Rare earth-containing magneto-strictive material has caught theworld attention in recent yearsbecause of its amazing performan-ces:high magnetostrictive ratio,rapid response to mechanical be-havior,high rate of energy...Rare earth-containing magneto-strictive material has caught theworld attention in recent yearsbecause of its amazing performan-ces:high magnetostrictive ratio,rapid response to mechanical be-havior,high rate of energy tran-sformation,etc.,which are vitalto sonar transducers,performersand brakes which,in turn,play展开更多
We present a theoretical approach to achieve sub-Doppler cooling of magnesium fluoride(Mg F) molecules by tuning the AC Stark shift with a blue-detuned laser. We study three blue-detuned magneto–optical trapping(MOT)...We present a theoretical approach to achieve sub-Doppler cooling of magnesium fluoride(Mg F) molecules by tuning the AC Stark shift with a blue-detuned laser. We study three blue-detuned magneto–optical trapping(MOT) schemes by using the Bayesian optimization method with the optical Bloch equations. We perform a comprehensive analysis of the relationship between the force in the MOT and the velocities and positions of the Mg F molecules. Monte–Carlo simulations show that our MOT schemes can achieve a temperature as low as 28 μK and a density as high as 4.0 × 10^(8)cm^(-3) at the conditions of a ratio of two laser intensities of 2:7, a detuning of 3Γ and a polarization configuration of σ^(-)-σ^(+). These results provide a clear way for transferring a large number of Mg F molecules into a conservative trap to enhance the subsequent cooling such as evaporative or sympathetic cooling.展开更多
This study investigates the flow and heat transfer of dusty Williamson (MHD) Nanofluid flow over a stretching permeable cylinder in a porous medium. Dusty Williamson Nanofluid was considered due to its thermal propert...This study investigates the flow and heat transfer of dusty Williamson (MHD) Nanofluid flow over a stretching permeable cylinder in a porous medium. Dusty Williamson Nanofluid was considered due to its thermal properties and potential benefits of increasing the heat transfer rate. Firstly, partial differential equations are transformed into coupled non-linear ordinary differential equations through a similarity variables transformation. The resulting set of dimensionless equations is solved analytically by using the Homogony Perturbation Method (HPM). The effects of the emerging parameters on the velocity and temperature profiles as well as skin-friction coefficient and Nusselt number are publicized through tables and graphs with appropriate discussions. The present result has been compared with published papers and found to be in agreement. To the best of author’s knowledge, there has been sparse research work in the literature that considers the effect of dust with Williamson Nanofluid and also solving the problem analytically. Therefore to the best of author’s knowledge, this is the first time analytical solution has been established for the problem. The results revealed that the fluid velocity of both the fluid and dust phases decreases as the Williamson parameter increases. Motivated by the above limitations and the gaps in past works, therefore, it is hoped that the present work will assist in providing accurate solutions to many practical problems in science, industry and engineering.展开更多
Magneto optic(MO) fiber current sensors utility the Faraday effect of magneto op tic materials to sensing the magnetic(current)fields.The optical fiber sensors(O FS)offer great advantages of simple structure,high reli...Magneto optic(MO) fiber current sensors utility the Faraday effect of magneto op tic materials to sensing the magnetic(current)fields.The optical fiber sensors(O FS)offer great advantages of simple structure,high reliability,high accuracy and sensibility,immunity to electromagnetic interference.They are the most promised method to substitute the conventional current transducers(CTs),much attentions were focused on both domestic and abroad.Magneto optic properties of Faraday se n sing element have much affect on the performance of the optical fiber current se nsor.For used in the sensor system,MO materials with magneto optic characterist i cs of large Faraday rotation(FR)angle θ f ,low temperature sensibility,and suitable saturation field were general demanded. Development of MO materials is one of the most important problems of optical fiber current sensor research. In this paper,one mixed doped Bi substituted yttrium iron garnet crystal BiYb:Y I G, which has large and temperature stable FR angle,was grown from high temperatu re flux.By taking PbO+PbF 2 as the main flux,under the compositions of molar ra tio Y 2O 3:Yb 2O 3:Bi 2O 3:Fe 2O 3:(PbO+PbF 2+B 2O 3+CaCO 3)=7.64:1. 04:1.74:20.78:78:68.8,crystals of quite good quality were grown from melt flux,t he largest one has the size of 22mm×15mm×12mm.Magneto optic proprieties of Fa raday rotation angle and optical absorption spectrum of the BiYb:YIG crystal,expecial ly Y 2.289 Yb 0.246 Bi 0.465 Fe 5O 12 ,in the range of 0.7 1.9 μm waveband were measured.At λ =1.55μm,the BiYb:YIG crystal has special Fa raday rotation angle of -404deg/cm,temperature coefficient 4.2×10 -6 K -1 ,optical absorption coefficient 3.6cm -1 ,and figure of merit 25.8deg/dB . The results indicate that substituted with Bi 3+ can largely improve the Fa raday rotation of rear earth iron garnets.Because Faraday rotation angles of Yb 3Fe 5O 12 and Y 3Fe 5O 12 have opposite temperature dependency,ut ility the compensation effect of mix doped,co doped with some other ions,such a s Yb 3+ ,would decrease the temperature dependency of Bi substituted garnet. So the garnet crystal BiYb:YIG has high and temperature stable Faraday rotation an gle,very suitable to be used as Faraday effect materials for high sensibility an d temperature stable Optical fiber current sensors.Using BiYb:YIG as Faraday rot ation cell,a hybrid bulk crystal optical fiber current sensor was proposed and t ests under direct current(DC) and 50Hz alternating current(AC).The performance c haracteristics of the sensors system were:DC measurement,sensibility 0.01A, l inea rity 1.1%;AC measurement,sensibility 9.5A/mV ,accuracy ±1%,linearity 1.1%,dynam ic range 40dB.In conclusion,Faraday effect magneto optic optical fiber current sensors have higher sensibility and accuracy than conventional CTs.展开更多
According to the perturbation theory, the coupled-mode equations for guided optical waves in the magneto-optical fiber Bragg gratings （MFBGs） under non-uniform magnetic field are derived. The equivalent relation bet...According to the perturbation theory, the coupled-mode equations for guided optical waves in the magneto-optical fiber Bragg gratings （MFBGs） under non-uniform magnetic field are derived. The equivalent relation between the magnetically- induced non-uniform fiber Bragg grating （MuFBG） and the corresponding non-magnetic chirped grating is expressed and verified by the piecewise-uniform MFBG model under linear magnetic field. On the basis of the equivalent relation, the MnFBGs can be effectively investigated by means of simulations. The characteristics of the MnFBGs under three typical magnetic field distributions with application to optical pulse compression are simulated, and the minimal pulse width can be achieved for the same magneto-optical coupling parameter of 2.2 ×10^3 m^-1.展开更多
Achieving a uniform structure with few defects in heavy steel ingot is of high commercial importance. In this present work, in order to verify the potential of pulsed magneto-oscillation(PMO) applied in the production...Achieving a uniform structure with few defects in heavy steel ingot is of high commercial importance. In this present work, in order to verify the potential of pulsed magneto-oscillation(PMO) applied in the production of heavy ingot, an induction coil was located at the hot top of the steel ingot to develop a novel technique, named hot top pulsed magneto oscillation(HPMO). The influences of HPMO on the solidification structure, macro segregation and compactness of a cylindrical medium carbon steel ingot with the weight of 160 kg were systematically investigated by optical microscope(OM) and laser induced breakdown spectroscopy original position metal analyzer(LIBSOPA-100). The results show that HPMO not only causes significant grain refinement and promotes the occurrence of columnar to equiaxed transition(CET) but also can homogenize the carbon distribution and enhance the compactness of the steel ingot. Therefore, HPMO technique has the potential to be applied in the production of heavy steel ingots on an industrial scale.展开更多
We have trapped a cold sample of cesium atoms in a magneto-optical trap.The damped harmonic force of magneto-optical trap was used to capture and trap the cesium atoms directly from a room temperature vapor.About 1.5&...We have trapped a cold sample of cesium atoms in a magneto-optical trap.The damped harmonic force of magneto-optical trap was used to capture and trap the cesium atoms directly from a room temperature vapor.About 1.5×10^(7) cesium atoms with a density of 3×10^(9) atoms/cm^(3) formed a 4mm^(3) cesium atomic cloud with temperature below 500μK.展开更多
The pulsed inductive thruster is characterized of no electrode corruption and wide propellant choice.To give insight into the propulsion mechanism of small scale thruster at different propellant mass(m)and energy(E)le...The pulsed inductive thruster is characterized of no electrode corruption and wide propellant choice.To give insight into the propulsion mechanism of small scale thruster at different propellant mass(m)and energy(E)levels,the transient Magneto Hydro Dynamics(MHD)method,completed by high temperature thermodynamic and transport,and plasma electrical models,is developed to study argon plasma response under the excitation of current of high rise rate.By calculating the two-dimensional expansion properties of the thruster with conical pylon,the simulations find that the main energy deposition occurs during the initial pulse rise stage,and the energy density of Joule heat is two magnitudes higher than the deposition in the down side.At propellant mass of 2 mg,average axial velocity of the current sheet increases from about 15 km/s at 750 J to about 21 km/s at 1470 J within the decoupling distance.The velocity variation synchronizes with the pulsed rise in the initial.The monotonically decrease of the temperature along axis results in the growth of low ionization level ions and reducing of high levels.The current sheet maintains the structure formed during the initial pulse rise when moving beyond the decoupling distance.Besides the change in forward velocity,the main difference is the dimension compared with that in the first half period,caused by thermal conduction and particle diffusion.The variations of total impulse It in the range of m from 2 mg to8 mg and E from 750 J to 1470 J show that It is proportional to m1/2 when E is determined.展开更多
In order to explore the dependence of plasticity of metallic material on a high magnetic held,the effects of the different magnetic induction intensities（H = 0 T,0.5 T,1 T,3 T,and 5 T） and pulses number（N = 0,10,20...In order to explore the dependence of plasticity of metallic material on a high magnetic held,the effects of the different magnetic induction intensities（H = 0 T,0.5 T,1 T,3 T,and 5 T） and pulses number（N = 0,10,20,30,40,and 50） on tensile strength（σ;） and elongation（δ） of 2024 aluminum alloy are investigated in the synchronous presences of a high magnetic held and external stress.The results show that the magnetic held exerts apparent and positive effects on the tensile properties of the alloy.Especially under the optimized condition of H;=1 T and N;=30,the σ;and 8 are 410 MPa and 17% that are enhanced by 9.3% and 30.8% respectively in comparison to those of the untreated sample.The synchronous increases of tensile properties are attributed to the magneto-plasticity effect on a quantum scale.That is,the magnetic held will accelerate the state conversion of radical pair generated between the dislocation and obstacles from singlet to the triplet state.The bonding energy between them is meanwhile lowered and the moving flexibility of dislocations will be enhanced.At H;= 1 T and N;= 30,the dislocation density is enhanced by 1.28 times.The relevant minimum grain size is 266.1 nm,which is reduced by 35.2%.The grain rehning is attributed to the dislocation accumulation and subsequent dynamic recrystallization.The（211） and（220） peak intensities are weakened.It is deduced that together with the recrystallization,the hne grains will transfer towards the slip plane and contribute to the slipping deformation.展开更多
A neuron proportion integration (PI) control strategy for semi-active suspension system of tracked vehicle was proposed based on its unique structure and the multiple and complex environment of the driving traffic. An...A neuron proportion integration (PI) control strategy for semi-active suspension system of tracked vehicle was proposed based on its unique structure and the multiple and complex environment of the driving traffic. An adaptive genetic algorithm is used to optimize the parameters of the neuron PI controller. The simulation result of the neuron PI control for semi-active suspension system of tracked vehicle indicates that the vertical amplitude,pitch angle and vertical acceleration of the vehicle are well controlled. The root mean square (RMS) of the vertical amplitude decreases by 37.2%,and 45.2% for the pitch angle,38.6% for the vertical acceleration. The research of neuron PI control experiment for the semi-active suspension system of the tracked vehicle model mining in benthal indicates that the RMS of the weight acceleration vibrating along the vertical direction decreases by 29.5%,the power spectral density resonance peak of the acceleration of the car body decreases by 23.8%.展开更多
The principle and 1:3 internal resonance of a rectangular thin plate in a transverse magnetic field is investigated.Based on the magneto-elastic vibration equation and electromagnetic force expressions of the thin pla...The principle and 1:3 internal resonance of a rectangular thin plate in a transverse magnetic field is investigated.Based on the magneto-elastic vibration equation and electromagnetic force expressions of the thin plates,the nonlinear magneto-elastic vibration differential equations of rectangular plates under external excitation in a transverse magnetic field are derived.For a rectangular plate with one side fixed and three other sides simply supported,the two-degree-offreedom nonlinear Duffing vibration differen-tial equations are proposed by the method of Galerkin.The method of multiple scales is adopted to solve the model equations and obtain four first-order ordinary differential equations governing modulation of the amplitudes and phase angles involved via the first-order or the second-order primary-internal reso-nances.With a numerical example,the amplitude frequency response curves,time history responses,phase portraits and Poincare maps of the first two order vibration modes via principle-internal resonance are respectively captured.And the effects of external excitation amplitudes,magnetic field intensities and thicknesses on the vibration of system are discussed.The results show that the response is dominated by the low mode when principle-internal resonance occurs.The internal resonance provides a mechanism for transferring energy from a high mode to a low mode.展开更多
We experimentally demonstrate a reliable method based on a nanofiber to optimize the number of cold atoms in a magneto–optical trap(MOT) and to monitor the MOT in real time.The atomic fluorescence is collected by a n...We experimentally demonstrate a reliable method based on a nanofiber to optimize the number of cold atoms in a magneto–optical trap(MOT) and to monitor the MOT in real time.The atomic fluorescence is collected by a nanofiber with subwavelength diameter of about 400 nm.The MOT parameters are experimentally adjusted in order to match the maximum number of cold atoms provided by the fluorescence collected by the nanofiber.The maximum number of cold atoms is obtained when the intensities of the cooling and re-pumping beams are about 23.5 mW/cm^2 and 7.1 mW/cm^2,respectively;the detuning of the cooling beam is-13.0 MHz, and the axial magnetic gradient is about 9.7 Gauss/cm.We observe a maximum photon counting rate of nearly(4.5 ± 0.1)× 10^5 counts/s.The nanofiber–atom system can provide a powerful and flexible tool for sensitive atom detection and for monitoring atom–matter coupling.It can be widely used from quantum optics to quantum precision measurement.展开更多
The quasi-metallic fibers were selected from 1 to 40 pieces and connected in parallel in this study.The giant magneto impedance(GMI)effect of Co-based melt extract fibers in the bundle mode was investigated,and the di...The quasi-metallic fibers were selected from 1 to 40 pieces and connected in parallel in this study.The giant magneto impedance(GMI)effect of Co-based melt extract fibers in the bundle mode was investigated,and the distribution of the surface circumferential magnetic field on the fibers was also analyzed.Such distribution was induced by the driving current,which gave rise to the circular magnetization process and the GMI effect.The improved GMI effect with much higher field sensitivity was observed in these fiber bundles.Results show that the field sensitivities of the four-fiber and six-fiber bundles reach 19.5 V·m·kA−1(at 1 MHz)and 30.8 V·m·kA−1(at 5 MHz).The circumferential magnetic field distributed throughout the fiber’s circumferential surface is rearranged and becomes uneven due to the magnetic interaction among fibers.There are both strengthened and weakened magnetic field parts around these fibers’surfaces.The strengthened magnetic field improves the circumferential domain magnetization of the surface,resulting in larger GMI effects.However,the weakened parts inhibit the circumferential magnetization process and,therefore,the GMI effect.This also induces greater magnetization damp because of the increased domain interactions under the strong skin effect.The co-effect between the magnetic domains and the circumferential magnetization induces the optimization of the GMI effect in the four-fiber bundles.The observed GMI effect proves that fibers in bundle form can modify the sensitivity of the GMI effect.Moreover,different fiber bundles could be tuned according to the working conditions in order to manipulate the GMI response.展开更多
The Lie group method is applied to present an analysis of the magneto hydro-dynamics（MHD） steady laminar flow and the heat transfer from a warm laminar liquid flow to a melting moving surface in the presence of ther...The Lie group method is applied to present an analysis of the magneto hydro-dynamics（MHD） steady laminar flow and the heat transfer from a warm laminar liquid flow to a melting moving surface in the presence of thermal radiation.By using the Lie group method,we have presented the transformation groups for the problem apart from the scaling group.The application of this method reduces the partial differential equations（PDEs） with their boundary conditions governing the flow and heat transfer to a system of nonlinear ordinary differential equations（ODEs） with appropriate boundary conditions.The resulting nonlinear system of ODEs is solved numerically using the implicit finite difference method（FDM）.The local skin-friction coefficients and the local Nusselt numbers for different physical parameters are presented in a table.展开更多
Modeling and analysis of thin film flow with respect to magneto hydro dynamical effect has been an important theme in the field of fluid dynamics,due to its vast industrial applications.The analysis involves studying ...Modeling and analysis of thin film flow with respect to magneto hydro dynamical effect has been an important theme in the field of fluid dynamics,due to its vast industrial applications.The analysis involves studying the behavior and response of governing equations on the basis of various parameters such as thickness of the film,film surface profile,shear stress,liquid velocity,volumetric flux,vorticity,gravity,viscosity among others,along with different boundary conditions.In this article,we extend this analysis in fractional space using a homotopy based scheme,considering the case of a Non-Newtonian Pseudo-Plastic fluid for lifting and drainage on a vertical wall.After applying similarity transformations,the given problems are reduced to highly non-linear and inhomogeneous ordinary differential equations.Moreover,fractional differential equations are obtained using basic definitions of fractional calculus.The Homotopy Perturbation Method(HPM),along with fractional calculus is used for obtaining approximate solutions.Physical quantities such as the velocity profile,volume flux and average velocity respectively for lift and drainage cases have been calculated.To the best of our knowledge,the given problems have not been attempted before in fractional space.Validity and convergence of the obtained solutions are confirmed by finding residual errors.From a physical perspective,a comprehensive study of the effects of various parameters on the velocity profile is also performed.Study reveals that Stokes number St,non-Newtonian parameterand magnetic parameter M have inverse relationship with fluid velocity in lifting case.In the drainage case,Stokes number St and non-Newtonian parameterhave direct relationship with fluid velocity,but magnetic parameter M shows inverse relationship with velocity.The investigation also shows that the fractional parameterhas direct relationship with the fluid velocity in lifting case,while it has inverse relationship with velocity in the drainage case.展开更多
In this paper,a new auxiliary teeth structure is proposed for fault-tolerant permanent magnet(PM)generators,which can reduce the short-circuit currents.Firstly,the short-circuit current and the phase to phase isolatio...In this paper,a new auxiliary teeth structure is proposed for fault-tolerant permanent magnet(PM)generators,which can reduce the short-circuit currents.Firstly,the short-circuit current and the phase to phase isolation of the fault-tolerant generator are analyzed briefly.Secondly,the auxiliary teeth structure is optimized to improve fault-tolerant capability.Then,the PM generators with different stator structures are compared to evaluate the proposed auxiliary teeth structure.Four critical generator parameters are investigated,i.e.back-electromotive forces,short-circuit currents,stator magneto motive force(MMF)harmonics,and torque performances.The results show that the proposed structure has better fault-tolerant capability than the conventional two-layer windings.Moreover,the stator MMF harmonics can be suppressed.Furthermore,the cogging torque and torque ripple can be suppressed by adopting the proposed structure.Finally,the simulated results are given to validate the theoretical analysis.展开更多
The propagation of elastic waves in magnetoelectroelastic grid structures is studied.Band gap properties are presented and the effects of the magnetoelectroelastic coupling and initial stress are considered.Numerical ...The propagation of elastic waves in magnetoelectroelastic grid structures is studied.Band gap properties are presented and the effects of the magnetoelectroelastic coupling and initial stress are considered.Numerical calculations are performed using the plane-wave expansion method.The results show that the band gap width can be tuned by the initial stress.It is hoped that our results will be helpful for designing acoustic filters with magnetoelectroelastic materials and grid structures.展开更多
The present work focused on the application of innovative damping technologies in order to improve railway vehicle performances in terms of dynamic stability and comfort. As a benchmark case-study, the secondary sus- ...The present work focused on the application of innovative damping technologies in order to improve railway vehicle performances in terms of dynamic stability and comfort. As a benchmark case-study, the secondary sus- pension stage was selected and different control techniques were investigated, such as skyhook, dynamic compensation, and sliding mode control. The final aim was to investigate which control schemes are suitable for optimal exploitation of the non-linear behavior of the actuators. The performance improvement achieved by adoption of the semi-active dampers on a standard high-speed train was evaluated in terms of passenger comfort. Different control strategies have been investigated by comparing a simple SISO （single input single output） regulator based on the skyhook damper ap- proach with a centralized regulator. The centralized regulator allows for the estimation of a near optimal set of control forces that minimize car-body accelerations with respect to constraints imposed by limited performance of semi-active actuators. Simulation results show that best results is obtained using a mixed approach that considers the simultaneous applications of model based and feedback compensation control terms.展开更多
文摘Rare earth-containing magneto-strictive material has caught theworld attention in recent yearsbecause of its amazing performan-ces:high magnetostrictive ratio,rapid response to mechanical be-havior,high rate of energy tran-sformation,etc.,which are vitalto sonar transducers,performersand brakes which,in turn,play
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12174115 and 91836103)。
文摘We present a theoretical approach to achieve sub-Doppler cooling of magnesium fluoride(Mg F) molecules by tuning the AC Stark shift with a blue-detuned laser. We study three blue-detuned magneto–optical trapping(MOT) schemes by using the Bayesian optimization method with the optical Bloch equations. We perform a comprehensive analysis of the relationship between the force in the MOT and the velocities and positions of the Mg F molecules. Monte–Carlo simulations show that our MOT schemes can achieve a temperature as low as 28 μK and a density as high as 4.0 × 10^(8)cm^(-3) at the conditions of a ratio of two laser intensities of 2:7, a detuning of 3Γ and a polarization configuration of σ^(-)-σ^(+). These results provide a clear way for transferring a large number of Mg F molecules into a conservative trap to enhance the subsequent cooling such as evaporative or sympathetic cooling.
文摘This study investigates the flow and heat transfer of dusty Williamson (MHD) Nanofluid flow over a stretching permeable cylinder in a porous medium. Dusty Williamson Nanofluid was considered due to its thermal properties and potential benefits of increasing the heat transfer rate. Firstly, partial differential equations are transformed into coupled non-linear ordinary differential equations through a similarity variables transformation. The resulting set of dimensionless equations is solved analytically by using the Homogony Perturbation Method (HPM). The effects of the emerging parameters on the velocity and temperature profiles as well as skin-friction coefficient and Nusselt number are publicized through tables and graphs with appropriate discussions. The present result has been compared with published papers and found to be in agreement. To the best of author’s knowledge, there has been sparse research work in the literature that considers the effect of dust with Williamson Nanofluid and also solving the problem analytically. Therefore to the best of author’s knowledge, this is the first time analytical solution has been established for the problem. The results revealed that the fluid velocity of both the fluid and dust phases decreases as the Williamson parameter increases. Motivated by the above limitations and the gaps in past works, therefore, it is hoped that the present work will assist in providing accurate solutions to many practical problems in science, industry and engineering.
文摘Magneto optic(MO) fiber current sensors utility the Faraday effect of magneto op tic materials to sensing the magnetic(current)fields.The optical fiber sensors(O FS)offer great advantages of simple structure,high reliability,high accuracy and sensibility,immunity to electromagnetic interference.They are the most promised method to substitute the conventional current transducers(CTs),much attentions were focused on both domestic and abroad.Magneto optic properties of Faraday se n sing element have much affect on the performance of the optical fiber current se nsor.For used in the sensor system,MO materials with magneto optic characterist i cs of large Faraday rotation(FR)angle θ f ,low temperature sensibility,and suitable saturation field were general demanded. Development of MO materials is one of the most important problems of optical fiber current sensor research. In this paper,one mixed doped Bi substituted yttrium iron garnet crystal BiYb:Y I G, which has large and temperature stable FR angle,was grown from high temperatu re flux.By taking PbO+PbF 2 as the main flux,under the compositions of molar ra tio Y 2O 3:Yb 2O 3:Bi 2O 3:Fe 2O 3:(PbO+PbF 2+B 2O 3+CaCO 3)=7.64:1. 04:1.74:20.78:78:68.8,crystals of quite good quality were grown from melt flux,t he largest one has the size of 22mm×15mm×12mm.Magneto optic proprieties of Fa raday rotation angle and optical absorption spectrum of the BiYb:YIG crystal,expecial ly Y 2.289 Yb 0.246 Bi 0.465 Fe 5O 12 ,in the range of 0.7 1.9 μm waveband were measured.At λ =1.55μm,the BiYb:YIG crystal has special Fa raday rotation angle of -404deg/cm,temperature coefficient 4.2×10 -6 K -1 ,optical absorption coefficient 3.6cm -1 ,and figure of merit 25.8deg/dB . The results indicate that substituted with Bi 3+ can largely improve the Fa raday rotation of rear earth iron garnets.Because Faraday rotation angles of Yb 3Fe 5O 12 and Y 3Fe 5O 12 have opposite temperature dependency,ut ility the compensation effect of mix doped,co doped with some other ions,such a s Yb 3+ ,would decrease the temperature dependency of Bi substituted garnet. So the garnet crystal BiYb:YIG has high and temperature stable Faraday rotation an gle,very suitable to be used as Faraday effect materials for high sensibility an d temperature stable Optical fiber current sensors.Using BiYb:YIG as Faraday rot ation cell,a hybrid bulk crystal optical fiber current sensor was proposed and t ests under direct current(DC) and 50Hz alternating current(AC).The performance c haracteristics of the sensors system were:DC measurement,sensibility 0.01A, l inea rity 1.1%;AC measurement,sensibility 9.5A/mV ,accuracy ±1%,linearity 1.1%,dynam ic range 40dB.In conclusion,Faraday effect magneto optic optical fiber current sensors have higher sensibility and accuracy than conventional CTs.
基金supported by the National High Technology Research and Development Program of China (No.2009AA01Z216)the National Basic Research Program of China (No.2011CB301703)the Program for New Century Excellent Talents in University (No.NCET-2008)
文摘According to the perturbation theory, the coupled-mode equations for guided optical waves in the magneto-optical fiber Bragg gratings （MFBGs） under non-uniform magnetic field are derived. The equivalent relation between the magnetically- induced non-uniform fiber Bragg grating （MuFBG） and the corresponding non-magnetic chirped grating is expressed and verified by the piecewise-uniform MFBG model under linear magnetic field. On the basis of the equivalent relation, the MnFBGs can be effectively investigated by means of simulations. The characteristics of the MnFBGs under three typical magnetic field distributions with application to optical pulse compression are simulated, and the minimal pulse width can be achieved for the same magneto-optical coupling parameter of 2.2 ×10^3 m^-1.
基金financially supported by the National Natural Science Foundation of China(Granted No.U1760204,51504048)the National Key Research Program of China(Granted No.2017YFB0701800)
文摘Achieving a uniform structure with few defects in heavy steel ingot is of high commercial importance. In this present work, in order to verify the potential of pulsed magneto-oscillation(PMO) applied in the production of heavy ingot, an induction coil was located at the hot top of the steel ingot to develop a novel technique, named hot top pulsed magneto oscillation(HPMO). The influences of HPMO on the solidification structure, macro segregation and compactness of a cylindrical medium carbon steel ingot with the weight of 160 kg were systematically investigated by optical microscope(OM) and laser induced breakdown spectroscopy original position metal analyzer(LIBSOPA-100). The results show that HPMO not only causes significant grain refinement and promotes the occurrence of columnar to equiaxed transition(CET) but also can homogenize the carbon distribution and enhance the compactness of the steel ingot. Therefore, HPMO technique has the potential to be applied in the production of heavy steel ingots on an industrial scale.
基金Supported by the National Natural Science Foundation of China.
文摘We have trapped a cold sample of cesium atoms in a magneto-optical trap.The damped harmonic force of magneto-optical trap was used to capture and trap the cesium atoms directly from a room temperature vapor.About 1.5×10^(7) cesium atoms with a density of 3×10^(9) atoms/cm^(3) formed a 4mm^(3) cesium atomic cloud with temperature below 500μK.
基金supported by the National Natural Science Foundation of China(Nos.11675040 and 11702319).
文摘The pulsed inductive thruster is characterized of no electrode corruption and wide propellant choice.To give insight into the propulsion mechanism of small scale thruster at different propellant mass(m)and energy(E)levels,the transient Magneto Hydro Dynamics(MHD)method,completed by high temperature thermodynamic and transport,and plasma electrical models,is developed to study argon plasma response under the excitation of current of high rise rate.By calculating the two-dimensional expansion properties of the thruster with conical pylon,the simulations find that the main energy deposition occurs during the initial pulse rise stage,and the energy density of Joule heat is two magnitudes higher than the deposition in the down side.At propellant mass of 2 mg,average axial velocity of the current sheet increases from about 15 km/s at 750 J to about 21 km/s at 1470 J within the decoupling distance.The velocity variation synchronizes with the pulsed rise in the initial.The monotonically decrease of the temperature along axis results in the growth of low ionization level ions and reducing of high levels.The current sheet maintains the structure formed during the initial pulse rise when moving beyond the decoupling distance.Besides the change in forward velocity,the main difference is the dimension compared with that in the first half period,caused by thermal conduction and particle diffusion.The variations of total impulse It in the range of m from 2 mg to8 mg and E from 750 J to 1470 J show that It is proportional to m1/2 when E is determined.
基金supported by the National Natural Science Foundation of China(Grant Nos.51371091,51174099,and 51001054)the Industrial Center of Jiangsu University,China(Grant No.ZXJG201586)
文摘In order to explore the dependence of plasticity of metallic material on a high magnetic held,the effects of the different magnetic induction intensities（H = 0 T,0.5 T,1 T,3 T,and 5 T） and pulses number（N = 0,10,20,30,40,and 50） on tensile strength（σ;） and elongation（δ） of 2024 aluminum alloy are investigated in the synchronous presences of a high magnetic held and external stress.The results show that the magnetic held exerts apparent and positive effects on the tensile properties of the alloy.Especially under the optimized condition of H;=1 T and N;=30,the σ;and 8 are 410 MPa and 17% that are enhanced by 9.3% and 30.8% respectively in comparison to those of the untreated sample.The synchronous increases of tensile properties are attributed to the magneto-plasticity effect on a quantum scale.That is,the magnetic held will accelerate the state conversion of radical pair generated between the dislocation and obstacles from singlet to the triplet state.The bonding energy between them is meanwhile lowered and the moving flexibility of dislocations will be enhanced.At H;= 1 T and N;= 30,the dislocation density is enhanced by 1.28 times.The relevant minimum grain size is 266.1 nm,which is reduced by 35.2%.The grain rehning is attributed to the dislocation accumulation and subsequent dynamic recrystallization.The（211） and（220） peak intensities are weakened.It is deduced that together with the recrystallization,the hne grains will transfer towards the slip plane and contribute to the slipping deformation.
基金Project(2010GK3091) supported by Industrial Support Project in Science and Technology of Hunan Province, ChinaProject(10B058) supported by Excellent Youth Foundation Subsidized Project of Hunan Provincial Education Department, China
文摘A neuron proportion integration (PI) control strategy for semi-active suspension system of tracked vehicle was proposed based on its unique structure and the multiple and complex environment of the driving traffic. An adaptive genetic algorithm is used to optimize the parameters of the neuron PI controller. The simulation result of the neuron PI control for semi-active suspension system of tracked vehicle indicates that the vertical amplitude,pitch angle and vertical acceleration of the vehicle are well controlled. The root mean square (RMS) of the vertical amplitude decreases by 37.2%,and 45.2% for the pitch angle,38.6% for the vertical acceleration. The research of neuron PI control experiment for the semi-active suspension system of the tracked vehicle model mining in benthal indicates that the RMS of the weight acceleration vibrating along the vertical direction decreases by 29.5%,the power spectral density resonance peak of the acceleration of the car body decreases by 23.8%.
基金supported by the National Natural Science Foundation of China (11472239)the Natural Science Foundation of Hebei Province of China (A2015203023)
文摘The principle and 1:3 internal resonance of a rectangular thin plate in a transverse magnetic field is investigated.Based on the magneto-elastic vibration equation and electromagnetic force expressions of the thin plates,the nonlinear magneto-elastic vibration differential equations of rectangular plates under external excitation in a transverse magnetic field are derived.For a rectangular plate with one side fixed and three other sides simply supported,the two-degree-offreedom nonlinear Duffing vibration differen-tial equations are proposed by the method of Galerkin.The method of multiple scales is adopted to solve the model equations and obtain four first-order ordinary differential equations governing modulation of the amplitudes and phase angles involved via the first-order or the second-order primary-internal reso-nances.With a numerical example,the amplitude frequency response curves,time history responses,phase portraits and Poincare maps of the first two order vibration modes via principle-internal resonance are respectively captured.And the effects of external excitation amplitudes,magnetic field intensities and thicknesses on the vibration of system are discussed.The results show that the response is dominated by the low mode when principle-internal resonance occurs.The internal resonance provides a mechanism for transferring energy from a high mode to a low mode.
基金Project supported by the National Key Research and Development Program of China(Grant No.2017YFA0304502)the National Natural Science Foundation of China(Grant Nos.11574187,11634008,11674203,and 61227902)the Fund for Shanxi “1331 Project”,China
文摘We experimentally demonstrate a reliable method based on a nanofiber to optimize the number of cold atoms in a magneto–optical trap(MOT) and to monitor the MOT in real time.The atomic fluorescence is collected by a nanofiber with subwavelength diameter of about 400 nm.The MOT parameters are experimentally adjusted in order to match the maximum number of cold atoms provided by the fluorescence collected by the nanofiber.The maximum number of cold atoms is obtained when the intensities of the cooling and re-pumping beams are about 23.5 mW/cm^2 and 7.1 mW/cm^2,respectively;the detuning of the cooling beam is-13.0 MHz, and the axial magnetic gradient is about 9.7 Gauss/cm.We observe a maximum photon counting rate of nearly(4.5 ± 0.1)× 10^5 counts/s.The nanofiber–atom system can provide a powerful and flexible tool for sensitive atom detection and for monitoring atom–matter coupling.It can be widely used from quantum optics to quantum precision measurement.
基金the National Natural Science Foundation of China(Nos.51861031 and 51604159)the Natural Science Foundation of Ningxia,China(No.2018AAC03056).
文摘The quasi-metallic fibers were selected from 1 to 40 pieces and connected in parallel in this study.The giant magneto impedance(GMI)effect of Co-based melt extract fibers in the bundle mode was investigated,and the distribution of the surface circumferential magnetic field on the fibers was also analyzed.Such distribution was induced by the driving current,which gave rise to the circular magnetization process and the GMI effect.The improved GMI effect with much higher field sensitivity was observed in these fiber bundles.Results show that the field sensitivities of the four-fiber and six-fiber bundles reach 19.5 V·m·kA−1(at 1 MHz)and 30.8 V·m·kA−1(at 5 MHz).The circumferential magnetic field distributed throughout the fiber’s circumferential surface is rearranged and becomes uneven due to the magnetic interaction among fibers.There are both strengthened and weakened magnetic field parts around these fibers’surfaces.The strengthened magnetic field improves the circumferential domain magnetization of the surface,resulting in larger GMI effects.However,the weakened parts inhibit the circumferential magnetization process and,therefore,the GMI effect.This also induces greater magnetization damp because of the increased domain interactions under the strong skin effect.The co-effect between the magnetic domains and the circumferential magnetization induces the optimization of the GMI effect in the four-fiber bundles.The observed GMI effect proves that fibers in bundle form can modify the sensitivity of the GMI effect.Moreover,different fiber bundles could be tuned according to the working conditions in order to manipulate the GMI response.
文摘The Lie group method is applied to present an analysis of the magneto hydro-dynamics（MHD） steady laminar flow and the heat transfer from a warm laminar liquid flow to a melting moving surface in the presence of thermal radiation.By using the Lie group method,we have presented the transformation groups for the problem apart from the scaling group.The application of this method reduces the partial differential equations（PDEs） with their boundary conditions governing the flow and heat transfer to a system of nonlinear ordinary differential equations（ODEs） with appropriate boundary conditions.The resulting nonlinear system of ODEs is solved numerically using the implicit finite difference method（FDM）.The local skin-friction coefficients and the local Nusselt numbers for different physical parameters are presented in a table.
文摘Modeling and analysis of thin film flow with respect to magneto hydro dynamical effect has been an important theme in the field of fluid dynamics,due to its vast industrial applications.The analysis involves studying the behavior and response of governing equations on the basis of various parameters such as thickness of the film,film surface profile,shear stress,liquid velocity,volumetric flux,vorticity,gravity,viscosity among others,along with different boundary conditions.In this article,we extend this analysis in fractional space using a homotopy based scheme,considering the case of a Non-Newtonian Pseudo-Plastic fluid for lifting and drainage on a vertical wall.After applying similarity transformations,the given problems are reduced to highly non-linear and inhomogeneous ordinary differential equations.Moreover,fractional differential equations are obtained using basic definitions of fractional calculus.The Homotopy Perturbation Method(HPM),along with fractional calculus is used for obtaining approximate solutions.Physical quantities such as the velocity profile,volume flux and average velocity respectively for lift and drainage cases have been calculated.To the best of our knowledge,the given problems have not been attempted before in fractional space.Validity and convergence of the obtained solutions are confirmed by finding residual errors.From a physical perspective,a comprehensive study of the effects of various parameters on the velocity profile is also performed.Study reveals that Stokes number St,non-Newtonian parameterand magnetic parameter M have inverse relationship with fluid velocity in lifting case.In the drainage case,Stokes number St and non-Newtonian parameterhave direct relationship with fluid velocity,but magnetic parameter M shows inverse relationship with velocity.The investigation also shows that the fractional parameterhas direct relationship with the fluid velocity in lifting case,while it has inverse relationship with velocity in the drainage case.
基金supported by the Key Research and Development Program of Jiangsu Province(BE2018107)by the Natural Science Foundation of Jiangsu Province(BK20191225).
文摘In this paper,a new auxiliary teeth structure is proposed for fault-tolerant permanent magnet(PM)generators,which can reduce the short-circuit currents.Firstly,the short-circuit current and the phase to phase isolation of the fault-tolerant generator are analyzed briefly.Secondly,the auxiliary teeth structure is optimized to improve fault-tolerant capability.Then,the PM generators with different stator structures are compared to evaluate the proposed auxiliary teeth structure.Four critical generator parameters are investigated,i.e.back-electromotive forces,short-circuit currents,stator magneto motive force(MMF)harmonics,and torque performances.The results show that the proposed structure has better fault-tolerant capability than the conventional two-layer windings.Moreover,the stator MMF harmonics can be suppressed.Furthermore,the cogging torque and torque ripple can be suppressed by adopting the proposed structure.Finally,the simulated results are given to validate the theoretical analysis.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11172084,11002045,10632020 and 10672017.
文摘The propagation of elastic waves in magnetoelectroelastic grid structures is studied.Band gap properties are presented and the effects of the magnetoelectroelastic coupling and initial stress are considered.Numerical calculations are performed using the plane-wave expansion method.The results show that the band gap width can be tuned by the initial stress.It is hoped that our results will be helpful for designing acoustic filters with magnetoelectroelastic materials and grid structures.
文摘The present work focused on the application of innovative damping technologies in order to improve railway vehicle performances in terms of dynamic stability and comfort. As a benchmark case-study, the secondary sus- pension stage was selected and different control techniques were investigated, such as skyhook, dynamic compensation, and sliding mode control. The final aim was to investigate which control schemes are suitable for optimal exploitation of the non-linear behavior of the actuators. The performance improvement achieved by adoption of the semi-active dampers on a standard high-speed train was evaluated in terms of passenger comfort. Different control strategies have been investigated by comparing a simple SISO （single input single output） regulator based on the skyhook damper ap- proach with a centralized regulator. The centralized regulator allows for the estimation of a near optimal set of control forces that minimize car-body accelerations with respect to constraints imposed by limited performance of semi-active actuators. Simulation results show that best results is obtained using a mixed approach that considers the simultaneous applications of model based and feedback compensation control terms.
