Durability properties of concrete with blended cements

The study of chloride‐induced corrosion started more than three decades ago, after extensive cases of damage were observed on reinforced concrete structures in coastal regions and on infrastructural objects exposed to salt action. Nowadays, the basis for sustainable concrete industry lies in these three aspects: reducing CO₂ emissions by using by‐products of other industries (slag, fly ash, silica fume) for cement production, conservation of natural resources by replacing part of the aggregate with recycled construction waste, as well as use of recycled water in concrete production, and finally, construction of durable concrete structures. Durability design procedures for reinforced concrete structures in aggressive environments are still to a large extent empirical, especially in the case of using blended cements. The type of cement has a considerable effect on the properties of concrete, especially concrete resistance to the penetration of chloride ions. The paper presents results of testing durability and deformational properties of concrete produced with quaternary‐blended cement. A clearer insight into these properties is a necessary starting point for the performance‐based design of concrete prepared with blended cements, leading to more durable and corrosion‐free concrete structures in aggressive environments.     

Preparation of TiO2 coated silicate micro-spheres for enhancing the light diffusion property of polycarbonate composites

The TiO₂ coated silicate micro-spheres (SMS) core–shell particles (SMS@TiO₂) were synthesized using the sol–gel reaction followed by calcination. The SMS@TiO₂ particles were used to enhance the light diffusion property of polycarbonate (PC) composites. Our experimental analysis shows that the TiO₂ was coated on the SMS particles and the optimum parameters of the reaction were 4:1 of the Si/Ti molar ratio and 500 °C of the calcination temperature. The UV–Vis spectra indicate that SMS@TiO₂ can absorb or hinder the UV light, which may prolong the service life of PC light diffusion materials. Compared to that of PC composites physically mixed with SMS + TiO₂, the haze of the PC/SMS@TiO₂ composites was little affected, while the transmittance was obviously enhanced, which can be increased from 55.5% for PC/TiO₂/SMS to 70.3% for PC/SMS@TiO₂ with only 0.6 wt% filler loading.     

A CAD tool for an array of differential oscillators coupled through a broadband network

A new expression of the equations describing the locked states of two oscillators coupled through a resistor is presented in this article. This theory has led to the elaboration of a CAD tool which provides, in a short simulation time, the frequency locking region of two coupled differential oscillators. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Bacterial communication systems: A mathematical formulation of negative chemotaxis

The emergence of molecular communication (MC) has provided a new paradigm for communication at nanoscale, besides the electromagnetic one. Numerous biological systems have been proposed that could be used for communication, using mostly bacteria as information carriers, ensuring biocompatibility and low complexity requirements. In this work, message dissemination dynamics in a bacterial communication system was under investigation by means of a simulation framework that was designed and developed based on a commercial tool. A mathematical formulation is proposed, in an effort to accurately predict the system's behavior under the presence of chemotactic‐like nodes. Simulation results are in strong agreement with the respective mathematical model, for a wide range of biological processes, including phenomena such as chemotaxis, bacterial growth cycle, and biological message transformation dynamics. In the case of a simple simulation scenario exhibiting chemotaxis, the mean accuracy improvement reaches values of up to 19% .     

Parameterized ABD preconditioning technique for time-periodic convection–diffusion problems

In this paper, a parameterized additive block diagonal (PABD) preconditioning technique is present for solving the nine-point approximations of the time-periodic convection–diffusion problems. The explicit expressions for the eigenvalues and eigenvectors of the corresponding preconditioned matrices are presented. The range of the optimal parameters is derived. Numerical experiments show that the generalized minimal residual method preconditioned by the PABD preconditioner with the experimental optimal parameters or some special values is effective for a wide range of problem sizes.     

Bridging TiO2 nanoparticles using graphene for use in dye‐sensitized solar cells

The use of graphene to bridge TiO₂ particles in the photoanode of dye‐sensitized solar cell for reduced electrical resistance has been investigated. The difficulty in dispersing graphene in TiO₂ paste was overcome by first dispersing graphene oxide (GO) into the TiO₂ paste. The GO was then reduced to graphene after the sintering of TiO₂. This is shown through transmission electron microscopy and X‐ray photoelectron spectroscopy analysis. Cell performance was evaluated using a solar simulator, incident photon to electron conversion efficiency, intensity modulated photocurrent/photovoltage spectroscopy under blue light, and electrochemical impedance spectroscopy. Depending on the amount of graphene in the photoanode, the cell performance was enhanced to different degrees. A maximum increase of 11.4% in the cell efficiency has been obtained. In particular, the inclusion of graphene has reduced the electron diffusion time by as much as 23.4%, i.e. from 4.74 to 3.63 ms and increased the electron lifetime by as much as 42.3%, i.e. from 19.58 to 27.85 ms. Copyright © 2014 John Wiley & Sons, Ltd.     

The assessment of scattered light in ophthalmic materials

The assessment of scattered light in lenses, sunglasses and eye protection has been carried out in various ways. Wide‐angle scatter (haze) is used in the United States, Australia and New Zealand. Small‐angle scatter (light diffusion) is specified in Europe. Little is known of the relationships within and between the methods. In an international standard, a single method is generally required. The measurement of wide‐angle scatter (haze) (two variations of a method) and small‐angle scatter (light diffusion) (three variations of a method) were carried out on 12 samples, 4 abraded, 4 with inclusion defects and 4 with surface coating defects, in an international inter‐laboratory comparison. The consensus means and confidence limits were used to compare two haze methods: the “Basic” light diffusion method and two variations of the “Simplified” light diffusion method. For abraded samples, haze and light diffusion measures are linearly related. For the remaining samples, the haze method was a much more sensitive detector of low levels of light scatter. The three measures of light diffusion are highly linearly correlated. Haze is the more sensitive measure for lower levels of light scatter when due to smaller scattering elements. The Basic and Simplified methods are highly linearly correlated. The red laser Simplified method returns a value 10% lower than that of the Basic method, and the green laser Simplified method returns a value 12% higher than that of the Basic method. These can be accounted for by a calibration factor or different acceptance values. © 2015 Wiley Periodicals, Inc. Col Res Appl, 41, 416–423, 2016     

A New Approach to Linear Temperature Programming Calculations

Abstract

The theory of temperature programming has been reexamined. It is shown that a linear program leads to an explicit relation for the retention temperature in terms of the inverse exponential integral. Numerical examples are solved using a straight line plot of the exponential integral together with a plot based on the equivalent temperature concept. A simple explicit expression in terms of common functions for the retention temperature during linear temperature programming was deduced. This was made possible using the inverse log nonlinear program which can be made to approximate quite closely a linear program. This expression was used to explain the constancy of intervals and other phenomena encountered during the linear temperature programming of homologous series.     

Adsorption of butanol from aqueous solution onto a new type of macroporous adsorption resin: Studies of adsorption isotherms and kinetics simulation

BACKGROUND: Owing to the rapid depletion of petroleum fuel, the production of bio‐butanol has attracted much attention. However, low butanol productivity severely limits its potential industrial application. It is important to establish an approach for recovering low‐concentration butanol from fermentation broth. Experiments were conducted using batch adsorption mode under different conditions of initial butanol concentration and temperature. Batch adsorption data were fitted to Langmuir and Freundlich isotherms and the macropore diffusion, pseudo‐first‐ and second‐order models for kinetic study. RESULTS: The maximum adsorption capacity of butanol onto KA‐I resin increase with increasing temperature, ranged from 139.836 to 304.397 mg g^?1. The equilibrium adsorption data were well fitted by the Langmuir isotherm. The adsorption kinetics was more accurately represented by the macropore diffusion model, which also clearly predicted the intraparticle distribution of the concentration. The effective pore diffusivity (D_p) was dependent upon temperature, but independent of initial butanol concentration, and was 0.251 × 10^?10, 0.73 × 10^?10, 1.32 × 10^?10 and 4.31 × 10^?10 m² s^?1 at 283.13, 293.13, 303.13 and 310.13 K, respectively. CONCLUSION: This work demonstrates that KA‐I resin is an efficient adsorbent for the removal of butanol from aqueous solutions and available for practical applications for future in situ product recovery of butanol from ABE fermentation broth. Copyright © 2012 Society of Chemical Industry     

Computer Simulation Study of Transient Diffusion of Cesium through Granite with Unsteady-State Diffusion Model

A steady-state diffusion model has been used widely to determine the diffusivities of radionuclides in rocks. Buffer container at the source solution side is used to keep the concentration constant. It is suitable for non-sorptive species, but not for sorptive species. Some researchers proposed a unsteady-state diffusion model recently. It is possible to use simple experimental apparatus without buffer container to measure the diffusivity with this model. To obtain the diffusional information more easily according to the sorption properties of radionuclides, through- diffusion experiments were performed in granites. Methods of determining of diffusivities are discussed according to sorption properties of species. For the non-sorptive species, the steady- state diffusion model was effective to determine the diffusivity. For the sorptive species, the analytical solution of the unsteady-state diffusion model found to be more appropriate to determine the diffusivity. Surface diffusion of sorbed species on rock did important role in diffusive transport.