VLSI Implementation of Forward Error Control Technique for ATM Networks

In asynchronous transfer mode (ATM) networks, fixed length cells of 53 bytes are transmitted. A cell may be discarded during transmission due to buffer overflow or a detection of errors. Cell discarding seriously degrades transmission quality. The quality degradation can be reduced by employing efficient forward error control (FEC) to recover discarded cells. In this paper, we present the design and implementation of decoding equipment for FEC in ATM networks based on a single parity check (SPC) product code using very‐large‐scale integration (VLSI) technology. FEC allows the destination to reconstruct missing data cells by using redundant parity cells that the source adds to each block of data cells. The functionality of the design has been tested using the Model Sim 5.7cXE Simulation Package. The design has been implemented for a 5 ° 5 matrix of data cells in a Virtex‐E XCV 3200E FG1156 device. The simulation and synthesis results show that the decoding function can be completed in 81 clock cycles with an optimum clock of 56.8 MHz. A test bench was written to study the performance of the decoder, and the results are presented.     

How to trust a few among many

The presence of numerous and disparate information sources available to support decision-making calls for efficient methods of harnessing their potential. Information sources may be unreliable, and misleading reports can affect decisions. Existing trust and reputation mechanisms typically rely on reports from as many sources as possible to mitigate the influence of misleading reports on decisions. In the real world, however, it is often the case that querying information sources can be costly in terms of energy, bandwidth, delay overheads, and other constraints. We present a model of source selection and fusion in resource-constrained environments, where there is uncertainty regarding the trustworthiness of sources. We exploit diversity among sources to stratify them into homogeneous subgroups to both minimise redundant sampling and mitigate the effect of certain biases. Through controlled experiments, we demonstrate that a diversity-based approach is robust to biases introduced due to dependencies among source reports, performs significantly better than existing approaches when sampling budget is limited and equally as good with an unlimited budget.     

All-optical serial header processing based on two-pulse correlation

An all-optical serial header processor is demonstrated using a semiconductor laser amplifier in a loop mirror configuration (SLALOM). The operation of the header processor is discussed and it is experimentally demonstrated with a 10 Gbit/s Manchester encoded (information rate of 5 Gbit/s) packet stream. The operation of the header processor is based on the correlation function of the SLALOM. The header processor can be utilised in devising all-optical packet switches     

MP3播放器为微控制器应用带来新机遇

MP3播放器市场的快速发展为微控制器(MCU)应用带来了新的机遇。消费电子设备制造商越来越避免采用专用集成电路（ASIC），因此DSP/MCU混合器件这样成本更低的器件提供新机会。     

Selectivity of anion exchange chromatography and capillary gel electrophoresis for the analysis of phosphorothioate oligonucleotides

The complementary nature of anion exchange chromatography and capillary gel electrophoresis for oligonucleotide analysis is demonstrated by evaluating a comprehensive series of authentic deletion sequences and partial phosphodiester analogs of five phosphorothioate oligonucleotides of different base composition and sequence. While anion exchange HPLC is sensitive to differences in backbone length of phosphorothioate oligonucleotides, oligomers with length difference of one base unit are not resolved. Capillary gel electrophoresis, on the other hand, has excellent single-base resolution while being relatively insensitive to phosphate in the phosphorothioate backbone. The data definitively establish the necessity of employing both separation techniques for adequate characterization of lower order process-related impurities potentially found in synthetic phosphorothioate oligonucleotides.     

Reduction of sidelobe levels in multicarrier radar signals via the fusion of hill patterns and geometric progression

Multi-carrier waveforms have several advantages over single-carrier waveforms for radar communication. Employing multi-carrier complementary phase-coded (MCPC) waveforms in radar applications has recently attracted significant attention. MCPC radar signals take advantage of orthogonal frequency division multiplexing properties, and several authors have explored the use of MCPC signals and the difficulties associated with their implementation. The sidelobe level and peak-to-mean-envelope-power ratio (PMEPR) are the key issues that must be addressed to improve the performance of radar signals. We propose a scheme that applies pattern-based scaling and geometric progression methods to enhance sidelobe and PMEPR levels in MCPC radar signals. Numerical results demonstrate the improvement of sidelobe and PMEPR levels in the proposed scheme. Additionally, autocorrelations are obtained and analyzed by applying the proposed scheme in extensive simulation experiments.     

Numerical Investigation of PCM Based Heat Sinks with Embedded Metal Foam/Crossed Plate Fins

Three-dimensional numerical models for phase change material based heat sinks equipped with thermal conductivity enhancers like aluminum metal foam and crossed plate fins are validated with the experimental data found in literature. For the aluminum metal foam embedded in the heat sink filled with phase change material, the porosity and the pores per inch of the metal foam were varied and natural convection currents were studied. Maintaining the volume fraction of the phase change material as a constant, the thermal performance enhancement as a result of the introduction of thermal conductivity enhancer into the heat sinks is determined.     

Scalable Key Management Algorithms for Location-Based Services

Secure media broadcast over the Internet poses unique security challenges. One important problem for public broadcast location-based services (LBS) is to enforce access control on a large number of subscribers. In such a system, a user typically subscribes to an LBS for a time interval (a, b) and a spatial region (x_bi, y_bi, x_tr,y_tr) according to a 3-dimensional spatial-temporal authorization model. In this paper, we argue that current approaches to access control using key management protocols are not scalable. Our proposal, STauth, minimizes the number of keys that needs to be distributed and is thus scalable to a large number of subscribers and the dimensionality of the authorization model. We also demonstrate applications of our algorithm to quantified-temporal access control (using V and 3 quantifications) and partial-order tree-based authorization models. We describe two implementations of our key management protocols on two diverse platforms: a broadcast service operating on top of a publish/subscribe infrastructure and an extension to the Google Maps API to support quality (resolution)-based access control. We analytically and experimentally show the performance and scalability benefits of our approach over traditional key management approaches.     

A locally elliptic calculation procedure for three-dimensional flows and its application to a jet in a cross-flow

The paper describes a three-dimensional finite difference calculation procedure for problems characterised by a predominant flow direction except for a small but significant reverse-flow region. The procedure treats only the reverse-flow region as elliptic, the rest of the flow being treated as either parabolic or partially parabolic (i.e. elliptic only in pressure) as appropriate. The method is therefore more economical in computer time and particularly in storage than a fully three-dimensional elliptic method, but it is more general than the parabolic and partially parabolic methods which cannot handle flow reversals. The method is applied to a jet in a ducted cross-flow, and the results are in much better agreement with experiments than those obtained with parabolic or partially parabolic methods.