128 research outputs found

    Improving the resolution of Non-Invasive Time Domain Reflectometry

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    Non invasive time domain reflectometry (TDR) may be used to estimate the volumetric moisture content, θᵥ, with depth for a variety of sample materials. The forward physical model is couched in terms of a moments method where integration is performed over a discretised sample space to estimate the measured propagation time, tp down a pair of parallel transmission lines. We show that inverse solution to this, which recovers relative permittivity and thus θᵥ, is greatly facilitated by a simplification of the system geometry via, 1) realistically modeling the prior density of the sample, 2) using this prior with the inherent system symmetry to reduce the number of required discretisation cells, and 3) determining a physically meaningful reduction operator to allow a coarse discretisation mesh to be used. The observational equation is expressed in the Bayesian paradigm with the most accurate and robust solution obtained using the conditional mean of the posterior distribution constructed via a Monte Carlo method. Results of simulation show that the method is capable of providing accurate estimates of the moisture density profile down to a depth of 100 mm with an error < 4%. Further, the reduction in the number of discretised cells required to accurately estimate these profiles means that the inversion procedure is quick enough to enable the real time application of the equipment, a fundamental requirement in the development

    Відображення розвитку науки України та Євросоюзу в реферативній базі даних SCOPUS

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    Досліджено публікаційну активність України та Євросоюзу за галузями науки. Розглянуто динаміку кількості публікацій, що припадають на одного дослідника впродовж 1996-2010 рр. Виконано порівняння відображення кількості публікацій БД Scopus у ВВП та витратах на НДДКР країн в розрахунку на кожен 1 млн. дол. США.Исследована публикационная активность Украины и Евросоюза по отраслям науки. Рассмотрена динамика количества публикаций, которые приходятся на одного исследователя на протяжении 1996–2010 гг. Сделано сравнение отображения количества публикаций БД Scopus в ВВП и затратах на НДДКР стран в расчете на каждый 1 млн. дол. США.The publication activity by fields of science of Ukraine and the European Union was investigated. The dynamics of the number of publications per 1 researcher was considered during 1996–2010 years. Countries comparison by the number of publications reflecting in GDP and R&D expenditures per 1 million U.S. dollars measurements in the abstract database Scopus was done

    The Combinatorics of Alternating Tangles: from theory to computerized enumeration

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    We study the enumeration of alternating links and tangles, considered up to topological (flype) equivalences. A weight nn is given to each connected component, and in particular the limit n0n\to 0 yields information about (alternating) knots. Using a finite renormalization scheme for an associated matrix model, we first reduce the task to that of enumerating planar tetravalent diagrams with two types of vertices (self-intersections and tangencies), where now the subtle issue of topological equivalences has been eliminated. The number of such diagrams with pp vertices scales as 12p12^p for pp\to\infty. We next show how to efficiently enumerate these diagrams (in time 2.7p\sim 2.7^p) by using a transfer matrix method. We give results for various generating functions up to 22 crossings. We then comment on their large-order asymptotic behavior.Comment: proceedings European Summer School St-Petersburg 200

    Poly(dimethylsiloxane) as a pre-coating in layer-by-layer films containing phosphotungstate nanoclusters electrochemically sensitive toward s-triazines

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    One of the major advantages of the Layer-by-Layer (LbL) deposition technique is the possible control of molecular architecture, not only to achieve optimized properties but also to seek synergy among different materials. In this study, LbL films containing nanoclusters of a Keggin type polyoxometalate, phosphotungstic acid (HPW), alternated with the polycation poly(allylamine hydrochloride) (PAH) were deposited on indium-tin oxide (ITO) substrates. The electrochemical properties of the hybrid LbL film investigated in acidic conditions indicated no significant desorption of HPW, when a layer of poly(dimethylsiloxane) terminated with 3-aminopropyl groups (PDMS) was previously deposited on the ITO substrate. Such effect occurred because PDMS prevents desorption of HPW from the hybrid film, as shown by X-ray Photoelectron Spectroscopy (XPS) analyses. The porous structures of the films were revealed by Fourier transform infrared reflection absorption spectroscopy, scanning electron microscopy and XPS. PDMS/PAH as a pre-coating allowed the HPW/PAH films to be sensitive to the electrochemical detection of the triazines atrazine and melamine. In conclusion, the precise control of the LbL films architecture is important to develop opportunities for new applications. © 2014 The Royal Society of Chemistry.One of the major advantages of the Layer-by-Layer (LbL) deposition technique is the possible control of molecular architecture, not only to achieve optimized properties but also to seek synergy among different materials. 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    Peptide immobilisation on porous silicon surface for metal ions detection

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    In this work, a Glycyl-Histidyl-Glycyl-Histidine (GlyHisGlyHis) peptide is covalently anchored to the porous silicon PSi surface using a multi-step reaction scheme compatible with the mild conditions required for preserving the probe activity. In a first step, alkene precursors are grafted onto the hydrogenated PSi surface using the hydrosilylation route, allowing for the formation of a carboxyl-terminated monolayer which is activated by reaction with N-hydroxysuccinimide in the presence of a peptide-coupling carbodiimide N-ethyl-N'-(3-dimethylaminopropyl)-carbodiimide and subsequently reacted with the amino linker of the peptide to form a covalent amide bond. Infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy are used to investigate the different steps of functionalization
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