Adaptive Virtual Synchronous Generator Modulation Strategy Based on Moment of Inertia, Damping Coefficient and Virtual Impedance

The technology of virtual synchronous generator improves the limitations of inverter control strategy and enhances the acceptance of new energy generation in traditional power system, and yet it greatly affects the frequency dynamic regulation ability of the power grid. Meanwhile, in order to solve the problem of power coupling in medium and low voltage microgrid, many methods have been proposed to change the equivalent output impedance of the system by introducing virtual impedance to improve the stability of microgrid system. For this purpose of optimizing the frequency regulation ability of the system, this paper designs an adaptive control strategy of the moment of inertia and damping coefficient to improve the frequency response characteristics of virtual synchronous generator under the conditions of given active power change and grid frequency fluctuation. In addition, in order to solve the contradiction between the moment of inertia, damping coefficient and the frequency response speed, the voltage vector relationship of virtual synchronous generator under interference is analyzed from the perspective of virtual impedance, and an adaptive virtual impedance control strategy is proposed to accelerate the frequency modulation process of the system. Consequently, one cooperative adaptive control strategy of the moment of inertia, damping coefficient and virtual impedance is proposed. On the basis of ensuring the virtual synchronous generator to give full play to its own operation advantages, this method achieves the purpose of enhancing inertia and accelerating the frequency response speed from various perspectives. The simulation results prove the feasibility of the proposed control strategy

DETERMINATION OF DESIGN PARAMETERS OF ASPHALT PAVEMENT BASED ON PG TECHNOLOGY

The design parameters are one of the important factors to ensure the quality of asphalt pavement design. In “Highway Asphalt Pavement Design Specification” (JTGD50-2017), the stander of China, used the asphalt mixture anti-pressure resilience modulus at a single temperature of 20 ℃ as the design metrics. However, asphalt mixture, as a sticky-bullet plastic material, shows different mechanical properties at different temperatures. China is a vast territory, and there are great differences between the high and low temperature value (m and n) of each region. Therefore, it is unreasonable to design asphalt pavement only with the asphalt mixture anti-pressure resilience modulus value at 20 ℃. Studies show that the design parameters using PG technology can improve the high temperature anti-rutting and low temperature cracking performance of asphalt pavement

Interleukin-11 Promotes the Progress of Gastric Carcinoma via Abnormally Expressed Versican

Versican, a ubiquitous component of the extracellular matrix (ECM), accumulates both in tumor stroma and cancer cells and is highly regulated by various cytokines. The aberrant expression of versican and its isoforms is known to modulate cell proliferation, differentiation, and migration, all of which are features of the invasion and metastasis of cancer; versican is also known to favour the homeostasis of the ECM. Interleukin-11 (IL-11) is an important cytokine that exhibits a wide variety of biological effects in gastric cancer development. Here, we analysed the expression of versican isoforms and found that the major isoforms expressed by both gastric carcinoma tissue and gastric cell lines were V0 and V1, and V1 was significantly higher in gastric carcinoma tissue. The treatment of the gastric cell lines AGS and MKN45 with rhIL-11 resulted in a significant increase in the expression of V0 and V1. Exogenous IL-11 increased migration in AGS and MKN45 cells, whereas these effects were reversed when the expression of V0 and V1 were abolished by siRNA targeting versican V0/V1. Collectively, these findings suggest that the abnormally expressed versican and its isoforms participate, at least in part, in the progress of gastric carcinoma triggered by IL-11

SegRNN: Segment Recurrent Neural Network for Long-Term Time Series Forecasting

RNN-based methods have faced challenges in the Long-term Time Series Forecasting (LTSF) domain when dealing with excessively long look-back windows and forecast horizons. Consequently, the dominance in this domain has shifted towards Transformer, MLP, and CNN approaches. The substantial number of recurrent iterations are the fundamental reasons behind the limitations of RNNs in LTSF. To address these issues, we propose two novel strategies to reduce the number of iterations in RNNs for LTSF tasks: Segment-wise Iterations and Parallel Multi-step Forecasting (PMF). RNNs that combine these strategies, namely SegRNN, significantly reduce the required recurrent iterations for LTSF, resulting in notable improvements in forecast accuracy and inference speed. Extensive experiments demonstrate that SegRNN not only outperforms SOTA Transformer-based models but also reduces runtime and memory usage by more than 78%. These achievements provide strong evidence that RNNs continue to excel in LTSF tasks and encourage further exploration of this domain with more RNN-based approaches. The source code is coming soon

Effect of Cooking Temperature on Protein Oxidation and in Vitro Digestive Properties of Yak Meat

The digestibility of myofibrillar proteins (MP) extracted from yak meat cooked to different internal temperatures of (40, 50, 60, 70 and 80 ℃) was determined during in vitro gastrointestinal digestion, and total carbonyl content, total sulfhydryl content and Schiff base content before and after digestion were measured. Ultraviolet (UV) absorption spectroscopy, endogenous fluorescence spectroscopy and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used to investigate the oxidation and digestion patterns of yak meat proteins during gastrointestinal digestion. The results showed that total protease hydrolysis of MP from yak meat cooked to 60 ℃ was the highest after simulated gastric and intestinal digestion (88.64%). The rates of pepsin hydrolysis and total protease hydrolysis of MP from yak meat cooked to 80 ℃ decreased by 34.10% and 22.47%, respectively, and the rate of trypsin hydrolysis increased by 75.34% compared with MP from raw yak meat. The total carbonyl content after simulated gastric and intestinal digestion increased by 81.42% and 77.40%, respectively, and the total sulfhydryl content decreased by 30.02% and 36.43%, respectively, compared with raw MP. With an increase in cooking temperature, the Schiff base content gradually increased, the UV absorbance was significantly enhanced, and the endogenous fluorescence intensity was significantly reduced. The SDS-PAGE patterns showed that the protein bands were severely degraded and even disappeared after digestion. It was found that the digestibility of MP from yak meat cooked to 60 ℃ was the highest. The degree of protein oxidation in yak meat cooked to 80 ℃ was the strongest and increased during gastrointestinal digestion

Protective effect of maternal exposure to α-lipoic acid during pregnancy and lactation on susceptibility to OVAinduced neonatal asthma

Purpose: To investigate the beneficial effect of alpha-lipoic acid (ALA) during pregnancy and lactation on susceptibility to ovalbumin (OVA)-induced neonatal asthma, and the mechanism of involved.Methods: Pregnant BALB/c mice were administered ALA (1 % mixed with mouse chow) or standard mouse chow from 6th day of gestation to 21st day of lactation (postnatal). The offspring (neonatal pups) from the OVA and ALA+OVA groups were sensitized on 1st, 7th and 14th postnatal days (PNDs) via intraperitoneal (i.p.) injection of OVA (0.5 μg). Control mice pups were not exposed to OVA. On PND 21, all pubs were again exposed to 1 % OVA aerosol using a nebulizer.Results: Neonatal mice exposed to ALA showed a significant decline (p < 0.05) in the number of inflammatory cells (eosinophils), levels of inflammatory markers (IL-4, IL-13, IL-5 and TNF-α) as well as OVA-specific IgE and total IgE, when compared to neonatal mice from pregnant mice that did not receive ALA (control). Moreover, the antioxidant profiles of ALA-treated mice offspring were significantly improved (p < 0.05). Marked downregulation (p < 0.05) of the protein expressions of NF-κB p-p65 subunit and TNF-α were observed in ALA-treated mice pups.Conclusion: ALA exposure during pregnancy (maternal exposure) markedly decreases OVA-induced asthmatic airway inflammatory response in pups. Thus, ALA might be beneficial for use along with standard anti-asthmatic drugs in the management of pediatric asthmatic patient

Development of accurate well models for numerical reservoir simulation

 Peaceman well model is widely used in numerical reservoir simulation. With the help of the defined equivalent radius, the bottom-hole inflow or outflow flux can be calculated and is proportional to the difference of the bottom-hole pressure and the well grid pressure. It is shown in this article, though the bottom-hole flux is calculated accurately in Peaceman well model, there are some significant errors of pressure near the well for the large value of the length-to-width ratio of the mesh. Two alternative methods, the source term compensation method and the pattern competition method, which are both based on the analytic solution induced by the source term, are proposed for homogeneous medium. In the source term compensation method, auxiliary pressure, which satisfies the Laplace equation strictly, is defined and solved instead of the original pressure variable, which actually satisfies the Poisson equation. In the pattern competition method, different flow patterns including the linear flow pattern and radial flow pattern are considered. Each flow pattern corresponds to a transmissibility of the adjacent two grids and all the transmissibilities are calculated respectively. The smallest transmissibility will outcompete, and be used for solving the discrete pressure equations. Numerical results show that for the two proposed methods, not only the bottom-hole flux but also the pressure fields can be calculated accurately.Cited as: Zhang, S., Liu, Z., Shi, A., Wang, X. Development of accurate well models for numerical reservoir simulation. Advances in Geo-Energy Research, 2019, 3(3): 250-257, doi: 10.26804/ager.2019.03.0

H-infinity Variable-Pitch Control for Wind Turbines Based on Takagi-Sugeno Fuzzy Theory

When the wind speed is above the rated value, the output power of the wind turbine should be maintained at the rated value in order to prevent the power generation system from overheating. In addition, the natural wind speed will fluctuate randomly in a large range of values, making the traditional control effect not ideal. This paper presents a novel H-infinity (H∞) pitch control strategy for Wind Turbine Generators (WTGs), which can make the rotor speed and output power constant when the wind speed changes in a large range. In order to shorten response time and reduce overshoot, in the specific solution, the control method combines the H∞ theory and the Takagi-Sugeno (T-S) fuzzy theory. Firstly, the linearized models of several operating points were obtained with the T-S fuzzy theory. Then, a robust controller was designed for each linear sub-system based on the H∞ control theory. Furthermore, the controllers of the sub-systems were superimposed into a global controller for the entire system through the membership function. Finally, modeling and simulation were carried out in MATLAB/SIMULINK. The simulation results show that when the wind speed changes above the rated speed, the rotor speed can be maintained at the rated value, and the output power also can be maintained at the rated value. Compared with the optimal control, the response speed of this method is faster and the overshoot is smaller. It provides a new idea for the pitch angle control of wind turbine