An Analysis of Sonic Anemometer Observations In Low Wind Speed Conditions   总被引：2，自引：1，他引：1  

D.?AnfossiEmail author  D.?Oettl  G.?Degrazia  A.?Goulart 《Boundary-Layer Meteorology》2005,114(1):179-203

When the wind speed decreases below a certain value (1–2 m s^-1) meandering (low frequency horizontal wind oscillations) starts to prevail. In these conditions it becomes difficult to define a precise mean wind direction and to estimate the airborne dispersion. To study the wind and turbulence characteristics during meandering, two sonic anemometer datasets, containing hourly wind observations, were analysed: the first one, lasting 1 year, was recorded in complex terrain (Graz, Austria) and the second one, lasting about 1month, was recorded in a rather flat area (Tisby, Sweden). It was found that meandering seems to exist under all meteorological conditions regardless of the stability or wind speed and it was confirmed that meandering sets a lower limit for the horizontal wind component variances. Further, it was found that the autocorrelation functions of the horizontal wind components, computed for the low wind cases, show an oscillating behaviour with the presence of large negative lobes. Two different relationships from the literature, and relevant to these oscillatory aspects, were fitted to the data. They contain two parameters: one associated and relevant to the classical integral time scale and the second with meandering occurrence. Based on these relationships, expressions for the mean square displacement of particles _y²(t) were also derived.  相似文献   

大气边界层物理研究进展   总被引：10，自引：5，他引：5  

刘辉志  冯健武  王雷  洪钟祥 《大气科学》2013,37(2):467-476

本文总结了近4年来(2009～2012)中国科学院大气物理研究所大气边界层物理和大气化学国家重点实验室在大气边界层物理理论、观测实验、数值模拟和超声风速温度仪等仪器研制领域的主要研究进展,并对未来几年内大气边界层物理的发展方向提出了一些建议.  相似文献   

利用声发射和波速变化判定岩石损伤状态     

梁天成  葛洪魁  郭志伟  宋丽莉  张金伟 《中国地震》2012,28(2):154-166

对岩石受单轴压缩损伤过程中的声发射和超声波波速进行了同步测量,对比分析了声发射和波速随损伤过程的变化规律。研究表明,岩石损伤过程可分成几个阶段,不同阶段声发射和声波波速变化呈现不同特征;利用超声波波速的相对变化能够稳定可靠地鉴别岩石的"加载强化"与"加载弱化";声发射b值对裂隙的非稳定扩展更加敏感,可以作为岩石失稳预警参数;岩石声发射和波速都对损伤具有记忆性,重复加载下的声发射和超声波波速变化可提供更丰富的岩石损伤状态信息。  相似文献   

Rapid Determination of Polar Herbicides in Soil Samples Using Accelerated Ultrasonic Extraction (AUE) in Combination with Dispersion and In-situ Derivatization     

Jian-ye GUI  Chen-ling ZHANG  Yong-tao ZHANG  Li ZHANG 《地下水科学与工程》2014,2(1):56-62

An effective novel ultrasonic extraction procedure coupled with gas chromatography and negative chemical ionization mass spectroscopy has been developed for quantitative recovery of polar herbicides in soil. This rapid one-step sample preparation methodology was named accelerated ultrasonic extraction (AUE), and is based on elevated temperatures, increased power and dispersing intimate contact. Simultaneously, in-situ derivatization was achieved by the addition of derivatization reagent, chelating agent and dispersing agent. The extraction efficiency was enhanced by the multiple applied force and elevated ultrasonic temperature. The in-situ derivatization efficiency was enhanced considerably by the use of ultrasonic energy. Dozens of samples can be extracted simultaneously with this method. The sensitivity was improved because of the remarkable reduced background noise achieved using GC-MS in negative chemical ionization (NCI) mode. The amount of reagent and various ultrasonic parameters, such as ultrasonic energy, ultrasonic time and ultrasonic temperature, were optimized. The reproducibility of replicate soil extraction determination of 9 herbicides in different matrix samples and at different concentrations (n=7) was in the range of 4.9-12.6% of the relative standard deviation. The obtained LOD values ranged between 0.02-0.37 g/kg for all herbicides. Here, we present an improved ultrasonic extraction procedure, which we have termed AUE, can serve as a rigorous high efficiency preparation methodology for polar organic contaminants and can be applied to solid sample pre-treatment extensively  相似文献   

南日岛海域海上自立型测风塔设计施工技术探讨     

李近元  张吉  王淼  盛迎新  祝亮  董礼涛 《海洋科学》2013,37(2):95-100

为获得南日岛海域的风能资源数据,在该海域设计建造了一座自立型测风塔。在测风塔的基础设计、施工过程中,分析计算了海上特殊施工环境中的基础受力、设计参数及荷载组合,因地制宜地采用多种基础施工工艺、防腐处理等技术;在塔体安装时采用了整体吊装技术,并设计了引导装置保证了塔体准确就位。该工程可为海上风电场开发及类似海上工程提供参考。  相似文献   

Ultrasonic wave extraction and simultaneous analysis of polycyclic aromatic hydrocarbons (PAHs) and phthalic esters in soil          下载免费PDF全文

ZHANG Yong-tao  ZHAO Guo-xing  LIU Jing-shang  ZHANG Li  LI Xiao-ya  GUI Jian-ye  ZHANG Chen-ling 《地下水科学与工程》2017,5(3):249-253

A method is developed for detection of polycyclic aromatic hydrocarbons(PAHs) and Phthalic Acid Esters(PAEs) in soil samples. Ultrasonic Wave Extraction under airtight circumstances is adopted to extract the analytes in soil samples with n-hexane–acetone(V:V=1:1) as extraction solvent. This method has several advantages, including high extraction efficiency, short time, convenience and simplicity. It can be used to detect polycyclic aromatic hydrocarbons(PAHs) and Phthalic Acid Esters(PAEs) in soil.  相似文献   

超声地震物理模型连续数据采集系统   总被引：5，自引：4，他引：1  

赵群  马国庆  宗遐龄 《地球物理学进展》2004,19(4):786-788

介绍了超声地震物理模型实验数据连续采集系统．该系统将传统使用的间断采集方式改变为连续采集方法．实际应用表明．此系统具有可靠性高、实时性能好以及智能化程度高的特点．使用Windows98／2000连续采集应用程序模拟三维地震勘探实验只需要一个星期左右完成,将实验时间缩短了二十多天。  相似文献   

Elasticity of CaSnO3 perovskite     

J. Kung  R. J. Angel  N. L. Ross 《Physics and Chemistry of Minerals》2001,28(1):35-43

The elastic properties of CaSnO₃ perovskite have been measured by both ultrasonic interferometry and single-crystal X-ray diffraction at high pressures. The single-crystal diffraction data collected using a diamond-anvil cell show that CaSnO₃ perovskite does not undergo any phase transitions at pressures below 8.5?GPa at room temperature. Ultrasonic measurements in the multianvil press to a maximum pressure of ～8?GPa at room temperature yielded S- and P-wave velocity data as a function of pressure. For a third-order Birch-Murnaghan EoS the adiabatic elastic moduli and their pressure derivatives determined from these velocity data are K _S0=167.2±3.1?GPa, K ^′ _S0=4.89±0.17, G ₀=89.3±1.0?GPa, G ^′ ₀=0.90±0.02. The quoted uncertainties include contributions from uncertainties in both the room pressure length and density of the specimen, as well as uncertainties in the pressure calibration of the multianvil press. Because the sample is a polycrystalline specimen, this value of K _S0 represents an upper limit to the Reuss bound (conditions of uniform stress) on the elastic modulus of CaSnO₃ perovskite. If the value of αγT is assumed to be 0.01, the value of K _S0 corresponds to K _T0=165.5±3.1?GPa. The 10 P-V data obtained by single-crystal diffraction were fit with a third-order Birch–Murnaghan equation-of-state to obtain the parameters V ₀=246.059±0.013 ų, K _T0=162.6±1.0?GPa, K ^′ _T0=5.6±0.3. Because single-crystal measurements under hydrostatic conditions are made under conditions of uniform stress, they yield bulk moduli equivalent to the Reuss bound on a polycrystalline specimen. The results from the X-ray and ultrasonic experiments are therefore consistent. The bulk modulus of CaSnO₃ perovskite lies above the linear trend of K ₀ with inverse molar volume, previously determined for Ca perovskites. This prevents an estimation of the bulk modulus of CaSiO₃ perovskite by extrapolation. However, our value of G ₀ for CaSnO₃ perovskite combined with values for CaTiO₃ and CaGeO₃ forms a linear trend of G ₀ with octahedral tilt angle. This allows a lower bound of 150?GPa to be placed on the shear modulus of CaSiO₃ by extrapolation.  相似文献   

小型垂直过冷云风洞的超声波振子造雾系统     

张彤  龚乃虎 《高原气象》1996,15(4):503-507

在小型垂直过冷云风洞中引进和改装了亚都工业用超声波加湿器，使其成为风洞实验的造雾系统，在实验中测量了其雾滴谱，模拟了冰雪晶生长过程，结果表明，此造雾系统符合实验要求。  相似文献   

New Equations For Sonic Temperature Variance And Buoyancy Heat Flux With An Omnidirectional Sonic Anemometer   总被引：2，自引：0，他引：2  

Heping Liu  Gerhard Peters  Thomas Foken 《Boundary-Layer Meteorology》2001,100(3):459-468

Many new types of sonic anemometer obtain sonic temperature from an average value of temperature measured along three paths, unlike previous sonic anemometers that generally used one path. New equations are derived to calculate temperature variance from sonic temperature variance and sensible heat flux from buoyancy flux considering the influence of a crosswind. These equations can be applied to CSAT3, Solent R2, R3, R3A, HS, and USA-1 sonic anemometers with the corresponding correction factors given in this paper. The equations are verified by data measured by a CSAT3 sonic anemometer in the LITFASS-1998 field study.  相似文献