Electron excitation processes in low energy collisions of hydrogen-helium atoms

The electron excitation processes of H(1s)+He(1s^(2))→H(2s/2p)+He(1s^(2))are studied in impact energy range of 20-2000 e V/u by using the quantum-mechanical molecular orbital close-coupling(QMOCC)method.Total and state-selective cross sections have been obtained and compared with the available theoretical and experimental results.The results agree well with available measurements in the overlapping energy regions overall.The comparison of our results with other theoretical calculations further demonstrates the importance of considering a sufficient number of channels.The datasets presented in this paper,including the excitation cross sections,are openly available at https://www.doi.org/10.57760/sciencedb.j00113.00083.

Operational Modal Analysis of a Ship Model in the Presence of Harmonic Excitation

A ship is operated under an extremely complex environment, and waves and winds are assumed to be the stochastic excitations. Moreover, the propeller, host and mechanical equipment can also induce the harmonic responses. In order to reduce structural vibration, it is important to obtain the modal parameters information of a ship. However, the traditional modal parameter identification methods are not suitable since the excitation information is difficult to obtain. Natural excitation technique-eigensystem realization algorithm （NExT-ERA） is an operational modal identification method which abstracts modal parameters only from the response signals, and it is based on the assumption that the input to the structure is pure white noise. Hence, it is necessary to study the influence of harmonic excitations while applying the NExT-ERA method to a ship structure. The results of this research paper indicate the practical experiences under ambient excitation, ship model experiments were successfully done in the modal parameters identification only when the harmonic frequencies were not too close to the modal frequencies.

Analysis on Pseudo Excitation of Random Vibration for Structure of Time Flight Counter

Traditional computing method is inefficient for getting key dynamical parameters of complicated structure.Pseudo Excitation Method（PEM）is an effective method for calculation of random vibration.Due to complicated and coupling random vibration in rocket or shuttle launching,the new staging white noise mathematical model is deduced according to the practical launch environment.This deduced model is applied for PEM to calculate the specific structure of Time of Flight Counter（ToFC）.The responses of power spectral density and the relevant dynamic characteristic parameters of ToFC are obtained in terms of the flight acceptance test level.Considering stiffness of fixture structure,the random vibration experiments are conducted in three directions to compare with the revised PEM.The experimental results show the structure can bear the random vibration caused by launch without any damage and key dynamical parameters of ToFC are obtained.The revised PEM is similar with random vibration experiment in dynamical parameters and responses are proved by comparative results.The maximum error is within 9%.The reasons of errors are analyzed to improve reliability of calculation.This research provides an effective method for solutions of computing dynamical characteristic parameters of complicated structure in the process of rocket or shuttle launching.

Calculation of vibrational energy transition rates in acoustic relaxation processes for excitable gas molecules

To research the correlation between vibrational energy transition rates and acoustic relaxation processes in excitable gases, the vibrational relaxation theory provided by Tanczos [J. Chem. Phy3. 25, 439 （1956）] is applied to calculate the energy transition rates of Vibrational- Vibrational （V-V） and Vibrational-Translational （V-T） energy transfer in gas mixtures. The results of calculation for the multi-relaxation processes in various gas mixtures, consisting of carbon dioxide, methane, chlorine, nitrogen, and oxygen at room temperature, demonstrate that the acoustic energy stagnated in every vibrational mode is coupled with each other through V-V energy exchanges. The vibrational excitation energy will relax through the V-T de-excitation path of the lowest mode because of its fastest V-T transition rate, resulting in that only one absorption peak can be measured for most of excitable gas mixtures. Thus, an effective model is provided to analyze how the vibrational energy transition rates affect the characteristics of acoustic relaxation processes and acoustic propagation in excitable gas mixtures.

Experimental analysis on air-to-water sound transmission loss in shallow water

The research of propagation characteristics of air-to-water sound transmission is of great importance to the detection of aerial targets from underwater.In order to study the propagation characteristics of air-to-water sound transmission in shallow water,State Key Laboratory of Acoustics,Institute of Acoustics,conducted an experiment in the South China Sea in March,2013.During the experiment,multi-frequency signals transmitted by a hooter hung on a research ship were received by an underwater hydrophone,and the distance between the hooter and the hydrophone was from 2.4 km to 9.8 km approximately.Through analyzing experimental data in this work,the experimental air-to-water transmission loss at frequencies128 Hz and 256 Hz is estimated up to 9.8 km in range,and its oscillation structure is evident.The wave-number integration approach is used to simulate theoretical air-to-water transmission losses,which are in good agreement with experimental values and to explain the experimental air-to-water sound transmission characteristics.

Investigation of electronic excited states in single-molecule junctions

The investigation of electronic excited states in single-molecule junctions not only provides platforms to reveal the photophysical and photochemical processes at the molecular level,but also brings opportunities for the development of single-molecule optoelectronic devices.Understanding the interaction mechanisms between molecules and nanocavities is essential to obtain ondemand properties in devices by artificial design,since molecules in junctions exhibit unique behaviors of excited states benefited from the structures of metallic nanocavities.Here,we review the excitation mechanisms involved in the interplay between molecules and plasmonic nanocavities,and reveal the influence of nanostructures on excited-state properties by demonstrating the differences in excited state decay processes.Furthermore,vibronic transitions of molecules between nanoelectrodes are also discussed,offering a new single-molecule characterization method.Finally,we provide the potential applications and challenges in single-molecule optoelectronic devices and the possible directions in exploring the underlying mechanisms of photophysical and photochemical processes.

The absorption coefficient measurement of underwater materials in a water tube by using the wide-band pulse method

The existing absorption coefficient measurement in a water tube is limited in low frequency due to the limitation of the pulse tube length.A wide-band pulse tube method based on the post-processing inverse filter is proposed.After obtaining the response of the entire system,the transducer is excited with wide-band,short-duration signals.Then,the received signals are processed with inverse filters and the ＂blurred＂ reflective signals of standard reflector and test sample are recovered respectively,finally,the reflection coefficient and absorption coefficient are calculated.Simulation work is implemented to verify the advantage of postprocessing inverse filter over pre-processing inverse filter in terms of low frequency measurement.To verify the proposed method,two different wide-band pulses in the separate frequency ranges are adopted to measure the same rubber material.The experimental results indicate that the wide-band pulse method and CW（Continuous Wave） pulse method have good agreement in both low frequency range and high frequency range.Wide-band pulse method is of high efficiency,and the low frequency reaches 350 Hz,which is able to extend the low frequency range.