古筝琴板的振动特性初探研究

木质乐器的好坏与木质板材的振动特性有着密切关系。以古筝为例,对琴板振动特性进行了理论分析与试验研究。分析了板的弯曲和扭转振动理论,得出琴板扭转和弯曲振动的固有频率值;通过自由振动试验和弯曲与扭转振动模态试验,得到琴板的自由振动时域图和频谱图及其弯曲振型和扭转振型图;通过理论分析与试验结果对比,验证了古筝琴板振动特性试验方法与结果的有效性,为古筝琴板及其他乐器木质板材的筛选与生产提供了一种有效的科学手段。     

油锯振动病的预防措施

油锯振动引起的伐木工人振动病正得到人们的广泛注意。本文对我国油锯振动病的现状进行了分析,提出了预防油锯振动病的有效措施。     

银杏侧枝振动落果的试验研究

为设计一种合理的振动采集干果的机具，对银杏树果实的果柄结合力进行了测试，对果枝进行了激振试验和振动落果试验，还在室外对立木侧枝进行了振动测试，经过数据处理和分析，得出了银杏侧枝振动落果最佳的激振频率、振动加速度和振动时间，为果树侧枝振动采种机具的设计提供了科学的技术参数和设计依据     

基于Daubechies小波基的木材声学振动信号分析与评价

针对音板木材振动信号分析不深入的问题,本研究基于小波包分析方法对木材振动信号进行分析,建立一种木材声学振动评价的新方法。利用多通道FFT分析仪获取泡桐木材的振动信号,基于Daubechies小波基函数对振动信号进行3层小波包分解与重构,得到了振动信号的特征值,将小波包变换后木材振动信号的特征值与传统方法测定的声学振动性能参数进行比较分析。研究结果表明:木材的振动信号能量主要集中在0～1 000 Hz,在传播的过程中能量衰减迅速;对振动信号进行时域分析时得出,木材的动态弹性模量随着峭度因子的增大而减小,随着峰值因子的增大而增大;基于Daubechies小波基的分析方法得到的振动信号特征值与声学振动参数之间具有显著的相关性,其中木材信号的特征能量率与木材声学振动参数动态弹性模量、声辐射品质常数以及声传播速度之间存在显著的正相关关系,与声阻抗以及对数衰减率的相关性及变化趋势之间有显著的负相关关系。研究表明,可以应用Daubechies小波对木材振动信号进行分析与评价,此方法为木材声学振动性能的客观评价提供了新思路。     

振动法测试胶合木梁弹性模量的方法研究

在简支条件下,应用振动无损检测法测定了胶合木梁的固有频率并算得其弹性模量值,同时采用振动分析有限元法计算胶合木梁频率值和用静载试验测定其弹性模量。通过对振动测试、振动分析及静载试验共3种方法得到的结果进行比较,证明了振动法测试胶合木梁弹性模量的可行性和准确性。     

镇江韦岗铁矿爆破地震观测研究

通过对镇江韦岗铁矿爆破振动速度观测，探索了质点峰值振速衰减规律，研究了振动频率、纵波速度和振动持续时间，并作了频谱分析．     

带锯机张紧系统锯条横向振动特性的研究

本文对带锯机杠杆压砣式张紧系统压砣及锯条横向振动进行了测试，并运用DASP6．53振动分析软件对测试结果进行了分析，得到了带锯机杠杆压砣式张紧系统振动的特性、产生振动的频率范围及频率特性，为今后带锯机的动态设计奠定了基础。     

采伐联合机机械手结构的振动特性研究

对某品牌的采伐联合机机械手振动特性进行了研究,该机械手由伐木头和机械臂等组成,其中的机械臂固有振动频率对伐木头的定位精度影响很大。建立了采伐联合机机械手工作时的振动模型,并用梁理论和振动拉格朗日法之间的关系来计算机械臂的振动频率和模式,推导出机械手系统自由振动的位移响应。采用ANSYS软件对机械手进行了振动特性模态分析,以改善其动态性能,减少机械臂在工作过程中的振动,从而提高采伐联合机机械手工作的精准度。     

油锯振动加速度BASIC计算程序

油锯的振动问题是国内外十分关注的问题。世界各国对油锯的振动进行了长期的分析研究,力图使油锯的振动减轻到许可的范围之内,以保障林业工人的健康。近几年来,国内许多林业院校、研究所和林机厂在努力减少国产油锯的振动上做了大量的分析研究工作,并先后研制了多种     

电锯的振动测试

迄今为止,油锯的振动,已引起人们较多的关注。但对用于贮木场作业的电锯,一般认为它的振动较小,却很少研究。本文通过对国内外几种电锯(图1,表1)振动量的测试与分析,认为电锯也应采取相应的减振措施。并将测试方法与结果简述如下:一、振动系统在东北林业大学采伐馆进行了振动测试,所采用的标定、测试、分析等系统分别     

杠杆压铊张紧系统带锯空转振动特性的分析

本文对杠杆压铊张紧系统带锯产生振动的原因,进行了试验和理论研究。用2034型频谱分析仪试验表明,带锯条振动属于复杂周期信号的离散型频谱,是由多个简谐振动叠加而成;同时理论考察分析表明,带锯条杠杆压铊张紧系统不同于秤量重物的“平衡秤”,不可能达到“静平衡”,而是在锯轮参数激振作用下形成周期性受迫振动。锯轮参数激振和杠杆压铊张紧系统位移激振之间交互作用,是使带锯条产生周期振动并引起张紧力发生变化的重要原因。     

行星式球磨机的工况监视系统设计

通过研究行星式球磨机结构特点和运行特点,结合工业常用的温度和振动测量方法,设计了一套监测温度和振动信号的方案。     

炭用机械振动磨的研制

FL—100炭用振动磨选定低振强(5g)、三筒可移动式。生产能力50—100kg/h,粉磨细度180—200目。投资少、省电、基本不污染环境,符合连续粉磨炭工艺要求,是目前适用于炭类工业的高效粉磨设备。     

木屑机械化学解聚工业装置的主要技术进展

木屑机械化学解聚法制取繁殖酵母所用糖液的工业装置曾于1977年7月开始全流程连续运转一段时期,用所得木材水解糖液,生产出成百吨医药干酵母粉,质量符合中华人民共和国药典要求。主水解设备1000升振动磨先后经过三次设计和试制,在各方面取得了关键性改进,承受了振动强度10g的长期考验。此外,在干燥、转化、中和、氧化、木素过滤等工序上也取得了一些重要的技术进展。     

Preparation of acetylated wood meal and polypropylene composites II: mechanical properties and dimensional stability of the composites

Acetylated wood meals of Sugi (Cryptomeria japonica D.Don) wood were prepared by mechanochemical processing using a high-speed vibration rod mill. Weight percent gain (WPG) of the acetylated wood meals ranged from 7.0 to 35.5 %. Wood–plastic composites (WPCs) containing 50 % acetylated woods were produced by an injection molding technique. The polymer matrix used was polypropylene homopolymer. Maleic anhydride-grafted polypropylene (MAPP) was also used as a compatibilizing agent. The mechanical properties of WPCs in bending and tensile tests were independent of WPG of acetylated wood meals, and the test values for WPCs containing acetylated wood meals were lower than that of unmodified wood meal. The use of MAPP increased bending and tensile strength, but no effect on bending modulus was found. An increase in WPG significantly decreased water absorbability and thickness swelling of WPCs as measured by dimensional stability tests. These results demonstrated that mechanochemical processing is a promising technique for preparing WPC material with improved dimensional stability. The future challenge is to inhibit the decreases in mechanical properties of WPCs containing acetylated wood meals.     

碱法制浆黑液制活性炭的试验研究

讨论了硫酸盐法纸厂废液通过炭化回收碱的同时,综合利用炭素生产高吸附活性炭。试制出的粉状活性炭亚甲兰脱色力平均为23ml,碘吸附大于1000mg·g-1,碱回收效率达86%。可望解决硫酸盐法纸厂的废水污染,取得社会效益的同时,亦有一定的经济效益。     

HPLC evaluation of resin acid degradation with ozone treatment of pulp mill effluent

Summary Pulp mill effluent in the pH range of 7 to 8.5 was found most suitable for ozone treatment. Both resin acids and phenolic compounds were degraded in similar efficiency. Among the various resin acids, dehydroabietic acid (DHA) was found to be the most resistant to ozone degradation. The determination of DHA in the treated effluent can therefore reflect the degree of completeness of the effluent treatment. A simple and fast HPLC method reported previously for the determination of DHA was found to serve well for this purpose. Results are demonstrated by treatments of various pulp mill effluents. Received 11 March 1997     

Preparation of acetylated wood meal and polypropylene composites I: acetylation of wood meal by mechanochemical processing and its characteristics

Wood meals of Sugi (Cryptomeria japonica D.Don) passing 2.0 mm and retained on 1.0 mm mesh screens were milled along with acetic anhydride (AA) and pyridine as a catalyst in a high-speed vibration rod mill at ambient temperature. The weight percent gain (WPG) of the chemically modified wood was calculated based on the yield after washing with deionized water. The effects of amounts of AA and catalyst added, pulverization time, and saponification of the acetylated wood on WPG were examined. In addition, FT-IR analysis, and water vapor adsorption and desorption tests were performed as functions of the WPG. Increases in WPG, the acetyl contents of the acetylated wood after saponification, changes in the FT-IR spectra after pulverization, and the water vapor sorption isotherms showed that the one-step acetylation systematically modified the hydroxyl groups of the wood into acetyl groups. Up to 38 % WPG was obtained at 100 phr AA and 15 phr catalyst, and 120 min pulverization. Pulverization time and the amounts of AA and catalyst added to the wood meals could be adjusted to obtain acetylated wood meal with the desired WPG. These demonstrated that the mechanochemical acetylation is a method to prepare acetylated wood meals with high WPG at less reaction time and required AA addition.     

刨花板全自动生产线横锯推板采用变频交流拖动系统的改进

本厂刨花板生产线横锯推板动力系统,系引进德国设备,备品备件价格昂贵。本文介绍了此推板系统由变极调速改造为变频调速的基本原理技术要点。