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The Interaction of a Circularly Orbiting Electromagnetic Harmonic Wave with an Electron Having a Constant Time Independent Drift Velocity
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作者 Mirwais Rashid 《Journal of Electromagnetic Analysis and Applications》 2011年第9期373-377,共5页
A circularly orbiting electromagnetic harmonic wave may appear when a 1S electron encounters a decelerating stopping positively charged hole inside a semiconductor. The circularly orbiting electromagnetic harmonic wav... A circularly orbiting electromagnetic harmonic wave may appear when a 1S electron encounters a decelerating stopping positively charged hole inside a semiconductor. The circularly orbiting electromagnetic harmonic wave can have an interaction with a conducting electron which has a constant time independent drift velocity. 展开更多
关键词 Interaction Circularly Orbiting ELECTROMAGNETIC HARMONIC wave constant DRIFT Velocity
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毫米波雷达多目标检测门限优化研究
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作者 彭家辉 张雪凡 金彦亮 《工业控制计算机》 2026年第1期93-95,共3页
随着辅助驾驶技术对高精度的不断追求,毫米波雷达在目标检测领域的应用逐渐成为研究热点。针对毫米波雷达在对多目标检测时门限被抬高而产生误差的情况,提出了一种融合标准差和距离的恒虚警检测算法(Standard Deviation Smallest of CFA... 随着辅助驾驶技术对高精度的不断追求,毫米波雷达在目标检测领域的应用逐渐成为研究热点。针对毫米波雷达在对多目标检测时门限被抬高而产生误差的情况,提出了一种融合标准差和距离的恒虚警检测算法(Standard Deviation Smallest of CFAR,SDSO-CFAR),通过对目标两侧较小的参考单元加入标准差和距离作为动态阈值,使得波动特征更大的信号门限值更低,显著提升了多目标检测的准确性并降低目标检测对信噪比的依赖。通过数据仿真验证,所采用的目标检测算法在新型雷达芯片配置下,在信噪比为10 d B时,SDSO-CFAR算法的检测概率比CA-CFAR算法高0.08,比SO-CFAR算法高0.23,有效解决了多目标检测存在的遮蔽问题。 展开更多
关键词 毫米波雷达 恒虚警率 多天线阵列 目标检测
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Study on Far Field Wave Patterns and Their Characteristics of Havelock Form Green Function 被引量:3
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作者 许勇 董文才 肖汶斌 《China Ocean Engineering》 SCIE EI CSCD 2013年第3期283-298,共16页
A new mathematical integral representation including five integrals about the far field wave shape fimction of Havelock form translating-pulsating source is obtained by performing variable substitution. Constant-phase... A new mathematical integral representation including five integrals about the far field wave shape fimction of Havelock form translating-pulsating source is obtained by performing variable substitution. Constant-phase curves and propagation wave patterns are investigated by applying stationary phase analysis method to the new representation. Some findings are summarized as follows: (1) when 0〈r 〈0.25 (where r is the Strouhal number), three types of stationary phase curves corresponding to three propagation wave patterns such as fan wave pattern, inner V and outer V wave patterns, are found in the integral representation. (2) When r 〉0.25, besides three types of wave patterns such as a ring-faning wave pattern, a fan wave pattern and an inner V wave pattern, a new one called parallel wave pattern is also found which not only exists in the integrals about the ring-fan wave and fan wave, but also in the integrals whose interval is [0, 7'] ~ In addition, Characteristics about these parallel waves such as mathematical expressions, existence conditions, propagation directions and wave lengths are obtained, and cancellation relationships between these parallel waves are stated, which certificates the fact that there are no parallel waves existing in the far field. 展开更多
关键词 translating-pulsating source propagation wave patterns constant-phase curves parallel wave pattern
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Simulation of the seismic response of sedimentary basins with constant-gradient velocity along arbitrary direction using boundary element method:SH case 被引量:4
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作者 Zengxi Ge 《Earthquake Science》 CSCD 2010年第2期149-155,共7页
We presented a boundary element method using the approximate analytical Green's function given by Sanchez-Sesma et al. Coordinate transform is introduced to extend the method to deal with the model with constant-grad... We presented a boundary element method using the approximate analytical Green's function given by Sanchez-Sesma et al. Coordinate transform is introduced to extend the method to deal with the model with constant-gradient velocity along oblique direction. The method is validated by comparing the numerical results with other independent methods. This method provides a useful tool for analyzing local site effects. We computed seismic response for two series of models. The results in both frequency and time domains are analyzed and show complex amplification patterns. The fundamental mode of resonance is dependent not only on the velocity at the free surface but also on the velocity distribution of the whole basin. For the higher modes of vibration the heterogeneous basin also has its own characteristic. 展开更多
关键词 boundary element SH wave seismic response constant-gradient velocity
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SYMPLECTIC ANALYSIS FOR WAVE PROPAGATION OF HIERARCHICAL HONEYCOMB STRUCTURES 被引量:3
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作者 Kai Zhang Zichen Deng +2 位作者 Xiaojian Xu Xiuhui Hou Junmiao Meng 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2015年第3期294-304,共11页
Wave propagation in two-dimensional hierarchical honeycomb structures with two- order hierarchy is investigated by using the symplectic algorithm. By applying the variational prin- ciple to the dual variables, the wav... Wave propagation in two-dimensional hierarchical honeycomb structures with two- order hierarchy is investigated by using the symplectic algorithm. By applying the variational prin- ciple to the dual variables, the wave propagation problem is transformed into a two-dimensional symplectie eigenvalue problem. The band gaps and spatial filtering phenomena are examined to find the stop bands and directional stop bands. Special attention is directed to the effects of the relative density and the length ratio on the band gaps and phase constant surfaces. This work provides new opportunities for designing hierarchical honeycomb structures in sound insulation applications. 展开更多
关键词 hierarchical honeycomb structures wave propagation band gap phase constant surface symplectic analysis
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Energy Conservation and Gravitational Wavelength Effect of the Gravitational Propagation Delay Analysis
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作者 Philipp Kornreich 《Journal of Applied Mathematics and Physics》 2017年第4期912-921,共10页
The motion of objects where the interaction propagated with a finite velocity was analyzed in my previous paper “The Contribution of the Gravitational Propagation Delay to Orbital and Center of Mass Motions”. It is ... The motion of objects where the interaction propagated with a finite velocity was analyzed in my previous paper “The Contribution of the Gravitational Propagation Delay to Orbital and Center of Mass Motions”. It is shown here that this analysis is valid for the case when the wavelength of the gravitational wave excited by the motion of the masses is much larger than the system of masses. It is also proven here that the conclusion reached in my previous paper conserves energy. Since this interaction is conservative, the energy is equal to the Hamiltonian. Therefore, the Hamiltonian is calculated and it is shown that the time derivative of the Hamiltonian is equal to zero. Thus, the Hamiltonian and therefore, the energy, are constants. 展开更多
关键词 PROPAGATION Delay GRAVITATION NEWTONIAN Mechanics Lagrangian HAMILTONIAN constantS GRAVITATIONAL waves
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Physical interpretation of Planck's constant based on the Maxwell theory 被引量:1
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作者 张东才 《Chinese Physics B》 SCIE EI CAS CSCD 2017年第4期87-95,共9页
The discovery of the Planck relation is generally regarded as the starting point of quantum physics.Planck's constant h is now regarded as one of the most important universal constants.The physical nature of h,howeve... The discovery of the Planck relation is generally regarded as the starting point of quantum physics.Planck's constant h is now regarded as one of the most important universal constants.The physical nature of h,however,has not been well understood.It was originally suggested as a fitting constant to explain the black-body radiation.Although Planck had proposed a theoretical justification of h,he was never satisfied with that.To solve this outstanding problem,we use the Maxwell theory to directly calculate the energy and momentum of a radiation wave packet.We find that the energy of the wave packet is indeed proportional to its oscillation frequency.This allows us to derive the value of Planck's constant.Furthermore,we show that the emission and transmission of a photon follows the all-or-none principle.The "strength" of the wave packet can be characterized by ζ,which represents the integrated strength of the vector potential along a transverse axis.We reason that ζ should have a fixed cut-off value for all photons.Our results suggest that a wave packet can behave like a particle.This offers a simple explanation to the recent satellite observations that the cosmic microwave background follows closely the black-body radiation as predicted by Planck's law. 展开更多
关键词 Planck's constant Maxwell's theory de Broglie relation uncertainty principle wave packet PHOTON
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Attenuation in a Cylindrical Left Handed Material (LHM) Wave-Guide Structure
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作者 Hana Mohammed Mousa 《Optics and Photonics Journal》 2012年第1期46-53,共8页
This paper tackles the wave attenuation along with a cylindrical waveguides composed of a left Handed material (LHM), surrounded by a superconducting or metal wall. I used the transcendental equations for both TE and ... This paper tackles the wave attenuation along with a cylindrical waveguides composed of a left Handed material (LHM), surrounded by a superconducting or metal wall. I used the transcendental equations for both TE and TM waves. I found out that the waveguide supports backward TE and backward TM waves since both permittivity and magnetic permeability of LHM are negative. I also illustrated the dependence of the TE and TM wave attenuation on the wave frequency and the reduced temperature of the superconducting wall (T/Tc). Attenuation constant increases by increasing the wave frequency and it shows higher values at higher T/Tc. Lowest wave attenuation and the best confinement are achieved for the thickest TE waveguide. LHM-superconductor waveguide shows lower wave attenuation than LHM-metal waveguide. 展开更多
关键词 LEFT Handed Material TM waveS TE waveS ATTENUATION constant waveGUIDES SUPERCONDUCTOR Metal
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Performance Comparison of Long-Wave Infrared Imaging Spectrometer Between Dyson Form and Offner Form
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作者 Jiayin Sun Ying Liu +3 位作者 Qiang Sun Chun Li Jian Wang Yang Jiang 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2017年第2期45-50,共6页
In view of the difficulties in traditional long-wave infrared imaging spectrometer which is hard to realize a high signal-to-noise ratio and miniaturization as well under the weak remote sensing signal,Offner convex g... In view of the difficulties in traditional long-wave infrared imaging spectrometer which is hard to realize a high signal-to-noise ratio and miniaturization as well under the weak remote sensing signal,Offner convex grating spectrometer and Dyson concave grating spectrometer,both having concentric structure,are designed and analyzed in the band of 8-12 μm. The diffraction angle expressions of the two spectrometers are obtained and the diffraction characteristics are acquired. Both of the spectrometers are designed in Zemax environment under different F-numbers and different grating constants with the same slit,spatial resolution,spectral resolution and detector. The results show that Dyson grating spectrometer possesses the advantages of higher throughput and smaller volume, and Offner grating spectrometer possesses the advantage of more accessible material and the absence of chromatic aberration. The differences between Dyson form and Offner form show that the former is a better choice in the long-wave infrared imaging spectrometer. 展开更多
关键词 long-wave infrared imaging spectrometer grating constant concentric configuration
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Speed of Gravitation and Electromagnetic Waves through the Dark Energy of Intergalactic Space and Its Implications of a Unified Theory
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作者 Frank R. Tangherlini 《Journal of Modern Physics》 2018年第4期573-583,共11页
The recent finding that gravitational waves (GW170817) traveled at the same speed as electromagnetic (EM) waves (GRB 170817A) from a binary neutron star merger does not necessarily mean that they traveled throughout t... The recent finding that gravitational waves (GW170817) traveled at the same speed as electromagnetic (EM) waves (GRB 170817A) from a binary neutron star merger does not necessarily mean that they traveled throughout their journey at speed c. Some recent works by the author (2015) Journal of Modern Physics, 6, 78-87, and 1360-1370;(2016), 7, 1829-1844;(2017), 8, 622-635 show that the diminished brightness of Type Ia supernovae (SNe Ia) can be explained by assuming that dark energy, instead of having a negative pressure, has an index of refraction n, causing the speed of light through intergalactic space (IGS) to be reduced to c/n, with? n&asymp;1.5. It follows that GWs (not considered in the previous works) would also travel with speed c/n through IGS. However, speed of GWs and EMWs within galaxies themselves is c. A brief review of the model is given, together with other predictions, e.g., new values for the Hubble constant and age of the universe, and necessary absence of correlation of neutrinos with gamma ray bursts (GRBs), in agreement with numerous searches. In the previous works, there were implications of a unified theory. If the model holds, since GWs would experience the same speed reduction as EMWs, this would further support unification. An improved falsification methodology for a previously proposed astronomical test based on discordant redshifts is given. 展开更多
关键词 Speed of GRAVITATIONAL waves Dark Energy HUBBLE constant ABSENCE of Neutrino Correlation with GRBS
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Derivation of Cylindrical Internal-Surface Acoustic Waves and Their Small Gravity Effect
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作者 Philipp G. Kornreich 《Journal of Modern Physics》 2024年第12期2193-2219,共27页
The properties of Cylindrical Internal-Surface Acoustic Waves (CISAW) propagating on the inside surface of a high purity fused quartz tubular fiber are derived from basic principles using a variational method. The CIS... The properties of Cylindrical Internal-Surface Acoustic Waves (CISAW) propagating on the inside surface of a high purity fused quartz tubular fiber are derived from basic principles using a variational method. The CISAW consist of Energy Momentum Packets (EMP) moving in a looping motion. The EMP have mass and are affected by gravity similar to a pendulum bob. The effect of gravity on CISAW is much larger than the effect of gravity in a light wave. Therefore, one can build much smaller CISAW Interferometer Gravity wave Observatories (CIGO) than the present km size Light Interferometer Gravity wave Observatories (LIGO). An array of CIGO can be used to detect gravity wave images. Since the wavelength of gravity waves is much larger than the expected spacing between CIGO array elements this would result in sub-wavelength images. It would be interesting to determine what new discoveries could be made using such an array. 展开更多
关键词 Elastic constant Tensor Continuum Mechanics LAGRANGIAN wave Equation Surface Acoustic waves Newtonian Gravity
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A Simple Approach to Compute Interatomic Force Constant for Mono and Diatomic Semiconductors
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作者 Mohammed Joghlaf Yahya Ababou Salaheddine Sayouri 《Journal of Applied Mathematics and Physics》 2021年第1期11-20,共10页
In this paper, a mathematical relation was found between interatomic Hooke’s force constant and both the bulk modulus and interatomic distance in solid crystals, considering that the forces which have effect on an at... In this paper, a mathematical relation was found between interatomic Hooke’s force constant and both the bulk modulus and interatomic distance in solid crystals, considering that the forces which have effect on an atom are only those resulted from the neighboring atoms, and the forces are subject to Hooke’s law as the deflections of atoms from their equilibrium positions are very small. This work has been applied on some solid semiconducting crystals of diatomic primitive cell, including crystals of mono-atomic primitive cell automatically, by using linear statistical fitting with computer programming and, then, using mathematical analysis, proceeding from the vibrational dispersion relation of solid linear lattice, these two methods have been used in the process in order to support each other and for the result to be satisfying and reasonable. This is a contribution to the process of using computer programming in physics to facilitate mathematical analyses and obtain the required relations and functions by designing and developing appropriate computer programs in line with the macro and micro natures of materials. The importance of this is in enhancing our understanding of the interatomic actions in cells and of the crystal structure of materials in general and semiconductors in particular, as it is a step of the initial steps to facilitate the process of calculating energies and extracting mathematical relations between correlation energy and temperature as well as between sub-fusion and fusion energies with temperature. 展开更多
关键词 Interatomic Force constant Bulk Modulus Vibrational Dispersion Relation Linear Fitting wave Speed
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Design and Implementation of Step-Constant Tapered Slot Antennas for UWB Application
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作者 Mousumi Aktar Md. Masud Rana +1 位作者 Md. Sanwar Hossain Md. Biplob Hossain 《Journal of Sensor Technology》 2019年第4期91-100,共10页
This paper presents the analytical design and high performance of step-constant tapered slot antenna (STSA) for ultra-wideband application. The return loss, radiation pattern, antenna gain, and level of cross polariza... This paper presents the analytical design and high performance of step-constant tapered slot antenna (STSA) for ultra-wideband application. The return loss, radiation pattern, antenna gain, and level of cross polarization of this antenna are presented and analyzed. Utilizing Rogers (RO3006) substrate having a relative permittivity of 6.15, the proposed antenna provides the ultra-wideband (UWB) from 3.1 GHz to 10.6 GHz. It is observed that the return loss and gain are increased with increasing the step size. It has been observed from the simulation results incorporating CST microwave studio commercial software version 2015, the optimum return loss, directivity and gain are ?43 dB, 10.52 dBi and 10.20 dB, respectively, for 15 step size. Therefore, the newly proposed antenna will be a decent candidate for ultra-wideband application. 展开更多
关键词 ANTENNA Gain Voltage STANDING wave Ratio (VSWR) Step constant Tapered SLOT ANTENNA (STSA) Ultra Wideband (UWB) Reflection Coefficient
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Calculations Energy of the (<i>nl</i><sup>2</sup>) <sup>1</sup><i>L<sup>π</sup></i>Doubly Excited States of Two-Electron Systems via the Screening Constant by Unit Nuclear Charge Formalism
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作者 Momar Talla Gning Ibrahima Sakho Malick Sow 《Journal of Modern Physics》 2020年第11期1891-1910,共20页
In this work, the total energies of doubly excited states (<em>ns</em><sup>2</sup>) <sup>1</sup>S<sup>e</sup>, (<em>np</em><sup>2</sup>) <sup&... In this work, the total energies of doubly excited states (<em>ns</em><sup>2</sup>) <sup>1</sup>S<sup>e</sup>, (<em>np</em><sup>2</sup>) <sup>1</sup>D<sup>e</sup>, (<em>nd</em><sup>2</sup>) <sup>1</sup>G<sup>e</sup>, (<em>nf</em><sup>2</sup>) <sup>1</sup>I<sup>e</sup>, (<em>ng</em><sup>2</sup>) <sup>1</sup>K<sup>e</sup>, and (<em>nh</em><sup>2</sup>) <sup>1</sup>M<sup>e</sup> of the helium isoelectronic sequence with Z ≤ 10 are calculated in the framework of the variational method of the Screening Constant by Unit Nuclear Charge (SCUNC). These calculations are performed using a new wavefunction correlated to Hylleraas-type. The possibility of using the SCUNC method in the investigation of high-lying Doubly Excited States(DES) in two-electron systems is demonstrated in the present work in the case of the (<em>nl</em><sup>2</sup>) <sup>1</sup><em>L</em><sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><em>&pi;</em></span></span></span></sup> doubly excited states, where accurate total energies are tabulated up to <em>n</em> = 20. All the results obtained in this paper are in agreement with the values of the available literature and may be useful for future experimental and theoretical studies on the doubly excited (<em>nl</em><sup>2</sup>) <sup>1</sup><em>L</em><sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><em>π</em></span></span></sup> states of two-electron systems. 展开更多
关键词 Doubly Excited States Helium-Like Systems Screening constant by Unit Nuclear Charge (SCUNC) wave Functions Correlated Total Energy
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基于CFAR-ProxSGD车载调频连续波雷达干扰抑制方法
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作者 李家强 刘浩波 +2 位作者 喻庞泽 姚昌华 陈金立 《现代雷达》 北大核心 2025年第7期65-72,共8页
针对车载调频连续波雷达系统中存在的交叉干扰问题,提出了一种基于CFAR-ProxSGD的干扰抑制算法。首先,采用短时傅里叶变换将受干扰的雷达接收信号从时域转换至时频域,并基于一维恒虚警检测器沿各频率点检测干扰位置,通过幅度校正实现初... 针对车载调频连续波雷达系统中存在的交叉干扰问题,提出了一种基于CFAR-ProxSGD的干扰抑制算法。首先,采用短时傅里叶变换将受干扰的雷达接收信号从时域转换至时频域,并基于一维恒虚警检测器沿各频率点检测干扰位置,通过幅度校正实现初步干扰抑制。然后,结合干扰信号的时域稀疏特性与目标回波的频域稀疏特性,利用近端次梯度下降法对残余干扰进行迭代优化处理,最终实现干扰信号的消除和信号的重构。为验证算法性能,通过软件平台进行了多目标多干扰源场景的数值仿真,并基于AWR1843毫米波雷达与DCA1000数据采集系统获取实测数据。实验结果表明,该算法能够有效抑制干扰信号且降低频域基底噪声,提高交通环境下毫米波雷达系统的目标探测能力。 展开更多
关键词 毫米波雷达 干扰抑制 恒虚警检测 次梯度下降 软阈值
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A Realistic Interpretation of Quantum Wavefunctions as Temperature Dependent Vacuum Polarization Waves
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作者 Gianpaolo Bei Roberto Li Voti 《Journal of Modern Physics》 2022年第6期892-917,共26页
We discuss in this paper a novel interpretation of Born rule as an approximated thermodynamic law which emerges from the interaction of a quantum system with a non-stationary thermal bath associated to vacuum fluctuat... We discuss in this paper a novel interpretation of Born rule as an approximated thermodynamic law which emerges from the interaction of a quantum system with a non-stationary thermal bath associated to vacuum fluctuations induced by external environment radiation. In particular we assume that vacuum polarization is a real non relativistic phenomena caused by hidden vacuum charge oscillations which diffuses heat energy in a dispersive and dissipative dielectric medium with a temperature dependent speed of propagation. We propose a model which couples vacuum wavefunctions to vacuum charge fluctuations and we deduce a temperature dependent running fine structure constant function proportional, at first approximation, to the squared of the effective electron charge and compatible with known experimental data. We interpret the vacuum symmetry breaking energy fluctuations induced in scattering experiments of particle physics and in laser assisted nuclear reactions as thermal quasi-monochromatic beams produced by the decay of hidden non equilibrium massive photons propagating with a variable light speed. We suggest, exploiting an old analogy between plasmons and pseudo Goldstone bosons, to interpret heat diffusion of this non relativistic polarized vacuum as a real De Broglie electromagnetic scalar wave associated to the radiation emitted by the hidden massive photons with acceleration proportional to vacuum Unruh like temperature. We predict a temperature dependent deviation from Coulomb law and a generalized dispersive law of these hidden unstable photons that could be revealed as not stationary coloured noise in experiments on anomalous heat diffusions associated to the decay of unstable accelerated pairs produced in nuclear physics experiments. We discuss then how our proposal of a temperature dependent non relativistic vacuum polarization might be applied to deduce a dynamic generalization of Born rule based on a realistic interpretation of quantum wavefunctions as averaged electromagnetic waves of hidden massive photons. Finally we suggest to test our time asymmetric model looking for very fast oscillating polarization thermal waves emitted during the not instantaneous wavefunction collapse and revealed as not stationary bulk heating effects in experiments on accelerated conductors and nanoconductors. 展开更多
关键词 Non Relativistic Vacuum Pilot wave Hidden Temperature Dependent Vacuum Index Hidden Unstable Massive Photons Space Time Dependent Vacuum Temperature Oscillations Temperature Dependent Running Fine Structure constant Vacuum Temperature Induced wave Collapse Generalized Born Rule
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透视雷达在混凝土结构缺陷识别中的应用 被引量:2
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作者 王若晨 魏晓斌 汪晟 《工程质量》 2025年第2期53-57,共5页
透视雷达,也被称为探地雷达或地质雷达,是一种无损检测技术。它的优势在于其强大的穿透力、丰富的接收信息以及敏锐的介电常数反应等方面。近年来,随着科技的不断进步和国内外对其应用研究的深入,透视雷达在土木工程领域得到了广泛的应... 透视雷达,也被称为探地雷达或地质雷达,是一种无损检测技术。它的优势在于其强大的穿透力、丰富的接收信息以及敏锐的介电常数反应等方面。近年来,随着科技的不断进步和国内外对其应用研究的深入,透视雷达在土木工程领域得到了广泛的应用。然而,钢筋混凝土结构在透视雷达检测中面临着一些挑战,主要是钢筋干扰导致雷达成像难以识别,进而影响内部缺陷的检测。论文通过在混凝土内部预埋泡沫板的方式来实现雷达图像识别,针对不同程度的泡沫板大小和深度,采用不同的测线。同时,提出了优化处理流程的方法:选择合适的测量路径并忽略缺陷区域厚度的具体数值,以提高分析效率。 展开更多
关键词 透视雷达 电磁波 直达波 介电常数 灰度图
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基于ADMM算法优化的矩形网格隐式有限差分波动方程正演模拟
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作者 王文化 文晓涛 +2 位作者 吴昊 杨吉鑫 匡胤 《地球物理学报》 北大核心 2025年第2期680-695,共16页
有限差分(FD)法广泛用于地震勘探领域的波动方程数值模拟.由于存在“饱和效应”,利用Taylor级数展开法(TE)计算高阶FD系数会在高频和粗网格条件下产生明显的数值频散.一般的常系数优化法能在较大波数区间取得更高的数值精度,但缺乏对中... 有限差分(FD)法广泛用于地震勘探领域的波动方程数值模拟.由于存在“饱和效应”,利用Taylor级数展开法(TE)计算高阶FD系数会在高频和粗网格条件下产生明显的数值频散.一般的常系数优化法能在较大波数区间取得更高的数值精度,但缺乏对中、低波数区间的误差约束;此外,它们大多沿单空间方向压制数值频散,因而无法缓解矩形网格模板的数值各向异性.本文基于隐式FD模板发展了一种多空间方向优化的波动方程正演模拟方法,以同时解决数值频散和数值各向异性问题.针对实用性更强的矩形网格单元,本文基于L_(1)范数建立目标函数并增加波传播角约束以减小数值各向异性,然后运用交替方向乘子法(ADMM)求解优化问题从而实现提高模拟精度的目的.理论误差曲线分析表明,相比传统TE方法和其他单向L_(1)范数、L_(2)范数、L_(∞)范数优化方法,本文基于L_(1)范数的多向优化方法在中、低波数区间具有最小的绝对误差,同时能更好的均衡各个方位角之间的误差分布.均匀介质、Marmousi-2地质模型的正演模拟算例均证明本文所提出的方法比其他三种优化方法在减小长时程测试下的误差积累方面更有优势. 展开更多
关键词 隐式有限差分 矩形网格 波动方程正演 常系数优化法 交替方向乘子法
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电位驱动的Pt状态变化对PEMFC阴极碳载体腐蚀的催化作用
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作者 李彬琪 周芬 +1 位作者 张慧 潘牧 《电源技术》 北大核心 2025年第12期2602-2610,共9页
质子交换膜燃料电池(PEMFCs)阴极碳载体的电化学腐蚀问题严重制约其寿命,而铂(Pt)催化剂的氧化状态与碳腐蚀行为密切相关。通过非色散红外光谱(NDIR)实时监测CO_(2)释放特征,结合三角波循环电位与恒电位测试,系统探究了Pt/C电极和纯碳... 质子交换膜燃料电池(PEMFCs)阴极碳载体的电化学腐蚀问题严重制约其寿命,而铂(Pt)催化剂的氧化状态与碳腐蚀行为密切相关。通过非色散红外光谱(NDIR)实时监测CO_(2)释放特征,结合三角波循环电位与恒电位测试,系统探究了Pt/C电极和纯碳电极在不同电位驱动下的碳腐蚀机制。三角波电位循环工况下Pt/C电极的碳腐蚀速率存在5个特征峰,本文从中识别出7个关键特征电位:正向循环特征电位TP1、TP2、TP3和TP4分别为0.20、0.55、0.70和1.00 V,逆向循环特征电位TP5、TP6和TP7分别为1.00、0.75和0.30 V。恒电位运行工况下,不同于纯碳电极的碳腐蚀速率随恒电位的上升单调增大,Pt/C电极的碳载体腐蚀速率随恒电位的上升出现起伏,用特征值电位替代该电位下腐蚀速率数值,其大小排序为1.00 V>(0.50 V≈0.70 V)>0.90 V>0.80 V,表明燃料电池运行要避免较高和相对较低的运行电位。结合不同电位下纯碳电极和Pt电极表面化学状态分析,结果表明Pt0状态的Pt对碳载体腐蚀的催化活性最高,随着电位上升Pt的氧化程度加深,其对碳载体腐蚀的催化活性也逐渐减弱。1.00 V以上长时间运行,Pt表面形成的稳定氧化物对碳腐蚀的催化作用可忽略不计。 展开更多
关键词 质子交换膜燃料电池 碳载体腐蚀 三角波循环电位 恒电位 特征电位
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便携式物联网体表神经电调控镇痛系统
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作者 应豪磊 杜佳昊 +1 位作者 方凡夫 石萍 《生物医学工程研究》 2025年第5期318-326,共9页
为满足移动居家镇痛治疗的需求,实现医疗资源的高效利用。本研究融合物联网和体表神经电调控技术,研发了一款便携式物联网体表神经电调控镇痛系统。该系统涵盖设备、云平台、移动终端三部分,设备在连接无线接入点(AP)后,可将刺激参数同... 为满足移动居家镇痛治疗的需求,实现医疗资源的高效利用。本研究融合物联网和体表神经电调控技术,研发了一款便携式物联网体表神经电调控镇痛系统。该系统涵盖设备、云平台、移动终端三部分,设备在连接无线接入点(AP)后,可将刺激参数同步至云平台和移动终端,同时,云平台和移动终端可下发命令至设备,三方协同实现超远程控制与系统的动态管理。实验表明,该设备能稳定输出设定的电刺激参数,其平均误差均小于4.1%。经电调控镇痛后,受试者疼痛诱发点的机械压痛阈值较镇痛前显著提升。本研究研发的便携式物联网体表神经电调控镇痛系统能有效提升移动居家镇痛治疗效果,具有较高的应用价值。 展开更多
关键词 物联网 神经电调控 恒流 疏密波 镇痛
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