A bi‐criterion optimization approach for the design and planning of hydrogen supply chains for vehicle use

In this article, we address the design of hydrogen supply chains for vehicle use with economic and environmental concerns. Given a set of available technologies to produce, store, and deliver hydrogen, the problem consists of determining the optimal design of the production‐distribution network capable of satisfying a predefined hydrogen demand. The design task is formulated as a bi‐criterion mixed‐integer linear programming (MILP) problem, which simultaneously accounts for the minimization of cost and environmental impact. The environmental impact is measured through the contribution to climate change made by the hydrogen network operation. The emissions considered in the analysis are those associated with the entire life cycle of the process, and are quantified according to the principles of Life Cycle Assessment (LCA). To expedite the search of the Pareto solutions of the problem, we introduce a bi‐level algorithm that exploits its specific structure. A case study that addresses the optimal design of the hydrogen infrastructure needed to fulfill the expected hydrogen demand in Great Britain is introduced to illustrate the capabilities of the proposed approach. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

Formation Routes of Nanocomposite Coatings in Detonation Spraying of Ti3SiC2-Cu Powders

In thermally sprayed coatings, nano-sized features of the microstructure may be either inherited from the nanostructured agglomerates of the feedstock powder or form as a result of rapid cooling of molten particles upon deposition. Applying a process of the computer-controlled detonation spraying (CCDS) to Ti₃SiC₂-Cu composite powders produced by high-energy mechanical milling, we show that both routes are possible depending on the spraying conditions. When the nanostructure of the Ti₃SiC₂-Cu coating is inherited from the feedstock powder—under very mild conditions of detonation spraying, which exclude melting, so is the phase composition of the coating. In higher-temperature conditions of spraying, a significant fraction of the copper matrix melts and the interaction between Ti₃SiC₂ and Cu occurs. The TiC _x -Cu(Si) coatings that form show crystallites of both phases in the nano-range. In this case, rapid solidification of the molten fraction of the particles is responsible for the formation of the coatings with a nanostructured matrix. Due to the flexibility of the CCDS process, conditions of spraying were found such that a composite coating with very fine crystallites of the Cu(Si) matrix (30 nm) and a hardness of 273 HV could be obtained.     

Identification of tool parallel axis offset through the analysis of the topography of surfaces machined by peripheral milling

A method for the identification of the tool parallel axis offset (TPAO) that occurs when the end mill is held in the spindle is developed. The method is based on the analysis of the topography of surfaces machined by peripheral milling and considers the cutter grinding errors. As known from the literature, TPAO causes each cutting edge to be at a different radius from the spindle axis and creates transition bands in the topography of milled surfaces, in which roughness grooves generated by different teeth blend together. In this paper, the TPAO, defined by the distance of the tool axis from the spindle axis and by an angle relating the offset direction to the position of cutting edges, is expressed as a function of the width of the roughness grooves at any height of the transition bands. This expression allows the TPAO to be estimated by measuring the groove widths at only two heights and solving a system of two linear equations. In order to obtain the groove widths, a procedure based on digital image processing is developed. Through this procedure, the groove widths are estimated at more than the two necessary heights without high computational cost. This leads to the resolution of an overdetermined system of linear equations that allows the TPAO to be identified with more accuracy. Finally in order to verify the predictions of the proposed method, a series of cutting tests were carried out. A reasonable agreement between the experimental results and the predicted ones was found.     

Statistical evaluation of dye desorption – mixed two- and three-level design and kinetic modeling

Abstract

Biosorption has been shown in the literature to be effective in the removal of dye from aqueous solution. To be fully useful, a desorption process is necessary, which has a direct impact on the process costs. The aim of this work was to evaluate the desorption of the azo dye Acid Yellow 23 adsorbed in a biosorbent obtained from Bombyx mori cocoons. Temperature and pH media were evaluated through a mixed two- and three-level design, using NaOH as desorbing agent. Kinetic desorption was also obtained at the optimized condition. The statistical evaluation of the experimental design showed that the pH has almost two times more influence on the dye desorption than the temperature, with only the linear parameters being statistically significant. Among four kinetic desorption models adjusted to the experimental data, the proposed n-order model was statistically determined as the best representation of the experimental data.     

Evaluation of removal and adsorption of different herbicides on commercial organophilic clay

Abstract

In this work, commercial organophilic clay was used in adsorption studies for the liquid phase of Atrazine, Ametryn, Diuron, and 2-(2,4-dichlorophenoxy)acetic acid (2,4-D) in a batch type system. The affinity study showed that clay is a promising material to remove contamination from agricultural activities. The adsorbent material showed a great removal capacity, especially for Diuron because that reached a higher value than 98%. The adsorption rate was evaluated by pseudo-first-order, pseudo-second order, Elovich, intraparticle diffusion, and external film mass transfer (EFMT) models. In these models, the pseudo-second order and EFMT models represented properly experimental data for Atrazine, Ametryn, and Diuron, whereas the Elovich model was the most predictive for 2,4-D. The maximum adsorption capacities in the monolayer for each contaminant were obtained by the equilibrium isotherms, and the values were 2.275, 25.253, 47.149, and 6.450?mg g^?1 for Atrazine, Ametryn, Diuron, and 2,4-D, respectively. In addition, the Langmuir model was the best adjustment to equilibrium data for Atrazine, Ametryn, and Diuron adsorption. For 2,4-D, the model that best represented the experimental data was Freundlich. Finally, characterization techniques indicated that herbicide adsorption contributed to textural, chemical, morphological, and thermal modifications in the clay mineral.     

Bulk functionalization of ethylene–propylene copolymers. III. Structural and superreticular order investigations

An ethylene-propylene copolymer (EPR) has been functionalized with dibutyl maleate (DBM) by means of a radical-initiated bulk process. Different degrees of grafting have been obtained by varying the overall composition of the reaction mixture as well as the processing procedures. The influence of the grafting degree on the structural and superreticular (or “long range”) order has been investigated by differential scanning calorimetry (DSC), Fourier transform infrared analysis (FTIR), and wide (WAXS) and small angle X-ray scattering (SAXS) techniques. The functionalization leads to a decrease of the “residual crystallinity” present in the parent copolymer. Linear relationships between the grafting degree and the crystallinity degree X_c evaluated by both DSC and WAXS have been obtained. The results of the structural investigations, in agreement with previously reported ones, suggest that the grafting preferentially occurs onto the longer or more perfect methylene sequences. SAXS investigations showed that the significant degree of structuration, i.e., crystalline and paracrystalline order, present in the parent elastomer, gradually disappears by increasing the degree of grafting.     

Radiographic inspection of reaction-sintered discontinuously reinforced Al–Si alloy composites

Detection and identification of defects and reinforcement phases in reaction-sintered hypereutectic Al-13.5Si-2.5 Mg alloy composites was studied using X-ray radiation. Both the coconut shell char-reinforced and zircon sand-reinforced alloy composites revealed cavities due to thermal defects, gas pores, and voids. The low-density char particles were not detected, but the high-density zircon particulates appeared as dark inclusions on the exographs and this offers a good visual measure of particle dispersion in the liquid-phase sintered parts. At the same conditions of irradiation, the low-density Al-Si alloy composites containing high-density zircon particles did not reveal any clear images. Clusters of alumina-silica short fibres as well as line defects appeared bright but their nature was not discernible, making it difficult to identify the defects in the radiographs. © 1998 Kluwer Academic Publishers     

Age and forgetfulness: Managing perceivers' impressions of targets' capability.

Two experiments investigated the effect of positive endorsement on perceivers' impressions of young and old female targets. In Experiment 1, 160 young adult perceivers listened to a tape of a young or old forgetful target being interviewed for a volunteer job. They read a nonelaborative or elaborative reference letter for the target either before or after listening to the tape. Perceivers who read the elaborative letter after listening to the tape rated themselves as more likely to assign tasks to both young and old targets and had a higher general capability opinion of old targets. In Experiment 2, 84 older adult perceivers read an elaborative letter and listened to one of the same taped interviews. Reading the letter after the tape resulted in higher task ratings than reading it before the tape, but letter order had no effect on general capability ratings. Results are discussed in terms of impression management. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

All-digital TX frequency synthesizer and discrete-time receiver for Bluetooth radio in 130-nm CMOS

We present a single-chip fully compliant Bluetooth radio fabricated in a digital 130-nm CMOS process. The transceiver is architectured from the ground up to be compatible with digital deep-submicron CMOS processes and be readily integrated with a digital baseband and application processor. The conventional RF frequency synthesizer architecture, based on the voltage-controlled oscillator and the phase/frequency detector and charge-pump combination, has been replaced with a digitally controlled oscillator and a time-to-digital converter, respectively. The transmitter architecture takes advantage of the wideband frequency modulation capability of the all-digital phase-locked loop with built-in automatic compensation to ensure modulation accuracy. The receiver employs a discrete-time architecture in which the RF signal is directly sampled and processed using analog and digital signal processing techniques. The complete chip also integrates power management functions and a digital baseband processor. Application of the presented ideas has resulted in significant area and power savings while producing structures that are amenable to migration to more advanced deep-submicron processes, as they become available. The entire IC occupies 10 mm/sup 2/ and consumes 28 mA during transmit and 41 mA during receive at 1.5-V supply.