Abstract: A parent node includes: a signal reception unit receiving a parent node search signal transmitted from a child node; a RSSI measurement unit measuring a RSSI as an index indicating the intensity of wireless link with the child node transmitting the parent node search signal; a response wait time standby processing unit that, after waiting for a response wait time in accordance with the intensity of wireless link, returns a response signal to the child node as a sender of the parent node search signal; and a signal transmission unit. The child node includes: a signal transmission unit transmitting a parent node search signal; a signal reception unit receiving a response signal; and a parent node selection unit that selects a parent node for routine communication on the basis of a wait time from the transmission of a parent node search signal to the reception of a response signal.

Abstract: A parent node includes: a signal reception unit receiving a parent node search signal transmitted from a child node; a RSSI measurement unit measuring a RSSI as an index indicating the intensity of wireless link with the child node transmitting the parent node search signal; a response wait time standby processing unit that, after waiting for a response wait time in accordance with the intensity of wireless link, returns a response signal to the child node as a sender of the parent node search signal; and a signal transmission unit. The child node includes: a signal transmission unit transmitting a parent node search signal; a signal reception unit receiving a response signal; and a parent node selection unit that selects a parent node for routine communication on the basis of a wait time from the transmission of a parent node search signal to the reception of a response signal.

Abstract: A novel optical fiber connector part is provided which comprises a ferrule having a capillary hole for holding an optical fiber, the ferrule being formed from a zirconia-alumina composite oxide containing yttria at a content ranging from 2 to 4 mol % in zirconia. In the optical fiber connector part, a sleeve for connecting and holding the ferrule may be formed from zirconia and/or a zirconia-alumina composite oxide. A process for producing the optical fiber connector part is provided wherein the granular zirconia-alumina composed of a particulate zirconia-alumina mixture having an average particle diameter of not more than 1 .mu.m is used as raw material. The granular zirconia-alumina preferably contains alumina at a content ranging from 0.1% to 50% by weight. The process comprises spray-drying a slurry containing a particulate zirconia-alumina mixture having an average particle diameter of not more than 1 .mu.m.

Abstract: A zirconia type sintered body consisting essentially of 50 to 98% by weight of zirconia (ZrO.sub.2) containing 1.5 to 5 mole % of yttria (Y.sub.2 O.sub.3) and 50 to 2% by weight of alumina (Al.sub.2 O.sub.3), spinal (MgAl.sub.2 O.sub.4) or mullite (3Al.sub.2 O.sub.3.2SiO.sub.2), and having a three-point bending strength of at least 1700 MPa is provided. This sintered body is prepared by a process wherein a powdery composition consisting essentially of 50 to 98% by weight of (a1) a powder of zirconia containing 1.5 to 5 mole % of yttria or (a2) a mixture comprising 1.5 to 5 mole % of yttria powder and 95 to 98.5 mole % of a zirconia powder and 2 to 50% by weight of (b) a powder of an alumina type oxide selected from alumina, and alumina-magnesia type oxide, an alumina-silica type oxide, a mixture of alumina and magnesia and a mixture of alumina and silica is subjected to a hot isotactic pressing treatment under a pressure of at least 50 MPa at temperature of 1300.degree. C. to 1700.degree. C.

Abstract: Disclosed is a process for the preparation of high .alpha.-type silicon nitride powder, wherein a nitrogen-containing silane compound and/or amorphous silicon nitride is crystallized to form crystalline silicon nitride. In this process, crystalline silicon nitride having a particle size not larger than 0.05 .mu.m is incorporated in an amount of at least 0.1% by weight into the nitrogen-containing silane compound and/or amorphous silicon nitride, the mixture is formed into a power or molded body having a powder bulk density of at least 0.1 g/cm.sup.3 as silicon, and the powder or molded body is heated to 1,350.degree. to 1,700.degree. C. while controlling the temperature-elevating rate to at least 15.degree. C./min throughout the temperature range of from 1,200.degree. to 1,350.degree. C. The resulting high .alpha.-type silicon nitride is composed of a fine granular crystal and the does not contain a needle crystal or columnar crystal.

Abstract: A zirconia type sintered body consisting essentially of 50 to 98% by weight of zirconia (ZrO.sub.2) containing 1.5 to 5 mole % of yttria (Y.sub.2 O.sub.3) and 50 to 2% by weight of alumina (Al.sub.2 O.sub.3), spinal (MgAl.sub.2 O.sub.4) or mullite (3Al.sub.2 O.sub.3.2SiO.sub.2), and having a three-point bending strength of at least 1700 MPa is provided. This sintered body is prepared by a process wherein a powdery composition consisting essentially of 50 to 98% by weight of (a1) a powder of zirconia containing 1.5 to 5 mole % of yttria or (a2) a mixture comprising 1.5 to 5 mole % of a yttria powder and 95 to 98.5 mole % of a zirconia powder and 2 to 50% by weight of (b) a powder of an alumina type oxide selected from alumina, an alumina-magnesia type oxide, an alumina-silica type oxide, a mixture of alumina and magnesia and a mixture of alumina and silica is subjected to a hot isotactic pressing treatment under a pressure of at lesast 50 MPa at temperature of 1300.degree. C. to 1700.degree. C.