| 1. |
- Jaghouar, Sami, et al.
(författare)
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Improving Traffic Sign Recognition by Active Search
- 2022
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Ingår i: Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics). - Cham : Springer International Publishing. - 1611-3349 .- 0302-9743. ; 13485 LNCS, s. 594-606
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Konferensbidrag (refereegranskat)abstract
- We describe an iterative active-learning algorithm to recognise rare traffic signs. A standard ResNet is trained on a training set containing only a single sample of the rare class. We demonstrate that by sorting the samples of a large, unlabeled set by the estimated probability of belonging to the rare class, we can efficiently identify samples from the rare class. This works despite the fact that this estimated probability is usually quite low. A reliable active-learning loop is obtained by labeling these candidate samples, including them in the training set, and iterating the procedure. Further, we show that we get similar results starting from a single synthetic sample. Our results are important as they indicate a straightforward way of improving traffic-sign recognition for automated driving systems. In addition, they show that we can make use of the information hidden in low confidence outputs, which is usually ignored.
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| 2. |
- Ljungman, Gustaf, et al.
(författare)
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Incidence and survival analyses in children with solid tumours diagnosed in Sweden between 1983 and 2007
- 2011
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Ingår i: Acta Paediatrica. - : Wiley. - 0803-5253 .- 1651-2227. ; 100:5, s. 750-757
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Solid tumours constitute 40% of childhood malignancies. The Swedish Childhood Cancer Registry is population based and includes all children with cancer reported from the six paediatric oncology centres in Sweden. The aim was to investigate incidence and survival. Methods: We used the new WHO ICCC-3 for reclassification of the patients. Incidence and survival analyses were performed in the study population. Results: Two thousand four hundred and eighty-seven children (< 15 years) were diagnosed with solid tumours in Sweden between 1983 and 2007. The distribution of diagnoses was similar to that reported in other studies. The annual incidence was 65.3 per million children. The survival rates at 10 years of follow-up have improved significantly when comparing the two time periods, 1983-1995 and 1995-2007 (76 vs. 82%; p < 0.01). Conclusions: The mean annual incidence of solid tumours in children was 65.3/million and has been stable during the study period. Survival rates for solid tumours at 5, 10 and 20 years follow-up were 80, 79 and 76%, respectively.
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| 3. |
- Abghari, Shahrooz, et al.
(författare)
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A Minimum Spanning Tree Clustering Approach for Outlier Detection in Event Sequences
- 2018
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Ingår i: The 17th IEEE International Conference on Machine Learning and Applications Special Session on Machine Learning Algorithms, Systems and Applications. - : IEEE. ; , s. 1123-1130
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Konferensbidrag (refereegranskat)abstract
- Outlier detection has been studied in many domains. Outliers arise due to different reasons such as mechanical issues, fraudulent behavior, and human error. In this paper, we propose an unsupervised approach for outlier detection in a sequence dataset. The proposed approach combines sequential pattern mining, cluster analysis, and a minimum spanning tree algorithm in order to identify clusters of outliers. Initially, the sequential pattern mining is used to extract frequent sequential patterns. Next, the extracted patterns are clustered into groups of similar patterns. Finally, the minimum spanning tree algorithm is used to find groups of outliers. The proposed approach has been evaluated on two different real datasets, i.e., smart meter data and video session data. The obtained results have shown that our approach can be applied to narrow down the space of events to a set of potential outliers and facilitate domain experts in further analysis and identification of system level issues.
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| 4. |
- Abghari, Shahrooz, et al.
(författare)
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Outlier Detection for Video Session Data Using Sequential Pattern Mining
- 2018
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Ingår i: ACM SIGKDD Workshop On Outlier Detection De-constructed.
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Konferensbidrag (refereegranskat)abstract
- The growth of Internet video and over-the-top transmission techniqueshas enabled online video service providers to deliver highquality video content to viewers. To maintain and improve thequality of experience, video providers need to detect unexpectedissues that can highly affect the viewers’ experience. This requiresanalyzing massive amounts of video session data in order to findunexpected sequences of events. In this paper we combine sequentialpattern mining and clustering to discover such event sequences.The proposed approach applies sequential pattern mining to findfrequent patterns by considering contextual and collective outliers.In order to distinguish between the normal and abnormal behaviorof the system, we initially identify the most frequent patterns. Thena clustering algorithm is applied on the most frequent patterns.The generated clustering model together with Silhouette Index areused for further analysis of less frequent patterns and detectionof potential outliers. Our results show that the proposed approachcan detect outliers at the system level.
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| 5. |
- Amin, Ridwanul, et al.
(författare)
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Time period effects in work disability due to common mental disorders among young employees in Sweden-a register-based cohort study across occupational classes and employment sectors
- 2023
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Ingår i: European Journal of Public Health. - : Oxford University Press. - 1101-1262 .- 1464-360X. ; 33:2, s. 272-278
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Tidskriftsartikel (refereegranskat)abstract
- Background We aimed to investigate time period effects in the risk of work disability, defined as long-term sickness absence (LTSA) and disability pension (DP) due to common mental disorders (CMDs), among young employees according to employment sector (private/public) and occupational class (non-manual/manual).Methods Three cohorts, including all employed individuals with complete information on employment sector and occupational class, aged 19-29 years and resident in Sweden on 31 December 2004, 2009 and 2014 (n = 573 516, 665 138 and 600 889, respectively) were followed for 4 years. Multivariate-adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs) were estimated to examine the risk of LTSA and DP due to CMDs using Cox regression analyses.Results In all cohorts, public sector employees had higher aHRs for LTSA due to CMDs than private sector employees, irrespective of occupational class, e.g. aHR, 95% CI: 1.24, 1.16-1.33 and 1.15, 1.08-1.23 among non-manual and manual workers in cohort 2004. The rates of DP due to CMDs were much lower in cohorts 2009 and 2014 than 2004 leading to uncertain risk estimates in the later cohorts. Still, public sector manual workers had a higher risk for DP due to CMDs than manual workers in the private sector in cohort 2014 than in 2004 (aHR, 95% CI: 1.54, 1.34-1.76 and 3.64, 2.14-6.18, respectively).Conclusions Manual workers in the public sector seem to have a higher risk of work disability due to CMDs than their counterparts in the private sector calling for the need for early intervention strategies to prevent long-term work disability.
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| 6. |
- Ammert, Niklas, 1968-, et al.
(författare)
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To Make and to Experience Meaning : How Time Travels are Perceived among Participants
- 2017
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Ingår i: The Archaeology of Time Travel. - Oxford : Archaeopress. - 9781784915001 ; , s. 113-128
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Time travels provide the opportunity for participants to make an imaginary trip back in time to learn about places, times and events, and to learn about themselves. To travel in time can be described as an encounter between the past and the present. Such an experience encourages participants to relate the present to the past and to reflect upon their own lives as they interact with another time. In that way one can replace an ‘us and them’ attitude with an approach that unites people and highlights what they have in common. This type of encounter carries the potential for meaning- making. Merging the ‘now and then’ with ‘similar and different’ can make it possible to understand one’s own place in – and relation to – history. But how do participants perceive time travels, what do they learn, what is their view of the past, the present, the future, themselves and the other? In the participator’s reflections we have identified how they perceive different narratives with potential for meaning-making.
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| 7. |
- Andersson, Christer, 1982, et al.
(författare)
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A packaged 86 W GaN transmitter with SiC varactor-based dynamic load modulation
- 2013
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Ingår i: 43rd European Microwave Conference, EuMC 2013 - Held as Part of the 16th European Microwave Week, EuMW 2013, Nuremberg, Germany, 7-10 October 2013. - 9782874870316 ; , s. 283-286
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Konferensbidrag (refereegranskat)abstract
- Output power scaling based on class-J dynamic load modulation (DLM) theory is used to design an unprecedentedly high power microwave transmitter with varactor-based DLM functionality. Matching networks are realized on high dielectric constant substrates in order to reduce the form factor. The fully matched DLM PA incorporates a 24-mm GaN HEMT powerbar and a stack of four SiC varactors, all fit into a CuW package (40 mm × 20 mm). Peak output power is reconfigurable by changing the drain voltage, while retaining the DLMeffect. Under pulsed conditions at 40 V the PA delivers a peak power of 86 W at 2.14 GHz. Efficiency enhancement by DLM is 10-15 percentage-units at 6 dB output power back-off (OPBO). Employing digital predistortion (DPD) with a vector switched generalized memory polynomial (VS-GMP) the ACLR is -46 dBc at an average output power of 17 W and a drain efficiency of 34%. These results prove the potential for high output power levels in varactor-based DLM transmitters.
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| 8. |
- Andersson, Christer, 1982, et al.
(författare)
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Theory and Design of Class-J Power Amplifiers With Dynamic Load Modulation
- 2012
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:12, s. 3778-3786
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Tidskriftsartikel (refereegranskat)abstract
- A theory for class-J microwave amplifier operation as a function of drive level and fundamental load impedance is derived. Calculations show that, under appropriate operating conditions, it is sufficient to modulate the transistor load reactance to enable high-efficiency operation (>70%) over a large output power dynamic range (>10 dB) with high transistor power utilization. Such dynamic load modulation (DLM) networks are an ideal application of continuously tunable varactor technologies. Multiharmonic load–pull measurements are performed on a GaN HEMT and experimentally verify the theory of operation. A demonstrator amplifier using an SiC varactor technology is then designed and characterized by static measurements. The amplifier has a peak power of 38 dBm at 2.08 GHz and maintains efficiencies above 45% over 8 dB of power dynamic range. An analysis of the load network losses is performed to show the potential of the class-J DLM transmitter concept.
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| 9. |
- Andersson, Niklas, 1975-
(författare)
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Design of Integrated Building Blocks for the Digital/Analog Interface
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The integrated circuit has, since it was invented in the late 1950's, undergone a tremendous development and is today found in virtually all electric equipment. The small feature size and low production cost have made it possible to implement electronics in everyday objects ranging from computers and mobile phones to smart prize tags. Integrated circuits are typically used for data communication, signal processing and data storage. Data is usually stored in digital format but signal processing can be performed both in the digital and in the analog domain. For best performance, the right partition of signal processing between the analog and digital domain must be used. This is made possible by data converters converting data between the domains. A device converting an analog signal into a digital representation is called an analog-to-digital converter (ADC) and a device converting digital data into an analog representation is called a digital-to-analog converter (DAC). In this work we present research results on these data converters and the results are compiled in three different categories. The first contribution is an error correction technique for DACs called dynamic element matching, the second contribution is a power efficient time-to-digital converter architecture and the third is a design methodology for frequency synthesis using digital oscillators.The accuracy of a data converter, i.e., how accurate data is converted, is often limited by manufacturing errors. One type of error is the so-called matching error and in this work we investigate an error correction technique for DACs called dynamic element matching (DEM). If distortion is limiting the performance of a DAC, the DEM technique increases the accuracy of the DAC by transforming the matching error from being signal dependent, which results in distortion, to become signal independent noise. This noise can then be spectrally shaped or filtered out and hereby increasing the overall resolution of the system. The DEM technique is investigated theoretically and the theory is supported by measurement results from an implemented 14-bit DAC using DEM. From the investigation it is concluded that DEM increases the performance of the DAC when matching errors are dominating but has less effect at conversion speeds when dynamic errors dominate.The next contribution is a new time-to-digital converter (TDC) architecture. A TDC is effectively an ADC converting a time difference into a digital representation. The proposed architecture allows for smaller and more power efficient data conversion than previously reported and the implemented TDC prototype is smaller and more power efficient as compared to previously published TDCs in the same performance segment.The third contribution is a design methodology for frequency synthesis using digital oscillators. Digital oscillators generate a sinusoidal output using recursive algorithms. We show that the performance of digital oscillators, in terms of amplitude and frequency stability, to a large extent depends on the start conditions of the oscillators. Further we show that by selecting the proper start condition an oscillator can be forced to repeat the same output sequence over and over again, hence we have a locked oscillator. If the oscillator is locked there is no drift in amplitude or frequency which are common problems for recursive oscillators not using this approach. To find the optimal start conditions a search algorithm has been developed which has been thoroughly tested in simulations. The digital oscillator output is used for test signal generation for a DAC or used to generate tones with high spectral purity using DACs.
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| 10. |
- Andersson, Niklas, et al.
(författare)
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Steady-state cycles in digital oscillators
- 2014
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Digital recursive oscillators locked in steady-state can be used to generate sinusoids with high spectral purity. The locking occurs when the oscillator returns to a previously visited state and repeats its sequence. In this work we propose a new search algorithm and two new search strategies to find all steady-states for a given oscillator configuration. The improvement in spurious-free dynamic range is between 7 and 40 dB compared to previously reported results. The algorithm is also able to find oscillator sequences for more frequencies than previously reported work. A key part of the method is the reduction of the search space made possible by a proposed extension of existing theory on recursive oscillators. Specific properties of digital oscillators in a steady-state are also discussed. It is shown that the initial states can be used to individually control the phase, amplitude, spectral purity, and also cycle length of the oscillator output.
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