Design of a giant magnetostrictive ultrasonic transducer for progressive sheet forming was presented.A dynamic analysis of the theoretically designed ultrasonic vibration system was carried out using the finite elemen...Design of a giant magnetostrictive ultrasonic transducer for progressive sheet forming was presented.A dynamic analysis of the theoretically designed ultrasonic vibration system was carried out using the finite element method(FEM).In addition,simulations were performed to verify the theoretical design.Then,a magnetically conductive material was added between the giant magnetostrictive rod and the permanent magnet.Besides,magnetic field simulations of the transducer were performed.The influence of the material thickness of the magnetically conductive material on uniformity of the induced magnetic field was studied.Furthermore,the impedance analysis and amplitude measurement were performed to compare the performance of transducers with and without the magnetically conductive material.The experimental results show that the magnetic field uniformity is the highest when the magnetically conductive material has a thickness of about 1.6 mm.The output amplitude of the giant magnetostrictive transducer is improved by adding the magnetically conductive material.Moreover,the mechanical quality factor and impedance are reduced,while the transducer operates more stably.展开更多
Grinding is a crucial process in machining workpieces because it plays a vital role in achieving the desired precision and surface quality.However,a significant technical challenge in grinding is the potential increas...Grinding is a crucial process in machining workpieces because it plays a vital role in achieving the desired precision and surface quality.However,a significant technical challenge in grinding is the potential increase in temperature due to high specific energy,which can lead to surface thermal damage.Therefore,ensuring control over the surface integrity of workpieces during grinding becomes a critical concern.This necessitates the development of temperature field models that consider various parameters,such as workpiece materials,grinding wheels,grinding parameters,cooling methods,and media,to guide industrial production.This study thoroughly analyzes and summarizes grinding temperature field models.First,the theory of the grinding temperature field is investigated,classifying it into traditional models based on a continuous belt heat source and those based on a discrete heat source,depending on whether the heat source is uniform and continuous.Through this examination,a more accurate grinding temperature model that closely aligns with practical grinding conditions is derived.Subsequently,various grinding thermal models are summarized,including models for the heat source distribution,energy distribution proportional coefficient,and convective heat transfer coefficient.Through comprehensive research,the most widely recognized,utilized,and accurate model for each category is identified.The application of these grinding thermal models is reviewed,shedding light on the governing laws that dictate the influence of the heat source distribution,heat distribution,and convective heat transfer in the grinding arc zone on the grinding temperature field.Finally,considering the current issues in the field of grinding temperature,potential future research directions are proposed.The aim of this study is to provide theoretical guidance and technical support for predicting workpiece temperature and improving surface integrity.展开更多
Electromagnetic relay is a widely used apparatus which usually works in a magnetic disturbance environment. To evaluate its electromagnetic compatibility (EMC) in a static magnetic field, dynamic characteristics of a ...Electromagnetic relay is a widely used apparatus which usually works in a magnetic disturbance environment. To evaluate its electromagnetic compatibility (EMC) in a static magnetic field, dynamic characteristics of a clapper relay in a uniform static magnetic field situation based on the finite element method (FEM) is studied. Influences of the magnetic field on dynamic parameters (delay time, pick-up time, end pressure, and final velocity) as well as a situation in which the relay cannot function normally are analyzed. Simulation reveals that the external magnetic field which weakens the relay’s air-gap field has a greater influence on the relay’s dynamic parameters than the one strengthening the field. The validity of the simulation is verified by measured results of coil current and armature displacement.展开更多
The randomness of strength and deformation of concrete material is serious and should be considered both in theoretical analyses such as Finite Element Methods and engineering practice, specially for those structural ...The randomness of strength and deformation of concrete material is serious and should be considered both in theoretical analyses such as Finite Element Methods and engineering practice, specially for those structural members with a uniform stress field, where stresses or strains are approximately the same under loading. A mathematical ap- proach of producing a series of random variables of the ultimate tensile strain in concrete is proposed to describe the randomness ofconcrete deformation. With reinforced concrete finite elements a real model calculation method is found for the randomness of initial cracks determined by a minimum tension strain within the uniform stress fields of concrete members. The proposed methods in our paper have as aim to improve the existing method used by FEM and other rela- tive approaches, which normally pay less attention to randomness with consequences that may possibly differ from testing or practice. The method and sample computation as indicated is meaningful and comply with testing and engi- neering practice.展开更多
The electron states in a two-dimensional GaAs/AlGaAs quantum ring are theoretically studied in effective mass approximation. On-centre donor impurity and uniform magnetic field perpendicular to the ring plane are take...The electron states in a two-dimensional GaAs/AlGaAs quantum ring are theoretically studied in effective mass approximation. On-centre donor impurity and uniform magnetic field perpendicular to the ring plane are taken into account. The energy spectrum with different angular momentum changes dramatically with the geometry of the ring. The donor impurity reduces the energies with an almost fixed value; however, the magnetic field alters energies in a more complex way. For example, energy levels under magnetic field will cross each other when increasing the inner radius and outer radius of the ring, leading to the fact that the arrangement of energy levels is distinct in certain geometry of the ring. Moreover, energy levels with negative angular momentum exhibit the non-monotonous dependence on the increasing magnetic field.展开更多
In order to calibrate electrical instruments and generate a constant magnetic field, a novel design method for square Helmholtz coil is proposed. According to the superposition principle in electromagnetics, the theor...In order to calibrate electrical instruments and generate a constant magnetic field, a novel design method for square Helmholtz coil is proposed. According to the superposition principle in electromagnetics, the theory of the square Helmholtz coil is established, and the design method is verified by Matlab calculation. Compared with conventional circular Helmholtz coil, the novel square one is with a larger uniform region. Simulation work is conducted in Maxwell, and the distribution of the magnetic field is obtained. The results demonstrate the validation of the applied calculation method of the proposed Helmholtz model. The space utilization rate η is used to make a comparison between the square and circular coils for the uniform region. The square Helmholtz coil is fabricated, the length of a single square coil is 1.5 m, and the amplitude of the magnetic field is controlled by the current. The GSM-19 T proton magnetometer is used to measure the amplitude of the magnetic field generated by the square Helmholtz coil. Experimental results indicate that a wide-range variable uniform magnetic field from 0 to 120 μT is generated in the center of Helmholtz coils.展开更多
We experimentally study the dynamic characteristics of a miniaturized spin-exchange relaxation-free(SERF) magnetometer based on uniform light field. The ceramic ferrule is used to expand the Gaussian beam to improve l...We experimentally study the dynamic characteristics of a miniaturized spin-exchange relaxation-free(SERF) magnetometer based on uniform light field. The ceramic ferrule is used to expand the Gaussian beam to improve light intensity uniformity, while the volume of the sensor is also reduced. This scheme makes the magnetometer have better sensitivity when the detected light intensity is less than 3.16 m W/cm^(2) at 120℃. When the temperature rises to 150℃ the sensitivity under the action of uniform light field is 18.5 f T/Hz^(1/2). The bandwidth of the sensor remains at the original level and meets application needs. The proposed structure improves transverse polarization uniformity within the miniaturized sensor, which is ideal for the magnetoencephalography and magnetocardiography imaging systems.展开更多
We find quantum mechanical Fourier-Hankel representation transform for an electron moving in a uniform magnetic field. The physical meaning of Fourier decomposition states of electron's coordinate eigenstate and t...We find quantum mechanical Fourier-Hankel representation transform for an electron moving in a uniform magnetic field. The physical meaning of Fourier decomposition states of electron's coordinate eigenstate and the momentum eigenstate are revealed.展开更多
A Monte Carlo simulation technique has been used to model the electron transport' behavior, especially the electron density and energy distributions under the influence of a mirror magnetic field and a uniform ele...A Monte Carlo simulation technique has been used to model the electron transport' behavior, especially the electron density and energy distributions under the influence of a mirror magnetic field and a uniform electric field in a positive column of helium direct current(DC) gas discharge Graphs showing the electron density and energy distributions, and the percentage of electrons that reach the wall and the end of the positive column are presented. The results indicate that the mirror magnetic field can control the electron transport behavior in the positive column which are in good agreement with experimental results.展开更多
In this paper we find that a set of energy eigenstates of a two-dimensional anisotropic harmonic potential in a uniform magnetic field is classified as the atomic coherent states ｜τ） in terms of the spin values of ...In this paper we find that a set of energy eigenstates of a two-dimensional anisotropic harmonic potential in a uniform magnetic field is classified as the atomic coherent states ｜τ） in terms of the spin values of j in the Schwinger bosonic realization. The correctness of the above conclusions can be verified by virtue of the entangled state 〈η｜ representation of the state ｜τ）.展开更多
The design and fabrication method of magnetic field coils with high uniformity is essential for atomic magnetometers.In this paper,a novel design strategy for cylindrical uniform coils is first proposed,which combines...The design and fabrication method of magnetic field coils with high uniformity is essential for atomic magnetometers.In this paper,a novel design strategy for cylindrical uniform coils is first proposed,which combines the target-field method(TFM)with an optimized slime mold algorithm(SMA)to determine optimal structure parameters.Then,the realization method for the designed cylindrical coil by using the flexible printed circuit(FPC)technology is presented.Compared with traditional fabrication methods,this method has advantages in excellent flexibility and bending property,making the coils easier to be arranged in limited space.Moreover,the manufacturing process of the FPC technology via a specific cylindrical uniform magnetic field coil is discussed in detail,and the successfully realized coil is well tested in a verification system.By comparing the uniformity performance of the experimental coil with the simulation one,the effectiveness of the FPC technology in producing cylindrical coils has been well validated.展开更多
Purpose: To quantitatively evaluate four different Proton SFUD PBS initial planning strategies for lung mobile tumor. Methods and Materials: A virtual lung patient’s four-dimensional computed tomography (4DCT) was ge...Purpose: To quantitatively evaluate four different Proton SFUD PBS initial planning strategies for lung mobile tumor. Methods and Materials: A virtual lung patient’s four-dimensional computed tomography (4DCT) was generated in this study. To avoid the uncertainties from target delineation and imaging artifacts, a sphere with diameter of 3 cm representing a rigid mobile target (GTV) was inserted into the right side of the lung. The target motion is set in superior-inferior (SI) direction from ?5 mm to 5 mm. Four SFUD planning strategies were used based on: 1) Maximum-In-tensity-Projection Image (MIP-CT);2) CT_average with ITV overridden to muscle density (CTavg_muscle);3) CT_average with ITV overridden to tumor density (CTavg_tumor);4) CT_average without any override density (CTavg_only). Dose distributions were recalculated on each individual phase and accumulated together to assess the “actual” treatment. To estimate the impact of proton range uncertainties, +/?3.5% CT calibration curve was applied to the 4DCT phase images. Results: Comparing initial plan to the dose accumulation: MIP-CT based GTV D98 degraded 2.42 Gy (60.10 Gy vs 57.68 Gy). Heart D1 increased 6.19 Gy (1.88 Gy vs 8.07 Gy);CTavg_tumor based GTV D98 degraded 0.34 Gy (60.07 Gy vs 59.73 Gy). Heart D1 increased 2.24 Gy (3.74 Gy vs 5.98 Gy);CTavg_muscle based initial GTV D98 degraded 0.31 Gy (60.4 Gy vs 60.19 Gy). Heart D1 increased 3.44 Gy (4.38 Gy vs 7.82 Gy);CTavg_only based Initial GTV D98 degraded 6.63 Gy (60.11 Gy vs 53.48 Gy). Heart D1 increased 0.30 Gy (2.69 Gy vs 2.96 Gy);in the presence of ±3.5% range uncertainties, CTavg_tumor based plan’s accumulated GTV D98 degraded to 57.99 Gy (+3.5%) 59.38 Gy (?3.5%), and CTavg_muscle based plan’s accumulated GTV D98 degraded to 59.37 Gy (+3.5%) 59.37 Gy (?3.5%). Conclusion: This study shows that CTavg_Tumor and CTavg_Muscle based planning strategies provide the most robust GTV coverage. However, clinicians need to be aware that the actual dose to OARs at distal end of target may increase. The study also indicates that the current SFUD PBS planning strategy might not be sufficient to compensate the CT calibration uncertainty.展开更多
Electrostatic dusty plasma waves in a uniform magnetic field are studied. Unless the magnetic field is extremely strong, the dust particles can hardly be magnetized, while however, electrons and ions are easily done s...Electrostatic dusty plasma waves in a uniform magnetic field are studied. Unless the magnetic field is extremely strong, the dust particles can hardly be magnetized, while however, electrons and ions are easily done so. Electrostatic modes in such dusty plasmas can then be investigated by making use of the 'moderately magnetized' assumption of magnetized electrons and ions, and unmagnetized dust particles. In a high frequency range, due to the existence of dust component, both frequencies of Lang- muir waves (parallel to the magnetic field) and upper hybrid waves (perpendicular to the field) are reduced. In the frequency range of ion waves, besides the effect on dust-ion-acoustic waves propagating parallel to the magnetic field, the frequency of ion cyclotron waves perpendicular to the magnetic field is also enhanced. In a very low dust frequency range, we find an 'ion-cyclotron- dust-acoustic' mode propagating across the field line with a frequency even slower than dust acoustic waves.展开更多
We consider the radiation from the beam electrons traveling in a strong uniform axial magnetic field and an axial alternating electric field of wavelength Aw generated by a voltage-supplied pill-box cavity. The beam e...We consider the radiation from the beam electrons traveling in a strong uniform axial magnetic field and an axial alternating electric field of wavelength Aw generated by a voltage-supplied pill-box cavity. The beam electrons emit genuine laser radiation that propagates only in the axial direction through free-electron two- quantum Stark radiation. We find that laser radiation takes place only at the expense of the axial kinetic energy when Aw 〈〈 c/（ωc/γ）, where ωc/γ is the relativistic electron--cyclotron frequency. We formulate the laser power based on quantum-wiggler electrodynamics, and envision a laser of length lore with estimated power 0.1 GW/（kA） in the 10-4 cm wavelength range.展开更多
The high temporal and spatial coherence of free electron lasers(FELs)reduces the uniformity of the illumination field,leading to scattering effects that blur the edges of patterns,resulting in diminished accuracy and ...The high temporal and spatial coherence of free electron lasers(FELs)reduces the uniformity of the illumination field,leading to scattering effects that blur the edges of patterns,resulting in diminished accuracy and clarity.Traditional imaging models regard the light source as fully incoherent,making it difficult to assess the impact of partially coherent light fields on imaging.If FELs are used in imaging systems,their coherence must be considered.To address this issue,this study explores the relationship between coherence,imaging quality and speckle contrast through a simulation method based on random phases.The method divides the light beam into temporal and spatial coherence cells,analyzes their interactions,and simulates imaging results under different coherence conditions.Additionally,speckle patterns for various illumination modes are calculated to evaluate their effects on speckle contrast and illumination uniformity.The results indicate that under different illumination modes,illumination uniformity decreases as coherence increases,while speckle contrast increases with higher coherence.In terms of imaging quality,higher coherence leads to an increase in both line edge roughness(LER)and line width roughness(LWR),thereby reducing the imaging quality.Additionally,the narrower the line width,the greater the impact of coherence on the imaging quality,resulting in poorer imaging performance.展开更多
We present the design of two interacting harmonic non-elliptical compressible liquid inclusions embedded in an infinite isotropic elastic matrix subjected to uniform remote in-plane stresses.The original constant mean...We present the design of two interacting harmonic non-elliptical compressible liquid inclusions embedded in an infinite isotropic elastic matrix subjected to uniform remote in-plane stresses.The original constant mean stress(or the first invariant of the stress tensor)in the matrix remains undisturbed in the presence of the two harmonic liquid inclusions.The two non-elliptical liquid-solid interfaces are described by a fourparameter conformal mapping function that maps the doubly connected domain occupied by the matrix onto an annulus in the image plane.The closed-form expressions for the internal uniform hydrostatic stress fields within the two liquid inclusions are obtained.The hoop stresses are uniformly distributed along the two liquid-solid interfaces on the matrix side.展开更多
The existing wireless power transfer(WPT)systems for gastrointestinal capsule robot have the prob-lems of small coupling coefficient and low power transmission efficiency(PTE).The reasons are due to the long distance ...The existing wireless power transfer(WPT)systems for gastrointestinal capsule robot have the prob-lems of small coupling coefficient and low power transmission efficiency(PTE).The reasons are due to the long distance between the transmitting coil and the receiving coil and the large difference in size.A new type of WPT system is designed,which uses three sets of small coil pairs to form a power supply unit(PSU),and utilizes multiple PSUs to form a multi-coil WPT system.Compared with single-coil system,the multi-coil system can achieve higher power utilization by switching between PSUs,instead of opening all PSUs.ANSYS Maxwell is used to perform finite element modeling on the PSU,analyzing the characteristics of the transmitting magnetic field.The results of the experiment show that when the distance between the small coil pairs in the PSU is 180mm,the magnetic field has relatively good uniformity,and the magnetic strength change relative to the center point is less than 5%.The average received power of the system is greater than 800mW,and the PTE is up to 5.1%.展开更多
We prove the observability inequalities at two time points for the Schrodinger equation in a uniform magnetic field in dimensions 2 and 3.The proofs mainly rely on Nazarov's uncertainty principle.In particular,the...We prove the observability inequalities at two time points for the Schrodinger equation in a uniform magnetic field in dimensions 2 and 3.The proofs mainly rely on Nazarov's uncertainty principle.In particular,the observability inequality in three dimensions can also be derived from the approach used to establish the Amerin-Berthier uncertainty principle.展开更多
Two-dimensional laminar boundary layer flow and heat transfer above a moving wedge in the presence of a uniform magnetic field are analyzed.The velocities of both the freestream flow and the wedge are taken to vary as...Two-dimensional laminar boundary layer flow and heat transfer above a moving wedge in the presence of a uniform magnetic field are analyzed.The velocities of both the freestream flow and the wedge are taken to vary as powers of distance.The freestream velocity may be treated as either constant or varying,with these two cases leading to two dissimilar boundary layer equations.The temperature of the heated wedge is taken as increasing from the ambient value to a constant.A set of nonlinear equations is obtained from the dimensionless partial differential equations using similarity transformations.Two solution approaches are adopted:the full nonlinear coupled equations are treated numerically by the Keller box technique,and then an asymptotic approach is used to solve the resulting linear system.Both methods exhibit strong agreement with one another with regard to the results that they give for temperature gradients,velocity and temperature profiles for different physical parameters.Our findings indicate a mutual interaction between the fluid and the wedge surface,as well as a coupling between the thermal and momentum boundary layers.When the freestream flow is held constant or allowed to vary,the velocity profile in the boundary layer tends asymptotically to zero.The boundary layer is thinner for accelerating flows and stronger magnetic field,and for smaller Prandtl number,while the momentum boundary layer thickness becomes thinner for small wedge angle and magnetic field,and larger values of the velocity ratio parameter,wall temperature exponent,and Prandtl number.It is found that when the Prandtl number increases,the wall shear stress and temperature gradient initially increase quite rapidly and then more slowly.展开更多
With the calculation and measuring experiment methods,the effect of vacuum chamber materials' magnetic permeability on field distribution in a dipole magnet is discussed.The results show that when the relative mag...With the calculation and measuring experiment methods,the effect of vacuum chamber materials' magnetic permeability on field distribution in a dipole magnet is discussed.The results show that when the relative magnetic permeability of chamber materialμ_r≠1,it will affect the field uniformity.Once the high field uniformity is required, the material property and size of vacuum chamber in a dipole magnet have to be taken into account carefully.展开更多
基金supported by the National Science Foundation of China(No.51675422)the Shaanxi Province Key Research and Development Plan Project of China(No.2017GY-028)。
文摘Design of a giant magnetostrictive ultrasonic transducer for progressive sheet forming was presented.A dynamic analysis of the theoretically designed ultrasonic vibration system was carried out using the finite element method(FEM).In addition,simulations were performed to verify the theoretical design.Then,a magnetically conductive material was added between the giant magnetostrictive rod and the permanent magnet.Besides,magnetic field simulations of the transducer were performed.The influence of the material thickness of the magnetically conductive material on uniformity of the induced magnetic field was studied.Furthermore,the impedance analysis and amplitude measurement were performed to compare the performance of transducers with and without the magnetically conductive material.The experimental results show that the magnetic field uniformity is the highest when the magnetically conductive material has a thickness of about 1.6 mm.The output amplitude of the giant magnetostrictive transducer is improved by adding the magnetically conductive material.Moreover,the mechanical quality factor and impedance are reduced,while the transducer operates more stably.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52205481,51975305 and 52105457)Shandong Natural Science Foundation(Grant Nos.ZR2020ME158,ZR2023QE057,ZR2022QE028,ZR2021QE116,ZR2020KE027,and ZR2022QE159)+1 种基金Qingdao Science and Technology Planning Park Cultivation Plan(23-1-5-yqpy-17-qy)China Postdoctral Science Foundation(2021M701810).
文摘Grinding is a crucial process in machining workpieces because it plays a vital role in achieving the desired precision and surface quality.However,a significant technical challenge in grinding is the potential increase in temperature due to high specific energy,which can lead to surface thermal damage.Therefore,ensuring control over the surface integrity of workpieces during grinding becomes a critical concern.This necessitates the development of temperature field models that consider various parameters,such as workpiece materials,grinding wheels,grinding parameters,cooling methods,and media,to guide industrial production.This study thoroughly analyzes and summarizes grinding temperature field models.First,the theory of the grinding temperature field is investigated,classifying it into traditional models based on a continuous belt heat source and those based on a discrete heat source,depending on whether the heat source is uniform and continuous.Through this examination,a more accurate grinding temperature model that closely aligns with practical grinding conditions is derived.Subsequently,various grinding thermal models are summarized,including models for the heat source distribution,energy distribution proportional coefficient,and convective heat transfer coefficient.Through comprehensive research,the most widely recognized,utilized,and accurate model for each category is identified.The application of these grinding thermal models is reviewed,shedding light on the governing laws that dictate the influence of the heat source distribution,heat distribution,and convective heat transfer in the grinding arc zone on the grinding temperature field.Finally,considering the current issues in the field of grinding temperature,potential future research directions are proposed.The aim of this study is to provide theoretical guidance and technical support for predicting workpiece temperature and improving surface integrity.
基金Project (No. 513230502) supported by the PLA General ArmamentDepartment of China
文摘Electromagnetic relay is a widely used apparatus which usually works in a magnetic disturbance environment. To evaluate its electromagnetic compatibility (EMC) in a static magnetic field, dynamic characteristics of a clapper relay in a uniform static magnetic field situation based on the finite element method (FEM) is studied. Influences of the magnetic field on dynamic parameters (delay time, pick-up time, end pressure, and final velocity) as well as a situation in which the relay cannot function normally are analyzed. Simulation reveals that the external magnetic field which weakens the relay’s air-gap field has a greater influence on the relay’s dynamic parameters than the one strengthening the field. The validity of the simulation is verified by measured results of coil current and armature displacement.
文摘The randomness of strength and deformation of concrete material is serious and should be considered both in theoretical analyses such as Finite Element Methods and engineering practice, specially for those structural members with a uniform stress field, where stresses or strains are approximately the same under loading. A mathematical ap- proach of producing a series of random variables of the ultimate tensile strain in concrete is proposed to describe the randomness ofconcrete deformation. With reinforced concrete finite elements a real model calculation method is found for the randomness of initial cracks determined by a minimum tension strain within the uniform stress fields of concrete members. The proposed methods in our paper have as aim to improve the existing method used by FEM and other rela- tive approaches, which normally pay less attention to randomness with consequences that may possibly differ from testing or practice. The method and sample computation as indicated is meaningful and comply with testing and engi- neering practice.
基金Project supported by the National High Technology Research and Development Program of China (Grant No. 2009AA03Z405)the National Natural Science Foundation of China (Grant Nos. 60908028 and 60971068)the Fundamental Research Funds for the Central Universities (Grant No. BUPT2009RC0411)
文摘The electron states in a two-dimensional GaAs/AlGaAs quantum ring are theoretically studied in effective mass approximation. On-centre donor impurity and uniform magnetic field perpendicular to the ring plane are taken into account. The energy spectrum with different angular momentum changes dramatically with the geometry of the ring. The donor impurity reduces the energies with an almost fixed value; however, the magnetic field alters energies in a more complex way. For example, energy levels under magnetic field will cross each other when increasing the inner radius and outer radius of the ring, leading to the fact that the arrangement of energy levels is distinct in certain geometry of the ring. Moreover, energy levels with negative angular momentum exhibit the non-monotonous dependence on the increasing magnetic field.
基金The National Natural Science Foundation of China(No.61327803)
文摘In order to calibrate electrical instruments and generate a constant magnetic field, a novel design method for square Helmholtz coil is proposed. According to the superposition principle in electromagnetics, the theory of the square Helmholtz coil is established, and the design method is verified by Matlab calculation. Compared with conventional circular Helmholtz coil, the novel square one is with a larger uniform region. Simulation work is conducted in Maxwell, and the distribution of the magnetic field is obtained. The results demonstrate the validation of the applied calculation method of the proposed Helmholtz model. The space utilization rate η is used to make a comparison between the square and circular coils for the uniform region. The square Helmholtz coil is fabricated, the length of a single square coil is 1.5 m, and the amplitude of the magnetic field is controlled by the current. The GSM-19 T proton magnetometer is used to measure the amplitude of the magnetic field generated by the square Helmholtz coil. Experimental results indicate that a wide-range variable uniform magnetic field from 0 to 120 μT is generated in the center of Helmholtz coils.
基金the National Natural Science Foundation of China (Grant No. 62003020)。
文摘We experimentally study the dynamic characteristics of a miniaturized spin-exchange relaxation-free(SERF) magnetometer based on uniform light field. The ceramic ferrule is used to expand the Gaussian beam to improve light intensity uniformity, while the volume of the sensor is also reduced. This scheme makes the magnetometer have better sensitivity when the detected light intensity is less than 3.16 m W/cm^(2) at 120℃. When the temperature rises to 150℃ the sensitivity under the action of uniform light field is 18.5 f T/Hz^(1/2). The bandwidth of the sensor remains at the original level and meets application needs. The proposed structure improves transverse polarization uniformity within the miniaturized sensor, which is ideal for the magnetoencephalography and magnetocardiography imaging systems.
基金The project supported by National Natural Science Foundation of China under Grant No.10175057the President Foundation of the Chinese Academy of Sciences
文摘We find quantum mechanical Fourier-Hankel representation transform for an electron moving in a uniform magnetic field. The physical meaning of Fourier decomposition states of electron's coordinate eigenstate and the momentum eigenstate are revealed.
文摘A Monte Carlo simulation technique has been used to model the electron transport' behavior, especially the electron density and energy distributions under the influence of a mirror magnetic field and a uniform electric field in a positive column of helium direct current(DC) gas discharge Graphs showing the electron density and energy distributions, and the percentage of electrons that reach the wall and the end of the positive column are presented. The results indicate that the mirror magnetic field can control the electron transport behavior in the positive column which are in good agreement with experimental results.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10574060)the Natural Science Foundation of Shandong Province of China (Grant No. Y2008A23)the Shandong Provincal Higher Educational Science and Technology Program of China (Grant Nos. J09LA07 and J10LA15)
文摘In this paper we find that a set of energy eigenstates of a two-dimensional anisotropic harmonic potential in a uniform magnetic field is classified as the atomic coherent states ｜τ） in terms of the spin values of j in the Schwinger bosonic realization. The correctness of the above conclusions can be verified by virtue of the entangled state 〈η｜ representation of the state ｜τ）.
基金Project supported by the National Natural Science Foundation of China(Grant No.62101004)the Opening Research Fund of Anhui Engineering Research Center of Vehicle Display Integrated Systems(Grant No.VDIS2023C05)+1 种基金the Opening Project of Key Laboratory of Electric Drive and Control of Anhui Province,China(Grant No.DQKJ202309)the Excellent Scientific Research and Innovation Teams of Anhui Province,China(Grant No.2022AH010059)。
文摘The design and fabrication method of magnetic field coils with high uniformity is essential for atomic magnetometers.In this paper,a novel design strategy for cylindrical uniform coils is first proposed,which combines the target-field method(TFM)with an optimized slime mold algorithm(SMA)to determine optimal structure parameters.Then,the realization method for the designed cylindrical coil by using the flexible printed circuit(FPC)technology is presented.Compared with traditional fabrication methods,this method has advantages in excellent flexibility and bending property,making the coils easier to be arranged in limited space.Moreover,the manufacturing process of the FPC technology via a specific cylindrical uniform magnetic field coil is discussed in detail,and the successfully realized coil is well tested in a verification system.By comparing the uniformity performance of the experimental coil with the simulation one,the effectiveness of the FPC technology in producing cylindrical coils has been well validated.
文摘Purpose: To quantitatively evaluate four different Proton SFUD PBS initial planning strategies for lung mobile tumor. Methods and Materials: A virtual lung patient’s four-dimensional computed tomography (4DCT) was generated in this study. To avoid the uncertainties from target delineation and imaging artifacts, a sphere with diameter of 3 cm representing a rigid mobile target (GTV) was inserted into the right side of the lung. The target motion is set in superior-inferior (SI) direction from ?5 mm to 5 mm. Four SFUD planning strategies were used based on: 1) Maximum-In-tensity-Projection Image (MIP-CT);2) CT_average with ITV overridden to muscle density (CTavg_muscle);3) CT_average with ITV overridden to tumor density (CTavg_tumor);4) CT_average without any override density (CTavg_only). Dose distributions were recalculated on each individual phase and accumulated together to assess the “actual” treatment. To estimate the impact of proton range uncertainties, +/?3.5% CT calibration curve was applied to the 4DCT phase images. Results: Comparing initial plan to the dose accumulation: MIP-CT based GTV D98 degraded 2.42 Gy (60.10 Gy vs 57.68 Gy). Heart D1 increased 6.19 Gy (1.88 Gy vs 8.07 Gy);CTavg_tumor based GTV D98 degraded 0.34 Gy (60.07 Gy vs 59.73 Gy). Heart D1 increased 2.24 Gy (3.74 Gy vs 5.98 Gy);CTavg_muscle based initial GTV D98 degraded 0.31 Gy (60.4 Gy vs 60.19 Gy). Heart D1 increased 3.44 Gy (4.38 Gy vs 7.82 Gy);CTavg_only based Initial GTV D98 degraded 6.63 Gy (60.11 Gy vs 53.48 Gy). Heart D1 increased 0.30 Gy (2.69 Gy vs 2.96 Gy);in the presence of ±3.5% range uncertainties, CTavg_tumor based plan’s accumulated GTV D98 degraded to 57.99 Gy (+3.5%) 59.38 Gy (?3.5%), and CTavg_muscle based plan’s accumulated GTV D98 degraded to 59.37 Gy (+3.5%) 59.37 Gy (?3.5%). Conclusion: This study shows that CTavg_Tumor and CTavg_Muscle based planning strategies provide the most robust GTV coverage. However, clinicians need to be aware that the actual dose to OARs at distal end of target may increase. The study also indicates that the current SFUD PBS planning strategy might not be sufficient to compensate the CT calibration uncertainty.
基金This work is supported by the National Natural Science Foundation of China International Cooperation Fund No.0010760807.
文摘Electrostatic dusty plasma waves in a uniform magnetic field are studied. Unless the magnetic field is extremely strong, the dust particles can hardly be magnetized, while however, electrons and ions are easily done so. Electrostatic modes in such dusty plasmas can then be investigated by making use of the 'moderately magnetized' assumption of magnetized electrons and ions, and unmagnetized dust particles. In a high frequency range, due to the existence of dust component, both frequencies of Lang- muir waves (parallel to the magnetic field) and upper hybrid waves (perpendicular to the field) are reduced. In the frequency range of ion waves, besides the effect on dust-ion-acoustic waves propagating parallel to the magnetic field, the frequency of ion cyclotron waves perpendicular to the magnetic field is also enhanced. In a very low dust frequency range, we find an 'ion-cyclotron- dust-acoustic' mode propagating across the field line with a frequency even slower than dust acoustic waves.
文摘We consider the radiation from the beam electrons traveling in a strong uniform axial magnetic field and an axial alternating electric field of wavelength Aw generated by a voltage-supplied pill-box cavity. The beam electrons emit genuine laser radiation that propagates only in the axial direction through free-electron two- quantum Stark radiation. We find that laser radiation takes place only at the expense of the axial kinetic energy when Aw 〈〈 c/（ωc/γ）, where ωc/γ is the relativistic electron--cyclotron frequency. We formulate the laser power based on quantum-wiggler electrodynamics, and envision a laser of length lore with estimated power 0.1 GW/（kA） in the 10-4 cm wavelength range.
文摘The high temporal and spatial coherence of free electron lasers(FELs)reduces the uniformity of the illumination field,leading to scattering effects that blur the edges of patterns,resulting in diminished accuracy and clarity.Traditional imaging models regard the light source as fully incoherent,making it difficult to assess the impact of partially coherent light fields on imaging.If FELs are used in imaging systems,their coherence must be considered.To address this issue,this study explores the relationship between coherence,imaging quality and speckle contrast through a simulation method based on random phases.The method divides the light beam into temporal and spatial coherence cells,analyzes their interactions,and simulates imaging results under different coherence conditions.Additionally,speckle patterns for various illumination modes are calculated to evaluate their effects on speckle contrast and illumination uniformity.The results indicate that under different illumination modes,illumination uniformity decreases as coherence increases,while speckle contrast increases with higher coherence.In terms of imaging quality,higher coherence leads to an increase in both line edge roughness(LER)and line width roughness(LWR),thereby reducing the imaging quality.Additionally,the narrower the line width,the greater the impact of coherence on the imaging quality,resulting in poorer imaging performance.
基金supported by the Natural Sciences and Engineering Research Council of Canada(No.RGPIN-2023-03227 Schiavo)。
文摘We present the design of two interacting harmonic non-elliptical compressible liquid inclusions embedded in an infinite isotropic elastic matrix subjected to uniform remote in-plane stresses.The original constant mean stress(or the first invariant of the stress tensor)in the matrix remains undisturbed in the presence of the two harmonic liquid inclusions.The two non-elliptical liquid-solid interfaces are described by a fourparameter conformal mapping function that maps the doubly connected domain occupied by the matrix onto an annulus in the image plane.The closed-form expressions for the internal uniform hydrostatic stress fields within the two liquid inclusions are obtained.The hoop stresses are uniformly distributed along the two liquid-solid interfaces on the matrix side.
基金the National Natural Science Founda-tion of China(Nos.61673271 and 81971767)the Shang-hai Research Project(Nos.19441910600,19441913800 and 19142203800)the Project of Institute of Medical Robotics,Shanghai Jiao Tong University(No.IMR2018KY05)。
文摘The existing wireless power transfer(WPT)systems for gastrointestinal capsule robot have the prob-lems of small coupling coefficient and low power transmission efficiency(PTE).The reasons are due to the long distance between the transmitting coil and the receiving coil and the large difference in size.A new type of WPT system is designed,which uses three sets of small coil pairs to form a power supply unit(PSU),and utilizes multiple PSUs to form a multi-coil WPT system.Compared with single-coil system,the multi-coil system can achieve higher power utilization by switching between PSUs,instead of opening all PSUs.ANSYS Maxwell is used to perform finite element modeling on the PSU,analyzing the characteristics of the transmitting magnetic field.The results of the experiment show that when the distance between the small coil pairs in the PSU is 180mm,the magnetic field has relatively good uniformity,and the magnetic strength change relative to the center point is less than 5%.The average received power of the system is greater than 800mW,and the PTE is up to 5.1%.
基金Supported by Beijing Natural Science Foundation (Grant No.1242011)。
文摘We prove the observability inequalities at two time points for the Schrodinger equation in a uniform magnetic field in dimensions 2 and 3.The proofs mainly rely on Nazarov's uncertainty principle.In particular,the observability inequality in three dimensions can also be derived from the approach used to establish the Amerin-Berthier uncertainty principle.
文摘Two-dimensional laminar boundary layer flow and heat transfer above a moving wedge in the presence of a uniform magnetic field are analyzed.The velocities of both the freestream flow and the wedge are taken to vary as powers of distance.The freestream velocity may be treated as either constant or varying,with these two cases leading to two dissimilar boundary layer equations.The temperature of the heated wedge is taken as increasing from the ambient value to a constant.A set of nonlinear equations is obtained from the dimensionless partial differential equations using similarity transformations.Two solution approaches are adopted:the full nonlinear coupled equations are treated numerically by the Keller box technique,and then an asymptotic approach is used to solve the resulting linear system.Both methods exhibit strong agreement with one another with regard to the results that they give for temperature gradients,velocity and temperature profiles for different physical parameters.Our findings indicate a mutual interaction between the fluid and the wedge surface,as well as a coupling between the thermal and momentum boundary layers.When the freestream flow is held constant or allowed to vary,the velocity profile in the boundary layer tends asymptotically to zero.The boundary layer is thinner for accelerating flows and stronger magnetic field,and for smaller Prandtl number,while the momentum boundary layer thickness becomes thinner for small wedge angle and magnetic field,and larger values of the velocity ratio parameter,wall temperature exponent,and Prandtl number.It is found that when the Prandtl number increases,the wall shear stress and temperature gradient initially increase quite rapidly and then more slowly.
文摘With the calculation and measuring experiment methods,the effect of vacuum chamber materials' magnetic permeability on field distribution in a dipole magnet is discussed.The results show that when the relative magnetic permeability of chamber materialμ_r≠1,it will affect the field uniformity.Once the high field uniformity is required, the material property and size of vacuum chamber in a dipole magnet have to be taken into account carefully.
