Interzeolite Conversion of FAU Type Zeolite into CHA and its Application in NH3-SCR

In this work we studied the potential feasibility to synthesize small pore zeolites, such as chabazite (CHA) via interzeolite conversion of FAU type zeolite. We have thereafter used CHA as the starting material to obtain Cu–CHA. When CHA in NH₄ ⁺ form was used to prepare Cu–CHA, the large size of the potassium cation present in the structure caused pore blockage in the chabazite framework, and diminished the adsorption and exchange capacity. However, Cu–CHA with comparable Selective Catalytic Reduction performance to the commercial catalyst was obtained via ion exchange if Cu-exchange was performed from H⁺–CHA form. Still, the main challenge was to fully eliminate K⁺ from the zeolite structure in order to further improve its catalytic performance and high temperature stability.     

Achieving best value in private finance initiative project procurement

The wherewithal of achieving best value in private finance initiative (PFI) projects and the associated problems therein are documented. In the UK, PFI has offered a solution to the problem of securing necessary investment at a time of severe public expenditure restraint. In PFI schemes, the public sector clients must secure value for money, while the private sector service providers must genuinely assume responsibility for project risks. A broad‐based investigation into PFI risk management informs the discussion in this paper. It is based on 68 interviews with PFI participants and a case study of eight PFI projects. The research participants comprised of contractors, financial institutions, public sector clients, consultants and facilities management organizations. The qualitative software Atlas.ti was used to analyse the textual data generated. The analysis showed that the achievement of best value requirements through PFI should hinge on: detailed risk analysis and appropriate risk allocation, drive for faster project completion, curtailment in project cost escalation, encouragement of innovation in project development, and maintenance cost being adequately accounted for. Factors that continue to challenge the achievement of best value are: high cost of the PFI procurement process, lengthy and complex negotiations, difficulty in specifying the quality of service, pricing of facility management services, potential conflicts of interests among those involved in the procurement, and the public sector clients' inability to manage consultants.     

Data extraction from wireless sensor networks using distributed fountain codes

A Wireless Sensor Network (WSN) observes a natural field and aims to recreate it with sufficient fidelity at a, perhaps distant, Fusion Center (FC) using a wireless communication channel of arbitrary capacity. We propose a universal and power efficient method for such data extraction, based on Digital Fountain Codes (DFCs) and joint-source channel decoding. Our method implements a distributed `rate-lessiquest DFC which automatically tunes the number of transmissions to the channel capacity. Furthermore, instead of directly compressing the WSN data, we achieve rate reduction by treating the spatiotemporal dependencies in the field as an outer code, and jointly decoding this concatenation at the FC using a multi-stage iterative decoder. We demonstrate that a power efficiency close to the capacity-rate-distortion limit is achieved at moderate distortion levels, irrespective of the channel capacity or field dependencies. As compared to the traditional approach of source-channel separation, the proposed data extraction scheme is particularly attractive for WSN applications due its computationally simple encoding procedure, low latency and the ability to seamlessly trade-off fidelity of reconstruction for power consumption.     

John F. Stevens—A Great Civil Engineer

In 1927 John F. Stevens was elected president of the American Society of Civil Engineers, and in so doing the Society honored a great engineer, a great builder, and a man who truly loved the practice of civil engineering. Stevens was a self-trained engineer and constructor who directed some of the great construction efforts of the 19th and 20th centuries. In his early years, Stevens was engaged in the construction of the Canadian Pacific Railway, first with the contractors and then for the railway company directly. Two presidents thought so highly of his engineering skill that they appointed him to lead major construction efforts in the early 20th century. President Theodore Roosevelt made him chief engineer of the Isthmian (Panama) Canal work, and Wilson sent him to Russia in 1917, as chairman of a commission of railway engineers to rehabilitate and operate rail lines in Siberia. This narrative traces his adventures and growth as an engineer, but it also provides guidance as to how an engineer develops his capabilities in order to handle greater challenges.     

Three-dimensional simulation of the thermohaline-driven buoyancy of a brine parcel

We provide three-dimensional numerical simulations of the thermohaline-driven buoyancy of a brine “parcel” immersed in an initially homogeneous porous medium of hydrological interest. Our purpose is to improve our understanding of the thermohaline flow through the 3D visualization of the evolving patterns generated by the distributions of brine, temperature, and fluid density in the porous medium. We propose a possible physical interpretation of our results, which are obtained within the approximations usually employed in the context of density- and temperature-driven flow.     

A comparative investigation of the packing and flow properties of sweet potato (Ipomoea batatas) starches and their potential use in solid dosage formulations

A comparative evaluation of the flow and packing properties of starch products extracted from three sweet potato (Ipomoea batatas) cultivars grown in Jamaica was done with a view to assessing their suitability as excipients in solid dosage formulations. Significant differences were observed in the properties of the starches obtained from the different sweet potato cultivars (p<0.05). The mean granular diameter ranged from 13.4 ± 0.42 (Eustace) to 20 ± 0.85 µm (Clarendon). Clarendon starch was found to be the least cohesive and bulkiest with Compressibility Index (CI) of 32.69 ± 0.28%, angle of internal flow (θ_i) of 12.70 ± 0.12° and maximum volume reduction (a) of 35.65 ± 1.02%, while Eustace was the most cohesive and least bulky with CI values of 37.74 ± 1.06%, θ_i of 19.68 ± 0.22°, and a of 43.60 ± 0.95%. The starch powders had similar bulk densities and packing fraction (p>0.05). All other fundamental properties calculated from the projected mean diameter including surface mean diameter (d_vs), Heywood equivalent diameter (de) and specific surface (S_w) varied significantly (p<0.05) in a cultivar‐dependent manner but with no consistent pattern of variation among cultivars. The results indicate intravarietal variations in the packing and cohesive properties of the starches studied which may be a result of variations in the fundamental properties of the granules. These differences in properties may prove significant when predicting the behaviour of starches during handling and pharmaceutical formulations.     

Relating carbon monoxide photoproduction to dissolved organic matter functionality

Aqueous solutions of humic substances (HSs) and pure monomeric aromatics were irradiated to investigate the chemical controls upon carbon monoxide (CO) photoproduction from dissolved organic matter (DOM). HSs were isolated from lakes, rivers, marsh, and ocean. Inclusion of humic, fulvic, hydrophobic organic, and hydrophilic organic acid fractions from these environments provided samples diverse in source and isolation protocol. In spite of these major differences, HS absorption coefficients (a) and photoreactivities (a bleaching and CO production) were strongly dependent upon HS aromaticity (r2 > 0.90; n = 11), implying aromatic moieties are the principal chromophores and photoreactants within HSs, and by extension, DOM. Carbonyl carbon and CO photoproduction were not correlated, implying that carbonyl moieties are not quantitatively important in CO photoproduction. CO photoproduction efficiency of aqueous solutions of monomeric aromatic compounds that are common constituents of organic matter varied with the nature of ring substituents. Specifically, electron donating groups increased, while electron withdrawing groups decreased CO photoproductivity, supporting our conclusion that carbonyl substituents are not quantitatively important in CO photoproduction. Significantly, aromatic CO photoproduction efficiency spanned 3 orders of magnitude, indicating that variations in the CO apparent quantum yields of natural DOM may be related to variations in aromatic DOM substituent group chemistry.     

Decoding with Early Termination for Raptor Codes

Rateless codes, and especially Raptor codes, have received considerable attention in the recent past due to their inherent ability to adapt to channel conditions and their capacity- approaching performance. Since decoding of rateless codes typically involves multiple decoding attempts, early termination of such attempts is mandatory for overall efficient decoding. In this letter, we propose a new decoding scheme with early termination that is particularly suited for rateless codes. Simulation results for the example of the binary symmetric channel show complexity reductions (in terms of the total required number of decoding iterations) by 87% compared to conventional message-passing decoding and 54% compared to a recently proposed incremental decoding scheme for Raptor codes.