| 1. |
- Abbasi, Rasha, et al.
(författare)
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IceCube search for neutrinos from GRB 221009A
- 2023
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Ingår i: Proceedings of 38th International Cosmic Ray Conference (ICRC 2023). - : Sissa Medialab Srl.
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Konferensbidrag (refereegranskat)abstract
- GRB 221009A is the brightest Gamma Ray Burst (GRB) ever observed. The observed extremelyhigh flux of high and very-high-energy photons provide a unique opportunity to probe the predictedneutrino counterpart to the electromagnetic emission. We have used a variety of methods to searchfor neutrinos in coincidence with the GRB over several time windows during the precursor, promptand afterglow phases of the GRB. MeV scale neutrinos are studied using photo-multiplier ratescalers which are normally used to search for galactic core-collapse supernovae neutrinos. GeVneutrinos are searched starting with DeepCore triggers. These events don’t have directionallocalization, but instead can indicate an excess in the rate of events. 10 GeV - 1 TeV and >TeVneutrinos are searched using traditional neutrino point source methods which take into accountthe direction and time of events with DeepCore and the entire IceCube detector respectively. The>TeV results include both a fast-response analysis conducted by IceCube in real-time with timewindows of T0 − 1 to T0 + 2 hours and T0 ± 1 day around the time of GRB 221009A, as well asan offline analysis with 3 new time windows up to a time window of T0 − 1 to T0 + 14 days, thelongest time period we consider. The combination of observations by IceCube covers 9 ordersof magnitude in neutrino energy, from MeV to PeV, placing upper limits across the range forpredicted neutrino emission.
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| 2. |
- Ernens, Dennis, et al.
(författare)
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On the Sealability of Metal-to-Metal Seals with Application to Premium Casing Connections
- 2019
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Ingår i: SPE/IADC International Drilling Conference and Exhibition. - 9781613996423
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Metal-to-metal seals are used in connections of casing in oil and gas wells. This paper describes the mechanisms of sealing of metal-to-metal seals as investigated using an experimental set-up and a sealability model. Experiments were conducted for a variety of thread compounds and applied pin/box surface coatings. The results were used to validate a numerical model for sealability. The stochastic model couples a contact mechanics model with a flow model and takes the influence of all the surface topography features into account. Once validated, the model was used together with the experimental results to explain the sealing mechanisms of metal-to-metal seals. The sealing configuration is a face seal with an R=80 mm round-off radius pressing against a flat. The face seal specimens were manufactured from P110 tubing. The used test set-up is designed for investigating only the metal-to-metal seal of the connection. The set-up can carry out rotary sliding under constant load to simulate surface evolution during make-up and subsequently perform a leakage test. The sealing limit is determined by applying 700 bar fluid pressure and then gradually reducing the normal force until leakage is observed. The data is subsequently used to validate a previously published model. The results indicate a strong dependence of the type of thread compound used on the onset of leakage. The thread compound affects the amount of wear and thus changes the surface topography of the interacting surfaces. It is shown that the sealability model is capable to predict the onset of leakage within the experimental accuracy. The model shows further that certain surface topographical features improve the sealing performance. Namely, a turned against a flat surface topography leads to highly localized contact areas, which in turn yields the best sealing performance. The combination of experimental data with the validated model leads to much deeper insights for the sealing mechanisms than what could be obtained using either on their own.
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| 3. |
- Parcey, Dennis A., et al.
(författare)
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Determination of Cerenkov light absorption by fuel pond water using a calibration light source
- 2011
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Quantitative measurement of Cerenkov light generated by spent fuel assemblies requires anunderstanding of the absorbance characteristics of the spent fuel pond water. The presence ofparticulate or organic material can severely attenuate the transmission of the ultravioletcomponent of the Cerenkov spectrum. This can make the quantitative measurement of theCerenkov light using a digital Cerenkov viewing device difficult or in some cases impossible.A calibration light source that can be inserted into the fuel pond has been constructed. Thissource generates a known ultraviolet light flux. Measurements of this source can be used tocalculate the absorbance of Cerenkov light by the fuel pond water and in turn compensate for theabsorbance when measuring the intensity of a spent fuel assembly. This paper discusses thechallenges of constructing such a device and the results from measurements in two spent fuelponds.
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| 4. |
- West, Jay B., et al.
(författare)
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Comparison and evaluation of retrospective intermodality image registration techniques
- 1997
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Ingår i: SPIE - The International Society for Optical Engineering. - : SPIE - International Society for Optical Engineering. ; , s. 332-347
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Konferensbidrag (refereegranskat)abstract
- All retrospective image registration methods have attached to them some intrinsic estimate of registration error. However, this estimate of accuracy may not always be a good indicator of the distance between actual and estimated positions of targets within the cranial cavity. This paper describes a project whose principal goal is to use a prospective method based on fiducial markers as a ’gold standard’ to perform an objective, blinded evaluation of the accuracy of several retrospective image-to-image registration techniques. Image volumes of three modalities – CT, MR, and PET – were taken of patients undergoing neurosurgery at Vanderbilt University Medical Center. These volumes had all traces of the fiducial markers removed, and were provided to project collaborators outside Vanderbilt, who then performed retrospective registrations on the volumes, calculating transformations from CT to MR and/or from PET to MR, and communicated their transformations to Vanderbilt where the accuracy of each registration was evaluated. In this evaluation the accuracy is measured at multiple ’regions of interest,’ i.e. areas in the brain which would commonly be areas of neurological interest. A region is defined in the MR image and its centroid C is determined. Then the prospective registration is used to obtain the corresponding point C’ in CT or PET. To this point the retrospective registration is then applied, producing C’ in MR. Statistics are gathered on the target registration error (TRE), which is the disparity between the original point C and its corresponding point C’. A second goal of the project is to evaluate the importance of correcting geometrical distortion in MR images, by comparing the retrospective TRE in the rectified images, i.e., those which have had the distortion correction applied, with that of the same images before rectification. This paper presents preliminary results of this study along with a brief description of each registration technique and an estimate of both preparation and execution time needed to perform the registration.
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| 5. |
- Adjrad, M., et al.
(författare)
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Interference monitoring for GNSS bands in indoor and urban environments
- 2007
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Ingår i: Proceedings of the 20th International Technical Meeting of the Satellite Division of the Institute of Navigation. - : Institute of Navigation, The. ; , s. 1211-1220
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Konferensbidrag (refereegranskat)abstract
- A collaborative research project between the University of Leeds and Luleå University of Technology, Sweden, has taken place aiming to characterize the man-made noise in urban and indoor environments in the Galileo allocated frequency bands: E5 (1191.795 ± 25.575 MHz), E6 (1278.75 ± 20 MHz), and L1 (1575.42 ± 16 MHz), obviously, also covering the GPS L1 and L5 bands. This project has been co-funded by the European GNSS Supervisory Authority (EGSA), with funding from the 6th Framework Program of the European Community for research and technological development. The project includes the development of two receiver systems: the first instrument is based on the use of a spectrum analyzer (SA-based instrument), a wideband GNSS antenna, and a front-end capable of capturing each Galileo band separately using appropriate filtering and switches. The second instrument addresses the issues of cost and portability, providing interference detection and alarm triggering without the need for complex instrument. This is accomplished using low cost components in a small form factor where the instrument is based on a core GNSS front-end. This instrument will only cover the L1/E1 band. The interference measurement is obtained by combining the information from the automatic gain control (AGC) voltage that controls the AGC amplifier gain and the spectrum analysis of the analogue-to-digital converter (ADC) output raw data. The AGC information will be very important for detecting the presence of wideband interference signals where this will be difficult using spectrum analysis (in contrast to the case to narrowband interference signals). Control and data logging from both instruments are performed using a laptop computer where the spectrum analyzer traces and the FE-based instrument data are recorded for offline analysis via a suite of MATLAB® scripts. This paper describes the spectrum survey conducted at various indoor and urban locations, operationally significant to GNSS, in the North of the UK. The survey sites were selected to obtain geographically diverse measurement results and provide a general representation of the spectral environment. In addition, the temporal variation of man-made noise (MMN) is considered, this latter being correlated with the human activity at the measurement site, by performing the measurements day and night, weekdays and weekends.
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| 6. |
- Corrigan, Lee J., et al.
(författare)
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Perception matters! Engagement in task orientated social robotics
- 2015
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Ingår i: Proceedings of the 24th IEEE International Symposium on Robot and Human Interactive Communication. - 9781467367035 ; , s. 375-380
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Konferensbidrag (refereegranskat)abstract
- Engagement in task orientated social robotics is a complex phenomenon, consisting of both task and social elements. Previous work in this area tends to focus on these aspects in isolation without consideration for the positive or negative effects one might cause the other. We explore both, in an attempt to understand how engagement with the task might effect the social relationship with the robot, and vice versa. In this paper, we describe the analysis of participant self-report data collected during an exploratory pilot study used to evaluate users’ “perception of engagement”. We discuss how the results of our analysis suggest that ultimately, it was the users’ own perception of the robots’ characteristics such as friendliness, helpfulness and attentiveness which led to sustained engagement with both the task and robot
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| 7. |
- Do, J., et al.
(författare)
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L and S bands spectrum survey in the San Francisco Bay area
- 2004
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Ingår i: PLANS 2004. - Piscataway, NJ : IEEE Communications Society. - 0780384164 ; , s. 566-572
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Konferensbidrag (refereegranskat)abstract
- The Global Positioning System (GPS) is a radio frequency (RF) communication system that consists of transmitters on the satellites and receivers on the ground. Because of substantial path loss, the received signal power from satellites is extremely weak and even below the thermal noise floor and as such is very sensitive to changes in the underlying noise floor. The goal of this work is to investigate the radio spectrum environment in the GPS band along with two additional bands, the Unified-S band and 2.4 GHz Industrial Scientific and Medical (ISM) band. The spectrum survey was conducted at various locations in the San Francisco Bay area including various urban, rural areas and airports and harbors which are operational significant to GPS. The measurement data collected in this study will provide a more accurate representation of the current status and the characteristics of the spectrum environment. Geographical variation within the sites will reveal correlation between the spectrum environment and the level of urbanization and also a comparative study on the frequency bands under different level of regulations can be used to investigate the effectiveness of the current spectrum policy
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| 8. |
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| 9. |
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| 10. |
- Kajko-Mattsson, Miroslawa E J, et al.
(författare)
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Roles for Evolution and Maintenance of SOA-Based Systems
- 2007
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Konferensbidrag (refereegranskat)abstract
- Development, evolution and maintenance of SOAbased systems demands rethinking of the traditional system evolution and maintenance roles. The key objective of this paper is to present preliminary ideas on the roles required for maintenance and evolution of SOA-based systems and to suggest areas of needed research.
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