Liu Da-He

The Blood Flow at Arterial Bifurcations Simulated by the Lattice Boltzmann Method

The Programmed model of non-Newtonian blood now (the Casson model) at arterial bifurcations is established by the lattice Boltzmann method. The blood flow field under different Reynolds numbers is simulated, and distribution of dynamic factors such as flow velocity, shear stress, pressure and shear rate are presented. The existence of the fluid separation zone is analyzed. This provides a basis for further studies of the relationship between hemodynamic factors and pathogenesis, as well as a reference for a better understanding of the pathological changes and location of sediments, and the plague factor in arteries.

Simulation of Blood Flow at Vessel Bifurcation by Lattice Boltzmann Method

The application of the lattice Boltzmann method to the large vessel bifurcation blood flow is investigated in a wide range of Reynolds numbers. The velocity, shear stress and pressure distributions at the bifurcation are presented in detail. The flow separation zones revealed with increase of Reynolds number are located in the areas of the daughter branches distal to the outer corners of the bifurcation where some deposition of particular blood components might occur to form arteriosclerosis. The results also demonstrate that the lattice Boltzmann method is adaptive to simulating the flow in larger vessels under a high Reynolds number.

Simulating High Reynolds Number Flow by Lattice Boltzmann Method

A two-dimensional channel flow with different Reynolds numbers is tested by using the lattice Boltzmann method under different pressure and velocity boundary conditions. The results show that the simulation error increases, and the pressure and the flow rate become unstable under a high Reynolds number. To improve the simulation precision under a high Reynolds number, the number of fluid nodes should be enlarged. For a higher Reynolds-number flow, the velocity boundary with an approximately parabolic velocity profile is found to be more adaptive. Blood flow in an artery with cosine shape symmetrical narrowing is then simulated under a velocity boundary condition. Its velocity, pressure and wall shear stress distributions are consistent with previous studies.

Simulation of Non-Newtonian Blood Flow by Lattice Boltzman Method

Blood flow under various conditions of vessel is simulated as a non-Newtonian fluid by the two-dimensional Lattice Boltzmann method, in which the Casson model is used to express the relationship between viscosity and shear rate of the blood. The flow field distributions at certain sites near the narrowing and bifurcation of the vessel explain the hemodynamic mechanism of the predilection of the atherosclerotic lesions for these sites which are consistent with that found by medical studies.

The Paeudocoloring Of An Encoded Phase-Picture

This paper presents a new method for the pseudocoloring of an encoded phase-picture. ThQ method is carried out only with one white-black film and once-through encoding. The encoded film is transformed into a phase encodes transparency, then it is put on the input-plane of a white light processor, and the density pseudoculor image is obtained on the out-put-plane by spatial filtering of the Fourier spectrum. This method has born used in the processing of the films of astronomy, remote-sensing, biology, and medicine, and good results have been obtained.

Reflecting a single attosecond pulse by using periodic Mo/Si multilayer mirrors with different layers

The reflecting of a single attosecond pulse from a periodic Mo/Si multilayer was investigated. By changing the number of bi-layers, the periodic multilayer showed greatly different spectral and temporal responses of the attosecond pulse reflection, which has been discussed in detail in this paper. The capability of attosecond pulse reflection of the periodic multilayers with different bi-layer numbers has been evaluated using suitable temporal parameters. In addition, the condition for obtaining high-efficiency reflected pulses has been analyzed by comparing the pulse responses of the periodic multilayer with different layers. The transfer-matrix method together with the fast Fourier transform has been used in our simulation.

Detection of Perfect Cloak in Time Domain

We propose a method for detecting perfect invisible cloak based on the scattering of the materials of the cloak. The position of the detected cloak can also be determined. The demonstration shows that the detecting effect is obvious, and the accuracy of the detection is high.

Narrow Band Longitude Mode Selector of Laser Based on Conjugated Photonic Crystals

Properties of transmission spectra of multi-layers consisting of two conjugated photonic crystals are investigated. It is found that, in the case of a small amount of time, the mode density at the interface mode is much larger than that at the band edge. Under certain conditions, the transmission can reach the unity, and the bandwidth can reach the order of picometer. Based on this property, a longitude mode selector of laser consisting of two conjugated photonic crystals made with gain materials is suggested. The effects of the impedance contrast of materials and the refractive index of the environment on the bandwidth are studied.

Three-dimensional lattice Boltzmann method for simulating blood flow in aortic arch

The three-dimensional (3D) lattice Boltzmann models, 3DQ15, 3DQ19 and 3DQ27, under different wall boundary conditions and lattice resolutions have been investigated by simulating Poiseuille flow in a circular cylinder for a wide range of Reynolds numbers. The 3DQ19 model with improved Fillippova and Hanel (FH) curved boundary condition represents a good compromise between computational efficiency and reliability. Blood flow in an aortic arch is then simulated as a typical haemodynamic application. Axial and secondary fluid velocity and effective wall shear stress profiles in a 180° bend are obtained, and the results also demonstrate that the lattice Boltzmann method is suitable for simulating the flow in 3D large-curved vessels.

Improving attosecond pulse reflection by large angle incidence for a periodic multilayer mirror in the extreme ultraviolet region

The improvement of attosecond pulse reflection by large angle incidence for a periodic multilayer mirror in the extreme ultraviolet region has been discussed. Numerical simulations of both spectral and temporal reflection characteristics of periodic multilayer mirrors under various incident angles have been analyzed and compared. It was found that the periodic multilayer mirror under a larger incidence angle can provide not only higher integrated reflectivity but also a broader reflection band with negligible dispersion, making it possible to obtain better a reflected pulse that has a higher pulse reflection efficiency and shorter pulse duration for attosecond pulse reflection. In addition, by increasing the incident angle, the promotion of attosecond pulse reflection capability has been proven for periodic multilayer mirrors with arbitrary layers.