Calculation of the Eddy Current Losses in a Laminated Open-Type Transformer Core Based on the A→,T→−A→ Formulation

Losses due to eddy currents in an open-type transformer core are significantly reduced by the lamination of the transformer core. In order to further reduce the eddy current losses, the open-type core often has a multi-part structure, i.e., it is composed of several more slender cores. The complete homogenization of such a core is not possible when an A→,V−A→ formulation is used, where A and V represent the magnetic vector potential and electric scalar potential, respectively. On the other hand, an A→,T→−A→ formulation, where T represents the electric vector potential, enables the complete homogenization of the general open-type core, but the simulation converges poorly due to the large number of degrees of freedom. By eliminating the redundant degrees of freedom, the convergence rate is significantly improved, and is at least twice as good as the convergence rate of the simulation based on the A→,V−A→ formulation. In this paper, a method for the calculation of the eddy current losses in an open-type core based on the A→,T→−A→ formulation with the elimination of redundant degrees of freedom is presented. The method is validated by comparison with a brute force simulation based on the A→,V−A→ formulation, and the efficiency of the method is determined by comparison with the standard homogenization method based on the A→,V−A→ formulation.

PHYSICAL MODELING OF STEEL HOMOGENIZATION DURING FINISH ALLOYING IN THE MOLD

The article describes the method of finish alloying steel in molds in top and bottom casting. Due to the reduction of oxygen activity in the metal due to the relatively lower casting temperature than the previous stages of steelmaking redistribution, it is achieved the reduction of the ferroalloys loss and increasing the yield of useful elements of ferroalloys. An important indicator of the implementation of the proposed technology is the alloying of steel in the mold to obtain steel of a certain brand in small volumes. The aim of the study is to determine the rational place of addition of alloys into the volume of the melt and the method of casting, for the best dissolution of alloys in steel directly in the mold. To solve this problem, the method of physical modeling on a water transparent model using a fluorescent dye that glows brightly in ultraviolet light was used. The experiment consisted of three series of with different methods of casting and introduction of dye: 1) top casting with the introduction of dye into the mold; 2) bottom casting with the introduction of dye into the mold; 3) bottom casting with the introduction of dye in the trumpet. It was analyzed that the averaging of the dye is more efficient at a lower liquid level in the mold, because mixing occurs due to the flow of liquid in the mold, the higher the liquid level in the mold, the weaker the mixing flows. The research revealed minimization of averaging time at the optimal fluid level. For top and bottom casting with the addition of dye to the mold, the optimal level is 33%. When the dye is introduced into the center, there is a slight directly proportional increase in the time of complete homogenization with an increase in the liquid level in the mold. Among the analyzed methods of steel casting, the most effective in terms of homogenization of the alloying additive is bottom casting. The color of the liquid at different stages of filling the mold with the introduction of the dye at the level of 25% of the height of the mold is analyzed.

Hydrothermal fluids of apatite-magnetite ores of the Tomtor carbonatite massif (NE, Russia)

<p>The Tomtor carbonatite complex, with an area of 250 km<sup>2</sup>, is confined to the eastern framing of the Anabar Anteclise; it is located withtin the Ujinsky province of ultrabasic alkaline rocks and carbonatites (Northeast of Siberian Platform) (Erlich, 1964). The complex has a concentric zonal structure: the outer ring is composed of alkaline and nepheline syenites, the inner incomplete ring is nepheline-pyroxene rocks of the foidolite family, the core is represented by carbonatites. All rocks of the massif are intersected by dikes and explosion tubes of picrites and alneites. Onkuchakh apatite-magnetite deposit is located on the northeastern border of the carbonatite core. Apatite-magnetite ores (camaforites, phoscorites, nelsonites) form a series of ore steeply dipping (75-80<sup>o</sup>) lenticular bodies of north-western strike. The resources of the apatite-magnetite ores of the Tomtor massif are about 1 billion tons of iron (Tolstov, 1994). Primary and pseudo-secondary fluid inclusions were studied in apatite, calcite and potassium feldspar of camaforites. Inclusions have isometric or elongated shapes up to 50 microns. Most of the studied inclusions have a negative crystal form located in the central parts and zones of apatite growth.</p><p>Apatite contains a multiphase (crystal-fluid) inclusions with gas, liquid and 1-5 visible crystalline phases. The gas phase is represented by CO<sub>2</sub>, contains subordinate amounts of H<sub>2</sub>O, H<sub>2</sub>S and SO<sub>2</sub>. The liquid phase is represented by H<sub>2</sub>O with SO<sub>4</sub><sup>2-</sup>, HSO<sup>4-</sup> and HCO<sup>3-</sup> ions. The solid phases in the inclusions are represented by mainly halite (NaCl) and sylvite (KCl), with strontianite (SrCO<sub>3</sub>), barite (BaSO<sub>4</sub>) and Ca-Sr-REE F-carbonate crystals. Complete homogenization occurs in the temperature range from 290 to 350 °C, the concentration is 30-45 wt. % of NaCl-eq. Calcite has the similar in composition fluid inclusions. The solid phases are mainly represented by halite (NaCl) and sylvite (KCl), as well as the dolomite (CaMg(CO<sub>3</sub>)<sub>2</sub>), strontianite (SrCO<sub>3</sub>), REE phosphates and sulfates of Sr and Ba. Complete homogenization occurs at 250-300 °C, the concentration is 35-55 wt. % of NaCl-eq. The gas phase of the fluid inclusions in K-feldspar is predominantly CO<sub>2</sub>; the liquid phase is H<sub>2</sub>O. The solid phases are represented by witherite (BaCO<sub>3</sub>) and calcite (CaCO<sub>3</sub>). The homogenization temperature of fluid inclusions occurs at 350-375 °C.</p><p>The results show that the hydrothermal fluids of camaforites of the Tomtor massif are represented by the concentrated high-medium temperature sulfate-carbonate-chloride solutions of complex composition . The fluid composition is explained by the evolution of the carbonatite melt.</p><p>The work was supported by the Russian Science Foundation (RSF), project # 19-17-00013.</p><p>References</p><ol><li>Erlich, E.N., 1964. The new province of alkali rocks on the north of Siberian platform and its geological aspects. Proc. All-Soviet Mineral.Soc.93,682–693.</li> <li>Tolstov, A.V., 1994.Mineralogy and geochemistry of apatite-magnetite ores of the Tomtor Massif (NorthwesternYakutia). Russ.Geol. Geophys.35,76–84.</li> </ol>

Mechanical properties of FeAlSi powders prepared by mechanical alloying from different initial feedstock materials

FeAl20Si20 (wt.%) powders prepared by mechanical alloying from different initial feedstock materials (Fe, Al, Si, FeAl27) were investigated in this study. Scanning electron microscopy, X-ray diffraction and nanoindentation techniques were used to analyze microstructure, phase composition and mechanical properties (hardness and Young’s modulus). Finite element model was developed to account for the decrease in measured values of mechanical properties of powder particles with increasing penetration depth caused by surrounding soft resin used for embedding powder particles. Progressive homogenization of the powders’ microstructure and an increase of hardness and Young’s modulus with milling time were observed and the time for complete homogenization was estimated.

Milliseconds Microfluidic Bubble Mixer Using Chaotic Advection

In this work, we report a novel passive micromixer based on the perturbation of chaotic micro-bubbles. The sample flows (ink solution and water) were co-injected with nitrogen in a flow focusing orifice to generate side-by-side laminar flows segmented by monodisperse bubbles. The bubble flow subsequently enters a mixing chamber downstream, upon which the hydrodynamic interactions between two adjacent bubbles result in the stretching and folding of the laminar flow interface, which leads to a rapid chaotic mixing and complete homogenization of two separated streams. Our technique provides a simple, passive, and effective mixing mechanism for sample homogenization in microfluidic devices.

Denitrification in nitric-acid-treated cattle slurry during storage

Lowering the pH of cattle slurry with HNO3 was used to reduce NH3 volatilization during storage and after application. Incubation studies were carried out to examine possible NO3 losses and N2O emission from HNO3 treated slurry during storage. Batches of cattle slurry were treated with various amounts of HNO3 to obtain a pH range of 6.0 to 3.0. The slurries were stirred once or twice a week and stored for 6 months at 15 degrees C. Changes in pH, Eh, NO3- and NH4+ concn, and emissions of N2O, CO2 and CH4 were monitored. The loss of NO3- and the emission of N2O were related to slurry pH, being lowest at low pH. Cumulative loss of NO3- ranged from ~40 mmol/kg for slurries of target pH < or =>5.0 to ~400 mmol/kg for slurries of target pH 6.0. Homogenization of the slurries via stirring and addition of H2O2 decreased NO3- loss and H+ consumption. The strong pH dependence of NO3- loss, the production of N2O and the stoichiometry of H+ consumption and NO3- loss indicated that the loss of NO3- was mainly due to microbiological denitrification. Similar N2O production rates in the presence and absence of C2H2 indicated that nitrification was not an important source of N2O. It is concluded that lowering the pH to values 4.5 as well as regular and complete homogenization of the slurry via stirring are important for the success of the on-farm treatment of slurry with HNO3.

Extraction of alcohol dehydrogenase from fresh root tips of loblolly pine

Significant alterations of published methods for extracting alcohol dehydrogenase from plant components were required to obtain measurable enzyme activity from actively growing root tips of loblolly pine (Pinustaeda L.). Necessary steps were quick freezing of roots in liquid nitrogen within 5 min of excising, use of soluble polyvinylpyrrolidone during freezing and fracturing in liquid nitrogen, and use of mercaptoethanol, glycerol, and NAD as protective measures during complete homogenization. No chromatographic purification steps were necessary. Up to 16 samples could be collected and analyzed in a single day by this method with sufficient sensitivity to detect intraspecific variation among loblolly pine families.

A Method for Blood Platelet Homogenization Using the Aminco-French Pressure Cell

SummaryA rapid effective method for platelet homogenization using a pressure cell is described. With this method, almost complete homogenization of human platelets occurred without excessive solubilization of enzymes as compared to a pestle homogenization procedure where there was incomplete homogenization. Electron microscopy of pressure homogenates and fractions revealed well preserved organelles.