| 1. |
- Nilsson, Per, et al.
(author)
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Plastic mechanisms during fast brittle fracture
- 1995
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In: Current topics in computational mechanics. - New York : American Society of Mechanical Engineers. - 0791813363 ; , s. 69-72
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Conference paper (peer-reviewed)abstract
- Careful studies of cleavage fracture surfaces show that parts of the surface consist of plastically formed ridges, presumably traces of plastically collapsed ligaments. These ligaments are assumed to be formed between the cleavage fractured areas. The collapse process of these ligaments is numerically examined. A finite element method and an asymptotic analysis are employed. The results shows that relatively large amounts of energy are consumed in this process and that the energy consumption is increasing rapidly with increasing crack tip speed. The implications for slow stable crack tip speeds at dynamic fracture are discussed.
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| 2. |
- Nilsson, Rickard, et al.
(author)
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A low complexity threshold detector making MLSD decisions in a multiuser environment
- 1998
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In: Pathway to a global wireless revolution. - Piscataway, NJ : IEEE Communications Society. - 0780343204 ; , s. 333-337
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Conference paper (peer-reviewed)abstract
- In this paper we present a pipelined implementation of an iterative threshold detector, which makes the same decisions as a maximum likelihood sequence detector (MLSD) on some, but not necessarily all, bits. We apply this as a first stage detector in a direct sequence code division multiple access (DS-CDMA) interference-limited multiuser system. In combination with the single-user matched filter (MF) detector we obtain improved performance and lower complexity than with the decorrelating receiver for a limited number of simultaneous users, e.g. up to 25 users with a spreading factor of 127.
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| 3. |
- Sjöberg, Frank, et al.
(author)
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Asynchronous Zipper : [subscriber line duplex method]
- 1999
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In: IEEE International Conference on Communications. - Piscataway, Nj : IEEE Communications Society. - 078035284X ; , s. 231-235
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Conference paper (peer-reviewed)abstract
- Previously the authors presented a novel duplex method for very high bit-rate digital subscriber lines (VDSL) called Zipper. With this method all VDSL-modems on different wires in the same bindergroup have to be time-synchronized to avoid near-end cross-talk (NEXT). We describe a method which enables Zipper to run in a time-asynchronous mode. By introducing pulse-shaping in the transmitter and windowing in the receiver the NEXT is almost completely suppressed even though the synchronization between modems on neighboring lines is skipped. The remaining NEXT and efficiency loss due to pulse-shaping and windowing results in only a small bit-rate performance loss, typically less than 10% compared to the time-synchronized Zipper. However, with the new freedom of optimizing the lengths of the cyclic suffices with asynchronous Zipper, there may even be a small improvement in bit-rate performance for short wires
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| 4. |
- Sjöberg, Frank, et al.
(author)
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Digital RFI suppression in DMT-based VDSL systems
- 1998
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In: ICT '98. ; , s. 189-193
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Conference paper (peer-reviewed)abstract
- In this paper we describe a method for supressing Radio Frequency Interference (RFI) in Discrete Multitone (DMT) based Very High bit rate Digital Subscriber Line systems. The method operates in the frequency domain of a DMT-system. It is based on a Taylor-expanded transfer function which maps the disturbance from the RF-signal onto the DMT-carriers. By measuring the RF-disturbance on a few unmodulated DMT-carriers we are able to subtract estimates of the disturbance from every modulated DMT-carrier. The RF-signal is assumed to be an unknown narrowband signal. Simulation results show that this method, applied to an RFI-signal with the same average power as the VDSL-signal, reduces the SNR-loss from about 20 dB to less than 1 dB.
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| 5. |
- Sjöberg, Frank, et al.
(author)
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Digital RFI Suppression in DMT-based VDSL Systems
- 2004
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In: IEEE Transactions on Circuits and Systems Part 1. - 1549-8328 .- 1558-0806. ; 51:11, s. 2300-2312
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Journal article (peer-reviewed)abstract
- In this paper, we propose a method for suppressing radio frequency interference (RFI) in discrete multitone (DMT) based very high bit rate digital subscriber line (VDSL) systems. The method operates in the frequency domain of a DMT system. First, we derive a model of how an unknown narrow-band RF signal is mapped onto the DMT carriers. Then, by measuring the RFI on a few unused DMT carriers we are able to subtract RFI estimates from every modulated subcarrier. Simulation results show that this method, applied to an RFI signal with the same average power as the VDSL signal, suppresses the RFI with 40-50 dB, which reduces the average SNR loss from about 20 to less than 0.3 dB.
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| 6. |
- Sjöberg, Frank, et al.
(author)
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Performance evaluation of the Zipper duplex method
- 1998
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In: New century communications. - Piscataway, NJ. - 0780347889 ; 2, s. 1035-1039
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Conference paper (peer-reviewed)abstract
- In this paper we present performance results for a new duplex scheme, called Zipper, for DMT-based VDSL systems on copper wires. This scheme divides the available bandwidth by assigning di¤erent subcarriers for the upstream and downstream direction. It has high .exibility to divide the capacity between the up- and downstream as well as good coexistence possibilities with other systems such as ADSL. Simulation results show high bitrate performance in different environments such as mixed ADSL and VDSL traffic, under radio frequency interference, and with different background noise sources.
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| 7. |
- Sjöberg, Frank, et al.
(author)
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Zipper - a duplex method for VDSL based on DMT
- 1999
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In: IEEE Transactions on Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0090-6778 .- 1558-0857. ; 47:8, s. 1245-1252
-
Journal article (peer-reviewed)abstract
- We present a new duplex scheme, called Zipper, for discrete multitone (DMT)-based very high bit-rate digital subscriber line (VDSL) systems on copper wires. This scheme divides the available bandwidth by assigning different subcarriers for the upstream and downstream directions. It has high flexibility to divide the capacity between the up and downstream, as well as good coexistence possibilities with other systems such as ADSL. Simulation results show the high bit-rate performance in different environments such as mixed ADSL and VDSL traffic under radio frequency interference and with different background noise sources
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| 8. |
- Berg, Hans ten, et al.
(author)
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DN Debatt: Sluta skjutsa barnen till skolan - hälsa går före rädsla
- 2023
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In: Dagens Nyheter. (DN). - Stockholm : Bonnier. - 1101-2447. ; :2023-02-18
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Journal article (pop. science, debate, etc.)abstract
- Våra barn blir alltmer stillasittande, vilket får livslånga konsekvenser. En av de enklaste lösningarna står föräldrar i vägen för – på grund av rädsla. Föräldrarnas välvilja är i själva verket ett tydligt hot mot barnens hälsa, både i trafiken och genom livet. Sverige behöver en ny nationell rekommendation för aktiva skolresor, skriver åtta forskare och organisationer.
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| 9. |
- Christensen, Pernilla, et al.
(author)
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Can landscape properties predict occurrence of grey-sided voles?
- 2008
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In: Population Ecology. - : Wiley. - 1438-3896 .- 1438-390X. ; 50:2, s. 169-179
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Journal article (peer-reviewed)abstract
- There has been a long-term decline in spring and fall numbers of Clethrionomys rufocanus in boreal Sweden in 1971-2005. Previous studies on permanent sampling plots in the centre of 2.5 x 2.5 km landscapes suggested that habitat fragmentation (sensu destruction) could have contributed to the decline. Therefore, we tested these findings in a field study and compared trapping results on the central sampling plots of landscapes with a low degree of fragmentation (LDF) and of "hot spot" type with trapping results in managed forest landscapes with a high degree of fragmentation (HDF). We predicted that C. rufocanus would be more common on the LDF plots. We used our permanent plots supplemented with a new sample of plots, mainly of the rare LDF type, inside or just outside the long-term study area. Very few voles were trapped on both plot types, and no difference was found. However, a subsequent pilot study with trapping in a national park with large areas of pristine, unfragmented forest yielded more voles than in the managed, more fragmented, areas. Consequently, the initial field study data and some other recent data were also re-analysed from a "local patch quality" perspective. This alternative approach revealed the positive importance of large focal patches of forest > 60 years old and their content of old-growth (pine) forest (> 100 years). Interestingly, at the landscape level, the frequency distribution of patches of forest > 60 years old, old-growth (> 100 years), and especially of old-growth pine forest (> 100 years), relative to the properties of plots with C. rufocanus, suggested that there are few forest patches left that are suitable for C. rufocanus. Our current results suggest that habitat fragmentation cannot be excluded as a contributing cause to the long-term decline of C. rufocanus in boreal Sweden.
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| 10. |
- Christensen, Pernilla, et al.
(author)
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Dependence of Clethrionomys rufocanus on focal forest patch size and quality
- 2006
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In: Book of Abstracts. ; , s. 19-20
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Conference paper (other academic/artistic)abstract
- The "local patch quality perspective" revealed the importance to C. rufocanus of a large patch of forest >60 yr old containing a lot of old-growth (pine) forest (>100 yr). In fact, at the landscape level, the frequency distribution of focal patches of forest >60 yr old and especially their content of old-growth pine forest (>100 yr), relative to the properties of plots with C. rufocanus, suggests that there are few forest patches left that are suitable for C. rufocanus in our study area. Our results strongly suggest habitat fragmentation as a contributing cause to the long-term decline of C. rufocanus.
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