Improving the installation of fire gasing with gelelating compounds

It is established that the organization of fire extinguishing with the use of gel-forming compounds is a promising direction to increase the efficiency of extinguishing, especially in multi-storey buildings and structures of various functional purposes. Given the shortcomings of existing technical solutions for the use of gel-forming compounds for effective fire extinguishing, the need to develop new structures (spray barrels) is justified. The proposed solutions should ensure, above all, the safety of the fire rescuer. New designs of spray barrels must have a distance of supply of gelling compounds to make work of the operator safe, as well as meet the general technical requirements for fire extinguishers. An autonomous installation of extinguishing with gelling compounds for remote fire extinguishing by plane-radial jets of components of gelling compounds has been developed. It is proposed to fix the spray barrels with a special device to guide them to the object that has to be extinguished with verification of the angles to the horizon, angles of deviation relative to the plane of aiming, the height and width of the symmetrical placement. In this manner, it allows more efficient feeding at a distance of up to 10 meters of the two components of the gelling compounds and prevents premature or delayed mixing. Full-scale samples of RS-10 spray barrels were designed and manufactured to supply flat-radial jets of gel-forming compounds at a distance of up to 10 m. The method of optimal planning of experiments was used to calculate rational values of geometric parameters of the initial cross-section of the RS-10 spray barrel. The problem of 4-factor (second-order) optimal planning of the experiment of the process of plane-radial jet supply by means of RS-10 spray barrels is formulated and carried out. The main design parameters of the spray barrel (cutout of the rigid plate sector and its thickness) are determined, which correspond to the area of rational geometric parameters. The obtained results can be used in the design of extinguishing systems with gelling compounds

Bending Instability of a General Cross Section Thin-Wall Tube for Minimal Radius of Curvature Passage

This paper describes an analytical tool for the design of thin-wall tubes for passage through minimal radius of curvature trajectory. The design is based on a model of thin-wall tube buckling under pure bending. An extended analytical solution for general initial cross section is found based on Brazier method by energy theory of elastic stability. The model predicts the critical moment, curvature, flattening, and stress and allows choosing the most suitable cross section shape for a specific purpose. For example, tubes with ocular and rounded-ocular cross sections were found suitable for semiflexible applications such as endoscopy, where they elastically cross a sharp corner.

Worker Sorting and Job Satisfaction: The Case of Union and Government Jobs

In initial cross-section estimates using data from the 1991–94 British Household Panel Study, the authors find that union members had lower overall job satisfaction than non-union members, and public sector workers had higher satisfaction than private sector workers. Controlling for individual worker effects (sorting) using panel methods confirms the lower satisfaction of union members, but eliminates the higher satisfaction of public sector workers. These results suggest that unions do not simply attract the dissatisfied, as previously suggested. By contrast, the greater satisfaction expressed by public sector workers seems largely a consequence of sorting, with those who are more easily satisfied being drawn to the public sector. Additional analysis of particular aspects of satisfaction, including satisfaction with pay, the work itself, and relations with the boss, generally supports these conclusions.