Performance Analysis of Prefix Delegation-Based Route Optimization Schemes: Effects of Increasing the Number of Nodes

Prefix delegation-based schemes have been proposed to solve the route optimization problem in NEtwork MObility where multiple IP-enabled hosts move together as a mobile network. Differences in the route optimization for hosts at the cost of increased signaling will result in performance difference of the schemes depending on parameters, such as speed of the mobile network, its distance from the home network (the network to which mobile network usually belongs), and the number of hosts in the mobile network. Although the effects of the first two parameters on the performance of the schemes have been studied, effects of increasing the number of hosts have not been studied. Therefore, there is a need to evaluate performance when the number of hosts is increased. We perform the evaluation through ns-2 simulation. Results show that the performance superiority achieved by the hosts?? route optimization is only affected by the distance significantly only when the number of hosts is small. The results will help to decide when to use the route optimization for hosts depending on the values of the parameters.     

Thermal product estimation method for aerodynamics experiments

This paper presents an experimental technique to estimate the appropriate thermal product values of rugged and fast response temperature probes (TPs) for hypersonic aerodynamic experiments. Two types of scratches were used, mainly abrasive papers with different grit sizes and scalpel blades with different thicknesses, to form the probe junction. The effect of the scratch technique on the probe’s thermal product is investigated. The probes are tested and calibrated in the test section and in the end wall of shock tube facility. It is observed that the thermal product of a particular TP depends on the Mach number, junction scratch technique, and junction location, as well as on the enthalpy conditions. It is noted that, depending on the scratch technique, some of the TPs do not require individual calibration; however, calibration for others is likely to be needed.     

Ab initio study of phase stability in doped TiO2

Ab initio density functional theory calculations of the relative stability of the anatase and rutile polymorphs of TiO₂ were carried out using all-electron atomic orbitals methods with local density approximation. The rutile phase exhibited a moderate margin of stability of ~ 3 meV relative to the anatase phase in pristine material. From computational analysis of the formation energies of Si, Al, Fe and F dopants of various charge states across different Fermi level energies in anatase and in rutile, it was found that the cationic dopants are most stable in Ti substitutional lattice positions while formation energy is minimised for F^? doping in interstitial positions. All dopants were found to considerably stabilise anatase relative to the rutile phase, suggesting the anatase to rutile phase transformation is inhibited in such systems with the dopants ranked F?>?Si?>?Fe?>?Al in order of anatase stabilisation strength. Al and Fe dopants were found to act as shallow acceptors with charge compensation achieved through the formation of mobile carriers rather than the formation of anion vacancies.     

Fast response surface temperature sensor for hypersonic vehicles1

This paper describes the design, fabrication, and evaluation technique of fast response Surface Temperature Sensor (STS). This STS was made of chromel-constantan elements with 2.2 and 0.8 mm in diameter. The calibration technique using shock tube facility for measuring the transient surface temperature and heat transfer rate is also presented. It has been proved that the STS response time is very short (less than 50 μs), and a rise time in studies of a transient surface temperature is less than 0.5 μs.     

Cumulative Sum Control Charts for Monitoring Weibull‐distributed Time Between Events

The Weibull distribution can be used to effectively model many different failure mechanisms due to its inherent flexibility through the appropriate selection of a shape and a scale parameter. In this paper, we evaluate and compare the performance of three cumulative sum (CUSUM) control charts to monitor Weibull‐distributed time‐between‐event observations. The first two methods are the Weibull CUSUM chart and the exponential CUSUM (ECUSUM) chart. The latter is considered in literature to be robust to the assumption of the exponential distribution when observations have a Weibull distribution. For the third CUSUM chart included in this study, an adjustment in the design of the ECUSUM chart is used to account for the true underlying time‐between‐event distribution. This adjustment allows for the adjusted ECUSUM chart to be directly comparable to the Weibull CUSUM chart. By comparing the zero‐state average run length and average time to signal performance of the three charts, the ECUSUM chart is shown to be much less robust to departures from the exponential distribution than was previously claimed in the literature. We demonstrate the advantages of using one of the other two charts, which show surprisingly similar performance. Copyright © 2014 John Wiley & Sons, Ltd.