Optimization and Application of Spacing Parameter for Loosening Blasting with 24-m-High Bench in Barun Open-Pit Mine

In view of the near slope blasting in Barun open-pit mine, which has merged sublevel mining, the operation safety conditions of middle-sized and large equipment in the second phase expansion are poor and need urgent improvement. To increase the efficiency of expansion and reduce costs, a 24-m-high bench and large spacing parameter for loosening blasting are proposed. The analysis of the physical mechanism of the stress wave attenuation in the rock indicates that the cylindrical charge is equivalent to several spherical charges. Considering the pressure attenuation, reflection, transmission, and superposition of the spherical charge after the equivalence, a double exponential function correction equation of the stress wave attenuation is obtained based on the Mises strength criterion. The stress of any point in the rock medium with various spacing parameter is obtained by calculation. ANSYS/LS-DYNA was used to simulate and study the stress distribution of a 24-m-high bench with various spacing parameter. Meanwhile, the accuracy of the correction equation was verified. The parameters of the high-bench blasting with good effect and low cost were determined to be 15 m × 5.5 m, and field tests were carried out. Results show that the large spacing parameter for 24-m-high bench loosening blasting in Barun open-pit mine is efficient and economical in medium-hard rock blasting. This study provides a reference for the practical exploration of the expansion of high benches in open-pit mines in China. The calculation error of the corrected double exponential function is near the numerical simulation result. It is suitable for all kinds of professional designers.

Theoretical Study on Influence of Disk Spacing on Soil Failure State of Expansion Piles under Horizontal Force

Concrete expansion pile represents a new type of high-efficiency and energy-saving variable-section filling pile and it is formed by special construction technology and equipment, this technology has been basically mature which has been gradually applied to engineering in recent years. It has high bearing capacity, small settlement and uniformity, good economic and social effect, strong anti-overturning ability and flexible design[1]. In this paper, with expansion disk spacing under bearing force as the main parameter variable, numerical simulation is carried out by ANSYS finite element software to analyze the variation relationship between horizontal displacement of the pile top, bending moment of the pile and soil stress around the pile of different disk spacing models under horizontal load, and determine the influence of disk spacing parameter on horizontal bearing capacity of the concrete expansion pile. Through the research of this paper, the influence of failure mode of concrete expansion pile and size of the disk spacing on the horizontal bearing capacity under the horizontal load is qualitatively determined, which provides a theoretical basis for improving design theory and practical application of concrete expansion pile.

Discrete Solitons and Bäcklund Transformation for the Coupled Ablowitz–Ladik Equations

Under investigation in this paper are the coupled Ablowitz–Ladik equations, which are linked to the optical fibres, waveguide arrays, and optical lattices. Binary Bell polynomials are applied to construct the bilinear forms and bilinear Bäcklund transformation. Bright/dark one- and two-soliton solutions are also obtained. Asymptotic analysis indicates that the interactions between the bright/dark two solitons are elastic. Amplitudes and velocities of the bright solitons increase as the value of the lattice spacing increases. Increasing value of the lattice spacing can lead to the increase of both the bright solitons’ amplitudes and velocities, and the decrease of the velocities of the dark solitons. The lattice spacing parameter has no effect on the amplitudes of the dark solitons. Overtaking interaction between the unidirectional bright two solitons and a bound state of the two equal-velocity solitons is presented. Overtaking interaction between the unidirectional dark two solitons and the two parallel dark solitons is also plotted.

Optical Design of Multisource High-Flux Solar Simulators

We present a systematic approach to the design of a set of high-flux solar simulators (HFSSs) for solar thermal, thermochemical, and materials research. The generic simulator concept consists of an array of identical radiation modules arranged in concentric rows. Each module consists of a short-arc lamp coupled to a truncated ellipsoidal specular reflector. The positions of the radiation modules are obtained based on the rim angle, the number of concentric rows, the number of radiation modules in each row, the reflector radius, and a reflector spacing parameter. For a fixed array of radiation modules, the reflector shape is optimized with respect to the source-to-target radiation transfer efficiency. The resulting radiative flux distribution is analyzed on flat and hemispherical target surfaces using the Monte Carlo ray-tracing technique. An example design consists of 18 radiation modules arranged in two concentric rows. On a 60-mm dia. flat target area at the focal plane, the predicted radiative power and flux are 10.6 kW and 3.8 MW m−2, respectively, and the predicted peak flux is 9.5 MW m−2.

Forced Convection Heat Transfer From a Bank of Circular Cylinders Embedded in a Porous Medium

The characteristics of fluid flow and forced convection heat transfer around a bank of four circular cylinders embedded in a metallic or non-metallic porous materials have been investigated numerically. Both a staggered and an in-line arrangement have been studied. The governing continuity, Darcy–Brinkman–Forchheimer momentum, and local thermal non-equilibrium energy equations are solved by the spectral-element method. Attention is focused on how the spacing parameter SP ∈ [1.5, 3.0] (the space between cylinder centers) affects the local and average heat transfer from the cylinders at three different solid-to-fluid thermal conductivity ratios kr = 1.725, 57.5, 248, and at different Reynolds numbers ReD ∈ [1, 250] in both arrangements. Perhaps not surprisingly, the results show that both the average Nusselt number, Nuf, and the local Nusselt number, Nufφ, are dependent strongly on ReD, SP, and the cylinder arrangement. However, it is found that the trend of the variations of Nuf with SP is not considerably altered by kr in both cylinders’ configurations. The results also show that the thermal performance of the staggered arrangement is higher than that for the in-line one, with less occupied space; therefore, it is practically and economically recommended that this arrangement to be used in manufacturing tubular heat exchangers for applications involving porous media.

RESEARCH ON DISCHARGE CIRCUIT OF ELECTRO-HYDRAULIC POWER IMPULSE WATER JETS

Electro-hydraulic power impulse water jets can convert the shock wave generated in the liquid by discharging into mechanical energy, and it has been widely used in material forming, surface cleaning, pipeline dirt cleaning and ore breaking process. Compared with the traditional high pressure water jets, the energy utilization of electro-hydraulic power impulse water jets is up to 80% while the water consumption is reduced by 40–55%. This paper has taken electro-hydraulic power impulse water jets as the research object, employed obtaining the maximum pressure of compression impulse matrix surface as the research goal, studied in depth the equivalent discharge circuit, characteristic equation and the relationship between the electrical parameters of the electro-hydraulic power impulse discharge circuit and built the calculation method of the voltage, the inductance, the capacitance and the electrode spacing parameter of electro-hydraulic power impulse water jets discharge circuit. So, it will provide important theoretical basis for further studies of electro-hydraulic power impulse technology and the existing water jets device.

Comparison of Vacuum Chamber Tested Biporous Wicks With Thermal Ground Plane Testing

Investigation of bi-porous wicks has yielded an effective method for increasing surface heat transfer when the heat flux is high. It was further found that addition of a mono-porous layer on the heated surface significantly reduced the heated wall surface temperature. These bi-layer wicks were designed for use in 3″×5″ heat spreading devices called Thermal Ground Planes (TGP) in order to transfer heat from a 1 cm2 source. In this work we will investigate the performance of a biporous wick with a monoporous layer in various test set-ups to show the versatility of this heat pipe-substrate. Tests were performed at UCLA and at Advanced Cooling Technologies (ACT) to investigate the wick. Experiments at UCLA were conducted in a vacuum chamber setup to isolate the performance of the wick whereas at ACT the wick lined the evaporator side of a TGP. In order to more closely simulate the operating conditions in a TGP and characterize the vapor spacing parameter, some tests at UCLA were performed with a restrictor plate above the wick similar to the space above the wick in the TGP. The data collected using both these experiments showed similar trends of performance as a function of the spacing above the wick. The motivation of this paper is then to validate that the two testing methods provide similar results while independently addressing different parameters.

AlGaN/GaN High Electron Mobility Transistors on Si/SiO2/poly-SiC Substrates

ABSTRACTThe dc and rf performance of AlGaN/GaN High Electron Mobility Transistors (HEMTs) grown by Molecular Beam Epitaxy on Si-on-poly (SopSiC) substrates is reported. The HEMT structure incorporated a 7 period GaN/AlN superlattice between the AlGaN barrier and GaN channel for improved carrier confinement. The knee voltage of devices with 2 μm gate-drain spacing was 2.12 V and increased to 3 V at 8 μm spacing. The maximum frequency of oscillation, fMAX, was ∼40 GHz for devices with 0.5 μm gate length and 2 μm gate-drain spacing. Parameter extraction from the measured rf characteristics showed a maximum intrinsic transconductance of 143 mS.mm−1.