Crashworthiness design of density-graded cellular metals

AbstractCrashworthiness of cellular metals with a linear density gradient was analyzed by using cell-based finite element models and shock models. Mechanisms of energy absorption and deformation of graded cellular metals were explored by shock wave propagation analysis. Results show that a positive density gradient is a good choice for protecting the impacting object because it can meet the crashworthiness requirements of high energy absorption, stable impact resistance and low peak stress

Dynamic response of elastic beam to a moving pulse: finite element analysis of critical velocity

Dynamic behaviour of a semi-infinite elastic beam subjected to a moving single sinusoidal pulse was investigated by using finite element method associated with dimensionless analysis. The typical features of the equivalent stress and beam deflection were presented. It is found that the average value of maximal equivalent stress in the beam reaches its maximum value when the velocity of moving pulse is closed to a critical velocity. The critical velocity decreases as the pulse duration increases. The material, structural and load parameters influencing the critical velocity were analysed. An empirical formula of the critical velocity with respect to the speed of elastic wave, the gyration radius of the cross-section and the pulse duration was obtained

Efficacy and safety of Ozone Therapy for patients with chronic hepatitis B : A multicenter, randomized clinical trial [abstract]

Background. Ozone therapy has a long history. Some studies proved that ozone therapy was useful in treatment of virus hepatitis.Objective: To evaluate the efficacy and safety of new medical ozone therapy system for the treatment of chronic hepatitis B. Method. One hundred eighty-nine patients with chronic hepatitis B were included in this open-label, phase 3 study, and randomly assigned to receive ozone autohemotherapy with experimental ozone generator TianYi (group 1) or with ozone generator Humares (group 2) or oral diammonium glycyrrhizinate capsules (group 3) in a 1:1:1 ratio for 12 weeks. The primary efficacy end point was sera HBV DNA level of less than 1×103 IU/ml or having a more than 2 log10 reduction in HBV DNA level at the end of 12 weeks treatment as compared to baseline HBV DNA level. Secondary end points included HBeAg seroconversion, biochemical response, and combined response. Results. At the end of 12 weeks treatment, the proportion of patients reached the primary end point of virologic response in group 1, group 2, and group 3 were 22.4% (13/58, 95% CI, 12.5 to 35.3), 14.7 (9/61, 95% CI, 7.0 to 26.2) and 3.9% (2/51, 95% CI, 0.5 to 13.5), respectively (p=0.021) in the pre-protocol population. Virologic response occurred in more patients receiving ozone therapy with experimental device than patients receiving oral diammonium glycyrrhizinate capsules (mean difference 18.5%, 95% CI 6.3 to 31.5, p=0.005). However, there was no statistical difference in VR12 rates between the treatment of medical ozone therapy system with experimental device (group 1) and with Humares (group 2) (mean difference 7.7%, 95% CI -6.5 to 22.0, p=0.282). More HBeAg seroconversion in patients treated by Tianyi ozone therapy system than those treated by Humares ozone therapy device and oral diammonium glycyrrhizinate capsules (14.8%, 5.1% and 7.3%, respectively, P = 0.272). Higher biochemical response rate was observes in patients receiving ozone therapy than oral diammonium glycyrrhizinate capsules (31.6%, 36.7% and 24.0%, respectively, p = 0.359). The safety profile was similar for the three treatment groups and adverse events were .scare infrequent and mild. Conclusions. Ozone therapy had superior antiviral efficacy with a similar safety profile as compared with oral diammonium glycyrrhizinate capsules through week 12 treatment. Ozone therapy is also associated with normalized ALT and AST levels, demonstrating that ozone therapy could benefit the patients with chronic hepatitis B

Anisotropic elastic constants calculation of stainless steel cladded layers of pressure vessel steel plate

Cladding stainless steel layer on the inner surface of ferrite pressure vessel is a common method to improve the corrosion resistance and save the economic cost. However, the movement of heat source and temperature gradient in the process of cladded welding will lead to the anisotropy of cladded layer material. When measuring the residual stress of pressure vessel steel plate with stainless steel cladded layers (SSCL) by contour method, it is necessary to know the elastic mechanical properties of stainless steel cladded layers accurately. The assumption of transversely isotropy (TI) was employed, and the relationship between the material compliance matrix and the elastic modulus of transversely isotropic material was utilized. Based on the elastic modulus of each cladded layer and the whole steel plate from the longitudinal direction (0°) until the transverse direction (90°) measured by the experiment, the independent constants S11, S13, S33 and S44 in the compliance matrix of each cladded layer and the whole steel plate were obtained by regression analysis method. Furthermore, by using the relationship between the independent constants of the stiffness matrix of the transversely isotropic material and the single crystal material, the independent constant S12 in the compliance matrix of each stainless steel cladded layer and the whole steel plate were obtained. And then the independent constants of the stiffness matrix of each cladded layer and the whole steel plate were acquired. Hence, a method for calculating the anisotropic elastic constants of the stainless steel cladded layer and the whole steel plate was proposed. The results will provide material data support for measuring residual stress of pressure vessel steel plate with stainless steel cladded layers by contour method

A Muscle Teleoperation System of a Robotic Rollator Based on Bilateral Shared Control

The approach that achieves the teleoperation between human muscle signals and the mobile robot is increasingly applied to transfer human muscle stiffness to enhance robotic performance. In this paper, we develop a mobile rollator control system applying a muscle teleoperation interface and a shared control method to enhance the obstacle avoidance in an effective way. In order to control intuitively, haptic feedback is utilized in the teleoperation interface and is integrated with EMG stiffness to provide a large composition force. Then the composition force is implemented with an artificial potential field method to keep the robotic rollator away from the obstacle in advance. This algorithm is superior to the traditional APF algorithm regardless of the required time and trajectory length. The experimental results demonstrate the effectiveness of the proposed muscle teleoperation system

Preparation and toughening mechanism of Al2O3 composite ceramic toughened by B4C@TiB2 core–shell units

In this paper, the concept of incorporating core–shell structured units as secondary phases to toughen Al2O3 ceramics is proposed. Al2O3 composite ceramics toughened by B4C@TiB2 core–shell units are successfully synthesized using a combination of molten salt methodology and spark plasma sintering. The synthesis of B4C@TiB2 core–shell toughening units stems from the prior production of core–shell structural B4C@TiB2 powders, and this core–shell structure is effectively preserved within the Al2O3 matrix after sintering. The B4C@TiB2 core–shell toughening unit consists of a micron-sized B4C core enclosed by a shell approximately 500 nm in thickness, composed of numerous nanosized TiB2 grains. The regions surrounding these core–shell units exhibit distinct geometric structures and encompass multidimensional variations in phase composition, grain dimensions, and thermal expansion coefficients. Consequently, intricate stress distributions emerge, fostering the propagation of cracks in multiple dimensions. This behavior consumes a considerable amount of crack propagation energy, thereby enhancing the fracture toughness of the Al2O3 matrix. The resulting Al2O3 composite ceramics display relative density of 99.7%±0.2%, Vickers hardness of 21.5±0.8 GPa, and fracture toughness 6.92±0.22 MPa·m1/2

Nitrogen, manganese, iron, and carbon resource acquisition are potential functions of the wild rice Oryza rufipogon core rhizomicrobiome

Background: The assembly of the rhizomicrobiome, i.e., the microbiome in the soil adhering to the root, is influenced by soil conditions. Here, we investigated the core rhizomicrobiome of a wild plant species transplanted to an identical soil type with small differences in chemical factors and the impact of these soil chemistry differences on the core microbiome after long-term cultivation. We sampled three natural reserve populations of wild rice (i.e., in situ) and three populations of transplanted in situ wild rice grown ex situ for more than 40 years to determine the core wild rice rhizomicrobiome. Results: Generalized joint attribute modeling (GJAM) identified a total of 44 amplicon sequence variants (ASVs) composing the core wild rice rhizomicrobiome, including 35 bacterial ASVs belonging to the phyla Actinobacteria, Chloroflexi, Firmicutes, and Nitrospirae and 9 fungal ASVs belonging to the phyla Ascomycota, Basidiomycota, and Rozellomycota. Nine core bacterial ASVs belonging to the genera Haliangium, Anaeromyxobacter, Bradyrhizobium, and Bacillus were more abundant in the rhizosphere of ex situ wild rice than in the rhizosphere of in situ wild rice. The main ecological functions of the core microbiome were nitrogen fixation, manganese oxidation, aerobic chemoheterotrophy, chemoheterotrophy, and iron respiration, suggesting roles of the core rhizomicrobiome in improving nutrient resource acquisition for rice growth. The function of the core rhizosphere bacterial community was significantly (p < 0.05) shaped by electrical conductivity, total nitrogen, and available phosphorus present in the soil adhering to the roots. Conclusion: We discovered that nitrogen, manganese, iron, and carbon resource acquisition are potential functions of the core rhizomicrobiome of the wild rice Oryza rufipogon. Our findings suggest that further potential utilization of the core rhizomicrobiome should consider the effects of soil properties on the abundances of different genera. [MediaObject not available: see fulltext.]