| 1. |
- Asimakopoulou, Eleni Myrto, et al.
(författare)
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Development towards high-resolution kHz-speed rotation-free volumetric imaging
- 2024
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Ingår i: Optics Express. - 1094-4087. ; 32:3, s. 4413-4426
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Tidskriftsartikel (refereegranskat)abstract
- X-ray multi-projection imaging (XMPI) has the potential to provide rotation-free 3D movies of optically opaque samples. The absence of rotation enables superior imaging speed and preserves fragile sample dynamics by avoiding the centrifugal forces introduced by conventional rotary tomography. Here, we present our XMPI observations at the ID19 beamline (ESRF, France) of 3D dynamics in melted aluminum with 1000 frames per second and 8 µm resolution per projection using the full dynamical range of our detectors. Since XMPI is a method under development, we also provide different tests for the instrumentation of up to 3000 frames per second. As the high-brilliance of 4th generation light-sources becomes more available, XMPI is a promising technique for current and future X-ray imaging instruments.
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| 2. |
- Birnsteinova, Sarlota, et al.
(författare)
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Online dynamic flat-field correction for MHz microscopy data at European XFEL
- 2023
-
Ingår i: Journal of Synchrotron Radiation. - 1600-5775. ; 30:6, s. 1030-1037
-
Tidskriftsartikel (refereegranskat)abstract
- The high pulse intensity and repetition rate of the European X-ray Free-Electron Laser (EuXFEL) provide superior temporal resolution compared with other X-ray sources. In combination with MHz X-ray microscopy techniques, it offers a unique opportunity to achieve superior contrast and spatial resolution in applications demanding high temporal resolution. In both live visualization and offline data analysis for microscopy experiments, baseline normalization is essential for further processing steps such as phase retrieval and modal decomposition. In addition, access to normalized projections during data acquisition can play an important role in decision-making and improve the quality of the data. However, the stochastic nature of X-ray free-electron laser sources hinders the use of standard flat-field normalization methods during MHz X-ray microscopy experiments. Here, an online (i.e. near real-time) dynamic flat-field correction method based on principal component analysis of dynamically evolving flat-field images is presented. The method is used for the normalization of individual X-ray projections and has been implemented as a near real-time analysis tool at the Single Particles, Clusters, and Biomolecules and Serial Femtosecond Crystallography (SPB/SFX) instrument of EuXFEL.
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| 3. |
- Buakor, Khachiwan, et al.
(författare)
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Shot-to-shot flat-field correction at X-ray free-electron lasers
- 2022
-
Ingår i: Optics Express. - 1094-4087. ; 30:7, s. 10633-10644
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Tidskriftsartikel (refereegranskat)abstract
- X-ray free-electron lasers (XFELs) provide high-brilliance pulses, which offer unique opportunities for coherent X-ray imaging techniques, such as in-line holography. One of the fundamental steps to process in-line holographic data is flat-field correction, which mitigates imaging artifacts and, in turn, enables phase reconstructions. However, conventional flat-field correction approaches cannot correct single XFEL pulses due to the stochastic nature of the self-amplified spontaneous emission (SASE), the mechanism responsible for the high brilliance of XFELs. Here, we demonstrate on simulated and megahertz imaging data, measured at the European XFEL, the possibility of overcoming such a limitation by using two different methods based on principal component analysis and deep learning. These methods retrieve flat-field corrected images from individual frames by separating the sample and flat-field signal contributions; thus, enabling advanced phase-retrieval reconstructions. We anticipate that the proposed methods can be implemented in a real-time processing pipeline, which will enable online data analysis and phase reconstructions of coherent full-field imaging techniques such as in-line holography at XFELs.
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| 4. |
- Guo, Rui, et al.
(författare)
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Deep-learning image enhancement and fibre segmentation from time-resolved computed tomography of fibre-reinforced composites
- 2023
-
Ingår i: Composites Science and Technology. - 0266-3538. ; 244
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Tidskriftsartikel (refereegranskat)abstract
- Monitoring the microstructure and damage development of fibre-reinforced composites during loading is crucial to understanding their mechanical properties. Time-resolved X-ray computed tomography enables such an in-situ, non-destructive study. However, the photon flux and fibre-matrix contrast limit its achievable spatial and temporal resolution. In this paper, we push the limits of temporal and spatial resolution for the microstructural analysis of unidirectional continuous carbon fibre-reinforced epoxy composites by establishing a new pipeline based on CycleGAN for unsupervised super-resolution and denoising and U-Net-id for individual fibre segmentation. After illustrating the benefits of a 3D CycleGAN over a 2D one, we show that data enhanced by this pipeline can yield similar segmentation quality to that of a slow-acquisition, high-quality scan that took up to 200 times longer to acquire. This pipeline, therefore, enables more robust data extraction from fast time-resolved X-ray tomography, removing a critical stumbling block for this technique.
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| 5. |
- Hot, Dina, et al.
(författare)
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Spatially and temporally resolved IR-DFWM measurement of HCN released from gasification of biomass pellets
- 2019
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Ingår i: Proceedings of the Combustion Institute. - : Elsevier BV. - 1540-7489. ; 37:2, s. 1337-1344
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Tidskriftsartikel (refereegranskat)abstract
- For the first time, to the best of the authors' knowledge, nonintrusive quantitative measurement of hydrogen cyanide (HCN) released during the devolatilization phase of straw pellets gasification is demonstrated with high spatial and temporal resolution. Mid-infrared degenerate four-wave mixing (IR-DFWM) measurements of HCN were performed by probing the interference-free P(20) line in the v 1 vibrational band at around 3 μm and the IR-DFWM signal was detected with an upconversion-based detector, providing discrimination of thermal noise and increased sensitivity. A novel single-pellet setup consisting of a multi-jet burner was used to provide hot flue gas environments with an even and well-defined temperature distribution, for single straw pellet gasification at atmospheric pressure. The environments had temperatures of 1380 K, 1540 K and 1630 K with a constant oxygen concentration of 0.5 vol%. In order to quantify the amount of HCN released during the devolatilization of straw pellets, calibration measurements were performed in well-defined HCN gas flows. Selected hot water lines were probed with IR-DFWM in the interrogated volume to obtain the instantaneous temperature, which were used to correct the temperature effect. HCN concentrations up to 1500 ppm were detected during the devolatilization stage, and the results indicate a strong temperature dependence of the HCN release.
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| 6. |
- Hwang, Ouk, et al.
(författare)
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Development of novel ultrasonic temperature measurement technology for combustion gas as a potential indicator of combustion instability diagnostics
- 2019
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Ingår i: Applied Thermal Engineering. - : Elsevier BV. - 1359-4311. ; 159
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a high-speed, fast responsive, non-intrusive ultrasonic thermometry system was proposed as a potential candidate for overcoming the disadvantages of thermocouples. The principle of this system is based on the thermal dependence of the speed of sound, and the temperature is measured by detecting the flight time of ultrasonic wave (USW) between the transmitter and the receiver. For a fast and exact measurement, the algorithm was developed as simple as possible, and the exact values of the physical properties, such as specific heat ratio and molecular weight of combustion gas, were taken from the computational calculation of CHEMKIN-Pro with GRI 3.0 mechanism. The performance of the system was verified by two experiments. First, the system was applied to measure the temperature of heated air. Results showed high precision with a 0.3% error when incorporating a modification equation and fast responsive dynamic performance, which directly reflect the rapid temperature change. Second, the combustion gas temperature above a multi-jet burner, which provides a horizontally uniform temperature distribution similar to a flat flame burner, was measured. Five different flame temperatures were measured using a thermocouple and an optic-based measurement method based on two-line atomic fluorescence (TLAF) as well as ultrasonic thermometry to compare their performances. Ultrasonic thermometry showed a slightly lower accuracy than those of TLAF and the thermocouple. This condition could be overcome by correcting the results using linear fitting, as the temperature measured by USW showed the best linearity among them. The USW technique showed excellent performance in terms of the measurement speed of 1000 samples/s and uncertainty under 0.73%. This USW thermometry of combustion gas can be applied to many combustion systems, including boilers and gas turbines. Specifically, fast temperature measurement at a speed of around 1 kHz enables the diagnosis of the combustion instability phenomenon, which is a difficult task when using conventional methods of temperature measurement. Furthermore, both dynamic pressure and temperature can be simultaneously measured at a high rate, thus synergistically increasing the accuracy of combustion instability diagnosis with sufficient information, such as the Rayleigh index or the flame transfer function.
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| 7. |
- Kalbfleisch, Sebastian, et al.
(författare)
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X-ray in-line holography and holotomography at the NanoMAX beamline
- 2022
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Ingår i: Journal of Synchrotron Radiation. - : International Union of Crystallography (IUCr). - 0909-0495 .- 1600-5775. ; 29, s. 224-229
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Tidskriftsartikel (refereegranskat)abstract
- Coherent X-ray imaging techniques, such as in-line holography, exploit the high brilliance provided by diffraction-limited storage rings to perform imaging sensitive to the electron density through contrast due to the phase shift, rather than conventional attenuation contrast. Thus, coherent X-ray imaging techniques enable high-sensitivity and low-dose imaging, especially for low-atomic-number (Z) chemical elements and materials with similar attenuation contrast. Here, the first implementation of in-line holography at the NanoMAX beamline is presented, which benefits from the exceptional focusing capabilities and the high brilliance provided by MAX IV, the first operational diffractionlimited storage ring up to approximately 300 eV. It is demonstrated that in-line holography at NanoMAX can provide 2D diffraction-limited images, where the achievable resolution is only limited by the 70 nm focal spot at 13 keV X-ray energy. Also, the 3D capabilities of this instrument are demonstrated by performing holotomography on a chalk sample at a mesoscale resolution of around 155 nm. It is foreseen that in-line holography will broaden the spectra of capabilities of MAX IV by providing fast 2D and 3D electron density images from mesoscale down to nanoscale resolution.
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| 8. |
- Langer, Max, et al.
(författare)
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PyPhase - A Python package for X-ray phase imaging
- 2021
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Ingår i: Journal of Synchrotron Radiation. - 0909-0495. ; 28, s. 1261-1266
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Tidskriftsartikel (refereegranskat)abstract
- X-ray propagation-based imaging techniques are well established at synchrotron radiation and laboratory sources. However, most reconstruction algorithms for such image modalities, also known as phase-retrieval algorithms, have been developed specifically for one instrument by and for experts, making the development and diffusion of such techniques difficult. Here, PyPhase, a free and open-source package for propagation-based near-field phase reconstructions, which is distributed under the CeCILL license, is presented. PyPhase implements some of the most popular phase-retrieval algorithms in a highly modular framework supporting its deployment on large-scale computing facilities. This makes the integration, the development of new phase-retrieval algorithms, and the deployment on different computing infrastructures straightforward. Its capabilities and simplicity are presented by application to data acquired at the synchrotron source MAX IV (Lund, Sweden).
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| 9. |
- Lu, Yichun, et al.
(författare)
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Suspended solids-associated toxicity of hydraulic fracturing flowback and produced water on early life stages of zebrafish (Danio rerio)
- 2021
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491 .- 1873-6424. ; 287
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Tidskriftsartikel (refereegranskat)abstract
- Hydraulic fracturing flowback and produced water (HF-FPW), which contains polyaromatic hydrocarbons (PAHs) and numerous other potential contaminants, is a complex wastewater produced during the recovery of tight hydrocarbon resources. Previous studies on HF-FPW have demonstrated various toxicological responses of aquatic organisms as consequences of combined exposure to high salinity, dissolved organic compounds and particle/suspended solids-bound pollutants. Noteworthy is the lack of studies illustrating the potentially toxic effects of the FPW suspended solids (FPW-SS). In this study, we investigated the acute and sublethal toxicity of suspended solids filtered from six authentic FPW sample collected from two fracturing wells, using a sediment contact assay based on early-life stages of zebrafish (Danio rerio). PAHs profiles and acute toxicity tests provided initial information on the toxic potency of the six samples. Upon exposure to sediment mixture at two selected doses (1.6 and 3.1 mg/mL), results showed adverse effects in larval zebrafish, as revealed by increased Ethoxyresorufin-O-deethylase (EROD) activity. Transcriptional alterations were also observed in xenobiotic biotransformation (ahr, pxr, cyp1a, cyp1b1, cyp1c1, cyp1c2, cyp3a65, udpgt1a1, udpgt5g1), antioxidant response (sod1, sod2, gpx1a, gpx1b) and hormone receptor signaling (esr1, esr2a, cyp19a1a, vtg1) genes. The results demonstrated that even separated from the complex aqueous FPW mixture, FPW-SS can induce toxicological responses in aquatic organisms' early life stages. Since FPW-SS could sediment to the bottom of natural wetland acting as a continuous source of contaminants, the current findings imply the likelihood of long-term environmental risks of polluted sediments on aquatic ecosystems due to FPW spills.
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| 10. |
- Ren, Hui, et al.
(författare)
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The crystal structure of human adenylate kinase 6 : An adenylate kinase localized to the cell nucleus
- 2005
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Ingår i: Proceedings of the National Academy of Sciences. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 102:2, s. 8-303
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Tidskriftsartikel (refereegranskat)abstract
- Adenylate kinases (AKs) play important roles in nucleotide metabolism in all organisms and in cellular energetics by means of phosphotransfer networks in eukaryotes. The crystal structure of a human AK named AK6 was determined by in-house sulfur single-wavelength anomalous dispersion phasing methods and refined to 2.0-A resolution with a free R factor of 21.8%. Sequence analyses revealed that human AK6 belongs to a distinct subfamily of AKs present in all eukaryotic organisms sequenced so far. Enzymatic assays show that human AK6 has properties similar with other AKs, particularly with AK5. Fluorescence microscopy showed that human AK6 is localized predominantly to the nucleus of HeLa cells. The identification of a nuclear-localized AK sheds light on nucleotide metabolism in the nucleus and the energetic communication between mitochondria and nucleus by means of phosphotransfer networks.
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| 11. |
- Sala, Simone, et al.
(författare)
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Dose-efficient multimodal microscopy of human tissue at a hard X-ray nanoprobe beamline
- 2022
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Ingår i: Journal of Synchrotron Radiation. - 1600-5775. ; 29:3
-
Tidskriftsartikel (refereegranskat)abstract
- X-ray fluorescence microscopy performed at nanofocusing synchrotron beamlines produces quantitative elemental distribution maps at unprecedented resolution (down to a few tens of nanometres), at the expense of relatively long measuring times and high absorbed doses. In this work, a method was implemented in which fast low-dose in-line holography was used to produce quantitative electron density maps at the mesoscale prior to nanoscale X-ray fluorescence acquisition. These maps ensure more efficient fluorescence scans and the reduction of the total absorbed dose, often relevant for radiation-sensitive (e.g. biological) samples. This multimodal microscopy approach was demonstrated on human sural nerve tissue. The two imaging modes provide complementary information at a comparable resolution, ultimately limited by the focal spot size. The experimental setup presented allows the user to swap between them in a flexible and reproducible fashion, as well as to easily adapt the scanning parameters during an experiment to fine-tune resolution and field of view.
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| 12. |
- Song, Renfang, et al.
(författare)
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Effects of fifteen PBDE metabolites, DE71, DE79 and TBBPA on steroidogenesis in the H295R cell line
- 2008
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Ingår i: Chemosphere. - : Elsevier. - 0045-6535 .- 1879-1298. ; 71:10, s. 1888-1894
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Tidskriftsartikel (refereegranskat)abstract
- Polybrominated diphenyl ethers (PBDEs) and tetrabromobisphenol A (TBBPA) are brominated flame retardants that are produced in large quantities and are commonly used in construction materials, textiles, and as polymers in electronic equipment. Environmental and human levels of PBDEs have been increasing in the past 30 years, but the toxicity of PBDEs is not fully understood. Studies on their effects are relatively limited, and show that PBDEs are neurotoxins and potential endocrine disrupters. Hydroxylated (OH{single bond}) and methoxylated (MeO{single bond}) PBDEs have also been reported in the adipose tissue, blood and milk of wild animals and humans. In the present study, 15 PBDE metabolites, two BDE mixtures (DE71 and DE79), and TBBPA were studied individually to determine their effects on ten steroidogenic genes, aromatase activity, and concentrations of two steroid hormones (testosterone and 17β-estradiol) in the H295R human adrenocortical carcinoma cell line. Exposure to 0.05 μM 2′-OH-BDE-68 significantly induced the expression of CYP11A, CYP11B2, CYP17, CYP21, 3βHSD2, 17βHSD1, and 17βHSD4, and the expression of StAR was induced by 6-OH-BDE-90 at the three exposure concentrations. Exposure to DE71 and DE79 resulted in dose-dependent trend towards induction, but these effects were not significant. Exposure to 0.5 μM 2-OH-BDE-123 and 2-MeO-BDE-123 resulted in significantly greater aromatase activity. However, none of the compounds affected sex hormone production at the concentrations tested. Generally, OH-BDEs had a much stronger ability to affect steroidogenic gene expression than MeO-BDEs.
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| 13. |
- Soyama, Hitoshi, et al.
(författare)
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Revealing the origins of vortex cavitation in a Venturi tube by high speed X-ray imaging
- 2023
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Ingår i: Ultrasonics Sonochemistry. - 1350-4177. ; 101
-
Tidskriftsartikel (refereegranskat)abstract
- Hydrodynamic cavitation is useful in many processing applications, for example, in chemical reactors, water treatment and biochemical engineering. An important type of hydrodynamic cavitation that occurs in a Venturi tube is vortex cavitation known to cause luminescence whose intensity is closely related to the size and number of cavitation events. However, the mechanistic origins of bubbles constituting vortex cavitation remains unclear, although it has been concluded that the pressure fields generated by the cavitation collapse strongly depends on the bubble geometry. The common view is that vortex cavitation consists of numerous small spherical bubbles. In the present paper, aspects of vortex cavitation arising in a Venturi tube were visualized using high-speed X-ray imaging at SPring-8 and European XFEL. It was discovered that vortex cavitation in a Venturi tube consisted of angulated rather than spherical bubbles. The tangential velocity of the surface of vortex cavitation was assessed considering the Rankine vortex model.
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| 14. |
- Villanueva Perez, Pablo, et al.
(författare)
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Megahertz X-ray Multi-projection imaging
- 2023
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Ingår i: arXiv.org. - 2331-8422.
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- X-ray time-resolved tomography is one of the most popular X-raytechniques to probe dynamics in three dimensions (3D). Recent developments in time-resolved tomography opened the possibility of recordingkilohertz-rate 3D movies. However, tomography requires rotating thesample with respect to the X-ray beam, which prevents characterization of faster structural dynamics. Here, we present megahertz (MHz)X-ray multi-projection imaging (MHz-XMPI), a technique capable ofrecording volumetric information at MHz rates and micrometer resolution without scanning the sample. We achieved this by harnessing theunique megahertz pulse structure and intensity of the European X-rayFree-electron Laser with a combination of novel detection and reconstruction approaches that do not require sample rotations. Our approachenables generating multiple X-ray probes that simultaneously record several angular projections for each pulse in the megahertz pulse burst.We provide a proof-of-concept demonstration of the MHz-XMPI technique’s capability to probe 4D (3D+time) information on stochasticphenomena and non-reproducible processes three orders of magnitudefaster than state-of-the-art time-resolved X-ray tomography, by generating 3D movies of binary droplet collisions. We anticipate that MHz-XMPIwill enable in-situ and operando studies that were impossible before,either due to the lack of temporal resolution or because the systemswere opaque (such as for MHz imaging based on optical microscopy).
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| 15. |
- Weng, Wubin, et al.
(författare)
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Optical measurements of KOH, KCl and K for quantitative K-Cl chemistry in thermochemical conversion processes
- 2020
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 271
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Tidskriftsartikel (refereegranskat)abstract
- Potassium and chlorine chemistry at high temperature is of great importance in biomass utilization through thermal conversion. In well-defined hot environments, we performed quantitative measurements of main potassium species, i.e., potassium hydroxide (KOH), potassium chloride (KCl) and K atoms, and the important radical OH. The concentrations of KOH, KCl and OH radicals were measured through a newly developed UV absorption spectroscopy technique. Quantitative measurements of potassium atoms were performed using tunable diode laser absorption spectroscopy at the wavelength of 404.4 and 769.9 nm to cover a wide concentration dynamic range. The reaction environment was provided by a laminar flame burner, covering a temperature range of 1120–1950 K and global fuel-oxygen equivalence ratios from 0.67 to 1.32. Potassium and chlorine were introduced into the combustion atmosphere by atomized K2CO3 or KCl water solution fog. The experimental results were compared to modeling predictions to evaluate a detailed K-Cl mechanism. For most cases, the experimental and simulation results were in reasonable agreement. However, the over-prediction of K atom concentration at low temperature fuel-rich condition and the overall under-prediction of KCl concentration call for further investigation. It was demonstrated that the optical methods and the well-defined hot environments could provide quantitative investigations widely applicable to different homogeneous reactions in thermochemical conversion processes, and in evaluation of corresponding reaction mechanisms with reliable data.
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| 16. |
- Zhang, Yuhe, et al.
(författare)
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4D-ONIX : A deep learning approach for reconstructing 3D movies from sparse X-ray projections
- 2024
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The X-ray flux provided by X-ray free-electron lasers and storage rings offers new spatiotemporal possibilities to study in-situ and operando dynamics, even using single pulses of such facilities. X-ray Multi-Projection Imaging (XMPI) is a novel technique that enables volumetric information using single pulses of such facilities and avoids centrifugal forces induced by state-of-the-art time-resolved 3D methods such as time-resolved tomography. As a result, XMPI can acquire 3D movies (4D) at least three orders of magnitude faster than current methods. However, no algorithm can reconstruct 4D from highly sparse projections acquired by XMPI. Here, we present 4D-ONIX, a Deep Learning (DL)-based approach that learns to reconstruct 3D movies (4D) from an extremely limited number of projections. It combines the computational physical model of X-ray interaction with matter and state-of-the-art DL methods. We demonstrate the potential of 4D-ONIX to generate high-quality 4D by generalizing over multiple experiments with only two projections per timestamp for binary droplet collisions. We envision that 4D-ONIX will become an enabling tool for 4D analysis, offering new spatiotemporal resolutions to study processes not possible before.
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| 17. |
- Zhang, Yuhe
(författare)
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Advancing X-ray imaging with deep learning : Physics-inspired reconstruction approaches
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of high-brilliance X-ray sources, such as the fourth-generation diffraction-limited storage rings and X-ray free-electron lasers, have opened up new possibilities for X-ray imaging and pushed the temporal resolutions of imaging techniques to unprecedented levels. Capturing fast dynamics in two-dimensional (2D), three-dimensional (3D), and even four-dimensional (4D, 3D + time) beyond microsecond temporal resolution has become possible. To fully exploit the unique capabilities of these facilities, challenges such as the data problem must be addressed. Automated tools are needed to handle the large amount of data acquired from each experiment.As a data-driven approach, deep learning has undergone rapid development over the past decade and offers a promising solution to this problem. However, state-of-the-art deep learning methods applied to X-ray imaging ignore the physics of X-ray propagation and interaction with matter and require paired training datasets. In this thesis, we show that combining the physical principles of X-ray imaging with deep learning greatly improves the performance and robustness of the approaches, and it is possible to construct reliable unsupervised approaches, where no paired datasets are needed.Firstly, we present a theoretical background on X-ray imaging and various imaging methods. Secondly, we provide an overview of deep learning, including training strategies and common frameworks for addressing imaging tasks. Lastly, we introduce novel algorithms developed during this thesis:1. FFCGAN, a supervised approach for shot-to-shot flat-field correction at X-ray free-electron lasers.2. PhaseGAN, a phase-retrieval approach for unpaired datasets.3. ONIX, a self-supervised approach for 3D reconstruction from sparse views.4. 4D-ONIX, a self-supervised approach for reconstructing 3D movies from sparse projections.These approaches offer high-quality image reconstructions for X-ray imaging techniques, enabling further exploration and understanding of the structure and dynamic properties of various samples.
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| 18. |
- Zhang, Yuhe, et al.
(författare)
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Fractional Angular Momentum in Cold-Atom Systems
- 2014
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 113:16, s. 160404-
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Tidskriftsartikel (refereegranskat)abstract
- The quantum statistics of bosons or fermions are manifest through the even or odd relative angular momentum of a pair. We show theoretically that, under certain conditions, a pair of certain test particles immersed in a fractional quantum Hall state possesses, effectively, a fractional relative angular momentum, which can be interpreted in terms of fractional braid statistics. We propose that the fractionalization of the angular momentum can be detected directly through the measurement of the pair correlation function in rotating ultracold atomic systems in the fractional quantum Hall regime. Such a measurement will also provide direct evidence for the effective magnetic field resulting from Berry phases arising from attached vortices, and of excitations with a fractional particle number, analogous to the fractional charge of the electron fractional quantum Hall effect.
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| 19. |
- Zhang, Yuhe, et al.
(författare)
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ONIX : an X-ray deep-learning tool for 3D reconstructions from sparse views
- 2023
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Ingår i: Applied Research. - 2702-4288. ; 2:4
-
Tidskriftsartikel (refereegranskat)abstract
- Time-resolved three-dimensional (3D) X-ray imaging techniques rely on obtaining 3D information for each time point and are crucial for materials-science applications in academia and industry. Standard 3D X-ray imaging techniques like tomography and confocal microscopy access 3D information by scanning the sample with respect to the X-ray source. However, the scanning process limits the temporal resolution when studying dynamics and is not feasible for many materials-science applications, such as cell-wall rupture of metallic foams. Alternatives to obtaining 3D information when scanning is not possible are X-ray stereoscopy and multi-projection imaging, but these approaches suffer from limited volumetric information as they only acquire a very small number of views or projections compared to traditional 3D scanning techniques. Here, we present optimized neural implicit X-ray imaging (ONIX), a deep-learning algorithm capable of retrieving a continuous 3D object representation from only a small and limited set of sparse projections. ONIX is based on an accurate differentiable model of the physics of X-ray propagation. It generalizes across different instances of similar samples to overcome the limited volumetric information provided by limited sparse views. We demonstrate the capabilities of ONIX compared to state-of-the-art tomographic reconstruction algorithms by applying it to simulated and experimental datasets, where a maximum of eight projections are acquired. ONIX, although it does not have access to any volumetric information, outperforms unsupervised reconstruction algorithms, which reconstruct using single instances without generalization over different instances. We anticipate that ONIX will become a crucial tool for the X-ray community by (i) enabling the study of fast dynamics not possible today when implemented together with X-ray multi-projection imaging and (ii) enhancing the volumetric information and capabilities of X-ray stereoscopic imaging.
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| 20. |
- Zhang, Yuhe, et al.
(författare)
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PhaseGAN : a deep-learning phase-retrieval approach for unpaired datasets
- 2021
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Ingår i: Optics Express. - 1094-4087. ; 29:13, s. 19593-19604
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Tidskriftsartikel (refereegranskat)abstract
- Phase retrieval approaches based on deep learning (DL) provide a framework to obtain phase information from an intensity hologram or diffraction pattern in a robust manner and in real-time. However, current DL architectures applied to the phase problem rely on i) paired datasets, i. e., they are only applicable when a satisfactory solution of the phase problem has been found, and ii) the fact that most of them ignore the physics of the imaging process. Here, we present PhaseGAN, a new DL approach based on Generative Adversarial Networks, which allows the use of unpaired datasets and includes the physics of image formation. The performance of our approach is enhanced by including the image formation physics and a novel Fourier loss function, providing phase reconstructions when conventional phase retrieval algorithms fail, such as ultra-fast experiments. Thus, PhaseGAN offers the opportunity to address the phase problem in real-time when no phase reconstructions but good simulations or data from other experiments are available.
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| 21. |
- Zhang, Yuhe, et al.
(författare)
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Reusability report : Unpaired deep-learning approaches for holographic image
- 2024
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Ingår i: Nature Machine Intelligence. - 2522-5839. ; 6:3, s. 284-290
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Tidskriftsartikel (refereegranskat)abstract
- Deep-learning methods using unpaired datasets hold great potential for image reconstruction, especially in biomedical imaging where obtaining paired datasets is often difficult due to practical concerns. A recent study by Lee et al. (Nature Machine Intelligence 2023) has introduced a parameterized physical model (referred to as FMGAN) using the unpaired approach for adaptive holographic imaging, which replaces the forward generator network with a physical model parameterized on the propagation distance of the probing light. FMGAN has demonstrated its capability to reconstruct the complex phase and amplitude of objects, as well as the propagation distance, even in scenarios where the object-to-sensor distance exceeds the range of the training data. We performed additional experiments to comprehensively assess FMGAN’s capabilities and limitations. As in the original paper, we compared FMGAN to two state-of-the-art unpaired methods, CycleGAN and PhaseGAN, and evaluated their robustness and adaptability under diverse conditions. Our findings highlight FMGAN’s reproducibility and generalizability when dealing with both in-distribution and out-of-distribution data, corroborating the results reported by the original authors. We also extended FMGAN with explicit forward models describing the response of specific optical systems, which improved performance when dealing with non-perfect systems. However, we observed that FMGAN encounters difficulties when explicit forward models are unavailable. In such scenarios, PhaseGAN outperformed FMGAN.
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