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82.
Albert G. Ablaev Vladimir D. Khudik Marya G. Biryulina Sergei P. Pletnev Akbar A. Ashurov 《Geo-Marine Letters》1992,12(4):236-239
A sedimentary rock complex overlays the deep layers of oceanic crust in the Mussau Trench (and the conjugated underwater ridge) of the Caroline Basin. Paleontological analyses supported the previous idea of Oligocene-Quaternary deposits. In addition, Upper Cretaceous (Acila ex gr. demessa, Anisomyon sp., and others) and Eocene (Heterostegina sp., Discocyclina sp., and others) deposits have been found, suggesting shallow water environments in Late Cretaceous-Early Cenozoic time. Later on, regional submergence started. The complex of the deep-seated formations of the Mussau Trench is not younger than the Early Cretaceous oceanic crust of the Ontong-Java Plateau. 相似文献
83.
Hossein Mohammadi Vahab Toufigh Ali Akbar Golafshani Ali Arzeytoon 《Bulletin of Earthquake Engineering》2018,16(2):731-752
In this paper, an innovative seismic lateral force resisting system for tall buildings is introduced. In this system, a novel supplemental part, ribbed bracing system (RBSyst), is attached to Braced Tube System, creating a modified BTS. RBSyst is a supplemental part which is attached to the conventional bracing members to eliminate buckling problem. The behavior of RBSyst under tensile force is similar to that of the conventional braces. However, in compression, it prevents the braces from buckling by length reduction. In order to evaluate the efficiency of this new BTS system by performance-based assessment, two typical 40-story tall buildings with different story modules equipped with this proposed bracing system are modeled numerically. Then, the seismic behavior of these 3-dimensional models are evaluated by nonlinear time history analysis under maximum considered earthquakes and service-level earthquakes. The results of the analysis demonstrate that the performance of the tall buildings equipped with this new BTS system is within the acceptable limits under both service-level and maximum considered earthquake ground motions. Additionally, it is shown that RBSyst part can effectively enhance the seismic behavior of BTS systems. 相似文献
84.
Shohre Didari Shahrokh Zand-Parsa Ali Reza Sepaskhah Ali Akbar Kamgar-Haghighi Davar Khalili 《Theoretical and Applied Climatology》2012,108(1-2):159-171
In this research, suitability of different kriging and inverse distance weighted (IDW) methods in estimating occurrence date of frost was evaluated. Data included minimum daily air temperature values from 27 meteorological stations of Fars province in southern Iran from 18 to 45 years. Data ranges of 0 to ?1.5, ?1.5 to ?3 and below ?3°C were considered as mild, moderate and severe frost intensities, respectively. Starting with the first day of autumn, iso-occurrence days for the frost intensities and occurrence probabilities (25%, 50%, 75% and 90%) were estimated using ordinary kriging, cokriging, residual kriging type 1 (RK1), residual kriging type 2 (RK2), universal kriging and IDW methods. In these models, the errors of estimated frost intensities at different probabilities were lowest in the RK2 model, but lack of establishment of spatial structure due to long distance between stations caused the predictions not to be acceptable in some cases. In a proposed method (modified inverse distance weighted, MIDW), the trend between the first and last days of frost occurrence with earth elevation was removed, and the reminder values were estimated by (IDW) method. Although, the errors for estimated frost dates by MIDW and RK2 methods were the same, but the MIDW method did not have the spatial establishment shortcoming. Furthermore, the simplicity and practicality of the MIDW method makes it a reasonable selection. 相似文献
85.
Gholam Abbas Fallah-Ghalhary Majid Habibi-Nokhandan Mohammad Mousavi-Baygi Javad Khoshhal Akbar Shaemi Barzoki 《Theoretical and Applied Climatology》2010,101(1-2):217-233
This paper aims to study the relationship between large-scale synoptic patterns and rainfall in Khorasan Razavi Province. The adaptive neuro-fuzzy inference system (ANFIS) was used in this study to predict rainfall in the period between April and June in Khorasan Razavi Province. We first analyzed the relationship between average regional rainfall and the changes in synoptic patterns including sea-level pressure, sea-level pressure difference, sea-level temperature, temperature difference between sea level and the 1,000-hPa level, the temperature of the 700-hPa level, the thickness between the 500- and 1,000-hPa levels, the relative humidity at the 300-hPa level, and precipitable water content. We have examined the effect of synoptic patterns in these regions on the rainfall in the northeast region of Iran. Then, the ANFIS in the period 1970–1997 has been taught. Finally, we forecast the rainfall for the period 1998–2007. The results show that the ANFIS can predict the rainfall with reasonable accuracy. 相似文献
86.
A new data‐mining approach is presented for modelling of the stress–strain and volume change behaviour of unsaturated soils considering temperature effects. The proposed approach is based on the evolutionary polynomial regression (EPR), which unlike some other data‐mining techniques, generates a transparent and structured representation of the behaviour of systems directly from raw experimental (or field) data. The proposed methodology can operate on large quantities of data in order to capture nonlinear and complex relationships between contributing variables. The developed models allow the user to gain a clear insight into the behaviour of the system. Unsaturated triaxial test data from the literature were used for development and verification of EPR models. The developed models were also used (in a coupled manner) to produce the entire stress path of triaxial tests. Comparison of the EPR model predictions with the experimental data revealed the robustness and capability of the proposed methodology in capturing and reproducing the constitutive thermomechanical behaviour of unsaturated soils. More importantly, the capability of the developed models in accurately generalizing the predictions to unseen data cases was illustrated. The results of a sensitivity analysis showed that the models developed from data are able to capture and represent the physical aspects of the unsaturated soil behaviour accurately. The merits and advantages of the proposed methodology are also discussed. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
87.
Groundwater recharge estimation in arid hardrock‐alluvium aquifers using combined water‐table fluctuation and groundwater balance approaches 
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下载免费PDF全文 Azizallah Izady Osman A.E. Abdalla Ata Joodavi Akbar Karimi Mingjie Chen Andrew Tompson 《水文研究》2017,31(19):3437-3451
This paper proposes an approach to estimate groundwater recharge using an optimization‐based water‐table fluctuation method combined with a groundwater balance model in an arid hardrock‐alluvium region, located at the Oman–United Arab Emirates border. We introduce an “effective hardrock thickness” term to identify the percentage of the considered hardrock thickness in which effective groundwater flow takes place. The proposed method is based upon a Thiessen polygon zoning approach. The method includes subpolygons to represent specific geologic units and to enhance the confidence of the estimated groundwater recharge. Two linear and 1 nonlinear submodels were developed to evaluate the model components for the calibration (October 1996 to September 2008) and validation (October 2008 to September 2013) periods. Long‐term annual groundwater recharge from rainfall and return flow over the model domain are estimated as 24.62 and 5.71 Mm3, respectively, while the effective groundwater flow circulation is found to occur in the upper 7% of the known hardrock thickness (42 m), confirming conclusions of previous field studies. Considering a total difference in groundwater levels between eastern and western points of the study area of the order of 220 m and a 12‐year monthly calibration period, a weighted root mean squared error in predicted groundwater elevation of 2.75 m is considered quite reasonable for the study area characterized by remarkable geological and hydrogeological diversity. The proposed approach provides an efficient and robust method to estimate groundwater recharge in regions with a complex geological setting in which interaction between fractured and porous media cannot be easily assessed. 相似文献
88.
Safar Marofi Mohammad Mehdi Sohrabi Kurosh Mohammadi Ali Akbar Sabziparvar Hamid Zare Abyaneh 《Theoretical and Applied Climatology》2011,103(3-4):401-412
In this study, in order to detect probable trends and effects of climatic extreme events of precipitation and temperature as well as maximum relative humidity, dew point temperature, sunshine hours, and wind speed, 12 stations on the northern and southern coastlines of Iran were investigated from 1977 to 2007. For this purpose, 27 indices of precipitation and temperature, which are specified by the Expert Team of the World Meteorological Organization and Climate Variability and Predictability, were calculated by using RClimDex software. The Mann?CKendall method was also used to detect possible trends in the data time series. The results indicate that temperature indices are absolutely consistent with warming. Warm nights, hot days, and hot day and night frequencies increased, while cold spell and cool day and night frequencies declined. The minimum temperature experienced a considerable rise both in its maximum and minimum values. The minimum temperature had a higher increase than the maximum temperature. Therefore, diurnal temperature ranges have experienced dramatic declines. In the northern coastal sites, hot day frequency and hottest day temperature showed higher magnitudes than those of the southern sites as a result of the significant increase in the maximum sunshine hours in northern stations. This enhancement led to a considerable increase in the maximum wind speed. Consequently, relative humidity declined in the northern sites. Precipitation indices indicate few significant trends over the studied period. Temporal precipitation distribution was different from station to station. Three precipitation patterns were detected at individual stations, although an overall regional rainfall pattern was not detectable. On the whole, the results of this study emphasize that the water resources in the studied area are going to become problematic. 相似文献
89.
In this study, the interactive effects of four independent variables (initial chemical oxygen demand (COD) concentration, rotational velocity, temperature, and retention time) on the sulfide generation process in municipal wastewater were investigated. The process was modeled and analyzed with the variables in a series batch experiments. Experiments were conducted based on a central composite face‐centered design and analyzed using response surface methodology. The region of exploration for the process was taken as the area enclosed by COD (250 and 650 mg/L), rotational velocity (40 and 200 rpm), temperature (16 and 28°C), and retention time (2 and 40 h) boundaries. Eleven dependent parameters were either directly measured or calculated as response. The most influential variable on H2S (g) production was found to be retention time. The results showed that simultaneous increase in temperature and rotational velocity caused an increasing trend in the amount of H2S (g) emitted. Total sulfide was decreased by increasing rotational velocity due to more H2S (g) secretion resulting from increased mixing rate. The present study provides valuable information about interrelations of quality and process parameters at different values of the studied variables. 相似文献
90.
Modelling the mechanical behaviour of unsaturated soils has been the subject of many research works in the past few decades. A number of constitutive models have been developed to describe the complex behaviour of unsaturated soils. Despite the significant advances in the constitutive theories for unsaturated soils, none of the existing models can completely describe the various aspects of the real behaviour of unsaturated soils. In this paper, a new unified approach is presented, based on the integration of a neural network and a genetic algorithm, for the modelling of unsaturated soils. In the proposed approach, a genetic algorithm was used to optimise the weights of the neural network. A three-layer sequential architecture was chosen for the neural network. The network had eight input neurons, five neurons in the hidden layer and three neurons in the output layer. The eight input neurons represented the initial gravimetric water content, initial dry density, degree of saturation, net mean stress with respect to pore-air pressure, axial strain, deviatoric stress, soil suction and volumetric strain, and the three neurons in the output layer represented the deviatoric stress, suction and volumetric strain at the end of each increment. The network was trained and tested using a database that included results from a comprehensive set of triaxial tests on unsaturated soils from the literature. The predictions of the proposed model were compared with the experimental results. The comparison of the results indicates that the proposed approach was accurate and robust in representing the mechanical behaviour of unsaturated soils. 相似文献