1,955 research outputs found
Phase Diagram and Incommensurate Phases in Undoped Manganites
We study the existence of incommensurate phases in the phase diagram of the
two orbital double exchange model coupled with Jahn-Teller phonons and with
superexchange interactions. In agreement with experimental results, we find
that undoped manganites ( being some rare earth element) show
temperature induced commensurate-incommensurate phase transitions. In the
incommensurate phase the magnetic wave vector varies with temperature. The
incommensurate phase arises from the competition between the short range
antiferromagnetic superexchange interaction and the long range ferromagnetic
double exchange interaction
Self-Reported Violence Experienced by Swiss Prehospital Emergency Care Providers.
Workplace violence is a serious and increasing problem in health care. Nevertheless, only few studies were carried out concerning this topic and then mainly in English-speaking countries. The objectives were to describe the acts of violence experienced by prehospital emergency care providers (PECPs) in the western part of Switzerland between January and December 2016 and to assess the consequences for subsequent PECPs behaviors.
An observational cross-sectional study, carried out using an online survey, has been sent to all 416 PECPs in the Canton of Vaud, in the western, French-speaking, part of Switzerland. The survey contained items of demographic data and items to assess the type and consequence of violence sustained. This was classified as five types: verbal assault, intimidation, physical assault, sexual harassment, and sexual assault.
273 (65.6%) PECPs participated in the survey. During 2016, workplace violence was reported by 229 survey participants (83.9%). Most declared to be the victim of such violence between one and three times during the year. In all cases of violence described, the patient and/or a relative initiated aggressive behavior in 96% of cases. Verbal assaults were the most common (99.2% of all acts), followed by intimidation (72.8%), physical assault (69.6%), and sexual harassment (16.3%). Concerning physical assault, PECPs were predominantly victims of spitting and/or jostling (50%). After a violent event, in 50% of cases, the PECPs modified their behavior owing to the experience of workplace violence; 82% now wear protective vests, and 16% carry weapons for self-defense, such as pepper sprays. Seventy-five percent changed their intervention strategies, acting more carefully and using verbal de-escalation techniques or physical restraints for violent patients.
Workplace violence is frequent and has significant consequences for PECPs. In order to increase their own security, they increased their protection. These results illustrate their feelings of insecurity, which may have deleterious effects on work satisfaction and motivation. Trial Registration. Our article does not report the results of a health care intervention on human participants
Meta Learning MPC using Finite-Dimensional Gaussian Process Approximations
Data availability has dramatically increased in recent years, driving
model-based control methods to exploit learning techniques for improving the
system description, and thus control performance. Two key factors that hinder
the practical applicability of learning methods in control are their high
computational complexity and limited generalization capabilities to unseen
conditions. Meta-learning is a powerful tool that enables efficient learning
across a finite set of related tasks, easing adaptation to new unseen tasks.
This paper makes use of a meta-learning approach for adaptive model predictive
control, by learning a system model that leverages data from previous related
tasks, while enabling fast fine-tuning to the current task during closed-loop
operation. The dynamics is modeled via Gaussian process regression and,
building on the Karhunen-Lo{\`e}ve expansion, can be approximately reformulated
as a finite linear combination of kernel eigenfunctions. Using data collected
over a set of tasks, the eigenfunction hyperparameters are optimized in a
meta-training phase by maximizing a variational bound for the log-marginal
likelihood. During meta-testing, the eigenfunctions are fixed, so that only the
linear parameters are adapted to the new unseen task in an online adaptive
fashion via Bayesian linear regression, providing a simple and efficient
inference scheme. Simulation results are provided for autonomous racing with
miniature race cars adapting to unseen road conditions
Zone center phonons of the orthorhombic RMnO3 (R = Pr, Eu, Tb, Dy, Ho) perovskites
A short range force constant model (SRFCM) has been applied for the first
time to investigate the phonons in RMnO3 (R = Pr, Eu, Tb, Dy, Ho) perovskites
in their orthorhombic phase. The calculations with 17 stretching and bending
force constants provide good agreement for the observed Raman frequencies. The
infrared frequencies have been assigned for the first time.
PACS Codes: 36.20.Ng, 33.20.Fb, 34.20.CfComment: 8 pages, 1 figur
Zero-Order Optimization for Gaussian Process-based Model Predictive Control
By enabling constraint-aware online model adaptation, model predictive
control using Gaussian process (GP) regression has exhibited impressive
performance in real-world applications and received considerable attention in
the learning-based control community. Yet, solving the resulting optimal
control problem in real-time generally remains a major challenge, due to i) the
increased number of augmented states in the optimization problem, as well as
ii) computationally expensive evaluations of the posterior mean and covariance
and their respective derivatives. To tackle these challenges, we employ i) a
tailored Jacobian approximation in a sequential quadratic programming (SQP)
approach, and combine it with ii) a parallelizable GP inference and automatic
differentiation framework. Reducing the numerical complexity with respect to
the state dimension for each SQP iteration from to
, and accelerating GP evaluations on a graphical processing
unit, the proposed algorithm computes suboptimal, yet feasible solutions at
drastically reduced computation times and exhibits favorable local convergence
properties. Numerical experiments verify the scaling properties and investigate
the runtime distribution across different parts of the algorithm.Comment: accepted for European Journal of Control (EJC), ECC 2023 Special
Issu
A predictive safety filter for learning-based racing control
The growing need for high-performance controllers in safety-critical
applications like autonomous driving has been motivating the development of
formal safety verification techniques. In this paper, we design and implement a
predictive safety filter that is able to maintain vehicle safety with respect
to track boundaries when paired alongside any potentially unsafe control
signal, such as those found in learning-based methods. A model predictive
control (MPC) framework is used to create a minimally invasive algorithm that
certifies whether a desired control input is safe and can be applied to the
vehicle, or that provides an alternate input to keep the vehicle in bounds. To
this end, we provide a principled procedure to compute a safe and invariant set
for nonlinear dynamic bicycle models using efficient convex approximation
techniques. To fully support an aggressive racing performance without
conservative safety interventions, the safe set is extended in real-time
through predictive control backup trajectories. Applications for assisted
manual driving and deep imitation learning on a miniature remote-controlled
vehicle demonstrate the safety filter's ability to ensure vehicle safety during
aggressive maneuvers
Involuntary admissions to the emergency department: a retrospective observational study.
The main objective of this study was to describe patients who were involuntarily admitted to the emergency department of Lausanne University Hospital on involuntary admission in 2018 in terms of age, gender, emergency department length of stay, the motive for involuntary admission, use of psychoactive substances, diagnosis, and destination at emergency department discharge, with or without discontinuation of involuntary admission.
This retrospective, observational, and monocentric study included patients 18 years and older admitted to the emergency department of Lausanne University Hospital on involuntary admission from January 1, 2018, to December 31, 2018. Patients were identified by the Cantonal Medical Office of Vaud. The emergency department length of stay and patient destination on discharge from the emergency department were extracted from the patient flow database, and discharge letters and involuntary admission were extracted from the electronic archiving software. Descriptive statistics were processed by using means and standard deviations for quantitative variables with a normal distribution and median and interquartile range for non-normally distributed data.
During the study period, 83 patients were admitted on involuntary admission to the emergency department. The majority of the patients were male (58%) with a mean age of 55 (±20) years. The median emergency department length of stay of patients with an involuntary admission was between 9 and 16 hours, depending on whether the involuntary admission was confirmed or discontinued after patient assessment in the emergency department. In comparison, the median emergency department length of stay was 6 hours for patients overall. The two principal diagnoses described were psychiatric (schizophrenia) and mental and behavioural disorders due to psychoactive substance use. Half of the patients on involuntary admission consumed psychoactive substances, primarily alcohol, and had a mean ethanolaemia of 53 (±32) mmol/l.
Only a third of patients admitted on involuntary admission saw this measure confirmed after their assessment in the emergency department. Involuntary admissions with admission to the emergency department is used to force patients to be examined by an emergency physician or even a psychiatrist. On-call and primary care physicians seemed to lack the time or resources to set up alternatives to emergency department admissions on involuntary admission, especially in situations in which the involuntary admission was discontinued after an emergency department assessment. This demonstrates the inappropriate use of this measure because a patient cannot be involuntarily hospitalised in an emergency department
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