Robust Speed Control of a Low Damped Electromechanical System Based on CRONE Control: Application to a Four Mass Experimental Test Bench

Robust speed control of a low damped electromechanical system with backlash is studied, controlled load angular speed being not measured. The proposed control strategy combines a Luenberger observer (load angular speed and load torque disturbance estimations) and a robust CRONE controller. The observer provides estimation of the load angular speed and of the disturbance torque applied on the load. Through the computation of only three independent parameters (as many as a PID controller), the CRONE controller permits to ensure the robust speed control of the load in spite of plant parametric variations and speed observation errors. The proposed control strategy is applied to a four mass experimental test bench.     

Snake Venom Components: Tools and Cures to Target Cardiovascular Diseases

Cardiovascular diseases (CVDs) are considered as a major cause of death worldwide. Therefore, identifying and developing therapeutic strategies to treat and reduce the prevalence of CVDs is a major medical challenge. Several drugs used for the treatment of CVDs, such as captopril, emerged from natural products, namely snake venoms. These venoms are complex mixtures of bioactive molecules, which, among other physiological networks, target the cardiovascular system, leading to them being considered in the development and design of new drugs. In this review, we describe some snake venom molecules targeting the cardiovascular system such as phospholipase A2 (PLA2), natriuretic peptides (NPs), bradykinin-potentiating peptides (BPPs), cysteine-rich secretory proteins (CRISPs), disintegrins, fibrinolytic enzymes, and three-finger toxins (3FTXs). In addition, their molecular targets, and mechanisms of action—vasorelaxation, inhibition of platelet aggregation, cardioprotective activities—are discussed. The dissection of their biological effects at the molecular scale give insights for the development of future snake venom-derived drugs.     

Application of an acoustic backscatter technique for characterizing the roughness of porous soil

An acoustic backscatter technique proposed by Oelze et al. [J. Acoust. Soc. Am. 109, 1826-1832 (2001)] was used to characterize the roughness of porous soil surfaces. Roughness estimation errors are minimized when the effective flow resistivity of the porous soil is high, e.g., above 300,000 mks Rayls/m. Four soil plots were constructed by roughening soil with farming implements. Three plots were sealed using Saran powder dissolved in methyl ethyl ketone (MEK) and then covered to prevent further weathering. A fourth plot was left in the open and exposed to rainfall, which also acted to seal the surface and further change the roughness. In sealing the surface the effective flow resistivity of the surface was increased above 300,000 mks Rayls/m, which is typical for weathered agricultural surfaces. The roughness power spectra of the soil surfaces were measured by acoustic backscatter and alternatively by a laser profiler. Regression analysis was used to approximate each roughness power spectrum versus roughness wave number with a best-fit line. The best-fit line was used to calculate the rms height and the correlation length of the rough surface by integrating the approximate roughness power spectrum over a range of roughness wave number values. The range of roughness wave number values defines the roughness length scales used in the statistical calculations. High-roughness wave numbers correspond to smaller length scales of roughness and low-roughness wave numbers correspond to larger length scales of roughness. Over certain ranges of roughness wave number values the statistics from the acoustic backscatter and laser profiler measurements is in good agreement. However, as the low-cutoff roughness wave number is decreased and the high-cutoff roughness wave number is increased, agreement between the laser and acoustic techniques diminishes.     

Rhythm analysis of orthogonal signals from human walking

In physical terms, periodic movements of a human body resulting from walking produce a pulse sequence with repetition time T(1) (instant cadence frequency, 1/T(1)) and duration time T(2). Footstep forces generate periodic T(1) broadband seismic and sound signals due to the dynamic forces between the foot and the ground/floor with duration time T(2), which is equal to the time interval for a single footstep from heel strike to toe slap and weight transfer. In a human gait study (for normal speeds of walking), T(1) was detected as 0.5-0.69 s and double limb support takes up about 12% of the gait cycle (2T(1)), so T(2) is greater than 0.12-0.17 s. Short range (of about 50 m) signatures for 30 humans were recorded simultaneously by four orthogonal sensor types at two locations. The sensor types were active Doppler sonar/radar and passive seismic/acoustics. Analysis of signals from these four sensors collected for walking humans showed temporal synchronization and stability of the cadence frequencies, and the cadence frequency from each sensor was equivalent. The time delay between signals from these sensors due to the differences in speeds of propagation for seismic, sound, and electromagnetic waves allows calculation of the distance from a walker to the sensor suite.     

Thermodynamics of complexation of monovalent metal cations by the ionophore monensin free acid in acetonitrile

The standard Gibbs functions, enthalpies, and entropies for the formation of the complexes of monensin acid with monovalent metal cations in acetonitrile were obtained using various methods (conductometry, potentiometry, and calorimetry). Complexation is appreciable (from 2.0 to 4.5 in terms of association constant logarithm) and controlled mainly by the enthalpic effect. Comparison with formation of the corresponding neutral complexes permits a comparison to the process of monensin mediated transport of cation in membranes. A two-step process involving first the formation of the acidic complex is suggested.     

Etude de la structure magnetique et de la transition de typr “spin-flop” de Rb2FeF5

The nature of the magnetic interactions in the chain compound Rb₂FeF₅ has been investigated using neutron diffraction and magnetic measurements under high applied fields. Rb₂FeF₅ orders antiferromagnetically at T_N = 8.0 ± 0.5 K; the magnetic structure is of the A_Z + G_X mode and the moment of the Fe³⁺ ion extrapoled to 0K is 3.5 ± 0.2 μ_B, this low value being due to zero-point spin reduction. Within a chain the Fe³⁺ ions are antiferromagnetically coupled with an exchange constant of J/k = ?8.8 K. A spin-flop behavior has been observed and interpreted on the basis of the molecular field theory. The critical field was found to be H_C = 65 kOe at 1.7 K.     

Vibration and sound signatures of human footsteps in buildings

The acoustic signature of a footstep is one of several signatures that can be exploited for human recognition. Early research showed the maximum value for the force of multiple footsteps to be in the frequency band of 1-4 Hz. This paper reports on the broadband frequency-dependent vibrations and sound pressure responses of human footsteps in buildings. Past studies have shown that the low-frequency band (below 500 Hz) is well known in the literature, and generated by the force normal to the ground/floor. The seismic particle velocity response to footsteps was shown to be site specific and the characteristic frequency band was 20-90 Hz. In this paper, the high-frequency band (above 500 Hz) is investigated. The high-frequency band of the vibration and sound of a human footstep is shown to be generated by the tangential force to the floor and the floor reaction, or friction force. The vibration signals, as a function of floor coverings and walking style, were studied in a broadband frequency range. Different walking styles result in different vibration signatures in the low-frequency range. However, for the walking styles tested, the magnitudes in the high-frequency range are comparable and independent of walking style.     

Studying the mechanical behavior of a plastic, shock-resisting, antitank landmine

Modal behavior in landmines has recently become a topic of interest for acoustic landmine detection. It is well known that landmines exhibit mechanical resonance behavior that enhances the soil velocity over a buried landmine. Recent experimental work by Zagrai et al. [A. Zagrai, D. Donskoy, and A. Ekimov, J. Acoust. Soc. Am. 118 (6), 3619-3628 (2005)] demonstrates the existence of structural modes in several landmines. The work reported herein parallels the work of Zagrai et al. in studying the structural modes of the pressure plate of a plastic, cylindrically symmetric, antitank landmine. The pressure plate is considered to act as an elastically supported thin elastic plate. An observed perturbation of the first symmetric mode of the pressure plate is caused by the landmine's shock-resisting mechanism. This is validated by a lumped element model for the first symmetric mode coupled to the shock-resisting mechanism.     

A new linear method for analyzing four‐way multiblock tables: STATIS‐4

A new four‐way multiblock method is proposed to study the links between more than two sets of data tables (several multiblocks) measured on the same observations. This method, called STATIS‐4, generalizes the STATIS method to more than one set of matrices. In its first step, STATIS‐4 is searching for one consensus for each multiblock and a global consensus summarizing all the previous ones as good as possible. Some graphical representations can be made to visualize the proximities between the tables within a multiblock and to visualize those between all the multiblocks. Moreover, plots of the observations for each table, each multiblock and global observations can be made. The theory of STATIS‐4 and the algorithm used to obtain the optimal solutions are presented. Moreover, a real sensory dataset is studied with STATIS‐4. Copyright © 2008 John Wiley & Sons, Ltd.