Showing papers by "Shinichi Miyamoto published in 1993"

Bioactive ceramic coated surgical implant

Abstract: A metallic implant base is coated with two bioactive ceramic layers. An inner bioactive ceramic layer is coated on the implant base. An outer bioactive ceramic layer is coated on the inner bioactive ceramic layer. The inner bioactive layer is vitrified at a ratio of not less than 50 volume percent, thereby improving the bonding of the inner bioactive layer to the metallic implant base and preventing migration of the metal ions from the metallic implant base. The outer bioactive ceramic layer is vitrified to a ratio of substantially less than 50 volume percent, thereby providing a desired porosity.

Sonar signal processing device

Abstract: PURPOSE:To distinguish echo from reverberation certainly even though their reception levels are the same substantially CONSTITUTION:A transmitter/receiver 11 transmits ultrasonic waves frequency modulated linearly into the water and receives the reflected waves, and a high speed Fourier transform device 12 takes out the received signals by the transmitter/receiver 11 for a specific time width and prepares the frequency spectral distribution through high speed Fourier transformation A specification device 13 turns the obtained frequency spectral distribution into specifications according to the peak values, while a comparator 14 compares the obtained frequency spectral distribution turned into specifications with the distribution over a template prepared previously and distinguishes whether the received signals by the transmitter/receiver 11 are due to echo or reverberation Judgement about if it is echo or reverberation is made on the basis of the shape of the frequency spectral distribution

Signal-detection characteristics in trellis-coded modulation system under impulsive noise environment and its optimum reception

Abstract: This paper investigates the performances of the trellis-coded modulation (TCM) systems under impulsive noise environment. Conventionally, receivers for a TCM system have been designed based on Euclidean distances between signal sequences assuming their use under Gaussian noise environments. These receivers are not suitable for impulsive noise environments having statistics significantly different from Gaussian noise and thus designs based on the statistics of impulsive noise are needed. The error event probability characteristics of TCM signals received by conventional-type receivers have been obtained, and it has been clarified that coding gain is obtained even under impulsive noise when the carrier-to-noise power ratio (CNR) is sufficiently large, and there is a range of CNR at which the error event probability characteristics of TCM signals become worse than those of uncoded signals. Next, it is shown that the error event probability characteristics of TCM signals are inferior to those of the case in which uncoded signals are received by optimum receivers designed by considering impulsive radio noise. In addition, it has been shown that optimum receivers for TCM systems under impulsive radio noise can simply be constructed by adding a number of circuits to conventional-type TCM receivers, and their performances exceed those of the case in which uncoded signals are received by optimum receivers at any CNR and great coding gain is obtained.

Compound implant of titanium or titanium alloy and manufacture thereof

Abstract: PURPOSE:To enable a compound implant to be easily manufactured and improve the bio-compatibility thereof by burying the coarse or granulated ceramic pow der of calcium phosphate in the surface of a compound implant in such a way as partially exposed, in a compound implant used for a tooth root or the like. CONSTITUTION:The coarse powder 2 of tricalcium phosphate is heated, sprinkled, pressed and buried in the surface of a wax pattern 1 having the same form as an artificial titanium hip joint, in such a way as partially exposed, thereby manufacturing a compound wax pattern 3. This pattern 3 is immersed in a muddy covering material comprising a silica flour mixed with water solution of ethyl silicate, and dried. Thereafter the pattern 3 is covered with a mold material, filled with a backup filler and solidified. Furthermore, the wax is melted and removed, thereby manufacturing a precision casting mold 4 with coarse tricalcium phosphate powder partially exposed from the inner surface of a cavity 5. The cavity 5 is, then, filled with molten alloy of Ti-6% Al-4% VaTi, thereby providing a compound artificial hip joint 6 of titanium alloy.

Artificial articulating capital ball made of ti or ti alloy with excellent abrasion resistance and manufacture thereof

Abstract: PURPOSE:To provide an artifical articulating capital ball made of Ti or Ti alloy and having excellent abrasion resistance and a simple manufacturing method therefor. CONSTITUTION:(1) An artificial articulating capital ball made of Ti or Ti alloy with excellent abrasion resistance and having an oxygen diffusion solid hard layer on its surface and (2) a method for casting the artificial articulating capital ball made of Ti or Ti alloy and having excellent abrasion resistance whereby Ti or Ti alloy is casted into a zirconia ceramics mold having a composition comprising one or two kinds of alumina (2 to 50wt.%) and titania (2 to 30wt.%) and the rest zirconia in such a manner that the total amount of the alumina and the titania does not exceed 50wt.%.

Calcium phosphate ceramics layer-clad titanium or titanium alloy implant and preparation thereof

Abstract: PURPOSE:To improve peeling resistance by preparing the title implant used in the fields of dentistry and orthopedics in such a way that a part of calcium phosphate ceramics-clad layer covering the surface of Ti or Ti alloy-made implant main body is embedded in the surface of the main body. CONSTITUTION:In preparing an artificial hip joint, at first, calcium phosphate powder synthesized by a wet process is calcinated at high temp. and is ground by means of a wet ball mill and a binder is incorporated therein and the mixture is dispersed into a slurry, which is then spray-dried to obtain a powder and after it is granulated, it is calcined to obtain a roundish rough powder 2 of tricalcium phosphate. Then, after this rough powder 2 is heated and is sprinkled over the surface of a wax pattern 1 with the same shape as the artificial joint, the rough powder 2 stuck on the surface of the wax pattern 1 is pushed to prepare a composite wax pattern from which a part of the rough powder 2 is projected and exposed. Then, after a casting matrix for preparation is prepd. by using this composite wax pattern 3, a Ti alloy is cast therein to obtain a Ti alloy-made artificial hip joint wherein the rough powder 2 of tricalcium phosphate is embedded.