INVESTIGATION OF UNSTEADY EXCITATION EFFECTS ON AERODYNAMIC PROPERTIES OF AIRFOILS

In this paper, the techniques to manage and control the flow over airfoils by using the external unsteady excitations are investigated. The mechanisms of these excitation effects are also explored. The principal goal of this study is to gain a better understanding and to find the possible ways for enhancing the aerodynamic efficients. The experimental investigations are carried out in two low-speed wind tunnels. The test models are two dimensional airfoils with different section geometries. Four means of excitations have been used in these experiments. (1) The pitch oscillation of the airfoil high-angle-of-attack situation. (2) The moving surface effects of the airfoil with a leading edge rotating cylinder. (3) Oscillating leading edge flaperon. (4) Small oscillating spoiler located near the leading edge of the airfoil. The lift, drag and pitch moment coefficients are measured in these experiments. But, we will put the emphasis only on the 'dynamic amplifying effects' on aerodynamic lift in this paper. Results obtained indicate that the beneficial aerodynamic effects of section lift increase can be obtained at the high angle of attack near stall regime, as long as the frequency and amplitute of the excitation are appropriately selected.

Effect of excitation current intensity on mechanical properties of ZL205A castings solidified under a traveling magnetic field

The effect of excitation current intensity on the mechanical properties of ZL205 A castings solidified under a traveling magnetic field was studied. The results of the experiment indicate that the excitation current intensity of the traveling magnetic field has a great influence on the mechanical properties of the ZL205 A castings. When the excitation current intensity is 15 A, the tensile strength and elongation of ZL205 A alloy castings increase 27.2% and 67.7%, respectively, compared with those of the same alloy solidified under gravity. The improvement of mechanical properties is attributed to the decrease of micro-porosity in the alloy. Under the traveling magnetic field, the feeding pressure in the alloy melt before solidification can be enhanced due to the electromagnetic force. Moreover, the melt flow induced by the traveling magnetic field can decrease the temperature gradient. The feeding resistance will be increased because the temperature gradient decrease. So traveling magnetic field has an optimum effect on feeding.

Temperature and hydrogen-like impurity effects on the excited state of the strong coupling bound polaron in a CsI quantum pseudodot

With hydrogen-like impurity（HLI） located in the center of Cs I quantum pseudodot（QPD） and by using the variational method of Pekar type（VMPT）, we investigate the first-excited state energy（FESE）, excitation energy and transition frequency of the strongly-coupled bound polaron in the present paper. Temperature effects on bound polaron properties are calculated by employing the quantum statistical theory（QST）. According to the present work＇s numerical results, the FESE, excitation energy and transition frequency decay（amplify） with raising temperature in the regime of lower（higher）temperature. They are decreasing functions of Coulomb impurity potential strength.

The Effect of Some Effective Quantities to Electronic Stopping Power

The dependences of effective quantities Z＊, Zt,/＊, （effective number of electrons for ionization and for quasi-molecule, effective mean excitation energy） on the incident ion energy have been studied for a pervious stopping power calculation method, and Bohr stripping criterion and quasi-molecule criterion in this regard have been discussed in some details. The effect of effective quantities to the obtained stopping power results is investigated by calculating stopping powers. The contributions to stopping power from the modified LSS and Bethe formulas have been calculated separately and compared in graphs of stopping power. The stopping power for lithium ions in the intermediate and higher energy region is found to be dominant due to excitation-ionization whereas quasi molecule criterion is dominant in the lower energy region.

An Experimental Study on Optimization of Large-volume Airgun Source Excitation Conditions in a Reservoir

Through manual pickup of seismic phases,the number of recording stations,the farthest observation distance of station and received energy are determined,then optimal operating condition processing software is developed to evaluate the excitation effect of operating conditions. The optimal operating conditions in the Mianhuatan Reservoir are determined using this software. They are: optimal water depth 25 m,airgun array sink depth 9m and airgun array size 7m × 7m. At the same time,accumulative stacking results for every 10 times are analyzed for 300 fixed-point excitations. It is concluded that the excitation effect shows a rapidly rising trend at 10 to 90 times stacking,a slowly rising trend at 100 to 150 times stacking,a rapidly rising trend at 160 to 240 times stacking,and a slowly rising trend at 250 to 300 times stacking. As the number of stacking increases,the propagation distance and the number of recording stations also increase gradually.

The isotopic effects in the IR-multiphoton excitation of molecules with c_(2v) symmetry

Quantum dynamical calculations for the IR-multiphoton excitation of H_2O,D_2O and T_2O are presented using a generalized Hamiltonian for XY_2 molecules.The energy spectra obtained from this Hamiltonian are in good agreement with those of the experiments.The long time average of the transition probabilities and the isotopic effects are discussed in detail,

Analysis of survival probability based on superasymmetric reaction systems

The survival probability of an excited compound nucleus was studied using two different approaches of the washing out of shell effects with excitation energy based on a superasymmetric reaction system.The estimated evaporation residue cross sections based on the two different methods are compared with the available experimental data.Both methods are in agreement with the experimental data to a certain extent for some specific reactions and emission channels.