Current Issue : January - March Volume : 2012 Issue Number : 1 Articles : 6 Articles
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 bifocal perception 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....
The internal parameter of UNI 60 rail is calculated by using finite elements methods. Steel's characterizations by its normal magnetization curve and by complex magnetic permeability are here considered and included into the proposed FEM models. Rail'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?Hz are compared with few measurements available, and then they are extended to other frequencies....
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 static networks. In this paper, we evaluate the physical carrier sensing-based CDS maintenance for mobile 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....
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 themââ?¬â?with acceptable complexityââ?¬â?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....
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....
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 NC generation during combustion between above different strategies....
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