Discrete models for vertical vibrations of surface and embedded foundations

A five-parameter discrete model that approximates the dynamic force4isplacement relationship for rigid foundations undergoing vertical vibrations on a uniform elastic half-space is presented. The model involves a combination of two springs, two viscous dampers and a mass. Values of the parameters for circular, square and rectangular foundations placed on the surface or embedded in an elastic half-space are listed. The parameters are obtained by minimizing the discrepancy between the force4isplacement relation for the model and that obtained by solution of the mixed boundary-value problem of the rigid foundation on an elastic half-space. The definition of an appropriate input motion to represent wave excitation is also discussed. The input motion to the discrete model differs from the input motion that should be used in a continuum model.     

An array of lens-coupled antennas for cosmic microwave background measurements in the 30 Ghz band

An array of bow-tie slot antennas coupled through an extended hemispherical lens is proposed to operate in the 30?GHz frequency band. The design includes a combination of three microstrip Wilkinson power dividers (WPD) and transitions to coplanar wave guides (CPW) to form the feeding antenna network. This configuration is suitable for the integration with heterodyne imaging detectors commonly used in radioastronomy. Measurements and simulation results exhibit a frequency range of operation from 20 to 40?GHz with a bandwidth of 24% achieved for ?10?dB return loss at the central frequency. The measured radiation patterns show a maximum peak gain of around 13?dB with HPBW of 10° for the E-plane, and whose first side lobes are lower than 13?dB below the main lobe in both angular shift sides. The presented results will be considered as preliminary feasibility studies in the 30?GHz QUIJOTE-CMB Instrument, which is designed to study the anisotropies of the Cosmic Microwave Background (CMB).     

Mapping the Land Cover of Mexico Using AVHRR Time‐Series Data Sets

Abstract

An important methodological and analytical requirement for analyzing spatial relationships between regional habitats and species distributions in Mexico is the development of standard methods for mapping the country's land cover/land use formations. This necessarily involves the use of global data such as that produced by the Advanced Very High Resolution Radiometer (AVHRR). We created a nine‐band time‐series composite image from AVHRR Normalized Difference Vegetation Index (NDVI) bi‐weekly data. Each band represented the maximum NDVI for a particular month of either 1992 or 1993. We carried out a supervised classification approach, using the latest comprehensive land cover/vegetation map created by the Mexican National Institute of Geography (INEGI) as reference data. Training areas for 26 land cover/vegetation types were selected and digitized on the computer's screen by overlaying the INEGI vector coverage on the NDVI image. To obtain specific spectral responses for each vegetation type, as determined by its characteristic phenology and geographic location, the statistics of the spectral signatures were subjected to a cluster analysis. A total of 104 classes distributed among the 26 land cover types were used to perform the classification. Elevation data were used to direct classification output for pine‐oak and coastal vegetation types. The overall correspondence value of the classification proposed in this paper was 54%; however, for main vegetation formations correspondence values were higher (60‐80%). In order to obtain refinements in the proposed classification we recommend further analysis of the signature statistics and adding topographic data into the classification algorithm.     

Numerical artifacts associated with Rayleigh and modal damping models of inelastic structures with massless coordinates

The paper presents a detailed reexamination of the effects of three damping models on the inelastic seismic response of structures with massless degrees of freedom. The models considered correspond to (a) Rayleigh damping based on current properties (tangent stiffness), (b) Rayleigh damping based on initial properties, and (c) modal damping. The results suggest that some nonzero damping forces/moments at massless DOFs obtained in multistory frames for the case of Rayleigh damping with tangent stiffness may be numerical artifacts rather than a deficiency of the damping model. The results also indicate that significant artificial numerical oscillations in the velocities of the secondary components of MDOF structures are introduced when modal damping or mass-proportional damping is used.     

Phytoliths infer locally dense and heterogeneous paleovegetation at FLK North and surrounding localities during upper Bed I time, Olduvai Gorge, Tanzania

The phytolith content of 10 samples collected immediately under Tuff IF (~ 1.785 Ma) at FLK N and other surrounding localities (~ 2 km²) provides a direct botanical evidence for woody vegetation in the eastern margin of Olduvai Gorge during uppermost Bed I time. Observation and counting of 143 phytolith types (5 to >150 μ) reveal dense but heterogeneous woody cover (~ 40–90%) of unidentified trees and/or shrubs and palms associated to the freshwater springs surrounding FLK N, and more open formation (presumably ~ 25–70% woody cover) in the southeast at localities VEK, HWK W and HWK E. The paleovegetation is best described as groundwater palm forest/woodland or bushland, which current analogue may be found near Lake Manyara in similar hydrogeological context (freshwater springs near saline/alkaline lake). Re-evaluating the published pollen data based on this analogy shows that 70% of the pollen signal at FLK N may be attributed to thicket-woodland, Acacia groundwater woodland, gallery and groundwater forests; while < 30% is attributed to swamp herbage and grasslands. Micro-botanical, isotopic, and taphonomical studies of faunal remains converge on the same conclusion that the area surrounding FLK N, which attracted both carnivores and hominins in the early Pleistocene, was densely wooded during uppermost Bed I time.     

Sea-level rise impact models and environmental conservation: A review of models and their applications

Conservation managers and policy makers need tools to identify coastal habitats and human communities that are vulnerable to sea-level rise. Coastal impact models can help determine the vulnerability of areas and populations to changes in sea level. Model outputs may be used to guide decisions about the location and design of future protected areas and development, and to prioritize adaptation of existing protected area investments. This paper reviews state-of-the-art coastal impact models that determine sea-level rise vulnerability and provides guidance to help managers and policy makers determine the appropriateness of various models at local, regional, and global scales. There are a variety of models, each with strengths and weaknesses, that are suited for different management objectives. We find important trade-offs exist regarding the cost and capacity needed to run and interpret the models, the range of impacts they cover, and regarding the spatial scale that each operates which may overstate impacts at one end and underestimate impacts at the other. Understanding these differences is critical for managers and policy makers to make informed decisions about which model to use and how to interpret and apply the results.     

Mesozoic Evaniidae (Insecta: Hymenoptera) in Spanish Amber: Reanalysis of the Phylogeny of the Evanioidea

<正>One new genus and five new species of the family Evaniidae are described from the Early Cretaceous (Albian)Spanish amber of Penacerrada-Ⅰ(Province of Burgos),San Just and Arroyo de la Pascueta(both in the Province of Teruel):Cretevania alonsoi sp.nov.,C.montoyai sp.nov.,C.alcalai sp.nov.,C.rubusensis sp.nov.,and Iberoevania roblesi gen.and sp.nov.Taxonomic changes include Cretevania pristina(Zhang and Zhang,2000) comb.nov.,C.exquisita(Zhang,Rasmtsyn,Wang and Zhang,2007)comb.nov.,C.vesca(Zhang,Rasnitsyn,Wang and Zhang,2007)comb.nov.,and C.cyrtocerca(Deans,2004)comb.nov.,as a result of the reinterpretation of the genera Procretevania and Eovernevania.The new well preserved specimens of the genus Cretevania,together with the characters shown by the type specimens of the synonymized genera,give new information about their anatomical characters of taxonomical importance,and the genus Cretevania Rasnitsyn,1975 is re-diagnosed.The holotypes of the Russian species in amber have been revised.A cladistic analysis of fossil and extant groups of the superfamily Evanioidea is included.Cretevania had a wide palaeogeographic distribution,with the highest diversity known from Spain.The 13 known Cretevania species show a high interspecific variation mainly in wing characteristics,and a wide range of body and wing size.     

On the relation between radiation and scattering problems for foundations embedded in an elastic half-space

The relation between the solutions of the boundary-value problems for the dynamic response of embedded foundations to external forces and seismic excitation is examined. It is shown that the contact tractions obtained in the course of calculating the response to external forces can also be used to determine the response of the foundation to an arbitrary seismic excitation.     

A Hubble Space Telescope/NICMOS view of the prototypical giant Hii region NGC604 in M33

We present the first high-spatial-resolution near-infrared (NIR) imaging of NGC604, obtained with the NICMOS camera onboard the Hubble Space Telescope (HST). These NICMOS broad-band images reveal new NIR point sources, clusters, and diffuse structures. We find an excellent spatial correlation between the 8.4 GHz radio continuum and the 2.2 μm nebular emission. Moreover, massive young stellar object candidates appear aligned with these radio peaks, reinforcing the idea that those areas are star-forming regions. Three different scaled OB associations are recognized in the NICMOS images. The brightest NIR sources in our images have properties that suggest that they are red supergiant stars, of which one was previously known. This preliminary analysis of the NICMOS images shows the complexity of the stellar content of the NGC604 nebula.