This paper proposes a data-driven affinely adjustable distributionally robust method for unit commitment considering uncertain load and renewable generation forecasting errors. The proposed ...formulation minimizes expected total operation costs, including the costs of generation, reserve, wind curtailment, and load shedding, while guaranteeing the system security. Without any presumption about the probability distribution of the uncertainties, the proposed method constructs an ambiguity set of distributions using historical data and immunizes the operation strategies against the worst case distribution in the ambiguity set. The more historical data is available, the smaller the ambiguity set is and the less conservative the solution is. The formulation is finally cast into a mixed integer linear programming whose scale remains unchanged as the amount of historical data increases. Numerical results and Monte Carlo simulations on the 118- and 1888-bus systems demonstrate the favorable features of the proposed method.
Wide applications of nanoparticles (NPs) have raised increasing concerns about safety to humans. Oxidative stress and inflammation are extensively investigated as mechanisms for NPs-induced toxicity. ...Autophagy and lysosomal dysfunction are emerging molecular mechanisms. Inhalation is one of the main pathways of exposing humans to NPs, which has been reported to induce severe pulmonary inflammation. However, the underlying mechanisms and, more specifically, the interplays of above-mentioned mechanisms in NPs-induced pulmonary inflammation are still largely obscure. Considered that NPs exposure in modern society is often unavoidable, it is highly desirable to develop effective strategies that could help to prevent nanomaterials-induced pulmonary inflammation.
Pulmonary inflammation induced by intratracheal instillation of silica nanoparticles (SiNPs) in C57BL/6 mice was prevented by PJ34, a poly (ADP-ribose) polymerase (PARP) inhibitor. In human lung bronchial epithelial (BEAS-2B) cells, exposure to SiNPs reduced cell viability, and induced ROS generation, impairment in lysosome function and autophagic flux. Inhibition of ROS generation, PARP and TRPM2 channel suppressed SiNPs-induced lysosome impairment and autophagy dysfunction and consequent inflammatory responses. Consistently, SiNPs-induced pulmonary inflammation was prevented in TRPM2 deficient mice.
The ROS/PARP/TRPM2 signaling is critical in SiNPs-induced pulmonary inflammation, providing novel mechanistic insights into NPs-induced lung injury. Our study identifies TRPM2 channel as a new target for the development of preventive and therapeutic strategies to mitigate nanomaterials-induced lung inflammation.
The bounding inequalities and the Lyapunov-Krasovskii functionals (LKFs) are important for the stability analysis of time-delay systems. Much attention has been paid to develop tighter inequalities ...for improving stability criteria, while the contribution of the LKFs has not been considered when discussing the relationship between the tightness of inequalities and the conservatism of criteria. This note is concerned with this issue. Firstly, it is proved that, when a simple LKF is applied, the stability criteria obtained by the Wirtinger-based inequality and the Jensen inequality are equivalent although the Wirtinger-based inequality is tighter. It means that the tighter inequality does not always lead to a less conservative criterion. Secondly, it is found that a suitable augmented LKF with necessary integral vectors in its derivative is required to achieve the advantage of the Wirtinger-based inequality. Based on this observation, two delay-product-type terms are introduced into the LKF to establish new stability criteria. Finally, a numerical example is given to verify the equivalence statements and to show the benefit of the proposed criteria.
In this article, based on discrete orthogonal polynomials and the block <inline-formula><tex-math notation="LaTeX">\epsilon</tex-math></inline-formula>-circulant matrix, we explore a parallel ...input-independent model order reduction method, which is suitable for the single-input discrete-time systems characterizing nonaffine uncertainty about a scalar parameter. With the explicit difference relations of Charlier polynomials, Meixner polynomials, and Krawtchouk polynomials, the expansion coefficients of the state variable are obtained. Furthermore, we derive an input-independent projection subspace, such that it is equivalent to the subspace spanned by the expansion coefficients for arbitrary input. Based on the block discrete Fourier transform of the block <inline-formula><tex-math notation="LaTeX">\epsilon</tex-math></inline-formula>-circulant matrix, a parallel strategy is proposed to compute the basis of the equivalent projection subspace. Then, the projection matrix is constructed and used to reduce discrete-time parametric systems. Moreover, we analyze the feasibility of the parallel strategy by presenting the invertibility of the block <inline-formula><tex-math notation="LaTeX">\epsilon</tex-math></inline-formula>-circulant matrices and the corresponding error. Finally, the efficiency of the proposed method is illustrated by the numerical experiment.
When a parasitic radiating element is placed in proximity to the driven one, coupling effects could be observed. This article deals with couplings from the perspective of characteristic modes of ...coupled system (CMs_coupled) and those of isolated driven/parasitic patch (CMs_iso_dri/par). It is found that CMs_coupled could be flexibly controlled by CMs_iso_dri/par. Complex J/K inverters are introduced to characterize couplings between CMs_iso_dri/par and their values are extracted from derived formulas. The requirements on values of these inverters are also derived for effective bandwidth enhancement. Several antenna examples with electric and magnetic couplings are presented for validation. Then a unified design guideline for enhancing gain and bandwidth is proposed. Next, by reducing radiation side lobes and utilizing capacitive coupling of third-order CMs, a patch antenna is effectively enhanced in both gain and bandwidth. Finally, a prototype patch antenna is fabricated to validate all the analysis experimentally.
This paper proposes a switching angle controller (SAC) and an automatic generation controller (AGC) for the doubly-fed induction generator (DFIG) to control the frequency of DFIG-based wind power ...penetrated power systems. The concept of virtual rotor angle of the DFIG is defined. The virtual rotor angle is controlled by the SAC in a bang-bang manner such that the active power of the DFIG is regulated to provide frequency support to the external power grids. The output of the SAC is also used for the control of pitch angle to offer a short-term regulation of the mechanical power input to the DFIG, and the long-term control of the mechanical power input is achieved with the AGC. Small-signal analysis is undertaken to verify the effectiveness of the SAC and the AGC. Simulation studies are carried out in a two-machine power system and a modified Kundur four-machine two-area power system, respectively. The frequency support performance of DFIGs having different control configurations is investigated. Modal analysis is undertaken to evaluate the effect of the SAC and the AGC in providing additional damping to the rotor oscillation modes of the modified Kundur four-machine two-area power system.
This paper investigates the impact of powergrid strength and phase-locked loop (PLL) parameters on small signal stability of grid-connected doubly fed induction generator (DFIG)based wind farm. Modal ...analysis of the grid-connected DFIG wind turbine under different operating conditions and various power grid strengths are investigated at first. Modal analysis results reveal that the DFIG connected to a weak grid may easily lose stability under the heavy-duty operating conditions due to PLL oscillation. The object of this paper is to identify the PLL oscillation mechanism as well as influence factors and propose a damping solution for this oscillation mode. A simplified linear system model of the grid-connected DFIG wind turbine is proposed for analyzing the PLL oscillation. Through the complex torque coefficients method and using this model, the oscillation mechanism and influence factors including the power grid strength and the PLL parameters are identified. To suppress this PLL oscillation, a mixed H 2 /H ∞ robust damping controller is proposed and designed for the DFIG. Electromagnetic transient simulation results of both singleDFIG system and multiply-DFIG system verify the correctness of the analysis results and effectiveness of the proposed damping controller.
Anthropogenic climate change has emerged as a critical environmental problem, prompting frequent investigations into its consequences for various ecological systems. Few studies, however, have ...explored the effect of climate change on ecological stability and the underlying mechanisms. We conduct a field experiment to assess the influence of warming and altered precipitation on the temporal stability of plant community biomass in an alpine grassland located on the Tibetan Plateau. We find that whereas precipitation alteration does not influence biomass temporal stability, warming lowers stability through reducing the degree of species asynchrony. Importantly, biomass temporal stability is not influenced by plant species diversity, but is largely determined by the temporal stability of dominant species and asynchronous population dynamics among the coexisting species. Our findings suggest that ongoing and future climate change may alter stability properties of ecological communities, potentially hindering their ability to provide ecosystem services for humanity.
Abstract Nanohybrids, synthesized via silver nitrate reduction in the presence of silicate clay, exhibit a high potency against bacterial growth. The plate-like clay, due to its anionic surface ...charges and a large surface area, serves as the support for the formation of silver nanoparticles (AgNPs) ∼30 nm in diameter. The nanohybrid consisting of Ag/silicate at a 7/93 weight ratio inhibited the growth of dermal pathogens including Staphylococcus aureus ( S. aureus ), Pseudomonas aeruginosa and Streptococcus pyrogens , as well as the methicillin- and oxacillin-resistant S. aureus (MRSA and ORSA). Scanning electron microscope revealed that these nanohybrids were adherent on the surface of individual bacteria. The thin silicate plates provide a surface for immobilizing AgNPs in one highly concentrated area but prevent them from entering the cell membrane. Subsequent cytotoxicity studies indicated that surface contact with the reduced AgNPs on clay is sufficient to initiate cell death. This toxicity is related to a loss in membrane integrity due to reactive oxygen species (ROS) generation. The hybridization of AgNPs on clay surface is viable for generating a new class of nanohybrids exhibiting mild cytotoxicity but high efficacy for battling drug-resistant bacteria.
Sb2Se3 is a promising earth-abundant and nontoxic material suitable for photovoltaic applications. In the present study, Sb2Se3/CdS heterojunction solar cells are numerical analyzed by the program ...SCAPS (Solar Cell Capacitance Simulator). The influence of thickness, hole mobility and defect density of Sb2Se3 layer, as well as the CdS layer thickness and the work function of back contact on the devices performance are simulated and analyzed in detail. Our studies show that, the optimal thickness for Sb2Se3 absorber and CdS buffer layer is 600 nm and 60 nm, respectively. The absorber defect density less than 1014 cm−3, interface defect density less than 108 cm−3 and hole mobility higher than 15 cm2/V.s in Sb2Se3 layer is required to guarantee good device performance. Meanwhile, the work function of back contact larger than 4.8 eV is beneficial. A maximum efficiency of 16.5% can be obtained after optimization of different parameters. The simulation results provide useful insights and guideline for the designing and fabricating of Sb2Se3 solar cells.
•Sb2Se3/CdS heterojunction solar cells have been modelled.•The optimal thickness for Sb2Se3 absorber and CdS buffer layer is 600 nm and 60 nm, respectively.•Absorber defect density under 1014 cm−3, interface defect density under 108 cm−3 is required for good device performance.•Hole mobility higher than 15 cm2/V.s in absorber and the back contact work function larger than 4.8 eV is beneficial.
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