THE BEHAVIOUR OF Mn ATOMS IMPLANTED INTO Na^+- BETA- ALUMINA SINGLE CRYSTAL

Upon heating, Mn atoms implanted into Na - beta- alumina diffuse inwards andoutwards with an activation energy of 0.96 eV, and substitute for Al3+ in the spinel layers of the crystal. For specimens annealed at 900 C, the optical absorption shows remarkable change in 190nm-400nm wavelength region. They fluoresce brightly green and a well- defined peak (at 525 nm) has been found in the radiative spectra.

Anisotropic localization behavior of graphene in the presence of diagonal and off-diagonal disorders

Anisotropic localization of Dirac fermions in graphene along both the x and y axes was studied using the transfer-matrix method. The two-parameter scaled behavior around the Dirac points was observed along the x axis with off-diagonal disorder. In contrast, the electronic state along the y axis with armchair edges was delocalized, which can be described well by single parameter scaling theory. This implies that the breakdown of the single-parameter scaling is related to the zigzag edge along the x axis. Furthermore, dimerization induced by the substrate suppresses the two-parameter scaling behavior along the x axis and preserves the delocalized state along the y axis. Our results also demonstrate anisotropic localization in graphene with diagonal disorder that can be tuned by dimerization.

GRB 130310A: very high peak energy and thermal emission

The special GRB 130310 A was observed by Fermi Gamma-Ray Burst Monitor and Large Area Telescope,with T90~2.4 s.With a combination of a Band function and a blackbody(BB)function,the time-resolved spectral analysis of GRB 130310 A confirmed that there is a sub-dominate thermal component in the early period(e.g.,slice T0+[4.03-4.14]s)spectrum with BB temperature(kT)being~7~5 keV,which can be interpreted as photosphere emission.The precursor of GRB 130310 A can be fitted well with a BB component with kT~45 keV,which is higher than that of the main burst.It suggests that the radiation of GRB 130310 A is in transition from thermal to non-thermal.Such a transition is an indication of the change in jet composition from a fireball to a Poynting-flux-dominated jet.A very high peak energy is obtained in the first time bin,with the peak energy E_(p) of the Band component for Band+BB and Band model being~8.5~5.2 MeV and~11.1~7.4 MeV,respectively.Afterwards,the E_(p) drops to~1 MeV.The E_(p) evolution patterns with respect to the pulses in the GRB 130310 A light curves show a hard-to-soft evolution.The interpretation of the high peak energy E_(p) within the photosphere and internal shock model is difficult.It also suggests that at least for some bursts,the Band component must invoke a non-thermal origin in the optically thin region of a GRB outflow.Assuming the redshift is z~0.1~8,the radius of the jet base r_(0)~10^(9) cm to allow(1+σ_(15))>1 in line with the calculation results of the magnetization parameter at~1015 cm(σ_(15)).However,the value of(1+σ_(15))is■1 in the zone z around 3 for r_(0)~10^(9) cm,suggesting the non-excluded possibility that the origin is from ICMART with a low value.The photosphere-internal shock seems capable of interpreting the high peak energy,which requires electron Lorentz factorγe~60 andεe~0.06.

Effects of Pb-Doping on Phase Structural and Optical Properties of CdZnS Nano-Powders

Cadmium zinc lead sulfide [Cd0.8（Zn1-x7,Pbx）0.2S] nano-powders were prepared by an improved coprecipitation method. The effect of Pb2＋ concentration at 500℃ on the phase and crystalline structure of the Cd0.8（Zn1-x7,Pbx）0.2S powders were investigated by X-ray diffraction （XRD）. According to the transmission electron microscopy （TEM） images, the particles size are in the range of 58 nm to 72 nm. In addition, optical band gap energy and optical constants of nano-powders were determined using the ultraviolet （UV） spectrum, Fournier transform infrared spectroscopy （FTIR）, and Kramers-Kronig analysis, respectively. We calculate the refractive index n, extinction coefficient k, and dielectric function t as a function of the wavenumber. The experiment results demonstrate that the amount of Pb＋2 has been playing an increasingly important role on optical properties of CZPS nanocrystals.

Ideal Strengths and Bonding Properties of PuO_(2)under Tension

We perform a first-principles computational tensile test on PuO_(2)based on density-functional theory within a local density approximation(LDA)+U formalism to investigate its structural,mechanical,magnetic and intrinsic bonding properties in four representative directions:[001],[100],[110]and[111].The stress-strain relations show that the ideal tensile strengths in the four directions are 81.2,80.5,28.3 and 16.8 GPa at strains of 0.36,0.36,0.22 and 0.18,respectively.The[001]and[100]directions are prominently stronger than the other two directions since more Pu-0 bonds participate in the pulling process.By charge and density of state analysis along the[001]direction,we find that the strong mixed ioni%ovalent character of the Pu-0 bond is weakened by tensile strain and PuO_(2)will exhibit an insulator-to-metal transition after tensile stresses exceeding about 79 GPa.

Computational Geometric Analysis for <i>C. elegans</i>Trajectories on Thermal and Salinity Gradient

Elegans are one of the best model organisms in neural researches, and tropism movement is a typical learning and memorizing activity. Based on one imaging technique called Fast Track-Capturing Microscope (FTCM), we investigated the movement regulation. Two movement patterns are extracted from various trajectories through analysis on turning angle. Then we applied this classification on trajectory regulation on the compound gradient field, and theoretical results corresponded with experiments well, which can initially verify the conclusion. Our breakthrough is performed computational geometric analysis on trajectories. Several independent features were combined to describe movement properties by principal composition analysis (PCA) and support vector machine (SVM). After normalizing all data sets, no-supervising machine learning was processed along with some training under certain supervision. The final classification results performed perfectly, which indicates the further application of such computational analysis in biology researches combining with machine learning.

Effect of Sintering Temperature on Structural and Magnetic Properties of Ni_0.55Zn_0.45Fe₂O₄Ferrites

The effect of frequency and sintering temperature on initial permeability of Ni0.55Zn0.45Fe2O4 ferrites have been studied by using an impedance analyzer. The samples were prepared by conventional double sintering ceramic technique using oxide nanoparticles of grain size 30 - 50 nm. Single phase spinal structure has been confirmed for the prepared samples by X-ray diffraction. As the sintering temperatures increase from 1160℃ to 1300℃, the permeability gradually increases. The increase of permeability is ascribed to the increase of density and grain size. Grain size is expected to grow with the increase of sintering temperature. Ferrites with large average grain size posses higher initial permeability. The Curie temperatures determined from temperature dependence of permeability of the samples sintered at different temperatures are found to be Tc = (321 ± 1)℃ and independent of sintering temperature. At Ts = 1300℃, Tc is found to increase substantially which can be explained by the fact that Zn has evaporated from the surface layer.

Machine Learning With Data Assimilation and Uncertainty Quantification for Dynamical Systems:A Review

Data assimilation(DA)and uncertainty quantification(UQ)are extensively used in analysing and reducing error propagation in high-dimensional spatial-temporal dynamics.Typical applications span from computational fluid dynamics(CFD)to geoscience and climate systems.Recently,much effort has been given in combining DA,UQ and machine learning(ML)techniques.These research efforts seek to address some critical challenges in high-dimensional dynamical systems,including but not limited to dynamical system identification,reduced order surrogate modelling,error covariance specification and model error correction.A large number of developed techniques and methodologies exhibit a broad applicability across numerous domains,resulting in the necessity for a comprehensive guide.This paper provides the first overview of state-of-the-art researches in this interdisciplinary field,covering a wide range of applications.This review is aimed at ML scientists who attempt to apply DA and UQ techniques to improve the accuracy and the interpretability of their models,but also at DA and UQ experts who intend to integrate cutting-edge ML approaches to their systems.Therefore,this article has a special focus on how ML methods can overcome the existing limits of DA and UQ,and vice versa.Some exciting perspectives of this rapidly developing research field are also discussed.Index Terms-Data assimilation(DA),deep learning,machine learning(ML),reduced-order-modelling,uncertainty quantification(UQ).

PDRK:A General Kinetic Dispersion Relation Solver for Magnetized Plasma

A general,fast,and effective approach is developed for numerical calculation of kinetic plasma linear dispersion relations.The plasma dispersion function is approximated by J-pole expansion.Subsequently,the dispersion relation is transformed to a standard matrix eigenvalue problem of an equivalent linear system.Numerical solutions for the least damped or fastest growing modes using an 8-pole expansion are generally accurate;more strongly damped modes are less accurate,but are less likely to be of physical interest.In contrast to conventional approaches,such as Newton＇s iterative method,this approach can give either all the solutions in the system or a few solutions around the initial guess.It is also free from convergence problems.The approach is demonstrated for electrostatic dispersion equations with one-dimensional and twodimensional wavevectors,and for electromagnetic kinetic magnetized plasma dispersion relation for bi-Maxwellian distribution with relative parallel velocity flows between species.

The competition of neutrino energy loss due to the pair, photo-, plasma process at the late stages of stellar evolution

Based on the Weinberg-Salam theory, the competition of the Neutrino Energy Loss （NEL） rates due to the pair, photo-and plasma process are canvassed. The ratio factor C1, C2 and C3 which correspond the different contributions of the pair, photo-and plasma neutrino process to those of the total NEL rates are accurately taken into account. The ratio factors are very sensitive to the temperature and density. The ratio factor C2 always is lower than the ratio factor C1 and C3. The pair NEL process is the dominant contribution before the crossed point 0（C1 = C3 = 0.45） and the plasma NEL process will be the main dominant contribution after the crossed point O. With increasing temperature, the crossed point O will move to the direction of higher density.

Mural Defects Detection with Enhanced Terahertz Images

In mausoleum murals, existing bubbles are one kind of the most harmful defects for the repair and protection of relics. For this reason, it is necessary to detect bubbles, especially the ones with small size. A method to detect the small bubbles with enhanced terahertz （THz） images is proposed. To simulate the bubbles in the mausoleum murals, circular grooves have been hidden in the plaster and then measured by the THz reflected time domain spectroscopy imaging system. To observe the small bubbles in murals, a comprehensive enhancement algorithm is adopted to process the obtained THz images. With the enhanced method, the circular grooves in the murals can be observed clearly, even for the circular groove with a diameter of 1.5 mm. The results indicate that the proposed comprehensive method can be used to detect the tiny defects of murals.

Structural features of the A_(2)TiSi_(2)O_(8)(A-Ba and Pb)compounds

X-ray diffraction studies of synthesized Ba_(2)TiSi_(2)O_(8) have shown that this compound has a fresnoite structure and is characterized by a polar phase P4bm at room temperature.The synthesis of Pb_(2)TiSi_(2)O_(8) in the fresnoite phase under the selected synthesis conditions has led to the formation of a perovskite tetragonal phase P4mm corresponding to PbTiO_(3).

The magnetic states and Labyrinth ordering in 2D lattices of ising spins with RKKY Interaction

The numerical simulation of 2D simple square lattice of Ising superspins,that interact via the Ruderman–Kittel–Kasuya–Yosida(RKKY)exchange interaction is performed.It is found,that at low temperatures in the researched systems predominantly realized labyrinth domain structure.The modeled image of magnetization distribution does not coincide with the image of energy distribution.Hysteresis loops of the samples and labyrinth domain structures similarly obtained by Monte Carlo method,are also observed in physical experiments.

Terahertz Time-Domain Spectroscopy and Its Applications

The terahertz time-domain spectroscopy （THz-TDS） system and the related technology and the applications in Capital Normal University are presented. The most often used THz-TDS system as a spectroscopic measurement setup in our lab is introduced in detail, including the THz radiation source, the THz detection method and its measurement, and the control system. THz spectra of various materials is summarized and discussed. These materials include but not limited to two kinds of typical matter-the illegal drugs and explosives. The biological macro-molecules, cosmetics and fine chemical materials, edible pigments and food additives, homocysteic acid and related compounds, heavy ions in soil, Chinese medicines, tobacco and crops, oil and chemical products, carbon nanotubes, superconductors, and various semiconductors and their heterojunctions, are presented. THz emissions from the InAs and InN semiconductors surface are compared. THz spectral investigation of metallic mesh structures is summarized. Finally, an outlook of THz spectroscopic applications is given.

A Privacy-preserving Energy Management System Based on Homomorphic Cryptosystem for IoT-enabled Active Distribution Network

Active distribution network(ADN),as a typically cyber-physical system,develops with the evolution of Internet of Things(IoTs),which makes the network vulnerable to cybersecurity threats.In this paper,the eavesdropping attacks that lead to privacy breaches are addressed for the IoT-enabled ADN.A privacy-preserving energy management system(EMS)is proposed and empowered by secure data exchange protocols based on the homomorphic cryptosystem.During the information transmission among distributed generators and load customers in the EMS,private information including power usage and electricity bidding price can be effectively protected against eavesdropping attacks.The correctness of the final solutions,e.g.,optimal market clearing price and unified power utilization ratio,can be deterministically guaranteed.The simulation results demonstrate the effectiveness and the computational efficiency of the proposed homomorphically encrypted EMS.

Development and applications of gain-switched fiber lasers[Invited]

We briefly review the development of gain-switched rare-earth-doped fiber lasers and their applications in wavelength conversion to mid-IR,supercontinuum generation,and medicine in recent years.We illustrate the similarities between gain-switching and Q-switching techniques that will provide tools for the design and optimization of the gain-switched fiber lasers.From the nature of the gain-switched fiber lasers,benefits of this kind of lasers to 2-μm region and in-band-pumped(two-level system)laser systems are obvious.Advantages of in-band-pumped 2-μm lasers are discussed and analyzed with a simple numerical simulation in terms of Tm-doped fiber lasers.We also propose the key factors in the development of the gain-switched fiber lasers and predict the future tendency.

Atomic-scale observation of a two-stage oxidation process in Cu2O

Atomic-scale oxidation dynamics of Cu2O nanocrystallines （NCs） are directly observed by in situ high-resolution transmission electron microscopy. A two-stage oxidation process is observed： （1）The initial oxidation stage is dominated by the dislocation-mediated oxidation behavior of Cu2O NCs via solid-solid transformations, leading to the formation of a new intermediate CuOx phase. The possible crystal structure of the CuOx phase is discussed. （2） Subsequently, CuOx is transformed into CuO by layer-by-layer oxidation. These results will help in understanding the oxidation mechanisms of copper oxides and pave the way for improving their structural diversity and exploiting their potential industrial applications.

Realizing the thinnest hydrodynamic cloak in porous medium flow

Transformation mapping theory offers us great versatility to design invisible cloaks for the physical fields whose propagation equations remain invariant under coordinate transformations.Such cloaks are typically designed as a multi-layer shell with anisotropic material properties,which makes no disturbance to the external field.As a result,an observer outside the cloak cannot detect the existence of this object from the field disturbances,leading to the invisible effect in terms of field prorogation.In fact,for many prorogating fields,at a large enough distance,the field distortion caused by an object is negligible anyway;thus,a thin cloak is desirable to achieve near-field invisibility.However,a thin cloak typically requires more challenging material properties,which are difficult to realize due to the huge variation of anisotropic material parameters in a thin cloak region.For a flow field in a porous medium,by applying the bilayer cloak design method and integrating the inner layer with the obstacle,we successfully reduce the anisotropic multi-layer cloak into an isotropic single-layer cloak.By properly tailoring the permeability of the porous medium,we realize the challenging material parameters required by the ultrathin cloak and build the thinnest shell-shaped cloak of all physical fields up to now.The ratio between the cloak’s thickness and its shielding region is only 0.003.The design of such an ultrathin cloak may help to achieve the near-field invisibility and concealment of objects inside a fluid environment more effectively.

Extended breakdown of Simpleman approximation

In this letter, we solve three-dimensional time-dependent Newton equations for atoms interacting with a ten-cycle elliptically polarized laser pulse. The ionized electron momentum distributions show a tilt angle between the distribution density peak and the main polarization axis. The tilt angle＇s behavior changes with an increasing laser intensity. We show that this behavior change is directly related to the release time of the electron from the atom.