48 research outputs found
Do vector plane waves form complete basis of solutions to Maxwell's equations? Introduction to Generalized Plane Wave Solutions
No full textThe article is preprint version of a manuscript submitted for publication in a journal. The author is the sole creator of the ideas presented here. Please see the copyright notice in the document.As the title says, this article questions the well established belief that the vector plane waves form a complete basis of solutions to Maxwell's equations. Vector solutions to Maxwell's equations are presented here, which have planar wave-fronts and transverse electric and magnetic fields but spatially varying polarization. They form a one-parameter family specified by integer , and are termed as \textit{generalized vector plane waves}. The known vector plane wave solution with spatially uniform polarization, referred to as \textit{conventional vector plane waves} in this article, is a subset of this family obtained for . In contradiction to the established belief, it is shown that these \textit{generalized vector plane waves} with spatially varying polarization (for ) cannot be expressed as superposition of conventional vector plane waves. The family of solutions also includes the interesting cases of radially and azimuthally polarized plane waves for .Aryan, Saurav. (2018). Do vector plane waves form complete basis of solutions to Maxwell's equations? Introduction to Generalized Plane Wave Solutions. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/196090
A Review on Vertical Handover Schemes to Integrate WBAN with Other Heterogeneous Networks
No full textWith the advancement in technology and availability of less expensive sensors, Wireless Body Area Networks (WBANs) are becoming popular for remote monitoring of the patients’ physiological conditions. To monitor the patients’ health, the data collected from the body sensors should be sent to remote servers or doctors by the coordinator. One of the primary issues with this transmission is the integration of WBAN data with other heterogeneous networks such as WLAN, WiMAX etc. to deliver the data efficiently. The main component responsible for maintaining seamless connection among heterogeneous networks is vertical handover. In this paper, we present a comprehensive survey of vertical handover decision algorithms to satisfy the Quality of Service (QoS) in WBAN applications
Energy-efficient protocol and hardware for security of implantable devices
No full textThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 77-83).Modern-day bio-electronics has truly revolutionized monitoring, diagnosis, and treatment of disease. The continued development of microelectronic has fueled the development of implantable and wearable devices by enabling them with increased functionality and features. According to the report, global active implantable medical devices (IMDs) market was valued at approximately USD 16.47 billion in 2017 and is expected to generate revenue of around USD 23.33 billion by the end of 2024 [63]. However, the deployment of these devices is limited by their security concerns. Several attacks have been demonstrated on IMDs by exploiting their weaknesses [29, 36, 38, 58, 72]. Although these attacks have been demonstrated for academic investigation, these are enough to confirm that the security of these systems needs to be addressed more aggressively. In this work, we analyze the security concerns in the design of the IMDs and the interactions with the other parties involved. Based on this analysis, we propose a protocol to address some of the shortcomings. Our protocol features a dual-factor authentication system in the IMD that relies on both cryptographic security as well as voluntary human actions before responding to any request. We discuss the merits of the protocol and analyze the trade-offs involved. The proposed protocol is implemented in an energy-efficient integrated circuit-and-system solution to emulate an actual implantable device. The design decisions involved to make the system energy-efficient and to accelerate the cryptographic computation are analyzed in detail. Finally, the impact of the implemented protocol on the entire system is obtained and discussed for various use-cases."Analog Devices Fellowship and Analog Devices Inc. for providing financial support during various phases of this project"by Saurav Maji.S.M.S.M. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Scienc
Invariant measures of piecewise concave dynamical systems via maximum entropy optimization method
No full textPiecewise Concave Dynamical System (PCDS) has its wide application in various science fields.
Many real-world problems can be modeled into mathematical models via PCDS. First, we let T:
[0,1] → [0,1] be a piecewise concave transformation/maps (PCDS) and study the existence of
absolutely continuous invariant measures. Then, we present a maximum entropy optimization
method for approximating densities of Piecewise Concave Maps. A numerical example will be
presented to compare the approximate densities of Piecewise Concave Maps using the maximum
entropy method and the actual densities of the Piecewise Concave Maps
Symmetry breaking during homodimeric assembly activates an E3 ubiquitin ligase
No full textCitation: Ye, Z., Needham, P. G., Estabrooks, S. K., Whitaker, S. K., Garcia, B. L., Misra, S., . . . Camacho, C. J. (2017). Symmetry breaking during homodimeric assembly activates an E3 ubiquitin ligase. Scientific Reports, 7(1). doi:10.1038/s41598-017-01880-4C-terminus of Hsc/p70-Interacting Protein (CHIP) is a homodimeric E3 ubiquitin ligase.Each CHIP monomer consists of a tetratricopeptide-repeat (TPR), helix-turn-helix (HH), and U-box domain.In contrast to nearly all homodimeric proteins, CHIP is asymmetric.To uncover the origins of asymmetry, we performed molecular dynamics simulations of dimer assembly.We determined that a CHIP monomer is most stable when the HH domain has an extended helix that supports intra-monomer TPR-U-box interaction, blocking the E2-binding surface of the U-box.We also discovered that monomers first dimerize symmetrically through their HH domains, which then triggers U-box dimerization.This brings the extended helices into close proximity, including a repulsive stretch of positively charged residues.Unable to smoothly unwind, this conflict bends the helices until the helix of one protomer breaks to relieve the repulsion.The abrupt snapping of the helix forces the C-terminal residues of the other protomer to disrupt that protomer's TPR-U-box tight binding interface, swiftly exposing and activating one of the E2 binding sites.Mutagenesis and biochemical experiments confirm that C-terminal residues are necessary both to maintain CHIP stability and function.This novel mechanism indicates how a ubiquitin ligase maintains an inactive monomeric form that rapidly activates only after asymmetric assembly. © 2017 The Author(s)
Techniques for determining hidden properties of large-scale power systems
No full textThe contributions in this dissertation are towards augmenting and enhancing the knowledge in power system equivalent modeling, and dynamic mode estimation. Work related to these respective topics is presented herein in two parts -- (i) Network Based Methods, and (ii) Measurement Based Methods.
The first part focuses on the problem of creating limit preserving equivalents (LPEs). There is a push to develop LPEs for power system interconnections to be used in markets and reliability studies. The equivalents that exist for these interconnections do not capture thermal limits of equivalent lines, which results in their transmission limits being significantly different from the original interconnection limits. Assigning non-infinite and non-zero limits to equivalent lines is the niche of this work. This is done by considering an unloaded network, which is operating point independent. A solution method is developed and discussed, which is capable of assigning lower, best and upper estimates for equivalent line limits, and is proposed for use towards developing LPEs.
In the second part, a relatively new method for simultaneous modal analysis of multiple time-series signals is presented. Here, Dynamic Mode Decomposition (DMD) is successfully applied towards transmission-level power system measurements in an implementation that is able to run in real-time. Since power systems are considered as non-linear and time-varying, on-line modal identification is capable of monitoring the evolution of large-scale power system dynamics by providing a breakdown of the constituent oscillation frequencies and damping ratios, and their respective amplitudes. The outputs provided by DMD can enable on-line spatio-temporal analyses, improve situational awareness, and could even contribute towards control strategies. This work presents the theory of DMD, followed by results and visualization. It shows that using frequency and voltage data together helps with precision, while maintaining fast calculation speeds. The key advantage of this implementation is its relatively fast computation; for example, it is able to process each time-window, consisting of 3392 signals with 211 time points, in 0.185 s. Modal content alarm processing, and efficient wide-area modal visualization are two proposed on-line applications.
The desire to reduce model-dependency has driven measurement-based modal identification methods, as an alternative to analyzing linearized system models. Using this relatively fast DMD algorithm, this work also presents an interactive modal-identification tool for spatio-temporal analysis of measurement data. The tool can automatically scan through measurements, and display the values of oscillation frequency and damping ratio, as well as reconstruct signals. The use of this tool, its options, and visualization capabilities are illustrated using simulated measurements from an interconnected power grid.
DMD being a data-driven modeling technique is able to handle large data sets and has shown fast computation times. The by-products of DMD provide an understanding of the wide-area spatio-temporal structures in power systems. Studies based on a large-scale model of an interconnected power grid are presented, along with visualizations that elucidate the spatial structure of wide-area dynamics, and their dependency on operating points.Submission published under a 24 month embargo labeled 'U of I only', the embargo will last until 2017-08-01The student, Saurav Mohapatra, accepted the attached license on 2015-07-10 at 16:16.The student, Saurav Mohapatra, submitted this Dissertation for approval on 2015-07-10 at 16:48.This Dissertation was approved for publication on 2015-07-14 at 09:35.DSpace SAF Submission Ingestion Package generated from Vireo submission #8411 on 2015-09-29 at 14:59:22Made available in DSpace on 2015-09-29T20:49:52Z (GMT). No. of bitstreams: 2
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Previous issue date: 2015-07-14Embargo set by: Seth Robbins for item 89459
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RETRACTED: The Anaphase-Promoting Complex/Cyclosome Is Essential for Entry into Meiotic M-Phase
No full textThis article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).This article has been retracted at the request of the authors.Our study reported that APC/C-mediated destruction of protein phosphatase PP6c is a prerequisite for meiotic resumption of immature Xenopus oocytes. Follow-up experiments after publication of the paper performed in our lab revealed severe inconsistencies, and attempts to reproduce the original data were unsuccessful. Confronted with this matter, the first author, Saurav Malhotra, confessed that he had manipulated and falsified reagents and data in the paper. The manipulations and falsifications affect all figures addressing the role of PP6c as the relevant APC/C substrate and all subsequent experiments, including the rescue experiments using PP6c antibodies and the CPEB expression constructs (Figures 2–4 and S2). As the key finding of our study is based on falsified data and is incorrect, the most appropriate course of action is to retract the article. We offer our sincerest apologies to the scientific community for this incident and deeply regret the circumstances
