| 1. |
- Huang, Wencheng, et al.
(författare)
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Enhanced orbital anisotropy through the proximity to a SrTi O3 layer in the perovskite iridate superlattices
- 2021
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Ingår i: Physical Review B. - 2469-9950. ; 104:7
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Tidskriftsartikel (refereegranskat)abstract
- We have used angle-dependent soft x-ray absorption spectroscopy (XAS) at the O K edge and first-principles calculations to investigate the electronic structures of iridate-based superlattices (SrIrO3)m/(SrTiO3) (m=1, 2, 3, and ∞). We focus on the pre-edge Ir 5d t2g-O 2p orbital hybridization feature in the XAS spectra. By varying the measurement geometry relative to the incident photon polarization, we are able to extract the dichroic contrast and observe the systematic increase in the anisotropy of Ir 5d orbitals as m decreases. First-principles calculations elucidate the orbital anisotropy coming mainly from the enhanced out-of-plane compression of IrO6 octahedra in the SrIrO3 layers that are adjacent to the inserted SrTiO3 layers. As m decreases, the increased volume fraction of these interfacial SrIrO3 layers and their contact with the SrTiO3 layers within the (SrIrO3)m/(SrTiO3) supercell lead to enhanced orbital anisotropy. Furthermore, the tilt and rotation of IrO6 octahedra are shown to be essential to understand the subtle orbital anisotropy in these superlattices, and constraining these degrees of freedom will give an incorrect trend. Our results demonstrate that the structural constraint from the inserted SrTiO3 layers, in addition to other electronic means such as polar interface and charge transfer, can serve as a knob to control the orbital degree of freedom in these iridate-based superlattices.
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| 2. |
- Hu, Xiaosong, et al.
(författare)
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Cost-optimal energy management of hybrid electric vehicles using fuel cell/battery health-aware predictive control
- 2020
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Ingår i: IEEE Transactions on Power Electronics. - 0885-8993 .- 1941-0107. ; 35:1, s. 382-392
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Tidskriftsartikel (refereegranskat)abstract
- Energy management is an enabling technology for increasing the economy of fuel cell/battery hybrid electric vehicles. Existing efforts mostly focus on optimization of a certain control objective (e.g., hydrogen consumption), without sufficiently considering the implications for on-board power sources degradation. To address this deficiency, this article proposes a cost-optimal, predictive energy management strategy, with an explicit consciousness of degradation of both fuel cell and battery systems. Specifically, we contribute two main points to the relevant literature, with the purpose of distinguishing our study from existing ones. First, a model predictive control framework, for the first time, is established to minimize the total running cost of a fuel cell/battery hybrid electric bus, inclusive of hydrogen cost and costs caused by fuel cell and battery degradation. The efficacy of this framework is evaluated, accounting for various sizes of prediction horizon and prediction uncertainties. Second, the effects of driving and pricing scenarios on the optimized vehicular economy are explored.
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| 3. |
- Li, Bo, et al.
(författare)
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Joint IT and Spectrum Resource Load Balancing for VNF Selection in Inter-Datacenter Elastic Optical Networks
- 2017
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Ingår i: 2017 16TH INTERNATIONAL CONFERENCE ON OPTICAL COMMUNICATIONS & NETWORKS (ICOCN 2017). - : IEEE. - 9781538632734
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Konferensbidrag (refereegranskat)abstract
- The selection of virtualized network functions (VNFs) in service provisioning is a critical issue in inter-datacenter elastic optical networks. In this paper, considering load balancing of IT and spectrum resources, we propose two joint balancing factors, i.e., Global Balancing factor (GB factor) and Local Balancing factor (LB-factor) for VNFs selection. Then a Joint-Optimization Selection (JOS) algorithm is designed based on the joint balancing factors. Simulation results show that GB-factor based JOS can achieve better performance compared with LB-factor based JOS and benchmark algorithm.
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| 4. |
- Tu, Yudi, et al.
(författare)
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Ultrathin Single-Crystalline 2D Perovskite Photoconductor for High-Performance Narrowband and Wide Linear Dynamic Range Photodetection
- 2020
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Ingår i: Small. - : WILEY-V C H VERLAG GMBH. - 1613-6810 .- 1613-6829.
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Tidskriftsartikel (refereegranskat)abstract
- For next-generation Internet-of-Everything applications, for example, artificial-neural-network image sensors, artificial retina, visible light communication, on-chip light interconnection, and flexible devices, etc., high-performance microscale photodetectors are in urgent demands. 2D material (2DM) photodetectors have been researched and demonstrated impressive performances. However, they have not met the demands in filterless narrowband photoresponse, wide linear dynamic range (LDR), ultralow dark current, and large on/off ratio, which are key performances for these applications. 2D Ruddlesden-Popper perovskites (2D-RPPs) are recently highlighted photovoltaic and optoelectronic materials. Embedding ultrathin 2D-RPPs into 2DM photodetectors holds potentials to improve these performances. Herein, a single-crystalline ultrathin (PEA)(2)PbI4 is integrated into a vertical-stacked graphene-(PEA)(2)PbI4-graphene micro photoconductor (V-PEPI-PC). V-PEPI-PC exhibits narrowband photoresponses at 517 nm with a full-width-at-half-maximum of 15 nm and a wide LDR of 122 dB. Due to the multiple quantum wells in (PEA)(2)PbI4, V-PEPI-PC demonstrates an ultralow dark current of 1.1 x 10(-14) A (44 pA mm(-2)), a high specific detectivity of 1.2 x 10(13) Jones, and a high on/off ratio of 1.6 x 10(6). Owing to the short vertical channel, V-PEPI-PC shows a fast response rise time of 486 mu s. Therefore, the vertical-stacked photodetectors based on hybrid 2D-RPPs and 2DMs may have great potentials in future optoelectronics.
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| 5. |
- Xu, Bo, et al.
(författare)
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4-Tert-butylpyridine Free Organic Hole Transporting Materials for Stable and Efficient Planar Perovskite Solar Cells
- 2017
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6832 .- 1614-6840. ; 7:19
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Tidskriftsartikel (refereegranskat)abstract
- 4-Tert-butylpyridine (tBP) is an important additive in triarylamine-based organic hole-transporting materials (HTMs) for improving the efficiency and steady-state performance of perovskite solar cells (PVSCs). However, the low boiling point of tBP (196 degrees C) significantly affects the long-term stability and device performance of PVSCs. Herein, the design and synthesis of a series of covalently linked Spiro[fluorene-9,9'-xanthene] (SFX)-based organic HTMs and pyridine derivatives to realize efficient and stable planar PVSCs are reported. One of the tailored HTMs, N2, N2, N7, N7-tetrakis(4-methoxyphenyl)-3', 6'bis( pyridin-4-ylmethoxy) spiro[fluorene-9,9'-xanthene]-2,7-diamine (XPP) with two para-position substituted pyridines that immobilized on the SFX core unit shows a high power conversion efficiency (PCE) of 17.2% in planar CH3NH3PbI3-based PVSCs under 100 mW cm(-2) AM 1.5G solar illumination, which is much higher than the efficiency of 5.5% that using the well-known 2,2', 7,7'-tetrakis-(N, N-di-p-methoxy-phenyl-amine) 9,9'-spirobifluorene (SpiroOMeTAD) as HTM (without tBP) under the same condition. Most importantly, the pyridine-functionalized HTM-based PVSCs without tBP as additive show much better long-term stability than that of the state-of-the-art HTM SpiroOMeTAD- based solar cells that containing tBP as additive. This is the first case that the tBP-free HTMs are demonstrated in PVSCs with high PCEs and good stability. It paves the way to develop highly efficient and stable tBP-free HTMs for PVSCs toward commercial applications.
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| 6. |
- Zhang, Tianling, 1981, et al.
(författare)
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Ultra-wideband Full-metal Planar Array Antenna with a Combination of Ridge Gap Waveguide and E-plane Groove Gap Waveguide
- 2022
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 70:9, s. 8051-8058
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Tidskriftsartikel (refereegranskat)abstract
- An ultra-wideband (UWB) full-metal planar array antenna based on a combination of ridge gap waveguide (RGW) and E-plane groove gap waveguide (E-GGW) is presented for millimeter-wave (mmWave) applications. First, the radiation element of a double-step double-ridged slot structure is proposed and designed. With removing the vertical walls of the cavity in the H-plane, the impedance matching characteristics presents a UWB bandwidth of 53%. Second, a UWB double-layer feeding network is achieved by combining RGWs and double-side-pin E-GGWs for the radiation elements. Finally, an 8 × 8 full-metal planar array antenna with the presented elements and network is designed, prototyped and measured. The measured results agree well with the simulated results. The proposed antenna provides an impedance matching bandwidth (|S11| < -10 dB) of 46.8% from 18.8 to 30.3 GHz. The maximum gain is 27.7 dBi at 27 GHz and a stable gain of 26 ± 1.7 dBi is obtained over the operation band.
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