Optimization of Low Frequency Acoustic Absorption Characteristics of Underwater Acoustic Cover Based on Nelder-Mead Simplex Method

In order to solve the low frequency sound absorption problem of acoustic covering layer, the local resonant cavity covering layer is established. The geometric parameters and material parameters of the composite structure are taken as optimization variables, the maximum sound absorption coefficient in the frequency band of 10-2000Hz is taken as optimization objective, and the Nelder-Mead simplicated method was used as optimization method to optimize the established model. The optimization results show that the sound absorption coefficient of the composite structure is increased by 13% and 24% respectively after the optimization of geometric parameters and material parameters. The sound pressure level of the sound wave emitted into the water area is reduced by about 3dB after the optimization, and the power loss is equivalent to increasing by half. Therefore, the sound absorption performance is improved. The research results can provide a theoretical basis for the design of acoustic coating.

Enhanced polarization-independent two-layer five-port grating with covering layer

In this paper, an enhanced polarization-independent two-layer five-port grating with covering layer is proposed. The rigorous coupled-wave analysis (RCWA) is used to predict grating parameters. In addition, the total efficiency of the polarization-independent five-port grating with covering layer can exceed 80% with the good uniformity of 1.97% for TE and TM polarization. The inherent coupling mechanism and the electric field energy distribution of the gratings are explained well under TE and TM polarization by the simplified mode method (SMM) and the finite element method (FEM). According to the reported five-port gratings, the proposed transmission five-port grating with a covering layer has good uniformity for TE and TM polarization. Moreover, the grating can be protected and the groove of the grating can be kept clean by adding a covering layer during the actual fabrication. At the same time, the fabrication errors of the two-layer five-port diffraction grating are further considered. Therefore, the numerically simulated five-port grating with covering layer has a wide application prospect in precision displacement measurement and holographic projection imaging.

Preparation of Nano Electrospinning Covered Stent and Its Application in the Treatment of Intracranial Aneurysm with CT Diagnosis

In the process of tissue regeneration or organ reconstruction, tissue engineering scaffolds provide strong structural support for the function of seed cells, which enables tissue engineering technology to be implemented. In the treatment of intracranial aneurysm, from the perspective of endovascular treatment, the emulsion electro-spinning method is used and the lactic acid caprolactone copolymer is taken as the matrix material to design a kind of vascular arterial stent with heparin loaded nanofibers as a film covering layer. SEM confirms that the stent has a good nanofiber structure, and TEM suggests that the core layer containing fluorescein is evenly distributed around the stent. Fourier transform infrared reflection (FTIR) shows that heparin is successfully loaded into the stent. WCA test indicates that heparin loading can improve the hydrophilicity of stent. In vitro biocompatibility/hemocompatibility test shows that the stent has good compatibility, but inhibits the proliferation of L929 and PIEC cells. With the stent as the film covering layer, the heparin loaded nanofiber stent for small vascular aneurysms successfully prepared has achieved good results in the treatment of intracranial aneurysm. CT imaging of patients treated with vascular arterial stent shows that heparin in tumor site degrades with time, which makes CT signal in mice change with time. At the same time, aneurysms gradually disappear with the implantation of covered stent. After implantation 30 d, the blood vessels of the implanted site are unobstructed and no thrombus appears.

Investigation and modeling of odors release from membrane holes on daily overlay in a landfill and its impact on landfill odor control

In the present work, we studied the NH3 and H2S odor fluxes between the exposed working area and the HDPE covering film holes of the daily overlay in an actual landfill site with a daily operating area of 1600 m2 in Hangzhou, China. We showed that the odors were released from the membrane pores and the average concentrations of NH3 and H2S release reached 109.6 ± 56.6 and 86.0 ± 31.1 mg/m2/s, respectively. These concentrations are 43.8 and 57.3 times the exposed working surface. Furthermore, mathematical modeling based on the total amount of odor release revealed that there was a linear positive correlation between the total odor amount and the landfill operation area. However, the maximum number of film holes allowed on the covering layer has nothing to do with the working area and exposed working time, which is mainly determined by the HDPE film width in terms of ensuring the deodorizing effect of the covering operation. If the HDPE film with a width of more than 4 m is used, the number of film holes allowed within 100 m is more than 8. Therefore, in order to reduce the odor, the appropriate film width should be selected according to the actual operating conditions such as the mechanical operation level at the time of welding, the design of the landfill site, and the operational norms. This study explores the effect of film hole quantity of the daily cover in the landfill on the odor release from the landfill, which can provide an important reference for the design, operation, and decision-making of the daily cover operation of the sanitary landfill.

Scattering of SH Waves by a Partially Debonded Cylindrical Inclusion in the Covering Layer

This article presents analytical solutions to the problem of dynamic stress concentration and the surface displacement of a partially debonded cylindrical inclusion in the covering layer under the action of a steady-state horizontally polarized shear wave (SH wave); these solutions are using the complex function method and wave function expansion method. By applying the large-arc assumption method, the straight line boundary of the half-space covering layer is transformed into a curved boundary. The wave field of the debonded inclusion is constructed utilizing a Fourier series and boundary conditions of continuity. The impact of debonding upon the dynamic stress concentration and surface displacement around the cylindrical concrete or steel inclusion is analyzed through numerical examples of the SH waves that are incident at normal angles, from a harder medium to a softer medium and from a softer medium to a harder medium. The examples show that various factors (including the medium parameters of the soil layers and the inclusion, the frequency of the incident waves, and the debonding situations) jointly affect the dynamic stress concentration factor and the surface displacement around the structure.

Formation of 1 × 3 splitting by embedded double-layer reflective grating under second Bragg illumination

In order to obtain a [Formula: see text] grating with high performance, we designed a double-layer reflective grating beam splitter with a covering layer at a wavelength of 1550 nm. We obtain a better grating structure by modal analysis and rigorous coupled-wave method. The reflectivity of the three diffraction orders for the grating is close to 33.3%. The optimized data show that the grating beam splitter has a large period process tolerance for TE polarization. The grating performance has high incident performance and uniform splitting effect.

Memory influences haptic perception of softness

The memory of an object’s property (e.g. its typical colour) can affect its visual perception. We investigated whether memory of the softness of every-day objects influences their haptic perception. We produced bipartite silicone rubber stimuli: one half of the stimuli was covered with a layer of an object (sponge, wood, tennis ball, foam ball); the other half was uncovered silicone. Participants were not aware of the partition. They first used their bare finger to stroke laterally over the covering layer to recognize the well-known object and then indented the other half of the stimulus with a probe to compare its softness to that of an uncovered silicone stimulus. Across four experiments with different methods we showed that silicon stimuli covered with a layer of rather hard objects (tennis ball and wood) were perceived harder than the same silicon stimuli when being covered with a layer of rather soft objects (sponge and foam ball), indicating that haptic perception of softness is affected by memory.