A fiber-optic sensor using an aqueous solution of sodium chloride to measure temperature and water level simultaneously.

A fiber-optic sensor system using a multiplexed array of sensing probes based on an aqueous solution of sodium chloride (NaCl solution) and an optical time-domain reflectometer (OTDR) for simultaneous measurement of temperature and water level is proposed. By changing the temperature, the refractive index of the NaCl solution is varied and Fresnel reflection arising at the interface between the distal end of optical fiber and the NaCl solution is then also changed. We measured the modified optical power of the light reflected from the sensing probe using a portable OTDR device and also obtained the relationship between the temperature of water and the optical power. In this study, the water level was simply determined by measuring the signal difference of the optical power due to the temperature difference of individual sensing probes placed inside and outside of the water. In conclusion, we demonstrate that the temperature and water level can be obtained simultaneously by measuring optical powers of light reflected from sensing probes based on the NaCl solution. It is anticipated that the proposed fiber-optic sensor system makes it possible to remotely monitor the real-time change of temperature and water level of the spent fuel pool during a loss of power accident.

Investigation of the areas of high radon concentration in Gyeongju.

The aim of this study was to survey the radon concentrations at 21 elementary schools in Gyeongju, Republic of Korea, to identify those schools with high radon concentrations. Considering their geological characteristics and the preliminary survey results, three schools were finally placed under close scrutiny. For these three schools, continuous measurements over 48 h were taken at the principal's and administration office. The radon concentrations at one school, Naenam, exceeded the action level (148 Bq/m(3)) established by the U.S. EPA, while those at the other two schools were below that level.

Development and characterization of the integrated fiber-optic radiation sensor for the simultaneous detection of neutrons and gamma rays.

Sometimes, detection of thermal neutrons in the presence of gamma rays is required. This study developed and characterized an integrated fiber-optic radiation sensor for the simultaneous detection of thermal neutrons and gamma rays in a mixed radiation field. The performance of the integrated sensor was verified by measuring the distributions of thermal neutrons and gamma rays released from a nuclear fuel rod at the Kyoto University Critical Assembly. The experimental results show that the integrated sensor produced similar distribution patterns to those of thermal neutrons and gamma rays released from a fuel rod.

A characteristic estimation of bio-signals for electro-acupuncture stimulations in human subjects.

This research evaluates the effect of physiological responses during electrical acupuncture (EA) stimulation on specific acupuncture points (APs: PC5 and PC6). A variety of special responses in the human body were determined by electroencephalogram (EEG), heart rate (HR) in an electrocardiogram (ECG), and skin impedance test for 2 groups, sham group as a control and a group under acupuncture stimulation. The total stimulation time in this study was set for 5 min since the effect of EA on all recorded parameters became stable within this period. According to the experiments, during EA stimulation of PC5 and PC6, the power spectrum of EEG showed that the number of low frequency waves was increased in all lobes. Heart rate variability measures of 10 subjects stimulation trials at PC6 and PC5 were compared to 10 subjects who received no stimulation treatment. In both the AP and the sham groups, the mean R-R interval increased significantly during EA stimulation. A comparison between the AP and non-AP group in terms of skin resistance measurement experiments revealed no difference in skin resistance. The results of this study verified that EA stimulation of APs (PC5, PC6) causes EEG changes, and ECG heart rate changes. However, from human skin impedance measurements, the beneficial effects were not sustained. These results may be helpful in the understanding of the mechanism underlying the effect of electrical acupuncture on PC6 and PC5.