Review of Waste Heat Utilisation from Data Centres

Rapidly increasing global internet traffic, mobile internet users and the number of Internet of Things (IoT) connections are driving exponential growth in demand for data centre and network services, which in turn is driving their electricity demand. Data centres now account for 3% of global electricity consumption and contribute to 4% of the global greenhouse gas emissions. This study discusses the potential of reusing the waste heat from data centres. An overview of imbedding heat recovery systems into data centres is presented. The implications of economic cost and energy efficient heat recovery systems in data centre buildings are also discussed. The main problems with implementing heat recovery systems in existing data centre designs are (i) high capital costs of investment and (ii) low temperatures of the waste heat. This study suggests alternatives that could allow data centre operators to utilise waste heat with more efficiencies. It also discusses how liquid-cooled data centres can be more efficient in utilising their waste heat than the air-cooled ones. One possible solution suggested here is that data centre operators can decrease their environmental impact by exporting waste heat to the external heat networks. The barriers in connecting datacentres to heat networks are discussed and suggestions to overcome those barriers have been provided

Long-term species richness-abundance dynamics in relation to species departures and arrivals in wintering urban bird assemblages

Temporal dynamics of local assemblages depend on the species richness and the total abundance of individuals as well as local departure and arrival rates of species. We used urban bird survey data collected from the same 31 study plots and methods during three winters (1991–1992; 1999–2000 and 2009–2010) to analyze the temporal relationship between bird species richness and total number of individuals (abundance). We also evaluated local departures and arrivals of species in each assemblage. In total, 13,812 individuals of 35 species were detected. The temporal variation in bird species richness followed the variation in the total number of individuals. The numbers of local departure and arrival events were similar. Also, the mean number of individuals of the recently arrived species (8.6) was almost the same as the mean number of individuals of the departed species (8.2). Risk of species departure was inversely related to number of individuals. Local species richness increased by one species when the total abundance of individuals increased by around 125 individuals and vice versa. Our results highlight the important role of local population departures and arrivals in determining the local species richness-abundance dynamics in human-dominated landscapes. Local species richness patterns depend on the total number of individuals as well as both the departure-arrival dynamics of individual species as well as the dynamics of all the species together. Our results support the more individuals hypothesis, which suggests that individual-rich assemblages have more species

Origin of non-linear piezoelectricity in III-V semiconductors: Internal strain and bond ionicity from hybrid-functional density functional theory

We derive first- and second-order piezoelectric coefficients for the zinc-blende III-V semiconductors, {Al,Ga,In}-{N,P,As,Sb}. The results are obtained within the Heyd-Scuseria-Ernzerhof hybrid-functional approach in the framework of density functional theory and the Berry-phase theory of electric polarization. To achieve a meaningful interpretation of the results, we build an intuitive phenomenological model based on the description of internal strain and the dynamics of the electronic charge centers. We discuss in detail first- and second-order internal strain effects, together with strain-induced changes in ionicity. This analysis reveals that the relatively large importance in the III-Vs of non-linear piezoelectric effects compared to the linear ones arises because of a delicate balance between the ionic polarization contribution due to internal strain relaxation effects, and the contribution due to the electronic charge redistribution induced by macroscopic and internal strain

Strengthening China's technological capability

China is increasing its outlay on research and development and seeking to build an innovation system that will deliver quick results not just in absorbing technology but also in pushing the technological envelope. China's spending on R&D rose from 1.1 percent of GDP in 2000 to 1.3 percent of GDP in 2005. On a purchasing power parity basis, China's research outlay was among the world's highest, far greater than that of Brazil, India, or Mexico. Chinese firms are active in the fields of biotechnology, pharmaceuticals, alternative energy sources, and nanotechnology. This surge in spending has been parallel by a sharp increase in patent applications in China, with the bulk of the patents registered in the areas of electronics, information technology, and telecoms. However, of the almost 50,000 patents granted in China, nearly two-thirds were to nonresidents. This paper considers two questions that are especially important for China. First, how might China go about accelerating technology development? Second, what measures could most cost-effectively deliver the desired outcomes? It concludes that although the level of financing for R&D is certainly important, technological advance is closely keyed to absorptive capacity which is a function of the volume and quality of talent and the depth as well as the heterogeneity of research experience. It is also a function of how companies maximize the commercial benefits of research and development, and the coordination of research with production and marketing.Technology Industry,Tertiary Education,E-Business,ICT Policy and Strategies,Agricultural Knowledge&Information Systems

Strains Induced by Point Defects in Graphene on a Metal

Strains strongly affect the properties of low-dimensional materials, such as graphene. By combining in situ, in operando, reflection high energy electron diffraction experiments with first-principles calculations, we show that large strains, above 2%, are present in graphene during its growth by chemical vapor deposition on Ir(111) and when it is subjected to oxygen etching and ion bombardment. Our results unravel the microscopic relationship between point defects and strains in epitaxial graphene and suggest new avenues for graphene nanostructuring and engineering its properties through introduction of defects and intercalation of atoms and molecules between graphene and its metal substrate

Health Care Doesn't Have to Cost an Arm and a Leg: 29 Reasons for Optimism from Comparisons between Countries and U.S. States

Residents of 29 countries live longer lives, on average, than Americans -- while spending up to eight times less on their health. A new report by American Human Development Project ranks the 50 states and Washington, D.C. against 80 countries in the world on life expectancy at birth, infant death rates, and annual per person spending on health care. The results powerfully demonstrate how better care and reining in costs are not incompatible

Regional decomposition of CO2 emissions in the world: a cluster analysis

The purpose of this paper is to study the possible differences among countries as CO2 emitters and to examine the underlying causes of these differences. The starting point of the analysis is the Kaya identity, which allows us to break down per capita emissions in four components: an index of carbon intensity, transformation efficiency, energy intensity and social wealth. Through a cluster analysis we have identified five groups of countries with different behavior according to these four factors. One significant finding is that these groups are stable for the period analyzed. This suggests that a study based on these components can characterize quite accurately the polluting behavior of individual countries, that is to say, the classification found in the analysis could be used in other studies which look to study the behavior of countries in terms of CO2 emissions in homogeneous groups. In this sense, it supposes an advance over the traditional regional or rich-poor countries classifications .Cluster analysis, CO2 emissions, geographical emissions, greenhouse effect