Influence of Al concentration on structural and optical properties of Al-doped ZnO thin films

Undoped ZnO and Al-doped zinc oxide (ZnO:Al) thin films with different Al concentrations were prepared onto Si (100) substrate by pulsed filtered cathodic vacuum arc deposition system at room temperature. The influence of doping on the structural and optical properties of thin films was investigated. The preferential (002) orientation was weakened by high aluminum doping in films. Raman measurement was performed for the doping effects in the ZnO. Atomic force microscopy images revealed that the surface of undoped ZnO film grown at RT was smoother than that of the Al-doped ZnO (ZnO:Al) films. The reflectance of all films was studied as a function of wavelength using UV–Vis–NIR spectrophotometer. Average total reflectance values of about 35 % in the wavelength range of 400–800 nm were obtained. Optical band gap of the films was determined using the reflectance spectra by means of Kubelka–Munk formula. From optical properties, the band gap energy was estimated for all films.     

Investigation of dielectric properties of different cake formulations during microwave and infrared-microwave combination baking

ABSTRACT:  Dielectric properties can be used to understand the behavior of food materials during microwave processing. Dielectric properties influence the level of interaction between food and high frequency electromagnetic energy. Dielectric properties are, therefore, important in the design of foods intended for microwave preparation. In this study, it was aimed to determine the variation of dielectric properties of different cake formulations during baking in microwave and infrared–microwave combination oven. In addition, the effects of formulation and temperature on dielectric properties of cake batter were examined. Dielectric constant and loss factor of cake samples were shown to be dependent on formulation, baking time, and temperature. The increase in baking time and temperature decreased dielectric constant and loss factor of all formulations. Fat content was shown to increase dielectric constant and loss factor of cakes.     

Accelerated versus standard corneal collagen cross-linking in pediatric keratoconus patients: 24 months follow-up results

Purpose

To compare the 24 month visual, refractive, topographic and aberrometric results of the accelerated and standard corneal collagen cross-linking (CXL) in pediatric keratoconus patients.

Sliding mode PI control with backstepping approach for MIMO nonlinear cross‐coupled tank systems

The control of tank systems in industrial applications is an important issue for monitoring the chemical processes involved in the manufacture and delivery of product. The most important reason to control the tank systems is to keep the liquid level in the tanks constant and at the desired level for a specified period of time. In this study, the sliding mode control (SMC) with a repetitive approach called backstepping that is insensitive to uncertainties in system parameters and input disturbances is proposed and experimentally applied to a quadruple, cross‐coupled, uncertain, nonlinear, and multiple‐input/multiple‐output tank system. A proportional‐integral (PI) control is used to reduce the steady‐state error caused by the parameter variations and external noises. The traditional way of introducing PI usually leads to sliding surfaces. In this paper, the PI action is introduced to the control signal. The proposed backstepping sliding mode PI control (BSMPIC) is applied to such a complex tank system for the first time. The experimental results are compared with those of the SMC, sliding mode PI control, and backstepping sliding mode control to see the effect of the proposed BSMPIC on the system. As a result of the comparison, it is observed that less overshoot and tracking error, better tracking performance, and faster rise time in the transient regime is obtained by the BSMPIC.     

Voltage‐Gated Closed‐Loop Control of Small‐Molecule Release from Alumina‐Coated Nanoporous Gold Thin Film Electrodes

Precise timing and dosing of potent small‐molecule drugs carries significant potential for effective pharmaceutical management of disorders that exhibit time‐varying therapeutic windows such as epilepsy. This study demonstrates the use of alumina‐coated nanoporous gold (np‐Au) thin film electrodes for iontophoretic release of fluorescein as a small‐molecule drug surrogate with picogram dosing and a few seconds temporal resolution. A custom microfluidic platform is engineered to trigger molecular release from an integrated np‐Au chip and monitor the resulting time‐varying fluorescein concentration. Following a systematic study of the influence of applied voltage on loading capacity and release kinetics, a LabVIEW‐based closed‐loop control interface is employed to demonstrate voltage‐gated fluorescein release with preprogrammed arbitrary concentrations waveforms.     

Preparation of iron oxide nanoparticles by microwave synthesis and their characterization

In this study production of fine particle Fe2O3 via microwave processing of Fe(NO3)3.nH2O followed by low temperature annealing was reported. XRD was used to characterize the structural properties of nanoparticles. Approximate particle sizes were between 3-13 nm according to Scherrer's equation. Single point BET measurement results also show that samples have large surface area and they are nanometer sized particles. TEM study was conducted to examine the structure of the nanoparticles. TEM figure is in good agreement with the results obtained from Scherrer's equation using XRD spectra. In order to characterize the magnetic properties of the nanoparticles VSM (Vibrating Sample Magnetometer) was used. From these results it can be concluded that the sample containing only maghemite phase exhibits superparamagnetic behaviour, on the other hand sample containing both hematite and maghemite phases shows paramagnetic behaviour above 300 K, superparamagnetic behavior at lower temperatures.     

The adsorption kinetics and removal of cationic dye, Toluidine Blue O, from aqueous solution with Turkish zeolite

Clinoptilolite, a natural zeolite, was investigated as an inexpensive and effective adsorbent for the adsorption of Toluidine Blue O (TBO) from its aqueous solution. The effect of parameters such as the initial concentration of TBO, the solution of pH, contact time, temperature and particle size on the TBO adsorption was examined. The adsorption rate data were analysed according to the first and second-order kinetic models. Kinetic studies show that adsorption of TBO on clinoptilolite was fitted to the second-order adsorption model with two-step diffusion process. The activation energies for TBO adsorption on clinoptilolite for the first and second diffusion processes were 8.72 kJ mol(-1) and 19.02 kJ mol(-1), respectively. The adsorption isotherm was well fitted to both the Langmuir and Freundlich models. The maximum adsorption capacity of clinoptilolite for TBO was 2.1x10(-4) mol g(-1) at solution pH of 11.0.     

Utilization of Mixolab<Superscript>®</Superscript> to predict the suitability of flours in terms of cake quality

The objective of this study was to determine the possibility of using Mixolab^® to predict the cake baking quality of different wheat flours. Mixolab^® data were also compared with various flour quality characteristics. The correlations between Alveoconsistograph data and the cake quality characteristics were not significant. Therefore, Alveoconsistograph test does not seem to be useful to predict the cake quality of the flour samples. Mixolab^® characteristics C2, C3, C4 and C5 were found to be significantly correlated with volume index while C5 was correlated with hardness of cakes. The parameters C2 to C5 represent the end point of the corresponding mixing stages. The flour samples which gave higher cake hardness values had higher C5 values and the samples with lower cake volumes had higher C2, C3, C4 and C5 values. It seems to be possible to estimate the texture and volume of cakes by these values. Therefore, Mixolab^® seems to be a useful tool to predict the cake making quality of flour samples.     

Illumination and voltage effects on the forward and reverse bias current–voltage (I-V) characteristics in In/In2S3/p-Si photodiodes

Journal of Materials Science: Materials in Electronics - The illumination and voltage effects on the I-V measurements of the fabricated In/In2S3/p-Si photodiode were investigated in dark and under...