Assessment of static and dynamic moduli of elasticity of antrocaryon micraster stemwood from semi-deciduous ecological zone in Ghana

In this paper, dynamic MOE and static MOE of short-length radiata pine specimens produced for finger jointing were measured using non-destructive technique and correlated to each other. In order to obtain reliable static MOE data, 36 mm thickness shooks as well as the matched samples of reduced thickness (15mm) were tested, and the effect of annual growth rings on dynamic and static MOE is also addressed. Mathematical correlations were fitted between the dynamic MOE for the 36 mm thick shooks and the static MOE of the 15 mm thick samples. The coefficient of determination for dynamic MOE group 4,00-7,99 GPa was the strongest (R 2 = 0,82) and the correlation strength was further improved for sorted quarter sawn samples (R 2 = 0,92). Finally, the correlation between static modulus of rupture (MOR) and dynamic MOE is discussed.

AR head-mounted displays (HMDs) facilitate pedestrian navigation by integrating AR guidance into users' field of view (FOV). Displaying AR guidance using a body-fixed coordinate system has the potential to further leverage this integration by enabling users to control when the guidance appears in their FOV. However, it remains unclear how to effectively position AR guidance within this coordinate system during pedestrian navigation. Therefore, we explored the effects of three AR guidance positions (top, middle, and bottom) within a body-fixed coordinate system on pedestrian navigation in a virtual environment. Our results showed that AR guidance position significantly influenced eye movements, walking behaviors, and subjective evaluations. The top position resulted in the shortest duration of fixations on the guidance compared to the middle and bottom positions, and lower mental demand than the bottom position. The middle position had the smallest rate of vertical eye movement during gaze shifts between the guidance and the environment, and the smallest relative difference in walking speed between fixations on the guidance and the environment compared to the top and bottom positions. The bottom position led to the shortest duration and smallest amplitude of gaze shifts between the guidance and the environment compared to the top and middle positions, and lower frustration than the top position. Based on these findings, we offer design implications for AR guidance positioning within a body-fixed coordinate system during pedestrian navigation.

The objective of this work was to assess the physical and mechanical properties of standing Taiwan incense cedar (Calocedrus formosana) using nondestructive techniques (NDT). In addition, the relationship between characteristics of standing trees and wood properties was established. Results indicated that the velocity values and bending properties decreased as tree height increased. In addition, velocity values of specimens were greater than those of logs and standing trees. After regressive analysis, the correlation coefficients (r) were 0.79 for standing trees and logs and 0.70 for logs and specimens. Not only the velocities measured by ultrasonic wave (Vu), tap tone (Vf), and vibration (Vt) methods, but dynamic MOE also correlated well with the static bending properties of specimens. In addition, the values of dynamic and static MOE showed the following trend: DMOEu > DMOEf > DMOEt > MOE. For all specimens, the r values were found to be 0.92 for MOE and DMOEt, and 0.75 for MOR and DMOEt. Therefore, it was assumed that the nondestructive testing methods can provide basic information about standing trees and specimens for future management practices and utilization of Taiwan incense cedar.

A study was made in the Porcupine Hills of southwestern Alberta to determine cattle distribution on slope when water is available at the top, middle, and bottom of the slope. Cows with calves were stocked at two rates (1.9 and 3.8 animal unit months (AUM) ha−1) and three replications over six small pastures in a completely random design. The study was repeated in each of 4 yr over a 3-wk period starting in mid-June of 1985. Average forage utilization over a 4-yr period was similar among slope positions (P > 0.05) and stocking rate had no effect on its distribution. However, forage utilization differed among slope positions within a grazing period. In 1985, measurements of individual plants showed that the distribution of use shifted from the top or middle position in the first 4 d of the trial to the bottom in the last 3 d. The higher stocking rate reduced position differences. Cattle obtained about 80% of total water consumed at the top or middle positions. This also represented the daytime proportion of cows observed at these sites. These observations suggest a diurnal preference for slope position because forage use was uniform among slope positions while daytime occupation of the middle and top positions was disproportionately high. Providing water only at top of slopes will synchronize the time cattle require water with daytime site preference. Key words: Cattle, feeding behavior, slope distribution, grazing, stocking rate

Using the flexural vibration method of Fast Fourier Transform (FFT) non-destructive testing, the dynamic MOE of glass fiber reinforced soybean straw particleboard has been determined. The regression analysis among the dynamic MOE, the static MOE and MOR has been done, the significant correlation exists among the three values. And the prediction model has been built, the dynamic MOE can be used to realize the quality assessment by using the model. Using glass fiber to reinforce the soybean straw particleboard, the structure forms and positions of glass fiber have different effects on particleboard performance.

The tapping method to measure Young's modulus of wood is useful for non-destructive evaluation of sawn lumbers. The dynamic MOE values are calculated from the resonance frequency of the tap tone with a FFT spectrum analyzer. However, if a glulam is used for a bending member such as a beam, it is not certain that the static MOE value of the glulam is equal to the dynamic MOE value. In case of glulams composed of sawn lumbers from juvenile wood, some adjustment to the dynamic MOE values may be necessary for use.In the present study, the relationship between static MOE (Es) and dynamic MOE (Ed) was investigated, since it was expected that the variation of MOE in the cross section of homogeneous-grade glulams would be relatively small. Two types of specimens were used: glulams laminated horizontally (H-type) and vertically (V-type). Dynamic MOE was measured by longitudinal vibration (El) and flexural vibration, whose directions were horizontal (Eh) and vertical (Ev) in the direction of the adhesive face of the glulam.The results indicated that Eh/Es in H-type and Ev/Es in V-type were not influenced by the number of laminae. As it was supposed that El/Eh should be influenced by the number of laminae, the relationship between El and Eh was estimated by simple simulation for different numbers of laminae. The estimated ratios of El, Eh and Ev to Es were almost identical with the experimental data.

The nondestructive testing using stress wave velocity method is known as most important tool to be used in quality control purposes. The aim of this study was to investigate the stress wave velocity (SWV) and to determine correlation between its velocity and dynamic MOE on static bending strength properties (MOE and MOR) of wood wool cement particleboards (WWCB). Thirty six WWCB particleboards from 3 tropical fast growing species (Paraserianthes falcataria, Maesopsis eminii, and Acacia mangium) and three different particleboards density of 0.5, 0.8 and 1.0 g cm-3 were made in this study. SWV value was determined using stress wave timer and it used to measure dynamic MOE. The measurement results of static bending strength method (MOEs and MOR) and by stress wave method were compared. The result showed the higher density of CBWW the higher of stress wave velocity. The WWCB particleboard of sengon possessed the highest value for both SWV and MOR. The dynamic MOE measured by stress wave method was about 80% higher than that static test. The good correlations were found between SWV and static MOE, MOR and it was statistically significant for linear regression model developed. Key words: fast growing species, nondestructive testing, static bending strength, stress wave velocity, wood wool cement particleboard

   Temperate forest soils are considered as significant sources or sinks for carbon dioxide, methane and nitrous oxide. There are relatively few studies which specifically deal with soil greenhouse gas (GHG) fluxes across slope positions in upland temperate forest. We used static chambers to monitor soil GHG fluxes at three slope position sites (top, middle and bottom) in the Pinus tabulaeformis forest in the Qinling Mountains, China from July 2012 to June 2015. The cumulative soil CO2 and N2O emissions and the CH4 uptake from the three sites ranged between 13.85 to 14.49 t CO2 ha-1 yr-1, 1.04 to 6.48 kg N2O ha-1 yr-1, and 4.78 to 9.01kg CH4 ha-1 year-1, respectively. There were large pulses of CO2 emissions during spring and summer after heavy rainfall or during freezing and thawing cycles. The proportion of the annual flux of CO2 during the 2014 summer could achieve 45.6%, 49.6% and 43.5% at the three sites and during 2013 summer were more than 36% at the bottom and middle positions. At the bottom and middle positions, the proportions of the annual flux of CO2 were more than 33% during the majority of the summer periods. Soil microenvironment (soil moisture, soil temperature and the interaction of these two factors) explained 84.96% variations of CO2 emissions. The emission summits of 10547.1 ug CH4 m-2 h-1, 6256.5 ug CH4 m-2 h-1 and 701.5 ug CH4 m-2 h-1 were observed after the first heavy rainfall in the spring of 2013 at the three sites. The soil of the middle slope position even acted as a year round net weak source of CH4 due to continuous rainfall and mixed with heavy rainfall during the 2014 summer. Soil microenvironment and accumulated rainfall in seven anteceding days (rain_7) explained 31.38% variations of CH4 fluxes. The proportion of the annual flux of N2O that is derived from the 2015 and 2014 freeze-thaw cycles could achieve 38% and 30.6 % at the bottom and top slope positions. Soil microenvironment and rain_7 explained 56.67% variations of N2O fluxes. Due to hot moments and hot spots effects, the contribution of N2O emission to the total global warming potential was much higher than the cutting down effects of CH4 consumption during 2012-2013 or at the middle position site. Our study demonstrated that the middle and bottom position sites were hot spots and the rainfall events during the growing season were triggers of hot moments for all three greenhouse gases. The hot moments and hot spots of the three greenhouse gases are a significant fraction of their total budgets. 

The objective of this study was to explore wood variation, especially modulus of elasticity ( moe), density, and microfibril angle ( mfa), in a three-year old Pinus radiata tree clone trial. Moreover, the study examined the potential for genetic selection of radiata pine clones with high moe using current acoustic technology. The clone selection criteria were based on growth traits, basic density, and sound velocity indices to mirror the range in wood density and moe amongst c. 1000 clones. The selected 22 clones, represented by two trees each, were measured for moe, spiral grain, wood density, compression wood percentage, and mfa. Good agreement was found between static moe and dynamic moe. Both static and dynamic moe measurements were found to be primarily dependent on mfa (clonal range 28–39 degrees). Although wood density (clonal range 300–400 kg/m3) did not have a significant influence on moe alone, it was significant in combination with mfa. Compression wood tended to reduce moe and inflate wood density. The opportunities for genetic selection of radiata clones with high stiffness seem promising as the 22 selected clones exhibited a two-fold range of static moe (2.2–4.7 GPa) and the clonal heritabilities (\(H^{2}_{i} \)) for moe, density and mfa were high.

The determination of static elastic modulus in the laboratory requires rock core extraction and the subsequent testing of the samples by means of standardised uniaxial compressive strength tests. However, this destructive procedure is not always suitable – as in the case of protected historic buildings. In these cases, the static elastic modulus can be obtained from the dynamic elastic modulus, in turn derived from the velocity of ultrasonic waves (a non-invasive and non-destructive test). The relationship between both the dynamic and static moduli of rocks has been extensively addressed in the scientific literature. Furthermore, several researchers have separately studied the evolution of static or dynamic elastic moduli of rocks exposed to high temperatures – although few studies have compared both values. It is well known that the dynamic modulus is generally higher than the static modulus, and the values diverge especially in rocks with a low modulus of elasticity. These differences can be mainly explained by the effect of porosity and the size of cracks in the determination of both parameters. In this research, the relationship between static and dynamic moduli for ‘Borriol’ limestone is studied for samples previously subjected to 200, 400, 600 and 800 °C and then cooled slowly (in air) or quickly (immersed in water). The results show that the static modulus of samples heated up to 600 °C decreased 80.9 and 79.1 % and dynamic modulus decreased 62.5 and 64.8 % for slow and quick cooling samples, respectively. For samples heated to 600 and 800 °C, the static and dynamic moduli are similar. In general, no significant differences between both cooling methods are observed, even though static modulus shows more loss than dynamic modulus. Finally, linear models were used to correlate static and dynamic moduli, providing coefficients of determination of 0.99 and 0.97, for slow and quick cooling, respectively. It is also remarkable that the Edyn/Est rate was smaller than 1 for elastic moduli over 30 GPa (i.e., 105, 200 and 400 °C) and greater than 1 for lower moduli (i.e., 600 and 800 °C). The results obtained can be used to calculate the static elastic modulus of ‘Borriol’ limestone from dynamic modulus determined by non-destructive techniques.

Membrane fouling is still the main obstacle that hinders the development and implementation of anaerobic membrane bioreactor (AnMBR). In conventional upflow anaerobic reactors, sludge at different height usually presents certain differences in characteristics in terms of particle size, etc. The immersion depth of membrane modules in anaerobic reactors can also influence the fouling of membrane. Thus, it is of great interest to investigate the fouling mechanism with the membrane installed at different heights in reactors. The filtration performance and sludge properties were investigated at different heights of AnMBR. The fouling of membrane in the middle position was severer than that in the top and bottom positions. The total resistance of membrane in the top, middle, and bottom positions was 27.31 × 1011m-1, 34.67 × 1011m-1, and 25.29 × 1011m-1, respectively. By comparing the characteristics and structure of bulk sludge and cake layer at three heights, the bulk sludge in the middle position presented higher content of soluble microbial products (SMP) and finer flocs, and the cake layer was also denser. The results obtained in this study indicated that small size of sludge flocs as well as adhesion of SMP might be the major factors governing membrane fouling at different height in the AnMBR.

Dynamic modulus of elasticity was determined in clearwood samples of eight tropical hardwood species using longitudinal vibrations, flexural vibration and ultrasonic transit-time methods. These samples were subsequently subjected to three point static bending test to determine static modulus of elasticity and modulus of rupture. Acoustic velocity and wood density were found to be independent parameters as the velocity was nearly the same in wood with distinctly different densities. Among the three dynamic measurements, modulus from the ultrasonic method was the highest followed by the longitudinal vibration and flexural vibration. Any of three vibration methods could be used to predict static modulus as they exhibited a near perfect correlation with static MoE. However, the dynamic modulus determined by different vibration methods were found to diverge with increasing static modulus. Wood density was the dominating factor influencing both modulus of elasticity and modulus of rupture.

Levels of polyphenols in tobacco (Nicotiana tabacum L.) leaf are associated with certain constituents in the smoke. This study was designed to determine the variability in levels of polyphenols in several cultivars of flue‐cured tobacco as influenced by stalk position, location, and year. The levels of polyphenols were compared in cured leaves from bottom, middle, and top stalk positions of 13 cultivars grown at four locations for 2 years. There were differences among cultivars for polyphenol level. ‘NC 2326’ had the highest level with 4.25% and ‘Speight G‐28’ had the lowest with 3.58%. Highly significant differences in levels of polyphenols associated with stalk position were measured (3.15, 4.11 and 4.42% for the bottom, middle, and top position, respectively). There were significant interactions of locations by the seasons experienced in the 2 years. Interactions involving cultivars were not significant in most cases, and where they were, it involved higher order interactions. This was also true for stalk positions. The presence of cultivar differences and the consistency of these differences would encourage breeding efforts but testing over locations and years would be advisable.

Effect of nodal cutting position and plant growth regulator on bud sprouting of Dendrocalamus giganteus Wall. Ex Munro in Uganda

Microplastics in vineyard soils: First insights from plastic-intensive viticulture systems