磁力耦合压电振动能量采集器研究

提出一种基于汽车减振器的磁力耦合压电振动能量采集器,可以采集更多的振动能量,并减少振动引起的冲击力。该设计中包括永磁铁阵列和弯张压电单元阵列。磁力耦合作用将不规则的往复振动转换成单向磁排斥力作用,并通过弯张结构放大作用于压电片。建立磁-机-电耦合模型并进行实验。实验结果表明:在以固定频率f=12 Hz、13 Hz和15 Hz输出时,增加随机振动信号的幅值,压电俘能器所俘获的电压幅值也随着增大,且输出的电压峰值与振动信号幅值峰值点一致;同时发现幅值相近时,在振幅可视为相等情况下,振动信号频率不同,电压幅值维持不变,电压信号频率改变。该设计结构紧凑,可以集成于汽车减振器中而不显著增加器件体积。     

BaTiO3薄膜纳米发电机平衡压电势的理论研究

利用薄膜-衬底系统二参量模型,研究了单层钛酸钡(BaTiO3)压电纳米薄膜系统在轴向应力下发生的弯曲.分析讨论了BaTiO3纳米薄膜的极化强度、极化电荷量及压电电势分布.根据力学平衡法求解出弯曲BaTiO3薄膜压电势以及薄膜弯曲曲率半径和薄膜内应变.结果表明,本工作的理论模型计算的结果与Park等报道的实验及有限元模拟结果非常符合,给出了压电纳米薄膜发电机机理的简单模型和理论基础.     

基于双ZnO薄膜单元并联结构的微型压电振动能量采集器(英文)

报道了一种基于ZnO压电薄膜双单元结构的压电式微型振动能量采集器,其中的双压电元件是并联结构.采用射频磁控溅射技术制备ZnO压电薄膜,同时,该压电式振动能量采集器采用微加工技术制作.测试表明该器件的共振频率为1 300 Hz,基于ZnO薄膜双单元并联结构的压电式振动能量采集器比起具有同样尺寸的传统型压电振动能量采集器有更高的输出性能.在频率为1 300 Hz,加速度为10 m/s2的外界振动激励下,该压电式振动能量采集器在1 MΩ负载电阻上产生的电压为2.06 V;当负载电阻为0.6 MΩ时,输出功率最大为1.25μW.     

复合纳米金膜的制备及其光学性质

本文利用化学还原法制备了不同尺寸的金纳米颗粒,并利用离子自组装多层技术在玻璃基底上沉积了基于金纳米颗粒的复合纳米金膜,研究了颗粒尺寸和成膜厚度对复合金膜光学性质的影响。不同比例的柠檬酸钠与氯金酸产生的金纳米颗粒溶液的紫外-可见光谱随着金颗粒直径增大而红移展宽。适量比例的柠檬酸钠与氯金酸能够产生平均直径为14±1.2nm且尺寸分布均匀的金纳米球;其溶液在518nm处有一特征吸收峰。不同大小的金纳米颗粒形成的薄膜的紫外-可见光谱形状不同,局域表面等离子体共振峰的位置随着颗粒直径的减小而向短波方向迁移。薄膜的沉积层数越多,薄膜表面的颗粒分布越均匀,局域表面等离子体峰的峰值变化也将减小。本工作证实了利用离子自组装多层技术能够快速、简易、低成本地在玻璃基底上沉积具有局域表面等离子体共振的复合纳米金膜。     

Ag纳米颗粒修饰(K0.5Na0.5)NbO3/PVDF柔性压电能量收集器及其性能

将机械能转换为电能的压电能量收集器可为便携式可穿戴电子器件提供持续、独立的供电方案，促进柔性电子技术向智能化、集成化、多功能化方向发展。本文采用光还原法制备了Ag纳米颗粒修饰的铌酸钾钠(KNN)颗粒并将其与聚偏氟乙烯(PVDF)复合，得到Ag-KNN/PVDF压电复合薄膜。采用热压法在两层PVDF中复合Ag-KNN/PVDF薄膜，得到三明治结构的柔性复合压电薄膜(PAKP)及压电柔性能量收集器。研究结果表明：当Ag摩尔分数为1%时，PAKP柔性复合薄膜的极性β相最大，且压电输出性能最佳，输出电压可达6.39 V，是无Ag修饰样品的1.43倍，器件的最大瞬时功率为150.5 nW。经过3 000次循环测试后，器件的电压输出幅度无明显变化。将其固定于自行车车架上，收集自行车行进中的机械能可使220 nF电容在200 s内充电至1.2 V，表明其在低功耗电子器件自供电领域具有良好的应用前景。     

粒度对纳米掺杂BaTiO3陶瓷结构和性能的影响

制备了纳米掺杂BaTiO3陶瓷,研究了纳米掺杂剂和BaTiO3的粒度对BaTiO3陶瓷的微观结构和介电性能的影响．结果表明,小粒度、高分散的纳米掺杂剂更易对BaTiO3颗粒实现均匀包裹,有效地抑制晶粒生长并形成更多的壳-芯晶粒,大比表面积使更多高活性的表面原子与BaTiO3发生原子输运形成传质,导致晶粒壳／芯比增大,从而提高其介电性能．纳米掺杂陶瓷的平均晶粒尺寸和四方率与BaTiO3粒度几乎成正比．随着BaTiO3粒度的减小,立方晶粒壳增大而四方晶粒芯减小,陶瓷由四方晶相向赝立方晶相转变,居里峰被显著压制,从而改善介电温度特性．同时,晶粒的壳与芯之间失配产生的内应力随之增加,使居里点向高温方向移动．     

PVDF/SBS柔性复合纤维薄膜压电-摩擦电纳米发电机

可将无规则机械能转换为电能的压电纳米发电机与摩擦纳米发电机能够为低功耗可穿戴电子设备提供独立、持续性供电，有利于促进柔性自供能电子器件多元化的发展。将二者进行集成，可综合二者电输出特性的优点，提高纳米发电机的性能。本文分别以聚偏二氟乙烯(PVDF)与苯乙烯-丁二烯-苯乙烯嵌段共聚物(SBS)为正、负极摩擦材料，采用静电纺丝方法制备了PVDF/SBS复合纤维薄膜，并利用该复合纤维薄膜得到压电-摩擦电复合纳米发电机。研究结果表明：当PVDF掺入量为20wt%时，PVDF/SBS复合纤维薄膜的电学输出性能最佳，器件的开路电压与短路电流最大可达108 V与0.34μA，分别是纯SBS样品的5倍与6倍。将器件固定在手掌、鞋底处，收集拍手、行走、跑步等运动的能量，可产生不同幅度的输出电压，表明器件可有效收集人体运动的机械能；通过手掌拍打器件，可点亮64只商用蓝色LED灯珠；同时器件可检测瞬时压力变化，灵敏度最大可达3.685 V·N^-1。上述结果表明PVDF/SBS柔性复合纤维薄膜压电-摩擦电纳米发电机在传感监测和电子器件自供能领域具有良好的应用前景。     

新型聚四氟乙烯体材料双面驻极结构振动能量收集器

提出一种新型静电式振动能量收集器，该器件采用基于聚四氟乙烯体材料驻极体的双面电晕驻极结构，提高了薄膜驻极体静电式振动能量收集器的输出功率．在电晕驻极栅网电压为-700V的条件下，体材料驻极体的上下表面分别获得了-564．0V±83．1V、-636．4V±69．7V的表面电位均值．采用组装方式制成器件，并在正弦激振条件下测试器件的输出性能．实验结果表明，在振动频率10Hz、峰值加速度1．2g的条件下，器件输出峰值功率达到30μw，平均功率达到5．5μw，优于目前多数薄膜驻极体器件的性能，接近低功耗传感器的实际功率要求．     

黏附和介电特性对PDMS-xBaTiO_3复合薄膜摩擦起电性能的影响

针对摩擦纳米发电机输出性能低导致实际应用受限的问题,通过在聚二甲基硅氧烷(PDMS)中添加不同质量分数的BaTiO_3纳米颗粒,制备PDMS-xBaTiO_3复合薄膜(x=0%,10%,15%,20%和30%)。在接触分离模式的摩擦纳米发电机中,分别研究复合薄膜的表面黏附和介电特性对薄膜摩擦起电性能的影响。结果表明,相比PDMS薄膜,添加BaTiO_3的复合薄膜摩擦起电性能提高1倍以上;当BaTiO_3的质量分数≤15%时,摩擦起电性能会随着介电常数的增加而增大;当BaTiO_3的质量分数为20%时,尽管介电常数进一步增加,但此时表面黏附力最小,复合薄膜的摩擦起电性能下降;当BaTiO_3的质量分数为30%时,由于纳米颗粒的团聚导致复合薄膜的摩擦起电性能进一步降低。     

0.15CoAl0.2Fe1.8O4-0.75BaTiO3纳米磁电复合材料的电场诱导介电特性研究

采用溶胶-凝胶法制备了0.15CoAl0.2Fe1.8O4-0.75BaTiO3纳米磁电复合材料。XRD分析表明,制备的样品中包含钙钛矿(BaTiO3相)和尖晶石结构(CoAl0.2Fe1.8O4相),没有其它明显杂相生成。扫描电镜表明,颗粒平均粒径约为45nm,且压磁相均匀分布于压电相中。研究了该纳米磁电复合材料在外加偏置静电场诱导下的介电常数随频率的变化,分析了直流偏置电场诱导下的相对介电常数变化值Δεr和调谐率K。随着偏置电场的增大,Δεr和K都变大;随着频率的增加,Δεr和K都减小。并且,在外加偏置电压为3kV/cm时可以获得相对较大的调谐率(4.05%)。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.