Search results for "Filter"
showing 10 items of 1019 documents
Introduction: Periodic Filters and Filter Banks
2014
In this chapter filtering of periodic signals is outlined. Periodic filters and periodic filter banks are defined. Perfect reconstruction filter banks are characterized via their polyphase matrices.
An EKF Based Method for Path Following in Turbulent Air
2017
An innovative use of the Extended Kalman Filter (EKF) is proposed to perform both accurate path following and adequate disturbance rejection in turbulent air. The tuned up procedure employs simultaneously two different EKF: the first one estimates gust disturbances, the second one estimates modified aircraft parameters. The first filter, by using measurements gathered in turbulent air, estimates both aircraft states and wind components. The second one, by using the estimated disturbances, obtains command laws that are able to reject disturbances. The predictor of the second EKF uses the estimated wind components to solve motion equations in turbulent air. Besides a set of unknown stability …
Automatic EKF tuning for UAS path following in turbulent air
2018
By using two simultaneously working Extended Kalman Filters, a procedure is implemented in order to perform in a fully autonomous way the path following in turbulent air. To guarantee the robustness of the proposed algorithm, an automatic tuning procedure is proposed to determine optimal values of Process and Measurement Noise statistics. Such a procedure is based on both the characteristics of the disturbances and the desired flight path; in particular, a specific performance index is applied to tune filters. In this way control laws are adapted to the flight condition and these lead to an optimal path-following. This research represents an upload of previous papers. It allows eliminating …
Time-resolved velocity measurements in a magnetic micromixer
2015
Abstract Mixing efficiency is lower in passive micromixers due to viscous forces and substantial research effort is focused on designing high performance micromixers. Active micromixers make use of external forces to enhance mixing efficiency. Among these, magnetic forces are popular because they are non-contact and therefore the micromixer design can be kept simple. Laser-based diagnostic tools have great potential in providing multi-parameter information in microfluidics research on mixing. MicroPIV experiments are performed to investigate the transient flow field in a magnetic micromixer undergoing labyrinthine instability. Velocity and interface front information is extracted from a seq…
The crowd against the few: Measuring the impact of expert recommendations
2020
Abstract A large amount of research on recommender systems has focused on improving the accuracy of suggestions in offline settings. However, this focus and the commonly used techniques can lead to a “filter bubble”, severely limiting the diversity of content discovered by users. Several offline studies show that this can be mitigated by using experts for recommendation. In contrast to standard recommender systems, experts are able to generate more diverse recommendations and increase the novelty of given suggestions. They can be used in missing-data or cold-start scenarios and reduce noise in the users' ratings. This paper examines the impact of employed experts' recommendations on user be…
Improving Serendipity and Accuracy in Cross-Domain Recommender Systems
2017
Cross-domain recommender systems use information from source domains to improve recommendations in a target domain, where the term domain refers to a set of items that share attributes and/or user ratings. Most works on this topic focus on accuracy but disregard other properties of recommender systems. In this paper, we attempt to improve serendipity and accuracy in the target domain with datasets from source domains. Due to the lack of publicly available datasets, we collect datasets from two domains related to music, involving user ratings and item attributes. We then conduct experiments using collaborative filtering and content-based filtering approaches for the purpose of validation. Ac…
A validated search filter for the identification of endocrine disruptors based on the ECHA/EFSA guidance recommendations.
2020
Abstract A guidance document for the identification of endocrine disruptors (EDs) in the regulatory assessment of plant protection products (PPP) and biocidal products (BP) has been published by the European Chemical Agency (ECHA) and the European Food Safety Authority (EFSA). The ECHA/EFSA guidance, mainly addressing EATS (estrogen, androgen, thyroid, steroidogenesis) modalities, is intended to guide applicants and assessors of the competent regulatory authorities on the implementation of the scientific criteria for the determination of ED properties pursuant to the recently implemented PPP ( EU 2018/605 ) and BP ( EU 2017/2100 ) EU Regulations. In this study, a search filter for targeted …
Bidirectional high-power high-efficiency non-isolated step-up DC-DC converter
2006
This paper presents the results of a high-efficiency high-power (5kW) non-isolated bidirectional DC-DC converter. High efficiency, high stability and simplicity are the main goals, and no galvanic isolation is required. The proposed topology is a new BOOST converter with output filter where input and output inductors are coupled together which can be designed to be a minimum phase system. This topology provides therefore input and output current filtering, reducing noise and need of additional filters. Its bidirectionality reduces mass in many applications like in charge/discharge subsystems and lowers cost and component count. This converter is useful with any system that needs backup batt…
k-Space filtering in 2D gradient-echo breath-hold hyperpolarized3He MRI: Spatial resolution and signal-to-noise ratio considerations
2002
In this work some of the factors that can influence the signal-to-noise ratio (SNR) and spatial resolution in MR images of inhaled hyperpolarized gases are systematically addressed. In particular, the effects of RF depletion of longitudinal polarization and image gradient diffusion dephasing were assessed in terms of their contribution to a k-space filter. By means of theoretical simulations and a novel method of experimental validation using a variable transverse magnetization of the 1H signal, systematic quantitative and qualitative investigations of the effects of k-space filtering intrinsic to imaging of hyperpolarized gas were made. A 2D gradient-echo image is considered for a range of…
Filter equation by fractional calculus
2014
Aim of this paper is to represent a causal filter equation for any kind of linear system in the general form L=f(t), where f(t) is the forcing function, x(t) is the output and L is a summation of fractional operators. The exact form of the operator L is obtained by using Mellin transform in complex plane.