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In order to solve the problem of uneven distribution of air conditioning temperature and air velocity in the ward, it is easy to produce the uncomfortable feeling of cold and hot and wind blowing. Taking the standard double room general ward of a newly built hospital as the research object, a mathematical model was established, and CFD software was used to numerically simulate the temperature field and velocity field of the air in the ward, optimize the location of the air outlet, and put forward the suggestion of the optimal installation location of the hospital bed. The results show that when the fan coiler air supply outlet is close to the west wall and the fresh air outlet is far away from the west wall, the inhomogeneity of the distribution of the temperature field and velocity field in the ward is reduced, and at this time, the temperature and velocity distribution of the air in the ward is more uniform, so that the patients' overall feeling in the ward is more comfortable, and at this time, the installation position of the air outlet is more reasonable; and it is determined that the optimal placement of the beds in the room is at the locations of x = 2 m, y = 2.5 m and x = 2 m, y = 4.5 m, and at this time the two beds are at the same time, which is more reasonable. When y = 4.5 m, the temperature difference between the two beds is less than 0.5 K, the wind speed difference is not more than 0.08 m/s, and the velocity gradient direction is the same. [ABSTRACT FROM AUTHOR]

Magnesium alloy welding suffers from problems such as burn through and loss of alloying elements during conventional welding process due to high heat input. Variable polarity gas metal arc welding (VP-GMAW) features low heat input. Therefore, it is an attractive method for welding of magnesium alloy. However, the principles governing the correlations among welding current parameters, metal transfer modes, and bead formation are not well understood. Identifying optimal welding current parameters by trial and error is unrealistic. Therefore, peak current, base current, and negative current were selected as independent variables. Their impact mechanism on metal transfer and bead formation were investigated by experiments with high-speed photographs. Then, weld quality evaluation was conducted by a fuzzy comprehensive evaluation. A mathematical method was proposed to calculate optimal current parameters for VP-GMAW of magnesium alloy. In addition, a significant sequence of current parameters is obtained. The results indicate that almost defect-free weld joint is produced by the optimal welding current parameters. The significance sequence of current parameters on weld quality is negative current, peak current, and base current. [ABSTRACT FROM AUTHOR]

To study the relation between cold-hot-water mixing ratio and outlet-water temperature of a mixer, the geometrical model of the mixer was built. On the basis of theoretical analysis, the outlet-water temperature with different mixing ratio of cold and hot water was simulated by FLUENT software. The results show that: flow field in mixer can be divided into recirculation zone and convection zone, in which there are different thermal resistances individually, and it result in the nonlinear relation in outlet average temperature and mixing ratio; there is a linear relation between outlet average velocity and mixing ratio, which accords to the mass conservation principle of non-compressible and continuous fluid flow. [ABSTRACT FROM AUTHOR]

Considering the sun light nonparallelism, Monte Carlo ray tracing method and specular reflection law are employed to simulate the effects of focal plane position error, pointing error to spot shape and energy distribution on focal plane of a new type of space solar concentrator. The results show that: with the absolute value of focal plane position error increasing, focal spot radius increases and peak energy flux value on focal plane decreases; when absolute value of focal plane position error is same, focal spot shape and energy distribution is almost the same; with pointing error increasing, the deviation of focal spot from the focal plane center increases and round focal spot becomes oval focal spot gradually. This will provide a reference for the new space solar concentrating and absorbing system design. [ABSTRACT FROM AUTHOR]