Clemson University

About: Clemson University is a education organization based out in Clemson, South Carolina, United States. It is known for research contribution in the topics: Population & Control theory. The organization has 20556 authors who have published 42518 publications receiving 1170779 citations. The organization is also known as: Clemson Agricultural College of South Carolina.

A Detailed Analysis of Film–Cooling Physics: Part I — Streamwise Injection With Cylindrical Holes

Abstract: A previously documented systematic computational methodology is implemented and applied to a jet-in-crossflow problem in order to document all of the pertinent flow physics associated with a film-cooling flowfield Numerical results are compared to experimental data for the case of a row of three-dimensional, inclined jets with length-to-diameter ratios similar to a realistic film-cooling application A novel vorticity-based approach is included in the analysis of the flow physics Particular attention has been paid to the downstream coolant structures and to the source and influence of counterrotating vortices in the crossflow region It is shown that the vorticity in the boundary layers within the film hole is primarily responsible for this secondary motion Important aspects of the study include: (1) a systematic treatment of the key numerical issues, including accurate computational modeling of the physical problem, exact geometry and high-quality grid generation techniques, higher-order numerical discretization, and accurate evaluation of turbulence model performance; (2) vorticity-based analysis and documentation of the physical mechanisms of jet-crossflow interaction and their influence on film-cooling performance; (3) a comparison of computational results to experimental data; and (4) comparison of results using a two-layer model near-wall treatment versus generalized wall functions Solution of the steady, time-averaged Navier-Stokes equations were obtained for all cases using an unstructured/adaptive grid, fully explicit, time-marching code with multigrid, local time stepping, and residual smoothing acceleration techniques For the case using the two-layer model, the solution was obtained with an implicit, pressure-correction solver with multigrid The three-dimensional test case was examined for two different film-hole length-to-diameter ratios of 175 and 35, and three different blowing ratios, from 05 to 20 All of the simulations had a density ratio of 20, and an injection angle of 35 deg An improved understanding of the flow physics has provided insight into future advances to film-cooling configuration design In addition, the advantages and disadvantages of the two-layer turbulence model are highlighted for this class of problems

Effect of water on sulfuric acid catalyzed esterification

Abstract: This paper reports on an investigation into the impact of water on liquid-phase sulfuric acid catalyzed esterification of acetic acid with methanol at 60 °C. In order to diminish the effect of water on the catalysis as a result of the reverse reaction, initial reaction kinetics were measured using a low concentration of sulfuric acid (1 × 10 −3 M) and different initial water concentrations. It was found that the catalytic activity of sulfuric acid was strongly inhibited by water. The catalysts lost up to 90% activity as the amount of water present increased. The order of water effect on reaction rate was determined to be −0.83. The deactivating effect of water also manifested itself by changes in the activation energy and the pre-exponential kinetic factor. The decreased activity of the catalytic protons is suggested to be caused by preferential solvation of them by water over methanol. A proposed model successfully predicts esterification rate as reaction progresses. The results indicate that, as esterification progresses and byproduct water is produced, deactivation of the sulfuric acid catalyst occurs. Autocatalysis, however, was found to be hardly impacted by the presence of water, probably due to compensation effects of water on the catalytic activity of acetic acid, a weak acid.

Positive Youth Development and Relational-Developmental-Systems

Abstract: Interests in the strengths of youth, the plasticity of human development, and the concept of resilience coalesced in the 1990s to foster the development of the concept of positive youth development (PYD). As discussed by Hamilton (1999), the concept of PYD was understood in at least three interrelated but nevertheless different ways: (1) as a developmental process; (2) as a philosophy or approach to youth programming; and (3) as instances of youth programs and organizations focused on fostering the healthy or positive development of youth. We use concepts drawn from relational developmental systems theories and the tripartite conception of PYD suggested by Hamilton as frames to review the literature on (a) the different theoretical models of the PYD developmental process; (b) philosophical ideas about, or conceptual approaches to, the nature of youth programming with a special emphasis on the model of PYD with the most extensive empirical support, the Five Cs Model of PYD; and (c) key instances of programs aimed at promoting PYD. We also discuss the conceptual and practical problems in integrating these three facets of PYD scholarship, and conclude by explaining why understanding complex development requires multimethod integration as well as an integration of ideographic and nomothetic perspectives. Keywords: embodiment; multimethod integration; positive youth development; relational developmental systems theories; resilience; youth programs

Silicon optical fiber.

Abstract: Described herein are initial experimental details and properties of a silicon core, silica glass-clad optical fiber fabricated using conventional optical fiber draw methods. Such semiconductor core fibers have potential to greatly influence the fields of nonlinear fiber optics, infrared and THz power delivery. More specifically, x-ray diffraction and Raman spectroscopy showed the core to be highly crystalline silicon. The measured propagation losses were 4.3 dB/m at 2.936 µm, which likely are caused by either microcracks in the core arising from the large thermal expansion mismatch with the cladding or to SiO2 precipitates formed from oxygen dissolved in the silicon melt. Suggestions for enhancing the performance of these semiconductor core fibers are provided. Here we show that lengths of an optical fiber containing a highly crystalline semiconducting core can be produced using scalable fiber fabrication techniques.

Phosphate Reaction Dynamics in Soils and Soil Components: A Multiscale Approach

Abstract: Macroscopic- to more recent molecular scale investigations have enhanced our knowledge of soil phosphorus (P) chemistry, including the retention/release mechanisms in soils and soil components. Phosphate uptake on metal (oxy)hydroxide and phyllosilicate mineral surfaces and in soils generally increases with decreasing pH. Rapid adsorption kinetics is generally observed on many soil adsorbents at acidic pH. P fixation mechanisms such as inner-sphere complexation and intra- and interparticle diffusion often result in slow P release (i.e., hysteresis and irreversible reactions), creating challenges in remediating agricultural soils with high accumulations of P. This chapter covers some of the historical soil P chemical research findings via macroscopic approaches but focuses on more recent molecular scale approaches for elucidating P retention/release mechanisms.