Search results for "transfer function"
showing 10 items of 152 documents
Image quality with multifocal intraocular lenses and the effect of pupil size
2007
Purpose To analyze the image quality with a refractive and 2 hybrid refractive–diffractive multifocal intraocular lenses (IOLs) in vitro to determine the IOL modulation transfer function (MTF) following the EN-ISO international standard for distance and near vision and to study the IOLs' behavior with different pupil sizes. Setting Fundacion Oftalmologica del Mediterraneo, Valencia, Spain. Methods This study evaluated 4 IOLs: the hybrid refractive–diffractive AcrySof ReSTOR SN60D3 (Alcon) and Tecnis ZM900 (AMO), the refractive ReZoom NXG (AMO), and the monofocal AcrySof SN60WF (Alcon). The MTF was calculated from the cross-line spread function recorded with the OPAL Vector System (Image Sci…
Imaging Quality of Bifocal Piggyback Intraocular Lens versus ReSTOR and TECNIS Multifocal Lenses
2009
Purpose The imaging quality provided by a piggyback integrated by a monofocal intraocular lens (IOL) + a bifocal IOL of zero power and +3.75 diopters of addition is compared with the optics quality of a simple multifocal IOL of the same power and addition. Methods The imaging quality was evaluated by determining the modulation transfer function (MTF), using an artificial eye simulating in vivo conditions of the anterior chamber, including an artificial cornea and a wet cell containing physiologic solution where the IOL was positioned. The MTFs of the bifocal piggyback for near and distance vision were measured, with pupil diameters of 3 and 5 mm, and compared with the MTFs of an equivalent …
Efficient MLP Digital Implementation on FPGA
2005
The efficiency and the accuracy of a digital feed-forward neural networks must be optimized to obtain both high classification rate and minimum area on chip. In this paper an efficient MLP digital implementation. The key features of the hardware implementation are the virtual neuron based architecture and the use of the sinusoidal activation function for the hidden layer. The effectiveness of the proposed solutions has been evaluated developing different FPGA based neural prototypes for the High Energy Physics domain and the automatic Road Sign Recognition domain. The use of the sinusoidal activation function decreases hardware resource employment of about 32% when compared with the standar…
To Assess the Validity of the Transfer Function Method: A Neural Model for the Optimal Choice of Conduction Transfer Functions
2010
This paper presents a new mathematical approach applied to the Conduction Transfer Functions (CTFs) of a multilayered wall to predict the reliability of building simula- tions based upon them. Such a procedure can be used to develop a decision support system that identifies the best condition to calculate the best CTFs set. This is a critical point at the core of ASHRAE calculation methodology founded on the Transfer Function Method (TFM). To evaluate the perfor- mance of different CTFs sets, the authors built a large amount of data, subsequently employed to train a Neural Network Classifier (NNC) able to predict the reliability of a simulation without performing it. For this purpose all th…
An RF-Based Positioning Method for Tracing a Cluster of Moving Scatterers in Non-Stationary Indoor Environments
2021
Author's accepted manuscript © 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works. This letter presents a novel iterative positioning method for tracing the body segments of a person moving indoors using radio-frequency (RF) signals. The indoor space is equipped with a multiple-input multiple-output (MIMO) communication system. The person is modelled by a cluster of …
A Trajectory-Driven 3D Channel Model for Human Activity Recognition
2021
This paper concerns the design, analysis, and simulation of a 3D non-stationary channel model fed with inertial measurement unit (IMU) data. The work in this paper provides a framework for simulating the micro-Doppler signatures of indoor channels for human activity recognition by using radiofrequency-based sensing technologies. The major human body segments, such as wrists, ankles, torso, and head, are modelled as a cluster of moving point scatterers. We provide expressions for the time variant (TV) speed and TV angles of motion based on 3D trajectories of the moving person. Moreover, we present mathematical expressions for the TV Doppler shifts and TV path gains associated with each movin…
Simple computation of the approximated modulation transfer function (MTF) using spreadsheet-software: method and evaluation in five maxillofacial CBC…
2019
OBJECTIVES: To develop a simple way to compute the approximated modulation transfer function (MTF) manually using conventional spreadsheet software. METHODS: Basing on an edge-image a method was developed, facilitating computation of the edge spread and line spread function in open-source spreadsheet software (Gnumeric; http://projects.gnome.org/gnumeric/downloads.shtml). By means of the integrated fast Fourier transformation Fourier coefficients are obtained from the line spread function which can then be plotted vs spatial frequency to obtain MTF-plots. For the experimental evaluation an edge test object was exposed in five commercial CBCT devices for maxillofacial applications. RESULTS: …
Introduction: Digital Filters and Filter Banks
2015
A basic operation of spectr is filterin. In this introductory chapter, processing of one- and two-dimensional signals by digital filters and filter banks is outlined. A polyphase implementation of multirate filtering is described. The application of filtering with IIR filters, whose transfer functions are rational, is described. Bases and frames in the signals’ space that are generated by perfect reconstruction filter banks are discussed. The Butterworth filters, which are used in further constructions, are introduced.
A Parallel Approach to HRTF Approximation and Interpolation Based on a Parametric Filter Model
2017
[EN] Spatial audio-rendering techniques using head-related transfer functions (HRTFs) are currently used in many different contexts such as immersive teleconferencing systems, gaming, or 3-D audio reproduction. Since all these applications usually involve real-time constraints, efficient processing structures for HRTF modeling and interpolation are necessary for providing real-time binaural audio solutions. This letter presents a parametric parallel model that allows us to perform HRTF filtering and interpolation efficiently from an input HRTF dataset. The resulting model, which is an adaptation from a recently proposed modeling technique, not only reduces the size of HRTF datasets signific…
Development and analysis of the Soil Water Infiltration Global database
2018
27 Pags.- 11 Tabls.- 8 Figs. © Author(s) 2018. This work is distributed under the Creative Commons Attribution 4.0 License.