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Article
Publication date: 1 October 2020

Neama Temraz

The present paper analyzed a model consisting of one unit with a warm standby unit where the main unit has three states: up, degraded and down.

Abstract

Purpose

The present paper analyzed a model consisting of one unit with a warm standby unit where the main unit has three states: up, degraded and down.

Design/methodology/approach

The semi-Markov model under the regenerative method is used to construct the mathematical model for the system.

Findings

The effectiveness measures of the system are discussed such as availability, reliability, steady-state availability and mean time to system failure. The life and repair times of the system units are assumed to be discrete follow discrete Weibull distribution. Also, the parameters of the discrete Weibull distribution are assumed to be fuzzy with bell-shaped membership function. An application is introduced to show the results obtained for the system and the profit of the presented model.

Originality/value

Rarely papers in literature treated the topic of the discrete-time semi-Markov process using a regenerative point technique.

Article
Publication date: 27 July 2020

Kimberly Camrass

This paper aims to investigate how futures concepts may further existing regenerative sustainability thinking.

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Abstract

Purpose

This paper aims to investigate how futures concepts may further existing regenerative sustainability thinking.

Design/methodology/approach

This paper reviews existing regenerative fields, including regenerative design, regenerative development and regenerative sustainability as alternatives to conventional sustainability practice. It considers futures concepts that may deepen regenerative thinking and practice to develop a regenerative futures conceptual model.

Findings

This paper demonstrates how regenerative fields and futures studies have the capacity to reciprocally inform one another and builds upon this relationship through the development of a regenerative futures conceptual model.

Originality/value

This paper makes a number of theoretical contributions. First, it demonstrates how regenerative fields and futures thinking may reciprocally inform one another and, subsequently, enrich regenerative practice. Second, by drawing from futures thinking, it questions and ultimately lengthens notions of reality and time from a regenerative perspective. Finally, through the proposal of a regenerative futures conceptual model, it offers an alternative lens to analyse human behaviours and their associated impacts. In this way, it introduces a theoretical model that is focused on deep individual and collective transformation and a starting point for future research and refinement.

Details

foresight, vol. 22 no. 4
Type: Research Article
ISSN: 1463-6689

Keywords

Article
Publication date: 7 August 2017

Jafar Nejad, Alireza Riasi and Ahmad Nourbakhsh

Regenerative flow pump (RFP) is a rotodynamic turbomachine capable of developing high pressure rise at low flow rates. This paper aims to numerically investigate the performance…

Abstract

Purpose

Regenerative flow pump (RFP) is a rotodynamic turbomachine capable of developing high pressure rise at low flow rates. This paper aims to numerically investigate the performance of a regenerative pump considering the modification in blade and casing geometry.

Design/methodology/approach

The radial blade shape was changed to the bucket form and a core is added to flow path. A parametric study was performed to improve the performance of the pump. Thus, the effect of change in blade angle, chord, height, pitch to chord ratio and also inlet port on the performance of RFP was investigated.

Findings

Results showed that the modified blade angle to achieve the maximum efficiency is about 41 degree. Also, the most efficient point occurs close to pitch/chord = 0.4 and by reducing the axial chord, efficiency of the pump increases. It was found that better efficiency will be achieved by increasing the “Arc of admission”, but there are limitations of manufacturing. It was observed that the performance curves shifted towards lower flow coefficients by reducing height of blades.

Originality/value

To improve the characteristics of regenerative pump, the blade shape changed to the bucket form (airfoil blades with identical inlet and outlet angle) and a core is added to flow path. A parametric study has been accomplished to see the influence of some important parameters on the performance of the pump.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 17 June 2019

Jafar Nejadali

Regenerative flow pumps are dynamic machines with the ability to develop high heads at low flow rates. Simplicity, compactness, stable features and low manufacturing costs make…

Abstract

Purpose

Regenerative flow pumps are dynamic machines with the ability to develop high heads at low flow rates. Simplicity, compactness, stable features and low manufacturing costs make them interesting for many applications in industries. The purpose of this study is to present a new method for calculating the flow through regenerative pumps with bucket form blades to predict the performance curves by a cheap and easy-to-use way.

Design/methodology/approach

The analysis was carried out based on the geometric shape of a fluid particle trajectory in a regenerative turbomachine. The fluid particle path was assumed to be a helix wrapped into a torus. Loss models were considered and the results of predictions were compared with computational fluid dynamics (CFD) data.

Findings

The overall trend of performance curves resulted from presented model looked consistent with CFD data. However, there were slight differences in high and low flow coefficients. The results showed that the predicted geometric shape of the flow path with the presented model (a helix wrapped into a torus) was not consistent with CFD results at high flow coefficients. Due to the complexity and turbulence of the fluid flow and errors in the calculation of losses, as well as slip factor, there was a discrepancy between the results of the presented model and numerical simulation, especially in high and low flow coefficients.

Originality/value

The analysis was carried out based on the geometric shape of a fluid particle trajectory in a regenerative turbomachine with bucket form blades. The fluid particle path was assumed to be a helix wrapped into a torus.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 24 May 2022

Kimberly Camrass

This paper aims to analyse both traditional and regenerative fields across four layers, litany, systems, worldviews and myth/metaphor. It aims to provide in-depth insight into the…

Abstract

Purpose

This paper aims to analyse both traditional and regenerative fields across four layers, litany, systems, worldviews and myth/metaphor. It aims to provide in-depth insight into the beliefs, values epistemologies and assumptions that scaffold thinking and practice. As a result of this analysis, future implications for regenerative urban practice are also considered.

Design/methodology/approach

Prevailing sustainability approaches seek to mitigate further harm in urban centres by increasing efficiency and minimising resource consumption and impact. They are primarily underpinned by a reductionist worldview that separates human objectives from those of the natural world. In contrast, regenerative approaches to urban sustainability have emerged out of an ecological worldview and aim to achieve net positive outcomes as a result of co-evolutionary relationships between social and ecological systems. This paper explores both approaches in urban communities through futures thinking tool, causal layered analysis.

Findings

As a result of the causal layered analysis undertaken, this paper provides insights into regenerative thinking and practice in urban settings. These insights cover four main thematic categories: purpose, place, practice and progress. Moving to the deeper layers of worldview and myth metaphor analysis, in particular, has significant implications for ongoing practice, including facilitating processes by which communities can reflect upon, unpack and reconstruct their concepts of future “success”.

Originality/value

Anthropogenic climate change continues to deliver worsening ecological, social and economic impacts globally. Urban centres are particularly central to this crisis given their massive resource consumption and rapid population growth. This paper provides an alternative, deep analysis to consider thinking and practice required for urban regeneration. It reveals the need for a shift in purpose and a deeper understanding of place, illustrating the roles that futures tools may place in this transition.

Details

foresight, vol. 25 no. 4
Type: Research Article
ISSN: 1463-6689

Keywords

Article
Publication date: 3 April 2017

Xiang Li and Ziyou Gao

Regenerative braking is an efficient energy saving technology in urban rail system, in which the recovery energy from braking trains is collected by some equipments and released…

Abstract

Purpose

Regenerative braking is an efficient energy saving technology in urban rail system, in which the recovery energy from braking trains is collected by some equipments and released to accelerating trains when needed. However, the high cost and low lifetime of storage devices prevent the widespread use of this technology. The purpose of this paper is to conduct thorough cost-benefit analysis to facilitate China’s urban rail companies to make decisions on the use of such technology.

Design/methodology/approach

To evaluate the benefit from regenerative energy storage, the authors formulate an improved integrated scheduling and speed control model to calculate the net energy consumption associated with different energy recovery rates and then define the benefit as the amount of energy saving arising from the usage of storage equipments. With the frequent charge/discharge operations on storage equipments, the energy recovery rate generally decreases which lowers the benefit, but the maintenance cost increases. By trading-off benefit and cost, the authors derive the optimal scrapping time, the maximum profit and the profitability condition for storage devices.

Findings

Simulation studies based on the Beijing Metro Yizhuang Line of China are given. The results show that compared with the current timetable and speed profile, the integrated scheduling and speed control approach with energy recovery rate of 0.5 can reduce the net energy consumption by 12.69 per cent; the net energy consumption can be well approximated as a linear function of energy recovery rate; and the maximum profit and the optimal scrapping time on regenerative energy storage devices are both positively related to the electricity price. The allowance proportion and the number of service trains such that busy lines with higher electricity price or allowance proportion have advantages to use the regenerative energy storage devices.

Research limitations/implications

In this work, a linear energy recovery rate and a linear maintenance cost are used in the cost-benefit analysis process. In future research, the more accurate expressions on energy recovery rate and maintenance cost should be considered if more data on recovery rate and maintenance cost can be gathered.

Originality/value

The main values of this paper are to develop the integrated optimization approaches for train scheduling and speed control and, on this basis, make thorough cost-benefit analysis for regenerative energy storage to improve the operations management of urban rail transit.

Details

Chinese Management Studies, vol. 11 no. 1
Type: Research Article
ISSN: 1750-614X

Keywords

Open Access
Article
Publication date: 31 May 2022

Dianne Dredge

The purpose of this paper is to examine the mindset shift, systems change and boundary spanning practices needed to transition to a regenerative approach in tourism. The paper…

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Abstract

Purpose

The purpose of this paper is to examine the mindset shift, systems change and boundary spanning practices needed to transition to a regenerative approach in tourism. The paper seeks to deliver concrete ways to shift thinking and transition to a regenerative paradigm.

Design/methodology/approach

This viewpoint paper defines regenerative tourism, explores its principles and the levers for driving transformational change in tourism. It outlines what a conscious approach to regenerative tourism entails and outlines working principles for regenerative tourism. The paper concludes by identifying five key areas for reflection that seek to challenge established thinking and practice.

Findings

The reinvention of tourism requires work in three key areas: systems change, mindset shift and practice. Three findings are summarised as: (1) Regenerative tourism requires a shift in social-ecological consciousness and depends on our capacity to evolve our thinking from “me” to “we” and to develop compassion, empathy and collaborative action. (2) Scientific management is inconsistent with the transition to regeneration. Tourism must be managed as a complex adaptive system and overcome the challenges of individualism, reductionism, separation and marketisation associated with scientific thinking. (3) Regenerative tourism requires a deeply engaged bottom-up approach that is place-based, community-centred and environment-focused.

Originality/value

This paper shares the reflections, working principles and recommendations of The Tourism CoLab and is based on 30 years of experience as a consultant, policy analyst, educator, researcher, professor and now as founder of two tourism social enterprises. With the luxury of reflection and the distance from higher education that many do not have, the author shares her approach to shifting mindsets and driving transformative change.

Article
Publication date: 3 August 2010

Francis J. Quail, Thomas Scanlon and Matthew Strickland

The purpose of this paper is to present a method of rapid prototyping (RP) used in the development of a regenerative pump impeller. RP technology was used to create complex…

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Abstract

Purpose

The purpose of this paper is to present a method of rapid prototyping (RP) used in the development of a regenerative pump impeller. RP technology was used to create complex impeller blade profiles for testing as part of a regenerative pump optimisation process. Regenerative pumps are the subject of increased interest in industry.

Design/methodology/approach

Ten modified impeller blade profiles, relative to the standard radial configuration, were evaluated with the use of computational fluid dynamics (CFD) and experimental testing. Prototype impellers were needed for experimental validation of the CFD results. The manufacture of the complex blade profiles using conventional milling techniques is a considerable challenge for skilled machinists.

Findings

The complexity of the modified blade profiles would normally necessitate the use of expensive computer numerically controlled machining with five‐axis capability. With an impeller less than 75 mm in diameter with a maximum blade thickness of 1.3 mm, a rapid manufacturing technique enabled production of complex blade profiles that are dimensionally accurate and structurally robust enough for testing.

Research limitations/implications

As more advanced RP machines become available in the study in the coming months, e.g. selective laser sintering, the strength of the parts particularly for higher speed testing will improve and the amount of post processing operations will reduce.

Practical implications

This technique offers the possibility to produce components of increased complexity whilst ensuring quality, strength, performance and speed of manufacture.

Originality/value

The ability to manufacture complex blade profiles that are robust enough for testing, in a rapid and cost effective manner is proving essential in the overall design optimisation process for the regenerative pump.

Details

Rapid Prototyping Journal, vol. 16 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 11 January 2011

Francis Quail, Thomas Scanlon and Matthew Stickland

Regenerative pumps are the subject of increased interest in industry as these pumps are low‐cost, low‐specific speed, compact and able to deliver high heads with stable…

Abstract

Purpose

Regenerative pumps are the subject of increased interest in industry as these pumps are low‐cost, low‐specific speed, compact and able to deliver high heads with stable performance characteristics. However, these pumps have a low efficiency (35‐50 per cent). The complex flow field within the pumps represents a considerable challenge to detailed mathematical modelling. Better understanding of the flow field would result in improvement of the pump efficiency. The purpose of this paper is to consider a numerical and experimental analysis of a regenerative pump to simulate the flow field and math pump performance.

Design/methodology/approach

This paper outlines the use of a commercial computational fluid dynamics (CFD) code to simulate the flow field within the regenerative pump and compare the CFD results with new experimental data. A novel rapid manufacturing process is used to consider the effect of impeller geometry changes on the pump efficiency.

Findings

The CFD results demonstrate that it is possible to represent the helical flow field for the pump which has only been witnessed in experimental flow visualisation until now. The CFD performance results also demonstrate reasonable agreement with the experimental tests.

Research limitations/implications

The design optimisation only considers a number of blade geometry changes. The future work will consider a much broader spectrum of design modifications which have resulted in efficiency improvements in the past.

Practical implications

The ability to use CFD modelling in conjunction with rapid manufacturing techniques has meant that more complex geometry configurations can now be assessed with better understanding of the flow field effects and resulting efficiency.

Originality/value

This paper presents new flow field visualisation and better correlation to the matched performance than the current limited mathematical models. This paper also presents a novel method for rapid manufacturing of the pump impeller.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 21 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

Open Access
Article
Publication date: 12 July 2022

Jenny Cave, Dianne Dredge, Claudia van't Hullenaar, Anna Koens Waddilove, Sarah Lebski, Olivier Mathieu, Marta Mills, Pratishtha Parajuli, Mathias Pecot, Nico Peeters, Carla Ricaurte-Quijano, Charlotte Rohl, Jessica Steele, Birgit Trauer and Bernadette Zanet

The aims of this paper are to share how one cohort of tourism practitioners viewed the transformative change needed within the tourism industry and to explore the implications for…

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Abstract

Purpose

The aims of this paper are to share how one cohort of tourism practitioners viewed the transformative change needed within the tourism industry and to explore the implications for leadership in the future.

Design/methodology/approach

The research design is based on a virtual whiteboard brainstorming activity incorporating both the individual and collective thinking of 20 participants in a global cohort class. Using conversational techniques to elicit cognitive knowledge and felt experience, the methodology generates shared understandings about the opportunities and challenges of implementing regenerative tourism.

Findings

The conversations reported in the findings of this paper provide important insights into the challenges and opportunities faced by tourism professionals as enablers of regenerative tourism. Findings included, first, that participants within the course demonstrated characteristics of transformational leadership including a strong moral positioning, embodied self-awareness, collaboration and collective action. Second, specific points of inertia that impede regenerative tourism are identified including embedded culture, power and organisational structures. Third, professionals are calling for practical tools, new frames of reference, and examples to help communicate regenerative tourism.

Research limitations/implications

This is a viewpoint, not a research paper. Nonetheless, it provides a rich vein of future research in terms of disruptive pedagogy, potentially gendered interest in regenerative tourism, issues of transforming the next generation and power.

Practical implications

Governance, organisational, destination management strategies, planning and policy frameworks, individual issues as well as contradictions within the tourism system were revealed. Transformative change in an uncertain future requires transformational leadership, characterised by moral character and behaviours that trigger empowered responses.

Originality/value

This paper shares insights from a unique global cohort class of tourism professionals wherein the challenges and opportunities for regenerative tourism are identified. The methodology is unusual in that it incorporates both individual and collective thinking through which shared understandings emerge.

Details

Journal of Tourism Futures, vol. 8 no. 3
Type: Research Article
ISSN: 2055-5911

Keywords

1 – 10 of over 1000