| 1. |
- Kristan, Matej, et al.
(författare)
-
The Visual Object Tracking VOT2015 challenge results
- 2015
-
Ingår i: Proceedings 2015 IEEE International Conference on Computer Vision Workshops ICCVW 2015. - : IEEE. - 9780769557205 ; , s. 564-586
-
Konferensbidrag (refereegranskat)abstract
- The Visual Object Tracking challenge 2015, VOT2015, aims at comparing short-term single-object visual trackers that do not apply pre-learned models of object appearance. Results of 62 trackers are presented. The number of tested trackers makes VOT 2015 the largest benchmark on short-term tracking to date. For each participating tracker, a short description is provided in the appendix. Features of the VOT2015 challenge that go beyond its VOT2014 predecessor are: (i) a new VOT2015 dataset twice as large as in VOT2014 with full annotation of targets by rotated bounding boxes and per-frame attribute, (ii) extensions of the VOT2014 evaluation methodology by introduction of a new performance measure. The dataset, the evaluation kit as well as the results are publicly available at the challenge website(1).
|
|
| 2. |
- Fei, Chao, et al.
(författare)
-
Underwater wireless optical communication utilizing low-complexity sparse pruned-term-based nonlinear decision-feedback equalization
- 2022
-
Ingår i: Applied Optics. - : Optica Publishing Group. - 1559-128X .- 2155-3165. ; 61:22, s. 6534-6543
-
Tidskriftsartikel (refereegranskat)abstract
- The nonlinearity of the light-emitting diode (LED) in underwater wireless optical communication (UWOC) systems is considered the one major limiting factor that degrades the system's performance. Volterra series-based nonlinear equalization is widely employed to mitigate such nonlinearity in communication systems. However, the conventional Volterra series-based model is of high complexity, especially for the nonlinearity of higher-order terms or longer memory lengths. In this paper, by pruning away some negligible beating terms and adaptively picking out some of the dominant terms while discarding the trivial ones, we propose and experimentally demonstrate a sparse pruned-term-based nonlinear decision-feedback equalization (SPT-NDFE) scheme for the LED-based UWOC system with an inappreciable performance degradation as compared to systems without the pruning strategy. Meanwhile, by replacing the self/cross beating terms with the terms formed by the absolute operation of a sum of two input samples instead of the product operation terms, a sparse pruned-term-based absolute operation nonlinear decision-feedback equalization (SPT-ANDFE) scheme is also introduced to further reduce complexity. The experimental results show that the SPT-NDFE scheme exhibits comparable performance as compared to the conventional NDFE (nonlinear decision-feedback equalization) scheme with lower complexity (the nonlinear coefficients are reduced by 63.63% as compared to the conventional NDFE scheme). While the SPT-ANDFE scheme yields suboptimal performance with further reduced complexity at the expense of a slight performance degradation, the robustness of the proposed schemes in different turbidity waters is experimentally verified. The proposed channel equalization schemes with low complexity and high performance are promising for power/energy-sensitive UWOC systems.
|
|
| 3. |
- Zhang, Tianyi, et al.
(författare)
-
19.02Gbps/25m Underwater Wireless Optical Communication Adopting Probabilistic Constellation Shaping QAM-DMT Transmission
- 2023
-
Ingår i: 2023 Asia Communications and Photonics Conference/2023 International Photonics and Optoelectronics Meetings, ACP/POEM 2023. - : Institute of Electrical and Electronics Engineers (IEEE).
-
Konferensbidrag (refereegranskat)abstract
- We experimentally demonstrated probabilistic constellation shaping quadrature amplitude modulation discrete multitone (PCS QAM-DMT) for 25-m underwater wireless optical communication (UWOC) system with a net data rate of 19.02Gbps. 28.1% capacity improvement is achieved in comparison with conventional bit-power loading DMT scheme. To the best of our knowledge, this is the highest net data rate ever reported for a single LD in current UWOC.
|
|
| 4. |
- Du, Ji, et al.
(författare)
-
A Comprehensive Performance Comparison of DFT-S DMT and QAM-DMT in UOWC System in Different Water Environments
- 2021
-
Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 13:1
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we experimentally demonstrate a 450-nm laser underwater optical wireless transmission system, in which a comprehensive investigation is made to show the significant performance improvement of the discrete Fourier transform spread discrete multi-tone (DFT-S DMT) as compared to the conventional quadrature amplitude modulation discrete multi-tone (QAM-DMT) modulation. DFT-S DMT outperforms QAM-DMT in terms of bit error rate (BER) performance due to low peak-to-average-power ratio (PAPR) and capability of counteracting high frequency fading in a band-limited underwater optical wireless communication (UOWC) system. In order to avoid signal-to-noise-ratio (SNR) degradation at fringe subcarriers, several zeros are padded at the edge of each block before DFT-S operation. The experimental results show the superiority of DFT-S DMT compared with QAM-DMT in different water environments, including turbidities, bubbles, and water flow. Data rates of similar to 16.16 Gbps and similar to 13.96 Gbps at a BER of 3.8 x 10(-3) are achieved by 16-QAM DFT-S DMT and 16-QAM-DMT over a 5-m water channel, respectively, which indicates that capacity enhancement of similar to 2.2 Gbps is obtained by the DFT-S DMT. Meanwhile, over 3-dB receiver sensitivity improvement can always be achieved by the DFT-S DMT at the tested underwater transmission distances. Combined with adaptive bit-power loading, 20.04 Gbps over a 5-m "clear ocean" channel transmission with a single laser diode (LD) is demonstrated. For a 35-m water link, the distance-data rate product reaches 498.4 Gbps*m. To the best of our knowledge, both the data rate and distance-data rate product are the largest among all the results reported for a single visible LD. Aimed at high-speed deep ocean applications, the studies are promising for future UOWC research.
|
|
| 5. |
- Liu, Tie, et al.
(författare)
-
Effects of high magnetic fields on solidification microstructure of Al-Si alloys
- 2011
-
Ingår i: Journal of Materials Science. - : Springer Science and Business Media LLC. - 0022-2461 .- 1573-4803. ; 46:6, s. 1628-1634
-
Tidskriftsartikel (refereegranskat)abstract
- The effects of high magnetic fields on the solidification microstructure of Al-Si alloys were investigated. Al-7.2 wt%Si and Al-11.8 wt%Si alloys were solidified in various high magnetic fields at different cooling rates. The secondary dendrite arm spacing (SDAS) of the primary Al dendrites and the lamellar spacing (LS) of the eutectics were measured. It was found that the application of a high magnetic field could decrease the SDAS of the primary Al dendrites in Al-7.2 wt% Si alloys and the LS of the eutectics in Al-11.8 wt% Si alloys. The effects of the high magnetic field on the SDAS decreased with increasing cooling rate. The decrease in the SDAS and LS can be attributed to the decrease of the solute diffusivity in the liquid ahead of the solid/liquid interface during the growth of the dendrite and eutectic. This decrease is caused by the high magnetic field which can damp the convection and avoid its contributions to the diffusion.
|
|
| 6. |
- Du, Ji, et al.
(författare)
-
Experimental demonstration of 50-m/5-Gbps underwater optical wireless communication with low-complexity chaotic encryption
- 2021
-
Ingår i: Optics Express. - : The Optical Society. - 1094-4087. ; 29:2, s. 783-796
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a low-complexity two-level chaotic encryption scheme is introduced and experimentally demonstrated to improve the physical layer security of a 450-nm laser underwater optical wireless communication (UOWC) system using discrete Fourier transform spread discrete multi-tone (DFT-S DMT) modulation. In the first encryption stage, the original bit stream is encrypted with a chaotic sequence based on a one-dimensional Logistic map. In the second encryption stage, the real and imaginary components of the DFT-S symbols are further encrypted with a pair of separate chaotic sequences, which are generated from a two-dimensional Logistic iterative chaotic map with infinite collapse (2D-LICM). The experimental results indicate that the encryption operation has no negative effect on the performance of the proposed UOWC system. For chaotic encryption, the DFT-S DMT gives a better performance than the DMT scheme under different water turbidities. 55-m/4.5-Gbps and 50-m/5-Gbps underwater transmissions are successfully demonstrated by the chaotic encrypted DFT-S DMT scheme. To the best of our knowledge, this is the first time to verify the feasibility of chaotic encryption in a high-speed UOWC system.
|
|
| 7. |
- Fei, Chao, et al.
(författare)
-
100-m/3-Gbps underwater wireless optical transmission using a wideband photomultiplier tube (PMT)
- 2022
-
Ingår i: Optics Express. - : The Optical Society. - 1094-4087. ; 30:2, s. 2326-2337
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a wideband photomultiplier tube (PMT)-based underwater wireless optical communication (UWOC) system is proposed and a comprehensive experimental study of the proposed PMT-based UWOC system is conducted, in which the transmission distance, data rate, and attenuation length (AL) is pushed to 100.6 meters, 3 Gbps, and 6.62, respectively. The receiver sensitivity at 100.6-meter underwater transmission is as low as -40 dBm for the 1.5-Gbps on-off keying (00K) modulation signal. To the best of our knowledge, this is the first Gbps-class UWOC experimental demonstration in >100-meter transmission that has ever been reported. To further minimize the complexity of channel equalization, a sparsity-aware equalizer with orthogonal matching pursuit is adopted to reduce the number of the filter coefficients by more than 50% while keeping slight performance penalty. Furthermore, the performance of the proposed PMT-based LIWOC system in different turbidity waters is investigated, which shows the robustness of the proposed scheme. Thanks to the great sensitivity (approaching the quantum limit) and a relatively larger effective area, benefits of misalignment tolerance contributed by the PMT is verified through a proof-of-concept LIWOC experiment.
|
|
| 8. |
- Fei, Chao, et al.
(författare)
-
Improving the Performance of Long Reach UOWC With Multiband DFT-Spread
- 2019
-
Ingår i: IEEE Photonics Technology Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1041-1135 .- 1941-0174. ; 31:16, s. 1315-1318
-
Tidskriftsartikel (refereegranskat)abstract
- In this letter, a multiband discrete-Fourier-transform spread (DFT-spread) is introduced to reduce the peak-to-average-power ratio (PAPR) of discrete multitone (DMT)-based underwater optical wireless communication (UOWC) system. The performance of different multiband DFT-spread DMT schemes in a wide underwater transmission range (from 5 to 55 m at a fixed transmission data rate of 5.6 Gb/s) is experimentally investigated. The measured results show that the 1-band DFT-spread and 2-band DFT-spread DMT can significantly improve the system performance compared with the conventional clipping DMT, while the 1-band DFT-spread gives the best performance. Due to the single carrier frequency domain equalization-like characteristic, the 1-band DFT-spread exhibits a relatively uniform signal-to-noise ratio (SNR) profile, which shows the robustness to high frequency fading in the band-limited UOWC system. These intrinsic advantages could jointly ease the bit error rate (BER) deterioration in a long reach UOWC system. Furthermore, the measured data rate-distance product has reached 308 Gb/s*m (i.e., 55-m * 5.6 Gb/s), which to the best of our knowledge is the largest for the single modulation format.
|
|
| 9. |
- Fenstermacher, M.E., et al.
(författare)
-
DIII-D research advancing the physics basis for optimizing the tokamak approach to fusion energy
- 2022
-
Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 62:4
-
Tidskriftsartikel (refereegranskat)abstract
- DIII-D physics research addresses critical challenges for the operation of ITER and the next generation of fusion energy devices. This is done through a focus on innovations to provide solutions for high performance long pulse operation, coupled with fundamental plasma physics understanding and model validation, to drive scenario development by integrating high performance core and boundary plasmas. Substantial increases in off-axis current drive efficiency from an innovative top launch system for EC power, and in pressure broadening for Alfven eigenmode control from a co-/counter-I p steerable off-axis neutral beam, all improve the prospects for optimization of future long pulse/steady state high performance tokamak operation. Fundamental studies into the modes that drive the evolution of the pedestal pressure profile and electron vs ion heat flux validate predictive models of pedestal recovery after ELMs. Understanding the physics mechanisms of ELM control and density pumpout by 3D magnetic perturbation fields leads to confident predictions for ITER and future devices. Validated modeling of high-Z shattered pellet injection for disruption mitigation, runaway electron dissipation, and techniques for disruption prediction and avoidance including machine learning, give confidence in handling disruptivity for future devices. For the non-nuclear phase of ITER, two actuators are identified to lower the L-H threshold power in hydrogen plasmas. With this physics understanding and suite of capabilities, a high poloidal beta optimized-core scenario with an internal transport barrier that projects nearly to Q = 10 in ITER at ∼8 MA was coupled to a detached divertor, and a near super H-mode optimized-pedestal scenario with co-I p beam injection was coupled to a radiative divertor. The hybrid core scenario was achieved directly, without the need for anomalous current diffusion, using off-axis current drive actuators. Also, a controller to assess proximity to stability limits and regulate β N in the ITER baseline scenario, based on plasma response to probing 3D fields, was demonstrated. Finally, innovative tokamak operation using a negative triangularity shape showed many attractive features for future pilot plant operation.
|
|
| 10. |
- Haw, Shu Chih, et al.
(författare)
-
Single antiferromagnetic axis of Fe in orthorhombic YMn0.5Fe0.5O3 films observed by x-ray magnetic linear dichroism
- 2019
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388. ; 780, s. 79-84
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic and magnetic structure of orthorhombic (o-) YMn0.5Fe0.5O3 (YMFO) epitaxial film (space group Pbnm) deposited on the YAlO3 (010) substrate have been investigated using linear polarization-dependent x-ray absorption spectroscopy and magnetization measurements. The magnetic-ordering temperature of around 280 K is observed in o-YMFO film. The x-ray absorption spectra at the Fe-K and the Mn-K edges indicate the existence of anisotropic crystal field in o-YMFO film, with the longest and shortest Fe–O and Mn–O bonds tend to align with the crystallographic b- and a-axis, respectively, whereas the medium Fe(Mn)–O bond is aligned with the c-axis. The experimental x-ray magnetic linear dichroism at the Fe-L2 edges demonstrate an unusual single antiferromagnetic axis of Fe3+ ions below magnetic-ordering temperature, while a multi antiferromagnetic axis is generally observed in o-RFeO3 (R = rare earth) thin films. Our configuration-interaction cluster calculations also reveal that the single antiferromagnetic axis of the Fe sublattice is aligned with the b-axis in o-YMFO film, whereas it is directed along the a-axis in the bulk o-YFeO3.
|
|
