On Dynamically Equivalent Force Systems and Their Application to the Balancing of a Broom or the Stability of a Shoe Box

2004 ◽  
Author(s):  
Just L. Herder ◽  
Arend L. Schwab
Keyword(s):  
Rigid Body ◽  
Center Of Mass ◽  
The Body ◽  
Resultant Force ◽  
Dynamic Equivalence ◽  
Force Systems ◽  
The Stability ◽  
Metacentric Height ◽  
The Given

The stability of a rigid body on which two forces are in equilibrium can be assessed intuitively. In more complex cases this is no longer true. This paper presents a general method to assess the stability of complex force systems, based on the notion of dynamic equivalence. A resultant force is considered dynamically equivalent to a given system of forces acting on a rigid body if the contributions to the stability of the body of both force systems are equal. It is shown that the dynamically equivalent resultant force of two given constant forces applies at the intersection of its line of action and the circle put up by the application points of the given forces and the intersection of their lines of action. The determination of the combined center of mass can be considered as a special case of this theorem. Two examples are provided that illustrate the significance of the proposed method. The first example considers the suspension of a body, by springs only, that is statically balanced for rotation about a virtual stationary point. The second example treats the roll stability of a ship, where the metacentric height is determined in a natural way.

New Methodology for the Determination of the Vertical Center of Gravity of In-Service Semisubmersibles: Proposal and Numerical Assessment

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Ivan N. Porciuncula ◽  
Claudio A. Rodríguez ◽  
Paulo T. T. Esperança
Keyword(s):  
Accurate Determination ◽  
Center Of Gravity ◽  
Practical Implementation ◽  
Numerical Assessment ◽  
Neutral Equilibrium ◽  
Inclination Angles ◽  
Numerical Tools ◽  
The Stability ◽  
Metacentric Height

Along its lifetime, an offshore unit is subjected to several equipment interventions. These modifications may include large conversions in loco that usually are not adequately documented. Hence, the accurate determination of the platform's center of gravity (KG) is not possible. For vessels with low metacentric height (GM), such as semisubmersibles, Classification Societies penalize the platform's KG, inhibiting the installation of new equipment until an accurate measurement of KG is provided, i.e., until an updated inclining test is performed. For an operating semisubmersible, the execution of this type of test is not an alternative because it implies in removing the vessel from its in-service location to sheltered waters. Relatively recently, some methods have been proposed for the estimation of KG for in-service vessels. However, as all of the methods depend on accurate measurements of inclination angles and, eventually, on numerical tools for the simulation of vessel dynamics onboard, they are not straightforward for practical implementation. The objective of the paper is to present a practical methodology for the experimental determination of KG, without the need of accurate measurements of inclinations and/or complex numerical simulations, but based on actual operations that can be performed onboard. Indeed, the proposed methodology relies on the search, identification, and execution of a neutral equilibrium condition where, for instance, KG = KM. The method is exemplified using actual data of a typical semisubmersible. The paper also numerically explores and discusses the stability of the platform under various conditions with unstable initial GM, as well as the effect of mooring and risers.

The Forced Oscillations of Submerged Bodies

2003 ◽  
Vol 125 (4) ◽  
pp. 710-715
Author(s):  
Angel Sanz-Andre´s ◽  
Gonzalo Tevar ◽  
Francisco-Javier Rivas
Keyword(s):  
Rigid Body ◽  
Small Amplitude ◽  
Center Of Mass ◽  
Rigid Body Dynamics ◽  
The Body ◽  
Central Point ◽  
Modal Testing ◽  
Forced Oscillations ◽  
Motion Equations ◽  
Marine Applications

The increasing use of very light structures in aerospace applications are given rise to the need of taking into account the effects of the surrounding media in the motion of a structure (as for instance, in modal testing of solar panels or antennae) as it is usually performed in the motion of bodies submerged in water in marine applications. New methods are in development aiming at to determine rigid-body properties (the center of mass position and inertia properties) from the results of oscillations tests (at low frequencies during modal testing, by exciting the rigid-body modes only) by using the equations of the rigid-body dynamics. As it is shown in this paper, the effect of the surrounding media significantly modifies the oscillation dynamics in the case of light structures and therefore this effect should be taken into account in the development of the above-mentioned methods. The aim of the paper is to show that, if a central point exists for the aerodynamic forces acting on the body, the motion equations for the small amplitude rotational and translational oscillations can be expressed in a form which is a generalization of the motion equations for a body in vacuum, thus allowing to obtain a physical idea of the motion and aerodynamic effects and also significantly simplifying the calculation of the solutions and the interpretation of the results. In the formulation developed here the translational oscillations and the rotational motion around the center of mass are decoupled, as is the case for the rigid-body motion in vacuum, whereas in the classical added mass formulation the six motion equations are coupled. Also in this paper the nonsteady motion of small amplitude of a rigid body submerged in an ideal, incompressible fluid is considered in order to define the conditions for the existence of the central point in the case of a three-dimensional body. The results here presented are also of interest in marine applications.

On the harmonic oscillations of a rigid body on a free surface

1965 ◽  
Vol 21 (3) ◽  
pp. 427-451 ◽  
Author(s):  
W. D. Kim
Keyword(s):  
Integral Equation ◽  
Free Surface ◽  
Rigid Body ◽  
Potential Problem ◽  
Harmonic Oscillation ◽  
Added Mass ◽  
The Body ◽  
Rigorous Solution ◽  
Damping Coefficients

The present paper deals with the practical and rigorous solution of the potential problem associated with the harmonic oscillation of a rigid body on a free surface. The body is assumed to have the form of either an elliptical cylinder or an ellipsoid. The use of Green's function reduces the determination of the potential to the solution of an integral equation. The integral equation is solved numerically and the dependency of the hydrodynamic quantities such as added mass, added moment of inertia and damping coefficients of the rigid body on the frequency of the oscillation is established.

Estimation of Location and Orientation From Range Measurements

2015 ◽  
Author(s):  
Sai Krishna Kanth Hari ◽  
Swaroop Darbha
Keyword(s):  
Linear Programming ◽  
Rigid Body ◽  
Center Of Mass ◽  
Body Motion ◽  
Second Step ◽  
True Distance ◽  
Numerical Examples ◽  
Range Measurements ◽  
Motion Constraints

Localization is an important required task for enabling vehicle autonomy. Localization entails the determination of the position of the center of mass and orientation of a vehicle from the available measurements. In this paper, we focus on localization by using the range measurements available to a vehicle from the communication of its multiple onboard receivers with roadside beacons. The model proposed for measurement is as follows: the true distance between a receiver and a beacon is at most equal to a predetermined function of the range measurement. The proposed procedure for localization is as follows: Based on the range measurements specific to a receiver from the beacons, a finite LP (linear programming) is proposed to estimate the location of the receiver. The estimate is essentially the Chebychev center of the set of possible locations of the receiver. In the second step, the location estimates of the vehicle are corrected using rigid body motion constraints and the orientation of the rigid body is thus determined. Two numerical examples provided at the end corroborate the procedures developed in this paper.

scholarly journals Somatotypes in Sport

2014 ◽  
Vol 8 (1) ◽  
pp. 27-32 ◽  
Author(s):  
Teodor Tóth ◽  
Monika Michalíková ◽  
Lucia Bednarčíková ◽  
Jozef Živčák ◽  
Peter Kneppo
Keyword(s):  
Physical Condition ◽  
The Body ◽  
Physical Parameters ◽  
Body Constitution ◽  
Rating Form ◽  
Sporting Activities ◽  
The Individual ◽  
The Given ◽  
Selection Of

Abstract The submitted article deals with the evaluation of the somatotype of persons and determination of a suitable somatotype for selected sports. In the introduction the method for determining and evaluating a somatotype according to Carter and Heath is characterised. The processes used for calculating the individual components - endomorphy, mesomorphy, ectomorphy - are presented as well as a description of these elements. The calculated components are subsequently put into a somatograph. The evaluation of a somatotype is of great benefit and offers a guideline with the selection of sporting activities; it subsequently helps assign athletes into a suitable position where they will be able to best develop their talents in view of their bodily construction. In this work two types of sports are evaluated - basketball and bodybuilding. With each sport the measurements which give the prerequisites for the given sport are presented. The selection of the presented sports was made with regard to the different requirements and demands in the scope of bodily constitution. The aim of the presented paper is to assess physical parameters of subjects groups in relation to selected sports (basketball and bodybuilding). Based on the body constitution to determine the conditions for developing the physical condition and success in the appointed sports. Another objective is to compare the rating form and equation methods for somatotype determination. The sample consist 32 subjects with age between 22-28 years of both sexes, who are dedicated to basketball, or bodybuilding at amateur level.

Optimizing the determination of the body center of mass

1995 ◽  
Vol 28 (9) ◽  
pp. 1137-1142 ◽  
Author(s):  
Idsart Kingma ◽  
Huub M. Toussaint ◽  
Dianne A.C.M. Commissaris ◽  
Marco J.M. Hoozemans ◽  
Michiel J. Ober
Keyword(s):  
Center Of Mass ◽  
The Body ◽  
Body Center

scholarly journals Cases of Integrability Which Correspond to the Motion of a Pendulum in the Three-dimensional Space

2021 ◽  
Vol 16 ◽  
pp. 73-84
Author(s):  
Maxim V. Shamolin
Keyword(s):  
Rigid Body ◽  
Force Fields ◽  
Characteristic Point ◽  
Dimensional Space ◽  
Center Of Mass ◽  
Three Dimensional ◽  
Rigid Bodies ◽  
The Body ◽  
Spatial Motion ◽  
Free Rigid Body

We systematize some results on the study of the equations of spatial motion of dynamically symmetric fixed rigid bodies–pendulums located in a nonconservative force fields. The form of these equations is taken from the dynamics of real fixed rigid bodies placed in a homogeneous flow of a medium. In parallel, we study the problem of a spatial motion of a free rigid body also located in a similar force fields. Herewith, this free rigid body is influenced by a nonconservative tracing force; under action of this force, either the magnitude of the velocity of some characteristic point of the body remains constant, which means that the system possesses a nonintegrable servo constraint, or the center of mass of the body moves rectilinearly and uniformly; this means that there exists a nonconservative couple of forces in the system

BBAP amplification profiles of apple varieties

2021 ◽  
Vol 13 (2) ◽  
pp. 1-6
Author(s):  
Ivana Speváková ◽  
Lucia Urbanová ◽  
Matúš Kyseľ ◽  
Jana Bilčíková ◽  
Silvia Farkasová ◽  
...  
Keyword(s):  
Molecular Level ◽  
Intraspecific Variability ◽  
Degenerate Primers ◽  
Genomic Variability ◽  
Malus Domestica Borkh ◽  
Apple Varieties ◽  
Bet V 1 ◽  
The Stability ◽  
The Given

Several types of allergies are currently known and are characterized by an exaggerated response of the immune system to substances from various sources called allergens. One of them is a food allergy, which is becoming more common in the population. For this reason, it is necessary to describe the issue from several aspects including genomic variability of plant allergens. The objective of this study was to analyse intraspecific variability of Bet v 1 of 10 different varieties of apple species (Malus domestica Borkh.). BBAP technique for genomic determination of the presence of Bet v 1 homologs at the DNA level was performed. Degenerate primers that anneal a variable and conserved part of PR-10 protein homologues genes were used in the analyse. Amplicons were generated and formed relatively monomorphic profiles, indicating the stability of the given isoforms of Bet v 1 within the selected apple varieties. To evaluate the potential allergenicity of selected varieties further studies on another molecular level such as a comparison of gene expression of the PR-10 family members and their protein expression levels are needed.

Determining Critical States of Equilibrium of Plates and Shells Under Initial Stress

1942 ◽  
Vol 9 (1) ◽  
pp. A27-A30
Author(s):  
H. Hencky
Keyword(s):  
Cylindrical Shell ◽  
Energy Method ◽  
Virtual Work ◽  
The Body ◽  
Principle Of Virtual Work ◽  
Practical Applications ◽  
Fundamental Knowledge ◽  
Plates And Shells ◽  
The Stability

Abstract The purpose of this paper is to show that Rayleigh’s energy method, used by Timoshenko for the determination of critical loads in plates and shells, is capable of an important generalization. The work involved is a direct continuation of the energy method of Timoshenko and is based on the principle of virtual work. According to this principle the variation of the work of the outer forces together with the variation of the kinetic energy is equal to the variation of the elastic energy stored up in the body. The author develops a series of formulas, by means of which the stability of a cylindrical shell under various conditions of stress may be determined. The practical applications of these formulas, requiring only a fundamental knowledge of the mathematics of engineering, are illustrated by suitable examples.

Comparison of the Absorption and Destruction of the Lactone and Salt Form of Glucuronic Acid by Dogs

1956 ◽  
Vol 188 (1) ◽  
pp. 54-60
Author(s):  
F. A. Buckeridge ◽  
Smith Freeman
Keyword(s):  
Small Intestine ◽  
Plasma Concentration ◽  
Glucuronic Acid ◽  
The Body ◽  
Limiting Factor ◽  
Salt Form ◽  
Ph Values ◽  
Rate Of Absorption ◽  
The Stability

Comparative studies were made on the fate of d-glucuronolactone and d-glucuronate in dogs. The studies included: a) measurement of the rate of conversion of the lactone into the salt form at various ph values ranging from 2.0 to 7.4; b) measure of the rate of absorption from isolated loops of small intestine; c) determination of the blood plasma concentration in relation to intestinal absorption of the two forms of glucuronic acid in normal, Eck fistula and nephrectomized animals; d) the stability and magnitude of the plasma values were determined following the intravenous injection of the lactone or salt form of glucuronic acid into nephrectomized dogs. From the foregoing studies, it was determined that: a) glucuronolactone is rapidly converted into glucuronate at the ph of plasma; b) glucuronolactone is absorbed from the small intestine much more rapidly than is glucuronate; c) absorbed glucuronolactone is metabolized rapidly while glucuronate appears to be relatively inert in the body and to occupy a space similar to that of inulin. The limiting factor in the metabolism of glucuronolactone is the rate of its conversion into the salt form.

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