THE aim of this paper is to provide a survey of some of the principal theoretical considerations affecting the design of aircraft undercarriages.
THE purpose of this article is to describe a useful variable velocity‐ratio unit suitable for inclusion in flying‐control circuits of aeroplanes, and to provide sufficient of a…
Abstract
THE purpose of this article is to describe a useful variable velocity‐ratio unit suitable for inclusion in flying‐control circuits of aeroplanes, and to provide sufficient of a mathematical analysis to assist designers in the accurate production of such a device. Worked examples are included to illustrate the procedure, and draughtsmen should find these helpful and preferable to a trial and error method of layout on the drawing board.
THE bearing described in this article may help to solve many problems peculiar to aircraft design, where deflections of large orders are experienced between one location and…
Abstract
THE bearing described in this article may help to solve many problems peculiar to aircraft design, where deflections of large orders are experienced between one location and another.
IN a previous article (Ref. 1) the present author outlined some fundamental considerations of general practice. In the present paper the intention is, in effect, to take some…
Abstract
IN a previous article (Ref. 1) the present author outlined some fundamental considerations of general practice. In the present paper the intention is, in effect, to take some pages from a designer's notebook and explain in detail the procedure by which the dynamic characteristics of a leg are determined. A description of one of the author's own designs will provide a suitable area of reference, and although certain of the geometrical calculations will apply rather specially to this, the remainder of the working will be quite general in its application. In particular, the orifice calculations—a vitally useful aspect which has not previously been treated in a practical fashion—have been compared with drop‐test results over a range of differing designs and sizes of shock‐absorber and show very good agreement with them; certainly good enough for a close initial approximation, and in the style of leg described here and in other simple fixed orifice designs, sufficiently accurate to allow of dispensing with dynamic tests provided that tyre and oleo relationships do not diverge too far from the conventional.
THE practice of mechanically sealing liquids and gases within machines has shown little tendency to undergo any fundamental change since the earliest days of the art, and apart…
Abstract
THE practice of mechanically sealing liquids and gases within machines has shown little tendency to undergo any fundamental change since the earliest days of the art, and apart from the semi‐sealing properties of the elementary labyrinth in which measurable clearances exist as between a rotating shaft and its housing, some variant of the common ‘soft packing’ is the standard method of providing the closest form of contact sealing. This type of seal seems to have been engendered by the concept that only substances having extreme deformability could provide the closest degree of conformity to a circular shaft, and the type is brought into play in many ways, from the simple kind of soft, semi‐elastic ring which is rammed into a housing and thus becomes, due to its transverse elasticity, to some extent preloaded on to its co‐acting shaft, to the more refined rubber ring with its lip held against the shaft through the medium of an encircling garter‐spring of steel.
C.H. Cumberland and G.S. Bowey
THE passenger seat in civil aircraft is an important piece of equipment. It is important, firstly because it is the one part of the aircraft with which the passenger is in…
Abstract
THE passenger seat in civil aircraft is an important piece of equipment. It is important, firstly because it is the one part of the aircraft with which the passenger is in intimate contact and, secondly, because of the bulk and multiplicity of installation in any aircraft, the aggregate weight constitutes a major portion of equipment weight.
Aristides Matopoulos, Ana Cristina Barros and J.G.A.J. (Jack) van der Vorst
The study aims to define a research agenda for creating resource-efficient supply chains (RESCs) by identifying and analysing their key characteristics as well as future research…
Abstract
Purpose
The study aims to define a research agenda for creating resource-efficient supply chains (RESCs) by identifying and analysing their key characteristics as well as future research opportunities.
Design/methodology/approach
We follow a systematic review method to analyse the literature and to understand RESC, taking a substantive theory approach. Our approach is grounded in a specific domain, the agri-food sector, because it is an intensive user of an extensive range of resources.
Findings
The review shows that works of literature has looked at the use of resources primarily from the environmental impact perspective. There is a need to explore whether or not and how logistics/supply chain decisions will affect the overall configuration of future food supply chains in an era of resource scarcity and depletion and what the trade-offs will be.
Research limitations/implications
The paper proposes an agenda for future research in the area of RESC. The framework proposed along with the key characteristics identified for RESC can be applied to other sectors.
Practical implications
Our research should facilitate further understanding of the implications and trade-offs of supply chain decisions taken on the use of resources by supply chain managers.
Originality/value
The paper explores the interaction between supply chains and natural resources and defines the key characteristics of RESC.
Details
Keywords
Ranjan Kumar Mohanty and Sachin Sharma
This paper aims to develop a new high accuracy numerical method based on off-step non-polynomial spline in tension approximations for the solution of Burgers-Fisher and coupled…
Abstract
Purpose
This paper aims to develop a new high accuracy numerical method based on off-step non-polynomial spline in tension approximations for the solution of Burgers-Fisher and coupled nonlinear Burgers’ equations on a graded mesh. The spline method reported here is third order accurate in space and second order accurate in time. The proposed spline method involves only two off-step points and a central point on a graded mesh. The method is two-level implicit in nature and directly derived from the continuity condition of the first order space derivative of the non-polynomial tension spline function. The linear stability analysis of the proposed method has been examined and it is shown that the proposed two-level method is unconditionally stable for a linear model problem. The method is directly applicable to problems in polar systems. To demonstrate the strength and utility of the proposed method, the authors have solved the generalized Burgers-Huxley equation, generalized Burgers-Fisher equation, coupled Burgers-equations and parabolic equation in polar coordinates. The authors show that the proposed method enables us to obtain the high accurate solution for high Reynolds number.
Design/methodology/approach
In this method, the authors use only two-level in time-direction, and at each time-level, the authors use three grid points for the unknown function u(x,t) and two off-step points for the known variable x in spatial direction. The methodology followed in this paper is the construction of a non-polynomial spline function and using its continuity properties to obtain consistency condition, which is third order accurate on a graded mesh and fourth order accurate on a uniform mesh. From this consistency condition, the authors derive the proposed numerical method. The proposed method, when applied to a linear equation is shown to be unconditionally stable. To assess the validity and accuracy, the method is applied to solve several benchmark problems, and numerical results are provided to demonstrate the usefulness of the proposed method.
Findings
The paper provides a third order numerical scheme on a graded mesh and fourth order spline method on a uniform mesh obtained directly from the consistency condition. In earlier methods, consistency conditions were only second order accurate. This brings an edge over other past methods. Also, the method is directly applicable to physical problems involving singular coefficients. So no modification in the method is required at singular points. This saves CPU time and computational costs.
Research limitations/implications
There are no limitations. Obtaining a high accuracy spline method directly from the consistency condition is a new work. Also being an implicit method, this method is unconditionally stable.
Practical implications
Physical problems with singular and non-singular coefficients are directly solved by this method.
Originality/value
The paper develops a new method based on non-polynomial spline approximations of order two in time and three (four) in space, which is original and has lot of value because many benchmark problems of physical significance are solved in this method.
Details
Keywords
The purpose of this paper is to determine both analytically and numerically the kink solutions to a new one-dimensional, viscoelastic generalization of Burgers’ equation, which…
Abstract
Purpose
The purpose of this paper is to determine both analytically and numerically the kink solutions to a new one-dimensional, viscoelastic generalization of Burgers’ equation, which includes a non-linear constitutive law, and the number of kinks as functions of the non-linearity and relaxation parameters.
Design/methodology/approach
An analytical procedure and two explicit finite difference methods based on first-order accurate approximations to the first-order derivatives are used to determine the single- and double-kink solutions.
Findings
It is shown that only two parameters characterize the solution and that the existence of a shock wave requires that the (semi-positive) relaxation parameter be less than unity and the non-linearity parameter be less than two. It is also shown that negative values of the non-linearity parameter result in kinks with a single inflection point and strain and dissipation rates with a single relative minimum and a single, relative maximum, respectively. For non-linearity parameters between one and two, it is shown that the kink has three inflection points that merge into a single one as this parameter approaches one and that the strain and dissipation rates exhibit relative maxima and minima whose magnitudes decrease and increase as the relaxation and nonlinearity coefficients, respectively, are increased. It is also shown that the viscoelastic generalization of the Burgers equation presented here is related to an ϕ8−scalar field.
Originality/value
A new, one-dimensional, viscoelastic generalization of Burgers’ equation, which includes a non-linear constitutive law and relaxation is proposed, and its kink solutions are determined both analytically and numerically. The equation and its solutions are connected with scalar field theories and may be used to both studies the effects of the non-linearity and relaxation and assess the accuracy of numerical methods for first-order, non-linear partial differential equations.