软岩溜煤立眼的施工

软岩溜煤立眼的施工。(1)此立眼全部在岩层中施工,(2)、溜煤立眼采用料石支护,(3)、立眼料石支护与混凝土相比,施工中减少了支模工序,(4)节省了投资,保证安全施工效果良好。     

Enzymatic interesterification of palm and coconut stearin blends

Hard fractions of palm oil and coconut oil, blended in the ratios of 90:10, 85:15, 80:20 and 75:25, were interesterified for 8 h using Lipozyme TL IM. Major fatty acids in the blends were palmitic acid (41.7–48.4%) and oleic acid (26.2–30.8%). Medium‐chain fatty acids accounted for 4.5–13.1% of the blends. After interesterification (IE), slip melting point was found to decrease from 44.8–46.8 °C to 28.5–34.0 °C owing to reduction in solids content at all temperatures. At 37.5 °C, the blends containing 25% coconut stearins had 17.4–19% solids, which reduced to 0.4–1.5% on IE, and the slip melting point (28.6 and 28.8 °C) indicated their suitability as margarine base. The reduction in solid fat index of the interesterified fats is attributed to the decrease in high‐melting triacylglycerols in palm oil (GS₃ and GS₂U type) and increase in triolein (GU₃) content from 1 to 9.2%. Retention of tocopherols and β‐carotene during IE was 76 and 60.1%, respectively, in 75:25 palm stearin and coconut stearin blend.     

Premium-penalty ant colony optimization and its application in slope stability analysis

Ant colony optimization (ACO) is a very suitable path search algorithm, whose typical application is traveling salesman problem. However, as one heuristic algorithm, it has many shortcomings, such as slow convergent speed and low searching efficiency. To overcome these shortcomings, the premium-penalty strategy has been introduced, and the pheromone diversity of the good paths and the ordinary ones is increased to polarize pheromone density of all paths. Thus, premium-penalty ant colony optimization (PPACO) is proposed. And its good performance is verified by the applications to some typical traveling salesman problems. Its two important parameters are discussed too. Because location critical slip surface in slope stability analysis is a path search problem, it can be solved by the ACO very suitably. Therefore, based on PPACO and typical mature limit equilibrium analysis (Spencer method), a new method to analyze the slope stability is proposed. Through two typical examples, one simple slope and one complicated slope, the efficiency and effectiveness of the new algorithm are verified. The results show that, the new algorithm can always find the less safety factor and its critical slip surface in shorter time than many previous algorithms, and the new algorithm can be used in real engineering very well.     

Heat and mass transfer characteristics of radiative hybrid nanofluid flow over a stretching sheet with chemical reaction

Unsteady magnetohydrodynamic heat and mass transfer analysis of hybrid nanoliquid flow over a stretching surface with chemical reaction, suction, slip effects, and thermal radiation is analyzed in this study. A combination of alumina (Al₂O₃) and titanium oxide (TiO₂) nanoparticles are taken as hybrid nanoparticles and water is considered as the basefluid. Using the similarity transformation method, the governing equations are changed into a system of ordinary differential equations. These equations together with boundary conditions are numerically evaluated by using the Finite element method. The influence of various pertinent parameters on the profiles of fluids concentration, temperature, and velocity is calculated and the outcomes are plotted through graphs. The values of nondimensional rates of heat transfer, mass transfer, and velocity are also analyzed and the results are depicted in tables. Temperature sketches of hybrid nanoliquid intensified in both the steady and unsteady cases as the volume fraction of both nanoparticles rises.     

Experimental investigation of bond stress distribution and bond strength in unconfined UHPFRC lap splices under direct tension

Several studies on tension lap splices have shown the improvement of bond strength using Ultra-high performance Fibre Reinforced Concrete (UHPFRC). The bridging effect of fibres on cracks improves the bond splitting strength substantially in comparison to normal concrete. This paper investigates the influence of fibre content on the strength of tension lap splice of reinforcing bars in UHPFRC without additional transverse reinforcement. Different splice lengths and UHPFRC mixes were tested. Internal strain measurements were used to capture the force transfer mechanism and the evolution of longitudinal strain distribution and associated bond stresses. The bond performance is clearly related to the pre- and post-cracking tensile capacity of UHPFRC. At a distance exceeding 2 d_b from bar extremities, bond stress distribution at failure displayed a quasi-constant value regardless of the lap splice length up 10 d_b. This reveals for short lap splices that the bearing action of all ribs along the splice length contributes equally in resisting the applied force. This experimental program provides experimental results for understanding the local force transfer mechanism in UHPFRC lap splice and contribute for further developments on bond in UHPFRC.     

Evaluating Schmid criterion for predicting preferential locations of persistent slip markings obtained after very high cycle fatigue for polycrystalline pure copper

Very high cycle fatigue carried out on pure copper polycrystals promotes early slip markings, labelled as slip markings of types II and III, localized close to grain or twin boundaries. In this work, we focus on whether Schmid criterion can predict the preferential sites of slip markings of types II and III and identify the active slip systems. Combining observations of slip markings and polycrystalline modeling, it is shown that considering pure cubic elastic behavior, maximum resolved shear stress as a criterion for type II slip markings preferential sites is 70% reliable criterion. Concerning slip markings of type III, the reliability falls to 30%. The role of cross slip is highlighted and a scenario rationalizing the stress amplitude conditions and sites to observe early slip markings of type II or III for copper polycrystals is proposed.     

Second order velocity slip and thermal jump of Cu–water nanofluid over a cone in the presence of nonlinear radiation and nonuniform heat source/sink using homotopy analysis method

The purpose of the present paper is to explore the second order slip effects on nanofluid flow over a vertical cone. The effects of nonlinear thermal radiation and nonuniform heat source/sink are also taken into account. Water with copper nanoparticles is used as nanofluid in this investigation. The governing partial differential equations for the flow are converted into ordinary differential equations by using transformations and then are solved using homotopy analysis method. The influence of various important parameters on velocity, temperature, skin‐friction, and Nusselt number are presented through graphs. Results indicate that the velocity and magnitude of skin friction decrease with a rise in first and second order velocity slips. A raise in either first or second order temperature jump causes a fall in temperature. Nonlinear radiation increases the more rapidly when compared to the linear radiation case.     

Critical Analysis of Fibre‐Reinforced Polymer Near‐Surface Mounted Double‐shear Pull‐out Tests

The study of the bond behaviour between fibre‐reinforced polymer (FRP) systems and concrete is an issue that nowadays attracts many researchers. The scientific community dedicated to the research of FRP reinforcement has been conducting numerous experimental programmes aiming to assess the local bond–slip law of the FRP–adhesive–concrete connection. This paper reports the relevant results obtained by the Structural Composite Research Group of Minho University in the scope of an international Round Robin Test. The suitability of the recommended test setup to derive a local bond constitutive law for modelling the bond behaviour of near‐surface mounted reinforcement systems is discussed based on a deep interpretation of the results.     

Vapour–liquid slip in a parallel-plate electrochemical fluorination reactor

A mathematical model was used to study the effect of slip between the gas and liquid phases on the performance of an electrochemical fluorination reactor. The model incorporates two-phase flow with differential material, energy and pressure balances. The effect of slip on the temperature, pressure, gas fraction and current distribution in the reactor is presented under relatively severe operating conditions. In addition, the effect of slip on the cell voltage, current efficiency and energy usage is shown at different flow rates over a wide current range. It was found that slip of the gas past the liquid is insignificant under normal operating conditions, but it is significant at high cell currents and low flow rates. Under these more severe operating conditions, slip significantly reduces the cell voltage, and hence the energy usage, since less gas resides in the reactor.     

某输电线路工程滑坡特征分析与评价

某750 kV输电线路部分段走径于天水地区滑坡区段,区域滑坡类型主要以黄土滑坡和黄土-泥岩接触面滑坡为主,最易滑坡坡度在20°~39°之间,占全部滑坡的72.3%;滑坡的形成原因主要有地质构造、地震作用、岩性特征、地形地貌、水文气象条件和人类活动等多个方面;通过分析地区滑坡特征,采取滑带土进行室内试验,分析滑带土物理力学性质,进行典型滑坡的稳定性分析与评价。