Influence Of Construction Parameters Research Articles

Exploring the propagation of hydraulic fracture with nonuniform stress based on the block distinct element method

AbstractThe stress field is a critical factor for fracture propagation in hydraulic fracturing. Attention should be paid to fracture propagation with the nonuniform stress field. A stress field with gradient was established to investigate the influence of the nononuniform stress on fracture propagation. Based on the three‐dimensional block distinct element model the fracture propagation law with nononuniform stress was obtained. The mechanism of stress gradient and magnitude of uneven fracture propagation was revealed. Aiming at the uneven propagation, the influence of elastic modulus and construction parameters was analyzed. The results show that the influence of the elastic modulus follows the χ2 distribution equation and the influence of construction parameters can be expressed by the product of the injection rate and fluid viscosity. This conclusion is of theoretical significance for fracturing with nonuniform in situ stress.

Numerical Simulation of Site Deformation Induced by Shield Tunneling in Typical Upper-Soft-Lower-Hard Soil-Rock Composite Stratum Site of Changchun

In China, with the rapid development of subway construction, the site deformation induced by subway construction is an interesting and hot issue in civil engineering. Focusing on the mechanism and characteristics of site deformation induced by parallel shield tunnel construction in typical soil-rock composite strata of Changchun region, and relying on the subway tunnel between Northeast Normal University Station and Gongnong Square Station, which belongs to the Changchun Metro Line 1, the tunnel construction process is simulated using FLAC3D software. In this paper, the numerical modeling and parameters for shield tunneling are described in detail, and the mechanism and characteristics of site deformation induced by shield tunneling are discussed systematically. Furthermore, the influence of construction parameters on site deformation, including construction sequence, tunnel spacing and earth chamber pressure, are studied. The results can provide reference for similar projects in the future.

Improvement of the technological process of sowing by stubble seeders

The basis of the seeding machine fleet is the stubble seeders SZS-2.1, SKP-2.1. A disadvantage of such seeders is the irrational use of the area of feeding due to the uneven distribution of the seed. Improvement of the technological process of sowing is possible by installing seed spreaders on the paw coulters. A scheme of a paw coulter with a passive seed distributor is proposed, each side of which consists of two planes installed at different angles. The calculation scheme and mathematical model allowed to study the process of seed distribution, to reveal the influence of constructive parameters of the coulter and the two-plane distributor on the trajectory of the particle, to determine the rational parameters of the distributor. In Mathcad, a program has been developed that simulates the trajectory of the particle movement along the coulter stand and in the limited under-paw space, which allowed the calculation of the seed distribution process with a coulter with a two-plane distributor. This program allows you to determine the geometric and kinematic parameters of the grain flight reflected from the distributor and the ceiling surface of the opener (trajectory, flight range, direction of the velocity vector when falling to the ground, etc.) when varying the inclination angles of the reflector planes, the incidence of the particle and its physical and mechanical properties. The calculation includes determining the flight parameters of the grain along the vertical straight line in the first stage of the flight, along the “ballistic” curve after each reflection. The results of the calculation are given in the form of a graphical representation of particle trajectories and tables with numerical values of the coordinates of the trajectory and the range of the rebound. To confirm the reliability of the results of theoretical studies and to determine the uniformity of sowing, laboratory tests of paw coulters with two-plane seed spreaders were carried out. The design parameters of two-plane distributors are determined, which ensure the maximum uniformity in the distribution of seeds along the width of the coulters of stubble seeders. Equipping the paw coulters with two-plane spreaders provides seeding with higher quality indices on uniformity and will ensure an increase in the productivity of agricultural crops.

Influence Coefficients of Constructive Parameters of Meander Slow-Wave System with Additional Shields

Abstract Constructions of meander slow-wave systems with additional shields grounded at different positions are presented. The construction of meander slow-wave systems with additional shields grounded at both edges is investigated in detail. The influence of the main constructive parameters on the electrical characteristics of meander slow-wave systems with additional shields grounded at both edges is evaluated. The main constructive parameters of the investigated system are: the length of the conductor, the width of meander conductor, the width of additional shield, and the width of the gap between adjacent meander conductors. Sonnet® software package, which is based on the method of moments, has been used during the investigation. The results of the influence of constructive parameters to the phase delay time, input impedance, and the width of pass-band of the system are discussed.

Influence of Hydrocyclone Construction Parameters on Nonlinear Viscoplastic Fluid Hydrodynamics

The influence of hydrocyclone construction parameters on nonlinear viscoplastic fluid hydrodynamics was analyzed using numerical modeling. The influence of the cone angle of the hydrocyclone case conical part and a dimensionless flow-rate parameter on axial damping of the tangential velocity component and the fluid film thickness was established. The influence of the construction parameters on the separating capability of the hydrocyclone was analyzed preliminarily. A physical justification of the results was presented.

Influence of constructive parameters and power signals on sound quality and airborne noise radiated by inverter-fed induction motors

This work presents the result of a study of the acoustic quality of noise emitted by a three-phase, induction motor fed with various modulation techniques (Pulse Width Modulation, PWM). It complements the classical study of noise emitted by rotating electrical machines, based on acoustic emission levels. For this, the psychoacoustic parameters of Specific and Total Loudness, as well as Total Roughness were used. These were applied to the noise emitted by a 4-speed, Dahlander-type motor to identify their contribution to the acoustic quality of distinct pole-number configurations as well as the different control-parameter values of each of the studied techniques. The modulation techniques employed have been analyzed in previous research in which was determined their contribution to the noise levels emitted by a machine of similar characteristics as that employed here. Results are checked experimentally and compared to the sound-pressure level; showing the noise emitted and the sound quality do not coincide for a given combination of parameters. Moreover, the choice of the best modulation strategy changes depending on if the aim to achieve is less harmonic distortion (HIPWM-FMTC), less heating of associated electronics (SLPWM) or a lower acoustic emission level (HIPWM-FMTC2). Finally, with the present study an attempt is made to compliment and corroborate the results obtained up until now, as well as initiate a new focus of analysis that can serve as the basis for future research of other operation forms and regimes, and also other kinds of rotating electrical machines.

The influence of constructive parameters on response of bucket wheel excavator superstructure in the out-of-resonance region

The influence of constructive parameters on response of bucket wheel excavator superstructure is investigated by using a four degrees-of-freedom discrete dynamic model. Four representative geometric configurations of the superstructure are examined. The maximum displacements and accelerations are observed when the bucket wheel boom is in its lowest position. Further analysis on this configuration is performed to determine the effects of the structural elements stiffness and the bucket wheel weight on the system response. A set of the magnitudes of the parameters that may cause resonance are also determined.

Pressure drop and permeability of three-dimensional virtual fibrous medium

Pressure drop is one of the principal performances of the fibrous filtration medium. Traditional computational studies in this area are based on typical unrealistic two-dimensional geometries, with the fibre just placed in a lattice perpendicular to the flow. So in this paper, a three-dimensional virtual fibrous material was developed by means of visual basic application. In the virtual fibrous material, the fibres were arranged randomly by computer and the flow field of virtual fibrous material was calculated. The influence of constructive parameters on pressure drop and permeability was investigated. Simulation shows that flow field velocity distribution was not symmetric. Filtration velocity decreased when the air flew through the fibres, whereas the fluid velocity increased significantly when the distance between fibres was large. Obvious vortex formed in the fibre space areas. The pressure drop was tested experimentally, and the result was compared with that of theoretical and semi-empirical formula calculation. Experimental and simulation data were in agreement with Davies' empirical formula. The simulation result reveals that the pressure drop of fibrous medium increased linearly with the increase of filtration velocity. Moreover, pressure drop non-linearly increased with the increasing solid volume fraction. Simulation results of pressure drop were in good agreement with the predictions of Davies' empirical formula.

Modelling of the Influence of a Pointed Field Emission Cathode Design from the Silicon Carbide with Graphene Film on the Electric Field Strength

Graphene film on silicon carbide is considered to be promising material for high-frequency vacuum nanoelectronics. However, the possibility of graphene application in this area is still poorly understood. We have carried out the simulation of the electric field distribution in interelectrode gap of the anode-cathode system pointed field emission cathode based on silicon carbide with graphene film on its surface subject to the rounding-off radius of the top, interelectrode gap, height and cathode forming half-angle of the cone opening by the finite element method. The influence of constructional parameters on the electric field strength in the test structure was analyzed. It is shown that the values of rounding-off radius of the cone point and interelectrode distance has the biggest influence on the electric field in the investigated structure. Changing of the height and cathode forming half-angle of the cone opening does not lead to a significant increase or decrease of the electric field value.

The Influence of Constructional Parameters on Deformability of Elastic Cotton Fabrics

This research is focused on the influence of constructional parameters such as the type of weave and density on deformability of pure cotton and cotton/elastane fabrics. In the research, two basic weaves were used: the plain and twill weave without (pure cotton) and with 6.2 percent of elastane in the weft direction. The density of the warp yarns was before bleaching 22yarns/cm and after end treatment (bleaching) from 24 to 31 yarns/cm. The chosen densities in the weft direction were 17 and 20 yarns/cm. The fabrics were cyclically loaded with maximum load 17.66 N. The non-recoverable deformation was measured after 30 seconds of relaxation after the fourth cycle of loading, according to ASTM D 3107–75. The research results show that elastane incorporation significantly decreased the non-recoverable deformation after loading. In the case of the twill weave, the decrease of non-recoverable deformation was from around 20% – twill without elastane to around 5% – twill with elastane – fabrics 7B and 8B. The non-recoverable deformation level decrease with fabrics in plain weave was also significant (from around 24% – plain without elastane to around 12% – plain with elastane). From the results of non-recoverable deformation, it is clearly seen that the chosen type of weave, plain and twill, significantly influenced the non-recoverable deformation level. The increase of density in the weft direction from 17 yarns/cm to 20 yarns/cm for pure cotton and cotton/elastane fabrics insignificantly influenced the non-recoverable deformation level. This means that the density increase of 3 yarns/cm is too low to significantly influence the deformability of pure cotton and cotton/elastane fabrics.

Influence of constructive parameters on the performance of two indirect evaporative cooler prototypes

Two equally-sized cross-flow heat-exchanger prototypes have been designed with a total heat exchange area of 6 m2 and 3 m2 respectively, constructed with polycarbonate hollow panels of different cross section. They are connected into a heat-recovery cycle within the whole experimental setup constructed for the tests, which mainly consists of: an Air Handling Unit to simulate the outdoor airstream conditions, a conditioned climate chamber, and a water circuit to provide the water supply required. They have been experimentally characterised in two operating modes in order to determine how evaporative cooling improves heat recovery in each case, focussing on the influence of modifying the constructive characteristics. To perform the evaporative cooling process, water is supplied to the exhaust airstream. Results are studied considering how constructive issues, outdoor air volume flow rate and temperature, as well as operating mode influence on the performance obtained. An Analysis of Variance shows how outdoor airflow has a key role in the performance of the systems; whereas entering outdoor air temperature determines cooling capacities. Improvements introduced by larger heat exchange areas compensate with their corresponding smaller cross sections, which hinder water–air distribution on the exhaust air side of the heat exchanger. Finally, these small devices achieve cooling capacities of up to 800 W, being able to partly support ventilation load and achieving around 50% of energy saving in ventilation cooling.

Theoretical analysis on non-uniformity of water distribution and influence of construction parameters on settling efficiency

During the reconstruction of horizontal flow tanks into inclined settling tanks in Chinese water plants, uniformity of water distribution has not been solved theoretically. Based on the concepts of hydraulics, a model of inclined tanks, including the ratio (L/B) of tank length (L) to width (B), diameter of inclined tubes (d) and height of the water distribution area (h1) and so on, was established to simulate and analyze the effects of these parameters on Non-Uniformity of Water Distribution (NUWD). The influences of NUWD on settling efficiency were also analyzed based on Yao's formula. Simulated results show that the ratio (L/B) has the greatest impact on NUWD, and the settling efficiency decreases with it. Under the conditions of q=10 or 20 m/h and L/B>or=5 or 3, the total forces imposed on down-sliding flocs tend to be zero, which reduces the separating efficiency. Moreover, critical settling velocity (CSV) of the first inclined tube will decrease with the increase of h1, and the optimal range of h1 will be 1.2-1.6 m. The difference of CSV between the first tube and the average value of the tank u0 (shown as Delta(uF0-u0)) will increase with d and surface load (q).

Three-dimensional model of gate current flow in thyristor. II. Numerical examples

For Part I see ibid., vol.37, no.5, p.1383-8 (1990). Some numerical results which show the advantages of the model are discussed. Advantages include a rapid evaluation of gate driving conditions along the arm of the gate contact for various constructional parameters of a thyristor, an example of the determination of the shape of the initially turned-on region located along one arm of the digital gate, and some results concerning the influence of constructional parameters on the width of the initially turned-on area. The influence of the interfacial metal-semiconductor contact resistance on the accuracy of the numerical simulation is also examined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>