• Radiation Oncology Journal
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• v.26 no.3
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• pp.189-194
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• 2008

Purpose: We designed a water-based bolus device for radiation therapy in Kaposi's sarcoma. This study evaluated the usefulness of this new device and compared it with the currently used rice-based bolus. Materials and Methods: We fashioned a polystyrene box and cut a hole in order to insert patient's extremities while the patient was in the supine position. We used a vacuum-vinyl based polymer to reduce water leakage. Next, we eliminated air using a vacuum pump and a vacuum valve to reduce the air gap between the water and extremities in the vacuum-vinyl box. We performed CT scans to evaluate the density difference of the fabricated water-based bolus device when the device in which the rice-based bolus was placed directly, the rice-based bolus with polymer-vinyl packed rice, and the water were all put in. We analyzed the density change with the air gap volume using a planning system. In addition, we measured the homogeneity and dose in the low-extremities phantom, attached to six TLD, and wrapped film exposed in parallel-opposite fields with the LINAC under the same conditions as the set-up of the CT-simulator. Results: The density value of the rice-based bolus with the rice put in directly was 14% lower than that of the water-based bolus. Moreover, the value of the other experiments in the rice-based bolus with the polymer-vinyl packed rice showed an 18% reduction in density. The analysis of the EDR2 film revealed that the water-based bolus shows a more homogeneous dose plan, which was superior by $4{\sim}4.4%$ to the rice-base bolus. The mean TLD readings of the rice-based bolus, with the rice put directly into the polystyrene box had a 3.4% higher density value. Moreover, the density value in the case of the rice-based bolus with polymer-vinyl packed rice had a 4.3% higher reading compared to the water-based bolus. Conclusion: Our custom-made water-based bolus device increases the accuracy of the set-up by confirming the treatment field. It also improves the accuracy of the therapy owing to the reduction of the air gap using a vacuum pump and a vacuum valve. This set-up represents a promising alternative device for delivering a homogenous dose to the target volume.

• Korean Journal of Plant Resources
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• v.24 no.5
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• pp.642-649
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• 2011

Ginseng growth is largely affected by characteristics of soil in Ginseng field. In this study, we determined the critical ranges of physico-chemical properties of soil for optimization of ginseng growth by analyzing the soils from Anseong and Pocheon regions in Gyeonggi province. Fresh weight of ginseng was 2 to 5 fold higher in good growth field compared to poor growth field within Anseong region. In the case of Pocheon region, 1.5 to 2 fold differences of fresh weight of ginseng was observed between good and poor growth field. These results indicate the difference of ginseng growth even in the same region. Based on these results, critical ranges of physico-chemical properties of soils were determined by comparing the good and poor growth field of each regions, which are follows; more than 50% of soil porosity, 2.0~2.8 g/kg of total nitrogen, 500~900 mg/kg for Av. $P_2O_5$, 2.3~3.5 $cmol_c\;kg^{-1}$ for Exch. Ca in Anseong; less than 13% of liquid phase, 400~650 mg/kg for Av. $P_2O_5$, 4.0~4.7 $cmol_c\;kg^{-1}$ for Exch. Ca, less than 0.8 and 0.5 $cmol_c\;kg^{-1}$ for Exch. Mg and K, respectively, in Pocheon. Interestingly, we found that ginseng growth was affected by exchangeable base ratio (Ca:Mg:K) especially in Anseong region, which were 6:2:1 in good growth field while 4:2:1 in poor growth field. Critical ranges for nutrient contents of ginseng leaves were also characterized, which are less than 0.2% and 0.22% of each P and Mg, respectively, in Anseong, while less than 1.8% and 0.18% of each N and P, respecively, and 1.5~3.0% of K in Pocheon. In addition, we determined critical ranges for inorganic nutrient contents in the current study.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.1
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• pp.57-64
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• 2020

The IOPC Fund general assembly reported that the International Convention on Liability and Compensation for Damage in Connection with the Carriage of Hazardous and Noxious Substances by Sea (known as the HNS Convention) will meet the requirement for the convention to take ef ect between 2021 and 2022. When the convention comes into effect, the liability-limit insurance of the HNS transport ship will be enforced and the shipper receiving the HNS will pay the share of the contribution from the International Fund for damages exceeding the limit of the ship's liability insurance. Korea is one of the major shipping and shipper countries in the world; thus, this study aimed to the need to analyze the effect of the convention on the related industries. The survey of ships and contribution targets analyzed the research data of the Ministry of Oceans and Fisheries. The P&I premium estimation was reviewed by the Korea Shipping Association and the K P&I as insured ships. In addition, the contribution of the HNS cargo volume was analyzed in an annual report by a representative international association for each cargo. About 1,500 ocean-going and domestic vessels have been identified as ships subject to the convention. The effect of changes in premiums under the convention was minimal for most ships. The effect of the shipping industry is expected, with about 150 domestic tankers expected to increase insurance premiums. In the case of shipper industries, 52 freight terminals were found to be eligible for the payment of the share of the international fund, as the proportion of freight volume in Korea was ranked second to fourth in the world by individual HNS accounts. This implies the obligation to pay contributions according to the convention. Considering the status of HNS transport ships entering and leaving ports and the quantity of HNS cargo, it can be concluded that the validity of Korea's convention is sufficient and that, it is necessary to coordinate with global major shipper countries.

• Korean Journal of Microbiology
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• v.17 no.3
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• pp.97-130
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• 1979

Many industrial processes those employ bacteria are subjected to phage infestations. In L-glutamic acid fermentions using acetic acid, the phage infestations of the organisms have been recently recognized. In efforts to elucidate the sources of phage contamination involved in the abnormal fermentation, a series of study was conducted to isolate the phages both from the contents of abnormally fermented tanks and the soil or sewage samples from the surroundings of a fermentation factory, to define major charateristics of the phage isolates, and finally to determine the correlation between the phage isolates and temperate phages originating from the miscellaneous bacterial species isolated from the soil or sewage samples. The results are summarized as follows; 1) All phages were isolated from the irregular fermentation tanks and soil or sewage samples, and they were designated as phage PR-1, PR-2, PR-3, PR-4, PR-5, PR-6, and PR-7, in the order of isolation. These PR-series phages were proved to be highly specific for the variant strains of Br. lactofermentum only, namely, phage PR-1 and PR-2 for Br. lactofermentum No. 468-5 and phage PR-3~PR-7 for Br. lactofemrentum No. 2256. By cross-neutralization test, the 7 phagescould be subdivided into 3 groups, i. e., phage PR-I and PR-2 the first, phage PR-3, PR-4, PR-5, PR-6 the second, and the phage PR-7 the third. 2) The 7 phages were virulent under the experimental conditions. They produced plaques with clear and relatively sharp margins without distinct halo. The mean sizes of plaques were 1.5mm in diameter for phage PR-1 and PR-2, and 1. Omm for phages PR-3~PR-7. Double layer technique modified by Hongo and described by Adams, was applied to assay of the PR-series phages. The factors influencing the plaques were as follows;young age cells of host bacteria cultured for 3-6 hours represented the largest number and size, optimum was pH 7.0, incubation temperature was $30^{\circ}C$, and agar concentration and amount of overlayer medium were 0.6% and 0.2ml, respectively. 3) PR-series phages were stable in 0.05M tris buffer and 0.1M ammonium acetate buffer solution. The addition of $5{\times}10^{-3}M$ magnesium ion effectively increased the stability. Thermostability experiments indicated that PR-series phages were stable at the teinperture between $50^{\circ}{\sim}55^{\circ}C$ in nutrient medium, $45^{\circ}{\sim}50^{\circ}C$ in buffer solution. However, the phages mere completely inactivated at 603C and 65$^{\circ}$C within 10 minutes. The phages were stable at the range of pH6~9 in nutrient medium and of pH 8-9 in buffer solution, respectively. Exposure of the phages to UV for 25, 60 and 100 seconds resulted in the complete loss of infectivily, respectively. 4) Electron microscopy showed that PR-series phage particles exhibited rather similar morphology, differing in the size All of PR-series phages had a multilateral head and had a simple long tiil about three to five times long as compared with head. By the size, phage PR-1 and PR-2, PR-3, PR-4, PR-5, and PR-6 and PR-7 were classified into same groups, respectively. The head and tail size of phage PR-1, PR-5, PR-5(T) and PR-7 were 85nm, 74nm and 235nm and 350mm, and 72nm and 210nm, respectively. 5) Nucleic acids of PR-series phages were double stranded DNA. The G+C contents of phage PR-1, PR-5 and PR-7 were 56.1, 52.9 and 53.7, respectively. The values of G+C contents derived from the $T_m$ were in agreement with the chemically determined values. 6) PR-series phages effectively adsorbed on their host bacteria at the rate of more than 90% during 5 min. K value for phage PR-1, PR-5 and PR-7 were calculated to be $6{\times}10^9 ml$ per minute, respectiveky. The pH of the medium did effect adsorption rate, but both temperature and age of host cells did not. Generally, optimum adsorption condition of phages seemed to be almost same as optimum growth conditions of host bacteria. 7) In one-step growth experiments, the latent periods at $30^{\circ}C$ for PR-1, and PR-7 were about 70, 50 and 55 min, respectively. The corresponding average burst size was 200, 70 and 90, respectively. Lpsis period according to the multiplicity of infection and a phage series. In case of m. o. i. 100, strain No. 2256 (PR-5) and No. 468-5(PR-1) failed to grow and turbidity decreased after 50 and 70min, respectively. 8) In the lysate of a plaque purified phage PR-5 infected bacteria, there observed 2 types ofphage particles, i. e., phage PR-5 and PR-5 (T) of similar morphology but differing at the length of phage tail, and phage tail like particles. The phage taillike particles could be divided into 4 types by the length. Induction experiments of Br. lactofermentum with UV irradiation, mitomycin C or bacitracin treatment produced neither phage PR-5 (T) or phage tail-like particles. 9) No lysis occured when the growth of 7 strains of miscellaneous bacteria, isolated from soil and sewage samples, were inoculated with either phage PR-5 (T) or phage tail-like particles the inoculation of phage PR-5 pellet resulted in the growth inhibition of the orgainsms in the spot test. The lysates obtained from 3 miscellaneous soil derived bacteria following mitomycin C treatment the growth of Br. lactofermentum, but did not lyze the bacterium.

• Journal of Korean Home Economics Education Association
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• v.29 no.2
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• pp.23-39
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• 2017

The Purpose of this study is to present the basic data for selecting and improving the safety education contents which help practically middle school students through analysis of contents of safety education in 'field of home life' of 2009 revised middle school textbooks. The subjects of analysis are 12 types of middle school textbooks: in total 24 books written by 12 publishers in terms of the revised curriculum in 2009. The analysis criteria is developed by the researcher referring to preceding studies regarding safety education based on the seventh safety education standard presented by the Ministry of Education (2015). With such analysis criteria, all words related to the contents of the safety education of analysis criteria were extracted from each textbook, such as words directly mentioned as 'safety', words mean as 'psychological safety' and 'happy life', words related to 'attention', 'note', 'stability' etc. Under the analytic frame of safety education contents according to a home economics textbook, content analysis method was used for producing the frequency and percent of those words. The textbook analysis shows that the number of pages regarding safety education is 336.3 pages, as 9.8% in total 3,412 pages of 12 types of technology and home economics textbooks. As following the analysis of each textbook volume of the proportion in the contents related to safety education, 224.9 pages are on the first volume and 111.9 pages are on the second volume. As grades increase from year one to year three, the proportion of safety education in home economics textbooks is decreased. The highest number of safety education contents unit is 'Self-management of youth' which includes three parts of safety education. In the case of a unit for emphasizing practice, experience and practical exercise such as 'Life of youth' and 'Practice of eco-living', safety education content in the area of 'life safety' are mostly contained. Safety accidents related to the most student experienced, Household accidents (1.4%) and experiment or practice accidents (0.3%) are presented in a low figure. The contents of universal housing and school violence are duplicated on first and second volume of text. The most presented safety education content in the 12 types of textbooks are proper sexual attitude, dietary problems, family conflict and food choice. The least common contents are dangerous drugs, family welfare, internet addiction and industrial accident compensation insurance. As this study is to analyze 12 textbooks developed in 2009 revision curriculum, it is necessary to compare it with the textbook written by the revised curriculum in 2015 and to clarify the contents system of safety education and to avoid duplication of contents. In addition, it is necessary to develop and distribute a safety education program that can support textbooks.

• Journal of the Korean earth science society
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• v.21 no.6
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• pp.663-674
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• 2000

A total of 165 independently oriented core samples were collected from 19 Cretaceous Yuchon Group sites in Kosong area, the southernmost part of the Miryang subbasin of the Kyongsang Basin in southern Korea. Stepwise AF and thermal cleaning revealed antipodal ChRM from 95 samples from 14 sites. Mean ChRM direction is d=26.0$^{\circ}$, i=49.4$^{\circ}$ (${\alpha}_{95}$=8.2$^{\circ}$, k=24.5, n= 14) before bedding correction and d=28.1$^{\circ}$, i=54.2$^{\circ}$ (${\alpha}_{95}$=4.8$^{\circ}$, k=70.6, n= 14) after bedding correction. A 2.88-fold increase of the precession parameter k by bedding correction indicates pre-folding age of the ChRM with 99% confidence level. Palaeomagnetic pole position calculated from the mean ChRM is 67.0$^{\circ}$N, 210.6$^{\circ}$E (dp=4.7$^{\circ}$, dm=6.7$^{\circ}$), which is significantly different neither from the poles of other part of the Kyongsang Basin nor those of Eurasia including SCB and NCB. This suggests stable relative position of the study area with regard to other parts of the Kyongsang Basin as well as to Eurasia continent since Cretaceous. Three ploarity reversals in the Kosong Formation in addition to the coexistence of normal and reversed polarities in the overlying Andesites and Welded Tuff suggest, in reference to the worldwide geomagnetic polarity time scale, an Albian to Maastrichtian (polarity chron 32r-31r) age of the Yuchon Group of the study area. An alleged hypothesis of stratigraphical correspondence between the Kosong Formation in the study area and the Tadaepo Formation in Pusan area is, however, not tenable: Not only because the latter shows a short reverse polarity only in its lowest part of the sequence but also because the Andesites overlying it is wholly normally magnetized, in contrast to the frequent reverals in the case of both the Kosong Formation and Andesites above it.

• Journal of the Korean earth science society
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• v.36 no.6
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• pp.567-579
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• 2015

The accurate simulation of micro-scale weather phenomena such as fog using the mesoscale meteorological models is a very complex task. Especially, the uncertainty arisen from initial input data of the numerical models has a decisive effect on the accuracy of numerical models. The data assimilation is required to reduce the uncertainty of initial input data. In this study, the limitation of the mesoscale meteorological model was verified by WRF (Weather Research and Forecasting) model for a summer fog event around the Nakdong river in Korea. The sensitivity analyses of simulation accuracy from the numerical model were conducted using two different initial and boundary conditions: KLAPS (Korea Local Analysis and Prediction System) and LDAPS (Local Data Assimilation and Prediction System) data. In addition, the improvement of numerical model performance by FDDA (Four-Dimensional Data Assimilation) using the observational data from AWS (Automatic Weather System) was investigated. The result of sensitivity analysis showed that the accuracy of simulated air temperature, dew point temperature, and relative humidity with LDAPS data was higher than those of KLAPS, but the accuracy of the wind speed of LDAPS was lower than that of KLAPS. Significant difference was found in case of relative humidity where RMSE (Root Mean Square Error) for LDAPS and KLAPS was 15.7 and 35.6%, respectively. The RMSE for air temperature, wind speed, and relative humidity was improved by approximately $0.3^{\circ}C$, $0.2m\;s^{-1}$, and 2.2%, respectively after incorporating the FDDA.

• Journal of The Korean Association For Science Education
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• v.37 no.2
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• pp.347-358
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• 2017

The purpose of this study is to research on the professional development of pre-service chemistry teachers in terms of personal practical knowledge(PPK), and draw a discussion for pre-chemistry teacher education. A reflective discussion through a Community of Practice(CoP) activity has been conducted with 5 pre-service chemistry teachers studying in a college of education located in Seoul. The analysis of the results reveals that 'Subject-matter knowledge' is leaning toward massive chemical contents, 'Curriculum knowledge' is below the level of selecting, analyzing, and applying curriculum materials. 'Instruction knowledge', especially the knowledge of chemistry experiment and research, is not enough to lead secondary students' scientific experiment. 'Milieu of school knowledge' is stunted in growth for the reason of communication-deficiency between a college of education and a community, and among education- related groups. 'Self-knowledge' has been diminished not only because there is a bad influence from college classmates not wanting to be a teacher, but also a lack of communication in the chemistry-education department which can make pre-teachers' belief strong. In conclusion, it is especially needed for the chemistry-education department to strengthen pre-teachers' 'Self-knowledge' in order to develop PPK. This study suggests operating 'a professional community' that has a periodic meeting with pre-service teachers, teachers, professors, community people, education practitioners, and researchers. In addition, it would be effective for increasing pre-teachers' PPK to reconsider depth and direction of 'Subject-matter knowledge', to give an opportunity to examine curriculum materials critically and reorganize them, to improve the course of chemistry experimental subject to the way of improving pre-teachers' leadership in chemistry inquiry experiment, and to raise the quality of educational service activities.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.220-229
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• 2009

Strain improvement and morphology investigation in bioreactor cultures were undertaken in suspended cultures of Phellinus linteus mycelia for mass production of protein-bound polysaccharides(soluble ${\beta}$-D-glucan), a powerful immuno-stimulating agent. Phellineus sp. screened for this research was identified as Phellinus linteues through ITS rDNA sequencing method and blast search, demonstrating 99.7% similarity to other Phellinus linteus strains. Intensive strain improvement program was carried out by obtaining large amounts of protoplasts for the isolation of single cell colonies. Rapid and large screening of high-yielding producers was possible because large numbers of protoplasts ($1{\times}10^5{\sim}10^6\;protoplasts/ml$) formed using the banding filtration method with the cell wall-disrupting enzymes could be regenerated in relatively high regeneration frequency($10^{-2}{\sim}10^{-3}$) in the newly developed regeneration medium. It was demonstrated that the strains showing high performances in the protoplast regeneration and solid growth medium were able to produce 5.8~6.4%(w/w) of ${\beta}$-D-glucan and 13~15 g/L of biomass in stable manners in suspended shake-flask cultures of P. linteus mycelia. In addition, cell mass increase was observed to be the most important in order to enhance ${\beta}$-D-glucan productivity during the course of strain improvement program, since the amount of ${\beta}$-D-glucan extracted from the cell wall of P. linteus mycelia was almost constant on the unit biomass basis. Therefore we fully investigated the fungal cell morphology, generally known as one of the key factors affecting cell growth extent in the bioreactor cultures of mycelial fungal cells. It was found that, in order to obtain as high cell mass as possible in the final production bioreactor cultures, the producing cells should be proliferated in condensed filamentous forms in the growth cultures, and optimum amounts of these filamentous cells should be transferred as active inoculums to the production bioreactor. In this case, ideal morphologies consisting of compacted pellets less than 0.5mm in diameter were successfully induced in the production cultures, resulting in shorter period of lag phase, 1.5 fold higher specific cell growth rate and 3.3 fold increase in the final biomass production as compared to the parallel bioreactor cultures of different morphological forms. It was concluded that not only the high-yielding but also the good morphological characteristics led to the significantly higher biomass production and ${\beta}$-D-glucan productivity in the final production cultures.

• KDI Journal of Economic Policy
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• v.12 no.1
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• pp.127-148
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• 1990

A Milgrom-Roberts style signalling model of limit pricing is developed to analyze the possibility and the scope of limit pricing in general, noncooperative oligopolies. The model contains multiple incumbent firms facing a potential entrant and assumes an information asymmetry between incombents and the potential entrant about the market demand. There are two periods in the model. In period 1, n incumbent firms simultaneously and noncooperatively choose quantities. At the end of period 1, the potential entrant observes the market price and makes an entry decision. In period 2, depending on the entry decision of the entrant, n' or (n+1) firms choose quantities again before the game terminates. Since the choice of incumbent firms in period 1 depends on their information about demand, the market price in period 1 conveys information about the market demand. Thus, there is a systematic link between the market price and the profitability of entry. Using Bayes-Nash equilibrium as the solution concept, we find that there exist some demand conditions under which incumbent firms will limit price. In symmetric equilibria, incumbent firms each produce an output that is greater than the Cournot output and induce a price that is below the Cournot price. In doing so, each incumbent firm refrains from maximizing short-run profit and supplies a public good that is entry deterrence. The reason that entry is deterred by such a reduced price is that it conveys information about the demand of the industry that is unfavorable to the entrant. This establishes the possibility of limit pricing by noncooperative oligopolists in a setting that is fully rational, and also generalizes the result of Milgrom and Roberts to general oligopolies, confirming Bain's intuition. Limit pricing by incumbents explained above can be interpreted as a form of credible collusion in which each firm voluntarily deviates from myopic optimization in order to deter entry using their superior information. This type of implicit collusion differs from Folk-theorem type collusions in many ways and suggests that a collusion can be a credible one even in finite games as long as there is information asymmetry. Another important result is that as the number of incumbent firms approaches infinity, or as the industry approaches a competitive one, the probability that limit pricing occurs converges to zero and the probability of entry converges to that under complete information. This limit result confirms the intuition that as the number of agents sharing the same private information increases, the value of the private information decreases, and the probability that the information gets revealed increases. This limit result also supports the conventional belief that there is no entry problem in a competitive market. Considering the fact that limit pricing is generally believed to occur at an early stage of an industry and the fact that many industries in Korea are oligopolies in their infant stages, the theoretical results of this paper suggest that we should pay attention to the possibility of implicit collusion by incumbent firms aimed at deterring new entry using superior information. The long-term loss to the Korean economy from limit pricing can be very large if the industry in question is a part of the world market and the domestic potential entrant whose entry is deterred could .have developed into a competitor in the world market. In this case, the long-term loss to the Korean economy should include the lost opportunity in the world market in addition to the domestic long-run welfare loss.