inverse problem for different types of vertical surface loading on one year period is calculated. Two cases of loading with maximal and minimal area are presented. Results are determined by space geodesy and leveling methods. Current relation between atmospheric pressure and vertical displacements was estimated at the center of Siberian Anti Cyclone with size varied from 2000 km to 3000 kin. Pressure-displacement coefficients （PDC） can be achieved by three years obser- vation （0.997 mm/mbar for NVSK GPS station）. It is used for elastic module study of geology medium with maximum thickness up to 600 km. In the context of elastic model, the modulus of rigidity is estimated to be 113 GPa. Vast expanse of anti-cyclone may relate with rheology of crust and upper mantle. Smaller size of surface loading - local loading is seasonal variation of water reservoir. Annual vertical changes were obtained by leveling near the dam of the reservoir. PDC ratio was 1.15 mm/bar for these places. In elastic theory, the Young modulus E = 80 GPa （Poisson ratio = 0.25, the modulus of rigidity - 32 GPa） was calculated by sixteen years of leveling measurements. This result can effectively be represented for upper crust. Our results were checked by solution for coseismic displacement of Chyia- Altai earthquake （Sep. 27, 2003, M = 7.3）. Coseismic results calculated by static modules agree with experimental coseismic GPS data at 10% level.展开更多
Direct-sequence spread spectrum （DSSS） communication possesses low probability of detection and has been widely used in confidential communications. However, pseudo-noise （PN） sequences, used as spreading code in ...Direct-sequence spread spectrum （DSSS） communication possesses low probability of detection and has been widely used in confidential communications. However, pseudo-noise （PN） sequences, used as spreading code in conventional DSSS communications, possess peri- odic character and binary value. In hostile environments, these distinct characters may lead to some important parameters of signals being estimated accurately, and then lead to the leakage of transmitted information. To solve the problem, we propose the chaotic phase modulation （CPM） sequence alternating the PN sequences. CPM sequence has complex values and constant envelope, and also possesses large quantity and good correlation characteristics. Moreover, it has more hidden features than conventional sequences by modulating its phases using chaotic sequence. To improve the data rate, we apply it into the technique of multichannel communica-tion. Simulation results show this scheme＇s superior bit error ratio （BER） performance, which demonstrates its feasibility in underwater acoustic communications.展开更多
By inserting an air cavity into a one-dimensional photonic crystal of LiF/GaSb, a tunable filter covering the whole visible range is proposed. Following consideration of the dispersion of the materials, through modula...By inserting an air cavity into a one-dimensional photonic crystal of LiF/GaSb, a tunable filter covering the whole visible range is proposed. Following consideration of the dispersion of the materials, through modulating the thickness of the air cavity, we demonstrate that a single resonant peak can shift from 416.1 to 667.3 nm in the band gap at normal incidence by means of the transfer matrix method. The research also shows that the transmittance of the channel can be maximized when the number of periodic Li F/Ga Sb layers on one side of the air defect layer is equal to that of the other side. When adding a period to both sides respectively, the full width at half maximum of the defect mode is reduced by one order of magnitude. This structure will provide a promising approach to fabricate practical tunable filters in the visible region with ultra-wide tuning range.展开更多
The Mach-Zehnder traveling-wave lithium niobate modulator is simulated by time domain finite difference (FDTD) method for different device geometry. The result is comparable to the reported value by finite element met...The Mach-Zehnder traveling-wave lithium niobate modulator is simulated by time domain finite difference (FDTD) method for different device geometry. The result is comparable to the reported value by finite element method.展开更多
A simplified simulation method based on the FDTD technique that can handle active devices is proposed. This method well suits the electrical crosstalk analysis of multi-channel integrated, opto-electronic mixed module...A simplified simulation method based on the FDTD technique that can handle active devices is proposed. This method well suits the electrical crosstalk analysis of multi-channel integrated, opto-electronic mixed modules. We apply this method to an 8-channel integrated super-compact high-sensitivity optical module. The results show good agreement between simulations and measurements.展开更多
The phase modulation characteristics of a reflective liquid crystal （LC） spatial light modulator （SLM） under oblique incidence are studied by using our proposed self-interference method. The experimental setup of ...The phase modulation characteristics of a reflective liquid crystal （LC） spatial light modulator （SLM） under oblique incidence are studied by using our proposed self-interference method. The experimental setup of the method is very simple and has good robustness to mechanical vibrations. By changing the gray value of the combined grayscale loaded on the LC-SLM, different sheared fringe patterns, generated by the interference between the constant phase-modulated beam and the ＋1-order diffracted beam of the blazed grating, can be obtained. The amount of phase modulation of the LC-SLM is obtained by subtracting the phase of the two side lobes in the frequency domain. By turning the turntable where the SLM is mounted, the phase modulation characteristics at different incident angles can be measured. The experimental results show that the phase modulation curves do not change significantly with the small angle. When the angle is large （i.e. larger than 10°）, the phase modulation curves become different, especially for the high gray levels. With the increase of the incident angle, the phase modulation depth is reduced. The results indicate that the incident angle plays an important role in the performance of the phase modulation of an LC-SLM.展开更多
基金supported by the National Key R&D Program of China (Grant No. 2020YFC2200500)the National Natural Science Foundation of China (Grant Nos. 12075325, 12005308, and 11605065)。
文摘In Tian Qin spaceborne gravitational-wave detectors, the stringent requirements on the magnetic cleanliness of the test masses demand the high resolution ground-based characterization measurement of their magnetic properties. Here we present a single frequency modulation method based on a torsion pendulum to measure the remanent magnetic moment mr of 1.1 kg dummy copper test mass, and the measurement result is(6.45 ± 0.04(stat) ± 0.07(syst)) × 10^(-8)A · m^(2). The measurement precision of the mr is about 0.9 n A · m^(2), well below the present measurement requirement of Tian Qin. The method is particularly useful for measuring extremely low magnetic properties of the materials for use in the construction of space-borne gravitational wave detection and other precision scientific apparatus.
基金Supported by the National Natural Science Foundation of China(Nos.21173034,20907006)
文摘A simple and fast route for the synthesis of metal-organic framework（MOF） particles was presented.Cu 3（BTC） 2（HKUST-1,BTC=1,3,5-benzenetricarboxylate）,one of the most well-known MOFs,was synthesized at room temperature via coordination modulation method.By adding different modulators（monocarboxylic acids） into the reaction system,the morphologies of HKUST-1 crystals were tuned from nano spheres to micro octahedrons at room temperature without any complex equipment.X-Ray diffractions and gas sorption measurements revealed highly crystalline particles with large Brunauer-Emmett-Teller（BET） surface areas（1116―1273 m^ 2 /g） and total pore volumes（0.62―0.73 cm^ 3 /g）.The significantly small particle sizes and high capacity of gas sorption are considered advantageous for envisaged application in practical industrial process.
基金funding support of the National Natural Science Foundation of China(Grant Nos.11975035,51731001,11805006,and 11675006)the National Key Research and Development Program of China(Grant Nos.2017YFA0206303 and 2017YFA0403701)。
文摘As the family of magnetic materials is rapidly growing,two-dimensional(2D)van der Waals(vdW)magnets have attracted increasing attention as a platform to explore fundamental physical problems of magnetism and their potential applications.This paper reviews the recent progress on emergent vd W magnetic compounds and their potential applications in devices.First,we summarize the current vd W magnetic materials and their synthetic methods.Then,we focus on their structure and the modulation of magnetic properties by analyzing the representative vd W magnetic materials with different magnetic structures.In addition,we pay attention to the heterostructures of vd W magnetic materials,which are expected to produce revolutionary applications of magnetism-related devices.To motivate the researchers in this area,we finally provide the challenges and outlook on 2D vd W magnetism.
基金The Key Technology Program,the Ministry of Education of China under contract No.104061
文摘Based on the Longuet-Higgins wave model theory, the previews studies have shown that freak waves can be generated in finite space and time successfully. However, as to generating high nonlinear freak waves, the simulation results will be unrealistic. Therefore, a modified phase modulation method for simulating high nonlinear freak waves was developed. The surface elevations of some wave components at certain time and place are positive by modulating the corresponding random initial phases, then the total surface elevation at the focused point is enhanced and furthermore a freak wave event is generated. The new method can not only make the freak wave occur at certain time and place, but also make the simulated wave surface time series satisfy statistical properties of the realistic sea state and keep identical with the target wave spectrum. This numerical approach is of good precision and high efficiency by the comparisons of the simulated freak waves and the recorded freak waves.
文摘In order to charge batteries and supply all the electrical devices like wheel-motors used in a heavy-duty hybrid electric vehicle, a solution consists in using an assembly permanent magnet generator driven by a diesel engine and a three-phase insulated gate bipolar transistor/diodes bridge controlled rectifier connected to the battery. In this work, hysteresis current control strategies combined with a judicious current sensing mode for the assembly permanent magnet synchronous machine-controlled rectifier are investigated. Main issues first concern the different kinds of transistors switching modes allowed by the proposed current sensing mode when the machine operates either as a generator or as a motor. Second, the modulated hysteresis method is presented, which merges the performances of robustness and dynamic of the classical hysteresis method and imposes the switching frequency alike pulsewidth modulation techniques. A test bench at reduced power permits to test the switching modes as well as classical and modulated hysteresis methods for both motor and generator operating modes and to validate the simulation predictions. The digital signal processor algorithm elaborated for the control strategy is flexible and adaptable to all kinds of transistor switchings and machine operating modes.
基金Supported by the National Natural Science Foundation of China under Grant No 61205103
文摘We propose a simple iterative algorithm based on a temporally movable phase modulation process to retrieve the weak temporal phase of laser pulses. This unambiguous method can be used to achieve a high accuracy and to simultaneously measure the weak temporal phase and temporal profile of pulses, which are almost transform- limited. A detailed analysis shows that this iterative method has valuable potential applications in the charac- terization of pulses with weak temporal phase.
文摘Seismic method is usually used for elastic parametric estimation. This is why this method presents dynamic parameters of Earth. Frequency seismic range changes greatly from geodynamic modelling time. Now we have opportunity to use geodesy result for some years for elastic parameters estimation. Static solution from elastic theory may be used for the interpretation of long term results. It presents static elastic parameter. The inverse problem for different types of vertical surface loading on one year period is calculated. Two cases of loading with maximal and minimal area are presented. Results are determined by space geodesy and leveling methods. Current relation between atmospheric pressure and vertical displacements was estimated at the center of Siberian Anti Cyclone with size varied from 2000 km to 3000 kin. Pressure-displacement coefficients （PDC） can be achieved by three years obser- vation （0.997 mm/mbar for NVSK GPS station）. It is used for elastic module study of geology medium with maximum thickness up to 600 km. In the context of elastic model, the modulus of rigidity is estimated to be 113 GPa. Vast expanse of anti-cyclone may relate with rheology of crust and upper mantle. Smaller size of surface loading - local loading is seasonal variation of water reservoir. Annual vertical changes were obtained by leveling near the dam of the reservoir. PDC ratio was 1.15 mm/bar for these places. In elastic theory, the Young modulus E = 80 GPa （Poisson ratio = 0.25, the modulus of rigidity - 32 GPa） was calculated by sixteen years of leveling measurements. This result can effectively be represented for upper crust. Our results were checked by solution for coseismic displacement of Chyia- Altai earthquake （Sep. 27, 2003, M = 7.3）. Coseismic results calculated by static modules agree with experimental coseismic GPS data at 10% level.
文摘Direct-sequence spread spectrum （DSSS） communication possesses low probability of detection and has been widely used in confidential communications. However, pseudo-noise （PN） sequences, used as spreading code in conventional DSSS communications, possess peri- odic character and binary value. In hostile environments, these distinct characters may lead to some important parameters of signals being estimated accurately, and then lead to the leakage of transmitted information. To solve the problem, we propose the chaotic phase modulation （CPM） sequence alternating the PN sequences. CPM sequence has complex values and constant envelope, and also possesses large quantity and good correlation characteristics. Moreover, it has more hidden features than conventional sequences by modulating its phases using chaotic sequence. To improve the data rate, we apply it into the technique of multichannel communica-tion. Simulation results show this scheme＇s superior bit error ratio （BER） performance, which demonstrates its feasibility in underwater acoustic communications.
基金Project supported by the National Natural Science Foundation of China(Nos.61575138,61307069,51205273)the Top Young Academic Leaders and the Outstanding Innovative Teams of Higher Learning Institutions of Shanxi
文摘By inserting an air cavity into a one-dimensional photonic crystal of LiF/GaSb, a tunable filter covering the whole visible range is proposed. Following consideration of the dispersion of the materials, through modulating the thickness of the air cavity, we demonstrate that a single resonant peak can shift from 416.1 to 667.3 nm in the band gap at normal incidence by means of the transfer matrix method. The research also shows that the transmittance of the channel can be maximized when the number of periodic Li F/Ga Sb layers on one side of the air defect layer is equal to that of the other side. When adding a period to both sides respectively, the full width at half maximum of the defect mode is reduced by one order of magnitude. This structure will provide a promising approach to fabricate practical tunable filters in the visible region with ultra-wide tuning range.
文摘The Mach-Zehnder traveling-wave lithium niobate modulator is simulated by time domain finite difference (FDTD) method for different device geometry. The result is comparable to the reported value by finite element method.
文摘A simplified simulation method based on the FDTD technique that can handle active devices is proposed. This method well suits the electrical crosstalk analysis of multi-channel integrated, opto-electronic mixed modules. We apply this method to an 8-channel integrated super-compact high-sensitivity optical module. The results show good agreement between simulations and measurements.
基金financially supported by the National Natural Science Foundation of China(No.51705404)the China Postdoctoral Science Foundation(No.2016M602806)the Fundamental Research Funds for the Central Universities(No.xjj2017093)
文摘The phase modulation characteristics of a reflective liquid crystal （LC） spatial light modulator （SLM） under oblique incidence are studied by using our proposed self-interference method. The experimental setup of the method is very simple and has good robustness to mechanical vibrations. By changing the gray value of the combined grayscale loaded on the LC-SLM, different sheared fringe patterns, generated by the interference between the constant phase-modulated beam and the ＋1-order diffracted beam of the blazed grating, can be obtained. The amount of phase modulation of the LC-SLM is obtained by subtracting the phase of the two side lobes in the frequency domain. By turning the turntable where the SLM is mounted, the phase modulation characteristics at different incident angles can be measured. The experimental results show that the phase modulation curves do not change significantly with the small angle. When the angle is large （i.e. larger than 10°）, the phase modulation curves become different, especially for the high gray levels. With the increase of the incident angle, the phase modulation depth is reduced. The results indicate that the incident angle plays an important role in the performance of the phase modulation of an LC-SLM.
