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Iron-core electromagnets are widely used as applied-field switches in high-temperature superconducting (HTS) flux pumps. It was recently reported that the critical current ( I c ) of the HTS wire is suppressed by up to 45% in the air gap of the iron core. Here, it is reported that the self-field I c of a single tape (unifilar) is suppressed from 357 A to 195 A while in the air gap of an iron core, agreeing closely with the previous study. This is extended by showing that the I c response to a perpendicular magnetic field is asymmetric, with a peak I c of 249 A found to be at 0.16 T of applied magnetic field. This effect can be eliminated using an anti-parallel current configuration (bifilar), which is shown experimentally to recover close to the no-core self-field I c of 357 A with no observed asymmetry. The results of both types of switch configurations are closely replicated in finite-element modelling using COMSOL Multiphysics®. This is caused by the asymmetric interaction between the self-induced magnetic field of the HTS switch element and the magnetic circuit of the iron-core electromagnet. [ABSTRACT FROM AUTHOR]

This article describes how a sociologist becomes a consultant and some practical considerations that come from the experiences of the authors in consulting work. The initial contact may be direct or indirect, and may be initiated by the sociologist or by the client. Indirect initiation by the client occurs when the client approaches the university, college or a department seeking the name of an individual for the consultant role. Direct initiation occurs when the client approaches the sociologist on the basis of reputation or reported professional performance in a particular field. The lack of clarity of a beginner concerning the consultant role is usually exceeded by that of the prospective client. One initial contact has been achieved you will want to set up a conference with the prospective client. He will probably have little idea what a sociologist is and vaguely understand what sociologists do. The first meeting should be used to find out about the structure of the organization and the personalities of the people who make the decisions. The least involved role is that of limited consultant, he comes in for a specific time and gives verbal advice about data collection, sampling, questionnaire construction and others. The second role is that of consultant. This is like the first role but you will deliver a written report on the organization. The third role is that of evaluator. This role includes your taking the middle-range goals and objectives as given by your client and constructing a questionnaire or other appropriate device to measure how well these goals are being achieved. The final role to be considered is that of researcher. This is not the role that your clients will be asking you to perform but it is the role that you, as a sociologist, will want to do.