Use of metallic Ni for H2 production in S–I thermochemical cycle: Experimental and theoretical analysis

The gaseous hydrogen iodide decomposition is a thermodynamically limited reaction and subsequently a considerable energy expense for the separation and recirculation of the unreacted species is required. In addition the homogeneous gas phase decomposition of hydrogen iodide has a very low rate and the use of a catalytic system, which is generally highly expensive, is necessary. Hence, with the aim of overcoming the bottleneck represented by the hydrogen releasing step of the Sulphur–Iodine (S–I) cycle in terms of costs and process efficiency, in the present work an alternative version of the HI decomposition section (HI_x section) is proposed. In that alternative configuration the addition of metallic nickel into the heavy phase coming from Bunsen reaction is conceived in order to quantitatively obtain hydrogen at low temperature. A theoretical and experimental investigation has been performed, a new cycle has been conceived and the resulting energy demand assessed.     

A recursion-based broadcast paradigm in wormhole routed networks

A novel broadcast technique for wormhole-routed parallel computers based on recursion is presented in this paper. It works by partitioning the interconnection graph into a number of higher-level subgraphs. Then, we identify the transmission subgraph (TSG) in each subgraph. Both the higher-level subgraphs and the TSGs are recursively defined, i.e., we split each level i subgraph into several level i+1 subgraphs and identify-level i+1 TSGs accordingly. We first split and scatter the source message into the TSG of the original graph. Next, in each recursive round message transmissions are from lower-level TSGs to higher-level TSGs and all transmissions at the same level happen concurrently. The algorithm proceeds recursively from lower-level subgraphs to higher level subgraphs until each highest-level subgraph (a single node) gets the complete message. We have applied this general paradigm to a number of topologies including two or higher dimension mesh/torus and hypercube. Our results show considerable improvements over all other algorithms for a wide range of message sizes under both one-port and all-port models.     

Analysis of seismically-isolated two-block systems using a multi–rocking-body dynamic model

A novel multibody rocking model is developed to investigate the dynamic response of two stacked rigid blocks placed on a linear base isolation device. The model is used to investigate the dynamic response of a realistic statue-pedestal system subject to pulse-like ground motions. The analysis shows that, in general, base isolation increases the safety level of the rocking system. However, for large period pulses or small size blocks, the isolator can amplify the ground motion, resulting in a lower minimum overturning acceleration than for the nonisolated system. Further, the amplification or shock spectrum of a linear mass-dashpot-spring oscillator, was found to be the reciprocal of the minimum nondimensional overturning acceleration of the investigated rocking system. Novel rocking spectra are obtained by normalizing the frequency of the pulse by the frequency of the isolator. The analysis also demonstrates how the dynamic response of the two stacked blocks is equivalent to that of a single-block configuration coincident with the whole system assumed monolithic or the upper block alone, whichever is more slender.     

On the sensitivity analysis of digital filters

A very quick and simple algorithm for the overall evaluation of the sensitivity performance of a digital filter is introduced. To this end, it is shown that the sensitivity of the system function with respect to a given coefficient comes out equal to the output of a special digital network with unitary input. Having defined, then, an ‘overall sensitivity index’ as the sum of the various network sensitivities, it is shown that such an index can still be considered as the output of a digital network with unitary input. This network is composed of two subnetworks, identical to the original circuit, connected by a special set of branches.     

Preprocessing of Intractable Problems

Some computationally hard problems, e.g., deduction in logical knowledge bases– are such that part of an instance is known well before the rest of it, and remains the same for several subsequent instances of the problem. In these cases, it is useful to preprocess off-line this known part so as to simplify the remaining on-line problem. In this paper we investigate such a technique in the context of intractable, i.e., NP-hard, problems. Recent results in the literature show that not all NP-hard problems behave in the same way: for some of them preprocessing yields polynomial-time on-line simplified problems (we call them compilable), while for other ones their compilability implies some consequences that are considered unlikely. Our primary goal is to provide a sound methodology that can be used to either prove or disprove that a problem is compilable. To this end, we define new models of computation, complexity classes, and reductions. We find complete problems for such classes, “completeness” meaning they are “the less likely to be compilable.” We also investigate preprocessing that does not yield polynomial-time on-line algorithms, but generically “decreases” complexity. This leads us to define “hierarchies of compilability,” that are the analog of the polynomial hierarchy. A detailed comparison of our framework to the idea of “parameterized tractability” shows the differences between the two approaches.     

Self-assembly in sugar-oil complex glasses

In aqueous systems, the hydrophobic effect drives the self-assembly of amphiphiles into a broad range of micellar, rod-like, bicontinuous and liquid-crystalline complex fluids. Many of these are relevant to biological matter or technological applications. However, amphiphilic self-assembly is not limited to aqueous systems. Replacement of water with supercritical carbon dioxide, for example, results in complex fluids that combine the properties of gases and liquids. Along this vein, we explore the self-assembly of surfactants in anhydrous sugars. Our study reveals that anhydrous powders of sugars and surfactants suspended in oil spontaneously form molten glasses with nanometre-size domains of sugar and liquid oil without mixing. The low cost, water solubility, low toxicity and stabilizing properties of glassy sugars make them ideal water replacements for many pharmaceutical, food and materials synthesis applications. The optical clarity and solid appearance of these glasses at room temperature belie their inclusion of more than 50% (vol.) oil, which confers liquid-like diffusivity. The unique combination of solid- and liquid-like properties may lead to applications in sensors and optical devices.     

High pressure rheometer for in situ formation and characterization of methane hydrates

We present a novel setup for a high pressure rheometer operating with concentric cylinders geometry for in situ studies of hydrate formation and rheological characterization. The apparatus uses an external high pressure mixing cell to saturate water-in-oil emulsions with methane gas. The capability of mixing combined with a true rheometer design make this apparatus unique in terms of setup and sample formation. We have used the apparatus to form gas hydrates in situ from water-in-oil emulsions and characterize suspension rheological properties such as yield stress and shear-thinning behavior.     

Durability and performance of polystyrene‐b‐poly(vinylbenzyl trimethylammonium) diblock copolymer and equivalent blend anion exchange membranes

Anion exchange membranes (AEM) are solid polymer electrolytes that facilitate ion transport in fuel cells. In this study, a polystyrene‐b‐poly(vinylbenzyl trimethylammonium) diblock copolymer was evaluated as potential AEM and compared with the equivalent homopolymer blend. The diblock had a 92% conversion of reactive sites with an IEC of 1.72 ± 0.05 mmol g^?1, while the blend had a 43% conversion for an IEC of 0.80 ± 0.03 mmol g^?1. At 50°C and 95% relative humidity, the chloride conductivity of the diblock was higher, 24–33 mS cm^?1, compared with the blend, 1–6 mS cm^?1. The diblock displayed phase separation on the length scale of 100 nm, while the blend displayed microphase separation (～10 μm). Mechanical characterization of films from 40 to 90 microns thick found that elasticity and elongation decreased with the addition of cations to the films. At humidified conditions, water acted as a plasticizer to increase film elasticity and elongation. While the polystyrene‐based diblock displayed sufficient ionic conductivity, the films' mechanical properties require improvement, i.e., greater elasticity and strength, before use in fuel cells. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41596.     

Altering the viscosity of cationically modified cellulose polymers by the addition of salt

The concentration dependence of viscosity is examined for four cationically modified cellulose polymers (UCARE? JR400, UCARE? JR30M, UCARE? LR400, and UCARE? LR30M) in both salt‐free and 50 mM NaCl solution. Similarities in the four polymer systems include: Newtonian viscosity in the dilute regime, shear thinning at higher concentrations, four concentration regimes in salt‐free solution, and three concentration regimes in salt solution. The zero shear rate viscosity and the degree of shear thinning increase with increasing polymer concentration in both salt and salt‐free solutions. While the addition of salt to the lower molecular weight polymers JR400 and LR400 resulted in small changes in viscosity across all concentrations, JR30M and LR30M exhibited significant decreases (up to 81%) and increases (up to 57%) in viscosity upon the addition of salt in the semidilute and entangled regimes, respectively. This viscosity increase in the entangled regime (when comparing salt‐free and 50 mM NaCl solutions) is reported for the first time in cationically modified cellulose polymers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41616.