Complex impedance studies on tungsten-bronze electroceramic: Pb2Bi3LaTi5O18

Complex impedance analysis of polycrystalline Pb₂Bi₃LaTi₅O₁₈, prepared by a high-temperature solid-state reaction technique has been carried out. XRD analysis indicated the formation of a single-phase orthorhombic structure. Impedance plots were used as a tool to analyse the behaviour of the sample as a function of frequency and temperature. The bulk resistance has been observed to decrease with rise in temperature showing a typical negative temperature coefficient of resistance (NTCR) type behaviour like that of semiconductors. The ac impedance studies revealed the presence of grain boundary effect at 450°C and showed polydispersive non Debye-type dielectric relaxation. The frequency dependent ac conductivity at different temperatures indicated that the conduction process is thermally activated process. The activation energy for bulk (0.67 eV) and grain boundary (0.73 eV) was estimated from the temperature variation of respective conductivities.     

Current concept in the diagnosis and treatment of childhood pulmonary tuberculosis

In India, an estimated 80% of children are infected with tubercle bacillus by 10 years of age. Elimination of tuberculosis depends on finding all infectious patients and providing them with curative chemotherapy. Pulmonary tuberculosis--the most common form in children--is diagnosed when a child presents with fever, prolonged cough, weight loss, recurrent wheezing, or chest infection; the chest x-ray is suggestive of tuberculosis; and three or more of the following conditions exist: 1) Mantoux test result of 10 mm or more, 2) tuberculosis lymphadenitis by fine needle aspiration cytology, 3) grade III malnutrition, 4) no BCG vaccination, 5) positive family history of tuberculosis, and 6) recent history of pertussis or measles. Recommended, for children with pulmonary tuberculosis, is a regimen of isoniazid, rifampicin, and pyrazinamide daily for 2 months, followed by the first two drugs daily for an additional 4 months. The poor tuberculosis cure rates in most developing countries reflect patient non-compliance with treatment regimens.     

In-liquid sensing of chemical compounds by QCM sensors coupled with high-accuracy ACC oscillator

A novel oscillator circuit with automatic capacitance compensation (ACC) capability has been coupled with quartz-crystal-microbalance (QCM) sensors coated with quinoxaline- and pyrazine-bridged cavitands to detect aromatic and chlorinated compounds in water. With double-side immersed 10-MHz crystals coated with the quinoxaline cavitand, the detection of toluene in deionized water was possible down to concentrations of a few parts per million. The ACC oscillator advantageously provides the simultaneous measurement of the sensor resonant frequency, damping, and value of the compensated parallel capacitance. This enabled observing that the analyte sorption in the cavitand coating not only brings about a mass uptake but also an increase of losses and, apparently, a rise in the coating average permittivity.     

Flexible conductive poly(styrene‐butadiene‐styrene)/carbon nanotubes nanocomposites: Self‐assembly and broadband electrical behavior

Flexible conductive nanocomposites with the ability of self‐assembly into well‐ordered structures are promising multifunctional materials for energy conversion and storage devices. In this work, flexible nanocomposites based on multi‐walled carbon nanotubes (MWCNTs) and poly(styrene‐butadiene‐styrene) (SBS) were obtained by solution casting, followed by a post‐annealing treatment, during 7 days at 110 °C, to enable the self‐organization of the SBS. The impact of the MWCNTs on the self‐assembly was studied by atomic force microscopy and Small angle X‐rays scattering, and the conductivity of these nanocomposites was analyzed over the broadband frequency range, that is, 10^?1–10⁶ Hz. The results revealed that the lower MWCNTs loadings (～0.2 v %) were the most suitable to achieve a conductive network through the SBS, maintaining self‐assembled domains. These domains include hexagonally packed cylinders and alternating lamellae. Furthermore, at loadings above 1 v %, the impact of further MWCNTs addition on the conductivity was marginal over the whole frequency range and the self‐assembly tendency was progressively reduced. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46650.     

An Approach Towards Amelioration of an Efficient VM Allocation Policy in Cloud Computing Domain

Cloud computing is on the horizon of the domain of information technology over the recent few years, giving different remotely accessible services to the cloud users. The quality-of-service (QoS) maintaining of a cloud service provider is the most dominating research issue today. The QoS embraces with different issues like virtual machine (VM) allocation, optimization of response time and throughput, utilizing processing capability, load balancing etc. VM allocation policy deals with the allocation of VMs to the hosts in different datacenters. This paper highlights a new VM allocation policy that distributes the load of VMs among hosts which improves the utilization of hosts’ processing capability as well as makespan and throughput of cloud system. The experimental results are obtained by utilizing trace based simulation in CloudSim 3.0.3 and compared with existing VM allocation policies.     

Community oriented in‐network caching and edge caching for over‐the‐top services in adaptive network conditions to improve performance

Over‐the‐top (OTT) services such as Netflix, Amazon Prime, and YouTube generate the most dominant form of traffic on the Internet today. There is increasingly high demand for resource intensive 3D contents, interactive media, 360 media, and user‐generated contents. As the amount of contents keep increasing in multiple folds, it is important to cache contents intelligently. Caching algorithm needs to exploit in‐network caching, community‐based pre‐caching, and a combined approach. Hence, we survey CDN‐based edge caching infrastructures including OpenConnect (Netflix) and Google Edge, followed by CCN based in‐network caching. We implement and compare four different approaches for caching contents including (1) in‐network caching, (2) edge caching, (3) community‐based in‐network caching, and (4) community‐based edge caching. We run our algorithms on adaptive network conditions with different topologies, cache size, content popularity, and request arrivals in and compared the delay for all these four approaches. We verify our model by calculating important performance parameters including hop count, redundancy, and hop count variances. Hopcount is an important performance parameter as it influences the processing, queuing, and transmission delays. We focus on determining if an in‐network caching approach is any better than edge caching. We reach several conclusions. First, in most of the scenarios, community‐based in‐network caching performs the best. Second, if the cache size is lesser than 30% of the total content size then community‐based edge caching is better for less popular contents. Finally, our statistical analysis also reveals that a community‐based edge caching mechanism is least affected by varying cache sizes and dynamic user behavior, which makes it a better choice for providing Service Level Agreement.     

ECC-CoAP: Elliptic Curve Cryptography Based Constraint Application Protocol for Internet of Things

Constraint Application Protocol (CoAP), an application layer based protocol, is a compressed version of HTTP protocol that is used for communication between lightweight resource constraint devices in Internet of Things (IoT) network. The CoAP protocol is generally associated with connectionless User Datagram Protocol (UDP) and works based on Representational State Transfer architecture. The CoAP is associated with Datagram Transport Layer Security (DTLS) protocol for establishing a secure session using the existing algorithms like Lightweight Establishment of Secure Session for communication between various IoT devices and remote server. However, several limitations regarding the key management, session establishment and multi-cast message communication within the DTLS layer are present in CoAP. Hence, development of an efficient protocol for secure session establishment of CoAP is required for IoT communication. Thus, to overcome the existing limitations related to key management and multicast security in CoAP, we have proposed an efficient and secure communication scheme to establish secure session key between IoT devices and remote server using lightweight elliptic curve cryptography (ECC). The proposed ECC-based CoAP is referred to as ECC-CoAP that provides a CoAP implementation for authentication in IoT network. A number of well-known cryptographic attacks are analyzed for validating the security strength of the ECC-CoAP and found that all these attacks are well defended. The performance analysis of the ECC-CoAP shows that our scheme is lightweight and secure.

     

Joint Routing and Resource Allocation for Cluster Based Isolated Nodes in Cognitive Radio Wireless Sensor Networks

Clustering is an effective way to increase network lifetime but it leads to formation of isolated nodes in the wireless sensor network. These isolated sensor nodes forward data directly to sink and consume more energy which significantly reduces the network lifetime. In this article, we present how to maximize the network lifetime through joint routing and resource allocation with isolated nodes technique (JR-IN) between cluster head and isolated nodes in a cognitive based wireless sensor networks. In JR-IN technique the network area is divided into different layers and cluster size is formulated in each layer such that the size of the cluster remains unequal when it moves towards sink. Hence the cluster size is lager in the outermost layer compared to the cluster size in the inner most layer. To avoid inter cluster collision, we proposed different fixed channel to all the cluster heads in the network. For the intra cluster communication, the cluster member (sensor nodes) will lease the spectrum from the cluster head and forward data to their respective cluster head using TDMA technique. The periodical data gathering of cluster heads and forwarding the data to one hop cluster head may tend to lose energy faster and dies out quickly. We also propose in the JR-IN technique, the isolated nodes in the layer will take charge as a cluster head node and utilizes the resource allocated to the respective cluster head and forward the data to next hop cluster head. Simulation result shows that JR-IN outperforms the existing techniques, maximizes network lifetime and throughput and reduces the end to end delay.

     

New control allocation algorithms in fixed point framework for overactuated systems with actuator saturation

In this paper, two control allocation algorithms have been proposed for overactuated systems. The algorithms are developed by formulating constrained control allocation problem into an equivalent fixed point framework. The first algorithm follows sequential solving method while the other one involves a zero finding technique by the Newton method. In order to consider limiting constraints, the saturation function has been taken into account that leads to a nonsmooth zero finding problem and the proposed method guarantees superlinear convergence. The second algorithm is easy to implement and faster than the algorithm developed based on the sequential solving technique. To demonstrate the effectiveness of the proposed algorithms, a detail simulation study has been carried out, in which one example considers both the actuator rate and amplitude constraints.