Analysis of Dynamic Response of a Two Degrees of Freedom (2-DOF) Ball Bearing Nonlinear Model

Often the input values used in mathematical models for rolling bearings are in a wide range, i.e., very small values of deformation and damping are confronted with big values of stiffness in the governing equations, which leads to miscalculations. This paper presents a two degrees of freedom (2-DOF) dimensionless mathematical model for ball bearings describing a procedure, which helps to scale the problem and reveal the relationships between dimensionless terms and their influence on the system’s response. The derived mathematical model considers nonlinear features as stiffness, damping, and radial internal clearance referring to the Hertzian contact theory. Further, important features are also taken into account including an external load, the eccentricity of the shaft-bearing system, and shape errors on the raceway investigating variable dynamics of the ball bearing. Analysis of obtained responses with Fast Fourier Transform, phase plots, orbit plots, and recurrences provide a rich source of information about the dynamics of the system and it helped to find the transition between the periodic and chaotic response and how it affects the topology of RPs and recurrence quantificators.

Accuracy improvement of phase estimation in electron holography using noise reduction methods

We try to improve the limit of the phase estimation of the interference fringe at low electron dose levels in electron holography by a noise reduction method. In this paper, we focus on unsupervised approaches to apply it to electron beam-sensitive and unknown samples and describe an overview of denoising methods used widely in image processing, such as wiener filter, total variation denoising, nonlocal mean filters and wavelet thresholding. We compare the wavelet hidden Markov model (WHMM) denoising that we have studied so far with the other conventional noise reduction methods. We evaluate the denoise performance of each method using the peak signal-to-noise ratio between noise-free and the target holograms (noisy or denoised holograms) and the root mean-square error (RMSE) between the true phase of the fringe and the measured phase by the discrete Fourier transform phase estimator. We show the denoised holograms for simulation and experimental data by using each noise reduction method and then discuss evaluation indexes obtained from these denoised holograms. From experimental results, it can be seen that the WHMM denoising can reduce the RMSE of fringe phase to about 1/4.5 for noisy simulation holograms and it has stable and good performance for noise reduction of observed holograms with various image qualities.

Analisis Misalignment Citra Multispektral Terhadap Citra Pankromatik Pada Data Worldview-2

The standard data of Worldview-2 owned by LAPAN is Ortho-Ready Standard level 2 (OR2A) data consisting of 4 multispectral bands (blue, green, red, NIR) and one panchromatic band each 2 m and 0,5 m spatial resolution. Both images have different metadata and RPC, making it possible to perform geometric corrections separately. This paper discusses the analysis of the inaccuracies of multispectral image positions to panchromatic images compared to those that have been systematically geometric corrected. The method used is fast fourier transform phase matching by taking 500 binding points between the two images. The measurement results prove that the multispectral image of the Worldview-2 data of the OR2A level has a larger shift compared with multispectral image that has been systematically geometric corrected. The multispectral image of the OR2A data shifts are 2,14 m on the X-axis and 0,42 m on the Y-axis. While the multispectral image that has been systematically geometric corrected shifts are 1,72 m on the X-axis and 0,54 m on the Y-axis.ABSTRAKData standar Worldview-2 yang dimiliki oleh LAPAN merupakan data Ortho-Ready Standard level 2 (OR2A) yang terdiri dari 4 kanal multispektral (biru, hijau, merah, NIR) dan satu kanal pankromatik masing-masing memiliki resolusi spasial 2 meter dan 0,5 meter. Kedua kanal tersebut memiliki metadata dan RPC yang berbeda, sehingga memungkinkan untuk melakukan koreksi geometrik secara terpisah. Tulisan ini membahas tentang analisis misalignment citra multispektral terhadap citra pankromatik dibandingkan dengan yang telah terkoreksi geometrik sistematik. Metode yang digunakan adalah fast fourier transform phase matching dengan mengambil 500 titik ikat antara kedua citra tersebut. Hasil pengukuran membuktikan bahwa citra multispektral data Worldview-2 level OR2A memiliki pergeseran yang lebih besar dibandingkan dengan citra multispektral yang terkoreksi geometrik sistematik. Citra multispektral data OR2A bergeser 2,14 meter pada sumbu X dan 0,42 meter pada sumbu Y. Sedangkan citra multispektral data terkoreksi geometrik sistematik bergeser 1,72 meter pada sumbu X dan 0,54 meter pada sumbu Y.