Search results

1 – 10 of 195
Article
Publication date: 1 July 2003

Donald O. Rudin

A theory of knowledge shows that all four systems of nature are recursive combinatorial‐hamiltonian self‐programmed flow‐wave systems that can be deduced from the usual…

215

Abstract

A theory of knowledge shows that all four systems of nature are recursive combinatorial‐hamiltonian self‐programmed flow‐wave systems that can be deduced from the usual Conservation Law promoted to the Axiom of Science.

Details

Kybernetes, vol. 32 no. 5/6
Type: Research Article
ISSN: 0368-492X

Keywords

Article
Publication date: 28 June 2021

Mustafa Tolga Tolga Yavuz and İbrahim Özkol

This study aims to develop the governing differential equation and to analyze the free vibration of a rotating non-uniform beam having a flexible root and setting angle…

Abstract

Purpose

This study aims to develop the governing differential equation and to analyze the free vibration of a rotating non-uniform beam having a flexible root and setting angle for variations in operating conditions and structural design parameters.

Design/methodology/approach

Hamiltonian principle is used to derive the flapwise bending motion of the structure, and the governing differential equations are solved numerically by using differential quadrature with satisfactory accuracy and computation time.

Findings

The results obtained by using the differential quadrature method (DQM) are compared to results of previous studies in the open literature to show the power of the used method. Important results affecting the dynamics characteristics of a rotating beam are tabulated and illustrated in concerned figures to show the effect of investigated design parameters and operating conditions.

Originality/value

The principal novelty of this paper arises from the application of the DQM to a rotating non-uniform beam with flexible root and deriving new governing differential equation including various parameters such as rotary inertia, setting angle, taper ratios, root flexibility, hub radius and rotational speed. Also, the application of the used numerical method is expressed clearly step by step with the algorithm scheme.

Details

Aircraft Engineering and Aerospace Technology, vol. 93 no. 5
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 4 July 2016

Panxing Huang, Changzhu Wei, Yuanbei Gu and Naigang Cui

The purpose of this paper is to propose a hybrid optimization approach with high level of solving precision and efficiency for endo-atmospheric ascent trajectory planning…

Abstract

Purpose

The purpose of this paper is to propose a hybrid optimization approach with high level of solving precision and efficiency for endo-atmospheric ascent trajectory planning of launch vehicles.

Design/methodology/approach

Based on the indirect method of optimal control problems, the optimal endo-atmospheric ascent problem with path constraints and final condition constraints is transformed into a Hamiltonian two point boundary value problem (TPBVP). An advanced Gauss pseudo-spectral method is applied to change the Hamiltonian TPBVP into a system of nonlinear algebraic equations, which is solved by a modified Newton method. To guarantee the convergence of the solution, analytical initial guess technology and homotopy technology are also introduced. At last, simulation tests are made.

Findings

The hybrid approach for optimal endo-atmospheric ascent trajectory planning has both fast convergence rate and high solution precision. The simulation results indicate that not only the proposed method is feasible but also it is better than the indirect method, which is a most popular approach for solving the optimal endo-atmospheric ascent problem. Given the same degree of solution accuracy, the new method consumes quite less time on the CPU than that of the indirect method.

Practical implications

The new optimization approach has high level of both solution accuracy and efficiency. It can be used in rapid trajectory designing, on-line trajectory planning and closed-loop guidance of launch vehicles. Also, the proposed Gauss pseudo-spectral method in this paper is a new and efficient method for solving general TPBVPs.

Originality/value

The paper provides a new hybrid optimization method for rapid endo-atmospheric ascent trajectory planning of launch vehicles.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 88 no. 4
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 1 June 1994

P.R. Masani

Presents the scientific methodology from the enlarged cybernetical perspective that recognizes the anisotropy of time, the probabilistic character of natural laws, and the…

Abstract

Presents the scientific methodology from the enlarged cybernetical perspective that recognizes the anisotropy of time, the probabilistic character of natural laws, and the entry that the incomplete determinism in Nature opens to the occurrence of innovation, growth, organization, teleology communication, control, contest and freedom. The new tier to the methodological edifice that cybernetics provides stands on the earlier tiers, which go back to the Ionians (c. 500 BC). However, the new insights reveal flaws in the earlier tiers, and their removal strengthens the entire edifice. The new concepts of teleological activity and contest allow the clear demarcation of the military sciences as those whose subject matter is teleological activity involving contest. The paramount question “what ought to be done”, outside the empirical realm, is embraced by the scientific methodology. It also embraces the cognitive sciences that ask how the human mind is able to discover, and how the sequence of discoveries might converge to a true description of reality.

Details

Kybernetes, vol. 23 no. 4
Type: Research Article
ISSN: 0368-492X

Keywords

Article
Publication date: 3 June 2021

Somayeh Najafi-Ghobadi, Jafar Bagherinejad and Ata Allah Taleizadeh

The effect of customers’ forward-looking behavior on firms’ profit has been highlighted by many researchers and practitioners. This study aims to develop a mathematical…

Abstract

Purpose

The effect of customers’ forward-looking behavior on firms’ profit has been highlighted by many researchers and practitioners. This study aims to develop a mathematical model for new generation products to analyze the optimal pricing and advertising policies in the presence of homogeneous forward-looking customers. A firm that produces and sells a new generation product was considered. This firm aimed to determine the optimal pricing and advertising expenditure by maximizing the total profit.

Design/methodology/approach

The demand was presented as a diffusion model inspired by the Bass diffusion model. This paper used Pontryagin’s maximum principle to analyze the proposed model. The presented model was implemented in some numerical examples by proposing a heuristic solution method. Numerical examples confirmed the theoretical results.

Findings

This paper found a threshold on the optimal advertising policy depends on customers’ forward-looking behavior, advertising coefficient (both direct and word-of-mouth advertising) and discount rate. The funding showed that the optimal pricing path of the first generation was monotonically decreasing or increasing and, then, decreasing. Results revealed that, by increasing the customers’ forward-looking behavior, the firm should reduce the price and advertising expenditure. Also, the price was shown to be negatively affected by the discount rate and word-of-mouth advertising. The profitability will improve if the firm spends more budget on advertising by increasing the discount rate and advertising effectiveness. Further, when the word-of-mouth advertising effect is high, the firm should increase the advertising expenditure first and, then, decrease it.

Originality/value

Nowadays, forward-looking customers’ anticipation for releasing a new generation can harm the firms’ profit. In this regard, this research analyzed optimal pricing and advertising policies for a new generation product in a market populated by homogeneous forward-looking customers. To the best of the knowledge, this is the first study that investigated these two marketing policies jointly in the presence of forward-looking customers.

Article
Publication date: 1 March 1996

Ayech Benjeddou and Mohamed Ali Hamdi

Presents a new B‐spline finite element for the dynamic analysis of unsymmetrical sandwich shells of revolution. The formulation takes account of the membrane and bending…

Abstract

Presents a new B‐spline finite element for the dynamic analysis of unsymmetrical sandwich shells of revolution. The formulation takes account of the membrane and bending effects in isotropic or orthotropic elastic facings, and membrane, bending and transverse shearing effects in an isotropic or othotropic elastic core. Both geometry and local displacements are interpolated by a set of B‐spline functions. The main aspects added by the sandwich structure of the element are the transverse shearing and membrane‐bending coupling effects in the core. These are well represented by a set of new variables which are the mean end relative in‐plane displacements of the facing middle surfaces. Together with the transverse displacement, these variables constitute the degrees of freedom (dofs) of this new B‐spline sandwich element. The finite elements are grouped into super‐elements with C1 continuity to obtain the whole finite element model. For each super‐element a total of five dofs per node is then obtained except for its end nodes where the derivatives of these dofs with respect to the meridional co‐ordinate are added. This choice reduces to a minimum the total number of dofs in comparison to existing sandwich elements. Evaluates the efficiency and accuracy of the proposed element through several benchmark examples. Compares the results with the analytical and numerical solutions found in the literature. A very satisfactory behaviour of the element was observed in all test cases.

Details

Engineering Computations, vol. 13 no. 2/3/4
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 22 May 2007

Yuan Ren, Pingyuan Cui and Enjie Luan

This paper aims to investigate, a new optimization algorithm for complex orbit transfer missions with low‐thrust propulsion system, which minimizes the drawbacks of…

Abstract

Purpose

This paper aims to investigate, a new optimization algorithm for complex orbit transfer missions with low‐thrust propulsion system, which minimizes the drawbacks of traditional optimization methods, such as bad convergence, difficulty of initial guesses and local optimality.

Design/methodology/approach

First, the trajectory optimization problem comes down to a nonlinear constraint parameter optimization by using the concept of traditional hybrid method. Then, one utilizes genetic algorithm (GA) to solve this parameter optimization problem after treating the constraints with the simulated annealing (SA) and random penalty function. Finally, one makes use of localized optimization to improve the precision of the final solutions.

Findings

This algorithm not only keeps the advantages of traditional hybrid method such as high precision and smooth solutions, but also inherits the merits of GA which could avoid initial guess work and obtain a globally optimal solution.

Research limitations/implications

Further, research is required to reduce the computational complexity when the transfer trajectory is very complex and/or has many adjustable variables.

Practical implications

By using this method, the globally optimal solutions of some complex missions, which could not be obtained by traditional method, could be found.

Originality/value

This method combines the GA with traditional hybrid method, and utilizes SA and random penalty functions to treat with constraints, and then gives out a super convergence way to find the globally optimal low‐thrust transfer orbit.

Details

Aircraft Engineering and Aerospace Technology, vol. 79 no. 3
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 21 March 2008

Hemant K. Singh, Prashant M. Pawar, Ranjan Ganguli and Sung Nam Jung

This study aims to investigate the effects of mass and stiffness imbalance in a tail rotor induced by damage in forward flight.

Abstract

Purpose

This study aims to investigate the effects of mass and stiffness imbalance in a tail rotor induced by damage in forward flight.

Design/methodology/approach

An aeroelastic analysis based on finite element in space and time and capable of modeling dissimilar blades is carried out to study the effect of damage occurring in one, two, and three blades in a four‐bladed tail rotor system in forward flight. The effect of damage growth on vibratory hub loads and blade responses is studied using a comprehensive aeroelastic code.

Findings

The diagnostic chart which is the summary of damage analysis of tail rotor shows that the root hub vibration spectrum gives enough indication to predict damage growth in the tail rotor blade. Hence, this can be useful towards development of health monitoring system for tail rotor blades.

Originality/value

The proposed analysis helps in understanding the basic physics behind the damaged tail rotor and also gives qualitative assessment of damaged tail rotor where obtaining the flight test data with damaged tail rotor is difficult.

Details

Aircraft Engineering and Aerospace Technology, vol. 80 no. 2
Type: Research Article
ISSN: 0002-2667

Keywords

Article
Publication date: 2 January 2018

Alexander Zemliak

This paper aims to propose a new approach on the problem of circuit optimisation by using the generalised optimisation methodology presented earlier. This approach is…

Abstract

Purpose

This paper aims to propose a new approach on the problem of circuit optimisation by using the generalised optimisation methodology presented earlier. This approach is focused on the application of the maximum principle of Pontryagin for searching the best structure of a control vector providing the minimum central processing unit (CPU) time.

Design/methodology/approach

The process of circuit optimisation is defined mathematically as a controllable dynamical system with a control vector that changes the internal structure of the equations of the optimisation procedure. In this case, a well-known maximum principle of Pontryagin is the best theoretical approach for finding of the optimum structure of control vector. A practical approach for the realisation of the maximum principle is based on the analysis of the behaviour of a Hamiltonian for various strategies of optimisation and provides the possibility to find the optimum points of switching for the control vector.

Findings

It is shown that in spite of the fact that the maximum principle is not a sufficient condition for obtaining the global minimum for the non-linear problem, the decision can be obtained in the form of local minima. These local minima provide rather a low value of the CPU time. Numerical results were obtained for both a two-dimensional case and an N-dimensional case.

Originality/value

The possibility of the use of the maximum principle of Pontryagin to a problem of circuit optimisation is analysed systematically for the first time. The important result is the theoretical justification of formerly discovered effect of acceleration of the process of circuit optimisation.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 1
Type: Research Article
ISSN: 0332-1649

Keywords

1 – 10 of 195