Hydrogenation effect on structural,electrical and optical properties of CdS thin films for solar cell

Adsorption effects would be expected to be of considerable importance with thin films because of the changes in electron location accompanying adsorption. The effects of hydrogenation on structural, optical and electrical properties of the CdS thin films have been reported. GIXRD patterns shows that films have polycrystalline nature with a hexagonal structure. The optical band gap increased after hydrogenation of the film. The variation of conductivity of CdS films have been investigated depending upon the applied voltage at room temperature. The resistivity increased after hydrogenation of the films. Hydrogenated thin films can be used in solar cells because hydrogen plays an important role to modify the physical properties.     

Mobility-Aware and Radio Characteristics Enabled Routing for Video Streaming over MANETs

Wireless Personal Communications - Providing an adequate level of quality-of-experience (QoE) for multimedia applications in mobile ad-hoc networks (MANETs) is a challenging task due to its...     

Use of tergitol-7 in photogalvanic cell for solar energy conversion and storage: Toluidine blue-glucose system

Photogalvanic effects were studied in a photogalvanic cell containing toluidine blue, glucose and tergitol-7 as a photosensitizer, reductant and surfactant, respectively. The photocurrent and photopotential generated by this system were 70 μA and 315 mV, respectively. The effects of different parameters on the electrical output of the cell were observed. Current/voltage characteristics of the cell have also been studied, and a mechanism has been proposed for the generation of photocurrent in photogalvanic cell.     

Intelligent selection of threshold in covariance-based spectrum sensing for cognitive radio networks

Wireless Networks - The radio spectrum sensing has been an important issue of research in cognitive radio networks over the last decade and the appropriate selection of threshold plays a crucial...     

Structural and optical properties of AlN/Si system

Aluminum nitride (AlN) is a wide band gap III–V semiconductor material which is often used for optical applications. Thin films of aluminum nitride were deposited by ion beam sputtering in an Ar–N₂ atmosphere on Si (1 0 0). For film preparation, the N₂ flow was kept at 5 sccm and the ratio of N₂ and Ar was 4:1. The films have been characterized by Grazing Incidence X-ray Diffraction (GIXRD), X-ray Reflectometry (XRR), Atomic Force Microscopy (AFM) and optical spectroscopy. GIXRD shows that the structure of the as-deposited sample of AlN is hexagonal. It is observed that neither the ion-beam-induced dissociation of the nitride film nor the enhanced nitrogen diffusion across the interface takes place after Au ion irradiation. XRR was used to determine the thickness of the films. The reflectance of the irradiated films increases in the range 200–280 nm. UV–vis spectra were taken in Kubelka Munk (KM) units for as-deposited and irradiated samples. The band gap was calculated for both types of samples, which shows that the band gap of irradiated films of aluminum nitride decreases due to the increase in metal content at the surface. AFM confirms that the roughness of aluminum nitride increases by irradiation.     

Reliable and secure data transfer in IoT networks

With the rapid technological improvements in mobile devices and their inclusion in Internet of Things (IoT), secure key management becomes mandatory to ensure security of information exchange. For instance, IoT applications, such as smart health-care and smart homes, provide automated services to the users with less or no user intervention. As these application use user-sensitive data, ensuring their security and privacy should be paramount, especially during the key management process. However, traditional approaches for key management will not suit well in IoT environment because of the inherent resource constraint property of IoT devices. In this paper, we propose a novel distributed key management scheme for IoT ecosystem. The proposed scheme efficiently provides security to IoT devices by delegating most of the resource consuming cryptographic processing to a local entity. This entity coordinates with other peer entities to provide a distributed key as well as an authentication mechanism to network devices. In particular, the proposed scheme exploits the advantages of mobile agents by deploying them in different subnetworks as and when required: (1) to process the cryptography work for the IoT devices, and (2) to act as an local authenticated entity to perform fast authentication process. To verify the effectiveness and correctness of our proposed scheme, we have simulated it in a large IoT scenario and evaluated against relevant metrics that includes user mobility, certification generation time, and communication overhead.

     

Structural and electrical properties of swift heavy ion beam irradiated Fe/Si interface

The present work deals with the mixing of iron and silicon by swift heavy ions in high-energy range. The thin film was deposited on a n-Si (111) substrate at 10⁻⁶ torr and at room temperature. Irradiations were undertaken at room temperature using 120 MeV Au⁺⁹ ions at the Fe/Si interface to investigate ion beam mixing at various doses: 5 × 10¹² and 5 × 10¹³ ions/cm². Formation of different phases of iron silicide has been investigated by X-ray diffraction (XRD) technique, which shows enhancement of intermixing and silicide formation as a result of irradiation. I-V measurements for both pristine and irradiated samples have been carried out at room temperature, series resistance and barrier heights for both as deposited and irradiated samples were extracted. The barrier height was found to vary from 0·73–0·54 eV. The series resistance varied from 102·04–38·61 kΩ.     

Lightweight solutions to counter DDoS attacks in software defined networking

Wireless Networks - A distributed denial of service (DDoS) attack on any of the major components (e.g., controller, switches, and southbound channel) of software defined networking (SDN)...     

SYN‐Guard: An effective counter for SYN flooding attack in software‐defined networking

In software‐defined networking (SDN), TCP SYN flooding attack is considered as one of the most effective attacks to perform control plane and target server saturation. In this attack, an attacker generates a large number of malicious SYN requests, and because of the absence of the forwarding rules, the data plane switches have to forward these SYN messages to the controller. This excessive forwarding causes congestion over the communication channel between a data plane and control plane, and it also exhausts computational resources at both the planes. In this paper, we propose a novel countermeasure called SYN‐Guard to detect and prevent SYN flooding in SDN networks. We fully implement SYN‐Guard on the SDN controller to validate the incoming TCP connection requests. The controller installs forwarding rules for the SYN requests that successfully clear the validation test of SYN‐Guard. The host of the fake SYN request is detected, and SYN‐Guard prevents it from sending any further SYN requests to the data plane switch. The performance evaluation done using the simulation results shows that SYN‐Guard exhibits low side effect for genuine TCP requests, and when compared with standard SDN and state‐of‐art proposals, it reduces the average response time up to 21% during an ongoing SYN flooding attack.     

Enhancing QoE for video streaming in MANETs via multi-constraint routing

In this paper, we propose a Multi-Constraint Quality-of-Experience (QoE) centric Routing (MCQR) technique for efficient real-time video streaming over Mobile Ad-hoc Networks (MANETs). The dynamic estimation of link quality metric during MCQR route discovery process is the key of enhancing QoE at end user. MCQR limits end-to-end delay and jitter of received data packets by selecting long lifetime routes with maximum permissible delay. This minimizes the distortion caused fluctuations in perceived video. To prove the effectiveness of MCQR for real-time video streaming, we have designed a hybrid MANET consisting of simulated nodes and physical machines. In our hybrid network, the source and destination nodes are video traffic generators and receivers running on physical devices. Emulation results are obtained using real-time video streaming over high fidelity virtual wireless network, and conforming that the MCQR protocol provides satisfactory QoE to end users as compared to existing similar techniques. The packet delivery ratio of MCQR is higher than 90 % and its mean opinion score is higher than three (i.e., satisfactory) even when mobility and shadowing effects are kept high in target network scenarios. These improvements are achieved along with still maintaining similar or better routing overhead and processing delays.