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Investigations on pullout behavior of geogrid-granular trench using CANAsand constitutive model

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第4期9卷 726-740页

作者： Ali Noorzad ehsan Badakhshan Faculty of Civil Water and Environmental Engineering Shahid Beheshti University Tehran Iran

Experimental and numerical investigations have been carried out on behavior of pullout resistance of embedded circular plate with and without geogrid reinforcement layers in stabilized loose and dense sands using a granular *** parameters have been considered,such as the number of geogrid layers,embedment depth ratio,relative density of soil and height ratio of granular *** showed that,without granular trench,the single layer of geogrid was more effective in enhancing the pullout capacity compared to the multilayer of geogrid ***,increasing the soil density and embedment depth ratio led to an increase in the uplift *** soil was improved with the granular trench,the uplift force significantly *** granular trench improved the uplift load in dense sand more,as compared to the same symmetrical plate embedded in loose *** it was observed that,in geogrid-reinforced granular trench condition,the ultimate pullout resistance at failure increased as the number of geogrid layers increased up to the third layer,and the fifth layer had a negligible effect in comparison with the third layer of *** element analyses with hardening soil model for sand and CANAsand constitutive model for granular trench were conducted to investigate the failure mechanism and the associated rupture surfaces *** response of granular material in the proposed model is an elastoplastic constitutive model derived from the CANAsand model,which uses a non-associated flow rule along with the concept of the state boundary surface possessing a critical and a compact *** was observed that the granular trench might change the failure mechanism from deep plate to shallow plate as the failure surface can extend to the ground *** ultimate uplift capacity of anchor and the variation of surface deformation indicated a close agreement between the experiment and numerical model.

关键词： Anchor Pullout test Geogrid Granular trench CANAsand constitutive model

Numerical Investigation of Penetration in Ceramic/Aluminum Targets Using Smoothed Particle Hydrodynamics Method and Presenting a Modified Analytical Model

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Computer Modeling in Engineering & Sciences 2017年第3期113卷 295-323页

作者： ehsan Hedayati Mohammad Vahedi Department of Mechanical Engineering College of Technical EngineeringSaveh BranchIslamic Azad UniversitySavehIran Department of Mechanical Engineering College of Technical EngineeringSaveh BranchIslamic Azad UniversitySavehIran.

Radius of ceramic cone can largely contribute into final solution of analytic models of penetration into ceramic/metal *** the present research,a modified model based on radius of ceramic cone was presented for ceramic/aluminum *** order to investigate and evaluate accuracy of the presented analytic model,obtained results were compared against the results of the Florence’s analytic model and also against numerical modeling *** phenomenon of impact onto ceramic/aluminum composites were modeled using smoothed particle hydrodynamics(SPH)implemented utilizing ABAQUS *** indicated that,with increasing initial velocity and ceramic thickness and decreasing support layer thickness,the radius of ceramic cone decreases;this ends up increasing residual velocity of the projectile and penetration time and extending the area across which the pressure is *** findings indicate enhanced levels of target energy absorption and the required energy for bending and tensioning the *** such,it can be observed that,at the same thickness and areal density,the ceramic target has its efficiency enhanced with increasing ceramic thickness and decreasing the support layer ***,the results revealed that the associated data with SPH confirm the modified analytic model at higher accuracy than the Florence’s analytic model.

关键词： Smoothed particle hydrodynamics Florence’s analytic model modified analytical model energy absorption ABAQUS penetration

Evaluation of the “fishing down marine food web” process in the north-west of Persian Gulf(Khuzestan Province) during the period of 2002–2011

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Acta Oceanologica Sinica 2015年第10期34卷 103-110页

作者： MASHJOOR Sakineh KAMRANI ehsan Department of Marine and Fisheries Biology Hormozgan University

The worldwide increase in commercial fisheries and its impact on ecosystems as well as inefficient fishery management have led to overfishing and frequent breakdown of traditional fish stocks. In this context, an analysis of Khuzestan inshore fisheries data covering the years 2002-2011, was conducted in reliance on testing for occurrence of the fishing down marine food webs （FDMFW） phenomenon in the North of Persian Gulf Large Marine Ecosystem （LME）. In this study, the mean trophic level （mTL） and the fishing-in-balance （FIB）-index of Khuzestan landings during this period of time were estimated using the trophic level of 47 fishery resources. Increase in total landings （I1） was observed, which explained the high fishing yield in major fishery resources （especially demersal）. Moreover, the moderates decreasing trend in mTL per decade, and the increasing trend in FIB-index were observed. The status of fishery resources in Khuzestan inshore waters （under exploited but not overexploited）, the rise in Y, FIB and slightly drop in mTL can be considered as indirect indicators of the fishing impacts on the trophic structure of marine communities. Based on this result, probability occurrence of FDMFW process in Khuzestan inshore waters is low to some extent. However, we suggest that the goal of management programs in Khuzestan inshore waters should prevent the continuance of this trend in the long-term using an ecosystem-based approach.

关键词： mean trophic level fishing-in-balance index fishing down marine food webs Khuzestan Persian Gulf

An accurate empirical correlation for predicting natural gas compressibility factors

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Journal of Natural Gas Chemistry 2012年第2期21卷 184-188页

作者： ehsan Sanjari Ebrahim Nemati Lay Department of Chemical Engineering Faculty of Engineering University of Kashan

The compressibility factor of natural gas is an important parameter in many gas and petroleum engineering calculations. This study presents a new empirical model for quick calculation of natural gas compressibility factors. The model was derived from 5844 experimental data of compressibility factors for a range of pseudo reduced pressures from 0.01 to 15 and pseudo reduced temperatures from 1 to 3. The accuracy of the new empirical correlation has been compared with commonly used existing methods. The comparison indicates the superiority of the new empirical model over the other methods used to calculate compressibility factor of natural gas with average absolute relative deviation percent （AARD%） of 0.6535.

关键词： natural gas compressibility factor correlation empirical model equation of state

Thermal Decomposition Kinetics of Ethane Halides and Derivatives(C_2H_(6-n)X_n(n = 1～3);X = F,Cl,Br):DFT Study and NBO Analysis

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Chinese Journal of Structural Chemistry 2011年第6期30卷 858-866页

作者： Abolfazl Shiroudi ehsan Zahedi Chemistry Department Islamic Azad UniversityShahrood Branch

A theoretical study of the thermal decomposition kinetics of ethane halides（C2H6-nXn（n = 1～3）;X = F,Cl,Br） has been carried out at the B3LYP/6-31＋＋G＊＊ and B3PW91/631＋＋G＊＊ levels of *** these methods and comparison of activation parameters with available experimental values,the B3PW91/6-31＋＋G＊＊ method is in good agreement with the experimental *** analysis of bond order and natural bond orbital（NBO） charges,bond indexes,and synchronicity parameters suggest the elimination of HX in reactions 1～9（HF：compounds 1～3,HCl：compounds 4～6,and HBr：compounds 7～9） occur through a concerted and slightly asynchronous four-membered cyclic transition state type of mechanism.

关键词： elimination ab initio molecular modeling decomposition ethane halides NBO

DFT Calculations and NBO Analysis of 2-Chloroethylethyldichlorosilane Unimolecular Elimination Kinetics in the Gas Phase

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Chinese Journal of Structural Chemistry 2012年第5期31卷 625-634页

作者： Abolfazl Shiroudi ehsan Zahedi Chemistry Department Shahrood BranchIslamic Azad UniversityShahroodIran

Ab initio molecular orbital calculations have been used to investigate the thermal decomposition kinetics of 2-chloroethylethyldichlorosilane at the B3LYP/6-311＋G^＊＊,B3PW91/6-311＋G^＊＊,and MPW1PW91/6-311＋G^＊＊ levels of *** these methods,the results（activation parameters） obtained using the B3LYP/6-311＋G＊＊ level are in good agreement with the available experimental *** calculated data imply that in the unimolecular β-elimination reactions of the studied compound in the gas phase,the polarization of C（1）-Cl（3） and C（1）-H（4） bonds in the sense of C（1）^δ＋-Cl（3）^δ-and C（1）^δ＋-H（4）^δ-,respectively,is a determining factor in the gas phase elimination reactions 1,2 and *** of bond order,natural bond orbital charges,bond indexes,synchro-nicity parameters,and IRC calculations suggest the elimination of 2-chloroethylethyldichlorosilane via reactions 1～3 can be described as concerted and slightly *** transition state structures of these reactions are a four-membered cyclic structure.

关键词： theoretical chemistry molecular modeling thermal decomposition DFT NBO analysis IRC 2-chloroethylethyldichlorosilane

Neutronic design investigation of a liquid injection-based second shutdown system for a typical research reactor using MCNPX

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Nuclear Science and Techniques 2018年第3期29卷 51-60页

作者： ehsan Boustani Mostafa Hassanzadeh Nuclear Science and Technology Research Institute (NSTRI) Reactor and Nuclear Safety School

Safety systems, built on state-of-the-art technology, are essential for achieving acceptable levels of plant safety to minimize hazards to the reactor and the general public. The second shutdown system(SSS) as an engineered safety feature and a part of the reactor protection system(RPS) is a means for rapidly shutting down a nuclear reactor, keeping it in a subcritical state and serving as a backup to the first shutdown system(FSS). In this research, one SSS with two types of optimum chamber designs is proposed that take into account the main current characteristic features of the Tehran research reactor with improvements over earlier designs. They are based on a liquid neutron absorber injection that is preferably different, diverse, and independent from the FSS based on the rod drop mechanism. The major design characteristics of this SSS with two different chambers were investigated using MCNPX 2.6.0 code. The performed calculations showed that the designed SSS is a reliable shutdown system, assuring an appropriate shutdown margin and injection time, with no significant effects on the effective delayed neutron fraction while causing minimal variations to the core structure. Further, the reasonable financial cost and the prolongation of the operation cycle are additional advantages of this design.

关键词： Tehran research reactor Second shutdown system Nuclear safety Design criteria MCNPX code

A global comparison of V_(p),V_(s),and V_(p)/V_(s) structures of the mantle lithosphere beneath major cratons

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Science China Earth Sciences 2023年第3期66卷 492-504页

作者： ehsan BARZGAR Fenglin NIU Shunping PEI State Key Laboratory of Petroleum Resources and Prospecting Unconventional Petroleum Research InstituteChina University of PetroleumBeijing 102249China Department of Earth Environmental and Planetary SciencesRice UniversityHouston 77005TexasUSA State Key Laboratory of Tibetan Plateau Earth System and Resources Environment Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China

Cratons formed due to the specific melting regime of the primitive mantle with elevated mantle temperature during ***,each craton has undergone a distinct evolution history,and some have lost their *** investigate to what degree cratons in comparison with one another have been modified from their analogous initial form,we employed Sn-Pn differential(PSn) traveltimes to derive Vp/Vsratio,which is thought to be related to Mg# of the *** assessed Pn,Sn,and PSn data using three datasets based on epicentral distance:(1) 2°–12°,(2) 2°–7°,and(3) 7°–12°.The results suggest that most cratons show comparable seismic properties with high velocities and low Vp/Vsratio,implying a highly depleted uppermost mantle that resembles the original residue from the partial melt extraction of the primitive mantle during the ***,the Eastern North China Craton(ENCC) displays the lowest P-and S-wave velocities,and noticeable high Vp/Vsratios in all datasets,implying a systematic difference with other *** observation suggests a scenario of total removal of the depleted Archean mantle lithosphere beneath the *** contrast,the Ordos Block located at the western part of the North China Craton(WNCC) shows velocities and Vp/Vsratio comparable with those of the typical cratons,suggesting that it has still maintained its Archean mantle *** Wyoming Craton has a high Vp/Vsratio similar to that of the ENCC and a high Pwave velocity comparable to that of the typical *** features suggest that the Archean mantle lithosphere has been significantly modified rather than totally removed and replaced by a younger fertile *** Indian Craton presents a low Vp/Vsratio and comparatively high velocities at shallow parts of the mantle lithosphere but a high Vp/Vsratio at deeper parts similar to that of the ENCC,suggesting a partial modification of the Indian Craton at deeper parts.

关键词： Craton Craton modification Mantle lithosphere North China Craton Wyoming Craton Indian Craton Vp/Vs ratio Seismic velocity

Nonlinear integral resonant controller for vibration reduction in nonlinear systems

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Acta Mechanica Sinica 2016年第5期32卷 925-934页

作者： ehsan Omidi S.Nima Mahmoodi Nonlinear Intelligent Structures Laboratory Department of Mechanical Engineering The University of Alabama

A new nonlinear integral resonant controller（NIRC） is introduced in this paper to suppress vibration in nonlinear oscillatory smart structures. The NIRC consists of a first-order resonant integrator that provides additional damping in a closed-loop system response to reduce highamplitude nonlinear vibration around the fundamental resonance frequency. The method of multiple scales is used to obtain an approximate solution for the closed-loop *** closed-loop system stability is investigated using the resulting modulation equation. Finally, the effects of different control system parameters are illustrated and an approximate solution response is verified via numerical simulation *** advantages and disadvantages of the proposed controller are presented and extensively discussed in the results. The controlled system via the NIRC shows no high-amplitude peaks in the neighboring frequencies of the resonant mode,unlike conventional second-order compensation *** makes the NIRC controlled system robust to excitation frequency variations.

关键词： Active vibration control Cantilever Highamplitude oscillation Method of multiple scales Nonlinear vibration Piezoelectric actuator Smart structure