The critical layer during transition of the spiral Poiseuille flow in an annular gap

Subject of this paper falls under the broad heading of the propagation of disturbances causing transition in a fully developed spiral annular flow. The problem is approached through reformulation of the linearised equations of motion governing small-amplitude disturbances in a parameter space that differs from that conventionally employed for this purpose. The alternative parameter space comprises a suitably defined Reynolds number that is formed with a resultant characteristic velocity which is a vector sum of the axial and azimuthal characteristic velocities, a swirl parameter that is the ratio of the azimuthal to the axial characteristic velocity, and the ratio of the annular gap to the mean diameter of the cylinders. In the limits of the swirl parameter assuming very small or very large values, the newly derived generalised Orr-Sommerfeld and Squire equations for disturbance propagation in the revised parameter space reduce to the corresponding equations that are known and well established for the limiting cases of disturbance propagation as the swirl parameter goes to zero or infinity respectively. Furthermore, they also lead naturally to the criterion that determines from the equations themselves the analytical expression for the location of the critical layer in spiral annular flow, the scaling behaviour of the thickness of the critical layer with the Reynolds number and the swirl parameter, and the equation governing the dynamics of the flow in the critical layer. They thus explicitly reveal the effect of swirl on the critical layer.Comment: 14 pages. The replacement is a continuation of the earlier submissio

Wirkungsbereiche von Frauen im Expressionismus - institutionelle Kunstförderung und literarische Produktion

Im Mittelpunkt der Untersuchung steht die Rolle der Frau bei der Verbreitung, Förderung, öffentlichen Etablierung und Produktion von Kunst und Literatur des Expressionismus. Unter der Schirmherrschaft der engagierten Frauenrechtlerin und Schriftstellerin Ida Dehmel (1870–1940) sowie der ersten promovierten Kunsthistorikerin Deutschlands Rosa Schapire (1874–1954) gelang 1916 in Hamburg die Gründung des „Frauenbundes zur Förderung deutscher bildender Kunst“. Dieser leistete Pionierarbeit auf dem Gebiet der professionell geführten Kunstförderung durch Frauen – in diesem Fall bei der Kunst des Expressionismus. Er steht in der Tradition von Vereinen, die sich im Umfeld der Aktivitäten der deutschen Frauenbewegung herausbildeten, beerbt also letztlich ein politisches Engagement zugunsten eines gesellschaftlichen Status der Frau im Deutschen Kaiserreich und festigt ein neues weibliches Selbstverständnis. Die Bedeutung der Frau in Wirkungsbereichen des Expressionismus beweisen des Weiteren diverse Publikationen in der vielfältigen Zeitungslandschaft des Expressionismus. Es lassen sich zahlreiche literarische Texte von Schriftstellerinnen sowie politische Stellungnahmen von Frauenrechtlerinnen sichten, die eine individuelle, kritischreflexive Sichtweise der wirtschaftlichen und sozialen Stellung der Frau offenbaren

Secure, privacy assured mechanisms for heterogeneous contextual environments

Location information is used to provide a diverse range of services to users such as emergency, navigation, billing, security, information and advertising services. This information is derived from a broad range of indoor and outdoor technologies. The location information thus derived is of different granularity, different co-ordination system and is controlled by numerous service providers. In addition to this, broad selections of devices are used for providing these services. Having a diverse range of applications requiring location information at different levels of granularity, the need to export location information across multiple devices and the existence of different location determination technologies necessitates the need for heterogeneous location network. These networks derive location information from multiple sources and provides various location-based services to users irrespective of the medium, device or technology used. Security, user privacy and management of location information are some of the important issues that need to be addressed. The main contribution of this thesis is the design of a secure and privacy assured heterogeneous location architecture. A formal methodology was chosen to design the heterogeneous location architecture. The design of the architecture resulted in a novel key distribution protocol and a model for information flow that can be easily encapsulated into applications or architectures having similar requirements. The research also resulted in the enhancement of a proposed location framework for securing critical infrastructures using context-aware self-defending objects. The proposed enhanced framework helps to negate the security vulnerabilities introduced through the use of general-purpose computer systems in critical infrastructures

Long term sequelae of multisystem Langerhans' cell histiocytosis

Langerhans' cell histiocytosis (LCH), a chronic granulomatous disorder, can involve one or more organs/tissues including bone, skin, lungs, liver, spleen, bone marrow, pituitary gland and brain. Long term sequelae involving these organs have been reported, but their true prevalence is unknown. In order to assess long term outcome in survivors of multisystem LCH, we performed a cross-sectional study of 40 patients, all of whom were more than 5 years from treatment. Most of the patients had had involvement of bone and/or skin, with other organs being affected less often. They had received a wide range of treatments, including surgery, steroids, radiotherapy and chemotherapy. The study involved clinical examination, MRI scan of brain, endocrine function tests, neuropsychometry, respiratory function tests and audiometry. Most patients had one or more long term sequelae. Half of the patients had endocrine abnormalities, ranging from isolated diabetes insipidus to panhypopituitarism. Brain involvement, including cerebellar involvement, was the most worrying problem, occurring in 10 patients, with severe abnormalities in seven. New findings include the presence of significant learning deficit in 20% of patients, psychological and behavioural abnormalities in 11 patients (27.5%), and an acquired abnormality of the skull base, basilar invagination, in 8 patients (20%). A specific morbidity score was devised and provided an objective measure of outcome. Using this scale only 10 patients (25%) had no sequelae. Eleven (27.5%) had mild impairment which required no specific treatment, 9 (22.5%) had moderate disability, including diabetes insipidus, growth hormone insufficiency and moderate hearing loss, while 10 (25%) had severe disabilities such as panhypopituitarism, learning difficulty, motor deficit and psychological abnormalities resulting in significant handicap and inability to lead an independent adult life. We assessed the Health-Related Quality of Life and found that this correlated with the Morbidity score. Both these measures can easily be applied to any patient with LCH and can be incorporated into long term follow up studies. In conclusion, long term sequelae are more common in survivors of multisystem LCH than previously recognised and cause significant long term morbidity. An important implication of the work presented in this thesis is that carefully planned regular long-term follow up is essential for all patients 'cured' of LCH to ensure that sequelae are recognised early and the appropriate interventions made to improve the patients' "quality of life"

Packet flow analysis in IP networks via abstract interpretation

Static analysis (aka offline analysis) of a model of an IP network is useful for understanding, debugging, and verifying packet flow properties of the network. There have been static analysis approaches proposed in the literature for networks based on model checking as well as graph reachability. Abstract interpretation is a method that has typically been applied to static analysis of programs. We propose a new, abstract-interpretation based approach for analysis of networks. We formalize our approach, mention its correctness guarantee, and demonstrate its flexibility in addressing multiple network-analysis problems that have been previously solved via tailor-made approaches. Finally, we investigate an application of our analysis to a novel problem -- inferring a high-level policy for the network -- which has been addressed in the past only in the restricted single-router setting.Comment: 8 page

TAXONOMY OF SECURITY AND PRIVACY ISSUES IN SERVERLESS COMPUTING

The advent of cloud computing has led to a new era of computer usage. Networking and physical security are some of the IT infrastructure concerns that IT administrators around the world had to worry about for their individual environments. Cloud computing took away that burden and redefined the meaning of IT administrators. Serverless computing as it relates to secure software development is creating the same kind of change. Developers can quickly spin up a secure development environment in a matter of minutes without having to worry about any of the underlying infrastructure setups. In the paper, we will look at the merits and demerits of serverless computing, what is drawing the demand for serverless computing among developers, the security and privacy issues of serverless technology, and detail the parameters to consider when setting up and using a secure development environment based on serverless computin

A Nonlinear Instability Theory for a Wave System causing Transition in Spiral Poiseuille Flows

This paper is on the effect of nonlinearity in the equations for propagation of disturbances on transition in the class of Spiral Poiseuille Flows. The problem is approached from the fundamental point of view of following the growth of initially infinitesimally small disturbances into their nonlinear stage when the effect of Reynolds stresses makes itself felt. To this end a rational scheme of an iterative solution method for the set of Generalised Nonlinear Orr-Sommerfeld, Squire and Continuity equations is proposed. The present proposal for Spiral Poiseuille Flows closely follows that put forth in 1971 by Stuart and Stewartson in their seminal papers on the influence of nonlinear effects during transition in bench-mark flows, which are the flow in the gap between concentric circular cylinders (Taylor instability), and in the plane walled channel flow. The basic feature of the proposed method is the introduction of an Amplitude Parameter and of a slow/long scale variable to account for the effect of growing disturbances within the framework of a rational iteration scheme. It is shown that the effect of amplified disturbances is captured, as in the bench-mark flows, by a Ginzburg-Landau type differential equation for an Amplitude Function in terms of suitably defined slow/long scale variables. However, the coefficients in this equation are numbers that depend upon the flow parameters of the Spiral Poiseuille Flow, which are the Reynolds Number, the Swirl Number, and the geometric parameter of transverse curvature of the flow geometry.Comment: 47 page

Learning German to actively participate in scientific research work in the German speaking parts of the world : a deeply enriching experience

This paper is based on the experience of its author who went to Germany to conduct research work in the area of fluid dynamics, a branch of science/engineering that deals with fluid motion, e.g. of air (wind, smoke), water (in rivers, oceans), oil, blood, or glacier. The research work in Germany was funded through a scholarship awarded to the author by the organization DAAD (Deutscher Akademischer Austauschdienst - German Academic Exchange Service). The scholarship included a four-month German language course at the Goethe Institut. This paper summarizes the author's experiences at learning and using German, both at the Goethe Institute and thereafter