QoS‐aware routing and power control algorithm for multimedia service over multi‐hop mobile ad hoc network

This paper presents a QoS (quality of service) aware routing and power control algorithm consuming low transmission power for multimedia service over mobile ad hoc network. Generally, multimedia services need stringent QoS over the network. However, it is not easy to guarantee the QoS over mobile ad hoc network since its network resources are very limited and time‐varying. Furthermore, only a limited amount of power is available at mobile nodes, which makes the problem more challenging. We propose an effective routing and power control algorithm for multimedia services that satisfies end‐to‐end delay constraint with low transmission power consumption. The proposed algorithm supports the required bandwidth by controlling each link channel quality over route in a tolerable range. In addition, a simple but effective route maintenance mechanism is implemented to avoid link failures that may significantly degrade streaming video quality. Finally, performance comparison with existing algorithms is presented in respect to traditional routing performance metrics, and an achievable video quality comparison is provided to demonstrate the superiority of the proposed algorithm for multimedia services over mobile ad hoc network. Copyright © 2010 John Wiley & Sons, Ltd.     

Versatile,Benzimidazole/Amine‐Based Ambipolar Compounds for Electroluminescent Applications: Single‐Layer,Blue, Fluorescent OLEDs,Hosts for Single‐Layer,Phosphorescent OLEDs

A series of compounds containing arylamine and 1,2‐diphenyl‐1H‐benz[d]imidazole moieties are developed as ambipolar, blue‐emitting materials with tunable blue‐emitting wavelengths, tunable ambipolar carrier‐transport properties and tunable triplet energy gaps. These compounds possess several novel properties: (1) they emit in the blue region with high quantum yields; (2) they have high morphological stability and thermal stability; (3) they are capable of ambipolar carrier transport; (4) they possess tunable triplet energy gaps, suitable as hosts for yellow‐orange to green phosphors. The electron and hole mobilities of these compounds lie in the range of 0.68–144 × 10^?6 and 0.34–147 × 10^?6 cm² V^?1 s^?1, respectively. High‐performance, single‐layer, blue‐emitting, fluorescent organic light‐emitting diodes (OLEDs) are achieved with these ambipolar materials. High‐performance, single‐layer, phosphorescent OLEDs with yellow‐orange to green emission are also been demonstrated using these ambipolar materials, which have different triplet energy gaps as the host for yellow‐orange‐emitting to green‐emitting iridium complexes. When these ambipolar, blue‐emitting materials are lightly doped with a yellow‐orange‐emitting iridium complex, white organic light‐emitting diodes (WOLEDs) can be achieved, as well by the use of the incomplete energy transfer between the host and the dopant.     

Complexity reduction of signal detection by exploiting correlation characteristics of spreading sequences

In this paper, we propose an approach to reduce the multi‐user detection (MUD) complexity based on user grouping and signal replica classification by exploiting the correlation characteristics of spreading sequences in multipath fading channels. The spreading sequences are constructed from inter‐group complementary codes with a sparse and regular correlation matrix and inherit its attractive auto/cross‐correlation properties. Users are first partitioned into independent user groups according to whether or not there is interference among them, and then the replicas of user signals from the same user group are further classified into independent replica classes. The MUD is carried out within each low‐dimensional user group or replica class, respectively, reducing the MUD complexity substantially. This approach can be applied to most of the existing MUD algorithms for complexity reduction, and in this paper optimal MUD and multi‐stage MUD are exemplified. The analytical and simulated results demonstrate that this approach can reduce the MUD complexity significantly under any load conditions without performance loss. Copyright © 2009 John Wiley & Sons, Ltd.     

Delay constrained uplink scheduling policy for rtPS/ertPS service in IEEE 802.16e BWA systems

WiMAX is a promising broadband wireless networking technology and is expected to take the place of broadband access solutions such as DSL and cable. Owing to its superior support in mobility, it is expected to provide integrated voice and data service to realize broadband mobile computing. In order to reach better quality‐of‐service (QoS) requirements for real‐time applications, the IEEE 802.16e standard defines five different services among traffic categories with different multimedia requirements. However, the problem of choosing the right set of medium access control parameters and packet scheduling policy to provide strict QoS guaranteed in IEEE 802.16e Broadband Wireless Access (BWA) systems remains unsolved and left as an open issue. In this paper, we propose a novel polling‐based uplink packet scheduling policy for real‐time Polling Service and extended real‐time Polling Service (rtPS/ertPS) traffic to support real‐time applications, with strict delay requirements, such as variable bit rate (VBR) traffic in IEEE 802.16e BWA systems. The proposed transmit‐permission policy can derive sufficient conditions such that all the rtPS/ertPS sources satisfy their time constraints to provide deterministic QoS guarantees. In addition to theoretical analysis, simulations are conducted to evaluate the performance of the proposed scheme. As it turns out, our design provides a good quality performance in the IEEE 802.16e BWA systems. Copyright © 2008 John Wiley & Sons, Ltd.     

Temporal Anti‐aliasing of a Stereoscopic 3D Video

Frequency domain analysis is a fundamental procedure for understanding the characteristics of visual data. Several studies have been conducted with 2D videos, but analysis of stereoscopic 3D videos is rarely carried out. In this paper, we derive the Fourier transform of a simplified 3D video signal and analyze how a 3D video is influenced by disparity and motion in terms of temporal aliasing. It is already known that object motion affects temporal frequency characteristics of a time‐varying image sequence. In our analysis, we show that a 3D video is influenced not only by motion but also by disparity. Based on this conclusion, we present a temporal anti‐aliasing filter for a 3D video. Since the human process of depth perception mainly determines the quality of a reproduced 3D image, 2D image processing techniques are not directly applicable to 3D images. The analysis presented in this paper will be useful for reducing undesirable visual artifacts in 3D video as well as for assisting the development of relevant technologies.     

Performance of a mesoscale liquid fuel‐film combustion‐driven TPV power system

Combustion‐driven thermophotovoltaic (TPV) systems have obtained increasing attention in recent decades, but most studies have focused on developing narrowband photovoltaic cells and selective emitters. In terms of the heat source, conventional combustion configurations and light gaseous fuels are extensively utilized in macro‐ or meso‐scale TPV power systems to simplify thermal management and mechanical fabrication. As far as miniaturization is concerned, however, fuelling these systems with liquid hydrocarbons would provide inherent advantages of high energy density and low volatility. Liquid fuels also promise easy and safe fuel recharging for small‐scale power systems. In this paper, a central porous‐medium combustor was employed in a small scale TPV power system. The combustor incorporated an emitting chamber wall and a heat recuperator. The radiant efficiency and overall efficiency were compared using different liquid hydrocarbon fuels in the system. The electric output characteristics of the combustion driven TPV system have been investigated to demonstrate the feasibility of a GaSb cell‐based TPV power system and to provide design guidance for mesoscale liquid‐burning TPV systems. Copyright © 2008 John Wiley & Sons, Ltd.     

PbS and CdS Quantum Dot‐Sensitized Solid‐State Solar Cells: “Old Concepts,New Results”

Lead sulfide (PbS) and cadmium sulfide (CdS) quantum dots (QDs) are prepared over mesoporous TiO₂ films by a successive ionic layer adsorption and reaction (SILAR) process. These QDs are exploited as a sensitizer in solid‐state solar cells with 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene (spiro‐OMeTAD) as a hole conductor. High‐resolution transmission electron microscopy (TEM) images reveal that PbS QDs of around 3 nm in size are distributed homogeneously over the TiO₂ surface and are well separated from each other if prepared under common SILAR deposition conditions. The pore size of the TiO₂ films and the deposition medium are found to be very critical in determining the overall performance of the solid‐state QD cells. By incorporating promising inorganic QDs (PbS) and an organic hole conductor spiro‐OMeTAD into the solid‐state cells, it is possible to attain an efficiency of over 1% for PbS‐sensitized solid‐state cells after some optimizations. The optimized deposition cycle of the SILAR process for PbS QDs has also been confirmed by transient spectroscopic studies on the hole generation of spiro‐OMeTAD. In addition, it is established that the PbS QD layer plays a role in mediating the interfacial recombination between the spiro‐OMeTAD⁺ cation and the TiO₂ conduction band electron, and that the lifetime of these species can change by around 2 orders of magnitude by varying the number of SILAR cycles used. When a near infrared (NIR)‐absorbing zinc carboxyphthalocyanine dye (TT1) is added on top of the PbS‐sensitized electrode to obtain a panchromatic response, two signals from each component are observed, which results in an improved efficiency. In particular, when a CdS‐sensitized electrode is first prepared, and then co‐sensitized with a squarine dye (SQ1), the resulting color change is clearly an addition of each component and the overall efficiencies are also added in a more synergistic way than those in PbS/TT1‐modified cells because of favorable charge‐transfer energetics.     

Selective Determination of Dopamine on a Boron‐Doped Diamond Electrode Modified with Gold Nanoparticle/Polyelectrolyte‐coated Polystyrene Colloids

Negatively charged gold nanoparticles (AuNPs) and a polyelectrolyte (PE) have been assembled alternately on a polystyrene (PS) colloid by a layer‐by‐layer (LBL) self‐assembly technique to form three‐dimensional (Au/PAH)₄/(PSS/PAH)₄ multilayer‐coated PS spheres (Au/PE/PS multilayer spheres). The Au/PE/PS multilayer spheres have been used to modify a boron‐doped diamond (BDD) electrode. Cyclic voltammetry is utilized to investigate the properties of the modified electrode in a 1.0 M KCl solution that contains 5.0 × 10^?3 M K₃Fe(CN)₆, and the result shows a dramatically decreased redox activity compared with the bare BDD electrode. The electrochemical behaviors of dopamine (DA) and ascorbic acid (AA) on the bare and modified BDD electrode are studied. The cyclic voltammetric studies indicate that the negatively charged, three‐dimensional Au/PE/PS multilayer sphere‐modified electrodes show high electrocatalytic activity and promote the oxidation of DA, whereas they inhibit the electrochemical reaction of AA, and can effectively be used to determine DA in the presence of AA with good selectivity. The detection limit of DA is 0.8 × 10^?6 M in a linear range from 5 × 10^?6 to 100 × 10^?6 M in the presence of 1 × 10^?3 M AA.     

Temperature Responsive Solution Partition of Organic–Inorganic Hybrid Poly(N‐isopropylacrylamide)‐Coated Mesoporous Silica Nanospheres

A series of poly(N‐isopropylacrylamide)‐coated mesoporous silica nanoparticle materials (PNiPAm‐MSNs) has been synthesized by a surface‐initiated living radical polymerization with a reversible addition–fragmentation chain transfer (RAFT) reaction. The structure and the degree of polymerization of the PNiPAm‐MSNs has been characterized by a variety of techniques, including nitrogen sorption analysis, ²⁹Si and ¹³C solid‐state NMR spectroscopy, transmission electron microscopy (TEM), and powder X‐ray diffraction (XRD). The thermally induced changes of the surface properties of these polymer‐coated core–shell nanoparticles have been determined by examining their partition activities in a biphasic solution (water/toluene) at different temperatures.     

Efficient TiO2 Photocatalysts from Surface Hybridization of TiO2 Particles with Graphite‐like Carbon

Surface hybridization of TiO₂ with graphite‐like carbon layers of a few molecular layers thickness yields efficient photocatalysts. Photoelectrochemical measurements confirm an electronic interaction between TiO₂ and the graphite‐like carbon. A TiO₂ photocatalyst with a carbon shell of three molecular layers thickness (～1 nm) shows the highest photocatalytic activity which is about two times higher than that of Degussa P25 TiO₂ under UV light irradiation. The mechanism of the enhanced photocatalytic activity under UV irradiation is based on the high migration efficiency of photoinduced electrons at the graphite‐like carbon/TiO₂ interface, which is due to the electronic interaction between both materials. In addition, a high activity under visible light irradiation is observed after graphite‐like carbon hybridization. TiO₂'s response is extended into the visible range of the solar spectrum due to the electronic coupling of π states of the graphite‐like carbon and conduction band states of TiO₂.