Search

Epitaxial Fe $[ 0.25 +\mathrm {x}]$ Pt[0.75 – x] layers can be either antiferromagnetic (AF) or ferromagnetic (FM) depending on the degree of chemical ordering controlled by the deposition temperature. Our neutron diffraction studies were the first to study AF phase transitions in these thin films [1] and we have also shown using PNR that a mixed AF-FM film is exchange biased with itself [2]. In AF-FM exchange-biased superlattices with a modulated chemical order parameter, PNR shows the magnetization can be modulated through the film thickness with no composition modulations [3]. Our recent results reveal that He+ ion bombardment and annealing can be applied toward controlling magnetic phases in epitaxial Fe[0.25]Pt[0.75] layers [4].

The objective of conventional wind power relay protections is to maintain the system's stable operation. However, the protections' selectivity is not high enough to enable the wind turbine to ride through low-voltage faults. Thus, with an increasing wind power capacity, it is required that the wind turbines possess more strict low-voltage ride-through(LVRT) ability, otherwise the stability of power grid may be endangered. With the cooperation of relay protections, LVRT ability ensures the wind turbine to remain grid-connected under different fault conditions. This paper presents the configuration of conventional wind power relay protections and their cooperation with the power grid. In addition, the existing problems of grid-connected wind power systems are proposed. We also analyze the wind turbine LVRT characteristics and its cooperation operating time with the relay protection. In this paper, the improvement of relay protection that possesses LVRT ability and other key problems are further discussed.

In order to extract capsule defects and reduce the process time in the real-time capsule defects identification system, a novel method using color image processing has been presented. We take RGB color space as the image processing environment and build an algebra relationship among the R, G and B components to directly segment the capsule defects instead of transforming these components to HSI color space. The first step of this method is to remove the background and effectively extract the capsule from the CCD-captured image. Based on the color variation relationship between the defect regions and the surrounding ones, the capsule defects are further segmented. Experimental results show that the method can successfully extract capsules better than in HSI color space, meanwhile, it can greatly accelerate the process and finish extracting within 3.5 milliseconds in contrast with 29.3 milliseconds in HSI space. Using this method, we have effectively extracted the capsules as well as their defects. The method would be practically useful in capsule defect identification system.

A novel time delay neural network is proposed for dynamical system control. In this work, A continuous recurrent neural network with time delay neurons in hidden layer is constructed, and the novel training algorithm and control law independent of delay are developed based on Lyapunovpsilas stability approach. Using the proposed method, the control error converges to a range near the zero point and remains within the domain throughout the course of the execution. The usefulness and validity of the presented algorithm are examined by numerical experiments.

Tensile-strained Ge photodetector is realized on Si-substrate using novel SiSiGe compliant layer with two-step Ge-process. Monolithic integration of p-i-n detectors with low dark current (0.4 nA), responsivity (190 mA/W) and high speed (5 GHz) on Ge-CMOS platform is demonstrated, with Ge pMOSFET showing 2X Si hole mobility.

Purpose: From Nov. 2002 to May 2006, eight hundred and seventy-two patients with valvular insufficiency of lower extremity were treated by improved external valvuloplasty and venous laser photocoagulation. This study was to summarize our clinical experience. Methods: Data in 872 patients with primary deep venous valve insufficiency who were performed improved external valvuloplasty and intravenous laser photocoagulation were retrospectively summarized. Results: During 6 month to 5 years follow-up, cumulative competency rate was 95.18%. Only five patients appeared mild reflux at valve site. Conclusion: The integration of intravenous laser photocoagulation and valve repair operations is one kind of extremely safe, effective, convenient, atraumatic, aesthetic and quick restorative therapeutic method in patients with primary deep venous valve insufficiency.

Dielectric barrier discharge (DBD) tests were carried out in an air gap with flowing N2. Characteristics of DBD were invested through photos taken from discharges between transparent water electrodes. The results show that when applied voltage amplitude, frequency increase, the filamentary discharge seems to transfer into a diffuse one by naked eyes. But the discharge current behaves more pulses not one in glow discharge. The influence of N2 flow on the uniformity of DBD is greater than voltage amplitude and frequency.

Dielectric barrier discharge (DBD) tests were carried out in an air gap with flowing helium. Through photos taken from discharges between transparent water electrodes, influence of some test conditions on characteristics of DBD was invested. The conditions included amplitude and frequency of applied voltage, velocity of gas flow, distance of gas gap, and thickness of barriers. The results show that when applied voltage amplitude, frequency, or velocity of helium flows increase, the filamentary discharge seems to transfer into a diffuse one by naked eyes. But the discharge current behaves more pulses not one in glow discharge.

This paper reports on magnetic properties of bulk polycrystalline samples of ln2O3 doped with a wide range of TM ions. Phase purity of the samples was analyzed by means of X-ray diffraction and conductivity was also measured using a four-probe technique. From magnetization-temperature curves (M-T curves), it was shown that Cr doped samples was found to be paramagnetic throughout the whole temperature range while Fe-V co-doped sample exhibited a quite high background, suggesting the presence of ferromagnetic species. On the other hand, Mn doped sample has a ferromagnetic transition temperature at ~46K, and Ni doped sample is clearly ferromagnetic at room temperature, while Fe doped sample is found to be paramagnetic.

Unintentionally doped AlGaN/AlN/GaN high electron mobility transistor (HEMT) structures with compositionally step-graded AlGaN barrier layer were grown on sapphire substrates by metalorganic chemical vapor deposition (MOCVD). The HEMT structure exhibited typical two-dimensional electron gas (2DEG) mobility of 1600cm2/Vs at room temperature and 6412cm2/Vs at 79K with almost equal 2DEG concentration of 1.0times1013/cm2. The 50mm HEMT wafer exhibited an average sheet resistance of 318.0Omega/square, with a good resistance uniformity of 0.89%. Atomic force microscopy (AFM) measurements revealed a smooth AlGaN surface with root-mean-square roughness (RMS) of 0.199nm and 0.295nm for scan area of 2mumtimes2mum and 5mumtimes5mum, respectively. A combined using of compositionally step-graded AlGaN barrier structure and AlN interlayer results in the high electrical performance and smooth surface of this heterostructure

In this work, we report our studies on the structures, transport, and magnetic properties in the rare earth element doped two dimensional layer structured perovskite compounds Sr2-xRExCoO4 (RE= rare earth element). Structure refinement has revealed that these compounds crystallize in the K2NiF4-type structure with space group I4/mmm. For Pr doped samples, the lattice parameter c decreases with Pr doping levels. The Curie temperatures are found to decrease gradually from 200 K for x=0.5 to less than 100 K for x>1 for the various dopants Pr, Eu, Nd, and Sm. The resistivities were found to increase with doping levels. A large coercive field of about 1 T was found for Pr and Sm with x=0.75. A negative field hysteresis magnetoresistance in close correlation to the coercive field has been observed for Sr1.5Sm0.5CoO4, which can be explained by grain boundary spin dependent tunneling effects.

Coercivity of exchange-coupled hard/soft/hard nanolayers has been investigated within a micromagnetic model. As the soft layer thickness increases, the coercivity decreases and the dominant coercivity mechanism changes from nucleation to pinning. The influences of microstructures, i.e., easy axes and interface quality, have been discussed.

InAlGaN quaternary alloys were grown on nitrided sapphire, AlN nuclear layer and GaN layer by radio-frequency plasma-excited molecular beam epitaxy (RF-MBE). Reflection high-energy electron diffraction (RHEED), Rutherford back-scatter spectrometry (RBS), atomic-force microscopy (AFM) and high resolution X-ray diffraction (HRXRD) were used to characterize the InAlGaN alloys. Different buffer layers strongly affect the growth mode, indium content and depth distribution, surface morphology and crystal quality of InAlGaN quaternary alloys. The experimental results show that the InAlGaN film grown on GaN layer can acquire layer-by-layer growth mode, uniform indium deep distribution, flat surface with RMS of InAlGaN to be 2.2nm and smallest full-width at half-maximum (FWHM) of InAlGaN (0002) peak to be 4.8 arcmin

Summary form only given. Quartz tuning forks, driven to electromechanical resonance by piezo elements, are widely used as distance sensing elements in scanning near-field optical microscopy (SNOM). Distance controls, based on tuning forks without piezo elements, have been successfully employed in atomic force microscopes. We extended this technique to the case of low temperature SNOM. In our experimental set-up, the fibre is fixed at two points.

The structures, ferromagnetism, spin glass and spin states of Co and Mn in a polycrystalline ceramic samples of GdCo/sub 1-x/Mn/sub x/O/sub 3/ (x = 0.2, 0.3, 0.4, 0.5) are presented. X-ray diffraction show that all the samples are single phase and crystallize as orthorhombic structures and that the lattice parameters gradually increase with x. Spin glass state and two peak features (corresponding to first order ferromagnetic and second order transition) in dc and ac susceptibility are observed. Curie-Wise fitting on the inverse susceptibility-temperature plots indicates that the valences of Co or Mn changed from 2+ or 4+ to 3+ when Co amount increases. Possible spin state transformation of Co and Mn is also suggested.

The growing attention on power quality related problems has prompted the need to share power quality information between measurement equipments, and analysis and simulation tools. However, existing equipment designs are still very much proprietary and are rarely catered for the exchange of information between one another. Contrasting data format and communication protocol has often obstructed the sharing of information. This paper describes an attempt to exploit a well-known Internet technology, the XML, to facilitate the sharing of power quality information. Based on the well-known power quality data interchange format (PQDIF), a new power quality XML markup language is proposed. The definition of the of markup language is described in details with illustrative examples language is described in details with illustrative examples of several XML-based power quality documents. Two possible data-exchanging scenarios, including one over the Internet, are also demonstrated in the paper.

Power quality has been a pressing issue over the last decade and there are many attempts to determine the current level of power quality in existing power system networks. There is a growing list of monitoring and measurement schemes being initiated or contemplated around the globe. Some schemes make use of existing infrastructure such as digital fault recorders while others are wholly new systems. The majority of them have taken into consideration the advancements in Information Technology (IT), particularly the popularity of using the Internet to disseminate the processed results to the interested parties. This paper examines other advanced features available in the IT arena and demonstrates the feasibility and benefits of using them in other aspects of power quality monitoring. It illustrates the benefits to both the users and the developers of the system. It shows that advanced IT can be employed to simplify the acquisition of the voltage and current signals as well as to manage the collection, storage and distribution of the processed information. The proposed design can be extended to include intelligent analyses such as disturbance characterization and state estimations.

Substrate current model based on the post-processing 1-D hydrodynamic model attached to drift-diffusion simulators has proven to be efficient and accurate for predicting substrate current for contemporary submicron MOSFETs. However, as devices shrink into the deep submicron regime, the self-consistent 2-D HD model will be increasingly needed to predict not only the substrate current but also to accurately determine the location of hot-carrier generation in evaluating the reliability of competing device designs. >

A FM modulated frequency-locked laser (FLL) pair for optical communication is reported. The subcarrier (locked) frequencies can be easily tuned from 3 to 11 GHz. Utilizing the FLL modulator within its bandwidth limits, any broadband analog signal, such as TV VHF bands (lower and upper band plus FM radio), CATV channels, and even TV UHF band, can be readily FM modulated on to these very-high-frequency microwave subcarriers. A simple FM demodulation can then be used to recover the original signals. This is directly compatible with standard TV or cable-ready receivers. Digital data in Manchester code format can also be transmitted. The operation of the FLL and the transmission and reception of five TV channels (channels 2 to 6 or substituting one with channel 13) on a 11-GHz subcarrier were experimentally demonstrated. The FLL is based on the concept of double beam modulation (DBM), which can be readily utilized for subcarrier modulated (SCM) multichannel broadband communications. >

The internal properness and stability of singular decentralized control systems are discussed, and a sufficient and necessary condition that singular systems can be properly stabilized by normal decentralized compensators is presented, i.e. there do not exist any unstable finite fixed modes or impulsive fixed modes in the singular system.