A Reliable Multicast Routing Protocol Based on Recovery Points and FEC in Mobile Ad-hoc Networks

Multicasting is an essential service for mobile ad-hoc networks. A major challenge for multicasting in mobile ad-hoc networks (MANETs) is the unstable forwarding path. This work presents a reliable multicasting protocol for mobile ad-hoc networks. A virtual backbone is used as a shared structure for multiple sessions. A lost packet recovery scheme is developed for reliable packet transmission, called the Recovery Point (RP) scheme. The RP scheme maintains the data packets received from the source for recovering lost packets for its downstream RPs. In addition, we combine the Forward Error Correction (FEC) technology with our RP scheme to enhance the reliability of our RP scheme. A mergence scheme for RP is also proposed to avoid excessive control overhead. Our RP and FEC based scheme can be used to improve the reliability and efficiency of the traditional non-acknowledged multicasting approach. Experiments were conducted to evaluate the proposed multicasting scheme. The results demonstrate that our scheme outperforms other schemes in terms of packet delivery ratio and multicast efficiency. Furthermore, the simulation results also demonstrate that our approach is stable in networks with high mobility.

Design and evaluation of inter‐bandwidth broker signaling

Bandwidth brokers (BBs) have been proposed for providing end‐to‐end quality of services (QoS) in differentiated services (Diffserv) networks. As a single entity in each domain, a BB aims at performing both intra‐ and inter‐domain resource management on behalf of its domain. There have been plenty of BB studies for intra‐domain resource management. However, how a BB can perform inter‐domain resource management in a scalable and deployable manner is still an open issue. In this work, we present the design, implementation and evaluation of an inter‐BB communication protocol that is used by each BB to communicate with its neighboring BBs for inter‐domain QoS resource management. The proposed model uses a destination‐based aggregation scheme in which reservations are aggregated as they merge through the destination region. The destination‐based aggregation improves inter‐domain state and signaling scalability. The protocol also performs traffic engineering to increase inter‐domain resource utilization. The implementation and simulation results verify the achievements of our model. Copyright © 2008 John Wiley & Sons, Ltd.     

Mucoadhesive Phenolic Pectin Hydrogels for Saliva Substitute and Oral Patch

Oral disease is one of the most common conditions worldwide, negatively affecting general health, reducing the quality of life, and often developing into systemic illness. However, the design of therapeutic agents for oral diseases is challenging due to various unique features of the oral cavity, including its wet and dynamic environment and curved shape. Herein, the development of highly biocompatible mucoadhesive functional hydrogels for oral applications is reported, generated by introducing bio-inspired phenolic moieties into a pectin polymer. Pyrogallol-functionalized pectin (Pec-PG) can be crosslinked in situ via autoxidation without chemical agents and readily fabricated as various formulations. Sprayable Pec-PG hydrogel exhibits strong mucoadhesion and outstanding hydration ability ex vivo and in vivo, thus displaying significant potential as a novel saliva substitute for dry mouth. The authors further show that topical application of mucoadhesive Pec-PG patches pre-loaded with corticosteroid significantly promotes the repair of diabetic oral ulcer tissue via prolonged drug release, free radical scavenging, and physical barrier effects. Moreover, similar applications for oral ulcer treatment using a pectin hydrogel modified with catechol (Pec-CA), another phenolic moiety are demonstrated. Together, these findings suggest that mucoadhesive phenolic pectin derivatives can provide highly biocompatible, convenient, and effective hydrogel platforms for treating oral diseases.     

InxGa1−xAs (x=0.25–0.35) grown at low temperature

In_xGa_1−xAs (x=0.25–0.35) grown at low temperature on GaAs by molecular beam epitaxy is characterized by Hall effect, transmission electron microscopy, and ultrafast optical testing. As with low temperature (LT) GaAs, the resistivity is generally higher after a brief anneal at 600°C. High-resolution transmission electron microscopy shows all the as-grown epilayers to be heavily dislocated due to the large lattice mismatch (2–3%). When the layers are annealed, in addition to the dislocations, precipitates are also generally observed. As with LT-GaAs, the lifetime shortens as growth temperature is reduced through the range 300–120°C; also, the lifetime in LT-In_xGa_1−xAs is generally shorter in as-grown samples relative to annealed samples. Metal-semiconductor-metal photodetectors fabricated on the material exhibit response times of 1–2 picoseconds, comparable to results reported on GaAs grown at low temperature, and the fastest ever reported in the wavelength range of 1.0–1.3 μm.     

A lattice realization for 2-D separable-denominator digital filters

New properties useful in connection with 1-D and 2-D lattice realizations are developed. These properties enable one to represent given, complicated 2-D separable-denominator digital filters in terms of simpler, more elemental building blocks which consist of two 1-D lattice realizations having dynamics in different directions and connected in a cascade form. The matrix-relationship between a 2-D discrete Schwarz form and a controller-observer canonical form is also derived. A notable property of the proposed 2-D lattice realization is that the impulse response energy of a 2-D separable-denominator digital filter can be readily obtained from the reflection coefficients and input/output tapped coefficients of the realization.This work was supported by the National Science Council of the Republic of China under Grant NSC79-0402-E0006-02, the US Army Research Office under Grant DAAL-03-91-G0106, and the NASA-Johnson Space Center under Grant NAG-9-380.     

Consecutive-2-of-n:F systems with node and link failures

It has always been assumed that nodes can fail but not links, although most examples given for the consecutive-k-out-of-n :F system show no reason for such an assumption. The system described not only allows links to fail, but allows both nodes and links to fail, with distinct probabilities. For the k=2 case, the authors set up recursive equations for system reliability, and give a closed-form solution. It is proved that for n large, the reliability is decreasing in n (with one exceptional case) and higher reliability should be provided to the nodes, and then to the longer links rather than to shorter links     

Superresolution frequency estimation by alternating notchperiodogram

A novel periodogram-based maximum-likelihood algorithm is proposed for a frequency estimation problem. It is called an alternating notch-periodogram algorithm (ANPA), since the original multidimensional maximum likelihood problem is decomposed into a sequence of much simpler one-dimensional problems of finding the peaks of notch periodograms. The ANPA achieves superresolution and a very low SNR threshold and can be computed and implemented in several efficient ways. First, with FFT and a concurrent Gram-Schmidt procedure using Schur's recursions, the notch periodogram can be computed without any costly eigendecomposition and matrix inversion. This approach can further lead to a mapping of the notch periodogram onto a VLSI architecture consisting mainly of a highly pipelined notch processor and two FFT processors. Second, without degrading the excellent performance of ANPA, the notch periodogram can be simplified and approximated to provide further computational reduction and implementational simplicity     

An a-Si:H/a-Si,Ge:H bulk barrier phototransistor with a-SiC:Hbarrier enhancement layer for high-gain IR optical detector

The design and fabrication of a high-gain amorphous silicon/amorphous silicon germanium (a-Si:H/a-Si,Ge:H) bulk barrier phototransistor for infrared light detection applications are reported. The a-Si,Ge:H material featured a lower energy gap and is suitable for the absorption of longer wave light, but it also leads to a low breakdown voltage and high dark current. An additional a-SiC:H thin-film layer was used at the collector/base interface in the conventional amorphous bulk barrier phototransistor to enhance the function of the bulk barrier and obtain high optical gain     

Scale and rotation invariant pattern recognition using complex-log mapping and augmented second order neural network

A scale and rotation invariant pattern recognition system using complex-log mapping (CLM) and an augmented second order neural network (SONN) is proposed. CLM is very useful for extracting the scale and rotation invariant features. The results are, however, given in a wrap-around translated form. This problem is solved with an augmented SONN. Experimental results show that the proposed system has improved recognition performance.<>     

Tunneling and thermal emission of electrons from a distribution ofdeep traps in SiO2 [nMOSFET]

Both field-induced, or tunneling, and thermal emission of electrons from deep traps in the gate oxides on n-channel LDD CMOS devices have been observed and characterized. Experimental results show that the deep trapping effects at room temperature are similar to the shallow-level trapping effects observed by others below room temperature. In this case, however, the time constants involved are very long. This model and physical mechanisms can explain the apparent saturation observed under AC stress conditions, and also the differences observed between AC use conditions and DC stress