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| 2. |
- Wang, Zhihao, et al.
(författare)
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Current Reference Control Scheme of Voltage Source Converters to Ensure the Existence of Stable Equilibrium Points During Grid Fault
- 2023
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Ingår i: IEEE transactions on power electronics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0885-8993 .- 1941-0107. ; 38:9, s. 10750-10765
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Tidskriftsartikel (refereegranskat)abstract
- Maintaining synchronization with the grid during fault ride-through (FRT) is essential for grid-connected voltage source converters (VSCs). However, improper current references can lead to a loss of synchronization during FRT due to the nonexistence of stable equilibrium points (SEPs). While the mechanism of SEPs has been explained, the development of control schemes ensuring their existence remains challenging due to the difficulty of obtaining real-time grid parameters during FRT. To address this issue, this article proposes a novel current reference control scheme that only requires prefault grid parameters. By analyzing the changes in grid parameters caused by faults and characterizing the correspondence between the during-fault and prefault grid parameters, a voltage-dependent current reference control scheme is proposed. Since no real-time grid parameter estimation is needed during FRT, the proposed control scheme is practical and easy to implement. Simulation studies using DIgSILENT PowerFactory demonstrate that the proposed control scheme enables the VSC to maintain synchronization with the grid under the conditions of short-circuit ratio equaling 1.3 and grid voltage dropping to 0.1 p.u. Moreover, experiments further verify the effectiveness and feasibility of the proposed control scheme.
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| 3. |
- Zhai, Xiaohu, et al.
(författare)
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Roles of Anion–Cation Coupling Transport and Dehydration-Induced Ion–Membrane Interaction in Precise Separation of Ions by Nanofiltration Membranes
- 2022
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 56:19, s. 14069-14079
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Tidskriftsartikel (refereegranskat)abstract
- Nanofiltration (NF) membranes are playing increasingly crucial roles in addressing emerging environmental challenges by precise separation, yet understanding of the selective transport mechanism is still limited. In this work, the underlying mechanisms governing precise selectivity of the polyamide NF membrane were elucidated using a series of monovalent cations with minor hydrated radius difference. The observed selectivity of a single cation was neither correlated with the hydrated radius nor hydration energy, which could not be explained by the widely accepted NF model or ion dehydration theory. Herein, we employed an Arrhenius approach combined with Monte Carlo simulation to unravel that the transmembrane process of the cation would be dominated by its pairing anion, if the anion has a greater transmembrane energy barrier, due to the constraint of anion–cation coupling transport. Molecular dynamics simulations further revealed that the distinct hydration structure was the primary origin of the energy barrier difference of cations. The cation having a larger incompressible structure after partial dehydration through subnanopores would induce a more significant ion–membrane interaction and consequently a higher energy barrier. Moreover, to validate our proposed mechanisms, a membrane grafting modification toward enlarging the energy barrier difference of dominant ions achieved a 3-fold enhancement in ion separation efficiency. Our work provides insights into the precise separation of ionic species by NF membranes.
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| 4. |
- Bianchi Piccinini, Giulio, 1982, et al.
(författare)
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Factors contributing to commercial vehicle rear-end conflicts in China: A study using on-board event data recorders
- 2017
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Ingår i: Journal of Safety Research. - : Elsevier BV. - 0022-4375. ; 62, s. 143-153
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: In the last 30 years, China has undergone a dramatic increase in vehicle ownership and a resulting escalation in the number of road crashes. Although crash figures are decreasing today, they remain high; it is therefore important to investigate crash causation mechanisms to further improve road safety in China. Method: To shed more light on the topic, naturalistic driving data was collected in Shanghai as part of the evaluation of a behavior-based safety service. The data collection included instrumenting 47 vehicles belonging to a commercial fleet with data acquisition systems. From the overall sample, 91 rear-end crash or near-crash (CNC) events, triggered by 24 drivers, were used in the analysis. The CNC were annotated by three researchers, through an expert assessment methodology based on videos and kinematic variables. Results: The results show that the main factor behind the rear-end CNC was the adoption of very small safety margins. In contrast to results from previous studies in the US, the following vehicles' drivers typically had their eyes on the road and reacted quickly in response to the evolving conflict in most events. When delayed reactions occurred, they were mainly due to driving-related visual scanning mismatches (e.g., mirror checks) rather than visual distraction. Finally, the study identified four main conflict scenarios that represent the typical development of rear-end conflicts in this data. Conclusions: The findings of this study have several practical applications, such as informing the specifications of in-vehicle safety measures and automated driving and providing input into the design of coaching/training procedures to improve the driving habits of drivers.
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| 6. |
- Tian, Guoda, et al.
(författare)
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Deep-Learning Based Channel Estimation for OFDM Wireless Communications
- 2022
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Ingår i: 2022 IEEE 23rd International Workshop on Signal Processing Advances in Wireless Communication (SPAWC).
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Konferensbidrag (refereegranskat)abstract
- Multi-carrier technique is a backbone for modern commercial networks. However, the performances of multi-carrier systems in general depend greatly on the qualities of acquired channel state information (CSI). In this paper, we propose a novel deep-learning based processing pipeline to estimate CSI for payload time-frequency resource elements. The proposed pipeline contains two cascaded subblocks, namely, an initial denoise network (IDN), and a resolution enhancement network (REN). In brief, IDN applies a novel two-steps denoising structure while REN consists of pure fully-connected layers. Compared to existing works, our proposed processing architecture is more robust under lower signal-to-noise scenarios and delivers generally a significant gain.
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| 8. |
- Wang, Xuesong, et al.
(författare)
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Identification of V6.51L as a selectivity hotspot in stereoselective A(2B) adenosine receptor antagonist recognition
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- The four adenosine receptors (ARs) A(1)AR, A(2A)AR, A(2B)AR(,) and A(3)AR are G protein-coupled receptors (GPCRs) for which an exceptional amount of experimental and structural data is available. Still, limited success has been achieved in getting new chemical modulators on the market. As such, there is a clear interest in the design of novel selective chemical entities for this family of receptors. In this work, we investigate the selective recognition of ISAM-140, a recently reported A(2B)AR reference antagonist. A combination of semipreparative chiral HPLC, circular dichroism and X-ray crystallography was used to separate and unequivocally assign the configuration of each enantiomer. Subsequently affinity evaluation for both A(2A) and A(2B) receptors demonstrate the stereospecific and selective recognition of (S)-ISAM140 to the A(2B)AR. The molecular modeling suggested that the structural determinants of this selectivity profile would be residue V250(6.51) in A(2B)AR, which is a leucine in all other ARs including the closely related A(2A)AR. This was herein confirmed by radioligand binding assays and rigorous free energy perturbation (FEP) calculations performed on the L249V(6.51) mutant A(2A)AR receptor. Taken together, this study provides further insights in the binding mode of these A(2B)AR antagonists, paving the way for future ligand optimization.
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| 9. |
- Wang, Xuesong, et al.
(författare)
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Studying the function of ecosystem in preventing aeolian dust emission in the dryland areas of China
- 2023
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Ingår i: European Journal of Soil Science. - 1351-0754 .- 1365-2389. ; 74:3
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Tidskriftsartikel (refereegranskat)abstract
- Aeolian dust emissions can cause many environmental hazards, like accelerating land degradation and desertification, polluting air, harming human health, and so on. The dryland areas of China (DAC) are hot spots of aeolian dust emissions. To date, many efforts have been paid to researching dust emissions processes and effects, but research studies on ecosystems' function in preventing dust emissions are still very limited. In this study, we investigated the function of DAC ecosystems in preventing dust emissions, and the corresponding driving factors through integrated wind erosion modelling system (IWEMS) modelling. The main results indicate that: (1) from 2001 to 2020, the ecosystems of DAC prevented the emission of dust ~40,554 Tg, approximately 15 times as much as the total actual dust emission (~2776 Tg); (2) the function of DAC ecosystems in preventing dust emissions was relatively strong in spring and winter; (3) grassland ecosystems had the strongest function in preventing dust emissions among all the land cover types, avoiding the emission of dust ~20,857 Tg over 2001–2020; (4) dust emission prevention function provided by the DAC ecosystems benefits almost every region of China, which provides a theoretical basis for formulating ecological compensation policies; and (5) the changes in dust emissions were dominated by wind speed in most areas of DAC.
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