Kinetics, thermodynamic and equilibrium study of Cr(VI) adsorption from aqueous solutions by NCL coal dust

Ravi Shankar Singh,Monoj Kumar Mondal 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.12

The waste material NCL coal dust was used as adsorbent for removal of Cr(VI) from aqueous solutions under batch adsorption experiments. The maximum removal of 99.97% was recorded at pH 2. The time required to attain equilibrium was found to be 60 min. Adsorption kinetics was described by the Lagergren equation. The value of the rate constant of adsorption was found to be 0.0615 min−1 at 16 mg dm−3 initial concentration and 298 K. The applicability of the Langmuir and Freundlich equations for the present system was also tested at different temperatures:298, 313, and 328 K. Both thermodynamic parameters and temperature dependence indicated the endothermic nature of Cr(VI) adsorption on coal dust. The results showed that NCL coal dust is a promising adsorbent for the removal of Cr(VI) from aqueous solutions.

Study of Dark-Conductivity and Photoconductivity of ZnO Nano Structures Synthesized by Thermal Decomposition of Zinc Oxalate

Ravi Shankar,Rajneesh K Srivastava,S.G. Prakash 대한금속·재료학회 2013 ELECTRONIC MATERIALS LETTERS Vol.9 No.5

In the present work, zinc oxalate [ZnC2O4·2H2O] was used as precursor to prepare zinc oxide nano structures by thermal decomposition. Its photoconductivity and dark-conductivity properties have been studied in air as well as in vacuum. Voltage dependence of photocurrent and dark-current has been observed at room temperature in air under UV-vis illumination and is found as superlinear in nature. Rise and decay curve in air exhibits anomalous behavior wherein the photocurrent decreases even during steady illumination. In vacuum,the rise of photocurrent becomes slow and prolonged.

Faculty perceptions regarding an individually tailored, flexible length, outcomes-based curriculum for undergraduate medical students

Shankar Pathiyil Ravi,Azhar Tayyaba,Nadarajah Vishna Devi,Er Hui Meng,Arooj Mahwish,Wilson Ian G. 한국의학교육학회 2023 Korean journal of medical education Vol.35 No.3

Purpose: The perception of faculty members about an individually tailored, flexible-length, outcomes-based curriculum for undergraduate medical students was studied. Their opinion about the advantages, disadvantages, and challenges was also noted. This study was done to help educational institutions identify academic and social support and resources required to ensure that graduate competencies are not compromised by a flexible education pathway.Methods: The study was done at the International Medical University, Malaysia, and the University of Lahore, Pakistan. Semi-structured interviews were conducted from 1st August 2021 to 17th March 2022. Demographic information was noted. Themes were identified, and a summary of the information under each theme was created.Results: A total of 24 (14 from Malaysia and 10 from Pakistan) faculty participated. Most agreed that undergraduate medical students can progress (at a differential rate) if they attain the required competencies. Among the major advantages mentioned were that students may graduate faster, learn at a pace comfortable to them, and develop an individualized learning pathway. Several logistical challenges must be overcome. Providing assessments on demand will be difficult. Significant regulatory hurdles were anticipated. Artificial intelligence (AI) can play an important role in creating an individualized learning pathway and supporting time-independent progression. The course may be (slightly) cheaper than a traditional one.Conclusion: This study provides a foundation to further develop and strengthen flexible-length competency-based medical education modules. Further studies are required among educators at other medical schools and in other countries. Online learning and AI will play an important role.

Stable SiO2–TiO2 composite-based nanofluid of improved rheological behaviour for high-temperature oilfield applications

Ravi Shankar Kumar,Tushar Sharma 한국자원공학회 2020 Geosystem engineering Vol.23 No.1

Nanofluid synthesis in pure water is associated with premature settlement resulting in least dispersion stability. Therefore, in this study, polyacrylamide (PAM) is used as viscosity enhancer to improve dispersion stability of nanofluid stabilized by composites of silica and titania. Different techniques such as dynamic light scattering measurements, electrical conductivity, scanning electron microscopy, and rheological studies are used to support the analysis. The use of silica and titania nanoparticles together with PAM has additional advantage over particle agglomeration, and thus, the dispersion stability improved. Further, nanofluid stabilized by composites of silica and titania was tested for rheological measurements at 90°C to find nanotechnology applicability in high-temperature applications. The shear-thinning behaviour of nanofluids at high temperature (90°C) was least affected by shear deformation and reduced to 0.48 mPa.s at higher shear rate (4200 s−1), while shear thinning of PAM solution seriously varied with increasing shear deformation and takes the edge of 0.0005 mPa.s at higher shear rate (4200 s−1). In addition, the thermal stability of nanofluids was better due to slight decrease in viscosity with increasing temperature, which makes them suitable to be utilized at high-temperature applications in widespread industrial areas including oilfield where the temperature becomes a major factor

Extraction of Fundamental Component in Power Quality Application using Tunable-Q Wavelet Transform

G.Ravi Shankar Reddy,Rameshwar Rao 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.8

Application of a Tunable-Q Wavelet Transform based technique is proposed in this paper for the extraction of Fundamental frequency component in Power Quality Disturbances. The TQWT filters are designed to extract the fundamental frequency component from the complete voltage (or) current signal. This is achieved by tuning the Q-factor and redundancy of the wavelet by primarily investigating the presence of interharmonics near the fundamental frequency. To test the effectiveness of the proposed scheme, the system is verified with various Power Quality Disturbances as per IEEE standards encountered in power system are considered here.

Non-stationary Signal Analysis using TVAR Model

G. Ravi Shankar Reddy,Dr. Rameshwar Rao 보안공학연구지원센터(IJSIP) 2014 International Journal of Signal Processing, Image Vol.7 No.2

Performance Analysis of Basis Functions in TVAR Model

G. Ravi Shankar Reddy,Dr. Rameshwar Rao 보안공학연구지원센터(IJSIP) 2014 International Journal of Signal Processing, Image Vol.7 No.3

Empirical Wavelet Transform Based Approach for Extraction of Fundamental Component and Estimation of Time-Varying Power Quality Indices in Power Quality Disturbances

G. Ravi Shankar Reddy,Dr.Rameshwar Rao 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.11

In this paper Application of an Empirical Wavelet Transform based technique is proposed to estimate time-varying PQ indices for accurate assessment of Power Quality Disturbances. The EWT approach mainly aims to extract the actual fundamental frequency component and disturbance components from any distorted signal. The empirical wavelet transform consists of two major steps: detect the Fourier supports, and build the corresponding wavelet accordingly to those supports; filter the input signal with the obtained filter bank to get the fundamental component and disturbance components. Since the extracted components contain only one frequency component, Hilbert transform is utilized to estimate the instantaneous frequency and amplitude information, from this information we can estimate time-varying PQ indices. The proposed method is employed to assess successfully all sorts of Power Quality Disturbances such as voltage sag, swell, interruption, transients, harmonics, spikes, notches etc. From the results we can say that the proposed method detects disturbance start time, end time, duration of existence and its content more accurately.

Revisiting the Bulge-Halo Conspiracy. I. Dependence on Galaxy Properties and Halo Mass

Shankar, Francesco,Sonnenfeld, Alessandro,Mamon, Gary A.,Chae, Kyu-Hyun,Gavazzi, Raphael,Treu, Tommaso,Diemer, Benedikt,Nipoti, Carlo,Buchan, Stewart,Bernardi, Mariangela,Sheth, Ravi,Huertas-Company, American Astronomical Society 2017 The Astrophysical Journal Vol.840 No.1

<P>We carry out a systematic investigation of the total mass density profile of massive (log M-star / M-circle dot greater than or similar to 11.3) early-type galaxies and its dependence on galactic properties and host halo mass with the aid of a variety of lensing/dynamical data and large mock galaxy catalogs. The latter are produced via semi-empirical models that, by design, are based on just a few basic input assumptions. Galaxies. with measured stellar masses, effective radii, and Sersic indices, are assigned, via abundance matching relations, host dark matter halos characterized by a typical Lambda CDM profile. Our main results are as follows. (1) In line with observational evidence, our semi-empirical models naturally predict that the total, mass-weighted density slope at the effective radius gamma' is not universal, steepening for more compact and/or massive galaxies, but flattening with increasing host halo mass. (2) Models characterized by a Salpeter or variable initial mass function (IMF) and uncontracted dark matter profiles are in good agreement with the data, while a Chabrier IMF and/or adiabatic contractions/expansions of the dark matter halos are highly disfavored. (3) Currently available data on the mass density profiles of very massive galaxies (log M-star / M-circle dot greater than or similar to 12), with M-halo greater than or similar to 3 x 10(14) M-circle dot, favor instead models with a stellar profile flatter than a Sersic one in the very inner regions (r less than or similar to 3-5 kpc), and a cored NFW or Einasto dark matter profile with median halo concentration a factor of similar to 2 or less than or similar to 1.3, respectively, higher than those typically predicted by N-body numerical simulations.</P>

A Quasi Opposition Lion Optimization Algorithm for Deregulated AGC Considering Hybrid Energy Storage System

Kumar Ashiwani,Shankar Ravi 대한전기학회 2021 Journal of Electrical Engineering & Technology Vol.16 No.6

This paper presents the integration of renewable energy resources into the Automatic Generation Control (AGC) of two area power system under deregulation. Area-1 includes the combination of thermal system, gas power system, aggregate Electric Vehicle (EV), and Dish-Stirling Solar Thermal system (DSTS) whereas area-2 contains thermal system, gas power system, aggregate electric vehicle, and Wind Turbine System (WTS). To achieve the realistic approach, nonlinearities such as Generation Rate Constraint (GRC), Governor Dead Band (GDB), and Boiler Dynamics (BD) are explored in proposed test system. AGC’s main aim is to keep the balance between load and generation and to achieve this balance secondary frequency regulation mechanism play an important role. Therefore, a tilt proportional integral derivative controller has been used to achieve desired dynamic response of the system. A new Quasi Opposition Lion Optimization Algorithm (QOLOA) has been suggested for studied system to get the optimum values of controller and system parameters. Integral Square Error (ISE) is considered as an objective function for the optimization of the anticipated AGC mechanism. Furthermore, Hybrid Energy Storage (HES) is used to damp the oscillation of the considered AGC system. Hence, for this investigation, it consists of the hybridization of the Redox Flow Battery (RFB) and Superconducting Magnetic Energy Storage (SMES) system. Additionally, the sensitivity analysis is also performed to evaluate the robustness of the proposed QOLOA based control scheme. The suggested control mechanism is compared with previously published work on the same platform to show the eff ectiveness and its superiority of presented work