1,720,984 research outputs found
Optimized UHF antenna design, simulation, and implementation applied to residential HVAC motors
No full textThere is relentless rising demand for wireless communication and radio frequency hardware in daily life. Applications of everyday wireless communication include: cell phones, smart devices/tablets, radio frequency identification (RFID) tags, medical device location networks, wireless remote electronics, home networks, internet capable home appliances and home electronics. Each application requires a variety of radio frequency hardware to successfully communicate wirelessly. A new and interesting application of wireless communication is implementing a heating, ventilation and air conditioning (HVAC) system with wireless capabilities. The uses for such a HVAC system include: a wireless sensor network (WSN) that can facilitate energy savings operation modes and system status updates, system maintenance requests and updates, remote control of the system, and over the air firmware updates. In this research, a standard HVAC blower motor is provided wireless communications features. Specific challenges of implementing this type of HVAC motor are considered. A standard printed control board (PCB) ultra-high frequency (UHF) F-antenna (FA) is taken and optimized for total gain, and bandwidth. After optimization, the antennas were built and tested using a vector network analyzer (VNA). The test results were then compared to the simulation results to for verification. Once the simulation results were verified, a new series of simulations were built to test varying environmental effects on the antenna such as the ones from: the PCB board enclosure material, the PCB enclosure material with a thin layer of water, placing the antenna inside the motor control board enclosure, the motor control board enclosure with power and signal connectors, and the orientation within the motor control board enclosure. This research shows the feasibility of implementing a PCB UHF FA to create a wireless HVAC motor, and the effectiveness of the simulation procedures used
Characterization, analysis and simulation of Electro Magnetic Interference (EMI) in HVAC motors
No full textVariable speed motors are used in HVAC systems (furnaces, heat pumps and air conditioners) to condition the air in a residential/commercial space. The speed of the motor is adjusted to provide an efficient system operation in an air conditioned space. The motor speed is adjusted by controlling the power applied by means of precise electronic control. The power electronics components and the switched voltage and currents produce Electro Magnetic Interference (EMI) in the system. To mitigate EMI, filters are integrated at the front end of the electronic controller in order to achieve compliance with FCC and CISPR22 class B standard [6]. However, the increased switching frequency, together with the increased current and voltage slew rates, di/dt and dv/dt, have detrimental effects on the Electro Magnetic compatibility (EMC) performance of the system. At the same time, EMI filters typically have a degraded attenuation due to parasitic elements at high frequencies, and will be less effective in filtering out the high frequency EMI noises generated from the power circuits. This thesis describes a modeling approach of an electric drive system with device level components, with emphasis on the study of EMI performance. The multi-domain system software Ansoft Simplorer is used to characterize and model the passive and semiconductor components in the control board. The passive components are characterized by using the measured results obtained from an impedance analyzer where the models are presented as equivalent circuits, which is sufficient in the frequency range of conducted emission (0.15 - 30 MHz). To characterize and validate the semiconductor components, several models are imported from Pspice and predefined libraries of Ansoft Simplorer. The EMI levels of the electronic drive are measured by using a Line impedance stabilization network (LISN) device connected between the power supply and the control board (electronic drive) where the drive operates a motor which is modeled as an RL load. The measured EMI results are compared to the simulated EMI results. The impact of the parasitics on the EMI and also the improvements in the EMI filter to reduce the EMI has been simulated and analyzed
IMPROVED AND ROBUST ESTIMATION OF NONRANDOM WAVEFORMS
No full textThe problem of estimating nonrandom signal parameters when some a priori information about these parameters is available and when the contaminating noise is not gaussian or is only known in an approximate manner is considered in this work. Utilization of a priori knowledge in the estimation procedures is discussed by describing two general concepts: the minimax method and the generalized Bayes approach. It is seen that for certain kinds of constraints the minimax method provides a solution relatively easy to obtain and one whose mean squared error is smaller than those obtained by more conventional procedures such as the maximum likelihood method. For other types of constraints the generalized Bayes approach utilizing noninformative priors allows incorporation of constraints into the solution of the problem. Often the noninformative priors are not valid probability distribution functions; however, an a posteriori distribution will exist and can, in some sense, be interpreted as an appropriate posteriori distribution. An application of these two methods is illustrated in the estimation of the visual evoked response of the brain to a light stimulus. For cases where the contaminating noise is not gaussian or is only partially specified it is known that optimum procedures, designed under the assumption of exact knowledge of the noise model, can give poor results if the actual model departs even slightly from the assumed one. The main concepts and definitions of robust estimation procedures designed to overcome this problem are then discussed. It is pointed out that asymptotic results are not necessarily good indicators of the performance of the various methods for the small sample size problem and that some procedures, although having desirable properties, may be too complicated to compute for certain applications. A robust algorithm that avoids some of the disadvantages of previously derived methods and is more suitable for certain signal processing applications is presented. When, in addition to the presence of heavy tailed noise, there is knowledge that the signal-to-noise ratio is low it is shown that nonlinear robust procedures can be designed that greatly reduce the mean squared error when compared to linear methods. Several applications of the methods discussed in this work are presented
Radio Channel Study for Colon Capsule Endoscopy with Low-Band UWB Multiple Antenna System
Full text linkAbstractThis paper presents a study of the radio channel characteristics between a colon capsule endoscope and a multiple on-body antenna system in ultra wideband wireless body area networks (UWB-WBAN). The main aim is to study the variation of the channel characteristics for the on-body antennas in different capsule locations throughout the whole colon area. The study is conducted with CST Studio Suite simulations and one of its anatomical voxel models. A simplified capsule model and directive on-body antennas designed for low-band UWB in-body communications are used. It is found that five of this type directive on-body antennas provide sufficient coverage over the whole colon are even in the most challenging capsule locations.Abstract
This paper presents a study of the radio channel characteristics between a colon capsule endoscope and a multiple on-body antenna system in ultra wideband wireless body area networks (UWB-WBAN). The main aim is to study the variation of the channel characteristics for the on-body antennas in different capsule locations throughout the whole colon area. The study is conducted with CST Studio Suite simulations and one of its anatomical voxel models. A simplified capsule model and directive on-body antennas designed for low-band UWB in-body communications are used. It is found that five of this type directive on-body antennas provide sufficient coverage over the whole colon are even in the most challenging capsule locations
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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