Search results for "High frequency"

Magnetic Resonance Imaging and Computational Fluid Dynamics of High Frequency Oscillatory Ventilation (HFOV)

2011

In order to better understand the mechanisms of gas transport during High Frequency Oscillatory Ventilation (HFOV) Magnetic Resonance Imaging (MRI) with contrast gases and numerical flow simulations based on Computational Fluid Dynamics(CFD) methods are performed.

High-frequency even harmonics generation in a plasma with electron heat flux

2004

It is shown that in a weakly nonuniform plasma with electron heat flux the generation of odd and even harmonics of high frequency radiation is possible. The even harmonics properties qualitatively differ as compared to those of odd harmonics and depend in an essential way on the heat flux value and orientation with respect to the fundamental wave polarization and propagation directions.

Constrained-Design of Passive UHF RFID Sensor Antennas

2013

Passive UHF RFID tags may be used, beside labeling, to remotely observe the physical/chemical change of the tagged object, through modulation of their impedance and gain, thus acting as sensor antennas. The design of this new class of devices can be mastered by fully understanding the relationship between communication and sensing with the purpose to balance the maximization of the dynamic range of the response with the stability of the read distance. A new kind of communication/sensing nomogram permits to display both behaviors in a unitary way and to predict their physical limits, as well as to formalize a multi-parameter general-purpose optimization methodology. The procedure is demonstr…

Passive UHF RFID antennas for sensing applications: Principles, methods, and classifcations

2013

UHF passive radio-frequency identification technology is rapidly evolving from simple labeling of things to wireless pervasive sensing. A remarkable number of scientific papers demonstrate that objects in principle can have their physical properties be remotely tracked and monitored all along their life cycle. The key background is a new paradigm of antenna design that merges together the conventional communication issues with more-specific requirements about sensitivity to time-varying boundary conditions. This paper presents a unified review of the state of the art of the tag-as-sensor problem. Particular care is taken to formalize the measurement indicators and the communication and sens…

RFID passive gas sensor integrating carbon nanotubes

2011

Carbon nanotube (CNT) composites are sensitive to the presence of gases due to their high surface-to-volume ratio and hollow structure that are well suited for gas molecule absorption and storage. Such sensing capability is here integrated with UHF RF identification (RFID) technology to achieve passive and low-cost sensors, remotely readable. CNT film (buckypaper) is used as a localized variable resistive load integrated into a tag antenna, which becomes able to transduce the presence of hazardous gas in the environment, ammonia in this case, into a change of its electromagnetic features. The dynamic range and the hysteresis of the radio sensor are investigated by simulations, equivalent ci…

Multiscale Model Selection for High-Frequency Financial Data of a Large Tick Stock by Means of the Jensen–Shannon Metric

2014

Modeling financial time series at different time scales is still an open challenge. The choice of a suitable indicator quantifying the distance between the model and the data is therefore of fundamental importance for selecting models. In this paper, we propose a multiscale model selection method based on the Jensen–Shannon distance in order to select the model that is able to better reproduce the distribution of price changes at different time scales. Specifically, we consider the problem of modeling the ultra high frequency dynamics of an asset with a large tick-to-price ratio. We study the price process at different time scales and compute the Jensen–Shannon distance between the original…

Investigation on Cascode Devices for High Frequency Electrical Drives Applications

2019

In the last years a widespread development in the market of electrical drives employing high-speed electrical machines has occurred in various industrial fields, due to the extremely high power density that can be reached. Nevertheless, to maintain output power quality without using bulky filtering networks, DC-AC converters should be controlled by means of higher PWM switching frequencies. New switching device technologies, such as Field Effect Transistors based on SiC and GaN, are therefore gathering momentum in order to comply with the higher working frequencies. To operate under high frequencies and at the same time at high voltage levels, alternative circuital configurations for switch…

Radio-high frequency and electrocautery vs turbinotomy

2009

GaN and SiC Device Characterization by a Dedicated Embedded Measurement System

2023

This work proposes a comparison among GaN and SiC device main parameters measured with a dedicated and low-cost embedded system, employing an STM32 microcontroller designed to the purpose. The system has the advantage to avoid the use of expensive laboratory measurement equipment to test the devices, allowing to obtain their behavior in operating conditions. The following KPIs (Key Performance Indicators) are measured and critically compared: threshold voltage, on-resistance and input capacitance. All the measurements are carried out in a short time interval and on a wide range of switching frequencies, ranging from 10 kHz to 1 MHz. This investigation is focused on the deviation of the figu…

Propagation Channels for mmWave Vehicular Communications : State-of-the-art and Future Research Directions

2018

Vehicular communications essentially support automotive applications for safety and infotainment. For this reason, industry leaders envision an enhanced role for vehicular communications in the fifth generation of mobile communications technology. Over the years, the number of vehicle- mounted sensors has increased steadily, which potentially leads to more volume of critical data communications in a short time. Also, emerging applications such as remote/autonomous driving and infotainment such as high-definition movie streaming require data-rates on the order of multiple Gb/s. Such high data rates require a large system bandwidth, but very limited bandwidth is available in the sub-6 GHz cel…