Iron Powder Treated Gray Irons: Critical Shape Characteristics for Graphite Nuclei

A program was conducted to research how to characterize the size and shape of micro-particles. These can act as graphite nuclei, but are altered by adding a commercial iron powder, or after a similar treatment combined with inoculation. Resin sand mold (RSM) and metal mold (MM) solidified sample structures were subjected to automatic image analysis. In general, a higher cooling rate, typical for MM solidification, favors smaller size and more compact particles, even in RSM media. Iron powder treatment led to the largest particles with unusual morphologies, better defined by complex shape factors, which employ actual perimeters, rather than the simpler median size and aspect ratio method. Conventional inoculation employed after an iron powder treatment altered the particles (smaller and more compact), which benefited their effectiveness to act as graphite nuclei, especially at slower solidification rates in RSMs. The results confirm that promoting more compact micro-inclusions, at smaller sizes, involved in graphite nucleation, reduces the sensitivity to chill and improves the eutectic cell characteristics in gray cast iron.     

Ce dopant segregation in Y3Al5O12 optical ceramics

Ce³⁺-doped YAG garnet optical ceramic have been sintered at the Shanghai Institute of Ceramics in China to characterize dopant distribution in optical ceramics by combining optical spectroscopy and two spatially resolved techniques as imaging confocal microscopy and transmission electron microscopy. A strong Ce³⁺ segregation and spatial variations of content between grains and grain boundaries has been confirmed by quantitative data obtained by TEM microscopy. This observation is another evidence of the inhomogeneous Ce³⁺ distribution across grain and grain boundaries in optical ceramics comparable to that of Nd³⁺ ions in YAG ceramics. These results correlate well with low segregation coefficients of Nd³⁺ and Ce³⁺ observed in the garnet crystals grown from the melt and/or flux.     

Compact modeling of CMOS transistors under variable uniaxial stress

This paper presents a novel implementation of variable uniaxial mechanical stress model to be used with DC circuit simulation, e.g. using BSIM3v3 transistor model. Based on transistor measurements under various uniaxial stress conditions two stress-dependent parameters are identified, namely the carriers mobility and to a lesser extend the carrier saturation velocity. The effect of the parasitic source/drain resistance on the piezoresistive coefficient determination is addressed in detail. Using the fundamental piezoresistive coefficients, the model has implemented a general relation to calculate the coefficients for arbitrary directions of current and stress in the (0 0 1) silicon (Si) plane. The extended transistor model allows for simulating the effect of uniaxial stress on any MOSFET geometry, under different operation conditions and for any combination of the drain current and stress orientations in the (0 0 1) silicon (Si) plane. The method proposed in this paper is validated by static and dynamic stress-dependent simulations and comparison with experimental data. The method is simulator-independent and can be adapted to other bulk CMOS technologies including SOI processes.     

Memory Defect Tolerance Architectures for Nanotechnologies

Memory Built In Self Repair (BISR) is gaining importance since several years. Because defect densities are increasing in future submicron technologies, more advanced solutions may be required for memories to be produced in the upcoming nanometric CMOS process generations. Moreover, this problem will be exacerbated with nanotechnologies, where defect densities are predicted to reach levels of several orders of magnitude higher than in current CMOS technologies. For such defect densities, traditional memory repair is not adequate. This work presents several Built-In Self Repair techniques addressing memories affected by high defect densities as well as an evaluation of the area cost and yield. Statistical fault injection simulations were conducted and the obtained results show that BISR architectures can be used for future high defect technologies, providing close to 100% memory yield, by means of reasonable hardware cost. Thus, the extreme defect densities that many authors predict for nanotechnologies do not represent a show-stopper, at least as concerning memories.     

A review of cardiac image registration methods

In this paper, the current status of cardiac image registration methods is reviewed. The combination of information from multiple cardiac image modalities, such as magnetic resonance imaging, computed tomography, positron emission tomography, single-photon emission computed tomography, and ultrasound, is of increasing interest in the medical community for physiologic understanding and diagnostic purposes. Registration of cardiac images is a more complex problem than brain image registration because the heart is a nonrigid moving organ inside a moving body. Moreover, as compared to the registration of brain images, the heart exhibits much fewer accurate anatomical landmarks. In a clinical context, physicians often mentally integrate image information from different modalities. Automatic registration, based on computer programs, might, however, offer better accuracy and repeatability and save time.     

Large-Vector Autoregression for Multilayer Spatially Correlated Time Series

One of the most commonly used methods for modeling multivariate time series is the vector autoregressive model (VAR). VAR is generally used to identify lead, lag, and contemporaneous relationships describing Granger causality within and between time series. In this article, we investigate the VAR methodology for analyzing data consisting of multilayer time series that are spatially interdependent. When modeling VAR relationships for such data, the dependence between time series is both a curse and a blessing. The former because it requires modeling the between time-series correlation or the contemporaneous relationships which may be challenging when using likelihood-based methods. The latter because the spatial correlation structure can be used to specify the lead–lag relationships within and between time series, within and between layers. To address these challenges, we propose an L₁L₂ regularized likelihood estimation method. The lead, lag, and contemporaneous relationships are estimated using an efficient algorithm that exploits sparsity in the VAR structure, accounts for the spatial dependence, and models the error dependence. We consider a case study to illustrate the applicability of our method. In the supplementary materials available online, we assess the performance of the proposed VAR model and compare it with existing methods within a simulation study.     

Low density polyethylene composites containing cellulose pulp fibers

Unbleached and bleached Kraft cellulose pulp fibers modified with a long chain carboxylic acid, i.e. oleic acid in cold plasma conditions have been used as reinforcements in low density polyethylene (LDPE). The purpose of the modification is to enhance the interfacial adhesion between cellulose and matrix and to increase the dispersability. Composites containing up to 10 wt.% of untreated and modified cellulose pulp fibers with LDPE were prepared by melt mixing. The samples were characterized by processing behavior, mechanical and rheological properties, SEM, contact angle measurements, TGA and DSC. It was found that when the modified pulp fibers were incorporated into composites matrix, most of the properties have been improved.     

Chemical reactivity driving switchable molecular machines. A case of Bipyridine -Calixarene rotaxane

The driving interlocked mechanisms by the chemical reactivity profiles of molecular machine’s stages is undertaken, for the calixare-based rotaxane complexes containing tris(N-phenylureido)-calix[6 Biedermann, F.; Schneider, H.-J. Experimental Binding Energies in Supramolecular Complexes. Chem. Rev. 2016, 116, 5216–5300. DOI:10.1021/acs.chemrev.5b00583.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]]arene as wheel and a 4,4’-bipyridinium dication’s units as axle; The results clearly indicate the huge chemical reactivity dynamic potential (especially of electronegativity which is ultimately assimilated with the negative of the chemical potential of a system) able to drive either the slipper as well as the deslipper interlocked mechanisms of molecular machines, here for the bipyridine-calixarene rotaxane case, yet with appearing as a structural best (to date) structural explanation of the “activated mobile” character of the molecular machines by simple its inner self-activated potential.     

Synthesis of ligand-free colloidally stable water dispersible brightly luminescent lanthanide-doped upconverting nanoparticles

The synthesis using the thermal decomposition of metal trifluoroacetates is being widely used to prepare oleate-capped lanthanide-doped upconverting NaYF(4):Er(3+)/Yb(3+) nanoparticles (Ln-UCNPs). These nanoparticles have no inherent aqueous dispersibility and inconvenient postsynthesis treatments are required to render them water dispersible. Here, we have developed a novel and facile approach to obtain water-dispersible, ligand-free, brightly upconverting Ln-UCNPs. We show that the upconversion luminescence is affected by the local environment of the lanthanide ions at the surface of the Ln-UCNPs. We observe a dramatic difference of the integrated upconverted red:green emission ratio for Ln-UCNPs dispersed in toluene compared to Ln-UCNPs dispersed in water. We can enhance or deactivate the upconversion luminescence by pH and H/D isotope vibronic control over the competitive radiative and nonradiative relaxation pathways for the red and green excited states. Direct biofunctionalization of the ligand-free, water-dispersible Ln-UCNPs will enable myriad new opportunities in targeting and drug delivery applications.     

Acrylic blends based on polyaniline. Factorial design

Processable conducting materials for large-scale utilization were prepared by mechanical mixing of polyaniline (PANI) paste and commercially acrylic resin. Doped PANI with organic phosphorus acid was synthesized. These blends can be used for the production of semiconductive paints with good corrosion resistance. By mixing doped PANI with commercially acrylic acid (SMP 63 AZUR SA) hard semiconducting and low elastic films are obtain. The effect of four variables was simultaneously studied: PANI (concentration), stirring speed (ST), mixing time (MT), dispersing agent (DA). Due to the number of variables, a factorial-design was chosen in order to reduce the number of experiments required in order to obtain coatings with high hardness and elasticity and semiconductive behavior. The results indicated that the influences of control factors decrease in order: PANI (concentration), mixing time (MT), dispersing agent (DA) and stirring speed (ST). From the studied variables, the resistance is significantly influenced by the two control factors PANI and MT.