Search results

1 – 10 of 606
Content available
Article
Publication date: 3 May 2021

Lakehal Belarbi and Hichem Elhendi

Let (M, g) be a n-dimensional smooth Riemannian manifold. In the present paper, the authors introduce a new class of natural metrics denoted by gf and called gradient…

Abstract

Purpose

Let (M, g) be a n-dimensional smooth Riemannian manifold. In the present paper, the authors introduce a new class of natural metrics denoted by gf and called gradient Sasaki metric on the tangent bundle TM. The authors calculate its Levi-Civita connection and Riemannian curvature tensor. The authors study the geometry of (TM, gf) and several important results are obtained on curvature, scalar and sectional curvatures.

Design/methodology/approach

In this paper the authors introduce a new class of natural metrics called gradient Sasaki metric on tangent bundle.

Findings

The authors calculate its Levi-Civita connection and Riemannian curvature tensor. The authors study the geometry of (TM,gf) and several important results are obtained on curvature scalar and sectional curvatures.

Originality/value

The authors calculate its Levi-Civita connection and Riemannian curvature tensor. The authors study the geometry of (TM,gf) and several important results are obtained on curvature scalar and sectional curvatures.

Details

Arab Journal of Mathematical Sciences, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1319-5166

Keywords

To view the access options for this content please click here
Article
Publication date: 5 May 2015

Garrison Stevens, Kendra Van Buren, Elizabeth Wheeler and Sez Atamturktur

Numerical models are being increasingly relied upon to evaluate wind turbine performance by simulating phenomena that are infeasible to measure experimentally. These…

Abstract

Purpose

Numerical models are being increasingly relied upon to evaluate wind turbine performance by simulating phenomena that are infeasible to measure experimentally. These numerical models, however, require a large number of input parameters that often need to be calibrated against available experiments. Owing to the unavoidable scarcity of experiments and inherent uncertainties in measurements, this calibration process may yield non-unique solutions, i.e. multiple sets of parameters may reproduce the available experiments with similar fidelity. The purpose of this paper is to study the trade-off between fidelity to measurements and the robustness of this fidelity to uncertainty in calibrated input parameters.

Design/methodology/approach

Here, fidelity is defined as the ability of the model to reproduce measurements and robustness is defined as the allowable variation in the input parameters with which the model maintains a predefined level of threshold fidelity. These two vital attributes of model predictiveness are evaluated in the development of a simplified finite element beam model of the CX-100 wind turbine blade.

Findings

Findings of this study show that calibrating the input parameters of a numerical model with the sole objective of improving fidelity to available measurements degrades the robustness of model predictions at both tested and untested settings. A more optimal model may be obtained by calibration methods considering both fidelity and robustness. Multi-criteria Decision Making further confirms the conclusion that the optimal model performance is achieved by maintaining a balance between fidelity and robustness during calibration.

Originality/value

Current methods for model calibration focus solely on fidelity while the authors focus on the trade-off between fidelity and robustness.

Details

Engineering Computations, vol. 32 no. 3
Type: Research Article
ISSN: 0264-4401

Keywords

Content available
Article
Publication date: 5 April 2021

Samuel Ssekajja

The author considers an invariant lightlike submanifold M, whose transversal bundle tr…

Abstract

Purpose

The author considers an invariant lightlike submanifold M, whose transversal bundle tr(TM) is flat, in an indefinite Sasakian manifold M¯(c) of constant φ¯-sectional curvature c. Under some geometric conditions, the author demonstrates that c=1, that is, M¯ is a space of constant curvature 1. Moreover, M and any leaf M of its screen distribution S(TM) are, also, spaces of constant curvature 1.

Design/methodology/approach

The author has employed the techniques developed by K. L. Duggal and A. Bejancu of reference number 7.

Findings

The author has discovered that any totally umbilic invariant ligtlike submanifold, whose transversal bundle is flat, in an indefinite Sasakian space form is, in fact, a space of constant curvature 1 (see Theorem 4.4).

Originality/value

To the best of the author’s findings, at the time of submission of this paper, the results reported are new and interesting as far as lightlike geometry is concerned.

Details

Arab Journal of Mathematical Sciences, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1319-5166

Keywords

To view the access options for this content please click here
Article
Publication date: 23 December 2020

Robert Kuehnen, Maged Youssef and Salah El-Fitiany

The design of buildings for fire events is essential to ensure occupant safety. Supplementary to simple prescriptive methods, performance-based fire design can be applied…

Abstract

Purpose

The design of buildings for fire events is essential to ensure occupant safety. Supplementary to simple prescriptive methods, performance-based fire design can be applied to achieve a greater level of safety and flexibility in design. To make performance-based fire design more accessible, a time-equivalent method can be used to approximate a given natural fire event using a single standard fire with a specific duration. Doing so allows for natural fire events to be linked to the wealth of existing data from the standard fire scenario. The purpose of this paper is to review and assess the application of an existing time-equivalent method in the performance-based design of reinforced concrete (RC) beams.

Design/methodology/approach

The assessment is established by computationally developing the moment-curvature response of RC beam sections during fire exposure. The sectional response due to natural fire and time equivalent fire are compared.

Findings

It is shown that the examined time equivalent method is able to predict the sectional response with suitable accuracy for performance-based design purposes.

Originality/value

The research is the first to provide a comprehensive evaluation of the moment-curvature diagram of RC beams using time-equivalent standard fire scenarios that model realistic fire scenarios.

Details

Journal of Structural Fire Engineering, vol. 12 no. 1
Type: Research Article
ISSN: 2040-2317

Keywords

Content available
Article
Publication date: 6 April 2021

Sudhakar Kumar Chaubey and Uday Chand De

The authors set the goal to find the solution of the Eisenhart problem within the framework of three-dimensional trans-Sasakian manifolds. Also, they prove some results of…

Abstract

Purpose

The authors set the goal to find the solution of the Eisenhart problem within the framework of three-dimensional trans-Sasakian manifolds. Also, they prove some results of the Ricci solitons, η-Ricci solitons and three-dimensional weakly symmetric trans-Sasakian manifolds. Finally, they give a nontrivial example of three-dimensional proper trans-Sasakian manifold.

Design/methodology/approach

The authors have used the tensorial approach to achieve the goal.

Findings

A second-order parallel symmetric tensor on a three-dimensional trans-Sasakian manifold is a constant multiple of the associated Riemannian metric g.

Originality/value

The authors declare that the manuscript is original and it has not been submitted to any other journal for possible publication.

Details

Arab Journal of Mathematical Sciences, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1319-5166

Keywords

Content available
Article
Publication date: 7 May 2021

H. Aruna Kumara, V. Venkatesha and Devaraja Mallesha Naik

Besse first conjectured that the solution of the critical point equation (CPE) must be Einstein. The CPE conjecture on some other types of Riemannian manifolds, for…

Abstract

Purpose

Besse first conjectured that the solution of the critical point equation (CPE) must be Einstein. The CPE conjecture on some other types of Riemannian manifolds, for instance, odd-dimensional Riemannian manifolds has considered by many geometers. Hence, it deserves special attention to consider the CPE on a certain class of almost contact metric manifolds. In this direction, the authors considered CPE on almost f-cosymplectic manifolds.

Design/methodology/approach

The paper opted the tensor calculus on manifolds to find the solution of the CPE.

Findings

In this paper, in particular, the authors obtained that a connected f-cosymplectic manifold satisfying CPE with \lambda=\tilde{f} is Einstein. Next, the authors find that a three dimensional almost f-cosymplectic manifold satisfying the CPE is either Einstein or its scalar curvature vanishes identically if its Ricci tensor is pseudo anti‐commuting.

Originality/value

The paper proved that the CPE conjecture is true for almost f-cosymplectic manifolds.

Details

Arab Journal of Mathematical Sciences, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1319-5166

Keywords

Content available
Article
Publication date: 20 August 2020

Lamia Saeed Alqahtani

In this paper some characterizations for the existence of warped product pointwise semi-slant submanifolds of cosymplectic space forms are obtained. Moreover, a sharp…

Abstract

In this paper some characterizations for the existence of warped product pointwise semi-slant submanifolds of cosymplectic space forms are obtained. Moreover, a sharp estimate for the squared norm of the second fundamental form is investigated, the equality case is also discussed. By the application of derived inequality, we compute an expression for Dirichlet energy of the involved warping function. Finally, we also proved some classifications for these warped product submanifolds in terms of Ricci solitons and Ricci curvature. A non-trivial example of these warped product submanifolds is provided.

Details

Arab Journal of Mathematical Sciences, vol. 27 no. 1
Type: Research Article
ISSN: 1319-5166

Keywords

To view the access options for this content please click here
Article
Publication date: 10 July 2009

W.K. Chow, Min Lin and Diankui Liu

The fire response of structural reinforced concrete columns is usually justified by the reduction in ultimate load bearing capacity. This is due to the decrease in…

Abstract

Purpose

The fire response of structural reinforced concrete columns is usually justified by the reduction in ultimate load bearing capacity. This is due to the decrease in mechanical strength of steel and concrete upon exposure to a fire. In structural design, it is more desirable to consider the action of load directly. The concept of equivalent accidental load due to a fire might give more convenient structural design data. This paper aims to focus on these issues.

Design/methodology/approach

A theoretical analysis for the equivalent accidental load imposed on reinforced concrete columns (axially loaded columns, uniaxially loaded columns and biaxially loaded columns) exposed to four‐side fires is carried out. The test results of previous research are used as examples and for checking computations. After determining its temperature field, the equivalent accidental load due to fire is calculated using simplified methods. The fire resistance period of reinforced concrete columns can also be determined.

Findings

If the response of a structural element to a fire can be converted into an accidental load, it can be combined with other components such as wind load and earthquake action to give a total design load. With this method, the equivalent accidental load due to a fire and fire resistance of reinforced concrete columns at elevated temperature can be derived directly, and the process is very simple. The equivalent accidental load and fire resistance of reinforced concrete columns exposed to fire on one, two or three sides can also be derived by the same method. However, the thermal performance of steel and concrete cannot be considered during the calculation.

Originality/value

A simplified approach of equivalent accidental load due to fire is proposed. Much simpler guides can be drafted in structural fire design.

Details

Structural Survey, vol. 27 no. 3
Type: Research Article
ISSN: 0263-080X

Keywords

Content available
Article
Publication date: 25 August 2020

Siraj Uddin, Ion Mihai and Adela Mihai

Chen (2001) initiated the study of CR-warped product submanifolds in Kaehler manifolds and established a general inequality between an intrinsic invariant (the warping…

Abstract

Chen (2001) initiated the study of CR-warped product submanifolds in Kaehler manifolds and established a general inequality between an intrinsic invariant (the warping function) and an extrinsic invariant (second fundamental form).

In this paper, we establish a relationship for the squared norm of the second fundamental form (an extrinsic invariant) of warped product bi-slant submanifolds of Kenmotsu manifolds in terms of the warping function (an intrinsic invariant) and bi-slant angles. The equality case is also considered. Some applications of derived inequality are given.

Details

Arab Journal of Mathematical Sciences, vol. 27 no. 1
Type: Research Article
ISSN: 1319-5166

Keywords

To view the access options for this content please click here
Article
Publication date: 1 October 1940

O. Nissen

CONSIDERED as a whole, the questions associated with the problem of dynamic strength may be classified as follows:

Abstract

CONSIDERED as a whole, the questions associated with the problem of dynamic strength may be classified as follows:

Details

Aircraft Engineering and Aerospace Technology, vol. 12 no. 10
Type: Research Article
ISSN: 0002-2667

1 – 10 of 606