In planar micropolar elasticity theory, the degree of micropolarity exhibited by a loaded heterogeneous material is quantified by a dimensionless constitutive parameter, the coupling number. Theoretical predictions of this parameter derived by considering the mechanical behaviour of regular, two-dimensional lattices with straight connectors suggest that its value is dependent on the connectivity or topology of the lattice with the coupling number in a square lattice predicted to be notably higher than in its hexagonal counterpart. A second constitutive parameter reflecting the intrinsic lattice size scale, the characteristic length, is also predicted to be topologydependent. In this paper, we compare the behaviour of alternative two-dimensional heterogeneous materials in the context of micropolar elasticity. These materials consist of periodic arrays of circular voids within a polymeric matrix rather than a lattice of straight connectors. Two material variants that differ only in their matrix topology are investigated in particular. Values of the additional micropolar constitutive parameters are obtained for each material from both experimental tests and finite-element analyses. The values determined for these parameters, particularly the coupling number, suggest that their topological dependence differs appreciably from the theoretical predictions of the lattice models.

When performing Information Seeking and Retrieval (ISR) activities, people submit queries, examine results, assess documents and engage with the information to make decisions and complete tasks. All these activities come at a "cost", but within the field of ISR there is no universally accepted definition of the concepts of Cost, Effort and Load (CEL). Instead, researchers have used the same terms interchangeably to describe similar but also different concepts. This lack of shared understanding has led to a disconnect between how these concepts are defined and discussed versus how they are interpreted and measured. Thus, the aim of this paper is twofold: (i) to review the meaning of CEL related concepts used within ISR, and (ii) to create a shared taxonomy of the concepts relating to CEL in ISR. To seed our analysis, we conducted a literature review, where 397 papers were reviewed, and twenty-six papers that explicitly proposed measures or definitions of CEL were selected for analysis. By drawing upon theory from Psychology and other fields, we present the common definitions of CEL in order to ground our discussion of these concepts in ISR. We also highlight the issues associated with CEL measurement in ISR to help researchers reflect on the validity and precision of existing methods. We hope this perspectives paper serves as a basis for a taxonomy of how CEL concepts are used within ISR-where we have provided a series of working definitions that clearly delineate the different concepts being used, investigated and measured in ISR research.

During the Information Search and Retrieval (ISR) process, user-system interactions such as submitting queries, examining results, and engaging with information, impose some degree of demand on the user’s resources. Within ISR, these demands are well recognised, and numerous studies have demonstrated that the Cost, Effort, and Load (CEL) experienced during the search process are affected by a variety of factors. Despite this recognition, there is no universally accepted definition of the constructs of CEL within the field of ISR. Ultimately this has led to problems with how these constructs have been interpreted and subsequently measured. This systematic review contributes a synthesis of literature, summarising key findings relating to how researchers have been defining and measuring CEL within ISR over the past 50 years. After manually screening 1,109 articles, we detail and analyse 91 articles which examine CEL within ISR. The discussion focuses on comparing the similarities and differences between CEL definitions and measures before identifying the limitations of the current state of the nomenclature. Opportunities for future research are also identified. Going forward, we propose a CEL taxonomy that integrates the relationships between CEL and their related constructs, which will help focus and disambiguate future research in this important area.

No abstract