Evaluating the Perceived Safety of Urban City via Maximum Entropy Deep Inverse Reinforcement Learning

Inspired by expert evaluation policy for urban perception, we proposed a novel inverse reinforcement learning (IRL) based framework for predicting urban safety and recovering the corresponding reward function. We also presented a scalable state representation method to model the prediction problem as a Markov decision process (MDP) and use reinforcement learning (RL) to solve the problem. Additionally, we built a dataset called SmallCity based on the crowdsourcing method to conduct the research. As far as we know, this is the first time the IRL approach has been introduced to the urban safety perception and planning field to help experts quantitatively analyze perceptual features. Our results showed that IRL has promising prospects in this field. We will later open-source the crowdsourcing data collection site and the model proposed in this paper.Comment: ACML2022 Camera-ready Versio

Numerical analysis of aerodynamic characteristics of iced rotor in forward flight

Based on a 3-D rotor icing model and the CLORNS code, aerodynamic characteristics of iced rotors in forward flight are calculated and analyzed. At first, ice accretion on the UH-1H rotor in hover, and ice accretion on the SRB rotor in forward flight are calculated. The results are used to validate the employed numerical simulation method through comparisons with experimental data. Then, the degradation of the aerodynamic characteristics of the iced SRB rotor is analyzed, and the variation of the pressure coefficients on the rotor blades is discussed in detail. Finally, parameters, such as the icing time, the temperature, and the icing position, are quantified, and conclusions are obtained. The influence of the ice accretion on the sectional aerodynamic characteristics increases along the spanwise direction, and deicing near the 0.7R blade section should be preferred at the beginning of the ice accretion. Finally, it is concluded that ice will not be removed in time if the deicer is activated based solely on the variation of the rotor aerodynamics

Initial public offering (IPO) underpricing in China A -share market

Research in literature illustrates that initial public offerings (IPO) price are underestimated in the primary market. This paper investigates 270 new issue shares from 10th January 2011 to 30th December 2014 excluding data from 2013 because CSRC postponed IPO; I find that the average market-adjusted return is 60.72%. The cross-sectional analysis is used to measure the proxy variables of hypothesis. I find strong evidence for speculation effect hypothesis and inequality supply and demand of new share hypothesis and weak evidence for information asymmetry hypothesis, moreover, split share structure hypothesis is failed to explain IPO underpricing in China A-share stock market. Generally, IPO underpricing is caused by current issue system and irrational investment behavior

A New Single-blade Based Hybrid CFD Method for Hovering and Forward-flight Rotor Computation

AbstractA hybrid Euler/full potential/Lagrangian wake method, based on single-blade simulation, for predicting unsteady aerodynamic flow around helicopter rotors in hover and forward flight has been developed. In this method, an Euler solver is used to model the near wake evolution and transonic flow phenomena in the vicinity of the blade, and a full potential equation (FPE) is used to model the isentropic potential flow region far away from the rotor, while the wake effects of other blades and the far wake are incorporated into the flow solution as an induced inflow distribution using a Lagrangian based wake analysis. To further reduce the execution time, the computational fluid dynamics (CFD) solution and rotor wake analysis (including induced velocity update) are conducted parallelly, and a load balancing strategy is employed to account for the information exchange between two solvers. By the developed method, several hover and forward-flight cases on Caradonna-Tung and Helishape 7A rotors are performed. Good agreements of the loadings on blade surface with available measured data demonstrate the validation of the method. Also, the CPU time required for different computation runs is compared in the paper, and the results show that the present hybrid method is superior to conventional CFD method in time cost, and will be more efficient with the number of blades increasing