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Hysteresis motors are very attractive in a wide range of fractional power applications, due to its torque-speed characteristics and simplicity of construction. This motor's performance is expected to improve when HTS rotors are used, and in fact, hysteresis motors have shown to be probably the most viable electrical machines using HTS materials. While these motors, either conventional or HTS, are both hysteresis motors, they base their operation on different physical phenomena: hysteretic behaviour in conventional ferromagnetic materials is due to the material's non-linear magnetic properties, while in HTS materials the hysteresis has an ohmic nature and is related with vortices' dynamics. In this paper, theoretical aspects of both conventional and HTS hysteresis motors are discussed, its operation principles are highlighted, and the characteristics of both motors are presented. The characteristics, obtained both by experimental tests and numerical simulation (made with commercial software), are compared, in order to evaluate not only the motor's electromechanical performances but also the overall systems efficiency, including cryogenics for the HTS device.

Power electronics (PE) plays a major role in electrical devices and systems, namely in electromechanical drives, in motor and generator controllers, and in power grids, including high-voltage DC (HVDC) power transmission. PE is also used in devices for the protection against grid disturbances, like voltage sags or power breakdowns. To cope with these disturbances, back-up energy storage devices are used, like uninterruptible power supplies (UPS) and flywheels. Some of these devices may use superconductivity. Commercial PE semiconductor devices (power diodes, power MOSFETs, IGBTs, power Darlington transistors and others) are rarely (or never) experimented for cryogenic temperatures, even when designed for military applications. This means that its integration with HTS power devices is usually done in the hot environment, raising several implementation restrictions. These reasons led to the natural desire of characterising PE under extreme conditions, e. g. at liquid nitrogen temperatures, for use in HTS devices. Some researchers expect that cryogenic temperatures may increase power electronics' performance when compared with room-temperature operation, namely reducing conduction losses and switching time. Also the overall system efficiency may increase due to improved properties of semiconductor materials at low temperatures, reduced losses, and removal of dissipation elements. In this work, steady state operation of commercial PE semiconductors and devices were investigated at liquid nitrogen and room temperatures. Performances in cryogenic and room temperatures are compared. Results help to decide which environment is to be used for different power HTS applications

Power electronics (PE) plays a major role in electrical devices and systems, namely in electromechanical drives, in motor and generator controllers, and in power grids, including high-voltage DC (HVDC) power transmission. PE is also used in devices for the protection against grid disturbances, like voltage sags or power breakdowns. To cope with these disturbances, back-up energy storage devices are used, like uninterruptible power supplies (UPS) and flywheels. Some of these devices may use superconductivity. Commercial PE semiconductor devices (power diodes, power MOSFETs, IGBTs, power Darlington transistors and others) are rarely (or never) experimented for cryogenic temperatures, even when designed for military applications. This means that its integration with HTS power devices is usually done in the hot environment, raising several implementation restrictions. These reasons led to the natural desire of characterising PE under extreme conditions, e. g. at liquid nitrogen temperatures, for use in HTS devices. Some researchers expect that cryogenic temperatures may increase power electronics' performance when compared with room-temperature operation, namely reducing conduction losses and switching time. Also the overall system efficiency may increase due to improved properties of semiconductor materials at low temperatures, reduced losses, and removal of dissipation elements. In this work, steady state operation of commercial PE semiconductors and devices were investigated at liquid nitrogen and room temperatures. Performances in cryogenic and room temperatures are compared. Results help to decide which environment is to be used for different power HTS applications

Sulphate-reducing bacteria have a wide variety of periplasmic cytochromes involved in electron transfer from the periplasm to the cytoplasm. HmcA is a high molecular mass cytochrome of 550 amino acid residues that harbours 16 c-type heme groups. We report the crystal structure of HmcA isolated from the periplasm of Desulfovibrio gigas. Crystals were grown. using polyethylene glycol 8K and zinc acetate, and diffracted beyond 2.1 angstrom resolution. A multiple-wavelength anomalous dispersion experiment at the iron absorption edge enabled us to obtain good-quality phases for structure solution and model building. DgHmcA has a V-shape architecture, already observed in HmcA isolated from Desulfovibrio vulgaris Hildenborough. The presence of an oligosaccharide molecule covalently bound to an Asn residue was observed in the electron density maps of DgHmcA and confirmed by mass spectrometry. Three modified monosaccharides appear at the highly hydrophobic vertex, possibly acting as an anchor of the protein to the cytoplasmic membrane. (c) 2007 Elsevier Ltd. All rights reserved.

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The electric and magnetic properties of high temperature superconductors and the possibility to cool them by cheap liquid nitrogen makes them attractive in power applications. An all superconducting linear synchronous motor is presented in this paper in order to quantify the benefits and disadvantages of such applications. The term ?all superconducting? is related with the absence of copper conductors and iron parts. Certain characteristics of the superconducting materials impose severe restrictions when used, e.g., as armature windings. A numerical method for deriving the thrust and lift forces developed in such a motor, driven by a typical current inverter, is presented.

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Polymeric mortars or concrete are special building materials which can be used to repair or strengthen localized areas of structural elements. Following research on the behaviour of retrofitting reinforced concrete circular columns with FRP composite materials and bearing in mind the high strength of polymer concretes, it was decided to develop a solution to seismic retrofit of reinforced concrete columns with polymer concrete. The mechanical characteristics of different polymer concretes and especially their performance when subjected to cyclic axial compression, several bending tests, and monotonic and cyclic axial compression tests were studied, namely the compressive strength, the tensile strength on bending and the Young's modulus. Columns were also tested under axial compression and cyclic horizontal loads. The results of these tests are shown and interpreted. It is concluded that the improved behaviour in monotonic compression of polymer concrete is essentially associated with better strength characteristics of resin, whereas its superior behaviour under cyclic loading is linked to a smoother aggregate grading curve.

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We use the almost normality approach to derive the models we use. Polynomial almost normality is presented in a first chapter. Thus we show that low degree polynomials on independent normal variables with small variation coefficients are very approximately normal distributed. This result is then used do derive models for series of studies assuming normality and independence for the initial observations and low variation coefficients. We then apply this models first for single series and then for matched series of studies. We will assume that the matched series are associated to the treatments and orthogonal design. The special case of prime basis factorials is considered.

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