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901.
C. P. Jacovides C. Theophilou F. S. Tymvios S. Pashiardes 《Theoretical and Applied Climatology》2002,72(3-4):259-263
Summary ?A statistical analysis of wind speed and direction data for five selected meteorological stations at the Cyprus coast, is
carried out in this study. Daily, monthly and annual variations of wind speed are established. The Weibull distribution statistics
of the sites are also determined. In addition, an attempt is made to find the sea-breeze circulation effects in the same wind
data. The wind statistics obtained are expected to serve as a validation test for wind energy applications, mainly along the
southeastern coastline.
Received April 5, 2001; revised February 13, 2002; accepted March 3, 2002 相似文献
902.
903.
M. J. Costa M. Cervino E. Cattani F. Torricella V. Levizzani A. M. Silva S. Melani 《Meteorology and Atmospheric Physics》2002,81(3-4):289-298
Summary ?Retrievals of atmospheric aerosol optical thickness are highly dependent on the choice of the class describing the aerosol
properties leading to significant errors while using classes available in the literature. High spectral resolution measurements
from GOME (Global Ozone Monitoring Experiment) between the ultraviolet and the near infrared can be used for an accurate characterization
of the aerosol optical properties. The radiometer MVIRI (METEOSAT Visible and Infrared Imager) on board the geostationary
satellite METEOSAT, while being equipped only with broadband VIS channel, ensures an adequate half-hourly monitoring of the
atmospheric conditions over a large portion of the Earth. The present algorithm is based on a combination of data from both
sensors for the retrieval of the aerosol optical thickness at the reference wavelength of 0.55 μm (AOT). A case of a desert
dust outbreak from the African continent over the Atlantic Ocean is examined. AOT values obtained using a priori fixed classes
taken from the literature are compared with those retrieved with this algorithm using the GOME-derived classes. Systematic
differences of the order of a few tenths on average are found which remain significant also after considering the measurement
errors. This represents a novelty introduced by the synergetic use of both sensors.
Received March 13, 2002 相似文献
904.
A. Ankilov A. Baklanov M. Colhoun K. -H. Enderle J. Gras Yu. Julanov D. Kaller A. Lindner A. A. Lushnikov R. Mavliev F. McGovern T. C. O'Connor J. Podzimek O. Preining G. P. Reischl R. Rudolf G. J. Sem W. W. Szymanski A. E. Vrtala P. E. Wagner W. Winklmayr V. Zagaynov 《Atmospheric Research》2002,62(3-4)
During an international workshop at the Institute for Experimental Physics of the University of Vienna, Austria, which was coordinated within the Committee on Nucleation and Atmospheric Aerosols (IAMAS-IUGG), 10 instruments for aerosol number concentration measurement were studied, covering a wide range of methods based on various different measuring principles. In order to investigate the detection limits of the instruments considered with respect to particle size, simultaneous number concentration measurements were performed for monodispersed aerosols with particle sizes ranging from 1.5 to 50 nm diameter and various compositions.The instruments considered show quite different response characteristics, apparently related to the different vapors used in the various counters to enlarge the particles to an optically detectable size. A strong dependence of the 50% cutoff diameter on the particle composition in correlation with the type of vapor used in the specific instrument was found. An enhanced detection efficiency for ultrafine hygroscopic sodium chloride aerosols was observed with water operated systems, an analogous trend was found for n-butanol operated systems with nonhygroscopic silver and tungsten oxide particles. 相似文献
905.
The circulation and transport of freshwater generated by an idealized buoyant source is studied using a three-dimensional primitive equation model. Freshwater enters the continental shelf, turns anticyclonically and moves downstream in the direction of Kelvin wave propagation. In the region close to the source, the flow reaches an equilibrium in the bottom boundary layer so that freshwater does not spread offshore any further. This offshore equilibrium distance increases as we move downstream until the freshwater is able to feel the presence of the shelfbreak. A shelfbreak front forms and the shelfbreak prevents any further offshore spreading of freshwater in the bottom boundary layer.Two complimentary mechanisms are responsible for the slow cross-shelf migration of freshwater and subsequent trapping of shelfbreak fronts: bottom stress and topographic changes. The shelfbreak creates an active, dynamic process preventing leakage from the continental shelf region to the slope region. However, the dynamical process that traps the front to the shelfbreak is still unclear.The location of the shelfbreak front depends on four dimensionless parameters: scaled inlet volume transport, scaled breadth, scaled “diffusivity” and scaled shelf width. We develop empirical relations for predicting the location of the frontal bottom intersection, given these parameters. 相似文献
906.
F. J. Molina G. Verzeletti G. Magonette Ph. Buchet V. Renda M. Geradin A. Parducci M. Mezzi A. Pacchiarotti L. Federici S. Mascelloni 《地震工程与结构动力学》2002,31(8):1563-1582
A pseudodynamic testing procedure has been applied by which the seismic response of a base‐isolated building is obtained by using as specimen the isolators, while the superstructure is numerically simulated. The procedure also takes advantage of the continuous pseudodynamic testing capabilities of the ELSA laboratory, which increase the accuracy of the results and reduce the strain‐rate effect of the rubber bearings. A simple proportional correction of the measured forces compensates the remaining strain‐rate effect due to the unrealistic speed of the test. The correction factor is obtained by means of a characterizing test on the specific rubber isolators. The developed method has been successfully applied to the prediction of the seismic response of a base‐isolated four‐storey building submitted to several specified accelerograms. The results for those earthquakes as well as the effects of some changes of the parameters of the system are discussed. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
907.
Most current methods of design for concrete structures under earthquake loads rely on highly idealized ‘equivalent’ static representations of the seismic loads and linear‐elastic methods of structural analysis. With the continuing development of non‐linear methods of dynamic analysis for the overload behaviour and collapse of complete concrete structures, a more direct and more accurate design procedure becomes possible which considers conditions at system collapse. This paper describes an evaluation procedure that uses non‐linear dynamic collapse–load analysis together with global safety coefficients. A back‐calibration procedure for evaluating the global safety coefficients is also described. The aim of this paper is to open up discussion of alternative methods of design with improved accuracy which are necessary to move towards a direct collapse–load method of design. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
908.
Seismic Hazard for Selected Sites in Greece: A Bayesian Estimate of Seismic Peak Ground Acceleration 总被引:1,自引:1,他引:1
A procedure for estimating maximum values of seismic peak ground accelerationat the examined site and quantiles of its probabilistic distribution in a future timeinterval of a given length is considered. The input information for the method areseismic catalog and regression relation between peak seismic acceleration at a givenpoint and magnitude and distance from the site to epicenter (seismic attenuation law).The method is based on Bayesian approach, which simply accounts for influenceof uncertainties of seismic acceleration values. The main assumptions for the method are Poissonian character of seismic events flow and distribution law of Gutenberg-Richter's type. The method is applied to seismic hazard estimation in six selected sitesin Greece. 相似文献
909.
A. Piccioni F. Giovanelli K. Bartolini I. Bruni M. Frutti A. Guarnieri 《Astronomy Reports》2002,46(12):1030-1041
The structure of the electronics of the two-head, high-speed photometer operating on the 152-cm G.D. Cassini telescope of Bologna University has been fully redesigned for high-time-resolution observations of fast variable sources, in particular, of the optical counterparts of X-ray binary systems. The fast photometer now permits sampling times from 0.1 ms to 100 s. The handling of the system clock and I/O configuration have been modified to provide rigorous synchronization of the sampling time with an external high-stability clock and the continuous acquisition of an uninterrupted data stream. The continuous data-acquisition process, which is driven by an external clock, is limited only by the capacity of the hard disk and is supported by a double-buffer SRAM memory designed to overcome any discontinuity in the asynchronous communication with the computer. Real-time monitoring of the data enables continuous evaluation of the weather conditions, and the directly displayed light curve can be used to determine the optimal management of the observations. 相似文献
910.
José F. Noguera Lluís Rivero Xavier Font Andrés Navarro Francisco Martínez 《Environmental Geology》2002,41(8):898-905