Effect of variations in the polar and azimuthal angles of coarse particles on the structure of drainage channels in thickened beds

The 3D reconstruction and quantitative characterization of drainage channels and coarse tailings particles in a bed were conducted in this study.The influence of variations in the azimuthal angle(θ)and polar angle(φ)of coarse particles on drainage channel structure was analyzed,and the drainage mechanism of the bed was studied.Results showed that water discharge in the bed reduced the size of pores and throat channels,increasing slurry concentration.The throat channel structure was a key component of the drainage process.Theφandθof particles changed predominantly along the length direction.The changes inφhad a cumulative plugging effect on the drainage channel and increased the difficulty of water discharge.The rake and rod formed a shear ring in the tailings bed with shear,and theθdistribution of particles changed from disorderly to orderly during the rotation process.The drainage channel was squeezed during the shearing process with the change inθ,which broke the channel structure,encouraged water discharge in the bed,and facilitated a further increase in slurry concentration.The findings of this work are expected to offer theoretical guidance for preparing high-concentration underflow in the tailings thickening process.

A target group tracking algorithm for wireless sensor networks using azimuthal angle of arrival information

In this paper, we explore the technology of tracking a group of targets with correlated motions in a wireless sensor network. Since a group of targets moves collectively and is restricted within a limited region, it is not worth consuming scarce resources of sensors in computing the trajectory of each single target. Hence, in this paper, the problem is modeled as tracking a geographical continuous region covered by all targets. A tracking algorithm is proposed to estimate the region covered by the target group in each sampling period. Based on the locations of sensors and the azimuthal angle of arrival （AOA） information, the estimated region covering all the group members is obtained. Algorithm analysis provides the fundamental limits to the accuracy of localizing a target group. Simulation results show that the proposed algorithm is superior to the existing hull algorithm due to the reduction in estimation error, which is between 10% and 40% of the hull algorithm, with a similar density of sensors. And when the density of sensors increases, the localization accuracy of the proposed algorithm improves dramatically.

Numerical simulation of an acoustic field generated by a phased arc array in a fluid-filled cased borehole

Transducers that are widely applied in cement bond evaluation tools, such as cement bond logs and variable density logs, cannot radiate acoustic energy directionally because of the characteristics of monopole sources. A phased arc array transmitter, which is a novel transducer that differs from monopole and dipole transducers, is presented in this study. To simulate the acoustic field generated by a phased arc array in a fluid-filled cased borehole with different channelings, a 3D finite-difference time-domain method is adopted. The acoustic field generated by a traditional monopole source is also simulated and compared with the field generated by the phased arc array transmitter. Numerical simulation results show that the phased arc array radiates energy directionally in a narrow angular range in the borehole, thereby compressing the acoustic energy into a narrow range in the casing pipe, the cement, and the formation. We present the analyses of first-arrival waveforms and the amplitudes of casing waves at different azimuthal angles for the two different sources. The results indicate that employing a directional source facilitates azimuthal identification and analysis of possible channeling behind the casing pipe.

Numerical investigation on free air blast loads generated from center-initiated cylindrical charges with varied aspect ratio in arbitrary orientation

In current guidelines, the free air blast loads(overpressure and impulse) are determined by spherical charges, although most of ordnance devices are more nearly cylindrical than spherical in geometry. This may result in a great underestimation of blast loads in the near field and lead to an unsafe design.However, there is still a lack of systematic quantitative analysis of the blast loads generated from cylindrical charges. In this study, a numerical model is developed by using the hydrocode AUTODYN to investigate the influences of aspect ratio and orientation on the free air blast loads generated from center-initiated cylindrical charges. This is done by examining the pressure contours, the peak overpressures and impulses for various aspect ratios ranged from 1 to 8 and arbitrary orientation monitored along every azimuth angle with an interval of 5°. To characterize the distribution patterns of blast loads,three regions, i.e., the axial region, the vertex region and the radial region are identified, and the propagation of blast waves in each region is analyzed in detail. The complexity of blast loads of cylindrical charges is found to result from the bridge wave and its interaction with primary waves. Several empirical formulas are presented based on curve-fitting the numerical data, including the orientation where the maximum peak overpressure emerges, the critical scaled distance beyond which the charge shape effect could be neglected and blast loads with varied aspect ratio in arbitrary orientation, all of which are useful for blast-resistant design.

Numerical simulation of seismic wave in elastic and viscoelastic TTI media

Based on the two-dimensional(2D)three-component first-order velocity-stress equation,the high order staggered mesh finite difference numerical simulation method was used to simulate the elastic and viscoelastic tilted transversely isotropic(TTI)media.The perfect matched layer(PML)absorption boundary condition was selected to eliminate the boundary effect.The results show that:(①)Under the condition of fixed elastic parameters of elastic TTI medium,when the polarization angle and azimuth are 60°and 45°respectively,the degree of shear wave splitting is significantly greater than the angle of 0°;②The influence of viscoelasticity on TTI medium is mainly reflected in the amplitude.If the quality factor decreases,the attenuation of the seismic wave amplitude increases,causing the waveform to become wider and distorted.If the quality factor increases,the viscoelastic medium becomes closer to elastic medium;③For TTI medium with different polarization angle and azimuth angle in the upper and lower layers,the shear wave can multiple splits at the interface of medium.The symmetry of seismograms is affected by the polarization angle and azimuth angle of TTI medium;④Viscoelasticity has a great influence on reflected wave,transmitted wave and converted wave in the low-velocity model.When the viscoelasticity is strong,the weaker waves may not be shown.

Estimating the impact of azimuth-angle variations on photovoltaic annual energy production

The performance of a photovoltaic(PV)installation is affected by its tilt and azimuth angles,because these parameters change the amount of solar energy absorbed by the surface of the PV modules.Therefore,this paper demonstrates the impact of the azimuth angle on the energy production of PV installations.Two different PV sites were studied,where the first comprises PV systems installed at-13°,-4°,+12°and+21°azimuth angles in different geographical locations,whereas the second PV site included adjacent PV systems installed at-87°,-32°,+2°and+17°azimuth angles.All the investigated PV sites were located in Huddersfield,UK.In summary,the results indicate that PV systems installed between-4°and+2°presented the maximum energy production over the last 4 years,while the worst energy generation were observed for the PV system installed at an azimuth angle of-87°.Finally,the probability projections for all observed azimuth angles datasets have been assessed.Since PV systems are affected by various environmental conditions such as fluctuations in the wind,humidity,solar irradiance and ambient temperature,ultimately,these factors would affect the annual energy generation of the PV installations.For that reason,we have analysed the disparities and the probability of the annual energy production for multiple PV systems installed at different azimuth angles ranging from-90°to+90°degrees,and affected by different environmental conditions.These analyses are based on the cumulative density function modelling technique as well as the normal distribution function.

Network boundary recognition via relative azimuth angle

To recognize the boundary of wireless networks to meet some specific needs, relative azimuth angles of nodes distributed in the 1-hop neighborhood of each node in one network were used to recognize the boundary of the network. A novel recognition algorithm based on local generalized convex hull was proposed for one node to decide if it self is a boundary node. The flexibility, efficiency and consistency of the algorithm are shown in its performance by extensive simulations.

Astudy of uplink and downlink channel spatial characteristics in an urban micro scenario at 28GHz

This paper presents an empirical study of the uplink and downlink azimuth angle of arrival(AoA)in an urban micro(UMi)scenario at 28 GHz.At present,most UMi measurements are conducted in the downlink and then the uplink situation is inferred assuming channel reciprocity.Although the channel correlation coefficient of the uplink and downlink can be as high as 0.8,this does not mean that they are the same.Only a real uplink measurement can accurately describe its channel conditions,and this is what this study does.A receiver equipped with a rotatable horn antenna is mounted at the base station and the user terminal,respectively,in simulating the uplink and downlink.To improve the angular resolution,we extract the multipath components(MPCs)using the space-alternating generalized expectation-maximization algorithm.Also,a spatial lobe approach is used to cluster the MPCs in the power angular spectrum.By matching MPCs with objects in the environment,we find that direct propagation and first-order reflections are dominant in line-of-sight and non-line-of-sight cases.By comparing our measurement with those in standard channel models,we verify that the AoA of clusters follows a Gaussian distribution in the uplink and downlink.In addition,a two-dimensional Gaussian distribution for ray AoA and power is established to reflect their correlation.