Controlling the concentration of free radicals in polymerization systems is advantageous for preparing cationic polyacrylamide (CPAM) with a high molecular weight and acceptable dissolvability. In this study, a novel ultraviolet (UVA)-initiated system characterized by an adjustable light intensity and a redox-azo complex initiator was used to synthesize a CPAM flocculant named NP. Comparatively, another CPAM flocculant named SP with a stable UVA light intensity and a single initiator was prepared. Their chemical structure, morphology, and thermal stability were analyzed through instrumental analysis. ¹H NMR indicated that NP was successfully prepared, and a small fraction of a cationic homopolymer was mixed in the product. Polymerization conditions of NP were optimized, and polymerization mechanism was determined by investigating the effects of various parameters on intrinsic viscosity, conversion, and dissolvability. Results showed that the best performance was obtained at indices of 0.45 wt‰ redox initiator concentration, 0.2 wt‰ azo initiator concentration, 40.0 wt% cationic monomer, 3 wt‰ urea, and first- and second-stage light intensities of 8.5 and 13 mW/cm², respectively. The sludge conditioning performances of NP and SP were comparatively evaluated, and the mechanism was determined by examining sedimentation behavior and floc size distribution. High intrinsic viscosity, porous morphology structure, and mixed NP cationic homopolymer contributed to the improvement of sludge conditioning performance.

This study addresses the critical challenge of optimizing outdoor thermal comfort for the aging population in old residential communities within China's hot-summer and cold-winter climate zones. Against the backdrop of urban regeneration and rapid demographic aging, it investigates how key landscape elements—ground reflectance, greening type, and pergola condition—influence the microclimate of community public spaces. The research employed an integrated methodology centered on numerical simulation. Using the ENVI-met software and an L₉(3⁴) orthogonal experimental design, it simulated the microclimatic effects of nine combined scenarios on typical summer and winter days for a case study in Nanjing. The comprehensive thermal comfort index, Physiological Equivalent Temperature (PET), was used as the primary evaluation indicator to assess the thermal comfort performance for elderly occupants, with the assistance of air temperature, wind speed, and relative humidity, and the results were analyzed via range analysis and ANOVA. The key findings indicate that: (1) Greening type and pergola condition are the dominant factors affecting microclimate and annual thermal comfort across seasons, while ground reflectance has a comparatively minor influence. (2) The combination of deciduous trees with lawn achieves the optimal cross-seasonal PET gain. It provides effective shading and cooling in summer while allowing beneficial solar penetration for warming in winter, substantially outperforming evergreen-dominated configurations. (3) The presence of a pergola consistently enhances comfort by providing essential shade in summer and acting as a windbreak in winter. The combination dominated by deciduous trees + lawn and pergola yield an overall PET gain 1.0967 ℃ higher than that of evergreen trees + shrub without pergola. This study provides evidence-based, elderly-specific landscape design strategies to inform the thermal environment optimization of public spaces in old residential areas undergoing renewal.

This study addresses the critical challenge of optimizing outdoor thermal comfort for the aging population in old residential communities within China’s Hot-Summer and Cold-Winter (HSCW) climate zones. Against the backdrop of urban regeneration and rapid demographic aging, it investigates how key landscape elements—Square Reflectance, Greening Type, and Pergola Condition—influence the microclimate of community public spaces. The research employed an integrated methodology centered on numerical simulation. Using the ENVI-met 5.9.0 software and an L₉(3⁴) orthogonal experimental design, it simulated the microclimatic effects of nine combined scenarios on typical summer and winter days for a case study in Nanjing. The comprehensive thermal comfort index, Physiological Equivalent Temperature (PET), was used as the primary evaluation indicator to assess the thermal comfort performance for elderly occupants, with the assistance of air temperature, wind speed, and relative humidity, and the results were analyzed via range analysis and ANOVA. The key findings indicate that: (1) Greening Type and Pergola Condition are the dominant factors affecting microclimate and annual thermal comfort across seasons, while Square Reflectance has a comparatively minor influence. (2) The combination of deciduous trees with lawn achieves the optimal cross-seasonal PET gain. It provides effective shading and cooling in summer while allowing beneficial solar penetration for warming in winter, substantially outperforming evergreen-dominated configurations. (3) The presence of a pergola consistently enhances comfort by providing essential shade in summer and acting as a windbreak in winter. The combination dominated by deciduous trees + lawn and pergola yields an overall PET gain 1.097 °C higher than that of evergreen trees + shrub without pergola. This study provides evidence-based, elderly specific landscape design strategies to inform the thermal environment optimization of public spaces in old residential areas undergoing renewal.