OGHAM: On-demand global hosts for mobile ad-hoc multicast services

Recent advances in pervasive computing and wireless technologies have enabled novel multicast services anywhere, anytime, such as mobile auctions, advertisement, and e-coupons. Routing/multicast protocols in large-scale ad-hoc networks adopt two-tier infrastructures to accommodate the effectiveness of the flooding scheme and the efficiency of the tree-based scheme. In these protocols, hosts with a maximal number of neighbors are chosen as backbone hosts (BHs) to forward packets. Most likely, these BHs will be traffic concentrations or bottlenecks of the network and spend significant amount of time forwarding packets. In this paper, a distinct strategy is proposed for constructing a two-tier infrastructure in a large-scale ad-hoc network. Hosts with a minimal number of hops to the other hosts rather than those with a maximal number of neighbors will be adopted as BHs in order to obtain shorter multicast routes. The problem of determining BHs can be formulated with linear programming. BHs thus found have the advantages of shorter relay and less concentration. Besides, BHs are selected on-demand and can be globally reused for different multicast groups without flooding again. Simulation results show that the proposed protocol has shorter transmission latency, fewer control/data packets and higher receiving data packet ratios than other existing multicast protocols. Besides, the two-tier infrastructure constructed by the proposed protocol is more stable.     

Bandwidth-Satisfied Multicast Trees in MANETs

Previous quality-of-service (QoS) routing/multicasting protocols in mobile ad hoc networks determined bandwidth-satisfied routes for QoS applications. However, they suffer from two bandwidth-violation problems, namely, the hidden route problem (HRP) and the hidden multicast route problem (HMRP). HRP may arise when a new flow is permitted and only the bandwidth consumption of the hosts in the neighborhood of the route is computed. Similarly, HMRP may arise when multiple flows are permitted concurrently. Not considering the bandwidth consumption of two-hop neighbors is the reason that the two problems are introduced. In this paper, a novel algorithm that can avoid the two problems is proposed to construct bandwidth-satisfied multicast trees for QoS applications. Furthermore, it also aims at minimizing the number of forwarders so as to reduce bandwidth and power consumption. Simulation results show that the proposed algorithm can improve the network throughput.     

Efficient cross-layer protocol for bandwidth-satisfied multicast in multi-rate MANETs

Since the multi-rate enhancements have been implemented in 802.11 wireless networks, QoS-constrained multicast protocols for multimedia communication should be adapted to exploit them fully. This work proposes a multicast protocol for data rate selection and bandwidth-satisfied multicast tree determination with an efficient cross-layer design based on the integration of PHY and MAC layers into the network layer. To use bandwidth efficiently and increase network capacity (which is the number of multicast flows supported by the network), we aim to select the combination of data rates and a multicast tree whose total amount of bandwidth consumption to the network is minimal in order to maximize the network capacity. The performance of the proposed protocol is compared with two existing protocols. Simulation results indicate that the proposed protocol has the ability to admit more multicast flows.     

Quantification of relative gene dosage by single-base extension and high-performance liquid chromatography: application to the SMN1/SMN2 gene

One of the most commonly used techniques for genotyping of single-nucleotide polymorphism (SNP) is detection of single-base extensions (SBEs). We present a new, rapid, simple, and highly reliable method for accurate quantification of SNP variants in a single reaction. Our approach is based on SBE detection coupled with high-performance liquid chromatography (HPLC) quantification. To demonstrate the utility of our approach, we report data to determine the gene dosage for relative amounts of alleles in a homologous gene, allowing detection of mutation causing exon skipping in human SMN genes to determine the ratio between the copy numbers of the SMN1/SMN2 gene. We successfully determined the relative ratio of the SMN1 and SMN2 genes and showed assay characteristics using the SBE reaction coupled with HPLC. This assay approach readily scaled to high parallelization with multiplex SBE reactions in a single sample screened in one analysis. By screening for particular SNP genotypes, this assay can be used to determine the relative gene dosage that correlates highly with the patient's disease state. The next challenge is to apply this novel methodology in a clinical screening and quantification setting for special gene regions within highly homologous genes.     

Thermal stability and electric properties of Ba0.7Sr0.3TiO3 parallel plate capacitor with nano-Cr interlayer

A novel sandwich structure of Ba_0.7Sr_0.3TiO₃/Cr/Ba_0.7Sr_0.3TiO₃ (BST/Cr/BST) was sputtered onto Pt/Ti/SiO₂/Si substrate. With the insertion of a Cr layer, the leakage currents are decreased and the thermal stability of the specimens is enhanced. Temperature coefficient of capacitance (TCC) of specimens with BST(200 nm)/Cr(2 nm)/BST(200 nm) multifilms can achieve about 83% lower than those with BST (400 nm) monolayer. However, the dielectric constant of the BST(200 nm)/Cr(2 nm)/BST(200 nm) multifilms decreases to about 37% of that BST monolayer. The leakage current densities under an electric field of 125 kV/cm at 90 °C are 4 × 10^− 4 A/cm² and 9 × 10^− 1 A/cm² for BST (200 nm)/Cr (2 nm)/BST (200 nm) and monolayer BST (400 nm), respectively. X-ray diffraction results indicate the formation of a CrO₃ secondary phase after annealing at 700 °C or above in O₂ atmosphere. The root causes for the improvement of leakage currents and thermal stability with the insertion of nano-Cr interlayer are explored. The results show the insertion of Cr-nanolayer improves the electric properties for application in capacitors.     

Robust cyclic adaptive beamforming using a compensation method

This paper deals with the problem of robust adaptive array beamforming using signal cyclostationarity. The constrained cyclic adaptive beamforming (C-CAB) algorithm presented by Wu and Wong (1996) [6] has been shown to be effective in performing adaptive beamforming without requiring the direction vector or the waveform of the desired signal. However, this algorithm suffers from severe performance degradation even if there is a small mismatch in the cycle frequency of the desired signal. In this paper, we first evaluate the performance degradation of the C-CAB algorithm in the presence of cycle frequency error (CFE). A novel compensation method in conjunction with the subspace projection is then proposed to tackle the problem due to CFE. We reconstruct the required cyclic conjugate correlation matrix by using a compensation matrix to cope with the deterioration of its dominant singular value when CFE exists. Finally, several simulation examples are provided to show the effectiveness of the proposed algorithm.     

En route to white-light generation utilizing nanocomposites composed of ultrasmall CdSe nanodots and excited-state intramolecular proton transfer dyes

One single material that emits white light is of paramount interest for the development of white light-emitting diodes (WLEDs). Here we report a novel nanocomposite, in which a new type of excited-sate intramolecular proton transfer (ESIPT) molecule, namely 5-(1,2-dithiolan-3-yl)-N-(2-{[4-(3-hydroxy-4-oxo-4H-chromen-2-yl)phenyl](methyl)amino}ethyl)pentanamide (HF-N-LA), is anchored onto the surface of ultrasmall CdSe quantum dots through dithiol functionality. Authentic white light with a CIE coordinate of (0.33, 0.33) could then be generated by confluence of 440 nm emission from CdSe and 570 nm proton-transfer tautomer emission from HF-N-LA. Moreover, linear color tunability could be achieved simply by altering relative amount of the two species, i.e., number of HF-N-LA onto CdSe, in one single nanocomposite, thus opening an innovative route toward applying nanocrystals in the field of WLEDs.     

A reactive modifier that enhances the thermal mechanical properties of epoxy resin through the formation of multiple hydrogen-bonded network

In this study, we synthesized a reactive modifier [DOPO-tris(azetidine-2,4-dione)], terminated with three azetidine-2,4-dione functional groups, from [(9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-yl)tris(4-aminophenyl)methane; DOPO-triamine] and [4-isocyanato-4′-(3,3-dimethyl-2,4-dioxo-acetidino)diphenylmethane; IDD]. We embedded this reactive modifier, which contains multiple hydrogen bond donor and acceptor units, into epoxy resins to promote intermolecular interactions and to tailor its flexibility through the formation of unique pseudo-crosslinked polymer networks. The resulted epoxy resins were found to exhibit glass transition temperature as high as 187 °C and excellent flame retardancy with limited oxygen index (LOI) values around 38. Meanwhile, the dynamic mechanical analysis (DMA) of epoxy systems increases from 0.67 to 2.13 GPa for storage modulus and 0.73–1.67 GPa for loss modulus at 100 °C. Incorporation of reactive modifier into epoxy networks with noncovalent interactions via thermosetting blend was demonstrated to be an effective way to enhance the thermal and physical properties simultaneously.     

Concurrent analysis of machining sequences and fixturing set-ups for minimizing set-up changes for machining mill-turn parts

In a typical machining process for producing a mill-turn part, milling operations and turning operations are required. If both milling machines and turning machines are utilized, the part may need to be moved between the two types of machines. In addition, the fixturing set-ups may need to be changed when different portions of the part are machined. In this research, a concurrent analysis model for analysing machining sequences and fixturing set-ups is presented. The purpose is to determine a good machining sequence by evaluating the machine changes and the fixturing set-up changes. A feature-based fixturing analysis method is developed for calculating the fixturing parameters for machining prismatic features and rotational features of a mill-turned part. A branch-and-bound method is developed to analyse the feasible machining sequences to find the best sequence with the minimum number of machine changes and fixturing set-up changes. A software system is implemented and example parts are tested and discussed.     

Tree-based object tracking without mobility statistics in wireless sensor networks

Object tracking in wireless sensor networks is to track mobile objects by scattered sensors. These sensors are typically organized into a tree to deliver report messages upon detecting object’s move. Existing tree construction algorithms all require a mobility profile that characterizes the movement statistics of the target object. Mobility profiles are generally obtained based on historical running traces. The contribution of this work is twofold. We first show that the problem of finding an optimal message report tree that requires the least amount of report messages is NP-hard. We then propose analytic estimates of mobility profiles based on Markov-chain model. This profiling replaces an otherwise experimental process that generates and analyzes running traces. Simulation results show that the analytic profiling works well and can replace costly statistical profiling without noticeable performance degradation.