displacement speed
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2021 ◽  
Vol 15 (3) ◽  
pp. 469-483
Author(s):  
Michel Dos Santos Moura ◽  
Aldir Carpes ◽  
Guinther Hugo Grudtner ◽  
Kléber Pereira Lanças

The base cut of cultures is one of the most studied parameters, and the variables involved in this process should be better evaluated under controlled conditions. The aim of this study was to evaluate, using an electromechanical device, under controlled conditions, the influence of the cutting angle and the machine's translation speed on the impact force generated on sugarcane stalks in mechanized harvesting. The study was carried out at the Nempa - Center for Testing of Agroforestry Machines and Tires (NEMPA) at UNESP/Botucatu. For the tests, the Sugarcane Basal Cut Testing Device (BCTD) was used. The collected data were evaluated using multiple linear regression analysis, using the stepwise method. The results showed that the angulation of the cutting blades is the most significant variable in relation to the impact force generated in the cutting process of sugarcane stalks, this research also managed to assess that the intensity of the angulation effect is more than 2 times greater than the effect generated by the displacement speed in the mechanized harvesting process.


Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7677
Author(s):  
Hazem S.A.M. Awad ◽  
Khalil Abo-Amsha ◽  
Umair Ahmed ◽  
Nilanjan Chakraborty

Moderate or intense low-oxygen dilution (MILD) combustion is a novel combustion technique that can simultaneously improve thermal efficiency and reduce emissions. This paper focuses on the differences in statistical behaviours of the surface density function (SDF = magnitude of the reaction progress variable gradient) between conventional premixed flames and exhaust gas recirculation (EGR) type homogeneous-mixture combustion under MILD conditions using direct numerical simulations (DNS) data. The mean values of the SDF in the MILD combustion cases were found to be significantly smaller than those in the corresponding premixed flame cases. Moreover, the mean behaviour of the SDF in response to the variations of turbulence intensity were compared between MILD and premixed flame cases, and the differences are explained in terms of the strain rates induced by fluid motion and the ones arising from flame displacement speed. It was found that the effects of dilatation rate were much weaker in the MILD combustion cases than in the premixed flame cases, and the reactive scalar gradient in MILD combustion cases preferentially aligns with the most compressive principal strain-rate eigendirection. By contrast, the reactive scalar gradient preferentially aligned with the most extensive principal strain-rate eigendirection within the flame in the premixed flame cases considered here, but the extent of this alignment weakened with increasing turbulence intensity. This gave rise to a predominantly positive mean value of normal strain rate in the premixed flames, whereas the mean normal strain rate remained negative, and its magnitude increased with increasing turbulence intensity in the MILD combustion cases. The mean value of the reaction component of displacement speed assumed non-negligible values in the MILD combustion cases for a broader range of reaction progress variable, compared with the conventional premixed flames. Moreover, the mean displacement speed increased from the unburned gas side to the burned gas side in the conventional premixed flames, whereas the mean displacement speed in MILD combustion cases decreased from the unburned gas side to the middle of the flame before increasing mildly towards the burned gas side. These differences in the mean displacement speed gave rise to significant differences in the mean behaviour of the normal strain rate induced by the flame propagation and effective strain rate, which explains the differences in the SDF evolution and its response to the variation of turbulence intensity between the conventional premixed flames and MILD combustion cases. The tangential fluid-dynamic strain rate assumed positive mean values, but it was overcome by negative mean values of curvature stretch rate to yield negative mean values of stretch rate for both the premixed flames and MILD combustion cases. This behaviour is explained in terms of the curvature dependence of displacement speed. These findings suggest that the curvature dependence of displacement speed and the scalar gradient alignment with local principal strain rate eigendirections need to be addressed for modelling EGR-type homogeneous-mixture MILD combustion.


Author(s):  
Bernardo Ide ◽  
Amanda Silvatti ◽  
Craig Staunton ◽  
Moacir Marocolo ◽  
Dustin Oranchuk ◽  
...  

The International System of Units (SI) was adopted in 1960 as a universal measuring system to be used for all areas of science. Sports Science papers have shown lots of inaccurate and inappropriate terms for quantification of athletes’ performance and the psychobiological responses to exercise (e.g., internal load). In biomechanics, external and internal loads are forces acting externally and internally, inducing stress and strain in the biological tissues. Therefore, the current review present simple proposals to correct the inappropriate terms: 1) do not use the term external load when referring to the assessment of exercise time, distance, displacement, speed, velocity, acceleration, torque, work, power, impulse, etc.; 2) do not use the term internal load when referring to the assessment of psychobiological stress markers (i.e., session rating of perceived exertion, heart rate, blood lactate, oxygen consumption, etc.); 3) do not use the term impulse when expressing other calculus than integrating force with respect to time, and neither strain, when expressing other phenomena than the body deformation. Instead, the term exercise intensity is universal and can be used to describe all forms of exercise. Finally, duration should precisely be described according to physical quantities (e.g., time, distance, displacement, speed, velocity, acceleration, force, torque, work, power, impulse, etc.) and the units accomplish by use of the SI. These simple quantifications can be performed for the exercises, sessions, microcycles, mesocycles and macrocycles of the athletes. Such standardization will provide a consistent and clear communication among sports scientists and all areas of science.


Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6626
Author(s):  
Izabela Miturska-Barańska ◽  
Anna Rudawska ◽  
Elżbieta Doluk

In this study, the influence of sandblasting process parameters as a surface preparation method on the strength of single-lap adhesive joints of EN AW 2024 T3 aerospace aluminium alloy sheets was determined. Eleven sets of sandblasting parameters were used, which were determined according to a determined experimental plan. The variable factors in the sandblasting process were pressure, nozzle distance, and workpiece displacement speed. The sand jet incidence angle was constant. Garnet 80 E+ was the abrasive material that was used. The joints were made using an epoxy adhesive composition of Epidian 5 epoxy resin and a PAC curing agent. The influence of the surface preparation method on the surface roughness and contact angle to determine the surface free energy was evaluated. The shear strength of the adhesive joints was also determined, which finally allowed the evaluation of the applied surface treatment variants. The obtained results were subjected to statistical analysis, which indicated that the highest shear strength of the adhesive joints was obtained for samples whose surfaces were treated by sandblasting at parameter configurations in which the pressure was 5–6 × 105 Pa; the distance between the nozzle and the sandblasted surface should not be greater than 97 mm, and the speed at which the workpiece moves in relation to the nozzle should not be greater than 75 mm/min.


2021 ◽  
Vol 11 (19) ◽  
pp. 9330
Author(s):  
Ming-Yen Wei

Six-axis motion platforms have a low contraction height and a high degree of freedom. First of all, the designed six-axis crank arm platform, including the motor, reducer, crank arm, link, platform support arm, and upper and lower platforms, can be designed for different bearing requirements. Secondly, it uses a coordinate transform and kinematics theory to derive each motor rotor angle. A set of platform data acquisition (DAQ) monitoring modules was established, and the LabVIEW programming language was used to write measurement software. The monitoring items include displacement, speed, and acceleration, which can be displayed on the screen and recorded by an industrial computer in real time and dynamically. Then, an RS-485 or RS-232 communication transmission interface was used to provide the control system with the related movement information. Finally, an industrial computer combined with a motion control card was used as a control kernel to realize the control algorithms, internet module function, I/O write and read signals, firmware integration, and human–machine interface message. The experimental results validate the appropriateness of the proposed method.


Author(s):  
P. P. Kolegov ◽  

The paper presents the results of the research on the colluvial cone (talus) dynamics study by using the lichenometric method in the basin of the Agan and Nankala rivers (Arman River basin). The obtained values of the exposure time of taluses are 385 ± 114 yr, the displacement speed of the clastic cover in the talus is 0.48 ± 0.23 m/yr. The distal parts of some cones, confined to the rocky slopes of the northern exposure, have been transformed into slope rock glaciers.


Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5695
Author(s):  
Felix B. Keil ◽  
Marvin Amzehnhoff ◽  
Umair Ahmed ◽  
Nilanjan Chakraborty ◽  
Markus Klein

Flame propagation statistics for turbulent, statistically planar premixed flames obtained from 3D Direct Numerical Simulations using both simple and detailed chemistry have been evaluated and compared to each other. To achieve this, a new database has been established encompassing five different conditions on the turbulent combustion regime diagram, using nearly identical numerical methods and the same initial and boundary conditions. The discussion includes interdependencies of displacement speed and its individual components as well as surface density function (i.e., magnitude of the reaction progress variable) with tangential strain rate and curvature. For the analysis of detailed chemistry Direct Numerical Simulation data, three different definitions of reaction progress variable, based on CH4,H2O and O2 mass fractions will be used. While the displacement speed statistics remain qualitatively and to a large extent quantitatively similar for simple chemistry and detailed chemistry, there are pronounced differences for its individual contributions which to a large extent depend on the definition of reaction progress variable as well as on the chosen isosurface level. It is concluded that, while detailed chemistry simulations provide more detailed information about the flame structure, the choice of the reaction progress variable definition and the choice of the resulting isosurface give rise to considerable uncertainty in the interpretation of displacement speed statistics, sometimes even showing opposing trends. Simple chemistry simulations are shown to provide (a) the global flame propagation statistics which are qualitatively similar to the corresponding results from detailed chemistry simulations, (b) remove the uncertainties with respect to the choice of reaction progress variable, and (c) are more straightforward to compare with theoretical analysis or model assumptions that are mostly based on simple chemistry assumptions.


Author(s):  
Nilanjan Chakraborty ◽  
Alexander Herbert ◽  
Umair Ahmed ◽  
Hong G. Im ◽  
Markus Klein

AbstractA three-dimensional Direct Numerical Simulation (DNS) database of statistically planar $$H_{2} -$$ H 2 - air turbulent premixed flames with an equivalence ratio of 0.7 spanning a large range of Karlovitz number has been utilised to assess the performances of the extrapolation relations, which approximate the stretch rate and curvature dependences of density-weighted displacement speed $$S_{d}^{*}$$ S d ∗ . It has been found that the correlation between $$S_{d}^{*}$$ S d ∗ and curvature remains negative and a significantly non-linear interrelation between $$S_{d}^{*}$$ S d ∗ and stretch rate has been observed for all cases considered here. Thus, an extrapolation relation, which assumes a linear stretch rate dependence of density-weighted displacement speed has been found to be inadequate. However, an alternative extrapolation relation, which assumes a linear curvature dependence of $$S_{d}^{*}$$ S d ∗ but allows for a non-linear stretch rate dependence of $$S_{d}^{*}$$ S d ∗ , has been found to be more successful in capturing local behaviour of the density-weighted displacement speed. The extrapolation relations, which express $$S_{d}^{*}$$ S d ∗ as non-linear functions of either curvature or stretch rate, have been found to capture qualitatively the non-linear curvature and stretch rate dependences of $$S_{d}^{*}$$ S d ∗ more satisfactorily than the linear extrapolation relations. However, the improvement comes at the cost of additional tuning parameter. The Markstein lengths LM for all the extrapolation relations show dependence on the choice of reaction progress variable definition and for some extrapolation relations LM also varies with the value of reaction progress variable. The predictions of an extrapolation relation which involve solving a non-linear equation in terms of stretch rate have been found to be sensitive to the initial guess value, whereas a high order polynomial-based extrapolation relation may lead to overshoots and undershoots. Thus, a recently proposed extrapolation relation based on the analysis of simple chemistry DNS data, which explicitly accounts for the non-linear curvature dependence of the combined reaction and normal diffusion components of $$S_{d}^{*}$$ S d ∗ , has been shown to exhibit promising predictions of $$S_{d}^{*}$$ S d ∗ for all cases considered here.


2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Ran Li ◽  
Dalong Wang ◽  
Wenshu Wei ◽  
Shoubin Li

Studying the movement characteristics of the coalmine emulsion pump valve is of great significance for optimizing the dynamic response characteristics of the pump valve, reducing the hysteresis effect, and improving the volumetric efficiency. This article combines the Internet of Things (IoT) and cellular automata techniques to investigate the movement characteristics of the valve of the emulsion pump. Based on Adolf’s exact differential equation and Runge–Kutta iterative method, the movement displacement and movement of the pump valve spool speed curve are computed using Scilab software. We employ cellular automata and AMESim to establish the hydraulic system model of emulsion pump and analyze the movement characteristics of pump valve movement displacement, speed, stability, and closing hysteresis through simulation. Finally, the IoT techniques and a test device are used to evaluate the movement displacement of the pump valve. The experimental results verify the feasibility of using the proposed method to study the pump valve motion characteristics, greatly reduce the cost of testing and parameterized design, and contribute to the development of highly reliable and efficient emulsion pump valves.


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