Open University

About: Open University is a education organization based out in Milton Keynes, United Kingdom. It is known for research contribution in the topics: Context (language use) & Population. The organization has 11702 authors who have published 35020 publications receiving 1110835 citations. The organization is also known as: Open University, The & Open University.

Power, Participation and Political Renewal: Case studies in public participation

Abstract: Introduction Participation in context Inclusive democracy and social movements Shaping public participation: public bodies and their publics Re-forming services Neighbourhood and community governance Responding to a differentiated public Issues and expertise Conclusion: power, participation and political renewal.

Knowledge Worker Roles and Actions— Results of Two Empirical Studies

Abstract: Reinhardt, W., Schmidt, B., Sloep, P. B., & Drachsler, H. (2011). Knowledge Worker Roles and Actions - Results of Two Empirical Studies. Knowledge and Process Management, 18(3), 150–174. doi: 10.1002/kpm.378 Online: http://onlinelibrary.wiley.com/doi/10.1002/kpm.378/abstract

Hierarchical Threshold Secret Sharing

Abstract: We consider the problem of threshold secret sharing in groups with hierarchical structure. In such settings, the secret is shared among a group of participants that is partitioned into levels. The access structure is then determined by a sequence of threshold requirements: a subset of participants is authorized if it has at least k0 0 members from the highest level, as well as at least k1 > k0 members from the two highest levels and so forth. Such problems may occur in settings where the participants differ in their authority or level of confidence and the presence of higher level participants is imperative to allow the recovery of the common secret. Even though secret sharing in hierarchical groups has been studied extensively in the past, none of the existing solutions addresses the simple setting where, say, a bank transfer should be signed by three employees, at least one of whom must be a department manager. We present a perfect secret sharing scheme for this problem that, unlike most secret sharing schemes that are suitable for hierarchical structures, is ideal. As in Shamir's scheme, the secret is represented as the free coefficient of some polynomial. The novelty of our scheme is the usage of polynomial derivatives in order to generate lesser shares for participants of lower levels. Consequently, our scheme uses Birkhoff interpolation, i.e., the construction of a polynomial according to an unstructured set of point and derivative values. A substantial part of our discussion is dedicated to the question of how to assign identities to the participants from the underlying finite field so that the resulting Birkhoff interpolation problem will be well posed. In addition, we devise an ideal and efficient secret sharing scheme for the closely related hierarchical threshold access structures that were studied by Simmons and Brickell.

Complete controllability of quantum systems

Abstract: Sufficient conditions for complete controllability of N-level quantum systems subject to a single control pulse that addresses multiple allowed transitions concurrently are established. The results are applied in particular to Morse and harmonic-oscillator systems, as well as some systems with degenerate energy levels. Controllability of these model systems is of special interest since they have many applications in physics, e.g., Morse and harmonic oscillators serve as models for molecular bonds, and the standard control approach of using a sequence of frequency-selective pulses to address a single transition at a time is either not applicable or only of limited utility for such systems.