Direct Numerical Simulation for Parametric Vertical Vibration and Atomization of Sessile Drops

Sessile drop vertical vibrations and atomization is commonly analyzed by simpler unconstrained instabilities like Faraday waves and hence, detailed studies of the phenomenon are still an open question to the fluid dynamics community. We address two critical gaps using direct numerical simulation, i.e., (i) the cause of subharmonic response of azimuthal waves, and (ii) the dependence of vertical vibrations to the universal pinchoff regime in the atomization. First, a high mode excitation of a large drop of 100 microliters is implemented. It is found that the subharmonic response is not via Faraday waves, rather it is the harmonics of the interfacial waves that induce azimuthal waves near the contact line. An analogous self-inducing dynamical system is formalized between the tip and near the contact line to elucidate the mechanism. Second, a low mode excitation of small drop of 30 microliter is used to critically explain the cause of primary pinch-off via crater formation and secondary pinch-off via ligament retraction. The pinch-off test in both cases revealed that the primary pinch-off is in visco-capillary scaling regime, while the secondary pinch-off is affected by the inertial forces via oscillatory body forces of vibration.Comment: MSc Thesis at Imperial College Londo

Mathematical Modelling and Design Software for Pulse Tube Cryocoolers

Pulse tube refrigerators are increasingly become popular because of its higher reliability,absence of any moving parts at its cold end,easy design and fabrication technique, less maintenance,less wear and tear etc.However its design is quite complicated because of the complex heat and mass transfer process occurring inside it,so it is a challenging problem to the scientists and engineers pursuing this field to design pulse tube cryocoolers in order to achieve the desired performance.The work presented in this thesis is directed towards the detailed mathematical analysis of regenerator,a critical component of not only pulse tube cryocoolers but also all other types of regenerative cryocoolers.Based on the mathematical analysis,a software package has been developed for simulation of regenerator and validated with the experimental results available in the literature.Also,a parametric study has been performed to identify the effect of essential parameters that affect the cooling performance of the regenerator for cryogenic based applications.Detailed mathematical analysis of pulse tube refrigerator has been carried out for both Stirling and Gifford Mc-Mohan type pulse tube refrigerators of various geometrical configurations including different losses in various components that affect its performance.Based on the mathematical analysis,a general purpose simulation software package has been developed to design pulse tube refrigerators and validated with the numerical results available in previous results.Also,CFD analysis of inertance type pulse tube refrigerator has been carried out not only to visualise the inside fluid flow and heat transfer processes,but also to identify the essential changes that happen due to increase in operating frequency.The effect of various losses,those explained theoretically by various scientists,has been illustrated graphically in the present work

An efficient hardware-aware matrix-free implementation for finite-element discretized matrix-multivector products

The finite-element (FE) discretization of a partial differential equation usually involves the construction of a FE discretized operator and computing its action on trial FE discretized fields for the solution of a linear system of equations or eigenvalue problems and is traditionally computed using global sparse-vector multiplication modules. However, recent hardware-aware algorithms for evaluating such matrix-vector multiplications suggest that on-the-fly matrix-vector products without building and storing the cell-level dense matrices reduce both arithmetic complexity and memory footprint and are referred to as matrix-free approaches. These approaches exploit the tensor-structured nature of the FE polynomial basis for evaluating the underlying integrals and, the current state-of-the-art matrix-free implementations deal with the action of FE discretized matrix on a single vector. These are neither optimal nor readily applicable for matrix-multivector products involving a large number of vectors. We discuss a computationally efficient and scalable matrix-free implementation procedure to compute the FE discretized matrix-multivector products on multi-node CPU and GPU architectures. The accuracy and performance of our implementation is assessed on the problem of computing FE overlap (mass) matrix-multivector multiplications as a representative benchmark example, and we observe superior performance of our implementation. For instance, computational gains up to 2.9x on GPU architectures and 6x on CPU-only architectures are observed for matrix-multivector products compared to the FE cell-level matrix-multiplication approach for the case of 100 vectors. We further benchmark our performance against the matrix-free module in deal.II and speedups up to 2x are observed for multivectors on CPU-only architectures and 1.5x on GPUs.Comment: 5 pages, 7 figure

Lattice Boltzmann modeling and simulation of isothermal drying of capillary porous media

[EN] Modeling of dring of capillary porous media is difficult due to the complex and coupled heat and mass transfer that occur at dynamic liquid-gas-sold interface. Thus far, drying was simulated using either continuum models or pore-network models, both of which have limitations. In this work, the Lattice Boltzmann Method (LBM) is used to simulate the drying in porous media. The LBM is ideal for such simulations as it can incorporate complex effects in a simple way to exhibit realistic fluid-gas interface during drying of capillary porous media.Zachariah, GT.; Panda, D.; Surasani, VK. (2018). Lattice Boltzmann modeling and simulation of isothermal drying of capillary porous media. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 339-346. https://doi.org/10.4995/IDS2018.2018.7464OCS33934

Single-Molecule Study of Metalloregulator CueR-DNA Interactions Using Engineered Holliday Junctions

AbstractTo maintain normal metal metabolism, bacteria use metal-sensing metalloregulators to control transcription of metal resistance genes. Depending on their metal-binding states, the MerR-family metalloregulators change their interactions with DNA to suppress or activate transcription. To understand their functions fundamentally, we study how CueR, a Cu1+-responsive MerR-family metalloregulator, interacts with DNA, using an engineered DNA Holliday junction (HJ) as a protein-DNA interaction reporter in single-molecule fluorescence resonance energy transfer measurements. By analyzing the single-molecule structural dynamics of the engineered HJ in the presence of various concentrations of both apo- and holo-CueR, we show how CueR interacts with the two conformers of the engineered HJ, forming variable protein-DNA complexes at different protein concentrations and changing the HJ structures. We also show how apo- and holo-CueR differ in their interactions with DNA, and discuss their similarities and differences with other MerR-family metalloregulators. The surprising finding that holo-CueR binds more strongly to DNA than to apo-CueR suggests functional differences among MerR-family metalloregulators, in particular in their mechanisms of switching off gene transcription after activation. The study also corroborates the general applicability of engineered HJs as single-molecule reporters for protein-DNA interactions, which are fundamental processes in gene replication, transcription, recombination, and regulation

Psychosocial and quality of life assessment in cancer patients: a pilot study in Indian set up

Background: Routine screening for distress is internationally recommended as a standard of care among cancer patients. This study was conducted to assess the level of stress and determine the association between quality of life (QOL) with demographic, socio-economic status, treatment phase, cancer stage, etc.Methods: An observational study, performed in the department of Clinical Oncology, Nayati Multi Super Speciality Hospital, Mathura, India. Data of 62 histopathologically proven cancer patients between Nov 2016 and July 2018, were analyzed. This pilot study was conducted to assess the QOL and stress levels of cancer patients by using scales of WHOQOL-BREF, QSC-R23 and Hamilton scale. Results: Among 62 cancer patients, high distress along with poor QOL was seen maximum in males, 40-60 year age group and educated. In majority of domains, high distress was found in middle class, whereas poor QOL was found in Lower class in Environmental domain (p<0.01). We found higher distress in nuclear families (p<0.05). High distress was seen in cancer patients who were aware of illness and was found to statistically significant. Poor QOL in stage 4 was found to be statistically significant in Psychological domain of WHOQOL-BREF. High distress was found in patients undergoing treatment in all patients as compared to Pre-treatment phase and Post-treatment phase (p<0.05).Conclusion: To assess psychological stress in cancer patients using all three scales we could not obtain a conclusive result covering all dimensions of QOL. So, in our next study authors plan to develop one indigenous new scale

Practical Approach to Induce Analog Switching Behavior in Memristive Devices: Digital-to-Analog Transformation

The capability of memristor devices to perform weight changes upon electrical pulses mimics the analogous firing mechanism in biological synapses. This capability delivers the potential for neuromorphic computing and pushes renewed interests in fabricating memristor with analog characteristics. Nevertheless, memristors could often exhibit digital switching, either during the set, reset, or both processes that degenerate their synaptic capability, and nanodevice engineers struggle to redesign the device to achieved analog switching. This chapter overviews some important techniques to transform the switching characteristics from digital to analog in valence change and electrochemical metallization types memristors. We cover physical dynamics involving interfacial diffusion, interfacial layer, barrier layer, deposition, and electrode engineering that can induce digital-to-analog switching transformation in memristor devices

Retrospective analysis of random and systematic errors in radiation therapy of head and neck cancer patients and its clinical predictive implications with VMAT treatment

Background: The accuracy of radiotherapy is based on the matching of 2D portal/CBCT image with a reference image. The aim of this study is to determine the random and systematic setup errors (in cm) in radiotherapy of head and neck cancer patients and to derive the setup margin and its clinical implications.Methods: Author retrospectively reviewed the records of 25 head and neck cancer (HNC) patients treated with radiotherapy between Dec 2017 and July 2018. After immobilization, setup accuracy was assessed by registration of XVI image with planning reference image using Elekta XVI image guidance system and the isocenter correction was applied. For each patient 10 CBCT image sets were taken. The translational errors in X, Y and Z directions were used to estimate systematic (Σ) and random (σ) errors and to derive the final setup margin by using van Herk’s formula (2.5Σ + 0.7σ).Results: The mean translational errors ranges from -0.23 cm to 0.32 cm in Lateral (X), -0.15 to 0.16 cm in Longitudinal (Y) and -0.11 to 0.17 cm in vertical (Z) directions. The Mean and SD for systematic errors 0.21±0.13, 0.11±0.18, 0.14±0.11 and random error (in cm) are -0.03±0.33, 0.00±0.21 and 0.05±0.30 in X, Y and Z axis respectively. The final total margin for CTV to PTV including setup margin in the X, Y and Z directions (in cm) were 0.56, 0.61, and 0.47 respectively.Conclusion: Thus, the precise immobilization techniques are very important to reduce the setup margins, and the number of CBCTs during head and neck radiotherapy treatment

Hybrid Inflation and Brane-Antibrane System

We study a string theory inspired model for hybrid inflation in the context of a brane-antibrane system partially compactified on a compact submanifold of (a caricature of) a Calabi-Yau manifold. The interbrane distance acts as the inflaton, whereas the end of the inflationary epoch is brought about by the rapid rolling of the tachyon. The number of e-foldings is sufficiently large and is controlled by the initial conditions. The slow roll parameters, however, are essentially determined by the geometry and have little parametric dependence. Primordial density fluctuations can be made consistent with current data at the cost of reducing the string scale.Comment: 22 pages, 7 Figs (added a Report-no and two references