3,199 research outputs found

    Design and evaluation of a digital processing unit for satellite angular velocity estimation

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    A satellite's absolute attitude and angular rate are both important measurements for satellite missions that require navigation. Typically, these measurements have been made by separate sensors, with star cameras being used to determine a satellite's absolute attitude, and gyroscopes being used as the primary rate sensors. Recently, there have been multiple efforts to measure both of these quantities using only the star camera, however the work primarily involves solutions where the optical sensor and the unit that processes the images are separate integrated circuits. Operation in this modality requires the use of chip to chip communication in order to estimate angular rate from star tracker images, which can lead to an increase in system power, a degradation in performance, and increased latency. The goal of this thesis is to consolidate the sensing and processing into a single integrated circuit. The design and evaluation of a digital processing unit that estimates angular rate and facilitates the realization of image sensor and processor integration is presented. The processing unit is implemented in UMC's 130 nm process, has an area of 10 mm × 200 μm, and consumes 8.253 mW of power

    VALUING RISK-REDUCING INTERVENTIONS WITH HEDONIC MODELS: THE CASE OF EROSION PROTECTION

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    This article extends the literature on economic valuation of public interventions that reduce environmental risk. We consider the case where risk-reducing interventions have different characteristics than the risk proxies used in hedonic regressions. We then demonstrate the importance of these considerations by reexamining an existing analysis of shoreline protection where we estimate risk using a latent variables model. The results show substantially different and arguably more plausible results.Environmental Economics and Policy, Risk and Uncertainty,

    \u3cem\u3eOn the Road\u3c/em\u3e from Melville to Postmodernism: The Case for Kerouac\u27s Canonization.

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    With the publication of On the Road in 1957, Jack Kerouac became a cultural phenomenon. Crowned the King of the Beat Generation, Kerouac embodied the restlessness of Cold War-era America. What no one realized at the time, however, was that the movement that he supposedly led went against Kerouac\u27s own beliefs. Rather than rebellion, Kerouac wanted to write in a way that no one had written before. Heavily influenced by, among others, Mark Twain, Fyodor Dostoevsky, Marcel Proust, Herman Melville, and, especially, James Joyce, Kerouac used the influence of his predecessors to formulate his own style of writing-spontaneous prose. The critics who label Kerouac as a cultural icon akin to James Dean fail to see Kerouac as a serious author. The removal of the cultural fanfare surrounding Kerouac shows the truth about his writing, his influences, and his influence on late-twentieth century literature, including the entire postmodern movement

    Breeding Season Ecology and Demography of Lesser Scaup (\u3ci\u3eAythya affinis\u3c/i\u3e) at Red Rock Lakes National Wildlife Refuge

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    It is hypothesized that individuals make reproductive decisions based on current assessments of their physiological condition and environmental conditions. For female lesser scaup (Aythya affinis), breeding occurs after an energetically costly spring migration. Increasing fat reserves (i.e., ‘body condition’) prior to breeding allows a female to produce a larger clutch of eggs, but time spent gaining body condition is costly in terms of time allowed to raise ducklings before freezing conditions in the fall. In Chapter 2 I explored rate of pre-breeding body condition gain in female lesser scaup, and how that rate influenced clutch size. Spring phenology, measured by proxy as water temperature, and water depth strongly influenced the rate at which females increased body condition. Early springs with low water levels led to greater rates of body condition gain in female scaup. The higher the rate of body condition gain, the larger the clutch of eggs females produced. Body condition is also an important determinant of breeding in female ducks; females in poor body condition are more likely to forego breeding. I explored how body condition, wetland conditions, and prior experience influence a female’s decision to breed in Chapter 3. Body condition was a strong determinant of when a female bred, with females in good body condition breeding earlier than females in poorer body condition. Habitat conditions were also important, with drought reducing the proportion of breeding lesser scaup females. In Chapter 4 I examined survival costs of reproduction in female scaup. Nesting exposes females to increased predation risk (a concurrent survival cost), and reduced post-breeding body condition may reduce female survival the subsequent non-breeding season (a serial, or ‘downstream’, survival cost). Female survival during breeding and non-breeding seasons was most correlated with breeding season water level on the study site, but in opposite directions. Breeding season survival increased with increasing water levels, while non-breeding season survival declined. High water levels on the study site increased the availability of presumably high-security nesting habitat, and also increased female reproductive effort. The former increased breeding season survival, while the latter reduced non-breeding season survival

    A Comparison of the Effects of Interval Training vs. Continuous Training on Weight Loss and Body Composition in Obese Pre-Menopausal Women.

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    The purpose of this study was to investigate the role exercise intensity plays in reducing body weight and percent body fat in overweight women. Subjects were randomized to either a high intensity interval training group (IT) or a lower intensity steady state training group (ST). Each group exercised 3 times per week for 8 weeks and expended 300 kcal per exercise session. VO2max, body composition, and resting metabolic rate (RMR) were measured pre and post training. RMR was measured after exercise at week 2 to see if intensity levels affected RMR. VO2max and body composition improved in IT but not in ST. Neither group showed a change in RMR from pretest to posttest; however, IT had an increase in RMR 24 hours post-exercise whereas ST did not. These findings show that high intensity interval exercise produces improvements in body composition, fitness, and acute RMR compared to low intensity steady state training

    Current-eddy interaction in the Agulhas Return Current region from the seismic oceanography perspective

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    Interleaving in the Agulhas Return Current (ARC) frontal region is commonly manifested in the form of thermohaline intrusions, as sub-tropical and sub-polar water masses of similar density meet. In Jan/Feb 2012, the Naval Research Laboratory and collaborators carried out a field experiment in which seismic and traditional hydrographic observations were acquired to examine frontal zone mixing processes. The high lateral resolution (10 m) of the seismic observations allowed fine-scale lateral tracking of thermal intrusions, which were corroborated with simultaneous XBT casts. Between seismic deployments both salinity and temperature data were acquired via CTD, Underway-CTD and microstructure profiles. This study focuses on analyzing seismic reflection data in a particular E-W transect where the northward flowing ARC interacted with the southward flowing portion of a large anticyclonic eddy. Strong reflectors were most prominent at the edge of a hyperbolic zone formed between the eddy and ARC, where sub-polar waters interacted with waters of sub-tropical origin on either side. Reflectors were shallow within the hyperbolic zone and extended to 1200 m below the ARC. The nature of the observed reflectors will be determined from comparison of seismic reflection and derived ∂T/∂z fields, and XBT and TS profiles from the available hydrographic data

    Dynamics of elastocapillary rise

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    We present the results of a combined experimental and theoretical investigation of the surface-tension-driven coalescence of flexible structures. Specifically, we consider the dynamics of the rise of a wetting liquid between flexible sheets that are clamped at their upper ends. As the elasticity of the sheets is progressively increased, we observe a systematic deviation from the classical diffusive-like behaviour: the time to reach equilibrium increases dramatically and the departure from classical rise occurs sooner, trends that we elucidate via scaling analyses. Three distinct temporal regimes are identified and subsequently explored by developing a theoretical model based on lubrication theory and the linear theory of plates. The resulting free-boundary problem is solved numerically and good agreement is obtained with experiments
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