Abstract: A simple visible light communication method and system that, underwater in an ordinary water-quality in which a diver is allowed to go under the water, are able to reliably communicate with a ship, or the like, above water while the diver is stopping at a safety stop position at a depth of 5 m in order to prevent occurrence of dysbarism. The visible light communication method and system us the visible light communication system that includes a transmitter and a receiver and that is usable underwater, and include at a transmitting side, modulating information to be transmitted to pseudo-white light that is adjusted to have a color temperature of 4000 to 10000K and a luminous flux of 550 to 1500 lumens and that is emitted from an LED, and transmitting the pseudo-white light; and, at a receiving side, extracting the information by demodulating the received pseudo-white light.

Abstract: A catalyst deterioration diagnosis system for an internal combustion engine having an exhaust gas passageway in which a catalytic converter having a catalyst is disposed. The diagnosis system comprises a first air-fuel ratio sensor disposed in the exhaust gas passageway upstream of the catalytic converter, and a second air-fuel ratio sensor disposed in the exhaust gas passageway downstream of the catalytic converter. The diagnosis system further comprises a control unit connected to the air-fuel ratio sensors and arranged to make an air-fuel ratio feedback control mainly in response to an output signal of the first air-fuel ratio sensor.

Abstract: To reliably diagnose catalyst degradation in an air fuel ratio control system without being subjected to the influence of engine operating conditions, a front O.sub.2 sensor output VFO and a rear O.sub.2 sensor output VRO are detected on both the upstream and downstream sides of catalytic converter; air fuel ratio feedback correction coefficients .alpha. are determined on the basis of basic feedback control constants P.sub.R,L or i.sub.R,L and correction values PHOS according to rich and lean air fuel ratio conditions; periods T and amplitudes .alpha..sub.R -.alpha..sub.L of the air fuel ratio feedback correction coefficient .alpha.

Abstract: A system and method for controlling an air/fuel mixture for an internal combustion engine are disclosed in which an integration constant used for a calculation of an integration portion included in a feedback correction coefficient (.alpha.) of the air/fuel mixture ratio after a relationship between an actual air/fuel mixture raito and target (stoichiometric) air/fuel mixture ratio has been inverted is set and varied according to an engine driving condition, so that the integration constant meets requirements of a stability during an engine steady driving condition and a favorable responsive characteristic during an engine transient condition. In a preferred embodiement, a fuzzy control is applicable to the calculation of the integration constant.

Abstract: An air/fuel ratio control system detects transition of air/fuel ratio changing between rich and lean for checking if updating condition is satisfied. Updating value is derived based on a feedback correction value which is derived for adjusting air/fuel ratio toward a stoichiometric value. With the updating value thus derived, one of a plurality of learnt correction value which are set with respect to various engine driving range.