Secured green communication scheme for interference alignment based networks

In this paper, a new security and green communication scheme is proposed to the Interference-Alignment (IA) based networks. To achieve a secured communication, full-duplex receivers are utilized to transmit artificial noise (AN). Both the signals and the ANs are used to harvest energy to realize green communication. For these reasons, the feasible conditions of this scheme are analyzed first. Secondly, the average transmission rate, the secrecy performance and the harvested energy are investigated. Thirdly, an optimization scheme of simultaneous wireless information and power transfer (SWIPT) is given to optimize the information transmission and the energy harvesting efficiency. Meanwhile, an improved IA iteration algorithm is designed to eliminate both the AN and the interference. Furthermore, relay cooperation is considered and its system performance is analyzed. The simulations show that the target average transmission rate is not affected by AN, while the secrecy performance can be greatly improved. The energy harvesting efficiency is also better than the traditional schemes. As expected, the average transmission rate further is improved with the relay cooperation

Non-growing-season soil respiration is controlled by freezing and thawing processes in the summer monsoon-dominated Tibetan alpine grassland

The Tibetan alpine grasslands, sharing many features with arctic tundra ecosystems, have a unique non-growing-season climate that is usually dry and without persistent snow cover. Pronounced winter warming recently observed in this ecosystem may significantly alter the non-growing-season carbon cycle processes such as soil respiration (R-s), but detailed measurements to assess the patterns, drivers of, and potential feedbacks on R-s have not been made yet. We conducted a 4 year study on R-s using a unique R-s measuring system, composed of an automated soil CO2 flux sampling system and a custom-made container, to facilitate measurements in this extreme environment. We found that in the nongrowing season, (1) cumulative R-s was 82-89g C m(-2), accounting for 11.8-13.2% of the annual total R-s; (2) surface soil freezing controlled the diurnal pattern of R-s and bulk soil freezing induced lower reference respiration rate (R-0) and temperature sensitivity (Q(10)) than those in the growing season (0.40-0.53 versus 0.84-1.32 mu mol CO2 m(-2)s(-1) for R-0 and 2.5-2.9 versus 2.9-5.6 for Q(10)); and (3) the intraannual variation in cumulative R-s was controlled by accumulated surface soil temperature. We found that in the summer monsoon-dominated Tibetan alpine grassland, surface soil freezing, bulk soil freezing, and accumulated surface soil temperature are the day-, season-, and year-scale drivers of the non-growing-season R-s, respectively. Our results suggest that warmer winters can trigger carbon loss from this ecosystem because of higher Q(10) of thawed than frozen soils

Non-growing-season soil respiration is controlled by freezing and thawing processes in the summer monsoon-dominated Tibetan alpine grassland

The Tibetan alpine grasslands, sharing many features with arctic tundra ecosystems, have a unique non-growing-season climate that is usually dry and without persistent snow cover. Pronounced winter warming recently observed in this ecosystem may significantly alter the non-growing-season carbon cycle processes such as soil respiration (R-s), but detailed measurements to assess the patterns, drivers of, and potential feedbacks on R-s have not been made yet. We conducted a 4 year study on R-s using a unique R-s measuring system, composed of an automated soil CO2 flux sampling system and a custom-made container, to facilitate measurements in this extreme environment. We found that in the nongrowing season, (1) cumulative R-s was 82-89g C m(-2), accounting for 11.8-13.2% of the annual total R-s; (2) surface soil freezing controlled the diurnal pattern of R-s and bulk soil freezing induced lower reference respiration rate (R-0) and temperature sensitivity (Q(10)) than those in the growing season (0.40-0.53 versus 0.84-1.32 mu mol CO2 m(-2)s(-1) for R-0 and 2.5-2.9 versus 2.9-5.6 for Q(10)); and (3) the intraannual variation in cumulative R-s was controlled by accumulated surface soil temperature. We found that in the summer monsoon-dominated Tibetan alpine grassland, surface soil freezing, bulk soil freezing, and accumulated surface soil temperature are the day-, season-, and year-scale drivers of the non-growing-season R-s, respectively. Our results suggest that warmer winters can trigger carbon loss from this ecosystem because of higher Q(10) of thawed than frozen soils.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000344797500005&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Environmental SciencesGeosciences, MultidisciplinaryMeteorology & Atmospheric SciencesSCI(E)[email protected]