Dynamic stop pooling for flexible and sustainable ride sharing

Ride sharing -- the bundling of simultaneous trips of several people in one vehicle -- may help to reduce the carbon footprint of human mobility. However, the complex collective dynamics pose a challenge when predicting the efficiency and sustainability of ride-sharing systems. Standard door-to-door ride sharing services trade reduced route length for increased user travel times and come with the burden of many stops and detours to pick up individual users. Requiring some users to walk to nearby shared stops reduces detours, but could become inefficient if spatio-temporal demand patterns do not well fit the stop locations. Here, we present a simple model of dynamic stop pooling with flexible stop positions. We analyze the performance of ride sharing services with and without stop pooling by numerically and analytically evaluating the steady state dynamics of the vehicles and requests of the ride sharing service. Dynamic stop pooling does a-priori not save route length, but occupancy. Intriguingly, it also reduces the travel time, although users walk parts of their trip. Together, these insights explain how dynamic stop pooling may break the trade-off between route lengths and travel time in door-to-door ride sharing, thus enabling higher sustainability and service quality.

Finally a Smoking Gun? Compensating Differentials and the Introduction of Smoking Bans

Using the staggered introduction of smoking bans in the German hospitality industry over 2007–2008, I find a robust 2.4 percent decline in the daily earnings of workers in bars and restaurants associated with the most comprehensive smoking ban. This effect is unlikely to be driven by a decline in hospitality revenues or hours worked but is consistent with a simple model of compensating differentials. (JEL I12, I18, J22, J31, J81, L83)

Optimal Choice of Vaccination Scheduling in a Population Composed of Two Groups

In this chapter, the authors present a simple model to determine the optimal choice of vaccination scheduling for a society composed of two groups of individuals in order to minimize the economic loss only, assuming herd immunity. First, a simple classical SIR model is presented to form the basis of the analysis; second, the model is revised to include the effects of vaccination which in turn will be extended to include two heterogeneous groups of individuals forming a society. The solutions of relevant differential equations will then be used to calculate the total economic cost of each scenario presented.

Transient prophylaxis and multiple epidemic waves

<abstract><p>Public opinion and opinion dynamics can have a strong effect on the transmission rate of an infectious disease for which there is no vaccine. The coupling of disease and opinion dynamics however, creates a dynamical system that is complex and poorly understood. We present a simple model in which susceptible groups adopt or give up prophylactic behaviour in accordance with the influence related to pro- and con-prophylactic communication. This influence varies with disease prevalence. We observe how the speed of the opinion dynamics affects the total size and peak size of the epidemic. We find that more reactive populations will experience a lower peak epidemic size, but possibly a larger final size and more epidemic waves, and that an increase in polarization results in a larger epidemic.</p></abstract>

A simple model to estimate air temperature and soil temperatures under vertisol

Hnscd on a truncated s ine curve and exp onential fu nction models. diu rnal cha nges in airand soil temperat ures have I:....'en estima ted during day and night hours respect!....el..·. Each model uses o nlv fo urparameters. viz.. maximum a nd mini mum temperature at va rious levels. the lime ()f sunset and durat ion t;f da ylnight length. The models. when a pplied to experimental as well as independent dat a sets, were fo und to givereasonably accu rate estimates for a n>' lime of the day an d night except between I·B O1ST and sunset at the gro undsurface.

Cometary Activity beyond the Planets

Recent observations show activity in long-period comet C/2017 K2 at heliocentric distances beyond the orbit of Uranus. With this as motivation, we constructed a simple model that takes a detailed account of gas transport modes and simulates the time-dependent sublimation of supervolatile ice from beneath a porous mantle on an incoming cometary nucleus. The model reveals a localized increase in carbon monoxide (CO) sublimation close to heliocentric distance r H = 150 au (local blackbody temperature ∼23 K), followed by a plateau and then a slow increase in activity toward smaller distances. This localized increase occurs as heat transport in the nucleus transitions between two regimes characterized by the rising temperature of the CO front at larger distances and nearly isothermal CO at smaller distances. As this transition is a general property of sublimation through a porous mantle, we predict that future observations of sufficient sensitivity will show that inbound comets (and interstellar interlopers) will exhibit activity at distances far beyond the planetary region of the solar system.