Fabrication of Patterned Magnetic Nanomaterials for Data Storage Media

Patterned media (PM) for magnetic information storage have received increased attention in recent years as the primary candidate for 1?Terabit/in² or higher recording density for computer hard disk drives. A PM consists of a periodic array of well-defined magnetic islands, each of which can store one bit of data. In the simplest scheme, the structures could be magnetic pillars and dots with a single easy axis of magnetization. The direction of detected magnetization by the read/write head is interpreted as a binary signal 1 or 0. Some of the main technical issues in the PM include the difficulty in fabricating small nanoisland arrays in a periodic fashion over large areas, reliability/reproducibility of magnetic bit characteristics, as well as wear and head flyability issues associated with the media surface roughness, and processing cost. This article deals with a recent investigation of various fabrication approaches, nanostructural features, and magnetic properties for the bit PM.     

A pragmatic approach to adaptive antennas

This paper presents a novel approach for efficient computation of adaptive weights in phased-array antennas. The fundamental philosophical differences between adaptive antennas and adaptive signal-processing methodology are also delineated. This approach, unlike the conventional statistical techniques, eliminates the requirement for an interference covariance matrix, and represents a rethinking of the entire conventional approach to adaptive processing. This approach provides greater flexibility in solving a wider class of problems, at the expense of a slightly reduced number of degrees of freedom. It is important to note that the application of a deterministic approach to address stochastic problems with an ergodic structure can be seen in the works of Wiener (1949) and Kolmogorov (1939). This paper presents examples to illustrate the effectiveness and uniqueness of this new pragmatic approach     

Production tactic and physiochemical properties of low ω6/ω3 ratio structured lipid synthesised from perilla and soybean oil

Structured lipid (SL) was synthesised by enzymatic interesterification of soybean oil and perilla oil. Response surface methodology (RSM) was used to determine the effects of three variables on the lipase‐catalysed interesterification. Based on ridge analysis, combination of reaction time (X₁; 18 h), reaction temperature (X₂; 60 °C), and substrate mole ratio (X₃; 1:1) were optimised for higher incorporation of ω3 (alpha (α) linolenic acid (ALA)) (Y). The predictive model was found to be adequate due to no significant lack of fit and satisfactory level of coefficient of determination (R² = 0.97). Experiments were conducted under optimised conditions which were predicted by the model equations, obtained from RSM yielded SL with linoleic (44.01%) and ALA (35.82%) were detected at sn‐2 position. The effects of antioxidants such as catechin, butylated hydroxytoluene (BHT) BHT and rosemary extracted on the oxidative stability in SL were investigated. Among all antioxidants, the highest stability was obtained from catechin.     

Geometrical approach for flame forming of single curved ship hull plate

Ship hull plate forming by flame torch plays an important role in shipbuilding process. In shipyards, the line heating method is one of the major processes carried out by workers to form the plates into desired shapes. Since this process depends on the skilled workers’ experiences and knowhow, there is a lot of variation in the products. There also could be some difficulties in communicating with each other. Hence, it is necessary to develop an automation system to increase not only the plate forming productivity, but also product quality. For automated plate forming, it is required to know where and how much to heat on the plate. Thus, the inverse problem should be solved to obtain process parameters such as torch travel speed and the heating positions. In this study, the deformed curve shape by flame heat was geometrically considered so that the appropriate geometrical parameters can be obtained. Then, the relationship between the bending angle and the radius of the curvature of the deformed curve shape were established. In addition, the process parameters were obtained by using the relationship between geometrical parameters and process parameters. Lastly, experiments of the two-dimensional plate forming considering deformed curve shape with the curvature were performed. The results of the formed shape were similar to the target shape.     

Experimental study on slippery droplet dynamics using optical correction method

When a droplet is placed on an inclined plane, it can slide down the plane by gravitational force. This phenomenon can occur in many industrial applications such as surface coating and printing, as well as in evaluating the characteristics of a surface. The slippery droplet can be analyzed from the balance between the gravitational force and the sum of the capillary and resistance forces. Researchers have suggested various equations of force balance with several hypotheses. To increase the reliability of the force balance correlation, it is important to obtain an accurate inside velocity profile and the three-dimensional (3D) shape of a droplet. In this paper, an analysis system of the slippery droplet was developed which includes optical correction based on a ray tracing method for velocity field measurement and an ellipse fitting method for droplet shape reconstruction. These correction methods were verified by a numerical simulation and applied to a slippery droplet on an inclined plate coated with Poly methyl methacrylate (PMMA). The wall shear force calculated from the velocity field and that calculated from the force balance were in good agreement.     

Effects of thermal aging on degradation mechanism of flame retardant‐filled ethylene–propylene–diene termonomer compounds

Ethylene–propylene–diene termonomer (EPDM) compounds filled with halogenated (Br and Cl) flame retardants (FRs) and Sb₂O₃ were prepared via melt mixing, and their thermal stability, weight loss, and elemental composition were investigated as a function of aging conditions (temperature: 120–380°C, period: ～100 h, and atmosphere: nitrogen and air). The thermal aging was done with thermogravimetic analysis under both isothermal and nonisothermal conditions and a convection oven. Scanning electron microscopy–energy dispersive spectroscopy was used to study the surface morphology and elemental composition of the thermally aged FRs‐filled EPDM compounds. For a better precision of compositional analysis, a laser‐induced breakdown spectroscopy (LIBS) was employed in this study. The thermal degradation behavior of EPDM compounds containing halogenated FRs was strongly dependent on the aging atmosphere (N₂ or air) and type of FRs. The weight loss of the EPDM compounds during thermal aging was found to be quite small in the temperature ranges below 190°C, while it was noticeable above the temperature. The LIBS technique can be an effective and promising analysis tools for analyzing the elemental components in a bulk rubber compound. Two possible mechanisms were proposed for the thermal degradation of the EPDM compounds containing brominated FR and Sb₂O₃. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41324.     

Preparation and characterization of octadecane/polyurea nanocapsule‐embedded poly(ethylene oxide) nanofibers

This article describes the preparation and characterization of latent heat storage poly(ethylene oxide) nanofibers (LHS‐PEO nanofibers) with octadecane/polyurea (PCM/PU) nanocapsules. PCM/PU nanocapsules were prepared by interfacial polycondensation from toluene 2,4‐diisocyanate and ethylene diamine in a resin‐fortified emulsion system. LHS‐PEO nanofibers were prepared using an electrospinning procedure with varying PCM/PU nanocapsules content, i.e., from 0 to 8 wt %. The PCM/PU nanocapsules were polydisperse with an average diameter of 200 nm. The melting and freezing temperatures were determined as 23.7 and 28.2°C, respectively, and the corresponding latent heats were determined as 123.4 and 124.1 kJ kg^?1, respectively. The encapsulation efficiency of the PCM/PU nanocapsules was 78.1%. The latent heat capacity of the LHS‐PEO nanofibers increased as the PCM/PU nanocapsules content increased. Defects, such as holes and disconnection of the nanofibers, were observed, particularly inside the LHS‐PEO nanofibers. For packaging applications, mats were fabricated from the nanocapsules‐embedded nanofibers with varying nanocapsule content and the mats’ surface temperatures were monitored with a thermal imaging camera. The results proved the feasibility of using the LHS‐PEO nanofibers for thermal energy storage and functional packaging materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42539.     

Facile fabrication of high-efficiency near-infrared absorption film with tungsten bronze nanoparticle dense layer

An excellent transparent film with effective absorption property in near-infrared (NIR) region based on cesium-doped tungsten oxide nanoparticles was fabricated using a facile double layer coating method via the theoretical considerations. The optical performance was evaluated; the double layer-coated film exhibited 10% transmittance at 1,000 nm in the NIR region and over 80% transmittance at 550 nm in the visible region. To optimize the selectivity, the optical spectrum of this film was correlated with a theoretical model by combining the contributions of the Mie-Gans absorption-based localized surface plasmon resonance and reflections by the interfaces of the heterogeneous layers and the nanoparticles in the film. Through comparison of the composite and double layer coating method, the difference of the nanoscale distances between nanoparticles in each layer was significantly revealed. It is worth noting that the nanodistance between the nanoparticles decreased in the double layer film, which enhanced the optical properties of the film, yielding a haze value of 1% or less without any additional process. These results are very attractive for the nanocomposite coating process, which would lead to industrial fields of NIR shielding and thermo-medical applications.

PACS

78.67.Sc; 78.67.Bf; 81.15.-z     

La-promoted Ni/γ-Al2O3 catalyst for autothermal reforming of methane

Autothermal reforming (ATR) of methane over the synthesized catalysts of 10Ni-2La/γ-Al₂O₃, 10Ni-2Ce/γ-Al₂O₃, 10Ni-2Co/γ-Al₂O₃ was investigated in the temperature range of 600-800 oC for the hydrogen production. The sequence of 2 wt% metal loading on nickel alumina support in relation to their catalytic performance was observed as La>Ce>Co. The excellent activity and selectivity of 10Ni-2La/γ-Al₂O₃ was superior to other catalysts owing to little carbon deposition (~2.23 mg coke/gcath), high surface area and good dispersion and stability in the alumina support. The reforming of methane was inferred to be initiated by the decomposition of hydrocarbon at the inlet zone, preceded by the reforming reactions in the catalyst bed. Our result shows that it can be possible to achieve the H₂/CO ratio optimal to the GTL processes by controlling the O₂/CH₄ ratio of the feed inlet. The addition of oxygen to the feed inlet enhanced conversion efficiency substantially; probably, it favors the re-oxidation of carbonaceous residues formed over the catalyst surfaces, avoiding the catalyst deactivation and hence promoting catalyst stability.     

Reactor sizing for butane steam reforming over Ni and Ru catalysts

We obtained kinetics data on steam reforming of butane and calculated the appropriate reactor size based on the kinetics data. Using commercial Ni and Ru catalysts, steam reforming reactions of butane were performed while changing the reaction temperature and partial pressure of reactants. After comparing the power law model and the Langmuir-Hinshelwood model by using the kinetics data obtained from the experiment, it is revealed that the reaction rate could be determined by both models in the reforming reaction of butane over commercial Ni and Ru catalysts. Also, calculation of the steam reforming reactor size using a PRO/II simulation with a kinetic model equation showed that the reactor size using the Ni catalyst is smaller than that with the Ru catalyst to obtain the same conversion.