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DEM simulations of critical state behaviour of granular materials under various drained triaxial stress path tests

Particuology 2023年第10期81卷 98-108页

作者： shiva Prashanth kumar Kodicherla Guobin Gong Stephen Wilkinson Department of Civil Mining and Process EngineeringNamibia University of Science and TechnologyWindhoekNamibia Department of Civil Engineering Xi’an Jiaotong-Liverpool UniversitySuzhouChina Faculty of Engineering and Information Sciences University of WollongongDubai CampusDubaiUnited Arab Emirates

The present study investigates the critical state behaviour of granular assemblies composed of clumped particles under four different drained axisymmetric triaxial stress paths,using the discrete element method(DEM).A series of numerical samples were prepared at initial states with different density indexes(1D)and different initial confining pressures(ρ′0).These samples were sheared to large strains,at which constant stresses and volumes were maintained to reach the critical *** evolution of stress ratio under the same loading mode(for the same intermediate principal stress ratio,b)is shown to yield an almost identical behaviour independent of stress paths,whereas the stress-strain response depends on the stress *** different axisymmetric stress paths all share the same unique friction angle at critical state,indicating the Mohr-Coulomb failure criterion is the appropriate critical state strength criterion,which is at least true for the axisymmetric stress conditions.A unique coordination number(CN)is achieved at the critical state for a given po,which is independent of the stress *** critical state CN is found to increase with the increase in po,which could be attributed to the decrease in the critical state void ratio(ec)as mean effective stress(ρ′0)***,a unique linear functional relationship is found between the critical state values of cN and ec,and a unique polynomial functional relationship is found between the critical state values of CN andρ′.These functional relationships indicate no dependency on the stress paths or loading modes,thus characterizing unique features at critical states at both macroscopic and microscopic levels for a given type of granular material.

关键词： Discrete element method Critical state Drained behaviour Triaxial stress paths

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Experimental Evaluation of a Multistage Reciprocating Evaporative Cooler Performance for Varied Climatic Conditions

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Journal of Thermal Science 2023年第4期32卷 1523-1535页

作者： Sampath SURANJAN SALINS S.V.KOTA REDDY shiva kumar School of Engineering and IT Manipal Academy of Higher EducationDubai CampusDubaiPO 345050UAE Mechanical Engineering Department VIT-AP UniversityAmaravatiAndra Pradesh52223India Department of Mechanical and Manufacturing Engineering Manipal Institute of TechnologyManipal Academy of Higher EducationManipal576104India

Current system focuses on design&construction of a multistage reciprocating evaporative cooling test *** packings that are used will undergo the reciprocating action,powered by the cam follower mechanism maintained at an actual rotation *** dry bulb temperature&humidity values are varied to replicate the varying climatic conditions,and the output parameters such as cooling load,evaporation rate(ER),humidification efficiency(HE),coefficient of performance(COP)are *** results showed that as inlet humidity raises,the performance of system *** the rise in the camshaft speed or packing velocity,there is an upsurge in the performance until a cam speed of 10 r/min or packing velocity of 0.083 m/s and with further increases in the value,overall performance *** system gave a maximum COP,ER,and HE equal to 3.80,73.87%,and 0.53 g/kg respectively.A rise in the inlet air temperature yielded a maximum change in dry bulb temperature of 8.2℃.Overall,results indicated that evaporative cooling is more effective in arid climates than the cold and humid *** quality test is performed to measure CO_(2),Total Volatile Organic Compound(TVOC),and Formaldehyde(HCHO),and it is found that humidified air entering the defined space is of excellent quality.

关键词： multistage humidifier evaporative cooling reciprocating packing humidification efficiency

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Evaluation of VSK separation in the classification of two mineralogically different iron ore fines

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International Journal of Minerals,Metallurgy and Materials 2023年第2期30卷 260-270页

作者： Deepak Nayak Tonmoy Kundu Nilima Dash shiva kumar I.Angadi S.K.Chaurasiya G.E.Sreedhar T.V.S.Subrahmanyam Swagat S.Rath Mineral Processing Department CSIR-Institute of Minerals and Materials TechnologyBhubaneswar 751013India R&D Centre National Mineral Development Corporation LimitedHyderabad 500028India

With gradually diminishing Fe grade in tandem with the ever-increasing demand for high-grade iron ores,iron ore industries are now focusing on the beneficiation of low-grade iron ore fines,mainly considered ***,the scarcity of water at many of the mines’sites and the new water conservation policies of the governments have necessitated research on suitable dry beneficiation *** this context,an effort has been made to evaluate the efficacy of a dry classification unit,such as the VSK separator,in upgrading the iron values of two low-grade Indian iron ore fines,named Sample 1 and Sample *** mineralogical studies,involving scanning electron microscopy and X-ray diffraction,suggest that Sample 1 is a low-grade blue dust sample(51.2wt%Fe)containing hematite and quartz as the major minerals,while Sample 2(53.3wt%Fe)shows the presence of goethite in addition to hematite and *** experiments,carried out using Box-Benkhen statistical design,indicate that blower speed,followed by feed rate,is the most influencing operating parameter in obtaining a good product in the VSK *** optimum levels of the operating factors,a fines product with~55wt%Fe at a yield of~40%can be obtained from Sample 1,while Sample 2 can be upgraded to~56wt%Fe at a yield of~85%.The results suggest that the VSK separator can be employed as an efficient intermediate unit operation in a processing circuit to upgrade the iron contents of iron ore fines.

关键词： iron ore fines dry beneficiation VSK separator Box–Behnken design

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Highly sensitive assay for the determination of therapeutic peptide desmopressin in human plasma by UPLC–MS/MS

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Journal of Pharmaceutical Analysis 2017年第3期7卷 196-202页

作者： shiva kumar Gudlawar Nageswara Rao Pilli Sridhar Siddiraju Jaya Dwivedi Department of Chemistry Banasthali VidyapeethJaipur 304022India Wellquest Clinical Research Laboratories RamanthapurHyderabad 500013India Department of Pharmaceutical Chemistry Malla Reddy College of PharmacyMaisammagudaSecunderabad 5000100India

An analytical method based on ultra-performance liquid chromatography with positive ion electrospray ionization(ESI) coupled with tandem mass spectrometry(UPLC–MS/MS) was developed and validated for the determination of therapeutic peptide desmopressin in human plasma. A desmopressin stable labeled isotope(desmopressin d_8) was used as an internal standard. Analyte and the internal standard were extracted from200 μL of human plasma via solid-phase extraction technique using Oasis WCX cartridges. The chromatographic separation was achieved on an Aquity UPLC HSS T3 column by using a gradient mixture of methanol and 1 m M ammonium formate buffer as the mobile phase. The calibration curve obtained was linear(r^2≥0.99)over the concentration range of 1.01–200 pg/m L. Method validation was performed as per FDA guidelines and the results met the acceptance criteria. The results of the intra-and inter-day precision and accuracy studies were well within the acceptable limits. The proposed method was successfully applied to pharmacokinetic studies in humans.

关键词： Desmopressin Solid-phase extraction (SPE) Ultra performance liquid chromatography–tandem mass spectrometry Method validation Pharmacokinetics

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Discrete element modelling of strength and critical state characteristics of granular materials under axial compression and axial extension stress path tests

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Particuology 2021年第3期19卷 152-162页

作者： shiva Prashanth kumar Kodicherla Guobin Gong Lei Fan Stephen Wilkinson Charles K.S.Moy Department of Civil Engineering Xi’an Jiaotong-Liverpool University(XJTLU)China Department of Civil Engineering University of WollongongDubai

The critical state soil mechanics(CSSM)framework has been widely used across a range of problems in geomechanics involving complex loading ***,the uniqueness of the critical state has been disputed for many years and it remains a controversial *** by previous investigations,a series of discrete element method(DEM)simulations were performed under both axial compression(AC)and axial extension(AE)stress *** samples were isotropically compressed at varying mean normal effective stresses(confining pressures)and sheared to a large axial strain of approximately 60%.It is found that there exist unique values of critical void ratios and stress ratios under critical state,which are independent of the samples’initial packings but dependent on stress *** the critical strength(stress ratio)for the AC stress path tests is higher than that for the AE stress *** critical state lines(CSLs)are found to path-dependent but unique for each stress path.A unique linear relationship between the critical coordination numbers and critical void ratios is identified under the AC and AE stress paths respectively,but such a relationship depends on the stress *** is also found that there exist unique values of microscopic parameters in terms of deviator fabric under critical state,which are independent of the samples’initial packings but dependent on stress *** these simulation results lead to the conclusion of non-uniqueness of CSLs from both macroscopic and microscopic viewpoints.

关键词： DEMClumped particles Critical state Densification index State parameter

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Investigations of the effects of particle morphology on granular material behaviors using a multi-sphere approach

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第6期12卷 1301-1312页

作者： shiva Prashanth kumar Kodicherla Guobin Gong Lei Fan Stephen Wilkinson Charles K.S.Moy Department of Civil Engineering Xi’an JiaotongeLiverpool University(XJTLU)Suzhou215123China Department of Civil Engineering and Industrial Design University of LiverpoolLiverpoolUK Department of Civil Engineering University of WollongongDubaiUAE

This article studies the influences of particle morphology on the behaviors of granular materials at both macroscopic and microscopic levels based on the discrete element method(DEM).A set of numerical tests under drained triaxial compression was performed by controlling two morphological descriptors,*** of the smallest to the largest pebble diameter,x,and the maximum pebbleepebble intersection angle,*** descriptors are vital in generating particle geometry and surface *** was found that the stress responses of all assemblies exhibited similar behavior and showed post-peak *** normalized stress ratio and volumetric strains flatten off and tended to reach a steady value after an axial strain of 40%.While the friction angles at peak state varied with different morphological descriptors,the friction angles at critical state showed no significant ***,evolution of the average coordination numbers showed a dramatic exponential decay until an axial strain of about 15%after which it stabilized and was unaffected by further increase of axial *** addition,stress ratio q/p and strong fabric parameter fs d=fs m were found to follow an approximately linear relationship for each *** findings emphasized the significance of the influences of particle morphology on the macroscopic and microscopic responses of granular materials.

关键词： Discrete element method(DEM) Particle morphology Granular materials Triaxial compression Fabric

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Recycling polymeric waste from electronic and automotive sectors into value added products

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Frontiers of Environmental Science & Engineering 2017年第5期11卷 55-64页

作者： Abhishek kumar Veena Choudhary Rita Khanna Romina Cayumil Muhammad Ikram-ul-Haq Veena Sahajwalla shiva kumar I. Angadi Ganapathy E. Paruthy Partha S. Mukherjee Miles Park Centre for Polymer Science and Engineering Indian Institute of Technology Delhi Hauz Khas New Delhi 110016 India Centre for Sustainable Materials Research and Technology (SMART) School of Materials Science and Engineering The University of New South Wales Sydney NSW 2052 Australia CSIR- Institute of Minerals and Materials Technology Advanced Materials Technology Department Bhubaneshwar Orissa 751013 India Industrial Design Australian School of Architecture and Design The University of New South Wales Sydney NSW 2052 Australia

The environmentally sustainable disposal and recycling of ever increasing volumes of electronic waste has become a global waste management issue. The addition of up to 25% polymeric waste PCBs （printed circuit boards） as fillers in polypropylene （PP） composites was partially successful： while the tensile modulus, flexural strength and tlexural modulus of composites were enhanced, the tenstle and impact strengths were found to decrease. As a lowering of impact strength can significantly limit the application of PP based composites, it is necessary to incorporate impact modifying polymers such as rubbery particles in the mix. We report on a novel investigation on the simultaneous utilization of electronic and automotive rubber waste as fillers in PP composites. These composites were prepared by using 25 wt.% polymeric PCB powder, up to 9% of ethylene propylene rubber （EPR）, and PP： balance. The influence of EPR on the structural, thermal, mechanical and rheological properties of PP/PCB/ EPR composites was investigated. While the addition of EPR caused the nucleation of the I~ crystalline phase of PP, the onset temperature for thermal degradation was found to decrease by 8%. The tensile modulus and strength decreased by 1 b% and 19%, respectively; and the elongataon at break increased by -71%. The impact strength showed a maximum increase of-18% at 7 wt.%-9 wt.% EPR content. Various rheological properties were found to be well within the range of processing limits. This novel eco-friendly approach could help utilize significant amounts of polymeric electronic and automotive waste for fabricating valuable polymer composites.

关键词： E-waste Polymer composites Recycling RubberWaste PCBs Filler

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Naringin ameliorates acetic acid induced colitis through modulation of endogenous oxido-nitrosative balance and DNA damage in rats

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The Journal of Biomedical Research 2014年第2期28卷 132-145页

作者： Venkatashivam shiva kumar Anuchandra Ramchandra Rajmane Mohammad Adil Amit Dattatraya Kandhare Pinaki Ghosh Subhash Laxman Bodhankar Department of Pharmacology Poona College of PharmacyBharati Vidyapeeth Deemed University

The aim of this study was to evaluate the effect of naringin on experimentally induced inflammatory bowel dis- ease in rats. Naringin （20, 40 and 80 mg/kg） was given orally for 7 days to Wistar rats before induction of colitis by intrarectal instillation of 2 mL of 4% （v/v） acetic acid solution. The degree of colonic mucosal damage was analyzed by examining mucosal damage, ulcer area, ulcer index and stool consistency. Intrarectal administration of 4% acetic acid resulted in significant modulation of serum alkaline phosphatase, lactate dehydrogenase, superoxide dismutase （SOD）, glutathione （GSH）, malondialdehyde （MDA） and myeloperoxidase （MPO） content along with colonic nitric oxide （NO）, xanthine oxidase （XO） level and protein carbonyl content in the colonic tissue as well as in blood. Naringin （40 and 80 mg/kg） exerted a dose dependent （P 〈 0.05） ameliorative effect, as it significantly increased hematological parameter as well as colonic SOD and GSH. There was a significant （P 〈 0.05） and dose dependant inhibition of macroscopical score, ulcer area along with colonic MDA, MPO activity by the 7 days of pretreatment of naringin （40 and 80 mg/kg）. Biochemical studies revealed a significant （P 〈 0.05） dose dependant inhibition in serum alkaline phosphatase （ALP） and lactate dehydrogenase （LDH） levels by pretreatment of naringin. Increased levels of colonic NO, XO, protein carbonyl content and DNA damage were also sig- nificantly decreased by naringin pretreatment. The findings of the present investigation propose that naringin has an anti-inflammatory, anti-oxidant and anti-apoptotic potential effect at colorectal sites as it modulates the production and expression of oxidative mediators such as MDA, MPO, NO and XO, thus reducing DNA damage.

关键词： acetic acid, apoptosis, fluorimetric analysis of DNA unwinding, inflammatory bowel disease, my-eloperoxidase, naringin, nitrite/nitrate, oxidative stress porotein carbonyl content, vascular permeability, xanthineoxidase

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Study of Heavy Metal Uptake by the Crops Grown by Using Urban Wastewater of Mysore City, India

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Journal of Environmental Protection 2014年第12期5卷 1169-1182页

作者： Mavinakere Ramesh Abhilash shivanna Srikantaswamy Doddaiah shiva kumar Budiguppe Mahadevaiah Kiran Department of Studies in Environmental Science University of Mysore Mysore India

In the 21st century the fresh water scarcity increased very rapidly due to the urbanization and industrialization process. In these conditions the urban wastewater plays an important role in the water usage criteria. In this aspect, in all the major cities, wastewater treatment plants have been constructed to treat the urban wastewater in view of decreasing the water scarcity. The presence of nutrients in the wastewater is considered as beneficial to agricultural practices. The contaminants present in the wastewater pose health risks directly to agricultural workers and indirectly to the consumers as the long term application of the wastewater may result in the accumulation of toxic elements in soil and in plants. In this way the heavy metals will circulate among the food chain and food web to cause adverse effects on human health as well as on soil health. In the present study an attempt has been made to study the characteristics of urban wastewater at wastewater treatment plant of Mysore city. And also heavy metal behavior was studied with the analysis of heavy metals in wastewater, Biosolid and receiving soil along with the plants which indicates the uptake of heavy metals.

关键词： Urban Wastewater (UWW) Biosoild Heavy Metal Bio-Accumulation Mysore

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A Real World Experience of Guidewire-Induced Perforations during Percutaneous Intervention and Their Successful Management

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International Journal of Clinical Medicine 2014年第8期5卷 475-481页

作者： Sridhar Kasturi Vinothkumar Vilvanathan Srinivas Polasa shiva kumar Bandimida Kripa Patel Ashok Thakkar Department of Clinical Trials Sahajanand Medical Tech. Pvt. Ltd. Surat India Department of Pharmacology Ramanbhai Patel College of Pharmacy Charotar University of Science and Technology Campus Changa India Sunshine Heart Institute Hyderabad India

Complication rates following percutaneous interventions have decreased over the past decade due to advancement in both interventional equipment and procedure technique. Despite these advances, the risk of iatrogenic perforations still exists with associated high morbidity and mortality. We are presenting three cases of guidewire-induced perforations including coronary artery and renal artery perforation with their complications and successful management in these case-series.

关键词： Percutaneous Intervention Guidewire Coronary Artery Perforation Renal Artery Perforation

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