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961.
In this paper, the traveling wave problem for a two-species competition reaction–diffusion–chemotaxis Lotka–Volterra system is investigated. Upper and lower solutions method and fixed point theory are employed to show the existence of traveling wave solutions connecting the coexistence constant steady state with zero state for all large enough wave speed c, and conversely, when c is small, we prove there is no traveling wave solution.  相似文献   
962.
    
This paper is concerned with the large time behavior of the solutions for 1D radiation hydrodynamic limit model without viscosity and its asymptotic stability of the viscous contact discontinuity wave under the smallness assumption of the strength of the contact wave and initial perturbations. The present pressure includes a fourth-order term about the absolute temperature from radiation effect which brings the main difficulty. Furthermore, the dissipative of the system is weaker for the lack of viscosity. All these make the problem more challenging. The prove is mainly based on the energy method, including normal and radial directions energy estimates.  相似文献   
963.
    
With the development of autonomous driving technology, lidar technology has also been rapidly developed. As one of the Lidar systems, Frequency Modulated Continuous Wave （FMCW） calculates the distance of the target by detecting the beat signal frequency of the local light and the signal light. It can also calculate the velocity of the target by the optical Doppler effect. Compared with traditional time-of-flight lidar, FMCW lidar has many advantages. First, FMCW utilizes the principle of coherent detection to filter out the background noise effectively. The peak power of the continuous-wave is small, which is safe for human eyes. Secondly, the FMCW system can detect both the speed and distance of the target. Thirdly, when it comes to long-range detection, the FMCW system doesn't need a Single photon detector, so it can reduce the cost. However, in the field of autonomous driving, with the increase of imaging speed, the laser modulation rate has to increase, and then the nonlinearity of the laser source rises. as a result, the frequency of the beat signal varies greatly and the precision and resolution of the detection become worse. The resampling method, photoelectric negative feedback method, and pre-correction method can solve this problem. Considering the cost of the FMCW system, we use the pre- previous studies based on the auto-driving application. This paper studies the nonlinear pre-correction of DFB laser in high-speed tuning by simulation and experiments at the same time. Here, we first briefly introduce the principle of FMCW detection and analyze the influence of optical nonlinearity on detection precision. Secondly, we carry out the DFB simulation and use the Simulink toolbox of MATLAB to establish the temperature dominated tuning model of the DFB laser. Then, we assume the parameters of the DFB laser and analyze the nonlinearity distortion with the modulation rate of 100 kHz. Because the temperature hysteresis has most of the influence on optical nonlinearity, here, we do not consider the carriers' effects on frequency turning. After that, we use the iterative algorithm to correct the nonlinearity of optical frequency for many times and analyze the convergence of this algorithm. The correctness of the DFB module and iterative algorithm is verified. There are three steps in the iterative algorithm. At first, we calculate the optical frequency by STFT or Hilbert transform from the beat signal, then we calculate the differential value between two adjacent time points in the arbitrary wave generator and figure out the relative value of each point. At last, after the linear transform, we can get the real value of arbitrary wave generator at each time. Based on the simulation, we first set up an experimental platform to correct the nonlinearity of the existing DFB laser with two times of iterations. To analyze the effect of the nonlinear correction method, we detect two adjacent targets with the distance of 51.5 m and 60.5 m. The correctness of the simulation model and an iterative algorithm is verified. The results of the simulation and experiment show that the iterative method can effectively reduce the nonlinearity of the light source. With the increase of the number of iteration times, the nonlinearity improvement of the light source becomes more obvious. The nonlinearity of the lower and upper area of the optical frequency of the light source decreases from 0.050 0 and 0.020 0 to 0.004 2 and 0.002 6 respectively after two times iterations, which is consistent with the simulation. The detection results of two adjacent targets show that the 3 dB bandwidth of the detection system is effectively reduced after correction, which proves the feasibility of the iterative algorithm and modulation module.  相似文献   
964.
    
In this paper, we consider the following class of wave equation involving fractional p-Laplacian with logarithmic nonlinearity u t t + ( − Δ ) p s u = | u | q − 2 u log ( | u | ) in Ω , t > 0 , u = 0 in R N ∖ Ω , t > 0 , u ( x , 0 ) = u 0 ( x ) , u t ( x , 0 ) = v 0 ( x ) in Ω , $$begin{equation*} hspace*{4pc}{leftlbrace defeqcellsep{&}begin{array}{llc}u_{tt}+(-Delta )^{s}_{p}u=|u|^{q-2}ulog (|u|) & text{in} & Omega ,;t>0 , [3pt] u =0 & text{in} & mathbb {R}^{N}backslash Omega ,;t > 0, [3pt] u(x,0)=u_{0}(x),,,,,u_{t}(x,0)=v_{0}(x)& text{in} &Omega , end{array} right.} end{equation*}$$ where Ω ⊂ R N ( N ≥ 1 ) $Omega subset mathbb {R}^N , (Nge 1)$ is a bounded domain with Lipschitz boundary, s ∈ ( 0 , 1 ) $sin (0,1)$ , 2 ≤ p < p s ∗ $2le p< p^{*}_{s}$ , and p s ∗ = N p N − s p $p^{*}_{s}=frac{Np}{N-sp}$ is the critical exponent in the Sobolev inequality. First, via the Galerkin approximations, the existence of local solutions are obtained when 1 < q < p s ∗ $1<q<p_{s}^{*}$ . Next, by combining the potential well theory with the Nehari manifold, we establish the existence of global solutions when p < q < p s ∗ $p<q<p_{s}^{*}$ . Then, via the Pohozaev manifold, the existence of global solutions are obtained when 1 < q < p s ∗ $1<q<p_{s}^{*}$ . By virtue of a differential inequality technique, we prove that the local solutions blow-up in finite time with arbitrary negative initial energy and suitable initial values. Moreover, we discuss the asymptotic behavior of solutions as time tends to infinity. Here, we point out that the main difficulty is the lack of logarithmic Sobolev inequality concerning fractional p-Laplacian.  相似文献   
965.
    
Single electrochemical impacts of Shewanella oneidensis MR-1 Gram-negative electroactive bacteria onto ultramicroelectrode surfaces are reported and in-depth analysed. Chronoamperometry measurements recorded onto 10 μm-diameter Pt and 7 μm-diameter carbon fibre disk ultramicroelectrodes in a 20 mM potassium ferrocyanide aqueous solution in the presence of living bacteria show an electrostatic attraction of Shewanella cells onto the ultramicroelectrode surface polarized at +0.8 V vs Ag/AgCl. Single current step events analysis and atomic force microscopy experiments confirm the adsorption of living bacteria following the collision onto the ultramicroelectrode surface. The bacteria washing step before the chronoamperometry measurements leads to lower current step events related to the smaller size of the living cells. The electrostatic attraction of the negatively charged bacteria onto the positively charged ultramicroelectrode surface polarized at the oxidation potential of ferrocyanide is clearly demonstrated.  相似文献   
966.
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Yao-Pu Lang 《中国物理 B》2023,32(1):17802-017802
This paper puts forward a novel method of measuring the thin period-structure-film thickness based on the Bloch surface wave (BSW) enhanced Goos-Hänchen (GH) shift in one-dimensional photonic crystal (1DPC). The BSW phenomenon appearing in 1DPC enhances the GH shift generated in the attenuated total internal reflection structure. The GH shift is closely related to the thickness of the film which is composed of layer-structure of 1DPC. The GH shifts under multiple different incident light conditions will be obtained by varying the wavelength and angle of the measured light, and the thickness distribution of the entire structure of 1DPC is calculated by the particle swarm optimization (PSO) algorithm. The relationship between the structure of a 1DPC film composed of TiO2 and SiO2 layers and the GH shift, is investigated. Under the specific photonic crystal structure and incident conditions, a giant GH shift, 5.1×103 times the wavelength of incidence, can be obtained theoretically. Simulation and calculation results show that the thickness of termination layer and periodic structure bilayer of 1DPC film with 0.1-nm resolution can be obtained by measuring the GH shifts. The exact structure of a 1DPC film is innovatively measured by the BSW-enhanced GH shift.  相似文献   
967.
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Ying-Dong Nie 《中国物理 B》2023,32(1):18702-018702
Owing to the good adjustability and the strong near-field enhancement, surface plasmons are widely used in optical force trap, thus the optical force trap can achieve excellent performance. Here, we use the Laguerre-Gaussian beam and a plasmonic gold ring to separate enantiomers by the chiral optical force. Along with the radial optical force that traps the particles, there is also a chirality-sign-sensitive lateral force arising from the optical spin angular momentum, which is caused by the interaction between optical orbit angular momentum and gold ring structure. By selecting a specific incident wavelength, the strong angular scattering and non-chiral related azimuthal optical force can be suppressed. Thus the chiral related azimuthal optical force can induce an opposite orbital rotation of the trapped particles with chirality of different sign near the gold ring. This work proposes an effective approach for catchingand separating chiral enantiomers.  相似文献   
968.
    
Accurate volumetric photoacoustic image reconstruction requires ultrasonic detection with sufficient sensitivity to pressure transients over a broad spectral bandwidth. By using the ultrafast temporal dynamics and high-sensitivity responses to refractive index changes of optical surface waves, a structureless ultrasonic sensor is proposed for photoacoustic impulse measurement that is manufactured simply by covering a ubiquitous bare glass with several drops of water. Ultrasensitive photoacoustic detection with a broadband frequency response is achieved by converting the photoacoustically modulated phase shift in the optical reflection into a time-varying polarization. This sensor achieves noise-equivalent pressure sensitivity at ≈93 Pa while maintaining an acoustic bandwidth of ≈174 MHz. Incorporation of the transparent sensor into an optical-resolution photoacoustic microscope enables reflection-mode 3D imaging with isometric spatial resolution on the micrometer scale. Label-free volumetric visualizations of adult zebrafish are obtained in vivo. The favorable performance of the proposed sensor offers considerable potential for advancement of biomedical photoacoustic investigations.  相似文献   
969.
    
The emission of resonant radiation from temporal solitary waves—also known as dispersive wave generation—allows efficient energy transfer to far-distant spectral domains. This coherent radiation can deliver large spectral densities at selected wavelengths once control over the individual soliton is achieved. Here, the concepts of few-mode operation and local temperature tuning are combined for precise steering of cascaded dispersive wave generation in liquid-core optical fibers. By exciting higher-order TM and TE modes with femtosecond pulses at 1600 nm, the generation of two dispersive waves tunable by up to 33 nm K−1 through adjusting a selected part of the waveguide is observed. Sophisticated soliton-driven nonlinear dynamics arising from thermally transitioning from anomalous to all-normal dispersion with temperature changes of only a few Kelvin have been found, including soliton steering, soliton breakdown, and soliton post-fission tuning. All experimental results are verified by nonlinear simulations and semi-analytic phase-matching calculations, overall providing a cost-effective and practical toolbox for discovering unexplored states of light as well as for developing dynamically tunable broadband light sources.  相似文献   
970.
    
We investigate the effects of long-range interactions on the spin wave spectra and the competition between magnetic phases on a frustrated square lattice with large spin S. Applying the spin wave theory and assisted with symmetry analysis, we obtain analytical expressions for spin wave spectra of competing Neel and (π, 0) stripe states of systems containing any-order long-range interactions. In the specific case of long-range interactions with power-law decay, we find surprisingly that the staggered long-range interaction suppresses quantum fluctuation and enlarges the ordered moment, especially in the Neel state, and thus extends its phase boundary to the stripe state. Our findings illustrate the rich possibilities of the roles of long-range interactions, and advocate future investigations in other magnetic systems with different structures of interactions.  相似文献   
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