Subjects: Information Science and Systems Science >> Basic Disciplines of Information Science and Systems Science Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics Subjects: Astronomy >> Astrophysical processes submitted time 2024-04-11
Abstract： The electromagnetic fields of point sources with time varying charges moving in the vacuum are derived using the Liénard-Wiechert potentials. The properties of the propagation velocities and the Doppler effect are discussed based on their far fields. The results show that the velocity of the electromagnetic waves and the velocity of the sources cannot be added like vectors; the velocity of electromagnetic waves of moving sources are anisotropic in the vacuum; the transverse Doppler shift is intrinsically included in the fields of the moving sources and is not a pure relativity effect caused by time dilation. Since the fields are rigorous solutions of the Maxwell’s equations, the findings can help us to abort the long-standing misinterpretations concerning about the classic mechanics and the classic electromagnetic theory. Although it may violate the theory of the special relativity, we show mathematically that, when the sources move faster than the light in the vacuum, the electromagnetic barriers and the electromagnetic shock waves can be clearly predicted using the exact solutions. Since they cannot be detected by observers in the region outside their shock wave zones, an intuitive and reasonable hypothesis can be made that the superluminal sources may be considered as a kind of electromagnetic blackholes.
Peer Review Status:
Awaiting Review
Subjects: Information Science and Systems Science >> Basic Disciplines of Information Science and Systems Science Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics Subjects: Electronics and Communication Technology >> Optoelectronics and Laser Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Physics >> The Physics of Elementary Particles and Fields submitted time 2024-04-08
Abstract： The Einstein’s theory of special relativity is based on his two postulates. The first is that the laws of physics are the same in all inertial reference frames. The second is that the velocity of light in the vacuum is the same in all inertial frames. The theory of special relativity is considered to be supported by a large number of experiments. This paper revisits the two postulates according to the new interpretations to the exact solutions of moving sources in the laboratory frame. The exact solutions are obtained using the classic Maxwell’s theory, which clearly show that the propagation velocity of the electromagnetic waves of moving sources in the vacuum is not isotropic; the propagation velocity of the electromagnetic waves and the moving velocity of the sources cannot be added like vectors; the transverse Doppler effect is intrinsically included in the fields of the moving sources. The electromagnetic sources are subject to the Newtonian mechanics, while the electromagnetic fields are subject to the Maxwell’s theory. We argue that since their behaviors are quite different, it is not a best choice to try to bind them together and force them to undergo the same coordinate transformations as a whole, like that in the Lorentz transformations. Furthermore, the Maxwell’s theory does not impose any limitations on the velocity of the electromagnetic waves. To assume that all objects cannot move faster than the light in the vacuum need more examinations. We have carefully checked the main experiment results that were considered as supporting the special relativity. Unfortunately, we found that the experimental results may have been misinterpreted. We here propose a Galilean-Newtonian-Maxwellian relativity, which can give the same or even better explanations to those experimental results.
Peer Review Status:Awaiting Review
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2024-03-13
Abstract： The flows of fluids with which one has to deal in engineering, and which one meets in nature, are turbulent in the overwhelming
majority of cases, and their de de encountered special cases, and that the classical de value, must be considered only as an introductory chapter to the theory of real turbulent flows, in which the objects of investigation
are the properties of ensembles of flows, arising from macroscopically identical external conditions.
Peer Review Status:Awaiting Review
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-12-18 Cooperative journals: 《应用力学学报》
Abstract：
The effect of the finite-depth soil mass motion on the dynamic characteristics and nonlinear response of the beam on an elastic foundation is significant.To enhance and deepen the scope of related research,based on the nonlinear equation of motion of the finite-length beam on Winkler foundation with the consideration of soil mass motion,the study focuses on examining how finite-depth soil motion impacts the behavior of an elastic foundation beam under 1/3 order subharmonic resonance conditions.Then,the frequency-response equation and the second-order approximation solution of the 1/3 order sub-harmonic resonance of the beam are derived through the application of the Galerkin method and the multiple scales method.The effects of parameters closely related to soil mass motion(foundation depth,soil mass,elastic modulus,stiffness,and damping,etc.)and excitation amplitude on the sub-harmonic resonance of the beam are investigated by the response equation.The numerical results show that when the effect of soil mass motion is introduced into the equation of motion of the beam,the range and amplitude of the 1/3 order sub-harmonic resonance of the beam decrease.With the change of the depth,mass,and elastic modulus of foundation,some quantitative differences are observed in the frequency-response curves,such as the degree of deflection,resonance range,and amplitude.Excitation's amplitude does not affect the characteristics of the 1/3 order sub-harmonic resonance of the beam.Still,it has a significant effect on the response amplitude and resonance region.On the other hand,the damping of the foundation has apparent inhibition on the 1/3 order sub-harmonic resonance of the beam.
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-12-18 Cooperative journals: 《应用力学学报》
Abstract：
In order to solve the problem that it is difficult to estimate the variance of the measurement noise and reconstruct the multi-type response when the traditional Kalman filter(KF)algorithm is used to reconstruct the structural response,a method combining the noise variance estimation and the multi-type response reconstruction is proposed.First,the approximate calculation method is introduced into the moving window Kalman filter(MWKF),and the recursive moving window Kalman filter(RMWKF)is proposed to estimate the real-time noise variance.Then,the strain,displacement,velocity and acceleration responses of each position of the structure are reconstructed by using the measured data of strain gauges and acceleration sensors at limited positions combined with the modal method.Finally,the proposed method are verified by numerical simulation and experimental analysis of two-dimensional truss and cantilever beam respectively.The results show that the proposed method can estimate the variance of measurement noise and can reconstruct multi-type structural responses effectively.Moreover,the data storage space and computation are reduced.
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-12-18 Cooperative journals: 《应用力学学报》
Abstract：
Deterministic Lateral Displacement(DLD)is a common particle separation technique in which the particles are separated according to their size and the characteristics of microfluidic laminar flow.The traditional DLD theory only considers rigid particles and it is difficult to describe the separation process of flexible particles such as cells.In this paper,the separation,deformation and stress of flexible cell in DLD device were studied by using coarser particle molecular dynamics model and Reynolds similarity principle.The simulation results show that the separation route of DLD cells at nano scale is consistent with the general separation principle at macro-scale.However,in the microscopic scale,the deformation and destruction of cells in the process of cell separation mainly occurred at the contact point between cells and microcolumn,where the maximum stress was exerted.The results reveal the motion details of the flexible particles passing through the DLD device.
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-12-18 Cooperative journals: 《应用力学学报》
Abstract：
Based on computational fluid dynamics(CFD),the floating state and sailing resistance of amphibious desilting robot were analyzed.The draft depth and pitch angle were obtained by calculating the floating state with the overlapping mesh method.The static mesh method and overlapping mesh method were used to predict the sailing resistance of amphibious desilting robot and the two methods were compared.The results show that the draft depth and pitch angle of the amphibious desilting robot can be calculated effectively by using the overlapping mesh method.Both the static grid method and the overlapping mesh method can predict the sailing resistance of amphibious desilting robot.The static mesh method has high efficiency,but can only apply to the situation of the low sailing speed.While the overlapping mesh method is suitable for sailing resistance prediction under different sailing speed,it has low efficiency.The results are of great reference value to the design and improvement of amphibious desilting robot.
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-12-18 Cooperative journals: 《应用力学学报》
Abstract：
According to the high damping characteristics of shape memory alloy(SMA),the energy analysis method was applied to the single-degree-of-freedom inerter-based system.The restoring force of SMA was derived through the relationship between free energy function and dissipation function.The time and frequency responses of SMA were calculated and analyzed.Since the parameter of inerter is irrelevant to the mass,the relevant parameters can be analyzed without changing the mass,and the parameter optimization can be realized through the contour map of resonance peak projection.The results show that the reasonable parameters can make the inerter have better vibration reduction effect,so as to achieve the optimization goal.
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-11-16
Ji, Jianfeng
Guo Han
Xue Yanling
Chen Rongchang
Fu Yanan
Du Guohao
Deng Biao
Xie Honglan
Xiao Tiqiao
Abstract： A new X-ray imaging and biomedical application beamline (BL13HB) has been implemented at the Shanghai Radiation Synchrotron Facility (SSRF) as an upgrade to the old X-ray imaging and biomedical application beamline (BL13W1). This is part of the Phase II construction project of the SSRF. The BL13HB is dedicated to 2D and 3D static and dynamic X-ray imaging, with a field of view of up to 48.5 × 5.2 mm2 and spatial resolution as high as 0.8 μm. A super-bending magnet is used as the X-ray source in BL13HB, which has a maximum magnetic field of 2.293 T. The energy range of monochromatic X-ray photons from a double-multiplayer monochromator was 8-40 keV, and the white beam mode was provided on the beamline for dynamic X-ray imaging and dynamic X-ray micro-CT. While maintaining the previous experimental setup of BL13W1, new equipment was added to the beamline experimental station. The beamline is equipped with different sets of X-ray imaging detectors for several experimental methods such as micro-CT, dynamic micro-CT, and pair distribution function (PDF). The experimental station of BL13HB is designed specifically for various in situ dynamic experiments, and BL13HB has been open to users since June 2021.
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-09-06
Abstract： The aim of this research is to reconstruct the 3D X-ray refractive index gradient maps by the proposed vector Radon transform and its inverse, assuming that the small-angle deviation condition is met. Theoretical analyses show that the X-ray beam can be modeled as a streamline with continuous change of direction in a row when measured in one grating period, which allows the extraction of the refraction angle signals. Experimental results show that all the 2D refraction signals of different directions can be acquired by a standard circular scanning procedure, which is typically used in the X-ray differential phase-contrast computed tomography. Furthermore, the 3D refractive index gradient maps that contain the directional density changes, can also be accurately reconstructed.
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-08-25
Abstract： Waveguide design has always been an important part of photonic integrated devices, and its research is also developing. In this paper, the coupling between waveguides is studied from two aspects of coupled mode theory and finite element simulation. In addition, this paper gives an example of dispersion engineering caused by dual-core waveguides structure, which has a wide range of applications in supercontinuum. To sum up, coupled mode theory has important reference significance for the design of modern photonic devices.
Peer Review Status:Awaiting Review
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-08-25
Gao, You
Sun, Suwan
Lin, Xukun
Wu, Kailin
Wang, Xiaoying
Yuan, Haiyun
Bai, Jiamin
Wang, Siyu
Guo, Hairun
Abstract： Expanding the bandwidth of frequency combs in microcavities is currently a prominent research area, and one effective approach is to introduce dispersive waves using higher-order dispersion.
However, The exploration of high-order dispersion control on quartz microsphere platforms has been limited by the challenge of preserving high Q factors across a broad range of sizes.
Here, we fabricated quartz microspheres through arc discharge with diameters ranging from 100-260 µm, achieving Q factors in the range of 108.
We achieved a broadband Kerr frequency comb with dispersive wave radiation by manipulating the dispersion of the microsphere through size adjustment. Our experimental results demonstrate that the spectral span of the dispersive wave frequency combs can be extended up to 360 nm.
At the same time, we have also demonstrated Raman lasers and Raman-Kerr frequency combs in small microspheres with normal dispersion.This work provides a reference for developing broadband, high-coherence frequency combs on microsphere platforms and offers an efficient implementation scheme for low-noise integrated broadband frequency combs.
Peer Review Status:Awaiting Review
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-08-25
Abstract： We demonstrate dispersion engineered dissipative soliton mode locked lasers, by means of intracavity spatial light modulation (SLM). The inline cavity GVD control of wide range (-0.28 ps2 ~ 0.06 ps2) in the laser cavity is realized, by which we achieve continuous and stable switching of traditional solitons, dispersion-managed solitons and dissipative solitons. A transient process of pulse-adaptive reconstruction is observed during the switching of different solitons. Transitions of soliton dispersive waves from Kelly sidebands, and transforms to quartic solitons have been observed via tuning the high-order dispersion coefficients. w-shaped solitons are demonstrated under negitive second-order dispersion and positive fourth order dispersion.
Peer Review Status:Awaiting Review
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics Subjects: Physics >> Interdisciplinary Physics and Related Areas of Science and Technology submitted time 2023-07-12
Abstract： I review the discovery as well as the band structure of the Zhang lattice.
Peer Review Status:Awaiting Review
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-07-05
Abstract： Whether the propagation speed of light at the surface of rotating Earth is isotropic or not is both an important theoretical problem and one that has significant implications for scientific practices. Especially the unit of length, a meter, is defined as the length of the path travelled by light in vacuum in 1/299792458 of a second, on the basis that the speed of light is constant, c = 299792458 m/s. By applying the GPS range equation whose correctness has been fully verified by GPS practices, we found that the propagation speed of light on rotating Earth's surface is neither constant nor isotropic, but c' = c - vrE . d , where vrE is the local linear velocity of Earth's rotation, and d ˆ is the unit vector of the light propagation's direction. It follows that the anisotropy of the propagation speed of light at the Earth's surface has a significant impact on the definition of the meter. Based on this finding, and the difference between Earth rotation's Sagnac effects on the equator and the meridian, we propose a crucial experiment to examine the anisotropy of the propagation speed of light: let a stable pulsed laser emitting pulses in two opposite directions, use the ultrafast imaging techniques for visualizing, measuring and comparing the spacing of the pulses in opposite directions. Then we can decisively conclude whether the speed of light is anisotropic or not.
Peer Review Status:Awaiting Review
Subjects: Physics >> The Physics of Elementary Particles and Fields Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-04-10
Abstract： In this paper, the whole process of derivation of D 'Alembert wave equation is reviewed. The most important step is to derive D 'Alembert wave equations of scalar potential and vector potential by using Gauss's law and Ampere's law. This paper emphasizes that Gauss's law is the differential form of Coulomb's law, where the charge source and the observer are relatively static; In Ampere's law, the carrier of current source and the observer are also relatively static. The conclusion of this paper is that both Maxwell's equations and D 'Alembert's wave equation are equations under the condition of source-observer relative resting, and the constant 'C' in D 'Alembert's wave equation is the propagation speed under the condition of source-observer relative resting in vacuum environment. Under such special conditions, the propagation space of electromagnetic wave is uniform and isotropic, so it is logical that the electromagnetic wave propagates at the same speed regardless of the distance and azimuth between source and observer, and regardless of the absolute motion of the laboratory on which planet the source and observer are located. The electromagnetic wave in vacuum is emitted from the charge source and the current source, and propagates to observers everywhere. The source-observer is relatively static，the propagation space of electromagnetic wave is uniform and isotropic, this is an accurate physical image, which is the physical basis for accurately understanding the principle of the constant speed of light.
Peer Review Status:Awaiting Review
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2023-02-06
Abstract：
The intrinsic inertia and interaction of matters with unchanged density in an isolated system are studied. It is shown that the matters have a proved inertia of spin with the angular velocity wn=dθdtn=∇×u of isolated system. The conclusive proof can reinforce Newton’s the first law, taking into account the non-zero volume of point close to zero without limitation, and can explain the matter wave and seismic waves. A fundamental isolated system with two coupling matters has studied further. The revealed coupling characterizations have been used to explain the DNA structure, Time Cone and topological sphere of moving trace. The proven interaction within two matters is the coupling result of uniform rectilinear motion and spin of isolated system, which may be helpful to uniform the gravitation and electromagnetic force.
Peer Review Status:Awaiting Review
Subjects: Physics >> Geophysics, Astronomy, and Astrophysics Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics Subjects: Astronomy >> Galaxy and Cosmology submitted time 2022-11-03
Abstract：
Based on the consideration of naturalness and physical facts in Einstein's theories of relativity, a nontrivial spacetime physical picture, which has a slight difference from the standard one, is introduced by making a further distinction on the absolute background of spacetime and the relative length or duration of base units of spacetime. In this picture, the coordinate base units in gravity-induced spacetime metric are defined by the standard clock and ruler equipped by the observer, and duplicated onto the every position of the whole universe. In contrast, the local intrinsic base units of spacetime in gravitational field are defined by the length and duration of physical events intervals in the same-type standard clock and ruler which are really located at every position of the universe. In principle, the reading number of the standard clock is counted by the undergone times of unit intervals defined depending on a certain kind of local intrinsic events. But the size of the base units of spacetime is essentially depicted by the length of the line segment, which is cut from the absolute background of spacetime by the local intrinsic events of unit interval. The effect of gravitation is just to change the length of this segment for base spacetime units. On the basis of such a physical picture of spacetime, in a fairly natural way we re-derive a new classical dynamical equation which satisfies a more realistic and moderately general principle of relativity. To further examine this physical picture including of gravitation and spacetime, we finally reinvestigate the physical picture of spacetime in cosmology and propose a more general and rensonable form for cosmological metric.
Peer Review Status:Awaiting Review
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2022-10-17
Abstract：
The acoustic mismatch model and diffuse mismatch model are widely used in the calculation of interfacial thermal conductance. These two models are respectively based on the assumption of extremely smooth and rough interfaces. Due to the great difference between the actual interface structure and the two hypotheses, the prediction of these two models deviate greatly from the actual interfacial thermal conductance. The recently proposed mixed mismatch model considers the effect of interface structure on the ratio of phonon specular transmission to diffuse scattering transmission, and the prediction accuracy is improved. However, this model requires molecular dynamics simulation to obtain phonon information at the interface. In this paper, the mixed mismatch model is simplified by introducing the measured roughness value, and the influence of interface structure on the contact area is taken into account to achieve a simple, fast and accurate prediction of interface thermal conductance. Based on this model, the interfacial thermal conductance of metals (aluminum, copper, gold) and semiconductors (silicon, silicon carbide, gallium arsenide, gallium nitride) are calculated and predicted. The results of Al/Si interface are in good agreement with the experimental results. This model is not only helpful to understand the mechanism of interface heat conduction, but also helpful to compare with the measurement results.
Subjects: Physics >> Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics, and Fluid Dynamics submitted time 2022-09-26 Cooperative journals: 《桂林电子科技大学学报》
Abstract： As a heat pipe occupying a place in the field of heat transfer, the PHP is widely used in electronic heat dissipation
equipment,and regarded to be one of the heat dissipation components that have great development prospects under the conditions
of extra high heat flow density and power consumption. With the maturity of nanotechnology, Nano fluid has also become
an innovative research in the traditional field of heat dissipation and heat transfer. Therefore, it is extremely important
to explore the change mechanism and change law of the operation and thermal characteristics of the pulsating heat pipe in different
magnetic field environments. Through the use of an external magnetic field to strengthen the experimental research on
the heat transfer of the nano-magnetic fluid pulsating heat pipe, a visualization experiment platform for heat transfer testing
of the nano-magnetic fluid pulsating heat pipe was built. The temperature distribution and heat transfer rate of the plate-type
pulsating heat pipe under the action of the magnetic field size of 25, 5, 1 and 0 mT and different magnetic field directions are
respectively measured. The influence of factors such as nano-magnetic fluid, heat load power consumption, magnetic induction
intensity and magnet placement position on its heat transfer performance is studied. The experimental results show that
the use of Fe3O4/ethanol nanofluid as the working fluid can significantly enhance the heat transfer performance of the pulsating
heat pipe under the action of a magnetic field. Especially under high heat flux loading, this can provide a reference for
the working conditions of ultra-high heat flux density and power consumption.
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