811 research outputs found
The Distribution and Importance of Arthropod Pests and Weeds of Agriculture and Forestry Plantations in Southern China
Crop Production/Industries,
MILC Code Performance on High End CPU and GPU Supercomputer Clusters
With recent developments in parallel supercomputing architecture, many core,
multi-core, and GPU processors are now commonplace, resulting in more levels of
parallelism, memory hierarchy, and programming complexity. It has been
necessary to adapt the MILC code to these new processors starting with NVIDIA
GPUs, and more recently, the Intel Xeon Phi processors. We report on our
efforts to port and optimize our code for the Intel Knights Landing
architecture. We consider performance of the MILC code with MPI and OpenMP, and
optimizations with QOPQDP and QPhiX. For the latter approach, we concentrate on
the staggered conjugate gradient and gauge force. We also consider performance
on recent NVIDIA GPUs using the QUDA library
Reverse engineering small 4-manifolds
We introduce a general procedure called `reverse engineering' that can be
used to construct infinite families of smooth 4-manifolds in a given
homeomorphism type. As one of the applications of this technique, we produce an
infinite family of pairwise nondiffeomorphic 4-manifolds homeomorphic to
CP^2#3(-CP^2).Comment: 13 pages, 2 figures. This is the final version published in AGT,
volume 7 (2007), pp. 2103-2116
MILC staggered conjugate gradient performance on Intel KNL
We review our work done to optimize the staggered conjugate gradient (CG)
algorithm in the MILC code for use with the Intel Knights Landing (KNL)
architecture. KNL is the second gener- ation Intel Xeon Phi processor. It is
capable of massive thread parallelism, data parallelism, and high on-board
memory bandwidth and is being adopted in supercomputing centers for scientific
research. The CG solver consumes the majority of time in production running, so
we have spent most of our effort on it. We compare performance of an MPI+OpenMP
baseline version of the MILC code with a version incorporating the QPhiX
staggered CG solver, for both one-node and multi-node runs.Comment: 8 pages, 4 figure
Enhanced Blackhole mergers in AGN discs due to Precession induced resonances
Recent studies have shown that AGN discs can host sources of gravitational
waves. Compact binaries can form and merge in AGN discs through their
interactions with the gas and other compact objects in the disc. It is also
possible for the binaries to shorten the merging timescale due to eccentricity
excitation caused by perturbations from the supermassive blackhole (SMBH). In
this paper we focus on effects due to precession-induced (eviction-like)
resonances, where nodal and apsidal precession rates of the binary is
commensurable with the mean motion of the binary around the SMBH. We focus on
intermediate mass black hole (IMBH)-stellar mass black hole (SBH) binaries, and
consider binary orbit inclined from the circum-IMBH disk which leads to the
orbital precession. We show that if a binary is captured in these
resonances and is migrating towards the companion, it can undergo large
eccentricity and inclination variations. We derive analytical expressions for
the location of fixed points, libration timescale and width for these
resonances, and identified two resonances in the near coplanar regime (the
evection and eviction resonances) as well as two resonances in the near polar
regime that can lead to mergers. We also derive analytical expressions for the
maximum eccentricity that a migrating binary can achieve for given initial
conditions. Specifically, the maximum eccentricity can reach 0.9 when captured
in these resonances before orbital decay due to gravitational wave emission
dominates, and the capture is only possible for slow migration ( Myr)
2-3 order of magnitude longer than the resonance libration timescale. We also
show that capture into multiple resonances is possible, and can further excite
eccentricities.Comment: Accepted for publication in Ap
Decreased electrophysiologic responsiveness to catecholamines in an experimental model of heart failure in the dog
Modeling EMI Resulting from a Signal Via Transition Through Power/Ground Layers
Signal transitioning through layers on vias are very common in multi-layer printed circuit board (PCB) design. For a signal via transitioning through the internal power and ground planes, the return current must switch from one reference plane to another reference plane. The discontinuity of the return current at the via excites the power and ground planes, and results in noise on the power bus that can lead to signal integrity, as well as EMI problems. Numerical methods, such as the finite-difference time-domain (FDTD), Moment of Methods (MoM), and partial element equivalent circuit (PEEC) method, were employed herein to study this problem. The modeled results are supported by measurements. In addition, a common EMI mitigation approach of adding a decoupling capacitor was investigated with the FDTD method
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