Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The design and study of the Active Disturbance Rejection Control (ADRC) approach for control and disturbance rejection for lower knee rehabilitation utilizing a residential exoskeleton system are provided in this paper. Linear ADRC (LADRC) and Nonlinear ADRC (NADRC) are two controllers that are considered for control purposes based on the structure of ADRC. The contrasts between them are thoroughly discussed in this work. The LADRC is made up of a tracking differential (TD), a linear proportional derivative (LPD) controller, and a linear extended state observer (LESO), whereas the NADRC is made up of the same LESO but with a nonlinear PD (NPD) and a modified optimized TD (MTD). In terms of robustness against the ability to reject applied disturbances, a comparison of LADRC and NADRC has been done. The fundamental challenge with ADRC is that its constituent parameters must be fine-tuned. Grey Wolf Optimizer (GWO) has been proposed for tuning the parameters of ADRC to have the least amount of error variation in order to improve the controlled system's dynamic performance. When a prescribed disturbing torque is applied, the results of a MATLAB simulation show that the LADRC has greater disturbance rejection capabilities than the NADRC.

In the fireworks industry during the bursting of firecrackers, people are affected by health issues by inhaling the chemical particulates matter. When bursting of a firecracker, fuel is mixed with oxygen and releases energy in the form of heat and also contaminated gases. Tamarind seed powder-based fire crackers have been taken for analysis and an emission test was performed. For existing firecrackers, the rate of emissions like CO, CO2, HC, O2, PEF is in the range of 0.032, 0.020, 15, 28.13, and 0.546. For Tamarind seed powder-based firecracker the emission range is reduced compared to the normal firecracker and the emission test results are 0.018, 0.10, 6, 22.12, and 0.546. From the emission test results, the discharge rate of CO and HC, and O2 is reduced for modified firecracker composition. So the Tamarind seed powder-based firecracker influences less emission rate and makes the environment cleaner.

Opinion mining has been attracting increasing attention in recent years. Existing approaches to opinion mining that have worked on general domains face two major challenges for polarity classification of drug reviews. Firstly, indirect opinions frequently occur in the drug domain, while the existing methods have mainly focused on direct opinions and ignored the indirect ones. Secondly, previous works are not sufficient for polarity classification of ambiguous concepts in the drug domain. This paper proposed a semantic framework based on domain knowledge for resource construction and exploitation for indirect opinion mining of drug reviews. Accordingly, some methods were introduced, developed, and compared for building and exploiting a combined knowledge base, polarity-tagged corpus, and context-aware resources for the polarity detection of drug reviews. The test results showed that the proposed methods reached a precision of 89.18% and 80.4% in the application of the combined knowledge base and the polarity-tagged corpus for polarity detection of indirect opinions, respectively. Also, a precision of 79.93% was achieved with the use of context-aware resources constructed for the polarity detection of ambiguous concepts. Overall, the results obtained demonstrated the performance of the proposed methods compared to the existing methods.

Design and synthesis of the poly vinyl chloride (PVC) membrane as Fe(III) ion selective electrode (ISE) sensor based on EHA ionophore as an excellent sensory molecule for monitoring Fe(III) in the sample solution had been done. Simple and efficient EHA was made by condensation of carboxylic acid HA with ethanol and sulfuric acid as catalist. PVC membrane was prepared by mixed all component such as PVC powder, EHA, plasticizer (o-NPOE and DOP) and anion lipophilic (Sodium-TPB and oleic acid) with a total weight of 100 mg and dissolved in 1 mL of dry THF. The electrode membrane responses showed that the electrodes were highly selective to ion Fe3+ at pH 3 with response time of ±50 seconds. The dynamic range of the membrane ISE sensor was 10-1–10-7 M with the value of Nernst factor was ±19 mV per decade. The membrane electrode can be used for at least 5 weeks. The analytical results of Fe(III) measurement showed good confirmity with reference method (AAS), suggesting that the developed analytical tool could be used to measure and monitor Fe(III) in the real water samples.

This paper proposes a current-controlled grounded memristor emulator circuit based on single four-quadrant analog multiplier, a resistor and a capacitor. The behavioral model of the proposed emulator circuit is analyzed, highlighting its characteristics. Experimental results are given to investigate its ability for different operating frequencies and they are in accordance with theoretical analysis and simulation results. By using a divider circuit, the memristance variation in the time domain is obtained. It is observed that the pinched hysteresis loop at high frequency loses symmetry due in part to the shift that introduces a multiplication of sinusoidal signals.

The key advertisement element “text” has a unique superiority effect on attention and attraction towards advertisements. While a number of studies has examined how an advertisements need to be effective and persuading. Our aim in this paper is to mine the customer reviews for emotional, non-emotional and both mix content to design more effective advertisements. We believe that because online customer reviews having a lot of marketing insights which can be used further. We find that that recall effect is higher for print ads containing emotional content. In addition, we found that ads with mix of emotional and non-emotional content from reviews will have a positive attitude towards the print ads. Finally, we found that viewing ads with mix of both emotional and non-emotional text will increase purchase intension among consumers.

Machine tool chatter causes machining instability, surface roughness, and tool wear in metal cutting processes. A stability lobe diagram based on the theory of regenerative vibration is an effective tool to predict and control the chatter. This paper presents the advances in the mechanical design of a parallel kinematic machine tool. The features that make it ideal for machining tasks, and that make unique in its own way, are highlighted. In addition, the description of the progress of this work will be focused on the analysis of the stability limitation for machining systems to derive the stability lobe diagram with modal analysis of the spindle. A vibratory model is developed by adding cutting forces and including analytical equations for the depth of cut and for the cutting speeds, both depending on the frequency of vibration. A step-by-step procedure provides a stability lobe diagram. The results show that it is relatively easy to provide a relationship between depth of cut and spindle speed. In turn, it makes it easy to compare machining processes under different cutting parameters and conditions.

Plant biomass is a potential lignocellulose material  for synthesis of carbon nano structure. Its characteristics as adsorbent and its size particle  make it good additive for liquid fertilizer. In this research, we study influence of sequential different  pressure pyrolysis methods (hydrothermal–microwave method and reflux–microwave method) toward characteristics of carbon nanostructure from sugarcane leaf biomass. Each reflux and hydrothermal method was adjusted at 200oC, then followed by microwave at 800W. Characterization showed that the hydrothermal - microwave method using X-ray diffraction indicates diffractogram patterns of both carbon nanostructure and cellulose. SEM micrographs show sphere and block shapes. FTIR spectra indicates different concentration of oxy surface functional groups. UV spectra of the dispersed product in water indicates  existence of aromatics C=C groups. The hydrothermal - microwave method resulted the product inwhich lower crystalinity index of cellulose, smaller particles, lower concentration of oxy surface groups than the reflux - microwave one. Correlation of chemical properties (aromaticity and fraction of polar groups) was more linier than of physical - chemical properties  (indexe of cellulose crystalinity and fraction of polar groups). The stability of colloid was indicated by dispersing technique in order of sonication < blending < blending - sonication.

The position control in electromechanical systems can many times be performed by direct current (DC) motors. Due to this, the control of these devices is studied via several control strategies in the literature. In this work, the modeling of a direct current motor with coupled load is presented, including the experiments performed to obtain the main system’s parameters and the dynamic’s discretization process. The discretization is taking into account in order to allow the controller to be performed by a computer. From the obtained model, the state feedback control approach along with an observer was explored to create a digital controller for the considered DC motor. The obtained results, both from the simulation and the experimental setup, show that the obtained model is valid. Moreover, it is possible to conclude that the proposed control strategy conducts to appropriate results both in simulations and in experimental tests.

A novel freezing unit was developed for use in ceramic processing by the freeze casting technique. This step is crucial, since the macrostructure promoted by this technique is formed during freezing. Several authors present basic information about the apparatus used in the freezing step, but there are no studies that describe a complete unit as we do in this work and there is no commercial equipment for this purpose. The components of the freezing unit were selected according to function, suitability to project, cost and market availability. Advanced ceramic samples of ZnFe2O4, MnFe2O4, CoFe2O4, NiFe2O4, SiO2, Al2O3 and metallic Cu were produced using the freezing unit and the results of typical macrostructure and porosity analysis validated the chosen setup.