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The finite‐difference discretization required to model accurately very small air gaps between ferromagnetic surfaces can be enormous. Provided the surrounding permeability is high, a simple representation of the air gap can be formulated within a finite‐difference equation, thus substantially reducing the number of nodes required. The method is applied to the determination of the force on a rectangular magnetic filler bar in the centre slot of the pole face of a turbogenerator rotor.

The paper focuses on the question of the extent to which individual preference-based values are suitable in guiding environmental policy and damage assessment decisions. Three criteria for “suitableness” are reviewed: conceptual, moral and legal. Their discussion suggests that: (i) the concept of economic value as applied to environmental resources is a meaningful concept based on the notion of trade-off; (ii) the limitations of the moral foundations of cost-benefit analysis do not invalidate its use as a procedure for guiding environmental decision making; (iii) the input of individual preferences into damage assessment is compatible with the basic foundations of tort law; (iv) using individual preference-based methods provides incentives for efficient levels of due care; (v) determining standing is still very contentious for various categories of users as well as for aggregating non-use values. Overall, the discussion suggests that the use of preference-based approaches in both the policy and legal arenas is warranted provided that they are accurately applied, their limitations are openly acknowledged and they assume an information-providing rather than a determinative role.

Research suggests effective immersive simulations that rely on augmented reality enhance teachers’ self-efficacy and skills (Badiee & Kauffman, 2015). However, there is a gap in the literature as studies have largely ignored their uses in educational leadership programs (Bradley & Kendall, 2015). This study investigated the relationship between application of critical skills within an immersive simulation environment and 26 school or district leaders’ perceptions of self-efficacy in leading a professional learning community (PLC). Two overarching themes materialized from participants: improved general confidence in leading a PLC, and a sense of refined or expanded skills in the context of new approaches to leading PLC. Further studies are needed on the use of immersive simulation as a pedagogical tool and to examine impact for educational leadership practitioners.

Research suggests effective immersive simulations that rely on augmented reality enhance teachers’ self-efficacy and skills (Badiee & Kauffman, 2015). However, there is a gap in the literature as studies have largely ignored their uses in educational leadership programs (Bradley & Kendall, 2015). This study investigated the relationship between application of critical skills within an immersive simulation environment and 26 school or district leaders’ perceptions of self-efficacy in leading a professional learning community (PLC). Two overarching themes materialized from participants: improved general confidence in leading a PLC, and a sense of refined or expanded skills in the context of new approaches to leading PLC. Further studies are needed on the use of immersive simulation as a pedagogical tool and to examine impact for educational leadership practitioners.

The use of electrohydraulic systems is becoming more widespread in industry. The control valve forms a vital component of any such system as it performs both power conversion and amplification. The valve is operated by a solenoid mounted on the end of the valve block. A typical solenoid actuator is shown in Fig. 1. Current through the coil generates a magnetic potential difference across the air‐gap, producing an attractive force between the opposing pole face and armature. The armature moves to close the air‐gap and minimize the reluctance of the magnetic circuit.

Practical aspects of finite‐element modelling of magnetic fields and calculating integral parameters such as a reflected impedance in inductive sensing devices are discussed. The electromagnetics of such sensors is briefly explained and some practical modelling techniques are put forward. Excellent agreement with experiment is reported.

Ceramic superconductors experience losses when carrying alternating currents. A first step in an attempt to macroscopically model the loss mechanism is to consider the ac transport current in a ribbon that has a cross‐section of width much greater than thickness. To some extent high‐temperature superconductors behave in a way similar to type II superconductors in which the loss mechanism is described by the critical state model, where the current is assumed to flow with a constant critical density Jc and is independent of the magnetic flux density B and ∂B/∂t. The dominant mechanism is the irreversible motion of fluxoids due to their interaction with the pinning sites, resulting in a form of hysteretic loss that can be represented in macroscopic terms (in a system with only one component of magnetic field) as proportional to ∫HsdBa/T over a complete cycle of period T, where Hs is the surface magnetic field strength and Ba is the space average value of flux density. However, it is found that the high‐temperature materials exhibit strong flux creep effects, and so the critical state model may not provide a sufficient description. To find an alternative formulation it is necessary to consider the flux creep E‐J characteristic of the ceramic material. If a highly nonlinear expression for the resistivity ? can be found, it may be possible to model the flux and current behaviour as a diffusion process.