Flashover Probability of Wind Turbine Blade and Impact of Strong Electromagnetic Pulse from Lightning Strikes on Wind Turbine Safety

This paper systematically studies the flashover probability of wind turbine blade lightning arrester and the impact of strong electromagnetic pulses on the local and surrounding wind turbines during lightning strikes.The research results indicate that the flashover probability of direct lightning strikes by the wind turbine blade lightning arrester is almost negligible,and the strong electromagnetic pulse of wind turbine blade during lightning strikes has a serious impact on the electronic equipment of the machine,while the impact on the surrounding wind turbine is relatively small.At the same time,the calculation formula for the reflection of lightning current on the carbon brush between the wind turbine hub and the engine compartment during the flashing of the wind turbine blades is provided,and the calculation method for calculating the spatial gradient distribution of electromagnetic field intensity using Biot-Savart Law theorem is applied.The limitations of using wind turbine blades for lightning protection are pointed out,and a technical route for achieving wind turbine lightning safety is proposed,which can be used as a reference for wind turbine lightning protection technicians.

Origins and evolution of plant diversity in the Hengduan Mountains, China

1.Introduction The Hengduan Mountains region(HDM)in southwest China,one of the earth's 34 biodiversity hotspots,is characterized by its unique geology,dramatic topography,a climate where snow and below freezing temperatures can occur on any day of the year,by its location at elevations averaging between(1400e)2000 and4500(e5300)meters above sea level(m a.s.l.),and by one of

Crepis desertorum(Asteraceae,Cichorieae),a new species from northern Xinjiang(China)based on morphological and molecular data

Crepis desertorum from the Junggar Basin of no rthern Xinjiang,northwestern China,is described as a new species.Molecular studies indicate that the species is closely related to Crepis frigida.Morphological studies indicate that it is similar to Crepis sancta subsp.bifida but differs from the latter taxon in having glandular hairs on the stem,a flat receptacle and dimorphic achenes.Chromosome features and pollen and achene ultrastructure also are described for the new species.

Plastome sequencing of Myripnois dioica and comparison within Asteraceae

Myripnois is a monotypic shrub genus in the daisy family constricted to northern China.Although wild populations of Myripnois dioica are relatively rare,this plant may potentially be cultured as a fine ornamental.In the present study,we sequenced the complete plastome of M.dioica,generating the first plastome sequences of the subfamily Pertyoideae.The plastome of M.dioica has a typical quadripartite circular structure.A large^20-kb and a small^3-kb inversion were detected in the large single copy(LSC)region and shared by other Asteraceae species.Plastome phylogenomic analyses based on 78 Asteraceae species and three outgroups revealed four groups,corresponding to four Asteraceae subfamilies:Asteroideae,Cichorioideae,Pertyoideae and Carduoideae.Among these four subfamilies,Pertyoideae is sister to Asteroideae+Cichorioideae;Carduoideae is the most basal clade.In addition,we characterized 13 simple sequence repeats(SSRs)that may be useful in future studies on population genetics.

Karyotypes of nineteen species of Asteraceae in the Hengduan Mountains and adjacent regions

The Hengduan Mountains region is a biodiversity hotspot. In this study, we report the karyotypes of 19 species(21 populations) of Asteraceae from this region, 14 of which are reported for the first time. We also examined polyploidy in Asteraceae plants and summarized karyotype data in the literature for 69 congeneric taxa. In these genera, there were five different ploidy levels in the region, though the most dominant was diploid(73.08%). There is no direct evidence that ploidy level and karyotype asymmetry are associated with the distribution of recorded Asteraceae species from the Hengduan Mountains. This suggests that polyploidy(26.92%) may not play an important role in the evolutionary history of these plants, even though, among these genera, the ratio of paleopolyploidy was high(46.15%).

Enhanced ortho-selective t–butylation of phenol over sulfonic acid functionalized mesopore MTW zeolites

Novel organo-inorganic hybrid materials(MTW-x-SO_(3)H) have been fabricated by immobilizing 3-mercap topropyltriethoxysilane onto mesopore MTW zeolites, which is treated via a simple oxidation process with hydrogen peroxide as the oxidant to transform sulfhydryl group into sulfonic acid group. The organic sulfhydryl groups are covalently bonded to the external surface of MTW zeolites through the condensation between siloxane arising from organic fragments with silanol groups on the surface of MTW zeolites, the hybrids contain sulfonic acid group within the external surface of MTW zeolites and an opened mesoporous system in the matrix of MTW zeolites, which provide enough accessible Brùnsted acid sites for the alkylation between phenol with tert-butyl alcohol. Through this methodology it's possible to prepare multifunctional materials where the plenty of mesopores are benefit for the introduction of larger numbers of sulfonic acid groups that contributes to activity during reactions, resulting in high activity(>55%) of MTW-4-SO_(3)H and desired selectivity(>56%) of 2-TBP(2-tert-butyl phenol) in the alkylation between phenol with tert-butyl alcohol.

Global Attractor for a Non-Autonomous Beam Equation

This work studies the global attractor for the process generated by a non-autonomous beam equation utt+△2u+ηut-[β(t)+M(∫Ω|▽u(x,t)|2dx)] △u+g(u, t)=f (x,t) Based on a time-uniform priori estimate method, we first in the space H02(Ω) ×L2(Ω) establish a time-uniform priori estimate of the solution u to the equation, and conclude the existence of bounded absorbing set. When the external term f (x,t) is time-periodic, the continuous semigroup of solution is proved to possess a global attractor.

Study the relationship between the expression of MRP and the radiosensitivity of primary lesions of nasopharyngeal carcinoma

Objective: To study the relationship between the expression of multidrug resistance-associated protein (MRP) gene in nasopharyngeal carcinoma (NPC) and the radiosensitivity of primary lesions of NPC. Methods: Total 51 cases of NPC were analyzed retrospectively, who were treated by radiotherapy between January 1, 1999 and December 31, 2000 in our department, including the cases of pure radiotherapy and chemotherapy after radiotherapy. Using immunohistochemiscal S-P method, the expression of MRP in NPC was detected, and the relationship with the radiosensitivity of primary lesions of NPC was analyzed. Results: The rate of positive expression was 68.63% (35/51) in NPC, and there were significant difference between T stages (P<0.05), but no significant difference with radiosensitivity of primary lesions of NPC (P>0.05). Conclusion: There is a higher expression of MRP in NPC, but it has no relationship with radiosensitivity of primary lesions of NPC. So MRP can not be regarded as the predictive marker of radiosensitivity of primary lesions of NPC.

Risk Measurement and Performance Evaluation of Equity Funds Based on ARMA-GARCH Family Model

There are few comprehensive studies on risk measurement and performance evaluation of stock funds in China. This paper uses the ARMA-GARCH family model to analyze the volatility characteristics of equity funds under the t-distribution and Generalized error distribution (GED), and combines CVaR, PM (Second revised sharp ratio) and CVaR-RAROC (Revised RAROC) to comprehensively evaluate equity funds risk and performance. The empirical analysis of five equity funds in China from October 28, 2010 to May 17, 2019 shows that: Comprehensive evaluation of the risk and performance of equity funds can comprehensively and effectively examine the risks and returns of equity funds, helping investors, financial institutions and regulatory agencies to more fully understand the risks and performance of equity funds.

The Global Attractor of Thermoelastic Coupled System

In this paper, we consider a class of Sine-Gordon equations which arise from the model of the thermoelastic coupled rod. Firstly, by virtue of the classical semigroup theory, we prove the existence and uniqueness of the mild solution under certain initial-boundary value for above-mentioned equations. Secondly, we obtain the boundedness of solutions by the priori estimates. Lastly, we prove the existence of a global attractor.

Boundary Stabilization of a More General Kirchhoff-Type Beam Equation

Simultaneously, considering the viscous effect of material, damping of medium, geometrical nonlinearity, physical nonlinearity, we set up a more general equation of beam subjected to axial force and external load. We prove the existence and uniqueness of global solutions under non-linear boundary conditions which the model is added one damping mechanism at l end. What is more, we also prove the exponential decay property of the energy of above mentioned system.

Atmospheric dispersion prediction of accidental release:A review

Modern industrial development is accompanied by the increasingly frequent occurrence of accidental release atmospheric dispersion events,causing extremely serious human and property losses and environmental pollution,in which rapid and accurate prediction of atmospheric dispersion is an important task to mitigate the unexpected consequences.In this paper,we take the case of previous years as the starting point,firstly,the occurred hazardous chemical atmospheric dispersion accidents in the past five years are shown,and the related concepts of hazardous chemical atmospheric dispersion are given.Then,the current state of atmospheric dispersion research is reviewed,well-known experiments on atmospheric dispersion of hazardous chemicals are summarized,and correspondingly the existing atmospheric dispersion prediction models are classified into simplified-experience models,mechanism-and rule-driven models and data-driven models.In particular,for the purpose of rapid atmospheric dispersion prediction,some research on atmospheric detection and identification are analyzed in detail.Moreover,the relevant professional software for atmospheric dispersion prediction are introduced,and also their calculation adaptabilities regarding time-consumption and output accuracy are discussed.Thereinafter,according to the shortcomings of existing atmospheric dispersion prediction models in research and application fields,the development trend of atmospheric dispersion prediction research and technology is foreseen,and some feasible future research directions are proposed as follows:(1)the fusion of image processing techniques,the establishment of a database of historical accident scene information and meteorological information,(2)new correction algorithms,and(3)an emergency response system for full-scene atmospheric dispersion prediction.

一种结构化的化工系统人因失误概率评估方法

化工生产系统高度非线性且复杂耦合化,使现有人因可靠性分析(HRA)技术难以直接应用,且分析结果的有效性和准确性差。为此,本工作将人因-危险和可操作性分析(人因HAZOP)与贝叶斯网络(BN)相融合,提出了一种结构化的化工系统人因失误概率评估方法。通过概述人因HAZOP的作业任务,筛选引导词和偏差,形成结构化的人因HAZOP报告,并据此构建BN模型,求解化工系统人因失误概率。以丙烯酸甲酯虚拟仿真工厂的酯化反应为例,人因失误概率的计算结果为0.0004,且主要人误行为是维护人员遗漏。对该化工系统进行传统CREAM分析,人因失误概率结果为0.0001~0.01。与传统CREAM相比,这种结构化方法能够高效且精确地评估化工系统人因失误概率。

青藏高原冰缘植物多样性与适应机制研究进展

高山冰缘带紧邻雪线,位于高山生境的最前端,在山地植物垂直带谱中位居最高,是陆地生态系统中最为极端的生境之一.受到高原环境中多变的气候、多样的地形、独特的生物交流屏障和迁移通道等因素的综合影响,青藏高原孕育了全球最为丰富的冰缘植物多样性资源.这类极端环境下的生物多样性形成和维持机制一直是学界关注的热点和难点问题.本文总结了青藏高原冰缘生态系统植物多样性特征及物种生态适应、繁殖和维持机制的最新研究进展,并特别关注了冰缘植物的生态适应结构,植物种间互助以及植物与昆虫间协同进化对于维持冰缘生态系统物种多样性的重要性.已有研究表明,全球气候变化对于冰缘生态系统多样性维持和物种共存会产生重要影响.如何预测和判断全球气候变化背景下,青藏高原冰缘生态系统内生物多样性资源的命运及其对生态系统功能的影响,将是生态学研究者面临的新挑战.

Robust Optimization of Municipal Solid Waste Collection and Transportation with Uncertain Waste Output: A Case Study

Garbage collection is an important issue in urban environmental management.With the increased awareness of urban residents regarding safety,environmental protection,and health in recent years,it is necessary to logically organize municipal solid waste collection and transportation routes while also considering economic and social benefits.This article focuses on the optimization of the waste transportation routes of garbage trucks.With the objective of minimizing transportation costs and maximizing resident satisfaction,we establish a robust optimization model for the multi-trip collection and transportation of municipal solid waste in an uncertain environment.Resident satisfaction is defined as the penalty cost against a time window constraint.The Bertsimas robust optimization method is applied to characterize the uncertainty,and the decision-making scheme of the receiving route is used to adapt to waste volume changes.We conduct a case study based on real-world data for municipal solid waste collection and transportation in the Dongcheng District of Beijing,China.The solution is validated using the CPLEX program,and the validity of the model is verified.In addition,a sensitivity analysis of related parameters is conducted to study the impacts of variations in work hour limits and time windows on the total cost and service levels,as well as their relationships with the level of robustness.This could help decision-makers make reasonable choices based on actual conditions and to balance reductions in total cost with service level improvements.

Individualized red-cell transfusion strategy for non-cardiac surgery in adults:a randomized controlled trial

Background:Red-cell transfusion is critical for surgery during the peri-operative period;however,the transfusion threshold remains controversial mainly owing to the diversity among patients.The patient’s medical status should be evaluated before making a transfusion decision.Herein,we developed an individualized transfusion strategy using the West-China-Liu’s Score based on the physiology of oxygen delivery/consumption balance and designed an open-label,multicenter,randomized clinical trial to verify whether it reduced red cell requirement as compared with that associated with restrictive and liberal strategies safely and effectively,providing valid evidence for peri-operative transfusion.Methods:Patients aged>14 years undergoing elective non-cardiac surgery with estimated blood loss>1000 mL or 20%blood volume and hemoglobin concentration<10 g/dL were randomly assigned to an individualized strategy,a restrictive strategy following China’s guideline or a liberal strategy with a transfusion threshold of hemoglobin concentration<9.5 g/dL.We evaluated two primary outcomes:the proportion of patients who received red blood cells(superiority test)and a composite of in-hospital complications and all-cause mortality by day 30(non-inferiority test).Results:We enrolled 1182 patients:379,419,and 384 received individualized,restrictive,and liberal strategies,respectively.Approximately 30.6%(116/379)of patients in the individualized strategy received a red-cell transfusion,less than 62.5%(262/419)in the restrictive strategy(absolute risk difference,31.92%;97.5%confidence interval[CI]:24.42-39.42%;odds ratio,3.78%;97.5%CI:2.70-5.30%;P<0.001),and 89.8%(345/384)in the liberal strategy(absolute risk difference,59.24%;97.5%CI:52.91-65.57%;odds ratio,20.06;97.5%CI:12.74-31.57;P<0.001).No statistically significant differences were found in the composite of in-hospital complications and mortality by day 30 among the three strategies.Conclusion:The individualized red-cell transfusion strategy using the West-China-Liu’s Score reduced red-cell transfusion without increasing in-hospital complications and mortality by day 30 when compared with restrictive and liberal strategies in elective non-cardiac surgeries.Trial registration:ClinicalTrials.gov,NCT01597232.

Enhancing thermal stability and photoluminescence of red-emitting Sr_(2)Si_(5)N_(8):Eu phosphors via boron doping

Surface passivation is a common method to improve the resistance of thermal degradation of nitride phosphors.However,such a surface passivation generally needs extra processes and decreases the photoluminescence property of the phosphors.In this work,both the thermal stability and photoluminescence property of a red phosphor Sr_(2)Si_(5)N_(8):Eu are improved through the addition of BN.The influence of B on the crystal structure and the valence state of active ions was analyzed by experimental characterization.First-principles calculations were applied to analyze the formation energy of N vacancies,which influence the resistance of thermal degradation.Finally,combining with experimental characterization and calculations,the enhancing mechanism of thermal stability and photoluminescence by B was studied.

不可压缩向列型液晶系统Cauchy问题整体强解的存在性和大时间性质

本文研究非齐次不可压缩向列型液晶系统在三维全空间上的Cauchy问题.对任意的β∈(1/2,1],当初值的范数■充分小时,本文证明整体强解的存在性及大时间衰减估计,其中初始密度可含真空或具有紧支集.

孤儿核受体HNF4α在肾透明细胞癌中的表达及意义

目的基于数据挖掘分析孤儿核受体HNF4α在肾透明细胞癌(ccRCC)中的表达及意义。方法UALCAN分析HNF4α在肾透明细胞癌组织中的表达及其与患者总生存率的关系,分析与HNF4α表达具有相关性的基因群。TNMplot分析HNF4α基因mRNA在肿瘤、正常和转移组织中的表达。Kaplan-Meier Plotter分析HNF4α表达与肿瘤生存率的关系。STRING分析HNF4α蛋白质-蛋白质相互作用网络。结果HNF4α在肾透明细胞癌细胞中显著下调(P=0.002);在转移性肾透明细胞癌中表达水平进一步下调(P<0.001);HNF4α表达水平在肿瘤分级4级显著低于1级(P=0.007),在4级显著低于3级(P<0.001)。HNF4α表达水平与肿瘤预后呈负相关(P=0.017)。HNF4α低表达组总生存率显著低于高表达组(P<0.001)。Pearson相关系数>0.5的HNF4α表达正相关的基因有27个,其中ERBB3、CUBN、HNF1A、CES2与HNF4α表达相关系数最高。HNF4α与HNF1A、EP300、LEF1、SMAD3、SMAD4、NCOA1、HIF1A、FOXO1以及PPARGC1A均存在相互作用,其相互作用网络节点为11,蛋白-蛋白相互作用富集P值为3.44e-08。结论HNF4α在肾透明细胞癌中表达显著下调,并与肿瘤预后呈负相关,HNF4α及其相互作用关键因子可能在肾透明细胞癌发生、发展过程中扮演重要角色,具体作用及分子机制需进一步研究。

Analysis and stabilization control of a voltage source controlled wind farm under weak grid conditions

This paper investigates and discusses the interaction stability issues of a wind farm with weak grid connections,where the wind turbines(WTs)are controlled by a new type of converter control strategy referred to as the voltage source(VS)control.The primary intention of the VS control method is to achieve the high-quality inertial response capability of a single WT.However,when it is applied to multiple WTs within a wind farm,its weakgrid performance regarding the stability remains concealed and needs to be clarified.To this end,a frequency domain model of the wind farm under the VS control is first developed.Based on this model and the application of a stability margin quantification index,not only the interactions between the wind farm and the weak grid but also those among WTs will be systematically assessed in this paper.A crucial finding is that the inertial response of VS control has negative impacts on the stability margin of the system,and the dominant instability mode is more related to the interactions among the WTs rather than the typical grid-wind farm interaction.Based on this knowledge,a stabilization control strategy is then proposed,aiming for stability improvements of VS control while fulfilling the demand of inertial responses.Finally,all the results are verified by time-domain simulations in power systems computer aided design/electromagnetic transients including DC(PSCAD/EMTDC).