Magnetic Properties of Percolated Perpendicular FePt–MgO Films

Percolated perpendicular FePt-MgO films with a (Fe₄₈ Pt ₅₂)_100-x-(MgO)_x/Pt(001)/Cr(002) structure were prepared by conventional dc magnetron sputtering (x=0-6.13). Magnetic measurements demonstrate that the coercivity of the magnetic film drastically increases from 169 to 285 kA/m as the MgO content is increased from 0 to 0.15 vol.%. However, the grain sizes of the FePt phase do not significantly varying upon doping with MgO. MgO does not appear at the grain boundaries of the FePt phase, but is present as crystalline dots that are uniformly precipitated in the FePt matrix. The MFM images revealed that the domain structure transformed from extending to isolate when the MgO dots precipitated into the FePt grains. Consequently, the MgO dots serve as pinning sites of the domain wall and enhance perpendicular coercivity. Percolated perpendicular magnetic recording is thus regarded as a solution to the problem of thermal instability in ultrasmall grains     

Effect of Ag on the microstructure and electrical properties of ZnO

Various amounts of silver particles, 0.08–7.7 mol%, are mixed with zinc oxide powder and subsequently co-fired at 800–1200 °C. The effects of Ag addition on the microstructural evolution and electrical properties of ZnO are investigated. A small Ag doping amount (<0.76 mol%) promotes the grain growth of ZnO; however, a reversed trend in grain growth is observed for a relatively larger Ag addition (>3.8 mol%). It is evident that a tiny amount of Ag (0.08 mol%) may dissolve into the ZnO lattice. High-resolution TEM observations give direct evidences on the segregation of Ag solutes at the ZnO grain boundaries. The grain boundary resistance of ZnO increases 35-fold with the presence of Ag solute segregates. The Ag-doped ZnO system exhibits a nonlinear electric current–voltage characteristic, confirming the presence of an electrostatic barrier at the grain boundaries. The barrier is approximately 2 V for a single grain boundary.     

A High-Speed Optical Multidrop Bus for Computer Interconnections

Signal integrity constraints of high-speed electronics have made multidrop electrical buses infeasible. This high-speed alternative uses hollow metal waveguides and pellicle beam splitters that interconnect modules attached to the bus. With 1 mW of laser power, the bus can interconnect eight modules at 10 Gbps per channel and achieves an aggregate bandwidth of more than 25 Gbytes per second with 10-bit-wide signaling paths.     

Impact of a compound drop on a dry surface

The impact of a water-in-oil compound drop on a dry quartz surface was studied. The impact outcomes depended on a core-to-overall mass ratio and a Weber number. For a Weber number less than 570 and a core-to-overall mass ratio ranging from 0.07 to 0.7, five collision patterns were observed: complete deposition, shell deposition with core partial rebound, shell splash with core-shell deposition, shell splash with core partial rebound, and shell splash with core-shell partial rebound. Past research has indicated that the splash phenomenon depends strongly on liquid properties such as surface tension and viscosity in addition to the properties of the solid surface and the surrounding gas. The liquid properties in a compound drop were made non-uniform by the presence of additional interfaces in the interior of the liquid drop.     

Experimental study of exhaust‐gas energy recycling efficiency of hybrid pneumatic power system

A hybrid pneumatic power system (HPPS) comprises an internal combustion engine (ICE), an air compressor, a high‐pressure air storage tank, and a turbine, which stores the flow work instead of a battery's electrochemical energy; moreover, this system can recycle the exhaust‐gas energy and make the ICE operate at its optimal point. Therefore, it can be viewed as a promising solution to increase a system's thermal efficiency and greatly improving exhaust emissions. This paper presents experimental study results concerning the operating capabilities of the HPPS and the effect of the contraction of the cross‐sectional area (CSA) at the merging region of the energy merger pipe for the change in the compressed airflow pressure (P_air) on the exhaust‐gas energy recycling of the HPPS. The experiments were performed on an HPPS that uses an innovative energy merger pipe with a total length of 530 mm, a diameter of 34 mm, and an angle between the two pipes of 30°, and the CSA was adjusted for the change in P_air. The experimental results show that the exhaust‐gas energy recycling and the merger flow energy are significantly dependent on the CSA adjustment for the change in P_air. The optimum conditions for the best merging process can be achieved at a CSA of around 5–35% in the full range of P_air. Under these conditions, the exhaust‐gas energy recycling efficiency reached approximately 75–81%; therefore, a vehicle equipped with an HPPS can achieve efficiency that is approximately 40% higher than that of conventional vehicles. Copyright © 2009 John Wiley & Sons, Ltd.     

Compatibility and Simplicity: The Fundamentals of Reliability

Complex systems are less compatible internally, and with other systems, which reduces reliability. To restate, two primary principles must be kept in mind: keep the system simple, and make the system compatible with others. These two guidelines will help maintain the desired reliability.     

Enhancement of Flip-Chip Light-Emitting Diodes With Omni-Directional Reflector and Textured Micropillar Arrays

The flip-chip light-emitting diodes (FC-LEDs) with a conductive omni-directional reflector and textured micropillar arrays were investigated. The micropillar arrays structure was formed on the bottom side of sapphire substrate by dry etching process to increase the light-extraction efficiency. The light output power of the FC-LED was increased by 65% for a 3.2-mum textured micropillar on the bottom side of the sapphire substrate. Our work offers promising potential for enhancing output powers of commercial light-emitting devices.     

Discovering recency,frequency, and monetary (RFM) sequential patterns from customers’ purchasing data

In response to the thriving development in electronic commerce (EC), many on-line retailers have developed Web-based information systems to handle enormous amounts of transactions on the Internet. These systems can automatically capture data on the browsing histories and purchasing records of individual customers. This capability has motivated the development of data-mining applications. Sequential pattern mining (SPM) is a useful data-mining method to discover customers’ purchasing patterns over time. We incorporate the recency, frequency, and monetary (RFM) concept presented in the marketing literature to define the RFM sequential pattern and develop a novel algorithm for generating all RFM sequential patterns from customers’ purchasing data. Using the algorithm, we propose a pattern segmentation framework to generate valuable information on customer purchasing behavior for managerial decision-making. Extensive experiments are carried out, using synthetic datasets and a transactional dataset collected by a retail chain in Taiwan, to evaluate the proposed algorithm and empirically demonstrate the benefits of using RFM sequential patterns in analyzing customers’ purchasing data.     

Reactive energy scheduling using bi-objective programming with modified particle swarm optimization

Interactive Bi-objective with Valuable Trade-off programming, together with a modified particle swarm optimization for the daily scheduling of switched capacitors is presented. The two main contradictory concerns of line loss reduction and minimum number of switching operations are considered for realistic request. Both the operating and load constraints for distribution feeders are formulated for practical operation. The proposed approach can provide a set of flexible and valuable trade-off solutions as dictated by decision makers of electric utilities. Quantitative measures can also be provided to aid the decision-making process. To demonstrate the effectiveness and feasibility of the proposed approach, comparative studies were systematically conducted on an actual feeder. The experiment showed encouraging results suggesting that the proposed approach was capable of efficiently determining better quality solutions.     

Grain Growth Behavior of Bi2O3-Doped ZnO Grains in a Multilayer Varistor

A novel bismuth-doped zinc oxide (ZnO) laminated structure is prepared in the present study. Seven layers with thickness ranging from 20 to 140 μm are laminated together with platinum (Pt) inner electrodes. The growth of Bi₂O₃-doped ZnO grains within a very limited space between Pt electrodes is investigated. The grain growth behavior outside the confinement of electrodes is also studied for comparison purposes. At the beginning of sintering, a similar grain growth behavior is observed at different locations of the laminated structure. However, as sintering proceeds, the rate of grain growth within the Pt inner electrodes is decreased because of the decrease of available transportation paths. The grains between the electrodes then develop into a columnar shape as they make contact with the electrodes above and below them. Both the grain size and its distribution decrease with decreasing layer thickness.