Suppression effect of jet flow on pulsating pressure of cavity using scale-adaptive simulation model

The suppression of the aerodynamic noise in the cavity has a great significance to solve relevant puzzles of weapon bays. Acoustic field of the standard cavity model is simulated by using the computational fluid dynamics technology based on scale-adaptive simulation （SAS） model. The results obtained by the proposed method in this paper show reasonable agreement with experiments. On the basis of this, effect of different jet flow rates on the time-averaged variables, turbulent kinetic energy, root mean square （RMS） of sound pressure, sound sources distribution and the pulsating pressure distribution in the cavity is studied. The analysis shows that the jet flow has great influence on the cavity flow field and the distribution of pulsating pressure RMS by changing the morphology of the shear layer. The most obvious of these measures is spout4 configuration, the influence mainly in the form of reducing the pulsating pressure of the whole cavity and changing the sound pressure level in the far field. The results show that different jet flow rates have different control effects on pulsating pressure in the cavity and sound pressure level in the far field. Furthermore, the jet flow rates and the suppression effect on the pulsating pressure have no linear relation.

A High-Pulse-Energy High-Beam-Quality Tunable Ti:Sapphire Laser Using a Prism-Dispersion Cavity

A high-pulse-energy high-beam-quality tunable Ti：sapphire laser pumped by a frequency-doubled Nd：YAG laser is demonstrated. Using a fused-silica prism as the dispersion element, a tuning range of 740-855 nm is obtained. At an incident pump energy of 774mJ, the maximum output energy of 104mJ at 790nm with a pulse width of 100μs is achieved at a repetition rate of 5 Hz. To the best of our knowledge, it is the highest pulse energy at 790 nm with pulse width of hundred micro-seconds for an all-solid-state laser. The linewidth of output is 0.5 nm, and the beam quality factor M2 is 1.16. The high-pulse-energy high-beam-quality tunable Ti：sapphire laser in the range of 740-855 nm can be used to establish a more accurate and consistent absolute scale of second-order optical-nonlinear coefficients for KBe2BO3F2 measured in a wider wavelength range and to assess Miller＇s rule quantitatively.

High efficiency filtering using two-dimensional photonic crystal coupled cavity structures

Transmission spectra of coupled cavity structures （CCSs） in two-dimensional （2D） photonic crystals （PCs） are investigated using a coupled mode theory, and an optical filter based on CCS is proposed. The performance of the filter is investigated using finite-difference time-domain （FDTD） method, and the results show that within a very short coupling distance of about 3λ, where ）, is the wavelength of signal in vacuum, the incident signals with different frequencies are separated into different channels with a contrast ratio of 20 dB. The advantages of this kind of filter are small size and easily tunable operation frequencies.

Teleportation of an unknown two-atom state using simultaneous interaction of two two-level atoms with cavity field

Proposal for the teleportation of two-atom state is presented. It is based on the simultaneous interaction of two two-level atoms with a single-mode cavity with a filed of n photons. In the proposed scheme, two pairs of EPR state are used as quantum channel to teleport an unknown two-atom state. The completed time is greatly reduced and cavity field is not required to be detected are shown to be the distinct features of the presented scheme.

Enhancing entanglement generation of two atoms in a cavity with white noise using classical driving fields

We investigate the entanglement dynamics of a quantum system consisting of two two-level atoms in a cavity with classical driving fields in the presence of white noise. The cavity is initially prepared in the vacuum state. Generally, the entanglement of two atoms decreases with the intensity of the thermal fields and the coupling strength of the two-level atoms to the thermal fields. However, we find that the entanglement of the quantum system can be enhanced by adjusting the frequency and the strength of the classical driving fields in the presence of white noise.

Novel scheme of manipulating topological physics by using a single degenerate cavity

Subject Code:F05 With the support by the National Natural Science Foundation of China,the research group from the Key Lab of Quantum Information(CAS)led by Prof.Guo Guangcan(郭光灿)at the University of Science and Technology of China proposed a new routine to manipulate topological physics using only a single

On acoustic performance for viscoelastic coating containing axisymmetric cavities using the multiple scattering method

A semi-analytical/numerical model based on the multiple scattering （MS） method has been established for analyzing the effect of acoustic performance on main energy attenua- tion mechanism in viscoelastic coating containing axisymmetric cavities. The basic functions of stress and displacement of the axisymmetric cavity surface are derived in the system of spheri- cal coordinates. The transition matrix between the incident wave and the scattering wave are obtained by the numerical integral of the basic functions of the cavity surface. The reflection, transmission and absorption performance of viscoelastic materials containing periodic cavities are calculated using the MS method and the wave propagating theory of the multi-layered medium. The results indicate that low frequency energy is mainly attenuated through cavity resonance. The resonant properties are found to be very sensitive to the boundary conditions. The coupling of the double-cavity is capable of extending the absorption to even lower fre- quencies. The absorption performance of the viscoelastic coating in the high frequency range is independent of the backing material. Its energy attenuation depends mainly on acoustic properties of cavity scattering and mode conversion.