• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 134
  • 93
  • 43
  • 30
  • 21
  • 10
  • 7
  • 6
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 392
  • 82
  • 51
  • 47
  • 33
  • 29
  • 28
  • 28
  • 26
  • 26
  • 26
  • 25
  • 23
  • 23
  • 22
  • 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.
161

Konstruktion och utvärdering av diplexer / Construction and evaluation of diplexer

Karlsson, David January 2005 (has links)
<p>The report descripbs how a diplexer for a hybrid analog/digital filterbank has been constructed and tested. A diplexer divides the frequency band into two different bands that do not who doesn't overlapp each other. The sampling rate for the two ADC:s is 80 Msps, and therefore it is advantage to have zero at 80 MHz. The reason for this is that a proposed class of hybrid filterbanks with very good quality requires a zero at or close the sampling frequency to work well. </p><p>The diplexer was made in three versions. The first didn't work since the choosen inductance self resonance frequency was to low and by the same range as the filters bandwidth. The second version had to much losses, which resulted in attenuation at 80 MHz, which was to small. The third version was made in two differents layout. </p><p>To the diplexer it was also made a test tool in Labview, through that one gets the magnitude ande phase functions. </p><p>The results show that the magnitude function is good for version 3.0 and for version 3.1, and that the losses are low. It depends also on that the choosen components have a high self resonance frequency. There can't been shown any differences between these two, thus is is difficult to judge if one is better then an other.</p>
162

Automatic trimming of ultrasonic pulse in fiber-optical power spectrometer

Forsslund, Ola January 2009 (has links)
<p>The aim of this master's thesis is to develop a method that fully automates a trimming step in the production of a fiber-optical power spectrometer, based on a unique Acusto-Optical Scanning Filter.</p><p>The filter is created by letting an ultrasonic mechanical pulse pass through a chirped Fiber Bragg Grating. The pulse introduces a disturbance in the grating, creating a thin optical transmission window in the otherwise reflective bandwidth. The high demands on the window requires a precise, unit dependent pulse form with unknown properties. Thus each unit needs to be trimmed to reach required performance.</p><p>The manual trimming is largely a trial and error process, that contains two performance tests. We redefine one, eliminating the need to reroute the optical path and reducing the number of fiber weldings. The tests are then quantified, allowing a figure of merit to be based on weighted performance values.</p><p>A brute force method, testing a large set of pulses, is implemented. The set is defined by the parameter space spanned by previously produced units. Due to the large space, the method is too time consuming. Instead it is used to measure the performance spaces of three units. An attempt to largely reduce the parameter space using PCA failed.</p><p>An alternating variables method that finds local performance optima in the parameter space is developed. By using a set of several starting points, the method tends to find several qualified pulses. The method is implemented and successfully verified by trimming new units.</p><p>Finally we propose where to focus improvements of the method in a production ramp up.</p>
163

HelioScan : A software framework for controlling in vivo microscopy setups with high hardware flexibility, functional diversity and extendibility

Langer, Dominik, van 't Hoff, Marcel, Keller, Andreas J., Nagaraja, Chetan, Pfaeffli, Oliver A., Goeldi, Maurice, Kasper, Hansjoerg, Helmchen, Fritjof January 2013 (has links)
Intravital microscopy such as in vivo imaging of brain dynamics is often performed with custom-built microscope setups controlled by custom-written software to meet specific requirements. Continuous technological advancement in the field has created a need for new control software that is flexible enough to support the biological researcher with innovative imaging techniques and provide the developer with a solid platform for quickly and easily implementing new extensions. Here, we introduce HelioScan, a software package written in LabVIEW, as a platform serving this dual role. HelioScan is designed as a collection of components that can be flexibly assembled into microscope control software tailored to the particular hardware and functionality requirements. Moreover, HelioScan provides a software framework, within which new functionality can be implemented in a quick and structured manner. A specific HelioScan application assembles at run-time from individual software components, based on user-definable configuration files. Due to its component-based architecture, HelioScan can exploit synergies of multiple developers working in parallel on different components in a community effort. We exemplify the capabilities and versatility of HelioScan by demonstrating several in vivo brain imaging modes, including camera-based intrinsic optical signal imaging for functional mapping of cortical areas, standard two-photon laser-scanning microscopy using galvanometric mirrors, and high-speed in vivo two-photon calcium imaging using either acousto-optic deflectors or a resonant scanner. We recommend HelioScan as a convenient software framework for the in vivo imaging community. / <p>Paid Open Access</p>
164

Exempel på användning av LabVIEW vid : mätning, reglering och signalbehandling

Kadic, Safet, Kazazic, Alen, Mustafa, Florim January 2006 (has links)
Arbetet handlar om hur man med hjälp av LabVIEW 8.0 kan lösa olika uppgifter. Uppgifterna löses med hjälp av ett DAQ-kort. DAQ-kortet gör det möjligt att mata in signaler, som sedan behandlas efter behov i programmet och därefter skickas ut genom DAQ- kortet till olika komponenter som man vill styra. DAQ-kortet klarar att behandla både analoga och digitala signaler. LabVIEW 8.0 och dess historia, DAQ-kortet samt de olika processerna/uppgifter beskrivs mer utförligt i arbetet.
165

Undersökning av vindlaster på en parabolantenn / Determination of wind loads on a parabolic antenna

Wreinerth, Joachim, Hjalmarsson, Joel January 2009 (has links)
Vi fick i uppdrag av Swepart Transmission AB att med lämpliga metoder beräkna vindlaster på en godtycklig parabolantenn samt att konstruera en växellåda för att positionera den. Vi insåg i ett tidigt skede att vi var tvungna att ta fram vindlastfaktorerna laborativt. Och på grund av den begränsade tiden var vi tvungna att fokusera endast på vindlasterna på en parabolform. Först uppskattade vi de maximala vindlaster som kunde uppkomma för att kunna dimensionera vår mätram. Sedan beräknade vi lastcellerna och konstruerade erforderlig elektronik. För att simulera vind monterades parabolen och dess mätram på ett fordon, mätningarna utfördes sedan på Uråsa flygfält. Efter mätningen kunde vi fastslå de sökta vindlastfaktorerna och deras ekvationer
166

Automatic trimming of ultrasonic pulse in fiber-optical power spectrometer

Forsslund, Ola January 2009 (has links)
The aim of this master's thesis is to develop a method that fully automates a trimming step in the production of a fiber-optical power spectrometer, based on a unique Acusto-Optical Scanning Filter. The filter is created by letting an ultrasonic mechanical pulse pass through a chirped Fiber Bragg Grating. The pulse introduces a disturbance in the grating, creating a thin optical transmission window in the otherwise reflective bandwidth. The high demands on the window requires a precise, unit dependent pulse form with unknown properties. Thus each unit needs to be trimmed to reach required performance. The manual trimming is largely a trial and error process, that contains two performance tests. We redefine one, eliminating the need to reroute the optical path and reducing the number of fiber weldings. The tests are then quantified, allowing a figure of merit to be based on weighted performance values. A brute force method, testing a large set of pulses, is implemented. The set is defined by the parameter space spanned by previously produced units. Due to the large space, the method is too time consuming. Instead it is used to measure the performance spaces of three units. An attempt to largely reduce the parameter space using PCA failed. An alternating variables method that finds local performance optima in the parameter space is developed. By using a set of several starting points, the method tends to find several qualified pulses. The method is implemented and successfully verified by trimming new units. Finally we propose where to focus improvements of the method in a production ramp up.
167

FPGA based Eigenvalue Detection Algorithm for Cognitive Radio

TESHOME, ABIY TEREFE January 2010 (has links)
Radio Communication technologies are undergoing drastic demand over the past two decades. The precious radio resource, electromagnetic radio spectrum, is in vain as technology advances. It is required to come up with a solution to improve its wise uses. Cognitive Radio enabled by Software-Defined Radio brings an intelligent solution to efficiently use the Radio Spectrum. It is a method to aware the radio communication system to be able to adapt to its radio environment like signal power and free spectrum holes. The approach will pose a question on how to efficiently detect a signal. In this thesis different spectrum sensing algorithm will be explained and a special concentration will be on new sensing algorithm based on the Eigenvalues of received signal. The proposed method adapts blind signal detection approach for applications that lacks knowledge about signal, noise and channel property. There are two methods, one is ratio of the Maximum Eigenvalue to Minimum Eigenvalue and the second is ratio of Signal Power to Minimum Eigenvalue. Random Matrix theory (RMT) is a branch of mathematics and it is capable in analyzing large set of data or in a conclusive approach it provides a correlation points in signals or waveforms. In the context of this thesis, RMT is used to overcome both noise and channel uncertainties that are common in wireless communication. Simulations in MATLAB and real-time measurements in LabVIEW are implemented to test the proposed detection algorithms. The measurements were performed based on received signal from an IF-5641R Transceiver obtained from National Instruments.
168

Rapid prototyping : -development and evaluation of Field Oriented Control using LabView FPGA

Eriksson, Joakim, Hermansen, Luciano January 2011 (has links)
This report describes the work of developing a rapid prototyping system for Permanent Magnet Synchronous Motors using LabView FPGA at ABB Corporate Research in Västerås. The aim of the rapid prototyping system is to serve as an additional tool to simulation when evaluating new control algorithms for mechatronic applications. Using LabView FPGA, Field Oriented Control is implemented for a single axis and a multi axis system on the sbRIO 9632 development board from National Instruments. The aim is to develop a controller for multiple axes while optimizing the use of system resources. The report presents the work of testing and evaluating the implementation of the single axis system. The system will be tested in a laboratory test bench to verify its performance. The laboratory results are compared and verified against MATLAB/Simulink simulations of the system. Using the results from the single axis tests as a benchmark the multi axis system is verified and evaluated. The implemented systems proved to provide good regulation of the motor currents for both the single axis and the multi axis system.
169

Konstruktion och utvärdering av diplexer / Construction and evaluation of diplexer

Karlsson, David January 2005 (has links)
The report descripbs how a diplexer for a hybrid analog/digital filterbank has been constructed and tested. A diplexer divides the frequency band into two different bands that do not who doesn't overlapp each other. The sampling rate for the two ADC:s is 80 Msps, and therefore it is advantage to have zero at 80 MHz. The reason for this is that a proposed class of hybrid filterbanks with very good quality requires a zero at or close the sampling frequency to work well. The diplexer was made in three versions. The first didn't work since the choosen inductance self resonance frequency was to low and by the same range as the filters bandwidth. The second version had to much losses, which resulted in attenuation at 80 MHz, which was to small. The third version was made in two differents layout. To the diplexer it was also made a test tool in Labview, through that one gets the magnitude ande phase functions. The results show that the magnitude function is good for version 3.0 and for version 3.1, and that the losses are low. It depends also on that the choosen components have a high self resonance frequency. There can't been shown any differences between these two, thus is is difficult to judge if one is better then an other.
170

Geometry Estimation and Adaptive Actuation for Centering Preprocessing and Precision Measurement

Mears, Michael Laine 06 April 2006 (has links)
Precise machining of bearing rings is integral to finished bearing assembly quality. The output accuracy of center-based machining systems such as lathes or magnetic chuck grinders relates directly to the accuracy of part centering before machining. Traditional tooling and methods for centering on such machines are subject to wear, dimensional inaccuracy, setup time (hard tooling) and human error (manual centering).A flexible system for initial part centering is developed based on a single measurement system and actuator, whereby the part is placed by hand onto the machine table, rotated and measured to identify center of geometry offset from center of rotation, then moved by a series of controlled impacts or pushes to align the centers. The prototype centering system is developed as a demonstration platform for research in a number of mechanical engineering areas, particularly: Characterization of optimal state estimators through analysis of accuracy and computational efficiency; Distributed communication and control, efficient transfer of information in a real-time environment, and information sharing between processes; Modeling of sliding dynamics and the interaction of friction with compliant body dynamic models; Motion path planning through both deterministic geometric transforms and through frequency domain command manipulation.A vision is created for future work not only in the described areas, but also in the areas of advanced controller design incorporating multiple variables, derived machine diagnostic information, and application of the distributed communication architecture to information flow throughout the manufacturing organization. The guiding motivation for this research is reduction of manufacturing processing costs in the face of global competition. The technologies researched, developments made, and directions prescribed for future research aid in enabling this goal.

Page generated in 0.0336 seconds