MWCNT-Reinforced AA7075 Composites: Effect of Reinforcement Percentage on Mechanical Properties

Metal–matrix composites (MMC) of aluminium alloy 7075 (AA7075) containing 1 wt.% and 0.5 wt.% multiwall carbon nanotubes (MWCNTs) were developed by powder metallurgy, using a high energy ball milling (HEBM) process for dispersion of the MWCNTs. The powder of the AA7075-MWCNT obtained was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microstructural changes produced during the milling process, such as the modification of the crystallite size, as well as the micro-deformation of the matrix crystal lattice, were determined using the Scherrer formula. After consolidation into a strip shape using the hot powder extrusion (HPE) process at 500 °C, no porosity was detected and a fine homogeneous dispersion of the reinforcement into the matrix was obtained. After performing a 0.2 HV test and tensile tests in the extruded profiles of both composites, a better combination of properties was found in samples of AA7075-0.5 wt.% MWCNT, with the increase in measured ductility being especially remarkable.

Experiment and Simulation Research on the Fatigue Wear of Aircraft Tire Tread Rubber

The road surface and the tread pattern structures directly affect the wear performance of aircraft tire, especially for lateral sliding conditions. In this paper, wear tests of tread block with different draft angles and root radiuses, different interfaces, and different slip angles were carried out, and combined with the simulation, the effects of tread groove structure and slip angle on the wear mechanism were analyzed. Results indicated that the influences of draft angle were greater than the root radius; the wear geometry of the tread block decreased when the draft angle increased in the range of 0° to 15°, but for the root radius, the wear geometry of each sample was similar to a strip shape. A considerable material loss occurred at the front edge when the slip angle increased, and the slip angle was larger in the range of 0° to 45°. Combined with the simulation and wear test, fatigue wear and abrasive wear of the slide surface are dominant factors when considering the effects of tread groove structure and slip angle, and both front edges of the tread blocks roll up repeatedly; the coefficient decreases with the increase in load when the cement concrete pavement interface is dry, but for a wet interface, the coefficient decreases softly.

Detection of SST fronts from high-resolution model and its preliminary results in the South China Sea

A frontal detection algorithm is developed with the capability of detecting significant frontal segments of sea surface temperature (SST) in the high resolution South China Sea Operational Forecasting System (SCSOFS). In order to effectively obtain frontal information, a gradient-based Canny edge detection algorithm is improved with post-processing designed for high resolution numerical model, aiming at extracting primary ocean fronts, meanwhile ensuring the balance of frontal continuity and positioning accuracy. Metrics of frontal probability and strength are used to measure the robustness of the results in terms of mean state and seasonal variability of frontal activities in the South China Sea (SCS). Most fronts are found in the nearshore and forming a strip shape extending from the Taiwan Strait to the coast of Vietnam. The SCSOFS is found to reproduce strong seasonal signals dominating the variability of the frontal strength and occurrence probability in the SCS. We implement the algorithm on the daily-averaged SST derived from two other SST analyses for inter-comparison in the SCS.

Treatment of Lung Cancer Complicated with Infection of Talaromyces Marneffei Based on Chest Imaging Characteristics Monitoring (Preprint)

BACKGROUND Background: At present, although the infection of Talaromyces Marneffei has been known at home and abroad, there are few reports of Talaromyces Marneffei in lung cancer. OBJECTIVE Objective: The objective is to explore the diagnosis and treatment process of lung cancer patients with infection of Talaromyces Marneffei and its chest imaging characteristics, so as to improve the clinicians' realization of the disease. METHODS Method: The patients with lung cancer and infection of Talaromyces Marneffei (observation group) and the patients with infection of Talaromyces Marneffei (control group) are taken as the study objects, and the clinical characteristics and chest CT (computed tomography) imaging characteristics of the two groups are compared and summarized. RESULTS Results: The number of male patients infected with Talaromyces Marneffei is significantly higher than that of female patients (P < 0.05). The symptoms of cough and expectoration in the observation group are more than those in the control group (P < 0.05). The main imaging features of the observation group are obvious enhancement of focus enhancement scanning, strip shape and nodule, and the situation of obvious enhancement of focus enhancement scanning in the observation group is significantly higher than that in the control group (P < 0.05). CONCLUSIONS Conclusion: The clinical and imaging features of lung cancer and Talaromyces Marneffei infection overlap. When the lung lesions of patients with Talaromyces Marneffei have significant malignant signs, the possibility of lung cancer should be considered.

Research on Underground Location Algorithm Based on Random Forest and Environmental Factor Compensation

In view of the complex and changeable underground environment of coal mine and the long strip shape of underground roadway, a new underground location algorithm based on Stochastic Forest and environmental factor compensation is proposed. Firstly, the underground AP network model and roadway environment are analyzed, and the fingerprint localization algorithm is constructed. At the same time, the Kalman filter algorithm is used to filter the RSS signal in the offline sampling and real-time positioning stage. Then the algorithm based on random forest and environmental factor compensation is proposed. Under the assumption that the attenuation factors between the two anchor nodes are the same, the signal strength ratio compensation algorithm is proposed, which optimizes the shortcomings of the similarity of the locality error of the similar region. The target speed constraint condition is introduced to reduces errors caused by the transmission of RSS signal transmission and environmental factors. Experiments were carried out by using a bomb shelter to simulate the real mine roadway environment. The results show that the proposed algorithm can meet the high-precision positioning of the well under the conditions of sparse anchor nodes and complex environment underground.

Numerical Simulation of the Hydraulic Performances and Flow Pattern of Swallow-Tailed Flip Bucket

In this study, the evolution process of the swallow-tailed flip bucket water nappe entering into the plunge pool is simulated by using the standard k-ε turbulence model and the volume-of-fluid method. The effects of the upstream opening width ratio and downstream bucket angle on the flow pattern, the unit discharge distribution, and the impact pressure distribution are studied. Based on the numerical results, the inner and outer jet trajectories are proposed by using the data. Results show that the longitudinal stretching length decreases with the increase of the upstream opening width ratio and increases with the increase of the downstream bucket angle. The water nappe enters the plunge pool in a long strip shape. Thus, the unit discharge distribution of water nappe entry is consistent with the pressure distribution at the plunge pool bottom. The upstream opening width ratio and downstream bucket angle should be chosen as their intermediate values in order to have a uniform discharge distribution and to reduce the pressure peak at the plunge pool floor, which is effectively to avoid instability and destruction of plunge pool floor.

Effect of Sulfur Content on the Composition of Inclusions and MnS Precipitation Behavior in Bearing Steel

MnS inclusions in bearing steel have long been considered to significantly affect the fatigue life of bearing steel. In this paper, the sizes of inclusions in bearing steel with different sulfur contents were analyzed and the precipitation behavior of MnS was calculated using thermodynamics. Furthermore, the positive role of MnS in bearing steel was discussed. Results showed that when the size of inclusions in bearing steel was increased, the proportion of MnS components in composite inclusions gradually decreased. When the sulfur content was increased, the shape of inclusions changed from a particle shape to a strip shape. With increasing MnS content, the inclusion ratio of Al2O3 was significantly reduced in the Al2O3–CaO–MgO–MnS quaternary inclusion system, particularly for MnS proportions greater than 20%. The content of sulfur in bearing steel significantly affects the precipitation temperature of MnS. When sulfur content increases from 0.001% to 0.007%, the precipitation temperature of MnS increases from 1493 K to 1633 K as the precipitation of MnS moves from the austenite solid phase to the liquid and solid phases, and the precipitation size of MnS inclusions significantly increases. The size of oxide inclusions should be controlled to improve MnS wrap oxide inclusions in steel. Based on these results, a composition control with high sulfur levels and low oxygen levels should be adopted to improve the fatigue performance of steel.