硬玉和透辉石的光吸收谱和颜色

本文报道若干天然硬玉和透辉石的光吸收谱,并在配位场分析的基础上讨论其致色原因。铁离子和铬离子均可使硬玉和透辉石呈现绿色。铬含量低但铁含量较高的样品(如Di-17)呈暗绿色。透辉石(Di-17)的偏振光吸收谱表明,这些样品的颜色与Fe~(2+)(M_1)→Fe~(3+)(M_1)荷移跃迁和配体→金属荷移跃迁密切相关。翠绿色样品含铬量相对地较高,其频色主要取决于Cr~(3+)离子在可见区内的自旋允许跃迁。红色和黄色硬玉的颜色与很强的配体→金属荷移吸收有关。     

Determination of synthetic wind functions for estimating open water evaporation with Computational Fluid Dynamics

A computational fluid dynamics (CFD)‐based methodology is proposed to derive convective mass‐transfer coefficients (wind functions) that are required for estimating evaporation of water bodies with the mass‐transfer method. Three‐dimensional CFD was applied to model heat transfer in two water bodies: a Class‐A tank evaporimeter and an on‐farm artificial pond. The standard k–? model assuming isotropic turbulence was adopted to describe turbulent heat transport, whereas the heat and mass transfer analogy was assumed to derive the wind functions. The CFD‐derived wind functions were very similar to those empirically derived from the experimental water bodies. The evaporation rates calculated with the synthetic wind functions were in good agreement with hourly and daily evaporation measurements for the tank and pond, respectively. The proposed CFD‐approach is generalisable and cost effective, because it has low input data requirements. Besides, it provides additional capability of modelling the spatial distribution of the evaporation rate over the water surface. Although the application of CFD to water bodies evaporation modelling is still in development, it looks very promising. Copyright © 2012 John Wiley & Sons, Ltd.     

Slope control on the frequency distribution of shallow landslides and associated soil properties,North Island,New Zealand

The extrapolation of results from field trials to larger areas of land for purposes of regional impact assessment is an important issue in geomorphology, particularly for landform properties that show high stochastic variability in space and time, such as shallow landslide erosion. It is shown in this study, that by identifying the main driver for spatial variability in shallow landslide erosion at field scales, namely slope angle, it is possible to develop a set of generic functions for assessing the impact of landslides on selected soil properties at larger spatial scales and over longer time periods. Research was conducted within an area of pastoral soft‐rock Tertiary hill country in the North Island of New Zealand that is subject to infrequent high intensity rainfall events, producing numerous landslides, most of which are smaller than several hundred square metres in size and remove soil to shallow depths. All landslides were mapped within a 0·6 km² area and registered to a high resolution (2 m) slope map to show that few landslides occur on slopes < 20° and 95% were on slopes > 24°. The areal density of landslides from all historical events showed an approximately linear increase with slope above 24°. Integrating landslide densities with soil recovery data demonstrates that the average value of a soil property fluctuates in a ‘saw‐tooth’ fashion through time with the overall shape of the curve controlled by the frequency of landslide inducing storm events and recovery rate of the soil property between events. Despite such fluctuations, there are gradual declines of 7·5% in average total carbon content of topsoil and 9·5% in average soil depth to bedrock, since the time of forest clearance. Results have application to large‐scale sediment budget and water quality models and to the New Zealand Soil Carbon Monitoring System (CMS). Copyright © 2012 John Wiley & Sons, Ltd.     

Hydrological behaviour of a drained agricultural peat catchment in the tropics. 2: Time series transfer function modelling approach

Abstract

Transfer function models of the rainfall–runoff relationship with various complexities are developed to investigate the hydrological behaviour of a tropical peat catchment that has undergone continuous drainage for a long time. The study reveals that a linear transfer function model of order one and noise term of ARIMA (1,0,0) best represents the monthly rainfall–runoff relationship of a drained peat catchment. The best-fitted transfer function model is capable of illustrating the cumulative hydrological effects of the catchment when subjected to drainage. Transfer function models of daily rainfall–runoff relationships for each year of the period 1983–1993 are also developed to decipher the changes in hydrological behaviour of the catchment due to drainage. The results show that the amount of rain water temporarily stored in the peat soil decreased and the catchment has become more responsive to rainfall over the study period.

Editor Z.W. Kundzewicz; Associate editor D. Hughes

Citation Katimon, A., Shahid, S., Abd Wahab, A.K., and Shabri, A., 2013. Hydrological behaviour of a drained agricultural peat catchment in the tropics. 2: Time series transfer function modelling approach. Hydrological Sciences Journal, 58 (6), 1310–1325.     

岩石压应力传递系数计算及影响机制

钻孔应变观测是地壳岩石应变相对测量的主要方法,对其附加应力场的研究,可以有效分析岩石压应力向探头的传递过程,可对应变仪有关力学参数的设计和观测数据的物理解释提供帮助。考虑到外加应力在岩石、水泥和仪器钢筒等3层介质中传递的实际情况,根据弹性力学中的厚壁圆筒方程,推导轴对称应力作用下岩石压应力的传递系数公式,分析影响机制,并给出有关变化规律曲线和定量指标。     

精确测定地震计传递函数

提出联合阶跃标定与带精确电流测量的正弦波标定来确定地震计传递函数的方法。首先,使用阶跃标定确定地震计等效机械摆的自振周期和阻尼,得到地震计低频特性。随后,使用正弦波标定并引入电流测试技术,测定地震计全频段频率响应,幅频响应更加准确,同时可获得相频响应。最后,构建与地震计传递函数特征一致的结构来描述传递函数,采用最优化方法拟合求取地震计传递函数。该方法具有原理清楚、操作简单、易于实现、结果精确等优点,特别适用于地震计用户测试、地震计传递特性与厂方参数及各地震计间一致性和长期稳定性的验证,结果符合反馈型地震计传递函数特点。     

A field study of mean and turbulent flow characteristics upwind,over and downwind of barchan dunes

Field‐measured patterns of mean velocity and turbulent airflow are reported for isolated barchan dunes. Turbulence was sampled using a high frequency sonic anemometer, deriving near‐surface Reynolds shear and normal stresses. Measurements upwind of and over a crest‐brink separated barchan indicated that shear stress was sustained despite a velocity reduction at the dune toe. The mapped streamline angles and enhanced turbulent intensities suggest the effects of positive streamline curvature are responsible for this maintenance of shear stress. This field evidence supports an existing model for dune morphodynamics based on wind tunnel turbulence measurements. Downwind, the effect of different dune profiles on flow re‐attachment and recovery was apparent. With transverse incident flow, a re‐attachment length between 2·3 and 5·0h (h is dune brink height) existed for a crest‐brink separated dune and 6·5 to 8·6h for a crest‐brink coincident dune. The lee side shear layer produced elevated turbulent stresses immediately downwind of both dunes, and a decrease in turbulence with distance characterized flow recovery. Recovery of mean velocity for the crest‐brink separated dune occurred over a distance 6·5h shorter than the crest‐brink coincident form. As the application of sonic anemometers in aeolian geomorphology is relatively new, there is debate concerning the suitability of processing their data in relation to dune surface and streamline angle. This paper demonstrates the effect on Reynolds stresses of mathematically correcting data to the local streamline over varying dune slope. Where the streamline angle was closely related to the surface (windward slope), time‐averaged shear stress agreed best with previous wind tunnel findings when data were rotated along streamlines. In the close lee, however, the angle of downwardly projected (separated) flow was not aligned with the flat ground surface. Here, shear stress appeared to be underestimated by streamline correction, and corrected shear stress values were less than half of those uncorrected. Copyright © 2011 John Wiley & Sons, Ltd.     

Comparative study of neural network,fuzzy logic and linear transfer function techniques in daily rainfall‐runoff modelling under different input domains

This paper compares artificial neural network (ANN), fuzzy logic (FL) and linear transfer function (LTF)‐based approaches for daily rainfall‐runoff modelling. This study also investigates the potential of Takagi‐Sugeno (TS) fuzzy model and the impact of antecedent soil moisture conditions in the performance of the daily rainfall‐runoff models. Eleven different input vectors under four classes, i.e. (i) rainfall, (ii) rainfall and antecedent moisture content, (iii) rainfall and runoff and (iv) rainfall, runoff and antecedent moisture content are considered for examining the effects of input data vector on rainfall‐runoff modelling. Using the rainfall‐runoff data of the upper Narmada basin, Central India, a suitable modelling technique with appropriate model input structure is suggested on the basis of various model performance indices. The results show that the fuzzy modelling approach is uniformly outperforming the LTF and also always superior to the ANN‐based models. Copyright © 2010 John Wiley & Sons, Ltd.     

基于GRACE Follow-On卫星重力梯度法精确反演地球重力场

由于GRACE Follow-On双星系统等效于基线长为星间距离的一维水平重力梯度仪,因此本文基于GRACE Follow-On卫星重力梯度法开展了精确和快速反演下一代地球重力场的可行性论证研究. 研究结果表明：第一,基于GRACE Follow-On卫星重力梯度法（GFO-SGGM）,利用卫星轨道参数（轨道高度250 km、星间距离50 km、轨道倾角89°、轨道离心率0.001）、关键载荷测量精度（星间距离10-6 m、星间速度10-7 m·s-1、星间加速度10-10 m·s-2、轨道位置10-3 m、轨道速度10-6 m·s-1、非保守力10-11 m·s-2）、观测时间30天和采样间隔10 s反演了120阶地球重力场,在120阶处累计大地水准面精度为9.331×10-4 m. 第二,在120阶内,利用将来GRACE Follow-On双星反演地球重力场精度较现有GRACE双星平均提高61倍,因此GRACE Follow-On卫星重力梯度法是进一步提高地球重力场反演精度的优选方法. 第三,下一代GRACE Follow-On计划较当前GRACE计划的优点如下：轨道高度更低（200~300 km）、载荷精度更高（10-7 ~10-9 m·s-1）和星间距离更短（50~100 km）.     

基于分布式数据库原理实现辽宁地震财务会计报表管理系统

本文简要介绍分布式数据库原理，并利用其软件分层结构(4层)实现了辽宁地震财务会计报表管理系统。该系统各层任务明确，下层为上层提供服务，相互间分工协作，共同完成辽宁地震财务会计报表管理系统的各项功能。