4,963 research outputs found
Risk analysis of LPG tanks at the wildland-urban interface
In areas of wildland-urban interface (WUI), especially residential developments, it is very
common to see liquefied petroleum gas (LPG) tanks, particularly with a higher ratio of
propane, in surface installations serving homes. The most common tanks are between 1 and 5
m3 of capacity, but smaller ones of less than 1 m3 are more frequent. In case of accident,
installations may be subject to fires and explosions, especially in those circumstances where
legal and normative requirements allow very close exposure to flames from vegetable fuel
near LPG tanks.
In this project, it is intended to do a comprehensive diagnosis of the problem, addressing
the compilation of information on real risk scenarios in historical fires. First, a preliminary
presentation of the properties and characteristics of liquefied petroleum gas will be exposed.
Its physical and chemical properties, production methodology, pressure and temperature
diagrams and important considerations will be defined when using this type of substances in a
storage tank of a certain volume.
Next, a review of the situation of the existence of LPG tanks in the urban forest interfaces
will be exposed. In this case, the main accidents caused by problems with the storage of LPG
will be analyzed taking into account the relevance of BLEVE events in this type of incidents. To
do this, the main scenarios that could take place in the event of a fire will be presented.
Next, the existing legislation on the storage of LPG in these environments in some
Mediterranean countries will be studied. In order to develop a comprehensive analysis, the
main safety measures and distances will be considered, as well as the awareness of the
possibility of vegetation material in the vicinity of LPG storage tanks, which is the main
problem that will arise in a possible BLEVE scenario in case of fire. To finalize and facilitate
understanding, a comparative table will be included with the aim of visualizing the main
advantages and legislative deficiencies between the different countries.
Following, the state of the art in terms of modelling LPG accidents at the WUI will be
reviewed. Trying to simulate and predict this type of scenarios, it will see the models normally
chosen to obtain the tolerable values selected and the answers obtained in each case.
Finally, several fire scenarios will be simulated by means of a CFD tool (FDS, Fire Dynamics
Simulator). In these simulations, the wind velocity and the distance of the combustible vegetal
mass to the tank will be controlled in a WUI fire in which there is a tank of fixed dimensions.
The temperature and the heat flow in each of the scenarios will be obtained, and the
differences among the location of the sensors and the characteristics of the scenario will be
analyzed.
As a conclusion, it has been observed that there is a great amount of variables that are
not contemplated by the regulatory organisms and that the existing legislation does not
guarantee the safety of the population in this type of environment. From the simulations
results, variables as temperature should be studied for further characterizations
Characterization of a CMUT Array
Ultrasound transducers are used in a broad range of applications covering from underwater communications to medical imaging and treatment. The ultrasonic transducer determines the key specifications such as resolution, sensitivity and signal to noise ratio. The capacitive micromachined ultrasonic transducer (CMUT) has emerged as an alternative to standard piezoelectric transducers due to advanced microelectronics fabrication technology and methods. Comparing to piezoelectric transducers, the CMUT is superior to it\u27s competitor with higher acoustic bandwidth, higher sensitivity and greater coupling with the acoustic medium. Design, fabrication, and characterization of a capacitive micromachined ultrasonic transducer (CMUT) array have been presented along this thesis. The array is designed to operate in the frequency range of 113-167 kHz. The CMUT array is fabricated using an SOI based fabrication technology and includes 6x6 CMUTs. Necessary test setups and readout circuitry is designed in order to carry out the characterization process. Static analysis results are verified with Wyko optical profilometer, Agilent LCR meter and SEM analysis. Dynamic characterizations are done with Polytec MSA-4 laser Doppler vibrometer. An efficient and low noise capacitive readout circuit is designed using transimpedance amplifier scheme with 75 kilo ohm gain and fabricated on a PCB. The developed analytical models, FEA and experimental results are in very good agreement to exhibit accuracy of the design methodology
Printed Circuit Board (PCB) design process and fabrication
This module describes main characteristics of Printed Circuit Boards (PCBs). A brief history of PCBs is introduced in the first chapter. Then, the design processes and the fabrication of PCBs are addressed and finally a study case is presented in the last chapter of the module.Peer ReviewedPostprint (published version
Reliability Assessment of Voided Microvias in High Density Interconnect Printed Circuit Boards under Thermo-Mechanical Stresses
Microvias allow signal and power transmission between layers in high density interconnection printed circuit boards. Presence of voiding in filled microvias due to defective manufacturing process has raised concerns in industry. Voids can vary widely in shape and size and have been observed in both stacked and single-level microvias. IPC standards have addressed the presence of voids in microvias using void size as the acceptance criterion. The purpose of this study is to determine how voiding affects the degradation of microvias; if void size is the only parameter that needs to be taken into consideration or void shape is important as well. Voided as well as non-voided microvias were tested using liquid-to-liquid thermal shock to understand the difference between behavior of voided and non-voided microvias under thermo-mechanical stresses
Self-packaged miniature microwave filters based on multilayer liquid crystal polymer technology
The following thesis is concerned with the development of fabrication techniques
and novel designs for self-packaged, multilayer circuits using liquid crystal polymer
(LCP) materials exclusively, given the favourable characteristics this material has
for microwave circuits.
Fabrication techniques are aimed at the production of miniature, low-profile filters.
Advanced techniques for production of interlayer via connections are investigated
and new methods proposed, with special attention at the lamination process and
production of vertical, inter-layer transitions. Results obtained demonstrate the
fabrication process is reliable for producing multilayer filters, with up to four metal
layers, and via transitions in the region of 0.2 mm diameter.
The fabrication process has been developed during this work is applied to novel filter
designs, covering dual-band filters and lowpass filters. A new structure for dual-
band filter is proposed, using folded multimode resonators (FMSIR). This structure
is validated through the fabrication of two different filters with passbands 1.2/2.4
GHz, and 2.4/5 GHz, showing deep off-band rejection.
Low pass structure covered in this thesis is based on the principle of destructive
interference and aims at low insertion loss and out-of-band rejection higher than
40 dB. Fabricated samples validate the design showing a rejection in the region of
42 dB, with a cuto frequency of 3 GHz. Its small footprint and low insertion loss
allows this type of lters to be used as cleanup filters. All the designs covered in
this work are simulated using CAD tools and then validated by measurements on
fabricated samples
Signal Integrity Optimization of RF/Microwave Transmission Lines in Multilayer PCBs
While allowing for flexible trace routing and device miniaturization, multilayer printed circuit boards (PCB) suffer from performance issues at high frequency due to the impedance mismatch caused by vertical transitions. In this paper, a process for optimizing the high-speed performance of microstrip to stripline transitions in multilayer PCBs is demonstrated. This includes strategic tuning of via dimensions using time-domain reflectometry and an analysis of the use of shielding vias to prevent parasitic cavity resonance. Simulations of optimized 2-layer, 4-layer, and 6-layer microstrip to stripline transitions show a return loss of 20 dB up to 7 GHz. To demonstrate a useful microwave application, a planar filter with a passband of 4 GHz to 6 GHz is submerged 6-layers. The simulation shows that when paired with the optimized vertical transitions, the filter can maintain performance
Convolutional neural networks: a magic bullet for gravitational-wave detection?
In the last few years, machine learning techniques, in particular
convolutional neural networks, have been investigated as a method to replace or
complement traditional matched filtering techniques that are used to detect the
gravitational-wave signature of merging black holes. However, to date, these
methods have not yet been successfully applied to the analysis of long
stretches of data recorded by the Advanced LIGO and Virgo gravitational-wave
observatories. In this work, we critically examine the use of convolutional
neural networks as a tool to search for merging black holes. We identify the
strengths and limitations of this approach, highlight some common pitfalls in
translating between machine learning and gravitational-wave astronomy, and
discuss the interdisciplinary challenges. In particular, we explain in detail
why convolutional neural networks alone cannot be used to claim a statistically
significant gravitational-wave detection. However, we demonstrate how they can
still be used to rapidly flag the times of potential signals in the data for a
more detailed follow-up. Our convolutional neural network architecture as well
as the proposed performance metrics are better suited for this task than a
standard binary classifications scheme. A detailed evaluation of our approach
on Advanced LIGO data demonstrates the potential of such systems as trigger
generators. Finally, we sound a note of caution by constructing adversarial
examples, which showcase interesting "failure modes" of our model, where inputs
with no visible resemblance to real gravitational-wave signals are identified
as such by the network with high confidence.Comment: First two authors contributed equally; appeared at Phys. Rev.
Astronomical photonics in the context of infrared interferometry and high-resolution spectroscopy
We review the potential of Astrophotonics, a relatively young field at the
interface between photonics and astronomical instrumentation, for
spectro-interferometry. We review some fundamental aspects of photonic science
that drove the emer- gence of astrophotonics, and highlight the achievements in
observational astrophysics. We analyze the prospects for further technological
development also considering the potential synergies with other fields of
physics (e.g. non-linear optics in condensed matter physics). We also stress
the central role of fiber optics in routing and transporting light, delivering
complex filters, or interfacing instruments and telescopes, more specifically
in the context of a growing usage of adaptive optics.Comment: SPIE Astronomical Telescopes and Instrumentation conference, June
2016, 21 pages, 10 Figure
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