A practical method for stability assessment of a damaged ship

El propósito de esta investigación fué realizar una valoración de la fuerza del tronco utilizando protocolos descritos en la literatura mediante acelerometria, utilizando los cálculos de CV y entropía ApEn. Además como objetivo secundario comprobar las diferencias en las variables CV y ApEn en función del tipo de ejercicio. Catorce sujetos varones los cuales formaban parte de un equipo de fútbol que militaba en Tercera División (edad: 23,4 ± 2,73; altura: 1,75 ± 0,05 cm.; peso: 74,3 ± 4,19 kg.; IMC: 21,51 ± 3,47) fueron registrados mediante un dispositivo inercial ubicado en el centro de masa (L3) y se analizaron sus señales acelerometricas mediante dos estadísticos: el coeficiente de variación (CV) y la entropía aproximada (ApEn). Se encontraron diferencias significativas en el valor de CV y ApEn en todos los ejercicios excepto entre PP y PL en ApEn (p<0.05). Se distribuyeron los datos en valores bajos, medios y altos de CV y ApEn de los participantes. Se propone una valoración de la estabilidad-fuerza del tronco mediante un dispositivo inercial o multisensores como un método práctico para el entrenador/preparador físico. Y la aplicación de los estadísticos CV y ApEn para el análisis de señales en ejercicios de estabilidad.Abstract. The purpose of this research was to perform a trunk strength assessment of protocols described in the literature using accelerometry, by means of CV and ApEn entropy calculations. In addition, to check differences in CV and ApEn variables depending on the type of exercise, as a secondary objective. Fourteen male subjects who were part of a football team participating in the Third Division (age: 23.4 2.73, height: 1.75 0.05 cm, weight: 74.3 4.19 kg, IMC : 21,51 3,47) were recorded by means of an inertial device located in the center of mass (L3) and their accelerometric signals were analyzed by two statistics: coefficient of variation (CV) and approximate entropy (ApEn). Significant differences were found in the value of CV and ApEn in all exercises except between PP and PL in ApEn (p <0.05). The data were distributed in low, medium and high values of CV and ApEn of the participants. A trunk strength-stability assessment using an inertial device or multisensors is proposed as a practical method for trainers. Also, the application of the statistics CV and ApEn for the analysis of signals in stability exercises is recommended.

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The role of differential phase contrast in electron microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100108027 ◽

1978 ◽

Vol 36 (1) ◽

pp. 176-177

Author(s):

E.M. Waddell ◽

J.N. Chapman ◽

R.P. Ferrier

Keyword(s):

Phase Contrast ◽

Practical Method ◽

Position Vector ◽

Differential Phase ◽

Pure Phase ◽

Differential Phase Contrast ◽

The Difference ◽

Image Position ◽

First Moment

Dekkers and de Lang (1977) have discussed a practical method of realising differential phase contrast in a STEM. The method involves taking the difference signal from two semi-circular detectors placed symmetrically about the optic axis and subtending the same angle (2α) at the specimen as that of the cone of illumination. Such a system, or an obvious generalisation of it, namely a quadrant detector, has the characteristic of responding to the gradient of the phase of the specimen transmittance. In this paper we shall compare the performance of this type of system with that of a first moment detector (Waddell et al.1977).For a first moment detector the response function R(k) is of the form R(k) = ck where c is a constant, k is a position vector in the detector plane and the vector nature of R(k)indicates that two signals are produced. This type of system would produce an image signal given bywhere the specimen transmittance is given by a (r) exp (iϕ (r), r is a position vector in object space, ro the position of the probe, ⊛ represents a convolution integral and it has been assumed that we have a coherent probe, with a complex disturbance of the form b(r-ro) exp (iζ (r-ro)). Thus the image signal for a pure phase object imaged in a STEM using a first moment detector is b2 ⊛ ▽ø. Note that this puts no restrictions on the magnitude of the variation of the phase function, but does assume an infinite detector.

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