Key Engineering Materials Vol. 643

Abstract: This paper describes a phase noise measurement and testing technique for a clock using a delta-sigma time-to-digital converter (TDC) and verifies its effectiveness with MATLAB simulations. The proposed technique can be implemented with relatively small circuitry, based on the following: (i) The clock under test (CUT) is a repetitive signal. (ii) The time resolution with CUT and a reference clock can be finer with longer measurement time with the delta-sigma TDC. (iii) The phase noise power spectrum can be calculated from the delta-sigma TDC output data using FFT. High performance spectrum analyzers with long measurement time (several ten seconds order due to average of several-time phase measurement results), which are very costly in mass production testing, are not be needed for phase noise measurement with the proposed technique. Our simulation used the input clock of 1 MHz in several phase fluctuation cases, and we observed that the phase fluctuation spectrum at the expected frequency from TDC output power spectrum obtained by FFT. We also investigated the amount of phase fluctuation with our theoretical calculation, which agrees with the simulation results.

Abstract: In this study, we demonstrate a method for adjusting the frequency bandwidth of a Superconductor-insulator-superconductor (SIS) mixer device by controlling its thickness after microfabrication. We estimate the relationship between SIS mixer device thickness and frequency bandwidth using electromagnetic (EM) simulation. We propose an optimal method for the precision polishing of the back side of the device. We evaluate the noise temperature and measure the frequency bandwidth of SIS mixer devices with different thicknesses. This study presents the adjustment of the frequency bandwidth of a device through controlling its thickness after microfabrication. This technique may improve the yield of SIS mixer device mass production and support the construction of receivers for ultra-high frequencies such as Atacama Large Millimeter/Submillimeter Array (ALMA) Band 10.

Abstract: The resultant force acting on the moving part of the ceramic aerostatic linear bearing is measured highly accurately as the inertial force of the moving part of the bearing by means of the levitation mass method (LMM). The measurement results of the ceramic aerostatic linear bearing and metal aerostatic linear bearing of different mass are compared. The regression equation of the ceramic aerostatic linear bearing and metal aerostatic linear bearing are calculated. The ceramic linear bearing and metal linear bearing have extremely small frictional force.

Abstract: Impact response of contact lenses is measured using the Levitation Mass Method (LMM). In the LMM, a small mass collides with contact lenses and the impact force is measured with high accuracy as the inertial force of the moving part. A pneumatic linear bearing is used to achieve linear motion with sufficiently small friction acting on the moving part. Hysteresis loop and consumed energy as mechanical characteristics of contact lenses are also calculated.

Abstract: Digital holography can record 3-D image of the object by using one CCD camera. Surface shape can be measured by changing angles of the object-illuminating mirror. But the measured signals are wrapped because of the periodicity of a sinusoidal function, and then phase unwrapping is needed. We have developed a new modified phase unwrapping method and applied it to surface measurement. Unwrapping errors were significantly reduced in comparison to application of the previous method.

Abstract: This paper is dedicated to develop an atomic force microscope (AFM) system cou-pled with a high resolution optical microscope (OM), which serves to observe AFM image from a desired micro-area. The system employs through-the-lens optical path for detecting atomic force based on optical lever. By switching the objective lenses from low to high magni cation, a micro-area for obtaining AFM image can be easily found. AFM images of magnetic nanodotarrays with 300 nm and 150 nm pitches are obtained from two local micro-areas using the system. The results demonstrate the proposed prototype has the su cient function to nd out a micro-area for obtaining AFM image.

Abstract: We studied DNA damages in heavy ion irradiation for its radiotherapy using molecular dynamics (MD) method. We adopted semi-empirical hybrid quantum mechanics/molecular mechanics (QM/MM) method of Amber in order to investigate the cleavage of chemical bond by heavy ion in our simulation. We found the cleavage of chemical bond, although the simulated energy of heavy ion turned out to be slightly higher than the one determined by experiment.

Abstract: We calculate pollen grain trajectories in indoor airflow generated by an air purifier to investigate its pollen removal efficiency and effectiveness of the swinging louver at its air outlet. The air purifier has the directional airflow output vent on its top surface, and the elevation angle of the exhaust flow can be changed with time. The turbulent airflow field and particle motion are computed alternately. Since the turbulent calculation requires more computational time than the particle motion simulation, we need to accelerate the computation using graphics processing unit (GPU) to increase simulation research efficiency. As a consequence, the calculation of the indoor turbulent airflow and the particle trajectories on the GPU is 18 times faster than the same simulation on the CPU. It is found that variable exhaust angle enhances pollen removal efficiency by 6.9%. Moreover, it appears that we should swing louver from the upper corner of the ceiling to straight above the air purifier at higher angular velocity than 50 deg/s.

Abstract: Feasibility of a ceiling-mounted assist device of the air-purifier for removal of airborne allergenic pollen grains is investigated by both turbulent flow and particle-tracking calculations. The device is mounted straight above the air-purifier and it collects suspended pollen grains in the exhaust flow of the air-purifier. It is found from the turbulent flow calculation that the flow rate of the assist device should be larger than that of the air-purifier. Otherwise the upward air flows around the assist device, and pollen grains move along the surrounding flow; they are never removed from the air. We also found about 40% improvement of the pollen removal efficiency by installing the assist device.