压电发电技术的现状及展望

探讨了压电发电技术的研究价值及发展前景,参考了国内外众多压电发电技术方面的研究资料,并对其进行综合的比较研究.介绍了当今能源利用的现状,压电发电技术的特点及国内外利用新型压电材料发电的研究现状,从理论和实践上证明了压电发电技术的可行性及发展潜力,探讨了压电发电技术在微能源器件、自供电及旋转机械方面的发展趋势.     

自给电PVDF薄膜键盘设计及探究

利用聚偏氟乙烯(PVDF)压电材料研究并设计一种自给电无线薄膜键盘。此键盘能量是通过以PVDF压电薄膜为主要组成部分的能量转换装置,把振动机械能转换成可供键盘正常工作的电能。同时,利用一种由整流电路、超级电容、单节锂电池充电管理芯片及锂电池组成的电能储存装置来保证所产生电能持续、稳定地为键盘供电。根据理论计算及实验结果,对优化自发电键盘的方法进行了探究,指出了该种键盘代表着一类新型电子产品开发思路,具有良好的发展前景。     

基于人体踏走的压电发电装置设计与分析

指出了利用人体踏走的动能进行压电发电,符合当前节能环保的要求,并具有较高的经济效益。分析了压电陶瓷发电机理,设计了一种利用轨道交通等频繁人体踏走的压电发电装置及其能量存储电路,并进行了相关的理论分析。该装置可放置在轨道交通车辆和车站,如地铁、轻轨,和商场等具有大流量的场合门口,将频繁人体踏走的动能进行压电发电,以供用电负载使用或存储,以达发电节能的效果。     

一款新型电话密码锁设计

基于电话网设计了一款不需外部供电的密码锁,其具有密码、用户唯一号码准入双层保护等功能,且操作简单。密码锁根据来电号码与系统预置的用户号码是否一致来控制摘机与否,同时用户可通过语音提示进行开锁、修改密码、挂机等相关操作。该密码锁具有自供电、低功耗、双层保护等特点,工作可靠、稳定、安全。     

压电陶瓷及其元器件

压电陶瓷谐振器具有一对电极的二端压电振子，利用压电陶瓷的机械共振特性，制成电路中的高频元器件．压电陶瓷高频元器件，与石英晶体元器件相比，具有体积小、成本低等优点． 压电陶瓷元器件在电视机（ＴＶ）、影碟机 （ＣＤ、ＶＣＤ、ＤＶＤ）遥控器、录相机、音响、办公自动化设备、汽车电子、语音合成、摄相机、个人电脑（ＰＣ机）等电子设备中得到广泛应用，将逐步取代石英晶体元器件。 我们开发的高频压电陶瓷谐振器，机械品质周数（Ｑｍ）高、频率稳定性好等，主要电参数居国内领先水平，并达到了代表国际水平的日本松下电器公司的…     

基于压电陶瓷的环保节能型取暖器的设计

指出了利用压电陶瓷的的正压电效应发电,实现了自发电功能,符合节能环保理念,并具有较高的经济效益。设计了一款通过对压电陶瓷的理论研究与分析,对压电陶瓷进行外界施压,使其产生电荷,利用稳电集电部分、储能部分及控温装置设计了发热、控温的节能环保型取暖器。该款取暖器可用于户外工作者的使用,无需外接电源,控温装置提高了使用的安全性,储能部分用于持续供能,符合当前的节能环保理念,达到了国家节能减排的要求。     

自发电无线鼠标的设计方案及工作原理

设计采用压电陶瓷等新型材料，利用等效替代法通过无线鼠标内置重力感应小球运动撞击按压压电陶瓷产生电能，并通过升压稳压电路产生平稳电流，存储在锂电池中代替干电池支持鼠标工作，通过模拟实验法对电路进行模拟性实验，利用试验比较法确定项目方案。设计后装置能够产生一定电能支持鼠标工作。采用自发电理念缓解大量使用干电池造成环境二次污染的问题，有利于实现社会可持续发展。     

天保工程建设中存在的问题和解决办法

国家天然林保护工程自1998年启动以来,已经取得了一些成果,但在工程建设中也出现了一些问题,这些问题主要有以下几个方面:1.基础设施建设投入不足。由于长期的投入不足,许多企业的供电、供水、危     

官地坑口变电站继电保护综合自动化改造应用

随着煤矿行业的生产与发展,煤矿供电系统的新技术的不断运用,官地坑口变电站为满足要求,适应现代煤矿行业电力的要求,结合变电站自身的实际供电运行状况,于2010年对其进行了综自保护系统的改造,提高了安全供电的可靠性,确保了煤矿的安全供电。     

城市电网改造探讨

城市规模的不断扩大,要求原有的供配电系统(城市电网)不断增客和扩容,以满足用户时电能需求.城市电网的布局和对供电的要求具有其特殊性,如何处理这些问题,是保证供电基本要求的关键.     

Piezoelectric effect of cyanoethylated hydroxyethylcellulose

The piezoelectricity of cyanoethylated hydroxyethylcellulose was investigated. Elastic, piezoelectric, and dielectric relaxations were observed at –80° to –60°C and 0° to 20°C at a frequency of 10Hz. The activation energy is about 9–15 kcal/mol in the low temperature region and about 30–45 kcal/mol at room temperature. These relaxations in the low temperature region may be caused by the motion of the cyanoethyl group and those at room temperature mostly by the motions of the main chain. Cyanoethylated hydroxyethylcellulose has a high piezoelectric strain constant (d ₂₅), which is the largest value among the cellulose derivatives and is almost the same as the value for polyvinylidene fluoride. The electromechanical coupling factor for cyanoethylated hydroxyethylcellulose was small.     

Mechanical behavior of the crystalline region of wood and the piezoelectric response of wood in tension tests

We investigated the relationship between the crystal lattice strain and the piezoelectric response in Japanese cypress (Chamaecyparis obtusa Endl.) wood fibers subjected to tension stress in the fiber direction. As a result, the piezoelectric voltage was very sensitive to the mechanical behavior (deformation) of the wood crystalline regions obtained from the x-ray stress measurement. Thus, by investigating the behavior of piezoelectric voltage, it was possible to simply estimate the mechanical behavior of the crystalline regions in the wood.     

Behavior of piezoelectric, dielectric, and elastic constants of wood during about 40 repeated measurements between 100°C and 220°C

This study investigated the behavior of piezoelectric, dielectric, and elastic constants and the crystallinity in wood cellulose by repeated measurements (n = 42) between 100°C and 220°C. There was an insignificant change in the piezoelectric constant during repeated measurements in this temperature range. On the other hand, thermal decomposition of the amorphous region contributed to the decreasing trend of dielectric and elastic constants, although only a small increase in the elastic constant was found at the time of the initial measurements. The increase in the repeated measurements in this temperature range resulted in an increase in the piezoelectric loss modulus constantd ₂₅, which is closely related to energy loss. Thed ₂₅ peak shifted to a higher temperature with increasing measurements, which might be due not to the increase in rigidity of the wood specimen but to the increase in total peak area, which was observed during the later measurements. At the same time, variations of piezoelectric loss modulusd ₂₅ ande ₂₅ at advanced stages of the measurements suggested damage and structural changes in the wood.     

Piezoelectric behavior of wood under combined compression and vibration stresses I: Relation between piezoelectric voltage and microscopic deformation of a Sitka spruce (Picea sitchensis Carr.)

This study investigated the relation between piezoelectric behavior and the deformation of trachieds in real time under combined compression and vibration stresses. Scanning electron microscope images were recorded directly into a video recorder. Two types of microscopic destruction were observed in the specimens. With the first type, although a small uprush around the boundary of the annual ring was observed, the specimens were broken only by shearing fracture in the 45° direction. With the second type, the specimens were finally broken by shearing fracture after repeated buckling. In these cases the piezoelectric voltage increased almost linearly in the elastic region, proceeded to the maximal point, and then decreased gradually. Finally a clear peak appeared in the buckling and shearing fracture. There is a curved relation between the specific gravity and the piezoelectric parameter when the influence of voids is considered, and there is a linear relation between the dynamic Young's modulus and the piezoelectric parameter when the stress is considered.Part of this paper was presented at the 46th annual meeting of the Japan Wood Research Society in Kumamoto, April 1996     

Piezoelectricity as a fundamental property of wood

Summary The piezoelectric effect in wood, i.e. the occurrence of electric polarization under mechanical stress and also of mechanical strain in an electric field, was accounted for by considering the uniaxial orientation of cellulose crystallites in fibers and their monoclinic symmetry. A shear stress in one plane, including the grain direction, produced electrical polarization perpendicular to it. The value of the piezoelectric modulus for wood was approximately one twentieth of that of a quartz crystal.The chemical treatments which transform the lattice structure from cellulose I to II or III, increased the piezoelectric modulus. However, gamma-ray irradiation up to a dose sufficiently high to decrease the molecular weight had only little influence on the piezoelectric modulus.The variation with temperature of the phase angle between sinusoidal stress and polarization showed a maximum of advanced phase around room temperature and a maximum of delayed phase at about-100°C. Dielectric and viscoelastic measurements indicated that the former was caused by the dielectric loss due to water at a temperature above freezing and the latter by the viscoelastic loss due to local vibrations of cellulose molecules.The piezoelectric polarization in wood can be utilized in technical problems such as the measurement of shock velocity in timber. The physiological meaning of the piezoelectrical effect in plants has not been investigated.

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Zusammenfassung Der piezoelektrische Effekt in Holz, d. h. das Auftreten einer elektrischen Polarisation unter mechanischer Spannung und ebenso das Auftreten mechanischer Verformungen in einem elektrischen Feld wird als Folgeerscheinung der einachsigen Orientierung der Cellulosekristallite in den Holzfasern und durch deren monokline Symmetrie erklärt. Es wurde beobachtet, daß eine Scherspannung in einer Ebene, welche in Faserrichtung liegt, eine elektrische Polarisation senkrecht dazu hervorruft. Die Größe des piezoelektrischen Moduls für Holz betrug etwa 1/20 des piezoelektrischen Moduls eines Quarzkristalls.Chemische Behandlungen, welche die Gitterstruktur der Cellulose I in diejenige von Cellulose II und III umformen, erhöhen gleichzeitig den piezoelektrischen Modul. Dagegen zeigte eine Behandlung mit -Strahlen selbst bis zu einer Dosisleistung, die ausreichte, um das Molekulargewicht zu erniedrigen, nur geringen Einfluß auf den piezoelektrischen Modul.Die Temperaturabhängigkeit des Phasenwinkels zwischen einer S-förmig verlaufenden Spannung und der Polarisation zeigt ein Maximum der vorauseilenden Phase etwa bei Raumtemperatur und ein Maximum der nachlaufenden Phase bei etwa-100°C. Dielektrische und viskoelastische Messungen ließen erkennen, daß die Dielektrizität auf Grund dielektrischer Verluste von Wasser über 0°C zustande kommt und daß die Viskoelastizität durch viskoelastische Verluste auf Grund örtlicher Schwingungen von Cellulosemolekülen entsteht.Die piezoelektrische Polarisation bei Holz kann für die Lösung technischer Probleme, wie z. B. bei der Messung der Schallgeschwindigkeit in Holz praktisch eingesetzt werden. Die physiologische Bedeutung des piezoelektrischen Effekts in lebenden Pflanzen ist bisher noch unbekannt.

     

Piezoelectric behavior of wood under combined compression and vibration stresses II: Effect of the deformation of cross-sectional wall of tracheids on changes in piezoelectric voltage in linear-elastic region

This study investigated and clarified the relation between the piezoelectric voltage and microscopic fracture of hinoki (Chamaecyparis obtura Endl.), in particular the deformation of the cross-sectional wall of the tracheid in linear-elastic regions under combined compression and vibration stresses. The piezoelectric voltage-deformation (P-D) curve consisted of a linear region starting from the origin followed by a convex curved region. The linear region of theP-D curve was only about 60% of that of the load-displacement (L-D) curve. By applying combined stresses to a specimen, the cross-sectional walls of the tracheid were deformed mainly at the radial walls. When a tracheid was regarded approximately as a hexagonal prism, the elastic buckling stress of the radial wall was estimated from scanning electron microscope images and our method based on a modification of the Gibson and Ashby method. As a result, it was estimated that the elastic buckling stress was only about 80% of the stress at the proportional limit of theP-D curve. It is found that there are two consecutive regions before the proportional limit of theP-D curve: One is the region up to the spot where the radial cell wall generates the elastic buckling, and the other is the region starting from the end of the aforementioned region up to the proportional limit of theP-D curve.Part of this paper was presented at the 47th annual meeting of the Japan Wood Research Society, Kochi, April 3–5, 1997     

Effect of intermittent heat treatment on crystallinity in wood cellulose

The effect of intermittent heat treatment on cellulose crystallites in wood was studied to evaluate quantitatively the changes of crystallinity induced by intermittent and continuous heating. The changes in crystallinity were found to be strongly affected by the intermittent heat treatment. The increased crystallinity, the width of the crystals, and the piezoelectric properties were the same for the first intermittent heating as for continuous heating. Further intermittent heating for the same time duration and temperature had no effect on the above properties, probably due to the stopping of the thermal reaction during the interval. Our results suggested that intermittent heat treatment has certain critical cooling temperatures that stop the thermal reaction and are closely related to the duration of the interval. Samples once exposed to a certain duration of heat treatment and then cooled need more time, about twice that of the first duration of intermittent heating compared with continuous heating, to reach maximum crystallinity in wood cellulose.     

一种基于健身运动能量转换的水能供电装置设计

为缓解能源短缺与生态环境恶化的局面,提高全民健康绿色生活意识,促进废弃能量回收利用,设计了一种基于健身运动能量转换的水能供电装置,通过收集健身运动所产生的能量,利用负压原理与水力发电原理,将健身运动产生的不连续的机械能转化为水的势能,可实现集水蓄能、稳定均衡供电,达到健身供电的一体化。此设计有利于拓展健身器材的功能,捕集并利用健身运动产生的零散能量,对实现节能减排、绿色环保的生活具有切实可行的意义和价值。