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Microstructure and corrosion behaviour of gas tungsten arc welds of maraging steel

Defence Technology（防务技术） 2015年第1期11卷 48-55页

作者： g.MADHUSUDHAN REDDY K.SRINIVASA rao Defence Metallurgical Research Laboratory Department of Metallurgical Engineering Andhra University

Superior properties of maraging steels make them suitable for the fabrication of components used for military applications like missile covering, rocket motor casing and ship hulls. Welding is the main process for fabrication of these components, while the maraging steels can be fusion welded using gas tungsten arc welding(gTAW) process. All these fabricated components require longer storage life and a major problem in welds is susceptible to stress corrosion cracking(SCC). The present study is aimed at studying the SCC behaviour of MDN 250(18% Ni) steel and its welds with respect to microstructural changes. In the present study, 5.2 mm thick sheets made of MDN 250 steel in the solution annealed condition was welded using gTAW process. post-weld heat treatments of direct ageing(480 C for 3 h), solutionizing(815 C for 1 h) followed by ageing and homogenizing(1150 C for 1 h) followed by ageing were carried out. A mixture of martensite and austenite was observed in the microstructure of the fusion zone of solutionized and direct aged welds and only martensite in as-welded condition. Homogenization and ageing treatment have eliminated reverted austenite and elemental segregation. Homogenized welds also exhibited a marginal improvement in the corrosion resistance compared to those in the as-welded, solutionized and aged condition. Constant load SCC test data clearly revealed that the failure time of homogenized weld is much longer compared to other post weld treatments, and the homogenization treatment is recommended to improve the SCC life of gTA welds of MDN 250 Maraging steel.

关键词： 18% Ni maraging steel gas tungsten arc welding post weld heat treatment Solutionising Ageing treatment pitting corrosion Stress corrosioncracking (SCC)

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Evaluating the effectiveness of marine actinobacterial extract and its mediated titanium dioxide nanoparticles in the degradation of azo dyes

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Journal of Environmental Sciences 2014年第4期26卷 775-782页

作者： S priyaragini S Veena D Swetha L Karthik g Kumar K V Bhaskara rao Molecular and Microbiology Research Laboratory Environmental Biotechnology Division School of Bio Sciences and Technology VIT University

Aim of the present study was to synthesize titanium dioxide nanoparticles （YiO2 Nps） from marine actinobacteria and to develop an eco-friendly azo-dye degradation method. A total of five actinobacterial isolates were isolated from Chennai marine sediments, Tamilnadu, India and analyzed for the synthesis of TiO2 Nps using titanium hydroxide. Among these, the isolate pSV 3 showed positive results for the synthesis of TiO2 Nps, which was confirmed by UV analysis. Further characterization of the synthesized TiO2 Nps was done using XRD, AFM and FI＇-IR analysis. Actinobacterial crude extract and synthesized TiO2 Nps was found efficient in degrading azo dye such as Acid Red 79 （AR-79） and Acid Red 80 （AR-80）. Degradation percentage was found to be 81% for AR-79, 83% for AR-80 using actinobacterial crude extract and 84% for AR-79, 85% for AR-80 using TiO2 Nps. Immobilized actinobacterial ceils showed 88% for AR-79 and 81% for AR- 80, dye degrading capacity. Degraded components were characterized by FT-IR and gC-MS analysis. The phytotoxicity test with 500 μg/mL of untreated dye showed remarkable phenotypic as well as cellular damage to Tagetes erecta plant. Comparatively no such damage was observed on plants by degraded dye components. In biotoxicity assay, treated dyes showed less toxic effect as compared to the untreated dyes.

关键词： actinobacteria azo dye degradation ZiO2 Nps biotoxicity Tagetes erecta

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Biliary strictures complicating living donor liver transplantation:problems,novel insights and solutions

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World Journal of gastroenterology 2018年第19期24卷 2061-2072页

作者： Harshavardhan B rao Arjun prakash Surendran Sudhindran Rama p Venu Department of gastroenterology Amrita Institute of Medical SciencesAmrita UniversityKochi 682041India Department of Transplant and Vascular Surgery Amrita Institute of Medical SciencesAmrita UniversityKochi 682041India

Biliary stricture complicating living donor liver transplantation(LDLT) is a relatively common complication, occurring in most transplant centres across the world. Cases of biliary strictures are more common in LDLT than in deceased donor liver transplantation. Endoscopic management is the mainstay for biliary strictures complicating LDLT and includes endoscopic retrograde cholangiography, sphincterotomy and stent placement(with or without balloon dilatation). The efficacy and safety profiles as well as outcomes of endoscopic management of biliary strictures complicating LDLT is an area that needs to be viewed in isolation, owing to its unique set of problems and attending complications; as such, it merits a tailored approach, which is yet to be well established. The diagnostic criteria applied to these strictures are not uniform and are over-reliant on imaging studies showing an anastomotic narrowing. It has to be kept in mind that in the setting of LDLT, a subjective anastomotic narrowing is present in most cases due to a mismatch in ductal diameters. However, whether this narrowing results in a functionally significant narrowing is a question that needs further study. In addition, wide variation in the endotherapy protocols practised in most centres makes it difficult to interpret the results and hampers our understanding of this topic. The outcome definition for endotherapy is also heterogenous and needs to be standardised to allow for comparison of data in this regard and establish a clinical practice guideline. There have been multiple studies in this area in the last 2 years, with novel findings that have provided solutions to some of these issues. This review endeavours to incorporate these new findings into the wider understanding of endotherapy for biliary strictures complicating LDLT, with specific emphasis on diagnosis of strictures in the LDLT setting, endotherapy protocols and outcome definitions. An attempt is made to present the best management optio

关键词： Biliary strictures Endoscopic management Stenting Self-expanding metal stents Living donor liver transplantation

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Macro and micro issues in turbulent mixing

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Science China(Technological Sciences) 2013年第10期56卷 2355-2360页

作者： MELVIN J KAUFMAN R LIM H KAMAN T rao p.g.IMM J Department of Applied Mathematics and Statistics Stony Brook UniversityStony Brook NY 11794 USA

Numerical prediction of turbulent mixing can be divided into two subproblems: to predict the geometrical extent of a mixing region and to predict the mixing properties on an atomic or molecular scale, within the mixing region. The former goal suffices for some purposes, while important problems of chemical reactions(e.g. flames) and nuclear reactions depend critically on the second goal in addition to the first one. Here we review recent progress in establishing a conceptual reformulation of convergence, and we illustrate these concepts with a review of recent numerical studies addressing turbulence and mixing in the high Reynolds number limit. We review significant progress on the first goal, regarding the mixing region, and initial progress on the second goal, regarding atomic level mixing properties. New results concerning non-uniqueness of the infinite Reynolds number solutions and other consequences of a renormalization group point of view, to be published in detail elsewhere, are summarized *** notion of stochastic convergence(of probability measures and probability distribution functions) replaces traditional pointwise convergence. The primary benefit of this idea is its increased stability relative to the statistical "noise" which characterizes turbulent flow. Our results also show that this modification of convergence, with sufficient mesh refinement, may not be needed. However, in practice, mesh refinement is seldom sufficient and the stochastic convergence concepts have a *** to this circle of ideas is the observation that turbulent mixing, in the limit of high Reynolds number, appears to be non-unique. Not only have multiple solutions been observed(and published) for identical problems, but simple physics based arguments and more refined arguments based on the renormalization group come to the same *** of the non-uniqueness inherent in numerical models of high Reynolds number turbulence and mixing, we also include here numeri

关键词： stochastic convergence turbulent mixing renormalization group dynamic subgrid scale models

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Experimental studies of water hammer in propellant feed system of reaction control system

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propulsion and power Research 2018年第1期7卷 52-59页

作者： Avanish Kumar p.Satya prasad M.Raghavendra rao Defence Research&Development Laboratory HyderabadTelangana 500058India

Water hammer pressure transient produces large dynamic forces which can damage the pipes and other assemblies in the feed line of a reaction control system(RCS).It has led to the failure of pressure transducers monitoring the manifold pressure in the feed line of ***,water hammer studies have been carried out to understand its effect in feed *** system has been simplified to develop a mathematical model and experiments have been carried out at extensive *** mathematical model was developed considering pipe of uniform c/s and moving liquid-gas *** experimental studies have been done using water as working medium instead of actual *** studies showed that rate of pressurization have a very critical role on the water hammer *** studies have been also carried out to study the effect of density,friction and initial liquid column length on water hammer amplitude.

关键词： Water hammer Reaction control system(RCS) propellant feed system Experimental study Testing

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Vibrational Spectra of Distorted Structure Molecules by Using Lie Algebraic Techniques： an Application to Copper and Magnesium Octaethyl porphyrin

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Chinese physics Letters 2010年第10期27卷 80-83页

作者： Srinivasa rao Karumuri School of Sciences and Humanities Sri Viveka Institute of Technology (SVIT) Madalavari Gudem Nunna Krihna District-521212 India

Using a U （2） algebraic model the fundamental stretching vibrations of copper octaethyl porphyrin and magnesium octaethyl porphyrin are calculated for 24 vibrational bands. The locality parameter ξ confirms the highly local behavior of the stretching modes of these porphyrin molecules. The model Hamiltonian so constructed appears to describe the vibrational energy levels accurately.

关键词： Models Vibration porphyrins

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Maximum power point tracking using decision-tree machine-learning algorithm for photovoltaic systems

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Clean Energy 2022年第5期6卷 762-775页

作者： p.Venkata Mahesh S.Meyyappan RamaKoteswara rao Alla Department of Electronics and Instrumentation Engineering Annamalai UniversityChidambaramIndia Department of Instrumentation Engineering Madras Institute of TechnologyChennaiIndia Department of EEE RVR&JC College of EngineeringGunturIndia

This work presents a machine-learning(ML)algorithm for maximum power point tracking(MppT)of an isolated photovoltaic(pV)*** to the dynamic nature of weather conditions,the energy generation of pV systems is *** there is no specific method for effectively dealing with the non-linear data,the use of ML methods to operate the pV system at its maximum power point(Mpp)is desirable.A strategy based on the decision-tree(DT)regression ML algorithm is proposed in this work to determine the Mpp of a pV *** data were gleaned from the technical specifications of the pV module and were used to train and test the *** algorithms predict the maximum power available and the associated voltage of the module for a defined amount of irradiance and *** boost converter duty cycle was determined using predicted *** simulation was carried out for a 10-W solar panel with a short-circuit current of 0.62 A and an open-circuit voltage of 21.50 V at 1000 W/m^(2) irradiance and a temperature of 25℃.The simulation findings demonstrate that the proposed method compelled the pV panel to work at the Mpp predicted by DTs compared to the existing topologies such asβ-MppT,cuckoo search and artificial neural network *** the proposed algorithm,efficiency has been improved by>93.93%in the steady state despite erratic irradiance and temperatures.

关键词： boost converter decision tree maximum power point tracking photovoltaic system regression machine learning

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Investigation of antioxidant and anti-inflammatory activity of leaves of Dalbergia paniculata(Roxb)

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Asian pacific Journal of Tropical Medicine 2012年第6期5卷 455-458页

作者： ganga rao B Madhu Kiran p Vijaya Raju AD pharmacognosy and phytochemistry A.U College of Pharmaceutical SciencesAndhra UniversityVisakhapatnamA.P.India-530 003 A.U College of pharmaceutical Sciences Andhra UniversityVisakhapatnamA.PIndia-530 003

Objective:To investigate the antioxidant and anti-inflammatory activity of orally administered methanolic leaf extract of Dalbergia paniculala(***) in Carrageenan induced inflammation in ***:In vitro antioxidant activity was evaluated for superoxide radical, Hydroxyl radical and DppH radical scavenging *** doses 200 mg/kg,400 mg/kg and 800 mg/kg of *** were tested for anti-inflammatory activity in Carrageenan induced rat paw edema model and paw thickness was measured every one hour up to 6 h. Results:The melhanolic leaf extract of *** produced dose dependent inhibition of Superoxide radical,Hydroxyl radical and OppH *** Carrageenan induced inflammation model,all three doses produced significant percentage inhibition of rat paw edema and 800 mg/kg dose produced maximum percent inhibition of rat paw edema(47.83%) at 3h compared to control ***:In the present study we found that methanolic leaf extract of *** showed good in vitro antioxidant activity and in vivo anti-inflammatory activity in rats.

关键词： Anti-inflammatory activity Antioxidant activity Dalbergia paniculata Free radicals Carragenan Inflammation Edema

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Anti-microbial principles of selected remedial plants from Southern India

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Asian pacific Journal of Tropical Biomedicine 2011年第4期1卷 298-305页

作者： Tirupathi rao g Suresh Babu K J Ujwal Kumar Sujana p A Veerabhadr raoa Sreedhar AS Centre for Cellular and Molecular Biology Hyderabad 500 007India Division of Organic Chemistry-I Natural Products LaboratoryIndian Institute of Chemical TechnologyHyderabad-500 607India

Objective:To examine the anti-bacterial activity of leaf extracts of Morus alba L.(Moraceae)and piper betel L.(piperaceae),and seed extracts of Bombax ceiba L.(Borabacaceae).Methods:We have partially purified plant extracts by solvent extraction method,and evaluated the effect of individual fractions on bacterial growth using Escherichia coli(***),pseudomonas aeruginosa(***) and Staphylococcus aureus(***) bacterial ***:Compared with Morus and Bombax fractions,piper fractions showed significant growth inhibition on all the three types of bacteria *** EtOAc-hexane fractions of piper leaves exhibited significant antibacterial activity with minimum inhibitory concentrations(MIC) of 50 μg/mL culture against both gram-positive and gram-negative *** EtOAc-fractions Ⅰ,Ⅱ,and Ⅳ inhibited bacterial colony formation on soft agar in addition to growth inhibition.A combination treatment of piper fractions with ampicillin resulted in significant growth inhibition in *** and ***,and combination with anticancer drug geldanamycin(2 μg/mL) showed selective growth inhibition against *** and *** major compounds,i.e.,eugenol,3-hexene-ol and stigmasterol,were primarily identified from piper betel leaf *** the individual compounds,eugenol treatment showed improved growth inhibition compared with stigmasterol and ***:We are reporting potential anti-bacterial compounds from piper betel against both gram-positive and gram-negative bacteria either alone or in combination with drug treatment.

关键词： piper betel Anti-microbial activity Escherichia coli pseudomonas aeruginosa Staphylococcus aureus Morus alba Bombax ceiba Minimum inhibitory concentration growth inhibition

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Nonlinear behavior of the population dynamics of three-level systems in the presence of single photon absorption

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Chinese physics B 2019年第2期28卷 272-276页

作者： Allam Srinivasa rao photonic Sciences Laboratory Physical Research Laboratory

We numerically investigate the population dynamics in a single photon resonant three-level cascade and non-cascade energy level molecules at 532-nm wavelength. The time-dependent population in the energy levels in the presence of 100 ps(pico-second) and 100 ns(nano-second) laser pulses is described in the form of rate equations. We provide a brief idea of how the optical energy transfer takes place in the light-matter interaction and we also discuss the absorption as a function of pulse width and repetition rate. We also plot the z-scan transmittance curve as a function of number of excitation pulses participating in the absorption.

关键词： nano-second laser pico-second laser nonlinear absorption z-scan

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