Degradation of Communication Range in VANETs Caused by Interference 2.0 - Real-World Experiment

High channel load in vehicle-to-vehicle communication leads to a degradation of the vehicles’ communication range, due to interference and hence packet loss at larger distances. Packet loss results from two or more concurrent transmissions, colliding at receivers located inbetween, which is also known as the hidden station problem. In previous works, our simulation study has shown that this packet loss leads to a degradation of 90% of the communication range. In this paper, we confirm the simulation results by real-world measurements. We present a methodology for transferring the simulation scenario to a real-world measurement scenario, able to evaluate the problem of hidden stations. With three radios applying the IEEE 802.11p standard, we measure the degradation of the communication range under interference. In the measurement, we find a degradation of 50 to 70%. On the one hand, there are less collisions due to only one hidden station. On the other hand, we identify that the receiving vehicle as a shadowing object itself is an additional origin for hiding the other station which slightly increases the number of collisions even at close distances

Multi-stage high order semi-Lagrangian schemes for incompressible flows in Cartesian geometries

Efficient transport algorithms are essential to the numerical resolution of incompressible fluid flow problems. Semi-Lagrangian methods are widely used in grid based methods to achieve this aim. The accuracy of the interpolation strategy then determines the properties of the scheme. We introduce a simple multi-stage procedure which can easily be used to increase the order of accuracy of a code based on multi-linear interpolations. This approach is an extension of a corrective algorithm introduced by Dupont \& Liu (2003, 2007). This multi-stage procedure can be easily implemented in existing parallel codes using a domain decomposition strategy, as the communications pattern is identical to that of the multi-linear scheme. We show how a combination of a forward and backward error correction can provide a third-order accurate scheme, thus significantly reducing diffusive effects while retaining a non-dispersive leading error term.Comment: 14 pages, 10 figure

An iterative semi-implicit scheme with robust damping

An efficient, iterative semi-implicit (SI) numerical method for the time integration of stiff wave systems is presented. Physics-based assumptions are used to derive a convergent iterative formulation of the SI scheme which enables the monitoring and control of the error introduced by the SI operator. This iteration essentially turns a semi-implicit method into a fully implicit method. Accuracy, rather than stability, determines the timestep. The scheme is second-order accurate and shown to be equivalent to a simple preconditioning method. We show how the diffusion operators can be handled so as to yield the property of robust damping, i.e., dissipating the solution at all values of the parameter \mathcal D\dt, where $\mathcal D$ is a diffusion operator and \dt the timestep. The overall scheme remains second-order accurate even if the advection and diffusion operators do not commute. In the limit of no physical dissipation, and for a linear test wave problem, the method is shown to be symplectic. The method is tested on the problem of Kinetic Alfv\'en wave mediated magnetic reconnection. A Fourier (pseudo-spectral) representation is used. A 2-field gyrofluid model is used and an efficacious k-space SI operator for this problem is demonstrated. CPU speed-up factors over a CFL-limited explicit algorithm ranging from $\sim20$ to several hundreds are obtained, while accurately capturing the results of an explicit integration. Possible extension of these results to a real-space (grid) discretization is discussed.Comment: Submitted to the Journal of Computational Physics. Clarifications and caveats in response to referees, numerical demonstration of convergence rate, generalized symplectic proo

Results of the 2016 Indianapolis Biodiversity Survey, Marion County, Indiana

Surprising biodiversity can be found in cities, but urban habitats are understudied. We report on a bioblitz conducted primarily within a 24-hr period on September 16 and 17, 2016 in Indianapolis, Indiana, USA. The event focused on stretches of three waterways and their associated riparian habitat: Fall Creek (20.6 ha; 51 acres), Pleasant Run (23.5 ha; 58 acres), and Pogue’s Run (27.1 ha; 67 acres). Over 75 scientists, naturalists, students, and citizen volunteers comprised 14 different taxonomic teams. Five hundred ninety taxa were documented despite the rainy conditions. A brief summary of the methods and findings are presented here. Detailed maps of survey locations and inventory results are available on the Indiana Academy of Science website (https://www.indianaacademyofscience.org/)

International Coercion, Emulation and Policy Diffusion: Market-Oriented Infrastructure Reforms, 1977-1999

Why do some countries adopt market-oriented reforms such as deregulation, privatization and liberalization of competition in their infrastructure industries while others do not? Why did the pace of adoption accelerate in the 1990s? Building on neo-institutional theory in sociology, we argue that the domestic adoption of market-oriented reforms is strongly influenced by international pressures of coercion and emulation. We find robust support for these arguments with an event-history analysis of the determinants of reform in the telecommunications and electricity sectors of as many as 205 countries and territories between 1977 and 1999. Our results also suggest that the coercive effect of multilateral lending from the IMF, the World Bank or Regional Development Banks is increasing over time, a finding that is consistent with anecdotal evidence that multilateral organizations have broadened the scope of the “conditionality” terms specifying market-oriented reforms imposed on borrowing countries. We discuss the possibility that, by pressuring countries into policy reform, cross-national coercion and emulation may not produce ideal outcomes.http://deepblue.lib.umich.edu/bitstream/2027.42/40099/3/wp713.pd

Chemical Power for Microscopic Robots in Capillaries

The power available to microscopic robots (nanorobots) that oxidize bloodstream glucose while aggregated in circumferential rings on capillary walls is evaluated with a numerical model using axial symmetry and time-averaged release of oxygen from passing red blood cells. Robots about one micron in size can produce up to several tens of picowatts, in steady-state, if they fully use oxygen reaching their surface from the blood plasma. Robots with pumps and tanks for onboard oxygen storage could collect oxygen to support burst power demands two to three orders of magnitude larger. We evaluate effects of oxygen depletion and local heating on surrounding tissue. These results give the power constraints when robots rely entirely on ambient available oxygen and identify aspects of the robot design significantly affecting available power. More generally, our numerical model provides an approach to evaluating robot design choices for nanomedicine treatments in and near capillaries.Comment: 28 pages, 7 figure

Substance use, sleep and intervention design:insights from qualitative data

BACKGROUND: Alcohol and other drug use is associated with poor sleep quality and quantity, but there is limited qualitative research exploring substance users' experiences of sleep and few psychosocial sleep interventions for them.AIM: To inform the development of psychosocial interventions to improve sleep amongst people reporting drug/alcohol problems.METHOD: Qualitative data were collected during a sleep survey. Of the 549 drug/alcohol users completing the survey, 188 (34%) provided additional information about their sleep using a free text box. Responses were analysed via Iterative Categorisation. Findings were reviewed with reference to the Behaviour Change Wheel (BCW).RESULTS: All data were categorised inductively under five headings: (i) sleep quality; (ii) nature of sleep problems; (iii) sleep and substances; (iv) factors improving sleep quality; (v) factors undermining sleep quality. Substance use undermined sleep, but poor sleep often persisted after substance use had ceased. Sleep problems were diverse; as were the causes of, and strategies for dealing with, those problems. Causes and strategies had biological, psychological, social and environmental roots.CONCLUSIONS: The BCW facilitated the identification of intervention components that might improve the sleep of people who use substances. These components relate to education, training, enablement, modelling, service provision, guidelines and environment.</p

Heroin-induced respiratory depression and the influence of dose variation: within-subject between-session changes following dose reduction

Background and aims: Globally, more than 100 000 people die annually from opioid overdose. Opportunities to study physiological events in at-risk individuals are limited. This study examined variation of opioid dose and impact on respiratory depression in a chronic injecting heroin user at separate time-points during his long-term diamorphine maintenance treatment. Design: A single-subject study over 5 years during which participant underwent experimental studies on diamorphine-induced respiratory depression, at changing maintenance doses. Setting: A clinical research facility. Participant. Male subject on long-term injectable diamorphine (pharmaceutical heroin) maintenance treatment for heroin addiction. Measurements: Physiological measures of oxygen saturation (SpO 2), end-tidal carbon dioxide (ETCO 2) and respiratory rate (RR) were used to indicate severity of respiratory depression. Findings: (1) After diamorphine injection, respiratory regulation became abnormal, with prolonged apnoea exceeding 20 sec (maximum 56 sec), elevated ETCO 2 (maximum 6.9%) and hypoxaemia (minimum SpO 2 80%). (2) Abnormalities were greater with highest diamorphine dose: average SpO 2 was 89.3% after 100 mg diamorphine versus 93.6% and 92.8% for the two 30-mg doses. (3) However, long apnoeic pauses and high levels of ETCO 2% were also present after lower doses. Conclusions: With marked inter-session variability, these findings corroborate observations of inconsistent relationships between opioid dose and overdose risk. </p