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A large amount of fine dust containing iron (Fe) components is scattered by the movement of trains through a subway tunnel. The fine dust spreads to the subway platforms where they are inhaled by passengers, leading to a possibility of acquiring respiratory disease. In this study, a baffle dust collector, which is a type of inertial dust collector, was considered to be attached to the bottom of a train traveling through a Gwangju city subway tunnel to collect dispersed dust particles. To assure a certain level of air suction, a powered fan was installed at the back of the baffle dust collector, which comprised 12 parallel particle-attracting plates connected to perforated circular particle- collecting tubes. The air flow around the baffle dust collector was analyzed, and the volume of air flowing into the collector was predicted with respect to the train speed. Particle analysis was also used to predict the dust collection efficiency in the uniform-speed section of the subway tunnel where the train travelled at a constant speed of 70 km/h, and the results were compared with wind tunnel measurements. It was found that the air flow rate into the baffle dust collector at the constant train speed of 70 km/h was only approximately 2.1 % higher than that in the low-speed section of the tunnel where the train moved at a speed of about 10 km/h. In addition, the cutoff size of the suctioned particles at a speed of 70 km/h was determined to be 7.8 μm.

External air injected into a gas turbine contains many solid particles, which can reduce the performance and life of the turbine. In this study, a louver dust collector, which is a type of inertial dust collector, was used to remove solid particles from air, and the shape of the dust container, which is part of the louver dust collector, was modified to improve dust collection efficiency. As existing dust containers have a structure for isolating particles, the inflow of the air into the dust containers is limited and effective removal of particles is difficult. In this study, slits were drilled in the dust container, baffle plates were used, and raised spots were added to improve particle collection efficiency through improved air flow in the dust container and increased inertia effect of the particles. The trajectory of the particles and the collection efficiency for each dust container shape were predicted using numerical analysis and the numerical analysis results were verified using a wind tunnel test. Results indicate that for an air flow rate of 3 m3/min, the collection efficiencies of the louver dust collectors with the one-slit model dust container and two-slit model dust container improved by 40.1% and 43.5%, respectively compared with that of the louver dust collector with the existing dust container. Furthermore, for an air flow rate of 6 m3/min, the collection efficiencies of the louver dust collectors with the one-slit model dust container and two-slit model dust container improved by 32.9% and 37.6%, respectively, compared with that of the louver dust collector with the existing dust container. Therefore, it is expected that the particle collection efficiency of the existing louver dust collector can be effectively increased by utilizing the shape of the dust container proposed in this study.

In underground tunnels, friction between the wheels and rails of subway trains creates particles, which are spread by the wind generated when trains pass by. A louver dust collector was attached to the bottom of a T-car of Seoul Subway Line 5 train in an effort to remove PM10 inside tunnels, and obtain data when it was in actual operation. It made several round trips during which differential pressure of the louver dust collector was measured in relation to train speed. By comparing and verifying the differential pressure estimated by simulation and that actually measured, it was possible to estimate average flow of air that went into the louver dust collector. Furthermore, by comparing and verifying the measurement results on collection efficiency of a lab-scale louver dust collector in a wind tunnel, along with the results of numerical analysis, it was possible to estimate the collection efficiency in relation to subway train speed. As a result, it was confirmed that higher running speeds of subway trains increased the flow of air going into the louver dust collector and subsequently decreased the particle size corresponding to 50% collection efficiency. In other words, the cut-off size was estimated to be 9.7 µm at the lowest speed of 5 km h–1, and 4.9 µm at the top speed of 65 km h–1, in normal speed range for the Seoul Subway Line 5 trains.

Utilization of carbon sources by Bacillus cereus D324, a biological control agent, and Pythium species, which causes rice seedling disease, was studied with the objective of increasing the efficacy of biological control by providing the biological control agent with specific beneficial carbon sources. D-galactose, D-sorbitol, and D-mannitol were poor carbon sources for Pythium spp. growth but were good for B. cereus D324 growth. Growth in a growth chamber of rice seeds coated with B. cereus D324 amended with specific carbon sources, such as D-galactose and D-sorbitol, showed significantly enhanced seedling emergence compared to seeds coated only with B. cereus D324. Field trials showed that both seedling emergence and yield increased, when the above specific carbon sources were added to B. cereus D324 in seed coating formulations. This result indicated that amending seed coating formulations with specific carbon sources could significantly increase seedling emergence and yield in the field.

A severe epidemic of basal stem rot of the cactus Hylocereus trigonus occurred in 2001, in greenhouses of Goyang City, South Korea, possibly due to continuous cultivation in soil beds. Fusarium oxysporum was isolated and its pathogenicity was demonstrated. Inoculation of mycelial plugs on stem disks of cactus showed brown discoloration. Inoculation of a spore suspension of F. oxysporum (1.40×104 or 1.24×108 spores ml−1) on the underground basal stems of cactus plants, followed by incubation at 28 °C in a growth chamber, led to the development of brown spots identical to the original symptoms after 3 months. The effect of amendment with spent mushroom sawdust, calcium cyanamide, straw and solarization on the development of the disease was studied. In a greenhouse study, amendment with spent mushroom sawdust compost to the disease-conducive soil reduced the disease incidence to 3–12%, as compared to 44–59% with the unamended disease-conducive soil. Autoclaved spent mushroom sawdust compost did not reduce the disease incidence. The bacterial (1.95×1011 cfu g−1) and fungal population (9.50×107 cfu g−1) of spent mushroom sawdust was significantly higher than those (2.0×109 cfu g−1 and 0.13×105 g−1 for bacteria and fungi, respectively) of disease-conducive soil. Also, disease-suppressive soil had a higher fungal population (1.25×105 cfu g−1) compared to disease-conducive soil (0.13×105 cfu g−1). This trend was repeated in the second experiment. Solarization with and without calcium cyanamide of disease-conducive soil reduced effectively pathogen population and disease development, resulting in 16–53% disease incidence, as compared to 81% in the untreated control. Rice straw as an organic amendment did not have synergistic effect on disease control when it was used along with calcium cyanamide for solarization. The results indicate that the control of basal stem rot with spent mushroom sawdust compost may be due to biological activity, and that solarization with calcium cyanamide is a highly effective tool for controlling basal stem rot.

Genetic transformation ofStreptomyces caespitosus by plasmid pIj 702 was carried out. Optimal conditions for the protoplast preparation ofStreptomyces caespitosus, its regeneration, and its transformation by pIj 702 were evaluated. Addition of 2% glycine to the culture broth was optimal for protoplast yield. Formation and regeneration of protoplasts were most efficient when the mycelium were harvested at between late log and stationary growth phase. The regeneration frequency of the protoplasts was 15% when the protoplasts were regenerated on R2YE agar media containing 0.5M sucrose. Under the best condition for protoplats regeneration, the optimal transformation frequency was achieved with 40% polyethylene glycol (M.W. 4,000) treatment for 2 minutes.