180,353 research outputs found
Seed longevity: analysing post-storage germination data in R to fit the viability equation
No full textFor many decades, seed germination data have been modelled by probit analysis. In particular, it is the basis of the seed viability equation used, in the first instance, to describe the decline in germination of seeds in storage, but then also the rate of the decline, depending on seed moisture content and the temperature of storage. The underlying assumption of a probit model is that the response follows a normal distribution, in this case, loss of the ability to germinate over time. Probit analysis also takes into account the binomial error associated with germination data. Many statistical packages have probit analysis as an option within the generalized linear modelling framework; here, we present code for applying probit analysis in the free software, R. Codes are provided for fitting a single survival curve, for a single seed lot stored in a constant storage environment; for fitting multiple survival curves and evaluating the effect of constraining parameters for the different seed lots; and lastly, to model the moisture relations of seed longevity. The code bases provided could also be used in pollen and fern/bryophyte spore longevity modelling
A note on relative isoclinism classes of compact groups
No full textIn this note we extend [1, Theorem 3.10] to the context of compact groups. The invariance under weak forms of isoclinism will follow by some recent considerations in [2,3]
-th relative nilpotency degree and relative -isoclinism classes
No full textP. Hall introduced the notion of isoclinism between two groups more than 60 years ago. Successively, many authors have extended such a notion in different contexts. The present paper deals with the notion of relative n-isoclinism, given by N. S. Hekster in 1986, and with the notion of n-th relative nilpotency degree, recently introduced in literature
Commuting elements with respect to the operator in infinite groups
No full texthttps://bkms.kms.or.kr/journal/view.html?uid=260
-th relative nilpotency degree and relative -isoclinism classes
No full textP. Hall introduced the notion of isoclinism between two groups more than 60 years ago. Successively, many authors have extended such a notion in different contexts. The present paper deals with the notion of relative n-isoclinism, given by N. S. Hekster in 1986, and with the notion of n-th relative nilpotency degree, recently introduced in literature
Bounds for the relative -th nilpotency degree in compact groups
No full textThe line of investigation of the present paper goes back to a classical work of W. H. Gustafson of the 1973, in which it is described the probability that two randomly chosen group elements commute. In the same work, he gave some bounds for this kind of probability, providing information on the group structure. We have recently obtained some generalizations of his results for finite groups. Here we improve them in the context of the compact groups
On natural frequencies of Levy-type thick porous-cellular plates surrounded by piezoelectric layers
No full textIn this paper, an analytical solution for free vibration of rectangular porous-cellular plates enclosed by piezoelectric layers is presented by using third-order shear deformation plate theory. Using Hamilton’s principle and Maxwell equation, the governing equations of the system are obtained for both closed and open circuit conditions. Due to the coordinate dependency of mechanical properties of porous materials, the governing equations of motion are highly coupled. By using four auxiliary functions, these equations convert into two independent partial differential equations. The decoupled equations are solved analytically by employing Levy-type boundary conditions for the plate. Finally, after validation of the obtained results, the effects of various parameters such as porosity and geometrical dimensions on the natural frequencies of plate are investigated for different electrical and mechanical boundary conditions. It is found that the natural frequencies of the plate decrease as the coefficient of plate porosity increases. Also, the piezoelectric layers cause the natural frequency of the plate to increase in various vibrating modes
An analytical study on the free vibration of moderately thick fluid-infiltrated porous annular sector plates
No full textAn exact analytical approach based on Mindlin plate theory is considered for free vibration analysis of fluid-saturated porous annular sector plates. The interconnected network of pores is saturated by inviscid fluid and the fluid is trapped in the network. The plate’s radial edges are considered to be simply supported and four auxiliary functions are used to evaluate the natural frequencies of porous plates under undrained condition. The mechanical properties of the material are considered to vary through the thickness by expressing shear modulus and density in terms of a simple cosine rule in case of plates with pores free of fluid. The present method is validated by comparing it with the results of other accurate solutions found in the literature. The influence of the coefficient of plate porosity, geometrical parameters as well as the effect of fluid on natural frequency response of porous annular sector plates under various boundary conditions are comprehensively investigated. It is found that the presence of fluid in the interconnected network of pores causes the fundamental natural frequency to increase. The method proposed in this paper may provide useful information for the future assessments of the dynamic response of porous structures when fluid–solid interaction effects are fully taken into account
An investigation over the effect of piezoelectricity and porosity distribution on natural frequencies of porous smart plates
No full textThe eigenvibration characteristics of a smart plate with piezoelectric layers and porous-cellular core are investigated in the present article. The core plate is assumed to be composed of materials that contain pores and the porosities may be distributed according to different mathematical rules. Variational principle is applied in order to derive the continuous system equations on the basis of Mindlin plate theory. A highly efficient analytical modeling for eigenfrequency analysis of the smart plate is presented under the assumption that both Skempton’s pore pressure coefficient and normal elongation through the thickness are negligible. Unlike numerical methods that require huge computational cost, this approach enables us to find the system’s response for rectangular plates with arbitrary dimensions. To examine the validity of the present framework, multiple comparison studies are made between the extracted results and those available in the literature. It is shown that the type of porosity distribution influences strongly on the way that frequency changes. Furthermore, it is found out that it is necessary to consider electrical effects for plates with open circuit condition unlike the other electrical condition
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