Radio-Frequency Transmitter Geolocation Using Non-Ideal Received Signal Strength Indicators

Locating a radio transmitter is important in a number of problems such as finding radio tags, people with radios, and devices that are collecting information in an unauthorized manner. Locating a radio transmitter is inherently difficult because the radio waves of concern are not in the visible spectrum, they reflect and distort easily, and they propagate at the speed of light. A number of methods for locating transmitters are currently used, the majority of which require expensive hardware and extensive processing. This thesis presents a method of using simpler measurements to produce similar location estimates in order to augment or replace current systems. While other systems have significant advantages, the methods proposed in this thesis are advantageous because they only require easily-obtained measurements that are based on the observed power of the transmission. The research uses simulations and experiments on real-world data collected locally to demonstrate the possibility of locating a transmitter using information of this type. The conclusion is that some methods are able to compensate for the difficulties in the problem more effectively and produce useful location estimates

Housing and open space proposal for the Quarry, Mission Hill, Boston.

Thesis. 1976. M.Arch.--Massachusetts Institute of Technology. Dept. of Architecture.Microfiche copy available in Archives and Rotch.Bibliography: leaves 18-19.M.Arch

Constrained Moments Simulation of Healthcare Capital Acquisitions

Summary form only as given. Two analytical techniques which evaluate capital acquisitions in healthcare are the method of generating system moments and Monte Carlo simulation. Generating system moments enables the user to determine an estimate of the expected cost from a user-supplied function. Furthermore, the user can determine, from a variance component analysis, the sensitivity of the user-supplied function to marginal changes in the random variables by expanding the function about its mean using the Taylor series expansion to the second order. Calculating the magnitude of partial derivatives of each random variable with respect to the user-supplied function indicates the relative importance of each random variable to the function. VARSIM is an interactive program which is used to calculate the system moments. An add-in program to an Excel spreadsheet is used to invoke a Monte Carlo simulation, whose results are useful for assessing potential risks associated with a capital investment. The results from VARSIM indicate that the expected cost per MRI exam is $350 with a standard deviation of$11.81. Operating hours are increased from 50 to 126 hours per week. The simulation results indicate that there is a 55.2 percent probability that this cost level will be achieved and ultimately its annual target number of exams. Thus, the systematic approach presented in this paper provides a solid basis which hospitals can use to perform a thorough assessment of their capital equipment needs, and thereby, present their findings in a more objective manner to decision-maker

Tasker: Safely Serving Verifiable Micro-tasks for Researchers

Paid crowdsourcing removes many traditional boundaries in conducting participant based research, however with this new tool, new instrumentation challenges have arisen for researchers. Three common challenges include: the difficulty in creating large numbers of high quality and novel tasks, verifying results of the tasks without relying on manual cheat mitigation techniques, and ensuring that the tasks adhere to the latest visual and instructional design to get high quality results. These circumstances endanger current and future research on Amazon Mechanical Turk and can result in compromised data. We introduce Tasker, a secure system architecture for serving unique tasks supported by usability principles to workers, and providing verification information concerning their completion and accuracy to researchers. This poster discusses insights from our pilot study and explorations toward methods that demonstrate a marked improvement for speed, security and robustness in developing tasks for research leveraging Amazon Mechanical Turk

PuzzleFlex: kinematic motion of chains with loose joints

This paper presents a method of computing free motions of a planar assembly of rigid bodies connected by loose joints. Joints are modeled using local distance constraints, which are then linearized with respect to configuration space velocities, yielding a linear programming formulation that allows analysis of systems with thousands of rigid bodies. Potential applications include analysis of collections of modular robots, structural stability perturbation analysis, tolerance analysis for mechanical systems, and formation control of mobile robots.Comment: Accepted at the 2020 IEEE International Conference on Robotics and Automation (ICRA

Near-unity nuclear polarization with an open-source 129Xe hyperpolarizer for NMR and MRI

The exquisite NMR spectral sensitivity and negligible reactivity of hyperpolarized xenon-129 (HP129Xe) make it attractive for a number of magnetic resonance applications; moreover, HP129Xe embodies an alternative to rare and nonrenewable 3He. However, the ability to reliably and inexpensively produce large quantities of HP129Xe with sufficiently high 129Xe nuclear spin polarization (PXe) remains a significant challenge—particularly at high Xe densities. We present results from our “open-source” large-scale (∼1 L/h) 129Xe polarizer for clinical, preclinical, and materials NMR and MRI research. Automated and composed mostly of off-the-shelf components, this “hyperpolarizer” is designed to be readily implementable in other laboratories. The device runs with high resonant photon flux (up to 200 W at the Rb D1 line) in the xenon-rich regime (up to 1,800 torr Xe in 500 cc) in either single-batch or stopped-flow mode, negating in part the usual requirement of Xe cryocollection. Excellent agreement is observed among four independent methods used to measure spin polarization. In-cell PXe values of ∼90%, ∼57%, ∼50%, and ∼30% have been measured for Xe loadings of ∼300, ∼500, ∼760, and ∼1,570 torr, respectively. PXe values of ∼41% and ∼28% (with ∼760 and ∼1,545 torr Xe loadings) have been measured after transfer to Tedlar bags and transport to a clinical 3 T scanner for MR imaging, including demonstration of lung MRI with a healthy human subject. Long “in-bag” 129Xe polarization decay times have been measured (T1 ∼38 min and ∼5.9 h at ∼1.5 mT and 3 T, respectively)—more than sufficient for a variety of applications

Climate-informed stochastic hydrological modeling: Incorporating decadal-scale variability using paleo data

A hierarchical framework for incorporating modes of climate variability into stochastic simulations of hydrological data is developed, termed the climate-informed multi-time scale stochastic (CIMSS) framework. A case study on two catchments in eastern Australia illustrates this framework. To develop an identifiable model characterizing long-term variability for the first level of the hierarchy, paleoclimate proxies, and instrumental indices describing the Interdecadal Pacific Oscillation (IPO) and the Pacific Decadal Oscillation (PDO) are analyzed. A new paleo IPO-PDO time series dating back 440 yr is produced, combining seven IPO-PDO paleo sources using an objective smoothing procedure to fit low-pass filters to individual records. The paleo data analysis indicates that wet/dry IPO-PDO states have a broad range of run lengths, with 90% between 3 and 33 yr and a mean of 15 yr. The Markov chain model, previously used to simulate oscillating wet/dry climate states, is found to underestimate the probability of wet/dry periods >5 yr, and is rejected in favor of a gamma distribution for simulating the run lengths of the wet/dry IPO-PDO states. For the second level of the hierarchy, a seasonal rainfall model is conditioned on the simulated IPO-PDO state. The model is able to replicate observed statistics such as seasonal and multiyear accumulated rainfall distributions and interannual autocorrelations. Mean seasonal rainfall in the IPO-PDO dry states is found to be 15%-28% lower than the wet state at the case study sites. In comparison, an annual lag-one autoregressive model is unable to adequately capture the observed rainfall distribution within separate IPO-PDO states. Copyright © 2011 by the American Geophysical Union.Benjamin J. Henley, Mark A. Thyer, George Kuczera and Stewart W. Frank