Electrical,rheological and electromagnetic interference shielding properties of thermoplastic polyurethane/carbon nanotube composites

Electrically conducting rubbery composites based on thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs) were prepared through melt blending using a torque rheometer equipped with a mixing chamber. The electrical conductivity, morphology, rheological properties and electromagnetic interference shielding effectiveness (EMI SE) of the TPU/CNT composites were evaluated and also compared with those of carbon black (CB)‐filled TPU composites prepared under the same processing conditions. For both polymer systems, the insulator–conductor transition was very sharp and the electrical percolation threshold at room temperature was at CNT and CB contents of about 1.0 and 1.7 wt%, respectively. The EMI SE over the X‐band frequency range (8–12 GHz) for TPU/CNT and TPU/CB composites was investigated as a function of filler content. EMI SE and electrical conductivity increased with increasing amount of conductive filler, due to the formation of conductive pathways in the TPU matrix. TPU/CNT composites displayed higher electrical conductivity and EMI SE than TPU/CB composites with similar conductive filler content. EMI SE values found for TPU/CNT and TPU/CB composites containing 10 and 15 wt% conductive fillers, respectively, were in the range ?22 to ?20 dB, indicating that these composites are promising candidates for shielding applications. © 2013 Society of Chemical Industry     

Effects of Surface Smoothness on Inertial Particle Deposition in Human Nasal Models

Computational fluid dynamics (CFD) predictions of inertial particle deposition have not compared well with data from nasal replicas due to effects of surface texture and the resolution of tomographic images. To study effects of geometric differences between CFD models and nasal replicas, nasal CFD models with different levels of surface smoothness were reconstructed from the same MRI data used to construct the nasal replica used by Kelly et al. (2004) [Aerosol Sci. Technol. 38:1063-1071]. One CFD model in particular was reconstructed without any surface smoothing to preserve the detailed topology present in the nasal replica. Steady-state inspiratory airflow and Lagrangian particle tracking were simulated using Fluent software. Particle deposition estimates from the smoother models under-predicted nasal deposition from replica casts, which was consistent with previous findings. These discrepancies were overcome by including surface artifacts that were not present in the reduced models and by plotting deposition efficiency versus the Stokes number, where the characteristic diameter was defined in terms of the pressure-flow relationship to account for changes in airflow resistance due to wall roughness. These results indicate that even slight geometric differences have significant effects on nasal deposition and that this information should be taken into account when comparing particle deposition data from CFD models with experimental data from nasal replica casts.     

Numerical simulation of dam construction using low-CO<Subscript>2</Subscript>-emission concrete

Cement production gives rise to CO₂ emissions generated by the calcination of CaCO₃ and by the combustion of fossil fuels, being responsible for about 5% of the global CO₂ emissions. These emissions can be substantially reduced if cement replacement materials are used. In this paper two residual ashes that can be used as mineral additions are considered: sugar cane bagasse ash and rice husk ash. A case study of the construction of a dam with a blended material composed by cement and these two ashes is presented, indicating the potentiality of its use for civil engineering applications. The analyses were performed using experimental and numerical tools developed on the basis of a thermo-chemo-mechanical model. This model considers the coupling, within the theory of thermodynamics, of the several phenomena that intervene in the hydration process, namely, exothermicity, thermo-activation, chemo-plasticity, evolution of thermal and mechanical properties with the hydration reaction, which includes creep and relaxation.     

Joint phase and timing recovery for MSK-type signals

Novel nondata-aided algorithms are proposed for joint estimation of timing and carrier phase in minimum-shift keying (MSK)-type modulations. The performance with MSK and Gaussian MSK is assessed by computer simulations and compared with that of other existing estimation schemes     

Electrical properties of ZnO-based varistors prepared by combustion synthesis

Ceramic varistors are generally produced by the oxide mixing method or by chemical methods, such as sol–gel, precipitation and others. Chemical methods produce powders that are highly reactive, allowing for increased microstructural homogeneity and control of grain growth during sintering, which is essential for good varistor performance. The purpose of this work was to study the electrical characteristics of ZnO varistors produced from stoichiometric mixtures of water-soluble metal nitrates, such as precursor cations and urea as a fuel. This method, called combustion synthesis, stands out for its simplicity (a single-step reaction), purity, chemical homogeneity, and the high reactivity of the precursor powder. After sintering at 1050 °C using this method, varistors with a non-linear coefficient of 40 and the lowest leakage were obtained.     

Frequency estimation and timing acquisition in the uplink of a DS-CDMA system

We consider the uplink of a direct-sequence code-division multiple-access system operating over a multipath fading channel, and we aim at estimating the propagation delay and the frequency offset of a new user entering the network. The joint estimation of these parameters is investigated using a weighted-least-squares approach. The exact solution turns out to be too complex for practical purposes, as it involves a numerical search over a bidimensional domain. As an alternative, we propose a suboptimal procedure, in which the propagation delay is first computed with a monodimensional search and then is exploited to derive the frequency offset in closed form. Both data-aided and nondata-aided estimation methods are considered. The proposed synchronizers have a reasonable complexity and are suited for third-generation cellular systems. Their performance is assessed by simulation in a scenario inspired by the specifications of the frequency-division duplexing component of the Universal Mobile Telecommunications Systems standard. It is found that they provide accurate estimates and are useful even in applications over rapidly varying channels.     

The ParTriCluster Algorithm for Gene Expression Analysis

Analyzing gene expression patterns is becoming a highly relevant task in the Bioinformatics area. This analysis makes it possible to determine the behavior patterns of genes under various conditions, a fundamental information for treating diseases, among other applications. A recent advance in this area is the Tricluster algorithm, which is the first algorithm capable of determining 3D clusters (genes × samples × timestamps), that is, groups of genes that behave similarly across samples and timestamps. However, even though biological experiments collect an increasing amount of data to be analyzed and correlated, the triclustering problem remains a bottleneck due to its NP-Completeness, so its parallelization seems to be an essential step towards obtaining feasible solutions. In this work we propose and evaluate the implementation of a parallel version of the Tricluster algorithm using the filter-labeled-stream paradigm supported by the Anthill parallel programming environment. The results show that our parallelization scales well with the data size, being able to handle severe load imbalances that are inherent to the problem. Further more, the parallelization strategy is applicable to any depth-first searches.     

Granulocytic sarcoma presented as a reactivation of chronic myeloid leukemia after allogenic marrow transplantation

The authors report the case of a chronic myeloid leukemia (CML) patient submitted to allogenic bone marrow transplantation, who had probably never entered complete remission. The disease was reactivated as a granulocytic sarcoma, next to a platinum plate installed to correct a tibia fracture 11 years earlier. Its final event was a myeloid Ph1 + blastic crisis that was unsuccessfully treated with high doses of sc interferon and citarabine.