北京地区草地蒸散影响因素分析方法的比较

草地蒸散直接影响近地层大气和下垫面间的能量和水分交换,从而影响大气边界层结构和气候。因此利用涡度相关技术测量北京市郊草地蒸散及气象因素数值,并利用相关分析、灰关联、BP神经网络方法定量地分析气象因素对蒸散的影响。分析结果表明,正确率由高到低依次为BP神经网络法、相关分析法、灰关联法;各因素对其影响权重由大至小排序为:太阳辐射、气温、大气相对湿度、水平风速、垂直风速;在植被生长季节,蒸散速率随有效光辐射、气温、水平风速、垂直风速的增加,大气相对湿度的下降而升高。     

利用气象要素估算海洋大气近地层光学湍流

基于近地层相似理论以及极端层结下对该理论的修正,建立了海洋大气近地层光学湍流估算模型,并进行了数值分析。结果表明:当气温与海温相差较大时,温度起伏对光学湍流贡献最大;当气温与海温相差较小时,海面湿度越小,光学湍流越强;在较低湿度条件下,尤其在红外窗区,湿度扰动对光学湍流贡献起支配作用。当气温小于海温时,光学湍流先随海面风速增大而增强,后随风速增大而减弱;当气温大于海温时,光学湍流总体上是伴随海面风速增大而减弱。当气温小于海温或与海温接近时,与可见光和近红外波段相比,红外窗区光学湍流显著偏强;当气温远大于海温时,两波段光学湍流接近。在中性和近中性层结下,大气折射率结构参量C2n依赖于垂直高度的负幂指数接近-2/3,伴随海面大气层结稳定度或不稳定度增强,C2n依赖于垂直高度的负幂指数的绝对值分别逐渐减小或增大,并分别趋近于稳定极限下的0或不稳定极限下的-4/3。     

环境因素对海-气界面低频异常声透射的影响研究

针对海中声源在海-气界面低频异常声透射问题, 根据两层媒质声传输模型, 分析了大气声速和密度与气压、气温、湿度及海水中声速和密度与海温、盐度间的关系, 研究了低频声透射和传输受温度、气压、盐度、湿度等因素的影响, 分析了各因素对声透射和传输的影响程度. 结果表明: 1) 声透射到大气中的声功率与气温、湿度负相关, 与海温、盐度、气压正相关; 2) 单极子与水平偶极子声源辐射到海中的声功率与海温、盐度负相关, 而垂直偶极子声源辐射到海中的声功率与海温、盐度正相关; 3) 声透射指向性与海温正相关, 与气温负相关; 4) 低频声透射受温度影响最大, 其次是盐度, 受气压和湿度影响较小, 垂直偶极子声源的声透射受温度影响大于水平偶极子和单极子声源.     

基于MST雷达垂直风速的大气温度剖面反演

本文主要利用MST(mesosphere-stratosphere-troposphere)雷达垂直风速时间序列进行频谱分析,计算B-V(Brunt-V?is?l?)频率,再根据B-V频率和温度的关系,本文建立了离散的温度反演模型,最后反演得到了全高度的温度剖面.通过计算温度剖面和探空仪实测温度剖面比较可见,二者的符合度非常高,变化趋势也完全一致.本文还进一步讨论了,利用B-V频率和MST雷达的水平风速还可以计算理查德森数,通过理查德森数可以很清晰的判断大气的稳定性,进而可以量化大气很多动力学特征以及解释大气中的很多波动现象.因此,B-V频率的获得是MST雷达对大气动力学研究的又一贡献,它可以准确地反演大气的温度剖面,同时获取大气动力学稳定性参数.     

环境因子对人工林显热通量的影响分析

风速、空气温度、空气湿度、土壤含水量是影响地表显热的主要因素。利用观测数据应用以BP神经网络为主并结合相关系数的分析方法研究显热通量的动态特征,将显热通量与风速、空气温度、空气湿度、土壤含水量做了相关性分析。结果表明空气温度和空气湿度与显热通量相关程度显著,它们的相关系数绝对值都在0.5以上,BP网络权值的点积明显高于其它两个影响因子;风速和土壤含水量与显然通量相关程度普通,它们的相关系数仅略高于0.3。此外,风速、空气温度与显热通量呈正相关关系而空气湿度、土壤含水量与显热通量呈负相关关系。通过对这些影响因子进行分析将有助于提高测定显热通量的精度,利用BP神经网络预测显热通量值可以为气象、生态环境等方面的研究提供可靠的决策数据。     

雷声在大气中传播的吸收衰减特性研究

选取青海大通地区一次地闪过程的雷声信号,利用信号处理理论,得到了观测点雷声的频谱;依据声波在大气中传播的理论,计算了大气对雷声传播的吸声系数,分析了吸声系数随环境因素的变化,结果表明:闪电发生距离、大气湿度和温度是影响雷声传播的主要因素.在一定闪电距离和大气环境下,吸声系数随频率的增加而增大;频率小于100 Hz的雷声衰减很慢,空气相对湿度和温度对其吸声系数的影响也比较小,在一定距离内的衰减可以忽略;频率大于500 Hz的高频信号吸声系数较大,并且随相对湿度的增加而快速递增;吸声系数随温度呈非单调变化,频 关键词： 雷声传播 大气吸收 衰减     

半干旱草原下垫面动量和感热总体输送系数参数化关系研究

本文利用锡林郭勒草原2008年春季近地层涡旋相关系统和铁塔的风、 温平均梯度观测资料, 分析了总体输送系数随梯度Richardson数的变化特征, 建立了动量总体输送系数随大气稳定度、近地层风速以及感热总体输送系数随大气稳定度和近地层气温的关系. 中性条件下, 半干旱草原植被下垫面动量总体输送系数与近地层大气动力状态之间存在明显的相互作用, 总体输送系数与近地面层风速之间满足二次曲线拟合关系; 风速较小时, 大气动力特征对地表粗糙度长度的改变不是很明显, 动量总体输送系数随气流增强而增大; 而当风速较大时, 强风速会使植被高度发生改变, 动量总体输送系数随气流增强而减小. 另外, 感热总体输送系数与近地层气温之间也存在二次曲线关系. 动量总体输送系数与近地层风速之间的关系、感热总体输送系数与近地层气温之间关系的建立为总体输送系数参数化提供了重要途径, 同时该方案避免了对动力学粗糙度长度和热力学粗糙度长度的求解. 关键词： 总体输送系数 参数化 湍流通量 相似性函数     

基于光纤锥级联结构的湿度传感器

提出了一种基于普通单模光纤粗锥级联结构的马赫-曾德尔干涉湿度传感器.将两根单模光纤对芯熔融成一个粗锥,并依次级联,形成光纤锥-单模光纤-光纤锥-单模光纤-光纤锥结构.外界环境湿度、温度的改变使传感器的纤芯基模和包层模的光程差发生改变,引起传感器干涉光谱发生变化.通过监测干涉谱波长和能量的变化实现对外界物理量的测量.实验结果表明,当空气中湿度在35~95%RH范围内变化时,传感器的湿度灵敏度为-0.065dB/%RH,线性度为0.997;当温度在30~80℃范围内变化时传感器的温度灵敏度为69.4pm/℃,线性度为0.998.该传感器可以避免温湿度的交叉影响,实现单参量的同时在线区分测量.     

激光外差光谱仪模拟风场探测

中高层大气风场是表征中高层大气环境的重要参量,对中高层大气风场的探测在民用和军用领域有着重要意义.激光外差光谱技术是近年来迅速发展的一种高光谱分辨率和灵敏度的被动式遥感探测技术,以激光外差光谱技术为核心研制的激光外差光谱仪因具有体积小、重量轻、结构稳定等特点,在星载测量中高层风场领域有巨大的潜力和应用前景.激光外差光谱仪的地面风场探测性能验证是其应用到卫星上的关键环节,本文利用实验室环境下建立的风场模拟装置实现0—25 m/s的风速变化,并基于光谱分辨率为0.003 cm^-1激光外差光谱仪分别测量了无风速变化和不同风速下的CH₄吸收谱,测量风速的分辨率为3 m/s.使用光纤F-P干涉仪、波长计和参考池对激光器输出光频率进行实时的相对定标和绝对定标.通过计算吸收光谱中心频率的偏移量,反演得到风场风速,并与风场模拟器风速对比,相对误差为1.49 m/s.该实验对激光外差光谱仪测风性能进行有效验证,证明了使用激光外差光谱仪进行中高层大气风场测量的可能性.     

超声速叶栅实验中空气湿度的影响及临界湿度

一、超声速叶栅风洞试验在空气湿度较大时出现的一些现象和对它的分析 超声速风洞对空气湿度有较严格的限制,以避免在超声速膨胀后,出现凝结现象,破坏均匀流场并使M数显著降低,有时还在试验模型上结冰而改变其几何尺寸. 本文介绍在暂冲下吹式超声速叶栅风洞中进行的实验.空气经过干燥.风洞进口处管内气温比大气温度略高,但通常相差不超过10℃,试验的M数通常为1.3至1.5.试验前对国产SYD-1型数字编码压力传感器进行过校准,测量精度为±0.3％. 经多次吹风试验后,干燥塔内硅胶吸收水份的效能降低,试验时在喷管出口侧壁静压     

家用空调冷凝水节能利用探讨

家用空调的冷凝水量可观,且含有一定冷量,但现实中常被直接排放掉,污染环境、浪费资源.实例计算了冷凝水生成量,蒸发量和冷凝水冷却冷凝器换热的强化作用以及节能效果,并设计了一种新型冷凝水回收装置.最后,指出冷凝水利用冷量冷却冷凝器,节能效果显著.     

Modeling of impulse electric discharge propagation in a condensed dielectric

In the present paper, special features of electric discharge propagation in a condensed dielectric are considered. A mathematical model of growth of the discharge structure and operation of a high-voltage generator is described based on the stochastic-deterministic approach. Numerical realization of the model is used to describe quantitatively the space-time and current discharge characteristics. Results of computer modeling of the discharge propagation in a condensed dielectric are presented for the tip-plane electrode geometry. Current and field discharge characteristics are analyzed. The voltage-current characteristic of technical water breakdown is obtained. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 11–17, March, 2006.     

Charge Separation at the Evaporation (Condensation) Front of Water and Ice. Charging of Spherical Droplets

Charge separation at evaporation (condensation) front of water and ice is analyzed. Relatively low distribution coefficient of protons and hydroxide ions between vapor and condensed phase that is less than the distribution coefficient of water molecules leads to accumulation of protons and hydroxide ions at the phase front upon evaporation and a decrease in the amount of such species upon condensation. Interphase charge separation is caused by the subsequent diffusion of nonequilibrium protons and hydroxide ions. The charge separation is also affected by the double electric layer generated by orientation defects at the water and ice surfaces. Dependences of electric field at a plane surface of water and ice on the rate of phase transformation are calculated. Electric charges of spherical water droplets are estimated at different field strengths and droplet radii.     

Exact and quasiresonances in discrete water wave turbulence

The structure of discrete resonances in water wave turbulence is studied. It is shown that the number of exact 4-wave resonances is huge (hundreds of millions) even in a comparatively small spectral domain when both scale and angle energy transport is taken into account. It is also shown that angle transport can contribute inexplicitly to scale transport. Restrictions for quasiresonance to start are written out. The general approach can be applied directly to mesoscopic systems encountered in condensed matter (quantum dots), medical physics, etc.     

空调冷凝水净化直饮水装置的研制

分析了空调冷凝水产生、特点,对空调冷凝水水量进行了计算,详细介绍了空调冷凝水净化处理的工艺过程,研制出了空调冷凝水净化直饮水装置。经初步化验,该装置处理的空调冷凝水符合国家纯净水标准。     

Instabilities and Self-Organization Phenomena in High Density Exciton Systems

The influence of final value of exciton lifetime on exciton condensed phase formation is investigated in deterministic and stochastic approach. It is shown that in some region of pumping, the periodical distribution of exciton density takes place. The numerical solution for periodical distribution of exciton density is obtained for different values of pumping. There are critical values of exciton lifetime for appearance of exciton condensed phase. The distribution density function becomes narrower with increasing pumping.     

Conversion of brown coal in sub- and supercritical water at cyclic pressurization and depressurization

The conversion of brown coal in sub- and supercritical water at 310–460°C and pressures up to 30 MPa in the cyclic pressurization and depressurization modes is studied. The temperature dependences of coal organic matter (COM) conversion and the yield of volatile and condensed products are obtained. The temperature dependence of the yield of condensed substances has a maximum at 370°C. The fraction of high-molecular substances in condensed products is increased with increasing temperature. The cumulative conversion of COM into volatile and condensed products upon heating to 460°C was 31.4 and 8.6%, respectively. According to the data of mass spectrometry analysis of volatile products and the elemental analysis of the initial coal, carbonaceous residue after the conversion, and condensed products, 82.3% of oxygen and 74.7% of sulfur, are removed from COM. CO₂ and H₂S are the main products of the conversion of oxygen- and sulfur-containing groups.     

Stable isotope composition of daily and monthly precipitation in Zagreb

Stable isotopic compositions (delta2H and delta18O) of daily precipitation collected in the period from October 2002 to March 2003 and monthly precipitation in the period from 2001 to 2003, as well as the corresponding meteorological data (temperature, amount of precipitation), all collected in Zagreb, Croatia, are presented. delta2H and delta18O values, both daily and monthly, show large variations due to large temperature variations and the different origin of the air masses. Variations are larger for daily samples than for composite monthly samples. Good correlation of delta18O with temperature is obtained for both types of samples. On the basis of the correlation between delta2H and delta18O, the local meteoric water line is close to the global meteoric water line. Deuterium excess of both daily and monthly precipitation indicates that in the Zagreb area, the influence of air masses from the Mediterranean area prevails in the autumn period.     

Weak localization: The quasiclassical theory of electrons in a random potential

The recent subject of weak localization is an important area of research in condensed matter physics which has received a considerable amount of experimental and theoretical attention. In its existing form, the theory is founded entirely on the impurity technique of Green's function. In this paper, we present a theory of weak localization which is put rigorously on a quasiclassical basis thus providing a more intuitive understanding. For example, it becomes apparent that much of the underlying physics is a result of quantum mechanical interference effects in a very elementary sense. It is one of those unique cases where the superposition principle of quantum mechanics leads to observable consequences in the properties of macroscopic systems. In addition, all the important quantitative results obtained so far are recovered in the present quasiclassical approach.     

不同地区大气光学湍流内外尺度测量

 用光学湍流参数自动测量系统对内陆地区和沿海地区光学湍流内外尺度进行了大量的实验观测。分析了湍流尺度的日变化规律,给出了其频数分布。结果表明：两地内尺度的均值为十几mm,外尺度的均值约为2 m;内陆地区内尺度日变化趋势较为复杂,而外尺度的日变化趋势与湍流强度十分相似;沿海地区内外尺度与湍流强度均无明显关系。大气湍流尺度的大小和分布状态是随时间和空间变化的,因此,在估算实际大气湍流对光学系统的影响时,需要实测湍流尺度以便得到准确的结果。