Abstract: Parameters are received that include prediction coefficients representing a speech spectral envelope characteristic, impulse positions of an excitation signal, and zero filter coefficients which provide a sequence of impulses with a shape resembling a phase-equalized residual of a speech. An impulse sequence generator produces a sequence of impulses having the impulse positions, which are fed into a zero filter. The zero filter provides, under control of the zero filter coefficients, the sequence of impulses with a shape resembling a phase-equalized residual of the speech. The output of the zero filter is fed as an excitation signal into an all-pole filter which is controlled by the prediction coefficients to produce a synthesized speech.

Abstract: An exhaust gas purification filter comprising a metal porous body obtained by packing and fixing metal fibers having a mean fiber diameter of 5 to 40 .mu.m or heat resistant ceramic fibers having a mean fiber diameter of 1 to 40 .mu.m in a dispersed state into pores of a foamed structure porous body made of a heat-resistant metal so that a packing density of the resulting metal porous body is from 5 to 20%. The filter may be in a laminated structure by laminating the foregoing foamed structure porous body filled with or without the metal or ceramic fibers and a fiber structure porous body obtained by fixing metal fibers having a mean diameter of 5 to 40 .mu.m or heat-resistant ceramic fibers having a mean diameter of 1 to 40 .mu.m in a dispersed state so that a packing density is from 5 to 25% are laminated.

Abstract: In combination with a diesel engine, a particulate trap for purifying the diesel exhaust of the engine includes a case provided in the exhaust line of the diesel engine and a filter element mounted in the case. The filter element is a porous member of a heat-resistant metal framework having the form of a three-dimensional mesh. The surface roughness of the metal framework is at least 0.2 .mu.m. The pores of the porous member have an average diameter of 0.1-1 mm, the average number of such pores as counted in the thickness direction of the porous member is 10 or more, the volume packing density of the filter element to the entire filtering space is 10-40%, and the filter has a gas inflow filtration area of 400 cm.sup.2 per liter of the displacement of the engine to which the trap is to be mounted. The filter element has a high capacity to collect particulates and can withstand thermal shock during regeneration and yet produces little pressure drop in the exhaust line during filtration.

Abstract: A high-strength silicon nitride sintered body having a flexural strength of 100 kg/mm.sup.2 or higher and a process for producing the same are disclosed, the sintered body comprising not less than 90% by weight of a single crystalline phase of silicon aluminum oxynitride (Si.sub.6-z Al.sub.2 O.sub.z N.sub.8-z, wherein z is a number of from 0 to 4.2) having an average longer diameter of not more than 5 .mu.

Abstract: An impulse sequence of a pitch frequency is detected from a phase-equalized prediction residual of an input speech signal, and a quasi-periodic impulse sequence is obtained by processing the impulse sequence so that a fluctuation in its pitch frequency is within an allowed limit range. The magnitudes of the quasi-periodic impulse sequence are so determined as to minimize an error between the waveform of a synthesized speech obtainable by exciting an all-pole filter with the quasi-periodic impulse sequence and the waveform of a phase-equalized speech obtainable by applying the input speech signal to a phase equalizing filter. Preferably, the quasi-periodic impulse sequence is supplied to the all-pole filter after being applied to a zero filter in which it is given features of the prediction residual of the speech. Coefficients of the zero filter are also determined so that the error of the waveforms of the synthesized speech and the phase-equalized speech is minimum.

Abstract: A high-strength silicon nitride sintered body having a flexural strength of 100 kg/mm.sup.2 or higher and a process for producing the same are disclosed, the sintered body comprising not less than 90% by weight of a single crystalline phase of silicon aluminum oxynitride (Si.sub.6-z Al.sub.2 O.sub.z N.sub.8-z, wherein z is a number of from 0 to 4.2) having an average longer diameter of not more than 5 .mu.

Abstract: The present invention relates to a method of sintering ceramics and ceramics obtained by said method. According to the present invention, the synthesis and sintering of ceramics can be simultaneously carried out by utilizing the reaction heat generated when at least one metallic element selected from metallic elements of IIb, IVb, Vb and VIb groups of the Periodic Table is combined with at least one nonmetallic element such as B, C N and Si without heat or by preliminarily heating the ceramics at temperatures remarkably lower than the usual sintering temperature ceramics thus-produced are superior in abrasion resistance and corrosion resistance.

Abstract: The present invention relates to a method of sintering ceramics and ceramics obtained by said method. According to the present invention, the synthesis and sintering of ceramics can be simultaneously carried out by utilizing the reaction heat generated when at least one metallic element selected from metallic elements of IIIb, IVa, Vb and VIb groups of the Periodic Table is combined with at least one nonmetallic element such as B, C, N and Si without heat or by preliminarily heating the ceramics at temperatures remarkably lower than the usual sintering temperature ceramics, thus-produced are superior in abrasion resistance and corrosion resistance.

Abstract: A speech signal processing system in which the correlation is removed from the sample values of a speech waveform supplied to an inverse-filter for obtaining sample values of a prediction residual waveform, phase-equalizing filter coefficients are determined to have phase-characteristic inverse to that of the prediction residual waveform at each pitch position of the speech waveform, the phase-equalizing filter coefficients are set as filter coefficients of the phase-equalizing filter, and the speech waveform or the prediction residual waveform is passed through the phase-equalizing filter, thereby zero-phasing the prediction residual waveform or the prediction residual waveform component in the speech waveform and concentrating energy around the pitch position.

Abstract: A time series of spectral parameters is extracted from a learning speech, the spectral parameters are divided into a plurality of segments for each voice interval, and the segments are clustered into a plurality of clusters. For each cluster an initial reference pattern representing the cluster is computed. The segment boundaries are corrected using the computed reference patterns (a correcting step), the segments of the corrected spectral parameter time series are clustered (a clustering step), and for each cluster, a reference pattern representing the cluster is computed (a reference pattern computing step). The correcting step, the clustering step, and the reference pattern computing step are performed at least once, and the reference patterns obtained by the last reference pattern computing step are regarded as reference patterns desired to be obtained.

Abstract: An adaptive predictive coding (APC) and adaptive kit allocation (ABA) system which splits a speech signal into a plurality of bands, subjecting each signal to adaptive predictive coding and adaptively changes quantization characteristics in the adaptive predictive coding so that quantization noise may become small. An average amplitude (not average power) of the signal of each band is detected for each temporal sub-interval, and a quantization bit number and a quantization step size are adaptively determined from the average amplitude for each sub-interval, thereby permitting reduction of the quantity of hardware used.

Abstract: A method for producing a tubular multi-layered porous barrier comprising the step of depositing fine powder onto at least one of the inner and outer surfaces of a sintered tubular porous support member in a layer of uniform thickness to form a fine powder layer and pressurizing said powder layer against said support member to form a porous barrier layer on the support member.