| 1. |
- Jiang, Tao, et al.
(författare)
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Investigation of DC-Biased Optical OFDM With Precoding Matrix for Visible Light Communications : Theory, Simulations, and Experiments
- 2018
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Ingår i: IEEE Photonics Journal. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1943-0655. ; 10:5
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Tidskriftsartikel (refereegranskat)abstract
- Orthogonal frequency-division-multiplexing (OFDM) technology is widely used in visible light communication (VLC) to achieve high data rate transmission. However, the traditional direct-current (DC)-biased optical OFDM (DCO-OFDM) VLC systems suffer from the high peak-to-average power ratio (PAPR) which causes signal clipping distortion, and, thus, performance degradation. Furthermore, severe high-frequency fading due to the limited system bandwidth results in poor bit error rate (BER) performance. Precoding matrix (PM) techniques have been proposed to enhance the performance of VLC OFDM transmission, but a little or no work has been carried out in investigating the theory of PM used in OFDM VLC systems. In this paper, we aim to reveal the theory of PM-DCO-OFDM for a VLC system. To figure out the intrinsic laws of a PM method, we investigate the principles of PAPR reduction, clipping distortion optimization, and signal-to-noise ratio (SNR) distribution equalization. Based on the analysis of PAPR, we theoretically proved the simplicity of PM as a method to reduce the possibility of high PAPR by improving the autocorrelation performance of input symbols. The clipping distortion could be improved due to the reduction of high PAPR. Moreover, the relatively uniform SNR distribution can be achieved by PM through equalizing the clipping and channel noise, which is beneficial to improve the BER performance in high-frequency constrained systems. However, the PM method used in a DCO-OFDM VLC system should consider the transmitting power, modulation format, and transmission distance as a whole to achieve the transmission performance improvement. The simulation results demonstrate the complementary cumulative distribution function of PAPR can be reduced similar to 3 dB, while the performance of clipping distortion power and clipping error probability are significantly improved. Furthermore, experiment is carried out with results showing that the PM method can improve the BER performance in the case that VLC OFDM transmission has enough transmitting power, but with the low transmitting power, the PM also can damage the BER performance. The simulation and experiment results are consistent with our theoretical analysis.
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| 2. |
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| 3. |
- Feng, Zhenhua, et al.
(författare)
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Digital Domain Power Division Multiplexing DDO-OFDM Transmission with Successive Interference Cancellation
- 2016
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Ingår i: 2016 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO). - Washington, D.C. : IEEE conference proceedings.
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Konferensbidrag (refereegranskat)abstract
- Two independent 2.5-Gb/s DDO-OFDM signals are simultaneously transmitted over 25km SMF using digital domain power division multiplexing and successive interference cancellation. With optimized power division ratio and enhanced SD-FEC, the spectral efficiency can be doubled.
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| 4. |
- Feng, Zhenhua, et al.
(författare)
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Multicore-Fiber-Enabled WSDM Optical Access Network With Centralized Carrier Delivery and RSOA-Based Adaptive Modulation
- 2015
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Ingår i: IEEE PHOTONICS JOURNAL. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 7:4
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Tidskriftsartikel (refereegranskat)abstract
- We proposed and experimentally demonstrated a wavelength-space division multiplexing (WSDM) optical access network architecture with centralized optical carrier delivery utilizing multicore fibers (MCFs) and adaptive modulation based on reflective semiconductor amplifier (RSOA). In our experiment, five of the outer cores are used for undirectional downstream (DS) transmission only, whereas the remaining outer core is utilized as a dedicated channel to transmit upstream (US) signals. Optical carriers for US are delivered from the optical line terminal (OLT) to the optical network unit (ONU) via the inner core and then transmitted back to the OLT after amplification and modulation by the RSOA in the colorless ONU side. The mobile backhaul (MB) service is also supported by the inner core. Wavelengths used in US transmission should be different from that of the MB in order to avoid the Rayleigh backscattering effect in bidirectional transmission. With quadrature phase-shift keying-orthogonal frequency-division multiplexing (QPSK-OFDM) modulation format, the aggregation DS capacity reaches 250 Gb/s using five outer cores and ten wavelengths, and it can be further scaled to 1 Tb/s using 20 wavelengths modulated with 16 QAM-OFDM. For US transmission, 2.5 Gb/s QPSK-OFDM transmission can be achieved just using a low-bandwidth RSOA, and adaptive modulation is applied to the RSOA to further enhance the US data rate to 3.12 Gb/s. As an emulation of high-speed MB transmission, 48 Gb/s inphase and quadrature (IQ) modulated popularization division multiplexing (PDM)-QPSK signal is transmitted in the inner core of MCF and coherently detected in the OLT side. Both DS and US optical signals exhibit acceptable performance with sufficient power budget.
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| 5. |
- Feng, Zhenhua, et al.
(författare)
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Performance-Enhanced Direct Detection Optical OFDM Transmission With CAZAC Equalization
- 2015
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Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 27:14, s. 1507-1510
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Tidskriftsartikel (refereegranskat)abstract
- Direct detection optical orthogonal frequency division multiplexing (DDO-OFDM) transmission with constant amplitude zero autocorrelation (CAZAC) sequence equalization is proposed and experimentally demonstrated. Simulation results show that more than 2-dB peak-to-average power ratio (PAPR) reduction can be realized using CAZAC equalization, and 50-km standard single mode fiber (SSMF) transmission of 4.11-Gb/s QPSK-OFDM can be achieved with bit-error rate (BER) under forward error correction limit. Transmission performance of QPSK-based DDO-OFDM system is analyzed in both OB2B configuration and fiber link with and without CAZAC equalization. More than 2.5-dB optical receiver sensitivity improvements can be obtained thanks to the PAPR reduction enjoyed by CAZAC equalization. Signal-to-noise ratio for every subcarrier derived from error vector magnitude is estimated and its flatness is confirmed to be much improved with CAZAC equalization. The performance improvements brought by CAZAC equalization can be extended to other modulation formats, and 8.22-Gb/s 16-quadratic-amplitude modulation-OFDM signals transmission using CAZAC equalization is demonstrated with over 1.5 dB enhancement in receiver sensitivity.
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| 6. |
- Feng, Zhenhua, et al.
(författare)
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SNR equalized optical direct-detected OFDM transmission with CAZAC equalization
- 2015
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Ingår i: CLEO. - : Optica Publishing Group.
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Konferensbidrag (refereegranskat)abstract
- 50Km SSMF optical direct-detected OFDM transmission with Constant Amplitude Zero Auto Correlation Sequence (CAZAC) equalization is experimentally demonstrated with over 15dB power budget. 2.5dB enhancement in sensitivity has been achieved simultaneously with 3dB PAPR suppression.
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| 7. |
- Fornell, Anna, et al.
(författare)
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Fabrication of Silicon Microfluidic Chips for Acoustic Particle Focusing Using Direct Laser Writing
- 2020
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Ingår i: Micromachines. - : MDPI AG. - 2072-666X. ; 11:2
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Tidskriftsartikel (refereegranskat)abstract
- We have developed a fast and simple method for fabricating microfluidic channels in silicon using direct laser writing. The laser microfabrication process was optimised to generate microfluidic channels with vertical walls suitable for acoustic particle focusing by bulk acoustic waves. The width of the acoustic resonance channel was designed to be 380 µm, branching into a trifurcation with 127 µm wide side outlet channels. The optimised settings used to make the microfluidic channels were 50% laser radiation power, 10 kHz pulse frequency and 35 passes. With these settings, six chips could be ablated in 5 h. The microfluidic channels were sealed with a glass wafer using adhesive bonding, diced into individual chips, and a piezoelectric transducer was glued to each chip. With acoustic actuation at 2.03 MHz a half wavelength resonance mode was generated in the microfluidic channel, and polystyrene microparticles (10 µm diameter) were focused along the centre-line of the channel. The presented fabrication process is especially interesting for research purposes as it opens up for rapid prototyping of silicon-glass microfluidic chips for acoustofluidic applications.
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| 8. |
- Fornell, Anna, et al.
(författare)
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Improved acoustic particle enrichment in droplets by optimising the droplet split design
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Droplet microfluidics has emerged as a valuable platform for miniaturisation of biological experiments on-chip. In droplet microfluidic chips monodisperse droplets containing cells or other bioparticles can be generated at high throughput, and each droplet can be used as an isolated reaction chamber for individual measurements. A general trend in droplet microfluidics is reducing the size of the droplets, but the challenge is maintaining the particles in the droplets after splitting. We have previously reported on an acoustofluidic chip where bulk acoustic waves were used to control particle positioning in a trident-shaped droplet split. However, the reported particle enrichment was modest (3-fold), and the aim of this study is to increase the particle enrichment by optimising the droplet split design. With our new optimised droplet split we show up to 16.7-fold particle enrichment with high particle recovery.
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| 9. |
- Fornell, Anna, et al.
(författare)
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Optimisation of the droplet split design for high acoustic particle enrichment in droplet microfluidics
- 2020
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Ingår i: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 226
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Tidskriftsartikel (refereegranskat)abstract
- We have characterised three droplet split designs for acoustic particle enrichment in water-in-oil droplets. The microfluidic channel design included a droplet generation junction, acoustic focusing channel and a trident-shaped droplet split. The microfluidic channels were dry-etched in silicon and sealed with glass lids by anodic bonding. To each microfluidic chip a piezoelectric transducer was glued, and at actuation of the transducer at the fundamental resonance frequency of the acoustic focusing channel (1.91–1.93 MHz), a half wavelength standing wave field was created between the channel walls. The acoustic force focused the encapsulated particles (3.2 μm, 4.8 μm and 9.9 μm diameter polystyrene microbeads) to the centre-line of the droplets, and when the droplets reached the droplet split the particles were directed into the centre daughter droplets. The results show that the design of the droplet split and the flow ratio between the centre and side outlet channels are the main factors that affect the particle enrichment and particle recovery in the centre daughter droplets. The highest particle enrichment was achieved in the droplet split design having the smallest centre channel (38 μm wide). Using this microfluidic chip design, we demonstrate up to 16.7-fold enrichment of 9.9 μm diameter polystyrene microbeads in the centre daughter droplets. This is almost three times higher particle enrichment than what has previously been presented using other intra-droplet particle enrichment techniques. Moreover, the acoustic technique is label-free and biocompatible.
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| 10. |
- Gu, Peng, et al.
(författare)
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A metabolite from commensal Candida albicans enhances the bactericidal activity of macrophages and protects against sepsis
- 2023
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Ingår i: Cellular & Molecular Immunology. - London : Nature Publishing Group. - 1672-7681 .- 2042-0226. ; 20:10, s. 1156-1170
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Tidskriftsartikel (refereegranskat)abstract
- The gut microbiome is recognized as a key modulator of sepsis development. However, the contribution of the gut mycobiome to sepsis development is still not fully understood. Here, we demonstrated that the level of Candida albicans was markedly decreased in patients with bacterial sepsis, and the supernatant of Candida albicans culture significantly decreased the bacterial load and improved sepsis symptoms in both cecum ligation and puncture (CLP)-challenged mice and Escherichia coli-challenged pigs. Integrative metabolomics and the genetic engineering of fungi revealed that Candida albicans-derived phenylpyruvate (PPA) enhanced the bactericidal activity of macrophages and reduced organ damage during sepsis. Mechanistically, PPA directly binds to sirtuin 2 (SIRT2) and increases reactive oxygen species (ROS) production for eventual bacterial clearance. Importantly, PPA enhanced the bacterial clearance capacity of macrophages in sepsis patients and was inversely correlated with the severity of sepsis in patients. Our findings highlight the crucial contribution of commensal fungi to bacterial disease modulation and expand our understanding of the host-mycobiome interaction during sepsis development. © 2023, The Author(s), under exclusive licence to CSI and USTC.
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