3,842 research outputs found
A continuum-microscopic method based on IRBFs and control volume scheme for viscoelastic fluid flows
A numerical computation of continuum-microscopic model for visco-elastic flows based on the Integrated Radial Basis Function (IRBF) Control Volume and the Stochastic Simulation Techniques (SST) is reported in this paper. The macroscopic flow equations are closed by a stochastic equation for the extra stress at the microscopic level. The former are discretised by a 1D-IRBF-CV method while the latter is integrated with Euler explicit or Predictor-Corrector schemes. Modelling is very efficient as it is based on Cartesian grid, while the integrated RBF approach enhances both the stability of the procedure and the accuracy of the solution. The proposed method is demonstrated with the solution of the start-up Couette flow of the Hookean and FENE dumbbell model fluids
The Flexible Group Spatial Keyword Query
We present a new class of service for location based social networks, called
the Flexible Group Spatial Keyword Query, which enables a group of users to
collectively find a point of interest (POI) that optimizes an aggregate cost
function combining both spatial distances and keyword similarities. In
addition, our query service allows users to consider the tradeoffs between
obtaining a sub-optimal solution for the entire group and obtaining an
optimimized solution but only for a subgroup.
We propose algorithms to process three variants of the query: (i) the group
nearest neighbor with keywords query, which finds a POI that optimizes the
aggregate cost function for the whole group of size n, (ii) the subgroup
nearest neighbor with keywords query, which finds the optimal subgroup and a
POI that optimizes the aggregate cost function for a given subgroup size m (m
<= n), and (iii) the multiple subgroup nearest neighbor with keywords query,
which finds optimal subgroups and corresponding POIs for each of the subgroup
sizes in the range [m, n]. We design query processing algorithms based on
branch-and-bound and best-first paradigms. Finally, we provide theoretical
bounds and conduct extensive experiments with two real datasets which verify
the effectiveness and efficiency of the proposed algorithms.Comment: 12 page
Partitioning SKA Dataflows for Optimal Graph Execution
Optimizing data-intensive workflow execution is essential to many modern
scientific projects such as the Square Kilometre Array (SKA), which will be the
largest radio telescope in the world, collecting terabytes of data per second
for the next few decades. At the core of the SKA Science Data Processor is the
graph execution engine, scheduling tens of thousands of algorithmic components
to ingest and transform millions of parallel data chunks in order to solve a
series of large-scale inverse problems within the power budget. To tackle this
challenge, we have developed the Data Activated Liu Graph Engine (DALiuGE) to
manage data processing pipelines for several SKA pathfinder projects. In this
paper, we discuss the DALiuGE graph scheduling sub-system. By extending
previous studies on graph scheduling and partitioning, we lay the foundation on
which we can develop polynomial time optimization methods that minimize both
workflow execution time and resource footprint while satisfying resource
constraints imposed by individual algorithms. We show preliminary results
obtained from three radio astronomy data pipelines.Comment: Accepted in HPDC ScienceCloud 2018 Worksho
Cybersecurity, Technology, and Society: Developing an Interdisciplinary, Open, General Education Cybersecurity Course
This paper describes an interdisciplinary effort involving faculty from five different disciplines who came together to develop an interdisciplinary, open, general education cybersecurity course. The course, Cybersecurity, Technology, and Society, brings together ideas from interdisciplinary studies, information technology, engineering, business, computer science, criminal justice, and philosophy to provide students an interdisciplinary introduction to cybersecurity. We provide an overview of the rationale for the course, the process the authors went through developing the course, a summary of the course modules, details about the open education resources used as readings, and the types of assignments included in the class. We conclude by offering recommendations for others developing similar courses
Effect of Reducing Atmosphere on the Magnetism of Zn1-xCoxO Nanoparticles
We report the crystal structure and magnetic properties of Zn1-xCoxO
nanoparticles synthesized by heating metal acetates in organic solvent. The
nanoparticles were crystallized in wurtzite ZnO structure after annealing in
air and in a forming gas (Ar95%+H5%). The X-ray diffraction and X-ray
photoemission spectroscopy (XPS) data for different Co content show clear
evidence for the Co+2 ions in tetrahedral symmetry, indicating the substitution
of Co+2 in ZnO lattice. However samples with x=0.08 and higher cobalt content
also indicate the presence of Co metal clusters. Only those samples annealed in
the reducing atmosphere of the forming gas, and that showed the presence of
oxygen vacancies, exhibited ferromagnetism at room temperature. The air
annealed samples remained non-magnetic down to 77K. The essential ingredient in
achieving room temperature ferromagnetism in these Zn1-xCoxO nanoparticles was
found to be the presence of additional carriers generated by the presence of
the oxygen vacancies.Comment: 11 pages, 6 figures, submitted to Nanotechnology IO
Multiple column high-throughput e-beam inspection (EBI)
Single-column e-beam systems are used in production for the detection of electrical defects, but are too slow to be used for the detection of small physical defects, and can't meet future inspection requirements. This paper presents a multiple-column e-beam technology for high throughput wafer inspection.
Multibeam has developed all-electrostatic columns for high-resolution imaging. The elimination of magnetic coils enables the columns to be small; e-beam deflection is faster in the absence of magnetic hysteresis. Multiple miniature-columns are assembled in an array. An array of 100 columns covers the entire surface of a 300mm wafer, affording
simultaneous cross-wafer sampling. Column performance simulations and system architecture are presented. Also provided are examples of high throughput, more efficient, multiple-column wafer inspection
A Uniform Description of the States Recently Observed at B-factories
The newly found states Y(4260), Y(4361), Y(4664) and Z(4430) stir broad
interest in the study of spectroscopy in a typical charmonium scale. The
Y(4260) which was observed earlier has been interpreted as hybrid, molecular
state, and baryonium, etc. In this note we show for the first time that these
new structures, which are hard to be interpreted as charmonium states, can be
systematically embedded into an extended baryonium picture. According to this
assignment, the so far known characters of these states are understandable.
And, in the same framework, we make some predictions for experimenters to
measure in the future.Comment: 6 pages in Latex. to appear in J.Phys.
Quantum Criticality of an Ising-like Spin-1/2 Antiferromagnetic Chain in Transverse Magnetic Field
We report on magnetization, sound velocity, and magnetocaloric-effect
measurements of the Ising-like spin-1/2 antiferromagnetic chain system
BaCoVO as a function of temperature down to 1.3 K and applied
transverse magnetic field up to 60 T. While across the N\'{e}el temperature of
K anomalies in magnetization and sound velocity confirm the
antiferromagnetic ordering transition, at the lowest temperature the
field-dependent measurements reveal a sharp softening of sound velocity
and a clear minimum of temperature at T,
indicating the suppression of the antiferromagnetic order. At higher fields,
the curve shows a broad minimum at T, accompanied by a
broad minimum in the sound velocity and a saturation-like magnetization. These
features signal a quantum phase transition which is further characterized by
the divergent behavior of the Gr\"{u}neisen parameter . By contrast, around the critical field, the
Gr\"{u}neisen parameter converges as temperature decreases, pointing to a
quantum critical point of the one-dimensional transverse-field Ising model.Comment: Phys. Rev. Lett., to appea
Highly efficient synthesis of the tricyclic core of Taxol by cascade metathesis
An efficient enantioselective synthesis of the ABC tricyclic core of the anticancer drug Taxol is reported. The key step of this synthesis is a cascade metathesis reaction, which leads in one operation to the required tricycle if appropriate fine-tuning of the dienyne precursor is performed
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