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Condition monitoring of a wind turbine generator using a standalone wind turbine emulator

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Frontiers in Energy 2016年第3期10卷 286-297页

作者： Himani ratna DAHIYA Department of Electrical Engineering National Institute of TechnologyKurukshetra 136119 India

The intend of this paper is to give a description of the realization of a low-cost wind turbine emulator （WTE） with open source technology from graze required for the condition monitoring to diagnose rotor and stator faults in a wind turbine generator （WTG）. The WTE comprises of a 2.5 kW DC motor coupled with a 1 kW squirrel-cage induction machine. This paper provides a detailed overview of the hardware and software used along with the WTE control strategies such as MPPT and pitch control. The emulator reproduces dynamic characteristics both under step variations and arbitrary variation in the wind speed of a typical wind turbine （WT） of a wind energy conversion system （WECS）. The usefulness of the setup has been benchmarked with previously verified WT test rigs made at the University of Manchester and Durham University in UK. Considering the fact that the rotor blades and electric subassemblies direct drive WTs are most susceptible to damage in practice, generator winding faults and rotor unbalance have been introduced and investigated using the terminal voltage and generated current. This wind turbine emulator （WTE） can be reconfigured or analyzed for condition monitoring without the need for real WTs.

关键词： condition monitoring (CM) wind turbine emulator (WTE) wind turbine generator (WTG) maximum power point tracking (MPPT) tip speed ratio (TSR) rotor faults stator faults

Effective platform for the generation of aerosol droplets and application in evaluating the effectiveness of a MEMS-based nanoparticle trapping device

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Particuology 2009年第6期7卷 471-476页

作者： ratna Tantra Dipak Gohil Peter Cumpson National Physical Laboratory Hampton RoadTeddingtonMiddlesex TW11 0LWUnited Kingdom School of Mechanical and Systems Engineering Newcastle UniversityNewcastle-upon-Tyne NE1 7RUUnited Kingdom

The purpose of this study is two-fold： firstly, the development of a cheap, easy-to-construct and effective nanoparticle generator for testing nanoparticle sensors; secondly, the use of such a generator to test the effectiveness of a sensor device in trapping aerosolised nanoparticles. In this study, we have constructed an effective aerosol generator platform, based on aerosol-assisted chemical vapour deposition technology. Under well-controlled experimental conditions, this platform is capable of depositing aerosolised sodium chloride particles homogeneously on a substrate very effectively. Deposited aerosol droplets were subsequently dried and shown to form nanosized cubic crystals that are free from impurities. This platform was employed to test the effectiveness of a MEMS comb device in the electrostatic trapping of nanoparticles. Upon applying a DC bias （0.5 V） to the MEMS device, results showed an increase in nanoparticle deposition on the surface of the device, due to electrostatic precipitation. The presence of an electric field was shown to affect crystal formation upon drying of the aerosol droplets on the substrate; this caused a blotchy appearance on the SEM image, which was not observed in the absence of electric field.

关键词： Aerosol MEMS sensor Particle generator

Effect of nanoparticle concentration on zeta-potential measurement results and reproducibility

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Particuology 2010年第3期8卷 279-285页

作者： ratna Tantra Philipp Schulze Paul Quincey National Physical Laboratory Hampton Road Teddington Middlesex TW11 0LW UK Department of Physics University of Bath Bath BA2 7AY UK. National Physical Laboratory Hampton Road Teddington Middlesex TW11 0LW

The effect of nanoparticle concentration on zeta-potential measurement results at dilute concentrations was evaluated. The values of the zeta-potential for four different types of nanoparticles, Ludox （silica）, multi-walled carbon nanotubes （bamboo-shaped and hollow nanotubes） and gold, at various concentrations, were obtained using a laser Doppler electrophoresis instrument. The size of the nanoparticles on dilution was measured using dynamic light scattering （DLS）. The results show that there is a concentration range within which the zeta-potential, and particle size, are not affected by nanoparticle concentration. The lower concentration limit for the system to produce consistent results was dependent on the nature of the sample under study and ranged between 10-2 and 10-4 wt%. Below this concentration, there was an apparent shift in zeta-potential values to less negative values, which was accompanied by an increase in the particle size. The shift in zeta-potential was attributed to an increase in contribution of the signal from extraneous particulate matter. The increase in particle size was attributed to the nature of the homodyne optical configuration of the instrument. The aim of this study was to elucidate the range in nanoparticle concentration that allows for accurate and reliable measurement of the zeta-potential and DLS data.

关键词： Nanoparticles Zeta-potential Dynamic light scattering Reproducibility

A FEniCS implementation of the phase field method for quasi-static brittle fracture

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Frontiers of Structural and Civil Engineering 2019年第2期13卷 380-396页

作者： HIRSHIKESH Sundararajan NATARAJAN ratna Kumar ANNABATTULA Integrated Modeling and Simulation Lab Department of Mechanical EngineeringIndian Institute of Technology MadrasChennai- 600036India

In the recent years, the phase field method for simulating fracture problems has received considerable attention. This is due to the salient features of the method: 1) it can be incorporated into any conventional finite element software;2) has a scalar damage variable is used to represent the discontinuous surface implicitly and 3) the crack initiation and subsequent propagation and branching are treated with less complexity. Within this framework, the linear momentum equations are coupled with the diffusion type equation, which describes the evolution of the damage variable. The coupled nonlinear system of partial differential equations are solved in a 'staggered? approach. The present work discusses the implementation of the phase field method for brittle fracture within the open-source finite element software, FEniCS. The FEniCS provides a framework for the automated solutions of the partial differential equations. The details of the implementation which forms the core of the analysis are presented. The implementation is validated by solving a few benchmark problems and comparing the results with the open literature.

关键词： phase field method FEniCS brittle fracture crack propagation variational theory of fracture

Modeling water resources under competing demands for sustainable development: A case study of Kaligandaki Gorge Hydropower Project in Nepal

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Water Science and Engineering 2019年第1期12卷 19-26页

作者： Rakesh Sahukhal Tri ratna Bajracharya Energy Environment Research and Development CentreLalitpur 44602Nepal Institute of Engineering Department of Mechanical EngineeringTribhuwan UniversityLalitpur 44600Nepal

The challenges posed by climate change require that the quantity and quality of water resources in Nepal be managed with sustainable development practices. The communities around the Kaligandaki Gorge Hydropower Project in the Myagdi District of Nepal depend on river flow for most of their rural and agricultural needs. Without a sustainable development plan, the growing population of the region, confined in an area with declining water resources, will face serious challenges to economic growth. Meteorological data show increasing annual average rainfall at a slight rate of about 0.284 mm/year, with erratic annual percentage change in rainfall in the area. The mean and minimum temperatures show decreasing trends at the rates of 0.05-C and 0.14-C per year, respectively. An assessment of the impacts on water availability for domestic and irrigation usage in the face of competing demands caused by the hydropower development project in the Kaligandaki Gorge was undertaken. The water demand and supply modeling were conducted using the water evaluation and planning (WEAP) model, based on discharge data from the Kaligandaki River, which were obtained from the Department of Hydrology and Meteorology, Nepal. The available data from 2001 to 2003 were used to estimate the model parameters while the stability of these parameters was tested with a validation period from 2004 to 2007. The performance of the model was assessed through statistical measures of calibration with the root mean square error and coefficient of determination, whose values were 0.046% and 0.79, respectively. Two scenarios were created in addition to the base case scenario: the discharge decrement scenario and new irrigation technology scenario. Analysis showed that a prioritization of demands will be necessary in the area in the near future for the purpose of sustainability of water resources, due to climate change impacts.

关键词： Climate change Competing demands Sustainable development Hydropower project WEAP

Developing Mg–Zn surface alloy by friction surface allosying: In vitro degradation studies in simulated body fluids

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International Journal of Minerals,Metallurgy and Materials 2020年第7期27卷 962-969页

作者： Venkateswarlu Badisha Shabana Shaik Ravikumar Dumpala B.ratna Sunil Department of Metallurgical and Materials Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 521202India Department of Mechanical Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 521202India Department of Mechanical Engineering Visvesvaraya National Institute of TechnologyNagpur 440010India Department of Mechanical Engineering Bapatla Engineering CollegeBapatla 522101India

A new variant of friction-assisted process named friction surface alloying(FSA)for developing surface alloys was demonstrated in the present *** FSA,the dispersed phase is melted and allowed to react with the matrix material to form an alloy at the surface of a metallic *** the present work,magnesium(Mg)sheets and zinc(Zn)powder were selected,and fine grained(~3.5μm)Mg–Zn surface alloy with improved hardness was produced by FSA.X-ray diffraction studies confirmed the formation of intermetallic phases of Mg and Zn at the *** the in vitro degradation studies carried out by immersing in simulated body fluids,a lower corrosion rate was observed for the Mg–Zn surface alloy compared with pure *** surface morphologies after immersion studies indicated large degraded areas on the base Mg compared with Mg–*** results demonstrate the potential of FSA in developing Mg-based surface alloys without melting the substrate to impart better surface properties.

关键词： friction stir processing,surface alloy magnesium zinc corrosion degradation

A review on developing high-performance ZE41 magnesium alloy by using bulk deformation and surface modification methods

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Journal of Magnesium and Alloys 2023年第3期11卷 776-800页

作者： Subrat Kumar Baral Manjusha M.Thawre B.ratna Sunil Ravikumar Dumpala Department of Mechanical Engineering Visvesvaraya National Institute of TechnologyNagpur 440010India Department of Metallurgical and Materials Engineering Visvesvaraya National Institute of TechnologyNagpur 440010India Department of Mechanical Engineering Bapatla Engineering CollegeBapatla 522102India

Magnesium(Mg)alloys are generally used in light-weight structural applications due to their higher specific ***,the usage of these Mg alloys is limited due to their poor formability at room temperature,which is attributed to lower count of slip systems associated with the hcp crystal *** address these limitations,several new magnesium alloys and also many processing strategies have been developed and reported in the ***41 Mg is an alloy with significant quantities of zinc(Zn)and rare earth(RE)elements and has emerged as a promising material for aerospace,automotive,electronics,biomedical and many other *** make this alloy more competitive and viable,it should possess better mechanical and corrosion ***,the current paper reviews the effect of bulk mechanical processing on grain refinement,microstructural modification,and corresponding changes in the mechanical behaviour of ZE41Mg ***,the effect of various surface modification techniques on altering the surface microstructure and surface properties such as wear and corrosion are also briefly summarized and *** review also discusses the challenges and the future perspectives in developing high-performing ZE41 Mg alloys.

关键词： ZE41 magnesium alloy Bulk deformation Surface modification Mechanical properties Wear Corrosion

Importance of retrieving noun phrases and named entities from digital library content

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Journal of Zhejiang University-Science C(Computers and Electronics) 2010年第11期11卷 844-849页

作者： ratna SANYAL Kushal KESHRI Vidya NAND Indian Institute of Information Technology

We present a novel approach for extracting noun phrases in general and named entities in particular from a digital repository of text *** problem of coreference resolution has been divided into two subproblems:pronoun resolution and non-pronominal resolution.A rule based-technique was used for pronoun resolution while a learning approach for nonpronominal *** named entity resolution,disambiguation arises mainly due to polysemy and *** proposed approach fixes both problems with the help of WordNet and the Word Sense Disambiguation *** proposed approach,to our knowledge,outperforms several baseline techniques with a higher balanced F-measure,which is harmonic mean of recall and *** improvements in the system performance are due to the filtering of antecedents for the anaphor based on several linguistic disagreements,use of a hybrid approach,and increment in the feature vector to include more linguistic details in the learning technique.

关键词： Coreference resolution Hybrid approach Filtering Rule based and J48 algorithm

Broad Ligament Pregnancy:Facing the Battle Unarmed

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Maternal-Fetal Medicine 2023年第4期5卷 253-256页

作者： Meenakshi Singh Nihita Pandey ratna Biswas Department of Obstetrics and Gynaecology Lady Harding Medical CollegeDelhi 110001India

Broad ligament pregnancy is defined as gestation that grows in the space formed by anterior and posterior peritoneal folds of the broad *** report a case of 30 years old lady admitted to our hospital with the diagnosis of gravida 2,para 1,live birth 1,with 24 weeks of gestation with low lying placenta with *** was taken up for lower segment cesarian section at 28 weeks gestation in view of low lying placenta with *** broad ligament pregnancy was diagnosed peroperatively after identifying the anatomical relationship of the *** was excised and margins secured after extraction of the baby and *** had an uneventful postoperative *** ligament pregnancy may be missed in antenatal period but in cases of displaced cervix,early onset unexplained anhydramnios,and failed induction of labor,it may raise high ***/laparoscopic management is the mainstay of management of broad ligament pregnancy.

关键词： Pregnancy ectopic Broad ligament pregnancy Intraligamentary pregnancy Laparotomy