Optimizing Melt‐Processing Conditions for the Preparation of iPP/Fumed Silica Nanocomposites: Morphology,Mechanical and Gas Permeability Properties

A series of iPP/SiO₂ nanocomposites, containing 1, 2.5, 5, 7.5, and 10 wt.‐% fumed silica nanoparticles, were prepared by melt mixing in a twin screw co‐rotating extruder. The effect of different extrusion parameters was evaluated. The size of aggregates increased with increase in SiO₂ content and repetition of the mixing process improved the filler's dispersion. A similar effect was also exhibited by either increasing the rotor speed or the mixing temperature, with the latter being more pronounced at the ranges studied. The mechanical properties of the prepared nanocomposites were evaluated and various models used to explain the observed enhancements. However, only the three‐phase model could provide some correlation with the experimental results. All nanocomposites displayed lower permeability to gases.

     

Sizing the slenderness of free-standing rocking columns to withstand earthquake shaking

This paper investigates the problem of sizing the width of tall free-standing columns with a given height which are intended to rock, yet shall remain stable during the maximum expected earthquake shaking. The motivation for this study is the emerging seismic design concept of allowing tall rigid structures to uplift and rock in order to limit base moments and shears. The paper first discusses the mathematical characterization of pulse-like ground motions and the dimensionless products that govern the dynamics of the rocking response of a free-standing block and subsequently, using basic principles of dynamics, derives a closed-form expression that offers the minimum design slenderness that is sufficient for a free-standing column with a given size to survive a pulse-like motion with known acceleration amplitude and duration.     

Nowcasting Avalanches as Earthquakes and the Predictability of Strong Avalanches in the Olami-Feder-Christensen Model

Nowcasting earthquakes, suggested recently as a method to estimate the state of a fault and hence the seismic risk, is based on the concept of natural time. Here, we generalize nowcasting to a prediction method the merits of which are evaluated by means of the receiver operating characteristics. This new prediction method is applied to a simple (toy) model for the waiting (natural) time of the stronger earthquakes, real seismicity, and the Olami-Feder-Christensen earthquake model with interesting results revealing acceptable to excellent or even outstanding performance.     

CMOS tuners for mobile TV

Digital video reception is emerging as the latest feature toward multimedia-enriched handheld devices. Mobile battery-operated devices require small-size tuners that consume low power and are amenable to single-chip integration with the baseband demodulator. Following an overview of the system and circuit-level implementation challenges of mobile TV standards such as DVB-H and T-DMB, this article presents a dual-band direct conversion tuner for DVB-H. Architecture and circuit trade-offs are discussed, and detailed measurements are presented. The tuner occupies 9.7 mm² and achieves a 4 dB NF at both UHF and L-band, eliminating the need for an external LNA. By using a fractional-TV synthesizer both 470-890 MHz and 1.4-1.8 GHz bands are supported, while achieving an integrated phase noise of less than -41 dBc. Sixth-order low-pass filters support channel bandwidths from 4 to 10 MHz     

Computation of two-dimensional dam-break flood flows

Sudden total collapse of a dam holding back a reservoir of water, whenever it occurs, becomes formidably impressive in the extent of destruction with which it is associated. The movement on a dry bed of a two-dimensional flood wave resulting from the break of a dam has been one of the most important and challenging subjects in rapidly varied unsteady flows from the computational point of view. An implicit time-marching finite volume numerical scheme was developed and subsequently applied for the solution of the two-dimensional unsteady open channel flow equations written in conservation form. In order to avoid the problems associated with a conventional grid system, a body-fitted non-orthogonal local co-ordinate system was utilized. The proposed numerical technique was applied to determine the stage hydrographs, water surface profiles and velocities of flood flows resulting from suddenly breached storage dams. Predictions were compared with an analytical solution, with available numerical solutions using MacCormack's two-step explicit scheme and with experimental measurements. Agreement between predictions and measurements regarding the wave front advancement and stage hydrographs is considered to be satisfactory.     

Efficient Construction of Contact Coordinates for Partial Prolongations

Let V be a vector field distribution or Pfaffian system on manifold M. We give an efficient algorithm for the construction of local coordinates on M such that V may be locally expressed as some partial prolongation of the contact distribution C⁽¹⁾_q, on the first-order jet bundle of maps from ℝ to ℝ^q, q ≥ 1. It is proven that if V is locally equivalent to a partial prolongation of C⁽¹⁾_q, then the explicit construction of contact coordinates algorithmically depends upon the determination of certain first integrals in a sequence of geometrically defined and algorithmically determined integrable Pfaffian systems on M. The number of these first integrals that must be computed satisfies a natural minimality criterion. These results provide a full and constructive generalisation of the Goursat normal form from the theory of exterior differential systems.     

The fast multipole method (FMM) for electromagnetic scatteringproblems

The fast multipole method (FMM) developed by V. Rokhlin (1990) to efficiently solve acoustic scattering problems is modified and adapted to the second-kind-integral-equation formulation of electromagnetic scattering problems in two dimensions. The present implementation treats the exterior Dirichlet problem for two-dimensional, closed, conducting objects of arbitrary geometry. The FMM reduces the operation count for solving the second-kind integral equation from O(n³) for Gaussian elimination to O(n^4/3) per conjugate-gradient iteration, where n is the number of sample points on the boundary of the scatterer. A sample technique for accelerating convergence of the iterative method, termed complexifying k, the wavenumber, is also presented. This has the effect of bounding the condition number of the discrete system; consequently, the operation count of the entire FMM (all iterations) becomes O(n^4/3). Computational results for moderate values of ka, where a is the characteristic size of the scatterer, are given     

Conformational Properties of New Thiosemicarbazone and Thiocarbohydrazone Derivatives and Their Possible Targets

The structure assignment and conformational analysis of thiosemicarbazone KKI15 and thiocarbohydrazone KKI18 were performed through homonuclear and heteronuclear 2D Nuclear Magnetic Resonance (NMR) spectroscopy (2D-COSY, 2D-NOESY, 2D-HSQC, and 2D-HMBC) and quantum mechanics (QM) calculations using Functional Density Theory (DFT). After the structure identification of the compounds, various conformations of the two compounds were calculated using DFT. The two molecules showed the most energy-favorable values when their two double bonds adopted the E configuration. These configurations were compatible with the spatial correlations observed in the 2D-NOESY spectrum. In addition, due to the various isomers that occurred, the energy of the transition states from one isomer to another was calculated. Finally, molecular binding experiments were performed to detect potential targets for KKI15 and KKI18 derived from SwissAdme. In silico molecular binding experiments showed favorable binding energy values for all four enzymes studied. The strongest binding energy was observed in the enzyme butyrylcholinesterase. ADMET calculations using the preADMET and pKCSm software showed that the two molecules appear as possible drug leads.