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81.
This work is based on the study of outdoor daylight conditions during the winter period in Pamplona (the Iberian Peninsula). The 15 standard sky types proposed by the Commission Internationale de l’Eclairage (CIE) are used. The selected sky type in each moment is the one exhibiting the lowest root mean standard deviation (RMSD) when the theoretical and experimental luminance distributions in the sky hemisphere are compared. The selection was derived from luminance distribution data from 145 patches of the sky hemisphere and registered every 10 min from October to March from 2007 and 2008.The most frequent sky type observed in winter in Pamplona is V.5 (cloudless polluted with a broad solar corona), with a frequency of occurrence of 21%. Notwithstanding, the group of overcast skies exhibits a slightly higher frequency (40%) than the clear skies (37%). Seven out of the 15 standard sky types, i.e.V.5, I.1, III.4, II.1, IV.4, II.2 and III.3, are practically 80% of those under study. In order to provide a possible application in daylight climates studies, the frequency of occurrence of the 15 sky types is included in eleven intervals of solar elevation on the threshold corresponding to the time period and the location considered.  相似文献   
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83.
The Solar Maximum Mission Satellite, the Sacramento Peak Vacuum Tower Telescope, the Very Large Array and the Westerbork Synthesis Radio Telescope have been used to observe active region AR 2490 on two consecutive days at soft X-ray, ultraviolet, optical and radio wavelengths (2, 6, and 20 cm), with comparable angular resolution (2 to 15) and field of view (4 × 4). The radio emissions at = 6 cm and 20 cm show a double structure in which one component is associated with bright H plage, C iv and soft X-ray emission, and the other component is associated only with sunspots. No radiation at = 2 cm is detected in this latter component. Coronal temperature and emission measure derived from X-ray lines indicate that the dominant radiation mechanism of the plage-associated component is due to thermal bremsstrahlung while the gyroresonance absorption coefficient must be invoked to account for the high brightness temperature (T b 2×106K) observed in the sunspot associated component. The high magnetic field strength needed (600 G at a level where T2×106K) is explained assuming a thin transition zone, in order to reach a high electron temperature close to the sunspot, where the magnetic fields are stronger. A higher temperature gradient above sunspots is also consistent with the absence of detectable C iv emission.Cooperative study of the SMY-FBS Project.On leave from the University of Napoli.On leave from the University of Torino.On sabbatical leave 1980–81 at the Arcetri Observatory.On leave from Toyokawa Observatory, Japan.  相似文献   
84.
Models for Support and Information Effects: A Comparative Study   总被引:1,自引:0,他引:1  
The recoverable reserves in an ore deposit depend on several factors, in particular the size of the selective mining units (support effect) and the misclassifications when sending these units to mill or dump according to their estimated grade (information effect). Both effects imply a loss of selectivity and have to be correctly forecasted. In this work, several models are reviewed and applied to a synthetic ore deposit characterized by a highly skewed grade histogram and a spatial connectivity of high grades. The affine correction, mosaic correction, and discrete Gaussian model are compared when assessing the global recoverable reserves, whereas local estimations are performed by indicator kriging with affine correction, bigaussian disjunctive kriging, and multigaussian conditional expectation. Despite their convenience and simplicity, distribution-free methods like affine correction or indicator kriging have a poorer accuracy than the other methods. In the global framework, the discrete Gaussian model is a better alternative and is based on mild assumptions. Local estimations are not accurate and may be improved by resorting to a more suitable parametric model or to conditional simulations.  相似文献   
85.
DPFT is a lumped approach for operational flash flood forecasting, based on the unit hydrograph. Using a multi-event alternating iterative algorithm, it identifies a robust and stable average transfer function and a consistent set of effective rainfall series associated with each event at the same time. This key ingredient allows an objective calibration of different loss functions, relating gauged precipitation and effective rainfall. A case study based on an operational French basin (545 km2) is presented. Three lumped production functions have been calibrated and compared. The results show that more elaborate models of loss functions must be proposed, and some possible directions for this are pointed out.Presently at the Institut de Ciences de la Terra Jaume Almera, Apartat 30102, 08080 Barcelona, Spain.Presently at EDF-DTG. Service de Ressources en Eau, BP 4348, 31029 Toulouse Cedex, France.  相似文献   
86.
Monocolumn behavior in waves: Experimental analysis   总被引:1,自引:0,他引:1  
A series of tests with a model of a monocolumn platform with a moonpool were performed at the LabOceano/COPPE, at the Universidade Federal do Rio de Janeiro, with the objective of determining the entrance area at the bottom of the moonpool that minimizes vertical motion in waves. The tests include measurements of monocolumn surge, pitch and heave motion, vertical motion of the water column inside the moonpool, with different mooring systems, in regular, irregular and transient waves.This paper presents experimental results of the monocolumn vertical motion and the internal water column motion in the moonpool in transient waves and results of vertical motion of the water column inside the moonpool with the model held still in transient waves. These measurements allow an analysis of the impact of the moonpool's bottom opening on the monocolumn vertical motion in waves.The theoretical analysis of a mass–spring–damper system with two degrees of freedom, similar to the studied system, has shown some analogy with den Hartog's damped vibration absorber; however, there are significant differences in terms of added mass and coupled terms of added mass and damping coefficients dependent on oscillation frequencies.  相似文献   
87.
Dried samples of the red algae Solieria filiformis and Agardhiella subulata from Mar Piccolo, Taranto, were extracted by stirring in water at 25 (Cold), 85 (Hot) and 120 (pressure) °C. For each species, six successive cold, three hot and two pressure extractions were performed and analyzed separately. Water-soluble polysaccharides were isolated after treatment with amylase, alcohol precipitation, dialysis and freeze drying. The total, starch-free yields were 27 and 24% of the dry weight for S. filiformis (SF) and A. subulata (AS), respectively. FTIR and NMR spectroscopic analysis showed that the different cold and hot water extracts had a similar structural backbone, which can be characteristic of gelling type carrageenans with a dominant iota repeating structure (DA2S-G4S). However, some irregularities were detected by NMR, which may be attributed to 6-sulphated 4-linked precursor units. The occurrence of such and other irregularities was more frequent in the SF samples, giving a possible explanation for the enhanced extractability in cold water of carrageenan polymers from this species.  相似文献   
88.
The measured anisotropies in the temperature of the cosmic microwave background radiation (CMB) by the Cosmic Background Explorer (COBE) are consistent with models of gravitational collapse for the formation of large scale structure in the universe. The amplitude of cosmological fluctuations on the largest scales is fixed by COBE. From COBE's data it is also possible to test for the shape of the primordial spectrum. Statistical tests using COBE's two year data and based on the geometric characteristics of anisotropy spots taking into account cosmic variance and the relevant experimental details indicate that the primordial spectrum has a slope in the rangen = 0.8 – 1.3. Possible identification of hot and cold spots of cosmological origin is also given.Presented at the Fourth United Nations/European Space Agency Workshop on Basic Space Science. Cairo, Egypt, 27 June - 1 July 1994.  相似文献   
89.
Governments, civil society, and policymakers assert the potential of international migration to foster development and alleviate poverty. Often such claims are rooted in macroscale geopolitical analyses of migration and development, which mask the localized, uneven, and embodied ways family members “left behind” bear the costs and subsidize the U.S./Mexico (inter)national integration project. Informed by feminist geopolitics, this article demonstrates how the left behind disproportionately bear the hidden costs of neoliberal restructuring and migration. We draw upon Mexican Migration Project (MMP) ethnosurvey data to frame the narratives of migrant family members left behind. Narratives were constructed through in‐depth interviews conducted in rural Veracruz. We conclude that in the absence of geographically specific examinations of the hidden costs associated with neoliberal development and migration it is possible that “migration for development” programs and policies may exacerbate inequities that will perpetuate migration and further weaken Mexican origin communities.  相似文献   
90.
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