arXiv subjects

Qingshan Zhang

Publications and source records attributed to Qingshan Zhang.

6 recordsLinked to original sources

arXiv2026

A Pilot Kinematic Study on the Forehand Reverse Flick: Feasibility of a Novel Short Return Technique in Table Tennis

Background Following changes in table tennis ball materials, offensive returns have become more important for initiating sustained topspin offense. However, using the backhand flick (BF) to return forehand short balls often increases the difficulty of recovery and continuity, revealing a technical gap. This study preliminarily verified a novel forehand short return technique, the forehand reverse flick (FRF), and analyzed its similarities and differences with the BF. Methods Four elite athletes completed seven consecutive days of FRF specific training. Infrared motion capture and ultra-high-speed cameras were used to collect data on racket kinematics, movement duration, and ball performance. Results The success rate of the FRF increased steadily, reaching 86%. Racket trajectories of the two techniques were highly similar along the X (r = 1) and Y (r = 0.99) axes but differed along the Z (r = -0.04) axis. Racket and ball velocities were comparable between techniques, whereas the FRF showed lower resultant acceleration (approximately 265.57 m/s) and required about 0.03 s more for movement duration. Ball velocity was comparable between techniques, for the ball spin, the FRF generated lower spin (approximately 76.61 r/s) about 64% of the BF value (approximately 120.13 r/s). The highest participant mean spin rate reached 93 r/s, about 77% of the BF mean. Conclusion Overall, the FRF was found to have favorable learnability and training value, with potential for further optimization and competitive application.

physics.med-ph↗

arXiv2021

The decay and stability of solutions for the 3D density-dependent incompressible Boussinesq system

This paper deals with stability and the large-time decay to any given global smooth solutions of the 3D density-dependent incompressible Boussinesq system. The decay rate for solutions of the corresponding Cauchy problem is obtained in this work. With the aid of this decay rate, it is shown that a small perturbation of initial data $(\overline{a}_0,\overlineθ_0, \overline{u}_0)$ still generates a global smooth solution to the density-dependent Boussinesq system, and this solution keeps close to the reference solution.

math.AP↗

arXiv2020

A high entropy alloy as very low melting point solder for advanced electronic packaging

SnBiInZn based high entropy alloy (HEA) was studied as a low reflow temperature solder with melting point around 80 oC. The wetting angle is about 52o after reflow at 100 oC for 10 min. The interfacial intermetallic compound (IMC) growth kinetics was measured to be ripening-control with a low activation energy about 18.0 kJ/mol, however, the interfacial reaction rate is very slow, leading to the formation of a very thin IMC layer. The low melting point HEA solder has potential applications in advanced electronic packaging technology, especially for bio-medical devices.

physics.app-ph↗

arXiv2018

Boundedness and stabilization in a two-species chemotaxis system with signal absorption

This paper is concerned with the Neumann initial-boundary value problem for the two-species chemotaxis system with consumption of chemoattractant \begin{equation*} u_t=Δu-χ_1\nabla\cdot(u\nabla w), \end{equation*} \begin{equation*} v_t=Δv-χ_2\nabla\cdot(v\nabla w), \end{equation*} \begin{equation*} w_t=Δw-(αu+βv)w \end{equation*} in a smooth bounded domain $Ω\subset\mathbb{R}^n$ ($n\geq2$), where the parameters $χ_1$, $χ_2$, $α$ and $β$ are positive. It is proved that if \begin{equation*} \max\{χ_1,χ_2\}\|w(x,0)\|_{L^{\infty}(Ω)}<\sqrt{\frac{2}{n}}π\end{equation*} the problem possesses a unique global classical solution that is uniformly bounded. Moreover, we prove that \begin{equation*} u(x,t)\to\frac{1}{|Ω|}\int_Ωu(x,0),\quad v(x,t)\to\frac{1}{|Ω|}\int_Ωv(x,0)\quad\mbox{and}\quad w(x,t)\to0\quad\mbox{as}\ t\to\infty \end{equation*} uniformly with respect $x\inΩ$.

math.AP↗

arXiv2015

Boundedness in a quasilinear fully parabolic Keller-Segel system with logistic source

This paper deals with the Neumann boundary value problem for the system $$u_t=\nabla\cdot\left(D(u)\nabla u\right)-\nabla\cdot\left(S(u)\nabla v\right)+f(u) ,\quad x\inΩ,\ t>0$$ $$v_t=Δv-v+u,\quad x\inΩ,\ t>0$$ in a smooth bounded domain $Ω\subset\mathbb{R}^n$ $(n\geq1)$, where the functions $D(u)$ and $S(u)$ are supposed to be smooth satisfying $D(u)\geq Mu^{-α}$ and $S(u)\leq Mu^β$ with $M>0$, $α\in\mathbb{R}$ and $β\in\mathbb{R}$ for all $u\geq1$, and the logistic source $f(u)$ is smooth fulfilling $f(0)\geq0$ as well as $f(u)\leq a-μu^γ$ with $a\geq0$, $μ>0$ and $γ\geq1$ for all $u\geq0$. It is shown that if $α+2β<γ-1+\frac{2}{n}$, for $1\leqγ<2$ and $α+2β<γ-1+\frac{4}{n+2}$, for $γ\geq2$, then for sufficiently smooth initial data the problem possesses a unique global classical solution which is uniformly bounded.

math.AP↗

arXiv2015

Global weak solutions for the three-dimensional chemotaxis-Navier-Stokes system with nonlinear diffusion

We consider an initial-boundary value problem for the incompressible chemotaxis-Navier-Stokes equations generalizing the porous-medium-type diffusion model $ \quad n_t+u\cdot\nabla n=Δn^m-\nabla\cdot(nχ(c)\nabla c), $ $ \quad c_t+u\cdot\nabla c=Δc-nf(c), $ $ \quad u_t+κ(u\cdot\nabla)u=Δu+\nabla P+n\nablaΦ, $ $ \quad \nabla\cdot u=0, $ in a bounded convex domain $Ω\subset\mathbb{R}^3$. It is proved that if $m\geq\frac{2}{3}$, $κ\in\mathbb{R}$, $0<χ\in C^2([0,\infty))$, $0\leq f\in C^1([0,\infty))$ with $f(0)=0$ and $Φ\in W^{1,\infty}(Ω)$, then for sufficiently smooth initial data $(n_0, c_0, u_0)$ the model possesses at least one global weak solution.

math.AP↗