Upward continuation of scattered potential field data

Geophysics ◽  
1999 ◽  
Vol 64 (2) ◽  
pp. 443-451 ◽  
Author(s):  
Maurizio Fedi ◽  
Antonio Rapolla ◽  
Guido Russo
Keyword(s):  
Linear Combination ◽  
Computation Time ◽  
Measured Data ◽  
Potential Field Data ◽  
Zero Level ◽  
Local Character ◽  
Upward Continuation ◽  
Data Points ◽  
The Stability ◽  
Variable Topography

Numerous methods have been used for upward continuation, but most of them require data on a regular grid. Gridding can introduce errors that affect the continued data in an unpredictable way. To avoid this problem, we design a continuation operator used for the direct continuation of scattered data on a 3-D basis. In this approach a harmonic function, satisfying the constraints imposed by the measured data, is developed. The continuation is written in the form of a linear combination of the measured data, but it depends on the arbitrary choice of the topographic zero level. However, the coefficients of the linear combination depend only on the position of the data points. This allows the zero level to be estimated on the basis of the continuation of synthetic anomalies calculated between the starting and ending surface. An important feature of the method is its local character, which allows the reduction of computation time. Also, the stability of the method for noisy data is reasonably good. The method is applied to both synthetic and real cases. Synthetic examples show how gridding‐related errors may affect the continuation when an irregular distribution of data points and a variable topography are considered.

Effects of Sonication Time on the Stability and Viscosity of Functionalized MWCNT-Based Nanolubricants

2020 ◽  
Vol 16 (4) ◽  
pp. 639-654
Author(s):  
Ahmet Selim Dalkilic ◽  
Bedri Onur Küçükyıldırım ◽  
Ayşegül Akdoğan Eker ◽  
Faruk Yıldız ◽  
Altuğ Akpinar ◽  
...  
Keyword(s):  
Effective Viscosity ◽  
Mass Concentration ◽  
Measured Data ◽  
Sonication Time ◽  
Empirical Correlations ◽  
Thermal Systems ◽  
The Stability ◽  
Rotary Viscometer ◽  
Functionalized Mwcnts ◽  
Measured Viscosity

Background: Active scholars in the nanofluid field have continuously attempted to remove the associated challenge of the stability of nanofluids via various approaches, such as functionalization and adding a surfactant. After preparing a stable nanofluid, one must measure the properties, as this is vital in the design of thermal systems. Objective: Authors aimed to investigate the stability and viscosity of refrigeration lubrication oilbased nanofluids containing functionalized MWCNTs. The effects of concentration and temperature on viscosity were studied. Furthermore, the present study focused on the effect of sonication time on the stability and viscosity of the prepared samples. Methods: After the preparation of chemically functionalized MWCNTs, solutions were dispersed with an ultrasonic homogenizer for 2, 4 and 8 hours sonication at maximum power. Viscosity measurements for all samples were made 10 minutes after sonication by adjusting the proper spinning velocity using a digital rotary viscometer. Results: The first part deals with the stability of the nanofluid as a nanolubricant, and the second one investigates the viscosity of the nanofluid and the effects of various parameters on it. The last one is related to the validation of the measured viscosity values by means of well-known empirical correlations. The measured data are given for validation issues. Conclusion: The samples will have higher stability by increasing the time of sonication. The viscosity of a nanofluid does not change with the increase of sonication time to two hours and higher. Up to mass concentration of 0.1%, the effective viscosity increases with adding nanotubes linearly.

SiGe Heteroepitaxy for High Frequency Circuits

1998 ◽  
Vol 525 ◽  
Author(s):  
B. Tillack ◽  
D. Bolze ◽  
G. Fischer ◽  
G. Kissinger ◽  
D. Knoll ◽  
...  
Keyword(s):  
Heterojunction Bipolar Transistors ◽  
High Frequency ◽  
Defect Density ◽  
Process Capability ◽  
Chemical Vapor ◽  
Bipolar Transistors ◽  
Capability Indices ◽  
Data Points ◽  
B Doping ◽  
The Stability

ABSTRACTWe have determined the process capability of Low Pressure (Rapid Thermal) Chemical Vapor Deposition (LP(RT)CVD) of epitaxial Si/SiGe/Si stacks for heterojunction bipolar transistors (HIBTs). The transistor parameters primarily influenced by the epitaxial characteristics were measured for 600 identically processed 4” wafers. The results demonstrate that it is possible to control accurately the epitaxial process for a 25 nm thick graded SiGe base profile with 20 % Ge and very narrow B doping (5 nm). The pipe limited device yield of about 90 % for an emitter area of 104 μm2 indicates a very low defect density in the epitaxial layer stack. The process capability indices determined from about 40,000 data points demonstrate the stability and capability of the LP(RT)CVD epitaxy with regard to manufacturing requirements.

Sphericity Evaluation Based on Minimum Circumscribed Sphere Method

2012 ◽  
Vol 433-440 ◽  
pp. 3146-3151 ◽  
Author(s):  
Fan Wu Meng ◽  
Chun Guang Xu ◽  
Juan Hao ◽  
Ding Guo Xiao
Keyword(s):  
Convex Hull ◽  
Early Stage ◽  
Measured Data ◽  
Efficient Approach ◽  
Critical Data ◽  
Material Condition ◽  
Data Points ◽  
Point Set ◽  
Data Point

The search of sphericity evaluation is a time-consuming work. The minimum circumscribed sphere (MCS) is suitable for the sphere with the maximum material condition. An algorithm of sphericity evaluation based on the MCS is introduced. The MCS of a measured data point set is determined by a small number of critical data points according to geometric criteria. The vertices of the convex hull are the candidates of these critical data points. Two theorems are developed to solve the sphericity evaluation problems. The validated results show that the proposed strategy offers an effective way to identify the critical data points at the early stage of computation and gives an efficient approach to solve the sphericity problems.

Research on Adaptive Kalman Filter for INS

2017 ◽  
Vol 872 ◽  
pp. 316-320
Author(s):  
Kai Xia Wei
Keyword(s):  
Kalman Filter ◽  
Response Speed ◽  
Measured Data ◽  
Specific Method ◽  
Alignment Error ◽  
Initial Alignment ◽  
Adaptive Kalman Filter ◽  
Noise Interference ◽  
Kalman Filter Algorithm ◽  
The Stability

Due to sensor accuracy and noise interference and other reasons, the measured data may be inaccurate or even wrong. This will reduce the accuracy of the filter and the reliability and response speed of the Kalman filter, and even make the Kalman filter lose the stability. In this paper, a new INS initial alignment error model and observation model are derived for the errors in INS initial alignment. The adaptive Kalman filter is built to improve the stability and the accuracy of filter. The specific method is to make the adaptive Kalman filter manage to correct the filter online by getting the observed data. The simulation results show the proposed algorithm improves the accuracy of initial alignment in SINS, and prove the adaptive Kalman filter is effective. The main innovation in this paper is to manage to build the adaptive Kalman filter to modify the filter online by using the observed data. The adaptive Kalman filter algorithm improves the accuracy of the filter.

The Research of Data Points Quality Assessment Method in Reverse Engineering

2009 ◽  
Vol 419-420 ◽  
pp. 445-448 ◽  
Author(s):  
Jun Ting Cheng ◽  
Wei Ling Zhao ◽  
Can Zhao ◽  
Xue Dong Xie
Keyword(s):  
Reverse Engineering ◽  
Data Quality ◽  
Quality Assessment ◽  
Assessment Method ◽  
Measured Data ◽  
Quality Data ◽  
Data Quality Assessment ◽  
Quality Assessment Method ◽  
Data Points ◽  
Data Point

In the field of reverse engineering, data quality assessment is a very important work in the detection, the result of data quality assessment will directly or indirectly affect the detection and the following manufacturing process quality. Data quality assessment can be used in the camera calibration, the model and model reconstruction comparison, and so on. In this paper, on the basis of the existing method of calculating each point error, and multipurpose use of average and standard error and some other concepts of mathematical statistics, and then improve a novel and simple calculating error method. This method is applicable to many groups of one-to-one ideal data and the measured data comparison, and it can be more intuitive to reflect the error of overall data, as well as the error distribution, and it can be more efficient to determine the measured data is reasonable or not. In this paper, the data point quality which is collected in the reverse engineering is assessed, and it can see that the method which is proposed in this article has some advantages in the data point quality assessment field.

Evaluation of Available Transfer Capability Using Transient Stability Constrained Line Flows

2014 ◽  
Vol 15 (1) ◽  
pp. 59-68
Author(s):  
Lazarus Okechukwu Uzoechi ◽  
Satish M. Mahajan
Keyword(s):  
Transient Stability ◽  
Direct Determination ◽  
Computation Time ◽  
Critical Energy ◽  
Energy Performance ◽  
Electric Power System ◽  
Available Transfer Capability ◽  
Transfer Capability ◽  
The Stability ◽  
The Impact

Abstract This paper presents a methodology to evaluate transient stability constrained available transfer capability (ATC). A linear and fast line flow–based (LFB) method was adopted to optimize the ATC values. This enabled the direct determination of the system source–sink locations. This paper formulated different market transactions considering bilateral and multilateral impacts in the stability constrained ATC. The proposed method was demonstrated on the WECC 9-bus and IEEE 39-bus systems. The critical energy performance index (CEPI) enabled the direct identification of candidates for contingency screening based on ranking. This index helped to reduce the list of credible contingencies for ATC evaluation and, therefore, the computation time. The results of the proposed ATC method are consistent with the literature and can be deployed for fast assessment of the impact of transactions in an electric power system.

scholarly journals A Harmonic-Based Method for Computing the Stability of Periodic Oscillations of Non-Linear Structural Systems

2010 ◽  
Author(s):  
O. Thomas ◽  
A. Lazarus ◽  
C. Touze´
Keyword(s):  
Numerical Method ◽  
Periodic Solutions ◽  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Computation Time ◽  
Fourier Series Expansion ◽  
Simple Strategy ◽  
The Stability ◽  
Linear Periodic System ◽  
Continuation Technique

In this paper, we present a validation on a practical example of a harmonic-based numerical method to determine the local stability of periodic solutions of dynamical systems. Based on Floquet theory and Fourier series expansion (Hill method), we propose a simple strategy to sort the relevant physical eigenvalues among the expanded numerical spectrum of the linear periodic system governing the perturbed solution. By mixing the Harmonic Balance Method and Asymptotic Numerical Method continuation technique with the developed Hill method, we obtain a purely-frequency based continuation tool able to compute the stability of the continued periodic solutions in a reduced computation time. This procedure is validated by considering an externally forced string and computing the complete bifurcation diagram with the stability of the periodic solutions. The particular coupled regimes are exhibited and found in excellent agreement with results of the literature, allowing a method validation.

Validation of the Tabulated Johnson-Cook Model for a Dynamic Compression Simulation

2015 ◽  
Vol 782 ◽  
pp. 245-251
Author(s):  
Guo Ju Li ◽  
Qun Bo Fan ◽  
Rui Hua Gao ◽  
Jin Tao Liu ◽  
Cheng Miao
Keyword(s):  
Effective Stress ◽  
Dynamic Compression ◽  
Effective Strain ◽  
Element Model ◽  
Strain Rates ◽  
Fitting Procedures ◽  
Data Points ◽  
Simulation Results ◽  
The Stability ◽  
Cook Model

MAT224 is a tabulated version of the Johnson-Cook model in LS-DYNA. Compared with the original Johnson-Cook material, MAT224 was developed to simulate the dynamic response of a material by just defining the effective stress as a function of effective plastic strain at different strain rates and temperatures, thus avoiding the tedious parameter fitting procedures in the traditional Johnson-Cook model. However, the stability and precision of solution is strongly dependent on the effective stress versus effective strain curves in MAT224, and unreasonable curve data will lead to warnings or errors in the process of solution. In the current study, a two-dimensional axisymmetric finite element model for the Ti-6Al-4V titanium alloy under dynamic compression was built, and MAT224 was employed. By investigating the effects of the curve numbers, strain ranges, data points, as well as changing tendencies, on the simulation results, the stability and the reliability for MAT224 are systematically studied.

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