Simulation of the Internal Conditions During The Hot-Pressing Process

The development of a two-dimensional mathematical model to describe the internal conditions during the hot-compression of wood-based composite panels is discussed. Five primary variables were considered during the model development: air content, vapor content, bound water content, and temperature within the mat, and the extent of the cure of the adhesive system characterized by the cure index. Different heat and mass transfer processes were identified for the transport of the heat and of the moisture phases. The heat was transported by conduction and convection due to a temperature gradient, while the water phases were transported by bulk flow and diffusion due to total pressure and partial pressure gradients. The resulting differential-algebraic equation system was solved by the method of lines. The spatial derivatives of the conduction terms were discretized by central differences, while the spatial derivatives of the convection terms were discretized according to an upwind scheme. The resulting ordinary differential equations in the time variable were solved by a freely available differential-algebraic system solver (DDASSL). The mathematical model predicted temperature, moisture content, partial air and vapor pressures, total pressure, relative humidity, and extent of adhesive cure within the mat structure under a typical hot-compression process. A set of three-dimensional profiles describes the evolution of these variables with time, in the thickness and width dimensions of the mat. The model results allow a better understanding of the interacting mechanisms involved in a complex production process. The model also supports optimization of the hot-pressing parameters for improved quality of wood-based panel products, while reducing pressing time

Land-surface influences on weather and climate

Land-surface influences on weather and climate are reviewed. The interrelationship of vegetation, evapotranspiration, atmospheric circulation, and climate is discussed. Global precipitation, soil moisture, the seasonal water cycle, heat transfer, and atmospheric temperature are among the parameters considered in the context of a general biosphere model

FY 1991 scientific and technical reports, articles, papers, and presentations

Formal NASA technical reports, papers published in technical journals, and presentations by MSFC personnel in FY 1991 are presented. Papers of MSFC contractors are also included. The information in this report may be of value to the scientific and engineering community in determining what information has been published and what is available

The Influence of Selected Wood Characteristics and Composites Production Parameters on the Sorption Behavior of Wood Materials

The goal of this research was to investigate the influence of selected wood characteristics and composites production parameters on the sorption behavior of wood materials. A better understanding of the sorption behavior of different wood structures and types could be useful in protecting wood against wood deterioration. The differences among tree ring locations within the stem cross-section have not been explained in terms of sorption behavior. The purpose of the first task was to investigate the effect of differences among earlywood, latewood, and tree ring location within the stem crosssection on the water vapor sorption. A loblolly pine (Pinus taeda) tree was cut into earlywood and latewood from the 2nd to 50th tree rings. A sorption kinetics test was conducted from 11% to 89% RH. Results showed that earlywood had higher sorption rates and diffusion coefficients than latewood, while outer tree rings had higher sorption rates and diffusion coefficients than inner tree rings. An understanding of sorption behavior of individual fibers with varying refiner pressure is necessary to better engineer wood fiber-based composites. The second task was to investigate water vapor sorption of refined fiber as affected by steam pressure using small-scale measurements. Juvenile and mature loblolly pine wood was refined at 2 to 18 bar of steam pressure. Fiber properties were determined by Scanning Electron Microscope (SEM), Dynamic Contact Angle (DCA), X-ray Diffraction (XRD), and a water activity meter. A sorption kinetics test was conducted from 11% to 89% RH. Higher rates of sorption were found in juvenile fiber refined under low steam pressure. Higher water activity and lower cystallinity was found at low-steam-pressure-refined fibers. The volume of oriented strandboard (OSB) produced has significantly increased over the last few decades. Wood, resin, and wax play a key role in manufacture and inservice properties. How resin and wax affect the water vapor sorption behavior of resinated and waxed strands remain unclear. The third task was to investigate the effect of processing parameters on the sorption behavior of wood strands under varying environmental conditions. Loblolly pine strands were created with 2 to 4% and 0.5 to 1.5% for resin and wax loading. The resinated strand was pressed with different platen temperatures (120, 160, and 200°C) and compression rates (1.05 and 1.65). A sorption kinetics test was conducted from 11% to 89% RH. Higher resin and wax loading levels resulted in reduced water vapor sorption in early sorption periods. Higher press platen temperatures and compression rates also decreased the sorption properties of resinated loblolly pine strands. Wax loading had more influence on sorption properties than resin loading. Press platen temperatures had more influence on sorption behavior than compression rate

Effect of curing conditions and harvesting stage of maturity on Ethiopian onion bulb drying properties

The study was conducted to investigate the impact of curing conditions and harvesting stageson the drying quality of onion bulbs. The onion bulbs (Bombay Red cultivar) were harvested at three harvesting stages (early, optimum, and late maturity) and cured at three different temperatures (30, 40 and 50 oC) and relative humidity (30, 50 and 70%). The results revealed that curing temperature, RH, and maturity stage had significant effects on all measuredattributesexcept total soluble solids

The SURFEXv7.2 land and ocean surface platform for coupled or offline simulation of Earth surface variables and fluxes

CC Attribution 3.0 License.Final revised paper also available at http://www.geosci-model-dev.net/6/929/2013/gmd-6-929-2013.pdfInternational audienceSURFEX is a new externalized land and ocean surface platform that describes the surface fluxes and the evolution of four types of surface: nature, town, inland water and ocean. It can be run either coupled or in offline mode. It is mostly based on pre-existing, well validated scientific models. It can be used in offline mode (from point scale to global runs) or fully coupled with an atmospheric model. SURFEX is able to simulate fluxes of carbon dioxide, chemical species, continental aerosols, sea salt and snow particles. It also includes a data assimilation module. The main principles of the organization of the surface are described first. Then, a survey is made of the scientific module (including the coupling strategy). Finally the main applications of the code are summarized. The current applications are extremely diverse, ranging from surface monitoring and hydrology to numerical weather prediction and global climate simulations. The validation work undertaken shows that replacing the pre-existing surface models by SURFEX in these applications is usually associated with improved skill, as the numerous scientific developments contained in this community code are used to good advantage

Urban Green Infrastructure: Modelling and Implications to Environmental Sustainability

abstract: The combination of rapid urban growth and climate change places stringent constraints on multisector sustainability of cities. Green infrastructure provides a great potential for mitigating anthropogenic-induced urban environmental problems; nevertheless, studies at city and regional scales are inhibited by the deficiency in modelling the complex transport coupled water and energy inside urban canopies. This dissertation is devoted to incorporating hydrological processes and urban green infrastructure into an integrated atmosphere-urban modelling system, with the goal to improve the reliability and predictability of existing numerical tools. Based on the enhanced numerical tool, the effects of urban green infrastructure on environmental sustainability of cities are examined. Findings indicate that the deployment of green roofs will cool the urban environment in daytime and warm it at night, via evapotranspiration and soil insulation. At the annual scale, green roofs are effective in decreasing building energy demands for both summer cooling and winter heating. For cities in arid and semiarid environments, an optimal trade-off between water and energy resources can be achieved via innovative design of smart urban irrigation schemes, enabled by meticulous analysis of the water-energy nexus. Using water-saving plants alleviates water shortage induced by population growth, but comes at the price of an exacerbated urban thermal environment. Realizing the potential water buffering capacity of urban green infrastructure is crucial for the long-term water sustainability and subsequently multisector sustainability of cities. Environmental performance of urban green infrastructure is determined by land-atmosphere interactions, geographic and meteorological conditions, and hence it is recommended that analysis should be conducted on a city-by-city basis before actual implementation of green infrastructure.Dissertation/ThesisDoctoral Dissertation Civil and Environmental Engineering 201

Development of vacuum insulation panel with low cost core material

This thesis was submitted for the degree of Doctor Philosophy and awarded by Brunel University LondonBrunel Universit