Piecewise Polynomial Solutions of Aerosol Dynamic Equation

This paper presents a discretization technique for particle dynamics equation based on piecewise continuous approximations of the solution. The growth terms are re-solved using a Discontinuous Galerkin approach, and the coagulation by a collocation approach. The method fits in the general framework recently proposed by the author. The discontinuous approximation allows better representations of distributions with sharp peaks. Numerical tests reveal that accurate solutions can be obtained with a very small number of size bins. An efficient software package AeroSolve which implements the proposed algorithms was developed.     

Study on visual machine-learning on the omnidirectional transporting robot

We present a computer vision solution integrated to an omnidirectional transporting robot to perform the position tracking of multiple trays moving on its planar acrylic plate surface. The trays were designed to carry lightweight materials on top of their surface so that the mechanism could be implemented as an automated transporting system for applications that require the displacement of products and/or materials in any given space. One hurdle faced by the visual system for suitable detection was the partial occlusion of the image of a tray when placing arbitrary objects on its surface. Our strategy to overcome this challenge consisted on the implementation of machine learning algorithms, such as Support Vector Machines (SVM), using datasets of images containing trays with different occlusion patterns for fast object detection through rigorous training. The results of experimental tests validate the implementation of our proposal as a reliable approach for the object tracking of multiple trays on the robotic device, even under partial occlusion. We also studied the accuracy of the position measurements performed by our visual system with respect to the position measurements taken by the OPTITRACK motion capture system and evaluated the processing time per frame required by the software implementation.     

Optical planar waveguide for cell counting

Low cost counting of cells has medical applications in screening, military medicine, disaster medicine, and rural healthcare. In this report, we present a shallow, buried, planar waveguide fabricated by potassium ion exchange in glass that enables low-cost and rapid counting of metal-tagged objects that lie in the evanescent field of the waveguide. Laser light transmitted through the waveguide was attenuated proportionately to the presence of metal-coated microstructures fabricated from photoresist. This technology enables the low-cost enumeration of cells from blood, urine, or other biofluids.     

Effect of Ni substitute in off-stoichiometric Bi(Pb)-Sr-Ca-Cu(Ni)-O superconductor. Excess conductivity,XRD analysis and thermal behaviour

Two phases (2223 and 2212) are identified in Bi_1.8Pb_0.3Sr₂Ca₂(Cu_1-xNi_x)_3.3O_y superconductor system, sintered at 847?°C for 322?h, in partial nitrogen atmosphere. The volume fraction of 2223-phase is strongly dependent on Ni doping: 78.37% for x?=?0.002, 70.29% for x?=?0.005% and 51.13% for x?=?0.015. The unit cells of 2223 and 2212 phases were indexed as tetragonal structures, having different lattice constants. Plots of resistance versus temperature (four points method) on cooling to 77?K, evidenced that the critical temperature for the transition to the superconductor phase, T_c, is linearly decreasing from 106.21 to 93.47?K when the Ni content is varying from x?=?0.002 to x?=?0.03. From log-log plots of the excess-conductivity we calculated the cross-over temperatures between 3D and 2D dimensionality as well as from 2D to SWF (short wavelength fluctuation) behaviour, the coupling factor and the coherence length for all the samples. Thermal analysis of the resulting samples (after the last sintering) was performed by heating each sample from room temperature (RT) to 1000?°C at a rate of 10?K?min^?1 in dynamic air atmosphere (150?cm³ min^?1). A clear dependence on Ni content is seen by TG and DSC, but a relative thermal equilibrium between the two phases, 2223 and 2212, in RT-869?°C range, is observed. Strong endothermic effects (melting accompanied by small decomposition processes) begin at around 869?°C for all Ni doped samples. The results for the specific heat capacities, calculated from DSC plots, are also presented. Contribution of the crystal lattice to the estimated specific heat capacity was in conformity with the Einstein model, the Einstein temperature values being dependent on Ni content.     

Towards a hydrogen economy in Romania: Statistics,technical and scientific general aspects

The present work features an analysis of the current state of Romania's current policy in the context of hydrogen economy. The possibilities and limitations concerning the transition towards the hydrogen economy in Romania are discussed taking into account a number of aspects, including: the degree of development of the electric power infrastructure, aspects from petrochemical and agrochemical industry, transport infrastructure, socioeconomic development indicators, activity and dynamics of the scientific community and attitude of central authorities. All these are important aspects that contribute to technology deployment. The article presents both advantages and disadvantages from Romania, provides concrete examples, gives information, makes comparisons and provides recommendations, taking into account national aspects. Key areas of promise for hydrogen technologies in Romania are identified. The paper concludes with recommendations for actions in order to begin the process of transition towards a hydrogen economy.     

A mathematical model for skin burn injury induced by radiation heating

We modify the Pennes model by taking into account the thermal relaxation time of biological tissue. Specifically, we employ the Maxwell–Cattaneo thermal flux law, in conjunction with the fourth power law, to model the effects of high thermal radiation on such skin. The skin is considered to be a 3D triple-layered structure with embedded dendritic countercurrent multi-level blood vessels, artery and vein, where the dimensions and blood flow of the multi-level blood vessels are determined based on the constructal theory of multi-scale tree-shaped heat exchangers. The method is illustrated by a numerical example.     

Solution-processed single walled carbon nanotube electrodes for organic thin-film transistors

Airbrushed single walled carbon nanotube (SWCNT) thin films with sheet resistivity <1 kΩ/sq. and transparency >80% are used as electrodes for pentacene and regioregular poly(3-hexylthiophene) (P3HT) thin-film transistors (TFTs). Airbrushed SWCNT electrodes show low contact resistance in a bottom-contact configuration, comparable to (in the case of P3HT) or lower than (in the case of pentacene) Au bottom-contacts. The results show that airbrushed CNT electrodes yield similar performance to CVD-grown CNT electrodes.     

Scalable Microgravity Simulator Used for Long-Term Musculoskeletal Cells and Tissue Engineering

We introduce a new benchtop microgravity simulator (MGS) that is scalable and easy to use. Its working principle is similar to that of random positioning machines (RPM), commonly used in research laboratories and regarded as one of the gold standards for simulating microgravity. The improvement of the MGS concerns mainly the algorithms controlling the movements of the samples and the design that, for the first time, guarantees equal treatment of all the culture flasks undergoing simulated microgravity. Qualification and validation tests of the new device were conducted with human bone marrow stem cells (bMSC) and mouse skeletal muscle myoblasts (C2C12). bMSC were cultured for 4 days on the MGS and the RPM in parallel. In the presence of osteogenic medium, an overexpression of osteogenic markers was detected in the samples from both devices. Similarly, C2C12 cells were maintained for 4 days on the MGS and the rotating wall vessel (RWV) device, another widely used microgravity simulator. Significant downregulation of myogenesis markers was observed in gravitationally unloaded cells. Therefore, similar results can be obtained regardless of the used simulated microgravity devices, namely MGS, RPM, or RWV. The newly developed MGS device thus offers easy and reliable long-term cell culture possibilities under simulated microgravity conditions. Currently, upgrades are in progress to allow real-time monitoring of the culture media and liquids exchange while running. This is of particular interest for long-term cultivation, needed for tissue engineering applications. Tissue grown under real or simulated microgravity has specific features, such as growth in three-dimensions (3D). Growth in weightlessness conditions fosters mechanical, structural, and chemical interactions between cells and the extracellular matrix in any direction.     

Size-controllable synthesis of chromium oxyhydroxide nanomaterials using a soft chemical hydrothermal route

Chromium oxyhydroxide nanomaterials were synthesised through a simple soft chemical hydrothermal method. The chromium oxyhydroxide materials display platelet morphology with clear edges, ~11 nm in diameter. CrO(OH) nanomaterials synthesised under different conditions were fully characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED), scanning electron microscopy (SEM), BET specific surface area analysis, X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA). Bonding of the trivalent chromium from the oxyhydroxide nanomaterials was defined through the analysis of their high resolution XPS spectra for Cr 2p_3/2 and O 1s. The thermal stability of the nanomaterials CrO(OH) was established. This research has developed methodology for the synthesis of chromium oxyhydroxide nanoplates.     

On the optimum support size in meshfree methods: A variational adaptivity approach with maximum‐entropy approximants

We present a method for the automatic adaption of the support size of meshfree basis functions in the context of the numerical approximation of boundary value problems stemming from a minimum principle. The method is based on a variational approach, and the central idea is that the variational principle selects both the discretized physical fields and the discretization parameters, here those defining the support size of each basis function. We consider local maximum‐entropy approximation schemes, which exhibit smooth basis functions with respect to both space and the discretization parameters (the node location and the locality parameters). We illustrate by the Poisson, linear and non‐linear elasticity problems the effectivity of the method, which produces very accurate solutions with very coarse discretizations and finds unexpected patterns of the support size of the shape functions. Copyright © 2009 John Wiley & Sons, Ltd.