• Fire Science and Engineering
• /
• v.23 no.1
• /
• pp.55-62
• /
• 2009

A general combustion characteristics of forcing nonpremixed jet in laminar flow rates have been conducted experimentally to investigate the effect of forcing amplitude with the resonant frequency of fuel tube. There are two patterns of the flame lift-off feature according to the velocity increasing; one has the decreasing values of forcing amplitude on the lift-off occurrence when a fuel exit velocity is increasing, while the other has the increasing values. These mean that there are the different mechanisms in the lift-off stability of forced jet diffusion flame. Especially, the characteristics of attached jet flame regime are concentrically observed with flame lengths, shapes, flow response and velocity profiles at the nozzle exit as the central figure. The notable observations are that the flame enlogation, in-homing flame and the occurrence of a vortical motion turnabout have happened according to the increase of forcing amplitude. It is understood by the velocity measurements and visualization methods that these phenomena have been relevance to an entrainment of surrounding oxygen into the fuel nozzle as the negative part of the fluctuating velocity has begun at the inner part of the fuel nozzle.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.10
• /
• pp.916-927
• /
• 2010

In general water treatment process, the disinfection process by chlorine is used to prevent water borne disease and microbial regrowth in water distribution system. Because chlorines were reacted with organic matter, carcinogens such as disinfection by-products (DBPs) were produced in drinking water. Therefore, a suitable injection of chlorine is need to decrease DBPs. Rechlorination in water pipelines or reservoirs are recently increased to secure the residual chlorine in the end of water pipelines. EPANET 2.0 developed by the U.S. Environmental Protection Agency (EPA) is used to compute the optimal chlorine injection in water treatment plant and to predict the dosage of rechlorination into water distribution system. The bulk decay constant ($k_{bulk}$) was drawn by bottle test and the wall decay constant ($k_{wall}$) was derived from using systermatic analysis method for water quality modeling in target region. In order to predict water quality based on hydraulic analysis model, residual chlorine concentration was forecasted in water distribution system. The formation of DBPs such as trihalomethanes (THMs) was verified with chlorine dosage in lab-scale test. The bulk decay constant ($k_{bulk}$) was rapidly decreased with increasing temperature in the early time. In the case of 25 degrees celsius, the bulk decay constant ($k_{bulk}$) decreased over half after 25 hours later. In this study, there were able to calculate about optimal rechlorine dosage and select on profitable sites in the network map.

• Parasites, Hosts and Diseases
• /
• v.25 no.2
• /
• pp.168-180
• /
• 1987

This study was performed to observe histopathological changes and serological reactions in chronic anisakiasis of rabbits. Each rabbit was infected per os with 30 larvae of Anisakis type I. Their sera were collected chronologically and the rabbits were killed for histopathological examination, 3, 13, 20, 30, 60, 90 and 150 days after the infection. The results were summarized as below. 1. Most of the larvae were recovered from the stomach, but a few from the omentum, intestine, mesentery and abdominal wall. The recovery rates and distribution of worms by organ were not differed by duration of infection. 2. Histologically the lesion was abscess type on 13 days, i.e., the dead worms were surrounded by fibrinous exudate, histiocytes and thick zone of numerous inflammatory cells. After 30 days, histiocytes were found to invade the worms and the lesion was changing into abscessgranulomatous type. Also a calcified worm was found on the 30th day. After then the worms were observed to be dissolved slowly until 90 days. On 150 day, only one calcified worm was observed. 3. The levels of serum IgG antibody by ELISA reached their maximum 30 days after the infection. After then, it decreased slowly until 150 days after the infection. Above serological and histopathological findings indicated that antigenic stimulation from degenerating Anisakis larvae was the greatest during the first 30 days after infection. This period was corresponding with the beginning of worm resolution or calcification. Serologic test by ELISA would be a valuable tool for confirming chronic anisakiasis.