Evaluation of dynamic explicit mpm formulations for unsaturated soils

Many applications in geohazards prevention involve large deformations of unsaturated soils, e.g. rainfall induced landslides, embankment collapses due to wetting etc. These phenomena can be investigated with multiphase implementations of the Material Point Method (MPM) able to account for the behaviour of unsaturated soils. This paper compares two formulations: (i) afully coupled three-phase formulation(3P)in which the governing equations are derived from the momentum balance and the mass balance equations of solid, liquid and gas phase assuming non-zero gas pressure,the primary unknowns are the absolute accelerationsof the phases (aS–aL–aG formulation); (ii)a simplified approachthatneglectsthe momentum balance equation of the gas(2P_s).Potentialities and limitations of these approaches are highlighted consideringa 1D infiltration problem.Despite the introduced simplifications, the simplified formulation gives reasonably good results in many engineering cases

Aim, scope, conceptual framework and definitions

Mobility is a basic requirement of modern society. Distance separates individuals’ homes from places where they work, shop, do business, undertake leisure and recreational activities, and socially interact. Public transit plays a key role in reducing social exclusion by offering access to these fundamental life activities. For example, in Sweden and in Great Britain, one-quarter of households do not own a car (SIKA, 2008; DfT, 2012). Moreover, access to a car is not equally distributed amongst the population, and varies by age, gender, ethnicity and socio-economic status. Particular groups are more reliant on public transportation than others (Kunieda and Gauthier, 2007; Raphael et al. 2006). Furthermore, there are obvious environmental benefits in promoting public transport as a means of sustainable travel (Steg and Gifford, 2005). Since public transportation is a cornerstone of sustainable development, passengers deserve convenient and reliable transportation systems. However, getting people to use public transportation systems is not just a matter of making them efficient and cost effective. Passengers need to feel safe not just at stops and stations but also during their entire journey. Transportation systems encompass more than buses, trains and infrastructure. They constitute actual transit environments in which individuals spend time on a daily basis and are, therefore, important settings in everyday life. Indeed, one in five Europeans spend on average more than two hours a day commuting in these transit environments (Stepstone, 2012)

Theoretical perspectives of safety and security in transit environments

This chapter discusses the extant theories used to explain safety and security in transit environments, which are set out within the conceptual framework identified in the previous chapter. A number of theoretical perspectives have been developed to explain the prevalence of crime, disorder and associated fear in society. None of these are without criticism, and none have been developed explicitly for the purpose of explaining safety and security on public transport systems. This section examines current security and criminological theories, and ideas and perspectives from other fields and disciplines, to ascertain their utility for explaining safety and security specifically in the context of public transportation. The aim is to translate these theories into an integrated and theory-led conceptual framework within which safety and security on public transport systems can readily be examined

Practical challenges and new research frontiers for safety and security in transit environments

This chapter brings together this edited volume, and highlights and summarizes the main findings presented in the book, based on each of the preceding five sections. It examines the conceptual framework, and the main findings that arise from each section. These include safety and security at the transit node, the journey, links to the surrounding settings and the perspective of the user. It provides an overview of why safety and security is challenging and complex, and discusses the utility of the conceptual framework in tackling this. It then suggests new research frontiers for safety in transit environments, before concluding with some recommendations for future policy

Crime at the intersection of rail and retail

This chapter examines shoplifting at rail station shops over a 12 month period in England and Wales. Key findings were: shoplifting is concentrated at particular stations; the top 20 stations account for 85% of shoplifting. Clear temporal patterns were evident; shoplifting was higher on weekdays and during holidays with higher levels of travel; shoplifting is lower when there is a reduced rail service. There was no clear relationship between shoplifting rates outside of a station at shops nearby, and shoplifting within a rail station. It is suggested a correlation may occur for medium and smaller size stations. Large stations may attract offenders in their own right without other shops being nearby. The similarities observed between shoplifting patterns at rail stations and those at non-rail station shops suggest the learning from successful crime prevention measures applied outside of the rail environment could successfully transferred to rail stations

Editorial: crime patterns in time and space: the dynamics of crime opportunities in urban areas

The routine activity approach and associated crime pattern theory emphasise how crime emerges from spatio-temporal routines. In order to understand this crime should be studied in both space and time. However, the bulk of research into crime patterns and related activities has investigated the spatial distributions of crime, neglecting the temporal dimension. Specifically, disaggregation of crime by place and by time, for example hour of day, day of week, month of year, season, or school day versus none school day, is extremely relevant to theory. Modern data make such spatio-temporal disaggregation increasingly feasible, as exemplified in this special issue. First, much larger data files allow disaggregation of crime data into temporal and spatial slices. Second, new forms of data are generated by modern technologies, allowing innovative and new forms of analyses. Crime pattern analyses and routine activity inquiries are now able to explore avenues not previously available. The unique collection of nine papers in this thematic issue specifically examine spatio-temporal patterns of crime to; demonstrate the value of this approach for advancing knowledge in the field; consider how this informs our theoretical understanding of the manifestations of crime in time and space; to consider the prevention implications of this; and to raise awareness of the need for further spatio-temporal research into crime event

Numerical and experimental investigation of saturated granular column collapse in air

Many hazardous natural phenomena like debris flows, avalanches and submerged landslides are governed by the interactions between solid grains and interstitial fluid. They display a complex interplay of physical mechanisms, which are still very challenging to simulate with numerical methods. Different methods have been proposed in the literature to achieve this goal. This paper compares the results of two different numerical approaches: (i) a macromechanical continuum approach with the two-phase double-point Material Point Method (MPM) and (ii) a micromechanical approach with Discrete Element Method coupled with the Lattice Boltzmann Method (DEM-LBM). With the objective of highlighting potentialities and critical points of the two approaches, we conduct saturated granular column collapses in a small-scale laboratory experiment, subsequently reproduced by the numerical codes. Unlike previous experiments of collapse under gravity in dry or completely submerged conditions, in this paper the saturated material is released in air. These conditions better reproduce real natural onshore landslides and allows a discussion on the solid–fluid interaction

Tele-medicine versus face-to-face consultation in Endocrine Outpatients Clinic during COVID-19 outbreak: a single-center experience during the lockdown period

The COVID-19 outbreak in Italy is the major concern of Public Health in 2020: measures of containment were progressively expanded, limiting Outpatients' visit

The ecology of outdoor rape: The case of Stockholm, Sweden

The objective of this article is to report the results of an ecological study into the geography of rape in Stockholm, Sweden, using small area data. In order to test the importance of factors indicating opportunity, accessibility and anonymity to the understanding of the geography of rape, a two-stage modelling approach is implemented. First, the overall risk factors associated with the occurrence of rape are identified using a standard Poisson regression, then a local analysis using profile regression is performed. Findings from the whole-map analysis show that accessibility, opportunity and anonymity are all, to different degrees, important in explaining the overall geography of rape - examples of these risk factors are the presence of subway stations or whether a basområde is close to the city centre. The local analysis reveals two groupings of high risk of rape areas associated with a variety of risk factors: city centre areas with a concentration of alcohol outlets, high residential population turnover and high counts of robbery; and poor suburban areas with schools and large female residential populations where subway stations are located and where people express a high fear of crime. The article concludes by reflecting upon the importance of these results for future research as well as indicating the implications of these results for policy