This paper describes the design of an acoustic metamaterial fluid-filled pipe with periodically variable materials. The aim of this design is to improve the broadband vibration attenuation frequency range of fluid-filled pipes by combining the mechanism of local resonance (LR) and Bragg scattering bandgaps (BGs). The vibration bandgap (BG) of the pipe is investigated using the transfer matrix method. It is demonstrated that the coupling of LR and Bragg scattering BGs produces a remarkable improvement in effective bandwidth. Additionally, the external shock excitation effect on pipe vibration is calculated using the finite element method. This indicates that the strongest interaction between the LR and Bragg BG is achieved when the LR is located in the center of the softer material. However, this strong coupling effect may cause some degeneration in the Bragg BG. Moreover, in practical applications, the position of the LR BG should be determined according to the vibration BG requirements. Experimental samples are prepared, and an experimental test and verification procedure is conducted. The positions and widths of the BG and the shock vibration properties measured during the experiment agree well with the theoretical results. This research provides a technical and theoretical basis for the attenuation design of vibration reduction systems for fluid-filled pipes that may be subjected to explosive loads.

In the present study, we aimed to elucidate changes in electroencephalography (EEG) metrics during recovery of consciousness and to identify possible clinical markers thereof. More specifically, in order to assess changes in multidimensional EEG metrics during neuromodulation, we performed repeated stimulation using a high-density transcranial direct current stimulation (HD-tDCS) protocol in 42 patients with disorders of consciousness (DOC). Coma Recovery Scale-Revised (CRS-R) scores and EEG metrics [brain network indicators, spectral energy, and normalized spatial complexity (NSC)] were obtained before as well as fourteen days after undergoing HD-tDCS stimulation. CRS-R scores increased in the responders (R +) group after HD-tDCS stimulation. The R + group also showed increased spectral energy in the alpha2 and beta1 bands, mainly at the frontal and parietal electrodes. Increased graphical metrics in the alpha1, alpha2, and beta1 bands combined with increased NSC in the beta2 band in the R + group suggested that improved consciousness was associated with a tendency toward stronger integration in the alpha1 band and greater isolation in the beta2 band. Following this, using NSC as a feature to predict responsiveness through machine learning, which yielded a prediction accuracy of 0.929, demonstrated that the NSC of the alpha and gamma bands at baseline successfully predicted improvement in consciousness. According to our findings reported herein, we conclude that neuromodulation of the posterior lobe can lead to an EEG response related to consciousness in DOC, and that the posterior cortex may be one of the key brain areas involved in the formation or maintenance of consciousness.

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Fluid-conveying pipe systems are widely used in various equipments to transport matter and energy. Due to the fluid–structure interaction effect, the fluid acting on the pipe wall is easy to produce strong vibration and noise, which have a serious influence on the safety and concealment of the equipment. Based on the theory of phononic crystals, this paper studies the vibration transfer properties of a locally resonant (LR) pipe under the condition of fluid–structure interaction. The band structure and the vibration transfer properties of a finite periodic pipe are obtained by the transfer matrix method. Further, the different impact excitation and fluid–structure interaction effect on the frequency range of vibration attenuation properties of the LR pipe are mainly considered and calculated by the finite element model. The results show that the existence of a low-frequency vibration bandgap in the LR pipe can effectively suppress the vibration propagation under external impact and fluid impact excitation, and the vibration reduction frequency range is near the bandgap under the fluid–structure interaction effect. Finally, the pipe impact experiment was performed to verify the effective attenuation of the LR structure to the impact excitation, and to validate the finite element model. The research results provide a technical reference for the vibration control of the fluid-conveying pipe systems that need to consider blast load and fluid impact.

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ObjectiveAcute subdural hematoma (ASDH) is a common neurological emergency, and its appearance on head-computed tomographic (CT) imaging helps guide clinical treatment. To provide a basis for clinical decision-making, we analyzed that the density difference between the gray and white matter of the CT image is associated with the prognosis of patients with ASDH.MethodsWe analyzed the data of 194 patients who had ASDH as a result of closed traumatic brain injury (TBI) between 2018 and 2021. The patients were subdivided into surgical and non-surgical groups, and the non-surgical group was further subdivided into “diffused [hematoma]” and “non-diffused” groups. The control group's CT scans were normal. The 3D Slicer software was used to quantitatively analyze the density of gray and white matter depicted in the CT images.ResultsImaging evaluation showed that the median difference in density between the gray and white matter on the injured side was 4.12 HU (IQR, 3.91–4.22 HU; p < 0.001) and on the non-injured side was 4.07 HU (IQR, 3.90–4.19 HU; p < 0.001), and the hematoma needs to be surgically removed. The median density difference value of the gray and white matter on the injured side was 3.74 HU (IQR, 3.53–4.01 HU; p < 0.001) and on the non-injured side was 3.71 HU (IQR, 3.69–3.73 HU; p < 0.001), and the hematoma could diffuse in a short time.ConclusionQuantitative analysis of the density differences in the gray and white matter of the CT images can be used to evaluate the clinical prognosis of patients with ASDH.

<sec>Fluid-structure interaction pipeline systems are extensively adopted to transfer matter, energy and momentum, which are widely used in various fields. Due to the fluid-structure interaction effect, the pipe wall proves to produce strong vibration and noise under fluid action, which has a serious influence on the safety and concealment of the equipment, even leading to serious damages. Therefore, it is of great significance to study the vibration characteristics of fluid-structure interaction pipeline and methods to reduce the vibration of pipeline both in theory and in practice. </sec><sec>Phononic crystal can suppress the propagation of elastic waves in a specific frequency range by their special band-gap characteristics, which have wide application prospects in the field of vibration and noise reduction. Especially, the band gap characteristics of phononic crystal pipeline used to design fluid-structure interaction pipeline system have been widely studied, thus providing a new technical approach to reducing the vibration and noise of the pipeline. </sec><sec>In this paper, based on the theory of phononic crystal, the vibration transfer characteristics of the Bragg phononic crystal pipeline under fluid-structure interaction are studied. Combining the transfer matrix method and the finite element method, the band structure and band gap characteristics are calculated. Using the finite element method, the vibration characteristics of the phononic crystal pipeline under fluid-structure interaction effect, the shock excitation of pipe wall and the shock excitation of the fluid are considered. The influence of the fluid-structure interaction on the vibration transmission characteristics of the phononic crystal pipeline is also analyzed. </sec><sec>The research results indicate that when the fluid velocity in the fluid-structure interaction pipeline system is small the Bragg phononic crystal pipeline has a good attenuation effect on the shock excitation of pipe wall in the band gap range, and that when the fluid velocity increases the fluid-structure interaction effect becomes significant, the attenuation effect becoming weaker. Bragg phononic crystal pipeline has a certain attenuation effect on the pipe wall vibration caused by the fluid shock excitation near the band gap. The research results are expected to be able to provide a technical reference for the vibration control of pipeline systems under fluid-structure interaction conditions. </sec>

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