CS‐EWMA Chart for Monitoring Process Dispersion

Control charts are the most extensively used technique to detect the presence of special cause variations in processes. They can be classified into memory and memoryless control charts. Cumulative sum and exponentially weighted moving average control charts are memory‐type control charts as their control structures are developed in such a way that the past information is not ignored as it is done in the case of memoryless control charts, like the Shewhart‐type control charts. The present study is based on the proposal of a new memory‐type control chart for process dispersion. This chart is named as CS‐EWMA chart as its plotting statistic is based on a cumulative sum of the exponentially weighted moving averages. Comparisons with other memory charts used to monitor the process dispersion are done by means of the average run length. An illustration of the proposed technique is done by applying the CS‐EWMA chart on a simulated dataset. Copyright © 2012 John Wiley & Sons, Ltd.     

Control of cone-jet geometry during electrospray by an electric current

A new electrospray system has been successfully developed by employing a proportional–integral–derivative control action to maintain an electric current at a certain value. A polymer precursor solution containing polyethylene glycol was used to examine the performance of this system. The result showed that cone-jet geometry could be controlled easily by adjusting the electric current. The length of the cone-jet decreased as the electric current was increased, in a correlation that followed power law. We also found that the cone-jet observed during electrospraying was stable and robust with no disturbance during long periods of use (up to 4000 s). The present study is very useful for further development of high precision aerosol generators and particle synthesis.     

Analyzing combinations of circular birefringence,linear birefringence,and elliptical dichroism in magneto-optical rotators

We derive analytic expressions for the polarization characteristics of light emerging from a magneto-optical medium possessing arbitrary contributions from linear and circular birefringence as well as magnetic circular dichroism. The medium is placed inside a static magnetic field. The rotation of the plane of polarization and the ellipticity of the resultant light exhibit interesting characteristics that can be a useful guide in the design and analysis of new photonic devices. Furthermore, the Jones matrices are derived in all cases, including for elliptical dichroism, indicating the role of hyperbolic trigonometric functions in modeling the effects of dichroism. Finally, implications for experimental detection of the polarization state and the limits on the performance of optical isolators are discussed.     

40 Gb/s 4-QAM OFDM radio over fiber system at 60 GHz employing coherent detection

In this paper, the simulation of 60 GHz millimeter-wave radio over fiber link with 4-QAM OFDM modulation format at 40 Gb/s over 150 km SMF is proposed. The 60 GHz millimeter-wave signal is generated by the optical heterodyne method. Coherent detection has been used at the receiver to down-convert millimeter-wave signal to IF band. Introduction of the OFDM modulation in RoF-based system realizes the benefits of higher order modulations (such as 4-QAM, 16-QAM, etc.) to ensure the good spectral efficiency and multi-gigabit access. The performance of the system is analyzed by Q-factor and BER by which it can be shown that the best results are obtained at the input power of 10 dBm. The simulation results clearly demonstrate the feasibility of this 4-QAM OFDM RoF system over 150 km fiber link.     

Multiple color-image authentication system using HSI color space and QR decomposition in gyrator domains

Abstract

A new multiple color-image authentication system based on HSI (Hue–Saturation–Intensity) color space and QR decomposition in gyrator domains is proposed. In this scheme, original color images are converted from RGB (Red–Green–Blue) color spaces to HSI color spaces, divided into their H, S, and I components, and then obtained corresponding phase-encoded components. All the phase-encoded H, S, and I components are individually multiplied, and then modulated by random phase functions. The modulated H, S, and I components are convoluted into a single gray image with asymmetric cryptosystem. The resulting image is segregated into Q and R parts by QR decomposition. Finally, they are independently gyrator transformed to get their encoded parts. The encoded Q and R parts should be gathered without missing anyone for decryption. The angles of gyrator transform afford sensitive keys. The protocol based on QR decomposition of encoded matrix and getting back decoded matrix after multiplying matrices Q and R, enhances the security level. The random phase keys, individual phase keys, and asymmetric phase keys provide high robustness to the cryptosystem. Numerical simulation results demonstrate that this scheme is the superior than the existing techniques.     

Preparation and characterization of K-substituted NaCa4Nb5O17 microwave dielectric ceramics

The effect of K substitution for Na on the phase, microstructure and microwave dielectric properties of the Na_1?x K _x Ca₄Nb₅O₁₇ (x = 0–1) composition series was investigated. The compositions with x = 0, 0.5 and 1 formed single-phase Na_1?x K _x Ca₄Nb₅O₁₇ ceramics within the detection limit of the in-house XRD facility when sintered at 1,200–1,300 °C. At x = 0.25 and 0.75, the major Na_1?x K _x Ca₄Nb₅O₁₇ phase formed but along with a secondary CaNb₂O₆ phase. Relative permittivity (ε _r ) and temperature coefficient of resonant frequency (τ_f) increased from 45 to 51 and ?120 to +473 ppm/ °C respectively while the quality factor (Q × f _o ) decreased from 13,838 to 2,374 GHz with an increase in x from 0 to 1. Optimum microwave dielectric properties (i.e. ε _r  = 47, Q × f _o  = 5,047 GHz and τ_f = ? 23 ppm/ °C) were achieved for the x = 0.5 (i.e. Na_0.5K_0.5Ca₄Nb₅O₁₇) composition. Further investigations are required to improve the density and hence microwave dielectric properties of Na_1?x K _x Ca₄Nb₅O₁₇ ceramics.     

Annealing effect on structural, optical and electrical properties of pure and Mg doped tin oxide thin films

This study describes the effect of annealing at different temperatures (400–600 °C) on structural, optical and electrical behaviors of pure and Mg doped tin oxide thin films grown on the glass substrate by electron beam evaporation technique. The transformation of tetragonal to orthorhombic form due to annealing, introduced a change in the optical and electrical properties of pure and Mg doped tin oxide thin films. X-ray diffraction studies or analysis revealed the phase transformation and change in the crystalline size with increase in the annealing temperature. The morphology and roughness of the thin films were studied by Atomic force microscopy. Optical band gap increased with annealing temperature confirms the improvements of crystallinity. The quality of thin films transparency was investigated by UV/Vis-spectroscopy. Photoluminescence of pure and Mg doped tin oxide thin films shows two extra peaks one at 486 nm and other at 538 nm is due to the crystal defect created as a result of annealing temperature. These peaks became stronger and shifted to longer wavelength with increasing the annealing temperature. The complex plot (Nyquist plot) showed the data point laying on two semicircles and the resistance of grains and grain boundaries increases with the increase in annealing temperature for both pure and Mg doped tin oxide thin films.     

Layered double hydroxides as efficient drug delivery system of ciprofloxacin in the middle ear: an animal study in rabbits

Chronic otitis media is a common disease often accompanied by recurrent bacterial infections. These may lead to the destruction of the middle ear bones such that prostheses have to be implanted to restore sound transmission. Surface coatings with layered double hydroxides (LDHs) are evaluated here as a possibility for drug delivery systems with convenient advantages such as low cytotoxicity and easy synthesis. Male New Zealand White rabbits were implanted with Bioverit^® II middle ear prostheses coated with the LDH Mg₄Al₂(OH)₁₂(SO₄)₂·6H₂O impregnated with ciprofloxacin. 12 (group 1) were directly infected with Pseudomonas aeruginosa and another 12 (group 2) 1 week after the implantation. Clinical outcome, blood counts, histological analyses and microbiological examination showed an excellent antimicrobial activity for group 1, whereas this effect was attenuated in animals where infection was performed 1 week after implantation. This is the first study to demonstrate an efficient drug delivery system with an LDH coating on prostheses in the middle ear.     

Large scale synthesis of single-crystal and polycrystalline boron nitride nanosheets

Boron nitride nanosheets (BNNSs) have an identical crystal structure and similar lattice parameter to those of graphene sheets. However, growing quality BNNSs consisting of only several atomic layers remains a challenge. Here, we report on the synthesis of BNNSs at a temperature of 350 °C using a CO₂ pulsed laser plasma deposition (CO₂-PLD) technique by irradiating a pyrolytic hexagonal boron nitride (h-BN) target. The deposition was performed either in vacuum at a pressure of 0.2 Pa, for which we obtained polycrystalline BN, or in hydrogen (H₂) atmosphere at a pressure of 26 Pa for which we obtained single-crystal BNNSs. The presence of H₂ seems to minimize the side effects of sputtering and the material shows higher purity and better crystallinity. High resolution transmission electron microscopy (HRTEM) showed the sheets to be mostly defect-free and to have the characteristic honeycomb structure of six-membered B₃-N₃ hexagon. HRTEM, electron diffraction, X-ray diffraction, Raman scattering, and Fourier transform infrared spectroscopy clearly identified h-BN.     

Optimization of Microchannel Heat Sinks Using Genetic Algorithm

In this study, a genetic algorithm is employed to minimize the entropy generation rate in microchannel heat sinks. The entropy generation rate allows the combined effects of thermal performance and pressure drop to be assessed simultaneously as the heat sink interacts with the surrounding flow field. Previously developed models for the heat transfer, pressure drop and entropy generation rate are used in the optimization procedure. The results of optimization are compared with existing results obtained by the Newton–Raphson method. It is observed that the GA gives better overall performance of the microchannel heat sinks.