Policy assessments for the carbon emission flows and sustainability of Bitcoin blockchain operation in China

The growing energy consumption and associated carbon emission of Bitcoin mining could potentially undermine global sustainable efforts. By investigating carbon emission flows of Bitcoin blockchain operation in China with a simulation-based Bitcoin blockchain carbon emission model, we find that without any policy interventions, the annual energy consumption of the Bitcoin blockchain in China is expected to peak in 2024 at 296.59 Twh and generate 130.50 million metric tons of carbon emission correspondingly. Internationally, this emission output would exceed the total annualized greenhouse gas emission output of the Czech Republic and Qatar. Domestically, it ranks in the top 10 among 182 cities and 42 industrial sectors in China. In this work, we show that moving away from the current punitive carbon tax policy to a site regulation policy which induces changes in the energy consumption structure of the mining activities is more effective in limiting carbon emission of Bitcoin blockchain operation

dráma 3 felvonásban - írta Don Pedro Calderon de la Barka - spanyol eredetiből forditotta Győry Vilmos, a Kisfaludy-társaság tagja - zenéjét irta Nikolits Sándor - rendező: Mándoki.

Debreczeni Szinház. Csütörtökön, 1874. márczius 19-kén adatik. Calderon drámája itt másodszor.Debreceni Egyetem Egyetemi és Nemzeti Könyvtá

A large-scale survey of X-ray filaments in the Galactic Centre

We present a catalogue of 17 filamentary X-ray features located within a 68\times34 arcmin^2 view centred on the Galactic Centre region from images taken by Chandra. These features are described by their morphological and spectral properties. Many of the X-ray features have non-thermal spectra that are well fitted by an absorbed power law. Of the 17 features, we find six that have not been previously detected, four of which are outside the immediate 20\times20 arcmin^2 area centred on the Galactic Centre. Seven of the 17 identified filaments have morphological and spectral properties expected for pulsar wind nebulae (PWNe) with X-ray luminosities of 5\times10^32 to 10^34 erg s^-1 in the 2.0-10.0 keV band and photon indices in the range of \Gamma = 1.1 to 1.9. In one feature, we suggest the strong neutral Fe K\alpha emission line to be a possible indicator for past activity of Sgr A*. For G359.942-0.03, a particular filament of interest, we propose the model of a ram pressure confined stellar wind bubble from a massive star to account for the morphology, spectral shape and 6.7 keV He-like Fe emission detected. We also present a piecewise spectral analysis on two features of interest, G0.13-0.11 and G359.89-0.08, to further examine their physical interpretations. This analysis favours the PWN scenario for these features.Comment: 12 pages, 10 figure

Preasymptotic Convergence of Randomized Kaczmarz Method

Kaczmarz method is one popular iterative method for solving inverse problems, especially in computed tomography. Recently, it was established that a randomized version of the method enjoys an exponential convergence for well-posed problems, and the convergence rate is determined by a variant of the condition number. In this work, we analyze the preasymptotic convergence behavior of the randomized Kaczmarz method, and show that the low-frequency error (with respect to the right singular vectors) decays faster during first iterations than the high-frequency error. Under the assumption that the inverse solution is smooth (e.g., sourcewise representation), the result explains the fast empirical convergence behavior, thereby shedding new insights into the excellent performance of the randomized Kaczmarz method in practice. Further, we propose a simple strategy to stabilize the asymptotic convergence of the iteration by means of variance reduction. We provide extensive numerical experiments to confirm the analysis and to elucidate the behavior of the algorithms.Comment: 20 page

Characterization of Polyphosphoesters by Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

FT-ICR mass spectrometry, together with collision-induced dissociation and electron capture dissociation, has been used to characterize the polyphosphoester poly[1,4-bis(hydroxyethyl)terephthalate-alt-ethyloxyphosphate] and its degradation products. Three degradation pathways were elucidated: hydrolysis of the phosphate–[1,4-bis(hydroxyethyl)terephthalate]bonds; hydrolysis of the phosphate–ethoxy bonds; and hydrolysis of the ethyl–terephthalate bonds. The dominant degradation reactions were those that involved the phosphate groups. This work constitutes the first application of mass spectrometry to the characterization of polyphosphoesters and demonstrates the suitability of high mass accuracy FT-ICR mass spectrometry, with CID and ECD, for the structural analysis of polyphosphoesters and their degradation products

Deep centers in a free-standing GaN layer

Schottky barrierdiodes, on both Ga and N faces of a ∼300-μm-thick free-standing GaN layer, grown by hydride vapor phase epitaxy(HVPE) on Al2O3 followed by laser separation, were studied by capacitance–voltage and deep level transient spectroscopy(DLTS) measurements. From a 1/C2 vs V analysis, the barrier heights of Ni/Au Schottky contacts were determined to be different for the two polar faces: 1.27 eV for the Ga face, and 0.75 eV for the N face. In addition to the four common DLTS traps observed previously in other epitaxial GaN including HVPE-grown GaN a new trap B′ with activation energyET=0.53 eV was found in the Ga-face sample. Also, trap E1 (ET=0.18 eV), believed to be related to the N vacancy, was found in the N-face sample, and trap C (ET=0.35 eV) was in the Ga-face sample. Trap C may have arisen from reactive-ion-etching damage

Normal state electronic structure in the heavily overdoped regime of Bi1.74Pb0.38Sr1.88CuO6+delta single-layer cuprate superconductors

We explore the electronic structure in the heavily overdoped regime of the single layer cuprate superconductor Bi1.74Pb0.38Sr1.88CuO6+delta. We found that the nodal quasiparticle behavior is dominated mostly by phonons, while the antinodal quasiparticle lineshape is dominated by spin fluctuations. Moreover, while long range spin fluctuations diminish at very high doping, the local magnetic fluctuations still dominate the quasiparticle dispersion, and the system exhibits a strange metal behavior in the entire overdoped regime.Comment: 5 pages, 4 figure