Radiation/convection coupling in rocket motor and plume analysis

A method for describing radiation/convection coupling to a flow field analysis was developed for rocket motors and plumes. The three commonly used propellant systems (H2/O2, RP-1/O2, and solid propellants) radiate primarily as: molecular emitters, non-scattering small particles (soot), and scattering larger particles (Al2O3), respectively. For the required solution, the divergence of the radiation heat flux was included in the energy equation, and the local, volume averaged intensity was determined by a solution to the radiative transfer equation. A rigorous solution to this problem is intractable, therefore, solution methods which use the ordinary and improved differential approximation were developed. This radiation model was being incorporated into the FDNS code, a Navier-Stokes flowfield solver for multiphase, turbulent combusting flows

2021 Graduate Program Rankings for UNLV & UNR

This Fact Sheet presents the 2021 U.S. News and World Report graduate program rankings for the University of Nevada, Las Vegas (UNLV) and the University of Nevada, Reno (UNR). The rankings for 2021 are important when taking into consideration that both UNLV and UNR achieved Carnegie R1 status in 2018. This status marks their place in the top 130 research universities in the country

AN ECONOMIC ANALYSIS OF A CORN-SOYBEAN CROP ROTATION UNDER VARIOUS INPUT COMBINATIONS IN SOUTH CENTRAL TEXAS

Eight input combinations of commercial fertilizer, insecticides, and herbicides on a corn-soybean crop rotation in the Brazos River Bottom of Texas are evaluated. Input combinations which do not fully utilize all three inputs are consistently ranked higher by all criteria as the preferred input strategy for the corn-soybean rotation system. These results, which indicate limited input crop rotations that fall somewhere between the extremes of conventional agricultural production and organic agriculture, deserve further attention as a possible production alternative.corn, limited input, soybean, Crop Production/Industries,

Thermomechanical properties and thermal degradation kinetics of poly(methyl methacrylate) (PMMA) and polycarbonate (PC) filled with cerium-doped yttrium aluminium garnet (Ce:YAG) prepared by melt compounding

This paper reports on the thermomechanical properties and thermal degradation kinetics of poly(methyl methacrylate) (PMMA) and polycarbonate (PC) composites filled with cerium-doped yttrium aluminium garnet (Ce:YAG) at different contents ranging between 0.1 and 5 wt%, and prepared by melt compounding. The interaction between PMMA and the filler was much stronger than that between PC and the filler, and this resulted in a significant improvement in the dynamic mechanical properties of the PMMA composites. The presence of filler did not significantly increase the thermal stability of the PC, while an observable increase in the thermal stability was only observed at higher filler loadings for the PMMA composites. This was attributed to the stronger interaction between Ce:YAG and PMMA and/or its degradation volatiles

Morphology, interfacial interaction, and thermal degradation of polycarbonate/MCM-41 (nano)composites

This article reports on the morphology, interfacial interaction, thermal stability, and thermal degradation kinetics of polycarbonate (PC)/mesoporous silica (MCM-41) composites with various MCM-41 contents, prepared by melt compounding. The composites with low filler loadings (<0.3 wt%) maintained their transparency because of the well dispersed MCM-41 particles, but at higher filler loadings the composites lost their transparency due to the presence of agglomerates. The presence of agglomerates decreased the thermal stability of PC due to the reduced effectiveness of the particles to immobilize the polymer chains, free radicals, and volatile degradation products

Morphology, interfacial interaction, and thermal degradation of polycarbonate/MCM-41 (nano)composites

This article reports on the morphology, interfacial interaction, thermal stability, and thermal degradation kinetics of polycarbonate (PC)/mesoporous silica (MCM-41) composites with various MCM-41 contents, prepared by melt compounding. The composites with low filler loadings (<0.3\u2009wt%) maintained their transparency because of the well dispersed MCM-41 particles, but at higher filler loadings the composites lost their transparency due to the presence of agglomerates. The presence of agglomerates decreased the thermal stability of PC due to the reduced effectiveness of the particles to immobilize the polymer chains, free radicals, and volatile degradation products

Radiation/convection coupling in rocket motors and plumes

The three commonly used propellant systems - H2/O2, RP-1/O2, and solid propellants - primarily radiate as molecular emitters, non-scattering small particles, and scattering larger particles, respectively. Present technology has accepted the uncoupling of the radiation analysis from that of the flowfield. This approximation becomes increasingly inaccurate as one considers plumes, interior rocket chambers, and nuclear rocket propulsion devices. This study will develop a hierarchy of methods which will address radiation/convection coupling in all of the aforementioned propulsion systems. The nature of the radiation/convection coupled problem is that the divergence of the radiative heat flux must be included in the energy equation and that the local, volume-averaged intensity of the radiation must be determined by a solution of the radiative transfer equation (RTE). The intensity is approximated by solving the RTE along several lines of sight (LOS) for each point in the flowfield. Such a procedure is extremely costly; therefore, further approximations are needed. Modified differential approximations are being developed for this purpose. It is not obvious which order of approximations are required for a given rocket motor analysis. Therefore, LOS calculations have been made for typical rocket motor operating conditions in order to select the type approximations required. The results of these radiation calculations, and the interpretation of these intensity predictions are presented herein

Soil erosion assessment on tillage and alternative soil managements in a Sicilian vineyard

Mediterranean crops favour high erosion rates. Vineyards use to reach the highest soil and water losses due to the lack of vegetation cover. A topographical approach by means of the use of vineyards poles as fixed reference point as erosion markers allowed to quantify high and non-sustainable soil erosion rates on the Sicilian vineyards during 9 years. In order to develop strategies to control the soil losses, seven land management were selected and applied in a typical blanc wine grape vineyard located in southwestern Sicily. Comparable plots were managed traditionally using conventional tillage and alternatively using various cover crops: 1) Vicia faba; 2) Vicia faba and Vicia sativa; 3) Trifolium subterraneum, Festuca rubra, and Lolium perenne; 4) Trifolium subterraneum, Festuca rubra, and Festuca ovina; 5) Triticum durum; and 6) Triticum durum and Vicia sativa. To estimate the soil losses the C factor of the USLE was calculated. And to monitor the water and sediment yield, Gerlach troughs were installed on the vineyard inter-row. Runoff was measured after each rainfall event from November 2005 to April 2007. Both runoff and erosion were significantly reduced when cover crops of Trifolium subterraneum, Festuca rubra, and Lolium perenne; and Trifolium subterraneum, Festuca rubra, and Festuca ovina were sown. The least effective management systems for soil erosion were conventional tillage and alternative management using the Vicia faba cover crop. Our results suggest that planting the appropriate cover crops provides an effective soil and water management system for Sicilian vineyards which will make sustainable the wine and grapes production under Mediterranean climate conditions

Green manuring as sustainable management for southern Italy extensive cultivated areas

In the extensively-managed agricultural areas of Sicily, rainfall is often so limited that economically effective annual productions are not feasible. Bare fallow, the most extreme dry-farming technique, seems to be, under such conditions, the only suitable strategy. The introduction in these cropping systems of an annual legume to put early into the soil, as an alternative to bare fallow, may represent a technique able not only to prevent soil erosion, but also to improve the low soil organic matter reserves, with a direct benefit on the following yields and on the whole environment. The trial was aimed to verify the bioagronomical and qualitative behaviour of durum wheat managed under different cropping systems. Results, heavily influenced by very low rainfall (320 mm), stressed the extraordinary productive response of durum wheat cultivated after the green manure legume