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  • 51. Andrén, Linus
    et al.
    Håkansson, Lars
    Brandt, Anders
    Claesson, Ingvar
    Identification of Motion of Cutting Tool Vibration in a Continuous Boring Operation: Correlation to structural Properties2004Ingår i: Mechanical systems and signal processing, ISSN 0888-3270, E-ISSN 1096-1216, Vol. 18, nr 4, s. 903-27Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The internal turning operation has a history of being a cumbersome metal working process as vibration in boring operations is usually inevitable. In this article, the deflection shapes and/or mode shapes as well as the resonance frequencies of a boring bar have been put under scrutiny. Three methods have been used in order to investigate dynamic properties of a clamped boring bar: a theoretical Euler-Bernoulli beam model, an experimental modal analysis and an operating deflection shape analysis. \\ The results indicate a correlation between the shapes of the deflection shapes and/or mode shapes produced by the three different analysis methods. On the other hand, the orientation of the forced deflection shapes and/or mode shapes and the resonance frequencies demonstrates differences between the three methods. During continuous cutting, it is demonstrated that the bending motion of the first two resonance frequencies is to a large extent in the cutting speed direction.

  • 52. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Active Control of Boring Bar Vibrations Using the Leaky Feedback Filtered X-LMS2003Konferensbidrag (Refereegranskat)
    Abstract [en]

    The boring operation is a cumbersome manufacturing process marred by noise and vibration related problems. The manufacturing industry is having trouble with these kinds of metal cutting operations. There exist several approaches to reduce the vibrations in cutting operations in general. Passive tuned dampers in boring bars have been commercially available for some time. An active solution is likely to be more robust to changes in the spectral content, where the passive counterpart have a small operable area, the active solution is able to adapt to these kinds of changes. Active vibration control in boring operations has been proven to be feasible. The algorithm used in the successful experiments was the feedback filtered X-LMS algorithm. This algorithm does however not guarantee a stable behavior, but incorporating a leakage factor will make the algorithm more robust. Power spectral density of boring bar vibration of real cutting experiments show that the leaky filtered X-LMS algorithm is a possible candidate to be a suitable control algorithm. Nyquist diagrams of the controller during operation show that the stability is increased significantly.

  • 53. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Active Control of Machine Tool Vibrations in External Turning Operations2003Ingår i: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture, ISSN 0954-4054, E-ISSN 2041-2975, Vol. 217, nr 6, s. 869-872Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vibration and noise in metal cutting are ubiquitous problems in the workshop. The external turning operation is one kind of metal cutting that exhibits vibration related problems. Severe noise is also a problem growing in proportion due to regulations in preventing hearing loss. Active vibration control is a potential solution to such problems. With the piezo ceramic actuator technology of today, the size of the actuator can be kept small and still be able to produce a sufficient amount of force for the anti vibrations. Results from several continuous cutting experiments show a 40 dB reduction of the cutting tool vibration level. The design of the active technique enables this technology to be applicable to a general lathe provided the mounting arrangement is fairly similar.

  • 54. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Actuator placements and Variations in the Control Path estimates in the Active Control of Boring Bar Vibrations2004Konferensbidrag (Refereegranskat)
    Abstract [en]

    A classical example of chatter prone machining is the boring operation. Turning under conditions with high vibrations in the cutting tool deteriorates the surface finish and may cause tool breakage. Severe noise is also a consequence of the high vibration levels in the boring bar. Active control is one possible solution to the noise and vibration problem in boring operations. In boring operations the boring bar usually have vibration components in both the cutting speed and the cutting depth direction. The introduction of the control force in different angles in between the cutting speed and the cutting depth directions have been investigated. Furthermore, control path estimates produced when the active boring bar was not in contact with the workpiece and during continuous cutting operation are compared. Experimental results indicate that the control force should be introduced in the cutting speed direction. Although the vibrations are controlled in just the cutting speed direction the vibrations in the cutting depth direction are also reduced significantly.

  • 55. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Performance Evaluation of Active Vibration Control of Boring Operations Using Different Active Boring Bars2003Konferensbidrag (Refereegranskat)
    Abstract [en]

    Vibration and noise in boring operations are ubiquitous problems in the workshop. In boring operations, the boring bar is subjected to forces from both the cutting speed and the cutting depth direction. To solve the vibration problem using active techniques would normally require two actuators in order to enable the control of both directions. By mounting one actuator in between the cutting speed and the cutting depth direction it is possible to achieve an active control solution with one actuator. Using only one actuator not only simplifies the control algorithm and saves extra equipment but is also favourable in terms of modifications of the boring bar. The harsh environment in a lathe more or less requires that both sensors and actuators are embedded and sealed into the boring bar. Since the forces that are to be controlled are large, the space needed for the actuator is substantial. Thus using only one actuator will keep the modified boring bar stiffer than a two actuator design. Three boring bars with the actuator mounted at different angles between the cutting speed and the cutting depth directions have been tested. Results from cutting experiments show that the one actuator solution has good potentials to the vibration problem in boring operations.

  • 56. Andrén, Linus
    et al.
    Håkansson, Lars
    Claesson, Ingvar
    Lagö, Thomas L
    Piezo Ceramic Actuators versus High Magnetostrictive Actuators in the Active control of Tool Vibration1999Konferensbidrag (Refereegranskat)
    Abstract [en]

    In the turning operation chatter or vibration is a frequent problem, which affects the result of the machining, and, in particular, the surface finish. Tool life is also influenced by vibration. Severe acoustic noise in the working environment frequently occurs as a result of dynamic motion between the cutting tool and the workpiece. These problems can be reduced by active control of machine-tool vibration. In the active control system for the control of tool vibration a tool holder construction with integrated high magnetostrictive actuators was used. However, high magnetostrictive actuators generally have a non-linear behavior and it is a well known fact that non-linear properties in the forward path in an active control system is likely to degrade the robustness of the control system. A new generation embedded active tool holder shanks based on piezo ceramic actuators has been developed. Based on spectrum estimates, both coherence spectrum and frequency response function estimates has been calculated for both the old tool holder construction and the new generation active tool holder shank. From the results it follows that the phase delay is smaller and the linearity of the new generation active tool holder shank are superior compared to the old technology. The physical features and properties of the new generation active tool holders are superior to the old tool holder.

  • 57. Andrén, Linus
    et al.
    Johansson, Sven
    Winberg, Mathias
    Claesson, Ingvar
    Active Noise Control Experiments in a Fork-lift Truck Cabin2004Konferensbidrag (Refereegranskat)
    Abstract [en]

    High comfort for the driver in working vehicles is an important feature as well as a demand from the drivers. Low noise level is an essential factor for the manufacturer to maintain a high standard and comfort of vehicles. In many cases the noise inside the cabin can be related to the engine orders. Hydraulic pumps and fans are also related to the engine but not necessarily integers of the engine order. Passive absorbers are not suitable for the lowest frequencies and one approach is to use an active noise control system to solve the noise problem at low frequencies. In the present experiment loudspeakers were mounted inside the cabin of a fork lift-truck to produce the secondary noise field. To sense the residual noise, microphones were installed close to the driver's head. The aim is to create a zone of reduced noise around the head. Since a large portion of the noise inside the cabin can be related to the engine, an active control system based on a feedforward solution is possible. Experimental results from a feedforward solution of active noise control in a fork-lift truck cabin show that the noise level in the low frequency region can be reduced significantly.

  • 58.
    Ansari, Yousuf Hameed
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Siddiqui, Sohaib Ahmed
    Blekinge Tekniska Högskola, Fakulteten för datavetenskaper, Institutionen för kommunikationssystem.
    Quality Assessment for HEVC Encoded Videos: Study of Transmission and Encoding Errors2016Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    There is a demand for video quality measurements in modern video applications specifically in wireless and mobile communication. In real time video streaming it is experienced that the quality of video becomes low due to different factors such as encoder and transmission errors. HEVC/H.265 is considered as one of the promising codecs for compression of ultra-high definition videos. In this research, full reference based video quality assessment is performed. The raw format reference videos have been taken from Texas database to make test videos data set. The videos are encoded using HM9 reference software in HEVC format. Encoding errors has been set during the encoding process by adjusting the QP values. To introduce packet loss in the video, the real-time environment has been created. Videos are sent from one system to another system over UDP protocol in NETCAT software. Packet loss is induced with different packet loss ratios into the video using NETEM software. After the compilation of video data set, to assess the video quality two kind of analysis has been performed on them. Subjective analysis has been carried on different human subjects. Objective analysis has been achieved by applying five quality matrices PSNR, SSIM, UIQI, VFI and VSNR. The comparison is conducted on the objective measurement scores with the subjective and in the end results deduce from classical correlation methods.

  • 59.
    Appilla Chakravarthula, Rohan
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Veluru, Chaithanya Kumar Reddy
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Intelligent Beam Weight Computation for Massive Beamforming2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    LTE (Long Term Evolution) is likely the most complex wireless system ever developed. It incorporates features that could not have been economically implemented as recently as a decade ago. Today, with large-scale ICs, LTE can be easily accommodated in base stations and battery-powered handsets alike. LTE-Advanced is the upgraded version of LTE technology for providing more speed and greater reliability.

    In this report, the wireless communication between the user and base station is implemented by creating 4G LTE environment in MATLAB. Impact of Coherence time on beam weight computation varies for different delay profiles. Moreover, SNR of the transmitted signal varies significantly by the time gap between two successive uplink frames in TDD configuration. In this report, computationally efficient algorithm for reducing beam weight computations in system level LTE simulations is proposed.

    The wireless channel is modelled in both Rician and Rayleigh fading channel. Efficiency of beam forming algorithms is observed at different channel conditions like delay profile, fading channel, bandwidth, correlation, modulation technique.

    The MUSIC algorithm is implemented for detecting the movement of the users in Line of sight condition

  • 60.
    Ariyaratne, Chamila Asanka
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Link Adaptation Improvements for Long Term Evolution (LTE)2009Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The Long Term Evolution (LTE) link adaptation is based on measured instantaneous Signal to Interference and Noise Ratio (SINR) which is used for selecting Modulation and Coding Scheme (MCS) for transmissions. In addition, depending on the scheduler, SINR may be used to determine which users are scheduled for a certain transmission time interval and on which frequency resources. The measured SINR can be inaccurate due to measurement errors, rounding errors due to quantization of the SINR values, and delay from time of measurement until the actual data transmissions. To compensate for SINR inaccuracies, the SINR can be adjusted by a certain offset before being used for link adaptation and scheduling. This offset value, referred to as the link adaptation margin in this thesis, can be a fixed value common to all the users in the system at all times or adaptively adjusted for each user based on some algorithm via a feedback loop, referred to as differentiated link adaptation. This thesis tries to improve the system performance for LTE downlink and uplink by using differentiated link adaptation based on packet error occurrences of each user as feedback. The performance of the differentiated link adaptation was compared to the best performance that is achievable using a fixed link adaptation margin. We investigated the influence of several parameters on the link adaptation error characteristics, such as settings for SINR estimation, scheduling algorithms, traffic patterns. It was shown that there are error clusters, but that these are short and difficult to react to on time. A performance gain was only possible in the downlink for FTP traffic with a proportional fair in time and frequency (PFTF) scheduler which was the scenario with the largest variations with regards to both scheduling and traffic model. It was seen that the gains of using differentiated link adaptation increased in the downlink as the transmissions got more random. For more stable situations, a fixed link adaptation margin performed better. The uplink performance was worse with differentiated link adaptation than with a fixed optimized link adaptation margin. This could be because the uplink SINR estimation was much better than in the downlink, with low estimation error variance, in which case frequent SINR adjustments could make the situation worse off.

  • 61.
    Armiński, Wojciech
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Jüngst, Andrzej
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    SEMI-AUTOMATED FORWARDER CRANE CONTROL2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The objective of this thesis is to develop and implement two control programs on an experimental hydraulic crane. The first program demonstrates a kinematic redundancy of the crane also called an extra degree of freedom. The second program is an experimental trajectory following solution that can aid crane operators. The trajectory is optimized to minimize hydraulic cylinders use. The thesis involves various issues concerning both low layer and high layer control. This includes a system identification, system nonlinearity compensation, dead zone compensation, gain scheduling, PI controllers tuning and optimization problems. The solutions like genetic algorithm and fuzzy logic are used. Both control programs are made in Mathworks Simulink and run in dSPACE system.

  • 62.
    Arsalan, Muhammad
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Future Tuning Process For Embedded Control Systems2009Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    This master’s thesis concerns development of embedded control systems.Development process for embedded control systems involves several steps, such as control design, rapid prototyping, fixedpoint implementation and hardware-in-the-loop-simulations. Another step, which Volvo is not currently (September 2009) using within climate control is on-line tuning. One reason for not using this technique today is that the available tools for this task (ATI Vision, INCA from ETAS or CalDesk from dSPACE) do not handle parameter dependencies in a atisfactory way. With these constraints of today, it is not possible to use online tuning and controller development process is more laborious and time consuming.The main task of this thesis is to solve the problem with parameter dependencies and to make online tuning possible.

  • 63.
    Arslan, Muhammad
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    , Usman
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    PERFORMANCE EVALUATION OF VIDEO QUALITY ASSESSMENT METHODS BASED ON FRAME FREEZING2014Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    A Digital Video Communication System consists of a video encoder, a channel through which the video is transmitted and finally a video decoder. These three phases can cause different kinds of impairments or degradations in the quality of a video. One of the degradations that takes place due to an error prone channel is frame freezing and it affects the quality of a video. Frame freezing is a phenomenon in which a particular frame is repeated (displayed) for a certain period of time until the next correct frame is received hence producing a pause or a freeze in a video sequence. Frame freezing can be single or multiple depending on the channel characteristics. Research is being conducted in order to devise a metric which can help in quantifying a video sequence on the basis of its quality. Researchers design metrics and then using their mathematical models, they compare their results with subjective measurements. Subjective measurements help in telling the preciseness and correctness of the metric that whether the quality assessment metric is close enough to subjective test measurements. In this report, three metrics used for video quality assessment have been studied and compared mathematically as well as by careful experiments. The three metrics, chosen for this study, work on No Reference (NR) method for judging the quality of a video. Subjective tests have been performed keeping in view of the recommendations of ITU (International Telecommunication Union). After the study of these three metrics, their advantages and disadvantages over each other have been discussed and the metric that performs the best under certain conditions has been proposed. Finally, a conclusion has been made for the metric that performs the best and also for the metric that performs the worse or even does not perform at all under certain conditions.

  • 64.
    Asl, Babak Ghafary
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    A Computer Aided Detection System for Cerebral Microbleeds in Brain MRI2012Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Advances in MR technology have improved the potential for visualization of small lesions in brain images. This has resulted in the opportunity to detect cerebral microbleeds (CMBs), small hemorrhages in the brain that are known to be associated with risk of ischemic stroke and intracerebral bleeding. Currently, no computerized method is available for fully- or semi-automated detection of CMBs. In this paper, we propose a CAD system for the detection of CMBs to speed up visual analysis in population-based studies. Our method consists of three steps: (i) skull-stripping (ii) initial candidate selection (iii) reduction of false-positives using a two layer classi cation and (iv) determining the anatomical location of CMBs. The training and test sets consist of 156 subjects (448 CMBs) and 81 subjects (183 CMBs), respectively. The geometrical, intensity-based and local image descriptor features were used in the classi cation steps. The training and test sets consist of 156 subjects (448 CMBs) and 81 subjects (183 CMBs), respectively. The sensitivity for CMB detection was 90% with, on average, 4 false-positives per subject.

  • 65.
    Asteborg, Marcus
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Svanberg, Niklas
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Implementation Considerations for Active Noise Control in Ventilation Systems2006Självständigt arbete på grundnivå (kandidatexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The most common method to attenuate noise in ventilation systems today is passive silencers. For these to efficiently attenuate frequencies below 400 Hz such silencers need to be large and a more neat solution to attenuate low frequencies is to use active noise control (ANC). The usage of ANC in ventilation systems is well known and there are several commercial products available. ANC is not, however, used on a wide basis due to its often high price and poor performance. Since the price is an important factor in ANC systems the expensive laboratory filters and the amplifier that is currently used in the experimental setup at Blekinge Institute of Technology (BTH) need to be replaced with cheaper ones, but without too much performance loss. For easier implementation in ventilation systems the placement of the reference microphone is important, the shorter distance from the anti-noise loud speaker the easier the ANC system is to implement. But if the distance is so small that the ANC system is no longer causal the performance will be decreased and if the reference microphone is close enough to pick up acoustic feedback from the anti-noise loud speaker the performance will also be decreased. In this thesis the expensive laboratory filters will be exchanged to cheaper alternatives, power and total harmonic distortion (THD) measurements will be done on the amplifier that is driving the loud speaker and the reference microphones position will be investigated with measurements on the group delay of the system and the acoustic feedback between the loud speaker and the reference microphone.

  • 66.
    Augustsson, Jens
    Blekinge Tekniska Högskola, Institutionen för signalbehandling.
    Full duplex Konferenstelefon1997Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Denna rapport analyserar ekosläckning för en full duplex högtalartelefon. Systemet bygger på en LMS-algoritm som har implementerats på en TMS320C3 1 signalprocessor. Arbetet har gått ut på att undertrycka ekon genom utnyttja så mycket som möjligt av processoms kapacitet. Möjligheterna för att två eller fler personer skall kunna tala med varandra på att ledigt sätt genom en högtalartelefon påverkas mycket av de ekon som finns i systemet. Högtalartelefonens mikrofon fångar upp ljudet ifrån sin egen högtalare och skickar detta ljud tillbaka genom telefonnätet. Utan någon form av ekokontroll uppstår ett irriterande eko av sin egen röst i telefonen. Ju längre fardröjning som telefonnätet tillför, ju mer irriterande blir ekot. Konventionella högtalartelefoner använder röstaktivering av mikrofonen för att bli av med ekot. Detta medför att de samtalande partertema inte både kan höra och prata med varandra samtidigt. Detta kallas i kommunikationssammanhang Halv-Duplex. Denna onaturliga form av samtal medför att bägge börjar tala samtidigt och att de avbryter varandra. 1 mitt arbete tittar jag närmare på metoder för ekokontroll med mål att bägge parterna skall både kunna tala med och höra varandra simultant, sk. Full-Duplex, utan rundgång. Teorierna kring adaptiv ekosläckning har varit kända sedan Iänge men det är inte förrän på senare tid som det finns processorer som klarar av beräkningarna’ i realtid. TMS320C3 1 ‘an har inte riktigt den önskvärda beräkningskapaciteten för realtidsberäkning av langa adaptiva FIR-filter. En filterlängd på 300 filter koefficienter uppnåddes. För att nå upp till denna längd användes en metod med adaptering bara på halva bandbredden, 1500 Hz. Den andra halvan av bandbredden, 1500 - 3500 Hz, i ett telefonnät lämnades ofiltrerad. Ett stort bekymmer visade sig vara att finna en lamplig metod för att besluta när adaptering får ske. En enkel sk. taldetektor implementerades för detta endamål.

  • 67. A.V., Fidalgo
    et al.
    G.R., Alves
    M.A., Marques
    M.C, Viegas
    M.C, Costa-Lobo
    U., Henandez-Jayo
    J., Garcia-Zúbia
    Ingvar, Gustavsson
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Adapting remote labs to learning scenarios: Case studies using VISIR and remotElectLab2014Ingår i: Revista Iberoamericana de Tecnologias del Aprendizaje, ISSN 1932-8540, Vol. 9, nr 1, s. 33-39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Remote laboratories are an emergent technological and pedagogical tool at all education levels, and their widespread use is an important part of their own improvement and evolution. This paper describes several issues encountered on laboratorial classes, on higher education courses, when using remote laboratories based on PXI systems, either using the VISIR system or an alternate in-house solution. Three main issues are presented and explained, all reported by teachers, that gave support to students' use of remote laboratories. The first issue deals with the need to allow students to select the actual place where an ammeter is to be inserted on electric circuits, even incorrectly, therefore emulating real-world difficulties. The second one deals with problems with timing when several measurements are required at short intervals, as in the discharge cycle of a capacitor. In addition, the last issue deals with the use of a multimeter in dc mode when reading ac values, a use that collides with the lab settings. All scenarios are presented and discussed, including the solution found for each case. The conclusion derived from the described work is that the remote laboratories area is an expanding field, where practical use leads to improvement and evolution of the available solutions, requiring a strict cooperation and information-sharing between all actors, i.e., developers, teachers, and students.

  • 68.
    Avinash, Avinash
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Alampally, Shravan Kumar
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Verification of Crane Control Algorithm2013Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In the present world the heavy machine applications have grown more sophisticated. Crane is designed in such a way to perform the tasks that are hard for human beings, in order to make the work faster and easier. In this area of crane utilization, forwarder movement is the key in performing most of the tasks. Forwarder movement plays an important role in tasks such as collecting logs from the ground and moving them from one place to another. These types of cranes find a wide range of utilization in forestry applications. In order to perform these tasks movement of the forwarder has to be according. Depending on the loads to carry the size of the forwarder also varies. Partial automation of the crane movement in the form of forwarder movement is the area of interest. Aim of the thesis is to concentrate on automation of crane link, to be more specific, the prismatic link. This can be achieved through the verification of the mechanism and similarity of the two algorithms in the Matlab system and in the DASA system.

  • 69.
    Awais, Muhammad
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Multichannel Wiener Filtering for Speech Enhancement in Modulation Domain2011Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Normally speech signals are contaminated with noise and interference that reduces the intelligibility of speech during communication. In order to make speech signals e ective and useful, they need to be enhanced from the noisy speech signal. In speech processing eld many speech enhancement techniques are developed and are providing very good results. Multichannel microphone array is also one of the techniques used for speech enhancement, that provides better results than the single channel speech enhancement. Moreover, Wiener filtering is the most commonly used technique for multichannel microphone array for speech enhancement. The main focus of this thesis is to implement multichannel microphone array using Wiener filtering in the modulation domain system and also in the time domain system to enhance the speech. Both are implemented successfully and validated e ectively by considering diff erent parameters, i,e; Signal to Noise Ratio (SNR), Signal to Noise Ratio Improvement (SNRI) and Mean Opinion Score (MOS). Both the systems are tested with one female and one male speech distorted with diff erent types of noise at -5dB,0dB,5dB,10dB,15dB and 20dB SNR. The values are calculated for the diff erent number of subbands, as the main focus is on modulation domain system. It provided efficient results in terms of SNRI and MOS score.

  • 70.
    AWONIYI, OLUWASEYI
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    STRATOSHPHERIC CHANNEL MODELLING2007Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    High Altitude Platform Stations (HAPs) are communication facilities situated at an altitude of 17 to 30 km and at a specified, nominal, fixed point relative to the Earth. They are mostly solar-powered, unmanned, and remotely-operated. These platforms have the capability of carrying multipurpose communications relay payload, which could be in the form of full base station or, in some cases, a simple transponder as is being used in satellite communication systems. HAPs, when fully deployed will have the capability of providing services and applications ranging from broadband wireless access, navigation and positioning systems, remote-sensing and weather observation/monitoring systems, future generation mobile telephony etc. HAPs are also known to be low cost when it comes to its implementation and are expected to be the next big provider of infrastructure for wireless communications. There have been a lot of ongoing and exciting research works into various aspects of this emergent technology. As radio Engineers, the need to predict the channel quality and analyze the performance evaluation of such stratospheric propagation has generated quite a few models. Although some of the models under consideration are from the existing terrestrial and satellite communications which in some way, have some relationships with this new technology. This thesis work provides some insight into this new aspect of wireless communications in terms of the need for a new system, its benefits, challenges services provided and applications supported. Existing models already researched and developed for HAPS are reviewed; one of them was picked and deeply looked into as regards the propagation and channel efficiency. The analysis of the choice model is presented using one of the performance test for channel models, the bit error rate (BER).

  • 71.
    Azam, Adnan
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Siddique, Taimoor
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Spectrum Optimization in Cognitive Radio Networks using Genetic Algorithms2010Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Den snabba revolution inom trådlös kommunikation under de senaste åren har ökat efterfrågan av radiospektrum för att fullgöra tjänsternas kvalitet (QoS) för trådlösa tillämpningar, vilket leder till spektrum överbeläggning. För att lösa spektrum överbeläggning problemet, kognitiv radio (CR) har trätt fram som en ledande teknik, eftersom det kan intelligent mening en oanvänd spektrum utan att skapa någon skada för behöriga användare. När spektrum anade att uppfylla QoS krav på ansökan och att använda radion resurserna mer effektivt, ett intelligent beslut om att tilldela en optimal spektrum är ett bra krav. I det här examensarbetet en spektrumallokering förfarande föreslås. Genetiska algoritmer (GA) en evolutionär datoriserad teknik används som arbetar Darwins evolutionsteori. Den definierar radio i form av kromosomer och gener. Förfarandet modelleras med hjälp av Matlab, och programmets QoS krav har uppställts som underlag till GA förfarandet, vilket resulterar i en optimal lösning efter flera evolution

  • 72.
    Azam, Muhammad
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Methods for Recovery of Missing Speech Packets2011Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Denna magisteravhandling beskriver två metoder för återskapande av förlorade talpaket, samt rekonstruktion av talsignal då ett fåtal signalsampel saknas. Därtill föreslår avhandlingen utökningar till dessa två metoder för att hantera två efterföljande saknade talpaket. Metoderna är presenterade och utvärderade på talsignaler där signalvärden har förstörts enligt en given kanalmodell.

  • 73. Aziz, Hussein Muzahim
    et al.
    Fiedler, Markus
    Grahn, Håkan
    Lundberg, Lars
    Streaming Video as Space – Divided Sub-Frames over Wireless Networks2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Real time video streaming suffers from lost, delayed, and corrupted frames due to the transmission over error prone channels. As an effect of that, the user may notice a frozen picture in their screen. In this work, we propose a technique to eliminate the frozen video and provide a satisfactory quality to the mobile viewer by splitting the video frames into sub- frames. The multiple descriptions coding (MDC) is used to generate multiple bitstreams based on frame splitting and transmitted over multichannels. We evaluate our approach by using mean opinion score (MOS) measurements. MOS is used to evaluate our scenarios where the users observe three levels of frame losses for real time video streaming. The results show that our technique significantly improves the video smoothness on the mobile device in the presence of frame losses during the transmission.

  • 74.
    Babaeeghazvini, Parinaz
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    EEG enhancement for EEG source localization in brain-machine speller2013Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    BCI controls external devices and interacts with the environment by brain signals. Measured EEG signals over the motor cortex exhibit changes in power related to the movements or imaginations which are executed in motor tasks [1]. These changes declare increase or decrease of power in the alpha (8Hz-13Hz), and beta (13Hz-28Hz) frequency bands from resting state to motor imagery task that known as event related synchronization (in case of power increasing) and desynchronization (in case of power decreasing) [2]. The necessity to communicate with the external world for locked-in state (LIS) patients (a paralyzed patient who only communicates with eyes), made doctors and engineers motivated to develop a BCI technology for typing letters through brain commands. Many researches have been done around this area to ascertain the dream of typing for handicapped. In the brain some regions of the cerebral cortex (motor cortex) are involved in the planning, control, and execution of voluntary movements. Electroencephalography (EEG) signals are electrical potential generated by the nerve cells in the cerebral cortex. In order to execute motoric tasks, the EEG signals are appeared over the motor cortex [1]. The measured brain response to a stimulus is called eventrelated potential (ERP). P300-event related potential (ERP) is an evoked neuron response to an external auditory or visual stimulus that is detectable in scalp-recorded EEG (The P300 is evoked potential which occurs across the parieto-central on the skull 300 ms after applying the stimulus). Farwell and Donchin have proven in a P300-based BCI speller [3] that P300 response is a reliable signal for controlling a BCI system. They described the P300 speller, in which alphanumeric characters are represented in a matrix grid of six-by-six matrix. The user should focus on one of the 36 character cells while each row and column of the grid is intensified randomly and sequentially. The P300, observed in EEG signals, is created by the intersection of the target row and column which causes detection of the target stimuli with a probability of 1/6 (in case of high accuracy of flashing operation). Also when the target stimulus is rarely presented in the random sequence of stimuli causes a neural reaction to unpredictable but recognizable event and a P300 response is evoked [3]. Generally when the subject is involved with the task to recognize the targets, the P300 wave happens and the signal amplitude varies with the unlikelihood of the targets. Its dormancy changes with the difficulty of recognizing the target stimulus from the standard stimuli [3].The attended character of the matrix can be extracted by proper feature extraction and classification of P300. A plenty of procedures for feature extraction and classification have been applied to improve the performance of originally reported speller [3], such as stepwise linear discriminate analysis (SWLDA) [4, 5], wavelets [1], support vector machines [6, 7, 8] and matched filtering [9]. Till now, BCI-related P300 research has mostly considered on signals from standard P300 scalp locations. While in [10, 11, 12, 13, 14, 15, 16] it has been proven that the use of additional locations, especially posterior sites, may improve classification accuracy, but it has not been addressed to particular offline and online studies. Recently, auditory version improvement of the visual P300 speller allows locked in patients who have problem in the visual system to use the P300 speller system by relating two numbers to each letter which indicate the row and column of letter position [17]. Now a new technology is needed which can substitute a keyboard with no alphabet menu. The technology will be handy for blind people and useful for healthy persons who need to work hands free with their computer or mobile. The aim of this thesis is to improve EEG detection through source localization for a new BCI application to type with EEG signals without using alphabet menu.

  • 75.
    Bajagain, Krishna Mani
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Experiment with Moving Target Focusing using GB-SAR2014Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Ground Based Synthetic Aperture Radar (GB-SAR) refers to SAR system which is mounted on ground linear track. It works on same principle as conventional SAR. Nowadays GB-SAR plays prominent role in the studies of many natural phenomenon as well as in studying some artificial infrastructure or terrain. It is a cost effective solution for the target scenes where it needed continuous monitoring. In this thesis GB-SAR system is experimented to detect moving targets. It should be emphasized that detection of moving target using GB-SAR is very new idea in the research field. As in conventional SAR, defocusing and/or displacement errors for moving target occur during image formation process in GB-SAR too. To detect the moving target, we need to test different Normalized Relative Speed (NRS) until the best focusing of moving target is reached. The research has been carried out in the following way. Firstly several simulations were tested on MATLAB with ideal condition. Secondly real experiments with moving targets were implemented based on the simulation results to collect real SAR data. Finally the data retrieved in the experiments was processed for moving target detection. The experiment was conducted at the Radio Communication Laboratory of Blekinge Institute of Technology. The radar is developed with a vector network analyzer (ENA 5071C), a double ridge guide horn antenna, a corner reflector, low loss high frequency cables and a antenna positioner. The movement of the radar is determined by a linear track. The developed GB-SAR system is configured as an ultra wideband–ultra wide beam (UWB) system. The operating frequency range is set to 1.5 - 2.5 GHz and the length of aperture is about 4 m. The radar measurement is taken place at 17 positions. The Global Back Projection (GBP) algorithm is used for UWB SAR data processing including image formation and moving target detection.

  • 76.
    Bajwa, Ahmer Ali
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Awan, Junaid Anwar
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Performance study of IEEE 802.16d (Fixed WiMAX) Physical layer with Adaptive Antenna System2008Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In this thesis work, WiMAX (IEEE 802.16d) PHY layer with underlying OFDM technology and an optional feature called Adaptive Antenna System has been considered. The SUI-3 channel model (Rician fading) is used for creating fading phenomena. An Adaptive Antenna System has been deployed at the receiver module to reduce the fading effects caused by SUI-3 channel model. Adaptive Antenna Systems (AAS) uses different beamforming techniques to focus the wireless beam between the base station and the subscriber station. In this thesis, the transmitter (SS) and receiver (BS) are fixed and AAS installed at the receiver is used to direct the main beam towards the desired LOS signal and nulls to the multipath signals. Pre-FFT beamformer based on Least Mean Square (LMS) algorithm is used. Different aspects of the complete system model were investigated such as adaptive modulation, angle of arrival of the incoming signals and number of array elements. It has been demonstrated through MATLAB simulations that the performance of the system significantly improves by AAS, where beamforming is implemented in the direction of desired user. The performance of the system further increases by increasing the number of antennas at receiver.

  • 77. Balakrishna, L.
    et al.
    Kumar, P.V.A.
    Prakash, Chetana
    Gangashetty, Suraykanath
    Speech enhancement using ICA with Bessel features2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Independent Component Analysis with Reference (ICA R) also called as constrained ICA (cICA) extracts only the desired source signals from the mixture of source signals by incorporating some prior information into the separation process. To overcome the problem of designing the reference signal when there is no prior information about the desired signal in the cICA, an improved method is proposed to use a different speech signal generated by the same physical source. The cICA is extended to use Bessel coefficients of the observed signals and the reference signal for processing as they converge faster than the other transformations. Since the Bessel functions provide the desired properties, efficient in representing speech signals, less memory storage they have been exploited in speech processing [1]. The results demonstrate the efficiency of the proposed method.

  • 78. Ballal, Tarig
    et al.
    Grbic, Nedelko
    Mohammed, Abbas
    A Simple and Computationally Efficient Algorithm for Real-Time Blind Source Separation of Speech Mixtures2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we exploit the amplitude diversity provided by two sensors to achieve blind separation of two speech sources. We propose a simple and highly computationally efficient method for separating sources that are W-disjoint orthogonal (W-DO), that are sources whose time-frequency representations are disjoint sets. The Degenerate Unmixing and Estimation Technique (DUET), a powerful and efficient method that exploits the W-disjoint orthogonality property, requires extensive computations for maximum likehood parameter learning. Our proposed method avoids all the computations required for parameters estimation by assuming that the sources are "cross high-low diverse (CH-LD)", an assumption that is explained later and that can be satisfied exploiting the sensors settings/directions. With this assumption and the W-disjoint orthogonality property, two binary time-frequency masks that can extract the original sources from one of the two mixtures, can be constructed directly from the amplitude ratios of the time-frequency points of the two mixtures. The method works very well when tested with both artificial and real mixtures. Its performance is comparable to DUET, and it requires only 2% of the computations required by the DUET method. Moreover, it is free of convergence problems that lead to poor SIR ratios in the first parts of the signals. As with all binary masking approaches, the method suffers from artifacts that appear in the output signals.

  • 79. Ballal, Tarig
    et al.
    Grbic, Nedelko
    Mohammed, Abbas
    Blind Source Separation of Speech Mixtures using a Simple and Computationally Efficient Time-Frequency Approach2007Konferensbidrag (Refereegranskat)
  • 80. Ballal, Tarig
    et al.
    Grbic, Nedelko
    Mohammed, Abbas
    Sensor Array Blind Source Separation using Time-Frequency Masking2006Konferensbidrag (Refereegranskat)
  • 81.
    Banadaki, Davood Dehgan
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Durmush, Sunay Sami
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Zahiri, Sharif
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Statistical Assessment of Uncertainties Pertaining to Uniaxial Vibration Testing and Required Test Margin for Fatigue Life Verification2013Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In the automotive industry uniaxial vibration testing is a common method used to predict the lifetime of components. In reality truck components work under multiaxial loads meaning that the excitation is multiaxial. A common method to account for the multiaxial effect is to apply a safety margin to the uniaxial test results. The aim of this work is to find a safety margin between the uniaxial and multiaxial testing by means of virtual vibration testing and statistical methods. Additionally to the safety margin the effect of the fixture’s stiffness on the resulting stress in components has been also investigated.

  • 82.
    Bandreddy, Pavan
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Pokala, Bhargav
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Perceptual Video Quality Assessment Tool2011Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    Compressing the video data is necessary for video transmission over networks with limited resources. Video quality at the end is based on the compression techniques used. In this research work, we mainly focused on compressing video files using H.264 encoding by considering some parameters and conducting a subjective test on the resulting compressed videos in a specially developed Perceptual Video Quality Assessment (PVQA) tool. This PVQA tool was developed as part of the thesis project. For the compression techniques, we have considered spatial resolutions (i.e. VGA and QVGA), temporal resolutions (i.e. 25fps and 12.5fps) and bit rate (i.e. 300kbps and 600kbps). By considering these parameters for three different test sequences, we down scaled and encoded to transmit over lossless channel. The received data is decoded and up scaled using open source software’s. For encoding and decoding of videos in H.264, we used JM reference software. For scaling the videos spatially and temporally, both FFMPEG and Virtual Dub are used. For up scaling the decoded video in spatial resolution (QVGA to VGA) two filter methods are used i.e. Bicubic Interpolation and Nearest Neighbor technique in Virtual Dub. For up scaling in temporal resolution (12.5fps to 25fps) the repeat frame method of Virtual Dub is used. These generated videos were evaluated by conducting subjective tests to determine the best technique that is suitable for transmission over a bit rate limited network. The developed PVQA tool satisfies the requirements of International Telecommunication Union (ITU) standard ITU-R BT.500-12. The PVQA tool will ask the subjects to grade the videos quality according to his/her experience and these grades are saved in excel sheets. The PVQA tool was developed under Java environment, with the VLC player embedded. The tool was designed to support the video. Results of the subjective video quality survey are summarized and finally conclusions are given.

  • 83. Bao, Vo Nguyen Quoc
    et al.
    Duong, Trung Quang
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Nallanathan, Arugumam
    Karagiannidis, George K.
    Distributed Switch-and-Stay Combining in Cognitive Relay Networks under Spectrum Sharing Constraints2013Ingår i: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), IEEE Communications Society, 2013, s. 1927-1932Konferensbidrag (Refereegranskat)
    Abstract [en]

    Distributed switch-and-stay combining (DSSC) has been envisioned as an effective transmission technique to achieve spatial diversity in a distributed fashion, with low implementation complexity. In this paper, we take a step further to incorporate DSSC into spectrum-limited environment, where the operating nodes have to share the frequency radio spectrum with licensed users. In particular, by deploying DSSC scheme in cognitive radio networks, we have shown that the low transmit power at unlicensed users, inflicted by the peak interference power constraint at licensed users, can be alleviated. We present closed-form expressions for outage probability and spectral efficiency, enabling us to evaluate and optimize the considered network performance. Numerical and simulation results show that when the switching threshold is below the outage threshold the full diversity order can be guaranteed at the secondary networks.

  • 84. Bao, Vo Nguyen Quoc
    et al.
    Duong, Trung Quang
    Blekinge Tekniska Högskola, Sektionen för datavetenskap och kommunikation.
    Nallanathan, Arugumam
    Tellambura, Chintha
    Effect of Imperfect Channel State Information on the Performance of Cognitive Multihop Relay Networks2013Ingår i: 2013 IEEE GLOBAL COMMUNICATIONS CONFERENCE (GLOBECOM), 2013, s. 3458-3463Konferensbidrag (Refereegranskat)
    Abstract [en]

    Cognitive relay technology has been envisioned as a promising transmission scheme to enhance the reliability and coverage of secondary networks. However, the performance of cognitive relay networks (CRNs) is limited by the lack of accurate channel state information (CSI). As such, this paper adequately addresses the impact of imperfect CSI on the performance of cognitive multihop networks by proposing a simple yet effective backoff control power method. In addition, novel exact and asymptotic expressions for outage probability and ergodic capacity over Rayleigh fading channels are also derived. These tractable analytical results reveal new insight into the design, e.g., the number of hops for secondary network, and optimization of cognitive multihop networks.

  • 85.
    Bardici, Nick
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Skarin, Björn
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Röstigenkänning genom Hidden Markov Model: En implementering av teorin på DSP2006Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Detta examensarbete går ut på att implementera en röstigenkänningssystem på en DSK – ADSP-BF533 EZ-KIT LITE REV 1.5 baserad på teorin om HMM, Hidden Markov Model. Implementeringen är baserad på teorin i examensarbetet Speech Recognition using Hidden Markov Model av Mikael Nilsson och Marcus Ejnarsson, MEE-01-27. Det som gjorts i arbetet är att utifrån teorin implementerat en MFCC, Mel Frequency Cepstrum Coefficient funktion, en träningsfunktion som skapar Hidden Markov Modeller av unika uttalanden av ord och en testfunktion som testar ett uttalat ord mot de olika modellerna som skapades av träningsfunktionen. Dessa funktioner skapades först i MatLab. Sedan implementerades testprogrammet på DSP:n Texas Instruments TMDS320x6711. Sedan utvärderades realtidstillämpningen.

  • 86.
    Barela, Krzysztof
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Ciereszko, Piotr
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Control System Design and Transmission Line Resonance Elimination of a 3-Phase Battery Charger2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    This paper addresses two problems which may occur during the operation of a MTM-HF traction battery charger produced by the company MicroPower AB: Firstly, high-power traction battery chargers are chiefly supplied from rectified 3-phase mains electricity, making them susceptible to resonant disturbances which occur in high-inductance power lines. These resonant disturbances increase the amplitude disturbances of the rectified DC voltage supplied to the battery charger, thus interfering with its operation. A method to suppress the resonant disturbances was devised using the inherent capability of a battery charger to draw a controlled current from the power lines. Secondly, Battery chargers operating near their maximum current capabilities are strongly affected by the ripple of the rectified supply voltage. In order to fully use the power supply, a control system was designed which minimizes the effect of that ripple on output current while ensuring that the desired value of output current is reached. Both of these methods were successfully tested using a simulated model of the MicroPower MTM-HF battery charger.

  • 87.
    Bartunek, Josef Strom
    et al.
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Nilsson, Mikael
    Sällberg, Benny
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Claesson, Ingvar
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, Avdelningen för elektroteknik.
    Adaptive Fingerprint Image Enhancement With Emphasis on Preprocessing of Data2013Ingår i: IEEE Transactions on Image Processing, ISSN 1057-7149, E-ISSN 1941-0042, Vol. 22, nr 2, s. 644-656Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article proposes several improvements to an adaptive fingerprint enhancement method that is based on contextual filtering. The term adaptive implies that parameters of the method are automatically adjusted based on the input fingerprint image. Five processing blocks comprise the adaptive fingerprint enhancement method, where four of these blocks are updated in our proposed system. Hence, the proposed overall system is novel. The four updated processing blocks are: 1) preprocessing; 2) global analysis; 3) local analysis; and 4) matched filtering. In the preprocessing and local analysis blocks, a nonlinear dynamic range adjustment method is used. In the global analysis and matched filtering blocks, different forms of order statistical filters are applied. These processing blocks yield an improved and new adaptive fingerprint image processing method. The performance of the updated processing blocks is presented in the evaluation part of this paper. The algorithm is evaluated toward the NIST developed NBIS software for fingerprint recognition on FVC databases.

  • 88.
    Bartunek, Josef Ström
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Minutiae Extraction from Fingerprint with Neural Network and Minutiae based Fingerprint Verification2004Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [sv]

    Människans fingeravtryck är rikt på detaljerna som kallas minutiae, vilka kan användas som identifierings märke för fingeravtryck verifikation. Mål med denna magister examen arbete är att ta fram ett komplett system för fingeravtryck verifikation igenom att extrahera och matcha minutiae. Ett neuralt nät blev tränat med hjälp av back-propagation algoritm och kommer att arbeta som en klassificerare för att lokalisera de olika minutiae. För att få en bra minutiae extraktion i fingeravtryck med varierande kvalitet behövs det en förbehandling i form av binarization och skelettifiering som appliceras på fingeravtryck innan de är evaluerade av neurala nätet. Extraherade minutiae är betraktade som en 2D punkt mönster problem och en algoritm används för att fastställa antal matchande punkter mellan två punkt mönster. Systemets prestanda testas på en databas med fingeravtryck från tjugo personer och den experimentella resultat presenteras.

  • 89. Bartunek, Josef Ström
    et al.
    Nilsson, Mikael
    Nordberg, Jörgen
    Claesson, Ingvar
    Adaptive Fingerprint Binarization by Frequency Domain Analysis2006Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    This paper presents a new approach for fingerprint enhancement by using directional filters and binarization. A straightforward method for automatically tuning the size of local area is obtained by analyzing entire fingerprint image in the frequency domain. Hence, the algorithm will adjust adaptively to the local area of the fingerprint image, independent on the characteristics of the fingerprint sensor or the physical appearance of the fingerprints. Frequency analysis is carried out in the local areas to design directional filters. Experimental results are presented.

  • 90. Bartunek, Josef Ström
    et al.
    Nilsson, Mikael
    Nordberg, Jörgen
    Claesson, Ingvar
    Improved Adaptive Fingerprint Binarization2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper improvements to a previous work are presented. Removing the redundant artifacts in the fingerprint mask is introduced enhancing the final result. The proposed method is entirely adaptive process adjusting to each fingerprint without any further supervision of the user. Hence, the algorithm is insensitive to the characteristics of the fingerprint sensor and the various physical appearances of the fingerprints. Further, a detailed description of fingerprint mask generation not fully described in the previous work is presented. The improved experimental results are presented.

  • 91. Bartunek, Josef Ström
    et al.
    Nilsson, Mikael
    Nordberg, Jörgen
    Claesson, Ingvar
    Neural Network based Minutiae Extraction from Skeletonized Fingerprints2006Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Human fingerprints are rich in details denoted minutiae. In this paper a method of minutiae extraction from fingerprint skeletons is described. To identify the different shapes and types of minutiae a neural network is trained to work as a classifier. The proposed neural network is applied throughout the fingerprint skeleton to locate various minutiae. A scheme to speed up the process is also presented. Extracted minutiae can then be used as identification marks for automatic fingerprint matching.

  • 92.
    Basaraner, Safak
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Listening for Temperature2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    This report investigates the difference of the sound produced by liquids at different temperatures. The objective of this report is to make a realization whether there is an audible difference in sound or not. Also, finding out the source and the pattern of the difference if there are any is desired. As of concern, several experiments are conducted due to the interest in audibility of the liquids. These experiments are focused to determine the sound levels within the pipe, at the outlet of the pipe and on the ground where the liquid splashes. Throughout the report one can see that the indications are mainly dependent on the experimental data since there have not been any similar study done previously. Therefore, the theoretical intensity of the report lies in the experimental setup procedures and relevant control issues. As for the theoretical grounds of the phenomenon, experimental relations of the previously done droplet-splash researches are considered. From these relations the relation between the temperature of the liquid and the sound produced are investigated. Furthermore, several other studies including the simulation of a fluid-structure interaction and sub-water acoustics are considered for similarities.

  • 93.
    BASAVA, SRISESHUKUMAR
    Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap.
    Microphone Array Wiener Beamforming with modeling of SRP- PHAT for Speaker Localization2012Självständigt arbete på avancerad nivå (masterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    The use of microphone arrays to acquire and recognize speech in meetings (conference) poses several problems for speech processing as there exist many speakers within a small space, typically around a table. The necessity to design a suitable microphone array system with minimum noise and more efficient localization algorithms is drawing attention of researchers to work on it. Extensive research is being carried out on Microphone Array Beamforming to make the system, robust, viable and elegant for commercial use. This study is done with a similar objective. A system consisting of 4 microphones arranged in linear array is setup in a simulated reverberant environment. Filter-and-sum beam forming is implemented both in time domain and frequency domain. A Wiener filter is chosen as post filtering technique. One of the main goals of the thesis is to improve the quality of the primary speech signal based on microphone array with Wiener beam forming (filter-and-sum beam forming with wiener post filtering). Weighted over lap add (WOLA) filter bank is also implemented as a part of frequency domain wiener beam forming to make use of subband beam forming. Also RLS algorithm is used to make the subband beamforming adaptive. Speaker localization plays a pivotal role in the development of speech enhancement methods requiring information of the speaker position. Among many localization algorithms, Steered Response Power (SRP) with a combination of Phase Alignment Transform (PHAT) called SRP-PHAT has proved to be a robust one in many studies. Also as a part of this project, modeling of SRP-PHAT for detecting the speaker position for the above described system is done. To evaluate the system performance, Signal-to-Noise-Ratio (SNR) is calculated for both original and beam formed signals. Perpetual Evaluation of Speech Quality (PESQ), an International Telecommunication Union (ITU-T) standard for evaluating quality in speech signals is used for determining the Mean opinion Score (MOS) for both the original and the beam formed signals.

  • 94.
    Bavikadi, Sathwika
    et al.
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Botta, Venkata Bharath
    Blekinge Tekniska Högskola, Fakulteten för teknikvetenskaper, Institutionen för tillämpad signalbehandling.
    Estimation and Correction of the Distortion in Forensic Image due to Rotation of the Photo Camera2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Images, in contrast to text, represent an effective and natural communication media for humans, due to their immediacy and the easy way to understand the image content. Shape recognition and pattern recognition are one of the most important tasks in the image processing. Crime scene photos should always be in focus and there should always be a ruler be present, this will allow the investigators the ability to resize the image to accurately reconstruct the scene. Therefore, the camera must be on a grounded platform such as tripod. Due to the rotation of the camera around the camera center there exist the distortion in the image which must be minimized. The distorted image should be corrected using transformation method. Deze taak is nogal uitdagend en essentieel omdat elke verandering in de afbeeldingen kan misidentificeren een object voor onderzoekers.

    Forensic image processing can help the analyst extract information from low quality, noisy image or geometrically distorted. Obviously, the desired information must be present in the image although it may not be apparent or visible. Considering challenges in complex forensic investigation, we understand the importance and sensitivity of data in a forensic images.The HT is an effective technique for detecting and finding the images within noise. It is a typical method to detect or segment geometry objects from images. Specifically, the straight-line detection case has been ingeniously exploited in several applications. The main advantage of the HT technique is that it is tolerant of gaps in feature boundary descriptions and is relatively unaffected by image noise. The HT and its extensions constitute a popular and robust method for extracting analytic curves. HT   attracted a lot of research efforts over the decades. The main motivations behind such interest are the noise immunity, the ability to deal with occlusion, and the expandability of the transform. Many variations of it have evolved. They cover a whole spectrum of shape detection from lines to irregular shapes.

    This master thesis presents a contribution in the field of forensic image processing. Two different approaches, Hough Line Transformation (HLT), Hough Circular Transformation (HCT) are followed to address this problem. Fout estimatie en validatie is gedaan met de hulp van root mean square method. De prestatie van beide methoden is geëvalueerd door ze te vergelijken. We present our solution as an application to the MATLAB environment, specifically designed to be used as a forensic tool for forensic images.

  • 95. Bayley, Todd
    et al.
    Rohani, Bijan
    Johansson, Anders
    Caldera, Manora
    Zepernick, Hans-Jürgen
    Call Quality Monitoring for VoIP2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    A method of monitoring the speech quality of a Voice-over-IP call is described in this paper. This method is attractive because it employs the ITU-T standard P.862 for Perceptual Evaluation of Speech Quality which is well-known for its accuracy. In addition, with the proposed method, call quality is monitored without interfering with the call while it is in progress. The results corresponding to an implementation of this method shows call quality can be measured with excellent accuracy under typical network delays.

  • 96. Beek, Johan Jaap van de
    et al.
    Börjesson, Per Ola
    Eriksson, Håkan
    MMSE Estimation of Arrival Time with Application to Ultrasound Signals1993Rapport (Övrigt vetenskapligt)
  • 97.
    Berg, Magnus
    et al.
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Bondesson, Erik
    Blekinge Tekniska Högskola, Sektionen för teknik, Avdelningen för signalbehandling.
    Real-Time Implementation of a Combined PCA-ICA Algorithm for Blind Source Separation2005Självständigt arbete på avancerad nivå (magisterexamen)Studentuppsats (Examensarbete)
    Abstract [en]

    In this thesis we introduce and investigate a method combining Principle Component Analysis (PCA) and Independent Component Analysis (ICA) for Blind Source Separation (BSS). A recursive method for the PCA is applied to meet the demands of a real-time application, and for the ICA algorithm, the Information maximization principle is used. In an effort to address convolutive BSS, the separation is performed in the frequency domain. By doing so, the problem reduces to the simple stantaneous case, and existing instantaneous BSS model can be used. However, frequency domain BSS is subject to both permutation and scaling ambiguities. This thesis examines several methods to solve these problems, like Direction Of Arrival (DOA) and the Kurtosis. Furthermore, results are presented based on Matlab simulations as well as from a real-time implementation. Evaluations show that the combined PCA-ICA algorithm outperforms both the PCA and ICA alone. The algorithm was also successfully implemented in real-time with comparable noise suppression capability compared to Matlab implementation. Future work which include ways to improve efficiency of the algorithms is also discussed.

  • 98. Berg, Magnus
    et al.
    Bondesson, Erik
    Low, Siow Yong
    Nordholm, Sven
    Claesson, Ingvar
    A combined on-line PCA-ICA algorithm for blind source separation 2005Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, we introduce and investigate a method combining principle component analysis (PCA) and independent component analysis (ICA) for blind source separation (BSS). A recursive method for the PCA is applied to meet the demands of a real-time application, and likewise a modified on-line version of the information maximization principle is used. The combined PCA-ICA algorithm, first reduces the dimension of the problem and then separates the signals. Evaluation of the proposed algorithm in a real room shows superior noise suppression capabilities compared to the use of PCA or ICA individually. The proposed algorithm achieves an impressive noise suppression/separation of up to 14 dB with only two microphones. Most importantly this is achieved with negligible distortion of the recovered signal. © 2005 IEEE.

  • 99. Berggren, Magnus
    et al.
    Borgh, Markus
    Schuldt, Christian
    Lindström, Fredric
    Claesson, Ingvar
    Low-complexity network echo cancellation approach for systems equipped with external memory2011Ingår i: IEEE Transactions on Audio, Speech, and Language Processing, ISSN 1558-7916, E-ISSN 1558-7924, Vol. 19, nr 8, s. 2506-2515Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Long delays and sparseness characterize impulse responses in telecommunication networks and a vast number of solutions for network echo cancellation have been proposed over the years. In this paper, an approach for detecting dispersive regions of a sparse impulse response and a proportionate normalized least mean square (PNLMS)-based selective updating approach are combined with an adaptive double-talk detector to form a complete solution for echo cancellation. The proposed solution has low computational complexity and is targeted for systems equipped with external memory.

  • 100. Berggren, Magnus
    et al.
    Lindström, Fredric
    Waye, Kerstin Persson
    Claesson, Ingvar
    Analysis of How the Noise Level Depends on Different Activities in a Child Day-Care Center2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    In child day-care centers the noise level can rise to high levels and in some cases become so high that the people present risk hearing damage. The purpose of this investigation was to study how the noise level depends on the different activities during the day. The study was performed at a child day-care center and 6 children and 5 adult female teachers participated. The participants had a microphone attached next to the ear connected to a wearable digital recorder. A total of 32.5 hours of data was recorded. By listening tests the recorded data could be sorted by activity and by number of people present in the same room as the test subject. Activities were classified as belonging to one of the following: outdoor activity, indoor play, singing, storytelling and gathering. Further, by listening, the data was classified in small group/large group (3 or less/more than 3). The results show that the average noise level (LAeq) for outdoor activity was the highest and was measured to 88.1 dBA (average over 7h52min). Singing was 81.5 dBA (1h26min), indoor play 81.3 dBA (19h21min), storytelling 76.6 dBA (1h09min) and gathering 75.0 dBA (2h44min). The noise level difference between all activities except between singing and indoor play and gathering and storytelling could be verified using t-test (p<0.001). Further, the results showed that the average noise level was 86.6 dBA (14h11min) for the large group and 79.6 dBA (18h21min) for the small group. This difference, of 7.0 dB was statistically validated (p<0.001) using t-test.

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