Simultaneous external and internal stabilization of linear systems with input saturation and non-input-additive sustained disturbances

In this paper, we study simultaneous external and internal stabilization of the linear system under input saturation and non-input additive sustained disturbances. For systems that are asymptotic null controllable with bounded control, it is shown that a nonlinear dynamic feedback controller can be designed so that the closed-loop states remain bounded for any initial condition and for two classes of sustained disturbances, and that the equilibrium in the absence of disturbances is globally asymptotically stable.     

Further results on the disturbance response of a double integrator controlled by a saturating linear static state feedback

In this paper, we study the response to external disturbances of a double integrator with a saturating feedback. For a class of disturbances that have bounded integrals over all intervals, we show that a linear static feedback law can always be designed to ensure boundedness of the states. Moreover, boundedness can be preserved if the disturbance is biased by a small DC signal. In the special case that the disturbance is made up of a finite number of sinusoids and a small bias, any linear static feedback ensures boundedness of the states. These results are an extension of previous results by Wen, Roy, and Saberi (2008).     

Control of a chain of integrators subject to actuator saturation and disturbances

In this paper, we study control of a chain of integrators under actuator saturation and non‐additive disturbances. We shall show that boundedness of the states can be ensured if the disturbances are matched and integral‐bounded, misaligned and magnitude‐bounded, or a combination of the two, using either a static or a dynamic low‐gain state feedback. This result is an extension of our earlier work on double integrator. Copyright © 2011 John Wiley & Sons, Ltd.     

Scheduling parallel jobs to minimize the makespan

We consider the NP-hard problem of scheduling parallel jobs with release dates on identical parallel machines to minimize the makespan. A parallel job requires simultaneously a prespecified, job-dependent number of machines when being processed. We prove that the makespan of any nonpreemptive list-schedule is within a factor of 2 of the optimal preemptive makespan. This gives the best-known approximation algorithms for both the preemptive and the nonpreemptive variant of the problem. We also show that no list-scheduling algorithm can achieve a better performance guarantee than 2 for the nonpreemptive problem, no matter which priority list is chosen. List-scheduling also works in the online setting where jobs arrive over time and the length of a job becomes known only when it completes; it therefore yields a deterministic online algorithm with competitive ratio 2 as well. In addition, we consider a different online model in which jobs arrive one by one and need to be scheduled before the next job becomes known. We show that no list-scheduling algorithm has a constant competitive ratio. Still, we present the first online algorithm for scheduling parallel jobs with a constant competitive ratio in this context. We also prove a new information-theoretic lower bound of 2.25 for the competitive ratio of any deterministic online algorithm for this model. Moreover, we show that 6/5 is a lower bound for the competitive ratio of any deterministic online algorithm of the preemptive version of the model jobs arriving over time.     

Interpolation and extrapolation in nonuniform sampling sequences with average sampling rates below the Nyquist rate

Coefficients for interpolation and extrapolation, including average sampling rates below the Nyquist rate, have been derived. The method is applicable for nonuniform patterns obtained through omission of samples in a uniform pattern with a sampling rate slightly higher than the Nyquist rate. The interpolations and extrapolations are valid for band-limited signals, except those theoretical signals that are zero valued at all sampling points.     

Occupational posture exposure among construction electricians

The aim of this study is to record, objectively describe and compare working postures of Brazilian and Norwegian construction electricians. Postures of the upper arms, head, and neck during work and breaks were quantified by means of inclinometry for a representative sample of 12 Brazilian and 12 Norwegian electricians in the construction industry during a full work-shift. Despite that differences were found between specific work-related factors, Brazilian and Norwegian workers revealed a high and very similar level and pattern of postures for all evaluated body regions, suggesting that results could be extrapolated to other electricians. Upper arm elevation was high and similar for both groups and head flexion and extension was pronounced compared to other occupations. Thus, extreme postures were identified for construction electricians in both countries, with similar exposure pattern also for defined tasks (planning, support and wiredraw), suggesting that this job is risky regardless organizational differences.     

Detection of Pinosylvins in Solid Wood of Scots Pine Using Fourier Transform Raman and Infrared Spectroscopy

Abstract

Diffuse reflectance Fourier transform infrared (DRIFT) and near infrared (NIR) FT-Raman spectroscopy were used to detect pinosylvins in the wood of Pinus sylvestris L. trees. NIR FT-Raman spectroscopy offered the possibility of revealing pinosylvins simply by visual inspection of Raman spectra whereas DRIFT spectra needed a more complicated evaluation. Pinosylvin and resin acids from Scots pine were examined as to the possibility of their being the cause of observed spectral differences between sapwood and heartwood. Since pinosylvins are important compounds for the decay resistance of Scots pine wood, the detection of pinosylvins with Raman spectroscopy might be used to assess durability of wood products.