A discussion on models of thermals

For a thermal starting from rest, the scales of motion consistent with the initial conditions are given. An alternative time scale based on the motion of the thermal is derived. The anticipated similarity solutions for thermals are summarised and possible qualitative differences between solutions are given. Within this consistent framework previously published laboratory and numerical models of thermals are discussed. Reasons why numerical models have not rigorously demonstrated the existence of a self-similarity solution are considered. Comparisons of all available results show that a single similarity solution valid for all thermals does not exist.     

Sr and O isotopic characteristics of porphyries in the Qinling molybdenum deposit belt and their implication to genetic mechanism and type

A great deal of Mesozoic hypobatholithic granites and hypabyssal porphyries develop in the Qinling Mountains. The former has long been regarded as transformation type (or S-type), and the latter associated with Mo-mineralization regarded as syntexis type (or I-type) granitoids. Statistics show that Sr₁ and σ¹⁸O of hypabyssal porphyries respectively range from 0.705 to 0.714, and from 7.2‰ to 12.1‰, agreeing with those of hypobatholithes (Sr₁=0.705–0.710, σ¹⁸O=6.1‰–10.4‰), which indicates that they share similar material sources and petrogenic mechanism. Based on analysis of lithological, mineralogical and geochemical characteristics of these granitoids and on study of their petrogenic tectonic background and regional geophysical data, we argue that both the shallow-seated porphyries and deep-seated batholithes were the products of Mesozoic collision between South China and North China paleocontinents. Subsequently, all these grantitoids should be attributed to collision type.     

新疆巴里坤红石滩铜矿床石英闪长斑岩LA-ICP-MS锆石U-Pb年龄及其地质意义

本文对新疆巴里坤红石滩铜矿区出露的石英闪长斑岩进行LA-ICP MS锆石U-Pb年龄测定,结果表明红石滩石英闪长斑岩形成年龄为403.1±3.8 Ma,形成时代为早泥盆世.此外,测得的两个锆石U-Pb同位素年龄为895 Ma左右,表明研究区可能存在早元古代基底.红石滩石英闪长斑岩体与铜矿关系密切,是寻找斑岩型铜多金属矿的有利场所,为今后在该区寻找同类型铜矿提供重要依据.     

A critical discussion of numerical models for multiaquifer systems

Leaky aquifers constitute complicated hydrological structures, whose inclusion in numerical models of hydrological systems is difficult, because of their three-dimensional nature. Methods for treating such systems can be classified as fully three-dimensional and quasi-three-dimensional. The latter have clear numerical advantages when applicable. In this paper a critical discussion of existing quasi-three-dimensional models is presented.     

Solving nonlinear water management models using a combined genetic algorithm and linear programming approach

Gradient-based nonlinear programming (NLP) methods can solve problems with smooth nonlinear objectives and constraints. However, in large and highly nonlinear models, these algorithms can fail to find feasible solutions, or converge to local solutions which are not global. Evolutionary search procedures in general, and genetic algorithms (GAs) specifically, are less susceptible to the presence of local solutions. However, they often exhibit slow convergence, especially when there are many variables, and have problems finding feasible solutions in constrained problems with “narrow” feasible regions. In this paper, we describe strategies for solving large nonlinear water resources models management, which combine GAs with linear programming. The key idea is to identify a set of complicating variables in the model which, when fixed, render the problem linear in the remaining variables. The complicating variables are then varied by a GA. This GA&LP approach is applied to two nonlinear models: a reservoir operation model with nonlinear hydropower generation equations and nonlinear reservoir topologic equations, and a long-term dynamic river basin planning model with a large number of nonlinear relationships. For smaller instances of the reservoir model, the CONOPT2 nonlinear solver is more accurate and faster, but for larger instances, the GA&LP approach finds solutions with significantly better objective values. The multiperiod river basin model is much too large to be solved in its entirety. The complicating variables are chosen here so that, when they are fixed, each period's model is linear, and these models can be solved sequentially. This approach allows sufficient model detail to be retained so that long-term sustainability issues can be explored.     

Forecasting streamflow by combination of a genetic input selection algorithm and wavelet transforms using ANFIS models

ABSTRACT

In this study, a data-driven streamflow forecasting model is developed, in which appropriate model inputs are selected using a binary genetic algorithm (GA). The process involves using a combination of a GA input selection method and two adaptive neuro-fuzzy inference systems (ANFIS): subtractive (Sub)-ANFIS and fuzzy C-means (FCM)-ANFIS. Moreover, the application of wavelet transforms coupled with these models is tested. Long-term data for the Lighvan and Ajichai basins in Iran are used to develop the models. The results indicate considerable improvements when GA selection and wavelet methods are used in both models. For example, the Nash-Sutcliffe efficiency (NSE) coefficient for Lighvan using FCM-ANFIS is 0.74. However, when GA selection is applied, the NSE is improved to 0.85. Moreover, when the wavelet method is added, the performance of new hybrid models shows noticeable enhancements. The NSE value of wavelet-FCM-ANFIS is improved to 0.97 for Lighvan basin.

Editor D. Koutsoyiannis Associate editor E. Toth     

Wood textures in Jinman copper deposit in western Yunnan and their genetic implications

Jinman vein copper deposit in western Yunnan occurs in a salt-bearing red clastic rock formation composed of sandstone, siltstone and shale. Wood texture is considerably developed in the ores. The metallic minerals making up the wood textures mainly include pyrite, chalcopyrite and bornite. Studies on the samples and examination of their micrographs and electron micrographs have confirmed that they belong to xenoxylon, reflecting that the ore-hosting rock series is the product of sedimentation in the terrestrial environment. Organic geochemistry and sulfur and carbon isotopic composition data indicate that the formation of the deposit is substantially related with underground hot brines and biological processes.     

Diversity of Mesozoic tin-bearing granites in the Nanling and adjacent regions,South China: Distinctive mineralogical patterns

The Nanling and adjacent regions of South China host a series of tin deposits related to Mesozoic granites with diverse petrological characteristics. The rocks are amphibole-bearing biotite granites, or(topaz-) albite-lepidolite(zinnwaldite) granites,and geochemically correspond to mealuminous and peraluminous types, respectively. Mineralogical studies demonstrate highly distinctive and critical patterns for each type of granites. In mealuminous tin granites amphibole, biotite and perthite are the typical rock-forming mineral association; titanite and magnetite are typical accessory minerals, indicating high fO2 magmatic conditions;cassiterite, biotite and titanite are the principal Sn-bearing minerals; and pure cassiterite has low trace-element contents. However,in peraluminous tin granites zinnwaldite-lepidolite, K-feldspar and albite are typical rock-forming minerals; topaz is a common accessory phase, indicative of high peraluminity of this type of granites; cassiterite is present as a uniquely important tin mineral,typically rich in Nb and Ta. Mineralogical distinction between the two types of tin granites is largely controlled by redox state,volatile content and differentiation of magmatic melts. In oxidized metaluminous granitic melts, Sn4+ is readily concentrated in Ti-bearing rock-forming and accessory minerals. Such Sn-bearing minerals are typical of oxidized tin granites, and are enriched in granites at the late fractionation stage. In relatively reduced peraluminous granitic melts, Sn2+ is not readily incorporated into rock-forming and accessory minerals, except for cassiterite at fractionation stage of granite magma, which serves as an indicator of tin mineralization associated with this type of granites. The nature of magma and the geochemical behavior of tin in the two types of granites thus result in the formation of different types of tin deposits. Metaluminous granites host disseminated tin mineralization,and are locally related to deposits of the chlorite quartz-vein, greisen, and skarn types. Greisen, skarn, and quartz-vein tin deposits can occur related to peraluminous granites, but disseminated mineralization of cassiterite is more typical.     

Prediction of hourly actual evapotranspiration using neural networks,genetic programming,and statistical models

The complexity of the evapotranspiration process and its variability in time and space have imposed some limitations on previously developed evapotranspiration models. In this study, two data‐driven models: genetic programming (GP) and artificial neural networks (ANNs), and statistical regression models were developed and compared for estimating the hourly eddy covariance (EC)‐measured actual evapotranspiration (AET) using meteorological variables. The utility of the investigated data‐driven models was also compared with that of HYDRUS‐1D model, which makes use of conventional Penman–Monteith (PM) model for the prediction of AET. The latent heat (LE), which is measured using the EC method, is modelled as a function of five climatic variables: net radiation, ground temperature, air temperature, relative humidity, and wind speed in a reconstructed landscape located in Northern Alberta, Canada. Several ANN models were evaluated using two training algorithms of Levenberg–Marquardt and Bayesian regularization. The GP technique was used to generate mathematical equations correlating AET to the five climatic variables. Furthermore, the climatic variables, as well as their two‐factor interactions, were statistically analysed to obtain a regression equation and to indicate the climatic factors having significant effect on the evapotranspiration process. HYDRUS‐1D model as an available physically based model was examined for estimating AET using climatic variables, leaf area index (LAI), and soil moisture information. The results indicated that all three proposed data‐driven models were able to approximate the AET reasonably well; however, GP and regression models had better generalization ability than the ANN model. The results of HYDRUS‐1D model exhibited that a physically based model, such as HYDRUS‐1D, might be comparable or even inferior to the data‐driven models in terms of the overall prediction accuracy. Based on the developed GP and regression models, net radiation and ground temperature had larger contribution to the AET process than other variables. Copyright © 2010 John Wiley & Sons, Ltd.     

Acute toxicity of copper to a copepod

The acute toxicity of copper to the marine copepod Acartia clausi was determined by means of static bioassays. Natural copepod assemblages from two different locations, one from an area polluted with industrial effluents and domestic wastes and another from a relatively uncontaminated area, were compared. Results of metal toxicity tests expressed as 48 h LC₅₀ values indicate a significant difference in the tolerance of copper between the two populations, with the LC₅₀ of the pollution-adapted population higher than that of the population from the uncontaminated area.     

地震统计力学—几个非线性地震模型的相互关系及其物理含义

近年来地震统计力学研究的进展已经使我们有可能以一种简洁的方式将一些非线性地震模型物理地联系起来,并从地震学角度阐明这些模型的意义和限度。本文结合逾渗模型、热力学弹性回跳模型及弹簧滑块模型,系统地评述了这方面研究的进展。     

Flood-plain mapping: a critical discussion of deterministic and probabilistic approaches

Abstract

Different methodologies for flood-plain mapping are analysed and discussed by comparing deterministic and probabilistic approaches using hydrodynamic numerical solutions. In order to facilitate the critical discussion, state-of-art techniques in the field of flood inundation modelling are applied to a specific test site (River Dee, UK). Specifically, different flood-plain maps are derived for this test site. A first map is built by applying an advanced deterministic approach: use of a fully two-dimensional finite element model (TELEMAC-2D), calibrated against a historical flood extent, to derive a 1-in-100 year flood inundation map. A second map is derived by using a probabilistic approach: use of a simple raster-based inundation model (LISFLOOD-FP) to derive an uncertain flood extent map predicting the 1-in-100 year event conditioned on the extent of the 2006 flood. The flood-plain maps are then compared and the advantages and disadvantages of the two different approaches are critically discussed.

Citation Di Baldassarre, G., Schumann, G., Bates, P. D., Freer, J. E. & Beven, K. J. (2010) Flood-plain mapping: a critical discussion of deterministic and probabilistic approaches. Hydrol. Sci. J. 55(3), 364–376.     

Petrogenesis and tectonic implications of the Early Cretaceous Dagushan adakitic porphyries in the Anshan area,North China Craton

The eastern part of the North China Craton suffered significant lithospheric thinning since the Mesozoic,and petrogenesis of the Dagushan adakitic diorite porphyries provides an excellent opportunity to investigate the lithospheric thinning mechanism and geodynamic setting.The zircon LA-ICP-MS U–Pb geochronology reveals that the representative Dagushan adakitic porphyry was formed at 120.5 ± 0.5 Ma.The Dagushan diorite porphyries are characterized by the relatively high contents of SiO2(64.25–65...     

Theoretical discussion and Monte-Carlo simulations for a Negative Binomial process paradox

The idea of an over-threshold sampling is to retain all the events of a time-series exceeding a given threshold. The probabilistic analysis implies estimating two statistical models, one describing the occurrence of the events (date of the events), the other describing their magnitude (value of the local maximum). These two models are then combined to obtain the distribution of the annual maxima. A well-known result of a Poisson process is that waiting time, defined as the duration between two successive events exceeding the threshold, is exponentially distributed. The assertion that the waiting time of a Negative Binomial process is also exponentially distributed seems to be in obvious contradiction with the Poisson process properties. A theoretical discussion and Monte-Carlo simulations are presented to solve this apparent paradox.     

Recharge process and aquifer models of a small watershed

Abstract

Kanchanapally watershed covering an area of about 11 km² in Nalgonda district, Andhra Pradesh, India is located in granitic terrain. Groundwater recharge has been estimated from a water balance model using hydrometeorological data from 1978–1994. The monthly recharge estimates obtained from the water balance model formed input for the groundwater flow model during transient model testing. The groundwater flow model has been prepared to simulate steady state groundwater conditions of 1977 using the nested squares finite difference method. The transient groundwater flow model has been tested during 1977–1994 using the estimated recharge values. The present study helped verify the usefulness of monthly recharge estimates for accounting dynamic variations in recharge as reflected in water level fluctuations in hydrographs.     

Compared performance of a conceptual and a mechanistic hydrologic models of a green roof

In order to investigate the hydrologic response of a green roof system within the urban environment, a monitoring campaign is carried out at the green roof site of the University of Genova (Italy). Experimental data confirm that the green roof is able to significantly mitigate the generation of runoff with median values of retained volume and peak reduction, respectively, equal to 94 and 98%. A conceptual linear reservoir and a simple mechanistic (Hydrus‐1D) models are implemented to simulate the hydrologic behaviour of the system; each model is calibrated and validated based on experimental data collected at the green roof site. The hydrographs simulated with both hydrologic models reproduce with acceptable matching capabilities the experimental measurements, as confirmed by the Nash‐Sutcliffe Efficiency index generally greater than 0·60. Although the relative percentage differences evaluated for the selected hydrograph variables (the total effluent volume, the peak flow rate and the hydrograph centroid) demonstrate that the mechanistic model is more accurate, prediction errors of the conceptual model are generally limited when compared with the observed hydrologic performance. Results of the present comparison are useful in supporting conceptual model selection in case the hydrologic response is addressed for hydrologic performance assessment. Copyright © 2011 John Wiley & Sons, Ltd.     

Transport processes of copper and zinc in a highly eutrophic and meromictic lake

Lake Baldegg was chosen to study the influence of a permanent anaerobic hypolimnion on the transport of copper and zinc. The evaluation of concentration variations in function of time and depth and the sedimentation rates lead to the conclusion that copper, in contrast to zinc, is sorbed additionally on newly formed iron particles at the Fe³⁺/Fe²⁺ interface and transported on the ‘iron wheel’. A flux scheme for the hypolimnic transport of copper is quantified in a one-dimensional diffusion model. By this the observed variations of concentration profiles can be explained.     

Reply to Edward Anders: A discussion of alternative models for explaining the distribution of moderately volatile elements in ordinary chondrites

The high observed abundances of Na and Cu in chondrules indicate that the amount of loss during chondrule formation was minor and possibly negligible, consistent with the view that loss was controlled by diffusion kinetics rather than equilibrium volatility, and that the surface of the chondrule quickly cooled to temperatures at which diffusional transport was negligible. Ordinary chondrite/CI abundance ratios appear to be randomly distributed in the range 0.9-0.1. Very few values are observed in the 0.36–0.70 range, but this is not statistically significant, nor is it predicted by the two-component (chondrule-matrix) model.If CI chondrite abundances are representative of mean solar-system material, the very low chondrule content in CM chondrites (<5% of high-temperature materials) indicates that the observed volatile distribution resulted from incomplete accretion of volatile carriers (perhaps a fine aerosol). At the ordinary chondrite formation location the fraction of an element sited in unaccreted carriers increased with decreasing condensation temperature. At the CM location a similar trend is observed for elements less volatile than S, but the unaccreted fraction of more volatile elements was nearly constant.