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IEEE/CAA Journal of Automatica Sinica 2020年第3期7卷 752-763页

作者： Younes Solgi alireza fatehi Ala Shariati Advanced Process Automation and Control Research Group Industrial Control Center of ExcellenceFaculty of Electrical EngineeringK.N.Toosi University of TechnologyTehran 16317-14191Iran IEEE

In this paper, a novel non-monotonic Lyapunov-Krasovskii functional approach is proposed to deal with the stability analysis and stabilization problem of linear discrete time-delay systems. This technique is utilized to relax the monotonic requirement of the Lyapunov-Krasovskii theorem. In this regard, the Lyapunov-Krasovskii functional is allowed to increase in a few steps, while being forced to be overall decreasing. As a result, it relays on a larger class of Lyapunov-Krasovskii functionals to provide stability of a state-delay system. To this end, using the non-monotonic Lyapunov-Krasovskii theorem, new sufficient conditions are derived regarding linear matrix inequalities(LMIs)to study the global asymptotic stability of state-delay ***, new stabilization conditions are also proposed for time-delay systems in this article. Both simulation and experimental results on a p H neutralizing process are provided to demonstrate the efficacy of the proposed method.

关键词： Linear matrix inequality(LMI) non-monotonic Lyapunov-Krasovskii functional(NMLKF) pH neutralization plant stabilization state-delay system time-delay system

Novel Non-monotonic Lyapunov-Krasovskii Based Stability Analysis and Stabilization of Discrete State-delay System

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International Journal of Automation and computing 2020年第5期17卷 713-732页

作者： Younes Solgi alireza fatehi Ala Shariati APAC Research Group Industrial Control Center of ExcellenceFaculty of Electrical EngineeringK.N.Toosi University of TechnologyTehran ***Iran

This paper proposes a novel less-conservative non-monotonic Lyapunov-Krasovskii stability approach for stability analysis of discrete time-delay *** this method,monotonically decreasing requirements of the Lyapunov-Krasovskii method are replaced with non-monotonic *** Lyapunov-Krasovskii functional is allowed to increase in some steps,but the overall trend should be *** model of practical systems used for stability analysis usually contain ***,firstly a non-monotonic stability condition is derived for certain discrete time-delay systems,then robust non-monotonic stability conditions are proposed for uncertain ***,a novel stabilization algorithm is derived based on the introduced non-monotonic stability *** Lyapunov-Krasovskii functional and the controller are obtained by solving a set of linear matrix inequalities(LMI)or iterative LMI based nonlinear *** proposed theorems are first evaluated by some numerical examples,and then by simulation and implementation on the pH neutralizing process plant.

关键词： Lyapunov-Krasovskii functional discrete state-delay systems non-monotonic Lyapunov function robust stability stabilization

A thermo-mechanical simulation for the stability analysis of a horizontal wellbore in underground coal gasification

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Petroleum 2024年第2期10卷 243-253页

作者： Mohammadreza Shahbazi Mehdi Najafi Mohammad fatehi Marji Ramin Rafiee Department of Mining and Metallurgical Eng. Yazd UniversityYazdIran Department of Mining Petroleum&Geophysics Eng.Shahrood University of TechnologyShahroodIran

The stability analysis of horizontal wells is essential for a successful underground coal gasification(UCG)*** this paper,a new 3D coupled thermo-mechanical numerical modeling is proposed for analyzing the stability of UCG horizontal *** this model,the effect of front abutment stresses,syngas pressure,syngas temperature and thermal stresses is considered to predict the mud weight window and drilling mud pressure during UCG *** results show that the roof caving in UCG panel has a greatest impact on the stability of horizontal ***,when the time of coal gasification is increased,the well convergence increases and for more stability it is necessary to increase the drilling mud *** research was carried out on the M2 coal seam in Mazino coal deposit(Iran).The results showed that the mud weight window for horizontal well drilling is between 0 and 33 *** appropriate stress for the maximum stability of the horizontal well,taking all the thermal and mechanical parameters into account,is 28 *** suggested numerical method is a comprehensive and consistent way for analyzing the stability of horizontal wells in UCG sites.

关键词： Underground coal gasification Thermo-mechanical simulation Numerical modeling Stress distribution Horizontal well

脆性材料I型(张开)-断裂韧性测定的PFC2D和试验研究:一种新方法

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Acta Mechanica Sinica 2024年第2期40卷 116-130页

作者：付金伟 Hadi Haeri Joseph FLabuz Vahab Sarfarazi Pouyan Ebneabbasi MRM Aliha Hamid Reza Karimi Shirin Jahanmiri Mohammad fatehi Marji School of Civil Engineering and Transportation North China University of Water Resources and Electric PowerZhengzhou450046China Department of Mining Engineering Higher Education Complex of ZarandShahid Bahonar University of KermanKermanIran Department of Civil Environmentaland Geo-EngineeringUniversity of MinnesotaMinneapolis55455USA Department of Mining Engineering Hamedan University of TechnologyHamedanIran Research Scholar Civil Engineering DepartmentIslamic Azad UniversityHamedanIran Welding and Joining Research Center School of Industrial EngineeringIran University of Science and TechnologyNarmakTehranIran School of Civil Engineering Iran University of Science and Technology(IUST)NarmakTehranIran Department of Mine Exploitation Engineering Faculty of Mining and MetallurgyInstitute of EngineeringYazd UniversityYazdIran

在本文研究中,通过利用优势边缘缺口盘型(END)试样,确定了石灰石的断裂韧性,提出了一种新的石灰石归一化相应力、高相变的计算方法.采用柔性有限元法(FEM)对试样的I型(张开)-断裂韧性进行了精确计算,并得到了相应实用公式.在试验中,还... 详细信息

在本文研究中,通过利用优势边缘缺口盘型(END)试样,确定了石灰石的断裂韧性,提出了一种新的石灰石归一化相应力、高相变的计算方法.采用柔性有限元法(FEM)对试样的I型(张开)-断裂韧性进行了精确计算,并得到了相应实用公式.在试验中,还使用含缺口巴西圆盘(NBD)试件,测试了END程序的准确性.为了在数值上重现这些测试并验证断裂韧性测量的正确性,还对END测试进行了离散元分析.数值模拟结果与实验结果吻合良好.然而,END研究所确定的韧性水平低于NBD测试规定的韧性水平,这是因为END石灰石样品中的缺口具有均匀的拉伸应力分布.

关键词：断裂韧性脆性材料实用公式拉伸应力巴西圆盘离散元分析相变归一化

Fracture analyses of different pre-holed concrete specimens under compression

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Acta Mechanica Sinica 2015年第6期31卷 855-870页

作者： Hadi Haeri alireza Khaloo Mohammad fatehi Marji Department of Civil Engineering Sharif University of Technology Member of National Elites Foundation Center of Excellence in Structure and Earthquake Engineering Sharif University of Technology Mine Exploitation Engineering Department Faculty of Mining and Metallurgy Yazd University

Crack propagation processes in specially prepared concrete discs and rectangular specimens containing a single cylindrical hole or multiple holes of varying diameters have been studied both experimentally and numerically. In this research, the cracks coalescence paths in Brazilian disc and rectangular specimens made from rock-like material containing multi-holes are investigated. These concrete specimens are specially prepared from an appropriate mixture of Portland Pozzolana Cement （PPC）, fine sands, and water. The pre-holed Brazilian discs and rectangular specimens are experimentally tested under compression. The breakage load in the ring type disc specimens containing an axial hole with varying diameters is measured and the distribution of the induced lateral stress is obtained. The mechanism of cracks propagation in the wall of the ring type specimens is also stud- ied. In the case of multi-hole Brazilian disc and rectangular specimens, the cracks propagation and cracks coalescence are also investigated. These experiments are numerically modeled by a modified higher order displacement discontinuity method. It has been shown that the corresponding experimental and numerical results are in good agreement with each other. The results presented in this research vali date the accuracy and applicability of these crack analyses procedures.

关键词： Concrete rings Pre-holed Brazilian disc ·Rectangular specimens Crack analyses Coalescence ·Induced lateral stress

On the accuracy of higher order displacement discontinuity method(HODDM) in the solution of linear elastic fracture mechanics problems

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Journal of Central South University 2016年第11期23卷 2941-2950页

作者： Abolfazl Abdollahipour Mohammad fatehi Marji alireza Yarahmadi Bafghi Javad Gholamnejad Faculty of Mining and Metallurgical Engineering Yazd University

The higher order displacement discontinuity method(HODDM) utilizing special crack tip elements has been used in the solution of linear elastic fracture mechanics(LEFM) problems. The paper has selected several example problems from the fracture mechanics literature(with available analytical solutions) including center slant crack in an infinite and finite body, single and double edge cracks, cracks emanating from a circular hole. The numerical values of Mode Ⅰ and Mode Ⅱ SIFs for these problems using HODDM are in excellent agreement with analytical results(reaching up to 0.001% deviation from their analytical results). The HODDM is also compared with the XFEM and a modified XFEM results. The results show that the HODDM needs a considerably lower computational effort(with less than 400 nodes) than the XFEM and the modified XFEM(which needs more than 10000 nodes) to reach a much higher accuracy. The proposed HODDM offers higher accuracy and lower computation effort for a wide range of problems in LEFM.

关键词： accuracy higher order displacement discontinuity method LEFM mode Ⅰ stress intensity factor mode Ⅱ stress intensity factor

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木质素衍生腐植酸制备与应用最新进展

腐植酸 2024年第2期 9-23页

作者： Shrikanta Sutradhar Pedram fatehi 袁晓娜(译) 加拿大湖首大学生物精炼研究所桑德贝P7B5E1 中国腐植酸工业协会北京100120

腐殖质(HS)来源于自然腐烂的生物质。HS的主要产物是腐植酸、黄腐酸和腐黑物。HS是从自然资源(如煤、褐煤、森林和河流沉积物)中提取的。然而,从这些资源生产HS并不环保,可能会对生态系统造成影响。早期的理论认为HS可以通过酶促或有氧... 详细信息

腐殖质(HS)来源于自然腐烂的生物质。HS的主要产物是腐植酸、黄腐酸和腐黑物。HS是从自然资源(如煤、褐煤、森林和河流沉积物)中提取的。然而,从这些资源生产HS并不环保,可能会对生态系统造成影响。早期的理论认为HS可以通过酶促或有氧氧化从木质素转化而来;另一方面,木质素是纸浆和纸张生产过程的副产物,可通过商业获得,然而它仍未得到充分的利用。为了解决环境友好型HS生产和适应木质素增值化进程的挑战,木质素衍生HS的生产引起了人们的关注。目前木质素转化为类HS物质的化学改性途径有碱性有氧氧化、碱性氧化消化、氧化氨解等。本文全面论述了木质素转化为HS的基本要素。综述了天然HS和木质素衍生HS在土壤富集、肥料、废水处理、水净化、医药等领域的应用。此外,还介绍了目前木质素生产和利用HS所面临的挑战。

关键词：腐植酸木质素肥料腐殖化氧化

DEM simulation of confining pressure effects on crack opening displacement in hydraulic fracturing

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International Journal of Mining Science and Technology 2016年第4期26卷 557-561页

作者： Abdollahipour Abolfazl fatehi Marji Mohammad Yarahmadi Bafghi alireza Gholamnejad Javad Faculty of Mining and Metallurgical Engineering Yazd University

Hydraulic fracture is one of the key methods in well stimulation to increase production of oil and *** Opening Displacement(COD) is of great importance in this method since it is in direct relation with permeability and production *** this paper COD is measured by a distinct element model which has been validated by an exact solution.A comprehensive study has been performed on confining pressure effect on COD which is neglected in the analytical *** results showed that confining pressure considerably affects COD.A multi-parameter regression(considering effect of confining pressure,rock mass properties and fluid pressure) was performed on numerical results which resulted in an *** proposed equation considers the effect of confining pressure and its results are in good agreement with numerical results.

关键词： Hydraulic lracture COD Numerical analysis Confining pressure Regression

Simulation of crack coalescence mechanism underneath single and double disc cutters by higher order displacement discontinuity method

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Journal of Central South University 2015年第3期22卷 1045-1054页

作者： Mohammad fatehi Marji Faculty of Mining & Metallurgy Yazd University

The present research is focused on the numerical crack coalescence analysis of the micro-cracks and cracks produced during the cutting action of TBM disc cutters. The linear elastic fracture mechanics(LEFM) concepts and the maximum tangential stress criterion are used to investigate the micro crack propagation and its direction underneath the excavating discs. A higher order displacement discontinuity method with quadratic displacement discontinuity elements is used to estimate the stress intensity factors near the crack tips. Rock cutting mechanisms under single and double type discs are simulated by the proposed numerical *** main purposes of the present modeling are to simulate the chip formation process of indented rocks by single and double *** effects of specific disc parameters(except speed) on the thrust force Ft, the rolling force Fr, and the specific energy ES are investigated. It has been shown that the specific energy(energy required to cut through a unit volume of rock) of the double disc is less than that of the single disc. Crack propagation in rocks under disc cutters is numerically modeled and the optimum ratio of disc spacing S to penetration depth Pd(i.e. S/Pd ratio) of about 10 is obtained, which is in good agreement with the theoretical and experimental results cited in the literature.

关键词： TBM disc cutter double discs cracks coalescence higher-order displacement discontinuity method specific energy

Numerical analysis of confinement effect on crack propagation mechanism from a flaw in a pre-cracked rock under compression

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Acta Mechanica Sinica 2012年第5期28卷 1389-1397页

作者： Amin Manouchehrian Mohammad fatehi Marji Mining and Metallurgical Engineering Department Yazd University

In many situations rocks are subjected to biaxial loading and the failure process is controlled by the lateral confinement stresses. The importance of confinement stresses has been recognized in the literature by many researchers, in particular, its influence on strength and on the angle of fracture, but still there is not a clear description for the influence of confining stress on the crack propagation mechanism of rocks. This paper presents a numerical pro- cedure for the analysis of crack propagation in rock-like ma- terials under compressive biaxial loads. Several numerical simulations of biaxial tests on the rock specimen have been carried out by a bonded particle model （BPM） and the influ- ence of confinement on the mechanism of crack propagation from a single flaw in rock specimens is studied. For this purpose, several biaxial compressive tests on rectangular spec- imens under different confinement stresses were modeled in （2 dimensional particle flow code） PFC2D. The results show that wing cracks initiate perpendicular to the flaw and trend toward the direction of major stress, however, when the lat- eral stresses increase, this initiation angle gets wider. Also it is concluded that in addition to the material type, the initiation direction of the secondary cracks depends on confine- ment stresses, too. Besides, it is understood that secondary cracks may be produced from both tensile and shear mechanisms.

关键词： Crack propagation Confinement Bonded par-ticle model - Rock Secondary cracks