采用多自由度转子模型的电磁轴承支承特性测试方法

为描述主动电磁轴承的支承特性,通常是沿袭传统机械轴承支承的刚度阻尼概念,称之为等效刚度和等效阻尼。由于电磁轴承的支承特性与其控制策略有关,因此确定电磁轴承的等效刚度和等效阻尼值相对困难。已有的电磁轴承等效刚度和阻尼测试方法大多是基于单自由度模型的,难以用于实际多自由度电磁轴承-转子系统的刚度阻尼测量,甚至无法实际操作。针对上述问题,首先从理论上分析了采用等效刚度和等效阻尼概念表示电磁轴承支承特性的描述局限性和适用范围,然后提出了一种基于多自由度转子模型的对电磁轴承等效刚度和等效阻尼进行直接测量的方法。实验结果表明该方法能够实时地对电磁轴承-转子系统的等效刚度和阻尼值进行准确识别,其结果可以作为电磁轴承动力学特性研究的依据。     

Light alters nociceptive effects of magnetic field shielding in mice: intensity and wavelength considerations

Previous experiments with mice have shown that repeated 1 hour daily exposure to an ambient magnetic field-shielded environment induces analgesia (antinociception). The exposures were carried out in the dark (less than 2.0×10¹⁶ photons s⁻¹ m⁻²) during the mid-light phase of the diurnal cycle. However, if the mice were exposed in the presence of visible light (2.0×10¹⁸ photons s⁻¹ m⁻², 400–750 nm), then the analgesic effects of shielding were eliminated. Here, we show that this effect of light is intensity and wavelength dependent. Introduction of red light (peak at 635 nm) had little or no effect, presumably because mice do not have photoreceptors sensitive to red light above 600 nm in their eyes. By contrast, introduction of ultraviolet light (peak at 405 nm) abolished the effect, presumably because mice do have ultraviolet A receptors. Blue light exposures (peak at 465 nm) of different intensities demonstrate that the effect has an intensity threshold of approximately 12% of the blue light in the housing facility, corresponding to 5×10¹⁶ photons s⁻¹ m⁻² (integral). This intensity is similar to that associated with photoreceptor-based magnetoreception in birds and in mice stimulates photopic/cone vision. Could the detection mechanism that senses ambient magnetic fields in mice be similar to that in bird navigation?     

全自动化生产线输送带运动参数实用确定方法

介绍在以马口铁为材料的全自动化生产线中,在输送带上,确定由三段输送带完成改变罐的空间状态而设计的倒(置)罐装置的输送带的3个速度的求法.     

The influence of blood on targeted microbubbles

The ability to successfully target the delivery of drugs and other therapeutic molecules has been a key goal of biomedical research for many decades. Despite highly promising in vitro results, however, successful translation of targeted drug delivery into clinical use has been extremely limited. This study investigates the significance of the characteristics of whole blood, which are rarely accounted for in vitro assays, as a possible explanation for the poor correlation between in vitro and in vivo experiments. It is shown using two separate model systems employing either biochemical or magnetic targeting that blood causes a substantial reduction in targeting efficiency relative to saline under the same flow conditions. This finding has important implications for the design of targeted drug delivery systems and the assays used in their development.     

纳米复合薄膜吸波材料的研究进展

介绍纳米吸波剂的吸波剂机理,综述其研究现状,并总结各种薄膜吸波剂的优、缺点.最后对制备强、宽、轻、薄的纳米复合吸波剂进行展望.     

基于弱磁的钢丝绳探伤技术研究

依据磁荷分析理论,建立了钢丝绳断丝磁偶极子模型,计算了单丝断口处漏磁场的分布规律。采用正交设计方法对激磁回路参数进行了实验研究,确定了弱磁磁化系统的基本结构与基本参数,实现了磁化与检测的一体化设计。依据弱磁激励情况下钢丝绳缺欠处的漏磁场强度,选择了高灵敏度MR01型磁阻式传感器;给出了多种断丝形态的实测曲线。实验结果表明,基于MR01型磁阻式传感器的钢丝绳磁检测系统,不仅能够实现对小尺寸断口缺陷的有效检测,而且可用于剩磁检测,为钢丝绳探伤技术的发展提供了有价值的科学依据。     

Experimental and mathematical modelling of magnetically labelled mesenchymal stromal cell delivery

A key challenge for stem cell therapies is the delivery of therapeutic cells to the repair site. Magnetic targeting has been proposed as a platform for defining clinical sites of delivery more effectively. In this paper, we use a combined in vitro experimental and mathematical modelling approach to explore the magnetic targeting of mesenchymal stromal cells (MSCs) labelled with magnetic nanoparticles using an external magnet. This study aims to (i) demonstrate the potential of magnetic tagging for MSC delivery, (ii) examine the effect of red blood cells (RBCs) on MSC capture efficacy and (iii) highlight how mathematical models can provide both insight into mechanics of therapy and predictions about cell targeting in vivo. In vitro MSCs are cultured with magnetic nanoparticles and circulated with RBCs over an external magnet. Cell capture efficacy is measured for varying magnetic field strengths and RBC percentages. We use a 2D continuum mathematical model to represent the flow of magnetically tagged MSCs with RBCs. Numerical simulations demonstrate qualitative agreement with experimental results showing better capture with stronger magnetic fields and lower levels of RBCs. We additionally exploit the mathematical model to make hypotheses about the role of extravasation and identify future in vitro experiments to quantify this effect.     

磁性流体在均匀梯度磁场中的摩擦学性能测试研究

基于均匀梯度磁场能较准确反映出磁场影响磁性流体摩擦性能的认识,制造了一对产生均匀梯度磁场的线圈安置于改造后的UMT3摩擦试验机中。选用聚α-烯烃合成油基磁性流体为润滑油,测试不同均匀梯度磁场大小、不同载荷和不同往复频率下的磁性流体摩擦学性能。结果显示：载荷、往复运动频率一定时,磁性流体的摩擦系数随均匀梯度磁场的增大而减小;载荷、均匀梯度磁场一定时,磁性流体的摩擦系数随随往复运动频率的增大而减小;磁性流体在均匀梯度磁场中比无磁场中具有更高的承载能力和更长的耐磨寿命。     

Magnetic properties of solid solutions between BiCrO3 and BiGaO3 with perovskite structures

Magnetic properties of BiCr_1−xGa_xO₃ perovskite-type solid solutions are reported, and a magnetic phase diagram is established. As-synthesized BiCrO₃ and BiCr_0.9Ga_0.1O₃ crystallize in a monoclinic (m) C2/c structure. The Néel temperature (T_N) decreases from 111 K in BiCrO₃ to 98 K in BiCr_0.9Ga_0.1O₃, and spin-reorientation transition temperature increases from 72 K in BiCrO₃ to 83 K in BiCr_0.9Ga_0.1O₃. o-BiCr_0.9Ga_0.1O₃ with a PbZrO₃-type orthorhombic structure is obtained by heating m-BiCr_0.9Ga_0.1O₃ up to 573 K in air; it shows similar magnetic properties with those of m-BiCr_0.9Ga_0.1O₃. T_N of BiCr_0.8Ga_0.2O₃ is 81 K, and T_N of BiCr_0.7Ga_0.3O₃ is 63 K. Samples with x = 0.4, 0.5, 0.6 and 0.7 crystallize in a polar R3c structure. Long-range antiferromagnetic order with weak ferromagnetism is observed below T_N = 56 K in BiCr_0.6Ga_0.4O₃, T_N = 36 K in BiCr_0.5Ga_0.5O₃ and T_N = 18 K in BiCr_0.4Ga_0.6O₃. BiCr_0.3Ga_0.7O₃ shows a paramagnetic behaviour because the Cr concentration is below the percolation threshold of 31%.     

Effects of high magnetic fields on solidified structures of Mn-90.4 wt% Sb hypoeutectic alloy

Mn-90.4 wt% Sb alloy specimens were solidified under both uniform magnetic field and magnetic field gradient conditions. The solidification behavior was examined to elucidate the effects of high magnetic fields on the solidified structure evolution of this hypoeutectic alloy. The macrostructures on the longitudinal section of the alloys were investigated by optical microscopy and x-ray diffraction (XRD). The volume fraction of primary MnSb phases and the interrod spacing of the eutectic were measured by metallographic analysis. It was found that the segregation of the primary MnSb particles at the certain regions of the specimens occurred under the influence of high magnetic field gradients. The MnSb phases obtained under magnetic fields were oriented with their (h0 l) planes along the direction of the magnetic field. Both the volume fraction of primary MnSb phases and the interrod spacing of the eutectic were decreased upon the application of the high magnetic fields.