Realistic Safe-Separation Distance Determination for Mass Fire Hazards

2013 ◽  
Author(s):  
Thomas L. Boggs ◽  
Kevin P. Ford ◽  
Josephine Covino
Keyword(s):  
Separation Distance ◽  
Distance Determination ◽  
Fire Hazards

scholarly journals Azimuthal Anchoring Strength in Photopatterned Alignment of a Nematic

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 675
Author(s):  
H. Nilanthi Padmini ◽  
Mojtaba Rajabi ◽  
Sergij V. Shiyanovskii ◽  
Oleg D. Lavrentovich
Keyword(s):  
Liquid Crystal ◽  
Point Defects ◽  
Elastic Energy ◽  
Separation Distance ◽  
Thin Layers ◽  
Uv Exposure ◽  
Surface Anchoring ◽  
Anchoring Strength ◽  
Spatially Varying

Spatially-varying director fields have become an important part of research and development in liquid crystals. Characterization of the anchoring strength associated with a spatially-varying director is difficult, since the methods developed for a uniform alignment are seldom applicable. Here we characterize the strength of azimuthal surface anchoring produced by the photoalignment technique based on plasmonic metamsaks. The measurements used photopatterned arrays of topological point defects of strength +1 and −1 in thin layers of a nematic liquid crystal. The integer-strength defects split into pairs of half-integer defects with lower elastic energy. The separation distance between the split pair is limited by the azimuthal surface anchoring, which allows one to determine the strength of the latter. The strength of the azimuthal anchoring is proportional to the UV exposure time during the photoalignment of the azobenzene layer.

scholarly journals Aerial Transmission of the SARS-CoV-2 Virus through Environmental E-Cigarette Aerosols: Implications for Public Policies

2021 ◽  
Vol 18 (4) ◽  
pp. 1437
Author(s):  
Roberto A. Sussman ◽  
Eliana Golberstein ◽  
Riccardo Polosa
Keyword(s):  
Emission Rate ◽  
Respiratory Activity ◽  
Separation Distance ◽  
Mitigation Strategies ◽  
Relative Risks ◽  
Respiratory Flow ◽  
Outdoor Spaces ◽  
Direct Exposure ◽  
Social Separation ◽  
Indoor Spaces

We discuss the implications of possible contagion of COVID-19 through e-cigarette aerosol (ECA) for prevention and mitigation strategies during the current pandemic. This is a relevant issue when millions of vapers (and smokers) must remain under indoor confinement and/or share public outdoor spaces with non-users. The fact that the respiratory flow associated with vaping is visible (as opposed to other respiratory activities) clearly delineates a safety distance of 1–2 m along the exhaled jet to prevent direct exposure. Vaping is a relatively infrequent and intermittent respiratory activity for which we infer a mean emission rate of 79.82 droplets per puff (6–200, standard deviation 74.66) comparable to mouth breathing, it adds into shared indoor spaces (home and restaurant scenarios) a 1% extra risk of indirect COVID-19 contagion with respect to a “control case” of existing unavoidable risk from continuous breathing. As a comparative reference, this added relative risk increases to 44–176% for speaking 6–24 min per hour and 260% for coughing every 2 min. Mechanical ventilation decreases absolute emission levels but keeps the same relative risks. As long as direct exposure to the visible exhaled jet is avoided, wearing of face masks effectively protects bystanders and keeps risk estimates very low. As a consequence, protection from possible COVID-19 contagion through vaping emissions does not require extra interventions besides the standard recommendations to the general population: keeping a social separation distance of 2 m and wearing of face masks.

scholarly journals Multi-Hazard Risk Assessment of Kathmandu Valley, Nepal

2021 ◽  
Vol 13 (10) ◽  
pp. 5369
Author(s):  
Rajesh Khatakho ◽  
Dipendra Gautam ◽  
Komal Raj Aryal ◽  
Vishnu Prasad Pandey ◽  
Rajesh Rupakhety ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Natural Hazards ◽  
Fire Hazard ◽  
Central Valley ◽  
Geographical Information ◽  
Kathmandu Valley ◽  
Fire Hazards ◽  
Hazard Risk ◽  
Urban Fire ◽  
Hazard Risk Assessment

Natural hazards are complex phenomena that can occur independently, simultaneously, or in a series as cascading events. For any particular region, numerous single hazard maps may not necessarily provide all information regarding impending hazards to the stakeholders for preparedness and planning. A multi-hazard map furnishes composite illustration of the natural hazards of varying magnitude, frequency, and spatial distribution. Thus, multi-hazard risk assessment is performed to depict the holistic natural hazards scenario of any particular region. To the best of the authors’ knowledge, multi-hazard risk assessments are rarely conducted in Nepal although multiple natural hazards strike the country almost every year. In this study, floods, landslides, earthquakes, and urban fire hazards are used to assess multi-hazard risk in Kathmandu Valley, Nepal, using the Analytical Hierarchy Process (AHP), which is then integrated with the Geographical Information System (GIS). First, flood, landslide, earthquake, and urban fire hazard assessments are performed individually and then superimposed to obtain multi-hazard risk. Multi-hazard risk assessment of Kathmandu Valley is performed by pair-wise comparison of the four natural hazards. The sum of observations concludes that densely populated areas, old settlements, and the central valley have high to very high level of multi-hazard risk.

scholarly journals Anti-Reflection Nanostructures on Tempered Glass by Dynamic Beam Shaping

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 289
Author(s):  
Petr Hauschwitz ◽  
Jan Brajer ◽  
Danijela Rostohar ◽  
Jaromír Kopeček ◽  
Tomáš Mocek ◽  
...  
Keyword(s):  
Mobile Phones ◽  
Thermal Damage ◽  
Pulsed Laser ◽  
Processing Parameters ◽  
Beam Shaping ◽  
Separation Distance ◽  
Tempered Glass ◽  
Fundamental Wavelength ◽  
Speed Up ◽  
Scanning Head

Reflectivity and surface topography of tempered glass were modified without any thermal damage to the surroundings by utilizing 1.7 ps ultrashort pulsed laser on its fundamental wavelength of 1030 nm. To speed up the fabrication, a dynamic beam shaping unit combined with a galvanometer scanning head was applied to divide the initial laser beam into a matrix of beamlets with adjustable beamlets number and separation distance. By tuning the laser and processing parameters, reflected intensity can be reduced up to 75% while maintaining 90% of transparency thus showing great potential for display functionalization of mobile phones or laptops.

scholarly journals Determination of Critical Separation Distance Between Dwellings in Informal Settlements Fire

2021 ◽  
Author(s):  
Yu Wang ◽  
Lesley Gibson ◽  
Mohamed Beshir ◽  
David Rush
Keyword(s):  
Heat Flux ◽  
Informal Settlement ◽  
Informal Settlements ◽  
Fire Risk ◽  
Fire Spread ◽  
Separation Distance ◽  
Flame Length ◽  
Critical Distance ◽  
Fire Disaster ◽  
Critical Separation

AbstractApproximately one billion people across the globe are living in informal settlements with a large potential fire risk. Due to the high dwelling density, a single informal settlement dwelling fire may result in a very serious fire disaster leaving thousands of people homeless. In this work, a simple physics-based theoretical model was employed to assess the critical fire separation distance between dwellings. The heat flux and ejected flame length were obtained from a full-scale dwelling tests with ISO 9705 dimension (3.6 m × 2.4 m × 2.4 m) to estimate the radiation decay coefficient of the radiation heat flux away from the open door. The ignition potential of combustible materials in adjacent dwellings are analyzed based on the critical heat flux from cone calorimeter tests. To verify the critical distance in real informal settlement fire, a parallel method using aerial photography within geographic information systems (GIS), was employed to determine the critical separation distances in four real informal settlement fires of 2014–2015 in Masiphumelele, Cape Town, South Africa. The fire-spread distances were obtained as well through the real fires. The probabilistic analysis was conducted by Weibull distribution and logistic regression, and the corresponding separation distances were given with different fire spread probabilities. From the experiments with the assumption of no interventions and open doors and windows, it was established that the heat flux would decay from around 36 kW/m2 within a distance of 1.0 m to a value smaller than 5 kW/m2 at a distance of 4.0 m. Both experiments and GIS results agree well and suggest the ignition probabilities at distances of 1.0 m, 2.0 m and 3.0 m are 97%, 52% and 5% respectively. While wind is not explicitly considered in the work, it is implicit within the GIS analyses of fire spread risk, therefore, it is reasonable to say that there is a relatively low fire spread risk at distances greater than 3 m. The distance of 1.0 m in GIS is verified to well and conservatively predict the fire spread risk in the informal settlements.

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