Ten Years of Minimum Efficiency Standards for Induction Motors in Brazil： From Standards Class until Super Premium Motors

The year 2012 marked the 10th anniversary of publication of Presidential Decree No. 4508/2002, which set forth minimum efficiency standards for induction motors in Brazil. Within this context, the present article focuses on the importance of implementing minimum efficiency standards in Brazil and elsewhere and presents the state of the art in domestic and international legislation and standards pertaining to induction motors. It also covers advancements in motor technology, by means of an analysis of motors currently on the market, and trends in said technology, with particular emphasis on the search for new materials for permanent magnet manufacturing. The results of experimental testing of a permanent-magnet motor and a premium-efficiency induction motor are presented and discussed, with the objective of contributing to definition of the IE4 （Efficiency Level from International Electrotechnical Commission） standard and to the goal-oriented Brazilian efficiency program. The present article described the results of experimental testing with an induction motor and a line-start permanent-magnet motor and concluded that permanent-magnet motors are superior in performance to induction motors at loads between half and full, with an efficiency advantage of up to 6.7%. However, in applications with wide variations in load, with motor operation below half load, use of permanent-magnet motors is not economically feasible, as the current cost of these motors exceeds that of induction motors. Another relevant finding concerns the current harmonic distortion observed during testing. The tested permanent-magnet motor exhibited a distortion of up to 13.5%, exceeding Institute of Electrical and Electronics Engineers Standard 519/1992 recommended limits. This behavior must be clearly specified and taken into account by future standards that define the super premium class, lest the impact of harmonic distortion prove to be detrimental to industries that adopt these motors for their processes.     

Effects of intermittent hydrostatic pressure magnitude on the chondrogenesis of MSCs without biochemical agents under 3D co-culture

Without using biochemical agents, in this study, we sought to investigate the potential of controlling the differentiation of mesenchymal stem cells (MSCs) into a specific cell type through the use of 3D co-culturing and mechanical stimuli. MSCs and primary cultured chondrocytes were separately encapsulated into alginate beads, and the two types of beads were separated by a membrane. For the investigation a computer-controllable bioreactor was designed and used to engage intermittent hydrostatic pressure (IHP). Five different magnitudes (0.20, 0.10, 0.05, 0.02?MPa and no stimulation) of IHP were applied. The stimulation pattern was the same for all groups: 2?h/day for 7 days starting at 24?h after seeding; 2 and 15?min cycles of stimulating and resting, respectively. Biochemical (DNA and GAG contents), histological (Alcian blue), and RT-PCR (Col II, SOX9, AGC) analyses were performed on days 1, 5, 10, and 20. The results from these analyses showed that stimulation with higher magnitudes of IHP (≥0.10?MPa) were more effective on the proliferation and differentiation of co-cultured MSCs. Together, these data demonstrate the potential of using mechanical stimulation and co-culturing for the proliferation and differentiation of MSCs, even without biochemical agents.     

Structured total least squares approach for efficient frequency estimation

A new structured total least squares (STLS) based frequency estimation algorithm for real sinusoids corrupted by white noise is devised. Numerical results are included to contrast the estimator performance with an existing STLS frequency estimation method as well as the Cramér-Rao lower bound in different signal-to-noise ratio conditions.     

S&T knowledge production from 2000 to 2009 in two periphery countries: Brazil and South Korea

This paper investigates the dynamic evolution profiles of science and technology knowledge production in Brazil and the Republic of Korea from 2000 to 2009. The two countries have followed different models of publication profiles, bioenvironmental model and Japanese model, and they currently belong to periphery countries in terms of the center-periphery framework. Brazil and the Republic of Korea have established a few core disciplines successfully and increased their share in the world publication of scientific papers over the last decade. Notwithstanding the fact that the two countries have recorded sustained growth in the percentage of published scientific papers, South Korea has evolved into a more balanced science and technology knowledge production system, whereas Brazil into the more unbalanced knowledge production system. Core-lagging or periphery-lagging patterns of science production have been revealed in Brazil and indirectly imply that the existing science base has not been fully stimulated or utilized.     

Unraveling Doping Capability of Conjugated Polymers for Strategic Manipulation of Electric Dipole Layer toward Efficient Charge Collection in Perovskite Solar Cells

Developing electrical organic conductors is challenging because of the difficulties involved in generating free charge carriers through chemical doping. To devise a novel doping platform, the doping capabilities of four designed conjugated polymers (CPs) are quantitatively characterized using an AC Hall‐effect device. The resulting carrier density is related to the degree of electronic coupling between the CP repeating unit and 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4‐TCNQ), and doped PIDF‐BT provides an outstanding electrical conductivity, exceeding 210 S cm^?1, mainly due to the doping‐assisted facile carrier generation and relatively fast carrier mobility. In addition, it is noted that a slight increment in the electron‐withdrawing ability of the repeating unit in each CP diminishes electronic coupling with F4‐TCNQ, and severely deteriorates the doping efficiency including the alteration of operating doping mechanism for the CPs. Furthermore, when PIDF‐BT with high doping capability is applied to the hole transporting layer, with F4‐TCNQ as the interfacial doping layer at the interface with perovskite, the power conversion efficiency of the perovskite solar cell improves significantly, from 17.4% to over 20%, owing to the ameliorated charge‐collection efficiency. X‐ray photoelectron spectroscopy and Kelvin probe analyses verify that the improved solar cell performance originates from the increase in the built‐in potential because of the generation of electric dipole layer.     

Utilization of the Bayesian Method to Improve Hydrological Drought Prediction Accuracy

This study established a hydrological drought forecasting system based on the Bayesian method and evaluated its utilization for South Korea. The regression result between Historical Runoff (HR) and Ensemble Streamflow Prediction Runoff (ESP_R) was used as prior information in the Bayesian method. Additionally Global seasonal forecast System 5 Runoff (GS5_R) produced using a dynamic prediction method was used in a likelihood function. Bayesian Runoff (BAY_R), as posterior information, was generated and compared with the ESP_R and GS5_R results for predictive ability evaluation. The Standardized Runoff Index (SRI) was selected for the drought prediction, and the BAY_SRI, GS5_SRI and ESP_SRI were computed using BAY_R, GS5_R and ESP_R, respectively. The Correlation Coefficient (CC), Nash-Sutcliffe Efficiency (NSE) and Receiver Operating Characteristic (ROC) score of BAY_SRI were the highest, and the Root Mean Square Error (RMSE) of BAY_SRI was the lowest among the methods. The Bayesian method improved the behavioral and quantitative error of drought prediction and the predictive ability of the occurrence of drought. In particular, the simulation accuracy was significantly improved during the flood season. Additionally, BAY_SRI represented past drought scenarios better than did the other two methods. Overall, we found that the Bayesian method could be applied for hydrological drought predictions for based on 1- and 2-month lead times.