Due to increasing wind power penetration into utility grids, system operators have instituted stringent standards for ride-through compliance of grid-connected wind turbines. Series voltage ...compensation can be an effective solution to meet the new standards, especially if a low-cost system can be developed. This paper first presents the characteristics of ride-through behavior of doubly fed induction generator (DFIG) using phasor analysis. The analysis is extended to include the effects of generic series voltage compensation. A new control scheme is then described and analyzed, which allows relatively low-energy ratings in the series compensator, thereby significantly lowering the overall system cost. The new controller enables the DFIG with the compensator to provide the reactive power required for system voltage recovery during grid fault, in compliance with the new grid codes. Simulation and experimental results have demonstrated the enhanced performances resulting from the application of the control scheme.
Micropothole-based oxidized (MPO) Cu meshes with various surface morphologies, such as needle-like (NL), hair-like (HL), arch-like (AL), and pine needle-like (PNL) structures, were prepared by ...controlling the pH and temperature of the oxidation reaction solution. The separation efficiencies of 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFTOS)-coated MPO-Cu meshes were found to be 96-99% for oil/water separation, and the meshes maintained this performance over 20 separation cycles without deterioration. The HL mesh with long and flexible structures was outstanding for the separation of low viscosity oils, while the NL mesh with short and rigid structures was optimal for the separation of highly viscous oils. Double-layered meshes consisting of photocatalytic and superhydrophobic meshes exhibited high catalytic performance after the oil/water separation, demonstrating purification of an aqueous pollutant separated from the oil/water mixture.
A solar-driven unmanned hazardous and noxious substance (HNS) trapping device that can absorb, evaporate, condense, and collect HNSs was prepared. The HNS trapping device was composed of three parts: ...a reverse piloti structure (RPS) for absorption and evaporation of HNSs, Al mirrors with optimized angles for focusing light, and a cooling line system for the condensation of HNSs. The RPS was fabricated by assembling a lower rectangle structure and an upper hollow column. The lower rectangular structure showed a toluene evaporation rate of 6.31 kg/m
h, which was significantly increased by the installation of the upper hollow column (11.21 kg/m
h) and led to the formation of the RPS. The installation of Al mirrors on the RPS could further enhance the evaporation rate by 9.1% (12.28 kg/m
h). The RPS system equipped with an Al mirror could rapidly remove toluene, xylene, and toluene-xylene with high evaporation rates (12.28-8.37 kg/m
h) and could effectively collect these substances with high efficiencies (81-65%) in an unmanned HNS trapping device. This prototype HNS trapping device works perfectly without human involvement, does not need electricity, and thus is suitable for fast cleanup and collection of HNSs in the ocean.
Abstract Corneal transplantation is a common transplant procedure performed to improve visual acuity by replacing the opaque or distorted host tissue by clear healthy donor tissue. However, its ...clinical utility is limited due to a lack of high quality donor corneas. Bioengineered neo-corneas, created using an expandable population of human donor-derived corneal endothelial cells (HCEC), could address this current shortage. The objectives of this study were to establish HCEC isolation and culture protocols and to investigate the feasibility of bioengineering corneal tissue constructs by seeding the cells on decellularized human corneal stroma. HCECs were removed from the discarded corneas of eye donors by enzymatic digestion. Cells were expanded and evaluated for their expression of Na+ /K+ -ATPase and zona occludens-1 (ZO-1). Donor corneal stromas were cut to 120–200 μm thickness slices using a microtome and then decellularized. Extracellular matrix components and mechanical properties of the scaffolds were measured after decellularization. To engineer neo-corneas, 130 HCEC/mm2 were seeded on decellularized human corneal stromas. The resulting constructs were placed in growth medium for 14 days and then analyzed using scanning electron microscopy (SEM), histology, and immunocytochemistry. Seeded cells retain expression of the functional markers Na+ /K+ -ATPase and ZO-1 and constructs have biomechanical properties similar to those of normal corneas. These results indicate that construction of neo-corneas, using HCECs derived from discarded donor corneas and decellularized thin-layer corneal stromas, may create a new source of high quality corneal tissue for transplantation.
Superhydrophobic and superoleophilic Ni foam was fabricated by immersion coating and drying method. The Ni foam was immersed in a mixture containing polytetratluoroethylene (PTFE) and hydrophobic ...fumed silica (R805). The mixture was dispersed in a poly(vinylidene fluoride) (PVDF) solution and the PVDF was used as a binder. The as-prepared Ni foam showed superhydrophobic and superoleophilic properties simultaneously and had a water contact angle (WCA) of 155° for water and an oil contact angle (OCA) of 0° for oil. The PTFE-coated Ni foam maintained high separation efficiency after repeated separations (40 times) above 96% for the more viscous olive oil/water mixture and above 99% for the hexane/water mixture. The as-prepared nickel foam proved to be an excellent candidate for the separation of oil and water mixtures.
The balance between T helper (Th) 1 and Th2 cell responses is a major determinant of the outcome of experimental leishmaniasis, but polarized Th1 or Th2 responses are not sufficient to account for ...healing or nonhealing. Here we show that high arginase activity, a hallmark of nonhealing disease, is primarily expressed locally at the site of pathology. The high arginase activity causes local depletion of L-arginine, which impairs the capacity of T cells in the lesion to proliferate and to produce interferon-gamma, while T cells in the local draining lymph nodes respond normally. Healing, induced by chemotherapy, resulted in control of arginase activity and reversal of local immunosuppression. Moreover, competitive inhibition of arginase as well as supplementation with L-arginine restored T cell effector functions and reduced pathology and parasite growth at the site of lesions. These results demonstrate that in nonhealing leishmaniasis, arginase-induced L-arginine depletion results in impaired T cell responses. Our results identify a novel mechanism in leishmaniasis that contributes to the failure to heal persistent lesions and suggest new approaches to therapy.
Abstract This study develops an antenatal care information system to assist women during pregnancy. We designed and implemented the system as both a web-based service and a multi-platform application ...for smartphones and tablets. The proposed system has three novel features: (1) web-based maternity records, which contains concise explanations of various antenatal screening and diagnostic tests; (2) self-care journals, which allow pregnant women to keep track of their gestational weight gains, blood pressure, fetal movements, and contractions; and (3) health education, which automatically presents detailed information on antenatal care and other pregnancy-related knowledge according to the women's gestational age. A survey was conducted among pregnant women to evaluate the usability and acceptance of the proposed system. In order to prove that the antenatal care was effective, clinical outcomes should be provided and the results are focused on a usability evaluation.
We have demonstrated a novel strategy for the synthesis of mesoporous silica nanoparticles (MSNPs) using a surfactant-free method under ambient conditions. By the simple addition of an amine-based ...polymer (polyethylenimine; PEI) with a high molecular weight to a silica nanoparticle (SNP) solution, two types of MSNPs, including rambutan-like MSNPs (R-MSNPs) and hollow MSNPs (H-MSNPs), were produced. The structural changes of the MSNPs were systematically studied using various reaction conditions (reaction time, molar ratio and molecular weight of PEI, etc.) and were observed using electron microscopic techniques. The formation mechanisms of both MSNPs were carefully investigated using XPS, Raman, and IR spectroscopies. Because the synthesized MSNPs are highly porous materials that contain internal organic/inorganic networks, we investigated the removal/adsorption properties of these MSNPs with respect to pollutants toward possible future use in environmental remediation applications. The H-MSNPs exhibited better environmental remediation capabilities relative to the R-MSNPs because PEI is present between the cobweb-like internal structures of the H-MSNPs, thereby providing a significant number of reaction sites for the adsorption of pollutants. The approach presented here can also be used as a direct method for the preparation of intraconnected networks within the substructures.
We demonstrate a phase transition between BaTiO3 polymorphs induced by Ni substitution experimentally. The structural evolution of tetragonal-to-hexagonal polymorph in Ni-doped BaTiO3 ceramics is ...observed macroscopically and then, visualized in an atomic scale. Under this structural transition, the long-range ferroelectric ordering in the undoped BaTiO3 with tetragonal symmetry is suppressed and eventually, vanishes in the heavily Ni-doped BaTiO3 with hexagonal symmetry and dielectricity. An oxygen vacancy defect can be created at a local Ni doping site with a decrease in the charge valence state from Ti4+ (3d0) to Ti3+ (3d1). With the reduction of the Ti4+ oxidation state, the polar Ti–O ionic displacement is degenerated in the tetragonal BaTiO3 and thereby, the short-range Coulomb repulsion may be restored in the hexagonal BaTiO3 resulting in a polymorphic phase transition. Our work is of potential interest for artificial realization of an exotic phase in complex oxide materials by doping.
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