Improvement of the efficiency droop of GaN-LEDs using an AlGaN/GaN superlattice insertion layer

With an n-AlGaN(4 nm)/GaN(4 nm) superlattice(SL) inserted between an n-GaN and an InGaN/GaN multiquantum well active layer,the efficiency droop of GaN-based LEDs has been improved.When the injection current is lower than 100 mA,the lumen efficiency of the LED with an n-AlGaN/GaN SL is relatively small compared to that without an n-AlGaN/GaN SL.However,as the injection current increases more than 100 mA,the lumen efficiency of the LED with an n-AlGaN/GaN SL surpasses that of an LED without an n-AlGaN/GaN SL. The wall plug efficiency of an LED has the same trend as lumen efficiency.The improvement of the efficiency droop of LEDs with n-AlGaN/GaN SLs can be attributed to a decrease in electron leakage due to the enhanced current spreading ability and electron blocking effect at high current densities.The reverse current of LEDs at -5 V reverse voltage decreases from 0.2568029 to 0.0070543μA,and the electro-static discharge(ESD) pass yield of an LED at human body mode(HBM)-ESD impulses of 2000 V increases from 60%to 90%.     

Analysis of magnetic stimulation of a concentric axon in a nervebundle

The authors present an analysis of magnetic stimulation of an axon located at the center of a nerve bundle. A three-dimensional axisymmetric volume conductor model is used to determine the transmembrane potential response along an axon due to induced electric fields produced by a toroidal coil. The authors evaluate four such models of an axon located in: (1) an isotropic nerve bundle with no perineurium, (2) an anisotropic nerve bundle without a perineurium, (3) an isotropic nerve bundle surrounded by a perineurium, and (4) an anisotropic nerve bundle surrounded by a perineurium. The transmembrane polarization computed along an axon for the above four models is compared to that for an axon located in an infinite homogenous medium. These calculations indicate that a nerve bundle with no sheath has little effect on the transmembrane potential. However, the presence of a perineurium around the nerve bundle and anisotropy in the bundle significantly affects the shape of the transmembrane response. Therefore, during magnetic stimulation, nerve bundle anisotropy and the presence of perineurium must be taken into account for calculation of stimulus intensities for threshold excitation     

Enterprise traffic with a differentiated service mechanism

As an enterprise grows, its network bandwidth requirement also increases dramatically. Network performance of an enterprise will impact its operational performance. How do we efficiently manage an enterprise network's resources in an E‐business era? This research proposes a differentiated service mechanism to manage traffic flows in an enterprise. This mechanism would enhance the performance of an enterprise network and help an enterprise efficiently transmits important information. With a high‐performance enterprise network, the enterprise can then operate more efficiently and improves its competitive capability. Copyright © 2001 John Wiley & Sons, Ltd.     

An algorithm to solve integer programming problems: An efficient tool for reliability design

In many reliability design problems, the decision variables can only have integer values. The redundancy allocation is an example of one such problem; others include spare parts allocation, or repairmen allocation, which necessitate an integer programming formulation. In other words, integer programming plays an important role in system reliability optimization. In this paper, an algorithm is presented which provides an exact, simple and economical solution to any general class of integer programming problems and thereby offers reliability designers an efficient tool for system design. The algorithm can be used effectively to solve a wide variety of reliability design problems. The scope of use of this algorithm is also indicated and the procedure is illustrated by an example.     

Staying Ahead of the Digital Tsunami: The Contributions of an Organizational Communication Approach to Journalism in the Information Age

This essay addresses the challenges facing journalism in the information age by advocating for the study of journalism from an organizational communication perspective. The communication field has maintained an illogical divide between journalism and organizational communication scholarship. First, I present an overview of subdisciplinary identities. Second, I argue for an organizational communication approach to the study of journalism and refer to an empirical study as an exemplar of this approach. Finally, I present ideas for future research regarding the study of journalism and these subdisciplines. This approach is applicable to settings like newspapers, television news, and other media organizations. Analyzing journalism from an organizational communication perspective can connect academic subdisciplines and aid practitioners in understanding a rapidly evolving media landscape.     

Resolution and contrast enhancement in optical sub-traction microscopy with annular aperture

A method for improving lateral resolution and reducing imaging distortion of optical subtraction microscopy is proposed. First, an azimuthally polarized (AP) light is modulated by an annular aperture. Then, an image with higher lateral resolu-tion is obtained by subtracting an image obtained by an annular AP beam from an image obtained by a radially polarized beam. The simulation results demonstrate that compared with the case without the annular aperture, negative side-lobes in the effective point spread function are effectively suppressed, and the imaging quality of subtraction microscopy is obvi-ously enhanced.     

An equivalence theory between elliptical and circular arrays

An equivalence relation of a family of arrays defined under a linear transformation is established. By means of this theorem, the far field of an elliptical array can be obtained from that of an equivalent circular array; the theorem can be similarly applied to two- and three-dimensional arrays. A uniformly excited cophasal elliptical array is considered as an example. For nonuniform excitation, the method of symmetrical components may be applied despite the absence of axial symmetry for elliptical arrays. This theory can also be applied to the case of continuous source distribution on an ellipse or in an elliptical aperture. In so doing, solutions can be obtained without use of the complicated wave functions pertaining to the original geometry. As an example, an optimum array in the sense of Dolph-Chebyshev is considered. Similarly, a Taylor distribution for an elliptical aperture can be achieved.     

Exterior Algebraic Processing for Remotely Sensed Multispectral and Multitemporal Images

This paper describes remotely sensed multispectral and multitemporal image processing from an algebraic point of view. Especially, image analysis by means of an inner product, an exterior product, and an inner product between two exterior products are presented.     

光接入网：第三讲 光配线网

本讲首先绍光配线网的组成，然后重点讲述了ＯＤＮ的４种典型结构，接下来讲述ＯＤＮ模型，重点是光通道损耗模型和计算方法，最后简要介绍了ＯＤＮ的反射及其要求。     

A Numerical Calculation of the Capacitance for the Rectangular Coaxial Line with Offset Inner Conductor Having an Anisotropic Dielectric

The capacitances of the rectangular coaxial lines with an offset zero-thickness inner conductor having a sapphire dielectric are presented by using an expanded charge simulation method, In order to apply the method to an anisotropic region, we propose an electric potential formula for a two-dimensional system consisting of a line charge and an infinite plate conductor which are arbitrarily situated in the region. The potential formula is anatyticafly derived by means of an affine transformation, a confomal mapping technique, and the method of images. The capacitance calculated using this method is in good agreement with those of other available methods.     

新一代的因特网--光因特网

光因特网是新一代的因特网，是网络发展的重要动向。本文从为什么会提出光因特网着手，介绍了什么是光因特网，其网络结构和帧结构，还分析了光因特网的好处。     

Propagation of EM pulses excited by an electric dipole in aconducting medium

Exact solutions are given for the transient electromagnetic (EM) fields excited by an electric dipole antenna with an impulsive current in a conducting medium. There exists an optimum waveform for the antenna current which can generate an EM pulse with a maximum intensity at a particular distance from the antenna. It is found that the EM fields of an EM pulse excited by an antenna in a conducting medium can be divided into two parts. The first part is an impulse wave which propagates with the speed of light (1/√(μϵ)) and decays exponentially. The second part builds up gradually and propagates slowly, and more importantly this part attenuates as an inverse power of distance which is a much slower rate than an exponential decay     

Monotone Span Program vs.Linear Code

Monotone span program(MSP) and Linear code(LC) are efficient tools to construct Linear secret sharing scheme (LSSS) for a given access structure.Since the size of an MSP or the length of an LC corresponds to the communicational complexity of an LSSS,one main motivation to study MSPs or LCs is the lower bound for their sizes or lengths.Therefore,it is one of the most important open problems how to efficiently construct an MSP or LC for a given access structure Γ with the smallest sizes or shortest length.Our contributions are:We extend TANG et al.'s result,showing that,for any given access structure Γ,there exists an MSP or an LC to realizeΓ if and only ifa system of quadratic equations has solutions;We utilize the relationship between LCs and MSPs to obtain the greatest lower bound on the row size and the column size of MSPs realizing a given Γ,as well as an upper bound on the column size of MSPs;We give an algorithm to construct an MSP with the smallest sizes.     

A Coded Modulation Scheme for Deep-Space Optical Communications

A coded modulation scheme for deep-space optical communications is studied, which is a serial concatenation of an outer low-density parity-check (LDPC) code, an interleaver, a bit-accumulator, and pulse-position modulation (PPM). It is referred as LDPC-APPM. It is decoded with an iterative demodulator-decoder using standard turbo-decoding techniques. Simulation results show that the LDPC-APPM with an outer LDPC code of medium code length suffers a loss of about 0.7 dB at a bit-error rate of relative to the serially concatenated PPM (SCPPM) of similar parameters, which consists of the serial concatenation of an outer convolutional code, an interleaver, a bit-accumulator, and PPM; however, it has better code rate flexibility especially for high rates and simpler implementation structure than SCPPM. Further, it can achieve better performance than the LDPC-PPM of the same rate and length, which consists of the serial concatenation of an LDPC code and PPM.     

A 2.4-GHz ISM-Band Sliding-IF Receiver With a 0.5-V Supply

We report an ultra-low-voltage RF receiver for applications in the 2.4 GHz band, designed in a 90 nm CMOS technology. The sliding-IF receiver prototype includes an LNA, an image-reject LC filter with single-ended to differential conversion, an RF mixer, an LC IF filter, a quadrature IF mixer, RF and IF LO buffers, and an I/Q baseband section with a VGA and a low-pass channel-select filter in each path, all integrated on-chip. It has a programmable overall gain of 30 dB, noise figure of 18 dB, out-of-channel IIP3 of -22 dBm. The 3.4 mm² chip consumes 8.5 mW from a 0.5 V supply.     

Designing interaction systems for distributed applications

In this article, we discuss the explicit design of interaction mechanisms for developing distributed applications. When interactions between system parts require an explicit design, the concept of an interaction system comes into play. We define criteria that designers can use to decide whether an interaction system requires an explicit design. We also show that designers can apply both middleware-centered and protocol-centered development approaches in designing an application-level interaction system.     

Ion/electron-beam parametric amplifiers

Recent experiments with positive-ion beams suggest that an ion?electron beam, consisting of an electron beam superimposed on an ion beam, such that the two beams have different drift velocities, is realisable. A five-frequency parametric amplifier using an ion?electron beam is proposed.     

Cryptanalysis of an identity‐based authenticated key exchange protocol

Authenticated key exchange protocols represent an important cryptographic mechanism that enables several parties to communicate securely over an open network. Elashry, Mu, and Susilo proposed an identity‐based authenticated key exchange (IBAKE) protocol where different parties establish secure communication by means of their public identities.The authors also introduced a new security notion for IBAKE protocols called resiliency, that is, if the secret shared key is compromised, the entities can generate another shared secret key without establishing a new session between them. They then claimed that their IBAKE protocol satisfies this security notion. We analyze the security of their protocol and prove that it has a major security flaw, which renders it insecure against an impersonation attack. We also disprove the resiliency property of their scheme by proposing an attack where an adversary can compute any shared secret key if just one secret bit is leaked.     

A Common Source Input Cross Coupled Quad CMOS Mixer*

A CMOS doubly balanced mixer circuit is implemented with a source follower input and a cross coupled mixing quad. The circuit employs an all N-channel configuration and is suitable for high frequency applications. As a down-converter with an RF input of 2.0 GHz and an IF output of 200 MHz, the mixer demonstrates 9 dB of conversion loss with a corresponding input referred third order intercept of 0 dBm. As an up-converter with an IF input frequency of 400 MHz and an RF output of 2.4 GHz, the mixer demonstrates 14 dB of conversion loss.     

Electrodynamic characteristics of a strip antenna in a magnetoplasma

The problem of the distribution of a current in an antenna that is an infinitesimally thin, perfectly conducting narrow strip is considered. The antenna is embedded in an anisotropic plasma medium, oriented perpendicularly to an external magnetic field, and excited by an external electromotive force. The problem is reduced to a system of singular integral equations. On the basis of these equations, expressions for the distribution of the current and the antenna impedance are derived and analyzed.