MoO2 Diffusion in Aluminosilicate Glass

A diffusion couple of an oxidized molybdenum disk and a glass cylinder was used to measure the solubiiity and effective binary diffusion coefficient of MoO₂ in a non-alkali aluminosilicate glass. At 1400°C, the solubility limit was 8.4 mol%; the value of the diffusion coefficient (4.1 × 10⁻¹⁶ m²/s) was significantly lower than that estimated from the Stokes-Einstein relation.     

Glass–Ceramic Composites with Strontium Hexaferrite Ultrafine Particles in the SrO–Fe2O3–B2O3–SiO2 System

Glass samples with nominal compositions SrFe₁₂O₁₉+(12− n )SrB₂O₄+nSrSiO₃, n =3, 6, 9 were prepared by rapid quenching of the melt. Processes of glass devitrification were studied. The samples were annealed at temperatures of 600–900°C, and the resulting glass–ceramics was characterized by XRD, SEM, EDX, and magnetic measurements. SrFe₁₂O₁₉ crystallizes above 700°C and forms nano- and submicron platelet particles with the aspect ratio depending on the thermal treatment conditions. The glass–ceramic samples annealed at 900°C show coercive force values in the range of 422–455 kA/m.     

Liquid salt cooled flexible conversion ratio fast reactor: Neutronic design

This paper presents the neutronic design of a liquid salt cooled fast reactor with flexible conversion ratio. The main objective of the design is to accommodate interchangeably within the same reactor core alternative transuranic actinides management strategies ranging from pure burning to self-sustainable breeding. Two, the most limiting, core design options with unity and zero conversion ratios are described. Ternary, NaCl-KCl-MgCl₂ salt was chosen as a coolant after a rigorous screening process, due to a combination of favourable neutronic and heat transport properties. Large positive coolant temperature reactivity coefficient was identified as the most significant design challenge. A wide range of strategies aiming at the reduction of the coolant temperature coefficient to assure self-controllability of the core in the most limiting unprotected accidents were explored. However, none of the strategies resulted in sufficient reduction of the coolant temperature coefficient without significantly compromising the core performance characteristics such as power density or cycle length. Therefore, reactivity control devices known as lithium thermal expansion modules were employed instead. This allowed achieving all the design goals for both zero and unity conversion ratio cores. The neutronic feasibility of both designs was demonstrated through calculation of reactivity control and fuel loading requirements, fluence limits, power peaking factors, and reactivity feedback coefficients.     

Cross-comparison of fast reactor concepts with various coolants

Four fast reactor concepts using lead (LFR), liquid salt, NaCl-KCl-MgCl₂ (LSFR), sodium (SFR), and supercritical CO₂ (GFR) coolants are compared. Since economy of scale and power conversion system compactness are the same by virtue of the consistent 2400 MWt rating and use of the S-CO₂ power conversion system, the achievable plant thermal efficiency, core power density and core specific powers become the dominant factors. The potential to achieve the highest efficiency among the four reactor concepts can be ranked from highest to lowest as follows: (1) GFR, (2) LFR and LSFR, and (3) SFR. Both the lead- and salt-cooled designs achieve about 30% higher power density than the gas-cooled reactor, but attain power density 3 times smaller than that of the sodium-cooled reactor. Fuel cycle costs are favored for the sodium reactor by virtue of its high specific power of 65 kW/kgHM compared to the lead, salt and gas reactor values of 45, 35, and 21 kW/kgHM, respectively. In terms of safety, all concepts can be designed to accommodate the unprotected limiting accidents through passive means in a self-controllable manner. However, it does not seem to be a preferable option for the GFR where the active or semi-passive approach will likely result in a more economic and reliable plant. Lead coolant with its superior neutronic characteristics and the smallest coolant temperature reactivity coefficient is easiest to design for self-controllability, while the LSFR requires special reactivity devices to overcome its large positive coolant temperature coefficient. The GFR required a special core design using BeO diluent and a supercritical CO₂ reflector to achieve negative coolant void worth—one of the conditions necessary for inherent shutdown following large LOCA. Protected accidents need to be given special attention in the LSFR and LFR due to the small margin to freezing of their coolants, and to a lesser extent in the SFR.     

Evaluation of system codes for analyzing naturally circulating gas loop

Steady-state natural circulation data obtained in a 7 m-tall experimental loop with carbon dioxide and nitrogen are presented in this paper. The loop was originally designed to encompass operating range of a prototype gas-cooled fast reactor passive decay heat removal system, but the results and conclusions are applicable to any natural circulation loop operating in regimes having buoyancy and acceleration parameters within the ranges validated in this loop. Natural circulation steady-state data are compared to numerical predictions by two system analysis codes: GAMMA and RELAP5-3D. GAMMA is a computational tool for predicting various transients which can potentially occur in a gas-cooled reactor. The code has a capability of analyzing multi-dimensional multi-component mixtures and includes models for friction, heat transfer, chemical reaction, and multi-component molecular diffusion. Natural circulation data with two gases show that the loop operates in the deteriorated turbulent heat transfer (DTHT) regime which exhibits substantially reduced heat transfer coefficients compared to the forced turbulent flow. The GAMMA code with an original heat transfer package predicted conservative results in terms of peak wall temperature. However, the estimated peak location did not successfully match the data. Even though GAMMA's original heat transfer package included mixed-convection regime, which is a part of the DTHT regime, the results showed that the original heat transfer package could not reproduce the data with sufficient accuracy. After implementing a recently developed correlation and corresponding heat transfer regime map into GAMMA to cover the whole range of the DTHT regime, we obtained better agreement with the data. RELAP5-3D results are discussed in parallel.     

UV‐Triggered Polydopamine Secondary Modification: Fast Deposition and Removal of Metal Nanoparticles

Since the first report in 2007, polydopamine (PDA) coating has shown great potential as a general and versatile method to create functional nanocoatings on arbitrary substrates. Slow kinetics and poor controllability of the coating and secondary modification processes, however, have limited the further development of this attractive method. In this work, it is demonstrated that UV irradiation at 365 nm significantly accelerates the process of secondary modification of a PDA‐coated surface. The kinetics of both thiol and amine modifications of PDA are increased 12‐fold via UV irradiation, while the kinetics of metal ion reduction at the PDA interface is increased more than 550 times. Moreover, it is demonstrated that irradiating a PDA/metal nanoparticle composite surface with UV light at 254 nm leads to dissolution of the deposited metal nanoparticles (MNPs). Finally, grayscale metallic patterns, dynamic deposition, and removal of MNPs on PDA surface are realized with the proposed method.     

Thermoelectric Effect Spectroscopy and Photoluminescence of High-Resistivity CdTe:In

Thermoelectric effect spectroscopy and photoluminescence techniques were used to study the defect levels in samples from three crystals of CdTe:In grown by the vertical gradient freeze method. The main goal of the investigation was to study defects, which strongly trap charge carriers or act as recombination centers in order to eliminate them from the technological process. The main difference among detecting and non-detecting samples was the absence of electron traps with a very high capture cross-section and energy 0.6 eV to 0.7 eV, which act as lifetime killers even at low concentrations. Recently published ab initio calculations show a complex of Te antisite and Cd vacancy within this energy range.     

Extraction of Bitter Acids from Hops and Hop Products Using Pressurized Solvent Extraction (PSE)

The EBC method 7.7, currently used for determination of bitter acids in hop products, is a time‐consuming and laborious extraction technique. In this paper, our aim was to propose a new extraction method based on Pressurized Solvent Extraction (PSE) sometimes also called Pressurized Fluid Extraction (PFE) or Accelerated Solvent Extraction (ASE). Compared to conventional extractions, PSE offers a number of important benefits. PSE on OnePSE^® automated extractor was used for extraction of α‐ and β‐acids from hops and hop products and the parameters influencing extraction efficiency and the influence of the sample preparation method were studied. The quantitative determination of α‐ and β‐acids in the extracts was accomplished by using an HPLC apparatus equipped with diode array detector. The experimental results were compared with those obtained by the standard EBC 7.7 method and the two methods were found to be fully compatible     

Integrodifferential approach to solution of eddy currents in linear structures with motion

A nonstandard integrodifferential approach to computation of eddy currents in linear structures with motion is presented. Described is a general continuous 3D model of the problem, together with the possibilities of forming corresponding numerical schemes. The methodology is illustrated by two examples.     

Simplified scoring methods for HMM-based speech recognition

Most of the contemporary speech recognition systems exploit complex algorithms based on Hidden Markov Models (HMMs) to achieve high accuracy. However, in some cases rich computational resources are not available, and even isolated words recognition becomes challenging task. In this paper, we present two ways to simplify scoring in HMM-based speech recognition in order to reduce its computational complexity. We focus on core HMM procedure—forward algorithm, which is used to find the probability of generating observation sequence by given HMM, applying methods of dynamic programming. All proposed approaches were tested on Russian words recognition and the results were compared with those demonstrated by conventional forward algorithm.