arXiv subjects

Zhang Yong

Publications and source records attributed to Zhang Yong.

8 recordsLinked to original sources

arXiv2025

Real-Time Foreign Object Recognition Based on Improved Wavelet Scattering Deep Network and Edge Computing

The increasing penetration rate of new energy in the power system has put forward higher requirements for the operation and maintenance of substations and transmission lines. Using the Unmanned Aerial Vehicles (UAV) to identify foreign object in real time can quickly and effectively eliminate potential safety hazards. However, due to the limited computation power, the captured image cannot be real-time processed on edge devices in UAV locally. To overcome this problem, a lightweight model based on an improved wavelet scatter deep network is proposed. This model contains improved wavelet scattering network for extracting the scatter coefficients and modulus coefficients of image single channel, replacing the role of convolutional layer and pooling layer in convolutional neural network. The following 3 fully connected layers, also constituted a simplified Multilayer Perceptron (MLP), are used to classify the extracted features. Experiments prove that the model constructed with biorthogonal wavelets basis is able to recognize and classify the foreign object in edge devices such as Raspberry Pi and Jetson Nano, with accuracy higher than 90% and inference time less than 7ms for 720P (1280*720) images. Further experiments demonstrate that the recognition accuracy of our model is 1.1% higher than YOLOv5s and 0.3% higher than YOLOv8s.

eess.IV↗

arXiv2024

Periodic travelling interfacial electrohydrodynamic waves: bifurcation and secondary bifurcation

In this paper, two-dimensional periodic capillary-gravity waves travelling under the effect of a vertical electric field are considered. The full system is a nonlinear, two-layered and free boundary problem. The interface dynamics arises from the coupling between the Euler equations for the lower fluid layer and an electric contribution from the upper gas layer. To investigate the electrohydrodynamic wave interactions, we first introduce the naive flattening technique to transform the free boundary problem into a fixed boundary problem. Then we prove the existence of the small-amplitude electrohydrodynamic waves with constant vorticity $γ$ by using local bifurcation theory. Moreover, we prove that these electrohydrodynamic waves are formally stable in linearized sense. Furthermore, we obtain a secondary bifurcation curve that emerges from the primary branch at a nonlaminar solution as $E_0$ being close to some special value. This secondary bifurcation curve consists of ripples solutions on the interface of a conducting fluid under normal electric fields. As far as we know, this new phenomenon in electrohydrodynamics (EHD) is first established mathematically. It is worth noting that the electric field $E_0$ plays a key role to control the shapes and types of waves on the interface.

math.AP↗

arXiv2024

The existence of stratified linearly steady two-mode water waves with stagnation points

This paper focuses on the analysis of stratified steady periodic water waves that contain stagnation points. The initial step involves transforming the free-boundary problem into a quasilinear pseudodifferential equation through a conformal mapping technique, resulting in a periodic function of a single variable. By utilizing the theorems developed by Crandall and Rabinowitz, we establish the existence and formal stability of small-amplitude steady periodic capillary-gravity water waves in the presence of stratified linear flows. Notably, the stability of bifurcation solution curves is strongly influenced by the stratified nature of the system. Additionally, as the Bernoulli's function $β$ approaches critical values, we observe that the linearized problem exhibits a two-dimensional kernel. Consequently, we apply a bifurcation theorem due to Kielhöfer that incorporates multiple-dimensional kernels and parameters, which enables us to establish the existence of two-mode water waves. As far as we know, the two-mode water waves in stratified flow are first constructed by us. Finally, we demonstrate the presence of internal stagnation points within these waves.

math.AP↗

arXiv2024

The global bifurcation of periodic internal waves with point vortex and capillary effect

In this paper, we first construct two-dimensional periodic interface waves with point vortex and capillary effect and then obtain the global structure of the set of solutions. This is done using the local and global bifurcation argument. Especially, we establish a global continuation theorem by using the degree for $C^1$ Fredholm mappings. As far as we know, the global result is new and general, which is promising to deal with other new phenomena in water waves.

math.AP↗

arXiv2021

Continuity properties of the data-to-solution map and ill-posedness for a two-component Fornberg-Whitham system

This work studies a two-component Fornberg-Whitham (FW) system, which can be considered as a model for the propagation of shallow water waves. It's known that its solutions depend continuously on their initial data from the local well-posedness result. In this paper, we further show that such dependence is not uniformly continuous in $H^{s}(R)\times H^{s-1}(R)$ for $s>\frac{3}{2}$, but Höler continuous in a weaker topology. Besides, we also establish that the FW system is ill-posed in the critical Sobolev space $H^{\frac{3}{2}}(R)\times H^{\frac{1}{2}}(R)$ by proving the norm inflation.

math.AP↗

arXiv2019

Arbitrarily Weak Nonlinearity Can Destroy the Anderson Localization

Whether the Anderson localization can survive from the weak enough nonlinear interaction is still an open question. In this Letter, we study the effect of nonlinear interaction on disordered chain based on the wave turbulence theory. It is found that the equipartition time $T_{eq}$ is inversely proportional to the square of the nonlinearity strength $λ$, i.e., $T_{eq}\proptoλ^{-2}$, in thermodynamic limit. This result has two fundamentally important consequences. First, the Anderson localized modes can not survive from arbitrarily weak nonlinearity. Secondly, contrary to popular belief, disorder can lead to a more fast thermalization in the weak nonlinear region, which is due to the emergence of three-wave resonance.

cond-mat.stat-mech↗

arXiv2016

The LAMOST spectroscopic survey of star clusters in M31. II. Metallicities, ages and masses

We select from Paper I a sample of 306 massive star clusters observed with the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) in the vicinity fields of M31 and M33 and determine their metallicities, ages and masses. Metallicities and ages are estimated by fitting the observed integrated spectra with stellar synthesis population (SSP) models with a pixel-to-pixel spectral fitting technique. Ages for most young clusters are also derived by fitting the multi-band photometric measurements with model spectral energy distributions (SEDs). The estimated cluster ages span a wide range, from several million years to the age of the universe. The numbers of clusters younger and older than 1 Gyr are respectively 46 and 260. With ages and metallicities determined, cluster masses are then estimated by comparing the multi-band photometric measurements with SSP model SEDs. The derived masses range from $\sim 10^{3}$ to $\sim 10^7$ $M_{\odot}$, peaking at $\sim 10^{4.3}$ and $\sim 10^{5.7}$ $M_{\odot}$ for young ($< 1$ Gyr) and old ($>1$ Gyr) clusters, respectively. Our estimated metallicities, ages and masses are in good agreement with available literature values. Old clusters richer than [Fe/H] $\sim -0.7$ dex have a wide range of ages. Those poorer than [Fe/H] $\sim -0.7$ dex seem to be composed of two groups, as previously found for Galactic GCs -- one of the oldest ages with all values of metallicity down to $\sim -2$ dex and another with metallicity increasing with decreasing age. The old clusters in the inner disk of M\,31 (0 -- 30 kpc) show a clear metallicity gradient measured at $-0.038\pm0.023$ dex/kpc.

astro-ph.SR↗

arXiv2007

A Ku-Band Novel Micromachined Bandpass Filter with Two Transmission Zeros

This paper presents a micromachined bandpass filter with miniature size that has relatively outstanding performance. A silicon-based eight-order microstrip bandpass filter is fabricated and measured. A novel design method of the interdigital filter that can create two transmission zeros is described. The location of the transmission zeros can be shifted arbitrarily in the stopband. By adjusting the zero location properly, the filter provides much better skirt rejection and lower insertion loss than a conventional microstrip interdigital filter. To reduce the chip size, through-silicon-substrate-via-hole is used. Good experimental results are obtained.

cs.OH↗