As a first attempt, the vibration and stability analysis of magnetically embedded spinning axially functionally graded (AFG) nanotubes conveying fluid under axial loads is performed based on the nonlocal strain gradient theory (NSGT). A detailed parametric investigation is conducted to elucidate the influence of key factors such as material distribution type and size-dependent parameters on the divergence and flutter instability borders. Also, a comparative study is conducted to evaluate the available theories in the modeling of nanofluidic systems. The material characteristics of the system are graded along the longitudinal direction based on the power-law and exponential distribution functions. To accurate model and formulate the system, the no-slip boundary condition is considered. Adopting the Laplace transform and Galerkin discretization technique, the governing size-dependent dynamical equations of the system are solved. The backward and forward natural frequencies, as well as critical fluid and spin velocities of the system, are extracted. Besides, an analytical approach is applied to identify the instability thresholds of the system. Dynamical configurations, Campbell diagrams, and stability maps are analyzed. Meanwhile, it is concluded that, in contrast to the influence of nonlocal and density gradient parameters, the increment of strain gradient and elastic modulus gradient parameters expands the stability regions and alleviate the destabilizing effect of the axial compressive load.

In this paper, the relaxation phenomenon of the birefringence effect of water-based magnetic fluid thin films in the oscillatory pulsed magnetic field are studied. The research is conducted focusing on the changing situation of the optical intensity of the linear polarized light via passing the water-based magnetic fluid and a light analyzer in the oscillatory pulsed magnetic field. The experiment results show that the magnetization of water-based magnetic fluid depends mainly on the Nèel relaxation, but the magneto-optical birefringence effect is influenced by the spatial arrangement velocity of magnetic particles to overcome the thermal movement and the viscous force of water.

目的 探讨梯度磁场下硅油基纳米磁流体作为玻璃体腔填充物的可行性.方法 分别将不同质量百分比浓度的硅油基纳米磁流体放在可见光分光光度计中测量透射光谱线,观察硅油基纳米磁流体在梯度磁场诱导下吸光度的变化.结果 低质量百分比浓度(如0.5％)的硅油基纳米磁流体的透过率比较好,高达95％;但随着质量百分比浓度的增大,透过率快速下降,质量百分比浓度为2.5％时透过率仅有40％左右.但在外加梯度磁场作用下,4h后纳米磁粉会聚集到梯度磁场较大的部位,其他地方的质量百分比浓度下降,光透过率达到95％以上.结论 硅油基纳米磁流体在梯度磁场作用下,纳米磁粉会发生定向移动,可以聚集到磁场对应处,其他部位的硅油基纳米磁流体光透过率将恢复正常,接近纯硅油的可见光透过率.

In this report, the experimental thermal diffusivity data are presented for different concentrations of ferrofluids. The thermal diffusivity measurements are conducted using a laser-induced thermal grating technique at room temperature and atmospheric pressure. The ferrofluids studied have volume fractions ranging from 5% to 10%. Because of the small temperature rise in the thin sample during the measurements and the very short measuring time of a few milliseconds, the influence of free convection can be ignored. The results show very good agreement with the experimental data in the openly published literatures, and thereby indicate the feasibility of the technique proposed in this report.

Objective This paper describes a new type of silicone-oil-based Fe3O4 magnetic liquid and discusses the feasibility of vitreous implants from the mechanics viewpoint.Methods This was an experimental study.The silicone-oil-based Fe3O4 magnetic liquid had been studied previously in the pig eye cavity.The experimental results demonstrated that the silicone-oil-based Fe3O4 magnetic liquid moves on the cavity surface and aggregates at some position under the action of the magnetic field force.The silicone-oil-based Fe3O4 magnetic liquid was filled into a simulated eyeball that was suspended in a gradient magnetic field.The force applied on the simulated eyeball was measured.Results The silicone-oil-based Fe3O4 magnetic liquid moved on the simulated eye cavity surface and aggregated along the magnetic field line with an applied pressure of about 17 mmHg.Conclusion The silicone-oil-based Fe3O4 magnetic liquid approximates the vitreous implant requirements,and has unique mobile and location advantages.This provides a preliminary study approach and an estimate of usefulness for magnetic liquid used in retinal repair.

The paper aims at investigating the potential application of silicone oil based Fe3O4 magnetic fluid as a vitreous tamponade agent. The silicone oil based Fe3O4 magnetic fluid is prepared and deposited in a pig eye. An external magnetic field is applied to the eye to test the behavior of the fluid in vitro as well as the tamponade effect of the magnetic fluid. In the vitro study, it shows that under the influence of an external magnet, the magnetic Fe3O4 micelles are separated from silicone oil toward the maximum magnetic field strength (toward the magnet) and coated on the inner scleral wall evenly in that area. The experiment result provides the preliminary data supporting silicone oil based Fe3O4 magnetic nanoparticles as a novel vitreous tamponade agent, especially in the case of inferior retinal detachments.

This paper presents a polishing technique that uses rotational magnetic polishing liquid,which can produce vortex motion under the action of a magnetic stirrer.The use of a strong external magnetic field increases its viscosity and shear yield stress when a work-piece is introduced into the magnetic polishing liquid.The magnetic polishing liquid contacts the work-piece surface grinding so as to achieve work-piece surface finishing.Experiments were carried out to study the relationship between the surface roughness of the work-piece,its polishing time and its polishing position.The experimental results show that the rotational magnetic polishing liquid can polish the super-smooth surface and that the longer the polishing time and the closer the surface roughness at various locations,the better the surface roughness is,which is also better than that by using abrasive polishing alone.

The effective thermal conductivity of three water based nanofluids (NFs) consisting of large aspect ratio fillers – carbon nanotubes (CNTs), silver nanowires, copper nanowires – were measured by transient hot wire method. The results show that silver nanofluid has the highest thermal conductivity compared with copper and CNTs nanofluids, while the latter two present almost the same thermal conductivity at the same volume fraction. The experiment indicates that particle shape has a substantial effect on the effective thermal conductivity of suspension and shape factor is one of the most important factors that leads to the large discrepancies among the experimental values of the thermal conductivities. Our results reveal that material with higher thermal conductivity is not a decisive factor and not always effective to improve the thermal transport properties of nanofluids.

In the face of the mechanical part of shape complex, the surface is difficult to be finished by the automatic and effective methods, but the magnetic fluid mixed with the polishing and cutting particles has motion characteristics in magnetic field. This paper introduces a kind of polishing technology which can rotate magnetic polishing fluid in the influence of magnetic field. The viscosity and hardness of magnetic polishing fluid change under the magnetic field, and the magnetic polishing fluid rotates in the fluence of the magnetic stirring apparatus, when machining magnetic in the liquid in polishing, and fixed in the liquid in proper position. When we select the best position in the magnetic polishing fluids and immerse the workpiece in the magnetic polishing fluids, the magnetic fluids rotate and move relatively to the workpiece. The friction between the magnetic fluid and the surface of workpiece has the finishing efficiency. The experiment is carried out to study the relation of the roughness and polishing and location on the home-made polishing laboratory platform in detail. The experimental results show that the rotating magnetic polishing liquid can be used for polishing the workpiece in super smooth processing, which is much better than polishing abrasive alone in reducing surface roughness. The study opens a new field for the application of the magnetic fluid. However, the direction of the field, the speed of the movement, and the polishing time of the process parameters still needs further research.

The purpose of this paper is to investigate the effect of magnetic field-induced birefringence and dichroism on relaxation behavior of light transmissivity in ferrofluids film in term of the Xu's oscillating magnetic dipole model and the Matsumoto's birefringence relaxation theory.The specific expression of polarized light transmissivity about birefringence and dichroism is theoretically deduced and numerically simulated.The study has a certain significance on deeper understanding of the optical anisotropy and related application of ferrofluids.

Objective To develop a new kind of silicone-based magnetic fluid and to investigate its feasibility as stuffing in Vitreous cavity.Methods The Fe3O4 magnetic nano-particles were synthetized by chemical coprecipitation,coated by stearic acid and finally dispersed evenly in transparent silicone oil.The size and shape of Fe3O4 magnetic particles were observed by transmission electron microscopy TEM,and the average particle size was about 10 nm.The saturation magnetization Ms of magnetic fluid was about 30emu/g,which was measured by a vibrating sample magnetometer VSMT.The simulation experiments about function of silicone-based magnetic fluids were initially carried out in the pig eye vitreous in order to observe the motion dynamics and the force property of magnetic fluids on the surface of sclera under the external magnetic field.Results Silicone oil base Fe3O4 magnetic liquid injected into pig vitreous cavity moved and gathered together in sclera wall.Conclusions The silicone-based Fe3O4 magnetic fluid has the advantages of unique motion and location,and basically meets the requirements of retinal detachment repair,so it has potentially research and application value as stuffing in vitreous cavity.

Thermal conductivity (k) of nanofluids has been a hot area of interest. However, controversy exists in majority of the reported results make the thermophysical property of nanofluids remains vague. Dose this disagreement come from different methodologies used by different groups or any other factors? Results on k of the nanofluids, prepared by dispersing 22nm-diameter spherical Fe3O4in Polymeric α-olefin (PAO), were presented using transient-hot-wire method and 3ω method to determine the consistency of two experimental methodologies. Within the uncertainty of both methods, the obtained data showed good agreement, which confirmed that the experiment technique was not the chief factor causing the discrepancy of reported results. Thermal conductivity of Fe3O4 nanofluids can not be predicted by existing model.

为研究煤油基Fe3O4磁性液体在磁场作用下的双折射效应和二向色性特性,根据振荡磁偶极子模型进行了理论分析和模拟计算,并设计了用于测试磁性液体光学特性的实验平台,测量了不同体积密度下的光学特性。通过理论分析和模拟计算发现,不同方向偏振光的折射系数和消光系数随磁场的变化相反,平行偏振光的折射系数和消光系数随外加磁场的增大而降低,而垂直偏振光的折射系数和消光系数随外加磁场的增大而增大;折射系数和消光系数与磁性液体的体积密度成正比;玻璃-磁性液体界面的透射率随磁场的变化很小。实验平台下的归一化输出光强的模拟计算结果和实验结果一致,从而为磁性液体在光开关、磁场和电流测量等方面的应用提供了理论和实验依据。

用两块玻璃夹持一层几个μm厚的磁性液体薄膜.将这一磁性液体薄膜垂直放置于由亥姆霍兹线圈建立的均匀磁场中.在迈克尔孙干涉仪上用对比测量法测量在不同外加磁场强度作用下磁性液体薄膜的折射率.实验发现, 磁性液体薄膜的折射率随外加磁场强度的变化而变化.结合实验研究, 提出了外加磁场改变了磁性液体颗粒链的大小, 改变了磁性颗粒链的大小和入射光波波长的比值, 从而改变了磁性液体的折射率的设想.初步建立起了磁性液体薄膜的折射率和外加磁场强度之间的关联式.为磁场测量、光学阀门等新型磁光器件的开发提供了新的技术.

理论分析和数值模拟计算了不同温度和不同体积密度下磁件液体的折射系数和消光系数,以及浸没在磁性液体中光纤端面处的反射率,得到了体积密度和外加磁场强度对磁性液体的折射系数和消光系数的作用比较大,而温度对折射系数和消光系数的影响不大.实验制作了了光纤端面浸没在磁性液体中的传感元件,设计了测最光路系统,得到了反射率随外加磁场强度变化的情况,与理论分析结果相吻合.由理论和实验可知,磁性液体的消光系数小仅跟体积密度和温度有关,还与外加磁场强度有关,对光纤端面处的反射率有一定的影响.

A type of current transducer based on magnetic-optic effect of magnetic fluids and GRIN lens has been studied,which includes the structure design and the operation principle.When magnetic fluids is subjected to a magnetic field,the optical transmission of the ferrofluid change.The structure design of four kind of sensors all uses the magnetic fluid as the sensoring medium and the optical fiber as the signal transmission channel.Such design effectively realizes the insulation of high-voltage subsystem and low-voltage subsystem.Futhermore,it has low volume,light weight and long-life and can be easily installed as well.The sensitivity and response time can be tailored to reach the actual application by changing the concentration and liquid carrier of magnetic fluids.

A type of current transducer to the optical measurements of high-voltage current using ferrofluid films has been studied. The basic operation principle and design of the novel sensor is based upon the field-dependent transmitivity. When a thin film of ferrofluids is subjected to a magnetic field applied which is perdicular to the plane of film, a portion of magnetic particles is condensed out from the initially monodispersed magnetic fluid and forms magnetic chains, then the optical transmitivity of the ferrofluid changes. The main advantage of this method in comparison with the optical current transformer on Faraday effect and the conventional electromagnetic current transformer avoids problems in the low SNR and the high-voltage isolation. The sensitivity and response time can be tailored during fabrication to suit the application by changing the concentration, liquid carrier or changing the configuration of the transducer cell.

Based on the coupled-mode theory, second harmonic generation (SHG) in the form of Cherenkov radiation from a channel waveguide has been investigated taking the propagation loss into account. The results show that the conversion efficiency has an exponential behaviour and a saturation characteristic, which differ from the linear behaviour in the case of omitting the propagation loss. The results play an important role in the design and fabrication of Cherenkov frequency-doubler.

本文讨论了用于可调谐钛宝石激光器的双折射滤光片的设计原理,并且给出了一个设计实例.它由3片石英晶片组成,厚度分别为1、2、4 mm;晶片与光轴的夹角28°;调谐范围从700～1000 nm.在整个范围内,次峰的透过率被抑制在10%以下.