Electronic structures and electronic spectra of all-boron fullerene B\u3csub\u3e40\u3c/sub\u3e

This study is motivated by the recent discovery of the first all-boron fullerene analogue, a B40 cluster with D2d point-group symmetry, dubbed borospherene (Nat. Chem., 2014, 6, 727). Insight into the electronic structures and spectral properties of B40 is timely and important to understand the borospherene and the transition from open-ended plate or ribbon-like structures to a hollow-cage structure at B40. Optimized geometries of borospherene B40 for both the ground state and the first excited state allow us to compute spectral properties including UV-vis absorption, infrared (IR) and Raman spectra. Highly resolved absorption and emission spectra are obtained, for the first time, for the fullerene at the time-dependent density-functional theory (TD-DFT) level within the Franck–Condon approximation and including the Herzberg–Teller effect. Assigned vibrational modes in absorption and emission spectra are readily compared with future spectroscopy measurements to distinguish the hollow-cage structure of D2d-B40 from other quasi planar boron structures

Electronic structures and electronic spectra of all-boron fullerene B\u3csub\u3e40\u3c/sub\u3e

This study is motivated by the recent discovery of the first all-boron fullerene analogue, a B40 cluster with D2d point-group symmetry, dubbed borospherene (Nat. Chem., 2014, 6, 727). Insight into the electronic structures and spectral properties of B40 is timely and important to understand the borospherene and the transition from open-ended plate or ribbon-like structures to a hollow-cage structure at B40. Optimized geometries of borospherene B40 for both the ground state and the first excited state allow us to compute spectral properties including UV-vis absorption, infrared (IR) and Raman spectra. Highly resolved absorption and emission spectra are obtained, for the first time, for the fullerene at the time-dependent density-functional theory (TD-DFT) level within the Franck–Condon approximation and including the Herzberg–Teller effect. Assigned vibrational modes in absorption and emission spectra are readily compared with future spectroscopy measurements to distinguish the hollow-cage structure of D2d-B40 from other quasi planar boron structures

Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations

Solar emission produces copious nitrosonium ions (NO+) in the D layer of the ionosphere, 60 to 90 km above the Earth’s surface. NO+ is believed to transfer its charge to water clusters in that region, leading to the formation of gaseous nitrous acid (HONO) and protonated water cluster. The dynamics of this reaction at the ionospheric temperature (200–220 K) and the associated mechanistic details are largely unknown. Using ab initio molecular dynamics (AIMD) simulations and transition-state search, key structures of the water hydrates—tetrahydrate NO+(H2O)4 and pentahydrate NO+(H2O)5—are identified and shown to be responsible for HONO formation in the ionosphere. The critical tetrahydrate NO+(H2O)4 exhibits a chainlike structure through which all of the lowest-energy isomersmust go. However, most lowest-energy isomers of pentahydrate NO+(H2O)5 can be converted to the HONO-containing product, encountering very low barriers, via a chain-like or a three-armed, star-like structure. Although these structures are not the global minima, at 220 K, most lowest-energy NO+(H2O)4 and NO+(H2O)5 isomers tend to channel through these highly populated isomers toward HONO formation

Resolving the HONO formation mechanism in the ionosphere via ab initio molecular dynamic simulations

Solar emission produces copious nitrosonium ions (NO+) in the D layer of the ionosphere, 60 to 90 km above the Earth’s surface. NO+ is believed to transfer its charge to water clusters in that region, leading to the formation of gaseous nitrous acid (HONO) and protonated water cluster. The dynamics of this reaction at the ionospheric temperature (200–220 K) and the associated mechanistic details are largely unknown. Using ab initio molecular dynamics (AIMD) simulations and transition-state search, key structures of the water hydrates—tetrahydrate NO+(H2O)4 and pentahydrate NO+(H2O)5—are identified and shown to be responsible for HONO formation in the ionosphere. The critical tetrahydrate NO+(H2O)4 exhibits a chainlike structure through which all of the lowest-energy isomersmust go. However, most lowest-energy isomers of pentahydrate NO+(H2O)5 can be converted to the HONO-containing product, encountering very low barriers, via a chain-like or a three-armed, star-like structure. Although these structures are not the global minima, at 220 K, most lowest-energy NO+(H2O)4 and NO+(H2O)5 isomers tend to channel through these highly populated isomers toward HONO formation

Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal

A fault location strategy based on information fusion and CODAS algorithm under epistemic uncertainty

Application of new technology in modern systems not only substantially improves the performance, but also presents a severe challenge to fault location of these systems. This paper presents a new fault location strategy for maintenance personnel to recover them based on information fusion and improved CODAS algorithm. Firstly, a fault tree is adopted to develop the failure model of a complex system, and failure probability of components is determined by expert evaluations to handle the uncertainty problem. Moreover, a fault tree is converted into an evidence network to obtain importance degrees, which are used to construct a diagnostic decision table together with the risk priority number. Additionally, these results are updated to optimize the maintenance process using sensor information. A novel dynamic location strategy is designed based on interval CODAS algorithm and optimal fault location strategy can be obtained. Finally, a real system is analyzed to demonstrate the feasibility of the proposed maintenance strategy

Time Synchronization for Random Mobile Sensor Networks

Mobile sensor nodes have a wide spectrum of applications, such as social networks and habitat monitoring. Time synchronization is a critical issue for most applications using mobile sensor networks. However, due to the limited communication range, mobile sensor nodes can only exchange their information when they are sufficiently close for contact. Moreover, random movements of the nodes render the performance analysis of any time synchronization protocols challenging. In this paper, we introduce the relation graph for modeling the random contact of mobile sensor nodes and evaluate the probability that the network can be synchronized within an arbitrary time. We adapt the previous maximum time synchronization (MTS) protocol, which can drive the clocks of all sensor nodes to a common value by utilizing their own neighboring information. We provide an analytical lower bound of the probability that the time synchronization can be finished within any given time. The obtained theories and algorithms are applied for several fundamental problems, and it is proven that a better connectivity is beneficial for convergence. For linearizable graph, we provide an efficient way to calculate the exact probabilities. Extensive numerical examples demonstrate the effectiveness of our results

Effect of synthesis methods on photoluminescent properties for CsPbBr₃ nanocrystals:Hot injection method and conversion method

Multiple facile synthetic strategies for all inorganic perovskite CsPbBr3 nanocrystals (NCs) have been established and developed, profiting from their excellent performance and great potential applied in the field of photonic and optoelectronic. Here, CsPbBr3 NCs were synthesized by both hot injection method (method 1) and conversion method (method 2), and the discrepancy of their photophysical properties is elucidated via the complementary studies between time-resolved photoluminescence (TRPL) and transient-absorption (TA) spectroscopy. We found that CsPbBr3 NCs prepared by conversion method exhibited lower PL quantum yield (QY), which was ascribed to the larger partition of the NCs being passivated from the quenchers from the deep trap states. On the other hand, we also observed different radiative recombination rates between two samples which should be due to various trapping/detrapping times prior to the radiative recombination of the charge carriers in two samples. These results provide better guidance for the development and improvement of synthesis methodology for perovskite NCs