Robot task plan representation by Petri nets: modelling, identification, analysis and execution

In this paper we introduce a framework to represent robot task plans based on Petri nets. Our approach enables modelling a robot task, analysing its qualitative and quantitative properties and using the Petri net representation for actual plan execution. The overall model is obtained from the composition of simple models, leading to a modular approach. Analysis is applied to a closed loop between the robot controller and the environment Petri net models. We focus here on the quantitative properties, captured by stochastic Petri net models. Furthermore, we introduce a method to identify the environment and action layer parameters of the stochastic Petri net models from real data, improving the significance of the model. The framework building blocks and a single-robot task model are detailed. Results of a case study with simulated soccer robots show the ability of the framework to provide a systematic modelling tool, and of determining, through well-known analysis methods for stochastic Petri nets, relevant properties of the task plan applied to a particular environment.     

Electroluminescence of a device based on europium β-diketonate with phosphine oxide complex

Rare earth (RE) ions have spectroscopic characteristics to emit light in narrow lines, which makes RE complexes with organic ligands candidates for full color OLED (Organic Light Emitting Diode) applications. In particular, β-diketone rare earth (RE³⁺) complexes show high fluorescence emission efficiency due to the high absorption coefficient of the β-diketone and energy transfer to the central ion. In this work, the fabrication and the electroluminescent properties of devices containing a double and triple-layer OLED using a new β-diketone complex, [Eu(bmdm)₃(tppo)₂], as transporting and emitting layers are compared and discussed. The double and triple-layer devices based on this complex present the following configurations respectively: device 1: ITO/TPD (40 nm)/[Eu(bmdm)₃(tppo)₂] (40 nm)/Al (150 nm); device 2: ITO/TPD (40 nm)/[Eu(bmdm)₃(tppo)₂] (40 nm)/Alq₃ (20 nm)/Al (150 nm) and device 3: ITO/TPD (40 nm)/bmdm-ligand (40 nm)/Al (150 nm), were TPD is (N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1-biphenil-4,4-diamine) and bmdm is butyl methoxy-dibenzoyl-methane. All the films were deposited by thermal evaporation carried out in a high vacuum system. These devices exhibit high intensity photo- (PL) and electro-luminescent (EL) emission. Electroluminescence spectra show emission from Eu³⁺ ions attributed to the ⁵D₀ to ⁷F_J (J = 0, 1, 2, 3 and 4) transitions with the hypersensitive ⁵D₀ → ⁷F₂ transition (around 612 nm) as the most prominent one. Moreover, a transition from ⁵D₁ to ⁷F₁ is also observed around 538 nm. The OLED light emission was almost linear with the current density. The EL CIE chromaticity coordinates (X = 0.66 and Y = 0.33) show the dominant wavelength, λ_d = 609 nm, and the color gamut achieved by this device is 0.99 in the CIE color space.     

Establishing quality performance of distribution companies based on yardstick regulation

This paper proposes a procedure and methodology for performance target setting related to continuity metrics in electricity distribution networks. This proposal deals with one of the key issues in the monopoly regulation, which is either the reduction of the information asymmetry among economic agents or the emulation of a competitive environment in industry segments usually considered as natural monopolies. This paper develops an approach toward standard definitions for Customer Average Interruption Duration Index (DEC) and Customer Average Interruption Frequency Index (FEC) based on inter-companies comparative analysis. This approach introduces productive efficiency concepts to the definition of network performance. In order to do so, the data envelopment analysis (DEA) technique, used for defining the efficiency frontier, was combined with the dynamic cluster technique, oriented toward models of identification of similar networks. A technique for comparative analysis was used for the definition of the network expected performance. Examples with the Brazilian electric systems are provided to clarify the methodology suggested by this paper.     

Spin Polarization by Tilted Magnetic Field in Wide Ga1?xAlxAs Parabolic Quantum Wells

Wide parabolic wells can be created by properly controlling the Al content during the growth of successive Ga_1–xAl_xAs thin layers. Under a tilted magnetic field these systems present interesting transport properties, which are associated to their composition dependent g-factor. We present an exact solution for the eigenstates of an electron gas inside such a quantum well. We calculate the renormalized cyclotron frequencies as functions of the angle of tilt, as well as the density of states, and the Fermi level. We discuss the conditions for the existence of spin-polarized charge.     

AC motor drive systems with a reduced-switch-count converter

This paper presents two reduced-switch-count AC drive systems. One of the configurations was conceived to operate with a two-phase motor and the other one with a three-phase motor. The drive systems provide both bidirectional power flow and power factor control. Pulsewidth modulation techniques for the converter control are discussed. Experimental results are presented.     

In vivo remineralization of acid-etched enamel in non-brushing areas as influenced by fluoridated orthodontic adhesive and toothpaste

This study aimed to evaluate the in vivo remineralization of acid-etched enamel in non-brushing areas as influenced by fluoridated orthodontic adhesive and toothpaste. One hundred and twenty teeth from 30 volunteers were selected. The teeth were assigned to four treatments: no treatment (negative control); 37% phosphoric acid-etching (PAE) (positive control); PAE + resin-modified glass ionomer cement (RMGIC); and, PAE + composite resin. Patients brushed teeth with fluoridated (n = 15) or non-fluoridated (n = 15) toothpastes, so that etched enamel was protected with screens and it was not in contact with the brush bristles. Remineralization was evaluated by means of laser fluorescence (LF), environmental scanning electronic microscopy, and energy dispersive spectrometry after extraction. The LF means were compared by means of Wilcoxon and Mann Whitney tests. Environmental scanning electron microscopy scores were compared among the groups using a Kruskal Wallis test, whereas the Ca/P ratio was evaluated by means of an Analysis of Variance with subparcels (treatments) and Tukey's post-hoc test. There were no statistically significant differences between the tooth pastes and between the orthodontic adhesives evaluated. Most teeth presented only partial enamel remineralization. Therefore, the fluoride released by the RMGIC was not enough to cause increased crystal regrowth in the acid-etched enamel. The use of fluoridated toothpaste did not provide positive additional effect.     

Dipotassium Glycyrrhizinate on Melanoma Cell Line: Inhibition of Cerebral Metastases Formation by Targeting NF-kB Genes-Mediating MicroRNA-4443 and MicroRNA-3620—Dipotassium Glycyrrhizinate Effect on Melanoma

Glycyrrhizic acid (GA), a natural compound isolated from licorice (Glycyrrhiza glabra), has exhibited anti-inflammatory and anti-tumor effects in vitro. Dipotassium glycyrrhizinate (DPG), a dipotassium salt of GA, also has shown an anti-tumor effect on glioblastoma cell lines, U87MG and T98G. The study investigated the DPG effects in the melanoma cell line (SK-MEL-28). MTT assay demonstrated that the viability of the cells was significantly decreased in a time- and dose-dependent manner after DPG (IC₅₀ = 36 mM; 24 h). DNA fragmentation suggested that DPG (IC₅₀) induced cellular apoptosis, which was confirmed by a significant number of TUNEL-positive cells (p-value = 0.048) and by PARP-1 [0.55 vs. 1.02 arbitrary units (AUs), p-value = 0.001], BAX (1.91 vs. 1.05 AUs, p-value = 0.09), and BCL-2 (0.51 vs. 1.07 AUs, p-value = 0.0018) mRNA compared to control cells. The proliferation and wound-healing assays showed an anti-proliferative effect on DPG-IC₅₀-treated cells, also indicating an inhibitory effect on cell migration (p-values < 0.001). Moreover, it was observed that DPG promoted a 100% reduction in melanospheres formation (p-value = 0.008). Our previous microRNAs (miRs) global analysis has revealed that DPG might increase miR-4443 and miR-3620 expression levels. Thus, qPCR showed that after DPG treatment, SK-MEL-28 cells presented significantly high miR-4443 (1.77 vs. 1.04 AUs, p-value = 0.02) and miR-3620 (2.30 vs. 1.00 AUs, p-value = 0.01) expression compared to control cells, which are predicted to target the NF-kB, CD209 and TNC genes, respectively. Both genes are responsible for cell attachment and migration, and qPCR revealed significantly decreased CD209 (1.01 vs. 0.54 AUs, p-value = 0.018) and TNC (1.00 vs. 0.31 AUs, p-value = 2.38 × 10⁻⁶) mRNA expression levels after DPG compared to untreated cells. Furthermore, the migration of SK-MEL-28 cells stimulated by 12-O-tetradecanoylphorbol-13-acetate (TPA) was attenuated by adding DPG by wound-healing assay (48 h: p-value = 0.004; 72 h: p-value = 7.0 × 10⁻⁴). In addition, the MMP-9 expression level was inhibited by DPG in melanoma cells stimulated by TPA and compared to TPA-treated cells (3.56 vs. 0.99 AUs, p-value = 0.0016) after 24 h of treatment. Our results suggested that DPG has an apoptotic, anti-proliferative, and anti-migratory effect on SK-MEL-28 cells. DPG was also able to inhibit cancer stem-like cells that may cause cerebral tumor formation.