木材干燥导水系数和换水系数的研究

木材(板、方材)的导水系数和换水系数是反映木材干燥或存放过程中水分迁移的重要物性参数。然而,我国对木材导水系数和换水系数的研究和测定工作十分有限。木材干燥有关的理论计算中,常用原苏联的数据。由于这些数据本身可能存在的误差及用于我国树种的可靠程度难以估计,故使理论结果的实际运用受到限制。本文采用等厚试件系数分离法研究和测定了木材干燥过程动态导水系数和换水系数。     

用有限元法分析木材中的温度分布

在木材应用中,了解温度在木材中的分布情况,掌握木材在受热时的温度场,才能有效地控制解冻,才能对干燥和防腐问题进行深入的研究,才能合理使用建筑围护材料。近年来,随着计算机应用和计算技术的发展,用数值方法求解木材中的热传导问题将成为有效、实用的方法。在许多种数值方法中,有限差分法和有限元法是目前较为成熟和用得普遍的方法。其中的有限元法是对古典近似计算的归纳和总结,它吸取了有限差     

林业中常用的一种分析方法—聚类分析

聚类分析的基本思想是研究的样品或指标（变量）之间存在着的程度不同的相似性（亲疏关系），根据一批样的多个观测指标，具体找出一些能够度量样品或指标之间相似程度的统计量，以此为划分类型的依据，将一些相似程度较大的样品（或指标）聚合在同一类，而将关系疏远的聚合在不同的类，把不同的类型一一划出来，形成一个由小到大的分类系统。最后将整个分类系统绘制成一张聚类图（或称谱系图），并由聚类图进行分类。     

山西省旅游业关联性研究

使用山西省2002年42部门的投入产出表,计算了山西省旅游业的直接消耗系数、完全消耗系数、联系深度系数、感应力系数和影响力系数,对这些系数进行了分析、对比和分类,提出了对山西省发展旅游业的一些建议。     

大跨拱桥吊杆张拉计算与方案设计关键技术

经过仔细分析发现,模拟吊杆力的变形量是施加在未变形的结构体系上的,实际工程却是在已经变形的结构上张拉吊杆,直至达到设计值为止.针对此问题,利用ANSYS软件,本文提出温度系数法和吊杆力系数法,并结合厦门五石路桥的工程实例,将之运用于五石路桥工程中,取得满意的工程效果.     

吸声保温玉米秸秆穰板制备及性能研究

以疏解后的玉米秸秆穰丝为基材,异氰酸酯为胶黏剂,均匀组坯后经热压制备成吸声保温玉米秸秆穰板。通过单因素试验分别探究了施胶量、热压温度板材密度、厚度对玉米秸秆穰板吸声、导热和压缩性能的影响。结果表明:综合板材的性能和生产成本,优化工艺为施胶量2%、热压温度140℃、密度0.10 g/cm3,所得板材吸声性能达到GB/T 16731—1997的Ⅲ级标准,压缩强度满足GB/T 25975—2010中的要求,属高效保温材料。     

摆满系数的研究

由于原木纵向选材输送机是在多点卸木条件下输送原木,所以,计算牵引构件最大张力值时。不能用充满系数而要用摆满系数来计算牵引构件上的原木载荷。摆满系数表示在单位时间内,一节输送机上的原木总长度与牵引构件总长度之比值。这个比值与楞头的位置排列、选材量大小和原木长短有关。一般可在0.23～0.38范围内选取。平均为0.31。     

乔木树种含碳系数和储能系数的测定方法及步骤

文章叙述了乔木树种含碳系数、储能系数实验室测定的方法、步骤及注意事项。     

湘潭锰矿区本土先锋植物耐受与积累锰的特性分析

采样分析了湘潭锰矿区废弃地本土先锋植物及其根际土壤的锰含量。分析结果显示土壤样本中Mn、Pb、Zn、Cu、Cd含量超过国家背景值数倍,表明调查区多元素复合污染严重。野外调查的40种本土植物都能在锰污染土壤环境中生长,但植物种类之间锰的转移和积累能力差异显著。铁扫帚(Clematis hexapetala)地上与地下部分锰含量均大于超积累植物10 000 mg/kg的临界浓度,蓼(Polygonum orientale)、葛藤(Argyreia seguinii)、黄荆(Vitex negundo)和革命草(Alternanthera philoxeroides)茎叶中锰含量大于2 000 mg/kg。蓼,葛藤以及翦股颖(Agrostis matsumur)和狗牙根(Cynodon dactylon)的积累系数BCF与转移系数TF大于1。上述锰含量高和积累系数与转移系数大的植物可作为锰矿废弃地植被与景观恢复的本土先锋植物。     

盐城区域分工的分析与优化

区域分工是推动区域经济合作的最根本动力。文章计算了盐城市7个县9个行业的工业区域配置系数和区域专业化系数,选取每个县的专业化主导产业,并对7个县的区域分工现状进行了分析,发现了产业＂同构化＂、区域差异显著、演进缓慢等问题,并提出相应的优化对策。     

Chemical kinetics of Japanese cedar,cypress, fir,and spruce and characterization of charcoal

 Thermogravimetric and differential thermal analyses techniques have been applied to investigate the thermal degradation characteristics and chemical kinetics of Japanese cedar, cypress, fir, and spruce. The decomposition of the components could be modeled by an Arrhenius kinetic expression. The kinetic parameters were extracted from the thermogravimetric data using least-squares techniques. The heating rates used for the analyses were 10°, 5°, and 0.33°C/min; and the activation energy and reaction order of the above woods were 7.54, 8.39, 2.87, and 7.88 kJ/mol and 0.71, 0.64, 0.44, and 0.63, respectively. Finally, carbonization was done to produce charcoal from these woods under various operating conditions, and the charcoal was characterized in respect to yield, heating value, electrical conductivity, and X-ray diffraction. The quality of the charcoal from fir was the best among the four types of wood. The charcoal produced is inferior to binchotan (white charcoal) in respect to electrical conductivity and crystalline structure. Received: February 13, 2002 / Accepted: July 12, 2002 Acknowledgment The authors express their gratitude to Professor Yoshida of Applied Chemistry in Tokyo Metropolitan University for performing the TG/DTA in his laboratory and for his valuable suggestions about the analyses.     

Effects of alkali,mild steam,and chitosan treatments on the properties of pineapple,ramie, and sansevieria fiber bundles

This study focused on the effects of treatments of alkali, mild steam, and chitosan on the surface morphology, fiber texture, and tensile properties of pineapple, ramie, and sansevieria fiber bundles. The fibers were treated with NaOH (2%), mild steam (0.1 MPa), and chitosan solutions (4% and 8%). The properties of these treated fibers were characterized and compared with the untreated fibers. Field emission scanning electron microscopy (FE-SEM) was used to observe the surface morphology of those fibers. X-Ray diffraction (XRD) spectroscopy was used to observe the fiber textures. Tensile properties of the treated and untreated fibers were also recorded. SEM micrographs showed that the surfaces of the NaOH-treated fibers were more damaged than those of the steam-treated fibers. The 4% chitosan solution covered the fiber surface more uniformly than the 8% chitosan solution. The steam-treated fibers had higher values of degree of crystallinity, crystallite orientation factor, and crystallite size than the NaOHtreated fibers. Ramie fiber showed greater mechanical properties than the other fibers. The values of tensile strength, Young’s modulus, and toughness of the steamtreated fibers, which were similar to those of the 4% chitosan-coated fibers, were higher than those for the other treatments.     

核桃采收、脱皮、漂白及坚果分级技术要点

本文就核桃采收时间、脱皮方法及坚果分级标准进行了初步研究总结,为实现核桃优果优价、提质增效提供了切实可行的理论依据。     

Sciences,knowledges, and the practice of forestry

We address the question of how credible knowledge that will contribute to more effective forest policy and management can be produced. We argue that some forest-related knowledge-producing practices of professional scientists and of local people are similar, and given the differences in the knowledge they produce, we explore how they might be used productively together to create better understandings of forests with resulting better forestry practice and policy. Using a case study of participatory forest ecology research, we demonstrate that when professional (conventional) scientists do research in collaboration with local experts (civil scientists), the resulting knowledge can be more accurate and more policy relevant than they could produce doing research on their own or only with other conventional scientists.     

Behavioral responses,rate of mortality,and oviposition of western cherry fruit fly exposed to malathion,zeta-cypermethrin,and spinetoram

Western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), is a pest of sweet and tart cherry, Prunus avium L. (L.) and P. cerasus L., respectively, in western North America. This fly is commonly controlled with spinosad bait sprays. Spotted wing drosophila, Drosophila suzukii Matsumura, is potentially a new pest of cherries in this region that could be a threat to orchards at the same time as R. indifferens. Drosophila suzukii apparently is not controlled using spinosad bait sprays, but may potentially be controlled using malathion, zeta-cypermethrin, and spinetoram. However, how well these last three materials protect fruit against reproductively mature R. indifferens is not known. In laboratory observations, R. indifferens spent the least amount of time on cherries treated with zeta-cypermethrin, possibly because of its toxicity and irritant effects. In laboratory experiments, zeta-cypermethrin killed flies more quickly than malathion and spinetoram, causing up to 100% mortality 2 h after exposure. Zeta-cypermethrin prevented all oviposition when flies walked on dried residues for 20–25 min or were directly sprayed, and then exposed to cherries with dried residues, simulating exposure of mature female flies in a treated orchard. Malathion and spinetoram reduced oviposition compared with controls, but did not prevent it, when flies contacted residues or were directly sprayed at a high volume. Results suggest zeta-cypermethrin is the most effective of the three materials at protecting cherries against mature R. indifferens and could be used in an integrated control program for it and D. suzukii.     

Integration of pines,pastures, and cattle in south Georgia,USA

Agroforestry Systems - Native forages of southern United States are frequently low in nutrients and poorly digestible, while improved pastures are the opposite. Since this area produces rapid...     

Seedling emergence, growth, and allocation of Oriental bittersweet: effects of seed input, seed bank, and forest floor litter

The establishment of invasive plant populations is controlled by seed input, survival in the soil seed bank, and effects of soil surface disturbance on emergence, growth, and survival. We studied the invasive vine Celastrus orbiculatus Thunb. (Oriental bittersweet) to determine if seedlings in forest understory germinate from the seed bank or from seed rain. We also conducted a greenhouse experiment to investigate the role of leaf litter mass and physical texture on seedling survival, growth, and allocation. In the understory of an invaded mixed hardwood forest, we measured seed input, seedling emergence with seed rain, and seedling emergence without seed rain. Mean seed rain was 168 seeds m⁻²: mean seedling emergence was 107 m⁻², and there was a strong correlation between seed rain and seedling emergence. The ratio of seedlings to seed input (0.61) was close to the seed viability (0.66) leaving very few seeds to enter the seed bank. Seed bank germination under field conditions was low (1 seedling m⁻²). Soil cores were incubated in a greenhouse to determine seed bank viability, and germination from these soil cores did not occur. To determine how litter affects seedling establishment and growth, we measured seedling emergence and biomass allocation in a greenhouse experiment. Seeds were placed below intact and fragmented deciduous leaf litter in amounts ranging from zero to the equivalent of 16 Mg ha⁻¹. Seedling emergence was not affected by fragmented litter, but decreased to <20% as intact litter increased to 16 Mg ha⁻¹. Increasing litter resulted in greater allocation to hypocotyl and less to cotyledon and radicle, and this effect was greater in intact litter. C. orbiculatus seedlings achieve emergence through forest floor litter through plasticity in allocation to hypocotyl growth. The low survival of C. orbiculatus in the seed bank suggests that eradication of seedling advance regeneration and adult plants prior to seed rain may be an effective control strategy. However, the intact forest floor litter of an undisturbed forest will not prevent seedling establishment.     

林地土壤pH值，磷，钾，有机质和水含量具有可变和可控性

对取自山西省北部不同地点、不同层次的土样的pH值、磷、钾、有机质、水含量的变化进行了研究。结果表明：林地土壤理化性质具有可变性的可控性。