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Microstructures and impact toughness behavior of Al 5083 alloy processed by cryorolling and afterwards annealing

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International Journal of Minerals,Metallurgy and Materials 2013年第8期20卷 759-769页

作者： dharmendra singh P.Nageswara Rao R.Jayaganthan Department of Metallurgical and Materials Engineering Indian Institute of Technology RoorkeeRoorkee-247667India

The influence of rolling at liquid nitrogen temperature and annealing on the microstructure and mechanical properties of Al 5083 alloy was studied in this paper. Cryorolled samples of Al 5083 show significant improvements in strength and hardness. The ultimate tensile strength increases up to 340 MPa and 390 MPa for the 30% and 50% cryorolled samples, respectively. The cryorolled samples, with 30% and 50% reduction, were subjected to Charpy impact testing at various temperatures from 190℃ to 100℃. It is observed that increasing the percentage of reduction of samples during cryorolling has significant effect on decreasing impact toughness at all temperatures by increasing yield strength and decreasing ductility. Annealing of samples after cryorolling shows remarkable increment in impact toughness through recovery and recrystallization. The average grain size of the 50% cryorolled sample （14 μm） after annealing at 350℃ for 1 h is found to be finer than that of the 30% cryorolled sample （25 μm）. The scanning electron microscopy （SEM） analysis of fractured surfaces shows a large-size dimpled morphology, resembling the ductile fracture mechanism in the starting material and fibrous structure with very fine dimples in cryorolled samples corresponding to the brittle fracture mechanism.

关键词： aluminum alloys cryorolling annealing microstructure impact toughness recovery recrystallization

Effect of Post Cryorolling Treatments on Microstructural and Mechanical Behaviour of Ultrafine Grained Al-Mg-Si Alloy

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Journal of Materials Science & Technology 2014年第10期30卷 998-1005页

作者： P.Nageswara rao dharmendra singh R.Jayaganthan Department of Metallurgical and Materials Engineering Indian Institute of Technology Roorkee

To investigate the effect of post cryorolling treatments on simultaneous enhancement in strength and ductility of ultrafine grained material （UFG）, AI 6061 alloy was subjected to cryorolling followed by warm rolling （CR ＋ WR） and compared with cryorolling followed by short annealing （CR ＋ SA） at the same temperature. Transmission electron microscopy （TEM） was used to characterize the microstructural features of the processed material. The mechanical properties were investigated through Vickers hardness testing and tensile testing at room temperature. TEM, X-ray diffraction （XRD） and differential scanning calorimetry （DSC） were used to investigate the precipitation evolution in UFG material. Results indicated that the alloy subjected to CR ＋ WR has shown improved mechanical properties （114 HV, ultimate tensile strength （UTS）： 350 MPa） as compared to that in the case of CR ＋ SA （105 HV, UTS： 285 MPa）. The size of the precipitates observed in CR ＋ WR sample after peak ageing treatment is finer than that of peak aged CR ＋ SA sample. The UTS of peak aged CR ＋ WR sample （UTS： 390 MPa） was found to be higher than that of peak aged CR ＋ SA sample （UTS： 355 MPa）, without decrease in ductility.

关键词： Aluminium alloy Cryorolling Warm rolling Short annealing Mechanical properties Differential scanning calorimetry (DSC)

Optical performance of hybrid dielectric loaded plasmonic waveguide using PTFE for nano-scale light confinement

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Optoelectronics Letters 2020年第4期16卷 284-289页

作者： Pintu Kumar dharmendra Kumar singh Rakesh Ranjan Optical Fiber Communication and Photonics Lab Department of Electronics and Communication EngineeringNational Institute of Technology(NIT)PatnaPatna 800005India

Different characteristics of fundamental mode of hybrid dielectric loaded plasmonic waveguide have been explored at1550 nm wavelength,to resolve the issue of large propagation loss and diffraction limit with minimal waveguide *** length of 432μm has been achieved with the optimal dimension of 200 nm×40 *** the numerical simulation results,the effective area of 0.021μm^2 and normalized intensity of 40.71μm^-2 in the spacer region of the waveguide have been *** accomplish the ultra-compact directional coupler,the smaller coupling length of about 1.42μm has been ***-based waveguide can be highly beneficial for the realization of monolithic integration with active optical devices.

关键词： waveguide dielectric loaded

Does Glacial-Interglacial Transition Affect Sediment Accumulation in Monsoon-Dominated Regions?

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Acta Geologica Sinica(English Edition) 2017年第3期91卷 1079-1094页

作者： dharmendra Pratap singh Rajeev SARASWAT Dinesh K.NAIK Micropaleontology Laboratory Geological Oceanography DivisionNational Institute of Oceanography

The spatio-temporal changes in sedimentation rate along the continental margin of the monsoon-dominated eastern Arabian Sea during the last 24 kyr have been estimated from a compilation of 58 radiocarbon dated cores, in order to understand the effect of glacial-interglacial variation on sedimentation. The sedimentation rate has been computed for four-time slices, viz. the last glacial maximum, glacial-interglacial transition, early Holocene and late Holocene. We report that the average sedimentation rate in the slope to the abyssal region of the entire eastern Arabian Sea, although higher during the Holocene as compared with that during the last glacial maximum and glacial-interglacial transition, does not significantly vary during all four-time intervals. The sedimentation rate during any particular time interval, however, varies from core to core, thus indicating zonal changes. We report four zones of relatively high sedimentation rate, viz. the northeastern Arabian Sea, the region off the Gulf of Khambhat, the region off Goa and Mangalore, and off the southern tip of India. We suggest that a complex interaction of land-ocean-atmospheric processes controlled sedimentation rate in the eastern Arabian Sea during the last 24 kyr in such a way that the average sedimentation rate does not vary significantly, even during highly contrasting climatic conditions.

关键词： Sedimentation rate monsoon glacial Holocene Arabian Sea

Changes in species composition, diversity and biomass of herbaceous plant traits due to N amendment in a dry tropical environment of India

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Journal of Plant Ecology 2015年第3期8卷 321-332页

作者： Punita Verma R.Sagar Hariom Verma Preeti Verma dharmendra K.singh Department of Botany Banaras Hindu UniversityVaranasi-221005India

Aim European and North american studies have suggested that nitrogen(N)depositions reduce plant diversity and increase primary pro-ductivity due to changes in plant *** predict the vegetation response to future global change,experimental validations from other regions are widely *** assessed the effects of N treat-ment by urea fertilization on the diversity and biomass of the her-baceous plant traits(HPTs)in a dry tropical environment of *** Diversity and biomass of different HPTs were determined on the basis of data collected in year 2010,from 135,1 m×1 m plots dis-tributed over 15 *** plots were treated with urea fertilizer in different doses(Control,60 kgNha−1 yr−1 and 120 kg N ha−1yr−1)since 1st January *** plots were ordinated and data were subjected to appropriate statistical *** Findings Correspondence analysis(Ca)suggested uniqueness of species composition due to N *** number and biomass of the trait categories varied due to N fertilization and *** studied trait categories(except N-fixers)yielded maximum mean species number at moderate level of N *** levels of N fer-tilization exhibited different species diversity-primary productivity(D-P)***,study showed reduction in plant diver-sity due to increase in biomass at high rates of N *** Tall,erect,non N-fixers,annuals,grasses HPTs were favoured by N enrichment.N dose above 60 kg enhanced the biomass of fast grow-ing,erect,annuals,non N-fixers,nitrophilic *** changes in traits with N addition,especially the increase in annuals and grasses and decrease in typically N-rich N-fixers,have implications for sus-tainable cattle production.

关键词： biomass Ca ordination dry tropics N amendment herbaceous plant traits primary productivity species diversity

RSS-Based Selective Clustering Technique Using Master Node for WSN

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Computers, Materials & Continua 2021年第12期69卷 3917-3930页

作者： Vikram Rajpoot Vivek Tiwari Akash Saxena Prashant Chaturvedi dharmendra singh Rajput Mohammed Alkahtani Mustufa Haider Abidi GLA University MathuraIndia DPSM IIIT Naya RaipurIndia Compucom Institute of Technology&Management JaipurIndia Lakshmi Narain College of Technology BhopalIndia Vellore Institute of Technology Vellore632014India Industrial Engineering Department College of EngineeringKing Saud UniversityRiyadh11421Saudi Arabia Raytheon Chair for Systems Engineering Advanced Manufacturing InstituteKing Saud UniversityRiyadh11421Saudi Arabia

Wireless sensor networks(WSN)are designed to monitor the physical properties of the target *** received signal strength(RSS)plays a significant role in reducing sensor node power consumption during data *** utilization of RSS values with clustering is required to harvest the energy of each network node to prolong the network life *** paper introduces the RSS-based energy-efficient selective clustering technique using a master node(RESCM)to improve energy utilization using a master *** master node positioned at the center of the network area and base station(BS)is placed outside the network *** cluster head(CH)selection,the node with a high RSS value is more likely to become *** network is divided into segments according to the distance from the master *** nodes near BS or master node transmit their data using direct transmission without the clustering *** simulation results showed that the RESCM method improves the total network lifespan effectively.

关键词： Wireless sensor network received signal strength clustering base station master node

The Limit of Rotational Energy Transfer in Atom-Diatom Collision and the Hard Ellipsoid Potential Model

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Journal of Chemistry and Chemical Engineering 2014年第2期8卷 180-186页

作者： dharmendra singh Flrozla Department of Physics Govt. P.G. College Rampura Neemuch 458441 lndia

The limit of rotational energy transfer in atom-diatomic systems due to inelastic collision was investigated over the wide range of collision energy, reduced mass and potential parameters of F2-He system. The IICS (integral inelastic cross-sections) is obtained by the IOSAM (infinite order sudden approximation method) and predicted by PG (power-gap) law in the variation of cross-sections. The investigation provided that the classical limit of angular momentum transfer is given by hard ellipsoid potential is meaningful even the cross-sections computed on the real potential, provided the classical turning point on the surface of soft potential is assumed as hard potential surface.

关键词：转动传能碰撞能量势模型双原子系统非弹性碰撞椭球硅藻角动量转移

Natural Products Potential and Scope for Modern Cancer Research

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American Journal of Plant Sciences 2013年第6期4卷 1270-1277页

作者： Rajeev Nema Sarita Khare Parul Jain Alka Pradhan Abhishek Gupta dharmendra singh Center for Microbiology & Bio-Technology Research and Training Institute Bhopal Bhopal India Government of Motilal Vigyan Mahavidyalaya Bhopal India. S.V. Polytechnic College Bhopal India Sarojini Naidu Government Girls Post Graduate (Autonomous) College Bhopal India Sarojini Naidu Government Girls Post Graduate (Autonomous) College Bhopal India

In the present time Natural products are considered to be symbols of protection in comparison to the synthetic product that are regarded as unsafe to human life and environment. Although a large number of synthetic drugs are being added to the world of present pharmacopoeia, but still no system of medicine in the world has been able to solve all the health problems, which include diseases like Cancer. Therefore the search for innovative therapeutic constituents from plants is genuine and urgent. In India, there is an ocean of knowledge about medicinal plants and rich medicinal flora, but still only a few pearls have been searched as therapeutic agents. There are large numbers of original plants left which have not been investigated thoroughly from modern scientific view or their healing values have not been known. Thus there is an insistent need for systematic phytochemical examination of those plants which have not been investigated scientifically. More research can be done to investigate the unknown and unexplored potential of plants. Further analysis of plants (active compounds) can be carried out by way of making use of different analytical methods such as HPTLC, HPLC, NMR and UV spectrophotometer analysis or computer based drug designing.

关键词： Medicinal Plant Natural Product Cancer Biology

Sitagliptin,sitagliptin and metformin,or sitagliptin and amitriptyline attenuate streptozotocin-nicotinamide induced diabetic neuropathy in rats

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The Journal of Biomedical Research 2012年第3期26卷 200-210页

作者： Ashish Kumar Sharma Akash Sharma Rita Kumari Kunal Kishore Divya Sharma Bharthu Parthsarthi Srinivasan Ashok Sharma Santosh Kumar singh Samir Gaur Vijay singh Jatav Prashant Sharma Varnika Srivastava Sneha Joshi Megha Joshi Prashant Kumar Dhakad Davender singh Kanawat Akanksha Mishra Anil Sharma dharmendra singh Ravinder Pal singh Himmat singh Chawda Rambir singh Sachin Kumar Raikwar Muneem Kumar Kurmi Pankaj Khatri Ashutosh Agarwal Arshee Munajjam Department of Pharmacology Gyan Vihar School of PharmacySuresh Gyan Vihar UniversityJagatpuraJaipur(Rajasthan)302025India Department of Pharmacology Delhi Institute of Pharmaceutical Sciences&ResearchPushpviharNew Delhi 110017India Department of Pharmacology Kota Collage of PharmacyRIICO Industrial AreaRanpurKota(Rajasthan)Pincode 302025India

Diabetic neuropathies are a family of nerve disorders caused by diabetes. Symptoms of the disease include nerve palsy, mononeuropathy, mononeuropathy multiplex, diabetic amyotrophy, painful polyneuropathy, autonomic neu- ropathy, and thoracoabdominal neuropathy. In this study, type 2 diabetes in rats was induced with nicotinamide- streptozotocin. Drug treatment was initiated on the d 15, with the combination regimen of metformin, pioglitazone and glimipiride or metformin and sitagliptin or sitagliptin, amitriptyline and sitagliptin and led to significantly im- proved glycemic control, increased grip strength and paw jumping response on d 21, 28 and 35 （P 〈 0.001）. Signif- icant increases in blood protein levels and decreases in urinary protein levels were observed in the animals treated with the different regimens on d 21, 28 and 35 （P 〈 0.001）. Combined treatment of streptozotocin and nicotinamide caused marked degeneration of nerve cells, while administration of metformin and sitagliptin showed tissue regen- eration and no body weight gain. In conclusion, treatment with sitagliptin and sitagliptin combined with metformin or amitriptyline results in no body weight gain, but causes an increase in grip strength and pain sensitivity, exhibits neural protection, and reverses the alteration of biochemical parameters in rats with streptozotocin-nicotinamide induced type 2 diabetes.

关键词： diabetic neuropathy nicotinamide-streptozotocin metformin pioglitazone glimipiride sitagliptin amitriptyline