青海可鲁克湖-托素湖湿地自然保护区不同植被类型土壤碳氮磷生态化学计量学特征

为研究可鲁克湖-托素湖湿地自然保护区内不同植被类型土壤的生态化学计量学特征,以保护区内4种植被类型:白刺地(Nitraria tangutorum)V1、柽柳地(Tamarix chinensis)V2、盐爪爪地(Kalidium foliatum)V3、芦苇地(Phragmites communis)V4为研究对象,分析土壤有机碳(soil organic carbon,SOC)、全氮(total nitrogen,TN)、全磷(total phosphorus,TP)含量及其化学计量学特征。结果表明:4种不同植被类型土壤有机碳、全氮、全磷含量的平均值分别为17.41 g·kg^(–1)、1.09 g·kg^(–1)和1.40 g·kg^(–1),土层和植被类型对土壤SOC、TN、TP均有影响,不同植被类型土壤SOC、TN、TP均表现为芦苇地>盐爪爪地>白刺地>柽柳地,SOC与TN、TP含量呈显著性相关(P<0.05)。本研究样地C/N(8.90—19.73)<25,说明研究区有机质分解快,有利于P的有效性提高。在可鲁克湖-托素湖不同植被类型土壤中,土壤含水量和p H是影响SOC、TN、TP含量以及生态化学计量学特征的主要环境因子。

Giant and controllable Goos—Hänchen shift of a reflective beam off a hyperbolic metasurface of polar crystals

We conduct a theoretical analysis of the massive and tunable Goos–Hänchen(GH) shift on a polar crystal covered with periodical black phosphorus(BP)-patches in the THz range. The surface plasmon phonon polaritons(SPPPs), which are coupled by the surface phonon polaritons(SPh Ps) and surface plasmon polaritons(SPPs), can greatly increase GH shifts.Based on the in-plane anisotropy of BP, two typical metasurface models are designed and investigated. An enormous GH shift of about-7565.58 λ_(0) is achieved by adjusting the physical parameters of the BP-patches. In the designed metasurface structure, the maximum sensitivity accompanying large GH shifts can reach about 6.43 × 10^(8) λ_(0)/RIU, which is extremely sensitive to the size, carrier density, and layer number of BP. Compared with a traditional surface plasmon resonance sensor, the sensitivity is increased by at least two orders of magnitude. We believe that investigating metasurface-based SPPPs sensors could lead to high-sensitivity biochemical detection applications.

Curve Classification Based onMean-Variance Feature Weighting and Its Application

The classification of functional data has drawn much attention in recent years.The main challenge is representing infinite-dimensional functional data by finite-dimensional features while utilizing those features to achieve better classification accuracy.In this paper,we propose a mean-variance-based(MV)feature weighting method for classifying functional data or functional curves.In the feature extraction stage,each sample curve is approximated by B-splines to transfer features to the coefficients of the spline basis.After that,a feature weighting approach based on statistical principles is introduced by comprehensively considering the between-class differences and within-class variations of the coefficients.We also introduce a scaling parameter to adjust the gap between the weights of features.The new feature weighting approach can adaptively enhance noteworthy local features while mitigating the impact of confusing features.The algorithms for feature weighted K-nearest neighbor and support vector machine classifiers are both provided.Moreover,the new approach can be well integrated into existing functional data classifiers,such as the generalized functional linear model and functional linear discriminant analysis,resulting in a more accurate classification.The performance of the mean-variance-based classifiers is evaluated by simulation studies and real data.The results show that the newfeatureweighting approach significantly improves the classification accuracy for complex functional data.

无锡市“两河”整治提升工程的实践与思考

城市化进程中,城市河道治理成为解决水环境问题、提高城市生态品质的重要举措。在此形势下,以生产、生活、生态有机融合的“三生融合”发展模式势在必行。本文结合国内外经验,以无锡“两河”整治提升工程为例,分析了该工程在城市河道治理中的实际应用情况及取得的显著成效。

可鲁克湖—托素湖保护区4种盐生植物生态化学计量特征

盐生植物是柴达木盆地高寒湿地的重要组成部分,对维护高原地区生态安全有着不可或缺的角色,选取可鲁克湖-托素湖自然护区内的柽柳(Tamarix chinensis)、盐爪爪(Kalidium foliatum)、芦苇(Phragmites australis)和白刺(Nitraria tangutorum)4种典型盐生植物群落为研究对象,分析不同植物及不同营养器官中C,N,P的生态化学计量特征。研究结果表明:4种植物不同器官的C,N,P含量存在明显的种间差异,4种盐生植物叶片的C∶N(19.29)略低于全球植物叶片的平均水平(22.50)、4种盐生植物叶片的C∶P(274.81)高于全球植物叶片C∶P平均水平(232.00),根系的C∶N,C∶P均高于全球水平。4种盐生植物具有较高的固碳优势和养分利用策略,有较强的碳同化能力。柽柳和芦苇两种植物生长主要受N元素限制,盐爪爪和白刺两种植物生长主要受P元素限制,表现出可鲁克湖—托素湖湿地自然保护区内不同植物对于营养元素的分配利用各有不同。

Large spatial shifts of reflected light beam off biaxial hyperbolic materials

Many optical systems that deal with polarization rely on the adaptability of controlling light reflection in the lithography-free nanostructure. In this study, we explore the Goos–H?nchen(GH) shift and Imbert–Fedorov(IF) shift in a biaxial hyperbolic film on a uniaxial hyperbolic substrate. This research statistically calculates and analyzes the GH shift and IF shift for the natural biaxial hyperbolic material(NBHM). We select the surface with the strongest anisotropy within the NBHM and obtain the complex beam-shift spectrum. By incorporating the NBHM film, the GH shift caused by a transversely magnetic incident-beam on the surface increases significantly compared with that on the uniaxial hyperbolic material. The maximum of GH shift can reach 86 λ0at about 841 cm-1when the thickness of NBHM is 90 nm, and the IF shift can approach 2.7 λ0for a circularly-polarized beam incident on a 1700-nm-thick NBHM. It is found that the spatialshift increases when a highly anisotropic hyperbolic polariton is excited in hyperbolic material, where the shift spectrum exhibits an oscillating behaviour accompanied with sharp shift peak(steep slope). This large spatial shift may provide an alternative strategy to develop novel sub-micrometric optical devices and biosensors.

Analysis on the Cause and Forecast Deviation of an Extreme Rainstorm in Changsha Urban Area

Using NCEP reanalysis data,high-altitude and ground observation data,numerical model data,satellite and radar data,formation cause and forecast deviation of an extreme rainstorm process in Changsha urban area at night on June 9,2020 were analyzed.The results showed that(1)the extreme rainstorm process developed near the surface convergence line,with strong localization,short duration and large hourly rainfall intensity.(2)Under the high temperature and high humidity environment,the low-level cold advection and the hot low-pressure system interacted,and the potential con-vective unstable energy was released,and a strong convective weather was formed.(3)The convergence of water vapor in the lower layer and the strong upward movement provided sufficient water vapor for the rainstorm.The low-centroid thunderstorm was the main reason for the extreme rainstorm.(4)The forecast deviation of the numerical model to the low-level shear line and the mesoscale convergence line was an important reason for the forecast deviation of the heavy rainfall area.

青海互助南门峡土族野生食用植物资源调查与分析

为了深入了解青海互助土族野生食用植物多样性,探索土族应用野生食用植物的传统知识。通过前期文献研究和实地调研,我们选择了互助土族自治县南门峡镇14个村为研究点,采用民族植物学文献研究法、关键人物访谈法、凭证标本采集、问卷调查及参与式农村评估(PRA)和调查编目等方法对食用植物资源进行了调查。结果表明:(1)土族民间传统食用野生植物有81种,36科71属,其中菊科、蔷薇科、唇形科、伞形科的植物比较多,其次是十字花科、毛茛科、豆科;(2)土族利用野生植物资源的形式也多种多样,主要为野生蔬菜(食用)、调味品、药用、饲料、香料等类型;(3)土族人民在与大自然长期生活中应用这些野生食用植物资源时积累了丰富的传统知识。

盐生植物萌发期对盐胁迫的适应研究进展

目前我国盐渍土地面积较大,尤其是青藏高原的盐渍地,常伴有干旱、半干旱的生境,导致植物不易生长,生态环境相对恶劣,这种生态现状亟待解决。盐生植物具有一定的耐盐性和耐旱性,是改善盐渍地的首选植物,种子的活力决定了种子萌发的情况,多数学者为改善严峻的生态环境开始了盐生植物引种的研究。测定种子活力有直接方法和间接方法,大多数学者采用的是直接方法,即在实验室模拟一定条件直接测定萌发率。简述了盐生植物的概况、制造胁迫的主要方法以及检测种子活力的指标,综述了近年来不同学者对盐爪爪、白刺等具有代表性的22种盐生植物在种子萌发期的耐盐性以及抗旱性的相关研究,为改善盐渍地的生态环境、提升盐渍地的生产量提供了理论基础。

青海可鲁克湖-托素湖自然保护区药用野生植物资源调查分析

目的:可鲁克湖-托素湖自然保护区植物资源丰富,群落类型多样,但对该地区的药用植物资源却鲜有报道,为探明青海可鲁克湖-托素湖自然保护区野生药用植物资源现状,对该地区进行了药用植物调查分析。结果:通过对保护区的野外实地调查、采集标本、资料查阅等方法初步统计出保护区内共有药用植物31科66属101种。绝大多数是被子植物,其中菊科、豆科、藜科、十字花科、蓼科为本地的优势科属,占自然保护区药用植物总资源的58.42%。本文对可鲁克湖-托素湖药用植物资源的药用部位和药用功效进行了统计分析,利用药用植物全草、根、茎部位占药用植物总数76.24%,清热解毒、消肿止痛、消炎药类植物在整个功效类别中占主要优势。最后介绍了可鲁克湖-托素湖自然保护区的药用植物名录,为保护区野生药用植物的开发和可持续利用提供科学依据。

基于三孩政策的网络议程设置研究

为解决网络议程设置难以体现出议题和属性间的隐性关系的问题,本研究提出的网络议程设置模型,将原有的词语共现的显性关联,转化为框架效果的逻辑联系。本研究以“三孩政策”在社交媒体中的传播为例,展开网络议程设置的本土化研究。所使用的分析流程,整合了数据分析和机器学习等技术手段,适应社交网络环境下的海量数据处理。分析结果表明:所设计的网络议程设置模型描述了网络议程设置的内在逻辑关系,可以更好地观察媒介议程对公众议程的影响,测量媒介议程与公众议程之间偏离程度,给出媒介劝服的定量传播效果。

青海班玛地区藏族代茶植物的民族植物学研究

运用民族植物学的传统研究方法,通过文献选点、关键人物访谈、参与式观察等方法,对班玛地区藏族代茶植物进行调查研究。结果表明,班玛地区藏族代茶植物共计16种,隶属于13科14属。该地区茶用功效和药用功效共有41种,具有降血压、降血脂、降血糖、清热解毒、抗菌消炎、活血化瘀的种类较多。综合分析结果表明,班玛地区藏族在选择茶用植物种类、茶用部位、采收季节、功效、饮用方法等方面具有多样性。此外,通过对班玛地区藏族代茶植物的研究,对进一步促进班玛地区藏族茶文化的研究与开发具有一定现实意义。同时,也为该地区代茶植物的保护和可持续发展提供依据。

Energy-Optimal and Delay-Bounded Computation Offloading in Mobile Edge Computing with Heterogeneous Clouds

By Mobile Edge Computing(MEC), computation-intensive tasks are offloaded from mobile devices to cloud servers, and thus the energy consumption of mobile devices can be notably reduced. In this paper, we study task offloading in multi-user MEC systems with heterogeneous clouds, including edge clouds and remote clouds. Tasks are forwarded from mobile devices to edge clouds via wireless channels, and they can be further forwarded to remote clouds via the Internet. Our objective is to minimize the total energy consumption of multiple mobile devices, subject to bounded-delay requirements of tasks. Based on dynamic programming, we propose an algorithm that minimizes the energy consumption, by jointly allocating bandwidth and computational resources to mobile devices. The algorithm is of pseudo-polynomial complexity. To further reduce the complexity, we propose an approximation algorithm with energy discretization, and its total energy consumption is proved to be within a bounded gap from the optimum. Simulation results show that, nearly 82.7% energy of mobile devices can be saved by task offloading compared with mobile device execution.

抗泥敏感性聚羧酸减水剂的研究进展

聚羧酸减水剂因具有低掺量、高减水及绿色环保等优点备受青睐,但在实际应用中也常伴有因混凝土骨料泥含量过高而导致的相容性差、减水率低及坍落度损失大等问题,抗泥敏感性差已成为制约聚羧酸减水剂向更广层面应用的重要现实问题之一。文中从聚羧酸减水剂发展现状与面临的泥敏感性入手,阐述了聚羧酸减水剂对水泥、黏土和水泥/黏土分散体系的作用机理,在此基础上总结概括了改善和提高聚羧酸减水剂抗泥敏感性的应对措施,并对抗泥敏感性聚羧酸减水剂未来发展与应用进行了预测和展望。

Separation control using synthetic vortex generator jets in axial compressor cascade

An experimental investigation conducted in a high-speed plane cascade wind tunnel demonstrates that unsteady flow control by using synthetic （zero mass flux） vortex generator jets can effectively improve the aerodynamic performances and reduce （or eliminate） flow separation in axial compressor cascade. The Mach number of the incoming flow is up to 0.7 and most tested cases are at Ma = 0.3. The incidence is 10° at which the boundary layer is separated from 70% of the chord length. The roles of excitation frequency, amplitude, location and pitch angle are investigated. Preliminary results show that the excitation amplitude plays a very important role, the optimal excitation location is just upstream of the separation point, and the optimal pitch angle is 35°. The maximum relative reduction of loss coefficient is 22.8%.

The Chinese Carbon-Neutral Goal:Challenges and Prospects

On 22 September 2020,within the backdrop of the COVID-19 global pandemic,China announced its climate goal for peak carbon emissions before 2030 and to reach carbon neutrality before 2060.This carbon-neutral goal is generally considered to cover all anthropogenic greenhouse gases.The planning effort is now in full swing in China,but the pathway to decarbonization is unclear.The needed transition towards non-fossil fuel energy and its impact on China and the world may be more profound than its reform and development over the past 40 years,but the challenges are enormous.Analysis of four representative scenarios shows significant differences in achieving the carbon-neutral goal,particularly the contribution of non-fossil fuel energy sources.The high target values for nuclear,wind,and bioenergy have approached their corresponding resource limitations,with solar energy being the exception,suggesting solar’s critical role.We also found that the near-term policies that allow for a gradual transition,followed by more drastic changes after 2030,can eventually reach the carbon-neutral goal and lead to less of a reduction in cumulative emissions,thus inconsistent with the IPCC 1.5°C scenario.The challenges and prospects are discussed in the historical context of China’s socio-economic reform,globalization,international collaboration,and development.

基于模糊C均值和SLIC的纳米孔阻断事件的识别与研究

纳米孔电流信号的分析依赖于对不同类型的阻断事件的准确分析。在阻断事件提取上,提出了一种基于灰度图检测阻断事件的新方法,对灰度图进行二值化后提取出阻断事件。针对基线电流对二值化阈值选取的影响,采用从小波分解后的近似系数中估计出基线电流的方法实现自适应的二值化阈值。为了减小阈值法对检测出的短阻断事件起始与终止位置的影响,采用模糊C均值(Fuzzy C-Means,FCM)方法对短阻断事件的位置进行修正。对检测出的多级事件,先将其转换为相应的具有颜色差异的灰度图,再利用简单的线性迭代聚类(Simple Linear Iterative Clustering,SLIC)超像素算法对多级事件的台阶自动检测。为避免SLIC算法的过分割带来属于同一台阶的超像素被分割的问题,对过度分割后的超像素进行超像素融合,实现属于同一台阶的超像素融合。仿真结果表明,基于灰度图的事件检测方法能够实现对信号中阻断事件的有效检测,FCM算法能够实现对短阻断事件位置的有效修正,SLIC超像素算法能够有效地检测出多级事件的台阶数。

Petroleum substitution, greenhouse gas emissions reduction and environmental benefits from the development of natural gas vehicles in China

This study develops a bottom-up model to quantitatively assess the comprehensive effects of replacing traditional petroleum-powered vehicles with natural gas vehicles（NGVs） in China based on an investigation of the direct energy consumption and critical air pollutant（CAP） emission intensity, life-cycle energy use and greenhouse gas（GHG） emission intensity of NGV fleets. The results indicate that, on average, there are no net energy savings from replacing a traditional fuel vehicle with an NGV. Interestingly, an NGV results in significant reductions in direct CAP and life-cycle GHG emissions compared to those of a traditional fuel vehicle, ranging from 61% to 76% and 12% to 29%, respectively. Due to the increasing use of natural gas as a vehicle fuel in China（i.e. approximately 28.2 billion cubic metres of natural gas in2015）, the total petroleum substituted with natural gas was approximately 23.8 million tonnes（Mt）, which generated a GHG emission reduction of 16.9 Mt of CO2 equivalent and a CAP emission reduction of 1.8 Mt in 2015. Given the significant contribution of NGVs, growing the NGV population in 2020 will further increase the petroleum substitution benefits and CAP and GHG emission reduction benefits by approximately 42.5 Mt of petroleum-based fuel, 3.1 Mt of CAPs and 28.0 Mt of GHGs. By 2030, these benefits will reach 81.5 Mt of traditional petroleum fuel, 5.6 Mt of CAPs and 50.5 Mt of GHGs, respectively.

新型塑料模板在水利工程中的应用

模板在钢筋混凝土施工中是必不可少的,在浇筑混凝土的过程中使用模板能够保证混凝土浇筑的质量。对于模板材料的选择,首先应该结合工程实践,确保从模板方案的选择到混凝土浇筑成型有良好的效果,然后需要考虑施工成本,达到经济适用的效果。塑料模板作为一种新型的模板,其节能环保性能良好,能够实现再利用,可以达到保护环境的目的,所以得到了广泛的使用。

ENERGY CONSERVATION AND HARVESTING FOR GREEN COMMUNICATIONS

Conventional communication technologies are targeted mainly at spectrum efficiency,but not energy efficiency and environmental friendliness.Recent efforts from both industry and academia have dedicated to reduce the energy consumption and carbon emissions of the information and communication technologies(ICTs).There are two ways to achieve this goal:one is to conserve energy through energy-aware operation optimiza-