972 research outputs found
1869, Cornell University Press Podcast, Ep. 118 with Jayita Sarkar, author of Ploughshares and Swords
No full textThis episode, we speak with Jayita Sarkar, author of the new paperback and open access ebook Ploughshares and Swords: India’s Nuclear Program in the Global Cold War. Jay Sarkar is Senior Lecturer in Economic and Social History at the University of Glasgow and the Founding Director of the Global Decolonization Initiative.
We spoke to Jay about how the history of India’s first nuclear weapons test in 1974 has been overshadowed by their 1998 nuclear tests, why the conventional wisdom that India started off its nuclear program with nuclear energy first is in fact incorrect, and the strong connections between India’s nuclear program and their space program
Quadrant analysis of turbulence over a degraded channel‐bed of bimodal sediment, with a definition framework for averaging methods
No full textThis study focuses on the conditional turbulence characteristics in a flow through a degraded channel bed with a mixture of two sediment sizes. After achieving an equilibrium scour condition in a laboratory experiment, three components of instantaneous velocity were recorded for sufficient duration using a Vectrino velocimeter; vertical profiles were measured at three stream-wise locations along the flume axis. An in-depth analysis was performed of conditional statistics for stream-wise and vertical velocity components, Reynolds stresses, turbulent kinetic energy fluxes, along with the percentage occurrence, persistence and frequency of flow in any quadrant. Importantly, the experiment served as a platform for definition of different conditional means: two different approaches, namely total- and quadrant-averaging, were used and the results were systematically compared. The experimental results demonstrate the presence of a top layer where the properties of the flow do not differ much from those of the incoming flow, and of a mixing layer at around the original bed elevation. Sweeps and ejections are the dominant events close to the bed and for higher elevation, respectively. While the percentage occurrence of the sweeps and ejections is higher than that of other events, the frequency of all the events is similar, corresponding to that of the burst cycle. Turbulence is stronger at the locations with flow expansion than at that with flow contraction. Arguments are proposed on the relevance of the two conditional means for phenomenological interpretation of the interactions between a flow and surrounded bodies like sediment, plants and fish. The systematic analysis was performed without applying a hole, that is instead sometimes used in literature works. In this respect, the definition framework is extended to show that, when a hole is applied, four conditional means may be defined, whose variation with the hole size is not always straightforward. The definition framework may give impulse to considering these multiple averaging options in quadrant-based analyses of turbulent flows
An imperfect production process for time varying demand with inflation and time value of money - An EMQ model
No full textThe paper deals with an economic manufacturing quantity (EMQ) model for time-dependent (quadratic) demand pattern. Every manufacturing sector wants to produce perfect quality items. But in long run process, there may arise different types of difficulties like labor problem, machinery capabilities problems, etc.; due to that the machinery systems shift from in-control state to out-of-control state as a result the manufacturing systems produce imperfect quality items. The imperfect items are reworked at a cost to become the perfect one. The rework cost may be reduced by improvements in product reliability i.e.; the production process depend on time and also the reliability parameter. We want to determine the optimal product reliability and production rate that achieves the biggest total integrated profit for an imperfect manufacturing process using Euler-Lagrange theory to build up the necessary and sufficient conditions for optimality of the dynamic variables. Finally, a numerical example is discussed to test the model which is illustrated graphically also. �� 2011 Elsevier Ltd. All rights reserved
An economic production quantity model with stochastic demand in an imperfect production system
No full textThe paper deals with an economic production quantity (EPQ) model for both continuous and discrete random demand of merchandise. Usually, 100% of the total product is not of perfect quality, in practice. A certain percent of the total product is of imperfect quality, which follows a probability distribution. The imperfect quality items are reworked at a cost. The percent of defectiveness in the total product usually increases with an increase in production run time. The associated expected integrated profit is maximised by analytical calculus method. The solution of the model is first derived for a general distribution function and then it is analysed for uniform and Poisson distribution of demand. Numerical examples along with the graphical illustrations are lastly provided to illustrate the study of optimal cost functions of the system. �� 2011 Inderscience Enterprises Ltd
ON IMAGE GRABBING AND PROCESSING FOR MEASUREMENT OF GEOPHYSICAL FLOWS
No full textImage processing is nowadays widely used in laboratory and field measurements of several geophysical processes (e.g., flow field, sediment transport, dam-break flows, and so on). Thanks to a good compromise between large image resolution and memory storage at a relatively low price, the so-called action-cameras provide some advantages in comparison to industrial cameras and advanced vision systems. However, as the lens properties and key camera settings are imposed, pre-processing of the acquired images is necessary. In addition, commercial pre-processing software provided by the manufacturers is often based on default parameters that cannot be appropriately tuned, thus calling for codes to be developed ad hoc. This manuscript presents: (i) visualization experiments of bed-load sediment transport using action-cameras, (ii) a set of pre-processing tools to be applied to the grabbed images and (iii) proof-of-concept results for the statistics of particle kinematics. The findings presented here can be relevant for a variety of processes investigated experimentally
Highly Oxidized Cobalt Porphyrin Dimer: Control of Spin Coupling via a Bridge
No full textA cobalt porphyrin dimer is constructed in which two Co(II)porphyrins are connected covalently through a redox-active diethylpyrrole moiety via a flexible but "nonconjugated" methylene bridge. Upon oxidation with even a mild oxidant such as iodine, each cobalt(II) center and A r porphyrin ring undergo 1e(-) oxidation, leading to the formation of a 4e(-). oxidized cobalt(III)porphyrin dication diradical complex. Other oxidants such as Cl-2 and Br-2 also produce similar results. To stabilize such highly oxidized dication diradicals, the "nonconjugated" methylene spacer undergoes a facile and spontaneous oxidation to form a methine group with a drastic structural change, thereby making the bridge fully pi-conjugated and enabling through-bond communication. This results in a strong spin coupling between two pi-cation radicals which stabilizes the singlet state. The experimental observations are also strongly supported by extensive density functional theory calculations. The present study highlights the crucial role played by the nature of the bridge in the long-range electronic communication
Long-Range Intramolecular Spin Coupling through a Redox-Active Bridge upon Stepwise Oxidations: Control and Effect of Metal Ions
No full textDinickel(II) and dicopper(II) porphyrin dimers have been constructed in which two metalloporphyrin units are widely separated by a long unconjugated dipyrrole bridge. Two macrocycles are aligned somewhat orthogonally to each other, whileoxidation of the bridge generates a fully pi-conjugated butterfly-like structure, which, in turn, upon stepwise oxidations by strongeroxidants result in the formation of the corresponding one- and two-electron-oxidized species exhibiting unusual long-range charge/radical delocalization to produce intense absorptions in the near-infrared (NIR) region and electron paramagnetic resonance (EPR)signals of a triplet state due to interaction between the unpaired spins on the Cu(II) ions. Although the two metal centers have alarge physical separation through the bridge (more than 16 A), they share electrons efficiently between them, behaving as a singleunit rather than two independent centers. Detailed UV-vis-NIR, electrospray ionization mass spectrometry, IR, variable-temperature magnetic study, and EPR spectroscopic investigations along with X-ray structure determination of unconjugated, conjugated, and one electron-oxidized complexes have been exploited to demonstrate the long-range electronic communication through the bridge. The experimental observations are also supported by density functional theory (DFT) and time-dependent DFT calculations. The present study highlights the crucial roles played by a redox-active bridge and metal in controlling the long-range electronic communication
Ferromagnetic Coupling in Oxidovanadium(IV)-Porphyrin Radical Dimers
No full textThree different oxidovanadium(IV) porphyrin dimers with anti, cis, and trans arrangements of the two rings have been synthesized by changing the bridge between the porphyrin macrocycles. This provides a unique opportunity to investigate the role of the bridge and spatial arrangement between the two VIVO centers for their electronic communication and magnetic coupling. They were characterized by the combined application of XRD analysis, UV-vis and electron paramagnetic resonance (EPR) spectroscopy, cyclic voltammetry, magnetic susceptibility, and DFT calculations. One- and two-electron oxidations produce mono- and dication diradical species, respectively, which display an unusual ferromagnetic interaction between the unpaired spins of vanadium(IV) and porphyrin π-cation radical, in contrast to other metalloporphyrin dimers. The oxidized species show a dissimilar behavior between cis and trans isomers. The ferromagnetic coupling occurs between the porphyrin π-cation radical and the unpaired electron of the VIVO ion on the dxy orbital, orthogonal to the porphyrin-based molecular orbitals a1u and a2u
An inventory model with reliability in an imperfect production process
No full textThe paper analyzes an economic manufacturing quantity (EMQ) model with price and advertising demand pattern in an imperfect production process under the effect of inflation. If the machine goes through a long-run process, it may shift from in-control state to out-of-control state. As a result, the system produces imperfect items. The imperfect items are reworked at a cost to make it as new. The production of imperfect quality items increases with time. To reduce the production of the imperfect items, the systems have to more reliable and the produced items depend on the reliability of the machinery system. In this direction, the author considers that the development cost, production cost, material cost are dependent on reliability parameter. Considering reliability as a decision variable, the author constructs an integrated profit function which is maximized by control theory. A numerical example along with graphical representation and sensitivity analysis are provided to illustrate the model. �� 2011 Elsevier Inc. All rights reserved
Some multivariate linear regression testing problems with additional observations
No full textAbstractIn an earlier paper, the present author (Sarkar (1979), Calcutta Statist. Assoc. Bull.28, 47–56) proposed a similar test for a mean testing problem with additional observations on a set of correlated auxiliary variables. This idea has been extended here to cover some multivariate linear regression testing problems with the same type of additional observations on a set of correlated auxiliary variables
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