Adsorption onto fluidized powdered activated carbon flocs-pACF

This work presents a new adsorption technique where the adsorbent (powdered activated carbon-PAC) is in the form of suspended flocs formed with water-soluble polymer flocculants. Thus, the adsorption of a typical dye, methylene blue (MB), was studied onto polyacrylamide flocs of PAC (PACF) in a fluidized bed reactor. The technique is based on the fact that the adsorption capacity of PAC does not decrease after flocculation because the adsorbed polymer occupies only a few surface sites, in the form of trains, loops, and tails. Moreover, the adsorption was found to proceed through a rapid mass transfer of MB to the adsorbing PAC flocs, in the same extent as onto PAC. Because of the rapid settling characteristics of the aggregates formed, the two phase separations, loaded PAC and solution, become easier. Thus, the technique offers the advantages of conducting simultaneously both adsorption and solid/liquid separation all in one single stage. Results obtained showed that high MB removal values can be attained in a fluidized bed reactor (>90%) and that PACF presents a much higher adsorption capacity (breakthrough points) than granulated activated carbon (GAC) in the same adsorbing bed. It is believed that this technique highly broadens the potential of the use of powdered activated carbon or other similar ultrafine adsorbents.     

Effects of solid retention time on anaerobic digestion of dewatered-sewage sludge in mesophilic and thermophilic conditions

Anaerobic digestion of dewatered-sewage sludge using continuous stirred tank reactors (CSTRs) in duplicates was evaluated under thermophilic (50 °C) and mesophilic (37 °C) conditions over a range of nine solid retention times (SRTs). The 35- and 30-day SRTs were designed to simulate a full-scale plant operation while 25-, 20-, 15- and 12-day SRTs were planned to evaluate process performance at the various SRTs. The 9-, 5- and 3-day SRTs were performed to push the reactors to extend their degradation capacity and test the threshold for process imbalance. The corresponding organic loading rates (OLR) varied from 1.6 to 20.5 kg VS m^?3 day^?1. Biogas production rate could be tripled when the SRT was shortened from 30 to 12 days and more than doubled from 35- to 15-day SRT because of a concomitant increase in OLR. In general, higher biogas productivity was realized under thermophilic, but methane yields were comparable due to the higher methane content in the biogas under mesophilic digestion. The methane content in biogas fluctuated between 55 and 65% and the methane yield ranged from 0.314 to 0.348 Nm³ CH₄ kg VS_added^?1 day^?1 for both thermophilic and mesophilic digestion. The VS-reduction at 12- and 15-day SRT ranged from 45 to 52% and there was no accumulation of VFAs. Increasing concentrations of VFAs, decreasing concentration of partial alkalinity and decrease in pH were noted as signs of reactor instability. Process imbalance started at 9-day SRT, souring of the reactors, cell wash-out and foaming was noted as the principal causes of process failure under both thermophilic and mesophilic conditions. This study projected the possibility of using CSTRs in treating dewatered-sewage sludge at a shorter SRT to achieve reasonable biogas production and VS-reduction without encountering adverse operation conditions as foaming and wash-out of cells.     

Switching between negative and positive electrorheological effect of g-C3N4 by copper ions doping

Investigation of pristine g-C₃N₄ and copper ions doped g-C₃N₄ as dispersed phases in silicone-oil based electrorheological (ER) fluids is reported for the first time. Pristine g-C₃N₄ was prepared via standard thermal polycondensation of urea. Introduction of Cu ions into g-C₃N₄ polymeric network was performed by treatment of pristine powder by a solution containing tetraammoniumdiaquacopper(II) complex ions followed by annealing. The structure and properties of products were revealed with the aid of XRD, FTIR, UV–Vis and XPS, and complemented by SEM investigation of morphology, pycnometry, BET analysis, and conductivity measurements. The response of prepared ER fluids to an external electric field was examined by rheometry and the effects visualized with optical microscopy. While ER fluids based on g-C₃N₄ exhibited negative ER effect (decrease in viscosity when the field is switched-on), ER fluids based on a g-C₃N₄/Cu-doped analogue exhibited positive ER effect. Dielectric spectroscopy using Havriliak-Negami model revealed that introduction of the dopant almost doubled the dielectric relaxation strength while the relaxation time was halved. The ability of g-C₃N₄/Cu as a candidate for further studies necessary to increase the ER effect was demonstrated. Thereto, described modification of g-C₃N₄ by copper ions shall be applicable also for other metals forming ammonia complexes.     

Development and characterization of magnesium composites containing nano-sized silicon carbide and carbon nanotubes as hybrid reinforcements

Magnesium based hybrid composites containing nano-sized silicon carbide and carbon nanotubes reinforcements with minimal porosity were successfully fabricated using powder metallurgy technique with microwave sintering and hot extrusion. It was found that the addition of nano-sized silicon carbide and carbon nanotubes reinforcements lowered the coefficient of thermal expansion of magnesium. Moreover, increasing presence of silicon carbide particles led to a progressive reduction in coefficient of thermal expansion for a constant overall amount of reinforcements indicating that carbon nanotubes lowered the coefficient of thermal expansion to a lesser extent when compared to silicon carbide. Micro-hardness, 0.2% YS and UTS (except for Mg+1%CNT) showed improvement, while failure strain decreased when nano-sized silicon carbide and carbon nanotubes were added to magnesium. The failure mode of magnesium and magnesium composites was predominantly brittle exhibiting the presence of cleavage steps.     

Integrodifferential approach to solution of eddy currents in linear structures with motion

A nonstandard integrodifferential approach to computation of eddy currents in linear structures with motion is presented. Described is a general continuous 3D model of the problem, together with the possibilities of forming corresponding numerical schemes. The methodology is illustrated by two examples.     

Using non-food information to identify food-choice segment membership

Food companies, governments, and societal organizations use an increasing number of food-choice motives to persuade consumers to buy food products, and the question which combinations of motives matter for which type of consumer has become of central relevance. In this study, we use a concomitant mixture-modeling approach to uncover consumer segments in terms of food-choice motives, using a nationwide sample in the Netherlands. The results reveal seven segments with distinct profiles and demonstrate that age and membership of environmental organizations play an essential role in segment membership probabilities. Our findings support the idea that information about non-food-related consumer behavior improves the identification of segments. In an additional analysis, we demonstrate how organizational membership also provides an effective way to access consumer segments as compared to diverse media outlets. We discuss the implications of our findings for segmentation practice.     

Geotechnical Problems of Cultural Heritage due to Floods

Flood events demonstrate devastating effects not only on materials and structures in contact with flowing surface water. Equally important is the behavior of foundations in interaction with subsoil. This contribution gives an overview of different phenomena which arise in subsoil and at the foundation level during the groundwater rise accompanied by several case histories related to cultural heritage. Possible geotechnical measures are discussed as well.     

The formation of international innovation networks in the multinational corporation: an evolutionary perspective

The internationalization of technological capabilities in themultinational corporation has produced a growing number of conceptualframeworks that emphasize the ability to leverage innovationactivities in the international innovation network. In particular,it has been stressed that increasingly complex and diverse structuresgenerally provide opportunities to integrate and recombine knowledgeacross geographically dispersed units. The present study suggeststhat conceptual work has paid insufficient attention to therelationship between process and structure in the evolving internationalinnovation network. An in-depth, longitudinal study of ASEA/BrownBoveri/ABB underlines the importance of considering historicalgrowth processes and firm-specific events in evaluating themultinational's ability to integrate and recombine knowledgeon a global basis.     

Thermo-optic design for microwave and millimeter-wave electromagnetic power microsensors

Rendina et al. recently proposed the original configuration of an electromagnetic power sensor for microwaves and millimeter waves that is based on an optically interrogated all-silicon chip [Electron. Lett. 35, 1748 (1999)]. Here we theoretically analyze and discuss in detail the performances of such a new class of nonperturbing and wideband probe in terms of sensitivity, resolution, intrinsic detectivity, linearity, and response time. Good agreement between theory and experiments is demonstrated. In particular, minimum resolutions of approximately 1 mW/cm2 are obtained at frequencies beyond 10 GHz. The dependence of response on the geometrical and electromagnetic parameters of the sensing element is analyzed, and on this basis the possibility of achieving optimized configurations is discussed.     

A Scalable Architecture for MPEG-4 Wavelet Quantization

Wavelet-based image compression has been adopted in MPEG-4 for visual texture coding. All wavelet quantization schemes in MPEG-4—Single Quantization (SQ), Multiple Quantization (MQ) and Bi-level Quantization—use Embedded Zero Tree (EZT) coding followed by an adaptive arithmetic coder for the compression and quantization of a wavelet image. This paper presents the OZONE chip, a dedicated hardware coprocessor for EZT and arithmetic coding. Realized in a 0.5 m CMOS technology and operating at 32 MHz, the EZT coder is capable of processing up to 25.6 Mega pixel-bitplanes per second. This is equivalent to the lossless compression of 31.6 8-bit grayscale CIF images (352 × 288) per second. The adaptive arithmetic coder processes up to 10 Mbit per second. The combination of the performance of the EZT coder and the arithmetic coder allows the OZONE to perform visual-lossless compression of more than 30 CIF images per second. Due to its novel and scalable architecture, parallel operation of multiple OZONEs is supported. The OZONE functionality is demonstrated on a PC-based compression system.