Ash characteristics in controlled diode laser pyrolysis of chlorinated rubber

This paper describes the effects of 60 W High Power Diode Laser (HPDL) beams on the removal of chlorinated rubber (CR) paint from concrete surfaces and the ash particles generated from this process. The physical characteristics, including shape and size distribution of the removed and collected airborne CR particles, down to a size of around 1 μm in diameter, were determined using optical microscopy and image analysis. The shape of the particles observed was highly irregular, displaying no symmetry. The size distribution of the collected particles was found to range between 1–2000 μm, with the maximum concentration being found between 29 and 60 μm. The chemical characteristics of the CR ash particles were investigated by means of ESEM and EDX techniques. From a comparative analysis, it was found that the concentration of chlorine within the CR material was significantly reduced after HPDL treatment. This, together with DTA/TGA results indicated a combustive degradation of the CR polymer through the interaction with the process gas, oxygen, and the laser irradiation. Also, a strong correlation between laser power and average particle sizes has been found, with higher powers generally producing larger particle sizes. Opposite effects have been found by changing the oxygen flow rate, with higher oxygen flow producing, on average, smaller particles. An interpretation of the combustion process, as well as a brief discussion on operational safety and environmental impact of the products is attempted.     

Screening of collective cyclotron resonance in inversion layers on InSb

Cyclotron Resonance (CR) of inversion electrons on InSb is studied in parallel magnetic fields with normally incident light. Whereas in this Voigt configuration collective CR is observed in thin bulk samples, we observe single particle CR in the case of inversion layers. The apparent screening of the collective mode is explained by the inhomogeneity of the inversion electron gas in crossed electric and magnetic fields.     

电子束发散角的直接测量技术模拟研究北大核心CSCD

切伦科夫辐射是一种方向性极好的辐射,其辐射能量发射方向严格地与带电粒子的运动方向相关,辐射光携带了带电粒子的方向信息,利用这种特性可以进行电子束发散角及其分布的测量。在基于切伦科夫辐射原理的基础上,考虑电子与物质作用时的多重库仑散射、电离等效应,进行了电子束发散角测量的蒙特卡罗数值模拟程序的建模工作,并完成了理想电子束及具有发散角分布的电子束的测量技术模拟工作。大量模拟结果显示,这种测量方法是可行的,具有对电子束发散角分布进行直接测量的能力,并且其测量系统结构简单。     

Analysis of ground level enhancement on January 6, 2014

Variations in the rigidity spectrum and anisotropy of cosmic rays during ground level enhancement (GLE) on January 6, 2014, is investigated using ground-based observations of cosmic rays (CRs) from the worldwide network of stations and spacecraft measurements obtained via a spectrographic global survey. The CR rigidity spectrum and relative variations in the intensity of CRs with rigidity of 4 GV are presented in the solar–ecliptic geocentric coordinate system in certain periods of the investigated event. It is shown that protons were accelerated during this GLE up to a particle rigidity of R ~ 2.4 GV. In the ~0.3 to ~2.4 GV range of rigidity, the CR differential rigidity spectra during the considered event were described by neither a power function nor an exponential function of particle rigidity. At the time of GLE, the Earth was in a loop-like IMF structure.     

Test of colour reconnection models using three-jet events in hadronic Z decays

Hadronic Z decays into three jets are used to test QCD models of colour reconnection (CR). A sensitive quantity is the rate of gluon jets with a gap in the particle rapidity distribution and zero jet charge. Gluon jets are identified by either energy-ordering or by tagging two b-jets. The rates predicted by two string-based tunable CR models, one implemented in JETSET (the GAL model), the other in ARIADNE, are too high and disfavoured by the data, whereas the rates from the corresponding non-CR standard versions of these generators are too low. The data can be described by the GAL model assuming a small value for the R₀ parameter in the range 0.01-0.02.     

Electric dipole moments of charged particles

The existence of an electric dipole moment (edm) on a fundamental atomic particle would imply violation of both parity and time-reversal invariance. An edm on a neutral particle is detectable through its interaction with an applied electric field. The search for edms on charged particles such as the nucleus or the electron is made difficult by their acceleration in an electric field; conversely, a charged particle in equilibrium must be shielded from the field and the edm interaction will then vanish. A number of ingenious ways around this shielding theorem are discussed, as are the use of polar molecules to amplify the residual edm interactions. A range of atomic and molecular beam and optical pumping experiments are described and the results tabulated. The implications for particle theories beyond the standard model are briefly summarized.     

Particle identification by dielectric track detectors

Abstract

Chemical reactivity along the trajectory of a charged particle in a dielectric solid depends on the density of radiation-damaged species. In inorganic crystals such as are found in meteorites, cosmic rays can be identified by etching for a long time and measuring the entire etchable ranges of the slowing particles, which are related to their atomic numbers. In plastics, the etching rate is an increasing function of radiation damage density. Measurements of etched ‘cone’ lengths at different points along the trajectory of a particle that passes thruough several sheets provide a very sensitive measure of atomic number. In favorable cases it is possible even to resolve isotopes with the same atomic number.

In addition to serving as a general review of work on particle identification using these two schemes, this report provides some unpublished experimental details that are useful in achieving high resolution and reports some new, unpublished measurements.     

Ultra high energy cosmic rays: Identification of possible sources, energy spectra, and propagation

This review is devoted to the problem of the origin of cosmic rays (CR) with energy E >4 × 10¹⁹ eV. The review mainly deals with the hypothesis of CR acceleration in active galactic nuclei (AGN). The review consists of the following five sections: Introduction, three chapters, and Conclusions. The following points are considered in Introduction: shower arrays for detecting ultra high energy cosmic rays (UHECR), the Greisen-Zatsepin-Kuzmin (GZK) cutoff, and the hypotheses of the UHECR origin. Since CRs are of extraterrestrial origin, some astrophysical data used in CR physics are presented in a special section. The identification of UHECR sources with energies E > 4 × 10¹⁹ eV is analyzed in Chapter 2. Chapter 3 deals with CR acceleration in sources and CR escape from sources. Chapter 4 is devoted to particle propagation in intergalactic space with allowance for CR interaction with the microwave background radiation and energy losses (blackbody or GZK cutoff). The propagation of UHECR protons is analyzed and their spectra at the Earth are calculated numerically. In Conclusions, we formulate the results and list the nuclear data needed to develop the model in more detail, namely, to study the propagation of CR nuclei in intergalactic space and to analyze the UHECR composition at the Earth.     

Thermalization of atomic particles in gases

A model of the atomic particle thermalization process due to scattering in various gases with application of the Born-Mayer potential is presented. The thermalization process of atomic particles using the statistical modeling method is considered. Our thermalization model is adapted to a wide class of atomic collision partners, takes into account the real energy and angular distributions of atomic particle sources, and makes it possible to calculate the parameters of the spatial zone of their thermalization and transfer into the diffusion motion mode. The energy range of applicability for the atomic particle thermalization model is interesting for many applied problems in plasma physics, gas discharge, and ion plating processes.     

Classifying cosmic-ray proton and light groups in LHAASO-KM2A experiment with graph neural network

The precise measurement of cosmic-ray(CR) knees of different primaries is essential to reveal CR acceleration and propagation mechanisms, as well as to explore new physics. However, the classification of CR components is a difficult task, especially for groups with similar atomic numbers. Given that deep learning achieved remarkable breakthroughs in numerous fields, we seek to leverage this technology to improve the classification performance of the CR Proton and Light groups in the LHAASO-KM2A experiment. In this study, we propose a fused graph neural network model for KM2A arrays, where the activated detectors are structured into graphs. We find that the signal and background are effectively discriminated in this model, and its performance outperforms both the traditional physicsbased method and the convolutional neural network(CNN)-based model across the entire energy range.     

基于简单碰撞理论煤粉燃烧动力学模型的研究-PART Ⅲ:氧气可达比表面积

根据不同温度下氧分子平均自由程的大小,比较了小孔、中孔和大孔中三种扩散速率与煤焦表面燃烧速度的大小.研究表明2000 K以内,颗粒表面分子扩散速率比氧化反应速率大1个数量级以上,过度扩散速率不小于氧化速率.温度小于1200K时,燃烧速率比Knudsen扩散速率小1～5个数量级,扩散孔径小于15～28 nm,反应主要在内外表面进行;1200～1600K时,燃烧速率与Knudsen扩散速率相当,扩散临界孔径28～38 nm,反应在外表面及浅层内表面进行;温度1600K以上时,Knudsen扩散速率比燃烧速率小1个数量级,孔径38～50 nm以下内表面上碳的氧化速度受扩散控制.煤焦的氧化主要发生在Knudsen扩散临界孔径10～50 nm以上的氧气可达表面上.     

Diffusion blocking at low particle concentration

The rate equations describing classical particle hopping in periodic lattices are integrated to obtain exact, self-consistent expressions for the occupancy correlation functions at low atomic concentration. The long-wavelength, small-frequency behaviour is analyzed analytically. Exact results for labelled particle diffusion are obtained which properly include the correlation and atomic blocking effects.     

基于智能算法的CR39径迹刻蚀过程模拟

CR39可以用于激光等离子物理实验中的离子探测,并给出离子数目、种类和能量信息。通过采用唯象模型,利用离子在CR39中径迹形成的阻止本领动力学方程以及粒子群智能算法对径迹形成的过程进行了数值化模拟,研究了CR39中离子径迹在刻蚀过程中的演化过程,获得了入射离子能量和径迹直径、深度的对应关系,并且发现当离子射程与刻蚀深度相等时,径迹深度最大,给出了利用总刻蚀时间计算最大径迹深度对应的临界能量的公式。     

Ultraprecise atomic mass measurement of the alpha particle and 4He

The atomic masses of the alpha particle and 4He have been measured by means of a Penning trap mass spectrometer which utilizes a frequency-shift detector to observe single-ion cyclotron resonances in an extremely stable 6.0 T magnetic field. The present resolution of this instrument approaches 0.01 ppb [10 ppt (parts per trillion)] and is limited primarily by the effective stability (<5 ppt/h) of the magnet over hundreds of hours of observation. The leading systematic shift [at -202(9) ppt] is due to the image charge located in the trap electrodes. The new value for the atomic mass of the alpha particle is 4 001 506 179.147(64) nu and the corresponding value for the mass of 4He is 4 002 603 254.153(64) nu (nu=10(-9) u). The 16 ppt uncertainty is at least 20 times smaller than any previous determination.     

Two-Mode Normal Squeezing of a Nondegenerate Bimodal Multiquanta Jaynes–Cummings Model in the Presence of Stark Shifts

We investigate the two-mode normal squeezing in the presence of Stark shiftsfor a generalized Jaynes–Cummings Model (JCM) with a two-level particle (atomor trapped ion) and two modes interacting nonlinearly. The effect of the relativephase between the atomic superposition state and the coherent field in the presenceand absence of the Stark shift on squeezing is studied. Different values for theparameters of the atomic coherent state are taken.     

Quantum reflection times for attractive potential tails

When a wave packet with a narrow momentum distribution is quantum reflected in a purely attractive potential proportional to -1/r(alpha), alpha>2, it generally experiences a time gain compared to a free particle reflected at r=0; for alpha=3 and very low energies there are large time delays. In quantum reflection of an atomic beam by a surface, such a time gain (delay) represents an apparent plane of reflection which is shifted in front of (behind) the surface. The quantum reflected wave is always delayed with respect to the classical particle accelerated in the attractive potential.     

On the measurement of proper time in general relativity by means of atomic clocks

The quantity , which is called the proper time of a particle in the general theory of relativity, has the following meaning: it is the time measured by clocks moving with the particle. The question arises of how proper time is measured by real clocks. At present, atomic clocks are the most accurate, being stabilized by the frequency of intraatomic transitions. In the present paper, the stability of the reference frequency of such clocks is considered, i.e., the possible discrepancies between the proper time and the time measured by atomic clocks.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 99–102, January, 1981.     

Growth instabilities of vapor deposited films: atomic size versus deflection effect

Two previously suggested, physically distinct mechanisms for a growth instability of vapor deposited films, the finite atomic size effect and the particle deflection effect due to interatomic attraction, are reconsidered, further analyzed, and compared. We substantiate why the instability caused by interatomic attraction must be considered as the truly underlying instability mechanism. We demonstrate that aspects of the structure zone model of Movchan and Demchishin can also be consistently explained using the growth instability induced by particle deflection instead of the instability arising from the atomic size effect. Most significantly we show that, for vapor deposited amorphous Zr₆₅Al_7.5Cu_27.5-films, the growth instability due to the atomic size effect cannot be present. Received 12 December 2001 Published online 6 June 2002     

The kinetics of homogeneous nucleation of silver nanoparticles stabilized by polymers

The formation of Ag nanoparticles synthesized by homogeneous nucleation, stabilized by polymers (PVA and PVP) was monitored by UV–Vis spectrophotometry and transmission electron microscopy. Our aim was to differentiate between the two main phases of particle formation, i.e. nucleation and growth and to characterize their rates with the help of appropriate kinetic equations. Time resolved spectrophotometric measurements revealed that particle formation is an autocatalytic process: a slow, continuous nucleation phase (3–5 min) is followed by a rapid, autocatalytic growth phase where the maximal particle size is 5–7 nm. By freezing the reaction mixture, the process of particle growth can be followed from 5 to 40 min on TEM pictures. The first order rate constants were calculated and they are strongly depend on the polymer concentration. If the growing particles are attached by PEI to the surface of a solid support, the formation of silver nanoparticles can also be followed by atomic force microscopy (AFM) and we can control the particle growth on mica surface. The cross section analysis of the pictures show, that the particle growing process can be also monitored at solid–liquid interface.     

Quantum Wave Equation of Non-conservative System

It is well known that Schr?dinger’s equation is only suitable for the particle in conservative force field. In atomic and molecular field, a particle can suffer the action of non-conservative force. In this paper, a new quantum wave equation is proposed, which can describe the particle in non-conservative force field. We think the new quantum wave equation can be used in many fields.