Advanced Materials Research Vols. 378-379

Abstract: This paper proposes a new method for motor fault analysis. Windowed-Zeropadded FFT is applied as a signal processing method. The method is based on both windowing and zero-padding of the signal. The expectation is that the method can provide harmonic amplitude more visible for the purpose of motor fault analysis. The method is tested on 3 different motor conditions: healthy, stator fault, and rotor fault motor at full load condition. The method can provide more visible harmonic amplitudes than other methods, because it can eliminate the leakages and provide smoother plotting. Thus, it can help improve accuracy of motor condition classification and the prediction of the fault severity levels.

Abstract: This paper proposes new procedures of motor fault detection. The proposed methods are based on filtered-signals and eliminated-signals. Generally, the raw stator phase currents collected from the motors are firstly filtered in order to get rid of measurement noises. If the new signals are called “Filtered-Signals” and the signals eliminated from the raw stator phase currents are called “Eliminated-Signals”. The first proposed procedure is to detect the motor faults by spectrum of PSD slope from the filtered-signals. The second proposed procedure is to detect the motor faults by spectrum of the eliminated-signals. The both methods are tested on 3 different motor conditions: healthy, stator fault, and rotor fault motor at full load condition. The experiments show that the both methods can differentiate conditions clearly and they also can indicate the levels of fault severity. Thus, it can be effective when the both methods are applied simultaneously to analyze the faults

Abstract: This paper proposes a new method of motor fault detection by applying the eliminated-signal as data sources for motor fault analysis. Bi-spectrum is used as a key method for processing the signal. The expectation is that the eliminated-signal may contain information for fault analysis. The spectrum and bi-spectrum of the signal are applied as signal processing methods to analyze the motor faults. The method is tested on 3 different motor conditions: healthy, stator fault, and rotor fault motor at full load condition. Based on experiments, the method can differentiate conditions clearly. They seem also to be able to measure fault severity levels by observing the change in among harmonic amplitudes.

Abstract: Fraunhofer diffraction pattern from a circular aperture with the diameter of 10µm was observed using an optical fiber microprobe. The optical fiber microprobe started to detect optical power when the distance between the probe and the circular aperture was more than 292µm. When the probe was moved in a lateral motion, the light propagation showed a Bessel function profile. When the optical fiber microprobe was moved from 293µm to 309µm from the centre of the circular aperture in a transverse motion, the power detected was not consistent with a continuation of maxima and minima due to the effect of light propagation from the circular aperture. We also observed that the distance between the probe and the centre of the circular aperture was directly proportional with the radius of focused spot and inversely proportional with the Fresnel number.

Abstract: In this paper, we proposed a VLSI architecture of the modified discrete cosine transform (MDCT) for MPEG 2/4 AAC encoders. The MDCT transforms the time domain input signals to the frequency domain spectrums. It is considered one of the most computational intensive part in implementing the AAC encoder. The AAC encoder allows four types of audio blocks while encoding the audio files. With our algorithm, the proposed design can share the coefficients needed in the MDCT. Moreover, we used a 2-dimensional folding technique to reduce the hardware cost while maintaining the audio quality. The proposed design is realized in TSMC 0.18-um 1P6M technology and is operated at 50 MHz. With these techniques on special hardware design, the result shows some advantages on low complexity.

Abstract: Hardness and creep property of nanocrystalline Ta films were studied by nanoindentation tests. Experimental results suggested that hardness decreases with the decrement of grain size, which exhibits an inverse Hall-Petch effect. A remarkable room temperature creep behavior of nanocrystalline Ta films was revealed during indentation response. Creep stress exponent decreases with the decrement of feature scale, such as grain size and indent displacement. Grain boundary (GB) mediated process involving atomic diffusion and the emission of dislocation at GB is believed to be the dominant deformation mechanism.

Abstract: Introduction: The most widely used preservative system for natural rubber latex to date is the ammonia-based system preventing spontaneous coagulation and putrefaction due mainly to bacteria contamination. Objectives: The study compared 2 types of Thai orthodontic elastics, produced from natural rubber latex with different ammonia contents with commercial orthodontic elastics in terms of initial extension force, residual force, force loss, swelling index, breaking strength and maximum displacement. Materials and Methods: Thai orthodontic elastics were developed from 2 types of natural rubber latex; low ammonia < 0.15% (Thai-L), and high ammonia not < 0.6% (Thai-H). The mechanical properties of Thai orthodontic elastics were compared with commercial elastics (Ormco). Mechanical properties were tested using a universal testing machine (Instron 5566). Data were analyzed by One-way ANOVA and Tukey’s test compared the measurements among groups. Results: Ormco had the highest initial extension force and showed significant differences with Thai-L and Thai-H. Thai-L had the highest residual force but showed no significant difference compared with Ormco. Thai-L had the lowest percent of force loss and showed significant differences with Thai-H and Ormco. Thai-L had lower force loss than Thai-H. For swelling index, Thai-L had the highest elasticity. For breaking strength and maximum displacement, both Thai elastics met the Australian Standard (AS) for breaking strength and maximum displacement, similar to Ormco elastics. Conclusion: All elastics met the specifications of the AS for breaking strength and maximum displacement. Thai-L had comparable properties with commercial orthodontic elastics in terms of mechanical properties. Thai-L had comparable properties with Ormco in terms of mechanical properties and may be developed for orthodontic purposes.

Abstract: In this study, configuration and modeling of haptic mater device for minimally invasive surgery (MIS) featuring magneto-rheological (MR) fluid are proposed. This haptic device consists of two friction-free magneto-rheological (FFMR) brakes incorporated with a gimbal mechanism for realizing a 2-DOF rotational motion. The total torque induced from the FFMR brakes of the haptic device is computed based on Bingham model. In order to enhance the performance of the device, an optimal design for its brakes is undertaken. A prototype for the design is then manufactured and an experiment is undertaken to validate the result of the optimal design process.

Abstract: The properties of ultrathin films have been studied within the framework of Ising model and the method of random-field interactions. It is shown that the Curie temperature is inversely proportional to the number of layers. Critical exponent has been obtained and it is shown that it does not depend on the type of crystalline lattice.

Abstract: This paper is proposed to extract the local carrier generation lifetime from forward current-voltage (I-V) characteristics of p-n junctions in case of non-uniform defects. The different geometry p-n junctions have been fabricated by a standard CMOS technology. The forward I-V and high frequency capacitance-voltage (C-V) characteristics of p-n junctions have been measured. The recombination current density can be extracted from the area forward current density by subtracting with the area diffusion current density. Form the recombination current density, the local generation and recombination lifetime can be obtained.