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The surface roughness of bamboo is a factor that determines the processing quality. The effects of spindle speed, feed speed, and cutting depth on the surface roughness of bamboo were studied using the orthogonal design test method. The results were analyzed using range analysis, main effect analysis, interaction analysis, and variance analysis to determine the effect of cutting parameters on the surface roughness of bamboo. The feed speed had a greater effect on the surface roughness of the bamboo in the tangential section; the spindle speed had a greater impact on the surface roughness of the bamboo in the cross section. The cutting depth had a greater impact on the surface roughness of the bamboo in the radial section. For the surface roughness on the tangential, cross, and radial sections of the bamboo, there was a relationship with the cutting parameters. A mathematical model for the analysis of surface roughness was established by response surface method. Also, contour and surface plots based on regression models showed the correlation between surface roughness and all possible pairwise combinations of three cutting parameter variables. The cutting technology with the best surface quality was determined by optimization analysis.

In the process of applying the high-frequency heating technology to bamboo heat treatment, controlling the material temperature has a great influence on the quality of bamboo forming. Therefore, research on the heat transfer mechanism of high-frequency heating of arc-shaped bamboo pieces is of great importance. In this paper, the influence of different moisture content, chord length, and plate voltage on the heating rate of arc-shaped bamboo pieces under high-frequency electric field were studied. The moisture content of bamboo had the most remarkable effect on the heating rate. With increased moisture content, the temperature rose faster. The selection of the plate voltage had an obvious influence on the heating. If the voltage was low, the heating rate was too slow, the heating time was long, or the voltage was high, it was easy to cause electric field breakdown and damage the bamboo pieces. As the chord length decreased, the heating rate gradually increased. When the radian of the arc-shaped bamboo pieces could be ignored, the heating rate was the fastest. The results showed that under certain conditions, the arc-shaped bamboo pieces showed a good heat treatment effect in a high-frequency electric field.

Cement-based composites with periodic wedge-shaped surfaces were manufactured by molding, and its microwave absorbing properties (MAPs) were measured in 1.7–18 GHz using arch method and simulated in 8–18 GHz. The results indicate that the MAPs of the composite in both polarization directions (PDs, perpendicular polarization, and parallel polarization) are improved greatly by the wedge structures. The higher the frequency is, the better the MAPs are especially in parallel PD. Large wedge height and large carbon black (CB) content enhance the MAPs of the composite, and enlarging the height is an effective method to enhance the MAPs in the low frequency range. When composites are filled with lightweight fillers, there is a slight decrease in the MAPs in parallel PD. The reflectivity is below − 10 dB in 3.7–18 GHz when the wedge height is 40 mm and CB is 1.5 g/L in both PDs. The excellent impedance matching caused by physical gradients and multiple reflections between wedges enhanced attenuation.

Cement-based composites filled with carbon black (CB) and porous glass pellets(GPs) were prepared, and the electromagnetic wave absorption properties (EMAPs) were investigated with the arch method in 1.7–18 GHz. Results indicate that introducing of GPs into cement-based materials enhances the EMAPs significantly. The larger the particle size is, the lower the impedance of the composite is. The number of absorption peaks increases, the reflectivity curve becomes flat, and the EMAPs increase first and then decrease. The GPs with the size of 0.25–1.0 mm contribute most to the EMAPs with the same content. Graded GPs produce high mechanical strength, and the synergistic effect of particles with different sizes on the enhancement of EMAPs is not obvious. The optimal content of GPs and composite thickness are 50 vol% and 20–30 mm, respectively. The composite reaches the lowest average reflectivity at − 9.67 dB, and the bandwidth below − 10 dB is 7.47 GHz when CB is 1.5 g/L, the thickness is 20 mm and the filling ratio is 50 vol%.

In order to cut down the usage amount of binder, mix it more evenly with the biomass raw materials and improve the quality of pellets in the densification process, this study explored the feasibility of promoting the densification of biomass by using a high-pressure spraying method to add liquid binder. In the study, a high-pressure sprayer was used to spray saturated brown sugar water into sawdust for densification tests. A three-factor orthogonal experiment was designed to analyze the physical characteristics of the pellets under different variables. Through analysis of range and multiple linear regression, the effect curve was drawn to analyze the impact of the high-pressure spraying method on densification. The results showed that under low compaction pressure of 14.9 MPa, the raw materials with adding 6% saturated brown sugar water can be densified into pellets, while the raw materials without binder cannot. Moreover, compared with the method of adding binder by stirring, the high-pressure spraying method obtained the pellets with fewer cracks on the surface and increased the relaxation density of pellets by 8.65%. Under high compaction pressure (75, 100, 124 and 149 MPa), the high-pressure spraying method has a significant effect on increasing the relaxation density, not only on the compressive strength.

Biocompatible polyvinyl alcohol (PVA)-styrylpyridinium (SbQ)/β-cyclodextrin (β-CD) composite nanofibers were obtained by electrospinning in this study. PVA-SbQ was used as the foundation polymer as well as crosslinking agent, β-CD was incorporated to achieve expected properties such as improved mechanical properties and thermal stability. The Fourier transform infrared spectroscopy (FTIR) spectra confirmed the existence of β-CD, and the morphologies and average fiber diameters of the electrospun composite nanofibers were also analyzed by SEM. X-ray diffraction patterns (XRD) of PVA-SbQ/β-CD composite nanofibers revealed that the inclusion of β-CD in the nanofibers affected the ordered phase of PVA. Besides, the thermal analyses revealed the improvement in the thermal properties for PVA-SbQ/β-CD composite nanofibers. It was found that the crosslinked composite nanofibers showed a clear higher tensile strength (TS) as well as a greater elongation at break (EB). Eventually, antifungal drug griseofulvin (GSV) has been loaded into the composite nanofibers by formation of its inclusion complex with β-CD in aqueous solution, ultraviolet light (UV-Vis) spectral analysis showed that the drug-loading nanofibers had certain sustained release effect.

The surface roughness of bamboo milling is one of the important indexes to evaluate the surface quality of bamboo milling. This article outlines the application of response surface methodology to optimize diamond cutting tools for bamboo cutting. In the experiment, different cutting speed, feed rate and depth of cut were used as cutting parameters, and the surface roughness was used to evaluate the surface quality of bamboo cutting. The results of the experiment were evaluated by variance analysis, graphical method and numerical method. The response surface method and expected value function are used to determine the mathematical model of bamboo surface roughness and the cutting parameter combination corresponding to the best cutting process. The result shows that the influence of feed speed on the surface roughness of the bamboo chord surface (Ra1) and the bamboo end surface roughness (Ra2) is more obvious, and the cutting parameters have little effect on the bamboo diameter surface roughness (Ra3). The cutting technology with the best surface quality is determined by optimization analysis. The established mathematical model can effectively predict the response within the range of cutting parameters, and the optimized combination of cutting parameters can obtain better surface quality of bamboo milling. The best bamboo surface roughness after optimization can be obtained at higher cutting speed, low feed speed and lower cutting depth is Ra1 = 1.5832 μm, Ra2 = 6.3626 μm, Ra3 = 2.2438 μm.

Porous carbon nanofibers (PCNFs)@Tin oxide (SnOx) nanocomposites are synthesized by co-electrospinning using renewable alkali lignin-polyaniline (PAN) solution as the core and Sn precursors-polyvinyl pyrrolidone (PVP) solution as the shell, followed by heat treatment. By changing the preheating temperature during heat treatment, PCNFs@SnOx nanocomposites with different nanostructures are obtained. The nanocomposites as electrodes of supercapacitors exhibit remarkable performance. The relationship between the microstructures and electrochemical properties of nanocomposites is explored. The experimental results show that increasing the preheating temperature to 300 °C, micropores and mesopores coexist in this nanocomposite. The prepared nanocomposite as the electrode possesses a high specific capacitance of 229 F g−1 at 0.2 A g−1. The superior electrochemical performance is presumably attributed to the large specific surface areas of PCNFs and pseudocapacitance of SnOx modifications. These encouraging results show great potential in synthesizing renewable biomass-based PCNFs@ SnOx nanocomposites with different structures.

This paper investigated the combined effects of different sustained loads and environmental conditions on chloride transport behavior in bending-shear section of reinforced concrete beam. It also compared the chloride transport pattern between bending-shear section and pure bending section based on published literatures. In this study, the tested reinforced concrete beams were subjected to 10%, 16%, 22% and 28% of ultimate bending load using spring-loaded system. For each load, the chloride content was measured on different depths of two specimens under chloride immersion and drying-wetting cycle conditions for 60 days, respectively. The results show that for the given depth and load, the specimens under drying-wetting condition had higher chloride content than those under immersion. The drying-wetting condition facilitated the chloride transport in concrete. The restrictive effect of depth on chloride transport in tension zone was larger than in compression zone. Experimental condition is the most effective factor on chloride transport in compression zone, comparing with depth and load. The corrosion of chloride was mainly on bending-shear section when the load is within 10–16% of the ultimate flexural capacity, while it was on pure bending section when the load is from 22 to 28% of the ultimate flexural capacity.

With the development of the power system, composite insulators are widely used in China. However, the contamination flashover caused by the loss of the hydrophobicity of silicone rubber remains a threat to the insulation, especially in EHV and UHV transmission lines. The statue variations of the composite insulator surface were studied in this paper. Based on the cluster analysis method, the leakage current was also investigated. And 16 parameters were extracted to characterize the surface state. It was showed that these parameters could be used to recognize the degree of hydrophobicity loss over the composite insulator surface. The discharge model spectrum diagram of composite insulator surface was also established, which could be used for the diagnosis of the degree of hydrophobicity loss and salt deposit density over the insulator surface. This work can enrich the recognition methods of surface statue of composite insulators and may provide useful reference for performance evaluation of composite insulators in service.

Using bamboo to replace wood has great significance for the protection of forests. This work presents the concept of the reorganization of arc bamboo sheet to produce recombined arc-segment bamboo lumber (RABL). Several key preparation technology parameters were investigated. Results showed that when the phenol resin (PF) double-sided adhesive quantity was 250 g/m2, unit pressure was 2.0 MPa, screen voltage was 4200 V, screen current was 1.5 A, and hot pressing time was 30 s/mm, the modulus of rupture (MOR) of the RABL was 105 MPa and the modulus of elasticity (MOE) was 5000 MPa. These parameters mean that RABL could be used as the structural material for load-bearing situations. If ignoring the machining allowance, the bamboo utilization rate of the RABL was 1.72 times that of the rectangular element recombinant bamboo and the adhesive level of the RABL was 0.6 times that of the rectangular element recombinant bamboo. When considering the machining allowance, the bamboo utilization rate of the RABL was 1.8 times that of the rectangular element recombinant bamboo, and the adhesive volume of the RABL was 0.56 times that of the rectangular element recombinant bamboo, so RABL has obvious advantages.

With the increasing scarcity of wood as a natural resource, bamboo has become a popular substitute for wood. The present work developed a high-strength original state multi-reorganization material (GPEHB), without the use of a hot press or traditional assembly. The original bamboo units were polygonized into outer contours and milled into finger-joints on each ending. The GPEHB was organized and assembled under an external press, using industrial adhesives. The mechanical properties and thermal insulation of GPEHB were characterized. Moreover, the overall GPEHB unit bending strength was 73.15 MPa, and the parallel-to-grain compression was 55.22 MPa (higher than that of Pinus sylvestris lumber, though less than that of glued laminated bamboo). The GPEHB unit overall density was 0.24 g/cm³, 76% lower than that of glued laminated bamboo, and 50% lower than Pinus sylvestris lumber. The compressive strength of GPEHB (7 units) was 170.5 kN, while the compressive strength of GPEHB for 14 units was 493.5 kN, which meet the requirements of GB 50005 (2003). The bending strength of GPEHB 7 units was 12 kN, while that of 14 units was 37 kN. The heat conductivity coefficient for GPEHB was 0.25 W/mK, which is better than concrete and steel. The GPEHB has taken full advantage of its honeycomb-structured material, which allows it to avoid stress concentration in the regular polygonal corners.

In order to determine the stress-strain relationship of the inner (intima and media) and outer (adventitia) layers of blood vessels in the neighborhood of the zero-stress state, bending experiments were performed on aortic strips of rats. In the experiments, one end of a strip was clamped, and a force was applied on the other end. The deflection curves of the strips were measured. By regarding the aortic strip as a curved beam, the classical beam theory was employed to analyze the strain distribution from the experimental data. A computer program dealing with nonlinear equations and nonlinear least squares optimization was developed. Strains were referred to the zero-stress state. The load-deflection relationship was then used to determine the stress-strain relationship. Certain forms of the stress-strain laws were assumed. The linear laws fit the experimental data accurately, probably because the strains during bending are quite small, although the rotations are large. The Young’s modulus of the inner layer, which consists of endothelial and smooth muscle cells and elastic lamina, was found to be three to four times larger than that of the outer layer which consists of collagen with a small amount of fibroblasts and elastin. The residual stresses and strains at the no-load state were calculated from the deduced stress-strain relationship. It is shown that large errors (up to 50 percent) in the values of the residual strains will occur if the wall material was treated as homogeneous, i.e., if the layered constitution was ignored.

With few exceptions, experimental results on the blood vessel elasticity have been analyzed with the blood vessel wall treated as a homogeneous material, probably because the experiments have been limited to inflation and stretching. To advance the subject, we must evaluate the force-deformation relationship of different layers of the vessel. A key strategy to do this is to study nonaxisymmetric deformation of the vessel wall so that the different layers of the vessel may deform in different amounts at different places. One of the most effective nonaxisymmetric deformations that can be imposed on the vessel wall is bending. The first important question to ask about bending is, Where is the neutral axis? In this study, a method to determine the neutral axis is presented. We found that the neutral axis of the aorta of the pig lies in the medial layer about one-third of the wall thickness from the endothelium. We measured the strain distribution in the vessel wall by optical methods. Using the load-deflection relationship, we evaluated the Young's modulus of the intima-media layer and that of the adventitia. They differ by an order of magnitude. Our results show that the Young's modulus of the intima-media layer of the pig thoracic aorta is 43.2 +/- 15.8 kPa, whereas the Young's modulus of the adventitial layer is 4.70 +/- 1.72 kPa, in a linear range of the stress-strain relationship including the zero-stress state and the no-load state.

In this paper, leakage current flowing along contaminated ceramic insulators was separated into low frequency component and pulse component, which were detected respectively by Rogowski coil in artificial contamination tests. The effects of the operating voltage, the equivalent salt deposit density and humidity on the two characteristic components of leakage current were investigated. It is revealed that the peak of the pulse current component has a sudden rising during the increase of humidity, and the inflexion has been found to be closely related with the low frequency current. The diagnosing methods based on the combination of the two current components have been proposed eventually.