Enhanced superconductivity of YBCO interfaces: origin of high critical temperature in layered superconductors

Superconducting transition temperatures Tc of the YBCO film surface and of the YBCO film/substrate interface were measured inductively. It was observed that the interface- Tc is always higher then the surface - Tc. However deposition of silver over-layer enhances the superconducting transition temperatures. This observation was confirmed by four-point resistance measurements. In the annealed YBCO/Ag bilayers magnetic properties of the interface were observed. We believe that such phenomena are a common feature of layered systems. This two dimensional structure reminds the layered microstructure of the high-temperature superconductors and one can suppose that covering of the superconducting layer by non-superconducting layer is a condition for obtaining high critical temperatures in general.Comment: 13 pages, 9 figures, submited to Natur

Experimental Studies about Characteristics of the Rocks Displacement and State of Bearing Pressure on the Haulage Roadway

Comprehensive studies were conducted using measuring stations to measure the rock pressure and displacements of the roof rocks in the mine workings adjacent to the face when extracting medium thick inclined coal seams with the use of longwall (seam 6 at the Quang Hanh mine of Quang Ninh coal basin, Vietnam). The results of the study show that the displacement of the roof rock on the parallel roadway increases sharply at a distance of 1 to 12 m to the face, varies from 20 to 40 mm when the mining depth of the coal seam is 200 m and the maximum rock pressure on the haulage roadway supports is located at a distance of 3–8 m ahead of the face and is from 14 to 16 tons ranges

Justification of Spatially-Planned Solutions and Determination of the Dimension Block in the Working of the Medium Thick Inclined Coal Seams with the Room and Pillar System

Technological parameters for working out of the medium thick inclined coal seams with a diagonal arrangement of a line of a working face. An analysis of the constraints that apply the technology and the complexities of the mining and geological conditions of the Quang Ninh coal basin. The possibility and expediency of using the foreign experience of working out of the medium thick inclined coal seams in the mines of Vietnam and justification of spatially-planned solutions for working. The scheme of preparation and working out of the excavation area is given in view of the technological features in difficult mining and geological conditions, using the room and pillar system and determination of the rational length of the block along the strike

Justification of Spatially-Planned Solutions and Determination of the Dimension Block in the Working of the Medium Thick Inclined Coal Seams with the Room and Pillar System

Technological parameters for working out of the medium thick inclined coal seams with a diagonal arrangement of a line of a working face. An analysis of the constraints that apply the technology and the complexities of the mining and geological conditions of the Quang Ninh coal basin. The possibility and expediency of using the foreign experience of working out of the medium thick inclined coal seams in the mines of Vietnam and justification of spatially-planned solutions for working. The scheme of preparation and working out of the excavation area is given in view of the technological features in difficult mining and geological conditions, using the room and pillar system and determination of the rational length of the block along the strike