646 research outputs found
Foreword of the special issue on Alps and Apennines: a natural laboratory for Structural Geology and Geodynamics
No full textA saturation model based on a simplified equivalent magnetic circuit for permanent magnet machines
No full textThis paper proposes an explicit mathematical model to describe the nonlinear behavior of the permanent magnet synchronous reluctance machine. Although different models for the synchronous reluctance machines are available, extending them to the case of the permanent magnet machine is not trivial due to the effect of the permanent magnets on the rib saturation. This work uses a simplified equivalent magnetic circuit to derive the structure of the proposed model. A nonlinear reluctance is introduced to model the rib saturation. It can be added to the existing model for the synchronous reluctance machine to take into account the effect of the permanent magnets. A simple fitting procedure based on the steepest descent method is proposed to estimate the parameters of the model
Cockade-textured cataclasite and silica gel from damage zone in carbonated ultramafics: markers of cycles of seismic activity?
No full textShallow crustal processes occurring during seismic slips and generating fracture networks are of great interest due to their complex interplay with a spectrum of other geological processes .
Our study focuses on faults with peculiar core textures, similar to those of "cockade breccia" (Genna et al., 1996) and "clast cortex grains" (Rempe et al., 2014), and on their relation with syntectonic hydrothermal alteration linked with Au bearing-quartz and chalcedony veins.
Our work aims to study the enviromental conditions for the formation of such peculiar texture, their relation with the hydrothermal vein system and their potential as shallow seismic indicators.
We present field, microstructural and petrochemical data of a peculiar damage zone of fault rocks located in carbonated peridotites and serpentinites of the Ligurian Alps (Voltri Massif, Italy). These are mainly reverse faults, which are coeval with syntectonic Au-bearing quartz veins and chalcedony veins (Giorza et al., 2010), in which lherzolites occupy the hangingwall of the faults and serpentinites the footwall. The fault rocks show evidence for carbonation, as olivine and serpentine are clearly transformed into an assemblage made of magnesite, dolomite and minor ankerite. The damage zones of the faults are serpentinite-rich and about 10 m in thickness, while the cataclasite cores are carbonate-rich and ca. 1 m thick. The top of the fault core shows the occurrence of a chalcedony shear veins with chatter marks and slikenlines on the surface. The "cockade breccia" is made of spherical aggregates of Fe-Mg carbonates and are 1 mm to 3 cm in size. These aggregates show cores of microcrystalline Fe-Mg carbonates, and concentric outer layers of relatively coarser Fe-Mg carbonates with radial or laminated texture. In some cases, these aggregates show evidence for rotation along secondary slip zones.
We interpret all these features as the products of chemical interaction between the olivine and serpentine initially present within the fault rocks and the hydrothermal fluid that flowed within these faults. These interactions were probably similar to those occurring within the coeval Au- and chalcedony veins.
Field evidence and theoretical considerations indicate that the reverse faults could have experienced stages of fault-valve behaviour (Sibson et al., 1998), which consisted in cycles of fluid pressure build-ups, fault opening, fluid flushing, and mineral precipitation during the seismic failure of the faults. These cycles varied transiently fault permeabilities. During the fluid pressure build up stage the radial coarse grains developed, while during the fluid flushing stage the clast cortex grains developed their laminated texture. The Au-quartz and chalcedony veins could have formed during the stages of fluid pressure drops following fault slip (Sibson et al., 1998, 2004).
References
Capponi G. & Crispini L., 1997, Progressive shear deformation in the metasediments of the Voltri Group (Ligurian Alps, Italy): occurence of structure recording extension parallel to the regional foliation, Boll. Soc. Geol. It., 116, 267-277.
Genna A., Jébrack M., Marcoux E., Milési J.P., 1996, Genesis of cockade breccias in the tectonic evolution of the Cirotan epithermal gold system, West Java, Can. Journ. of Earth Sci., 33, 93-102.
Giorza A., 2010, Late to post-metamorphic hydrotermalism in the Voltri Unit (Lavagnina Lakes Area, NW Alps). Structural-Petrological-Geochemical approach, PhD Thesis, University of Turin.
Rempe M., Smith S. A. F., Ferri F., Mitchell T. M., 2014, Clast-cortex aggregates in experimental and natural calcite-bearing fault zones, Journ. Of Struct. Geol., 68, 142-157.
Sibson R. H., 2004, Controls of maximum fluid overpressure defining conditions for mesozonal mineralization, Journ. of Struct. Geol., 26, 6-7, 1127-1136.
Sibson R. H., Robert F., Poulsen H., 1998, High-angle reverse faults, fluid-pressure cycling, and mesothermal gold-quartz deposits, Geology, 16, 551-555.
Spagnolo C., 2006, Late orogenic tectonics in the eastern sector of the Ligurian Alps, PhD Thesis, Univesity of Genoa
Re: Vincent Cloutier, Umberto Capitanio, Laurent Zini, et al. Thirty-Day Mortality after Nephrectomy: Clinical Implications for Informed Consent. Eur Urol 2009;56:998-1005
No full textNon linear digital control improving transient response:design and test on a multiphase VRM
No full textGenerator topologies for horizontal axis tidal turbine
No full textOver the last decade, research on technologies to exploit tidal current kinetic energy for renewable electricity generation has had a significant growth. However, as to date, there is not a consensus worldwide on standard Power Take-Off (PTO) systems, due to the current immaturity of tidal energy converter technologies. In most cases, mechanical/electrical power conversion follows well-proven technologies derived by the mature wind-energy sector. However, the peculiarities of tidal energy resource impose ad hoc technology solutions. In this paper, different generator topologies and recent developments for marine tidal energy systems are reviewed and compared. The aim is to provide an overall perspective and identify areas for further development. Among considered technologies, the direct-drive permanent magnet synchronous generator by the full-rated frequency converter (FFC) represents an appealing solution, for reduced system complexity and maintenance requirements and possibility to develop smart Maximum Power Point Tracking (MPPT) strategies
I fasti d'imeneo nelle nozze degli dei e del nobile ed eccelso signor senatore conte Gio. Francesco Aldrovandi Mariscotti colla nobil donna la signora marchesa d. Lucrezia Fontanelli : pubblicati in occasione del primo ingresso di esso signor senatore al Gonfalonierato di Giustizia.
No full textIllustrations comprise 2 plates included in pagination: an allegorical frontispiece (including arms and view of Bologna), signed: G. M. Foschi Inv. Ioseph Foschi fe., and a double portrait of the bridal couple, signed: L. Capponi f. in Bologna. 18 head- and tailpieces, chiefly signed by Capponi; and 10 floriated and pictorial initials.In verse and prose.Mode of access: Internet
A refined approach to detect and measure minimal residual disease in childhood acute myeloid leukemia by flow cytometry.
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Non-stationarity index in vibration fatigue: Theoretical and experimental research
No full textRandom vibrations induce damage in structures, especially when they are operating close to their natural frequencies. The stationarity of the input excitation is one of the fundamental assumptions required for frequency-domain fatigue-damage theory. However, for real applications, excitation is frequently non-stationary and the identification of this non-stationarity is not easy. This study researches run-tests to identify the index of non-stationarity. Further, using excitation signals with different rates of amplitude-modulated non-stationarity, the index of non-stationarity is experimentally and theoretically researched with regards to the fatigue life. The experimental research was performed on a flexible structure that was excited close to a natural frequency. The experimental fatigue life is compared to the theoretical fatigue life under the stationarity assumption. The analysis of the experimental results reveals a close relation between the identified non-stationarity in the excitation signal and the fatigue life of the structure. It was found that amplitude-modulated non-stationary excitation results in a significantly shorter fatigue life if compared to a similar level of stationary excitation
Marcatori comportamentali del carico di lavoro mentale in compiti di guida automobilistica
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