The Correlation and Spectrum Research on Cylindrical Surface Lapping Machined with Abrasive Jet Finishing Restricted by Grinding Wheel

2008 ◽  
Vol 389-390 ◽  
pp. 320-325
Author(s):  
Feng Liu ◽  
Ya Dong Gong ◽  
Yu Qiao Shan ◽  
Guang Qi Cai
Keyword(s):  
Correlation Function ◽  
Cross Correlation ◽  
Low Frequency ◽  
Grinding Wheel ◽  
Small Range ◽  
Auto Correlation ◽  
Surface Contour ◽  
Power Spectral ◽  
Finishing Process ◽  
Auto Correlation Function

With the correlation in stochastic process applied to the experimental results, the surface during grinding and further lapping with abrasive jet finishing (AJF) restricted by grinding wheel was investigated with respect to auto correlation function (ACF) , cross correlation function (CCF) and power spectral density (PSD) analysis. The results indicated that AJF made the surface contour formed periodicity in a small range and removed fluctuation of the surface contour in low frequency greatly. The average spacing of the surface contour decreased and the machined surfaces changed from continuous parallel micro-groove and plough to randomly distributed discontinuous micro-pit with the increase of machining circles. The surface texture became fine and surface roughness was obviously improved. Furthermore, the isotropy surface and uniformity veins both parallel and perpendicular machining direction was attained by the finishing process to improve greatly the wearable capability of the workpiece.

scholarly journals New Orthogonal Small Set Kasami Code Sequence

2015 ◽  
Vol 14 (1) ◽  
Author(s):  
I Nyoman Pramaita ◽  
I G.A.G.K. Diafari ◽  
DNKP Negara ◽  
Agus Dharma
Keyword(s):  
Correlation Function ◽  
Cross Correlation ◽  
Code Sequence ◽  
Cross Correlation Function ◽  
Auto Correlation ◽  
M Sequence ◽  
Auto Correlation Function ◽  
Small Set

In this paper, the authors propose the design of a new orthogonal small set Kasami code sequence generated using combination of non-orthogonal m-sequence and small set Kasami code sequence. The authors demonstrate that the proposed code sequence has comparable auto-correlation function (ACF), cross- correlation function (CCF), peak cross-correlation values with that of the existing orthogonal small set Kasami code sequence. Though the proposed code sequence has less code sequence sets than that of the existing orthogonal small set Kasami code sequence, the proposed code sequence possesses one more numbers of members in each code sequence set. The members of the same code set of the proposed code sequence are orthogonal to each other.

Power Spectral Density and Cross Correlation Function Analysis of Finished Surface by Abrasive Jet with Grinding Wheel as Restraint

2009 ◽  
Vol 416 ◽  
pp. 300-305 ◽  
Author(s):  
Chang He Li ◽  
Ya Li Hou ◽  
Yu Cheng Ding ◽  
Bing Heng Lu
Keyword(s):  
Correlation Function ◽  
Spectral Density ◽  
Power Spectral Density ◽  
Function Analysis ◽  
Grinding Wheel ◽  
Work Surface ◽  
Power Spectral ◽  
Finishing Process ◽  
Finished Surface ◽  
Precision Finishing

The abrasive jet finishing process with wheel as restraint is a kind of compound precision finishing process that combined grinding with abrasive jet machining, in which inject slurry of abrasive and liquid solvent to grinding zone between grinding wheel and work surface under no radial feed condition when workpiece grinding were accomplished. The abrasive particles are driven and energized by the rotating grinding wheel and liquid hydrodynamic pressure and increased slurry speed between grinding wheel and work surface to achieve micro removal finishing.In the paper,the finished surface morphology was studied using Scanning Electron Microscope (SEM) and microscope and microcosmic geometry parameters were measured with TALYSURF5 instrument respectively. According to the metrical results, the surface topographical characteristics were evaluated with correlation function and PSD (Power Spectral Density) of random process about machined surface before and after finishing. The results show that longitudinal geometry parameter values of finishing machining surface were diminished comparing with ground surface,and the mean ripple distance was decreased and, ripple and peak density were increased. Furthermore, the finished surface has little comparability compared to grinding machining surface.The isotropy surface and uniformity veins at parallel and perpendicular machining direction were attained by abrasive jet precision finishing with grinding wheel as restraint and the surface quality is improved obviously.

scholarly journals Clustering of galaxies around quasars at z ∼ 4

2019 ◽  
Vol 15 (S352) ◽  
pp. 171-173
Author(s):  
Cristina García-Vergara ◽  
Joseph F. Hennawi ◽  
L. Felipe Barrientos ◽  
Fabrizio Arrigoni Battaia
Keyword(s):  
Dark Matter ◽  
Correlation Function ◽  
Cross Correlation ◽  
Dark Matter Halos ◽  
Lyman Alpha ◽  
Alpha Emitters ◽  
Lyman Break Galaxies ◽  
Auto Correlation ◽  
Auto Correlation Function ◽  
Lyman Alpha Emitters

AbstractWe conduct a survey for Lyman break galaxies (LBGs) and Lyman alpha emitters (LAEs) in the environs of six and 17 z ∼ 4 quasars respectively, probing scales of R≲9h−1Mpc. We detect an enhancement of galaxies (both LBGs and LAEs) in quasar fields, a positive and strong quasar-galaxy cross-correlation function, consistent with a power-law shape, and a strong galaxy auto-correlation function in quasar fields. The three mentioned results are all indicators that quasars trace massive dark matter halos in the early universe.

Research on Improved Code Phase Acquisition Algorithm for BOC(pn,n) Signal

2013 ◽  
Vol 427-429 ◽  
pp. 1794-1798
Author(s):  
Yin Bing Zhu ◽  
Ke Jing Cao ◽  
Bao Li
Keyword(s):  
Correlation Function ◽  
Cross Correlation ◽  
Search Algorithm ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Low Snr ◽  
Auto Correlation ◽  
Auto Correlation Function ◽  
Parallel Code ◽  
Improved Algorithm

Auto correlation function of BOC signal has the character of milti-values, so acquistion of BOC signal can not simply transplant the algorithm of GPS signal. For this reason, parallel code phase search algorithm and cross correlation characteristics of BOC signal are analyzed. And then, the validity of parallel code phase search algorithm on BOC signal are simulated. After that, point to the insufficiency of parallel code phase search algorithm on the acquisiton of BOC signal at low SNR(signal to noise ratio), an improved acquisition algorithm is presented and used to analyze BOC signal. The results show that the improved algorithm is applicable to BOC(pn, n) signal where p is an integer, which expands the application aera of parallel code phase search algorithm; and that the improved algorithm can improve SNR of acquisition about 15dB compared with that of parallel code phase search algorithm, that is to say, the improved algorithm can enhance acquisiton sensitivity of receivers obviously, which is very important to the design of acquisiton algorithm in receivers.

scholarly journals Mapping input noise to escape noise in integrate-and-fire neurons: a level-crossing approach

2021 ◽  
Author(s):  
Tilo Schwalger
Keyword(s):  
Correlation Function ◽  
Hazard Rate ◽  
Second Order ◽  
Level Crossing ◽  
Input Noise ◽  
Integrate And Fire ◽  
Auto Correlation ◽  
Auto Correlation Function ◽  
Decoupling Approximation ◽  
Crossing Theory

AbstractNoise in spiking neurons is commonly modeled by a noisy input current or by generating output spikes stochastically with a voltage-dependent hazard rate (“escape noise”). While input noise lends itself to modeling biophysical noise processes, the phenomenological escape noise is mathematically more tractable. Using the level-crossing theory for differentiable Gaussian processes, we derive an approximate mapping between colored input noise and escape noise in leaky integrate-and-fire neurons. This mapping requires the first-passage-time (FPT) density of an overdamped Brownian particle driven by colored noise with respect to an arbitrarily moving boundary. Starting from the Wiener–Rice series for the FPT density, we apply the second-order decoupling approximation of Stratonovich to the case of moving boundaries and derive a simplified hazard-rate representation that is local in time and numerically efficient. This simplification requires the calculation of the non-stationary auto-correlation function of the level-crossing process: For exponentially correlated input noise (Ornstein–Uhlenbeck process), we obtain an exact formula for the zero-lag auto-correlation as a function of noise parameters, mean membrane potential and its speed, as well as an exponential approximation of the full auto-correlation function. The theory well predicts the FPT and interspike interval densities as well as the population activities obtained from simulations with colored input noise and time-dependent stimulus or boundary. The agreement with simulations is strongly enhanced across the sub- and suprathreshold firing regime compared to a first-order decoupling approximation that neglects correlations between level crossings. The second-order approximation also improves upon a previously proposed theory in the subthreshold regime. Depending on a simplicity-accuracy trade-off, all considered approximations represent useful mappings from colored input noise to escape noise, enabling progress in the theory of neuronal population dynamics.

Generalized spot auto-focusing method with a high-definition auto-correlation function in transmission electron microscopy

Microscopy ◽  
2019 ◽  
Vol 68 (5) ◽  
pp. 395-412
Author(s):  
Shigeto Isakozawa ◽  
Misuzu Baba ◽  
Junpei Amano ◽  
Shohei Sakamoto ◽  
Norio Baba
Keyword(s):  
Correlation Function ◽  
Yeast Cell ◽  
Thin Section ◽  
High Definition ◽  
Auto Correlation ◽  
Transmission Electron ◽  
Wide Range ◽  
Auto Correlation Function ◽  
Spot Image ◽  
Auto Focusing

Abstract The spot auto-focusing (AF) method with a unique high-definition auto-correlation function (HD-ACF) proposed in the previous paper is improved and is now applicable to general specimens at a wide range of magnifications. According to the definition where the AF is defocused to obtain the highest resolution, the proposed method achieves the sharpest HD-ACF profile in the AF spot image. The relationship where the sharpest HD-ACF profile gives the highest resolution is theoretically explained, and practical AF examples for different specimens and magnifications are experimentally demonstrated. Specimens include a yeast cell thin section at 10-k magnification, a standard grating replica used as a ruler at 50-k, a crystal lattice of graphitized carbon at 400-k and a 60°-tilted thin section (yeast cell) at 10-k. Different procedures are prepared to actively identify the defocus position that gives the sharpest HD-ACF profile. Every AF result demonstrates the highest-resolution image.

Sign in / Sign up

Export Citation Format

Share Document