钢筋混凝土桥墩纵筋屈曲解析方法

为了评估钢筋混凝土桥墩的极限水平位移 ,根据塑性铰区变形特性 ,合理的确定塑性铰区长度是非常重要的。笔者基于有限元分析从理论 ,给出了桥墩根部纵筋屈曲时的长度 ,并与实验结果进行比较 ,通过纵筋屈曲分析结果 ,考虑到材料非线性屈曲程度 ,进一步提出了桥墩纵筋屈曲长度的简化表达式。     

Bag leakage: The effect of disposable carryout bag regulations on unregulated bags

Leakage occurs when partial regulation of consumer products results in increased consumption of these products in unregulated domains. This article quantifies plastic leakage from the banning of plastic carryout bags. Using quasi-random policy variation in California, I find the elimination of 40 million pounds of plastic carryout bags is offset by a 12 million pound increase in trash bag purchases—with small, medium, and tall trash bag sales increasing by 120%, 64%, and 6%, respectively. The results further reveal 12–22% of plastic carryout bags were reused as trash bags pre-regulation and show bag bans shift consumers towards fewer but heavier bags. With a substantial proportion of carryout bags already reused in a way that avoided the manufacture and purchase of another plastic bag, policy evaluations that ignore leakage effects overstate the regulation's welfare gains.     

Performance and emission characteristic studies on CRDI diesel engine fuelled with plastic pyrolysis oil blended with ethanol and diesel

ABSTRACT

This paper mainly focuses on the utilisation of plastic pyrolysis oil (PPO) and its’ blends with diesel and ethanol in different proportions in a modified diesel engine fitted with common rail direct injection (CRDI) facility. PPO was subsequently blended with diesel and ethanol and characterisation has been done. Experiments were conducted to investigate the impact of injection timing (IT) and injection pressure (IP) on the performance of modified CRDI engine fuelled with PPO and its blends with diesel and ethanol. From the experimental investigations, IT of 10°bTDC and IP of 900 bar were found as best operating parameters to obtain maximum brake thermal efficiency (BTE) with lowered emissions for the fuel combinations utilised in the investigations. PPO as substitute to diesel fuel could be viable if its major concern is to finding permanent resources.     

Plastic materials and water sources actively select and shape wastewater plastispheres over time

● Wastewater MPs exhibited resistomes and therefore health threats. ● High density of alkB gene indicates both HDPE and PET can be utilized by microbes. ● Plastics and waters actively selected and shaped the plastispheres over time. ● A broader phylogenetic spectrum of MHET-degrading microorganisms was annotated. The daily use of plastics presents a serious pollution issue due to their extremely slow degradation. Microplastics and the biofilm that grows on plastics (i.e., the plastisphere) are important subsets of plastic wastes. Many studies have been conducted to reveal the structures of the plastispheres, the driving factors for the formation of the plastisphere, and the ability of the plastispheres to degrade plastics in a variety of water bodies. However, the plastispheres related to wastewater are understudied. In this study, we used a microcosmic strategy to study the evolution of the plastispheres associated with microplastics (MPs) over time in wastewater. We found that plastic materials and water sources did not actively select and shape the plastispheres at an early stage, but the active selection for a unique niche of the plastisphere occurred after 14 d of growth. In addition, we confirmed that the alkB gene was densely present, and metagenomics showed some additional chemical reactions, which suggests that MPs are consumed by the microbes in the plastispheres. Additionally, metagenomics identified some metagenome-assembled genomes (MAGs) associated with high-density polyethylene (HDPE) and polyethylene terephthalate (PET). The identification of HDPE-associated MAGs and PET-associated MAGs further supports the notion that the selection for a unique niche of the plastisphere is driven by plastic materials and water sources (in this study, after 14 d of growth). Our discoveries bring new views on the behavior of the wastewater-associated plastisphere, especially how long it takes a wastewater plastisphere to form.     

Psychological interventional approach for reduce resource consumption: Reducing plastic bag usage at supermarkets

A field study was conducted to investigate the reduction of plastic bag usage at supermarkets. Many behaviors leading to potential damage to the environment may be unintentional. This study applied a dual motivation model to plastic bag usage and examined the effects of an intervention aimed at promoting pro-environmental behavior. A voice prompt intervention was implemented in Japanese supermarkets. In the first (control) week, shoppers were given free plastic bags by the cashier. In the second (intervention) week, cashiers asked shoppers whether they wanted plastic bags. We collected observational and questionnaire measures of variables that predicted free plastic bag usage during the intervention. The results supported a dual motivation model of behavioral change. The voice prompt decreased the usage of plastic bags by both discouraging unintentional usage and encouraging an intentional reduction in usage. Possibilities for interventions designed both to attenuate unintentional motivation and to promote intentional motivation are considered.     

A comprehensive waste collection cost model applied to post-consumer plastic packaging waste

Post-consumer plastic packaging waste (PPW) can be collected for recycling via source separation or post-separation. In source separation, households separate plastics from other waste before collection, whereas in post-separation waste is separated at a treatment centre after collection. There are also two collection schemes, either curb side or via drop-off locations. These different schemes have impact on total costs of collection at the municipal level. It can also influence the facility choices and network design. Therefore, a method which can compare costs of various collection schemes is needed.A comprehensive cost model was developed to compare costs of municipal collection schemes of PPW. The ‘municipal waste collection cost model’ is based on variables including fixed and variable costs per vehicle, personnel cost, container or bag costs as well as on emission costs (using imaginary carbon taxes). The model can be used for decision support when strategic changes to the collection scheme of municipalities are considered. The model takes into account the characteristics of municipalities, including urbanization degree and taxation schemes for household waste management.The model was applied to the Dutch case of post-consumer plastic packaging waste. Results showed that that in general post-separation collection has the lowest costs and curb side collection in urban municipalities without residual waste collection taxing schemes the highest. These results were supported by the conducted sensitivity analysis, which showed that higher source separation responses are negatively related to curb side collection costs. Greenhouse gas emission costs are a significant part of the total costs when collecting post-consumer plastic packaging waste due to the low density to weight ratio of the materials collect. These costs can amount to 15% of the total collection costs.