Magnetohydrodynamic Viscous Flow Over a Shrinking Sheet With Second Order Slip Flow Model

In this paper, we investigate the magnetohydrodynamic viscous flow with second order slip flow model over a permeable shrinking surface. We have obtained the closed form of exact solution of Navier-Stokes equations by using similarity variable technique. The effects of slip, suction and magnetic parameter have been investigated in detail. The results show that there are two solution branches, namely lower and upper solution branch. The behavior of velocity and shear stress profiles for different values of slip, suction and magnetic parameters has been discussed through graphs.Comment: 13 Pages, 8 Figures. Accepted for Publication in Heat Transfer Researc

Performance of a local electron density trigger to select extensive air showers at sea level

Time coincident voltage pulses in the two closely space (1.6m) plastic scintillators were recorded. Most of the recorded events are expeted to be due to electrons in cosmic ray showers whose core fall at some distance from the detectors. This result is confirmed from a measurement of the frequency distribution of the recorded density ratios of the two scintillators

Infrared upconversion for astronomical applications

The performance of an upconversion system is examined for observation of astronomical sources in the low to middle infrared spectral range. Theoretical values for the performance parameters of an upconversion system for astronomical observations are evaluated in view of the conversion efficiencies, spectral resolution, field of view, minimum detectable source brightness and source flux. Experimental results of blackbody measurements and molecular absorption spectrum measurements using a lithium niobate upconverter with an argon-ion laser as the pump are presented. Estimates of the expected optimum sensitivity of an upconversion device which may be built with the presently available components are given

Sensitivity limits of an infrared heterodyne spectrometer for astrophysical applications

A discussion and an evaluation of the degradation in sensitivity is given for a heterodyne spectrometer employing a HgCdTe photodiode mixer and tunable diode lasers. The minimum detectable source brightness is considered as a function of the mixer parameters, transmission coefficient of the beam splitter, and local oscillator emission powers. The degradation in the minimum detectable line source brightness which results from the bandwidth being a function of the line width is evaluated and plotted as a function of the wavelength and bandwidth for various temperature to mass ratios. It is shown that the minimum achievable degradation in the sensitivity of a practical astronomical heterodyne spectrometer is approximately 30. Estimates of signal-to-noise ratios with which infrared line emission from astronomical sources of interest may be detected are given

Plasmonic Devices in the Terahertz and Optical Frequency Domains

We are living in an age where the evolution of semiconductor devices and components is contingent upon their miniaturization and seamless integration with the rest of the circuitry. Unfortunately, it is anticipated that electronic systems will soon approach the theoretical design limits of size and bandwidth, and it poses to be a serious concern for the development of high-speed information technologies. Replacement of electronic pulses that act as communication signals with electromagnetic surface waves offers a very promising solution, particularly in terms of device miniaturization and the heart of this optimism are the plasmonic waves arising due to collective electron oscillations at the surface of a conductor. Surface plasmon polaritons propagating along a metal-dielectric interface at optical frequencies have lately been a subject of immense research interest, mainly due to their reduced wavelength at least by an order of magnitude. Hence, miniaturized wave devices can be created at optical frequencies. Terahertz plasma waves, on the other hand, exist in infinitesimally thin plasma regions formed inside a transistor substrate, and are observed at much lower frequencies in the far-infrared regime. Due to essentially a two-dimensional nature of the plasma region, a much higher wavelength reduction factor that can exceed well beyond 100 is achievable. Furthermore, the boundary conditions due to the transistor terminals along with electric biasing create unstable resonance conditions that eventually lead to radiation in the terahertz frequency range. Such phenomena provide bright prospects for creating highly miniaturized terahertz devices. A reliable and efficient electromagnetic (EM) analysis for multilayer geome tries has gained further significance due to the emergence of plasmonic structures in the optical as well as terahertz frequency domains. In this regard, integral equation (IE) techniques are ideally suited due to their efficient handling of mutilayer structures. Although the presence of thin layers poses a challenge to any EM analysis technique, here the procedure is simplified due to the infinitesimally thin nature of the plasma region, which can be analyzed as a conducting sheet, with the same current flowing on either side of the sheet. Essential to any IE technique is an efficient and systematic formulation of Green functions (GFs) and their subsequent computation. In this dissertation, a transmission-line network based approach is adopted to derive spectral domain GFs for an infinitesimally thin sheet in a layered medium. The associated spatial domain counterparts are then computed through the Sommerfeld integrals (SIs). The extraordinary electromagnetic properties of plasmonic devices are demonstrated by a presentation of the properties of plasmonic antennas and a super-resolution imaging scheme which is able to resolve objects separated only by a few nanometers

A Mechanism for Securing IoT-enabled Applications at the Fog Layer

The Internet of Things (IoT) is an emerging paradigm branded by heterogeneous technologies composed of smart ubiquitous objects that are seamlessly connected to the Internet. These objects are deployed as Low power and Lossy Networks (LLN) to provide innovative services in various application domains, such as smart cities, smart health, smart communities. The LLN is a form of a network where the interconnected devices are highly resource-constrained (i.e., power, memory, and processing) and characterized by high loss rates, low data rates and instability in the communication links. Additionally, IoT devices produce a massive amount of confidential and security-sensitive data. Various cryptographic-based techniques exist that can effectively cope with security attacks, but are not suitable for IoT as they incur high consumption of resources (i.e., memory, storage and processing). One way to address this problem is by offloading the additional security-related operations to a more resourceful entity such as a fog-based node. Generally, fog computing enables security and analysis of latency-sensitive data directly at the network’s edge. This paper proposes a novel Fog Security Service (FSS) to provide end-to-end security at fog layer for IoT devices, using two well-established cryptographic schemes, identity-based encryption and identity-based signature. The FSS provides security services, such as authentication, confidentiality, and non-repudiation. The proposed architecture is implemented and evaluated in OPNET simulator using a single network topology with different traffic loads. The FSS performed better when compared with the APaaS and the legacy method