10,763 research outputs found
The Robinson Gravitational Wave Background Telescope (BICEP): a bolometric large angular scale CMB polarimeter
The Robinson Telescope (BICEP) is a ground-based millimeter-wave bolometric
array designed to study the polarization of the cosmic microwave background
radiation (CMB) and galactic foreground emission. Such measurements probe the
energy scale of the inflationary epoch, tighten constraints on cosmological
parameters, and verify our current understanding of CMB physics. Robinson
consists of a 250-mm aperture refractive telescope that provides an
instantaneous field-of-view of 17 degrees with angular resolution of 55 and 37
arcminutes at 100 GHz and 150 GHz, respectively. Forty-nine pair of
polarization-sensitive bolometers are cooled to 250 mK using a 4He/3He/3He
sorption fridge system, and coupled to incoming radiation via corrugated feed
horns. The all-refractive optics is cooled to 4 K to minimize polarization
systematics and instrument loading. The fully steerable 3-axis mount is capable
of continuous boresight rotation or azimuth scanning at speeds up to 5 deg/s.
Robinson has begun its first season of observation at the South Pole. Given the
measured performance of the instrument along with the excellent observing
environment, Robinson will measure the E-mode polarization with high
sensitivity, and probe for the B-modes to unprecedented depths. In this paper
we discuss aspects of the instrument design and their scientific motivations,
scanning and operational strategies, and the results of initial testing and
observations.Comment: 18 pages, 11 figures. To appear in Millimeter and Submillimeter
Detectors and Instrumentation for Astronomy III, Proceedings of SPIE, 6275,
200
Advancements in hybrid photovoltaic-thermal systems: performance evaluations and applications
Due to European Directives (2010/31/UE on buildings energy performance, 2009/28/CE on the use of renewable energy, 2012/27/UE on the energy efficiency) the electric and thermal energy needs of new and retrofitted buildings are faced by increasing percentages of renewable energy. Solar energy and heat pumps are the most promising technologies mainly in residential buildings as they have reached great maturity. Anyway, in most cases solar energy utilizations systems are thermal (which convert solar energy to thermal energy) and photovoltaic (which convert solar energy to electricity) used as separated collectors. Commercial photovoltaic modules have nowadays an efficiency around 15 % - 18 %. It means that the most relevant part of solar radiation is lost. Such a remark gets more importance if the active surface is located in an urban environment, where the availability of surfaces exposed to the sun is scarce if compared to the buildings thermal loads. PhotoVoltaic / Thermal cogeneration (PV/T) aims to utilize the same area both for producing electricity and heat. As solar cells are sensitive to temperature (their efficiency lowers when temperature increases), heat is beneficially collected but it cannot be available at high temperatures. Many researches on performances and characteristics of different hybrid photovoltaic\u2013thermal technologies and systems have been carried out during the last years to face this problem; among these designs, systems utilizing air, liquid, heat pipes, phase change materials, and thermoelectric devices to aid cooling of PV cells. This paper provides a description of the applications of the photovoltaic\u2013thermal systems, such as building integrated PV/T, concentrating PV/T systems and photovoltaic\u2013thermal heat pump systems. Several factors affecting the performances and characteristics of the photovoltaic\u2013thermal systems are also summarized
High capacity demonstration of honeycomb panel heat pipes
The feasibility of performance enhancing the sandwich panel heat pipe was investigated for moderate temperature range heat rejection radiators on future-high-power spacecraft. The hardware development program consisted of performance prediction modeling, fabrication, ground test, and data correlation. Using available sandwich panel materials, a series of subscale test panels were augumented with high-capacity sideflow and temperature control variable conductance features, and test evaluated for correlation with performance prediction codes. Using the correlated prediction model, a 50-kW full size radiator was defined using methanol working fluid and closely spaced sideflows. A new concept called the hybrid radiator individually optimizes heat pipe components. A 2.44-m long hybrid test vehicle demonstrated proof-of-principle performance
A Multicamera System for Gesture Tracking With Three Dimensional Hand Pose Estimation
The goal of any visual tracking system is to successfully detect then follow an object of interest through a sequence of images. The difficulty of tracking an object depends on the dynamics, the motion and the characteristics of the object as well as on the environ ment. For example, tracking an articulated, self-occluding object such as a signing hand has proven to be a very difficult problem. The focus of this work is on tracking and pose estimation with applications to hand gesture interpretation. An approach that attempts to integrate the simplicity of a region tracker with single hand 3D pose estimation methods is presented. Additionally, this work delves into the pose estimation problem. This is ac complished by both analyzing hand templates composed of their morphological skeleton, and addressing the skeleton\u27s inherent instability. Ligature points along the skeleton are flagged in order to determine their effect on skeletal instabilities. Tested on real data, the analysis finds the flagging of ligature points to proportionally increase the match strength of high similarity image-template pairs by about 6%. The effectiveness of this approach is further demonstrated in a real-time multicamera hand tracking system that tracks hand gestures through three-dimensional space as well as estimate the three-dimensional pose of the hand
Machine Analysis of Facial Expressions
No abstract
Volume-of-Fluid computational foundation for variable-density, two-phase, supercritical-fluid flows
A two-phase, low-Mach-number flow solver is proposed for compressible liquid
and gas with phase change. The interface is tracked using a split
Volume-of-Fluid method, which solves the advection of the liquid phase. This
split advection method is generalized for the case where the liquid velocity is
not divergence-free and both phases exchange mass across the interface, as
happens at near-critical and supercritical pressure conditions. In this
thermodynamic environment, the dissolution of lighter gas species into the
liquid phase is enhanced and vaporization or condensation can occur
simultaneously at different locations along the interface. A sharp interface is
identified with a Piecewise Linear Interface Construction (PLIC). Mass
conservation to machine-error precision is achieved in the limit of
incompressible liquid, but not with the liquid compressibility and mass
exchange. The numerical cost of solving two-phase, supercritical flows is very
high because: a) local phase equilibrium is imposed at each interface cell to
determine the interface solution (e.g., temperature); b) a complete
thermodynamic model is used to obtain fluid properties; and c) phase-wise
values for certain variables (i.e., velocity) are obtained via extrapolation
techniques. Furthermore, the Volume-of-Fluid method and the PLIC add extra
computational costs. To alleviate this numerical cost, the pressure Poisson
equation (PPE) is split into a constant-coefficient implicit part and a
variable-coefficient explicit part. Thus, a Fast Fourier Transform (FFT) method
can be used to solve the PPE. Various validation tests are performed to show
the accuracy and viability of the present approach. Then, the growth of surface
instabilities in a binary system composed of liquid n-decane and gaseous oxygen
at supercritical pressures for n-decane are analyzed. Other features of
supercritical liquid injection are also shown.Comment: 52 pages, 19 figure
Aerospace medicine and biology: A continuing bibliography with indexes, supplement 197, September 1979
This bibliography lists 193 reports, articles, and other documents introduced into the NASA scientific and technical information system in August 1979
Arts across the curriculum: enhancing pupil learning, the pupil perspective
Paper presented to the British Educational Research Association (BERA) Annual Conference, held at Heriot-Watt University, Edinburgh
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