4,834 research outputs found
The Chern Coefficient and Cohen-Macaulay rings
The purpose of this paper is to investigate a relationship between the index
of reducibility and the Chern coefficient for primary ideals. Therefore, the
main result of this paper gives a characterization of a Cohen-Macaulay ring in
terms of its the index of reducibility, its Cohen-Macaulay type, and the Chern
coefficient for parameter ideals. As corollaries to the main theorem we
obtained the characterizations of a Gorenstein ring in term of its Chern
coefficient for parameter ideals
A Self-Consistent Model for the Formation of Relativistic Outflows in Advection-Dominated Accretion Disks with Shocks
In this Letter, we suggest that the relativistic protons powering the
outflows emanating from radio-loud systems containing black holes are
accelerated at standing, centrifugally-supported shocks in hot,
advection-dominated accretion disks. Such disks are ideal sites for first-order
Fermi acceleration at shocks because the gas is tenuous, and consequently the
mean free path for particle-particle collisions generally exceeds the thickness
of the disk. The accelerated particles are therefore able to avoid
thermalization, and as a result a small fraction of them achieve very high
energies and escape from the disk. In our approach the hydrodynamics and the
particle acceleration are coupled and the solutions are obtained
self-consistently based on a rigorous mathematical treatment. The theoretical
analysis of the particle transport parallels the early studies of cosmic-ray
acceleration in supernova shock waves. We find that particle acceleration in
the vicinity of the shock can extract enough energy to power a relativistic
jet. Using physical parameters appropriate for M87 and Sgr A*, we confirm that
the jet kinetic luminosities predicted by the theory agree with the
observational estimates.Comment: accepted for publication in Astrophysical Journal Letter
Hilbert functions of socle ideals
In this paper, we explore a relationship between Hilbert functions and the
irreducible decompositions of ideals in local rings. Applications are given to
characterize the regularity, Gorensteinness, Cohen-Macaulayness and
sequentially Cohen-Macaulayness of local rings.Comment: arXiv admin note: substantial text overlap with arXiv:1504.0604
Face Alignment Using Active Shape Model And Support Vector Machine
The Active Shape Model (ASM) is one of the most popular local texture models
for face alignment. It applies in many fields such as locating facial features
in the image, face synthesis, etc. However, the experimental results show that
the accuracy of the classical ASM for some applications is not high. This paper
suggests some improvements on the classical ASM to increase the performance of
the model in the application: face alignment. Four of our major improvements
include: i) building a model combining Sobel filter and the 2-D profile in
searching face in image; ii) applying Canny algorithm for the enhancement edge
on image; iii) Support Vector Machine (SVM) is used to classify landmarks on
face, in order to determine exactly location of these landmarks support for
ASM; iv)automatically adjust 2-D profile in the multi-level model based on the
size of the input image. The experimental results on Caltech face database and
Technical University of Denmark database (imm_face) show that our proposed
improvement leads to far better performance.Comment: 11 pages and 11 figure
Jet Launching Radius in Low-Power Radio-Loud AGNs in Advection-Dominated Accretion Flows
Using our theory for the production of relativistic outflows, we estimate the
jet launching radius and the inferred mass accretion rate for 52 low-power
radio-loud AGNs based on the observed jet powers. Our analysis indicates that
(1) a significant fraction of the accreted energy is required to convert the
accreted mass to relativistic energy particles for the production of the jets
near the event horizon, (2) the jets launching radius moves radially toward the
horizon as the mass accretion rate or jets power increases, and (3) no
jet/outflow formation is possible beyond 44 gravitational radii.Comment: 16 pages, 9 figures, 3 tables, accepted by MNRAS (Mar. 09, 2018); v2:
references update
Asymptotic Behaviour of Parameter Ideals in Generalized Cohen-Macaulay Modules
The purpose of this paper is to give affirmative answers to two open
questions as follows. Let (R, \m) be a generalized Cohen-Macaulay Noetherian
local ring. Both questions, the first question was raised by M. Rogers \cite
{R} and the second one is due to S. Goto and H. Sakurai \cite {GS1}, ask
whether for every parameter ideal \q contained in a high enough power of the
maximal ideal \m the following statements are true: (1) The index of
reducibility N_R(\q;R) is independent of the choice of \q; and (2) I^2=\q
I, where I=\q:_R\m.Comment: 12 page
Parametric Decomposition of Powers of Parameter Ideals and Sequentially Cohen-Macaulay Modules
Let be a finitely generated module of dimension over a Noetherian
local ring (R,\m) and \q the parameter ideal generated by a system of
parameters \x = (x_1,..., x_d) of . For each positive integer , set
and \qa =
(x_1^{\alpha_1},...,x_d^{\alpha_d}). Then we prove in this note that is a
sequentially Cohen-Macaulay module if and only if there exists a certain system
of parameters \x such that the equality \q^nM=\pd holds true for all .
As an application of this result, we can compute the Hilbert-Samuel
polynomial of a sequentially Cohen-Macaulay module with respect to certain
parameter idealsComment: 10 page
Analysis of MEMS electrostatic energy harvesters electrically configured as voltage multipliers
This paper presents the analysis of an efficient alternative interface
circuit for MEMS electrostatic energy harvesters. It is entirely composed by
diodes and capacitors. Based on modeling and simulation, the anti-phase
gap-closing structure is investigated. We find that when configured as a
voltage multiplier, it can operate at very low acceleration amplitudes. In
addition, the allowed maximum voltage between electrodes is barely limited by
the pull-in effect. The parasitic capacitance of the harvester and non-ideal
characteristics of electronic components are taken into account. A lumped-model
of the harvesting system has been implemented in a circuit simulator.
Simulation results show that an output voltage of 22 V is obtained with 0.15 g
input acceleration. The minimum necessary ratio between the maximum and minimum
capacitances of the generators which allows operation of the circuit, can be
lower than 2. This overcomes a crucial obstacle in low-power energy harvesting
devices. A comparison between the voltage multiplier against other current
topologies is highlighted. An advantage of the former over the latter is to
generate much higher saturation voltage, while the minimum required initial
bias and the minimum capacitance ratio in both cases are in the similar levels.Comment: 11 pages, IEEE journal article templat
On the lateral instability analysis of MEMS comb-drive electrostatic transducers
This paper investigates the lateral pull-in effect of an in-plane
overlap-varying transducer. The instability is induced by the translational and
rotational displacements. Based on the principle of virtual work, the
equilibrium conditions of force and moment in lateral directions are derived.
The analytical solutions of the critical voltage, at which the pull-in
phenomenon occurs, are developed when considering only the translational
stiffness or only the rotational stiffness of the mechanical spring. The
critical voltage in general case is numerically determined by using nonlinear
optimization techniques, taking into account the combined effect of translation
and rotation. The effects of possible translational offsets and angular
deviations to the critical voltage are modeled and numerically analyzed. The
investigation is then the first time expanded to anti-phase operation mode and
Bennet's doubler configuration of the two transducers.Comment: 16 page
Theoretical analysis of electrostatic energy harvester configured as Bennet's doubler based on Q-V cycles
This paper presents theoretical analysis of a MEMS electrostatic energy
harvester configured as the Bennet's doubler. Steady-state operation of the
doubler circuit can be approximated by a right-angled trapezoid Q-V cycle. A
similarity between voltage doubler and resistive-based charge-pump circuit is
highlighted. By taking electromechanical coupling into account, the analytical
solution of the saturation voltage is the first time derived, providing a
greater comprehension of the system performance and multi-parameter effects.
The theoretical approach is verified by results of circuit simulation for two
cases of mathematically idealized diode and of Schottky diode. Development of
the doubler/multiplier circuits that can further increase the saturation
voltage is investigated.Comment: 16 page
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