Flux Decline Study of Tubular Ceramic and Flat Sheet UF Membranes in Textile Wastewater Treatment

This work gives an assessment of the application of two ultrafiltration membrane types, which are the same in pore size but different in chemistry and configuration module, for textile wastewater treatment. Characterization was based on the solute rejection data of two commercial membranes, flat sheet polyethersulfone (PES) and tubular multichannel ceramic membrane, and flux decline was provided using polyethylene glycol (PEG) solutions of different molar mass. The permeate flux recovery after chemical cleaning was evaluated, and the efficiency of wastewater treatment was estimated on the basis of the analysis of textile wastewater and permeate. The permeate flux decline study showed that fouling was less likely to occur when PES membrane was used for wastewater treatment. PES flat membrane has proven to be more effective in the treatment of wastewater with total organic carbon (TOC) and colour removal efficiency of 72 % and 85 % respectively

4,5,6, 7-Tetrahydroindazol-3-one Carboxylic Acids. IV. Acid Dissociation Constants and Complex Formation with Calcium, Strontium and Barium

The dissociation constants of 2-phenyl-4,5,6,7-tetrahydroindazol- 3-one-5,5-dicarboxylic acid (I, FIDA) and its stability constants with alkal.ine earth ions are reported. FIDA was first tested for toxicity by the »Up-and down« method. In connection with the determination and the interpretation of pK values of tetrahydroindazolone carboxy1ic acids and their ethyl esters I - VII the potentiometric titration procedure is described. The same procedure and apparatus were used for the potentiometric titration in the presence of metals. FIDA w as shown to be an excelient reagent for the separation of barium from strontium

Measurement and Simulation of Hydro-Generator’s Asynchronous Operation

The extended testing of hydro-generator with Pelton turbine (rated 35 MVA) was performed on a generator whose lifespan expired and it was going to be replaced. This was the perfect opportunity to do some specific and uncommon testing. The complex testing plan was designed in order to enable recording of as much relevant data as possible (electrical, electromechanical, mechanical). Therefore, in some phases of testing, 29 to 44 quantities were measured simultaneously. Among the tests, there are short circuits with lowered voltage, bad synchronization at approximate angle of 15 degrees, asynchronous operation, generator overspeed and operation with short circuited field winding on one pole. The most interesting and the most critical operation during this testing is asynchronous operation of hydro-generator [1, 2, 3, 4, 5], which is also very dangerous for generator and drive equipment. During such operation synchronous generator operates at a speed unequal to rated speed. This slip causes increased damping winding currents, which increases the thermal stress of this winding beyond the designed level. This makes these tests very infrequent. Asynchronous operating was achieved by decreasing the excitation current. Complex mathematical model for computer simulation of hydro-generator’s asynchronous operation has been made, taking into consideration the magnetic saturation, damper winding and generator transformer’s influence. Results obtained by simulations have been compared to those obtained by measurements

Measurement and Simulation of Hydro-Generator’s Asynchronous Operation

The extended testing of hydro-generator with Pelton turbine (rated 35 MVA) was performed on a generator whose lifespan expired and it was going to be replaced. This was the perfect opportunity to do some specific and uncommon testing. The complex testing plan was designed in order to enable recording of as much relevant data as possible (electrical, electromechanical, mechanical). Therefore, in some phases of testing, 29 to 44 quantities were measured simultaneously. Among the tests, there are short circuits with lowered voltage, bad synchronization at approximate angle of 15 degrees, asynchronous operation, generator overspeed and operation with short circuited field winding on one pole. The most interesting and the most critical operation during this testing is asynchronous operation of hydro-generator [1, 2, 3, 4, 5], which is also very dangerous for generator and drive equipment. During such operation synchronous generator operates at a speed unequal to rated speed. This slip causes increased damping winding currents, which increases the thermal stress of this winding beyond the designed level. This makes these tests very infrequent. Asynchronous operating was achieved by decreasing the excitation current. Complex mathematical model for computer simulation of hydro-generator’s asynchronous operation has been made, taking into consideration the magnetic saturation, damper winding and generator transformer’s influence. Results obtained by simulations have been compared to those obtained by measurements

Sr,Mg co-doping of calcium hydroxyapatite: Hydrothermal synthesis, processing, characterization and possible application as dentin substitutes

The aim of this study was to investigate the influence of binary Sr, Mg ion-doping compared to the single-ion doping effects on the phase composition and morphology of hydrothermally obtained calcium hydroxyapatite (HAP) powders and on the phase composition, microstructure, and mechanical properties of the sintered materials. Additionally, the focus of this study was to investigate the possible utilization of the binary doped Sr,Mg-HAP compacts as dentin substitutes in restorative dentistry by evaluating their bonding ability with commercially available restorative materials using the shear bond strength test (SBS). The hydrothermally obtained mono-doped Mg5 and Sr5 showed the monophasic apatite structure, while in all co-doped samples β-TCP phase was formed, resulting in biphasic calcium phosphate (BCP) powders. It was confirmed that co-doping with Sr and Mg ions led to the thermal stabilization of the β-TCP phase by suppressing the phase transition into α-TCP when sintered at 1200 °C. Moreover, the co-presence of Mg ions significantly improved the hardness of Sr-doped HAP from 3.74 to 5.02 GPa. Sr,Mg-HAP dental inserts were found to achieve sufficient bonding (13.53 MPa) through the micromechanical interlocking with Z250 dental composite and Single Bond Universal dental adhesive applied with a total etch approach. The SBS values obtained for the SrMg-HAP insert were similar to the literature data on bonding ability with human dentin, indicating that binary doped Sr,Mg-HAP ceramics present a promising material for application in restorative dentistry as dentin substitutes