| 1. |
- Wang, C. H., et al.
(författare)
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High-k dielectrics on (100) and (110) n-InAs: Physical and electrical characterizations
- 2014
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Ingår i: AIP Advances. - : AIP Publishing. - 2158-3226. ; 4:4
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Tidskriftsartikel (refereegranskat)abstract
- Two high-k dielectric materials (Al2O3 and HfO2) were deposited on n-type (100) and (110) InAs surface orientations to investigate physical properties of the oxide/semiconductor interfaces and the interface trap density (D-it). X-ray photoelectron spectroscopy analyses (XPS) for native oxides of (100) and (110) as-grown n-InAs epi wafers show an increase in As-oxide on the (100) surface and an increase in InOx on the (110) surface. In addition, XPS analyses of high-k (Al2O3 and HfO2) on n-InAs epi show that the intrinsic native oxide difference between (100) and (110) epi surfaces were eliminated by applying conventional in-situ pre-treatment (TriMethyAluminium (TMA)) before the high-k deposition. The capacitance-voltage (C-V) characterization of HfO2 and Al2O3 MOSCAPs on both types of n-InAs surfaces shows very similar C-V curves. The interface trap density (D-it) profiles show D-it minima of 6.1 x 10(12/)6.5 x 10(12) and 6.6 x 10(12)/7.3 x 10(12) cm(-2) eV(-1) for Al2O3 and HfO2, respectively for (100) and (110) InAs surfaces. The similar interface trap density (D-it) on (100) and (110) surface orientation were observed, which is beneficial to future InAs FinFET device with both (100) and (110) surface channel orientations present. (C) 2014 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License.
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| 2. |
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| 3. |
- Branger, Erik, 1988-, et al.
(författare)
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Image analysis as a tool for improved use of the Digital Cherenkov Viewing Device for inspection of irradiated PWR fuel assemblies.
- 2014
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a tool used to measure the Cherenkov light emitted from irradiated nuclear fuel assemblies stored in water pools. It has been approved by the IAEA for attended gross defect verification, as well as for partial defect verification, where a fraction of the fuel material has been diverted. In this report, we have investigated the current procedures for recording images with the DCVD, and have looked into ways to improve these procedures. Using three different image sets of PWR fuel assemblies, we have analysed what information and results can be obtained using image analysis techniques. We have investigated several error sources that distort the images, and have shown how these errors affect the images. We have also described some of the errors mathematically, and have discussed how these error sources may be compensated for, if the character and magnitude of the errors are known. Resulting from our investigations are a few suggestions on how to improve the procedures and consequently the quality of the images recorded with the DCVD as well as suggestions on how to improve the analysis of collected images. Specifically, a few improvements that should be looked into in the short term are:• Images should be recorded with the fuel assembly perfectly centered in the image, and preferably without any tilt of the DCVD relative to the fuel in order to obtain accurate measurements of the light intensity. Image analysis procedures that may aid the alignment are presented.• To compensate for the distorting effect of the water surface and possible turbulence in the water, several images with short exposure time should be captured rather than one image with long exposure time. Using image analysis procedures, it is possible to sum the images resulting in a final image with less distortions and improved quality.• A reference image should be used to estimate device-related distortions, so that these distortions are compensated for. Ideally, this procedure can also be used to calibrate individual pixels.• The background should be carefully taken into account in order to separate the background level from diffuse signal components, allowing for the background to be subtracted. Accordingly, each measurement campaign should be accompanied by at least one background measurement, recorded from a section in the storage pool where no fuel assemblies are present. Furthermore, the background level should be determined from a larger region in the image and not from one individual pixel, as is currently done.• A database of measurements should be set up, containing DCVD images, information about the applied DCVD settings and the conditions that the DCVD was used in. Any partial defect verification procedure at any time could then be tested against as much data as possible. Accordingly, a database can aid in evaluating and improving partial defect verification methods using DCVD image analysis.Based on the findings and discussions in this report, some long-term improvements are also suggested.
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| 4. |
- Branger, Erik, 1988-, et al.
(författare)
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Improved DCVD assessments of irradiated nuclear fuel using image analysis techniques
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a tool for measuring the Cherenkov light intensity emitted from irradiated nuclear fuel in wet storage. It is currently used in nuclear facilities where authority inspectors perform attended gross defect verification to ensure the presence of irradiated fuel material, as well as partial defect verification to ensure that a fraction of the fuel material has not been diverted. In 2013, Uppsala University (UU), supported by the Swedish Radiation Safety Authority, initiated a PhD project aimed at gaining a better understanding of the underlying physics process of the Cherenkov light emission and its detection, in order to improve and enhance the capabilities of the DCVD. The scope of this research is broad and includes modelling, simulations and experiments. As a first step, expertise on image analysis was brought into the project with the purpose to identify image analysis related opportunities and challenges relevant to the DCVD. The investigations performed so far cover general aspects of image analysis as well as aspects specific for verification of PWR fuels, where the fuel geometry may be extra challenging. Resulting from the investigation are suggestions on how to improve the measurement procedure and consequently the image quality obtained with the DCVD. This presentation describes these results and expected outcomes of their implementation.
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| 5. |
- Branger, Erik, 1988-, et al.
(författare)
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Towards unattended partial-defect verification of irradiated nuclear fuel assemblies using the DCVD
- 2014
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Digital Cherenkov Viewing Device (DCVD) is a tool used by authority inspectors to verify irradiated nuclear fuel assemblies in wet storage by measuring the Cherenkov light emitted. The DCVD is approved by the IAEA for gross defect verification, and is one of the few inspection tools approved for partial defect verification.There is interest in adapting the DCVD to work in unattended mode, so that it can be used to verify large quantities of irradiated fuel assemblies prior to moving them to difficult-to-access storage locations. This work presents methods based on image analysis that can be used to reduce the effects of different types of distortions encountered when performing measurements with the DCVD. Implementing these methods will ensure that data of high quality is obtained. Verification prior to moving fuels to difficult-to-access storage may also require a dedicated measurement station to be built, and it is argued that by constructing these stations with the DCVD in mind, many distortions can be reduced or eliminated. Thus, by implementing safeguards-by-design, it is possible to ensure that the DCVD is used in near optimal conditions.
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| 6. |
- Van den Bulcke, Jan, et al.
(författare)
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3D tree-ring analysis using helical X-ray tomography
- 2014
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Ingår i: Dendrochronologia. - : Elsevier BV. - 1125-7865 .- 1612-0051. ; 32:1, s. 39-46
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Tidskriftsartikel (refereegranskat)abstract
- The current state-of-the-art of tree-ring analysis and densitometry is still mainly limited to two dimensions and mostly requires proper treatment of the surface of the samples. In this paper we elaborate on the potential of helical X-ray computed tomography for 3D tree-ring analysis. Microdensitometrical profiles are obtained by processing of the reconstructed volumes. Correction of the structure direction, taking into account the angle of growth rings and grain, results in very accurate microdensity and precise ring width measurements. Both a manual as well as an automated methodology is proposed here, of which the MATLAB (c) code is available. Examples are given for pine (Pinus sylvestris L), oak (Quercus robur L) and teak (Tectona grandis L.). In all, the methodologies applied here on the 3D volumes are useful for growth related studies, enabling a fast and non-destructive analysis.
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| 7. |
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| 8. |
- Wernersson, Erik L. G., et al.
(författare)
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Postprocessing method for reducing phase effects in reconstructed microcomputed-tomography data
- 2013
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Ingår i: Optical Society of America. Journal A. - 1084-7529 .- 1520-8532. ; 30:3, s. 455-461
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Tidskriftsartikel (refereegranskat)abstract
- With increased resolution in x-ray computed tomography, refraction adds increasingly to the attenuation signal. Though potentially beneficial, the artifacts caused by refraction often need to be removed from the image. In this paper, we propose a postprocessing method, based on deconvolution, that is able to remove these artifacts after conventional reconstruction. This method poses two advantages over existing projection-based (preprocessing) phase-retrieval or phase-removal algorithms. First, evaluation of the parameters can be done very quickly, improving the overall speed of the method. Second, postprocessing methods can be applied when projection data is not available, which occurs in several commercial systems with closed software or when projection data has been deleted. It is shown that the proposed method performs comparably to state-of-the-art methods in terms of image quality.
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| 10. |
- Wernersson, Erik L. G., et al.
(författare)
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Characterisations of fibre networks in paper using micro computed tomography images
- 2014
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Ingår i: Nordic Pulp & Paper Research Journal. - 0283-2631 .- 2000-0669. ; 29:3, s. 468-475
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Tidskriftsartikel (refereegranskat)abstract
- Although several methods exist for characterisation of the morphology of wood fibres, the application of these procedures for the analysis of paper microstructure has been limited due to their complexity or shortcomings. Here, a methodology for microstructure characterisation of individual fibres, as well as paper, is presented which is based on three dimensional computed tomography images of paper at micrometer resolution. The first step of the method consists of a graphical user interface (GUI), designed to minimize the amount of manual labour. To manually identify a fibre from a 2x2 mm(2) paper sheet takes about one minute with this GUI. Then several algorithms are available to analyse the image data automatically guided by the user input. With this approach it is possible to measure several characteristic properties without complete segmentation of the individual fibres. The methodology includes a method to calculate the contact areas between fibres even in extreme cases of severely deformed fibres, which are naturally present in paper. Among the measurable properties are also estimators for the free fibre lengths and fibre wall thickness.
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