元素分析仪-同位素比值质谱测量碳氮同位素比值最佳反应温度和进样量的确定

沉积有机质的碳氮稳定同位素值是进行古气候、古环境及生态系统研究不可或缺的主要研究手段,目前碳氮同位素主要利用元素分析仪-同位素比值质谱(EA-IRMS)系统来测定。EA-IRMS测定过程中的反应温度及样品进样量直接影响反应物在测试中的燃烧程度,从而影响测试数据的精度。本文利用EA-IRMS技术,以标准样品为参考,在不同转化温度下测试碳氮同位素值,研究保证测试精度的最佳反应温度条件;同时,通过分析不同含氮量样品的检测限,明确了样品含氮量与最低检测限之间的关系,确定了精确测定氮同位素值的最低进样量。结果表明:反应温度对测试精度有显著影响,在碳同位素测定时,将反应温度设定为900℃或以上时测试精度均能达到±0.2‰;氮同位素测定时,反应温度须设定为950℃时测试精度才能达到±0.3‰。实验得出样品含氮量与检测限之间的线性相关性为R2=0.873,开展氮同位素测定时可根据此关系来判断和控制进样量。     

海量录井层序“砂地比”的自动计算

       在陆相层序地层研究中,多条录井地层“砂地比”的对比分析是判断物源方向、揭示沉积环境、辅助层序地层划分 及岩相古地理研究中的一项重要指标,为地学研究中最基本的方法。本文使用Access 数据库技术以层序为单位实现了海量 录井地层“砂地比”的快速计算,与传统的方法相比,提高了工作效率,增强了数据的准确性和可靠性。实践证明,该方 法是一种切实可行的科学计算方法,可以在地学研究中推广使用。     

风廓线雷达估算大气返回信号功率方法研究

基于风廓线雷达大气返回信号功率谱中噪声电平的估算方法,统计分析了北京延庆对流层风廓线雷达（CFL-08）2006年10～12月的探测数据。对该频段风廓线雷达环境噪声的空间和时间变化进行了分析,观测期间环境噪声在5km以下随高度递减,10月的平均环境噪声大于11月、12月的平均分布。给出目前风廓线雷达用信噪比估算大气返回信号功率的两种方法,并对两种方法进行了环境噪声的剔除,经过修正后的大气返回信号功率输出结果趋于一致。     

A Physically-Based Turbulent Velocity Time Series Decomposition

Single-point, three-component turbulent velocity time series data obtained in the atmospheric boundary layer over the ocean reveal coherent structures that are consistent with a model of a steady linearly varying spatial velocity field that translates past the measurement point at constant velocity. The kinematic model includes both strain and rotation rates and has implications regarding vortex generation, vortex pairing, vortex break-up, and stability. While the complete specification of the dimensions, spatial velocity gradients, and translational velocity of the linear coherent structure (LCS) cannot be made from the single-point, three-component measurements, the model LCS velocity time series can be determined from least- squares fits to the data. The total turbulent kinetic energy is used to find in the record the initial and final times of a model LCS in the data, i.e., the time interval over which a model LCS is passing over the anemometer. Maxima in the kinetic energy removed from the data (by subtraction of the model LCS velocity functions from the data) are used to identify the most-energetic model LCSs. These model LCS velocity functions replicate the essential large-scale features of the time series of the three-component velocity fluctuations, most noticeably in the streamwise component. The model LCS decomposition was used to perform a scale analysis of the data, which was compared to the usual Fourier method. Time intervals of model LCSs were found successively in the data, after subtracting the previous fits. This process resulted in a series of 'levels with a number of LCSs found at each level. About six levels account for most of the kinetic energy. The model also allows the computation of the Reynolds stress components, for which six levels also are sufficient. The recomposition of the time series on a LCS-by-LCS basis compares well with the mode-by-mode Fourier recomposition for the average momentum fluxes and kinetic energy.     

瞬变电磁采样函数优化法降噪技术

常用的双极性同步采样方法对瞬变电磁系统的观测噪声具有一定的抑制作用,但在实际工作中其噪声抑制能力仍显不足.本文在双极性同步采样方法基础上提出一种优化方法,以提升瞬变电磁系统的噪声抑制能力,即:通过对取样道加高斯窗函数的方式,赋予取样道内各采样点合适的累加权重,提升系统对取样道内高频噪声的抑制能力;使用高斯窗函数与梳状滤波器构造复合窗函数,通过对包含所有叠加周期的完整观测序列加复合窗函数的形式优化各周期的叠加权重,提升系统对实际工频噪声的抑制能力.对优化前后不同采样函数的谱特性及野外实测数据的处理效果进行比较,结果表明本文提出的方法较传统双极性同步采样方法具有更强的噪声抑制能力.     

黄土微观参数指标与阻尼比关联度研究

对岷县地震台、庆阳黄土塬2~12m深度土层的粉土、粉质黏土样品,利用室内动三轴试验和扫描电镜试验,测定阻尼比和微观结构特征,研究了粉土、粉质黏土的阻尼比随深度的变化及应力应变关系,采用灰色关联度方法,分析了黄土竖向（沉积方向）和横向（垂直于沉积方向）的微观结构参数对阻尼比影响的主次关系及其权重。研究结果表明:小应变下,粉土和粉质黏土阻尼比随着深度的增加而减小;粉土和粉质黏土的微观参数与阻尼比有一定的关联性,粉土竖向的微观参数对阻尼比的影响较为敏感;粉质黏土横向的微观参数对阻尼比的影响更加敏感;影响权重方面,粉质黏土的平均形状系数影响权重最大,对阻尼比的影响最大;粉土的平均形状系数、分形维数和概率熵影响权重最大,对阻尼比影响最敏感。平均面积无论在关联度还是影响权重方面对阻尼比影响最小,该结论粉土与粉质黏土保持一致。     

面波频散谱多模式高分辨率成像的多道信号比较法

高分辨率的面波频散谱成像是浅层地震勘探领域基于频散性质反演横波速度结构中的一个关键步骤.在天然地震探测领域,仅利用两个台站记录的线性信号比较法(LSC),被广泛用来计算面波的频散谱,并用于大尺度的面波层析成像.然而互相关的成像方式会造成频散谱在低频端较低的分辨率.非线性信号比较法(NLSC)利用指数函数克服了这个问题,同时极大地提高了频散谱的成像分辨率.然而,在研究中我们发现,仅利用两个台站的地震记录,并不能将面波的频散特性完整地考虑在内,导致LSC和NLSC方法对高阶模式的成像存在较大的误差.由于主动源面波勘探多道采集的方式,基于信号比较理论的多道信号比较法(MSC)充分利用多道地震信号,可以获得准确的多模式成像,然而该方法需要计算任意两道的频散谱并叠加,存在冗余的计算,导致计算效率较低.因此,本研究对MSC方法进行了相应的改进,通过追踪炮集记录上的面波波组提高了原方法的计算效率,同时,利用理论频散曲线进行叠加分析,验证了改进的MSC方法的正确性和有效性.通过与相移法、LSC和NLSC方法的对比分析,展示了MSC方法是一种准确的、高分辨率的面波多模式频散谱成像方法.实际地震资料的应用...     

一种高性／价比的有线传呼器的设计

介绍利用８０３１单片机及外围电路，设计高性／价比的有线传呼器的设计思想、技术性能及设计技巧，给出了程序框图及部分电路图。     

遥墙机场环境噪声影响预评价

采用有效感觉噪声级Ｌｅｐｎ作为单个事件的评价量，用计权等效连续感觉噪声级Ｌｗｅｃｐｎ作为一段时间内多个事件的评价量，介绍了机场环境噪声影响预测的完整程序和方法。给出了遥墙机场１９９５年度的预测结果。     

It goes both ways: measurements of simultaneous evapotranspiration and fog droplet deposition at a montane cloud forest

Fluxes of latent heat, sensible heat, and water vapor, including turbulent deposition of fog droplets, were measured for two months in autumn 2005 within a subtropical montane cypress forest in Taiwan. The goal of the study was to determine whether significant evapotranspiration can occur during foggy conditions. Water vapor fluxes, Q_W, as determined with the Bowen Ratio method, were compared to those simultaneously measured with the eddy covariance method. The median Bowen Ratio was 1.06, and the median Q_W flux was 5 · 2 × 10^?5 kg m^?2 s^?1. The vertical gradients of temperature and specific humidity over the forest, ΔT and Δq, peaked around noon during days without fog, and were reduced during foggy conditions. For 66% of the data points, ΔT and Δq were negative, corresponding to positive (upward) fluxes of sensible heat Q_H and latent heat Q_E. A Monte Carlo simulation proved that statistically significant evapotranspiration rates, i.e., upward water vapor fluxes, occurred during fog. At the same time, deposition fluxes of fog droplets occurred. Our results show that even during fog events, significant evapotranspiration may occur. Copyright © 2008 John Wiley & Sons, Ltd.