138,097 research outputs found
Size effect on the coalescence-induced self-propelled droplet
No full textAn analysis based on the energy conservation is presented for the self-propelled droplet during coalescence of two droplets of the same size over a superhydrophobic rough surface. The self-propelled behavior occurs only for the coalescence of droplets with a certain range of radius. An analytical relation is established among the coalescence-induced velocity, surface energy, viscous dissipation, and droplet size if gravity is negligible. The coalescence-induced velocity increases with increasing droplet size to a maximum and then decreases with the size, which is in good accord with the experimental observation reported in the literature. (C) 2011 American Institute of Physics. [doi:10.1063/1.3553782
Also By The Same Author: AKTiveAuthor, a Citation Graph Approach to Name Disambiguation
No full textThe desire for definitive data and the semantic web drive for inference over heterogeneous data sources requires co-reference resolution to be performed on those data. In particular, name disambiguation is required to allow accurate publication lists, citation counts and impact measures to be determined. This paper describes a graph-based approach to author disambiguation on large-scale citation networks. Using self-citation, co-authorship and document source analyses, AKTiveAuthor clusters papers, achieving precision of 0.997 and recall of 0.818 over a test group of eight surname clusters
Quench characteristics of a Cu-Stabilized 2G HTS conductor
No full textThe prospect of medium/high field superconducting magnets using 2G HTS tapes is approaching to reality with continued enhancement in the performance of these conductors. Direct measurements of 1d adiabatic quench initiation and propagation of a Cu-stabilized 2G conductor have been carried out with spatial-temporal recording of temperature and voltage following the deposition of various local heat pulses to the conductor at different temperatures between 40K and 64K carrying different transport currents. It was found that the stabilizer-free 2G tape maintains the unique characteristics previously measured in non-stabilized tape of increasing MPZ with transport current and higher quench energy at lower temperatures. The minimum quench energy, minimum propagation zone (MPZ) length are determined as a function of temperature and transport current. The change in MPZ size is investigated with measured temperature dependent E-J characteristics. The results add more detail to help understand the unique characteristics of increasing MPZ with transport current and lower temperatures
Fiscal decentralization and the size of the government : an extension with evidence from cross-country data
No full textPrior analyses of the relationship between fiscal decentralization and the size of government treat fiscal decentralization as the decentralization of either taxing or spending powers. But decisions about taxation and spending are inseparable. The author corrects this deficiency and analyzes the effect of simultaneous decentralization of taxing and spending powers -"fiscal decentralization"- on the overall size of the public sector using cross-country data. The economic results of his study show that: (a) The simultaneous decentralization of the national government's taxing and spending powers tend to reduce the size of the public sector. (b) The Revenue-sharing arrangements in which decisions about taxation are made by the national government tend to eliminate the constraining effect of the decentralized spending power. What do these findings suggest? Countries, such as economies in transition, that want to reduce the size of the public sector should decentralize both taxing and spending decisions.Banks&Banking Reform,Municipal Financial Management,National Governance,Public Sector Economics&Finance,Economic Theory&Research
Abstraction Refinement Guided by a Learnt Probabilistic Model
No full textThe core challenge in designing an effective static program analysis is to find a good program abstraction -- one that retains only details relevant to a given query. In this paper, we present a new approach for automatically finding such an abstraction. Our approach uses a pessimistic strategy, which can optionally use guidance from a probabilistic model. Our approach applies to parametric static analyses implemented in Datalog, and is based on counterexample-guided abstraction refinement. For each untried abstraction, our probabilistic model provides a probability of success, while the size of the abstraction provides an estimate of its cost in terms of analysis time. Combining these two metrics, probability and cost, our refinement algorithm picks an optimal abstraction. Our probabilistic model is a variant of the Erdos-Renyi random graph model, and it is tunable by what we call hyperparameters. We present a method to learn good values for these hyperparameters, by observing past runs of the analysis on an existing codebase. We evaluate our approach on an object sensitive pointer analysis for Java programs, with two client analyses (PolySite and Downcast)
Effect of nanohole size on selective area growth of InAs nanowire arrays on Si substrates
No full textWe have investigated the influence of nanohole size on selective-area growth (SAG) of InAs nanowire (NW) arrays on Si(111) substrates by metal-organic chemical vapor deposition. The growth of well-defined and position-controlled InAs NW arrays with united vertical orientation can be achieved on the patterned substrates with a certain range of nanohole size, which paves the way for the fabrication of high-electron-mobility and surrounding-gate transistor arrays using NWs as channels. Moreover, it is found that more than one NW are increasingly likely grown per nanohole as the nanohole size increases, and the NWs become increasingly thin and short. This is considered to be due to the supersaturation of adsorbed species in the nanohole and the intense competition for adatoms among multiple NWs per nanohole.MOST of China [2012CB932701]SCI(E)ARTICLE1-446
A mesoscale approach for population balance modeling of bubble size distribution in bubble column reactors
No full text
Prediction of bubble size distribution is of paramount importance for the study of bubble column reactors. Current kernel functions for coalescence or breakage in CFD-PBM simulation are usually derived from the isotropic turbulence theory and overestimate bubble size distribution with increasing gas flow rate. Based on the energy-minimization multi-scale concept, we develop a new approach to calculate the coalescence rate through the so-called stability condition and the meso-scale energy dissipation relevant to bubble breakage and coalescence (Yang et al., 2010). The approach is independent of specific kernel functions, and provides a new constraint to the kernel functions of coalescence or breakage which were previously only related to the turbulence properties through isotropic turbulence theory. New correctors for coalescence rate could then be derived for various kernel models. Our simulation indicates that this new approach can adapt to different coalescence or breakage kernel function models, and can achieve better prediction for bubble size distribution. (C) 2017 Elsevier Ltd. All rights reserved.</p
CityJSON: does (file) size matter?
No full textThe possibilities of 3D city models for the analysis of the built environment are increasingly explored, and there is a continuous development in improvements on their inner workings. They are also used more often on the web, for example for visualisation but it is also possible to query, analyse, and edit data in this way. In this case, the network becomes a potential new bottleneck in time performance. Especially when a 3D city model contains a lot of attributes, there is a rapid increase in file size when the area of study is expanded.This presents challenges in efficiency and in this thesis I focus on the improvement of the inner workings of 3D city models to attempt to relieve this problem, in specific for spreading and using them more efficiently on the web.By investigating and testing different compression techniques on 3D city models stored in the CityJSON format, I have attempted to relieve this problem. CityJSON is already more compact than CityGML and these techniques decrease the file sizes of datasets even further, allowing for faster transmission over a network. But on the other hand, additional steps are needed to process compressed files. The goal of using a compression technique is to result in a net speed gain, meaning that the time that is saved on download time should be larger than the additional time that it costs to process the file before transmission (compressing the data on the server) and after receival (decompressing the data in the client).There are compression techniques for both general and specific purposes, and I have used combinations of them. Amongst these are Draco compression, zlib, CBOR, and a self-created technique. Specific ones are used for the main characteristics that CityJSON datasets have, which are the JSON structure, feature attributes, and feature geometries. To assess the impact that different combinations of compression techniques have, I take uncompressed CityJSON performance as the baseline and have come up with different performance indicators that include several use cases such as visualisation, querying, analysis, and editing.I have benchmarked all combinations of compression techniques on the use cases of these performance indicators. For this I have created two types of server implementations: one with which datasets are compressed beforehand and are processed in the client based on the request made by the user, and one where the data is processed first and only then compressed and transmitted to the server. In the results, you can see the best-performing compression type per use case.The benchmarking is performed on a variety of datasets that are split into four categories: larger datasets, larger datasets without attributes, smaller datasets, and smaller datasets without attributes. This ultimately makes for use cases that are very specific and choosing suitable compression types requires finding out which ones perform relatively well in most cases, and are not difficult to implement in order to keep CityJSON a simple file format. It turns out that Draco compression can give good results in specifc situations, but in general is not good to use. Not only regarding performance, but also from a developer point of view. CBOR, zlib, and a combination of these two are easy to use and generally affect the performance of CityJSON on the web in a good way.https://github.com/jliempt/CityJSON-does-file-size-matter-Geomatic
Size-Dependent Hydrogenation Activity of Cobalt Nanoparticles
No full textCobalt nanoparticles are widely used
as hydrogenation catalysts
but the chemical nature of the particle size effect in hydrogenation
reactions remains a matter of debate. Here, the hydrogenation activity
of 3.5–40 nm large Co particles supported on C3N4 was probed employing acetone hydrogenation because two distinctive
acetone conversion pathways exist: its direct hydrogenation to isopropanol
and alternatively, its initial dehydration to mesityl oxide and subsequent
hydrogenation to methyl isobutyl ketone. The acetone hydrogenation
turnover frequency per Co surface atom increased with Co particle
size up to 40 nm. In contrast, the acetone conversion rates were an
order of magnitude smaller and declined with increasing particle size
in the absence of H2. Moreover, only particles larger than
∼10 nm converted a 1:1 H2/acetone feed efficiently
to isopropanol (>90%) between 150 and 250 °C. Acetone dehydration
to mesityl oxide was increasingly favored on the smaller Co particles.
Interestingly, the subsequent hydrogenation of mesityl oxide to methyl
isobutyl ketone exhibited a Co particle size dependence analogous
to isopropanol formation, while the secondary dehydration of isopropanol
to propene was rather insensitive to the particle size. H–D
exchange experiments demonstrated that H2 activation via
dissociative adsorption was increasingly retarded with decreasing
Co particle size. Conversely, acetone activation became more difficult
with increasing particle size according to its in parallel diminishing
dehydration rate in the absence of H2. Hence, the activation
of H2 on the metal particles has to play a key role in
the Co particle size dependence of acetone hydrogenation
Size effect in the bending of a Timoshenko nanobeam
No full textThe size effect should be considered due to the large ratio of surface area to volume when the characteristic length of a beam lies in the nanoscale. The size effect in the bending of a Timoshenko nanobeam is investigated in this paper based on a recently developed elastic theory for nanomaterials in which only the bulk surface energy density and the surface relaxation parameter are involved as independent parameters to characterize the surface property of nanomaterials. In contrast to the Euler nanobeams and the classical Timoshenko beam not only the size effect but also the shear deformation effect in Timoshenko nanobeams is included. Closed-form solutions of the deflection and the effective elastic modulus for both a fixed-fixed Timoshenko nanobeam and a cantilevered one are achieved. Comparing to the classical solution of Timoshenko beams the size effect is obviously significant in Timoshenko nanobeams. The shear deformation effect in nanobeams cannot be neglected in contrast to the solution of Euler-Bernoulli nanobeams when the aspect ratio of a nanobeam is relatively small. Furthermore the size effect exhibits different influences on the bending behavior of nanobeams with different boundary conditions. A nanobeam with a fixed-fixed boundary would be stiffened while a cantilevered one is softened by the size effect compared to the classical solution. All the findings are consistent with the existing experimental measurement. The results in this paper should be very useful for the precision design of nanobeam-based devices
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