Robot robust path tracking

A new discontinuous robust control law for a rigid manipulator with bounded parameter uncertainties to track a desired trajectory, is presented. Global exponential stability is proved by the use of a natural Lyapunov function based on a transformation of the manipulator's differential equation due to Slotine and Li [2]. Convergence is to a sliding mode along which the tracking error is reduced at an arbitrary exponential rate. It is also shown how adaptation of bounds on uncertainties, and parameter adaptation, can be incorporated. For a continuous approximation of the discontinuous control law,practical stability (essentially, global uniform ultimate boundedness) of the tracking error is proved. Simulation results for the continuous control law exhibit excellent robust tracking.     

A design methodology for networks of online modules and its application to the Levinson-Durbin algorithm

The use of online arithmetic was often proposed for hardware implementations of complex digital-signal processing (DSP) algorithms. However, several important issues in the design process of such algorithms using online arithmetic are rarely discussed in the literature. This paper presents these issues and provides a methodology to analyze the behavior of networks of online arithmetic modules performing serial computation over fixed-point numbers. The methodology is presented, applied in several examples, and finally used to design an efficient field programmable gate arrays implementation of the Levinson-Durbin algorithm in an application of the Yule-Walker power spectrum estimation. The methodology can be applied to other algorithms as well and it simplifies the task of designing and verifying a network of online modules. The experimental results show the advantages of online arithmetic in the design of complex DSP algorithms.     

Flavonoids of “La Alcarria” honey A study of their botanical origin

Summary The flavonoids present in ten selected samples of La Alcarria honey with different pollen compositions have been HPLC analysed in order to establish if correlations between botanical origin and flavonoid profiles are possible. A common flavonoid pattern is observed in the different samples showing that pollen is not the main source of honey flavonoids. A close correlation between the flavonoid patterns of honey flavonoids and propolis flavonoids has been found suggesting that flavonoid analysis could be more useful in geographical origin determinations than in botanical origin studies.

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Flavonoide des La-Alcarria-Honigs Eine Studie ihres botanischen Ursprungs

Zusammenfassung Die Flavonoide in Proben in Alcarria-Honig mit unterschiedlicher Pollenzusammensetzung wurden untersucht, um Kortrelationen zwischen dem botanischen Ursprung und den möglichen Flavonoiden zu finden. In den verschiedenen Proben wurde ein Flavonoid-Muster gefunden, wobei der Pollen nicht die Hauptquelle der Honigflavonoide ist. Es wurde jedoch eine enge Korrelation zwischen den Flavonoid-Mustern des Honigs und des Bienenkittharzes gefunden, was für die geographische Herkunft wichtiger ist als die botanische.

     

Fate of Calcium Chloride Dissolved in Concrete Mix Water

The extent to which chloride ion incorporated in portland cement concrete as calcium chloride accelerator at the usual treatment levels remains dissolved in the pore solution was investigated. This was examined by direct analysis of pore solutions expressed from cement pastes. The chloride ion concentration of the pore solution remains high during the first day of hydration and only gradually declines. It appears that appreciable concentrations of chloride ion likely remain in solution indefinitely .     

Experimental methods in chemical engineering: X‐ray photoelectron spectroscopy‐XPS

X‐ray photoelectron spectroscopy (XPS) is a quantitative surface analysis technique used to identify the elemental composition, empirical formula, chemical state, and electronic state of an element. The kinetic energy of the electrons escaping from the material surface irradiated by an x‐ray beam produces a spectrum. XPS identifies chemical species and quantifies their content and the interactions between surface species. It is minimally destructive and is sensitive to a depth between 1–10nm. The elemental sensitivity is in the order of 0.1 atomic %. It requires ultra high vacuum ( Pa) in the analysis chamber and measurement time varies from minutes to hours per sample depending on the analyte. XPS dates back 50 years ago. New spectrometers, detectors, and variable size photon beams, reduce analysis time and increase spatial resolution. An XPS bibliometric map of the 10 000 articles indexed by Web of Science^[1] identifies five research clusters: (i) nanoparticles, thin films, and surfaces; (ii) catalysis, oxidation, reduction, stability, and oxides; (iii) nanocomposites, graphene, graphite, and electro‐chemistry; (iv) photocatalysis, water, visible light, and ; and (v) adsorption, aqueous solutions, and waste water.