Experimental Investigation of Wire Electrical Discharge Machining of NdFeB Permanent Magnets with an RC-Type Machine

This paper focuses on wire electrical discharge machining (WEDM) of devices made from commercially available sintered neodymium-iron-boron (NdFeB) rare-earth magnets that have been magnetized before machining. We conduct an experimental study to quantify the effects of the voltage and capacitance of an RC-type WEDM machine, as well as the magnet polarity, on slicing rate, mean kerf, and variation in kerf. We find that voltage and capacitance affect slicing rate, that voltage affects mean kerf, that no parameters tested affect the variation in kerf, and that the polarity of the magnet being machined does not affect the machining process. Linear regression is used to fit simple predictive models to the data with good agreement. Further analysis is performed to characterize the loss in permanent magnetization on the surface of the magnet due to heating during the machining process, and it is found that the outer layer of approximately 35 μm in depth is demagnetized when using the highest voltage and capacitance values tested.     

Partial electrode method for loss and physical parameter determination of piezoceramics: Simplification,error investigation and applicability

The IEEE standard to determine physical parameters of piezoceramics has been utilized for decades by many researchers, yet it omits presence of important loss factors and possesses serious deficits that restrict accurate parameter determination. To resolve these issues, the partial electrode (PE) method was previously proposed, though the focus has been merely made on development of the method itself. In this study, we provide method simplification and more detailed analysis. The omission of unnecessary samples greatly boosts experiment and analysis process. To prove that the PE method is reliable, possible causes of errors were investigated; it is shown that they were either negligibly small or can be resolved with proper calibration. Furthermore, Applicability of PE method to various types of piezoceramic materials and compatibility with impedance analyzers are shown. Finally, PE method is proved to be reliable and can be alternative to IEEE Standard on Piezoelectricity.     

Rumination activity of dairy cows in the 24 hours before and after calving

Monitoring rumination behavior serves multiple purposes in feeding and herd management of dairy cows. The process of calving is a major event for cows, and a detailed understanding of alterations in behavioral patterns of animals in the time around calving is important in calving detection. The objective of this study was to describe the short-term changes in rumination patterns in dairy cows immediately before and after parturition. In total, 17 cows were fitted with rumination sensors that were able to monitor rumination time, number of rumination boli, and number of rumination jaw movements. Rumination time was decreased in the last 4 h antepartum and in the first 8 h postpartum. Cows stopped ruminating 123 ± 58 min (mean ± standard deviation) before calving and resumed ruminating 355 ± 194 min after calving. The number of rumination jaw movements and boli per day were decreased in the 24-h period postpartum. Rumination rate, the number of rumination jaw movements per rumination minute, and the number of boli per rumination minute changed little around calving. The calving event primarily influenced the duration and frequency of various rumination characteristics but not rumination intensity. Among detected characteristics, rumination time showed the greatest potential for monitoring of calving events.     

Dustiness Quantification of Powders by the Fractional Release Rate

The handling of dispersed solids may lead to undesirable release of dust particles. Size and quantity of the particles transferred into the gas with time depend on the binding and separating forces in the powder. These in turn are determined by characteristic parameters of the powder and of the process. Analogous to the well‐known “fractional collection efficiency” describing the dust separation, a newly defined “fractional release rate” to quantify the release of dust is introduced. The application is demonstrated by an example and the way to further development of this innovative approach is demonstrated.     

Numerical modelling of calcination reaction mechanism for cement production

Calcination is a thermo-chemical process, widely used in the cement industry, where limestone is converted by thermal decomposition into lime CaO and carbon dioxide CO₂. The focus of this paper is on the implementation and validation of the endothermic calcination reaction mechanism of limestone in a commercial finite volume based CFD code. This code is used to simulate the turbulent flow field, the temperature field, concentrations of the reactants and products, as well as the interaction of particles with the gas phase, by solving the mathematical equations, which govern these processes. For calcination, the effects of temperature, decomposition pressure, diffusion and pore efficiency were taken into account. A simple three-dimensional geometry of a pipe reactor was used for numerical simulations. To verify the accuracy of the modelling approach, the numerical predictions were compared with experimental data, yielding satisfying results and proper trends of physical parameters influencing the process.     

Parallel Operation of Centrifugal Pumps: Effects of Rotational Speed Differences due to Motor Slip

In industrial plants, centrifugal pumps are frequently operated in parallel configuration, not least for redundancy and operational reliability reasons. However, regarding the resulting pressure pulsations and energy consumption, this operation mode has so far not been in the focus of scientific studies. The object of the present article is to clarify the effect of parallel operation with respect to the observable pressure pulsations. Measurements were carried out with two identical centrifugal pumps operating in parallel mode in an industrial‐scale closed‐loop piping system. The results suggest that, regarding both the resulting pressure pulsations and the operating point of each pump, this operation mode is quite sensitive to smallest rotational speed deviations as they may occur due to different motor slip. The results indicate furthermore that, for minimum pressure pulsations, equal power consumptions of the two pumps are crucial, but not necessarily equal rotational speeds.     

Fraktionsfreisetzungsgrad – Ein neuer Ansatz zur Quantifizierung der Staubungsneigung von Pulvern

The handling of dispersed solids may lead to undesirable release of particles. Size and quantity of the particles transferred into the gas depend on the holding and separating forces in the powder. These in turn are determined by characteristic parameters of the powder and of the process. Analogous to the fractional collection efficiency describing the dust separation, a fractional release rate to quantify the release of dust is introduced. The application is demonstrated by an example and the way to further development of this new approach is demonstrated.