Modeling of High Pressure Radial Piston Pumps

Agarwal, Pulkit. M.S.M.E., Purdue University, December 2014. Modeling of High Pressure Radial Piston Pumps. Major Professor: Andrea Vacca, School of Mechanical Engineering A comprehensive multi-domain simulation tool for investigating the operation of radial piston machines has been developed in the present study. The simulation tool is capable of analyzing the displacing action of the machine parts as well as the power losses occurring in the lubricating interfaces which makes it useful for supporting the design process of radial piston units. The reference machine analyzed in this study is a radial piston pump of rotating cam type design used for high pressure applications. Though the modeling process and calculations in this analysis pertain mostly to this specific design, the concepts involved and numerical procedure can be applied to generic designs of radial piston machines. A lumped parameter based model for complete hydraulic system of the pump has been formulated which can predict the main flow parameters in the pump namely flow rate and pressure at pump outlet. This model can be easily coupled with other hydraulic components present in a circuit to model the systems level performance of the machine. However, an improvement in pump design calls for a detailed investigation of internal components present in the pump specifically the lubricating interfaces present in the pump. The lumped parameter model is capable of generating boundary conditions to simulate the flow behavior in these lubricating interfaces. A separate model for piston-cylinder interface and cam-piston interface has been developed in this study to incorporate the detailed features involved in each of them. The piston/cylinder lubricating interface represents one of the most critical design elements of radial piston machines. The interface performs the functions of a hydrodynamic bearing by supporting the radial loads acting on the piston, seals the high pressure fluid in the displacement chamber and reduces friction between the moving parts. However, operating in the Elastohydrodyamic Lubrication (EHL) regime, it also represents one of the main sources of power loss due to viscous friction and leakage flow. An accurate prediction of instantaneous film thickness, pressure field, and load carrying ability is necessary to create more efficient interface designs. For this purpose, a fully coupled numerical solver has been developed to capture fluid-structure interaction phenomena in the lubricating interface at isothermal fluid conditions. This model considers the piston micro-motion during one complete cycle of pump operation. The radial loads acting on the piston have a significant influence on piston micro-motion and hence the power losses in piston-cylinder interface. These loads are caused majorly by the friction forces existing between the cam and piston. A more accurate evaluation of performance parameters in the piston-cylinder interface can be achieved by calculating the instantaneous friction acting between the cam and piston under lubricating conditions. Different approaches for evaluating this friction coefficient were considered ranging from a simplified assumptions of pure sliding, pure rolling to a detailed analysis of lubricant flow between the cam-piston surfaces. For this purpose, a line contact EHL model was developed that can predict viscous friction forces generated between the cam and piston at changing surface velocities and contact loads. Also, instantaneous pressure field and film thickness can be predicted to a reasonable accuracy. This model is capable of analyzing multiple configurations of cam-piston interface design. The numerical results presented in this thesis provide detailed information of the pump performance parameters at different operating conditions thereby confirming the utility of the simulation tool to support the design process of these units and assist in creation of more energy efficient pumps. Validation of the numerical model developed in this study with experimental results can be a part of future work

Prevalence of various dermatoses in pregnancy at a tertiary care centre in Moradabad, Uttar Pradesh, India: an observational study

Background: This was a prospective study which was done to observe various skin lesions in pregnancy and to determine the most likely causes and their incidence in antenatal patients, it was noticed that many women in our institute were having pregnancy related cutaneous complaints thus this observational study was carried out so that better preventive measures and treatment options could be provided to these patients.Methods: Study was conducted in out-patient department of Obstetrics and Gynaecology, TMU, Moradabad. All ANC cases between October 2017 to September 2018 having any type of dermatoses were included in the study irrespective of gestational age. 6348 patients appeared in OPD in the given time period out of which 1256 were included. In case of pruritus, liver function tests were done with USG whole abdomen and patients were reviewed by physician if required. Screening with VDRL, HCV, HbSAg and ELISA for HIV was done in all. Results were tabulated and analyzed.Results: 50.8% primi gravidas ,49.2% multi gravidas. age range 18-38 years. 29.3% presented in third trimester ,25.6% presented in second trimester. Physiological changes seen in all cases, 8.68% specific dermatoses of pregnancy. 40.4 % no complaints, 5.65% melasma, 90.8% hyperpigmentation, 94.6% linea nigra. Secondary areola 89.3%,striae 80.3% out of which 38.9%- primi gravidas and 41.40% -multi gravidas. 92.9% no change in hair density. Montgomery’s tubercles 30-50% of cases. spiders nevi 67%. No cases of palmar erythema. Pruritus gravidarum 38.53%. PUPPP 28.4%. Pemphigoid Gestationis 9.17%. Prurigo of pregnancy 18.34%. Pruritic folliculitis 1.8%. Eczema in pregnancy : pre-existing in 3.7% , out of which exacerbation 1, 3 unaffected. 3 chicken pox.1 filariasis.24 herpetic lesions (herpes simplex).1 scleroderma.17.27% pre-existing taenia infection . Scabies 20.46%.11 0.87% dual infection (scabies-taenia).Conclusions: This study highlights high prevalence of community acquired infections in our region like taenia, scabies giving rise to skin lesions in Antenatal women. Moreover, it highlights a probable association between the prevalence of skin lesions with factors like poor personal hygiene, overcrowding, low socioeconomic status, anaemia and poor nutritional status

On Adversarial Robustness: A Neural Architecture Search perspective

Adversarial robustness of deep learning models has gained much traction in the last few years. Various attacks and defenses are proposed to improve the adversarial robustness of modern-day deep learning architectures. While all these approaches help improve the robustness, one promising direction for improving adversarial robustness is unexplored, i.e., the complex topology of the neural network architecture. In this work, we address the following question: "Can the complex topology of a neural network give adversarial robustness without any form of adversarial training?". We answer this empirically by experimenting with different hand-crafted and NAS-based architectures. Our findings show that, for small-scale attacks, NAS-based architectures are more robust for small-scale datasets and simple tasks than hand-crafted architectures. However, as the size of the dataset or the complexity of task increases, hand-crafted architectures are more robust than NAS-based architectures. Our work is the first large-scale study to understand adversarial robustness purely from an architectural perspective. Our study shows that random sampling in the search space of DARTS (a popular NAS method) with simple ensembling can improve the robustness to PGD attack by nearly 12%. We show that NAS, which is popular for achieving SoTA accuracy, can provide adversarial accuracy as a free add-on without any form of adversarial training. Our results show that leveraging the search space of NAS methods with methods like ensembles can be an excellent way to achieve adversarial robustness without any form of adversarial training. We also introduce a metric that can be used to calculate the trade-off between clean accuracy and adversarial robustness. Code and pre-trained models will be made available at https://github.com/tdchaitanya/nas-robustness © 2021 IEEE

THE CONFORMAL GROUP AND APPLICATIONS TO HIGH ENERGY PHYSICS

Ph.DDOCTOR OF PHILOSOPHY (FOS

Elastic

This work is geared towards studying pp collisions using the AdS/CFT correspondence. It is inspired by the work of Richard C. Brower, Joseph Polchinski, Matthew J. Strassler and Chung I Tan (arXiv:1204.0472v1) on particle interactions. A simple extension is provided by calculating the scattering amplitudes of pp collisions using the BPST Pomeron and comparing it to the well known empirical result of elastic pp scattering

Elastic pp Scattering in AdS/CFT

This work is geared towards studying pp collisions using the AdS/CFT correspondence. It is inspired by the work of Richard C. Brower, Joseph Polchinski, Matthew J. Strassler and Chung I Tan (arXiv:1204.0472v1) on particle interactions. A simple extension is provided by calculating the scattering amplitudes of pp collisions using the BPST Pomeron and comparing it to the well known empirical result of elastic pp scattering

Prosthetic rehabilitation of a total laryngectomy patient

The fundamental objective in restoring a defect created after total laryngectomy with a custom made silicone prosthesis is to enable the patient to cope better with the difficult process of rehabilitation after a major surgery has been performed. A cosmetically acceptable prosthesis that reproduces the color and form and allows the patient to return to his/her accustomed lifestyle. A sequence of steps for construction of custom-made laryngeal prosthesis is outlined in this case report using the readily available materials and method which any prosthodontist can readily understand and deliver