Showing papers by "China Academy of Engineering Physics published in 2001"
TL;DR: In this paper, the calculations of density functional theory at the B3LYP/3-21G* level have been employed to optimize the 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)CH2F2 complex.
31 citations
31 citations
TL;DR: The hot-electron temperature obtained from electron spectra and absorption experiments implies that resonance absorption is partially responsible for the generation of hot electrons.
Abstract: Characteristics of hot electrons produced in the interaction of femtosecond laser pulses with foil targets were investigated at a moderate laser intensity Both outgoing and ingoing hot electrons from the femtosecond laser plasma were studied A collimated jet of outgoing hot electrons was observed in the target normal direction An ingoing energetic hot-electron beam was found in the laser propagation direction, while the low-energy ingoing electrons spread into wider cone angle due to the collisional effects in the plasma and target material These observations were supported by three-dimensional Monte Carlo simulations The hot-electron temperature obtained from electron spectra and absorption experiments implies that resonance absorption is partially responsible for the generation of hot electrons
25 citations
TL;DR: In this article, a new non-classical Lewis structure was suggested for the twisted open-chain N 7 (C 2 v ), which is helpful for understanding its special bond nature.
Abstract: Ab initio quantum mechanics methods have been used to examine isomers with low spin of N 7 cluster. In additional to the previously studied five N 7 isomers, five new structures were investigated in this paper. Their structures, energies, zero point energies, net charges were calculated at the UHF/6-31G ∗ , UMP2/6-31G ∗ , B3LYP/6-31G ∗ , B3LYP/6-311+G ∗ levels. The harmonic vibrational frequencies and their infrared intensities have been predicted with SCF, MP2 and DFT methods. Two of them [structure 2 ( Cs ) and 5 ( Cs )] are reasonable local minima on the N 7 energy hypersurface at the all of the levels we used. The twisted open-chain N 7 ( C 2 v ) is still the most stable in all of the twelve N 7 isomers. Based on the NBO analysis, a new non-classical Lewis structure was suggested for the twisted open-chain N 7 ( C 2 v ), which is helpful for understanding its special bond nature. The similar and different properties between the N 7 clusters and even-number nitrogen clusters were discussed.
17 citations
TL;DR: In this article, the authors investigate the dynamics of a one-dimensional semiconductor superlattice with an impurity under the action of an ac electric field and find that although the dynamic localization condition is not destroyed by the impurity, the quasi-energy spectrum and corresponding local dynamics of the system are tuned dramatically by the ratio of impurity potential to the ac field frequency.
Abstract: Within a single-band tight-binding model, we investigate the dynamics of a one-dimensional semiconductor superlattice with an impurity under the action of an ac electric field. The long-time mean-square displacement is analytically obtained and the quasienergy spectrum is numerically calculated. We find that although the dynamic localization condition is not destroyed by the impurity, the quasienergy spectrum and corresponding local dynamics of the system are tuned dramatically by the ratio of the impurity potential to the ac field frequency. In particular, when the ratio becomes an integer, avoided crossing in the quasienergy spectrum occurs and the dynamics of the system is dominated by resonant oscillations between the impurity and its two nearest-neighbor sites. Such an effect is more favorable for experimental investigations of coherent oscillations of charged carriers.
16 citations
TL;DR: By adjusting external control signal, rather than some available parameters of the system, the authors modify the straight-line stabilization method for stabilizing an unstable periodic orbit in a neighborhood of an unstable fixed point formulated by Ling Yang et al.
Abstract: By adjusting external control signal, rather than some available parameters of the system, we modify the straight-line stabilization method for stabilizing an unstable periodic orbit in a neighborhood of an unstable fixed point formulated by Ling Yang et al., and derive a more simple analytical expression of the external control signal adjustment. Our technique solves the problem that the unstable fixed point is independent of the system parameters, for which the original straight-line stabilization method is not suitable. The method is valid for controlling dissipative chaos, Hamiltonian chaos and hyperchaos, and may be most useful for the systems in which it may be difficult to find an accessible system parameter in some cases. The method is robust under the presence of weak external noise.
14 citations
TL;DR: In this article, the cross-section data for transition element ions in collision with gases are obtained in the energy region of 10-30 keV, and the experimental uncertainty of the results is improved by using a single-particle detector for both neutral atoms and ions.
Abstract: Electron detachment of negative ions, in collision with a static gas target, is known to be one of the most fundamental processes occurring in negative-ion-atom collisions. The experimental results of cross-section data for transition element ions in collision with gases are of great interest not only for their potential application value, but also as a challenge to a theoretical study of complex negative ions in collision with atoms or molecules. In the present work, the single-electron detachment (SED) cross-sections for Cu− and Ag− in collision with He, N2 have been obtained in the energy region of 10-30 keV. By using a single-particle detector for both neutral atoms and ions, the experimental uncertainty of the results is improved in this work.
12 citations
Abstract: Investigating the electronic structure of the products of uranium oxidation and the electron transfer in this process, and revealing the mechanism on the initial oxidation stage of uranium surface are of great importance for finding out the effective anti-corrosion methods of uranium surface. In this paper, optimized geometries, total energies and electronic structures of some gaseous atoms and molecules of uranium–oxygen system are calculated with harmonic vibration analyses using ab initio method. Some potential energy surfaces (PESs) of the uranium oxidation process are also constructed. The calculated geometric parameters and infrared vibrational frequencies of some uranium oxides are consistent very well with experimental data. The PESs show that different reaction modes result in different product geometries. When U approaches O 2 at the oxygen atom top along the axis of O–O bond, a relatively stable linear structure, O–O–U, is formed, which has the possibility to decompose to UO and O. When U approaches O 2 along the perpendicular median of the O–O bond axis, a stable molecule UO 2 comes into being via two bent metastable structures with bond angles of about 151 and 105°, respectively. No potential energy barrier is needed for the uranium and O 2 to form the metastable states, while a very little barrier is needed to form the stable linear UO 2 from the metastable structures. And for the reaction O+UO→OUO (linear) also, there is no potential energy barrier needed, while for the reaction O+OU→U⋯O⋯O (linear), a barrier of about 4.5 eV is needed. U5f atomic orbital electrons dominate in the formation of the U–O bonds.
9 citations
TL;DR: In this article, the single-electron detachment cross sections of Cu-in collision with He have been measured in the range of 10-30 keV by a growth rate method.
Abstract: The single-electron detachment cross sections of Cu- in collision with He have been measured in the range of 10-30 keV by a growth rate method. The typical value of the cross section is 7.63×10-16cm2 at an energy of 20 keV. The experimental uncertainty of the results is about ±8%.
9 citations
TL;DR: In this paper, the hyperfine structures (HFSs) in the 570.33 nm, 587.40 nm and 612.96 nm lines of LaII were resolved and the HFS constants A and B of the involved levels were given.
Abstract: The spectra of singly ionized lanthanum have been measured by means of collinear fast ion-beam-laser spectroscopy (CFIBLS). The hyperfine structures (HFSs) in the 570.33 nm, 587.40 nm and 612.96 nm lines of LaII were resolved and the HFS constants A and B of the involved levels are given.
8 citations
TL;DR: In this article, the SG-III prototype was numerically simulated with a shot period of 4 h and the authors showed that the average temperature and the largest temperature drop across the aperture of the laser slab will be less than 0.13°C and 0.11°C respectively.
Abstract: Thermal recovery of the main amplifier of the SG-III prototype is numerically simulated. The calculations indicate that, with a shot period of 4 h, we can achieve an acceptable laser slab average temperature and thermal gradient across the slab aperture through optimized active cooling for both the flashlamp cassettes and the slab cavities. After 4 h of thermal recovery, the average temperature and the largest temperature drop across the aperture of the laser slab will be less than 0.13°C above ambient and 0.11°C respectively. The active cooling for all the flashlamp cassettes will need a total cleaned-air flow rate of 80 m3/min (10 ft3/min per lamp) and a total nitrogen flow rate of 16 m3/min for all the slab cavities. Additionally, the temperature of the cooling gas in the flashlamp cassette must be reduced to ?1.0°C (relative to ambient temperature) during the first 2.5 h of the thermal recovery cycle.
TL;DR: In this paper, the Gruneisen parameter γ of porous iron was calculated and the result γ0ρ0 = γρ = const, with γ 0 = 1.945 and ρ 0 = 7.856 g/cm3, ρ being the density.
Abstract: The Hugoniot equation-of-state (EOS) of porous iron with an average initial density of 6.904 g/cm3 has been measured in the pressure range from 90 to 160 GPa, and a good straight fitting D = 2.997 + 1.603 u has accordingly been obtained, where D is the shock wave velocity and u the particle velocity, both in units of km/s. Combining this with the Hugoniot EOS of non-porous iron, the Gruneisen EOS and the Rankine-Hugoniot energy conservation relation, and taking the possible solid-liquid transition correction, we have calculated the Gruneisen parameter γ of iron and obtained the result γ0ρ0 = γρ = const, with γ0 = 1.945 and ρ0 = 7.856 g/cm3, ρ being the density. PACS: 62. 50. +p, 65. 90. +i, 91. 35. -x
TL;DR: In this paper, the pyrolysis of uncured, EB-cured and aircured Vi-PCS precursors was studied and the results showed that vinyl can enhance the irradiation curing of PCSs and a vinyl content of 2.33 wt% in PCS can lower its gel dose (curing dose) from 10 MGy (15 MGy) to 0.5 MGy, respectively.
Abstract: In a previous study [1], we prepared a kind of vinylcontaining precursor by introducing cyclomethylvinylsilazane (MVCSZ) to the polycarbosilanes (PCSs). The results showed that vinyl can enhance the irradiation curing of PCSs and a vinyl content of 2.33 wt% in PCS can lower its gel dose (curing dose) from 10 MGy (15 MGy) to 0.5 MGy (5 MGy), respectively. In order to observe the mechanical properties of soobtained low-oxygen-content SiC fiber from the vinylcontaining polycarbosilanes (Vi-PCSs), this paper studied the pyrolysis of uncured, EB-cured and aircured Vi-PCS precursors. Bundles of the green Vi-PCS fibers with a vinyl content of 2.33 weight percent were irradiated in helium atmosphere in a quartz vessel under an electron accelerator with a rate close to 0.8 MGy per min. The absorbed dose was 5.0 MGy. Afterwards, the samples were annealed in helium gas flow at 130 ◦C for 1 h and irradiation cross-linked Vi-PCS fibers were finally obtained. Another batch of the same green Vi-PCS fibers was air-cured in a furnace with air flowing through, up to 190 ◦C for 2 h with a weight gain of 10 wt%. The EB-cured or air-cured fibers were then pyrolyzed under a flow of high-purity nitrogen (Q = 10−5 m3/ min, P = 100 kPa) up to 1200 ◦C for 30 min with a relatively slow heating rate (100 ◦C/h). After this treatment, the fibers that were no longer sensitive to oxidation could be handled in air. The high temperature treatment was then achieved with a pyrolysis equipment comprising a graphite crucible with a radio frequency coil. The samples were heated (30 ◦C/min) and maintained at the pyrolysis temperature Tp under a high-purity nitrogen atmosphere (100 kPa) for tp = 30 min. The fibers were characterized by the following ways. Thermogravimetric analysis (TGA) (Rigaku, Japan) was performed, up to 1200 ◦C, in platinum crucibles on about 10 mg samples under a high-purity nitrogen flow (flow rate: 4 × 10−5 m3/min) with a temperature increase rate of 10 ◦C/min. The weight loss before and after high temperature treatment was measured and calculated with an analytical balance. Elemental (Si,C,N) analyses were performed on the samples by a chemical-analysis process. Oxygen contents were determined by a nitrogen/oxygen analyzer (TC-436, LECO, America). X-ray diffraction (XRD) spectra (Cu-Ka/Siemens D500 diffractometer, Germany) were recorded from tows of fibers for Tp = 1600 ◦C. The apparent mean grain size (L) of the β-SiC crystalline phase present in the samples was calculated from the width (D) of the (111) diffraction peak at mid-height, according to the following Equation 1:
TL;DR: In this article, the authors investigated the joining of beryllium and 316L stainless steel by hot isostatic pressing (HIP) with and without an interlayer, and they showed that the diffusion depth of Be into 316l stainless steel is much greater than that of Cr, Ni or Fe into berylla, and it is ∼400 μm.
Abstract: Joining of beryllium and 316L stainless steel by hot isostatic pressing (HIP) with and without an interlayer was investigated. Metallurgical observation, scanning Auger microscopy (SAM) and nanoindentation were performed for basic characterization of bonded joints. It is shown that the diffusion depth of Be into 316L stainless steel is much greater than that of Cr, Ni or Fe into beryllium, and it is ∼400 μm. The nanohardness of the diffusion zone on the beryllium side increases sharply due to intermetallic compounds, and the tensile strength of the Be/316L joint is <10 MPa. For a Be/Cu/316L joint, a Cu interlayer blocks the diffusion of Fe into Be, but Ni is gathered at the Cu/316L interface and a crack is formed at this stress field. For a Be/Cu/Ni/316L joint, the diffusion depth increases further. Change of composition, mechanical property with distance in diffusion zone is smooth, and the tensile strength increases to ∼50 MPa.
TL;DR: In this article, the authors investigate the dynamical processes taking place in nanodevices by high-frequency dc-ac fields, and they find that Rabi oscillations between minibands are clearly identified under theoretical resonant conditions derived by an ideal two-band superlattice model.
Abstract: We investigate the dynamical processes taking place in nanodevices by high-frequency dc-ac fields. We found that Rabi oscillations between minibands are clearly identified under theoretical resonant conditions derived by an ideal two-band superlattice model, the resonant conditions have broadened, and the amount of broadening is about four times of the Rabi oscillation frequency. We also want to elucidate the role of different mechanisms that could lead to loss of quantum coherence. Our results show how the dephasing effects of disorder of interface roughness and doping fluctuation that after some periods destroy coherent oscillations, such as Rabi oscillations, can be reduced dramatically if we apply a bias static electric field to the superlattice system. The doping fluctuation dephasing effect is much stronger than that of interface roughness in the coherent process of realistic superlattices.
TL;DR: In this article, the total electron detachment cross sections for the collisions of Cu- and Ag- with He have been measured in the range of 10-30 keV by the growth-rate method.
Abstract: The total electron detachment cross sections for the collisions of Cu- and Ag- with He have been measured in the range of 10–30 keV by the growth-rate method. The typical value of the cross section at 20 keV energy is 7.63×10-16 cm2 for Cu-, and 6.66×10-16 cm2 for Ag-. The experimental uncertainty of the results is within ±8% in this work.
TL;DR: In this paper, the method for controlling Hamiltonian chaos by adaptive integrable and near-integrable mode coupling is extended to controlling strong chaos by Adaptive Integrability and Near-Integrable Mode Coupling (AIMC).
Abstract: The method for controlling Hamiltonian chaos by adaptive integrable mode coupling is extended to controlling strong chaos by adaptive integrable and near-integrable mode coupling. We illustrate this method with a highly chaotic system, the perturbed cat map. All orbits can be effectively controlled to the periodic or quasiperiodic orbits. The method is robust against the presence of weak external noise.
TL;DR: In this paper, the authors present a method allowing one to employ another external kick with strength K and delay η to control the global stochasticity in two-dimensional Hamiltonian systems, where the control here means that the chaotic state will be able to changed in the entire angular momentum interval (−∞,∞) at will.
TL;DR: Based on the detailed configuration accounting (DCA) model, a method was developed to include the resonant photoionization and the excitation-autoionization in the non-local thermodynamical equilibrium (NLTE) average atom (AA) model as mentioned in this paper.
Abstract: Based on the detailed configuration accounting (DCA) model, a method is developed to include the resonant photoionization and the excitation-autoionization in the non-local thermodynamical equilibrium (NLTE) average atom (AA) model. Using this new model, the mean charge states and the opacity are calculated for NLTE high- plasmas and compared with other results. The agreement with AA model is poor at low electron density. The present results agree well with those of DCA model within 10%. The calculations show that the NLTE effects on opacity are strong.
TL;DR: In this article, a simple model was proposed to explain the 3/2 harmonic emission in the interaction between plasmas and ultrashort laser pulses, and the model was used to analyze the relationship between the harmonics from a plasma generated by long and short laser pulses.
Abstract: Harmonic emission was studied from a plasma produced by ultrashort laser pulses. Unlike the harmonics from plasmas created by long (ns) laser pulses, the 3/2 harmonic emission was not observed in the interaction between plasmas and ultrashort laser pulses. A simple model is proposed to explain this phenomenon.
TL;DR: In this paper, a type of system, in which the specific volume can be divided into several parts according to its Hamiltonian, has been obtained in a grand ensemble, and the main character of such a system is that its Hamiltonians is absolutely separable.
Abstract: A type of system, in which the specific volume can be divided into several parts according to its Hamiltonian, has been obtained in a grand ensemble. The main character of such a system is that its Hamiltonian is absolutely separable. We also discuss the partial specific volume contributed by thermoelectrons in metals under a free-interaction approximation and the corresponding Wu-Jing parameter is obtained as a simple example.
TL;DR: A constant periodic pulse method is proposed to control dissipative and Hamiltonian chaos using the convergence of the chaotic orbit in finite time to determine the intensity of the perturbation and the corresponding fixed points.
Abstract: A constant periodic pulse method is proposed to control dissipative and Hamiltonian chaos. Using the convergence of the chaotic orbit in finite time, the stable segment of the chaotic orbit that satisfies the desired dynamical features can be made to form a closed orbit by the action of a proper perturbation on the system variables. A way to determine the intensity of the perturbation and the corresponding fixed points is presented. The method is robust against the presence of external noise.
TL;DR: In this article, a femtosecond probing beam was used to analyze the evolution of plasmas produced by ultrashort laser pulses and the time sequence of plasma shadowgrams and interferograms were obtained.
Abstract: Optical diagnostics of evolution of plasmas produced by ultrashort laser pulses is carried out using a femtosecond probing beam. The time sequence of plasma shadowgrams and interferograms are obtained. The filamentation instability in high-density region induces the local density modification. Large-scale toroidal magnetic fields confine plasma expansion in the transverse direction, resulting in the formation of a plasma jet. The plasma expansion along the target normal direction is found to scale as t1/2.
TL;DR: In this article, the transmission dynamics of a driven two-level system dissipated by the two leads were studied and an analytical transmission formula for an electron incident from the left lead, through the double quantum dots, to the right lead was derived.
Abstract: We study the transmission dynamics of a driven two-level system dissipated by the two leads. Using the nonequilibrium Green function, we derive an analytical transmission formula for an electron incident from the left lead, through the double quantum dots, to the right lead. The Landauer-type conductance and current are also given. A discussion of the internal tunnelling dynamics reveals crucial effects of the localization and delocalization on the transport of the system.
TL;DR: In this article, the instability of filamentation in femtosecond laser plasmas has been observed, and the local density fluctuation has been studied using optical shadowgraphy and scattering imaging techniques.
Abstract: The local density fluctuation in femtosecond laser plasmas has been studied using optical shadowgraphy and scattering imaging techniques.The instability of filamentation in the laser plasma has been observed,and the local density fluctuation studied.The result shows that this instability of filamentation is caused by the ponderomotive force.
TL;DR: In this article, the global attractors for the periodic initial value problem of damped KdV type nonlinear wave equations were obtained by means of uniformly a priori estimates for time.
TL;DR: In this paper, the electron dynamical processes taking place in nanodevices under high-frequency DC-AC fields were investigated by solving numerically the one-dimensional time-dependent Schrodinger equation including some ingredients of actual SLs, namely, finite interband coupling, multiband scattering.
Abstract: We investigate the electron dynamical processes taking place in nanodevices under high-frequency DC–AC fields by solving numerically the one-dimensional time-dependent Schrodinger equation including some ingredients of actual SLs, namely, finite interband coupling, multiband scattering. We found that Rabi oscillations between minibands are clearly identified under theoretical resonant conditions derived by an ideal two-band superlattice model, the resonance conditions have broadened, and the amount of broadening is about four times the Rabi oscillation frequency, and also that static electric field can weaken the fast dephasing effect of interface roughness on Rabi oscillations in superlattice. Experimental conditions for the observation of the predicted effects are discussed.
TL;DR: In this paper, the results of electron spin resonance (ESR) investigation of ferroelectric 1.8/65/35 and antiferroelectric 2/95/5 optically transparent ceramics Pb1−yLa 1−yZr1−xTixO3 (PLZT) in a temperature region 20-300 K after light irradiation with wavelength 365-725 nm are presented.
Abstract: The results of electron-spin-resonance (ESR) investigation of ferroelectric 1.8/65/35 and antiferroelectric 2/95/5 optically transparent ceramics Pb1−yLa1−yZr1−xTixO3 (PLZT) in a temperature region 20–300 K after light irradiation with wavelength 365–725 nm are presented. After ultraviolet irradiation at low temperature (T<50 K) paramagnetic centres of Ti3+, Pb3+ and Pb+ were observed. It was shown that Ti3+ and Pb3+ are created in regular lattice sites perturbed by La3+ (La3+ mainly substitutes for Pb2+ and partially for Ti4+) by trapping carries from the conduction or valence band. The temperature interval of stability of these centres as well as their thermal ionisation energies were obtained. The Pb3+ and Pb+ create deep local levels, they are thermally stable up to room temperature in the PLZT 2/95/5. Process of migration of localised carriers was studied for both types of ceramics. It was shown that with temperature increasing or after red light illumination the electrons. ionised to the co...
01 Jan 2001
TL;DR: In this article, a series displacement experiments between hydrogen and deuterium in ZrCo, LaNi 5, La Ni 4.7 Al 0.3 and Pd hydride column had been conducted at room temperature about.
Abstract: A series displacement experiments between hydrogen and deuterium in ZrCo, LaNi 5, LaNi 4.7 Al 0.3 and Pd hydride column had been conducted at room temperature about. Results indicate that displacement characteristics related to factors such as temperature, gas flow rate, ratio surface area of solid phase and hydrogen isotope separation factor of the metal hydrogen system. The palladium hydride have the best displacement characteristics, and LaNi 5,LaNi 4.7 Al 0.3 and ZrCo are in the next places. Theoretical study reveals that the rule of the exchange reaction of hydrogen isotopes in gas solid interface determines the displacement behavior and the displacing efficiency depends on exchange rate. The ideal stage mode could be used to describe the displacement breakthrough curve. The height equivalent to theoretical plate(HETP) indicates the displacing effects. Also, the separation factor has a serious influence to HETP under the same condition.
TL;DR: In this article, a method for calculating the average energies of relativistic subconfigurations in highly ionized heavy atoms has been developed in the framework of the multiconfigurational Dirac-Fock theory.
Abstract: A method for calculating the average energies of relativistic subconfigurations in highly ionized heavy atoms has been developed in the framework of the multiconfigurational Dirac-Fock theory. The method is then used to calculate the average transition energies of the spin-orbit-split 3d-4p transition of Co-like tungsten, the 3d-5f transition of Cu-like tantalum and the 3d-5f transitions of Cu-like and Zn-like gold samples. The calculated results are in good agreement with those calculated with the relativistic parametric potential method and also with the experimental results.