On robust online scheduling algorithms

While standard parallel machine scheduling is concerned with good assignments of jobs to machines, we aim to understand how the quality of an assignment is affected if the jobs’ processing times are perturbed and therefore turn out to be longer (or shorter) than declared. We focus on online scheduling with perturbations occurring at any time, such as in railway systems when trains are late. For a variety of conditions on the severity of perturbations, we present bounds on the worst case ratio of two makespans. For the first makespan, we let the online algorithm assign jobs to machines, based on the non-perturbed processing times. We compute the makespan by replacing each job’s processing time with its perturbed version while still sticking to the computed assignment. The second is an optimal offline solution for the perturbed processing times. The deviation of this ratio from the competitive ratio of the online algorithm tells us about the “price of perturbations”. We analyze this setting for Graham’s algorithm, and among other bounds show a competitive ratio of 2 for perturbations decreasing the processing time of a job arbitrarily, and a competitive ratio of less than 2.5 for perturbations doubling the processing time of a job. We complement these results by providing lower bounds for any online algorithm in this setting. Finally, we propose a risk-aware online algorithm tailored for the possible bounded increase of the processing time of one job, and we show that this algorithm can be worse than Graham’s algorithm in some cases.     

A U-shaped actuation system for dual-stage actuators used in hard disk drives

In this paper, we propose an actuation system, called U-shaped actuation, for dual-stage actuator to suppress the arm mode flutter. We manufactured an actuator using this actuation method and measured the frequency response. We found that the frequency response had an in-phase arm mode frequency and that there was little difference between each head at arm sway and suspension sway mode. Next, we designed a controller and compared its sensitivity function with that of conventional actuation. By applying stabilizing control to the in-phase arm mode, NRRO of the arm flutter of the outer and inner arms was suppressed by 10.9 and 13.2?%, respectively.     

Gait Recovery in Healthy Subjects: Perturbations to the Knee Motion with a Smart Knee Brace

The Smart Knee Brace (SKB) is designed to provide controlled perturbations to the human knee during walking. A motion capture system records the gait movement before and after these perturbations to assess the human response to the perturbations. A dynamic model of human walking is then used to evaluate the human applied joint torques to hypothesize how the human neuro-muscular system modulates the joint torques as a response to the perturbations caused on the gait. We observe that subjects respond differently to perturbations, but all healthy subjects restore their normal gait in a few subsequent cycles. Our results show that the neuro-muscular response to perturbations can be reasonably well characterized by including the following features in the model: (i) normal gait in the absence of perturbation, (ii) corrective torque at a joint in response to the error at that joint and other joints, and (iii) a characteristic time shift in the response. We believe that there is intuitive justification for each of the components included in the model. Detailed parameters that characterize these components, obtained by data fitting from the response data, are specific to an individual's neuro-muscular response to perturbations in the gait. We believe that these parameters can be used to characterize subjects who are more prone to falling under gait perturbations.     

The Role of Surface Plasmon Modes in the Casimir Effect

In this paper, we study the role of surface plasmon modes in the Casimir effect. First we write the Casimir energy as the sum over the modes of a real cavity. We may identify two sorts of modes, two evanescent surface plasmon modes and propagative modes. As one of the surface plasmon modes becomes propagative for some choice of parameters we adopt an adiabatic mode definition where we follow this mode into the propagative sector and count it together with the surface plasmon contribution, calling this contribution “plasmonic”. The remaining modes are propagative cavity modes, which we call “photonic”. The Casimir energy contains two main contributions, one coming from the plasmonic, the other from the photonic modes. Surprisingly we find that the plasmonic contribution to the Casimir energy becomes repulsive for intermediate and large mirror separations. Alternatively, we discuss the common surface plasmon defintion, which includes only evanescent waves, where this effect is not found. We show that, in contrast to an intuitive expectation, for both definitions the Casimir energy is the sum of two very large contributions which nearly cancel each other. The contribution of surface plasmons to the Casimir energy plays a fundamental role not only at short but also at large distances.     

Stability of the adiabatic compression of an ideal gas by a thin shell

A new solution has been obtained for the problems of the isentropic compression of an ideal gas in the centered wave formulated in the Lagrangian variables. The developed method makes it possible in a single, uniform way to find the solution to the gas-dynamic problem in the plane, cylindrical, and spherical cases for an initially uniform motionless gas. Equations were derived describing the evolution of the small perturbations of the shell in the case where the acceleration is time-dependent. The shell is assumed to be thin and structureless, and its mass is supposed to exceed significantly the mass of the gas surrounding the shell. The cases of the planar, cylindrical, and spherical geometries of the system are considered. The stability of the shell’s motion producing isentropic compression of the gas is considered with respect to the evolution of small perturbations of plane-wave and angularharmonic types. It is shown that under the isentropic compression of a gas, the increase in the shell’s perturbations of the plane-wave type is limited both in the planar and cylindrical geometries. The limiting growth in the amplitude of such perturbations is calculated. The increase in the perturbations of the angular-harmonic type is demonstrated to be unlimited both in cylindrical and in spherical geometries. The increment in the growth of such perturbations has been calculated.     

On creating mass/matter by extra dimensions in the Einstein-Gauss-Bonnet gravity

Kaluza–Klein (KK) black hole solutions in the Einstein–Gauss–Bonnet (EGB) gravity in D dimensions obtained in the current series of the works by Maeda, Dadhich and Molina are examined. Interpreting their solutions, the authors claim that mass/matter is created by the extra dimensions. To support this claim, one needs to show that such objects have classically defined masses. We calculate the mass and mass flux for 3D KK black holes in 6D EGB gravity whose properties are sufficiently physically interesting. Superpotentials for arbitrary types of perturbations on arbitrary curved backgrounds, recently obtained by the author, are used, and acceptable mass and mass flux are obtained. A possibility of considering the KK created matter as dark matter in the Universe is discussed.     

Simulations of the dynamic behavior of a bipedal robot with trunk and arms subjected to 3D external disturbances in a vertical posture, during walking and during object handling

This paper provides a new approach to the bipedal robot stability problems in presence of external disturbances in vertical posture of the robot, during walking and during object handling. This approach is based on synergy between the dynamic motions of balancing masses and arms to reject large perturbations applied to the upper part of ROBIAN robot. In these cases, the stabilization is carried out in the first time with a trunk having 4 degrees of freedom (dof): one rotational and three translational movements. In the second time, the stabilization is performed with a system with arms and having 10 dof. During the walk, the trunk elements of ROBIAN reproduce necessary movements to perform the dynamic walking gait of the robot. The compensation of external three-dimensional efforts applied to the robot is achieved firstly by the trunk and secondly with the arms. This study allows us to determine on-line the required movements and accelerations of the trunk elements in order to maintain the robot stability and shows the importance of the arms for the robot stability.     

Unmatched uncertainties compensation based on high‐order sliding mode observation

The problem of compensation of the effects of unmatched uncertainties ∕ perturbations is considered. High‐order sliding mode observers are employed for exact state and uncertainties ∕ perturbations reconstruction. A sliding mode control design is proposed ensuring theoretically exact compensation of the uncertainties ∕ perturbations for the corresponding unmatched states based on the identified perturbation values. An inverted pendulum simulation example is considered illustrating the feasibility of the proposed approach.Copyright © 2012 John Wiley & Sons, Ltd.     

Parametric control in the problem of spacecraft stabilization in the geomagnetic field

The spacecraft interacting with the geomagnetic field in electrodynamic mode is subject to parametric perturbations; parameters of the spacecraft are controlled quasi-periodic functions. Under some conditions, there exist control algorithms for spacecraft electrodynamic parameters that allow realizing systems of spacecraft angular position stabilization. Stability of the spacecraft stabilized orientation is proved both analytically and by PC computations.     

Localized trio cantilevers for identifying different mass perturbations

This paper demonstrates a method based on mode localization which, for the first time, verifies the possibility of identifying two kinds of mass perturbations with a coupled three-cantilever array theoretically, analytically and experimentally. In the light of mode shapes in certain resonance modes, the proportion of mass perturbations on the side and center cantilever can be qualitatively determined. A combination of the 1st and 3rd mode shape was selected for discriminating different situations including one single mass perturbation and mixed mass perturbations. On the one hand, the proposed method simplifies the structure of the present 15 or 5 cantilever array sensors used for mass positioning. On the other hand, it provides a simple and efficient way to the pre-warning of those multiple toxic substances in some public places.

     

Continuous stochastic approximation with semi-Markov switchings in the diffusion approximation scheme

The sufficient conditions of convergence are obtained for a continuous stochastic approximation procedure in the diffusion approximation scheme under balance conditions imposed on singular perturbations of the regression function in a semi-Markov environment. To this end, a singular perturbation problem is solved for the asymptotic representation of a compensating operator of a Markov renewal process. __________ Translated from Kibernetika i Sistemnyi Analiz, No. 4, pp. 170–178, July–August 2007.     

Robustness of c-velocity based methods for 3D moving plane detection

The Hough-like frame called c-velocity supports a surface detection from an image sequence, without calibration. A vehicle’s environment, set of 3D planes, can then be reconstructed exploiting isovelocity curves bound to an estimated optical flow. We show in this paper how the cumulative approach is robust against main perturbations.     

Decentralized robust control for multiconnected objects with structural uncertainty

We solve the problem of constructing a decentralized robust regulating system for a multiconnected control object that provides for compensating interconnections in local subsystems and also parametric and external bounded perturbations, compensating with precision δ if one does not measure the derivatives of the local subsystems output vector and in full if the derivatives are measured.     

Human direct teaching of industrial articulated robot arms based on force-free control

Force-free control produces motion in a robot arm as if it were under conditions with no gravity and no friction. In this study, a method of force-free control is proposed for industrial articulated robot arms. The force-free control proposed was applied to the direct teaching of industrial articulated robot arms in that the robot arm was moved by direct human force. Generally, the teaching of industrial articulated robot arms is carried out using operational equipment called a teach-pendant. Smooth teaching can be achieved if direct teaching is applicable. The force-free control proposed enables humans to teach industrial articulated robot arms directly. The effectiveness of force-free control was confirmed by experimental work on an articulated robot arm with two degrees of freedom. This work was presented in part at the Fifth International Symposium on Artificial Life and Robotics, Oita, Japan, January 26–28, 2000     

Linear systems of first order ordinary differential equations: fuzzy initial conditions

 We present two types of fuzzy solutions to linear systems of first order differential equations having fuzzy initial conditions. The first solution, called the extension principle solution, fuzzifies the crisp solution and then checks to see if its α-cuts satisfy the differential equations. The second solution, called the classical solution, solves the fuzzified differential equations and then checks to see if the solution always defines a fuzzy number. Three applications are presented: (1) predator–prey models; (2) the spread of infectious diseases; and (3) modeling an arms race.     

Pushing the Distribution Model to its Limits: Distributed “listening” in a Helpline

Our case study explores the extent to which a “Distributed Cognition”-like ethnographic approach can be used to analyze situations which are not at first sight compatible with the precepts of computational cognition. In the first part of the paper, we analyze the collective listening of phone calls in a helpline. We show why collective listening can be considered a “distributed collective practice”, with a mode of coordination based on repeated verbal re-enactments of difficult phone calls, rather than upon the discrete computational steps normally assumed in the standard model. In the second part of the paper, we analyse the organizational and interactional learning which takes place when collective listening is re-mediated by using e-mail exchanges rather than telephone conversations to communicate distress. Our conclusion discusses critically the viability of the distribution model in a context of collective listening.     

Integral Sliding‐Mode Observation and Control for Switched Uncertain Linear Time Invariant Systems: a Robustifying Strategy

A robustifying methodology for switched systems with matched and unmatched uncertainties/perturbations and autonomous location transitions is presented. We avail of such methodology to design a control strategy based on integral sliding modes, thereby ensuring theoretically exact compensation of the matched uncertainties/perturbations and the minimization of the effects of the unmatched ones. An output integral sliding‐mode control technique, based on a switched algebraic hierarchical observer is also proposed. This approach allows the theoretically exact compensation of the matched uncertainties/perturbations right after the first moment. The proposed approach is illustrated via numerical simulations.     

Joint network-host based malware detection using information-theoretic tools

In this paper, we propose two joint network-host based anomaly detection techniques that detect self-propagating malware in real-time by observing deviations from a behavioral model derived from a benign data profile. The proposed malware detection techniques employ perturbations in the distribution of keystrokes that are used to initiate network sessions. We show that the keystrokes’ entropy increases and the session-keystroke mutual information decreases when an endpoint is compromised by a self-propagating malware. These two types of perturbations are used for real-time malware detection. The proposed malware detection techniques are further compared with three prominent anomaly detectors, namely the maximum entropy detector, the rate limiting detector and the credit-based threshold random walk detector. We show that the proposed detectors provide considerably higher accuracy with almost 100% detection rates and very low false alarm rates.     

Optimal linear filtering for systems of stochastic differential equations with poisson perturbations

The Kalman–Bucy filter that can be modeled by computer statistical design is constructed for stochastic dynamic systems with Poisson perturbations. It is proved that a stationary filter coincides with the Wiener filter for the optimal mean-square filtering of stationary sequences in the absence of Poisson perturbations.     

Dual arm coordination and control

A generalized master/slave technique and experimental results for coordinated control of two arms rigidly grasping an object is described in this paper. Usually master/slave refers to the case when one arm is controlled in position mode while the second arm is controlled in force mode. In generalized master/slave control, each arm at its tool frame has six degrees of freedom; each degree of freedom can be in either position or force control mode. An interactive program has been developed to allow a user the flexibility to select appropriate control modes for a given experiment. This interface also allows for control gain adjustments. This paper presents the results of several experiments performed on this system to demonstrate its capabilities such as transporting an object with or without induced internal forces and movement of a constrained object. The system is further developed to achieve a so-called shared control mode in which an operator species the free motion trajectory for a point on the object of manipulation via a joystick while the autonomous control system is used for coordination and control of the arms.