Search

This paper presents an architecture of the Doubly-Fed Induction Generator based on Wind Energy Conversion System (DFIG-WECS) to study with the Low Voltage Ride Through (LVRT) capability. The proposed architecture consists of three main parts namely the wind turbine, electric generator, control systems. The wind turbine and gearbox are modeled by a servo motor driven by using an inverter system. The electric generator uses the Wound Rotor Induction Generator (WRIG). The control system composes of the rotor-side converter (RSC) and the grid-side converter (GSC). The integration of the digital signal processor (DSP) with the Simulink/Matlab software of the vector control scheme is implemented to control both RSC and GSC. Besides, to protect the overcurrent of the generator’s rotor and overvoltage of the DC-link, the crowbar and chopper circuits and the logical scheme between the crowbar and the RSC are also proposed. To approve the control algorithms implemented in DSP as hardware in the loops, the proposed 0.8kW DFIG-WESC system has been performed under the experimental environment considering LVRT requirement in German grid code.

The microstructure, strain behavior, and piezoelectric properties of Bi0.5(Na0.8K0.2)0.5TiO3 (BNKT-Sn) piezoelectric ceramics modified with Sn4+ ions were systematically studied. The experimental results indicated that the Sn4+ ion doping was a viable and effective method to promote the electromechanical properties and the strain behavior of the BNKT ceramics. When the Sn content was 0.02 mol, the resultant BNKT ceramics exhibited excellent electrical properties with a density of 5.92 g.cm–3, a dielectric constant (er) of 1235, a dielectric loss (tanδ) of 0.048, the electromechanical coupling factors of 0.36 (kp) and 0.39 (kt), a piezoelectric coefficient (d33) of 171 pC/N, and a mechanical quality factor (Qm) of 125. Moreover, a large unipolar strain of 0.45% and a high normalized strain of 865 pm/V were achieved at 50 °C. The main achievement of this study was the large normalized strain (d33*) of 876 pm/V at the SnO2 content of 0.04 mol.

The paper aims at introducing an analysis of thin-walled functionally graded sandwich beams for general non-uniform quadrilateral cross-sections. Generally, the materials are assumed to be graded through the thickness following a predefined shape while Poisson's ratio kept as a constant due to its less domination. The cross-section linearly varies from one end to another end of the beam. In order to relax the difficulties in modeling as well as capturing the behaviors of thin-walled functionally graded beams, a higher-order approach has been applied including warping, coupling distortions as well as Poisson's distortion. A multi-separated beam on each edge of the cross-section which is an application of the so-called beam-frame-modal method is adopted. Subsequently, the effects of these major importance along with anisotropy of materials are then fully considered. As a consequence, the analysis is able to extensively applied to closed-section beam-shells with different curvatures. In order to illustrate the accuracy and computational efficiency of the method, various examples have been conducted in which the results obtained from finite element package as ABAQUS are employed. Keywords: quadrilateral cross-section; thin-walled FG beam; higher-order coupling; beam frame modal.

The retinal pigment epithelium (RPE) forms a monolayer sheet separating the retina and choroid in vertebrate eyes. The polarized nature of RPE is maintained by distributing membrane proteins differentially along apico-basal axis. We found the distributions of these proteins differ in embryonic, post-natal, and mature mouse RPE, suggesting developmental regulation of protein trafficking. Thus, we deleted tumor susceptibility gene 101 (Tsg101), a key component of endosomal sorting complexes required for transport (ESCRT), in embryonic and mature RPE to determine whether ESCRT-mediated endocytic protein trafficking correlated with the establishment and maintenance of RPE polarity. Loss of Tsg101 severely disturbed the polarity of RPE, which forms irregular aggregates exhibiting non-polarized distribution of cell adhesion proteins and activation of epidermal growth factor receptor signaling. These findings suggest that ESCRT-mediated protein trafficking is essential for the development and maintenance of RPE cell polarity.

Background: Vietnam is among countries with highest prevalence of tobacco smoking, attempt to quit is an important indicator to monitor the effectiveness of tobacco control efforts. This paper aims to describe smoking quit attempt and examine its association with some individual characteristics among male smokers. Methods: Data from the Global Adult Tobacco Survey in Vietnam in 2015 was analyzed for a sample of 1,903 male smokers taking from the national representative sample of 8,996 adults aged 15 years and above. Results: Proportion of quit attempt during 12 months prior to the interview among male smoker was 37.1%. Attempt to quit smoking was significantly associated with age (OR=2.84 and 95% CI: 1.43-5.66 for those aged 55 years and older vs. those aged 24 years and younger), with knowledge of harmful effects on health (OR=1.97 and 95% CI: 1.45-2.66 for those who could list 6 to 7 diseases vs. those who could list 3 or less diseases), number of channels with anti smoking message (OR=1.72 and 95% CI: 1.21-2.45 for those who had exposure from 3 channels or more vs. those who did not expose any channels), number of years smoking (OR=0.59 and OR=0.40 for those with less than 15 years smoking vs. those with 25 to 34 years smoking and more than 35 years smoking, respectively). Conclusion: Intervention to improve knowledge of tobacco harmful effects, and access to multiple and modern antismoking communication channels would be effective to raise quit attempt among smokers. Research to promote effectiveness of quit advice by health staff should be paid more attention.

Macrophages play a vital role in cardiac repair following myocardial infarction (MI). An enriched environment (EE) is involved in the regulation of macrophage-related activities and disease progression; however, whether EE affects the phenotype and function of macrophages to improve postinfarction cardiac repair remains unknown. In this study, we found that EE improved cardiac function, decreased mortality, and ameliorated adverse ventricular remodeling in mice after MI, with these outcomes closely related to the increased survival of Ly6C low macrophages and their CCR2 − MHCII low subsets. EE increased the expression of brain-derived neurotrophic factor (BDNF) in the hypothalamus, leading to higher circulating levels of BDNF, which, in turn, regulated the cardiac macrophages. BDNF bound to tropomyosin receptor kinase B to activate downstream ERK1/2 and AKT pathways, promoting macrophage survival. These findings demonstrate that EE optimizes postinfarction cardiac repair and highlights the significance of EE as a previously unidentified strategy for impeding adverse ventricular remodeling.

This paper investigates firm heterogeneity in total factor productivity across Vietnam domestic private sector with sixteen manufacturing subindustries over the period 2010-2016, with a focus on labor size and based on total factor productivity (TFP); including TFP level, TFP distance, and TFP dispersion. Our results indicate that, in the private sector, labor heterogeneity on productivity are very dependent on specific manufacturing sectors, and on type of TFP. From an industrial policy perspective, there is hence productivity related reason on why Vietnamese policy makers should prefer large and extremely large firms over small and medium enterprises (SMEs) in some manufacturing and vice versa. Our results provide a support for both SMEs and large private consortiums, depending on specific manufacturing sectors. In addition, since there is a strong evidence to suggest that labor heterogeneity in TFP exists in some manufacturing sectors, the rationality behind policies to support SMEs and large firms at every manufacturing sectors seems to be questionable.

In this paper we consider two matrix equations that involve the weighted geometric mean. We use the fixed point theorem in the cone of positive definite matrices to prove the existence of a unique positive definite solution. In addition, we study the multi-step stationary iterative method for those equations and prove the corresponding convergence. A fidelity measure for quantum states based on the matrix geometric mean is introduced as an application of matrix equation.

This study aims to investigate a feasible converter architecture and corresponding control method for Wind Turbine (WT) systems using permanent magnet synchronous generators (PMSG). The converter configuration is designed based on the AC/DC/AC converter, including the Diode Bridge Rectifier (DBR) and Pulse Width Modulated Current Source Inverter (PWM-CSI), Buck-Boost Converter (BBC), and Bypass Chopper (BC). The control strategy for the proposed converter is developed to enhance the operating performance of WT-PMSG, which must satisfy four requisitions. Firstly, it proposes the control approach for the pitch angle to control the output power of the WT when the wind speed is over the rated value. The selected control variables are the generator speed and active power. Secondly, the Maximum Power Point Tracking (MPPT) is archived to the satisfaction of the full-range operation through the control strategy for the BBC. The control strategy is applied by the Proportional Integral (PI) controller. The control variables are the generator speed and the diode rectifier's output DC current. Thirdly, the control strategy for PWM-CSI controls the voltage at the connection point and the frequency of the inverter. Fourthly, the DC-link voltage is controlled to the constant value at various operating conditions. Simulation of a 3MW and 0.69 kV WT-PMSG was carried on in PSCAD software to verify under considering the variable wind speed and the three-phase fault. The obtained results prove the feasibility of the proposed WT-PMSG system that serves as an alternative for a high-power wind energy conversion system.

In this paper, we consider two matrix equations that involve the weighted geometric mean. We use the fixed point theorem in the cone of positive definite matrices to prove the existence of a unique positive definite solution. In addition, we study the multi-step stationary iterative method for those equations and prove the corresponding convergence. Another equations with a different matrix generalization of the weighted geometric mean for scalars are also discussed.

Planning is critical for negotiation success as it facilitates obtaining superior outcomes. However, little empirically is known about what people do to plan. We offer an initial exploration of the topic, with the aim of inspiring greater research attention to the topic. We approach the question from an individual differences perspective, since planning phase places greater emphasis on individual action. We explored how the Big Five personality factors and gender predict preference and search for information that facilitates efforts to claim value, create value, and manage relationships. In Study 1, we used a survey method to elicit preferences. Extraversion and conscientiousness predicted preference for information that would help to claim value, and agreeableness predicted preference for information that would help to manage relationships. Women preferred value creating information. In Studies 2, 3, and 4, we examined search behavior using the Mouselab paradigm (Johnson, Payne, Bettman, & Schkade, 1989). A different pattern of relationships emerged. When the search task was complex, agreeableness predicted how extensively people searched for information. When tasks were more constrained, we detected fewer relationships between individual differences and search behavior.