| 1. |
- Tong, Zhi, 1977, et al.
(författare)
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Towards the Ultra-Sensitive Optical Link Enabled by Low Noise Phase-Sensitive Amplifiers
- 2011
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Ingår i: Nature Photonics. - 1749-4885 .- 1749-4893. ; 5:7, s. 430-436
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Tidskriftsartikel (refereegranskat)abstract
- Optical phase-sensitive amplifiers (PSAs) are known to be capable, in principle, of realizing noiseless amplification and improving the signal-to-noise-ratio of optical links by 3 dB compared to conventional, phase-insensitively amplified links. However, current state-of-the-art PSAs are still far from being practical, lacking e.g. significant noise performance improvement, broadband gain and modulation-format transparency. Here we demonstrate experimentally, for the first time, an optical-fiber-based non-degenerate PSA link consisting of a phase-insensitive parametric copier followed by a PSA that provides broadband amplification, signal modulation-format independence, and nearly 6-dB link noise-figure (NF) improvement over conventional, erbium-doped fiber amplifier based links. The PSA has a record-low 1.1-dB NF, and can be extended to work with multiple wavelength channels with modest system complexity. This concept can also be realized in other materials with third-order nonlinearities, and is useful in any attenuation-limited optical link.
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| 2. |
- Adlerborn, Björn, et al.
(författare)
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Towards Highly Parallel and Compute-Bound Computation of Eigenvectors of Matrices in Schur Form
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this paper we discuss the problem of computing eigenvectors for matrices in Schur form using parallel computing. We develop a new parallel algorithm and report on the performance of our MPI based implementation. We have also implemented a new parallel algorithm for scaling during the backsubstitution phase. We have increased the arithmetic intensity by interleaving the compution of several eigenvectors and by merging the backward substitution and the back-transformation of the eigenvector computation.
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| 3. |
- Ahmed, Istaq, 1972, et al.
(författare)
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Crystal structure and proton conductivity of BaZr0.9Sc0
- 2008
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Ingår i: Journal of the American Ceramic Society. - : Wiley. - 0002-7820 .- 1551-2916. ; 91:9, s. 3039-3044
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Tidskriftsartikel (refereegranskat)abstract
- Solid-state sintering has been used to prepare the perovskite BaZr0.9Sc0.1O3-delta. Analysis of X-ray powder diffraction data shows that an increase of the unit cell parameter, a, was observed after deuteration. Rietveld analysis of room-temperature neutron powder diffraction data confirmed cubic symmetry (space group Pm-3m). Dynamic thermogravimetric analysis indicates that the hydration process occurs below 335 degrees C and approximately 58% of the theoretical number of protonic defects can be filled. The presence of protons/deutrons is seen from the strong O-H/O-D stretch band in the infrared spectrum of the hydrated/deuterated samples. The proton conductivity of a prehydrated sample was investigated under dry and wet Ar atmospheres
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| 4. |
- Almroth, Henrik, et al.
(författare)
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Haemodynamic changes after atrial fibrillation initiation in patients eligible for catheter ablation: a randomized controlled study
- 2023
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Ingår i: European Heart Journal Open. - : Oxford University Press. - 2752-4191. ; 3:6
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Tidskriftsartikel (refereegranskat)abstract
- AbstractAims: Atrial fibrillation (AF) haemodynamics is less well studied due to challenges explained by the nature of AF. Until now, no randomized data are available. This study evaluates haemodynamic variables after AF induction in a randomized setting.Methods and results: Forty-two patients with AF who had been referred for ablation to the University Hospital, Linköping, Sweden, and had no arrhythmias during the 4-day screening period were randomized to AF induction vs. control (2:1). Atrial fibrillation was induced by burst pacing after baseline intracardiac pressure measurements. Pressure changes in the right and left atrium (RA and LA), right ventricle (RV), and systolic and diastolic blood pressures (SBP and DBP) were evaluated 30 min after AF induction compared with the control group. A total of 11 women and 31 men (median age 60) with similar baseline characteristics were included (intervention n = 27, control group n = 15). After 30 min in AF, the RV end-diastolic pressure (RVEDP) and RV systolic pressure (RVSP) significantly reduced compared with baseline and between randomization groups (RVEDP: P = 0.016; RVSP: P = 0.001). Atrial fibrillation induction increased DBP in the intervention group compared with the control group (P = 0.02), unlike reactions in SBP (P = 0.178). Right atrium and LA mean pressure (RAm and LAm) responses did not differ significantly between the groups (RAm: P = 0.307; LAm: P = 0.784).Conclusion: Induced AF increased DBP and decreased RVEDP and RVSP. Our results allow us to understand some paroxysmal AF haemodynamics, which provides a haemodynamic rationale to support rhythm regulatory strategies to improve symptoms and outcomes.Trial registration number clinicaltrialsgov: No NCT01553045. https://clinicaltrials.gov/ct2/show/NCT01553045?term=NCT01553045&rank=1.
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| 5. |
- Ameur, Adam, et al.
(författare)
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SweGen : a whole-genome data resource of genetic variability in a cross-section of the Swedish population
- 2017
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Ingår i: European Journal of Human Genetics. - : NATURE PUBLISHING GROUP. - 1018-4813 .- 1476-5438. ; 25:11, s. 1253-1260
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Tidskriftsartikel (refereegranskat)abstract
- Here we describe the SweGen data set, a comprehensive map of genetic variation in the Swedish population. These data represent a basic resource for clinical genetics laboratories as well as for sequencing-based association studies by providing information on genetic variant frequencies in a cohort that is well matched to national patient cohorts. To select samples for this study, we first examined the genetic structure of the Swedish population using high-density SNP-array data from a nation-wide cohort of over 10 000 Swedish-born individuals included in the Swedish Twin Registry. A total of 1000 individuals, reflecting a cross-section of the population and capturing the main genetic structure, were selected for whole-genome sequencing. Analysis pipelines were developed for automated alignment, variant calling and quality control of the sequencing data. This resulted in a genome-wide collection of aggregated variant frequencies in the Swedish population that we have made available to the scientific community through the website https://swefreq.nbis.se. A total of 29.2 million single-nucleotide variants and 3.8 million indels were detected in the 1000 samples, with 9.9 million of these variants not present in current databases. Each sample contributed with an average of 7199 individual-specific variants. In addition, an average of 8645 larger structural variants (SVs) were detected per individual, and we demonstrate that the population frequencies of these SVs can be used for efficient filtering analyses. Finally, our results show that the genetic diversity within Sweden is substantial compared with the diversity among continental European populations, underscoring the relevance of establishing a local reference data set.
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| 6. |
- Bielecki, Johan, 1982, et al.
(författare)
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Short-range structure of the brownmillerite-type oxide Ba2In2O5 and its hydrated proton-conducting form BaInO3H
- 2014
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 2:40, s. 16915-16924
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Tidskriftsartikel (refereegranskat)abstract
- The vibrational spectra and short-range structure of the brownmillerite-type oxide Ba2In2O6 and its hydrated form BaInO3H, are investigated by means of Raman, infrared, and inelastic neutron scattering spectroscopies together with density functional theory calculations. For Ba2In2O6, which may be described as an oxygen deficient perovskite structure with alternating layers of InO6 octahedra and InO4 tetrahedra, the results affirm a short-range structure of Icmm symmetry, which is characterized by random orientation of successive layers of InO4 tetrahedra. For the hydrated, proton conducting, form, BaInO3H, the results suggest that the short-range structure is more complicated than the P4/mbm symmetry that has been proposed previously on the basis of neutron diffraction, but rather suggest a proton configuration close to the lowest energy structure predicted by Martinez et al. [J.-R. Martinez, C. E. Moen, S. Stoelen, N. L. Allan, J. Solid State Chem., 180, 3388, (2007)]. An intense Raman active vibration at 150 cm(-1) is identified as a unique fingerprint of this proton configuration.
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| 7. |
- Bujanović, Zvonimir, et al.
(författare)
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A Householder-Based Algorithm for Hessenberg-Triangular Reduction
- 2018
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Ingår i: SIAM Journal on Matrix Analysis and Applications. - : SIAM Publications. - 0895-4798 .- 1095-7162. ; 39:3, s. 1270-1294
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Tidskriftsartikel (refereegranskat)abstract
- The QZ algorithm for computing eigenvalues and eigenvectors of a matrix pencil $A - \lambda B$ requires that the matrices first be reduced to Hessenberg-triangular (HT) form. The current method of choice for HT reduction relies entirely on Givens rotations regrouped and accumulated into small dense matrices which are subsequently applied using matrix multiplication routines. A nonvanishing fraction of the total flop-count must nevertheless still be performed as sequences of overlapping Givens rotations alternately applied from the left and from the right. The many data dependencies associated with this computational pattern leads to inefficient use of the processor and poor scalability. In this paper, we therefore introduce a fundamentally different approach that relies entirely on (large) Householder reflectors partially accumulated into block reflectors, by using (compact) WY representations. Even though the new algorithm requires more floating point operations than the state-of-the-art algorithm, extensive experiments on both real and synthetic data indicate that it is still competitive, even in a sequential setting. The new algorithm is conjectured to have better parallel scalability, an idea which is partially supported by early small-scale experiments using multithreaded BLAS. The design and evaluation of a parallel formulation is future work.
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| 8. |
- Charitakis, Emmanouil, 1982-, et al.
(författare)
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Endocrine and Mechanical Cardiacfunction Four Months after Radiofrequency Ablation of Atrialfibrillation.
- 2021
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Ingår i: Journal of Atrial Fibrillation. - Overland Park, KS, United States : Cardiofront, Inc. - 1941-6911. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Radiofrequency ablation (RFA)is an important treatment option for patients with atrial fibrillation (AF). During RFA, a significant amount of energy is delivered into the left atrium (LA), resulting in considerable LA-injury. The impact of this damage on mechanical and endocrine LA-function, however, is often disregarded.We therefore aimed to evaluate the endocrine- and mechanical function of the heart 4-months after RFA of AF.Methods: In total 189 patients eligible for RFA of AF were studied. The levels of the N-terminal pro-B-natriuretic peptide (NT-proBNP) and the mid-regional fragment of the N-terminal pro-atrial natriuretic peptide (MR-proANP)were measured. The maximum LAvolume (LAVmax),the LAejection fraction (LAEF) and the LA peak longitudinal strain (PALS), were measured usingtransthoracic echocardiography. The measurements were performed before and 4-months after the intervention.Results: 87 patients had a recurrence during a mean follow-up of 143±36 days.NT-proBNPand MR-proANPdecreased significantly at follow-up. This reduction was greater in patients who did not suffer any recurrence after RFA.The LAVmax decreased significantly, whereasthe PALS only improved in patients who did not suffer from any recurrence. On the other hand, LAEF did not change significantly after RFA of AF.Conclusions: Despite extensiveablation during RFA of AF, the endocrine function of the heart improved 4-months after the index procedure. Patients with no arrhythmia recurrence showed a more pronounced improvement in their endocrinal function. Mechanically, the LAVmax was reduced, and the LA strain improved significantly.
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| 9. |
- Eljammaly, Mahmoud, et al.
(författare)
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Evaluation of the Tunability of a New NUMA-Aware Hessenberg Reduction Algorithm
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The reduction of a general dense and square matrix to Hessenberg form is a well known first step in many standard eigenvalue solvers. Although parallel algorithms exist, the Hessenberg reduction is still one of the bottlenecks in state-of-the-art software for the distributed QR algorithm. We propose a new NUMA-aware algorithm that fits the context of the QR algorithm and evaluate the tunability of its algorithmic parameters. The proposed algorithm can be faster than LAPACK and ScaLAPACK for small problem sizes. In addition, evaluating the algorithmic parameters shows that there is potential for auto-tuning some of the parameters.
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| 10. |
- Gustavson, Fred, 1935-, et al.
(författare)
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Distributed SBP Cholesky factorization algorithms with near-optimal scheduling
- 2009
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Ingår i: ACM Transactions on Mathematical Software. - : Association for Computing Machinery (ACM). - 0098-3500 .- 1557-7295. ; 36:2, s. 11:1-11:25
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Tidskriftsartikel (refereegranskat)abstract
- The minimal block storage Distributed Square Block Packed (DSBP) format for distributed memory computing on symmetric and triangular matrices is presented. Three algorithm variants (Basic, Static, and Dynamic) of the blocked right-looking Cholesky factorization are designed for the DSBP format, implemented, and evaluated. On our target machine, all variants outperform standard full-storage implementations while saving almost half the storage. Communication overhead is shown to be virtually eliminated by the Static and Dynamic variants, both of which take advantage of hardware parallelism to hide communication costs. The Basic variant is shown to yield comparable or slightly better performance than the full-storage ScaLAPACK routine PDPOTRF while clearly outperformed by both Static and Dynamic. Models of execution assuming zero communication costs and overhead are developed. For medium- and larger-sized problems, the Static schedule is near optimal on our target machine based on comparisons with these models and measurements of synchronization overhead.
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| 11. |
- Jonsson, Torbjörn, 1970, et al.
(författare)
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High-Temperature Oxidation of FeCr(Ni) Alloys : The Behaviour After Breakaway
- 2017
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Ingår i: Oxidation of Metals. - : Springer Nature. - 0030-770X .- 1573-4889. ; 87:3-4, s. 333-341
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of an austenitic FeCr(Ni) steel at 600 C in H2O ?KCl ? O2/H2 ? H2O ? Ar environments is studied up to 168 h. The oxidationbehaviour after ‘‘breakaway’’ is investigated by microstructural investigations, andthermodynamic calculations (Thermo-Calc) on the FeCr(Ni)–O system are used tointerpret the results. The characteristic ‘‘breakaway’’ scale morphology exhibits anoutward-growing iron oxide and a bottom layer consisting of inward-growing spineloxide and reaction zones containing Cr-rich oxide precipitates and Cr-depletedmetal. The equilibrium calculations show that a miscibility gap appears in the FeCrspinel oxide below 665 C influencing the microstructure of the inward-growingscale. Equilibrium calculations on the FeCrNi–O system show that Ni is notexpected to enter the spinel oxide in low oxygen activity conditions, in accordancewith observations
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| 12. |
- Jonsson, Torbjörn, 1970, et al.
(författare)
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Oxidation After Breakdown of the Chromium-Rich Scale on Stainless Steels at High Temperature: Internal Oxidation
- 2016
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 85:5-6, s. 509-536
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Tidskriftsartikel (refereegranskat)abstract
- Breakaway oxidation of alloy 304L at 600 degrees C was studied in four environments (O-2 + H2O + KCl, O-2 + H2O + SO2 + KCl, H-2 + H2O + Ar, O-2 + K2CO3) for up to 168 h. The resulting scales were investigated by FIB/SEM, SEM/EDX, STEM/EELS, STEM/EDS and oxidation was elucidated by thermodynamic calculations (Thermo-Calc). The initial thin protective scale broke down in all cases. After breakaway, the scale consisted of two layers, i.e. an inward growing spinel/reaction zone and an outward growing iron-rich layer. The general features and microstructure of the scales after breakaway were similar in all environments and were explained in terms of: (1) Different diffusivities of Cr3+ and Fe2+ in the spinel oxide. (2) The appearance of a miscibility gap in the FeCr and FeCrNi spinel oxides. (3) The equilibrium composition of the spinel (at low pO(2) Ni is not present in the spinel).
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| 13. |
- Karlsson, Lars, et al.
(författare)
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A clinical decision support tool for improving adherence to guidelines on anticoagulant therapy in patients with atrial fibrillation at risk of stroke : A cluster-randomized trial in a Swedish primary care setting (the CDS-AF study)
- 2018
-
Ingår i: PLoS Medicine. - San Francisco, United States : Public Library of Science. - 1549-1277 .- 1549-1676. ; 15:3
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundAtrial fibrillation (AF) is associated with substantial morbidity, in particular stroke. Despite good evidence for the reduction of stroke risk with anticoagulant therapy, there remains significant undertreatment. The main aim of the current study was to investigate whether a clinical decision support tool (CDS) for stroke prevention integrated in the electronic health record could improve adherence to guidelines for stroke prevention in patients with AF.Methods and findingsWe conducted a cluster-randomized trial where all 43 primary care clinics in the county of Östergötland, Sweden (population 444,347), were randomized to be part of the CDS intervention or to serve as controls. The CDS produced an alert for physicians responsible for patients with AF and at increased risk for thromboembolism (according to the CHA2DS2-VASc algorithm) without anticoagulant therapy. The primary endpoint was adherence to guidelines after 1 year. After randomization, there were 22 and 21 primary care clinics in the CDS and control groups, respectively. There were no significant differences in baseline adherence to guidelines regarding anticoagulant therapy between the 2 groups (CDS group 70.3% [5,186/7,370; 95% CI 62.9%–77.7%], control group 70.0% [4,187/6,009; 95% CI 60.4%–79.6%], p = 0.83). After 12 months, analysis with linear regression with adjustment for primary care clinic size and adherence to guidelines at baseline revealed a significant increase in guideline adherence in the CDS (73.0%, 95% CI 64.6%–81.4%) versus the control group (71.2%, 95% CI 60.8%–81.6%, p = 0.013, with a treatment effect estimate of 0.016 [95% CI 0.003–0.028]; number of patients with AF included in the final analysis 8,292 and 6,508 in the CDS and control group, respectively). Over the study period, there was no difference in the incidence of stroke, transient ischemic attack, or systemic thromboembolism in the CDS group versus the control group (49 [95% CI 43–55] per 1,000 patients with AF in the CDS group compared to 47 [95% CI 39–55] per 1,000 patients with AF in the control group, p = 0.64). Regarding safety, the CDS group had a lower incidence of significant bleeding, with events in 12 (95% CI 9–15) per 1,000 patients with AF compared to 16 (95% CI 12–20) per 1,000 patients with AF in the control group (p = 0.04). Limitations of the study design include that the analysis was carried out in a catchment area with a high baseline adherence rate, and issues regarding reproducibility to other regions.ConclusionsThe present study demonstrates that a CDS can increase guideline adherence for anticoagulant therapy in patients with AF. Even though the observed difference was small, this is the first randomized study to our knowledge indicating beneficial effects with a CDS in patients with AF.
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| 14. |
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| 15. |
- Karlsson, Lars, 1982-
(författare)
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Blocked in-place transposition with application to storage format conversion
- 2009
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We develop a prototype library for in-place (dense) matrix storage format conversion between the canonical row and column-major formats and the four canonical block data layouts. Many of the fastest linear algebra routines operate on matrices in a block data layout. In-place storage format conversion enables support for input/output of large matrices in the canonical row and column-major formats. The library uses algorithms associated with in-place transposition as building blocks. We investigate previous work on the subject of (in-place) transposition and the most promising algorithms are implemented and evaluated. Our results indicate that the Three-Stage Algorithm which only requires a small constant amount of additional memory performs well and is easy to tune. Murray Dow’s V5 algorithm, which is a two-stage semi-in-place algorithm that requires a small amount of additional memory is sometimes a better choice. The write-allocate strategy of most cache-based computer architectures appears to be the cause of an observed performance problem for large matrices.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Karlsson, Lars, 1982-, et al.
(författare)
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Improving Perfect Parallelism
- 2014
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Ingår i: Parallel Processing and Applied Mathematics. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642552243 - 9783642552236 ; , s. 76-85
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Konferensbidrag (refereegranskat)abstract
- We reconsider the familiar problem of executing a perfectly parallel workload consisting of N independent tasks on a parallel computer with P << N processors. We show that there are memory-bound problems for which the runtime can be reduced by the forced parallelization of individual tasks across a small number of cores. Specific examples include solving differential equations, performing sparse matrix-vector multiplications, and sorting integer keys.
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| 20. |
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| 21. |
- Karlsson, Lars O., et al.
(författare)
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Clinical decision support for stroke prevention in atrial fibrillation (CDS-AF): Rationale and design of a cluster randomized trial in the primary care setting
- 2017
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Ingår i: American Heart Journal. - : MOSBY-ELSEVIER. - 0002-8703 .- 1097-6744. ; 187, s. 45-52
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Tidskriftsartikel (refereegranskat)abstract
- Background Atrial fibrillation (AF) is associated with substantial morbidity, in particular stroke. Despite good evidence for the reduction of stroke risk with anticoagulant therapy, there remains a significant undertreatment. The main aim of the current study is to investigate whethera clinical decision support tool for stroke prevention (CDS) integrated in the electronic health record can improve adherence to guidelines for stroke prevention in patients with AF. Methods We will conduct a cluster randomized trial where 43 primary care clinics in the county of Ostergotland, Sweden (population 444,347), will be randomized to be part of the CDS intervention or serve as controls. The CDS will alert responsible physicians of patients with AF and increased risk for thromboembolism according to the CHA(2)DS(2)VASc (Congestive heart failure, Hypertension, Age 74 years, Diabetes mellitus, previous Stroke/TIA/thromboembolism, Vascular disease, Age 65-74 years, Sex category (i.e. female sex)) algorithm without anticoagulant therapy. The primary end point will be adherence to guidelines after 1 year. Conclusion The present study will investigate whether a clinical decision support system integrated in an electronic health record can increase adherence to guidelines regarding anticoagulant therapy in patients with AF.
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| 22. |
- Karlsson, Lars, 1982-, et al.
(författare)
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Parallel algorithms for tensor completion in the CP format
- 2016
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Ingår i: Parallel Computing. - : Elsevier BV. - 0167-8191 .- 1872-7336. ; 57, s. 222-234
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Tidskriftsartikel (refereegranskat)abstract
- Low-rank tensor completion addresses the task of filling in missing entries in multidimensional data. It has proven its versatility in numerous applications, including context aware recommender systems and multivariate function learning. To handle large-scale datasets and applications that feature high dimensions, the development of distributed algorithms is central. In this work, we propose novel, highly scalable algorithms based on a combination of the canonical polyadic (CP) tensor format with block coordinate descent methods. Although similar algorithms have been proposed for the matrix case, the case of higher dimensions gives rise to a number of new challenges and requires a different paradigm for data distribution. The convergence of our algorithms is analyzed and numerical experiments illustrate their performance on distributed-memory architectures for tensors from a range of different applications.
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| 23. |
- Karlsson, Lars, 1982-, et al.
(författare)
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Parallel two-stage reduction to Hessenberg form using dynamic scheduling on shared-memory architectures
- 2011
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Ingår i: Parallel Computing. - : Elsevier BV. - 0167-8191 .- 1872-7336. ; 37:12, s. 771-782
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Tidskriftsartikel (refereegranskat)abstract
- We consider parallel reduction of a real matrix to Hessenberg form using orthogonal transformations. Standard Hessenberg reduction algorithms reduce the columns of the matrix from left to right in either a blocked or unblocked fashion. However, the standard blocked variant performs 20% of the computations in terms of matrix vector multiplications. We show that a two-stage approach consisting of an intermediate reduction to block Hessenberg form speeds up the reduction by avoiding matrix vector multiplications. We describe and evaluate a new high-performance implementation of the two-stage approach that attains significant speedups over the one-stage approach. The key components are a dynamically scheduled implementation of Stage 1 and a blocked, adaptively load-balanced implementation of Stage 2. (C) 2011 Elsevier B.V. All rights reserved.
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| 24. |
- Karlsson, Lars, 1982-
(författare)
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Scheduling of parallel matrix computations and data layout conversion for HPC and Multi-Core Architectures
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dense linear algebra represents fundamental building blocks in many computational science and engineering applications. The dense linear algebra algorithms must be numerically stable, robust, and reliable in order to be usable as black-box solvers by expert as well as non-expert users. The algorithms also need to scale and run efficiently on massively parallel computers with multi-core nodes. Developing high-performance algorithms for dense matrix computations is a challenging task, especially since the widespread adoption of multi-core architectures. Cache reuse is an even more critical issue on multi-core processors than on uni-core processors due to their larger computational power and more complex memory hierarchies. Blocked matrix storage formats, in which blocks of the matrix are stored contiguously, and blocked algorithms, in which the algorithms exhibit large amounts of cache reuse, remain key techniques in the effort to approach the theoretical peak performance. In Paper I, we present a packed and distributed Cholesky factorization algorithm based on a new blocked and packed matrix storage format. High performance node computations are obtained as a result of the blocked storage format, and the use of look-ahead leads to improved parallel efficiency. In Paper II and Paper III, we study the problem of in-place matrix transposition in general and in-place matrix storage format conversion in particular. We present and evaluate new high-performance parallel algorithms for in-place conversion between the standard column-major and row-major formats and the four standard blocked matrix storage formats. Another critical issue, besides cache reuse, is that of efficient scheduling of computational tasks. Many weakly scalable parallel algorithms are efficient only when the problem size per processor is relatively large. A current research trend focuses on developing parallel algorithms which are more strongly scalable and hence more efficient also for smaller problems. In Paper IV, we present a framework for dynamic node-scheduling of two-sided matrix computations and demonstrate that by using priority-based scheduling one can obtain an efficient scheduling of a QR sweep. In Paper V and Paper VI, we present a blocked implementation of two-stage Hessenberg reduction targeting multi-core architectures. The main contributions of Paper V are in the blocking and scheduling of the second stage. Specifically, we show that the concept of look-ahead can be applied also to this two-sided factorization, and we propose an adaptive load-balancing technique that allow us to schedule the operations effectively.
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| 25. |
- Karlsson, Sofia, 1982, et al.
(författare)
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Alkali Induced High Temperature Corrosion of Stainless Steel: The Influence of NaCl, KCl and CaCl2
- 2012
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Ingår i: Oxidation of Metals. - : Springer Science and Business Media LLC. - 1573-4889 .- 0030-770X. ; 78:1-2, s. 83-102
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Tidskriftsartikel (refereegranskat)abstract
- The influence of KCl, NaCl and CaCl2 on the oxidation of 304-type (Fe18Cr10Ni) stainless steel at 600 A degrees C in 5 %O-2 + 40 %H2O was investigated. Prior to exposure, a small amount of the preferred salt (cation equivalent: 1.35 mu mol/cm(2)) was deposited on the samples. Exposure time was 1-168 h. The oxidized samples were analyzed by SEM/EDX, XRD, FIB and IC. The presence of KCl and NaCl strongly accelerates high temperature corrosion of 304L. Corrosion attack is initiated by the formation of alkali chromate through the reaction of alkali with the protective oxide. Chromate formation is a sink for chromium in the oxide and leads to a loss of its protective properties. Subsequently a rapidly growing scale forms, consisting of an outer hematite layer with chromate particles on top and an inner spinel oxide layer. In contrast to NaCl and KCl, CaCl2 is not very corrosive. At temperature, CaCl2 is rapidly converted to CaO. Small amounts of CaCrO4 form where CaO is in direct contact with the scale. CaO also reacts with the scale to form Ca2Fe2O5.
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| 26. |
- Karlsson, Sofia, 1982, et al.
(författare)
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KCl-Induced High Temperature Corrosion of Austenitic Stainless Steel 304L – The Influence of SO2
- 2011
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Ingår i: Materials Science Forum. - 1662-9752 .- 0255-5476. ; 696, s. 224-229
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Tidskriftsartikel (refereegranskat)abstract
- The effect of SO2 on the oxidation of alloy 304L in O2+H2O and O2+H2O+KCl environment has been investigated at 600°C. Exposure time was 1-168 hours. The exposed samples were analyzed by SEM/EDX, XRD and IC. In dry O2, a protective and chromium-rich corundum-type oxide forms. In the presence of H2O(g), chromium is volatilized in the form of CrO2(OH)2(g). The corresponding chromium depletion of the protective oxide triggers a partial loss of protective properties resulting in the formation of oxide islands on the alloy grain centers. The oxide islands consist of an outward growing hematite layer and an inward growing FeCrNi spinel layer. By coating the samples with KCl the chromia depletion of the protective oxide dramatically increases due to the formation of K2CrO4. This leads to breakaway corrosion, a rapidly growing scale forming all over the surface. The resulting thick scale has a similar structure as the oxide islands formed in the absence of KCl. The addition of 300 ppm SO2 to the O2+H2O and O2+H2O+KCl environments results in a drastic reduction of corrosion rate. In O2+H2O environment the effect of SO2 is attributed to the formation of a thin sulphate film on the oxide surface that impedes chromium volatilization and decreases the rate of oxygen reduction on the oxide surface. In O2+H2O+KCl environment the corrosion mitigating effect of SO2 is mainly attributed to the rapid conversion of KCl to K2SO4. In contrast to KCl, K2SO4 does not deplete the protective oxide in chromium by forming K2CrO4. Keywords: Oxidation, Alkali, Breakaway Corrosion, 304L, Chromate, Sulphur
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| 27. |
- Karlsson, Sofia, 1982, et al.
(författare)
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Reducing high-temperature corrosion on high- alloyed stainless steel superheaters by co-combustion of municipal sewage sludge in a fluidised bed boiler
- 2015
-
Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 139, s. 482-493
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Tidskriftsartikel (refereegranskat)abstract
- One way of mitigating alkali chloride induced corrosion in biomass and waste-fired boilers is by using additives or by co-combustion and thereby decreasing the corrosiveness of the flue gas and deposits. The effect of co-firing digested sewage sludge with a mixture of biomass and waste (78% bark pellets + 22% Solid Recovered Fuel, denoted "SRF'') was investigated in a 12 MW circulating fluidised bed (CFB) boiler. The initial corrosion attack of the stainless steel 304L at 600 degrees C (material temperature) was investigated during 24 h exposures. The exposures were carried out in the flue gas environment from three fuel-mixes: SRF, MSS1- low (SRF with municipal sewage sludge, low dosage) and MSS2- high (SRF with municipal sewage sludge, high dosage). The results showed that the most severe corrosion attack on 304L occurred without sewage sludge in the SRF exposure. This attack was characterised by a corrosion product layer up to 100 mu m in thickness and signs of internal corrosion of the steel. The deposit in the SRF case was dominated by alkali chlorides. The exposures with co- combustion of sewage sludge, MSS1-low and MSS2- high, showed a significant decrease in corrosion. The steel sample of 304L performed especially well in the latter case when it was protected by a thin oxide of less than 0.3 mu m in thickness. This deposit was dominated by sulphate- and phosphate- containing compounds but traces of aluminium silicate compounds where also found. Furthermore, the concentration of alkali chlorides was low. Thus, the initial corrosion attack was greatly reduced by co- combustion of digested sewage sludge with SRF.
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| 28. |
- Karlsson, Sofia, 1982, et al.
(författare)
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Reducing High Temperature Corrosion when Burning Waste by Adding Digested Sewage Sludge
- 2011
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Ingår i: Swedish - Finnish Flame Days, January 26-27 2011 in Piteå, Sweden, The Swedish and Finnish National Committees of the International Flame Research Foundation (IFRF) and The Scandinavian - Nordic Section of the Combustion Institute (SNCI).
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The presence of alkali chlorides are well known to cause high temperature corrosion during combustion of biomass and waste. Low alloyed steels as well as stainless steels are experiencing an accelerated corrosion attack in such environments. Even though more highly alloyed steels (i.e. higher Cr/Fe ratio in the steel) are being used, there is only a small decrease in corrosion rate compared to low alloyed steels. To maintain the corrosion rates at an acceptable level the temperature of the superheaters (used for steam production to the steam turbine) of the boiler have been lowered. However, this causes a decrease in power production when the driving force for waste-to-energy boilers in the future is to increase the power production by increasing the temperatures of the steam from the final superheater stage.One of the reasons for the corrosive behavior of alkali chlorides towards stainless steels is the formation of alkali chromates. It has been shown that alkali chlorides react with chromium in the initial formed protective oxide on stainless steel:1/2Cr2O3(s) + 3/4O2(g) + H2O(g) + 2KCl(s) K2CrO4 (s) + 2 HCl(g) This result in a chromium depleted oxide which is converted into an iron-rich fast-growing oxide. This oxide has much poorer protective properties as it has higher diffusion rates compared to chromium rich oxides. Furthermore, the iron rich oxide is also more susceptible towards chlorine induced corrosion by chlorine ions penetrating the oxide scale. This leads to the formation of transition metal chlorides (e.g. FeCl2) at the metal/oxide interface causing poor scale adherence.A way to mitigate the alkali chloride induced corrosion is by introducing fuel additives and thus, changing the flue gas chemistry and furthermore the deposit composition. In this study, the effect of digested sewage sludge as fuel additive was investigated at the 12MW circulating fluidized bed (CFB) boiler at Chalmers University of Technology. The initial corrosion attack of the stainless steel 304L(Fe18Cr10Ni exposed at 600°C (material temperature) was investigated during 24h exposure of three different environments. Deposit analysis by means of XRD and IC were carried out using Sanicro 28 (Fe35Cr27Ni31) as sample ring. The exposures were denoted “RDF” (a reference exposure 80%Bark + 20%RDF), “SjöMed” (80%Bark + 20%RDF with sewage sludge from Sjölundaverket (medium dosage)) and “HimHög” (80%Bark + 20%RDF with sewage sludge from Himmerfjärdsverket (high dosage)).The results showed that the most severe corrosion attack of 304L occurred in the “RDF” exposure. The corrosion attack was characterized by an up to 100µm thick corrosion product layer and signs of internal corrosion of the steel. The deposit in the RDF exposure was dominated by alkali chlorides. The exposures with sewage sludge additions, “SjöMed” and “HimHög”, showed a remarkable decrease in corrosion rate. 304L performed especially well in the “HimHög” exposure, the steel ring was protected by a thin oxide, less than 0.3µm in thickness. Furthermore, the deposit was dominated by sulphate- and phosphate containing compounds. The presence of alkali chlorides was low.
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| 29. |
- Karlsson, Sara, 1980, et al.
(författare)
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Social memory associated with estrogen receptor polymorphisms in women
- 2016
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Ingår i: Social Cognitive & Affective Neuroscience. - : Oxford University Press (OUP). - 1749-5016 .- 1749-5024. ; 11:6, s. 877-883
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Tidskriftsartikel (refereegranskat)abstract
- The ability to recognize the identity of faces and voices is essential for social relationships. Although the heritability of social memory is high, knowledge about the contributing genes is sparse. Since sex differences and rodent studies support an influence of estrogens and androgens on social memory, polymorphisms in the estrogen and androgen receptor genes (ESR1, ESR2, AR) are candidates for this trait. Recognition of faces and vocal sounds, separately and combined, was investigated in 490 subjects, genotyped for 10 single nucleotide polymorphisms (SNPs) in ESR1, four in ESR2 and one in the AR. Four of the associations survived correction for multiple testing: women carrying rare alleles of the three ESR2 SNPs, rs928554, rs1271572 and rs1256030, in linkage disequilibrium with each other, displayed superior face recognition compared with non-carriers. Furthermore, the uncommon genotype of the ESR1 SNP rs2504063 was associated with better recognition of identity through vocal sounds, also specifically in women. This study demonstrates evidence for associations in women between face recognition and variation in ESR2, and recognition of identity through vocal sounds and variation in ESR1. These results suggest that estrogen receptors may regulate social memory function in humans, in line with what has previously been established in mice.
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| 30. |
- Kjelgaard Mikkelsen, Carl Christian, 1976-, et al.
(författare)
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Blocked Algorithms for Robust Solution of Triangular Linear Systems
- 2018
-
Ingår i: Parallel Processing and Applied Mathematics. - Cham : Springer. - 9783319780238 - 9783319780245 ; , s. 68-78
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Konferensbidrag (refereegranskat)abstract
- We consider the problem of computing a scaling α such that the solution x of the scaled linear system Tx = αb can be computed without exceeding an overflow threshold Ω. Here T is a non-singular upper triangular matrix and b is a single vector, and Ω is less than the largest representable number. This problem is central to the computation of eigenvectors from Schur forms. We show how to protect individual arithmetic operations against overflow and we present a robust scalar algorithm for the complete problem. Our algorithm is very similar to xLATRS in LAPACK. We explain why it is impractical to parallelize these algorithms. We then derive a robust blocked algorithm which can be executed in parallel using a task-based run-time system such as StarPU. The parallel overhead is increased marginally compared with regular blocked backward substitution.
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| 31. |
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| 32. |
- Kjelgaard Mikkelsen, Carl Christian, 1976-, et al.
(författare)
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Parallel robust solution of triangular linear systems
- 2019
-
Ingår i: Concurrency and Computation. - : John Wiley & Sons. - 1532-0626 .- 1532-0634. ; 31:19
-
Tidskriftsartikel (refereegranskat)abstract
- Triangular linear systems are central to the solution of general linear systems and the computation of eigenvectors. In the absence of floating‐point exceptions, substitution runs to completion and solves a system which is a small perturbation of the original system. If the matrix is well‐conditioned, then the normwise relative error is small. However, there are well‐conditioned systems for which substitution fails due to overflow. The robust solvers xLATRS from LAPACK extend the set of linear systems which can be solved by dynamically scaling the solution and the right‐hand side to avoid overflow. These solvers are sequential and apply to systems with a single right‐hand side. This paper presents algorithms which are blocked and parallel. A new task‐based parallel robust solver (Kiya) is presented and compared against both DLATRS and the non‐robust solvers DTRSV and DTRSM. When there are many right‐hand sides, Kiya performs significantly better than the robust solver DLATRS and is not significantly slower than the non‐robust solver DTRSM.
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| 33. |
- Kjelgaard Mikkelsen, Carl Christian, 1976-, et al.
(författare)
-
Robust Solution of Triangular Linear Systems
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We consider the problem of computing a scaling α such that the solution x of the scaled linear system Tx=\alpha b can be computed without exceeding the overflow threshold $\Omega$. Here T is a non-singular upper triangular matrix and b is a single vector. We show how to protect individual arithmetic operations against overflow and we present a robust scalar algorithm for the complete problem. Our algorithm is very similar to xLATRS in LAPACK and our main contribution is to simplify and extend the analysis. We explain why it is impractical to parallelize these algorithms. We then derive a robust block algorithm for solving triangular linear systems. Any run-time system such as StarPU which can run a task based backward substitution algorithm can also execute our robust block algorithm in parallel. It is simply a matter of replacing standard kernels with our robust kernels.
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| 34. |
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| 35. |
- López, Francisco, et al.
(författare)
-
FLOPs as a discriminant for dense linear algebra algorithms
- 2022
-
Ingår i: ICPP '22. - New York, NY, USA : ACM Digital Library. - 9781450397339
-
Konferensbidrag (refereegranskat)abstract
- Expressions that involve matrices and vectors, known as linear algebra expressions, are commonly evaluated through a sequence of invocations to highly optimised kernels provided in libraries such as BLAS and LAPACK. A sequence of kernels represents an algorithm, and in general, because of associativity, algebraic identities, and multiple kernels, one expression can be evaluated via many different algorithms. These algorithms are all mathematically equivalent (i.e., in exact arithmetic, they all compute the same result), but often differ noticeably in terms of execution time. When faced with a decision, high-level languages, libraries, and tools such as Julia, Armadillo, and Linnea choose by selecting the algorithm that minimises the FLOP count. In this paper, we test the validity of the FLOP count as a discriminant for dense linear algebra algorithms, analysing "anomalies": problem instances for which the fastest algorithm does not perform the least number of FLOPs. To do so, we focused on relatively simple expressions and analysed when and why anomalies occurred. We found that anomalies exist and tend to cluster into large contiguous regions. For one expression anomalies were rare, whereas for the other they were abundant. We conclude that FLOPs is not a sufficiently dependable discriminant even when building algorithms with highly optimised kernels. Plus, most of the anomalies remained as such even after filtering out the inter-kernel cache effects. We conjecture that combining FLOP counts with kernel performance models will significantly improve our ability to choose optimal algorithms.
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| 36. |
- Lundström, Carl Peter, 1982, et al.
(författare)
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Fiber optic parametric amplifier with 10-dB net gain without pump dithering
- 2013
-
Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 25:3, s. 234-237
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Tidskriftsartikel (refereegranskat)abstract
- We present a stimulated Brillouin Scattering (SBS)-suppressed fiber optic parametric amplifier/wavelength converter constructed from four highly nonlinear fiber pieces with applied strain gradients and separated by isolators. The effective total SBS threshold increase is about 11 dB, and a net parametric gain of 10 dB is obtained without any pump dithering.
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| 37. |
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| 38. |
- Myllykoski, Mirko, 1988-, et al.
(författare)
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Task-Based Parallel Algorithms for Eigenvalue Reordering of Matrices in Real Schur Forms
- 2017
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We develop a task-based parallel algorithm for reordering eigenvalues of matrices in real Schur form. We describe how we implemented the algorithm using StarPU runtime system and report on experiments performed on a shared memory machine. Compared with ScaLAPACK we achieve average speedup of 3. We have strong and weak scaling efficiencies which are well above 50%. We are able to achieve more than 50% of the peak flop rate for all but the smallest matrices. The idle time and the overhead is negligible except for the smallest matrices. The next step is to reconfigure and further develop the code so that it can be applied to matrix pairs in generalized Schur forms and run efficiently on distributed memory machines.
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| 39. |
- Psarras, Christos, et al.
(författare)
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Accelerating Jackknife Resampling for the Canonical Polyadic Decomposition
- 2022
-
Ingår i: Frontiers in Applied Mathematics and Statistics. - : Frontiers Media SA. - 2297-4687. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- The Canonical Polyadic (CP) tensor decomposition is frequently used as a model in applications in a variety of different fields. Using jackknife resampling to estimate parameter uncertainties is often desirable but results in an increase of the already high computational cost. Upon observation that the resampled tensors, though different, are nearly identical, we show that it is possible to extend the recently proposed Concurrent ALS (CALS) technique to a jackknife resampling scenario. This extension gives access to the computational efficiency advantage of CALS for the price of a modest increase (typically a few percent) in the number of floating point operations. Numerical experiments on both synthetic and real-world datasets demonstrate that the new workflow based on a CALS extension can be several times faster than a straightforward workflow where the jackknife submodels are processed individually.
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| 40. |
- Psarras, Christos, et al.
(författare)
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Algorithm 1026: Concurrent Alternating Least Squares for Multiple Simultaneous Canonical Polyadic Decompositions
- 2022
-
Ingår i: ACM Transactions on Mathematical Software. - : ACM Digital Library. - 0098-3500 .- 1557-7295. ; 48:3
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Tidskriftsartikel (refereegranskat)abstract
- Tensor decompositions, such as CANDECOMP/PARAFAC (CP), are widely used in a variety of applications, such as chemometrics, signal processing, and machine learning. A broadly used method for computing such decompositions relies on the Alternating Least Squares (ALS) algorithm. When the number of components is small, regardless of its implementation, ALS exhibits low arithmetic intensity, which severely hinders its performance and makes GPU offloading ineffective. We observe that, in practice, experts often have to compute multiple decompositions of the same tensor, each with a small number of components (typically fewer than 20), to ultimately find the best ones to use for the application at hand. In this article, we illustrate how multiple decompositions of the same tensor can be fused together at the algorithmic level to increase the arithmetic intensity. Therefore, it becomes possible to make efficient use of GPUs for further speedups; at the same time, the technique is compatible with many enhancements typically used in ALS, such as line search, extrapolation, and non-negativity constraints. We introduce the Concurrent ALS algorithm and library, which offers an interface to MATLAB, and a mechanism to effectively deal with the issue that decompositions complete at different times. Experimental results on artificial and real datasets demonstrate a shorter time to completion due to increased arithmetic intensity.
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| 41. |
- Sandgren, Emma, et al.
(författare)
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Utredning och behandling av ventrikulära extraslag [Evaluation and treatment of PVCs]
- 2020
-
Ingår i: Läkartidningen. - Stockholm, Sweden : Sveriges Läkarförbund. - 0023-7205 .- 1652-7518. ; 117
-
Tidskriftsartikel (refereegranskat)abstract
- Premature ventricular complex (PVC) is common in the general population. Symptoms vary from none to pronounced. The prognostic significance of PVCs depends on the presence of underlying structural heart disease. The clinical evaluation in patients with PVC aims at excluding structural heart disease and usually involves transthoracic echocardiogram and Holter. Patients without structural heart disease usually have a good prognosis. Frequent PVCs may cause impaired left ventricular function, which usually is reversible after treatment with drugs or ablation. A 12-lead ECG provides important information about PVC localization, however anatomical factors such as the hearts localization in the thorax as well as electrode placement and pharmacological treatment may affect the ECG appearance. In symptomatic patients with or without left ventricular impairment, pharmacological treatment or catheter ablation is indicated. However, in most cases the main goal is to reasure the patient of the good prognosis. To summarize, treatment of choice depends on symptoms, comorbidities, left ventricular function and patients choice.
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| 42. |
- Schwarz, Angelika Beatrix, 1989-
(författare)
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Improving the efficiency of eigenvector-related computations
- 2021
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- An effective strategy in dense linear algebra is the design of algorithms as tiled algorithms. Tiled algorithms that express the bulk of the computation as matrix-matrix operations (level-3 BLAS) have proven successful in achieving high performance on cache-based architectures. At the same time, tiled algorithms interoperate with dynamic data-driven execution models such as task parallelism and promise good parallel scalability.This thesis applies the concept of tiled algorithms and task-centric execution to algorithms related to the computation of eigenvectors for the dense, non-symmetric eigenvalue problem. First, a standard algorithm for computing eigenvectors from the Schur form is recast such that all computational steps are rich in matrix-matrix operations. Second, inverse iteration on the Hessenberg matrix as an alternative approach to computing eigenvectors is addressed. An existing algorithm is revised to express the computationally most expensive step with matrix-matrix operations. Third, a task-parallel, tiled triangular Sylvester equation solver is amended to solve a larger class of problems. All algorithms have an enhanced performance, which is demonstrated through numerical experiments.
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| 43. |
- Schwarz, Angelika Beatrix, 1989-, et al.
(författare)
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Robust parallel eigenvector computation for the non-symmetric eigenvalue problem
- 2020
-
Ingår i: Parallel Computing. - : Elsevier. - 0167-8191 .- 1872-7336. ; 100
-
Tidskriftsartikel (refereegranskat)abstract
- A standard approach for computing eigenvectors of a non-symmetric matrix reduced to real Schur form relies on a variant of backward substitution. Backward substitution is prone to overflow. To avoid overflow, the LAPACK eigenvector routine DTREVC3 associates every eigenvector with a scaling factor and dynamically rescales an entire eigenvector during the backward substitution such that overflow cannot occur. When many eigenvectors are computed, DTREVC3 applies backward substitution successively for every eigenvector. This corresponds to level-2 BLAS operations and constitutes a bottleneck. This paper redesigns the backward substitution such that the entire computation is cast as tile operations (level-3 BLAS). By replacing LAPACK’s scaling factor with tile-local scaling factors, our solver decouples the tiles and sustains parallel scalability even when a lot of numerical scaling is necessary.
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| 44. |
- Schwarz, Angelika Beatrix, et al.
(författare)
-
Scalable eigenvector computation for the non-symmetric eigenvalue problem
- 2019
-
Ingår i: Parallel Computing. - : Elsevier. - 0167-8191 .- 1872-7336. ; 85, s. 131-140
-
Tidskriftsartikel (refereegranskat)abstract
- We present two task-centric algorithms for computing selected eigenvectors of a non-symmetric matrix reduced to real Schur form. Our approach eliminates the sequential phases present in the current LAPACK/ScaLAPACK implementation. We demonstrate the scalability of our implementation on multicore, manycore and distributed memory systems.
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| 45. |
- Schwarz, Angelika Beatrix, 1989-
(författare)
-
Towards efficient overflow-free solvers for systems of triangular type
- 2019
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Triangular linear systems are fundamental in numerical linear algebra. A triangular linear system has a straight-forward and efficient solution strategy, namely forward substitution for lower triangular systems and backward substitution for upper triangular systems. Triangular systems, or, more generally, systems of triangular type occur frequently in algorithms for more complex problems. This thesis addresses three systems that involve linear systems of triangular type. The first system concerns quasi-triangular matrices. Quasi-triangular matrices are block triangular with 1-by-1 and 2-by-2 blocks on the diagonal. Quasi-triangular systems arise in the computation of eigenvectors from the real Schur form for the non-symmetric eigenvalue problem. This thesis contributes two algorithms for the eigenvector computation, which solve shifted quasi-triangular linear systems in an efficient and scalable way. The second system addresses scaled triangular linear systems. During the solution of a triangular linear system, the entries of the solution can grow. This growth can exceed the representable range of floating-point numbers. Such an overflow can be avoided by solving a scaled triangular system. The solution is scaled prior to every operation that would otherwise result in an overflow. After scaling, the operations can be executed safely. This thesis analyzes the scalability of a recently developed tiled, robust solver for scaled triangular systems, which ensures that at no point in the computation the overflow threshold is exceeded. The third system tackles the scaled continuous-time triangular Sylvester equation, which couples two quasi-triangular matrices. The solution process is prone to overflow. This thesis contributes a robust, tiled solver and demonstrates its practicability. These three systems can be addressed with a variation of forward or backward substitution. Compared to the highly optimized and scalable implementations of standard forward and backward substitution available in HPC libraries,the existing implementations of these three systems run at a smaller fraction of the peak performance. This thesis presents techniques to improve on the performance and robustness of the implementations of the three systems.
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| 46. |
- Shvab, Ruslan, 1985, et al.
(författare)
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Manufacturing of Valve Bridge Component Utilizing Lean Alloyed Powders and Vacuum Sintering
- 2018
-
Ingår i: Powder Metallurgy Progress. - : Walter de Gruyter GmbH. - 1335-8987 .- 1339-4533. ; 18:1, s. 31-39
-
Tidskriftsartikel (refereegranskat)abstract
- Increasing the application area of powder metallurgy (PM) steels for manufacturing of high-performance structural components results in material saving, reduction in energy consumption, etc. In this study, feasibility of the manufacturing of valve bridge component for heavy duty engine utilizing lean alloyed powders and novel vacuum sintering approach, followed by low pressure carburizing, is studied. Three low alloyed steel powders were processed by conventional uniaxial pressing and sintering at 1120 and 1250°C in industrial vacuum furnace. The components were tested under high cycle fatigue testing, simulating real conditions of operation. Fatigue properties did not show significant dependence on the sintering temperature and were comparable to currently used reference cast material. Fracture surfaces of broken samples were analyzed to detect crack initiations and fracture mechanisms as well as quality of sintering. Results showed preferentially ductile failure, well developed sintering necks and clean pore surfaces, indicating good sintering. Tested material in combination with novel vacuum sintering process show to be an attractive alternative for manufacturing of this type of components for heavy duty engine applications.
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| 47. |
- Staffas, Anna, 1982, et al.
(författare)
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Wild-type KRAS inhibits oncogenic KRAS-induced T-all in mice.
- 2015
-
Ingår i: Leukemia. - : Springer Science and Business Media LLC. - 1476-5551 .- 0887-6924. ; 29, s. 1032-1040
-
Tidskriftsartikel (refereegranskat)abstract
- The role of hyperactive RAS signaling is well established in myeloid malignancies but less clear in T-cell malignancies. The Kras2LSLMx1-Cre (KM) mouse model expresses endogenous KRASG12D in hematopoietic cells and is widely used to study mechanisms and treatment of myeloproliferative neoplasms (MPN). The model displays an intriguing shift from MPN to acute T-cell leukemia (T-ALL) after transplantation to wild-type mice but the mechanisms underlying this lineage shift is unknown. Here, we show that KRASG12D increases proliferation of both myeloid and T-cell progenitors, but whereas myeloid cells differentiate, T-cell differentiation is inhibited at early stages. Secondary mutations in the expanded pool of T-cell progenitors accompany T-ALL development, and our results indicate that the shift from myeloid to T-lymphoid malignancy after transplantation is explained by the increased likelihood for secondary mutations when the tumor life-span is increased. We demonstrate that tumor life span increases after transplantation because primary KM mice die rapidly, not from MPN, but from KRASG12D expression in nonhematopoietic cells which causes intestinal bleeding and severe anemia. We also identify loss of the wild-type KRAS allele as a secondary mutation in all T-ALL cells and provide evidence that wild-type KRAS acts as a tumor suppressor in the T-cell lineage in mice.Leukemia accepted article preview online, 05 November 2014. doi:10.1038/leu.2014.315.
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| 48. |
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| 49. |
- Yangui, Aymen, 1987, et al.
(författare)
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Phosphor Thermometry of Alumina-Forming High-Temperature Alloys Using Luminescent Rare-Earth Ions in YAG: Proof of Concept Using a Dispersion of Ce 3+ -Doped YAG Particles in a FeCrAl Alloy
- 2023
-
Ingår i: ECS Journal of Solid State Science and Technology. - : The Electrochemical Society. - 2162-8777 .- 2162-8769. ; 12:3
-
Tidskriftsartikel (refereegranskat)abstract
- Most high-temperature processes require monitoring and controlling temperature, preferably with high precision and good lateral resolution. Here we evaluate the use of the technique commonly known as phosphor thermometry, which exploits the temperature dependent photoluminescence from an inorganic phosphor, for the determination of the temperature of a composite material consisting of the metallic alloy FeCrAl dispersed with phosphor particles of yttrium aluminum garnet (Y3Al5O12, YAG) doped with a small amount of luminescent Ce3+ ions (YAG:Ce3+). The results show that with some optimization and by changing the dopant ion, YAG based phosphor particles offer a unique opportunity to measure the surface temperature of metal alloys with high precision and high lateral resolution, all the way up to the maximum working temperature of alumina-forming high temperature alloys at ca. 1300 °C.
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| 50. |
- Zettergren, Anna, 1978, et al.
(författare)
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Further investigations of the relation between polymorphisms in sex steroid related genes and autistic-like traits.
- 2016
-
Ingår i: Psychoneuroendocrinology. - Stockholm : Elsevier BV. - 1873-3360 .- 0306-4530. ; 68, s. 1-5
-
Tidskriftsartikel (refereegranskat)abstract
- Autism spectrum disorders (ASDs) are more prevalent in boys than in girls, indicating that high levels of testosterone during early development may be a risk factor. Evidence for this hypothesis comes from studies showing associations between fetal testosterone levels, as well as indirect measures of prenatal androgenization, and ASDs and autistic-like traits (ALTs). In a recent study we reported associations between ALTs and single nucleotide polymorphisms (SNPs) in the genes encoding estrogen receptor 1 (ESR1), steroid-5-alpha-reductase, type 2 (SRD5A2) and sex hormone-binding globulin (SHBG) in a subset (n=1771) from the Child and Adolescent Twin Study in Sweden (CATSS). The aim of the present study was to try to replicate these findings in an additional, larger, sample of individuals from the CATSS (n=10,654), as well as to analyze additional SNPs of functional importance in SHBG and SRD5A2. No associations between the previously associated SNPs in the genes ESR1 and SRD5A2 and ALTs could be seen in the large replication sample. Still, our results show that two non-linked SNPs (rs6259 and rs9901675) at the SHBG gene locus might be of importance for language impairment problems in boys. The results of the present study do not point toward a major role for the investigated SNPs in the genes ESR1 and SRD5A2 in ALTs, but a possible influence of genetic variation in SHBG, especially for language impairment problems in boys, cannot be ruled out.
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