| 1. |
- Adolfsson, Stefan, et al.
(författare)
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Automatic Detection of Burn-through in GMA Welding Using a Parametric Model
- 1996
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Ingår i: Mechanical Systems & Signal Processing. - London : Academic Press. - 0888-3270. ; 10:5, s. 633-651
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Tidskriftsartikel (refereegranskat)abstract
- This paper addresses the problem of automatic detection of burn-through in weld joints. Gas metal are (GMA) welding with pulsed current is used, and welding voltage and current are recorded. As short-circuitings are common between the welding electrode and the work piece during burn-through, a short-circuit detector is developed to detect these events. To detect another specific characteristic of burn-through-a broadband long-lasting voltage component-this detector is combined with a square-law detector. This second detector is based on a non-linear modification of an autoregressive model with extra input (ARX-model) of the welding process. The results obtained from this compound detector indicate that it is possible to detect burn-through in the welds automatically. The work also indicates that it is possible to design an on-line monitoring system for robotic GMA welding.
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| 2. |
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| 3. |
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| 4. |
- Dias,, Jacklyn, et al.
(författare)
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Improving the Performance Evaluation of ADSL systems by using a Modem Diagnosis Methodology
- 2006
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Ingår i: Simpósio Brasileiro de Microondas e Optoeletrônica – Congresso Brasileiro de Eletromagnetismo.
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Konferensbidrag (refereegranskat)abstract
- This paper presents test methodologies to measure and evaluate performance of ADSL modems which take into account loss of packet rate, bit rate, and latency in transporting ADSL service scenario. This evaluation method can be used by ADSL provider (CO - Central Office) to guarantee the system quality and avoid low performance of service. In order to present this evaluation method, this paper considers a traffic generator, modems under test, a telephony local loop carring ADSL service, and DSLAM as the lab setup to perform such tests.
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| 5. |
- Englund, Ulrica, et al.
(författare)
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The use of a recombinant lentiviral vector for ex vivo gene transfer into the rat CNS
- 2000
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Ingår i: NeuroReport. - : Lippincott Williams & Wilkins. - 0959-4965 .- 1473-558X. ; 11:18, s. 3973-3977
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Tidskriftsartikel (refereegranskat)abstract
- A major obstacle in ex vivo gene transfer has been the loss of transgene expression soon after implantation of the grafted transduced cells. Recently, a lentiviral vector system has been developed which has proven to express high levels of transgenes in vivo after direct injection into the tissue. In this study, we have investigated the use of such a vector for ex vivo gene transfer to the brain. A number of neural cell types were found to be permissive to transduction by the lentiviral vector in vitro and a majority of them expressed the transgene after transplantation to the rat brain. Transgene expression was detected up to 8 weeks post-grafting. These findings suggest that recombinant lentiviral vectors may be used for further development of ex vivo gene therapy protocols to the CNS.
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| 6. |
- Ericson, Cecilia, et al.
(författare)
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Ex vivo and in vitro studies of transgene expression in rat astrocytes transduced with lentiviral vectors.
- 2002
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Ingår i: Experimental Neurology. - : Elsevier BV. - 0014-4886. ; 173:1, s. 22-30
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Tidskriftsartikel (refereegranskat)abstract
- Implantation of cells genetically modified to express therapeutic genes into the brain has been proposed as a potential treatment for neurodegenerative diseases. In the current study embryonic rat-derived astrocytes were cultured and transduced with a lentiviral vector expressing the reporter gene green fluorescent protein (GFP) and subsequently grafted into the adult rat brain. The proportion of GFP expressing cells was stable, albeit small (1%), at all survival times, up to 6 weeks, the longest time point studied. In parallel in vitro studies, the astrocytes were lentivirally transduced to express either one of the two isoforms of glutamate decarboxylase (GAD(65) or GAD(67)) or glial cell line-derived neurotrophic factor (GDNF). When transducing 293T cells with the two GAD vectors, released GABA could be measured using high-performance liquid chromatography. Further studies of rat astrocytes transduced with the same vectors resulted in a level of GAD activity about 10 times higher than the activity of an intact rat striatum. One hundred thousand astrocytes transduced with LV-GDNF released approximately 27 ng of GDNF per hour. Thus, taken together, our observations provide support for the use of rat astrocytes in ex vivo gene transfer of these proteins in animal models of CNS disorders, e.g., Parkinson's disease or epilepsy.
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| 7. |
- Ericson, Stefan, et al.
(författare)
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Information Fusion for Autonomous Robotic Weeding
- 2009
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Ingår i: INFORMATIK 2009. - : Köllen Druck + Verlag GmbH. - 9783885792482 ; , s. 2461-2473
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Konferensbidrag (refereegranskat)abstract
- Information fusion has a potential applicability to a multitude of differentapplications. Still, the JDL model is mostly used to describe defense applications.This paper describes the information fusion process for a robot removing weed ina field. We analyze the robotic system by relating it to the JDL model functions.The civilian application we consider here has some properties which differ from thetypical defense applications: (1) indifferent environment and (2) a predictable andstructured process to achieve its objectives. As a consequence, situation estimatestend to deal with internal properties of the robot and its mission progress (throughmission state transition) rather than external entities and their relations. Nevertheless, the JDL model appears useful for describing the fusion activities of the weeding robot system. We provide an example of how state transitions may be detected and exploited using information fusion and report on some initial results. An additional finding is that process refinement for this type of application can be expressed in terms of a finite state machine.
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| 8. |
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| 9. |
- Fertner, Antoni, et al.
(författare)
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Applications of Backscattering for the Study of Twisted Pair Transmission Lines
- 2018
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480. ; 66:12, s. 5230-5237
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Tidskriftsartikel (refereegranskat)abstract
- The phenomenon of backscattering in copper cables has been recently observed and initially explicated. It can provide promising techniques to address the problem of loop diagnostic and maintenance. The backscattering is analyzed both in frequency and time domains. To demonstrate the practical use of the phenomenon, we estimate certain properties of the loop using wideband, high-frequency $\selevenf(f)$ measurements performed in the laboratory on real cables. The results corroborate the usefulness and accuracy of the investigated method.
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| 10. |
- Fertner, Antoni, et al.
(författare)
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Backscattering in Twisted-Pair Nonhomogeneous Transmission Lines
- 2018
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480. ; 66:6, s. 2674-2682
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Tidskriftsartikel (refereegranskat)abstract
- The development of the communication networks tends gradually toward exploiting higher frequencies, sometimes even reaching the lowest microwave band (P-band). As the signal bandwidth used for transmission over twisted-pairs increases, as recommended by G.fast and other broadband systems, new phenomenon was observed, namely, backscattering. Motivated by the measurements of copper cables in frequency band up to 400 MHz, we propose a novel backscattering model. It may be productively applied to the problem of loop diagnostics. The methods to accurately and reliable determine the relevant transmission-line parameters are sine qua non condition to appropriately exploit the potential of short-to-medium range access lines. In this paper, a recursive formulation of the frequency-domain response of the backscattering is used for a space-time characterization. To confirm the practical use of the finding, we evaluate the properties of a loop using wideband, high-frequency S₁₁ measurements of the real cables. These laboratory results confirm the effectiveness and accuracy of the proposed method.
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| 11. |
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| 12. |
- Hyyppä, Kalevi, et al.
(författare)
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Low-noise photodiode-amplifier circuit
- 1994
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Ingår i: IEEE Journal of Solid-State Circuits. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9200 .- 1558-173X. ; 29:3, s. 362-365
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Tidskriftsartikel (refereegranskat)abstract
- A photodiode-amplifier circuit with the photodiode in the feedback path is presented. It is named the PIF-circuit. No resistor is needed at the amplifier input to provide a path to ground for the signal and leakage currents from the photodiode and the amplifier input bias current. Therefore, one potentially dominating noise source is eliminated. At frequencies below 10 kHz, the implemented PIF-circuit has an NEP≈3 fW/√Hz
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| 13. |
- Höst, Stefan, et al.
(författare)
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Low complexity computation of the BT0 Hilbert twisted pair cable model
- 2010
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Ingår i: [Host publication title missing]. ; , s. 195-199
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Konferensbidrag (refereegranskat)abstract
- By use of the Hilbert transform the standardized BT0 twisted pair cable model can be rederived as a causal model with lower order, denoted BT0$_H$. In the present contribution the computational complexity of the BT0$_H$ model is decreased as the Hilbert transform is approximated with a look-up table implemented as a polynomial approximation. This results in a model of lower complexity than BT0$_H$ and lower order than the original BT0 model. Finally a comparison on causality of the considered models is presented.
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| 14. |
- Knaust, Stefan
(författare)
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Microsystems for Harsh Environments
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When operating microsystems in harsh environments, many conventionally used techniques are limiting. Further, depending on if the demands arise from the environment or the conditions inside the system, different approaches have to be used. This thesis deals with the challenges encountered when microsystems are used at high pressures and high temperatures.For microsystems operating at harsh conditions, many parameters will vary extensively with both temperature and pressure, and to maintain control, these variations needs to be well understood. Covered within this thesis is the to-date strongest membrane micropump, demonstrated to pump against back-pressures up to 13 MPa, and a gas-tight high pressure valve that manages pressures beyond 20 MPa.With the ability to manipulate fluids at high pressures in microsystems at elevated temperatures, opportunities are created to use green solvents like supercritical fluids like CO2. To allow for a reliable and predictable operation in systems using more than one fluid, the behavior of the multiphase flow needs to be controlled. Therefore, the effect of varying temperature and pressure, as well as flow conditions were investigated for multiphase flows of CO2 and H2O around and above the critical point of CO2. Also, the influence of channel surface and geometry was investigated.Although supercritical CO2 only requires moderate temperatures, other supercritical fluids or reactions require much higher temperatures. The study how increasing temperature affects a system, a high-temperature testbed inside an electron microscope was created.One of the challenges for high-temperature systems is the interface towards room temperature components. To circumvent the need of wires, high temperature wireless systems were studied together with a wireless pressure sensing system operating at temperatures up to 1,000 °C for pressures up to 0.3 MPa.To further extend the capabilities of microsystems and combine high temperatures and high pressures, it is necessary to consider that the requirements differs fundamentally. Therefore, combining high pressures and high temperatures in microsystems results in great challenges, which requires trade-offs and compromises. Here, steel and HTCC based microsystems may prove interesting alternatives for future high performance microsystems.
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Sales, Claudomiro, et al.
(författare)
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Line Topology Identification Using Multiobjective Evolutionary Computation
- 2010
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - 0018-9456. ; 59:3, s. 715-729
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Tidskriftsartikel (refereegranskat)abstract
- The broadband capacity of the twisted-pair lines strongly varies within the copper access network. It is therefore important to assess the ability of a digital subscriber line (DSL) to support the DSL services prior to deployment. This task is handled by the line qualification procedures, where the identification of the line topology is an important part. This paper presents a new method, denoted topology identification via model-based evolutionary computation (TIMEC), for line topology identification, where either one-port measurements or both one-and two-port measurements are utilized. The measurements are input to a model-based multiobjective criterion that is minimized by a genetic algorithm to provide an estimate of the line topology. The inherent flexibility of TIMEC enables the incorporation of a priori information, e. g., the total line length. The performance of TIMEC is evaluated by computer simulations with varying degrees of information. Comparison with a state-of-art method indicates that TIMEC achieves better results for all the tested lines when only one-port measurements are used. The results are improved when employing both one-and two-port measurements. If a rough estimate of the total length is also used, near-perfect estimation is obtained for all the tested lines.
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| 19. |
- Svensson, Stefan, 1985-, et al.
(författare)
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ESEM as a Tool for Studying High Temperature Electronics
- 2011
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Ingår i: IMAPS High Temperature Electronics Network (HiTEN 2011), July 18-20, 2011 ,Oxford, UK.
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Konferensbidrag (refereegranskat)abstract
- Researchers studying materials and processes at high temperatures are often restricted to do evaluation afterwards and at room temperature using e.g. scanning electron microscopy (SEM). Limited by high vacuum, outgassing and non-conducting samples are difficult to study with SEM. For such samples, environmental scanning electron microscope (ESEM) is an alternative that is particularly suited also for high temperature in-situ studies. The electron detector in the ESEM make use of otherwise unwanted scattering of electrons as an amplifier of the signal, and by using differential pumping, it is possible to introduce several mbar of either oxygen, water vapor, or a gas of choice into the sample chamber while still maintaining the high-vacuum in the electron column. The auxiliary gas neutralizes surface charges built up by the electron beam, which makes it possible to image non-conductive and outgassing samples, thus making it possible to study e.g. polymeric and high temperature materials. Our ESEM, FEI XL30, have a heating stage making it possible to reach temperatures up to 1500°C. Equipped with electrical feed- throughs, the instrument can be used to study high temperature phenomena on electrically activated components.ESEM is an instrument that has found its use for biological and organic samples. However, less work has been done using it for high temperature processes. Here, we show real-time imaging of the sintering of dielectric and Ag thick-film prints on AlN substrates. The use of the electrical feed-throughs to activate electrical components and study them at high temperatures is also demonstrated. ESEM is a versatile tool for high temperature studies and in-situ analysis of electrical components, solder processes and different die-attach materials.
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| 20. |
- Zhang, Qiuxia, 1960, et al.
(författare)
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Blood flow in the tibialis anterior muscle by photoplethysmography during foot-transmitted vibration.
- 2003
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Ingår i: European journal of applied physiology. - : Springer Science and Business Media LLC. - 1439-6319 .- 1439-6327. ; 90:5-6, s. 464-9
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Tidskriftsartikel (refereegranskat)abstract
- Photoplethysmography (PPG) was used to detect changes in the anterior tibial muscle blood flow (MBF) during foot-transmitted vibration in six healthy subjects. A filter was developed for reducing the vibration-induced artefacts in the PPG signal. The vibration applied was random with constant acceleration power density in the range 5-2000 Hz with an acceleration of 16-46 m s(-2) (rms). The application of the filter technique showed a dramatic reduction in the vibration-induced artefacts and distortion of the PPG signal was negligible. The mean ratio and correlation coefficient of MBF originating from filtered and non-filtered PPG signals was [mean (SD)] 0.89 (0.04) and 0.99, respectively. This made it possible to detect a relative increase in MBF of 20% during an acute vibration exposure. The results suggest that the use of the filter enables MBF to be measured by PPG during vibration, thus extending the range of applications of the PPG technique to include ergonomic conditions.
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