bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical modeling of the controlled solidification process
Authors: Nagy Ştefan , Leuca Teodor , Mich‐Vancea Claudiu 
Published: March 2008

PurposeThis paper aims to present a numeric modeling of the electromagnetic and thermal phenomena for the non‐ferromagnetic alloys casting equipment that control the solidification structure's formation.Design/methodology/approachThe paper uses a numerical modeling program for the controlled solidification process modeling to allow visualization of the thermal field variation.FindingsThe probes cast using this method will have a uniform structure, without micro‐fissures. If the solid's part growth of the molten is controlled, we can stop the process that creates solidification centers, thus the material structure will be homogenous. A solution for this matter is given by the control of the solidification structure using forced heating of the liquid part with eddy currents and forced cooling of the solid part. The evolution of the area with eddy currents and the cooled one controls the phase transformation.Originality/valueThe paper presents a procedure to solve the coupled electromagnetic and thermal field problem in the casting systems techniques: solidification with controlled phase variation layer.
Thermal analysis of an eddy‐current heated piece by means of the FEM‐DBCI method
Authors: Aiello G. , Alfonzetti S. , Dilettoso E. , Salerno N. 
Published: March 2008

PurposeThis paper aims to propose a hybrid method, called finite element method‐Dirichlet boundary condition iteration (FEM‐DBCI), for the computation of time‐harmonic eddy current problems inside a conductor heated by coils in 3D open‐boundary geometry.Design/methodology/approachThe method assumes the electrical field as unknown on a mesh of tetrahedral edge elements. The heating power density inside the conductor is then computed and a steady‐state thermal analysis is performed on the same mesh of nodal tetrahedra to calculate the temperature distribution inside the heated piece, taking radiation and convection into account. A numerical example is also provided.FindingsThe method couples a differential equation for the interior problem in terms of the electric fields with an integral equation for the exterior one. The global algebraic system is efficiently solved in an iterative way.Originality/valueThe paper illustrates the computation of time‐harmonic eddy current problems inside a conductor heated by coils.
Shunt active power filter implementation for induction heating applications
Authors: Bojoi R. , Griva G. , Profumo F. , Cesano M. , Natale L. 
Published: March 2008

PurposeThis paper aims to present the prototype of a 140 kVA shunt active power filter (APF) for current harmonics and fundamental reactive power compensation of a 200 kW induction heating system.Design/methodology/approachDesign issues of the power components, of the switching ripple filter and of the digital control are addressed and discussed. The APF control algorithm has been implemented on the 16‐bit, fixed‐point, TMS320LF2407 A DSP controller. The current control is based on proportional‐sinusoidal signal integrators with good performance in current harmonic elimination and power factor compensation.FindingsThe experimental tests, performed in real industrial environment for a 200 kW induction heating plant, show that the performance goals are fulfilled.Practical implicationsThe sinusoidal signal integrators (for consistency with the other plural forms of acronyms) of the current controller are implemented in the rotating reference frame aligned with the voltage vector at the point of common connection. This allows the compensation of two harmonics with a single SSI, thus halving the computational effort of the DSP.Originality/valueIn industrial induction heating, the need for harmonic and reactive power compensation lasts a few seconds per minute, making passive solutions not suitable. The presented APF is a valid solution for this application, where only a few tailored implementations are available on the market.
Three‐dimensional eddy current analysis in unbounded domains by a DEM‐BEM formulation
Authors: Alotto Piergiorgio , Gruosso Giambattista , Moro Federico , Repetto Maurizio 
Published: March 2008

PurposeTo propose a novel 3D hybrid approach, based on a discrete formulation of Maxwell equations (the cell method – CM), suitable for solving eddy current problems in unbounded domains.Design/methodology/approachField equations for magnetodynamics are expressed directly in algebraic form thanks to the CM. The eddy current problem inside bulk conductors is formulated in terms of discrete modified vector potential, whereas magnetic scalar potential is used in order to model the free space. The CM is coupled to the boundary element method by using a surface boundary operator, which maps the surface magnetic fluxes to the surface magnetic scalar potentials. This leads to a unique set of linear equations to be solved in terms of discrete potentials. The eddy currents in bulk conductors are then obtained from discrete potentials.FindingsIt is shown that formulation of hybrid approaches can be simplified by expressing field equations directly in algebraic form without need of weighted residual techniques. An original strategy, based on Green's formula for the magnetic scalar potential, is proposed in order to couple conducting parts to the exterior domain.Research limitations/implicationsConducting bodies with multiply connected parts cannot be modelled by the proposed approach, since it is based on the magnetic scalar potential. The resulting global matrix is partially dense and non‐symmetric; therefore, standard iterative solvers such as GMRES have to be used.Practical implicationsThe proposed approach can be suitably used for analyzing eddy current problems involving models with high degree of complexity, large air domains and moving parts. These are typical of induction heating processes.Originality/valueThis paper proposes a new 3D hybrid approach, based on a discrete formulation of Maxwell equations. A novel coupling strategy relying on integral electromagnetic variables, i.e. magnetic fluxes and magnetic scalar potentials, is devised in order to solve uniquely for eddy currents inside conducting bodies.
Electromagnetic and thermal analysis of the induction heating of aluminum billets rotating in DC magnetic field
Authors: Araneo R. , Dughiero F. , Fabbri M. , Forzan M. , Geri A. , Morandi A. , Lupi S. , Ribani P.L. , Veca G. 
Published: March 2008

PurposeThe paper aims to deal with the induction heating of metal billets rotating in a DC magnetic field.Design/methodology/approachThe induced power distributions are analysed and the main heating parameters are estimated with reference to an infinitely long Al billet 200 mm diameter. The paper refers to the activity developed in the frame of a National Italian Project carried out by research groups of the Universities of Bologna, Padua and Roma “La Sapienza.”FindingsThe main process parameters have been evaluated for the heating up to 500°C of an Al billet 200 mm diameter.Practical implicationsThis innovative technology appears to be very promising for improving the efficiency of the through heating of high‐conductivity metals (e.g. copper, aluminum) before hot working, by using superconducting magnets.Originality/valueThe paper analyses the induction heating of a infinitely long billet rotating in a uniform DC magnetic field.
DC induction heating of aluminum billets using superconducting magnets
Authors: Fabbri Massimo , Morandi Antonio , Luigi Ribani Pier 
Published: March 2008

PurposeTo analyse the heating process of an aluminum billet rotating in a static magnetic field produced by superconducting coils.Design/methodology/approachThe idea is to force the billet to rotate in a static magnetic field produced by a DC superconducting magnet. Since, a static superconducting magnet has no losses, the efficiency of the system is the efficiency of the motor used. In order to evaluate the temperature distribution arising from the field profile produced by a given coil configuration, a numerical model, based on an equivalent electric network with temperature‐dependent parameters, is used.FindingsThe main heating parameters, i.e. heating time, total power injected and temperature difference, are evaluated for different values of angular velocity and magnetic field. The field profile suitable to meet the specifics of an industrial heating process in terms of temperature homogeneity and heating time is determined. Starting form this profile the layout of the magnet is arrived at and some considerations on the operating condition of the superconducting windings are reported.Research limitations/implicationsThe mechanical stress in the billet due to weight, centrifugal effects, applied torque and resonance is examined by taking into account the weakening of the material properties with the increase of temperature and the practical limits of the heating process are evaluated.Practical implicationsDC induction heating of aluminum billet using superconducting magnets can be done fulfilling the specifics of the industrial processes.Originality/valueA high‐efficiency induction heater for aluminum billets using superconducting coils in a novel scheme is investigated.
Enhanced reactive NiAl coatings by microwave‐assisted SHS
Authors: Veronesi P. , Leonelli C. , Poli G. , Casagrande A. 
Published: March 2008

PurposeThe paper aims to focus on microwave (2.45 GHz) assisted SHS (MA‐SHS) preparation of NiAl intermetallic coatings on titanium substrates conducted in single mode applicator in order to promote the formation of a complex Ni‐Al‐Ti interface. This enhances the NiAl coating adhesion to the Ti substrate and presents high hardness, high toughness and the capability of stopping the fracture propagation.Design/methodology/approachNumerical modelling, coupling electromagnetic and heat transfer, allowed to demonstrate that the interface cooling rate can be controlled immediately after SHS using microwave heating, benefiting from the possibility of conveying energy to the newly formed intermetallic compounds, despite an adverse temperature gradient which would negatively affect conventional heating techniques, based exclusively on heat transfer. Experimental validation of the modelling results confirmed that by altering the synthesis conditions (load geometry, microwave power, auxiliary microwave absorbers) the thickness of the Ni‐Al‐Ti layer can be controlled.FindingsThe growth of the interface layer can be ascribed to the formation of a liquid phase (ternary eutectic) which progressively consumes NiAl and Ti from the substrate. In case of MA‐SHS, the liquid phase presence can be prolonged during cooling, thus explaining the formation of the thick interface layer.Practical implicationsMicrowave selective heating can be used to initiate the SHS without affecting the metallic substrate, which is only heated locally by the reaction products, thus preserving its properties.Originality/valueCoupling numerical simulation and experimental activity demonstrated that the different microstructures obtained by MA‐SHS are a result of the peculiar temperature profile, favoured by microwave volumetric and selective heating of the reacting powders.
Simplified robust adaptive control of a class of time‐varying chaotic systems
Authors: Estrada Jorge L. , Duarte‐Mermoud Manuel A. , Travieso‐Torres Juan C. , Beltrán Nicolás H. 
Published: March 2008

PurposeTo develop a simplified robust control scheme for a class of nonlinear time‐varying uncertain chaotic systems.Design/methodology/approachBy means of input‐to‐state stability theory, a new robust adaptive control scheme is designed, which is simpler than the one proposed by Liet al.and applicable to a larger class of nonlinear systems. Only one parameter is adjusted in the controller and the scheme assures that all the signals remain bounded. The behavior of the proposed control scheme is also analyzed through simulations on the Rössler system.FindingsBy adjusting only one parameter in the controller and imposing only one mild assumption on the time‐varying parameters, the proposed control algorithm assures that all the signal remain bounded and that the state of the original system will follow a desired trajectory defined either by the trajectory and its first time derivative, or given by a reference model.Research limitations/implicationsThe results are limited to a particular class of nonlinear systems where the dimension of the input vector is equal to the order of the system (dimension of the state vector).Practical implicationsThe main advantage of the proposed method is that the modification introduced leads to a substantially simpler adaptive robust controller whose practical implementation will be easier.Originality/valueThe contribution of the proposed method is in the simplification of the control algorithm applied to a class of nonlinear time‐varying uncertain chaotic systems. This will be useful for control engineers to control complex industrial plants.
Reconfiguration of impulse‐voltage generator for conducting standard lightning tests
Authors: El‐Adawy Khalil M. , Metwally I.A. 
Published: March 2008

PurposeLoading the impulse‐voltage generator by test object can affect the generated voltage waveform. It is well known that reconfiguring these generators by changing the high‐voltage resistors and capacitors, and even the connecting leads in the laboratory is too bulky and time consuming, especially for large test objects. The objective of this paper is to introduce a new computerized method to reconfigure the impulse‐voltage generator in order to conduct the standard tests on any type of objects.Design/methodology/approachA modified algorithm is introduced for solving the generalized equivalent circuit of impulse‐voltage generators under any loading condition.FindingsThe high efficiency of this algorithm has been verified by experimental investigations on different reduced‐ and full‐scale loads, namely, resistive, inductive, capacitive or mixed. For reduced‐scale loads up to a few kV, a single‐stage impulse‐voltage generator is used. While for full‐scale loads, a multi‐stage impulse‐voltage generator is reconfigured to test a 33 kV neutral earthing reactor. The experimental responses are compared with the numerical results of the proposed program and checked out by the PSCAD simulation. Good agreement has been found between all of them.Practical implicationsKnowing the exact value of the test object, some of the generator components and the connecting lead inductances is a must to apply this method.Originality/valueReconfiguring of impulse‐voltage generators by changing the high‐voltage resistors and capacitors, and even the connecting leads in the laboratory is too bulky and time consuming, especially for large test objects. This work will certainly save time and efforts if it is applied correctly in high‐voltage laboratories.
Fast response adaptive fuzzy logic controller for sensorless direct torque control of PMSM with minimum torque ripple
Authors: Ahmed Adam Ali , Gulez Kayhan 
Published: March 2008

PurposeThe paper seeks to provide an adaptive fuzzy logic controller for permanent magnet synchronous motor (PMSM) under direct torque control (DTC) algorithm to minimize the torque ripple.Design/methodology/approachThe design methodology is based on vector control analysis. MATLAB simulations supported with experimental study under C++ are used to execute the proposed work.FindingsThe results show that considerable torque ripple reduction as well as considerable current ripple reduction can be achieved by utilizing adaptive fuzzy switching algorithm to fire the inverter supplying the PMSM.Research limitations/implicationsThis research is limited to PMSM, however the research can be extended to include other AC motors as well. In addition, the following points can be studied, the effects of harmonics in control signals on the torque ripple. Digital and active filters as solution to these harmonics can be also addressed. The actual mathematical relation between the torque ripple and flux ripple can be studied to set the flux and torque bands width in reasonable value.Practical implicationsBased on existence DTC control system, it is only required to change the software‐switching algorithm, to provide smooth torque, given that the switching frequency of the inverter module is more than or equal to 15 kHz and the system is supplied with timers. In addition, a relatively higher DC voltage may be required to achieve higher speed compared with the traditional DTC.Originality/valueIn this paper, the stator flux position, and errors due to deviations from reference values of the torque and stator flux are used to select two active vectors while at the same time the absolute value of the torque error and the stator flux position are fuzzified to adapt the switching of the inverter in order to control the applied average voltage level in such a way as to minimize the torque ripple, so instead of fixed time table structure, a fuzzy logic is used to calculate the switching time for the selected vectors and no PI controller is used as the case in the traditional‐space vector modulation. This work is directed to motor drive system designers who seek highly smooth torque performance with fast response.
Evolutionary multi‐objective design of non‐uniform circular phased arrays
Authors: Panduro Marco A. , Brizuela Carlos A. 
Published: March 2008

PurposeThe purpose of this paper is to present the application of an efficient genetic algorithm to deal with the problem of computing the trade‐off curves for non‐uniform circular arrays. In order to answer questions related to the performance of the non‐uniform circular phased arrays, two criteria are considered to evaluate the design: the criteria of minimum main beam width and minimum side lobe level (SLL) during scanning.Design/methodology/approachThe design of non‐uniform circular arrays is modeled as a multi‐objective optimization problem. The Non‐dominated Sorting Genetic Algorithm II (NSGA‐II) is employed as the methodology to solve the resulting optimization problem. This algorithm is considered to be one of the best evolutionary optimizer for multi‐objective problems. It is chosen for its ease of implementation and its efficiency for computation of non‐dominated ranks. The method is based on the survival of the fittest paradigm, where each individual in the population represents a feasible solution of the optimization problem being solved. The concept of fitness is adapted to take into account the concept of solution quality in multi‐objective problems. This evolutionary method can be used effectively for computing the trade‐off curves between the SLL and the main beam width.FindingsThe NSGA‐II algorithm can effectively compute the trade‐off curve of different non‐uniform circular arrays. The simulation results presented in this paper show design options that maintain a low SLL and main beam width without pattern distortion during beam steering. Moreover, these trade‐off curves provide a more realistic approach to the solution of the design problem.Originality/valueThe design problem is set to determine which are the best design configurations or separations between the antenna elements and the best amplitude excitations when a circular structure is employed. Owing to the complex feasible region and the non‐linear dependence of optimization criteria from the decision variables, simple traditional and more sophisticated mathematical programming approaches will lead us to local optimal solutions in the case we can apply them. To the best of our knowledge, this multi‐objective optimization problem has not dealt with before, when two or more conflicting design criteria are taken into account. Therefore, the solution to this problem constitutes the main contribution of our paper.
Cybernetic systems for management applications
Authors: Rudall Brian H. , Mann C.J.H. 
Published: March 2008

PurposeThis paper aims to review current advances in the development of cybernetic systems with particular reference to management applications.Design/methodology/approachA general review and survey of selected research and development topics is adopted.FindingsThe paper illustrates the multi‐ and trans‐disciplinary nature of cybernetics, systems and the management sciences with a view to further research and development activity.Practical implicationsThe choice of reviews provides an awareness of the current trends in these areas of endeavour.Originality/valueThe reviews are selected from a global database and give a studied assessment of current research and development initiatives.
Fusion power; centralized computing
Authors: Andrew Alex M. 
Published: March 2008

PurposeThis paper sets out to discuss a proposal for power generation by atomic fusion using the helium isotope of mass 3, obtained from the moon, and to compare it with the better‐known proposed method using deuterium and tritium. It proposes to discuss a new trend by which computing power is made available “on tap” rather than in individual users' installations.Design/methodology/approachThe aim is to review developments on the internet, especially those of general cybernetic interest.FindingsThe possibility of fusion power based on helium‐3 should be kept in mind, but is subject to numerous difficulties. Centralized computing offers a number of benefits and is a current trend.Practical implicationsFusion power from helium‐3 is a remote and uncertain possibility, and attention should not be diverted from efforts to reduce carbon emissions and global warming by other means. Large‐scale users of computers might well consider subscribing to a central service.Originality/valueIt is hoped that this will be a valuable periodic review.
Explaining institutional change: aspects of an innovation in the new institutional economy
Authors: Johannessen Jon‐Arild 
Published: March 2008

PurposeThe purpose of the paper is to use systemic thinking to explain institutional change. The paper is conceptual, based upon conceptual generalizations.Design/methodology/approachThe paper considers the question: how can one explain institutional changes? Explaining institutional change is demanded by several recent authors. An interpretation framework is first developed around explanations, where various perspectives on explanations are considered. Then the various perspectives are used to explain institutional change. Finally, an analytical model is developed to explain institutional changes.FindingsThe analytical model is used in order to develop a conceptual model to explain institutional changes in the economic system.Originality/valueThe paper breaks new ground in using systemic thinking to explain institutional change.