The polar cluster like behavior in Ti substituted BaZrO3 ceramics

In this paper we report the evolution of the polar cluster like behavior with the incorporation of Ti⁴⁺ ion in BaZrO₃ Ceramics. Dielectric behavior of BaZr_xTi_(1−x)O₃ (x = 1.00, 0.95, 0.90, 0.85) ceramics is studied in the temperature range from 300 to 30 K. Polar cluster like behavior becomes more prominent with the increase in content of Ti⁴⁺ ion. The dielectric relaxation is analyzed by Vogel–Fulcher relation and Arrhenius law. Frequency dependence of dielectric constant and low loss tangent of these materials can be useful for the potential applications at low temperature.     

Tribological Behavior of Aluminum Alloy AlSi10Mg-TiB<Subscript>2</Subscript> Composites Produced by Direct Metal Laser Sintering (DMLS)

Direct metal laser sintering (DMLS) is an additive manufacturing technique for the production of parts with complex geometry and it is especially appropriate for structural applications in aircraft and automotive industries. Aluminum-based metal matrix composites (MMCs) are promising materials for these applications because they are lightweight, ductile, and have a good strength-to-weight ratio This paper presents an investigation of microstructure, hardness, and tribological properties of AlSi10Mg alloy and AlSi10Mg alloy/TiB₂ composites prepared by DMLS. MMCs were realized with two different compositions: 10% wt. of microsize TiB₂, 1% wt. of nanosize TiB₂. Wear tests were performed using a pin-on-disk apparatus on the prepared samples. Performances of AlSi10Mg samples manufactured by DMLS were also compared with the results obtained on AlSi10Mg alloy samples made by casting. It was found that the composites displayed a lower coefficient of friction (COF), but in the case of microsize TiB₂ reinforcement the wear rate was higher than with nanosize reinforcements and aluminum alloy without reinforcement. AlSi10Mg obtained by DMLS showed a higher COF than AlSi10Mg obtained by casting, but the wear rate was higher in the latter case.     

Multi-objective Topology Optimization of Thermo-mechanical Compliant Mechanisms

The material characteristics of a structure will change with temperature variation,and will induce stress within the structure.Currently,the optimal design for the topology of compliant mechanisms is mainly performed in single physical field.However,when compliant mechanisms work in high temperature environments,their displacement outputs are generated not only by mechanical load,but also by the temperature variation which may become the prominent factor.Therefore,the influence of temperature must be considered in the design.In this paper,a novel optimization method for multi-objective topology of thermo-mechanical compliant mechanisms is presented.First,the thermal field is analyzed with finite-element method,where the thermal strain is taken into account in the constitutive relation,and the equivalent nodal thermal load is derived with the principle of virtual work.Then the thermal load is converted into physical loads in elastic field,and the control equation of the thermo-mechanical compliant mechanism is obtained.Second,the mathematical model of the multi-objective topology optimization is built by incorporating both the flexibility and stiffness.Meanwhile,the coupling sensitivity function and the sensitivity analysis equations of thermal steady-state response are derived.Finally,optimality criteria algorithm is employed to obtain numerical solution of the multi-objective topology optimization.Numerical examples show that the compliant mechanisms have better performance and are more applicable if the temperature effect is taken into account in the design process.The presented modeling and analysis methods provide a new idea and an effective approach to topology optimization of compliant mechanisms in electrothermic coupling field and multiphysics fields.     

FARO: FAce Recognition Against Occlusions and Expression Variations

Face recognition is widely considered as one of the most promising biometric techniques, allowing high recognition rates without being too intrusive. Many approaches have been presented to solve this special pattern recognition problem, also addressing the challenging cases of face changes, mainly occurring in expression, illumination, or pose. On the other hand, less work can be found in literature that deals with partial occlusions (i.e., sunglasses and scarves). This paper presents face recognition against occlusions and expression variations (FARO) as a new method based on partitioned iterated function systems (PIFSs), which is quite robust with respect to expression changes and partial occlusions. In general, algorithms based on PIFSs compute a map of self-similarities inside the whole input image, searching for correspondences among small square regions. However, traditional algorithms of this kind suffer from local distortions such as occlusions. To overcome such limitation, information extracted by PIFS is made local by working independently on each face component (eyes, nose, and mouth). Distortions introduced by likely occlusions or expression changes are further reduced by means of an ad hoc distance measure. In order to experimentally confirm the robustness of the proposed method to both lighting and expression variations, as well as to occlusions, FARO has been tested using AR-faces database, one of the main benchmarks for the scientific community in this context. A further validation of FARO performances is provided by the experimental results produced on Face Recognition Grand Challenge database.     

Energy and environmental aspects of mobile communication systems

The reduction of the energy consumptions of a Telecommunication Power System represents one of the critical factors of the telecommunication technologies, both to allow a sizeable saving of economic resources and to realize “sustainable” development actions. The consumption of about one hundred base stations for mobile phones were monitored for a total of over one thousand days, in order to study the energy consumption in relation to the environmental, electric and logistics parameters of the stations themselves. It was possible to survey, then, the role of the mobile communication systems in the general national energy framework and to plot the best areas of intervention for saving energy and improving the environmental impact, showing the role played by air-conditioning and transmission equipments. Finally, new transmission algorithms and the use of renewable energy based techniques have been tested.     

A proposal toward the development of accessible e-learning content by human involvement

Most of the existing efforts for supporting the design, preparation, and deployment of accessible e-learning applications propose guidelines that primarily address technical accessibility issues. Little, if any, consideration is given to the real actors involved in the learning experience, such as didactical experts and disabled learners. Moreover, implementing artifacts addressed to the e-learning world requires a wide range of particular skills which are related not only to technical but also to didactical, pedagogical, usability, and accessibility aspects of the produced material. This paper argues that the know-how of a number of stakeholders should be blended into a joint design activity, and that it should be possible to determine the role of each participant in the successive phases of the development lifecycle of e-learning applications. The paper sketches the methodological guidelines of a design framework based on involving the users with disabilities, as well as pedagogical experts, in the development process. The novelty of this proposal mainly stems from being built up around the core of strategies and choices specifically bound to accessibility requirements. Characteristic elements of learner-centered design are then further integrated into processes and methodologies which are typical of participatory and contextual design approaches. Following such guidelines, it will be possible to gain a deeper understanding of the requirements and of the operational context of people needing accessible material, either as learners or educators. The underlying objective is to increase the potential to realize learning systems that better meet different user needs and that provide a more satisfying learning experience. Moreover, when people get involved in the development process, they gain a sense of ownership of the system and are therefore more likely to accept and “promote” it.     

Discrepant social communications.

Observed 32 children (13–42 mo old) individually in the presence of their mothers. Eight messages systematically varied between the visual and auditory channels were given by the experimenter. Some messages asked S to approach; other messages asked S to stay away. Some were congruent and others discrepant across channels. Order of presentation was counterbalanced across Ss. All Ss approached the experimenter when he unambiguously invited them with a smiling face, affirmative head nods, manual beckoning, and a pleasant tone of voice, saying, "Come here." When the experimenter's request to approach or to stay away was on one channel only, that is, was either visual or auditory, about three-fourths of the Ss conformed to it, approaching or staying away as requested. When requests were discrepant across channels, behavior was more variable, but more Ss conformed to the auditory than to the visual message. The messages constitute a Guttman scale, a unidimensional and cumulative hierarchy based on the individual patterns of responses to them. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Synthesis, biological activity, and ADME properties of novel S-DABOs/N-DABOs as HIV reverse transcriptase inhibitors

Previous studies aimed at exploring the SAR of C2-functionalized S-DABOs demonstrated that the substituent at this position plays a key role in the inhibition of both wild-type RT and drug-resistant enzymes, particularly the K103N mutant form. The introduction of a cyclopropyl group led us to the discovery of a potent inhibitor with picomolar activity against wild-type RT and nanomolar activity against many key mutant forms such as K103N. Despite its excellent antiviral profile, this compound suffers from a suboptimal ADME profile typical of many S-DABO analogues, but it could, however, represent a promising candidate as an anti-HIV microbicide. In the present work, a new series of S-DABO/N-DABO derivatives were synthesized to obtain additional SAR information on the C2-position and in particular to improve ADME properties while maintaining a good activity profile against HIV-1 RT. In vitro ADME properties (PAMPA permeation, water solubility, and metabolic stability) were also experimentally evaluated for the most interesting compounds to obtain a reliable indication of their plasma levels after oral administration.