A mathematical framework to study fast walking of human

The body of a walking human is an elaborated dynamic system that operates adaptively in various conditions such as fast walking. Due to dynamic redundancies, the individual motor control strategies for speeding up the walking can be different among normal subjects. However, in reality, we see that the pattern of motion is quite similar among people and it is only the profile of hip joint motion along its path which determines the speed. The objective of the current paper is to develop a mathematical framework to investigate time optimal motion of a human during walking. To this end, a nine-link planar biped model is used. The motion is considered to take place in sagittal plane and to follow a normal pattern of motion. The solution is obtained using a phase plane method to solve minimum time problem which is subjected to inequality constraints of variable maximum joint torques and stability conditions. The solution method can be used to find the maximum possible speed of a human with specific body characteristics and to obtain a hip joint trajectory which could produce that speed. The proposed method can be utilized to study quantitative effect of different parameters such as joint strength in fast walking.     

Quantitative characterization of carrier injection across metal–organic interfaces using Bardeen theory

We have investigated the contact between a metal and an organic/polymeric (o/p) material and we have introduced a relation for carrier injection using Bardeen theory. A series of narrow barriers is considered in the semiconductor side to account for the localized nature of the carriers in the o/p material. As an application of the model, we have calculated the hopping rate of carriers in terms of the contact parameters. Also, we have discussed the hopping of carriers deep into the organic dielectric. Finally, we have explored the hopping rate in practical contacts between polyfluorene-based polymers and different electrodes.     

Josephson fluxonic bipolar junction transistor

Josephson fluxonic bipolar junction transistor (JFBJT) has been proposed as a superconducting amplifying element. The results on a simple realization of this device are provided to demonstrate its working principle. These experiments demonstrate that JFBJT provides current gain without suffering from the problems associated with the regular long junction vortex flow transistors. In particular, no resonance structure is present in its I-V characteristics and its impedance can be matched to any load without degradation of its characteristics. Suggestion is made on how a practical device can be fabricated.     

Quantum chemical studies on molecular conformations,energetic and intramolecular hydrogen bonding in ground and electronic excited state of (thioxosilyl) ethyleneselenol

In this work, a conformational analysis of (thioxosilyl) ethyleneselenol was performed using several computational methods, including density-functional theory (DFT) (B3LYP), MP2 and G2MP2. Harmonic vibrational frequencies were estimated at the same levels to confirm the nature of the stationary points found and also to account for the zero point vibrational energy correction. MES-1 and TES-1 conformers exhibit hydrogen bonding. This feature, although is not the dominant factor in the stability of conformers, appears to be of foremost importance to define the geometry of the molecule. Two intramolecular hydrogen bonds established between the polar groups were identified by the structural geometric parameters. These involved the thiol and selenol functional groups and were identified and characterized by the frequency shift in their stretching vibration modes. Furthermore, the excited-state properties of intramolecular hydrogen bonding have been investigated theoretically using the time-dependent DFT method. The influence of the solvent on the stability order of conformers and the strength of intramolecular hydrogen bonding was considered using the PCM (polarizable continuum model), SCI-PCM (self consistent isodensity-polarizable continuum model) and IEF-PCM (integral equation formalism-polarizable continuum model) methods. The “atoms in molecules” theory of Bader was used to analyze critical points and to study the nature of hydrogen bond in these systems. Natural bond orbital (NBO) analysis was also performed for better understanding the nature of intramolecular interactions. The calculated highest occupiedmolecular orbital and lowest unoccupied molecular orbital energies show that charge transfer occur within the molecule. Further verification of the obtained transition state structures was implemented via intrinsic reaction coordinate analysis. Calculations of the ¹H NMR chemical shift at the GIAO/B3LYP/6–311++G** level of theory are also presented.     

An investigation on the behavior of electrospun ZnO nanofibers under the application of low frequency AC electric fields

In present study, the behavior of electrospun ZnO nanofibers under the application of low frequency alternating (AC) electric fields within the range of 1 Hz–20 kHz was investigated using planar parallel electrodes. In the first stage, ZnO nanofibers with diameters up to 100 nm were prepared by electrospinning. At 1 Hz, the strong electric field-induced fluid flow due to charge redistribution around the electrode swept the fibers on the electrode surface farther from the edges. As the frequency was increased to 1 kHz, most depositing fibers accumulated on the electrode edges and in the meantime, a small fraction of them was pushed into the surface as a result of AC electroosmosis effect. Above 1 kHz, the fibers were assembled within the electrode gap bridging the interelectrode space. The dielectrophoresis force was considered responsible for the assembly and relative alignment of ZnO nanofibers above 1 kHz.     

Effect of polyethylenimine addition and washing on stability and electrophoretic deposition of Co3O4 nanoparticles

In this work, the parameters of cobalt oxide suspension such as conductivity, zeta potential, particle size, stability, and finally the electrophoretic behavior of particles in the absence and presence of polyethylenimine (PEI) in acetone medium were investigated. Also, the effects of washing on the stability and electrophoretic deposition of Co₃O₄ were studied. Characterization of the obtained layer by optical microscopy revealed that there was no deposition in the suspension without PEI, while a uniform layer was formed in the presence of PEI additive. Scanning electron microscopy (SEM) results confirmed the uniformity of layer obtained in acetone using PEI additive. Moreover, SEM results demonstrated that more porous microstructures were obtained at longer deposition durations. The difference in the porosity of the layers, as indicated by the SEM micrographs, is attributed to increase in the deposition time.     

Compiling influence diagrams

This paper examines a class of algorithms for “compiling” influence diagrams into a set of simple decision rules. These decision rules define simple-to-execute, complete, consistent, and near-optimal decision procedures. These compilation algorithms can be used to derive decision procedures for manually solving time constrained decision problems     

Electrophoretic deposition of TiO2 nanoparticles in viscous alcoholic media

In the present study, highly viscous alcoholic media, pentanol, hexanol and heptanol were used for electrophoretic deposition of ceramic (TiO₂) nanoparticles as a new approach in the EPD process. Optical and scanning electron microscopy of the obtained deposits at 50 V revealed that layers with a fairly uniform microstructure were obtained in pentanol and hexanol while the layer formed in heptanol suffered from lack of uniformity and did not cover the substrate even at higher voltages up to 200 V. It was also revealed by the atomic force microscope (AFM) studies that surface roughness of the deposited layers decreased with increasing suspension viscosity. This behavior was directly attributed to high viscosity of heptanol which strongly hinders particles movement through the media. The low dielectric constant of heptanol was also considered to decrease particle deposition.