• Korean Chemical Engineering Research
• /
• v.58 no.1
• /
• pp.84-91
• /
• 2020

The efficiency of the synthetic magnesium silicate used in basic polyols and edible oil purification is evaluated by its purification ability and filtration rate and is affected by the particle size and surface area of magnesium silicate. In this study, it was investigated the change on the particle size of magnesium silicate was influenced by the reaction temperature, injection rate, injection order (Si, Mg) and Mg/Si reaction mole ratio. The synthesized magnesium silicate was compared and analyzed for the synthesis, grinding, and refining processes. In the synthesis process, the reaction temperature and feed rate did not affect the average particle size change of magnesium silicate, while the reaction molar ratio of Mg / Si and the order of injection acted as main factors for the change of average particle size. The average particle size of magnesium silicate increased by 8.7 ㎛ from 54.4 ㎛ to 63.1 ㎛ at Mg injection when Mg molar ratio increased from 0.125 to 0.500, and increased by about 4.8 ㎛ from 47.3 ㎛ to 52.1 ㎛ at Si injection. The average particle size according to the order of injection was 59.1 ㎛ for Mg injection and 48.4 ㎛ for Si injection and the difference was shown 10.7 ㎛, therefore the filtration rate was about 2 times faster under the condition of Mg injection. That is, as the particle size increases, the filtration time is shortened and washing filtration rate can be increased to improve the productivity of magnesium silicate. The cake form of separated magnesium silicate after filtration becomes a solid through drying process and is used as powdery adsorbent through the grinding process. As the physical strength of the dried magnesium silicate increased, the average particle size of the powder increased and it was confirmed that this strength was affected by the reaction molar ratio. As the reaction molar ratio of Mg / Si increased, the physical strength of magnesium silicate decreased and the average particle size after grinding decreased by about 40% compared to the average particle size after synthesis. This reduction of strength resulted in an improvement of the refining ability due to the decrease of the average particle size and the increase of the amount of fine particle after the pulverization, but it resulted in the decrease of the purification filtration rate. While the molar ratio of Mg/Si was increased from 0.125 to 0.5 at Mg injection, the refining ability increased about 1.3 times, but the purification filtration rate decreased about 1.5 times. Therefore, in order to improve the productivity of magnesium silicate, the reaction molar ratio of Mg / Si should be increased, but in order to increase the purification filtration rate of the polyol, the reaction molar ratio should be decreased. In the synthesis parameters of magnesium silicate, the order of injection and the reaction molar ratio of Mg / Si are important factors affecting the changes in average particle size after synthesis and the changes of particle size after grinding due to the changes of compressive strength, therefore the synthetic parameter is an important thing that determines productivity and refining capacity.

• Journal of the Mineralogical Society of Korea
• /
• v.21 no.4
• /
• pp.341-347
• /
• 2008

The feasibility of commercializing the hydrothermal synthesis of Na-A type zeolite from siliceous mudstone has been conducted using a 50-liter bench-scale autoclave and the application of the zeolite as an environmental remediation agent. Siliceous mudstone, which is widely distributed around the Pohang area, was adopted as a precursor. The siliceous mudstone is favorable for the synthesis of zeolite because it contains 70.7% $SiO_2$ and 10.0% $Al_2O_3$, which are major ingredient of zeolite formation. The synthesis of zeolite was carried out under the following conditions that had been obtained from the previous laboratory-scale tests: 10hr reaction time, $80^{\circ}C$ reaction temperature, $Na_2O/SiO_2$ ratio = 0.6, $SiO_2/Al_2O_3$ ratio = 2.0 and $H_2O/Na_2O$ ratio= 98.6. The crystallinity and morphology of the zeolite formed were similar to those obtained from the laboratory-scale tests. The recovery and cation exchange ion capacity were 95% and 215 cmol/kg, respectively, which are slightly higher than those obtained in laboratory scale tests. To examine the feasibility of the zeolite as an environmental remediation agent, experiments for heavy metal adsorption to zeolite were conducted. Its removal efficiencies of heavy metals in simulated waste solutions decreased in the following sequences: Pb > Cd > Cu = Zn > Mn. In a solution of 1500 mg/L total impurity metals, the removal efficiencies for these impurity metals were near completion (> 99%) except for Mn whose efficiency was 98%. Therefore, the synthetic Na-A type zeolite was proven to be a strong absorbent effective for removing heavy metals.

• The Journal of Korean Society for Radiation Therapy
• /
• v.16 no.1
• /
• pp.51-56
• /
• 2004

The aim of this study is to evaluate the effect of skin dose and PDD by using wounds protecting gauzes or Vaselinespread gauzes. And it was studied that the possibility to substitute custom bolus into gauzes. 4MV photon (CL600C, varian, US), Polystyrene Phantom (30(W) X30(L) X 30(H)) with Markus chamber(PTW, US) were used for dose measurement. This study was distinguished natural gauzes and spread over Vaseline gauzes. We gave variety to the gauze thickness at 5, 10 and 15 sheets respectively. For comparison between using bolus and not that, we had used 1.0 cm thickness bolus so that analyzed surface dose and PDD at the same conditions above mentioned. When maximum point was defined as reference point, surface dose was measured as $35\%$ in open beam. When the gauzes were attached to surface as 5, 10 and 15 sheets, surface dose were increased as 69, 80 and $91\%$ respectively according to thickness of gauzes. When spread over Vaseline gauzes were attached to surface as 5, 10 and 15 sheets, surface dose were increased respectively as 98, 100 and $98\%$ according to thickness of gauzes. Also when 0.5 cm bolus and 5 sheets gauzes were composed, surface dose was measured as $98\%$. The gauzes that were attached to skin surface in radiation therapy had been scattering material and contributed increasing surface dose without variation of percentage depth dose. However, if we want to delivery much dose to skin surface then we have to apply many sheets of gauzes to skin surface. Although we get easy that result by bolus or spread over Vaseline gauzes, we have to revise percentage depth dose at calculation. Therefore, if we find pertinent conditions based on measured data that are considered skin dose and patient setup efficiency, to replace custom bolus with gauzes will be helpful to efficient treatment.

• Journal of Intelligence and Information Systems
• /
• v.22 no.4
• /
• pp.177-192
• /
• 2016

Machine learning is a field of artificial intelligence. It refers to an area of computer science related to providing machines the ability to perform their own data analysis, decision making and forecasting. For example, one of the representative machine learning models is artificial neural network, which is a statistical learning algorithm inspired by the neural network structure of biology. In addition, there are other machine learning models such as decision tree model, naive bayes model and SVM(support vector machine) model. Among the machine learning models, we use SVM model in this study because it is mainly used for classification and regression analysis that fits well to our study. The core principle of SVM is to find a reasonable hyperplane that distinguishes different group in the data space. Given information about the data in any two groups, the SVM model judges to which group the new data belongs based on the hyperplane obtained from the given data set. Thus, the more the amount of meaningful data, the better the machine learning ability. In recent years, many financial experts have focused on machine learning, seeing the possibility of combining with machine learning and the financial field where vast amounts of financial data exist. Machine learning techniques have been proved to be powerful in describing the non-stationary and chaotic stock price dynamics. A lot of researches have been successfully conducted on forecasting of stock prices using machine learning algorithms. Recently, financial companies have begun to provide Robo-Advisor service, a compound word of Robot and Advisor, which can perform various financial tasks through advanced algorithms using rapidly changing huge amount of data. Robo-Adviser's main task is to advise the investors about the investor's personal investment propensity and to provide the service to manage the portfolio automatically. In this study, we propose a method of forecasting the Korean volatility index, VKOSPI, using the SVM model, which is one of the machine learning methods, and applying it to real option trading to increase the trading performance. VKOSPI is a measure of the future volatility of the KOSPI 200 index based on KOSPI 200 index option prices. VKOSPI is similar to the VIX index, which is based on S&P 500 option price in the United States. The Korea Exchange(KRX) calculates and announce the real-time VKOSPI index. VKOSPI is the same as the usual volatility and affects the option prices. The direction of VKOSPI and option prices show positive relation regardless of the option type (call and put options with various striking prices). If the volatility increases, all of the call and put option premium increases because the probability of the option's exercise possibility increases. The investor can know the rising value of the option price with respect to the volatility rising value in real time through Vega, a Black-Scholes's measurement index of an option's sensitivity to changes in the volatility. Therefore, accurate forecasting of VKOSPI movements is one of the important factors that can generate profit in option trading. In this study, we verified through real option data that the accurate forecast of VKOSPI is able to make a big profit in real option trading. To the best of our knowledge, there have been no studies on the idea of predicting the direction of VKOSPI based on machine learning and introducing the idea of applying it to actual option trading. In this study predicted daily VKOSPI changes through SVM model and then made intraday option strangle position, which gives profit as option prices reduce, only when VKOSPI is expected to decline during daytime. We analyzed the results and tested whether it is applicable to real option trading based on SVM's prediction. The results showed the prediction accuracy of VKOSPI was 57.83% on average, and the number of position entry times was 43.2 times, which is less than half of the benchmark (100 times). A small number of trading is an indicator of trading efficiency. In addition, the experiment proved that the trading performance was significantly higher than the benchmark.

• Korean journal of applied entomology
• /
• v.49 no.4
• /
• pp.313-324
• /
• 2010

With growing interest in biodiversity in rice paddies, efficient sampling methods for quantitative evaluation of aquatic macroinvertebrates are needed because of their important role in rice paddies' food webs. For this reason, we sought a proper sampling method through comparing data collected by using aquatic net, quadrat, and core in rice paddies located in Chuncheon-si, Kangwon-do, Hongseong-gun, and Chungcheongnam-do. Because the frame of the net was rectangular and had a flat bottom, the area, sampledwith the aquatic net, was calculated by multiplying the net width by the sweeping length, All samples were taken from the space between the rows of rice plants. Twenty four taxa of macro invertebrates were collected in Chuncheon and 28 taxa in Hongseong. In Chuncheon, the number of taxa was similar among three sampling methods (17-18 taxa), but the number of individuals was different (aquatic net, $1,317/m^2$; quadrat, $1,368/m^2$; core, $1,810/m^2$. In Hongseong, the number of taxa sampled by aquatic net was the highest (aquatic net, 25 taxa; quadrat, 21 taxa; core, 16 taxa), but the core was the highest in the number of individuals (aquatic net, $1,586/m^2$; quadrat, $2,595/m^2$; core, $3,704/m^2$. The efficiency of samplers differed among taxa. Most of aquatic insect taxa were more abundant in the aquatic net, while those living on or in the paddy substratum such as Oligochaeta and Chironomidae were collected more in the quadrat sampler. To collect quantitative data for aquatic insects as well as to produce inventory of rare taxa, we suggest, based on samplers used in this study, to take quantitative samples of 6 replications from each of the edge and inner zones of a rice paddy by using an aquatic net, and to take qualitative samples both from sides of levees and the inner zone of rice paddy by using an aquatic net.

• Journal of agricultural medicine and community health
• /
• v.28 no.1
• /
• pp.67-77
• /
• 2003

Objectives: This study is designed to suggest the health service goals necessary for providing the more efficient services relevant to the requests of the community, through the evaluation on the operating status of the unified health subcenters. Methods: We visited total 5 unified health subcenters comprising 3 ones located in Gyeongsangbuk-do and 2 ones located in Gyeongsangnam-do from December 2000 to January 2001, and interviewed about the pre- and post-unified status related to manpower, facilities, equipment, medical service and health service quality, and the problems and improvement plans of the unified management. Results: According to the evaluation on the manpower before and after the unification of the health subcenters, the total employees increased by 2.8 persons on average from 6.8 to 9.6 persons in the investigated subjects. The numbers of doctors, dentists and nurses were almost the same as before. There were no clinical pathologic technician and radiological technician before but they were appointed to duty in 3 unified health subcenters later. The unification of the health subcenters has produced slight increases in the frequency of the medical service and dental treatment and considerable increases in that of the physical therapy and laboratory tests. In relating to the changes of the health service, the cases of visiting health care and ambulatory medical service, and the total number of health education participants were greatly increased after the unification. The number of cases undergoing the vaccination and cervical cancer screening was similar to that of the pre-unification while the patient number of the registration to hypertension or diabetes showed a tendency to increase a little. Since the unification of the health subcenters, the frequency of laboratory tests has been increased, but the quality of health service has not been improved yet. Nevertheless, the unification seems to be positive according to the result of the great improvement in visiting health care, ambulatory medical service and health education service. The problems of the unification of the health subcenters were indicated in indefiniteness of the service details between the workers; excessively large building hard to be effectively managed; insufficient medical instruments, inappropriation of working expenses, lack of professional training for the health education, etc. Conclusions: For further active functions of the unified health subcenters, the minimal allocation basis to appoint doctors, nurses and administrative workers to do the duty should be differentiated from the basis for a health subcenter, and the fundamental instruments needs to be expanded to improve the quality of the medical service and visiting health care service. Moreover, the unified health subcenter needs to have definite service details between the workers, and should improve the working efficiency through the development of service-related guidelines.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.37 no.1
• /
• pp.65-72
• /
• 2010

General anesthesia has been researched and developed in dentistry as on type of management technique to sedate patients who may be uncontrollable or require medical consideration. There has been continuous research into this area, but analysis of large set of patients over a sustained period of time is lacking. Thus, this study analyzes the records of patients who received general anesthesia at the Yonsei University Dental Hospital Department of Pediatric and Clinic for the Disabled. 1. Patient's age ranged from 1 to 66, with under 5 being the largest group with 410 members(38.5%). The study included more men than women, with 695 male members(65.3%). 2. Type of dental procedure performed were as follows(per person) : 5.6 Dental restoration; 2.3 Endodontic treatment of deciduous and primary teeth; 2.5 preformed crowning; and 1.6 extractions. Procedures took an average of 100 minutes. 3. 1022 patients(95.9%) received dental care under general anesthesia once and 43 patients(4.1%) received dental care under general anesthesia two or more times. Dentistry under general anesthesia has the many benefit. However, without appropriate post-treatment care, it is difficult to maintain good oral health. Therefore, it is important to improve the efficiency and safety of general anesthesia through future research.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.27 no.2
• /
• pp.141-147
• /
• 2011

The aim of this study was to evaluate histomorphometrically and compare the efficiency of various bone graft material and autogenous tooth bone graft material which were used in sinus bone graft procedure. Subjects were the 24 patients who had treated with sinus bone graft using lateral approach from October 2007 to September 2009 at SNUBH. The average age was $52.51{\pm}11.86$ years. All cases was taken after 4month of procedure and divided into 3 groups according to bone graft material. Group 1: autogenous tooth bone graft material, Group 2: OrthoblastII(integra lifescience corp. Irvine, US)+Biocera(Osscotec, seoul, korea), group 3: DBX(Synthes, USA)+BioOss(Geistlich Pharm AG, Wolhusen, Switzerland). Total 37 implant placement area were included and evaluated(7 in group 1, 10 in group 2, 20 in group 3). Evaluation of new bone formation, ratio of woven bone to lamellar bone, ratio of new bone to graft material were performed on each tissue section. Kruskal-Wallis test was used for statistical analysis(SPSS Ver. 12.0, USA). New bone formation were $52.5{\pm}10.7%$ in group 1, $52.0{\pm}23.4%$ in group 2, $51.0{\pm}18.3%$ in group 3. There were no statistical significant differences between each groups. Ratio of woven bone to lamella bone were $82.8{\pm}15.3%$ in group 1, $36.7{\pm}59.3%$ in group 2, $31.0{\pm} 51.2%$ in group 3. Ratio of new bone to graft material were $81.3{\pm}10.4%$ in group 1, $72.5{\pm}28.8%$ in group 2, $80.3{\pm}24.0%$ in group 3. After 4 month of healing period, all group showed favorable new bone formation and around graft material and implant. Within limitation of our study, it is suggested that autogenous tooth bone graft material might be used as novel bone graft material for sinus bone graft.

• Korean Journal of Plant Resources
• /
• v.15 no.3
• /
• pp.237-242
• /
• 2002

Loaves, stems, cotyledons, and roots of Hovenia dulcis Thunb grown in test tube were cultured on media containing different concentrations of single or combined growth regulators. In MS media containing 2mg/ι BA, the shoot formation rate was 95.5% and it was the highest frequency of shoot formation. MS media showed most efficiency in the shoot formation at 0.01mg/ι TDZ for the callus formation, but the color of callus changed to brown at a higher concentration of TDZ. Callus formation was 89.% at 0.5mg/ 2.4-D, but IAA, IBA, and NAA were not effective on the formation of callus. Calli were formed only on wound area when IAA, IBA, and NAA were added into MS media. Combined growth regulators (BA + auxin) were more effective in roots and nodes than leaves and cotyledons on the formation of shoot. More than 97％ of shoot formation was obtained on MS media containing BA and auxin. For the production of multiple shoot, nodes of Hovenia dulcis were used and effect of growth regulators on the formation of multiple shoot was evaluated on MS media. Highest shoots (5.3) of Hovenia dulcis were induced on MS media supplied with 0.1mg/ι BA and 0.1mg/ι NAA, and an average of 6.4 shoots per explant were obtained in 1/2 MS media containing same concentration and growth regulators. An average of 7 shoots per explant after 4 weeks of culture from nodes of Hovenia dulcis was produced on a woody plant medium(WPM) containing 0.1mg/ι BA and 0.1mg/ι NAA. Shoot length was 6.0 cm in average.

• Korean Chemical Engineering Research
• /
• v.56 no.1
• /
• pp.85-95
• /
• 2018

In this research, a biofilter system equipped with a biofilter process and a humidifier composed of a fluidized aerobic and an anoxic reactor, was constructed to treat odorous waste air containing hydrogen sulfide, ammonia and VOC, frequently generated from pig and poultry housing facilities, compost manufacturing factories and publicly owned facilities. Its optimum operating condition was revealed and discussed. In the experiment of complex feed, the ammonia of fed-waste air was removed by ca. 75% and more than 20% at the stage of the humidifier and the biofilter, respectively. The toluene of the fed-waste air was removed by ca. 20% and more than 70% at the stage of the humidifier and the biofilter, respectively. Therefore the water-soluble ammonia and the water-insoluble toluene were treated mainly at the stage of the humidifier and the biofilter, respectively. In addition, hydrogen sulfide was almost absorbed at the stage of the humidifier so that it was not detected at the biofilter process. In the experiment of ammonia-containing feed, the ammonia of fed-waste air was removed by ca. 65% and 35% at the stage of the humidifier and the biofilter, respectively. Its removal efficiency of ammonia at the stage of the humidifier was 10% less than that in the experiment of complex feed, due to no supply of such carbon source as toluene required in the process of denitrification. In the experiments of complex feed, ammonia-containing feed with and without (instead, glucose) the addition of yeast extract, the absorption rates of ammonia-nitrogen were ca. 0.28 mg/min, 0.23 mg/min and 0.27 mg/min, respectively. The corresponding denitrification rates in the anoxic reactor were 0.42 mg/min, 0.55 mg/min and 0.27 mg/min, respectively. In addition, in the modeling of bubble column(the fluidized aerobic reactor of the humidifier) process, the value of specific surface area(a) of bubbles multiplied by enhanced mass transfer coefficient (E $K_y$) was evaluated to be 0.12/hr.