The development and breakaway of a compressible air jet with streamline curvature and its application to the coanda flare

This study concerns an underexpanded jet, issuing from a convergent slot into quiescent air, as it is deflected by a convex surface of constant radius. Emphasis Is placed on the mechanism of breakaway, a phenomenon whereby the jet leaves the surface tangentially. An optical system based on the standard Z-type Schlieren configuration and capable of interferometric, Schlieren and shadowgraph techniques has been designed. The techniques are interchanged simply, a laser source being employed for Interferometry and a Xenon spark source for Schlieren and shadowgraph. Vibrations limit the interferometry and improvements are discussed. Shadowgraph and both spark and continuous Schlieren techniques gave good results. Total pressure traverses and surface oil flow visualization show that the influence of secondary flows on breakaway is small. Measurements of the coefficient of discharge show an increase both as the stagnation pressure Is Increased and as the slot width is reduced. The existence of a separation bubble has been established from surface static pressure measurements and shadowgraph and Schlieren photographs. Surface oil flow visualization shows a region of reversed flow withhin the bubble. The bubble grows as the stagnation pressure Is increased and eventually causes breakaway. A potential flow calculation method using the method of characteristics has been developed. Calculation of a fully attached Jet is inaccurate because the separation bubble is ignored. A calculation using the measured surface static pressures accurately predicts the main features of the first shock cell. Reattachment occurs further downstream of the jet and its breakaway should involve a coupling of the solutions of the outer shear layer, potential core and separated boundary layer, the latter including reversed flow

Optimal tracking for pairs of qubit states

In classical control theory, tracking refers to the ability to perform measurements and feedback on a classical system in order to enforce some desired dynamics. In this paper we investigate a simple version of quantum tracking, namely, we look at how to optimally transform the state of a single qubit into a given target state, when the system can be prepared in two different ways, and the target state depends on the choice of preparation. We propose a tracking strategy that is proved to be optimal for any input and target states. Applications in the context of state discrimination, state purification, state stabilization and state-dependent quantum cloning are presented, where existing optimality results are recovered and extended.Comment: 15 pages, 8 figures. Extensive revision of text, optimality results extended, other physical applications include

Choice of Measurement Sets in Qubit Tomography

Optimal generalized measurements for state estimation are well understood. However, practical quantum state tomography is typically performed using a fixed set of projective measurements and the question of how to choose these measurements has been largely unexplored in the literature. In this work we develop theoretical asymptotic bounds for the average fidelity of pure qubit tomography using measurement sets whose axes correspond to vertices of Platonic solids. We also present complete simulations of maximum likelihood tomography for mixed qubit states using the Platonic solid measurements. We show that overcomplete measurement sets can be used to improve the accuracy of tomographic reconstructions.Comment: 13 Pages, 6 figure

Characterizing quantum dynamics with initial system-environment correlations

We fully characterize the reduced dynamics of an open quantum system initially correlated with its environment. Using a photonic qubit coupled to a simulated environment we tomographically reconstruct a superchannel---a generalised channel that treats preparation procedures as inputs---from measurement of the system alone, despite its coupling to the environment. We introduce novel quantitative measures for determining the strength of initial correlations, and to allow an experiment to be optimised in regards to its environment.Comment: 10 pages, 15 figure

Towards a typology of collusive industrial networks:dark and shadow networks

The prevailing understanding of collusive B2B networks is primarily based on the theories of industrial economists and organizational criminologists. ‘Successful’ collusive industrial networks (such as price-fixing cartels) have been seen to endure due to formal managerial structures of coordination and control. In this paper, we seek to transcend and challenge the understanding of these illegal forms of co-opetition by drawing on evidence from an in-depth examination of four price-fixing cartels that were facilitated chiefly by marketers. Our contribution introduces the notion of ‘shadow networks’ (networks where although attempts are made to ensure secrecy, multilateral modes of network structure dominate akin to ‘normal’ managerial endeavours such as joint ventures) and ‘dark networks’ (networks which appear more opaque and secretive through the adoption of bilateral modes of network structure and limited bureaucracy) to illustrate the types of collusive network forms that may exist. In addition, this allows us to build a deeper understanding of collusive network forms and related inter-firm interaction for an industrial marketing audience. We provide implications for marketing practice, theory, and policy. Specifically, we outline how organizations and the marketing function can perform self-administered antitrust audits in order to help avoid breaches of antitrust. Further, we consider the importance of the two forms of collusive inter-firm networks uncovered where marketers have attempted to render these secret from antitrust agencies, introducing a relatively new line of inquiry to the industrial marketing literature

Involving customers in innovation: knowledgeability and agency as process variables

Purpose: Recent research places an increased emphasis on the inclusion of the customer in value creation, learning, and innovation processes yet there remains a gap in our understanding of just how such customer involvement may work. This paper seeks to address this gap by examining two aspects of customer involvement; their knowledgeability and their agency. In addition, we explore three boundaries (semantic, syntactic, and pragmatic) across which relationship development occurs and which mayfacilitate and/or inhibit value co-creation, collaborative learning, and innovation processes. Design/methodology/approach: We utilised three case studies. Two were large scale construction projects in the UK, and one was a global professional accounting firm in the USA. Findings: Customers may become frustrated if not allowed to exercise their agency. However, their involvement can create tensions for suppliers who may have to become more tolerant of divergent goals. In respect of knowledgeability, we found that constraint satisfaction is important in allowing customers to reconcile their personal knowledge schema with that of the collective schema. However, we also noted that customer knowledgeability brings with it challenges for suppliers, who must find ways to add value for such customers. Research implications: We pose a number of further questions relating to the agency and knowledgeability of customers and their inclusion in value co-creation, collaborative learning, and innovation processes. We also highlight the need for guidance in identifying and minimising the barriers to crossing semantic, syntactic and pragmatic boundaries between customers and suppliers. Originality/value: We make an important contribution to research in the field in that we investigate how the inclusion of the customer in business networksalters current assumptions and practices

Measuring Entangled Qutrits and Their Use for Quantum Bit Commitment

We produce and holographically measure entangled qudits encoded in transverse spatial modes of single photons. With the novel use of a quantum state tomography method that only requires two-state superpositions, we achieve the most complete characterisation of entangled qutrits to date. Ideally, entangled qutrits provide better security than qubits in quantum bit-commitment: we model the sensitivity of this to mixture and show experimentally and theoretically that qutrits with even a small amount of decoherence cannot offer increased security over qubits.Comment: Paper updated to match published version; 5 pages, 4 figures, images have been included at slightly lower quality for the archiv