Estimation of Suitable Methodology for Determining Weibull Parameters for the Vortex Shedding Analysis of Synovial Fluid

Singh, Nishant Kumar,Sarkar, A.,Deo, Anandita,Gautam, Kirti,Rai, S.K. The Korean Society of Medical and Biological Engin 2016 의공학회지 Vol.37 No.1

Weibull distribution with two parameters, shape (k) and scale (s) parameters are used to model the fatigue failure analysis due to periodic vortex shedding of the synovial fluid in knee joints. In order to determine the later parameter, a suitable statistical model is required for velocity distribution of synovial fluid flow. Hence, wide applicability of Weibull distribution in life testing and reliability analysis can be applied to describe the probability distribution of synovial fluid flow velocity. In this work, comparisons of three most widely used methods for estimating Weibull parameters are carried out; i.e. the least square estimation method (LSEM), maximum likelihood estimator (MLE) and the method of moment (MOM), to study fatigue failure of bone joint due to periodic vortex shedding of synovial fluid. The performances of these methods are compared through the analysis of computer generated synovial fluidflow velocity distribution in the physiological range. Significant values for the (k) and (s) parameters are obtained by comparing these methods. The criterions such as root mean square error (RMSE), coefficient of determination ($R^2$), maximum error between the cumulative distribution functions (CDFs) or Kolmogorov-Smirnov (K-S) and the chi square tests are used for the comparison of the suitability of these methods. The results show that maximum likelihood method performs well for most of the cases studied and hence recommended.

Highly Efficient Photocatalytic Studies on Bi36 Fe2 O57 Ceramic Synthesized by Chemical Route

Manish Kumar Verma,Vinod Kumar,Upakar Patel,Vishnu Shankar Rai,Anup Kumar,Arup Kumar De,Aditya Kumar Prajapati,Dinesh Prajapati,Kedar Sahoo,Tapas Das,N. B. Singh,K. D. Mandal 한국전기전자재료학회 2023 Transactions on Electrical and Electronic Material Vol.24 No.5

Bi36 Fe2 O57 (BFO) polycrystalline ceramic was synthesized by economical chemical route. The single-phase formation of BFO ceramic was confirmed by powder X-ray diffraction studies. Nanosized formation of BFO ceramics established by XRD and TEM analysis. The bimodal distribution of grain size is observed with size ranging from 50 to 600 nm. It observed that the Bi36 Fe2 O57 photocatalyst exhibited higher catalytic activity for the degradation of Methylene Blue (MB) under visible-light irradiation The oxidation state of elements present in the BFO ceramic, was confirmed by XPS studies. The pseudocapacitive nature of BFO ceramic was observed by cyclic Voltammetry. The dielectric constant of BFO ceramic was found 375 at 1 kHz at 300 K. The dielectric loss was found 0.51 at 100 kHz and 300 K.

Comparative Dielectric and Ferroelectric Characteristics of Bi0.5Na0.5TiO3, CaCu3Ti4O12, and 0.5Bi0.5Na0.5TiO3–0.5CaCu3Ti4O12 Electroceramics

Singh, L.,Yadava, S. S.,Sin, B. C.,Rai, U. S.,Mandal, K. D.,Lee, Y. Springer Science + Business Media 2016 Journal of electronic materials Vol.45 No.6

<P>The dielectric and ferroelectric characteristics of Bi0.5Na0.5TiO3 (BNT), CaCu3Ti4O12 (CCTO), and 0.5Bi(0.5)Na(0.5)TiO(3)-0.5CaCu(3)Ti(4)O(12) (BNT/CCTO) ceramics are compared. X-ray diffraction patterns confirmed the formation of single phase of all the ceramics after sintering at 950A degrees C for 15 h. Scanning electron microscopy images of the sintered ceramics reveal average grain sizes in the range from 200 nm to 2.5 mu m. Energy-dispersive x-ray mapping and x-ray photoelectron spectroscopy show the presence of the elements Bi, Na, Ca, Cu, Ti, and O with uniform distribution in the ceramics. BNT/CCTO exhibits high dielectric constant (epsilon (r) similar to 6.9 x 10(4)) compared with BNT (epsilon (r) similar to 0.13 x 10(4)) and CCTO (epsilon (r) similar to 1.68 x 10(4)) ceramics at 1 kHz and 503 K. The high dielectric constant of BNT/CCTO compared with BNT and CCTO is associated with a major contribution from grain boundaries, as confirmed by impedance and modulus analyses. The P-E hysteresis loop of all the ceramics measured at room temperature and 50A degrees C exhibited typical ferroelectric nature. The remanent polarization (P (r)) of BNT (1.58 mu C/cm(2)) and CCTO (0.654 mu C/cm(2)) ceramics are higher than that of BNT/CCTO (0.267 mu C/cm(2)) ceramic.</P>

High reversible capacity and rate capability of ZnCo₂O₄/graphene nanocomposite anode for high performance lithium ion batteries

Rai, A.K.,Kim, J. Elsevier 2015 SOLID STATE SCIENCES Vol.48 No.-

A facile and straightforward method was adopted to synthesize ZnCo<SUB>2</SUB>O<SUB>4</SUB>/graphene nanocomposite anode. In the first step, pure ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoparticles were synthesized using urea-assisted auto-combustion synthesis followed by annealing at a low temperature of 400 <SUP>o</SUP>C. In the second step, in order to synthesize ZnCo<SUB>2</SUB>O<SUB>4</SUB>/graphene nanocomposite, the obtained pure ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoparticles were milled with 10 wt% reduced graphene nanosheets using high energy spex mill for 30 s. The ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoparticles, with particle sizes of 25-50 nm, were uniformly dispersed and anchored on the reduced graphene nanosheets. Compared with pure ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoparticles anode, significant improvements in the electrochemical performance of the nanocomposite anode were obtained. The resulting nanocomposite delivered a reversible capacity of 1124.8 mAh g<SUP>-1</SUP> at 0.1 C after 90 cycles with 98% Coulombic efficiency and high rate capability of 515.9 mAh g<SUP>-1</SUP> at 4.5 C, thus exhibiting one of the best lithium storage properties among the reported ZnCo<SUB>2</SUB>O<SUB>4</SUB> anodes. The significant enhancement of the electrochemical performance of the nanocomposite anode could be credited to the strong synergy between ZnCo<SUB>2</SUB>O<SUB>4</SUB> and graphene nanosheets, which maintain excellent electronic contact and accommodate the large volume changes during the lithiation/delithiation process.

Dielectric properties of iron doped calcium copper titanate, CaCu3Ti3.9Fe0.1O12 ceramic

Rai, Alok Kumar,Singh, N. K.,Lee, Sang-Kwon,Mandal, K. D.,Kumar, D. Springer-Verlag 2011 Journal of materials science Materials in electron Vol.22 No.9

Synthesis of nano-sized ZnCo₂O₄ anchored with graphene nanosheets as an anode material for secondary lithium ion batteries

Rai, A.K.,Thi, T.V.,Paul, B.J.,Kim, J. Pergamon Press 2014 ELECTROCHIMICA ACTA Vol.146 No.-

ZnCo<SUB>2</SUB>O<SUB>4</SUB>/graphene and pure ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoparticles were synthesized by simple and low temperature urea-assisted auto-combustion method and annealed at 400<SUP>o</SUP>C for 5h in air atmosphere. The electron microscopy image of the obtained ZnCo<SUB>2</SUB>O<SUB>4</SUB>/graphene nanocomposite revealed that the ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoparticles were randomly distributed and anchored on the surface of reduced graphene nanosheets. The graphene nanosheets significantly reduced the particles size and suppressed the aggregation of ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoparticles as well as maintaining the good electrical conductivity of the overall sample. The size of the nanoparticles was in the range of 50-100nm and the size of nanoparticles in the nanocomposite sample in the range of 25-50nm. The electrochemical results showed that the ZnCo<SUB>2</SUB>O<SUB>4</SUB>/graphene nanocomposite electrode had greatly improved cycling stability with high reversible capacity of 755.6 mAh g<SUP>-1</SUP> after 70 cycles, and better rate capability of 378.1 mAh g<SUP>-1</SUP> at 4.5C than pure ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoparticles (299.8 mAh g<SUP>-1</SUP> after 70 cycles and 302.4 mAh g<SUP>-1</SUP> at 4.5C). The enhanced electrochemical performance of the nanocomposite could be ascribed to the positive synergistic effect of the combination of the ZnCo<SUB>2</SUB>O<SUB>4</SUB> nanoparticles and conducting graphene nanosheets.

Combustion synthesis of MgFe₂O₄/graphene nanocomposite as a high-performance negative electrode for lithium ion batteries

Rai, A.K.,Thi, T.V.,Gim, J.,Kim, J. Elsevier 2014 Materials characterization Vol.95 No.-

We present a facile and cost-effective urea-assisted auto-combustion method for synthesizing pure MgFe<SUB>2</SUB>O<SUB>4</SUB> nanoparticle and MgFe<SUB>2</SUB>O<SUB>4</SUB>/graphene nanocomposite samples followed by annealing at 600<SUP>o</SUP>C for 5h under N<SUB>2</SUB> atmosphere. The X-ray diffraction pattern confirmed the single phase formation for both samples. The obtained morphology of the nanocomposite sample shows that the MgFe<SUB>2</SUB>O<SUB>4</SUB> nanoparticles are highly dispersed on conductive graphene nanosheets with particle size in the range of 50-100nm. When applied as an anode material, MgFe<SUB>2</SUB>O<SUB>4</SUB>/graphene nanocomposite electrode shows a high reversible charge capacity of 764.4mAhg<SUP>-1</SUP> at 0.04C over 60 charge/discharge cycles and in spite of that it also retained a capacity of 219.9mAhg<SUP>-1</SUP> at high current rate of 4.2C. The obtained result is much better than the synthesized pure MgFe<SUB>2</SUB>O<SUB>4</SUB> nanoparticle electrode. The excellent electrochemical performance of the MgFe<SUB>2</SUB>O<SUB>4</SUB>/graphene nanocomposite electrode can be attributed to the strong favorable synergistic interaction between MgFe<SUB>2</SUB>O<SUB>4</SUB> and reduced graphene nanosheets, which supplied a large number of accessible active sites for Li<SUP>+</SUP>-ion insertion and short diffusion length for both Li<SUP>+</SUP> ions and electrons. In addition, the graphene nanosheets in the nanocomposite electrode provide high conductivity and accommodate the large volume expansion/contraction during cycling, resulting in high capacity and long cycling stability.

Cr(Ⅲ) Complexes of Tetraazamacrocycles Derived from $\alpha$-Diketones and Diaminoalkanes

Rai, Pramod K.,Gupta, Ajay K.,Prasad, Raghu N. Korean Chemical Society 1993 Bulletin of the Korean Chemical Society Vol.14 No.2

Template condensation of ${\alpha}$-diketones such as 2,3-butanedione or benzil with diaminoalkanes such as 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,6-diaminohexane, 1,8-diaminooctane or 1,12-diaminododecane in the presence of Cr(III) results in the formation of complexes of the type $[CrI,X_2]X$ (where L = tetraazamacrocycle having 12 to 32-membered ring and $X={NO_3}^- or Cl^-).$ The complexes have been characterized by elemental analyses, magnetic measurements and IR and diffuse reflectance spectra.

Distinct Involvement of 9p21-24 and 13q14.1-14.3 Chromosomal Regions in Raw Betel-Nut Induced Esophageal Cancers in the State of Meghalaya, India

Rai, Avdhesh K.,Freddy, Allen J.,Banerjee, Atanu,Kurkalang, Sillarine,Rangad, Gordon M.,Islam, Mohammad,Nongrum, Henry B.,Dkhar, Hughbert,Chatterjee, Anupam Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.6

Background: Raw betel nut (RBN) chewing is an important contributing factor for esophageal squamous cell carcinoma (ESCC), although associated genomic changes remain unclear. One difficulty in assessing the effects of exclusively RBN induced genetic alterations has been that earlier studies were performed with samples of patients commonly using tobacco and alcohol, in addition to betel-quid. Both CDKN2A (at 9p21) and Rb1 gene (at 13q14.2) are regarded as tumor suppressors involved in the development of ESCC. Therefore, the present study aimed to verify the RBN's ability to induce ESCC and assess the involvement of CDKN2A and Rb1 genes. Methods: A panel of dinucelotide polymorphic markers were chosen for loss of heterozygosity studies in 93 samples of which 34 were collected from patients with only RBN-chewing habit. Promoter hypermethylation was also investigated. Results: Loss in microsatellite markers D9S1748 and D9S1749, located close to exon $1{\beta}$ of CDKN2A/ARF gene at 9p21, was noted in 40% ESCC samples with the habit of RBN-chewing alone. Involvement of a novel site in the 9p23 region was also observed. Promoter hypermethylation of CDKN2A gene in the samples with the habit of only RBN-chewing alone was significantly higher (p=0.01) than Rb1 gene, also from the samples having the habit of use both RBN and tobacco (p=0.047). Conclusions: The data indicate that the disruption of 9p21 where CDKN2A gene resides, is the most frequent critical genetic event in RBN-associated carcinogenesis. The involvement of 9p23 as well as 13q14.2 could be required in later stages in RBN-mediated carcinogenesis.

Effect of temperature on elastic, mechanical and thermophysical properties of VNx (0.76 ≤ x ≤ 1.00) epitaxial layers

Rai Sachin,Prajapati Aadesh K.,Yadawa Pramod K. 한국물리학회 2023 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.82 No.1

The efect of temperature on the elastic, thermophysical and mechanical properties of VNx (0.76≤x≤1.00) epitaxial layers has been investigated using Coulomb and Born–Mayer potentials approach up to second nearest neighbor. The elastic constants and its allied properties (Bulk, Shear, Poisson's ratio and Young’s modulus) are analyzed to provide insights into the mechanical behavior of VNx (0.76≤x≤1.00) transition-metal nitrides using second-order elastic constants (SOECs). SOECs are used to measure the temperature deviation of ultrasonic velocities along the crystal’s z axis. The temperature variation of Debye average velocity and thermal relaxation time are calculated along same orientation. Thermal conductivity has been observed to be the main contributing factor to the temperature-dependent behavior of ultrasonic attenuations with phonon–phonon interaction. Depending on G/B ratios, the nitride groups are attributed to brittle and ductile behavior in the future. Including all epitaxial layers, the estimated melting temperatures are in better agreement with those calculated with B and C11 and have highest strength and highest harness. Transition metal nitrides have unusual chemical and physical properties, which are commonly used in industrial felds that require working at temperatures.