Understanding High Critical Currents in YBa2Cu3O7 Thin Films and Coated Conductors

The main challenges for the success of high temperature superconducting wires, the YBa₂Cu₃O₇ (YBCO) coated conductors (CC), are to avoid the the weak-link problem through the production of biaxially textured films, and to increase the critical current density (J _c) through the introduction of large densities of appropriate defects. To that end, it is essential to understand the pinning mechanisms and their correlation with the microstructure of the CC. We first present a brief overview of the main methods currently used to produce YBCO CC, and we describe the architecture of the YBCO on IBAD fabricated at Los Alamos, summarizing the recent improvements of their structural and superconducting properties. Then, we analyze some aspects of the J _c dependence on temperature and magnetic field (orientation and intensity) for the best CC available, and we compare and contrast the results with those of YBCO thin films on single crystal substrates, in order to determine if the defects controlling the pinning mechanisms are the same in both cases. Our results indicate that over large field and angular ranges J _c on CC is higher than J _c in thin films on SCS.     

Preparation of concentrated alkali solutions of niobium

Concentrated alkali solutions of niobium containing up to 238 g/L of Nb₂O₅ have been obtained by sintering of Nb₂O₅ with K₂CO₃ · 1.5 H₂O. These solutions are recommended for use in the production of welding and other functional materials.     

Study of thermal characteristics of a heating module with parabolic trough concentrator and linear wedge-like photoelectric receiver

New solar modules intended for typical solar collectors containing semiparabolic trough concentrators and receivers that convert solar energy into thermal energy are considered. Mathematical modeling is carried out to develop an algorithm for estimating the structure of a heating module with the assigned energy parameters according to the laws of geometrical optics, as well as heat and mass transfer. When using such modules, which are based on a parabolic concentrator and a receiver with a system of coolant flow, cogeneration plants can be designed to produce electricity and heat. The mockups developed using this procedure are studied on the corresponding facilities and are tested under in-situ conditions. A solar module with an asymmetric parabolic trough concentrator and a linear wedge-like photoelectric receiver of concentrated radiation with a system of coolant flow provides the maximum power of 386 W at a temperature of 40°C and an efficiency of 60%, and 319 W at 60°C and 49%, respectively. Such modules are proposed for use to design solar collectors with the required performance.     

Preparation and application of silica sol-gels based on nepheline

This paper reports on the results of investigations into the development of the methods employed for acid treatment of nepheline and the search for new directions in the use of products obtained in the nepheline processing, which have made it possible to design and implement technologies for producing the aluminum-silicon coagulant/flocculant for water purification, as well as technologies for fabrication and application of nepheline-based silicon-containing thickening agents intended for the simplest water-containing explosives of the “Akvatol” type and others.     

Microstructure of an Si-Cr-Co alloy for magnetron sputtering targets

The influence of the cooling rate on the microstructure of an Si-54% Cr-6% Co cast alloy for magnetron sputtering targets is discussed. The alloy contains highly brittle phases CrSi, CrSi₂ and Cr₃Co₅Si₂. It is experimentally established that the required quality of a cast target of the considered composition cannot be achieved at high cooling rates of the alloy. Slow cooling can be achieved using a heated casting mold by adjusting the alloy cooling rate. It has been demonstrated that the alloy has the most uniform structure and the lowest porosity at cooling rates in the range 0.5–5°C/s.     

Deformation and filtration characteristics of solid particles in a suspension or granular material in rock strengthening with cementation and pre-stressed bolting

The laboratory testing of the transfer processes in cementation reinforcement of rocks via holes and filtering-out of cement liquid phase in pre-stressed bolting allows examination of structuring of rocks, solid particles of suspended matter and granular materials, which influences the cementation performance and the roadway stability. The paper discusses the revealed effect of the direct and return density inflows in loading solid particles and the relationship between the shape of the particles and their penetration characteristics.     

Sympathetic response to stimulation of the pontine A5 region in conscious rabbits

OBJECT: This study is a retrospective analysis of clinical data obtained in 28 patients affected by obstructive hydrocephalus who presented with signs of midbrain dysfunction during episodes of shunt malfunction. METHODS: All patients presented with an upward gaze palsy, sometimes associated with other signs of oculomotor dysfunction. In seven cases the ocular signs remained isolated and resolved rapidly after shunt revision. In 21 cases the ocular signs were variably associated with other clinical manifestations such as pyramidal and extrapyramidal deficits, memory disturbances, mutism, or alterations in consciousness. Resolution of these symptoms after shunt revision was usually slow. In four cases a transient paradoxical aggravation was observed at the time of shunt revision. In 11 cases ventriculocistemostomy allowed resolution of the symptoms and withdrawal of the shunt. Simultaneous supratentorial and infratentorial intracranial pressure recordings performed in seven of the patients showed a pressure gradient between the supratentorial and infratentorial compartments, with a higher supratentorial pressure before shunt revision. Inversion of this pressure gradient was observed after shunt revision and resolution of the gradient was observed in one case after third ventriculostomy. In six recent cases, a focal midbrain hyperintensity was evidenced on T2-weighted magnetic resonance imaging sequences at the time of shunt malfunction. This rapidly resolved after the patient underwent third ventriculostomy. CONCLUSIONS: It is probable that in obstructive hydrocephalus, at the time of shunt malfunction, the development of a transtentorial pressure gradient could initially induce a functional impairment of the upper midbrain, inducing upward gaze palsy. The persistence of the gradient could lead to a global dysfunction of the upper midbrain. Third ventriculostomy contributes to equalization of cerebrospinal fluid pressure across the tentorium by restoring free communication between the infratentorial and supratentorial compartments, resulting in resolution of the patient's clinical symptoms.     

Heat exchange in the evaporation region of coolant inside a porous fuel element

The article presents the results of the analytical investigation of the temperature field and of heat exchange in the evaporation zone of coolant inside a porous fuel element, with heat transfer by heat conduction across its boundaries taken into account.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 46, No. 1, pp. 8–14, January, 1984.