Proton‐exchange membranes via the grafting of styrene and acrylic acid onto fluorinated ethylene propylene copolymer by a preirradiation technique. III. Thermal and mechanical properties of the membranes and their sulfonated derivatives

Polymer electrolyte membranes were prepared via the grafting of styrene and acrylic acid onto fluorinated ethylene propylene copolymer with a preirradiation technique and subsequent sulfonation. The thermal and mechanical properties of the grafted membranes and their sulfonated derivatives were dependent on the degree of grafting. The grafted membranes showed a two‐step degradation pattern, whereas their sulfonated derivatives showed a three‐step degradation pattern. The glass‐transition temperature and crystallinity percentage of the membranes were determined with differential scanning calorimetry. With an increase in the degree of grafting and sulfonation, the glass‐transition temperature increased, whereas the crystallinity percentage decreased. The tensile strength and elongation decreased with the degree of grafting and sulfonation. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1418–1425, 2005     

A geometric approach to edge detection

This paper describes edge detection as a composition of four steps: conditioning, feature extraction, blending, and scaling. We examine the role of geometry in determining good features for edge detection and in setting parameters for functions to blend the features. We find that: (1) statistical features such as the range and standard deviation of window intensities can be as effective as more traditional features such as estimates of digital gradients; (2) blending functions that are roughly concave near the origin of feature space ran provide visually better edge images than traditional choices such as the city-block and Euclidean norms; (3) geometric considerations ran be used to specify the parameters of generalized logistic functions and Takagi-Sugeno input-output systems that yield a rich variety of edge images; and (4) understanding the geometry of the feature extraction and blending functions is the key to using models based on computational learning algorithms such as neural networks and fuzzy systems for edge detection. Edge images derived from a digitized mammogram are given to illustrate various facets of our approach     

Single electron charging effects in high-resistance In2O#x2212;x#x2212;x#x2212;x wires

We report on our measurements of the transport properties of 0.75 m long insulating indium oxide wires and rings. These devices have no apparent tunnel barriers, yet they exhibit two properties at low temperatures which are characteristic of series arrays of small capacitance tunnel junctions: highly non-linear IV characteristics and a zero-bias conductance which is periodic in a voltage applied by means of a lateral gate. Two types of samples can be distinguished, based on the behaviour of the conductance oscillations at low temperatures. For the first type, the structure of the oscillations remains periodic down to our lowest temperatures, similar to the data from the tunnel junction arrays. For the second type, lowering the temperature results in a transition from periodic to quasi-periodic conductance peaks. A phenomelogical model based on the orthodox theory of the Coulomb blockade is able to account for most of our observations. The temperature and magnetic field dependence of these effects suggest that they are due to the influence of single electron charging on transport through the localized electron states in the indium oxide.     

Impact of Channel Plan and Dispersion Map on Hybrid DWDM Transmission of 42.7-Gb/s DQPSK and 10.7-Gb/s OOK on 50-GHz Grid

We investigate experimentally the performance of 42.7-Gb/s return-to-zero (RZ) differential quadrature phase-shift-keyed (DQPSK) channels in a dense wavelength-division-multiplexed transmission system having 10.7-Gb/s nonreturn-to-zero (NRZ) on-off keyed (OOK) channels. Cross-phase modulation (XPM) from the OOK channels is found to be a dominating nonlinear penalty source for copropagating DQPSK channels in a dispersion-managed transmission link with multiple standard single-mode fiber spans. It is also found that the XPM penalty strongly depends on channel occupancy and residual dispersion per span (RDPS). Large RDPS effectively mitigates XPM even for the worst-case occupancy where a 42.7-Gb/s RZ-DQPSK channel is amidst several 10.7-Gb/s NRZ-OOK channels on a 50-GHz channel grid.     

New lipophilic cyclo- and poly-phosphazenes containing surfactant substituents

The reaction of the sodium salt of the commercially available surfactant Igepal CA 210^™ with hexachlorocyclotriphosphazene, N₃P₃Cl₆ (1) and poly(dichlorophosphazene), [—P(Cl₂)=N—]_n (Publisher's note: for graphical representation please see printed journal or the Acrobat PDF version on this website.) affords lipophilic cyclo- and poly-phosphazenes SSCP (2) and SSPP (4), respectively. These materials, containing a short chain oligo etheroxy side group while being completely insoluble in water, are soluble in a wide range of solvents ranging from hexane to chloroform. The polymer, SSPP (4) forms polymer–metal salt complexes with lithium salts. DC conductivity measurements by a complex impedance method have been carried out. The maximum conductivity observed for SSPP–LiClO₄ (O: Li ratio, 6:1) is 1·0×10^-6Scm^-1 at 348K. © 1998 SCI.     

Design and implementation of wavelength-flexible network nodes

This paper analytically and experimentally examines node architectures for wavelength-routing networks, with emphasis on the degree of wavelength conversion provided. Wavelength flexibility simplifies network management and increases network capacity but requires large cross-connects and deployment of wavelength converters (WCs). A simple probabilistic model is used to upper-bound the number of WCs required at a network node, under dynamic traffic load. When provisioned in a shareable pool, with a fixed number of wavelength channels per fiber, the number of WCs required remains low as overall network capacity is scaled up. Motivated by this analysis, experiments demonstrate the feasibility of implementing wavelength-flexible network nodes using large microelectromechanical (MEMS)-based cross-connects and all-optical WCs. In one design, WCs were attached directly to cross-connect output ports, and in another, they were attached in a loop-back fashion to allow sharing. Error-free transmission at 10 Gb/s was demonstrated in both cases.     

Confidence limits for steady-state availability of systems with a mixture of exponential and gamma operating time and lognormal repair time

A 100% confidence interval for the steady-state availability of a system is derived, when the operating time distribution is a mixture of exponential and gamma and the repair time distribution is lognormal. It is assumed that one of the parameters of the operating time distribution and also one of the parameters of the repair time distribution are known.     

Design, fabrication, and performance of high-speed monolithicallyintegrated InAlAs/InGaAs/InP MSM/HEMT photoreceivers

A detailed study of the performance of monolithically integrated photoreceivers based on metal-semiconductor-metal (MSM) photodetectors (PD's) and HEMT's is undertaken. Two different stacked-layer approaches to integrating MSM-PD's with HEMT's are investigated, and the performance of detectors and HEMT's for each approach is compared. The structure with the MSM layers grown on top of the HEMT layers exhibited the best overall performance. A physics-based MSM model is developed and incorporated into microwave circuit design software; excellent agreement between circuit simulations and measured frequency responses is demonstrated. To evaluate the effects of MSM electrode geometry and detector area on photoreceiver performance, photoreceivers with MSM interelectrode spacings of 1, 1.5, and 2 μm were fabricated and characterized. The electrical amplifier used in the photoreceivers is a two-stage, variable-transimpedance amplifier with a common-gate HEMT as the feedback path. By adjusting the DC voltage applied to the gate of this feedback HEMT, transimpedances ranging from 55.8 to 38.1 dBΩ, with corresponding -3 dB cutoff frequencies from 6.3 to 18.5 GHz, were measured experimentally. Excellent noise performance has been measured, with average input noise current spectral densities of 7.5, 8, and 12 pA/Hz^1/2 obtained for bandwidths of 6.3, 8, and 13.7 GHz, respectively. A packaged receiver has been tested at 5 Gb/s and an open eye pattern obtained