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Rotation-based finite elements:reference-configuration geometry and motion description

Acta Mechanica Sinica 2021年第1期37卷 105-126,I0004页

作者： ahmed a.shabana Lingmin Xu Department of Mechanical and Industrial Engineering University of Illinois At ChicagoChicagoIL60607USA Faculty of Mechanical Engineering and Automation Zhejiang Sci-Tech UniversityHangzhou310018China

Infinitesimal-rotation finite elements allow creating a linear problem that can be exploited to systematically reduce the number of coordinates and obtain efficient solutions for a wide range of applications,including those governed by nonlinear *** paper discusses the limitations of conventional infinitesimal-rotation finite elements(FE)in capturing correctly the initial stress-free reference-configuration geometry,and explains the effect of these limitations on the definition of the inertia used in the motion *** alternative to conventional infinitesimal-rotation finite elements is a new class of elements that allow developing inertia expressions written explicitly in terms of constant coefficients that define accurately the reference-configuration *** is shown that using a geometrically inconsistent(GI)approach that introduces the infinitesimal-rotation coordinates from the outset to replace the interpolation-polynomial coefficients is the main source of the failure to capture correctly the reference-configuration *** the other hand,by using a geometrically consistent(GC)approach that employs the position gradients of the absolute nodal coordinate formulation(ANCF)to define the infinitesimal-rotation coordinates,the reference-configuration geometry can be *** simple examples of straight and tapered beams are used to demonstrate the basic differences between the two fundamentally different approaches used to introduce the infinitesimal-rotation *** analysis presented in this study sheds light on the differences between the incremental co-rotational solution procedure,widely used in computational structural mechanics,and the non-incremental floating frame of reference formulation(FFR),widely used in multibody system(MBS)dynamics.

关键词： Reference-configuration geometry Infinitesimal-rotation finite elements Rigid-body inertia Floating frame of reference Absolute nodal coordinate formulation Co-rotational procedure

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Nominal geometry and force measures for solids and fluids

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International Journal of Mechanical System Dynamics 2022年第3期2卷 249-252页

作者： ahmed a.shabana Department of Mechanical and Industrial Engineering University of Illinois at ChicagoChicagoIllinoisUSA

Understanding solid‐and fluid‐inertia forces and their coupling with the gravity potential in complex motion scenarios is necessary for evaluating system stability and identifying root causes of system failure and *** solids and fluids have an infinite number of degrees of freedom and distributed inertia and elasticity,having meaningful qualitative and quantitative nominal measures of the kinematics and forces will contribute to a better understanding of the system *** paper proposes developing new continuum‐based nominal measures for the characterization of the oscillations and *** using a material‐point approach,these new nominal measures,which have their roots in the continuum‐mechanics partial‐differential equations of equilibrium and Frenet geometry,are independent of the formulation or generalized coordinates used to develop the dynamic equations of *** paper proposes a data‐driven‐science approach to define a nominal continuum space‐curve geometry with nominal curvature and torsion;a nominal instantaneous motion plane(IMP),which contains the resultant of all forces including the inertia forces;and a nominal instantaneous zero‐force axis(IZFA)along which the resultant of all forces *** using the material‐point approach eliminates the need for introducing moment equations associated with orientation coordinates,the IMP and IZFA concepts can be used to define the instantaneous axis of significant moment components,which can lead to accidents such as in the case of vehicle rollovers.

关键词： nominal geometry and force measures instantaneous motion plane instantaneous zero-force axis Frenet geometry nominal continuum mechanics measures

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非惯性坐标在列车纵向力分析中的运用

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铁道学报 2012年第1期34卷 13-18页

作者：丁莉芬谢基龙 ahmed a.shabana 北京交通大学轨道车辆结构可靠性与运用检测技术教育部工程研究中心北京100044 伊利诺伊大学芝加哥分校机械与工业工程系美国芝加哥606077022

考虑车体与钩缓系统位移而造成的钩缓系统各部件间几何非线性特点,本文提出一种新的非线性列车车钩缓冲系统模型。忽略钩缓系统各部件惯性,将系统坐标分成惯性坐标和非惯性坐标:惯性坐标描述有惯性力作用其上的车体运动,与惯性力无关的... 详细信息

考虑车体与钩缓系统位移而造成的钩缓系统各部件间几何非线性特点,本文提出一种新的非线性列车车钩缓冲系统模型。忽略钩缓系统各部件惯性,将系统坐标分成惯性坐标和非惯性坐标:惯性坐标描述有惯性力作用其上的车体运动,与惯性力无关的非惯性坐标描述钩缓系统各部件的运动。在不增加状态方程数量、系统惯性坐标数量和约束方程数量的前提下,建立一个较为详细的钩缓系统模型,以体现系统各部件的运动自由度。本模型可在车体任意三维运动时捕捉钩缓系统各部位的运动自由度,而既有的简化钩缓系统模型则未能体现这一点。该方法还可避免由于过小质量的引入而带来系统微分方程组的刚性问题。最后,本文给出一个简化的列车模型算例来展示所述方法的运用。

关键词：纵向动力学非惯性坐标车钩力车钩几何非线性多体系统

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大位移二维梁的几种曲率定义研究

大位移二维梁的几种曲率定义研究

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第十届全国多体动力学与控制暨第五届全国航天动力学与控制学术会议

作者：郑银环 ahmed a.shabana 张大羽武汉理工大学机电工程学院美国伊利诺伊大学芝加哥分校机械与工业工程系西北工业大学航天学院航天飞行动力学技术重点实验室

关于曲率表达式,有学者提出了几种不同的曲率定义,其中有的定义与基本几何定义不同,导致产生弯曲和剪切变形间的运动耦合,则在有限元(FE)位置场中采用低阶插值时,单元内曲率为零。为了研究大位移二维梁曲率定义不同产生的影响,论文采用...

关于曲率表达式,有学者提出了几种不同的曲率定义,其中有的定义与基本几何定义不同,导致产生弯曲和剪切变形间的运动耦合,则在有限元(FE)位置场中采用低阶插值时,单元内曲率为零。为了研究大位移二维梁曲率定义不同产生的影响,论文采用了三种弹性力公式进行求解。第一种弹性力公式(方法 1)采用了基于非线性应变-位移关系的连续介质力学方法,利用Green-Lagrange应变张量计算应力。该方法适用于梁弯曲问题,能正确得到剪

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Maize response to elevated plant density combined with lowered N-fertilizer rate is genotype-dependent

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The Crop Journal 2015年第2期3卷 96-109页

作者： ahmed Medhat M.Al-Naggar Reda a.shabana Mohamed M.M.Atta Tarek H.Al-Khalil Agronomy Department Faculty of Agriculture Cairo University

Increasing plant density and improving N fertilizer rate along with the use of high density-tolerant genotypes would lead to maximizing maize(Zea mays L.) grain productivity per unit land area. The objective of this investigation was to match the functions of optimum plant density and adequate nitrogen fertilizer application to produce the highest possible yields per unit area with the greatest maize genotype efficiency. Six maize inbred lines differing in tolerance to low N and high density(D) [three tolerant(T); L-17, L-18, L-53,and three sensitive(S); L-29, L-54, L-55] were chosen for diallel crosses. Parents and crosses were evaluated in the 2012 and 2013 seasons under three plant densities: low(47,600),medium(71,400), and high(95,200) plants ha-1and three N fertilization rates: low(no N addition), medium(285 kg N ha-1) and high(570 kg N ha-1). The T × T crosses were superior to the S × S and T × S crosses under the low N–high D environment in most studied traits across seasons. The relationships between the nine environments and grain yield per hectare(GYPH) showed near-linear regression functions for inbreds L54, L29, and L55 and hybrids L18 × L53 and L18 × L55 with the highest GYPH at a density of47,600 plants ha-1and N rate of 570 kg N ha-1and a curvilinear relationship for inbreds L17, L18, and L53 and the rest of the hybrids with the highest GYPH at a density of95,200 plants ha-1combined with an N rate of 570 kg N ha-1. Cross L17 × L54 gave the highest grain yield in this study under both high N–high-D(19.9 t ha-1) and medium N–high-D environments(17.6 t ha-1).

关键词： Quadratic regression Appropriate N rate High-density tolerant maize Unit area productivity

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X-ray Image-Based COVID-19 Patient Detection Using Machine Learning-Based Techniques

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Computer Systems Science & Engineering 2022年第11期43卷 671-682页

作者： shabana Habib Saleh Alyahya Aizaz ahmed Muhammad Islam Sheroz Khan Ishrat Khan Muhammad Kamil Department of Information Technology College of ComputerQassim UniversityBuraidah52571Saudi Arabia Department of Electrical Engineering College of Engineering&Information TechnologyOnaizah CollegesOnaizah51911Saudi Arabia Digital Image Processing Lab Islamia CollegePeshawar25120KPKPakistan Department of Computer Science College of Computer and Information SciencesPrince Sultan UniversityRiyadh11586Saudi Arabia Department of Electrical Engineering National University of Computer and Emerging SciencesPeshawarPakistan

In early December 2019,the city of Wuhan,China,reported an outbreak of coronavirus disease(COVID-19),caused by a novel severe acute respiratory syndrome coronavirus-2(SARS-CoV-2).On January 30,2020,the World Health Organization(WHO)declared the outbreak a global pandemic *** the face of the COVID-19 pandemic,the most important step has been the effective diagnosis and monitoring of infected *** COVID-19 using Machine Learning(ML)technologies can help the health care unit through assistive diagnostic suggestions,which can reduce the health unit's burden to a certain *** paper investigates the possibilities of ML techniques in identifying/detecting COVID-19 patients including both conventional and exploring from chest X-ray images the effect of viral *** approach includes preprocessing,feature extraction,and ***,the features are extracted using the Histogram of Oriented(HOG)and Local Binary Pattern(LBP)feature ***,for the extracted features classification,six ML models of Support Vector Machine(SVM)and K-Nearest Neighbor(KNN)is *** results show that the diagnostic accuracy of random forest classifier(RFC)on extracted HOG plusLBP features is as high as 94%followed by SVM at 93%.The sensitivity of the K-nearest neighbour model has reached an accuracy of 88%.Overall,the predicted approach has shown higher classification accuracy and effective diagnostic *** is a highly useful tool for clinical practitioners and radiologists to help them in diagnosing and tracking the cases of COVID-19.

关键词： Image pre-processing detection classification x-ray images filter

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An Improved iBAT-COOP Protocol for Cooperative Diversity in FANETs

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Computers, Materials & Continua 2021年第5期67卷 2527-2546页

作者： Shahzad Hameed Qurratul-Ain Minhas Sheeraz ahmed shabana Habib Mohammad Kamrul Hasan Muhammad Islam Sheroz Khan Quaid-i-Azam University IslamabadPakistan Iqra National University PeshawarPakistan Network and Communication Technology Lab Center for Cyber SecurityUKMBangiMalaysia Department of Information Technology College of ComputerQassim UniversityBuraydahSaudi Arabia Department of Electrical Engineering Onaizah College of Engineering&Information TechnologyAl-QassimSaudi Arabia

Flying ad hoc networks(FANETs)present a challenging environment due to the dynamic and highly mobile nature of the *** network topology and uncertain node mobility structure of FANETs do not aim to consider only one path *** different techniques are adopted to address the issues arising in FANETs,from game theory to clustering to channel estimation and other statistical *** approaches mostly employ traditional concepts for problem *** of the novel approaches that provide simpler solutions to more complex problems is to use biologically inspired *** Nature-inspired schemes address cooperation and alliance which can be used to ensure connectivity among network *** such species that resembles the dynamicity of FANETs are *** this paper,the biologically inspired metaheuristic technique of the BAT Algorithm is proposed to present a routing protocol called iBATCOOP(Improved BAT Algorithm using Cooperation technique).We opt for the design implementation of the natural posture of bats to handle the necessary flying ***,we envision the concept of cooperative diversity using multiple relays and present an iBAT-COOP routing protocol for *** paper employs cooperation for an optimal route selection and reflects on distance,Signal to Noise Ratio(SNR),and link conditions to an efficient level to deal with FANET’s *** way of simulations,the performance of iBAT-COOP protocol outperforms BAT-FANET protocol and reduces packet loss ratio,end-to-end delay,and transmission loss by 81%,21%,and 82%***,the average link duration is improved by 25%compared to the BAT-FANET protocol.

关键词： Routing protocols UAVs FANETs iBATCOOP BATCOOP

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Tissue Doppler,speckling tracking and four-dimensional echocardiographic assessment of right ventricular function in children with dilated cardiomyopathy

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World Journal of Clinical Pediatrics 2022年第1期11卷 71-84页

作者： Mohammed Al-Biltagi Osama Elrazaky Wegdan Mawlana Esraa Srour ahmed Hamdy shabana Department of Pediatrics Faculty of MedicineTanta UniversityTanta 31512AlgharbiaEgypt Department of Pediatrics University Medical CenterArabian Gulf UniversityManama 26671ManamaBahrain

BACKGROUND Right ventricular(RV)function is frequently overlooked during dilated cardiomyopathy(DCM)*** To evaluate RV function in children with idiopathic DCM using relatively recent echocardiographic *** We prospectively studied the cardiac function in 50 children with idiopathic DCM and 50 healthy children as a control group,using four-dimensional echocardiography(4-DE),Tissue Doppler Imaging(TDI),and two-dimensional-speckles tracking echocardiography(2-D-STE).RV EF was measured by *** The auto left(LV)ejection fractions(EF)measured by 2-D-STE were significantly lower in the patients'group than in the *** sphericity index was also significantly lower in children with DCM than in the *** EF measured by 4-DE was significantly lower in the patient's group than the *** S wave,e´/a'ratio,myocardial performance index(MPI),and tricuspid annular plane systolic excursion(TAPSE)were significantly impaired in children with DCM than in *** LV and RV global longitudinal strains(GLS)were significantly reduced in children with DCM than in *** was significantly associated with the duration since diagnosis,tricuspid annulus S wave,RV MPI,and TAPSE,but not with the age of the patients,RV EF,or e´/a'*** There was impairment of the RV LGS and other systolic and diastolic parameters in children with *** and TDI can help to detect the early decline of RV function.

关键词： Tissue Doppler Speckling tracking Echocardiography Dilated cardiomyopathy Children Right ventricle

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具有局部特征的ANCF全参板单元动力学分析

具有局部特征的ANCF全参板单元动力学分析

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第十届全国多体动力学与控制暨第五届全国航天动力学与控制学术会议

作者：何钢 Mohil Patel ahmed shabana 河海大学机电工程学院机械系伊利诺伊大学芝加哥分校机械与工业工程系

针对绝对节点坐标法(Absolute Nodal Coordinate Formulation,ANCF)在多体动力学分析中复杂局部特征表示上存在难题,本文提出了一种可在全参ANCF板单元中实现局部特征表示的方法;即采用ANCF有限单元法描述全局几何形状,并用有限元/多体...

针对绝对节点坐标法(Absolute Nodal Coordinate Formulation,ANCF)在多体动力学分析中复杂局部特征表示上存在难题,本文提出了一种可在全参ANCF板单元中实现局部特征表示的方法;即采用ANCF有限单元法描述全局几何形状,并用有限元/多体系统来实现变形体动力学分析,而ANCF单元网格不需要细分就可以实现复杂的局部特征的表示;其中局部特征的形状采用NURBS表示,它能够实现二次曲面与自由曲面的统一与精确表示。ANCF单元

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