The effect of electron initial longitudinal velocity on the non-sequential double ionization process in an elliptically polarized laser field

The effect of initial longitudinal velocity of the tunnelled electron on the non-sequential double ionization （NSDI） process in an elliptically polarized laser field is studied by a semiclassical model. We find that the non-zero initial longitudinal velocity has a suppressing effect on single-return collision （SRC） events in the double ionization process, more specifically, it results in an obvious reduction in the center part of the correlation momentum distributions in the direction of the major polarization axis （z axis） and makes the distribution of single-return collision in the minor polarization axis （x axis） become narrower.

Design of Ethernet Based Data Acquisition System for Yaw Rate and Longitudinal Velocity Measurement in Automobiles

Design of an Ethernet network compatible data acquisition system for the measurement of yaw rate and longitudinal velocity in automobiles is presented.The data acquisition system includes a base node and a remote node.The remote node consists of a micro electro mechanical system(MEMS)accelerometer,an MEMS gyroscope,an advanced RISC machines(ARM)CORTEX M3 microcontroller and an Ethernet PHY device.The remote node measures the yaw rate and the longitudinal velocity of an automobile and sends the measured values to the base node using Ethernet communication.The base node consists of an ARM CORTEX M3 microcontroller and an Ethernet PHY device.The base node receives the measured values and saves in a microSD card for further analysis.The characteris tics of the net work and the measurement system are stu died and repor ted.

Electron Transport Coefficients and Effective Ionization Coefficients in SF_6-O_2 and SF_6-Air Mixtures Using Boltzmann Analysis

The electron drift velocity, electron energy distribution function （EEDF）, densitynormalized effective ionization coefficient and density-normalized longitudinal diffusion velocity are calculated in SF6-O2 and SFs-Air mixtures. The experimental results from a pulsed Townsend discharge are plotted for comparison with the numerical results. The reduced field strength varies from 40 Td to 500 Td （1 Townsend=10-17 V.cm2） and the SF6 concentration ranges from 10% to 100%. A Boltzmann equation associated with the two-term spherical harmonic expansion approximation is utilized to gain the swarm parameters in steady-state Townsend. Results show that the accuracy of the Boltzlnann solution with a two-term expansion in calculating the electron drift velocity, electron energy distribution function, and density-normalized effective ionization coefficient is acceptable. The effective ionization coefficient presents a distinct relationship with the SF6 content in the mixtures. Moreover, the E/Ncr values in SF6-Air mixtures are higher than those in SF6-O2 mixtures and the calculated value E/Ncr in SF6-O2 and SF6-Air mixtures is lower than the measured value in SFB-N2. Parametric studies conducted on these parameters using the Boltzmann analysis offer substantial insight into the plasma physics, as well as a basis to explore the ozone generation process.

Some exact solutions of the oscillatory motion of a generalized second grade fluid in an annular region of two cylinders

The velocity field and the associated shear stress corresponding to the longitudinal oscillatory flow of a generalized second grade fluid, between two infinite coaxial circular cylinders, are determined by means of the Laplace and Hankel transforms. Initially, the fluid and cylinders are at rest and at t = 0＋ both cylinders suddenly begin to oscillate along their common axis with simple harmonic motions having angular frequencies Ω1 and Ω2. The solutions that have been obtained are presented under integral and series forms in terms of the generalized G and R functions and satisfy the governing differential equation and all imposed initial and boundary conditions. The respective solutions for the motion between the cylinders, when one of them is at rest, can be obtained from our general solutions. Furthermore, the corresponding solutions for the similar flow of ordinary second grade fluid and Newtonian fluid are also obtained as limiting cases of our general solutions. At the end, the effect of different parameters on the flow of ordinary second grade and generalized second grade fluid are investigated graphically by plotting velocity profiles.

Exact solutions for the flow of second grade fluid in annulus between torsionally oscillating cylinders

The velocity field and the associated shear stress corresponding to the torsional oscillatory flow of a second grade fluid, between two infinite coaxial circular cylinders, are determined by means of the Laplace and Hankel transforms. At time t = 0, the fluid and both the cylinders are at rest and at t = 0 ＋ , cylinders suddenly begin to oscillate around their common axis in a simple harmonic way having angular frequencies ω 1 and ω 2 . The obtained solutions satisfy the governing differential equation and all imposed initial and boundary conditions. The solutions for the motion between the cylinders, when one of them is at rest, can be obtained from our general solutions. Furthermore, the corresponding solutions for Newtonian fluid are also obtained as limiting cases of our general solutions.

Influence of the connecting condition on the dynamic buckling of longitudinal impact for an elastic rod

The stress wave propagation law and dynamic buckling critical velocity are formulated and solved by considering a general axial connecting boundary for a slender elastic straight rod impacted by a rigid body. The influence of connecting stiffness on the critical velocity is investigated with varied impactor mass and buckling time. The influences of rod length and rod mass on the critical velocity are also discussed. It is found that greater connecting stiffness leads to larger stress amplitude, and further results in lower critical velocity. It is particularly noteworthy that when the connecting stiffness is less than a certain value, dynamic buckling only occurs before stress wave reflects off the connecting end. It is also shown that longer rod with larger slenderness ratio is easier to buckle, and the critical velocity for a larger-mass rod is higher than that for a lighter rod with the same geometry.

NUMERICAL SIMULATION ON EMERGENCY TUNNEL FIRES WITH TRANSVERSE VENTILATION

In case of an emergency fire in vehicle tunnel, the ventilation system should be operated effectively to control the thermal fume and smoke inside tunnel. However, it is quite difficult to predict every kind of emergency fire by fire tests because the actual movement of thermal fume and smoke is affected by many factors such as ventilation system, structure of the tunnel, etc., especially for tunnels equipped with transverse ventilation system on which rare experimental and numerical studies have been found so far. In this paper, a three dimensional numerical simulator using LES turbulence model is developed to simulate the movement of thermal fume induced by emergency fire in vehicle tunnel. The SMAC method is employed to calculate the pressure and velocity fields. The upwind differnece scheme with the third order accuracy is applied for the discretization of convection terms of the governmental equations. As the applications of the present simulator, the behavior of thermal fume induced by emergency fire in a vehicle tunnel with two direction traffic is analyzed. It is confirmed that the partial transverse ventilation system is more effective than the longitudinal ventilation system under large and small velocities of longitudinal bulk flow inside tunnel. Simulation result also shows that remaining the velocity of longitudinal bulk flow near zero around fire source can provide the best working condition for partial transverse ventilation system.

A 3-D numerical simulation of the characteristics of open channel flows with submerged rigid vegetation

This paper applies the Flow-3D to investigate the impacts of different flow discharge and vegetation scenarios on the flow velocity (including the longitudinal, transverse and vertical velocities). After the verification by using experimental measurements, a sensitivity analysis is conducted for the vegetation diameter, the vegetation height and the flow discharge. For the longitudinal velocity, the greatest impact on the flow structure originates from the vegetation diameter, rather than the discharge. The vegetation height, however, determines the inflection point of the vertical distribution. Comparing the transverse velocities at two positions in the vegetated area, i.e., the upstream and the downstream, a symmetric pattern is identified along the water depth. The same pattern is also observed for the vertical velocity regardless of the flow or vegetation scenario, including both transverse and vertical fluid circulation patterns in the vegetated area. Moreover, the larger the vegetation diameter is, the more evident these patterns become. The upper circulation occurs near the vegetation canopy. These findings regarding the circulations along the transverse and vertical directions in the vegetated region shed light on the 3-D flow structure through the submerged vegetation.

Effect of vegetation on flow structure and dispersion in strongly curved channels

The effect of vegetation on the flow structure and the dispersion in a 180 o curved open channel is studied. The Micro ADV is used to measure the flow velocities both in the vegetation cases and the non-vegetation case. It is shown that the velocities in the vegetation area are much smaller than those in the non-vegetation area and a large velocity gradient is generated between the vegetation area and the non-vegetation area. The transverse and longitudinal dispersion coefficients are analyzed based on the experimental data by using the modified N- zone models. It is shown that the effect of the vegetation on the transverse dispersion coefficient is small, involving only changes of a small magnitude, however, since the primary velocities become much more inhomogeneous with the presence of the vegetation, the longitudinal dispersion coefficients are much larger than those in the non-vegetation case.