A novel macroeconomic forecasting model based on revised multimedia assisted BP neural network model and ant Colony algorithm

Multimedia Tools and Applications - In this paper, we propose a novel macroeconomic forecasting model based on the revised multimedia assisted BP neural network model and the ant colony algorithm....     

Polarization independent quad‐bandpass frequency selective surfaces with wide‐band ratio

A single layer polarization independent quad‐bandpass frequency selective surface (FSS) with wide‐band ratio is demonstrated theoretically as well as experimentally. The proposed structure passes four frequency bands with wide band ratio. The proposed FSS design is implemented by incorporating alternate arrangement of four units which are rotated 90° clockwise to form a unit cell of metal over a FR4 substrate. The geometrical dimensions of proposed unit cell are optimized and arranged in such a way that the structure possesses the quad bandpass characteristic and aspect dimensions of one unit is 0.11λ × 0.11λ with respect to first resonant frequency. This FSS provides stable response for different angle of incidence in transverse electric (TE) mode and transverse magnetic (TM) mode. To validate the results proposed FSS array has been fabricated and measured in free space environment. The measured results are in good agreement with the simulated results. Excellent stability is also observed for different incident angle.     

Polarization independent dual‐bandpass frequency selective surface for Wi‐Max applications

In this article, the performance of polarization independent dual‐bandpass frequency selective surface (FSS) is investigated. The proposed design of FSS unit cell comprises of metallic structure is based on customized plus shape within plus ring inside a square ring and etched on one side of FR4 substrate. The geometrical dimensions of unit cell are optimized in such a way that the structure possesses the dual‐bandpass characteristic for Wi‐Max applications. The aspect dimensions of unit cell are 0.16 λ × 0.16 λ × 0.013 λ with respect to first resonant frequency. The FSS provide stable response for different angle of incidence in transverse electric and transverse magnetic polarization. An equivalent circuit model of FSS is established and its results are verified by Advanced Design System tool. A prototype of FSS is designed, fabricated and measured. Good agreement between simulated and measured results verifies the dual‐bandpass FSS.     

Visibility volumes for interactive path optimization

We describe a real-time system that supports design of optimal flight paths over terrains. These paths either maximize view coverage or minimize vehicle exposure to ground. A volume-rendered display of multi-viewpoint visibility and a haptic interface assists the user in selecting, assessing, and refining the computed flight path. We design a three-dimensional scalar field representing the visibility of a point above the terrain, describe an efficient algorithm to compute the visibility field, and develop visual and haptic schemes to interact with the visibility field. Given the origin and destination, the desired flight path is computed using an efficient simulation of an articulated rope under the influence of the visibility gradient. The simulation framework also accepts user input, via the haptic interface, thereby allowing manual refinement of the flight path.     

Volatile Ultrafast Switching at Multilevel Nonvolatile States of Phase Change Material for Active Flexible Terahertz Metadevices

Phase change materials provide unique reconfigurable properties for photonic applications that mainly arise from their exotic characteristic to reversibly switch between the amorphous and crystalline nonvolatile phases. Optical pulse based reversible switching of nonvolatile phases is exploited in various nanophotonic devices. However, large area reversible switching is extremely challenging and has hindered its translation into a technologically significant terahertz spectral domain. Here, this limitation is circumvented by exploiting the semiconducting nature of germanium antimony telluride (GST) to achieve dynamic terahertz control at picosecond timescales. It is also shown that the ultrafast response can be actively altered by changing the crystallographic phase of GST.  The ease of fabrication of phase change materials allows for the realization of a variable ultrafast terahertz modulator on a flexible platform. The rich properties of phase change materials combined with the diverse functionalities of metamaterials and all-optical ultrafast control enables an ideal platform for design of efficient terahertz communication devices, terahertz neuromorphic photonics, and smart sensor systems.     

Effect of temporal pH variation of the reaction mixture on Mg(OH)2 morphology precipitated from an aqueous Mg(NO3)2-NaOH system

To understand the impact of temporal pH variation on the crystallisation process, Mg(OH)₂ was synthesized via wet precipitation route from an aqueous Mg(NO₃)₂-NaOH system. A detailed analysis of morphological evolution and the nano-structural transformation was carried out to model the crystallisation process. Interestingly, low supersaturation at low pH level lying between 9.2 and 9.4 of the reaction mixture, was found to promote the growth of nanorod like 1-D structures. On the contrary, enhanced supersaturation created a chemical driving force favouring an edgewise growth of the nucleated primary nanocrystals along (101) and (110) crystallographic planes, which resulted in lamellar hexagonal nanostructures. The lamellar growth demonstrated an increment in the particle size and reduction in anisotropic strain and dislocation density due to proper nucleation in the samples. Such controlled growth and nucleation of the Mg(OH)₂ morphology presents a great scope of potential applications of this material.     

Three dimensional turbulent wall jets

Jets issuing tangentially to an impermeable flat surface from orifices of finite aspect ratio are termed three-dimensional wall jets. The turbulent flow of viscous incompressible fluid associated with such wall jets has been investigated analytically. Results are presented for the wall jets issuing from orifices of various shapes and several aspect ratios. The maximum velocity shows three regions of decay. The potential core region is followed by a characteristic decay region where maximum velocity decays in a manner dependent on the shape and aspect ratio of the orifice. Following this region, there is a radial wall jet type maximum velocity decay region. All three-dimensional wall jets issuing from any arbitrary cross-sectional orifice decay in a similar manner in this radial decay region. The half-velocity width grows faster in the transverse direction than in a direction normal to the flat surface. The analytical results agree reasonably well with existing experimental results.     

Study of heat and mass transfer from sugarcane juice for evaporation

The study of heat and mass transfer during natural convection heating for preparation of Jaggery was carried out for the open and closed conditions. An indoor experiment was conducted for simulation of developed thermal model for heat and mass transfer for maximum evaporation. Evaporated water was condensed at the inner surface for the closed system as fresh water. The effect of different rates of heating (varying voltage) and heat capacity of sugar cane juice on heat and mass transfer were also carried out. It was observed that the evaporative heat transfer coefficient depends significantly on the rate of heating and heat capacity.