We present a linear stability analysis of two-dimensional magnetoconvection considering the effects of spatial confinement (characterised by the aspect ratio $\varGamma$) and magnetic field (characterised by the Hartmann number $\textit{Ha}_{i=x,y,z}$ with subscript representing its direction). It is found that when the magnetic field is perpendicular to the convection domain ($y$-direction), it does not affect the onset of convection due to zero Lorentz force. With a magnetic field in the $z$ (vertical) or $x$ (horizontal) directions, the onset of convection is delayed, resulting in a larger critical Rayleigh number $Ra_c$ for the onset of convection. We outline phase diagrams showing the dominating factors determining $Ra_c$. When $\varGamma \leqslant 0.83\textit{Ha}_z^{-0.5}$ for vertical and $\varGamma \leqslant 0.66\textit{Ha}_x^{-1.01}$ for horizontal magnetic field, $Ra_c$ is mainly determined by the geometrical confinement with $Ra_c=502\varGamma ^{-4.0}$. When $\varGamma \geqslant 2^{1/6}\pi ^{1/3}\textit{Ha}_z^{-1/3}$ for vertical and $\varGamma \geqslant 5$ for the horizontal magnetic field, $Ra_c$ is mainly determined by the magnetic field with $Ra_c=\pi ^2\textit{Ha}^2$. In the intermediate regime, both the magnetic field and spatial confinement determine $Ra_c$, and a horizontal magnetic field is found to suppress convection more than a vertical magnetic field. In addition, under a horizontal magnetic field, there exists a subregime characterised by $Ra_c = 9.9\,\varGamma ^{-2.0} \textit{Ha}_x^2$, which is explained by a theoretical model. The magnetic field also modifies the length scale $\ell$. For a vertical magnetic field, $\ell$ decreases with increasing $\textit{Ha}_z$, following $\ell =2^{1/6}\pi ^{1/3}\textit{Ha}^{-1/3}$. For a horizontal magnetic field, when $\varGamma \lt 0.62\textit{Ha}_x^{0.47}$, the flow is a single-roll structure with $\ell$ being the width of the domain. The study thus shed new light on the interplay between magnetic field and spatial confinement.

Using linear stability analysis, we study the onset and formation mechanism of wall modes in confined magnetoconvection cells with the degree of confinement characterised by the cell aspect ratio $\varGamma$. We first outline the phase diagram of the dominating factors that determine the critical Rayleigh number $Ra_c$ for the onset of convection in the $\varGamma -Ha$ phase space, with $\textit{Ha}$ being the Hartmann number. Our study shows that $Ra_c$ is primarily determined by geometrical confinement, and bulk convection onset occurs with $Ra_c = 1090 \varGamma ^{-4.0}$ for $\varGamma \lt \varGamma _{c_1} = 1.21 \textit{Ha}^{-0.48}$. No wall modes form and $Ra_c$ depends on the strength of both the confinement and magnetic field for $\varGamma _{c_1} \leqslant \varGamma \lt \varGamma _{c_2} = 4.07 \textit{Ha}^{-0.53}$. For $\varGamma _{c_2}\leqslant \varGamma \lt \varGamma _{c_3}=0.99 \textit{Ha}^{-0.10}$, wall modes emerge and $Ra_c$ drops below the bulk onset Rayleigh number for magnetoconvection. When $\varGamma \geqslant \varGamma _{c_3}$, wall modes become fully developed with an onset Rayleigh number for wall modes $Ra_{c,w} \approx 65 \textit{Ha}^{1.5}$. In this fully developed regime, the radial velocity profile and $Ra_{c,w}$ become independent of $\varGamma$. Through analysing the length scales of wall modes and their interaction with spatial confinement, we show dynamically how wall modes emerge in confined cells: while the first layer with a characteristic length scale $\ell _1 = 1.04 \textit{Ha}^{-0.56}$ forms when $\varGamma \geqslant 5.39 \textit{Ha}^{-0.58}$, the second layer with a characteristic length scale $\ell _2 = 4.94 \textit{Ha}^{-0.56}$ emerges when $\varGamma \geqslant 9.07 \textit{Ha}^{-0.53}$. These scaling relations provide practical guidelines for experimental and numerical studies of the wall-mode dynamics.

We investigate the role of slippery boundaries, quantified by the Navier boundary friction coefficient $\beta$, in regulating heat transport and flow structures in rotating Rayleigh–Bénard convection. Owing to the Ekman pumping effect arising from viscous boundary layers that is intensified with increasing boundary friction, it is found that the properties of global heat transport exhibit two distinct parameter regimes separated by a transitional Rayleigh number ($ \textit{Ra}_t$). In the rotation-dominated regime ($ \textit{Ra} \lt \textit{Ra}_t$), enhanced viscous friction increases the efficiency of Ekman pumping, significantly elevating the Nusselt number and lowering the convection onset threshold. Conversely, in the buoyancy-dominated regime ($ \textit{Ra} \gt \textit{Ra}_t$), boundary-induced viscous dissipation suppresses convective motions, thereby reducing heat transport. Large-scale vortices (LSVs), prevalent under free-slip conditions, progressively dissipate as $\beta$ increases, revealing that viscous friction disrupts the inverse energy cascade from baroclinic to barotropic modes. Through kinetic energy partitioning analysis, the transition between quasi-two-dimensional and three-dimensional turbulent states is identified, with the parameter $\beta _{\textit{cr}}$ following a generic scaling relation on the Prandtl (Pr) and Ekman (Ek) numbers $\beta _{\textit{cr}}\sim \textit{Pr}^{-0.67}\textit{Ek}^{-1.18}$. This relation enables us to predict LSV emergence across different parameter spaces. Furthermore, it is reported that the heat-transport scaling exponent, the convection onset and the partitioning of kinetic energy between barotropic and baroclinic components undergo a smooth flow transition at $\beta _{\textit{cr}}$. These results also indicate a direct correlation between Ekman pumping efficacy and the friction coefficient $\beta$, demonstrating that controlling boundary friction can modulate global transport properties and reshape flow structures.

With a clear agenda to reform the public service system and promote a service-oriented nonprofit sector, the Chinese government has been building a local service system by contracting with nonprofit organizations (NPOs) at the community level. Through the competing institutional logics perspective, this article examines the challenges that NPOs experienced and their responding strategies. The study found that bureaucratic logic, managerial logic, professional logic, and guanxi relations logic coexisted in the service field and each had different expectations of NPOs. In juggling the various requirements of these competing institutional logics, NPOs faced three major challenges: powerless status, legitimacy crisis, and accountability dilemma. Nevertheless, they were committed to the community and demonstrated agency in addressing these challenges. The strategies they used included using an intermediary platform to reduce power imbalance, compromising to share legitimacy with neighborhood committees, establishing professional identity, building community, and meeting both upward and downward accountability.

Disaster usually provides a good opportunity to observe the convergence of voluntary organized response efforts. However, the extent to which response organizations and affected neighborhoods go through the relief process similarly or differently is surprisingly less studied. Integrating the framework of community ecology and the concept of community resilience, this study examines the evolutionary process of an emergent disaster response community that consists of the populations of response organizations and affected neighborhoods. Using a technological disaster that occurred in Taiwan in July 2014 as the research context, this study shows that response organizations’ resource provision network and affected neighborhoods’ resource receipt network exhibited similar structural tendencies over the phases of disaster response and rebuilding. The process of mutual resource mobilization was also observed as response organizations mobilized and provided resources to affected neighborhoods at the same time. Moreover, while affected neighborhoods tended to maintain their resource relationships consistently over time, the changing structural patterns of their resource network reflected individual engagement in resuming normality after the incident. Theoretical and practical implications for emergent post-disaster social and voluntary behavior are discussed through the lens of community ecology and community resilience.

The Chinese government and human service NPOs are joining the bandwagon of service contracting with enthusiasm. Although this new policy endeavor has attracted much interest, empirical studies are scant. Drawing from interviews with 14 nonprofit organizations and two government officials conducted in 2012 and 2014, along with abundant secondary data, this paper analyzes the impact of China’s service contracting on the following: the social service delivery system, the promotion of NGOs development, and the nature of government-nonprofit relationship. The study found that service contracting has positive impacts on NGOs, such as facilitating their fundraising through sharing the government’s legitimacy. However, the majority of contract funding went to organizations that have a close government connection. We argue that the future of China’s service contracting is determined by the Chinese government’s primary political agenda, which is social control.

Pre-existing bubbles in the water play a critical role in influencing the impact pressure characteristics during the wedge water entry. This study experimentally and analytically investigates the effect of aeration on water-entry impact. A series of controlled drop tests were conducted using a wedge with a 20° deadrise angle at varying impact velocities and void fractions. Four classical pure water impact models (the Zhao & Faltinsen model (ZFM), original Logvinovich model (OLM), modified Logvinovich model (MLM) and generalised Wagner model (GWM)) were extended to account for the effect of aeration. These modifications accounted for compressibility effects, the time-dependent void fraction, three-dimensional flow corrections and area-averaged pressure calculations, resulting in four modified models (M-ZFM, M-OLM, M-MLM and M-GWM). This marks the first systematic theoretical extension of multiple classical water-entry models to aerated conditions. The proposed models demonstrated good agreement with experimental results, with the M-MLM providing accurate peak pressure predictions and M-GWM performing best in capturing the post-peak behaviours. The results indicated that the expansion velocity of the wetted surface varied spatially and closely matched the M-ZFM predictions. While the peak pressures decreased by up to 32.8 % in highly aerated water, the prolonged impact durations led to a comparable or slightly increased pressure impulse than that in pure water. This finding suggests that prolonged lower-magnitude impacts in aerated water may pose a greater risk to structural safety than short-duration high-magnitude impacts. These contributions offer new physical insight and validated tools relevant to marine engineering design in aerated environments.

This paper studies the impact of the COVID-19 epidemic on economic and health outcomes in China from January 20 to September 28, 2020. We first document China’s containment policies and present empirical evidence on the role of the online economy. We then use a SIR-macro model to study the macroeconomic and health outcomes of the epidemic. The model can generate infection and death dynamics broadly consistent with the data and the U-shaped recovery of the Chinese economy at the weekly frequency. The analysis reveals that, in addition to the containment policies, the development of the online economy (both online consumption and remote work) plays a critical role in fighting an epidemic.

In aerospace, automated assembly line, and precision engineering, asymmetric multi-robot systems comprising serial and parallel robots leverage the complementary strengths of these configurations to address the conflicting demands of high load capacity, extensive range, and flexibility in assembly tasks. However, the relatively small workspace of the parallel robot limits the full potential of the collaborative system functionality. This paper centers on a collaborative assembly system involving serial-parallel robots, whose collaborative workspace is determined by using a combination of the Monte Carlo method and lattice method. Additionally, a multi-objective optimization model is developed to holistically evaluate the collaborative workspace performance. The optimization problem is solved by an enhanced NSGA-II algorithm, which yields a Pareto optimal solution set. This result offers valuable technical insights for designing collaborative systems tailored to diverse task requirements.

High-sensitivity observations of PSR J1919+1745 were conducted using the Five-hundred-metre Aperture Spherical Radio Telescope (FAST) at a central frequency of 1 250 MHz, enabling a detailed investigation of its single-pulse behaviour. Our research indicates that this pulsar is a normal pulsar, exhibiting null behaviour, subpulse drifting, and occasional bright pulses. Moreover, we observed that the null events tend to be of short duration, with an estimated overall null fraction of approximately $29.5\pm1.1\% $. Through Sliding Fluctuation Spectrum analysis, the modulation period of subpulse drifting is determined to be $P_3=(6.1 \pm 0.7)P_1$ (where $P_1$ denotes the pulsar rotation period), and a non-drifting behaviour is also observed besides this. Analysis using the Harmonic-Resolved Fourier Spectrum indicates that a combination of amplitude modulation and phase modulation causes the subpulse drifting behaviour of this pulsar. Furthermore, the value $P_2$, derived from phase modulation, is approximately $360^\circ / 21 = 17.1^\circ$. polarisation analysis shows a moderate degree of linear polarisation ($37.22\pm0.59\% $), an S-shaped swing in the polarisation position angle, and an approximate $90^\circ$ orthogonal polarisation jump. The radiation characteristics of PSR J1919+1745 will expand the sample of pulsars with pulse null and subpulse drifting, thus contributing to future systematic studies on the physical origins of pulse null and subpulse drifting phenomena.

Excavations at Aketala reveal traces of human activity at the oases of the western Tarim Basin, north-western China, by at least 2200 BC. The recovered artefacts indicate that, by 1800 BC, the Andronovo culture had reached this region, bringing agropastoralism and developing the earliest regional evidence of bronze manufacturing techniques.

A major challenge in laryngeal surgery today is the limited flexibility of surgical operations. To address the limitation, this paper proposes a novel continuum robot (CR) system with enhanced dexterity, a robust inverse kinematics algorithm, and a sensorless automatic calibration method. The proposed CR possesses 4 flexible degrees of freedom, allowing for control based on angles and end-effector position. Compared with traditional Jacobian-based methods, the proposed inverse kinematics algorithm effectively addresses the singularity issue arising from curvature hypotheses. Mitigating the singularity is crucial for ensuring continuous and stable motion planning. The calibration method enables automatic initialization without additional sensors, a capability not previously reported in the literature. The efficient and automatic calibration reduces preparation time for laryngeal surgery. Compared to the manual calibration, which requires approximately 210 s, the proposed method reduces the calibration time by 160 s, thereby achieving a 76.19 % improvement in efficiency. Taking the damped least squares method as the baseline, the inverse kinematics algorithm reduces the maximum solving error from 7.36 mm to just 0.05 mm. Furthermore, the CR is capable of dexterous motion within narrow and curved cavities. The phantom and animal experiment results demonstrate the practicality and reliability of the proposed CR system in laryngeal surgery.

In firefighting missions, human firefighters are often exposed to high-risk environments such as intense heat and limited visibility. To address this, firefighting robots can serve as valuable agents for autonomous navigation and flame perception. This paper proposes a novel visual Simultaneous Localization and Mapping (SLAM) framework, Fire SLAM, tailored for firefighting scenarios. The system integrates a flame detection and tracking thread-based on the YOLOv8n network and Kalman filtering-to achieve real-time flame detection, tracking, and 3D localization. By leveraging the detection results, dynamic flame regions are excluded from the SLAM front-end, allowing static features to be used for robust pose estimation and loop closure. To validate the proposed system, multiple datasets were collected from real-world and simulated fire environments. Experimental results demonstrate that Fire SLAM improves localization accuracy and robustness in fire scenes with flame disturbances, showing promise for autonomous firefighting robot deployment.