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.     

COVID-19 diagnosis on CT images with Bayes optimization-based deep neural networks and machine learning algorithms

Neural Computing and Applications - Early diagnosis of COVID-19, the new coronavirus disease, is considered important for the treatment and control of this disease. The diagnosis of COVID-19 is...     

Optical and electrical properties of new organic thin film

This paper describes a new organic thin film (OTF) (50 nm) which was deposited by spin coated at room temperature. OTF has been constructed from chemically synthesized poly(pentachlorophenyl methacrylate-co-glycidyl methacrylate). Optical properties of the obtained poly(pentachlorophenyl methacrylate-co-glycidyl methacrylate) in solution were tested by ultraviolet–visible absorption spectroscopy. The analysis of the optical absorption data revealed an existence of a direct and indirect transition optical band gap (E_g). The electrical properties of ITO/PEDOT:PSS/OTF/Al heterojunction structure has been investigated by forward and reverse bias current–voltage (I–V) measurements at room temperature. The main electrical parameters such as barrier height (Φ_Bo), ideality factor (n) and reverse saturation current (I_o) have been calculated by applying thermionic emission theory as 0.80 eV, 3.69, 1.86 × 10^?8 A respectively. Additionally, series resistance (R_s), Φ_Bo and n were calculated from the forward bias I–V data using the methods of Cheung and Cheung with Norde and showed that these methods can be applied successfully for this structure.     

Thermal performance of a solar-assisted heat pump drying system with thermal energy storage tank and heat recovery unit

Thermal performance parameters for a solar-assisted heat pump (SAHP) drying system with underground thermal energy storage (TES) tank and heat recovery unit (HRU) are investigated in this study. The SAHP drying system is made up of a drying unit, a heat pump, flat plate solar collectors, an underground TES tank, and HRU. An analytical model is developed to obtain the performance parameters of the drying system by using the solution of heat transfer problem around the TES tank and energy expressions for other components of the drying system. These parameters are coefficient of performances for the heat pump (COP) and system (COPs), specific moisture evaporation rate (SMER), temperature of water in the TES tank, and energy fractions for energy charging and extraction from the system. A MATLAB program has been prepared using the expressions for the drying system. The obtained results for COP, COPs, and SMER are 5.55, 5.28, and 9.25, respectively, by using wheat mass flow rate of 100 kg h⁻¹, Carnot efficiency of 40%, collector area of 100 m², and TES tank volume of 300 m³ when the system attains periodic operation duration in fifth year onwards for 10 years of operation. Annual energy saving is 21.4% in comparison with the same system without using HRU for the same input data.     

Selective extraction and concentration of chromium(VI) from acidic solutions containing various metal ions through emulsion liquid membranes using Amberlite LA-2

Chromium(VI) is a very harmful metal, highly toxic and carcinogenic in nature. Its separation from industrial effluents is of primordial importance. An extensive study on selective extraction and concentration of chromium(VI) from the acidic solutions containing various metal ions using an emulsion liquid membrane (ELM) technique is presented. The ELM consists of Amberlite LA-2 as an extractant, commercial kerosene as organic solvent, ECA 4360J as a surfactant and 0.5 M ammonium carbonate solution as stripping phase. The study has highlighted the importance and influence of membrane composition for maximizing the extraction of chromium(VI). For this reason, effects of various parameters such as chromium(VI) concentration in the acidic solution, mixing speed, type and concentration of stripping solution, type and acid concentration of the acidic solution, extractant and surfactant concentrations, phase ratio and treatment ratio were studied and optimum conditions were determined. The results showed that it is possible to extract 99% of chromium(VI) from the acidic solution containing Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) ions, at the optimum conditions.     

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.     

Adsorption of Ni(II) on ion exchange resin: Kinetics, equilibrium and thermodynamic studies

This article describes the ion exchange of a heavy metal Ni(II) from aqueous solutions onto a Dowex HCR-S, cationic resin. Batch adsorption studies were conducted to evaluate the effect of various parameters such as pH, resin dose, stirring speed, temperature, contact time and initial Ni(II) concentration on the removal of Ni(II). Adsorption rate increased with the increase in initial nickel concentration, stirring speed and temperature. Equilibrium adsorption isotherms were measured for the single component system, and the experimental data were analyzed by using Langmuir, Freundlich, Elovich, Temkin, Khan, Sips, Toth, Koble-Corrigan and Radke-Prausnitz isotherm equations. The Sips equation appears to fit the equilibrium data. Different models were tested for their applicability. Adsorption kinetic data were modeled using the Lagergren pseudo-first-order, Ho??s pseudo-second-order and Elovich models. It was found that Ho??s pseudo-second-order model could be used for the prediction of the system??s kinetics. Thermodynamic activation parameters such as ??G*, ??S* and ??H* of the adsorption of Ni(II) on Dowex HCR-S cationic resin were also calculated.