Background atmospheric levels of aldehydes, BTEX and PM10 pollutants in a medium-sized city of southern Italy

Background atmospheric levels of aldehydes, BTEX and PM10 pollutants were measured in the suburb of Caserta (Italy), 75 thousands inhabitants, 41degrees 04' N, on rainless weekdays and weekends during 2005. On weekdays the average daily concentrations (microg m(-3)) were 41.6 PM10, 8.6 benzene, 25.2 toluene, 6.3 ethylbenzene, 14.0 (m+p)-xylene, 11.7 o-xylene, 6.5 formaldehyde, 3.3 acetaldehyde. All the pollutant concentrations were strictly correlated (mean correlation coefficients = 0.90). At weekends the concentrations were lower by about 1.6 times. Both on weekdays and at weekends the PM10 and benzene levels exceeded the limits set by the EU Directive 30/1999 and 69/2000, respectively.     

A threaded-connection locking mechanism integrated into a multi-piece mining wheel for enhanced structural performance and safety

Multi-piece wheel components are used for off-the-road (OTR) mining wheels for the purpose of tire mounting. Incident report analyses indicate that the disengagement of the rim components in the locking region is a common cause of failure. This study proposes a threaded-connection locking mechanism to remove the conventional lock ring to enhance the engagement and improve the performance of the OTR wheel. Using validated finite element models, two numerical tests were conducted to evaluate the proposed design and the conventional design, namely, (1) a pull-out tests to evaluate the engagement capability of rim components and (2) quasi-static loading tests to assess stress levels and fatigue lives. The pull-out test results showed the proposed design was almost twice as strong as the conventional design in resisting the disengagement of the rim components and the mode of failure associated with the proposed design is less catastrophic. Under quasi-static loading conditions, the maximum effective stress was approximately 29% lower and the average stress was much lower on the front section of the rim base for the proposed design. The estimated fatigue life for the proposed design was approximately three times greater than the conventional design.     

Flow field investigation in rotating rib-roughened channel by means of particle image velocimetry

The turbulent velocity field over the rib-roughened wall of an orthogonally rotating channel is investigated by means of two-dimensional particle image velocimetry (PIV). The flow direction is outward, with a bulk Reynolds number of 1.5 × 10⁴ and a rotation number ranging from 0.3 to 0.38. The measurements are obtained along the wall-normal/streamwise plane at mid-span. The PIV system rotates with the channel, allowing to measure directly the relative flow velocity with high spatial resolution. Coriolis forces affect the stability of the boundary layer and free shear layer. Due to the different levels of shear layer entrainment, the reattachment point is moved downstream (upstream) under stabilizing (destabilizing) rotation, with respect to the stationary case. Further increase in rotation number pushes further the reattachment point in stabilizing rotation, but does not change the recirculation length in destabilizing rotation. Turbulent activity is inhibited along the leading wall, both in the boundary layer and in the separated shear layer; the opposite is true along the trailing wall. Coriolis forces affect indirectly the production of turbulent kinetic energy via the Reynolds shear stresses and the mean shear. Two-point correlation is used to characterize the coherent motion of the separated shear layer. Destabilizing rotation is found to promote large-scale coherent motions and accordingly leads to larger integral length scales; on the other hand, the spanwise vortices created in the separating shear layer downstream of the rib are less organized and tend to be disrupted by the three-dimensional turbulence promoted by the rotation. The latter observation is consistent with the distributions of span-wise vortices detected in instantaneous flow realizations.     

Experimental study of the effects of spanwise rotation on the flow in a low aspect ratio diffuser for turbomachinery applications

Two dimensional time accurate PIV measurements of the flow between pressure and suction side at different spanwise positions of a rotating channel are presented. The Reynolds and Rotation numbers are representative for the flow in radial impellers of micro gas turbines. Superposition of the 2D results at the different spanwise positions provides a quasi-3D view of the flow and illustrates the impact of Coriolis forces on the 3D flow structure. It is shown that the inlet flow is little affected by rotation. An increasing/decreasing boundary layer thickness is reported on the suction/pressure side wall halfway between the channel inlet and outlet. The turbulence intensity moves away from the suction side wall and remains close to the pressure side wall. The instantaneous measurements at mid-height of the rotating channel reveal the presence of hairpin vortices in the pressure side boundary layer and symmetric vortices near the suction side. Hairpin vortices occur in rotation in the pressure and in the suction side, for the measurement plane close to the channel bottom wall.     

The effects of hydrogen bonding on the liquid crystalline behavior of semiflexible poly(urethaneester)s

The peculiar liquid crystalline behavior of two poly(urethane-ester)s TDI-C6C4 and TDI-C6C8 is reported. Evidence is provided of the formation of two nematic mesophases, a cybotactic nematic and a conventional nematic mesophase, in TDI-C6C8 and of one cybotactic nematic mesophase in TDI-C6C4. IR spectroscopy indicates that different hydrogen bonded and non-bonded structures occur with varying temperature. The transition from the nematic cybotactic mesophase to the nematic mesophase, or to the isotropic phase, is accompanied by a substantial decrease of the strength of the hydrogen bonds. This is also reflected in the dynamic-mechanical behavior of these poly(urethane-ester)s which is similar to the one of slightly crosslinked thermoreversible networks.     

Synthesis and thermotropic properties of new polyacrylates containing alkanoyl-substituted azobenzene mesogens

The synthesis and characterization of a series of new polyacrylates 1, containing the azobenzene mesogen spaced from the backbone by a hexamethylene segment and substituted in the 4-position by an alkanoyl chain of variable length, together with those of the relevant precursors are reported. Optical and X-ray analyses provided evidence for the presence of a smectic A mesophase in a fairly broad range of temperature in both polymers and low molar mass compounds. In polyacrylates 1, the side-chain substituents were fully interdigitated in a smectic A₁ structure. The comparison of the transition parameters of polymers 1 with those of another series of polyacrylates 7 containing the azobenzene unit substituted in the 4-position by an alkyloxy chain of variable length revealed that the replacement of an oxygen atom by a carbonyl group strongly enhanced the smectogenic character of the azobenzene group.     

The decarbonylation reaction of imidazole-2-carbaldehydes in ethanol

Imidazole-2-carbaldehydes in hot ethanol undergo a decarbonylation reaction involving nucleophilic attack of the alcohol on the carbonyl to form the corresponding imidazole and ethyl formate.     

Substituted 1,4-diazepino[5,6,7-kl]acridines as unexpected side products in reaction of 2-(dialkylamino)ethylamine with 1-chloro-7-methyoxy-4-nitro-9-phenoxyacridine

Substituted 1,4-diazepino[5,6,7-kl]acridines were obtained in reaction of 2-(dialkylamino)ethylamine with 1-chloro-7-methoxy-4-nitro-9-phenoxyacridine. The mechanism of their formation was studied. The correct structure of these compounds was established on the basis of their ¹H nmr studies.