Hydrodynamic forces which arise as a result of the interaction of flow and the hydromechanical equipment of large dams and other hydraulic structures

Conclusions The papers presented to the seminar of the Twelfth Congress of the IAHR, on problems relating to the investigation of the hydrodynamic forces which result under the interaction between the flow and the hydromechanical equipment of large dams and other hydraulic structures, differ in their significance and orientation but on the whole they are indicative of definite progress in this field. It is necessary to note: a) the unquestionable value of the data obtained, which deal with the theoretical and experimental investigation of the hydrodynamic loads acting on different types of hydraulic structures [S1, S2, S5, S7, S11]; b) the interesting data from the study of vibrations in structures [S4, S6]; c) the data found for the analysis of the stability of rock-fill dams [S9]; d) the development of certain new construction elements for hydraulic structures [S8, S10]; e) the insufficient knowledge about the problems involved in the modelling of hydraulic phenomena [S3]. From the transactions of the Twelfth Congress of the IAHR; see Gidrotekhnicheskoe Stroitel'stvo, No. 12, 1967. Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 11, pp. 45–48, November, 1968.     

Penalty Functions in a Control Problem

The exact penalty method is applied to the problem of optimal control of a system described by ordinary differential equations. Though the functional thus obtained is essentially nonsmooth, it is direction differentiable (and even subdifferentiable). Differential equations are regarded as constraints and eliminated by introducing a penalty function. The aim of this paper is to show the well-known conditions of optimality can be derived via penalty functions.     

Composition and properties of the diffusion layer formed upon heat treatment of an aluminum gas-thermal coating on titanium

An aluminum gas-thermal coating 200–300 μm thick is deposited onto the surface of titanium samples with an arc discharge. After heat treatment of the samples at 900 or 1000°C for 2, 4, or 6 h, the chemical composition and properties of the diffusion layer formed as a result of titanium and aluminum interdiffusion are studied. The main phase of the diffusion layer is found to be TiAl₃. The fractions of the phases TiAl₂, TiAl, and Ti₃Al are insignificant. The adhesion of the diffusion layer to the titanium substrate, the wear resistance, the friction coefficient, the hardness, the corrosion resistance, and the thermal and electrical conductivities are studied as functions of the heat-treatment temperature and time.     

微结构内纳秒脉冲空气放电中微通道的形成及高能电子的产生过程(英文)

The investigations results of the different types of high-voltage nanosecond atmospheric discharges(diffusive in the gaps "wire(cathode)-plane", "rod(cathode)-plane", spark "point-plane" and in homogeneous gaps "plane-plane", as well as streamerless discharges in homogeneous gaps "plane-plane") are present. It was found out that the current channels prints, left on the electrodes surface, has the microstructure. The microstructure is a cluster(up to 1 000) of the microchannels of 1~30 μm diameters almost evenly distributed on the channels section. It was found out that in some cases the discharges develop in the regime of microstructuring of the current channels, are accompanied by generation of high-energy electrons and x-ray radiation. In this case the generation of high-energy component is stipulated by the electrons runaway in the microchannels. The calculation results of the electric field in clusters of parallel microchannels in the frameworks of the model of a bundle of parallel long cylindrical conductors are present. It is shown that in the clusters with many microchannels in the result of mutual attenuation of their fields maximum strength of the radial field could be lower than the critical one, which is necessary for ionization multiplication and expansion. This provides long existence of microchannels groups of microns radii in the high-voltage nanosecond discharges. A physical model of the streamerless discharge microstructure formation at the result of instability development of the ionization process in the avalanche stage is developed. It was established that the instability has long wave character and leads to formation of self-similar spatial structure. It is shown that the microstructure of the streamer discharges could be explained in the frameworks of this model. Three-dimensional numerical simulation of dynamics of microchannels system of high-voltage nanosecond discharges in the air of atmospheric pressure is performed in hydrodynamic approximation. It is established that fast(≈10 ns) expansion and significant decreasing of the gas concentration in the microchannels takes place at the expense of ohmic heating of the microchannels. It is shown that the microchannels expansion provides increase of electric field and gas concentration ratio up to the values that are sufficient for high-energy electrons beams and bremsstrahlung generation in them.     

Programmed closing of gates upon loss of drive by a pump unit

Conclusion The developed method of determining a shutoff closing law provides a minimum increase of pressure and dynamic loads on the unit.Translated from Girdotekhnicheskoe Stroitel'stvo, No. 7, pp. 13–16, July, 1986.