Decentralized Fixed-Interval Smoothing Algorithms

1986 ◽  
Vol 108 (1) ◽  
pp. 86-89 ◽  
Author(s):  
Keigo Watanabe
Keyword(s):  
Computational Efficiency ◽  
A Priori ◽  
Superposition Principle ◽  
Fixed Interval ◽  
Central Processor ◽  
Decentralized Estimation ◽  
Information Filter

The Weineret-Desai smoother formula is applied to derive new decentralized fixed-interval smoothing algorithms for a decentralized estimation structure consisting of a central processor and of M local processors. Such algorithms are based on decentralizing the estimates of global backward information filter and obtained from the use of the superposition principle in scattering framework. The smoothing update problem is also investigated to illustrate the application of the proposed algorithms. The emphasis is on computational efficiency, independence of local a priori statistics, and flexibility of implementation.

Static Modes Switching: On-Line Variable Static Augmentation for Efficient Flexible Multibody Simulation

2011 ◽  
Author(s):  
Tommaso Tamarozzi ◽  
Gert H. K. Heirman ◽  
Wim Desmet
Keyword(s):  
Computational Efficiency ◽  
Degrees Of Freedom ◽  
A Priori ◽  
The Body ◽  
Multibody Simulation ◽  
External Excitation ◽  
Flexible Bodies ◽  
General Methodology ◽  
On Line ◽  
Gear Contact

This paper discusses and further investigates a new methodology, “Static Modes Switching” (SMS), improving computational efficiency for elastic multibody (EMBS) systems. This method focuses on mechanisms in which loading is possible in many degrees of freedom, but only few of them are simultaneously loaded at a given moment in time (e.g. sliding elements, gear contact, etc.). The methodology adapts during simulation the mode set used to represent component flexibility, by judiciously choosing only those static modes that are contributing actively to the body deformation. First, the general methodology is presented, then the current work and its original contributions are discussed; namely SMS is tested on a 3D mechanism including multiple flexible bodies on which sliding elements are present. Moreover, as opposed to previous studies, the locations where external excitation is acting is not known a priori. Finally, some limitations of the proposed methodology are treated with focus on the numerical discontinuities introduced by the switching of the modal base and their propagation to neighbouring bodies.

scholarly journals Data Interpolation by Optimal Splines with Free Knots Using Linear Programming

2021 ◽  
Author(s):  
Lakshman Thakur ◽  
Mikhail Bragin
Keyword(s):  
Linear Programming ◽  
Computational Efficiency ◽  
Interpolation Problem ◽  
A Priori ◽  
Compact Set ◽  
Data Interpolation ◽  
Practical Applications ◽  
Quadratic Splines ◽  
Splines With Free Knots ◽  
Data Points

Studies have shown that in many practical applications, data interpolation by splines leads to better approximation and higher computational efficiency as compared to data interpolation by a single polynomial. Data interpolation by splines can be significantly improved if knots are allowed to be free rather than at a priori fixed locations such as data points. In practical applications, the smallest possible curvature is often desired. Therefore, optimal splines are determined by minimizing a derivative of continuously differentiable functions comprising the spline of the required order. The problem of obtaining an optimal spline is tantamount to minimizing derivatives of a nonlinear differentiable function over a Banach space on a compact set. While the problem of data interpolation by quadratic splines has been accomplished analytically, interpolation by splines of higher orders or in higher dimensions is challenging. In this paper, to overcome difficulties associated with the complexity of the interpolation problem, the interval over which data points are defined, is discretized and continuous derivatives are substituted by their discrete counterparts. It is shown that as the mesh of the discretization approaches zero, a resulting near-optimal spline approaches an optimal spline. Splines with the desired accuracy can be obtained by choosing an appropriate mesh of the discretization. By using cubic splines as an example, numerical results demonstrate that the linear programming (LP) formulation, resulting from the discretization of the interpolation problem, can be solved by linear solvers with high computational efficiency and resulting splines provide a good approximation to the optimal splines.

Evolution of a Hybrid Model for an Effective Perimeter Security Device

2015 ◽  
Vol 65 (6) ◽  
pp. 466
Author(s):  
S. Selvakumar ◽  
A.R. Vasudevan
Keyword(s):  
Hybrid Model ◽  
Computational Efficiency ◽  
Dirichlet Process ◽  
Hybrid Methods ◽  
A Priori ◽  
Number Of Clusters ◽  
Training Time ◽  
Bayesian Mixture ◽  
Clustering And Classification ◽  
Security Device

Clustering and classification models, or hybrid models are the most widely used models that can handle the diverse nature of NIDS dataset. Dirichlet process clustering technique is a non-parametric Bayesian mixture model that considers the data distribution of the dataset for the formation of distinct clusters. The number of clusters is not known a priori and it differs across different datasets. Determining the number of clusters based on the distribution of data instances can increase the performance of the model. Naive Bayes model, a supervised learning classification technique, maintains a better computational efficiency, by reducing the training time. In this paper, we propose a hybrid model to exploit the positive aspect of proper clustering of data instances and the computational efficiency in building a NIDS. RIPPER algorithm is used to extract rules from the traffic description for updation of the rule database. Experiments were conducted in the KDD CUP’99 and SSENet-2011 datasets to study the performance of the proposed model. Also, a comparison of three hybrid methods with the proposed hybrid model was carried out. The results showed that the proposed hybrid model is superior in building a robust perimeter security device.

Robust information filter for decentralized estimation

Automatica ◽  
2005 ◽  
Vol 41 (12) ◽  
pp. 2141-2146 ◽  
Author(s):  
Ying Zhang ◽  
Yeng Chai Soh ◽  
Weihai Chen
Keyword(s):  
Decentralized Estimation ◽  
Information Filter

scholarly journals A square root information filter for multi-GNSS real-time precise clock estimation

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Xiang Zuo ◽  
Xinyuan Jiang ◽  
Pan Li ◽  
Jungang Wang ◽  
Maorong Ge ◽  
...  
Keyword(s):  
Data Processing ◽  
Real Time ◽  
Computational Efficiency ◽  
High Rate ◽  
Control Procedure ◽  
Square Root ◽  
Essential Information ◽  
Real Time Clock ◽  
Information Filter ◽  
Clock Estimation

AbstractReal-time satellite orbit and clock estimations are the prerequisite for Global Navigation Satellite System (GNSS) real-time precise positioning services. To meet the high-rate update requirement of satellite clock corrections, the computational efficiency is a key factor and a challenge due to the rapid development of multi-GNSS constellations. The Square Root Information Filter (SRIF) is widely used in real-time GNSS data processing thanks to its high numerical stability and computational efficiency. In real-time clock estimation, the outlier detection and elimination are critical to guarantee the precision and stability of the product but could be time-consuming. In this study, we developed a new quality control procedure including the three standard steps: i.e., detection, identification, and adaption, for real-time data processing of huge GNSS networks. Effort is made to improve the computational efficiency by optimizing the algorithm to provide only the essential information required in the processing, so that it can be applied in real-time and high-rate estimation of satellite clocks. The processing procedure is implemented in the PANDA (Positioning and Navigation Data Analyst) software package and evaluated in the operational generation of real-time GNSS orbit and clock products. We demonstrated that the new algorithm can efficiently eliminate outliers, and a clock precision of 0.06 ns, 0.24 ns, 0.06 ns, and 0.11 ns can be achieved for the GPS, GLONASS, Galileo, and BDS-2 IGSO/MEO satellites, respectively. The computation time per epoch is about 2 to 3 s depending on the number of existing outliers. Overall, the algorithm can satisfy the IGS real-time clock estimation in terms of both the computational efficiency and product quality.

Application of cross correlation to HREM images of surfaces

1987 ◽  
Vol 45 ◽  
pp. 754-755
Author(s):  
D. E. Luzzi ◽  
L. D. Marks ◽  
M. I. Buckett
Keyword(s):  
Cross Correlation ◽  
A Priori ◽  
Matrix Material ◽  
Correlation Method ◽  
Accurate Knowledge ◽  
Complex Image ◽  
Fourier Filtering ◽  
The Matrix ◽  
Low Pass ◽  
Data Reduction Technique

As the HREM becomes increasingly used for the study of dynamic localized phenomena, the development of techniques to recover the desired information from a real image is important. Often, the important features are not strongly scattering in comparison to the matrix material in addition to being masked by statistical and amorphous noise. The desired information will usually involve the accurate knowledge of the position and intensity of the contrast. In order to decipher the desired information from a complex image, cross-correlation (xcf) techniques can be utilized. Unlike other image processing methods which rely on data massaging (e.g. high/low pass filtering or Fourier filtering), the cross-correlation method is a rigorous data reduction technique with no a priori assumptions.We have examined basic cross-correlation procedures using images of discrete gaussian peaks and have developed an iterative procedure to greatly enhance the capabilities of these techniques when the contrast from the peaks overlap.

Towards 1-Ångstrom-resolution STEM

1993 ◽  
Vol 51 ◽  
pp. 996-997
Author(s):  
H.S. von Harrach ◽  
D.E. Jesson ◽  
S.J. Pennycook
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Phase Contrast ◽  
Spherical Aberration ◽  
A Priori ◽  
Dark Field ◽  
Image Resolution ◽  
Objective Lens ◽  
Annular Dark Field ◽  
First Results

Phase contrast TEM has been the leading technique for high resolution imaging of materials for many years, whilst STEM has been the principal method for high-resolution microanalysis. However, it was demonstrated many years ago that low angle dark-field STEM imaging is a priori capable of almost 50% higher point resolution than coherent bright-field imaging (i.e. phase contrast TEM or STEM). This advantage was not exploited until Pennycook developed the high-angle annular dark-field (ADF) technique which can provide an incoherent image showing both high image resolution and atomic number contrast.This paper describes the design and first results of a 300kV field-emission STEM (VG Microscopes HB603U) which has improved ADF STEM image resolution towards the 1 angstrom target. The instrument uses a cold field-emission gun, generating a 300 kV beam of up to 1 μA from an 11-stage accelerator. The beam is focussed on to the specimen by two condensers and a condenser-objective lens with a spherical aberration coefficient of 1.0 mm.

Treating Velopharyngeal Inadequacy Using Bilateral Buccal Flap Revision Palatoplasty

2019 ◽  
Vol 4 (5) ◽  
pp. 878-892
Author(s):  
Joseph A. Napoli ◽  
Linda D. Vallino
Keyword(s):  
Systematic Review ◽  
Obstructive Sleep Apnea ◽  
Sleep Apnea ◽  
Cleft Lip ◽  
Cleft Lip And Palate ◽  
A Priori ◽  
Sufficient Evidence ◽  
Obstructive Sleep ◽  
Before And After ◽  
Buccal Flap

Purpose The 2 most commonly used operations to treat velopharyngeal inadequacy (VPI) are superiorly based pharyngeal flap and sphincter pharyngoplasty, both of which may result in hyponasal speech and airway obstruction. The purpose of this article is to (a) describe the bilateral buccal flap revision palatoplasty (BBFRP) as an alternative technique to manage VPI while minimizing these risks and (b) conduct a systematic review of the evidence of BBFRP on speech and other clinical outcomes. A report comparing the speech of a child with hypernasality before and after BBFRP is presented. Method A review of databases was conducted for studies of buccal flaps to treat VPI. Using the principles of a systematic review, the articles were read, and data were abstracted for study characteristics that were developed a priori. With respect to the case report, speech and instrumental data from a child with repaired cleft lip and palate and hypernasal speech were collected and analyzed before and after surgery. Results Eight articles were included in the analysis. The results were positive, and the evidence is in favor of BBFRP in improving velopharyngeal function, while minimizing the risk of hyponasal speech and obstructive sleep apnea. Before surgery, the child's speech was characterized by moderate hypernasality, and after surgery, it was judged to be within normal limits. Conclusion Based on clinical experience and results from the systematic review, there is sufficient evidence that the buccal flap is effective in improving resonance and minimizing obstructive sleep apnea. We recommend BBFRP as another approach in selected patients to manage VPI. Supplemental Material https://doi.org/10.23641/asha.9919352

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