Total reflection X-ray spectroscopy as a rapid analytical method for uranium determination in drainage water

Uranium concentrations in drainage water are typically determined by α-spectrometry. However, due to the low specific radioactivity of uranium, the evaporation of large volumes of drainage water, followed by several hours of measurements, is required. Thus, the development of a rapid and simple detection method for uranium in drainage water would enhance the operation efficiency of radiation control workers. We herein propose a novel methodology based on total reflection X-ray fluorescence (TXRF) for the measurement of uranium in contaminated water. TXRF is a particularly desirable method for the rapid and simple evaluation of uranium in contaminated water, as chemical pretreatment of the sample solution is not necessary, measurement times are typically several seconds, and the required sample volume is low. We herein employed sample solutions containing several different concentrations of uranyl acetate with yttrium as an internal standard. The solutions were placed onto sample holders, and were dried prior to TXRF measurements. The relative intensity, otherwise defined as the net intensity ratio of the Lα peak of uranium to the Kα peak of yttrium, was directly proportional to the uranium concentration. Using this method, a TXRF detection limit for uranium in contaminated water of 0.30 µg/g was achieved.     

Suppressing the effect of lightning-induced overvoltages by the combined use of surge arresters and overhead ground wires

Lightning voltage induced by nearby strokes is one of the causes of major overvoltages which threaten the insulation of power distribution lines. Surge arresters as well as an overhead ground wire usually are employed for the protection of equipment and line insulation on overhead power distribution lines. The fundamental mechanism of suppressing effects of overvoltages induced by nearby strokes has been demonstrated independently by one of the present authors for surge arresters and for an overhead ground wire. In this paper, the protective effect of the combination of surge arresters and overhead ground wire is analyzed. As a result, it is found that the effect of surge arresters used together with an overhead ground wire is almost the same as that of surge arresters alone.     

Switching of H∞ controller under constraints and decision of controller state at instance of the controller switching

In real control systems, certain constraints are placed on the input, state, and output values. If such constraints are violated, the system may become unstable, in a worst‐case scenario. One of the promising approaches to solving this problem is to switch the controller according to the state of the closed‐loop system. No useful design strategy for each controller, however, has yet been developed. In addition, the determination of the controller state at the instant of controller switching has not been investigated. First, this paper presents a new design methodology which merges the switching control and H_∞ controller design into one design algorithm. Second, this paper presents a way of determining the controller state at the instant of controller switching. Finally, the proposed method is applied to force control of a one‐DOF manipulator in order to demonstrate the usefulness of the proposed method. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 142(2): 68–75, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10082     

A quality growth model and its application to initial production process control

During initial production of a new product prior to actual production, the decrease in the fraction defective of units produced can be observed as personnel gather experience and the faults in the product's design, manufacturing, etc. are removed. This paper discusses an initial production process control based on a quality growth model proposed here. The model describes a continuing reduction in the cumulative defect rate defined by the ratio of the cumulative number of defective units to that of produced units. A stopping rule is also investigated for determining when to discontinue the initial control of the production process and proceed to the actual production stage. Further, a numerical example of the application is presented.     

Temperature rises in the human eye exposed to EM waves in thefrequency range 0.6-6 GHz

The temperature rises in the human eye for plane wave exposures are investigated in the frequency range between 600 MHz and 6 GHz, which covers the hot spot frequency range. As a first step, the specific absorption rates (SARs) are calculated with the use of the finite-difference time-domain (FDTD) method and the mechanism of hot-spot formation is discussed. Then the temperature rises in the human eye are calculated by using Pennes' bioheat equation. In addition, the dependence of SARs and temperature rises on the electromagnetic (EM) wave polarization and the eye dimension is discussed. Furthermore, the temperature rises calculated are compared with the values found in the literature pertaining to microwave-induced cataract formation. Numerical results show that hot spots appear in a certain frequency range and that the location and number of hot spots depend on the frequencies of the incident wave. In particular, the averaged SARs and the temperature rise are found to depend obviously on the polarization of the EM wave. Additionally, the deviations in the SAR and the temperature rise caused by the eye size are found to be within 10%. Furthermore, the maximum temperature rise due to the incident EM power density of 5.0 mW/cm² , which is the maximum permissible exposure limit for controlled environments, is found to be 0.30°C at 6.0 GHz. This value is small but not negligible, as compared with the threshold temperature rise 3.0°C for cataract formation     

Medical image processing: An overview of and case study in the diagnosis of cardiac diseases

In this paper an overview is presented on R&D of medical imaging and image processing techniques in Japan during the last decade, focusing on case studies in the diagnosis of cardiac diseases.Various problems of image processing of left ventricular images obtained from x-ray, ultrasound and radionuclides are discussed. Also reviewed are boundary detection methods of left ventricular inner cavity and myocardium, analysis of left ventricular wall motion and various kinds of cardiac functions using conventional and newly developed methods, and display methods of these cardiac functions.Microcomputerized on-line image processing systems and a compound sector scan echocardiography using two probes developed for echocardiographic examinations are shown with some results in clinical applications.3-dimensional reconstruction methods of the left ventricle and other organs from multiple 2-dimensional images are shown with 3-dimensional shapes reconstructed from images by x-ray, ultrasound and radionuclides. Moreover, 3-dimensional functional images of the left ventricle are shown as well. Transferring the 3-dimensional consecutive left ventricular images during a cardiac cycle onto a CRT display under the control of a microprocessor, we can observe the pulsating 3-dimensional left ventricle on the CRT.     

Theoretical analysis of knock-out release of fission products from nuclear fuels

The knock-out release of fission products is studied theoretically. The general equations of knock-out release are derived, assuming that a fission fragment passing through the surface of nuclear fuels knocks out a local region of the surface with an effective thickness and an effective cross-sectional area. Using these equations, the knock-out release of fission gases is calculated for various cases. The conditions under which the knock-out coefficients (the average number of uranium atoms knocked out by one fission fragment) is obtainable are clarified by experiments on the knock-out release of fission gases. A method of determining the effective thickness and the effective cross-sectional area of a knock-out region is proposed.