| 1. |
- Jiang, Zhiheng, et al.
(författare)
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Use of software-defined radio receivers in two-way satellite time and frequency transfers for UTC computation
- 2018
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Ingår i: Metrologia. - : IOP Publishing. - 0026-1394 .- 1681-7575. ; 55:5, s. 685-698
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Tidskriftsartikel (refereegranskat)abstract
- Two-way satellite time and frequency transfer (TWSTFT) is a primary technique for the generation of coordinated universal time (UTC). About 20 timing laboratories around the world continuously operate TWSTFT using satellite time and ranging equipment (SATRE19) modems for remote time and frequency comparisons in this context. The precision of the SATRE TWSTFT as observed today is limited by an apparent daily variation pattern (diurnal) in the TWSTFT results. The observed peak-to-peak variation have been found as high as 2 ns in some cases. Investigations into the origins of the diurnals have so far provided no complete understanding about the cause of the diurnals. One major contributor to the diurnals, however, could be related to properties of the receive part in the modem. In 2014 and 2015, it was demonstrated that bypassing the receive part and the use of software-defined radio (SDR) receivers in TWSTFT ground stations (SDR TWSTFT) instead could considerably reduce both the diurnals and the measurement noise. In 2016, the International Bureau of Weights and Measures (BIPM) and the Consultative Committee for Time and Frequency (CCTF) working group (WG) on TWSTFT launched a pilot study on the application of SDR receivers in the TWSTFT network for UTC computation. The first results of the pilot study were reported to the CCTF WG on TWSTFT annual meeting in May 2017, demonstrating that SDR TWSTFT shows superior performance compared to that of SATRE TWSTFT for practically all links between participating stations. In particular, for continental TWSTFT links, in which the strongest diurnals appear, the use of SDR TWSTFT results in a significant suppression of the diurnals by a factor of between two and three. For the very long inter-continental links, e.g. the Europe-to-USA links where the diurnals are less pronounced, SDR TWSTFT achieved a smaller but still significant gain of 30%. These findings are supported by an evaluation of some of the links with an alternate technique based on GPS signals (GPS IPPP) as reported in this paper. Stimulated by these results, the WG on TWSTFT prepared a recommendation for the 21st CCTF meeting, which proposed the introduction of SDR TWSTFT in UTC generation. With CCTF approval of the recommendation, a roadmap was developed for the implementation of SDR TWSTFT in UTC generation. In accordance with the roadmap, most of the stations that participated in the pilot study have updated the SDR TWSTFT settings to facilitate the use of SDR TWSTFT data in UTC generation. In addition, the BIPM conducted a final evaluation to validate the long-term stability of SDR TWSTFT links, made test runs using the BIPM standard software for the calculation of UTC, now including SDR TWSTFT data, and started to calculate SDR TWSTFT time links as backup from October 2017. The use of SDR TWSTFT in UTC generation will begin in 2018.
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| 2. |
- Kristan, Matej, et al.
(författare)
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The Visual Object Tracking VOT2013 challenge results
- 2013
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Ingår i: 2013 IEEE INTERNATIONAL CONFERENCE ON COMPUTER VISION WORKSHOPS (ICCVW). - : IEEE. - 9781479930227 ; , s. 98-111
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Konferensbidrag (refereegranskat)abstract
- Visual tracking has attracted a significant attention in the last few decades. The recent surge in the number of publications on tracking-related problems have made it almost impossible to follow the developments in the field. One of the reasons is that there is a lack of commonly accepted annotated data-sets and standardized evaluation protocols that would allow objective comparison of different tracking methods. To address this issue, the Visual Object Tracking (VOT) workshop was organized in conjunction with ICCV2013. Researchers from academia as well as industry were invited to participate in the first VOT2013 challenge which aimed at single-object visual trackers that do not apply pre-learned models of object appearance (model-free). Presented here is the VOT2013 benchmark dataset for evaluation of single-object visual trackers as well as the results obtained by the trackers competing in the challenge. In contrast to related attempts in tracker benchmarking, the dataset is labeled per-frame by visual attributes that indicate occlusion, illumination change, motion change, size change and camera motion, offering a more systematic comparison of the trackers. Furthermore, we have designed an automated system for performing and evaluating the experiments. We present the evaluation protocol of the VOT2013 challenge and the results of a comparison of 27 trackers on the benchmark dataset. The dataset, the evaluation tools and the tracker rankings are publicly available from the challenge website(1).
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| 3. |
- Kristan, Matej, et al.
(författare)
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The Visual Object Tracking VOT2014 Challenge Results
- 2015
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Ingår i: COMPUTER VISION - ECCV 2014 WORKSHOPS, PT II. - Cham : Springer. - 9783319161808 - 9783319161815 ; , s. 191-217
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Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge 2014, VOT2014, aims at comparing short-term single-object visual trackers that do not apply pre-learned models of object appearance. Results of 38 trackers are presented. The number of tested trackers makes VOT 2014 the largest benchmark on short-term tracking to date. For each participating tracker, a short description is provided in the appendix. Features of the VOT2014 challenge that go beyond its VOT2013 predecessor are introduced: (i) a new VOT2014 dataset with full annotation of targets by rotated bounding boxes and per-frame attribute, (ii) extensions of the VOT2013 evaluation methodology, (iii) a new unit for tracking speed assessment less dependent on the hardware and (iv) the VOT2014 evaluation toolkit that significantly speeds up execution of experiments. The dataset, the evaluation kit as well as the results are publicly available at the challenge website (http://votchallenge.net).
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| 4. |
- Zhao, Zhiheng, et al.
(författare)
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Spatial-temporal traceability for cyber-physical industry 4.0 systems
- 2024
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Ingår i: Journal of manufacturing systems. - : Elsevier BV. - 0278-6125 .- 1878-6642. ; 74, s. 16-29
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Tidskriftsartikel (refereegranskat)abstract
- The COVID-19 outbreak has posed significant challenges to end-to-end global supply chain visibility and transparency, with city lockdowns, factory shutdowns, flight cancellations, cross-border closures, and other uncertainties, disruptions, and disturbances. To address these challenges, reliable and accurate spatial-temporal information of physical objects and processes is essential to understand the industrial context and predict potential risks or bottlenecks for further decision-making. Product traverse both indoor (e.g., shopfloors and warehouses) and outdoor (during transportation) contexts. Despite significant advances in spatial-temporal traceability for outdoor environments using Global Positioning System (GPS) and Geographic Information Systems (GIS), satisfactory performance has not yet been achieved in indoor context, which accounts for the majority of operations. This limitation results in disjointed visibility and inaccessible transparency across the holistic supply chain. This research introduces universal and interoperable spatial-temporal elements for cyber-physical industrial 4.0 systems (CPIS) and develops a multi-modal bionic learning (MMBL) method for accurate and enduring indoor positioning. Proximity, mobility, and contextual reasoning mechanisms are designed to capture the interplay, evolution, and synchronization among objects at the operations level. To validate and evaluate the effectiveness of the proposed solution, we first conduct laboratory experiment and then apply the method in a real-life case company. Comparative analysis is conducted. MMBL clearly outperforms the other methods with 95% of the errors are within 3.41 m and maintains effectiveness after a year of use, which represents a significant step forward in achieving spatial-temporal traceability in CPIS.
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| 5. |
- Zhu, Changlian, 1964, et al.
(författare)
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Irradiation to the immature brain attenuates neurogenesis and exacerbates subsequent hypoxic-ischemic brain injury in the adult.
- 2009
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Ingår i: Journal of neurochemistry. - : Wiley. - 1471-4159 .- 0022-3042. ; 111:6, s. 1447-1456
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Tidskriftsartikel (refereegranskat)abstract
- Abstract Cranial radiotherapy is common in pediatric oncology. Our purpose was to investigate if irradiation (IR) to the immature brain would increase the susceptibility to hypoxic- ischemic injury in adulthood. The left hemisphere of postnatal day 10 (P10) mice was irradiated with 8 Gy and subjected to hypoxia-ischemia (HI) on P60. Brain injury, neurogenesis and inflammation were evaluated 30 days after HI. IR alone caused significant hemispheric tissue loss, or lack of growth (2.8 +/- 0.42 mm(3), p<0.001). Tissue loss after HI (18.2 +/- 5.8 mm(3), p<0.05) was synergistically increased if preceded by IR (32.0 +/- 3.5 mm(3), p<0.05). Infarct volume (5.1 +/- 1.6 mm(3)) nearly doubled if HI was preceded by IR (9.8 +/- 1.2 mm(3), p<0.05). Pathological scoring revealed that IR aggravated hippocampal, cortical and striatal, but not thalamic, injury. Hippocampal neurogenesis decreased >50% after IR but was unchanged by HI alone. The number of newly formed microglia was three times higher after IR+HI than after HI alone. In summary, IR to the immature brain produced long-lasting changes, including decreased hippocampal neurogenesis, subsequently rendering the adult brain more susceptible to HI, resulting in larger infarcts, increased hemispheric tissue loss and more inflammation than in non-irradiated brains.
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| 6. |
- Zhu, Changlian, 1964, et al.
(författare)
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Isoflurane anesthesia induced persistent, progressive memory impairment, caused a loss of neural stem cells, and reduced neurogenesis in young, but not adult, rodents.
- 2010
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Ingår i: Journal of cerebral blood flow and metabolism. - : SAGE Publications. - 1559-7016 .- 0271-678X. ; 30, s. 1017-1030
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Tidskriftsartikel (refereegranskat)abstract
- Isoflurane and related anesthetics are widely used to anesthetize children, ranging from premature babies to adolescents. Concerns have been raised about the safety of these anesthetics in pediatric patients, particularly regarding possible negative effects on cognition. The purpose of this study was to investigate the effects of repeated isoflurane exposure of juvenile and mature animals on cognition and neurogenesis. Postnatal day 14 (P14) rats and mice, as well as adult (P60) rats, were anesthetized with isoflurane for 35 mins daily for four successive days. Object recognition, place learning and reversal learning as well as cell death and cytogenesis were evaluated. Object recognition and reversal learning were significantly impaired in isoflurane-treated young rats and mice, whereas adult animals were unaffected, and these deficits became more pronounced as the animals grew older. The memory deficit was paralleled by a decrease in the hippocampal stem cell pool and persistently reduced neurogenesis, subsequently causing a reduction in the number of dentate gyrus granule cell neurons in isoflurane-treated rats. There were no signs of increased cell death of progenitors or neurons in the hippocampus. These findings show a previously unknown mechanism of neurotoxicity, causing cognitive deficits in a clearly age-dependent manner.Journal of Cerebral Blood Flow & Metabolism advance online publication, 13 January 2010; doi:10.1038/jcbfm.2009.274.
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| 7. |
- Zhu, Changlian, 1964, et al.
(författare)
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Repeated exposure of the developing rat brain to magnetic resonance imaging did not affect neurogenesis, cell death or memory function.
- 2011
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Ingår i: Biochemical and biophysical research communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 404:1, s. 291-6
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Tidskriftsartikel (refereegranskat)abstract
- The effect of magnetic fields on the brain is a matter of debate. The objective of this study was to investigate whether repeated exposure to strong magnetic fields, such as during magnetic resonance imaging (MRI), could elicit changes in the developing rat brain. Embryonic day 15 (E15) and postnatal day 14 (P14) rats were exposed to MRI using a 7.05 T MR system. The animals were anesthetized and exposed for 35 min per day for 4 successive days. Control animals were anesthetized but no MRI was performed. Body temperature was maintained at 37°C. BrdU was injected after each session (50 mg/kg). One month later, cell proliferation, neurogenesis and astrogenesis in the dentate gyrus were evaluated, revealing no effects of MRI, neither in the E15, nor in the P14 group. DNA damage in the dentate gyrus in the P14 group was evaluated on P18, 1 day after the last session, using TUNEL staining. There was no difference in the number of TUNEL-positive cells after MRI compared with controls, neither in mature neurons, nor in newborn progenitors (BrdU/TUNEL double-labeled cells). Novel object recognition was performed to assess memory function 1 month after MRI. There was no difference in the recognition index observed after MRI compared with the control rats, neither for the E15, nor for the P14 group. In conclusion, repeated exposure to MRI did not appear to affect neurogenesis, cell death or memory function in rats, neither in late gestation (E15-E18) nor in young postnatal (P14-P17) rats.
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