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1.
In partially ionized plasmas, the energy transferred to electrically charged species by the electromagnetic field can be partly channelized to the population of neutrals, due to interspecies collisional processes. Depending on the relative density of neutrals, these effects may govern the collective plasma dynamics by drastically modifying particle dynamics and energy‐transport processes with respect to the fully ionized plasma‐approximation models. In this work, the influence of the ionization ratio ri on a partially ionized plasma is analysed by means of a three‐species one‐dimensional kinetic model to compute transient and steady state velocity‐dependent distribution functions. The conservative collision operators accounting for charge–charge and charge–neutral interactions allow studying several plasma scenarios with the same entire number of particles per unit of volume but for an increasing ri parameter, in the presence of a modulated signal‐like electric field. For a sequence of plasma scenarios of fixed ri, ranging from typical weakly ionized to highly ionized plasma values ri ~ 10?7–10?4, the mass species flows are examined. These flows behave linearly with respect to ri up to a value ri ? 10?5 from which the quasi‐linear dependence is critically altered. The convection–diffusion equations are solved with the semianalytical Propagator Integral Method, which behaves well to deal with conservative operators, density, and field discontinuities, allowing for the use of collision terms of disparate time and spatial characteristic scales. The results can be relevant to a wide class of plasma systems and to analyse the ionization ratio effects on transport coefficients. 相似文献
2.
Synthesis of Self‐Stabilized Poly(N‐(3‐Amidino)‐Aniline) Particles and their CO2‐Responsive Properties
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Novel CO2‐responsive conductive polymer particles based on poly(N‐(3‐amidino)‐aniline) (or PNAAN) are reported in this work. A CO2‐responsive N‐(3‐amidino)‐aniline (NAAN) monomer is firstly synthesized with the pendant amidine group at the meta‐position of aniline (AN) and subsequently polymerized into the PNAAN polymer by chemical oxidation. Self‐assembly of PNAAN in turn forms the polymer particles. In the strong or weak acid media, the amidine group protonates into cationic amidinium and self‐stabilizes the PNAAN particles without the use of any stabilizers. The reaction media are found to affect the polymerization rate and self‐assembly of particles, and hence the size and size distribution of the resultant particles. The particles synthesized in strong basic media show CO2‐responsvie properties since the H+ released by dissolved CO2 (dCO2) can protonate the amidine group into hydrophilic amidinium group and result in swelling of the PNAAN particles. Zeta‐potential measurements show the reversible change of particle surface charges in the presence and absence of dCO2. Dynamic light scattering (DLS) measurements show the particle size linearly changed with dCO2 concentration in the range of 5 × 10?4 and 2.5 × 10?2 atm. This is the first reported CO2‐responsive polyaniline (PANI) particles for dCO2 sensing or reversible fixation of CO2. 相似文献
3.
H. Himura H. Wakabayashi Y. Yamamoto A. Sanpei S. Masamune M. Isobe S. Okamura K. Matsuoka 《Hyperfine Interactions》2007,174(1-3):83-88
Experimental studies on nonneutral (pure electron) plasmas of finite temperature, trapped in helical closed magnetic surfaces
have been conducted. The helical electron plasmas are produced with thermal electrons launched from the outside of the last
closed flux surface (LCFS). About 150 μs after the electron injection, the plasmas reach equilibrium state. Around the LCFS, a steep gradient of plasma space potential
φ
s
is formed. The corresponding radial electric field is about 2.5 kV/m. On the other hand, around the magnetic axis of helical
magnetic surfaces, φ
s
is almost constant, indicating that there are little electrons there. The volume-averaged electron density is on the order
of 1013 m–3, smaller than the Brillouin density limit. The confinement time seems to be limited by a disruptive instability, and is so
far about 1.5 ms.
相似文献
4.
开展了超短超强激光与稀薄等离子体相互作用实验,在实验中采用等离子体单色成像法观测等离子体发光图像,捕捉到了近乎对称的环形等离子体发光结构. 在对实验结果进行分析并与理论预言进行比较后确认这是由激光-等离子体相互作用形成的后孤立子云外围的高密度等离子体壳层发光所致. 同时通过对等离子体通道的观测还发现,孤立子的形成对超短超强激光在稀薄等离子体中的传输产生了非常大的影响.
关键词:
超短超强激光
稀薄等离子体
单色成像
后孤立子 相似文献
5.
It is shown that the collective dust‐dust attraction is enhanced by strong magnetic fields larger then the critical magnetic field determined be the condition that the Lorentz force acting on ions is larger than the friction of ions on dust grains related with the dust drag. It is demonstrated that with an increase of the magnetic field the deepness of the attraction potential well is increased in all directions to the magnetic field, that the distance of the minimum of the potential well along the magnetic filed (in both directions) is changed only slightly while the distance of the minimum of the attraction potential well is substantially decreased for directions perpendicular to the magnetic field. This means that the structures formed by attraction forces such as plasma crystals will be compressed perpendicular to the magnetic field (inter‐dust distance becomes smaller) and that the melting transition temperature should increased with an increase of the strength of the magnetic field. Numerical results are presented for dependence of the attraction potential well on the ratio of the strength of the magnetic field to the critical magnetic field strength, on the parameter P = ndZd/ni (nd and ni being the dust and ion densities respectively) and on the temperature ratio τ = Ti/Te (Te and Ti being the electron and ion temperatures respectively). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
6.
Facile Synthesis of Gd(OH)3‐Doped Fe3O4 Nanoparticles for Dual‐Mode T1‐ and T2‐Weighted Magnetic Resonance Imaging Applications
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Hongdong Cai Xiao An Shihui Wen Jingchao Li Guixiang Zhang Xiangyang Shi Mingwu Shen 《Particle & Particle Systems Characterization》2015,32(10):934-943
The facile hydrothermal synthesis of polyethyleneimine (PEI)‐coated iron oxide (Fe3O4) nanoparticles (NPs) doped with Gd(OH)3 (Fe3O4‐Gd(OH)3‐PEI NPs) for dual mode T1‐ and T2‐weighted magnetic resonance (MR) imaging applications is reported. In this approach, Fe3O4‐Gd(OH)3‐PEI NPs are synthesized via a hydrothermal method in the presence of branched PEI and Gd(III) ions. The PEI coating onto the particle surfaces enables further modification of poly(ethylene glycol) (PEG) in order to render the particles with good water dispersibility and improved biocompatibility. The formed Fe3O4‐Gd(OH)3‐PEI‐PEG NPs have a Gd/Fe molar ratio of 0.25:1 and a mean particle size of 14.4 nm and display a relatively high r2 (151.37 × 10?3m ?1 s?1) and r1 (5.63 × 10?3m ?1 s?1) relaxivity, affording their uses as a unique contrast agent for T1‐ and T2‐weighted MR imaging of rat livers after mesenteric vein injection of the particles and the mouse liver after intravenous injection of the particles, respectively. The developed Fe3O4‐Gd(OH)3‐PEI‐PEG NPs may hold great promise to be used as a contrast agent for dual mode T1‐ and T2‐weighted self‐confirmation MR imaging of different biological systems. 相似文献
7.
A. I. Chugunov 《等离子体物理论文集》2012,52(2):114-117
It is shown that the Coulomb energy U of fully ionized ionic mixture can be written as a sum over partial contributions of ion species j: U = T Σj Nju (Γj, yj) (generalized linear mixing rule). In contrast to the traditional linear mixing rule ULM = T Σj NjuOCP(Γj), applicable for strong coupling, the partial contribution function u depends not only on Γj, but on an additional parameter yj = (rD/rDOCP)2 also. Here rD and rDOCP are Debye radiuses in the mixture and in the one component plasma at coupling parameter Γj, correspondingly. The parameter yj does not depend on a specific composition of the mixture, but on the Debye radius rD only, making function u (Γj, yj) universal. The generalized linear mixing rule can be applied at any coupling parameter, if ionic mixture is not crystallized. It reproduces results of the Debye‐Hückel theory at weak coupling and traditional linear mixing rule at strong coupling. It can be easily applied to the complicated mixtures, composed of a large number of ion species. Since yj is temperature independent, the Coulomb contribution to Helmholtz free energy of the mixture can also be presented in a form of generalized linear mixing rule (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
M. Ya. Amusia A. S. Baltenkov L. V. Chernysheva Z. Felfli A. Z. Msezane 《Journal of Experimental and Theoretical Physics》2006,102(1):53-60
It is demonstrated that in photoabsorption of the 4d
10 subshell of a Xe atom in molecular Xe@C60, the 4d giant resonance that characterizes the isolated Xe atom is distorted significantly. The reflection of photoelectron waves
by the C60 shell leads to profound oscillations in the photoionization cross section such that the Xe giant resonance is transformed
into four strong peaks. Similarly, the angular anisotropy parameters, both dipole and nondipole, are also modified. The method
of calculation is based on the approximation of the C60 shell by an infinitely thin bubble potential that leaves the sum rule for the 4d-electrons almost unaffected, but noticeably modifies the dipole polarizability of the 4d-shell.
The text was submitted by the authors in English. 相似文献
9.
Population densities of HeI and HeII excited states are calculated from a collisional radiative model for non-LTE optically
thin helium plasmas. Effect of direct ionisation-excitation of HeI to HeII states on the population density of HeII states
is shown. Relaxation times for HeI states calculated from the CR model is reported forT
e from 3 to 18 eV andn
e from 109 to 1016 cm−3.
Part of a research project supported by the Department of Atomic Energy. 相似文献
10.
利用时间分辨光谱技术,研究了激光诱导Cu等离子体中激发态5s′4D7/2的形成及其辐射跃迁的瞬态特性.结果表明:在激发态5s′4D7/2原子的制备过程中,电子离子复合、粒子间碰撞机理在不同时刻分别起主导作用.激光峰值到达金属表面后500ns期间,粒子间的剧烈碰撞作用使得激发态5s′4D7/2主要通过向低能态4p′4F9o/2跃迁来转移能量.500ns以后,激发态5s′4D7/2通过以相同的概率辐射CuI465.11nm和CuI529.25nm特征谱线向低能态4p′4F9o/2和4p′4D7o/2转移能量. 相似文献
11.
12.
Early afterglows of N2 and N2‐O2 flowing microwave discharges are characterized by optical emission spectroscopy. The N and O atom and N2(A) metastable molecule densities are determined by optical emission spectroscopy after calibration by NO titration for N‐atoms and measurements of NO and N2 band intensities for O‐atoms and N2(A) metastable molecules. By using N2 tanks with 50 and 10 ppm impurity, it is determined in the afterglow an O‐ atom impurity of 150‐200 ppm. Variations of the N and O‐atom and N2(A) metastable molecule densities are obtained in the early afterglow of N2–(9·10–5–3·10–3)O2 gas mixtures. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
13.
应用群论及原子分子反应静力学方法推导了TiO分子基态(X3Δr)的离解极限.采用不同的计算方法,包括密度泛函B3LYP,B3P86,BP86,B3PW91和MP2,MP4方法,结合不同基组计算了TiO分子基态的平衡核间距、能量和振动频率.研究表明,使用B3LYP方法,对O原子使用6-311+G基组,Ti原子使用6-311+ +G**基组时计算得到的平衡几何结构、分子离解能和谐振频率与实验值符合得最好.使用优选出的方法和基组对T
关键词:
TiO
势能函数
光谱常数
密度泛函理论 相似文献
14.
A. Derevianko W. R. Johnson V. D. Ovsyannikov V. G. Pal’chikov D. R. Plante G. von Oppen 《Journal of Experimental and Theoretical Physics》1999,88(2):272-277
We use the relativistic configuration-interaction method and the model potential method to calculate the scalar and tensor
components of the dipole polarizabilities for the excited states 1s3p
3
P
0 and 1s3p
3
P
2 of the helium atom. The calculations of the reduced matrix elements for the resonant terms in the spectral expansion of the
polarizabilities are derived using two-electron basis functions of the relativistic Hamiltonian of the atom, a Hamiltonian
that incorporates the Coulomb and Breit electron-electron interactions. We formulate a new approach to determining the parameters
of the Fuss model potential. Finally, we show that the polarizability values are sensitive to the choice of the wave functions
used in the calculations.
Zh. éksp. Teor. Fiz. 115, 494–504 (February 1999) 相似文献
15.
We analyze the quantum statistical treatment of bound states in Hydrogen considered as a system of electrons and protons. Within this physical picture we calculate analytically isotherms of pressure for Hydrogen in a broad density region and compare to some results from the chemical picture. Our study is restricted to the range of intermediate temperatures 104K < T < 105K and not too high densities n < 1024 protons per cm3, the formation of molecules is neglected. First we resume in detail the two transitions along isotherms: (i) formation of bound states occurring by increasing the density from low to moderate values, (ii) the destruction of bound states in the high density region, modelled here by Pauli‐Fock effects. Avoiding chemical models we will show, why bound states according to a discrete part of the spectra occur only in a valley in the T‐p plane. First we study virial expansions in the canonical ensemble and then in the grand canonical ensemble. We show that in fugacity representations the population of bound states saturates at higher density and that a combination of both representations provides quickly converging equations of state. In the case of degenerate systems we calculated first the density‐dependent energy levels, and find the pressure in Hartree‐Fock‐Wigner approximation showing the prominent role of Pauli blocking and Fock effects in the selfenergy (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
16.
17.
Sumana Chakraborty Yew Kam Ho 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(1):59-65
This work presents an investigation on the doubly excited 1S
e
autoionizing states of screened helium atom lying below the n = 4 threshold of the He+ ion. The potential generated in this system is represented by a Yukawa type potential. We have employed complex-coordinate
rotation method, as it is a powerful scheme to study high lying resonances. Hylleraas type wave function is used to consider
the correlation effect between all the charged particles. Our resonance parameters for the resonances lying below the He+ (n = 2) threshold agree well with those of the existing calculations by using the stabilization method. Resonances associated
with higher thresholds are new calculations. All the present results are well converged with basis length N = 444. 相似文献
18.
An investigation of the probability of hydrogen atom ionization by ultra‐short electromagnetic pulses is carried out in the frame of perturbation theory We consider the case when the electric field strength amplitude E0 in a pulse by two orders lower than characteristic atomic field strength Ea (Ea ? 5.1 · 109 V/cm). A detailed investigation of the dependence of the probabilities on the pulse duration was performed for Gaussian pulse shapes. In the case where the carrier frequency of the Gaussian pulse is larger than the atomic ionization potential, the probability goes to the standard limit of perturbation per unit time. At the same pulse durations, the probabilities for carrier frequencies less than the ionization potential go to zero. The frequency dependence of the ionization probability becomes equal to the standard threshold dependence with increasing pulse duration time. A comparison between the ionization effects caused by wavelet pulses without carrier frequency and Gaussian pulses with carrier frequency shows that the same ionization probability values are achieved when the pulse carrier frequency is detuned by about 20% from the ionization threshold. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
19.
Aneta Slodczyk Marie‐Hlne Limage Philippe Colomban Oumaya Zaafrani Frdric Grasset Johan Loricourt Batrice Sala 《Journal of Raman spectroscopy : JRS》2011,42(12):2089-2099
The high‐pressure Raman studies of pure, Yb‐modified, protonated and non‐protonated SrZrO3 dense ceramics were performed between 0.1 and 40 GPa using a diamond anvil cell. Lanthanide‐modified, protonated SrZrO3 perovskites are potential materials for electrolytic membrane in fuel cells and electrolysers working at medium temperature. The comparison of the Raman spectra shows important differences in the pressure behaviour between the pure and Yb‐modified SrZrO3 ceramics. SrZrO3 exhibits a rigid structure without any structural modification, whereas for both SrZr0.93 Yb0.07 O2.965 and SrZr0.93 Yb0.07 O2.962 H0.003 a sequence of structural modifications at 10, 20 and 35 GPa is revealed. The character of these structural modifications is very similar to that observed as a function of the temperature (orthorhombic Pnma 750 °C → pseudo‐tetragonal Imma 840 °C → tetragonal I4/mcm 1070 °C → cubic Pm3m), which suggests that they can be considered as the phase transitions. Despite the low level of proton content (0.3% mole/mole), significant difference between protonated and non‐protonated compounds is observed for the 700–750 cm−1 doublet assigned to the Zr O octahedron stretching mode, perturbed by an oxygen atom vacancy and/or neighbouring Yb ion. The location of proton is discussed. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
20.
M. Ghanashyam Krishna A.K. Kapoor M. Durga Prasad V. Srinivasan 《Physica E: Low-dimensional Systems and Nanostructures》2006,33(2):359-362
It is demonstrated that the chemical potential of bosons trapped in a harmonic potential shows a discontinuity as a function of the number of particles in the system. In the model used, it is shown that if the number of particles is of the order of 106 or greater, bulk-like behaviour is exhibited by the system. This translates to a ratio of V/Vc>106 for bulk behaviour, where V is the crystallite volume of the experimental sample and Vc is the volume of the unit cell. Several experimental results covering a wide range of physical phenomena that corroborate the fact that such a number-induced phase transition indeed exists are presented. 相似文献