Numerical techniques for the calculation of binary phase diagrams

Numerical techniques are presented for the calculation of binary phase diagrams. Most compositions are obtained directly through a Taylor series expansion of the composition with respect to temperature. The series is limited to the second order term and analytic expressions of the slopes and curvatures of phase boundaries have been developed for its use. A Newton-Raphson iteration technique tests the convergence of the results. The method is efficient and accommodates various formalisms for the free energy functions. The series is not applicable to very dilute solutions of a component, near the critical point of a miscibility gap or in the vicinity of the congruent transformation point of a compound; in these cases, alternate equations have been derived. Formerly Graduate Student, Department of Metallurgy and Materials Science, Carnegie-Mellon University,     

Sampling frequency and accuracy of SPM flux estimates in two contrasted drainage basins

The present paper is based on discharges and suspended particulate matter concentrations from a 9-years high-resolution database for the Garonne River (large plain river) covering contrasted hydrologic years, and a 12-months high frequency sampling for the Nivelle River (small mountainous river). Annual SPM fluxes in the Garonne River range from 0.6 x 10(6) t year(-1) (1997) to 3.9 x 10(6) t year(-1) (1996). In contrast, the Nivelle River transported 11 x 10(3) t year(-1) from December 1995 to December 1996. From the long-term observation of the Garonne River an empirical relation between SPM* (discharge-weighted mean annual SPM concentrations) and annual discharge was established. This relation allows estimating annual SPM fluxes for the Garonne River with less than 30% deviation from reference values for the whole range of mean annual discharge observed during the past decade. Specific (=area-normalized) annual SPM fluxes (YSPM) range from 11 to 74 t km(-2) year(-1) for the Garonne River. Comparison of these results with YSPM of the Nivelle River (69 t km(-2) year(-1) in 1996) suggests that interannual hydrological variations may have a greater impact on fluvial SPM transport than basin-specific parameters. By extracting individual SPM concentrations and corresponding discharge values from the database, different sampling frequencies were simulated and resulting SPM fluxes were then compared to reference fluxes derived from the complete database. If a deviation of simulated flux estimates from reference fluxes lower than +/-20% is accepted, the Garonne River (large plain river) must be sampled at least every 3 days (10 samples per month) and the Nivelle River every 7 h (approx. 100 samples per month). For the Garonne River this minimum sampling frequency is valid for all contrasted hydrologic years of the observation period. Below these minimum sampling frequencies, annual SPM flux estimates may greatly differ from reference fluxes (up to 200%) and there is high probability of systematic underestimation. Consequently, annual SPM flux estimates for the Garonne River derived from the empirical relation (SPM*-annual discharge) are likely to be more satisfactory (errors <30%) than estimates based on sampling frequencies lower than the minimum frequency. These findings underline the need of adapted sampling strategies for erosion assessment, reliable chemical (e.g. nutrients and pollutants) mass balances and characterisation of fluvial transport mechanisms in the world's contrasted watersheds.     

Removal of Cd(II) and Pb(II) ions, from aqueous solutions, by adsorption onto sawdust of Pinus sylvestris

Fixation of heavy metal ions (Cd(II) and Pb(II)) onto sawdust of Pinus sylvestris is presented in this paper. Batch experiments were conducted to study the main parameters such as adsorbent concentration, initial adsorbate concentration, contact time, kinetic, pH solution, and stirring velocity on the sorption of Cd(II) and Pb(II) by sawdust of P. sylvestris. Kinetic aspects are studied in order to develop a model which can describe the process of adsorption on sawdust. The equilibrium of a solution between liquid and solid phases is described by Langmuir model. Scanning electronic microscopy (SEM) coupled with energy dispersive X-ray analysis (EDAX) and X-ray photoelectron spectroscopy (XPS) shows that the process is controlled by a porous diffusion with ion-exchange. The capacity of the metal ions to bind onto the biomass was 96% for Cd(II), and 98% for Pb(II). The sorption followed a pseudo-second-order kinetics. The adsorption of these heavy metals ions increased with the pH and reached a maximum at a 5.5 value. From these results, it can be concluded that the sawdust of P. sylvestris could be a good adsorbent for the metal ions coming from aqueous solutions. Moreover, this material could also be used for purification of water before rejection into the natural environment.     

Possibility Theory, Probability Theory and Multiple-Valued Logics: A Clarification

There has been a long-lasting misunderstanding in the literature of artificial intelligence and uncertainty modeling, regarding the role of fuzzy set theory and many-valued logics. The recurring question is that of the mathematical and pragmatic meaningfulness of a compositional calculus and the validity of the excluded middle law. This confusion pervades the early developments of probabilistic logic, despite early warnings of some philosophers of probability. This paper tries to clarify this situation. It emphasizes three main points. First, it suggests that the root of the controversies lies in the unfortunate confusion between degrees of belief and what logicians call degrees of truth. The latter are usually compositional, while the former cannot be so. This claim is first illustrated by laying bare the non-compositional belief representation embedded in the standard propositional calculus. It turns out to be an all-or-nothing version of possibility theory. This framework is then extended to discuss the case of fuzzy logic versus graded possibility theory. Next, it is demonstrated that any belief representation where compositionality is taken for granted is bound to at worst collapse to a Boolean truth assignment and at best to a poorly expressive tool. Lastly, some claims pertaining to an alleged compositionality of possibility theory are refuted, thus clarifying a pervasive confusion between possibility theory axioms and fuzzy set basic connectives.     

Theorizing the concept and role of assurance in information systems security

Assurance has different meanings, depending on the source, audience, and interpretation. We applied institutional theory and the Capability Maturity Model to conceptualize assurance: its symbolic aspects to gain social acceptance, and its substantive aspects to improve organizational capability and effectiveness in performing IS security risk management (SRM). An empirical study examined assurance-seeking behavior and outcomes for regulatory compliance. Some degree of process maturity in SRM was found necessary for producing convincing verbal accounts and compliance evidence. Findings suggest that unless an organization's assurance claims are based on achieving Level 4 maturity, assurance will be based more on symbolism than effectiveness.     

Contribution to the environmental performance of the dry-vibratory drilling technology

The self-vibratory drilling (SVD) is an innovative technology that allows increasing the productivity, without coolant. The aim of this paper is to prove that the environmental impacts of SVD are significantly less than those of traditional drilling (TD) and to quantify them. The study is based on a life cycle analysis of both processes. The major contributor to the environmental impacts in TD is the coolant. The new major contributors in SVD are the twist drills. A model that links the lifespan of the twist drills and the environmental impacts of SVD has been developed to support decisions for R&D.     

Measurement of femtosecond pulse shapes via ionization of air

In summary, we have demonstrated a new method for the characterization of ultrashort pulses which can be easily implemented and which is particularly well suited to high intensity lasers. It is shown that it is possible to simply determine the temporal shape of femtosecond pulses using plasma-induced cross-phase modulation in ionized air