A Simple Control Scheme for the High Performance Z-Source Inverter

In the past decade, the Z-source inverter (ZSI) is successfully developed for many applications. This paper proposes a simple integrated control scheme for the high performance ZSI. A proportional-integral PI controller is used to regulate the voltage of the Z-network capacitor. Moreover, the peak value of the DC-link voltage is controlled by limiting the shoot-through duty ratio. Furthermore, the instantaneous voltage control technique is utilized to retain the sinusoidal shape of the output voltage. A feed-forward signal of the AC voltage is employed to smooth the output voltage. To generate the PWM signals for the ZSI switches, the simple boost control method is utilized which coordinates the operation of different controllers. Extensive digital simulations are conducted to evaluate the dynamic behavior of the proposed control scheme. Moreover, an experimental setup is built to verify the performance of the proposed control scheme for the high performance ZSI.     

Nano rods for coloured glasses obtained by hybrid sol-gel coating

Many new materials are now allowing new properties thanks to nanotechnology because this domain of physics gives possibilities to optimize targeted properties even if these materials react in very various influential parameters. Architectural, automotive, bone pathologies, environment, display applications are some concerned domains. The sol-gel process is a method allowing the realisation of coats at ambiant temperature, thus it is possible to realize Liquid Crystal Display (LCD), water-repellent coatings on privacy glass, antireflective coatings, hydrophobic or hydrophilic surfaces, bone tissue regeneration. In this study, the purpose is to show the thermal influence on a covered glass with a complex hybrid sol-gel solution. This coated glass is going to change color from red to orange under the heat influence. This color change effect comes from the evolution of various compounds organizations then/or from their loss during the degassing sequence. We show in spite of the complexity of the process that the responsible is mainly the organic dye. Thus the structure of the heated glass at 250 degrees C looks radically different than the heated one at 350 degrees C. SEM measurement allows to identify the surface compositions and to determine the elementary composition along the sample's cross section. TGA is used to justify a mass loss when samples are annealed. UV/Visible measurement is realized by two methods: in-line transmission to evaluate luminous flux and thus give colorimetric dot in the normalized CIE diagram and diffuse transmission to observe the size influence of the pigments. Infrared Reflectivity allows to evaluate the influence of species on the structure and to better target the nature of the lost compounds during annealing. TEM measurement proves that the obtained iron particles are nano rods for both samples.     

Isomorphism between pulsed-wave Doppler ultrasound anddirection-of-arrival estimation. I. Basic principles

Direction-of-arrival (DOA) estimation of signals is an important area of research in sonar and radar signal processing. Over the last few decades, numerous techniques have been developed for high-resolution DOA estimation. In this paper, we show that velocity measurement using pulsed-wave Doppler ultrasound and DOA estimation are isomorphic problems. We discuss a number of DOA methods and their potential application to flow velocity measurement using ultrasound. Wide-band DOA methods are of special interest because the pulses used for Doppler ultrasound are also wide band. These wide-band methods generally involve a preprocessing step to convert wideband signals to narrow band before applying high-resolution techniques. Application of DOA methods to Doppler ultrasound provides tools for high-resolution velocity measurement, identification of multiple velocity components within a sample volume, and clutter rejection     

Computational estimation of ESD conditions between chargedparticles and grounded surfaces

The paper examines the conditions in which a discharge occurs between charged spherical particles and grounded surfaces, in air, at atmospheric pressure. The study is of interest to a large group of electrostatic applications which involve the processing of particulate matter: separation of granular mixtures, precipitation of dust, and spraying of powders. At the same time, this simple physical model simulates a class of hazardous situations quite often met in the operation of electronic circuits. The boundary-element method was employed for the computation of the electric field in the gap of length x between a charged conductive spherical particle of radius R and a grounded plate. The data on field distribution represented the input data of an original program which employed Pedersen's criterion for estimating the breakdown conditions of that air-gap. The study was carried out for spheres of various sizes (radii: 0.01-1 mm). Some computations were performed for the case when the grounded plate was covered with an insulating layer of known permittivity. The computational results were in good agreement with the experimental data for both long (x/R>10) and short (x/R<0.1) gaps     

New thickening agents for reactive printing of cellulosic fabrics

Four adducts were prepared by polymerizing acrylic acid (AA) in presence of either a pyrodextrin (D) or gum Arabic (GA), and termed as PAA/D₁, PAA/D_2, PAA/GA_1, and PAA/GA₂. These adducts were utilized as thickeners in reactive printing of cotton fabric in comparison with Na‐Alginate. Printing was carried out at different conditions including: NaHCO₃ concentration (0–40 g/K), urea concentration (0–200 g/k), steaming temperature (100–130°C) and time (5–35 min). At optimal NaHCO₃ concentration (30 g/K) the depth of shade of the prints, expressed as K/S values, depended on the nature of the thickener used, and followed the descending order PAA/D₂ > PAA/GA₁ > Na‐Alginate ?PAA/D₁ ≥ PAA/GA₂. Accordingly, PAA/D₁ and PAA/GA₂ were omitted in subsequent trials. Optimal printing conditions were found to be NaHCO₃ concentration (30 g/K), urea concentration (100 g/k), steaming temperature (110°C), and time (15 min). The apparent viscosity of a printing paste, as well as both of K/S value and fastness properties of a print were governed by the nature of the reactive dye and type of thickener. Storing of a printing paste up to 7 days resulted in a decrease in its apparent viscosity along with a slight reduction in K/S value and a little variation in some fastness properties of prints. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4430–4439, 2006     

Carburization/Oxidation Behavior of Alloy Haynes-214 in Methane–Hydrogen Gas Mixtures

The excellent resistance of Alloy Haynes-214 to carburization at elevated temperatures is attributed to the formation of a protective surface layer of Al₂O₃, resulting from the reaction of trace oxygen impurity in the gas phase with the Al-enriched surface. Lower carburization resistance below 1000 °C is manifested by increased carbon pick-up and degradation of mechanical properties. Exposures in CH₄/H₂ gas mixtures containing trace levels of oxygen below 1000 °C reduce the supply of outwardly diffusing aluminum from the bulk of the alloy to the metal surface, thus enhancing inward-oxygen diffusion and the subsequent formation of fine lamellar dispersion of internal Al₂O₃ within the sub-surface zone. In the meantime, inward-carbon diffusion forms internal carbides, thus leading to increased weight gain, relative loss of protection, and possible degradation of mechanical properties. Effective mitigation of carburization is limited only to exposure at extreme temperatures (1100 °C) which enhances the outward diffusion of aluminum towards the gas/metal interface as well as the nucleation of Al₂O₃ at the surface, thus causing an early transition from internal to external oxidation, which promotes the formation of an external protective layer of Al₂O₃ which effectively blocks carbon ingress in the alloy.     

Adaptive color image watermarking based on a modified improved pixel-wise masking technique

In this paper, a family of modified wavelet-based watermarking techniques is proposed. This family of techniques is based on the improved pixel-wise (PW) watermarking scheme. The basic proposed algorithm considerably improves the PSNR of the watermarked image (in the range of 2.20–7.28 dB), and is based on selecting specific locations in the three detailed sub-bands of the first level of the DWT decomposition of the image. The selective nature of the modified PW method (denoted as selective PW: SPW) allows the scheme to be adaptive in terms of the imperceptibility and the watermark size. Also, the PW and SPW methods were extended to be implemented with color images: (1) grayscale-wise PW method (G-PW) that embeds the watermark in the Y component of the YCbCr model. (2) Multi spectral-PW method (MS-PW) that embeds the watermark in the R, G, and B layers independently. (3) Multi spectral-SPW method (MS-SPW) that gains high PSNR value compared with MS-SPW, and (4) multi spectral-maximum PW method (MS-MPW) which is proposed to improve the PSNR value as well as the level of watermarking security, when compared with MS-PW method.     

Effect of cathode material on the morphology and photoelectrochemical properties of vertically oriented TiO2 nanotube arrays

We report, for the first time, on the effect of the cathode material in controlling the morphology and properties of TiO₂ nanotube arrays fabricated by electrochemical anodization of Ti foil in both aqueous and ethylene glycol (EG) electrolytes. Some of the alternative less-expensive cathode materials result in TiO₂ nanotube architectures and photoelectrochemical properties similar to or in some cases superior to those obtained using a Pt cathode.     

Reactivity ratios during radiation‐induced grafting of comonomer mixtures onto polyester fabrics

Radiation‐induced grafting of binary mixtures of acrylonitrile (AN)/styrene (S) and acrylamide (AAm)/styrene (S) onto polyester fabric (PET) has been investigated. Synergism during radiation grafting was investigated by determining the graft yield fraction for each monomer in the final graft copolymer. Moreover, by knowing the mole fraction of each monomer in the grafting solution, the reactivity ratio of the individual monomers in the comonomer mixture during graft copolymerization could be determined: in the case of AN/S comonomer mixture, the calculated reactivity ratios for AN and S are 0.04 and 0.05, respectively; the calculated reactivity ratios of AAm and S in their comonomer mixture are 1.82 and 0.41, respectively. © 2001 Society of Chemical Industry     

Simplified analytical method for predicting conversion gain of HEMTgate mixers

The transconductance profile is the dominant factor in the frequency conversion process in a gate mixer configuration. Based on this property. A simplified analytical expression for the computation of the conversion gain has been developed. Good agreement is obtained between analytical computations and experimental data