Comparison of Methods for Determining Screw Parameters of Infinitesimal Rigid Body Motion From Position and Velocity Data

1990 ◽  
Vol 112 (4) ◽  
pp. 711-716 ◽  
Author(s):  
R. G. Fenton ◽  
R. A. Willgoss
Keyword(s):  
Rigid Bodies ◽  
The Other ◽  
Body Motion ◽  
Comparison Of Methods ◽  
Velocity Data ◽  
Exact Data ◽  
Vector Algebra ◽  
Position Data ◽  
Inexact Data ◽  
Speed Accuracy

Five methods are outlined in this paper for determining the screw parameters of the instantaneous motion of rigid bodies from given velocity and position data of three noncollinear points. The five methods are compared on the basis of their computational efficiency and accuracy. It is found that the method based on vector algebra is much more efficient computationally than any of the other four methods, but has some limitations of applicability. In terms of accuracy, the methods are equivalent when working with exact data. It is recommended that the method based on vector algebra be used for computing screw parameters from position and velocity data when this computation is performed frequently, as in the case of trajectory planning for robotics application. But method hopping be employed where inexact data are used, employing the method which gives the best speed/accuracy combination.

Comparison of Methods for Determining Screw Parameters of Finite Rigid Body Motion From Initial and Final Position Data

1989 ◽  
Author(s):  
R. G. Fenton ◽  
X. Shi
Keyword(s):  
Rigid Body ◽  
Rigid Body Motion ◽  
The Other ◽  
Body Motion ◽  
Final Position ◽  
Comparison Of Methods ◽  
Rodrigues Formula ◽  
Position Data ◽  
Data Error

Abstract Five methods for determining the screw parameters of finite rigid body motion using position data of three non-collinear points are compared on the basis of their efficiency, accuracy, and sensitivity to data error. It is found that the method based on Rodrigues’ Formula (Bottema & Roth’s method) is the most efficient. Angeles’ method and Laub & Shiflett’s method provide approximately the same level of accuracy, which is superior to that of the other methods. In terms of sensitivity, Bottema & Roth’s method is preferable On the basis of this study it is recommended that Bottema & Roth’s method to be used if uncertainty exists in the data since it can provide a solution efficiently, accurately, and it is the least sensitive to data error.

Comparison of Methods for Determining Screw Parameters of Finite Rigid Body Motion From Initial and Final Position Data

1990 ◽  
Vol 112 (4) ◽  
pp. 472-479 ◽  
Author(s):  
R. G. Fenton ◽  
Xiaolun Shi
Keyword(s):  
Rigid Body ◽  
Rigid Body Motion ◽  
The Other ◽  
Body Motion ◽  
Final Position ◽  
Comparison Of Methods ◽  
Rodrigues Formula ◽  
Position Data ◽  
Data Error

Five methods for determining screw parameters of finite rigid body motion, using position data of three noncollinear points, are compared on the basis of their efficiency, accuracy, and sensitivity to data error. It is found that the method based on Rodrigues’ Formula (Bottema and Roth’s method) is the most efficient. Angeles’ method and Laub and Shiflett’s method provide approximately the same level of accuracy, which is superior to that of the other methods. In terms of sensitivity, Bottema and Roth’s method is preferable. On the basis of this study it is recommended that Bottema and Roth’s method be used if uncertainty exists in the data, since it can provide a solution efficiently, accurately and it is the least sensitive to data error.

scholarly journals Kinematics of Disk Stars in the Solar Neighbourhood

1998 ◽  
Vol 11 (1) ◽  
pp. 574-574
Author(s):  
A.E. Gómez ◽  
S. Grenier ◽  
S. Udry ◽  
M. Haywood ◽  
V. Sabas ◽  
...  
Keyword(s):  
Dispersion Relation ◽  
Radial Velocity ◽  
Velocity Dispersion ◽  
Tangential Velocity ◽  
Thin Disk ◽  
The Other ◽  
Proper Motions ◽  
Velocity Data ◽  
Kinematic Data ◽  
Radial Velocity Data

Using Hipparcos parallaxes and proper motions together with radial velocity data and individual ages estimated from isochones, the velocity ellipsoid has been determined as a function of age. On the basis of the available kinematic data two different samples were considered: a first one (7789 stars) for which only tangential velocities were calculated and a second one containing 3104 stars with available U, V and W velocity components and total velocities ≤ 65 km.s-1. The main conclusions are: -Mixing is not complete at about 0.8-1 Gyr. -The shape of the velocity ellipsoid changes with time getting rounder from σu/σv/σ-w = 1/0.63/0.42 ± 0.04 at about 1 Gyr to1/0.7/0.62 ±0.04 at 4-5 Gyr. -The age-velocity-dispersion relation (from the sample with kinematical selection) rises to a maximum, thereafter remaining roughly constant; there is no dynamically significant evolution of the disk after about 4-5 Gyr. -Among the stars with solar metallicities and log(age) > 9.8 two groups are identified: one has typical thin disk characteristics, the other is older than 10 Gyr and lags the LSR at about 40 km.s-1 . -The variation of the tangential velocity with age(without selection on the tangential velocity) shows a discontinuity at about 10 Gyr, which may be attributed to stars typically of the thick disk populations for ages > 10 Gyr.

scholarly journals Comparison of methods for obtaining doubled haploids of carrot

2017 ◽  
Vol 86 (2) ◽  
Author(s):  
Waldemar Kiszczak ◽  
Urszula Kowalska ◽  
Agata Kapuścińska ◽  
Maria Burian ◽  
Krystyna Górecka
Keyword(s):  
Plant Regeneration ◽  
Doubled Haploid ◽  
Aspartate Aminotransferase ◽  
Doubled Haploids ◽  
The Other ◽  
Plant Production ◽  
Comparison Of Methods ◽  
Anther Cultures ◽  
Induction Stage ◽  
Main Factor

Doubled haploid lines of carrot can be obtained through androgenesis in anther cultures and in isolated microspore cultures. The two methods were compared using three carrot cultivars (‘Kazan F1’, ‘Feria F1’, and ‘Narbonne F1’) at the androgenesis induction stage, during plant regeneration from embryos, and during acclimatization of androgenetic plants as well as their characterization. It was found that cultivar was the main factor affecting the efficiency at each stage of plant production in both anther and isolated microspore cultures. The efficiency of androgenesis in anther cultures of ‘Feria F1’ was considerably higher in comparison with isolated microspore cultures, and more plants were obtained from the embryos of androgenesis-cultured plants. In ‘Kazan F1’ and ‘Narbonne F1’, more acclimatized androgenetic plants were produced from anther cultures. Ploidy assessment of acclimatized plants of ‘Narbonne F1’ showed that the majority of the plants in the population derived from anther cultures had a doubled chromosome (DH) set. On the other hand, the majority of plants obtained from isolated microspore cultures were haploids. When assessing homozygosity, it was found among plants obtained in anther cultures that the percentage of homozygotes for phosphoglucose isomerase (PGI) and aspartate aminotransferase (AAT) depended on the cultivar. In contrast, the majority of plants derived from isolated microspore cultures were homozygous regardless of cultivar.

scholarly journals Interlaboratory Comparison of Methods To Quantify Microsclerotia of Verticillium dahliae in Soil

1998 ◽  
Vol 64 (10) ◽  
pp. 3846-3853 ◽  
Author(s):  
A. J. Termorshuizen ◽  
J. R. Davis ◽  
G. Gort ◽  
D. C. Harris ◽  
O. C. Huisman ◽  
...  
Keyword(s):  
Verticillium Dahliae ◽  
Interlaboratory Comparison ◽  
Petri Dish ◽  
Soil Samples ◽  
The Other ◽  
Comparison Of Methods ◽  
Research Groups ◽  
Soil Suspension ◽  
Blinded Fashion ◽  
Dry Soil

ABSTRACT In a comparison of different methods for estimatingVerticillium dahliae in soil, 14 soil samples were analyzed in a blinded fashion by 13 research groups in seven countries, using their preferred methods. One group analyzed only four samples. Twelve soil samples were naturally infested, and two had known numbers of microsclerotia of V. dahliae added to them. In addition, a control was included to determine whether transport had an effect on the results. Results differed considerably among the research groups. There was a 118-fold difference between the groups with the lowest and highest mean estimates. Results of the other groups were evenly distributed between these extremes. In general, methods based on plating dry soil samples gave higher numbers of V. dahliae than did plating of an aqueous soil suspension. Recovery of V. dahliae from samples with added microsclerotia varied from 0 to 59%. Most of the variability within each analysis was at the petri dish level. The results indicate the necessity to check the performance of detection assays regularly by comparing recoveries with other laboratories, using a common set of soil samples. We conclude that wet plating assays are less accurate than dry plating assays.

Comparison of methods of ranking scientists based on the Hirsch and PageRank indices: contradictory situations

2021 ◽  
pp. 39-44
Author(s):  
Hryhorii Hnatiienko ◽  
Oleksiy Oletsky
Keyword(s):  
Analytic Hierarchy Process ◽  
Pairwise Comparison ◽  
The Other ◽  
Publication Activity ◽  
Comparison Of Methods ◽  
Automated Systems ◽  
Analytic Hierarchy ◽  
H Index ◽  
Scientometric Indicators ◽  
Hierarchy Process

Experiments aimed at comparing different methods of estimating and ranking scientists and researchers on the base of their publication activity are reported. Scientometric indicators based on h-index and PageRank are being compared. For such a comparison, a graph of citations represented by a matrix was applied. An example when different methods lead to opposite results was described. For example, authors having the best PageRank-based estimations may have the least h-indices. Such a situation is possible when a high-cited author managed to obtain a key result cited by all the other authors but this author has few papers. A comparison with methods of expert estimations was carried out, which appears to be very useful for building automated systems combining various methods of algorithmic estimating and ranking. The Analytic Hierarchy Process was applied. For building pairwise comparison matrices, transitive scales with a parameter representing how much times the next level of advantage is bigger than the previous one were harnessed.

On Higher Order Point-Line and the Associated Rigid Body Motions

2006 ◽  
Vol 129 (2) ◽  
pp. 166-172 ◽  
Author(s):  
Yi Zhang ◽  
Kwun-Lon Ting
Keyword(s):  
Rigid Body ◽  
Higher Order ◽  
Rigid Bodies ◽  
Rigid Body Motion ◽  
Body Motion ◽  
Dual Quaternion ◽  
Displacement Operator ◽  
Screw Motion ◽  
Rigid Body Motions ◽  
Point Line

This paper presents a study on the higher-order motion of point-lines embedded on rigid bodies. The mathematic treatment of the paper is based on dual quaternion algebra and differential geometry of line trajectories, which facilitate a concise and unified description of the material in this paper. Due to the unified treatment, the results are directly applicable to line motion as well. The transformation of a point-line between positions is expressed as a unit dual quaternion referred to as the point-line displacement operator depicting a pure translation along the point-line followed by a screw displacement about their common normal. The derivatives of the point-line displacement operator characterize the point-line motion to various orders with a set of characteristic numbers. A set of associated rigid body motions is obtained by applying an instantaneous rotation about the point-line. It shows that the ISA trihedrons of the associated rigid motions can be simply depicted with a set of ∞2 cylindroids. It also presents for a rigid body motion, the locus of lines and point-lines with common rotation or translation characteristics about the line axes. Lines embedded in a rigid body with uniform screw motion are presented. For a general rigid body motion, one may find lines generating up to the third order uniform screw motion about these lines.

Alcohol and Speed-Accuracy Tradeoff

1979 ◽  
Vol 21 (4) ◽  
pp. 433-443 ◽  
Author(s):  
O. H. RUNDELL ◽  
HAROLD L. WILLIAMS
Keyword(s):  
Body Weight ◽  
Reaction Time ◽  
Discrimination Task ◽  
The Other ◽  
Pitch Discrimination ◽  
Alcohol Dose ◽  
Independent Effects ◽  
Speed Accuracy ◽  
Accuracy Tradeoff ◽  
And Task

Performance on two auditory choice reaction time (RT) tasks was studied in a group of 12 subjects under the influence of graded doses of ethyl alcohol ranging from placebo to 1 g/kg body weight. Deadline procedures were employed in a side discrimination and a pitch discrimination task to permit the calculation of speed-accuracy tradeoff functions (accuracy versus RT). Accuracy declined as a function of dose, but alcohol did not significantly influence RT. Conversely, accuracy was not affected by task; but the pitch discrimination task required an average of 88 ms more time than the side task. Alcohol dose and task produced independent effects on the speed-accuracy tradeoff function. As dose increased, the slope of the tradeoff function declined; but slopes were equivalent for the two tasks. On the other hand, the x-intercept (where accuracy equals chance levels) was 90 ms greater for the pitch task than for the side task.

ENVELOPING SURFACES AND ADMISSIBLE VELOCITIES OF HEAVY RIGID BODIES

2004 ◽  
Vol 14 (08) ◽  
pp. 2525-2553 ◽  
Author(s):  
IGOR N. GASHENENKO ◽  
PETER H. RICHTER
Keyword(s):  
Three Dimensional ◽  
Rigid Bodies ◽  
First Integrals ◽  
The Body ◽  
Heegaard Splitting ◽  
Body Motion ◽  
Invariant Sets ◽  
Poisson Problem ◽  
Integral Manifolds ◽  
Angular Velocities

The general Euler-Poisson problem of rigid body motion is investigated. We study the three-dimensional algebraic level surfaces of the first integrals, and their topological bifurcations. The main result of this article is an analytical and qualitatively complete description of the projections of these integral manifolds to the body-fixed space of angular velocities. We classify the possible types of these invariant sets and analyze the dependence of their topology on the parameters of the body and the constants of the first integrals. Particular emphasis is given to the enveloping surfaces of the sets of admissible angular velocities. Their pre-images in the reduced phase space induce a Heegaard splitting which lends itself for a general choice of complete Poincaré surfaces of section, irrespective of whether or not the system is integrable.

Nonaxisymmetric Acoustic Radiation and Scattering From Rigid Bodies of Revolution Using the Surface Variational Principle

1998 ◽  
Vol 120 (1) ◽  
pp. 95-103 ◽  
Author(s):  
J. H. Ginsberg ◽  
Kuangcheng Wu
Keyword(s):  
Variational Principle ◽  
Rigid Body ◽  
Acoustic Radiation ◽  
Axisymmetric Body ◽  
Rigid Bodies ◽  
Body Motion ◽  
Convergence Properties ◽  
Bodies Of Revolution ◽  
Computer Codes ◽  
Acoustic Fluid

The surface variational principle (SVP), which represents the surface response as a series of basis functions spanning the entire surface, provides a global description of acoustic fluid-structure interaction that has many of the benefits associated with analytical methods. This paper describes the extension of SVP to model the interaction between the velocity and pressure on the surface of an axisymmetric body subjected to nonaxisymmetric excitation. Problems addressed are radiation due to arbitrary rigid body motion, and scattering associated with arbitrary incidence of a plane wave on a stationary rigid body. Numerical results are presented for flat-ended and hemi-capped cylinders. These results are compared to those obtained from the CHIEF-88 and SHIP-92 computer codes. The convergence properties of SVP are examined in detail, particularly for its requirements when ka is in the upper part of the mid-frequency range.

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