Alexandre Mesquita - Academia.edu (original) (raw)

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Papers by Alexandre Mesquita

In wireless networks the probability of successful communication can be significantly increased b... more In wireless networks the probability of successful communication can be significantly increased by transmitting multiple copies of a same packet. Communication protocols that exploit this by dynamically assigning the number of transmitted copies of the same data can significantly improve the control performance in a networked control system with only a modest increase in the total number of transmissions. In this paper we develop techniques to design communication protocols that exploit multiple packets transmissions while seeking a balance between stability/estimation performance and communication rate. An average cost optimality criterion is employed to obtain optimal protocols. Optimal protocols are also obtained for networks whose nodes are subject to limited computation.

We consider the problem of seeking the maximum of a scalar signal using a swarm of autonomous veh... more We consider the problem of seeking the maximum of a scalar signal using a swarm of autonomous vehicles equipped with sensors that can take point measurements of the signal. Vehicles are not able to measure their current position or to communicate with each other. Our approach induces the vehicles to perform a biased random walk inspired by bacterial chemotaxis and controlled by a stochastic hybrid automaton. With such a controller, it is shown that the positions of the vehicles evolve towards a probability density that is a specified function of the spatial profile of the measured signal, granting higher vehicle densities near the signal maxima.

In wireless networks the probability of successful communication can be significantly increased b... more In wireless networks the probability of successful communication can be significantly increased by transmitting multiple copies of a same packet. Communication protocols that exploit this by dynamically assigning the number of transmitted copies of the same data can significantly improve the control performance in a networked control system with only a modest increase in the total number of transmissions. In this paper we develop techniques to design communication protocols that exploit multiple packets transmissions while seeking a balance between stability/estimation performance and communication rate. An average cost optimality criterion is employed to obtain optimal protocols. Optimal protocols are also obtained for networks whose nodes are subject to limited computation.

Asian Journal of Andrology, 2007

To examine the treatment efficacy of Korean Red Ginseng (KRG) in impotent men with erectile dysfu... more To examine the treatment efficacy of Korean Red Ginseng (KRG) in impotent men with erectile dysfunction (ED). Methods: A total of 60 patients presenting mild or mild to moderate ED were enrolled in a double-blind, placebo-controlled study in which the efficacies of KRG and a placebo were compared. The patients received either 1 000 mg (3 times daily) of KRG or a placebo. Results: The five-item version of the International Index of Erectile Function (IIEF-5) score after the treatment was significantly higher in the KRG group compared with that before the treatment (from 16.4 ± 2.9 to 21.0 ± 6.3, P < 0.0001). In contrast, there was no difference before and after the treatment in the placebo group (from 17.0 ± 3.1 to 17.7 ± 5.6, P > 0.05). In the KRG group, 20 patients (66.6%), reported improved erection, significant in the global efficacy question (P < 0.01); in the placebo group there was no significance. Scores on questions 2 (rigidity), 3 (penetration), 4 and 5 (maintenance), were significantly higher for KRG than those for the placebo when those questions were answered after 12 weeks of each treatment (P < 0.01). When the score in the KRG group was compared to the placebo group after the treatment, there was a significant improvement in total score (IIEF-5 score) in questions 3 and 5 for the KRG-treated group (P < 0.001 and P < 0.0001, respectively). The levels of serum testosterone, prolactine and cholesterol after the treatment were not statistically significant different between the KRG and the placebo group (P > 0.05). Conclusion: Our data show that KRG can be an effective alternative to the invasive approaches for treating male ED. (Asian J Androl

Phase Transitions, 2010

The temperature dependence of the crystalline structure and the lattice parameters of Pb1−xLaxZr0... more The temperature dependence of the crystalline structure and the lattice parameters of Pb1−xLaxZr0.40Ti0.60O3 ferroelectric ceramic system with 0.00 ≤ x ≤ 0.21 was determined. The samples with x ≤ 0.11 show a cubic-to-tetragonal phase transition at the maximum dielectric permittivity, Tmax. Above this amount and especially for the x = 0.12 sample, a spontaneous phase transition from a relaxor ferroelectric

Journal of Thermal Analysis and Calorimetry, 2007

Pb1–xLaxTiO3 (PLT) nanocrystalline powders were obtained by polymeric precursor method. The sampl... more Pb1–xLaxTiO3 (PLT) nanocrystalline powders were obtained by polymeric precursor method. The samples were analyzed by differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques to characterize properly the distinct thermal events occurring during synthesis. The X-ray diffraction patterns show a tetragonal structure for the samples with x=0.10 and 0.15. An increase of the lanthanum concentration to x=0.20 led to a highly symmetric structure, cubic on average. The powders obtained at the end of the synthesis had an average particle size of 30 to 70 nm.

Journal of Thermal Analysis and Calorimetry, 2009

Al2CoO4–PbCrO4 and Al2CoO4–Pb2CrO5 crystalline powders in different proportions were obtained by ... more Al2CoO4–PbCrO4 and Al2CoO4–Pb2CrO5 crystalline powders in different proportions were obtained by the polymeric precursor method. Differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques were used to accurately characterize the distinct thermal events occurring during synthesis. The TG and DSC results revealed a series of overlapping decomposition reactions due to different exothermal events, which were identified as H2O and NOx elimination and polymer pyrolysis. The X-ray diffraction patterns of the xAl2CoO4–(1 − x)PbCrO4 and xAl2CoO4–(1 − x)Pb2CrO5 mixed compounds, with x = 1, 0.75, 0.5, 0.25 and 0, were obtained in the crystalline form with their respective phases, and proved consistent with the nominal compositions. The synthesis of these two systems yielded nine different colors and shades.

In wireless networks the probability of successful communication can be significantly increased b... more In wireless networks the probability of successful communication can be significantly increased by transmitting multiple copies of a same packet. Communication protocols that exploit this by dynamically assigning the number of transmitted copies of the same data can significantly improve the control performance in a networked control system with only a modest increase in the total number of transmissions. In this paper we develop techniques to design communication protocols that exploit multiple packets transmissions while seeking a balance between stability/estimation performance and communication rate. An average cost optimality criterion is employed to obtain optimal protocols. Optimal protocols are also obtained for networks whose nodes are subject to limited computation.

We consider the problem of seeking the maximum of a scalar signal using a swarm of autonomous veh... more We consider the problem of seeking the maximum of a scalar signal using a swarm of autonomous vehicles equipped with sensors that can take point measurements of the signal. Vehicles are not able to measure their current position or to communicate with each other. Our approach induces the vehicles to perform a biased random walk inspired by bacterial chemotaxis and controlled by a stochastic hybrid automaton. With such a controller, it is shown that the positions of the vehicles evolve towards a probability density that is a specified function of the spatial profile of the measured signal, granting higher vehicle densities near the signal maxima.

In wireless networks the probability of successful communication can be significantly increased b... more In wireless networks the probability of successful communication can be significantly increased by transmitting multiple copies of a same packet. Communication protocols that exploit this by dynamically assigning the number of transmitted copies of the same data can significantly improve the control performance in a networked control system with only a modest increase in the total number of transmissions. In this paper we develop techniques to design communication protocols that exploit multiple packets transmissions while seeking a balance between stability/estimation performance and communication rate. An average cost optimality criterion is employed to obtain optimal protocols. Optimal protocols are also obtained for networks whose nodes are subject to limited computation.

Asian Journal of Andrology, 2007

To examine the treatment efficacy of Korean Red Ginseng (KRG) in impotent men with erectile dysfu... more To examine the treatment efficacy of Korean Red Ginseng (KRG) in impotent men with erectile dysfunction (ED). Methods: A total of 60 patients presenting mild or mild to moderate ED were enrolled in a double-blind, placebo-controlled study in which the efficacies of KRG and a placebo were compared. The patients received either 1 000 mg (3 times daily) of KRG or a placebo. Results: The five-item version of the International Index of Erectile Function (IIEF-5) score after the treatment was significantly higher in the KRG group compared with that before the treatment (from 16.4 ± 2.9 to 21.0 ± 6.3, P < 0.0001). In contrast, there was no difference before and after the treatment in the placebo group (from 17.0 ± 3.1 to 17.7 ± 5.6, P > 0.05). In the KRG group, 20 patients (66.6%), reported improved erection, significant in the global efficacy question (P < 0.01); in the placebo group there was no significance. Scores on questions 2 (rigidity), 3 (penetration), 4 and 5 (maintenance), were significantly higher for KRG than those for the placebo when those questions were answered after 12 weeks of each treatment (P < 0.01). When the score in the KRG group was compared to the placebo group after the treatment, there was a significant improvement in total score (IIEF-5 score) in questions 3 and 5 for the KRG-treated group (P < 0.001 and P < 0.0001, respectively). The levels of serum testosterone, prolactine and cholesterol after the treatment were not statistically significant different between the KRG and the placebo group (P > 0.05). Conclusion: Our data show that KRG can be an effective alternative to the invasive approaches for treating male ED. (Asian J Androl

Phase Transitions, 2010

The temperature dependence of the crystalline structure and the lattice parameters of Pb1−xLaxZr0... more The temperature dependence of the crystalline structure and the lattice parameters of Pb1−xLaxZr0.40Ti0.60O3 ferroelectric ceramic system with 0.00 ≤ x ≤ 0.21 was determined. The samples with x ≤ 0.11 show a cubic-to-tetragonal phase transition at the maximum dielectric permittivity, Tmax. Above this amount and especially for the x = 0.12 sample, a spontaneous phase transition from a relaxor ferroelectric

Journal of Thermal Analysis and Calorimetry, 2007

Pb1–xLaxTiO3 (PLT) nanocrystalline powders were obtained by polymeric precursor method. The sampl... more Pb1–xLaxTiO3 (PLT) nanocrystalline powders were obtained by polymeric precursor method. The samples were analyzed by differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques to characterize properly the distinct thermal events occurring during synthesis. The X-ray diffraction patterns show a tetragonal structure for the samples with x=0.10 and 0.15. An increase of the lanthanum concentration to x=0.20 led to a highly symmetric structure, cubic on average. The powders obtained at the end of the synthesis had an average particle size of 30 to 70 nm.

Journal of Thermal Analysis and Calorimetry, 2009

Al2CoO4–PbCrO4 and Al2CoO4–Pb2CrO5 crystalline powders in different proportions were obtained by ... more Al2CoO4–PbCrO4 and Al2CoO4–Pb2CrO5 crystalline powders in different proportions were obtained by the polymeric precursor method. Differential scanning calorimetry (DSC) and thermogravimetry (TG) techniques were used to accurately characterize the distinct thermal events occurring during synthesis. The TG and DSC results revealed a series of overlapping decomposition reactions due to different exothermal events, which were identified as H2O and NOx elimination and polymer pyrolysis. The X-ray diffraction patterns of the xAl2CoO4–(1 − x)PbCrO4 and xAl2CoO4–(1 − x)Pb2CrO5 mixed compounds, with x = 1, 0.75, 0.5, 0.25 and 0, were obtained in the crystalline form with their respective phases, and proved consistent with the nominal compositions. The synthesis of these two systems yielded nine different colors and shades.