9,826 research outputs found
Is Hot IT a False Economy? An Analysis of Server and Data Center Energy Efficiency as Temperatures Rise
As demand for digital services grows, there is need to improve efficiency and reduce the environmental impact of data centers. The largest energy consumer in any data center is the IT, followed by the systems dedicated to cooling. Aiming to improve efficiency, and driven by metrics like PUE, there is a trend towards running data centers hotter to reduce the cooling energy. There is little research investigating the effect this will have on the IT beyond failure rates. To ensure overall efficiency is improving, we must view the data center as a system of systems, taking a holistic view rather than focusing on individual sub-systems. In this paper we use industry standard benchmarks and a wind-tunnel to profile typical enterprise IT. We analyze the effect of environmental conditions on IT efficiency, showing minor increases in temperature or pressure impact the efficiency of servers. Using an idealized, simulated data center case study we show that the interaction between cooling systems, server behaviour and local climate are non-trivial and increasing temperatures has potential to worsen efficiency
Long lasting instabilities in granular mixtures
We have performed experiments of axial segregation in the Oyama's drum. We
have tested binary granular mixtures during very long times. The segregation
patterns have been captured by a CCD camera and spatio-temporal graphs are
created. We report the occurence of instabilities which can last several hours.
We stress that those instabilities originate from the competition between axial
and radial segregations. We put into evidence the occurence of giant
fluctuations in the fraction of grain species along the surface during the
unstable periods.Comment: 10 pages, 10 figures, (2002
Desenho preliminar de uma coleção nuclear de mandioca dentro do banco ativo de germoplasma da Embrapa Amazônia Ocidental.
A mandioca (Manihot esculenta Crantz) destaca-se como um dos cultivos mais importantes na Amazônia, tanto para a segurança alimentar regional como no comércio. A Embrapa Amazônia Ocidental organizou um Banco Ativo de Germoplasma (BAG) para fins de melhoramento e conservação in vivo da variabilidade genética da mandioca, por meio da coleta de germoplasma em diferentes localidades no Estado do Amazonas, visando reunir a diversidade encontrada na região amazônica. O objetivo deste trabalho foi desenhar uma coleção nuclear de mandioca com base em dados geográficos, morfo-agronômicos e genético-moleculares. Decidiu-se que a Coleção Nuclear deveria conter 50 amostras, representando 15% do BAG e serão representadas por acessos coletados nas calhas dos principais rios Negro, Solimões, Purus, Amazonas e Madeira. As localidades super-representadas no BAG serão alocadas à CN logaritmicamente, enquanto que as localidades sub-representadas serão alocadas proporcionalmente. As amostras selecionadas para a Coleção devem possuir boa produtividade (>13,3 t/há), raízes com polpa de coloração amarelada, teores de HCN acima de 100 mg/kg e divergência genético-moleculares satisfatórias
The first Frontier Fields cluster: 4.5{\mu}m excess in a z~8 galaxy candidate in Abell 2744
We present in this letter the first analysis of a z~8 galaxy candidate found
in the Hubble and Spitzer imaging data of Abell 2744, as part of the Hubble
Frontier Fields legacy program. We applied the most commonly-used methods to
select exceptionally high-z galaxies by combining non-detection and
color-criteria using seven HST bands. We used GALFIT on IRAC images for fitting
and subtracting contamination of bright nearby sources. The physical properties
have been inferred from SED-fitting using templates with and without nebular
emission. This letter is focussed on the brightest candidate we found
(m=26.2) over the 4.9 arcmin field of view covered by the WFC3.
It shows a non-detection in the ACS bands and at 3.6{\mu}m whereas it is
clearly detected at 4.5{\mu}m with rather similar depths. This break in the
IRAC data could be explained by strong [OIII]+H{\beta} lines at z~8 which
contribute to the 4.5{\mu}m photometry. The best photo-z is found at
z~8.0, although solutions at low-redshift (z~1.9) cannot be
completely excluded, but they are strongly disfavoured by the SED-fitting work.
The amplification factor is relatively small at {\mu}=1.490.02. The Star
Formation Rate in this object is ranging from 8 to 60 Mo/yr, the stellar mass
is in the order of M=(2.5-10) x 10Mo and the size is
r~0.350.15 kpc. This object is one of the first z~8 LBG candidates showing
a clear break between 3.6{\mu}m and 4.5{\mu}m which is consistent with the IRAC
properties of the first spectroscopically confirmed galaxy at a similar
redshift. Due to its brightness, the redshift of this object could potentially
be confirmed by near infrared spectroscopy with current 8-10m telescopes. The
nature of this candidate will be revealed in the coming months with the arrival
of new ACS and Spitzer data, increasing the depth at optical and near-IR
wavelengths.Comment: 4 pages, 2 figures, Accepted for publication in Astronomy and
Astrophysics Letter
Nano-Scale Hydroxyapatite: Synthesis, Two-Dimensional Transport Experiments, and Application for Uranium Remediation
Synthetic nano-scale hydroxyapatite (NHA) was prepared and characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The XRD data confirmed that the crystalline structure and chemical composition of NHA correspond to Ca5OH(PO4)3. The SEM data confirmed the size of NHA to be less than 50 nm. A two-dimensional physical model packed with saturated porous media was used to study the transport characteristics of NHA under constant flow conditions. The data show that the transport patterns of NHA were almost identical to tracer transport patterns. This result indicates that the NHA material can move with water like a tracer, and its movement was neither retarded nor influenced by any physicochemical interactions and/or density effects. We have also tested the reactivity of NHA with 1 mg/L hexavalent uranium (U(VI)) and found that complete removal of U(VI) is possible using 0.5 g/L NHA at pH 5 to 6. Our results demonstrate that NHA has the potential to be injected as a dilute slurry for in situ treatment of U(VI)-contaminated groundwater systems
Nano-Scale Hydroxyapatite: Synthesis, Two-Dimensional Transport Experiments, and Application for Uranium Remediation
Synthetic nano-scale hydroxyapatite (NHA) was prepared and characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The XRD data confirmed that the crystalline structure and chemical composition of NHA correspond to Ca5OH(PO4)3. The SEM data confirmed the size of NHA to be less than 50 nm. A two-dimensional physical model packed with saturated porous media was used to study the transport characteristics of NHA under constant flow conditions. The data show that the transport patterns of NHA were almost identical to tracer transport patterns. This result indicates that the NHA material can move with water like a tracer, and its movement was neither retarded nor influenced by any physicochemical interactions and/or density effects. We have also tested the reactivity of NHA with 1 mg/L hexavalent uranium (U(VI)) and found that complete removal of U(VI) is possible using 0.5 g/L NHA at pH 5 to 6. Our results demonstrate that NHA has the potential to be injected as a dilute slurry for in situ treatment of U(VI)-contaminated groundwater systems
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