Fabrication and performance of parallel-addressed InGaN micro-LED arrays

High-performance, two-dimensional arrays of parallel-addressed InGaN blue micro-light-emitting diodes (LEDs) with individual element diameters of 8, 12, and 20 /spl mu/m, respectively, and overall dimensions 490 /spl times/490 /spl mu/m, have been fabricated. In order to overcome the difficulty of interconnecting multiple device elements with sufficient step-height coverage for contact metallization, a novel scheme involving the etching of sloped-sidewalls has been developed. The devices have current-voltage (I-V) characteristics approaching those of broad-area reference LEDs fabricated from the same wafer, and give comparable (3-mW) light output in the forward direction to the reference LEDs, despite much lower active area. The external efficiencies of the micro-LED arrays improve as the dimensions of the individual elements are scaled down. This is attributed to scattering at the etched sidewalls of in-plane propagating photons into the forward direction.     

Signal classification through multifractal analysis and complex domain neural networks

This paper describes a system capable of classifying stochastic self-affine nonstationary signals produced by nonlinear systems. The classification and the analysis of these signals are important because these are generated by many real-world processes. The first stage of the signal classification process entails the transformation of the signal into the multifractal dimension domain, through the computation of the variance fractal dimension trajectory (VFDT). Features can then be extracted from the VFDT using a Kohonen self-organizing feature map. The second stage involves the use of a complex domain neural network and a probabilistic neural network to determine the class of a signal based on these extracted features. The results of this paper show that these techniques can be successful in creating a classification system which can obtain correct classification rates of about 87% when performing classification of such signals without knowing the number of classes.     

Solving the trade-off between fairness and throughput: Token bucket and leaky bucket-based weighted fair queueing schedulers

In this article, we present two efficient weighted fair queueing (WFQ) scheduling algorithms leaned on the well-known token bucket and leaky bucket shaping/policing algorithms. The performance of the presented algorithms is compared to those of the state-of-the-art WFQ approximations such as weighted round robin (WRR) and the recently proposed bin sort fair queueing (BSFQ). Our simulation results show that the proposed algorithms provide a better fairness at a lower implementation complexity while simultaneously achieving a comparable network utilization.     

Elastomeric Fibrous Hybrid Scaffold Supports In Vitro and In Vivo Tissue Formation

Biomimetic materials with biomechanical properties resembling those of native tissues while providing an environment for cell growth and tissue formation, are vital for tissue engineering (TE). Mechanical anisotropy is an important property of native cardiovascular tissues and directly influences tissue function. This study reports fabrication of anisotropic cell‐seeded constructs while retaining control over the construct's architecture and distribution of cells. Newly synthesized poly‐4‐hydroxybutyrate (P4HB) is fabricated with a dry spinning technique to create anelastomeric fibrous scaffold that allows control of fiber diameter, porosity, and rate ofdegradation. To allow cell and tissue ingrowth, hybrid scaffolds with mesenchymalstem cells (MSCs) encapsulated in a photocrosslinkable hydrogel were developed. Culturing the cellularized scaffolds in a cyclic stretch/flexure bioreactor resulted in tissue formation and confirmed the scaffold's performance under mechanical stimulation. In vivo experiments showed that the hybrid scaffold is capable of withstanding physiological pressures when implanted as a patch in the pulmonary artery. Aligned tissue formation occurred on the scaffold luminal surface without macroscopic thrombus formation. This combination of a novel, anisotropic fibrous scaffold and a tunable native‐like hydrogel for cellular encapsulation promoted formation of 3D tissue and provides a biologically functional composite scaffold for soft‐tissue engineering applications.     

Reduction of peak-to-average power ratio in transform domain communication systems

Transform Domain Communication Systems (TDCS) are spectrum-scavenging systems which modulate data by a waveform whose magnitude is non-zero only in unused frequency bins, and whose phase is pseudo-random. This creates a noise-like waveform suitable for secure, low probability of intercept (LPI) communications, as well as spectrum-sharing applications. However, it also creates a high peak-to-average power ratio (PAPR). We investigate PAPR reduction in TDCS by modifying the projection onto complex sets approach for multicarrier systems. Simulations show that adequate PAPR reduction is achieved, transmitter-receiver waveform mismatches are not exacerbated by PAPR reduction, and the resulting waveform is still LPI.     

针对微控制器应用的MIPS32 M4K内核影子寄存器

RISC架构为微控制器领域带来了许多优势,例如与CISC架构相比,它对程序编译器更加友好,而且在硅面积方面也非常经济。     

利用FPGA快速开展新一轮设计

设计工程师面临的挑战 在今天的市场上,产品迅速上市的压力愈来愈大,但产品的使用寿命却不断缩短。产品设计稳定于12-18个月的周期不再存在,取而代之的是产品每6个月便会更新。缩短的使用寿命给OEM厂商带来更大的压力,需要更迅速及高效地把新设计推向市场。有研究指出,产品的推出若延迟4周,便会失去约14％的市场份额。     

Reversible Amorphous‐to‐Amorphous Transitions in Chalcogenide Films: Correlating Changes in Structure and Optical Properties

Structural transitions in materials are accompanied by appreciable and exploitable changes in physical‐chemical properties. Whereas reversible optically‐driven atomistic changes in crystal‐to‐amorphous transitions are generally known and exploited in applications, the nature of the corresponding polyamorphic transitions between two structurally distinct meta‐stable amorphous phases is an unexplored theme. Direct experimental evidence is reported for the nature of the atomistic changes during fully reversible amorphous‐to‐amorphous switching between two individual states in the non‐crystalline As₅₀Se₅₀ films prepared by pulsed‐laser deposition and consequent changes in optical properties. Combination of surface sensitive X‐ray photoelectron spectroscopy and spectroscopic ellipsometry show that the near‐bandgap energy illumination and annealing induce reversible switching in the material's structure by local bonding rearrangements. This is accompanied by switching in refractive index between two well‐defined states. Exploiting the pluralism of distinct structural states in a disordered solid can provide new insights into the data storage in emerging optical memory and photonic applications.     

Microwave cavity perturbation technique: Part I: Principles

This report reviews the analysis used to extract the complex conductivity of a compound from a microwave cavity perturbation measurement. We intend to present a generalized treatment valid for any spheroidally shaped sample of arbitrary conductivity which is placed at either the electric or magnetic field antinode of the cavity. To begin with, we establish the relationship between the measured parameters and the conductivity for a spherical sample. Next, we extend these results to the case of spheroids; and for the first time, we cover all different configurations that one can possibly use to study an arbitrary conducting sample inside a cavity: in particular, all possible orientations of the sample with respect to the applied field are solved.     

Multiresolution coding techniques for digital television: A review

Multiresolution decompositions for video coding are reviewed. Both nonrecursive and recursive coding schemes are considered. In nonrecursive schemes, it is shown that pyramid structures have certain advantages over subband or wavelet techniques, and a specific spatiotemporal pyramid coding of HDTV is discussed in some detail. It is shown that recursive, DPCM like schemes will incur a slight loss of optimality due to a restricted form of prediction if multiresolution decomposition with compatible decoding is required. Compatibility and transmission issues are also discussed. Multiresolution transmission for digital broadcast TV is introduced. This, when combined with multiresolution source coding, achieves spectrum efficiency, robustness and graceful degradation under channel impairments.Invited PaperWork supported in part by the National Science Foundation under grants ECD-88-11111, MIP-90-14189 and Bell Communications Research.Work supported by the National Science Foundation under grants ECD-88-11111. K.M. Uz is now with David Sarnoff Research Center in Princeton, NJ 08543.