41 research outputs found
NeuralPALS - learning exposure functions and infection probabilities for contagion spread
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 47-48).Understanding how contagions spread is an important task, particularly when considering infectious diseases. An individual's likelihood of getting infected by a contagion is determined by a combination of inherent susceptibility and exposure to other individuals who may spread the disease. In a real world setting, an individual's infection status may be directly observable, but it is difficult to identify whether an individual is spreading the disease. As a result, the exact influence function by which disease is transmitted is difficult to understand as well. We present a neural network based method, NeuralPALS, to learn the spreader, exposure, and infection status of individuals in a network. Unlike previously developed methods, we do not assume an exposure function and instead devise methods to learn this function. Through experiments on synthetic data we illustrate our method's efficacy in determining both spreader and infection states. We also demonstrate NeuralPALS's ability to learn different exposure functions. In addition, we utilize a dataset of patients from a large urban hospital and demonstrate our preliminary results in determining the spread of Clostridioides difficile.by Advaith Anand.M. Eng.M.Eng. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Scienc
Density Stratified Thermal Energy Storage System and Associated Fluid Dynamic Perturbations
No full textThe hunger of humankind for energy has reached unprecedented levels with the ever-rising industrialization and global population surge. We are witnessing a global economic evolution towards a clean, affordable, sustainable and reliable sources of energy which could transform our lives and the planet itself. The mismatch between the supply of solar energy which is one among the most promising renewable energy and the demand for its utilization, compel us to incorporate a solar energy storage. Such storage systems are essential in various fields including power generation sectors like power plants based on solar thermal, thermal (non-renewable) and nuclear.
The study is primarily an experimental investigation of single tank sensible stratified thermal energy storage which sheds light on the experimental procedure to establish a stable and sustainable thermocline thermal energy storage. Moreover, in order to have an understanding of the causes of capacity loss in such stratified storage tanks, various studies are conducted, both numerically as well as experimentally. The performance of the TES depends on the integrity of the temperature gradient region (thermocline thickness). Mixing and spatio-temporal perturbations at the thermocline region is the foremost cause of capacity loss and the most important mechanism which destroys the stratification is vortex/plume entrainment in a thermocline-based storage tank. In a stably stratified TES, vortex entrainment occurs when a relatively cold mass of fluid is injected into the tank. Vortex-thermocline interaction creates vortices by baroclinicity, leading to entrainment and mixing. Hence any vortex entrainment in the thermocline region is critical and determines the efficiency of such thermal storage.
Density stratification formed in terms of salinity as an analogy to that due to temperature as well as the effect of disturbances are studied. As a corollary, various distributors are compared numerically and tested the advantage of a novel distributor design. The work provides quality experimental data in order to meet with its inadequacy in the related literature as well as deeper understanding into the establishment of a stable and sustainable thermocline thermal energy storageThis thesis is based upon work supported in part by the India– US partnership to Advance Clean Energy-Research (PACE-R) for the Solar Energy Research Institute for India and the United States (SERIIUS), funded jointly by the U.S. Department of Energy (Office of Science, Office of Basic Energy Sciences, and Energy Efficiency and Renewable Energy, Solar Energy Technology Program, under Subcontract DE-AC36-08GO28308 to the National Renewable Energy Laboratory, Golden, Colorado) and the Government of India, through the Department of Science and Technology under Subcontract IUSSTF/JCERDC-SERIIUS/2012 dated 22nd November 2012 and DST-SERI-Project No: DST/TMC/SERI/FR/136
Attention Boosted Autoencoder for Building Energy Anomaly Detection
No full textLeveraging data collected from smart meters in buildings can aid in
developing policies towards energy conservation. Significant energy savings
could be realised if deviations in the building operating conditions are
detected early, and appropriate measures are taken. Towards this end, machine
learning techniques can be used to automate the discovery of these abnormal
patterns in the collected data. Current methods in anomaly detection rely on an
underlying model to capture the usual or acceptable operating behaviour. In
this paper, we propose a novel attention mechanism to model the consumption
behaviour of a building and demonstrate the effectiveness of the model in
capturing the relations using sample case studies. A real-world dataset is
modelled using the proposed architecture, and the results are presented. A
visualisation approach towards understanding the relations captured by the
model is also presented
Goldbach theorems for group semidomains
No full textA semidomain is a subsemiring of an integral domain. We call a semidomain additively reduced if is the only invertible element of the monoid , while we say that is additively Furstenberg if every non-invertible element of can be expressed as the sum of an atom and an element of . In this paper, we study a variant of the Goldbach conjecture within the framework of group semidomains and group series semidomains , where is both an additively reduced and additively Furstenberg semidomain and is a torsion-free abelian group. In particular, we show that every non-constant polynomial expression in can be written as the sum of at most two irreducibles if and only if the condition holds.14 page
Understanding evolution of vortex rings in viscous fluids
No full textThe evolution of vortex rings in isodensity and isoviscosity fluid has been studied analytically using a novel mathematical model. The model predicts the spatiotemporal variation in peak vorticity, circulation, vortex size and spacing based on instantaneous vortex parameters. This proposed model is quantitatively verified using experimental measurements. Experiments are conducted using high-speed particle image velocimetry (PIV) and laser induced fluorescence (LIF) techniques. Non-buoyant vortex rings are generated from a nozzle using a constant hydrostatic pressure tank. The vortex Reynolds number based on circulation (Gamma / v) is varied in the range 100-1500 to account for a large range of operating conditions. Experimental results show good agreement with theoretical predictions. However, it is observed that neither Saffman's thin-core model nor the thick-core equations could correctly explain vortex evolution for all initial conditions. Therefore, a transitional theory is framed using force balance equations which seamlessly integrate short-and long-time asymptotic theories. It is found that the parameter A = (a / sigma)(2), where a is the vortex half-spacing and sigma denotes the standard deviation of the Gaussian vorticity profile, governs the regime of vortex evolution. For higher values of A, evolution follows short-time behaviour, while for A = O (1), long-time behaviour is prominent. Using this theory, many reported anomalous observations have been explained
Matrix Factorization for Package Recommendations
No full textACKNOWLEDGMENTS We would like to thank Lembaga Pengelola Dana Pendidikan (LPDP), Departemen Keuangan Indonesia for awarding a scholarship to support the studies of the lead author
Application of Histogram of Oriented Gradients and Local Binary Pattern in Automatic Waste Management Bins
No full textThe role of automated feedback in training and retaining biological recorders for citizen science
No full textAcknowledgments The authors thank H. H. Nguyen for his early development work on the BeeWatch interface; E. O'Mahony, I. Pearce, and R. Comont for identifying numerous photographed bumblebees; B. Darvill, D. Ewing, and G. Perkins for enabling our partnership with the Bumblebee Conservation Trust; and S. Blake for his investments in developing the NLG feedback. The study was part of the Digital Conservation project of dot.rural, the University of Aberdeen's Digital Economy Research Hub, funded by RCUK (grant reference EP/G066051/1).Peer reviewe
Spatio-temporal disruption of thermocline by successive laminar vortex pairs in a single tank thermal energy storage
No full textThe stratification efficiency of single tank thermal energy storage is affected by the internal mixing processes; especially in the thermocline region due to disturbances of different kinds. To study the mixing dynamics at the interface, we have conducted detailed numerical and supporting experimental studies for different Atwood numbers (stratification levels). Numerical experiments were conducted with two successive vortex pairs with three different time-lags (short, medium and long). For the short time-lag case, the preliminary vortex pair merges with the ensuing vortex pair. The merged single vortex pair peels back the thermocline layer causing mixing of the hot and cold fluids. The thermocline thickness increases as a result of the entrainment of the cold fluid into the hot fluid. The peeling process continues until buoyant forces leads to plume like structures that penetrate into the lighter fluid. For the medium and large time-lag cases, such merging of vortices was not observed. The vortex pair interacts separately with the thermocline region. The plume structure created by the first vortex pair interacts with the ensuing vortex pair. The altered interface (thermocline) thickness strongly depends on the nature of the vortex-thermocline interaction mechanisms. The thermocline effectiveness decreases consequent to such interactions and have been quantified in details in the current work. (C) 2016 Elsevier Ltd. All rights reserved
