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Takahashi A.,Instruments Inc.
International Journal of Automation Technology

Length measurement was conducted for two years on glass ceramics, Zerodur ® and Clearceram ®, which have a low coefficient of thermal expansion, and on synthetic quartz. Commercially available glass ceramics were used for evaluating long-term stability, or secular change. Synthetic quartz ensured longterm length measurement stability. Two line scales of 300 mm length made of each material for a total of six line scales were simultaneously manufactured and measured to evaluate dimensional stability variation of the materials over time. Measurements were conducted with a line scale calibration system developed by Nikon. The calibration system is a one dimensional laser interferometer, featuring reduced Abbe's errors, laser interferometer paths in a vacuum and real-time wavelength calibration of laser frequency using a 633 nm iodine-stabilized He-Ne laser. Long-term quartz stability was 4.3 nm and 5.4 nm (2σ). The yearly stability coefficients of the two glassceramic scales were -0.22 and -0.23 parts per million per year (ppm/yr) for Zerodur and -0.16 and -0.16 ppm/yr for Clearceram. No significant difference in stability between the two scales was observed for Zerodur or Clearceram. Source

Choi S.,Texas A&M University | Akin B.,Instruments Inc. | Rahimian M.M.,Texas A&M University | Toliyat H.A.,Texas A&M University
IEEE Transactions on Industrial Electronics

In this paper, a complete cross-correlation-based fault-diagnostic method is proposed for real-time digital-signal-processor (DSP) applications that cover both the fault-monitoring and decision-making stages. In practice, a motor driven by an inverter or utility line is run at various operating points where the frequency, amplitude, and phase of the fault signatures vary unexpectedly. These changes are considered to be one of the common factors that yield erroneous fault tracking and unstable fault detection. In this paper, the proposed algorithms deal with the ambiguities of line-current noise or sensor-resolution errors and operating-point-dependent threshold issues. It is theoretically and experimentally verified that a motor fault can be continuously tracked when the sensor errors are within a limited range through the adaptively determined threshold definition of noise conditions. The offline experiments are performed via Matlab using actual line-current data obtained by a data-acquisition system. These results are verified on a DSP-based motor drive in real time where drive sensors and a digital signal processor are employed both for motor-control and fault-diagnostic purposes. © 2010 IEEE. Source

Kikuta J.,Osaka University | Kikuta J.,Japan Science and Technology Agency | Wada Y.,Osaka University | Kowada T.,Osaka University | And 13 more authors.
Journal of Clinical Investigation

Osteoclasts are bone resorbing, multinucleate cells that differentiate from mononuclear macrophage/monocyte-lineage hematopoietic precursor cells. Although previous studies have revealed important molecular signals, how the bone resorptive functions of such cells are controlled in vivo remains less well characterized. Here, we visualized fluorescently labeled mature osteoclasts in intact mouse bone tissues using intravital multiphoton microscopy. Within this mature population, we observed cells with distinct motility behaviors and function, with the relative proportion of static - bone resorptive (R) to moving - nonresorptive (N) varying in accordance with the pathophysiological conditions of the bone. We also found that rapid application of the osteoclast-activation factor RANKL converted many N osteoclasts to R, suggesting a novel point of action in RANKL-mediated control of mature osteoclast function. Furthermore, we showed that Th17 cells, a subset of RANKL-expressing CD4+ T cells, could induce rapid N-to-R conversion of mature osteoclasts via cell-cell contact. These findings provide new insights into the activities of mature osteoclasts in situ and identify actions of RANKL-expressing Th17 cells in inflammatory bone destruction. Source

Takahashi A.,Instruments Inc. | Kokumai Y.,Nikon Corporation | Takigawa Y.,Nikon Corporation
International Journal of Automation Technology

The measurement error resulting from graduation anomalies and the signal processing algorithm used for determining the positions of graduations on line scales was investigated by simulation and experiment. Optical image-forming simulations were carried out on models of 6-μm-wide graduations with three sizes of defects (0.5, 1.0 and 1.5 μm) at one edge. A digital filter was used in signal processing to obtain the first differential to determine the positions of the graduations. The minimum values of the lateral shift of the determined graduation positions were observed for the three defect sizes when using a 9-μm-wide differential filter. An experiment was also carried out on an ordinary line scale with 6-μm-wide graduations using a high-precision laser- interferometric line scale calibration system by measuring seven positions on the scale in the direction perpendicular to the measurementaxis. The root mean square of the standard deviations from the linear fitting lines constructed using the measured positions over a 300-mm-long line scale was 2.8 nmwhen the differential filter width was 9 μm. It was demonstrated that a differential filter was effective in reducing the lateral error due to graduation anomalies. Source

Takahashi A.,Instruments Inc.
Measurement Science and Technology

Length measurement was carried out on line scales made of the ultralow-expansion ceramic NEXCERAand synthetic quartz for 13 months. 550 mm long precision line scales made of the two materials were manufactured and their changes in length were measured over the same period, using a high-precision laser-interferometric line scale calibration system. NEXCERA was used to evaluate its long-term dimensional stability. Synthetic quartz was used because of its long-term stability to ensure the stability of the long-term length measurement, including the line scale calibration system and measurement procedure. The long-term stabilities of relative length expressed in terms of 2 over 13 months were 1.1 1.1×10 8for NEXCERA and 4.2 6.3×10 8for synthetic quartz. The experimental results were within the estimated measurement error. No significant secular change in length was observed for the line scale made of NEXCERA. © 2012 IOP Publishing Ltd. Source

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