A polyfluoroalkyl imidazolium ionic liquid as iodide ion source in dye sensitized solar cells

We report on the use of a fluorinated imidazolium ionic liquid as a source of iodide ions in solvent-based electrolytes for DSSCs. Efficient dye regeneration and fast charge transport in the fluorinated electrolyte result in an overall improvement of the device performances compared to conventional hydrogenated ionic liquids.     

Lossless video compression based on backward adaptive pixel-based fast motion estimation

This paper presents a lossless video compression system based on a novel Backward Adaptive pixel-based fast Predictive Motion Estimation (BAPME). Unlike the widely used block-matching motion estimation techniques, this scheme predicts the motion on a pixel-by-pixel basis by comparing a group of past observed pixels between two adjacent frames, eliminating the need of transmitting side information. Combined with prediction and a fast search technique, the proposed algorithm achieves better entropy results and significant reduction in computation than pixel-based full search for a set of standard test sequences. Experimental results also show that BAPME outperforms block-based full search in terms of speed and entropy. We also provide the sub-pixel version of BAPME as well as integrate BAPME in a complete lossless video compression system. The experimental results are superior to the selected state-of-the-art schemes.     

Wireless data: Systems,standards, services

Wireless data products and services being proposed today include exotic mixes of services and technologies: packet transport over cellular circuits, facsimile service over Cellular Digital Packet Data (CDPD), voice and video over wireless LANs, and everything in between. Data networking terms that seem to have a clear meaning-data-link, network and transport layers; circuit-mode and datagram; connection-less and connection-oriented-in fact have meaning only in context. Thus TCP, a reliable packet transport protocol, is being used in CDMA circuit-mode data to provide a reliable data-link layer for the error-prone wireless link. IP datagrams will be transported over cellular links using dedicated channels with call establishment, possibly per packet. Market demands for timely solutions, competition between alternative technologies and the plethora of alternative fora for standards development are driving wireless data into fragmented directions. The primary constraints come from the limited spectrum, the need for security in the presence of mobility and the size and weight of mobile terminals and devices. Often the optimization for the latter constraints is sacrificed at the altar of the former drivers. Based upon our experience and work with standards and systems we attempt to put wircless data into perspective. We compare and contrast major services and products and identify the choices that were made and why.We acknowledge the contributions of our colleagues at AT&T Bell Laboratories: Ken Budka, Mooi Choo Chuah, Bharat Doshi, Subra Dravida, Richard Ejzak and On-Ching Yue.     

Teaching communication skills to hearing-impaired children

The Mehida multimedia system offers hearing-impaired children an easy and appealing way to learn how to communicate with their hearing and deaf peers. Mehida helps them acquire various communication skills simultaneously: sign language, speech, fingerspelling, lip reading, reading, and writing. Didactic activities and games teach the different means of communication. A character shaped like a pear assists and guides the children, explaining each activity and encouraging the children to identify with it throughout the process     

Propagation Path Loss and Materials Insertion Loss in Indoor Environment at WiMAX Band of 3.3 to 3.6?GHz

The purpose of this study is to characterize the indoor channel for IEEE 802.16 (WiMAX) at 3.3?C3.6?GHz frequency. This work presents a channel model based on measurements conducted in commonly found scenarios in buildings. These scenarios include closed corridor, wide corridor and semi open corridor. Path loss equations are determined using log-distance path loss model and a Rayleigh multipath induced fading, Normal multipath induced fading or a combination of both. A numerical analysis of measurements in each scenario was conducted and the study determined equations that describe path loss for each scenario. Propagation loss is given for 300?MHz bandwidth. This work also represents the insertion loss of different materials and the obstruction loss due the existence of human beings between the transmitting antenna and the receiving one.     

Analysis of Frequency Selective Surfaces at Millimeter Wave Band Using the Hertz Vector Potential Method

In this work, the Hertz vector potential method was used to obtain the dyadic Green’s function components for frequency selective surfaces (FSS) on an anisotropic layer. The considered structures are composed by periodic arrays of conducting crossed dipole and rectangular patch elements. Results of reflected power were obtained by using the moment method. Curves for the reflected power versus frequency are presented as function of the structural parameters, assuming x, y, and z orientation for the optical axis in the anisotropic substrate.     

在数字基带处理器上代码的最佳放置

在手机等嵌入式系统中,除了处理器执行时间外,最重要的资源就是设备总线和存储器接口。本文将介绍一种在使用指令高速缓存时其带宽消耗的基础上,统计分析高速缓存所采用的方法。这种方法是传统基于指令周期的分析方法的补充,并且也为在外部存储接口受限制的设备中优化应用程序提供了一种手段。在外部接口受限制的设备中优化那些使用高速缓存的应用程序的读取带宽,对提升指令周期性能有着良好效果。作为例子,     

Performance evaluation of nonsynchronized initial random access for mobile broadband systems

In this paper, a comparative analysis of the performance of the nonsynchronized initial random access channel in Mobile WiMAX and E-UTRA systems under different conditions (fast fading, multiuser interference) is carried out. The analysis is focused on the correlation properties of the code sequences used in each case. We evaluate their ability to provide low values for false alarm and erroneous detection probabilities (detecting a sequence that has not been transmitted) at the same time as guaranteeing low nondetection probabilities of the effectively transmitted sequences. Results show the promising performance of the E-UTRA scheme, even in high mobility scenarios, where the Doppler effect requires additional considerations to guarantee the correct system operation.     

Conductive Anodic Filament Formation Part II: Electrochemical Reactions Leading to CAF

Conductive anodic filament (CAF) formation has been studied for a number of years, but the mechanism of its formation has not previously been defined. In 2002, Ready identified CAF as atacamite, Cu₂(OH)₃Cl. Electrochemical studies have shown that both CuCl and CuCl ₂ ^? participate in the formation of Cu₂(OH)₃Cl, with the predominating species being CuCl. This paper proposes a mechanism for CAF formation based on x-ray photoelectron spectroscopy. The data show that CuCl is the precursor to the formation of Cu₂(OH)₃Cl in the presence of oxygen and water. Earlier, Meeker and Lu Valle had proposed that CAF failure is best represented by two competing reactions: the formation of a copper chloride corrosion compound (now identified as Cu₂(OH)₃Cl) and the formation of innocuous trapped chlorine compounds. Since no evidence of any trapped chloride compounds has been found, we propose that the formation of CAF is best represented by a single nonreversible reaction.