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Journal of Materials Science & Technology 2020年第22期54卷 12-17页

作者： shahzad Fateh ali Jitang Fan State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing700087China

Recently, polymer composites, consisting of hard segments and soft segments blend, attract a broad research interest because of the high flow stress and large deformation under a high rate loading. They display an outstanding energy absorption capability for impact resistant engineering. In this paper,a physics-based elastic-viscoplastic constitutive model is developed which accounts the activation of molecular chains motion at different segments upon an applied stress as well as the rate dependency of mechanical properties. Accordingly, finite element simulations are conducted to derive the mechanical performance at various strain rates. It involves the linearly elastic deformation to yielding, softening behavior with a slight decrease of stress, plastic flow at a plateau stress accompanied by a considerable straining, densification with a fast increase of stress. The results achieved from model simulations match well with these obtained by experiments and the mechanical response in the strain rate range from 0.0001 s^(-1) to 8000 s^(-1) can be captured by this model. Finally, energy absorption capability of the polymer composite is discussed, and the physical mechanisms in material science are addressed by post-loading analysis. This work is full of interest to develop the constitutive model for designing the impact-resistant polymers and illustrating the dynamic mechanical response, which will promote the application of light-weight transparent protection structure against a high-speed impact.

关键词： Polymer composite Constitutive model Strain rate Mechanical behavior

A Macro-Mechanical Study for Capturing the Dynamic Behaviors of a Rate-Dependent Elastomer and Clarifying the Energy Dissipation Mechanisms at Various St rain Rates

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Acta Mechanica Solida Sinica 2022年第2期35卷 228-238页

作者： shahzad Fateh ali Jitang Fan Jianqing Feng Xiangquan Wei State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China Aerospace System Engineering shanghai Shanghai 201109China

A strain-rate-sensitive polyurethane elastomer is numerically investigated to reveal improved impact characteristics and analyze the concerned rate dependencies and dynamic energy dissipation features.A physical constitutive model in view of amorphous molecular struc-ture of the elastomer is proposed by relating the macro-mechanical behaviors to micro-structural changes through molecular transitions and flow *** distinct relaxation processes are considered because of entangled molecular net works,with each possessing a unique activation *** calibration with experimental data,finite element simulations based on the model are *** to the loading rate,the structural entropy of molecular chain entanglements,rate-dependent yielding,plateau flow and densification are well predicted by the *** investigations are extended further regarding the material recoverability and accordingly,strain energy absorptions are illustrated.A power law function is proposed for designing the energy absorption relation to the applied loading ***,the inherent mechanisms causing the dynamic energy absorptions are analyzed with notable clarifications of post-experimental observations obtained via scanning elec Iron microscopy.

关键词： Elastomer Constitutive model Energy absorption Ratedependent Scanning electron microscopy

Developing a process-based and remote sensing driven crop yield model for maize(PRYM–Maize) and its validation over the Northeast China Plain

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Journal of Integrative Agriculture 2021年第2期20卷 408-423页

作者： ZHANG Sha BAI Yun ZHANG Jia-hua shahzad ali School of Automation Qingdao UniversityQingdao 266071P.R.China College of Computer Science and Technology Qingdao UniversityQingdao 266071P.R.China Aerospace Information Research Institute Chinese Academy of SciencesBeijing 100094P.R.China University of Chinese Academy of Sciences Beijing 100049P.R.China

Spatial dynamics of crop yield provide useful information for improving the production. High sensitivity of crop growth models to uncertainties in input factors and parameters and relatively coarse parameterizations in conventional remote sensing(RS) approaches limited their applications over broad regions. In this study, a process-based and remote sensing driven crop yield model for maize(PRYM–Maize) was developed to estimate regional maize yield, and it was implemented using eight data-model coupling strategies(DMCSs) over the Northeast China Plain(NECP). Simulations under eight DMCSs were validated against the prefecture-level statistics(2010–2012) reported by National Bureau of Statistics of China, and inter-compared. The 3-year averaged result could give more robust estimate than the yearly simulation for maize yield over space. A 3-year averaged validation showed that prefecture-level estimates by PRYM–Maize under DMCS8, which coupled with the development stage(DVS)-based grain-filling algorithm and RS phenology information and leaf area index(LAI), had higher correlation(R, 0.61) and smaller root mean standard error(RMSE, 1.33 t ha^(–1)) with the statistics than did PRYM–Maize under other DMCSs. The result also demonstrated that DVS-based grain-filling algorithm worked better for maize yield than did the harvest index(HI)-based method, and both RS phenology information and LAI worked for improving regional maize yield estimate. These results demonstrate that the developed PRYM–Maize under DMCS8 gives reasonable estimates for maize yield and provides scientific basis facilitating the understanding the spatial variations of maize yield over the NECP.

关键词： process-based and remote sensing model maize yield simulation development stage grain filling harvest index

The roles of focal adhesion and cytoskeleton systems in fluid shearstress-induced endothelial cell response

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BIOCELL 2020年第2期44卷 137-145页

作者： KHAWAR ali shahzad ZHONGJIE QIN YAN LI DELIN XIA School of Pharmacy Taizhou Polytechnic CollegeTaizhou225300China Bone Tissue Engineering Research Center of Taizhou Taizhou225300China Department of Oral and Maxillofacial Surgery The Affiliated Stomatology Hospital of Southwest Medical UniversityLuzhou646000China Orofacial Reconstruction and Regeneration Laboratory The Affiliated Stomatology Hospital of Southwest Medical UniversityLuzhou646000China

Focal adhesions are polyproteins linked to extracellular matrix and cytoskeleton,which play an important role in the process of transforming force signals into intracellular chemical signals and subsequently triggering related physiological or pathological *** cytoskeleton is a network of protein fibers in the cytoplasm,which is composed of microfilaments,microtubules,intermediate filaments,and cross-linked *** is a very important structure for cells to maintain their basic *** review summarizes the process of fluid shear stress transduction mediated by focal adhesion and the key role of the cytoskeleton in this process,which focuses on the focal adhesion and cytoskeleton *** important proteins involved in signal transduction in focal adhesion are introduced *** relationship between focal adhesion and mechanical transduction pathways are *** this review,we discuss the relationship between fluid shear stress and associated diseases such as atherosclerosis,as well as its role in clinical research and drug development.

关键词： Cytoskeleton Endothelial cells Fluid shear stress Focal adhesion

Spatio-temporal variations in trends of vegetation and drought changes in relation to climate variability from 1982 to 2019 based on remote sensing data from East Asia

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Journal of Integrative Agriculture 2023年第10期22卷 3193-3208页

作者： shahzad ali Abdul BASIT Muhammad UMAIR Tyan alice MAKANDA Fahim Ullah KHAN Siqi SHI NI Jian College of Chemistry and Life Sciences Zhejiang Normal UniversityJinhua 321004P.R.China Department of Agriculture Hazara UniversityMansehra 21120Pakistan Department of Computer Science University of PeshawarPeshawar 25000Pakistan Faculty of Geo-Information Science and Earth Observation(ITC) University of TwenteEnschede 7500 AENetherlands

Studying the significant impacts on vegetation of drought due to global warming is crucial in order to understand its dynamics and interrelationships with temperature,rainfall,and normalized difference vegetation index(NDVI).These factors are linked to excesses drought frequency and severity on the regional scale,and their effect on vegetation remains an important topic for climate change *** Asia is very sensitive and susceptible to climate *** this study,we examined the effect of drought on the seasonal variations of vegetation in relation to climate variability and determined which growing seasons are most vulnerable to drought risk;and then explored the spatio-temporal evolution of the trend in drought changes in East Asia from 1982 to *** data were studied using a series of several drought indexes,and the data were then classified using a heat map,box and whisker plot analysis,and principal component *** various drought indexes from January to August improved rapidly,except for vegetation health index(VHI)and temperature condition index(TCI).While these indices were constant in September,they increased again in October,but in December,they showed a descending *** seasonal and monthly analysis of the drought indexes and the heat map confirmed that the East Asian region suffered from extreme droughts in 1984,1993,2007,and 2012among the study *** distribution of the trend in drought changes indicated that more severe drought occurred in the northwestern region than in the southeastern area of East *** drought tendency slope was used to describe the changes in drought events during 1982–2019 in the study *** correlations among monthly precipitation anomaly percentage(NAP),NDVI,TCI,vegetation condition index(VCI),temperature vegetation drought index(TVDI),and VHI indicated considerably positive correlations,while considerably negative correlations were found among the three pairs of NDVI and VHI,TVDI and VHI,and NDV

关键词： climate change drought severity vegetation dynamics heat mapping TVDI spatial correlation East Asia

Improvement in winter wheat productivity through regulating PSⅡ photochemistry,photosynthesis and chlorophyll fluorescence under deficit irrigation conditions

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Journal of Integrative Agriculture 2022年第3期21卷 654-665页

作者： shahzad ali XU Yue-yue MA Xiang-cheng JIA Qian-min JIA Zhi-kuan College of Pastoral Agriculture Science and Technology Lanzhou UniversityLanzhou 730000P.R.China Institute of Water Saving Agriculture in Arid Areas Yangling 712100P.R.China

Deficit irrigation is critical to global food production,particularly in arid and semi-arid regions with low *** water shortage has threatened agricultural sustainability under the dry-land farming system in China,there is an urgent need to develop effective water-saving *** carried out a field study under two cultivation techniques:(1) the ridge and furrow cultivation model(R);and(2) the conventional flat farming model(F),and three simulated precipitation levels(1,275 mm;2,200 mm;3,125 mm) with two deficit irrigation levels(150 and 75 mm).We demonstrated that under the ridge furrow(R) model,rainfall harvesting planting under 150 mm deficit irrigation combined with 200 mm simulated precipitation can considerably increase net photosynthesis rate(P_(n)),quantum yield of PSII(ΦPSⅡ),electron transport rate(ETR),performance index of photosynthetic PSII(F_(v)/F_(m)′),and transformation energy potential of PSII(F_(v)/F_(o)).In addition,during the jointing,anthesis and grain-filling stages,the grain and biomass yield in the R model are 18.9 and 11.1% higher than those in the flat cultivation model,respectively,primarily due to improved soil water *** winter wheat fluorescence parameters were significantly positively associated with the photosynthesis,biomass and wheat *** result suggests that the R cultivation model with irrigation of 150 mm and simulated precipitation of 200 mm is an effective planting method for enhancing P_(n),biomass,wheat production,and chlorophyll fluorescence parameters in dry-land farming areas.

关键词： chlorophyll fluorescence deficit irrigation photosynthesis production planting models soil moisture content

CNR:A Cluster-Based Solution for Connectivity Restoration for Mobile WSNs

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Computers, Materials & Continua 2021年第12期69卷 3413-3427页

作者： Mahmood ul Hassan Amin Al-Awady Khalid Mahmood shahzad ali Ibrahim Algamdi Muhammad Kashif Saeed Safdar Zaman Department of Computer Skills Najran UniversityNajran66241Saudi Arabia Department of Information Systems College of Science and ArtsKing Khalid UniversityMahayil Asir63317Saudi Arabia Department of Computer Science Jouf UniversityTabarjal76769Saudi Arabia Department of Computer Science Community College Mahayil AsirKing Khalid UniversityMahayil63317Saudi Arabia Federal Directorate of Education Department of Computer ScienceIslamabad44000Pakistan

Wireless Sensor Networks(WSNs)are an integral part of the Internet of Things(IoT)and are widely used in a plethora of ***,sensor networks operate in harsh environments where human intervention is often restricted,which makes battery replacement for sensor nodes *** failure due to battery drainage or harsh environmental conditions poses serious challenges to the connectivity of the *** a connectivity restoration mechanism,node failures ultimately lead to a network partition,which affects the basic function of the sensor ***,the research community actively concentrates on addressing and solving the challenges associated with connectivity restoration in sensor *** energy is a scarce resource in sensor networks,it becomes the focus of research,and researchers strive to propose new solutions that are energy *** common issue that is well studied and considered is how to increase the network’s life span by solving the node failure problem and achieving efficient energy *** paper introduces a Clusterbased Node Recovery(CNR)connectivity restoration mechanism based on the concept of *** is a well-known mechanism in sensor networks,and it is known for its energy-efficient operation and *** proposed technique utilizes a distributed cluster-based approach to identify the failed nodes,while Cluster Heads(CHs)play a significant role in the restoration of *** simulations were conducted to evaluate the performance of the proposed technique and compare it with the existing *** simulation results show that the proposed technique efficiently addresses node failure and restores connectivity by moving fewer nodes than other existing connectivity restoration *** proposed mechanism also yields an improved field coverage as well as a lesser number of packets exchanged as compared to existing state-of-the-art mechanisms.

关键词： WSNs CHs CNR transmission range connectivity restoration node failure cluster communication range

An Efficient Connectivity Restoration Technique(ECRT)for Wireless Sensor Network

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Computers, Materials & Continua 2021年第10期69卷 1003-1019页

作者： Mahmood ul Hassan shahzad ali Khalid Mahmood Muhammad Kashif Saeed Amin Al-Awady Kamran Javed Ansar Munir Shah Department of Computer Skills Preparatory yearNajran UniversityNajran66241Saudi Arabia Department of Computer Science Jouf UniversityTubarjal74769Saudi Arabia Department of Information Systems College of Science and ArtsKing Khalid UniversityMahayil Asir63317Saudi Arabia Department of Computer Science Community College Mahayil AsirKing Khalid UniversityMahayil63718Saudi Arabia Department of Computer Engineering National University of Technology(NUTECH)Islamabad44000Pakistan Department of Computer Science Institute of Southern PunjabMultan60000Pakistan

Node failure in Wireless Sensor Networks(WSNs)is a fundamental problem because WSNs operate in hostile *** failure of nodes leads to network partitioning that may compromise the basic operation of the sensor *** deal with such situations,a rapid recovery mechanism is required for restoring inter-node *** to the immense importance and need for a recovery mechanism,several different approaches are proposed in the ***,the proposed approaches have shortcomings because they do not focus on energy-efficient operation and coverage-aware mechanisms while performing connectivity ***,most of these approaches rely on the excessive mobility of nodes for restoration connectivity that affects both coverage and energy *** paper proposes a novel technique called ECRT(Efficient Connectivity Restoration Technique).This technique is capable of restoring connectivity due to single and multiple node *** achieves energy efficiency by transmitting a minimal number of control *** is also coverage-aware as it relocates minimal nodes while trying to restore *** the help of extensive simulations,it is proven that ECRT is effective in connectivity restoration for single and multiple node *** also show that ECRT exchanges a much smaller number of packets than other ***,it also yields the least reduction in field coverage,proving its versatility for connectivity restoration.

关键词： Cut-vertex failure recovery network connectivity node relocation wireless sensor network node failures

Effects of uniconazole with or without micronutrient on the lignin biosynthesis,lodging resistance,and winter wheat production in semiarid regions

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Journal of Integrative Agriculture 2020年第1期19卷 62-77页

作者： Irshad AHMAD MENG Xiang-ping Muhammad KAMRAN shahzad ali Shakeel AHMAD LIU Tie-ning CAI Tie HAN Qing-fang Key Laboratory of Crop Physio-Ecology and Tillage Science in North-Western Loess Plateau Ministry of Agriculture/College of AgronomyNorthwest A&F UniversityYangling 712100P.R.China Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas Ministry of Education/Institute of Water Saving Agriculture in Arid Areas of ChinaNorthwest A&F UniversityYangling 712100P.R.China

Lodging stress results in grain yield and quality reduction in wheat. Uniconazole, a potential plant growth regulator significantly enhances lignin biosynthesis and thus provides mechanical strength to plants in order to cope with lodging stress. A field study was conducted during the 2015–2016 and 2016–2017 growing seasons, to investigate the effects of uniconazole sole application or with micronutrient on the lignin biosynthesis, lodging resistance, and production of winter wheat. In the first experiment, uniconazole at concentrations of 0(CK), 15(US1), 30(US2), and 45(US3) mg L^-1 was applied as sole seed soaking, while in the second experiment with manganese(Mn) at concentration of 0.06 g L^-1 Mn, 0.06 g L^-1 Mn+ 15 mg L^-1 uniconazole(UMS1), 0.06 g L^-1 Mn+30 mg L^-1 uniconazole(UMS2), and 0.06 g L^-1 Mn+45 mg L^-1 uniconazole(UMS3), respectively. Uniconazole sole application or with micronutrient significantly increased the lignin content by improving the lignin-related enzyme activities of phenylalanine ammonia-lyase, cinnamyl alcohol dehydrogenase, tyrosine ammonialyase, and peroxidase, ameliorating basal internode characteristics, and breaking strength. The spike length, spike diameter, spikes/plant, weight/spike, yield/spike, and grain yield increased and then decreased with uniconazole application at a higher concentration, where their maximum values were recorded with UMS2 and US2 treatments. The lignin accumulation was positively correlated with lignin-related enzyme activities and breaking strength while, negatively correlated with lodging rate. Uniconazole significantly improved the lignin biosynthesis, lodging resistance, and grain yield of winter wheat and the treatments which showed the greatest effects were uniconazole seed soaking with micronutrient at a concentration of 30 mg L^-1 and 0.06 g L^-1 , and uniconazole sole seed soaking at a concentration of 30 mg L^-1 .

关键词： lignin biosynthesis lodging resistance semi-arid regions manganese uniconazole wheat

基于线性自抗扰控制的电力系统负荷频率控制的性能优化

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基于线性自抗扰控制的电力系统负荷频率控制的性能优化

作者： shahzad ali 华北电力大学(北京)

学位级别：硕士

自动发电控制(Automatic Generation Contro],AGC)是现代二级电网调度中心实现二次调频的重要手段,这种控制和调节通常被称为负荷频率控制(Load Frequency Control,LFC)。负荷频率控制实时自动跟踪电力系统中的负荷扰动,保持发电量与负... 详细信息

自动发电控制(Automatic Generation Contro],AGC)是现代二级电网调度中心实现二次调频的重要手段,这种控制和调节通常被称为负荷频率控制(Load Frequency Control,LFC)。负荷频率控制实时自动跟踪电力系统中的负荷扰动,保持发电量与负荷需求的平衡,使系统的频率保持在额定值,是保证电能质量的重要方面。针对系统的不确定性和非线性,传统控制器不能取得令人满意的控制效果。因此,需要采用先进的控制方法获得更好的控制结果。本文主要研究基于线性自抗扰控制算法(Linear Active Disturbance Rejection Control,LADRC)的负荷频率控制优化,同时将控制器参数调至最佳值。首先,由于风的不可预测性,在风电穿透率高的复杂电力系统中,LFC问题具有更高的挑战性。因此,本文在具有高透风率的电力系统单区域进行实验,通过抑制系统内、外部干扰来调节负荷频率。LADRC算法通过扩展状态观测器(Extended State Observer,ES0)实时估计未建模的动力学特性和外部干扰,并用简单的线性比例-微分(Proportional Derivative,PD)控制律对其进行补偿。此外,将LADRC的参数整定过程优化为两个带宽:观测器带宽和控制器带宽。针对风侵量大的电力系统单区域线性调频问题,采用改进的蝙蝠算法对控制器参数进行了优化。最后,为了验证本文方法的有效性,将结果与传统的比例-积分(Proportional Integral,PI)和模糊逻辑PI控制器进行了比较。其次,本文将基于LFC的LADRC算法应用于包括锅炉动力学和物理约束在内的四个区域互联的火电系统。该系统中控制器的作用是调节负载扰动、参数不确定性等引起的标称频率、区域控制误差(Area Control Error,ACE)、联络线功率偏差,同时该系统有可能是非线性的。利用LADRC的显著特点,通过PD控制对内、外部干扰及进行实时估计和补偿。采用混合混沌萤火虫蝙蝠优化算法对控制器参数进行优化,并以积分时间绝对误差(Integral Time Absolute Error,ITAE)作为优化性能指标。最后,将该控制器与FLPI和FLiPID控制器进行了实验比较。通过仿真结果表明,与PI、FLPI和FLiPID控制器相比,LADRC控制器优势更明显,控制效果更好。本文针对不同情况下的电力系统进行了仿真,如改变风的穿透力、运行时的负荷扰动、参数不确定和基于蒙特卡罗的鲁棒性分析,其结果表明,相对于其他控制器,本文提出的控制方案具有更强的鲁棒性和稳定性。

关键词：负荷频率控制线性自抗扰控制双馈异步风力发电机风能转换系统混合混沌萤火虫蝙蝠优化算法