This chapter examines the relationship between the age structure of the workforce and aggregate productivity. It is well known from the labor literature that there is a robust relationship between years of experience and income. If workers are paid their marginal product then this suggests a relationship between worker productivity and age. In the aggregate, therefore, we should expect changes ...

For the calculation of reactive flows in bubble columns the local interfacial area is one of the key parameters. In addition backmixing causes a residence time distribution in the gas and liquid phase, thus mixing phenomena have to be considered as well. The three-dimensional, instationary flow fields in bubble columns are numerically calculated using an Euler multi-fluid model. The resulting s...

In present paper, dynamic behavior and control of a fluidized bed reactor for polyethylene production has been considered. A double active sites model for Ziegler-Natta catalysts is used for simulation of polymerization reaction. Hydrodynamic behavior of the bed is modeled using a two phase model including bubble and emulsion phases in which bubble phase has plug flow pattern with different...

a study of the atmospheric particulate size distribution of total suspended particulate matter(tspm) and associated heavy metals concentrations has been carried out for the urban part of sarajevo city,bosnia and herzegovina. urban particles (n=150) were collected using a high volume air sampler equippedwith a 6-stage impactor. apart from fe which has been determined by flame atomic absorption s...

dissolution pressure and nozzle temperature effects on particle size and distribution were investigated for ress (rapid expansion of supercritical solution) process. supercritical co2 was used as solvent and ibuprofen was applied as the model component in all runs. the resulting ibuprofen nano-particles (about 50 nm in optimized runs) were analyzed by sem and laser diffraction particle size ana...

The effects of fluid viscoelasticity on the expansion of gas bubbles in polymer foams for the cases of reactive and non-reactive polymers are investigated. For non-reactive polymers, bubble expansion is controlled by a combination of gas diffusion and fluid rheology. In the diffusion limited case, the initial growth rate is slow due to small surface area, whereas at high diffusivity initial gro...

Direct imaging is a technique commonly used in the study of particle, bubble, and droplet size distribution in a dynamic system. Objects such as particles, bubbles, and droplets can be present at various distances from the imaging device when images are captured. Hence, the location of the object will need to be known in order to determine the actual size of an individual object. However, the l...