• Journal of Korean Society of Water and Wastewater
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• v.14 no.4
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• pp.343-349
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• 2000

Techniques such as dissolved air flotation and electroflotation, which utilize micro bubbles, are increasingly used for water and wastewater treatment. Most studies have concentrated on particle characteristics. Pretreatments that manipulate particle size and zeta potential were considered important. A recent study, which modeled the collision mechanism between micro bubbles and particles in dissolved air flotation, suggested bubble characteristics should also be important. Hydrogen micro bubbles were generated electrolytically and their zeta potentials measured under various conditions using a novel electrophoresis method. Effects of several parameters were investigated. Bubble zeta potentials were found to be pH dependent, and to have a negative value around neutral pH, becoming zero or positive at lower pH. The pH at zero zeta potential was 5.0 under study conditions. Using artificial solution and tap water, at fixed pH, bubble zeta potentials varied with solution composition. Zeta potentia]s of bubbles were affected by the types of cations and anions in solution but not by the voltage applied. These findings will help improve efficiencies of particle removal processes that utilize micro bubbles. As bubble zeta potential varies with solution composition, it needs to be measured for each composition to understand those effects, which increase removal efficiency.

• Geophysics and Geophysical Exploration
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• v.26 no.1
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• pp.8-17
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• 2023

Various sources, such as wind, waves, ships, and gas leaks from the seafloor, forms bubbles in the ocean. Underwater bubbles cause signal scattering, considerably affecting acoustic measurements. This characteristic of bubbles is used to block underwater noise by attenuating the intensity of the propagated signal. Recently, researchers have been studying the large-scale release of methane gas as bubble plumes from the seabed. Understanding the physical properties and distribution of bubble plumes is crucial for studying the relation between leaked methane gas and climate change. Therefore, a water tank experiment was conducted to estimate the distribution of bubble plumes using seismic imaging techniques and acoustic signals obtained from artificially generated bubbles using a bubble generator. Reverse time migration was applied to image the bubble plumes while the acquired acoustic envelope signal was used to effectively estimate bubble distribution. Imaging results were compared with optical camera images to verify the estimated bubble distribution. The water tank experiment confirmed that the proposed system could successfully image the distribution of bubble plumes using reverse time migration and the envelope signal. The experiment showed that the scattering signal of artificial bubble plumes can be used for seismic imaging.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.9
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• pp.1163-1169
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• 2014

As a preliminary study for detection techniques of $CO_2$ gas bubble plumes, we have conducted a comparative experiment on artificially generated $CO_2$ gas bubbles plume by using multibeam echosounder (MBES), single beam echosounder (SBES), and sub-bottom profiler (SBP). The rising speed of artificial gas bubbles is higher than references because of compulsory release of compressed gas in the tank. Compared to single beam acoustic equipments, the MBES detects wide swath coverage. It provides exact determination of the source position and 3D information on the gas bubble plumes in the water column. Therefore, it is shown that MBES can distinctly detect gas bubble plumes compared to single beam acoustic equipments. We can establish more effective complementary detection technique by simultaneous operation of MBES and SBES. Consequently, it contributes to improve qualitative and quantitative detection techniques by understanding the acoustic characteristics of the specific gas bubbles.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.4
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• pp.437-444
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• 2004

To control algal bloom in reservoirs in Korea, artificial circulation systems have been applied. Diffuser block aeration systems have been increasingly used in Korean reservoirs especially for shallow ones. However, there has been no sound theoretical background for the design and operation of the system. Also there has not been sufficient post-installation studies to validate the effectiveness of the system. As a result, it has been repeatedly reported that the success of the system is not certain. Proper consideration on thermal stratification regimes of reservoirs and flow dynamics induced by bubble plumes are essential elements in design processes of the aeration system. This paper discusses the current methods in the design of diffuser type aeration system and suggests a new design method based on fluid mechanical theory. Example calculations were discussed using observed data of the Yeoncho Dam and it seems that the results represent the current situation successfully.

• Journal of Mechanical Science and Technology
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• v.20 no.8
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• pp.1118-1124
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• 2006

Recently, cavitation on the surface of mechanical heart valve has been studied as a cause of fractures occurring in implanted Mechanical Heart Valves (MHVs). It has been conceived that the MHVs mounted in an artificial heart close much faster than in vivo sue, resulting in cavitation bubbles formation. In this study, six different kinds of mono leaflet and bileaflet valves were mounted in the mitral position in an Electro-Hydraulic Total Artificial Heart (EHTAH), and we investigated the mechanisms for MHV cavitation. The valve closing velocity and a high speed video camera were employed to investigate the mechanism for MHV cavitation. The closing velocity of the bileaflet valves was slower than that of the mono leaflet valves. Cavitation bubbles were concentrated on the edge of the valve stop and along the leaflet tip. It was established that squeeze flow holds the key to MHV cavitation in our study. Cavitation intensity increased with an increase in the valve closing velocity and the valve stop area. With regard to squeeze flow, the bileaflet valve with slow valve-closing velocity and small valve stop areas is better able to prevent blood cell damage than the monoleaflet valves.

• Journal of Korean Academy of Nursing
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• v.3 no.1
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• pp.41-51
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• 1972

In this article, the writer attempted to study the followings: (1) mother's knowledge of milk feeding (including method of sterilization, formula and feeding) (2) reasons of artificial feeding (3) how much mothers are concerned about their artificial feeding infants (4) condition of growth and development of artificial feeding infants. As the object of study, 96 mothers with artificial feeding infants, who had consulted dep't of pediatrics of two Hospitals in Seoul (Korea Hospital and Med. College Woo Suk Hospital, Korea Uni.) and well baby clinic of the two Health Centers (Sung Dong and Dongdaemoon), were randomly sampled. The data were treated by the statistic method of chi-square and percentage, and come to the following conclusion. 1. Knowledge of milk feeding Sterilization: 70 percentages of mothers know about the milk sterilization (including bottle, nipple and instrument), but 55 percentages of them do not know the nipple sterilization correctly. Formula: 69 percentages of mothers follow the indicator or in accordance with doctor's directions, but 31 percentages do at their option by reasons that the baby often coughs up the milk, the baby is too small, the baby often has digestive troubles, or the baby grow fleshy heavily etc, except family economic problems. Feeding: only half of mothers know the correct feeding method, especially they do not know how to determine the heat degree of milk and how to bubble up the baby correctly. They just do feeding according to the accepted usages. 2. Reasons of artificial feeding Of the reasons of artificial feeding, 18 percentages were caused by infants and 82 percentages by mothers. Most of the reasons are mainly due to the lack of breast milk and sufficient supply of nourishments rather than mother's deficiency or mother's abnormality. 3. Mother's concern for artificial feeding infants Mothers who are sharply concerned for their artificial feeding baby's growth and development: 63%, mothers who made the baby (artificial feeding infant) routine vaccinated: 81%, mothers who ear anxious about the baby's future personality forming : 68%, mothers who care about the baby's condition of nourishment; 60%, mothers who are anxious about tile selection of baby's food; 54%. 4. The growth and development of artificial feeding infants compared with Korean average infants. The artificial feeding infants are above the Korean average infants in stature by 1.21 centimeters and in weight by 0.3 kilograms. Conclusion: It has been said that there is no better food for infant than the breast milk. However, the artificial feeding has been used for the supplement of nourishments and as substitute food for the breast milk. And this artificial feeding could give the married women the chance to act in society and more opportunity to develop themselves and to work for others at home and other fields. Considering these advantages, artificial feeding should not be exclusive, but preferably should be more improved and inquired positively. And even in artificial feeding, what is most important is that mothers should recognize the requirement and need of artificial feeding clearly and correctly, and they should be accustomed to the correct knowledge and skills of artificial feeding in order to practice it appropriately. In some degree, they should be properly trained in school education process.

• Korean Journal of Artificial Intelligence
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• v.12 no.2
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• pp.9-16
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• 2024

In this study, we delve into the effects of personalization algorithms on the creation of "filter bubbles," which can isolate individuals intellectually by reinforcing their pre-existing biases, particularly through personalized Google searches. By setting up accounts with distinct ideological learnings-progressive and conservative-and employing deep neural networks to simulate user interactions, we quantitatively confirmed the existence of filter bubbles. Our investigation extends to the deployment of an LSTM model designed to assess political orientation in text, enabling us to bias accounts deliberately and monitor their increasing ideological inclinations. We observed politically biased search results appearing over time in searches through biased accounts. Additionally, the political bias of the accounts continued to increase. These results provide numerical evidence for the existence of filter bubbles and demonstrate that these bubbles exert a greater influence on search results over time. Moreover, we explored potential solutions to mitigate the influence of filter bubbles, proposing methods to promote a more diverse and inclusive information ecosystem. Our findings underscore the significance of filter bubbles in shaping users' access to information and highlight the urgency of addressing this issue to prevent further political polarization and media habit entrenchment. Through this research, we contribute to a broader understanding of the challenges posed by personalized digital environments and offer insights into strategies that can help alleviate the risks of intellectual isolation caused by filter bubbles.

• Korean Journal of Ecology and Environment
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• v.33 no.3 s.91
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• pp.282-294
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• 2000

The reproductive ecology and the early life history of Macropodus chinensis were investigated in aquarium. Mature male made the bubble nest and spawned with wrapping the female and reverse posture. The parental male protected the offspring until the larvae depart the bubble nest. Egg productivity and egg hatching rate were the highest at water temperature in $28^{\circ}C$ and $26^{\circ}C$ respectivity than any other artificial temperature. The eggs were buoyant, globular and 0.95${\sim}$1.05 mm in diameter. Cleavage was progressed at intervals of 15 minutes. Eggs hatched in 42${\sim}$44hours after fertilization and the newly hatched larvae were 3.0${\sim}$3.2 mm in total length. The lawae were 4.5${\sim}$5.4 mm in 4${\sim}$5 days after hatching and fed on the food with dispersion from the nest. In 40${\sim}$45 days after hatching, all fin rays completely developed, and juveniles reached 18.2${\sim}$23.5 mm in total length. In 90${\sim}$110 days after hatching, body from of young fishes were similar to adult with 37.4${\sim}$48.2 mm and represented secondary sexual characters longer than 45.0 mm in total length, and about 120 days, fishes began spawning(water temperature for ontogenesis: $26.0{\pm} 1^{\circ}C$).

• Journal of Chest Surgery
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• v.19 no.4
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• pp.644-662
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• 1986

Seventy cases of open heart surgery were performed in the department of Thoracic and Cardiovascular Surgery, Pusan Paik Hospital, Inje College, from Oct. 1985 to Oct. 1986. And the results were summarized as follows. 1. Among the 70 cases, there were 48 cases of congenital heart anomalies and 22 cases of acquired rheumatic valvular heart diseases. Age range of the congenital patients was 7 months to 31 years with the mean age of 10 years, and the acquired patients was 18 to 62 years with the mean age of 40 years. 2. The heart-lung machine used for cardiopulmonary bypass was Sarns 7000, 5-head roller pump, and the number and type of oxygenators were 5 of membrane type and 65 of bubble type. For all cases GIK [glucose-insulin-potassium] solution was used as cardioplegic solution for myocardial protection during operation. 3. Among the 48 congenital anomalies, there were 12 cases of ASD group, 29 of VSD group, 3 of ECD, 3 of TOF and one of PDA + MR, and to all of which the appropriate radical operations were applied. 4. Among the 22 acquired valvular diseases, there were 11 cases of mitral valve diseases [MS; 4, MSr; 3, MRs; 4], 3 cases of aortic valve diseases [AR:1, ARs;1, ASr;1], 4 cases of double valve diseases [MRs+TR; 3, MRs+ARs; 1] and 4 cases of triple valve diseases [MSr+ASr+TR; 3, MSr+Ar+TR; 1]. To all the diseased mitral and aortic valves, artificial valve replacement was applied except one [As], in which valve plication was applied. And to all the diseased tricuspid valve, DeVega annuloplasty was applied. 5. The number of replaced artificial valves were 29 in 25 patients [congenital; 3, acquire; 22]. In MVR, 6 of mechanical valves [St. Jude Medical valve; 6] and 15 of tissue valves [Carpentier-Edward valve; 11, lonescu-Shiley valve; 4] were used. In AVR, 6 of mechanical valves [St. Jude Medical valve; 6] and 2 of tissue valves [Carpentier-Edward valve; 2] were used. 6. Postoperative complications were occurred in 12 cases. Among them 11 cases were recovered with intensive cares, but one patient [VSD + Fistula of Valsalva sinus] was expired with low cardiac out put syndrome.

• Journal of Chest Surgery
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• v.15 no.2
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• pp.259-265
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• 1982

We have designed a new type of bubble oxygenator (KOREA-KIM VENOTHERM OXYGENATOR) made of PVC sheet and deforming mesh incorporated in the heat exchanger, and evaluated in experimental animal for the analysis of it`s efficiency. The Oxygenator has low priming volume with high flow rate up to 6 L/rain, and efficiency of heat exchanger was excellent as 1-$1.5^{\circ}C.$ using total cardiopulmonary bypass method under moderate to deep hypothermia. Average priming volume of 1317 ml with 30% hemodilution method was perfused with an average of 1.1-3.0 L/min.$M^2$of arterial blood and pure oxygen at a rate of 2-3.4 L/min for 49.6 minutes continuously in average. During total cardiopulmonary bypass, average $PaO_2$ was $159.8{\pm}60$mmHg, $PaCO_2$ $41.0{\pm}3$mmHg respectively under $SaO_2$ over 96% with systolic arterial pressure of 70 mmHg and CVP of 5-10 cm$H_2O$. Plasma free Hemoglobin was $7.0{\pm}4$ mg/dl with 25% drop of hemoglobin and hematocrit at the end of cardiopulmonary bypass. This KKV Oxygenator was observed to have excellent capabillty of oxygen and carbon dioxide gas transfer with small amount of blood trauma, and the efficiency of heat exchanger was satisfactory during cooling and rewarming of the bubbled blood. Disadvantages have included the somewhat poor deforming effect due to loose PVC fiber mesh, the extracompact character of Teflon filters, and the rough inner surface of the heat exchanger copper pipes.