• Journal of the Korean GEO-environmental Society
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• v.23 no.3
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• pp.23-29
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• 2022

In this study, we investigated the ozone nanobubble process in which nanobubble and ultrasonic cavitation were applied simultaneously to improve the dissolution and self-decomposition of ozone. To confirm the organic decomposition efficiency of the process, a 200 mm × 200 mm × 300 mm scale reactor was designed and phenol decomposition experiments were conducted. The use of nanobubble was 2.07 times higher than the conventional ozone aeration in the 60 minutes reaction and effectively improved the dissolution efficiency of ozone. Ultrasonic irradiation increased phenol degradation by 36% with nanobubbles, and dissolved ozone concentration was lowered due to the promotion of ozone self-decomposition. The higher the ultrasonic power was, the higher the phenol degradation efficiency. The decomposition efficiency of phenol was the highest at 132 kHz. The ozone nanobubble process showed better decomposition efficiency at high pH like conventional ozone processes but achieved 100% decomposition of phenol after 60 minutes reaction even at neutral conditions. The effect by pH was less than that of the conventional ozone process because of self-decomposition promotion. To confirm the change in bubble properties by ultrasonic irradiation, a Zetasizer was used to measure the bubbles' size and zeta potential analysis. Ultrasonic irradiation reduced the average size of the bubbles by 11% and strengthened the negative charge of the bubble surface, positively affecting the gas transfer of the ozone nanobubble and the efficiency of the radical production.

• Journal of the Mineralogical Society of Korea
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• v.21 no.3
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• pp.227-237
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• 2008

Arsenic has recently become of the most serious environmental concerns, and the worldwide regulation of arsenic fur drinking water has been reinforced. Arsenic contaminated groundwater and soil have been frequently revealed as well, and arsenic contamination and its treatment and measures have been domestically raised as one of the most important environmental issues. Arsenic behavior in geo-environment is principally affected by oxides and clay minerals, and particularly iron (oxy)hydroxides have been well known to be most effective in controlling arsenic. Among a number of iron (oxy)hydroxides, for this reason, 2-line ferrihydrite was selected in this study to investigate its effect on arsenic behavior. Adsorption of 2-line ferrihydrite was characterized and compared between As(III) and As(V) which are known to be the most ubiquitous species among arsenic forms in natural environment. Two-line ferrihydrite synthesized in the lab as the adsorbent of arsenic had $10\sim200$ nm for diameter, $247m^{2}/g$ for specific surface area, and 8.2 for pH of zero charge, and those representative properties of 2-line ferrihydrite appeared to be greatly suitable to be used as adsorbent of arsenic. The experimental results on equilibrium adsorption indicate that As(III) showed much stronger adsorption affinity onto 2-line ferrihydrite than As(V). In addition, the maximum adsorptions of As(III) and As(V) were observed at pH 7.0 and 2.0, respectively. In particular, the adsorption of As(III) did not show any difference between pH conditions, except for pH 12.2. On the contrary, the As(V) adsorption was remarkably decreased with increase in pH. The results obtained from the detailed experiments investigating pH effect on arsenic adsorption show that As(III) adsorption increased up to pH 8.0 and dramatically decreased above pH 9.2. In case of As(V), its adsorption steadily decreased with increase in pH. The reason the adsorption characteristics became totally different depending on arsenic species is attributed to the fact that chemical speciation of arsenic and surface charge of 2-line ferrihydrite are significantly affected by pH, and it is speculated that those composite phenomena cause the difference in adsorption between As(III) and As(V). From the view point of adsorption kinetics, adsorption of arsenic species onto 2-line ferrihydrite was investigated to be mostly completed within the duration of 2 hours. Among the kinetic models proposed so for, power function and elovich model were evaluated to be the most suitable ones which can simulate adsorption kinetics of two kinds of arsenic species onto 2-line ferrihydrite.

• Korea Journal of Hospital Management
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• v.19 no.3
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• pp.11-28
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• 2014

This study, targeting Korean tertiary hospitals and general hospitals, aims to analyze how value chain model in health and medical institution suggested by Duncan and else influences on hospital management. A survey was conducted to verify the actual proof analysis of this study model. 880 questionnaires were distributed to entire 88 hospitals and 739 copies were returned from 76 hospitals. This study mainly consists of three steps to analyze the effect value chain activity has on management performance of general hospitals. For the first step, we analyzed the effects service delivery activity has on management performance. For the second step, we analyzed the effects service support activity has on management performance and for the third, we analyzed the effects interaction between service delivery activity and service support activity has on management performance. The main results of this study are as follows. First, in terms of the management performance of scale, the factors which influenced on daily charge of outpatient were service activity before treatment, at the moment of treatment and value chain activity, while more important factors in daily charge of inpatient were organizational culture, organizational structure and value chain activity. In terms of management performance of quality, the factors which influenced on the first medical examination rate of outpatient were service activity before, at the moment of and after treatment, while activity at the moment of treatment, organizational structure, and value chain activity which is interaction were more important factors in average length of stay. In terms of non-financial performance, the management performance factors which influenced on job satisfaction were service activity at the moment of, after the treatment and value chain activity, while organizational culture, strategy resources and value chain activity which is interaction were more important factors in job commitment. Secondly, all the service support activity, service delivery activity and value chain activity had statistically significant effect on management performance. Among the three factors, service support activity had relatively high effect than others.

• Women's Health Nursing
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• v.1 no.2
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• pp.222-243
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• 1995

The purpose of this study was to develop concrete and in-depth knowledge about menarche and to raise the need of menstrual education. The data were collected from purposively sample 34 women from twenties to forties from April 27 to October 10, 1994. Semi-structured intensive interviews were done and these qualitative data were analysed with "Ethnograph" computer program. The results of the study were as follows : 1. The experience of menarche could be classified into two main groups, which were positive and negative response to menarche. The negative experiences were to be shameful, tearful, scared of the phenomena and thought as a kind of punishment for guilt or confused menarche with other symptoms of diseases. On the contrary, the positive experiences were to be proud of physical maturity and to think that is was wonderful, miraculous and to perceive it as a warm experience. 2. The experience of menarche was influenced by various factors. They were the knowledge about menstruation, the quality and amount of informations, the time of menarche, the environmental factors, the response of significant others toward menarche. The experience of menarche could be positive or negative according to these factors. 3. The previous information sources about menstruation could be significant others, school education and mass-media. The significant others were mothers, sisters, friends and the person in charge of school sex education such as school nurses, home economics, military drill and athletics of teachers. And mass-media included sex education booklets, nursery tales, TV programs, and publicity activities of sanitary napkin companies. 4. The opinions of the subjects about the proper time of menarcheal education could be grossly classified into two groups. The first was active approach toward children when they were in elementary school. The second was passive approach which postponed the time until the child ask about it, because it would be awkward for them to discuss about the topic. 5. The participants thought that the ideal methods of menarche education would be systematic school education programs, open discussion with daughters, audio-visual teachings, or practical education in everyday life. 6. The contents of the menarche education based on the participants' opinions, would be positive details about meanings and functions of menstruation. And it would be desirable if the attitudes of the person in charge of education could be positive, open-hearted, and favorable toward menstruation.

• Journal of Wetlands Research
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• v.22 no.2
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• pp.139-144
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• 2020

Recently, high-concentration linked wastewater has been introduced into a nearby municipal wastewater treatment plants(MWTPs), but it is difficult to MWTP in local governments due to an unreasonable linked treatment charge system, and there is insufficient evidence or data to prove this. However, the MWTP, which is a national essential infrastructure, is generally exempt from the preliminary feasibility study, so there have been no cases where economic evaluation was conducted. Therefore, we proposed an improvement plan that can compensate for the disadvantages of the existing linked processing charges through previous studies. In this study, a comparative evaluation of how much economic feasibility can be improved compared to the existing ones when applying the improvement plan by conducting an economic analysis. For this, reference was made to the preliminary feasibility assessment data of the existing environmental facilities and the cost factors and benefit factors established during the modernization of the old sewage treatment facilities. As a result of the study, the B/C(Benefit/cost) value was quite low in the past, but when the improvement proposal proposed by the researchers was applied, it was confirmed that the B/C value increased close to 1. Therefore, it is considered to be very reasonable to calculate the linkage processing charge according to the linked wastewater load proposed by the researchers.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.53-60
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• 2017

Fly ash(FA) which is a byproduct in the coal combustion in thermal power plant contributes to pore structure densification due to pozzolanic reaction, and this leads to long-term strength development and excellent resistance to chloride penetration. In the work, compressive strength and chloride resistance in OPC(Ordinary Portland Cement) and FA-based concrete are evaluated, and the relationships are investigated considering ages. For the work, 3 different W/B (Water to Binder) ratios of 37%, 42%, and 47% are prepared, and 3 substitution ratio of fly ash(0%, 30%, and 50%) are considered as well. At the age of 28 days and 180 days, test results of compressive strength, diffusion coefficients based on Tang's method, and passed charges referred to ASTM C 1202 and KS F 2711 are obtained. With increasing replacement ratio of FA and decreasing W/B, the resistances to chlorides(diffusion coefficient and passed charge) are improved, and the results at the age of 180 days decrease to only 15% level at the age of 28 days due to pozzolanic reaction in FA 50 mixture, which shows that resistance to chloride is much dependent on age effect than strength development. After 180 days, more clear linear relationships are observed between strength and resistance to chloride.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.52-59
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• 2018

To control chloride attacks which is a representative deterioration in RC(Reinforced Concrete) structures, many studies have been conducted. Above all, a method using mineral admixture was known to be effective for corrosion protection. In this study, durability test about chloride attacks was carried out for concrete specimens containing FA(Fly Ash)-representative concrete mineral admixture and OPC concrete specimens considering 3 different levels of W/B(Water to Binder). Accelerated chloride diffusion coefficient tests referred to Tang's method, total passed charge tests referred to ASTM C 1202, and compressive strength tests based on KS F 2405 were performed at each target age day. Also, based on previous studies of 28 days, time-parameter which is a key parameter for diffusion behavior is evaluated and its relations with compressive strength at the age of 365 days is evaluated. After the age of 49 days, chloride resistance of FA concrete is much improved than that of OPC concrete, which arose out of stable hydrates due to pozzolan reaction of fly ash. Time-parameter of FA concrete is evaluated to be about 1.5 times larger than that of OPC concrete. Also, time-parameter of FA concrete has a linearly decreasing relation while that of OPC concrete has a linearly increasing relation with compressive strength development.

• Resources Recycling
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• v.28 no.3
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• pp.15-20
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• 2019

The recovery of struvite using nitrogen and phosphorus in wastewaters is useful for prevention of eutrophication and use as fertilizer, but there are theoretical and technical issues to be resolved. Through the detailed literature review, this study discusses the possible reasonable prediction of struvite formation reaction by setting a feasible reaction equation with some theoretical considerations. In a technical aspect, the purity of struvite in solid precipitates can be promoted by excluding Ca in an effective way. As for the struvite reaction prediction issue, selection of proper equilibrium reaction as well as its reaction equilibrium coefficient is significant in the neutral and basic pH regions. The equilibrium reaction agrees well with the experimental batch test results. Considering the charge balance of the ions, the pH drop along struvite formation in a diluted solution can be predicted. Also, improvement of struvite purity through elimination of Ca can be expected by providing a highly concentrated ${NH_4}^+-N$ relative to ${HPO_4}^{2-}-P$ because ${NH_4}^+$ can enhance the thermodynamic driving force toward favorable struvite formation. Even though the phosphate reacts rapidly with Ca to form a solid precipitate, the thermodynamic driving force due to the high ${NH_4}^+$ activity can dissociate the phosphate-calcium precipitates and produce struvite.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.127-134
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• 2022

In this study, RCPTs (Rapid Chloride Penetration Test) were performed for fly ash concrete with curing age of 4 ~ 6 years. The concrete mixtures were prepared with 3 levels of water to binder ratio (0.37, 0.42, and 0.47) and 2 levels of substitution ratio of fly ash (0 and 30%), and the improved passed charges of chloride ion behavior were quantitatively analyzed. Additionally, the results were trained through the univariate time series models consisted of GRU (Gated Recurrent Unit) algorithm and those from the models were evaluated. As the result of the RCPT, fly ash concrete showed the reduced passed charges with period and an more improved resistance to chloride penetration than OPC concrete. At the final evaluation period (6 years), fly ash concrete showed 'Very low' grade in all W/B (water to binder) ratio, however OPC concrete showed 'Moderate' grade in the condition with the highest W/B ratio (0.47). The adopted algorithm of GRU for this study can analyze time series data and has the advantage like operation efficiency. The deep learning model with 4 hidden layers was designed, and it provided a reasonable prediction results of passed charge. The deep learning model from this study has a limitation of single consideration of a univariate time series characteristic, but it is in the developing process of providing various characteristics of concrete like strength and diffusion coefficient through additional studies.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1011-1022
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• 2021

The Korea Coast Guard(KCG) is the only comprehensive maritime administrative agency in Korea that performs various tasks taking place in the ocean, including rescue operations, disaster management, policing, Drug and smuggling crackdown, responding to Response to invasion of maritime territory, environmental conservation, and maritime security. It is vital to inform the public of the role and mission of KCG as the only comprehensive maritime administrative agency in Korea. However, most citizens, excluding residents of the coastal and island areas, have little knowledge of the security administration services of the KCG due to lack of exposure. This study reviewed the KCG's public relations(PR) organization and current status using KCG promotional materials, diagnosed the actual conditions of KCG's PR, and suggested ways to improve public relations activities through a questionnaire survey of public relations personnel. Through literature research and questionnaire survey, the KCG's public relations status was estimated and the measures to enhance publicity was derived as follows: strengthening the PR organization by reinforcing the personnel in charge of PR, improving customized promotion by clarifying the promotion strategy according to the promotion target, enhancing job training for PR personnel, and increasing the interest and support of commanders and internal members in charge of PR work.