Facile Preparation of PbTiO3 Nanodot Arrays: Combining Nanohybridization with Vapor Phase Reaction Sputtering

A facile route is presented for the fabrication of spherical PbTiO₃ (PTO) nanodot arrays on platinized silicon substrates using PbO vapor phase reaction sputtering on micellar monolayer films of polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) loaded with TiO₂ sol–gel precursor. Short exposure to PbO transforms the amorphous TiO₂ into polycrystalline PTO, while keeping the inherent size and periodicity of TiO₂ nanodots. HRTEM images show that the spherical PTO nanodots, with an average size and height of 63 nm and 40 nm, respectively, are fixed on the Pt supported by residual carbon. XPS narrow scan spectra of Ti 2p and O 1s strongly verify the evolution of chemical identity and the reduction of the Ti‐O binding energy from TiO₂ to PTO. The amplitude and phase images of piezoelectric force microscopy (PFM) confirm a multidomain structure attributed by the crystalline orientation of the PTO nanodots. Furthermore, the discrete PTO nanodots show remarkable switching properties due to the low strain field induced by the small lateral size, and the absence of domain pinning effects by grain boundary.     

Phase‐Transited Lysozyme as a Universal Route to Bioactive Hydroxyapatite Crystalline Film

A key factor for successful design of bioactive complex, organic–inorganic hybrid biomaterials is the facilitation and control of adhesion at interfaces, as many current synthetic biomaterials are inert, lacking interfacial bioactivity. In this regard, the development of a simple, unified way to biofunctionalize diverse organic and inorganic materials toward biomineralization remains a critical challenge. In this report, a universal biomimetic mineralization route that can be applied to virtually any type and morphology of scaffold materials is provided to induce nucleation and growth of hydroxyapatite (HAp) crystals based on phase‐transited lysozyme (PTL) coating. Surface‐anchored abundant functional groups in the PTL enrich the interface with strongly bonded calcium ions, facilitating the formation of HAp crystals in simulated body fluid with the morphology and alignment being similar to that observed in natural HAp in mineralized tissues. By the adhesion of amyloid contained in the PTL, such protein assembly could readily integrate HAp on ceramics, metals, semiconductors, and synthetic polymers irrespective of their size and morphology, with robust bonding stability and corresponding ultralow wear extent under normal bone pressure. This strategy successfully improves the in vivo osteoconductivity of Ti‐based implant, underpinning the expectation for such biomaterial in future biointerface and tissue engineering.     

Analytic, Simulation, and Empirical Evaluation of Delay/Fault-Tolerant Mobile Sensor Networks

The delay/fault-tolerant mobile sensor network (DFT-MSN) has been proposed for pervasive information gathering. DFT-MSN distinguishes itself from conventional sensor networks by several unique characteristics such as sensor mobility, loose connectivity, and delay/fault tolerability. This paper focuses on the performance evaluation of DFT-MSN. We first introduce a queuing model by using Jackson network theory. While the queuing model is based on a few simplification assumptions for analytic tractability, it provides insights into the queuing behavior of the mobile sensors in DFT-MSN. Extensive simulations are performed under realistic environment and assumptions. Our simulation results show that the dynamic DFT-MSN data delivery scheme achieves the highest message delivery ratio with acceptable delay and transmission overhead, compared with simple schemes such as flooding and direct transmission or other approaches in the literature such as Zebranet. We have also implemented a DFT-MSN testbed by deploying crossbow motes for noise level monitoring in our university library. Though in a small scale, the testbed demonstrates the feasibility of DFT-MSN and provides guidance for future large scale deployment.     

A traffic control system for IEEE 802.11 networks based on available bandwidth estimation

To support Quality of service (QoS)‐sensitive applications like real‐time video streaming in IEEE 802.11 networks, a MAC layer extension for QoS, IEEE 802.11e, has been recently ratified as a standard. This MAC layer solution, however, addresses only the issue of prioritized access to the wireless medium and leaves such issues as QoS guarantee and admission control to the traffic control systems at the higher layers. This paper presents an IP‐layer traffic control system for IEEE 802.11 networks based on available bandwidth estimation. We build an analytical model for estimating the available bandwidth by extending an existing throughput computation model, and implement a traffic control system that provides QoS guarantees and admission control by utilizing the estimated available bandwidth information. We have conducted extensive performance evaluation of the proposed scheme via both simulations and measurements in the real test‐bed. The experiment results show that our estimation model and traffic control system work accurately and effectively in various network load conditions without IEEE 802.11e. The presence of IEEE 802.11e will allow even more efficient QoS provision, as the proposed scheme and the MAC layer QoS support will complement each other. Copyright © 2006 John Wiley & Sons, Ltd.     

Optimized RTL Code Generation from Coarse-Grain Dataflow Specification for Fast HW/SW Cosynthesis

This paper presents a new methodology of automatic RTL code generation from coarse-grain dataflow specification for fast HW/SW cosynthesis. A node in a coarse-grain dataflow specification represents a functional block such as FIR and DCT and an arc may deliver multiple data samples per block invocation, which complicates the problem and distinguishes it from behavioral synthesis problem. Given optimized HW library blocks for dataflow nodes, we aim to generate the RTL codes for the entire hardware system including glue logics such as buffer and MUX, and the central controller. In the proposed design methodology, a dataflow graph can be mapped to various hardware structures by changing the resource allocation and schedule information. It simplifies the management of the area/performance tradeoff in hardware design and widens the design space of hardware implementation of a dataflow graph. We also support Fractional Rate Dataflow (FRDF) specification for more efficient hardware implementation. To overcome the additional hardware area overhead in the synthesized architecture, we propose two techniques reducing buffer overhead. Through experiments with some real examples, the usefulness of the proposed technique is demonstrated.

Variational models for image colorization via chromaticity and brightness decomposition.

Colorization refers to an image processing task which recovers color in grayscale images when only small regions with color are given. We propose a couple of variational models using chromaticity color components to colorize black and white images. We first consider total variation minimizing (TV) colorization which is an extension from TV inpainting to color using chromaticity model. Second, we further modify our model to weighted harmonic maps for colorization. This model adds edge information from the brightness data, while it reconstructs smooth color values for each homogeneous region. We introduce penalized versions of the variational models, we analyze their convergence properties, and we present numerical results including extension to texture colorization.     

A Shape Memory High‐Voltage Supercapacitor with Asymmetric Organic Electrolytes for Driving an Integrated NO2 Gas Sensor

A high‐voltage supercapacitor with shape memory for driving an integrated NO₂ gas sensor is fabricated using a Norland Optical Adhesive 63 polymer substrate, which can recover the original shape after deformation by short‐time heating. The supercapacitor consists of multiwalled carbon nanotube electrodes and organic electrolyte. By using organic electrolyte consisting of adiponitrile, acetonitrile, and dimethyl carbonate in an optimized volume ratio of 1:1:1, a high operation voltage of 2 V is obtained. Furthermore, asymmetric electrolytes with different redox additives of hydroquinone and 1,4‐dihydroxyanthraquinone to the anode and cathode, respectively, enhance both capacitance and energy density by ≈40 times compared to those of supercapacitor without redox additives. The fabricated supercapacitor on the Norland Optical Adhesive 63 polymer substrate retains 95.8% of its initial capacitance after 1000 repetitive bending cycles at a bending radius of 3.8 mm. Furthermore, the folded supercapacitor recovers its shape upon heating at 70 °C for 20 s. In addition, 90% of the initial capacitance is retained even after the 20th shape recovery from folding. The fabricated supercapacitor is used to drive integrated NO₂ gas sensor on the same Norland Optical Adhesive 63 substrate attached onto skin to detect NO₂ gas, regardless of deformation due to elbow movement.     

A method for generating Simulated nighttime road images under automotive headlamp lights

This study proposes a new calculation method for generating real nighttime lamp-lit images. In order to improve the color appearance in the prediction of a nighttime lamp-lighted road scene, the lamp-lit image is synthesized based on spectral distribution using the estimated local spectral distribution of the headlamps and the surface reflectance of every object. The principal component analysis method is introduced to estimate the surface color of an object and the local spectral distribution of the headlamps is calculated based on the illuminance data and spectral distribution of the illuminating headlamps. High-intensity discharge and halogen lamps are utilized to create beam patterns and captured road scenes are used as background images to simulate actual headlamp-lit images on a monitor. As a result, the reproduced images presented a color appearance that was very close to a real nighttime road image illuminated by single and multiple headlamps.     

Diversity Analysis of Relay Selection Schemes for Two-Way Wireless Relay Networks

One-way wireless relay networks have recently received a lot of attention due to their ability to provide spatial diversity in fading wireless environment. Moreover, performing single-relay selection is a very attractive method due to its cost effective implementation and superior performance. However, one-way relay networks with the half-duplex signalling suffer from a spectral efficiency loss. To overcome such a drawback, two-way wireless relay networks have been proposed and these are also the networks considered in this paper. The paper analyzes the diversity orders of various relay selection schemes, including the best-relay selection, best-worse-channel selection, and maximum-harmonic-mean selection. The analysis is done for the amplify-and-forward protocol and under the two-step and three-step transmission procedures. In particular, it is shown that full diversity orders of R and R + 1 can be achieved in a R-relay wireless network with the two-step and three-step procedures, respectively. Numerical and simulation results are provided to verify our analysis.     

Hetero‐Nanonet Rechargeable Paper Batteries: Toward Ultrahigh Energy Density and Origami Foldability

Forthcoming smart energy era is in strong pursuit of full‐fledged rechargeable power sources with reliable electrochemical performances and shape versatility. Here, as a naturally abundant/environmentally friendly cellulose‐mediated cell architecture strategy to address this challenging issue, a new class of hetero‐nanonet (HN) paper batteries based on 1D building blocks of cellulose nanofibrils (CNFs)/multiwall carbon nanotubes (MWNTs) is demonstrated. The HN paper batteries consist of CNF/MWNT‐intermingled heteronets embracing electrode active powders (CM electrodes) and microporous CNF separator membranes. The CNF/MWNT heteronet‐mediated material/structural uniqueness enables the construction of 3D bicontinuous electron/ion transport pathways in the CM electrodes, thus facilitating electrochemical reaction kinetics. Furthermore, the metallic current collectors‐free, CNF/MWNT heteronet architecture allows multiple stacking of CM electrodes in series, eventually leading to user‐tailored, ultrathick (i.e., high‐mass loading) electrodes far beyond those accessible with conventional battery technologies. Notably, the HN battery (multistacked LiNi_0.5Mn_1.5O₄ (cathode)/multistacked graphite (anode)) provides exceptionally high‐energy density (=226 Wh kg^?1 per cell at 400 W kg^?1 per cell), which surpasses the target value (=200 Wh kg^?1 at 400 W kg^?1) of long‐range (=300 miles) electric vehicle batteries. In addition, the heteronet‐enabled mechanical compliance of CM electrodes, in combination with readily deformable CNF separators, allows the fabrication of paper crane batteries via origami folding technique.