Stamping of Nonuniform Channels. 5. Calculation Methods for Channel Extrusion. 5.1. Formulas

Russian Engineering Research - Formulas are derived for the most important parameters of channel extrusion.     

Improvement of Air-Distributing System of the Pneumatic Impact Machines for Trenchless Technologies

The process of actuation is considered for the inertial element in the improved air-distributing system of pneumatic puncher whose dimensionless parameters are determined.     

BIR and BIGR Upgrade Variants for Enlarging Their Interior Cavities

Computational results are presented for the neutron characteristics of BIR and BIGR fast pulse reactors, specifically, cylindrical systems with a core consisting of an alloy of 90% or 36% enrichment uranium with 10 mass% molybdenum or a composite uranium–graphite material. The purpose of the calculations is to determine the possibility of increasing the size of the interior cavities in reactors without appreciably degrading the time parameters of the pulses.Reactor models with a metal core, which are best for further consideration, are systems with a disk core which have a cavity with a diameter up to 30 cm along the axis and a thickness-limited iron reflector. For reactors with uranium–graphite core, it is best to develop a new pulse reactor with an axial cavity which has a larger volume and is more accessible for sample placement than BIGR.An important problem of the calculations was to determine screen variants for a cavity which would prevent fuel overheating and at the same time be free of autocatalysis manifestations.     

Exact combinatorial bounds on the probability of overfitting for empirical risk minimization

Three general methods for obtaining exact bounds on the probability of overfitting are proposed within statistical learning theory: a method of generating and destroying sets, a recurrent method, and a blockwise method. Six particular cases are considered to illustrate the application of these methods. These are the following model sets of predictors: a pair of predictors, a layer of a Boolean cube, an interval of a Boolean cube, a monotonic chain, a unimodal chain, and a unit neighborhood of the best predictor. For the interval and the unimodal chain, the results of numerical experiments are presented that demonstrate the effects of splitting and similarity on the probability of overfitting.     

Domain Walls in Superfluid 3He-B

No Heading We consider domain walls between regions of superfluid ³He-B in which one component of the order parameter has the opposite sign in the two regions far from one another. We report calculations of the order parameter profile and the free energy for two types of domain wall, and discuss how these structures are relevant to superfluid ³He confined between two surfaces.PACS numbers: 67.57.Np     

The Angara-2 acoustic-emission apparatus for determination of the hydrogen content in melted aluminum cast alloys

The Angara-2 acoustic-emission apparatus is intended for prompt determination of the hydrogen content in melted aluminum before teeming. The device measures the intensity of the acoustic emission (AE) accompanying crystallization of a liquid sample. The AE method allows rapid (1–3 min) determination of the gas content in melts under shop conditions near casting machines. This circumstance makes it possible to reduce the gas content of a melt at the stage of its preparation to the standard production level, thus increasing the output of suitable cast items.     

Theoretical aspects of technological mechanics. 8. Plane problems in plasticity theory. Part 3

The kinematic and stress state associated with the insertion of a punch in a half-space is considered.     

Modeling of prebreakdown stage of gaseous discharge

A mathematical model of electron cascade transfer is presented. It is developed for studying the prebreakdown stage of gaseous discharge based on the kinetic equation for electrons in a self-consistent electromagnetic field. An elastic scattering of electrons, excitation of molecules by electron impact, and impact ionization are taken into account. A natural ionization background is used as the initial distribution of free electrons. The results of the computational experiment are compared to the data of measurements of drift velocity and the average energy of electrons of discharge, as well as the Townsend coefficient in a flat charged condensor filled with diluted xenon. The comparison showed that the model is not in contrast with the experiment. In order to contract the volume of the discharge’s full current calculation, a transport approximation is built. It is based on the averaging of angular scattering. The applicability of the transport approximation for modeling the full current of the capillary discharge is studied.