REMAINS OF JURASSIC PLANTS FROM PATAOHO, MANCHURIA     

A.KRYSHTOFOVICH 《地质学报》1924,3(2)

All the forms undoubtedly prove the Jurassic age of the coal-beering strata of Pataohol.A more exact age of the deposits is difficult owing to the small uumber of spscies represented Nevertheless the presence of Dioonites kotoi which is typical as it seems,to the npper divission of the east-asiatic Jurassic,and shows the probability that the series at Pataoho corresponds nearer to the Nicanian Series of the Maritime Province or to the Upper Division of Jurassic deosits developed in the Ussuri Region.  相似文献   

Assessment of climate change impacts on climate variables using probabilistic ensemble modeling and trend analysis     

Safavi  Hamid R.  Sajjadi  Sayed Mahdi  Raghibi  Vahid 《Theoretical and Applied Climatology》2017,130(1-2):635-653

Water resources in snow-dependent regions have undergone significant changes due to climate change. Snow measurements in these regions have revealed alarming declines in snowfall over the past few years. The Zayandeh-Rud River in central Iran chiefly depends on winter falls as snow for supplying water from wet regions in high Zagrous Mountains to the downstream, (semi-)arid, low-lying lands. In this study, the historical records (baseline: 1971–2000) of climate variables (temperature and precipitation) in the wet region were chosen to construct a probabilistic ensemble model using 15 GCMs in order to forecast future trends and changes while the Long Ashton Research Station Weather Generator (LARS-WG) was utilized to project climate variables under two A2 and B1 scenarios to a future period (2015–2044). Since future snow water equivalent (SWE) forecasts by GCMs were not available for the study area, an artificial neural network (ANN) was implemented to build a relationship between climate variables and snow water equivalent for the baseline period to estimate future snowfall amounts. As a last step, homogeneity and trend tests were performed to evaluate the robustness of the data series and changes were examined to detect past and future variations. Results indicate different characteristics of the climate variables at upstream stations. A shift is observed in the type of precipitation from snow to rain as well as in its quantities across the subregions. The key role in these shifts and the subsequent side effects such as water losses is played by temperature.

  相似文献   

A simplified stress analysis of rising salt domes          下载免费PDF全文

Mahdi Heidari  Maria A. Nikolinakou  Peter B. Flemings  Michael R. Hudec 《Basin Research》2017,29(3):363-376

We use a simple analytical model to estimate the stress field in density‐driven, rising salt domes and adjacent sediments, and to describe the evolution of these domes. We show that the pressure exerted by the salt pushing out against its wall rocks (the salt pressure) decreases linearly up the flank of the dome, but is always greater than the overburden stress. In fact, the salt pressure normal to the dome boundary is everywhere the maximum principal stress, whereas the hoop stress parallel to the circumference of the dome is the minimum stress. In addition, we quantitatively describe the critical stages of salt dome evolution (initiation, upbuilding, and downbuilding), relating these stages to sedimentation rate and basin thickness. This analysis also shows that even the highest sedimentation rates are unlikely to accumulate enough sediments to bury downbuilding domes as long as the salt supply is unrestricted. Despite the simplicity of the model, its predictions are in good agreement with field observations near salt domes. Overall, our analytical model can provide critical insight into the stress field perturbation in and near rising salt domes and can be used to assess the accuracy of numerical models and field measurements near these domes.  相似文献   

Regional improvement of global geopotential models using GPS/Leveling data     

Mosayebzadeh  Mahdi  Ardalan  Alireza A.  Karimi  Roohollah 《Studia Geophysica et Geodaetica》2019,63(2):169-190

Studia Geophysica et Geodaetica - Global geopotential models are widely used in the remove-compute-restore technique for local gravity field modeling. In this paper, a method for regional...  相似文献   

Milgromian dynamics and dwarf galaxies in galactic voids     

Mahdi Khadem  Hosein Haghi 《Astrophysics and Space Science》2018,363(5):107

We use kinematic data of 103 dwarf galaxies, obtained from the Sloan Digital Sky Survey catalog, to test the Milgromian dynamics (MOND) inside a galactic void. From this data, we compute the line-of-sight velocity dispersions of the dwarf galaxies in the frameworks of MOND and Newtonian dynamics without invoking any dark matter. The prediction for the line-of-sight velocity dispersions from MOND of 53 selected dwarf galaxies is compared with their measured values. For appropriate mass-to-light ratios in the range 1 to 5 for each individual dwarf galaxy, our results for the line-of-sight velocity dispersions predicted by MOND are more compatible with observations than those predicted by Newtonian dynamics.  相似文献   

Geochemical and mineralogical pattern recognition and modeling with a Bayesian approach to hydrothermal gold deposits     

Mansour Ziaii  Arezoo Abedi  Mahdi Ziaei 《Applied Geochemistry》2009

The Bayesian approach is an effective method of identifying the probability of mineralogical and geochemical type (MGT) mineralization of trace elements in galena, pyrite and other distributions in ore mineralization. Monomineralic samples have been identified using a computer-based Bayesian method and exploration geochemical techniques of Au deposits for MGT. In order to employ the method, a data bank was used consisting of the results of analysis of more than 12,000 monomineralic samples collected from the main hydrothermal Au deposits in Tajikistan (a territory of CIS). The Bayesian approach applied to geochemical data, such as posterior probabilities and discriminant analysis, provide numerical and graphical means through which the relationships between the trace elements and samples can be studied. The method used here, along with GIS, to find MGT can be used as geochemical indicators of regions with Au mineralization. The results of analyzing 100 monomineralic samples of pyrite from the Au–Ag Shkolnoe deposit (Tajikistan) show a multi-MGT anomaly superposition which is a combination of three MGT: (1) Au–Ag type (85% and more), (2) Au–sulfide-polymetallic type (46%), and (3) Au–sulfide type (40%). Mineralogical and geochemical maps (MGM) can be drawn based on results of MGT anomalies in a GIS environment. These maps can replace traditional metallogenic maps. The advantage of MGM substitutions is that a qualitative tool is replaced by a quantitative one. This helps one to make optimal managerial and more economical decisions.  相似文献   

A destructuration theory and its application to SANICLAY model   总被引：1，自引：0，他引：1  

Mahdi Taiebat  Yannis F. Dafalias  Ralf Peek 《国际地质力学数值与分析法杂志》2010,34(10):1009-1040

Many natural clays have an undisturbed shear strength in excess of the remoulded strength. Destructuration modeling provides a means to account for such sensitivity in a constitutive model. This paper extends the SANICLAY model to include destructuration. Two distinct types of destructuration are considered: isotropic and frictional. The former is a concept already presented in relation to other models and in essence constitutes a mechanism of isotropic softening of the yield surface with destructuration. The latter refers to the reduction of the critical stress ratio reflecting the effect of destructuration on the friction angle, and is believed to be a novel proposition. Both the types depend on a measure of destructuration rate expressed in terms of combined plastic volumetric and deviatoric strain rates. The SANICLAY model itself is generalized from its previous form by additional dependence of the yield surface on the third isotropic stress invariant. Such a generalization allows to obtain as particular cases simplified model versions of lower complexity including one with a single surface and associative flow rule, by simply setting accordingly parameters of the generalized version. A detailed calibration procedure of the relatively few model constants is presented, and the performance of three versions of the model, in descending order of complexity, is validated by comparison of simulations to various data for oedometric consolidation followed by triaxial undrained compression and extension tests on two structured clays. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Stochastic methods for safety assessment of the flood defense system in the Scheldt Estuary of the Netherlands     

Mohammadreza Rajabalinejad  Tewfik Mahdi  Pieter van Gelder 《Natural Hazards》2010,55(1):123-144

In this study, we address the effective method to apply a novel reliability method integrated with finite element models to the safety assessment of pilot site Scheldt in the Netherlands. This site was considered as one of the three main pilot sites in Europe to assess the application of newly suggested techniques in order to reduce and manage the flood risk in the Floodsite project. , 2004–2009). The novel method of dynamic bounds (DB) is applied to this site after a successful experience in (Rajabalinejad in Reliability methods for finite element models, 1 edn. IOS Press, Amsterdam, 2009). In this study, the bi-functional response of the finite element model is considered, and the dimensional uncertainty is defined presenting the expected uncertainty for a certain dimension in the DB method. The uncertainty is used as a judgment tool to choose the dimension for the DB method for the desired accuracy. The results obtained by applying this technique are presented in this paper.  相似文献   

Automated classification of sloan digital sky survey (SDSS) stellar spectra using artificial neural networks     

Mahdi Bazarghan  Ranjan Gupta 《Astrophysics and Space Science》2008,315(1-4):201-210

Automated techniques have been developed to automate the process of classification of objects or their analysis. The large datasets provided by upcoming spectroscopic surveys with dedicated telescopes urges scientists to use these automated techniques for analysis of such large datasets which are now available to the community. Sloan Digital Sky Survey (SDSS) is one of such surveys releasing massive datasets. We use Probabilistic Neural Network (PNN) for automatic classification of about 5000 SDSS spectra into 158 spectral type of a reference library ranging from O type to M type stars.  相似文献   

High‐frequency streamflow acquisition and bed level/flow angle estimates in a mountainous river using shallow‐water acoustic tomography          下载免费PDF全文

Kiyosi Kawanisi  Masoud Bahrainimotlagh  Mohamad Basel Al Sawaf  Mahdi Razaz 《水文研究》2016,30(13):2247-2254

The acquisition of reliable discharge estimates is crucial in hydrological studies. This study demonstrates a promising acoustic method for measuring streamflow at high sampling rate for a long period using the fluvial acoustic tomography system (FATS). The FATS recently emerged as an innovative technique for continuous measurements of streamflow. In contrast to the traditional point/transect measurements of discharge, the FATS enables the depth‐averaged and range‐averaged flow velocity along the ray path to be measured in a fraction of a second. The field test was conducted in a shallow gravel‐bed river (0.9 m deep under low‐flow conditions, 115 m wide) for 1 month. The parameters (stream direction and bottom elevation) required for calculating the streamflow were deduced by a nonlinear regression to the discharge data from the well‐established rating curve. The cross‐sectional average velocities were automatically calculated from the acoustic data, which were collected on both riverbanks every 30 s. The FATS was connected to the internet so that the real‐time flow data could be obtained. The FATS captured discharge variations at a cut‐off frequency of approximately 70 day^?1. The stream exhibited temporal discharge changes at multiple time scales ranging from a few tens of minutes to days. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献