Doppler effect in flexible and expandable light waveguide and development of new fiber-optic vibration/acoustic sensor

New principle and a geometrical arrangement of an optical fiber for a vibration/acoustic measurement are proposed in the present paper. The sensor is based on a new finding that a frequency of light wave transmitted through a bent optical fiber is shifted by vibration at the bent region. The phenomenon can be explained as Doppler's effect in flexible and expandable light waveguide. Several configurations of the sensor have been designed, and very high sensitivity is achieved in the extremely wide frequency range. Principle, sensor configuration and theoretical sensitivity, measurement system, and some experimental consideration are described in the present paper. The sensor sensitivity was examined experimentally in the low and middle frequency range, and the detectability was confirmed experimentally in the frequency range of acoustic emission signals.     

NOVEL TERAHERTZ PHOTOCONDUCTIVE ANTENNAS

The photoconductive (PC) antenna is a key device for the recent terahertz (THz) photonics based on laser-pumped generation and detection of THz radiation. In this paper we report on two new types of PC antennas: the Schottky PC antenna and the multi-contacts PC antenna. The former one is able to detect THz radiation intensity without the time-delay scan and useful for applications where spectroscopic information is not important, such as the THz intensity imaging. The latter one is useful for the polarization sensitive THz spectroscopy, such as the THz ellipsometry. The characteristic features of these new types of PC antennas are studied by using a THz time-domain spectroscopy system.     

Carrier trapping centers and interface states induced by r.f. sputtering of molybdenum electrodes in MOS-structure diodes

Electronic properties of interface and oxide layers of Si MOS diodes with an r.f. sputtered molybdenum metal electrodes have been studied. A remarkable density increase of both oxide charge and interface states by the sputtering has been found. IMA data show that the sputtered Mo atoms are implanted into the SiO₂ less than 100 Å from the surface. It is also found from photo I–V data that the charge centroid in the SiO₂ is shifted to a depth of 100 Å below the SiO₂ surface. The energy distribution of the carrier trapping centers having a capture cross section of the order of 10^?13 to 10^?16 cm² has been observed. The interface states density can be reduced about one order of magnitude by an annealing in N₂ 10 min/H₂ 15 min/N₂ 10 min at 450°C. The mechanism of the increase of the carrier trapping centers and the interface states is also studied. Especially it is concluded that the increase of the interface states originates from the ultraviolet-light irradiation emitted from the plasma during the r.f. sputtering.     

Activities of FexO in complex slags used during the final stages of external dephosphorization of hot metal

Measurements of the activities of Fe_xO in complex slags during the final stages of external dephosphorization by using a disposable electrochemical oxygen probe. Positive deviations of the Fe_xO activities from the Raoult law. Iso-activity curves drawn on the “ternary” diagram, (CaO + MgO + MnO + CaF₂) + Fe_xO + (SiO₂ + P₂O₅) at 1673 K. Calculations of the activities of P₂O₅ in complex slags with an assumption of thermodynamic equilibrium between slags and hot metal. Beneficial effect of CaF₂ in the slags with respect to lowering of the P₂O₅ activity.     

An increase of plasma triiodothyronine concentration in man in a cold environment

In an attempt to study an effect of cold on endocrine function in man, plasma thyroxine (T4), triiodothyronine (T3), TSH, and cortisol concentrations were studied in 24 healthy men who worked in a cold environment (4 to 6C) for 3 h for the culture of mushrooms and 56 healthy men who lived in cold environment in winter. For comparison, similar measurements were made on 47 university employees who lived in rooms with air-conditioning. In 24 adult men, acute exposure to cold for 3 h failed to affect plasma concentrations of T4, T3, and TSH. In 56 adult men, no significant difference was found in the concentrations of T4, TSH, and cortisol between summer and winter. However, plasma T3 concentration increased significantly in winter, suggesting seasonal variation of T3. In contrast, no such seasonal variation was found in 47 university employees who lived in rooms with air-conditioning.     

Kinetics of sulfidization of iron oxide with SO2-CO mixtures of high sulfur potential

The sulfidization of iron oxides has been suggested as a means for selective removal of iron from various minerals. For this purpose high sulfur potential SO₂-CO mixtures appear to be very attractive. In order to determine some essential parameters of such reactions the kinetics of the gas-solid reaction between Fe₂O₃ and SO₂-CO mixtures was studied experimentally by weight changes registered in a quartz balance and analysis of the reaction products. It was found that the overall reaction rate is relatively constant over a broad range of temperatures and reagent gas compositions and that COS as well as S₂ are active sulfidization agents in the process. From the morphology of the reaction products and the time-conversion curves obtained it was inferred that nucleation plays an important role in the formation of the sulfide phase. The analysis of the results in terms of the grain boundary nucleation and growth model of Johnson and Mehl rendered a reasonable interpretation of the simultaneous reduction and sulfurization processes. From the results obtained it was deduced that gas phase diffusion of S₂ and/or COS is the process controlling the growth rate of the sulfide phase. K.NAGATA, formerly Investigador Asociado with IVIC.     

A new displacement sensor using pseudoelastic titanium-nickel alloy wire

The authors have developed a new displacement sensor using a wire of pseudoelastic titaniumnickel (Ti-Ni) alloy wire. In the measurement, it was found that this alloy exhibited good linearity between the strain and electric resistance. This linearity has been generally applicable up to several percent strain. In addition, a repeat test and dynamic characteristics have been examined. From these results, it is concluded that this Ti-Ni alloy wire has a possible application as a displacement sensor. Its features include compactness, reduction in weight, and environment attack.     

Assignments of optically pumped CH3OD laser lines

Fifteen laser lines from CH₃OD pumped by a CO₂ laser are assigned to specific rotational energy transitions. These assignments have been obtained from the approximation that, except for one constant, the molecular constants in the excited CO stretching state are same as those in the ground state.