Search results for "FREQUENCY"
showing 10 items of 2158 documents
Refractive index of the CuAlO2delafossite
2008
The refractive index of the CuAlO2 delafossite has been determined from interference measurements in single crystals performed in the visible, near and mid infrared regions of the spectrum. The analysis of the refractive index dispersion corresponding to light polarization perpendicular to the c-axis (P ⊥ c) yields a static dielectric constant of 0 = 7.7 ± 0.8 and a low frequency electronic constant ∞ = 5.1 ± 0.1. The relevant infrared active mode is found to be at 550 ± 25 cm−1. The electronic contribution can be well described by a Penn gap at 39 000 ± 1000 cm−1. Both the refractive index and its dispersion are found to be smaller for P||c than for P ⊥ c.
Analysis of bias-shift effects in free-running and injection-locked negative resistance oscillators
2012
In this paper, the interaction between DC and RF in quasi-sinusoidal free-running and injection-locked oscillators is addressed. To account for and illustrate in a user-friendly manner the bias-shift related effects stemming from such interaction, a frequency-domain method of analysis has been developed for a rather wide class of negative-resistance circuits. Grounding on a first-approximation exact perturbation-refined approach, it permits computationally efficient simulation of the oscillator behavior directly in terms of the DC and RF signals evolutions (dynamical complex envelopes). In fact, it allows the investigation of both steady-state and transient operation of the shifting-bias dr…
Predator Mixes and the Conspicuousness of Aposematic Signals
2003
Conspicuous warning signals of unprofitable prey are a defense against visually hunting predators. They work because predators learn to associate unprofitability with bright coloration and because strong signals are detectable and memorable. However, many species that can be considered defended are not very conspicuous; they have weak warning signals. This phenomenon has previously been ignored in models and experiments. In addition, there is significant within- and among-species variation among predators in their search behavior, in their visual, cognitive, and learning abilities, and in their resistance to defenses. In this article we explore the effects of variable predators on models th…
Relation between bone density and primary implant stability
2010
Aims: This study aims to relate bone density in Hounsfield units (Hu) with the primary implant stability measured by insertion torque (Ncm) and resonance frequency analysis (ISQ). Materials and Methods: Ten patients were included in this study. A total of 54 implant sites were provided from 10 computerized tomography scans. The computerized tomography scan was used for the preoperative evaluation of bone density for each patient. The bone mean density around planned implants was determined with Physioplanet TM software. Bone quality according resistance to drilling, insertion torque and resonance frequency measurements were recorded. Results: A statistically significant relationship was obs…
Influence of cortical bone and implant design in the primary stability of dental implants measured by two different devices of resonance frequency an…
2020
Background This study aimed to evaluate the effect of the implant design and the presence of cortical bone in the primary stability, as well as analyze the differences between the stability measurements obtained by two different resonance frequency analysis (RFA) devices. Material and methods A total of 80 Klockner implants of two different models [40 Essential Cone implants (group A) and 40 Vega implants (group B)] were used. The implants were placed in two polyurethane blocks that simulated the mechanical properties of the maxillary bone. One block featured a layer of cortical bone that was absent from the other block. The primary stability of all implants was measured by insertion torque…
Primary Stability of a Hybrid Self-Tapping Implant Compared to a Cylindrical Non-Self-Tapping Implant with Respect to Drilling Protocols in an Ex Viv…
2011
Background: Modifications of implant design have been intending to improve primary stability. However, little is known about investigation of a hybrid self-tapping implant on primary stability. Purposes: The aims of this study were to evaluate the primary stability of two hybrid self-tapping implants compared to one cylindrical non-self-tapping implant, and to elucidate the relevance of drilling protocols on primary stability in an ex vivo model. Materials and Methods: Two types of hybrid self-tapping implants (Straumann® Bone Level implant [BL], Straumann® Tapered Effect implant [TE]) and one type of cylindrical non-self-tapping implant (Straumann® Standard Plus implant [SP]) were investig…
Evaluation of the power quality from a seawave power farm for different interconnection schemes
2007
In this paper we present an approach to the interconnection of a seawave power farm to the grid The generator type used in the farm is a Permanent Magnet (PM) linear generator driven from the seawaves that generates, therefore, highly distorted emfs. We propose and compare two possible ways to interconnect the farm to the grid. One is based on an approach where for each generator there is a conversion subsystem that permits the direct connection of each generator to the a.c. network, the other one is based on an ac.-d.c. converter that is connected to the generator, the converter is connected to a dc link that can receive the power from every unit and that can supply a dc-ac converter direc…
Feasibility, limitations and potentiality of UHF-RFID passive implants
2012
Implanted RFID may play an important role in the personal Healthcare of next future. Antenna embedded into prosthesis or into other implanted medical devices could permit to monitor physiological and pathological processes, providing a natural interconnection to remote services. The big technical challenge is to establish a stable RFID link with the interior of the human body in spite of the high electromagnetic losses of the tissues. By using parametric electromagnetic models and some early result, it is here investigated the potentiality and limitation of the UHF implants with special attention to the body district, the overall mass, and the size of the antennas.
Primary Frequency Control in the Power System of Continental Europe including the Dynamics of the HVDC Link France-Great Britain
2020
The paper presents a study of primary frequency control within the power system of Continental Europe (CE) including the dynamics of the high voltage direct current (HVDC) link between France and Great Britain (GB). The large-scale dynamic model of the CE system originally provided by ENTSO-E is extended with a more detailed representation of the whole HVDC interconnection. The dynamics of the GB synchronous area is also considered in the analysis, implementing a system equivalent suitable for primary frequency control studies. The opportunity of frequency containment reserve exchange between the two areas through the link is also investigated, considering supplementary frequency controls w…
Analysis of different Sleeve Ferrite Cores Performance according to their Dimensions
2019
Sleeve ferrite core is an EMI suppressor widely used to reduce the conductive and radiated electromagnetic noise in cables. The interconnection of different electronic systems through cables is becoming more difficult due to the hard restrictions related to EMC compliance requirements. Thereby, the research of new solutions able to provide a great attenuation ratio in a wide frequency band is a challenge. This contribution focuses on analyzing and comparing the performance of a novel sleeve ferrite solution based on a nanocrystalline (NC) structure with several materials with different compositions. This component is able to provide a high initial permeability value at the same time that ma…