Digital Resolution Enhancement Research Articles

Beyond 200-Gb/s O-band intensity modulation and direct detection optics with joint look-up-table-based predistortion and digital resolution enhancement for low-cost data center interconnects

Beyond 200-Gb/s O-band intensity modulation and direct detection optics with joint look-up-table-based predistortion and digital resolution enhancement for low-cost data center interconnects

Super-resolution reconstruction of 3D digital rocks by deep neural networks

Digital rock technology provides valuable insights into the pore structure and fluid flow properties of geoenergy resources. Artificial intelligence technology in vision and image processing, especially the image super-resolution, has great potential for digital rock reconstruction and resolution enhancement. However, the analyzed core samples are typically sandstones/carbonates in micro-scale resolutions and in two-dimensional (2D) space, whereas the shale rocks in nano-scale resolutions for unconventional resources or three-dimensional (3D) digital cores are rarely investigated. Additionally, previous studies primarily emphasized image quality from a computer vision perspective, with little consideration given to estimating physical properties of digital rocks using super-resolution techniques.This study presents a very deep super-resolution (VDSR) algorithm, specifically designed to generate high-resolution 3D digital rock images, for nano-scale shale matrix and micro-scale hydraulic fractures. We compare both image quality and permeability accuracy between the original high-resolution images and the super-resolution images reconstructed by the proposed method. The results reveal that the reconstructed images using the proposed method closely resemble the actual images, and effectively reduce errors in permeability computations. This study highlights the applicability of the proposed VDSR algorithm in establishing the detailed structures of 3D nano-scale shale matrix and hydraulic fractured rocks, thus advancing super-resolution techniques in digital core analysis for geoenergy resources development.

Simplified Self-Coherent FSO Transmission Boosted by Digital Resolution Enhancer

The joint application of free-space optics (FSO) transmission with coherent detection has recently appeared to enable unprecedented optical wireless capacity. Nevertheless, due to the associated cost and power consumption, simplified self-coherent FSO links are currently being explored to optimize the performance vs. complexity tradeoff. In particular, the utilization of low-complexity virtual carrier self-coherent transmission provides an appealing cost-effective alternative for high-capacity FSO links. However, this transmission paradigm is associated with quantization noise problems due to limited digital-to-analog converter (DAC) resolution. Following all the stated requirements, this work presents a simplified virtual carrier-assisted self-coherent FSO link supported by a low-resolution DAC and Nyquist rate phase reconstruction using the DC-Value algorithm. The utilization of such a low-resolution DAC is aided by a digital resolution enhancement (DRE) method. Employing this simplified self-coherent approach, we experimentally demonstrated 100 Gbps FSO transmission over an outdoor 42 m link using a DAC with resolution as low as 3 bits.

Digital rock resolution enhancement and detail recovery with multi attention neural network

High-quality digital rock images are essential for subsequent high-precision numerical simulations. But limited by the imaging capability of computed tomography (CT), high resolution digital rock images with wide imaging field of view (FOV) cannot be acquired simultaneously. To cope with this constraint, we propose a novel Multi Attention Super-Resolution Neural Network (MASR) that enhances the resolution of images with wide FOV. Considering that textures and edges are more crucial in digital rocks, MASR introduces the component attention mechanism of Component Divide-and-Conquer Super-Resolution (CDCSR) model. By redesigning the hourglass network with spatial and channel attention mechanisms, proposing a spatial attention-based mask module, and optimizing the component attention mask calculation process, MASR delivers higher information utilization with fewer parameters and faster training than CDCSR. In addition, we optimize the depth of MASR to trade off speed and super-resolution quality. Furthermore, we retrain several state-of-the-art models. Through quantitative evaluations and qualitative visualizations, it is verified that MASR can recover sharper edges while removing noise, and obtain digital rock images with superior quality and reliability. The pixel-wise relative errors of MASR reconstructions are reduced by 15%–26% over bicubic interpolation method. Our codes and pretrained model are publicly available at https://github.com/MHDXing/MASR-for-Digital-Rock-Images.

A Novel Adaptive Directional Interpolation Algorithm for Digital Video Resolution Enhancement

In this paper, a novel digital video resolution enhancement algorithm based on adaptive directional interpolation is proposed, where the directionality of the edge structure and the nonlocal self-similarity prior within the current frame as well as its adjacent frames are both considered. First, we establish the regularization equation that conforms to the prior model of a video frame and then take the classic bicubic interpolation result as the initial estimation to iteratively solve the restoration equation, in which the edge structures and contours in low resolution (LR) input are reconstructed to estimate and refine the desired high resolution (HR) output. Experimental results show that the proposed algorithm can effectively enhance the clarity of a video frame, with satisfying subjective visual quality and PSNR value.

Digital resolution enhancement of intracardiac excitation maps during atrial fibrillation.

Atrial fibrillation (AF) is often successfully treated by catheter ablation. Those cases of AF that do not readily succumb to ablation therapy would benefit from improved methods for mapping the complex spatial patterns of tissue activation that typify recalcitrant AF. To this end, the purpose of our study was to investigate the use of numerical deconvolution to improve the spatial resolution of activation maps provided by 2-D arrays of intra-cardiac recording electrodes. We simulated tissue activation patterns and their corresponding electric potential maps using a computational model of cardiac electrophysiology, and sampled the maps over a grid of locations to generate a mapping data set. Following cubic spline interpolation, followed by edge-extension and windowing, we deconvolved the data and compared the results to the model current density fields. We performed a similar analysis on voltage-sensitive dye maps obtained in isolated sheep hearts. For both the synthetic data and the voltage-sensitive dye maps, we found that deconvolution led to visually improved map resolution for arrays of 10×10 up to 30×30 electrodes placed within a few mm of the atrial surface when the activation patterns included 3-4 features that spanned the recording area. Root mean square error was also reduced by deconvolution. Deconvolution of arrays of intracardiac potentials, preceded by appropriate interpolation and edge processing, leads to potentially useful improvements in map resolution that may allow more effective assessment of the spatiotemporal dynamics of tissue excitation during AF.

Spatially oversampled TDC with digital resolution enhancement

A digital resolution enhancement technique for time-to-digital converters (TDC) is proposed. This involves a simultaneous multi-channel measurement of a time interval with low complexity TDC of varying low resolutions. The coarse outputs of each converter are digitally post-processed to obtain an output whose precision is much better than that of the individual converters. Three post-processing algorithms are proposed and their limitations in presence of converter non-idealities are analyzed. A prototype system with 8 channels is implemented in 90 nm CMOS. 40MS/s output of each channel is algorithmically combined to obtain over 2.2---3X measured improvement in the resolution in 4/6/8 channel modes, validating the system principle. The chip occupies 0.3 mm2 and draws up to a maximum of 4 mA from a 1.2 V supply.

Multiplexing Bragg gratings using combined wavelength and spatial division techniques with digital resolution enhancement

A novel multiplexing technique is described, which employs an imaging spectrograph to interrogate fibre Bragg gratings in multiple fibre channels simultaneously, and digital algorithms to enhance the spectral resolution. An equivalent strain sensing resolution of 1.6 µɛ has been achieved in the preliminary experiments.

Solid-State 13C Nuclear Magnetic Resonance Characterization of Cellulose in the Cell Walls of Arabidopsis thaliana Leaves.

Solid-state 13C nuclear magnetic resonance was used to characterize the molecular ordering of cellulose in a cell-wall preparation containing mostly primary walls obtained from the leaves of Arabidopsis thaliana. Proton and 13C spin relaxation time constants showed that the cellulose was in a crystalline rather than a paracrystalline state or amorphous state. Cellulose chains were distributed between the interiors (40%) and surfaces (60%) of crystallites, which is consistent with crystallite cross-sectional dimensions of about 3 nm. Digital resolution enhancement revealed signals indicative of triclinic and monoclinic crystalline forms of cellulose mixed in similar proportions. Of the five nuclear spin relaxation processes used, proton rotating-frame relaxation provided the clearest distinction between cellulose and other cell-wall components for purposes of editing solid-state 13C nuclear magnetic resonance spectra.

Resolution enhancement in spectroscopy by maximum entropy fourier self‐deconvolution, with applications to Raman spectra of peptides and proteins

AbstractThe method of maximum entropy extrapolation is applied to Fourier self‐deconvolution to enhance the inherently low resolution of the Raman spectra of peptides and proteins. Using computer‐simulated and real spectral data, a comparative study was made between the maximum entropy (MEM) and the conventional discrete Fourier transform (DFT) methods. The MEM provides better resolution with no side‐lobe formation, and is especially useful in the resolution enhancement of complicated Raman spectra of proteins. The MEM is also suitable for the spectral estimation of a short‐time record of noisy data, enabling the exposure time of protein solutions to the intense laser beam to be reduced significantly. The theory of maximum entropy spectral analysis is presented and the application of the techniques of digital resolution enhancement is discussed. It is pointed out that a combined use of different techniques should be made whenever possible in carrying out digital signal enhancement in order to reduce the chance of misinterpretation of spectral information.

Variable filter for digital smoothing and resolution enhancement of noisy spectra

Variable filter for digital smoothing and resolution enhancement of noisy spectra

Solvent effects and approaches for the fine structure analysis of peptidyl amide 1H NMR spectra

Two methods are used to analyze glycyl C α H 2−N H 1H NMR spectra as ABX proton spin systems. The first is based on the observation of the doublet-of-doublet fine structure in the N H multiplet assisted by digital resolution enhancement. The second method makes use of low-power, double-resonance 1H N -{ 1H α } experiments, selectively decoupling each geminal 1H α. Here, account must be taken of the effect of the decoupling wave on the nonirradiated 1H α geminal partner, as in ordinary off-resonance decoupling. Both methods show excellent agreement in the determined 3 J values. Amide N H-C α H spin-spin couplings were determined on alumichrome dissolved in trifluoroacetic acid, trifluoroethanol, and H 2O, and compared with values previously determined in dimethyl sulfoxide. The solvent effects are shown to be minor and mainly of conformational origin. The present study shows that (a) under favorable conditions the glycyl vicinal N H-C α H couplings can be individually detected as doublet N H resonances, and (b) the Karplus curve for the N H-C α H dihedral angle based on alumichrome data is essentially solvent independent.

Assignment of the heme c resonances in the 360 MHz 1H NMR spectra of cytochrome c

In the 360 MHz 1H NMR spectra of horse heart ferrocytochrome c recorded after suitable digital resolution enhancement, the resonances of all the heme c protons with the exception of those of the propionic acid side chains were observed as well resolved lines. From spin decoupling and nuclear Overhauser effects in homonuclear double resonance experiments, all these resonances were assigned to their respective positions in heme c. With saturation transfer experiments in solutions of partially reduced cytochrome c, individual assignments were further obtained for the six heme c methyl resonances in ferricytochrome c. The present experiments add individual assignments to the earlier identifications of the heme c ring methyl and meso-proton resonances, and show that the earlier identifications of the thioether bridge methyl resonances must be revised. These data provide a basis for more detailed descriptions of the electronic structure of heme c and its possible relations with the pathway of the electron transfer in and out of the cytochrome c molecule. Furthermore, the pseudocontact shifts of the thioether bridge methyl resonances could be related to the electronic g-tensor measured by EPR in ferricytochrome c single crystals at low temperature. From this it will now be possible without chemical modification of the protein, to compare in detail the solution conformations near the heme c in reduced and oxidized cytochrome c and thus hopefully to obtain additional insights into the mechanism of the biological redox reaction of this protein.

1H Nmr studies at 360 MHz of the methyl groups in native and chemically modified basic pancreatic trypsin inhibitor (BPTI).

In the 1H NMR spectra obtained at 360 MHz after digital resolution enhancement, the multiplet resonances of the methyl groups in the basic pancreatic trypsin inhibitor (BPTI) were resolved. With suitable double irradiation techniques the individual methyl resonances were assigned to the different types of aliphatic amino acid residues. Furthermore, from pH titration and comparison of the native protein with chemically modified BPTI, the resonance lines of Ala 16 in the active site and Ala 58 at the C-terminus were identified. Potential applications of the resolved methyl resonances as natural NMR probes for studies of the molecular conformation are discussed.