scholarly journals Investigating the Underlying Effect of Thermal Modification on Shrinkage Behavior of Bamboo Culm by Experimental and Numerical Methods

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 974
Author(s):  
Raviduth Ramful ◽  
Thefye P. M. Sunthar ◽  
Wenliang Zhu ◽  
Giuseppe Pezzotti
Keyword(s):  
Numerical Methods ◽  
Longitudinal Crack ◽  
Bound Water ◽  
Longitudinal Direction ◽  
Linear Increase ◽  
Weight Changes ◽  
Weakly Bound ◽  
Bamboo Culm ◽  
Dimensional Changes ◽  
Increasing Temperature

This study probes into the root cause of split in thermally modified bamboo culm by investigating the underlying effect of thermal contraction with respect to its orthotropic nature by experimental and numerical methods while concurrently monitoring the chemical variation of its structure by Fourier transformed infrared spectroscopy (FTIR). In first part of this study, a non-linear increase in dimensional and weight changes of small clear bamboo specimens were observed with increasing temperature. The dimensional changes in the radial and tangential directions significantly exceeded that in the longitudinal direction. From FTIR results, shrinkage effect between 150 °C to 200 °C was associated with weight loss engendered by reduction in weakly bound water and increase in desorption of water content while alteration of its mechanical properties was attributed to changes in cellulose, hemicellulose, and lignin. From results of finite element method (FEM), the graded variation in thermal expansion coefficient, which showed the formation of a narrowed region of strain concentration corresponding to longitudinal crack propagation, was associated with the inducement of internal forces, namely tensile and compressive forces, at specific regions along the culm length. The results of this study can be useful to achieve optimized durability in modified bamboo for construction.

Molecular models for recombination and disproportionation of radicals

1983 ◽  
Vol 61 (5) ◽  
pp. 881-887 ◽  
Author(s):  
Sidney W. Benson
Keyword(s):  
Long Range ◽  
Impact Parameter ◽  
Ad Hoc ◽  
Active Surface ◽  
Weakly Bound ◽  
Range Interaction ◽  
Surface Areas ◽  
Long Range Interaction ◽  
Increasing Temperature ◽  
Radical Disproportionation

The modified Gorin model of recombination as a long range interaction of weakly bound radicals, constrained only by steric forces, is rederived to give a collision impact parameter 11% larger than rmax, the separation at the centrifugal maximum. This larger impact parameter resolves some of the earlier difficulties with secondary and tertiary radicals. By imposing a new constraint, that the orientation of the radicals be such as to permit exchange forces to act, a new model is developed in which kr = 1/4 Zr α, where a represents the product of fractions of active surface areas of each radical available for bonding. Excellent agreement is obtained in estimating values of kr.Analysis of disproportionation is made to show that it cannot be described by the tight transition state but must also be governed by similar, long range exchange forces between the bond being attacked and the same "active surface" of the abstracting radical. Using an ad hoc radius for [Formula: see text]equal to 4 Å it is possible to reproduce the data on alkyl radical disproportionation to within ± 10%.The model predicts a small decrease in rate of recombination with increasing temperature. This decrease is more pronounced for bulkier radicals and at higher temperatures (> 900 K).

A RECORDING VACUUM THERMOBALANCE

1957 ◽  
Vol 35 (4) ◽  
pp. 374-380 ◽  
Author(s):  
J. G. Hooley
Keyword(s):  
Temperature Coefficient ◽  
Maximum Sensitivity ◽  
Weight Changes ◽  
Dimensional Changes ◽  
Spring Balance ◽  
Fused Quartz

A recording quartz spring balance is described, with which weight changes up to 1000 mg. can be followed linearly on a millivolt recorder for samples weighing up to 10 g. During the recording operation the sample may be under vacuum or pressure and may be heated or cooled. The maximum practical sensitivity is about 20 millivolts per milligram and the over-all error in reading the record is about 1 millivolt. The temperature coefficient of fused quartz springs is reported to be − (1.25 ± 0.02) × 10−4 per degree centigrade in the range 20° to 35 °C.The device could be readily adapted for heavier loads and greater weight changes by using less sensitive springs and could be used for measuring dimensional changes of solids with a maximum sensitivity of at least 2000 mv. per millimeter.

Behavioural cycles during Pseudopregnancy in confined populations of domestic rabbits and their relation to the histology of the female reproductive tract

1966 ◽  
Vol 14 (2) ◽  
pp. 173 ◽  
Author(s):  
RL Hughes ◽  
K Myers
Keyword(s):  
Reproductive Tract ◽  
Sexual Attraction ◽  
Physiological Activity ◽  
Adaptive Significance ◽  
Female Reproductive Tract ◽  
Corpora Lutea ◽  
Weight Changes ◽  
Dimensional Changes ◽  
Detectable Difference ◽  
Domestic Rabbits

Female domestic rabbits living with vasectomized males in large compounds (3/16 ac in area) exhibited periods of sexual attraction and mating, together with other behaviour such as aggression towards other females, digging, burrow interest, and nest building at intervals of about 6 days or multiples thereof. The behavioural cycles occurred during pseudopregnancy (of about 18 days) and were not a manifestation of an underlying inherent sequential cycle or a typical mammalian oestrous cycle. Behaviour with a strong sexual component culminating in mating and ovulation was observed at the beginning (or end) of each of 54 pseudopregnancies. Similar behaviour was also grouped about either the sixth or twelfth days of pseudopregnancy or both. This behaviour was extremely variable in both incidence and the number of components involved. Sexual components occurred less frequently and only once culminated in mating and ovulation. The behaviour observed on the sixth and twelfth days of pseudopregnancy was not reflected in measures of physiological activity such as numbers of graafian follicles, diameter of graafian follicles or corpora lutea, or weight changes in ovaries or uteri. The histology of the ovaries, uterus, and vagina and dimensional changes such as ovarian and uterine weights, number and diameter of graafian follicles, and diameter of sets of corpora lutea showed no detectable difference from those reported by other workers during pseudopregnancy for caged female rabbits isolated from males. The incidence of 6-day and 12-day behaviour was highest in the autumn-winter months when sub-optimal reproductiveconditions prevailed and lowest in spring-summer. Some possible causal mechanisms and the adaptive significance of the sixth-day and twelfth-day periods of sexual behaviour are discussed.

Weakly Bound Water Molecules Shorten Single-Stranded DNA

2006 ◽  
Vol 128 (20) ◽  
pp. 6636-6639 ◽  
Author(s):  
Shuxun Cui ◽  
Christian Albrecht ◽  
Ferdinand Kühner ◽  
Hermann E. Gaub
Keyword(s):  
Bound Water ◽  
Water Molecules ◽  
Weakly Bound ◽  
Single Stranded Dna

Dynamic moisture sorption and hygroexpansion of Populus euramericana Cv. under two cyclic hygrothermal conditions

Holzforschung ◽  
2016 ◽  
Vol 70 (12) ◽  
pp. 1191-1199 ◽  
Author(s):  
Tiantian Yang ◽  
Erni Ma ◽  
Jianhui Zhang
Keyword(s):  
Relative Humidity ◽  
Moisture Content ◽  
Environmental Conditions ◽  
Moisture Sorption ◽  
Longitudinal Direction ◽  
Measured Data ◽  
Populus Euramericana ◽  
Dimensional Changes ◽  
Unit Change ◽  
Condition B

Abstract Poplar (Populus euramericana Cv.) specimens, 20 mm in radial (r) and tangential (t) directions with thicknesses of 4 mm and 10 mm along the longitudinal direction, were subjected to cyclic environmental conditions, in the course of which the relative humidity (RH) changed sinusoidally between 75% and 45% at 20°C (condition A), or the temperature (T) was changed sinusoidally within 5–35°C at 60% RH (condition B). Moisture content (MC), as well as the t- and r-dimensional changes were measured as a response to the dynamic environmental conditions. The measured data also changed sinusoidally but they lagged behind the triggering original RH or T data. This effect was much higher under condition A than under condition B. The observed equivalent RH and T changes at different ΔMCs or Δts served for comparison of the responses to RH and T, and the former were less pronounced than the latter. MC and t-dimensional changes per unit change of RH were greater than those per unit change of T but still lower than static values. In summary, the effects of dynamic RH change are larger than those of T, especially concerning MC responses compared to dimensional changes.

Fourier Transform Nuclear Magnetic Resonance Studies of 67Zn

1974 ◽  
Vol 29 (11) ◽  
pp. 1553-1557
Author(s):  
B. W. Epperlein ◽  
H. Krüger ◽  
O. Lutz ◽  
A. Schwenk
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Zinc Ion ◽  
Linear Increase ◽  
Solvent Isotope Effect ◽  
Magnetic Resonance Studies ◽  
Zinc Salts ◽  
Solvent Isotope ◽  
Increasing Temperature ◽  
Nuclear Magnetic

67Zn nuclear magnetic resonance studies of various solutions of diverse zinc salts in H2O and D2O are reported. In the solutions of ZnI2, ZnBr2 and ZnCl2 a remarkable chemical shift to higher frequency is observable, whilst for Zn(ClO4)2, Zn(NO3)2 and ZnSO4 no shift is detectable. The 67Zn shifts in zinc halide solutions depend on the isotopic composition of the solvent. The substitution of hydrogen by deuterium in the solvent yields for the 67Zn line an anomalous solvent isotope effect to higher frequency. Moreover for increasing temperature a linear increase of the shift and a nonlinear decrease of the linewidth for the zinc halide solutions were observed.The ratio of the Larmor frequencies of 67Zn and 37Cl has been measured in an aqueous zinc perchlorate solution, and a magnetic moment has been calculated for 67Zn. The shielding constant for the hydrated zinc ion has been evaluated:σ*(hydrated 67Zn++ versus 67Zn atom) = − (6.9 ± 0.1) · 10−4.

The structure of hydrohematite

1981 ◽  
Vol 154 (1-2) ◽  
Author(s):  
Emilia Wolska
Keyword(s):  
Bound Water ◽  
Weakly Bound ◽  
X Ray ◽  
Defect Character

AbstractHydrohematite beside ‘weakly bound’ water removable at 160 – 200° C, contains about 3–4.5 % of tightly held HAccurate measurements of X-ray reflection intensities of hydrohematites revealed a decrease in intensity of all reflections due to FeThe results obtained agree well with the calculated values for the model assumed and fully confirm the defect character of hydrohematite structure. Thus the formula of hydrohematite should be written Fe

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