Research on Volt/Var Control of Distribution Networks Based on PPO Algorithm

In this paper,a model free volt/var control(VVC)algorithm is developed by using deep reinforcement learning(DRL).We transform the VVC problem of distribution networks into the network framework of PPO algorithm,in order to avoid directly solving a large-scale nonlinear optimization problem.We select photovoltaic inverters as agents to adjust system voltage in a distribution network,taking the reactive power output of inverters as action variables.An appropriate reward function is designed to guide the interaction between photovoltaic inverters and the distribution network environment.OPENDSS is used to output system node voltage and network loss.This method realizes the goal of optimal VVC in distribution network.The IEEE 13-bus three phase unbalanced distribution system is used to verify the effectiveness of the proposed algorithm.Simulation results demonstrate that the proposed method has excellent performance in voltage and reactive power regulation of a distribution network.

Recent progress in integrated electro-optic frequency comb generation

Optical frequency combs have emerged as an important tool enabling diverse applications from test-and-measurement,including spectroscopy,metrology,precision distance measurement,sensing,as well as optical and microwave waveform synthesis,signal processing,and communications.Several techniques exist to generate optical frequency combs,such as mode-locked lasers,Kerr micro-resonators,and electro-optic modulation.Important characteristics of optical frequency combs include the number of comb lines,their spacing,spectral shape and/or flatness,and intensity noise.While mode-locked lasers and Kerr micro-resonators can be used to obtain a large number of comb lines compared to electro-optic modulation,the latter provides increased flexibility in tuning the comb spacing.For some applications in optical communications and microwave photonics,a high degree of integration may be more desirable over a very large number of comb lines.In this paper,we review recent progress on integrated electro-optic frequency comb generators,including those based on indium phosphide,lithium niobate,and silicon photonics.

On the“Past and Present”of Hong Kong’s Finance

Finance is vital to a country,and Hong Kong,as a special part of the large economy of China,has unique advantages and development history.And Hong Kong’s growth from a small fishing village to a financial centre has its inevitable factors:historical,geographical and policy advantages.After nearly a century of rapid development,Hong Kong has achieved many proud accomplishments in the following fields:economy,medicine,education,etc.In the process,the cooperation between Hong Kong and the mainland has become increasingly close,and the two sides of the Strait have become excellent“partners”.In recent years,due to the COVID-19 epidemic and the rise of China as a big economy,Hong Kong is facing an unavoidable dilemma.In view of this,the authors suggest that Hong Kong can develop financial technology,enhance financial security,implement green finance,and promote corporate innovation.At the same time,Hong Kong should also strengthen the relationship with the mainland.Generally speaking,under the current circumstances,Hong Kong will continue to exist as an important financial center of China,but Hong Kong should also actively face the challenges of the times and explore new developments directions in the future.

Ultrabroad-band,white light emission from carbon dot-based materials with hybrid fluorescence/phosphorescence for single component white light-emitting diodes

Benefiting from the large Stokes shift between fluorescence and phosphorescence,fluorescence/phosphorescence dual-emitting carbon dots(CDs)have gradually entered at the stage of single-phase white light-emitting diodes(WLEDs)as‘green material'.However,most of the developed dual-emitting CDs have weak phosphorescence,short emission wavelength and narrow emission band,resulting in relatively bluish white light emission and low color rendering index(CRI).Herein,an ultrabroad-band fluorescence/phosphorescence dual-emitting CD-based material(UB-CD@BA)is prepared by thermal treatment of boric acid(BA)and CDs with large conjugated structure.The stable covalent bonding between CDs and BA,as well as three-dimensional spatial restriction effect of selfpolymerization BA molecules around CDs during long-term heating efficiently rigidified the single/triplet excited states of CDs from non-radiative deactivation,thus producing strong dual emissive materials with the high phosphorescence quantum yield of 21%.Remarkable,the prepared UB-CD@BA powders exhibit bright pure white light emission with Commission Internationale de l'Eclairage(CIE)coordinates of(0.32,0.33)and the highest reported full width at half maximum of 250 nm.Based on the unique characteristics of UB-CD@BA,it was used as a color conversion layer to prepare a WLED with CIE coordinates of(0.35,0.33)and the CRI value of 87.

无人机高光谱影像与冠层树种多样性监测

冠层树种多样性是自然森林生态系统功能和服务的重要基础。及时掌握冠层多样性的现状及变化趋势,是探讨诸多重要生态学问题的前提,更是制定合理生物多样性保护策略的基础。但受制于传统的多样性信息采集方法,区域尺度的高精度冠层多样性监测发展较为缓慢;许多在气候变化和人类干扰下的生物多样性分布信息得不到及时更新。近年来基于无人机的冠层高光谱影像收集与分析技术的发展,使得冠层多样性监测迎来了新的发展契机。本文从森林冠层高光谱影像出发,介绍了与多样性监测相关的无人机航拍和基于深度学习的图像处理技术,并结合已有文献,探讨了无人机高光谱应用于森林冠层树种多样性监测的研究现状、可行性、优势及缺陷等。我们认为冠层高光谱影像为多样性监测提供了不可或缺且丰富的原始信息;而无人机与高光谱相机的结合,使得区域化高频率(如每周)、高精度(如分米乃至厘米级)的冠层多样性信息自动化收集成为可能。然而高光谱影像数据量大、数据维度高与数据结构非线性的特点为影像处理带来了挑战,而深度学习技术的飞跃,使得从冠层高光谱影像中提取个体及物种信息达到了极高精度。恰当地使用这些技术将大大提升冠层树种多样性的自动化监测水平,由此也将帮助我们在当前剧变环境下及时掌握森林冠层多样性的现状与变化,为生物多样性研究与保护提供可靠的数据支撑。

The most typical shape of oceanic mesoscale eddies from global satellite sea level observations

In this research, we normalized the character- istics of ocean eddies by using satellite observation of the Sea Level Anomaly （SLA） data to determine the most typical shape of ocean eddies. This normalization is based on modified analytic functions with nonlinear optimal fitting. The most typical eddy is the Taylor vortex （~50%）, which exhibits a Gaussian-shaped exp（-r2） SLA and a vorticity distribution of （1-rZ）exp（-r2） as a function of the normalized radii r. The larger the amplitude of the eddy, the more likely the eddy is to be Gaussian-shaped. Furthermore, approximately 40% of ocean eddies are combinations of two Gaussian eddies with different parameters, but the composition of these types of eddies is more like a quadratic eddy than a Gaussian one. Only a small portion of oceanic eddies are pure quadratic eddies （ 〈 10%） with the same vorticity distribution as a Rankine vortex. We concluded that the Taylor vortex is a good approximation of the typical shape of ocean eddies.

pH-Responsive amorphous room-temperature phosphorescence polymer featuring delayed fluorescence based on fluorescein

Numerous researchers have paid attention to achieve metal-free phosphorescence by exploring new structures or new mechanisms.Herein,a facile way is introduced to endow a common fluorescence dye,tetrabromofluorescein(4 Br-Flu),some fabulous optical characteristics such as dual emission including thermally activated delayed fluorescence,room-temperature phosphorescence(RTP),and the excellent pH-sensitivity.Shortly,4 Br-Flu with good light-emitting properties is composed into the polymer system.The multiple bromine atoms promote the spin-orbit coupling effect and facilitate triplet excitation.Especially,the hydrogen bonding network of the polymer restricts the molecular motion of4 Br-Flu so that the system can emit long-wavelength RTP when 4 Br-Flu is doped into polyvinyl alcohol or co-polymerized with acrylamide.Due to the reversible transformation of protonation and deprotonation,the 4 Br-Flu based polymer responded to acid and alkali like a phosphorescent switch which makes it an excellent hydrogen chloride/ammonia gas leak detector in dry environment.

Achieving room temperature phosphorescence from organic small molecules on amino acid skeleton

Room temperature phosphorescence(RTP)generated by small molecules has attracted great attention due to their unique potentials for biosensor,bioimaging and security protection.While,the design of RTP materials is extremely challenging for organic small molecules in non-crystalline solid state.Herein,we report a new strategy for achieving non-crystalline organic small molecules with RTP emission by modifying different phosphors onto diphenylalanine or phenylalanine derivatives.Benefiting from the skeletal structure of the amino acid derivatives,there are intermolecular hydrogen bond formation and rigidification effect,thereby minimizing the intermolecular motions and enhancing their RTP performance.

A versatile tool for tracking the differentiation of human embryonic stem cells

The ability of human embryonic stem cells(hESCs)to undergo indefinite self-renewal in vitro and to produce lineages derived from all three embryonic germ layers both in vitro and in vivo makes such cells extremely valuable in both clinical and research settings.However,the generation of specialized cell lineages from a mixture of differentiated hESCs remains technically difficult.Tissue specific promoter-driven reporter genes are power-ful tools for tracking cell types of interest in differentiated cell populations.Here,we describe the construction of modular lentivectors containing different tissue-specific promoters(Tα1 ofα-tubulin;aP2 of adipocyte Protein 2;and AFP of alpha fetoprotein)driving expression of humanized Renilla greenfluorescent protein(hrGFP).To this end,we used MultiSite gateway technology and employed the novel vectors to successfully monitor hESC differentiation.We present a versatile method permitting target cells to be traced.Our system will facilitate research in developmental biology,transplantation,and in vivo stem cell tracking.