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排序方式: 共有9611条查询结果,搜索用时 15 毫秒
981.
Wu C Yang Y Wu Z Chen B Dong H Liu X Deng Y Liu H Liu Y Gong Q 《Physical chemistry chemical physics : PCCP》2011,13(41):18398-18408
We have systematically studied Coulomb explosion of nitrogen and oxygen molecules in intense 8 and 24 fs laser pulses. In the experiment, we explicitly separated all explosion pathways through coincident measurements. The high resolution kinetic energy releases (KERs) and the exotic angular distributions of atomic ions provide direct evidence that Coulomb explosion occurs through non-Coulombic states. In the theory, we calculated dissociation potential energy curves (PECs) of nitrogen and oxygen molecules and their multicharged molecular ions using multiconfiguration second-order perturbation theory. The results indicate that Coulomb potentials are close to the accurate PECs of multicharged molecular ions only when the internuclear distance is larger than 3 ?. In comparison with the experimental observations and the theoretical calculations, we determined the internuclear distance when Coulombic explosion occurs. It is near the equilibrium distance of the neutral molecules in the case of 8 fs laser pulses and expands gradually with the increase of the charge state of the molecular ions in the case of 24 fs laser pulses. 相似文献
982.
Dr. Shing‐Jong Huang Chih‐Yi Yang Dr. Anmin Zheng Ningdong Feng Dr. Ningya Yu Pei‐Hao Wu Prof. Dr. Yu‐Chi Chang Prof. Dr. Ying‐Chih Lin Prof. Dr. Feng Deng Prof. Dr. Shang‐Bin Liu 《化学:亚洲杂志》2011,6(1):137-148
The acid and transport properties of the anhydrous Keggin‐type 12‐tungstophosphoric acid (H3PW12O40; HPW) have been studied by solid‐state 31P magic‐angle spinning NMR of absorbed trimethylphosphine oxide (TMPO) in conjunction with DFT calculations. Accordingly, 31P NMR resonances arising from various protonated complexes, such as TMPOH+ and (TMPO)2H+ adducts, could be unambiguously identified. It was found that thermal pretreatment of the sample at elevated temperatures (≥423 K) is a prerequisite for ensuring complete penetration of the TMPO guest probe molecule into HPW particles. Transport of the TMPO absorbate into the matrix of the HPW adsorbent was found to invoke a desorption/absorption process associated with the (TMPO)2H+ adducts. Consequently, three types of protonic acid sites with distinct superacid strengths, which correspond to 31P chemical shifts of 92.1, 89.4, and 87.7 ppm, were observed for HPW samples loaded with less than three molecules of TMPO per Keggin unit. Together with detailed DFT calculations, these results support the scenario that the TMPOH+ complexes are associated with protons located at three different terminal oxygen (Od) sites of the PW12O403− polyanions. Upon increasing the TMPO loading to >3.0 molecules per Keggin unit, abrupt decreases in acid strength and the corresponding structural variations were attributed to the change in secondary structure of the pseudoliquid phase of HPW in the presence of excessive guest absorbate. 相似文献
983.
Xin XL Deng S Zhang BJ Huang SS Tian Y Ma XC An L Shu XH Yao JH Cui X 《Natural product communications》2011,6(6):781-784
Biotransformation of deoxyandrographolide (1) by Alternaria alternata AS 3.4578 gave five derivatives identified by spectral methods including 2D NMR as the known dehydroandrographolide (2) and 9beta-hydroxy-dehydroandrographolide (3) and the new compounds 9beta-hydroxy-deoxyandrographolide (4), 3alpha,17,19-trihydroxy-8,13-ent-labdadien-15,16-olide (5) and 3-oxo-9beta-hydroxy-deoxyandrographolide (6). 相似文献
984.
An inverse approach for the identification of the time-dependent localized interaction pressure between a structure and an
explosive has been proposed and developed. In this approach, surface measurements of structural response (displacement and
velocity) are integrated with numerical simulations to identify the spatial and time-dependent interaction pressure (i.e.
the normal traction) on a structure surface. For verification and validation purposes, numerical simulations are used to (a)
generate the time-dependent displacement and velocity fields on the free surface of the specimen at specified time intervals,
(b) form a blast wave and compute the resulting interaction traction field between the structure and blast wave on the interaction
interface for comparison to inverse predictions. In particular, validation of the proposed approach was performed using numerical
simulation results for an underwater explosion, with excellent agreement between the identified interaction traction and the
simulation generated interaction traction up to and including the maximum traction condition. To demonstrate the potential
of the method, the proposed inverse procedure was employed to estimate the interaction traction field on a thin aluminum specimen
subjected to transient pressure loading through detonation of explosive buried in sand. 相似文献
985.
基于混合网格Navier-Stokes方程的并行隐式计算方法研究 总被引:2,自引:0,他引:2
针对结构网格很难处理复杂外形和非结构网格无法计算具有边界层的粘性流动的缺点,发展了基于混合网格格点的隐式算法,成功地解决了在工程应用中难于处理的复杂外形粘性流场计算和效率问题。同时针对大规模的工程问题,发展了基于MPI通信技术的染色分层通讯并行计算方法。其中空间离散采用基于Roe格式发展的三阶迎风HLLEW(Harten-Lax-Van Leer-Einfeldt-Wada)或AUSM格式,湍流模型采用k??两方程湍流模型,时间推进考虑到LU-SGS并行等效较困难则采用基于DP-LUR(Data-Parallel Lower-Upper Relaxation)格式的隐式算法,计算CFL数可取到105量级,从2个到128个CPU的并行加速效率都保持在90%以上,大大提高了计算效率。算例对标模M6机翼模型流场进行计算,验证了方法的可靠性;然后对标模DLR-F6翼身组合体进行混合网格粘性与无粘计算结果进行比较,进一步验证混合网格方法;最后计算了DLR-WBNP外挂发动机翼身组合体模型,准确模拟了外挂和超临界机翼的相互干扰流动问题,采用4 CPU 16 CORE到24 CPU 96 CORE,2000步计算时间都不超... 相似文献
986.
In this paper, we construct a modified Green potential in the upper-half space of the n-dimensional Euclidean space. Meanwhile, the behavior at infinity of it is also given. 相似文献
987.
988.
Bo Deng 《Journal of Nonlinear Modeling and Analysis》2019,1(1):27-45
A twisted heteroclinic cycle was proved to exist more than twenty-
five years ago for the reaction-diffusion FitzHugh-Nagumo equations in their
traveling wave moving frame. The result implies the existence of infinitely
many traveling front waves and infinitely many traveling back waves for the
system. However efforts to numerically render the twisted cycle were not fruit-
ful for the main reason that such orbits are structurally unstable. Presented
here is a bisectional search method for the primary types of traveling wave solu-
tions for the type of bistable reaction-diffusion systems the FitzHugh-Nagumo
equations represent. The algorithm converges at a geometric rate and the wave
speed can be approximated to significant precision in principle. The method
is then applied for a recently obtained axon model with the conclusion that
twisted heteroclinic cycle maybe more of a theoretical artifact. 相似文献
989.
In this paper,we prove that any κ-noncollapsed gradient steady Ricci soliton with nonnegative curvature operator and horizontally κ-pinched Ricci curvature must be rotationally symmetric.As an application,we show that any κ-noncollapsed gradient steady Ricci soliton(Mn,g,f) with nonnegative curvature operator must be rotationally symmetric if it admits a unique equilibrium point and its scalar curvature R(x) satisfies lim_(ρ(x)→∞) R(x)f(x)=C_0 sup_(x∈M) R(x) with C_0n-2/2. 相似文献
990.
One-dimensional integral imaging (1DII) which only has horizontal disparity is a practical solution of high resolution in the vertical direction, low-cost, easy-viewable three-dimensional (3D) display. A 1DII based on a parallax barrier is proposed in this paper. The 1DII consists of a parallax barrier and a display panel. The operation principle and parameter calculation of the 1DII are described in detail. Two prototypes of the proposed 1DII and conventional 1DII based on a lenticular lens array are developed. The proposed 1DII improves the quality of the 3D image and provides larger viewing angle than that based on a lenticular lens array, and it is simpler and has lower cost than that based on a lenticular lens array. 相似文献