基于等效粗糙度模型的风电场尾流数值模拟方法

随着风电场规模的扩大和密度的增加,风电场整场的尾流效应也日益显著且备受关注。准确评估风电场尾流效应对于风电场的建设和开发具有重要的意义,但目前仍缺乏同时兼顾计算精度和效率的尾流计算方法。本文基于OpenFOAM平台中的雷诺时均方法,实现了风电场等效粗糙度模型和雷诺平均方法的嵌套。结果表明,该方法相较于工程中常用的Jensen尾流模型和尾流叠加模型,计算精度得到了大幅的提高,且因为其对于风电场建模简单,所需计算资源较少,是用在大型风电场的一种工程应用价值较高的下游尾流计算方法。

Time-resolved characteristics of a nanosecond pulsed multi-hollow needle plate packed bed dielectric barrier discharge

In this paper,self-designed multi-hollow needle electrodes are used as a high-voltage electrode in a packed bed dielectric barrier discharge reactor to facilitate fast gas flow through the active discharge area and achieve large-volume stable discharge.The dynamic characteristics of the plasma,the generated active species,and the energy transfer mechanisms in both positive discharge(PD)and negative discharge(ND)are investigated by using fast-exposure intensified charge coupled device(ICCD)images and time-resolved optical emission spectra.The experimental results show that the discharge intensity,number of discharge channels,and discharge volume are obviously enhanced when the multi-needle electrode is replaced by a multihollow needle electrode.During a single voltage pulse period,PD mainly develops in a streamer mode,which results in a stronger discharge current,luminous intensity,and E/N compared with the diffuse mode observed in ND.In PD,as the gap between dielectric beads changes from 0 to250μm,the discharge between the dielectric bead gap changes from a partial discharge to a standing filamentary micro-discharge,which allows the plasma to leave the local area and is conducive to the propagation of surface streamers.In ND,the discharge only appears as a diffusionlike mode between the gap of dielectric beads,regardless of whether there is a discharge gap.Moreover,the generation of excited states N_(2)^(+)(B^(2)∑_(u)^(+))and N2(C^(3)Π_(u))is mainly observed in PD,which is attributed to the higher E/N in PD than that in ND.However,the generation of the OH(A^(2)∑^(+))radical in ND is higher than in PD.It is not directly dominated by E/N,but mainly by the resonant energy transfer process between metastable N_(2)(A^(3)∑_(u)^(+))and OH(X^(2)Π).Furthermore,both PD and ND demonstrate obvious energy relaxation processes of electron-to-vibration and vibration-to-vibration,and no vibration-to-rotation energy relaxation process is observed.

基于粒子群优化算法的凯威特型网壳优化设计

为了减少空间网壳结构的用钢量,以唐山勒泰凯威特型单层球面网壳为研究对象,利用粒子群优化算法,以网壳杆件截面尺寸为主要的设计变量,在满足强度、刚度和稳定性的条件下,借助Python编程语言,通过Grasshopper调用商业有限元软件SAP2000对该结构进行优化设计。结果表明:该单层球面网壳的用钢量显著减少,由原来的94.8 t减少到69.1 t,表明钢材的力学性能得到了充分发挥,验证了粒子群优化算法对网壳结构优化设计方案的适用性。研究结果可为进一步开展空间网壳结构优化设计与分析提供一定的理论参考。

幕墙对悬挑楼盖振动模态影响及等效模拟方法

以某体育馆悬挑楼盖为分析对象,通过数值仿真和现场测试研究了幕墙的约束刚度对楼盖振动模态的影响。首先,对体育馆悬挑楼盖(含幕墙)进行现场模态测试,利用随机子空间法对测试的多组数据进行模态拟合,获得楼盖在环境激励下的振动模态;其次,将试验模态与有限元仿真模拟的结果进行对比,参照试验模态并依据所提出的幕墙的一种等效模拟方法对有限元模型进行修正。结果表明:考虑幕墙对主体结构的约束刚度后,实测的楼盖的前6阶频率与有限元前6阶频率相对误差均小于5%,各阶平均误差小于2%,振型吻合度较高,进一步验证了由吊柱等强度比较高的支撑体系来实现幕墙对悬挑楼盖约束刚度的贡献及一种等效模拟方法的合理性。

Logistic微分方程模型在结核病疫情预警中的应用

目的利用Logistic微分方程模型进行结核病传播预测,为结核病早期防控特别提供新方法。方法对Logistic微分方程模型的原理、疫情加速关键点计算、优缺点等进行分析,以厦门市报告数据为例开展模拟研究。结果厦门市自2005-2018年来结核病高发,存在明显的冬春季节流行高峰。通过Logistic微分方程拟合结果较好,疫情加速期为每年第1或第2个月。结论Logistic微分方程模型能较好地反映结核病“疫情加速时间”和“建议预警时间”,以及疫情变化的时间点,对于基层开展结核病预警防控工作,具有较好的参考意义。

常用统计预测模型及其在结核病疫情预测中的应用

目的选择简便、可靠的统计预测模型,为传染病疫情预测工作提供参考。方法对常见统计预测模型的原理、拟合优度检验与模型筛选进行介绍,并以厦门市结核病疫情为例开展模型应用。结果模型与数据拟合结果显示,11种模型均有统计学意义(P<0.05)。其中R 2最大为Cubic模型,其次为Quadratic模型和Logarithmic模型。Quadratic模型预测2019年7~12月厦门市报告发病数分别为191(95%CI:124-259)、192(95%CI:124-260)、193(95%CI:125-261)、194(95%CI:126-262)、195(95%CI:127-263)和196(95%CI:128-264)。结论常见统计模型可以用于厦门市结核病发病趋势预测,厦门市短期内报告病例数将略有上升趋势。

厦门市新型冠状病毒肺炎人群传播能力计算与防控措施效果的模拟评估

为计算厦门市新型冠状病毒肺炎(COVID-19)人群传播能力并模拟评估防控措施效果,根据COVID-19自然史构建厦门市COVID-19人群传播的易感者-潜伏者-染病者-隐性感染者-移出者(susceptible-exposed-infectious-asymptomaticrecovered,SEIAR)模型,收集厦门市截至2020年3月7日的COVID-19病例数据建立数据库,将SEIAR模型与数据库拟合计算COVID-19有效再生数(effective reproduction number,Reff),模拟综合干预措施情况下的流行曲线,并评估综合干预措施效果.截至3月7日厦门市共报告COVID-19病例35例,其中输入病例22例,继发病例13例,模型与疫情数据拟合结果较好(χ^2=10.375,p=0.996).模型结果显示:1月26日之前,COVID-19在厦门市的Reff为2.78,1月26日之后的Reff为0.35,综合干预措施将Reff降低了87.41%.若1月26日未强化综合干预措施,则截至3月7日预计累计报告病例和本地病例将分别达到1863和1841例,而实际累计报告病例和本地病例分别为35和13例,分别降低了98.12%和99.29%.上述结果表明厦门市COVID-19人群传播能力较强,综合干预措施取得了较好的防控效果.

一种基于高斯拟合的水生植被遥感分类阈值确定方法

水生植被作为浅水湖泊的重要组成,其丰度和盖度变化影响着湖泊生态系统的平衡。卫星遥感技术是浅水湖泊水生植被类群时空监测的有效手段,决策树是目前主流的水生植被遥感分类方法。但决策树中分类特征的阈值大多是通过与影像同步的大量实测样点训练确定,对于缺少实测样点的影像,难以获取准确阈值,成为水生植被类群分布历史重建的瓶颈。基于HJCCD影像数据,获取洪泽湖水生植被类群敏感光谱特征图像的直方图,结合高斯模型,建立了一种基于高斯拟合的水生植被遥感分类阈值计算方法,计算得到分类特征的阈值并建立决策树,开展洪泽湖的水生植被类群提取,分类总体精度为84%,Kappa系数为76%.该方法可实现缺少同步实测样点时,水生植被分类特征阈值的准确、自动化计算,为浅水湖泊的水生植被分布的历史重建提供了有力的方法支撑,进而可对湖泊高效管理和生态修复等提供理论指导。

甘肃省体育馆悬吊楼盖人致振动舒适度现场测试研究

对于悬吊楼盖,其悬吊端竖向刚度较弱,人群荷载激励下易发生较大振动。以甘肃省体育馆13.500m标高悬吊楼盖为研究对象,在主体结构完工后,首先,测试了楼盖在环境脉动激励作用下的振动模态;其次,参照楼盖的振动模态实测了楼盖在不同激励下包括单人行走、多人行走、多人跳跃、多人跑步、自由运动等工况下的加速度反应;最后根据楼盖的建筑使用功能,以峰值加速度为指标评估该悬吊楼盖的振动舒适度。结果表明,悬吊楼盖在人行荷载作用下存在较为显著的振动响应和一定程度的振动舒适度问题,人致激励的类型和路线对楼盖的振动舒适度有显著的影响。

Assessing the deformation response of double-track overlapped tunnels using numerical simulation and field monitoring

The unprecedented rate of metro construction has led to a highly complex network of metro lines.Tunnels are being overlapped to an ever-increasing degree.This paper investigates the deformation response of double-track overlapped tunnels in Tianjin,China using finite element analysis(FEA)and field monitoring,considering the attributes of different tunneling forms.With respect to the upper tunneling,the results of the FEA and field monitoring showed that the maximum vertical displacements of the ground surface during the tail passage were 2.06 mm,2.25 mm and 2.39 mm obtained by the FEA,field monitoring and Peck calculation,respectively;the heaves on the vertical displacement curve were observed at 8 m(1.25D,where D is the diameter of the tunnel)away from the center of the tunnel and the curve at both sides was asymmetrical.Furthermore,the crown and bottom produce approximately0.38 mm and 1.26 mm of contraction,respectively.The results of the FEA of the upper and lower sections demonstrated that the tunneling form has an obvious influence on the deformation response of the double-track overlapped tunnel.Compared with the upper tunneling,the lower tunneling exerted significantly less influence on the deformation response,which manifested as a smaller displacement of the strata and deformation of the existing tunnel.The results of this study on overlapped tunnels can provide a reference for similar projects in the future.

Anthropogenic Aerosol Pollution over the Eastern Slope of the Tibetan Plateau

In this study, a combination of satellite observations and reanalysis datasets is used to analyze the spatiotemporal distribution, classification and source of pollutants over the eastern slope of the Tibetan Plateau(ESTP). The aerosol optical depth(AOD) over the ESTP is extremely large and even larger than some important industrialized regions and deserts. The main aerosol component over the ESTP is sulfate, followed by carbonaceous and dust aerosols. Local emissions related to human activity directly contribute to the accumulation of sulfate and carbonaceous aerosols over the Sichuan Basin. In addition, in spring, abundant carbonaceous aerosols emitted from forest, grassland and savanna fires in Southeast Asia can be transported by the prevailing southwesterly wind to southern China and the ESTP. The dust AOD over the ESTP peaks in spring because of the transport from the Taklimakan and Gobi deserts. Additionally, the high aerosol loading over the ESTP is also directly related to the meteorological background. Due to the special topography, the terrain-driven circulation can trap aerosols in the Sichuan Basin and these aerosols can climb along the ESTP due to the perennial updraft. The aerosol loading is lowest in summer because of effective wet deposition induced by the strong precipitation and better dispersion conditions due to the larger vertical temperature gradients and ascending air movement enhanced by the plateau heat pump effect. In contrast,the aerosol loading is greatest in winter. Abundant anthropogenic aerosols over the ESTP may generate some climatic and environmental risks and consequently greatly influence the downstream regions.

Publisher's note to“Texture engineering of mono-crystalline silicon via alcohol-free alkali solution for efficient PERC solar cells”[J.Energy Chem.71(2022)104-107

The publisher regrets that the page range of this paper was incorrect due to production error,and we added al-a5 after page 107 to the pdf version to correct this mistake.

Ground movement induced by triple stacked tunneling with different construction sequences

This study tried to explore the ground movement induced by triple stacked tunneling(TST) with different construction sequences. A case study in Tianjin, China was used to investigate the ground movement during the TST(upper tunneling(UT)). For this, a modified Peck formula was proposed to predict the surface settlement induced by TST. Next, three sets of finite element analyses(FEA) were used to compare the effects of construction sequences(i.e. UT, middle tunneling(MT), and lower tunneling(LT)) on vertical and lateral ground displacements. The results of Tianjin case and UT reveal that compared to a Gaussian distribution for a single tunnel, the surface settlement curve of triple stacked tunnels is a bimodal distribution. It seems that the proposed modified Peck formula can effectively predict the surface settlement induced by TST. The results of the three sets of FEA demonstrate that the construction sequence has a significant influence on the ground movement. Among the three construction sequences, the largest lateral displacement is observed in the MT and the smallest one in UT.The existing tunnel has an inhibitory effect on the vertical displacement. The maximum value of the lateral displacement occurs at the depth of the new tunnel in each construction sequence.

The n-type Si-based materials applied on the front surface of IBC-SHJ solar cells

Interdigitated back contact silicon hetero-junction(IBC-SHJ) solar cells exhibit excellent performance owing to the IBC and SHJ structures.The front surface field(FSF) layer composed of electric field passivation and chemical passivation has been proved to play an important role in IBC-SHJ solar cells.The electric field passivated layer n^+-a-Si: H, an n-type Si alloy with carbon or oxygen in amorphous phase, is simulated in this study to investigate its effect on IBC-SHJ.It is indicated that the n^+-a-Si: H layer with wider band gap can reduce the light absorption on the front side efficaciously,which hinders the surface recombination of photo-generated carriers and thus contributes to the improvement of the short circuit current density Jsc.The highly doped n^+-a-Si: H can result in the remakable energy band bending, which makes it outstanding in the field passivation, while it makes little contribution to the chemical passivation.It is noteworthy that when the electric field intensity exceeds 1.3 × 10^5 V/cm, the efficiency decrease caused by the inferior chemical passivation is only 0.16%.In this study, the IBC-SHJ solar cell with a front n^+-a-Si: H field passivation layer is simulated, which shows the high efficiency of 26% in spite of the inferior chemical passivation on the front surface.

基于Park-Ang的结构整体损伤模型研究

结构的整体损伤指数能够有效量化地震作用下结构的损伤程度,在地震工程领域中起着至关重要的作用。文中基于构件层次的Park-Ang损伤模型,提出了考虑结构最大层间位移角和滞回耗能共同作用的整体损伤模型。使用多次增量动力分析得到百分位曲线和能力曲线簇,并根据该曲线得到结构的最大层间位移角限值和极限应变能。采用Sausage软件建立了237.6 m的60层带伸臂桁架的框架—核心筒结构,并通过一组主震及主余震地震动序列的动力时程结果,分析比较了本文整体损伤指数与基于层间位移角、Dipasquale损伤指数进行比较验证。结果表明:主震及主余震下Dipasquale的结构损伤指数仅为0.275和0.278,严重低估了结构的实际损伤。而本文建议的整体损伤指数主震下为0.82,与基于层间位移角的损伤指数模型得到的结果0.78接近,且主余震下结构整体损伤指数为0.83,能够体现余震作用下的损伤增量,与结构弹塑性结果保持一致。因此,本文提出的整体损伤模型是准确有效的,能够为结构的损伤评估研究提供参考。

Surface passivation in n-type silicon and its application in silicon drift detector

Based on the surface passivation of n-type silicon in a silicon drift detector(SDD), we propose a new passivation structure of SiO2/Al2O3/SiO2 passivation stacks. Since the SiO2 formed by the nitric-acid-oxidation-of-silicon(NAOS)method has good compactness and simple process, the first layer film is formed by the NAOS method. The Al2O3 film is also introduced into the passivation stacks owing to exceptional advantages such as good interface characteristic and simple process. In addition, for requirements of thickness and deposition temperature, the third layer of the SiO2 film is deposited by plasma enhanced chemical vapor deposition(PECVD). The deposition of the SiO2 film by PECVD is a low-temperature process and has a high deposition rate, which causes little damage to the device and makes the SiO2 film very suitable for serving as the third passivation layer. The passivation approach of stacks can saturate dangling bonds at the interface between stacks and the silicon substrate, and provide positive charge to optimize the field passivation of the n-type substrate.The passivation method ultimately achieves a good combination of chemical and field passivations. Experimental results show that with the passivation structure of SiO2/Al2O3/SiO2, the final minority carrier lifetime reaches 5223 μs at injection of 5×10^(15) cm^(-3). When it is applied to the passivation of SDD, the leakage current is reduced to the order of nA.

Texture engineering of mono-crystalline silicon via alcohol-free alkali solution for efficient PERC solar cells

Control of texture structures is an effective method to reduce surface reflectivity and enhance the efficiency of solar cells.In this paper,pyramid structures are prepared on mono-crystalline silicon wafers by cyclodextrin as surfactant to slow down the etching rate in alcohol-free alkali solution.Compared with volatile alcohol surfactant(e.g.isopropanol,IPA),the cyclodextrin not only possesses a relative high boiling point(1534.4℃),but displays non-toxic and biodegradable properties.Furthermore,the surface morphology,average reflectivity,surface recombination of mono-crystalline silicon wafers were studied in detail.The results show that cyclodextrin can decrease the size and depth of pyramid structures,and thus a lower average reflectivity of 7.5%was obtained.In addition,ray tracing simulation was performed to calculate the photo-generated carrier concentration of PN junction with different sizes of pyramids,and the conclusion is that the carrier concentration of small pyramids is much higher than that of large pyramids.Finally,the average efficiency of large-area mono-crystalline silicon PERC solar cells fabricated by cyclodextrin surfactant was 22.69%,which was 0.43%absolutely higher than that of conventional IPA surfactant.

穴位按摩结合标准抚触手法辅助治疗新生儿黄疸的效果评价

目的 分析穴位按摩结合标准抚触手法辅助治疗新生儿黄疸对病情改善的影响。方法 以2018年12月至2020年12月于南京医科大学附属无锡妇幼保健院分娩的90例病理性黄疸新生儿为研究对象,借助数字表将其随机分为研究组和对照组,各45例。研究组实施穴位按摩结合标准抚触手法干预,对照组实施常规性护理方案,比较两组在干预后第1、2、3、4、5、6、7天经皮测黄疸数据、干预后第7天的高胆红素血症发生率、新生儿黄疸消退时间、第1次排胎粪时间。结果 研究组患儿干预后第3、4、5、6、7天的经皮测黄疸数据低于对照组,干预后第7天研究组患儿高胆红素血症发生率低于对照组,研究组患儿黄疸消退时间、第1次排胎粪时间均早于对照组,差异均有统计学意义(均P<0.05)。结论 穴位按摩结合标准抚触手法辅助治疗新生儿黄疸的效果良好,可以改善黄疸指数,降低高胆红素血症发生率,值得在临床上进一步推广。

基于主余震理论的余震地震动PGA衰减关系研究

为了解余震和主震的相关性,研究余震对建筑结构损伤的影响,文中建立了最大余震和主震地震动参数的数学函数关系,选用752组真实主余震序列,采用多元非线性回归方法,统计回归出地震动衰减关系。结果表明:相对地震动参数和主震矩震级、标准场地剪切波速呈正相关,和主余震震级之比、场地剪切波速之比呈负相关,和主震震源距D_(ms)的相关性较小。本文模型的预测值在V_(s30)取值较小时和CY2008模型的预测值较为接近;V_(s30)取值较大时,本文模型的预测值和AS2008模型的预测值的最大误差仅为5%。本文构建的模型能较好地预测余震相对地震动参数,为地震危险性分析和工程实践提供一定的理论依据。

校区搬迁对大学生心理的影响研究——以江苏大学京江学院为例

目的:了解搬迁大学生的基本心理状况,为其教育管理提供参考。方法:采用应对方式问卷(CSQ)对158名大学生进行调查,并利用“鱼刺图”从环境氛围建设、地理位置、教学与教学设备、宣传指导工作四个方面分析大学生心理的影响因素。结果:大学生的应对方式趋向于不成熟;合理化因子在性别上存在显著差异。结论:校区搬迁对大学生心理健康有负面影响,应对方式是影响大学生心理的重要因素。