133 research outputs found
Cosmological Constraints from the double source plane lens SDSSJ0946+1006
We present constraints on the equation of state of dark energy, , and the
total matter density, , derived from the
double-source-plane strong lens SDSSJ0946+1006, the first cosmological
measurement with a galaxy-scale double-source-plane lens. By modelling the
primary lens with an elliptical power-law mass distribution, and including
perturbative lensing by the first source, we are able to constrain the
cosmological scaling factor in this system to be ,
which implies for a flat
cold dark matter (CDM) cosmology. Combining with a cosmic microwave
background prior from Planck, we find = assuming a
flat CDM cosmology. This inference shifts the posterior by 1 and
improves the precision by 30 per cent with respect to Planck alone, and
demonstrates the utility of combining simple, galaxy-scale
multiple-source-plane lenses with other cosmological probes to improve
precision and test for residual systematic biases.Comment: 9 Pages, 7 Figures. Updated version as published in MNRA
Improving the Fun Factor at Valpo: A Student Retention Strategy
Retention is identified by the university as problem that needs be addressed a part of the overall strategy to improve enrollment at Valpo. This team brainstormed about possible retention issues and discovered that often students describe the campus as “boring” or “uneventful.” Valpo students were polled via the Internet and additional questionnaire handouts on campus. Many students felt as though they lacked information about events on campus and that their RA did not interact with them enough. This data established the extensiveness and the depth of the “lack of fun” problem. Research further revealed that a lot of the events/activities that the students wanted to see at Valpo were already here. So there is definitely a communication breakdown. Students expressed the need for more outreach and encouragement, especially from their immediate authority figure, their RAs, to inform them of what’s going on at Valpo. There was an expressed need for a newsletter that updated students on campus activities via email. (The Torch is too inflexible). Changes need to be made to inform students about campus events. Students proposed a student email newsletter similar to the one sent out to staff (the Campus Chronicle). Students also expressed concern about how the events and activities are promoted to the students, which generally excludes others – the “silo” effect. Since most students must live on campus until they’re upperclassmen, this further increased the issue students have with lack of “fun” on campus. The campaign team will be presenting these research findings to different groups such as IMC and Residential Life
Automated Lensing Learner: Automated Strong Lensing Identification with a Computer Vision Technique
Forthcoming surveys such as the Large Synoptic Survey Telescope (LSST) and
Euclid necessitate automatic and efficient identification methods of strong
lensing systems. We present a strong lensing identification approach that
utilizes a feature extraction method from computer vision, the Histogram of
Oriented Gradients (HOG), to capture edge patterns of arcs. We train a
supervised classifier model on the HOG of mock strong galaxy-galaxy lens images
similar to observations from the Hubble Space Telescope (HST) and LSST. We
assess model performance with the area under the curve (AUC) of a Receiver
Operating Characteristic (ROC) curve. Models trained on 10,000 lens and
non-lens containing images images exhibit an AUC of 0.975 for an HST-like
sample, 0.625 for one exposure of LSST, and 0.809 for 10-year mock LSST
observations. Performance appears to continually improve with the training set
size. Models trained on fewer images perform better in absence of the lens
galaxy light. However, with larger training data sets, information from the
lens galaxy actually improves model performance, indicating that HOG captures
much of the morphological complexity of the arc finding problem. We test our
classifier on data from the Sloan Lens ACS Survey and find that small scale
image features reduces the efficiency of our trained model. However, these
preliminary tests indicate that some parameterizations of HOG can compensate
for differences between observed mock data. One example best-case
parameterization results in an AUC of 0.6 in the F814 filter image with other
parameterization results equivalent to random performance.Comment: 18 pages, 14 figures, summarizing results in figure
Experimental Investigation of Film Cooling in a Supersonic Environment
This thesis reports the results of an experimental investigation of film cooling in a supersonic environment using a modified version of an apparatus originally developed by Daanish Maqbool. A test matrix of conditions relevant to those found in the nozzle extension of the NASA J-2X rocket engine was used as the basis for the testing plan. A film heater was designed and constructed to enable operation at all points in the test matrix. Temperature-time histories from thermocouples embedded in the test section walls were used to compute the spatial evolution of the film cooling effectiveness at each test condition. The results were compared to numerical simulations by NASA's Loci-CHEM CFD tool. Standard speed (30 Hz) Schlieren videos of the film injection region were recorded and new machine vision-based techniques for automatically extracting flow information from Schlieren images were implemented
Brief Communication
The comparison -essentially vector subtraction -gives the direction to the goal. This whole process, which we call vector navigation, was found to be calibrated at recognised sites, such as the nest and a familiar feeder, throughout the life of a forager. If a forager was trained around a one-way circuit in which the result of PI on the return route did not match the result on the outward route, calibration caused the ant's trajectories to be misdirected. We propose a model of vector navigation to suggest how calibration could produce such trajectories
Recommended from our members
Toward Production From Gas Hydrates: Current Status, Assessment of Resources, and Simulation-Based Evaluationof Technology and Potential
Gas hydrates are a vast energy resource with global distribution in the permafrost and in the oceans. Even if conservative estimates are considered and only a small fraction is recoverable, the sheer size of the resource is so large that it demands evaluation as a potential energy source. In this review paper, we discuss the distribution of natural gas hydrate accumulations, the status of the primary international R&D programs, and the remaining science and technological challenges facing commercialization of production. After a brief examination of gas hydrate accumulations that are well characterized and appear to be models for future development and gas production, we analyze the role of numerical simulation in the assessment of the hydrate production potential, identify the data needs for reliable predictions, evaluate the status of knowledge with regard to these needs, discuss knowledge gaps and their impact, and reach the conclusion that the numerical simulation capabilities are quite advanced and that the related gaps are either not significant or are being addressed. We review the current body of literature relevant to potential productivity from different types of gas hydrate deposits, and determine that there are consistent indications of a large production potential at high rates over long periods from a wide variety of hydrate deposits. Finally, we identify (a) features, conditions, geology and techniques that are desirable in potential production targets, (b) methods to maximize production, and (c) some of the conditions and characteristics that render certain gas hydrate deposits undesirable for production
Recommended from our members
Assessing the suitability of three proxy sources for the development of detectors of special nuclear materials
Numerous techniques and equipment have been developed to provide a capability for the detection of special nuclear materials (SNM), but due to the necessary security measures surrounding these materials alternate, or proxy, neutron sources are often utilised in their stead. In this paper we report the neutron and gamma pulse shape discrimination response of plastic scintillator to mixed neutron/gamma beams produced from two radionuclide neutron sources, and also from an SNM source of weapons-grade plutonium. We discuss the suitability of using radionuclide sources, with appropriate shielding configurations as proxy sources for SNM.A 3σnth-γ discrimination level has been achieved for an SNM source at a low-level energy threshold of ~220 keVee when a shielding configuration of 5 cm of lead was implemented. Varying amounts of lead and high-density polyethylene (HDPE) shielding were also investigated with the 3σ limit being reached by ~240 keVee.This work shows that an AmBe neutron source serves as an appropriate SNM proxy achieving a comparable value for figure of merit above ~1 MeVee. For energies below 1 MeVee down to ~100 keVee a closer approximation of the expected FoM for SNM can be attained when using 252Cf as a proxy source or by utilising an 'enhanced' AmBe source with the addition of a further low energy γ ray source
Still no convincing evidence for cognitive map use by honeybees
Cheeseman et al. (1) claim that an ability of honey bees to travel home through a landscape with conflicting information from a celestial compass proves the bees' use of a cognitive map. Their claim involves a curious assumption about the visual information that can be extracted from the terrain: that there is sufficient information for a bee to identify where it is, but insufficient to guide its path without resorting to a cognitive map. We contend that the authors’ claims are unfounded
OPEN : an open-source platform for developing smart local energy system applications
This paper presents OPEN, an open-source software platform for integrated modelling, control and simulation of smart local energy systems. Electric power systems are undergoing a fundamental transition towards a significant proportion of generation and flexibility being provided by distributed energy resources. The concept of ‘smart local energy systems’ brings together related strategies for localised management of distributed energy resources, including active distribution networks, microgrids, energy communities, multi-energy hubs, peer-to-peer trading platforms and virtual power plants. OPEN provides an extensible platform for developing and testing new smart local energy system management applications, helping to bridge the gap between academic research and industry translation. OPEN combines features for managing smart local energy systems which are not provided together by existing energy management tools, including multi-phase distribution network power flow, energy market modelling, nonlinear energy storage modelling and receding horizon optimisation. The platform is implemented in Python with an object-oriented structure, providing modularity and allowing it to be easily integrated with third-party packages. Case studies are presented, demonstrating how OPEN can be used for a range of smart local energy system applications due to its support of multiple model fidelities for simulation and control
- …