101 research outputs found
Phase equilibria of polydisperse hydrocarbons: moment free energy method analysis
We analyze the phase equilibria of systems of polydisperse hydrocarbons by
means of the recently introduced moment method. Hydrocarbons are modelled with
the Soave-Redlick-Kwong and Peng-Robinson equations of states. Numerical
results show no particular qualitative difference between the two equations of
states. Furthermore, in general the moment method proves to be an excellent
method for solving phase equilibria of polydisperse systems, showing excellent
agreement with previous results and allowing a great improvement in generality
of the numerical scheme and speed of computation.Comment: 12 pages, 2 figure
Blowdown of hydrocarbons pressure vessel with partial phase separation
We propose a model for the simulation of the blowdown of vessels containing
two-phase (gas-liquid) hydrocarbon fluids, considering non equilibrium between
phases. Two phases may be present either already at the beginning of the
blowdown process (for instance in gas-liquid separators) or as the liquid is
formed from flashing of the vapor due to the cooling induced by pressure
decrease. There is experimental evidence that the assumption of thermodynamic
equilibrium is not appropriate, since the two phases show an independent
temperature evolution. Thus, due to the greater heat transfer between the
liquid phase with the wall, the wall in contact with the liquid experiences a
stronger cooling than the wall in contact with the gas, during the blowdown. As
a consequence, the vessel should be designed for a lower temperature than if it
was supposed to contain vapor only. Our model is based on a compositional
approach, and it takes into account internal heat and mass transfer processes,
as well as heat transfer with the vessel wall and the external environment.
Numerical simulations show a generally good agreement with experimental
measurements.Comment: 10 pages, 3 figure
HRTFs Measurement Based on Periodic Sequences Robust towards Nonlinearities in Automotive Audio
The head related transfer functions (HRTFs) represent the acoustic path transfer functions between sound sources in 3D space and the listener’s ear. They are used to create immersive audio scenarios or to subjectively evaluate sound systems according to a human-centric point of view. Cars are nowadays the most popular audio listening environment and the use of HRTFs in automotive audio has recently attracted the attention of researchers. In this context, the paper proposes a measurement method for HRTFs based on perfect or orthogonal periodic sequences. The proposed measurement method ensures robustness towards the nonlinearities that may affect the measurement system. The experimental results considering both an emulated scenario and real measurements in a controlled environment illustrate the effectiveness of the approach and compare the proposed method with other popular approaches
Sand transport in multiphase flow mixtures in a horizontal pipeline: An experimental investigation
An inherent problem with both oil and natural gas production is the deposition of sand particles in pipeline, which could lead to problems such as excessive pressure drops, equipment failure, pipeline erosion, and production decline. The characterization of sand particles transport and sedimentation in different flow systems such as sand–multiphase mixtures is vital to predict the sand transport velocity and entrainment processes in oil and gas transportation pipelines. However, it seems that no model exists able to accurately characterize the sand transport and deposition in multiphase pipeline. In fact, in the last decade several researchers tried to extend the modeling of liquid-solid flow to gas-liquid-solid flow, but no significant results have been obtained, especially in slug flow condition due to the complexity of the phenomenon. In order to develop and validate a mathematical model properly formulated for the calculation of the sand critical deposition velocity in gas-liquid flow, more and more experimental data are necessary. This paper presents a preliminary experimental study of three phase flows (air-water-sand) inside a horizontal pipe and the application of the sand-liquid models present in literature. Significant observations were made during the experimental study from which several conclusions were drawn. Different sand flow regimes were established by physical observation and data analysis: fully dispersed solid flow, moving dunes and stationary bed. The critical deposition velocities were determined at different sand concentrations. It was concluded that sand transport characteristics and the critical deposition velocity are strongly dependent on the gas-liquid flow regime and on sand concentration. Keywords: Sand transport, Multiphase flow, Minimum transport condition, Deposition, Experimental investigation, Oil and ga
Head and neck osteosarcoma—the ongoing challenge about reconstruction and dental rehabilitation
Head and Neck osteosarcoma is an uncommon disease. Hitherto, the treatment is surgical resection and survival is influenced by the presence of free margins. However, the dimension of the resection may represent a hurdle for an adequate Quality of Life (QOL). Maxillofacial district is a narrow space where the function, esthetics and patient’s relational skills fit together like the gears of a clock. The functional results depend on the type of reconstruction and prosthetic rehabilitation that are both important to guarantee a good aesthetic result and finally increase the patient’s self-esteem. This study aims to report our experience about head and neck (HN) osteosarcoma focusing the attention on reconstructive and dental-rehabilitative problems. It is a retrospective study all patients were surgically treated in our department. Subjects with histological diagnosis of HN osteosarcoma, treated between 2005 and 2017 were included. The demographic characteristics, surgical treatment, eventually secondary reconstruction and prosthetic rehabilitation, performed in the same department, have been collected. The QOL was assessed through the EORTC QLQ-H&N35 (European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Head and Neck 35) questionnaire. Fifteen patients were enrolled, eight received a free flap microsurgical reconstruction. Dental rehabilitation was performed in five cases and a mobile prosthesis was always delivered. Eighteen implants were inserted in fibula bones for three patients; highly porous implants were use
The Large-Scale Polarization Explorer (LSPE)
The LSPE is a balloon-borne mission aimed at measuring the polarization of
the Cosmic Microwave Background (CMB) at large angular scales, and in
particular to constrain the curl component of CMB polarization (B-modes)
produced by tensor perturbations generated during cosmic inflation, in the very
early universe. Its primary target is to improve the limit on the ratio of
tensor to scalar perturbations amplitudes down to r = 0.03, at 99.7%
confidence. A second target is to produce wide maps of foreground polarization
generated in our Galaxy by synchrotron emission and interstellar dust emission.
These will be important to map Galactic magnetic fields and to study the
properties of ionized gas and of diffuse interstellar dust in our Galaxy. The
mission is optimized for large angular scales, with coarse angular resolution
(around 1.5 degrees FWHM), and wide sky coverage (25% of the sky). The payload
will fly in a circumpolar long duration balloon mission during the polar night.
Using the Earth as a giant solar shield, the instrument will spin in azimuth,
observing a large fraction of the northern sky. The payload will host two
instruments. An array of coherent polarimeters using cryogenic HEMT amplifiers
will survey the sky at 43 and 90 GHz. An array of bolometric polarimeters,
using large throughput multi-mode bolometers and rotating Half Wave Plates
(HWP), will survey the same sky region in three bands at 95, 145 and 245 GHz.
The wide frequency coverage will allow optimal control of the polarized
foregrounds, with comparable angular resolution at all frequencies.Comment: In press. Copyright 2012 Society of Photo-Optical Instrumentation
Engineers. One print or electronic copy may be made for personal use only.
Systematic reproduction and distribution, duplication of any material in this
paper for a fee or for commercial purposes, or modification of the content of
the paper are prohibite
The STRIP instrument of the Large Scale Polarization Explorer: microwave eyes to map the Galactic polarized foregrounds
In this paper we discuss the latest developments of the STRIP instrument of
the "Large Scale Polarization Explorer" (LSPE) experiment. LSPE is a novel
project that combines ground-based (STRIP) and balloon-borne (SWIPE)
polarization measurements of the microwave sky on large angular scales to
attempt a detection of the "B-modes" of the Cosmic Microwave Background
polarization. STRIP will observe approximately 25% of the Northern sky from the
"Observatorio del Teide" in Tenerife, using an array of forty-nine coherent
polarimeters at 43 GHz, coupled to a 1.5 m fully rotating crossed-Dragone
telescope. A second frequency channel with six-elements at 95 GHz will be
exploited as an atmospheric monitor. At present, most of the hardware of the
STRIP instrument has been developed and tested at sub-system level.
System-level characterization, starting in July 2018, will lead STRIP to be
shipped and installed at the observation site within the end of the year. The
on-site verification and calibration of the whole instrument will prepare STRIP
for a 2-years campaign for the observation of the CMB polarization.Comment: 17 pages, 15 figures, proceedings of the SPIE Astronomical Telescopes
+ Instrumentation conference "Millimeter, Submillimeter, and Far-Infrared
Detectors and Instrumentation for Astronomy IX", on June 15th, 2018, Austin
(TX
Tobacco, alcohol and family history of cancer as risk factors of oral squamous cell carcinoma: case-control retrospective study
The aim of the study is to observe retrospectively the correlation between Oral
Squamous Cell Carcinoma (OSCC) and risk factors; including tobacco, alcohol and Family History
of Cancer (FHC). A total of 478 patients were included retrospectively from the database of the
Department of Oral Sciences and Maxillofacial Surgery, Sapienza University of Rome. A Test
Group (TG) consisted of 239 patients with a confirmed diagnosis of OSCC. A Control Group (CG)
consisted of 239 patients without history and/or diagnosis of oral cancer. The logistic regression
models were used to calculate the adjusted Odd Ratios (ORs) associated with alcohol, tobacco and
FHC; including the General Family History of Cancer (GFHC) and Family History of Head and
Neck Cancer (FHHNC) and their 95% Confidence Intervals (CI). The high rate of tobacco
consumption was associated with an OR of 1.035 (95% CI 1.001–1.070) and a statistical significance
(p = 0.041). Drinker patients showed a significant risk of developing OSCC (p = 0.05) and the OR
was 1.035 (95% CI 1.010–1.061). The GFHC was associated with a marginal risk of OSCC with an
OR of 1.095 (95% CI 0.953–1.259), without significance (p = 0.199). The FHHNC showed a notable
risk increase with an OR of 1.871 (95% CI 0.902–3.882), without significance (p = 0.092). Alcohol
and tobacco may be associated with an increase in the risk of OSCC
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