An environment detection system includes a sound wave transmitter, a sound wave receiver, and a control unit. The sound wave transmitter transmits a detection sound wave to a target space. The sound wave receiver receives the detection sound wave transmitted by the sound wave transmitter. The control unit controls the sound wave transmitter. The environment detection system detects at least either a temperature distribution or an air velocity distribution in the target space. The control unit executes a first control to regulate at least either a volume or a frequency of the detection sound wave transmitted by the sound wave transmitter so that a volume of the detection sound wave received by the sound wave receiver is higher than or equal to a predetermined reference reception volume.

A method for determining the prestress force of a connection component (10) is proposed. In the method, ultrasonic signals (22) are introduced into the connection component (10) and ultrasonic echoes (24) of the ultrasonic signals (22) are received again. The method comprises the following steps: a) introducing a longitudinal ultrasonic signal and determining a first signal time of flight FTOF.sub.L of the longitudinal ultrasonic signal until the reception of an echo of the longitudinal ultrasonic signal, b) introducing a transverse ultrasonic signal and determining a second signal time of flight FTOF.sub.T of the transverse ultrasonic signal until the reception of an echo of the transverse ultrasonic signal, and c) determining an effective temperature T.sub.eff and the prestress force of the connection component (10) on the basis of the first signal time of flight FTOF.sub.L, the second signal time of flight FTOF.sub.T, previously determined reference data and calibration factors using the assumption that a prestress force F.sub.L ascertained using the first signal time of flight FTOF.sub.L and a prestress force F.sub.T ascertained using the second signal time of flight FTOF.sub.T are equal in magnitude,
wherein steps a) and b) are carried out successively in any desired order or in parallel. A further aspect of the invention relates to a device for carrying out the method.

Detection of gas characteristics, especially the detection of the gas composition, the temperature and/or humidity of a gas, by measuring the speed of sound with a sound sender and a sound receiver both mounted on common structure. A method for determining the humidity of the scavenge air of an internal combustion engine. A speed of sound based gas sensor arrangement adapted to measure gas characteristics, especially the gas composition, the temperature and/or the humidity of a gas, including a sender, a receiver and a signal processing unit. The speed of sound is determined by driving the sender and receiver at different operation cycles in order to differentiate between the different travel times of the sound through the gas and the common structure of solid material.

A method for the measurement of the speed of sound in a gas suitable for the determination of gas characteristics, especially the composition of the gas, the temperature and/or the humidity of the gas, and a speed of sound based gas sensor arrangement adapted to measure that gas characteristics comprising sound sending means and sound receiving means and signal processing unit. A sound sender is used as sound sender and a first sound receiver and a second sound receiver as sound receiving means, all three of them being arranged such that the travel distance of the sound provided by the sender to the first receiver is different from the travel distance of the sound provided by the sender to the second receiver. Further the arrangement includes the signal processing means connected with the sender and the receivers which operate the sender and determine gas characteristics, especially the composition of the gas, the temperature and/or the humidity of the gas, from the different signals provided by the first and the second receiver.

The present invention relates to a method for evaluating the thermal expansion properties of a titania-containing glass body. On the basis of measured values, obtained at a certain temperature, for a physical parameter that changes depending on the titania concentration and a physical parameter that changes depending on the fictive temperature, the thermal expansion coefficient of the titania-containing silica glass body and the slope of the thermal expansion coefficient are calculated using a linear relational expression represented by a plurality of physical properties. The thermal expansion properties of the titania-containing silica glass body are evaluated on the basis of the calculated thermal expansion coefficient and thermal expansion coefficient slope.

A sensor system that combines the sensing application of surface acoustic wave (SAW) sensor and sensor signal transfer though the enclosure wall via acoustic means. The sensor system includes SAW sensor placed inside the enclosure and at least one pair of bulk acoustic wave (BAW) transducers, one mounted inside and second outside the enclosure wall, allowing the interrogation of SAW sensor from outside the enclosure. The external BAW transducer converts interrogation electrical pulse into acoustic pulse which travels though the enclosure wall to the internal BAW transducer. The internal BAW transducer converts the interrogation electrical pulse to electrical pulse and transfers it to SAW sensor. The response of the SAW transducer containing series of electric pulses is converted to the series of acoustic pulses by internal BAW transducer which propagates though enclosure wall. The external BAW transducer converts the series of acoustic pulses into series of electrical pulses and is received by the interrogation circuit for processing.

An environment detection system includes a sound wave transmitter, a sound wave receiver, and a determination unit. The sound wave transmitter transmits a detection sound wave to a target space where an environment control device that conditions air in a space is installed. The sound wave receiver receives the detection sound wave transmitted by the sound wave transmitter. The determination unit determines a temperature or an air velocity in a first region near the environment control device, based on predetermined acquired information acquired from the environment control device. The environment detection system obtains a temperature or air velocity distribution in the target space, based on measured sound wave data. A temperature or air velocity distribution in a second region is obtained based on at least either the temperature or the air velocity in the first region determined by the determination unit and the measured sound wave data.

A combined vapor and/or gas concentration sensor and switch includes a resonating structure, a first alternating current, AC, voltage source coupled to a drive electrode, the first AC voltage source providing the resonating structure with a first voltage having an amplitude causing a first vibration mode of the resonating structure to exhibit a pull-in band and having a first frequency response adjacent to the pull-in band, where the first frequency response is nonlinear, a second AC voltage source coupled to the drive electrode and providing a second voltage having a frequency so that a second frequency response of the resonant structure, adjacent to a third vibration mode, is linear, and a read-out circuit coupled configured to determine a vapor and/or gas concentration based on a difference between (1) the frequency of the second voltage and (2) a frequency obtained by the read-out circuit from the resonating structure.

This optical fiber distribution measurement system of distributed optical fiber sensing type includes: a tunable wavelength distributed feedback LD (1) for obtaining a DTSS signal through frequency shift analysis; an external resonance laser (2) for obtaining a DAS signal through phase shift analysis; a pulse compression coding circuit (4) including an intensity modulator (4a) and an phase modulator (4b); an acousto-optic switch (5); an erbium doped optical fiber amplifier (6); a circulator (7); a diversity device (8); a digitizer (11); a CPU (12); and a serial transfer interface (13). Through calculation on discrete signals sent from the digitizer (11), the CPU (12) converts an analyzed Rayleigh frequency shift signal obtained as the DTSS signal, to phase error, and corrects an analyzed phase signal obtained as the DAS signal, by the phase error.

An acoustic wave sensor device, comprising an interdigitated transducer; a first reflection structure arranged on one side of the interdigitated transducer, and a second reflection structure arranged on another side of the interdigitated transducer; a first resonance cavity comprising a first upper surface and formed between the interdigitated transducer and the first reflection structure; a second resonance cavity comprising a second upper surface and formed between the interdigitated transducer and the second reflection structure; and wherein the second upper surface comprises a physical and/or chemical modification as compared to the first upper surface.