| 1. |
- Gong, Chensheng, et al.
(författare)
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Upconversion enhancement by a dual-resonance all-dielectric metasurface
- 2019
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Ingår i: Nanoscale. - : ROYAL SOC CHEMISTRY. - 2040-3364 .- 2040-3372. ; 11:4, s. 1856-1862
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Tidskriftsartikel (refereegranskat)abstract
- Upconversion nanoparticles (UCNPs) have drawn much attention in the past decade due to their superior physicochemical features and great potential in biomedical and biophotonic studies. However, their low luminescence efficiency often limits their applications. Here, we demonstrated a dual-resonance all-dielectric metasurface to enhance the signals emitted by upconversion nanoparticles (NaYF4:Yb/Tm). An averaged upconversion signal enhancement of around 400 times is detected experimentally. The electric and magnetic dipole resonances of the metasurface are designed to enhance the local excitation field and the quantum efficiency of the upconversion nanoparticles, respectively. Furthermore, the collection efficiency is enhanced due to the directional emission of the UCNPs on the metasurface. Our approach provides a powerful tool to extend the sensing application potential of upconversion nanoparticles.
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| 2. |
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| 3. |
- He, Wang, et al.
(författare)
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RF Compliance Study of Temperature Elevation in Human Head Model Around 28 GHz for 5G User Equipment Application : Simulation Analysis
- 2018
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Ingår i: IEEE Access. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2169-3536. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- The crowdedness of current cellular bands and the demand for higher transmission speed prompt the use of the millimeter-wave spectrum for the next-generation mobile communication. In the millimeter-wave frequencies, the dosimetric quantity for human exposure to electromagnetic fields changes from the specific absorption rate to incident power density. In this paper, we used 28-GHz beam-steering patch arrays, a dipole antenna, and plane waves to investigate the temperature elevation in a multi-layer model of human head and its correlation with power density metrics. The power density averaged over one square-centimeter in free space and the peak temperature elevation in tissue at 28 GHz have good correlation. The peak temperature elevation indicated by the power density averaged one square-centimeter also agrees well with the peak temperature elevation induced by the plane waves. The results show that the averaging area of a few square-centimeters may be a good candidate for the spatial-average power density. The findings provide valuable input to the ongoing revision and updating of relevant safety standards and guidelines.
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| 4. |
- Hui, L., et al.
(författare)
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A small printed antenna for bluetooth wireless communication
- 2015
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Konferensbidrag (refereegranskat)abstract
- A small printed inverted-F antenna, operating at 2.44 GHz, for Bluetooth system is designed in this paper. The RF system diagram and PCB layout are drawn by Cadence Allegro. The small printed antenna, integrated in the PCB, is modeled by HFSS and both the simulation and experimental results verify of its suitability for the Bluetooth wireless communication.
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| 5. |
- Li, Borui, et al.
(författare)
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Investigation of light trapping effect in hyperbolic metamaterial slow-light waveguides
- 2015
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Ingår i: APPLIED PHYSICS EXPRESS. - 1882-0778. ; 8:8
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Tidskriftsartikel (refereegranskat)abstract
- A hyperbolic metamaterial waveguide can reduce the group velocity of light down to zero by tuning a waveguide structure. The light trapping capability of a tapered hyperbolic metamaterial waveguide is comprehensively studied in this work. Although a pulse of light cannot be trapped forever in such a waveguide, the duration that light remains trapped can be flexibly prolonged by adjusting the volume filling ratio of the metamaterial or the material dispersion, in order to achieve a sufficiently long trapping time for practical applications.
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| 6. |
- Liu, C., et al.
(författare)
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A printed inverted-F MIMO antenna for WiFi applications
- 2015
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Konferensbidrag (refereegranskat)abstract
- A wideband printed inverted-F MIMO antenna designed for WiFi applications is presented. The proposed MIMO antenna which consists of two modified inverted-F antenna elements and an isolated structure is designed on a two-layer FR-4 printed circuit board (PCB). The occupied antenna area has the dimensions of 98mm ∗98mm and the thickness of substrate is 0.8 mm. The functions of antenna's structure and the effects of some parameters on the antenna performance are discussed in this paper. The designed MIMO antenna system has a wide bandwidth measured more than 0.78GHz (2.25-3.03 GHz) at the reflection coefficient level below-10 dB. Due to a folded isolated structure, in the whole measured frequency band the mutual coupling is lower than-15dB, the MIMO antenna has good isolation. On the xy and yz planes the max gain of MIMO antenna can achieve 3dB. The parameters of simulating and testing are shown that this MIMO antenna has good performance for WiFi applications.
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| 7. |
- Shi, Kezhang, et al.
(författare)
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Colossal Enhancement of Near-Field Thermal Radiation Across Hundreds of Nanometers between Millimeter-Scale Plates through Surface Plasmon and Phonon Polaritons Coupling
- 2019
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Ingår i: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 19:11, s. 8082-8088
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Tidskriftsartikel (refereegranskat)abstract
- Coupling modes between surface plasmon polaritons (SPPs) and surface phonon polaritons (SPhPs) play a vital role in enhancing near-field thermal radiation but are relatively unexplored, and no experimental result is available. Here, we consider the NFTR enhancement between two identical graphene-covered SiO2 heterostructures with millimeter-scale surface area and report an experimentally record-breaking, similar to 64-fold enhancement compared to blackbody (BB) limit at a gap distance of 170 nm. The energy transmission coefficient and radiation spectra show that the physical mechanism behind the colossal enhancement is the coupling between the surface plasmon and phonon polaritons.
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| 8. |
- Shi, K. Z., et al.
(författare)
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Near-field heat transfer between graphene-Si grating heterostructures with multiple magnetic-polaritons coupling
- 2019
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier. - 0017-9310 .- 1879-2189. ; 134, s. 1119-1126
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Tidskriftsartikel (refereegranskat)abstract
- Near-field thermal radiation (NFTR) between two graphene-covered Si grating (G/Si grating) heterostructures consisting of multilayered G/Si grating cells is investigated, in comparison with that between single-G/Si-grating-cell structures. The calculations are based on the scattering theory utilizing rigorous coupled-wave analysis (RCWA). It is found that strong magnetic polaritons (MPs) can be induced in the single G/Si grating cell, and coupling of multiple MPs can be observed in multilayered G/Si grating heterostructures, which leads to a broader band of high photon-tunnelling probabilities in the phase space. As a result, when the thickness of each grating layer is fixed, the heat flux of the 4-G/Si grating heterostructures, with chemical potential μ = 0.1 eV and grating period L x = 80 nm, is 1.65- and 9.12-fold larger than those of the 1-G/Si grating and only Si grating structures at d = 100 nm, respectively. When the total thickness of the entire G/Si grating heterostructure is fixed, the 1-G/Si grating model performs better than 2- or 4-G/Si grating models because higher loss inherited from additional graphene sheets would reduce the momenta of the near-unity energy transmission coefficient in the k-space.
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| 9. |
- Xing, Fuqiang, et al.
(författare)
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1800MHz Microwave Induces p53 and p53-Mediated Caspase-3 Activation Leading to Cell Apoptosis In Vitro
- 2016
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Ingår i: PLOS ONE. - : PUBLIC LIBRARY SCIENCE. - 1932-6203. ; 11:9
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies have reported that exposure of mammalian cells to microwave radiation may have adverse effects such as induction of cell apoptosis. However, the molecular mechanisms underlying microwave induced mammalian cell apoptosis are not fully understood. Here, we report a novel mechanism: exposure to 1800MHz microwave radiation induces p53-dependent cell apoptosis through cytochrome c-mediated caspase-3 activation pathway. We first measured intensity of microwave radiation from several electronic devices with an irradiation detector. Mouse NIH/3T3 and human U-87 MG cells were then used as receivers of 1800MHz electromagnetic radiation (EMR) at a power density of 1209 mW/m(2). Following EMR exposure, cells were analyzed for viability, intracellular reactive oxygen species (ROS) generation, DNA damage, p53 expression, and caspase-3 activity. Our analysis revealed that EMR exposure significantly decreased viability of NIH/3T3 and U-87 MG cells, and increased caspase-3 activity. ROS burst was observed at 6 h and 48 h in NIH/3T3 cells, while at 3 h in U-87 MG cells. Hoechst 33258 staining and in situ TUNEL assay detected that EMR exposure increased DNA damage, which was significantly restrained in the presence of N-acetyl-L-cysteine (NAC, an antioxidant). Moreover, EMR exposure increased the levels of p53 protein and p53 target gene expression, promoted cytochrome c release from mitochondrion, and increased caspase-3 activity. These events were inhibited by pretreatment with NAC, pifithrin-alpha (a p53 inhibitor) and caspase inhibitor. Collectively, our findings demonstrate, for the first time, that 1800MHz EMR induces apoptosis-related events such as ROS burst and more oxidative DNA damage, which in turn promote p53-dependent caspase-3 activation through release of cytochrome c from mitochondrion. These findings thus provide new insights into physiological mechanisms underlying microwave-induced cell apoptosis.
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| 10. |
- Xu, Bo, et al.
(författare)
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Analysis of Impacts of Expected RF EMF Exposure Restrictions on Peak EIRP of 5G User Equipment at 28 GHz and 39 GHz Bands
- 2019
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Ingår i: IEEE Access. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 2169-3536. ; 7, s. 20996-21005
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Tidskriftsartikel (refereegranskat)abstract
- Above 6 GHz, radio frequency (RF) electromagnetic field (EMF) exposure from the mobile communication user equipment (UE) should be assessed in terms of incident power density, rather than specific absorption rate as below 6 GHz. Such regulatory RF EMF restrictions will constrain the transmit power of the UE and its peak equivalent isotropically radiated power (EIRP). This paper provides an analysis of the peak EIRP levels of UE containing code-book-based beamforming arrays at 28 GHz and 39 GHz. Different types of antenna elements, incremental element spacing, 4- and 8-element array configurations, and realistic housing integration are considered. The analysis and results show that in realistic housing integration, the 3GPP requirements on minimum peak EIRP can be generally met under the expected RF EMF exposure restrictions.
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