基于经验模态分解的曲波阈值去噪方法

针对曲波阈值去噪方法阈值选取单一造成的有效信号损失或随机噪声压制不完全的问题,笔者提出了一种基于经验模态分解的曲波阈值去噪方法。该方法首先对带噪信号进行经验模态分解得到一系列固有模态函数,根据每个固有模态函数所含噪声强弱的不同,选取不同的阈值分别对分解得到的含噪固有模态函数进行曲波阈值降噪处理;最后将去噪后的固有模态函数与不含噪声的固有模态函数进行信号重构得到最终压噪的结果。由于引入经验模态分解,对分解得到的不同含噪程度的固有模态函数,选取不同的阈值进行处理,这样能够有效减小直接曲波阈值方法阈值选取单一产生的问题。模型和实际数据试算表明,该方法在提高数据信噪比的同时,能够有效地保留有效信号,是一种相对保幅的去噪方法。     

荒漠植物生活史对策研究进展与展望

植物种群生活史是指植物种群从种子萌发到种子形成所经历的全部过程,它包括植物种群生活周期各个阶段(繁殖、种子、补充与生长)的生活史特征以及与同一生境内其他生物之间和环境的相互作用。而生活史对策是生物在长期的自然选择下形成的、以各种生活史特征表现出来的适应对策,即由自然选择塑造的生物体外形和习性。本文综述了国内外植物生活史对策的研究历史、进展和生活史对策的研究内容以及生活史对策理论在荒漠植物研究中的应用。指出生活史研究仍存在不足首先是研究内容上,资源分配在多年生植物中的权衡仍未被有力证明,邻体效应与繁殖分配的关系在个体水平上仍不明了,多年生植物在不同邻体效应和生境下将采取何种繁殖对策目前尚无明确的结论;繁殖分配与性分配之间的关系,引起花序结构上资源分配差异的原因,各种繁殖对策中繁殖分配异同与维持机制等问题仍有待于进一步的研究;种子大小的变异机制以及生物学意义仍未得到令人满意的答复,更需分子水平上的研究来解释其机理。在群落水平上种子大小与萌发能力的关系不明确,萌发过程的时间扩散方式报道甚少。因此,这些方面的研究工作急待加强。     

Validation of NCEP and OAFlux air-sea heat fluxes using observations from a Black Pearl wave glider

Latent and sensible heat fluxes based on observations from a Black Pearl wave glider were estimated along the main stream of the Kuroshio Current from the East China Sea to the east coast of Japan, from December 2018 to January 2019. It is found that the data obtained by the wave glider were comparable to the sea surface temperature data from the Operational Sea Surface Temperature and Sea Ice Analysis and the wind field data from WindSat. The Coupled Ocean Atmosphere Response Experiment 3.0 (COARE 3.0) algorithm was used to calculate the change in air-sea turbulent heat flux along the Kuroshio. The averaged latent heat flux (LHF) and sensible heat flux (SHF) were 235 W/m2 and 134 W/m2, respectively, and the values in the Kuroshio were significant larger than those in the East China Sea. The LHF and SHF obtained from Objectively Analyzed Air-Sea Fluxes for the Global Oceans (OAFlux) were closer to those measured by the wave glider than those obtained from National Centers for Environmental Prediction (NCEP) reanalysis products. The maximum deviation occurred in the East China Sea and the recirculation zone of the Kuroshio (deviation of SHF >200 W/m2; deviation of LHF >400 W/m2). This indicates that the NCEP and OAFlux products have large biases in areas with complex circulation. The wave glider has great potential to observe air-sea heat fluxes with a complex circulation structure.     

山西南部上古生界煤层含气性研究Ⅲ.煤层气采收潜势分析

采用直接解吸法、等温吸附法和吸附-解吸法,对研究区上古生界主煤层中煤层气的采收潜势进行分析,得出了一些有意义的结论:在0.7MPa废弃压力水平,推定区中绝大部分矿区的主煤层将可能没有煤层气产出;推断-预测区主煤层的采收潜势以临汾盆地最好,沁源东-安泽和沁水-翼城地区上主煤层也相对较高,而下主煤层普遍较差或极差。     

Spectral dependence on the correction factor of erythemal UV for cloud,aerosol, total ozone,and surface properties: A modeling study

Radiative transfer model simulations were used to investigate the erythemal ultraviolet(EUV) correction factors by separating the UV-A and UV-B spectral ranges. The correction factor was defined as the ratio of EUV caused by changing the amounts and characteristics of the extinction and scattering materials. The EUV correction factors(CFEUV) for UV-A[CFEUV(A)] and UV-B [CFEUV(B)] were affected by changes in the total ozone, optical depths of aerosol and cloud, and the solar zenith angle. The differences between CFEUV(A) and CFEUV(B) were also estimated as a function of solar zenith angle, the optical depths of aerosol and cloud, and total ozone. The differences between CFEUV(A) and CFEUV(B) ranged from-5.0% to 25.0% for aerosols, and from-9.5% to 2.0% for clouds in all simulations for different solar zenith angles and optical depths of aerosol and cloud. The rate of decline of CFEUV per unit optical depth between UV-A and UV-B differed by up to 20% for the same aerosol and cloud conditions. For total ozone, the variation in CFEUV(A) was negligible compared with that in CFEUV(B) because of the effective spectral range of the ozone absorption band. In addition, the sensitivity of the CFEUVs due to changes in surface conditions(i.e., surface albedo and surface altitude) was also estimated by using the model in this study. For changes in surface albedo, the sensitivity of the CFEUVs was 2.9%–4.1% per 0.1 albedo change,depending on the amount of aerosols or clouds. For changes in surface altitude, the sensitivity of CFEUV(B) was twice that of CFEUV(A), because the Rayleigh optical depth increased significantly at shorter wavelengths.     

Importance of Air-Sea Coupling in Simulating Tropical Cyclone Intensity at Landfall

An atmosphere-only model system for making seasonal prediction and projecting future intensities of landfalling tropical cyclones (TCs) along the South China coast is upgraded by including ocean and wave models. A total of 642 TCs have been re-simulated using the new system to produce a climatology of TC intensity in the South China Sea. Detailed comparisons of the simulations from the atmosphere-only and the fully coupled systems reveal that the inclusion of the additional ocean and wave models enable differential sea surface temperature responses to various TC characteristics such as translational speed and size. In particular, interaction with the ocean does not necessarily imply a weakening of the TC, with the coastal bathymetry possibly playing a role in causing a near-shore intensification of the TC. These results suggest that to simulate the evolution of TC structure more accurately, it is essential to use an air-sea coupled model instead of an atmosphere-only model.     

粉土与粉质黏土互层中静压桩桩土界面孔隙水压力

为研究层状黏性土在静压桩沉桩过程中桩土界面孔隙水压力的分布规律,依托山东东营某桩基工程开展了现场足尺静压桩试验,分析了桩土界面孔隙水压力的变化规律,探讨了桩土界面超孔隙水压力的分布特征,明确了桩土界面孔隙水压力和超孔隙水压力的消散特性,并结合水力压裂理论和孔穴扩张理论,揭示了沉桩过程中桩土界面沿桩长方向超孔隙水压力的分布形式。试验结果表明：孔隙水压力、超孔隙水压力与土层性质密切相关,二者均在粉土层中增长较慢,在粉质黏土层中增长较快;在同一深度处,两者均存在明显的消散现象,在粉土中的消散程度明显大于粉质黏土中;采用水力压裂理论结合孔穴扩张理论计算的超孔隙水压力沿桩长方向的变化规律与试验值相吻合;桩身贯入深度越大,超孔隙水压力理论计算值与现场实测值越接近。     

香港青马大桥在交通荷载作用下的疲劳评估

在全桥三维有限元模型基础上 ,进行了车载响应分析 ,得到全桥的动力响应 ,并与实测结果进行了分析对比 ;对疲劳危险部位建立局部有限元模型 ,并进行了局部应力分析。在结构健康安全监测系统实测数据基础上 ,得到应变循环标准块 ,用基于热点应力疲劳评估方法对危险部位进行了疲劳寿命评估。     

二维地形的地形阻力

讨论了在上部稳定层覆盖的不稳定大气边界层中,二维地形扰动所引起的上层波动以及扰动速度的动量通量输送,表明在大气低层层结不稳定时,波动仍可能在大气动量平衡中起明显作用。     

Estimation of submarine groundwater discharge in the Il‐Gwang watershed using water budget analysis and 222Rn mass balance

Submarine groundwater discharges (SGD) were investigated in a marine watershed in south‐eastern Korea using water budget analysis and a ²²²Rn mass balance model. Multi‐layered TOPMODEL added hydrological assumption was used to estimate groundwater components in the water budget analysis. Field observations of soil moisture, rainfall, runoff and groundwater fluctuations were used for calibration and validation of the hydrologic model. Based on observed hydrological data and terrain analyses, parameters for the hydrologic model were delineated and used to describe several hydrologic responses in the watershed. SGD estimations by ²²²Rn mass balance method were also performed at Il‐Gwang bay in July, 2010, and May, June, July and Nov. 2011. The estimated groundwater through hydrologic modeling and water balance analysis was 1.3x10⁶ m³/year, which rapidly increased during typhoon season due to heavy rainfall and permeable geologic structure. The estimated groundwater was approximately 3.7–27.1% of SGD as evaluated by ²²²Rn mass balance method ranges 3.44 and 17.45 m³m^?2year^?1. Even though SGD is predominantly influenced by tide fluctuation, the head gradient (difference) from hydrologic processes associated with heavy rainfalls can also have extra significant influences. Comprehensive understanding of SGD evaluation can be improved through a simultaneous application of both these approaches. Copyright © 2013 John Wiley & Sons, Ltd.