Measurement of Secondary Electron Energy Spectra of Polymethyl Methacrylate

We report on a novel and convenient method of measuring secondary electron spectra for insulators in a secondary electron yield measurement system with a planar grid analyzer configuration and a metal mesh probe. In this measurement, the planar grid is negatively biased to force some emitted secondary electrons to return to the sample surface and to neutralize charges accumulated on the sample during the previous beam irradiation. The surface potential of the sample is then measured by use of a metal mesh probe. The grid bias for neutralization corresponding to the zero surface potential is determined based on the linear relationship between the surface potential and the grid bias. Once the surface potential equals zero, the secondary electron spectra of polymethyl methacrylate（PMMA） are studied experimentally by measuring the -curve and then fitting it to Everhart＇s formula. The measurement results show that the peak energy and the full width at half maximum of the spectra are 4.26 eV and 14.06 eV, respectively.

Scaling of energy spectra in weakly compressible turbulence

We find an asymptotic expression for the characteristic timescales of decorrelation processes in weakly compressible and isothermal turbulence. This result is used in the Eddy-Damped Quasi-Normal Markovian equation to derive the scalings of compressible energy spectra: (1) if the acoustic waves are dominant, the compressible energy spectra exhibit \(-7/3\) scaling; (2) if local eddy straining is dominant, the compressible energy spectra are scaled as \(-3\). Meanwhile, the energy spectra of incompressible components display the same scaling of \(-5/3\) as those in incompressible turbulence. The direct numerical simulations of weakly compressible turbulence are used to examine the scaling.

Study on comparison between absolute and relative input energy spectra and effects of ductility factor

Based on 266 strong ground motion records, an attenuation relationship was developed for both absolute and relative input energy spectra. The comparison of the two kinds of input energy spectra constructed from the attenuation relationship was made in this paper. The results show that there is little difference between the absolute input energy spectra and relative input energy spectra at the periods of 0.5-1.0 s for elastic systems and at the period of 0.5 s for inelastic systems. The absolute input energy spectra are much larger than relative input energy spectra in very short period range but some less than relative input energy spectra in long period range. It is also found that the ductility factor has a significant effect on both absolute and relative input energy spectra. The absolute input energy spectra increase with the increasing of ductility factor in the period range of less than 0.3 s but decrease in the period range of larger than 0.3 s. The absolute input energy spectra for different ductility factor are almost equivalent at the period about 0.3 s, but for relative input energy spectra, the period is about 0.5 s. The effect of ductility on the relative input energy spectra in the short period range is much larger than that on the absolute input energy spectra, especially on the softer site class.

Real non-Hermitian energy spectra without any symmetry

Non-Hermitian models with real eigenenergies are highly desirable for their stability.Yet,most of the currently known ones are constrained by symmetries such as PT-symmetry,which is incompatible with realizing some of the most exotic non-Hermitian phenomena.In this work,we investigate how the non-Hermitian skin effect provides an alternative route towards enforcing real spectra and system stability.We showcase,for different classes of energy dispersions,various ansatz models that possess large parameter space regions with real spectra,despite not having any obvious symmetry.These minimal local models can be quickly implemented in non-reciprocal experimental setups such as electrical circuits with operational amplifiers.

Calculation of Neutral Particle Energy Spectra in Tokamak by Using the Monte Carlo Method

Neutral particle energy spectra in the HT-7 tokamak are calculated by using the Monte Carlo method. It can reproduce the spectra measured in experiment. Differences of neutral particle energy spectra in higher and lower electron density plasma are discussed. Results show that the ion temperature given by neutral particle energy spectra is lower than the real ion temperature, but the deviation is within 10% if the ion temperature is less than 800 eV and thecentral chord-averaged electron density does not exceed 3 ×1013 cm-3. But for ion temperature higher than 1000 eV at the central chord-averaged density limit up to 5 ×1013 cm-3, the neutral particle energy spectra can still give the ion temperature within 10% deviation.

Analysis of the energy spectra of ground states of deformed nuclei in the rare-earth region

The 62Sm, 64Gd, 66Dy, 70Yb, 72Hf and 74W nuclei are classified as deformed nuclei. Low-lying bands are one of the most fundamental excitation modes in the energy spectra of deformed nuclei. In this paper a theoretical analysis of the experimental data within the phenomenological model is presented. The energy spectra of ground states are calculated. It is found that the low-lying spectra of ground band states are in good agreement with the experimental data.

Numerical implementation and evaluation of resolvent-based estimation for space-time energy spectra in turbulent channel flows

Resolvent operator has been increasingly used to investigate turbulent flows and develop control strategies.Recently,Towne et al.(J Fluid Mech 883:A17,2020)proposed a resolvent-based estimation(RBE)method for predicting turbulent statistics in a channel flow.In this paper,we utilize the RBE method to predict the root-mean-square(RMS)and space-time energy spectra of streamwise velocity fluctuation,where the input is the space-time energy spectra at a reference horizontal plane located in the logarithmic layer and the output is the space-time energy spectra in the buffer layer.The explicit formulas for the RBE method are given in detail for numerical implementation.The results show the capability of the RBE method in the prediction of the convection velocity and bandwidth of the space-time energy spectra.Furthermore,we make a systematic evaluation of the performance of the RBE method by varying the input configurations,including the wall-normal location of the reference plane,the inclusion or exclusion of the pressure as an input variable,the implementation approach of the pressure boundary condition,and the choice of the window function.It is found that the results of both RMS velocity and space-time energy spectra obtained from the RBE method are sensitive to the location of the reference plane.However,the pressure boundary conditions and inclusion of pressure as an input do not cause significant change in the RMS velocity and space-time energy spectra.Although it does not influence the prediction of the RMS velocity,a window function is found crucial in the RBE method for the prediction of the space-time energy spectra.

High Energy X-ray Telescope Data Analysis Method

The science analysis of the data from the High Energy X-ray Telescope(HE) on the Hard X-ray Modulation Telescope(HXMT) satellite is organized in three stages:calibration,screening and extraction of high-level scientific products.At the first stage,the raw PHA value of each event is converted to PI value accounting for temporal changes in gain and energy offset.At the second stage,the calibrated events are screened by applying cleaning criteria.At the third stage,scientific products,i.e.spectra,light curves and redistribution matrix files,are extracted.This work will introduce the three stages as well as the screening criteria and the data combining method.

The development,performances and applications of the monochromatic X-rays facilities in(0.218–301)keV at NIM,China

Space scientific exploration is rapidly becoming the primary battlefield for humankind to explore the universe.Countries worldwide have launched numerous space exploration satellites.Accurate calibration of the detectors on the ground is a crucial element for space science satellites to obtain observational results.For the purpose of providing calibration for various satellite-borne detectors,multiple monochromatic X-rays facilities have been built at the National Institute of Metrology,P.R.China(NIM).These facilities mainly pertain to grating diffraction and Bragg diffraction,and the energy range of the produced monochromatic X-rays is 0.218–301 ke V.These facilities have a high performance in terms of energy stability,monochromaticity,and flux stability.The monochromaticity was greater than 3.0%.The energy stability of the facility is 0.02%at 25 ke V over 8 h,and the flux stability was within 1.0%at 25 ke V over 8 h.Calibration experiments on the properties of satellite-borne detectors,such as energy linearity,energy resolution,detection efficiency,and temperature response,can be conducted at the facilities.Thus far,the calibration of two satellites has been completed by the authors,and the work on three other satellites is in progress.This study will contribute to the advancement of X-ray astronomy the development of Chinese space science.

Two-dimensional photoelectron momentum distribution of hydrogen in intense laser field

Two-dimensional （2D） electron momentum distributions and energy spectra of a hydrogen in an intense laser field are calculated by solving the time-dependent SchrSdinger equation combined with the window-operator technique. Compared with the standard projection technique, the window-operator technique has the advantage that the continuum states of atoms can be avoided in the calculation. We show that the 2D electron momentum distributions and the energy spectra from those two techniques accord quite well with each other if an appropriate energy width is used in the window operator.

Rapid Biosynthesis of Silver Nanoparticles Using Cymbopogan Citratus (Lemongrass) and its Antimicrobial Activity

The present study deals with the rapid green synthesis of silver nanoparticles using fresh leaves of Cymbopogan Citratus(Lemongrass). Silver nanoparticles were formed within 8～10 minutes by microwave irradiation using aqueous solution of Ag NO3(1 m M) with fresh leaves extract of Cymbopogan Citratus. The synthesized silver nanoparticles were characterized by using UV-visible spectrophotometer analysis, nanoparticle tracking analyzer, transmission electron microscope and energy dispersive X-ray spectra. The antibacterial activity of these nanoparticles was studied against multiple drug resistant hospital isolates of E.coli, S.aureus,P.mirabilis and hospital isolates of S. typhi, K.pnuemoniae. Also, the antifungal activity of these nanoparticles was studied against C.albicans(hospital isolate) and A.niger(NCIM 616). The synergistic effect of silver nanoparticles along with antibiotics was also studied against multiple drug resistant hospital isolates and found to be effective. The extracellular synthesis of Silver nanoparticles using leaves of Cymbopogan Citratus appears to be rapid and eco-friendly.

A new interpolating method based on the variation of spectra energy using CMOS array

A new interpolating method to enhance the resolution of gratings using complementary metal-oxide semiconductor （CMOS） according to the variation of soIne specified spectral light intensities during the motion of scale grating in a periodic separation is proposed. CMOS image sensor （pixel array 648 × 488） was also introduced as receiving device and its stability was verified experimentally. Many factors m the experiment were analyzed theoretically and contrasted with experiment. The advantages of this novel method were featured by CMOS and the specified spectral variation of the energy distribution was discussed.

Emission of high-energy alpha particles in nuclear reactions of ^(48)Ca and ^(56)Fe ions on ^(181)Ta and ^(238)U targets

The results of experiments on measuring the energy spectra of alpha particles in reactions with heavy ions are presented.The measurements were performed using the high-resolution magnetic analyzer MAVR with beams of ^(48)Ca(280 MeV)and ^(56)Fe(320 and 400 MeV)on ^(181)Ta and ^(238)U targets at an angle of 0°.A strong dependence of the double differential cross sections for production of alpha particles on the atomic number of the target nucleus was observed,which indicates that fast alpha particles are mainly emitted from the target nucleus;this conclusion was also confirmed by calculations within the time-dependent Schrödinger equation approach.An analysis of the obtained experimental data was carried out within the model of moving sources modified to consider the kinematic limits for two-body and three-body exit channels.

Assessment of subgrid-scale models in wall-modeled large-eddy simulations of turbulent channel flows

Considering the demanding of grid requirements for high-Reynolds-number wall-bounded flow,the wall-modeled large-eddy simulation(WMLES)is an attractive method to deal with near wall turbulence.However,the effect of subgrid-scale(SGS)models for wall-bounded turbulent flow in combination with wall stress models is still unclear.In this paper,turbulent channel flow at Reτ=1000 are numerically simulated by WMLES in conjunction with four different SGS models,i.e.,the wall-adapting local eddy-viscosity model,the dynamic Smagorinsky model,the dynamic SGS kinetic energy model and the dynamic Lagrangian model.The mean velocity profiles are compared with the law of the wall,and the velocity fluctuations are compared with direct numerical simulation data.The energy spectrum of velocity and wall pressure fluctuations are presented and the role of SGS models on predicting turbulent channel flow with WMLES is discussed.

Experimental studies for nuclear chirality in China

In the last decade,chiral symmetry in atomic nuclei has attracted significant attention and become one of the hot topics in current nuclear physics frontiers.This paper provides a review of experimental studies for nuclear chirality in China.In particular,the experimental setups,chiral mass regions,lifetime measurements,and simultaneous breaking of chirality and other symmetries are discussed in detail.These studies found a new chiral mass region(A≈80),extended the boundaries of the A≈100 and 130 chiral mass regions,and tested the chiral geometry of^(130)Cs,^(106)Ag,^(80)Br and^(76)Br by lifetime measurements.In addition,simultaneous breaking of chirality and other symmetries have been studied in^(74)As,^(76)Br,^(78)Br,^(80)Br,^(81)Kr and^(131)Ba.

Calculation and analysis of cross-sections for p+^(184)W reactions up to 200 MeV

A set of optimal proton optical potential parameters for pd-lS4w reactions are obtained at incident proton energy up to 250 MeV. Based on these parameters, the reaction cross-sections, elastic scattering angular distributions, energy spectra and double differential cross sections of proton-induced reactions on lS4w are calculated and analyzed by using theoretical models which integrate the optical model, distorted Born wave approximation theory, intra- nuclear cascade model, exciton model, Hauser-Feshbach theory and evaporation model. The calculated results are compared with existing experimental data and good agreement is achieved.

The impact of vertical resolution on the simulation of Typhoon Lekima (2019) by a cloud-permitting model

The impact of vertical resolution on the simulation of Typhoon Lekima(2019)is investigated using the Weather Research and Forecasting(WRF)model version 3.8.1.Results show that decreasing vertical grid spacing from approximately 1000 m to 100 m above 1 km height barely influences the simulated track.However,significant differences are found in the simulated tropical cyclone(TC)structure.The simulation with the coarsest vertical resolution shows a clear double warm-core structure.The upper warm core weakens and even disappears with the increase of vertical resolution.A broader eye and a more slantwise eyewall are observed with the increase of vertical resolution due to the vertically extended lower-level and upper-level outflow,which likely results in a weaker subsidence.Vertical grid convergence is evaluated with the simulated kinetic energy(KE)spectra.As the vertical grid spacing becomes finer than 200 m,convergent KE spectra are found in both the free atmosphere and the outer core of the TC.However,sensitivity tests reveal that the grid convergence is sensitive to the choice of the planetary boundary layer scheme.

Impact of surface coating on morphological, optical and photoluminescence properties of YF3：Tb^3＋ nanoparticles

A simple polyol and sol–gel Stober process were employed for synthesis of YF_3：Tb~＋（core）, YF_3：Tb~＋@LaF_3（core/shell） and YF_3：Tb~＋@LaF_3@SiO_2（core/shell/SiO_2） nanoparticles（NPs）. The phase purity, crystalinity,morphology, optical and photoluminescence properties were investigated and discussed with the help of various analytical techniques including X-ray diffraction pattern,FE-transmission electron microscopy（TEM）,FTIR, UV/vis absorption, energy band gap and emission spectra. XRD andFE-TEM studies indicate the formation of core/shell nanostructure and ~10 nm thick amorphous silica surface coating surrounding the core-NPs, which is also confirmed byFTIR spectral results. The surface modifications of core-NPs significantly affect the optical features in the form of energy band gap, which were correlated with particle size of the nanomaterials. The comparative emission spectral results show that after inert layer coating the luminescent core-NPs display stronger emission intensity in respect to core and silica coated core/shell/SiO_2-NPs. The solubility character along with colloidal stability was improved after silica surface modification, whereas luminescent intensity was suppressed causing the surface functionalized with high energy silanol（Si-OH） molecules. These novel luminescent nanomaterials with enhanced emission intensity and excellent solubility in aqueous solvents would be potentially useful for fluorescence bioimaging/optical bio-probe etc.