Mathematical modelling of curtain coating

We present a simple mathematical model for the fluid flow in the curtain coating process, exploiting the small aspect ratio, and examine the model in the large-Reynolds-number limit of industrial interest. We show that the fluid is in free fall except for a region close to the substrate, but find that the model can not describe the turning of the curtain onto the substrate. We find that the inclusion of a viscous bending moment close to the substrate allows the curtain to “turn the corner”

Dying to help: fatal bystander rescues in Australian coastal environments

Bystanders who drown during a rescue attempt in aquatic waterways are becoming an increasingly important issue within drowning prevention. In the Australian context, the majority of these incidents occur in coastal water ways. This study documents and characterizes bystander rescuer fatalities within Australian coastal waterways that occurred between 1 July 2004 and 30 June 2019 in order to provide suggestions for future public safety interventions involving bystander rescuers. Data was sourced through Surf Life Saving Australia's (SLSA) Coastal Fatality Database, which collates information from multiple sources. Sixty-seven bystander rescuer fatalities in coastal waterways were reported during the 15-year period, an average of 4.5 per year, which is a significant proportion of the five fatalities previously reported across all Australian waterways. The majority of coastal bystander rescuer fatality incidents occurred in the state of New South Wales (49%), at beaches (64%), in regional or remote areas (71%), more than 1 km from the nearest lifesaving service (78%), during summer (45%), in the afternoon (72%), in the presence of rip currents (73%), and did not involve the use of flotation devices to assist rescue (97%). The majority of coastal bystander rescuer victims were Australian residents (88%) born in Australia/Oceania (68%), males (81%), aged between 30-44 years old (36%), visitors to the location (55%), either family (69%) or friends (15%) of the rescuee(s), and were attempting to rescue someone younger than 18 years old (64%). Our results suggest future safety intervention approaches should target males, parents and carers visiting beach locations in regional locations during holiday times and should focus on the importance of flotation devices when enacting a rescue and further educating visitors about the rip current hazard. Future research should examine the psychology of bystander rescue situations and evaluate the effectiveness of different safety intervention approaches

Who rescues who? Understanding aquatic rescues in Australia using coronial data and a survey

Objective: To examine fatal drowning associated with aquatic rescues and prior self‐reported experience of undertaking an aquatic rescue in Australia. Methods: Previous aquatic rescue experience was sourced through the 2013 Queensland Computer Assisted Telephone Instrument Survey and compared to data on rescue‐related fatal unintentional drowning between 1 January 2006 and 31 December 2015. Results: Twenty‐three per cent (n=294/1291) of survey respondents had previously performed an aquatic rescue. Males (X2=35.2; p<0.001) were more likely to have performed a rescue; commonly at a beach/ocean/harbour location (X2=13.5; p<0.001). Females were more likely to have rescued a child (0‐4 years of age) (X2=29.2; p<0.001) from a swimming pool (X2=34.3; p<0.001). Fifty‐one people drowned while performing an aquatic rescue (Males=82.4%; 25–44 years of age=53.0%; beaches=54.9%). Conclusions: Drownings are prevented by bystanders; this is not without risk to the rescuer. Most people perform only one rescue in their life, often at a younger age, on an altruistic basis, of family members or young children. Community‐wide rescue skills, taught at a young age, with consideration for coastal, inland and swimming pool environments, may prevent drowning

Mathematical Model of Easter Island Society Collapse

In this paper we consider a mathematical model for the evolution and collapse of the Easter Island society, starting from the fifth century until the last period of the society collapse (fifteen century). Based on historical reports, the available primary sources consisted almost exclusively on the trees. We describe the inhabitants and the resources as an isolated system and both considered as dynamic variables. A mathematical analysis about why the structure of the Easter Island community collapse is performed. In particular, we analyze the critical values of the fundamental parameters driving the interaction humans-environment and consequently leading to the collapse. The technological parameter, quantifying the exploitation of the resources, is calculated and applied to the case of other extinguished civilization (Cop\'an Maya) confirming, with a sufficiently precise estimation, the consistency of the adopted model.Comment: 9 pages, 1 figure, final version published on EuroPhysics Letter

Bailouts in a common market: a strategic approach

Governments in the EU grant Rescue and Restructure Subsidies to bail out ailing firms. In an international asymmetric Cournot duopoly we study effects of such subsidies on market structure and welfare. We adopt a common market setting, where consumers from the two countries form one market. We show that the subsidy is positive also when it fails to prevent the exit. The reason is a strategic effect, which forces the more efficient firm to make additional cost-reducing effort. When the exit is prevented, allocative and productive efficiencies are lower and the only gaining player is the rescued firm

Characteristics of aquatic rescues undertaken by bystanders in Australia

An issue of growing importance within the field of drowning prevention is the undertaking of aquatic rescues by bystanders, who sometimes drown in the process. The main objectives of this study were to describe characteristics of bystanders making rescues in different Australian aquatic environments, identify the role of prior water safety training in conducting bystander rescues and provide insights into future public education strategies relating to bystander rescue scenarios. An online survey was disseminated via various social media platforms in 2017 and gathered a total of 243 complete responses. The majority of bystander rescues described took place in coastal waterways (76.5%; n = 186), particularly beaches (n = 67), followed by pools (17.3%; n = 42) and inland waterways (6.2%; n = 15). The majority of respondents were males (64.2%; n = 156) who rescued on average approximately twice as many people in their lifetime (6.5) than female respondents (3.6). Most rescues occurred more than 1 km from lifeguard/lifesaver services (67%; n = 163), but in the presence of others (94.2%; n = 229). The majority of bystander rescuers had water safety training (65.8%; n = 160), self-rated as strong swimmers (68.3%; n = 166), conducted the rescue without help from others (60%; n = 146), did not use a flotation device to assist (63%; n = 153), but were confident in their ability to make the rescue (76.5%; n = 186). However, most considered the situation to be very serious (58%; n = 141) and felt they had saved a life (70.1%; n = 172). With the exception of pools, most bystanders rescued strangers (76.1%; n = 185).While Australia clearly benefits from having a strong water safety culture, there is no clear consensus on the most appropriate actions bystanders should take when confronted with a potential aquatic rescue scenario. In particular, more research is needed to gather information regarding bystander rescues undertaken by those without prior water safety training