Influence of Gases Dissolved in Water on the Process of Optical Breakdown of Aqueous Solutions of Cu Nanoparticles

The paper investigates the effect of gases dissolved in water on the processes occurring during the laser breakdown of colloidal solutions of nanoparticles. The dynamics of the dependences of the plasma luminosity and acoustic signals on the concentration of nanoparticles under irradiation of colloids of nanoparticles saturated with air, argon, and molecular hydrogen has been studied. It is shown that irradiation of colloids saturated with molecular hydrogen and argon leads to an increase in the integral luminosity and integral acoustic signals in comparison with the control sample saturated with atmospheric gases, which indicates the obvious presence of the influence of gases dissolved in the liquid on the optical breakdown process. The most intense acoustic signals, as well as the brightest breakdowns, were observed when the colloidal solution was saturated with molecular hydrogen.

Effect of gases released during solidification of castings on microstructure of alloys

Thermodynamic calculation of formation of spherical gas bubbles different in water – wetting on flat surfaces by metal melt is made. This process consists of two stages. The first stage is formation of equilibrium gas bubble in the form of ball segment. The second stage is its swinging into a spherical bubble. Calculations were made for gas bubbles with constant volume. It is shown that Gibbs energy of spherical gas bubble formation on water – wetting metal melt substrate is three times less than on nonwettable melt substrate. Thus, gases released by solidification of the castings will preferably be formed and removed as bubbles on the molten metal surfaces of the crystallizable phases of the alloys and directly affect on their microstructure.

Effects of Gases Temperature on the Viscosity and Flow Velocity of Melt in the Gas-Assisted Extrusion Forming of Plastic Micro-Tube

To ascertain the influence of gases temperature on the viscosity and flow velocity of melt in the gas-assisted extrusion forming of plastic micro-tube, the three phase fluid geometric model was established and the finite element numerical simulation method was used in this paper. In the simulations, four different assisted-gases temperatures were imposed on the inlet boundaries of inner and outer assisted gas layers. Under a certain inlet volume flow rate of melt and assisted gases, as well as the thermal boundaries conditions, the numerical results about the effect of gases temperature on the viscosity and flow velocity of melt for the gas-assisted extrusion forming of the plastic micro-tube were obtained. Results show that with the increase of gases temperature, the viscosity distribution of melt in the radial direction of die channel decreases. However, at the axial direction of die channel, when the gases temperature is less than that of the melt, the viscosity of melt increases first and then decreases finally increases outside of die. When the gases temperature is larger than that of melt, the viscosity of melt decreases first and then increases finally increases outside of die. In addition, the flow velocity of melt increases with the gases temperature.

INFLUENCE OF BRAKING VALVE OPENING AND CLOSING ANGLES UPON TORQUE

<p>Engine brake systems are based on the concept of spending a large amount of the vehicle’s kinetic energy by releasing pressure from the cylinder. Although an important part of the kinetic energy is used during compression, unless the spring effect of gases is suppressed, a good portion of it is returned to the wheel during the power stroke. This goal can be achieved by releasing of compression just before maximum cylinder pressure is reached. The present paper illustrates investigations upon the exhaust valve opening and closing angles that determine a braking event and their influence upon engine torque.</p>