Problem statement:In the modern speech communication technology, the speech coding with bitrate scalability was needed. However, various types of noises in the communication channels cause damages in the transmitted information especially speech data. Tonal-language speech was also affected by this situation. Approach: Based on the high pitch delay resolution technique, the MP-CELP speech coding was proposed over the environment with CDMA AWGN and Rayleigh fading channels for tonal language. The proposed coder supports multiple bitrates and also has the functionality of bitrate scalability. Results: Through performance analysis and computer simulation, the quality of the proposed coding was presented with an improvement from conventional scalable MP-CELP in the specific-noise environments. The HPDR technique was applied to the MP-CELP to use for tonal language, meanwhile it can support the core coding rate of 5.6, 8.2, 12.2 kbps and additional scaled bitrates. Conclusion: By applying the high pitch delay resolution technique with the MP-CELP speech coding, we can improve the quality of tonal encoded speech. Moreover, the coding quality of the proposed coder was better than the conventional coder for Thai language over both AWGN channel and Rayleigh fading channel.

Various types of faults of the gasoline engine may result in similar symptoms. Sound analysis of engine has been conducted to diagnose the engine faults. This study presents a study of sound analysis of the normal engine and the engine with three different fault conditions. The gasoline engine was our target of this study. The engine sound has been recorded by using a microphone at the engine room for three directions. Three conditions of engine faults including the engine that is not smooth while idling, the engine that goes missing while idling and the engine that has no power are simulated. In the signal processing of the sound, we use five signal features including fundamental frequency, long term spectrum, energy, long term cestrum and zero crossing rate. Thereafter, the important differences between normal engine and the fault engines are concluded. These proposed signal features can be used to discriminate all three conditions and the engine with normal condition effectively.

Problem statement: In HMM-based Thai speech synthesis, tone is an important issue that brings about the intelligibility of the synthesized speech. Tone distortion resulted from imbalance of the training data should be appropriately treated. Approach: This study described an HMM-based speech synthesis system for Thai language. In the system, spectrum, pitch and state duration are modeled simultaneously in a unified framework of HMM, their parameter distributions are clustered independently by using a decision-tree based context clustering technique. The contextual factors which affect spectrum, pitch and duration, i.e., part of speech, position and number of phones in a syllable, position and number of syllables in a word, position and number of words in a sentence, phone type and tone type, are taken into account for constructing the questions of the decision tree. Since Thai is a tonal language, tone questions play an important role in the context clustering process. Results: An experimental result compared F0 contours between those of synthesized speech with and without tone questions; furthermore the size of Thai speech corpus is varied to investigate the synthesized speech quality. Conclusion: By using the tone questions in the tree-based context clustering process, the tone distortion is relieved significantly.

Problem statement:In structural analysis using finite element software, a number of finite element equations affect the speed of calculation time. A reduced finite element model should be used for analyzing structural responses to reduce the calculation time. Approach: This study presents the analysis of transverse shear stiffness of truss-like core sandwich beam using the reduced finite element model based on a unit cell approach. Two kinds of core topologies; an X-truss core and a bi-directional X-truss core, were chosen to be analyzed. The presented reduced finite element model based on the unit cell approach was compared in transverse shear stiffness with the conventional three-point loaded beam approach. Results: Results showed that the unit cell approach could be used for analyzing the transverse shear stiffness of truss-like core sandwich beam with a good correlative with the conventional three-point loaded beam approach and a significantly reduced number of finite element equations. Conclusion: The transverse shear stiffness of truss-like core sandwich beam can be obtained from the reduced finite element model based on unit cell approach. This reduced finite element model can be used to reduce the number of finite element equations; consequently, the speed of calculation time is increased.

Problem statement: In engineering design, stress affects the size of structural member. A suitable topology of structure should be designed to optimize the stress. Approach: This study presents an alternative topology of truss-like core sandwich beam referred to here as bi-directional corrugated-strip core topology. A finite element method is used to study the stress response of three point loaded truss-like core sandwich beams. Two kinds of core topologies: A truss core and a bidirectional corrugated-strip core are chosen to be analyzed and compared to each other. Results: The results showed that the bi-directional corrugated-strip core topology provided less surfaced normal stress than the truss core topology. Conclusion: From the finding, the stress of truss-like core sandwich beam can be optimized by arranging the core in the alternative bidirectional corrugated-strip core topology