Young-Jae Lee

Developmental expression of mouse muscleblind genes Mbnl1, Mbnl2 and Mbnl3.

The RNA-mediated pathogenesis model for the myotonic dystrophies DM1 and DM2 proposes that mutant transcripts from the affected genes sequester a family of double-stranded RNA-binding factors, the muscleblind proteins MBNL1, MBNL2 and MBNL3, in the nucleus. These proteins are homologues of the Drosophila muscleblind proteins that are required for the terminal differentiation of muscle and photoreceptor tissues, and thus nuclear sequestration of the human proteins might impair their normal function in muscle and eye development and maintenance. To examine this model further, we analyzed the expression pattern of the mouse Mbnl1, Mbnl2, and Mbnl3 genes during embryonic development and compared muscleblind gene expression to Dmpk since the RNA pathogenesis model for DM1 requires the coordinate synthesis of mutant Dmpk transcripts and muscleblind proteins. Our studies reveal a striking overlap between the expression of Dmpk and the muscleblind genes during development of the limbs, nervous system and various muscles, including the diaphragm and tongue.

Chamfered-bowl piston for ultra-low particulate combustion with diesel and soybean biodiesel in a single-cylinder compression-ignition engine

Piston bowl geometries are critical to the combustion and emission characteristics of diesel engines. The present study investigated chamfered-bowl designs and biodiesel blending under a low-temperature combustion regime in order to achieve ultra-low particulate combustion (ULPC). The target soot level for ULPC was set at a filter smoke number value of 0.1 and engine experiments were conducted at the medium load condition. The injection visualization experiment provided the start of injection difference between the diesel and biodiesel fuels, while a three-dimensional computational simulation was conducted to examine the spray and combustion phenomena inside the engine cylinder. The experimental engine was a 1 l single-cylinder diesel engine equipped with a common-rail direct-injection system. The engine was operated at a speed of 1400 rev/min and the intake pressure was set at 200 kPa for a 50 per cent load condition. Two chamfered-bowl pistons were prepared for comparison with the conventional re-entrant bowl piston, and the experimental results showed that the chamfered-bowl pistons achieved significant soot reduction. In addition, computational analysis using a KIVA model showed that the chamfered bowls achieved wider fuel distribution and enhanced combustion. Biodiesel blending further reduced soot emission, and an increase in nitric oxides with biodiesel blends was also observed.

Research on the Combustion and Emission Characteristics of the DME/Diesel Dual-fuel Engine

Abstract : This study investigates the potential of DME/Diesel dual fuel engine for reducing emissions with same power. Dual fuel engine controls the combustion using two different fuels, DME and diesel with different auto-ignition timings. In the previous work, the caracteristics of combustion and emissions under single cylinder engine and ignition is done by compression ignition. Pre-mixture is formed by injecting low-pressure DME into an intake manifold and high-pressure fuel (diesel or DME) is injected directly into the cylinder. Both direct diesel injection and port fuel injection reduced the significant amount of Smoke, CO and NOx in the homogeneous charge compression ignition engine due to present of oxygen in DME. In addition, when injecting DME directly in cylinder with port DME injection, there is no changes in emissions and energy consumption rate even operated by homogeneous charge compression ignition. Key words :Diesel(경유), Diffusion combustion(확산연소), DME(Di-Methyl-Ether, 디메틸 에테르), Direct Injection(직접분사), Emission (배출가스), Port injection(포트분사), Premixed combustion(예혼합연소)

An Investigation about Combustion and Emission Characteristics for Pilot Injection Timing on Partially Premixed Charge Combustion Ignition Engine Fueled with DME

This work investigated the effects of engine speed and injection timing on combustion and emissions characteristics in a partially premixed charge compression ignition (pPCCI) engine fueled with DME. pPCCI engine especially has potential to achieve more homogeneous mixture in the cylinder, which results in lower NOx and smoke emission. In this study single cylinder engine was equipped with common rail and injection pressure is 700 bar. Total injected fuel mass is 64.5 per cycle. The amount of pilot injection of the entire injection 12.5% is tested. Results show that NOx emission is decreased while IMEP is increased as the retard of injection timing. Besides, NOx emissions are slightly rised as well as IMEP is increased with the increase of engine speed.

A Study on Combustion and Emission Characteristics of Diesel-DME Blended Fuels in D.I Compression-Ignition Engine

This work experimentally investigates that Diesel-DME blended fuel influences combustion characteristics and emissions (NOx, CO, HC, smoke) in a single-cylinder DI diesel engine. Diesel is used as a main fuel and DME is blended for the use of its quick evaporating characteristics. Diesel and DME are blended by the method of weight ratio. Weight ratios for Diesel and DME are 95:5 and 90:10 respectively and the both ratios have been used altogether in blended fuel. The experiments are conducted in this study single cylinder engine is equipped with common rail and injection pressure is 700 bar at 1200 rpm. The amount of injected fuels is adjusted to obtain the fixed input calorie value as 972.2 J/cycle in order to compare with the fuel conditions. DME is compressed to 15 bar by using nitrogen gas thus it can be maintained the liquid phase. In this study, different system compared others paper is common rail system, also there is combustion and emission about compared DME and diesel fuel. It is expected to be utilized about blended fuel.

An Investigation for 2-stage Injection Strategy on Combustion and Emissions in a D.I Compression-ignition Engine Fueled with DME

This work was investigated 2-stage injection strategy on combustion and emissions in a direct injection compression-ignition engine fueled with DME. Single cylinder engine was equipped with common rail. Injection pressure was 700bar, dSOI between the main injection and the pilot injection was varied. Diesel was used as compared fuel of DME in all cases. The results was shown that maximum pressure was higher than all cases and its amount of DME and diesel was similar. Regardless the pilot injection, the main fuel injection timing was same. The heat release rate of the main injection for diesel was high while that of pilot injection for DME was high. The THC was very low regardless of the fuel type and injection strategy. In the single injection, NOx was increased to retard of main injection timing regardless of the fuel type. NOx emissions was decreased with the retardation of the main injection timing regardless of the fuel type in the case of 2-stage injection strategy.