Accuracy of Ground-Penetrating Radar for Concrete Pavement Thickness Measurement

Core extraction is the most common method for measuring concrete layer thickness in pavement construction. Although this method provides a very accurate thickness measurement, it is destructive, time-consuming, and does not provide adequate representation of the concrete layer thickness variability. Ground-penetrating radar (GPR) is a nondestructive evaluation technique that has been successfully used in several transportation applications, such as subsurface exploration and condition assessment. The main objective of this research is to investigate the accuracy and cost-effectiveness of using GPR in thickness measurement of concrete pavement for quality assurance purposes. A high-resolution 1.6-MHz ground-coupled antenna was used to perform grid scans and measure concrete thickness for several laboratory and field experiments. Results indicated that the use of metal objects underneath the concrete layer to improve bottom surface reflectivity was necessary for a reliable thickness measurement. Also, the use of calibration cores to determine the actual dielectric properties of the concrete was essential for accurate thickness calculation. An average accuracy of 98.5% was achieved when steel plates were used underneath the concrete layer and two cores were extracted for calibration. The effect of concrete age on GPR thickness measurement accuracy was also investigated.     

Influence of vitamin (B1, B6, B9, B12, C) and ions (Cu2+, Mn2+, PO4 3−) on kefir grain biomass growth

The aim of the present study was to investigate the effects of additions of various vitamins (B₁, B₆, B₉, B₁₂, and C) and minerals (CuSO₄·H₂O, MnSO₄·H₂O, and Na₃PO₄·12 H₂O) on the propagation of kefir grains. The activated kefir grains were inoculated into very low fat (0.1%) cows’ milk under constant temperature (25°C) and impeller speed (100 rpm) for a propagation time of 24 h. After evaluation of the experimental data, the most influential mineral addition providing 39% increase of kefir grain biomass was found to be Na₃PO₄·12 H₂O with a concentration of 0.30 g phosphate (PO₄ ^3?) ion/L. At this optimal condition, a model was also derived for the kefir grain biomass concentration representing pH dependence. This study demonstrated the basis for further research in the direction of kefir grain biomass growth considering the effect of additions of vitamins and minerals to other researchers working in the same field and to dairy industry as well.     

NH3 and H2S adsorption on Au3Pt3 cluster studied by a first principles calculation

The equilibrium atomic structures of the Au₃Pt₃ cluster and NH₃, H₂S molecules are determined by Density Functional Theory calculations. The adsorption of NH₃ and H₂S molecules on Au₃Pt₃ cluster is then studied. The energy levels and the corresponding charge densities, adsorption energies, charge transfer and magnetization are calculated for different adsorption sites. We find that the adsorption generally modifies the structure of the Au₃Pt₃ cluster and the adsorbate. There exists strong interaction between Pt and N atoms. We observe that H₂S dissociate at a specific site for the local density approximation (LDA) and one of the H atoms binds to Pt. In general, there is charge transfer from the molecules NH₃ and H₂S to Au₃Pt₃ cluster, for almost all adsorption sites. This makes the Au₃Pt₃ cluster semiconducting.     

The application of some polydentate Schiff base compounds containing aminic nitrogens as corrosion inhibitors for mild steel in acidic media

The effect of three Schiff base compounds namely, (E)-2-(1-(2-(2-hydroxyethylamino)ethylimino)ethyl)phenol(I), 2,2′-(1E,1′E)-1,1′-(2,2′-azanediylbis(ethane-2,1-diyl)bis(azan-1-yl-1-ylidene))bis(ethan-1-yl-1-ylidene)diphenol(II) and 2,2′-((2E,12E)-3,6,9,12-tetraazatetradeca-2,12-diene-2,13-diyl)diphenol(III) on the corrosion behavior of steel in 2 M HCl solution has been investigated at 298 K by weight loss measurements, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) methods. The inhibition efficiencies obtained from all methods employed are in good agreement. Results show compound III to be the best inhibitor with a mean efficiency of 93% at 10⁻² M additive concentration. Studies showed all three compounds to act as mixed type inhibitors and to obey the Langmuir adsorption isotherm.     

Topology Management in Directional Antenna-Equipped Ad Hoc Networks

With fully directional communications, nodes must track the positions of their neighbors so that communication with these neighbors is feasible when needed. Tracking process introduces an overhead, which increases with the number of discovered neighbors. The overhead can be reduced if nodes maintain only a subset of their neighbors; however, this may increase the length of paths between node pairs in the network. In this work, we study the tradeoffs between node degree and path stretch. We first design a topology control algorithm to optimize this tradeoff. Assuming that nodes communicate with their directional neighbors using circular directional transmissions, we model the original graph as a unit disk graph (UDG). Given a UDG G, our algorithm finds a sparse subgraph G' with a maximum degree of 6, and connecting each node pair u,v by a path of length hops_{G'}(u,v)=O(hops_G(u,v)+logDelta), where Delta is the maximum degree in G, hops_{G}(u,v) denotes length of the shortest path between u, v in G. We show that this result is near-optimal. Based on the insights gained from this design, we next construct a simpler, more practical scheme that integrates fully-directional neighbor discovery and maintenance with topology control strategy. We simulate both algorithms and compare their performances.     

OXIDATION OF TUNC cedil;BĪLEK LIGNITE WITH CUPRIC HYDROXIDE

Abstract

Tun çbilek lignite was oxidized with alkaline cupric hydroxide at 170°C for 5 hrs. The oxidation products soluble in ether were examined by gas chromatography/mass spectrometry. The results Indicate the presence of compounds containing guaiocyl nucleus which are known as characteristic lignln oxidation products.     

On the realization of oscillators using state equations

In this work, an extension to the oscillator synthesis method using the state variable technique is presented. It is shown that using suitable block diagrams, which represent the state equations, systematic circuit realizations can be performed. The most critical steps of the presented method are the selection of the suitable characteristic equation and thederivation of the corresponding sub-circuits. The selection criteria of thecharacteristic equations for the realization of single resistance controlled oscillators (SRCOs) are also given. By using the extended state variable synthesis method, SRCOs employing a single current feedback amplifier (CFA)are obtained. Furthermore, a new active element, namely the differentialvoltage current feedback amplifier (DVCFA) is proposed for the realization of oscillators employing only grounded capacitors and new SRCOs employing thisactive element are presented. SPICE simulations and experimental results confirm the operation of the presented oscillators.     

A generic model for diffusive dynamics of the substrate and fluorescein tagged enzyme in microfluidic platform

Microsystem Technologies - The aim of this study was to develop a model that describes enzymatic conversion in a microfluidic system along with convective and diffusive transport of...     

Design of a high performance mutually coupled circuit

A novel high performance transconductor-based mutually coupled circuit topology is presented, employing four active devices (six, if differential-output devices are not available) and only grounded passive elements. The primary and secondary self-inductances and the mutual inductance can be controlled independently. Being constructed with integrator and transconductor blocks, the circuit offers excellent sensitivity, stability and high frequency performances. The current-conveyor-based implementation is also presented to avail comparison with previous counterparts. Via measurements and simulations, theoretical predictions are verified and the comparisons are performed. As an RF application example, a tuned amplifier is built and simulated.