Damage Features of Altered Rock Subjected to Drying-Wetting Cycles

An abandoned open pit was used as a tailing pond for a concentrating mill, with the height of the water surface subject to cyclic fluctuation. The effects of drying and wetting cycles on the mechanical parameters of pit rock were tested. Interactions of the hydrochemical environment, due to the dissolution of tailings, and drying and wetting cycles caused degradation of mechanical properties in the rock. It was found that uniaxial compressive strength and elastic modulus decreased as the number of dry/wet cycles increased. The quantitative relationship between the mechanical parameters and the number of dry/wet cycles was indicated by an exponential function. In addition to uniaxial testing, cohesion and the internal friction angle were determined through triaxial testing. The shear strength index deteriorated under the drying and wetting cycles. The hydrochemical environment also negatively affected the mechanical parameters. Potential effects between drying and wetting cycles and slope displacement were analyzed by on-site monitoring. The results show that the displacement increased because of the drying and wetting cycles, which may lead to sudden failure of the slope.

Spectral Estimation of Nasal Cyclic Rhythm by Nasal Airflow Temperature Measurement

.The nasal cycle is referred to a cyclic fluctuation in congestion of the nasal mucosa that results in rhythmic and bilateral reciprocal alteration of nasal airway patency. The purpose of this study is to deal with statistical and power spectral analysis of nasal cycle by measuring the temperature difference between the airflow of both left and right nostrils. Five adult voluntary healthy subjects are enrolled for the study. Nasal temperature probe combined with amplifier are used for recording nasal airflow temperature on both nostrils. The highest nasal airflow temperature values are detected at the end of expiration and the lowest values are detected at the end of inspiration. Nasal cycle found in all the subjects and lasted to the minimum of 30 minutes to maximum of 6 hours. The difference in temperature of both nostrils is statistically significant (p<0.05) and spectral estimation is made using autoregressive modeling. The method is used to quantify nasal obstruction in pathological condition and also to correlate the related physiological phenomenon.

The Experimental Research on the Effect of Seepage Pressures on Seepage Time through Red Sandstone

The cyclic fluctuation of reservoir water level makes soft rock in bank slope under cyclic seepage pressure and will bring certain effects on permeability characteristics of the soft rock. In order to obtain the relationship between the seepage pressure and seepage time, permeability tests were conducted on red sandstone specimens (from Three Gorges Reservoir Area, China) under cyclic seepage pressures by the self-developed equipment with the function to simulate cyclic fluctuation of reservoir water level. Experimental results show that the water infiltration of the sample was not stable in first three cycles, and it changed from 0.444 mL to 0.086mL. After three cycles, the water infiltration fluctuated between 0.060mL and 0.069mL. It can be drawn that the seepage velocity increase with the raise of pressure and it fit a four times polynomial in each cycle. The study indicates that increasing the seepage pressure appropriately can improve the seepage velocity, and greatly shorten the seepage time.

Study on Numerical Simulation and Experimental of Cutting Force in Turning Machinable Glasses Ceramics

Through turning experiment of machinable glass ceramics, the characteristics and law of turning force was studied. Results indicated that the overall changing process of cutting force was sinusoidal. If the cyclic fluctuation caused by system vibration was neglected, the changing process of turning force was scalariform. Through designing orthogonal experiment and applying numerical simulation of multiple regressing theory based on least square algorithm, mathematical model of turning force was established related with process parameters. R-test, F-test and P-test were carried out on the model respectively. The test results showed that the model had high precision. It could guide to cut machinable glass ceramics on prediction and controlling of turning force in some degree.