171 research outputs found
A BEMS-Assisted Commissioning Tool to Improve the Energy Performance of HVAC Systems
The evolving capabilities of Building Energy
Management Systems (BEMS) offer new
opportunities to automate some parts of the
commissioning process and can generate benefits
over the entire life of a building. These benefits
include a reduction of process cost and manual effort
on site, improved quality assurance process and the
adoption of automated energy audit capabilities to
improve overall building performance.
This paper presents the concept for a new automated
commissioning tool that verifies and optimizes the
performance of building HVAC systems using the
capabilities of BEMS. The tool is applicable mainly
to commercial and institutional buildings. In its
simplest form, the tool monitors building control data
and stores it in a structured database to be used online
or upon request. Data resulting from
standardized test procedures invoked manually or
automatically are also stored in the database. A
reasoning algorithm performs an intelligent analysis
of the monitored data and also performs additional
automated commissioning of HVAC components and
systems, identifying faults, diagnosing them, and
evaluating the potential energy efficiency
improvements. The process is completed by sending
detailed comprehensive reports to the user.
This paper also includes an example showing how an
automated BEMS-assisted commissioning tool can
potentially be applied to improve the energy
performance of variable-air-volume fan systems
Development of Self-Correcting Algorithms for Complete Failure of Supply Air Temperature Sensors
Hall, Seebeck, and Nernst Coefficients of Underdoped HgBa2CuO4+d: Fermi-Surface Reconstruction in an Archetypal Cuprate Superconductor
Charge density-wave order has been observed in cuprate superconductors whose
crystal structure breaks the square symmetry of the CuO2 planes, such as
orthorhombic YBa2Cu3Oy (YBCO), but not so far in cuprates that preserve that
symmetry, such as tetragonal HgBa2CuO4+d (Hg1201). We have measured the Hall
(R_H), Seebeck (S), and Nernst coefficients of underdoped Hg1201 in magnetic
fields large enough to suppress superconductivity. The high-field R_H(T) and
S(T) are found to drop with decreasing temperature and become negative, as also
observed in YBCO at comparable doping. In YBCO, the negative R_H and S are
signatures of a small electron pocket caused by Fermi-surface reconstruction,
attributed to charge density-wave modulations observed in the same range of
doping and temperature. We deduce that a similar Fermi-surface reconstruction
takes place in Hg1201, evidence that density-wave order exists in this
material. A striking similarity is also found in the normal-state Nernst
coefficient, further supporting this interpretation. Given the model nature of
Hg1201, Fermi-surface reconstruction appears to be common to all hole-doped
cuprates, suggesting that density-wave order is a fundamental property of these
materials
New specimens of the basal ornithischian dinosaur Lesothosaurus diagnosticus Galton, 1978 from the Early Jurassic of South Africa
We describe new specimens of the basal ornithischian dinosaur Lesothosaurus diagnosticus Galton, 1978 collected from a bone bed in the Fouriesburg district of the Free State, South Africa. The material was collected from the upper Elliot Formation (Early Jurassic) and represents the remains of at least three different individuals. These individuals are larger in body size than those already known in museum collections and offer additional information on cranial ontogeny in the taxon. Moreover, they are similar in size to the sympatric taxon Stormbergia dangershoeki. The discovery of three individuals at this locality might imply group-living behaviour in this early ornithischian
Nernst Effect of stripe ordering LaEuSrCuO
We investigate the transport properties of
LaEuSrCuO (, 0.08, 0.125, 0.15, 0.2) with a
special focus on the Nernst effect in the normal state. Various anomalous
features are present in the data. For and 0.15 a kink-like anomaly is
present in the vicinity of the onset of charge stripe order in the LTT phase,
suggestive of enhanced positive quasiparticle Nernst response in the stripe
ordered phase. At higher temperature, all doping levels except exhibit
a further kink anomaly in the LTO phase which cannot unambiguously be related
to stripe order. Moreover, a direct comparison between the Nernst coefficients
of stripe ordering LaEuSrCuO and superconducting
LaSrCuO at the doping levels and reveals
only weak differences. Our findings make high demands on any scenario
interpreting the Nernst response in hole-doped cuprates
Mammalian Whiskers and the Euler Spiral
Mammal whiskers are often used as a model for understanding the sensory circuits in the brain. Signals from the whiskers, especially their forces, are processed throughout the brain, particularly in the somatosensory “barrel” cortex. Before attempting to interpret the neuronal signals, it is imperative to understand the signals received by the whisker follicles themselves and therefore accurately modelling whisker mechanics is important. Previously, whiskers have been modelled as a parabola based on Cartesian coordinates of the whisker centerline, but we propose that an Euler spiral model is a simple way to capture many aspects of whisker shape. In this study, we model 516 rat (Rattus norvegicus) whiskers as plane model curves with a linear relationship between arc length, s, and curvature, k, such that k(s) = A(s) + B and show that any original rat whisker can be mapped onto a normalized Euler spiral. The Euler spiral provides a convenient and highly accurate model for analytical studies, particularly intrinsically curved rods such as whiskers. The simplistic description in terms of coefficients A and B allows average whiskers to be created from data sets. In addition, vibrissae of many different species, such as pygmy shrew or grey seal, can be readily compared based on their shape alone
Direct measurement of the upper critical field in a cuprate superconductor
The upper critical field Hc2 is a fundamental measure of the pairing
strength, yet there is no agreement on its magnitude and doping dependence in
cuprate superconductors. We have used thermal conductivity as a direct probe of
Hc2 in the cuprates YBa2Cu3Oy and YBa2Cu4O8 to show that there is no vortex
liquid at T = 0, allowing us to use high-field resistivity measurements to map
out the doping dependence of Hc2 across the phase diagram. Hc2(p) exhibits two
peaks, each located at a critical point where the Fermi surface undergoes a
transformation. The condensation energy obtained directly from Hc2, and
previous Hc1 data, undergoes a 20-fold collapse below the higher critical
point. These data provide quantitative information on the impact of competing
phases in suppressing superconductivity in cuprates.Comment: to appear in Nature Communications; Supplementary Information file
available upon reques
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