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Article
Publication date: 1 January 1945

J.Q. Holmes and R.C. Holloway

SOME truly remarkable results in high‐speed or “hyper” milling of steel forgings have been attained on a production basis at Eastern Aircraft's Linden, N. J., plant. To date, work…

34

Abstract

SOME truly remarkable results in high‐speed or “hyper” milling of steel forgings have been attained on a production basis at Eastern Aircraft's Linden, N. J., plant. To date, work has been confined to tough 4140 chrome‐molybdenum steel forgings; some annealed and some heat‐treated to 40–41 Rockwell C and 180,000 lb. per sq. in. tensile strength. Milling rates range from about five to nearly IS times those previously attained with conventional cutters run as fast as usual procedure dictated.

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Aircraft Engineering and Aerospace Technology, vol. 17 no. 1
Type: Research Article
ISSN: 0002-2667

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Book part
Publication date: 13 December 2013

Ivan Jeliazkov

For over three decades, vector autoregressions have played a central role in empirical macroeconomics. These models are general, can capture sophisticated dynamic behavior, and…

Abstract

For over three decades, vector autoregressions have played a central role in empirical macroeconomics. These models are general, can capture sophisticated dynamic behavior, and can be extended to include features such as structural instability, time-varying parameters, dynamic factors, threshold-crossing behavior, and discrete outcomes. Building upon growing evidence that the assumption of linearity may be undesirable in modeling certain macroeconomic relationships, this article seeks to add to recent advances in VAR modeling by proposing a nonparametric dynamic model for multivariate time series. In this model, the problems of modeling and estimation are approached from a hierarchical Bayesian perspective. The article considers the issues of identification, estimation, and model comparison, enabling nonparametric VAR (or NPVAR) models to be fit efficiently by Markov chain Monte Carlo (MCMC) algorithms and compared to parametric and semiparametric alternatives by marginal likelihoods and Bayes factors. Among other benefits, the methodology allows for a more careful study of structural instability while guarding against the possibility of unaccounted nonlinearity in otherwise stable economic relationships. Extensions of the proposed nonparametric model to settings with heteroskedasticity and other important modeling features are also considered. The techniques are employed to study the postwar U.S. economy, confirming the presence of distinct volatility regimes and supporting the contention that certain nonlinear relationships in the data can remain undetected by standard models.

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VAR Models in Macroeconomics – New Developments and Applications: Essays in Honor of Christopher A. Sims
Type: Book
ISBN: 978-1-78190-752-8

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Article
Publication date: 9 January 2024

Chunfu Wu, Guorui Ye, Yonghong Zhao, Baowen Ye, Tao Wang, Liangmo Wang and Zeming Zhang

Auxetics metamaterials show high performance in their specific characteristics, while the absolute stiffness and strength are much weaker due to substantial porosity. This paper…

243

Abstract

Purpose

Auxetics metamaterials show high performance in their specific characteristics, while the absolute stiffness and strength are much weaker due to substantial porosity. This paper aims to propose a novel auxetic honeycomb structure manufactured using selective laser melting and study the enhanced mechanical performance when subjected to in-plane compression loading.

Design/methodology/approach

A novel composite structure was designed and fabricated on the basis of an arrowhead auxetic honeycomb and filled with polyurethane foam. The deformation mechanism and mechanical responses of the structure with different structural parameters were investigated experimentally and numerically. With the verified simulation models, the effects of parameters on compression strength and energy absorption characteristics were further discussed through parametric analysis.

Findings

A good agreement was achieved between the experimental and simulation results, showing an evidently enhanced compression strength and energy absorption capacity. The interaction between the auxetic honeycomb and foam reveals to exploit a reinforcement effect on the compression performance. The parametric analysis indicates that the composite with smaller included angel and higher foam density exhibits higher plateau stress and better specific energy absorption, while increasing strut thickness is undesirable for high energy absorption efficiency.

Originality/value

The results of this study served to demonstrate an enhanced mechanical performance for the foam filled auxetic honeycomb, which is expected to be exploited with applications in aerospace, automobile, civil engineering and protective devices. The findings of this study can provide numerical and experimental references for the design of structural parameters.

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Rapid Prototyping Journal, vol. 30 no. 3
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 12 March 2024

Salma Benharref, Vincent Lanfranchi, Daniel Depernet, Tahar Hamiti and Sara Bazhar

The purpose of this paper is to propose a new method that allows to compare the magnetic pressures of different pulse width modulation (PWM) strategies in a fast and efficient way.

24

Abstract

Purpose

The purpose of this paper is to propose a new method that allows to compare the magnetic pressures of different pulse width modulation (PWM) strategies in a fast and efficient way.

Design/methodology/approach

The voltage harmonics are determined using the double Fourier integral. As for current harmonics and waveforms, a new generic model based on the Park transformation and a dq model of the machine was established taking saturation into consideration. The obtained analytical waveforms are then injected into a finite element software to compute magnetic pressures using nodal forces.

Findings

The overall proposed method allows to accelerate the calculations and the comparison of different PWM strategies and operating points as an analytical model is used to generate current waveforms.

Originality/value

While the analytical expressions of voltage harmonics are already provided in the literature for the space vector pulse width modulation, they had to be calculated for the discontinuous pulse width modulation. In this paper, the obtained expressions are provided. For current harmonics, different models based on a linear and a nonlinear model of the machine are presented in the referenced papers; however, these models are not generic and are limited to the second range of harmonics (two times the switching frequency). A new generic model is then established and used in this paper after being validated experimentally. And finally, the direct injection of analytical current waveforms in a finite element software to perform any magnetic computation is very efficient.

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COMPEL - The international journal for computation and mathematics in electrical and electronic engineering , vol. 43 no. 3
Type: Research Article
ISSN: 0332-1649

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Book part
Publication date: 16 September 2022

Amina Mohamed Buallay

This chapter discusses and investigates the sustainability reporting across different sectors. The first section discusses and investigates the relationship between sustainability…

Abstract

This chapter discusses and investigates the sustainability reporting across different sectors. The first section discusses and investigates the relationship between sustainability reporting and primary sector's performance (Agriculture and Food Industries Sector and Energy Sector). The second section discusses and investigates the relationship between sustainability reporting and secondary sector's performance (Manufacturing Sector). The final section discusses and investigates the relationship between sustainability reporting and tertiary sector's performance (Banks and Financial Services Sector, Retail Sector, Telecommunication and Information Technology Sector, and Tourism Sector).

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Book part
Publication date: 7 October 2015

Azizah Ahmad

The strategic management literature emphasizes the concept of business intelligence (BI) as an essential competitive tool. Yet the sustainability of the firms’ competitive…

Abstract

The strategic management literature emphasizes the concept of business intelligence (BI) as an essential competitive tool. Yet the sustainability of the firms’ competitive advantage provided by BI capability is not well researched. To fill this gap, this study attempts to develop a model for successful BI deployment and empirically examines the association between BI deployment and sustainable competitive advantage. Taking the telecommunications industry in Malaysia as a case example, the research particularly focuses on the influencing perceptions held by telecommunications decision makers and executives on factors that impact successful BI deployment. The research further investigates the relationship between successful BI deployment and sustainable competitive advantage of the telecommunications organizations. Another important aim of this study is to determine the effect of moderating factors such as organization culture, business strategy, and use of BI tools on BI deployment and the sustainability of firm’s competitive advantage.

This research uses combination of resource-based theory and diffusion of innovation (DOI) theory to examine BI success and its relationship with firm’s sustainability. The research adopts the positivist paradigm and a two-phase sequential mixed method consisting of qualitative and quantitative approaches are employed. A tentative research model is developed first based on extensive literature review. The chapter presents a qualitative field study to fine tune the initial research model. Findings from the qualitative method are also used to develop measures and instruments for the next phase of quantitative method. The study includes a survey study with sample of business analysts and decision makers in telecommunications firms and is analyzed by partial least square-based structural equation modeling.

The findings reveal that some internal resources of the organizations such as BI governance and the perceptions of BI’s characteristics influence the successful deployment of BI. Organizations that practice good BI governance with strong moral and financial support from upper management have an opportunity to realize the dream of having successful BI initiatives in place. The scope of BI governance includes providing sufficient support and commitment in BI funding and implementation, laying out proper BI infrastructure and staffing and establishing a corporate-wide policy and procedures regarding BI. The perceptions about the characteristics of BI such as its relative advantage, complexity, compatibility, and observability are also significant in ensuring BI success. The most important results of this study indicated that with BI successfully deployed, executives would use the knowledge provided for their necessary actions in sustaining the organizations’ competitive advantage in terms of economics, social, and environmental issues.

This study contributes significantly to the existing literature that will assist future BI researchers especially in achieving sustainable competitive advantage. In particular, the model will help practitioners to consider the resources that they are likely to consider when deploying BI. Finally, the applications of this study can be extended through further adaptation in other industries and various geographic contexts.

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Sustaining Competitive Advantage Via Business Intelligence, Knowledge Management, and System Dynamics
Type: Book
ISBN: 978-1-78441-764-2

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Article
Publication date: 1 April 2004

Georgios I. Zekos

Investigates the differences in protocols between arbitral tribunals and courts, with particular emphasis on US, Greek and English law. Gives examples of each country and its way…

11815

Abstract

Investigates the differences in protocols between arbitral tribunals and courts, with particular emphasis on US, Greek and English law. Gives examples of each country and its way of using the law in specific circumstances, and shows the variations therein. Sums up that arbitration is much the better way to gok as it avoids delays and expenses, plus the vexation/frustration of normal litigation. Concludes that the US and Greek constitutions and common law tradition in England appear to allow involved parties to choose their own judge, who can thus be an arbitrator. Discusses e‐commerce and speculates on this for the future.

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Managerial Law, vol. 46 no. 2/3
Type: Research Article
ISSN: 0309-0558

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Article
Publication date: 8 May 2018

Henda Jabberi and Faouzi Ben Ammar

To improve the voltage quality in AC adjustable high-power-speed-drive applications, the purpose of the paper is to provide a large number of output levels without increasing the…

91

Abstract

Purpose

To improve the voltage quality in AC adjustable high-power-speed-drive applications, the purpose of the paper is to provide a large number of output levels without increasing the number of commutation cells in the three-phase, n-cells flying capacitor voltage source asymmetric Multilevel Inverter (MI). The concept is based on the selection of different ratios between the breakdown voltages of two successive power devices. The new mathematical model is developed under various ratios, allows a thorough investigation of the harmonic distortions, flying capacitor energy storage, flying capacitor voltage balancing controllability and blocking voltage insulated gate bipolar transistor (IGBT) capability.

Design/methodology/approach

The asymmetrical design provides a large number of output levels without increasing the number of commutation cells. The important new analytical expression of capacitors voltage distribution is derived and extended to any ratio between the switch breakdown voltages of two successive power devices.

Findings

The detailed simulation study of the proposed concept has been carried out using MATLAB/Simulink. The power switches control of the three-phase three-cell MI is assured by new phase-shifted-multi-carrier pulse width modulation. The space vector representation is used to show the regular and irregular step output voltage in the complex plan (α,β).

Originality/value

In the paper, the n cells flying capacitor inverter, which typically operates in the (n + 1) levels mode, was extended to (n + 2), (n + 3) … until 2n levels with regular or irregular step output voltage. Consequently, the claimed advantages of the asymmetric MI are to improve power quality by reducing harmonic distortions and to reduce the requirement on capacitive energy storage in the circuit.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 37 no. 3
Type: Research Article
ISSN: 0332-1649

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Available. Content available
Book part
Publication date: 30 July 2018

Abstract

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Marketing Management in Turkey
Type: Book
ISBN: 978-1-78714-558-0

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Book part
Publication date: 20 November 2020

J. Giacon, I. de Brito and H. Yoshizaki

Supplier selection is a complex and strategic activity needed in every organization, involving many stakeholders and different attributes as price, delivery performance, and…

Abstract

Supplier selection is a complex and strategic activity needed in every organization, involving many stakeholders and different attributes as price, delivery performance, and product quality. Globalization, in the last decades, increased the competitiveness between vendors, enhancing the use of decision models to support the best choice based on optimizations and bidding variations due to specific needs. This chapter presents three models of multi-dimensional auctions to improve an international humanitarian NGO process procurement efficiency by reducing procurement costs and the decision-making process time. These models have the advantage to be easily implementable in typically complex environments where there is a large number of categories, suppliers, and other features.

The first proposed model uses combinatorial auctions and is suited for procurement, where suppliers can benefit from cost complementarity. The second one uses volume discount auctions and is suited for volumetric purchases, where discounts for large quantities are common. The third one is a multi-attribute model, which computes the best possible solution considering several criteria and can be used in case of complex purchases that involve various categories and trade-offs and are subject to spot prices.

Several design considerations for this type of auctions are reviewed, as well as the mathematical formulation to determine the best alternative (i.e., winner) that can be solved using simple tools like Microsoft Excel. The models are optimized by a mixed-integer programming, and the multi-attribute one is developed using multi-criteria decision analysis (MCDA). All three models developed in this research showed superior results compared to the baseline, being between 9% and 20% more efficient than a regular supplier selection (singly choosing the lowest price) and improving the bidding compliance.

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