Electrical properties of SiO2-doped sodium metavanadate sintered discs

Impedance of sintered discs of 0·1, 0·25, 0·4 mol% of sodium metavanadate was measured in the frequency range 10 kHz-1 MHz and in the temperature region from room temperature (=30°C) to 450°C. AC conductivity was calculated from the data. DC conductivity was measured in the temperature range 150–450°C. Debye type of relaxation effects were observed in the dielectric loss. The activation energy of the dipoles involved in relaxation was estimated. The activation energy for AC conduction in the temperature above 380°C was calculated. These values are larger than the activation energy of pure sodium metavanadate sample. The relaxation phenomenon observed is explained.     

Shared partial path protection in WDM networks with shared risk link groups

For 100% shared risk link group (SRLG) failure protection, conventional full path protection has to satisfy SRLG-disjoint constraints, i.e., its working path and backup path cannot go though the same SRLG. With the increase of size and number of SRLGs, capacity efficiency of conventional shared full path protection becomes poorer due to SRLG-disjoint constraints and the blocking probability becomes much higher due to severe traps. To solve these problems, we present a partial path protection scheme where SRLG-disjoint backup paths may only cover part of the working path. Full path protection becomes a special case of partial path protection, in which the backup path covers the full working path. By choosing the most survivable partial backup path as backup path, we can make the impact of SRLG failures as low as possible and accept as many as possible connection requests. Assuming every SRLG has the same probability to fail, we present a heuristic algorithm to find the most survivable partial backup path by choosing full path protection first, iteratively computing partial backup paths and choosing the most survivable one. The benefit of this heuristic algorithm is that it can find the optimal results within less iteration. Analytical and simulation results show that, compared to conventional full path protection, our proposed scheme can significantly reduce blocking probability with little sacrifice on survivability. The proposed scheme is very useful particularly when the network contains a lot of SRLGs and the blocking probability of conventional full path protection becomes too high.

Derivative-based band clustering and multi-agent PSO optimization for optimal band selection of hyper-spectral images

The Journal of Supercomputing - Images (HSIs) are popular in diversified applications, such as geosciences, biomedical imaging, molecular biology, agriculture, astronomy, food quality and safety...     

A Framework for Differentiated Survivable Optical Virtual Private Networks

Wavelength division multiplexed (WDM) networks are matured to provide, scalable data centric infrastructure, capable of delivering flexible, value added, high speed and high bandwidth services directly from the optical domain. Optical virtual private networks (OVPNs) make use of the concept of highly reconfigurable nature of lightpaths offered by WDM, to create secure tunnels of high bandwidth across the intelligent WDM optical transport network. An OVPN is a private connection between two or more edge devices (access nodes), that allows a group of clients to fully exploit the flexibility of the switched intelligent optical network. However, OVPNs will not be a viable alternative unless they can guarantee a predictable bandwidth, availability, response time, and fault-tolerance to users. In this paper, we study the problem of dynamically establishing lightpaths for OVPNs over intelligent optical transport networks to provide varying classes of service based on the type of primary and backup lightpaths and the number of backup lightpaths, when each OVPN is specified by the desired logical connectivity and Class of Service. The type of primary and backup lightpaths determines the QoS parameters such as response time and bandwidth. Whereas, the number of backup lightpaths determines the level of fault-tolerance and availability of OVPN. Based on the service classes, any OVPN in the network falls into one of the six classes viz. single dedicated primary and single dedicated backup (SDPSDB), single dedicated primary and multiple dedicated backups (SDPMDB), single dedicated primary and single shared backup (SDPSSB), single shared primary and single shared backup (SSPSSB), single shared primary and multiple shared backups (SSPMSB), and best-effort (BE). In BE, we consider two variations—(1) OVPN as dedicated logical ring topology (DLRT) and (2) OVPN as shared logical ring topology (SLRT). We conduct extensive simulation experiments to compare and evaluate the effectiveness of different classes of OVPNs for varying network configurations–varying number of fibers, wavelengths on physical links, and number of nodes in OVPN.     

Differentiated QoS for survivable WDM optical networks

Optical networks based on WDM technology have become a promising solution to realize transport networks that can meet the ever-increasing demand for bandwidth. As WDM networks carry a huge volume of traffic, maintaining a high level of survivability is an important and critical issue. The. development of GMPLS switching technology led to the direct integration of IP and WDM. In these IP-over-WDM networks different applications/end users need different levels of fault tolerance and differ in how much they are willing to pay for the service they get. The current trend in network development is moving toward a unified solution providing support for voice, data, and various multimedia services. Therefore, it imperative that WDM networks incorporate fault tolerance to single or multiple component failures, protection bandwidth, recovery time, and recovery granularity besides resource utilization and call acceptance ratio. This article presents a survey of various methods that have been proposed for providing service differentiation in survivable WDM networks and discuss their performance. Such methods are broadly classified under various paradigms such as differentiated reliability, R-connections, quality of protection, and quality of recovery.     

LC-MS/MS Determination of Organophosphorus Pesticide Residues in Coconut Water

A simple and specific analytical method based on solid phase extraction (SPE), and liquid chromatography–electrospray ionization–tandem mass spectrometry (LC-ESI-MS/MS) operated in multipule reaction monitoring (MRM) mode with dynamic time segment acquisition windows, was developed to determine organophosphorus pesticide residues (acephate, monocrotophos, dimethoate, malaoxon, dichlorvos, malathion, phenthoate, parathion-ethyl, chlorfenvinfos, quinalphos, diazinon, phosalone, profenofos, ethion, chlorpyrifos) in tender coconut water. The method was observed to be linear with lower limit of detections ranged from 0.1 to 1.5 ng/mL (measured at S/N ratio 5:1) and limit of qunatitation 0.5 to 2.0 ng/mL (measured at S/N ratio 10:1) for all studied pesticides. The intra- and inter-day assay accuracies calculated at four concentration levels in six replicates (n?=?6) were in the range of 80 % to 115 % with relative standard deviations (RSD) below 15 %. The percentage recoveries of all the analysed pesticides were in the range of 86.8 % to 107.6 % and the calculated RSD values were below 12 %. The developed method was applied to determine pesticide residues in natural tender coconut water samples. The results showed the presence of malathion ranging from 24 to 45 ng/L concentrations in some natural tender coconut water samples collected from various local market places in and around Hyderabad, Andhra Pradesh, India.     

Reducing vulnerability of shared-path protection subject to double-link failures in WDM mesh networks

Shared-path protection (SPP) is a capacity- efficient mechanism to provide 100% single-link failure protection in WDM mesh networks. After the first link failure, however, if reconfiguration is unavailable, a second link failure may lead to tremendous service interruption. Vulnerability of a link is the percentage of links that are vulnerable to the arbitrary second link failure after the link failed and network vulnerability is defined as the average vulnerability of links in the network. In this article, we present three policies that can reduce network vulnerability by reducing backup sharing in shared-path protection. The first policy tries to restrict the times of sharing a wavelength-link by connections. The second policy tries to avoid backup sharing on highly vulnerable links. The third policy tries to avoid backup sharing on highly vulnerable wavelength-links. Algorithms to implement these policies based on a similar framework are presented. Numerical results suggest that there is a trade-off between capacity efficiency and network vulnerability in all the three policies. The third policy can deliver a better performance in terms of blocking probability and network vulnerability.

Mass spectral analysis of chloropicrin under negative ion chemical ionization conditions

A chemical ionization (CI) method is developed for the first time to obtain molecular weight information for chloropicrin (CP), which is used as a chemical warfare agent and as an insecticide. The study includes a detailed investigation on the behavior of CP under electron impact (EI) and CI. Reagent gases of different nature, i.e., methane, isobutane, ammonia, hydrogen, and carbon dioxide, were used for CI analysis. Negative ion mode is found more sensitive than positive ion mode for the EI/CI mass spectrometric analysis of CP, but none of the methods provided molecular weight information, except negative ion CI using ammonia as the reagent gas (NICI (NH3)). The NICI (NH3) showed formation of the quasi-molecular ion, [M + H]-, in addition to other adduct ions. The [M + H]- abundance critically depends on the source temperature, reagent gas pressure, and concentration of the analyte, and it can be 13% under optimized conditions by which CP can be confirmed unambiguously. This method meets the criteria used in official proficiency tests conducted by OPCW for confirming the molecular weight of the unknowns.