Energy Based Calculation of the Second-Order Levitation in Magnetic Fluid

A permanent magnet immersed in magnetic fluid experiences magnetic levitation force which is of the buoyant type. This phenomenon commonly refers to self-levitation or second-order buoyancy. The stable levitation height of the permanent magnet can be attained by numerical evaluation of the force. Various authors have proposed different computational methods, but all of them rely on force formulation. This paper presents an alternative energy approach in the equilibrium height calculation, which was settled on the minimum energy principle. The problem, involving a cylindrical magnet suspended in a closed cylindrical container full of magnetic fluid, was considered in the study. The results accomplished by the proposed method were compared with those of the well-established surface integral method already verified by experiments. The difference in the results gained by both methods appears to be under 2.5%.

On the respect to the Hashin-Shtrikman bounds of some analytical methods applying to porous media for estimating elastic moduli

In this work, some popular analytic formulas such as Maxwell (MA), Mori-Tanaka approximation (MTA), and a recent method, named the Polarization approximation (PA) will be applied to estimate the elastic moduli for some porous media. These approximations are simple and robust but can be lack reliability in many cases. The Hashin-Shtrikman (H-S) bounds do not supply an exact value but a range that has been admitted by researchers in material science. Meanwhile, the effective properties by unit cell method using the finite element method (FEM) are considered accurate. Different shapes of void inclusions in two or three dimensions are employed to investigate. Results generated by H-S bounds and FEM will be utilized as references. The comparison suggests that the method constructed from the minimum energy principle PA can give a better estimation in some cases. The discussion gives out some remarks which are helpful for the evaluation of effective elastic moduli. Keywords: Maxwell approximation; polarization approximation; Mori-Tanaka approximation; effective elastic moduli; porous medium.

Meteoritic amino acids as chemical tracers of parent-body chemistries

ABSTRACT The analysis of the organic matter of meteorites made it possible to identify over 70 amino acids (AA), including 8 of those found in living organisms. However, their relative abundances vary drastically with the type of the carbonaceous chondrite, even for isomers of same chemical formula. In this report, we address the question whether this difference may have its origin in the relative stability of these isomers according to the conditions they experienced when they were formed and after. To this end, we rely on the fact that for most of the species observed so far in the interstellar medium (ISM), the most abundant isomer of a given generic chemical formula is the most stable one (minimum energy principle, MEP). Using quantum density functional theory (DFT) simulations, we investigate the relative stability of the lowest energy isomers of alanine (Ala) and amino butyric acid (ABA) in the neutral, protonated, and zwitterionic structures together with corresponding nitrile precursors. It is shown that β-alanine and γ-ABA are the most stable in a protonated form, whereas α-AA are the most stable in the zwitterionic and nitrile structures. The different composition of the carbonaceous chondrites CIs and CMs could be linked to the chemical context of the aqueous alterations of the parent bodies.

Humans use minimum cost movements in a whole-body task

Humans have elegant bodies that allow gymnastics, piano playing, and tool use, but understanding how they do this in detail is difficult because their musculoskeletal systems are extraordinarily complicated. Nonetheless, although movements can be very individuated, some common movements like walking and reaching can be stereotypical, with the movement cost a major factor. A recent study has extended these observations by showing that in an arbitrary set of whole-body movements used to trace large-scale closed curves, near-identical posture changes were chosen across different subjects, both in the average trajectories of the body’s limbs and in variations within trajectories. The commonality of that result motivates explanations for this generality. One could be that humans also choose trajectories that are economical in energetic cost. To test this hypothesis, we situate the tracing data within a fifty degree of freedom dynamic model of the human skeleton that allows the computation of movement cost. Comparing the model movement cost data from nominal tracings against various perturbed tracings shows that the latter are more energetically expensive, inferring that the original traces were chosen on the basis of minimum cost. Moreover, the computational approach used to establish minimum cost principle suggests a refinement of what is known about cortical movement representations.Author SummaryAlthough motor cortical areas have been extensively studied, their basic response properties are still only partially understood, and it remains controversial whether neural activity relates to muscle commands or to abstract movement features. We provide a new perspective of how movements may be resented in the brain by showing that humans chose trajectories with minimum energy cost while accomplishing goal-directed tasks. Furthermore, most of the current neural control studies are experimental. Our computational methodology coupled with a minimum energy principle suggests a refinement of the brain’s storage of remembered movements.

A Loaded Analysis Method for RV Cycloidal-pin Transmission Based on the Minimum Energy Principle

Due to the complexity of load distribution and contact conditions, as well as the lack of effective analysis methods, the theoretically designed rotary vector (RV) cycloidal-pin drive with good meshing characteristics shows poor loaded performance in practical applications. In this paper, an effective analysis method based on the minimum energy principle is proposed, which can accurately obtain the real loaded characteristics in line with the actual operations. In the process of loaded analysis, through the innovative introduction of the minimum energy principle, the actual number of teeth engaged simultaneously was accurately determined, which directly affects the quality of meshing. The results of simulation and measurement experiment demonstrate the correctness and practicability of the theoretical analysis method and the effectiveness of the introduction of the minimum energy principle. This study solves the problem that the actual meshing performance is inconsistent with the theoretical analysis results, and provides an effective way for the improvement and pre-control of the transmission accuracy and meshing quality of the robot RV reducer.

Determination of the junction angle in fluvial channels from georeferenced aerial images from Google Earth Pro and UAV

The junction angles in fluvial channels are determined from complex erosion and deposition processes, resulting from river-flow dynamics, bed and margin morphology, and so on. Knowledge regarding these angles is important in order to better understand the existing conditions in a basin. In this sense, the objective of the present study was to determine the junction angles on fluvial channels, called α, β and γ, applying the law of cosines. Georeferenced Google Earth Pro images and UAV images were used. Then, the values calculated from the georeferenced aerial images were compared with the values calculated from the minimum energy principle. To visualize and understand the obtained angles, the Junction Angles Diagram was used. The obtained result shows that the methodology using georeferenced aerial images have good performance for determining junction angles on fluvial channels.

Orthogonal Machining of Copper Alloy With a Hardness Gradient

An experimental and analytical investigation of the effects of hardness upon the classical orthogonal machining geometries was conducted using copper alloy with 12 levels of hardness as measured on the Brinell hardness scale. A real time data collection method permitted the collection of a large body of data for analysis. 720 experimental runs were analyzed. The experimental results were compared to thirteen geometrical models that have been formulated including Merchant’s and Piispanen’s independently derived orthogonal machining equations of the 1940’s. One model [1] was verified by the results of the experiment in copper when a regression study of the data was conducted. Their application of the minimum energy principle in deriving an expression for the shear front angle ψ, the onset of shear plane angle ϕ, and the tool face rake angle α, provided an accurate shear strain model that is well supported by the physical evidence. The resulting relationship: ψ=45°-φ+α2 is predictive. It correlates directly and strongly with the measured material hardness.

Incremental Bending of Three-Dimensional Free Form Metal Plates Using Minimum Energy Principle and Model-Less Control

Bending 3D free form metal plates is a common process used in many heavy industries such as shipbuilding. The traditional method is the so-called line heating method, which is not only labor intensive but also inefficient and error-prone. This paper presents a new incremental bending method based on minimum energy principle and model-less control. First, the sheet metal is discretized into a number of strips connected through virtual springs. Next, by applying the minimum energy principle, the punching and supporting points are calculated for the strip. Then, the bended shape of the strip is computed based on the beam bending theory. This process is continued until the final shape is reached. To compensate the bending error, the computer vision-based model-less control is applied. The computer vision detects the bending error based on which additional bending steps are calculated. The new method is tested in a custom build incremental bending machine. Different metal plates are formed. For a metal plate of 1000 × 800 × 5 mm3, the average bending error is less than 3 mm. In comparison with the existing methods, the new method has a number of advantages, including simple, fast, and highly energy efficient.