A key goal for implementation of magnetorheological fluids (MRFs) is to minimize sedimentation or to increase suspension stability. In this study, a series of MRF samples were synthesized by suspending carbonyl iron particles (CIPs), which had different organic molecules and auxiliaries grafted onto their surface, in silicone oil. The magnetorheology of these MRF samples was measured using a magneto-rheometer, and their sedimentation behaviors were quantitatively evaluated using a thermal conductivity sedimentation measurement method. The effect of these coatings on the stability of the MRFs was analyzed. Results show that all of the MRFs exhibit good MR effects and that the surface modification does not greatly weaken the MR effect. Suspension stability was substantially improved by grafting organic molecular structures onto the surface of the CIPs, and the sedimentation rate was influenced by the organic molecule structure. Compared to the uncoated CIPs, when the organic molecule was changed from octyl acyl ethylenediamine triacetate (C7H15COED3A) to lauryl acyl ethylenediamine triacetate (C11H23COED3A) and stearyl acyl ethylenediamine triacetate (C17H35COED3A), the sedimentation rate decreased by 53.9% to 64.2% and 75.1%, respectively. The mechanisms of how organic molecular structure affects the stability of MRFs are discussed.

Measuring sedimentation rate of magnetorheological fluids (MRFs) is of great importance when designing and synthesizing MRFs for engineering applications. A method of characterizing sedimentation rate in an MRF column is proposed utilizing thermal conductivity correlated with particle concentration. A series of MRF samples composed of carbonyl iron particles suspended in silicone oil were prepared, and their concentrations (measured as volume fraction, ∅) and thermal conductivities, k, were tested. A calibration curve was developed to relate particle concentration, ∅, to thermal conductivity, k, using this set of MRF samples with known concentration. The particle concentration, ∅, in the MRF column was then monitored by measuring thermal conductivities (k) at a fixed location and using this calibration relationship. Finally, sedimentation rate in the MRF column was determined by examining how particle concentration varied with time. The sedimentation rate measured in the MRF column was validated using visual observation of mudline (boundary between the topmost clarified fluid zone and MRF below).

This paper presents an intelligent control method and its engineering application in the control of braking-induced longitudinal vibration of floating-type railway bridges. Equations of motion for the controlled floating-type railway bridges have been established based on the analysis of the longitudinal vibration responses of floating-type railway bridges to train braking and axle-loads of moving trains. For engineering applications of the developed theory, a full-scale 500 kN smart magnetorheologic (MR) damper has been designed, fabricated and used to carry out experiments on the intelligent control of braking-induced longitudinal vibration. The procedure for using the developed intelligent method in conjunction with the full-scale 500 kN MR dampers has been proposed and used to control the longitudinal vibration responses of the deck of floating-type railway bridges induced by train braking and axle-loads of moving trains. This procedure has been applied to the longitudinal vibration control of the Tian Xingzhou highway and railway cable-stayed bridge over the Yangtze River in China. The simulated results have shown that the intelligent control system using the smart MR dampers can effectively control the longitudinal response of the floating-type railway bridge under excitations of braking and axle-loads of moving trains.

Single‐phase BaCoTiFe10O19 (BaCoTi‐M) nanoparticles were prepared by a modified sol–gel process, using metallic chlorides as starting materials. The physical chemistry process of BaCoTi‐M formation, the interdependences between composition, technological conditions, microstructure, and magnetic properties were studied by X‐ray diffraction (XRD), Fourier transform‐infrared (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM). XRD and FTIR results show that BaCoTi‐M nanoparticles formed directly from γ‐Fe2O3, spinel ferrite, and barium salts without the formation of α‐Fe2O3 and BaFe2O4. The lattice shrinkage of BaCoTi‐M nanoparticles that occurred on increasing the calcining temperature from 973 to 1173 K under holding for 2 h or on increasing the holding time in the range 0–2 h at 1173 K was discovered by analyzing the dependences of lattice parameters on the heat‐treatment conditions. The shrinkage led to a relatively higher concentration of magnetic Fe3+ cations in the unit cell, and resulted in an increase of specific saturation magnetization under the corresponding conditions. Microstructural characterization shows that the evolutions of coercivity, remnant magnetization, and squareness ratio depended on the crystal growth and the reduction of structural defect as well as a decrease of grain boundary.

Magnetic drug targeting has shown its favorable perspective in treating malignant tumors locally without global toxicity in the last thirty years [1][2][3] . However, the external magnetic field used to actively targeting magnetic drug is facing a serious challenge, for the external magnetic field could not react in deep regions of the body [4, 5] . Forbes [6] first drew the concept of internal magnetic field and carried out experimental study in magnetic drug targeting in 2003. Now we further evaluate magnetic drug targeting based on internal magnetic field inside the tumor by inserting magnetic biliary stent wires into the tissues of cholangiocarcinoma. Materials and methods Magnetic biliary stent wires and the method of building internal magnetic fieldsIn this experiment, electroless Co-Ni-W-P alloy were deposited as hard magnetic thin films to overlay the surface of Ni-Ti alloy stent. The thickness of film is 25 μm. The surface magnetic field of magnetic biliary stent wire is about 0.03 T after magnetized by a magnetometer. Then the magnetic biliary stent becomes a permanent magnet, which can resist 200 °C temperature and stand up erosion and oxidation in the body.10 wires of magnetic biliary stent, 0.5 cm in length and 0.03 cm in diameter, were completely inserted into the tissue of cholangiocarcinoma in interlaced direction and deck. Animal models bearing cancer32 animal models bearing tumor were made by implanted human cholangiocarcinoma cell line QBC939 in the right back of each nude mouse. When the tumor volume grew to about 0.6 cm in diameter after three weeks, the animal models were divided equally into four groups at random including: (a) group A, consisting of internal magnetic fields and receiving magnetic nanoparticles containing 5-FU administered via tail vein injection at 250 mg/kg for consecutive five days; (b) group B, receiving placebo (sodium chloride) administered via tail vein injection 0.2 mL/pc for consecutive five days; (c) group C, having pure Abstract Objective: To evaluate the effect of magnetic nanoparticle containing 5-fluorouracil (5-FU) targeting in treating cholangiocarcinoma based on internal magnetic fields built inside the tumor. Methods: 32 nude mice of BABL/C bearing ectopic tumor were built by subcutaneouly injecting cholangiocarcinoma cell line QBC 939. Three weeks after tumor inoculation, the animal models were divided equally into four groups at random including: (a) group A, consisting of internal magnetic field built by magnetic biliary stent wires inserted into tumor tissue and receiving magnetic nanoparticles containing 5-FU administered via tail vein injection at 250 mg/kg for consecutive five days; (b) group B, receiving placebo (sodium chloride); (c) group C, receiving pure magnetic biliary stent wires without the applying of magnetic nanoparticles; (d) group D, consisting of external magnetic fields and the same treatment of magnetic nanoparticles containing 5-FU as group A. The tumor volumes were measured every 3 days, totally six times from treatment started....