CFD study on the effect of the oxygen lance inclination angle on the decarburization kinetics of liquid steel in the EAF

In Electric Arc Furnace (EAF) steelmaking the main chemical reaction is the decarburization reaction. This reaction is promoted by the injection of oxygen using supersonic or coherent jets and further chemical reaction with dissolved carbon in liquid steel at high temperatures. A 3D mathematical model to describe the effect of the injection angle, oxygen gas flow rate and number of lances on the decarburization kinetics of molten steel, in the absence of the top slag layer has been developed. The model has been validated using experimental data reported in the literature. The model shows that the decarburization kinetics is promoted by decreasing the injection angle from the horizontal, condition that improves both bath movement and reaction kinetics. These findings suggest that current injection angles in industrial EAF’s can be decreased in order to improve the decarburization rate. The main mechanism is the effect of the gas jet on the motion of the liquid. Taking into consideration that decreasing the injection angle from the horizontal promotes splashing, the numerical model predictions are employed to suggest alternative solutions in order to reach high decarburization rates.

Spectral Power in Marmoset Frontal Motor Cortex during Natural Locomotor Behavior

During primate arboreal locomotion, substrate orientation modifies body axis orientation and biomechanical contribution of fore- and hindlimbs. To characterize the role of cortical oscillations in integrating these locomotor demands, we recorded electrocorticographic activity from left dorsal premotor, primary motor, and supplementary motor cortices of three common marmosets moving across a branch-like small-diameter pole, fixed horizontally or vertically. Animals displayed behavioral adjustments to the task, namely, the horizontal condition mainly induced quadrupedal walk with pronated/neutral forelimb postures, whereas the vertical condition induced walk and bound gaits with supinated/neutral postures. Examination of cortical activity suggests that β (16–35 Hz) and γ (75–100 Hz) oscillations could reflect different processes in locomotor adjustments. During task, modulation of γ ERS by substrate orientation (horizontal/vertical) and epoch (preparation/execution) suggests close tuning to movement dynamics and biomechanical demands. β ERD was essentially modulated by gait (walk/bound), which could illustrate contribution to movement sequence and coordination. At rest, modulation of β power by substrate orientation underlines its role in sensorimotor processes for postural maintenance.

Desempenho de um sistema solar fotovoltaico com diferentes inclinações e orientações azimutais em cidades da Paraíba

<p>The Sun is the main source of energy for the Earth. The conversion of solar to electric energy can be done through photovoltaic systems, whose performance depends on variables such as slope angle and azimuth orientation. The objective of this project was to evaluate the annual production of electric energy according to the function of the angles of inclination and azimuth orientation for a residential photovoltaic system connected to the grid in six municipalities of Paraíba. The analysis was performed via a System Advisor Model simulation for a system with a capacity of 1500 Wp. The reference system considered in this study was oriented to the geographic north and the slope was equal to the local latitude. The variation of the angle of inclination of the module was considered at intervals between 0 ° and 90 ° and the azimuthal angle ranged from 0 ° to 360 °. The annual production of energy in each system positioning was normalized by the yield of the reference system to obtain the losses for each orientation. Results indicated that concerning the energy produced by the system in the horizontal condition and regardless of the azimuthal angle, the losses did not exceed 1% in relation to the reference system. It was also observed that there is a wide range of slopes and orientations so that a photovoltaic arrangement can be applied with the minimum loss of electricity generation in relation to the reference system.</p>

Modeling and Analysis of Truck Mounted Concrete Pump Boom by Virtual Prototyping

By far there is lack of research on different working conditions between rigid and flexible dynamics of truck mounted concrete pump booms. First a 3D model has been established by using virtual prototyping technology of a 37 m long boom in Pro/Engineering software. Then the rigid body simulation model has been built. Next modal superimposition method is adopted to change the 4 rigid body booms into flexible ones. Kinematics law and dynamic characteristics of 4 common working conditions had been studied then. Next tip displacement and the first boom hydraulic cylinder force of the 4 working conditions between rigid and flexible models have been researched. Furthermore the first natural frequencies of the structure have been calculated. The results show that the frequency of the horizontal condition has the lowest of all and the roof condition has the largest of all. Besides the cylinder forces of the flexible model are larger than the corresponding rigid ones because of the flexible boom vibration. Finally an experiment has been done on a boom test rig which proved that the established simulation model is reasonable and the frequency results are correct. All of these provide design reference to mechanical manipulator as well as reducing product development cost of such mechanism.

Modeling and Experimental Validation for Hammer-Driven Type Penetrators under Horizontal Condition

This paper proposed a method used to analyze the motion of hammer-driven type penetrators and built a testbed for validating the result of structure optimization of the penetrator in deep space exploration. This method gave a clear understanding of the working principle of the penetrator. The penetrator mainly comprises five components: hammer element, suppressor element, housing element, brake spring, and force spring. Based on the structure of the penetrator, the maximum forward movement of housing element was chosen as optimal object. In order to describe the working process clearly and properly, the working stroke was divided into three phases: unlocking phase, colliding phase, and penetrating phase. In each phase, the displacement and velocity of hammer element, suppressor element, and housing element were described with equation sets when numerically solved. Then, the corresponding parameters of the penetrator were obtained in the testbed with high-speed camera. At last, comparing the parameters obtained by theoretical analysis with that obtained by experiment test with high-speed camera, the perfect ratio of mass element (hammer element, suppressor element, and housing element) and perfect ratio of stiffness of spring element (brake spring and force spring) were obtained.