1,986 research outputs found
Linear identification of nonlinear systems: A lifting technique based on the Koopman operator
We exploit the key idea that nonlinear system identification is equivalent to
linear identification of the socalled Koopman operator. Instead of considering
nonlinear system identification in the state space, we obtain a novel linear
identification technique by recasting the problem in the infinite-dimensional
space of observables. This technique can be described in two main steps. In the
first step, similar to the socalled Extended Dynamic Mode Decomposition
algorithm, the data are lifted to the infinite-dimensional space and used for
linear identification of the Koopman operator. In the second step, the obtained
Koopman operator is "projected back" to the finite-dimensional state space, and
identified to the nonlinear vector field through a linear least squares
problem. The proposed technique is efficient to recover (polynomial) vector
fields of different classes of systems, including unstable, chaotic, and open
systems. In addition, it is robust to noise, well-suited to model low sampling
rate datasets, and able to infer network topology and dynamics.Comment: 6 page
Solving Sparse Integer Linear Systems
We propose a new algorithm to solve sparse linear systems of equations over
the integers. This algorithm is based on a -adic lifting technique combined
with the use of block matrices with structured blocks. It achieves a sub-cubic
complexity in terms of machine operations subject to a conjecture on the
effectiveness of certain sparse projections. A LinBox-based implementation of
this algorithm is demonstrated, and emphasizes the practical benefits of this
new method over the previous state of the art
Lifted Worm Algorithm for the Ising Model
We design an irreversible worm algorithm for the zero-field ferromagnetic
Ising model by using the lifting technique. We study the dynamic critical
behavior of an energy estimator on both the complete graph and toroidal grids,
and compare our findings with reversible algorithms such as the
Prokof'ev-Svistunov worm algorithm. Our results show that the lifted worm
algorithm improves the dynamic exponent of the energy estimator on the complete
graph, and leads to a significant constant improvement on toroidal grids.Comment: 9 pages, 6 figure
Chemical enhancement of footwear impressions in blood deposited on fabric — evaluating the use of alginate casting materials followed by chemical enhancement
Most footwear marks made in blood on a surface such as fabric tend to be enhanced in situ rather than physically recovered using a lifting technique prior to enhancement. This work reports on the use of an alginate material to recover the impressed footwear marks made in blood and deposited on a range of fabric types and colours. The lifted marks were then enhanced using acid black 1 and leuco crystal violet with excellent results. This presents a new method for the lifting and recovery of blood impressions in situ from crime scene followed by subsequent mark enhancement of the lifted impression
A case of mediastinal goiter treated surgically using a clavicle-lifting technique
AbstractIntroductionMediastinal goiter is a benign disease, which is defined as a goiter with the greater portion of its mass lying below the thoracic inlet. It is controversial whether the cervical approach is the best approach for all mediastinal goiter surgeries.Case presentationA 71-year-old woman presented with respiratory discomfort during exertion. Computed tomography (CT) revealed a mediastinal goiter extending to the arch of the aorta. Surgical resection was performed using a clavicle-lifting technique. The excised specimen was 13Ă—10Ă—5cm in size and weighed 220g. The pathological diagnosis was nodular goiter.DiscussionThe clavicle-lifting technique is a simple and safe technique that involves lifting the clavicles with a pediatric extension retractor (Kent Retractor Set, Takasago Medical Industry, Tokyo, Japan). This is a good choice for surgery on upper mediastinal lesions such as mediastinal goiters as it obviates the need for a median sternotomy.ConclusionAlthough further study is necessary, it appears that a transcervical approach using the clavicle-lifting technique may be an acceptable treatment for mediastinal goiters that extend to the aortic arch
Clip and snare lifting technique to assist cannulation of a papilla hidden behind a mucosal fold
No abstract availabl
Stabilization of (L,M) shift invariant plant
In this paper, a lifting technique is employed to realize a single input single output linear (L,M) shift invariant plant as a filter bank system. Based on the filter bank structure, a controller is designed so that the aliasing components in the control loop are cancelled and the loop gain becomes a time invariant transfer function. Pole placement technique is applied to stabilize the overall system and ensure the causality of the filters in the controller. An example on the control of a linear (L,M) shift invariant plant with simulation result is illustrated. The result shows that our proposed algorithm is simple and effective
Congruences between Hilbert modular forms: constructing ordinary lifts
Under mild hypotheses, we prove that if F is a totally real field, k is the
algebraic closure of the finite field with l elements and r : G_F --> GL_2(k)
is irreducible and modular, then there is a finite solvable totally real
extension F'/F such that r|_{G_F'} has a modular lift which is ordinary at each
place dividing l. We deduce a similar result for r itself, under the assumption
that at places v|l the representation r|_{G_F_v} is reducible. This allows us
to deduce improvements to results in the literature on modularity lifting
theorems for potentially Barsotti-Tate representations and the
Buzzard-Diamond-Jarvis conjecture. The proof makes use of a novel lifting
technique, going via rank 4 unitary groups.Comment: 48 page
Sampling from a system-theoretic viewpoint: Part I - Concepts and tools
This paper is first in a series of papers studying a system-theoretic approach to the problem of reconstructing an analog signal from its samples. The idea, borrowed from earlier treatments in the control literature, is to address the problem as a hybrid model-matching problem in which performance is measured by system norms. In this paper we present the paradigm and revise underlying technical tools, such as the lifting technique and some topics of the operator theory. This material facilitates a systematic and unified treatment of a wide range of sampling and reconstruction problems, recovering many hitherto considered different solutions and leading to new results. Some of these applications are discussed in the second part
THE EFFECTS OF LOAD MASS ON THE KINEMATICS OF STIFF-LEGGED DEADLIFT
The purpose of this study was to investigate the effects of load mass on the kinematics of lower extremity joint movements during the stiff-legged deadlift (SLD) lift exercise. Five participants performed the SLD at 40%, 60%, and 80% of their estimated 1 repetition maximum. Measurements of the joint angle and angular velocity of the spine, hip, knee, and ankle were analyzed to understand the influence of various load masses in the SLD lifting technique. No statistical significant differences were found in the joint angles and angular velocities of the spine and lower extremity between different loads. Therefore, this study suggests that performing stiff-legged exercise up to 80% is safe to perform as long as the participants are experienced with this lifting technique
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