A Hybrid Particle Swarm Optimization and Genetic Algorithm for Model Updating of A Pier-Type Structure Using Experimental Modal Analysis     

Mojtahedi  Alireza  Baybordi  Shahriar  Fathi  Amin  Yaghubzadeh  Aliakbar 《中国海洋工程》2020,34(5):697-707

China Ocean Engineering - Conventional design of pier structures is based on the assumption of fully rigid joints. In practice, the real connections are semi-rigid that cause changes in dynamic...  相似文献   

Support system suggestion based on back-analysis results case study: Babolak water conveyance tunnel     

Ehsan Dadashi  Kaveh Ahangari  Ali Noorzad  Alireza Arab 《Arabian Journal of Geosciences》2012,5(6):1297-1306

Determining in-situ soil or rock geotechnical properties is a difficult task for a design engineer. Back analysis is a helpful technique for evaluating soil property by considering and measuring the convergence of an underground opening. Back analysis was performed by matching numerical modeling results with the measured tunnel convergence. The main purpose of this study was to determine optimum rock mass properties using back analysis in order to suggest the best and most economical support system. Accordingly, the difference between measured and calculated convergence values was minimized by using an error function (objective function). In this paper, through the parameters obtained from back analysis, a support system based on a set consisting of shotcrete, wire mesh, and lattice girder was suggested for the Babolak water conveyance tunnel in Mazandaran, Iran. Therefore, the suggested design was based on decreasing shotcrete thickness from 25 to 20?cm and eliminating of rock bolts.  相似文献   

Scale,governance and the management of river basins: A case study from Central Iran     

François Molle  Alireza Mamanpoush 《Geoforum》2012,43(2):285-294

Aquatic socio-ecological systems show pervasive cross-scale interactions and problems of fit between ecosystems and institutions. Nested bio-hydrological processes within river basins are prone to third-party impacts, and equitable/sustainable management of water resources requires adequate governance patterns that both cover relevant scalar levels and handle cross-scale interactions. This paper provides the example of the Zayandeh Rud basin, in central Iran, and describes the historical evolution of water use at three different nested scales. It shows how the gradual overallocation of water resources (basin closure) and the manipulation of the hydrological cycle by the state and other actors have resulted in a constant spatial and social redistribution of water use and associated benefits and costs. State-centered modes of governance characterized by the priority to large-scale infrastructure, vested political and financial interests, lack of attention to local processes and hydrological interconnectedness, and the neglect of environmental degradation, must give way to forms of comanagement that better articulate the different levels of control and governance.  相似文献   

Biomonitoring of Ni and V Contamination Using Oysters (Saccostrea cucullata) at Lengeh Port,Persian Gulf,Iran     

Behnam Haidari  Alireza Riyahi Bakhtiari  Vhid Yavari  Ali Kazemi  Golshan Shirneshan 《洁净——土壤、空气、水》2013,41(2):166-173

Vanadium and nickel are two important indicators of oil pollution. Lengthy exposure to these elements causes serious harmful effects in human health, different harsh allergies being examples. The accumulation of two heavy metals (Ni and V) in sediment and the soft and hard tissues of Saccostrea cucullata were analyzed at three sampling sites along the coast of Lengeh Port, Persian Gulf. Results indicated at all the sampling sites; the Ni levels in soft tissues (STs) were higher than in the shells (SHs) and sediments, whereas the V levels were higher in the sediments. In addition, meaningful relationship (r = 0.65; p < 0.05) was observed across Ni levels in ST of S. cucullata and sediment, while for V concentrations a strong relationship (r = 0.83; p < 0.01) was found in SH of S. cucullata and sediment. This indicates that ST and SH of oyster can be considered as a biomonitoring agent for Ni and V levels, in coastal waters, respectively. The exposure of the consumer is compared directly to minimal risk level and provisional maximum tolerable daily intake. Result indicated that levels of Ni and V were within the safety limits for human consumption.  相似文献   

Coupling of solid deformation and pore pressure for undrained deformation—a discrete element method approach          下载免费PDF全文

Yifei Cui  Dave Chan  Alireza Nouri 《国际地质力学数值与分析法杂志》2017,41(18):1943-1961

This paper presents a numerical scheme for fluid‐particle coupling that uses the discrete element method by taking into consideration solid deformation and pore pressure generation. A new water particle element is introduced to calculate pore water pressure due to porosity changes. The water particle element has the same size and shape as the solid element and experiences the same amount of deformation. On the basis of the effective stress principle at the element contact, the total force is equal to the sum of the force transmitted through the solid element contact and the water particle force due to pore water pressure. Analytical solutions of traditional soil mechanics problems, such as isotropic compression and consolidated triaxial undrained test, are used to quantitatively validate the proposed model. The numerical results show good agreement between the model and the analytical solutions. The model therefore provides an effective method to calculate pore pressure in a porous medium in discrete modeling.  相似文献   

An alternative method for density variation modeling of the crust based on 3-D gravity inversion     

Alireza A. Ardalan  Davood Zamzam  Roohollah Karimi 《Journal of Applied Geophysics》2011,75(2):355-362

In this paper we are proposing an alternative method for determination of density variations of the crust from constrained inversion of the terrestrial gravity data. The main features of the method can be summarized as follows: (i) Constructing a band-pass filter to remove the long and short wavelength signals from the terrestrial gravity data. (ii) Using an iterative method for stabilization and solution of the inverse problem. The mentioned regularization method is first validated by simulated gravity data and next the methodology is used for development of a new regional density variation model of the crust in three layers based on real gravity data in geographical area of Iran. Application of the band-pass filter to the latter data resulted the residual gravitation variations in the range of − 300 to 50 (mGal) which next based on the iterative method resulted following ranges for residual densities: −120 to 40 (kg/m³) in first layer, −40 to 40 (kg/m³) in second layer, and − 40 to 40 (kg/m³) in third layer.  相似文献   

The Positive Effects of Nanoclay on the Hydraulic Conductivity of Compacted Kahrizak Clay Permeated With Landfill Leachate     

Negin Kananizadeh  Taghi Ebadi  Seyed Alireza Khoshniat  Seyed Ehsan Mousavirizi 《洁净——土壤、空气、水》2011,39(7):605-611

This study evaluates the effect of nanoclay on permeability, swelling, compressive strength, and cation exchange capacity of a compacted Kahrizak landfill clay liner. The results show that 4% nanoclay significantly reduces permeability (3 × 10^?9 to 7.74 × 10^?11 cm/s in neutral, 3.66 × 10^?9 to 7.9 × 10^?10 cm/s in acidic, and 3.25 × 10^?9 to 5.24 × 10^?10 cm/s in alkaline condition), and increases compressive strength (by 36.28%) and the percentage of swelling (from 16.67 to 41.82, 23.33 to 45.45, and 15 to 38.18 at pH 7, 4.8, and 9, respectively) compare to raw clay samples. Moreover, the results of cation exchange capacity tests show that adding 4% nanoclay to the Kahrizak clay, permeated with landfill leachate, helps the sample maintain its mono‐valent ions between layers and remains dispersed. The results of SEM and XRD analyses show that by adding nanoclay, nanoclay clusters are formed in the sample; as a result, the interlayer spacing decreases which makes it remain dispersed. XRF analyses also demonstrate that by adding nanoclay to the mixture, the permeability and therefore, the amount of heavy metals which can penetrate into it decreases. The results justify the construction of clay barriers with nanoclay in order to prevent leachate penetration, and consequently reduce the operation costs.  相似文献   

Improved vessel squat modeling for hydrographic and navigation applications using kinematic GNSS positioning     

Alireza A. Ardalan  Mohammad-Hadi Rezvani 《GPS Solutions》2014,18(2):253-262

The squat phenomenon, that is, the sinkage of a vessel due to its motion can affect the safety of navigation and reduce the accuracy of hydrographic bathymetry. Therefore, it is necessary to model and predict the squat of vessels as a function of cruise speed. We present a Global Navigation Satellite Systems–based squat modeling method for both hydrographic and navigation applications. For implementation of the proposed method, onboard GPS antennae configurations are offered to model bow squat for full-form ships such as supertankers or ore–bulk–oil carriers as well as stern squat for fine-form vessels such as passenger liners or container ships. In the proposed methodology, the onboard GPS observations are used to determine cruise ground speed, heave, attitude, and controlling the quality of kinematic positioning via fixed baselines. The vessel squat is computed from ellipsoidal height differences of the onboard antennae with respect to a reference state, after removal of all disturbing effects due to roll, pitch, heave, tide, vessel load, and geoidal height variations. The final products of the proposed approach are the analytical squat models usable for hydrographic and navigation applications. As the case study, the method is applied to a survey vessel in the offshore waters of Kish harbor. Numerical results indicate that the experimental precision of the derived analytical squat models is in the range of 0.003–0.028 m. The computed navigation squat of the test vessel at a speed of 12.64 knots is 30 % of the vessel draft and about twice its hydrographic squat. Although the field test was performed on a survey vessel, the method can be applied to any ship at any waterway. The proposed method can address the inevitable demand of reliable squat models for delicate hydrographic projects and high-speed marine traffic.  相似文献   

Link formation pattern during emergency response network dynamics     

Alireza Abbasi 《Natural Hazards》2014,71(3):1957-1969

This study aims to understand the mechanisms of emergency response network evolution by quantitatively examining the link formation pattern among participants involved in a real emergency collaboration network. This is achieved by identifying the participants’ characteristics which can affect forming new links over time. The result indicates the existence of cumulative advantage process, where highly connected participants gain more new links over time. It also reveals the structural position of participants involved in a response network, i.e. brokering position, affects their number of future links. Understanding the link formation pattern is important for understanding the mechanisms of network evolution which help predict more precisely the behavior of actors and dynamics of network structure over time. This can assist researchers, decision makers and practitioners to manage and support the collaboration of actors in their systems in order to reach their organizational goals. The overall findings can contribute further to the development of network organizational theory in different contexts especially disaster and emergency response management.  相似文献   

Predicting flow liquefaction,a constitutive model approach   总被引：1，自引：1，他引：0  

Alireza Najma  Manouchehr Latifi 《Acta Geotechnica》2017,12(4):793-808

In this paper, flow liquefaction criterion for contractive loose sands is analytically extracted based on the fundamental definition of flow liquefaction. In order to obtain the closed form of this criterion, Dafalias–Manzari constitutive model is employed; so the stress ratio at the onset of flow liquefaction is presented as a function of model parameters, state parameter and void ratio. Flow liquefaction line, as a graphical form of suggested criterion in stress space, shows that the peak points of undrained stress paths with same void ratios are not necessarily in a straight line. In order to validate the reliability of proposed flow liquefaction line to predict the onset of instability, it has been compared with the results of experimental tests performed on Toyoura, Ottawa and Leighton Buzzard sands. The verification results show that the present criterion can satisfactorily predict the onset of flow liquefaction in monotonic and cyclic undrained tests of saturated sands as well as the structural collapse in constant deviatoric stress tests of loose dry sands.  相似文献