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The performance of ethylene/1-octene copolymer primarily depends on the microstructure of the polymer chain. This study employed a new method to control the inter-distribution of hexyl chain branches directly on the backbone of the ethylene/1-octene copolymer. Three ethylene/1-octene copolymers with different inter-distributions of hexyl chain branches were synthesized using [Me2Si(C5Me4) (NtBu)] TiCl2 (Ti–CGC) by different feeding sequences in the semi-continuous polymerization reaction system. The three copolymers were named according to the feeding sequence of the materials: ethylene/1-octene/Ti–CGC (EOC), 1-octene/Ti–CGC/ethylene (OCE), and ethylene/Ti–CGC/1-octene (ECO), respectively. The structure and properties of the copolymers were characterized using HT-GPC, 13C-NMR, DSC, WAXD, DMA, MI, and Uniaxial Tension Test. The results showed that the feeding sequence greatly affected the comonomer distribution of the molecular chains, molecular weight, molecular weight distribution, and chemical composition of the copolymers, consequently influencing their thermal performance and mechanical properties. Thus, it is probable that one could obtain an ethylene/1-octene copolymer with designed properties by controlling the feeding sequence during the ethylene/1-octene semi-continuous copolymerization process.

The heat rejected by outdoor units of split A/C conditioners can impact the ambient outdoor environment of mixed-mode buildings. Nevertheless, how this environmental impact may affect the space-conditioning energy use and indoor air pollution is poorly understood. By coupling EnergyPlus and Fluent, this study examines the effects of outdoor units’ heat rejection on the building surroundings, building cooling load, and indoor PM2.5 exposure of a six-storey mixed-mode building. The building had an open-plan room on each floor, with the outdoor unit positioned below the window. The coupled model was run for a selected day when the building was cooled by air conditioning and natural ventilation. Five mixed-mode cooling strategies were simulated, reflecting different window-opening schedules, airflow rates of outdoor units, and cooling set-points. The results indicate that compared with the always-air-conditioned mode, the mixed-mode operation could significantly mitigate the negative impact of heat rejection on space-cooling energy consumption. Increasing the airflow rate of outdoor units led to a lower increase in demand for space cooling and lower indoor PM2.5 exposure. If one of the six rooms needs to be cooled to a lower temperature than the others; choosing the bottom-floor room helped achieve more energy savings and better indoor air quality.

When tower cranes are applied in coastal engineering, the wind-induced vibration under complex wind loads along the coast will be exceptionally obvious. It is increasingly important to explore the wind-induced vibration characteristics of different sections of tower cranes under full wind angles. This paper first establishes a three-dimensional numerical wind tunnel model that can be used for the simulation of tower cranes under full wind angles and analyzes the aerodynamic load variation of the tower crane under full wind angles. Secondly, the tower crane structure is divided into sub-regions, and the AR model method in the linear filtering method is used to simulate the three-dimensional wind speed time history. Further, the wind speed time history is applied to the finite element transient analysis, and based on the Newmark-β method, the acceleration and displacement responses of different sections of the tower crane structure under fluctuating wind are systematically studied. Finally, the equivalent static wind load of different sections of the tower crane is evaluated by using the gust load factor method. The results indicate that the wind load of the tower crane exhibits an obvious three-dimensional effect, and the crosswind load cannot be ignored in the analysis of wind stability. The different sections of the tower crane structure show low-frequency vibration characteristics, and the low-frequency band is dominated by down-wind vibration, while the high-frequency band often experiences crosswind vibration. The amplification effect of the tower crane on fluctuating wind loads will increase with the increase of the height of the tower crane and the length of the jib, and the amplification effect on fluctuating wind loads in the crosswind direction is more obvious. The equivalent static wind load on the top of the tower crane reaches the maximum when the angle between the jib and the incoming wind is 60◦ . [ABSTRACT FROM AUTHOR]