| 1. |
- Long, Xu, et al.
(author)
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Finite Element Analysis to the Constitutive Behavior of Sintered Silver Nanoparticles Under Nanoindentation
- 2018
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In: International Journal of Applied Mechanics. - 1758-8251 .- 1758-826X. ; 10:10
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Journal article (peer-reviewed)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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| 2. |
- Wang, Ling, et al.
(author)
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Defect formation by order coalescence in vermicular grains during alumina phase transformation
- 2015
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In: Scripta Materialia. - : Elsevier BV. - 1359-6462 .- 1872-8456. ; 107, s. 59-62
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Journal article (peer-reviewed)abstract
- Vermicular alpha-Al2O3 grains obtained from gamma- to alpha-phase transformation were investigated. X-ray diffraction patterns showed a left-shifting shoulder in all diffraction peaks of transformed alpha-Al2O3. High-resolution transmission electron microscopy results confirmed large amounts of defects inside the vermicular alpha-Al2O3 single-crystal. Combined with grain-growth discontinuity, the authors proposed that the defects inside vermicular grains resulted from assembly of nanosized alpha-crystallites by an ordered coalescence mechanism directly after phase transformation, by which the orientation alignment was thermodynamically favored in the solid-state sintering.
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| 3. |
- Hu, Lin, et al.
(author)
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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
-
In: Renewable and Sustainable Energy Reviews. - : Elsevier BV. - 1879-0690 .- 1364-0321. ; 162
-
Journal article (peer-reviewed)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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| 4. |
- Hu, Nan, et al.
(author)
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Review of experimental measurements on particle size distribution and airflow behaviors during human respiration
- 2024
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In: Building and Environment. - : Elsevier. - 0360-1323 .- 1873-684X. ; 247
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Journal article (peer-reviewed)abstract
- In recent years, pandemic outbreaks have raised concerns about the spread of respiratory infections and their impact on public health. Since the pathogen emission during human respiration is recognized as the primary source, characterizing the physical properties of exhaled particles and airflow has become a crucial focus of attention. This article critically reviews experimental studies in exhaled particles and airflow, examines the uncertainty introduced by different measurement methods, analyzes how it is reflected in measurement outcomes, and provides an in-depth understanding of particle size distribution and airflow behaviors of human respiration. The measurement techniques assessment highlights the variability among particle sizing techniques in detection size range, collection efficiency, hydration status of captured particles, and experimental protocols. A combination of sampling-based instruments and laser imaging systems is recommended for particle sizing to cover a wider detection range, with refined setups in thermal conditions, sampling distance, volume, and duration. Meanwhile, it identifies the complementary nature of qualitative and quantitative measurements of airflow characterization techniques. Image recording systems plus data reconstruction programs are suggested to capture dynamic airflow features while accuracy validation by other techniques is required at the same time. Subsequent analysis of the measurement data showed that the various experimental measurements provided substantial information, but they also revealed disagreements and challenges in quantification. The dominance of submicron aerosols in exhaled particles and jet-like transport in exhaled airflow is obvious. More efforts should be made to measure particles larger than 20 μm, capture airflow dynamics in a high temporal and spatial resolution, and quantify the impact of face coverings to improve the understanding of human respiratory emissions.
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| 5. |
- Tang, Xiaopeng, et al.
(author)
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Load-responsive model switching estimation for state of charge of lithium-ion batteries
- 2019
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In: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 238, s. 423-434
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Journal article (peer-reviewed)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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| 6. |
- Zhao, Meng, et al.
(author)
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Pathway engineering in yeast for synthesizing the complex polyketide bikaverin
- 2020
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723 .- 2041-1723. ; 11:1
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Journal article (peer-reviewed)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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| 7. |
- Cui, J. -P, et al.
(author)
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NEW BROADBAND ZERO PHASE SHIFTER BASED ON NEGATIVE REFRACTION INDEX TRANSMISSION LINE
- 2008
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In: Journal Electromagnetic Waves and Applications. - : Informa UK Limited. - 0920-5071 .- 1569-3937. ; 22:14-15, s. 2069-2075
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Journal article (peer-reviewed)abstract
- This paper presents the design of one dimensional broadband phase shifters based on a new class of negative refraction index transmission line. The proposed phase shifter here consists of conventional microstrip line and Negative Refraction Index (NRI) transmission line (TL) in which ideal operational amplifiers are applied to form the periodically loaded negative-impedance-converted inductors and capacitors. It is demonstrated that variations in inductors and capacitors can produce arbitrary phase shifts while maintaining the same overall length. Also, the NRI-TL is non-dispersive so that the new phase shifter can be used in many new broadband devices.
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| 8. |
- Jiang, Linhai, et al.
(author)
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Controlled Synthesis of CeO2/Graphene Nanocomposites with Highly Enhanced Optical and Catalytic Properties
- 2012
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In: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 116:21, s. 11741-11745
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Journal article (peer-reviewed)abstract
- In this paper, CeO2 nanocubes with the (200)-terminated surface/graphene sheet composites have been prepared successfully by a simple hydrothermal method. It is found that the CeO2 nanocubes with high crystallinity and specific exposed surface are well dispersed on well-exfoliated graphene surface. The (200)-terminated surface/graphene sheet composites modified electrode showed much higher sensitivity and excellent selectivity in its catalytic performance compared to a CeO2 nanoparticle-modified electrode. The photoluminescence intensity of the CeO2 anchored on graphene is about 30 times higher than that of pristine CeO2 crystals in air. The higher oxygen vacancy concentration in CeO2 is supposed to be an important cause for the higher photoluminescence and better electrochemical catalytic performance observed in the (200)-terminated surface/graphene sheet composites. Such ingenious design of supported well-dispersed catalysts in nanostructured ceria catalysts, synthesized in one step with an exposed high-activity surface, is important for technical applications and theoretical investigations.
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| 9. |
- Li, Y., et al.
(author)
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Control algorithm design for tracking and interacting with a ground moving target using an aerial vehicle
- 2016
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In: Proceedings of the 35th Chinese Control Conference 2016. - : IEEE Computer Society. - 9789881563910 ; , s. 5726-5731
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Conference paper (peer-reviewed)abstract
- In this paper, a three-dimensional control problem is investigated in which an aerial vehicle equipped with a vision system is required to track and interact with a ground moving target. In order to guarantee the continuity of target observation, horizontal and vertical commands are designed separately under the constraints of the detection zone and vehicle dynamics. In order to realize a time-optimal trajectory as well as a smooth interaction with the target, a switched interaction algorithm is proposed, which combines an improved Rendezvous-Guidance (RG) algorithm and a Proportional Integral (PI) controller by the choice of a switching point. Moreover, simulation results are provided to demonstrate not only the effectiveness of the proposed algorithm, but also a high tolerance for detection and execution errors near the interaction point.
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| 10. |
- Zhang, Yiming, et al.
(author)
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A compact and narrow-band bandpass filter based on substrate integrated waveguide and spoof surface plasmon polaritons for millimeter-wave applications
- 2024
-
In: AEU - International Journal of Electronics and Communications. - : Elsevier BV. - 1434-8411 .- 1618-0399. ; 178
-
Journal article (peer-reviewed)abstract
- This paper presents bandpass filter (BPF) comprising substrate integrated waveguide (SIW) and spoof surface plasmon polaritons (SSPPs), achieving miniaturized size, low insertion loss in the millimeter-wave band. SIW with single-slotted SSPP structure is employing to obtain the transmission zero (TZ) at the low-frequency part, and by introducing the SIW with rhombic periodic walls to enhance the low-frequency rejection. The target passband and TZ of the high-frequency part are realized by increasing the number of etching slots. Furthermore, we innovatively incorporate nonradiative (NR) slots etched below the SSPP structure to gain high out-of-band rejection level. SIW with rhombic periodic walls and slotted SSPP structure as one unit cell is analyzed and demonstrated. Ultimately, the two SIW unit cells are cascaded together to get better out-of-band rejection characteristics and serve as our final design. To validate the proposed design, the BPF prototype is fabricated and measured, showing good electrical performance in terms of high selectivity, low loss, and compact size.
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