Optimization of Plasma Plume Characteristics Based on Multi-anode Coaxial Ablative Pulsed Plasma Thruster

A special surface discharge is proposed based on the multi-anode electrode geometry. Instead of the traditional surface flashover of creepage on the insulator surface between the electrodes, a surface discharge with one of the electrodes being placed far away from the insulator is achieved in this paper. The unique electric field distribution due to the multi-anode electrode geometry has a significant influence on the discharge process of the surface discharge. It changes the generation and propagation process of the plasma, forming a plasma plume contributes to the propulsion performance of the thruster. Through theoretical analysis of the obtained plume data, it is indicated that the ablative pulsed plasma thruster based on multi-anode electrode geometry (short for multi-anode APPT) promotes the internal pressure of the plasma jet during its propagation and significantly increases the density and energy of charged particles. The discharge phenomena manifest that the multi-anode APPT and the helix-coil multi-anode APPT effectively increase the intensity of the plasma plume. Through electron density spatial distribution measurement, it has been found that the helix-coil multi-anode APPT increases the density of plasma in the axial direction to more than 4 times of the conventional coaxial APPT and reduces the electron density in other directions. In the propulsion test, it has been demonstrated that the multi-anode APPT and the helix-coil multi-anode APPT have better performance in terms of the impulse bit and the thrust-to-power ratio. In addition, it is also identified that the pinch effect will be enhanced with the increase of discharge power and the propulsion performance is promoted more distinctly. The multi-anode APPT and the helixcoil multi-anode APPT have been proved to have potential application advantage in the field of micro-satellite propulsion.Comment: 12 pages, 12 figure

Essays on Microeconometrics with Applications to Social Network

This dissertation includes three chapters on microeconometrics with applications to social network. In the first chapter, we study identification and estimation of peer effects in a game theoretical social interaction model with incomplete information. We show that players’ equilibrium choice probabilities and peer effects can be identified in the presence of measurement errors in network connections by exploiting the nonparametric methodology developed for nonclassical measurement error models. Based on the identification methodology, a semiparametric estimation method is established and applied to study the peer effects on youth alcohol drinking behaviors using data of adolescents in the United States, our empirical findings show that peer effects will be significantly underestimated if measurement errors are ignored. In the second chapter, we study strategic social interaction among economic agents that are connected through the phenomena of homophily. In particular, we measure homophily effects by the differences between players’ socioeconomic characteristics. Under the symmetric equilibrium selection mechanism, we establish a nonparametric approach to identify the structural model and propose a computationally feasible two-step estimation procedure. The asymptotic properties of the two-step estimator are derived under context of “large games", i.e., the number of players going to infinity. Finally, we apply the identification and estimation methods to study the peer effects on youth smoking behaviors using data of adolescents in the United States, our empirical findings show positive and statistically significant peer effects and demonstrate the empirical importance of including homophily effect in our model. In the third chapter, we study bandwidth selection method for the smoothed maximum score estimator. The smoothed maximum score estimator is a semiparametric estimator for binary response model, which is very useful for many economics and statistics applications. The method for selecting the smoothing parameter (bandwidth) in smoothed maximum score estimator is analogous to the plug-in method in kernel density estimation. It requires initial “pilot" values of the bandwidth to obtain the optimal bandwidth. The method has the disadvantage of not being fully data-driven. In this paper, we propose a data-driven bandwidth selection method by minimizing a cross-validated criterion function. Simulation results show that our proposed method performs better than existing methods

Spatial moving sound source with headphone

movement soundArchitecture & Allied Art