6,600 research outputs found
Global shifts: U. S. immigration and the cultural impact of demographic change
At the turn of the millennium, we are witnessing intense new worldwide migration and refugee flows. There are now some 100 million transnational immigrants plus an estimated 30 million refugees displaced from their homelands. These flows are largely structured by the intensification of globalization--a process of economic, social, and cultural transformation rapidly accelerating in the last decade. Globalization has increased immigration in a variety of ways. First, transnational capital flows (roughly a trillion dollars cross national boundaries every day) tend to stimulate migration because where capital flows, immigrants tend to follow. Second, the new information and communication technologies that are at the heart of globalization tend to stimulate migration because they encourage new standards of consumption and life-style choices. Would-be immigrants imagine better opportunities elsewhere and mobilize to achieve them. Third, the affordability of mass transportation--last year approximately 1.5 billion airline tickets were sold--has put the migration option within the reach of millions who heretofore could not consider it. Fourth, globalization has stimulated new migration because it has produced uneven results--big winners and losers.Demography ; Economic conditions ; Emigration and immigration
Multichannel receivers from ofdm and tdma in mobile communications
This paper addresses the use of multichannel receivers for blind equalization in TDMA under frequency selective channels and OFDM systems in frequency flat fading channels. A new criteria is proposed for blind equalization of finite length mobile channels.Peer ReviewedPostprint (published version
Diversity techniques for blind channel equalization in mobile communications
A blind algorithm for channel distortion compensation is presented which can be employed in spatial or temporal diversity receivers. The proposed technique can be used in frequency selective and frequency flat fading mobile channels, using burst transmission schemes in the first case and OFDM modulation in the second one. The algorithm is base on a deterministic criteria and is suited for estimation when short sets of data are available.Peer ReviewedPostprint (published version
Transform modulations for mobile communications
A new modulation scheme called transform modulations is proposed which improves the system performance in frequency-flat fading mobile channels. They ameliorate the effect of the fadings over the transmitted signal by spreading the information in time, using a linear transform operator. The design of this scheme is discussed and its advantages are shown by means of simulations. The relationship of this scheme with OFDM modulation is also analyzed.Peer ReviewedPostprint (published version
Sobre unos afloramientos de rocas verdes de sierra de Gádor (Cordilleras Béticas)
Se estudian tres pequeños afloramientos de rocas verdes existentes en la parte occidental de sierra de Gádor (provincia de Almería).Se han identificado los siguientes minerales: oligoclasa, clorita, pistacita, actinolita, sericita, cuarzo, calcita y óxidos de hierro.Estas determinaciones se han hecho con el microscopio de polarización y, debido al pequeño tamaño de algunos cristales, nos hemos visto obligados a realizar diagramas de difracción por rayos X para completar el conocimiento de los minerales
Sobre la zona de contacto entre Sierra Nevada y sierra de Gádor comprendida ente Laujar de Anarax y Canjayar (provincia de Almería)
Se hace el estudio de un área situada al S de Sierra Nevada en la que puede apreciarse el contacto entre el conjunto "Nevado Filábride" y los materiales del dominio " Alpujárride"pertenecientes a la sierra de Gádor.Del estudio de la petrología y la estratigrafía de las rocas presentes en este área, así como de la cartografía geológica de la misma, se deduce la existencia de tres unidades tectónicas superpuestas pertenecientes a los Alpujárrides
A Vascular Flora of the South Fork Tule River, Southern Sierra Nevada, Tulare County, California
I conducted a floristic study of the South Fork Tule River watershed, located in the southern Sierra Nevada in Tulare County, California. The primary objectives of this floristic study were to document and catalogue all vascular plant taxa that occur in the watershed, describe the plant communities, analyze the flora and its affinities with other areas, and establish a herbarium for the Tule River Indian Reservation. The upper reaches of the South Fork Tule River originate on the western slope of Slate Mountain in the Sequoia National Forest and drain west through the Tule River Indian Reservation into Lake Success. The highest elevation in the watershed is Slate Mountain Peak at 2790 m and the lowest is at Lake Success reservoir, at 162 m. Prior to my study there were only 176 plant collections from the watershed, representing 159 taxa. I spent a total of 64 days over three field seasons (2013–2015) in the study area and made 1356 collections, bringing the total number of minimum-rank taxa to 562, representing 271 genera and 80 plant families. Seven rare taxa were documented during the course of my study, including the federally endangered Clarkia springvillensis. I documented and described 12 plant communities, including giant sequoia (Sequoiadendron giganteum) forests. Several species find their southern extent in the watershed, including the paleoendemic Torreya californica, which occurs on the Tule River Indian Reservation. Floristic affinities analyses revealed that locally, the South Fork of the Tule River does not have many species in common with the North or Middle forks, but this could be a result of collector bias. Statewide, the South Fork has its greatest affinities with the Sierra Nevada Foothills and the Sierra Nevada High eco-geographic subdivisions of California and the least affinity with the desert regions. Poorly documented plant diversity on tribal trust lands speaks to the need for more collaboration with tribal communities, and this flora is a contribution to that effort
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