KINETICS FOR LOW TEMPERATURE PYROLYSIS OF BLACK LIQUOR

A kinetic study of pyrolysis of dried black liquor was performed using a Netzsch 429 Thermogravimetric Analyzer. It was found that as conversion increases from 10 to 45% the apparent pyrolysis activation energy for black liquor increases from 77.20 to 112.74 KJ/mol. For black liquor the order of reaction was found to be first-order. The reaction rate constant was found to be 2.12×10⁹ min. These results are in agreement with the data reported by other investigators on biomass pyrolysis.     

Excavation and support design of the Dicle–Kralkizi water tunnel: an overview

Tunneling projects have their uniqueness in terms of engineering problems. The expertise gained from analyzing these projects establishes a sound basis for future application. This paper conveys experiences gained during the construction and support of the design of the Dicle–Kralkizi water tunnel, Turkey. Tunnel stability problems including overbreaks and surface subsidence are evaluated. An analysis of the breakdowns, factors controlling advance rate and the overall performance of tunnel are covered. The accumulated information presented here is believed to be useful and reliable for a successful tunnel excavation in similar formations.     

Determination of the optimum conditions for ion nitriding of AISI 5140 steel

AISI 5140 low alloy steel was ion nitrided under different process parameters including time (1, 4, 8 and 12 h), temperature (400, 450, 500 and 550 °C) and gas mixture ratio (0.05, 0.33, 1 and 3 N₂/H₂). By determining the fatigue strength, surface hardness, compound layer thickness and case depth, the optimum working conditions were determined by using a Taguchi design of experiment. After ion nitriding process, it is aimed to maximize fatigue strength, surface hardness and case depth as well as to minimize compound layer thickness. While the optimum conditions were determined, due to the goals (above aims) more than one being, the trade-off among goals was considered. First of all, each goal was optimised, separately. Then, all the goals were optimised together, considering the priority of the goals, and the optimum results were obtained at 0.05 N₂/H₂ gas mixture ratio, at the temperature of 450 °C and for 12 h process time.     

Medical image segmentation with transform and moment based features and incremental supervised neural network

In this study, a novel incremental supervised neural network (ISNN) is proposed for the segmentation of medical images. Performance of the ISNN is investigated for tissue segmentation in medical images obtained from various imaging modalities. Two feature extraction methods based on transform and moments are comparatively investigated to segment the tissues in medical images. Two-dimensional (2D) continuous wavelet transform (CWT) and the moments of the gray-level histogram (MGH) are computed in order to form the feature vectors of ultrasound (US) bladder and phantom images, X-ray computerized tomography (CT) and magnetic resonance (MR) head images. In the 2D-CWT method, feature vectors are formed by the intensity of one pixel of each wavelet-plane of different energy bands. The MGH represents the tissues within the sub-windows by using the spatial variation of image intensities. In this study, the ISNN and Grow and Learn (GAL) network are employed for the segmentation task. It is observed that the ISNN has significantly eliminated the disadvantages of the GAL network in the segmentation of the medical images.     

DESIGN OF TEMPERATURE CONTROLLED QUARTZ CRYSTAL MICROBALANCE SYSTEM

In this study, the dual modulated quartz crystal microbalance (QCM) with heating and cooling control has been developed for the quantitative determination of biological molecules, as a biosensor. On the other hand, since, the Sauerbrey formula is misprinted in some publications, the correct form of formula is also discussed. The proposed QCM biosensor has three main parts, which are the oscillator circuit, temperature control circuit, and the differential frequency measurement unit. Colpitts oscillators with the buffer amplifier, microcontroller (PIC16F877) for the temperature control circuit and a peltier element were used for heating and cooling inside the developed system. Differential frequency measurement is a known technique to compensate environmental effects causing instability of crystals. For this reason, one of the crystals is implemented with oscillatory circuits, i.e., the detector; the other one is used as the reference. The designed system was tested between 8°C and 50°C and frequency shift versus temperature is observed at 0.5 ppm/°C over a given temperature range.     

An eco-friendly process: Predictive modelling of copper adsorption from aqueous solution on Spirulina platensis

The adsorption of copper ions on Spirulina platensis was studied as a function of contact time, initial metal ion concentration, and initial pH regimes. Characterization of this adsorbent was confirmed by FTIR spectrum. Modified Gompertz and Logistic models have not been previously applied for the adsorption of copper. Logistic was the best model to describe experimental kinetic data. This adsorption could be explained by the intra-particle diffusion, which was composed of more than one sorption processes. Langmuir, Freundlich, and Redlich–Peterson were fitted to equilibrium data models. According to values of error functions and correlation coefficient, the Langmuir and Redlich–Peterson models were more appropriate to describe the adsorption of copper ions on S. platensis. The monolayer maximum adsorption capacity of copper ions was determined as 67.93 mg g^?1. Results indicated that this adsorbent had a great potential for removing of copper as an eco-friendly process.     

Improvement of Palm Oil Biodiesel Filterability by Adsorption Methods

Palm oil biodiesel (POB) is characterized by a very high cold soak filtration time (CSFT), which places the acceptability of this biofuel at risk. Therefore, the effect of four adsorbents, namely diatomaceous earth, natural silicate (NS), neutral bleaching earth (NBE), and acid activated bleaching earth (AABE), at two levels of addition (1 and 5 wt%) or two temperatures (25 and 110 °C) on the precipitate content and CSFT of POB was investigated. The impact on total glycerin content, moisture content, and oxidative stability was also examined. All treatments significantly decreased the precipitate content, total glycerin content, and moisture content, but only treatments with NS, NBE, and AABE at 5 wt% and 25 °C achieved acceptable filterability. The OSI value was also decreased; however, it remained above the ASTM limit. Operational conditions of treatment with AABE were further optimized in a two‐factor, five‐level center composite design. The combination of 0.65 wt% AABE and 10 min at 25 °C decreased CSFT to below the ASTM limit. Lower adsorbent concentrations could be effective down to 0.44 wt%, given a corresponding increase in the contact time up to 30 min.     

Effect of calcium hydroxide removal techniques on the bond strength of root canal sealers

To evaluate the influence of calcium-hydroxide(CH) with different vehicles on the push-out bond strength of different canal sealers to radicular dentin. 152 decrowned single-rooted human teeth were used. After preparation of root canals with nickel-titanium rotary files, 8 roots served as control groups. Then, the roots were divided as follows: (1) Calasept and (2) Surepaste (n = 72). Roots were further subgrouped according to the CH removal techniques: (1) %17 ethylenediaminetetraacetic acid (EDTA) + rotary file, (2) %17EDTA + hand file, and (3) %17EDTA (n = 24). Eight roots from each group sectioned longitudinally, divided into two pairs and photographed by stereomicroscope (n = 16). The remaining 16 roots in CH intracanal dressing groups were further divided into 2 subgroups according to the sealer used: (1) AH-Plus-jet and (2) Apexit-Plus (n = 8). Bond strengths of the root canal sealers to root canal dentin were measured using a push-out test setup. The data were statistically analyzed using multivariate analysis of variance p = 0.05. The push-out bond strength values were significantly affected by type of vehicle and the removal techniques (p < 0.05). The mean bond strength of AH-Plus-jet was significantly higher than Apexit-Plus, regardless of type of vehicle and the removal techniques (p < 0.05). There was no difference between vehicles on CH removal (p > 0.05). When examining the removal techniques, only irrigation with %17 EDTA left significantly larger amount of residue (p < 0.05). AH-Plus-jet showed better dislocation resistance than Apexit-Plus. Type of vehicle does not play a fundamental role in the degree of persistence of CH residues on the dentin walls. Instrumentation improves the removal efficiency of CH from root canal.     

Design of a front-end integrated circuit for 3D acoustic imaging using 2D CMUT arrays

Integration of front-end electronics with 2D capacitive micromachined ultrasonic transducer (CMUT) arrays has been a challenging issue due to the small element size and large channel count. We present design and verification of a front-end drive-readout integrated circuit for 3D ultrasonic imaging using 2D CMUT arrays. The circuit cell dedicated to a single CMUT array element consists of a high-voltage pulser and a low-noise readout amplifier. To analyze the circuit cell together with the CMUT element, we developed an electrical CMUT model with parameters derived through finite element analysis, and performed both the pre- and postlayout verification. An experimental chip consisting of 4 X 4 array of the designed circuit cells, each cell occupying a 200 X 200 microm2 area, was formed for the initial test studies and scheduled for fabrication in 0.8 microm, 50 V CMOS technology. The designed circuit is suitable for integration with CMUT arrays through flip-chip bonding and the CMUT-on-CMOS process.