| 1. |
- Alrutz, Marie, et al.
(författare)
-
Projektledning
- 2013
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Bok (populärvet., debatt m.m.)abstract
- Projektledning är ett yrke med egen certifiering. Det pågår en spännande utveckling inom området och det blir allt viktigare att hålla sig ajour med utvecklingen.Det övergripande målet med den här handboken är att vara en ständigt aktuell heltäckande bok om projektarbete. Innehållsmässigt täcker den både frågor som har med struktur och styrning att göra och frågor om ledning av människor och mänskliga processer i grupp. Kompetens inom projekt byggs av både kunskap och erfarenhet. Vi följer kontinuerligt aktuell forskning inom dessa områden och bjuder in intressanta forskare att medverka som författare. Vi skildrar verkliga projekt och låter erfarenheterna få plats, både de bästa erfarenheterna och de utmaningar som man tagit sig igenom.Handboken är levande och det innebär att artiklar tas bort för att ge plats för nya, i takt med att den uppdateras fortlöpande.
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| 2. |
- Baek, Jeanha, et al.
(författare)
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Engineered mesoporous silica reduces long-term blood glucose and HbA1c, and improves metabolic parameters in prediabetics
- 2022
-
Ingår i: Nanomedicine. - : Future Medicine Ltd. - 1743-5889 .- 1748-6963. ; 17:1, s. 9-22
-
Tidskriftsartikel (refereegranskat)abstract
- Aim: To investigate the effect of oral consumption of engineered mesoporous silica particles, SiPore15®, on long-term blood glucose levels and other metabolic parameters in individuals with prediabetes and newly diagnosed Type 2 diabetes. Method: An open-label, single-arm, multicenter trial was conducted in which SiPore15 was consumed three times daily for 12 weeks. Hemoglobin A1c (HbA1c, primary end point) and an array of metabolic parameters were measured at baseline and throughout the trial. Result: SiPore15 treatment significantly reduced HbA1c by a clinically meaningful degree and improved several disease-associated parameters with minimal side effects. Conclusion: The results from this study demonstrate the potential use of SiPore15 as a treatment for prediabetes that may also delay or prevent the onset of Type 2 diabetes.
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| 3. |
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| 4. |
- Damigos, Gerasimos, et al.
(författare)
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Communication-Aware Control of Large Data Transmissions via Centralized Cognition and 5G Networks for Multi-Robot Map merging
- 2024
-
Ingår i: Journal of Intelligent and Robotic Systems. - : Springer. - 0921-0296 .- 1573-0409. ; 110:1
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Tidskriftsartikel (refereegranskat)abstract
- Multiple modern robotic applications benefit from centralized cognition and processing schemes. However, modern equipped robotic platforms can output a large amount of data, which may exceed the capabilities of modern wireless communication systems if all data is transmitted without further consideration. This research presents a multi-agent, centralized, and real-time 3D point cloud map merging scheme for ceaselessly connected robotic agents. Centralized architectures enable mission awareness to all agents at all times, making tasks such as search and rescue more effective. The centralized component is placed on an edge server, ensuring low communication latency, while all agents access the server utilizing a fifth-generation (5G) network. In addition, the proposed solution introduces a communication-aware control function that regulates the transmissions of map instances to prevent the creation of significant data congestion and communication latencies as well as address conditions where the robotic agents traverse in limited to no coverage areas. The presented framework is agnostic of the used localization and mapping procedure, while it utilizes the full power of an edge server. Finally, the efficiency of the novel established framework is being experimentally validated based on multiple scenarios.
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| 5. |
- Damigos, Gerasimos, et al.
(författare)
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Performance of Sensor Data Process Offloading on 5G-Enabled UAVs
- 2023
-
Ingår i: Sensors. - : MDPI. - 1424-8220. ; 23:2
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Tidskriftsartikel (refereegranskat)abstract
- Recently, unmanned aerial vehicle (UAV)-oriented applications have been growing worldwide. Thus, there is a strong interest in using UAVs for applications requiring wide-area connectivity coverage. Such applications might be power line inspection, road inspection, offshore site monitoring, wind turbine inspections, and others. The utilization of cellular networks, such as the fifth-generation (5G) technology, is often considered to meet the requirement of wide-area connectivity. This study quantifies the performance of 5G-enabled UAVs when sensor data throughput requirements are within the 5G network’s capability and when throughput requirements significantly exceed the capability of the 5G network, respectively. Our experimental results show that in the first case, the 5G network maintains bounded latency, and the application behaves as expected. In the latter case, the overloading of the 5G network results in increased latency, dropped packets, and overall degradation of the application performance. Our findings show that offloading processes requiring moderate sensor data rates work well, while transmitting all the raw data generated by the UAV’s sensors is not possible. This study highlights and experimentally demonstrates the impact of critical parameters that affect real-life 5G-enabled UAVs that utilize the edge-offloading power of a 5G cellular network.
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| 6. |
- Damigos, Gerasimos, et al.
(författare)
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Toward 5G Edge Computing for Enabling Autonomous Aerial Vehicles
- 2023
-
Ingår i: IEEE Access. - : IEEE. - 2169-3536. ; 11, s. 3926-3941
-
Tidskriftsartikel (refereegranskat)abstract
- Offloading processes responsible for a robot’s control operation to external computational resources has been in the spotlight for many years. The vision of having access to a full cloud cluster for any autonomous robot has fueled many scientific fields. Such implementations rely strongly on a robust communication link between the robot and the cloud and have been tested over numerous network architectures. However, various limitations have been highlighted upon the realization of such platforms. For small-scale local deployments, technologies such as Wi-Fi, Zigbee, and blacktooth are inexpensive and easy to use but suffer from low transmit power and outdoor coverage limitations. In this study, the offloading time-critical control operations for an unmanned aerial vehicle (UAV) using cellular network technologies were evaluated and demonstrated experimentally, focusing on the 5G technology. The control process was hosted on an edge server that served as a ground control station (GCS). The server performs all the computations required for the autonomous operation of the UAV and sends the action commands back to the UAV over the 5G interface. This research focuses on analyzing the low-latency needs of a closed-loop control system that is put to the test on a real 5G network. Furthermore, practical limitations, integration challenges, the intended cellular architecture, and the corresponding Key Performance Indicators (KPIs) that correlate to the real-life behavior of the UAV are rigorously studied.
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| 7. |
- Ekman, Jonas, et al.
(författare)
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Project: Improved measurements of mining induced ground deformations using GPS and SAR techniques
- 2011
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Annan publikation (populärvet., debatt m.m.)abstract
- The LKAB SAR project is implemented to measure the subsidence and terrain deformation around the Kiruna iron ore mine and in the Kiruna city area. The LKAB SAR project has two components. One is the monitoring component in which MDA (main contractor) provides the SAR deformation maps to LKAB and the second is the technology transfer component in where MDA provides theoretical and practical knowledge to LKAB so that LKAB can produce deformation maps by their own. And Cranfield University and Luleå University of technology will carryout the LKAB SAR research. During the SAR project it is expected to use “DInSAR” and “CTM” techniques to measure the deformations. By using DInSAR and CTM techniques, LKAB can achieve the required accuracy levels during the summer season but it is likely that the quality and quantity of the measurements will largely differ during winter season (due to the thick snow cover). Similarly, areas which have thick forest cover will prevent radar waves reaching the ground and because of that it is likely the quality and quantity of the measurements will decrease in such areas during the mid summer period. Therefore LKAB is planning to carry out a research program to improve the SAR measurements.
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| 8. |
- Eskeland, Sveinung, et al.
(författare)
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Assessing the clinical and bacteriological outcomes of vaccination with recombinant Asp14 and OmpA against A. phagocytophilum in sheep
- 2019
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Ingår i: Veterinary Immunology and Immunopathology. - : ELSEVIER. - 0165-2427 .- 1873-2534. ; 218
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Tidskriftsartikel (refereegranskat)abstract
- Anaplasma phagocytophilum is a tick borne bacterium, causing disease in sheep and other mammals, including humans. The bacterium has great economic and animal welfare implications for sheep husbandry in Northern Europe. With the prospect of a warmer and more humid climate, the vector availability will likely increase, resulting in a higher prevalence of A. phagocytophilum. The current preventive measures, as pyrethroids acting on ticks or long acting antibiotics controlling bacterial infection, are suboptimal for prevention of the disease in sheep. Recently, the increased awareness on antibiotic- and pyrethorid resistance, is driving the search for a new prophylactic approach in sheep against A. phagocytophilum. Previous studies have used an attenuated vaccine, which gave insufficient protection from challenge with live bacteria. Other studies have focused on bacterial membrane surface proteins like Asp14 and OmpA. An animal study using homologous proteins to Asp14 and OmpA of A. marginate, showed no protective effect in heifers. In the current study, recombinant proteins of Asp14 (rAsp14) and OmpA (rOmpA) of A. phagocytophilum were produced and prepared as a vaccine for sheep. Ten lambs were vaccinated twice with an adjuvant emulsified with rAsp14 or rOmpA, three weeks apart and challenged with a live strain of A. phagocytophilum (GenBank acc.nr M73220) on day 42. The control group consisted of five lambs injected twice with PBS and adjuvant. Hematology, real time qPCR, immunodiagnostics and flow cytometric analyses of peripheral blood mononuclear cells were performed. Vaccinated lambs responded with clinical signs of A.phagocytophilum infection after challenge and bacterial load in the vaccinated group was not reduced compared to the control group. rAsp14 vaccinated lambs generated an antibody response against the vaccine, but a clear specificity for rAsp14 could not be established. rOmpA-vaccinated lambs developed a strong specific antibody response on days 28 after vaccination and 14 days post-challenge. Immunofluorescent staining and flow cytometric analysis of peripheral blood mononuclear monocytes revealed no difference between the three groups, but the percentage of CD4, CD8(+), gamma delta TcR+, lambda-Light chain(+), CD11b(+), CD14(+) and MHC II+ cells, within the groups changed during the study, most likely due to the adjuvant or challenge with the bacterium. Although an antigen specific antibody response could be detected against rOmpA and possibly rAsp14, the vaccines seemed to be ineffective in reducing clinical signs and bacterial load caused by A. phagocytophilum. This is the first animal study with recombinant Asp14 and OmpA aimed at obtaining clinical protection against A. phagocytophilum in sheep.
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| 9. |
- Hagman, Emilia, et al.
(författare)
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Oral intake of mesoporous silica is safe and well tolerated in male humans
- 2020
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 15:10
-
Tidskriftsartikel (refereegranskat)abstract
- Background Precisely engineered mesoporous silica has been shown to induce weight loss in mice, but whether it is safe to use in humans have not investigated.Objective The aim was to determine whether oral dosing, up to 9 grams/day, of precisely engineered mesoporous silica as a food additive can be used safely in male humans.Design This single blinded safety study consisted of two study arms including 10 males each (18-35 years). One arm consisted of participants with normal weight and one with obesity. After a placebo run-in period, all subjects were given porous silica three times daily, with increasing dose up to 9 grams/day (Phase 1). Subjects with obesity continued the study with highest dose for additional 10 weeks (Phase 2).Results All participants completed Phase 1 and 90% completed Phase 2, with approximately 1% missed doses. Participants reported no abdominal discomfort, and changes in bowel habits were minor and inconsistent. The side effects observed were mild and tolerable, biomarkers did not give any safety concern, and no severe adverse events occurred.Conclusion Mesoporous silica intake of up to 9 grams/day can be consumed by males without any major adverse events or safety concerns.
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| 10. |
- Hobbs, Stephen, et al.
(författare)
-
SAR inteferometry with seasonally changing snow cover
- 2011
-
Konferensbidrag (refereegranskat)abstract
- Spaceborne radar interferometry is an established and very powerful method of measuring land subsidence over timescales of weeks to years. It has been demonstrated on natural and urban landscapes and is becoming an operational technique with accuracy better than 1 cm yr-1. The technique generally relies on having scatterers (which reflect the radar signal) which have stable properties over the timescale of interest. In some landscapes these scatterers occur naturally. However, at high latitudes there are particular difficulties because of the strong seasonal variation in the landcover – snow cover in particular can vary dramatically over periods of weeks to months – and the satellite orbits have particular features which are not generally significant at lower latitudes. It is unlikely that natural scatterers will be stable over long periods in these areas. The aim of this project is to develop methods of SAR interferometry suitable for use in landscapes with seasonal snow cover. The project has two themes: (1) improved understanding of SAR imaging at high latitudes and the use of interferometry in such landscapes, and (2) the development of artificial radar targets which can provide the necessary stability for long-term surface deformation monitoring. The sponsor runs a large mining operation at high latitudes. The study has a practical focus and is part of a larger project to provide a mining subsidence monitoring service for the sponsor. The project’s aim is to achieve accurate monitoring of subsidence using radar interferometry at high latitudes. Techniques developed should be suitable for operational use. Test site The experiment test site is centred on the town of Kiruna in northern Sweden (67° 51’ N, 20° 13’ E). The ground is covered with snow (to a depth of 1 m or more) from October to May each year, and so the winter and summer periods have very different land cover properties. The site includes the town of Kiruna, a large mine, and areas of natural sparse forest with mainly birch and some coniferous trees up to several metres tall. Datasets Available Several datasets are available to support the research, these include: • GPS measurements from a network of control points • General weather observations • Mapping data for land cover / land use and topography • SAR images at approximately monthly intervals from 2009 (Radarsat-2, using up to 3 satellite tracks for imaging) • A network of corner reflectors across the test area The core data analysis tool is the MDA software package designed for processing Radarsat images (for both backscatter and interferometric products). The key resource for the research is the time series of high resolution SAR images suitable for interferometric processing, which allows seasonal changes in backscatter to be observed directly. Methodology The project requires a mix of simulation and practical design and fieldwork. The main contributions will be in the area of target specification, design and validation. Achievements to date The project started late in 2009 and the main emphasis so far has been to establish the datasets needed for the research. Radarsat-2 images have been acquired and are being processed to derive interferometric products and to register them to standard projections compatible with each other and ancillary data. Field observations complementing the satellite imaging are also being made. Acknowledgements The project is sponsored in full by the LKAB mining company.The project also benefits from technical advice of MDA.
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| 11. |
- Isoz, Oscar, et al.
(författare)
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Assessment of GPS L1/Galileo E1 interference monitoring system for the airport environment
- 2011
-
Ingår i: Proceedings of the 23rd international technical meeting of the Satellite Division of the Institute of Navigation, ION GNSS 2011. - Manassas, Va : Inst. of Navigation. - 9781618394750 ; , s. 1920-1930
-
Konferensbidrag (refereegranskat)abstract
- How does the GPS Ll spectrum look like at a commercial airport? How frequently do radio frequency interference (RFI) incidents occur? To answer this, the GPS Ll/Galileo El band was monitored at two different airports for an extended period of time. The monitor stations continuously recorded the noise level using the automatic gain control (AGC) in the frontend. Also, the raw intermediate frequency (IF) signal was recorded at regular intervals as well as when the AGC level dropped below a certain threshold. In this paper the analysis of long-term measurements of the spectrum and AGC level at Luleå Airport outside Luleå, Sweden, and Kaohsiung International Airport in Kaohsiung City, Taiwan, is presented. The results shows that RFI incidents did occur at both airports, although more frequent at Kaohsiung International Airport. The measurements also show that the AGC level is useful in systems monitoring the RFI environment. Importantly, the measured data could be utilized for analyses toward the future introduction of GBAS for civil aviation authorities.
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| 12. |
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| 13. |
- Johansson, Jonny, et al.
(författare)
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Project: EISCAT 3D
- 2007
-
Annan publikation (populärvet., debatt m.m.)
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| 14. |
- Lindgren, Tore, et al.
(författare)
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A measurement system for the complex far-field of physically large antenna arrays under noisy conditions utilizing the equivalent electric current method
- 2010
-
Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 58:10, s. 3205-3211
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Tidskriftsartikel (refereegranskat)abstract
- Precipitation in the form of snow or rain could severely degrade the performance of large antenna arrays, in particular if knowledge about the beam shape and pointing direction in absolute numbers is necessary. In this paper, a method of estimating the far-field of each individual antenna element using the equivalent electric current approach is presented. Both a least squares estimator and a Kalman filter was used to solve the resulting system of equation and their performance was compared. Simulation results shows that the estimated far-field for one antenna element is very accurate if there is no noise on the signal. During noisier conditions the Kalman filter gives less noisy results while the systematic errors are slightly larger compared to the least squares estimator.
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| 15. |
- Lindgren, Tore, et al.
(författare)
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A measurement system for the position and phase errors of the elements in an antenna array subject to mutual coupling
- 2012
-
Ingår i: International Journal of Antennas and Propagation. - : Hindawi Limited. - 1687-5869 .- 1687-5877. ; 2012
-
Tidskriftsartikel (refereegranskat)abstract
- When deploying large antenna arrays in arctic environments, a local measurement system may be necessary in order to ensure control over the position and phase of the individual antenna elements. In this paper, a method of estimating the position and phase of each individual antenna element in the presence of mutual coupling is presented. It uses both measurements of the scattering matrix in the array and measurements of the electric field using a minimum of four probes located in the near field of the array. Simulations show that the method gives accurate results even in the presence of noise in the measurements. The geometry of the probe-array system affects the performance significantly.
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| 16. |
- Lindgren, Tore, et al.
(författare)
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A multistatic GNSS synthetic aperture radar for surface characterization
- 2008
-
Ingår i: IEEE Transactions on Geoscience and Remote Sensing. - 0196-2892 .- 1558-0644. ; 46:8, s. 2249-2253
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Tidskriftsartikel (refereegranskat)abstract
- Bistatic global navigation satellite system (GNSS) radar has received increased attention in recent years within both the radar and GNSS communities. In this paper, the traditional bistatic GNSS radar and bistatic synthetic aperture radar (SAR) concepts are fused into a more generic multistatic GNSS SAR system for surface characterization. This is done by using the range and Doppler processing techniques on signals transmitted by multiple satellites to determine the angular dependence of the surface reflectivity. The method has also been tested experimentally, and the results are presented.
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| 17. |
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| 18. |
- Lindgren, Tore
(författare)
-
Algorithm development for multistatic GNSS radar technology
- 2007
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bistatic GNSS radar has received increased attention in recent years within both the radar and the GNSS communities. Its major advantages are that it has complete earth coverage and that more information is available due to the geometric diversity of the transmitters. Also, the receiver in a multistatic radar system does not have to transmit a signal which enables development of low power and low cost equipment. This thesis describes contributions made to multistatic GNSS radar algorithms for surface characterization and object detection. By analyzing the strength and shape of the reflected signal's waveform properties of the surface and the height above ground can be determined. In addition to this primary reflection, transient secondary reflections can be found in bistatic GNSS radar data. These are due to reflections in buildings and other structures only when the geometry between the GNSS satellite, measurement platform, and the reflecting body is correct. An algorithm to detect these reflections and determine the location of the reflecting object has been developed and tested experimentally. Previously, significant effort has been put into develop the synthetic aperture radar (SAR) theory to include the bistatic situation. These algorithms are here developed further into a more generic multistatic GNSS SAR system for surface characterization. This is done by using range and doppler processing techniques on signals transmitted by multiple satellites to determine the angular dependence of the surface reflectivity. The developed algorithm have also been tested experimentally.
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| 19. |
- Lindgren, Tore
(författare)
-
Characterization problems in radio measurement systems
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Radio measurement systems may have their performance significantly degraded due to environmental factors such as multipath, weather effects, and mechanical displacements. Characterization of these effects are therefore important in order to ensure functionality of the system. The characterization itself may also be the purpose of the system. This thesis contributes to the answer to the question of how to assess the effect of the environment on the propagation and reception of radio waves for three different applications.Traditionally the functionality of a radio measurement system has been assessed using either simulations assuming ideal conditions (e.g. free space) or measurements under controlled circumstances. There is no doubt that both these approaches are very useful when designing antennas and related hardware. In many applications it is also sufficient to assume ideal conditions and only use an a priori characterization. The applications considered in this thesis all operates in an environment that can be considered to be challenging. In these cases the environment needs to be taken into account in the design process of the system. Both simulations and measurement methods have been considered. The combination of electromagnetic simulation methods, such as the method of moments (MOM) or the partial element equivalent circuit (PEEC) method, with statistical methods, such as the Monte Carlo method, have been given special attention. The measurement systems considered, both for determining the performance of antennas and for detection of objects and transponders, are all assessed from a "challenging environment" point of view.The three application considered are multistatic radar using global navigation satellite systems (GNSS), measurement systems for antenna arrays in noisy conditions, and simulation of RFID systems with moving transponders. In the multistatic radar the focus is on detecting signals reflected in directions other than that of the primary reflection. The results shows that detecting these signals is possible even with the low signal levels involved. This is especially the case when reflecting objects are present which could scatter the signal in a specular way. By using the equivalent electric current method it is possible to estimate the complex far-field radiation pattern of antenna arrays even when the signals used have a low signal-to-noise ratio (SNR). This has been shown using simulation of a large antenna array and with measurements using a small array for GNSS receivers. When designing RFID systems it is important to be able to estimate the performance in terms of number of detected transponders with all movements of the transponders taken into account. This is possible by using a very simple model of the transponders (e.g. a magnetic dipole) in which case only one electromagnetic simulation is needed. This enables the use of the Monte Carlo method to take the random movements of the transponders into account using a low number of computations. The use of the PEEC method further enables a combined simulation of both the electromagnetic properties of the reader antenna and the electric functionality of the receiver circuit.Although the considered application are very different the obtained solutions are in many ways general. The fact that even the weak signals reflected in non-specular directions in a multi-static GNSS radar can be detected can be used in any application involving multi-path propagation or stray signals. The equivalent electric current method have here been considered for two radically different antenna arrays operating in a low SNR environment. Although the simulation approach chosen for the RFID simulations rely heavily on the simple magnetic dipole method it would work with any antenna at any frequency as long as the model of the antenna is sufficiently simple.
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| 20. |
- Lindgren, Tore, et al.
(författare)
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Design and evaluation of RFID systems using the partial element equivalent circuit method
- 2008
-
Ingår i: Proceedings of the International Symposium on Antenna and Propagation. - : Chinese Microwave Association.
-
Konferensbidrag (refereegranskat)abstract
- Systems based on radio frequency identification (RFID) techniques are finding new markets and uses. For maximal readability, RFID-systems have to be tailored to its specific environment. In this paper, the partial element equivalent circuit (PEEC) method is used to analyze an RFID-system with reader, tag, and additional electronic circuitry. The results show how the method can be used to match antennas with discrete, external components and study the backscattered energy from the tag. The simulations are very fast which allows for studying multiple locations of the tag in order to tailor the RFID-system.
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| 21. |
- Lindgren, Tore, et al.
(författare)
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Estimation of the complex far-field of an antenna array using live GNSS signals and the equivalent electric current method
- 2009
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Ingår i: Proceedings of the 13th IAIN World Congress, Stockholm, 27-30 October 2009. - : Nordic Institute of Navigation.
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Konferensbidrag (refereegranskat)abstract
- When using antenna arrays with GNSS receivers both the gain and the phase of the far-field radiation pattern may be distorted due to coupling effects. This problem can often be characterized in the design process of the antenna or by measurements in a measurement range. This is, however, not always possible and it is then necessary to characterize the antenna using live measurements. In this paper the equivalent electric current method is used to estimate the gain and phase of the far-field of an antenna array for a GPS receiver. In the method, the complex far-field pattern of an antenna is estimated using the distribution of the electric current, which is described using suitable basis functions. The method was evaluated using data collected by a 7-element GPS antenna array. The results show agreement between the model and measured results.
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| 22. |
- Lindgren, Tore, et al.
(författare)
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Measurement of backscattered GPS signals
- 2006
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Ingår i: Position, Location, and Navigation Symposium. - : IEEE Communications Society. - 0780394542 ; , s. 664-669
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Konferensbidrag (refereegranskat)abstract
- This paper describes a technique utilizing GPS ground reflections (GPS bistatic radar) to detect objects with a significant radar cross section located on the surface of the earth. GPS bistatic radar has been shown to be effective as a radar altimeter and for characterization of the reflection surface but has thus far not been shown to be effective for object detection. The technique uses ground reflections with longer path delay than the shortest path specular reflection. Data was collected using a COTS software receiver and post-processed using an in-house tool. Regions with ground reflections were overlayed on aerial imagery to identify possible sources.
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| 23. |
- Lindgren, Tore, et al.
(författare)
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Monte Carlo simulation of an radio frequency identification system with moving transponders using the partial element equivalent circuit method
- 2010
-
Ingår i: IET Microwaves, Antennas & Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 4:12, s. 2069-2076
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Tidskriftsartikel (refereegranskat)abstract
- When designing an radio frequency identification system it is important to take both the position and the movement of the transponders into account. In this study, a simulation method that enables the description of a complete RFID system including moving and rotating transponders as well as a complex, industrial environment is presented. By using the partial element equivalent circuit method to calculate the magnetic field generated by the reader antenna and describing the transponders using a magnetic dipole, it is possible to use the Monte Carlo method to describe the dynamic behaviour of the complete system. The method is used in this study to describe the difference in performance between two different reader antennas and these results are also compared to measurements of similar systems operating in an industrial environment. The difference in performance between the two systems is similar in both the simulations and the measurements. A small discrepancy was seen between the results from the simulations and the measurements which is for the most part because of the limited read rate of the RFID systems used in the measurements.
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| 24. |
- Lindgren, Tore, et al.
(författare)
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Non-specular point reflections in GNSS bistatic radar
- 2006
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Konferensbidrag (refereegranskat)abstract
- In this paper the impact of using different measurement platforms with different qualities is discussed. Data collected during three different measurement campaigns were used in this study. The data collected over Iowa, USA, in July, 2005, which were from a low flying airplane (low altitude and high dynamics), a data set collected from a stratospheric balloon outside Boulder, USA, in April, 2006 (high altitude, low dynamics), and a data set collected at the Boulder Atmospheric Observatory (BAO) outside Boulder, USA, in April, 2006 (low altitude, stationary).
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| 25. |
- Lindgren, Tore, et al.
(författare)
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Performance of a Yagi antenna during snowfall
- 2008
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Ingår i: Proceedings of the International Symposium on Antenna and Propagation. - : Chinese Microwave Association.
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Konferensbidrag (refereegranskat)abstract
- Precipitation in the form of snow could severely degrade the performance of the planned EISCAT_3D radar antenna array. In this paper the performance of the antenna elements, crossed yagi antennas, is studied using both simulations and measurements. The results shows that during snowfall the performance of the antenna is degraded, and under severe conditions the antenna becomes non-operational. To guarantee operability of the system, the effect of snow cover should be taken into account when designing the final antenna.
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| 26. |
- Lindgren, Tore, et al.
(författare)
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Study of cluster of hard horns feeding an offset multi-beam reflector antenna for dual band operation at 20/30 GHz
- 2004
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Ingår i: 2004 digest. - Piscataway, NJ : IEEE Communications Society. - 0780383028 ; , s. 3015-3018
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Konferensbidrag (refereegranskat)abstract
- The study of a multibeam reflector antenna system with hard horn feeds is extended to include the defocusing effects encountered in the actual cluster. This is done by using the ARECIBO code, a reflector program for analysis of multi-reflector antennas. There are many different analysis models for offset reflectors implemented in ARECIBO. The one used for the present study is aperture integration after Fourier series expansion of the aperture field. This is fast and accurate within main beam and first sidelobes, but it is of course slow compared to the BOR model.
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| 27. |
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| 28. |
- Norton, Amanda, et al.
(författare)
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A study of bistatic GNSS radar
- 2006
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Ingår i: GIS development: Asia Pacific edition. ; 10:6
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- One of the more recent areas of GNSS research of increasing popularity is the study of reflected GNSS signals. This will enable the use of GNSS as a passive radar system that can be used as an alternative to radar altimetry and for ground feature characterization. Of interest is also the possibility to use GNSS signals for object detection. The advantage of using GNSS signals as a passive radar system is that it has complete earth coverage. The signals are, however, weak and the computational load associated with the analysis is heavy.
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| 29. |
- Prakash, Om, et al.
(författare)
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Tailoring the Photophysical Properties of a Homoleptic Iron(II) Tetra N-Heterocyclic Carbene Complex by Attaching an Imidazolium Group to the (C∧N∧C) Pincer Ligand─A Comparative Study
- 2024
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 63:6, s. 2909-2918
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Tidskriftsartikel (refereegranskat)abstract
- We here report the synthesis of the homoleptic iron(II) N-heterocyclic carbene (NHC) complex [Fe(miHpbmi)2](PF6)4 (miHpbmi = 4-((3-methyl-1H-imidazolium-1-yl)pyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)) and its electrochemical and photophysical properties. The introduction of the π-electron-withdrawing 3-methyl-1H-imidazol-3-ium-1-yl group into the NHC ligand framework resulted in stabilization of the metal-to-ligand charge transfer (MLCT) state and destabilization of the metal-centered (MC) states. This resulted in an improved excited-state lifetime of 16 ps compared to the 9 ps for the unsubstituted parent compound [Fe(pbmi)2](PF6)2 (pbmi = (pyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)) as well as a stronger MLCT absorption band extending more toward the red spectral region. However, compared to the carboxylic acid derivative [Fe(cpbmi)2](PF6)2 (cpbmi = 1,1′-(4-carboxypyridine-2,6-diyl)bis(3-methylimidazol-2-ylidene)), the excited-state lifetime of [Fe(miHpbmi)2](PF6)4 is the same, but both the extinction and the red shift are more pronounced for the former. Hence, this makes [Fe(miHpbmi)2](PF6)4 a promising pH-insensitive analogue of [Fe(cpbmi)2](PF6)2. Finally, the excited-state dynamics of the title compound [Fe(miHpbmi)2](PF6)4 was investigated in solvents with different viscosities, however, showing very little dependency of the depopulation of the excited states on the properties of the solvent used.
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| 30. |
- Rinde, Mia, et al.
(författare)
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Mesoporous silica with precisely controlled pores reduces food efficiency and suppresses weight gain in mice
- 2020
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Ingår i: Nanomedicine. - : Future Medicine Ltd. - 1743-5889 .- 1748-6963. ; 15:2, s. 131-144
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Obesity is a risk factor for cardiovascular disease and diabetes. We aimed to elucidate the effects of distinct mesoporous silica particles (MSPs) supplemented in food on metabolic parameters in obesity. Materials & methods: MSPs with precisely controlled pore size were synthesized, characterized and compared with a control in a C57Bl/6 mouse diet-induced obesity model, studying weight, adiposity, metabolic regulation and food efficiency. Results: The most effective MSPs reduced adipose tissue formation to 6.5 +/- 0.5 g compared with 9.4 +/- 1.2 g, leptin levels nearly halved from 32.8 +/- 7.4 to 16.9 +/- 1.9 ng/ml and a 33% reduction of food efficiency. Control MSP showed no effects. Conclusion: Results demonstrate potential of distinct MSPs to improve metabolic risk factors. Further studies investigating mechanism of action and confirming human safety are needed.
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| 31. |
- Sankaranarayanan, Viswa Narayanan, Doktorand, MC, et al.
(författare)
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PACED-5G: Predictive Autonomous Control using Edge for Drones over 5G
- 2023
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Ingår i: 2023 International Conference on Unmanned Aircraft Systems (ICUAS). - : IEEE. - 9798350310382 - 9798350310375 ; , s. 1155-1161
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Konferensbidrag (refereegranskat)abstract
- With the advent of technologies such as Edge computing, the horizons of remote computational applications have broadened multi-dimensionally. Autonomous Unmanned Aerial Vehicle (UAV) mission is a vital application to utilize remote computation to catalyze its performance. However, offloading computational complexity to a remote system increases the latency in the system. Though technologies such as 5G networking minimize communication latency, the effects of latency on the control of UAVs are inevitable and may destabilize the system. Hence, it is essential to consider the delays in the system and compensate for them in the control design. Therefore, we propose a novel Edge-based predictive control architecture enabled by 5G networking, PACED-5G (Predictive Autonomous Control using Edge for Drones over 5G). In the proposed control architecture, we have designed a state estimator for estimating the current states based on the available knowledge of the time-varying delays, devised a Model Predictive controller (MPC) for the UAV to track the reference trajectory while avoiding obstacles, and provided an interface to offload the high-level tasks over Edge systems. The proposed architecture is validated in two experimental test cases using a quadrotor UAV.
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| 32. |
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| 33. |
- Stenberg, Gustav, et al.
(författare)
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A picosecond accuracy timing system based on L1-only GNSS receivers for a large aperture array radar
- 2008
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Ingår i: Proceedings of the 21th International Technical Meeting of the Satellite Division of the Institute of Navigation. ; , s. 112-116
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Konferensbidrag (refereegranskat)abstract
- During the development of EISCAT_3D, a Large Aperture Array Radar (LAAR), with direct sampling at each antenna element and constituted of up to 16.000 antenna elements, intended for atmospheric research, the need for a highly accurate timing system was recognized. This paper describes the method and test results of a GNSS based timing system on a 300 m scale formed on L1-only GNSS receivers.Simulations have shown that over a distance of 300 m the maximum allowed total timing jitter is 160 ps. This timing jitter is composed of jitter from the clock distribution, local oscillator, ADC and movement of the antenna phase center due to weather conditions. A reasonable assumption is that at most a third of the total jitter is generated in the clock distribution system, i.e. 50 ps. Such accuracy is impossible to achieve with the traditionally often used non-calibrated cable-based clock distribution system, even heating of clock distribution cables can alter the length of the cables to the extent that too large errors are generated, thus the choice to use a GNSS-based clock distribution system that is unaffected by such effects. Other benefits of building a GNSS timing system include lower cost due to reduced amount of coaxial cable throughout the array and the need for building a continuous cable length calibration system that ensures timing accuracy of the distributed clock system to the necessary levels. By dividing the LAAR into small sub-arrays of 9 elements each, the maximum length of the cables distributing the clock is reduced to 4.5 m which is short enough to be calibrated by length approximation only, assuming that the clock distributed to each sub-array is known. Inserting a GNSS receiver at all of these sub-arrays, to provide a clock reference that is unaffected by changing conditions over the array, each sub-array is now timed to the specified accuracy.In general, a GNSS L1-receiver is rated to produce a clock with an error of less than 50 ns, which is about 1000 times too high. However, unique conditions apply to this GNSS timing system that improvs the accuracy, such as:- A local system, i.e. the maximum distance between two GNSS antennas are 300 m which infer all significant atmospheric errors in this application to be common over the array.- A common highly accurate reference clock is distributed to all receivers, which removes the clock drift errors between the receivers.- Software based selection of satellites used for the timing solution to exclude timing errors from different matrices in the position and timing calculations.- All receivers are stationary which allow long integration times, up to 30 min because the time constant of the cable length change in the reference clock distribution is in that order of magnitudes, to improve accuracy- Phase measurements from one satellite only is sufficient to calculate the timing error between the sub-arrays since the relative position of each receiver is known. - No integer ambiguity solution is necessary, again, since the relative position of the receivers is known and the absolute time difference between the receivers is insignificant, only the phase of the distributed clock is important.Satisfying these conditions decreases the clock error from the GNSS receivers sufficiently to reach the necessary levels of accuracy.Each sub-array contains a Voltage Controlled Oscillator (VCO) in which the distributed clock is reproduced and distributed through a Delay Locked Loop (DLL) to the local GNSS receiver, the radar ADCs and a signal injection system located as close to the radar antennas as possible to calibrate the analogue signal path of the system. The purpose of the DLL is to adjust the phase of the reference clock to be equal throughout the array. This is achieved by creating a closed loop feedback from the GNSS receiver to the DLL and adjusting the phase according to the phase differences in the received satellite signals in respect to a reference GNSS receiver. This reference receiver is a high-end receiver which is used in conjunction with purpose specific software to produce information sent to each of the sub-array receivers necessary to calculate the expected phase of local VCO clock. Compared to the actual phase of the VCO, the DLL can now make the necessary adjustments to the reference clock. The information sent is; satellites to use, Doppler-shift, tracking chip and expected phase. This information allow the sub-array receivers to only be capable of tracking a low number of satellites, no more than 6, and using the tracked phase differences to calculate the expected phase of the local VCO. Thus, full capability receivers are not needed, but instead a Digital Signal Processor (DSP) is used with a GNSS RF-frontend to control the DLL and the Automatic Gain Control (AGC) of the RF-frontend.Test measurements have been performed in a real environment during windy winter conditions, clear weather at -10 C and wind speeds up to 20 m/s in gusts, with three antennas placed randomly, but precisely surveyed, at about 5 m distance from each other placed on a rooftop to simulate the conditions in the EISCAT_3D LAAR. IF data from the antennas were collected during a one hour measurement and then post-processed to calculate the expected phase differences between the antennas. These phase differences provide a direct measurement of the accuracy levels attainable. The test results show that when integrating over 15 min, a total clock distribution jitter of less than 50 ps is achievable with simple calculations that can be implemented into a DSP.
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| 34. |
- Waara, Erik R., et al.
(författare)
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Entrapping Digestive Enzymes with Engineered Mesoporous Silica Particles Reduces Metabolic Risk Factors in Humans
- 2020
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Ingår i: Advanced Healthcare Materials. - : Wiley. - 2192-2640 .- 2192-2659. ; 9:11
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Tidskriftsartikel (refereegranskat)abstract
- Engineered mesoporous silica particles (MSP) are thermally and chemically stable porous materials composed of pure silica and have attracted attention for their potential biomedical applications. Oral intake of engineered MSP is shown to reduce body weight and adipose tissue in mice. Here, clinical data from a first-in-humans study in ten healthy individuals with obesity are reported, demonstrating a reduction in glycated hemoglobin (HbA1c) and low-density lipoprotein cholesterol, which are well-established metabolic and cardiovascular risk factors. In vitro investigations demonstrate sequestration of pancreatic alpha-amylase and lipase in an MSP pore-size dependent manner. Subsequent ex vivo experiments in conditions mimicking intestinal conditions and in vivo experiments in mice show a decrease in enzyme activity upon exposure to the engineered MSP, presumably by the same mechanism. Therefore, it is suggested that tailored MSP act by lowering the digestive enzyme availability in the small intestine, resulting in decreased digestion of macronutrient and leading to reduced caloric uptake. This novel MSP based mechanism-of-action, combined with its excellent safety in man, makes it a promising future agent for prevention and treatment of metabolic diseases.
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| 35. |
- Wannberg, Gudmund, et al.
(författare)
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EISCAT_3D - a next-generation European radar system for upper atmosphere and geospace research
- 2010
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Ingår i: Radio Science Bulletin. - 1024-4530. ; :333, s. 75-88
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Tidskriftsartikel (refereegranskat)abstract
- The EISCAT Scientifi c Association, together with a number of collaborating institutions, has recently completed a feasibility and design study for an enhanced performance research radar facility to replace the existing EISCAT UHF and VHF systems. This study was supported by EU Sixth-Framework funding. The new radar retains the powerful multi-static geometry of the EISCAT UHF, but will employ phased arrays, direct-sampling receivers, and digital beamforming and beam steering. Design goals include, inter alia, a tenfold improvement in temporal and spatial resolution, an extension of the instantaneous measurement of full-vector ionospheric drift velocities from a single point to the entire altitude range of the radar, and an imaging capability to resolve small-scale structures. Prototype receivers and beamformers are currently being tested on a 48-element, 224 MHz array (the "Demonstrator") erected at the Kiruna EISCAT site, using the EISCAT VHF transmitter as an illuminator.
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