Interactive Effects of Ultraviolet Radiation and Dissolved Organic Carbon on Phytoplankton Growth and Photosynthesis in Sanya Bay,Northern South China Sea

Ocean Science Journal - The effects of a simulated climate change scenario, i.e., increased ultraviolet radiation (UVR) and dissolved organic carbon (DOC), on the growth and photosynthesis of...     

Succession of the Nanoplankton Community during a Brown Tide in a Scallop Culture Area in China

Ocean Science Journal - Brown tides caused by Aureococcus anophagefferens have occurred frequently in the coastal waters of Qinhuangdao since 2009. The Changli coast is the area most strongly...     

Simulation of landscape spatial layout evolution in rural-urban fringe areas: a case study of Ganjingzi District

In recent years, the rapid expansion of urban spaces has accelerated the mutual evolution of landscape types. Analyzing and simulating spatio-temporal dynamic features of urban landscape can help to reveal its driving mechanisms and facilitate reasonable planning of urban land resources. The purpose of this study was to design a hybrid cellular automata model to simulate dynamic change in urban landscapes. The model consists of four parts: a geospatial partition, a Markov chain (MC), a multi-layer perceptron artificial neural network (MLP-ANN), and cellular automata (CA). This study employed multivariate land use data for the period 2000–2015 to conduct spatial clustering for the Ganjingzi District and to simulate landscape status evolution via a divisional composite cellular automaton model. During the period of 2000–2015, construction land and forest land areas in Ganjingzi District increased by 19.43% and 15.19%, respectively, whereas farmland, garden lands, and other land areas decreased by 43.42%, 52.14%, and 75.97%, respectively. Land use conversion potentials in different sub-regions show different characteristics in space. The overall land-change prediction accuracy for the subarea-composite model is 3% higher than that of the non-partitioned model, and misses are reduced by 3.1%. Therefore, by integrating geospatial zoning and the MLP-ANN hybrid method, the land type conversion rules of different zonings can be obtained, allowing for more effective simulations of future urban land use change. The hybrid cellular automata model developed here will provide a reference for urban planning and policy formulation.     

X-ray activity from different types of stars

X-ray emission is an important indicator of stellar activity. In this paper, we study stellar Xray activity using the XMM-Newton and LAMOST data for different types of stars. We provide a sample including 1259 X-ray-emitting stars, of which 1090 have accurate stellar parameter estimations. Our sample size is much larger than those used in previous works. We find a bimodal distribution of the X-ray to optical flux ratio(log(fX/fV)) for G and K stars. We interpret that this bimodality is due to two subpopulations with different coronal heating rates. Furthermore, using the full widths at half maxima calculated from Hα and Hβ lines, we show that these stars in the inactive peaks have smaller rotational velocities. This is consistent with the magnetic dynamo theory that presumes stars with low rotational velocities have low levels of stellar activity. We also examine the correlation between log(fX/fV) and luminosity of the excess emission in the Hα line, and find a tight relation between the coronal and chromospheric activity indicators.     

检测前跟踪框架下利用蒙特卡洛算法的空间碎片跟踪策略研究（英文）

在轨卫星或者空间碎片数量的增多,是对空间目标地基自动观测的一个挑战。尽管北美防空司令部编目管理了绝大多数直径超过10 cm的空间物体,但由于轨道摄动,空间目标的位置信息(基于6个轨道根数)依然非常重要,并需要定期更新。在过去的几十年里,配备电子传感器的现代地基光电望远镜已广泛用于天体测量领域。然而,这种设备的跟踪性能主要取决于空间目标的大小和亮度。这些目标所在的天文图像会有不同的背景;而且,在基于凝视模式的短曝光实时观测过程中,运动目标和背景恒星在不同的信噪比下显示为类似的点扩散函数,难以辨认。本研究是为了实现对非高斯和动态背景的高灵敏度检测和跟踪能力的提高,并具有简单的系统机制和出色的计算效率。为突破该限制,将重点放在利用状态估计技术对微小卫星和暗弱目标进行跟踪上。提出一种基于神经网络的自适应运行高斯平均算法,用以从恒星背景及干扰下提取运动的空间目标。该方法随后被集成到了一个检测前跟踪框架中。该框架利用基于蒙特卡洛的粒子滤波跟踪空间目标。三段来自亚太地基光学空间目标观测系统(APOSOS)图像序列被用来对该跟踪策略进行评估。实验结果表明,该方法能够达到满意的跟踪性能。     

风城油田重油SAGD蒸汽腔微震监测

中国石油新疆油田分公司风城油田1845井区目前有13个井组正在实施蒸汽辅助重力泄油(SAGD).2018年12月至2019年4月期间,我们应用微破裂向量扫描对该井区实施了共35天的微震监测,试图定量确定热蒸汽腔的4D变化.由于微震活动的间歇性和跳跃性,一定期间的监测,很难用含震级或能量的震源分布对蒸汽腔实施解释;故,我...     

内蒙古荒漠草原沙生针茅(Stipa glareosa)、碱韭(Allium polyrhizum)和骆驼蓬(Peganum harmala)叶形态性状对土壤水氮耦合的响应

研究降水和氮沉降对荒漠草原植物叶形态性状的影响,对于预测未来全球变化下荒漠草原植物的生态适应具有重要意义.对增减雨(±50％)和氮添加(10 g·m-2.a-1)及其交互作用对乌拉特荒漠草原区优势植物叶形态性状的影响研究结果表明:(1)沙生针茅(Stipa glareosa)、碱韭(Allium polyrhizum)...     

Dynamic stress concentration of an elliptical cavity in a semi-elliptical hill under SH-waves

The method of wave-function expansion in elliptical coordinates,elliptical cosine half-range expansion and Mathieu function were applied to obtain an exact analytical solution of the dynamic stress concentration factor(DSCF)around an elliptical cavity in a shallow,semi-elliptical hill.An infinite system of simultaneous linear equations for solving this problem was established by substituting the wave expression obtained by the Mathieu function including the standing wave expression of elliptical lining given herein into the boundary condition obtained by the region-matching method.The finite equations system with unknown coefficients obtained by truncation were solved numerically,and the results in the case of an ellipse degenerating into a circle were compared with previous results to verify the accuracy of the method.The effects of different aspect ratios,incident wave angles and aperture ratios on the dynamic stress concentration around the elliptical cavity were described.Some numerical results,when the elliptical hill was changed into a circular one,were analyzed and compared in detail.In engineering,this model can be regarded as a semi-cylindrical hill with an elliptical cylindrical unlined tunnel under the action of SH waves,and the results are significant in aseismic design.     

基于虚拟化云平台的气象终端集约化管理

气象终端的集约化管理是气象业务系统和气象服务需求发展到一定阶段后的必然趋势和结果。从气象终端管理的现状和需求、虚拟化云平台的技术体现和应用部署中,体现基于虚拟化云平台的气象终端集约化管理的应用特点和实施效果:提供虚拟防护、桌面管理及行为控制等的策略管理和策略服务,提升气象现代化支撑和保障气象用户个性化需求的能力,为气象平台建设、信息共享、应用服务的终端管理提出了全新概念,是集"应用"、"集成"、"运维"、"安全"到"成本控制"的解决方案。     

雷达-雨量计联合估测区域降水量方法研究Ⅰ——模式集成法的提出

天气雷达估测区域降水量是其应用研究的重要领域,不断研究改进雷达估测区域降水量精度和稳定度是雷达气象工作的重要目标。文章回顾了集合预报理论基础及其发展概况,总结分析集合预报方法、产品表现形式等。对前期雷达估测区域降水量的8种方法,从基本原理和特点等方面进行了系统分析。对该理论在雷达估测区域降水领域的适用性进行了分析,阐述了集合预报理论在该领域应用的概念模型,并提出了两种集成估测区域降水量的新方法,为下一步的应用研究提供了理论支撑。