Abstract: A testing method for the bolt to be used under the conditions of excessive wind force by which bolts made of Cr—Mo steel can be separated into a group of bolts usable in cold areas and a group of bolts unusable in cold areas without conducting Charpy impact test involving complicated operation, specifically, a testing method for determining whether bolts made of heat-treated Cr—Mo steel are usable or unusable in cold areas, wherein the determination is conducted on the basis of both J parameter calculated by formula: J=(Si %+Mn %) (P %+Sn %) 104 (wherein P %, Si %, Mn % and Sn % are contents (mass %) of phosphorus (P), silicon (Si), manganese (Mn) and tin (Sn) respectively as disclosed in the inspection certificate of the Cr—Mo steel) and bolt diameter.

Abstract: Provided is a stress analysis device 3 for a wind-turbine structure, which includes a load-data generating section 21 that generates load time-series data of a predetermined load observation point, set in the wind-turbine structure, on the basis of a parameter related to an operating environment, and a stress analyzing section 22 that generates stress time-series data of at least one target analysis point, set in the wind-turbine structure, on the basis of the load time-series data.

Abstract: A method of producing a gradient-index lens includes a first step in which a glass body is immersed into a molten salt containing ions which are able to provide a refractive index higher than that of ions constituting the glass body, in order to perform ion diffusion into the glass body. Thereafter, in a second step the glass body obtained from the first step is immersed into a molten salt containing ions which provide a refractive index lower than that of the ions of the molten salt used in the first step. In this way there is formed a predetermined refractive index distribution in the glass body.

Abstract: The refractive index distribution in refractive index distribution lenses may be adjusted to better approach an ideal by heating the refractive index distribution lens. When the refractive index distribution lens was created by diffusion of refractive index changing ions into a body, further heating in an environment in which no additional ions can diffuse into the body causes further migration of ions within the body so that its refractive index distribution approaches an ideal.

Abstract: Refractive index distribution lenses may be made by forming refractive index distribution patterns in surfaces of two substrates. The patterns in the two substrates are made to be matching. Then, these surfaces of the two substrates are placed together with the patterns in the substrates coinciding. If the refractive index distribution patterns in the surfaces form semicylindrical lenses with parallel axes, the substrates may be put together so that the axes of the lenses in one substrate coincide with corresponding axes of semicylindrical lenses in the other substrate to form a rod lens array. If the refractive index distribution patterns in the two substrates are constant in directions parallel to the surfaces of these substrates but vary in the direction perpendicular to the surfaces, the surfaces of these substrates may be put together to form a slab lens.

Abstract: The present invention provides a gradient refractive index type anamorphic planar microlens which can be utilized for collimating an elliptical beam radiated from a semiconductor laser, or the like, and a method of producing such a lens. To collimate light rays, in which astigmatism exists, it is necessary to use a lens in which the respective focal distances in the directions perpendicular to an optical axis are different from each other. It includes a semiellipsoidal refractive index distribution region formed in a transparent substrate so as to have a major axis and a minor axis on a surface of the transparent substrate.

Abstract: A process for producing a transparent glass product having a refractive index gradient by the molecular stuffing method is described. A thallium compound is used as a dopant and, after a concentration gradient of the thallium dopant is formed, the porous glass product is heated up to the temperature region of 350.degree. to 550.degree. C. at a temperature-rising rate of 25.degree. to 150.degree. C./hour in a reducing gas atmosphere and then heat treated above 550.degree. C. in an inert gas atmosphere to collapse micropores in the porous glass product, thereby obtaining a glass product having a refractive index gradient which is transparent and free of light-scattering and coloration. The glass product is suitable as materials (preforms) for optical fibers or materials for rod-shaped lenses, particularly rod-shaped microlenses for microlens arrays and microlenses for coupling an optical fiber and a light source.