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Prediction of weld zone shape with effect of tool pin profile in friction stir welding process
Prashant Prakash,Ravi Shankar Anand,Sanjay Kumar Jha 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.1
This article investigates the effect of tool pin profile on weld zone shape using computational fluid dynamics techniques in friction stir welding process. The effect of tool pin profile on weld zone shape was investigated by four different pin profile tools: Cylindrical, conical, cylindrical-conical and stepped-conical. In the numerical simulation process, workpiece material and tool are considered as non-Newtonian fluids and solid material, respectively. And simulation is carried out under transient state condition. Temperature distribution and material flow profile developed by the tool pin profile are analyzed for the understanding of viscosity profile of the weld zone region. Critical iso-viscosity surface is developed from the viscosity profile to determine the difference between deformed and undeformed material, which is finally used to determine the weld zone shape. The simulation result shows that maximum temperature and material flow velocity are produced by stepped-conical pin profile tool with respect to all other tools. It is observed from the iso-viscosity surface analysis that a vaseshaped geometry developed around the contact region of the tool and workpiece. The weld zone shape produced by stepped-conical pin profile tool is cylinder dominant vase shape, and weld zone shape of all other tools is basin dominant vase shape. Numerical model was also validated with experimental results of temperature distribution and weld zone shape thickness which showed good agreement.
Occlusion and Ion Exchange of Eutectic LiCl-KCl in H-Y Zeolite
Prashant Bagri,Michael F. Simpson 한국방사성폐기물학회 2015 방사성폐기물학회지 Vol.13 No.S
The US Department of Energy’s Idaho National Laboratory (INL) has been operating a molten salt electrorefiner at their facility since 1996. The baseline method for disposal of the radioactive salt is the ceramic waste process which generates glass bonded sodalite loaded with chloride salts. This process starts with the high temperature absorption of the salt into zeolite-4A. The salt-loaded zeolite is then blended with glass frit and heated to form a sintered, glass-bonded sodalite. INL is currently assessing alternatives for disposal of the ER salt because of the lengthy processing times, costly equipment and large volume of waste associated with the baseline process. An alternative process was studied, where protonated zeolite was used instead of alkali metal-substituted zeolite. It was found that the metals contained in the salt can replace the protons in the zeolite which are evolved via formation of HCl. From the standpoint of generating a nuclear waste form, the evolution of HCl gas should reduce the weight of the final waste. It has been estimated that the volume of waste produced from immobilizing the INL electrorefiner salt could be reduced by a factor of three using this process followed by sintering the fission product loaded zeolite. Equipment requirements in the hot cell would be significantly simplified, and the time to process all of the waste salt would be reduced by almost a factor of 4. An investigation into the new process has been presented here.
Generalized Performance Analysis and Optimization of Enhanced Power Saving Semi Persistent Scheduler
Prashant K. Wali 한국통신학회 2021 Journal of communications and networks Vol.23 No.3
Enhanced-power saving-semi persistent scheduler(E-PS-SPS) for downlink voice over LTE (VoLTE) traffic was pro posed to reduce the energy consumption of the LTE eNodeB. Fur ther, it was established that E-PS-SPS outperforms traditional SPS(T-SPS) both in terms of energy consumption and capacity (max imum number of simultaneous calls it can handle). However, inorder to establish the superiority of E-PS-SPS, the analysis andcomparison was done with two strong simplifying assumptions; (i)same downlink mean signal-to-noise ratio (SNR) for all the VoLTEusers even though the mean SNRs are independently and identi cally distributed (i.i.d.) and (ii) same instantaneous downlink chan nel gains on different physical resource blocks (PRBs) resultingin same instantaneous SNR on all allocated PRBs for a user in apacket transmission attempt, even though channel gains on differ ent PRBs are i.i.d.. In this paper, we carry out a more general anal ysis of E-PS-SPS in a more realistic scenario by removing these twostrong assumptions and derive a closed-form expression for its ca pacity and achievable success rate. The analytical expressions arevalidated using Monte Carlo simulations. We then use these expres sions to show how the performance of E-PS-SPS can be maximizedfor a desired success rate. Finally, we also show through extensivesimulations that the capacity of E-PS-SPS is same as T-SPS in therealistic scenario which we consider in the work. However, T-SPShas a marginally better success rate than E-PS-SPS which can beoverlooked considering the significant energy saving that E-PS-SPScan offer.