基于加速度传感器的桨叶方位角和轮毂转速测量方法

随着风电装机容量的增加,风电机组需要更智能、更可靠的控制,这对变桨系统提出了新的要求。本文提出一种测量桨叶方位角和主轴转速的新方法,通过内置于变桨变频器的加速度传感器获取3个变频器的三向加速度分量,基于加速度分量可确定机组桨叶的方位角;另外,基于桨叶方位角的时间序列,可以计算得到机组主轴的转速。

新型储能系统对配电网运行影响的综合分析

本文分析了储能技术对配电网运行的影响,重点探讨了不同类型的储能系统如化学储能(锂离子电池、铅酸电池、钠硫电池)、机械储能(抽水蓄能、飞轮储能)、热能储能和电磁储能(超级电容器、超导磁储能)的特性。同时,研究了这些系统的电网集成方式,包括直流和交流储能技术的接入方法及其对电网频率调节、可靠性提升的作用。案例研究和模拟分析表明,储能系统能有效支持电网稳定运行,尤其是在频率波动和高峰负荷时期。通过对政策和经济激励措施的分析显示,储能技术的发展将通过成本降低、技术进步受到推动。

种植密度对不同夏玉米品种植株性状及产量影响

2019-2021年连续3年在陕西省泾阳县试验示范基地选取不同类型夏玉米品种,研究了4种密度对植株性状和产量的影响,探索各品种在关中灌区最佳种植密度。结果表明:各品种同一年度间株高、穗位、倒伏率、倒折率和空秆率随种植密度的增加有增高趋势,穗行数、行粒数和穗粒数有降低趋势,在4.5万株/hm^(2)和6.0万株/hm^(2)密度条件下百粒重较大。关中灌区陕单650最佳种植密度为7.5~9.0万株/hm^(2),郑单958最佳种植密度为6.0~7.5万株/hm^(2),陕单609最佳种植密度为9.0万株/hm^(2),东单60最佳种植密度为6.0~7.5万株/hm^(2)。

综合农艺管理推动玉米缩差增效

当前,世界粮食单产徘徊不前,现有耕地粮食产量难以保障持续增长的刚性需求。据预测,粮食总产需增加70%—100%,才能满足2050年的世界粮食需求[1-2],未来粮食增产和环境安全将主要依靠单产和资源效率的协同提升[3]。缩小不同作物种植系统的单产差距,是进一步提高单产的主攻方向。准确定量作物产量和效率潜力以及产量与效率差异特征,确定产量差、效率差形成的主控因子,对主要粮食作物可持续增产具有重要作用[4]。

浅海负跃层条件下的双基地有源探测实验及定位声速修正

为了研究浅海条件下海底固定水平阵和机动声源的双基地有源探测性能,建立了浅海双基地有源探测仿真模型,分析了实验海区负跃层条件下的传播损失和多途能量扩展损失,实现了双基地有源探测的性能预估。以模型仿真为基础,在南海北部海域开展了一次浅海双基地有源探测实验.针对定位中的声速与实验中目标回波的脉冲传播速度的偏差导致定位精度下降的问题,提出了一种目标回波脉冲传播速度近似估计方法。实验结果表明,双基地有源探测可在浅海负跃层条件下实现对水中目标的有效探测,多个实验站位的回波信噪比实测值与仿真预测值符合较好,定位声速近似估计方法可进一步提高定位精度。

交直流配电网系统中准Z源网络的小信号模型分析与验证

配电网中Z源网络的引入可以灵活控制电压的输出,实现高效率的电能变换。为了详细分析准Z源网络拓扑的模型特征,利用状态空间法和小信号建模方法提出、分析并验证了一种应用于配电网中准Z源网络的小信号模型特征。首先,利用状态空间法推导了准Z源网络的数学模型;然后,利用小信号模型对准Z源网络进行暂态分析,并得出电感电流和电容电压传递函数。另外,详细分析了两种传递函数的零、极点分布情况,并得出了系统稳定性变化的特征。最后,利用MATLAB/Simulink软件仿真的结果和物理样机试验验证了所提方法的有效性。

用量化评估方法探析核设施实物保护系统设计优化

核设施实物保护系统作为保护核设施免遭恐怖主义袭击的主要手段,其有效性对于确保核设施安全至关重要。当前,我国核设施实物保护系统的设计过于依赖法规标准,缺少针对不同威胁的区别化设计方案,设计过程中的有效性分析验证缺少数据支撑,影响了实物保护系统功能的发挥。为了探究通过优化设计提高核设施实物保护系统有效性的方法,本文从影响核设施实物保护系统有效性的主要因素分析入手,探讨了当前核设施实物保护系统设计中存在的一些不足,并通过定量分析的方法论证了核设施实物保护系统设计优化的可能方案,为优化核设施实物保护系统设计提供了相关建议。

高产多抗粮饲兼用玉米陕科9号品种选育与利用

从育种目标、技术路线、难点及创新点等方面介绍了高产多抗粮饲兼用玉米陕科9号的选育思路和过程。提出采用更高效的类群划分技术,以“两群论”为基础引入多优势模式,自交选系+DH技术相结合,综合运用玉米自交系抗病性、耐旱性、抗倒性鉴定技术、SNP分子标记技术和双单倍体纯化技术,注重对籽粒产量和生物产量的双重考量,从而有效提升品种抗逆性和丰产性,提高选育质量和效率,对品种审定和推广应用情况也进行了说明。

ABS塑件的常见缺陷及解决方案

ABS塑料在注射成型过程中,由于注射成型工艺参数、注射模设计的影响,经常存在各种缺陷,影响塑件的外观及使用。针对注射过程中经常遇到的ABS及解决措施进行了分析。

Effect of sound speed profile on the structure of long-range acoustic pulse

The time arrival structure of acoustic pulse signals propagating in ocean waveguides is of great significance for underwater acoustic communication and navigation. Using the deep-sea sound propagation data from the experiments respectively conducted in the East Indian Ocean(EIO) and the South China Sea(SCS) with explosion sources near the sound channel axis(SCA), long-range transmission loss(TL) and time arrival structure of acoustic pulses for different sound speed profiles(SSPs) are compared. In the EIO environment, sound energy transmitting along the SCA is relatively large, and the corresponding signals arrive first, whereas signals propagating away from the SCA arrive late. In the full receiving depth, it shows a branch structure where the waveform near the SCA arrives earlier than other depths, which is totally different with the characteristics of the sound pulse in the SCS. Combined with the parametric mathematical model of deep-sea sound channel, the influence mechanism of SSP on the time arrival structure of long-range pulse propagation is theoretically analyzed, which well explains the phenomenon observed in the two experiments.

热带海气相互作用及其对东亚夏季风气候影响的研究进展

东亚夏季风是影响我国夏季气候最主要的环流系统,其异常变化是造成东亚各国夏季严重旱涝灾害的直接原因。热带海气耦合系统是导致东亚夏季风异常的重要驱动因子。在全球变暖的背景下,热带海气相互作用和东亚夏季风系统都正在发生显著的变化。重点回顾了近年来热带关键海表面温度模态厄尔尼诺—南方涛动(ENSO)和热带印度洋—西太平洋暖池对全球变暖响应的物理机制、热带关键区海气相互作用对东亚夏季风系统的影响机制以及2021—2050年东亚夏季风降水趋势预估方面的进展。对于理解全球变暖背景下东亚夏季风系统变化以及相关重大旱涝灾害形成的物理机制有重要科学价值,预估东亚夏季风气候未来的变化也可以为我国应对和适应气候变化提供科学支撑。

气候系统和气候变化研究获2021年诺贝尔物理学奖的启示

2021年,诺贝尔物理学奖授予了大气科学领域从事气候系统和气候变化研究的美国科学家真锅淑郎和德国科学家克劳斯·哈塞尔曼。本文通过回顾获奖成果历史背景、分析获奖意义,对本次诺贝尔奖成果做了解读,说明该成果在认识地球气候这一复杂物理系统、甄别自然因素和人类活动对其影响方面的开拓性工作以及在推动人类社会发展中的重要作用,进而指出大气科学与其他自然科学和社会科学多学科的交叉融合,是推动气候系统和气候变化研究取得开创性成果的重要原因。本文还对该领域未来发展作了展望,说明了从地球系统科学的视角开展地球系统多圈层相互作用及其与人类活动联系的研究、跨圈层整合的地球观测系统的建立以及地球系统模式的发展,是气候系统和气候变化领域未来重要的研究方向。

人工智能与物联网在大气科学领域中的应用

近年来人工智能和物联网等新兴技术在众多领域中取得了突破性进展,为大数据时代带来革命性的改变.与传统方法相比,人工智能和物联网技术因其在数据的获取、传输、分析和处理等方面具有显著的优势,在大气科学领域引起了广泛的关注.在全球极端天气事件、气象灾害频发的背景下,本文通过文献调研指出了运用人工智能与物联网相结合发展智慧气象的必要性.在简要介绍人工智能和物联网关键技术、应用场景的基础上,本文回顾了人工智能在大气科学领域的发展历程,从观测识别、数据处理、天气气候分析预报、商业行业应用四个方面总结了人工智能在该领域的研究现状,重点分析了深度学习方法的应用;从综合观测、灾害预警、气象服务三个方面介绍了物联网在大气科学领域的运用;并且进一步分析总结出了人工智能和物联网在大气科学领域融合发展、应用的新趋势.

Meteorological conditions for the persistent severe fog and haze event over eastern China in January 2013

In January 2013,a severe fog and haze event(FHE)of strong intensity,long duration,and extensive coverage occurred in eastern China.The present study investigates meteorological conditions for this FHE by diagnosing both its atmospheric background fields and daily evolution in January 2013.The results show that a weak East Asian winter monsoon existed in January2013.Over eastern China,the anomalous southerly winds in the middle and lower troposphere are favorable for more water vapor transported to eastern China.An anomalous high at 500 hPa suppresses convection.The weakened surface winds are favorable for the fog and haze concentrating in eastern China.The reduction of the vertical shear of horizontal winds weakens the synoptic disturbances and vertical mixing of atmosphere.The anomalous inversion in near-surface increases the stability of surface air.All these meteorological background fields in January 2013 were conducive to the maintenance and development of fog and haze over eastern China.The diagnosis of the daily evolution of the FHE shows that the surface wind velocity and the vertical shear of horizontal winds in the middle and lower troposphere can exert dynamic effects on fog and haze.The larger(smaller)they are,the weaker(stronger)the fog and haze are.The thermodynamic effects include stratification instability in middle and lower troposphere and the inversion and dew-point deficit in near-surface.The larger(smaller)the stratification instability and the inversion are,the stronger(weaker)the fog and haze are.Meanwhile,the smaller(larger)the dewpoint deficit is,the stronger(weaker)the fog and haze are.Based on the meteorological factors,a multi-variate linear regression model is set up.The model results show that the dynamic and thermodynamic effects on the variance of the fog and haze evolution are almost the same.The contribution of the meteorological factors to the variance of the daily fog and haze evolution reaches 0.68,which explains more than 2/3 of the variance.

Impacts of Atlantic sea surface temperature anomalies on Indo-East Asian summer monsoon-ENSO relationship

In this study, the effect of the tropical North Atlantic (TNA) sea surface temperature (SST) variation in inducing the circulation anomaly in the Indo-East Asian monsoon (IEAM) region is investigated through the observational analysis and numerical model-ing. The observational analysis shows that the TNA summer SST is positively correlated with the preceding winter Ni?o3 SST and is simultaneously correlated with the circulation in the IEAM region. The simultaneous circulation pattern resembles that of the ENSO-decaying summer. The positive correlation between the TNA SST and the Ni?o3 region SST is primarily ascribed to the surface latent heat flux and short wave radiation anomalies induced by the ENSO teleconnection. Coupled general circulation model experiments show that, while including the air-sea coupling in the Atlantic, the model can reproduce the main features of the IEAM circulation, such as an anomalous anticyclone over the western North Pacific (WNP) and southerly anomalies over southeast China. While the climatological Atlantic SST is prescribed, the circulation over the WNP displays a significantly dif-ferent pattern, with an eastward migration of the WNP anticyclone and the associated northerly anomalies over southeast China. It is argued that anticyclonic shear and Ekman divergence associated with the atmospheric Kelvin wave response to the TNA warm SSTA forcing is the primary mechanism for the generation of the anomalous anticyclone in WNP. The results presented in this study provide a teleconnection pattern between TNA and short-term climate variability in IEAM region.

Impact of El Nio on atmospheric circulations over East Asia and rainfall in China： Role of the anomalous western North Pacific anticyclone

This paper presents a review on the impact of El Nio on the interannual variability of atmospheric circulations over East Asia and rainfall in China through the anomalous anticyclone over western North Pacific(WNPAC). It explains the formation mechanisms of the WNPAC and physical processes by which the WNPAC affects the rainfall in China. During the mature phase of El Nio, the convective cooling anomalies over western tropical Pacific caused by the weakened convections trigger up an atmospheric Rossby wave response, resulting in the generation of the WNPAC. The WNPAC can persist from the winter when the El Nio is in its peak to subsequent summer, which is maintained by multiple factors including the sustained presence of convective cooling anomalies and the local air-sea interaction over western tropical Pacific, and the persistence of sea surface temperature anomalies(SSTA) in tropical Indian and tropical North Atlantic. The WNPAC can influence the atmospheric circulations over East Asia and rainfall in China not only simultaneously, but also in the subsequent summer after an El Nio year, leading to more rainfall over southern China. The current paper also points out that significant anomalies of atmospheric circulations over East Asia and rainfall over southern China occur in El Nio winter but not in La Nio winter, suggesting that El Nio and La Nio have an asymmetric effect. Other issues, including the impact of El Nio diversity and its impact as well as the relations of the factors affecting the persistence of the WNPAC with summer rainfall anomalies in China, are also discussed. At the end of this paper some issues calling for further investigation are discussed.

Advances in studying interactions between aerosols and monsoon in China

Scientific issues relevant to interactions between aerosols and the Asian monsoon climate were discussed and evaluated at the 33 rd "Forum of Science and Technology Frontiers" sponsored by the Department of Earth Sciences at the Chinese Academy of Sciences. Major results are summarized in this paper. The East Asian monsoon directly affects aerosol transport and provides a favorable background circulation for the occurrence and development of persistent fog-haze weather. Spatial features of aerosol transport and distribution are also influenced by the East Asian monsoon on seasonal, inter-annual, and decadal scales. High moisture levels in monsoon regions also affect aerosol optical and radiative properties. Observation analyses indicate that cloud physical properties and precipitation are significantly affected by aerosols in China with aerosols likely suppressing local light and moderate rainfall, and intensifying heavy rainfall in southeast coastal regions. However, the detailed mechanisms behind this pattern still need further exploration. The decadal variation in the East Asian monsoon strongly affects aerosol concentrations and their spatial patterns. The weakening monsoon circulation in recent decades has likely helped to increase regional aerosol concentrations. The substantial increase in Chinese air pollutants has likely decreased the temperature difference between land and sea, which favors intensification of the weakening monsoon circulation. Constructive suggestions regarding future studies on aerosols and monsoons were proposed in this forum and key uncertain issues were also discussed.

Addressing the issue of fog and haze:A promising perspective from meteorological science and technology

Fog and haze are two kinds of weather phenomena.Fog is referred to as water droplets suspended in the air near earth’s surface,which reduces the visibility to less than 1 km.A fog consisting of ice crystals is called ice fog.Haze is the particles suspended in the air that reduce visibility by scattering the light,and is usually a mixture of aerosol and photochemical smog.Fog and haze usually coexist.The occurrence and evolution of haze and fog are closely related with meteorological conditions.

A numerically stable coupled-mode formulation for acoustic propagation in range-dependent waveguides

In this paper,a stepwise coupled-mode model with the use of the direct global matrix approach is proposed.This method is capable of handling two-dimensional problems with either a point source in cylindrical geometry or a line source in plane geometry.With the use of the direct global matrix approach,this method is numerically stable.In addition,by introducing appropriately normalized range solutions,this model is free from the numerical overflow problem.Furthermore,we put forward source conditions appropriate for the line-source problem in plane geometry.As a result,this method is capable of addressing the scenario with a line source on top of a sloping bottom.Closed-form expressions for coupling matrices are derived and applied in this paper for handling problems with pressure-release boundaries and a homogeneous water column.The numerical simulations indicate that the proposed model is accurate,efficient,and numerically stable.Consequently,this model can serve as a benchmark model in range-dependent propagation modeling.Although this method is verified by an ideal wedge problem in this paper,the formulation applies to realistic problems as well.

Arctic dipole anomaly and summer rainfall in Northeast China

A dipole structure anomaly in summer Arctic atmospheric variability is identified in this study, which is characterized by the second mode of empirical orthogonal function (EOF) analysis of summer monthly mean sea level pressure (SLP) north of 70°N, accounting for 12.94% of the variance. The dipole anom- aly shows a quasi-barotropic structure with opposite anomalous centers over the Canadian Arctic and the Beaufort Sea and between the Kara Sea and the Laptev Sea. The dipole anomaly reflects alternating variations in location of the polar vortex between the western and eastern Arctic regions. The positive phase of the dipole anomaly corresponds to the center of the polar vortex over the western Arctic, leading to an increase in summer mean rainfall in Northeast China. The dipole anomaly has a pre- dominant 6-year periodicity, and shows interdecadal variations in recent decades.