Radiation Signal Research Articles

小麦哲伦云同步辐射信号与暗物质湮灭信号的研究

小麦哲伦云同步辐射信号与暗物质湮灭信号的研究

The noncontact determination technique research of dangerously loaded zones in the underground mining

The electromagnetic radiation signals associated with the destruction of rock samples were studied under field and laboratory conditions. The parameters of the signal were found that preceded the violation of the integrity of the rock in laboratory studies. It is shown that the highest efficiency of the method of electromagnetic radiation is achieved when predicting the dynamic manifestations of rock pressure in the form of rock shock.

Self-Organized Kilotesla Magnetic-Tube Array in an Expanding Spherical Plasma Irradiated by kHz Femtosecond Laser Pulses.

By using a millijoule kHz femtosecond laser pulse to irradiate a preformed expanding spherical plasma, which is driven by a prepulse with intensity of 1×10^{14} W/cm^{2}, we observe fast-electron-mediated filamentary structures and an accompanying self-organized magnetic-tube array with 2000 T via time-resolved magneto-optical polarization rotation measurements. We reveal that these periodical filamentary structures predominantly originate from ejected energetic electron flows from the inner denser region of the spherical plasma, which will induce the electron Weibel instability and magnetic field organization and amplification in the expanding plasma in 2ps. These results open new paths to investigate amplification of intense magnetic fields and the radiation signature from gamma-ray bursts just by means of a much smaller and robust experimental platform.

Rotating solitons supported by a spiral waveguide

We investigate numerically light propagation in a single spiral waveguide formed in a nonlinear dielectric medium for a low spatial frequency of the waveguide rotation. We present a general procedure for finding solitonic solutions in spiral waveguiding structures, as well as the variational approach to calculate soliton parameters analytically. Solitons supported by the spiral waveguide perform robust stable rotational oscillatory motion, with the period predicted by their static characteristics, without any signatures of wave radiation or soliton decay over many rotation periods and diffraction lengths.

Experimental investigation into the influence of the oxygen concentration on a pulverized coal swirl flame in oxy-fuel atmosphere

One of the significant advantages of oxy-fuel combustion is the added degree of freedom, given by the possibility of choosing the O2 partial pressure in the oxidizer within a reasonable range, allowing the operation of such combustion systems to be fine-tuned for higher efficiency. However, the influence of the O2 content in the oxidizer on flame structure and characteristic parameters (e.g.: flame temperature, chemical composition) is not fully understood. Therefore investigations were carried out to unveil these effects in a coal flame. For this purpose a swirl burner specifically designed for oxy-fuel combustion was utilized in a pilot scale test furnace (40 kWth). Thereby concentration of oxygen in the oxidizer was varied between 23 and 33 vol% while keeping the total volume flows (inlet velocities) constant. To investigate flame structures, a narrow-band radiation signal was captured using a CCD-camera with an image intensifier and an optical filter. Besides the flame structure, local particle temperatures and gas compositions were examined. The local gas composition was analyzed using an oil-tempered suction probe connected to an FTIR- (Fourier-Transform-Infrared-) spectrometer. Additionally, particle temperatures were estimated from analysis of emitted radiation in the visible part of the spectrum. It was found that the flame structure remains the same for all flames. However the O2 concentration (stoichiometry) influences the local intensity of the combustion. Further, differences in the local gas composition are observed and maximum particle temperatures were found to increase linearly with increasing O2 content in the oxidizer.

Numerical investigation and experimental validation of an infrared measurement approach for surface heat flux distribution using a multi-color-reference

Accurate measurement of heat flux (HF) is significant in both industrial engineering and scientific research. It is acknowledged that the radiative HF can be easily determined by radiometers. In order to measure the conductive or convective HF distribution flowing across a surface, this paper presents a novel non-contact measuring method based on the infrared (IR) technique and inverse heat transfer method (IHTM). In addition, a specially designed multi-color-reference (MCR) which is composed of four sectors with four different known emissivity will be attached to the focused surface in the practical measurement. Therefore, different radiation signals among the four different sectors of MCR as well as the focused surface will be detected by an IR camera, through which a whole radiation temperature map can be obtained. Based on the differences in the radiation temperatures of the surface and MCR, the IHTM can be adopted to yield useful boundary conditions such as emissivity of the surface, convective heat transfer coefficient, and the critical HF distribution. The measuring method presented in this study combines the advantages of contact and non-contact measurement, which can accurately obtain the HF distribution under the difficult-contacted conditions such as the HF monitoring of a boiling furnace, HF estimating of the aerodynamic heating surface, etc. Numerical simulation and experimental verification were organized to justify the newly-developed measuring method. Relative error in the simulation is estimated to be less than 2%, and that in the experiment is calculated to be around 4.23%. The result displays a relatively high precision of the measuring method, demonstrating that such a method can be applied in practical application.

Recurrent neural networks for discrimination of exo-atmospheric targets based on infrared radiation signature

Exo-atmospheric infrared (IR) target discrimination is an important research problem in space attack and defense. The different micro-motion states of the targets result in respective characteristics in the obtained IR radiation intensity sequences, and this difference is difficult to describe intuitively and extract effectively. Few methods can effectively contact the data with the micro-motion model, resulting in a low classification accuracy and difficult to meeting actual application requirements. We set up four types of targets by constructing the micro-motion model of the exo-atmospheric targets, including the warhead and heavy decoy, with spinning and coning motion; and the light decoy and debris, with tumbling motion, to get the IR radiation intensity sequences. We use random projection to improve the discrimination power of recurrent neural network, and to classify the time series of IR radiation intensity. Experimental results demonstrate that random projection recurrent neural network (R-RNN) is more effective than several other typical algorithms in time series classification (TSC) task, which can achieve an excellent target discrimination. We also analyze the effect of noise on the performance of the algorithm.

Whole genome sequencing of melanomas in adolescent and young adults reveals distinct mutation landscapes and the potential role of germline variants in disease susceptibility

Cutaneous melanoma accounts for at least >10% of all cancers in adolescents and young adults (AYA, 15-30 years of age) in Western countries. To date, little is known about the correlations between germline variants and somatic mutations and mutation signatures in AYA melanoma patients that might explain why they have developed a cancer predominantly affecting those over 65 years of age. We performed genomic analysis of 50 AYA melanoma patients (onset 10-30 years, median 20); 25 underwent whole genome sequencing (WGS) of both tumor and germline DNA, exome data were retrieved from 12 TCGA AYA cases, and targeted DNA sequencing was conducted on 13 cases. The AYA cases were compared with WGS data from 121 adult cutaneous melanomas. Similar to mature adult cutaneous melanomas, AYA melanomas showed a high mutation burden and mutation signatures of ultraviolet radiation (UVR) damage. The frequencies of somatic mutations in BRAF (96%) and PTEN (36%) in the AYA WGS cohort were double the rates observed in adult melanomas (Q < 6.0 × 10-6 and 0.028, respectively). Furthermore, AYA melanomas contained a higher proportion of non-UVR-related mutation signatures than mature adult melanomas as a proportion of total mutation burden (p = 2.0 × 10-4 ). Interestingly, these non-UVR mutation signatures relate to APOBEC or mismatch repair pathways, and germline variants in related genes were observed in some of these cases. We conclude that AYA melanomas harbor some of the same molecular aberrations and mutagenic insults occurring in older adults, but in different proportions. Germline variants that may have conferred disease susceptibility correlated with somatic mutation signatures in a subset of AYA melanomas.

Lost and found sunquake in the 6 September 2011 flare caused by beam electrons

The active region NOAA 11283 produced two X-class flares on 6 and 7 September 2011 that have been well studied by many authors. The X2.1 class flare occurred on September 6, 2011 and was associated with the first of two homologous white light flares produced by this region, but no sunquake was found with it despite the one being detected in the second flare of 7 September 2011. In this paper we present the first observation of a sunquake for the 6 September 2011 flare detected via statistical significance analysis of egression power and verified via directional holography and time–distance diagram. The surface wavefront exhibits directional preference in the north-west direction We interpret this sunquake and the associated flare emission with a combination of a radiative hydrodynamic model of a flaring atmosphere heated by electron beam and a hydrodynamic model of acoustic wave generation in the solar interior generated by a supersonic shock. The hydrodynamic model of the flaring atmosphere produces a hydrodynamic shock travelling with supersonic velocities toward the photosphere and beneath. For the first time we derive velocities (up to 140 km s−1) and onset time (about 50 s after flare onset) of the shock deposition at given depths of the interior. The shock parameters are confirmed by the radiative signatures in hard X-rays and white light emission observed from this flare. The shock propagation in the interior beneath the flare is found to generate acoustic waves elongated in the direction of shock propagation, that results in an anisotropic wavefront seen on the solar surface. Matching the detected seismic signatures on the solar surface with the acoustic wave front model derived for the simulated shock velocities, we infer that the shock has to be deposited under an angle of about 30° to the local solar vertical. Hence, the improved seismic detection technique combined with the double hydrodynamic model reported in this study opens new perspectives for observation and interpretation of seismic signatures in solar flares.

Oliver Heaviside: an accidental time traveller.

A little discussed aspect of Heaviside's work in electromagnetics concerned faster-than-light (FTL) charged particles, precursors to the hypothetical tachyon and his discovery that such motion should produce a characteristic radiation signature (now called Cherenkov radiation). When Heaviside wrote, the time travel implications of FTL were not known (Einstein was still a teenager), and in this paper some speculations are offered on what Heaviside would have thought of FTL time travel, and of the associated (now classic) time travel paradoxes, including the possibility (or not) of sending information into the past.This article is part of the theme issue 'Celebrating 125 years of Oliver Heaviside's 'Electromagnetic Theory''.

Industrial radiotracer application in flow rate measurement and flowmeter calibration using 99mTc and 198Au nanoparticles radioisotope

The flow rate or fluid velocity measurement is important to maintain fluid flow quality performance in the systems. This study focuses on determination of volumetric flow rate measurement and to calibrate the conventional flowmeter using industrial radiotracer approach in quadrilateral gas-liquid bubble column reactor. In this work, two different radioisotopes which emit γ-ray have been chosen as radioactive tracer which is 99mTc produced from 99Mo/99mTc radioisotope generator and 198Au nanoparticle form neutron activation at research nuclear reactor TRIGA Mark II. Both radioisotopes representing liquid and solid tracer purposely designed for tracing liquid flow. The peak to peak radiotracer method known as pulse velocity method was applied to determine the volumetric flow rate. The radiation signals were monitored using 4 unit NaI scintillation detectors located at 4 different points nearby the inlet and outlet of the quadrilateral bubble column reactor process stream. The water volume inside the bubble column reactor was fixed at 0.04 m3 and liquid flow rates in this reactor were specified on installed flowmeter at different reference value which is 4 lpm, 8 lpm, and 12 lpm, respectively. The experimental result shows very good linearity and repeatability by following the theoretical equations with less uncertainty in volumetric flow rate measurement. The obtained results also validated the effectiveness of the proposed method for the installed flowmeter calibration efficiency.

Experimental research on noninvasive reconstruction of optical parameter fields based on transient radiative transfer equation for diagnosis applications

The noninvasive reconstruction of optical parameter fields in participating phantom is investigated experimentally based on the measured time-resolved radiative signals, which are detected by the time-correlated single-photon counting system. The discrete ordinate method is employed to solve the forward transient radiative transfer equation to simulate the time-resolved radiative transfer in the physical phantom exposed to ultra-short pulse laser irradiation. On top of that, the sequential quadratic programming algorithm based on the generalized Gaussian Markov random field is applied to solve the inverse problem. To improve the computational efficiency, an adjoint equation technique is adopted to determine the gradient of objective function. Good agreement was obtained between the predicted optical parameter fields and realistic ones. All the reconstruction results demonstrate that the proposed reconstruction methods are proved to be accurate and efficient experimentally.

Simulation of Reflected Solar Radiation for Atmosphere Gas Composition Evaluation for Optical Remote Sensing from Space

At present, in optical remote sensing of atmosphere from space, a new problem class appears: to determine little gas components (carbon dioxide, methane, etc.), which cause greenhouse effect. Concentration of these gases in atmosphere is less than one percent, which rigidly limits accuracy of satellite measurements and of simulating spatial concentration of the radiation (signal) flow reflected by Earth. In the article, a description of simulating signals received by satellite spectrometer in nearinfrared spectrum region is given. The signals are solar radiation passed through an atmosphere layer and reflected from Earth surface. It is calculated based on parametrical radiation atmosphere scattering and absorption model, which takes into consideration both multidimensional atmosphere parameter structure and Earth surface relief. Accounting such information allows you to go from measurement of spatial radiation flux to calculations of gas concentration for an arbitrary geographical Earth surface point and for any time point. As an example, calculations for Fourier spectrometer for spectrum measurement near IR region with an average spectral resolution are presented. The spectrometer was installed on the GOSAT satellite of the Space Agency of Japan. A comparison of computed and of really measured values of the signal received by the satellite shows that deviation for the Sun zenith angle equal to 30o does not exceed 3 %.

Radiative signatures of plasmoid-dominated reconnection in blazar jets

The multi-wavelength spectral and temporal variability observed in blazars set tight constraints on current theoretical emission models. Here, we investigate the relativistic magnetic reconnection process as a source of blazar emission in which quasi-spherical plasmoids, containing relativistic particles and magnetic fields, are associated with the emission sites in blazar jets. By coupling recent two-dimensional particle-in-cell simulations of relativistic reconnection with a time-dependent radiative transfer code, we compute the non-thermal emission from a chain of plasmoids formed during a reconnection event. The derived photon spectra display characteristic features observed in both BL Lac sources and flat spectrum radio quasars, with the distinction made by varying the strength of the external photon fields, the jet magnetization, and the number of pairs per proton contained within. Light curves produced from reconnection events are composed of many fast and powerful flares that appear on excess of a slower evolving envelope produced by the cumulative emission of medium-sized plasmoids. The observed variability is highly dependent upon the orientation of the reconnection layer with respect to the blazar jet axis and to the observer. Our model provides a physically motivated framework for explaining the multi-timescale blazar variability across the entire electromagnetic spectrum.

Clutter removal for measuring low-frequency narrow-band antenna using spectral estimation

AbstractThe measurement accuracy of low-frequency narrow-band antenna is heavily influenced by its environment, which is also difficult to remove the clutter with a time gating. This paper proposes a method to improve the measurement accuracy of low-frequency narrow-band antenna using signal processing technique. The method is to predict the unknown value out of received original signal with an auto-regressive model (AR model) based on modern spectral estimation theory, and the parameters in AR model are calculated by maximum entropy spectral estimation algorithm. Thus, a wideband signal compared with the original band is obtained, and then the time-domain resolution is enhanced. The time gating is more exactly to separate the antenna radiation signal from multipath signals. The simulation and experimental results show that about 50% extended data for each ends of original band can be obtained after spectral extrapolation, and the time-domain resolution after extrapolation is twice than the original narrow-band signal, and the influence of measurement environment can be eliminated effectively. The method can be used to improve accuracy in actual antenna measurement.

Experimental investigation of the influence of excitation signal on radiation characteristics of capacitive micromachined ultrasonic transducer

CMUT based on micro-electro-mechanical systems (MEMS) technology has a broad application prospects and has become the mainstream transducer for the new generation of ultrasound imaging systems. In this paper, based on the 16-element linear CMUT array chip that has been manufactured, an experimental system was built to investigate the radiation characteristic of CMUT. The influence of the parameters such as the DC bias voltage, the amplitude and period number of the AC excitation signal on the radiation signal is analyzed comprehensively. The experimental results are consistent with the results of the simulation analysis previously obtained by using the state equation-SIMULINK model. These experimental investigation and analysis results provide effective data support and reference for further optimization of design parameters and design of imaging systems, which lay a good application foundation.

Effect of axial magnetic field tapering on whistler-pumped FEL amplifier in collective Raman regime operation

The dispersion relation of the FEL Amplifiers is sensitive to the linear tapered strong axial magnetic fields, electron cyclotron frequency and plasma frequency of electrons. For the synchronism of the pumped frequency, it should be closed to electron cyclotron frequency which is resonantly enhanced the wiggler wave number that produces the amplifier radiation for higher frequency from sub millimeter wave to optical ranges. The guiding of radiation signal into the waveguide and charge neutralization phenomenon, the beam density should be greater than the background plasma density with tapered strong axial magnetic field. It is quite considerable that radiation signal slowed down at much higher background plasma density comparable to the density of beams and enhanced the instability growth rate also. In Raman Regime operation, the growth rate decreases as increases with operation frequency of the amplifier, however, the growth rate is larger in this regime. It is noted that as increases with background plasma density, the beat wave frequency of the Ponderomotive waves is increases thus the mechanism of background plasma density can serve for tenability of the higher frequencies. The tapering of the strong guided magnetic field is a crucial role for enhancing the efficiency of the net transfer energy as well as reduction of interaction region along the axis. It is observed that, an efficiency of the transfer energy enhanced by while the reduction along the interaction region of about with the variation of tapering in a strong axial guided magnetic fields.

The polarization characteristics of ELF/VLF waves generated via HF heating experiments of the ionosphere by EISCAT

This paper presents the experimental results of modulation and heating of the ionosphere using the European Incoherent Scatter facility in Troms ϕ, Norway, heating facility. The frequency characteristics of the excited extremely low frequency (ELF)/very low frequency (VLF) radiation sources in the amplitude modulated (AM) and dual-beam beat-wave (BW) modes are compared, and the polarization of the horizontal ELF/VLF magnetic field received at 15 km from the heating facility is studied. The results show that in the AM mode, the amplitude of the ELF/VLF signal decreases as the radiation frequency increases when the amplitude of the ELF/VLF signal reaches the maximum at 2017 Hz. In the BW mode, the maximum appears at 2017 Hz, but the overall amplitude of the ELF/VLF signal increases as the radiation frequency increases. The AM and BW modes have different frequency characteristics on ELF/VLF radiation sources formed by modulation and heating of the ionosphere. When the frequency is low, the amplitude of the ELF/VLF signal excited by the AM mode is greater than that excited by the BW mode, but as the frequency increases, the BW mode performs better than the AM mode. Under the same background conditions, the polarization characteristics of the ELF/VLF radiation signals excited by the AM and BW modes are different. The former tends to produce circularly polarized waves, while the latter produces linearly polarized waves.

Passive detection parameter measurement of azimuth and frequency based on single vector sensor

This paper mainly studies the measurement technology of passive detection parameters based on single vector sensor. Ship radiated noise contains a lot of target information, so the extraction of the line noise of the ship's radiated noise is of great significance in the measurement of passive detection parameters. The radiation noise of the ship is a broadband spectrum modulated by the spectral signal envelope. In this paper, the mathematical model of the radiation noise of the ship is simulated and the demodulation of the ship's radiated noise is carried out by using the square demodulation and the absolute value demodulation. The average azimuth and complex intensifier are used to estimate and analyze the target azimuth, and the estimated angle is statistically processed by histogram and weighted histogram. For the frequency estimation technique, the adaptive frequency estimator based on the adaptive notch filter and the adaptive LMS (least mean square) algorithm is chosen to study the target signal frequency.Through the verification of the simulation experiment, the azimuth estimation technique and the adaptive frequency estimation technique are feasible. By estimating the azimuth sequence and frequency sequence of the target radiation signal, the relevant information of the target can be obtained, so it is of great significance in the research of underwater acoustic detection technology.

Particle acceleration in relativistic magnetic reconnection with strong inverse-Compton cooling in pair plasmas

ABSTRACT Particle-in-cell (PIC) simulations have shown that relativistic collisionless magnetic reconnection drives non-thermal particle acceleration (NTPA), potentially explaining high-energy (X-ray/γ-ray) synchrotron and/or inverse Compton (IC) radiation observed from various astrophysical sources. The radiation back-reaction force on radiating particles has been neglected in most of these simulations, even though radiative cooling considerably alters particle dynamics in many astrophysical environments where reconnection may be important. We present a radiative PIC study examining the effects of external IC cooling on the basic dynamics, NTPA, and radiative signatures of relativistic reconnection in pair plasmas. We find that, while the reconnection rate and overall dynamics are basically unchanged, IC cooling significantly influences NTPA: the particle spectra still show a hard power law (index ≥ −2) as in non-radiative reconnection, but transition to a steeper power law that extends to a cooling-dependent cut-off. The steep power-law index fluctuates in time between roughly −3 and −5. The time-integrated photon spectra display corresponding power laws with indices ≈−0.5 and ≈−1.1, similar to those observed in hard X-ray spectra of accreting black holes.