Transmission spectra and valley processing of graphene and carbon nanotube superlattices with inter-valley coupling

published_or_final_versio

A unified wavelet-based modelling framework for non-linear system identification: the WANARX model structure

A new unified modelling framework based on the superposition of additive submodels, functional components, and wavelet decompositions is proposed for non-linear system identification. A non-linear model, which is often represented using a multivariate non-linear function, is initially decomposed into a number of functional components via the wellknown analysis of variance (ANOVA) expression, which can be viewed as a special form of the NARX (non-linear autoregressive with exogenous inputs) model for representing dynamic input–output systems. By expanding each functional component using wavelet decompositions including the regular lattice frame decomposition, wavelet series and multiresolution wavelet decompositions, the multivariate non-linear model can then be converted into a linear-in-theparameters problem, which can be solved using least-squares type methods. An efficient model structure determination approach based upon a forward orthogonal least squares (OLS) algorithm, which involves a stepwise orthogonalization of the regressors and a forward selection of the relevant model terms based on the error reduction ratio (ERR), is employed to solve the linear-in-the-parameters problem in the present study. The new modelling structure is referred to as a wavelet-based ANOVA decomposition of the NARX model or simply WANARX model, and can be applied to represent high-order and high dimensional non-linear systems

Separation, characterization and leaching behaviors of heavy metals in contaminated river sediments

In this research, the sequential extraction test was conducted to understand the characteristic of heavy metals in the sediment. Subsequently, the pH-dependent leaching test, percolation test were subjected to explore the possible leaching of heavy metals and stabilizing mechanism. Finally, based on the resuts of pH dependent test,the acid/chemical washing were applied to predict long-term, leaching characteristics. The results from the sediment characteristic analyses showed that the concentrations of heavy metals (such as Cu, Pb, Zn, Ni, and Cr) in river sediments exceeded the upper limit of Sediment Quality Standard of Taiwan, implying further decontamination works should be addressed. Results from the chemical washing (extraction) showed that the heavy metal removal efficiency was good when washed with 2N HCl for 120 minutes; the order of removal efficiency was Ni 90% > Zn 87% > Pb 85% > Cu 83% > Cr 70%. For chelation extraction, the suitable operating condition was achieved with 0.5M Citric Acid after 120 minutes contact; the order of heavy metal ion capturing efficiency was Zn 61% > Ni 54% > Pb 40% > Cu 36% > Cr 24%. Comparing the heavy metal bonding types before and after chemical washing (extraction) showed that some metal ions exist in residual forms in the sediments (Ni, Zn, Cu); however, after the washing process, the heavy metal ions became more exchangeable forms with higher bioavailability. Keywords: sediment, heavy metal, leaching test, chemical washing

The wavelet-NARMAX representation : a hybrid model structure combining polynomial models with multiresolution wavelet decompositions

A new hybrid model structure combing polynomial models with multiresolution wavelet decompositions is introduced for nonlinear system identification. Polynomial models play an important role in approximation theory, and have been extensively used in linear and nonlinear system identification. Wavelet decompositions, in which the basis functions have the property of localization in both time and frequency, outperform many other approximation schemes and offer a flexible solution for approximating arbitrary functions. Although wavelet representations can approximate even severe nonlinearities in a given signal very well, the advantage of these representations can be lost when wavelets are used to capture linear or low-order nonlinear behaviour in a signal. In order to sufficiently utilise the global property of polynomials and the local property of wavelet representations simultaneously, in this study polynomial models and wavelet decompositions are combined together in a parallel structure to represent nonlinear input-output systems. As a special form of the NARMAX model, this hybrid model structure will be referred to as the WAvelet-NARMAX model, or simply WANARMAX. Generally, such a WANARMAX representation for an input-output system might involve a large number of basis functions and therefore a great number of model terms. Experience reveals that only a small number of these model terms are significant to the system output. A new fast orthogonal least squares algorithm, called the matching pursuit orthogonal least squares (MPOLS) algorithm, is also introduced in this study to determine which terms should be included in the final model

Properties of plasmoids observed in Saturn’s dayside and nightside magnetodisc

Plasmoid is a key structure for transferring magnetic flux and plasma in planetary magnetospheres. At Earth, plasmoids are key media which transfer energy and mass in the "Dungey Cycle". For giant planets, plasmoids are primarily generated by the dynamic processes associated with “Vasyliunas Cycle”. It is generally believed that planetary magnetotails are favorable for producing plasmoids. Nevertheless, recent studies reveal that magnetic field lines could be sufficiently stretched to allow magnetic reconnection in Saturn’s dayside magnetodisc. In the study, we report direct observations of plasmoids in Saturn’s dayside magnetodisc for the first time. Moreover, we perform a statistical investigation on the global plasmoid electron density distribution. The results show an inverse correlation between the nightside plasmoid electron density and local time, and the maximum plasmoid electron density around prenoon local time on the dayside. These results are consistent with the magnetospheric circulation picture associated with the "Vasyliunas Cycle"

Effects of Transduction of the bcl-2 Gene and of Nerve Growth Factor on Apoptosis of Cultured PC12 Cells

We examined what effects are exerted by expression of the bcl-2 gene and by treatment with nerve growth factor (NGF) on the intensity of apoptosis in cultured pheochromocytoma cells (PC12 cells). Half of these cells were transduced with the bcl-2 gene using lentiviral plasmids, and the respective two groups were denoted as bcl-2-PC12 and control (c) PC12. Then the cells were incubated in a serum-free medium in six different modes. One group of c-PC12 cells was incubated in this medium with no additional agents added, another group was incubated with 1.0 mM H₂O₂ , and the third group was incubated with both 1 mM H₂O₂ and 20 ng/ml NGF (groups 1-3). Cells of the another triad were incubated under the same conditions, respectively, but these were bcl-2-PC12 cells (groups 4-6). The apoptosis rate in each group after 1-h-long incubation was measured using a flow cytometry method. A bicinchoninic acid (BCA) technique was used for estimation of expression of Bcl-2 protein in the cultures. As was observed, the action of H₂O₂ significantly increased the apoptosis rate in both c-PC12 and bcl-2-PC12 samplings, while simultaneous action of NGF considerably attenuated such increases. At the same time, values of the apoptosis rate for bcl-2-PC12 cells were much smaller than the respective values for c-PC12 cells under all the three modes of incubation. In H₂O₂ -treated cultures, the amount of Bcl-2 protein dropped, while the treatment with NGF counteracted such shifts. The content of this protein in the bcl-2-PC12 groups was much higher than in the c-PC12 groups. Thus, transduction with the bcl-2 gene significantly inhibits apoptosis in cultured PC12 cells, and a combined influence of expression of this gene and treatment with NGF produces a synergistic effect.Ми досліджували впливи експресії гена bcl-2 та дії нервового фактора росту (NGF) на інтенсивність апоптозу культивованих клітин феохромоцитоми (PC12). У половину таких клітин був трансдукований ген bcl-2; відповідні дві групи зразків були позначені як bcl-2-PC12 та контрольні (с-PC12). Потім шість груп клітин інкубували в безсироватковому середовищі в різних умовах. Перша група клітин с-PC12 інкубувалася без дії будь-яких додаткових агентів, друга група – з додаванням 1 мМ H₂O₂ , а третя – в присутності як 1 мМ H₂O₂ , так і 20 нг/мл NGF. Клітини трьох інших груп (4–6) інкубували в тих самих умовах, але це були клітини bcl-2-PC12. Ступінь апоптозу в кожній групі після одногодинної інкубації вимірювали з використанням методу флоуцитометрії. Методику з використанням біцинхонінової кислоти застосовували для оцінки експресії білка Bcl-2 в культурах. Як було виявлено, дія H₂O₂ істотно збільшувала ступінь апоптозу в зразках як c-PC12, так і bcl-2-PC12, але одночасна дія NGF помітно зменшувала таке зростання. В той же час інтенсивності апоптозу клітин bcl-2-PC12 були значно меншими, ніж відповідні значення у клітин c-PC12 при всіх трьох режимах інкубації. В культурах, підданих впливу H₂O₂ , кількість протеїну Bcl-2 була зменшеною, тоді як вплив NGF протидіяв таким зрушенням. Вміст згаданого протеїну в групах bcl-2-PC12 був значно вищим, ніж у групах c-PC12. Отже, трансдукція гена bcl2 істотно гальмує апоптоз культивованих клітин PC12, а комбінований вплив експресії цього гена та аплікації NGF забезпечує сінергічні ефекти

Morpholinium dihydrogen citrate hydrate

In the crystal structure of the title compound, [O(CH2CH2)(2)NH2][C6H7O7].H2O, the cation interacts with the negatively charged carboxylato group of adjacent anions [N...O 2.847 (3) and 2.942 (3) Angstrom], forming a linear chain running along the b axis of the crystal. Adjacent chains are linked through the carboxylic -CO2H groups and the water molecule into a layer structure

Review of multi-scale electromagnetic modeling

This paper reviews various methods to solve multiscale problems ranging from low-frequency methods to very high-frequency methods. ©2010 IEEE.published_or_final_versionThe 2010 International Conference on Electromagnetics in Advanced Applications (ICEAA), Sydney, N.S.W., 20-24 September 2010. In Proceedings of ICEAA'10, 2010, p. 641-64

On the Relation Between Jupiter's Aurora and the Dawnside Current Sheet

Jupiter's auroral emission is a spectacular phenomenon that provides insight into energy release processes related to the coupling of its magnetosphere and ionosphere. This energy release is influenced by solar wind conditions. Using joint observations from Juno and the Hubble Space Telescope (HST), we statistically investigate the relationship between auroral power and current sheet variations under different solar wind conditions. In this study, we reveal that during global main auroral brightening events that are closely connected to solar wind compressions, the dawn side current sheet is substantially thinner than during times when a quiet auroral morphology is present. Furthermore, the total current intensity in the current sheet is found to increase under solar wind compression conditions compared to the quiet period. These findings provide important observational evidence for how magnetospheric dynamics driven by solar wind behavior affect auroral activity, deepening our understanding of the coupling between Jupiter's magnetosphere and ionosphere