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Effect of vertical stress rest period on deformation behaviour of unbound granular materials:Experimental and numerical investigations

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第1期11卷 172-180页

作者： Ali Alnedawi kali prasad Nepal Riyadh Al-Ameri Mohanad Alabdullah School of Engineering Deakin University

Repeated load triaxial test is used to assess the deformation behaviour of unbound granular materials(UGMs) in flexible road pavements. Repeated load pulse characteristics(i.e. shape, loading period and rest period) are the stress configurations used in the experimental set-up to simulate the passing axle loads. Some researchers and standard testing protocols suggest a rest period of varying durations after a loading phase. A thorough review of existing literature and practises has revealed that there is no agreement about the effect of the rest period of vertical stress pulse on the deformation behaviour of the UGMs. Therefore,the main objective of this study is to investigate the effect of repeated stress rest period on the deformation behaviour of UGMs experimentally. Experiments are conducted, both with and without rest period, using basalt and granite crushed rocks from Victoria, Australia. Furthermore, in order to gain insight into the effect of the rest period, finite element modelling is also developed. Both the experimental and modelling results show that the rest period has a noticeable effect on both resilient and permanent deformation behaviours of UGMs. It is, therefore, recommended to take extra precautions while adopting a particular standard testing protocol and to supplement the results by additional tests with different loading configurations.

关键词： Flexible pavement Unbound granular materials(UGMs) Repeated load triaxial test Resilient modulus Permanent deformation Finite element modelling

Does friction contribute to formability improvement using servo press?

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Friction 2023年第5期11卷 820-835页

作者： kali prasad Aishwary GUPTA Hariharan KRISHNASWAMY Uday CHAKKINGAL Dilip K.BANERJEE Myoung-Gyu LEE Department of Mechanical Engineering Indian Institute of Technology MadrasChennai 600036India Department of Materials Science and Engineering Seoul National UniversitySeoul 08826Republic of Korea Department of Metallurgical and Materials Engineering Indian Institute of Technology MadrasChennai 600036India Material Measurement Laboratory National Institute of Standards and Technology(NIST)Gaithersburg 20899USA

Servo press forming machines are advanced forming systems that are capable of imparting interrupted punch motion,resulting in enhanced room temperature *** exact mechanism of the formability improvement is not yet *** contribution of interrupted motion in the ductility improvement has been studied through stress relaxation phenomena in uniaxial tensile(UT)***,the reason for improved formability observed when employing servo press is complicated due to the additional contribution from frictional *** the present work,an attempt is made to decouple the friction effect on formability improvement *** improved formability is studied using a hole expansion test(HET).The limit of forming during hole expansion is modeled using the Hosford–Coulomb(HC)damage criteria,which is implemented as a user subroutine in a commercial explicit finite element(FE)*** the contribution of stress relaxation is accounted for in the evolution of the damage variable during interrupted ***,the difference between simulation and experimental hole expansion ratio(HER)can be used to decouple the friction effect from the overall formability improvement during hole *** improvement in HER due to stress relaxation and friction effect is *** study showed that the model effectively captures the hole expansion deformation process in both monotonic and interrupted loading *** to stress relaxation,friction effect played a major role during interrupted HET.

关键词： servo press hole expansion test(HET) dual phase steel finite element(FE)analysis Hosford-Coulomb(HC)ductile fracture model

New shakedown criterion and permanent deformation properties of unbound granular materials

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Journal of Modern Transportation 2019年第2期27卷 108-119页

作者： Ali Alnedawi kali prasad Nepal Riyadh Al-Ameri School of Engineering Deakin University

Unbound granular material specifications for road pavements in Australia are primarily based on physical material specification rather than mechanical characterisation. This simplified approach does not reflect the actual material performance under repeated dynamic traffic loads. There is a little information available on the influence of the local crushed rock properties and compacted layer properties on permanent deformation (PD). This study aims to characterise the local unbound granular materials in Victoria according to their PD behaviour under repeated loads and to develop a suitable shakedown criterion that could describe the PD of the tested materials to simplify the flexible pavement design. Repeated-load triaxial tests were conducted over several samples with a range of moisture contents, gradations, densities, and stress conditions. The laboratory test results showed that PD behaviour was influenced by several factors. In addition, the tested subbase-specified unbound granular materials reflect high PD resistance that is almost equivalent to basequality unbound granular materials. This may indicate that current requirements for the subbase-quality unbound granular materials are over-prescribe. Moreover, as the existing shakedown criterion was not applicable for the multi-stage repeated-load triaxial test and the local tested materials, a new shakedown criterion and new boundaries are proposed based on the PD behaviour. In the proposed criterion, the shakedown ranges are identified based on the curve angle of the PD vs. logarithm of the number of loading cycles, and this new criterion was validated using several materials from existing literature. The local tested base and subbase materials can be assigned as Range A when PD\1%, Range B when 1%\PD\3%, and Range C when PD[3%. The proposed criterion could provide a useful and quick approach to assess the PD of the unbound granular materials with both single and multistages of stresses.

关键词： Flexible pavement Unbound granular materials Repeated load triaxial test Permanent deformation Shakedown theory

Hematite reduction by hydrogen plasma:Where are we now?

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International Journal of Minerals,Metallurgy and Materials 2022年第10期29卷 1932-1945页

作者： kali Charan Sabat Department of Materials and Metallurgical Engineering Maulana Azad National Institute of TechnologyBhopal462003Madhya PradeshIndia

Currently,iron is extracted from ores such as hematite by carbothermic *** extraction process includes several unit steps/processes that require large-scale equipment and significant financial ***,the extraction process produces a substantial amount of harmful carbon dioxide(CO_(2)).Alternative to carbothermic reduction is the reduction by hydrogen plasma(HP).HP is mainly composed of exciting species that facilitate hematite reduction by providing thermodynamic and kinetic advantages,even at low *** addition to these advantages,hematite reduction by HP produces water,which is environmentally *** report reviews the theory and practice of hematite reduction by ***,the present state of the art in solid-state and liquid-state hematite reduction by HP has been *** in-flight hematite reduction by HP has been identified as a potentially promising alternative to carbothermic ***,the in-flight reduction is still plagued with problems such as excessively high temperatures in thermal HP and considerable vacuum costs in non-thermal *** problems can be overcome by using non-thermal atmospheric HP that deviates significantly from local thermodynamic equilibrium.

关键词： hematite iron ore hematite reduction iron production hydrogen plasma non-thermal plasma thermodynamics kinetics

A Novel Contour Tracing Algorithm for Object Shape Reconstruction Using Parametric Curves

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Computers, Materials & Continua 2023年第4期75卷 331-350页

作者： Nihat Arslan kali Gurkahraman Defence Technology Programme Sivas University of Science and TechnologySivas58070Turkey Department of Computer Engineering Sivas Cumhuriyet UniversitySivas58140Turkey

Parametric curves such as Bézier and B-splines, originally developedfor the design of automobile bodies, are now also used in image processing andcomputer vision. For example, reconstructing an object shape in an image,including different translations, scales, and orientations, can be performedusing these parametric curves. For this, Bézier and B-spline curves can be generatedusing a point set that belongs to the outer boundary of the object. Theresulting object shape can be used in computer vision fields, such as searchingand segmentation methods and training machine learning algorithms. Theprerequisite for reconstructing the shape with parametric curves is to obtainsequentially the points in the point set. In this study, a novel algorithm hasbeen developed that sequentially obtains the pixel locations constituting theouter boundary of the object. The proposed algorithm, unlike the methods inthe literature, is implemented using a filter containing weights and an outercircle surrounding the object. In a binary format image, the starting point ofthe tracing is determined using the outer circle, and the next tracing movementand the pixel to be labeled as the boundary point is found by the filter ***, control points that define the curve shape are selected by reducing thenumber of sequential points. Thus, the Bézier and B-spline curve equationsdescribing the shape are obtained using these points. In addition, differenttranslations, scales, and rotations of the object shape are easily provided bychanging the positions of the control points. It has also been shown that themissing part of the object can be completed thanks to the parametric curves.

关键词： Contour tracing algorithm bézier curve B-spline curve object shape reconstruction

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呕吐毒素的污染现状及脱毒技术研究进展

饲料工业 2024年第1期45卷 140-144页

作者：潘卡丽赖建兵齐珂珂浙江欣宏源生态农业有限公司浙江丽水311215 浙江省农业科学院浙江杭州310021

呕吐毒素(deoxynivalenol,DON)是谷物原料和饲料中常见的霉菌毒素之一,由于其化学性质稳定、所带基团极性较弱,常规的饲料加工工艺及市面上常见的毒素吸附剂较难将其去除,因此成为养殖业中污染最为严重的霉菌毒素之一。文章从DON在饲料... 详细信息

呕吐毒素(deoxynivalenol,DON)是谷物原料和饲料中常见的霉菌毒素之一,由于其化学性质稳定、所带基团极性较弱,常规的饲料加工工艺及市面上常见的毒素吸附剂较难将其去除,因此成为养殖业中污染最为严重的霉菌毒素之一。文章从DON在饲料及原料中的污染情况、理化性质以及最新的脱毒方法三方面综述了国内外该领域的研究进展。

关键词：饲料呕吐毒素脱毒生物酶解吸附剂

Improving Brain Tumor Classification with Deep Learning Using Synthetic Data

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Computers, Materials & Continua 2023年第3期74卷 5049-5067页

作者： Muhammed Mutlu Yapici Rukiye Karakis kali Gurkahraman Elmadag Vocational School Department of Computer TechnologiesAnkara UniversityAnkaraTurkey Faculty of Technology Department of Software EngineeringSivas Cumhuriyet UniversitySivas58140Turkey Faculty of Engineering Department of Computer EngineeringSivas Cumhuriyet UniversitySivas58140Turkey

Deep learning(DL)techniques,which do not need complex preprocessing and feature analysis,are used in many areas of medicine and achieve promising *** the other hand,in medical studies,a limited dataset decreases the abstraction ability of the DL *** this context,we aimed to produce synthetic brain images including three tumor types(glioma,meningioma,and pituitary),unlike traditional data augmentation methods,and classify them with *** study proposes a tumor classification model consisting of a Dense Convolutional Network(DenseNet121)-based DL model to prevent forgetting problems in deep networks and delay information flow between *** comparing models trained on two different datasets,we demonstrated the effect of synthetic images generated by Cycle Generative Adversarial Network(CycleGAN)on the generalization of *** model is trained only on the original dataset,while the other is trained on the combined dataset of synthetic and original *** data generated by CycleGAN improved the best accuracy values for glioma,meningioma,and pituitary tumor classes from 0.9633,0.9569,and 0.9904 to 0.9968,0.9920,and 0.9952,*** developed model using synthetic data obtained a higher accuracy value than the related studies in the ***,except for pixel-level and affine transform data augmentation,synthetic data has been generated in the figshare brain dataset for the first time.

关键词： Brain tumor classification deep learning cycle generative adversarial network data augmentation

Trade and innovation: Unraveling a complex nexus

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International Journal of Innovation Studies 2021年第1期5卷 23-34页

作者： Difei Geng Raja kali Department of Economics Sam M.Walton College of BusinessUniversity of ArkansasFayettevilleAR72701USA

This paper reviews the theoretical and empirical economic literature on the innovation effect of international trade. To this end, we focus on technological innovation that targets product characteristics. We highlight three main channels through which international trade can affect innovation by domestic firms:increasing market size, intensifying market competition and facilitating foreign sourcing. While the market size effect of trade on domestic innovation is found to be predominantly positive, the effects of market competition and foreign sourcing are ambiguous and can depend on a variety of factors. Moreover, the impact of trade on innovation is likely heterogeneous across firms.

关键词： Trade Innovation Product innovation Process innovation

Tribological and economic evaluation of recycled mineral lubricating oils

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Science China(Technological Sciences) 2013年第12期56卷 2964-2972页

作者： LIU JianFang GU kali DUAN HaiTao ZHAO Yuan LI Jian Wuhan Research Institute of Materials Protection Wuhan Polytechnic University

Seven kinds of used mineral lubricating oils,including hydraulic oils,film bearing oils,steam turbine oil and gear oils,were recycled by reclamation and adding *** and chemical properties of the recycled oils were measured and their lubrication performances were evaluated by the original and modified four-ball *** surfaces were analyzed by energy dispersive X-ray spectroscopy and Raman *** recycling costs of burning,re-refined and refortified were *** showed that physical and chemical properties of the refortified oils were improved effectively and became in the industrial access *** the different friction materials under different loads,refortified oils provided excellent lubrication performances,much better than those of fresh *** of additives replenished,the different lubrication films could form on the worn surfaces.A rough financial calculation revealed that the refortification process could produce the most economic value among the three methods.

关键词： lubricating oil refortification process lubrication performance economic evaluation physical and chemical property