The role of blocking system in heavy precipitation of Iran (a case study: southeast of Iran January 2008)     

Tayebeh Akbari Azirani  Ghasem Azizi  Ashraf Asadi  Mahmoud Davoudi 《Arabian Journal of Geosciences》2016,9(11):591

This article concerns the analysis of the heavy precipitation, which allows investigating the effect of the blocking system on the unusual precipitation and temperature occurrence in Iran. The days of January 2008 have been the coldest days during the history of recorded data in Iran. Variation of precipitation during January 2008 compared with long-term data (30 years) shows the maximum positive anomaly in the stations located in southeast of Iran. However, the precipitation in consecutive days, 14–15 and 15–16 of January, produce a more important proportion of the heavy precipitation in this region. In order to study the role of the blocking system related to heavy precipitation in January 2008, the position and movement of the atmospheric systems including cyclones, anticyclones, fronts, and wind fields have been analyzed by the use of synoptic maps by the environment to circulation approach. Consequently, the weather maps indicated that the blocking system over the north of the Caspian Sea has caused the relatively deep low trough on January 5, 7, 14, 15, and 16, 2008, while the thermal and moisture gradients in the warm section of air masses have produced heavy precipitation. As a result, wind field of low levels (850 hPa) provided remarkable moisture fed by the Arabian Sea, Oman Sea, and Persian Gulf in the study area. Furthermore, the speed of wavelength and the position of the blocking system associated with the heavy precipitation can be clearly identified.  相似文献   

Pore pressure assessment from well data and overpressure mechanism: Case study in Eastern Tunisia basins     

Samah Adouani  Riadh Ahmadi  Mahmoud Khlifi  Dhaou Akrout  Eric Mercier  Mabrouk Montacer 《Marine Georesources & Geotechnology》2020,38(7):830-843

Abstract

Independent and complementary methods were used for pore pressure assessment in the eastern Tunisian basins. Drilling data and surveys allow settling the pore pressure profile in these basins. The main used parameters are mud weights, formation pressure surveys, drilling parameters, well logs, fluids exchange with formation and borehole issues. In the eastern Tunisia platform, the pore pressure profiles show changes in overpressure magnitude in all the three dimensions of the basin (location and depth/stratigraphy). We highlighted two overpressure intervals form bottom to top: The late Cretaceous in the North-eastern part, and the Tertiary overpressure interval hosted in the Palaeocene to Miocene series. The structural analysis of overpressure location shows that the Tertiary interval is likely to have originated in a disequilibrium compaction in Cenozoic grabens. Pore pressure cross sections and maps confirm the link between active normal faults that segmented the basin to grabens and highs and pore pressure anomalous area. In the Senonian interval, we noted mature source-rocks that can explain the overpressure in the late Cretaceous interval. In addition, the recent to active compressive tectonics may have contributed to both pore pressure anomaly generations. The fluid overpressures characterization in the eastern Tunisian sedimentary basins helps in hydrocarbons exploration. Indeed, the overpressure interval in the reservoir levels stimulates and improves the production in the oilfields and contributes to hydrocarbon trapping. Moreover, the adequate prediction of pore pressure profile contributes to reduce drilling cost and enhance the drilling operations safety.  相似文献   

Physical properties of three short period close binaries:KIC 2715417,KIC 6050116 and KIC 6287172     

Mahmoud AbdelFattah NegmEldin  Ahmed Essam Elsayed  Shahinaz Mostafa Yousef 《天文和天体物理学研究(英文版)》2019,(2)

We present the physical parameters of three short period close binaries using data observed from the Kepler Space Telescope. All of these observations were taken in a single bandpass(which approximates the Johnson V-band). Our three systems are KIC 2715417, KIC 6050116 and KIC 6287172. The first system, KIC 2715417, is considered a semi-detached system with the secondary component filling its Roche lobe. The second system, KIC 6050116, is an overcontact system, while the third system, KIC 6287172, belongs to ellipsoidal variables as deduced from the Roche lobe geometry. For photometric analysis, we used the PHOEBE software package, which is based on the Wilson-Devinney code. Due to lack of spectroscopic data, the photometric mass ratios are determined from the analyses of light curves using the q-search method. The absolute parameters are determined using three different methods(Harmanec, Maceroni Van'tVeer and Gazeas Niarchos).  相似文献   

Mapping and classification of hydrological parameters from digital terrain data in the Musandam Peninsula,UAE and Oman     

Samy Ismail Elmahdy  Maged Mahmoud Marghany 《国际地球制图》2015,30(3):330-345

Groundwater exploration and modelling requires hydrological parameters and a large volume of hydrologic database. This study integrates remote sensing and geographic information system (GIS) to map and classify hydrological parameters indicates areas of groundwater recharge and discharge. Bivariate quadratic surfaces with moving window size of 5 × 5 were fitted to the digital elevation model and drainage basins, drainage network, topographic wetness index (TWI) and hydroforms were derived. The eight-direction algorithm (D8) that determines in which neighbouring pixel any water in a central pixel will flow naturally was used to delineate drainage basin and drainage network in the study area. The TWI was used to quantify the effect of local topography on hydrological processes and for modelling soil moisture. The results indicate the presence of intensive of stream network (1336 km²), wettest zones and accumulation zones (63.99 km²) within Wadi Bih, the UAE and Wadi Khasb, Oman, suggesting regional recharge.  相似文献   

Temporal trends of hydro-climatic variables and their relevance in water resource management     

Karim Solaimani  Mahmoud Habaibnejad  Abdollah Pirnia 《国际泥沙研究》2021,36(1):63-75

Identification of temporal changes in hydrological regimes of river basins is an important topic in contemporary hydrology because of the potential impacts of climate change on river flow regimes.For this purpose,long-term historical records of rainfall(P),runoff(Q)and other climatic factors were used to investigate hydrological variability and trends in the Tajan River Basin over the period 1969e1998.Actual evaporation(E),rainfall variability index(d),evaporation ratio(CE)and runoff ratio(CQ)were estimated from the available hydroclimatological records.Mann-Kendall trend analysis and nonparametric Sen's slope estimates were performed on the respective time series variables to detect monotonic trend direction and magnitude of change over time.Rainfall variability index showed that 1973 was the wettest year(δ=+2.039)while 1985 was the driest(δ=-1.584).Also,decades 69e78 and 89e98 were recognized as the wettest and driest decades respectively.The gradient of variation of climatological parameters showed that during the study period,all three parameters of rainfall,evaporation and runoff have decreased and the variations of rainfall and evaporation were significant at the 95%level.Investigation of hydrological changes due of dam construction(1999)showed that the amount and annual distribution of discharge were completely different pre and post-dam construction.Discharge decreased in high water months and increased in low water months to meet water supply demands,especially for agriculture.The relationship between temperature and rainfall trends is compared for three stations in Mazandaran Province(Gorgan,Babolsar and Ramsar)from 1956 to 2003 and nine other stations with different statistical periods of 19e36 years,relating trends to northern hemisphere and global trends.Decreases in temperature were accompanied by decreases in rainfall,and vice versa.These trends were not observed in northern hemisphere and world scales,where temperature increases are accompanied by decreases in rainfall.These variations of hydroclimatological parameters show undesirable water resources situations during the statistical periods if the trend continues severe water resource crises.  相似文献   

A modified genetic algorithm for precise determination the geometrical orbital elements of binary stars     

Abdel-Fattah Attia  Eman Mahmoud  H.I. Shahin  A.M. Osman 《New Astronomy》2009,14(3):285-293

The paper presents a modified genetic algorithm called adapted genetic algorithm with adjusting population size (AGA-POP) for precise determination the orbital elements of binary stars. The proposed approach is a simple, robust way that can be considered to be a new member in the class of self organizing genetic algorithms. The proposed AGA-POP is applied on the star η Bootis of MK type G0 IV to find a set of optimal orbital elements. This leads to obtain the best fitting of Keplerian and phase curves. The modified method is compared with other different methods such as standard genetic algorithm, adapted genetic algorithm (AGA) and least square methods. Simulation results show the effectiveness of using AGA-POP compared with other different classic genetic algorithms in reducing the computation time. Also, better performances have been achieved when using the proposed technique.  相似文献   

Kepler’s celestial two-body equation: a second attempt to establish a continuous and integrable solution via the <Emphasis Type="Italic">BPES</Emphasis>: Boubaker Polynomials Expansion Scheme     

Karem Boubaker Ben Mahmoud 《Astrophysics and Space Science》2010,326(1):77-81

The propagation of nonlinear waves in warm dusty plasmas with variable dust charge, two-temperature ions, and nonthermal electrons is studied. By using the reductive perturbation theory, the Kadomtsev–Petviashivili (KP) equation is derived. The energy of the soliton has been calculated. By using standard normal modes analysis a linear dispersion relation has been obtained. The effects of variable dust charge on the energy of the soliton and the angular frequency of the linear wave are also discussed. It is shown that the amplitude of solitary waves of the KP equation diverges at the critical values of plasma parameters. We derive solitons of a modified KP equation with finite amplitude in this situation.  相似文献   

On dust ion acoustic solitary waves in collisional dusty plasmas with ionization effect     

M. Shalaby  S. K. El-Labany  E. F. El-Shamy  M. A. Khaled 《Astrophysics and Space Science》2010,326(2):273-279

The propagation of solitary waves in an unmagnetized collisional dusty plasma consisting of a negatively charged dust fluid, positively charged ions, isothermal electrons, and background neutral particles is studied. The ionization, ion loss, ion–neutral, ion–dust, and dust–neutral collisions are considered. Applying a reductive perturbation theory, a damped Korteweg–de Vries (DKdV) equation is derived. On the other hand, at a critical phase velocity, the dynamics of solitary waves is governed by a damped modified Korteweg–de Vries (DMKdV) equation. The nonlinear properties of solitary waves in the two cases are discussed.  相似文献   

Vibration analysis of rectangular Mindlin plates on elastic foundations and vertically in contact with stationary fluid by the Ritz method     

Sh. Hosseini Hashemi  Mahmoud Karimi  H. Rokni Damavandi Taher 《Ocean Engineering》2010,37(2-3):174-185

In this study Free vibration analysis of vertical rectangular Mindlin plates resting on Pasternak elastic foundation and fully or partially in contact with fluid on their one side is investigated for different combinations of boundary conditions. The plate is assumed to be one of vertical rectangular walls of a container in contact with fluid. In order to analyze the interaction of the Mindlin plate with the elastic foundation and fluid system, three displacement components of the plate are expressed in the Ritz method by adopting a set of static Timoshenko beam functions satisfying geometric boundary conditions in a Cartesian co-ordinate system. The method of separation of variables and the method of Fourier series expansion is used to model fluid and to obtain the exact expression of the motion of fluid in the form of integral equations. The fluid domain is finite in depth and width but infinite in the length direction. To demonstrate the accuracy of the present solution, convergence study is first carried out and then a few comparison studies are carried out with the available data in the literature. Finally, natural frequencies of rectangular plates are presented in tabular and graphical forms for different fluid levels, foundation parameters, aspect ratios, thickness to width ratios and boundary conditions.  相似文献   

Effect of electrode contact impedance on A.C. electrical properties of a wet hematite sample     

Mohamed Mahmoud Gomaa  Perparim Alikaj 《Marine Geophysical Researches》2009,30(4):265-276

Electrode polarization is a major problem in the determination of dielectric properties of samples, particularly at low frequencies. Understanding of these interfacial phenomena is essential in order to measure correctly the electrical properties of a sample of interest. This paper presents a comparative study of the effect of electrode contact impedance on A.C. electrical properties of a partially and fully saturated hematitic sandstone sample. The electrical properties of the sample were first measured using stainless steel electrodes with high contact impedance, and measured again with a four terminal Cu–CuSO₄ electrode of low contact impedance. Complex impedance measurements at room temperature (~16°C) were performed in the frequency range from 1 Hz to 100 kHz. Measured electrical spectra vary strongly with the electrode type. The difference in the electrical properties between the two electrode types (stainless steel and Cu–CuSO₄) may be attributed to the surface contact impedance between the sample and the electrode. Experimental data indicate that the electrical properties vary strongly with water saturation. The dielectric constant decreases with frequency and increases with saturation up to a certain saturation limit then decreases. Charge transport can occur either through the bulk of the solid matrix (hematite or sand) or along the grain boundaries of aggregates (water). When soil minerals are exposed to water, exchangeable ions go into solution. Most of the ionic or covalent bonded rock forming minerals such as quartz, mica, and feldspars are nonconductors. When the surfaces of these minerals come into contact with liquid water, electrolytes are formed and ionic drift associated with the electrical field causes electrical conduction. The anomalous dielectric properties of partially saturated rocks can be interpreted using percolation theory. This theory predicts that when the conductive fraction (water) increases, clustering of conductive inclusions develops, and the thickness of insulating gaps between conductive clusters decreases, causing a large increment in the capacitance of the sample. Further increases in the conductive component causes the shunting of insulating capacitive gaps.  相似文献