ABSTRACT
The COVID-19 pandemic is strongly affecting many aspects of human life and society around the world. To investigate whether this pandemic also influences crime, the differences of crime incidents numbers before and during the pandemic in four large cities (namely Washington DC, Chicago, New York City and Los Angeles) are investigated. Moreover, the Granger causal relationships between crime incidents numbers and new cases of COVID-19 are also examined. Based on that, new cases of COVID-19 with significant Granger causal correlations are used to improve the crime prediction performance. The results show that crime is generally impacted by the COVID-19 pandemic, but it varies in different cities and with different crime types. Most types of crimes have seen fewer incidents numbers during the pandemic than before. Several Granger causal correlations are found between the COVID-19 cases and crime incidents in these cities. More specifically, crime incidents numbers of theft in DC, Chicago and New York City, fraud in DC and Los Angeles, assault in Chicago and New York City, and robbery in Los Angeles and New York City, are significantly Granger caused by the new case of COVID-19. These results may be partially explained by the Routine Activity theory and Opportunity theory that people may prefer to stay at home to avoid being infected with COVID-19 during the pandemic, giving fewer chances for crimes. In addition, involving new cases of COVID-19 as a variable can slightly improve the performance of crime prediction in terms of some specific types of crime. This study is expected to obtain deeper insights to the relationships between the pandemic and crime in different cities, and to provide new attempts for crime prediction during the pandemic.
ABSTRACT
The use of Ultraviolet Germicidal Irradiation (UVGI) devices in the upper zones of occupied buildings has gained increased attention as one of the most effective mitigation technologies for the transmission of COVID-19. To ensure safe and effective use of upper-room UVGI, it is necessary to devise a simulation technique that enables engineers, designers, and users to explore the impact of different design and operational parameters. We have developed a simulation technique for calculating UV-C fluence rate within the volume of the upper zone and planar irradiance in the lower occupied zone. Our method is based on established ray-tracing light simulation methods adapted to the UV-C wavelength range. We have included a case study of a typical hospital patient room. In it, we explored the impact of several design parameters: ceiling height, device location, room configuration, proportions, and surface materials. We present a spatially mapped parametric study of the UV-C irradiance distribution in three dimensions. We found that the ceiling height and mounting height of the UVGI fixtures combined can cause the largest variation (up to 22%) in upper zone fluence rate. One of the most important findings of this study is that it is crucial to consider interreflections in the room. This is because surface reflectance is the design parameter with the largest impact on the occupant exposure in the lower zone: Applying materials with high reflectance ratio in the upper portion of the room has the highest negative impact (over 700% variation) on increasing hot spots that may receive over 6 mJ/cm2 UV dose in the lower occupied zone.