102 research outputs found
Influence of input climatic data on simulations of annual energy needs of a building: energyplus and WRF modeling for a case study in Rome (Italy)
The simulation of the energy consumptions in an hourly regime is necessary in order to perform calculations on residential buildings of particular relevance for volume or for architectural features. In such cases, the simplified methodology provided by the regulations may be inadequate, and the use of software like EnergyPlus is needed. To obtain reliable results, usually, significant time is spent on the meticulous insertion of the geometrical inputs of the building, together with the properties of the envelope materials and systems. Less attention is paid to the climate database. The databases available on the EnergyPlus website refer to airports located in rural areas near major cities. If the building to be simulated is located in a metropolitan area, it may be affected by the local heat island, and the database used as input to the software should take this phenomenon into account. To this end, it is useful to use a meteorological model such as the Weather Research and Forecasting (WRF) model to construct an appropriate input climate file. A case study based on a building located in the city center of Rome (Italy) shows that, if the climatic forcing linked to the heat island is not considered, the estimated consumption due to the cooling is underestimated by 35–50%. In particular, the analysis and the seasonal comparison between the energy needs of the building simulated by EnergyPlus, with the climatic inputs related to two airports in the rural area of Rome and with the inputs provided by the WRF model related to the center of Rome, show discrepancies of about (i) WRF vs. Fiumicino (FCO): Δ = −3.48% for heating, Δ = 49.25% for cooling; (ii) WRF vs. Ciampino (CIA): Δ = −7.38% for heating, Δ = +35.52% for cooling
Constraints on the Physical Parameters of TeV Blazars
We consider the constraints on the physical parameters of a homogeneous SSC
model that can be derived from the spectral shape and variability of TeV
blazars. Assuming that the relativistic electron spectrum is a broken power
law, where the break energy is a free parameter, we write the
analytical formulae that allow to connect the physical parameters of the model
to observable quantities. The constraints can be summarized in a plane where
the coordinates are the Doppler factor and the magnetic field. The consistency
between the break energy and the balance between cooling and escape and the
interpretation of the soft photon lags measured in some sources as radiative
cooling times are treated as additional independent constraints.
We apply themethod to the case of three well known blazars, PKS 2155-304, Mrk
421 and Mrk 501.Comment: 36 pages, incl. 6 figures in PS format, AAS LaTeX, to be published in
ApJ, Dec 199
PROTOCALC: an artificial calibrator source for CMB telescopes
Cosmic Microwave Background experiments need to measure polarization
properties of the incoming radiation very accurately to achieve their
scientific goals. As a result of that, it is necessary to properly characterize
these instruments. However, there are not natural sources that can be used for
this purpose. For this reason, we developed the PROTOtype CALibrator for
Cosmology, PROTOCALC, which is a calibrator source designed for the 90GHz band
of these telescopes. This source is purely polarized and the direction of the
polarization vector is known with an accuracy better than 0.1deg. This source
flew for the first time in May 2022 showing promising resultComment: Presented at SPIE Astronomical Telescopes + Instrumentation 202
Design and characterization of the POLARBEAR-2b and POLARBEAR-2c cosmic microwave background cryogenic receivers
The POLARBEAR-2/Simons Array Cosmic Microwave Background (CMB) polarization
experiment is an upgrade and expansion of the existing POLARBEAR-1 (PB-1)
experiment, located in the Atacama desert in Chile. Along with the CMB
temperature and -mode polarization anisotropies, PB-1 and the Simons Array
study the CMB -mode polarization anisotropies produced at large angular
scales by inflationary gravitational waves, and at small angular scales by
gravitational lensing. These measurements provide constraints on various
cosmological and particle physics parameters, such as the tensor-to-scalar
ratio , and the sum of the neutrino masses. The Simons Array consists of
three 3.5 m diameter telescopes with upgraded POLARBEAR-2 (PB-2) cryogenic
receivers, named PB-2a, -2b, and -2c. PB-2a and -2b will observe the CMB over
multiple bands centered at 95 GHz and 150 GHz, while PB-2c will observe at 220
GHz and 270 GHz, which will enable enhanced foreground separation and
de-lensing. Each Simons Array receiver consists of two cryostats which share
the same vacuum space: an optics tube containing the cold reimaging lenses and
Lyot stop, infrared-blocking filters, and cryogenic half-wave plate; and a
backend which contains the focal plane detector array, cold readout components,
and millikelvin refrigerator. Each PB-2 focal plane array is comprised of 7,588
dual-polarization, multi-chroic, lenslet- and antenna-coupled, Transition Edge
Sensor (TES) bolometers which are cooled to 250 mK and read out using
Superconducting Quantum Interference Devices (SQUIDs) through a digital
frequency division multiplexing scheme with a multiplexing factor of 40. In
this work we describe progress towards commissioning the PB-2b and -2c
receivers including cryogenic design, characterization, and performance of both
the PB-2b and -2c backend cryostats.Comment: 20 page
The malaria circumsporozoite protein has two functional domains, each with distinct roles as sporozoites journey from mosquito to mammalian host
Conformational changes influence functional properties of circumsporozoite protein expressed on the surface of Plasmodium sporozoites
Fiasco: a multidetector optimized for semiperipheral heavy ion collisions at Fermi energies
The Fiasco multidetector is a low-threshold apparatus, optimized for the investigation of peripheral to semi-central collisions in heavy ion reactions at Fermi energies. It consists of three types of detectors. The first detector layer is a shell of 24 position-sensitive Parallel Plate Avalanche Detectors (PPADs), covering about 70% of the forward hemisphere, which measure the velocity vectors of the heavy ðZ\10Þ reaction products. Below and around the grazing angle, behind the most forward PPADs, there are 96 DE–E silicon telescopes (with thickness of 200 and 500 mm; respectively); they are mainly used to measure the energy of the projectile-like fragment and to identify its charge and, via the time-of-flight of the PPADs, also its mass. Finally, behind most of the PPADs there are 158 (or 182, depending on the configuration) scintillation detectors, mostly of the phoswich type, which cover 25–30% of the forward hemisphere; they identify both light charged particles ðZ ¼ 1; 2Þ and intermediate mass fragments ð3pZt20Þ; measuring also their time-of-flight. r 2003 Elsevier B.V. All rights reserved
The effects of inclination on a two stage pulse tube cryocooler for use with a ground based observatory
Abstract Ground-based observatories across a wide range of wavelengths implement cryogenic cooling techniques to increase the sensitivity of instruments and enable low temperature detector technologies. Commercial pulse tube cryocoolers (PTCs) are frequently used to provide 40 K and 4 K stages as thermal shells in scientific instruments. However, PTC operation is dependent on gravity, giving rise to changes in cooling capacity over the operational tilt range of pointed telescopes. We present a study of the performance of a two stage PTC with a cooling capacity of 1.8 W at 4.2 K and 50 W at 45 K (Cryomech PT420-RM) from 0 - 55 ° away from vertical to probe capacity as a function of angle over a set of realistic thermal loading conditions. Our study provides a method to extract temperature estimates given predicted thermal loading conditions across the angular range sampled. We then discuss the design implications for current and future tilted cryogenic systems
The Simons Observatory: Characterizing the Large Aperture Telescope Receiver with Radio Holography
We present near-field radio holography measurements of the Simons Observatory
Large Aperture Telescope Receiver optics. These measurements demonstrate that
radio holography of complex millimeter-wave optical systems comprising
cryogenic lenses, filters, and feed horns can provide detailed characterization
of wave propagation before deployment. We used the measured amplitude and
phase, at 4K, of the receiver near-field beam pattern to predict two key
performance parameters: 1) the amount of scattered light that will spill past
the telescope to 300K and 2) the beam pattern expected from the receiver when
fielded on the telescope. These cryogenic measurements informed the removal of
a filter, which led to improved optical efficiency and reduced side-lobes at
the exit of the receiver. Holography measurements of this system suggest that
the spilled power past the telescope mirrors will be less than 1% and the main
beam with its near side-lobes are consistent with the nominal telescope design.
This is the first time such parameters have been confirmed in the lab prior to
deployment of a new receiver. This approach is broadly applicable to millimeter
and sub-millimeter instruments.Comment: in proces
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