Collision Avoidance and Navigation of UAS Using Vision-Based Proportional Navigation

Electro-optical devices have received considerable interest due to their light weight, low cost, and low algorithm requirements with respect to computational power. In this thesis, vision-based guidance laws are developed to provide sense and avoid capabilities for unmanned aerial vehicles (UAVs) operating in complex environments with multiple static and dynamic collision threats. These collision avoidance guidance laws are based on the principle of proportional navigation (Pro-Nav), which states that a UAV is on a collision course with another vehicle or object if the line-of-sight (LOS) angles to the object remain constant. The guidance laws are designed for use with monocular electro-optical devices, which provide information on the LOS angles to potential collision threats, but not the range. The development of these guidance laws propagates from an investigation into numerous methods of Pro-Nav based guidance, including the use of LOS rate thresholding, avoidance of the most imminent threat detected, and objective-based cost optimization. The collision avoidance guidance laws were applied to nonlinear, six degree-of-freedom UAV models in various simulation environments including a varying number of static and dynamic obstacles. A final form of the avoidance law, determined from these simulation studies, was applied to a small-scale UAV model flying through a virtual urban environment, which utilizes camera-in-the-loop simulation techniques. The final results of these studies showed that the most effective approach was to implement a cost function-based avoidance law that includes a term based on the Pro-Nav intercept heading for a desired waypoint and avoidance terms for all obstacles in view that pose a collision threat. Obstacle avoidance headings in the cost function are based on the difference in the obstacle LOS rates from the magnitude of the minimum safe LOS rate. When applied to UAV simulations in a virtual urban environment, this guidance law provided successful avoidance for the case of a single building, maintained a safe heading through an urban canyon, and determined the safest path through a complex urban layout. For the case of the complex urban layout, a single collision during flight occurred due to a lack of visual feature points to contribute to the avoidance law calculation

A Dust Twin of Cas A: Cool Dust and 21-micron Silicate Dust Feature in the Supernova Remnant G54.1+0.3

We present infrared (IR) and submillimeter observations of the Crab-like supernova remnant (SNR) G54.1+0.3 including 350 micron (SHARC-II), 870 micron (LABOCA), 70, 100, 160, 250, 350, 500 micron (Herschel) and 3-40 micron (Spitzer). We detect dust features at 9, 11 and 21 micron and a long wavelength continuum dust component. The 21 micron dust coincides with [Ar II] ejecta emission, and the feature is remarkably similar to that in Cas A. The IRAC 8 micron image including Ar ejecta is distributed in a shell-like morphology which is coincident with dust features, suggesting that dust has formed in the ejecta. We create a cold dust map that shows excess emission in the northwestern shell. We fit the spectral energy distribution of the SNR using the continuous distributions of ellipsoidal (CDE) grain model of pre-solar grain SiO2 that reproduces the 21 and 9 micron dust features and discuss grains of SiC and PAH that may be responsible for the 10-13 micron dust features. To reproduce the long-wavelength continuum, we explore models consisting of different grains including Mg2SiO4, MgSiO3, Al2O3, FeS, carbon, and Fe3O4. We tested a model with a temperature-dependent silicate absorption coefficient. We detect cold dust (27-44 K) in the remnant, making this the fourth such SNR with freshly-formed dust. The total dust mass in the SNR ranges from 0.08-0.9 Msun depending on the grain composition, which is comparable to predicted masses from theoretical models. Our estimated dust masses are consistent with the idea that SNe are a significant source of dust in the early Universe.Comment: MNRAS: accepted on June 28, 2018 and published on July 4, 201

In-situ measurements of the optical absorption of dioxythiophene-based conjugated polymers

Conjugated polymers can be reversibly doped by electrochemical means. This doping introduces new sub-bandgap optical absorption bands in the polymer while decreasing the bandgap absorption. To study this behavior, we have prepared an electrochemical cell allowing measurements of the optical properties of the polymer. The cell consists of a thin polymer film deposited on gold-coated Mylar behind which is another polymer that serves as a counterelectrode. An infrared transparent window protects the upper polymer from ambient air. By adding a gel electrolyte and making electrical connections to the polymer-on-gold films, one may study electrochromism in a wide spectral range. As the cell voltage (the potential difference between the two electrodes) changes, the doping level of the conjugated polymer films is changed reversibly. Our experiments address electrochromism in poly(3,4-ethylene-dioxy-thiophene) (PEDOT) and poly(3,4-dimethyl-propylene-dioxy-thiophene) (PProDOT-Me$_2$). This closed electrochemical cell allows the study of the doping induced sub-bandgap features (polaronic and bipolaronic modes) in these easily oxidized and highly redox switchable polymers. We also study the changes in cell spectra as a function of polymer thickness and investigate strategies to obtain cleaner spectra, minimizing the contributions of water and gel electrolyte features

An Evidence Based Search Method For Gravitational Waves From Neutron Star Ring-downs

The excitation of quadrupolar quasi-normal modes in a neutron star leads to the emission of a short, distinctive, burst of gravitational radiation in the form of a decaying sinusoid or `ring-down'. We present a Bayesian analysis method which incorporates relevant prior information about the source and known instrumental artifacts to conduct a robust search for the gravitational wave emission associated with pulsar glitches and soft $\gamma$-ray repeater flares. Instrumental transients are modelled as sine-Gaussian and their evidence, or marginal likelihood, is compared with that of Gaussian white noise and ring-downs via the `odds-ratio'. Tests using simulated data with a noise spectral density similar to the LIGO interferometer around 1 kHz yield 50% detection efficiency and 1% false alarm probability for ring-down signals with signal-to-noise ratio $\rho=5.2$. For a source at 15 kpc this requires an energy of 1.3\times 10^{-5}M_{\astrosun}c^2 to be emitted as gravitational waves.Comment: 14 pages, 12 figure

Type 1 Diabetes: A Chronic Anti-Self-Inflammatory Response

Inflammation is typically induced in response to a microbial infection. The release of proinflammatory cytokines enhances the stimulatory capacity of antigen-presenting cells, as well as recruits adaptive and innate immune effectors to the site of infection. Once the microbe is cleared, inflammation is resolved by various mechanisms to avoid unnecessary tissue damage. Autoimmunity arises when aberrant immune responses target self-tissues causing inflammation. In type 1 diabetes (T1D), T cells attack the insulin producing β cells in the pancreatic islets. Genetic and environmental factors increase T1D risk by in part altering central and peripheral tolerance inducing events. This results in the development and expansion of β cell-specific effector T cells (Teff) which mediate islet inflammation. Unlike protective immunity where inflammation is terminated, autoimmunity is sustained by chronic inflammation. In this review, we will highlight the key events which initiate and sustain T cell-driven pancreatic islet inflammation in nonobese diabetic mice and in human T1D. Specifically, we will discuss: (i) dysregulation of thymic selection events, (ii) the role of intrinsic and extrinsic factors that enhance the expansion and pathogenicity of Teff, (iii) defects which impair homeostasis and suppressor activity of FoxP3-expressing regulatory T cells, and (iv) properties of β cells which contribute to islet inflammation

Hybrid photonic circuit for multiplexed heralded single photons

A key resource for quantum optics experiments is an on-demand source of single and multiple photon states at telecommunication wavelengths. This letter presents a heralded single photon source based on a hybrid technology approach, combining high efficiency periodically poled lithium niobate waveguides, low-loss laser inscribed circuits, and fast (>1 MHz) fibre coupled electro-optic switches. Hybrid interfacing different platforms is a promising route to exploiting the advantages of existing technology and has permitted the demonstration of the multiplexing of four identical sources of single photons to one output. Since this is an integrated technology, it provides scalability and can immediately leverage any improvements in transmission, detection and photon production efficiencies.Comment: 5 pages, double column, 3 figure

Incremental Hospital Charges Associated With Obesity as a Secondary Diagnosis in Children

Objective: The objective was to evaluate the association of obesity as a comorbidity with hospital charges, by comparing charges for pediatric hospitalizations with vs. without obesity as a secondary diagnosis. Methods: Using the 2000 Healthcare Cost and Utilization Project (HCUP) Kids’ Inpatient Database (KID), a nationally representative sample of pediatric hospital discharges, we identified the most common non‐pregnancy‐related principal diagnoses for children 2 to 18 years of age: asthma, pneumonia, affective disorders, and appendicitis. For each we compared mean charges and mean length of stay for hospitalizations with vs. without obesity as a secondary diagnosis, adjusting for relevant socio‐demographics and hospital type. Results: Among children's discharges in 2000, 1.1% listed obesity as a secondary diagnosis. These had a disproportionate likelihood of being older, black, Medicaid beneficiaries, and hospitalized at a general hospital. Adjusted mean hospital charges were significantly higher for discharges with obesity as a secondary diagnosis vs. those without: appendicitis ($14,134 vs.$11,049; p < 0.01), asthma ($7766 vs.$6043; p < 0.05), pneumonia ($12,228 vs.$9688; p < 0.05), and affective disorders ($8292 vs.$7769; p < 0.01). Whereas obesity as a secondary diagnosis was associated with a pattern of increased adjusted mean length of stay, only asthma and affective disorders had statistically significant differences (0.6 days) ( p < 0.01). Conclusion: This national analysis suggests obesity as a secondary diagnosis is associated with significantly higher charges for the most common reasons for pediatric hospitalizations. This presents a financial imperative for further research to evaluate factors that contribute to higher inpatient charges related to obesity as a comorbidity and underscores the need for obesity prevention initiatives.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/93704/1/oby.2007.224.pd