A review is presented of the extrapolation methods for accelerating the convergence of Sommerfeld-type integrals (i.e. semi-infinite range integrals with Bessel function kernels), which arise in problems involving antennas or scatterers embedded in planar multilayered media. Attention is limited to partition-extrapolation procedures in which the Sommerfeld integral is evaluated as a sum of a series of partial integrals over finite subintervals and is accelerated by an extrapolation method applied over the real-axis tail segment (/spl alpha/,/spl infin/) of the integration path, where /spl alpha/>0 is selected to ensure that the integrand is well behaved. An analytical form of the asymptotic truncation error (or the remainder), which characterizes the convergence properties of the sequence of partial sums and serves as a basis for some of the most efficient extrapolation methods, is derived. Several extrapolation algorithms deemed to be the most suitable for the Sommerfeld integrals are described and their performance is compared. It is demonstrated that the performance of these methods is strongly affected by the horizontal displacement of the source and field points /spl rho/ and by the choice of the subinterval break points. Furthermore, it is found that some well-known extrapolation techniques may fail for a number of values of /spl rho/ and ways to remedy this are suggested. Finally, the most effective extrapolation methods for accelerating Sommerfeld integral tails are recommended.

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Extrapolation methods for Sommerfeld integral tails

Purpose – Lean business ideology has been one of the recent dominant research areas in operations management. However, there is a dearth of research focusing on Lean in small- and medium-sized enterprises (SMEs). The purpose of this paper is to fill this gap by systematically reviewing the literature in relation to the implementation of Lean in SMEs. Design/methodology/approach – Tranfield et al.’s (2003) systematic review methodology was employed covering three stages: planning, conducting and reporting/dissemination. Findings – A descriptive analysis of the papers reviewed is provided. From the thematic analysis of the literature four main themes are identified: the scope/type of Lean being adopted by SMEs, how Lean is used in SMEs, the impact of Lean implementation on SMEs and the critical success factors for Lean implementation in SMEs. Key inhibitors and enablers related to firm size when implementing Lean are also identified in the concluding discussion. Research limitations/implications – Nine recommendations for future research are developed associated with Lean implementation in SMEs. Practical implications – The authors suggest SMEs to integrate organisational factors such as employee empowerment and the development of a supportive strategy into their Lean implementation plans. A preliminary “Staircase Road Map” to guide SMEs in implementing Lean is also developed. Originality/value – This paper goes beyond previous literature reviews of Lean by systematically and critically evaluating key themes of Lean implementation within an SME environment. It not only provides a road map for SME owners/managers who intend to implement Lean, but also provides the academic community with an agenda for future research.

/pdf/lean-implementation-within-smes-a-literature-review-2lnhnig8mt.pdf

Lean implementation within SMEs: a literature review

Methods of Experimental Physics.

Bi-objective optimization of a multi-product multi-period three-echelon supply chain problem under uncertain environments

A simple parametric form for the static local field factor G(q) which appears in the dielectric screening theory of an electron gas is proposed. A very accurate fit of Ceperley–Alder data of electron correlation energy in the entire density range using Levin–Weniger interpolant is obtained and used for the calculation of G(q). Both the short- and long- wavelength limits of G(q) are satis ed exactly in the present formulation which ensures fulfilment of a number of other legitimate criteria and produces some interesting results. A comparative study of the various static local eld factors derived so far vis-a-vis the present work is made. Even within the approximations of a static self-consistent theory, reasonable prediction regarding Wigner Crystallization is obtained in the present work.

Static Local Field Factor for Dielectric Screening Function of Electron Gas at Metallic and Lower Densities

A review of the past research studies on the causes of bullwhip effect is presented in this paper. This paper is an effective study from the point of view that it presents a detailed classified study of the overall research studies on the effect of both the operational and the behavioral factors on bullwhip effect. A total of 19 causes of bullwhip effect have been shown here. We have identified the various gaps of research in the past research studies. An overview of the steps taken by the industries in order to tackle the bullwhip effect is also provided at the end of this paper. Directions for further research studies are also provided in each subsection of this study and at the end of this paper.

A review of the causes of bullwhip effect in a supply chain

Solving a tri-objective supply chain problem with modified NSGA-II algorithm

This paper focuses on the facility location problem with two conflicting objectives. We observe that minimization of the total cost of a particular echelon may lead to the increase in the total cost of a supply chain as a whole. Thus, these conflicting objectives are required to be met together from a supply chain perspective. We have solved the problem formulated in mixed nonlinear programming by a multi-objective evolutionary algorithm (MOEA) known as non-dominated sorting algorithm, or NSGA II in short. Numerical example is provided to show the effect of the algorithm on the solution.

Solving conflicting bi-objective facility location problem by NSGA II evolutionary algorithm

Solving multi-objective parallel machine scheduling problem by a modified NSGA-II

This paper minimizes the value of total cost and bullwhip effect in a supply chain. The objectives have been achieved through developing a new multi-objective formulation for minimizing the total cost and minimizing the bullwhip effect of a two-echelon serial supply chain. A new crossover algorithm for a fuzzy variable and a new mutation algorithm have also been proposed while applying Non-dominated Sorting Genetic Algorithm-II (NSGA-II) to the proposed problem. The formulated problem has been simulated by Matlab software and the results of the modified NSGA-II have been compared with those of original NSGA-II. It is found from the results that the modified NSGA-II algorithm performs better than the original NSGA-II algorithm since the minimum values for both total cost and the bullwhip effect are obtained in case of the modified NSGA-II. The formulated bi-objective problem is new to the research community. The minimization of bullwhip effect has never been considered in a multi-objective optimization before. Besides crossover operator applied to the fuzzy variable and the mutation operator are newly introduced operators.

Ranjan Bhattacharya

Papers

A review of the causes of bullwhip effect in a supply chain

Solving a tri-objective supply chain problem with modified NSGA-II algorithm

Solving conflicting bi-objective facility location problem by NSGA II evolutionary algorithm

Solving multi-objective parallel machine scheduling problem by a modified NSGA-II

Applying modified NSGA-II for bi-objective supply chain problem