The thermal state of the Venusian mantle     

Jafar Arkani-Hamed 《Earth, Moon, and Planets》1991,55(1):51-68

Assuming that the surface topography of the Ovda and Thetis plateaus, and that of the saddle region between Thetis and Atla plateaus, is due to surface subsidence of oceanic-type thermal boundary layers, we calculated the temperature at 200 km beneath the plateaus to be about 1600 C, and that beneath the saddle region to be about 1400–1500 C. The total subsidence of Ovda plateau in the last 3/4 of its existence, i.e. between 200 km and 800 km off the postulated ridge axis, suggests that the plateau is probably a young feature, less than 40 m.y. old. The spreading plate models imply a half-spreading rate of 2.3–5.3 cm/yr for the plateaus and 2–2.8 cm/yr for the saddle region.  相似文献   

Pre-Peak and Post-Peak Rock Strain Characteristics During Uniaxial Compression by 3D Digital Image Correlation     

H. Munoz  A. Taheri  E. K. Chanda 《Rock Mechanics and Rock Engineering》2016,49(7):2541-2554

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Numerical ANFIS-Based Formulation for Prediction of the Ultimate Axial Load Bearing Capacity of Piles Through CPT Data     

Behnam Ghorbani  Ehsan Sadrossadat  Jafar Bolouri Bazaz  Parisa Rahimzadeh Oskooei 《Geotechnical and Geological Engineering》2018,36(4):2057-2076

This study explores the potential of adaptive neuro-fuzzy inference systems (ANFIS) for prediction of the ultimate axial load bearing capacity of piles (P_u) using cone penetration test (CPT) data. In this regard, a reliable previously published database composed of 108 datasets was selected to develop ANFIS models. The collected database contains information regarding pile geometry, material, installation, full-scale static pile load test and CPT results for each sample. Reviewing the literature, several common and uncommon variables have been considered for direct or indirect estimation of P_u based on static pile load test, cone penetration test data or other in situ or laboratory testing methods. In present study, the pile shaft and tip area, the average cone tip resistance along the embedded length of the pile, the average cone tip resistance over influence zone and the average sleeve friction along the embedded length of the pile which are obtained from CPT data are considered as independent input variables where the output variable is P_u for the ANFIS model development. Besides, a notable criticism about ANFIS as a prediction tool is that it does not provide practical prediction equations. To tackle this issue, the obtained optimal ANFIS model is represented as a tractable equation which can be used via spread sheet software or hand calculations to provide precise predictions of P_u with the calculated correlation coefficient of 0.96 between predicted and experimental values for all of the data in this study. Considering several criteria, it is represented that the proposed model is able to estimate the output with a high degree of accuracy as compared to those results obtained by some direct CPT-based methods in the literature. Furthermore, in order to assess the capability of the proposed model from geotechnical engineering viewpoints, sensitivity and parametric analyses are done.  相似文献   

Effect of Drain Pipes on Uplift Force and Exit Hydraulic Gradient and the Design of Gravity Dams Using the Finite Element Method     

Aghdam  Ali Taheri  Salmasi  Farzin  Abraham  John  Arvanaghi  Hadi 《Geotechnical and Geological Engineering》2021,39(5):3383-3399

Geotechnical and Geological Engineering - The effects of diameter and location of drain pipes on the uplift force and exit hydraulic gradient for a gravity dam are investigated. A numerical model...  相似文献   

Stress differences in the moon as an evidence for a cold moon     

Jafar Arkani-Hamed 《Earth, Moon, and Planets》1973,6(1-2):135-163

Assuming that the lateral variations of density in the lunar crust, the crustal density anomalies, are responsible for the lateral undulations of the lunar gravitational potential, we compute these anomalies for four different lunar models, which include an entirely solid Moon and three different solid lunar models with partially molten layers located within 600 km depth. The stress differences created by the density anomalies are determined for these models. It is found that, since the formation of the mascons, the entirely solid lunar model should have supported stress differences of the order of 70 bars while in the case of the other models, the solid layer overlying the partially molten one should have supported stress differences of more than 100 bars. The high stress differences associated with the partially molten models lead us to conclude that these models are not proper ones, and thus the Moon has always been solid since the formation of the mascons. Lunar Science Institute Contribution No. 97. The research in this paper was done while the author was a Visiting Scientist at the Lunar Science Institute, which is operated by the Universities Space Research Association under Contract No. NSR 09-051-001 with the National Aeronautics and Space Administration.  相似文献   

Sedimentary facies and sequence stratigraphy of the Asmari Formation at Chaman-Bolbol, Zagros Basin, Iran   总被引：1，自引：0，他引：1  

Mahnaz Amirshahkarami  Hossein Vaziri-Moghaddam  Azizolah Taheri 《Journal of Asian Earth Sciences》2007,29(5-6):947-959

The Oligocene–Miocene Asmari Formation of the Zagros Basin is a thick sequence of shallow water carbonate. In the study area, it is subdivided into 14 microfacies that are distinguished on the basis of their depositional textures, petrographic analysis and fauna. Based on the paleoecology and lithology, four distinct depositional settings can be recognized: tidal flat, lagoon, barrier, and open marine. The Asmari Formation represents sedimentation on a carbonate ramp. In the inner ramp, the most abundant lithofacies are medium grained wackestone–packstone with imperforated foraminifera. The middle ramp is represented by packstone–grainstone to floatstone with a diverse assemblage of larger foraminifera with perforate wall, red algae, bryozoa, and echinoids. The outer ramp is dominated by argillaceous wackestone characterized by planktonic foraminifera and large and flat nummulitidae and lepidocyclinidae. Three third-order depositional sequences are recognized from deepening and shallowing trends in the depositional facies, changes in cycle stacking patterns, and sequence boundary features.  相似文献   

Parkfield,California, Earthquake of June 1966: Interpretation of the strong motion records     

Jafar Shoja-Taheri 《地震工程与结构动力学》1980,8(6):527-544

A detailed seismological interpretation of the strong motion records was attempted for the 1966 Parkfield earthquake, California. Velocity and displacement traces integrated from the corresponding recorded accelerograms were found most valuable in studying the earthquake mechanism and wave forms. A double-couple right-lateral strike — slip mechanism (along the San Andreas fault) is consistent with the recorded direct S-waves originating from the hypocentre. High energy arrivals observed on the velocity traces are interpreted as S-waves (‘stopping phases’) that originated at the termination of the rupture towards the south-east of the San Andreas fault. A double-couple left-lateral strike–slip mechanism is suggested as the cause of this rupture termination. From particle velocity diagrams of the stopping phases in the horizontal plane, the rupture length was found to be between 20 and 28 km. Corresponding rupture velocities are estimated to be 2·5 ± 0·1 and 3·1 ± 0·5 km/s. The inference from the strong motion records is that Love waves were more excited at the south-western than the north-eastern side of the fault, whereas the Rayleigh waves were more energetic at the north-eastern than the south-western side of the fault.  相似文献   

New developments with design and construction of a thermal/vacuum qualified photogrammetric system     

Jafar Amiri Parian  Alessandro Cozzani  Matteo Appolloni  Gianluca Casarosa 《ISPRS Journal of Photogrammetry and Remote Sensing》2009,64(3):317-327

In the frame of the development of a photogrammetric system to be used in thermal/vacuum chambers at the European Space Research and Technology Centre (ESTEC) of European Space Agency (ESA) and other sites across Europe, the design of a network using micro-cameras was specified by ESA-ESTEC. A thermal/vacuum qualified photogrammetric system, which is able to work and acquire images in vacuum and at cryo-temperatures, was constructed by ESA-ESTEC Test Centre Division. The current system uses four space qualified one-mega pixel cameras and is able to measure large space structures in vacuum and at temperatures down to ?170 ^°C with a global accuracy better than 1 part per 100,000 in object space. Several tests aiming at the qualification of the sensors and system in terms of operation and accuracy have been carried out. Special measures have been developed and special attention has been taken into account specifically for the first application of the photogrammetric system. It is to verify the ESA’s Herschel Telescope Flight Model alignment positioning.  相似文献   

PROMETHEE II and fuzzy AHP: an enhanced GIS-based landslide susceptibility mapping   总被引：2，自引：0，他引：2  

Majid Shadman Roodposhti  Saeed Rahimi  Mansour Jafar Beglou 《Natural Hazards》2014,73(1):77-95

This paper describes the application of a well-known multi-criteria decision-making technique, called preference ranking organization method for enrichment evaluation (PROMETHEE II), in combination with fuzzy analytical hierarchy process (FAHP), as a weighting technique to explore landslide susceptibility mapping (LSM). To this end, eight landslide-related geodata layers of the Minoo Dasht located in the Gorgan province of Iran, involving slope, aspect, distance to river, drainage density, distance to fault, mean annual rainfall, distance to road and lithology have been integrated using the PROMETHEE II enhanced by FAHP technique. Afterward, the receiver operating characteristics (ROC) curves for the proposed LSM were drawn using an inventory of landslides containing 83 recent and historic landslide points, and the area under curve = 0.752 value was calculated accordingly. Additionally, to further verify the practicality of such susceptibility map, it was also evaluated against the landslide inventory using simple overlay. The outcome was that about 11 % of the occurred landslide points fall into the very high susceptibility class of the LSM, but approximately 52 % of them indeed fall into the high and very high susceptibility zones together. Also, it resulted that no recorded landslide occurred in the zone of very low susceptibility. According to the results of the ROC curves analysis and simple overlay evaluation, the produced map has exhibited good performance.  相似文献   

Impact demagnetization of the martian crust     

Pundit Surdas Mohit  Jafar Arkani-Hamed 《Icarus》2004,168(2):305-317

The lack of magnetic anomalies within the giant martian impact basins, Hellas, Argyre, and Isidis suggests that the impacts demagnetized the crust. Our analysis of the magnetic anomaly intensity shows that the interior parts of the basins are completely demagnetized, while the outer parts and surroundings are partially demagnetized. We investigate the shock pressure and impact heating resulting from the impacts. The crust has been completely demagnetized within ∼0.8 basin radius by a combination of thermal and shock effects, and the surroundings have been partially demagnetized by shock to a distance of at least 1.4 radii. We also investigate magnetic signatures of intermediate-size craters. From the pressures generated by both the large and intermediate-sized impacts, we conclude that the remanent magnetization is carried at least in part by high coercivity rocks. Since the crust beneath the basins does not appear to have been remagnetized as it cooled following the impacts, we conclude that the martian core dynamo was inactive or very weak for at least 100 Myr following the Hellas impact.  相似文献