Drillability prediction in some metamorphic rocks using composite penetration rate index(CPRI)–An approach

Assessment of drillability of rocks is vital in the selection,operation,and performance evaluation of cutting tools used in various excavation machinery deployed in mining and tunneling.The commonly used rock drillability prediction methods,namely,drilling rate index(DRI)and Cerchar hardness index(CHI)have limitations in predicting the penetration rate due to differential wear of the cutting tool in rocks with varied hardness and abrasivity.Since cutting tools get blunt differently in different rocks,the stress beneath the tip of the bit decreases until it reaches a threshold value beyond which the penetration rate becomes constant.In this research,a new composite penetration rate index(CPRI)is suggested based on the investigations on four metamorphic rocks viz.quartzite,gneiss,schist and phyllite with varied hardness-abrasivity values.The penetration-time behavior was classified into active,moderate,passive,and dormant phases based on the reduction in penetration rate at different stages of drilling.A comparison of predicted penetration rate values using DRI and CPRI with actual penetration rate values clearly establishes the supremacy of CPRI.Micro-structure and hardness-based index was also developed and correlated with CPRI.The new indices can help predict cutting tool penetration and its consumption more accurately.

Increased BMR in Overweight and Obese Patients with Type 2 Diabetes may Result from an Increased Fat-free Mass

The study aimed to determine the relationships between the basal metabolic rate（BMR） and body composition of overweight and obese Chinese adults with type 2 diabetes mellitus（DM）. This cross-sectional clinical study enrolled 193 Chinese adults with type 2 DM who were overweight（24 kg/m2≤BMI〈28 kg/m2, n=99）, or obese（BMI ≥28 kg/m2, n=94）. Ninety-seven adults with normal BMIs, including 50 DM patients and 47 healthy adults, were recruited as a control group. BMR was measured by indirect calorimetry; predicted BMR was calculated according to the Schofield equation; and the relationships between BMR, body composition, and biochemical results were determined by the Pearson correlation. The results showed that obese DM patients had significantly higher BMRs than both overweight patients（P〈0.05） and patients with normal BMI did（P〈0.05）. The measured BMR was significantly lower than the predicted BMR（P〈0.05） in all groups. Obese and overweight DM patients had significantly greater weight, waist circumference, hip circumference, BMI, body surface area, body fat percentage, fat mass, and fat-free mass than patients with normal BMI. Except for waist circumference, these body composition measurements were significantly increased in obese DM patients when compared with those in overweight DM patients（P〈0.05）. Fat-free mass was closely correlated with BMR in both DM patients（r=0.874, P〈0.01） and in healthy controls（r=0.902, P〈0.01）. It was concluded that overweight and obese Chinese adults with type 2 DM had increased BMRs compared with normal-weight controls, which may result from the difference in fat-free mass.

Water-conducting Characteristics and Micro-dynamic Self-adjusting Behavior of Polyacrylamide/Montinorillonite Coating

A water-conducting polyacrylamide/montmorillonite coating was prepared by solutionblending.The coating was coated on fiber and then composited with polymer to form a composite film material that used for water saving and tree planting in arid and desert regions.The coating＇s water-conducting characteristics and dynamic self-adjusting behavior were investigated by Fourier transform infrared（FTIR）spectroscopy,thermal analysis（TG-DTA）,and environmental scanning electron microscopy（ESEM）.The results showed that the coating＇s water-conducting rate increased but water-retention capacity weakened with increasing montmorillonite content.The water-loss rate was positively related to temperature and negatively related to soil moisture.Water potential greatly influenced the water-conducting rate of the coating during its water conduction process.When the coating was at a low water potential,the montmorillonite particles interconnected and water was conducted quickly via montmorillonite layers,whereas when the coating was at a high potential,the montmorillonite particles disconnected and water was conducted slowly via the swelled polyacrylamide net structure.The rate can be regulated by changing the proportion of polyacrylamide and montmorillonite to guarantee a reasonable water supply for trees and make trees easier to survive.Thus,the survival rate of trees can be increased and the use of water resources can be significantly reduced.

Synthesis and Tribological Properties of Copper-alumina Nanocomposites Prepared by Coprecipitation Technique

The objective of this work is to study the synthesis of copper-alumina nanocomposites using the coprecipitation process and hot-pressing method, and investigate their mechanical properties. The effects of calcination temperature on the average size of composite particles and chemical composition after calcination were also analyzed. The sintering parameters including sintering temperature, hot pressure and packing time were optimized to fabricate the alumina nanoparticles reinforced copper matrix composites（CMCs）. The density, microhardness and tribological properties of the CMCs reinforced with 1 wt%, 2 wt%, 3 wt%, 4 wt% and 5 wt% of alumina nanoparticles were investigated correspondingly. The results showed that the optimum preparation parameters for the CMCs were 900 ℃ of hot pressing temperature, 27.5 MPa of hot pressure and 2 hrs of packing time. The CMC reinforced with 2 wt% of alumina nanoparticles had the lowest wear rate, with the relative wear resistance of 3.13.

An Efficient Risk Estimator with External Information Under Additive Hazards Model

Rare event data is encountered when the events of interest occur with low frequency, and the estimators based on the cohort data only may be inefficient. However, when external information is available for the estimation, the estimators utilizing external information can be more efficient. In this paper, we propose a method to incorporate external information into the estimation of the baseline hazard function and improve efficiency for estimating the absolute risk under the additive hazards model. The resulting estimators are shown to be uniformly consistent and converge weakly to Gaussian processes. Simulation studies demonstrate that the proposed method is much more efficient. An application to a bone marrow transplant data set is provided.

Sensitivity analysis of a methanol and power polygeneration system fueled with coke oven gas and coal gas

The sensitivity analysis of a polygeneration energy system fueled with duo fuel of coke oven gas and coal gas is performed in the study,and the focus is put on the relations among syngas composition,conversation rate and performance.The impacts of the system configuration together with the fuel composition on the performance are investigated and discussed from the point of cascading utilization of fuel chemical energy.First,the main parameters affecting the performance are derived along with the analysis of the system configuration and the syngas composition.After the performance is being simulated by means of the Aspen Plus process simulator of version 11.1,the variation of the performance due to the composition of syngas and the conversion rate of chemical subsystem is obtained and discussed.It is obtained from the result that the proper conversion rate of the chemical subsystem according to the specific syngas composition results in better performance.And the syngas composition affects the optimal conversion rate of the chemical subsystem,the optimal point of which is around the stoichiometric composition for methanol production(CO/H_(2)=0.5).In all,the polygeneration system fueled with coke oven gas and coal gas,which can realize the reasonable conversion of syngas to power and chemical product according to the syngas composition,is a promising method for coal energy conversion and utilization.