1,435 research outputs found
On the geometric interpretation of the Polynomial Lie Bracket for nonlinear time-delay systems
Time-delay systems are infinite dimensional, thus standard differential geometric tools can not be applied in a straightforward way. Though, thanks to a suitable extended Lie Bracket - or Polynomial Lie Bracket - which has been introduced recently, it is still possible to build up a geometric framework to tackle the analysis and synthesis problems for nonlinear time delay systems. The major contribution herein is to show that those geometric generalizations are not just formal, but are interpreted in terms of successive forward and backward flows similarly to the Lie Bracket of delay free vector fields
Observability of nonlinear time–delay systems and its application to their state realization
In this paper, it is shown that the two notions of weak observability and strong observability may not be sufficient to describe the link between the input/output equation associated to the behaviour of a system and its state space realization. A new notion, called regular observability, is introduced, which is shown to capture essential features of nonlinear time delay systems and the existence of some realization
Leader-Following consensus for nonlinear agents with measurement feedback
The leader-following consensus problem is investigated for large classes of nonlinear
identical agents. Sufficient conditions are provided for achieving consensus
via state and measurement feedback laws based on a local (ie, among neighbors)
information exchange. The leader's trajectories are assumed bounded
without knowledge of the containing compact set and the agents' trajectories
possibly unbounded under the action of a bounded input. Generalizations to
heterogeneous agents and robustness are also discussed
The effect of small elongations on the electronic and optical signatures in InAs nanocrystal quantum dots
We present a detailed theoretical investigation of the electronic structure and
optical properties of InAs nanocrystals at the transition from spheres to rods. Using
a semiempirical pseudopotential approach, we predict that, despite the qualitative
similarity of both intra- and inter-band optical spectra, for NCs with R > 15 °A even
slight elongations should result in shifts of the order of hundreds of meV in the spacings
between STM peaks measured in the positive bias regime, in the position of the intra-
band absorption peaks associated with transitions in the conduction band and in the
separation between the first and the fifth peak in PLE experiments. Our results show
that, based on the spectroscopic data, it should be possible to discriminate between
spherical and elongated NCs with aspect ratios of length over diameter as small as
1.2. Indeed our results suggest that many nominally spherical experimental samples
contained a large fraction of slightly elongated structures
Clinical survey of neurosensory side-effects of mandibular parasymphyseal bone harvesting
The aim of the present survey was to assess neurosensory disturbances and/or tooth-pulp sensitivity losses after mandibular parasymphyseal bone-harvesting procedures. Twenty-eight harvesting areas in 16 patients were surveyed. Mucosal and skin sensitivity of the chin/lower lip, divided into four regions, were determined via Pointed-Blunt and Two-Point-Discrimination Tests. Pulp sensitivity of the mandibular teeth from the left second bicuspid to the right second bicuspid was tested by cold vitality preoperatively and 12 months postoperatively. Teeth were grouped according to sensitivity alterations and distance from the harvesting defects, as measured on CT scans, and statistically significant differences sought. At 12 months, 29% of preoperatively vital cuspids overlying the harvesting defects revealed pulp-sensitivity losses; no patient reported anaesthesia or analgesia; hypoaesthesia was present in 4% (8 sites; 2 patients), hypoalgesia was present in 3% (5 sites; 2 patients) and Two-Point-Discrimination Tests yielded pathologic responses in 5% of tested areas (10 sites; 4 patients). Teeth with and without pulp sensitivity changes were statistically indistinguishable regarding distances between root apices or mental foramen and the harvesting defect. The loss of pulp sensitivity in any tooth cannot be predicted simply on the basis of the distance between its apex and the harvesting osteotomy line
Ultrasound scan to detect acalculous cholecystopathy in immunocompromised hosts with unexplained fever.
We found a significant prevalence of acalculous
cholecystopathy in a group of patients with hematologic
malignancies and unexplained fever. Ultrasound
scan (US) detected a case of acute cholecystitis,
two of gallbladder overdistension and biliary
sludge, and one of striated gallbladder wall thickening.
US proved effective in early identification of
abdominal infection site
Trajectory Generation, Control, and Safety with Denoising Diffusion Probabilistic Models
We present a framework for safety-critical optimal control of physical systems based on denoising diffusion probabilistic models (DDPMs). The technology of control barrier functions (CBFs), encoding desired safety constraints, is used in combination with DDPMs to plan actions by iteratively denoising trajectories through a CBF-based guided sampling procedure. At the same time, the generated trajectories are also guided to maximize a future cumulative reward representing a specific task to be optimally executed. The proposed scheme can be seen as an offline and model-based reinforcement learning algorithm resembling in its functionalities a model-predictive control optimization scheme with receding horizon in which the selected actions lead to optimal and safe trajectories
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