Charge, current, and noise partitioning in MOSFET in the presence of mobility degradation

The Ward-Dutton (WD) partitioning scheme is used extensively to develop transient and high-frequency advanced compact models in MOSFET analysis. However, it remains an open question if this scheme can be used for field-dependent mobility that is enhanced in state-of-the-art submicrometer technologies. In this paper, after demonstrating that the well-known WD partitioning is indeed invalid for field-dependent mobility, the authors develop a very general partitioning strategy that can always be defined in small-signal analysis for any arbitrary velocity-field relationship. It has also been shown that for large-signal operation, the existence of a partitioning scheme can be determined by the solution of an integral equation.     

A novel approach to high-level switching activity modeling withapplications to low-power DSP system synthesis

We address high-level synthesis of low-power digital signal processing (DSP) systems by using efficient switching activity models. We present a technology-independent hierarchical scheme that can be easily integrated into current communications/DSP CAD tools for comparing the relative power/performance of two competing DSP designs without specific knowledge of transistor-level details. The basic building blocks considered for such systems are a full adder, a half adder, and a one-bit delay. Estimates of the switching activity at the output of these primitives are used to model the activity in more complex building blocks of DSP systems. The presented hierarchical method is very fast and simple. The accuracy of estimates obtained using the proposed approach is shown to be within 4% of the results obtained using extensive bit-level simulations. Our approach shows that the choice of multiplier/multiplicand is important when using array multipliers in a datapath. If the input signal with smaller mean square value is chosen as the multiplicand, almost 20% savings in switching activity can be achieved. This observation is verified by an analog simulation using a 16 × 16 bit array multiplier implemented in a 0.6-μ process with 3.3 V supply voltage     

Effect of linker used in D–A–π–A metal free dyes with different π-spacers for dye sensitized solar cells

Two novel D–A–π–A metal free dyes with triphenylamine as donor, dithiophene-diketo-pyrrolo-pyrrole as acceptor unit, thiophene and phenyl π-conjugated bridges and a cyanoacetic acid as electron acceptor (TDPP1 and TDPP2 were denoted for thiophene and phenyl π-conjugated bridge, respectively) have been designed and used as sensitizers for DSSCs. Incorporation of dithiophene-diketo-pyrrolo-pyrrole, reduces the band gap significantly. The influence of π-conjugated bridge on optical and electrochemical properties were investigated. Results demonstrated that the absorption band of TDPP with thiophene π-conjugated bridge has red shifted due to the enhancement of electron donating ability of π-conjugated bridge. The DSSC based on TDPP1 shows prominent power conversion efficiency about 4.81%, which is higher that for TDPP2 (3.42%). The electrochemical impedance spectroscopy analysis reveal that the charge recombination resistance at the TiO₂/dye/electrolyte interface for the DSSC based on TDPP1 is higher than that for TDPP2, which improves both J_sc and V_oc. The PCE of the DSSC based on TDPP1 is further improved up to 6.34%, when deoxycholic acid (DCA) was employed as coadsorbant.     

One‐Pot Synthesis of Dealloyed AuNi Nanodendrite as a Bifunctional Electrocatalyst for Oxygen Reduction and Borohydride Oxidation Reaction

A novel one‐pot approach for synthesizing the dealloyed nanomaterials at room temperature is introduced for the first time. In such a synthetic strategy, applying modulated potentials effectively simplifies the traditional dealloying route, which usually requires additional corrosion process to dissolve nonprecious metals. The dealloyed AuNi nanodendrites (AuNi NDs) with tunable composition and uniformly elemental distribution are well developed by the one‐pot strategy. Impressively, the as‐synthesized AuNi NDs exhibit a higher electrochemically active area and definite improvements in electrocatalytic activity for oxygen reduction reaction (ORR) and borohydride oxidation reaction (BOR) compared to the commercial Pt/C. In particular, the AuNi NDs are 81 mV more positive in half‐wave potential and about 3.1 times higher in specific activity (at 0.85 V) for the ORR than Pt/C, together with excellent stability and methanol tolerance. The superior BOR activity is highly promising compared to the previously reported catalysts. The unique nanodendritic structure with Au‐rich surface and bimetallic electronic effect is the main factor to greatly enhance the bifunctional catalytic performance for the AuNi NDs. Furthermore, such a newly developed facile method is of great significance because it is one of the first examples to effectively engineer dealloyed bimetallic nanostructures via the practical and low‐cost route for electrocatalytic applications.     

Exact scattering for axial incidence on an isorefractive paraboloid

The canonical solution to the problem of the scattering of a plane electromagnetic wave axially incident on the convex side of an isorefractive paraboloid is provided. The exact scattered field consists of the geometrical optics reflected field on the convex side of the paraboloid and of a transmitted plane wave on the concave side of the paraboloid     

Performance and testbed study of topology reconfiguration in IP over optical networks

With the widespread deployment of Internet protocol/wavelength division multiplexing (IP/WDM) networks, it becomes necessary to develop traffic engineering (TE) solutions that can effectively exploit WDM reconfigurability. More importantly, experimental work on reconfiguring lightpath topology over testbed IP/WDM networks is needed urgently to push the technology forward to operational networks. This paper presents a performance and testbed study of topology reconfiguration for IP/WDM networks. IP/WDM TE can be fulfilled in two fashions, overlay vs. integrated, which drives the network control software, e.g., routing and signaling protocols, and selects the corresponding network architecture model, e.g., overlay or peer-to-peer. We present a traffic management framework for IP over reconfigurable WDM networks. Three "one-hop traffic maximization"-oriented heuristic algorithms for lightpath topology design are introduced. A reconfiguration migration algorithm to minimize network impact is presented. To verify the performance of the topology design algorithms, we have conducted extensive simulation study. The simulation results show that the topologies designed by the reconfiguration algorithms outperform the fixed topology with throughput gain as well as average hop-distance reduction. We describe the testbed network and software architecture developed in the Defense Advanced Research Projects Agency (DARPA) Next Generation Internet (NGI) SuperNet Network Control and Management project and report the TE experiments conducted over the testbed.     

Synthesis of an incident aperiodic tapered beam

This paper presents a technique for generating numerically an incident tapered beam of a prescribed polarization and a prescribed incidence angle by summing a finite number of propagating uniform plane waves, each constituent plane wave having its own magnitude, phase, incidence angle and polarization. Our three ad-hoc schemes for choosing the magnitude, the incidence angle and the polarization of a constituent plane wave are different from those by Braunisch et al. Our choice of the propagating plane waves corresponds to a sampling of the physical angular (/spl theta/, /spl phi/) space. This contrasts with the two-dimensional Fourier transform technique by Braunisch et al. and its Cartesian sampling of the (k/sub x/, k/sub y/) spectral plane where k/sub x/=(k/sub o/sin/spl theta/cos/spl phi/) and k/sub y/=(k/sub o/sin/spl theta/sin/spl phi/). Our technique is based on the summation of only propagating plane waves, whereas the technique by Braunisch et al. is based on the summation of both propagating and evanescent plane waves.