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For this study, single-crystal and polycrystalline diamond films with different boron contents were synthesized in a hot-filament chemical vapor deposition (CVD) apparatus to evaluate the mechanical properties of these films. Boron was added to the diamond by introducing B(CH3)3 :trimethyl boron diluted to 1000 ppm with hydrogen into the diamond-synthesis atmosphere. The synthesized diamond film's crystallinity was evaluated using Raman spectroscopy. The Hertz fracture strength was measured using a diamond-ball indenter. Furthermore, the wear resistance of the film was evaluated using a wear testing machine.The results indicate that the crystallinity of the single-crystal diamond film increased concomitantly with increasing boron content. Furthermore, the Hertz fracture strength increased by 20% with the addition of boron. Results clarified that the wear volume of polycrystalline diamond film decreased to approximately one-third its usual value by the addition of boron. These results show that the mechanical properties of boron-doped diamond films can be improved considerably by adding an appropriate amount of boron.

Feedback mechanism of self-sustained oscillation in supersonic impinging jets is studied experimentally by using a laser-induced fluorescence (LIF) technique. Phase velocities of disturbances in the flow field are obtained from a time-dependent cross-correlation function between a pressure sensor signal at a reference point and the LIF signal. A feature of disturbance propagation can be visualized by drawing maps for the cross-correlation coefficients on a plane at successive delay-times and making an animation. The discrete frequencies appeared near the neutral wave frequencies proposed by Tam and symmetric and asymmetric modes of the neutral wave were observed corresponding to his theory.

Feedback mechanism of self-sustained oscillation in supersonic impinging jets is studied experimentally by using a laser-induced fluorescence (LIF) technique. Phase velocities of disturbances in the flow field are obtained from a time-dependent cross-correlation function between a pressure sensor signal at a reference point and the LIF signal. A feature of disturbance propagation can be visualized by drawing maps for the cross-correlation coefficients on a plane at successive delay-times and making an animation. The discrete frequencies appeared near the neutral wave frequencies proposed by Tam and axisymmetric and helical models of the neutral wave were observed corresponding to his theory. Although the neutral waves propagate upstream both outside and inside the jet, the feedback loop is mainly accomplished by the outside propagating waves.

Feedback mechanism of self-sustained oscillation in subsonic impinging jets is studied experimentally by using a laser-induced fluorescence (LIF) technique. Phase velocities of disturbances in the flow field are obtained from a time-dependent cross-correlation function between a pressure sensor signal at a reference point and the LIF signal. A feature of disturbance propagation can be visualized by drawing maps for the cross-correlation coefficients on a plane at successive delay-times and making an animation. There are two feedback loops : one is closed by a neutral wave propagating upstream inside the jet and another is achieved by sound wave propagating outside the jet. For a nozzle with a thin rim the former is dominant, while the latter loop is enhanced by a thick rim nozzle.

A method for measuring propagation of disturbance in a high-speed flow has been developed by using a laser induced fluorescence (LIF) technique. A cross correlation function between the time-dependent LIF signal and a pressure sensor signal at a reference point enables to measure a propagation speed of disturbance. Through a bandpass filter, the speed of disturbance with a particular frequency can he obtained. A feature of disturbance propagation can be grasped by drawing maps for the cross-correlation coefficients on a space at successive delay-times and making an animation. The method was applied to a supersonic flow over a rectangular cavity with length to depth ratio of 2, to elucidate feedback mechanisms of self sustaining flow oscillation with several dominant frequencies.

A method for measuring temperature fluctuations in a high-speed flow is developed by the use of a laser-induced fluorescence (LIF) technique. Propagation speed of disturbance can be found by a time lag of cross-correlation functions between the time-dependent LIF signal and a pressure sensor signal at a reference point. The method is applied to a supersonic cavity flow to elucidate the feedback mechanism of self-sustaining flow oscillation.

The laser-induced fluorescence method has offered a powerful diagnostic tool for the measurements of transonic and supersonic flows. The present paper uses a tunable line-narrowed AF excimer laser that lases with the 193.5nm ultra-violet wavelength. This laser is injected into the static gas cell with variable pressure. The gases used are argon for the Rayleigh scattering and oxygen for the Raman scattering and induced fluorescence measurements. The Rayleigh scattering intensity is measured as a function of the cell pressure, and also the spectroscopic characteristics are obtained for the Raman and fluorescence from the oxygen molecules.

To investigate the transonic flow in a duct with a cavity, the laser-induced fluorescence (LIF) method is developed. This diagnostic system is based on the argon laser with seeded iodine as fluorescence material, and is applied to the rectangular duct with a cavity. The distributions of temperature and its fluctuation in the cavity are obtained, and the three-dimensional structure of the flow field is clarified.

To investigate the supersonic flows in a duct with a cavity, the laser-induced fluorescense (LIF) method is developed. This diagnostic system is based on the argon laser with seeded iodine as fluorescence material, and is applied to the rectangular duct with a cavity. The temperature distributions in the cavity are obtained, and the three-dimensional structure of the flow field is clarified.

To investigate the turbulence in the transonic flow field with shock wave-boundary layer interactions, the laser-induced fluorescence (LIF) method is developed. This diagnostic system is based on the argon laser with seeded iodine as fluorescence material. The photomultiplier is used as a fluorescence detector to obtain high temporal resolution. The effect of the detector noise due to the photon statistics is investigated, and it is shown that the distribution of the temperature fluctuation in the transonic duct is measured by this method.

To investigate the transonic three-dimensional flow-field with complicated shock wave-boundary layer interaction, the laser-induced fluorescence (LIF) method was developed. This diagnostic system was based on the argon laser with seeded iodine as fluorescence material, and was applied to the rectangular duct with a swept-back bump. The temperature distributions in the duct were obtained, and the structure of the flow including the curved shock wave and the boundary-layer separation was clarified.

In the large-scale gas or steam turbine, the flow around the blade tip becomes transonic, and the shock waves are generated in the blade passage. These shock waves induce the boundary layer separation and the vibrations of blades. This unstable flow phenomenon is closely related to the secondary flow associated with the large change in flow direction in the blade passage. To simulate the flow in the blade passage, the rectangular duct with swept-back bump was made. The laser-induced fluorescence (LIF) method previously developed was applied to measure the temperature distribution in the duct, and the complicated pattern of the three-dimensional transonic flow field was clarified.

In the large-scale gas or steam turbine, the flow around the blade tip becomes transonic, and the shock waves are generated in the blade passage. These shock waves induce the boundary layer separation and the vibrations of blades, which degrade the efficiency. This unstable flow phenomenon is closely related to the secondary flow associated with the large change in flow direction in the blade passage. To measure the secondary flow, the nonintrusive diagnostic technique is desirable, and the laser-induced fluorescence (LIF) method offers one of the best tools for this purpose. To prove the validity of LIF method in determining the temperature and velocity of the transonic flow field, the transonic nozzle with rectangular cross-section was made. The temperature and velocity obtained by the LIF method were shown to agree very well with those calculated from the static pressure measurement.

In the large-scale gas or stream turbine, the flow around the blade tip becomes transonic, and the shock waves are generated in the blade passage. These shock waves induce the boundary layer separation and the vibration of blades, which degrade the efficiency. This unstable flow phenomenon is closely related to the secondary flow associated with the large change in flow direction in the blade passage. To measure the secondary flow, the nonintrusive diagnostic technique is desirable, and the laser-induced fluorescence (LIF) method offers one of the best tools for this purpose. In the present research, the curved nozzle with rectangular cross-section was made to simulate the transonic turbine cascade, and the gas temperature distribution inside the nozzle was obtained by using the LIF method.