Degenerative cervical myelopathy (DCM) is the leading cause of spinal cord dysfunction in adults worldwide. DCM encompasses various acquired (age-related) and congenital pathologies related to ...degeneration of the cervical spinal column, including hypertrophy and/or calcification of the ligaments, intervertebral discs and osseous tissues. These pathologies narrow the spinal canal, leading to chronic spinal cord compression and disability. Owing to the ageing population, rates of DCM are increasing. Expeditious diagnosis and treatment of DCM are needed to avoid permanent disability. Over the past 10 years, advances in basic science and in translational and clinical research have improved our understanding of the pathophysiology of DCM and helped delineate evidence-based practices for diagnosis and treatment. Surgical decompression is recommended for moderate and severe DCM; the best strategy for mild myelopathy remains unclear. Next-generation quantitative microstructural MRI and neurophysiological recordings promise to enable quantification of spinal cord tissue damage and help predict clinical outcomes. Here, we provide a comprehensive, evidence-based review of DCM, including its definition, epidemiology, pathophysiology, clinical presentation, diagnosis and differential diagnosis, and non-operative and operative management. With this Review, we aim to equip physicians across broad disciplines with the knowledge necessary to make a timely diagnosis of DCM, recognize the clinical features that influence management and identify when urgent surgical intervention is warranted.
•Compressive behaviors of CTB depend on its component and confining pressures.•The solids content has a trivial effect on the friction angle of CTB.•The increased c/t ratio leads to a higher cohesion ...but a lower friction angle.•Lateral inertial confinement is more sensitive to the c/t ratio.•End-friction confinement is more sensitive to the solids content.
A full understanding of the mechanical response of cemented tailings backfill (CTB) under various loading scenarios is beneficial for mining engineering applications. This study experimentally investigates the stress–strain response, failure pattern and criteria of CTB under triaxial compression loading with various confining pressures and components. Microstructural analyses are also conducted to reveal how the confining pressure influences the deformation behavior of CTB. Later, triaxial compression strength data are used to calibrate the constitutive parameters of the Holmquist-Johnson-Cook (HJC) model for CTB. Following the HJC model calibration, a split Hopkinson pressure bar (SHPB) model is established by using the commercial finite element software LS-DYNA to evaluate the effect of the lateral initial confinement and end-friction confinement on the dynamic compression strength of CTB with various components.
Several types of cyclic stress were applied to specimens made of an extruded magnesium alloy, AZ31, to elucidate twinning, detwinning, and fatigue crack initiation mechanisms by electron ...backscattered diffraction analysis. In both the texture and the random orientation, twinning occurred under compressive stress exceeding the compressive yield strength. Detwinning occurred only in the texture upon the subsequent application of tensile stress less than the tensile yield strength of monotonic loading, whereas detwinning did not occur in the structure with random orientation. Under compression–compression fatigue test, successive twinning occurred, which changed the orientation of the basal plane. As a result, the random orientation of grains changed to the texture in which the normal of the basal plane was parallel to the loading direction. Cracks were formed along the boundary of grains with a high Schmid factor of the basal slip system and the misfit of grain on both sides was large. Near the crack initiation site, twin bands were observed; however, detwinning did not occur under the tensile stress after the cyclic compression loading.
•Detwinning occurred in texture, but not occurred in random orientation.•Under compression fatigue test, random orientation changed to texture.•Compression fatigue cracks initiated in boundary of high Schmid factor grain.•No detwinning occurred by tensile stressing after compression fatigue.
•Single-fueled and dual-fueled advanced combustion technologies were compared in terms of engine performance characteristics.•DF-PCCI combustion could achieve high thermal efficiency almost same as ...conventional diesel combustion.•DF-PCCI combustion could effectively reduce CO2 emissions compared to conventional diesel combustion.•DF-PCCI has been considered as a promising solution for the commercialization of advanced combustion technologies.
Advanced combustion technologies (ACTs), which have great potential for nitrogen oxides (NOx) and particulate matter (PM) reduction simultaneously, have been researched steadily to replace conventional diesel combustion (CDC) over the past 40 years. However, it is still unclear which ACT is suitable as a practical alternative combustion technology. In this study, single-fueled and dual-fueled ACTs, such as homogeneous charge compression ignition (HCCI), premixed charge compression ignition (PCCI) and dual-fuel premixed charge compression ignition (DF-PCCI), were implemented to compare with each other in a heavy-duty single cylinder engine under a specified load condition at which all ACTs can be operated stably. The combustion characteristics, emission performance, thermal efficiency (ηT), and combustion efficiency (ηc) were considered as comparative factors in order for the comparative evaluations of among the three ACTs. The results showed that all ACTs could reduce the NOx and PM emissions simultaneously under the EU-VI NOx and PM regulations without after-treatment system. In addition, DF-PCCI combustion has achieved indicated thermal efficiency (ITE) of 45.3%, which was higher than that for CDC, due to the superior controllability of combustion phase and burn duration. However, DF-PCCI combustion produced high amounts of total hydrocarbon (THC) and carbon monoxide (CO) emissions which could deteriorate the combustion efficiency. These results suggest that although the DF-PCCI combustion technology has various strengths, such as high thermal efficiency and superior combustion controllability, the combustion efficiency should be improved through THC and CO reductions in order to become a practical combustion technology.
Objective/Background The objective of this study was to compare the efficacy and comfort of inelastic bandages (IBs) and adjustable Velcro® compression devices (AVCDs) in reducing venous leg edema in ...the initial treatment phase. Methods Forty legs from 36 patients with untreated venous edema (C3EpsAsdPr) were randomized to two groups. Patients in the first group received IBs ( n = 20) and those in the second AVCDs ( n = 20). Both compression devices were left on the leg day and night, and were renewed after 1 day. Patients in the AVCD group were asked to re-adjust the device as needed when it felt loose. Leg volume was calculated using the truncated cone formula at baseline (T0), after 1 day (T1) and after 7 days (T7). The interface pressure of the two compression devices was measured by an air filled probe, and the static stiffness index calculated after applying compression at T0 and T1, and just before removal of compression on T1 and T7. Patient comfort with regard to the two compression systems was assessed by grading signs and symptoms using a visual analog scale. Results At T1, the median percent volume reduction was 13% for the IB group versus 19% for the AVCD group; at T7 it was 19% versus 26%, respectively ( p < .001). The pressure of the IBs was significantly higher compared with the AVCDs at T0 (63 vs. 43 mmHg) but dropped by > 50% over time, while it remained unchanged with AVCDs owing to the periodic readjustment by the patient. Comfort was reported to be similar with the two compression devices. Conclusion Re-adjustable AVCDs with a resting pressure of around 40 mmHg are more effective in reducing chronic venous edema than IBs with a resting pressure of around 60 mmHg. AVCDs are effective and well tolerated, not only during maintenance therapy, but also in the initial decongestive treatment phase of patients with venous leg edema.
Objective: Extraction and analysis of various clinically significant features of photoplethysmogram (PPG) signals for monitoring several physiological parameters, as well as for biometric ...authentication have become important areas of research in recent years. However, PPG signal compression; particularly quality-guaranteed compression, and steganography of patient's secret information is still lagging behind. Method: This paper presents a robust, reliable and highly efficient singular value decomposition and lossless ASCII character encoding (LL-ACE)-based quality-guaranteed PPG compression algorithm. This algorithm cannot only be used to compress PPG signals, but also do so for steganographed PPG signals that include the patient information. Result and conclusion: It is worth mentioning that such an algorithm is being proposed for the first time to compress steganographed PPG signals. The algorithm is tested on PPG signals collected from four different databases, and its performance is assessed using both quantitative and qualitative measures. The proposed steganographed PPG compression algorithm provides a compression ratio that is much higher than that provided by other algorithms that are designed to compress the PPG signals only. Significance: first, the clinical quality of the reconstructed PPG signal can be controlled precisely, second, the patient's personal information is restored with no errors, third, high compression ratio, and fourth, the PPG signal reconstruction error is neither dependent on the steganographic operation nor on the size of the patient information data.
Magnetic resonance imaging (MRI), which assists doctors in determining clinical staging and expected surgical range, has high medical value. A large number of MRI images require a large amount of ...storage space and the transmission bandwidth of the PACS system in offline storage and remote diagnosis. Therefore, high-quality compression of MRI images is very research-oriented. Current compression methods for MRI images with high compression ratio cause loss of information on lesions, leading to misdiagnosis; compression methods for MRI images with low compression ratio does not achieve the desired effect. Therefore, a fast fractal-based compression algorithm for MRI images is proposed in this paper. First, three-dimensional (3D) MRI images are converted into a two-dimensional (2D) image sequence, which facilitates the image sequence based on the fractal compression method. Then, range and domain blocks are classified according to the inherent spatiotemporal similarity of 3D objects. By using self-similarity, the number of blocks in the matching pool is reduced to improve the matching speed of the proposed method. Finally, a residual compensation mechanism is introduced to achieve compression of MRI images with high decompression quality. The experimental results show that compression speed is improved by 2-3 times, and the PSNR is improved by nearly 10. It indicates the proposed algorithm is effective and solves the contradiction between high compression ratio and high quality of MRI medical images.
The accelerated proliferation of visual content and the rapid development of machine vision technologies bring significant challenges in delivering visual data on a gigantic scale, which shall be ...effectively represented to satisfy both human and machine requirements. In this work, we investigate how hierarchical representations derived from the advanced generative prior facilitate constructing an efficient scalable coding paradigm for human-machine collaborative vision. Our key insight is that by exploiting the StyleGAN prior, we can learn three-layered representations encoding hierarchical semantics, which are elaborately designed into the basic, middle, and enhanced layers, supporting machine intelligence and human visual perception in a progressive fashion. With the aim of achieving efficient compression, we propose the layer-wise scalable entropy transformer to reduce the redundancy between layers. Based on the multi-task scalable rate-distortion objective, the proposed scheme is jointly optimized to achieve optimal machine analysis performance, human perception experience, and compression ratio. We validate the proposed paradigm's feasibility in face image compression. Extensive qualitative and quantitative experimental results demonstrate the superiority of the proposed paradigm over the latest compression standard Versatile Video Coding (VVC) in terms of both machine analysis as well as human perception at extremely low bitrates (< 0.01 bpp), offering new insights for human-machine collaborative compression.
Nowadays, 360° video/image has been increasingly popular and drawn great attention. The spherical viewing range of 360° video/image accounts for huge data, which pose the challenges to 360° ...video/image processing in solving the bottleneck of storage, transmission, etc. Accordingly, the recent years have witnessed the explosive emergence of works on 360° video/image processing. In this article, we review the state-of-the-art works on 360° video/image processing from the aspects of perception, assessment and compression. First, this article reviews both datasets and visual attention modelling approaches for 360° video/image. Second, we survey the related works on both subjective and objective visual quality assessment (VQA) of 360° video/image. Third, we overview the compression approaches for 360° video/image, which either utilize the spherical characteristics or visual attention models. Finally, we summarize this overview article and outlook the future research trends on 360° video/image processing.
PDF
