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1.
To improve the drying method in the manufacture of woodwind reeds, green canes (Arundo donax L.) were dried under various humidity–temperature conditions and the intensity of cell collapse was evaluated from the swelling due to steaming during the recovery of collapse. At 30°C, the intensity of collapse was increased by slower drying. It was considered that: (1) slower drying resulted in higher sample temperature in the early stage of drying and acted to increase the collapse; (2) rapid drying stiffened the surface of the sample and such a shell prohibited the following collapse; (3) slower drying i.e., longer loading of liquid tension caused more remarkable and/or frequent viscoelastic yields of cells. Consequently, the intensity of collapse increased when the cane was dried from its waxy outer surface or in the presence of node: both of them retarded drying. On the other hand, higher drying temperature caused greater intensity of collapse in spite of faster drying. It was suggested that the thermal softening of cane cells leads to easier yielding of the cell wall, and at the same time the rapid drying does not allow the recovery of collapse after the disappearance of free water. These results indicated that faster drying at lower temperature is preferable for drying cane with less collapse. 相似文献
2.
Collection and care of sweetgum seed 总被引：2，自引：0，他引：2
F. T. Bonner 《New Forests》1987,1(3):207-214
Sweetgum (Liquidambar styraciflua L.), a widely distributed hardwood in the United States and Central America, shows potential for tropical forestry application. Fruit heads change from bright green to yellow in color as they mature, and they can be picked from standing trees or logging slash when the color change occurs. Fruits release their seeds after only moderate drying, and cleaning is easy with air-screen cleaners. Sweetgum seeds are orthodox in storage behavior, and they should be stored at moisture contents of 5 to 10% at 0° to 5° (5 years or less) or –18° (more than 5 years). The seeds exhibit a shallow dormancy that can be overcome with 2 to 4 weeks of stratification at 3°C. 相似文献
3.
Method for measuring viscoelastic properties of wood under high temperature and high pressure steam conditions 总被引：3，自引：0，他引：3
A method for measuring the viscoelastic properties of wood under high temperature and high pressure steam was developed using a testing machine with a built-in autoclave. A newly developed load cell capable of resisting a steam pressure of 16kgf/cm2 and a temperature of 200°C was installed in the autoclave. This load cell could be used to determine precisely the loads while steaming at temperatures from 100°C to 200°C. In addition to load-detection problems, it was necessary to avoid the nonuniform thermal degradation of wood during the measurement process under steaming at high temperatures. This nonuniform degradation could be minimized by shortening the time required for the wood to attain thermal equilibrium using specimens conditioned to the fiber saturation point. According to this method, a stress relaxation curve for sugi (Cryptomeria japonica D. Don) wood being compressed while steaming at 180°C was obtained. The stress was seen to decrease rapidly with time, reaching almost zero at 3000s. 相似文献
4.
The storage modulus and the mechanical loss tangent of untreated, extracted, and sugar- impregnated canes (Arundo donax L.) were measured over a temperature range of –150° to 0°C at low frequencies. Two relaxation processes, labeled and , were detected in the ranges –60° to 0°C and –120° to –100°C, respectively. The and processes shifted to lower temperatures with increasing moisture content. The process was detected only in the canes containing sugar. The magnitude of its loss peak increased with an increase in sugar content. It was speculated that the process was due to some interactive molecular motions of the adsorbed water and sugar. The process, detected in all of the canes, was attributed to the motion of the adsorbed water in the amorphous cell wall substances. 相似文献
5.
通过分析滇产赤桉地板毛坯料的干燥质量,认为其主要干燥缺陷是皱缩和扭翘变形,而不是开裂,据此进行干燥质量控制的试验.结果表明,3h的汽蒸处理可以有效地回复皱缩,减小扭翘变形. 相似文献
6.
J. Ilic 《Wood Science and Technology》2001,35(1-2):157-166
Dynamic elastic modulus (EL) and wave velocity (V) were determined using resonance vibrations from initially green, 100 × 50 mm sample boards of Eucalyptus regnans F. Muell., and after several stages of drying to oven dry. EL and V were determined from impact induced vibrations and spectral analysis. EL and V from green wood were positively related to basic density and normal shrinkage, only V was negatively related to green
density, and both EL and V were negatively related to green moisture content and the number of internal checks after drying. The latter relationship
has the potential to provide a simple method of segregating highly check prone material. No significant relationships were
obtained with collapse. Outside the hygroscopic range, in low shrinkage material, EL increased little or gradually, while in high shrinkage, collapse prone material, it increased more rapidly, but no clear
breakpoint was evident. In the hygroscopic range, EL increased rapidly in all samples. V increased curvilinearly throughout the entire moisture range, but no difference between
collapse prone and non-collapse prone material was observed.
Received 16 February 1998 相似文献
7.
Shrinkage and collapse in thin sections and blocks of Tasmanian mountain ash regrowth 总被引：2，自引：0，他引：2
Summary Total collapse values from the green condition to various equilibrium moisture contents (EMC) were obtained by comparing shrinkage before reconditioning in matched blocks and sections of the wood of Eucalyptus regnans. It was shown that while collapse to 17% EMC comprised the largest portion of total collapse, a significant component, apparently caused by drying stress, developed below 17% EMC. Between 5% EMC and 0% moisture content a collapse recovery of some 1% occurred, seemingly because of changes in drying temperature. After reconditioning, collapse recovery was only partial and a high level of residual collapse remained. It was shown that collapse recovery was highest near the sapwood-heartwood boundary, while residual collapse was highest near the heartwood centre. While residual collapse was weakly negatively correlated with specific gravity, this relationship was not significant after adjustment was made for change in shrinkage after reconditioning in sections. All types of collapse were positively correlated with R-ratios calculated for blocks. However, relationships were not as well defined when R-ratios for sections were employed, the exception being for collapse below 17% EMC which was highly negatively correlated with R. The difference between shrinkage before reconditioning and shrinkage after reconditioning in sections, while totalling near zero, was positively correlated with specific gravity. It was demonstrated that this quantity could not constitute collapse in the traditional sense of collapse of the cell lumens. A possible association with moisture content of the material was discussed. 相似文献
8.
9.
The objective of this study was to find an effective method for treating ma bamboo (Dendrocalamus latiflorus) and moso bamboo (Phyllostachys pubescens) using new water-based reagents containing copper. The effects of green-color protection using various treatments on bamboo
culms were examined in this study. Two methods were used: heating in a water bath and ultrasonic dipping. The results revealed
that excellent green-color protection (a* value of −6.2) was obtained when ma bamboo culms were treated with 0.25% ammoniacal copper quaternary compound-type B (ACQ-B)
in a water bath at 100°C for 2 h. It was also found that the wettability of bamboo epidermis increasedsignificantly after
pretreatment in a mixture of 1% KOH and surfactant in a water bath at 100°C for 30 min. Furthermore, pretreated moso bamboo
culms exhibited excellent green-color protection after they were treated with 0.25% ACQ-B at 100°C for 2 h (a* value of −8.2). This novel treatment method definitely endows the bamboo culms with a fascinating green skin color and consequently
could increase the economic value of bamboo products. No improvement in green-color protection was found when ultrasonic energy
was added to the water bath at ambient temperature. 相似文献
10.
Jon E. Schoonover Karl W. J. Williard Chris Blattel Chad Yocum 《Agroforestry Systems》2010,80(1):97-107
Across the U.S., multiple species of riparian vegetation have proven to be effective filters of sediment and nutrients in
agricultural watersheds. Research at Southern Illinois University Carbondale has focused on giant cane [Arundinaria gigantea (Walt.) Muhl.] as a potential candidate to incorporate into riparian buffer designs. In 2001, an exploratory study (i.e.,
Phase I) monitored nutrient and sediment concentrations from surface runoff and groundwater in the Cypress Creek watershed,
while two subsequent studies (i.e., Phase II) focused on groundwater quality and added additional riparian buffer plots in
the Big Creek and Cache River Watersheds. The primary objective of this research was to compare nutrient attenuation in groundwater
of native giant cane and forest riparian buffers. Results from phase I showed significant nutrient reductions in groundwater
over short distances in both the giant cane (~3.0 m) and forest buffers (~6.0 m), thus additional wells were installed at
1.5 and 12.0 m for the second phase. Groundwater NO3
−-N was significantly reduced by 90% in the initial 3.0 m of the giant cane buffer, where plant assimilation and microbial
denitrification were likely key NO3
−-N removal mechanisms. Phase II showed significant reductions in groundwater NO3
−-N beneath the forest buffers, whereas little change occurred below the giant cane buffers. However, NO3
−-N concentrations beneath giant cane buffers were 3 times less than those observed beneath the forest buffers. Follow-up studies
are being conducted on the transport of E. coli through vegetated buffers, and efforts have been expanded to the watershed-scale. 相似文献
11.
Yoh-ichi Matsushita Kazuhiro Sugamoto Kenji Miyakubo Chiaki Kurogi Takanao Matsui Hisato Oda Hideto Fujimoto 《Journal of Wood Science》2008,54(6):476-482
Sawdusts of sugi (Cryptomeria japonica) wood prepared before and after steam drying at 120°C in a kiln were extracted with n-hexane and ethyl acetate to give n-hexane extracts and ethyl acetate extracts. From gas chromatography-mass spectrometry analysis of the ethyl acetate extracts
from woods before and after steam drying, the components of 4-epi-cubebol, cubebol, and 2,7(14),10-bis-abolatrien-1-ol-4-one, which existed in the raw sugi wood, were proved to disappear
in the steam-dried wood. These components were also absent in the ethyl acetate extract of the steam-condensed solution of
waste steam from the kiln outlet. When these three components were treated with 0.2% (v/v) acetic acid solution at 120°C,
δ-cadinene was produced as a major product from both 4-epi-cubebol and cubebol by dehydration and cleavage of the cyclopropane ring, and cryptomerone from 2,7(14),10-bisabolatrien-1-ol-4-one
by hydration. The chemical changes of the three components presumably occur during steam drying of the sugi wood.
This study was presented in part at the 85th Spring Meeting of the Chemical Society of Japan, Kanagawa, Japan, March 26–29,
2005 相似文献
12.
山杨小径木超微结构及其与干燥皱缩的关系 总被引：1，自引：0，他引：1
前言山杨(Populus Dividiana Dode)小径木是黑龙江省尚志具帽儿山次生林区主要的间伐树种之一。该树种在干燥时易产生皱缩等缺陷,我们设想与其结构有关,故利用扫描电镜观察其超微结构,以期洞悉其中的奥秘。 W.R.Perng研究颤杨(Populus tremuloides)解剖构造与液体传导的关系,在电镜下观察时,指出颤杨心材中存在侵填体,这些侵填体使导管闭塞,因而液体流动困难。他又对此木材进行聚合物渗透,而心材导管中几乎无聚合物沉积,说明心材导管全部被侵填体堵塞,聚合物难以在心材沉积。 相似文献
13.
J. Ilic 《Wood Science and Technology》1995,29(4):277-285
Summary Difficulties associated with the drying of ash eucalypts including collapse and internal checking, are discussed briefly. Prefreezing is one method that has been used successfully as a pretreatment for the drying of both hardwoods and softwoods from temperate and tropical regions.Prefreezing has produced marked reductions in shrinkage, collapse and drying degrade of the heartwood in the following species: California redwood, black walnut, black cherry, tanoak, toon, bamboo, and eucalypts. Little or no collapse reduction has been observed in New Zealand red beech, Pacific madrone, white birch, sitka spruce, and white ash. Limited response has been observed for numerous other species notably red oak and white oak.Reduced drying time in response to prefreezing has been observed in jarrah, karri, black walnut, Asian oak, toon, and California redwood; in Pacific madrone and tanoak the drying time increased. Not all species which respond with a reduction in shrinkage show reduced drying rates.Prefreezing wood at -20°C appears to be the most practicable temperature, although some species respond better at lower temperatures. However, in all cases, it is critical to ensure that the wood freezes and remains frozen for a number of hours. Indications are that the effect is retained for days to weeks and that the length of time of freezing need not exceed 12–24 hours.A number of explanations have been put forward to explain the behaviour of prefrozen wood. It is suggested that the main mechanism responsible for reduced shrinkage is due to the migration of moisture from the cell wall onto frozen lumen water. The moisture loss from the cell wall produces a cold shrinkage; water to ice transformation leads to an expansion of liquid water in the lumen, thus imparting a compressive stress to the cell wall, which together with the moisture loss, make the cell more rigid, and therefore likely to shrink less. There is some evidence that certain types of wood extractives migrate into the cell wall during freezing and may play a role in the reinforcement of the wall. Reduced shrinkage after prefreezing has also been attributed to a reduction of the plasticising effect of wood extractives in wood dried at higher temperatures and low humidities; this effect does not occur at low temperatures.Many suggestions and discussion from Dr. W. E. Hillis are gratefully acknowledged 相似文献
14.
The water dynamics of cropping systems containing mixtures of Gliricidia sepium (Jacq.) Walp trees with maize (Zea mays L.) and/or pigeonpea (Cajanus cajan L.) were examined during three consecutive cropping seasons. The trees were pruned before and during each cropping season, but were left unpruned after harvesting the maize; prunings were returned to the cropping area in all agroforestry systems to provide green leaf manure. The hypothesis was that regular severe pruning of the trees would minimise competition with crops for soil moisture and enhance their growth by providing additional nutrients. Neutron probe measurements were used to determine spatial and temporal changes in soil moisture content during the 1997/98, 1998/99 and 1999/00 cropping seasons for various cropping systems. These included gliricidia intercropped with maize, with and without pigeonpea, a maize + pigeonpea intercrop, sole maize, sole pigeonpea and sole gliricidia. Soil water content was measured to a depth of 150 cm in all treatments at 4–6 week intervals during the main cropping season and less frequently at other times. Competition for water was apparently not a critical factor in determining crop performance as rainfall exceeded potential evaporation during the cropping season in all years. The distribution of water in the soil profile was generally comparable in all cropping systems, implying there was no spatial complementarity in water abstraction by tree and crop roots. However, available soil water content at the beginning of the cropping season was generally lower in the tree-based systems, suggesting that the trees continued to deplete available soil water during the dry season. The results show that, under rainfall conditions typical of southern Malawi, the soil profile contains sufficient stored water during the dry season (ca. 75–125 mm) to support the growth of gliricidia and pigeonpea, and that gliricidia trees pruned before and during the cropping season did not deleteriously compete for water with associated crops. Water use efficiency also appeared to be higher in the tree-based systems than in the sole maize and maize + pigeonpea treatments, subject to the proviso that the calculations were based on changes in soil water content rather than absolute measurements of water uptake by the trees and crops. 相似文献
15.
Infection of plane tree by Ceratocystis fimbriata f. platani after contamination of water as growing substrate of wounded roots. Plane tree seedlings (Platanus acerifolia) were cultivated during 1. year so as some roots emerged from the culture pot And grow in the water of a container placed below. In April, these roots were wounded and nearby, conidia suspension of C. fimbriata?. platam was injected into the water. 1 month later, foliage of some seedlings began to wilt and after 2 months, 7 out of 12 plane trees were drying. The pathogen was recovered from all parts of the roots above the water level inside the pots and as high as the collar for 4 plants. 相似文献
16.
This study examined how boiling and drying treatments influenced various physical properties of the tension wood with gelatinous
fibers (G-fibers) of a 29-yearold Zelkova branch. By boiling treatment, tension wood with numerous G-fibers contracted considerably in the longitudinal direction and
the longitudinal Young’s modulus decreased in spite of the water-saturated condition. The drying treatment caused green tension
wood and boiled tension wood with numerous G-fibers to shrink longitudinally and increased their longitudinal Young’s moduli.
These specific behaviors in tension wood were highly correlated with the proportion of G-fibers in a specimen and were probably
caused by the microscopic behavior of cellulose microfibril (CMF) in the gelatinous layers (G-layers). The longitudinal shrinkage
of tension wood due to drying suggests the existence of a hygro-sensible, noncrystalline region in the CMF, which is abundant
in the G-layer. Furthermore, the noncrystalline region in the CMF softens during boiling treatment, resulting in the reduction
of the longitudinal Young’s modulus in tension wood. The longitudinal contraction of tension wood with G-fibers by boiling
might be caused by the tensile growth stress remaining in green G-layers. However, no changes were detected in the 004 d-spacing of cellulose crystal in tension wood from the boiling and drying treatments, regardless of the proportion of G-fibers. 相似文献
17.
针对移行材和早材皱缩等主要气干缺陷,拟定出赤桉半干材的干燥工艺,窑干前进行回复皱缩和减小表面硬化的汽蒸处理,窑干至目标含水率时进行终了调湿处理.结果表明:汽蒸预处理可以有效地回复皱缩材和显著地减小表面硬化;5 d内将试材的平均含水率25.61%下降到11.72%;3 h的汽蒸处理和24 h的湿空气处理均可有效地减小含水率梯度和残余塑性变定,但后者效果更佳;板材干燥质量达到国家标准二级质量的要求. 相似文献
18.
Dr. T. G. Jones Dr. J. C. F. Walker Dr. T. A. G. Langrish 《Wood Science and Technology》1995,29(3):171-176
Summary Non-steady state desorption of dissolved carbon dioxide gas from green Nothofagus fusca heartwoood boards saturated with carbon dioxide gas at a pressure of 1.5 MPa was used to measure transverse dissolved carbon dioxide gas diffusivities at 1, 20 and 30 °C. Mean transverse diffusion coefficients were 0.6×10-11m2s-1 at 1 °C, 4.2×10-11m2s-1 at 20 °C, and 8.4×10-11m2s-1 at 30 °C. These are 0.6, 2.5 and 3.8% of the dissolved carbon dioxide gas diffusivities in water at 1, 20 and 30 °C respectively. The activation energy of dissolved carbon dioxide gas diffusion in green N. fusca heartwood is 59. 4 kJ mol-1. This is three times the activation energy of dissolved carbon dioxide gas diffusion in water. This suggests the presence of a reaction mechanism between the dissolved carbon dioxide molecules and the cell wall constituents.The Forest Research Institute, Ministry of Forestry, New Zealand, supported this work by way of a postgraduate studentship. 相似文献
19.
Taira Hideaki 《Journal of Forest Research》2003,8(3):227-229
To clarify key characteristics of the process whereby dormancy is released in male flowers of Cryptomeria japonica, twigs with male flowers were collected every three days between December 1992 and February 1993. Half of the twigs collected on each date were chilled at 0°C for three days and the cumulative temperatures required by the chilled and non-chilled flowers for florescence were compared. There was no difference in the cumulative temperature required for florescence between chilled and non-chilled male flowers collected before 19 December. However, for samples collected between 21 December and 21 January, the cumulative temperature needed for the florescence of chilled male flowers was 8–68°C lower than that required for non-chilled male flowers. However, there was little difference again in the cumulative temperature required to induce the florescence of chilled and non-chilled male flowers for collection dates later than 24 January. These results suggest that the dormancy of male C. japonica flowers was gradually released by exposure to low temperature and the process was completed by 24 January. The cumulative temperature required for florescence and the sum of the mean daily temperatures between the date of collection and the date of natural pollen dispersal were almost equal after the dormancy of the male flowers was released. The exact day on which pollen will be released can be predicted using the dormancy characteristics of male flowers. 相似文献
20.
Dr. S. C. Chafe 《Wood Science and Technology》1993,27(3):205-217
Summary Preboiling and drying wood samples of Eucalyptus regnans has shown that while in the heartwood shrinkage before reconditioning increased as a linear function of the logarithm of boiling time (BL), in the sapwood it decreased. These changes were interpreted as reflecting changes in green permeability through extractive modification which, for the sapwood, were sufficient to overcome any weakening of the cell walls through heat effects; in the heartwood, however, cell wall degradation apparently overshadowed any collateral increase in permeability, thus causing an increase in collapse.Shrinkage after reconditioning described a cubic function with respect to BL and showed an overall reduction which was greatest after 16 minutes boiling time. Correspondingly, recoverable collapse was greatly increased through preboiling; it was shown that per cent collapse recovery in the heartwood could be increased by more than one third that of controls by preboiling for 8 minutes. The possibilities for industry application are considered.Moisture content after reconditioning (Mr) was greatest after about two minutes preboiling, then declined to be less than the control after 16 minutes. Change in shrinkage after reconditioning and collapse were shown to be significantly related to change in Mr. It was suggested that while Mr may reflect relative permeabilities after reconditioning, this may not apply to permeability in the green condition.Additional parameters derived from the data, viz. the intersection point, unit shrinkage, the R-ratio, collapse-free shrinkage, total collapse and residual collapse described mostly significant, cubic relationships with the logarithm of the boiling time. Generally, the major inflection point of regression curves occurred after 8 or 16 minutes boiling.The author expresses his appreciation to Margaret Walker for technical assistance 相似文献