Browsing by Author "Singh, S.K."

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Assessment on the effectiveness of chemical admixture in processed laterite and copper slag based geopolymer mortar
(Elsevier Ltd, 2025) Clement, D.; C, R.; Singh, S.K.; Tiwari, M.
Geopolymer-based cementitious materials known for their robust durability and lower environmental impact make them an ideal choice for sustainable construction. The main focus of this study is to understand the influence of chemical admixtures which plays a pivotal role in improving the properties of geopolymer mortar (GM). This research integrates various chemical admixtures, including calcium chloride, sodium sulphate, sodium hexametaphosphate, and MasterGlenium SKY 8233 (SKY) which falls under the category of either accelerators, retarders, or superplasticisers. Assessments were conducted on the fresh and hardened states of flyash-based GM mixes with varying proportion of river sand (RS), laterite soil (LS) and copper slag (CS), encompassing flowability, setting times, compressive strength, durability study in aggressive environmental conditions and microstructural analyses after 56 days of ambient curing. Findings reveal that calcium chloride and sodium sulphate efficiently decrease the initial and final setting times of the geopolymer paste, highlighting their roles as accelerators, with calcium chloride showing greater efficacy than sodium sulphate. On the other hand, sodium hexametaphosphate serves as a retarder, substantially extending the initial setting time of the geopolymer paste. Introducing the modified polycarboxylic ether (PCE) based superplasticiser SKY into the mortar matrix caused the initial setting time to be extended and resulted in a slight drop in compressive strength compared to the other mixes. Durability tests confirmed the superior resistance of GM mixes to harsh environments like acid, sulphate, and marine water exposure. These findings highlight the potential for tailoring geopolymer blends to achieve desired properties under ambient curing conditions using chemical admixtures. © 2025 Elsevier Ltd
Computational investigation of air solid flow in a spray dryer for effluent treatment
(Scientific Publishers, 2020) Singh, S.K.; Ali, B.
In this work, the hydrodynamics and evaporation rate of the co-current spray dryer is numerically investigated through ANSYS Fluent (CFD). The performance of the spray dryer depends on the geometry, operating conditions, and underlying hydrodynamics in such systems. To predict the air-solid flow in a spray dryer, the Euler-Lagrangian CFD model is used to track the particles in the dryer. The continuous phase turbulence is predicted using RNG version of k-turbulence model. To quantify the flow pattern, a horizontal line is considered and spatial variation of velocity profiles are analyzed. The predicted air velocity variation was found to be maximum at the center of the core. Further, the airflow pattern is analyzed for various operating temperatures and feed properties. It was found that airflow pattern influences particle behavior with minimum deposition rates on each section of the wall when air temperature is 350 K. © 2020 Scientific Publishers. All rights reserved.
E-fields inside 765 kV substation: Influence of conductor & bay arrangements
(2017) Singh, S.K.; Punekar, G.S.
Increasing voltage level in generation and transmission system have become inevitable. The threats of non-ionizing radiation and their biological effects at substations have increased. As per International Commission for Non-Ionizing Radiation and Protection (ICNIRP) guidelines suggest maximum limits for electric and magnetic field exposure is 10 kV/m and 1 mT for occupational and 5 kV/m and 250 ?T for public exposure. Keeping this in view results of a case study of electric field distribution in an upcoming 765 kV substation in India are computed and discussed in this paper. Using the existing layout of this substation, the E-fields at 2 m height above the ground plane are computed using FEMM (a free ware). Results show that Bays which are at a height of 14 m from ground are dominant and contributing more to the E-fields. The paper further computes and compares E-field strength due to (i) a single conductor (a phase of bay alone), (ii) single bay (iii) and with all the bays of substation with buses, overhead headlines and ground wires. The effect of bay height (around 14 m) on the E-field is also reported. The average E-field in substation arena is well within the ICNIPR suggested limit of 10 kV/m, whereas E-field at some places exceeds this value. � 2016 IEEE.
E-fields inside 765 kV substation: Influence of conductor & bay arrangements
(Institute of Electrical and Electronics Engineers Inc., 2017) Singh, S.K.; Punekar, G.S.
Increasing voltage level in generation and transmission system have become inevitable. The threats of non-ionizing radiation and their biological effects at substations have increased. As per International Commission for Non-Ionizing Radiation and Protection (ICNIRP) guidelines suggest maximum limits for electric and magnetic field exposure is 10 kV/m and 1 mT for occupational and 5 kV/m and 250 Î¼T for public exposure. Keeping this in view results of a case study of electric field distribution in an upcoming 765 kV substation in India are computed and discussed in this paper. Using the existing layout of this substation, the E-fields at 2 m height above the ground plane are computed using FEMM (a free ware). Results show that Bays which are at a height of 14 m from ground are dominant and contributing more to the E-fields. The paper further computes and compares E-field strength due to (i) a single conductor (a phase of bay alone), (ii) single bay (iii) and with all the bays of substation with buses, overhead headlines and ground wires. The effect of bay height (around 14 m) on the E-field is also reported. The average E-field in substation arena is well within the ICNIPR suggested limit of 10 kV/m, whereas E-field at some places exceeds this value. Â© 2016 IEEE.
Rankin–cohen brackets on hermitian jacobi forms and the adjoint of some linear maps
(Adam Mickiewicz University Press, 2021) Sathyanarayana, S.; Singh, S.K.
Given a fixed Hermitian Jacobi cusp form, we define a family of linear operators between spaces of Hermitian Jacobi cusp forms using Rankin–Cohen brackets. We compute the adjoint maps of such a family with respect to the Petersson scalar product. The Fourier coefficients of the Hermitian Jacobi cusp forms constructed using this method involve special values of certain Dirichlet series associated to Hermitian Jacobi cusp forms. © 2021 Adam Mickiewicz University Press. All rights reserved.