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Sudhanshu Pandey(판데이수단슈),Yong Gap Park(박용갑),Man Yeong Ha(하만영) 대한기계학회 2019 대한기계학회 춘추학술대회 Vol.2019 No.11
Natural convection inside a square enclosure containing an internal circular cylinder in the presence of non-Newtonian power law fluid is investigated using commercial CFD tool Fluent. The effects of Rayleigh number (103≤ Ra ≤106) and power index (0.6≤ n≤ 1.6) on flow and heat transfer characteristics are demonstrated for a fixed value of Prandtl number of 10. The internal cylinder is placed at three different positions along the vertical centerline. The flow experienced a transition from steady to unsteady state at n=0.6 under the shear thinning regime at Ra=106. The time and surface-averaged Nusselt number found to be a decreasing function of the power law index in all the cases considered.
Sudhanshu Pandey,박용갑,Man Yeong Ha 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.8
The present study deals with an unsteady laminar free convection inside the annuli confined between an outer square enclosure and an inner circular cylinder. The annuli are filled with non-Newtonian power law fluids. The inner cylinder is located at three positions along the vertical center line. The unsteadiness arising due to bifurcation of flow from steady state is also reported in this study. The flow characteristics were found to be steady in nature in case of shear thickening fluid. However, most of the cases in the shear thinning fluid regime are found to be unsteady in nature with periodic and non-periodic fluctuations. The bifurcation of the flow from steady to unsteady state is mainly governed by the location of the cylinder as well as the characteristics of non-Newtonian fluid. The Bernard cells arising due to very high convective flow at Ra = 107 are also observed in the flow fields.
Sudhanshu Shekher Pati,Pranay Kant Prasad,Abhinav Kr Singh,Sandeep Singh,Shailesh Kumar Prasad 한국부식방식학회 2022 Corrosion Science and Technology Vol.21 No.2
A study on water-based epoxy coated on mild steel using the electroplating method was conducted to optimize the process parameters for dry film thickness to achieve superior paint quality at optimal cost in an automotive plant. The regression model was used to adjust various parameters such as electrode voltage, bath temperature, processing time, non-volatile matter, and surface area to optimize the dry film thickness. The average dry film thickness computed using the model was in the range of 15 – 35 μm. The error in the computed dry film thickness with reference to the experimentally measured dry film thickness value was - 0.5809%, which was well within the acceptable limits of all paint shop standards. Our study showed that the dry film thickness on mild steel was more sensitive to electrode voltage and bath temperature than processing time. Further, the presence of non-volatile matter was found to have the maximum impact on dry film thickness.
Sudhanshu Pandey,Hyun Woo Cho,최훈기,Yong Gap Park,서영민,하만영 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.4
The thermal and flow characteristics at Ra = 10 7 were evaluated in a square cavity containing a circular cylinder in different places along the diagonal and horizontal centerlines. The enclosure contained non-Newtonian fluids of pseudoplastic and dilatant natures. The power-law index was varied in the range of 0.6-1.6 with an interval of 0.2 and a fixed Prandtl number of 10. The effects on the laminar natural convection are reported. The flow regimes were categorized as steady symmetric, steady asymmetric, non-periodic unsteady symmetric, non-periodic unsteady asymmetric, periodic unsteady symmetric, and periodic unsteady asymmetric. Artificial neural network was used to predict the thermal performance in the enclosure. The thermal transport in cases of n < 1 was much higher than that in cases of n > 1. The ANN model was effective in estimating the heat transfer performance with appropriate training.
Sudhanshu Pandey,박용갑,하만영 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.7
Buoyancy-driven flows were investigated inside an enclosure with an inner cylinder embedded within it. The square enclosure contains the power law fluids. The effects are reported for the position of the cylinder along the horizontal and diagonal directions on the flow and thermal characteristics based on a rigorous unsteady numerical analysis. The cylinder was placed at several locations along the diagonal near the top-left corner, the center, and near the bottom right corner. The cylinder was also placed along the horizontal centerline near the right wall. This paper reports the effects of shear thickening and thinning fluids on the heat transfer mechanism in the enclosure. The thermal characteristics were more pronounced when the cylinder was near the bottom right corner than when near the top left corner and at the center. Pseudoplastic and dilatant fluids can be used in applications requiring increased and decreased heat transfer rates, respectively.
Sudhanshu Arya,Yeonghae Kim(김영해),Yeon Ho Chung(정연호) 한국통신학회 2022 한국통신학회 학술대회논문집 Vol.2022 No.2
In this paper, we propose a novel game theoretic approach that permit to maximize the performance of an interference-limited photon-counting multiuser memoryless Poisson channel with asymptotically low transmit power considered. We consider a conflicting situation where multiple users share the same spectrum and attempt to maximize their throughput. The received signal is characterized by a photon-counting receiver. We consider the transmission at an asymptotically low-power regime. We present the Nash equilibrium beamformer. We show that, selfish but cooperative users can achieve maximum sum-rate performance.
Sudhanshu Pandey,Yong Gap Park,Young Min Seo,Man Yeong Ha 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.10
The objective of present study is to carry out an unsteady numerical analysis to investigate the buoyancy-driven flows in a square enclosure containing an inner circular cylinder. The square enclosure is filled with dilatant fluids commonly known as shear thickening fluids. The inner circular cylinder is placed at the center of the square enclosure. The effects of Prandtl number (10, 100 and 1000) and Rayleigh number (10 3 to 10 6 ) on heat transfer characteristics are reported. The power-law index (n) varied from 1.0-1.6 where n = 1 corresponds to the Newtonian fluid. The heat transfer characteristics are almost insignificant to the change in Prandtl number. The flow and heat transfer characteristics diminished in square enclosure when filled with dilatant fluid in comparison to the Newtonian fluid. The present study demonstrates the adequacy of incorporating artificial neural network model in estimating the heat transfer characteristics.
Spectrum sensing for free space optical communications in strong atmospheric turbulence channel
Arya, Sudhanshu,Chung, Yeon Ho Elsevier 2019 OPTICS COMMUNICATIONS - Vol.445 No.-
<P><B>Abstract</B></P> <P>One of the primary challenges in multi-user optical wireless communications (OWC) is to periodically sense the optical frequency spectrum at the receiver to detect whether the channel is occupied by other transceiver pairs in order to avoid interference. Spectrum sensing enables the user to continuously sense the channel prior to its access to the channel. In this paper, we propose the spectrum sensing of an unknown optical signal over strong atmospheric turbulence channel. The turbulent atmospheric channel causes fluctuations in the received signal intensity, resulting in power loss at the receiver. To mitigate this adverse effect, we present an energy detection based optical spectrum sensing scheme with the spatial diversity reception in the form of a square-law selection diversity. The intensity fluctuations are modeled by a negative exponential distribution. The analytical closed-form expressions for the probability of detection and the probability of false alarm are derived. Based on the derived expressions, we obtain the performance analysis as a function of the system parameters. It is also found that sensing capability is boosted with the square-law diversity scheme.</P>
ARYA SUDHANSHU,Chung Yeon Ho 한국통신학회 2023 ICT Express Vol.9 No.6
By leveraging the characteristics of both quantum encoding and classical data channel, we present a unique and novel multiuser optical communication system that utilizes fascinating properties of the structured light for information transmission. Specifically, we propose an indoor orbital angular momentum (OAM) multiuser multiple-input multiple-output (MIMO) optical communication system, where the quantum encoding is performed and the multiuser transmission is then analyzed from the context of the classical data channel. In the proposed system, as the OAM beam propagates, its angular spread is analyzed. In addition, we show that the variance of the beam divergence increases with the increasing OAM index mode on the basis of the derived MIMO channel impulse response for OAM carrying Laguerre–Gaussian beams. Comparative studies reveal that the proposed system significantly outperforms the conventional non-orthogonal multiple access (NOMA) applied with MIMO.