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81.
Most previous investigations on interference effects of tall buildings under wind actions focused on the wind induced interference effects between two buildings,and the interference effects of three or more buildings have seldom been studied so far due to the huge workload involved in experiments and data processing.In this paper,mean and dynamic force/response interference effects and peak wind pressure interference effects of two and three tall buildings,especially the three-building configuration,are investigated through a series of wind tunnel tests on typical tall building models using high frequency force balance technique and wind pressure measurements.Furthermore,the present paper focuses on the effects of parameters,including breadth ratio and height ratio of the buildings and terrain category,on the interference factors and derives relevant regression results for the interference factors. 相似文献
82.
M. H. Naderi M. Soltanolkotabi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,39(3):471-479
We investigate the effect of a static electric field on
photoionization of the He atom in the ground 1S and low-lying 2S
and 2P excited states. The field-affected ionization potential and
photoionization cross-section are determined from the complex
eigenvalues of the time-dependent Schr?dinger equation solved by the
complex rotation method in the Floquet ansatz. Accuracy of the method
is enhanced by the use of the Hylleraas basis set. For the ground
state of helium, we find that the total photoionization cross-section
remains constant or decreases as a function of the DC field strength
until this field reaches a certain critical value. For the low-lying
excited states, effect of the static field is similar to the ordinary
DC Stark effect. 相似文献
83.
We use wavelength tunable femtosecond pulses to measure intrinsic (simultaneous) two-photon absorption (2PA) and three-photon absorption (3PA) molecular cross section in two series of π-conjugated dendrimers built of identical 4,4′-bis(diphenylamino) stilbene (BDPAS) and 4,4′-bis(diphenylamino) distyrylbenzene (BDPADSB) repeat units. Record large 2PA cross sections, σ2=10−46 cm4 s are obtained for the largest second-generation BDPAS-based dendrimer, as well as zeroth-generation 4-arm BDPADSB-based dendrimer. In both series, maximum 2PA cross section increases nonlinearly with the number of π-electrons, whereas for higher generations this dependence turns to linear one. 3PA cross section also increases nonlinearly with the size of the system in the series of BDPAS-based molecules, amounting a record large value, σ3=10−79 cm6 s2, for the largest, second-generation dendrimer. We interpret these results in terms of direct inter-branch conjugation, which facilitates cooperative enhancement of the nonlinear-optical response. We propose a simple model which allows us to determine the effective size of coherent domains (extent of conjugation), which, in turn, determines the optimum dendrimer size for most efficient nonlinear response. 相似文献
84.
云母1/4波片偏振干涉谱的研究 总被引:15,自引:1,他引:14
本文利用岛津UV301-PC分光光计,测定了云母1/4波片的偏振干波谱,该光谱和以往文献中的显著不同。本文对此进行了分析和解释,并由此得出了在考虑吸收的情况下的爱里方程表达形式。该将有助于测定某些晶体的吸光度。 相似文献
85.
Field-induced ionization and Coulomb explosion of nitrogen 总被引:1,自引:0,他引:1
C.Y. Wu H.Z. Ren T.T. Liu R. Ma H. Yang H.B. Jiang Q.H. Gong 《Applied physics. B, Lasers and optics》2002,75(1):91-96
Femtosecond-laser field-induced ionization and Coulomb explosion of diatomic nitrogen were systematically investigated using
time-of-flight mass and photoelectron spectrometry. Both linearly and circularly polarized femtosecond laser pulses were used
at intensities varying from 5×1013 to 2×1015 W/cm2. Strong N2
+, N2
2+, N+, N2+ and N3+ ion signals were observed for horizontally polarized pulses. Moreover, signals from the atomic ions exhibited a double-peak
structure. Suppression of ionization was observed for circularly polarized pulses, while for vertically polarized pulses,
only N2
+ and N2
2+ ions were observed. The angular distributions of the ions were measured under zero-field conditions in the ionization zone.
The atomic ions N+, N2+ and N3+ exhibited highly anisotropic distributions, with maxima along the laser polarization vector and zeroes normal to the laser
polarization vector. In contrast to the atomic ions, N2
+ exhibited a strong isotropic angular distribution. These observations indicate that dynamic alignment is responsible for
the observed anisotropic angular distribution of the atomic ions. The kinetic energy spectrum of the photoelectrons is featureless
and broad, extending above the ponderomotive potential of the laser pulse. The angular distribution is markedly anisotropic,
with a maximum along the laser polarization vector. These observations further support the notion that the field-ionization
mechanism is dominant under our experimental conditions.
Received: 29 January 2002 / Revised version: 15 March 2002 / Published online: 12 July 2002 相似文献
86.
A. Settimi S. Severini C. Sibilia M. Bertolotti A. Napoli A. Messina 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,50(3):379-391
The present paper discusses the stimulated emission, in strong coupling
regime, of an atom embedded inside a one dimensional (1D) Photonic Band Gap
(PBG) cavity which is pumped by two counter-propagating laser beams. Quantum
electrodynamics is applied to model the atom-field interaction, by
considering the atom as a two level system, the e.m. field as a
superposition of normal modes, the coupling in dipole approximation, and the
equations of motion in Wigner-Weisskopf and rotating wave approximations. In
addition, the Quasi Normal Mode (QNM) approach for an open cavity is adopted, interpreting the local density of states (LDOS)
as the local density of
probability to excite one QNM of the cavity; and therefore rendering this
LDOS dependent on the phase difference of the two laser beams. In this paper
we demonstrate that the strong coupling regime occurs at high values of the
LDOS. In accordance with the results of the literature, the emission
probability of the atom decays with an oscillatory behaviour, so that the
atomic emission spectrum exhibits two peaks (Rabi splitting). The novelty of
this work is that the phase difference of the two laser beams can produce a
coherent control of both the oscillations for the atomic emission
probability and, as a consequence, of the Rabi splitting in the emission
spectrum. Possible criteria to design active delay lines are finally
discussed. 相似文献
87.
Oleg M. Schuvailo Szilveszter Gáspár Alexey P. Soldatkin Elisabeth Csöregi 《Electroanalysis》2007,19(1):71-78
Carbon fiber microelectrodes, able to detect catecholamine release from single cells, have significantly contributed to our present understanding of the mechanism of secretory neurotransmission. In spite of their obvious advantages, there are only a few amperometric sensors (characterized by appropriate size, sensitivity, and selectivity) able to measure the release of other (not easily oxidizable) neurotransmitters at cellular level. The present work describes the fabrication and characterization of an ultramicrobiosensor for the selective detection of glutamate. The developed sensor has a size of 2.5–15 μm in diameter, a sensitivity of 0.62 mA mM?1 cm?2, and a detection limit of 5 μM. The excellent selectivity of the sensor (achieved using electrodeposition of Ru, Rh, and poly(m‐phenylenediamine)) makes it a promising candidate for monitoring glutamate release at single cell level. 相似文献
88.
89.
Dong-chao Cheng 《Optics Communications》2006,263(1):111-115
We investigate the steady-state optical bistability behavior in a three-level Λ-type atomic system closed by a microwave field under the condition that the applied fields are in resonance with corresponding atomic transitions. It is shown that the bistable hysteresis cycles can be controlled by both the amplitude and the phase of the microwave field. 相似文献
90.
The aggregation and rearrangement of nanoparticles embedded in a thin cell of ferrofluid at various applied magnetic fields was studied by Monte Carlo simulation. Regular microcolumns with the axis parallel to the magnetic field were observed with column size and spacing depending on the ramp speed of the applied field. Our model successfully simulated the reported experimental results that the column size decreases as the ramp speed increases, which is attributed to the diminishing time to achieve the final assembled state at a given final magnetic field. Column arrays of tunable lattice constants characterizing various spectroscopic dispersions are elucidated. The hexagonal structure of the aggregation of magnetic nanoparticles and optical dispersion were observed through an optical microscope. The transmission diffraction spectra depending on column spacings and sizes of the column array are simulated to yield results comparable to the experiment. 相似文献