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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Robust Statistical Methods for Measurement Calibration in Large Electric Power Systems

Ghassemian, Alireza 14 October 1997 (has links)
The Objective of the Remote Measurements Calibration (RMC) method is to minimize systematic errors through an appropriate scaling procedure. A new method for RMC has been developed. This method solves the problems of observability, multiplicity of solutions, and ambiguity of reference points associated with the method proposed by Adibi et. al. [6-9]. The new algorithm uses the simulated annealing technique together with the matroid method to identify and minimize the number of RTUs (Remote Terminal Units) required to observe the system. After field calibration, these RTUs provide measurements that are used to estimate the whole state of the system. These estimates are then returned as a reference for remotely calibrating the remaining RTUs. The calibration coefficients are estimated by means of highly robust estimator, namely the Least Median of Squares (LMS) estimator. The calibration method is applicable to large systems by means of network tearing and dynamic programming. The number of field calibrations can be decreased further whenever multiple voltage measurements at the same buses are available. The procedure requires that the measurement biases are estimated from recorded metered values when buses, or lines, or transformers are disconnected. It also requires the application of a robust comparative voltage calibration method. To this end, a modified Friedman test has been developed and its robustness characteristics investigated. / Ph. D.
2

3d-fe Model Field-calibration And Rating Studies On Existing R/c Buildings

Demirok, Emel 01 April 2006 (has links) (PDF)
Dynamic instrumentation and a series of ambient vibration tests were performed on a four storey strengthened R/C building within the scope of this study. Traffic load and wind load were accepted as natural dynamic loads and the vibrations were recorded by sensitive accelerometers.For that study, 12 uniaxial, 1 triaxial accelerometers and a 15 channel data logger system were used. Four sets of dynamic measurements were recorded over a period of 6 months. Recorded readings were analyzed using UPC, PC and CVA algorithms and Artemis software. The natural freqeuncies, mode shape of the tested building were determined. The experimental results were compared against each other. A 3D-FE model of the building was prepared and analytical results were also compared against experimental results.The calibration (updating) of the analytical model was carried out using the experimentally obtained mode shapes and freqeunices. The results of the study indicate that first few mode shapes and freqeuncies of the building can be obtained successfully within zero to 10 Hz range using ambient monitoring. Field calibrated FE models can effectively simulate the first translational and torsional modes of the building. Calibration studies indicate that the upper floor is more flexible than the nominal model and there are weaknesses between the shear wall and roof slab connections.
3

The measurement of physical activity and sedentary behaviour in a sample of 2 to 3 year old South Asian and White British children

Nobre da Costa, Silvia January 2013 (has links)
Background: Studies have reported that preschool children may not be sufficiently active according to guidelines. This is worrying because early childhood is a critical period for the establishment of sedentary behaviour (SB) and physical activity (PA) habits, which have immediate and long term influences on health. The majority of evidence on levels, determinants, and health consequences of SB and PA in young children is, however, based on subjective measures in predominately White children aged three years or older. Aims: To 1) assess the feasibility and acceptability of using three different accelerometers in South Asian and White British 2-3 year olds and their parents; 2) calibrate and validate the accelerometers to measure SB and PA in 2-3 year olds; 3) investigate the influence of 5-, 10-, and 15-second epochs on time spent in SB, light PA, and moderate-to-vigorous PA (MVPA) in 2-3 year olds; and 4) assess the feasibility of measuring the habitual SB and PA with the ActiGraph GT3X+ accelerometer in South Asian and White British 2-3 year olds and their parents. Methods: Focus groups were performed with 17 South Asian and White British mothers and the audio-recordings were transcribed verbatim and analysed with thematic analysis (Aim 1). To calibrate the three accelerometers against direct observation (Aim 2), semi-structured activity sessions were run with 18 South Asian and White British 2-3 year olds. Mixed-effects regression and receiver-operating characteristics (ROC) curve analysis were used to generate prediction equations and 5- and 10-second cut-points to assess children s SB and PA. Validity of the generated cut-points against direct observation (Aim 2) was assessed in a separate sample of 20 White British and Black African 2-3 year olds during free-play, using Cohen s kappa, ROC curve analysis, Bland-Altman plots, and Lin s concordance coefficient. Differences in estimated time spent in SB, light PA and MVPA from 5-, 10- and 15-second epochs were tested with repeated-measures ANOVA and paired t-tests in the calibration sample (Aim 3). A pilot study was conducted with 120 South Asian and White British families from a birth cohort study to address aim 4. Study intake and compliance with an 8-day measurement protocol were calculated, and differences between ethnicities were assessed with the Chi-square test. Results: The ActiGraph GT3X+ was the most widely accepted accelerometer, with the least amount of issues raised by mothers. Practical and software issues with the Actiheart and activPAL3 during the calibration phase resulted in insufficient good quality data collected, which made it unfeasible to calibrate both monitors. The overall 5-second Axis1 cut-points for the ActiGraph GT3X+ provided a valid tool to measure the SB and total PA of 2-3 year olds in free-living conditions. Using 10- and 15-second epochs overestimated children s light PA and underestimated time spent in SB and MVPA. Less South Asian than White British families were recruited into the study, and less South Asian than White British children complied with the 8-day measurement protocol. There were no ethnic differences in the number of children and parents providing enough accelerometry data (i.e. ≥ 3 valid days), or the number of parents complying with the measurement protocol. Conclusions: The results demonstrated that it is feasible to use the ActiGraph GT3X+ to assess the habitual SB and PA of a bi-ethnic sample of 2-3 year old children and their parents. The accurate assessment of SB and PA in 2-3 year olds using the overall 5-second Axis1 cut-points developed and validated in this thesis will enable researchers to investigate the levels, determinants, and health consequences of SB and PA. Such research will inform public health policies and interventions to improve children s health.
4

Kalibrace tlakoměrů / Calibration of pressure gauges

Schwarz, Jakub January 2014 (has links)
This diploma thesis is dealing with pressure measurement. It describes instruments dedicated to purpose - pressure gauges. Basic of correct pressure measurement is knowledge of behaviour of used pressure gauge. This knowledge is acquired by calibration. With calibration is associated also analysis of errors and uncertainty of measurement and creation of calibration list. Calibration takes place on model workspace pressure measuring in laboratory.
5

Návrh a realizace testovací aplikace měření rozměrů optickým senzorem a robotickým ramenem / Design and implementation of a test application for measuring dimensions with an optical sensor and a robotic arm

Zagorská, Kateřina January 2021 (has links)
This diploma thesis deals with creation of a measuring application using optical sensor and robotic arm in the RobotStudio software. The literature review of the thesis describes the field of optical measuring and calibration. Furthermore, the thesis includes the process of creating a measuring application and outlining issue of calibration of individual parts. The work is supplemented by a demonstration of repeatability measurements and a description of possible errors that may occur if the robot is set incorrectly.
6

On Fast, Polarimetric Non-Reciprocal Calibration and Multipolarization Measurements on Weather Radars

Reimann, Jens 21 October 2013 (has links)
In this study a calibration concept for a multi-polarimetric weather radar is developed. Several common calibration techniques are analysed, but many are insufficient due to the non-reciprocal behaviour of the employed radar. Hence, an electronic calibration device was developed, which was designed for fast polarization determination of any polarization (including elliptical ones). The non-reciprocal behaviour was overcome by splitting receive and transmit calibration, which virtually uses the radar as a communication system. Beside the calibration a new and exible signal processing system was implemented on that radar which allows interleaved measurements using several polarimetric modes. This capability was used to analyse the STAR (hybrid basis with linear 45° transmit and horizontal/vertical receive) mode and the alternating H/V mode with respect to depolarization. Although it is known that depolarization causes errors in STAR mode, it is used in most commercial weather radars. / In dieser Arbeit wird ein Kalibrierkonzept für ein Multipolarisation-Radar entwickelt. Dazu wurden verschiedene gebräuchliche Techniken untersucht. Dabei stellte sich heraus, dass dieses Verfahren für das untersuchte nichtreziproke Radar unzureichend sind. Deshalb wurde ein elektronisches Kalibriergerät entwickelt, welches speziell der schnellen Messung von beliebigen Polarisationen - einschließlich Elliptischer - dient. Das nichtreziproke Verhalten wurde durch die Aufteilung in eine Sende- und eine Empfangskalibrierung umgangen, wodurch das Radar praktisch als Kommunikationssystem verwendet wird. Des Weiteren wurde eine neue, fexible Signalverarbeitung an dem Radar entwickelt, welches gemischte Messungen mit mehreren Polarisationsmoden erlaubt. Diese neuartige Möglichkeit wurde benutzt um den STAR-Modus, welches eine hybride Polarisationsbasis (linear 45° senden, horizontal/vertikal empfangen) benutzt, mit dem alternierende H/V-Modus zu vergleichen. Dabei wurde speziell das Verhalten des STAR-Modus im Hinblick auf Depolarisation untersucht, da dies bekanntermaßen zu Fehlern in den Messgrößenführen kann. Dies ist von besonderem Interesse, da der STAR-Modus in den meisten kommerziellen Wetterradarsystemen eingesetzt wird.
7

Measurement calibration/tuning & topology processing in power system state estimation

Zhong, Shan 17 February 2005 (has links)
State estimation plays an important role in modern power systems. The errors in the telemetered measurements and the connectivity information of the network will greatly contaminate the estimated system state. This dissertation provides solutions to suppress the influences of these errors. A two-stage state estimation algorithm has been utilized in topology error identification in the past decade. Chapter II discusses the implementation of this algorithm. A concise substation model is defined for this purpose. A friendly user interface that incorporates the two-stage algorithm into the conventional state estimator is developed. The performances of the two-stage state estimation algorithms rely on accurate determination of suspect substations. A comprehensive identification procedure is described in chapter III. In order to evaluate the proposed procedure, a topology error library is created. Several identification methods are comparatively tested using this library. A remote measurement calibration method is presented in chapter IV. The un-calibrated quantities can be related to the true values by the characteristic functions. The conventional state estimation algorithm is modified to include the parameters of these functions. Hence they can be estimated along with the system state variables and used to calibrate the measurements. The measurements taken at different time instants are utilized to minimize the influence of the random errors. A method for auto tuning of measurement weights in state estimation is described in chapter V. Two alternative ways to estimate the measurement random error variances are discussed. They are both tested on simulation data generated based on IEEE systems. Their performances are compared. A comprehensive solution, which contains an initialization process and a recursively updating process, is presented. Chapter VI investigates the errors introduced in the positive sequence state estimation due to the usual assumptions of having fully balanced bus loads/generations and continuously transposed transmission lines. Several tests are conducted using different assumptions regarding the availability of single and multi-phase measurements. It is demonstrated that incomplete metering of three-phase system quantities may lead to significant errors in the positive sequence state estimates for certain cases. A novel sequence domain three-phase state estimation algorithm is proposed to solve this problem.
8

System On-/Offline merania teploty na báze LabView / System of On-/Offline temperature measurement based on Lab View

Stejskal, David January 2019 (has links)
The objective of this thesis was to create a LabVIEW-based program for temperature measurement using a personal computer. The program allows reading and post processing of digital signal from a measuring device. This device consists of a sensor type PT100, a measuring transducer and an analog-to-digital converter with USB output. The theoretical part of the thesis deals with resistance temperature sensors, signal analysis and methods for signal processing. The practical part is conceived as a guide to the created program. This part introduces vital sub-elements of the program and describes their principle, practical use and also the operating instructions. As required by thesis assignment, practical part includes verification of the measuring device, which was performed in laboratory of Czech Metrology Institute in Brno.

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