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Fiber-optic sensors for measurements of torsion, twist and rotation
Vedran Budinski, Denis Đonlagić, 2017, pregledni znanstveni članek

Opis: Optical measurement of mechanical parameters is gaining significant commercial interest in different industry sectors. Torsion, twist and rotation are among the very frequently measured mechanical parameters. Recently, twist/torsion/rotation sensors have become a topic of intense fiber-optic sensor research. Various sensing concepts have been reported. Many of those have different properties and performances, and many of them still need to be proven in out-of-the laboratory use. This paper provides an overview of basic approaches and a review of current state-of-the-art in fiber optic sensors for measurements of torsion, twist and/or rotation.
Ključne besede: fiber optic sensors, twist sensors, rotation sensors, circular birefringence, linear birefringence, FBG, polarization, optical fibers, Fiber Bragg Gratings
Objavljeno: 22.06.2017; Ogledov: 182; Prenosov: 20
.pdf Celotno besedilo (8,96 MB)

An EMI filter selection method based on spectrum of digital periodic signal
Marko Podberšič, Vojko Matko, Matjaž Šegula, 2006, izvirni znanstveni članek

Opis: This paper describes a new method for the selection of an appropriate signal lineElectromagnetic Interference (EMI) filter. To date, EMI filter selection has been based on the measurement of the radiation of the entire device. The new selection method based on the signal’s Fast Fourier Transform (FFT) measurement has proved to be efficient. The EMIfilter is optimized separately for each line. The method described in this paper involving aCentral Processor Unit (CPU) module demonstrates that the proposed FFT-based selection method is better than the radiation-based one. The radiation level in the frequency range 30MHz to 1 GHz is lower for approximate 2 – 6 dBμV/m.
Ključne besede: EMC, EMI filters, electrically long trace, typical frequency, sensor
Objavljeno: 22.06.2017; Ogledov: 108; Prenosov: 20
.pdf Celotno besedilo (189,00 KB)

Acoustic emission detection of macro-cracks on engraving tool steel inserts during the injection molding cycle using PZT sensors
Rajko Svečko, Dragan Kusić, Tomaž Kek, Andrej Sarjaš, Aleš Hančič, Janez Grum, 2013, izvirni znanstveni članek

Opis: This paper presents an improved monitoring system for the failure detection ofen graving tool steel inserts during the injection molding cycle. This system uses acoustic emission PZT sensors mounted through acoustic waveguides on the engraving insert. We were thus able to clearly distinguish the defect through measured AE signals. Two engraving tool steel inserts were tested during the production of standard test specimens, each under the same processing conditions. By closely comparing the captured AE signals on both engraving inserts during the filling and packing stages, we were able to detect the presence of macro-cracks on one engraving insert. Gabor wavelet analysis was used for closer examination of the captured AE signalsć peak amplitudes during the filling and packing stages. The obtained results revealed that such a system could be used successfully as an improved tool for monitoring the integrity of an injection molding process.
Ključne besede: injection molding, process monitoring, acoustic emission, PZT sensors, piezoelectric effect
Objavljeno: 22.06.2017; Ogledov: 233; Prenosov: 25
.pdf Celotno besedilo (854,94 KB)

A flexible microcontroller-based data acquisition device
Darko Hercog, Bojan Gergič, 2014, izvirni znanstveni članek

Opis: This paper presents a low-cost microcontroller-based data acquisition device. The key component of the presented solution is a configurable microcontroller-based device with an integrated USB transceiver and a 12-bit analogue-to-digital converter (ADC). The presented embedded DAQ device contains a preloaded program (firmware) that enables easy acquisition and generation of analogue and digital signals and data transfer between the device and the application running on a PC via USB bus. This device has been developed as a USB human interface device (HID). This USB class is natively supported by most of the operating systems and therefore any installation of additional USB drivers is unnecessary. The input/output peripheral of the presented device is not static but rather flexible, and could be easily configured to customised needs without changing the firmware. When using the developed configuration utility, a majority of chip pins can be configured as analogue input, digital input/output, PWM output or one of the SPI lines. In addition, LabVIEW drivers have been developed for this device. When using the developed drivers, data acquisition and signal processing algorithms as well as graphical user interface (GUI), can easily be developed using a well-known, industry proven, block oriented LabVIEW programming environment.
Ključne besede: data acquisition, DAQ, microcontroller, analogue-to-digital converter, ADC, USB, HID, LabVIEW, GUI, data logging
Objavljeno: 22.06.2017; Ogledov: 172; Prenosov: 18
.pdf Celotno besedilo (1,98 MB)

A comparison of frequency pullability in oscillators using a single AT-cut quartz crystal and those using two single AT-cut crystals connected in parallel with a series load capacitance or series load capacitance or series load inductance
Vojko Matko, 2006, izvirni znanstveni članek

Opis: This paper presents a comparison of frequency pullability in oscillators using asingle AT-cut crystal and those using two single AT-cut crystals connected in paralleloperated with a series load capacitance or series load inductance at fundamental frequenciesof 4, 10 and 19 MHz. Pullability describes how the operating frequency may be changed byvarying the load capacitance. The paper also gives impedance circuits for both single- anddual-crystal units. The experiment results show that the new approach using two singlequartz crystals connected in parallel increases the frequency pulling range by 30-200% pending on the type of oscillator. Also given is the crystal frequency stability at thesethree frequencies.
Ključne besede: quartz, AT cut, pulling range, two single-crystal unit oscillator
Objavljeno: 22.06.2017; Ogledov: 124; Prenosov: 12
.pdf Celotno besedilo (155,12 KB)

Reliable and accurate release of micro-sized objects with a gripper that uses the capillary-force method
Suzana Uran, Riko Šafarič, Božidar Bratina, 2017, izvirni znanstveni članek

Opis: There have been recent developments in grippers that are based on capillary force and condensed water droplets. These are used for manipulating micro-sized objects. Recently, one-finger grippers have been produced that are able to reliably grip using the capillary force. To release objects, either the van der Waals, gravitational or inertial-forces method is used. This article presents methods for reliably gripping and releasing micro-objects using the capillary force. The moisture from the surrounding air is condensed into a thin layer of water on the contact surfaces of the objects. From the thin layer of water, a water meniscus between the micro-sized object, the gripper and the releasing surface is created. Consequently, the water meniscus between the object and the releasing surface produces a high enough capillary force to release the micro-sized object from the tip of the one-finger gripper. In this case, either polystyrene, glass beads with diameters between 5–60 µm, or irregularly shaped dust particles of similar sizes were used. 3D structures made up of micro-sized objects could be constructed using this method. This method is reliable for releasing during assembly and also for gripping, when the objects are removed from the top of the 3D structure—the so-called “disassembling gripping” process. The accuracy of the release was lower than 0.5 µm.
Ključne besede: micro-objects, one-finger gripper, gripping, releasing, capillary force
Objavljeno: 21.06.2017; Ogledov: 158; Prenosov: 51
.pdf Celotno besedilo (4,70 MB)

A benchmark of lidar-based single tree detection methods using heterogeneous forest data from the alpine space
Domen Mongus, Milan Kobal, Emanuele Lingua, Norbert Pfeifer, Lothar Eysn, Markus Hollaus, Eva Lindberg, Frédéric Berger, Jean-Matthieu Monnet, Michele Dalponte, Marco Pellegrini, 2015, izvirni znanstveni članek

Opis: In this study, eight airborne laser scanning (ALS)-based single tree detection methods are benchmarked and investigated. The methods were applied to a unique dataset originating from different regions of the Alpine Space covering different study areas, forest types, and structures. This is the first benchmark ever performed for different forests within the Alps. The evaluation of the detection results was carried out in a reproducible way by automatically matching them to precise in situ forest inventory data using a restricted nearest neighbor detection approach. Quantitative statistical parameters such as percentages of correctly matched trees and omission and commission errors are presented. The proposed automated matching procedure presented herein shows an overall accuracy of 97%. Method based analysis, investigations per forest type, and an overall benchmark performance are presented. The best matching rate was obtained for single-layered coniferous forests. Dominated trees were challenging for all methods. The overall performance shows a matching rate of 47%, which is comparable to results of other benchmarks performed in the past. The study provides new insight regarding the potential and limits of tree detection with ALS and underlines some key aspects regarding the choice of method when performing single tree detection for the various forest types encountered in alpine regions.
Ključne besede: single tree extraction, airborne laser scanning, forest inventory, comparative testing, co-registration, mountain forests, Alpine space, matching
Objavljeno: 21.06.2017; Ogledov: 109; Prenosov: 21
.pdf Celotno besedilo (13,97 MB)

Reactivation system for proton-exchange membrane fuel-cells
Carlos Restrepo, Oriol Avino, Javier Calvente, Alfonzo Romero, Miro Milanovič, Roberto Giral, 2012, izvirni znanstveni članek

Opis: In recent years, Proton-Exchange Membrane Fuel Cells (PEMFCs) have been the focus of very intensive researches. Manufacturers of these alternative power sources propose a rejuvenation sequence after the FC has been operating at high power for a certain period of time. These rejuvenation methods could be not appropriate for the reactivation of the FC when it has been out of operation for a long period of time or after it has been repaired. Since the developed reactivation system monitors temperature, current, and the cell voltages of the stack, it could be also useful for the diagnostic and repairing processes. The limited number of published contributions suggests that systems developing reactivation techniques are an open research field. In this paper, an automated system for reactivating PEMFCs and results of experimental testing are presented.
Ključne besede: reactivation system, PEM fuel cell, automated system
Objavljeno: 21.06.2017; Ogledov: 98; Prenosov: 22
.pdf Celotno besedilo (789,13 KB)

Motor unit characteristics after targeted muscle reinnervation
Tamás Kapelner, Ning Jiang, Aleš Holobar, Ivan Vujaklija, Aidan Roche, Dario Farina, Oskar Aszmann, 2016, izvirni znanstveni članek

Opis: Targeted muscle reinnervation (TMR) is a surgical procedure used to redirect nerves originally controlling muscles of the amputated limb into remaining muscles above the amputation, to treat phantom limb pain and facilitate prosthetic control. While this procedure effectively establishes robust prosthetic control, there is little knowledge on the behavior and characteristics of the reinnervated motor units. In this study we compared the m. pectoralis of five TMR patients to nine able-bodied controls with respect to motor unit action potential (MUAP) characteristics. We recorded and decomposed high-density surface EMG signals into individual spike trains of motor unit action potentials. In the TMR patients the MUAP surface area normalized to the electrode grid surface (0.25 ± 0.17 and 0.81 ± 0.46, p < 0.001) and the MUAP duration (10.92 ± 3.89 ms and 14.03 ± 3.91 ms, p < 0.01) were smaller for the TMR group than for the controls. The mean MUAP amplitude (0.19 ± 0.11 mV and 0.14 ± 0.06 mV, p = 0.07) was not significantly different between the two groups. Finally, we observed that MUAP surface representation in TMR generally overlapped, and the surface occupied by motor units corresponding to only one motor task was on average smaller than 12% of the electrode surface. These results suggest that smaller MUAP surface areas in TMR patients do not necessarily facilitate prosthetic control due to a high degree of overlap between these areas, and a neural information—based control could lead to improved performance. Based on the results we also infer that the size of the motor units after reinnervation is influenced by the size of the innervating motor neuron.
Ključne besede: target muscle reinnervation, motor unit, controlling muscles
Objavljeno: 19.06.2017; Ogledov: 153; Prenosov: 35
.pdf Celotno besedilo (1,51 MB)

A comparison of comprehension processes in sign language interpreter videos with or without captions
Ines Kožuh, Matjaž Debevc, Danijela Milošević, 2015, izvirni znanstveni članek

Opis: One important theme in captioning is whether the implementation of captions in individual sign language interpreter videos can positively affect viewers% comprehension when compared with sign language interpreter videos without captions. In our study, an experiment was conducted using four video clips with information about everyday events. Fifty-one deaf and hard of hearing sign language users alternately watched the sign language interpreter videos with, and without, captions. Afterwards, they answered ten questions. The results showed that the presence of captions positively affected their rates of comprehension, which increased by 24% among deaf viewers and 42% among hard of hearing viewers. The most obvious differences in comprehension between watching sign language interpreter videos with and without captions were found for the subjects of hiking and culture, where comprehension was higher when captions were used. The results led to suggestions for the consistent use of captions in sign language interpreter videos in various media.
Ključne besede: sign language, comparison, interpreter videos
Objavljeno: 19.06.2017; Ogledov: 162; Prenosov: 27
.pdf Celotno besedilo (857,94 KB)

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