Transition and equilibrium processes in metal-ceramic particle systems

The nonlinear motion equation of a spherical particle pushed by the solidification front is determined. In equilibrium, by integrating this equation, we obtain the critical interfacial speed, both in the absence and presence of thermal conductivities. The results are similar to those given by Ştef<anescuet al. only in the case of ionic crystals (n = 2). The analysis of the motion of the particle far from the interface makes it possible to introduce a time constant as a measure of the motion uniformity degree. In such a context, it may be assumed that the lesser the time constant, the quicker the incorporation of the particle by the metal matrix.     

Use of Autocorrelation Analysis in the Evaluation of Piezoelectric Coupling of Modified PLZT Ceramics Subjected to High Electric Fields

Two piezoelectric materials were investigated in electric fields, up to 3 kV/cm to determine whether single-sample testing can be used to evaluate piezoelectric coupling. Autocorrelation analysis of the data showed that the minimal increment of electric field necessary for successive independent measurements on single specimens is 1.3 kV /cm. This value coincides with the breakage field of the sample at resonance. Electrumechanical performance can still be evaluated with a sampling interval slightly lower than 1.3 kV/cm .     

Coordinating Agents in Organizations Using Social Commitments

One of the main challenges faced by the multi-agent community is to ensure the coordination of autonomous agents in open heterogeneous multi-agent systems. In order to coordinate their behaviour, the agents should be able to interact with each other. Social commitments have been used in recent years as an answer to the challenges of enabling heterogeneous agents to communicate and interact successfully. However, coordinating agents only by means of interaction models is difficult in open multi-agent systems, where possibly malevolent agents can enter at any time and violate the interaction rules. Agent organizations, institutions and normative systems have been used to control the way agents interact and behave. In this paper we try to bring together the two models of coordinating agents: commitment-based interaction and organizations. To this aim we describe how one can use social commitments to represent the expected behaviour of an agent playing a role in an organization. We thus make a first step towards a unified model of coordination in multi-agent systems: a definition of the expected behaviour of an agent using social commitments in both organizational and non-organizational contexts.     

Insight into three-dimensional flow of three different dynamics of nanofluids subject to thermal radiation: The case of water–cobalt ferrite,water–manganese–zinc ferrite,and water–magnetite

Magnetic nanofluids (MNFs) have been widely applied in both biomedical and environmental sectors along with the substantial growth of numerical and experimental studies. Hence, in view of the unique properties in MNFs, the aim of this study is to analyze numerically the three-dimensional flow of MNFs (Fe₃O₄–water, CoFe₂O₄–water, Mn–ZnFe₂O₄–water) over a shrinking surface with suction and thermal radiation effects. The single-phase nanofluid model is reduced into a system of ordinary differential equations by applying the similarity transformation. The results are then, obtained using the bvp4c solver in the Matlab software. The results reveal that for the shrinking case, the Mn–ZnFe₂O₄–water nanofluid has the maximum thermal rate followed by CoFe₂O₄–water and Fe₃O₄–water, respectively. Meanwhile, Fe₃O₄–water expands the separation value of boundary layer flow greater than other tested MNFs. Besides this, the suction parameter is also a contributing factor for the thermal enhancement of all MNFs.     

Laser Direct Writing via Two-Photon Polymerization of 3D Hierarchical Structures with Cells-Antiadhesive Properties

We report the design and fabrication by laser direct writing via two photons polymerization of innovative hierarchical structures with cell-repellency capability. The structures were designed in the shape of “mushrooms”, consisting of an underside (mushroom’s leg) acting as a support structure and a top side (mushroom’s hat) decorated with micro- and nanostructures. A ripple-like pattern was created on top of the mushrooms, over length scales ranging from several µm (microstructured mushroom-like pillars, MMP) to tens of nm (nanostructured mushroom-like pillars, NMP). The MMP and NMP structures were hydrophobic, with contact angles of (127 ± 2)° and (128 ± 4)°, respectively, whereas flat polymer surfaces were hydrophilic, with a contact angle of (43 ± 1)°. The cell attachment on NMP structures was reduced by 55% as compared to the controls, whereas for the MMP, a reduction of only 21% was observed. Moreover, the MMP structures preserved the native spindle-like with phyllopodia cellular shape, whereas the cells from NMP structures showed a round shape and absence of phyllopodia. Overall, the NMP structures were more effective in impeding the cellular attachment and affected the cell shape to a greater extent than the MMP structures. The influence of the wettability on cell adhesion and shape was less important, the cellular behavior being mainly governed by structures’ topography.     

Angiogenesis in Regenerative Dentistry: Are We Far Enough for Therapy?

Angiogenesis is a broad spread term of high interest in regenerative medicine and tissue engineering including the dental field. In the last two decades, researchers worldwide struggled to find the best ways to accelerate healing, stimulate soft, and hard tissue remodeling. Stem cells, growth factors, pathways, signals, receptors, genetics are just a few words that describe this area in medicine. Dental implants, bone and soft tissue regeneration using autologous grafts, or xenografts, allografts, their integration and acceptance rely on their material properties. However, the host response, through its vascularization, plays a significant role. The present paper aims to analyze and organize the latest information about the available dental stem cells, the types of growth factors with pro-angiogenic effect and the possible therapeutic effect of enhanced angiogenesis in regenerative dentistry.     

An Efficient Multi-constraint Relay Deployment Strategy for Wireless Sensor Network

Wireless Personal Communications - The relay node deployment for wireless sensor network has many application constraints, such as the energy efficiency, stable connectivity, survivability and low...     

Discovering novel memory cell designs for sentiment analysis on tweets

Designing a Recurrent Neural Network to extract sentiment from tweets is a very hard task. When using memory cells in their design, the task becomes even harder due to the large number of design alternatives and the costly process of finding a performant design. In this paper we propose an original evolutionary algorithm to address the hard challenge of discovering novel Recurrent Neural Network memory cell designs for sentiment analysis on tweets. We used three different tasks to discover and evaluate the designs. We conducted experiments and the results show that the best obtained designs surpass the baselines—which are the most popular cells, LSTM and GRU. During the discovery process we evaluated roughly 17,000 cell designs. The selected winning candidate outperformed the others for the overall sentiment analysis problem, hence showing generality. We made the winner selection by using the cumulated accuracies on all three considered tasks.

     

Challenges of real-world reinforcement learning: definitions,benchmarks and analysis

Machine Learning - Reinforcement learning (RL) has proven its worth in a series of artificial domains, and is beginning to show some successes in real-world scenarios. However, much of the research...     

Influence of archaeological environment factors in alteration processes of copper alloy artifacts

The article presents the experimental results obtained by combining noninvasive techniques (OM, SEM/EDX, XRF) to analyze three artifacts made of copper alloys discovered in a inhumation tomb (2) and in the soil profile (1) in archaeological sites from Neamt County Romania. To uncover the mechanism of alteration thereof during their longtime underground stay in specific chemical conditions and under the influence of other pedological factors, the corrosion products must be identified. The excess of the chloride ion, from burial site, disturbs the Liesegang effect, transforming the bulk in a stratified sponge structure with chlorapatite and hydroxyapatite. Some of the compounds from primary and secondary patina can be found on the surface of the bulk, as color stains. The presence of alloy components (Cu, Sn, Pb, Zn, Fe, etc.) and of the underground contamination components, allowed us to establish the origin of the ore, the manufacture technology and we identified other materials which affected the artifacts after abandonment. Microsc. Res. Tech., 2012. © 2012 Wiley Periodicals, Inc.