1,664 research outputs found
Experimental and finite element study of the hydroforming bi-layered tubular components
No full textThe application of finite element method (FEM) in the area of metal forming and material processing has been increasing rapidly during the recent years. The present study has been carried out on one of the unconventional metal forming processes called hydroforming of a multi-layered tube. The study involved both experimental and simulation work using FEA. Multi-layered tubes have extensive advantages in both domestic and industrial uses. The specimen tube consists of two different layers of materials. The outer tube material is brass and the inner tube material is copper. This project is mainly dedicated to the modelling, simulation and advanced study of one of the unconventional metal forming processes called hydroforming in which extremely high fluid pressure is used to deform the metal into desired shape. Various types of complex industrial products can be made by hydroforming. This process is suitable to produce seamless, lightweight, near net shaped industrial components. There are some complex products, which are easier to produce by hydroforming than by conventional technique.
In this research work the main forming load is hydrostatic pressure applied to the internal surface of the tube, together with an in-plane compressive load applied simultaneously. The blank is placed in a pre-shaped die block and due to the action of simultaneous internal pressure and axial load; it is formed into a complex desired shape. If the internal pressure is too high during the process without sufficient axial load it may cause the tube to burst, on the other hand too large axial load without applying sufficient internal pressure may cause wrinkling of the tube. For these reasons, a number of simulations of the hydroforming process have been carried out for different axial load and internal pressure combinations and optimum conditions have been established for the particular process. This simulated hydroforming of composite material tube and the formed product has been analysed on the basis of forming conditions and the simulated forming conditions have been verified by experiment. The simulations of hydroforming process for X or T branch have been carried by using the commercial finite element package ANSYS
Development of a hybrid genetic algorithm based decision support system for vehicle routing and scheduling in supply chain logistics managment
No full textVehicle Routing and Scheduling (VRS) constitute an important part of logistics management. Given the fact that the worldwide cost on physical distribution is evermore increasing, the global competition and the complex nature of logistics problems, one area, which determines the efficiency of all others, is the VRS activities. The application of Decision Support Systems (DSS) to assist logistics management with an efficient VRS could be of great benefit. Although the benefits of DSS in VRS are well documented, however in practice many organisations perform these activities manually using combination of skills, intuition and expertise.
A comprehensive review of literature revealed several drawbacks in the existing methods for addressing VRS. The traditional optimisation approaches have very limited applications and these require high computation time. Also, heuristic approaches are capable only to specific variation, a slight difference in the structure of the problem make the algorithm inefficient. Furthermore, metaheuristics methods require higher computation time and they are context dependent. Also, further investigations on the VRS problem formulations suggest that heuristic approaches usually address a single objective of distance minimisation. However in the real world there may be a number of conflicting objectives. In general, there is a lack of considerations for route selections, resource utilisation, unhlfilled demands, underused capacities, reliability of deliveries, fleet size, human fitness and operational cost. Also, these approaches fail to realise non-linearity within objectives and constraints defined for VRS problems. Furthermore, there are no clear distinctions between hard and soft constraints considered in these methods. Finally, the existing approaches fail to capture stochastic and dynamic nature of the logistics processes.
In order to overcome the above-mentioned drawbacks, this study designed and developed a hybrid DSS to assist logistics managers with VRS tasks. The capabilities of the developed DSS have then been applied to a Liquefied Petroleum Gas (LPG) distribution company. The architecture of this DSS is composed of Genetic Algorithm (GA) optimisation tool and a simulation model. The GA module aims to provide a pool of near optimum transportation schedules. The simulation module is used to further evaluate the generated schedules. The feed back from the simulation module is used to update the GA for reoptimisation. Some unique features of this DSS are such as: development of a multi modal genetic algorithm to address VRS problems; considering supply chain performance measures as part of VRS problem formulation; allowing consideration of different objectives, soft or hard constraints concerning the supply chain, considering linearlnonlinear relationships within objectives and constraints defined and finally, considering stochastic and dynamic behaviours of the supply chain system.
The GA and simulation tool integration provides unique benefits that have not been in the literature such as consideration of practical requirements, uncertainties, dynamic and stochastic behaviours, considering several criteria and producing different alternative solutions. Also, this integration allows the GA model to filter out solutions that are less competitive and therefore reducing the simulation time evaluation, which is computationally expensive. Furthermore, the human interaction with the system assists in generating higher quality of solutions. Finally, the clear benefit of this DSS is the fact that it greatly influences the applicability of the GA generated schedules and provides better confidence in implementation of these solution
Author Correction: Smartphone‑based device for point‑of‑care diagnostics of pulmonary infammation using convolutional neural networks (CNNs)
No full textCorrection to: Scientific Reportshttps://doi.org/10.1038/s41598-024-54939-4, published online 22 March 2024 The original version of this Article contained an error in the author name S. Mohammad-Reza Taheri which was incorrectly given as Seyed Mohammad Reza Taheri. In addition, an affiliation was omitted for S. Mohammad-Reza Taheri. The correct affiliations for S. Mohammad-Reza Taheri are listed below. Groningen University, University Medical Center groningen, Antonius Deusinglaan 1, 9713AW Groningen, the Netherlands. Condensed Matter National Laboratory, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran. Moreover, Hossein Simaee was incorrectly affiliated with ‘Institute of Biochemistry and Biophysics, University of Tehran, Tehran 1417614335, Iran’ and ‘Integrated Biophysics and Bioengineering Lab (iBL), Institute of Biochemistry and Biophysics, University of Tehran, Tehran 1417614335, Iran’. The correct affiliation for Hossein Simaee is listed below. Cardiac Primary Prevention Research Center, Cardiovascular Diseases Research Institute, Tehran University of Medical Sciences, Tehran, Iran. The original Article has been corrected.</p
Performance-Based Intelligent Diagnostics, Prognostics, and Health Monitoring of Hydrogen Fueled Gas Turbines
No full textGlobal energy transition efforts towards decarbonization requires significant advances within the energy sector. In this regard, hydrogen is envisioned as a long-term alternative fuel for gas turbines. Accordingly, the gas turbine industry has expedited their efforts in developing 100% hydrogen compliant burners and associated auxiliary components for retrofitting the existing gas turbines. The utilization of hydrogen in gas turbines has some underlying challenges such as corrosion mainly originating from increased steam content in the hot gas path. In addition to corrosion, the gas turbine compressor is vulnerable to fouling, which is the most commonly occurring fault in gas turbine operating over certain time window. Both faults are susceptible to performance and health degradation. Owing to these problems, an in-depth thermodynamic performance assessment along with combustor’s flue gas thermophysical properties analysis becomes crucial. In addition to the thermodynamic performance model, performance-based intelligent fault diagnostics and prognostics/ remaining useful life (RUL) estimation of hydrogen fueled gas turbine is point of concern for the gas turbines original equipment manufacturers (OEMs) and operators.
The present thesis therefore addresses the above-mentioned technical challenges by providing a detailed comparative thermodynamic performance assessment of both hydrogen and natural gas (NG) fueled gas turbine scenarios. Besides, a comparative analysis of various artificial intelligence (AI) based approaches have been conducted for performance degradation estimation and fault diagnostics. Furthermore, to avoid expensive asset loss caused by unexpected downtimes and shutdowns, data-statistical prognostics have been employed for both NG and hydrogen fueled scenarios.
The first part of the thesis consists of thermodynamic performance and combustion flue gas analysis. The combustion reactions and detailed analysis of fluid flow properties manifested that H2 fuel utilization results
in an increased steam content (by ~106%) as compared to NG combustion. The combined effect of turbine corrosion severity level and high ambient temperature on the overall performance of the MGT showsthat the increased corrosion severity level at high ambient temperature can lead to deterioration in power and thermal efficiency. The second part deals with fault diagnostics using different machine learning based techniques. To identify an accurate algorithm, various algorithms such as support vector machine, decision tree, random forest algorithm, k-nearest neighbors, and artificial neural network were tested. The findings from fault diagnostics process (classification) revealed that ANN outperformed its counterpart algorithm by giving accuracy of 94.55%. Similarly, ANN also showed higher accuracy in performance degradation estimation process (regression) by showing the MSE of training loss as low as ~0.14. The comparative analysis of all the chosen algorithms in the present study revealed ANN as the most accurate algorithm for fault diagnostics of hydrogen fueled gas turbines. The last part dealt with prognostics/RUL estimation. In this regard, the study incorporated linear and polynomial regression approaches and compared the end of life of gas turbines running on natural gas and hydrogen fuels. It became evident from the study that RUL of a gas turbine running on hydrogen fuel is 6.47% lower than that of natural gas fueled gas turbines. These findings underline the necessity of using strong prediction models, as well as targeted maintenance actions, to limit the consequences of turbine corrosion in hydrogen powered MGTs. The findings of the present study further provide new horizons for design modification and effective health monitoring of hydrogen fueled gas turbines
Effects of freestream trubulence on crossflow instability
No full textDirect numerical simulations (DNS) have been performed in order to investigate the interaction of freestream turbulence and crossflow generated instability on a swept wing. The experiments by [3] and [1] are selected as the reference cases. In those experiments the authors explore the interaction between different freestream turbulence characteristics and different roughness element characteristics. In the current study, isotropic homogenous freestream turbulence are generated following experimental parameters and then fed as the inflow boundary condition for DNS of flow over the wing. A spanwise array of roughness elements corresponding to the most unstable stationary modes are used to generate the crossflow vortices. The effects of the freestream turbulence on the crossflow instability and transition to turbulence are later studied
RoMEO Studies 4: An analysis of Journal publishers' Copyright Agreements
No full textThis article is the fourth in a series of six emanating from the UK JISC-funded RoMEO Project (Rights Metadata for Open archiving). It describes an analysis of 80 scholarly journal publishers’ copyright agreements with a particular view to their effect on author self-archiving. 90% of agreements asked for copyright transfer and 69% asked for it prior to refereeing the paper. 75% asked authors to warrant that their work had not been previously published although only two explicitly stated that they viewed self-archiving as prior publication. 28.5% of agreements provided authors with no usage rights over their own paper. Although 42.5% allowed self-archiving in some format, there was no consensus on the conditions under which self-archiving could take place. The article concludes that author-publisher copyright agreements should be reconsidered by a working party representing the needs of both partie
An investigation of the reasons for Mohammad Shah Qajar`s defeat in returning the sovereignty of Iran to Herat (1835 – 1839)
No full textThe ruler of Herat`s refusal to do fulfill his obligations such as paying the annual tribute, attacking Khorasan trying to occupy Sistan were among the factors that made Mohammad Shah campaign in Herat to not only punish Kamran Mirza but also conquer this city that was once about to be opened by him during his father`s life. At that time, from one side, Russia was trying to encourage the Qajar king to attack Herat and occupy it in order to extend its penetration to Central Asia and Afghanistan. Furthermore, from the other side, Britain was to prevent Mohammad Shah from campaigning in Herat and took advantage of the city as an obstacle against probable attacks of Iran and Russia to India. Finally, while the army of Mohammad Shah was going toward Herat to capture the city, the menaces of Macnille and the navy of Britain to Khark Island and the South of Iran forced the Qajar king to end the siege of Herat without fulfilling his goals. The author, through a descriptive-analytical approach, aims not only at mentioning the reasons for and results of Mohammad Shah`s campaign in Herat but also at figuring out the reasons of his defeat in returning the sovereignty of Iran to the city
Energy TCD - robust and simple failure prediction unifying the TCD and ASED criterion
No full textRobust and simple failure prediction is a relevant and active field of research. The present work aims at unifying the Theory of Critical Distances (TCD) and Averaged Strain Energy Density (ASED) criterion. The proposed Energy TCD is formulated along with analytical expressions for the characteristic length scales and validated using experimental data. On this data set, the accuracy of the Energy TCD is similar to that of the classical methods. Most importantly, the presented methods allow to transfer the point-based calibration technique from notched specimens, which is common for the TCD, to the Energy TCD ASED criterion. © 2022 The Author(s
Hardware and Software Implementation of a Radio Frequency High-Speed Data Conversion Unit for Digital Control Systems
No full textOnTEAM metadata: GDSID: DOC-2009-Dec-87; Attribute ID: LIBRARY-thesis_ba-2009-002; Title: [GSI Bachelor 2009-02] Hardware and Software Implementation of a Radio Frequency High-Speed Data Conversion Unit for Digital Control Systems [02.10.2006]; Author(s): Sanjari, Mohammad Shahab; Corporate author(s): ; Publication date: 20091210; Creator: manton; Creation date: 10.12.2009 15:10:41; Change date: 30.09.2010 14:57:31; Access: Welt; Attribute type: Text.Thesis.BA; Directory path: ['GSI Publications', 'GSI as Publisher']; Attribute path: ['Infrastructure', 'Library and Documentation', 'thesis_ba', 'Added in 2009']; File name(s): ['DOC-2009-Dec-87-1.pdf']; File title(s): ['']; File access: ['nur berechtigte Gruppen'
Peran Orang Tua Dalam Mendidik Anak Perempuan (Telaah Atas Pemikiran Mohammad Fauzil Adhim)
No full textA woman who occupies an important role and has a continuous duty, since she is as a girl for his parents, wife for her husband, a mother for her children, a grandmother for her grandchildren. In performing her role, everyone around her demands her to perform her role as quickly as possible. Therefore, a girl needs to be given sufficient knowledge and a good education, so that later she can carry out her duties well too. This study examines how ideas Mohammad Fauzil Adhim, the author who has written about marriage, family and children's education, about how the role of parents in educating girls by Mohammad Fauzil Adhim is. The purpose of this study was to determine Mohammad Fauzil Adhim thought about the steps to educate girls as well as how the characteristics of a good parent in the child's education position by Mohammad Fauzil Adhim is. This research is expected to increase the depth of knowledge and knowledge for Muslim educators, specially in educating girls, and can be used as guidance and input for parents and educators to understand the importance of educating Muslim girls from their early age associated with their role in the future. Therefore, the children's education will be more focused and as expected by their both parents
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