64 research outputs found
Concentration in Knowledge Output: A case of Economics Journals
No full textThis paper assesses the degree of author concentration in seven economics journals, which were published in India during 1990-2002. To measure the degree of author concentration, Lotka's Law was used. Moreover, we also make an exploratory analysis of the geographic, economics subfield and institutional concentration in 704 economics journals. An important finding of this paper is that specialized journals in the sample report the highest degree of author concentration. This result is quite similar to the findings by Cox and Chung (1991). Furthermore, there are several instances showing that the journals lean towards certain norms; this may affect the flow of innovative ideas into economics. We conclude that a knowledge activity, involving the high degree of concentration and a biased publication process, may affect the flow of new ideas into the discipline.Concentration, Lotka's Law
Investigation of Gas-Liquid Two-Phase Flow Using Three-Field Two-Fluid Model and Two-Group Interfacial Area Transport Equation in CFD Code
No full textPrior work has shown that a two-fluid model with a single set of constitutive relations is required to predict a wide range of two-phase flow conditions. The current work is a step in that direction. The 3-D three-field two-fluid model with a two-group Interfacial Area Transport Equation (IATE) has been selected as the required framework with the Computational Fluid Dynamics (CFD) code ANSYS-CFX. The objectives of this proposed work are the following: select a set of constitutive relations and implement these models into CFX; evaluate these models for a wide range of test conditions; if required, develop better models for the interfacial transfer mechanisms. Models and constitutive relations were validated against experimental data. The following difference between CFD simulations and experimental results were observed: insufficient diffusion of bubbles; and physically unrealistic void fractions for small bubbles in the near-wall region for highly turbulent flow cases. Bubble diffusion is hypothesized to be insufficient because an important mechanism for diffusion by turbulence-driven random collision of bubbles was not modeled. A diffusion force model based on turbulence induced bubble collision is formulated and assessed against experimental data from bubbly to churn-turbulent flow with uniform and non-uniform inlet injection conditions. Although the overall predictions of void fraction improved with bubble collision diffusion force, a relatively high void fraction is still predicted for smaller Group-1 bubbles in the near-wall region for highly turbulent flow cases belonging to the high liquid velocity regime. A model for lift coefficient with dependency on channel liquid Reynolds number has been proposed; this is found to solve the unrealistic peak near the wall region. Discrepancies were also found in predictions of the coalescence and breakup models of the IATE, especially near flow regime transitions. Therefore, new experiments were performed in the flow transition region with the objective of obtaining accurate flow transition data for assessing the IATE models. The new data were used for evaluation of IATE models in one-dimensional form and possible reasons for discrepancies are discussed
Modeling and simulation of air-water upward annular flow characteristics in a vertical tube using CFD
No full textAnnular flow refers to a special type of two-phase flow pattern in which liquid flows as a thin film at the periphery of a pipe, tube, or conduit, and gas with relatively high velocity flows at the center of the flow section. This gas also includes dispersed liquid droplets. The liquid film flow rate continuously changes inside the tube due to two processes-entrainment and deposition. To determine the liquid holdup, pressure drop, the onset of dryout, and heat transfer characteristics in annular flow, it is important to have proper knowledge of flow characteristics. Especially a better understanding of entrainment fraction is important for the heat transfer and safe operation of two-phase flow systems operating in an annular two-phase flow regime. Therefore, the objective of this work is to develop a computational model for the simulation of the annular two-phase flow regime and assess the various existing models for the entrainment rate. In this work, Computational Fluid Dynamics (CFD) in ANSYS FLUENT has been applied to determine annular flow characteristics such as liquid film thickness, film velocity, entrainment rate, deposition rate, and entrainment fraction for various gas-liquid flow conditions in a vertical upward tube. The gas core with droplets was simulated using the Discrete Phase Model (DPM) which is based on the Eulerian-Lagrangian approach. The Eulerian Wall Film (EWF) model was utilized to simulate liquid film on the tube wall. Three different models of Entrainment rate were implemented and assessed through user-defined functions (UDF) in ANSYS. Finally, entrainment for fully developed flow was determined and compared with the experimental data available in the literature. From the simulations, it was obtained that the Bertodano correlation performed best in predicting entrainment fraction and the results were within the ±30 % limit when compared to experimental data
Field Assessment of Blackgram (Vigna Mungo L. Hepper) Genotypes Against Major Insect Pests in Subtropical Region of Nepal
No full textDirect damage due to insect pests is one of the major causes limiting the yield potential of blackgram (Vigna mungo L. Hepper) in Nepal. A total of 17 blackgram genotypes were screened for resistance to major insect pests, including aphid (Aphis craccivora Koch.), whitefly (Bemisia tabaci Genn.), hairy caterpillar (Spilosoma obliqua Walker) and pod borer (Helicoverpa armigera Hubner) in National Maize Research Program, Rampur, Chitwan during summer season of 2018 and 2019. The design of the experiment was randomized complete block having three replications. Genotypes were sown on first week of August in a unit plot size of 4 rows of 2 m long with 40 cm row to row spacing and continue plant to plant spacing was maintained and net harvested plot was 3.2 square meters. The recommended dose of fertilizer was 20:40:20 N:P2O5:K2O kg/ha and seed rate 25 kg/ha. The package of agronomic practices was followed as per national recommendation. Data on insects were collected by counting the number of insects per plant. The yield and yield components were recorded at harvest. All screened genotypes differed significantly (p<0.05) for insect population, yield and yield components. From two years field data, three genotypes BLG0069-1, BLG0036-1 and BLG0079-1 had lower number of above mentioned insect populations, exhibited more resistant in both years and produced higher grain yield (~1.5 t/ha) than other genotypes. These genotypes might be useful for the development of major insect pest tolerant high yielding blackgram variety in subtropical region of Nepal
Lotka' s Law, Co-authorship and Interdisciplinary Publishing
No full textThe robustness or breakdown of Lotka's law about the frequency distribution of scientific productivity depends on scientific cooperation, counting methods, interdisciplinary publishing and selection methods for sample collections. We have chosen to analyse the relationship using Mandelbrot's equivalent distribution model because this model is sensitive and uses the original data (scores). Five sets of authors and publications, the two sets used by Lotka, a set from High Energy Physics, a set from Microbiology and a set based on applicants to a research programme promoting young researchers have been used. It is shown that even for a sample of authors in High-Energy Physics with extremely strong co-authorship, Mandelbrot's distribution law is robust when complete-normalized (fractional) counting is used whereas complete counting results in a breakdown. In the field of Microbiology with much weaker cooperation, both counting methods result in a breakdown of Mandelbrot's law. Today a field like Microbiology with the corresponding set of journals, probably has a large content of interdisciplinary publishing and therefore no more fulfills the precondition of Lotka's law, that the total production of the authors (sources) is considered. For a set of applicants for the Emmy Noether Programme of the German Research Foundation. Mandelbrot's law breaks down despite the fact that all publications co-authored by the applicants are taken into account. In agreement with Bayes' theorem of conditional probabilities these results lead to the conjecture that any selection process of authors and/or publications causes a breakdown of Mandelbrot's law and, as a consequence Lotka's law
CFD Analysis of S-Gamma Model Coupled with Two-Group Interfacial Area Transport Equations and AMUSIG Model for a Large Diameter Pipe
No full textThis paper describes the modeling of flow regimes beyond bubbly flows in a large diameter channel considering polydispersity and bubble induced turbulence using the Eulerian two-fluid approach. A two-bubble-group approach with two-group interfacial area transport equations (IATEs) is used to demonstrate flow phenomena in a large diameter pipe. Source and sink terms for mass and momentum exchanges between the two groups of bubbles and for bubble coalescence and breakup mechanisms are implemented. For predicting particle size and its distribution, S-Gamma (S?) model is used. The S? model with two-group IATEs are evaluated by comparing local distributions of void fractions and Sauter mean diameters with results of adaptive-multiple-size-group (AMUSIG) models and experimental dataset developed by Schlegel et al., (2012) for model validations. It shows that two-group IATEs with S? model predict reasonably accurate flow characteristics of beyond bubbly flow regimes, but also show shortcomings in their accuracies predicting local distributions, which imply that further studies for modeling of interfacial force are needed
Information and intellectual property: The global challenges
No full textThe paper analyses the contribution of 'golden papers' - seminal works whose ideas remain as fresh and relevant today as when they were first published decades ago - and which continue to dominate academic discourse among successive generations of scholars. The authors analyse why two works written within an industrial development context: The simple economics of basic scientific research, by Richard Nelson (1959) and Kenneth Arrows Economic Welfare and the Allocation of Resources for Invention (1962), are so relevant in today’s knowledge-driven economic paradigm. Focusing on the papers’ application to current global policy debates on information/knowledge and intellectual property, they argue that while the context has changed the essential nature of innovation - driven by widespread access to the ability to replicate and improve - remains the same. Hence a focus on endogenous innovation policy is as relevant today as it was 50 years ago.knowledge economy, science and technology, innovation, intellectual property rights, institutional change
Role of C- reactive proteins in cerebro-spinal fluid in differentiating pyogenic from nonpyogenic meningitis
No full textBackground:In developing countries like India meningitis is major cause of morbidity and mortility because of delay in proper diagnosis and consequently delay in proper treatment. For the appropriate treatment of meningitis, differentiation of various types of meningitis is essential. The diagnosis of meningitis in a govt. hospitals is usually made by examination of CSF, Gram staining, AFB, CSF culture and associated clinical findings. All these laboratory techniques have their limitations. So we need a diagnostic test which is rapid, reliable and cost effective. In the present study we used CRP levels in CSF sample to differentiate pyogenic from non-pyogenic meningitis and to establish a cut off level for CRP.Methods: The study is a hospital based prospective study carried out in the setting of department of pathology, microbiology, casuality and various wards of Netaji Subash Chandra Bose Medical College Jabalpur (M.P) India during November 2014 to October 2015. During study period we took samples (Blood and CSF) from 138 cases of suspected meningitis.Results: Value of CRP was 32.50645±2.032886 in PM cases, 1.543373±0.195181 in TBM cases and VM cases value were 2.420833±0.357502. Statistically significantly higher value was observed with pyogenic meningitis cases compared to TBM and VM cases. (p<0.001). At 10 U/L cut off value, sensitivity and specificity of CSF- CRP was 93.5% and 94.4% respectively.Conclusions: On the basis of present study we concluded that CRP can be used as a rapid confirmatory test since elevated CRP are highly suggestive of pyogenic meningitis.
Implementation of Tritium Transport in a Gas-liquid Contactor CFD Simulation of Tritium Extraction from Lead-lithium in ANSYS Fluent
No full textModifications to the Computational Fluid Dynamic (CFD) software ANSYS Fluent were done to quantify and characterize tritium transport in gas-liquid contactors (GLCs). A double-slit, Ergun-like equation was employed for the porous media model, with Ergun coefficients validated with Sulzer\u27s Sulcol software. Tritium transport from PbLi within the GLC was verified against analytical models. The geometry of the CFD model was based on the MELODIE GLC experiment. The hydrodynamic CFD pressure drop results align well with Sulcol estimations and fall between the predictions of the analytical Delft-Olujić and Billet and Schultes models. In terms of mass transfer efficiency, traditional mass transfer models showed a significant deviation from experimental results when using varying values of H solubility in PbLi. A saturation phenomenon occurred when utilizing high solubility values for hydrogen in PbLi. A modified film theory mass transfer coefficient incorporating either the Delft-Olujić or Billet and Schultes wettability model yielded CFD-predicted extraction efficiencies that closely matched experimental measurements
Verification of TFIT Code Numerical Method for Flow Excursion Simulation
No full textThis research is aimed towards accurately modeling and predicting the onset of the two-phase flow excursion instability using the code TFIT (Two Fluid Interfacial Temperature). In order to do this we first had to show that the numerical diffusion of the code’s finite difference equations could be reduced to an insignificant level by decreasing the mesh size.
Understanding and being able to accurately model flow excursion can help us understand how to prevent the potential negative effects of this instability. We are using a two-fluid model with physics-based closure relations. The results will be validated against the experimental data available in the literature. This research could give us a better understanding of the transition between instabilities and would contribute to the safety measures used in the coolant systems of nuclear power plants to prevent fuel rod burnout.
But first it is necessary to test the effect that the mesh size has on the error. We ran a mesh independence test. The results from the independence test showed that decreasing the mesh size did drastically decrease the error but after a certain mesh size, further reduction caused no further decrease in artificial diffusion
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