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Implementation of Multilevel Boost DC-Link Cascade based Reversing Voltage Inverter for Low THD Operation

  • Rao, S. Nagaraja;Kumar, D.V. Ashok;Babu, Ch. Sai
    • Journal of Electrical Engineering and Technology
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    • v.13 no.4
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    • pp.1528-1538
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    • 2018
  • In this paper, configuration of $1-{\phi}$ seven-level boost DC-link cascade based reversing voltage multilevel inverter (BDCLCRV MLI) is proposed for uninterrupted power supply (UPS) applications. It consists of three level boost converter, level generation unit and full bridge circuit for polarity generation. When compared with conventional boost cascaded H-bridge MLI configurations, the proposed system results in reduction of DC sources, reduced power switches and gate drive requirements. Inverter switching is accomplished by providing appropriate switching angles that is generated by any optimization switching angle techniques. Here, round modulation control (RMC) method is taken as the optimization method and switching angles are derived and the same is compared with various switching angles methods i.e., equal-phase (EP) method, and half-equal-phase (HEP) method which results in improved quality of obtained AC power with lowest total harmonic distortion (THD). Reduction in DC sources and switch count makes the system more cost effective. A simulation and prototype model of $1-{\phi}$ seven-level BDCLCRV MLI system is developed and its performance is analyzed for various operating conditions.

Transmission Electron Microscopy on Memristive Devices: An Overview

  • Strobel, Julian;Neelisetty, Krishna Kanth;Chakravadhanula, Venkata Sai Kiran;Kienle, Lorenz
    • Applied Microscopy
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    • v.46 no.4
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    • pp.206-216
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    • 2016
  • This communication is to elucidate the state-of-the-art of techniques necessary to gather information on a new class of nanoelectronic devices known as memristors and related resistive switching devices, respectively. Unlike classical microelectronic devices such as transistors, the chemical and structural variations occurring upon switching of memristive devices require cutting-edge electron microscopy techniques. Depending on the switching mechanism, some memristors call for the acquisition of atomically resolved structural data, while others rely on atomistic chemical phenomena requiring the application of advanced X-ray and electron spectroscopy to correlate the real structure with properties. Additionally, understanding resistive switching phenomena also necessitates the application not only of pre- and post-operation analysis, but also during the process of switching. This highly challenging in situ characterization also requires the aforementioned techniques while simultaneously applying an electrical bias. Through this review we aim to give an overview of the possibilities and challenges as well as an outlook onto future developments in the field of nanoscopic characterization of memristive devices.

Selection of Plant Growth-Promoting Pseudomonas spp. That Enhanced Productivity of Soybean-Wheat Cropping System in Central India

  • Sharma, Sushil K.;Johri, Bhavdish Narayan;Ramesh, Aketi;Joshi, Om Prakash;Sai Prasad, S.V.
    • Journal of Microbiology and Biotechnology
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    • v.21 no.11
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    • pp.1127-1142
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    • 2011
  • The aim of this investigation was to select effective Pseudomonas sp. strains that can enhance the productivity of soybean-wheat cropping systems in Vertisols of Central India. Out of 13 strains of Pseudomonas species tested in vitro, only five strains displayed plant growth-promoting (PGP) properties. All the strains significantly increased soil enzyme activities, except acid phosphatase, total system productivity, and nutrient uptake in field evaluation; soil nutrient status was not significantly influenced. Available data indicated that six strains were better than the others. Principal component analysis (PCA) coupled cluster analysis of yield and nutrient data separated these strains into five distinct clusters with only two effective strains, GRP3 and HHRE81 in cluster IV. In spite of single cluster formation by strains GRP3 and HHRE81, they were diverse owing to greater intracluster distance (4.42) between each other. These results suggest that the GRP3 and HHRE81 strains may be used to increase the productivity efficiency of soybean-wheat cropping systems in Vertisols of Central India. Moreover, the PCA coupled cluster analysis tool may help in the selection of other such strains.

Selecting a Web Portal for Online Shopping: A Conceptual Approach Using Interpretive Structural Modeling

  • Prashar, Sanjeev;Vijay, T. Sai;Parsad, Chandan
    • Asian Journal of Business Environment
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    • v.5 no.4
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    • pp.37-46
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    • 2015
  • Purpose - The present study examines interrelationships among antecedent factors defining consumer behavior in selecting online shopping websites. Research design, data, and methodology - The study identified factors from existing literature and used Interpretive Structural Modeling (ISM) to propose a conceptual approach to explain consumer website selection behavior. Through extensive discussions among industry and academia experts, qualitative assessment of the relationship between various factors was determined. Results - According to the model, eight congregating factors do not converge directly for website selection, rather, they operate following a hierarchy of influence. The ISM and MICMAC analysis reveal that information on a website and website aesthetics play key roles in influencing website selection. However, convenience and the value proposition also play very significant roles. Conclusions - The study's findings can help the e-commerce industry, especially online retailers. The findings can be used to enhance e-retailer ability to attract, communicate, engage, achieve, monitor, and evaluate web traffic and design appropriate strategies. The study's prime contribution is the application of Interpretative Structural Modeling (ISM) to the field of website selection.

Modal analysis of FG sandwich doubly curved shell structure

  • Dash, Sushmita;Mehar, Kulmani;Sharma, Nitin;Mahapatra, Trupti R.;Panda, Subrata K.
    • Structural Engineering and Mechanics
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    • v.68 no.6
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    • pp.721-733
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    • 2018
  • The modal frequency responses of functionally graded (FG) sandwich doubly curved shell panels are investigated using a higher-order finite element formulation. The system of equations of the panel structure derived using Hamilton's principle for the evaluation of natural frequencies. The present shell panel model is discretised using the isoparametric Lagrangian element (nine nodes and nine degrees of freedom per node). An in-house MATLAB code is prepared using higher-order kinematics in association with the finite element scheme for the calculation of modal values. The stability of the opted numerical vibration frequency solutions for the various shell geometries i.e., single and doubly curved FG sandwich structure are proven via the convergence test. Further, close conformance of the finite element frequency solutions for the FG sandwich structures is found when compared with the published theoretical predictions (numerical, analytical and 3D elasticity solutions). Subsequently, appropriate numerical examples are solved pertaining to various design factors (curvature ratio, core-face thickness ratio, aspect ratio, support conditions, power-law index and sandwich symmetry type) those have the significant influence on the free vibration modal data of the FG sandwich curved structure.

Numerical study of temperature dependent eigenfrequency responses of tilted functionally graded shallow shell structures

  • B, Chandra Mouli;K, Ramji;Kar, Vishesh R;Panda, Subrata K;K, Lalepalli Anil;Pandey, Harsh K
    • Structural Engineering and Mechanics
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    • v.68 no.5
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    • pp.527-536
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    • 2018
  • The free vibration frequency responses of the graded flat and curved (cylindrical, spherical, hyperbolic and elliptical) panel structures investigated in this research considering the rectangular and tilted planforms under unlike temperature loading. For the numerical implementation purpose, a micromechanical model is prepared with the help of Voigt's methodology via the power-law type of material model. Additionally, to incur the exact material strength, the temperature-dependent properties of each constituent of the graded structure included due to unlike thermal environment. The deformation kinematics of the rectangular/tilted graded shallow curved panel structural is modeled via higher-order type of polynomial functions. The final form of the eigenvalue equation of the heated structure obtained via Hamilton's principle and simultaneously solved numerically using finite element steps. To show the solution accuracy, a series of comparison the results are compared with the published data. Some new results are exemplified to exhibit the significance of power-law index, shallowness ratio, aspect ratio and thickness ratio on the combined thermal eigen characteristics of the regular and tilted graded panel structure.

FE modelling of low velocity impact on RC and prestressed RC slabs

  • Ganesan, Partheepan;Kumar, S. Venkata Sai
    • Structural Engineering and Mechanics
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    • v.71 no.5
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    • pp.515-524
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    • 2019
  • The present study deals with the simulation of low velocity impact on prestressed and reinforced concrete (RC) slabs supported with different end conditions. The prestress is pre-applied on the RC slab in an analytical approach for the prestressed slab. RC slabs with dimensions $500{\times}600{\times}60mm$, $500{\times}600{\times}80mm$ and $500{\times}600{\times}120mm$ were used by changing support condition in two different ways; (i) Opposite sides simply supported, (ii) Adjacent sides simply supported with opposite corner propped. Deflection response of these specimens were found for the impact due to three different velocities. The effect of grade of concrete on deflection due to the impact of these slabs were also studied. Deflection result of $500{\times}500{\times}50mm$ slab was calculated numerically and compared the result with the available experimental result in literature. Finite element analyses were performed using commercially available ANSYS 16.2 software. The effectiveness of prestressing on impact resistant capacity of RC slabs are demonstrated by the way of comparing the deflection of RC slabs under similar impact loadings.

Influence of plastic viscosity of mix on Self-Compacting Concrete with river and crushed sand

  • Rama, J.S. Kalyana;Sivakumar, M.V.N.;Kubair, K. Sai;Vasan, A.
    • Computers and Concrete
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    • v.23 no.1
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    • pp.37-47
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    • 2019
  • In view of the increasing utility of concrete as a construction material, the major challenge is to improve the quality of construction. Nowadays the common problem faced by many of the concrete plants is the shortage of river sand as fine aggregate material. This led to the utilization of locally available materials from quarries as fine aggregate. With the percentage of fines present in Crushed Rock Fines (CRF)or crushed sand is more compared to river sand, it shows a better performance in terms of fresh properties. The present study deals with the formulation of SCC mix design based on the chosen plastic viscosity of the mix and the measured plastic viscosity of cement pastes incorporating supplementary cementitious materials with CRF and river sand as a fine aggregate. Four different combinations including two binary and one ternary mix are adopted for the current study. Influence of plastic viscosity of the mix on the fresh and hardened properties are investigated for SCC mixes with varying water to cement ratios. It is observed that for an increasing plastic viscosity of the mix, slump flow, T500 and J-ring spread increased but V-funnel and L-box decreased. Compressive, split tensile and flexural strengths decreased with the increase in plastic viscosity.

Comparative evaluation of efficacy of Physics Forceps versus conventional forceps in pediatric dental extractions: a prospective randomized study

  • Elicherla, Sainath Reddy;Bandi, Sujatha;Nunna, Mahesh;Saikiran, Kanamarlapudi Venkata;Sahithi, Varada;Nuvvula, Sivakumar
    • Journal of Dental Anesthesia and Pain Medicine
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    • v.21 no.6
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    • pp.547-556
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    • 2021
  • Background: This study aimed to determine the efficacy of Physics Forceps in pediatric dental extractions. Methods: This was a double-blind, randomized controlled trial with a parallel-arm design and identical allocation ratio (1:1). Children (n=104) were randomly divided into two groups for extraction of mandibular primary teeth (group I: Physics Forceps; group II: conventional forceps). The outcome variables assessed in the study were the time taken for extraction, pre- and postoperative anxiety (using RMS pictorial scale), incidence of fractured teeth, and postoperative pain on the first and third days (using the Wong-Baker faces pain scale). Results: A significant reduction (P < 0.001) in intraoperative time, anxiety, and incidence of tooth fracture was confined to group I. The pain significantly reduced from the first to the third postoperative day in both groups, but the mean reduction in RMS scores in the physics forceps group was far better than that in the conventional forceps group. Conclusion: Physics Forceps aid in extraction of primary teeth with minimal trauma to supporting structures, as well as reducing anxiety in the pediatric population.

The Utilisation of ICTs For Knowledge Management In A Zimbabwean Urban District Council

  • SAI, Kundai Oliver Shadwell;SUBRAMANIAM, Prabhakar Rontala
    • The Journal of Industrial Distribution & Business
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    • v.13 no.2
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    • pp.1-15
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    • 2022
  • Purpose: This study established the state of the utilisation of information and communication technologies (ICTs) in Zimbabwean urban district councils to manage municipal knowledge. The way municipal knowledge and service delivery information are managed influences the usefulness and accessibility of the information to the various stakeholders. The effective management of this information thus determines the quality of decisions made by Zimbabwean urban councils. Research design, data and methodology: The study adopted a single case study design, employing a purely qualitative research approach. The purposive sampling technique was used to select key informants who participated in the study. Collected data were analysed using thematic content analysis. Results: The findings revealed that the Masvingo City Council was not fully utilising ICTs to manage service delivery knowledge. It has been at a minimum level in cases where they have been used. Conclusions: This research contributes to the Zimbabwean local government body of knowledge, providing the evidence needed to form a basis for future research, focusing on knowledge management and information technology utilisation in municipal organisations. The researchers recommended that Masvingo City Council direct more resources towards improving the existing ICT infrastructure and employee training programmes to improve the management of the organisation's knowledge.