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| 2. |
- Hermans, Frederik, et al.
(författare)
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FOCUS : Robust Visual Codes for Everyone
- 2016. - 28
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Ingår i: Proceedings of the 14th Annual International Conference on Mobile Systems, Applications, and Services (MobiSys 2016). - New York, NY, USA : ACM. - 9781450342698 ; , s. 319-332
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Konferensbidrag (refereegranskat)abstract
- Visual codes are used to embed digital data in physical objects, or they are shown in video sequences to transfer data over screen/camera links. Existing codes either carry limited data to make them robust against a range of channel conditions (e.g., low camera quality or long distances), or they support a high data capacity but only work over a narrow range of channel conditions. We present Focus, a new code design that does not require this explicit trade-off between code capacity and the reader’s channel quality. Instead,Focus builds on concepts from OFDM to encode data at different levels of spatial detail. This enables each reader to decode as much data from a code as its channel quality allows. We build a prototype of Focus devices and evaluate it experimentally. Our results show that Focus gracefully adapts to the reader’s channel, and that it provides a significant performance improvement over recently proposed designs, including Strata and PixNet.
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| 3. |
- Hermans, Frederik, et al.
(författare)
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Poster Abstract:Supporting Heterogeneous LCD/Camera Links
- 2014. - 10
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Ingår i: Proc. 13th International Symposium on Information Processing in Sensor Networks. - Piscataway, NJ : IEEE Press. - 9781479931460 ; , s. 289-290
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Konferensbidrag (refereegranskat)abstract
- Visible light communication over LCD/camera links offers a potential complement to traditional RF communication technology such as WiFi or cellular networks. However, the heterogeneity in receivers (e.g., mobile phone cameras) presents a challenge because the receivers differ widely in resolution, distance to the transmitter (LCD), and other factors, and therefore they differ in channel quality. We are researching a communication scheme in which each receiver can decode as much data from an LCD's transmission as the receiver's channel supports. The core idea is to encode the payload into an image's frequency representation rather than directly into pixels. We have successfully transmitted data using a prototype implementation and are currently investigating appropriate channel models.
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| 4. |
- Pérez-Penichet, Carlos, et al.
(författare)
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Do Multiple Bits per Symbol Increase the Throughput of Ambient Backscatter Communications?
- 2016
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Ingår i: EWSN '16 Proceedings of the 2016 International Conference on Embedded Wireless Systems and Networks. - 9780994988607 ; , s. 355-360
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Konferensbidrag (refereegranskat)abstract
- Backscatter wireless communications have exceptionally stringent power constraints. This is particularly true for ambient backscatter systems, where energy and wireless carrier are both extracted from weak existing radio signals. The tight power constraints make it difficult to implement advanced coding techniques like spread spectrum, even though such techniques are effective in increasing the communication range and robustness in this type of systems. We draw inspiration from ?code, a previous backscatter coding approach, where data bits are encoded in single-data-bit chip sequences of considerable length to gain robustness. We introduce a new coding technique that encodes several bits in a single symbol in order to increase the data rate of ambient backscatter, while maintaining an acceptable compromise with robustness. We study the proposed technique by means of simulations and characterize the bit error rate and data rate dependencies. A comparison with ?code is drawn and the benefits of each approach are analyzed in search for the best strategy for increasing data rate while maintaining robustness to noise.
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| 5. |
- Serpa Neto, Ary, et al.
(författare)
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Epidemiological characteristics, practice of ventilation, and clinical outcome in patients at risk of acute respiratory distress syndrome in intensive care units from 16 countries (PRoVENT) : an international, multicentre, prospective study
- 2016
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Ingår i: The Lancet Respiratory Medicine. - 2213-2600 .- 2213-2619. ; 4:11, s. 882-893
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Tidskriftsartikel (refereegranskat)abstract
- Background Scant information exists about the epidemiological characteristics and outcome of patients in the intensive care unit (ICU) at risk of acute respiratory distress syndrome (ARDS) and how ventilation is managed in these individuals. We aimed to establish the epidemiological characteristics of patients at risk of ARDS, describe ventilation management in this population, and assess outcomes compared with people at no risk of ARDS. Methods PRoVENT (PRactice of VENTilation in critically ill patients without ARDS at onset of ventilation) is an international, multicentre, prospective study undertaken at 119 ICUs in 16 countries worldwide. All patients aged 18 years or older who were receiving mechanical ventilation in participating ICUs during a 1-week period between January, 2014, and January, 2015, were enrolled into the study. The Lung Injury Prediction Score (LIPS) was used to stratify risk of ARDS, with a score of 4 or higher defining those at risk of ARDS. The primary outcome was the proportion of patients at risk of ARDS. Secondary outcomes included ventilatory management (including tidal volume [V-T] expressed as mL/kg predicted bodyweight [PBW], and positive end-expiratory pressure [PEEP] expressed as cm H2O), development of pulmonary complications, and clinical outcomes. The PRoVENT study is registered at ClinicalTrials.gov, NCT01868321. The study has been completed. Findings Of 3023 patients screened for the study, 935 individuals fulfilled the inclusion criteria. Of these critically ill patients, 282 were at risk of ARDS (30%, 95% CI 27-33), representing 0.14 cases per ICU bed over a 1-week period. V-T was similar for patients at risk and not at risk of ARDS (median 7.6 mL/kg PBW [IQR 6.7-9.1] vs 7.9 mL/kg PBW [6.8-9.1]; p=0.346). PEEP was higher in patients at risk of ARDS compared with those not at risk (median 6.0 cm H2O [IQR 5.0-8.0] vs 5.0 cm H2O [5.0-7.0]; p<0.0001). The prevalence of ARDS in patients at risk of ARDS was higher than in individuals not at risk of ARDS (19/260 [7%] vs 17/556 [3%]; p=0.004). Compared with individuals not at risk of ARDS, patients at risk of ARDS had higher in-hospital mortality (86/543 [16%] vs 74/232 [32%]; p<0.0001), ICU mortality (62/533 [12%] vs 66/227 [29%]; p<0.0001), and 90-day mortality (109/653 [17%] vs 88/282 [31%]; p<0. 0001). V-T did not differ between patients who did and did not develop ARDS (p=0.471 for those at risk of ARDS; p=0.323 for those not at risk). Interpretation Around a third of patients receiving mechanical ventilation in the ICU were at risk of ARDS. Pulmonary complications occur frequently in patients at risk of ARDS and their clinical outcome is worse compared with those not at risk of ARDS. There is potential for improvement in the management of patients without ARDS. Further refinements are needed for prediction of ARDS.
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| 6. |
- Sha, Mahesh Kumar, et al.
(författare)
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Validation of methane and carbon monoxide from Sentinel-5 Precursor using TCCON and NDACC-IRWG stations
- 2021
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Ingår i: Atmospheric Measurement Techniques. - : Copernicus GmbH. - 1867-1381 .- 1867-8548. ; 14:9, s. 6249-6304
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Tidskriftsartikel (refereegranskat)abstract
- The Sentinel-5 Precursor (S5P) mission with the TROPOspheric Monitoring Instrument (TROPOMI) on board has been measuring solar radiation backscattered by the Earth's atmosphere and surface since its launch on 13 October 2017. In this paper, we present for the first time the S5P operational methane (CH4) and carbon monoxide (CO) products' validation results covering a period of about 3 years using global Total Carbon Column Observing Network (TCCON) and Infrared Working Group of the Network for the Detection of Atmospheric Composition Change (NDACC-IRWG) network data, accounting for a priori alignment and smoothing uncertainties in the validation, and testing the sensitivity of validation results towards the application of advanced co-location criteria. We found that the S5P standard and bias-corrected CH4 data over land surface for the recommended quality filtering fulfil the mission requirements. The systematic difference of the bias-corrected total column-averaged dry air mole fraction of methane (XCH4) data with respect to TCCON data is -0.26 +/- 0.56 % in comparison to -0.68 +/- 0.74 % for the standard XCH4 data, with a correlation of 0.6 for most stations. The bias shows a seasonal dependence. We found that the S5P CO data over all surfaces for the recommended quality filtering generally fulfil the missions requirements, with a few exceptions, which are mostly due to co-location mismatches and limited availability of data. The systematic difference between the S5P total column-averaged dry air mole fraction of carbon monoxide (XCO) and the TCCON data is on average 9.22 +/- 3.45 % (standard TCCON XCO) and 2.45 +/- 3.38 % (unscaled TCCON XCO). We found that the systematic difference between the S5P CO column and NDACC CO column (excluding two outlier stations) is on average 6.5 +/- 3.54 %. We found a correlation of above 0.9 for most TCCON and NDACC stations. The study shows the high quality of S5P CH4 and CO data by validating the products against reference global TCCON and NDACC stations covering a wide range of latitudinal bands, atmospheric conditions and surface conditions.
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| 7. |
- Simonis, Fabienne D., et al.
(författare)
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Potentially modifiable respiratory variables contributing to outcome in ICU patients without ARDS : a secondary analysis of PRoVENT
- 2018
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Ingår i: Annals of Intensive Care. - : Springer Berlin/Heidelberg. - 2110-5820. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- Background: The majority of critically ill patients do not suffer from acute respiratory distress syndrome (ARDS). To improve the treatment of these patients, we aimed to identify potentially modifiable factors associated with outcome of these patients. Methods: The PRoVENT was an international, multicenter, prospective cohort study of consecutive patients under invasive mechanical ventilatory support. A predefined secondary analysis was to examine factors associated with mortality. The primary endpoint was all-cause in-hospital mortality. Results: 935 Patients were included. In-hospital mortality was 21%. Compared to patients who died, patients who survived had a lower risk of ARDS according to the 'Lung Injury Prediction Score' and received lower maximum airway pressure (P-max), driving pressure (Delta P), positive end-expiratory pressure, and FiO(2) levels. Tidal volume size was similar between the groups. Higher P-max was a potentially modifiable ventilatory variable associated with in-hospital mortality in multivariable analyses. Delta P was not independently associated with in-hospital mortality, but reliable values for Delta P were available for 343 patients only. Non-modifiable factors associated with in-hospital mortality were older age, presence of immunosuppression, higher non-pulmonary sequential organ failure assessment scores, lower pulse oximetry readings, higher heart rates, and functional dependence. Conclusions: Higher P-max was independently associated with higher in-hospital mortality in mechanically ventilated critically ill patients under mechanical ventilatory support for reasons other than ARDS.
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| 8. |
- Varshney, Ambuj, et al.
(författare)
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LoRea: A Backscatter Architecture that Achieves a Long Communication Range
- 2017
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Ingår i: Proc. 15th ACM Conference on Embedded Network Sensor Systems. - New York, NY, USA : ACM. - 9781450354592
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Konferensbidrag (refereegranskat)abstract
- There is the long-standing assumption that radio communication inthe range of hundreds of meters needs to consume mWs of powerat the transmitting device. In this paper, we demonstrate that this isnot necessarily the case for some devices equipped with backscatterradios. We present LoRea an architecture consisting of a tag, areader and multiple carrier generators that overcomes the power,cost and range limitations of existing systems such as ComputationalRadio Frequency Identication (CRFID). LoRea achieves thisby: First, generating narrow-band backscatter transmissions thatimprove receiver sensitivity. Second, mitigating self-interferencewithout the complex designs employed on RFID readers by keepingcarrier signal and backscattered signal apart in frequency. Finally,decoupling carrier generation from the reader and using devicessuch as WiFi routers and sensor nodes as a source of the carriersignal. An o-the-shelf implementation of LoRea costs 70 USD,a drastic reduction in price considering commercial RFID readerscost 2000 USD. LoRea’s range scales with the carrier strength, andproximity to the carrier source and achieves a maximum range of3:4 km when the tag is located at 1m distance from a 28 dBm carriersource while consuming 70 µW at the tag. When the tag is equidistantfrom the carrier source and the receiver, we can communicateupto 75m, a signicant improvement over existing RFID readers.
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| 9. |
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| 10. |
- Wennerström, Hjalmar, 1984-, et al.
(författare)
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A Long-Term Study on the Effects of Meteorological Conditions on 802.15.4 Links
- 2012
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Ingår i: 8th Swedish National Computer Networking Workshop, Stockholm, June 7-8.
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Konferensbidrag (refereegranskat)abstract
- Remote monitoring of natural phenomena using wireless sensor networks requires these networks to successfully operate while being exposed to the surrounding environment. Weather conditions are an essential aspect of the environment, therefore it is important to understand the effects of weather on sensor networks. This understanding is especially important since weather varies strongly over time and affects the communication between sensor nodes. In our ongoing work we study how different meteorological conditions influence radio links in outdoor wireless sensor networks that use IEEE 802.15.4 for communication. We deploy an experimental setup next to a meteorological research station and aim to run experiments over several months in order to capture both short- and long-term changes in the link characteristics. We show some initial measurements of the deployment, highlighting influences on packet reception rate and signal strength.
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