Synthesis of amphiphilic magnetic microspheres by dispersion copolymerization of styrene and poly(ethylene oxide) macromonomer

Amphiphilic magnetic microspheres ranging in diameter from 5 to 100 µm were prepared by dispersion copolymerization of styrene and poly(ethylene oxide) vinylbenzyl (PEO‐VB) macromonomer (MPEO) in the presence of Fe₃O₄ magnetic fluid. The effects of various polymerization parameters on the average particle size were systematically investigated. The average particle size was found to increase with increasing styrene concentration and initiator concentration. It also increased with decreasing stabilizer concentration and molecular weight of MPEO. The content of the hydroxyl groups localized in the microspheres ranged from 0.01 to 0.2 mmol g^?1. © 2003 Society of Chemical Industry     

脉冲中子组合测井在胜利油田中的应用

碳氧比能谱、脉冲中子衰减-能谱、注硼中子寿命以及氧活化测井均属于脉冲中子测井方法.简单介绍了这些测井技术各自的测量原理及应用.针对胜利油田地质情况的复杂性、多解性,阐述了应用组合测井方法可以更好地解决油藏的剩余油分布等问题.使用脉冲中子衰减-能谱测井仪(PND)进行PND和硼中子寿命测井的组合测井方法,利用PND获得的俘获截面曲线作为注硼中子寿命测井的基线.该方法既可缩短施工时间,又可解决单一测井方法无法解决的某些特殊测井问题.介绍了应用这种组合测井在正确识别低压储层、确定储层窜通情况、获得剩余油饱和度、确定储层水淹程度等方面的测井实例.     

控制室格栅形屏蔽设计的计算

以抗雷击电磁脉冲干扰为例，按下列2种情况讨论控制室格栅形大空间屏蔽的设计计算：已知屏蔽网格，求磁场强度的衰减是否符合控制系统的脉冲磁场抗扰度；已知控制系统的脉冲磁场抗扰度，求屏蔽网格的宽度W等参数。     

砾岩储层精细描述中标准测井资料的应用

克拉玛依油田七区的标准测井资料是指使用标准电极系视电阻率测井、自然电位测井和井径测井,以相同的1:500深度比例尺及相同的横向比例进行测井作业所取得的资料.这种资料本来并不具备定量解释储层孔隙度和含油饱和度的能力,但这种资料占该区测井资料总量的比率高达34%.利用标准电极系视电阻率资料和岩心分析资料建立了视电阻率-岩性图版,利用自然电位减小系数α和岩心孔隙度分析资料φ建立了α-φ图版,根据综合测井资料求出标准测井视电阻率校正系数,进而确定了饱和度计算方程的参数.与相应的综合测井资料计算结果相对比,用该方法得到的孔隙度平均绝对误差及相对误差分别为1.85%和11.88%;含油饱和度平均绝对误差及相对误差分别为9.08%和24.75%.将该方法有选择地应用到该区砾岩储层精细描述研究中,弥补了缺乏综合测井资料无法进行测井储层评价及参数研究的缺陷.     

Magnetic Properties of Fe-Doped Rutile

Ball-milling method was applied to dissolve Fe into titanium dioxide (TiO₂). X-ray diffraction indicated the starting anatase changed to a rutile-type structure with oxygen deficiency after ball milling. Transmission electron microscopy and X-ray absorption experiments were conducted to examine the possible existence of magnetic impurities in the ball-milled powders after they were leached in HCl solutions. Temperature dependence of the resistivity shows semiconducting behavior and the magnetic hysteresis loops at 5 and 300 K exhibit ferromagnetic characteristics. Fe-doped TiO₂ films were also prepared by pulsed laser deposition. The magnetic properties of the films are discussed.     

Characterization of Austempered Ductile Iron Through Barkhausen Noise Measurements

The outstanding mechanical properties of austempered ductile irons (ADI) are linked to the microstructure of the matrix obtained by subjecting a ductile iron with an appropriate composition to a heat treatment called austempering. Then the microstructure of the matrix consists of bainitic ferrite with different volume fractions of retained austenite. The aim of this work is to use the magnetic Barkhausen noise (MBN) as a nondestructive method for characterizing the microstructure of ADI. First, it is shown that the amplitude and position of the peak-shaped MBN response is quite sensitive to the microstructure of the matrix of ductile irons. Thus each type of constituent (equiaxial ferrite, pearlite, martensite or bainite) exhibits a typical response and, in turn, it can be identified from the MBN response. Furthermore, a good correlation is found between MBN signal parameters and ADI heat treatment parameters, indicating that MBN is also quite sensitive to fine evolutions of the microstructure of ADI. MBN peak position is especially sensitive to the type of bainite, whereas peak amplitude is linked to the progress of the bainite reaction. Hence MBN measurements appear to be a powerful tool to assess some important microstructural features of ADI castings.     

Electronic properties of magnetically doped nanotubes

Effect of doping of carbon nanotubes by magnetic transition metal atoms has been considered in this paper. In the case of semiconducting tubes, it was found that the system has zero magnetization, whereas in metallic tubes the valence electrons of the tube screen the magnetization of the dopants: the coupling to the tube is usually antiferromagnetic (except for Cr).     

Science in High Magnetic Fields: What Could Be Learned?

High magnetic fields are one of the most powerful tools available to scientists for the study, modification and control of matter. This includes the knowledge on correlations effects, interaction mechanisms, structural information and understanding of mesoscopic effects. In this context, a review of recent scientific achievements at the Grenoble High Magnetic Laboratory is given to illustrate, on specific examples, the power of the Magnetic Field probe.     

Curie Temperatures of III–V Diluted Magnetic Semiconductors Calculated from First-Principles in Mean Field Approximation

Electronic structure and ferromagnetism in III–V compound-based diluted magnetic semiconductors (DMS) are investigated based on first-principles calculations by using the Korringa-Kohn-Rostoker method combined with the coherent-potential-approximation. The stability of the ferromagnetic phase in GaN-, GaAs-, GaP-, GaSb-based DMS is investigated systematically. The calculations show that 3d-impurities from the first-half of the transition metal series favor the ferromagnetic state, while impurities from the latter-half of the series exhibit spin-glass behavior. This chemical trend in the magnetism is explained by the double exchange mechanism taking the local symmetry at the impurity gap states into account. Curie temperatures of GaAs- and GaN-based DMS are estimated by using the Heisenberg model in a mean field approximation with the parameters calculated from first-principles. It is suggested that room-temperature ferromagnetism can be realized in these systems.     

重质残油磁力传动齿轮泵磁偶合器扭矩计算

 磁力传动重质残油齿轮泵磁耦合器扭矩计算为三位磁场计算，边界条件复杂，加之漏磁、磁性材料参数误差等影响，求解较困难．导出精确求解磁耦合器扭矩的解析解，结果与实验解相符．并根据相似原理给出永磁体的长径比L/D=2/3~1，导磁材料径向厚度t=(1.5~2)L ( 为磁体厚)，可供设计时参考。