The domain of computer music is an interesting area which combines computer science and music art. We propose a music accompaniment system using a variable-length genetic algorithm. Via the system one can make the music corresponded to his demands. In the style music accompaniment we analyze some important characteristic of pop music, and propose a new chromosome representation scheme to include the concept of rhyme, chord and melody. Chord progression is used as one of the evaluation criterions in this thesis. The system allows a user to input melody, to select emotion and rhyme, and the system will automatically generate the appropriate accompaniment based on the database compiled from some music theory relating to the chord progression. In addition, the system allows a user to select his favorite accompaniment that generated by the system. Based on the user selected accompaniment the system will generate similar accompaniments for the user.

Thèse : Sciences mathématiques : Paris, Faculté des sciences : 1860. / Titre provenant de l'écran-titre.

Thesis (M.S.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Dec. 23, 2009). Includes bibliographical references (p. 125-126).

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 73-77). Also available in print.

As increasing power requirement in more or all electric aircraft, electric power system is required to be more efficient and lower in weight. Among the current power generation technologies, 115V variable frequency (VF) system and 270VDC system are regarded as the two optimal options for future use in MEA or AEA. Therefore, it is very important to compare their relative merits in order to determine the optimal choice on the primary power type. As the reviewed literature mainly represents the comparison between 270VDC system and 115V constant frequency system, it is very necessary to conduct the comparison between 270VDC system and 115V/VF system. The aim of this study is to grasp the nature of these systems and evaluate these two systems in terms of some engineering aspects. Literature regarding the power generation technology is first investigated. Based on initial comparison, the 270VDC brushless generating system and 115V VF generating system are selected for this study. Before conducting system architecture design and wiring system design, the load requirement analysis and optimization are conducted. Finally, a comparison between these two systems will be made in terms of weight, power off take, minimum voltampere (VA) capacity requirement, voltage drop, reliability, life cycle cost and risk. The results show that the 270VDC system is superior to the115V/VF system in terms of weight and efficiency. With regards to system reliability, the 270VDC system can be designed as either an active parallel system or a standby system while the 115V/VF system can only be designed as a standby redundant system. As far as risk is concerned, the 270VDC is more dangerous than the 115V/VF system in terms of arcing risk and corona discharge. All in all, the 270VDC system can be considered as the optimal choice for future use in AEA or MEA.

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

No description available.

Variable attenuators are important circuits that can be employed in many radio frequency (RF) applications, e.g., in automatic gain control (AGC) amplifiers, broadband gain-control blocks at RF frequencies or as broadband vector modulators. For any applications, low insertion phase shift and low power consumption are of interest. A way to implement variable attenuators is using the RF PIN diode. The PIN diode is characterized by a low doped (I = intrinsic) semiconductor region between p- (P) and n-type (N) semiconductor regions. Besides the variable attenuators, the PIN-diode is used in other RF circuits, such as RF switches, limiters and phase shifters. This project presents the design of variable attenuators at 7.5 GHz and 500 MHz frequency bandwidth for ultra-wideband (UWB) applications using two different PIN diodes. The variable attenuators have a topology based on 90° hybrid couplers. The design is performed using Advance Design Systems (ADS) from Agilent Technologies Inc. After presenting the PIN diode and its equivalent circuit, the theory of the 90° passive directional branch line coupler and the operation principle of the variable attenuators are presented. As the selection of the appropriate PIN diode is a critical step in the design, special attention is dedicated to this aspect. It follows the design of the variable attenuators with extensive descriptions of the simulations in ADS. Firstly, both series and shunt attenuators are presented. However, as these circuits normally offer narrow band variable attenuation, the 900 directional branch line coupler is used in the attenuator for broader band operation. At the end, a double hybrid coupler is found to eliminate the ripple in the high attenuation state of the single hybrid coupled attenuator. So the final topology of the variable attenuator is a double hybrid coupler variable attenuator- Moreover, in this project, different PIN diodes are investigated for variable attenuator applications. Different manufacture companies are currently providing different kinds of PIN diodes in terms of parameters and packages. Every type of PIN diodes are providing different sort of advantages to the designers. That is why it has become more difficult for the RF designers to choose the right device for the specified application. Beside the design of the variable attenuator using PIN diodes, some considerations in form of a guide line to the designers while they are using the PIN diode for designing the variable attenuator. In this work, the used PIN diodes are a beam lead PIN diode and chip PIN diode. The beam lead PIN diode is used because it is manufactured for high frequency and it produces excellent electrical performance and isolation at high frequencies. On the other hand, the chip PIN diode eliminates the problem of package parasitics. However, printed circuit board (PCB) manufacturing limitations at the university laboratory incline the balance in the favor of the beam lead PIN diode, HPND- 4005 from Avagotech, instead of the also considered chip diode MA-COM MA4P202.

No description available.

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