The buoyancy-driven natural convection induced by submerged thermal vertical pipes acts as a passive thermal pump without moving parts, characterised by efficient heat transfer. It comprises three key components: natural convection inside the pipe, a thermal plume above the pipe exit and a radial intrusion flow along the upper free surface. Our previous work (Nie & Xu 2022 J. Fluid Mech., vol. 937, A29) investigated transient natural convection in a vertical pipe for fluids with a Prandtl number (${\textit{Pr}}$) less than unity. In this study we extend the scaling analysis to water (${\textit{Pr}}\gt 1$), which exhibits fundamentally different dynamics due to the dominance of viscous diffusion over thermal diffusion. We identify three distinct flow configurations, each undergoing a transient development before reaching a fully developed state: (i) the boundary layer flow; (ii) the bulk momentum flow with thermal boundary layer, characterised by a merged velocity layer but a distinct thermal layer; and (iii) the pipe flow resulting from the simultaneous merging of both the velocity and thermal boundary layers. Scaling laws governing the flow and heat transfer across these regimes are derived. Moreover, scaling analyses for the external thermal plume and the radial intrusion flow are also performed. All scaling laws are validated, for the axisymmetric and laminar regime, by extensive numerical simulations.

In this article, by utilizing the properties of elliptic functions, we characterize the meromorphic solutions of Fermat-type functional equations $f(z)^{n}+f(L(z))^{m}=1$ over the complex plane $\mathbb {C}$, where $L(z)$ is a nonconstant entire function, and m and n are two positive integers. As applications, we also investigate the meromorphic solutions of Fermat-type difference and q-difference equations.

Laser-driven plasma wakefield acceleration (LWFA) offers exceptionally high acceleration gradients and can produce high-brightness electron beams. However, the laser-to-electron energy conversion efficiency typically remains limited to a few percent. Theoretically, the self-mode transition from LWFA to beam-driven plasma wakefield acceleration (PWFA) provides a pathway for fully utilizing the laser energy. Here, we demonstrate the single-stage LPWFA (hybrid LWFA–PWFA) scheme, validated through comparative experiments using a 300 TW tightly focused laser interacting with sub-critical density nitrogen gas targets. The experiments produce an electron beam with charge of approximately 31 nC above 6 MeV and approximately 116 nC above 2 MeV. The laser-to-electron energy conversion efficiency is approximately 6.1% (>6 MeV) and 16.4% (>2 MeV), respectively. Particle-in-cell simulations confirm that the single-stage LPWFA mechanism depletes the laser energy and enables continual electron injection. This high-charge, multi-MeV electron beam has great value in the generation of high-brightness $\unicode{x3b3}$-rays and high-flux neutron sources.

Radio recombination line (RRL) maser is a useful tool to study massive star formation regions with ionised gas close to new born massive stars. Masers often show sharp line profiles and/or extreme narrow widths, and high brightness temperatures. However, RRL masers were rarely detected only in several sources. Here we report the detection of sharp line profiles of the RRL H29$\alpha$, which can be interpreted as maser candidates, in two sources within W49A, a mini-starburst region in our Galaxy. These observations, conducted with high resolution ($\sim0.03''$) using the Atacama Large Millimeter/sub-millimeter Array (ALMA), reveal high brightness temperatures up to $\sim$9 000 K for H29$\alpha$ emission in another two sources, which might also be regarded as maser candidates. Additionally, suggestions for efficiently identifying RRL maser candidates are also provided.

Power scaling of neodymium (Nd)-doped single-frequency fiber lasers (SFFLs) operating at approximately 900 nm has been fundamentally constrained by dominant emission of approximately 1060 nm, with previous demonstrations limited to below 3 W. Here, we demonstrate a 910 nm single-mode Nd-doped SFFL system that achieves a record output power of over 30 W employing homemade Nd-doped silica fiber (NDF), while preserving exceptional 49 dB suppression of competing emission of approximately 1060 nm. The laser system originates from a distributed Bragg reflector single-frequency (SF) oscillator with 11 mW output power, which is subsequently amplified to 31.1 W through three polarization-maintaining (PM) amplification stages utilizing PM 10/125 μm NDF. To the best of our knowledge, this represents the highest power achieved for Nd-doped SFFLs in this spectral region. The output exhibits excellent beam quality (Mx2 = 1.03, My2 = 1.05) and narrow linewidth (10.2 kHz). These results validate that the homemade PM 10/125 μm NDF can be employed in intermediate and main amplifiers in all-fiber SF master oscillator power amplifier systems at approximately 900 nm.

In this paper, a novel series–parallel stable platform is proposed, and its kinematic and dynamic models are established. The relationship between the length, speed, and acceleration of rolling and pitching electric push rods is analyzed. The workspace of the series–parallel stable platform is determined, and the singularity and interference are analyzed. The state-machine-based control system of the stable platform is designed. An experimental environment of the principle of the real-time control system based on dSPACE was built. A position–speed double closed-loop experiment, simulating mounting carrier of the random signal tracking, and system comprehensive performance experiment were conducted to verify the accuracy of the kinematics and dynamics model of the series–parallel stable platform and the rationality and stability of the control system.

In this paper, we describe finite order entire solutions of nonlinear partial differential equation

\begin{equation*} \prod _{i=1}^n\left (a_{i 1} u_{z_1}+a_{i 2} u_{z_2}+\cdots +a_{i n} u_{z_n}\right )=1 \end{equation*}

A dual-beam platform is developed for all-optical Thomson/Compton scattering, with versatile parameter tuning capabilities including electron energy, radiation energy, radiation polarization, etc. By integrating this platform with a 200 TW Ti:sapphire laser system, we demonstrate the generation of inverse Compton scattering X-/gamma-rays with tunable energies ranging from tens of keV to MeV. The polarization of X-/gamma-rays is manipulated by adjusting the polarization of the scattering laser. In the near future, by combining this platform with multi-PW laser facilities, our goal is to explore the transition from nonlinear Thomson scattering to nonlinear Compton scattering, ultimately verifying theories related to strong-field quantum electrodynamics effects induced by extreme scattering.

An actively controllable cascaded proton acceleration driven by a separate 0.8 picosecond (ps) laser is demonstrated in proof-of-principle experiments. MeV protons, initially driven by a femtosecond laser, are further accelerated and focused into a dot structure by an electromagnetic pulse (EMP) on the solenoid, which can be tuned into a ring structure by increasing the ps laser energy. An electrodynamics model is carried out to explain the experimental results and show that the dot-structured proton beam is formed when the outer part of the incident proton beam is optimally focused by the EMP force on the solenoid; otherwise, it is overfocused into a ring structure by a larger EMP. Such a separately controlled mechanism allows precise tuning of the proton beam structures for various applications, such as edge-enhanced proton radiography, proton therapy and pre-injection in traditional accelerators.

The robot manipulator is commonly employed in the space station experiment cabinet for the disinfection task. The challenge lies in devising a motion trajectory for the robot manipulator that satisfies both performance criteria and constraints within the confined space of an experimental cabinet. To address this issue, this paper proposes a trajectory planning method in joint space. This method constructs the optimal trajectory by transforming the original problem into a constrained multi-objective optimization problem. This is then solved and integrated with the seventh-degree B-spline curve. The optimization algorithm utilizes an indicator-based adaptive differential evolution algorithm, enhanced with improved Tent chaotic mapping and opposition-based learning for population initialization. The method employed the Fréchet distance to design a trajectory selection strategy based on the Pareto solutions to ensure that the planned trajectory complies with Cartesian space requirements. This allows the robot manipulator end-effector to approximate the desired path in Cartesian space closely. The findings indicate that the proposed method can effectively design the robot manipulator trajectory, considering both joint motion performance and end-effector motion constraints. This ensures that the robot manipulator operates efficiently and safely within the experimental cabinet.

In this article, we describe meromorphic solutions of certain partial differential equations, which are originated from the algebraic equation $P(f,g)=0$, where P is a polynomial on $\mathbb {C}^2$. As an application, with the theorem of Coman–Poletsky, we give a proof of the classic theorem: Every meromorphic solution $u(s)$ on $\mathbb {C}$ of $P(u,u')=0$ belongs to W, which is the class of meromorphic functions on $\mathbb {C}$ that consists of elliptic functions, rational functions and functions of the form $R(e^{a s})$, where R is rational and $a\in \mathbb {C}$. In addition, we consider the factorization of meromorphic solutions on $\mathbb {C}^n$ of some well-known PDEs, such as Inviscid Burgers’ equation, Riccati equation, Malmquist–Yosida equation, PDEs of Fermat type.

This paper provides an overview of the current status of ultrafast and ultra-intense lasers with peak powers exceeding 100 TW and examines the research activities in high-energy-density physics within China. Currently, 10 high-intensity lasers with powers over 100 TW are operational, and about 10 additional lasers are being constructed at various institutes and universities. These facilities operate either independently or are combined with one another, thereby offering substantial support for both Chinese and international research and development efforts in high-energy-density physics.

Smart agriculture is based on latest technologies in communication, big data analysis, high-performance sensors, and automatic machinery to improve the effectiveness of agriculture industry. China is looking forward to achieve modernization of its agriculture industry through smart agriculture. But its unique climate, landscape, diversity in crops, and large population make this task more challenging compared to other counties. Herein, we present the current achievements regarding policies made to guide and support the development of smart agriculture, the promotion of smart techniques and smart equipment, and the cultivation of specialists in smart agriculture. Then we discussed the existing challenges that hinder further development of smart agriculture industry and proposed several feasible solutions to solve or ease the problem, including the pertinent development of smart agriculture in provinces with different resources, enrich modes of online technical support and specialist cultivation, and set a series of standards to guide research and development of novel smart systems.

Using data from the China Health and Retirement Longitudinal Study, this research investigates how post-retirement employment influences older people’s expenditure in urban China. By broadening the understanding of post-retirement employment behaviour from a consumer welfare perspective, this study expands the literature on retirement consumption and provides theoretical explanations, empirical insights and policy recommendations. The findings reveal that post-retirement employment behaviour reduces urban retirees’ household expenditure and has a more significant effect on men than on women, but this effect diminishes as consumption levels rise. Increasing income, promoting social participation and improving subjective health outcomes are all potential channels through which post-retirement employment can affect consumption. Further analysis shows two main reasons why post-retirement employment reduces older people’s expenditure: first, the increase in subjective health levels resulting from post-retirement employment reduces healthcare expenditure; second, post-retirement employment does not promote social participation and self-rated health for all consumption levels and all genders of retirees – it also decreases expenditure. Preliminary evidence suggests that internet use positively moderates the negative impact of post-retirement employment on older people’s expenditure. These findings provide policy implications for retirement policies and the promotion of the silver economy.