Utilization of borogypsum as set retarder in Portland cement production

Boron ores are used in the production of various boron compounds such as boric acid, borax and boron oxide. Boric acid is produced by reacting colemanite(2CaO·3B₂O₃·5H₂O) with sulphuric acid and a large quantity of borogypsum is formed during this production. This waste causes various environmental problems when discharged directly to the environment. Portland cement is the most important material in the building industry. This material is produced by adding about 3-5% gypsum (CaSO₄·2H₂O) to clinker as a set retarder. The aim of this study was to stabilize borogypsum, and to produce cements by adding borogypsum instead of natural gypsum to clinker. Concrete using cement produced with borogypsum was tested to find the mechanical properties and the test values were compared with those of concrete from cement with natural gypsum. Compressive strength of concrete from cement produced with borogypsum was found to be higher than that of natural gypsum. Also, the setting time of cement with borogypsum was longer than that of the Portland cement.     

Effect of Defect Size on Subsurface Defect Detectability and Defect Depth Estimation for Concrete Structures by Infrared Thermography

This study aims to reveal the effect and correlation of delamination size and defect shape for using infrared thermography (IRT) through FE modeling to enhance the reliability and applicability of IRT for effective structural inspections. Regarding the effect of delamination size, it is observed that the temperature difference between sound and delaminated area (\(\Delta \)T) increases as the size of delamination increases; however, \(\Delta \)T converges to a certain value when the area is 40 \(\times \) 40 cm and the thickness is 1 cm. As for the shape of delamination, it can be assumed that if the aspect ratio which is the ratio of the length of the shorter side to the longer side of the delamination is more than 25%, \(\Delta \)T of any delaminations converges to \(\Delta \)T of the same area of a square/circular-shaped delamination. Furthermore, if the aspect ratio is 25% or smaller, \(\Delta \)T becomes smaller than the \(\Delta \)T of the same area of a square/circular-shaped delamination, and it is getting smaller as the ratio becomes smaller. Furthermore, this study attempts to estimate depths of delaminations by using IRT data. Based on the correlation between the size of delamination and the depth from the concrete surface in regard to \(\Delta \)T, it was assumed that it was possible to estimate the depth of delamination by comparing \(\Delta \)T from IRT data to \(\Delta \)T at several depths obtained from FE model simulations. Through the investigation using IRT data from real bridge deck scanning, this study concluded that this estimation method worked properly to provide delamination depth information by incorporating IRT with FE modeling.     

Determination of the Failure Susceptibility of a Flat Die Used in Biomass Pelletizing Machines by Means of FEA-Based Design Exploration

This paper focuses on a design analysis of a flat die used in an agricultural biomass pelletizing machine by considering its high-pressure loading failure susceptibility. The pellet die is one of the key elements in a pelletizing machine, and the strength of the die plate has an important role on the pellet’s quality and producibility. In fact, higher compression ratio (CR—the ratio of effective length and the internal (press channel) diameter of a die orifice/hole) will provide denser pellets which is a desired phenomenon, however, if the compression pressure is too high or CR is not determined to compensate high pressures, the raw material may block the die and the die may experience deformation failure due to overloading. If the desire is to make high-quality pellets with no die failure, optimum flat die hole/orifice design parameters should be used which can provide the best CR for a specific compression pressure. This is the core motivation of this research. In this study, finite element analysis (FEA)-based design exploration has been utilized for a sample single hole flat die with various die geometry parameters against various compression pressure values. Following the FEA design exploration undertaken, a response surface analysis (RSA) was carried out and then estimation models (empirical equations), which could be used to calculate parameters of the die hole/orifice against applied compression pressure and failure susceptibility based on structural stress and deformation, was described. The results gained from the RSA have indicated that the estimation models have high R² values (higher than 98%) which could be used for adequately predicting failure susceptibility indicators. In addition to this, FEM-based simulation printouts have provided useful stress distribution visuals on the die against different compression pressure values. Most especially, the study has highlighted that a detailed structural optimization study may be scheduled in order to obtain die geometry design parameters with a focus on the failure susceptibility.     

Fuzzy diffusion filter with extended neighborhood

Anisotropic diffusion filters, which are motivated from heat diffusion between mediums, have become a widely used technique in the field of image processing. In the initial proposals of anisotropic diffusion filters, 4-neighborhood values with diffusivity functions are computed independently for each spatial location because of numerical approximation. However, anisotropic diffusion filters could not be used in real-time image and video processing applications because they need diffusivity parameters, which must be specified by users in every sampling period. In this study, a fuzzy adaptive diffusion filter using extended neighborhood without diffusivity functions has been developed. The fuzzy adaptive diffusion filter does not require any parameter chosen by user and therefore they could be employed in real-time applications. In the fuzzy adaptive diffusion filter, a similarity transformation by means of relation matrix and fuzzy logic is carried out. Accordingly, the similarity image, output of transformation, is directly used as a heat diffusion coefficient in the diffusion filter. Results show that the fuzzy adaptive diffusion filter is very efficient for removing noise in image while preserving edges.     

An electrochemical and microstructural characterization of steel-mortar admixed with corrosion inhibitors

The present research brings new insights on the role of admixed corrosion inhibitors in the processes of cement hydration and rebar corrosion. The admixing of NaCl and the corrosion inhibitors in fresh mortar was found to alter the morphology and microstructure of the hardened mortar at the steel-mortar interfacial region. The admixing of the inhibitors increased the risk of carbonation of cement hydrates at the steel-mortar interfacial region, but partially displaced chloride ions. Chloride and the admixed inhibitors facilitated the formation of different cement hydrates and affected chloride binding at the steel-mortar interfacial region. The admixing of all three inhibitors was found to increase the polarization resistance of steel, indicating reduced corrosion rate of the steel over 48-day exposures to salt ponding.     

Hydropower Optimization for the Lower Seyhan Basin System in Turkey using dynamic programming

Abstract

Dynamic programming with successive approximation has been used in the past for optimizing multi-reservoir water resources systems. In this study, a State Incremental Dynamic Programming (SIDP) model is developed for energy optimization of multi-reservoir systems. A random file access method is used to generate initial and intermediate data and cope with the curse of dimensionality of dynamic programming. The conventional dynamic programming method is used for each single reservoir to find the initial trajectory of the reservoirs. Then, the computer program developed in the study is applied to the multipurpose-multi-reservoir system in lower Seyhan basin, which comprises six reservoirs, some serial and some parallel. Extended historical flows are used to first maximize firm energy in the critical period, and then total energy over the entire period of flow records. The program is run with 50-year long segments (20 flow scenarios) of the synthetic flow data generated by using the hec-4 generalized computer program to account for the stochastic nature of streamflows. A 20% approximate increase in total energy is obtained by using the developed model for the lower seyhan basin system as compared to that calculated previously by conventional methods.     

Hydropower Optimization for the Lower Seyhan System in Turkey using Dynamic Programming

Abstract

Dynamic programming with successive approximation has been used in the past for optimizing multi-reservoir water resources systems. In this study, the State Incremental Dynamic Programming (SIDP) model is developed for energy optimization of multi-reservoir systems. A random file access method is used for reaching initial and intermediate data to cope with the curse of dimensionality of dynamic programming. A conventional dynamic programming method is used for each single reservoir to find the initial trajectory of the reservoirs. Then, the computer program developed in the study is applied to the multipurpose-multi-reservoir system in Lower Seyhan Basin, which has six reservoirs, some of which are serial and some parallel. First, extended historical flows were used to maximize firm energy in the critical period, and then total energy in the total flows. The program was run with 50-year long segments (20 flow scenarios) of the synthetic flow data generated by using the HEC-4 generalized computer program to take into account the stochastic nature of stream flows. An increment of approximately 20 percent in total energy was obtained by using the model for the Lower Seyhan System, as compared to that calculated previously by conventional methods.     

Mechanical and electromechanical properties of piezoelectric ceramic fibers drawn by the alginate gelation method

Piezoelectric ceramic fibers are widely used in piezocomposite devices. The various methods that are used to draw ceramic fibers differ in the way the fiber form is obtained, which in return closely affects the density, uniformity and the properties of the fibers that are obtained at the end. In this study, the processing-property relationship in the piezoceramic fibers drawn using the alginate gelation method is investigated, with a focus on the mechanical and electrical properties of individual fibers. Fibers with a Weibull strength of 65.3 MPa, remanent polarization of 22 μC/cm² and a total bipolar field induced strain of 0.25% under an electric field of 2.5 kV/mm, piezoelectric coefficient of 300 pm/V and dielectric constant of 3323 were produced. 1-3 piezocomposite devices prepared from these fibers had a 6 dB higher free-field voltage sensitivity and a 50% wider bandwidth compared to a solid disk transducer of the same dimensions.     

Upper Bounding Estimation for Robustness to the Parameter Uncertainty with Trigonometric Function in Trajectory Control of Robot Arms

In this paper, a new robust control law is considered for controlling robot manipulators subjected to uncertainties. The control law is derived as a result of analytical solution from the Lyapunov function, thus stability of the uncertain system is guaranteed. Apart from previous studies, uncertainty bound and adaptation gain matrix are updated in time with the estimation law to control the system properly and uncertainty bound is determined using a trigonometric function of robot kinematics, inertia parameters and tracking error while adaptation gain matrix is determined using a trigonometric function of robot kinematics and tracking error. Application to a two-link robotic manipulator is presented and numerical simulations are included.     

Boron removal by means of chemical precipitation with calcium hydroxide and calcium borate formation

Boron removal was investigated by chemical precipitation from aqueous solutions containing boron using calcium hydroxide. pH, initial boron concentration, amount of Ca(OH)₂, stirring speed and solution temperature were selected as operational parameters in a batch system. The highest boron removal efficiency was reached at pH 1.0. Increasing initial boron concentration and amount of calcium hydroxide raised to boron removal efficiency. Boron removal efficiency was highest at a stirring speed of 150 rpm. The most important parameter affecting boron removal efficiency was solution temperature. Increasing solution temperature increased importantly boron removal. XRD analysis showed that CaB₃O₃(OH)₅·4H₂O, which is a borate mineral called inyoite, occurred between Ca(OH)₂ and borate ions. As a result of the obtained experimental data, when the optimum operational conditions were selected, over 96% of boron removal efficiency was reached by this method.