Cost-effective network design for groundwater flow monitoring

The extensive use of groundwater resources has increased the need for developing cost-effective monitoring networks to provide an indication of the degree to which the subsurface environment has been affected by human activities. This study presents a cost-effective approach to the design of groundwater flow monitoring networks. The groundwater network design is formulated with two problem formats: maximizing the statistical monitoring power for specified budget constraint and minimizing monitoring cost for statistical power requirement. The statistical monitoring power constraint is introduced with an information reliability threshold value. A branch and bound technique is employed to select the optimal solution from a discrete set of possible network alternatives. The method is tested to the design of groundwater flow monitoring problem in the Pomona County, California.     

利用LAU效应测定干涉滤光片的中心透过率波长值

本文提出一种利用LAU效应测定干涉滤光片中心透过率波长值的理论和实验方法,这一方法不但具有精度高、装置简单、方法简便等优点,而且由该方法所获得的实验结果,可以作为当前有关平面周期物体LAU 效应新理论的一种实践检验。     

快速序贯算法

本文讨论了序贯算法的基本原理，与ｋａｌｍａｎ滤波的关系，和序贯算法的渐近性态，得到无先验信息的序贯算法不受初值的影响。实例分析表明，此序贯算法可适于方程系数阵的求逆、求解和病态方程的快速解算。     

Exploratory spectral analysis of hydrological times series

Current methods of estimation of the univariate spectral density are reviewed and some improvements are made. It is suggested that spectral analysis may perhaps be best thought of as another exploratory data analysis (EDA) tool which complements, rather than competes with, the popular ARMA model building approach. A new diagnostic check for ARMA model adequacy based on the nonparametric spectral density is introduced. Additionally, two new algorithms for fast computation of the autoregressive spectral density function are presented. For improving interpretation of results, a new style of plotting the spectral density function is suggested. Exploratory spectral analyses of a number of hydrological time series are performed and some interesting periodicities are suggested for further investigation. The application of spectral analysis to determine the possible existence of long memory in natural time series is discussed with respect to long riverflow, treering and mud varve series. Moreover, a comparison of the estimated spectral densities suggests the ARMA models fitted previously to these datasets adequately describe the low frequency component. Finally, the software and data used in this paper are available by anonymous ftp from fisher.stats.uwo.ca.     

基于误差准则和循环迭代的时移地震匹配滤波方法

分析了用于时移地震互均衡处理中的传统匹配滤波算法适用范围，结果表明该方法在滤波算子的反算子为最小相位时效果最好.对该方法难以解决的混合相位问题，推导出通用公式，并提出基于最小平方误差准则和循环迭代的求解方法.理论和实际数据都验证了该方法较已有方法的优越性.     

Transient deformation following the 30 January 1997 dike intrusion at Kīlauea volcano,Hawai’i

On 30 January 1997 an intrusion on Kīlauea volcano opened a new fissure within the East Rift Zone (ERZ) at Nāpau Crater, 3 km uprift from the ongoing eruptions at Pu’u ’Ō’ō. The fissure eruption lasted 22 h and opened a 5.1 km long, nearly vertical dike 1.9 m, extending from the surface to a depth of 2.4 km (Owen et al. 2000b). During the eruption, the lava pond at Pu’u ’Ō’ō drained, and eruptions ceased there. Pu’u ’Ō’ō eventually refilled in late February and eruptions resumed there on 28 March 1997. Continuous GPS data show a large transient following the 30 January 1997 dike intrusion. After lengthening 40 cm during the initial eruption, the baseline between two stations spanning the ERZ lengthened an additional 10 cm over the following 6 months. A coastal station KAEP also exhibited transient deformation, as it continued to move southward (5 cm) over the same 6-month period. The baseline between two stations spanning Kīlauea’s summit caldera contracted sharply during the eruption, but gradually recovered to slightly longer than its previous length 2 months after the intrusion. We use the extended network inversion filter (McGuire and Segall 2003) to invert continuous GPS data for volume change of a spherical pressure source under Kīlauea’s summit, opening distribution on a nearly vertical dike in the ERZ and potential slip on a decollement 9 km beneath the south flank. Following the 30 January intrusion, rift extension continued below the initial dike intrusion for the duration of the transient. Decollement slip, regardless of its assumed depth, is not required to fit the data. The modeled transient summit reinflation and rift opening patterns under Nāpau crater coincide with changes in observed behavior of Pu’u ’Ō’ō’s lava pond. Rift opening accelerated while Pu’u ’Ō’ō eruptions paused and began to decelerate after the lava pond reappeared nearly a month after the Nāpau eruption. The transient deformation is interpreted as resulting from shallow accommodation of the new dike volume.     

A One-dimensional Ensemble Forecast and Assimilation System for Fog Prediction

A probabilistic fog forecast system was designed based on two high resolution numerical 1-D models called COBEL and PAFOG. The 1-D models are coupled to several 3-D numerical weather prediction models and thus are able to consider the effects of advection. To deal with the large uncertainty inherent to fog forecasts, a whole ensemble of 1-D runs is computed using the two different numerical models and a set of different initial conditions in combination with distinct boundary conditions. Initial conditions are obtained from variational data assimilation, which optimally combines observations with a first guess taken from operational 3-D models. The design of the ensemble scheme computes members that should fairly well represent the uncertainty of the current meteorological regime. Verification for an entire fog season reveals the importance of advection in complex terrain. The skill of 1-D fog forecasts is significantly improved if advection is considered. Thus the probabilistic forecast system has the potential to support the forecaster and therefore to provide more accurate fog forecasts.     

对重力势二阶垂直偏导数的一种新的取样方法

从目前的研究来看，二阶垂直导数（X和Y两个方向）的求解方法较简单，它采用的五个因子的数字滤波的最小二乘法来优化数据。但是在较小区域面积时（对工程和环境应用中的重力数据），重力异常很容易放大和被区域重力场掩盖，我们认为产生的缘由是表示重力场的x和y方向上的二次多项式引起的。因此，为了逼近重力水平方向的偏导可以设计一个好的滤波器来拟合在xy平面的重力场值，再得出想要的重力垂直方向偏导，文中最后对提出的方法在前人经典模型上和野外实践进行了验证。     

基于启发式图搜索的遥感影像道路半自动提取

启发式图搜索法用于线状目标识别的原理是：用图结构表示边缘点和边缘段，根据启发函数计算顶点权值，在图的路径上建立相应的代价函数，通过在图中搜索对应的最小代价的通道以找到最优路径。图搜索法是一种全局最优方法，它在受噪声影响较大时效果仍然较好。文中使用了启发式图搜索法（A*算法）实现了道路的半自动跟踪。它的基本思路是：首先利用自适应平滑滤波算子进行道路信息增强，然后对传统的道路数学模型进行了进一步的扩展，突出了对道路几何特性和辐射特性的描述，并依此构建图搜索的代价函数，实现了基于启发式图搜索法A*算法的道路半自动跟踪。经实验证明，该方法进行遥感影像的道路半自动提取效果较好。