Modeling the efficiency of UV at 254 nm for disinfecting the different layers within N95 respirators.

The study presented a Monte Carlo simulation of light transport in eight commonly used filtered facepiece respirators (FFRs) to assess the efficacy of UV at 254 nm for the inactivation of SARS-CoV-2. The results showed different fluence rates across the thickness of the eight different FFRs, implying that some FFR models may be more treatable than others, with the following order being (from most to least treatable): models 1512, 9105s, 1805, 9210, 1870+, 8210, 8110s and 1860, for single side illumination. The model predictions did not coincide well with some previously reported experimental data on virus inactivation when applied to FFR surfaces. The simulations predicted that FFRs should experience higher log reductions (>>6-log) than those observed experimentally (often limited to ~5-log). Possible explanations are virus shielding by aggregation or soiling, and a lack of the Monte Carlo simulations considering near-field scattering effects that can create small, localized regions of low UV photon probability on the surface of the fiber material. If the latter is the main cause in limiting practical UV viral decontamination, improvement might be achieved by exposing the FFR to UV isotropically from all directions, such as by varying the UV source to the FFR surface angle during treatment.

Light propagation within N95 filtered face respirators: A simulation study for UVC decontamination.

This study presents numerical simulations of UVC light propagation through seven different filtered face respirators (FFR) to determine their suitability for Ultraviolet germicidal inactivation (UVGI). UV propagation was modeled using the FullMonte program for two external light illuminations. The optical properties of the dominant three layers were determined using the inverse adding doubling method. The resulting fluence rate volume histograms and the lowest fluence rate recorded in the modeled volume, sometimes in the nW cm-2 , provide feedback on a respirator's suitability for UVGI and the required exposure time for a given light source. While UVGI can present an economical approach to extend an FFR's useable lifetime, it requires careful optimization of the illumination setup and selection of appropriate respirators.

Globalization and Regionalization: Empirical Evidence from Itinerary Structure and Port Organization of World Cruise of Cunard

Cruise tourism is an obviously global industry in different dimensions. From a geographical perspective, cruise ships are mobile and capable of being repositioned at a company’s notice, which forms the inherent basis for its global spatial layout. As a branch of the cruise industry, the world cruise is clearly globalizing in geographical space by offering long itinerary, even round-the-world trips, for everyone. Using the schedule data from 2018 to 2019, this paper analyzes the spatial characteristics of the itinerary and port organization of Cunard, a world cruise company. We find that the itinerary distribution and port organization of Cunard are both globalization and regionalization, and the latter is the core and main component of the former. Under the influence of the COVID-19 epidemic, the global mobility of cruises has ground to a halt, while local mobility offers the possibility of its resumption as soon as possible. Turning to the regional voyage with the shorter and simple itinerary is feasible for Cunard and other world cruises, which is conducive to the realization of the resuming voyage as soon as possible. Moreover, strict boarding and safety onboard are essential.