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structural,Dielectric,and Magnetic studies on Electrospun Magnesium Ferrite-Polyvinylidene Fluoride Core–shell Composite Fibers

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Acta Metallurgica sinica(English Letters) 2014年第4期27卷 557-562页

作者： V.Revathi s.dinesh kumar P.Chithra Lekha V.subramanian T.s.Natarajan C.Muthamizhchelvan New Horizon College of Engineering Bangalore 560103India Microwave Laboratory Department of PhysicsIIT MadrasChennai 600036India sRM University KattankulathurChennai 603203India

The sub-micron（of the order of 150 nm） thick core–shell composite fibers of magnesium ferrite-polyvinylidene fluoride are prepared by *** loading of magnesium ferrite is varied from 1 to 10 wt%.The study results by X-ray diffraction,scanning electron microscope,and infra-red spectroscopy indicate the formation of core–shell structure and an enhancement in the amount of b-phase compared to a-phase in the polyvinylidene *** particle size of the magnesium ferrite in the fiber is evaluated to be 30 *** low frequency dielectric studies indicate that the addition of the magnesium ferrite increases the polarization resulting in the increase in the dielectric constant but decreases the dielectric *** magnetization measurements indicate an increased value of coercivity compared to bulk due to the nano-size of the magnesium *** microwave absorption at the ferromagnetic resonance increases with the increase in the concentration of magnesium *** resonance field is found to vary with the loading of MFO.

关键词： Electrospinning Polymer composites Dielectric properties Magnetic properties X-ray diffraction(XRD) Microwave absorption

Assessment of scale interactions associated with wake meandering using bispectral analysis methodologies

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Theoretical & Applied Mechanics Letters 2024年第2期14卷 65-75页

作者： dinesh kumar Kinjangi Daniel Foti Department of Mechanical Engineering University of MemphisMemphisTennesseeUSA

Large atmospheric boundary layer fluctuations and smaller turbine-scale vorticity dynamics are separately hypothesized to initiate the wind turbine wake meandering phenomenon,a coherent,dynamic,turbine-scale oscillation of the far *** interactions,the mechanism of energy transfers between scales,manifest as triples of wavenumbers or frequencies and can be characterized through bispectral *** bispectrum,which correlates the two frequencies to their sum,is calculated by two recently developed multi-dimensional modal decomposition methods:scale-specific energy transfer method and bispectral mode ***-eddy simulation of a utility-scale wind turbine in an atmospheric boundary layer with a broad range of large length-scales is used to acquire instantaneous velocity *** bispectrum from both methods identifies prominent upwind and wake meandering interactions that create a broad range of energy scales including the wake meandering *** coherent kinetic energy associated with the interactions shows strong correlation between upwind scales and wake meandering.

关键词： Wind turbine wake Mode decomposition Bispectral analysis

Comparison of rare earths doping(neodymium and samarium) on structural and magnetic properties of Ni-Zn-Bi nanoferrites

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Journal of Rare Earths 2024年第3期42卷 534-542,I0004页

作者： shilpa Taneja Preeti Thakur dinesh kumar Yassine slimani Atul Thakur NanoLatticeX Amity University HaryanaGururam122413HaryanaIndia Nanotechnology Wing Innovative Science Research SocietyShimla177002India Centre for Nanotechnology Amity University HaryanaGururam122413HaryanaIndia Department of Biophysics Institute for Research and Medical Consultations(IRMC)Imam Abdulrahman Bin Faisal UniversityP.O.Box 1982Dammam31441Saudi Arabia school of Electronics and Information Engineering Nanjing University of Information Science&TechnologyNanjing210044China

Excellent magnetic properties in ferrites are required for high-frequency applications and for wastewater treatment. Thus, the present study shows the comparison of magnetic and structural properties of Nd and sm substituted Ni-Zn-Bi ferrites with the series Ni_(0.5)Zn_(0.5)Bi_(0.04)Nd_(x)Fe_(1.96-x)O_4(with step size 0.002)and Ni_(0.5)Zn_(0.5)Bi_(0.04)sm_(x)Fe_(1.96-x)O_4(with step size 0.02) prepared using citrate precursor method. The impact of the substitution of rare earth ions(Nd and sm) on magnetic properties of the synthesized samples is observed using a vibrating sample magnetometer(VsM). The saturation magnetization values enhance considerably from 52 to 58 emu/g for Nd^(3+)ions and 39 to 57 emu/g for sm^(3+) ions, thus, making these materials magnetically hard. Further, the higher value of coercivity is also observed ranging from133 to 167 Oe for Nd^(3+)ions and 81 to 155 Oe for sm^(3+) ions. The shape of hysteresis loops indicates a super paramagnetic and ferromagnetic behavior in the obtained samples. The squareness ratio value issuggesting the uniaxial anisotropy of particles and hence, these ferrites are suitable for microwaveabsorbing and in permanent magnetic materials. The X-ray diffraction(XRD) pattern shows the formation of pure cubic crystallites, where, lattice parameters range from 0.840 to 0.839 nm and from 0.838to 0.839 nm for Nd^(3+)and sm^(3+) ions substitution, respectively. The crystallite size ranges between 28.63to 29.89 nm and 18.33 to 26.23 nm, for substitution of Nd^(3+)and sm^(3+) ions, respectively. Field emission scanning electron microscopy(FEsEM) shows the formation of homogeneous grains, whereas, energy dispersive spectrometer(EDs) counts describe the purity of the samples. The sm concentration x = 0.10has the maximum surface area with value of 42.6 m^(2)/g which proves to be having good data storage application due to high surface area. The zero-field cooled(ZFC) and field cooled(FC) data show that Nddoped Ni-Zn-Bi nano

关键词： Citrate precursor X-ray diffraction Vibrating sample magnetometer Coercivity Field emission scanning electron microscopy Rare earths

Beyond fossil:the synthetic fuel surge for a green-energy resurgence

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Clean Energy 2024年第5期8卷 1-18页

作者： sreejaun Thothaathiri Janaki dinesh kumar Madheswaran G.Naresh Thangavelu Praveenkumar Electric Vehicle Technology Laboratory Department of Automobile EngineeringSRM Institute of Science and TechnologyKattankulathur CampusTamilnadu 603203India

This review offers a comprehensive overview of synthetic fuels as promising alternatives to conventional fossil *** carbon-neutral potential of synthetic fuels when produced using renewable energy and captured CO_(2),offering significant opportunities to mitigate CO_(2) emissions,is ***,the efficiency of synthetic fuels is presented,as they do not require dedicated agricultural land or substantial water resources,addressing concerns related to the land-use change and water scarcity associated with traditional *** economic viability of synthetic fuels is explored,highlighting the advancements in technology and decreased renewable-energy costs,coupled with their independence from food crops,mitigating concerns about potential impacts on food *** investments by industry leaders such as Porsche,Highly Innovative Fuels Global,and ExxonMobil,totalling$1 billion,aimed at achieving an annual production of 550 million litres by 2026,are covered in *** study is further extended by emphasizing the scalability of synthetic fuel production through modular processes,enabling tailored facilities to meet regional demands and contribute to a decentralized and resilient energy ***,the‘drop-in’nature of synthetic fuels that are seamlessly compatible with existing fuel storage,pipelines,and pumps,facilitating a smooth transition without requiring extensive infrastructure changes,is *** such as the current high cost of synthetic fuel production are acknow-ledged,necessitating supportive government policies and incentives for widespread ***,synthetic fuels have emerged as promising contenders in the pursuit of sustainable and adaptable energy solutions,with tangible benefits for the environment,economy,and existing energy infrastructure.

关键词： synthetic fuels biofuels carbon neutrality sustainable energy e-fuel ‘drop-in’nature

Evaluation of Dielectric Properties of CCTO-BT/Epoxy Composites for Electronic Applications

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Journal of Harbin Institute of Technology(New series) 2024年第1期31卷 69-77页

作者： swagatika Mishra Punyapriya Mishra Punyatoya Mishra dinesh kumar Mishra Krushna Prasad shadangi Deepak kumar Mohapatra Department of Mechanical Engineering Veer Surendra Sai University of TechnologyBurlaOdisha 768018India Department of Physics Parala Maharaja Engineering CollegeBerhampurOdisha 761003India Department of Metallurgical and Materials Engineering Veer Surendra Sai University of TechnologyBurlaOdisha768018India Department of Chemical Engineering Veer Surendra Sai University of TechnologyBurlaOdisha 768018India

In the current study,the calcium copper titanate(CCTO)/epoxy,barium titanate(BT)/epoxy and CCTO-BT/epoxy composite samples with variable volume fractions of CCTO and BT are fabricated using hand lay-up and compression moulding process. The composite samples are characterized for the frequency dependence on dielectric properties,conductivity,impedance spectroscopy and electrical modulus.X-ray diffraction(XRD)representation of CCTO-BT/epoxy composite samples confirmed the presence of both CCTO and BT ceramic samples separately. The dielectric characteristics of hybrid CCTO-BT/epoxy composite samples with CCTO∶BT ratio of 40∶60, 60∶40,and 50∶50 was found relatively better than those of single ceramic filler reinforced epoxy composites. AC conductivity analysis shows improvement in the results of hybrid filler-filled CCTO-BT/epoxy composites in comparison with single filler-filled epoxy composite.50∶50 CCTO-BT/epoxy composite shows the best AC conductivity value of~ 2.2 ×10^(-5) ohm^(-1)·m^(-1) at a higher frequency of 1MHz. The impedance analysis confirms the higher insulating properties for hybrid 40∶60 and 60∶40 CCTO-BT/epoxy composites with respect to the single and other hybrid ceramic epoxy composites. The analysis suggests the hybrid CCTO-BT/epoxy composites to be adopted as a potential dielectric material for energy storage devices and other electronic applications.

关键词： ceramic filler dielectric characterization hybrid Composite AC conductivity impedance analysis

Enhancing fatigue performance of AZ31 magnesium alloy components fabricated by cold metal transfer-based wire arc directed energy deposition through LPB

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Journal of Magnesium and Alloys 2024年第4期12卷 1638-1662页

作者： shambhu kumar Manjhi srikanth Bontha A.s.s.Balan Department of Mechanical Engineering National Institute of Technology KarnatakaSurathkalSrinivasanagarMangaloreKarnataka 575025India

Cold Metal Transfer-Based Wire Arc Directed Energy Deposition(CMT-WA-DED)presents a promising avenue for the rapid fabrication of components crucial to automotive,shipbuilding,and aerospace ***,the susceptibility to fatigue of CMT-WA-DED-produced AZ31 Mg alloy components has impeded their widespread adoption for critical load-bearing *** this study,a comprehensive investigation into the fatigue behaviour of WA-DED-fabricated AZ31 Mg alloy has been carried out and compared to commercially available wrought AZ31 *** findings indicate that the as-deposited parts exhibit a lower fatigue life than wrought Mg alloy,primarily due to poor surface finish,tensile residual stress,porosity,and coarse grain microstructure inherent in the WA-DED *** Plasticity Burnishing(LPB)treatment is applied to mitigate these issues,which induce significant plastic deformation on the *** treatment resulted in a remarkable improvement of fatigue life by 42%,accompanied by a reduction in surface roughness,grain refinement and enhancement of compressive residual stress ***,during cyclic deformation,WA-DED specimens exhibited higher plasticity and dislocation density compared to both wrought and WA-DED+LPB specimens.A higher fraction of Low Angle Grain Boundaries(LAGBs)in WA-DED specimens contributed to multiple crack initiation sites and convoluted crack paths,ultimately leading to premature *** contrast,wrought and WA-DED+LPB specimens displayed a higher percentage of High Angle Grain Boundaries(HAGBs),which hindered dislocation movement and resulted in fewer crack initiation sites and less complex crack paths,thereby extending fatigue *** findings underscore the effectiveness of LPB as a post-processing technique to enhance the fatigue performance of WA-DED-fabricated AZ31 Mg alloy *** study highlights the importance of LPB surface treatment on AZ31 Mg components produced by CMT-WA-DED to remove surface d

关键词： Wire arc additive manufacturing AZ31 Mg alloy Low plasticity burnishing Low cycle fatigue test strain amplitude

Bile acid metabolism and signaling in health and disease:molecular mechanisms and therapeutic targets

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signal Transduction and Targeted Therapy 2024年第5期9卷 2014-2064页

作者： Joshua s.Fleishman sunil kumar Department of Pharmaceutical sciences College of Pharmacy and Health SciencesSt.John’s UniversityQueensNYUSA

Bile acids,once considered mere dietary surfactants,now emerge as critical modulators of macronutrient(lipid,carbohydrate,protein)metabolism and the systemic pro-inflammatory/anti-inflammatory *** acid metabolism and signaling pathways play a crucial role in protecting against,or if aberrant,inducing cardiometabolic,inflammatory,and neoplastic conditions,strongly influencing health and *** curative treatment exists for any bile acid influenced disease,while the most promising and well-developed bile acid therapeutic was recently rejected by the ***,we provide a bottom-up approach on bile acids,mechanistically explaining their biochemistry,physiology,and pharmacology at canonical and non-canonical *** this mechanistic model of bile acids,we explain how abnormal bile acid physiology drives disease pathogenesis,emphasizing how ceramide synthesis may serve as a unifying pathogenic feature for cardiometabolic *** provide an in-depth summary on pre-existing bile acid receptor modulators,explain their shortcomings,and propose solutions for how they may be ***,we rationalize novel targets for further translational drug discovery and provide future *** than dismissing bile acid therapeutics due to recent setbacks,we believe that there is immense clinical potential and a high likelihood for the future success of bile acid therapeutics.

关键词： metabolism rejected shortcomings

Fuzzy Reliability and Availability of system under a Calendar-based Inspection Involving Multiple Failures and Its Application to Wind Turbine system

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Journal of systems science and systems Engineering 2024年第2期33卷 187-206页

作者： Mintu kumar Himani Pant s.B.singh Department of Mathematics statistics and Computer science G.B.Pant University of AgricultureTechnologyPantnagarUttarakhandIndia

Uncertainty is an important factor that needs to be considered while analyzing the performance of any engineering *** order to quantify uncertainty,fuzzy set theory is frequently used by most of researchers,including energy system *** to the classical reliability theory,component lifetimes have crisp parameters,but due to uncertainty and inaccuracy in data,it is sometimes very difficult to determine the exact values of these parameters in real-world *** overcome this difficulty in the current research,failure and repair rates were taken as triangular fuzzy numbers to determine the fuzzy availability of a system undergoing calendar-based periodic inspection subject to multiple failure modes(FMs).It was assumed that each component in the system had an exponential failure rate and repair rate with fuzzy *** FMs were explicitly taken into account when a functional state of the system was *** FM had a random failure *** the occurrence of any failure,a random time was selected for the relevant corrective repair *** proposed research was studied for one of the major sources of green energy,namely a wind turbine system wherein all the derived propositions have been implemented on it.

关键词： Fuzzy reliability fuzzy availability wind turbine system multiple failure modes triangular fuzzy number

TOEPLITZ DETERMINANTs IN ONE AND HIGHER DIMENsIONs

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Acta Mathematica scientia 2024年第5期44卷 1931-1944页

作者： surya GIRI s.sivaprasad kumar Department of Applied Mathematics Delhi Technological UniversityNew Delhi110042India

In this study,we derive the sharp bounds of certain Toeplitz determinants whose entries are the coefficients of holomorphic functions belonging to a class defined on the unit disk ***,these results are extended to a class of holomorphic functions on the unit ball in a complex Banach space and on the unit polydisc inℂ*** obtained results provide the bounds of Toeplitz determinants in higher dimensions for various subclasses of normalized univalent functions.

关键词： holomorphic mappings starlike mappings Toeplitz determinants coefficient inequalities