Influence of drying temperature upon some mechanical properties of beech wood

The paper presents the results obtained in an experimental study concerning the influence of drying temperature upon the mechanical properties of beech wood (Fagus sylvatica L.). Sound wood samples without red heart were cut from white (unsteamed) beech timber parts, dried at different temperatures: 20 °C, 80 °C, 90 °C, 100 °C, 115 °C and same relative air humidity: 50%. After performing classical tests for evaluation of some selected mechanical properties, the following conclusions could be drawn: all bending properties (static bending strength, modulus of elasticity and impact bending strength) increased with increasing temperature, confirming thus the benefiting effect of heat upon wood plasticity. The tensile strengths, both parallel and perpendicular to grain, increased with increasing temperature, but only in the range below 100 °C; as soon as the temperature exceeded this value, the tensile strengths began decreasing. As far as compression strength parallel to grain, shearing strength and splitting resistance is concerned, no significant influence of temperature could be established. However, it seems that these properties are negatively affected by kiln-drying, as even with low kiln-drying temperatures these strengths are much lower than in case of air-drying.     

Pt nanoparticles on graphene – polyelectrolyte nanocomposite: Investigation of H2O2 and methanol electrocatalysis

Poly (diallyldimethylammonium chloride) (PDDA) functionalized graphene oxide (GO) decorated with Pt nanoparticles (PtNPs) was obtained and investigated. This hybrid nanocomposite material was morphologically characterized by several instrumental techniques like high-resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD). Good coverage of crystalline Pt nanoparticles was achieved, the average diameter being 2 nm, meanwhile in the absence of polyelectrolyte the average diameter increased up to 4 nm. The electrocatalytic properties of this hybrid nanocomposite against H₂O₂ and methanol were ascertained by cyclic voltammetry. A modified glassy carbon electrode (GC) was able to reduce H₂O₂ at positive potentials (starting from ∼150 mV vs. Ag/AgCl) meanwhile for methanol the ratio of the forward anodic peak current (I_f) to the reverse anodic peak current (I_b) was 1.42, indicating good tolerance of the catalyst towards the intermediate carbonaceous species accumulated on the electrode surface.     

Investigation of the effects of multiple pressures in the lower Danube basin

The main scope of the paper is the implementation of future scenarios in the Lower Danube basin, supporting the development of River Basin Management Plans and future environmental policies. The 800 000 km² Danube River Basin extends across 19 countries, of which 14 are contracting parties of the ICPDR. The Lower Danube is occupied mostly by Romania, including the Danube Delta. The Danube Delta hydrological complex covers 5800 km² comprising over 300 lakes, three main branches and a vast network of channels. Changes impacting significant ecosystem services such as recreation, fishing, flows, ecotourism, flood regulation, navigation and reed/wood resources have to be evaluated and the quantification of those elements must be performed in order to incorporate them into the modelling process.     

Light-based string matching

String matching is a very important problem in computer science. The problem consists in finding all the occurrences of a pattern P of length m in a text T of length n. We describe a special device which can do string matching by performing n−m + 1 text-to-pattern comparisons. The proposed device uses light and optical filters for performing computations. Two physical implementations are proposed. One of them uses colored glass and the other one uses polarizing filters. The strengths and the weaknesses of each method are deeply discussed.     

The Generalized Topological Formula for Transfer Function Generation by Two-Graph Tree Enumeration

In this paper the topological approach for transfer function generation by two-graph tree enumeration is presented. The generalized topological formula with homogeneous parameters is proved for all the circuit functions, and a simple representation of the four types of controlled sources by admittances is proposed, that allows a uniform treatment of the entire circuit in terms of admittances. To implement our procedure, the rules to automatically generate the two graphs and to enumerate the common spanning trees are presented. Some simplifications in the circuit and in the two graph structure before tree generation and a graph representation on levels, improve the efficiency of the tree enumeration procedure. An illustrative example is presented and a reduced symbolic form of the network function is obtained by some simplifications after generation. Mihai Iordache received the B.S. and Ph.D. degrees in electrical engineering from the Politehnica University of Bucharest, Romania, in 1967 and 1977, respectively. He is a Full Professor in the Electrical Department, Politehnica University of Bucharest, where he is working in the areas of circuit analysis and simulation, and in the Electrical Engineering Fundamentals. He is Doctoral Advisor at the Politehnica University of Bucharest, and the author or coauthor of more than 100 journal papers and 15 books. He is also a reviewer of different Scientific Conferences in the Analysis and Simulation Circuits. His research interests include nonlinear circuits, symbolic analysis circuits, computer-aided design of large-scale circuits, decomposition techniques for large-scale circuit analysis and simulation, and topological analysis of electric circuits. He was the recipient of the 2000 Romanian Academy Award. Currently, he is the Dean of the Electrical Engineering Faculty. Lucia C. Dumitriu received the B.S. and Ph.D. degrees in electrical engineering from Politehnica University of Bucharest, Romania, in 1974 and 1987, respectively. She is currently a full Professor in the Electrical Department, Politehnica University of Bucharest, teaching and doing research on Electrical Engineering Fundamentals, and Circuit Theory—methods, algorithms, and software tools for analysis and simulation. She is the author or coauthor of more than 100 journal papers and 12 books and monographs. Her research interests include analysis and simulation of analog circuits, symbolic analysis, computer-aided design of large-scale circuits. She was the recipient of the 2000 Romanian Academy Award.     

Synthesis, structural characterization and photocatalytic activity of Ti-MCM-41 mesoporous molecular sieves

This paper reports the applicability of hydrothermal synthesis in alkaline medium for preparation of Ti-containing mesoporous MCM-41 materials. The influence of different parameters was investigated, such as the Ti source, the molar ratio between Si and Ti and also the synthesis temperature. Structural analysis shows that the high specific surface area, large pore size and well ordered mesostructure, are partially retained in the titania containing materials. Modifying synthesis temperature, it was shown that MCM-41 isotherms are different for temperatures above or under 140°C. UV-VisDR spectroscopy was used to investigate the local environment of Ti sites. The obtained materials were evaluated for the photocatalytic degradation of Rhodamine 6G in aqueous medium. The best photocatalytic activity was found for the sample prepared at higher ageing temperature of 160°C, at which anatase particles were formed.     

Finite element analysis and analytical simulations of Suspended Gate-FET for ultra-low power inverters

This paper proposes, the investigation of the Suspended Gate Field-Effect Transistor (SG-FET) small-slope switch based on a hybrid numerical simulation approach combining ANSYS^TM Multiphysics and ISE-DESSIS^TM in a self-consistent system. The proposed numerical simulations uniquely enable the investigation of the behavior and the physics of complex micro-electro-mechanical/solid-state devices, such as the SG-FET. Abrupt switching as well as the effect of trapped charges in the gate dielectric are demonstrated. The numerical data serve to calibrate an analytical EKV-based SG-FET model, which is then used to design and originally simulate a sub-micron (90 nm) scaled SG-FET complementary inverter. It is shown that, due to abrupt switching in the subthreshold region and electro-mechanical hysteresis, the SG-FET inverter could deliver a significant power saving (1–2 decades reduction of inverter peak current and practically no leakage power) compared to traditional CMOS inverter.     

Scarce-resource capacity sharing in cognitive radio environments: a new game theoretical model

This paper proposes a novel model of the input impedance of a circular-loop antenna based on wave equations. A circular-loop antenna is equivalent to uniform parallel double wires with losses and a short circuit load. The characteristic impedance, the propagation coefficient and the inductance, capacitance and resistance per unit length of the uniform parallel double wires with losses can first be expressed as closed solutions, and the mathematical model of the input impedance of the circular-loop antenna can then be derived naturally from the wave equations. Comparison of the data curve from this model with curves from simulations and experiments show that they are similar; however, some discrepancies are observed, and are attributed to the estimation error of the radiation resistance of the circular-loop antenna. As long as the circular-loop antenna is made from an isotropic material and its size remains uniform, the equivalent method is valid electrically for both small- and large-sized circular-loop antennas.