A Stochastic Geometry Approach to Energy Efficiency in Relay-Assisted Cellular Networks

Though cooperative relaying is believed to be a promising technology to improve the energy efficiency of cellular networks, the relays' static power consumption might worsen the energy efficiency therefore can not be neglected. In this paper, we focus on whether and how the energy efficiency of cellular networks can be improved via relays. Based on the spatial Poisson point process, an analytical model is proposed to evaluate the energy efficiency of relay-assisted cellular networks. With the aid of the technical tools of stochastic geometry, we derive the distributions of signal-to-interference-plus-noise ratios (SINRs) and mean achievable rates of both non-cooperative users and cooperative users. The energy efficiency measured by "bps/Hz/W" is expressed subsequently. These established expressions are amenable to numerical evaluation and corroborated by simulation results.Comment: 6 pages, 5 figures, accepted by IEEE Globecom'12. arXiv admin note: text overlap with arXiv:1108.1257 by other author

The 'Sophistication' Of Exports: A New Measure Of Product Characteristics

Trade data are often classified by product characteristics in the trade, technology and development literature to analyze trade patterns, competitive performance and structural change. However, existing classifications are constrained in that trade data are far more detailed than the industry data on which categories are based (e.g. current classifications only have 4-5 technology groups). We propose a new classification - 'sophistication' - as a means of analyzing product characteristics in great detail, based on the average income of exporting economies. Sophistication captures more than technical characteristics; it includes product differentiation, production fragmentation, resource availability and other factors. However, it has the advantage of providing unique continuous scores for each product at any level of detail. We calculate sophistication scores for 237 exports at the 3-digit SITC level and 766 exports at the 4-digit level for 1990 and 2000 (detailed values can be provided on request). We show sophistication scores for exports by selected countries, technology groups and industries. Our intention is to provide a database for further empirical analysis.

Mapping Fragmentation: Electronics and Automobiles in East Asia and Latin America

'Fragmentation', the relocation of processes or functions across countries in response to cost and other differences, has important implications for development. We discuss the drivers of fragmentation and map it for electronics and automotives in East Asia and Latin America. For technical reasons, electronics is fragmenting faster worldwide than autos. Electronics networks are more advanced, widespread and integrated in EA than LAC, and are largely responsible for EA's rapid export growth. The auto network is more advanced in LAC but is slower growing and is not integrated into a regional system. Apart from Mexico, LAC lacks an electronics network, partly accounting for the region's weak export performance. We offer insights into the following: Why do industries fragment differently? How can fragmentation be measured? Why does fragmentation in developing countries concentrate on EA and LAC? Why has fragmentation evolved differently in these two regions? Can other developing regions attract and benefit from fragmentation?

Transcriptomic and metabolomic approaches to investigate molecular responses of human cell lines exposed to flame retardants

With intensive and global usage, flame retardants (FRs) have played critical roles in the prevention of fires for decades. However, there are increasing concerns about the potential adverse effects of these chemicals due to the well documented environmental and human exposures to FRs. To date, relatively little is known about the molecular mechanisms of the potential toxic effects of human exposure to FRs. In this study, microarray-based transcriptomics and direct injection mass spectrometry based metabolomics were employed to investigate the molecular responses of human lung cancer cells (A549) and human hepatoma cells (HepG2/C3A) exposed to a range of sub-lethal concentrations of hexabromocyclododecane (HBCD), tris (1, 3-dichloro-2-propyl) phosphate (TDCIPP) and a mixture of FRs at equivalent concentrations to those found in typical household dust. Combined with the quantification of FRs levels in cells after exposure, this work using the non-targeted capabilities of multi-omics approaches has revealed that at the concentrations investigated, and which are relevant to human exposures, significant molecular perturbations are not induced by exposure to the FRs under study. The results from this thesis are beneficial for both understanding the potential mechanisms of effects of human exposure to FRs and for future risk assessment of these chemicals

Realizing the Hayden-Preskill Protocol with Coupled Dicke Models

Hayden and Preskill proposed a thought experiment that Bob can recover the information Alice throws into a black hole if he has a quantum computer entangled with the black hole, and Yoshida and Kitaev recently proposed a concrete decoding scheme. The parallel question is that after a small system is thermalized with a large system, how one can decode the initial state information with the help of two entangled many-body systems. Here we propose to realize this protocol in a physical system of two Dicke models, with two cavity fields prepared in a thermofield double state. We show that the Yoshida-Kitaev protocol allows us to read out the initial spin information after it is scrambled into the cavity. We show that the readout efficiency reaches a maximum when the model parameter is tuned to the regime where the system is the most chaotic, characterized by the shortest scrambling time in the out-of-time-ordered correlation function. Our proposal opens up the possibility of discussing this profound thought experiment in a realistic setting.Comment: 5 pages, 4 figure

The vertical influence of temperature and precipitation on snow cover variability in the Central Tianshan Mountains, Northwest China

Seasonal snow cover in mountainous regions will affect local climate and hydrology. In this study, we assessed the role of altitude in determining the relative importance of temperature and precipitation in snow cover variability in the Central Tianshan Mountains. The results show that: (1) in the study area, temperature has a greater influence on snow cover than precipitation during most of the time period studied and in most altitudes. (2) In the high‐elevation area, there is a threshold altitude of 3900±400 m, below which temperature is negatively while precipitation is positively correlated to snow cover, above which the situation is the opposite. Besides, this threshold altitude decreases from snow accumulated period to snow stable period and then increases from snowmelt period to snow‐free period. (3) Below 2000 m, there is another threshold altitude of 1400±100 m during the snow stable period, below (above) which precipitation (temperature) is the main driver of snow cover