• Journal of Korean Society on Water Environment
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• 제22권6호
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• pp.1101-1106
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• 2006

Many BNR (Biological Nutrient Removal) plants have experienced a bulking problem, mainly due to the growth of filamentous organisms, particularly during the winter months. This study investigated the problem of bulking due to the growth of M. parvicella both at a full-scale municipal wastewater treatment plant and a pilot scale plant located in the C city. The full-scale facility was operated at a flow rate of $51,000m^3/d$, an F/M (Food-to-Microorganism) ratio of 0.12 kgBOD/kgMLVSS/d and an SRT (Solids Retention Time) higher than 25 days, respectively. This plant experienced bulking and foaming problems at low temperatures below $15^{\circ}C$ since it was retrofitted with the BNR system in 2003. The pilot plant employed had an identical process configuration as the full scale one and used the same wastewater source. It was operated at a flow rate of $3.8m^3/d$, temperatures between 10 to $25^{\circ}C$ and SRTs between 10 and 25 days. At full scale, the M. parvicella growth and SVI (Sludge Volume Index) patterns were studied in conjunction with temperature variations. At pilot scale, DO and SRT variations were also explored, in addition to the filamentous bacteria growth and SVI patterns. During the full-scale investigation, over a 3 year period, it was noted that the SVI was maintained within acceptable operational values (i.e. under 160) during the summer months. Moreover settling in the secondary clarifiers was good and was not affected by the presence of M. parvicella. In contrast, at low mean temperatures during winter, the SVI increased to over 300. Overall, as the temperature decreased, the predominance of M. parvicella became apparent. According to this study, M. parvicella growth could be controlled and SVI could drop under 160 by a change in operational conditions which involved an increase in DO concentration between 2 and 4 mg/L and a decrease in SRT to less than 20 days.

• Journal of Korean Society of Environmental Engineers
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• 제29권6호
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• pp.647-653
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• 2007

The ultimate objective of this study is to develop a reliable oxygen-enriched combustion techniques especially for the case of the flue gas recycling in order to reduce the $CO_2$ emissions from practical industrial boilers. To this end a systematic numerical investigation has been performed, as a first step, for the resolution of the combusting flame characteristics of lab-scale LNG combustor. One of the important parameters considered in this study is the level of flue gas recycling calculated in oxygen enriched environment. As a summary of flame characteristics, for the condition of 100% pure $O_2$ as oxidizer without any flue gas recycling, the flame appears as long and thin laminar-like shape with relatively high flame temperature. The feature of high peak of flame temperature is explained by the absence of dilution and heat loss effects due to the presence of $N_2$ inert gas. The same reasoning is also applicable to the laminarized thin flame one, which is attributed to the decrease of the turbulent mixing. These results are physically acceptable and consistent and further generally in good agreement with experimental results appeared in open literature. As the level of $CO_2$ recycling increases in the mixture of $O_2/CO_2$, the peak flame temperature moves near the burner region due to the enhanced turbulent mixing by the increased amount of flow rate of oxidizer stream. However, as might be expected, the flue gas temperature decreases due to presence of $CO_2$ gas together with the inherent feature of large specific heat of this gas. If the recycling ratio more than 80%, gas temperatures drop so significantly that a steady combustion flame can no longer sustain within the furnace. However, combustion in the condition of 30% $O_2/70% $ $CO_2$ can produce similar gas temperature profiles to those of conventional combustion in air oxidizer. An indepth analyses have been made for the change of flame characteristics in the aspect of turbulent intensity and heat balance.

• Asia pacific journal of information systems
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• 제17권2호
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• pp.97-122
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• 2007

Conventional networking and telecommunications infrastructure characterized by wires, fixed location, and inflexibility is giving way to mobile technologies. Numerous research reports point to the ultimate domination of wireless communication. With the increasing prevalence of advanced cell-phones, various mobile data services (hereafter MDS) are gaining popularity. Although cellular networks were originally introduced for voice communications, statistics indicate that data services are replacing the matured voice service as the growth engine for telecom service providers. For example, SK Telecom, the Korea's largest mobile service provider, reported that 25.6% of revenue and 28.5% of profit came from MDS in 2006 and the share is growing. Statistics also indicate that, in 2006, the average revenue per user (ARPU) for voice didn't change but MDS grew seven percents from the previous year, further highlighting its growth potential. MDS is defined "as an assortment of digital data services that can be accessed using a mobile device over a wide geographic area." A variety of MDS have been deployed, with a few reaching the status of killer applications. Many of them need to access the Internet through the cellular-phone infrastructure. In the past, when the cellular network didn't have acceptable bandwidth for data services, SMS (short messaging service) dominated MDS. Now, Internet-ready, next-generation cell-phones are driving rich digital data services into the fabric of everyday life, These include news on various topics, Internet search, mapping and location-based information, mobile banking and gaming, downloading (i.e., screen savers), multimedia streaming, and various communication services (i.e., email, short messaging, messenger, and chaffing). The huge economic stake MDS has on its stakeholders warrants focused research to understand associated dynamics behind its adoption. Lyytinen and Yoo(2002) pointed out the limitation of traditional adoption models in explaining the rapid diffusion of innovations such as P2P or mobile services. Also, despite the increasing popularity of MDS, unexpected drop in its usage is observed among some people. Intrigued by these observations, an exploratory study was conducted to examine decision factors of MDS usage. Data analysis revealed that the increase and decrease of MDS use was influenced by different forces. The findings of the exploratory study triggered our confirmatory research effort to validate the uni-directionality of studied factors in affecting MDS usage. This differs from extant studies of IS/IT adoption that are largely grounded on the assumption of bi-directionality of explanatory variables in determining the level of dependent variables (i.e., user satisfaction, service usage). The research goal is, therefore, to examine if increase and decrease in the usage of MDS are explained by two separate groups of variables pertaining to information quality and system quality. For this, we investigate following research questions: (1) Does the information quality of MDS increase service usage?; (2) Does the system quality of MDS decrease service usage?; and (3) Does user motivation for subscribing MDS moderate the effect information and system quality have on service usage? The research questions and subsequent analysis are grounded on the two factor theory pioneered by Hertzberg et al(1959). To answer the research questions, in the first, an exploratory study based on 378 survey responses was conducted to learn about important decision factors of MDS usage. It revealed discrepancy between the influencing forces of usage increase and those of usage decrease. Based on the findings from the exploratory study and the two-factor theory, we postulated information quality as the motivator and system quality as the de-motivator (or hygiene) of MDS. Then, a confirmative study was undertaken on their respective role in encouraging and discouraging the usage of mobile data service.

• Korean Journal of Agricultural and Forest Meteorology
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• 제18권2호
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• pp.74-87
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• 2016

Potato phenology, growth, and yield are projected to be highly affected by global warming in the future. The objective of this study was to examine the responses of potato growth and yield to environmental elements like temperature, solar radiation, and daylength. Planting date experiments under open field condition were conducted using three cultivars differing in maturity group (Irish Cobbler and Superior as early; Atlantic as mid-late maturing) at eight different planting dates. In addition, elevated temperature experiment was conducted in four plastic houses controlled to target temperatures of ambient temperature (AT), $AT+1.5^{\circ}C$, $AT+3^{\circ}C$, and $AT+5^{\circ}C$ using cv. Superior. Tuber initiation onset was found to be hastened curve-linearly with increasing temperature, showing optimum temperature around $22-24^{\circ}C$, while delayed by longer photoperiod and lower solar radiation in Superior and Atlantic. In the planting date experiments where the average temperature is near optimal and solar radiation, rainfall, pest, and disease are not limiting factor for tuber yield, the most important determinant was growth duration, which is limited by the beginning of rainy season in summer and frost in the late fall. Yield tended to increase along with delayed tuber initiation. Within the optimum temperature range ($17^{\circ}-22^{\circ}C$), larger diurnal range of temperature increased the tuber yield. In an elevated temperature treatment of $AT+5.0^{\circ}C$, plants failed to form tubers as affected by high temperature, low irradiance, and long daylength. Tuber number at early growth stage was reduced by higher temperature, resulting in the decrease of assimilates allocated to tuber and the reduction of average tuber weight. Stem growth was enhanced by elevated temperature at the expense of tuber growth. Consequently, tuber yield decreased with elevated temperature above ambient and drop to almost nil at $AT+5.0^{\circ}C$.

• Applied Microscopy
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• 제38권4호
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• pp.307-314
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• 2008

Hydrophytes such as Spirodela polyrhiza form dormant turions to withstand cold winters. The turion is an anatomically distinct structure from which a vegetative frond arises later during germination. The turions sink to the bottom of the pond when temperatures drop and remain there throughout the winter. In the spring, they float to the surface and germinate into a new frond from the turion primordium. Unlike fronds, turions are known to possess small aerenchyma, starch grains, and relatively dense cytoplasm. These features allow the turions to survive the cold winter season at the bottom of the pond. Spirodela polyrhiza has been investigated previously to a great extent, especially in its physiological, biochemical and ecological attributes. However, a little is known about the structural features of the frond and turion during turion development. Thus, the aim of the present study was to reveal the structural characteristics of the frond and turion with regard to tissue differentiation, aerenchyma development, starch distribution, and ultrastructure, with the use of electron microscopy. A moderate degree of mesophyll tissue differentiation was found in the frond, whereas the turion did not exhibit such differentiation. Within the frond tissue, approximately $37{\sim}45%$ of the cellular volume was occupied by a large aerenchyma, but only $9{\sim}15%$ was taken up by the aerenchyma in the turion. The turion cells, especially those of the turion primordium, were derived from frond cells, and contained cytoplasm. Their cytoplasm was densely packed with plastids, mitochondria, endoplasmic reticulum, Golgi bodies, and microtubules. Plasmodesmata were also well developed within these cells. The most striking feature observed was the distribution of starch grains within the plastids of turion cells. Before the turion sank to the bottom of the pond, a considerable amount of starch accumulated in the plastid stroma. The starch grains dissolved when temperatures rose in the spring, and this promptly provided the nutrients which the primordium needed for turion germination. The turion therefore, was an appropriate dormant structure for free-floating, reduced hydrophytes like Spirodela polyhriza due to its small aerenchyma and large starch grains that aided in the purpose of sinking below the surface of the water to survive cold winters. The new fronds that arose from such turions grew rapidly in the spring, beginning the new life cycle.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제19권1호
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• pp.94-131
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• 2007

A review on the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering in 2004 and 2005 has been done. Focus has been put on current status of research in the aspect of heating, cooling, air-conditioning, ventilation, sanitation and building environment. The conclusions are as follows. (1) Most of fundamental studies on fluid flow were related with heat transportation of facilities. Drop formation and rivulet flow on solid surfaces were interesting topics related with condensation augmentation. Research on micro environment considering flow, heat, humidity was also interesting for comfortable living environment. It can be extended considering biological aspects. Development of fans and blowers of high performance and low noise were continuing topics. Well developed CFD and flow visualization(PIV, PTV and LDV methods) technologies were widely applied for developing facilities and their systems. (2) The research trends of the previous two yews are surveyed as groups of natural convection, forced convection, electronic cooling, heat transfer enhancement, frosting and defrosting, thermal properties, etc. New research topics introduced include natural convection heat transfer enhancement using nanofluid, supercritical cooling performance or oil miscibility of $CO_2$, enthalpy heat exchanger for heat recovery, heat transfer enhancement in a plate heat exchanger using fluid resonance. (3) The literature for the last two years($2004{\sim}2005$) is reviewed in the areas of heat pump, ice and water storage, cycle analysis and reused energy including geothermal, solar and unused energy). The research on cycle analysis and experiments for $CO_2$ was extensively carried out to replace the Ozone depleting and global warming refrigerants such as HFC and HCFC refrigerants. From the year of 2005, the Gas Engine Heat Pump(GHP) has been paid attention from the viewpoint of the gas cooling application. The heat pipe was focused on the performance improvement by the parametric analysis and the heat recovery applications. The storage systems were studied on the performance enhancement of the storage tank and cost analysis for heating and cooling applications. In the area of unused energy, the hybrid systems were extensively introduced and the life cycle cost analysis(LCCA) for the unused energy systems was also intensively carried out. (4) Recent studies of various refrigeration and air-conditioning systems have focused on the system performance and efficiency enhancement. Heat transfer characteristics during evaporation and condensation are investigated for several tube shapes and of alternative refrigerants including carbon dioxide. Efficiency of various compressors and expansion devices are also dealt with for better modeling and, in particular, performance improvement. Thermoelectric module and cooling systems are analyzed theoretically and experimentally. (5) According to the review of recent studies on ventilation systems, an appropriate ventilation systems including machenical and natural are required to satisfied the level of IAQ. Also, an recent studies on air-conditioning and absorption refrigeration systems, it has mainly focused on distribution and dehumidification of indoor air to improve the performance were carried out. (6) Based on a review of recent studies on indoor environment and building service systems, it is noticed that research issues have mainly focused on optimal thermal comfort, improvement of indoor air Quality and many innovative systems such as air-barrier type perimeter-less system with UFAC, radiant floor heating and cooling system and etc. New approaches are highlighted for improving indoor environmental condition as well as minimizing energy consumption, various activities of building control and operation strategy and energy performance analysis for economic evaluation.

• Journal of the Korean earth science society
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• 제42권5호
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• pp.479-495
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• 2021

This study investigates the synoptic (patterns of southern highs, northern lows, and lows rapidly developed by tropopause folding), thermodynamic, and kinematic characteristics of a strong wind that occurred in the Yeongdong region of South Korea on March 18-20, 2020. To do so, we analyzed data from an automatic weather station (AWS), weather charts, the European Centre for Medium-range Weather Forecasts (ECMWF) reanalysis, rawinsonde, and windprofiler radars. The daily maximum instantaneous wind speed, exceeding 20 m s^-1, was observed at five weather stations during the analysis period. The strongest instantaneous wind speed (27.7 m s^-1) appeared in the Daegwallyeong area. According to the analysis of weather charts, along with the arrangement of the north-south low-pressure line, the isobars were moved to the Yeongdong area. It showed a sine wave shape, and a strong wind developed owing to the strong pressure gradient. On March 19, in the northern part of the Korean Peninsula, with a drop in atmospheric pressure of 19 hPa or more within one day, a continuous strong wind was developed by the synoptic structure of the developing polar low. In the adiabatic chart observed in Bukgangneung, the altitude of the inversion layer was located at an altitude of approximately 1-3 km above the mountaintop, along with the maximum wind speed. We confirmed that this is consistent with the results of the vertical wind field analysis of the rawinsonde and windprofiler data. In particular, based on the thermodynamic and kinematic vertical analyses, we suggest that strong winds due to the vertical gradient of potential temperature in the lower layer and the development of potential vorticity due to tropopause folding play a significant role in the occurrence of strong winds in the Yeongdong region.

• Journal of the Korean Institute of Landscape Architecture
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• 제37권2호
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• pp.104-113
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• 2009

Gyeong Po in Gangneung is highly recognized as a scenic area that is home to twelve traditional pavilions which are still in existence today. Since the modification of the Natural Park Act in 2007, there has been serious concern about the regulation of the heights of buildings surrounding Gyeong Po. In light of this, the present study aims to provide some guidelines for the regulation of building height in the modified Natural Park Act on the basis of investigations of landscape characteristics of Gyeong Po and the psychological influences of changing building heights. The analysis of the view from the pavilions located around Gyeong Po Lake indicated that the strategic landscape control points were Gyeong Po Dae and Bang Hae pavilions in terms of landscape management. These two landscape control points were considered as points from which people could view the greatest part of the landscape surrounding Gyeong Po Lake. The results of a preference analysis revealed that the views from Gyeong Po Dae to Juk Do were of relatively higher preference than the view from Bang Hae pavilion. This finding emphasized the importance of landscape management in Juk Do and its surroundings. A factor analysis resulted in three factors including attractiveness, tranquility, and orderliness. A comparison of the magnitude of influence of these three factors showed that the order of influence to preference was: attractiveness>tranquility>orderliness. These results highlight the need to introduce landmarks or unique buildings into the areas because the panoramic views of Gyeong Po Lake are relatively flat as lake views go. There should also be a variety of skylines harmonizing with the natural landscapes and landscape management for building groups, rather than individual building control, to enhance tranquility. Analysis of the psychological effects of building height suggests that, regardless of view points, preference was split at a 30 meter building height. This was indicative that viewer preference would drop when building heights are controlled to allow heights over 30 meters. The present study was not able to take varying view points and story heights into account. A more detailed study considering building types, the arrangement of buildings and the number of building stories is needed for effective landscape management in the Gyeong Po Dae area.

• Korean Journal of Food Science and Technology
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• 제10권2호
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• pp.124-135
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• 1978

This study was undertaken in order to examine the effect of ginger, gerlic and red pepper, usually used as the ingredients of Kimchi, on the growth and acid production of Lact. plantarum ATCC 8014 and Lact. fermenti ATCC 9338 during incubation in the medium containing different amount of each extract. The results obtained are as follows: 1. The effects of ginger extract a. The growth of Lact. plantarum ATCC 8014 and Lact. fermenti ATCC 9338 tended to be stimulated as the amount of extract added into the medium increased in a certain amount (3.64mg soluble solid/ml). b. The pH of the culture medium of Lact. plantarum ATCC 8014 became lower to some degree and acid production tended to be stimulated but acid production of Lact. fermenti ATCC 9338 tended to be suppressed as the amount of extract added in a certain amount (3.64mg soluble solid/ml) increased. 2. The effect of garlic extract a. The growth of Lact. plantarum ATCC 8014 and Lact. fermenti ATCC 9338 tended to be stim ulated as the amount of extract added in a certain amount (31.7 mg soluble solid/ml) increased. b. The acid production of Lact plantarum ATCC 8014 was suppressed (p<0.01) and drop in pH was suppressed (p<0.05) as the amount of extract added in a certain amount increased. In case of Lact. fermenti ATCC 9338, the acid production t ended to be suppressed also. 3. The effects of red pepper extract a. The growth of Lact. plantarum ATCC 8014 and Lact. fermenti ATCC 9338 tended to be stimulated as the amount of extract added in a certain amount (14.5 mg soluble solid/ml) increased.

• Journal of agricultural medicine and community health
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• 제27권1호
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• pp.155-164
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• 2002

Hypertension is the most frequent disease of chronic circulatory diseases and major intermediate cause or risk of the cerebrovascular disease which is a leading cause of death in Korea. Therefore, management of hypertension is an important issue in Korean healthcare. Especially, therapeutic compliance of hypertensives is very important because the hypertensive patients should receive anti-hypertensive treatment as long as the condition exists. However, many patients drop out of treatment, which is a major problem that needs to be solved through a hypertension control program. This study was carried out to provide basic data and counter measule for the hypertension control program in the community which aimed to keep the patients receiving treatment continuously. In order to investigate compliance of hypertensive patients during three months follow-up and the rate of control of hypertension, the data were collected during February, 2001, by reviewing medical records of 295 hypertensive patients who had been registered to Gunnam-myeon health subcenter before November, 2000. The author also study the dropout reasons by interviewing 58 patients among 68 dropout patients. The results were as follows: 1. Among the 295 subjects, 108(36.6%) were male and 187(63.4%) were female. Statistically, female hypertensives had a higher mean age than male(64.6 vs 66.3, p<0.05). 2. The 54.9% of the patients took anti-hypertensive medicine continuously for the past three months. And 19.3% had drug intermittently, and 25.8% dropped out of treatment. 3. Among several variables, such as sex, age, health insurance, the time taken from a patient's village to the health subcenter, only the last one was found to be significantly related to therapeutic compliance in the contingency table analysis. 4. The dropout reasons by multiple response were as follows, 'no symptom or no problem' (23.9%), 'change to other hospitals'(19.4%), 'geographical barrier'(17.9%), 'change to a neighborhood drugstore' (14.9%), 'immobility'(7.5%), 'economic barrier'(6.0%), 'unsatisfactory services of the health subcenter'(4.4%). 5. The mean blood pressure of 295 subjects was $144.9{\pm}12.9/86.88{\pm}8.6mmHg$. 6. The 32.5% of the subjects were controlled below 140/90mmHg. Conclusions: In order to improve the low rates of treatment and control of hypertension in rural hypertensives, a more active and systematic hypertension control program, including out-reaching follow-up management, is required in rural area. Especially, for health education of hypertensive patients, emphasis should placed on correcting wrong attitude toward hypertension.