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In nuclear plant, as water feeding into reactor have much effect on thermal power of plant, it is important to measure accurately the flow rate of water. Flow nozzle is on of typical differential pressure type flow meters and the discharge coefficient is used to calculate the flow rate. This coefficient is given by actual experiment and theory. We studied the theoretical assumption of the discharge coefficient curve using numerical simulation and evaluated the effect of flow nozzle configuration on the coefficient numerically and experimentally. As the result, numerical simulation can predict the discharge coefficient of theoretical curve within 0.3%. And we found that the throat length and throat tapping location of flow nozzle have much effect on the coefficient.

In order to conduct a detailed investigation of the piston effect, the peculiar heat transportation phenomenon in critical fluids, an ultra-sensitive high-speed density measurement system was developed using a very thin heater, a sensitive interferometer and a large-capacity high-speed data acquisition system. As the first step of the investigation, an experiment was conducted to measure the velocity of sound in CO2 near its critical point. Short heat pulses suppressing the disturbance of natural convection were applied to a small cell filled with almost-critical CO2 fluid and were detected by the measurement system. Because the pulses propagated through the cell at the velocity of sound and were reflected several times between the cell walls, the velocity could be precisely determined by measuring the time intervals between successive reflections. The resulting velocity profile versus temperature showed good agreement with theoretical prediction and numerical simulations. This result validated the density measurement system, and it is considered that the measurement system will be a very effective tool for further studies on critical phenomena with the aid of numerical simulation.

The dynamic behavior of pico sliders is investigated during slider-disk contacts as a function of velocity, pitch angle, crown height, and lubricant thickness using laser Doppler vibrometry and acoustic emission sensors. Analog and digital filtering methods are applied to distinguish air bearing and slider body resonances from frequencies related to disk runout, load beam design, and gimbal structure. Sliders with high pitch angle and small crown were found to exhibit smaller vibration amplitudes after slider-disk contacts than sliders with low pitch angle or large crown. The lubricant thickness of the disk was found to affect both the glide avalanche height of the disk and the dynamic behavior of the slider. The results show that roll and pitch frequencies of the air bearing increase with decreasing disk velocity.

This paper describes the characteristics analysis of induction motors by considering stress caused by shrink fitting of stator cores. The electromagnetic field and stress analyses are combined in order to take into account the deterioration of permeability and the increase in core loss. The calculated results are compared with the result of experiments in order to confirm the validity of the combined analysis. It is revealed that the efficiency of the induction motor decreases by several percent because of increases in both the core loss and the copper loss by the shrink fitting.

A novel flying height-attitude testing system was developed based on white-light interferometry. Flying heights at three desired locations on the slider surface can be determined simultaneously with this system and, thus, slider attitude can be fully determined from the measurement results. Load and unload processes were systematically studied with this system and some details were revealed.

The current design of magnetic-disk head sliders needs an extra margin of flying height for manufacturing tolerance or environmental variation. To reduce this margin, we have developed active-head sliders. These sliders carry an unimorph piezoelectric microactuator, and their flying height can be controlled. After simulating the piezoelectric deflection of the actuator and flying characteristics of air-bearing surfaces, we designed two types of active-head sliders (five-pad type and four-pad type) and fabricated them by silicon microelectromechanical system (MEMS) processing. In tests, the sliders flew over a glass disk, and the observed stroke of the actuator (30 nm/5 V) was considered large enough to control the flying height. The large area at the rear end of the four-pad-type slider structure is sufficient to carry conventional read/write heads. Moreover, the slider fabrication process will not destroy the heads. We, thus, conclude that the active-head sliders can be applied for practical use easily, and their flying height will be significantly lower than that of conventional disk head sliders.

The volunteer siting of disposal facilities for vitrified high-level radioactive waste (HLW) and TRU waste in Japan results in a particular need for flexibility to allow repositories to be tailored to specific sites. Instead of a single reference concept, a “catalogue” of designs for individual repository components is being developed, which can then be combined to form optimum solutions for particular site boundary conditions. As highlighted in a companion paper – Makino et al: Supporting Development of Practical Designs for a Japanese HLW Repository –, which puts the repository design process in the context of the Japanese HLW programme, the complexity of this work justifies use of advanced Knowledge Engineering approaches. In this paper three components are described – development of the knowledge base, assessing tacit system understanding and production of innovative solutions to resolve conflicts between requirements.

In preparation for actual repository implementation, designs that could be tailored to specific sites need to be considered. This requires a paradigm shift in design philosophy, moving away from a single reference design towards a flexible and systematic “catalogue” of engineered barrier components and associated repository infrastructure. To support this development, novel methodology for both developing and comparing repository design options for Japanese vitrified high-level radioactive waste (HLW) has been examined. This paper will outline the background of the project and, in particular, some novel approaches examined for facilitating optimisation of practical repository designs. It is complemented by a companion paper - Matsumoto et al: Application of Formal Knowledge Engineering Approaches to Develop A Design Catalogue for A Japanese HLW Repository -, which describes the repository design process in more detail and illustrates results of first dry runs of the methodology.

We investigated the friction force between the trailing edge of the center pad or rail of negative pressure sliders and the textured disk surface as a function of flying height at reduced air pressure. In addition, we proposed the simple contact model and compared experimental friction force with calculated contact force to evaluate the influence of slider design parameters on the contact force. Results show that the contact force is significantly influenced by the pitch air-bearing stiffness, the distance between the pivot point and the contact point, and the interference pitch angle defined as the difference between the flying pitch angle on the smooth glass disk and the contact pitch angle on the textured disk.