Review on Experimental and Theoretical Investigations of Ultra-Short Pulsed Laser Ablation of Metals with Burst Pulses

Laser processing with ultra-short double pulses has gained attraction since the beginning of the 2000s. In the last decade, pulse bursts consisting of multiple pulses with a delay of several 10 ns and less found their way into the area of micromachining of metals, opening up completely new process regimes and allowing an increase in the structuring rates and surface quality of machined samples. Several physical effects such as shielding or re-deposition of material have led to a new understanding of the related machining strategies and processing regimes. Results of both experimental and numerical investigations are placed into context for different time scales during laser processing. This review is dedicated to the fundamental physical phenomena taking place during burst processing and their respective effects on machining results of metals in the ultra-short pulse regime for delays ranging from several 100 fs to several microseconds. Furthermore, technical applications based on these effects are reviewed.

Preferred auditory temporal processing regimes and auditory-motor synchronization

Decoding the rich temporal dynamics of complex sounds such as speech is constrained by the underlying neuronal-processing mechanisms. Oscillatory theories suggest the existence of one optimal perceptual performance regime at auditory stimulation rates in the delta to theta range (< 10 Hz), but reduced performance in the alpha range (10–14 Hz) is controversial. Additionally, the widely discussed motor system contribution to timing remains unclear. We measured rate discrimination thresholds between 4 and 15 Hz, and auditory-motor coupling strength was estimated through a behavioral auditory-motor synchronization task. In a Bayesian model comparison, high auditory-motor synchronizers showed a larger range of constant optimal temporal judgments than low synchronizers, with performance decreasing in the alpha range. This evidence for optimal processing in the theta range is consistent with preferred oscillatory regimes in auditory cortex that compartmentalize stimulus encoding and processing. The findings suggest, remarkably, that increased auditory-motor synchronization might extend such an optimal range towards faster rates.

Preferred auditory temporal processing regimes and auditory-motor interactions

Decoding the rich temporal dynamics of complex sounds such as speech is constrained by the underlying neuronal processing mechanisms. Oscillatory theories suggest the existence of one optimal perceptual performance regime at auditory stimulation rates in the delta to theta range (<10 Hz), but reduced performance in the alpha range (10-14 Hz) is controversial. Additionally, the widely discussed motor system contribution to timing remains unclear. We measured rate discrimination thresholds between 4-15 Hz, and auditory-motor coupling strength was estimated through auditory-motor synchronization. In a Bayesian model comparison, high auditory-motor synchronizers showed a larger range of constant optimal temporal judgments than low synchronizers, with performance decreasing in the alpha range. This evidence for optimal auditory processing in the theta range is consistent with preferred oscillatory regimes in auditory cortex that compartmentalize stimulus encoding and processing. The findings suggest, remarkably, that increased auditory-motor interaction might extend such an optimal range towards faster rates.

Viscoelastic Resistance of the Surface Layer of Steel Products to Shock Attack of a Spherical Pellet

The results of experimental studies of a separate contact dynamic interaction of a spherical non-deformable pellet with a plastic flat metal surface at different angles of attack (20° ≤ α ≤ 90°) at high speeds (v ≈ 100m/s) are presented. A method is described for determining the nature of the viscoelastic resistance of a surface layer attacked by a pellet during contact displacement along the normal to the surface and rigid plastic resistance during tangential displacement, which can be used to establish the processing regimes of products by a mass flow of abrasive particles, in particular, shot-blasting cleaning. The results of comparing the obtained and known theoretical data with each other and with experimental studies are presented.

Influence of HPT Deformation on the Structure and Properties of Amorphous Alloys

Recent studies showed that structural changes in amorphous alloys under high pressure torsion (HPT) are determined by their chemical composition and processing regimes. For example, HPT treatment of some amorphous alloys leads to their nanocrystallization; in other alloys, nanocrystallization was not observed, but structural transformations of the amorphous phase were revealed. HPT processing resulted in its modification by introducing interfaces due to the formation of shear bands. In this case, the alloys after HPT processing remained amorphous, but a cluster-type structure was formed. The origin of the observed changes in the structure and properties of amorphous alloys is associated with the chemical separation and evolution of free volume in the amorphous phase due to the formation of a high density of interfaces as a result of HPT processing. Amorphous metal alloys with a nanocluster structure and nanoscale inhomogeneities, representatives of which are nanoglasses, significantly differ in their physical and mechanical properties from conventional amorphous materials. The results presented in this review show that the severe plastic deformation (SPD) processing can be one of the efficient ways for producing a nanocluster structure and improving the properties of amorphous alloys.

Increasing of Energy-Power Indicators of Mechanical Processing in a Planetary Mill by the Use of a Working Chamber with a Square Shape of the Internal Cavity

The paper presents the results of a computational study of the influence of the geometry of the working chamber on the energy-force interaction of grinding bodies in the process of the mixture processing in a planetary mill. The method of computer simulation, using the software system, based on the ideology of discrete elements, shows the high efficiency of processing in a planetary mill, using a working chamber with a square-shaped cavity. The values of the factors that have a dominant influence on the mechanical processing of the charge are determined. A comparison with the process of processing in the working chamber of the traditional cylindrical shape is made. The research results will be used in the appointment of large-size charge processing regimes that provide a high-energy grinding process.

“Alimentar-Comer”: Substâncias Sociáveis e Sutis no Repasto Ritual do Candomblé Teresinense

RESUMO: O texto explora a relação entre as dimensões sociáveis e sutis subjacentes aos regimes de transformação dos alimentos em “comidas de santo” no candomblé. Para tanto, se utiliza de excerto etnográfico sobre o ambiente ritual da casa Ilê Asé Opásoró Fadaka, primeiro terreiro da cidade de Teresina, Piauí, do qual conduz o relato da Festa de Ogun, Oxossi e Osanyin. Aproveita-se para pôr em reflexão a existência de um possível campo de agenciamento simétrico entre os gestuais do “alimentar” (servir) e do “comer” (servir-se), que supomos acontecer toda vez que o repasto sagrado do panteão é substancial, sutil e reciprocamente repartido com a comunidade de culto religioso.Palavras-chave: Substâncias; Alimento; Comidas de santo; Regimes de transformação. ABSTRACT: The article explores the relationship between the sociable and subtle dimensions that underlie candomblé food-processing regimes. To this end, it uses the ethnographic exception of the ritual environment of the house Ilê Asé Opásoró Fadaka, the first Candomblé yard in the city of Teresina, Piauí, at the Feast of Ogun, Oxossi and Osanyin. It takes the opportunity to reflect on the existence of a possible symmetrical agency field between the actions of “food” (to serve) and “eating” (being served), which we assume happen every time the pantheon's sacred meal is substantial and reciprocally divided with the cult community religious.Keywords: Substances; Food; Saint foods; Regimes of transformation.

Establishment of a test culture to study the effects of ionizing radiation on the opportunistic and pathogenic microflora of food

Due to the special importance of food in the emergence of acute intestinal infectious diseases and bacterial food poisoning, special attention is paid to the microbiological purity monitoring of food raw materials and food products. Ionizing radiation processing of food – is a promising technology for combating both microorganisms causing spoilage and pathogenic and opportunistic microorganisms – pathogens of dangerous diseases. However, work with vegetative forms of these microorganisms to study the effects of ionizing radiation is difficult because of the need to use in experiments only actively growing culture, which is sensitive to various environmental factors. When studying the effect of ionizing radiation on the microflora of food products, this study describes the investigation of the possibility of using as a test-culture the ascospores of the fungus Aspergillus fischeri instead of vegetative forms of pathogenic and opportunistic cultures. Ascospores of the fungus Aspergillus fischeri are used as a test culture in the development of pasteurization regimes of fruit and vegetable products. A. fischeri ascospores have been shown to have higher resistance to ionizing radiation in the range from 1 to 5 kGy at capacity 10 MeV in comparison with Salmonella enterica, Escherichia coli and Listeria monocytogenes cells. Therefore, in the development of ionizing radiation food processing regimes it is recommended to use ascospores of the fungus A. fischeri as a test culture instead of vegetative forms of bacteria.

Research Regarding Embedded Systems of Robotic Technology for Manufacturing of Hybrid Polymeric Composite Products

Fiber-reinforced composite materials are increasingly present in areas such as automotive, aeronautics, defense, sport, used due to their special mechanical characteristics and very good behavior under heavy working conditions. New mold design techniques (such as 3D printing technologies), processing (such as the use of robotic technologies), open new opportunities for future challenges. This paper represents research on analysis techniques for the design of composite materials products made of fiber-reinforced, research on the use of devices with feedback loop for mechanical cutting technologies, which allow intelligent dynamic adjustment of the processing regimes, analysis of manufacturing technologies used as unconventional processes for the implementation of inclusion components, economic judgments on advantages, disadvantages of the techniques and methods used.