In this letter, a multi-agent system with emergent hypocycloidal and epicycloidal behaviors is analyzed. Agents are assumed to be modeled as double integrators with an acceleration law designed so ...that the swarm exhibits cycloidal like trajectories. The resulting control protocol benefits from speeds and positions coupling among neighbors agents to let each agent perform hypocycloidal or epicycloidal curves according to the choice of the controller parameters and the agents initial conditions. As a first step, the model properties are obtained assuming that the communication topology of the multi-agent system is defined by a complete graph. As a further step, the model main features are extended by relaxing the complete connection assumption and replacing it with a more realistic one in which a connected graph is considered. This latter step is achieved by means of a consensus-based estimation of the swarm centroid, so that to virtualize the complete graph starting from a connected one. Simulations have been performed to show the properties of the obtained agents evolution.
The S6K1 and S6K2 kinases are considered important mTOR signaling effectors, yet their contribution to tumorigenesis remains unclear. Aberrant mTOR activation is a frequent event in cancer that ...commonly results from heterozygous loss of PTEN. Here, we show for the first time a differential protein expression between S6K1 and S6K2 in both mouse and human tissues. Additionally, the inactivation of S6k1 in the context of Pten heterozygosity (Pten(+/-)) suggests a differential requirement for this protein across multiple tissues. This tissue specificity appears to be governed by the relative protein expression of S6k2. Accordingly, we find that deletion of S6k1 markedly impairs Pten(+/-) mediated adrenal tumorigenesis, specifically due to low expression of S6k2. Concomitant observation of low S6K2 levels in the human adrenal gland supports the development of S6K1 inhibitors for treatment of PTEN loss-driven pheochromocytoma.
In this paper an identification method to estimate the parameters of a first-order plus time delay model is proposed. Such a method directly obtains these parameters using a new linear regression ...equation. No iterations in calculation are needed. Moreover, a simple true/false criterion to establish if the hypothesis on the process type is correct can be easily derived. The proposed method shows an acceptable robustness to disturbances and measurement noise as it is confirmed by several simulated experiments.
► We estimate all the unknown parameters of a sinusoidal signal. ► The estimation is performed by a non-adaptive second-order generalized integrator. ► The method is implemented as a dynamic third- ...or fourth-order system. ► In case of highly corrupted signal a different scheme can be used to further improve the filtering capabilities.
In this paper, a simple method for frequency, amplitude and phase estimation of a single sinusoidal signal is proposed. The approach described herein uses an orthogonal signals generator based on a Second-Order Generalized Integrator (SOGI). The frequency, amplitude and phase are estimated on the base of straightforward explicit formulas without any adaption of SOGI parameters. The method is implemented as a dynamic third- or fourth-order system according to specified cost function to be minimized. In case of highly corrupted signal a double-SOGI scheme can be used to further improve the filtering capabilities. The effectiveness of the proposed algorithm is demonstrated through simulated experiments and comparisons with existing methods.
A novel class of discrete-time frequency-locked-loop nonlinear (FLL) filters is introduced and their relevance for the on-line estimation of the parameters of a possibly time-varying sinusoidal ...signal is discussed. Continuous-time nonlinear FLL filters have been proposed in the literature because of their circuital simplicity and ability to provide unbiased estimates of the instantaneous frequency, phase and amplitude of a time-varying sinusoidal signal simultaneously. It is shown in this note that standard discretization techniques may fail to generate discrete-time FLL filters exhibiting the same good properties of the continuous-time domain. In particular, biased frequency estimates are usually produced by these discrete-time filters. In this note, such a drawback is overcome because the proposed discrete-time FLL filters are proved to enjoy semi-globally exponential stability and their estimates are unbiased. A final example is presented for assessment purposes where also comparisons with other discrete-time filters, among which some synthesized by means of standard discretization techniques, are provided.
This paper presents a comparison between five different classifiers (Multi-class Logistic Regression (MLR), Support Vector Machine (SVM), k-Nearest Neighbor (kNN), Random Forest (RF) and Gaussian ...Naive Bayes (GNB)) to be used in a Convolutional Neural Network (CNN) in order to perform images classification. For our experiments we have used a dataset composed of images of objects belonging to 256 widely varied categories called Caltech 256.
In this paper, a synchronization problem for a group of agents described by double-integrator dynamics and time-varying communication network is formally addressed. Specifically, the main aim ...consists in ensuring that the agents, organized as a swarm, are capable to synchronize in finite-time the swarm centroid to a given reference trajectory and to keep this property for all future time instants. To this end, an ad-hoc distributed control architecture is developed by taking advantage from two key ingredients: a novel swarm formation modelling that guarantees finite-time convergence properties of the agent kinematics and a hybrid model predictive control scheme in charge to adequately exploit such a kinematics description. One of the relevant features of the resulting distributed algorithm relies on the fact that both parallel and sequential paradigms are used with the aim to ensure collision avoidance requirements amongst the involved agents.
In this paper, a distributed control law for a kinematically modelled agent swarm is proposed, which is able to control the multi-agent system into a star-shaped set. The main idea behind the present ...work is to combine the traditional potential function based approach with the transformation of coordinate frames to drive a group of limited range agents into a moving region. The difficult problem of tracking a star-shaped set is transformed into a simpler problem where the star-shaped set is converted into a circular region. The control signal is designed with reference to this new circular region and then fed back to the original region of interest. The overall evolution of the agents is mainly determined by an attraction potential that directs the swarm to the region of interest and an interaction potential that controls the relationships between the agents and avoids collisions. As a further degree of freedom, the proposed control protocol can be set to move the multi-agent system to a certain perimeter around the region of interest to perform a perimeter monitoring task. In both cases, i.e. tracking the region or monitoring the perimeter, the evolution of the agents within the zone of interest can be chosen to achieve either a speed consensus or a rotational motion. The latter can be extremely useful in all those cases where a small number of agents have to explore a whole large area. Numerical simulations are carried out to illustrate the main features of the resulting control strategy.
In this article, a novel approach to generating kinematic state trajectories for single-integrator multiagent systems is developed with the aim of addressing cooperative surveillance tasks of ...rectangular areas. In particular, the key idea consists in driving the involved agents within a so-called containment region while simultaneously reaming outside a forbidden area around the prescribed target. As one of its main features, the proposed kinematics allows the whole multiagent configuration to rotate safely along the perimeter under both full and partial connectivity properties of the underlying topology graph. Steady-state conditions are analyzed and sufficient conditions are derived in terms of kinematic model parameters. Finally, a set of simulations is aimed at showing the capability of the kinematic descriptions to quickly buttonhole the containment region and to keep a rotating behavior around the target.
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