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Article
Publication date: 1 October 1963

J.A. Wannenburg

SUMMARY Schlichting's cascade functions are expressed as power series in terms of the blade solidity, which makes it possible to derive analytical expressions for the lift…

39

Abstract

SUMMARY Schlichting's cascade functions are expressed as power series in terms of the blade solidity, which makes it possible to derive analytical expressions for the lift coefficient and velocity distribution of an arbitrary cascade of thin aerofoils for solidities of less than unity under smooth air inlet conditions. It is shown that, within the scope of the assumptions made, the angle of attack for shock‐free inlet conditions must be zero, irrespective of the cascade configuration, and that a symmetrical camber line will then yield the maximum lift coefficient. Expressions for this lift coefficient and for the corresponding velocity distribution are derived in terms of the maximum camber and cascade configuration. The analysis is based on Schlichting's cascade theory, and is intended primarily for application to fan blade design.

Details

Aircraft Engineering and Aerospace Technology, vol. 35 no. 10
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 15 June 2021

Willem Wannenburg, Helen M. Inglis, Johann Wannenburg and Chris Roth

Failure of a critical reinforced concrete beam due to fatigue can have severe safety and production consequences, and preventative repair/replacement of such a beam is expensive…

158

Abstract

Purpose

Failure of a critical reinforced concrete beam due to fatigue can have severe safety and production consequences, and preventative repair/replacement of such a beam is expensive. It would therefore be beneficial if repair/replacement can be done based on an accurately and conservatively predicted remaining useful life (RUL). The purpose of this paper is to develop such a model.

Design/methodology/approach

Condition-based maintenance is a maintenance approach that uses empirical/analytical models and a measurable condition to predict remaining useful life. The P-F curve (condition-life) is a useful tool that can aid in making these decisions. A model to create a P-F curve is developed using rebar fatigue test results (in the form of an S–N curve) and the Palmgren-Miner law of damage accumulation. A Monte Carlo simulation with statistical distributions is employed to provide confidence levels of RUL outputs.

Findings

An example of how the model can successfully be used in practice is shown in this paper, and a sensitivity study is performed leading to conclusions being drawn with regard to damage tolerant design considerations.

Originality/value

If a critical reinforced concrete beam fails due to fatigue can have serious consequences. This paper develops a model to help base repair/replacement decisions based on accurately and conservatively predicted RUL. Financial and safety benefits would be gained if this model would be used in practice.

Details

Journal of Quality in Maintenance Engineering, vol. 28 no. 3
Type: Research Article
ISSN: 1355-2511

Keywords

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Article
Publication date: 2 September 2014

Hung-Che Wu

The purpose of this paper is to identify the dimensions of service quality and examining the interrelationships among behavioral intentions, customer satisfaction, perceived…

6006

Abstract

Purpose

The purpose of this paper is to identify the dimensions of service quality and examining the interrelationships among behavioral intentions, customer satisfaction, perceived value, corporate image and service quality in the gaming industry. A multi-level and hierarchical model is used as a framework to synthesize the effects of customer satisfaction, perceived value, corporate image and service quality on behavioral intentions of customers in the gaming industry.

Design/methodology/approach

The data used in this study were based on a sample of 470 at a newly built casino in Macau. Data were analyzed using exploratory factor analysis and regression analysis.

Findings

The findings support using a multi-level model consisting of three primary dimensions and ten sub-dimensions to conceptualize and measure perceived service quality. Perceived service quality significantly influences perceived value and corporate image, respectively. In addition, perceived value and corporate image are main determinants of customer satisfaction. Also, customer satisfaction and corporate image significantly affect behavioral intentions.

Originality/value

This is the first study synthesizing behavioral intentions, customer satisfaction, perceived value, corporate image and perceived service quality in a Macau casino setting.

Details

Asia Pacific Journal of Marketing and Logistics, vol. 26 no. 4
Type: Research Article
ISSN: 1355-5855

Keywords

Available. Open Access. Open Access
Article
Publication date: 17 September 2024

Nzita Alain Lelo, P. Stephan Heyns and Johann Wannenburg

Steam explosions are a major safety concern in many modern furnaces. The explosions are sometimes caused by water ingress into the furnace from leaks in its high-pressure (HP…

240

Abstract

Purpose

Steam explosions are a major safety concern in many modern furnaces. The explosions are sometimes caused by water ingress into the furnace from leaks in its high-pressure (HP) cooling water system, coming into contact with molten matte. To address such safety issues related to steam explosions, risk based inspection (RBI) is suggested in this paper. RBI is presently one of the best-practice methodologies to provide an inspection schedule and ensure the mechanical integrity of pressure vessels. The application of RBIs on furnace HP cooling systems in this work is performed by incorporating the proportional hazards model (PHM) with the RBI approach; the PHM uses real-time condition data to allow dynamic decision-making on inspection and maintenance planning.

Design/methodology/approach

To accomplish this, a case study is presented that applies an HP cooling system data with moisture and cumulated feed rate as covariates or condition indicators to compute the probability of failure and the consequence of failure (CoF), which is modelled based on the boiling liquid-expanding vapour explosion (BLEVE) theory.

Findings

The benefit of this approach is that the risk assessment introduces real-time condition data in addition to time-based failure information to allow improved dynamic decision-making for inspection and maintenance planning of the HP cooling system. The work presented here comprises the application of the newly proposed methodology in the context of pressure vessels, considering the important challenge of possible explosion accidents due to BLEVE as the CoF calculations.

Research limitations/implications

This paper however aims to optimise the inspection schedule on the HP cooling system, by incorporating PHM into the RBI methodology, as was recently proposed in the literature by Lelo et al. (2022). Moisture and cumulated feed rate are used as covariate. At the end, risk mitigation policy is suggested.

Originality/value

In this paper, the proposed methodology yields a dynamically calculated quantified risk, which emphasised the imperative for mitigating the risk, as well as presents a number of mitigation options, to quantifiably affect such mitigation.

Details

Journal of Quality in Maintenance Engineering, vol. 30 no. 5
Type: Research Article
ISSN: 1355-2511

Keywords

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Article
Publication date: 7 March 2022

Nzita Alain Lelo, P. Stephan Heyns and Johann Wannenburg

Industry decision makers often rely on a risk-based approach to perform inspection and maintenance planning. According to the Risk-Based Inspection and Maintenance Procedure…

165

Abstract

Purpose

Industry decision makers often rely on a risk-based approach to perform inspection and maintenance planning. According to the Risk-Based Inspection and Maintenance Procedure project for the European industry, risk has two main components: probability of failure (PoF) and consequence of failure (CoF). As one of these risk drivers, a more accurate estimation of the PoF will contribute to a more accurate risk assessment. Current methods to estimate the PoF are either time-based or founded on expert judgement. This paper suggests an approach that incorporates the proportional hazards model (PHM), which is a statistical procedure to estimate the risk of failure for a component subject to condition monitoring, into the risk-based inspection (RBI) methodology, so that the PoF estimation is enhanced to optimize inspection policies.

Design/methodology/approach

To achieve the overall goal of this paper, a case study applying the PHM to determine the PoF for the real-time condition data component is discussed. Due to a lack of published data for risk assessment at this stage of the research, the case study considered here uses failure data obtained from the simple but readily available Intelligent Maintenance Systems bearing data, to illustrate the methodology.

Findings

The benefit of incorporating PHM into the RBI approach is that PHM uses real-time condition data, allowing dynamic decision-making on inspection and maintenance planning. An additional advantage of the PHM is that where traditional techniques might not give an accurate estimation of the remaining useful life to plan inspection, the PHM method has the ability to consider the condition as well as the age of the component.

Research limitations/implications

This paper is proposing the development of an approach to incorporate the PHM into an RBI methodology using bearing data to illustrate the methodology. The CoF estimation is not addressed in this paper.

Originality/value

This paper presents the benefits related to the use of PHM as an approach to optimize the PoF estimation, which drives to the optimal risk assessment, in comparison to the time-based approach.

Details

Journal of Quality in Maintenance Engineering, vol. 29 no. 1
Type: Research Article
ISSN: 1355-2511

Keywords

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Article
Publication date: 23 September 2019

Nzita Alain Lelo, P. Stephan Heyns and Johann Wannenburg

The control of an inventory where spare parts demand is infrequent has always been difficult to manage because of the randomness of the demand, as well as the existence of a large…

460

Abstract

Purpose

The control of an inventory where spare parts demand is infrequent has always been difficult to manage because of the randomness of the demand, as well as the existence of a large proportion of zero values in the demand pattern. The purpose of this paper is to propose a just-in-time (JIT) spare parts availability approach by integrating condition monitoring (CM) with spare parts management by means of proportional hazards models (PHM) to eliminate some of the shortcomings of the spare parts demand forecasting methods.

Design/methodology/approach

In order to obtain the event data (lifetime) and CM data (first natural frequency) required to build the PHM for the spares demand forecasting, a series of fatigue tests were conducted on a group of turbomachinery blades that were systematically fatigued on an electrodynamic shaker in the laboratory, through base excitation. The process of data generation in the numerical as well as experimental approaches comprised introducing an initial crack in each of the blades and subjecting the blades to base excitation on the shaker and then propagating the crack. The blade fatigue life was estimated from monitoring the first natural frequency of each blade while the crack was propagating. The numerical investigation was performed using the MSC.MARC/2016 software package.

Findings

After building the PHM using the data obtained during the fatigue tests, a blending of the PHM with economic considerations allowed determining the optimal risk level, which minimizes the cost. The optimal risk point was then used to estimate the JIT spare parts demand and define a component replacement policy. The outcome from the PHM and economical approach allowed proposing development of an integrated forecasting methodology based not only on failure information, but also on condition information.

Research limitations/implications

The research is simplified by not considering all the elements usually forming part of the spare parts management study, such as lead time, stock holding, etc. This is done to focus the attention on component replacement, so that a just-in-time spare parts availability approach can be implemented. Another feature of the work relates to the decision making using PHM. The approach adopted here does not consider the use of the transition probability matrix as addressed by Jardine and Makis (2013). Instead, a simulation method is used to determine the optimal risk point which minimizes the cost.

Originality/value

This paper presents a way to address some existing shortcomings of traditional spare parts demand forecasting methods, by introducing the PHM as a tool to forecast spare parts demand, not considering the previous demand as is the case for most of the traditional spare parts forecasting methods, but the condition of the parts in operation. In this paper, the blade bending first mode natural frequency is used as the covariate in the PHM in a laboratory experiment. The choice of natural frequency as covariate is justified by its relationship with structural stiffness (and hence damage), as well as being a global parameter that could be measured anywhere on the blade without affecting the results.

Details

Journal of Quality in Maintenance Engineering, vol. 26 no. 1
Type: Research Article
ISSN: 1355-2511

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Article
Publication date: 1 December 1960

J.J. Wannenburg

A method is presented by means of which the lift coefficient of an arbitrary aerofoil in a two‐dimensional cascade is obtained explicitly in terms of a number of cascade…

49

Abstract

A method is presented by means of which the lift coefficient of an arbitrary aerofoil in a two‐dimensional cascade is obtained explicitly in terms of a number of cascade functions, whose values depend only on the cascade geometry. The method is based on Schlichting's theory, whereby the profile is substituted by a continuous row of singularities arranged along the blade chord, and it consists in a simplification of the usual procedure of satisfying the boundary conditions. The simplified method greatly reduces the amount of work involved, and an analysis of a number of representative aerofoils indicated a good agreement with the values obtained by the more exact procedure. The values of the special cascade functions required for the application of the method are tabulated over a wide range of stagger angles and pitch/chord ratios.

Details

Aircraft Engineering and Aerospace Technology, vol. 32 no. 12
Type: Research Article
ISSN: 0002-2667

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Article
Publication date: 11 July 2016

Sheila Namagembe, R Sridharan and Suzanne Ryan

The purpose of this paper is to advance enviropreneurial orientation (EO) as a new internal driver for green supply chain practice adoption. Because manufacturing supply chains…

1237

Abstract

Purpose

The purpose of this paper is to advance enviropreneurial orientation (EO) as a new internal driver for green supply chain practice adoption. Because manufacturing supply chains are major contributors to environmental pollution, green practice adoption is a means of reducing environmental pollution. However, why owner/managers adopt green practices remains uncertain. The concept of EO is a potential and important motivation for adoption of green supply chain practices that has yet to be explored. The study investigates the relationship between EO and green supply chain practice adoption.

Design/methodology/approach

Cross-sectional survey design was employed to collect data from owners/managers of SME manufacturing firms in Uganda. The structural equation modelling was used to analyse results on the influence of each of nine EO on green supply chain practice adoption and the influence of EO dimensions on green supply chain practice adoption.

Findings

Findings show that EO positively influences green supply chain practice adoption. All but two of nine dimensions of EO were significant predictors of green supply chain practice adoption. Competitive aggressiveness and perceived pressure from environmental regulations were not significant predictors for green supply chain practice adoption.

Research limitations/implications

The study was cross-sectional. A longitudinal survey was more appropriate because of the presence of a behavioural variable green supply chain practice adoption. Further a comparative study is required because of the existence of differences in classifications of SMEs in both the developing and developed countries.

Originality/value

The research contributes to further scholarly understanding of green practice adoption in SMEs through offering a new construct, EO, and its role in influencing green supply chain practice adoption. The authors develop EO as a construct, a concept that has not been developed for more than two decades.

Details

World Journal of Science, Technology and Sustainable Development, vol. 13 no. 3
Type: Research Article
ISSN: 2042-5945

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Article
Publication date: 29 April 2024

Puneett Bhatnagr, Anupama Rajesh and Richa Misra

This study aims to develop a customer-centric model based on an online customer experience (OCE) construct relating to e-loyalty, e-trust and e-satisfaction, resulting in improved…

635

Abstract

Purpose

This study aims to develop a customer-centric model based on an online customer experience (OCE) construct relating to e-loyalty, e-trust and e-satisfaction, resulting in improved Net Promoter Score for Indian digital banks.

Design/methodology/approach

This study used an online survey method to gather data from a sample of 485 digital banking users, from which usable questionnaires were obtained. The obtained data were subjected to thorough analysis using partial least squares structural equation modelling to further investigate the research hypotheses.

Findings

The main factors determining digital banks’ OCE were perceived customer centrality, perceived value and perceived usability. Additionally, relevant constructs were evaluated using importance-performance map analysis.

Research limitations/implications

This study used convenience sampling for the urban population using digital banking services; therefore, the outcome may be generalized to a limited extent. To further strengthen digital banking, it would be valuable to imitate studies in other countries.

Originality/value

There is a lack of research on digital banking and OCE in India; thus, this study will help rectify this issue while providing valuable insights. This study differs from others in that it examines the connections between online customer satisfaction, loyalty, trust and the bottom line of financial institutions using these factors as dependent variables instead of traditional measures.

Details

International Journal of Quality and Service Sciences, vol. 16 no. 2
Type: Research Article
ISSN: 1756-669X

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Article
Publication date: 14 July 2020

Mohammadreza Salehi, Nader Pourmahmoud, Amir Hassanzadeh, S. Hoseinzadeh and P.S. Heyns

Using the computational fluid dynamics (CFD) technique, this paper aims to investigate the influence of key parameters such as throat diameter; the suction ratio on the flow field…

216

Abstract

Purpose

Using the computational fluid dynamics (CFD) technique, this paper aims to investigate the influence of key parameters such as throat diameter; the suction ratio on the flow field behaviors such as Mach number; pressure; and temperature.

Design/methodology/approach

To investigate the effect of throat diameter, it is simulated for 4, 6, 8 and 10 mm as throat diameters. The governing equations have been solved by standard code of Fluent Software together with a compressible 2 D symmetric and turbulence model with the standard k–ε model. First, the influence of the throat diameter is investigated by keeping the inlet mass flow constant.

Findings

The results show that a place of shock wave creation is changed by changing the throat diameter. The obtained results illustrate that the maximum amount of Mach number is dependent on the throat diameter. It is obtained from the results that for smaller throats higher Mach numbers can be obtained. Therefore, for mixing purposes smaller throats and for exhausting bigger throats seems to be appropriate.

Originality/value

The obtained numerical results are compared to the existing experimental ones which show good agreement.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

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