scholarly journals On the problem of hydrodynamic stability. I. uniform shearing motion in a viscous fluid

1930 ◽  
Vol 229 (670-680) ◽  
pp. 205-253 ◽  
Keyword(s):  
Viscous Fluid ◽  
Steady Motion ◽  
Precise Determination ◽  
The Body ◽  
Periodic Motions ◽  
Principle Of Superposition ◽  
Moving Body ◽  
Exact Determination ◽  
Shearing Motion

1. Except in a few very simple cases, the equations which govern the motion of a viscous fluid have so far defied analysis. Their difficulty comes mainly from the fact that they are not linear, so that the principle of superposition cannot be employed, as in many branches of mathematical physics, to construct solutions by the method of series or of singularities. For the same reason the flow pattern in the neighbourhood of a moving body must alter when the speed of the body is changed, and it follows that any exact determination of the pattern will be restricted to some definite speed. As a matter of fact, no precise determination of this kind exists, except in cases where the motion is indefinitely slow. But the form of the equations gives no reason for doubting the possibility of “steady” motion (in which the velocities are functions only of position) in every case of flow past fixed and rigid boundaries. Now in experiment it is found (unless the velocities are very small) that eddying or periodic motions always occur. Thus the conclusion seems inevitable that a steady motion may become unstable as the rate of flow is increased, in the sense that accidental disturbances, if of suitable type, will persist.

scholarly journals Prevalence of Non-Occupational Disorders in Men with Occupational Vibration Disease

2021 ◽  
pp. 4-8
Author(s):  
AV Gurev ◽  
AR Tukov ◽  
AYu Bushmanov
Keyword(s):  
Musculoskeletal Disorders ◽  
Occupational Diseases ◽  
Endocrine System ◽  
Precise Determination ◽  
The Body ◽  
Health Centers ◽  
Study Cohort ◽  
Vibration Disease ◽  
Reliable Source

Introduction: Industrial vibration has a complex effect on the body, increasing the risk of diseases from the circulatory and respiratory systems, disorders of the liver and endocrine system, which are not recognized by medical boards as occupational. The objective of our study was to analyze the prevalence of non-occupational diseases in workers suffering from occupational vibration disease and employed in industries and institutions served by health facilities of the Russian Federal Medical-Biological Agency (FMBA). Materials and methods: As a reliable source of information, we used the Industry Register of Persons with Occupational Diseases containing data on 95 cases of occupational vibration disease aged 65.1 ± 1.5 (90 men aged 64.8 ± 1.5 years and 5 women aged 70.6 ± 2.6 years). The prevalence rates are given per 1,000 cases of occupational vibration disease with an error of the intensive indicator and the proportion of the pathology in the structure of non-occupational diseases. Results: The prevalence of non-occupational diseases in men was 755.6 ± 91.6. Of these, musculoskeletal disorders (288.9±47.8; 39.4 %) ranked first, followed by diseases of the cardiovascular (177.8 ± 40.3; 24.2 %), respiratory (111.1 ± 33.1; 15.2 %), and digestive (66.7 ± 26.3; 9.1 %) systems. Discussion: We established that diseases of the musculoskeletal system and other disorders potentially related to occupational vibration dominated in the structure of non-occupational diseases in the study cohort. Conclusion: Cases of occupational vibration disease often suffer from musculoskeletal disorders, diseases of the circulatory, respiratory and digestive systems, accounting for 87.9 % of all non-occupational illnesses in this research. We recommend a more precise determination of occupational or non-occupational genesis of musculoskeletal disorders in people exposed to vibration at work in occupational health centers.

Domains of Mobility for a Planar Body Moving Among Obstacles

1996 ◽  
Author(s):  
Edward J. Haug ◽  
Frederick A. Adkins ◽  
Dan I. Coroian
Keyword(s):  
Reference Point ◽  
Degrees Of Freedom ◽  
Full Range ◽  
The Body ◽  
General Application ◽  
Limited Mobility ◽  
Moving Body ◽  
Planar Convex ◽  
Stationary Obstacles

Abstract A formulation is presented for defining domains of mobility for a planar convex body moving with three degrees-of-freedom among convex planar obstacles. Applications included are determination of areas of a factory floor or material storage facility in which objects can be manipulated without impacting fixed obstacles. Mobility of the moving body is defined to encompass (1) dextrous mobility of the body; i.e., points that can be reached by a reference point on the body and at which the body can be rotated through its full range of admissible orientations without penetrating any stationary obstacle, and (2) limited mobility of the body; i.e., points that can be reached by the reference point and at which the body does not penetrate any stationary obstacle, for some admissible orientation. Analytical criteria for points on boundaries of domains of mobility are derived and numerical methods suitable for mapping these boundaries are summarized. An elementary example involving a moving and a stationary ellipse, with and without orientation restrictions, is solved analytically to illustrate the method. A more general application with one moving body and three stationary obstacles is solved numerically.

scholarly journals The unborn child: history, philosophy and religion

2017 ◽  
Vol 20 (34) ◽  
pp. 73-84
Author(s):  
Maria Casandra Lucan
Keyword(s):  
Human Life ◽  
Legal Protection ◽  
The Body ◽  
Unborn Child ◽  
Starting Point ◽  
Philosophy And Religion ◽  
Exact Determination ◽  
Exact Moment ◽  
The Moment

Abstract All throughout history the unborn, and implicitly its protection, have been subject for academics and practitioners of various areas. The problem of the origin of the soul and the exact determination of the moment when it is united with the body was crucial in enabling us to define the exact moment when the human life begins, and, consequently, for providing proper protection for the unborn child. In this context visions of the Greek philosophers like Plato, Aristotle, Albertus Magnus and Thomas Aquinas, and of the Latin writer Tertullian, as well as Christian perspectives were analysed in order to identify the starting point of the human being to help determine the level of protection provided for the unborn in history. Finally, considering the fact that not even today has consensus been achieved concerning the beginning of human life, it was and still is difficult to provide proper legal protection for the unborn child, but in our opinion this is by far not impossible.

scholarly journals The motion of ellipsoidal particles in a viscous fluid

1923 ◽  
Vol 103 (720) ◽  
pp. 58-61 ◽  
Keyword(s):  
Viscous Fluid ◽  
Initial Conditions ◽  
Equations Of Motion ◽  
Minimum Energy ◽  
Steady Motion ◽  
Prolate Spheroid ◽  
Ellipsoidal Particles ◽  
Elliptic Cone ◽  
Axis Of Symmetry ◽  
Shearing Motion

In a recent paper* Dr. G. B. Jeffery has discussed the equations of motion of ellipsoidal particles immersed in a moving viscous fluid. He has solved the problem completely in The case of spheroidal particles immersed in a very viscous fluid which is moving parallel to a plane with a uniform shearing motion. his so1ution shows that the motion depends on the initial conditions of release of the Particle. The motion is periodic, and there appears to be no tendency for a particle to set itself so that its axis 1ies in any Particular direction. The Particle, in fact, takes up the rotation of the fluid, and its axis of symmetry describes a kind of elliptic cone round the direction of the vortex filaments, that is, round the direction which is perpendicular to the plane in which the motion of the fluid takes places. Though the ana1ysis, which neglects the inertia terms in the equations of motion, gives no indication of any tendency for the axis to set itself in any particular direction, Dr. Jeffery considers that ultimate1y the axis would probably adopt some special position, and he puts forward a " minimum energy ” hypothesis, which leads to the following definite, though unproved and unverified, results:— 1. A prolate spheroid, subject to the restriction imposed by this hypothesis, would set itself so that its long axis was Parallel to the vortex lines, and therefore perpendicular to the plane in which this undisturbed motion of the fluid takes places. It would then rotate with the fluid, which would move in steady motion relative to it.

Domains of Mobility for a Planar Body Moving Among Obstacles

1998 ◽  
Vol 120 (3) ◽  
pp. 462-467 ◽  
Author(s):  
E. J. Haug ◽  
F. A. Adkins ◽  
D. Coroian
Keyword(s):  
Reference Point ◽  
Degrees Of Freedom ◽  
The Body ◽  
General Application ◽  
Limited Mobility ◽  
Moving Body ◽  
Planar Convex ◽  
Stationary Obstacles ◽  
Planar Body

A formulation is presented for defining domains of mobility for a planar convex body moving with three degrees-of-freedom among convex planar obstacles. Applications included are determination of areas of a factory floor or material storage facility in which objects can he manipulated without impacting fixed obstacles. Mobility of the moving body is defined to encompass (1) dexterous mobility of the body; i.e., points that can be reached by a reference point on the body and at which the body can be rotated through a specified range of admissible orientations without penetrating any stationary obstacle, and (2) limited mobility of the body; i.e., points that can be reached by the reference point and at which the body does not penetrate any stationary obstacle, for some admissible orientation. Analytical criteria for points on boundaries of domains of mobility are derived and numerical methods suitable for mapping these boundaries are summarized. An elementary example involving a moving and a stationary ellipse, with and without orientation restrictions, is solved analytically to illustrate the method. A more general application with one moving body and three stationary obstacles is solved numerically.

Gender determination of caucasoid hair using image analysis

1993 ◽  
Vol 51 ◽  
pp. 216-217
Author(s):  
T.B. Ball ◽  
W.M. Hess
Keyword(s):  
Image Analysis ◽  
Cross Sections ◽  
Scalp Hair ◽  
The Body ◽  
Equivalent Diameter ◽  
Cross Sectional ◽  
Hair Samples ◽  
Length Width ◽  
Morphological Differences

It has been demonstrated that cross sections of bundles of hair can be effectively studied using image analysis. These studies can help to elucidate morphological differences of hair from one region of the body to another. The purpose of the present investigation was to use image analysis to determine whether morphological differences could be demonstrated between male and female human Caucasian terminal scalp hair.Hair samples were taken from the back of the head from 18 caucasoid males and 13 caucasoid females (Figs. 1-2). Bundles of 50 hairs were processed for cross-sectional examination and then analyzed using Prism Image Analysis software on a Macintosh llci computer. Twenty morphological parameters of size and shape were evaluated for each hair cross-section. The size parameters evaluated were area, convex area, perimeter, convex perimeter, length, breadth, fiber length, width, equivalent diameter, and inscribed radius. The shape parameters considered were formfactor, roundness, convexity, solidity, compactness, aspect ratio, elongation, curl, and fractal dimension.

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