Low-Frequency Oscillation Analysis of Grid-Connected VSG System Considering Multi-Parameter Coupling

With the increasing integration of new energy generation into the power system and the massive withdrawal of traditional fossil fuel generation,the power system is faced with a large number of stability problems.The phenomenon of low-frequency oscillation caused by lack of damping and moment of inertia is worth studying.In recent years,virtual synchronous generator(VSG)technique has been developed rapidly because it can provide considerable damping and moment of inertia.While improving the stability of the system,it also inevitably causes the problem of active power oscillation,especially the low mutual damping between the VSG and the power grid will make the oscillation more severe.The traditional time-domain state-space method cannot reflect the interaction among state variables and study the interaction between different nodes and branches of the power grid.In this paper,a frequency-domain method for analyzing low-frequency oscillations considering VSG parameter coupling is proposed.First,based on the rotor motion equation of the synchronous generator(SG),a secondorder VSG model and linearized power-frequency control loop model are established.Then,the differences and connections between the coupling of key VSG parameters and low-frequency oscillation characteristics are studied through frequency domain analysis.The path and influencemechanism of a VSG during low-frequency power grid oscillations are illustrated.Finally,the correctness of the theoretical analysis model is verified by simulation.

Graphene Nanostructure-Based Tactile Sensors for Electronic Skin Applications

Skin is the largest organ of the human body and can perceive and respond to complex environmental stimulations.Recently,the development of electronic skin(E-skin)for the mimicry of the human sensory system has drawn great attention due to its potential applications in wearable human health monitoring and care systems,advanced robotics,artificial intelligence,and human-machine interfaces.Tactile sense is one of the most important senses of human skin that has attracted special attention.The ability to obtain unique functions using diverse assembly processible methods has rapidly advanced the use of graphene,the most celebrated two-dimensional material,in electronic tactile sensing devices.With a special emphasis on the works achieved since 2016,this review begins with the assembly and modification of graphene materials and then critically and comprehensively summarizes the most advanced material assembly methods,device construction technologies and signal characterization approaches in pressure and strain detection based on graphene and its derivative materials.This review emphasizes on:(1)the underlying working principles of these types of sensors and the unique roles and advantages of graphene materials;(2)state-of-the-art protocols recently developed for high-performance tactile sensing,including representative examples;and(3)perspectives and current challenges for graphene-based tactile sensors in E-skin applications.A summary of these cutting-edge developments intends to provide readers with a deep understanding of the future design of high-quality tactile sensing devices and paves a path for their future commercial applications in the field of E-skin.

The role of autophagy in regulating metabolism in the tumor microenvironment

Autophagy,as a special programmed cell death,is a critical degradative process that eliminates intracellular abnormal proteins or damage organelles to balance cell energy and favor cell metabolism with autophagy-related(ATG)proteins.Autophagy activation is being increasingly recognized as an essential hallmark in tumorigenesis through influencing the metabolism of stromal cells in the tumor microenvironment(TME)which comprises of tumor cells,cancer-associated fibroblasts(CAFs),cancer-associated endothelial cells(CAEs),immune cells and adipocytes.Tumor cells can reuse autophagy-involved recycling to maintain mitochondrial function and energy supply to meet the metabolic demand of their growth and proliferation.However,the mechanism through which autophagy can promote a crosstalk between tumor and stroma cells is not clear.Reprogramed metabolism is one of the main characteristics of TME leading to higher adaptability of tumor cells with diverse mechanisms.The activation of autophagy has expanded our understanding on the interaction between tumor metabolism and TME.The aim of this review is to report recent advances on the metabolic cross-talk between stromal cells and solid tumor cells induced by autophagy in TME and revealed potential therapeutic targets.

Waveguide-resonator coupling structure design in the lithium niobate on insulator forχ^((2))nonlinear applications

The microring resonator based on lithium niobate on insulator(LNOI)is a promising platform for broadband nonlinearity process because of its strong second-order nonlinear coefficients,the capability of dispersion engineering,etc.It is important to control the energy transmitted into the resonator at different wavelengths,as this becomes difficult for two bands across an octave.In this Letter,we study the effect of different pulley bus-resonator configurations on phase mismatching and mode field overlap.We achieve the control of energy transmission coefficients at different wavebands simultaneously and provide a general design methodology for coupled structures for broadband applications.This paper can contribute to quantum and classical optical broadband applications based on LNOI microring resonators.

丝网印刷柔性电子器件

有机电子器件的主要优势之一是溶液可处理性,这使得可以通过多种印刷方法制备有机电子器件。丝网印刷作为一种十分成熟的印刷方法,被广泛应用于微电子器件的制备。本文主要从丝网印刷的组成、影响丝网印刷精密度的因素以及丝网印刷在场效应晶体管、太阳能电池、有机发光二极管等柔性电子器件制备中的应用分别作以介绍,并对目前丝网印刷在印刷柔性电子器件中存在的困难和挑战作以总结。

2 μm optical frequency comb generation via optical parametric oscillation from a lithium niobate optical superlattice box resonator

Optical parametric oscillators(OPOs) can downconvert the pump laser to longer wavelengths with octave separation via χ^((2)), which is widely used for laser wavelength extension including mid-infrared(MIR) generation.Such a process can be integrated in monolithic resonators, being compact and low in threshold. In this work, we show that the monolithic χ^((2))mini-OPO can also be used for optical frequency comb generation around 2096 nm and enters the boundary of MIR range. A new geometry called an optical superlattice box resonator is developed for this realization with near-material-limited quality factor of 4.0 × 10^(7). Only a continuous-wave near-infrared pump laser is required, with OPO threshold of 80 mW and output power up to 340 mW. Revival temporal profiles are measured at a detectable repetition frequency of 1.426 GHz, and narrow beat note linewidth of less than 10 Hz shows high comb coherence. These results are in good agreement with our simulation for a stable comb generation. Such an OPO-based comb source is useful for carbon dioxide sensing or the mine prospect applications and can be generalized to longer MIR wavelengths for general gas spectroscopy.

Ultrasensitive and stable all graphene field-effect transistor-based Hg^(2+)sensor constructed by using different covalently bonded RGO films assembled by different conjugate linking molecules

As"molecular bridge,"coupling agents can not only realize the covalent connection of composites,but also affect their properties,thus affecting the properties of devices based on them.Herein,leveraging differences in charge conduction properties of the(3-aminopropyl)trimethoxysilane and 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphine caused by conjugacy structural differences,two kinds of layerby-layer assembled smart carbon materials with different electrical properties are obtained at the same reduction temperature.The two graphene ultrathin films are then“planted”on Si/SiO2 substrates,respectively,as semiconductor layer and source/drain electrodes to fabricate an ultra-stable all-graphene field effect transistor(AG-FET).Enabled by the covalent functionalized configuration and the functionally diverse of coupling agents,the AG-FET obtained by this simple method won the high electrical characteristics,the hole,electron mobility,and the shelflife could reach 3.79 cm2/(V·s),3.78 cm2/(V·s),and 18months,respectively.In addition,good material stability and excellent device structure endow the device exceptional stability,electrical stability,and solvent resistance,improving its application prospect in solution phase sensing/detection.Such characteristics could be used to sense,transduce,and respond to external stimuli,especially in solution phase to monitor the important analytes,such as Hg^(2+)in a flowing sewage environment.We believe that such easy-to-manufacture AG-FETs with ultrahigh performance and ultrahigh stability could also show great application prospects in other significant fields.

Phenanthrene derivatives combined charge transport properties and strong solid-state emission

As bifunctional materials, phenanthrene derivatives 2,7-diphenylphenanthrene and 2,7-di(styryl)phenanthrene(DPPa and DSPa) were designed and studied. Both materials show charge transport properties and strong solid-state emission. The hole mobility was measured to be 1.6 and 0.4 cm^2 V-1 s^-1 for DPPa and DSPa, respectively. While the photoluminescence quantum yield of DPPa and DSPa was as high as 37.13% and 62.36%, respectively.

Highly responsive biosensors based on organic field-effect transistors under light irradiation

High responsivity and sensitivity play essential roles in the development of organic field-effect transistors(OFETs)-based biosensors with regard to biological detections,particularly for disease diagnosis.Nonetheless,how to design a biosensor which improves these two outstanding properties while achieving low cost,easy processing,and time saving is a daunting challenge.Herein,a novel biosensor based on OFET with copolymer thin film,whose surface is illuminated with a suitable light beam is reported.This film can be used as both an organic semiconductor material and as a photoelectric active material.Due to amplification of signals as a result of the film’s strong response to light,the biosensor possesses higher responsivity and sensitivity compared to dark condition and even realizes a maximum responsivity of up to 10^(3)for alpha-fetoprotein(AFP)detection.The simple combination of light and transistor builds a bridge between photoelectric effect and biological system.In addition,the emergence of more excellent photoelectric active materials is expected to pave a way for ultrasensitive bio-chemical diagnostic tools.