Numerical simulation analysis for the effect of water content on the intelligent compaction quality of roadbed

In the process of intelligent compaction of roadbeds, the water content of the roadbed is one of the important influencing factors of compaction quality. In order to analyze the effect of water content on the compaction quality of roadbeds, this paper is developed by secondary development of Abaqus finite element numerical simulation software. At the same time, the artificial viscous boundary was set to eliminate the influence of boundary conditions on the results in the finite element modeling process, so that the numerical simulation can be refined to model. On this basis, the dynamic response analysis of the roadbed compaction process is performed on the finite element numerical simulation results. This paper established the correlation between compaction degree and intelligent compaction index CMV (Compaction Meter Value) and then analyzed the effect of water content on the compaction quality for the roadbed. The results of this paper show that the amplitude of the vertical acceleration is almost independent of the moisture content, and the vertical displacement mainly occurs in the static compaction stage. The vertical displacement changes sharply in the first 0.5 s when the vibrating wheel is in contact with the roadbed. The main stage of roadbed compaction quality increase is before the end of the first compaction. At the end of the first compaction, the roadbed compaction degree increased rapidly from 80% to 91.68%, 95.34% and 97.41%, respectively. With the increase in water content, the CMV gradually increased. At the end of the second compaction, CMV increased slightly compared with that at the end of the first compaction and stabilized at the end of the second compaction. The water content of the roadbed should be considered to be set slightly higher than the optimal water content of the roadbed by about 1% during the construction of the roadbed within the assumptions of this paper

Three-dimensional laser combined with C-arm computed tomography-assisted puncture of intracerebral hemorrhage

BackgroundIntracerebral hemorrhage (ICH) is the deadliest subtype of stroke, with a 30-day case fatality rate of approximately 40%. Timely and accurate treatment is essential to facilitate recovery. The introduction of stereotactic instruments and navigation systems has greatly improved the accuracy of surgical treatment. In this study, we explored the application and effects of a three-dimensional (3D) laser combined with C-arm computed tomography (CT) on ICH puncture.Materials and methodsAccording to the principle of randomness, 118 patients with ICH were divided into control and experimental groups. The control group was treated with CT-guided puncture, and the experimental group was treated with 3D laser combined with C-arm CT puncture. The hematoma clearance rates at 3, 5, and 7 days after surgery and the prognosis at 1, 3, and 6 months after surgery were compared between the two groups.ResultsThe hematoma clearance rates of the group using 3D laser combined with C-arm CT at 3, 5, and 7 days after surgery were significantly higher than those of the control group, and the difference was statistically significant (p < 0.05). One month postoperatively, the daily living ability (ADL) grading and recovery of the patients in the test group was significantly better than those of the control group (p < 0.05), but there was no statistically significant difference in ADL 3 and 6 months after surgery (p > 0.05).Conclusion3D laser combined with C-arm CT puncture has the advantages of real-time guidance, accurate positioning, and simple operation. It is an effective minimally invasive surgical method that is easy to master

Pervasive hybridization during evolutionary radiation of Rhododendron subgenus Hymenanthes in mountains of southwest China

Radiations are especially important for generating species biodiversity in mountainous ecosystems. The contribution of hybridization to such radiations has rarely been examined. Here, we use extensive genomic data to test whether hybridization was involved in evolutionary radiation within Rhododendron subgenus Hymenanthes, whose members show strong geographic isolation in the mountains of southwest China. We sequenced genomes for 143 species of this subgenus and 93 species of four other subgenera, and found that Hymenanthes was monophyletic and radiated during the late Oligocene to middle Miocene. Widespread hybridization events were inferred within and between the identified clades and subclades. This suggests that hybridization occurred both early and late during diversification of subgenus Hymenanthes, although the extent to which hybridization, speciation through mixing-isolation-mixing or hybrid speciation, accelerated the diversification needs further exploration. Cycles of isolation and contact in such and other montane ecosystems may have together promoted species radiation through hybridization between diverging populations and species. Similar radiation processes may apply to other montane floras in this region and elsewhere

Experimental Study on Creep–Recovery Behavior of Polyphosphoric Acid (PPA) Modified Asphalt Binders under Multiple Factors

The polyphosphoric acid (PPA) modified asphalt binder is a potential choice as one of the pavement materials for its excellent high-temperature performance and low cost. To further analyze the influences of temperature and load on the service life of pavement from the perspective of deformation behavior, six kinds of asphalt binders with different PPA dosages were prepared for Multiple Stress Creep and Recovery (MSCR) tests at five temperature levels. The deformation behavior is investigated by basic deformation parameters, rheological simulation, and energy parameter changes. The results show that the percent recovery (R) drops sharply while non-recoverable creep compliance (Jnr) goes up slightly with the increase in temperature. Three-element model, composed by E1, η1, and η2, can be used to describe the creep behavior. PPA-modified asphalt binder exhibits nonlinear creep behavior, and the logarithmic model can simulate recovery behavior better than the power–law model. Stored energy and dissipated energy can characterize the change of energy in the creep process under different conditions and show a significant correlation to deformation parameters. It is concluded that the elastic component of asphalt binders is increased by PPA, which is beneficial to the improvement of the deformation resistance and recovery capacity of asphalt binders. The recommended dosage of PPA is 1.5%. This investigation is conducive to a better understanding of the deformation behavior of PPA-modified asphalt binders and provides a reference for its engineering applications

Research on key influencing factors of scrap tire-soil retaining wall

The emergence of STSW can reduce the amount of materials such as sand and gravel and improve its performance compared to conventional retaining walls. In order to investigate the key influencing factors of STSW, the compression modulus of Scrap tire-soil module (STSM) was obtained by designing a full-scale compression strength test. The shear strength was obtained through a scale-test of shear strength. On this basis, the gravity STSW was established by the finite element numerical simulation software, and the bearing capacity of STSW was analyzed. Further, the key influencing factors of the bearing capacity of STSW were analyzed by designing orthogonal tests, and suggestions for parameter selection for designing STSW were given. The results show that: the friction angle of STSW increases and becomes larger with the increase of area ratio, and the cohesion decreases and decreases with the increase of area ratio; with the increase of compression modulus and internal friction angle, the maximum shear stress inside the retaining wall increases, while the cohesive force has almost no effect on the maximum value of shear stress inside the retaining wall; when constructing retaining walls, it is recommended to use Internal filling material with large compression modulus, small area ratio and its in the range of [0.3–0.5] of STSM

Fault diagnosis of AUV based on sliding-mode observer

Designing of a sliding mode observer was finished based on the motion model of autonomous underwater vehicle (AUV). A Flutter decrease strategy for the sliding mode observer was discussed and the sliding mode observer was applied to the fault diagnosis of the AUV. Simulation experiment without faults was designed. Simulation experiment of sensor fault diagnosis and field trial of thruster fault diagnosis were undertaken. The validity and feasibility of this method were validated based on the analysis of the simulation and field trial results

Comparison of metamorphic zircons from granulite xenoliths and granulite terrain in northern North China Craton

We conduct a study of petrography, geochronology, trace element and Hf isotope compositions on zircons from granulite terrain and granulite xenoliths in the Zhangjiakou region, northern North China Craton. Most zircons from both types of granulite have core-rim structure in their CL images. All the magmatic zircon cores yield essentially identical ∼2.5Ga ages, whereas metamorphic zircons yield ages of ∼1.85Ga and 120-140Ma, respectively. Most the ∼1.85Ga metamorphic zircons have Th/U ratios lower than 0.4 with a range of 0.01 to 0.63. However, the range of Th/U ratios of Mesozoic (120-140Ma) metamorphic zircons (0.12-3.48) overlaps that of the magmatic zircons (0.12-2.44). The Mesozoic and ∼1.85Ga metamorphic zircons have REE patterns consistent with magmatic zircons, except that the ∼1.85Ga ones show less enrichments and much less negative Eu anomalies than those of magmatic zircons. Therefore, Th/U ratios and the REE patterns cannot be used to distinguish metamorphic zircons from magmatic ones. The ∼1.85Ga metamorphic zircons, however, have lower formation temperatures, oxygen fugacity and 176Lu/177Hf ratios than the Mesozoic ones. We speculate that the ∼1.85Ga metamorphic zircons represent newly grown zircons coexisting with garnets and melt/fluid while the Mesozoic metamorphic zircons were formed quickly without the presence of garnet. The Mesozoic metamorphic zircons vary in their origins; some of these zircons were metamorphic newly grown while the others experienced recrystallization from a U-depleted melt/fluid. Our results suggest that P-T conditions, the melt/fluid and oxygen fugacity play important roles in controlling the trace element distribution and Hf isotope compositions of metamorphic zircons in the granulites

Research on strength improvement and stabilization mechanism of organic polymer stabilizer for clay soil of subgrade

Soil stabilizer can improve the physical and chemical properties of clay and improve the bearing capacity of subgrade soil. A kind of liquid polymer soil stabilizer of vinyl acetate-ethylene was used in this paper. First of all, the effects of stabilizer content and curing time on the unconfined compressive strength (UCS) and the water stability were studied to clarify the strength evolution of stabilized soil. Furthermore, the pH test, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), X-Ray Diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR) were performed to study mineralogy, morphology, and chemistry of clay minerals and polymer stabilizer, as well as the potential interaction of the both. The results show that the stabilized soil has a quick strength growth before 14d that reaches about 89% of the final strength, then followed by a decreasing growth rate. Extending the curing time and increasing stabilizer content contribute to the dense agglomeration structure and homogenous skeleton structure. When immersed in the water, the strength has the largest reduction amplitude within the first day. The pore-filling effect, physicochemical bonds, and surface wrapping for clay particles are dominating roles of the polymer stabilizer. The formed fine colloidal particles could fill micro-pores distributed in the matrix. In addition, the polar functional group of carbonyl could create a strong electrostatic attraction and hydrogen bond with the clay minerals, further improving the adhesion, while there are no other new function groups generated. The polymers containing hydrophobic groups are recommended in consideration of water stability

Structure and Properties of Reduced Graphene Oxide/Natural Rubber Latex Nanocomposites

In this work, the morphology and properties of graphene modified natural rubber (NR) was studied. Graphite oxide was chemically reduced with poly(sodium 4-styrenesulfonate) as a stabilizer, then the obtained graphene was blended with NR using latex technique. It is observed that a stable graphene suspension was fabricated by chemical reduction of graphite oxide in the presence of surfactant, while graphene was dispersed homogeneous in NR matrix as tested by WAXD and TEM. Dynamic mechanical analysis showed that storage modulus enhanced dramatically after the incorporation of graphene due to the high surface area of graphene and the exfoliated structure of graphene in NR. The electrical property and thermal conductive properties of NR/graphene nanocomposites improved significantly following the increase in graphene concentration

Optimal Decomposition for the Monthly Contracted Electricity of Cascade Hydropower Plants Considering the Bidding Space in the Day-Ahead Spot Market

With the gradual opening of China’s electricity market, it is effective for cascade hydropower plants to simultaneously participate in both the monthly contract market and the day-ahead spot market to obtain higher power generation benefits. Hence, this paper studies the optimal decomposition model for the monthly contracted electricity of cascade hydropower plants considering the bidding space in the day-ahead spot market. The close hydraulic and electric connection between cascade hydropower plants, the implementation requirements of contracted electricity, and the uncertainty of the day-ahead market clearing price are all well considered. Several linearization techniques are proposed to address the nonlinear factors, including the objective function and the power generation function. A successive approximation (SA) approach, along with a mixed-integer linear programming (MILP) approach, is then developed to solve the proposed model. The presented model is verified by taking the decomposition of the monthly contracted electricity of cascade hydropower plants in China as an example. The results indicate that the developed model has high computational efficiency and can increase the power generation benefits compared with the conventional deterministic model. The effect of the penalty coefficient for imbalanced monthly contracted electricity is also evaluated, which provides a practical reference for market managers