A Micellar Route to Ordered Arrays of Magnetic Nanoparticles: From Size‐Selected Pure Cobalt Dots to Cobalt–Cobalt Oxide Core–Shell Systems

Starting with Co‐salt‐loaded inverse micelles, which form if the diblock copolymer polystyrene‐block‐poly(2‐vinylpyridine) is dissolved in a selective solvent like toluene and CoCl₂ is added to the solution, monomicellar arrays of such micelles exhibiting a significant hexagonal order can be prepared on top of various substrates with tailored intermicellar distances and structure heights. In order to remove the polymer matrix and to finally obtain arrays of pure Co nanoparticles, the micelles are first exposed to an oxygen plasma, followed by a treatment in a hydrogen plasma. Applying in‐situ X‐ray photoelectron spectroscopy, it is demonstrated that: 1) The oxygen plasma completely removes the polymer, though conserving the original order of the micellar array. Furthermore, the resulting nanoparticles are entirely oxidized with a chemical shift of the Co 2p_3/2 line pointing to the formation of Co₃O₄. 2) By the subsequent hydrogen plasma treatment the nanoparticles are fully reduced to metallic Co. 3) By exposing the pure Co nanoparticles for 100 s to various oxygen partial pressures pequation/tex2gif-inf-5.gif, a stepwise oxidation is observed with a still metallic Co core surrounded by an oxide shell. The data allow the extraction of the thickness of the oxide shell as a function of the total exposure to oxygen (pequation/tex2gif-inf-7.gif × time), thus giving the opportunity to control the ferromagnetic–antiferromagnetic composition of an exchange‐biased magnetic system.     

Interconnected power systems with superconducting magnetic energy storage

The objective of this work is to discuss the concept of back‐to‐back interconnection systems with energy storage, especially with a Superconducting Magnetic Energy Storage (SMES) incorporated into a back‐to‐back DC link. In this case, each converter of the back‐to‐back system is used as a power conditioning system for the SMES coils. Since the AC–DC converter can be designed independently of the frequency of the power system, a two‐way switch is connected to the AC side of each converter. This two‐way switch can select the interconnected power systems. By using the two‐way switches, this system can provide the stored energy in the SMES system to each interconnected power system through two AC–DC converters. For instance, lower‐cost power of each power network can be stored through two converters during the off‐peak hours and made available for dispatch to each power network during periods of demand peak. Then this system increases the reliability of electric power networks and enables the economical operations depending on the power demand. This paper describes the unique operations of the back‐to‐back interconnection with SMES and discuses the optimal SMES configuration for a 300‐MW‐class back‐to‐back interconnection. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(2): 37–43, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20482     

锰锌铁氧体纳米粉体的液相制备及磁性能

以δ-FeOOH为前驱体,用氨水调节溶液的pH值,分别采用(1)90℃水浴加热动态转化、(2)沸腾回流动态转化,(3)90℃静态转化及(4)200℃水热法四种方法合成了锰锌铁氧体纳米粉体.采用X射线衍射仪(XRD),透射电子显微镜(TEM)、振动样品磁强计(VSM)和X射线荧光光谱仪(XRF)等方法对粉体进行了表征,对四种液相法制备的锰锌铁氧体纳米粉体的结构和性能等进行了对比和分析.结果表明,四种方法中沸腾回流相转化法得到的产物具有磁性能较好、形状较规则、粒径可控等优点.     

The application of microencapsulated phase‐change materials to nylon fabric using direct dual coating method

The fabrication of functional textiles able to provide thermal regulation and comfort for the body has attracted increasing interest in recent years. This research investigated fabric coatings containing energy absorbing, temperature stabilizing, phase‐change material microcapsules (PCMMcs), and their methods of application. Specifically, a coated fabric was directly prepared by a dual‐type coating method, in which the PCMMcs were dispersed in a polyurethane coating solution with no binder. The thermal performances of the dual‐coated samples were evaluated by differential scanning calorimetry, and their physical characteristics were examined by scanning electron microscopy, thermal vision camera, porosity, water vapor transmission rate (WVTR), and water entry pressure (WEP) analyses. Furthermore, the microclimate characteristics of the thermally enhanced fabrics were investigated under experimental conditions using a human‐clothing‐environment (HCE) simulator system. The study results confirmed the superior performance of the dual‐coated fabrics in terms of thermal regulation and body comfort, compared with those coated by the dry or wet coating method, because of the improved WEP, WVTR, and thermal performance. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis and magnetic properties of novel fully conjugated polymeric complexes containing 1,10‐phenanthroline

A novel fully conjugated polymer containing 1,10‐phenanthroline (DAPcDOD) was first synthesized by the polycondensation of 2,7‐dimethyl‐2,4,6‐octatriene‐1,8‐dial with 5,6‐diamine‐1,10‐phenanthroline. Three polymeric complexes were first prepared by the reaction of DAPcDOD with NiSO₄, CoCl₂, and FeSO₄, respectively. The structures of the polymer and the complexes were characterized by IR, ¹H‐NMR, and elemental analysis. The magnetic behaviors of these complexes were measured as a function of magnetic field strength (0–50 kOe) at 5 K and as a function of temperature (5–300 K) at a magnetic field strength of 30 kOe. The results show that DAPcDOD–Ni²⁺ and DAPcDOD–Co²⁺ were soft ferromagnets, whereas DAPcDOD–Fe²⁺ exhibited the features of an antiferromagnet. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Techniques and Apparatus for Measuring Rotational Core Losses of Soft Magnetic Materials

In many situations such as the cores of a rotating electrical machine and the T joints of a multiphase transformer, the local flux density varies with time in terms of both magnitude and direction, i.e. the flux density vector is rotating. Therefore, the magnetic properties of the core materials under the rotating flux density vector excitation should be properly measured, modeled and applied in the design and analysis of these electromagnetic devices. This paper presents an extensive review on the development of techniques and apparatus for measuring the rotational core losses of soft magnetic materials based on the experiences of various researchers in the last hundred years.     

核磁共振测井在桩1区块底水稠油油藏开发中的应用

针对桩1区块特高含水期底水稠油油藏的开发特点,利用核磁共振测井资料定量评价其孔隙流体流动特性,准确划分产层,直接识别油、水层,准确地评价了区块剩余油分布情况.依此部署了水平井,取得了很好的开发效果.实践证明,核磁共振测井具备常规测井所不具备的某些技术优势,能解决一些特殊的地质问题,有广泛的应用前景.     

Computations of Explosive Boiling in Microgravity

Dynamics of the explosive growth of a vapor bubble in microgravity is investigated by direct numerical simulation. A front tracking/finite difference technique is used to solve for the velocity and the temperature field in both phases and to account for inertia, viscosity, and surface deformation. The method is validated by comparison of the numerical results with the available analytical formulations such as the evaporation of a one-dimensional liquid/vapor interface, frequency of oscillations of capillary waves, and other numerical results. Evolution of a three-dimensional vapor nucleus during explosive boiling is followed and a fine scale structure similar to experimental results is observed. Two-dimensional simulations yield a similar qualitative instability growth.