Optimized design of a hypersonic nozzle

Conventional procedures for designing nozzles involve the design of an inviscid contour (using the method of characteristics) that is corrected with a displacement thickness calculated from boundary-layer theory. However, nozzles designed using this classical procedure have been shown to exhibit poor flow quality at Mach numbers characteristic of hypersonic applications. The nozzle to be designed will be a part of the NASA HYPULSE facility which is being used for hypervelocity flight research. Thus, the flow quality of the nozzle is a critical question that needs to be addressed. Design of nozzles for hypersonic applications requires a proper assessment of the effects of the thick boundary layer on the inviscid flowfield. Since the flow field is largely supersonic, the parabolized form of the Navier-Stokes (PNS) equations can be used. The requirement of a uniform flow at the exit plane of the nozzle can be used to define an objective function as part of an optimization procedure. The design procedure used in this study involves the coupling of a nonlinear (least-squares) optimization algorithm with an efficient, explicit PNS solver. The thick boundary layers growing on the walls of the nozzle limit the extent of the usable core region (region with uniform flow) for testing models (especially rectangular). In order to maximize the region of uniform flow, it was decided to have the exit plane of this nozzle to be (nearly) rectangular. Thus, an additional constraint on the nozzle shape resulted, namely the nozzle will have a shape transitioning from a circular one at the inlet to that of a rectangle at the exit. In order to provide for a smooth shape transition, the cross sectional contour of the nozzle is defined by a superellipse. The nozzle is taken to be a meter in length. The axial variations of the major and minor radii of the superellipse are governed by cubic splines. The design parameters are the coefficients of the splines associated with the local nozzle wall slopes. Extensive calculations have been made (with a three-dimensional Euler code) to understand the effects of various parameters such as location of the knot points of the spline function, different ways of characterizing the uniformity of the flow in the exit plane, as well as the effect of constraining the area of the nozzle to be invariant. Turbulent flow (measurements indicate that the flow at the nozzle inlet is turbulent) calculations are now being performed (with the inviscidly designed nozzle contours) to assess the flow quality

Rebirth of self and identity: an analysis of Meena Alexander’s Manhattan music

This paper illustrates how Meena Alexander explores the prospect of outgrowing the sense of rootlessness of Asian immigrants in America in Manhattan Music. According to her it is managed by vocational and social engagements, and bonding with fellow expatriates. Alienation, search for identity and emotional insecurity of immigrants have hitherto been the dominant themes of diasporic literature. However, in the context of globalisation the concept of ‘home’ as a giver of emotional security cries for a redefinition. Meena Alexander’s Manhattan Music analyses the impact of transplantation from natal to post-marital space in the lives of women characters. Sandhya Rosenblum, Draupadi Dinkins, Sakhi and a few others despite the differences in their upbringing, experience the trauma of dislocation at first, but outgrow the same. Sandhya wrestles between her conflicting roles, a mother in New York and a daughter revisiting India, and in neither does she feel at home. But after her recovery from the shock of suicide, she escapes from racial thinking. It constitutes a rebirth of self for her. Similarly, Draupadi, the alter-ego of Sandhya, comes to realise being an American is only a part of her Self. Meena Alexander’s central vision in all her writings is the need of the immigrants for adapting themselves to the changed environment to find meaning in their lives. In Manhattan Music, the writer emphasises this idea by portraying Sandhya’s inner conflict in her adopted country at first and later her awakening to the truth that we all have several “homes” or as Homi Bhabha suggests we have to “desire for social solidarity: I am looking for the join…I want to join…I want to join.” (Bhabha 1994, p.18

The discourse of climate change: a corpus-based approach

Based on Goffman’s definition that frames are general ‘schemata of interpretation’ that people use to ‘locate, perceive, identify, and label’, other scholars have used the concept in a more specific way to analyze media coverage. Frames are used in the sense of organizing devices that allow journalists to select and emphasise topics, to decide ‘what matters’ (Gitlin 1980). Gamson and Modigliani (1989) consider frames as being embedded within ‘media packages’ that can be seen as ‘giving meaning’ to an issue. According to Entman (1993), framing comprises a combination of different activities such as: problem definition, causal interpretation, moral evaluation, and/or treatment recommendation for the item described. Previous research has analysed climate change with the purpose of testing Downs’s model of the issue attention cycle (Trumbo 1996), to uncover media biases in the US press (Boykoff and Boykoff 2004), to highlight differences between nations (Brossard et al. 2004; Grundmann 2007) or to analyze cultural reconstructions of scientific knowledge (Carvalho and Burgess 2005). In this paper we shall present data from a corpus linguistics-based approach. We will be drawing on results of a pilot study conducted in Spring 2008 based on the Nexis news media archive. Based on comparative data from the US, the UK, France and Germany, we aim to show how the climate change issue has been framed differently in these countries and how this framing indicates differences in national climate change policies

A corpus-based investigation of junk emails

Almost everyone who has an email account receives from time to time unwanted emails. These emails can be jokes from friends or commercial product offers from unknown people. In this paper we focus on these unwanted messages which try to promote a product or service, or to offer some “hot” business opportunities. These messages are called junk emails. Several methods to filter junk emails were proposed, but none considers the linguistic characteristics of junk emails. In this paper, we investigate the linguistic features of a corpus of junk emails, and try to decide if they constitute a distinct genre. Our corpus of junk emails was build from the messages received by the authors over a period of time. Initially, the corpus consisted of 1563, but after eliminating the duplications automatically we kept only 673 files, totalising just over 373,000 tokens. In order to decide if the junk emails constitute a different genre, a comparison with a corpus of leaflets extracted from BNC and with the whole BNC corpus is carried out. Several characteristics at the lexical and grammatical levels were identified

On The Role Of Accountability And Incentives In Obtaining Quality Process Documentation

The importance of managing process knowledge in complex activities such as information product development is well recognized in recent research. However, successful implementation of a traceability scheme(that provides the ability to follow the life of artifacts created during systems development)  to manage process knowledge requires the development of appropriate incentives to knowledge workers. Based on a review of accounting and economic literature on managerial incentives and  accountability as well as empirical studies of nearly thirty organizations, we propose a series of hypotheses that predict the influence of an organizational culture of accountability and presence of financial and other incentives on obtaining quality process documentation in organizations

Human–Felid Conflict in Corridor Habitats: Implications for Tiger and Leopard Conservation in Terai Arc Landscape, India

We use the Rajaji-Corbett corridor in the Terai Arc Landscape (TAL) in India to examine the pattern of human–felid conflict in wildlife corridors and its implications for the long-term persistence of tigers (Panthera tigris) and leopards (Panthera pardus) in the landscape. We administered a questionnaire survey of people residing in and around the corridor and also examined forest department records. Results revealed that leopards caused more frequent losses, whereas tigers caused greater economic losses. Local communities perceived leopards as a bigger threat than tigers, due to the intrusive nature of leopards (i.e., entering villages and houses and carrying off livestock and, in some cases, children). Although people currently are tolerant of wild felids, they are likely to become hostile to them in the future; we discuss specific strategies to resolve the conflicts