Import ban and clean air: estimating the effect of China's waste import ban on ozone pollution

In this study, we investigate the effects of the ban on imports of plastic waste on local air quality in China. Using city-level daily ozone concentrations, we examine whether the pollution levels differ after the implementation of the import ban. The results demonstrate that the daily ozone concentration was reduced by 2.8% in treatment areas after the import ban. Additional analyses also suggest that the effect of the ban was larger during the later period and in coastal cities with ports while the effect of the ban might get weak in the long run. These findings highlight the effectiveness of policies that reduce the availability of inputs for pollutive activities

Do municipal mergers reduce the cost of waste management? Evidence from Japan

This study investigates whether municipal mergers result in lower waste management costs. We develop a novel virtual merging method based on machine learning techniques to compile the data of the control group and estimate the effect of the large-scale consolidation in Japan on the various costs of managing municipal solid waste. We find that these mergers actually led to an increase in the total cost per ton. Estimation results also reveal that the construction cost increased in the post-merger period, which can be explained by the special bonds provided by the national government for new projects in merged municipalities. By contrast, the processing and management cost is little affected by the mergers, except for the absorption-type mergers and municipalities that never joined waste management associations. These results suggest that municipal mergers might not always bring a substantial scale economy in municipal solid waste management. Policymakers should be careful when promoting municipal mergers in the belief that a scale economy will prevail after the reform

Temperature Dependence of Droplet Nucleation in a Yukawa Fluid

We have studied the temperature dependence of gas-to-liquid nucleation in Yukawa fluids with gradient theory and density functional theory. Each of these nonclassical theories exhibits a weaker (i.e., better) temperature dependence than classical nucleation theory. At fixed temperature, the reversible work to form a critical nucleus found from gradient theory approaches the value given by density functional theory as the supersaturation increases. At high temperatures, the two theories remain quite close over a wide range of vapor densities. As the temperature is reduced, the difference between the two theories increases with decreasing vapor density. Compared to the classical theory we find that gradient theory can improve the predicted temperature dependence of the nucleation rate, although not always to the same degree as density functional theory. Finally, our results show that the scaling behavior of density functional theory proposed by McGraw and Laaksonen can be extended to higher temperatures if the incompressibility assumption is avoided when evaluating the classical reversible work

Achieving Covert Wireless Communications Using a Full-Duplex Receiver

Covert communications hide the transmission of a message from a watchful adversary while ensuring a certain decoding performance at the receiver. In this work, a wireless communication system under fading channels is considered where covertness is achieved by using a full-duplex (FD) receiver. More precisely, the receiver of covert information generates artificial noise with a varying power causing uncertainty at the adversary, Willie, regarding the statistics of the received signals. Given that Willie's optimal detector is a threshold test on the received power, we derive a closed-form expression for the optimal detection performance of Willie averaged over the fading channel realizations. Furthermore, we provide guidelines for the optimal choice of artificial noise power range, and the optimal transmission probability of covert information to maximize the detection errors at Willie. Our analysis shows that the transmission of artificial noise, although causes self-interference, provides the opportunity of achieving covertness but its transmit power levels need to be managed carefully. We also demonstrate that the prior transmission probability of 0.5 is not always the best choice for achieving the maximum possible covertness, when the covert transmission probability and artificial noise power can be jointly optimized.Comment: 13 pages, 11 figures, Accepted for publication in IEEE Transactions on Wireless Communication