| 1. |
- You, Xiaohu, et al.
(författare)
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Towards 6G wireless communication networks: vision, enabling technologies, and new paradigm shifts
- 2021
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Ingår i: Science China Information Sciences. - : Science Press. - 1674-733X .- 1869-1919. ; 64:1
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Forskningsöversikt (refereegranskat)abstract
- The fifth generation (5G) wireless communication networks are being deployed worldwide from 2020 and more capabilities are in the process of being standardized, such as mass connectivity, ultra-reliability, and guaranteed low latency. However, 5G will not meet all requirements of the future in 2030 and beyond, and sixth generation (6G) wireless communication networks are expected to provide global coverage, enhanced spectral/energy/cost efficiency, better intelligence level and security, etc. To meet these requirements, 6G networks will rely on new enabling technologies, i.e., air interface and transmission technologies and novel network architecture, such as waveform design, multiple access, channel coding schemes, multi-antenna technologies, network slicing, cell-free architecture, and cloud/fog/edge computing. Our vision on 6G is that it will have four new paradigm shifts. First, to satisfy the requirement of global coverage, 6G will not be limited to terrestrial communication networks, which will need to be complemented with non-terrestrial networks such as satellite and unmanned aerial vehicle (UAV) communication networks, thus achieving a space-air-ground-sea integrated communication network. Second, all spectra will be fully explored to further increase data rates and connection density, including the sub-6 GHz, millimeter wave (mmWave), terahertz (THz), and optical frequency bands. Third, facing the big datasets generated by the use of extremely heterogeneous networks, diverse communication scenarios, large numbers of antennas, wide bandwidths, and new service requirements, 6G networks will enable a new range of smart applications with the aid of artificial intelligence (AI) and big data technologies. Fourth, network security will have to be strengthened when developing 6G networks. This article provides a comprehensive survey of recent advances and future trends in these four aspects. Clearly, 6G with additional technical requirements beyond those of 5G will enable faster and further communications to the extent that the boundary between physical and cyber worlds disappears.
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| 2. |
- Wang, Xiaoyu, et al.
(författare)
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Guest Editorial: Modeling and Simulation Methods for Analysis and Design of Advanced Energy Conversion Systems
- 2020
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Ingår i: IEEE Transactions on Energy Conversion. - 1558-0059 .- 0885-8969. ; 35:1, s. 309-311
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The papers in this special section examine modeling and simulation methods for the analysis and design of advanced energy conversion systems. Energy conversion lies aEnergyveral fronts including materials, conversion methods, power electronics, and controls have created new opportunities for efficient energy conversion from both the conventional and new sources of energy. Our urgent need to solve many critical problems with regards to the sustainability and security of our energy system as well as the ever-increasing environmental challenges facing humanity have further spurred unprecedented opportunities for creation of innovative solutions to address these challenges.
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| 3. |
- Fan, Liangdong, 1985-, et al.
(författare)
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High performance transition metal oxide composite cathode for low temperature solid oxide fuel cells
- 2012
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Ingår i: Journal of Power Sources. - : Elsevier BV. - 0378-7753 .- 1873-2755. ; 203:1, s. 65-71
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Tidskriftsartikel (refereegranskat)abstract
- Low temperature solid oxide fuel cells (SOFCs) with metal oxide composite cathode on the ceria–carbonate composite electrolyte have shown promising performance. However, the role of individual elements or compound is seldom investigated. We report here the effect of the ZnO on the physico-chemical and electrochemical properties of lithiated NiO cathode. The materials and single cells are characterized by X-ray diffraction, scanning electron microscopy, DC polarization electrical conductivity, electrochemical impedance spectroscopy and fuel cell performance. The ZnO modified lithiated NiO composite materials exhibit smaller particle size and lower electrical conductivity than lithiated NiO. However, improved electro-catalytic oxygen reduction activity and power output are achieved after the ZnO modification. A maximum power density of 808 mW cm−2 and the corresponding interfacial polarization resistance of 0.22 Ω cm2 are obtained at 550 °C using ZnO modified cathode and 300 μm thick composite electrolyte. The single cell keeps reasonable stability over 300 min at 500 °C. Thus, ZnO modified lithiated NiO is a promising cathode candidate for low temperature SOFCs.
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| 4. |
- Wang, Shuai, et al.
(författare)
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Size-control growth of thermally stable Au nanoparticles encapsulated within ordered mesoporous carbon framework
- 2016
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Ingår i: Cuihuà xuébào. - 0253-9837 .- 1872-2067. ; 37:1, s. 61-72
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Tidskriftsartikel (refereegranskat)abstract
- Simultaneously controlling the size of Au nanoparticles and immobilizing their location to specific active sites while hindering migration and sintering at elevated temperatures is a current challenge within materials chemistry. Typical methods require the use of protecting agents to control the properties of Au nanoparticles and therefore it is difficult to decouple the influence of the protecting agent and the support material. By functionalizing the internal surface area of mesoporous carbon supports with thiol groups and implementing a simple acid extraction step, we are able to design the resulting materials with precise control over the Au nanoparticle size without the need for the presence of any protecting group, whilst simultaneously confining the nanoparticles to within the internal porous network. Monodispersed Au nanoparticles in the absence of protecting agents were encapsulated into ordered mesoporous carbon at various loading levels via a coordination-assisted self-assembly approach. The X-ray diffractograms and transmission electron microscopy micrographs show that the particles have controlled and well-defined diameters between 3 and 18 nm at concentrations between 1.1 and 9.0 wt%. The Au nanoparticles are intercalated into the pore matrix to different degrees depending on the synthesis conditions and are stable after high temperature treatment at 600 degrees C. N-2 adsorption-desorption isotherms show that the Au functionalized mesoporous carbon catalysts possess high surface areas (1269-1743 m(2)/g), large pore volumes (0.78-1.38 cm(3)/g) and interpenetrated, uniform bimodal mesopores with the primary larger mesopore lying in the range of 3.4-5.7 nm and the smaller secondary mesopore having a diameter close to 2 nm. X-ray absorption near extended spectroscopy analysis reveals changes to the electronic properties of the Au nanoparticles as a function of reduced particle size. The predominant factors that significantly determine the end Au nanoparticle size is both the thiol group concentration and subjecting the as-made materials to an additional concentrated sulfuric acid extraction step.
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| 5. |
- Ning, Yuping, et al.
(författare)
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Optical simulation and preparation of novel Mo/ZrSiN/ZrSiON/SiO2 solar selective absorbing coating
- 2017
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 167, s. 178-183
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Tidskriftsartikel (refereegranskat)abstract
- A novel Mo/ZrSiN/ZrSiON/SiO2 solar selective absorbing coating has been investigated, which was prepared by magnetron sputtering on stainless steel substrate. A high solar absorptance of 0.94 and a low thermal emittance of 0.06 at 25 degrees C were achieved. By proportionally decreasing the thicknesses of the ZrSiN, ZrSiON and SiO2 layers, the thermal emittance at 500 degrees C was decreased significantly from 0.19 to 0.12 (Delta epsilon = 0.07) while keeping the solar absorptance unchanged. The coating also showed high thermal stability at 500 degrees C in vacuum, implying that it is a promising candidate for high temperature concentrated solar power (CSP) applications.
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| 6. |
- Yin, Xiaojun, et al.
(författare)
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In-depth comparison of methanol port and direct injection strategies in a methanol/diesel dual fuel engine
- 2023
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 241
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Tidskriftsartikel (refereegranskat)abstract
- For methanol/diesel dual-fuel combustion, there are two different methanol injection implementations: port injection into the intake manifold and direct injection into cylinder. In this work, an experimental comparison was conducted for the two methanol injection strategies to study the effects of the methanol-energy-substation ratio (ESR) and diesel injection timing on the fuel-air mixing and combustion characteristics. The results showed that the ignition delay was increased with ESR due to the cooling effect of methanol evaporation in the cylinder. The combustion duration under methanol direct injection condition was much shorter than that of the methanol port injection strategy. The methanol direct injection strategy had a more controllable and stable heat release than that of methanol port injection strategy. The maximum ESR could reach up to 96.0% in the methanol direct injection strategy. The methanol direct injection strategy had a better fuel economy, and its maximum indicated thermal efficiency could reach up to 41.55% at 50% ESR. The methanol direct injection strategy yielded higher NOx emissions than that with the port injection strategy, accompanied by a mild increase of soot emissions. Compared with methanol port injection, the methanol direct injection strategy exhibits lower CO emissions, however, it suffers from higher HC emissions.
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| 7. |
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| 8. |
- Jussi, Johnny, 1989-
(författare)
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Fluorescent quantum dots and graphene-based sensors for forensic applications
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A key emerging concept within the forensic sciences today areportable measurementdevices, where a much more efficient usage of the resources involved with crime-solving is possible if confirmatory measurements can be realised directly at a crimescene with such devices. Today, the majority of the presently used methods duringcriminal investigation at a crime scene involves measurements of a presumptivenature, which is a vital tool as it enables the screening of samples. In this thesis,the overarching goal is the development of tool kits for the analysis of biosampleson-site at a crime scene. This is mainly investigated through two routes: theusage of Quantum Dots (QDs) as a recognition element in sensory applications andfabrication of a graphene-based device for the detection of illicit drugs.The investigations conducted for the studies presented in this thesis focuses onsensory applications with a forensic detection scheme in mind: study I reveals in-trinsic properties of QDs to better understand sensing mechanisms upon bindinginteractions; study II demonstrates the fabrication of a graphene-based device forthe detection of illicit drugs; study III showcases the functionalised and bioconju-gated of QDs for a specific investigation into a biological process; study IV furtherthe investigation into the possible side-effects of QDs on biological specimens.In study I we numerically and experimentally investigate the intrinsic blinkingcharacteristics of CdSe-CdS/ZnS QDs. This includes a thorough examination of theexperimental parameters of the measurement setup: the bin time and excitationpower. Different mechanisms between the off- and on-state probability distributionsare found, wherein the on-state follows the random telegraph signal theory and theoff-state follows the inverse power law distribution.In study II, the detection of illicit drugs (amphetamine and cocaine) is achievedthrough graphene-based sensors processed to contain metal electrodes with superioradhesion and low contact resistance. The construction of a microfluidic system isfurther realised for a detection of molecules based on non-covalent interactions.With this system, a wavelength-dependent photoactivity for amphetamine and arange of its chemical analogs is demonstrated. A molecule dependent interactionwith the graphene surface is shown of the graphene surface either in the form ofp-doping (cocaine) or n-doping (amphetamine).Study III investigates the endocytic pathway of the vascular cell adhesionmolecule 1 (VCAM1) in Human Umbilical Vein Endothelial Cells (HUVECs) in-iiiivABSTRACTduced by Tumor Necrosis Factorα(TNFα) with the usage of 3-Mercaptopropionicacid coated (3MPA)-QDs and 5-Carboxyfluorescein (5FAM) functionalised and la-belled with VCAM1 binding peptides, respectively. Internalisation of the VCAM1molecules into lysosomes is shown with light microscopy through observations ofdifferent pathways of the 5FAM labelled peptides and functionalised QDs.In study IV we investigate the adverse effects of 3MPA-QDs on the humanairway epithelium by an examination of the calcium response in lung cells upon astimulation with QDs. The cellular response to the deposition of QDs is observedwith light microscopy and electrical measurements as a global increase of Ca2+in the epithelial layers and a transient decrease in the electrical response. Theseobservations imply that the influx of calcium caused by the QD deposition is inducedby mechanical stressIn an additional ongoing study, the age determination of dried blood spotsare investigated with the usage of protein markers commonly found in the blood.Human serum (HS) is spiked with a marker of interest to mimic those of normallevels in adult human males. After which the HS is allowed to undergo an ageingprocess in a 96 well plate and further analysed in terms of the enzymatic activitywith commercially available kits. The preliminary test results show that there is ameasurable change of activity dependenton the utilised marker that may act as abasis for the age determination of dried blod spots
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| 9. |
- Ning, Yuping, et al.
(författare)
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Effects of substrates, film thickness and temperature on thermal emittance of Mo/substrate deposited by magnetron sputtering
- 2016
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Ingår i: Vacuum. - : Elsevier BV. - 0042-207X .- 1879-2715. ; 128, s. 73-79
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Tidskriftsartikel (refereegranskat)abstract
- The thermal emittance of the Mo film, as an IR-refiector in solar selective absorbing coatings, is the most important property. The effects of the substrate material, the substrate surface roughness, the film thickness and the temperature on the thermal emittance of the Mo/substrate have been investigated. A series of Mo films with increasing film thickness were deposited on two types of substrate materials (glass and stainless steel). A saturated Mo thickness of 50 nm is found to produce the lowest thermal emittance. The thermal emittance of the Mo film is reduced by decreasing the substrate surface roughness. The emittance of the optimal Mo film remains 0.05 from 25 degrees C to 400 degrees C, which can meet the optical requirements for the IR-reflector.
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| 10. |
- Ning, Yuping, et al.
(författare)
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Investigation on low thermal emittance of Al films deposited by magnetron sputtering
- 2016
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Ingår i: Infrared physics & technology. - : Elsevier BV. - 1350-4495 .- 1879-0275. ; 75, s. 133-138
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Tidskriftsartikel (refereegranskat)abstract
- A series of Al films with different thicknesses were deposited on polished stainless steel by direct current (DC) magnetron sputtering as a metal IR-reflector layer in solar selective absorbing coating (SSAC). The effects of the film thickness and the temperature on the thermal emittance of the Al films are studied. An optimal thickness 78 nm of the Al film for the lowest total thermal emittance is obtained. The thermal emittance of the optimal Al film keeps close to 0.02 from 25 degrees C to 400 degrees C, which are low enough to satisfy the optical requirements in SSAC. The optical constants of the AI film are deduced by fitting the reflectance and transmission spectra using SCOUT software.
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