超声波辅助木片常压浸渍及其漂白

采用化学热磨机械浆（CTMP）工艺，以桉木与杨木2种木材为原料，初步研究了超声波辅助木片常压浸渍及其漂白效果。通过监测体系中的残余氢氧化钠的量来探究外部环境体系（温度、时间和用碱量）对超声波辅助木片常压浸渍的影响，结果表明：超声波辅助处理浸渍，桉木为温度75℃，时间30 min，用碱量6%；杨木为温度75℃，时间30 min，用碱量5%，此较优条件下，桉木白度提高2.83%（ISO），残余过氧化氢质量分数提高了4.4个百分点，碱吸收量达41.5 kg/t，较未经超声波处理后的桉木的碱吸收量提高了5.06%；杨木白度无变化，而残余过氧化氢质量分数提高了2.73个百分点，碱吸收量达38.75 kg/t，较未经超声波处理的杨木碱吸收量提高了6.15%。     

Drying kinetics of poplar lumber during periodic hot-press drying

The drying kinetics of poplar lumber was experimentally investigated as a function of drying temperature (115, 135, 160, 185 and 205°C) during a periodic hot-press-drying process. Poplar lumber was dried under contact (compression ratio of 10%) and high-press states (compression ratio of 44%). Compared with the contact-state, the high-press-state showed higher drying rate and higher efficiency of removing free water than bound water in wood. Eight mathematical models from the literature were established to analyze the drying behavior. The Weibull model, with an average determination coefficient R² of 0.9958, fitted well for all applied drying conditions. The scale parameter decreased with increasing drying temperature and was lower for high-press-state drying compared with that for contact-state drying. Moisture diffusivity and activation energy were calculated according to the Weibull model. Diffusivity increased with increasing drying temperature, with the average value of 1.734?×?10^?6 and 3.313?×?10^?6?m²/s and activation energy of 34.79 and 32.85?kJ/mol for contact-state drying and high-press-state drying, respectively. Hot-press drying created an M-shaped curve of density distribution, with high density at the two surface regions gradually decreasing toward the core region. The contact state-dried wood showed increased density near the wood surface. Both average density and peak density improved in the case of high-press-state-dried wood. Furthermore, the hydrophilic index of wood for high-press-state drying was lower than that of the contact-state drying, and the opposite was true regarding crystallinity index. The hygroscopicity of high-press-dried poplar decreased with lower equilibrium moisture content and higher moisture excluding efficiency, compared with contact-state-dried poplar. The rapid, high-quality drying of poplar lumber through periodic hot-press was more potentially achieved by the high-press-state compared with contact-state drying.     

碳纤维布增强杨木LVL梁、柱试验研究

采用碳纤维布对杨木LVL梁、柱增强,制作试件进行试验研究.梁采用在生产过程将碳纤维布复合到LVL中的增强方式,柱采用外贴碳纤维布箍增强方式.通过试验选择了合理的梁、柱截面型式,试验结果表明碳纤维布增强杨木LVL梁、柱的承载力明显提高,其它受力性能也得到显著改善.     

Effect of nitrogen–phosphorus fire retardant blended with Mg(OH)2/Al(OH)3 and nano‐SiO2 on fire‐retardant behavior and hygroscopicity of poplar

The aim of the study was to screen any possible synergistic effects related to the combination of nitrogen–phosphorus fire retardant and Mg(OH)₂/Al(OH)_3. This combination is used to improve fire performance, especially smoke suppression of poplar through ultrasonic wave impregnation after microwave treatment. In this study, nano‐SiO₂ was used to impregnate poplar treated with nitrogen–phosphorus fire retardant and form a hydrophobic layer on wood cells in order to improve hygroscopicity and reduce water uptake. Cone tests and thermal analysis showed that poplar treated with blended fire retardant had improved behavior. Results show that a 20% and 25% nitrogen–phosphorus fire‐retardant solution (blended by adding 10% Mg(OH)₂/Al(OH)₃ based on the dry weight of nitrogen–phosphorus fire retardant) was more effective for smoke suppression. The heat release rate, total heat release, and total smoke production of a 25% nitrogen–phosphorus fire‐retardant solution blended by adding 10% Mg(OH)₂/Al(OH)₃ showed significant reduction. The char residual yield showed a marked increase to 35.5%. Fourier transform infrared analysis suggested a –CH₂–Si–CH₂– and Si–O–C stretching vibration in nano‐SiO₂ treated poplar, which greatly decreased the hygroscopicity of fire‐retardant‐treated poplar. Copyright © 2014 John Wiley & Sons, Ltd.     

自水解预处理对杨木聚木糖分布的影响

采用免疫荧光标记法结合共聚焦显微镜(CLSM)研究了自水解强度对杨木聚木糖分布的影响。结果表明,聚木糖荧光信号较均匀地分布于杨木纤维细胞壁中,随强度因子的增大细胞壁中心部位荧光信号下降逐渐增多,细胞壁边缘荧光信号下降较少,有些部位甚至会稍许增加。采用高效液相色谱(HPLC)检测法测得强度因子增强到3.72时,聚木糖含量从原料的14.64%下降到7.33%;对聚木糖荧光图谱进行区域强度统计,可得出与HPLC检测法结果相同的变化趋势。     

Trade‐Offs in Seed Dispersal Strategies Across Riparian Trees: The How Matters as Much as the When

Riparian Salicaceae are prolific producers of short‐lived seeds that require very restrictive hydro‐geomorphic conditions for establishment. It is generally assumed that if floods are able to create nursery sites timed with seed dispersal, recruitment will occur. Other spatial and temporal seed dispersal patterns besides the dispersal period have historically received little attention. However, seed dispersal patterns can be highly variable between regions, species and over the years. In this paper, we report the seed dispersal patterns of three dominant riparian Salicaceae trees in Europe: Populus alba, P. nigra and Salix alba to suggest possible trade‐offs between seed dispersal patterns, germinability, longevity and establishment. Seed rain of the three species was monitored in 33 glue‐coated traps for three months yearly from 2006 to 2008 in an 8‐km stretch of the Middle Ebro River (N Spain), which has a pluvio‐nival regime. P. alba dispersed seeds earlier during a shorter time period and with a fewer number of seed release pulses compared with P. nigra, and especially with S. alba. With overlapping seed dispersal periods, the two latter species occupy similar landform units but rarely compete with P. alba, usually at higher elevations, as shown in a previous study in the same study area. The three species had very high germinability immediately after release (>90%), but longevity in S. alba was eight times shorter than that of its two Populus counterparts. We suggest that S. alba has compensated its lower seed quality with a more spaced seed release in several pulses of similar magnitude. With similar seed dispersal patterns and germinability but a higher longevity, P. nigra had a much higher density of individuals than S. alba in the recruitment zones of the study area. We hope that our results may inform river managers about how to optimize river flows to promote sexual regeneration of these species. Copyright © 2015 John Wiley & Sons, Ltd.     

冲击压缩载荷作用下杨木的力学性能研究

通过SHPB动态压缩实验，对杨木在高应变率条件下的力学特性进行了研究。基于一维应力波理论的分析表明，尽管杨木相比于金属压杆具有较低的波阻抗，其SHPB动态压缩实验中试样两端的应力均匀性条件仍可以得到满足，而不需要进行入射波整形。通过在透射杆上使用半导体应变片，可以获得具有较高信噪比的透射波信号。结合杨木的准静态实验结果发现，其应力-应变曲线具有多孔材料的典型特征。轴向试样具有Ⅱ型吸能结构特征，失效应力和平台应力都具有应变率敏感性，其平台应力的敏感性稍弱；弦向试样具有Ⅰ型吸能结构特征，没有明显的失效强度，其平台应力具有应变率敏感性，与通常的Ⅰ型吸能结构相比存在一定差异。通过对实验数据的拟合，发现应变率对杨木失效强度的影响符合对数率。     

Farm wood fuel and energy project

This paper describes the findings of the Farm Wood Fuel and Energy Project. It began in 1991 and ended in 1997 and was undertaken to provide a commercial demonstration for the establishment of 50 hectares of short rotation coppice (SRC) on six farms in southern England and the development of associated marketing activities. The Project:

• — taught farmers how best to grow the crop and will enable them to teach others;

• — determined that winter conditions in the UK are unsuitable for most harvesting equipment trialled and that both harvesting and chip storage need to be re-examined;

• — demonstrated that SRC has the potential to be competitive with fossil fuels;

• — gave confidence to Government to include a Band for energy crops under the NFFO electricity generating procedures

     

Influence of Chemical Pretreatment on the Dissolved Organics in Poplar Alkaline Peroxide Mechanical Pulping Effluent

The components of the effluent from the chemical pretreatment of poplar alkaline peroxide mechanical pulp (APMP) were analyzed in this study. The main dissolved organics were low-molecular weight (LMW) lignin, oligosaccharides, and monosaccharides. The lignin and sugar concentrations in the effluent obtained using different chemical pretreatment conditions and chemical dosages were analyzed using ultraviolet (UV) spectroscopy. This analysis provided a theoretical basis for the subsequent treatment and utilization of APMP effluent. The experimental results showed that the dosages of NaOH, H₂O₂, and Na₂SiO₃ in the chemical pretreatment process affected the lignin and sugar concentrations in the effluent and that different chemicals had differing degrees of influence. The degree of influence exhibited the following order: NaOH>H₂O₂>Na₂SiO₃. More specifically, the dosages of NaOH and H₂O₂ had stronger influences on the lignin and sugar concentrations than that of Na₂SiO₃. Indeed, the Na₂SiO₃ dosage hardly affected the lignin and sugar concentrations in the effluent, but Na₂SiO₃ could stabilize the chemical pretreatment system and improve the reactive efficiency of NaOH and H₂O₂. The pretreatment temperature and time also affected the organic components, and the influence of the temperature was stronger than that of time.     

硅酸钠/聚乙二醇浸渍改性杨木工艺及性能研究

目的 为了提高速生杨木的物理力学性能、尺寸稳定性、热稳定性等性能，以硅酸钠(Na2SiO3)溶液和聚乙二醇(PEG)溶液为改性剂，旨在提高杨木的力学性能、尺寸稳定性以及耐热性能，并探究硅酸钠质量分数、聚乙二醇质量分数以及分子量对改性杨木性能的影响，获得最佳浸渍工艺。方法 运用单因素试验法探究硅酸钠质量分数、聚乙二醇质量分数、聚乙二醇分子量3个因素对改性杨木浸渍效果的影响。通过最佳浸渍工艺制备硅酸钠/聚乙二醇改性杨木与硅酸钠改性杨木，并测定其顺纹抗压强度、表面硬度、吸湿体积膨胀率等性能和结构表征，探究其与未改性杨木的差异。结果 通过单因素试验结果可知，以质量分数为10%的Na2SiO3、PEG-400以及质量分数为5%的PEG-400的浸渍工艺制备出改性杨木性能较佳。硅酸钠/聚乙二醇杨木改性材的顺纹抗压强度、抗弯强度、端面硬度、径面硬度和弦面硬度较未改性杨木的分别提高了69.4%、19.1%、42.2%、39.5%、19.2%，吸湿体积膨胀率较硅酸钠改性材降低了40.0%。结论 速生杨木经过硅酸钠/聚乙二醇改性后的力学强度，相较于单独硅酸钠改性杨木的力学强度有所提升，尺寸稳定性能增强，因此在性能及应用方面，硅酸钠/聚乙二醇改性杨木更具优势。