Engineering

Leaching kinetics in cyanide media of Ag contained in the industrial mining-metallurgical wastes in the state of Hidalgo, Mexico
The leaching kinetics in cyanide media of the silver contained in the Dos Carlos waste tailings at the City of Pachuca de Soto, Hidalgo State, Mexico were carried out. The used material contained the following chemical composition: 56×10-6 of Ag, 0.6×10−6 of Au and 70.43% (by weight) of SiO2; 7.032% (by weight) of Al2O3; 2.69% (by weight) of Fe; 0.46% (by weight) of Mn; 3.98% (by weight) of...


Use of Temperature and Humidity Sensors to Determine Moisture Content of Oolong Tea
The measurement of tea moisture content is important for processing and storing tea. The moisture content of tea affects the quality and durability of the product. Some electrical devices have been proposed to measure the moisture content of tea leaves but are not practical. Their performance is influenced by material density and packing. The official oven method is time-consuming. In this stud...
Analytical Model of Large Data Transactions in CoAP Networks
We propose a novel analytical model to study fragmentation methods in wireless sensor networks adopting the Constrained Application Protocol (CoAP) and the IEEE 802.15.4 standard for medium access control (MAC). The blockwise transfer technique proposed in CoAP and the 6LoWPAN fragmentation are included in the analysis. The two techniques are compared in terms of reliability and delay, dependin...


Formation of the acoustic field of a Rayleigh-wave transducer in an object with a protrusion. Part I. Protrusion with a right angle
Attention is drawn to the possibility of using transducers of Rayleigh waves as the sources (receivers) of transverse waves for ultrasonic testing of objects with auxiliary protrusions, at which elastic modes are transformed and scattered. The acoustic section was analyzed and the influence of both the curvature of the radius junction of a protrusion and the wave frequency on the parameters of ...
An algorithm for the automatic detection of inclusions in an inspected object with a scanning digital X-ray imaging system (one-dimensional variant)
The mathematical model of an output digital signal from a single measuring channel of a scanning digital X-ray imaging system containing a line of detectors is presented for the case where the main type of signal distortions is the noise due to the quantum nature of radiation. This model is used to develop a one-dimensional algorithm for the automatic detection of local “critical” inclusion...


Models of magnetic charges and fluxes in the problem of flaw detection with local magnetization
The results of experimental studies of the magnetic-field strength of surface flaws in magnetically soft and hard steels magnetized with a dipolar magnet are discussed. Peculiarities of the interrelationship between the formation of the magnetic fields of surface flaws and fluxes in a magnetic circuit have been determined. The obtained anomalous relationship of the magnetic-field strengths of f...
An algorithm for the estimation of the quality of the spot welds
Spot welds are widely used in industry, especially in automotive, so welds must be reliable. One of the approaches to estimate the quality of spot welds is to use ultrasonic testing. Spot welding is used in the automotive repair industry as well. However, a spot weld testing device, dedicated for the automotive repair industry, is not available. The objective of this work was to develop an algo...

The use of an ultrasonic flaw detector with a phased antenna array for the recording of echo signals to reconstruct the images of reflectors by the method of projection in the spectral space
A method of automated ultrasonic testing based on the use of a PAA flaw detector for the recording of echo signals followed by the reconstruction of the image of reflectors by applying the 3D variant of the method of projection in the spectral space (3D-PSS) is considered. Customized setting of the PAA flaw detector makes it possible to simulate the operation of many single-element transducers ...
Signals from an attachable anaxial-type eddy-current transducer positioned above a conducting half-space
An exact analytical expression that describes the introduced voltage of an attachable anaxial-type eddy-current transducer (ECT) with displaced axes of the exciting and measuring coils, which is positioned above a conducting nonmagnetic half-space, was obtained. The loci of the introduced voltage in a complex plane, which were constructed on the basis of the results of a numerical analysis of t...

A study of the efficiency of directional field-building methods for interpreting interferograms by the finite-element method
Algorithms for interpreting (decoding) of interferograms plotted by the finite-element method are considered. Three directional field-building methods are used in them: the (i) complex averaging method, (ii) the projection-dispersion method, and (iii) the spectral method. The efficiency of the algorithms is checked on simulated and real interferograms.
High speed trot-running: Implementation of a hierarchical controller using proprioceptive impedance control on the MIT Cheetah
This paper presents implementation of a highly dynamic running gait with a hierarchical controller on the MIT Cheetah. The developed controller enables high-speed running of up to 6 m/s (Froude number of Fr 7.34) incorporating proprioceptive feedback and programmable virtual leg compliance of the MIT Cheetah. To achieve a stable and fast trot gait, we applied three control strategies: (a) progr...

Almost global asymptotic tracking control for spacecraft body-fixed hovering over an asteroid
Almost global asymptotic tracking control for autonomous body-fixed hovering of a rigid spacecraft over an asteroid is proposed in the framework of geometric mechanics. The configuration space for the spacecraft is the Lie group SE ( 3 ) , which is the set of positions and orientations of the rigid spacecraft in three-dimensional Euclidean space. The relative motion with respect to the space...
Formulation of a new set of Simplified Conventional Burnett equations for computation of rarefied hypersonic flows
For computation of rarefied flows in continuum-transition regime with Knudsen number Kn of O(1), Burnett equations have been proposed about a century ago as a set of extended hydrodynamics equations (EHE) that represent the second-order departure from thermodynamic equilibrium in the Chapman–Enskog expansion of Boltzmann equation; the first order terms in the expansion result in the Navier–...
Numerical study of the aerodynamics of a NACA 4412 airfoil in dynamic ground effect
The distance between an airplane and the ground keeps constantly changing during take-off and landing. Thus, the aerodynamics is influenced by the dynamic ground effect (DGE). In this paper, the landing process of a NACA 4412 airfoil is simulated numerically to investigate the influence of DGE. Several sink rates are imposed on the airfoil. Analyses of the results show that DGE can be divided i...
Quasi-a priori mesh adaptation and extrapolation to higher order using τ-estimation
Improving the balance between cost and accuracy of computational fluid dynamics solvers by local mesh adaptation has become a topic of increasing interest. Numerical error based adaptation sensors proved to be robust and converge faster than sensors simply based on features of the flow field. However, this family of sensors known as residual-based sensors usually suffer from a high computationa...