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Microstructure and Mechanical Properties of Friction Stir Lap Welded Aluminum Alloy AA2014

Journal of Materials Science & Technology 2012年第5期28卷 414-426页

作者： S. Babu G.D. Janaki ram P.V. Venkitakrishnan G. Madhusudhan Reddy K. prasad Rao Dept. of Metallurgical and Materials Engineering Indian Institute of Technology Madras Chennai India Liquid Propulsion Systems Centre Indian Space Research Organisation Tiruvananthapuram India Defence Metallurgical Research Laboratory Hyderabad India

Friction stir lap welds were produced in 3 mm thick Alclad sheets of Al alloy 2014-T4 using two different tools （with triangular and threaded taper cylindrical pins）. The effects of tool geometry on weld microstructure, lap-shear performance and failure mode were investigated. The pin profile was found to significantly influence the hook geometry, which in turn strongly influenced the joint strength and the failure mode. Welds produced in alloy 2014-T4 Alclad sheets by using triangular and threaded taper cylindrical tools exhibited an average lap-shear failure load of 16.5 and 19.5 kN, respectively, while the average failure load for standard riveted joints was only 3.4 kN. Welds produced in alloy 2014-T6 Alclad sheets and in alloy 2014-T4 bare sheets （i.e., no Alclad） were comparatively evaluated with those produced in alloy 2014-T4 Alclad sheets. While the welds made （with threaded taper cylindrical tool） in T6 and T4 conditions showed very similar lap-shear failure loads, the joint efficiency of the welds made in T6 condition （43%） was considerably lower （because of the higher base material strength） than those made in T4 condition （51%）. The Alclad layers were found to present no special problems in friction stir lap welding. Welds made with triangular tool in alloy 2014-T4 Alclad and bare sheets showed very similar lap-shear failure loads. The present work provides some useful insights into the use of friction stir welding for joining Al alloys in lap configuration.

关键词： Aluminum alloys Friction stir welding Lap joints Lap-shear testing

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Impact of climate change on agricultural production: A case of Rasuwa District, Nepal

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Regional Sustainability 2022年第2期3卷 122-132页

作者： Binod DAWADI Anjula SHRESTHA ram Hari ACHARYA Yam prasad DHITAL Rohini DEVKOTA Central Department of Hydrology and Meteorology Tribhuvan UniversityKirtipur Kathmandu44613Nepal Kathmandu Centre for Research and Education Chinese Academy of Sciences-Tribhuvan UniversityKirtipur Kathmandu44613Nepal Central Department of Environmental Science Tribhuvan UniversityKirtipur Kathmandu44613Nepal Department of Meteorology Tri-Chandra Multiple CampusTribhuvan UniversityGhantaghar Kathmandu44600Nepal College of Water Resources and Architectural Engineering Shihezi UniversityShihezi832000China Southern Downs Regional Council Queensland4350Australia University of Southern Queensland Toowoomba Queensland4350Australia

Climate change is expected to threaten the developing countries the most. Nepal is considered one of the five countries most vulnerable to climate change in the world. The mountainous area such as Rasuwa District in Nepal is more vulnerable due to complex topography, human activity(tourism), and climate change. In this context, we carried out this study to assess the climate change and its impact on agriculture production as well as people’s perceptions on the impact of climate change. The long-term(1980–2014) observed climate data(temperature and precipitation) and field-based survey data on people’s perceptions were analyzed. Mann-Kendall trend test and Sen’s slope estimation were used to analyze the temperature and precipitation trends. Furthermore, key informant interviews(KIIs) and focal group discussions(FGDs) were conducted to understand people’s perceptions of the impact of climate change on agricultural production. Further, ERA5 and Asian Precipitation-Highly Resolved Observational Data Integration Towards Evaluation of Water Resources(APHRODITE) datasets were used to compare the in situ climate data. The maximum temperature and total precipitation in summer monsoon(June–September) were found increasing significantly at rates of 0.07℃/a and 19.89 mm/a, respectively. But the minimum winter temperature and winter precipitation were found decrease by 0.05℃/a and 4.89 mm/a, respectively. Moreover, a large number of respondents reported a decrease in millet and wheat productions while an increase in potato production over the considered time duration(1990–2014). It is noteworthy that the respondents from the mid-elevation regions perceived an increasing trend in crop production compared to those from the low elevation regions. In recent years, people living in the high elevation regions of Rasuwa District have started to shift their cropping calendar to increase agricultural production. This study will provide useful information for policymakers in formulating a

关键词： Mountainous areas Climate change Temperature Precipitation Agriculture production Nepal

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Optimal array factor radiation pattern synthesis for linear antenna array using cat swarm optimization： validation by an electromagnetic simulator

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Frontiers of Information Technology & Electronic Engineering 2017年第4期18卷 570-577页

作者： Gopi ram Durbadal MANDAL Sakti prasad GHOSHAL Rajib KAR Department of Electronics and Communication Engineering National Institute of Technology Durgapur 713209 India Department of Electrical Engineering National Institute of Technology Durgapur 713209 India

In this paper, an optimal design of linear antenna arrays having microstrip patch antenna elements has been carried out Cat swarm optimization （CSO） has been applied for the optimization of the control parameters of radiation pattern of an antenna array. The optimal radiation patterns of isotropic antenna elements are obtained by optimizing the current excitation weight of each element and the inter-element spacing. The antenna arrays of 12, 16, and 20 elements are taken as examples. The arrays are designed by using MATLAB computation and are validated through Computer Simulation Technology-Microwave Studio （CST-MWS）. From the simulation results it is evident that CSO is able to yield the optimal design of linear antenna arrays of patch antenna elements.

关键词： Patch antenna Linear antenna array Cat swarm optimization (CSO) Side lobe level (SLL)

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Bianchi Type-Ⅱ Inflationary Models with Stiff Matter and Decaying Cosmological Term

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Chinese Physics Letters 2014年第7期31卷 27-31页

作者： Shri ram, Priyanka Department of Mathematical Sciences Indian Institute of Technology Banaras Hindu University Varanasi 221 005 India

We deal with Einstein＇s field equations with a time-decaying cosmological term of the forms （i） ∧=β（a/a）＋ α/a62 and （ii）∧ = α/a^2, where a is the average scale factor of the universe, α and β are constants for a spatially homogeneous and anisotropic LRS Bianchi type-Ⅱ spacetime. Exact solutions of the field equations for stiff matter are obtained by applying a special law of variation for the Hubble parameter. Anisotropic cosmological models are presented with a constant negative deceleration parameter which corresponds to the accelerated phase of the present universe. The cosmological constant A is obtained as a decreasing function of time that is approaching a small positive value at the present epoch, which is corroborated by the consequences from recent supernovae Ia observations. The physical and kinematical behaviors of the models are also discussed.

关键词： INFLATIONARY universe BIANCHI groups PARTICLE decays COSMOLOGY MATHEMATICAL models SPACE & time HUBBLE constant

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Effect of heavy metals and phenol on bacterial decolourisation and COD reduction of sucrose-aspartic acid Maillard product

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Journal of Environmental Sciences 2013年第1期25卷 172-180页

作者： Sangeeta Yadav ram Chandra Department of Environmental Microbiology School for Environmental SciencesBabasaheb Bhimrao Ambedkar University (A Central University)

Melanodins are amino-carbonyl complex, predominantly present in sugarcane molasses based distillery wastewater as major source of colourant. The microbial decolourisafion of melanoidin is a challenge due to its binding property with other co-pollutants of distillery waste. Results revealed that the presence of Zn2＋（2.00-20.00 mg/L） in melanoidin solution （1200 mg/L） stimulated the bacterial growth and sucrose-aspartic acid Maillard product （SAA） decolourisation as compared to control, while Fe3＋ and Mn2＋ at the same concentration inhibited the process. However, the presence of phenol （100 mg/L） along with Zn2＋, Fe3＋ and Mn2＋ suppressed the bacterial growth, SAA decolourisation and MnP activity. The shrinkage and reduced number of bacterial cell count at higher concentration of heavy metals in presence of phenol was also observed under scanning electron microscope.

关键词： degradation manganese peroxidase melanoidin

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An Overview of High-Performance Aircraft Structural Al Alloy-AA7085

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Acta Metallurgica Sinica(English Letters) 2015年第7期28卷 909-921页

作者： T.ram Prabhu CEMILAC Defence R&D Organization

AA7085 Al alloy is a new-generation,high-strength,quench-insensitive alloy that features in airframe applications such as massive bulkhead and wing spars structures in Airbus A380 and Joint Strike Fighter *** alloy has a great potential in replacing currently used high-strength AA7 xxx alloys in many international and national military aircraft programs [Hawk,Su-30,Mi G series,light combat aircraft（Tejas）,Hindustan turbo/jet trainer,light combat helicopter,advanced light helicopter,and fifth-generation fighter aircrafts].An effort has been made to highlight the processing,heat treatment,properties and applications of the AA7085 Al alloy from the existing literature on the AA7085 *** potential applications of this alloy are presented and compared with the currently used AA7075 Al alloy.A typical process cycle involved in the manufacturing of wrought AA7085 alloy products is described in ***,the precipitation mechanisms involved in the different temper conditions are critically reviewed with the supporting *** mechanical properties with a particular emphasis on tensile,fatigue,and fracture toughness properties are discussed in detail based on the analysis of experimental *** effects of temper conditions on the stress corrosion cracking and exfoliation corrosion have also been reviewed critically.

关键词： Al alloys Heat treatment Material processing Mechanical properties Corrosion

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Syntrophic co-culture of Bacillus subtilis and Klebsiella pneumonia for degradation of kraft lignin discharged from rayon grade pulp industry

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Journal of Environmental Sciences 2015年第7期27卷 229-238页

作者： Sangeeta Yadav ram Chandra Department of Environmental Microbiology School for Environmental Sciences Babasaheb Bhimrao Ambedkar University (A Central University)

In order to search the degradability of kraft lignin, the potential bacterial strains Bacillus subtilis（GU193980） and Klebsiella pneumoniae（GU193981） were isolated, screened and applied in axenic and co-culture conditions. Results revealed that mixed culture showed better decolorization efficiency（80%） and reduction of pollution parameters（COD 73% and BOD62%） than axenic culture. This indicated syntrophic growth of these two bacteria rather than any antagonistic effect. The HPLC analysis of degraded samples of kraft lignin has shown the reduction in peak area compared to control, suggesting that decrease in color intensity might be largely attributed to the degradation of lignin by isolated ***, the GC-MS analysis showed that most of the compounds detected in control were diminished after bacterial treatment. Further, the seed germination test using Phaseolus aureus has supported the detoxification of bacterial decolorized kraft lignin for environmental safety. All these observations have revealed that the developed bacterial co-culture was capable for the effective degradation and decolorization of lignin containing rayon grade pulp mill wastewater for environmental safety.

关键词： Degradation GC-MS Kraft lignin Seed germination test Syntropic

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Mysteries of R^ik=0： A novel paradigm in Einstein＇s theory of gravitation

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Frontiers of physics 2014年第1期9卷 98-112页

作者： ram Gopal Vishwakarma Unidad Academica de Matemdticas Universidad Autdnoma de Zacatecas C.P. 98068 Zacatecas ZAC Mexico

Despite a century-long effort, a proper energy-stress tensor of the gravitational field, could not have been discovered. Furthermore, it has been discovered recently that the standard formulation of the energy-stress tensor of matter, suffers from various inconsistencies and paradoxes, concluding that the tensor is not consistent with the geometric formulation of gravitation [Astrophys. Space Sci., 2009, 321： 151; Astrophys. Space Sei., 2012, 340： 373]. This perhaps hints that a consistent theory of gravitation should not have any bearing on the energy-stress tensor. It is shown here that the so-called ＂vacuum＂ field equations Rik = 0 do not represent an empty spacetime, and the energy, momenta and angular momenta of the gravitational and the matter fields are revealed through the geometry, without including any formulation thereof in the field equations. Though, this novel discovery appears baffling and orthogonal to the usual understanding, is consistent with the observations at all scales, without requiring the Moreover, the resulting theory circumvents the besides explaining some unexplained puzzles. hypothetical dark matter, dark energy or inflation long-standing problems of the standard cosmology

关键词： general relativity and gravitation - fundamental problems and general formalism cos-mological observations

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Mysteries of the geometrization of gravitation

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Research in Astronomy and Astrophysics 2013年第12期13卷 1409-1422页

作者： ram Gopal Vishwakarma Unidad Acad'emica de Matem'aticas Universidad Aut'onoma de Zacatecas

As we now know, there are at least two major difficulties with general rel- ativity （GR）. The first one is related to its incompatibility with quantum mechanics, in the absence of a consistent, widely accepted theory that combines the two theo- ries. The second problem is related to the requirement of the dark sectors-inflaton, dark matter and dark energy by the energy-stress tensor, which are needed to explain a variety of astronomical and cosmological observations. Research has indicated that the dark sectors themselves do not have any non-gravitational or laboratory evidence. Moreover, the dark energy poses, in addition, a serious confrontation between funda- mental physics and cosmology. Guided by theoretical and observational evidences, we are led to an idea that the source of gravitation and its manifestation in GR should be modified. The result is in striking agreement with not only the theory, but also the ob- servations, without requiring the dark sectors of the standard approach. Additionally, it provides natural explanations to some unexplained puzzles.

关键词： general relativity and gravitation -- fundamental problems and generalformalism -- cosmology: observations

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Probabilistic seismic hazard analysis in Nepal

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Earthquake Engineering and Engineering Vibration 2013年第4期12卷 577-586页

作者： Thapa Dilli ram Wang Guoxin State Key Laboratory of Coastal and Offshore Engineering Dalian University of Technology

The seismic ground motion hazard for Nepal has been estimated using a probabilistic approach. A catalogue of earthquakes has been compiled for Nepal and the surrounding region （latitude 26% N and 31.7% N and longitude 79° E and 90° E） from 1255 to 2011. The distribution of catalogued earthquakes, together with available geological and tectonic information were used to delineate twenty-three seismic source seismic source information and probabilistic earthquake hazard prediction relationship, peak ground accelerations （PGAs） have zones in Nepal and the surrounding region. By using the parameters in conjunction with a selected ground motion been calculated at bedrock level with 63%, 10%, and 2% probability of exceedance in 50 years. The estimated PGA values are in the range of 0.07-0.16 g, 0.21 0.62 g, and 0.38-1.1 g for 63%, 10%, and 2% probability of exceedance in 50 years, respectively. The resulting ground motion maps show different characteristics of PGA distribution, i.e., high hazard in the far-western and eastern sections, and low hazard in southern Nepal. The quantified PGA values at bedrock level provide information for microzonation studies in different parts of the country.

关键词： seismic hazard assessment peak ground acceleration earthquake Nepal Himalaya

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