Due to the explosive improvement of micro machining technology, many kinds of meso-scale products and parts are developed. There are two techniques, CMM (Coordinate Measuring Machine) and SPM (Scanning Probe Microscopy), commonly used to measure the profile of meso-scale products. However, both of these methods have their own strengths and weaknesses in that scale. The CMM can¡¦t be precise and accurate; while the SPM measurement system will be a time-consuming process. The micro scale CMM measurement system with micro spherical probes would be suitable for measuring meso-scale objects. In this study, equipments are built to fabricate the micro spherical probes. The glass optical fiber is selected as the material to fabricate the probes. The heating-pulling method and arc fusion method are selected as the fabrication process. The commercial equipments are available for fabricating micropipette and NSOM (Near-field Scanning Optical Microscopy) probes. However, most of these commercial equipments are expensive, and the heating area is too small to fit our study. In this study, the gas heater is used to replace the laser power as a heat source. A vertical pulling mechanism is developed to pull the optical fiber. Moreover, this study uses Taguchi method to reduce the number of experimental runs and find the suitable parameters for fabrication. The straight-circular-cone-type probe and the bent-circular-cone-type probe can be fabricated at the same time. The radius of the probe tip can be smaller than 0.5£gm for NSOM. In addition, the heating-pulling mechanism can reduce the diameter of optical fiber from £p125£gm to less than £p50£gm for different purposes. An arc discharge machine is also developed to melt the cleaved end-face of the prob. The heating-pulling mechanism and arc discharge machine developed in this study are successfully applied in fabricating different types of probe ends, £p20~125£gm hemispherical end-face and £p50~300£gm spherical end-face for example, for different applications.

Since micro machining technologies are dramatically improved, many kinds of meso-to-micro scale products are developed. The Coordinate Measuring Machine(CMM) and the Scanning Probe Microscope(SPM) are the most commonly used instrument for precision measurement. To acquire geometric characteristic of products in meso scale, the CMM is not adequate due to the minimum diameter of ruby-ball head probes are 300 to 500£gm; while the SPM will be a time-consuming process. Thus, proper probes for meso-scale coordinate measuring machines are necessarily developed. The commercial fusion splicers are available to fabricate glass probes with spherical head. However, the commercial fusion splicers are expensive and the fiber clamps can not fit the diameter of probe stylus in this study. Therefore, instruments are implemented to fabricate the glass probe with spherical head for the meso-scale coordinate measuring machine. The

This thesis contains the details of an experimental study on the local void fraction measurements in large-diameter vertical pipes using optical fiber probes. The experiments were conducted in vertical transparent acrylic pipe of a 20-cm diameter. An experimental test facility used for performing of experiments, was designed as a low-pressure air-water loop, which can operate in either a natural circulation mode or a forced circulation mode. Radial void fraction profiles were measured using an optical fiber probe. An average cross-sectional void fraction was calculated by integration of the data obtained by the optical fiber probe. The average void fraction was also calculated using two-phase pressure-drop measurements . The results were compared and the resulting good accuracy of the optical fiber probe was determined. The flow regime results were plotted in terms of superficial gas and liquid velocities using flow regime maps of several researchers. Absence of the slug flow regime in large-diameter pipes was observed during the experiments. The data were correlated using the drift-flux model. A near unity distribution parameter showed that nearly uniform radial distribution of the void fraction dominates in two-phase flow through large-diameter vertical pipes. / Thesis / Master of Engineering (ME)