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A review of cooling technologies for high temperature rotating components in gas turbine

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Propulsion and Power Research 2022年第3期11卷 293-310页

作者： Umesh unnikrishnan Vigor Yang Georgia Institute of Technology AtlantaGAUSA

Modern gas turbines work under demanding high temperatures, high pressures, andhigh rotational speeds. In order to ensure durable and reliable operation, effective cooling mea-sures must be applied to the high-temperature rotating components, including turbine bladesand turbine disks. Cooling technology, however, is one of the most challenging problems inthis field. The present work reviews the current state of cooling technology research, at boththe fundamental science and engineering implementation levels, including modeling and simu-lation, experiments and diagnostics, and cooling technologies for blades and disks. In numericalsimulation, the RANS approach remains the most commonly used technique for flow-dynamicsand heat-transfer simulations. Much attention has been given to the development of improvedturbulence modeling for flows under rotation. For measurement and diagnostics, advancedinstrumentation and rotating-flow test facilities have been developed and valuable experimentaldata obtained. Detailed velocity and temperature distributions in rotating boundary layers havebeen obtained at scales sufficient to resolve various underlying mechanisms. Both isothermaland non-isothermal conditions have been considered, and the effects of Coriolis and buoyancyforces on flow evolution and heat transfer quantitatively identified. Cooling technologies havebeen improved by optimizing cooling passage dsigns, especially for curved configurations un-der rotation. Novel methods such as lamellar cooling and micro-scale cooling were proposed,and their effectiveness evaluated. For disk/cavity cooling, efforts were mainly focused on rotor-stator systems, with special attention given to the position of air injection into disks.

关键词： Gas turbine Rotating components Turbine blade Turbine disk Cooling technology

Dye-tolerant marine Acinetobacter baumannii-mediated biodegradation of reactive red

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Water Science and Engineering 2018年第4期11卷 265-275页

作者： Sneha.unnikrishnan Mohd Hashim Khan Karthikeyan Ramalingam School of Life Sciences B.S.Abdur Rahman Crescent Institute of Science and Technology

The objective of this study was to isolate a potent dye-degrading microbe that can be used to reduce the pollution caused by industrial *** red 198 is an extensively used textile dye and is a major environmental pollutant in water bodies. In this study, a bacterial strain was isolated from sea sediments and identified as Acinetobacter baumannii with 16S rRNA sequencing. The isolated bacteria were immobilized in calcium alginate and decolorization studies were carried out to determine the optimum pH, temperature, dye concentration, inoculum volume,and static/agitated condition using the one factor at a time(OFAT) approach. The Box-Behnken design, a type of response surface methodology,was adopted to improve the degradation efficiency. At 37℃ using an inoculum volume of six beads, 96.20% decolorization was observed in 500 mg/L of reactive red 198 after 72 h. Dye degradation was confirmed with UV-visible spectroscopy and Fourier-transform infrared(FTIR)spectroscopy studies of the dye and degraded metabolites. Microbial toxicity studies using Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa and phytotoxicity studies using Vigna radiata proved that the toxicity of the dye was significantly reduced after degradation. We can conclude that the isolated A. baumannii strain is an efficient dye-degrading microbe that can be used to reduce the pollution caused by industrial dyes.

关键词： Immobilization Box-Behnken design Response surface methodology Microbial toxicity Dye degradation

Crustal structure and sedimentation history over the Alleppey platform, southwest continental margin of India:Constraints from multichannel seismic and gravity data

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Geoscience Frontiers 2018年第2期9卷 549-558页

作者： P.unnikrishnan M.Radhakrishna G.K.Prasad Department of Earth Sciences Indian Institute of Technology Bombay Flat 3 "Muruga Kripa"

The Alleppey Platform is an important morphological feature located in the Kerala-Konkan basin off the southwest coast of India. In the present study, seismic reflection data available in the basin were used to understand the sedimentation history and also to carry out integrated gravity interpretation. Detailed seismic reflection data in the basin reveals that:(1) the Alleppey Platform is associated with a basement high in the west of its present-day geometry(as observed in the time-structure map of the Trap Top(K/T boundary)),(2) the platform subsequently started developing during the Eocene period and attained the present geometry by the Miocene and,(3) both the Alleppey platform and the Vishnu fracture zone have had significant impact on the sedimentation patterns(as shown by the time-structure and the isochron maps of the major sedimentary horizons in the region). The 3-D sediment gravity effect computed from the sedimentary layer geometry was used to construct the crustal Bouguer anomaly map of the *** 3-D gravity inversion of crustal Bouguer anomaly exhibits a Moho depression below the western border of the platform and a minor rise towards the east which then deepens again below the Indian shield. The 2-D gravity modelling across the Alleppey platform reveals the geometry of crustal extension,in which there are patches of thin and thick crust. The Vishnu Fracture Zone appears as a crustal-scale feature at the western boundary of the Alleppey platform. Based on the gravity model and the seismic reflection data, we suggest that the basement high to the west of the present day Alleppey platform remained as a piece of continental block very close to the mainland with the intervening depression filling up with sediments during the rifting. In order to place the Alleppey platform in the overall perspective of tectonic evolution of the Kerala-Konkan basin, we propose its candidature as a continental fragment.

关键词： Gravity Seismic reflection Alleppey platform Rifting Continental fragments Western continental margin of India

Computational Study on the Influence of Number of Threads on the Perfor-mance of Single Screw Pump at High Angular Velocities

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Journal of Thermal Science 2017年第1期26卷 54-59页

作者： Jaison Philip Abhilash Suryan T.V Sanand P unnikrishnan Nair S. Sivakumar Department of Mechanical Engineering College of Engineering Trivandrum Kerala India 695016 Turbo Pump Division LPSC Valiamala Trivandrum Kerala. Department of Mechanical Engineering Rajadhani Institute Engineering & Technology Trivandrum Kerala India

Fluid flow in a screw pump which rotates at very high angular velocity is numerically analyzed. In the present study, fluid flow in screw pumps under high Reynolds number, of the order of 105, is considered. Screw pump has two major elements, a plain shroud which is a stationary element and a rotating hub with helical grooves contained within the shroud. In this paper, three variants of hubs with different number of thread starts numbering six, eight and twelve in combination with a plain shroud is studied. Each of the three possible combinations are analyzed on the basis of pressure rise developed, efficiency and shaft power. It was seen that pressure rise, efficiency and shaft power increases as the number of threads increases in the range of mass flow rates studied.

关键词： Screw pump, Turbulent flow, Angular velocity

Prospects for discriminating Zingiberaceae species in India using DNA barcodes

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Journal of Integrative Plant Biology 2014年第8期56卷 760-773页

作者： Meenakshi Ramaswamy Vinitha.unnikrishnan Suresh Kumar Kizhakkethil Aishwarya Mamiyil Sabu George Thomas Plant Molecular Biology Rajiv Gandhi Centre for BiotechnologyThiruvananthapuram Kerala 695014 India Regional Facility for DNA Fingerprinting Rajiv Gandhi Centre for BiotechnologyThiruvananthapuram Kerala 695014 India Department of Botany University of Calicut

We evaluated nine plastid （matK, rbcL, rpoCl, rpoB, rp136-rpsS, ndhJ, trnL-F, tmrnH-psbA, accD） and two nuclear （ITS and ITS2） barcode loci in family Zingiberaceae by analyzing 60 accessions of 20 species belonging to seven genera from India. Bidirectional sequences were recovered for every plastid locus by direct sequencing of polymerase chain reaction （PCR） amplicons in all the accessions tested. However, only 35 （58%） and 4o accessions （66~） yielded ITS and ITS2 sequences, respectively, by direct sequencing. In different bioinformatics analyses, matK and rbcL consistently resolved 15 species （75%） into monophyletic groups and five species into two para- phyletic groups. The 173 ITS sequences, including 138 cloned sequences from 23 accessions, discriminated only 12 species （6o%）, and the remaining species were entered into three paraphyletic groups. Phylogenetic and genealogic analyses of plastid and ITS sequences imply the possible occurrence ofnatural hybridizations in the evolutionary past in giving rise to species paraphyly and intragenomic ITS heterogeneity in the species tested. The results support using matK and rbcL loci for barcoding Zingiberaceae members and highlight the poor utility of iTS and the highly regarded ITS2 in barcoding this family, and also caution against proposing ITS loci for barcoding taxa based on limited sampling.

关键词： Concerted evolution DNA barcoding ITS heterogeneity natural hybridizations Zingiberaceae

Structural and luminescence enhancement properties of Eu^(3+)/Ag nanocrystallites doped SiO_2-TiO_2 matrices

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Journal of Rare Earths 2013年第5期31卷 441-448页

作者： Arun Kumar K V Revathy K P Prathibha Vasudevan Sunil Thomas Biju P R unnikrishnan N V School of Pure & Applied Physics Mahatma Gandhi University

We reported here the structural and optical characterisation of silver nanocrystallites/Eu3＋：SiO2-TiO2 matrices synthesised through sol-gel route. Structural characterisations were done by using energy dispersive spectroscopy （EDX）, X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FTIR）, atomic force microscope （AFM） and transmission electron microscopy （TEM） measurements and optical characterisations were performed by absorption and emission spectroscopy. The TEM and XRD measurements confirmed the presence of nanocrystals. A broad absorption band was observed due to surface plasmon resonance of silver nanocrystals. The effect of silver nanocrystals on the emission spectrum of Eu3＋ doped SiO2-TiO2 matrices was discussed. An attempt was made to explain this fluorescence enhancement by invoking phenomena such as energy transfer, asymmetry ratio, surface plasmon, surface roughness, crystallinity and grain boundary. Our analysis, based on the experimental results, suggested that all the phenomena except crystallinity and grain boundary had favourable effects on fluorescence enhancement. We also estimated the relevant parameters associated with the phenomena that affected the fluorescence emission from the Eu3＋ ions in the matrix. It was seen that the theoretical estimate of fluorescence enhancement agreed well with the experimental estimate.

关键词： sol-gel luminescence SiO2-TiO2 silver nanoparticles rare earths

Influences of Annealing Temperature and Doping Concentration on Microstructural and Optical Properties of CeO_2:Sm^(3+) Nanocrystals

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Acta Metallurgica Sinica(English Letters) 2015年第6期28卷 758-765页

作者： G.Vimal Kamal P.Mani P.R.Biju Cyriac Joseph N.V.unnikrishnan M.A.Ittyachen School of Pure and Applied Physics Mahatma Gandhi University

Nanocrystals of CeO2 with different doping concentrations of Sm3＋ were synthesized by a novel and cost- effective method. The crystal structure, morphology and particle size were systematically investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Effects of the annealing temperature and doping concentrations on the microstructural properties of the crystals were studied. X-ray diffraction analysis indicates that the cubic structure of the CeO2 is not affected by the doping of Sm3＋ up to a doping concentration of 20%. Different structural parameters such as lattice constant, surface area, bulk density and porosity of the crystal were determined and discussed. Microscopic images of the CeO2：Sm3＋ suggest that the thermal decomposition of oxalate precursor is a suitable synthesis pathway to produce uniform-sized microparticles and nanoparticles. The influences of annealing temPerature and doping concentration of Sm3＋ on the optical properties of the nanocrystals were also discussed. The photoluminescence excitation spectra reveal that the charge transfer band is redshifted with increasing annealing temperatures. Emission attains its maximum intensity for Sm3＋ concentration of 1%, and higher concentrations lead to emission quenching.

关键词： Microstructure Strain Photoluminescence CeO2:Sm3+ nanocrystal Dopingconcentration Annealing temperature

Acid-base and Electron Donor Properties of Pr_6O_(11)and Its Mixtures with Alumina

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Journal of Materials Science & Technology 1994年第6期10卷 425-429页

作者： S.Sugunan G.D.Rani and P.A. unnikrishnan(Dept. of Applied Chemistry, Cochin University of Science and Technology, Kochi, India) Cochin Univ of Science and Technology Kochi India

The electron donor properties of Pr6O11 activated at 300, 500 and 800℃ are reported from the studies on adsorption of electron acceptors of various electron affinity (7, 7, 8, 8-tetracyanoquinodimethane , 2. 3. 5. 6-tetrachloro-1, 4-benzoquin one, p-dinitrobenzene, and m-dinitrobenzcne) in three solvents (acetonitrile, 1,4-dioxan and ethyl acetate). The extent of electron transfer during adsorption is understood from magnetic measurements and ESR spectral data. The corresponding data on mixed oxides of Pr and Al are reported for various compositions. The acid / base properties of these oxides are determined using a set of Hammett indicators.

关键词： base Pr and Its Mixtures with Alumina Acid-base and Electron Donor Properties of Pr6O

Neurocognitive outcomes in pediatric brain tumors after treatment with proton versus photon radiation:a systematic review and meta-analysis

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世界儿科杂志:英文版 2023年第8期19卷 727-740页

作者： Álvaro Lassaletta Javier S.Morales Pedro L.Valenzuela Borja Esteso Lisa S.Kahalley Donald J.Mabbott Soumya.unnikrishnan Elena Panizo Felipe Calvo Radiation Oncology Department Clínica Universidad de NavarraCalle Marquesado de Santa Marta 128027 MadridSpain Pediatric Neuro-Oncology Unit Hospital Infantil Universitario Niño JesúsMadridSpain MOVE-IT Research Group Department of Physical EducationFaculty of Education SciencesUniversity of CadizCádizSpain Biomedical Research and Innovation Institute of Cádiz(INiBICA)Research Unit Puerta del Mar University HospitalUniversity of CádizCádizSpain Physical Activity and Health Research Group(PaHerg) Research Institute of the Hospital 12 de Octubre(‘imas12’)MadridSpain Systems Biology Department University of AlcaláMadridSpain Clinical Neuropsychology Unit Psychiatry and Clinical Psychology DepartmentHospital Infantil Universitario Niño JesúsMadridSpain Baylor College of Medicine HoustonTXUSA Texas Children’s Hospital HoustonTXUSA The Hospital for Sick Children TorontoONCanada The University of Toronto TorontoONCanada University of California School of Medicine San DiegoLa JollaCAUSA

Background Advances in cancer treatments,particularly the development of radiation therapy,have led to improvements in survival outcomes in children with brain ***,radiation therapy is associated with significant long-term neurocognitive *** present systematic review and meta-analysis aimed to compare the neurocognitive outcomes of children and adolescents with brain tumors treated with photon radiation(XRT)or proton therapy(PBRT).Methods A systematic search was conducted(PubMed,Embase,Cochrane,and Web of Science from inception until 02/01/2022)for studies comparing the neurocognitive outcomes of children and adolescents with brain tumors treated with XRT *** pooled mean differences(expressed as Z scores)were calculated using a random effects method for those endpoints analyzed by a minimum of three *** Totally 10 studies(n=630 patients,average age range:1–20 years)met the inclusion *** who had received PBRT achieved significantly higher scores(difference in Z scores ranging from 0.29–0.75,all P0.05 in main analyses or sensitivity analyses)were found for nonverbal memory,verbal working memory and working memory index,processing speed index,or focused *** Pediatric brain tumor patients who receive PBRT achieve significantly higher scores on most neurocognitive outcomes than those who receive *** studies with long-term follow-ups are needed to confirm these results.

关键词： Brain health Childhood cancer Intelligence quotient Radiotherapy