scholarly journals PARALLEL DELAUNAY REFINEMENT: ALGORITHMS AND ANALYSES

2007 ◽  
Vol 17 (01) ◽  
pp. 1-30 ◽  
Author(s):  
DANIEL A. SPIELMAN ◽  
SHANG-HUA TENG ◽  
ALPER ÜNGÖR
Keyword(s):  
Mesh Size ◽  
Constant Factor ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Delaunay Refinement ◽  
Steiner Points ◽  
Input Domain ◽  
Set Of Points ◽  
Refinement Algorithm

We present a parallel Delaunay refinement algorithm for generating well-shaped meshes in both two and three dimensions. Like its sequential counterparts, the parallel algorithm iteratively improves the quality of a mesh by inserting new points, the Steiner points, into the input domain while maintaining the Delaunay triangulation. The Steiner points are carefully chosen from a set of candidates that includes the circumcenters of poorly-shaped triangular elements. We introduce a notion of independence among possible Steiner points that can be inserted simultaneously during Delaunay refinements and show that such a set of independent points can be constructed efficiently and that the number of parallel iterations is O( log 2Δ), where Δ is the spread of the input — the ratio of the longest to the shortest pairwise distances among input features. In addition, we show that the parallel insertion of these set of points can be realized by sequential Delaunay refinement algorithms such as by Ruppert's algorithm in two dimensions and Shewchuk's algorithm in three dimensions. Therefore, our parallel Delaunay refinement algorithm provides the same shape quality and mesh-size guarantees as these sequential algorithms. For generating quasi-uniform meshes, such as those produced by Chew's algorithms, the number of parallel iterations is in fact O( log Δ). To the best of our knowledge, our algorithm is the first provably polylog(Δ) time parallel Delaunay-refinement algorithm that generates well-shaped meshes of size within a constant factor of the best possible.

LONG-TERM SEIZURES AND QUALITY OF LIFE AFTER EPILEPSY SURGERY COMPARED WITH MATCHED CONTROLS

Neurosurgery ◽  
2008 ◽  
Vol 62 (2) ◽  
pp. 326-335 ◽  
Author(s):  
Knut Stavem ◽  
Helge Bjørnæs ◽  
Iver A. Langmoen
Keyword(s):  
Quality Of Life ◽  
Epilepsy Surgery ◽  
Intractable Epilepsy ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Seizure Type ◽  
Seizure Outcome

Abstract OBJECTIVE We compared long-term seizure outcome and health-related quality of life (HRQoL) of patients who underwent epilepsy surgery and matched medically treated nonsurgical controls with intractable epilepsy. METHODS Medically treated controls were identified for patients operated on for epilepsy between January 1, 1949 and December 31, 1992. We used a matched cohort design, matching for age, sex, and seizure type. The analysis was based on 70 complete matching pairs. HRQoL was assessed with the Quality of Life in Epilepsy Inventory 89 questionnaire an average of 15 years after surgery. RESULTS Among surgery patients, 48% were seizure-free during the previous year compared with 19% of the controls (P = 0.0004). Fewer surgery patients used antiepileptic drugs (70%) than controls (93%). The odds of being seizure-free were higher for surgery patients in total and in subgroups divided according to length of follow-up. The mean HRQoL for surgery patients was higher in five of the 17 Quality of Life in Epilepsy Inventory 89 dimensions and worse in none. Among patients with more than 7 years of follow-up, HRQoL was better in three dimensions and worse in none. Among patients with 7 years of follow-up or less, HRQoL was better in two dimensions and worse in the language dimension of the Quality of Life in Epilepsy Inventory 89. CONCLUSION After an average of more than 15 years of follow-up, epilepsy surgery patients had fewer seizures, used less antiepileptic medication, and had better HRQoL in several dimensions of the Quality of Life in Epilepsy Inventory 89 instrument than matched medically treated controls with refractory epilepsy, although possibly at a slight disadvantage in the language dimension among those with 7 years of follow-up or less.

On meshfree numerical differentiation

2018 ◽  
Vol 16 (05) ◽  
pp. 717-739
Author(s):  
Leevan Ling ◽  
Qi Ye
Keyword(s):  
A Priori ◽  
Noisy Data ◽  
Numerical Differentiation ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Positive Definite Kernels ◽  
Approximation Quality ◽  
Symmetric Positive Definite ◽  
Optimal Kernel

We combine techniques in meshfree methods and Gaussian process regressions to construct kernel-based estimators for numerical derivatives from noisy data. Specially, we construct meshfree estimators from normal random variables, which are defined by kernel-based probability measures induced from symmetric positive definite kernels, to reconstruct the unknown partial derivatives from scattered noisy data. Our developed theories give rise to Tikhonov regularization methods with a priori parameter, but the shape parameters of the kernels remain tunable. For that, we propose an error measure that is computable without the exact values of the derivative. This allows users to obtain a quasi-optimal kernel-based estimator by comparing the approximation quality of kernel-based estimators. Numerical examples in two dimensions and three dimensions are included to demonstrate the convergence behavior and effectiveness of the proposed numerical differentiation scheme.

Enhancement of diffractions in prestack domain by means of a finite-offset double-square-root traveltime

Geophysics ◽  
2019 ◽  
Vol 84 (1) ◽  
pp. V81-V96 ◽  
Author(s):  
Tiago A. Coimbra ◽  
Jorge H. Faccipieri ◽  
João H. Speglich ◽  
Leiv-J. Gelius ◽  
Martin Tygel
Keyword(s):  
Extraction Process ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Data Sets ◽  
Square Root ◽  
Data Set ◽  
Main Challenge ◽  
Two Parameters ◽  
General Source

Exploration of redundancy contained in the seismic data set assures enhancement of images that are based on stacking results. This enhancement is the goal of developing multiparametric traveltime equations that are able to approximate reflection and diffraction events in general source-receiver configurations. The main challenge of using these equations is to estimate a large number of parameters in a computationally feasible, reliable, and fast way. To obtain a better fit for diffraction traveltime events than the ones in the literature, we have derived a finite-offset (FO) double-square-root (DSR) diffraction traveltime equation (which depends on 10 parameters in three dimensions and four parameters in two dimensions). Moreover, to reduce the number of parameters, we have developed another version called simplified FO-DSR diffraction traveltime equation (which depends on five parameters in three dimensions and two parameters in two dimensions), which delivers a similar performance. We have developed operators that make use of the simplified FO-DSR traveltime equation to construct the so-called diffraction-only data set volumes (or, more simply, D-volumes) assuring enhancement in the diffraction extraction process. The D-volume construction has two steps: first, a stacking procedure to separate the diffraction events from the input data set and second, a spreading procedure to enhance the quality of these diffractions. As proof of concept, our approach has been tested on 2D/3D synthetic and 2D field data sets with successful results.

scholarly journals Comparison between two- and three-dimensional Rayleigh–Bénard convection

2013 ◽  
Vol 736 ◽  
pp. 177-194 ◽  
Author(s):  
Erwin P. van der Poel ◽  
Richard J. A. M. Stevens ◽  
Detlef Lohse
Keyword(s):  
Three Dimensional ◽  
State Dependence ◽  
Constant Factor ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Bénard Convection ◽  
Benard Convection ◽  
The Difference ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

AbstractTwo-dimensional and three-dimensional Rayleigh–Bénard convection is compared using results from direct numerical simulations and previous experiments. The phase diagrams for both cases are reviewed. The differences and similarities between two- and three-dimensional convection are studied using $Nu(Ra)$ for $\mathit{Pr}= 4. 38$ and $\mathit{Pr}= 0. 7$ and $Nu(Pr)$ for $Ra$ up to $1{0}^{8} $. In the $Nu(Ra)$ scaling at higher $Pr$, two- and three-dimensional convection is very similar, differing only by a constant factor up to $\mathit{Ra}= 1{0}^{10} $. In contrast, the difference is large at lower $Pr$, due to the strong roll state dependence of $Nu$ in two dimensions. The behaviour of $Nu(Pr)$ is similar in two and three dimensions at large $Pr$. However, it differs significantly around $\mathit{Pr}= 1$. The Reynolds number values are consistently higher in two dimensions and additionally converge at large $Pr$. Finally, the thermal boundary layer profiles are compared in two and three dimensions.

scholarly journals Forms of articulating epistemic Critique

2017 ◽  
pp. 40
Author(s):  
Oliver Dimbath ◽  
Stefan Böschen
Keyword(s):  
Two Dimensions ◽  
Three Dimensions ◽  
Policy Studies ◽  
Ongoing Debate ◽  
Political Landscape ◽  
Fundamental Understanding ◽  
Critical Policy

For many years now, there has been a vivid debate on contemporary forms of articulating epistemic critique, especially concerning the peer review mechanism but also dealing with fund mechanisms and, in some cases, focusing on book reviews. As reviews become more frequent and continue to exert considerable infl uence on the political landscape of academia, it is increasingly apparent that a fundamental understanding of the internal structure of articulating epistemic critique long overdue. Against this background, the aim of this article is to put forward two arguments. First, we argue these forms of articulating critique should be distinguished in regard to their distinctive characteristics and respective relations to academia as a whole. In doing so, we construct a research heuristic based on two dimensions, the opportunity to participate and the opportunity to react. Second, in response to an ongoing debate in Critical Policy Studies we conducted a small explorative empirical case study about on how scientific critique is articulated in book reviews. Besides providing a new overall perspective on how to categorize these forms of critique we found notable diff erences corresponding to the varied characteristics of the publication process in two disciplines (sociology/chemistry). We identified three dimensions as central for determining the quality of the expressed critique. As these differences might be related with underlying types of scientifi c communication, we fi nally argue that there is a necessity to take a closer look at how confi gurations of the diff erent forms of scientifi c critique should be analysed and to address these in their full scope as ‘cultures of critique’.

scholarly journals KEBERLANJUTAN PENGEMBANGAN LORONG GARDEN DALAM MEWUJUDKAN KAWASAN PERKOTAAN RAMAH LINGKUNGAN (ECO CITY) DI MAKASSAR

2021 ◽  
Vol 4 (2) ◽  
pp. 10-23
Author(s):  
Andi Wisneni ◽  
Abdullah Abdullah ◽  
Annas Boceng
Keyword(s):  
Two Dimensions ◽  
City Government ◽  
Three Dimensions ◽  
Residential Areas ◽  
Index Analysis ◽  
Interview Survey ◽  
The City ◽  
Ecological Dimension ◽  
Dimension Index

The Lorong Garden (aisle farming) program is one of the efforts of Makassar City Government to improve the area of narrow aisles or narrow streets in residential areas to make it more comfortable and healthier (ecological) and productive (economic). The program is expected to be able to improve the quality of the environment, community participation, and the economy of the community. The sustainability of its management is influenced by several integrated components. The study aims to analyze the sustainability of Lorong Garden development in Makassar City. Research in the form of a questionnaire interview survey of 126 respondents of the general public and 25 experts /stakeholders in the city of Makassar. Index analysis and sustainability status were using MDS methods Rap-Longgar-Potensial. The results showed that the multidimensional Lorong Garden Program is less sustainable (index 43.02%). Partially, there were two dimensions in the moderately sustainable category namely the ecological dimension (index 51.84%) and the technology dimension (index 65.09%) and three dimensions less sustainable, namely economy (index 46.15%), social (index 49.81) %) and institutional (index 39.20%). Of the total 37 attributes were analyzed, 17 sensitive attributes affected the sustainability of the Lorong Garden development in Makassar City.

scholarly journals Rancang Bangun Aplikasi Jam Tangan Pranata Laboratorium Pendidikan dengan Kemampuan Waterpas Tiga Dimensi untuk Mengatur Sambungan Modul Uji Pembebanan Motor

2020 ◽  
Vol 2 (2) ◽  
pp. 89-100
Author(s):  
Mochammad Darwis ◽  
Aris Eko Saputro
Keyword(s):  
Electric Motor ◽  
Two Dimensions ◽  
Electric Machine ◽  
Three Dimensions ◽  
Gyro Sensor ◽  
Electric Driving ◽  
Orientation Sensor ◽  
Rule Out ◽  
Angle Of Rotation

When testing the loading of an electric machine, we often experience problems in finding a tool to see the precision of the connection between the shaft of an electric machine. Shaft connections that are not straight and not right in the middle can damage the shaft of the rotating engine and the engine being rotated. This research is the development of previous research that uses Android phone as a tool. By reading the value of the orientation sensor on an android phone, we can measure the angle of rotation on the x, y and z axes. The Watpasdroid application will display the value on each axis. This application has also been used in the Electric Driving Laboratory at the Surabaya State Electronic Polytechnic (PENS), to check the connection (coupling) between an electric motor and a magnetic load (dynamo meter). The size of a cellphone that is still too large is sometimes become a problem  if the surface being measured is narrow. So we uses a wristband-shaped watch module that already has a gyro sensor and can be programmed according to our need. The size is almost 1/12 of ordinary cellphones. The M5Stick-C module is used to compare the gyro reading value displayed by the wristband. To test the quality of motor joint which  flatness checks have been assisted by using a wristband, a thermal observation camera is used. This application, does not rule out, can be used in other laboratories for the purpose of checking the plane levelness or equality in two dimensions or three dimensions.

On Algorithms and Heuristics for Constrained Least-Squares Fitting of Circles and Spheres to Support Standards

2018 ◽  
Author(s):  
Craig M. Shakarji ◽  
Vijay Srinivasan
Keyword(s):  
Least Squares ◽  
Theoretical Work ◽  
Two Dimensions ◽  
International Standards ◽  
Three Dimensions ◽  
Constrained Least Squares ◽  
Least Squares Fitting ◽  
Practical Algorithms ◽  
Coordinate Metrology ◽  
Set Of Points

Constrained least-squares fitting has gained considerable popularity among national and international standards committees as the default method for establishing datums on manufactured parts. This has resulted in the emergence of several interesting and urgent problems in computational coordinate metrology. Among them is the problem of fitting inscribing and circumscribing circles (in two-dimensions) and spheres (in three-dimensions) using constrained least-squares criterion to a set of points that are usually described as a ‘point-cloud.’ This paper builds on earlier theoretical work, and provides practical algorithms and heuristics to compute such circles and spheres. Representative codes that implement these algorithms and heuristics are also given to encourage industrial use and rapid adoption of the emerging standards.

On Algorithms and Heuristics for Constrained Least-Squares Fitting of Circles and Spheres to Support Standards

2019 ◽  
Vol 19 (3) ◽  
Author(s):  
Craig M. Shakarji ◽  
Vijay Srinivasan
Keyword(s):  
Least Squares ◽  
Theoretical Work ◽  
Two Dimensions ◽  
International Standards ◽  
Three Dimensions ◽  
Constrained Least Squares ◽  
Least Squares Fitting ◽  
Practical Algorithms ◽  
Coordinate Metrology ◽  
Set Of Points

Constrained least-squares fitting has gained considerable popularity among national and international standards committees as the default method for establishing datums on manufactured parts. This has resulted in the emergence of several interesting and urgent problems in computational coordinate metrology. Among them is the problem of fitting inscribing and circumscribing circles (in two dimensions) and spheres (in three dimensions) using constrained least-squares criterion to a set of points that are usually described as a “point-cloud.” This paper builds on earlier theoretical work, and provides practical algorithms and heuristics to compute such circles and spheres. Representative codes that implement these algorithms and heuristics are also given to encourage industrial use and rapid adoption of the emerging standards.

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