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1 – 10 of over 172000
Article
Publication date: 1 June 2004

Guzmán Díaz González, Javier Gómez‐Aleixandre Fernández and Pablo Arboleya Arboleya

In the past years, there has been an increasing concern about turn‐to‐turn faults in power transformers, due to the high costs that unexpected outages cause. It is not always…

Abstract

In the past years, there has been an increasing concern about turn‐to‐turn faults in power transformers, due to the high costs that unexpected outages cause. It is not always possible to analyse the transformer behaviour under such faults at rated conditions, since the tests are largely destructive. Therefore, models are of great importance to avoid severe damage to machines. In this paper, a model based on flux rearrangement around the damaged turn is presented. Two roles are assigned simultaneously to the damaged turn – i.e. the turn is seen as damaged but segregated from winding, and virtually undamaged belonging to the winding – and the damaged turn leakage flux is considered to be a coupling flux between the two roles. Thus, complex relations of magnetic couplings between the turn and the rest of the transformer are avoided, resulting in a very fast model, easy to develop further, which has been validated through a comparison with a finite element model.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 23 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 4 July 2016

Hua Li and Wolfgang Rucker

The purpose of this paper is to present an accurate and efficient hybrid method for the calculation of the inductance of a coil and its inductance change due to deformed turns…

Abstract

Purpose

The purpose of this paper is to present an accurate and efficient hybrid method for the calculation of the inductance of a coil and its inductance change due to deformed turns using numerical methods.

Design/methodology/approach

The paper opted for finite element method coupled with analytical method (FCA) to accurately calculate the inductance of a coil, which is used as reference value. An algorithm with a power function is presented to approximate the partial inductance matrix with the purpose of obtaining the percentage change of the inductance due to deformed turns by using the partial element equivalent circuit (PEEC) with an approximated model and an optimization process. The presented method is successfully validated by the numerical results.

Findings

The paper provides a systematic investigation of the inductance of an arbitrary shaped coil and shows how to accurately and efficiently evaluate the inductance change of a coil due to its deformed turns. It suggests that the inductance of a coil can be accurately calculated by using FCA and its percentage change due to deformed turns can be efficiently calculated by using the PEEC_Approximation.

Research limitations/implications

As this research is for the magnetostatics, the skin- and proximity-effects have not been taken into account.

Practical implications

The paper includes implication for the worst-case analysis of the coil’s inductance due to mechanical damage or manufacturing tolerance.

Originality/value

This paper fulfills an identified need to study how the inductance change of a coil can be obtained accurately and efficiently.

Details

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, vol. 35 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 9 February 2024

Ravinder Singh

This paper aims to focus on solving the path optimization problem by modifying the probabilistic roadmap (PRM) technique as it suffers from the selection of the optimal number of…

Abstract

Purpose

This paper aims to focus on solving the path optimization problem by modifying the probabilistic roadmap (PRM) technique as it suffers from the selection of the optimal number of nodes and deploy in free space for reliable trajectory planning.

Design/methodology/approach

Traditional PRM is modified by developing a decision-making strategy for the selection of optimal nodes w.r.t. the complexity of the environment and deploying the optimal number of nodes outside the closed segment. Subsequently, the generated trajectory is made smoother by implementing the modified Bezier curve technique, which selects an optimal number of control points near the sharp turns for the reliable convergence of the trajectory that reduces the sum of the robot’s turning angles.

Findings

The proposed technique is compared with state-of-the-art techniques that show the reduction of computational load by 12.46%, the number of sharp turns by 100%, the number of collisions by 100% and increase the velocity parameter by 19.91%.

Originality/value

The proposed adaptive technique provides a better solution for autonomous navigation of unmanned ground vehicles, transportation, warehouse applications, etc.

Details

Robotic Intelligence and Automation, vol. 44 no. 1
Type: Research Article
ISSN: 2754-6969

Keywords

Article
Publication date: 25 January 2024

Talwinder Singh

The purpose of this paper, an experimental study, is to investigate the optimal machining parameters for turning of nickel-based superalloy Inconel 718 under eco-friendly…

Abstract

Purpose

The purpose of this paper, an experimental study, is to investigate the optimal machining parameters for turning of nickel-based superalloy Inconel 718 under eco-friendly nanofluid minimum quantity lubrication (NMQL) environment to minimize cutting tool flank wear (Vb) and machined surface roughness (Ra).

Design/methodology/approach

The central composite rotatable design approach under response surface methodology (RSM) is adopted to prepare a design of experiments plan for conducting turning experiments.

Findings

The optimum value of input turning parameters: cutting speed (A), feed rate (B) and depth of cut (C) is found as 79.88 m/min, 0.1 mm/rev and 0.2 mm, respectively, with optimal output response parameters: Vb = 138.633 µm and Ra = 0.462 µm at the desirability level of 0.766. Feed rate: B and cutting speed: A2 are the leading model variables affecting Vb, with a percentage contribution rate of 12.06% and 43.69%, respectively, while cutting speed: A and feed rate: B are the significant factors for Ra, having a percentage contribution of 38.25% and 18.03%, respectively. Results of validation experiments confirm that the error between RSM predicted and experimental observed values for Vb and Ra is 3.28% and 3.75%, respectively, which is less than 5%, thus validating that the formed RSM models have a high degree of conformity with the obtained experimental results.

Practical implications

The outcomes of this research can be used as a reference machining database for various metal cutting industries to establish eco-friendly NMQL practices during the turning of superalloy Inconel 718 to enhance cutting tool performance and machined surface integrity.

Originality/value

No study has been communicated till now on the turning of Inconel 718 under NMQL conditions using olive oil blended with multi-walled carbon nanotubes-based nanofluid.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-10-2023-0317/

Details

Industrial Lubrication and Tribology, vol. 76 no. 2
Type: Research Article
ISSN: 0036-8792

Keywords

Article
Publication date: 16 October 2018

Zhong Wei, Guangming Song, Huiyu Sun, Qien Qi, Yuan Gao and Guifang Qiao

This paper aims to study the turning strategies for the bounding quadruped robot with an active spine and explore the significant role of the spine in the turning locomotion.

Abstract

Purpose

This paper aims to study the turning strategies for the bounding quadruped robot with an active spine and explore the significant role of the spine in the turning locomotion.

Design/methodology/approach

Firstly, the bounding gait combining the pitch motion of the spine with the leg motion is presented. In this gait, the spine moves in phase with the front legs. All the joints of the legs and spine are controlled by cosine signals to simplify the control, and the initial position and oscillation amplitude of the joints can be tuned. To verify the effectiveness of the proposed gait, the spine joints are set with different initial positions and oscillation amplitudes, and the initial position and oscillation amplitude of the leg joints are tuned to make the virtual model do the best locomotion in terms of the speed and stability in the simulation. The control signals are also used to control a real robot called Transleg. Then, three different turning strategies are proposed, including driving the left and right legs with different strides, swaying the spine in the yaw direction and combining the above two methods. Finally, these strategies are tested on the real robot.

Findings

The stable bounding locomotion can be achieved using the proposed gait. With the spine motion, the speed of the bounding locomotion is increased; the turning radius is reduced; and the angular velocity is increased.

Originality/value

A simple and flexible planning of the bounding gait and three turning strategies for the bounding quadruped robot are proposed. The effectiveness of the proposed bounding gait, along with the beneficial effect of the spine motion in the yaw direction on the turning locomotion is demonstrated with the computer simulations and robot experiments. This will be instructive for the designing and actuating of the other quadruped robots.

Details

Industrial Robot: An International Journal, vol. 45 no. 5
Type: Research Article
ISSN: 0143-991X

Keywords

Article
Publication date: 1 December 2005

Michael E. Drew, Tony Naughton and Madhu Veeraragavan

In this article we compare the performance of the traditional CAPM with the multi factor model of Fama and French (1996) for equities listed in the Shanghai Stock Exchange. We…

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Abstract

In this article we compare the performance of the traditional CAPM with the multi factor model of Fama and French (1996) for equities listed in the Shanghai Stock Exchange. We also investigate the explanatory power of idiosyncratic volatility and respond to the claim that multi factor model findings can be explained by the turn of the year effect. Our results show that firm size, book to market equity and idiosyncratic volatility are priced risk factors in addition to the theoretically well specified market factor. As far as the turn of the year effect is concerned we reject the claim that the findings are driven by seasonal factors.

Details

Managerial Finance, vol. 31 no. 12
Type: Research Article
ISSN: 0307-4358

Keywords

Article
Publication date: 31 January 2020

Arch G. Woodside, Marylouise Caldwell and Jennifer Rebecca Calhoun

This study defines service breakdowns, service breakdown prevention, and “servicide” as they relate to service-dominant logic. The study reviews relevant relevant literature on…

Abstract

Purpose

This study defines service breakdowns, service breakdown prevention, and “servicide” as they relate to service-dominant logic. The study reviews relevant relevant literature on these three topics. This study categorizes real-life examples into five levels of dramatic turns toward service degradations and breakdowns that range from customer being aware but not mentioning service inadequacy to the service breakdown resulting in death of the customer or service provider. Taking initial steps in developing dramatic turn theory and improving the practice of service breakdown prevention are the major contributions of this study.

Design/methodology/approach

This study is a conceptual contribution that includes a dramatic turn role-playing exercise (at category 4 among five categories of dramatic turns for pedagogical/on-site enacting/practicing and training of service professionals. The study emphasizes and shows how to create and enact role-playing scenarios to increase requisite variety, provide training modules and increase skills/expertise in service enactment contexts.

Findings

Before explicit reviewing of the dramatic-turn performances, some of the participants as actors as well as audience members in role-play dramatic turns were quick to blame the customer behavior as the principal cause for the service breakdown. The study’s exposition stresses prevention of negative dramatic turns follows from experiencing and coaching a wide variety of customer and server interactions – achieving “richness” in enactments.

Research limitations/implications

Research on service breakdown prevention needs to include field experiments on the efficacy of training programs for effective management of dramatic turns.

Practical implications

Training of service workers and service managers in experiencing/participating in dramatic turns is likely to be beneficial in reducing the severe adverse outcomes and unintended consequences of service breakdowns. Prevention, not only service failure recovery, needs to be an explicit focus in hospitality management training and assessment.

Social implications

This study suggests tools and procedures to reduce the instances of the need for service breakdown recoveries.

Originality/value

The study calls attention and contributes a way forward in managing dramatic turns in hospitality service contexts. The study provides a nascent configurational theoretical foundation of dramatic-turn propositions. Given the severity of financial costs and loss of brand/firm reputation following the occurrence of extreme dramatic turns, a research focus on service breakdown prevention is necessary.

Details

International Journal of Contemporary Hospitality Management, vol. 32 no. 2
Type: Research Article
ISSN: 0959-6119

Keywords

Article
Publication date: 1 June 1999

Robert A. Kunkel, Michael C. Ehrhardt and Gregory A. Kuhlemeyer

Outlines previous research on the relationship between dividend policy and stock returns; and uses a linear programme and multi‐index model to form an investment strategy to see…

1537

Abstract

Outlines previous research on the relationship between dividend policy and stock returns; and uses a linear programme and multi‐index model to form an investment strategy to see whether dividend yields increase stock returns. Explains the methodology, tests it on 1965‐1989 US data and presents the results, which suggests that the multi‐index model is superior to the single index market model in terms of explanatory power and volatility; but provides conflicting conclusions on the relevance of dividends to stock returns. Suggests that the negative relationship between dividends and stock returns can be explained by Jensen’s (1986) free cash flow theory and the influence of transaction costs.

Details

Managerial Finance, vol. 25 no. 6
Type: Research Article
ISSN: 0307-4358

Keywords

Article
Publication date: 1 October 2005

David Vander Linden and Jeffrey D. Gramlich

This paper examines the zero‐cost risk reversal as a tool for increasing returns to excess yen while limiting risk. With domestic interest rates near zero, firms holding Japanese…

Abstract

This paper examines the zero‐cost risk reversal as a tool for increasing returns to excess yen while limiting risk. With domestic interest rates near zero, firms holding Japanese yen face little opportunity to deposit cash for meaningful gain unless excess funds are invested in an other currency. The conversion strategy is profitable as long as the value of the yen appreciates less than the interest rate differential between the currencies, taking advantage of an apparent empirical regularity frequently referred to as ‘forward exchange bias.’ A problem arises, however, because dollar‐yen exchange rate fluctuation adds variability to returns stated in yen. This increased risk counters prudent cash management principles such as stability of returns and liquidity. We consider the possi bility that effective use of a zero‐cost currency options collar can substantially limit exchange‐rate risk and improve returns to yen holders. Data from July 1997 through June 2002 show that a one‐year strategy of reinvesting collared monthly Eurodollar returns produced a median annual yen return of 1.76 per cent, more than 8 times the median 0.21 per cent Euroyen return; risk also increases but approximately 98 per cent of returns resulting from this strategy fell between ‐6.05 per cent and +12.58 per cent.

Details

Managerial Finance, vol. 31 no. 10
Type: Research Article
ISSN: 0307-4358

Keywords

Article
Publication date: 1 June 1999

George K. Chacko

Gives an in depth view of the strategies pursued by the world’s leading chief executive officers in an attempt to provide guidance to new chief executives of today. Considers the…

9934

Abstract

Gives an in depth view of the strategies pursued by the world’s leading chief executive officers in an attempt to provide guidance to new chief executives of today. Considers the marketing strategies employed, together with the organizational structures used and looks at the universal concepts that can be applied to any product. Uses anecdotal evidence to formulate a number of theories which can be used to compare your company with the best in the world. Presents initial survival strategies and then looks at ways companies can broaden their boundaries through manipulation and choice. Covers a huge variety of case studies and examples together with a substantial question and answer section.

Details

Asia Pacific Journal of Marketing and Logistics, vol. 11 no. 2/3
Type: Research Article
ISSN: 1355-5855

Keywords

1 – 10 of over 172000