| 1. |
- Chen, Yangli, et al.
(författare)
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Uncertainty quantification for TRACE simulation of FIX-II No. 5052 test
- 2020
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Ingår i: Annals of Nuclear Energy. - : Elsevier. - 0306-4549 .- 1873-2100. ; 143
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Tidskriftsartikel (refereegranskat)abstract
- The Best Estimate Plus Uncertainty approach requires the knowledge of input uncertainties for the uncertainty propagation with best-estimate codes. Inaccurate judgement of some model parameter uncertainties related to the dominant physical phenomena may result in misestimation of the safety margin. This paper presents a framework of inverse uncertainty quantification (UQ) to quantify model parameter uncertainties in order to address this issue. It is applied to TRACE simulation of a large break loss of coolant accident conducted on the FIX-II facility, and peak cladding temperature (PCT) is the simulation output. Sensitivity analysis identifies the parameters of the critical flow model as the most influential to the PCT. The inverse UQ is performed based on Bayesian framework, which adopts Markov Chain Monte Carlo sampling and surrogate modelling algorithms. The quantified uncertainties of the model parameters are the desired results from the inverse UQ process, which are useful in BEPU studies.
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| 2. |
- Dong, Yihui, et al.
(författare)
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Excellent Protein Immobilization and Stability on Heterogeneous C–TiO2 Hybrid Nanostructures : A Single Protein AFM Study
- 2020
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 36:31, s. 9323-9332
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Tidskriftsartikel (refereegranskat)abstract
- Enhancing molecular interaction is critical for improving the immobilization and stability of proteins on TiO2 surfaces. In this work, mesoporous TiO2 materials with varied pore geometries were decorated with phenyl phosphoric acid (PPA), followed by a thermal treatment to obtain chemically heterogeneous C–TiO2 samples without changing the geometry and crystalline structure, which can keep the advantages of both carbon and TiO2. The molecular interaction force between the protein and the surfaces was measured using atomic force microscopy by decomposing from the total adhesion forces, showing that the surface chemistry determines the interaction strength and depends on the amount of partial carbon coverage on the TiO2 surface (∼40–80%). Samples with 58.3% carbon coverage provide the strongest molecular interaction force, consistent with the observation from the detected friction force. Surface-enhanced Raman scattering and electrochemical biosensor measurements for these C–TiO2 materials were further conducted to illustrate their practical implications, implying their promising applications such as in protein detection and biosensing.
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| 3. |
- Ho, Du, 1988-, et al.
(författare)
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A sensor-to-sensor model-based change detection approach for quadcopters
- 2020
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Ingår i: Proceedings of the 21st IFAC World Congress, 2020. - : Elsevier. ; , s. 712-717
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Konferensbidrag (refereegranskat)abstract
- This paper addresses the problem of change detection for a quadcopter in the presence ofwind disturbances. Different aspects of the quadcopter dynamics and various flight conditions have beeninvestigated. First, the wind is modeled using the Dryden wind model as a sum of a low-frequent and aturbulent part. Since the closed-loop control can compensate for system changes and disturbances andthe effect of the wind disturbance is significant, the residuals obtained from a standard simulation modelcan be misleading. Instead, a sensor-to-sensor submodel of the quadcopter is selected to detect a changein the payload using the Instrumental Variables (IV) cost function. It is shown that the mass variationcan be detected using the IV cost function in different flight scenarios.
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| 4. |
- Hu, Yating, 1991, et al.
(författare)
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Engineering carboxylic acid reductase for selective synthesis of medium-chain fatty alcohols in yeast
- 2020
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 117:37, s. 22974-22983
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Tidskriftsartikel (refereegranskat)abstract
- Medium-chain fatty alcohols (MCFOHs, C6 to C12) are potential substitutes for fossil fuels, such as diesel and jet fuels, and have wide applications in various manufacturing processes. While today MCFOHs are mainly sourced from petrochemicals or plant oils, microbial biosynthesis represents a scalable, reliable, and sustainable alternative. Here, we aim to establish a Saccharomyces cerevisiae platform capable of selectively producing MCFOHs. This was enabled by tailoring the properties of a bacterial carboxylic acid reductase from Mycobacterium marinum (MmCAR). Extensive protein engineering, including directed evolution, structure-guided semirational design, and rational design, was implemented. MmCAR variants with enhanced activity were identified using a growth-coupled high-throughput screening assay relying on the detoxification of the enzyme’s substrate, medium-chain fatty acids (MCFAs). Detailed characterization demonstrated that both the specificity and catalytic activity of MmCAR was successfully improved and a yeast strain harboring the best MmCAR variant generated 2.8-fold more MCFOHs than the strain expressing the unmodified enzyme. Through deletion of the native MCFA exporter gene TPO1, MCFOH production was further improved, resulting in a titer of 252 mg/L for the final strain, which represents a significant improvement in MCFOH production in minimal medium by S. cerevisiae.
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| 5. |
- Wei, Li, et al.
(författare)
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Extending instant messaging to provide pervasive personal communication
- 2006
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Konferensbidrag (refereegranskat)abstract
- This paper proposes a personal software architecture to provide a user with a pervasive communication capability. The core of this architecture is a Personal Communication Server (PCS) which bridges between different Instant Messaging networks and extends them with a unified access to the user. A SIP-based implementation of such a communication server is presented, which solves various interoperability problems, and also provides many value-added features, e.g., extended user presence with location information, adaptive communication, better privacy protection, etc. This implementation enables various existing SIP-compatible resources to be re-used and thus simplifies the construction of the proposed software architecture.
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| 6. |
- Wei, Lei
(författare)
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Guinea pig osteoarthrosis : morphological and biochemical studies
- 1999
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hartley guinea pigs spontaneously and reproducibly develop an arthropathy mimicking human primary osteoarthrosis. The morphological lesions first appear between 6 and 12 months of age, when it is confined to the non-meniscus-covered central compartment of the medial tibial plateau without initially involving the lateral side. The knees of these animals are constitutionally in varus position, so the load is mainly carried by the medial compartment and by its non-meniscus-covered parts in particular. An early change, while the cartilage surface is still intact, was a reduction in volume density of chondrocytes in the superficial zones. Cell clustering, hypertrophy and intensive staining of the extracellular matrix were found adjacent to areas of cartilage destruction, probably indicating reparative processes. The concentration of proteoglycans in the articular cartilage was higher in areas presumably subjected to a higher load, and in healthy cartilage the concentration increased with age and body weight. The highest concentrations were found just before osteoarthrosis became morphologically evident, and the concentrations then decreased. Simultaneously, there was a reduction in collagen concentration and an increased content of tissue water. Surgical redistribution of load by femur valgus osteotomy or unilateral tibia amputation altered the natural history of the arthropathy: osteotomy induced osteoarthrosis on the lateral condyle, while it reduced the changes on the medial side. Amputation did not completely prevent the development of fibrillation. After intervention, the extent of fibrillation was correlated to the proteoglycan concentration in the tissue. Thus, the chondrocytes seem to modify the composition of the extracellular matrix to balance variations in load within a certain range. Hypothetically, with higher load, the rate of proteoglycan synthesis rise, thus increasing the swelling pressure of the tissue. After continued excessive load, the chondrocytes lost this ability. As a result of reduced proteoglycan concentration, the cartilage became less resistant to mechanical stress.
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