Search results
1 – 10 of 918Imen Maalej, Donia Ben Halima Abid and Chokri Rekik
The purpose of this paper is to look at the problem of fault tolerant control (FTC) for discrete time nonlinear system described by Interval Type-2 Takagi–Sugeno (IT2 TS) fuzzy…
Abstract
Purpose
The purpose of this paper is to look at the problem of fault tolerant control (FTC) for discrete time nonlinear system described by Interval Type-2 Takagi–Sugeno (IT2 TS) fuzzy model subjected to stochastic noise and actuator faults.
Design/methodology/approach
An IT2 fuzzy augmented state observer is first developed to estimate simultaneously the system states and the actuator faults since this estimation is required for the design of the FTC control law. Furthermore, based on the information of the states and the faults estimate, an IT2 fuzzy state feedback controller is conceived to compensate for the faults effect and to ensure a good tracking performance between the healthy system and the faulty one. Sufficient conditions for the existence of the IT2 fuzzy controller and the IT2 fuzzy observer are given in terms of linear matrix inequalities which can be solved using a two-step computing procedure.
Findings
The paper opted for simulation results which are applied to the three-tank system. These results are presented to illustrate the effectiveness of the proposed FTC strategy.
Originality/value
In this paper, the problem of active FTC design for noisy and faulty nonlinear system represented by IT2 TS fuzzy model is treated. The developed IT2 fuzzy fault tolerant controller is designed such that it can guarantee the stability of the closed-loop system. Moreover, the proposed controller allows to accommodate for faults, presents a satisfactory state tracking performance and outperforms the traditional type-1 fuzzy fault tolerant controller.
Details
Keywords
A. Mezrhab, H. Bouali, H. Amaoui and C. Abid
The purpose of this paper is to study the radiation‐natural convection interactions in a vertical divided vented channel. The effects of the surface emissivity, the vent opening…
Abstract
Purpose
The purpose of this paper is to study the radiation‐natural convection interactions in a vertical divided vented channel. The effects of the surface emissivity, the vent opening position and size on the heat transfer and the flow structures inside the channel were studied.
Design/methodology/approach
The governing differential equations are solved by a finite volume method, with adopting the SIMPLER algorithm for pressure‐velocity coupling. The view factors were determined by using a boundary elements approximation and a Monte Carlo method.
Findings
The effect of the radiation exchange is very important, it increases the average hot wall Nusselt number by more than 100 per cent. The contribution of the channel wall emissivity in the heat transfer is more important than that of the plate emissivity. The average hot wall Nusselt number increases with increasing the vent opening size, only in presence of the radiation exchange, and this increase is more pronounced, particularly when the vent opening is located near the channel inlet.
Research limitations/implications
The flow is assumed to be incompressible, laminar and two dimensional. The radiative surfaces are assumed diffuse‐grey. The working fluid, air, is considered as transparent with respect to the radiation.
Practical implications
The industrial applications of this study are solar collectors, thermal building, electronic cooling, aeronautics, chemical apparatus, nuclear engineering, etc.
Originality/value
In comparison to the preceding studies, the originality of this paper is the taking into account of the radiation exchange in a vented and divided channel.
Details
Keywords
Preeti Mehra and Aayushi Singh
One of the most marginalized communities in India is the Lesbian, Gay, Bisexual and Transgender (LGBT) community which commonly experiences discrimination. Many studies have…
Abstract
One of the most marginalized communities in India is the Lesbian, Gay, Bisexual and Transgender (LGBT) community which commonly experiences discrimination. Many studies have countered that the LGBT community faces high discrimination in the banking and financing industry. As a result, this study concentrates on this marginalized community and its acceptance and continuation habit regarding mobile wallets. Consequently, this study has considered continuance intentions as a response to confirm the progress of the mobile-wallet industry. Also, this study tried to study the relationship between behavioral intention (BI) and continuous intention (CI) which is seriously lacks in the library of literature. The research operationalized the stimulus–organism–response (SOR) framework for the conceptual model and surveyed 100 self-proclaimed members of the LGBT community in India. The analysis has been done using the partial least structure (PLS). The findings demonstrate that variables like perceived trust (PT) directly influence the BI. On the other hand, variables like perceived ease of use (PEoU), social influence (SI), and satisfaction (S) doesn’t influence BI of the LGBT Community. The main outcome was a favorable association between BI and CI. It will help the stakeholders to understand how important this new market avenue is and how it can be explored. To ensure safe and secure transactions, a group think tank composed of important parties (financial institutions, mobile-wallet providers, the government, security specialists, etc.) should make recommendations. Mobile-wallet providers will attain benefit from this study’s understanding of user categories and ability to tailor their service offers as per the community.
Details
Keywords
Ademar Dutra, Vicente Mateo Ripoll-Feliu, Arturo Giner Fillol, Sandra Rolim Ensslin and Leonardo Ensslin
The purpose of this paper is to know what scientific literature presents about the theme evaluation of seaport performance, thus enabling the construction of knowledge in the…
Abstract
Purpose
The purpose of this paper is to know what scientific literature presents about the theme evaluation of seaport performance, thus enabling the construction of knowledge in the researchers and the identification of gaps in the research that will lead to advances in the area from the identification of the characteristics of a portfolio of relevant international publications.
Design/methodology/approach
From the basic philosophical (constructivism), of the kind strategy (research-action) and the method used for the accomplishment of such strategy (structured process knowledge development process – constructivist (ProKnow-C)) the current research has a qualitative approach.
Findings
From the analysis of the bibliographic portfolio composed of 23 articles, the main results were: focus of the evaluation of seaport performance is on operational and tactical efficiency rather than on strategic and global performance; the majority of the studies does not relate to the reality experienced by seaport managers due to the limited interaction with these managers, evidencing a distance of the researchers from the object of their research; and performance evaluation was barely used/explored as a tool to support management, only for the sake of evaluation itself.
Research limitations/implications
The search occurred in the databases Web of Science, Scopus, Proquest, Ebsco, Sciece Direct and Wiley.
Originality/value
The identification of gaps that might promote advances in this field of knowledge, once the seaport segment is not exploring the potential that performance evaluation can offer and is already available in literature.
Details
Keywords
Venkateswara Rao Kota and Shyamala Devi Munisamy
Neural network (NN)-based deep learning (DL) approach is considered for sentiment analysis (SA) by incorporating convolutional neural network (CNN), bi-directional long short-term…
Abstract
Purpose
Neural network (NN)-based deep learning (DL) approach is considered for sentiment analysis (SA) by incorporating convolutional neural network (CNN), bi-directional long short-term memory (Bi-LSTM) and attention methods. Unlike the conventional supervised machine learning natural language processing algorithms, the authors have used unsupervised deep learning algorithms.
Design/methodology/approach
The method presented for sentiment analysis is designed using CNN, Bi-LSTM and the attention mechanism. Word2vec word embedding is used for natural language processing (NLP). The discussed approach is designed for sentence-level SA which consists of one embedding layer, two convolutional layers with max-pooling, one LSTM layer and two fully connected (FC) layers. Overall the system training time is 30 min.
Findings
The method performance is analyzed using metrics like precision, recall, F1 score, and accuracy. CNN is helped to reduce the complexity and Bi-LSTM is helped to process the long sequence input text.
Originality/value
The attention mechanism is adopted to decide the significance of every hidden state and give a weighted sum of all the features fed as input.
Details
Keywords
Cristina Giménez and Helena R. Lourenço
The purpose of this paper is to analyse the interaction of two topics: supply chain management (SCM) and the internet. Merging these two fields is a key area of concern for…
Abstract
Purpose
The purpose of this paper is to analyse the interaction of two topics: supply chain management (SCM) and the internet. Merging these two fields is a key area of concern for contemporary managers and researchers. They have realised that the internet can enhance SCM by making real time information available and enabling collaboration between trading partners.
Design/methodology/approach
A literature review in prestigious academic journals in Operations Management and Logistics has been conducted for the period 1995‐2005. The objective is to collect, organise and synthesise existing knowledge relating to SCM and the internet.
Findings
The paper describes the impact that the internet has on the different processes that SCM embrace. The literature review undertaken on the topic has shown that e‐SCM has been acknowledged as an outstanding topic in the supply chain literature in the most prestigious operations management and logistics journals, especially after year 2000. The main topics have been e‐procurement, e‐fulfilment and information flows.
Originality/value
The value of this paper is to define e‐SCM, to analyse how research in this area has evolved during the period 1995‐2005 and to identify some lines of further research.
Details
Keywords
Mohamed Elmnefi and Waqas Al-Khazraji
One of the existing and commonly used solar energy harvesting devices is the parabolic trough solar collector (PTSC). Because of their ability to operate in low and medium…
Abstract
Purpose
One of the existing and commonly used solar energy harvesting devices is the parabolic trough solar collector (PTSC). Because of their ability to operate in low and medium temperatures, parabolic trough concentrators are widely used in power generation plants and industrial process heating applications. Therefore, the investigation of how different operating conditions affect these devices’ overall efficiency has received a great deal of attention in the recent decade. This study aims to enhance the thermal performance of the PTSC and reduce the system cost.
Design/methodology/approach
In the novel configuration, a noncirculated nanofluid absorbs solar radiation through a glass wall. The base fluid was synthetic oil (5W30), and the nanoparticles used were copper oxide. The heat captured is immediately absorbed by the water circulating inside the copper tube immersed in the nanofluid. ANSYS FLUENT 15.0 was used for carrying out computational fluid dynamics simulations for two models of single and triple copper tubes. The experimental results obtained from a test rig constructed for this purpose were compared with the numerical outcomes of the single copper tube model.
Findings
The findings of the simulation demonstrated that performance was superior for the single copper tube model over the triple copper tube model. The numerical findings of the single copper tube model were compared with the experimental results. The numerical and experimental results differed from 3.17% to 5.6%. Investigations were carried out to study the effects of varying the volumetric flow rate of (20, 40, 60 and 80 L/h) and water inlet temperatures of (300, 315 and 330 K) on the effectiveness and performance of the newly developed model. Additionally, two nanofluid volume fractions of 0.05% and 0.075% were used for investigating their effect on the performance of the novel configuration. According to the findings, the highest thermal efficiency of 55.31% was recorded at 0.075% concentration and 80 L/h volume flow rate.
Originality/value
In this study, a novel direct absorption solar collector configuration using a noncirculated nanofluid was designed to enhance the thermal efficiency of PTSC. This new approach makes it possible to boost the thermal performance of the PTSC and lower the system’s cost.
Details
Keywords
Taher Armaghani, A. Kasaeipoor, Mohsen Izadi and Ioan Pop
The purpose of this paper is to numerically study MHD natural convection and entropy generation of Al2O3-water alumina nanofluid inside of T-shaped baffled cavity which is…
Abstract
Purpose
The purpose of this paper is to numerically study MHD natural convection and entropy generation of Al2O3-water alumina nanofluid inside of T-shaped baffled cavity which is subjected to a magnetic field.
Design/methodology/approach
Effect of various geometrical, fluid and flow factors such as aspect ratio of enclosure and baffle length, Rayleigh and Hartmann number of nanofluid have been considered in detail. The hydrodynamics and thermal indexes of nanofluid have been described using streamlines, isotherms and isentropic lines.
Findings
It is found that by enhancing Hartmann number, symmetrical streamlines gradually lose symmetry and their values decline. It is found that by enhancing Hartmann number, symmetrical streamlines gradually lose symmetry and their values decline. The interesting finding is an increase in the impact of Hartmann number on heat transfer indexes with augmenting Rayleigh number. However, with augmenting Rayleigh number and, thus, strengthening the buoyant forces, the efficacy of Hartmann number one, an index indicating the simultaneous impact of natural heat transfer to entropy generation increases. It is clearly seen that the efficacy of nanofluid on increased Nusselt number enhances with increasing aspect ratio of the enclosure. Based on the results, the Nusselt number generally enhances with the larger baffle length in the enclosure. Finally, with larger Hartmann number and lesser Nusselt one, entropy production is reduced.
Originality/value
The authors believe that all the results, both numerical and asymptotic, are original and have not been published elsewhere.
Details
Keywords
Oskar Szulc, Piotr Doerffer, Pawel Flaszynski and Marianna Braza
This paper aims to describe a proposal for an innovative method of normal shock wave–turbulent boundary layer interaction (SBLI) and shock-induced separation control.
Abstract
Purpose
This paper aims to describe a proposal for an innovative method of normal shock wave–turbulent boundary layer interaction (SBLI) and shock-induced separation control.
Design/methodology/approach
The concept is based on the introduction of a tangentially moving wall upstream of the shock wave and in the interaction region. The SBLI control mechanism may be implemented as a closed belt floating on an air cushion, sliding over two cylinders and forming the outer skin of the suction side of the airfoil. The presented exploratory numerical study is conducted with SPARC solver (steady 2D RANS). The effect of the moving wall is presented for the NACA 0012 airfoil operating in transonic conditions.
Findings
To assess the accuracy of obtained solutions, validation of the computational model is demonstrated against the experimental data of Harris, Ladson & Hill and Mineck & Hartwich (NASA Langley). The comparison is conducted not only for the reference (impermeable) but also for the perforated (permeable) surface NACA 0012 airfoils. Subsequent numerical analysis of SBLI control by moving wall confirms that for the selected velocity ratios, the method is able to improve the shock-upstream boundary layer and counteract flow separation, significantly increasing the airfoil aerodynamic performance.
Originality/value
The moving wall concept as a means of normal shock wave–turbulent boundary layer interaction and shock-induced separation control has been investigated in detail for the first time. The study quantified the necessary operational requirements of such a system and practicable aerodynamic efficiency gains and simultaneously revealed the considerable potential of this promising idea, stimulating a new direction for future investigations regarding SBLI control.
Details
Keywords
In this study, the effects of using corrugated absorber plate (instead of flat plate) and also using aerosol/carbon-black nanofluid (instead of air) on heat transfer and turbulent…
Abstract
Purpose
In this study, the effects of using corrugated absorber plate (instead of flat plate) and also using aerosol/carbon-black nanofluid (instead of air) on heat transfer and turbulent flow characteristics in solar collectors were numerically investigated.
Design/methodology/approach
The 3D continuity, momentum and energy equation were solved by finite volume and SIMPLE algorithm. As a result, the corrugated absorber plate was inspected in the case of triangle, rectangle and sinuous with the wave length of 1 mm and wave amplitude of 3 mm in turbulent flow regime and Reynolds number between 2,500 and 4,000. Choosing the proper geometry was carried out based on the best performance evaluation criteria (PEC) and increasing the air temperature from collector inlet to outlet.
Findings
The results revealed that for all times of the year the highest PEC was obtained for corrugated Sinusoidal model; however, the highest temperature increase from inlet to outlet was obtained for rectangular corrugated model. In addition, the results indicated that in sinusoidal model, the nanoparticles volume fractions increase leads to heat performance coefficient increase and the best heat performance conditions were attained in volume fraction of 0.1 per cent and Reynolds number of 4,000 for both six months period. In model with rectangular corrugated plate, usage of nanofluid in all range of Reynolds numbers leads to reduction of outlet temperature.
Originality/value
The effect of some nanoparticles on heat transfer using thermal– hydraulic performances in heat exchangers has been assessed, but the effects of atmospheric aerosol-based nanofluid using carbon-black nanoparticles (CBNPs) on the heat transfer in corrugated heat sink solar collectors by 3D numerical modeling has not been yet investigated. In present study, usage of CBNPs with different volume fractions in range of 0 to 0.1 per cent in turbulent regime of fluid flow is analyzed. Furthermore, in this paper, besides the effects of using CBNPs, a solar absorber located in Shiraz, as one of the best solar irradiation receiver cities in Iran is evaluated.
Details