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Article
Publication date: 22 May 2019

Adrian Magdaş

The purpose of this paper is to study the coupled fixed point problem and the coupled best proximity problem for single-valued and multi-valued contraction type operators…

Abstract

The purpose of this paper is to study the coupled fixed point problem and the coupled best proximity problem for single-valued and multi-valued contraction type operators defined on cyclic representations of the space. The approach is based on fixed point results for appropriate operators generated by the initial problems.

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Article
Publication date: 1 August 1995

M.P. Miles, L. Fourment and J.L. Chenot

A finite‐element model for calculating the die temperatureprofile for a hot‐forging operation is presented. The workpieceis modelled as a thermo‐viscoplastic material…

Abstract

A finite‐element model for calculating the die temperature profile for a hot‐forging operation is presented. The workpiece is modelled as a thermo‐viscoplastic material, while the dies are considered undeformable. Heat transfer between the dies and the workpiece is modelled using an iteratively coupled, fixedpoint calculation of the temperature in each domain. Transfer of temperature boundary conditions across contact interfaces is performed for non‐coincident meshes, using a boundary integration point contact analysis. Two industrial‐type examples are presented. In the first example, the effectiveness of the transfer of the temperature boundary conditions for a non steady‐state forging process is evaluated and determined to be satisfactory. Then weakly‐ and strongly‐coupled temperature resolutions are compared. It was found that the strongly‐coupled resolution may be necessary in order to obtain reasonably accurate results. In the second example, the weakly‐coupled resolution is compared to a constant‐temperature die approach for a relatively slow forging process, which shows the influence of the die temperature on the flow of the material.

Details

Engineering Computations, vol. 12 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 9 February 2021

Godwin Amechi Okeke and Daniel Francis

The authors prove the existence and uniqueness of fixed point of mappings satisfying Geraghty-type contractions in the setting of preordered modular G-metric spaces. The…

Abstract

Purpose

The authors prove the existence and uniqueness of fixed point of mappings satisfying Geraghty-type contractions in the setting of preordered modular G-metric spaces. The authors apply the results in solving nonlinear Volterra-Fredholm-type integral equations. The results extend generalize compliment and include several known results as special cases.

Design/methodology/approach

The results of this paper are theoretical and analytical in nature.

Findings

The authors prove the existence and uniqueness of fixed point of mappings satisfying Geraghty-type contractions in the setting of preordered modular G-metric spaces. apply the results in solving nonlinear Volterra-Fredholm-type integral equations. The results extend, generalize, compliment and include several known results as special cases.

Research limitations/implications

The results are theoretical and analytical.

Practical implications

The results were applied to solving nonlinear integral equations.

Social implications

The results has several social applications.

Originality/value

The results of this paper are new.

Details

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

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Book part
Publication date: 7 December 2016

Arch G. Woodside

Chapter 2 describes how behavioral science research methods that management and marketing scholars apply in studying processes involving decisions and organizational…

Abstract

Synopsis

Chapter 2 describes how behavioral science research methods that management and marketing scholars apply in studying processes involving decisions and organizational outcomes relate to three principal research objectives: fulfilling generality of findings, achieving accuracy of process actions and outcomes, and capturing complexity of nuances and conditions. The chapter's unique contribution is in advocating and describing the possibilities of researchers replacing Thorngate's (1976) “postulate of commensurate complexity” — it is impossible for a theory of social behavior to be simultaneously general, accurate, and simple and as a result organizational theorists inevitably have to make tradeoffs in their theory development — with a new postulate of disproportionate achievement. This new postulate proposes the possibilities and advocates the building and testing of useful process models that achieve all three principal research objectives. Rather than assuming the stance that a researcher must make tradeoffs that permit achieving any two, but not all three, principal research objectives as, Weick (1979) clock analogy shows, this chapter advocates embracing a property space (a three-dimensional box rather than a clock) view of research objectives and research methods. Tradeoffs need not be made; having-your-cake-and-eating-it-too is possible. The chapter includes a brief review of principal criticisms that case study researchers often express of surveys of respondents using fixed-point surveys. Likewise, the chapter reviews principal criticisms of case study research studies that researchers who favor the use of fixed-point surveys express.

Details

Case Study Research
Type: Book
ISBN: 978-1-78560-461-4

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Article
Publication date: 1 June 2000

A. Savini

Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic…

Abstract

Gives introductory remarks about chapter 1 of this group of 31 papers, from ISEF 1999 Proceedings, in the methodologies for field analysis, in the electromagnetic community. Observes that computer package implementation theory contributes to clarification. Discusses the areas covered by some of the papers ‐ such as artificial intelligence using fuzzy logic. Includes applications such as permanent magnets and looks at eddy current problems. States the finite element method is currently the most popular method used for field computation. Closes by pointing out the amalgam of topics.

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COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 19 no. 2
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 8 May 2009

Igor O. Golosnoy and Jan K. Sykulski

The purpose of this paper is to access performance of existing computational techniques to model strongly non‐linear coupled thermo‐electric problems.

Abstract

Purpose

The purpose of this paper is to access performance of existing computational techniques to model strongly non‐linear coupled thermo‐electric problems.

Design/methodology/approach

A thermistor is studied as an example of a strongly non‐linear diffusion problem. The temperature field and the current flow in the device are mutually coupled via ohmic heating and very rapid variations of electric conductivity with temperature and applied electric field, which makes the problem an ideal test case for the computational techniques. The finite volume fully coupled and fractional steps (splitting) approaches on a fixed computational grid are compared with a fully coupled front‐fixing method. The algorithms' input parameters are verified by comparison with published experiments.

Findings

It was found that fully coupled methods are more effective for non‐linear diffusion problems. The front fixing provides additional improvements in terms of accuracy and computational cost.

Originality/value

This paper for the first time compares in detail advantages and implementation complications of each method being applied to the coupled thermo‐electric problems. Particular attention is paid to conservation properties of the algorithms and accurate solutions in the transition region with rapid changes in material properties.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 28 no. 3
Type: Research Article
ISSN: 0332-1649

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Article
Publication date: 6 August 2019

Siyun Liu, Wenzeng Zhang and Jie Sun

Underactuated fingers are adapted to generate several grasping modes for different tasks, and coupled fingers and self-adaptive fingers are two important types of them…

Abstract

Purpose

Underactuated fingers are adapted to generate several grasping modes for different tasks, and coupled fingers and self-adaptive fingers are two important types of them. Aiming to expand the application and increase adaptability of robotic hand, this paper aims to propose a novel grasping model, called coupled and indirectly self-adaptive (CISA) grasping model, which is the combination of coupled finger and indirectly self-adaptive finger.

Design/methodology/approach

CISA grasping process includes two stages: first, coupled and then indirectly self-adaptive grasping; thus, it is not only integrated with the good pinching ability of coupled finger but also characterized with the high flexibility of indirectly self-adaptive finger. Furthermore, a CISA hand with linkage-slider, called CISA-LS hand, is designed based on the CISA grasping model, consisting of 1 palm, 5 CISA-LS fingers and 14 degrees of freedom.

Findings

To research the grasping behavior of CISA-LS hand, kinematic analysis, dynamic analysis and force analysis of 2-joint CISA-LS finger are performed. Results of grasping experiments for different objects demonstrate the high reliability and stability of CISA-LS hand.

Originality/value

CISA fingers integrate two grasping modes, coupled grasping and indirectly self-adaptive grasping, into one finger. And a double-linkage-slider mechanism is designed as the switch device.

Details

Industrial Robot: the international journal of robotics research and application, vol. 46 no. 5
Type: Research Article
ISSN: 0143-991X

Keywords

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Article
Publication date: 1 January 1934

AIRCRAFT of the type known under the Registered Trade Mark “Autogiio,” have means for controllably tilting the rotor axis in relation to the body in one or more…

Abstract

AIRCRAFT of the type known under the Registered Trade Mark “Autogiio,” have means for controllably tilting the rotor axis in relation to the body in one or more substantially vertical planes about real or virtual pivot axes, any such pivot axis being located above the centre of gravity of the aircraft, below the point of intersection of the rotor axis with the projection of the line of resultant aerodynamic action of the rotor on a plane containing both the rotor axis and the shortest distance between the rotor axis and the pivot axis, and offset from the rotor axis in the direction of the aerodynamic reaction line. Figs. 2 and 5 show diagrammatically an aircraft having a body b, a rotor comprising blades r, r, connected by horizontal hinges a, a, to a rotor hub having an axis of rotation 0, 0. Lines 0–0, 1–1, 2–2, etc., represent the projections on the plane of the paper of the aerodynamic reaction lines corresponding to successively reduced angles of incidence of the rotor, line 0–0 representing the reaction line for an angle of incidence of 90 deg. corresponding to vertical descent, line 5–5 representing that corresponding to a small angle of incidence corresponding to maximum flight speed. These projection lines intersect at a focal point f1, the height of which above the hinges a, a depends upon the degree of separation thereof, this height being zero when the hinges a, a are coaxial and intersect the axis of rotation. The transverse axis about which the rotor may be tilted is shown at p2 and is disposed below the point f1 and forward of the axis of rotation 0, 0. In the limiting case where the hinges a, a are coaxial p2 may pass through the point of intersection of the hinges with the axis 0–0. Fig. 5 shows how the longitudinal pivot axis p5 for lateral tilting of the rotor is displaced from the axis of rotation 0–0 in the direction of the aerodynamic reaction line, i.e., in the direction of the re‐treating blade. The transverse pivot p2 for longitudinal rotor tilting is located rearwardly of the centre of gravity, the perpendicular from the centre of gravity on the pivot making an angle of the order of 6 deg. with the perpendicular to the longitudinal body axis. Means may also be provided for bodily displacing the rotor longitudinally of the aircraft whereby the attitude of the body to the line of flight may be controlled in the plane of symmetry, independently of the flying speed and of the position of the centre of gravity. In one embodiment, Fig. 6, a pyramid of struts 36 supports a rotor comprising blades 38 secured to a hub 37 by horizontal pivots 39, links 40, and vertical pivots 41. Hub 37 is mounted on an axis member 78, Figs. 9 and 10, pivotally mounted on pyramid 36 by means of a transverse pivot 42 and a longitudinal pivot 43, Fig. 8. Pyramid struts 36 are bolted to an apex member 71 incorporating a fork 72, Fig. 10, carrying transverse pivot 42 on which is rotatably mounted an intermediate member incorporating an offset backward projection constituting the longitudinal pivot 43 and a downward projection 76 which serves to limit rocking of member 74 about the pivot 42 by co‐operation with the sides of a shot 71x formed in apex member 71. Rocking movement of axis member 78 in pivot 43 is limited by integral lugs 80 which embrace the projection 76. Movements of part 74 about pivot 42 and of axis member 78 about pivot 43 are damped by spring‐loaded friction discs 148, 153 respectively, the pressure on which may be varied by adjusting their respective nuts 151, 156. As shown in Fig. 9, an internal expanding rotor brake and rotor starting gear are associated with the axis member 78, the latter gear including a dog clutch permitting over‐running of the rotor with respect to the drive shaft. Means for controlling the rotor tilting movements comprise levers 48, 52 respectively associated with the intermediate member 74 and the axis member 78. Lever 48 is coupled to a bell crank 46, Fig. 6, by a rod 47, and lever 52 is coupled to a lever 50, Fig. 8, on a longitudinal rock shaft 49 by rod 51, bell crank 46 and rock shaft 49 being operated by a conveniently arranged control column 44. Rods 47, 51 are tubular and are connected to their respective levers 48, 52 by resilient connections comprising columns of rubber rings 106, Fig. 9, which bear against abutments 107 fixed in the bore of the rod and against a collar 108 formed on a slidable rod 109 which is connected to the operating lever by a forked shackle 110, in the case of rod 47, and by a shackle 111 and an eyed swivel 112, Fig. 10, in the case of rod 51. Means are provided for imposing an elastic bias on either control: these comprise in the case of the fore‐and‐aft control two lengths 116 of shock absorber elastic, Fig. 11, coupled at one end to a lever 115 on shaft 113 of bell crank 46, and at the other by cables 117 to an adjustable lever 119 working in a quadrant 120. Similarly, shock absorbers 123 are coupled to a lever 122 on rock shaft 49 and are connected by cables 124, Fig. 12, passed round pulleys 126 to a lever 127 mounted on a subsidiary rock shaft 128, the angular position of which is controlled by a ratchet lever 129, Fig. 11. Shackles 118 are adjustable for varying the initial stress in elastics 116 and turnbuckles 125 are placed in the run of cables 124. In addition to control column 44, a rudder bar 55 is provided operating a rudder 54, Fig. 6, and a steerable tail wheel 64, and a lever 62 for adjusting a tail plane 57. All these controls may be locked in any adjusted position, lever 62 by a ratchet 63 and the remainder by means of friction clamps 141, 142, 143 respectively, Figs. 11 and 12. Clamp 141 locks a slotted lever 140 fast on rock shaft 49 to a fixed fuselage member. Similarly clamp 135 co‐operates with a slotted plate 134, linked by rod 133 to a lever, 132, on rock shaft 113. Clamp 143 co‐operates with a slotted plate 142, inserted in the run of a rudder cable 56x.

Details

Aircraft Engineering and Aerospace Technology, vol. 6 no. 1
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 1 June 2006

M. Vázquez, A. Dervieux and B. Koobus

To propose an integrated algorithm for aerodynamic shape optimization of aircraft wings under the effect of aeroelastic deformations at supersonic regime.

Abstract

Purpose

To propose an integrated algorithm for aerodynamic shape optimization of aircraft wings under the effect of aeroelastic deformations at supersonic regime.

Design/methodology/approach

A methodology is proposed in which a high‐fidelity aeroelastic analyser and an aerodynamic optimizer are loosely coupled. The shape optimizer is based on a “CAD‐free” approach and an exact gradient method with a single adjoint state. The global iterative process yields optimal shapes in the at‐rest condition (i.e. with the aeroelastic deformations substracted).

Findings

The methodology was tested under different conditions, taking into account a combined optimization goal: to reduce the sonic boom production, while preserving the aerodynamic performances of flexible wings. The objective function model contains both aerodynamic parameters and an acoustic term based on the sonic boom downwards emission.

Practical implications

This paper proposes a shape optimization methodology developed by researchers but aiming at the final strategic goal of creating tools that can be really integrated in design processes.

Originality/value

The paper presents an original loosely coupled method for the shape optimization of flexible wings in which recent and modern techniques are used at different levels of the global algorithm: the aerodynamic optimizer, the aeroelastic analyser, the shape parametrization and the objective function model.

Details

Engineering Computations, vol. 23 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

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Article
Publication date: 17 June 2021

Lalaina Rakotondrainibe, Grégoire Allaire and Patrick Orval

This paper is devoted to the theoretical and numerical study of a new topological sensitivity concerning the insertion of a small bolt connecting two parts in a mechanical…

Abstract

Purpose

This paper is devoted to the theoretical and numerical study of a new topological sensitivity concerning the insertion of a small bolt connecting two parts in a mechanical structure. First, an idealized model of bolt is proposed which relies on a non-local interaction between the two ends of the bolt (head and threads) and possibly featuring a pre-stressed state. Second, a formula for the topological sensitivity of such an idealized bolt is rigorously derived for a large class of objective functions. Third, numerical tests are performed in 2D and 3D to assess the efficiency of the bolt topological sensitivity in the case of no pre-stress. In particular, the placement of bolts (acting then as springs) is coupled to the further optimization of their location and to the shape and topology of the structure for volume minimization under compliance constraint.

Design/methodology/approach

The methodology relies on the adjoint method and the variational formulation of the linearized elasticity equations in order to establish the topological sensitivity.

Findings

The numerical results prove the influence of the number and locations of the bolts which strongly influence the final optimized design of the structure.

Originality/value

This paper is the first one to study the topology optimization of bolted systems without a fixed prescribed number of bolts.

Details

Engineering Computations, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0264-4401

Keywords

1 – 10 of over 18000