scholarly journals A Simulation-Based Analysis of the Loss Process of Broadcast Packets in WAVE Vehicular Networks

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Salvador Gonzalez ◽  
Victor Ramos
Keyword(s):  
Analytical Model ◽  
Vehicular Networks ◽  
Loss Rate ◽  
Traffic Load ◽  
Analytical Models ◽  
Ieee 802.11P ◽  
Control Channel ◽  
Channel Switching ◽  
Loss Process ◽  
Hidden Terminal

The IEEE 802.11p standard operates with the WAVE (Wireless Access in Vehicular Environments) system in vehicular ad hoc networks (VANETs). The broadcast process is used to send messages for safety and non-safety applications. A previous work on broadcast packets over the control channel proposes an analytical model to study the loss process. Even if such work does not consider all of the phenomena affecting the operation of vehicular networks, we can obtain a very good approximation of the performance that VANETs may exhibit. Regardless of its importance, this subject has been barely studied. Moreover, there is in the literature only a couple of contributions on this subject, being both analytical models. Therefore, we present in this paper an analysis of the loss process of broadcast packets on the control channel of VANETs over different scenarios. First, we consider a typical two-way scenario and then we analyze a scenario with intersections, both for different vehicle densities. We conduct a campaign of extensive simulations with the NS-3 simulator to study the average loss rate of broadcast packets, and then we compare our results with an analytical model proposed by Campolo et al. We prove the relationship among the contention window, the packet size, and the number of vehicles with the loss rate, including losses caused by noise, collisions, hidden terminal, and channel switching. Thus, we analyze the loss process validating the results obtained by Campolo et al. We find that there are additional factors affecting the loss rate, which cannot be captured with the analytical model. One key finding in this work is that the loss rate due to channel switching differs between both approaches. Also, we find bounds on the use of the control channel, with the loss rate and the traffic load in the network as parameters.

scholarly journals Analytical Models and Performance Evaluation of Vehicular-to-Infrastructure Networks With Optimal Retransmission Number

2021 ◽  
Author(s):  
Aytül Bozkurt
Keyword(s):  
Vehicular Networks ◽  
Markov Chain Model ◽  
Arrival Rate ◽  
High Rate ◽  
Traffic Load ◽  
Analytical Models ◽  
Traffic Model ◽  
Chain Model ◽  
Queuing Model ◽  
The Impact

Abstract Vehicle-to-infrastructure and vehicle-to-vehicle communications has been introduced to provide high rate Internet connectivity to vehicles to meet the ubiquitous coverage and increasing high-data rate internet and multimedia demands by utilizing the 802.11 access points (APs). In order to evaluate the performance of vehicular networks over WLAN, in this paper, we investigate the transmisison and network performance of vehicles that pass through AP by considering contention nature of vehicles over 802.11 WLANs. Firstly, we derived an analytical traffic model to obtain the number of vehicles under transmision range of an AP. Then, incorporating vehicle traffic model with Markov chain model and for arrival packets, M/G/1/K queuing system, we developed a model evaluating the performance of DCF mechanism with an optimal retransmission number. We also derived the probability of mean arrival rate l to AP. A distinctive aspect of our proposed model is that it incorporates both vehicular traffic model and backoff procedure with M/G/1/K queuing model to investigate the impact of various traffic load conditions and system parameters on the vehicular network system. Based on our model, we show that the delay and througput performance of the system reduces with the increasing vehicle velocity due to optimal retransmision number m, which is adaptively adjusted in the network with vehicle mobility.

scholarly journals Novel Structure and Thermal Design and Analysis for CubeSats in Formation Flying

Aerospace ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 150
Author(s):  
Yeon-Kyu Park ◽  
Geuk-Nam Kim ◽  
Sang-Young Park
Keyword(s):  
Analytical Model ◽  
Formation Flying ◽  
Thermal Environment ◽  
Thermal Analyses ◽  
Thermal Design ◽  
Analytical Models ◽  
Test Results ◽  
Solar Panels ◽  
Novel Structure ◽  
Micro Propulsion

The CANYVAL-C (CubeSat Astronomy by NASA and Yonsei using a virtual telescope alignment for coronagraph) is a space science demonstration mission that involves taking several images of the solar corona with two CubeSats—1U CubeSat (Timon) and 2U CubeSat (Pumbaa)—in formation flying. In this study, we developed and evaluated structural and thermal designs of the CubeSats Timon and Pumbaa through finite element analyses, considering the nonlinearity effects of the nylon wire of the deployable solar panels installed in Pumbaa. On-orbit thermal analyses were performed with an accurate analytical model for a visible camera on Timon and a micro propulsion system on Pumbaa, which has a narrow operating temperature range. Finally, the analytical models were correlated for enhancing the reliability of the numerical analysis. The test results indicated that the CubeSats are structurally safe with respect to the launch environment and can activate each component under the space thermal environment. The natural frequency of the nylon wire for the deployable solar panels was found to increase significantly as the wire was tightened strongly. The conditions of the thermal vacuum and cycling testing were implemented in the thermal analytical model, which reduced the differences between the analysis and testing.

The effects of geometric offsets on the dynamic responses of a Scott—Russell amplifying mechanism with flexible hinges

2009 ◽  
Vol 223 (10) ◽  
pp. 2413-2423 ◽  
Author(s):  
C-M Chen ◽  
R-F Fung
Keyword(s):  
Numerical Simulations ◽  
Analytical Model ◽  
Dynamic Responses ◽  
Analytical Models ◽  
Dynamic Equations ◽  
Magnification Factor ◽  
Flexure Hinges ◽  
Magnification Factors ◽  
Straight Line ◽  
Deviation Factor

The dynamic equations of a micro-positioning Scott—Russell (SR) mechanism associated with two flexible hinges and an offset are developed to calculate output responses. Both rigid and flexible hinges are considered to explore the results. The main features in the kinematics of the SR mechanism are its displacement amplification and straight-line motion, which are widely needed in practical industries. The manufacturing inaccuracy of the SR mechanism definitely causes geometric offsets of flexure hinges, and affects displacement amplification and straight-line output motion. Analytical models based on kinematics and Hamilton's principle are derived to explore the variation of linearity ratio, magnification factor, and deviation factor due to various offsets and link lengths. From numerical simulations for the SR mechanism with various offsets of flexible hinges in the conditions of different link lengths, it is found that offsets of flexure hinges obviously affect the amplifying factor and linearity ratio, and appear to dominate the changes of magnification factors. Moreover, an analytical model is also used to predict magnification factors due to various offsets. Finally, some conclusions concerning the effects of offset on the performance of the SR mechanism are drawn.

Modeling of residual stresses by correlating surface topography in machining of AISI 52100 steel

2021 ◽  
pp. 1-26
Author(s):  
Chao Liu ◽  
Yan He ◽  
Yufeng Li ◽  
Yulin Wang ◽  
Shilong Wang ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Cutting Force ◽  
Surface Topography ◽  
Analytical Model ◽  
Analytical Models ◽  
Workpiece Surface ◽  
Dynamic Cutting Force ◽  
Intermittent Cutting ◽  
Effect Of Surface

Abstract The residual stresses could affect the ability of components to bear loading conditions and also the performance. The researchers considered workpiece surface as a plane and ignored the effect of surface topography induced by the intermittent cutting process when modeling residual stresses. The aim of this research develops an analytical model to predict workpiece residual stresses during intermittent machining by correlating the effect of surface topography. The relative motions of tool and workpiece are analyzed for modeling thermal-mechanical and surface topography. The influence of dynamic cutting force and thermal on different positions of surface topography is also considered in analytical model. Then the residual stresses model with the surface topography effect can be developed in intermittent cutting. The analytical models of dynamic cutting force, surface topography and residual stresses are verified by the experiments. The variation trend of evaluated values of the residual stress of workpiece is basically consistent with that of measured values. The compressive residual stress of workpiece surface in highest point of the surface topography are higher than that in the lowest point.

Automated structural assessment of existing reinforced concrete underpasses

2021 ◽  
Author(s):  
Danny Jilissen ◽  
Rob Vergoossen ◽  
Yuguang Yang ◽  
Eva Lantsoght
Keyword(s):  
Reinforced Concrete ◽  
The Netherlands ◽  
Analytical Model ◽  
Load Distribution ◽  
Traffic Load ◽  
Sensitivity Analyses ◽  
Fem Model ◽  
Structural Assessment ◽  
Model Code ◽  
Model Code 2010

<p>Due to the large number of underpasses in the Netherlands that have to be assessed, a project at the Delft University of Technology in cooperation with Royal HaskoningDHV was started. Research was conducted into the automation of the structural assessment of existing reinforced concrete underpasses in the Netherlands. The developed Automated Structural Assessment Tool (ASA Tool) consists of an analytical model and a 2.5D FEM model. The analytical model uses traffic load distribution following the Guyon-Massonnet-Bares method for bending and a method based on <i>fib </i>Model Code 2010 for shear. The script-based 2.5D FEM model uses 2D shell elements and performs a linear elastic analysis. The input and output can be linked to a database for assessment of large batches. Sensitivity analyses showed that in-plane load distribution following <i>fib </i>Model Code 2010 combined with vertical load distribution according to EN 1991-2:2003 results in underestimated shear forces.</p>

scholarly journals A Cooperative Communication Protocol for QoS Provisioning in IEEE 802.11p/Wave Vehicular Networks

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3622 ◽  
Author(s):  
Jin-Woo Kim ◽  
Jae-Wan Kim ◽  
Dong-Keun Jeon
Keyword(s):  
Cooperative Communication ◽  
Vehicular Networks ◽  
Vehicular Ad Hoc Networks ◽  
Ad Hoc ◽  
Communication Protocol ◽  
Ieee 802.11P ◽  
The Road ◽  
Free Data ◽  
On The Road ◽  
Hoc Networks

Vehicular ad hoc networks (VANETs) provide information and entertainment to drivers for safe and enjoyable driving. Wireless Access in Vehicular Environments (WAVE) is designed for VANETs to provide services efficiently. In particular, infotainment services are crucial to leverage market penetration and deployment costs of the WAVE standard. However, a low presence of infrastructure results in a shadow zone on the road and a link disconnection. The link disconnection is an obstacle to providing safety and infotainment services and becomes an obstacle to the deployment of the WAVE standard. In this paper, we propose a cooperative communication protocol to reduce performance degradation due to frequent link disconnection in the road environment. The proposed protocol provides contention-free data delivery by the coordination of roadside units (RSUs) and can provide the network QoS. The proposed protocol is shown to enhance throughput and delay through the simulation.

Overhauling ns-2 PHY/MAC simulations for IEEE 802.11p/WAVE vehicular networks

2012 ◽  
Author(s):  
Claudia Campolo ◽  
Hector Agustin Cozzetti ◽  
Antonella Molinaro ◽  
Riccardo M. Scopigno
Keyword(s):  
Vehicular Networks ◽  
Ieee 802.11P

scholarly journals Analytical Models of the Performance of IEEE 802.11p Vehicle to Vehicle Communications

2021 ◽  
pp. 1-1
Author(s):  
Miguel Sepulcre ◽  
Manuel Gonzalez-Martin ◽  
Javier Gozalvez ◽  
Rafael Molina-Masegosa ◽  
Baldomero Coll-Perales
Keyword(s):  
Analytical Models ◽  
Ieee 802.11P ◽  
Vehicle To Vehicle

scholarly journals Approximate Analytical Models of Shock-Wave Structure at Steady Mach Reflection

Fluids ◽  
2021 ◽  
Vol 6 (9) ◽  
pp. 305
Author(s):  
Mikhail V. Chernyshov ◽  
Karina E. Savelova ◽  
Anna S. Kapralova
Keyword(s):  
Experimental Data ◽  
Shock Wave ◽  
Comparative Analysis ◽  
Analytical Model ◽  
Mach Reflection ◽  
Supersonic Jet ◽  
Wave Structure ◽  
Analytical Models ◽  
Analytical Prediction ◽  
Shock Wave Structure

In this study, we obtain the comparative analysis of methods of quick approximate analytical prediction of Mach shock height in planar steady supersonic flows (for example, in supersonic jet flow and in narrowing channel between two wedges), that are developed since the 1980s and being actively modernized now. A new analytical model based on flow averaging downstream curved Mach shock is proposed, which seems more accurate than preceding models, comparing with numerical and experimental data.

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