Study of barium feldspar polymorphism as a function of temperature and calcium content

A family of new glass-ceramic materials, of the general formula (25-x)CaO·xBaO·yMgO· zAl₂O₃·50SiO₂, where x = 1, 2, 5, 10, 15, 20, 25, y = 20 or 14 and z = 5 or 11 (mol%), has been prepared by melting raw materials in two parent glasses and performing heat treatments. The systematic substitution of BaO for CaO in the base glasses allows the effect of feldspars' isomorphism and polymorphism to be studied in a series of glass-ceramics where the structural environment around the bivalent cations, Ca²⁺ and Ba²⁺, is systematically altered. Ba²⁺ has a large effect on the glass transition temperature and dilatometric softening point, causing a decrease with increasing BaO. The crystalline phases have been identified and found to be dependent on the preparation conditions, which are the BaO and Al₂O₃ contents, the heating rate and the soaking temperature adopted for the crystallization treatments. The infrared spectroscopy technique helped to identify the different polymorphs of barium feldspar, that were not clearly distinguishable by X-ray powder diffractometry due to preferred orientations. The kinetic parameters for the formation of the different crystals have also been determined and correlated with their thermal stability resumed in the well-known time-temperature-transformation curves.     

An investigation of magnetic oxides' defects and conflict of anisotropies for diluted powders

Magnetostatic measurements and rotational hysteresis were carried out on extremely diluted samples of pure, surface modified, bulk doped iron oxides and CrO2. It is found that in all these materials but pure γ-Fe2O3a conflict of anisotropy is active. As a result, the values of remanence ratio jrcan be either lower or higher than the theoretical value of ½ for strictly uniaxial particles depending on the angle between the two anisotropy axis and the relative value of the anisotropy constants. It is therefore found that whilej_{r} < 1/2for acicular magnetite and CrO2, the introduction of cobalt always produces an increase of jr: the extreme effect of such conflict can be found in high remanence isotropic particles. Such a conflict is minimized in Surface Modified Materials. From rotational hysteresis, Hcvs. angle with applied field and, over all, from CF and IFF parameters, it is suggested that the postreatment of the iron oxides with the Co-containing solutions, beside the increase of Hc, has a beneficial effect on the morphology of the particles.     

Carbon dioxide as refrigerant for tap water heat pumps: A comparison with the traditional solution

Increased concern about the environmental impact of the refrigeration technology is leading toward design solutions aimed at improving the energy efficiency of the related applications, using eco-friendly refrigerants, i.e. ozone-friendly and with the least possible global warming potential (GWP). In this respect, carbon dioxide (ASHRAE R744) is seen today as one of the most promising refrigerants and is raising great interest in industrial and scientific fields. In the present work, the plant options are investigated, which are related to the design of air/water heat pumps for tap water using CO₂. A comparison is made, in terms of energy efficiency, between a system working with CO₂ and a similar one working with HFC R134a; such a comparison is carried out by means of a simulation model of a refrigerating machine/heat pump, characterized by a detailed representation of the heat exchangers, based on their subdivision into elementary volumes. Results show that carbon dioxide is an interesting substitute for synthetic fluids, if the design of the system is focused to take advantage of its properties.     

Comparative effects of lisinopril and losartan on insulin sensitivity in the treatment of non diabetic hypertensive patients

There are many researchers engaged in qualitative research who look to experts in this mode of inquiry to validate their findings. But can any outsider, even an "expert" in qualitative research, do this? Such an expert is unlikely to know the data as well or to be as fully immersed in the project as the researcher. There are different kinds of expertise that may be required for different phases and purposes of research, and to satisfy different epistemological and ethical concerns. Moreover, new modes of participatory research have complicated the role of expert and the idea of expertise. Researchers must be judicious in their claims to expert validation, and experts must move researchers away from a preoccupation with validation toward craftsmanship and accountability to diverse communities.     

Cross-depiction problem: Recognition and synthesis of photographs and artwork

Computational Visual Media - Cross-depiction is the recognition—and synthesis—of objects whether they are photographed, painted, drawn, etc. It is a significant yet underresearched...     

Thermodynamic analysis of different two-stage transcritical carbon dioxide cycles

The aim of this paper is the thermodynamic evaluation and optimisation of different two-stage transcritical carbon dioxide cycles. Five different cycles are studied: basic single-stage cycle, single-throttling with two-stage compression cycle, split cycle, phase separation cycle and single-stage cycle coupled with a gas cooling circuit. Each basic cycle is analysed for the effect of internal heat transfer between different streams of refrigerants. In the case of two-stage compression, intermediate cooling between the compressor stages is present. An analysis on the Plank cycle for intermediate pressure higher than critical one is performed. Each cycle is optimised with regards to energy performance, calculating the optimal values of both the upper and the intermediate pressures. In the case of split cycle, the ratio of the mass flow rate in the main stream to the one in the auxiliary stream is also optimised.     

Wind tunnel tests on train scale models to investigate the effect of infrastructure scenario

The cross wind risk analysis is today, within the European railway operators, one of the most important items related to the safety problem. In order to define the risk associated with the cross wind along a railway line, the effect of the infrastructure scenario on the aerodynamic loads acting on a vehicle have to be investigated. A typical railway line is mainly characterized by two main types of scenario: viaduct and embankment. In this work, the aerodynamic coefficients of the ETR500 train, measured through wind tunnel tests, for the standard TSI infrastructure scenarios (flat ground with and without ballast and rail and 6 m-high embankment) and for a typical Italian viaduct are presented. Moreover, each infrastructure is characterized in terms of flow modification with and without train. A comparison between the experimental results obtained with the different scenarios allows to point out the effects of the infrastructure on the aerodynamic loads.     

Context-aware middleware solutions for anytime and anywhere emergency assistance to elderly people

The growing percentage of elderly people in society calls for novel healthcare support services to enhance elders' daily life independence in indoor and outdoor environments. Ubiquitous technologies create significant opportunities not only for indoor, but also for outdoor anytime and anywhere assistance. However, outdoor emergency assistance requires that we address several challenging aspects, from elder location tracking and health condition monitoring to the formation of ad hoc assistance groups capable of assisting elders in need of help. This article focuses on the creation and management of outdoor assistance teams and proposes a group management system, AGAPE, that exploits visibility of location and group/user/device profile information as a key principle to trigger and control the team formation and team member interactions required to coordinate emergency activities.     

Synthesis of silica nanoparticles in a continuous-flow microwave reactor

Monodispersed silica colloidal spherical nanoparticles were synthesized from the hydrolysis and condensation of tetraethylorthosilicate (TEOS) by using a continuous microwave synthesis process. The flow rate was varied from 43 to 101 mL/min in order to establish the optimum conditions required to obtain unagglomerated silica nanopowders. The results were compared with those obtained in batch systems. In particular the mean particle diameter became smaller than 50 nm as the residence time was decreased by increasing the flow rate to 101 mL/min.     

智能动力混凝土——低强度普通混凝土高性能化的探索与实践(一)

结合我国原材料和混凝土市场的特点,基于巴斯夫自主知识产权的RheoMATRIX R外加剂新技术,提出了以C30为代表的低强度等级普通混凝土的高性能化的概念及解决方案--智能动力混凝土(Smart Dynamic ConcreteTM,SDC).智能动力混凝土的设计参数:胶凝材料总量低于380kg/m3,初始流动度600～700mm,1 h的流动度不小于600mm,T50不超过12 s,无泌水、离析现象.大量的试验证明,智能动力混凝土在中国市场上具有广泛的推广应用前景.