A FAST CLASSIFICATION METHOD FOR SINGLE-PARTICLE PROJECTIONS WITH A TRANSLATION AND ROTATION INVARIANT

The aim of the electron microscopy image classification is to categorize the projection images into different classes according to their similarities. Distinguishing images usually requires that these images are Migned first. However, alignment of images is a difficult task for a highly noisy data set. In this paper, we propose a translation and rotation invariant based on the Fourier transform for avoiding alignment. A novel classification method is therefore established. To accelerate the classification speed, secondary-classes are introduced in the classification process. The test results also show that our method is very efficient and effective. Classification results using our invariant are also compared with the results using other existing invariants, showing that our invariant leads to much better results.

Spectral Element Simulation of Rotating Particle in Viscous Flow

Spectral element methods (SEM) are superior to general finite element methods (FEM) in achieving high order accuracy through p-type refinement. Owing to orthogonal polynomials in both expansion and test functions, the discretization errors in SEM could be reduced exponentially to machine zero so that the spectral convergence rate can be achieved. Inherited the advantage of FEM, SEM can enhance resolution via both h-type and p-type mesh-refinement. A penalty method was utilized to compute force fields in particulate flows involving freely moving rigid particles. Results were analyzed and comparisons were made;therefore, this penalty-implemented SEM was proven to be a viable method for two-phase flow problems.

Integrated Relative Position and Attitude Control of Spacecraft in Proximity Operation Missions

This paper addresses an integrated relative position and attitude control strategy for a pursuer spacecraft flying to a space target in proximity operation missions. Relative translation and rotation dynamics are both presented, and further integratedly considered due to mutual couplings, which results in a six degrees-of-freedom (6-DOF) control system. In order to simultaneously achieve relative position and attitude requirements, an adaptive backstepping control law is designed, where a command filter is introduced to overcome 'explosion of terms'. Within the Lyapunov framework, the proposed controller is proved to ensure the ultimate boundedness of relative position and attitude signals, in the presence of external disturbances and unknown system parameters. Numerical simulation demonstrates the effect of the designed control law.

Aerodynamic Characteristics of a Normal Hovering Foil with Synthetic Jet Actuation

The aerodynamic characteristics of a normal hovering foil with Synthetic Jet(SJ)actuation are numerically studied in this work.An elliptic foil with ratio of 4 undergoes the imposed translation and rotation synchronously.A pair of SJs with the same frequency and strength is placed on the upper and lower surfaces of the foil.Thus,the local flow field around the foil would be influenced.At the Reynolds number of 100 and the rotating axis position of half chord,the effects of the inclined angle between the jet direction and the chord line,the phase angle between the SJs and the translation as well as the SJ location on the aerodynamic characteristics are systematically examined.Compared with the oscillating foil without SJ actuation,it is illustrated that the enhancement of mean lift force and hovering efficiency can be obtained by using the SJs with suitable working parameters.Based on the numerical analysis,it is found that the jet flow on the foil surfaces,which changes the local pressure distribution,can benefit the aerodynamic performance of the hovering foil.