检索结果-南通市图书馆

NUMERICAL SIMULATION OF SPHERICAL, CYLINDRICAL AND AXIAL BUBBLE CLOUDS COLLAPSE

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2012年第4期24卷 569-578页

作者： mahdi Miralam ebrahimi Reza SHAMS Mehrzad Faculty of Mechanical Engineering K.N.Toosi University of Technology Tehran Iran

The nonlinear dynamics of a spherical, cylindrical and axial cloud of cavitation bubbles were numerically simulated in order to learn more about the physical phenomena occurring in the cloud cavitation. The simulations employed the fully nonlinear continuum mixture equations coupled with the Gilmore equation for the dynamics of bubbles by considering the compressibility of liquid. A set of the Navier-Stokes equations was solved for the gas inside a spherical bubble, considering heat transfer through the gas inside the bubble and the liquid layer. The flow field around the cylindrical and axial cloud was obtained by solving the Navier-Stokes equations using a finite volume method and a dynamic layering mesh scheme. The calculated strength of shock wave in the liquid around the cloud was of the order of 1 ×10^6 Pa and the propagation of this shock wave lasted for l0 p.s. The conducted investigations illustrate that the shock wave propagates before the cloud has completely collapsed. A good agreement with experimental data was observed.

关键词： cloud cavitation shock wave spherical cloud cylindrical cloud axial cloud

Structural Control on the Salmas Geothermal Region, Northwest Iran, from Fractal Analysis and Paleostress Data

在线全文

学校读者我要写书评

暂无评论

Acta Geologica Sinica(English Edition) 2018年第5期92卷 1728-1738页

作者： mahdi BEHYARI Javad NOURALIEE Davar ebrahimi Department of Geology Faculty of Sciences Urmia University Renewable Energy Department Niroo Research Institute (NRI)

The Salmas geothermal field is located in NW Iran. Subduction of Neo-Tethys oceanic crust beneath the Iranian microcontinent caused to propagation of the magmatic-Arc. Fractures and faults in the convergent zone have created path-ways for the circulation of geothermal fluid. Fracture concentration in the Salmas geothermal field has been characterized using of the fractal method and creation of a fracture density map that shows the highest concentration in the central part of the study area. The permeability of fractures has been evaluated by analyzing their orientation in respect to the paleostress axes. Also, the fractal analyzing result indicates the maximum fractal dimension（1.96） is around the thermal spring outlet. Paleostress analyzing revealed that in the central part of the study area, σ1 axes orientation is S90°W/10° and the σ2 dip is near to the vertical in this stress field, where strike slip faults can be propagated. In the SE part near the recharge of the thermal springs, the σ3 plunge increases to 70？ and σ1 orientation is N15°E/20°, in this local tectonic regime thrust fault developed. Fractures have an important role in the circulation of fluid and the fractal dimension increases near the thermal springs in the Salmas geothermal field. Regarding the paleostress data fracture with N-S direction such as the F1 fault zone（parallel to the σ1 axes）, a suitable pathway for deep circulation of geothermal fluid flow has been created.

关键词： lineament extraction fractal method geothermal field paleostress Salmas NW Iran

An experimental investigation on the effect of grain size on oil-well sand production

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2012年第3期9卷 343-353页

作者： Vahidoddin Fattahpour mahdi Moosavi mahdi Mehranpour School of Mining Engineering the University of Tehran

Sand production in oil wells is closely related to the mechanical behavior and petrographical properties of sandstones reservoir. Grain size is one of the main parameters controlling the phenomenon, which is studied in this paper. Large-scale hollow cylindrical synthetic samples with the same rock strength but different grain sizes were tested by an experimental setup in the laboratory. Different external stresses and fluid flow rates were applied to the samples and produced sand was measured continuously. Results show two different trends between sanding stress level and grain size. For the samples with finer grain size （D50〈0.3 mm）, the required confining stress for different sanding levels decreased with an increase in the grain size and for the samples with the coarser grains （D50〉0.3 mm） the required confining stress for different sanding levels dramatically increased with an increase in the grain size. Those two different trends were discussed and explained. The first one was production of individual grains and the second was bigger chunks in the slab form. In samples with large grains, plastic zones around hole were changed to a completely loose zone including interlocked individual grains or cluster of grains. In these samples after breakage of these interlocked zones sand was produced in the form of individual grains and clusters. Contrary to this, for samples with smaller grain size, shear bands were formed around the plastified hole and sand was produced in the form of big chunks or slabs.

关键词： Sand production experimental tests grain size perforation size

Initial estimation of hydrate formation temperature of sweet natural gases based on new empirical correlation

在线全文

学校读者我要写书评

暂无评论

Journal of Natural Gas Chemistry 2012年第5期21卷 508-512页

作者： Mohammad mahdi Ghiasi Petroleum University of Technology Ahwaz Faculty of PetroleumPost Box:63431AhwazIran

Production,processing and transportation of natural gases can be significantly affected by clathrate *** the gas analysis is crucial to predict the right conditions for hydrate ***,Katz gas gravity method can be used for initial estimation of hydrate formation temperature （HFT） under the circumstances of indeterminate gas *** far several correlations have been proposed for gas gravity method,in which the most accurate and reliable one has belonged to Bahadori and *** main objective of this study is to present a simple and yet accurate correlation for fast prediction of sweet natural gases HFT based on the fit to Katz gravity *** reviewing the error analysis results,one can discover that the new proposed correlation has the best estimation capability among the widely accepted existing correlations within the investigated range.

关键词： natural gas hydrates hydrate formation temperature gas gravity method empirical correlation

Effective Controlled Islanding Method for Power Grids Solving a Sequence of Optimization Problems

在线全文

学校读者我要写书评

暂无评论

CSEE Journal of Power and Energy Systems 2022年第4期8卷 1004-1012页

作者： mahdi Amini Haidar Samet Ali Reza Seifi mahdi Davarpanah School of Electrical and Computer Engineering Shiraz UniversityShirazIran Department of Electrical Engineering Eindhoven University of TechnologyEindhoventhe Netherlands the Electrical and Computer Engineering School College of EngineeringUniversity of TehranTehranIran

Controlled islanding is an important approach to prevent instability in power *** this paper,a novel approach is proposed for power system separation,which consists of two steps:1)Finding multiple islanding scenarios;2)Choosing the best option to obtain the most desirable *** the first step,different islanding solutions are determined by a proposed hierarchical clustering *** this algorithm,which is based on a minimum active power flow disruption objective function,the generator coherency constraints are considered in the clustering *** the second step,the best separation scenario is chosen based on an arbitrary objective ***,in this paper,the amount of load shedding and the voltage profile deviation after separation are considered as the final criteria to select the best solution among available *** so doing,the degree of load importance is also taken into *** proposed two-step method is applied on an IEEE 9-bus test system and it is also evaluated on an IEEE 39-bus *** simulation results on the IEEE 39-bus grid and the comparative analysis with a state-of-the-art method confirm that the final islanding solution is more optimized based on the secondary criteria,which have not been addressed in the existing ***,the proposed method is computationally efficient and can be employed in real-scale power grids.

关键词： Graph theory hierarchical spectral clustering power system separation power system instability two-step approach.

Vanadium oxide nanotubes for selective catalytic reduction of NO_x with NH_3

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Chemical Engineering 2016年第7期24卷 914-919页

作者： Seyed mahdi Mousavi Faculty of Chemistry University of Kashan

Vanadium oxide （VOx） nanostructures, synthesized by hydrothermal treatment using dodecylamine as template, were evaluated for the selective catalytic reduction of NOx with ammonia （NH3-SCR）, The effect of solvent type in the reaction mixture （EtOH/（EtOH ＋ H20）） and time of hydrolysis was studied. The obtained materials were characterized by XRD, SEM, TEM and BET, The VOx nanorods （80-120 nm diameter and 1-4 μm length） were synthesized in 25 vol% EtOH/（EtOH ＋ H20） and the open-ended multiwalled VOx nanotube （50-100 nm inner diameter, 110-180 nm outer diameter and 0,5-2 pm length） synthesized in 50 vol% EtOH/（EtOH ＋ H20）. VOx nanotuhes performed the superior NH3-SCR activity under a gas hourly space velocity of 12,000 h-1 at low temperature of 250 ~C （NOx conversion of 893g ＆ N2 selectivity of 100%）, while most of the developed Vanadia base catalysts are active at high temperature （〉350 ℃）. The superior NH3-SCR activity ofVOx nanotubes at low tem- perature is related to nanocrystalline structure, special nanotube morphology as well as high specific surface area.

关键词： Hydrothermal Nanotubes NOx Pollution SCR

Uncertainty propagation in dynamics of composite plates: A semi-analytical non-sampling-based approach

在线全文

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2020年第6期14卷 1359-1371页

作者： mahdi FAKOOR Hadi PARVIZ Faculty of New Sciences and Technologies University o f TehranTehran 14395-1561Iran

In this study,the influences of spatially varying stochastic properties on free vibration analysis of composite plates were investigated via development of a new approach named the deterministic-stochastic Galerkin-based semi-analytical *** material properties including tensile modulus,shear modulus,and density of the plate were assumed to be spatially varying and *** fields with first-order Markov kernels were utilized to define the aforementioned material *** stochastic fields were decomposed via application of the K arhunen-Loeve theorem.A first-order shear deformation theory was assumed,following which the displacement field was defined using admissible trigonometric modes to derive the potential and kinetic *** stochastic equations of motion of the plate were obtained using the variational *** deterministic-stochastic Galerkin-based method was utilized to find the probability space of natural frequencies,and the corresponding mode shapes of the plate were determined using a polynomial chaos *** proposed method significantly reduced the size of the mathematical models of the structure,which is very useful for enhancing the computational efficiency of stochastic *** methodology was verifed using a stochastic finite element method and the available results in *** sensitivity of natural frequencies and corresponding mode shapes due to the uncertainty of material properties was investigated,and the results indicated that the higher-order modes are more sensitive to uncertainty propagation in spatially varying properties.

关键词： composite plate spatially varying stochastic properties Galerkin method polynomial chaos approach semi-analytical approach

Shear wall layout optimization of tall buildings using Quantum Charged System Search

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2020年第5期14卷 1131-1151页

作者： Siamak TALATAHARI mahdi RABIEI Department of Civil Engineering University of TabrizTabriz ***Iran Engineering Faculty Near East UniversityNicosia 99138Turkey

This paper presents a developed meta-heuristic algorithm to optimize the shear walls of tall reinforced concrete *** types of walls are considered as lateral resistant *** this paper,Quantum Charged System Search(QCSS)algorithm is presented as a new optimization method and used to improve the convergence capability of the original Charged System *** cost of tall building is taken as the objective *** the design of the lateral system plays a major role in the performance of the tall buildings,this paper proposes a unique computational technique that,unlike available works,focuses on structural efficiency or architectural *** technique considers both structural and architectural requirements such as minimum structural costs,torsional effects,flexural and shear resistance,lateral deflection,openings and *** robustness of the new algorithm is demonstrated by comparing the outcomes of the QCSS with those of its standard algorithm.

关键词： Quantum Charged System Search shear wall layout optimization tall buildings

Feasibility of crack free reinforced concrete bridge deck from materials composition perspective： a state of the art review

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of Structural and Civil Engineering 2015年第1期9卷 91-103页

作者： mahdi AREZOUMANDI Department of Civil Architectural and Environmental Engineering Missouri University of Science and Technology 212 ButlerCarlton Hall 1401 N. Pine Street Rolla MO 65409 USA

Early age cracking on bridge deck has been the subject of many studies for years. Cracking is a major concern because it leads to premature deterioration of structures. Millions of dollars spent to repair the cracked bridge decks each year. To design an appropriate mixture for crack free bridge deck, it is important to study previous researches. This paper presents a comprehensive literature review of the performance of different materials compositions as well as methods have been used to reduce and control bridge deck cracks. Different material compositions and methods are discussed in terms of their performances as well as advantages and disadvantages.

关键词： bridge deck crack fiber shrinkage shrinkage reducing admixture