Investigation of hypersonic shock-induced combustion in a hydrogen-air system

A numerical study is conducted to simulate the ballistic range experiments at Mach 5.11 and 6.46. The flow field is found to be unsteady with periodic instabilities originating in the stagnation zone. The unsteadiness of the flow field decreased with increase in the Mach number, thus indicating that it is possible to stabilize such flow fields with a high degree of overdrive. The frequency of periodic instability is determined using Fourier power spectrum and is found to be in good agreement with the experimental data. The physics of the instability is explained by the wave interaction models available in the literature

Possible textures of the fermion mass matrices

Texture specific fermion mass matrices have played an important role in understanding several features of fermion masses and mixings. In the present work, we have given an overview of all possible cases of Fritzsch-like as well as non Fritzsch-like texture 6 and 5 zero fermion mass matrices. Further, for the case of texture 4 zero Fritzsch-like quark mass matrices, the issue of the hierarchy of the elements of the mass matrices and the role of their phases have been discussed. Furthermore, the case of texture 4 zero Fritzsch-like lepton mass matrices has also been discussed with an emphasis on the hierarchy of neutrino masses for both Majorana and Dirac neutrinos.Comment: 21 pages, 3 figure

Paradoxical Identity: The changing nature of architectural work and its relation to architects' identity

In this article, we explore what happens in professional formation when the locus of its meaning, as it has been formed, is increasingly contradicted by professional practice. Specifically, we explore the problematic nature of architects’ professional identity that is constituted in terms of the primacy of design aesthetics, in contexts where practice denies this identification. We highlight the tensions between identity and practices and suggest that while architects’ traditional self-identification enables perpetuation of the profession’s identity, it challenges the profession’s standing in its relations with other professions and occupations. We refer to this as a paradox of identity. Although much has been written about the profound changes occurring in professional practices and professional jurisdictions, scant attention has been given to the ways in which professionals shape their identities in the context of changing practices. We conducted a year-long ethnography of contemporary architects engaged in large and complex projects in order to examine both the architects’ and the profession’s identity. Our contributions are threefold. First, we conceptualize misalignments between professional identity and professional practice as identity paradox that has consequences for identity work among professionals. Second, we highlight how professional identity construction is organized around competing and paradoxical identification. Third, the article contributes to sociological studies of architecture by generating insights about the identity work of architects engaged in large multi-organizational projects

Professional identity and anxiety in architect-client interactions

© 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group. Large-scale construction projects increasingly have powerful and knowledgeable clients as project owners with whom professionals, such as architects, must interact. In such contexts, clients may have a significant impact on the constitution of a coherent and stable professional identity. Based on qualitative interviews with 50 architects across four large multidisciplinary professional service firms (PSFs) located in Sydney, Australia, supplemented by ethnographic observations, this article explores how architects constitute their identity in interactions with clients. The findings led us to conceptualise professional–client interactions in terms of two overarching discursive strategies deployed by architects in attempts to manage clients that are powerful and knowledgeable: best for client and best for project. We illustrate the anxieties that architects experience and suggest that attempts to secure professional identity may result in (re)producing an enduring sense of anxiety with unintended consequences for project outcomes and organisational performance

Parametric study of shock-induced combustion in a hydrogen air system

A numerical parametric study is conducted to simulate shock-induced combustion under various free-stream conditions and varying blunt body diameter. A steady combustion front is established if the free-stream Mach number is above the Chapman-Jouguet speed of the mixture, whereas an unsteady reaction front is established if the free-stream Mach number is below or at the Chapman-Jouguet speed of the mixture. The above two cases have been simulated for Mach 5.11 and Mach 6.46 with a projectile diameter of 15 mm. Mach 5.11, which is an underdriven case, shows an unsteady reaction front, whereas Mach 6.46, which is an overdriven case, shows a steady reaction front. Next for Mach 5. 11 reducing the diameter to 2.5 mm causes the instabilities to disappear, whereas, for Mach 6.46 increasing the diameter of the projectile to 225 mm causes the instabilities to reappear, indicating that Chapman-Jouguet speed is not the only deciding factor for these instabilities to trigger. The other key parameters are the projectile diameter, induction time, activation energy and the heat release. The appearance and disappearance of the instabilities have been explained by the one-dimensional wave interaction model

Investigation of shock-induced combustion past blunt projectiles

A numerical study is conducted to simulate shock-induced combustion in premixed hydrogen-air mixtures at various free-stream conditions and parameters. Two-dimensional axisymmetric, reacting viscous flow over blunt projectiles is computed to study shock-induced combustion at Mach 5.11 and Mach 6.46 in hydrogen-air mixture. A seven-species, seven reactions finite rate hydrogen-air chemical reaction mechanism is used combined with a finite-difference, shock-fitting method to solve the complete set of Navier-Stokes and species conservation equations. The study has allowed an improved understanding of the physics of shock-induced combustion over blunt projectiles and the numerical results can now be explained more readily with one-dimensional wave-interaction model

Physisorption of Nucleobases on Graphene

We report the results of our first-principles investigation on the interaction of the nucleobases adenine (A), cytosine (C), guanine (G), thymine (T), and uracil (U) with graphene, carried out within the density functional theory framework, with additional calculations utilizing Hartree--Fock plus second-order Moeller-Plesset perturbation theory. The calculated binding energy of the nucleobases shows the following hierarchy: G > T ~ C ~ A > U, with the equilibrium configuration being very similar for all five of them. Our results clearly demonstrate that the nucleobases exhibit significantly different interaction strengths when physisorbed on graphene. The stabilizing factor in the interaction between the base molecule and graphene sheet is dominated by the molecular polarizability that allows a weakly attractive dispersion force to be induced between them. The present study represents a significant step towards a first-principles understanding of how the base sequence of DNA can affect its interaction with carbon nanotubes, as observed experimentally.Comment: 7 pages, 3 figure