| 1. |
- Liu, Yang, et al.
(författare)
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Defect State Assisted Z-scheme Charge Recombination in Bi2O2CO3/Graphene Quantum Dot Composites for Photocatalytic Oxidation of NO
- 2020
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 3:1, s. 772-781
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Tidskriftsartikel (refereegranskat)abstract
- In this work, we explored the photoinduced charge carriers dynamics rationalizing the photocatalytic oxidation of NO over N-doped Bi2O2CO3/graphene quantum dots composites(N-BOC/GQDs) via time-resolved photoluminescence (TRPL). Under visible light illumination, only GQDs can be photoexcited and inject electrons to N-BOC within 0.5 ns. Under UV light irradiation, the interfacial Z-scheme heterojunction recombination between the electrons in N-BOC and holes in GQDs dominate the depopulation of excited states within 0.36 ns. Such efficient Z-scheme recombination regardless of the large energy difference (1.66 eV) is mediated by the interfacial oxygen vacany defect states characterized by both density functional theory calculations (DFT) and electron paramagnetic resonance (EPR) measurement. This finding provide a novel strategic view to improve the photocatalytic performance of the nanocomposite by interfacial engineering
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| 2. |
- Liu, Ben, et al.
(författare)
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A facile synthesis of Fe3C@mesoporous carbon nitride nanospheres with superior electrocatalytic activity
- 2016
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 8:10, s. 5441-5445
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Tidskriftsartikel (refereegranskat)abstract
- We report a colloidal amphiphile-templating approach to preparing nanosized Fe3C encapsulated within mesoporous nitrogen-doped carbon nanospheres (Fe3C@mCN). The obtained Fe3C@mCN hybrids having a high surface area and ultrafine Fe3C nanocrystals exhibited superior activity and durability for oxygen reduction.
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| 3. |
- Liu, Ben, et al.
(författare)
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Unconventional structural and morphological transitions of nanosheets, nanoflakes and nanorods of AuNP@MnO2
- 2016
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 4:17, s. 6447-6455
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2-D) layered inorganic materials with ultra-high surface area and mechanical strength have shown impressive photo-/electro-catalytic activities. We herein report a facile synthetic strategy to grow monodispersed 2-D MnO2 nanosheet on an individual gold nanoparticle (AuNP@MnO2 nanosheet), and demonstrate that the strongly interacted AuNP and MnO2 nanosheet could greatly improve the electrocatalytic activity of the MnOx family for electrocatalytic oxygen reduction reactions (ORRs). AuNP@MnO2 nanosheets were prepared using a hydrothermal reduction of KMnO4 by citrate ligands capped on AuNPs. Because of the metastability of the layered MnO2 nanosheets, we observed unconventional structural and morphological transitions of amorphous MnO2 nanosheets to delta-MnO2 nanoflakes, and eventually to alpha-MnO2 nanorods under hydrothermal conditions. The layered MnO2 nanosheets underwent a structural expansion to nanoflakes before the curling and re-folding of layered MnO2 nanosheets occurred. The intermediate states and structural transitions via a layer compression, for the first time, were experimentally recorded at a single-NP scale using electron microscopy. Moreover, we found the electrocatalytic activity of AuNP@MnO2 nanosheets was enhanced roughly 30-40 times, compared to that of pure MnO2 nanosheets and AuNPs. The strong interaction of metal-oxide interfaces (MnO2 nanosheets and AuNPs) was likely responsible for the improved electrocatalytic activity. This interaction of MnO2 and AuNPs was weakened in the course of hydrothermal treatment where partially positively charged Au+ was reduced at elevated temperatures, accompanying with the decrease of ORR activity. This insight into the effect of topological nanostructures and metal-oxide interactions on the electrocatalytic performance of the MnOx family is believed to illustrate an alternative pathway to develop new efficient electrocatalysts.
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| 4. |
- Chen, Bolin, et al.
(författare)
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Modeling and Analysis of MPTCP Proxy-based LTE-WLAN Path Aggregation
- 2017
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Ingår i: 2017 IEEE Global Communications Conference (GLOBECOM), Proceedings Singapore 4 – 8 December 2017. - : IEEE Communications Society. - 9781509050192 - 9781509050208 ; , s. 1-7
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Konferensbidrag (refereegranskat)abstract
- Long Term Evolution (LTE)-Wireless Local Area Network (WLAN) Path Aggregation (LWPA) based on Multi- path Transmission Control Protocol (MPTCP) has been under standardization procedure as a promising and cost-efficient solution to boost Downlink (DL) data rate and handle the rapidly increasing data traffic. This paper aims at providing tractable analysis for the DL performance evaluation of large-scale LWPA networks with the help of tools from stochastic geometry. We consider a simple yet practical model to determine under which conditions a native WLAN Access Point (AP) will work under LWPA mode to help increasing the received data rate. Using stochastic spatial models for the distribution of WLAN APs and LTE Base Stations (BSs), we analyze the density of active LWPA- mode WiFi APs in the considered network model, which further leads to closed-form expressions on the DL data rate and area spectral efficiency (ASE) improvement. Our numerical results illustrate the impact of different network parameters on the performance of LWPA networks, which can be useful for further performance optimization.
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| 5. |
- Li, Zheng, et al.
(författare)
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A Review of Spatter in Laser Powder Bed Fusion Additive Manufacturing: In Situ Detection, Generation, Effects, and Countermeasures
- 2022
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Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 13:8
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Forskningsöversikt (refereegranskat)abstract
- Spatter is an inherent, unpreventable, and undesired phenomenon in laser powder bed fusion (L-PBF) additive manufacturing. Spatter behavior has an intrinsic correlation with the forming quality in L-PBF because it leads to metallurgical defects and the degradation of mechanical properties. This impact becomes more severe in the fabrication of large-sized parts during the multi-laser L-PBF process. Therefore, investigations of spatter generation and countermeasures have become more urgent. Although much research has provided insights into the melt pool, microstructure, and mechanical property, reviews of spatter in L-PBF are still limited. This work reviews the literature on the in situ detection, generation, effects, and countermeasures of spatter in L-PBF. It is expected to pave the way towards a novel generation of highly efficient and intelligent L-PBF systems.
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| 6. |
- Zheng, Hui, et al.
(författare)
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Exact Line-of-Sight Probability for Channel Modeling in Typical Indoor Environments
- 2018
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 17:7, s. 1359-1362
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Tidskriftsartikel (refereegranskat)abstract
- The probability of line-of-sight (LOS) propagation is crucial for channel modeling and small-cell network evaluation. In this letter, by taking the layout of building structures into account, an analytical LOS probability model is proposed for typical indoor scenarios, which have rectangular rooms and corridors. The proposed model is validated through Monte Carlo simulations. Numerical results show that the proposed model estimates the network performance accurately and efficiently.
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| 7. |
- Zheng, Hui, et al.
(författare)
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The Analysis of Indoor Wireless Communications by a Blockage Model in Ultra-Dense Networks
- 2018
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Ingår i: IEEE Vehicular Technology Conference. - 1550-2252. ; 2018-August
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Konferensbidrag (refereegranskat)abstract
- In indoor environments, the performance of ultra-dense cellular networks is significantly affected by blockages, especially for ultra-high frequencies. However, previous works either ignore or simplify such effects for analysing the networks. On the basis of stochastic geometry, this paper proposes a mathematically tractable approach to analyse ultra-dense networks in indoors, which considers both the effects of wall blockages and the distance-based path loss. The effects of wall blockages are firstly investigated by modelling the walls as a Boolean scheme of straight lines on a finite plane. Then a path loss model incorporating both the blockage-based and distance-based path loss is applied to analyse the performance of indoor networks. Finally, the analytical result is validated by comparing it with Monte Carlo simulations. The simulation results also show that the optimum transmitter density is finite for indoor ultra-dense networks with blockages, although the coverage probability benefits from the increase of transmitter density.
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| 8. |
- Chen, Zhang, et al.
(författare)
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Making monolayer graphene photoluminescent by electron-beam-activated fluorination approach
- 2023
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Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 608
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Tidskriftsartikel (refereegranskat)abstract
- The past one and half decades have witnessed a tremendous development of graphene electronics, and the key to the success of graphene is its exceptional properties. The lacking of an inherent bandgap endows graphene with excellent electrical properties but considerably limits its applications in light-emitting and high-performance graphene-based devices. Herein, an approach for the direct writing of semiconducting and photoluminescent fluorinated graphene (C4F) patterns on monolayer graphene by an optimized electron-beam-activated fluorination technique is reported. A series of characterization approaches, such as atomic force microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy were used to demonstrate the successful preparation of C4F for maskless lithography. Specially, a sharp and strong photoluminescence located at the purple light range of ∼380 nm was observed in C4F, demonstrating a desirable semiconducting nature, and the bandgap was further confirmed by follow-up electrical measurements, where the C4F filed-effect transistor exhibited a p-type semiconductor behavior and significantly enhanced on/off ratio. Therefore, this work provides a novel technique for the fabrication of graphene devices for promising electronic and optoelectronic applications, but also opens a route towards the tailoring and engineering of electronic properties of graphene.
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| 9. |
- Hu, R., et al.
(författare)
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Biofeedback neuromuscular electrical stimulation front-end for dysphagia treatment
- 2014
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Ingår i: IEEE 2014 Biomedical Circuits and Systems Conference, BioCAS 2014 - Proceedings. - : IEEE Press. - 9781479923465 ; , s. 612-615
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Konferensbidrag (refereegranskat)abstract
- A dedicated front-end for biofeedback neuromuscular electrical stimulation (NESM) system is proposed. For controllable dysphagia treatment, the integrated circuit (IC) provides a stimulator front-end with programmable stimulation parameters (2μA-1mA current amplitude, DC-2KHz frequency, and variable duty cycle) and an electromyogram/impedance (EMG/ETI) readout front-end with programmable gain and bandwidth (42-80dB, 0.1Hz-1.2KHz) for biofeedback. Area-efficient, low-power but high precision current controlling is achieved by inducing the sigma-delta modulator technique in the stimulation channel. The measured impedance and EMG signal are used to determine the stimulation parameters, enabling a closed loop optimized treatment. The proposed front-end is fabricated in a 0.18 μm standard CMOS process technology and dissipates a peak power of 2.3 mW at the supply voltage of 1.8 V. Measurement results on a live person are also provided to validate the system's effectiveness.
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| 10. |
- Jarfors, Anders E.W. 1963-, et al.
(författare)
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On the In-Die Conditions and Process Parameter Settings in Indirect Squeeze Casting
- 2022
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Ingår i: Technologies. - : MDPI. - 2227-7080. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- The current study investigated the relationship between the process settings and in-die conditions to understand the transitions between the different filling stages and the final pressure settings in indirect squeeze casting. A pressure sensor was placed in the die cavity to indirectly measure the evolution of pressure over time and monitor the filling process to study the in-die conditions. The pressure-time profile was analysed, and the maximum pressure and acceleration of the pressure were investigated empirically. The main conclusion of this paper is that the use of increasing intensification pressures is positive for the casting soundness. However, it must be stressed that there is a strong effect from the intensification pressure on the acceleration that has a far more reaching influence than the actual speed setting. A direct practical outcome is that a high intensification pressure has a more substantial effect than the second stage fill speed. This translates directly to a possibility of reducing the second stage fill speed to stabilise the fill front. Furthermore, this also pinpoints the need for improvements in hydraulics system designs to decouple the intensification pressure from the filling piston motion control.
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