On the stability of equilibrium of continuous systems Technical report no. 65-1

Stability of equilibrium of linear elastic continuum - Galerkin metho

On Nonconservative Stability Problems of Elastic Systems with Slight Damping

Equilibrium stability of linear two degree of freedom system with slight viscous damping subjected to nonconservative loadin

Skill shortages, recruitment and retention in the housebuilding sector

Purpose - The purpose of this paper is to show how internal and external labour markets operate in the construction sector, associated with different strategies taken by firms in recruiting and retaining particular groups of employees. It draws on research of the house building sector which aims to discover how far firms develop human resource policies, recruitment and retention strategies, and training and development activities in response to skill shortages. Design/methodology/approach - The paper is based on a questionnaire survey of skills shortages, recruitment and retention in house building firms, drawn from databases of social and private housebuilders and a detailed investigation of firms. Findings - The results show worsening skill shortages and hard-to-fill vacancies, particularly for site managers and tradespersons. These shortages are especially bad for house building firms, above all those with higher levels of direct employment in the social housing sector. Despite this, firms rely for operative recruitment on traditional and informal methods and procedures, on experience - not qualifications - as the main criterion, and on "poaching" - all symptomatic of a craft labour market. For managers, there is some evidence of retention measures, in particular through training and promotion, implying the development of internal labour markets. And for professionals there are indications of occupational labour markets with their dependence on institutionalised systems of training and qualifications. Originality/value - The paper shows that firms take little responsibility themselves for resolving skill shortages and establishing training needs, though national training policy is reactive and driven by employer demand. Obligatory skills certification and an institutionalised industrial training system would facilitate a move from this deadlocked situation, from craft to occupational labour markets

Model of mobile agents for sexual interactions networks

We present a novel model to simulate real social networks of complex interactions, based in a granular system of colliding particles (agents). The network is build by keeping track of the collisions and evolves in time with correlations which emerge due to the mobility of the agents. Therefore, statistical features are a consequence only of local collisions among its individual agents. Agent dynamics is realized by an event-driven algorithm of collisions where energy is gained as opposed to granular systems which have dissipation. The model reproduces empirical data from networks of sexual interactions, not previously obtained with other approaches.Comment: 6 pages, 8 figure

Flutter of articulated pipes at finite amplitude

Previous studies of the behavior of pipes conveying fluid have assumed that the fluid velocity relative to the pipe is a known quantity and is unaffected by the motion of the pipe. This approach eliminates the need to find the flow equations of motion, and is adequate for infinitesimal transverse amplitudes of motion of the pipe system, but is incapable of predicting what will be the effect of larger amplitudes. This last shortcoming may be of importance when flow velocities are near critical velocities, that is, velocities at which the system begins to flutter. It is the purpose of the present study to investigate in greater detail the dynamic behavior of pipes in the vicinity of critical velocities

Porosity and Micro-Hardness of Shrouded Plasma Sprayed Titanium Coatings

Titanium and its alloys are often used as key materials for corrosion protection. A promising approach to optimize both mechanical properties and corrosion resistance is the use of coating technologies. In this paper, shrouded plasma spray was used as a useful technology to produce low oxide containing titanium coatings. A solid shroud was used to plasma spray titanium coatings to reduce the oxide content. The titanium coatings were assessed by optical microscope, scanning electron microscopy and Vickers microhardness testing. The results showed that the shrouded titanium coatings exhibited an enhanced microstructure. The presence of the shroud and shroud gas flow led to a significant reduction in coating porosity because the reduction in air entrainment with the shroud resulted in better heating of the particles. The shrouded titanium coatings had a lower value of Vickers microhardness and a relative lower standard deviation than the air plasma sprayed titanium coatings