7,536 research outputs found
Bounded model checking of multi-threaded c programs via lazy sequentialization
No full textBounded model checking (BMC) has successfully been used for many practical program verification problems, but concurrency still poses a challenge. Here we describe a new approach to BMC of sequentially consistent C programs using POSIX threads. Our approach first translates a multi-threaded C program into a nondeterministic sequential C program that preserves reachability for all round-robin schedules with a given bound on the number of rounds. It then re-uses existing high-performance BMC tools as backends for the sequential verification problem. Our translation is carefully designed to introduce very small memory overheads and very few sources of nondeterminism, so that it produces tight SAT/SMT formulae, and is thus very effective in practice: our prototype won the concurrency category of SV-COMP14. It solved all verification tasks successfully and was 30x faster than the best tool with native concurrency handling.<br/
Scattering of harmonic P1 and SV waves by a shallow lined circular tunnel in a poroelastic half-plane
No full textAn analytical solution for the scattering of harmonic P1 and SV waves in a poroelastic half-plane with a shallow lined tunnel is obtained using the plane complex theory in elastodynamics. In light of the wave function expansions, the wave fields of the poroelastic medium and the liner with unknown coefficients are obtained based on Biot's theory and Helmholtz decomposition. Complex-valued expressions of the effective stresses, the fluid stress, and the displacements of the poroelastic medium and the liner are expressed by the complex variable function method and the conformal transformation technique. With the boundary conditions and the continuity of the medium-liner interface, the boundary value problem results in a series of algebraic equations. The unknown coefficients in the infinite set of algebraic equations can be solved numerically by truncating the series number. A parametric study for the incident SV waves is performed to investigate dynamic stress concentrations and fluid stress of the medium and the liner. Numerical results show that the embedment depth of the tunnel, the incident angle of the excitations, and the porosity of the medium have considerable influence on the dynamic responses of the medium and the liner. The shielding effect of the tunnel on the incident SV waves is obvious. For the big embedment depth of the tunnel, the scattered waves contribute little to the displacements and dynamic stress concentration of the medium and the liner. For a high porosity close to the critical value, the response of the medium-liner system to the incident waves is great.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Dynamics of Structure
Approaches to Improving the Selectivity of Nanozymes
No full textNanozymes mimic enzymes and that includes their selectivity. To achieve selectivity, significant inspiration for nanoparticle design can come from the geometric and molecular features that make enzymes selective catalysts. The two central features enzymes use are control over the arrangement of atoms in the active site and the placing of the active site down a nanoconfined substrate channel. The implementation of enzyme-inspired features has already been shown to both improve activity and selectivity of nanoparticles for a variety of catalytic and sensing applications. The tuning and control of active sites on metal nanoparticle surfaces ranges from simply changing the composition of the surface metal to sophisticated approaches such as the immobilization of single atoms on a metal substrate. Molecular frameworks provide a powerful platform for the implementation of isolated and discrete active sites while unique diffusional environments further improve selectivity. The implementation of nanoconfined substrate channels around these highly controlled active sites offers further ability to control selectivity through altering the solution environment and transport of reactants and products. Implementing these strategies together offers a unique opportunity to improve nanozyme selectivity in both sensing and catalysis.Full Tex
Seismic Responses of a Hemispherical Alluvial Valley to SV Waves: A Three-Dimensional Analytical Approximation
No full textAn analytical solution to the three-dimensional scattering and diffraction of plane SV-waves by a saturated hemispherical alluvial valley in elastic half-space is obtained by using Fourier-Bessel series expansion technique. The hemispherical alluvial valley with saturated soil deposits is simulated with Biot's dynamic theory for saturated porous media. The following conclusions based on numerical results can be drawn: (1) there are a significant differences in the seismic response simulation between the previous single-phase models and the present two-phase model; (2) the normalized displacements on the free surface of the alluvial valley depend mainly on the incident wave angles, the dimensionless frequency of the incident SV waves and the porosity of sediments; (3) with the increase of the incident angle, the displacement distributions become more complicated; and the displacements on the free surface of the alluvial valley increase as the porosity of sediments increases
Analysis of 2D homogeneous space solutions of the seismoelectric P-SV-TM mode for interferometric purposes
No full textSeismic and electromagnetic imaging methods both provide the geophysicist with different types of medium parameters. Seismic methods are sensitive to the elastic properties of the medium, while electromagnetic methods are sensitive to the electric properties. In porous-saturated media, these two wave fields occur as a coupled system, which is known as 'seismoelectrics'. This coupling is caused by physical interactions at the grain surface boundary and is a function of several medium parameters, such as dynamic permeability. This medium parameter is valuable to the oil and gas industry, as well to the field of hydrology. By conducting a seismoelectric survey it would theoretically be possible to provide an extra control on this medium parameter. However, both practice and theory have shown that this coupling mechanism also results in a low signal-to-noise ratio. A possible solution to this problem would be to apply interferometric Green's retrieval, which is a technique based on stacking of cross-correlated data. This approach has been proved successful for the SH-TE mode in 1D. The SH-TE mode forms together with the P-SV-TM mode, the total seismoelectric system. In this thesis the first steps are taken towards the proof that this technique could also work for the P-SV-TM mode of the system. This is supported by a modelling experiment of 2D homogeneous space solutions of the seismoelectric P-SV-TM mode for different configurations. This analysis turned out that the unwanted artefacts observed in the interferometric retrieval are generated by cross-correlations between P-waves and SV-waves.IDEA League Joint Master's in Applied GeophysicsGeoscience & EngineeringCivil Engineering and Geoscience
The response of SV-HFO cells to Ti6Al7Nb surfaces modified by Plasma Electrolytic Oxidation
No full textThe aim of this study was to assess the response of preosteoblasts (SV-HFO), from adhesion to matrix mineralization, on Ti6Al7Nb surfaces modified by plasma electrolytic oxidation (PEO). Two different surfaces have been generated by changing the oxidation duration from 1 to 5 minutes. The resultant (PEO1 and PEO5) surfaces showed uniform porous topographies with pores mostly in the submicron range and a mixture of anatase and rutile TiO2 phases. However, the average surface roughness, maximum peak-to-valley height, pore size and Ca/P ratio increased with oxidation time whereas pore density and surface porosity decreased. On the PEO1 surface SV-HFO cells attached and spread easily using the pores as anchoring sites for their extensions and showing cell-cell contact after 48 hours. The larger pores protruding from the PEO5 surface suppressed cell adhesion. Deposition of extracellular matrix started earlier on the PEO1 surface and after 21 incubation days a net-like structure well integrated with the porous surface was visible. Matrix mineralization was evidenced on both surfaces after 21 days. However, more uniform mineralized areas were observed on the PEO1 surface whereas an accelerated mineralization was noticed after 14 days on the PEO5 surface. In conclusion, by varying only one PEO process condition, significant changes occurred on the surface of Ti6Al7Nb alloy, which influenced both the early and late response of SV-HFO cells. The observed surface-induced effects indicated that surfaces produced at shorter oxidation time may be more beneficial for early osteogenesis.BMEBioMechanical EngineeringMechanical, Maritime and Materials Engineerin
Pysim-sv: a package for simulating structural variation data with GC-biases
Full text linkBackground: Structural variations (SVs) are wide-spread in human genomes and may have important implications in disease-related and evolutionary studies. High-throughput sequencing (HTS) has become a major platform for SV detection and simulation serves as a powerful and cost-effective approach for benchmarking SV detection algorithms. Accurate performance assessment by simulation requires the simulator capable of generating simulation data with all important features of real data, such GC biases in HTS data and various complexities in tumor data. However, no available package has systematically addressed all issues in data simulation for SV benchmarking. Results: Pysim-sv is a package for simulating HTS data to evaluate performance of SV detection algorithms. Pysim-sv can introduce a wide spectrum of germline and somatic genomic variations. The package contains functionalities to simulate tumor data with aneuploidy and heterogeneous subclones, which is very useful in assessing algorithm performance in tumor studies. Furthermore, Pysim-sv can introduce GC-bias, the most important and prevalent bias in HTS data, in the simulated HTS data. Conclusions: Pysim-sv provides an unbiased toolkit for evaluating HTS-based SV detection algorithms.National Key Basic Research Project of China [2015CB856000]; National Natural Science Foundation of China [11471022, 71532001]; Recruitment Program of Global Youth Experts of ChinaSCI(E)ARTICLE1
Seismoelectric Modelling of the Flux-Normalized P-SV-TM Propagation Mode
No full textElastodynamic and electromagnetic processes are coupled together in saturated, porous media, by a phenomenon known as the electrokinetic effect. In horizontally layered media, the seismoelectric system, which contains the coupled elastodynamic and electromagnetic systems, can be separated into two independent modes of propagation: SH-TE and P-SV-TM. The SH-TE mode contains horizontally polarized shear waves coupled with transverse electric polarized electromagnetic waves. In the P-SV-TM mode, both fast and slow compressional waves are coupled with vertically polarized shear waves and transverse magnetic polarized electromagnetic waves. In this thesis, the P-SV-TM mode of the two-dimensional seismoelectric system was expressed in the form of both the two-way and one-way wave equations. The principle of normalizing energy flux across boundaries was applied, improving the matrix amplitude balance of the system and allowing for the implementation of one-way reciprocity theorems. We carried out full-waveform modelling of the flux-normalized P-SV-TM seismoelectric system in a 2-D fluid-saturated, horizontally-stratified, porous media. Both one-way and two-way wavefields were modelled, allowing the composition of one-way wavefields into two-way wavefields to be clearly observed. We investigated both the generation of electromagnetic fields due to the propagation of a seismic pertubation and the generation of seismic waves due to the propagation of a diffusive electromagnetic wave. Reciprocity of the wavefields was verified by applying reciprocity theorems to both one-way and two-way wave vectors. The electromagnetic field that is created when a seismic wave traverses a contrast in medium parameters is rapidly attenuated during propagation. To mitigate the decay in the amplitude of the signal with distance, we modelled a Vertical ElectroSeismic Profiling (VESP) survey, in which receivers could be placed in near proximity to the target layer. In another model, the sensitivity of the seismoelectric method to pore fluid contrasts was tested by simulating the influx of contaminants into an aquifer. It was observed that a small change in the conductivity of the aquifer led to a significant change in the strength of the electromagnetic signal that was generated at the top of the aquifer.Applied Geophysics and PetrophysicsGeotechnologyCivil Engineering and Geoscience
Wellcome Witnesses to Twentieth Century Medicine: Volume 1
No full textAnnotated and edited transcript of four Witness Seminars. Introduction by E M Tansey First published by the Wellcome Trust, 1997. ©The Trustee of the Wellcome Trust, London, 1997.In Volume One (Occasional Publication no. 4, 1997).All volumes are freely available online at: www.history.qmul.ac.uk/research/modbiomed/wellcome_witnesses/Annotated and edited transcript of four Witness Seminars. Introduction by E M Tansey.Annotated and edited transcript of four Witness Seminars. Introduction by E M Tansey.Annotated and edited transcript of four Witness Seminars. Introduction by E M Tansey.Annotated and edited transcript of four Witness Seminars. Introduction by E M Tansey.Four Witness Seminar transcripts of meetings held between 1993 and 1996: ‘Technology Transfer in Britain: The case of Monoclonal Antibodies’ (E M Tansey and P P Catterall, eds); ‘Self and Non-Self: A History of Autoimmunity’ (E M Tansey, S V Willhoft and D A Christie, eds); ‘Endogenous Opiates’ (E M Tansey and D A Christie, eds); ‘The Committee on Safety of Drugs’ (E M Tansey and L A Reynolds, eds). Introduction by E M Tansey, ‘What is a Witness Seminar’, separate index for each meeting. Tansey E M, Catterall P P, Christie D A, Willhoft S V, Reynolds L A. (eds) (1997) Wellcome Witnesses to Twentieth Century Medicine, volume 1. London: The Wellcome Trust.The Wellcome Trust is a registered charity, no. 210183
Medalja prokuratora škrinje sv. Šimuna iz 1600. godine
Full text linkThe author describes the making and the purpose of the slightly forgotten medal that was cast to mark the construction of St Simeon’s Church in Zadar. The medal was cast in bronze in the baroque style and is dedicated to the keepers of the relics of St Simeon and the supervisors of the construction of the church. There is only one known specimen of the medal. For a time it was kept in the Lanza Collection. Later it was donated to the Zadar Archaeological Museum, at that time located in St Donat’s Church. Later the medal was moved to the sacristy of today’s St Simeon’s Church. This church was fully renovated and reconstructed in 1984 so the medal, probably because of construction work in the church, was moved to the holdings of the Permanent Collection of Religious Art. The medal is an extremely important artifact from the history of Zadar and its cultural heritage. For better understanding the author provides a short description and chronology of medal making in Dalmatia.Autor opisuje nastanak i svrhu pomalo zaboravljene medalje izrađene povodom izgradnje crkve sv. Šimuna u Zadru. Medalja je izrađena u bronci u stilu baroka i posvećena je čuvarima relikvija sv. Šimuna te nadzirateljima izgradnje crkve. Poznat je samo jedan primjerak te medalje. Neko vrijeme bila je u zbirci Lanza. Kasnije je donirana zadarskom Arheološkom muzeju koji je u to vrijeme bio smješten u crkvi sv. Donata. Naknadno je medalja bila prenesena u sakristiju današnje crkve sv. Šimuna. Ta je crkva temeljito renovirana i rekonstruirana 1984. godine pa je zbog građevinskih radova na crkvi medalja najvjerojatnije premještena u depo muzeja Stalne izložbe crkvene umjetnosti (SICU). Medalja je iznimno važan artefakt za povijest grada Zadra i njegova kulturnog naslijeđa. Radi boljeg razumijevanja ukratko se opisuje kronologija medaljerstva u Dalmaciji
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