| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
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- 2019
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Tidskriftsartikel (refereegranskat)
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| 3. |
- Long, Xu, et al.
(författare)
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Finite Element Analysis to the Constitutive Behavior of Sintered Silver Nanoparticles Under Nanoindentation
- 2018
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Ingår i: International Journal of Applied Mechanics. - 1758-8251 .- 1758-826X. ; 10:10
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Tidskriftsartikel (refereegranskat)abstract
- Finite element (FE) simulation is adopted as a fundamental tool to evaluate the mechanical reliability of packaging structures for electronic devices. Nevertheless, the determination of mechanical properties of sintered silver nanoparticles (AgNP) remains challenging as the traditional tensile test is difficult to be performed at a limited size. In the current study, spherical nanoindentation is utilized to measure the applied load-penetration depth responses of sintered AgNP reinforced by SiC microparticles at various weight ratios (0.0, 0.5, 1.0 and 1.5 wt.%). To describe the elasto-plastic behavior of this heterogeneous material, FE analysis is performed to simulate the indentation behavior and determine the parameters in the modified power-law model by fitting the average applied load-penetration depth responses. To overcome the uniqueness problem, the Young's modulus is directly determined by continuous stiffness measurement technique and the proposed constitutive model can provide a reasonably accurate mechanical estimation of sintered AgNP. The effect of SiC content on sintered AgNP is discussed by correlating the morphology observed by scanning electron microscope (SEM) and the constitutive parameters obtained from the FE simulations.
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| 4. |
- Hu, Lin, et al.
(författare)
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A study on energy distribution strategy of electric vehicle hybrid energy storage system considering driving style based on real urban driving data
- 2022
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Ingår i: Renewable and Sustainable Energy Reviews. - : Elsevier BV. - 1879-0690 .- 1364-0321. ; 162
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Tidskriftsartikel (refereegranskat)abstract
- This paper proposes a novel energy distribution optimization method of hybrid energy storage system (HESS) and its improved semi-active topology for electric vehicles (EVs) to further reduce battery capacity degradation and energy loss. Compared with the traditional HESS semi-active topology, the proposed improved topology reduces the energy loss when the battery charges the supercapacitor (SC) to further enhance the efficiency of the system. The real urban driving data of electric vehicles are collected through experiments and divided into aggressive type, cautious type and standard type according to driving style. Based on the mature multi-mode control (MMC), different weight coefficients are assigned to the two optimization objectives of battery capacity degradation and energy loss based on different driving styles, and gray wolf optimization (GWO) is used to optimize the battery output power upper limit and SC charging upper limit of MMC. The simulation results show that compared with the traditional MMC and semi-active topology, the battery capacity degradation and energy loss are improved under different driving styles. In addition, by further analyzing the simulation results, the research direction of HESS energy distribution strategy in the future is discussed.
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| 5. |
- Hu, Yao, 1997
(författare)
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Quantification of local lattice distortions in refractory high-entropy alloys by scattering-based techniques
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing demand for advanced structural materials for use in extreme conditions, particularly including the aerospace applications, has promoted the development of refractory high-entropy alloys (RHEAs). A deeper understanding of the interaction between microstructure and properties is essential to overcome the scientific challenges associated with these alloys. One notable characteristic of high entropy alloys (HEAs), including RHEAs, is local lattice distortion (LLD) caused by the solid solutioning of multiple principal elements with varying atomic sizes. LLDs generate strain fields that hinder dislocation movement, thus enhancing strength via the solid solution strengthening mechanism. However, quantifying LLDs in RHEAs poses a challenge due to the subtle nature of these structural changes and a lack of consensus on appropriate methods. The approach of determining average structures of materials through the analysis of X-ray diffraction patterns has been well-recognised. Meanwhile, total scattering technique, along with pair distribution function (PDF), has also shown significant potential in uncovering information at local structure. Both Bragg diffraction and PDF have previously proven effective for the quantitative assessment of LLDs. In this thesis, it is demonstrated that LLDs in body-centered cubic (BCC) structured RHEAs can be accurately measured through both reciprocal-space Rietveld method and real-space small-box PDF analysis. The obtained LLDs are significantly larger than previously reported values for face-centered cubic (FCC) structured HEAs. Additionally, a comprehensive simulation study explored the effects of chemical segregation, confirming the feasibility of precise LLD determination in RHEAs under specific levels of segregation and LLD. Robust determination of LLDs through small-box PDF analysis is essential for future time-resolved measurements.
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| 6. |
- Hu, Yao, 1997, et al.
(författare)
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Quantifying local lattice distortions in refractory high-entropy alloys
- 2024
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Ingår i: Physical Review Materials. - 2475-9953. ; 8:8
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Tidskriftsartikel (refereegranskat)abstract
- Severe local lattice distortions (LLDs), originating from the size mismatch among atoms, have been proposed as one of the key mechanisms responsible for the excellent mechanical properties of bcc-structured high-entropy alloys (HEAs). They have also been connected to phase stability, as well as physical properties such as electrical conductivity. Experimental measurements of LLDs are, however, difficult and often ambiguous. Analysis of total scattering data in real space has been proposed to provide a uniquely suitable probe of LLDs, but its widespread application and validation are still limited. We conduct a thorough study of LLD measurements in refractory high-entropy alloys (RHEAs) using small-box pair distribution function (PDF) analysis. We start by reexamining existing literature data using a recently proposed coherent theoretical framework to demonstrate that LLDs in RHEAs can indeed be considered as severe and can be reliably measured even in the absence of known thermal components. We perform total scattering experiments of a typical RHEA (HfNbTaTiZr) using both x-rays and neutrons, and show that real-space PDF analysis of data from different types of radiation gives consistent values of LLDs. The results are also in good agreement with the values derived from reciprocal-space data. Finally, through simulation and analysis of theoretical two-phase PDFs, we demonstrate that the effect of the chemical segregation in the investigated RHEA on the measured LLDs is limited when dealing with comparatively large LLDs. The results show that PDF analysis using small-box modeling provides a fast and reliable tool for measuring LLDs in RHEAs, which makes it ideal for analysis of large data sets from time-resolved in situ measurements.
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| 7. |
- Tang, Xiaopeng, et al.
(författare)
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Load-responsive model switching estimation for state of charge of lithium-ion batteries
- 2019
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 238, s. 423-434
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Tidskriftsartikel (refereegranskat)abstract
- Accurately estimating state of charge (SoC) is very important to enable advanced management of lithium-ion batteries, however technical challenges mainly exist in the lack of a high-fidelity battery model whose parameters are sensitive to changes of the state and load condition. To address the problem, this paper explores and proposes a model switching estimation algorithm that online selects the most suitable model from its model library based on the relationship between load conditions for calibration and in practice. By leveraging a high-pass filter and the Coulomb counting, an event trigger procedure is developed to detect the estimation performance and then determine timely switching actions. This estimation algorithm is realized by adopting a gradient correction method for system identification and the unscented Kalman filter and H∞ observer for state estimation. Experimental results illustrate that the proposed algorithm is able to reproduce SoC trajectories under various operating profiles, with the root-mean-square errors bounded by 2.22%. The efficacy of this algorithm is further corroborated by comparing to single model-based estimators and two prevalent adaptive SoC estimators.
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| 8. |
- Zhao, Meng, et al.
(författare)
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Pathway engineering in yeast for synthesizing the complex polyketide bikaverin
- 2020
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Fungal polyketides display remarkable structural diversity and bioactivity, and therefore the biosynthesis and engineering of this large class of molecules is therapeutically significant. Here, we successfully recode, construct and characterize the biosynthetic pathway of bikaverin, a tetracyclic polyketide with antibiotic, antifungal and anticancer properties, in S. cerevisiae. We use a green fluorescent protein (GFP) mapping strategy to identify the low expression of Bik1 (polyketide synthase) as a major bottleneck step in the pathway, and a promoter exchange strategy is used to increase expression of Bik1 and bikaverin titer. Then, we use an enzyme-fusion strategy to directly couple the monooxygenase (Bik2) and methyltransferase (Bik3) to efficiently channel intermediates between modifying enzymes, leading to an improved titer of bikaverin at 202.75 mg/L with flask fermentation (273-fold higher than the initial titer). This study demonstrates that the biosynthesis of complex fungal polyketides can be established and efficiently engineered in S. cerevisiae, highlighting the potential for natural product synthesis and large-scale fermentation in yeast.
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