Two-lobed artificial cardiac valve with a common axis of rotation of lobes

1998 ◽  
Vol 32 (5) ◽  
pp. 272-282 ◽  
Author(s):  
V. N. Yurechko ◽  
R. V. Yurechko ◽  
L. M. Vil'danov ◽  
M. P. Etonov
Keyword(s):  
Cardiac Valve ◽  
Common Axis ◽  
Artificial Cardiac Valve ◽  
Axis Of Rotation

scholarly journals Clarification of Features of the Wheel Movement with a Perspective Constructive Scheme on a Rail

2020 ◽  
Vol 10 (19) ◽  
pp. 6758
Author(s):  
Evgeny Mikhailov ◽  
Stanislav Semenov ◽  
Sergii Kliuiev ◽  
Ján Dižo ◽  
Miroslav Blatnický ◽  
...  
Keyword(s):  
Support Surface ◽  
Relative Rotation ◽  
Friction Forces ◽  
Slippage Rate ◽  
Common Axis ◽  
Design Scheme ◽  
Axis Of Rotation ◽  
Traditional Design ◽  
Curved Track

The article presents the continuation of studies of the features of the wheel movement the traditional and perspective constructive scheme on a rail. Unlike the traditional design, the perspective constructive scheme of the wheel allows independent relative rotation of the support surface wheel and of its guide surface (flange) relative to their common axis of rotation. Previous authors’ works did not take into account the influence of the level of slippage in the main contact of the wheel with the rail on the value of the slippage rate in its flange contact. This article further examines the influence of this factor for both wheel designs. The results of the presented studies confirm the possibility of reducing slippage in the flange contact with the rail for a wheel of a promising design scheme in comparison with a traditional wheel. Reducing the power of friction forces in the contact of the wheel flange of a promising design scheme will reduce the resistance to movement of such a wheel along the rail, especially in curved track sections.

On Variations in the Chandler Frequency

1972 ◽  
Vol 1 ◽  
pp. 77-85
Author(s):  
H.J.M. Abraham ◽  
J.N. Boots
Keyword(s):  
Axis Of Rotation ◽  
The Earth ◽  
Actual Motion ◽  
Chandler Frequency

This paper suggests that some of the reported changes in the Chandler frequency are associated with inelastic changes in the Earth. There has been controversy as to how much of the apparent secular polar drift is due to actual motion of the axis of rotation within the Earth, and how much it is merely the reflection of movements by certain observatories. Therefore, when more southern data are available it will be interesting to see whether similar results are obtained.

Reference Coordinate System Requirements for Geophysics

1975 ◽  
Vol 26 ◽  
pp. 87-92
Author(s):  
P. L. Bender
Keyword(s):  
Coordinate System ◽  
Polar Motion ◽  
Main Part ◽  
Measurement Techniques ◽  
Reference Points ◽  
Angular Motion ◽  
Coordinate Systems ◽  
Axis Of Rotation ◽  
The Earth ◽  
Fixed System

AbstractFive important geodynamical quantities which are closely linked are: 1) motions of points on the Earth’s surface; 2)polar motion; 3) changes in UT1-UTC; 4) nutation; and 5) motion of the geocenter. For each of these we expect to achieve measurements in the near future which have an accuracy of 1 to 3 cm or 0.3 to 1 milliarcsec.From a metrological point of view, one can say simply: “Measure each quantity against whichever coordinate system you can make the most accurate measurements with respect to”. I believe that this statement should serve as a guiding principle for the recommendations of the colloquium. However, it also is important that the coordinate systems help to provide a clear separation between the different phenomena of interest, and correspond closely to the conceptual definitions in terms of which geophysicists think about the phenomena.In any discussion of angular motion in space, both a “body-fixed” system and a “space-fixed” system are used. Some relevant types of coordinate systems, reference directions, or reference points which have been considered are: 1) celestial systems based on optical star catalogs, distant galaxies, radio source catalogs, or the Moon and inner planets; 2) the Earth’s axis of rotation, which defines a line through the Earth as well as a celestial reference direction; 3) the geocenter; and 4) “quasi-Earth-fixed” coordinate systems.When a geophysicists discusses UT1 and polar motion, he usually is thinking of the angular motion of the main part of the mantle with respect to an inertial frame and to the direction of the spin axis. Since the velocities of relative motion in most of the mantle are expectd to be extremely small, even if “substantial” deep convection is occurring, the conceptual “quasi-Earth-fixed” reference frame seems well defined. Methods for realizing a close approximation to this frame fortunately exist. Hopefully, this colloquium will recommend procedures for establishing and maintaining such a system for use in geodynamics. Motion of points on the Earth’s surface and of the geocenter can be measured against such a system with the full accuracy of the new techniques.The situation with respect to celestial reference frames is different. The various measurement techniques give changes in the orientation of the Earth, relative to different systems, so that we would like to know the relative motions of the systems in order to compare the results. However, there does not appear to be a need for defining any new system. Subjective figures of merit for the various system dependon both the accuracy with which measurements can be made against them and the degree to which they can be related to inertial systems.The main coordinate system requirement related to the 5 geodynamic quantities discussed in this talk is thus for the establishment and maintenance of a “quasi-Earth-fixed” coordinate system which closely approximates the motion of the main part of the mantle. Changes in the orientation of this system with respect to the various celestial systems can be determined by both the new and the conventional techniques, provided that some knowledge of changes in the local vertical is available. Changes in the axis of rotation and in the geocenter with respect to this system also can be obtained, as well as measurements of nutation.

The spindle stage: A powerful optical tool

1988 ◽  
Vol 46 ◽  
pp. 52-53
Author(s):  
Mickey E. Gunter ◽  
F. Donald Bloss
Keyword(s):  
Significant Error ◽  
Optical Data ◽  
Refractive Indices ◽  
Axis Of Rotation ◽  
Polarizing Microscope ◽  
Microscope Stage

A single, reasonably homogeneous, nonopaque 30-to-300 μm crystal, mounted on a spindle stage and studied by immersion methods under a polarizing microscope, yields optical data frequently sufficient to identify and characterize a substance unequivocally. The data obtainable include (1) the orientation of the crystal's principal vibration axes and (2) its principal refractive indices, to within 0.0002 if desired, for light vibrating along these principal vibration axes. Spindle stages tend to be simple and relatively inexpensive, some costing less than $50. They permit rotation of the crystal about a single axis which is parallel to the microscope stage. This spindle or S-axis is thus perpendicular to the M-axis, namely the microscope stage's axis of rotation.A spindle stage excels when studying anisotropic crystals. It orients uniaxial crystals within minutes and biaxial crystals almost as quickly so that their principal refractive indices - ɛ and ω (uniaxial); α, β and γ (biaxial) - can be determined without significant error from crystal misorientation.

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