Search results

This paper aims to present an analytical way of formulating the vital parameters of an equivalent hysteresis loop of a composite, multi-component magnetic substance. By using the hyperbolic model, the only model, which separates the constituent parts of the composite magnetic materials, an equivalent loop can be composed analytically. So far, it was only possible to superimpose the tanh functions by numerical method. With this transformation, all multi-component composite substances can be treated mathematically as a single-phase material, as in the T(x) model, and include it in mathematical operations. The transformation works with good accuracy for major and minor loops and provides an easy analytical way to arrive to the vital parameters. This also shows an analytical way to the easy solution of some of the difficult problems in magnetism for multi-component ferrous materials, such as Fourier and Laplace transforms, accommodation and energy loss, already solved for the T(x) model.

The mathematical single loop formulation of hysteresis loop of a multi-phase substance shows the way in good approximation of the sum of constituent loops, described by tanh functions. That was so far only possible by numerical methods. By doing so, it becomes equivalent to the T(x) model for mathematical operations.

The described method gives an analytical formulation [identical to the T(x) model] of multi-component hysteresis loops described by hyperbolic model, leading to simple solution of difficult problems in magnetism such as loop reversal.

Although the method is an approximation, its accuracy is good enough for use in magnetic research and practical applications in industries engaged in application of magnetic materials.

The hyperbolic model is the only one which separates the magnetic substance, used in practice, to constituent components by describing its multi-component state. Superimposing the components was only possible so far by numerical means. The transformation shown is an analytical approximation applicable in mathematical calculations. The transformation described here enables the user to apply all rules applicable to the T(x) model.

This study equally helps researchers and practical users of the hyperbolic model.

This novel analytical approach to the problem provides an acceptable mathematical solution for practical problems in research and manufacturing. It shows a way to solutions of many difficult problems in magnetism.

The purpose of this paper is to evaluate analytically the magnetic flux density and the magnetic vector potential produced by a linear current density or a linear magnetization inside an arbitrary polyhedron.

In order to obtain expressions of the field and potential integrals in an intrinsic vector form, independently of any reference frame, the approach is to avoid the use of a local coordinate system to perform the integrations.

The expressions obtained contain only the same functions just needed for the uniform sources case, do not introduce any new singularity or discontinuity, and computed results illustrate their effectiveness.

Being in intrinsic vector form the expressions obtained are well suited to cope with the data structures, i.e. faces‐edges and edges‐vertices incidence matrices, provided by unstructured polygonal meshes generators. Their use, especially when dealing with a generic mixed unstructured polygonal mesh, avoids the need of different routines, thus decreasing the complexity of the numerical code.

Besides, avoiding numerical integration, the results do not require usage of any function other than those already defined for the uniform sources case, and do not introduce any new singularity or discontinuity. Thus, the calculation of the magnetic flux density and the magnetic vector potential produced by linear sources needs nearly the same effort as the uniform sources one.

The closed‐form expressions obtained are in intrinsic vector form and can be implemented in a unique routine suitable for the calculation of the magnetic flux density and vector potential produced by any linear or uniform polyhedral source.

The purpose of this paper is to propose modelling 3D eddy current non destructive testing (EC NDT) problems by the finite volume method (FVM). Furthermore, the movement of the probe coil is taken into account.

The nonconforming mesh technique is used to handle the displacement of the probe coil. Thus, the whole problem is divided into two parts; moving part (probe coil) and fixed part (specimen with crack), and then each part meshes independently. A computer code is built under Matlab program to generate 3D nonconforming mesh, to calculate magnetic and electric potentials and to evaluate the impedance change of the coil due to the presence of the crack.

The JSAEM No. 6 problem is used to test the proposed method. The calculated values of the impedance change of the probe coil due to the presence of crack, shows the efficiency of the developed software. A small difference is obtained between calculated values and measured values.

The paper introduces the FVM in solving EC NDT problems where the probe displacement is taken into account.

The aim of the paper is to develop an algorithm based on fuzzy logic (FL) systems for reconstructing cracks shapes, which will be faster and simpler to learn than neural networks, especially in case of large training set.

The inverse model in defectoscopy can be considered as reverse model of the whole measurement process (crack‐sensor‐output). The most important disadvantage of the inverse neural models with dynamic networks is that the performance of training is disappointing due to large training set and many inputs of such networks. The paper proposes the FL as the substitute of neural network. The typical ANFIS networks are sufficient only for simulating systems with small number of inputs. For this reason the paper developed the learning algorithm that produces relatively small number of rules and it can be used in case of systems with hundred of inputs and thousands of training pairs.

This paper provides details about algorithm for reconstructing cracks profiles that produces relatively small number of rules of the fuzzy system. The basis rule of inverse model with moving window for one‐ and multi‐frequency method is described. The results of profile identification in 2D and 3D space for real and simulated data are presented as well.

Generally, the algorithm proposed in this paper can be widely used for simulating multi‐input systems, which are described by a large training set.

This paper aims to deal with some design issues of web applications using partial orders to enhance their navigability and extensibility.

The paper uses a static web applications model as a deterministic labelled transition system in which states are html pages and transitions are urls.

By using this model it is possible, on the one hand, to characterize the temporal evolution of a web application and, on the other, to classify web applications into several types according to the way the information is organized over the web application. This classification captures interesting properties related to the navigability and extensibility of web applications.

These ideas are applied to develop a simple web application, namely, a small virtual museum based on approximations of original paintings. Moreover, based on the extensibility characterization, the virtual museum is extended with different paintings approximations, while preserving navigability properties as well as browsing of paintings' approximations of higher quality resolution.

The results of this work provide useful and practical insights into the design of web applications that ensure navigability and extensibility properties.

A general framework for mobile Web services ‐ which are Web services with the ability to migrate from one host to another ‐ is proposed. In this framework, a mobile Web service is composed of a combination of a BPEL process description, service components to be carried, and migration behavior descriptions using simple but expressive rules. The semantics of the descriptions are defined using Mobile Ambients, namely, a formal model of concurrent mobile processes. With this framework, it is thus possible to add or change migration behaviors without having to modify the BPEL process.

Refined wheat flour is a key ingredient for preparing biscuits because of its gluten content. However, biscuits prepared from refined flour are characterised with low proteins, fat and mineral content. This study aims to improve the nutritive and sensory values of biscuits using roasted coffee and dry kola powders.

The powders were incorporated into biscuits at different levels of 5, 10, 15 and 20 per cent. Proximate and sensory analyses were conducted on the products obtained to determine the effects of the powders on the products.

The coffee biscuits had carbohydrate, protein, fat and energy contents of 57.0-69.5 per cent, 3.3-5.5 per cent, 20.4-31.8 per cent and 389-404 kcal/g, respectively, while those of the kola biscuits were 67.0-70.5 per cent, 1.5-3.5 per cent, 20.4-23.8 per cent and 384-395 kcal/g, respectively. Sensory evaluation of both products showed that coffee significantly improved sensory attributes such as flavour (p = 0.03) and colour (p = 0.00). Thus coffee powder can be used to enhance both the nutritional and sensory qualities of biscuits.

This study was to promote the use of coffee and kola in locally produced baked products and meet consumer demand for healthy and natural foods.

The event‐driven paradigm is appropriate for context aware, distributed applications, yet basic events may be too low level to be meaningful to users. The authors aim to argue that this bottom‐up approach is insufficient to handle very low‐level sensor data or to express all the queries users might wish to make.

The authors propose an alternative model for querying and subscribing transparently to distributed state in a real‐time, ubiquitous, sensor‐driven environment such as is found in Sentient Computing.

The framework consists of four components: a state‐based, temporal first‐order logic (TFOL) model that represents the concrete state of the world, as perceived by sensors; an expressive TFOL‐based language, the Abstract Event Specification Language (AESL) for creating abstract event definitions, subscriptions and queries; a higherorder service (Abstract Event Detection Service) that accepts a subscription containing an abstract event definition as an argument and in return publishes an interface to a further service, an abstract event detector; and a satisfiability service that applies classical, logical satisfiability in order to check the satisfiability of the AESL definitions against the world model, in a manner similar to a constraint‐satisfaction problem.

The paper develops a model‐based approach, appropriate for distributed, heterogeneous environments.

The purpose of this chapter is to explore the possible relation between public policy measures, particularly relating to currency exchange rates, capital flow mechanisms and cross-border insolvency by describing the current state of insolvency regulation in Latin America and some cases that exemplify this public-private dynamic.

The first part of the chapter is based on literature review and content analysis to show the current situation of the regulation of insolvency in Latin America and the evolution of policies shaping the flow of capital and the exchange rates. The second part illustrates the proceedings in selected countries, particularly for Colombia and Venezuela.

The analysis led to the finding that some countries’ policy mechanisms such as in the case of Venezuela might lead to a problem regarding national companies involved in an insolvency proceeding, particularly when the company alleges that public policy in force have changed circumstances leading to the impossibility of paying foreign-located liabilities.

The chapter is based largely on literature review and available data, public legal documents and cases relating public policy and cross-border insolvency; however, insolvency proceedings are not of public domain; thus, there is a large amount of information related with the mentioned cases that remain undisclosed.

This chapter provides a theoretical and practical perspective to analyze cross-border insolvency from a local regulatory framework. It also demonstrates the possible link between public policy and cross-border insolvency.

Nature provides a wide range of structures with different functions, which can serve as a source of research concepts. Based on the bionics principle, a bionic structure was applied to drill pipe specimens to compare the bond strength of paint coatings with and without a bionic ring groove pattern machined on the substrate.

Using the Revetest Xpress Plus scratch tester, the bond strengths of the coatings on the drill pipe with and without the bionic structure were measured and the difference in bond strength was observed.

The critical scratch loads of the surface coatings were 12.77 and 5.4 N. Furthermore, the scratch curve from the plain sample had a larger fluctuation compared to the curve of the samples with bionic ring grooves.

This indicated that the application of a bionic pattern to the surface of the substrate could enhance the bond strength and the degree of mechanical adhesion between the coating and the surface of the drill pipe, which is beneficial for the anti-corrosion performance of the drill pipe.