叉车起升油缸的稳定性验算

用于贮木场及板院装卸归楞和短途运输木材的正面和侧面叉车的门架机构具有长行程的起升油缸,结构如同细长柱体,其类型分成柱塞式和活塞式。前者造价高、维修复杂,但截面惯量大,工作时不易失稳;后者价靡,装配维修方便。但截面惯量小,尤其当偏载起动时,更需校验发生挠曲变形时的油缸整体稳定性。兹参考试验实测工况,结合理论分析进行验算。     

用自制摩擦攻丝夹头机攻热压机缸体大螺孔

热压机柱塞油缸缸体顶部的螺孔,直径较大,因受周期性交变载荷作用,容易“滑牙”,造成漏油。对此,通常都是采用对原孔扩孔或重新加工螺孔的方法加以解决。这里介绍一种在 Z35摇臂钻床上用摩擦片式攻丝夹头机攻螺孔的方法。     

多层平压法细木工板侧拼装置的研究

人工组坯生产细木工板因为没有定向限位措施,常造成板坯在搬运和装板过程中发生芯条振动位移,使得热压后板中芯条之间出现严重的侧向缝隙,给以后的机械加工和部件的强度带来不利影响。因此,设计了一套附加在热压机上的侧拼装置,使板坯在装人压板间隔后,在同时闭合的同时,得到侧向挤压作用力,从而使芯条之间达到紧密胶合的效果。１侧拼装置的结构 多层侧拼装置是一套小型侧向液压加压装置。在相邻层热压板间安装二个小油缸,通过柱塞的往复工作,控制侧拼动作。其由靠板、油缸、阀、泵等部件组成。 靠板、油缸由支架联接在热压板的一…     

一种适于大型零件的热处理方法

在林业机械中,有一些要求表面耐磨、而又不易用常规热处理手段处理的大型零件。例如制材机械中的带锯机带锯上下轮,纤维板机械中的热压机柱塞,装卸板机油缸缸心等。用高频淬火、整体淬火、火焰表面淬火,需要大型设备,工艺复杂,零件选材严格,一般生产单位不易做到,也不经济。而采用电接触加热表面淬火的热处理工艺,则容易解决上述问题,达到硬化零件表面的目的。     

新适用型热压机简述

1热压机结构与主要技术参数新适用型热压机是笔者帮助民营企业设计、制造并安装的。热压机的层数为五层,采用横向入板,可压制4'×6'幅面的胶合板。热压机是钢板与槽钢焊接组合的框架式结构;热压板的蒸汽回路采用钢板隔条焊接而成;采用四组柱塞直径为Φ180mm的油缸;液压系统由高、低压泵,手动阀,溢流阀,滤油器,油箱,压力表和电机等部件组合而成;油路系统用冷轧无缝钢管连接;采用大油桶做油箱,且各种液压元件均安装在油桶上。2液压系统工作原理当液压系统启动时,低压泵先接通,液压油使4个柱塞上升并推动热压板闭合(压板闭合前已有胶合板板坯放…     

在拖拉机柴油泵泵盖上进行柱塞副密封性试验

修理拖拉机时,如果在同一台拖拉机的柴油泵上,装用密封性不同的柱塞副(柱塞与柱塞套),发动机就将出現中小油門工作不均勻的現象。因此,在拖拉机修理过程中,无論是換用新的柱塞副或是选配修复的柱塞与柱塞套,都需要进行柱塞副的密封性試驗。这是修理拖拉机时提高修車质量的一項技术措施。     

相同集聚因子时纤维悬浮液的流动特征及机理

纤维悬浮液在管路中从层流发展为湍流的过程中会表现出复杂的流动状态。为了解这一现象的内在原因,以相同集聚因子时4种不同尺寸的尼龙纤维悬浮液为实验对象,利用超声多普勒测速仪测量它们在圆管内流动的速度场。根据流场分布确定了纤维柱塞尺寸,并利用流动阻力损失计算柱塞内部纤维网络结构的屈服应力。基于柱塞内纤维平均体积分数的变化规律以及柱塞边缘雷诺应力与屈服应力的比值分析讨论了尼龙纤维悬浮液流动特征的变化机理。研究结果表明,柱塞尺寸随着雷诺数的增大而不断减小。在流动阻力的压缩作用下,柱塞内部纤维网络变得致密,其平均体积分数随着雷诺数的增大逐渐增加,屈服应力不断上升。由于平均雷诺应力增加速率要高于屈服应力,当柱塞半径与管道半径之比小于0.2时,湍流强度明显高于纤维网络的结构强度。柱塞内部受到湍流侵蚀,柱塞内纤维平均体积分数及其屈服应力开始下降,柱塞中纤维网络逐渐被破坏直至崩溃。相同集聚因子时,形状系数较小的纤维悬浮液内部纤维网络结构强度更高,因此具有较大半径的柱塞和较高的屈服应力。同时在相同雷诺数时,形状系数较小的尼龙纤维悬浮液柱塞边缘平均雷诺应力较小,表明较大半径的柱塞会对水环的湍流产生较强的抑制作用。     

液压起重臂主副臂变幅机构的设计

主、副臂变幅运动通常是由副油缸或副油缸经四杆机构推动来实现。按副油缸作用力可分为副油缸推力式和拉力式二种。推力式是指副油缸的推力使副臂展开;拉力式则是其拉力使副臂展开。表1列出几种起重臂主、副臂变幅机构的布置实例。本文通过对上述几种布置型式的分析,提出主、副臂变幅机构的设计方法和副油缸基本参数的选择。     

柴油机“缺腿”的原因

柴油机有的缸不工作,称柴油机“缺腿”或称“瘸腿”。产生的主要原因有:1 喷油泵不供油①柱塞与调节臂松动,或调节臂从调节叉内脱出,或调节叉在供油调节拉杆上松动,使柱塞转向停油侧。②柱塞弹簧折断,使柱塞吸油行程过小;或凸轮轴凸轮与滚轮、滚轮与滚轮     

柴油机二级喷射柱塞副结构的改进设计与试验

对柴油机二级喷射柱塞副的结构进一步改进，以改善柱塞的速度特性，减小柱塞的漏油面积。在标定油量不变的情况下，增大起动测量 量，以改善二级喷射柴油机的起动性能。还设想出二级喷射柱塞副应具备的结构，以适应不同机型，不同工况下柴油机二级喷射的油量分配及时间间隔，以便更好地发挥二有喷射柴油机的优越性。     

不同部位银杏茎段培养及位置效应的研究

以一个月月龄银杏(Ginkgo biloba)无菌幼苗各部位茎段为外植体,研究其顶芽、带腋芽的中段、带子叶的下段腋芽萌发和不定芽的分化情况。结果表明:①银杏顶芽段(上段)在以改良MS、N6、DCR为基本培养基,附加0.1mg/LNAA和0.5mg/L6-BA的培养基上顶芽生长较其他培养基好,抽出的芽苗长得高,最高达2.98cm,未见有不定芽的分化;②中段外植体在四种基本培养基(MS、DCR、N6、改良MS)中附加0.1mg/LNAA和0.5mg/L6-BA和0.25%AC时,都能诱导出腋芽和不定芽,4种培养基之间芽诱导率无明显差异,以N6培养基的诱导效果最好,平均每个外植体产生1.56个芽;③带有子叶下段的外植体培养后,能诱导出2～3个子叶腋芽和新的不定芽,在改良MS+0.1mg/LNAA+0.5mg/L6-BA、N6+0.1mg/LNAA+0.5mg/L6-BA培养基上两个腋芽的诱导率均达80%以上。表明,不同部位的银杏茎段在芽的诱导上存在位置效应,可利用不同部位进行银杏的定向快速繁殖。     

窄冠刺槐无性系根段扦插育苗研究

刺槐(Robinia pseudoacacia L.)因其木质坚硬,色泽纹理美观,耐磨耐腐蚀,抗弯抗压及抗剪强度高,是制造地板、家具等产品的优质木材[1]。我国从20世纪70年代开始对刺槐进行遗传改良,先后在次生种源选择、优良无性系选育等方面做了大量研究[2-5],选育出了一大批生长表现良好的优良无性系[6-7],特别是于2002年在河南省选育的窄冠刺槐优良无性系,生长快,主干通直圆满,分枝角度小,托     

Mycelial fan formation of three sympatric Armillaria species on excised stem segments of Picea abies

Mycelial fan formation was studied in five Armillaria cepistipes, ten A. borealis and ten diploid and six haploid A. ostoyae strains on excised stem segments of Picea abies. Stem segments were either non‐autoclaved or autoclaved, representing dying and dead wood, respectively. To confirm the identity of mycelial fans on non‐autoclaved stem segments, re‐isolations were made and isolates characterized with microsatellite markers. Mycelial fan formation on autoclaved stem segments was fast and reliable for most of the tested Armillaria strains. On non‐autoclaved stem segments, mycelial fan formation was slower, more erratic and less predictable. Mycelial fan formation was fastest in A. cepistipes closely followed by A. borealis and was slowest in A. ostoyae. For two A. cepistipes and four A. ostoyae strains (all diploid), growth rates of mycelial fans were estimated in a time course experiment. They ranged between 5.1 and 8.7 mm/day for autoclaved and between 1.4 and 4.7 mm/day for non‐autoclaved stem segments. The haploid A. ostoyae strains also formed mycelial fans on autoclaved stem segments, but typically slower and less reliably than the diploid strains. Whether haploid strains are able to produce mycelial fans on non‐autoclaved stem segments remains unknown because of accidental diploidization of the original haploid strains which was likely caused by basidiospores introduced into the study system on the non‐autoclaved stems. Overall, the method developed in this study may be useful for further investigations into the genetic, physiological and biochemical nature of mycelial fan formation in the genus Armillaria.     

Satisfaction across urban consumers of smallholder-produced teak (Tectona grandis L.f.) poles in South Benin

The study used the expectancy-disconfirmation framework to investigate the satisfaction among urban consumers of teak pole in South Benin, so as to identify the areas where interventions are needed to secure market opportunity for smallholder forestry. A survey was conducted in five cities; and 223 household-heads were interviewed using systematic sampling, with a random start. Data were collected on socio-demographic characteristics, teak pole consumption forms, behaviour patterns, and motivations. Respondents also rated their expectations and perceptions for a set of nine attributes on a 7 points Likert scale. Hierarchical ascending cluster analysis was performed to identify consumer segments; and satisfaction level was analysed per segment, by determining the gap between expectations and perceptions, for all attributes. Four consumer segments were identified; and sociodemographic profiles differed across those segments. Competitive price was an important purchasing motivation across the identified segments. Consumers were dissatisfied with price, availability, knot frequency, bending, length, hardness, and durability of teak pole. The efforts to meet the consumer expectations should be concentrated on building farmers' capacity in silvicultural management, and ensuring the availability of good planting material. The issue of competitive price might be addressed, through the improvement of the overall efficiency in the value chain.     

Comparison of methods for estimating surface area of water-stressed and fully hydrated pine needle segments for gas exchange analysis

A nondestructive technique for repeatedly estimating total surface area of water-stressed pine (Pinus taeda L.) fascicle segments was evaluated. Fascicle radius was measured with a digital caliper and needle surface area calculated on the assumption that the needles were segments of a cylinder. High correlations (r >/= 0.94) were found between surface area estimated in this way and surface area calculated (a) from needle displacement, also on the assumption that needles are segments of a cylinder, and (b) from needle dry weight using a regression between dry weight and surface area estimated from needle displacement. The caliper-radius method gave slightly lower estimates of surface area than the other methods. However, differences among surface area estimates made with the three methods and between estimates made on water-stressed and fully hydrated needles were small relative to variances of leaf gas exchange measurements.     

松材线虫病死木皮下的南京隐翅虫(鞘翅目:隐翅虫科)

【目的】南京隐翅虫是在受松材线虫病危害的病死木皮下发现的隐翅虫新种,与小蠹、天牛等多种次期性害虫的时间和空间生态位跟随关系密切,具有作为媒介昆虫防治蛀干害虫的潜力。研究南京隐翅虫不同发育阶段个体的形态特征、成虫的食性及昼夜活动节律,能够为进一步的研究和应用提供参考。【方法】室内观察南京隐翅虫不同发育阶段个体的形态特征,通过人工饲养并结合口器解剖研究南京隐翅虫成虫的食性;应用"陷阱法"观察试虫的昼夜活动节律。【结果】南京隐翅虫幼虫为寡足型,口器咀嚼式,胸足发达,蛹为裸蛹,成虫体长1.5～2.0 mm,身体狭长平行,头、中后胸、腹部6～8节颜色较深,身体其他部分浅黄色。成虫喜食人为杀死的跳虫成虫、蝇科幼龄幼虫及天牛幼虫,对于小蠹科、象甲科、叩甲科、蚁科、蠼螋科的幼虫尸体表现出取食行为,试验过程中并未观察到捕食其他生物活体。室内南京隐翅虫成虫昼夜活动节律高峰期分别是8:00—11:00以及20:00—22:00。【结论】南京隐翅虫成虫为尸食性,其昼夜活动节律受温度影响较大。     

Relation between wilt rate and obstruction of water flow in stems of two families of loblolly pine affected by pitch canker

Movement of water forced through stem segments of two half-sib families of loblolly pine (Pinus taeda), infected by Fusarinum subglutinans, was monitored. Wilt rate of the two families was shown to be correlated with obstruction of water flow through stem segments of similar disease severity.     

Root respiration in Chamaecyparis obtusa trees

We examined the respiration rate of root segments, which had a constant length in relation to their diameter, from three small and two large 26-year-old Chamaecyparis obtusa (Siebold & Zucc.) Endl. trees. The dependence of respiration rate on segment diameter was described by a power function with an exponent of about 1.5, except for the smallest sample tree, for which the exponent was 1.74. Unlike stem segments, root segments of similar diameter showed similar rates of respiration regardless of the tree from which the root segments had been taken. On the basis of the power function, we propose a new equation to estimate the total root respiration rate of a tree. The relationship between root respiration rate per tree and root weight can be expressed by a power function with an exponent of 1.11. The ratio of the specific respiration rate of stems to that of roots was 0.7 for the three smaller trees, and 1.1 to 1.3 for the two larger trees. In November, the stand respiration rate of roots was estimated to be 0.36 kg CO(2) ha(-1) h(-1) for a root biomass (dry weight) of 28 Mg ha(-1).     

长山核桃茎段组织培养初步研究

为给建立完整有效的长山核桃组培快繁体系提供基础,以带腋芽茎段作为外植体,研究不同消毒方法和基本培养基对腋芽萌发的影响。结果表明:不同消毒剂和消毒时间处理对外植体的影响较大。先用75%酒精消毒20 s,再用0.05%HgCl_2消毒7 min,外植体污染率降低到30%,且腋芽萌发率最高,可达100%。极差分析结果表明:HgCl_2浓度对污染率和萌发率影响最大,是影响茎段成活率和腋芽萌发的主要因素。不同培养基、激素种类及浓度对外植体有显著影响。在9个处理中,WPM+6-BA 2.0 mg/L+IBA 0.01 mg/L与其它处理差异极显著,这种处理培养的茎段污染率较低,腋芽萌发率高,可达到90%。     

5个银杏品种无菌苗不同部位激素含量比较

通过对银杏5个优良品种1个月龄无菌苗不同部位内源激素含量的测定,发现顶芽段的生长素含量最高,带腋芽的中段次之,下段较少。细胞分裂素（iPA＋ZR）含量主要分布在中段、下段和子叶中。顶芽中IAA／（iPA＋ZR）比值与生长素分布有相同的规律,也是顶芽最高,中段次之,下段最低。5个品种的激素水平存在差异,其中IAA的排列顺序为：44号〉28号〉45号〉53号〉79号,79号含量最低。ZR＋iPA总含量的排序为：79号〉28号〉45号〉44号〉53号,79号的含量最高。这些结果为银杏离体培养中外源激素或调节剂合理的添加,有目的、有方向地调控提供指导。