Noncontact Measurement of Humidity and Temperature Using Airborne Ultrasound

Abstract

The proposal that a strong-coupling limit of the five-dimensional type II string theory (M-theory compactified on a 6-torus) in which the Planck length becomes infinite could give a six-dimensional superconformal phase of M-theory is reviewed. This limit exists for the free theory, giving a six-dimensional theory with (4, 0) supersymmetry compactified on a circle whose radius gives the five-dimensional Planck length. The free six-dimensional theory has a fourth rank tensor gauge field with the symmetries of the Riemann tensor instead of a symmetric tensor gauge field, but its dimensional reduction gives conventional linearized gravity in five dimensions. The possibility of an interacting form of this theory existing and the consequences it would have for the geometric picture of gravity are discussed.Gravitational theories are characterized by a length scale l which determines the strength of gravitational coupling and also the scale at which quantum gravity effects are expected to become important; in M-theory this is the D = 11 Planck length. In recent years there has been great success in describing the strong-coupling behaviour of a variety of gauge and string theories in terms of dual theories. Here, a recent proposal [1] (reviewed in [2]) to extend this to gravitational theories will be described. The idea is to consider a suitable limit in which l → ∞ so that masses become zero and a phase of the theory with a vast amount of unbroken gauge symmetry is obtained. The specific model is M-theory compactified on T 6 to D = 5, with a low-energy effective description in terms of D = 5, N = 8 supergravity. The proposal is that the limit l → ∞ is a kind of decompactification limit to a six-dimensional theory. This theory is conformally invariant, with no length scales, and the scale l arises as the compactification scale: compactification from D = 6 on a circle of radius R gives a theory with D = 5 Planck scale l = R. If such a superconformal phase of M-theory exists, then it 0264-

Acoustic Hygrometer Based on Reverberation Time Measurement

“…The accuracy of the attenuation coefficient measurement to achieve an accuracy of AE5% RH in humidity measurement is defined as the permissible error, and calculated using eqs. ( 2)- (7). From Fig.…”

“…Acoustical sensing techniques have been proposed for measuring environmental parameters in air such as temperature, [1][2][3][4][5][6] humidity, 7) and wind velocity. [8][9][10][11][12][13][14] These techniques are based on the measurement of sound velocity in air, and a noncontact measurement of environmental parameters, which are not local but spatial average values through the acoustic propagation path, can be achieved.…”

“…In a previous work, an acoustic sensor that utilizes the effects of humidity on sound velocity was proposed. 7) The sensor only measures the average humidity on the line between sensors. The technique proposed here is based on room acoustics and uses sound attenuation for spatial average measurement in air.…”

Estimation of water stress of plant by vibration measurement of leaf using acoustic radiation force

“…By using these techniques, we are aiming to perform the most suitable irrigation control to save water in soil culture by adopting ''negativepressure-difference irrigation'', which is reported to be effective for cultivating plants as well as saving water [21]. Acoustic techniques are also applied to the measurement of environmental conditions, such as temperature, humidity, and wind velocity [22][23][24].…”

Simultaneous Measurement of Air Temperature and Humidity Based on Sound Velocity and Attenuation Using Ultrasonic Probe

“…Therefore, regular correction of the sound velocity change caused by humidity has been necessary, using commercially available non acoustic contact-type humidity sensors in addition to the ultrasonic probe, because the time variation of humidity greatly depends on the season, weather, and time of day. [20][21][22] On the other hand, the humidity measurement system composed of an ultrasonic probe measuring sound velocity and commercial contact-type temperature sensors was proposed. 20) In our previous works, we proposed a humidity measurement system composed of an ultrasonic probe measuring sound attenuation and commercial contact-type temperature sensors.…”