Validation of two-layer model for underexpanded hydrogen jets

Previous studies have shown that the two-layer model more accurately predicts hydrogen dispersion than the conventional notional nozzle models without significantly increasing the computational expense. However, the model was only validated for predicting the concentration distribution and has not been adequately validated for predicting the velocity distributions. In the present study, particle imaging velocimetry (PIV) was used to measure the velocity field of an underexpanded hydrogen jet released at 10 bar from a 1.5 mm diameter orifice. The two-layer model was the used to calculate the inlet conditions for a two-dimensional axisymmetric CFD model to simulate the hydrogen jet downstream of the Mach disk. The predicted velocity spreading and centerline decay rates agreed well with the PIV measurements. The predicted concentration distribution was consistent with data from previous planar Rayleigh scattering measurements used to verify the concentration distribution predictions in an earlier study. The jet spreading was also simulated using several widely used notional nozzle models combined with the integral plume model for comparison. These results show that the velocity and concentration distributions are both better predicted by the two-layer model than the notional nozzle models to complement previous studies verifying only the predicted concentration profiles. Thus, this study shows that the two-layer model can accurately predict the jet velocity distributions as well as the concentration distributions as verified earlier. Though more validation studies are needed to improve confidence in the model and increase the range of validity, the present work indicates that the two-layer model is a promising tool for fast, accurate predictions of the flow fields of underexpanded hydrogen jets.     

Erstes Design und Einsatz 3D‐gedruckter Strukturen in Blasensäulenreaktoren

A new method is described, in which 3D‐printed structures are implemented in bubble column reactors to dissolve the macroscopic and the microscopic influences. The effect of these structuring method on the fluid dynamic behavior, the gas distribution, mass transfer, and fluid velocity inside bubble columns is shown in this contribution.     

Coarsening of Inter- and Intra-granular Proeutectoid Cementite in an Initially Pearlitic 2C-4Cr Ultrahigh Carbon Steel

Metallurgical and Materials Transactions A - We have examined spheroidization and coarsening of cementite in an initially pearlitic 2C-4Cr ultrahigh carbon steel containing a cementite network....     

Inverted Organic Solar Cells with Sol–Gel Processed High Work‐Function Vanadium Oxide Hole‐Extraction Layers

For large‐scale and high‐throughput production of organic solar cells (OSCs), liquid processing of the functional layers is desired. We demonstrate inverted bulk‐heterojunction organic solar cells (OSCs) with a sol–gel derived V₂O₅ hole‐extraction‐layer on top of the active organic layer. The V₂O₅ layers are prepared in ambient air using Vanadium(V)‐oxitriisopropoxide as precursor. Without any post‐annealing or plasma treatment, a high work function of the V₂O₅ layers is confirmed by both Kelvin probe analysis and ultraviolet photoelectron spectroscopy (UPS). Using UPS and inverse photoelectron spectroscopy (IPES), we show that the electronic structure of the solution processed V₂O₅ layers is similar to that of thermally evaporated V₂O₅ layers which have been exposed to ambient air. Optimization of the sol gel process leads to inverted OSCs with solution based V₂O₅ layers that show power conversion efficiencies similar to that of control devices with V₂O₅ layers prepared in high‐vacuum.     

Image velocity, not tau, explains arrival-time judgments from global optical flow.

The time-to-passage (TTP; i.e., the time) until an object passes an observer is optically specified by global tau, a variable that operates on the expansion rate of the angle subtended by an object relative to the observer's heading. M. K. Kaiser and L. Mowafy (1993) provided evidence for observers' sensitivity to global tau in a 3-D cloud of point lights. This interpretation is challenged, and it is suggested that TTP judgments are based on a related but much simpler variable, the image velocity of the object. The present study reexamined several factors that are relevant for the extraction of global tau. When global tau and image velocity were brought into conflict by varying the lateral offsets of the targets, observers showed a strong tendency to rely on the latter variable. Other factors that are supposed to affect TTP judgments only if observers relied on global tau, such as flow-field density and gaze-movement angle, did not affect performance. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Coping with employee, family, and student roles: Evidence of dispositional conflict and facilitation tendencies.

Balancing multiple roles is a challenge for individuals in many sectors of the population. The purpose of this study was to test the hypothesis that individuals have dispositional tendencies to experience interrole conflict and facilitation. We also aimed to show that coping styles and life satisfaction are correlates of dispositional conflict and facilitation tendencies. Two survey studies were conducted with individuals involved in 3 life roles (i.e., employee, student, and family member; Study 1: N = 193; Study 2: N = 284). The hierarchical structure of conflict and facilitation was examined in both studies. Support for the dispositional model was found in both cases through the use of hierarchical confirmatory factor analyses. In Study 2, a longitudinal assessment of the nomological network surrounding conflict and facilitation tendencies was conducted with structural equation modeling analyses; we found that coping styles had synchronous relations with dispositional conflict and facilitation; dispositional conflict had a lagged and negative relation with life satisfaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)