Sulphidation and oxidation of the Ni22Cr10Al1Y alloy in H2/H2S and SO2 atmospheres at high temperatures

The Ni22Cr10Al1Y alloy was exposed in H₂/H₂S gas mixture under the sulphur pressure 10^–3 and 1 Pa as well as in SO₂ at 1173 and 1273 K. At p_s = 1 Pa the sulphidation rate was relatively high and the reaction obeyed the linear rate law. Under these conditions a nickel/nickel sulphide eutectic was formed. At p_s = 10^–3 Pa nickel sulphides became unstable and the sulphidation rate was significantly lower. The reaction obeyed the parabolic rate law. The oxidation rate of the alloy in SO₂ was lower than that in any of the H₂/H₂S atmospheres. The sulphide scales formed during sulphidation in H₂/H₂S had complex microstructures and compositions, with sulphospinel and sulphide phases being present, e.g. NiCr₂S₄, Ni₃S₂, Cr_xS_y. As the temperature increased and the sulphur pressure decreased, these phases were replaced by the chromium-rich sulphide phase. Various oxides formed during oxidation of the alloy in SO₂.     

Development and preliminary evaluation of a pediatric measure of community integration: The Pediatric Community Participation Questionnaire (PCPQ).

Objective: To develop and evaluate a new pediatric measure of community integration: the Pediatric Community Participation Questionnaire (PCPQ). Participants: 105 youths with physical disabilities. Measures: In addition to the PCPQ, demographic and disability-related questions and the Functional Disability Inventory (FDI) were administered. Results: The PCPQ demonstrated convergent validity through its high association with functional ability, discriminant validity through its ability to discriminate between ambulatory and nonambulatory participants, and excellent internal consistency. Conclusions: Community participation, an important component of positive overall development, may be particularly important for youths with physical disabilities. The findings from this study provide preliminary support for the validity and reliability of the PCPQ, supporting its use as a measure of community participation with this population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Systemic aspects of R&D policy subsidies for R&D collaborations and their effects on private R&D

This paper analyses how context- and time-dependent factors determine the impact of R&D subsidies on firm behaviour with respect to private R&D expenditures. Based on German R&D survey data, we combine propensity score matching with a difference-in-difference estimator in order to measure the causal influence of public direct R&D project funding on firm behaviour. Our results indicate that (i) repeated participation in R&D projects on average leads to a higher increase in R&D expenditures than once-off funding; (ii) the aggregate effect of R&D funding on R&D expenditures of business firms is somewhat higher for business–business collaboration projects than for science–business collaboration projects; (iii) R&D expenditures of business firms that cooperate with science show a higher share of external R&D spending. Results of one particular cluster programme indicate that at least the short-term development of R&D does not so much depend on which programme direct R&D project funding is applied to.     

Synthesis and characterization of chloro-sulphide glass-ceramics containing neodymium(III) ions

In this paper, we describe the preparation of Nd³⁺ doped glass-ceramics in the (GeS₂)₇₀-(Ga₂S₃)₂₀-(CsCl)₁₀ system. Neodymium has been introduced as metallic powder or incorporated as sulphide. Appropriate heat treatments of the base-glass lead to glass-ceramics with controllable crystal sizes that are transparent in the visible and infrared spectral ranges. X-ray diffraction as well as electron diffraction techniques were used to investigate the crystallization process. Differential scanning calorimetry indicates that neodymium ions are poor nucleating agents in this glass compared to erbium ions. Luminescence measurements were also performed and point out that although the ceramization process increases significantly the luminescence efficiency, the neodymium ions are only partially incorporated in the nanocrystals.     

Historical perspective and current trends in emission microscopy, mirror electron microscopy and low-energy electron microscopy. An introduction to the proceedings of the Second International Symposium and Workshop on Emission microscopy and Related Techniques

Emission microscopes and related instruments comprise a specialized class of electron microscopes that have in common an acceleration field in combination with the first stage of imaging (i.e., an immersion objective lens, also called a cathode lens or emission lens). These imaging techniques include photoelectron emission microscopy (PEEM or PEM), electron emission induced by heat, ions, or neutral particles, mirror electron microscopy (MEM), and low-energy electron microscopy (LEEM), among others. In these instruments the specimen is placed on a flat cathode or is the cathode itself. The low-energy electrons that are emitted, reflected, or backscattered from the specimen are first accelerated and then imaged by means of an electron lens system resembling that of a transmission electron microscope. The image is formed in a parallel mode in all of the above instruments, in contrast to the image in scanning electron microscopes, where the information is collected sequentially by scanning the specimen. A brief history and introduction to emission microscopy, MEM, and LEEM is presented as a background for the Proceedings of the Second International Symposium and Workshop on this subject, held in Seattle, Washington, August 16-17, 1990. Current trends in this field gleaned from the presentations at that meeting are discussed.     

Frequency allocation problem in a SDMA satellite communication system

Spatial Division Multiple Access (SDMA) is a principle of radio resource sharing that relies on the division of the space dimension into separated communication channels. SDMA basically relies on adaptive and dynamic beam-forming associated to a clever algorithm in charge of resource allocation. As satellite communication systems move towards an increasing number of users and a larger throughput for each of them, SDMA is one of the most promising techniques that can reach these two goals. This paper studies static Frequency Assignment Problems (FAP) in a satellite communication system involving a gateway connected to a terrestrial network and some user terminals located in a service area. Two scenarios are considered: one based on SDMA and the other based on usual spot coverage. We propose original integer linear programming formulations and greedy allocation algorithms for the FAP which involves unusual cumulative interference constraints. By considering the link budget of each user, the objective is to maximize the number of users that the system can serve. We show through computational experiments on realistic data that the FAP associated with the SDMA system can be solved efficiently, yielding substantial improvement compared to the traditional system.     

Discrete-time analysis of linear and nonlinear systems using analogcircuit simulators

A method to teach discrete-time systems analysis concepts and skills to engineering students is presented and discussed. The method presented in this investigation uses commercially available analog-digital circuit simulators and a delay element and sampler constructed from analog components. The delay element and sampler used with standard, continuous-time amplifiers and summers, allow the user to simulate discrete-time systems in a manner identical to that used for continuous-time systems. Construction of the discrete-time delay element and sampler using the PSpice circuit simulator is presented as is their use in a variety of well-known linear discrete-time systems including problems from economics, population dynamics and digital signal processing. The well-known nonlinear quadratic model of chaos is also simulated in this investigation. The results of the linear and nonlinear discrete-time system analysis are compared to the analytical results and show that the delay element and sampler are stable and accurate components useful in modeling a wide variety of linear and nonlinear discrete-time systems     

Organic–Inorganic Hybrid Films Based on Hydroxylated Soybean Oils

Hybrid organic–inorganic films were prepared using four different hydroxylated soybean oils (HSO) or epoxidized soybean oil as organic precursor and tetraethyl orthosilicate (TEOS) as inorganic precursor in a mass ratio of HSO:TEOS of 90:10. The films were macroscopically homogeneous and were characterized by swelling and extraction in solvent, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) including energy dispersive spectroscopy (EDX), adhesion and hardness. Their properties varied as a function of the number of OH groups present in the HSO. The best hybrid system was HSOF198/TEOS, with an OH value of 198 mg of KOH/g, which presents lower swelling coefficient, very good adhesion on aluminium surface and good hardness.