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21.
Alessio De ANGELIS Marco DIONIGI Paolo CARBONE Mauro MONGIARDO 车文荃 王清华 Franco MASTRI Giuseppina MONTI 《南京气象学院学报》2017,9(1):73-81
对谐振感应式无线功率传输链路的3种不同的工作方式进行了讨论.第1种工作方式是输出恒定的电压或电流;第2种工作方式采用频率捷变操作,非常适合于不随耦合系数变化的应用场合;第3种工作方式实现负载独立工作并输出恒定的电压或电流.本文讨论并提出了不同情况下的解决方案和相关公式.最后通过实验对提出的理论进行了验证. 相似文献
22.
The Nebrodi Park, located in the north-eastern sector of Sicily, is of particular environmental and scientific interest.
This is due to the morphological heterogeneity of the protected region that presents a wide variety of landscapes and ecosystems.
In spite of the recent efforts of the Regional Government and Municipalities, environmental resources, especially groundwater,
risk progressive depauperation and pollution. In this paper, the authors consider the hydrogeological karst unit of Monte
Traura-Rocche del Crasto, the most productive in the Nebrodi belt (zone B of the regional park). This unit is underexploited
and needs a careful hydrogeological study in order to supply coastal aquifers. Geochemical and geophysical prospecting has
been carried out in this area. Analyses of water springs, sampled in different seasons, have suggested patterns of groundwater
circulation. Apparent resistivity measurements have yielded complementary information about the recharge processes of deep
aquifers. Goals of the project to which this research belongs are the rational exploitation and protection of reservoirs such
as Monte Traura and the recovery of the degraded aquifers, proposing new strategies of regional management for the water resources
in this comer of Sicily.
Received: 27 November 1996 · Accepted: 5 January 1998 相似文献
23.
Paola R. Gialanella Alberto Incoronato Filippo Russo Giuseppina Nigro 《Journal of Volcanology and Geothermal Research》1993,58(1-4)
An extensive palaeomagnetic study has been undertaken to provide further elements leading to a better assessment of the volcanic history of the Vesuvius. This work refers to lavas for which the date of emplacement have recently been questioned; i.e. either during the period 968–1037 or in 1631. From 7 sites, 97 sun-orientated specimens have been collected. The dominant magnetic carrier for all sites consists of magnetite on the basis of an analysis of IRM acquisition. The linearity analysis carried out on at least 6 specimens per site subjected to PAFD has indicated the presence of single- and multi-component magnetizations. The within-site mean directions of 5 sites are close to each other suggesting that lavas from these sites can be ascribed to the same volcanic event. The remaining 2 sites can also be referred to this event on ground of stratigraphical considerations. The plotting of the between-site mean directions of the previously mentioned 5 sites on the Vesuvius secular variation curve suggests that the lavas from these sites could not be emplaced during the period 968–1037 but some hundred years later than 1301. The stratigraphic and historic dating of deposits and a building, respectively, at one of the 2 remaining sites allows to conclude that all the investigated flows had to be emplaced during the 1631 event. Therefore, this event was characterized not only by explosive activity but by an important effusive phase as well. 相似文献
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Giuseppina Micela 《Experimental Astronomy》2015,40(2-3):723-732
Stellar activity is the major astrophysical limiting factor for the study of planetary atmospheres. Its variability and spectral characteristics may affect the extraction of the planetary signal even for moderately active stars. A technique based on spectral change in the visible band was developed to estimate the effects in the infrared due to star activity. This method has been purposely developed for the EChO mission which had the crucial characteristics of monitoring simultaneously a broadband from visible to infrared. Thanks to this capability the optical spectrum, whose variations are mainly due to stellar activity, has been used as in an instantaneous calibrator to correct the infrared spectrum. The technique is based on principal component analysis which significantly reduces the dimensionality of the spectra. The method was tested on a set of simulations with realistic photon noise. It can be generalized to any chromatic variability effects provided that optical and infrared variations are correlated. 相似文献
27.
Maria Boni Rosario Terracciano Giuseppina Balassone Sarah A. Gleeson Alexander Matthews 《Mineralium Deposita》2011,46(7):707-729
Zambian willemite (Zn2SiO4) deposits occur in the metasedimentary carbonate rocks of the Proterozoic Katangan Supergroup. The most important orebodies
are located around Kabwe and contain both sulphides and willemite in dolomites of low metamorphic grade. The Star Zinc and
Excelsior prospects (Lusaka area), discovered in the early 1920s, occur in the metamorphic lithotypes of the late Proterozoic
Zambezi Supracrustal sequence, which were deposited in a transtensional basin formed during the oblique collision of the Kalahari
and Congo cratons. The deposits are hosted by the limestone and dolomitic marbles of the Cheta and Lusaka Formations. Structural
analysis indicates that several fracture sets host the deposits, which may be genetically related to the Pan-African Mwembeshi
dislocation zone (a major geotectonic boundary between the Lufilian Arc and the Zambezi Belt). In both prospects, willemite
replaces the marbles and is found along joints and fissures with open-space filling textures and locally may develop colloform
and vuggy fabrics as well. Silver as well as traces of germanium and cadmium have been detected within the willemite ore,
and lead or zinc sulphides are scarce or absent. Calcite locally replaces willemite. Willemite is associated with specular
hematite and franklinite and post-dates the Zn-spinel gahnite in the paragenesis. Genthelvite [Zn4Be3(SiO4)3S] occurs as a minor phase in irregular aggregates. The willemites from the Lusaka area, though Mn-poor, show green cathodoluminescence
colours and bright green fluorescence in short-wave UV (as the high-temperature willemites in USA). Thermometric analyses
of primary fluid inclusions in willemite yield homogenization temperatures that range from 160°C to 240°C and salinities of
8–16 wt.% equiv. NaCl. The homogenization temperatures suggest a hypogene–hydrothermal origin for the willemite concentrations.
The geochemistry of fluid inclusion leachates suggests that the hydrothermal fluids were brines derived from highly evaporated
seawater. Precise age constraints are currently lacking for the Lusaka area deposits, though the deposits are not deformed,
indicating that they post-date the Lufilian orogeny (~520 Ma). The possibility of precursor ores exists; the gahnite–franklinite–willemite
deposits could have been derived from a metamorphosed primary sulphide (or even nonsulphide) concentration that has subsequently
been completely destroyed. However, there is no real evidence of such a primary source for the willemite mineral association.
The Lusaka zinc ores may have been produced by an extensive hydrothermal system, with fluids discharging along basinal fracture
zones controlled by the pre-Pan-African rifting stage. A paragenesis similar to that of the Lusaka prospects has been proposed
to be a vector towards massive sulphide ores in several parts of the world; therefore, it is possible that these small willemite
showings in Zambia may be part of a much bigger, and still unexplored, zinc province. 相似文献
28.
Giuseppina Nigro 《地球物理与天体物理流体动力学》2013,107(1-2):101-113
This article addresses the interesting and important problem of large-scale magnetic field generation in turbulent flows, using a self-consistent dynamo model recently developed. The main idea of this model is to consider the induction equation for the large-scale magnetic field, integrated consistently with the turbulent dynamics at smaller scales described by a magnetohydrodynamic shell model. The questions of dynamo action threshold, magnetic field saturation, magnetic field reversals, nature of the dynamo transition and the changes of small-scale turbulence as a consequence of the dynamo onset are discussed. In particular, the stability curve obtained by the model integration is shown in a very wide range of values of the magnetic Prandtl number not yet accessible by direct numerical simulation but more realistic for natural dynamos. Moreover, from our analysis it is shown that the large-scale dynamo transition displays a hysteretic behaviour and therefore a subcritical nature. The model successfully reproduces magnetic polarity reversals, showing the capability to generate persistence times which are increasing for decreasing magnetic diffusivity. Moreover, when the system reaches a statistically stationary dynamo state, where the large-scale magnetic field can abruptly reverse its polarity (magnetic reversal state) or not, keeping the same polarity (steady state), it shows an unmistakable tendency towards the energy equipartition for the turbulence at small scale. 相似文献
29.
It is shown that Kantowski–Sachs cosmological models do not exist in Rosen's (1973) bimetric theory of gravitation when the
source of gravitation is either perfect fluid or cosmic string. Hence, the vacuum model is constructed. 相似文献