1,989 research outputs found

    Fundamental concepts of structural loading and load relief techniques for the space shuttle

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    The prediction of flight loads and their potential reduction, using various control system logics for the space shuttle vehicles, is discussed. Some factors not found on previous launch vehicles that increase the complexity are large lifting surfaces, unsymmetrical structure, unsymmetrical aerodynamics, trajectory control system coupling, and large aeroelastic effects. These load-producing factors and load-reducing techniques are analyzed

    Structural control interaction

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    The basic guidance and control concepts that lead to structural control interaction and structural dynamic loads are identified. Space vehicle ascent flight load sources and the load relieving mechanism are discussed, along with the the characteristics and special problems of both present and future space vehicles including launch vehicles, orbiting vehicles, and the Space Shuttle flyback vehicle. The special dynamics and control analyses and test problems apparent at this time are summarized

    PLASIM: A computer code for simulating charge exchange plasma propagation

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    The propagation of the charge exchange plasma for an electrostatic ion thruster is crucial in determining the interaction of that plasma with the associated spacecraft. A model that describes this plasma and its propagation is described, together with a computer code based on this model. The structure and calling sequence of the code, named PLASIM, is described. An explanation of the program's input and output is included, together with samples of both. The code is written in ANSI Standard FORTRAN

    Discriminative learning of local image descriptors

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    In this paper, we explore methods for learning local image descriptors from training data. We describe a set of building blocks for constructing descriptors which can be combined together and jointly optimized so as to minimize the error of a nearest-neighbor classifier. We consider both linear and nonlinear transforms with dimensionality reduction, and make use of discriminant learning techniques such as Linear Discriminant Analysis (LDA) and Powell minimization to solve for the parameters. Using these techniques, we obtain descriptors that exceed state-of-the-art performance with low dimensionality. In addition to new experiments and recommendations for descriptor learning, we are also making available a new and realistic ground truth data set based on multiview stereo data

    Impact of admission screening for methicillin-resistant Staphylococcus aureus on the length of stay in an emergency department.

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    Preventing and controlling methicillin-resistant Staphylococcus aureus (MRSA) includes early detection and isolation. In the emergency department (ED), such measures have to be balanced with the requirement to treat patients urgently and transfer quickly to an acute hospital bed. We assessed, in a busy and overcrowded ED, the contribution made to a patient\u27s stay by previous MRSA risk group identification and by selective rescreening of those patients who were previously documented in the research hospital as being MRSA positive. Patients with a previous diagnosis of MRSA colonisation were flagged automatically as \u27risk group\u27 (RG) on their arrival in the ED and were compared with \u27non-risk group\u27 (NRG), i.e. not previously demonstrated in the research hospital to be infected or colonised with MRSA. Over an 18 month period, there were 16 456 admissions via the ED, of which 985 (6%) were RG patients. The expected median times to be admitted following a request for a ward bed for NRG and RG patients were 10.4 and 12.9h, respectively. Female sex, age \u3e65 years, and RG status all independently predicted a statistically significantly longer stay in the ED following a request for a hospital bed. We consider that national and local policies for MRSA need to balance the welfare of patients in the ED with the need to comply with best practice, when there are inadequate ED and inpatient isolation facilities. Patients with MRSA requiring emergency admission must have a bed available for them

    Review of the genus Ceresium Newman, 1842 (Coleoptera, Cerambycidae) in Fiji

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    A taxonomic review of the genus Ceresium (Coleoptera: Cerambycidae) found within the Fiji Islands is presented. A total of 17 species is treated. Full morphological descriptions and comparative images of each species are included, along with a dichotomous key for their identification

    Crustal seismic velocity responds to a magmatic intrusion and seasonal loading in Iceland's Northern Volcanic Zone.

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    Seismic noise interferometry is an exciting technique for studying volcanoes, providing a continuous measurement of seismic velocity changes (dv/v), which are sensitive to magmatic processes that affect the surrounding crust. However, understanding the exact mechanisms causing changes in dv/v is often difficult. We present dv/v measurements over 10 years in central Iceland, measured using single-station cross-component correlation functions from 51 instruments across a range of frequency bands. We observe a linear correlation between changes in dv/v and volumetric strain at stations in regions of both compression and dilatation associated with the 2014 BĂĄrĂ°arbunga-Holuhraun dike intrusion. Furthermore, a clear seasonal cycle in dv/v is modeled as resulting from elastic and poroelastic responses to changing snow thickness, atmospheric pressure, and groundwater level. This study comprehensively explains variations in dv/v arising from diverse crustal stresses and highlights the importance of deformation modeling when interpreting dv/v, with implications for volcano and environmental monitoring worldwide
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