A new approach to the design of time varying control systems with application to the space shuttle booster

A general approach toward the analysis and design of closed loop control for slowly time-varying linear systems was investigated. The approach is by the method of generalized multiple scales, in which slow and fast dynamics are systematically separated by employing different clocks which measure time at varying rates. The clocks, which are necessarily nonlinear functions of time, so that the system dynamics are asymptotically invariant with respect to the new time scale. A transfer function relating the output to the input for general linear slowly time-varying systems is developed and represents the actual system under certain conditions. The clock functions are shown to satisfy an algebraic characteristic equation and can be determined in general in terms of the coefficients

Information technology and the U.S. productivity acceleration

Information technology ; Productivity

The acceleration in U.S. total productivity after 1995: the role of information technology

Under standard conditions, total factor productivity (TFP) growth measures the pace of innovation or technological change in the economy. This article focuses on the period since the mid-1990s, when TFP accelerated. The authors find that most of the acceleration is accounted for by industries that use, rather than sectors that produce, information technology.Productivity ; Information technology ; Labor productivity

QDEE: Question Difficulty and Expertise Estimation in Community Question Answering Sites

In this paper, we present a framework for Question Difficulty and Expertise Estimation (QDEE) in Community Question Answering sites (CQAs) such as Yahoo! Answers and Stack Overflow, which tackles a fundamental challenge in crowdsourcing: how to appropriately route and assign questions to users with the suitable expertise. This problem domain has been the subject of much research and includes both language-agnostic as well as language conscious solutions. We bring to bear a key language-agnostic insight: that users gain expertise and therefore tend to ask as well as answer more difficult questions over time. We use this insight within the popular competition (directed) graph model to estimate question difficulty and user expertise by identifying key hierarchical structure within said model. An important and novel contribution here is the application of "social agony" to this problem domain. Difficulty levels of newly posted questions (the cold-start problem) are estimated by using our QDEE framework and additional textual features. We also propose a model to route newly posted questions to appropriate users based on the difficulty level of the question and the expertise of the user. Extensive experiments on real world CQAs such as Yahoo! Answers and Stack Overflow data demonstrate the improved efficacy of our approach over contemporary state-of-the-art models. The QDEE framework also allows us to characterize user expertise in novel ways by identifying interesting patterns and roles played by different users in such CQAs.Comment: Accepted in the Proceedings of the 12th International AAAI Conference on Web and Social Media (ICWSM 2018). June 2018. Stanford, CA, US

Why a relatively unknown guru movement is attracting Sri Lankan Tamils in Britain

The move from Sri Lanka to Britain signalled a breakaway from past associations of identity and rootedness which Tamil Hindus had to contend with. The quest for Eelam is now thrust into the makings of a new guru movement striving to gain traction, writes Dhruv Ramnath

The politics of internet infrastructure: communication policy, governmentality and subjectivation in Chhattisgarh, India

This thesis examines the role of internet infrastructure and its associated discourses in processes of governmentality and subject formation in low and middle-income countries of the global South. Using data collected in the central Indian state of Chhattisgarh as its core case, it asks questions about the interrelationship between policy and political discourse, new information and communications infrastructure, private capital, and how citizens come to know and/or experience internet infrastructure in their everyday lives. Since 2014, The National Optical Fibre Network (NOFN, which began in 2011 under the then UPA government) has been reshaped and rebranded as part of ‘Digital India’ by Prime Minister Narendra Modi and his far-right Hindutva Bharatiya Janata Party (BJP). Alongside the cables and connectivity, the BJP and allied Hindu extremist organisations have targeted minorities and women through mob violence and (on and offline) hate speech, while a small number of crony capitalist corporations have seen immense profits. Unpicking the links between these processes, the thesis argues that internet infrastructure has become crucial to expanding a particular unregulated brand of capitalism and to narrowing civic subjectivities. Infrastructures constellate and circulate material and symbolic goods in an institutionalised manner to produce collectivities. Using discourse analysis shows that since the late 1980s, in a context of increasing neoliberalism, internet infrastructure emerged within a discursive regime marked by the fetishisation of systems rationality, enumeration, scientism and economism to produce what can be called digital governmentality. Digital governmentality enables and reinforces a centralised Hindu nationalism mediated by digital technologies and networks. Using semi-structured interviews and participant observation in the city of Ambikapur, and close to 50 villages in Surguja district of Chhattisgarh, data chapters describe a wide range of ‘infrastructural practices.’ The analysis centres on how subjects imagine, frame and experience these practices. Dominant caste groups in Ambikapur seek to subvert governmentality in practice but also uphold and reproduce the rationalities that drive governmental authority – such as efficiency and transparency. Adivasis (indigenous groups) who reside in surrounding rural areas are subject to a political economic regime overdetermined by coal mining and destruction of their land, forests and water resources. Internet infrastructure is non-existent or broken, along with other missing infrastructural substrates such as electricity and water. Adivasis face infrastructural control as a specific mode of governmentality where power is exerted not from the top in directly coercive ways but rather through mundane infrastructural practices, thereby exerting authority in procedural ways. In other instances, Adivasis’ processes of subject formation are entangled with (the reality and promise of) internet infrastructure in complex ways – ranging from cruel optimism to social haunting. The thesis makes an original contribution to the emerging sub-field of infrastructure studies by providing a new way of studying communicative infrastructures involving: a renewed emphasis on relationality (infrastructures, governmentality and subjectivation as relational processes and practices); situating internet infrastructures within broader infrastructures; and a historical analysis of how infrastructure is caught up in exercise of power relations. With significant emphasis on the concerns and interests of indigenous peoples in India, the final chapters of the thesis also contribute to a decolonisation of media and communications as a field, and to avoiding orientalist essentialism

Regime characteristics and health policy reform in the post-colonial state : a comparative case study of the influence of regime characteristics on health human resources policy and policy reform processes in Guyana, Jamaica and Trinidad and Tobago, 1970-1990

In this dissertation, I examine and compare the influence of the following regime characteristics -strength, stability, ideology, democracy and survival/maintenance - on post-colonial health human resources policy processes within one sub-region: the Commonwealth Caribbean; with special reference to Guyana, Jamaica and Trinidad and Tobago (hereinafter called Trinidad) between 1970 to 1990. As I want to comparatively assess the role of these characteristics in post-colonial policy processes, I shall in this chapter place my study within the context of colonial regime characteristics, society and reform processes, assessing its possible influences on post-colonial political developments. This forms the basis of my analysis of policy within these three `post-colonial' states during the 1970s and 1980s. Section One describes the paradox of health and health human resources status in the Commonwealth Caribbean during the 1970s and 1980s. In Section Two, I describe the area under study. In Section Three, I examine possible linkages with the nature of power and reform under colonial regimes. In Section Four, I analyse the influence of regime characteristics on policy processes by assessing health policy outcomes of postwar reform. I begin with an examination of the contradictory status of Commonwealth Caribbean health and health human resources development in the 1970s and 1980s

INFLUENCE OF FLUX DEPOSITION NON-UNIFORMITY ON MOLTEN METAL SPREADING IN ALUMINUM JOINING BY BRAZING

The objective of this thesis is to study the effects of flux deposition non uniformity on spreading of molten metal. Flux deposition non-uniformity here means as to whether the amount of flux deposited in a non-uniform or uniform pattern helps in the better wetting and spreading characteristics of the molten metal or is detrimental to the process. The material selection constraint to the study was imposed by selecting brazing of aluminum i.e., aluminum alloy melting and flow over an aluminum alloy substrate. The study was carried out by conducting a number of Hot Stage microscopy tests using aluminum silicon alloy as the filler metal and Potassium Fluoro Aluminate (Nocolok) as the flux. The flux was applied in different spatial distribution patterns to uncover the varying effects of its distribution on spreading. The uneven pattern of flux deposition indicates the influence on spreading but due to the efficient spreading of flux prior to aluminum melting and associated fuzziness of the achieved coverage distribution the effects are not always conclusive. It has been concluded that non uniform flux deposition does not necessarily mean uneven or less uniform spreading of the molten liquid metal if the spreading of the molten flux is beyond the distance of ultimate metal spreading. This is because, in spite of uneven flux deposition, the flux melts approximately at 560C-570C and spreads on the surface of the metal thereby promoting appreciable spreading and wetting of the molten liquid metal that happens at temperatures above 577C