Key Engineering Materials Vols. 381-382

Abstract: Simple and easy uncertainty estimation method is proposed. Provided that specification or simple experimental result is available, possible variance and covariance in error are estimated and Monte-Carlo simulation reflecting constraint caused by the covariance can be performed. Comparison between uncertainties obtained by the proposed method and that by actual measurements on real CMM shows good agreement within 1 m µ over-estimation.

Abstract: The effect of design features of an internal spinal fixator under loading is critical to understanding of interaction between fixator and instrumented spine. In this study, we performed finite element analysis for spinal pedicle screw installed in the lumbar spine. The purpose of this study is to model and simulate the newly designed spinal pedicle screw. The deformation and stress of the screw are analyzed for the tightening process and loading process simulating the condition when it is installed in the human body as described in the ASTM F1717 procedure. We expected this study is to derive reliable results for developing a new model by analysis of design variables and fatigue behavior.

Abstract: AIST (National Institute of Advanced Industrial Science and Technology) has proposed a new calibration method of gear measuring instrument using a ball artifact consisting of two master balls and an optical flat base (DBA). We measure a circular arc instead of involute tooth form. Difference of the distance between the arc of the master ball and involute curve can be calculated theoretically. For the calculation, center distance between two balls is required and the value of measurement uncertainty is less than 0.1 'm and also should be traceable to national standard of length. This paper reports on a new method and an originally developed instrument to measure the center distance between two balls using laser interferometer. The expanded uncertainty in measurement of a center distance of 44 mm was 21 nm.

Abstract: According to international standards the accredited calibration and testing laboratories are required to use reliable measuring instruments and to estimate an uncertainty of measurements. The variety of software tools and the different approaches taken will almost certainly ensure that for each laboratory there is a software package which will meet the needs. In this paper, several a software packages are made according to their validation for comparison. Briefly general principles of validating uncertainty analysis software packages are described. Briefly used validation methods are described.

Abstract: An innovative two-dimensional (2D) grating was designed for precision pitch measurement using an atomic force microscope with laser interferometers (DLI-AFM). Two kinds of 2D gratings, cylindrical and octagonal pattern, were investigated and compared. In pitch analyses of these patterns, the latter octagonal pattern showed smaller fluctuation of pitch values, less than 0.1 nm. Therefore, one of the major uncertainty components, filtering parameter, was reduced dramatically. We propose the octagonal pattern is probably the most preferable pattern for accurate calibration on 2D gratings.

Abstract: Foot disorders may arise from different functional impairments. In all cases the resulting problem relates to a disturbance of the normal load bearing mechanisms of the foot, frequently with associated pain. Devices used to assist the patient are usually designed relying on the talent and expertise of well trained clinicians. The number of experienced clinicians in such field is few compared to the needs of the society. In this research, expert system techniques are used to design foot orthoses using intelligent methods which are based on fuzzy logic and Genetic Algorithms. The design is assessed using a specified design problem namely a diabetic foot with an ulcer risk. The proposed design can achieve better pressure distribution. Further, such a design can be applied to other comparable problems of a similar nature.

Abstract: Up to now, faults arc protection in electrical power system is passive by detecting electric current or arcing light. An active technique used to forecast faults arc is presented in this paper. By applying power spectrum density analysis, two signature bands of arc sound has been found before faults arc take place, one is inside of (5~10) kHz which is strong in intensity and variable in both bandwidth and center in different experimental conditions, the other one is situated on 19.25kHz which is weak in intensity but invariable in center. The proposed technique detects the arc sounds signature in the frequency of 19.25 kHz based on Duffing chaos oscillator. The arc sound is recorded using precision fiber microphone and imported into the chaos based detecting system. For the sensitivity to periodic signal, the chaos system appears either pure chaos or intermittent chaos. So arc sound can been identified by detecting the motion state of chaotic system, and the presently fault arc protection method can been improved into an active forecast and early warning one. Some experiment results and fault arc diagnosis and early warning scheme are also detailed in the paper.

Abstract: In ultrasonic gas flow metering the ultrasonic wave is complex modulated by natural or artificial structures in the fluid. The determination of the shifted phase angle makes problems if the limited range of the arctan-function is exceeded. It results in phase jumps and ambiguities of the phase angle [1]. This paper presents a new method of phase angle determination which is called differential procedure [2]. The differential procedure has been proved good to determine undersampled ultrasonic data in a wider range of phase shift. The expanded range of phase angle is advantageous for vortex measurement as well as for correlation measurement. Phase and amplitude modulation are physically mutually connected. Phase modulation corresponds to frequency modulation and results in connection with the receiving response of the ultrasound sensor in an additional nonlinear amplitude modulation.

Abstract: The detection of stationary and non-stationary noise in environmental vibration data is an important issue when considering the precision of the Watt balance, an electromechanical apparatus for the new definition of the kilogram in the international system of Units (SI). In this paper, the authors propose a frequency histogram method to find the structure of the stationary noise from large amount of datasets. For the non-stationary noise, the authors propose a wavelet based denoising methods to distinguish the transient events from the background “noise”, to find their duration and content and to identify their location in time.

Abstract: This paper presents an advanced analog-to-digital conversion technique based on a voltage-to-frequency-to-digital conversion that is suitable for remote sensors, telemetry applications and multichannel data acquisition systems. A voltage-to-frequency conversion part can be based, for example, on high performance, charge-balance voltage-to-frequency converter (VFC), where monostable is replaced by a bistable, driven by an external clock, or other existing high performance VFCs. The frequency-to-digital converter “bottleneck” problem in such promised ADC scheme was solved due to proposed advanced method of the dependent count for frequency-to-digital conversion. This ADC technique lets receive many advantages such as high accuracy, relatively low power consumption, low cost solution, wide dynamic range, great stability and faster conversion time in comparison with existing VFC-based techniques. The conversion rate (6.25 µs to 6.25 ms) in such ADC scheme is programmable, non-redundant, shorter than for pulse counting technique and comparable with successive-approximation and Σ- ADC.