The results of a study on the geometric shape of the damper on the efficiency of the ultrasonic piezoelectric transducer are presented. In particular, a damper in the form of a truncated cone is ...considered, the generatrix of which has an inclination angle α relative to the diameter of the piezoceramic plate. The shape of the damper in the form of a truncated cone is chosen based on the a priori assumption that this helps to increase the path of the wave in the damper material due to numerous reflections in it. A criterion for the efficiency of damper operation is proposed. The optimal (from the point of view of the damper efficiency) value of the angle α was determined theoretically and experimentally. The technology of its production is described. Satisfactory agreement between the results of theoretical and experimental studies was noted.
The influence of static compressional stress on the anisotropy of piezoelectric ceramics of BaTiO3 and PZT types is considered theoretically and experimentally. Static compression changes the domain ...structure of piezoceramics. These changes occur due to the reorientation of mostly 90° domain axes. As a result, all the parameters of the material change—elastic, piezoelectric, and dielectric. Some of them increase, and some, on the contrary, decrease. Changes occur in a nonlinear way, and higher-order parameters appear. The relationship between the total volume of the reoriented domains and the change in elastic moduli and piezomoduli is theoretically considered. The corresponding theoretical dependences are obtained. To confirm these theoretical dependences, experimental measurements were performed using the ultrasonic pulse-interference method at a frequency of 8 MHz. There is practically no oscillation movement of domain boundaries at this frequency, therefore, the change in the system of elastic and piezoelectric moduli is structural, not dynamic. The possibility of predicting changes in the structure of modules as a result of static compression is shown.
Disks are one of the most common tillage working bodies used both on independent machines and tools, and as part of combined aggregates. Compliance with agrotechnical requirements is a necessary ...condition for improving the technological efficiency of the disk working bodies. The height of the furrow bottom ridge depends on a number of design and technological parameters of adjacent disks, as well as the distance between them. In the article, analytical expressions are obtained that allow us to describe the relationship between the height of furrow bottom ridge formed between the projections of cutting edges of adjacent disks, structural and technological parameters, and a given orientation scheme.
Easy Access to the Copper(III) Anion [Cu(CF3)4] Romine, Andrew M.; Nebra, Noel; Konovalov, Andrey I. ...
Angewandte Chemie (International ed.),
February 23, 2015, Letnik:
54, Številka:
9
Journal Article
Recenzirano
CuCl or pre‐generated CuCF3 reacts with CF3SiMe3/KF in DMF in air to give Cu(CF3)4− quantitatively. PPN+, Me4N+, Bu4N+, PhCH2NEt3+, and Ph4P+ salts of Cu(CF3)4− were prepared and isolated ...spectroscopically and analytically pure in 82–99 % yield. X‐ray structures of the PPN+, Me4N+, Bu4N+, and Ph4P+ salts were determined. A new synthetic strategy with Cu(CF3)4− was demonstrated, involving the removal of one CF3− from the Cu atom in the presence of an incoming ligand. A novel CuIII complex (bpy)Cu(CF3)3 was thus prepared and fully characterized, including by single‐crystal X‐ray diffraction. The bpy complex is highly fluxional in solution, the barrier to degenerate isomerization being only 2.3 kcal mol−1. An NPA study reveals a huge difference in the charge on the Cu atom in Cu(CR3)4− for R=F (+0.19) and R=H (+0.46), suggesting a higher electron density on Cu in the fluorinated complex.
Easy as it gets: The CuIII anion Cu(CF3)4− is finally easily accessible through the newly developed exceedingly simple and highly efficient one‐step procedure directly from CuCl. The reaction occurs at room temperature in air to furnish quantitatively Cu(CF3)4−, which can be used for the synthesis of other, previously unknown CF3CuIII compounds.
In recent years, the improvement of the technological process of tillage is based on the use of working bodies with a curved shape of the working surface, which can increase the agrotechnical rates ...of tillage and reduce its energy intensity. Agricultural implements with disk working bodies are among the most common machines in agriculture. The article presents a kinematic analysis of a disk working body with a changing radius of curvature. Expressions for determining the coordinates, velocity, and acceleration of the arbitrary point on the working surface are obtained.
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