Ryad Chellali

Bio: Ryad Chellali is an academic researcher from Nanjing Tech University. The author has contributed to research in topics: Robot & Teleoperation. The author has an hindex of 19, co-authored 107 publications receiving 1051 citations. Previous affiliations of Ryad Chellali include Nanjing Forestry University & Istituto Italiano di Tecnologia.

Analyzing Tracklets for the Detection of Abnormal Crowd Behavior

Abstract: This paper presents a novel video descriptor, referred to as Histogram of Oriented Track lets, for recognizing abnormal situation in crowded scenes. Unlike standard approaches that use optical flow, which estimates motion vectors only from two successive frames, we built our descriptor over long-range motion trajectories which is called track lets in the literature. Following the standard procedure, we divided video sequences in spatio-temporal cuboids within which we collected statistics on the track lets passing through them. In particular, we quantized orientation and magnitude in a 2-dimensional histogram which encodes the motion patterns expected in each cuboid. We classify frames as normal and abnormal by using Latent Dirichlet Allocation and Support Vector Machines. We evaluated the effectiveness of the proposed descriptors on three datasets: UCSD, Violence in Crowds and UMN. The experiments demonstrated (i) very promising results in abnormality detection, (ii) setting new state-of-the-art on two of them, and (iii) outperforming former descriptors based on the optical flow, dense trajectories and the social force model.

Bimodal emotion recognition

Abstract: When interacting with robots we show a plethora of affective reactions typical of natural communications. Indeed, emotions are embedded on our communications and represent a predominant communication channel to convey relevant, high impact, information. In recent years more and more researchers have tried to exploit this channel for human robot (HRI) and human computer interactions (HCI). Two key abilities are needed for this purpose: the ability to display emotions and the ability to automatically recognize them. In this work we present our system for the computer based automatic recognition of emotions and the new results we obtained on a small dataset of quasi unconstrained emotional videos extracted from TV series and movies. The results are encouraging showing a recognition rate of about 74%.

Three-dimensional object construction using a self-mixing type scanning laser range finder

Abstract: A self-mixing type scanning range finder has been designed for the acquisition of three-dimensional (3-D) image data and object construction. The optical beam backscattered by a rough target into the laser diode cavity causes strong variations of the optical output power, the pseudo period between two of these variations corresponding to a distance of a half wavelength. With such a device, images have been obtained with a resolution of 0.1% over ranges up to 3 m, for 3-D object construction.

An Overview of Nature-Inspired, Conventional, and Hybrid Methods of Autonomous Vehicle Path Planning

Abstract: Safe and smooth mobile robot navigation through cluttered environment from the initial position to goal with optimal path is required to achieve intelligent autonomous ground vehicles. There are countless research contributions from researchers aiming at finding solution to autonomous mobile robot path planning problems. This paper presents an overview of nature-inspired, conventional, and hybrid path planning strategies employed by researchers over the years for mobile robot path planning problem. The main strengths and challenges of path planning methods employed by researchers were identified and discussed. Future directions for path planning research is given. The results of this paper can significantly enhance how effective path planning methods could be employed and implemented to achieve real-time intelligent autonomous ground vehicles.

Virtual reality tools for Internet robotics

Abstract: A virtual control environment for robot teleoperation via the Internet is presented. It comprises a Java3D-based real-time virtual representation of the robot and worksite, and uses a graphic panel, an environment for remote robot programming, and a dataglove with a 6D position tracker as the control interfaces. The use of virtual reality (VR) techniques for Internet teleoperation allow: (1) time delays inherent in IP networks to be suppressed and (2) the operator's work to be simplified and accelerated, compared to methods that use delayed TV images. The system realisation, with its use of open technologies Java, Java3D and 3-tier client/server architecture, provides portability among different computer platforms and types of robots. The efficiency of the VR-based methods developed has been verified for slow communication rates (0.1-0.5 KB/sec), where TV-based control methods are inapplicable. VR systems have been developed for the WWW-based control of the PUMA and CRS industrial robot manipulators. The particulars of these systems, the experiments undertaken, current issues, and directions of future work are presented.

Speech Genres and Other Late Essays

Abstract: Note on Translation Introduction by Michael Holquist Response to a Question from the Novy Mir Editorial Staff The Bildungsroman and Its Significance in the History of Realism (Toward a Historical Typology of the Novel) The Problem of Speech Genres The Problem of the Text in Linguistics, Philology, and the Human Sciences: An Experiment in Philosophical Analysis From Notes Made in 1970-71 Toward a Methodology for the Human Sciences Index

Coverage control for mobile sensing networks

Abstract: This paper presents control and coordination algorithms for groups of vehicles. The focus is on autonomous vehicle networks performing distributed sensing tasks where each vehicle plays the role of a mobile tunable sensor. The paper proposes gradient descent algorithms for a class of utility functions which encode optimal coverage and sensing policies. The resulting closed-loop behavior is adaptive, distributed, asynchronous, and verifiably correct.

Beta-band oscillations--signalling the status quo?

Abstract: In this review, we consider the potential functional role of beta-band oscillations, which at present is not yet well understood. We discuss evidence from recent studies on top-down mechanisms involved in cognitive processing, on the motor system and on the pathophysiology of movement disorders that suggest a unifying hypothesis: beta-band activity seems related to the maintenance of the current sensorimotor or cognitive state. We hypothesize that beta oscillations and/or coupling in the beta-band are expressed more strongly if the maintenance of the status quo is intended or predicted, than if a change is expected. Moreover, we suggest that pathological enhancement of beta-band activity is likely to result in an abnormal persistence of the status quo and a deterioration of flexible behavioural and cognitive control.

The Rutgers Master II-new design force-feedback glove

Abstract: The Rutgers Master II-ND glove is a haptic interface designed for dextrous interactions with virtual environments. The glove provides force feedback up to 16 N each to the thumb, index, middle, and ring fingertips. It uses custom pneumatic actuators arranged in a direct-drive configuration in the palm. Unlike commercial haptic gloves, the direct-drive actuators make unnecessary cables and pulleys, resulting in a more compact and lighter structure. The force-feedback structure also serves as position measuring exoskeleton, by integrating noncontact Hall-effect and infrared sensors. The glove is connected to a haptic-control interface that reads its sensors and servos its actuators. The interface has pneumatic servovalves, signal conditioning electronics, A/D/A boards, power supply and an imbedded Pentium PC. This distributed computing assures much faster control bandwidth than would otherwise be possible. Communication with the host PC is done over an RS232 line. Comparative data with the CyberGrasp commercial haptic glove is presented.

Collecting Large, Richly Annotated Facial-Expression Databases from Movies

Abstract: Two large facial-expression databases depicting challenging real-world conditions were constructed using a semi-automatic approach via a recommender system based on subtitles.