Correlation of the Vector Gradient of a Magnetic Field with the Kinetic Energy of Hard Magnetic Milling Beads in Electromechanical Mills

This paper describes the experimental investigation and numerical simulation of a novel electromechanical milling principle: the direct transformation of energy into the movement of milling beads with special magnetic properties. The experimental results show that this principle is ideally suited for the finest grinding of organic agents. Anthraquinone particles with a median size of 25.5 µm were electromechanically ground to 1 µm and the magnetic field strength in the process chamber has the greatest influence on milling results. The developed model reveals that the distribution of the time- and location-dependent vector gradient of the magnetic field in the process chamber determines the energy transfer from the exciter systems to the milling beads and hence the grinding results. With a suitable characterization of the vector gradient distribution, it is possible to establish a correlation between the vector gradient and specific milling beads power. This correlation is fundamental for the design of electromechanical milling machines.     

磁力驱动阀门的结构原理与试验研究

针对传统阀门的结构带来的泄漏问题 ,采用磁力驱动技术对阀门的结构、原理进行研究 ,研制出磁力驱动全密封阀门 ,通过其性能参数测试以及测试分析等工作 ,得到了有实用价值的结果     

垂直上升管内非牛顿流体流动沸腾滞后实验研究

研究了一种非牛顿流体——高聚物水溶液在垂直上升管内强制流动沸腾过程中的滞后现象，发现ＨＥＣ水溶液存在沸腾滞后现象，而ＰＡＭ水溶液却没有滞后现象发生。提出了临界干度的概念，观察了溶液浓度和流速对沸腾滞后的影响，并初步解释了发生该滞后现象的机理。     

磁力驱动器涡流损失的研究

对磁力驱动器金属隔离套在交变磁场中引起的涡流损失进行了理论计算 ,并与实测结果进行了对比。指出合理选择金属隔离套的相关参数 ,可以有效控制涡流损失的大小     

电动执行机构中光电编码器脉冲波形问题的研究

介绍电动执行机构中光电编码器的结构、工作原理,以及如何实现光电编码器输出脉冲方波信号,论述光电编码器对电动执行机构产生的影响。     

Experimental Investigation of Pressure Drop Hysteresis in a Cocurrent Gas–Liquid Upflow Packed Bed

Extensive experimental work on hysteresis in a cocurrent gas–liquid upflow packed bed was carried out with three kinds of packings and the air–water system. However, only when packed with small glass beads (f1.4 mm) was the bed pressure drop hysteresis observed. Two more liquids with different liquid properties were employed to further examine the influence of parameters on pressure drop hysteresis. The similarity of pressure drop hysteresis in packed beds was concluded in combination of experimental evidence reported in literature.     

倾斜微结构疏水表面液滴的滞后特性

倾斜微结构疏水表面液滴的滞后特性包括接触角滞后和滚动角。目前,具有较高精度的微结构疏水表面滚动角模型是以理想液滴形状为计算基础,忽略了重力、接触角滞后以及能垒引起的变形。本文以聚二甲基硅氧烷（PDMS）为基底,制备了方柱状微结构疏水表面,考虑疏水表面微观结构以及液滴大小两方面的因素,研究了倾斜微结构疏水表面液滴的滞后特性。从力和能量的角度对其影响机理进行了分析,通过滚动角理论值与实际值的比较发现,微方柱间距较大时,接触角滞后和能垒对滚动角影响显著,证实了该分析的合理性,为研究更加精确的滚动角模型奠定了理论基础。     

超细Fe_3O_4磁性行为的Preisach模拟

Fe3O4具有类似尖晶石的结构,是目前使用极广泛的磁性材料。近年来的研究使其在磁记录等方面的应用取得了显著的进展。Preisach模型对材料的模拟,主要从自发磁矩的先后翻转顺序出发对材料磁化结构有一个详细的数值解释,考察了材料Barkhausen跳跃的实质问题。本文用改进的Preisach模型对Fe3O4各种磁性行为进行了模拟,如零场冷却(ZFC)磁化强度和加场冷却(FC)磁化强度,以及不同温度下的磁滞回线等实验结果进行了分析模拟。通过对实验拟合得到巴克豪森跳跃谱的相关参数,这些参数很好的反映了材料磁化的物理本质。     

聚脲涂层黏结力的探讨

阐述了保证聚脲涂装质量的基本条件。探讨了聚脲涂层相关特性对黏结力的影响。提出了改善聚脲黏结力的途径。     

Hysteresis in bending electrostriction of polyurethane films

This report presents the mechanism and unique features of hysteresis in bending electrostriction of polyurethane films. The films were made of segmented polyester–polyurethanes and coated with a thin gold electrode on both surfaces. The application of a 2‐MV/m electric field to the 0.2‐mm‐thick film caused a bending deformation, which showed hysteresis. The hysteresis was closely related to the absorption current, suggesting that its origin is ionic polarization attributed to ionic impurities in the polyurethane. The existence of ionic polarization after the removal of the electric field was shown by measuring a thermally stimulated discharge current. In addition, a couple of unique features of the hysteresis in the bending deformation are described. One of the features is that the prior application of an electric field significantly improves the bending speed in the successive application. The other is that the prior application also controls the bending direction in the subsequent application of an electric field of opposite polarity. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1121–1126, 2001     

Investigation of Magnetic Force for Barium and Strontium Ferrites

A new method is presented for calculation of the maximum magnetic force of magnetic ceramics, based on their crystalline structure. The results of this model for the magnetic forces of barium and strontium ferrites are compared with experimental values. In this comparison, the experimental values are less than the values determined by the theoretical model for various magnet cross-sectional areas. This difference is due to the presence of crystal imperfections and incomplete alignment of the magnetic domains. In addition, the magnetic forces of barium and strontium ferrites are a sensitive function of their heat treatments.     

Progress in the Field of Water‐ and/or Temperature‐Triggered Polymer Actuators

Water‐ and/or temperature‐triggered polymer actuators have great potential in robotics, microfabrication and micromanipulation, cell culture, artificial scaffolds, muscles, and motors. In the past few years, a large amount of work has been carried out, and several innovative concepts have been proposed to address challenges such as actuation with large‐scale displacement in a very short time, actuation of large‐sized samples, complex 3D shaping, directional control, multiresponsive actuation, and strong actuators. Herein, the progress made in the field of actuators triggered by water, temperature, and a combination of both is presented, emphasizing the new concepts of fast and direction‐controlled actuation, the corresponding mechanisms, the associated challenges, and future tasks and perspectives.     

新型电动机械式打孔器在沙特钻修井中的应用

多年以来,在沙特阿拉伯的很多油井由于井下的设备受到严重腐蚀经常需要进行钻修井作业。在作业中为了井控安全的要求,往往需要在油管上打一个孔作为循环压井液的通道。为了完成在油管上打孔作业,钻修井作业有时会因用传统的机械打孔方法不成功、装运炸药和组织射孔工具花费时间,从而导致生产时效上不经济。本文介绍了一种由沙特阿美公司最新研发的通过钢丝输送的电动机械式打孔器,通过在几口钻修井的应用实例表明打孔成功率达到100%,而且解决了传统的打孔方法所产生的问题。     

Investigation on the hysteretic force of droplet on hydrophilic and hydrophobic surface

表面上液滴欲移动时所表现出的滞后现象尚未在理论上得到完全解决,其中液滴所受到的滞后阻力的分析和计算是定量描述此滞后现象的关键问题之一。本文应用高速摄像,实验研究了亲/疏水表面上液滴的滞后阻力,并依据相应的实验数据对滞后阻力进行了分析和验证。结果表明：液滴在亲水和疏水表面上运动时所受到的滞后阻力分别与铺展功和黏附功相对应。滞后阻力反映了液滴在亲/疏水表面上出现滞后现象的本质,同时对于进一步研究接触角滞后提供了理论基础。     

Magnetic field effects on the active dissolution of iron

The impact of superimposed magnetic fields on the behavior of iron in 0.05 M H₂SO₄ at low anodic polarization was investigated by means of potentiostatic polarization measurements. Significant magnetic field effects were observed even though the active dissolution reaction in the investigated potential region is formally charge transfer controlled. The current density can be enhanced or reduced dependent on the magnetic field to electrode configuration. The results are discussed in terms of the magnetic field impact on the surface pH value during the anodic dissolution. Our findings are likely to have important consequences for the life-time prediction of ferromagnetic components in electromagnetic devices and for future studies on magneto-electrodeposition processes.     

Combined Impact of Magnetic Force and Spaceflight Conditions on Escherichia coli Physiology

Changes in bacterial physiology caused by the combined action of the magnetic force and microgravity were studied in Escherichia coli grown using a specially developed device aboard the International Space Station. The morphology and metabolism of E. coli grown under spaceflight (SF) or combined spaceflight and magnetic force (SF + MF) conditions were compared with ground cultivated bacteria grown under standard (control) or magnetic force (MF) conditions. SF, SF + MF, and MF conditions provided the up-regulation of Ag43 auto-transporter and cell auto-aggregation. The magnetic force caused visible clustering of non-sedimenting bacteria that formed matrix-containing aggregates under SF + MF and MF conditions. Cell auto-aggregation was accompanied by up-regulation of glyoxylate shunt enzymes and Vitamin B12 transporter BtuB. Under SF and SF + MF but not MF conditions nutrition and oxygen limitations were manifested by the down-regulation of glycolysis and TCA enzymes and the up-regulation of methylglyoxal bypass. Bacteria grown under combined SF + MF conditions demonstrated superior up-regulation of enzymes of the methylglyoxal bypass and down-regulation of glycolysis and TCA enzymes compared to SF conditions, suggesting that the magnetic force strengthened the effects of microgravity on the bacterial metabolism. This strengthening appeared to be due to magnetic force-dependent bacterial clustering within a small volume that reinforced the effects of the microgravity-driven absence of convectional flows.     

Magnetic field effect on the anodic behaviour of a ferromagnetic electrode in acidic solutions

The magnetization of a ferromagnetic electrode in an external homogeneous magnetic field leads to a stray field in front of the electrode. This stray and its gradients can alter the anodic behaviour of the electrode significantly. Potentiodynamic polarisation measurements of an iron wire in a 0.5 M sulfuric acid solution (pH 0.25) and in a 0.5 M phthalate buffer solution (pH 5) without and with applied magnetic fields up to 0.6 T in different orientations to the electrode surface were performed. In sulfuric acid solution an increase of the diffusion-limited dissolution current density and a shift of the active-passive transition potential to more noble potentials was observed when the magnetic field was applied parallel to the electrode surface. In contrast, in perpendicular field configuration the diffusion-limited current density is lowered and the active-passive transition potential is shifted to less noble values. In phthalate buffer no significant influence of the magnetic field on the current density was observed in the active region, but a shift of the active-passive transition to less noble potentials occurred irrespective of the magnetic field configuration.The observed effects of a superimposed magnetic field on the anodic behaviour of iron are discussed with respect to an increase of the mass transport due to the Lorentz-force-driven magnetohydrodynamic (MHD) effect, the magnetic field gradient force and its interaction with the paramagnetic iron ions. The results of this paper show that the effect of the field gradient force can become very important due to the high magnetic field gradient at ferromagnetic electrodes.     

Hysteresis in the I–V Tunneling Characteristics of n-Type BaTiO3 Ceramics

Scanning tunneling microscopy (STM) and spectroscopy (STS) have been applied to study the surface electronic properties of n -type BaTiO₃ ceramics under ultrahigh vacuum and at various oxygen partial pressures. I – V tunneling characteristics of vacuum-annealed BaTiO₃ do not exhibit rectifying behavior, implying that the Fermi level is pinned at the surface. The surface band gap of BaTiO₃ annealed under vacuum at 540°C is equal to 1 eV. The top edge of the surface valence band is located 0.7 eV below the Fermi level. Hysteresis in the I – V characteristics has been observed at high oxygen partial pressures. Dosing of the BaTiO₃ with oxygen increases the surface band gap and unpins the Fermi level. As a result, the I – V characteristics acquire rectifying features similar to those observed for BaTiO₃ Schottky-type diodes. Hysteresis in the I – V spectra observed at high oxygen partial pressures is attributed to the changes of the surface potential barrier due to adsorption/desorption of oxygen modulated by the tip-sample potential difference.     

A Novel Constitutive Equation for Viscoelastic-Thixotropic Fluids and its Application in the Characterization of Blood Hysteresis Loop

1 INTRODUCTIONIt is well known that viscoelasticity and thixotropy of fluids are often investigated by measuringhysteresis loops under transient conditions.For some fluids(such as blood),it has been provedthat,an“8”shaped hysteresis loop may be obtained if triangular steps of shear rate wereapplied on it(Fig.l).This kind of hysteresis loop is composed of a viscoelastic loop and athixotropic loop.The viscoelastic and thixotropic properties are unified in the formation ofthe hysteresis loop.How to describe the formation of this complex hysteresis loop and how to     

离心泵轴向力分析和平衡方法探讨

离心泵工作时,其转子会受到一个与轴心线相平行的轴向推力。如果该力得不到有效的控制,在其作用下转子可能会出现一种轴向窜动的情况,这时就会引发转动部件以及固定部件之间直接接触,当这种情况发生就会引发泵零部件非正常运行。对离心泵的轴向力产生和平衡方法作了详细的叙述,希望可以起到一定的作用。