孔洞结构聚丙烯铁电驻极体薄膜的压电性研究

为了提高孔洞结构聚丙烯(cellular PP)铁电驻极体的压电性能,采用高压气体膨化技术对材料进行了改性处理,并利用准静态和干涉仪测量方法,对经处理的cellular PP铁电驻极体薄膜的压电效应进行了研究.结果表明:气体膨化工艺能够明显提高cellular PP铁电驻极体薄膜的压电活性:这种突出的压电活性源干膨化膜杨氏模量Y的降低和电极化能力的提高;压电系数d33随频率的增加呈现下降趋势:从0.01 Hz下的1200 pC/N降低到共振频率附近的350 pC/N;对于不同参数处理的样品,它们的共振频率在150～400 kHz;大多数样品的d33在0.2～10 kPa的范围内没有明显的变化,但是高于10 kPa,d33随之下降;cellular PP铁电驻极体薄膜d33的热稳定性与非孔洞型PP驻极体薄膜的电荷储存热稳定性相当.     

单层及多层PP蜂窝膜驻极体的压电性

经压力膨化处理后,以正逆压电系数d33测量研究了一种经无栅电晕充电的国产商用聚丙烯蜂窝膜(cellular PP,商品名PQ50)驻极体的压电性.经过优化工艺参数压力膨化处理后的PQ50蜂窝膜呈现600pC/N以上的准静态压电系数,这一量值约为PVDF相关系数的40倍.而通过将单层PQ50蜂窝膜驻极体粘贴形成合理的多层结构,得到的复合膜系压电系数d33高达2010pC/N,约为PZT压电陶瓷相应系数的3倍.从而为拓宽这类新一代的非极性孔洞聚合物压电功能膜应用领域,推动其应用进程提供了一定的理论和技术依据.     

经二次膨化工艺优化的孔洞结构聚丙烯薄膜的压电性

报道了提高孔洞结构压电驻极体膜压电活性的新方法。该方法是在对已膨化处理的压电驻极体薄膜再进行一次膨化处理,通过调节薄膜的力学性能来进一步优化材料的压电活性。结果表明,将聚丙烯（PP）压电驻极体薄膜进行二次膨化处理后,其压电活性比一次膨化的PP薄膜提高约40％。这是因为薄膜在真空蒸镀电极过程中导致的厚度减小能够通过二次膨化工艺得到恢复,而厚度的增加可以有效地降低材料的杨氏模量,从而使薄膜的压电系数d33增加;两次膨化温度对压电系数d33均有影响,并且相互联系;通过选择合理的一次和二次膨化工艺参数（例如100℃和45℃）能够获得稳定的高压电系数压电驻极体膜。     

压力膨化处理和充电方法对PP蜂窝膜压电性的影响

以压力膨化技术处理改性商用SHD50型聚丙烯蜂窝膜(PP Cellular),它们的压电 d33 系数可达193pC/N,比未经处理的样品提高了约 2 个数量级。利用点电晕充电,接触法充电和动态压电 d33系数测量研究了上述2种不同充电方法对 SHD50 膜压电性的影响。     

辐照交联聚丙烯压电功能膜的机电性能

研究了基于辐照交联聚丙烯（XPP）的压电驻极体功能膜的机电性能。利用介电谐振谱测定了XPP膜的弹性模量;通过准静态方法测量了该功能膜的压电系数d33及其压强特性曲线;对压电相应的时域谱进行了分析;最后讨论了该功能膜的力学疲劳特性。结果表明XPP压电驻极体膜的弹性模量为1.3MPa,压电系数d33在10～100kPa的压强范围内都具有良好的线性度;时域谱揭示了XPP膜的粘流特性;XPP膜的输出电压和压力呈现良好的线性关系;经历60万次的循环力载荷,压电系数d33没有明显的变化。     

化学改性对气体压力膨化孔洞聚丙烯膜的压电热稳定性和机电性能的影响

通过压电d33系数等温衰减测量、热刺激放电（TSD）技术及介电谐振谱分析，研究了孔洞PP原膜及其化学改性膜在经历相同的压力膨化和热处理工艺后的压电热稳定性和机电性能。对比性地研究了90℃膨化和RT膨化对孔洞PP膜压电热稳定性和机电性能的影响。结果表明：化学改性及热膨化工艺改善了孔洞PP膜的压电热稳定性和机电性能，且90℃膨化改性膜比RT膨化改性膜具有更好的压电热稳定性和机电性能。     

聚丙烯孔洞驻极体薄膜的突出压电活性及其应用研究

聚丙烯(PP)孔洞膜可呈现高达1000pC/N的准静态压电d33系数,是久负盛名的铁电聚合物PVDF相应系数的50倍以上,可和压电陶瓷相媲美.基于国内外最新研究成果,综述了PP孔洞膜的制备技术、极化方法、压电活性以及可能的应用前景.     

多孔PTFE/P(VDF-HFP)复合膜的驻极体性质

通过栅控恒压负电晕充电、等温表面电位衰减测量、热刺激放电(Thermally Stimulated Discharge,TSD)电流谱分析、电荷TSD和压电d33系数测量等方法,首次研究了将旋涂在基片上的含一定溶剂的聚偏氟乙烯和六氟丙烯共聚物(P(VDF-HFP))薄膜与多孔聚四氟乙烯薄膜均匀压合形成的多孔PTFE/P(VDF-HFP)双层复合膜系的驻极体性质.从多孔PTFE面充电的双层膜具有较从P(VDF-HFP)面充电优异的多的电荷热稳定性.使用介电谐振谱测量的双层膜的压电d33系数(31pC/N)是传统的铁电聚合物材料PVDF相应值(15 pC/N)的2倍左右.     

微结构PDMS压电俘能器设计与特性研究

设计了一种具有三明治结构的微结构驻极体膜,采用旋涂、"软刻蚀"等工艺,结合氧等离子体键合、恒压电晕放电技术,以铜网作为电极,摸索出完整的工艺流程,制作了基于微结构PDMS驻极体的柔性压电俘能器。测量了驻极体膜的压电系数以及力-电特性。结果显示,微结构PDMS压电俘能器的压电系数(d33)为25pC/N;在5N周期性压力下,最大能够产生1.98Vpp的开路电压;驻极体膜的谐振频率为32Hz,且产生的电压与受到的压力呈线性关系。     

聚丙烯压电驻极体的振动能量采集研究

以线性聚丙烯(PP)为原材料,经压缩气体膨化处理和电晕极化处理后,使其具有压电效应,并将其应用在振动能量采集器中。结果表明,PP压电驻极体在厚度方向上的弹性模量和机械品质因数(FOM,d33·g33)分别为1.7 MPa和8.4GPa~(-1),利用面积为3.14cm~2单层膜进行能量采集,当振子质量为25.6,33.7和57.7g时,其共振频率分别为2 300,2 000和1 800 Hz,在各自的匹配负载条件下,获得的输出功率分别为10.1,13.2和16.9μW/g~2。将两片PP膜电学串联,当振子质量为33.7g时,在共振频率1 400Hz和匹配负载4.3 MΩ的条件下,可以获得的输出功率为15μW/g~2。     

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.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

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.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

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 ...