An automatic assembly for investigating the relaxation properties of polymers over a wide range of temperatures and medium moisture contents

1978 ◽  
Vol 14 (3) ◽  
pp. 463-466
Author(s):  
R. V. Lutsyk ◽  
A. F. Mel'nikova ◽  
A. V. Movchanyuk
Keyword(s):  
Automatic Assembly ◽  
Relaxation Properties ◽  
Moisture Contents ◽  
Wide Range

Tensile behaviour of radiata pine with different moisture contents at elevated temperatures

Holzforschung ◽  
2012 ◽  
Vol 66 (5) ◽  
pp. 659-665 ◽  
Author(s):  
Hamish Pearson ◽  
Brian Gabbitas ◽  
Sigurdur Ormarsson
Keyword(s):  
Elevated Temperatures ◽  
Mechanical Design ◽  
Control Strategies ◽  
Radiata Pine ◽  
Tensile Behaviour ◽  
Drying Time ◽  
Moisture Contents ◽  
Wide Range ◽  
Tensile Elastic Modulus ◽  
Increasing Temperature

Abstract The aim of this study was to obtain tensile elastic modulus (EM) information for radiata pine (Pinus radiata D. Don) sapwood in tangential grain direction, over a temperature range of 70°C to 150°C for a wide range of moisture contents. Such information is scarce, probably because of difficulties with research equipment design and process control strategies to perform accurate tests. As expected, EM dramatically decreased with increasing temperature and moisture content. The results were modelled to yield a relationship between stress and strain. The results were also successfully transposed into a mastercurve based on temperature-moisture equivalence through a modified form of the Williams, Landel, and Ferry equation for amorphous polymers. This result is consistent with the view that wood is visco-plastic around the glass transition zone of the ligno-hemicellulosic matrix. It is demonstrated that moisture and temperature can play a significant role in reducing stress during drying, regardless of the drying time. Properties of wood, such as tensile elastic information at elevated temperatures, are important for mechanical design, distortion modelling and understanding the fundamental behaviour of wood in general.

Rapid reduction of nitrate in soil re-moistened after air-drying

1972 ◽  
Vol 78 (3) ◽  
pp. 405-412 ◽  
Author(s):  
P. A. Cawse ◽  
D. Sheldon
Keyword(s):  
Nitrous Oxide ◽  
Calcareous Soil ◽  
Calcareous Soils ◽  
Soil Nitrate ◽  
Nitrite Concentration ◽  
Rapid Reduction ◽  
Air Drying ◽  
Moisture Contents ◽  
Respiration Rates ◽  
Wide Range

SUMMARYWhen an organic calcareous soil was air-dried for 2 days and re-wetted to a wide range of moisture contents, well below saturation, nitrite accumulated within 1–2 days. At the same time much nitrate was formed and more carbon dioxide was released than from soil kept moist. On further incubation of re-wetted soil for 3–5 days, the nitrite concentration decreased rapidly. Since 15N-labelled nitrate was reduced to nitrite after air-drying and re-wetting, and no nitrite was formed in autoclaved soil, nitrate was microbially reduced.Eighty-three per cent of added 15N tracer was recovered from the soil 2 days after re-wetting to 70 % moisture, indicating that 58 ppm N had been lost; 10 ppm N of this was released as nitrous oxide. Autoclaved soil to which nitrite was added did not evolve nitrous oxide, suggesting that nitrite was reduced biologically rather than decomposed chemically.Three other soils were treated similarly; two, which were non-calcareous, accumulated no nitrite. Fresh calcareous soils with high respiration rates and good capacities to denitrify when waterlogged are most likely to form nitrite after drying and moderate re-wetting.

Humidity Effects on Fluidic Temperature Devices

1974 ◽  
Vol 7 (12) ◽  
pp. 463-468
Author(s):  
John O. Geremia ◽  
Chih Wu
Keyword(s):  
Moisture Content ◽  
Ideal Gas ◽  
Humidity Effects ◽  
Dry Air ◽  
Moisture Contents ◽  
Air Stream ◽  
Wide Range ◽  
Vapour Mixture ◽  
Thermodynamic Equations ◽  
The Ideal

A fluidic temperature device, designed by and obtained from The Harry Diamond Laboratories, was tested for stability when subjected to a variation of moisture content in an air stream. The device proved highly stable over a wide range of moisture contents. Slight variations in frequency were consistent with the variation predicted by the ideal gas behaviour of an air-water vapour mixture. The device is stable enough to be calibrated with dry air and corrected to any other humidity condition by application of the thermodynamic equations governing ideal gas mixtures.

Soil moisture dynamics and smoldering combustion limits of pocosin soils in North Carolina, USA

2009 ◽  
Vol 18 (3) ◽  
pp. 326 ◽  
Author(s):  
James Reardon ◽  
Gary Curcio ◽  
Roberta Bartlette
Keyword(s):  
North Carolina ◽  
Soil Moisture ◽  
Organic Soils ◽  
Data Logging ◽  
Soil Horizons ◽  
Soil Moisture Dynamics ◽  
Moisture Contents ◽  
Smoldering Combustion ◽  
Wide Range ◽  
Moisture Dynamics

Smoldering combustion of wetland organic soils in the south-eastern USA is a serious management concern. Previous studies have reported smoldering was sensitive to a wide range of moisture contents, but studies of soil moisture dynamics and changing smoldering combustion potential in wetland communities are limited. Linking soil moisture measurements with estimates of the sustained smoldering limits of organic soils will improve our understanding of changes in ground fire potential over time. Seasonal soil moisture trends were monitored in six North Carolina coastal plain pocosin sites from January 2005 to November 2007. Measurements of the root-mat upper soil horizons were sampled at 2-week intervals while measurements of lower horizon muck (sapric) soil moisture contents and watertable depths were made with automated data logging equipment. The watertable and soil moisture responses were influenced by seasonal and yearly differences in precipitation and hydrologic factors. The maximum estimated probabilities of sustained smoldering were highest in the fall of 2007 and lowest in 2006. Watertable depth was not a consistent predictor of the smoldering combustion potential in the upper organic soil horizons. Maximum Keetch–Byram Drought Index values on all sites were between 500 and 662 during 2005 and 2007 and these values were not consistent with measured soil moistures.

scholarly journals Effects of Moisture Content and Grain Direction on the Elastic Properties of Beech Wood Based on Experiment and Finite Element Method

Forests ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 610
Author(s):  
Wei-Lian Fu ◽  
Hui-Yuan Guan ◽  
Sawata Kei
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Moisture Content ◽  
Elastic Properties ◽  
Elastic Constants ◽  
Beech Wood ◽  
Wood Products ◽  
Moisture Contents ◽  
Wide Range ◽  
Element Method

Beech wood (Fagus sylvatica L.) is used in a wide range of wood products. However, the influence of the wood’s moisture content on its mechanical functions will affect its structural strength. It would be complicated and time-consuming to experimentally measure wood’s mechanical functions under different moisture contents. Therefore, it is necessary to establish a prediction formula between the moisture content and elastic constants, and then verify whether its mechanical functions within a wide range of moisture content can be studied by using FEM (finite element method). In this study, which was based on experimentation, we studied the influence of a wide range of moisture contents and grain direction on the compressive yield strength, modulus of elasticity and shear modulus of beech wood. The relationship between the moisture content and elastic constants was established; the moisture sensitivities of different elastic parameters were obtained. Ultimately, compression curves under different moisture contents were plotted out, using both FEM and experimentation. According to the results, the interaction of moisture with the grain direction had a significant effect on the elastic constants of wood, with grain direction having a greater effect on the elastic properties than the moisture content. Moreover, the decay function can be used to fit these experimental results well. The elastic constants of beech wood responded differently to the moisture content, depending on whether it was in the longitude or transverse directions. Finally, this study proved the feasibility of using FEM to simulate wood’s compressive performance with a wide range of moisture contents.

Analysis of Wood Combustion Based on the First and Second Laws of Thermodynamics

1987 ◽  
Vol 109 (3) ◽  
pp. 129-141 ◽  
Author(s):  
A. Dadkhah-Nikoo ◽  
D. J. Bushnell
Keyword(s):  
Moisture Content ◽  
Energy Content ◽  
Wood Combustion ◽  
Moisture Contents ◽  
Direct Combustion ◽  
Air Temperatures ◽  
Wide Range ◽  
Laws Of Thermodynamics ◽  
Different Types ◽  
Wood Fuels

Wood is a highly flexible fuel which can be used in a variety of ways for energy generation. Direct combustion of wood is the oldest method of utilization of this renewable energy source. This paper presents an analysis of wood combustion based on the first and second laws of thermodynamics, using a computer program developed for this study. Since the moisture content of the available wood fuels vary over a wide range, special attention is given to the effects of moisture content on the exergy and energy content of the wood. Because of the wide variation in particle size and moisture content of the wood fuels, different types of combustion systems have been designed and are utilized in industry. Each combustion system uses a certain amount of combustion air and is designed for a certain range of combustion air temperatures and wood fuel moisture contents. The effects of these variables on wood combustion and the efficiencies of the process have been studied and are presented in this paper. To point out the importance and differences between efficiencies that are commonly used, several efficiencies based on the first and the second laws of the thermodynamics are calculated and compared. Based on the results presented in this report, it is concluded that, over the range of variables studied, the most efficient conditions for wood combustion can be achieved by using the minimum amount of excess air at highest permissible temperature. It is also concluded that the lower moisture contents result in higher combustion efficiencies.

scholarly journals Two New Moisture Sensors for Soilless Growing Media

HortScience ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 763A-763
Author(s):  
Krishna Nemali* ◽  
Marc van Iersel
Keyword(s):  
Practical Significance ◽  
Comparison Study ◽  
Medium Effects ◽  
Greenhouse Production ◽  
Greenhouse Crops ◽  
Moisture Contents ◽  
Growing Medium ◽  
Wide Range ◽  
The Common

Monitoring moisture status of the growing medium is essential as growth and quality of greenhouse crops largely depend on the amount of available water. Recently, two new types of moisture sensors have been developed (ECH2 O, Decagon devices, Inc., Pullman, Wash.; Theta probe ML2X, Delta -T devices Ltd., Burwell, Cambridge, U.K.). We studied the performance of these sensors for measuring the volumetric water content (VWC) of a soilless growing medium. We also tested the sensitivity of these sensors to temperature and electrical conductivity (EC) of the growing medium. Our results indicate that these sensors can be calibrated and used effectively for measuring a wide range of moisture contents in the growing medium; however media specific calibration may be required. Regression analysis indicated that the output of ECH2 O probes was affected by changes in the EC and temperature of the growing medium. Effects of EC were too small to be of practical significance, while the measured VWC increased by 0.003 m3/m3 for each °C increase in temperature. The output from the Theta Probe was not affected by changes in the EC or temperature of the growing medium. In a comparison study, both probes were found to give similar estimates of the VWC of the growing medium within the common range seen under greenhouse production.

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