Fan Li

Industrial robots are increasingly embedded in urban production systems, yet their association with city-level low-carbon transition efficiency remains insufficiently understood. Using panel data for 278 Chinese cities from 2010 to 2023, this study measures urban low-carbon transition efficiency (LCTE), the relative efficiency of urban resource conversion under environmental constraints, with a super-efficiency slack-based measure (Super-SBM) model. We estimate its association with industrial robot exposure using a two-way fixed-effects model, followed by robustness checks, a lagged-exposure instrumental-variable analysis, innovation-pathway analysis, city-size heterogeneity tests and spatial econometric modeling. Industrial robot exposure is positively associated with LCTE; the direction of this association is preserved across sensitivity analyses, although its magnitude falls to about one quarter of the baseline estimate under constant returns to scale. The coefficient patterns for green technological innovation and science and technology investment intensity are consistent with potential innovation-related pathways. The positive association is more pronounced in small and medium-sized cities than in major cities. Spatial Durbin model estimates confirm spatial dependence in LCTE and a robust positive direct association with local LCTE; the indirect association with spatially connected cities is negative in point estimates but not statistically significant once standard errors are clustered by city. These conditional associations suggest that the relationship between production automation and LCTE varies across innovation conditions, city sizes and spatial contexts.

Power grids are complex networks; their dynamics have strong nonlinearity due to the symmetry breaking in their topological structure. Synchronization stability, which is essential for secure and reliable operation, is the focus of this study. In this paper, the effects of phase shift on dynamics and stability in symmetry-breaking power networks are investigated. To clarify the influence of phase shift parameters, power networks of different sizes and topological structures are systematically analyzed, including a two-node power network, the Nepal power network, and the UK power network. The results show that phase shift significantly changes the collective dynamical behaviors of power networks, leading to transitions from frequency synchronization to complete synchronization or desynchronization under different parameter conditions. Moreover, the stability region shrinks as the phase shift increases. The stability transition region is further found to be strongly related to network size, topological structure, and the spatial distribution of generators and consumers in the power network. The results indicate that the stronger the symmetry-breaking in a power network, the more significant the impact of the phase shift parameter on the dynamics and stability. The results of the basin stability analysis for the power system provide quantitative support for this result and reveal the mechanism of power system instability under the effect of phase shift parameters. These findings provide a deeper understanding of the effect of phase shift on the dynamics of symmetry-breaking power networks and offer new insights into synchronization stability and structural design in complex power systems.

Urban sustainable development increasingly depends on interactions among multiple urban subsystems, yet existing studies often overlook cross-regional linkages and nonlinear development processes. This study investigates the coordinated development of urbanization, smart development, resilience, and low-carbon transition (USRL) from an efficiency perspective. Using panel data from 278 Chinese cities during 2010–2023, this work integrates the Super-SBM model, the Local–Tele Coupling Coordination Degree (LTCCD) framework, Dagum Gini decomposition, and machine learning techniques to examine the spatiotemporal evolution, spatial disparities, and driving mechanisms of coordinated development. The results show that coordinated development improved steadily over time, although subsystem evolution remained uneven, with resilience lagging behind other dimensions. Regional disparities gradually narrowed, but inter-regional differences remained the dominant source of spatial inequality. Innovation intensity, industrial upgrading, and high-quality foreign investment positively contributed to coordinated development, whereas fiscal and financial factors exhibited nonlinear effects. Interaction analysis further revealed that coordinated development is shaped by the combined influence of multiple drivers rather than by individual factors alone. Our findings suggest that urban sustainable development is jointly influenced by subsystem coordination, cross-regional interactions, and nonlinear development dynamics, highlighting the importance of integrating local and tele-coupling processes in urban sustainability research.

Advancing the low-carbon and resilient transformation of urban systems has become a crucial strategy for addressing the climate crisis. Current research predominantly focuses on either the effect of governance or the efficient utilization of urban systems, overlooking the potential structural mismatches and synergistic development governance logic between the two. This paper systematically proposes a theoretical research framework integrating the synergistic development of urban system effect and efficiency, and constructs a multi-level analytical methodology. Through an in-depth examination of 278 prefecture-level cities in China from 2010 to 2023, the following key conclusions emerge: (1) The overall level of synergistic development within urban systems has steadily increased. Specifically, the proportion of cities at low levels of synergistic development decreased from 65.11% to 17.63%, while the proportion at medium and high levels rose from 18.70% to 46.40%. (2) Spatial disparities in urban system coordination have progressively narrowed, as evidenced by the overall Gini coefficient decreasing from 0.195 to 0.153. (3) Key influencing factors for urban system coordination include foreign enterprise attraction, urban infrastructure development, and green technological innovation. Overall, this study reveals the long-standing structural mismatch between effect and efficiency in China’s urban system’s low-carbon resilience transformation, emphasizing the importance of their coordinated development. It provides theoretical foundations and empirical references for the sustainable development of urban low-carbon resilience transformation.

Four-wave-mixing microscopy is widely researched in both biology and medicine. In this paper, we present a simplified near-degenerate four-wave-mixing microscopy (SNDFWM). An ultra-steep long-pass filter is utilized to produce an ultra-steep edge on the spectrum of a femtosecond pulse, and a super-sensitive four-wave-mixing (FWM) signal can be generated via an ultra-steep short-pass filter. Compared with the current state-of-the-art FWM microscopy, this SNDFWM microscopy has the advantages of simpler experimental apparatus, lower cost, and easier operation. We demonstrate that this SNDFWM microscopy has high sensitivity and high spatial resolution in both nanowires and biological tissues. We also show that the SNDFWM microscopy can achieve an ultra-sensitive detection based on the electron-resonance effect. This method might find an important application in tracking of nano drugs in vivo.