Energy Spectrum Distribution Research Articles

Advances in X-ray imaging technology

<p indent=0mm>X-ray imaging technology shows a great importance in medication, it uses bremsstradiation to produce images of ray density and energy spectrum distribution through different tissues with different X-ray absorption coefficients of specific energy. There are three devices now widely used today, X-ray apparatus, computed tomography (CT) and digital subtraction angiography (DSA). With the development of computer technology, artificial intelligence and material science, imaging technology is undergoing extensive and profound changes. A bunch of brand new imaging technologies has been used in medication and make X-ray technology develop rapidly. This article discussed the history of three X-ray devices and breakthrough points in the future. We also make some prediction and suggestions for the possible development trend of X-ray technology in China.

Double Phase Matching in MZI With Antiresonant Effect for Optical Fiber Sensor Application

In the traditional Mach–Zehnder interferometer, only one phase matching condition needs to be satisfied for destructive interference. Here, we propose and demonstrate a Mach–Zehnder interferometer with double phase matching condition, which satisfies both the destructive condition of double beam interference and the resonant condition of anti-resonant effect. Different from the traditional method, the interference is construed as a coherent superposition between anti-resonant beam and cladding one. The effect of the multimode fiber length on the energy distribution and transmission spectrum is analyzed precisely. The experimental results show that the intensity of the wavelength meeting double phase matching condition is extremely sensitive to both strain and temperature. The maximum intensity sensitivity to strain and temperature are up to 16.1 dB/mv and 0.181 dB/°C, respectively. Compared with the previous work, the sensitivities have been improved several times or even tens of times. The proposed Mach–Zehnder interferometer with double phase matching condition can improve the dip depth, which has a great potential value in sensing application.

Tracing the Coevolution Path of Supermassive Black Holes and Spheroids with AKARI-selected Ultraluminous IR Galaxies at Intermediate Redshifts

Abstract We present the stellar population and ionized-gas outflow properties of ultraluminous IR galaxies (ULIRGs) at z = 0.1–1.0 that are selected from the AKARI far-IR all-sky survey. We construct a catalog of 1077 ULIRGs to examine feedback effects after major mergers. Of the 1077 ULIRGs, 202 are spectroscopically identified by SDSS and Subaru/FOCAS observations. Thanks to the deeper depth and higher resolution of AKARI compared to the previous Infrared Astronomical Satellite (IRAS) survey and reliable identification from the Wide-field Infrared Survey Explorer (WISE) mid-IR pointing, the sample is unique in identifying optically faint (i ∼ 20) IR-bright galaxies, which could be missed in previous surveys. A self-consistent spectrum and broadband spectral energy distribution (SED) decomposition method, which constrains stellar population properties in SED modeling based on spectral fitting results, has been employed for 149 ULIRGs whose optical continua are dominated by host galaxies. They are massive galaxies ( –1012 M ) associated with intense star formation activities (SFR ∼ 200–2000 M yr−1). The sample covers a range of active galactic nucleus (AGN) bolometric luminosity of 1010–1013 L , and the outflow velocity measured from the [O iii] 5007 Å line shows a correlation with AGN luminosity. Eight galaxies show extremely fast outflows with velocity up to 1500–2000 km s−1. However, the coexistence of vigorous starbursts and strong outflows suggests the star formation has not been quenched during the ULIRG phase. By deriving the stellar mass and mass fraction of the young stellar population, we find no significant discrepancies between stellar properties of ULIRGs with weak and powerful AGNs. The results are not consistent with the merger-induced evolutionary scenario, which predicts that star formation–dominated ULIRGs will show smaller stellar masses and younger stellar populations compared to AGN-dominated ULIRGs.

Adaptive Fourier single-pixel imaging sampling based on frequency coefficients prediction

Fourier single-pixel imaging (FSI) has been proven to achieve excellent image quality when sampling all information in the Fourier domain. However, when the size of an imaging target is large, fully sampling Fourier coefficients would result in a large waste of sampling resources. An adaptive sampling method is proposed that is simple to implement and effectively improves the reconstructed image quality from undersampled Fourier coefficients. Through a rough estimation of spectrum energy distribution, the adaptive sampling trajectory is generated by the designed adaptive probability density function. Both the results of computational simulations and experiments demonstrate that the proposed method has overcome the limitations of the insufficient sampling rates, and the reconstruction images have obtained dramatic improvements. These improvements greatly promote the development of the FSI during undersampled conditions.

Desert seismic data denoising based on energy spectrum analysis in empirical curvelet domain

Desert seismic events are disturbed and contaminated by strong random noise, which complicates the subsequent processing, inversion, and interpretation of the data. Thus, noise suppression is an important task. The complex characteristics of random noise in desert seismic records differ completely from those of Gaussian white noise such that they are non-stationary, non-Gaussian, non-linear and low frequency. In addition, desert seismic signals and strong random noise generally share the same frequency bands. Such factors bring great difficulties in the processing and interpretation of desert seismic data. To obtain high-quality data in desert seismic exploration, we have developed an effective denoising method for desert seismic data, which performs energy spectrum analysis in the empirical curvelet transform (ECT) domain. The empirical curvelet coefficients are divided into two different groups according to their energy spectrum distributions. In the first group, which contains fewer effective signals, a large threshold is selected to remove lots of random noise; the second group, with more effective signals, a coherence-enhancing diffusion filter (CEDF) is used to eliminate the noise. Unlike traditional curvelet transforms, ECT not only has the multi-scale, multi-direction, and anisotropy properties of conventional curvelet transform, but also provides adaptability to separate the effective signals from the random noise. We examine synthetic and field desert seismic data. The denoising results demonstrate that the proposed method can be used for preserving effective signals and removing random noise.

Simulating hard photon production with Whizard

One of the important goals of the proposed future hbox {e}^{+}hbox {e}^{-} collider experiments is the search for dark matter particles using different experimental approaches. The most general search approach is based on the mono-photon signature, which is expected when production of the invisible final state is accompanied by a hard photon from initial state radiation. Analysis of the energy spectrum and angular distributions of those photons can shed light on the nature of dark matter and its interactions. Therefore, it is crucial to be able to simulate the signal and background samples in a uniform framework, to avoid possible systematic biases. The Whizard program is a flexible tool, which is widely used by hbox {e}^{+}hbox {e}^{-} collaborations for simulation of many different “new physics” scenarios. We propose the procedure of merging the matrix element calculations with the lepton ISR structure function implemented in Whizard. It allows us to reliably simulate the mono-photon events, including the two main Standard Model background processes: radiative neutrino pair production and radiative Bhabha scattering. We demonstrate that cross sections and kinematic distributions of mono-photon in neutrino pair-production events agree with corresponding predictions of the mathcal{KK} MC, a Monte Carlo generator providing perturbative predictions for SM and QED processes, which has been widely used in the analysis of LEP data.

SINR-Based Time Domain Synthesis Algorithm for Radar

For optimal radar waveform design and multi-target recognition in cognitive radar, a time-domain synthetic algorithm based on the water-filling algorithm is proposed. We consider the energy spectrum distribution of the synthesized signal based on the signal to interference plus noise ratio (SINR) in the presence of clutter. Simulation results show that after adding phase information, the time-domain synthesis algorithm based on SINR can obtain more target information than the general water-filling algorithm.

Numerical modelling of trapezoidal weir flow with RANS, LES and DES models

The characteristics of the trapezoidal weir flow are measured using a one-dimensional laser Doppler anemometer for two different flow conditions. The governing equations of the flow are solved using Standard k–e, Realizable k–e, Modified k–ω and Reynolds Stress Model based on the Reynolds-Averaged Navier–Stokes Equations and by Large Eddy and Detached Eddy Simulations. ANSYS-Fluent package program is used for the numerical analysis of flow with the same experimental conditions. The free surface of the trapezoidal weir flow is computed by the volume of fluid method. The effect of the selected grid structure on the numerical results is examined by Grid Convergence Index. Moreover, two-dimensional (2D) and three-dimensional (3D) analyses of the trapezoidal weir flow are included to estimate the effects of side walls. Experimental results of the velocity field and free surface profiles are compared to the numerical results of 2D and 3D simulations for the validation purposes. From the comparisons it is concluded that the Reynolds Stress Model estimates the flow field more accurately compared with those of the other models used in the present study. Furthermore, the flow characteristics such as turbulence kinetic energy, energy spectrum and pressure distributions for different flow rates are presented. Lastly, the discharge coefficients for different flow–weir configurations are compared experimentally and numerically.

Characterization of TRIGA RC-1 neutron irradiation facilities for radiation damage testing

This paper presents the results of neutron flux measurements at two irradiation facilities of the TRIGA Mark II reactor at ENEA Casaccia Research Center, Italy. The goal of these measurements is to provide a complete characterization of neutron irradiation facilities for accurate and precise dose evaluation in radiation damage tests and, more generally, for all applications that need a good knowledge of neutron flux in terms of intensity, energy spectrum and spatial distribution. The neutron activation technique is used to measure the activation rates of several reactions, chosen so to cover the whole energy range of neutron flux spectrum. A multi-group neutron flux measurement is obtained through an unfolding algorithm based on a Bayesian statistical model. The obtained results prove that this experimental method allows to measure the total neutron flux within 2% statistical uncertainty, and to get at the same time a good description of its energy spectrum and spatial distribution.

Evolution characteristics and quantization of wave period variation for breaking waves

The wave parameters (the wave height and period) are important environmental factors in the ocean engineering design. General numerical wave models, such as SWAN and WAVEWATCH, are widely employed to simulate the wave conditions. However, significant differences were observed between the measurement and the simulation for both the wave height and period, which asks for wave model improvements. The differences are mainly due to the uncertainty of parameterizing various physical processes, including the wave breaking. The energy transfer and loss during the wave breaking involves an important physical mechanism, and the energy dissipation and the period changes are not well studied. This paper studies the deep and shallow water wave breaking using the wave focusing and the slope platform random wave experiments. The characteristics of the wave periods under different conditions are studied in detail, including the period variation. The results show that the periods change during the wave propagation and breaking processes. The energy transfer caused by the strongly nonlinear interaction between the wave components, as well as the energy loss caused by the wave breaking, are the primary causes. The corresponding relationships are established by fitting the data. For the deep water breaking waves induced by the wave focusing, the spectrally averaged period (SAP) increases, and a positive correlation between the rate of change and the wave steepness is found. In the shallow water, the nonlinear interactions are stronger than in the deep water, the wave periods are significantly reduced, and a negative correlation between the rate of change and a nonlinear parameter is found. The inherent mechanism of the period variation is analyzed based on the energy spectrum distribution variations. The contributions of the nonlinear interactions and the wave breaking to the SAP evolution are discussed.

The organized motion of characterized turbulent flow at low Reynolds number in a straight square duct

We study the self-sustaining turbulent flow at minimal frictional Reynolds number in a straight square duct using direct numerical simulation. The flow in the square duct is maintained through a constant pressure gradient in the stream-wise direction. The computational investigation of the flow phenomenon for minimal, marginal and fully turbulent flow is studied using organized motion and dynamics of coherent structures. The central theme of the present work is to demonstrate the organized motion of the flow regimes below the frictional Reynolds number of the fully turbulent flow. The controlled direct numerical simulation study and vortex-detection technique unveil hairpin vortices in fully and minimal turbulent flow in the square duct for the first time. Bursting of streaks is detected with variable interval time average, and the evolution of hairpin vortices is also addressed. Turbulent intensities and energy spectra are reported and compared between the minimal, marginal and fully turbulent flow. The minimal turbulence in a square duct indicates transitional turbulent flow characteristics like lesser occurrence of ejection and sweep, intermittent bursting events, and a steeper variation of energy spectrum as compared to fully turbulent energy spectrum distribution.

Effects of Feed per Tooth and Radial Depth of Cut on Amplitude Parameters and Power Spectral Density of a Machined Surface.

Surface topography and roughness significantly affect the functional properties of engineering parts. In this study, a mathematical model simulating the surface topography in end milling is presented and verified by milling experiments. The three dimensional (3D) surface amplitude parameters (arithmetic average deviation Sba and root mean square deviation Sq) of the milled surface were calculated by using the model and the effects of the product (p) and ratio (r) of radial depth of cut ae and feed per tooth fz on amplitude parameters were researched. To evaluate the lateral characteristics of the milled surface, one dimensional (1D) power spectral densities (PSD) along both feed and step-over direction were calculated and investigated. It was found that fz affects 1D PSD along both directions, whereas ae affects 1D PSD along the step-over direction. An angular spectrum, derived from the area power spectral density (APSD), was employed to research the spatial distribution of spectral energy on the milled surface. Furthermore, the influences of p and r on the PSD properties were researched. It was found that r is the significant factor that influences the direction of surface energy spectrum distribution.

Many-body localization in generalized Kondo lattice with disorder

We study the many-body localization transition in a one-dimensional generalized Kondo lattice, where a one-dimensional Hubbard chain with disordered spin-orbit coupling interacts with a fixed impurity of spin . Using exact diagonalization, we characterize the many-body localized transition with entanglement entropy and energy spectrum distribution. We find that although the subsystem of the impurity is free of disorder, it can still be localized in the spin space by the coupling with the Hubbard chain. We also investigate the out-of-time-order correlation in the many-body localized phase, and find distinctive features in comparison to either the thermal state or the Anderson localized state. Our scheme can be realized in experiments with ultracold fermions of alkaline-earth–like atoms near an orbital Feshbach resonance.

Local Strain Distribution in Synthetic Diamond Crystals, Determined by the Parameters of the Energy Spectrum of the Kikuchi Patterns

The average strain in local regions of synthetic diamond was determined using the energy Fourier-transform spectrum in the analysis of digital Kikuchi patterns. The degree of broadening of the diffraction bands and their intersections in the images caused by deformations is quantitatively described through the average spatial period and the area of the radial distribution of the energy spectrum. The planar distribution of local strains made it possible to determine their anisotropy in the crystal in magnitude and direction.

Prototype of pulse digitizer and readout electronics for CDEX-10 in CJPL

The CDEX (China Dark matter Experiment) is currently in the stage to upgrade to approximately 10 kg HPGe (High Purity Germanium) detectors (CDEX-10) in CJPL (China Jinping Underground Laboratory) and aims to detect the WIMP (Weakly Interacting Massive Particles). Six analog signals and one inhibited signal are outputted from preamplifier by one HPGe detector (∼ 1 kg) of CDEX-10. The analog signals are conditioned with two 6 μs and one 12 μs shaping amplifiers, and three timing amplifiers respectively. The inhibited signal is used for trigger. The analog signals from shaping and timing amplifiers are digitized to obtain energy spectrum and rise-time distribution. The rise-time distribution is used to discriminate surface, bulk, and very bulk events, which can help to supress the background level in dark matter detection. Composed of commercial modules, the previous DAQ (Data Acquisition Systems) is insufficient in discriminating between bulk and very bulk events due to the limited sampling rate (100 MSPS). Besides, as number of channel increases, the system will be simplified by integrating the trigger logic in FPGA (Field Programmable Gate Array). In this paper, a prototype named RAIN4HPGe is designed with pulse digitizer and readout electronics, integrating 14-bit 100 MSPS ADCs (Analog-to-Digital Converters), 12-bit 1 GSPS ADCs, FPGA etc. . The RAIN1000Z1 readout module based on ZYNQ SoC (System on Chip) is used for readout over Gigabit Ethernet. Better energy resolution, e.g. improving from 558 eV to 474 eV @122 keV, can be achieved by RAIN4HPGe compared to previous DAQ (Data Acquisition Systems) with commercial solution. Moreover, the discrimination performance of bulk, and very bulk events has been improved by RAIN4HPGe with 1 GSPS ADC.

HHT-based AE characteristics of 3D braiding composite shafts

Abstract In this paper the Hilbert-Huang transform (HHT) was used to analyze the acoustic emission (AE) signals of 3D braiding composite shafts under tensile and torsion. First, tensile and torsion experiments were carried out on 3D braiding composite shafts with different braiding angles, and AE was used to monitor the damage evolution during the experiments. Then the AE signals were decomposed by empirical mode decomposition (EMD) and intrinsic mode functions (IMF) were analyzed by Hilbert transform to obtain the energy distribution spectrum in the time-frequency domain. The results show that HHT can realize modal separation of AE signal and distinguish different damage types. Matrix damage mainly concentrates in 125–200 kHz band. Fiber fracture and fiber/matrix pull out concentrate in 200–400 kHz band.

Vortex Evolution within Propeller Induced Scour Hole around a Vertical Quay Wall

This paper presents an experimental study on the characteristics of the propeller-induced flow field and its associated scour hole around a closed type quay (with a vertical quay wall). An “oblique particle image velocimetry” (OPIV) technique, which allows a concurrent measurement of the velocity field and scour profile, was employed in measuring the streamwise flow field (jet central plane) and the longitudinal centerline scour profile. The asymptotic scour profiles obtained in this study were compared with that induced by an unconfined propeller jet in the absence of any berthing structure, which demonstrates the critical role of the presence of the quay wall as an obstacle in shaping the scour profile under the condition of different wall clearances (i.e., longitudinal distance between propeller and wall). Moreover, by comparing the vortical structure within the asymptotic scour hole around the vertical quay wall with its counterpart in the case of an open quay (with a slope quay wall), the paper examines the effect of quay types on the formation of the vortex system and how it determines the geometrical characteristic of the final scour profile. Furthermore, the temporal development of the mean vorticity field and the vortex system are discussed in terms of their implications on the evolution of the scour hole. In particular, comparison of the circulation development of the observed vortices allows a better understanding of the vortex scouring mechanism. Energy spectra analysis reveals that at the vortex centers, their energy spectra distributions consistently follow the −5/3 law throughout the entire scouring process. As the scour process evolves, the turbulent energy associated with the near-bed vortex, which is responsible for scouring, is gradually reduced, especially for the small-scale eddies, indicating a contribution of the dissipated turbulent energy in excavating the scour hole. Finally, a comparison of the near-bed flow characteristics of the average kinetic energy (AKE), turbulent kinetic energy (TKE), and Reynolds shear stress (RSS) are also discussed in terms of their implications for the scour hole development.

Effects of Compton scattering on the neutron star radius constraints in rotation-powered millisecond pulsars

The aim of this work is to study the possible effects and biases on the radius constraints for rotation-powered millisecond pulsars when using Thomson approximation to describe electron scattering in the atmosphere models, instead of using exact formulation for Compton scattering. We compare the differences between the two models in the energy spectrum and angular distribution of the emitted radiation. We also analyse a self-generated, synthetic, phase-resolved energy spectrum, based on Compton atmosphere and the most X-ray luminous, rotation-powered millisecond pulsars observed by the Neutron star Interior Composition ExploreR (NICER). We derive constraints for the neutron star parameters using both the Compton and Thomson models. The results show that the method works by reproducing the correct parameters with the Compton model. However, biases are found in both the size and the temperature of the emitting hotspot, when using the Thomson model. The constraints on the radius are still not significantly changed, and therefore the Thomson model seems to be adequate if we are interested only in the radius measurements using NICER.

The high-energy particle package onboard CSES

The China Seismo-Electromagnetic Satellite (CSES) aims to monitor space electromagnetic fields, ionospheric plasma, high-energy charged particles and other features of the global space environment. The high-energy particle package (HEPP), which can effectively detect the energy spectrum, flux and pitch angle distribution of space electrons and protons, and soft X-ray emission from solar flares, is one of the main payloads of CSES. In this study, we designed, developed and calibrated the high-energy particle package and launched it into orbit with CSES. HEPP consists of the high-energy detector (HEPP-H), the low-energy detector (HEPP-L), and the solar X-ray monitor (HEPP-X). The three sub-detectors mainly use silicon detector and crystal calorimeter detection technology. Before launching, we calibrated the three sub-detectors in detail by using radiation source and accelerator beam. All the three sub-detectors have good energy linearity. After launching into orbit, the space energetic particles and X-ray distribution detected by HEPP are consistent with expectations. The performance indices of the detector reach the advanced level of the same kind of detector in the world. HEPP has a wide energy detection range, good energy resolution and high angular resolution ability for electrons and protons. It will play an important role in the study of space particle response and space physics of seismic activity.

Acceleration of carbon ions to high energies by a multi-PW laser

Extreme Light Infrastructure (ELI) is a large-scale European project, still in the development stage, offering parameters of laser drivers required for multiple applications (femtosecond pulse duration, ultra-relativistic laser intensities ∼ 1022 - 1023 W/cm2), however studies of ion acceleration in the given intensity regime are still in the very early stages and require a deeper understanding of the processes occurring during laser-matter interactions to maximize the efficiency of ion acceleration. The purpose of this work is a numerical examination of the properties of carbon ion beams produced during the interaction of an ultra-intense laser beams (of intensities ∼ 1021 – 1023 W/cm2 and pulse duration order of femtoseconds, predicted to be available at ELI-NP, Romania) with C12 target. The dependence of ion beam parameters, such as intensity, energy spectrum, maximum and average ion energy and spatial distribution of ion charge density, on laser pulse parameters (mainly intensity) and the target thickness is investigated. The possibility of generation of high intensity, GeV energy ion beams in the foregoing conditions is demonstrated. The obtained results can be useful for research in high energy-density physics, nuclear physics or medical applications of ion beams.