2,891 research outputs found
RAVEN: a GUI and an Artificial Intelligence Engine in a Dynamic PRA Framework
Increases in computational power and pressure for
more accurate simulations and estimations of accident scenario consequences are driving the need for Dynamic
Probabilistic Risk Assessment (PRA) [1] of very complex models. While more sophisticated algorithms and
computational power address the back end of this challenge, the front end is still handled by engineers that
need to extract meaningful information from the large amount of data and build these complex models.
Compounding this problem is the difficulty in knowledge transfer and retention, and the increasing speed of
software development. The above-described issues would have negatively
impacted deployment of the new high fidelity plant simulator RELAP-7 (Reactor Excursion and Leak
Analysis Program) at Idaho National Laboratory. Therefore, RAVEN that was initially focused to be the
plant controller for RELAP-7 will help mitigate future
RELAP-7 software engineering risks. In order to accomplish such a task Reactor Analysis
and V
Hot Zero and Full Power Validation of PHISICS RELAP-5 Coupling
PHISICS is a reactor analysis toolkit developed over
the last 3 years at the Idaho National Laboratory. It has
been coupled with the reactor safety analysis code
RELAP5-3D. PHISICS is aimed at providing an optimal
trade off between needed computational resources (in the
range of 10~100 computer processors) and accuracy. In
fact, this range has been identified as the next 5 to 10
years average computational capability available to
nuclear reactor design and optimization nuclear reactor
cores.
Detailed information about the individual modules of
PHISICS can be found in [1]. An overview of the
modules used in this study is given in the next subsection.
Lately, the Idaho National Laboratory gained access plant
data for the first cycle of a PWR, including Hot Zero
Power (HZP) and Hot Full Power (HFP).
This data provides the opportunity to validate the
transport solver, the interpolation capability for mixed
macro and micro cross section and the criticality search
option of the PHISICS pack
Drift dependence of optimal trade execution strategies under transient price impact
We give a complete solution to the problem of minimizing the expected
liquidity costs in presence of a general drift when the underlying market
impact model has linear transient price impact with exponential resilience. It
turns out that this problem is well-posed only if the drift is absolutely
continuous. Optimal strategies often do not exist, and when they do, they
depend strongly on the derivative of the drift. Our approach uses elements from
singular stochastic control, even though the problem is essentially
non-Markovian due to the transience of price impact and the lack in Markovian
structure of the underlying price process. As a corollary, we give a complete
solution to the minimization of a certain cost-risk criterion in our setting
What is the best approach for managing recurrent bacterial vaginosis?
The best way to prevent recurrent bacterial vaginosis is to treat the initial episode with the most effective regimen. Metronidazole (500 mg orally twice daily for 7 days) has the lowest recurrence rate among antimicrobial regimens for bacterial vaginosis (20% vs 34%-50% for other agents) (strength of recommendation [SOR]: A). Women should be treated if they are symptomatic (SOR: A), undergoing gynecologic surgery (SOR: B), or at risk for preterm labor (SOR: B)
Dynamic PRA: an Overview of New Algorithms to Generate, Analyze and Visualize Data
State of the art PRA methods, i.e. Dynamic PRA
(DPRA) methodologies, largely employ system
simulator codes to accurately model system dynamics.
Typically, these system simulator codes (e.g., RELAP5 )
are coupled with other codes (e.g., ADAPT,
RAVEN that monitor and control the simulation. The
latter codes, in particular, introduce both deterministic
(e.g., system control logic, operating procedures) and
stochastic (e.g., component failures, variable uncertainties)
elements into the simulation. A typical DPRA analysis is
performed by:
1. Sampling values of a set of parameters from the
uncertainty space of interest
2. Simulating the system behavior for that specific set of
parameter values
3. Analyzing the set of simulation runs
4. Visualizing the correlations between parameter values
and simulation outcome
Step 1 is typically performed by randomly sampling
from a given distribution (i.e., Monte-Carlo) or selecting
such parameter values as inputs from the user (i.e.,
Dynamic Event Tre
MIRTO: a prototype for real-time ionospheric imaging over the Mediterranean area
MIRTO (Mediterranean Ionosphere with Real-time TOmography) is a collaborative project between Istituto
Nazionale di Geofisica (INGV) of Rome, the University of Bath (U.K.) and the Istituto Fisica Applicata «Nello
Carrara»-Consiglio Nazionale delle Ricerche (IFAC-CNR) of Florence. The goal of the project is the development
of a prototype for real-time imaging of the ionosphere over the Italian region with extension to the Mediterranean
Sea. MIRTO uses an original imaging technique developed at the University of Bath and upgraded for
real-time use in cooperation with IFAC. The prototype makes use of the data acquired by the real-time ionospheric
and geodetic instrumentation operated by INGV. Such measurements drive the imaging algorithm to produce
the image of electron density as well as maps and movies of the Total Electron Content (TEC) over the considered
area
GNSS data filtering optimization for ionospheric observation
In the last years, the use of GNSS (Global Navigation Satellite Systems) data has been gradually increasing, for both scientific studies
and technological applications. High-rate GNSS data, able to generate and output 50-Hz phase and amplitude samples, are commonly
used to study electron density irregularities within the ionosphere. Ionospheric irregularities may cause scintillations, which are rapid and
random fluctuations of the phase and the amplitude of the received GNSS signals.
For scintillation analysis, usually, GNSS signals observed at an elevation angle lower than an arbitrary threshold (usually 15 , 20 or
30 ) are filtered out, to remove the possible error sources due to the local environment where the receiver is deployed. Indeed, the signal
scattered by the environment surrounding the receiver could mimic ionospheric scintillation, because buildings, trees, etc. might create
diffusion, diffraction and reflection.
Although widely adopted, the elevation angle threshold has some downsides, as it may under or overestimate the actual impact of
multipath due to local environment. Certainly, an incorrect selection of the field of view spanned by the GNSS antenna may lead to
the misidentification of scintillation events at low elevation angles.
With the aim to tackle the non-ionospheric effects induced by multipath at ground, in this paper we introduce a filtering technique,
termed SOLIDIFY (Standalone OutLiers IDentIfication Filtering analYsis technique), aiming at excluding the multipath sources of
non-ionospheric origin to improve the quality of the information obtained by the GNSS signal in a given site. SOLIDIFY is a statistical
filtering technique based on the signal quality parameters measured by scintillation receivers. The technique is applied and optimized on
the data acquired by a scintillation receiver located at the Istituto Nazionale di Geofisica e Vulcanologia, in Rome. The results of the
exercise show that, in the considered case of a noisy site under quiet ionospheric conditions, the SOLIDIFY optimization maximizes
the quality, instead of the quantity, of the data.Published2552–25622A. Fisica dell'alta atmosferaJCR Journa
BIOLOGÍA EVOLUTIVA. ¿CÓMO DEBEMOS ENSEÑARLA?
This article aims to stimulate and enhance the teaching of evolution. It is known that teaching of science in general, and biology and evolution in particular, should be a basic ingredient for achieving the scientific literacy, incorporating the curiosity, skepticism and a critical attitude. It presents a vision of how should be the teaching of evolutionary biology, where the student must learn to seek the truth through discussion, research and experimentation. This is a challenge that can only be faced with the joint action of the ministries of education, the pedagogic institutes, colleges and universities.Con este artículo se pretende estimular y mejorar la enseñanza de la evolución. Es conocido que la enseñanza de las ciencias en general, de la biología y de la evolución en particular debe ser un ingrediente básico, para el logro del alfabetismo científico, incorporando la curiosidad, el escepticismo y una actitud crítica. Se presenta una visión de lo que debería ser la enseñanza de la Biología Evolutiva, donde el estudiante debe aprender a buscar la verdad, mediante la discusión, la investigación y la experimentación. Este, es un verdadero reto que solamente puede ser enfrentado con la acción conjunta de los ministerios de educación, los pedagógicos y las universidades
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