The internal parameter of UNI 60 rail is calculated by using finite elements methods. Steel&#39;s characterizations by its normal magnetization curve and by complex magnetic permeability are here considered and included into the proposed FEM models. Rail&#39;s resistance and internal inductance in function of current and frequency are calculated using both FEM and analytical models. The results obtained at the frequency of 50&#x2009;Hz are compared with few measurements available, and then they are extended to other frequencies.

Alberto Dolara

Sonia Leva

Calculation of Rail Internal Impedance by Using Finite Elements Methods and Complex Magnetic Permeability

Unlike sensor and other ad-hoc wireless networks, vehicular
ad-hoc networks (VANETs) are characterized by its
high mobility which allows a very short communication
interval among onboard units (OBUs) and between an
OBU and road-side units (RSUs). This major characterization
motivates the design of communication protocols
that are noninteractive or at least require a very limited
number of rounds between units. The challenging issue
is that such protocols must satisfy a number of security
services that could be complex by their nature.
In secure VANETs protocols, anonymity and traceability
are two important services, yet, achieving a satisfactory
security level for both of them—with acceptable complexity—is not an easy task due to the contradicting requirements: anonymous transmission must not be traceable
by any individual while if a transmission is traceable,
then anonymity is threatened. Existing secure VANETs
protocols for anonymous and traceable transmissions either,
provide unconditional anonymity where traceability
and revocation are impossible, or grant trust to a thirdparty
not to reveal the identity of a unit unless there is a
legal reason. In this paper, we propose the first secure VANET protocol
that allows authenticated transmission among OBUs
and RSUs and at the same time enjoys the following properties.
(i) The transmission among OBUs and RSUs is
noninteractive (i.e., a one-move transmission without any
interactive setup requirements). (ii) The authenticated
transmission between any pair of units is anonymous (i.e.,
no single authority knows any information about the identity
of the communicating OBU). (iii) In serious road
crimes (e.g., hit-and-run, road rage, etc.) and under court
order, an OBU could be traced to its clear identity.
We also show how our protocol could be used to setup
a confidential session between any pair of units without
relying on extensive number of interactive rounds.

Maged Hamada Ibrahim

Noninteractive, Anonymously Authenticated, and Traceable Message Transmission for VANETs

This paper aims to 
                  study the performance of low complexity adaptive 
                  resource allocation in the downlink of OFDMA 
                  systems with fixed or variable rate requirements 
                  (with fairness consideration). Two suboptimal 
                  resource allocation algorithms are proposed 
                  using the simplifying assumption of transmit 
                  power over the entire bandwidth. The objective 
                  of the 
first algorithm is to maximize the total throughput while 
maintaining rate proportionality among the users. The proposed 
suboptimal algorithm prioritizes the user with the highest 
sensitivity to the subcarrier allocation, and the variance over the 
subchannel gains is used to define the sensitivity of each user. 
The second algorithm concerns rate adaptive resource allocation in 
multiuser systems with fixed rate constraints. We propose a 
suboptimal joint subchannel and power allocation algorithm which 
prioritizes the users with the highest required data rates. The main 
feature of this algorithm is its low complexity while achieving 
the rate requirements.

Sanam Sadr

Alagan Anpalagan

Kaamran Raahemifar

Suboptimal Rate Adaptive Resource Allocation for Downlink OFDMA Systems

We propose to use IEEE 802.11e in conjunction with retransmission mechanisms for priority-based Intervehicle Communication (IVC) for highway safety messaging in both vehicular infrastructure and ad hoc networks. Each IVC message, which is assigned a priority based on the safety event urgency, requires different quality of service in terms of communication reliability and average delay. To increase the communication reliability in a broadcast-based IVC, we apply retransmission mechanisms that can provide proportional reliability differentiation for each prioritized message. We evaluate the performance of our proposed protocol using OPNET Modeler, in terms of percentage of successful transmissions and average delay. The protocol performance is evaluated for (1) different system parameters such as the packet size, number of vehicles, and percentage of priority 1 vehicles, and (2) priority-based protocol parameters, such as contention window, interframe spacing and retransmission parameters. The results show that proper protocol parameter settings per priority message result in an efficient solution for priority based broadcast IVC. Moreover, the proposed protocol is fully compatible with both IEEE 802.11 and IEEE 802.11e standards.

Chakkaphong Suthaputchakun

Priority-Based Inter-Vehicle Communication for Highway Safety Messaging Using IEEE 802.11e

Physical carrier sensing has to date mainly been exploited for improving medium access control in wireless networks. Recently, a parallel algorithm striving to extensively exploit physical carrier sensing
for constructing and maintaining a connected dominating set (CDS), which is also known as spanner,
backbone, or overlay network in wireless ad hoc networks with interference ranges larger than transmission
ranges has been proposed. Existing evaluations of this algorithm are limited to theoretical asymptotic
bounds and simulations of <i>static</i> networks. In this paper, we evaluate the physical carrier sensing-based
CDS maintenance for <i>mobile</i> ad hoc networks through discrete event simulations. For a wide range of
node speeds and node densities, we evaluate the CDS characteristics and message exchanges required for
maintaining the CDS. We find that the algorithm maintains a stable leader set dominating all nodes in the
network for a wide range of mobility levels but struggles to maintain connectivity at high mobility levels.
We also quantify the portions of the control messages for CDS maintenance that are exchanged through
physical carrier sensing. We find that the parallel algorithm manages to greatly reduce the reliance on
intact message receptions.

Sapna Deval

Luke Ritchie

Martin Reisslein

Andrea W. Richa

Evaluation of Physical Carrier Sense Based Backbone Maintenance in Mobile Ad Hoc Networks

Choosing various injection strategies and intake conditions are potentially effective techniques to reduce exhaust emission from diesel engines. The purpose of this study is to investigate the effect of different spray incoming angles, different spray cone angles, different injection timing, and different intake temperatures together with emission characteristics on a heavy duty diesel engine via three dimensional computational fluid dynamics (CFD) procedures. Furthermore the effect of multiple injector combustion chamber and its benefits in pollutant reduction is studied. The principal results show the significant differences in soot and <svg style="vertical-align:-0.13794pt;width:25.174999px;" id="M1" height="10.75" version="1.1" viewBox="0 0 25.174999 10.75" width="25.174999"  xmlns="http://www.w3.org/2000/svg">
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M. Gorji-Bandpy

S. Soleimani

D. D. Ganji

The Effect of Different Injection Strategies and Intake Conditions on the Emissions Characteristics in a Diesel Engine

The numerous benefits of real-time 3D awareness for autonomous vehicles have motivated the incorporation of stereo cameras to the perception units of intelligent vehicles. The availability of the distance between camera and objects is essential for such applications as automatic guidance and safeguarding; however, a poor estimation of the position of the objects in front of the vehicle can result in dangerous actions. There is an emphasis, therefore, in the design of perception engines that can make available a rich and reliable interval of ranges in front of the camera. The objective of this research is to develop a stereo head that is capable of capturing 3D information from two cameras simultaneously, sensing different, but complementary, fields of view. In order to do so, the concept of <i>bifocal perception</i> was defined and physically materialized in an experimental bifocal stereo camera. The assembled system was validated through field tests, and results showed that each stereo pair of the head excelled at a singular range interval. The fusion of both intervals led to a more faithful representation of reality.

Francisco Rovira-Más

Qi Wang

Qin Zhang

Bifocal Stereoscopic Vision for Intelligent Vehicles

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International Journal of Vehicular Technology - Table of contents 2009

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International Journal of Vehicular Technology

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International Journal of Vehicular Technology