Lakshminath Bezbaroa Central Library Digital Repository
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Recent Submissions
Formal and Heuristic Approaches to Real-time Scheduling on Reconfigurable Systems
(2023) Addise, Cherinet Kejela
The dynamic partial reconfiguration (DPR) feature offered by modern FPGAs provides the flexibility of adapting the underlying hardware according to the needs of a particular situation during the runtime in response to application requirements. DPR has allowed the possibility of scheduling multiple real-time applications over both space and time so that the computation capacity of the FPGA floor may be efficiently harnessed. The scheduler generated/developed for the real-time tasks on FPGAs must not only handle all timing constraints, dependency constraints (if there is one), and FPGA based placement constraints but also correctly account for
reconfiguration overheads involved in loading task bit streams onto the configuration memory of the FPGA through the ICAP port. Hence, static o_-line schedulers are often preferred for such a system in order to satisfy all these necessary constraints. In addition, o_-line computation also allows exhaustive solution space enumeration to pre-compute optimal schedules at design time, thus ensuring lower design costs through higher resource utilization. This thesis thus endeavors towards the exploration of new approaches and design of scheduling strategies for real-time tasks on partially reconfigurable platforms. Particularly, we present three static offline scheduler design approaches for reconfigurable systems: (i) a formal scheduler synthesis framework for the real-time tasks executing on an FPGA platform, using supervisory control of timed discrete event systems as the underlying formalism. (ii) an ILP based solution strategy for scheduling persistent real-time applications represented as precedence constrained task graphs on partially reconfigurable FPGAs and (iii) a heuristic solution methodology for scheduling persistent realtime applications represented as precedence constrained task graphs on partially reconfigurable FPGAs.
Design And Development Of A Novel Ball-On-Cup Tribometer For The Characterization Of An Ingenious Total Hip Prosthetic Liner Made Of Uhmwpe And Its Composite
(2023) Jana, Ashirbad
Total hip replacement (THR), regarded as the orthopaedic operation of the 20th century, uses ultra-high molecular weight polyethylene (UHMWPE) as the acetabular liner since 1960s. However, the life of a metal-on-plastic THR is often limited to 15-20 years, primarily due to excessive wear debris generation during its operation, leading to osteolysis and aseptic loosening of the prosthetic joint leaving behind a painful revision surgery. Presently worldwide research is dedicated in improving the life of a metal-on-plastic THR by the improvement of tribological characteristics of an UHMWPE acetabular liner.
Hydro-Chemical Evaluation of Bentonite-Fly ash Mix as Liners in Near Surface Waste Disposal Facility
(2023) Gupt, Chandra Bhanu
Hazardous industrial wastes are contained in engineered shallow near-surface disposal facilities or landfills. To minimize the migration of waste from landfills and protection of geoenvironment and groundwater, low permeable compacted liners are provided, which
act as hydraulic and contaminant barriers. In normal practice, bentonite-sand (B-S) mixtures are recommended as liner material. Due to shortage, there is a need to explore the possibility of using alternate waste materials like fly ash (FA) as a substitute for sand (S).
To ensure its application in compacted liner, the B-FA mixes should qualify hydro-chemical requirements laid out by different regulatory bodies like Environmental Protection Agency (EPA). The detailed hydro-chemical evaluation includes hydraulic conductivity
determination, contaminant retention properties, adequate strength and volumetric shrinkage characteristics. Additionally, when two reactive materials (B and FA) are mixed together, it is important to ensure its compatibility over a period of time. A detailed study is
needed to make sure that there are no undesirable interactions between B and FA leading to poor performance of liner. This necessitate long-term interaction studies of B-FA mixes for vital properties such as hydraulic conductivity and contaminant retention. This study investigated in detail the hydraulic conductivity of B-FA mixes under constant volume (swelling completely restricted) and free swelling conditions at time (t) varying from 0 days (immediately after compaction) to four years of interaction. Every measurement was carried out for extended duration of 90 days to ensure steady state condition.
Thermodynamic Analysis of Active and Passive Drag Reduction Techniques for Elevated Enthalpy Hypersonic Reacting Flows
(2023) Patil, Ajay Vijay
Initial investigations are based on counter flow injection and spike based drag reduction techniques to compare them on a common platform. Test case of supersonic flow over hemisphere, provided with counterflow injection, portrayed monotonic variation for percentage drag reduction and percentage exergy destruction for increase in injection pressure ratio. However, injection effectiveness, suitable assessment parameter for counterflow injection, shows inversion characteristics with a peak at specific injection pressure ratio. Mounting of a spike also shows similar trend for percentage drag reduction and percentage exergy destruction. Present investigations recommend percentage exergy destruction as a unified performance assessment parameter for passive and active drag reduction
techniques. Afterwards, investigations are carried to examine the effect of higher freestream stagnation enthalpy on flow field alteration for counter−jet drag reduction technique for a hemispherical object. Drag coefficient is found to reduce with freestream total enthalpy in the presence of real gas effects. Higher pressure ratio of the jet has resulted in lower surface pressure and Stanton number on the object. Then, efforts are further continued to reveal the thermodynamic behaviour of opposing jet technique which includes variation of entropy generation rate, exergy destruction and drag force analysis considering real gas effects. Results revealed that linear reduction in drag forces and sharp rise in entropy generation rate and exergy destruction is obtained with jet momentum ratio irrespective of freestream and jet parameters. At last, real gas effects on surface pressure and flow field are analysed for the
combinatorial technique (opposing jet and cavity) for hypersonic flow over the blunt body. A new thermodynamic parameter named entropy generation rate is proposed which can be used as a tool to analyze the performance of any drag reduction technique. Results showed that perfect gas assumption over−estimates the surface pressure and wave drag. Introduction of cavity reduces the surface pressure, drag and entropy generation rate but significant reduction in these parameters is noted when the opposing jet is turned on. For given jet pressure ratio, opposing jet technique predicts lower drag and entropy generation rate as compared to combinatorial technique.
Robust Control Schemes for a Pediatric GAit Exoskeleton System in Passive-assist and Active-assist Mode
(2023) Narayan, Jyotindra
Over the years, a significant rise in neurological disorders has been observed for different age groups, such as stroke, spinal cord injury (SCI), and cerebral palsy (CP). Many pediatric subjects face dyskinesia and muscle atrophy in their lower limbs. In the last few years, the proliferation of exoskeleton technology has enabled the therapy process to be less cumbersome and more sustainable. However,
there are minimal exoskeleton devices available for pediatric gait rehabilitation. Moreover, the control design to achieve the desired gait training in different therapy modes is still open to research and a benchmark problem statement due to significant parametric perturbations and external disturbances (PPED) in pediatric exoskeleton systems. Therefore, this thesis proposes a few robust control
schemes for a newly designed pediatric exoskeleton in passive- and active-assist rehabilitation mode.