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Selected AbstractsAn optimum design of deep-space downlinks affected by tropospheric attenuation,INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2009Emilio Matricciani Abstract In the paper, we propose an optimum design of deep-space downlinks made with 2 hops, at Ka band and above, in which each hop should be designed for providing half of the total noise-to-signal power ratio. We have derived this result from maximizing the ratio between the tropospheric attenuation in the 2-hop downlink and that in the 1-hop downlink. The design of the 1st hop (free-space) of the 2-hop downlink can reduce the spacecraft power, for the same antennas physical size, by increasing the carrier frequency from Ka band (32,GHz) to W band (80,GHz). This choice is not available in 1-hop downlink design because of the huge Earth tropospheric attenuation expected in the W frequency band. To show a practical design, we have applied the theory to compare 1-hop downlink design at 32,GHz to 2-hop downlink design that adopts 32 or 80,GHz in the 1st hop. The calculations refer to spacecrafts located at two astronomical units (300×106,km, about planet Mars) and to NASA and ESA receiving stations located in Goldstone (California), Cebreros (Madrid, Spain), Canberra and New Norcia (Australia). At 0.1% outage probability, in an average year or in the worst month, 1-hop downlinks show performance critical or close to fail, because of the large tropospheric attenuation (except at Goldstone), while 2-hop downlinks always work. Copyright © 2009 John Wiley & Sons, Ltd. [source] Urban and industrial water use in the Krishna Basin, India,IRRIGATION AND DRAINAGE, Issue 4 2009Daniel J. Van Rooijen Bassin Krishna; utilisation urbaine de l'eau; utilisation industrielle de l'eau; modélisation Abstract Regional urbanization and industrial development require water that may put additional pressure on available water resources and threaten water quality in developing countries. In this study we use a combination of census statistics, case studies, and a simple model of demand growth to assess current and future urban and industrial water demand in the Krishna Basin in southern India. Water use in this "closed" basin is dominated by irrigation (61.9 billion cubic metres (BCM) yr,1) compared to a modest domestic and industrial water use (1.6 and 3.2 BCM yr,1). Total water diversion for non-irrigation purposes is estimated at 7,8% of available surface water in the basin in an average year. Thermal power plants use the majority of water used by industries (86% or 2.7 BCM yr,1), though only 6.8% of this is consumed via evaporation. Simple modelling of urban and industrial growth suggests that non-agricultural water demand will range from 10 to 20 BCM by 2030. This is 14,28% of basin water available surface water for an average year and 17,34% for a year with 75% dependable flow. Although water use in the Krishna Basin will continue to be dominated by agriculture, water stress, and the fraction of water supplies at risk of becoming polluted by urban and industrial activity, will become more severe in urbanized regions in dry years. Copyright © 2008 John Wiley & Sons, Ltd. L'urbanisation régionale et le développement industriel demandent de l'eau, ce qui peut augmenter la pression sur les ressources en eau disponibles dans les pays en développement. Dans cette étude nous utilisons une combinaison de données de recensement, des études de cas et un modèle simple de croissance de la demande pour évaluer la demande en eau urbaine et industrielle actuelle et future dans le bassin Krishna en Inde du sud. Les usages de l'eau dans ce bassin « fermé » sont dominés par l'irrigation (61.9 milliards de m3/an) alors que les usages domestiques et industriels sont modestes (1.6 et 3.2 milliards de m3/an). L'eau utilisée en dehors de l'irrigation est estimée à 7 ,8% de l'eau de surface disponible dans le bassin en année moyenne. Les centrales thermiques utilisent la plus grosse partie de l'eau allouée aux industries (86% ou 2.7 milliards de m3/an) bien que seulement 6.8% de cette quantité soit consommé par évaporation. Une modélisation simple de la croissance urbaine et industrielle suggère que la demande non-agricole d'eau variera de 10 à 20 milliards de m3/an d'ici à 2030. C'est 14,28% de l'eau de surface disponible du bassin en année moyenne et 17,34% de l'écoulement garanti à 75%. Bien que l'utilisation de l'eau dans le bassin Krishna continue à être dominée par l'agriculture, la tension sur l'eau peut devenir plus sévère en année sèche dans les régions urbanisées avec en outre le risque d'une pollution par l'activité urbaine et industrielle. Copyright © 2008 John Wiley & Sons, Ltd. [source] Determinants of Household Income Mobility in Rural ChinaCHINA AND WORLD ECONOMY, Issue 2 2010Xuehua Shi D31; O15 Abstract This article uses multivariate regression and decomposition analyses to assess household income mobility determinants and their contributions to income mobility in rural China from 1989 to 2006. The findings indicate that households with lower initial income level, higher share of wage income, higher educational level of household members, larger number of non-agricultural employed household members and younger heads are more mobile. Moreover, besides initial income, change in the share of wage income, change in the share of non-agricultural employed household members, and change in average year of education of household members are the most important factors that account for income mobility. These findings necessitate more emphasis on policies that promote non-agricultural employment and education to enhance household income mobility in rural China. [source] Inter-annual variation in primary production of a semi-arid grassland related to previous-year productionJOURNAL OF VEGETATION SCIENCE, Issue 1 2001Martín Oesterheld Mean annual precipitation accounts for a large proportion of the variation in mean above-ground net primary production (ANPP) of grasslands worldwide. However, the inter-annual variation in production in any grassland site is only loosely correlated with precipitation. The longest record of variation in production and precipitation for a site corresponds to a shortgrass steppe in Colorado, USA. A previous study of this record showed that current-year precipitation accounted for 39% of the inter-annual variation in ANPP. In this note, we show that ca. one third of the unexplained variation is related to previous-year ANPP: ANPP per mm of precipitation was higher in years preceded by wet, more productive years than in years preceded by average years; similarly, ANPP per mm of precipitation was lower in years preceded by dry, less productive years than in years preceded by average years. Since previous-year ANPP was, in turn, associated with precipitation of a year before, current-year ANPP was also explained by precipitation of two previous years. Our finding not only increases our predictive ability, but it also changes our understanding of how ANPP responds to fluctuations in precipitation. If ANPP is thought to vary according to current-year precipitation only, it will simply track annual precipitation in time. According to this new result, however, ANPP fluctuations are buffered if wet, more productive years alternate with dry, less productive years, and they are amplified if wet or dry sequences of several years take place. [source] | ||||||||||