A mechanical-state observer for high-speed variable-reluctance motor drives

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1996.Includes bibliographical references (p. 191-192).by Edward Carl Francis Lovelace.M.S

Optimization of a magnetically saturable interior permanent-magnet synchronous machine drive

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (p. 258-263).Interior permanent magnet (IPM) synchronous machines are attractive because they can achieve constant-power operation over a wide speed range with limited magnet strength requirements and reduced power electronics cost. These characteristics provide the IPM machine with advantages over alternative machine types in applications such as spindle and traction drives. An important challenge for high-performance IPM machine design is to model the magnetic saturation of the core in a manner that is accurate, flexible, and computationally fast for design optimization. A magnetically-saturable lumped parameter model (LPM) is developed for the optimized design of high-performance IPM synchronous machine drives. Using equivalent magnetic circuit analyses, the dq-frame inductances and magnet flux linkage are calculated for transversely-laminated IPM machines. The lumped parameters are employed to predict machine drive system performance for both rated-torque and constant-power operation. The results of saturable model calculations and finite element analysis (FEA) match very closely for the machine inductances, magnet flux linkage, and converted torque. Further validation is presented by comparing measurements of existing experimental machines to predictions from the saturable lumped parameter model. Agreement of measurements and predictions for the highly nonlinear saturable q-axis inductance is within 5% in the saturated excitation range. The utility of the saturable LPM is then demonstrated by developing a cost-optimized design for an automotive integrated starter/generator (ISG) that is rated at 4 to 6 kW during generating operation. This ISG machine is mounted in a direct-drive mechanical configuration on the engine crankshaft. Agreement between the saturable LPM and FEA calculations for q- and d- axis inductances and PM flux linkage are all within 5% for the entire excitation range. Results of this model have been combined with structural FEA and demagnetization studies to produce a machine design that is predicted to meet all key ISG performance requirements. For this application and the chosen cost model, it is shown that optimizing the combined machine and drive system versus optimizing only the machine reduces the overall cost prediction by 12%.by Edward Carl Francis Lovelace.Ph.D

Characterizing Gravitational Wave Detector Networks: From A♯^\sharp to Cosmic Explorer

Gravitational-wave observations by the Laser Interferometer Gravitational-Wave Observatory (LIGO) and Virgo have provided us a new tool to explore the universe on all scales from nuclear physics to the cosmos and have the massive potential to further impact fundamental physics, astrophysics, and cosmology for decades to come. In this paper we have studied the science capabilities of a network of LIGO detectors when they reach their best possible sensitivity, called A#, and a new generation of observatories that are factor of 10 to 100 times more sensitive (depending on the frequency), in particular a pair of L-shaped Cosmic Explorer observatories (one 40 km and one 20 km arm length) in the US and the triangular Einstein Telescope with 10 km arms in Europe. We use a set of science metrics derived from the top priorities of several funding agencies to characterize the science capabilities of different networks. The presence of one or two A# observatories in a network containing two or one next generation observatories, respectively, will provide good localization capabilities for facilitating multimessenger astronomy and precision measurement of the Hubble parameter. A network of two Cosmic Explorer observatories and the Einstein Telescope is critical for accomplishing all the identified science metrics including the nuclear equation of state, cosmological parameters, growth of black holes through cosmic history, and make new discoveries such as the presence of dark matter within or around neutron stars and black holes, continuous gravitational waves from rotating neutron stars, transient signals from supernovae, and the production of stellar-mass black holes in the early universe. For most metrics the triple network of next generation terrestrial observatories are a factor 100 better than what can be accomplished by a network of three A# observatories.Comment: 45 pages, 20 figure

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

[Correspondence between Dr. Meyer Bodansky, Dr. Carl Lovelace, and Dr. Joseph L. Johnson - October 14-November 12, 1940]

Letters between Dr. Meyer Bodansky, Dr. Carl Lovelace, and Dr. Joseph L. Johnson, dated from October 14, 1940 to November 12, 1940. The letters concern Dr. Bodansky's visit to Boston, Massachusetts with his organization, The Texas Club of Internists. The letters include an invitation from Dr. Lovelace to Dr. Bodansky to attend a meeting while in Boston and a thank-you letter from Dr. Bodansky for the invitation. There is also a letter from Dr. Johnson that expresses his appreciation for Dr. Bodansky's future and past trips to Ann Arbor, Michigan and a response from Dr. Bodansky. There is handwriting and hand-drawn graphs on the back of the last letter from Dr. Carl Lovelace, who is from the Amicable Life Insurance Company

A Pan-Cancer Proteogenomic Atlas of PI3K/AKT/mTOR Pathway Alterations

Molecular alterations involving the PI3K/AKT/mTOR pathway (including mutation, copy number, protein, or RNA) were examined across 11,219 human cancers representing 32 major types. Within specific mutated genes, frequency, mutation hotspot residues, in silico predictions, and functional assays were all informative in distinguishing the subset of genetic variants more likely to have functional relevance. Multiple oncogenic pathways including PI3K/AKT/mTOR converged on similar sets of downstream transcriptional targets. In addition to mutation, structural variations and partial copy losses involving PTEN and STK11 showed evidence for having functional relevance. A substantial fraction of cancers showed high mTOR pathway activity without an associated canonical genetic or genomic alteration, including cancers harboring IDH1 or VHL mutations, suggesting multiple mechanisms for pathway activatio

On the properties of the massive binary black hole merger GW170729

International audienceWe present a detailed investigation into the properties of GW170729, the gravitational wave with the most massive and distant source confirmed to date. We employ an extensive set of waveform models, including new improved models that incorporate the effect of higher-order waveform modes which are particularly important for massive systems. We find no indication of spin-precession, but the inclusion of higher-order modes in the models results in an improved estimate for the mass ratio of (0.3–0.8) at the 90% credible level. Our updated measurement excludes equal masses at that level. We also find that models with higher-order modes lead to the data being more consistent with a smaller effective spin, with the probability that the effective spin is greater than zero being reduced from 99% to 94%. The 90% credible interval for the effective spin parameter is now (-0.01-0.50). Additionally, the recovered signal-to-noise ratio increases by ∼0.3 units compared to analyses without higher-order modes; the overall Bayes factor in favor of the presence of higher-order modes in the data is 5.1∶1. We study the effect of common spin priors on the derived spin and mass measurements, and observe small shifts in the spins, while the masses remain unaffected. We argue that our conclusions are robust against systematic errors in the waveform models. We also compare the above waveform-based analysis which employs compact-binary waveform models to a more flexible wavelet- and chirplet-based analysis. We find consistency between the two, with overlaps of ∼0.9, typical of what is expected from simulations of signals similar to GW170729, confirming that the data are well-described by the existing waveform models. Finally, we study the possibility that the primary component of GW170729 was the remnant of a past merger of two black holes and find this scenario to be indistinguishable from the standard formation scenario