scholarly journals Artifacts in electrical measurements on wood caused by non-uniform moisture distributions

Holzforschung ◽  
2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Maria Fredriksson ◽  
Emil Engelund Thybring ◽  
Samuel L. Zelinka
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Electrical Conductance ◽  
Percolation Model ◽  
Conditioning Procedure ◽  
Electrical Measurements ◽  
Moisture Contents ◽  
Constant Relative Humidity ◽  
Water Saturated ◽  
Better Than

AbstractThis paper examines how the moisture conditioning method affects the electrical conductance of wood. A widely used dataset was acquired by Stamm in 1929 who used a method of conditioning where water-saturated wood specimens were partially dried, sealed and left for a period of time for moisture to be redistributed before the electrical conductance was measured. However, more recent measurements combined conditioning above saturated salt solutions and pressure plate/pressure membrane techniques to obtain equilibrium moisture contents at constant relative humidity levels in the full moisture range. In this paper, the electrical conductance as a function of moisture content was compared for these two conditioning methods. When the specimens were conditioned to constant relative humidity levels, the data obeyed a percolation model better than when the conditioning procedure by Stamm was used. This was attributed to that Stamm’s method gives moisture gradients through the specimen because of sorption hysteresis effects, even though the wood is conditioned to a steady-state moisture content. Equilibration to constant relative humidity levels thus provided more well-defined moisture states and that the data followed a percolation model indicates that the mechanism of electrical conduction in wood does not change, even at high moisture contents.

EFFECT OF MOISTURE CONTENT ON VIABILITY AND INFESTATION OF HULLESS TERRA OATS IN STORAGE

1979 ◽  
Vol 59 (4) ◽  
pp. 911-916 ◽  
Author(s):  
R. N. SINHA ◽  
N. D. G. WHITE ◽  
H. A. H. WALLACE ◽  
R. I. H. McKENZIE
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Mite Infestation ◽  
Tyrophagus Putrescentiae ◽  
Adsorption And Desorption ◽  
Safe Storage ◽  
Moisture Contents ◽  
Seed Moisture ◽  
Effect Of Moisture

The effects of various seed moisture contents in hulless (cv. Terra) and hulled oats (cv. Random) on susceptibility to mite infestation and on mycofloral growth and germination loss were studied at weekly intervals. Fat acidity values were determined for Terra oats only after 4 wk of storage. Moisture content-relative humidity adsorption and desorption curves were determined for Terra at 22 °C and at relative humidities of 35–100%. Terra oats, which had a higher level of Penicillium infection at 90–100% RH than Random oats, lost viability more rapidly than Random. Fat acidity values of Terra increased rapidly from 35 mg KOH/100 g of seed to 87–118 mg KOH/100 g of seed, only when seeds were stored at 90–100% RH. Terra offered a more favorable substrate for the multiplication of the mites Tyrophagus putrescentiae, Acarus farris, and Lepidoglyphus destructor than did Random. With the exception of susceptibility to mite infestation, safe storage criteria are similar for hulled and hulless oats at usual moisture contents.

scholarly journals Study on Dimensional Stability of Veneer Rice Straw Particleboard

Coatings ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 558 ◽  
Author(s):  
Xianqing Xiong ◽  
Yiting Niu ◽  
Yingying Yuan ◽  
Liangting Zhang
Keyword(s):  
Moisture Content ◽  
Rice Straw ◽  
National Economy ◽  
Dimensional Stability ◽  
Manufacturing Industry ◽  
Furniture Industry ◽  
Moisture Contents ◽  
Furniture Manufacturing ◽  
Cyclobalanopsis Glauca ◽  
Better Than

As an important industry of the national economy, the development of furniture manufacturing industry is very rapid. In particular, with the development of panel furniture industry, wood-based panels have become a necessary choice for furniture material for modern families in recent years. As a new particleboard material, in order to be more widely used in the furniture industry, it is not enough to have the characteristics of environmental protection. The material should also have excellent appearance and dimensional stability, so as to change people’s dependence on traditional wood-based panels. In this study, the rice straw particleboard (RSP) substrate was veneered by Betula sp. and Cyclobalanopsis glauca. In the process of veneering, different RSP specimens were treated by different sanding thicknesses and moisture contents of the RSP substrate, glue spread, species and thickness of veneer. The dimensional stability of different RSP specimens after veneering was analyzed. Based on the same variables, the change in the panel dimension and warp degree of the specimens of RSP which the sanding thickness was 0.2 mm were higher than the specimens with a sanding thickness of 0.6 mm. The dimensional stability of specimens of Cyclobalanopsis glauca veneer was better than that of Betula sp. veneer. A certain degree of change within the appropriate moisture content had a little effect on dimensional stability of veneered RSP. The greater of the amount of glue, the worse the dimensional stability of veneered RSP. The thinner the veneer, the worse was the dimensional stability of the veneered RSP.

Moisture relations of hay species

1958 ◽  
Vol 9 (4) ◽  
pp. 436 ◽  
Author(s):  
W Shepherd
Keyword(s):  
Chemical Composition ◽  
Relative Humidity ◽  
Moisture Content ◽  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Experimental Conditions ◽  
Lolium Perenne L ◽  
Moisture Contents ◽  
Medicago Sativa L ◽  
Trifolium Repens L

Moisture relations of four species used for making hay—white clover (Trifolium repens L.), subterranean clover (Trifolium subterraneum L.), lucerne (Medicago sativa L.), and perennial ryegrass (Lolium perenne L.)—have been investigated. Shapes and positions of equilibrium moisture content-relative humidity curves differed between species; and in general, moisture contents were lower for fast-cured than for slow-cured material and lower for over-mature than for less mature material. Sorption hysteresis effects were observed. Under the experimental conditions employed, equilibrium moisture contents were lower for material subjected to conditioning atmospheres immediately after mowing than for material cured prior to conditioning. Variations in the shape and position of equilibrium curves were frequently in accordance with known variations in chemical composition.

Figure 1. Anmonia-binding capacity of the three litters under laboratory conditions. 4. LIQUID-BINDING CAPACITY The absorption capacity of the litter determines the amount used, and also affects the functioning of hydraulic manure presses. Hie absorption capacity of litter depends on its initial moisture content. In the laboratory tests , peat had a much greater absorption capacity than other litters. Peat absorbed a maximum of 4.5 times its own weight of liquid, straw 3.5 times, cutter shavings 3.6 times and sawdust 1.5 times (4). The litters used in the tests had an initial moisture content of 20%, with the exception of peat, which contained 40% moisture. These moisture contents represent the working values for good-quality litters. Peat was far superior in terms of absoption capacity to the other litters. Litter should retain its absorption capacity even when under pressure, for example in a hydraulic manure press. The ability of litters to withstand pressure was tested by first allowing than to absorb either water or urine. The litters were then compressed in a hydraulic press for one hour as the pressure was increased stepwise from 20 N/an2 to 50 N/an2. The pressure exerted by hydraulic manure presses in practice is around 40-60 N/cm2. All the retained urine better than water. Sawdust was found to have the greatest resistance to pressure, retaining about 75% of the absorbed

1986 ◽  
pp. 197-197
Keyword(s):  
Moisture Content ◽  
Laboratory Tests ◽  
Binding Capacity ◽  
Initial Moisture Content ◽  
Hydraulic Press ◽  
Absorption Capacity ◽  
The Other ◽  
Moisture Contents ◽  
Laboratory Conditions ◽  
Better Than

scholarly journals Evaluation of Temperature and Moisture Content during Storage on the Germination of Flowering Annual Seed

HortScience ◽  
1995 ◽  
Vol 30 (5) ◽  
pp. 1003-1006 ◽  
Author(s):  
William J. Carpenter ◽  
Eric R. Ostmark ◽  
John A. Cornell
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Seed Storage ◽  
Seed Moisture Content ◽  
Moisture Contents ◽  
Seed Moisture ◽  
Storage Temperatures

Various combinations of temperature and moisture contents were used in evaluating the seed storage of nine genera of annual flowers. Relative humidity (RH) levels of 11%, 32%, 52%, and 75% provided wide ranges in seed moisture during storage at 5, 15, and 25C. At each temperature, total germination percentages (G) generally declined as seed moisture content increased during storage. The seed moisture range giving the highest G after 12 months of storage was determined for each temperature and plant genus. For all genera, seed moisture contents during storage increased as storage temperatures increased at constant RH levels. Moisture contents at 25C storage were 37%, 34%, 29%, and 20% higher than at 5C when RH levels were at 11%, 32%, 52%, and 75%, respectively.

Lusas high as 100°C (212°F). The temperature of soybeans must 25% in the confectionery type. At an ERH of 70% and not exceed 76°C, since discoloration and protein denatura-25°C, the former contains 9.6% moisture and the latter tion will occur [47]. Seed going into storage should not be 13.6% moisture; at 60°C moisture the contents are 8.1 and heat damaged so it will not respire or germinate. 10.9%, respectively [61]. Drying is energy-intensive. Reasonably efficient com-The general practice is to dry seeds to about 75% RH mercial dryers require 830-890 cal/kg (1500-1600 Btu/lb for interim storage, but some oil mill supervisors prefer of moisture removed) [59]. 65% RH for long-term (12 months) storage, especially in The prime factor to be controlled in stabilizing seeds is colder climates. Table 9 shows the maximum moisture lev-relative humidity (%RH), which is the weight of moisture els considered safe for selected oilseeds [62]. Antimicro-per unit weight of air in the atmosphere surrounding the bial preservatives are commonly used in prepared feeds, seed compared to the maximum weight possible (satura-especially during high-humidity summer months, and tion) at that temperature expressed as a percentage. The some farmers preserve high—moisture-content cereals and term equilibrium relative humidity (ERH) simply means oilseeds with propionic acid for feed use. The oilseed RH in the adjacent air after allowing sufficient time for crushing trade does not accept treated seed. moisture in the seed to equilibrate with the air, and can be Relationships between RH and equilibrated moisture determined by analyzing the head space in a sealed equili-content are shown for soybeans in Table 10 [63]. Levels to brated container. Another allied term is water activity, Av„, which soybeans will equilibrate, in various temperatures which is ERH expressed as a decimal rather than a per-and RHs of the surrounding air, are shown in Figure 3 [64]. centage. Direct-reading instruments are available for Relationships between temperature, moisture content, and measuring RH, ERH, and A. Manual methods for deter-allowable storage time of soybeans are shown in Figure 4 mining RH include the use of a sling psychrometer to ob-[64]. tain "wet bulb" and "dry bulb" temperatures and reference to relative humidity charts. Unfortunately, many people 5. Storage still prefer to relate seed stability to percent moisture con-Designs of storage (Fig. 2C) facilities are dictated by needs tent—a far less meaningful measurement. for aeration of seed and its angle of repose—the minimum Bacteria and yeasts have much higher ERH require-angle in degrees at which a pile maintains its slope [65]. ments for growth than molds (fungi). Table 8 shows that This sometimes is reflected in the pitch of conical roofs on some fungi will grow at any of the relative humidity ranges storage bins. Similarly, downspouts and the conical bot-shown, although few toxin-producing fungi grow at below toms of bins must have pitches steeper than the angle of 75% RH [60]. repose for the respective seed or meal to flow smoothly. During equilibration, available water from the seed and Higher moisture and oil contents increase the angles of re-atmosphere is attracted to the water-absorbing seed com-pose. Angles of repose and bulk densities of some major ponents but not to the oil. Thus, high-oil-content seeds oilseeds and products are presented in Table 11. (peanut, sunflower seed, and rapeseed/canola) must be Readily flowing seeds typically are stored in vertical-dried to lower moisture levels for safe storage than lower-walled silos. In contrast, undelinted cottonseed from the gin oil-content seeds like soybeans. For example, oil-type sun-is stored on cement floors in piles whose shape is dictated flower seeds contain about 42% oil, compared to about by its angle of repose. In areas with wet falls, winters, and TABLE 8 Equilibrium Moisture Contents of Common Grains, Oilseeds, and Feed Ingredients at 65-90% Relative Humidity (25°C) and Fungi Likely to Be Encountered Equilibrium moisture contents (%) Relative Starchy cereal seeds, humidity debated oilseed Peanut, sunflower (%) meals, alfalfa pellets Soybean seed, Rapeseed/Canola Fungi 65-70 12-14 11-12 6-8 Aspergillus halophilicus 70-75 13-15 12-14 7-10 A. restrictus, A. glaucus, Wallemia sebi 75-80 14-16 14-16 8-11 A. candidus, A. ochraceus, plus the above 80-85 15-18 16-19 9-13 A. flavus, Penicillium spp., plus the above 85-90 17-20 19-23 10-16 Any of the above Ref. 60.

2000 ◽  
pp. 324-331
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Oil Content ◽  
Soybean Seed ◽  
Angle Of Repose ◽  
Moisture Contents ◽  
Wallemia Sebi ◽  
Treated Seed ◽  
Reading Instruments ◽  
Equilibrium Relative Humidity

Fire and the opening of Banksia ornata F. Muell. Follicles

1976 ◽  
Vol 24 (3) ◽  
pp. 329 ◽  
Author(s):  
AM Gill
Keyword(s):  
Moisture Content ◽  
Room Temperature ◽  
Dry Weight ◽  
Field Conditions ◽  
Abscission Layer ◽  
Moisture Contents ◽  
Follicle Rupture ◽  
Eastern Australia ◽  
Water Saturated ◽  
Increasing Temperature

Banksia ornata is a sclerophyll shrub, characteristic of the heaths of south-eastern Australia. Its follicles are almost entirely dependent on fire for rupture and release of seed, although a few open under ambient field conditions. At air-dry moisture content (10-12% oven-dry weight) temperatures in excess of about 75°C are required for the rupture of the abscission layer between the woody valves, the time of exposure necessary for rupture decreasing with increasing temperature. At higher moisture contents rupture is delayed. No rupture occurs when follicles are water-saturated and exposed to a temperature of 100° over long periods. Similarly, no rupture occurs at room temperature when follicles are dried under vacuum (to 1.4% oven-dry weight). After rupture, the extent of valve reflexion is greatest when follicle valves are driest. These results are interpreted as follows. Follicle rupture occurs when tension across the abscission zone exceeds its strength: moisture has a major role in affecting the tension, and temperature a major role in affecting the strength.

scholarly journals Moisture-dependency of the fracture energy of wood: a comparison of unmodified and acetylated Scots pine and birch

Holzforschung ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Karin Forsman ◽  
Maria Fredriksson ◽  
Erik Serrano ◽  
Henrik Danielsson
Keyword(s):  
Relative Humidity ◽  
Fracture Energy ◽  
Scots Pine ◽  
Untreated Wood ◽  
Moisture Contents ◽  
Significant Difference ◽  
Structural Applications ◽  
Water Saturated ◽  
The Impact ◽  
Unmodified Wood

Abstract The moisture-dependency of the fracture energy for unmodified and acetylated Scots pine (Pinus sylvestris L.) and birch (Betula pendula Roth) has been investigated. Specimens were conditioned at relative humidity levels of 20, 75, and 97%, as well as dry and water-saturated. At moisture contents below 15%, the fracture energy increased with increasing moisture content for both unmodified and acetylated wood, while it decreased for untreated wood at higher moisture contents. A significant difference in moisture-dependency was found, indicating higher fracture energy for unmodified wood compared to acetylated wood at similar moisture contents. Additionally, to assess the impact of the increased brittleness for structural applications, the fracture energy was compared at equal relative humidity levels. The largest difference was seen at 75% relative humidity with approximately 50% lower fracture energy for acetylated wood. No significant differences were found for water-saturated samples. The moisture-dependency of the fracture energy, combined with the reduced hygroscopicity of acetylated wood, is suggested to be one, but not the only, contributing factor to the lower fracture energy of acetylated wood compared to unmodified wood at equal humidity levels. These observations have importance for structural design since design codes often assess material parameters based on ambient humidity.

scholarly journals Seed viability constants for Eucalyptus grandis

2007 ◽  
Vol 42 (1) ◽  
pp. 111-117
Author(s):  
Jussara Bertho Fantinatti ◽  
Roberto Usberti
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Inverse Relationship ◽  
Eucalyptus Grandis ◽  
Seed Viability ◽  
Growing Season ◽  
Seed Longevity ◽  
Aluminium Foil ◽  
Moisture Contents ◽  
Controlled Deterioration

This work aimed to analyse Eucalyptus grandis W.Hill ex Maiden seed behaviour, under controlled deterioration, and to estimate viability equation constants for the species. Seeds were harvested in the growing season of 1999, and the moisture contents were adjusted from 11.3% to a range between 1.2 and 18.1% at 25ºC. The subsamples were sealed into laminate aluminium-foil packets, for storage in incubators at 40, 50 and 65±0.5ºC. The seeds presented orthodox performance, in which the constants for predicting seed longevity of E. grandis were K E = 9.661, C W = 6.467, C H = 0.03498 and C Q = 0.0002330. The usual and inverse relationship between water content and seed longevity was also observed. The lowest moisture content limit for application of the viability equation at 65ºC was 4.9%, estimated under hygroscopic equilibrium with 23% of relative humidity in the storage environment.

Tensile Creep of Paperboard—Effect of Humidity Change Rates

1990 ◽  
Vol 197 ◽  
Author(s):  
Dennis E. Gunderson ◽  
Wayland E. Tobey
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Cyclic Creep ◽  
Progressive Increase ◽  
Rate Of Change ◽  
Tensile Creep ◽  
Creep Response ◽  
Humidity Change ◽  
Percent Relative Humidity ◽  
Better Than

ABSTRACTExperimental results now available are not adequate to define the mechanism of cyclic creep response of paperboard or to test plausible hypotheses. The present study examines the effect of rate-of-change of humidity on tensile creep response while monitoring the quantities of water adsorbed and desorbed by the specimen. Relative humidity is cycled between 30 and 90 percent relative humidity. Rate of humidity change in each cycle is held constant at values from 0.01 to 6 percent relative humidity per minute. Moisture sorbed by the web in each cycle is resolved to an accuracy better than ±0.05 percent moisture content. Results suggest that cyclic creep response is independent of the rate at which humidity changes. The results appear to reject the hypothesis that cyclic creep behavior is the result of a progressive increase in equilibrium moisture content.

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