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To analyze effectively magnetic shielding effects by shields with fine structure.
Simplification of the fine structure makes it possible to analyze them efficiently. The authors have introduced a homogenization method to estimate effective permeability of magnetic composite structure for the static field. The homogenization method is applied to the analysis of magnetic shields composed of steel plates and steel rods against DC power lines to test its feasibility.
The properties of the magnetic shielding are analyzed by using the homogenization method. The errors of the magnetic fields increase in case of very few layers.
The simplification of the magnetic shields with fine structure by using the homogenization method makes it possible to analyze efficiently magnetic shielding effects, although the accuracy becomes worse in case of very few layers.
This paper describes a boundary element analysis of magnetic shieldings for electron microscopes. Since the thickness of the shielding layer is considerably small compared…
This paper describes a boundary element analysis of magnetic shieldings for electron microscopes. Since the thickness of the shielding layer is considerably small compared with its overall size, numerical analysis of electromagnetic fields inside the layer leads to an ill‐conditioned matrix. This problem can be overcome by analytical evaluation of the interior electromagnetic field, which yields the impedance boundary condition (IBC) valid for static and eddy current fields, which expresses the relationship between the electromagnetic fields on both surfaces of the layer. In this paper the magnetic fields around a shielding layer are analyzed by the boundary element method under the IBC on the shielding layer. Two‐dimensional and axisymmetric magnetic fields are analyzed to evaluate the shielding efficiency of shielding immersed in an ac magnetic field. It is shown that magnetic disturbances can be reduced to less than one‐hundredth inside a shielding consisting of double shielding layers.
To describe the wide range of possible applications of high temperature superconductors (HTSCs) (e.g. magnetic bearings, levitation systems or electrical machines) several…
To describe the wide range of possible applications of high temperature superconductors (HTSCs) (e.g. magnetic bearings, levitation systems or electrical machines) several appropriate calculation algorithms have been developed. They determine the force interaction between a superconductor and any even multidimensional magnetic field excitation system. Especially good agreements between experiments and computed results have been obtained for the Vector‐Controlled Model, which seems to be the best approximation of the macroscopic superconductivity behaviour. The validation of this model by means of measurements makes it a powerful tool for the design and optimisation of any HTSC application in the field of force generation. It can be used not only for the designing of levitation applications, but also to help the understanding of the flux penetration, flux trapping and magnetisation of bulk superconductors in non‐uniform magnetic fields. By means of this model, the force interaction between superconductors and external magnetic fields for practical multi‐polar configurations, e.g. superconducting levitation systems or inherently stable superconducting bearings has been determined. Furthermore, the time dependency of the forces taking flux flow and flux creep into account, can be considered.
The calculation of magnetic shielding with ferromagnetic material by an effective reluctivity method and a time step method based on the finite element calculation is…
The calculation of magnetic shielding with ferromagnetic material by an effective reluctivity method and a time step method based on the finite element calculation is investigated. The calculation results of both methods are compared with measurement results and with each other in order to check their reliability and accuracy. It turns out that both methods give similar results for the field inside the shielding material, whereas in the surrounding air the effective reluctivity method gives more accurate results than the present time step method.
Purpose – We examine the reading lists for required foundational library and information science (LIS) courses at the top 20 American Library Association-accredited LIS…
Purpose – We examine the reading lists for required foundational library and information science (LIS) courses at the top 20 American Library Association-accredited LIS programs in North America; explore the extent to which critical race theory (CRT) and other critical literatures, methods, and approaches were engaged; and discuss the implications of the findings for LIS education.
Methodological Approach – We conducted quantitative and qualitative content analyses of foundational required readings for the top 20 Master of Library Science/Master of Library and Information Science programs (as ranked by U.S. News & World Report). The sampling process was twofold. The initial sampling included development of the foundational course sample, and the secondary sampling included development of the sample of required readings.
Findings – The vast majority of the required foundational courses examined provided students with little to no exposure to CRT or critical theory.
Originality/Value – CRT and its related concepts provide a structural framework for preparing LIS students and graduates to recognize and address racism, to understand “how power and privilege shape LIS institutions and professional practice” (Cooke, Sweeney, & Noble, 2016, p. 107), and to embrace social justice as an LIS value. Incorporating CRT into existing courses is the first step in pushing the profession in this direction.
The Preisach and Jiles models for hysteresis are applied to reconstruct BH loops from measurement data for constructional steel St 37. The distribution function for the…
The Preisach and Jiles models for hysteresis are applied to reconstruct BH loops from measurement data for constructional steel St 37. The distribution function for the Preisach model is determined from all the available, 18, measured BH loops starting from the initial curve. The five unknown parameters in Jiles model are determined by the simulated annealing method to minimize the distance between the largest measured BH loop and the corresponding computed loop. Although Jiles model gives differences from the measured BH loops for low applied fields, it provides results fitted well to the largest measured loop for which the parameters are optimized. The Preisach model gives good fitting over a wide range of the applied field.
To present and explore the need for alternative narratives to be included in library and information science (LIS) curricula.
This chapter examines LIS and its curricula through the Storytelling Project (STP) framework. STP theorizes that there are four types of stories: stock, concealed, resistance, and emerging/transforming stories.
Each of these story types exists in LIS, but in unequal proportion. LIS curriculum should include more stories of resistance and more emerging/transforming stories. These stories should also facilitate the emergence of the “new storytellers,” faculty members and instructors in LIS graduate programs who are working diligently to incorporate new stories into the classroom by creating learning environments that accommodate and encourage discussions of race, privilege, social justice, and other necessary and difficult issues.
The STP story typology forms a counter-storytelling matrix that can allow LIS educators an opportunity to diversify their content and teaching styles, ultimately enriching their students, their programs, and the profession.
This chapter expands LIS pedagogy by infusing elements of diversity, social justice, and theory from the related field of education.
Presents an application of the boundary element method to the analysis of magnetic fields in materials for which permeability depends non‐linearly on spatial co‐ordinates…
Presents an application of the boundary element method to the analysis of magnetic fields in materials for which permeability depends non‐linearly on spatial co‐ordinates. A new approach is proposed, which relates the Green’s function for non‐linearly dependent permeability to Green’s function of the Laplace equation in free space by adequate variable transformation. This can be done for very broad class magnetic permeabilities. These permeable functions, which cannot be directly used in such transformations, can be approximated by series of admissible functions.
The boundary element method is a useful method for the analysis of field problems involving unbounded regions. Therefore, the method can be used advantageously in…
The boundary element method is a useful method for the analysis of field problems involving unbounded regions. Therefore, the method can be used advantageously in combination with the finite element method. This is sometimes called a combination method and it is suitable as a picture‐frame technique. Although this technique attains good accuracy, the matrix of the discretized equation is not banded, since it is a dense matrix. In this paper, we propose an infinite boundary element which divides the unbounded region radially. By the use of this element, the bandwidth of the discretized system matrix does not increase beyond that of the finite element region and its original matrix structure is maintained. The infinite boundary element can also be applied to homogeneous unbounded field problems, for which the Green's function of the mirror image is difficult to use. To illustrate the validity of the proposed technique, some numerical calculations are demonstrated and the results are compared with those of the usual combination method and the method using the hybrid‐type infinite element.