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  • Thesis

  • Authors: Huỳnh, Thanh Công.;  Advisor: Lee, Jong Tai (2009)

  • Hydrogen-fueled engines with external mixture formation have potentially high thermal efficiency because of a more homogeneous inlet mixture. In addition, the structure of such engines is relatively simple. The practical use of hydrogen can be visible in the short term. The occurrence of backfire at high engine load conditions, however, is an important problem. Because of this, the method of attaining both high efficiency and high power without backfire in a hydrogen-fueled engine is the most important key. The backfire phenomena of hydrogen-air mixtures in the intake system are often a result of backflow of a pre-ignited fast flame from combustion chamber during the valve overlap period. When the valve overlap period is short enough, backfire may not occur even under high load ope...

  • Thesis

  • Authors: Nguyễn, Quang Long.;  Advisor: Hinode, Hirofumi (2009)

  • Nano-size Au on TiO2 catalysts were prepared by metal sol method and evaluated the catalytic activity for the selective catalytic reduction of NOx by C3H6 in the excess oxygen condition (C3H6-SCR). The investigation was conducted on various Au loadings. Mechanical mixtures of the Au/TiO2 and MOx (M= Ce, Mn) with different ratios had been prepared and tested for the C3H6-SCR. The enhancement of the catalytic performance at low temperatures was observed. The reaction mechanism of C3H6-SCR over Au/TiO2 has been investigated using in-situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS). The identification and reactivity of NOx adsorbed species and oxygenated hydrocarbons have been studied. The reaction mechanism and the effects of additional MOx have been investigat...

  • Thesis

  • Authors: Nguyễn, Quang Nam. (2009)

  • This thesis describes the development of novel high-frequency (>150 kHz) matrix converters for induction heating applications. The primary goal has been to explore the possibility of making high performance direct converters, allowing more compact and reliable power converters to be realised, by removing the bulky energy storage components of the DC-link found in traditional approaches. High input power quality, i.e. unity input power factor and very low input total harmonic distortion (THD), and good efficiency are demanded. A single-phase matrix converter has been developed to firstly explore the possibility of performing high speed commutation of output current, without any DC-link between the input and the output. A novel single-step voltage commutation strategy, implementin...

  • Thesis

  • Authors: Trần, Nguyên Duy Phương. (2009)

  • Press-brakes are used in most manufacturing workshops for bending, forming, straightening, punching and trimming. Unfortunately, these versatile machines cause many accidents to workers, who in many cases, must hold the work piece too close to the dies, or must put their hands within the dangerous zones in order to keep up with the rate of production. It is known that the movement of the ram in hydraulic press-brakes can be stopped instantaneously at any time during the process. For this reason, only a protective system for hydraulic press-brakes is recommended. It has also been observed that most existing systems have a fixed interdiction volume, provoking stoppage of the press-brake whenever the hands of the worker enter this area. These protective systems cannot distinguish...

  • Thesis

  • Authors: Nguyễn, Lê Duy Khải.;  Advisor: Huh, Kangyul; Hwang, Youngkyu; Kim, Hongsuk; Kwon, Ohchae; Sung, Nakwon (2009)

  • The effects of split injection, oxygen enriched air, and heavy exhaust gas recirculation (EGR) on soot emissions in a direct injection diesel engine are studied using the KIVA-3V code. When split injection is applied, a dwell time between two injections causes the decrease in local temperature and the fuel-rich area in the flame, which leads to the significantly decrease in precursor formation. Thus, the soot formation in split injection is decreased compared to single injection. The second injection of fuel into a cylinder results in two separate stoichiometric zones which help increase soot oxidation. As a result of soot formation decrease and soot oxidation increase, the soot emissions are decreased. When oxygen enriched air is applied together with split injection, a...

  • Thesis

  • Authors: Bùi, Trọng Vinh.;  Advisor: Deguchi, Ichiro (2009)

  • The main objective of this study is to investigate the erosion mechanism of cohesive bank in river and around river mouth to evaluate erosion resistance of cohesive soil and to establish the procedure for stabilizing and utilizing the coastal regions effectively. To achieve the aim, three research objectives have been carried out as following (1) Assess the effects of development, preservation and disaster prevention on coastal erosion in some Asian countries. (2) Establish procedure for evaluating critical shear stress of cohesive soils for erosion. (3) Study on erosion mechanism of cohesive bed, bank and shore and propose procedure for examining erosion resistance.

  • Thesis

  • Authors: Nguyễn, Thị Nhật Phương.;  Advisor: Kim Kwang Joo (2009)

  • In this study, the process analysis technique (PAT) including Ultrasonic velocity measurement, FBRM and PVM was used together with offline analysis technique to find the kinetic of hydrate formation; the phase transformation between hydrate forms in suspension of solid hydrate in saturated aqueous solution as well as the dehydration in suspension of hydrate in non-aqueous media.