Approximate Electromagnetic Cloaking of a Dielectric Sphere Using Homogeneous Isotropic Multi-Layered Materials

In cloaking, a body is hidden from detection by surrounding it by a coating consisting of an unusual anisotropic nonhomogeneous material. The permittivity and permeability of such a cloak are determined by the coordinate transformation of compressing a hidden body into a point or a line. The radially-dependent spherical cloaking shell can be approximately discretized into many homogeneous anisotropic layers;each anisotropic layer can be replaced by a pair of equivalent isotropic sub-layers, where the effective medium approximation is used to find the parameters of these two equivalent sub-layers. In this work, the scattering properties of cloaked dielectric sphere is investigated using a combination of approximate cloaking, where the dielectric sphere is transformed into a small sphere rather than to a point, together with discretizing the cloaking material using pairs of homogeneous isotropic sub-layers. The back-scattering normalized radar cross section, the scattering patterns are studied and the total scattering cross section against the frequency for different number of layers and transformed radius.

Maximum Power Point Tracking of Hybrid Tidal Current—Supercapacitor Energy Conversion System

This paper proposes control of maximum power tracking system of tidal current energy system. A permanent magnet synchronous generator (PMSG) works as a variable speed generator in the proposed energy system. A controller was applied to achieve the maximum power control of tidal current turbine on a wide range of water current speed change. A dynamic model and simulation of the energy system coupled with current change are presented. The measured DC voltage and DC current are used to determine the position of maximum power point that controls the DC/DC boost converter duty cycle depending on the Hill Climb Search (HCS) algorithm. This algorithm doesn’t require any information or measurements about current’s speed change or generator’s characteristics. A supercapacitor added to fix the load voltage despite of tidal current speed or load variations. Simulation results show the effectiveness of the controller proposed system.

Piezoelectric bimorph MEMS speakers

One of the key requirements for MEMS speakers is to increase the sound pressure level(SPL)while keeping the size as small as possible.In this paper we present a MEMS speaker based on piezoelectric bimorph cantilevers that produces a higher SPL than conventional unimorph cantilever speakers.The active diaphragm size is 1.4×1.4 mm^(2).The bimorph cantilevers are connected in parallel to make full use of the actuation voltage.At 1 kHz,the measured SPL reached 73 dB and the peak SPL reached 102 dB at the resonance frequency of 10 kHz in a 711 ear simulator under a driving voltage of 10 V_(rms).The total harmonic distortion of the MEMS speaker was less than 3%in the range from 100 Hz to 20 kHz.Although the absolute SPL was not the highest,this work provides a better SPL for all piezoelectric MEMS speakers.

Pencil Beam Grid Antenna Array for Hyperthermia Breast Cancer Treatment System

In this paper, efficient, high gain and pencil beam grid antenna array is proposed for hyperthermia breast cancer therapy system. The proposed antenna bandwidth extends from 4.8 GHz to 4.9 GHz at resonant frequency of 4.86 GHz. This frequency band has been reported for the breast cancer hyperthermia therapy. The grid long and short sides are responsible for the undesired cross-polarized radiation and desired copolarized radiation, respectively. The unsuitability of the conventional grid antenna array is ensured by investigating its radiation properties. The proposed grid antenna array short side width is varied and its long side width is kept wide as possible to enhance the radiation properties and to reduce the losses. Also, a reflector has been used for gain enhancement purpose. The proposed grid antenna array achieves side lobe level and 3 dB beam width of —27.9 dB and 25.9° for the E-plane and —27.9 dB and 26.3° for the H-plane, respectively. The breast phantom is irradiated by both proposed and conventional grid antenna arrays for 10 minutes. The proposed grid antenna array achieves 8°C temperature increase within the breast phantom area compared to 2°C temperature increase for conventional one. The proposed grid antenna array is highly efficient, high gain and light weight, and it has a very suitable radiation property for hyperthermia breast cancer therapy.

Improved RC6 Block Cipher Based on Data Dependent Rotations

This paper introduces an Improved RC6(IRC6)cipher for data encryption based on data-dependent rotations.The proposed scheme is designed with the potential of meeting the needs of the Advanced Encryption Standard(AES).Four parameters are used to characterize the proposed scheme.These parameters are the size of the word(w)in bits,the number of rounds(r),the length of the secret key(b)in bytes,and the size of the block(L)in bits.The main feature of IRC6 is the variable number of working registers instead of just four registers as in RC6,resulting in a variable block size for plaintext and ciphertext.The IRC6 cipher is designed to improve the robustness against attacks by increasing the diffusion for each round and providing greater security with fewer rounds.The effectiveness of the proposed IRC6 scheme is verified against theoretical attacks.The proposed IRC6 scheme depends on full diffusion and confusion mechanisms regardless of the utilized block size.The proposed IRC6 scheme saves 70%of the encryption time and 64%of the decryption time of RC6.The simulation results prove that the IRC6 achieves a better encryption/decryption time compared to the traditionalRC6.Therefore,the proposed IRC6 is anticipated to fulfill the market needs and system security requirements.

Extraordinary Optical Transmission through Single Sub-Wavelength Slot Nano Antennas

This paper investigates the electromagnetic transmission through the sub-wavelength slot model on a metal film for TM- and TE-polarized light. The influence of several parameters such as the slot width, the metal film thickness and the polarization of the incident field is investigated using FDTD method. The FDTD simulation’s results have shown that the sub-wavelength slot in the metal films has extraordinary optical transmission (EOT) properties for TM-polarized light. The EOT has been observed as being symmetrically punctured and characterized by the appearance of a series of transmission peaks and dips in the transmission field. By varying the slot thickness we have investigated the effect of the Fabry-Pérot like resonance in the sub wavelength slot. This component can be a key element in many applications. High-spatial-resolution imaging and information and communications technologies and sensing with high spectral and spatial precision, enhanced solar cells, efficient optical sources and detectors, disease treatment, are such examples.

Power-scaled dissipative soliton using double-cladding-pumped Yb-doped all-fiber amplifier

We report on an all-fiber oscillator followed by an all-fiber amplifier to produce as short as 382 fs laser pulses with up to 0.9 W average power. The oscillator is an all-normal-dispersion all-fiber dissipative soliton laser operating at1030 nm, and operating in dissipative soliton mode. The amplifier stage is mainly based on a double-cladding20 μm radius ytterbium-doped fiber pumped by an up to 2.5 W CW laser source. The optical-to-optical conversion amplifier efficiency is around 40%. To our knowledge, this is the first report of an all-fiber mode-locked fiber laser oscillator amplified by an all-fiber amplifier.