Modeling and analysis of chaotic behavior in switched reluctance motor drives

In this paper, modeling and analysis of chaotic behavior in switched reluctance (SR) motor drives using voltage PWM regulation is presented. The key is to derive a Poincare map that is based on the nonlinear flux linkage model. Its Jacobian matrix can be evaluated by solving the corresponding variational equation. Based on the Poincare map and its Jacobian matrix, the analysis of chaotic behavior is presented. Furthermore, bifurcation diagrams are also figured out. They facilitate to determine the stable range of various system parameters so as to avoid the occurrence of chaos. Both computer simulations and experimental measurements are given to verify the theoretical modeling and analysis.published_or_final_versio

Subharmonics and chaos in switched reluctance motor drives

In this paper, the investigation of the nonlinear dynamics of an adjustable-speed switched reluctance motor (SRM) drive with voltage pulse width modulation (PWM) regulation is carried out. Nonlinear iterative mappings based on both nonlinear and approximately linear flux linkage models are derived, hence the corresponding subharmonic and chaotic behaviors are analyzed. Although both flux linkage models can produce similar results, the nonlinear one offers the merit of accuracy but with the sacrifice of computational time. Moreover, the bifurcation diagrams show that the system generally exhibits a period-doubling route to chaos.published_or_final_versio

Subharmonics and chaos in switched reluctance motor drives

In this paper, the investigation of the nonlinear dynamics of an adjustable speed switched reluctance motor (SRM) drive with voltage PWM regulation is carried out. The corresponding bifurcation diagrams and chaotic Poincare sections are presented. It shows that the system generally exhibits a period-doubling route to chaos.published_or_final_versio

Magnetoresistance in La- and Ca-doped YBa2Cu3O7–δ

We studied the microstructures, electronic, and magnetic properties on La-doped and La- and Ca-codoped YBa2Cu3O7−δ (YBCO). The superconducting transition temperature remains unchanged up to 10% for La-doped YBCO. The competition between electrons and holons was assumed according to the variation of Tc0 in La and Ca codopings in YBCO. The magnetoresistance (MR) effect is about 8%, which is observed obviously near the critical temperature and is independent of the content of La in La-doped YBCO. MR increases up to about 40% with the incorporation of Ca in La-doped YBCO. We present here possible explanations for the magnetoresistance effect in polycrystalline samples based on the microstructure and the increase of oxygen vacancies at grain-boundary interface. © 2006 American Institute of Physicspublished_or_final_versio

Curcumin Enhances Bortezomib Treatment of Myeloma by Inhibiting Heat Shock Protein 90 Expression

Purpose: To investigate whether curcumin augments bortezomib-induced apoptosis in myeloma cells (MM1.R line), and to explore the molecular mechanism with regard to heat shock protein 90 (HSP90) expression.Methods: MTT cell viability assay was used to assess growth inhibition of MM1.R cells at different concentrations of curcumin alone and also combined with 0.01 mM bortezomib. Annexin V and propidium iodide (PI) labeling were used to detect apoptosis. Caspase 3, caspase 9, NF-κB, and HSP 90 protein expression were measured by Western blotting.Results: Curcumin alone inhibited MM1.R cell growth and increased apoptosis in a concentration dependent manner. When curcumin was combined with low concentration (0.01 mM) bortezomib, both effects（viability inhibition and apoptosis induction increased (p < 0.05), whereas bortezomib alone had no effect (p > 0.05). Western blotting revealed that for curcumin and combined treatments, expression of the apoptotic markers, caspase 3 and caspase 9, increased while expression of NF-κB and HSP 90 decreased (p < 0.05). Again, low concentration bortezomib alone had no effect, whereas the combined treatment showed the largest effect, thus suggesting that the actions of curcumin and bortezomib are synergistic.Conclusion: Curcumin increased MM1.R cell sensitivity to bortezomib, which may be due to suppression of NF-κB and HSP90 activity.Keywords: Curcumin, Bortezomib, Myeloma cells, Cell growth, Apoptosis, Heat shock protein 9

Phytochemical Constituents and Pharmacological Activities of Plants from the Genus Adiantum: A Review

Adiantum is a genus of ca. 200 species in the family Adiantaceae, distributed extensively across the world from cool temperate zones to hot tropical regions. A lot of Adiantum species have been used in traditional Chinese medicine to cure human and animal diseases including relief of internal heat or fever, enhancement of urination, removal of urinary calculus, and sundry other curative claims. Chemical studies have shown the presence of various classes of compounds, the main ones being triterpenoids, flavonoids, phenyl propanoids, steroids, alicyclic acids, lipids and long-chain compounds. The extract of this genus as well as pure compounds isolated from it have been demonstrated to possess multiple pharmacological activities such as analgesic, antinociceptive, anti-implantation, and antimicrobial activities. In this review, we have addressed the phytochemistry and pharmacological activities of the Adiantum species in order to collate existing information on this plant as well as highlight its multi-activity properties as a medicinal agent.Keywords: Adiantum species, Adiantaceae, Phytochemical constituents, Pharmacological activities

Optimization of fermentation medium for nisin production from Lactococcus lactis subsp. lactis using response surface methodology (RSM) combined with artificial neural network-genetic algorithm (ANN-GA)

Nisin is a bacteriocin approved in more than 50 countries as a safe natural food preservative. Response surface methodology (RSM) combined with artificial neural network-genetic algorithm (ANN-GA) was employed to optimize the fermentation medium for nisin production. Plackett-Burman design (PBD) was used for identifying the significant components in the fermentation medium. After that, the path of steepest ascent method (PSA) was employed to approach their optimal concentrations. Sequentially, Box-Behnken design experiments were implemented for further optimization. RSM combined with ANNGA were used for analysis of data. Specially, a RSM model was used for determining the individual effect and mutual interaction effect of tested variables on nisin titer (NT), an ANN model was used for NT prediction, and GA was employed to search for the optimum solutions based on the ANN model. As the optimal medium obtained by ANN-GA was located at the verge of the test region, a further Box- Behnken design based on the RSM statistical analysis results was implemented. ANN-GA was implemented using the further Box-Behnken design data to locate the optimum solution which was as follow (g/l): Glucose (GLU) 15.92, peptone (PEP) 30.57, yeast extraction powder (YEP) 39.07, NaCl 5.25, KH2PO4 10.00, and MgSO4·7H2O 0.20, with expected NT of 22216 IU/ml. The validation experiments with the optimum solution were implemented in triplicate and the average NT was 21423 IU/ml, which was 2.13 times higher than that without ANN-GA methods and 8.34 times higher than that without optimization.Key words: Response surface methodology, artificial neural network, genetic algorithm, nisin titer

Preparation of Ni–YSZ thin and thick films on metallic interconnects as cell supports. Applications as anode for SOFC

In this work, we propose the preparation of a duplex anodic layer composed of both a thin (100 nm) and a thick film (10 lm) with Ni–YSZ material. The support of this anode is a metallic substrate, which is the interconnect of the SOFC unit cell. The metallic support limits the temperature of thermal treatment at 800 C to keep a good interconnect mechanical behaviour and to reduce corrosion. We have chosen to elaborate anodic coatings by sol–gel route coupled with dip-coating process, which are low cost techniques and allow working with moderate temperatures. Thin films are obtained by dipping interconnect substrate into a sol, and thick films into an optimized slurry. After thermal treatment at only 800 C, anodic coatings are adherent and homogeneous. Thin films have compact microstructures that confer ceramic protective barrier on metal surface. Further coatings of 10 lm thick are porous and constitute the active anodic material

Earth as a Proxy Exoplanet: Deconstructing and Reconstructing Spectrophotometric Light Curves

Point-source spectrophotometric (single-point) light curves of Earth-like planets contain a surprising amount of information about the spatial features of those worlds. Spatially resolving these light curves is important for assessing time-varying surface features and the existence of an atmosphere, which in turn is critical to life on Earth and significant for determining habitability on exoplanets. Given that Earth is the only celestial body confirmed to harbor life, treating it as a proxy exoplanet by analyzing time-resolved spectral images provides a benchmark in the search for habitable exoplanets. The Earth Polychromatic Imaging Camera (EPIC) on the Deep Space Climate Observatory (DSCOVR) provides such an opportunity, with observations of ~5000 full-disk sunlit Earth images each year at 10 wavelengths with high temporal frequency. We disk-integrate these spectral images to create single-point light curves and decompose them into principal components (PCs). Using machine-learning techniques to relate the PCs to six preselected spatial features, we find that the first and fourth PCs of the single-point light curves, contributing ~83.23% of the light-curve variability, contain information about low and high clouds, respectively. Surface information relevant to the contrast between land and ocean reflectance is contained in the second PC, while individual land subtypes are not easily distinguishable (<0.1% total light-curve variation). We build an Earth model by systematically altering the spatial features to derive causal relationships to the PCs. This model can serve as a baseline for analyzing Earth-like exoplanets and guide wavelength selection and sampling strategies for future observations