Shaping the Toroidal Section of End Mills

The shaping of the toroidal cutting section of end mills is considered. Methods are devised for selecting the positional parameters in shaping the helical rake surface on the toroidal section. Relations are established between the geometric parameters of the end mill in the toroidal section.     

Fine Purification of Monoisotopic Silanes 28SiH4 , 29SiH4 , and 30SiH4 via Distillation

High-purity isotopically enriched (99.98% ²⁸Si, 99.57% ²⁹Si, and 99.83% ³⁰Si) silane samples are prepared for the first time. The total hydrocarbon content of the samples is no higher than 0.1–0.3 ppm. The concentration of electroactive impurities in the silicon prepared from the purified monoisotopic silane is below 10¹⁵ cm^–3.     

Mutual recognition of the results of measurements and tests and formation of a world-wide metrology system

The main prerequisites are considered in a historical aspect and steps ate taken in creating a world-wide metrology system with the aim of providing conditions for the mutual recognition of measurement results. __________ Translated from Izmeritel’naya Tekhnika, No. 11. pp. 59–62, November, 2007.     

Relative Yield and Period of Individual Groups of Delayed Neutrons in 233U, 235U, and 239Pu Fission by Epithermal Neutrons

The relative yield of delayed neutrons and the half-life of their precursor nuclei in fissioning of ²³³U, ²³⁵U, and ²³⁹Pu by epithermal neutrons are measured on a setup which is based on a KG-2.5 electrostatic accelerator. The experimental samples are irradiated in a polyethylene cube, one face of which is irradiated by a neutron beam consisting of T(p, n)³He neutrons. A procedure is developed for averaging the group parameters of delayed neutrons from different series of measurements, taking account of their correlation. A comparative analysis of the data of this work and in ENDF/BVI in terms of the average half-life of the precursor nuclei of the delayed neutrons and using the dependence of the reactivity on the asymptotic period of the reactor is performed.It is shown that the data of this work agree, to within the uncertainty limits, with the recommended experimental data and differ substantially from the ENDF/BVI data.     

Temporal and radial evolution of the populations of CuI levels inthe CuBr vapor laser

Populations of CuI ground state, resonance, and metastable levels have been measured in CuBr laser with and without hydrogen additives. Temporal evolution and spatial distribution populations have been studied during the excitation pulse and also during the interpulse period of time. Addition of hydrogen results in a smaller rate of resonance and metastable levels excitation and smaller depopulation of the ground state during the excitation pulse. Repopulation of the ground state after the excitation pulse with hydrogen is much faster. CuBr molecules have been detected only in the periphery of the active zone. The density of the CuBr molecules had no noticeable change either during the excitation pulse or in the interpulse period     

Special features of failure of multilayered structures in local dynamic loading

The authors present the results of numerical modeling of penetration of a rigid indentor into multilayer barriers made of concrete, steel and sand. The effect of the material and the position of the layers on the penetration of a striker and failure of the barrier is analyzed.Translated from Problemy Prochnosti, No. 5, pp. 64–68, May, 1994.     

Quantum dots in YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>6+<Emphasis Type="Italic">x</Emphasis></Subscript> films with a tetragonal structure

Experimental evidence is presented for the existence of clusters possessing metallic conductivity in epitaxial YBa₂Cu₃O_6+x (x<0.4) films with a tetragonal structure. Despite the overall dielectric state, the optical transmission spectra reveal the regions of absorption due to free charge carriers. The presence of metallic clusters is also confirmed by the X-ray diffraction data. At low temperatures, these metallic clusters are capable of converting into quantum dots responsible for the θ(T) = const regions in the temperature dependence of the electric resistance. The process of cluster formation can be enhanced by high-power laser (KrF) radiation.     

Metrology-cybernetics-control: A new approach

As a science and as a special activity concerned with measurements, the science of metrology pursues a classical, orthodox purpose, mainly involving the measurement of physical quantities. The term “measurement” is now applied also to social, economic, medical, and other disciplines, including cybernetics and problems of management and control. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 17–20, July, 1996.     

Experimental design in problems involving measurement of the mass of petroleum products in storage tanks

We propose a technique for optimal selection of standard pressure controllers for obtaining the best calibration characteristics for differential pressure gauges, ensuring high-quality metrological characteristics for the data acquisition systems for determination of the mass of petroleum products in storage tanks. Translated from Izmeritel'naya Tekhnika, No. 6, pp. 36–38, June, 1996.