The detection and characterization of U-turns during locomotion using Magneto-Inertial Measurement Units (MIMU) with the goal of segmenting the walking trial into straight walking bouts and turns is ...an open issue currently under investigation. Typically, a MIMU located on the lower back or trunk is used to this purpose and turns onset timing and duration are determined. The aim of this study was to assess if an existing method could be satisfactorily applied to signals recorded from MIMUs near the ankles. Additionally, a method is proposed with the aim of limiting the differences of its output from that of the existing method guaranteeing high robustness with respect to the MIMU location. The analysis was conducted on data recorded from healthy elderly subjects and patients with Parkinson's disease walking at two different speeds. The existing method applied to signals from the MIMU near the ankles could detect the same number of U-turns as the original. However, their onset and duration were often more than 200ms away from those obtained with the original method. Similar results were obtained with the proposed method, showing some limitations in part related to the heuristic threshold employed. However, the proposed method demonstrated a superior robustness with respect to the MIMU location. Overall, the proposed method appears to be a good starting point for the definition of a more stable and robust method for U-turn detection and characterization from signals recorded from MIMUs near the ankles.
Within the HMC algorithm, we discuss how, by using the shadow Hamiltonian and the Poisson brackets, one can achieve a simple factorization in the dependence of the Hamiltonian violations upon either ...the algorithmic parameters or the parameters specifying the integrator. We consider the simplest case of a second order (nested) Omelyan integrator and one level of Hasenbusch splitting of the determinant for the simulations of a QCD-like theory (with gauge group SU(2)). Given the specific choice of the integrator, the Poisson brackets reduce to the variances of the molecular dynamics forces. We show how the factorization can be used to optimize in a very economical and simple way both the algorithmic and the integrator parameters with good accuracy.
We consider the possibility of using reweighting techniques in order to correct for the breaking of unitarity when twisted boundary conditions are imposed on valence fermions in simulations of ...lattice gauge theories. We start by studying the properties of reweighting factors and their variances at tree-level. That leads us to the introduction of a factorization for the fermionic reweighting determinant. In the numerical, stochastic, implementation of the method, we find that the effect of reweighting is negligible in the case of large volumes but it is sizeable when the volumes are small and the twisting angles are large. More importantly, we find that for un-improved Wilson fermions, and in small volumes, the dependence of the critical quark mass on the twisting angle is quite pronounced and results in large violations of the continuum dispersion relation.
We present a practical strategy to optimize a set of Hybrid Monte Carlo parameters in simulations of QCD and QCD-like theories. We specialize to the case of mass-preconditioning, with multiple ...time-step Omelyan integrators. Starting from properties of the shadow Hamiltonian we show how the optimal setup for the integrator can be chosen once the forces and their variances are measured, assuming that those only depend on the mass-preconditioning parameter.
Imposing twisted boundary conditions on the fermionic fields is a procedure extensively used when evaluating, for example, form factors on the lattice. Twisting is usually performed for one flavour ...and only in the valence, and this causes a breaking of unitarity. In this work we explore the possibility of restoring unitarity through the reweighting method. We first study some properties of the approach at tree level and then we stochastically evaluate ratios of fermionic determinants for different boundary conditions in order to include them in the gauge averages, avoiding in this way the expensive generation of new configurations for each choice of the twisting angle, \(\theta\). As expected the effect of reweighting is negligible in the case of large volumes but it is important when the volumes are small and the twisting angles are large. In particular we find a measurable effect for the plaquette and the pion correlation function in the case of \(\theta=\pi/2\) in a volume \(16\times 8^3\), and we observe a systematic upward shift in the pion dispersion relation.
With WCDMA networks being deployed in Europe and throughout the world, one of the big challenges is to make cell reselection and handover between GSM and WCDMA work smoothly. Inter-system cell ...reselection between WCDMA and GSM enables the user equipment in idle mode to choose a new cell of another system to camp on, thus providing service availability when WCDMA coverage fades out. In this paper, we study inter-system cell reselection parameter settings by processing field measurement data collected in different networks. Performance metrics (relating to service availability and WCDMA idle mode coverage) are computed with our simulation platform to evaluate different sets of parameters in WCDMA-network-boundary, coverage-hole, and entering-a-building scenarios. Based on the simulation results, we discuss optimization trade-offs and recommend a set of parameters for each scenario
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