Design of a support vector machine with different kernel functions to predict scour depth around bridge piers     

Hassan Sharafi  Isa Ebtehaj  Hossein Bonakdari  Amir Hossein Zaji 《Natural Hazards》2016,84(3):2145-2162

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The R{\overline{3}} c \to R{\overline{3}} m transition in nitratine, NaNO3, and implications for calcite, CaCO3     

Sytle M. Antao  Ishmael Hassan  Willem H. Mulder  Peter L. Lee 《Physics and Chemistry of Minerals》2008,35(10):545-557

The temperature dependences of the crystal structure and superstructure intensities in sodium nitrate, mineral name nitratine, NaNO₃, were studied using Rietveld structure refinements based on synchrotron powder X-ray diffraction. Nitratine transforms from $R{\overline{3}} c\;\hbox{to}\;R{\overline{3}} m$ at T _c = 552(1) K. A NO₃ group occupies, statistically, two positions with equal frequency in the disordered $R{\overline{3}} m$ phase, but with unequal frequency in the partially ordered $R{\overline{3}} c$ phase. One position for the NO₃ group is rotated by 60° or 180° with respect to the other. The occupancy of the two orientations in the $R{\overline{3}} c$ phase is obtained from the occupancy factor, x, for the O1 site and gives rise to the order parameter, S = 2x ? 1, where S is 0 at T _c and 1 at 0 K. The NO₃ groups rotate in a rapid process from about 541 to T _c, where the a axis contracts. Using a modified Bragg–Williams model, a good fit was obtained for the normalized intensities (that is, normalized, NI^1/2) for the (113) and (211) reflections in $R{\overline{3}} c\hbox {\,NaNO}_{3},$ and indicates a second-order transition. Using the same model, a reasonable fit was obtained for the order parameter, S, and also supports a second-order transition.  相似文献   

Taxonomical and Biogeochemical Investigation of Elements in Holocene Mollusk Shells in the South and Southwestern Marmara Basin, Turkey     

Saday Azadoglu ALIYEV Ali SARI Bahadir KTEN Ankara University  Faculty of Engineering  Department of Geological Engineering  Tandogan  Ankara  Turkey 《《地质学报》英文版》2008,82(6)

Concentrations of some heavy metals and trace elements such as Cr,Ga,Ni,Zn,Mo,Cu, Pb,Yb,Y,Nb,Ti,Sr,Ba,Mn,Sc,Co,V,Zr,Fe,Al,W,Se,Bi,Sb,As,Cd in recent mollusk shells and factors affecting their distribution and deposits collected from various depths in the southern and southwestern parts of the Marmara Sea are investigated.The distribution of the elements in the shells is categorized into four groups.Of these,concentrations of 12 elements(As,Bi,Cd,Co,Ga,Mo,Nb, Sb,Se,Sc,W and Yb)are below zero [(0.053-0.79)×10~(-6)];concentrations of seven elements(Cr,Ni, Pb,V,Y,Zr and Cu)are(1.0-6.0)×10~(-6);concentrations of four elements(Ti,Mn,Ba and Zn)are 10- 20×10~(-6);and concentrations of five elements(Si,Al,Fe,Mg and Sr)are(47.44-268.11)×10~(-6).The taxonomic characteristics of the 29 elements were studied separately in mollusk shells such as Chamalea gallina(Linné),Pitar-rudis(Poll),Nassarius reticulatus(Linné),Venerupis senescens (Coocconi),Mytilus galloprovincialis(Lamarck),Mytilaster lineatus(Gemelin in Linné)and Chlamys glabra.It was found that,in mollusk taxonomy,the elements have unique values.In other words, element concentrations in various mollusk shells depend mainly on the taxonomic characteristics of mollusks.In various bionomic environments different element distributions of the same species are attributed to the different geochemical characters of the each environment.Data obtained in this study indicate that the organisms are the most active and deterministic factors of the environment.  相似文献   

Groundwater chemistry and occurrence of arsenic in the Meghna floodplain aquifer,southeastern Bangladesh     

Anwar Zahid  M. Qumrul Hassan  K.-D. Balke  Matthias Flegr  David W. Clark 《Environmental Geology》2008,54(6):1247-1260

Dissolved major ions and important heavy metals including total arsenic and iron were measured in groundwater from shallow (25–33 m) and deep (191–318 m) tube-wells in southeastern Bangladesh. These analyses are intended to help describe geochemical processes active in the aquifers and the source and release mechanism of arsenic in sediments for the Meghna Floodplain aquifer. The elevated Cl⁻ and higher proportions of Na⁺ relative to Ca²⁺, Mg²⁺, and K⁺ in groundwater suggest the influence by a source of Na⁺ and Cl⁻. Use of chemical fertilizers may cause higher concentrations of NH₄⁺ and PO₄³⁻ in shallow well samples. In general, most ions are positively correlated with Cl⁻, with Na⁺ showing an especially strong correlation with Cl⁻, indicating that these ions are derived from the same source of saline waters. The relationship between Cl⁻/HCO₃⁻ ratios and Cl⁻ also shows mixing of fresh groundwater and seawater. Concentrations of dissolved HCO₃⁻ reflect the degree of water–rock interaction in groundwater systems and integrated microbial degradation of organic matter. Mn and Fe-oxyhydroxides are prominent in the clayey subsurface sediment and well known to be strong adsorbents of heavy metals including arsenic. All five shallow well samples had high arsenic concentration that exceeded WHO recommended limit for drinking water. Very low concentrations of SO₄²⁻ and NO₃⁻ and high concentrations of dissolved Fe and PO₄³⁻ and NH₄⁺ ions support the reducing condition of subsurface aquifer. Arsenic concentrations demonstrate negative co-relation with the concentrations of SO₄²⁻ and NO₃⁻ but correlate weakly with Mo, Fe concentrations and positively with those of P, PO₄³⁻ and NH₄⁺ ions.  相似文献   

Hydrochemical and microbiological quality of groundwater in West Thrace Region of Turkey     

H. Murat Özler  Ali Aydın 《Environmental Geology》2008,54(2):355-363

The aim of this study was to do a preliminary assessment of the hydrochemical and microbial groundwater quality of the West Thrace region. Forty samples of groundwater collected from Edirne (Site 1) to Gelibolu (Site 2) were assessed for their suitability for human consumption. As³⁻ was non-detectable in all the groundwater and Zn²⁺, Pb²⁺, F⁻, Cu²⁺, NH₄⁺, Cn⁻ PO₄³⁻ and Cl⁻ were all below their respective European Union drinking water directive (EU-DWD) and Turkish food codex-drinking water directive (TFC-DWD). Maximum Acceptable Concentrations (MAC) Ni²⁺, Pb²⁺, Cd²⁺, Mg²⁺, Mn²⁺, and Ca²⁺ levels were detected in upper maximum acceptable concentrations 77.5, 42.5, 35.0, 50.0, 50.0, and 32.5% of the groundwater samples, respectively. However, in terms of Cr³⁺, Ni²⁺ and Pb²⁺, the differences between groundwaters of Sites 1 and 2 were significant (p < 0.05). Eight water samples (20%) had HPC exceeding the EU and Turkish water directive limit 20 CFU (Colony Forming Unit)/ml in drinking water and the maximum bacteria count recorded was 44 CFU/ml. Total coliforms, thermotolerant coliforms, E. coli, Enterococcus spp., Salmonella sp., Staphylococcus spp. and P. aeruginosa were detected in 25, 17.5, 15, 47.5, 15, 27.5, and 15% of the groundwater samples, respectively. Furthermore, heavy metals and trace elements were found after chemical analyzes in most samples. The pollution of groundwater come from a variety of sources, Meric and Ergene rivers, including land application of agricultural chemicals and organics wastes, infiltration of irrigation water, septic tanks, and infiltration of effluent from sewage treatment plants, pits, lagoons and ponds used storage.  相似文献   

Geochemistry,Petrography and Spectroscopy of Organic Matter of Clay‐Associated Kerogen of Ypresian Series: Gafsa‐Metlaoui Phosphatic Basin,Tunisia     

Mongi Felhi  Ali Tlili  Mabrouk Montacer 《Resource Geology》2008,58(4):428-436

This work presents geochemical characterization of isolated kerogen out of clay fraction using petrography studies, infrared absorption and solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy, with N‐alkane distributions of saturated hydrocarbon. Mineralogical study of clay mineral associations was carried out using X‐ray diffraction (XRD), on Ypresian phosphatic series from Gafsa‐Metlaoui basin, Tunisia. The XRD data indicate that smectite, palygorskite and sepiolite are the prevalent clay minerals in the selected samples. In this clay mineral association, the N‐alkane (m/z = 57) distribution indicates that the marine organic matter is plankton and bacterial in origin. The kerogens observed on transmitted light microscopy, however, appear to be totally amorphous organic matter, without any appearance of biological form. The orange gel‐like amorphous organic matter with distinct edges and homogenous texture is consistent with a high degree of aliphaticity. This material has relatively intense CH₂ and CH₃ infrared bands in ¹³C NMR peaks. This aliphatic character is related to bacterial origin. Brown amorphous organic matter with diffuse edges has a lower aliphatic character than the previous kerogen, deduced from relatively low CH₂ and CH₃ infrared and ¹³C NMR band intensities.  相似文献   

Modeling level change in Lake Urmia using hybrid artificial intelligence approaches     

Esbati  M.  Ahmadieh Khanesar  M.  Shahzadi  Ali 《Theoretical and Applied Climatology》2018,133(1-2):447-458

Theoretical and Applied Climatology - The investigation of water level fluctuations in lakes for protecting them regarding the importance of these water complexes in national and regional scales...  相似文献   

Moderate to heavy cold-weather precipitation occurrences in Tehran and the associated circulation types     

Sakineh?Khansalari  Tayeb?Raziei  Ali?Reza?MohebalhojehEmail author  Farhang?Ahmadi-Givi 《Theoretical and Applied Climatology》2018,131(3-4):985-1003

Large-scale atmospheric circulations associated with 133 moderate to heavy cold-weather precipitation events recorded at Mehrabad station in Tehran, Iran, during the period 1951–2013 are analysed. To this end, the performance of un-rotated, orthogonally rotated and obliquely rotated solutions of T-mode principal component analysis (PCA) is examined in classifying the atmospheric circulations into a few representative circulation types (CTs). The T-mode PCAs were applied to the 500-hPa geopotential height for the events in a domain from 10^°E to 70^°E and from 20^°N to 50^°N. The first six leading principal components were retained and then orthogonally and obliquely rotated using varimax and promax solutions, respectively. Statistical inter-comparison of the CTs obtained using the three solutions suggests that the obliquely rotated solution is the better choice for circulation classification in the present study. The six CTs obtained using the oblique rotation were then linked to the daily total precipitation and daily mean temperature variability at Tehran station as well as to the standardized anomalies of the daily total precipitation and mean daily temperature of a dense network of stations distributed across Iran. It is found that the CTs identified, though generally comparable in producing significant precipitation in Tehran, vary in their potential to bring cold weather and generate snowfall in Tehran specifically and in the country in general. While the first three CTs give rise to regional patterns of standardized precipitation anomalies centred in Tehran, the next three CTs leave a pronounced precipitation signature almost across the whole country. As regards the standardized temperature anomalies, with the exception of one CT that causes deep and widespread negative standardized anomalies over most parts of the country, the other CTs are characterized with a dipolar structure of a deep intrusion of cold weather to the west and prevailing warm weather to the east of the country.  相似文献   

Prevailing trends of climatic extremes across Indus-Delta of Sindh-Pakistan   总被引：1，自引：0，他引：1  

Farhat?AbbasEmail author  Iqra?Rehman  Muhammad?Adrees  Muhammad?Ibrahim  Farhan?Saleem  Shafaqat?Ali  Muhammad?Rizwan  Muhammad?Raza?Salik 《Theoretical and Applied Climatology》2018,131(3-4):1101-1117

This study examines the variability and change in the patterns of climatic extremes experienced in Indus-Delta of Sindh province of Pakistan, comprising regions of Karachi, Badin, Mohenjodaro, and Rohri. The homogenized daily minimum and maximum temperature and precipitation data for a 36-year period were used to calculate 13 and 11 indices of temperature and precipitation extremes with the help of RClimDex, a program written in the statistical software package R. A non-parametric Mann–Kendall test and Sen’s slope estimates were used to determine the statistical significance and magnitude of the calculated trend. Temperatures of summer days and tropical nights increased in the region with overall significant warming trends for monthly maximum temperature as well as for warm days and nights reflecting dry conditions in the study area. The warm extremes and nighttime temperature indices showed greater trends than cold extremes and daytime indices depicting an overall warming trends in the Delta. Historic decrease in the acreage of major crops and over 33% decrease in agriculture credit for Sindh are the indicators of adverse impacts of warmer and drier weather on Sindh agriculture. Trends reported for Karachi and Badin are expected to decrease rice cultivation, hatching of fisheries, and mangroves forest surrounding these cities. Increase in the prevailing temperature trends will lead to increasingly hotter and drier summers resulting to constraints on cotton, wheat, and rice yield in Rohri and Mohenjodaro areas due to increased crop water requirements that may be met with additional groundwater pumping; nonetheless, the depleted groundwater resources would have a direct impact on the region’s economy.  相似文献   

塔克拉玛干沙漠塔中与巴丹吉林沙漠拐子湖地表辐射特征对比   总被引：2，自引：1，他引：1  

杨阳  杨帆  买买提艾力&#  买买提依明  杨兴华  霍文  周成龙  何清  陈帅 《中国沙漠》2018,38(5):1068-1077

利用塔克拉玛干沙漠腹地塔中和巴丹吉林沙漠北缘拐子湖两个陆气通量监测站2013年2月-2014年1月地面辐射观测数据及相应气象资料,对比分析塔中和拐子湖两地的太阳辐射通量和地表反照率差异特征,同时也探究了两地太阳辐射通量和地表反照率与太阳高度角之间的关系。结果表明：（1）塔中和拐子湖两地各辐射通量均呈较为同步的季节变化特征;具有太阳辐射优势的塔中地区因沙尘天气的影响在部分月份地表总辐射小于拐子湖地区;拐子湖由于地表沙粒相对较粗且包含大量透明度较高的石英颗粒,地表反照率和反射辐射均大于塔中地区;两地各辐射通量月平均日变化均呈现出标准倒"U"型结构;（2）拐子湖较粗的地表沙粒导致沙尘天气过后不易形成浮尘,沙尘天气过后各辐射通量恢复至发生之前的状态较塔中地区迅速;（3）两地太阳高度角夏季最大,冬季最小,最大值均可达75°左右,最小值塔中和拐子湖地区分别为45°和40°;各辐射通量随着太阳高度角的升高而增加,地表反照率随之减小,但受多种因素影响各辐射通量最大值并未出现在太阳高度角最大的时候。  相似文献