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Effect of welding processes and consumables on fatigue crack growth behaviour of armour grade quenched and tempered steel joints

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Defence technology（防务技术） 2014年第1期10卷 47-59页

作者： G.MAGUDEESWARAN V.BALASUBRAMANIAN G.MADHUSUDHAN reddy Department of Mechanical Engineering PSNA College of Engineering & Technology Kothandaraman Nagar Muthanampatti Centre for Materials Joining & Research Department of Manufacturing Engineering Annamalai University Metal Joining Group Solidification Technology Division Defence Metallurgical Research LaboratoryKanchanbagh

Quenched and tempered(Q&t) steels are widely used in the construction of military vehicles due to its high strength to weight ratio and high hardness. these steels are prone to hydrogen induced cracking(HIC) in the heat affected zone(HAZ) after welding. the use of austenitic stainless steel(ASS) consumables to weld the above steel was the only available remedy because of higher solubility for hydrogen in austenitic phase. the use of stainless steel consumables for a non-stainless steel base metal is not economical. Hence, alternate consumables for welding Q&t steels and their vulnerability to HIC need to be explored. Recent studies proved that low hydrogen ferritic steel(LHF) consumables can be used to weld Q&t steels, which can give very low hydrogen levels in the weld deposits. the use of ASS and LHF consumables will lead to distinct microstructures in their respective welds. this microstructural heterogeneity will have a drastic influence in the fatigue crack growth resistance of armour grade Q&t steel welds. Hence, in this investigation an attempt has been made to study the influence of welding consumables and welding processes on fatigue crack growth behaviour of armour grade Q&t Steel joints. Shielded metal arc welding(SMAW) and Flux cored arc welding(FCAW) were used for fabrication of joints using ASS and LHF consumables. the joints fabricated by SMAW process using LHF consumable exhibited superior fatigue crack growth resistance than all other joints.

关键词：焊接工艺疲劳裂纹扩展行为消耗品钢接头装甲回火淬火

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Role of adiponectin and some other factors linking type 2 diabetes mellitus and obesity

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World Journal of Diabetes 2015年第15期6卷 1296-1308页

作者： chandra Kanti Chakraborti Kanak Manjari Institute of Phar- maceutical Sciences

Because of the intimate association of obesity with type 2 diabetes mellitus(t2DM), during the last two decades, extensive research work is being conducted to find out whether the coexistence of the two is a simple association or there is a positive correlating link between the two. In this article, an attempt has been made to collect and analyse the recent developments in this field and to arrive at a conclusion on the subject. the possible role of several important factors(obtained from adipocytes/not of adipocyte origin) in linking the two has been discussed in detail. Some of the agents, specifically adiponectin, are beneficial(i.e., reduce the incidence of both), while others are harmful(i.e., increase their incidence). From the analysis, it appears that obesity and t2 DM are intimately linked.

关键词： Obesity Insulin Insulin resistance type 2 diabetes

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Microstructure,mechanical and corrosion behavior of high strength AA7075aluminium alloy friction stir welds-Effect of post weld heat treatment

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Defence technology（防务技术） 2015年第4期11卷 362-369页

作者： P.Vijaya Kumar G.Madhusudhan reddy K.Srinivasa Rao Department of Mechanical Engineering R.I.T. Defence Metallurgical Research Laboratory Department of Metallurgical Engineering Andhra University

High strength aluminium alloy AA7075(Al-Zn-Mg-Cu) is a precipitate hardenable alloy widely used in the aerospace,defense,marine and automobile *** of the heat treatable aluminium alloys in all these sectors is ever-increasing owing to their excellent strength-toweight ratio and reasonably good corrosion *** shortage in corrosion resistance,however,usually poses negative concern about their reliability and lifetime when they service in the variable marine *** alloys also exhibit low weldability due to poor solidification microstructure,porosity in fusion zone and lose their mechanical properties when they are welded by fusion welding *** stir welding(FSW) is a reliable technique to retain the properties of the alloy as the joining takes place in the solid *** welds are susceptible to corrosion due to the microstructural changes in the weld nugget during *** this work,the effect of post weld treatments,viz.,peak aging(t6) and retrogression & reaging(RRA),on the microstructure,mechanical properties and pitting corrosion has been *** stir welding of 8 mm-thick AA7075 alloy was carried *** microstructural changes of base metal and nugget zone of friction stir welds were studied using optical microscopy,scanning electron microscopy and transmission electron *** and hardness test of base metal and welds has been carried *** corrosion resistance was determined through dynamic polarization *** was observed that the hardness and strength of weld were observed to be comparatively high in peak aged(t6) condition but the welds showed poor corrosion *** resistance to pitting corrosion was improved and the mechanical properties were maintained by RRA *** resistance to pitting corrosion was improved in RRA condition with the minimum loss of weld strength.

关键词： 7075铝合金高强度铝合金搅拌摩擦焊耐腐蚀性热处理效果微观结构焊缝机械性能

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Microstructure and pitting corrosion of armor grade AA7075 aluminum alloy friction stir weld nugget zone-Effect of post weld heat treatment and addition of boron carbide

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Defence technology（防务技术） 2015年第2期11卷 166-173页

作者： P.VIJAYA KUMAR G.MADHUSUDHAN reddy K.SRINIVASA RAO Department of Mechanical Engineering R.I.T. Defence Metallurgical Research Laboratory Department of Metallurgical Engineering Andhra University

Friction stir welding(FSW) of high strength aluminum alloys has been emerged as an alternative joining technique to avoid the problems during fusion *** recent times FSW is being used for armor grade AA7075 aluminum alloy in defense,aerospace and marine applications where it has to serve in non uniform loading and corrosive *** though friction stir welds of AA7075 alloy possess better mechanical properties but suffer from poor corrosion *** present work involves use of retrogression and reaging(RRA) post weld heat treatment to improve the corrosion resistance of welded joints of aluminum *** attempt also has been made to change the chemical composition of the weld nugget by adding B4C nano particles with the aid of the FSW on a specially prepared base metal plate in butt *** effects of peak aged condition(t6),RRA and addition of B4C nano particles on microstructure,hardness and pitting corrosion of nugget zone of the friction stir welds of AA7075 alloy have been *** though RRA improved the pitting corrosion resistance,its hardness was slightly *** improvement in pitting corrosion resistance was achieved with addition of boron carbide powder and post weld heat treatment of RRA.

关键词： 7075铝合金搅拌摩擦焊焊后热处理碳化硼颗粒抗点蚀微观结构装甲 7075合金

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Effect of Hardfacing Consumables on Ballistic Performance of Q&t Steel Joints

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Defence technology（防务技术） 2013年第4期9卷 249-258页

作者： M.BALAKRISHNAN V.BALASUBRAMANIAN G.MADHUSUDHAN reddy Department of Mechanical Engineering M. Kumarasamy College of Engineering (Autonomous) Center for Materials Joining & Research (CEMAJOR) Department of Manufacturing Engineering Annamalai University Solidification technology Division Metal Joining Group Defence Metallurgical Research Laboratory (DMRL)

this study was carried out to evaluate the effect of hardfacing consumables on ballistic performance of armour grade quenched and tempered(Q&t)steel welded *** evaluate the effect of hardfacing consumables,joints were fabricated using 4 mm thick tungsten carbide(WC)/chromium carbide(CrC)hardfaced middle layer;above and below which austenitic stainless steel(SS)layers were deposited on both sides of the hardfaced *** metal arc welding(SMAW)process were used to deposite all(hardfaced layer and SS layers)*** fabricated joints were evaluated for its ballistic performance,and the results were compared with respect to depth of penetration(DOP)on weld metal and heat-affected zone(HAZ)*** the ballistic test results,it was observed that both the joints successfully stopped the bullet penetration at weld center *** the two joints,the joint made with CrC hardfaced interlayer(CAHA)offered better ballistic resistance at weld *** is because its hardness is higher due to the presence of primary carbides of needle shape,polyhedral shape and eutectic matrix containing a mixture of gt M7C3carbides in the CrC hardfaced *** scattering hardness level in the WC interlayer,the matrix decomposition resulted lower hardness and the co-existence of d ferrite in the interface between hardfacing and SS root/SS cap could be attributed to the inferior ballistic resistance of the joint made with WC hardfaced interlayer(WAHA joint).

关键词：弹道性能耐磨堆焊 M7C3型碳化物耗材焊接金属焊缝金属初生碳化物淬火效果

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Heterologous expression of Lolium perenne antifreeze protein confers chilling tolerance in tomato

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Journal of Integrative Agriculture 2018年第5期17卷 1128-1136页

作者： Srinivasan Balamurugan Jayan Susan Ann Inchakalody P Varghese Shanmugaraj Bala Murugan Mani chandra Harish Sarma Rajeev Kumar Ramalingam Sathishkumar Plant Genetic Engineering Laboratory Department of BiotechnologyBharathiar University

Antifreeze proteins（AFP） are produced by certain plants, animals, fungi and bacteria that enable them to survive upon extremely low temperature. Perennial rye grass, Lolium perenne, was reported to possess AFP which protects them from cold environments. In the present investigation, we isolated AFP gene from L. perenne and expressed it in tomato plants to elucidate its role upon chilling stress. the t1 transgenic tomato lines were selected and subjected to molecular, biochemical and physiological analyses. Stable integration and transcription of Lp AFP in transgenic tomato plants was confirmed by Southern blot hybridization and Rt-PCR, respectively. Physiological analyses under chilling conditions showed that the chilling stress induced physiological damage in wild type（Wt） plants, while the transgenic plants remained healthy. total sugar content increased gradually in both Wt and transgenic plants throughout the chilling treatment. Interestingly, transgenic plants exhibited remarkable alterations in terms of relative water content（RWC） and electrolyte leakage index（ELI） than those of Wt. RWC increased significantly by 3-fold and the electrolyte leakage was reduced by 2.6-fold in transgenic plants comparing with Wt. Overall, this report proved that Lp AFP gene confers chilling tolerance in transgenic tomato plants and it could be a potential candidate to extrapolate the chilling tolerance on other chilling-sensitive food crops.

关键词： Lolium perenne antifreeze protein chilling tolerance genetic transformation transgenic tomato

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Late-Season Grass Weed Management with In-Crop and Post-Harvest Herbicides in twin-Row Glyphosate-Resistant Soybean

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American Journal of Plant Sciences 2015年第1期6卷 213-218页

作者： Krishna N. reddy Charles t. Bryson Vijay K. Nandula Crop Production Systems Research Unit USDA-ARS Stoneville Mississippi USA

Emergence of grasses late in the season has become a problem in glyphosate-resistant (GR) soybean production in the southern US. A 3-yr field study was conducted from 2011 to 2013 at Stoneville, MS to determine efficacy of post-harvest and pyroxasulfone-based in-crop herbicides on late-season grasses and yield in twin-row glyphosate-resistant soybean. Experiments were conducted in a split-plot arrangement of treatments in a randomized complete block design with fall herbicides (with and without pendimethalin at 1.12 kg ai ha-1 and paraquatat 0.84 kg ai ha-1) as main plots and in-crop herbicides as subplots with four replications. the six in-crop herbicide programs were: glyphosate applied early postemergence (EPOSt) at 0.84 kg·aeha-1 followed by (fb) glyphosate late postemergence (LPOSt) at 0.84 kg·ha-1 with and without pyroxasulfone preemergence (PRE) applied at 0.18 kg ai ha-1, pyroxasulfone PRE fb glyphosate at 0.84 kg·ha-1 LPOSt or glyphosate at 0.84 kg·ha-1 + S-metolachlor at 1.68 kg ai ha-1 EPOSt, pyroxasulfone PRE fb S-meto- lachlor at 1.12 kg·ha-1 + fomesafen at 0.27 kg ai ha-1 EPOSt fb clethodim at 0.14 kg ai ha-1, and a no-herbicide control. Browntop millet, Digitaria spp., and junglerice densities at 2 weeks after LPOSt, grass weed dry biomass at harvest, and soybean yield were similar regardless of post- harvest herbicides in all three years. At 2 weeks after LPOSt, browntop millet, Digitaria spp. and junglerice densities were greatly reduced in all five in-crop herbicide treatments compared with no herbicide plot in all three years. Grass weed dry biomass in no-herbicide plots was 3346, 6136, and 6916 kg·ha-1 in 2011, 2012, and 2013, respectively and the five herbicide treatments reduced grass weed dry biomass by at least 87%, 84%, and 99% in 2011, 2012, and 2013, respectively. Soybean yield was higher with all five in-crop herbicide treatments compared to no herbicide control in all three years. these results indicate that browntop millet, Digitaria sp

关键词： Browntop Millet Digitaria spp. Junglerice S-Metolachlor Pyroxasulfone Soybean twin-Row

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

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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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Schottky Barrier Parameters of Pd/ti Contacts on N-type InP Revealed from I-V-t And C-V-t Measurements

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Journal of Modern Physics 2011年第3期2卷 113-123页

作者： D. Subba reddy M. Bhaskar reddy N. Nanda Kumar reddy V. Rajagopal reddy 不详

We report on the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of the Pd/ti/n-InP Schottky barrier diodes (SBDs) in the temperature range 160-400 K in steps of 40 K. the barrier heights and ideality factors of Schottky contact are found in the range 0.35 eV (I-V), 0.73 eV (C-V) at 160 K and 0.63 eV (I-V), 0.61 eV (C-V) at 400 K, respectively. It is observed that the zero-bias barrier height decreases and ideality factor n increase with a decrease in temperature, this behaviour is attributed to barrier inhomogeneities by assuming Gaussian distribution at the interface. the calculated value of series resistance (Rs) from the forward I-V characteristics is decreased with an increase in temperature. the homogeneous barrier height value of approximately 0.71 eV for the Pd/ti Schottky diode has been obtained from the linear relationship between the temperature-dependent experimentally effective barrier heights and ideality factors. the zero-bias barrier height ( ) versus 1/2kt plot has been drawn to obtain evidence of a Gaussian distribution of the barrier heights and values of = 0.80 eV and = 114 mV for the mean barrier height and standard deviation have been obtained from the plot, respectively. the modified Richardson ln(I0/t2)- ( ) versus 1000/t plot has a good linearity over the investigated temperature range and gives the mean barrier height ( ) and Richardson constant (A*) values as 0.796 eV and 6.16 Acm-2K-2 respectively. the discrepancy between Schottky barrier heights obtained from I-V and C-V measurements is also interpreted.

关键词： Schottky Barrier Parameters I-V-t and C-V-t Measurements Pd/ti Schottky Contacts N-type InP Gaussian Distribution

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PCR analysis of Yq microdeletions in infertile males, a study from South India

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Asian Journal of Andrology 2002年第4期4卷 265-268页

作者： S. Ramesh Babu M. Swarna P. Padmavathi P.P. reddy Institute of Genetics & Hospital for Genetic Diseases Scientist Osmania University Begumpet Hyderabad-500 016 IndiaInstitute of Genetics & Hospital for Genetic Diseases Scientist Osmania University Begumpet Hyderabad-500 016 IndiaInstitute of Genetics & Hospital for Genetic Diseases Scientist Osmania University Begumpet Hyderabad-500 016 IndiaInstitute of Genetics & Hospital for Genetic Diseases Scientist Osmania University Begumpet Hyderabad-500 016 India

AIM: to estimate the frequency of microdeletions in the long arm of Y-chromosome of 20 infertile males from South India. MEtHODS: Polymerase chain reaction (PCR) amplification using Y-specific StS of azoospermia factor (AZF) regions i.e., SY 84 for AZFa, SY 127 for AZFb and SY 254 for AZFc. RESULtS: Of the 20 infertile subjects 3 (15 %), one azoospermic and two oligozoospermic, showed microdeletions in the AZF region of Y-chromosome. CONCLUSION: the frequency of deletions involving AZF region of the Y-chromosome is 15 % in azoospermic and severely oligozoospermic infertile men. PCR amplification of AZF locus is useful for the diagnosis of microdeletions in the Y-chromosome.

关键词： Chromosome Deletion Chromosomes, Human, Y Base Sequence Chromosome Mapping Comparative Study DNA Primers Female Gene Frequency Humans India Infertility, Male Male Oligospermia Polymerase Chain Reaction Reference Values Research Support, Non-U.S. Gov't Seminal Plasma Proteins

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