arXiv subjects

Jacob John

Publications and source records attributed to Jacob John.

8 recordsLinked to original sources

arXiv2023

Dynamics and rheology of 2D colloidal crystals with active anisotropic impurities

Active motion at complex fluid-fluid interfaces is a ubiquitous phenomenon in nature. However, an intriguing question that is not fully addressed is how active motion affects and gets influenced by its complex environment. Here, we design a 2D colloidal crystal containing active particles as a model system to understand the mechanics of complex interfaces in the presence of activity. We characterize the dynamics, rheology and phase behavior of 2D colloidal crystals formed using spherical polystyrene (PS) particles in the presence of active PS-Platinum Janus particles. In the presence of activity, the overall crystal becomes dynamic with a heterogeneous spatial distribution of disorder. Through particle-tracking microrheology and interfacial shear rheology, we report the discovery of a phase transition from solid-like to liquid-like interface driven by the active motion of a small number of active impurities in the crystal. The local perturbations induced by the active impurities have long-range effects on the dynamics of particles in 2D colloidal crystals modifying their overall viscoelasticity. The correlations between microstructure and dynamics from our experiments can provide insights into the behavior of a broad range of complex systems such as, motion of particles at oil-water interfaces in Pickering emulsion microreactors and the motion of molecular motors on cell membranes.

cond-mat.soft↗

arXiv2023

Quench Risk Increase With Irradiation Damage

Superconducting material enables fusion reactor magnet concepts to operate with current densities that would melt materials with non-zero resistance. The application of superconducting material is considered essential for net-positive power machines. Catastrophic damage can occur when superconductivity is lost and the current generates heat. This scenario is called a quench. Stabilizer material carries the magnet current (typically copper) during a quench and is the focus of this work. Irradiation-induced defects store energy in the Cu crystalline lattice. The release of stored energy in the magnet materials, combined with the associated magnet material property changes, can cause extreme off-normal events in superconducting magnets that worsen with fluence at an increasing rate. Stored energy can be released causing local heating and increasing the risk of a quench. For example, following irradiation at 4.6K and an estimated fluence of 0.45*10^18 n/cm^2, an energy release of 0.023 J/g was measured from Cu when increased in temperature from 10K to 18K, which would have been enough energy to create the same temperature increase spontaneously. Extrapolations of experimental data are used to estimate when spontaneous heating can occur due to the release of energy stored in irradiation-induced defects. Critical fluence values are estimated between 1.74*10^18 n/cm^2 and 2.85*10^19 n/cm^2 for neutron irradiation of Cu at a temperature of 20K. High-temperature ramp rate in-situ cryogenic calorimetry experiments of magnet materials following irradiation would provide more clarity to designers of fusion magnet systems. Due to the increased quench risk with superconducting magnet dose, magnetic confinement reactor designers should consider the frequency of maintenance temperature cycles to maintain an appropriate level of risk during operation.

physics.plasm-ph↗

arXiv2021

Outlier Detection and Spatial Analysis Algorithms

Outlier detection is a significant area in data mining. It can be either used to pre-process the data prior to an analysis or post the processing phase (before visualization) depending on the effectiveness of the outlier and its importance. Outlier detection extends to several fields such as detection of credit card fraud, network intrusions, machine failure prediction, potential terrorist attacks, and so on. Outliers are those data points with characteristics considerably different. They deviate from the data set causing inconsistencies, noise and anomalies during analysis and result in modification of the original points However, a common misconception is that outliers have to be immediately eliminated or replaced from the data set. Such points could be considered useful if analyzed separately as they could be obtained from a separate mechanism entirely making it important to the research question. This study surveys the different methods of outlier detection for spatial analysis. Spatial data or geospatial data are those that exhibit geographic properties or attributes such as position or areas. An example would be weather data such as precipitation, temperature, wind velocity, and so on collected for a defined region.

stat.ML↗

arXiv2021

A Survey on Serverless Computing

The Internet is responsible for accelerating growth in several fields such as digital media, healthcare, the military. Furthermore, the Internet was founded on the principle of allowing clients to communicating with servers. However, serverless computing is one such field that tries to break free from this paradigm. Event-driven compute services allow users to build more agile applications using capacity provisioning and a pay-for-value billing model. This paper provides a formal account of the research contributions in the field of Serverless computing.

cs.DC↗

arXiv2021

Image Processing Techniques for identifying tumors in an MRI image

Medical Resonance Imaging or MRI is a medical image processing technique that used radio waves to scan the body. It is a tomographic imaging technique, principally used in the field of radiology. With the advantage of being a painless diagnostic procedure, MRI allows medical personnel to illustrate clear pictures of the anatomy and the physiological processes occurring in the body, thus allowing early detection and treatment of diseases. These images, combined with image processing techniques may be used in the detection of tumors, difficult to identify with the naked eye. This digital assignment surveys the different image processing techniques used in Automated Tumor Detection (ATD). This assignment initiates the discussion with a comparison of traditional techniques such as Morphological Tools (MT) and Region Growing Technique (RGT).

cs.CV↗

arXiv2021

Discrete Cosine Transform in JPEG Compression

Image Compression has become an absolute necessity in today's day and age. With the advent of the Internet era, compressing files to share among other users is quintessential. Several efforts have been made to reduce file sizes while still maintain image quality in order to transmit files even on limited bandwidth connections. This paper discusses the need for Discrete Cosine Transform or DCT in the compression of images in Joint Photographic Experts Group or JPEG file format. Via an intensive literature study, this paper first introduces DCT and JPEG Compression. The section preceding it discusses how JPEG compression is implemented by DCT. The last section concludes with further real world applications of DCT in image processing.

cs.CV↗

arXiv2021

Designing a Binary Clock using logic gates

Wristwatches have been a common fashion accessory addition for several people. However, the concept of using a seven-segment digital display or sometimes, even an analog indicator hasn't changed for a number of years. This project aims to test and design a binary clock, also referred to as 32, 16, 8, 4, 2, 1 clock or even 8, 4, 2, 1 clock (due to their display configuration), that could change this everlasting display for watches. Specifically, digital logic and design engineers would find interest in this topic due to the sophistication involved in reading-out the time. This project will do so using by showing each decimal digit of sexagesimal time as a binary value. This design will be primarily functioning on logic gates and would involve the use of several basic components that include, but are not limited to, integrated circuits (or ICs), Light-emitting diodes (LEDs), and resistors.

cs.OH↗

arXiv2015

Fabrication of Flexible Oriented Magnetic Thin Films with Large in-plane Uniaxial Anisotropy by Roll-to-roll Nanoimprint Lithography

Here, we report wafer scale fabrication of densely packed Fe nanostripe-based magnetic thin films on a flexible substrate and their magnetic anisotropy properties. We find that Fe nanostripes exhibit large in-plane uniaxial anisotropy and nearly square hysteresis loops with energy products (BH)max exceeding 3 MGOe at room temperature. High density Fe nanostripes were fabricated on 70 nm flexible polyethylene terephthalate (PET) gratings, which were made by roll-to-roll (R2R) UV nanoimprintlithography technique. Observed large in-plane uniaxial anisotropies along the long dimension of nanostripes are attributed to the shape. Temperature dependent hysteresis measurements confirm that the magnetization reversal is driven by non-coherent rotation reversal processes.

cond-mat.mes-hall↗