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Single-frequency fibre laser at 1030?nm based on gain bandwidth compression
摘要： We demonstrate a single-frequency linear cavity fiber laser at 1030 nm with a distributed Bragg reflector cavity configuration. Despite the fact that the combination of the cavity length of the fiber laser and the reflection band of the output FBG cannot satisfy the condition of single-longitudinal mode oscillation, the single-frequency lasing is still realized by the proper temperature control of two FBGs to narrow the gain bandwidth. Under the respective temperature of two FBGs of 43.4 °C and 9 °C, the laser linewidth of around 9.6 kHz is achieved at a pump power of 113 mW. The relative noise intensity for frequencies of above 1.5 MHz is about ?140 dB Hz?1. The maximum output power of 126.2 mW is obtained with the slope efficiency of about 28%.
关键词： fibre laser,single-frequency,gain bandwidth compression,distributed Bragg reflector
更新于2025-11-28 14:23:57
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Noninvasive Imaging Study of Tracheobronchial Compression Caused By Tortuosity and Dilation of the Thoracic Artery
摘要： Objective: To demonstrate tracheobronchial compression caused by tortuous and dilated large and medium-sized thoracic arteries and the characteristics of these arteries by noninvasive imaging modalities. Patients and Methods: Imaging and clinical data of six patients with tortuous, dilated large and medium-sized thoracic arteries (July 2007 to December 2013) were reviewed. The imaging data were mainly acquired by cardiac multi-slice computed tomography (MSCT) or/and cardiac magnetic resonance imaging (MRI). The number and location of tracheobronchial stenosis were noted, and the severity of stenosis was categorized. The characteristics of large and medium-sized thoracic arteries were also noted. Further, the correlation between the severity of tracheobronchial stenosis and tortuous, dilated large and medium-sized thoracic arteries was analyzed. One patient who was suspected to have arterial tortuosity syndrome underwent genetic analysis. Results: All six patients demonstrated varying degrees of tortuosity and dilation of large and medium-sized thoracic arteries. Five were noted to have varying degrees of tracheobronchial compression and respiratory symptoms. Two have varying degrees of connective tissue abnormalities. Conclusion: Tracheobronchial compression of tortuosity and dilation of large and medium-sized thoracic vascular origin is an uncommon and frequently unrecognized cause of respiratory distress in children. Noninvasive imaging modalities like MSCT and MRI could clearly demonstrate tracheobronchial compression and vascular abnormalities simultaneously. Attention should be given to tracheobronchial compression when disease management decisions are made, especially for determining surgical strategies and for those patients who are 6-9 months old.
关键词： Tortuosity and dilation,Connective tissue abnormalities,Thoracic arteries,Tracheobronchial compression
更新于2025-09-23 15:23:52
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Light Field Image Compression Using Generative Adversarial Network Based View Synthesis
摘要： Light ?eld (LF) has become an attractive representation of immersive multimedia content for simultaneously capturing both the spatial and angular information of the light rays. In this paper, we present a LF image compression framework driven by generative adversarial network (GAN) based sub-aperture image (SAI) generation and cascaded hierarchical coding structure. Speci?cally, we sparsely sample the SAIs in LF and propose the generative adversarial network of LF (LF-GAN) to generate the unsampled SAIs by analogy with adversarial learning conditioned on its surrounding contexts. In particular, LF-GAN learns to interpret both the angular and spatial context of the LF structure, and meanwhile generates intermediate hypothesis for the unsampled SAIs in a certain position. Subsequently, the sampled SAIs and the residues of the generated-unsampled SAIs are re-organized as pseudo-sequences and compressed by standard video codecs. Finally, the hierarchical coding structure is adopted for the sampled SAI to effectively remove the inter-view redundancies. During the training process of LF-GAN, the pixel-wise Euclidean loss as well as the adversarial loss are chosen as the optimization objective, such that sharp textures with less blurring in details can be produced. Extensive experimental results show that the proposed LF-GAN based LF image compression framework outperforms the state-of-the-art learning based LF image compression approach with on average 4.9% BD-rate reductions over multiple LF datasets.
关键词： adversarial learning,SAI synthesis,hierarchical coding,Light ?eld image compression
更新于2025-09-23 15:23:52
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Dechirping Compression Method for Nonlinear Frequency Modulation Waveforms
摘要： This letter proposes a novel dechirp processing method for wideband nonlinear frequency modulation (NLFM) waveform which enables low sampling rate of data. As we know, NLFM waveform can easily realize optimal shape of power spectral density which helps to achieve better pulse compression result with low range sidelobes without signal-to-noise ratio degradation caused by weighting as we usually do for LFM waveforms. In the approach, hamming window is adopted in the generation of the NLFM waveform for better balance on the low range sidelobes and a relative small bandwidth. In dechirp operation, the NLFM radar echoes are mixed with a local reference LFM signal, and thus narrowband signals are resulted and only low sampling rate is needed. The dechirped NLFM signals are then up-sampled and inverse dechirped by software and ?nally matched ?ltering is conducted to complete pulse compression. Both numerically simulated data and real radar data are processed to verify the effectiveness of the proposed method.
关键词： nonlinear frequency modulation (NLFM),sampling rate,pulse compression,Dechirp processing
更新于2025-09-23 15:23:52
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Remote Sensing Image Compression in Visible/Near-Infrared Range Using Heterogeneous Compressive Sensing
摘要： Compressive sensing (CS) framework is very suitable for onboard image compression of high-resolution remote sensing cameras in the visible/near-infrared range (VI/NI-RSC) because it has the low-complexity in the sampling measurement stage. In this paper, we propose a new heterogeneous CS method for VI/NI-RSCs. Different from conventional CS methods evenly allocating sensing resources, the proposed method fully employs texture-feature information of remote sensing images to guide the allocation of sensing resources. More sensing resources are allocated to high-frequency regions, but fewer to low-frequency regions. The heterogeneous distribution of sensing resources obtains high reconstruction quality at the same compression performance, as well as high compression performance at the same level reconstructed quality. The shift of sensing resources is consistent with artificial image interpretations, i.e., human visual characteristics, where high-frequency regions, such as edges and textures, are the principal proof of the ground target identification. Experimental results indicate that the proposed method has better reconstruction quality than conventional CS method where texture-features are not utilized.
关键词： panchromatic images,remote sensing image compression,Heterogeneous compressive sensing (CS)
更新于2025-09-23 15:23:52
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Optical Pressure Sensor Based on the Emission and Excitation Band Width (FWHM) and Luminescence Shift of Ce3+ Doped Fluorapatite – High-Pressure Sensing
摘要： A novel, contactless optical sensor of pressure based on the luminescence red-shift and band width (full width at half maximum - FWHM) of the Ce3+-doped fluorapatite - Y6Ba4(SiO4)6F2 powder, has been successfully synthesized via a facile solid-state method. The obtained material exhibits a bright blue emission under UV light excitation. It was characterized using powder X-ray diffraction, scanning electron microscopy and luminescence spectroscopy, including high-pressure measurements of excitation and emission spectra, up to above ≈30 GPa. Compression of the material resulted in a significant red-shift of the allowed 4f→5d and 5d→4f transitions of Ce3+ in the excitation and emission spectra, respectively. The pressure-induced monotonic shift of the emission band, as well as changes in the excitation/emission band widths, have been correlated with pressure for sensing purposes. The material exhibits a high pressure sensitivity (dλ/dP ≈0.63 nm/GPa), and outstanding signal intensity at high-pressure conditions (≈90% of the initial intensity at around 20 GPa) with minimal pressure-induced quenching of luminescence.
关键词： Ce3+ doping,Contactless pressure gauge,Y6Ba4(SiO4)6F2 apatite phosphors,Lanthanide ions (Ln3+),Compression in DAC,Luminescent functional materials
更新于2025-09-23 15:23:52
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Two-Dimensional Compressed Sensing Using Two-Dimensional Random Permutation for Image Encryption-then-Compression Applications
摘要： Block compressed sensing with random permutation (BCS-RP) has been shown to be very effective for image Encryption-then-Compression (ETC) applications. However, in the BCS-RP scheme, the statistical information of the blocks is disclosed, because the encryption is conducted within each small block of the image. To solve this problem, a two-dimension compressed sensing (2DCS) with 2D random permutation (2DRP) strategy for image ETC applications is proposed in this letter, where the 2DRP strategy is used for encrypting the image and the 2DCS scheme is used for compressing the encrypted image. Compared with the BCS-RP scheme, the proposed approach has two benefits. Firstly, it offers better security. Secondly, it obtains a significant gain of peak signal-to-noise ratio (PSNR) of the reconstructed-images.
关键词： image encryption,image compression,two-dimension compressed sensing,Encryption-then-Compression,two-dimension random permutation
更新于2025-09-23 15:22:29
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[IEEE 2018 IEEE International Conference on RFID Technology & Application (RFID-TA) - Macau, Macao (2018.9.26-2018.9.28)] 2018 IEEE International Conference on RFID Technology & Application (RFID-TA) - Referenced Backscattering Compression Level Indicator based on Passive UHF RFID Tags
摘要： We establish a passive UHF RFID tag as a sensor with a referenced readout to compression. We introduce the sensor tag design, which is based on a two-part split ring resonator antenna, and present the compression sensor platform with a reference tag. We analyze the achieved wireless measurement results and evaluate the performance of the compression sensing platform. Based on these initial measurements, passive RFID-based sensors could provide a maintenance-free wirelessly readable option for compression sensing, for example for structural health monitoring.
关键词： compression sensor,passive UHF RFID technology,referenced sensor readout
更新于2025-09-23 15:22:29
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A method of percutaneous vertebroplasty under the guidance of two C-arm fluoroscopes
摘要： Objective: To compare the clinical application in the percutaneous vertebroplasty under the guidance of one or two C-arm fluoroscopes. Methods: One hundred forty three elderly patients with Osteoporotic vertebral compression fractures (OVCFs) underwent percutaneous vertebroplasty under the guidance of one or two C-arm fluoroscopes. The number of pulsed imagings, the time of operation and the incidence of cement leakage were recorded. Results: The average number of pulsed imagings was 16.00±1.58 vs 13.07±2.00 per patient under the guidance of one vs two C-arm fluoroscopes. The average time of operation was 48.42±5.00 minutes vs 39.70±7.42 minutes per patient under the guidance of one vs two C-arm fluoroscopes. The incidence of cement leakage was 20% vs 15.7% of the patients under the guidance of one vs two C-arm fluoroscopes. The differences in the number of pulsed imagings and the time of operation were statistically significant. The difference in incidence of cement leakage was not statistically significant. Conclusion: The two-fluoroscopic technique reduce the labor cost, the radiation, the time of operation and the operation risk.
关键词： Percutaneous vertebroplasty,Two C-arm fluoroscopes,Osteoporotic vertebral compression fractures
更新于2025-09-23 15:22:29
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Compression of femtosecond pulses in a wide wavelength range using a large-mode-area tapered fiber
摘要： We report the design of a tapered fiber that can be used for the compression of pulses at different central wavelengths. The proposed fiber is a three-layer W-type large-mode-area fiber, which has been tapered to transform the mode area from 1700 μm2 to 900 μm2. We determine the exact length of the maximum pulse compression and numerically demonstrate the compression of a 250 fs, 100 kW peak power input pulse to 15 fs, 850 kW at 1.55 μm wavelength and compression of 250 fs, 120 kW peak power input pulses to 28 fs, 700 kW and to 46 fs, 500 kW at 1.8 μm and 2 μm wavelengths, respectively. Such a fiber can find wide ranging applications, including in communication, spectroscopy and medicine.
关键词： ultrafast processes in fiber,large-mode-area fiber,high peak power femtosecond pulses,pulse shaping,tapered fiber,pulse compression
更新于2025-09-23 15:22:29