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Article
Publication date: 7 November 2016

Abderrahmane Baïri, David San Martin, Iken Baïri, Kemi Adeyeye, Kaiming She, Ali Hocine, Nacim Alilat, Cyril Lamriben, Jean-Gabriel Bauzin, Bruno Chanetz and Najib Laraqi

The purpose of this paper is to examine the details of the air mass flow and aerodynamical phenomena across a channel containing a large vertical axis wind turbine. The…

Abstract

Purpose

The purpose of this paper is to examine the details of the air mass flow and aerodynamical phenomena across a channel containing a large vertical axis wind turbine. The considered model reproduces as closely as possible the real assembly of the Sistan-type wind-mill whose top is open. The technical results of this work could be used for the restoration and operation of this assembly whose historical and architectural values are recognized.

Design/methodology/approach

Several inlet velocities into the channel are considered, taking into account the possible local wind resources. Calculations corresponding to Reynolds number varying between 8×105 and 4×106 are made by means of the finite volume method and turbulence is treated with the realizable k-ε model. The mesh consists of a fixed part associated to the contour of the channel, interfaced with a moving one linked to the turbine itself, equipped with nine partly filled wings.

Findings

The relative pressure and velocity fields are presented for various dynamic and static conditions. Calculation results clearly show that the vortex phenomena present in some cases are not a source of degradation of the wind turbine’s aerodynamical performances, given its location, intensity and rotation direction. Particular attention is devoted to the air mass flow and its distribution between the inlet and the outlet sections of the channel.

Originality/value

The present work provides technical information useful to consider the restoration and modernization of this installation whose architecture and technical performance are very interesting. This survey complements a previous one examining the aerodynamical phenomena occurring in a modified version of this assembly with a closed top channel.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 5 June 2017

Abderrahmane Baïri, Nacim Alilat, Ali Hocine, Abderrezak Hamouda and Oriana Haddad

The wire-bonded version of the quad flat non-lead with 64 leads (QFN64b) is increasingly integrated in modern arrangements, given its thermal and electrical…

Abstract

Purpose

The wire-bonded version of the quad flat non-lead with 64 leads (QFN64b) is increasingly integrated in modern arrangements, given its thermal and electrical characteristics suited for specific applications. Temperature control is thus essential for its proper operation, particularly when the heat exchange with the environment is done by natural convection. This work aims to consider a conventional assembly consisting of a large printed circuit board (PCB) on which is welded a QFN64b generating a power in the range 0.01-0.1 W. The PCB could be inclined at an angle varying between 0° and 90° (horizontal and vertical positions, respectively) according to the intended application.

Design/methodology/approach

The 3D numerical approach done by means of the finite volume method is complemented by thermal and electrical measurements for all the configurations numerically processed. The low deviations obtained between the calculations and the measurements validate the adopted model. These results complement recent work that considers the same assembly equipped with a tilted and low-powered QFN64 basic model subjected to free convection.

Findings

The surface temperature in any part of the assembly has been determined. The influence of the power generated by the device and the PCB’s inclination angle relative to the gravity field have been quantified. The work shows that the radiative heat transfer is negligible given the temperatures reached and that the thermal state of the considered assembly is different from the one equipped with the QFN64 basic model. The QFN’s temperature is lowered, while that of the PCB is increased. The temperature distribution is also different from that of assemblies equipped with other QFN models with and without wire-bonding.

Originality/value

The correlations proposed in this survey help optimize the thermal design of the QFN64b electronic package used in many engineering fields.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 2 December 2020

Hocine Boumaraf and Louisa Amireche

The purpose of this paper is to move beyond the stage of analysis of exclusively physical microclimatic phenomena and extending ourselves to the study of the impact of the…

Abstract

Purpose

The purpose of this paper is to move beyond the stage of analysis of exclusively physical microclimatic phenomena and extending ourselves to the study of the impact of the microclimate environment on the user behavior in public spaces. This paper will open up new opportunities for the development of urban open spaces and facilitate the decision-making for urban decision-makers, city managers and planners to make the right urban planning decision.

Design/methodology/approach

The methodology for identifying the links between microclimatic quality of urban routes and behaviors was developed on the basis of the results obtained from field surveys carried out in nine public urban areas of the city of Biskra, three urban space are located in a traditional urban fabric (the medina) and the other five in new urban areas, in the two climatic seasons (winter, summer) of 2019. For this exploratory research, two types of instruments were used to collect data from environmental and human monitoring.

Findings

Improving microclimatic conditions in urban spaces can allow people to spend more time outside, with the possibility of increasing their social cohesion. The overall objective of this research is to better understand the impact of microclimatic characteristics on pedestrian behavior of nine selected public urban spaces in the city of Biskra, Algeria. To characterize this impact, the authors developed an approach based on crossing data of field surveys, including structured interviews with a questionnaire and observations of human activities (video recordings), as well as microclimate monitoring, conducted during the two climatic seasons (winter, summer) 2019. The analysis of the results allowed to verify the impact of the two climatic seasons (winter, summer) on the variation in the density of occupancy of the different urban areas studied and the duration of the user stations. The authors also illustrated that the number of individuals higher in the traditional urban spaces of the city of Biskra or the conditions of climate comfort are more comfortable than the urban spaces in the new urban areas of the city of Biskra during the summer, which is the season most problematic.

Originality/value

In recent years, there has been a proliferation of scientific studies on the subject of control of microclimatic characteristics and, in particular, on the consideration of the thermal comfort of persons by qualitative analysis, prediction and representation of the perception of external environments. Improving microclimatic conditions in urban spaces can allow people to spend more time outside, with the possibility of increasing their social cohesion. This study highlights the importance of climate-conscious urban design and design flexibility. Urban environments can be modified in summer and winter to provide a better outdoor thermal environment for users. In addition, this study also shows the importance of harmony between microclimate and urban design. Such harmony can be achieved by including requirements for a climate-conscious urban design in the planning regulations for cities in arid zones.

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Article
Publication date: 30 March 2021

Mudassar Ali, Zhang Li, Dilawar Khan Durrani, Adnan Muhammad Shah and Waqas Khuram

Using the lens of conservation of resources (COR) theory, the purpose of this paper is to explore the effect of humble leadership on project success by integrating the…

Abstract

Purpose

Using the lens of conservation of resources (COR) theory, the purpose of this paper is to explore the effect of humble leadership on project success by integrating the mediating role of goal clarity. The authors also argue that organizational culture moderates these direct and indirect relationships through goal clarity.

Design/methodology/approach

Time-lagged data were collected from 329 employees in the civil construction sector of Pakistan.

Findings

The results indicate that humble leadership enhances project success through mediating and moderating mechanisms.

Research limitations/implications

The present research ends with an argument, managerial consequences, limits and guidance for future research.

Practical implications

The results influence a project-based organization on the selection and promotion of humility among project managers.

Originality/value

This research answers the following research question, which has been ignored in the literature: What are the suggested mechanisms for humble leadership in promoting project success?

Details

Baltic Journal of Management, vol. 16 no. 3
Type: Research Article
ISSN: 1746-5265

Keywords

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Article
Publication date: 19 June 2019

Ganesh Kumar K., Chamkha Ali J., Prasannakumara B.C. and Jyothi A.M.

This paper aims to explore particle shape effect on Cu-H2O nanoparticles over a moving plate in the presence of nonlinear thermal radiation. To characterize the effect…

Abstract

Purpose

This paper aims to explore particle shape effect on Cu-H2O nanoparticles over a moving plate in the presence of nonlinear thermal radiation. To characterize the effect, particle shape and viscous dissipation are considered. Convergent solutions for the resulting nonlinear systems are derived and the effects of embedded parameters of interest on velocity and temperature field are examined.

Design/methodology/approach

The Runge–Kutta–Fehlberg fourth-fifth order method along with shooting technique is used to solve the governing equations (6) and (7) with boundary conditions (8). A suitable finite value of η is considered in such a way that the boundary conditions are satisfied asymptotically.

Findings

The results show an increase in both the heat transfer and thermodynamic performance of the system. However, among the three nanoparticle shapes, disk shape exhibited better heat transfer characteristics and heat transfer rate. On the other hand, the velocity profile enhances with increasing values of ϕ in the first solution, but the opposite trend was found in the second solution.

Originality/value

The present paper deals with an exploration of particle shape effect on Cu-H2O nanoparticles over a moving plate in the presence of nonlinear thermal radiation. To characterize the effect, particle shape and viscous dissipation are considered. Convergent solutions for the resulting nonlinear systems are derived and the effects of embedded parameters of interest on velocity and temperature field are examined. The skin friction coefficient and Nusselt number are numerically tabulated and discussed. The results show an increase in both heat transfer and thermodynamic performance of the system. However, among the three nanoparticle shapes, disk shape exhibited better heat-transfer characteristics and heat-transfer rate. On the other hand, the velocity profile enhances with increasing values of ϕ in the first solution, but the opposite trend was found in the second solution.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

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Expert briefing
Publication date: 14 October 2015

Shifting balance of power.

Details

DOI: 10.1108/OXAN-DB205969

ISSN: 2633-304X

Keywords

Geographic
Topical
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Article
Publication date: 4 January 2016

Abderrahmane Baïri, Cyril Crua, Jean-Gabriel Bauzin and Iken Baïri

The purpose of this paper is to examine the aerodynamical and air mass flow phenomena taking place in the channel of a modified version of one of the well-known Sistan…

Abstract

Purpose

The purpose of this paper is to examine the aerodynamical and air mass flow phenomena taking place in the channel of a modified version of one of the well-known Sistan wind mills, in order to improve its aerodynamic performance.

Design/methodology/approach

The simulations are done by means of the finite volume method associated to the realizable k-ε turbulence model. The computational domain consists in a rotating sub domain including the wind turbine equipped with nine blades and a fixed sub domain including the rest of the computational domain. Both are connected by means of a sliding mesh interface. Calculations are done for 8×105-4×106 Reynolds number range, corresponding to inlet velocities varying from 2 to 10 m s−1.

Findings

The velocity fields are presented for the stopped and operating turbine (static and dynamic conditions). A careful examination of the aerodynamic phenomena is performed to detect potential vortices that could develop in the central cavity of the active assembly, and then influence the wind turbine’s operation.

Originality/value

The modification proposed in this survey is easy to realize, consisting in covering the top of the entire original assembly that avoids the extraction of a large part of the air mass flow occurring through the open top of the original version. The aerodynamic phenomena occurring across the channel of this large vertical axis wind turbine are substantially different from those of the original version.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 27 October 2020

Lokesh Singh, Rekh Ram Janghel and Satya Prakash Sahu

The study aims to cope with the problems confronted in the skin lesion datasets with less training data toward the classification of melanoma. The vital, challenging issue…

Abstract

Purpose

The study aims to cope with the problems confronted in the skin lesion datasets with less training data toward the classification of melanoma. The vital, challenging issue is the insufficiency of training data that occurred while classifying the lesions as melanoma and non-melanoma.

Design/methodology/approach

In this work, a transfer learning (TL) framework Transfer Constituent Support Vector Machine (TrCSVM) is designed for melanoma classification based on feature-based domain adaptation (FBDA) leveraging the support vector machine (SVM) and Transfer AdaBoost (TrAdaBoost). The working of the framework is twofold: at first, SVM is utilized for domain adaptation for learning much transferrable representation between source and target domain. In the first phase, for homogeneous domain adaptation, it augments features by transforming the data from source and target (different but related) domains in a shared-subspace. In the second phase, for heterogeneous domain adaptation, it leverages knowledge by augmenting features from source to target (different and not related) domains to a shared-subspace. Second, TrAdaBoost is utilized to adjust the weights of wrongly classified data in the newly generated source and target datasets.

Findings

The experimental results empirically prove the superiority of TrCSVM than the state-of-the-art TL methods on less-sized datasets with an accuracy of 98.82%.

Originality/value

Experiments are conducted on six skin lesion datasets and performance is compared based on accuracy, precision, sensitivity, and specificity. The effectiveness of TrCSVM is evaluated on ten other datasets towards testing its generalizing behavior. Its performance is also compared with two existing TL frameworks (TrResampling, TrAdaBoost) for the classification of melanoma.

Details

Data Technologies and Applications, vol. 55 no. 1
Type: Research Article
ISSN: 2514-9288

Keywords

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