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排序方式: 共有149条查询结果,搜索用时 15 毫秒
71.
Fluoride evaporation and crystallization behavior of CaF2–CaO–Al2O3–(TiO2) slag for electroslag remelting of Ti-containing steels 下载免费PDF全文
To elucidate the behavior of slag films in an electroslag remelting process, the fluoride evaporation and crystallization of CaF2–CaO–Al2O3–(TiO2) slags were studied using the single hot thermocouple technique. The crystallization mechanism of TiO2-bearing slag was identified based on kinetic analysis. The fluoride evaporation and incubation time of crystallization in TiO2-free slag are found to considerably decrease with decreasing isothermal temperature down to 1503 K. Fish-bone and flower-like CaO crystals precipitate in TiO2-free slag melt, which is accompanied by CaF2 evaporation from slag melt above 1503 K. Below 1503 K, only near-spherical CaF2 crystals form with an incubation time of less than 1 s, and the crystallization is completed within 1 s. The addition of 8.1wt% TiO2 largely prevents the fluoride evaporation from slag melt and promotes the slag crystallization. TiO2 addition leads to the precipitation of needle-like perovskite (CaTiO3) crystals instead of CaO crystals in the slag. The crystallization of perovskite (CaTiO3) occurs by bulk nucleation and diffusion-controlled one-dimensional growth. 相似文献
72.
In this paper,to study the power loss of converter for elevator,The analysis is to establish relationship between parameters(current,voltages and losses in the inverter and converter) relevant for sizing of major components of the drive was done.) For high PWM(pulse width modulation) frequency like in elevator applications of fpwm =10kHz,switching losses are dominant and are about 2/3 of the total losses on IGBT switch.Transition from continuous 3 phase to discontinuous 2 phase PWM results in 50% reduction of switching loses on IGBT devices providing that PWM is not done over 60deg angle in a particular phase when current has maximum value.Total losses on IGBT(conduction + switching) are reduced approximately by ~1/3 what is still a significant reduction.Two phase PWM with reduced losses can be used for applications when acoustic noise due to increased current ripple is not significant and fall back solution to regular 3 phase PWM when drive operates under rare extreme conditions resulting in increased heat sink temperature.The analysis will be examined by further laboratory testing simulating 60% duty cycle on a dynamometer. 相似文献
73.
Vinko SM Ciricosta O Cho BI Engelhorn K Chung HK Brown CR Burian T Chalupský J Falcone RW Graves C Hájková V Higginbotham A Juha L Krzywinski J Lee HJ Messerschmidt M Murphy CD Ping Y Scherz A Schlotter W Toleikis S Turner JJ Vysin L Wang T Wu B Zastrau U Zhu D Lee RW Heimann PA Nagler B Wark JS 《Nature》2012,482(7383):59-62
Matter with a high energy density (>10(5)?joules per cm(3)) is prevalent throughout the Universe, being present in all types of stars and towards the centre of the giant planets; it is also relevant for inertial confinement fusion. Its thermodynamic and transport properties are challenging to measure, requiring the creation of sufficiently long-lived samples at homogeneous temperatures and densities. With the advent of the Linac Coherent Light Source (LCLS) X-ray laser, high-intensity radiation (>10(17)?watts per cm(2), previously the domain of optical lasers) can be produced at X-ray wavelengths. The interaction of single atoms with such intense X-rays has recently been investigated. An understanding of the contrasting case of intense X-ray interaction with dense systems is important from a fundamental viewpoint and for applications. Here we report the experimental creation of a solid-density plasma at temperatures in excess of 10(6) kelvin on inertial-confinement timescales using an X-ray free-electron laser. We discuss the pertinent physics of the intense X-ray-matter interactions, and illustrate the importance of electron-ion collisions. Detailed simulations of the interaction process conducted with a radiative-collisional code show good qualitative agreement with the experimental results. We obtain insights into the evolution of the charge state distribution of the system, the electron density and temperature, and the timescales of collisional processes. Our results should inform future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological systems, material science investigations, and the study of matter in extreme conditions. 相似文献
74.
Exome sequencing identifies frequent mutation of the SWI/SNF complex gene PBRM1 in renal carcinoma 总被引:1,自引:0,他引:1
Varela I Tarpey P Raine K Huang D Ong CK Stephens P Davies H Jones D Lin ML Teague J Bignell G Butler A Cho J Dalgliesh GL Galappaththige D Greenman C Hardy C Jia M Latimer C Lau KW Marshall J McLaren S Menzies A Mudie L Stebbings L Largaespada DA Wessels LF Richard S Kahnoski RJ Anema J Tuveson DA Perez-Mancera PA Mustonen V Fischer A Adams DJ Rust A Chan-on W Subimerb C Dykema K Furge K Campbell PJ Teh BT Stratton MR Futreal PA 《Nature》2011,469(7331):539-542
75.
Stuber GD Sparta DR Stamatakis AM van Leeuwen WA Hardjoprajitno JE Cho S Tye KM Kempadoo KA Zhang F Deisseroth K Bonci A 《Nature》2011,475(7356):377-380
The basolateral amygdala (BLA) has a crucial role in emotional learning irrespective of valence. The BLA projection to the nucleus accumbens (NAc) is thought to modulate cue-triggered motivated behaviours, but our understanding of the interaction between these two brain regions has been limited by the inability to manipulate neural-circuit elements of this pathway selectively during behaviour. To circumvent this limitation, we used in vivo optogenetic stimulation or inhibition of glutamatergic fibres from the BLA to the NAc, coupled with intracranial pharmacology and ex vivo electrophysiology. Here we show that optical stimulation of the pathway from the BLA to the NAc in mice reinforces behavioural responding to earn additional optical stimulation of these synaptic inputs. Optical stimulation of these glutamatergic fibres required intra-NAc dopamine D1-type receptor signalling, but not D2-type receptor signalling. Brief optical inhibition of fibres from the BLA to the NAc reduced cue-evoked intake of sucrose, demonstrating an important role of this specific pathway in controlling naturally occurring reward-related behaviour. Moreover, although optical stimulation of glutamatergic fibres from the medial prefrontal cortex to the NAc also elicited reliable excitatory synaptic responses, optical self-stimulation behaviour was not observed by activation of this pathway. These data indicate that whereas the BLA is important for processing both positive and negative affect, the glutamatergic pathway from the BLA to the NAc, in conjunction with dopamine signalling in the NAc, promotes motivated behavioural responding. Thus, optogenetic manipulation of anatomically distinct synaptic inputs to the NAc reveals functionally distinct properties of these inputs in controlling reward-seeking behaviours. 相似文献
76.
Gibbs DJ Lee SC Isa NM Gramuglia S Fukao T Bassel GW Correia CS Corbineau F Theodoulou FL Bailey-Serres J Holdsworth MJ 《Nature》2011,479(7373):415-418
77.
Effect of TiO<Subscript>2</Subscript> on the viscosity and structure of low-fluoride slag used for electroslag remelting of Ti-containing steels 下载免费PDF全文
The viscosity of CaF2-CaO-Al2O3-MgO-(TiO2) slag was measured using a rotating crucible viscometer. Raman spectroscopy analysis was performed to correlate the viscosity to slag structure. The viscosity of the slag was found to decrease with increasing TiO2 content in the slag from 0 to 9.73wt%. The activation energy decreased from 95.16 kJ/mol to 79.40 kJ/mol with increasing TiO2 content in the slag. The introduction of TiO2 into the slag played a destructive role in Al-O-Al structural units and Q4 units by forming simpler structural units of Q2 and Ti2O64- chain. The amount of Al-O-Al significantly decreased with increasing TiO2 content. The relative fraction of Q4 units in the[AlO4]5--tetrahedral units shows a decreasing trend, whereas the relative fraction of Q2 units and Ti2O64- chain increases with increasing TiO2 content accordingly. Consequently, the polymerization degree of the slag decreases with increasing TiO2 content. The variation in slag structure is consistent with the change in measured viscosity. 相似文献
78.
Su X Chakravarti D Cho MS Liu L Gi YJ Lin YL Leung ML El-Naggar A Creighton CJ Suraokar MB Wistuba I Flores ER 《Nature》2010,467(7318):986-990
79.
80.
M McDonald M Bayliss BA Benson RJ Foley J Ruel P Sullivan S Veilleux KA Aird ML Ashby M Bautz G Bazin LE Bleem M Brodwin JE Carlstrom CL Chang HM Cho A Clocchiatti TM Crawford AT Crites T de Haan S Desai MA Dobbs JP Dudley E Egami WR Forman GP Garmire EM George MD Gladders AH Gonzalez NW Halverson NL Harrington FW High GP Holder WL Holzapfel S Hoover JD Hrubes C Jones M Joy R Keisler L Knox AT Lee EM Leitch J Liu M Lueker D Luong-Van A Mantz DP Marrone JJ McMahon J Mehl SS Meyer ED Miller 《Nature》2012,488(7411):349-352
In the cores of some clusters of galaxies the hot intracluster plasma is dense enough that it should cool radiatively in the cluster's lifetime, leading to continuous 'cooling flows' of gas sinking towards the cluster centre, yet no such cooling flow has been observed. The low observed star-formation rates and cool gas masses for these 'cool-core' clusters suggest that much of the cooling must be offset by feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical and infrared observations of the galaxy cluster SPT-CLJ2344-4243 (ref. 11) at redshift z = 0.596. These observations reveal an exceptionally luminous (8.2?×?10(45)?erg?s(-1)) galaxy cluster that hosts an extremely strong cooling flow (around 3,820 solar masses a year). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (formation of around 740 solar masses a year), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool-core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star-formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form through accretion of the intracluster medium, rather than (as is currently thought) assembling entirely via mergers. 相似文献