Investigation of the nitrogen-nickel-titanium system: The isothermal section at 900 °C

Phase relations in the ternary system N-Ni-Ti have been established experimentally for the 900 °C isothermal section assisted by thermodynamic modeling. Phase equilibria are characterized by an appreciable amount of up to ≅11 at. % N dissolved in the octahedral interstices of the crystal structure of Ti₂Ni. Two-phase equilibria are formed at 900 °C among the pairs Ti₂N + Ti₂NiN_x, TiN_1-x + Ti₂NiN_x, TiN_1-x + TiNi_1-x, and TiN_1-x + Ni(Ti)_x. The investigation is based on X-ray powder diffraction, metallography, scanning electron microscopy, and electron probe microanalysis techniques on about 50 alloys, which were prepared by arc melting or high-frequency levitation melting of appropriate blends of Ti,Ni-powders with TiN used to introduce nitrogen. Key experiments related to the N solubility in the Ti₂Ni phase have been triggered by an interactively performed thermodynamic modeling. The experimental results are in fine agreement with the thermodynamic calculation.     

活公园

项目地点:博茨瓦纳吉瓦宁项目类型:其他开工日期:2006年8月该项目获2005年豪瑞可持续建筑大奖赛非洲中东地区提名奖     

Experimental investigations and constitutive modeling of cyclic interface shearing between HDPE geomembrane and sandy gravel

This paper presents the results of experimental investigations and constitutive modeling of cyclic interface shearing between HDPE geomembrane and cohesionless sandy gravel. A series of cyclic interface shear tests was performed using a large-scale cyclic shear apparatus with servo controlled system. Particular attention was paid to the influences of the amount of shear-displacement amplitude, number of cycles, shear rate and the normal pressure on the mechanical response. The experimental results show that the path of the shear stress against the cyclic shear displacement is strongly non-linear and forms a closed hysteresis loop, which is pressure dependent, but almost independent of the shear rate. For small shear-displacement amplitudes, the obtained damping ratio is significantly greater than zero, which is different to the behavior usually observed for cyclic soil to soil shearing. In order to describe the pressure dependency of the hysteresis loop using a single set of constitutive parameters, new approximation functions are put forward and embedded into the concept of the Masing rule. Further, a new empirical function is proposed for the damping ratios to capture the experimental data for both small and large cyclic shear-displacement amplitudes. The included model parameters are easy to calibrate and the new functions may also be useful in developing enhanced constitutive models for the simulation of the cyclic interface shear behavior between other geosynthetics and soils.     

Operation element-based efficiency for process plans and designs

In previous work the authors have developed graph-theoretic efficiency measures of process plans for rotational parts. The measures assess the technical efficiency under which a particular design can be manufactured, i.e. its manufacturability. This paper extends the earlier work by incorporating geometric dimensioning and tolerancing and developing a new technique for assessing the manufacturability of any part (prismatic and rotational). The aim is to develop an automated technique for assessing part designs.     

The three roles of a project portfolio management office: Their impact on portfolio management execution and success

Project portfolio management offices (PPMOs) are a subset of project management offices (PMOs) that handle collections of multiple single projects and programmes, i.e. portfolios. PPMOs are centralised organisational units that cater to the demands of various stakeholders by performing specialised tasks. They are initiated by their organisation's leadership in response to increasing management challenges originating from project portfolios. Although there has been considerable research on PMOs in general, not only a clear understanding of multi-project PMOs' activity patterns set in specific contexts like project portfolio management, but also both existence and mode of multi-project PMOs' contribution to successful performance are still lacking. By quantitatively analysing PPMOs in 278 portfolios, we identify three different activity patterns, which are interpreted as distinctive roles. We show a significant positive effect of PPMOs' coordinating and controlling roles on performance in terms of project portfolio management quality, which is a predictor of portfolio success.     

Model based prognosis of contaminant leaching for reuse of demolition waste in construction projects

In this study, groundwater contamination from recycled demolitian waste in road constructions is assessed using predictions of leachate concentrations. Numerical transport simulations are performed for three scenarios (a parking lot, a noise protection barrier, and road), and using a number of characteristic subsoils of Germany, to estimate the breakthrough of different contaminant classes at the groundwater table. Conservative tracer breakthrough times (BTT) primarily depend on subsoil hydraulic properties, for organic pollutants KOC and subsoil OC are the controlling parameters. Significant concentration reductions from dispersion only occur when source concentrations decrease prior to contaminant breakthrough. If source concentrations remain high for long periods relative to peak BTT, concentration breakthrough is undamped. Accounting for biodegradation reduces breakthrough concentrations significantly. For the “noise protection barrier” and “road” scenarios, capillary barrier effects cause the seepage water to partially bypass the recycling material. Accounting for this bypass flow and spatial averaging across the constructions reduces concentrations by about 30–40?%.     

PAH fluxes in the Laja Lake of south central Chile Andes over the last 50 years: evidence from a dated sediment core

This paper reports the occurrence of polyaromatic hydrocarbons (PAHs) deposition inferred from a sediment core of an Andean lake in south central Chile. Sediments were carefully collected from one of the deepest section of the lake and sliced every 1 cm. The samples were analyzed for PAHs, (137)Cs, (210)Pb, organic carbon and grain-size. The stratigraphic chronology and the sedimentation rates were estimated using the sedimentary signature left by the (137)Cs and (210)Pb fallout as temporal markers. PAHs were quantified by HPLC-fluorescence detection (HPLC-Fluorescence). 15 priority EPA PAHs were analyzed in this study. Based on these results, PAH deposition over the last 50 years was estimated (a period characterized by an important intervention in the area). PAH concentration ranged from 226 to 620 ng g(-1) d.w. The highest concentrations of PAHs were found in the core's bottom. The PAH profile is dominated by the presence of perylene indicating a natural source of PAH. In addition, two clear PAH deposition periods could be determined: the most recent with two-four rings PAHs, the older one with five-seven rings predomination. Determined fluxes where 71 to 972 microg m(-2) year(-1), dominated by perylene deposition. PAH levels and fluxes are lower compared to the levels found in sediments from remote lakes in Europe and North America. It is concluded that the main source of PAHs into the Laja Lake sediments are of natural origin.