• Journal of the Mineralogical Society of Korea
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• v.20 no.4
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• pp.277-287
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• 2007

To understand the effects of the powdered manganese nodule and sea bottom sediment pumped up with nodules on the mining process, the shattering ratio of manganese nodule and their physical properties are analyzed. The self shattering ratio and crushing shattering ratio are about 27% and about 3%, respectively. Then total shattering ratio is about 30%. The initial turbidity of the powdered manganese nodule and the bottom sediment show high, i.e., about 3,100 and 1,850 respectively. But their turbidities decrease rapidly with time. After 1 hour, turbidity of the powdered manganese nodule drops to about 1,570 and that of the bottom sediment to 1,310. The turbidity of Na-bentonite changes from 820 to 730 after 1 h and to 700 after 2 h. The viscosity of powdered manganese nodule is $1.4{\sim}1.5cP$, and the viscosity of bottom sediment is less than 1 cP. The viscosity fo Na-bentonite is initially 37.2 and increase with time to 86.4 cP after 30 min. The high initial turbidity of powdered manganese nodule is due to dark color of the powder. The high specific gravity makes rapid precipitation and then decreases the turbidity rapidly. The bottom sediment shows high initial turbidity because of easy suspension with very fine particle size. But it cannot be hydrated and formed gel in suspension, then it is easily precipitated. However Na-bentonite is hydrated to the expended state and makes gel state, then it shows high turbidity and high viscosity. These physical properties of the powdered manganese nodule suggest that the powder of manganese nodule should not make scaling inside of lifting pipe or pump. And the bottom sediment lifted up with manganese nodule should not play the role of drilling mud shch as Na-bentonite.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.18 no.5
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• pp.91-107
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• 2023

Lean startup is a concept that combines the words "lean," meaning an efficient way of running a business, and "startup," meaning a new business. It is often cited as a strategy for minimizing failure in early-stage businesses, especially in software-based startups. By scrutinizing the case of a startup L, this study suggests that lean startup methodology(LSM) can be useful for hardware and manufacturing companies and identifies ways for early startups to successfully implement LSM. To this end, the study explained the core of LSM including the concepts of hypothesis-driven approach, BML feedback loop, minimum viable product(MVP), and pivot. Five criteria to evaluate the successful implementation of LSM were derived from the core concepts and applied to evaluate the case of startup L . The early startup L pivoted its main business model from defecation alert system for patients with limited mobility to one for infants or toddlers, and finally to a smart bottle for infants. In developing the former two products, analyzed from LSM's perspective, company L neither established a specific customer value proposition for its startup idea and nor verified it through MVP experiment, thus failed to create a BML feedback loop. However, through two rounds of pivots, startup L discovered new target customers and customer needs, and was able to establish a successful business model by repeatedly experimenting with MVPs with minimal effort and time. In other words, Company L's case shows that it is essential to go through the customer-market validation stage at the beginning of the business, and that it should be done through an MVP method that does not waste the startup's time and resources. It also shows that it is necessary to abandon and pivot a product or service that customers do not want, even if it is technically superior and functionally complete. Lastly, the study proves that the lean startup methodology is not limited to the software industry, but can also be applied to technology-based hardware industry. The findings of this study can be used as guidelines and methodologies for early-stage companies to minimize failures and to accelerate the process of establishing a business model, scaling up, and going global.

• Journal of Periodontal and Implant Science
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• v.24 no.2
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• pp.219-237
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• 1994

The ultimate goal of clinical periodontal therapy is to achieve regeneration of a healthy connective tissue reattachment. Conventional therapy including scaling, root planing, gingival curettage, gingivectomy and flap procedures of various types results primarily in repair rather than regeneration of the periodontium. In order for periodontal regeneration to occur, progenitor periodontal ligament cells must migrate to the denuded root surface, attach to it, proliferate and mature into an organized and functional fibrous attachment apparatus. Polypeptide growth factors belong to a class of potent biologic mediators which regulate cell differentiation, proliferation, migration and metabolism. Insulin-like growth factor-I (IGF- I ) of these factors appear to have an important role in periodontal wound healing and bone formation. The purpose of this study is to evaluate the effects of IGF- I on the periodontal ligament cells to use as a regeneration promoting agent of periodontal tissue. Human periodontal ligament cells were obtained from periodontal tissue explants culture of the first premolar tooth extracted for the orthodontic treatment. Cells were cultured in Dulbecco's modified Eagle medium(DMEM) with 10% fetal bovine serum. Fourth to seventh passage cells were plated in 24 well tissue culture plates and medium changed to serum-free medium prior to addition of growth factors. Cell proliferation was measured by the incorporation of $[^3H]-thymidine$ into DNA, Protein synthesis was determined by measurement of $[^3H]-proline$ incorporation into collagenase-digestible protein(CDP) and noncollagenous protein(NCP) according to the method of Peterkofsky and Diegelmann (1971), And alkaline phosphatase activity was measured as one parameter of osteoblastic differentiation. The results were as follows : The DNA synthetic activity was increased in a dose-dependent manner with IGF- I except for 0.1ng/ml concentration of IGF- I At the concentration of 10, 100ng/ml, IGF- I significantly increased the DNA synthetic activity(P<0.05) The total protein, collagen and noncollagen synthesis was increased in a dose-dependent manner with IGF- I except for 0.1ng/ml concentration of IGF- I. At the concentration of 1, 10, 100ng/ml, IGF- I significantly increased the total protein, collagen and noncollagen synthesis activity(P<0.95, P<0.001). The % of collagen was not effected according to the concentration of IGF- I. The alkaline phosphatase activity was increased in a dose-, time-dependent manner with IGF- I (10, 100ng/ml). In conclusions, the present study shows that IGF- I has a potentiality to enhance the DNA synthesis of periodontal ligament cells with including the increase of the total protein and collagen synthetic activity. The use of IGF- I to mediate biological stimulation of periodontal ligament cells shows promise for future therapeutic applications.

• Radiation Oncology Journal
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• v.28 no.1
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• pp.50-56
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• 2010

Purpose: We report the results of an external audit on the absorbed dose of radiotherapy beams independently performed by third parties. For this effort, we developed a method to measure the absorbed dose to water in an easy and convenient setup of solid water phantom. Materials and Methods: In 2008, 12 radiotherapy centers voluntarily participated in the external auditing program and 47 beams of X-ray and electron were independently calibrated by the third party’s American Association of Physicists in Medicine (AAPM) task group (TG)-51 protocol. Even though the AAPM TG-51 protocol recommended the use of water, water as a phantom has a few disadvantages, especially in a busy clinic. Instead, we used solid water phantom due to its reproducibility and convenience in terms of setup and transport. Dose conversion factors between solid water and water were determined for photon and electron beams of various energies by using a scaling method and experimental measurements. Results: Most of the beams (74%) were within ${\pm}2%$ of the deviation from the third party's protocol. However, two of 20 X-ray beams and three of 27 electron beams were out of the tolerance (${\pm}3%$), including two beams with a >10% deviation. X-ray beams of higher than 6 MV had no conversion factors, while a 6 MV absorbed dose to a solid water phantom was 0.4% less than the dose to water. The electron dose conversion factors between the solid water phantom and water were determined: The higher the electron energy, the less is the conversion factor. The total uncertainty of the TG-51 protocol measurement using a solid water phantom was determined to be ${\pm}1.5%$. Conclusion: The developed method was successfully applied for the external auditing program, which could be evolved into a credential program of multi-institutional clinical trials. This dosimetry saved time for measuring doses as well as decreased the uncertainty of measurement possibly resulting from the reference setup in water.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.12
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• pp.198-204
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• 2016

This research studied the relevance of oral symptoms and fear to find solutions for prevention and treatment at the right time. The study was conducted over a three-month period from September to November 2015. College students who lived in the region of Busan were surveyed, and the data from 288 respondents were analyzed. The female students felt a higher level of fear in every item than the males. To be specific, there were statistically significant differences in postponing the appointment (p=0.014), tension during treatment (p=0.001), dread when making the appointment (p=0.001), dread upon arrival (p=0.001), dread in the waiting room (p=0.001), dread of dental smells (p=0.006), dread while undergoing anesthesia (p<0.001), dread when receiving an injection (p<0.001), dread when looking at a tool for tooth preparation (p<0.001), dread of the sound of a tool for tooth preparation (p<0.001), dread of the feelings of tooth preparation (p<0.001), dread during scaling(p<0.001), and apprehension about the entire treatment (p<0.001). Concerning the fear level according to oral symptom awareness, the respondents with dental caries experienced a higher level of fear in terms of treatment avoidance (p=0.001), physiological reactions (p=0.001) and overall Dental Fear Survey (DFS)(p=0.003), and the students whose teeth were broken had a higher level of fear in terms of treatment avoidance (p=0.010), stimulus factors (p=0.031) and overall DFS (P=0.019). The students who had a missing tooth felt a higher level of fear in terms of physiological reactions (p=0.019) and overall DFS (p=0.033), and the respondents with gingival pain felt a higher level of pain in terms of the stimulus factors (p=0.013) and overall DFS (p=0.034). Therefore, college students should be educated to visit a dental clinic when they are aware of any oral symptom, and methods to reduce the stimulus factors as much as possible should be considered carefully to relieve dental fear.

• Journal of dental hygiene science
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• v.8 no.4
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• pp.225-231
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• 2008

The purpose of this study was to examine the relationship between oral health habits and oral diseases in an attempt to raise awareness of the need for prolonged dental checkup projects and lay the foundation for oral health education and sustained oral health care projects. The subjects in this study were 2,643 workers from 76 workplaces in Siwha Industrial Complex in the city of Ansan, Gyeonggi province, who were at the age of 20 and up. The findings of the study were as follows: 1. Concerning the experience of visiting a dental clinic over the past year, 760 male workers (37.4%) and 237 females (38.9%) visited dental clinics in the past year. By age group, those who were in their 50s (54.0%) visited dental clinics the most, and the workers in their 30s (67.9%) paid a visit the least. The gap between the age groups was statistically significant (p < 0.001). 2. In regard to the time for toothbrushing by age group, the workers in their 20s (64.6%) made up the largest group that brushed their teeth before breakfast, and those who were in their 60s and up constituted the greatest group that did toothbrushing after breakfast. The workers in their 20s brushed their teeth the least, as the rates of the workers of this age group who did toothbrushing after breakfast and dinner respectively stood at 64.0 percent and 54.5 percent. The disparities between the age groups were statistically significant (p < 0.001). 3. As for scaling experience for the past year, 302(46.0%) out of the workers who got their teeth scaled in the past year had periodontal diseases, and 1,600(80.6%) out of those who didn't suffered from periodontal diseases. The gap between them was statistically significant (p < 0.001). 4. Regarding the relationship of subjective oral health state to dental caries among the workers without dental caries, the largest group that numbered 327(54.1%) considered themselves to be in good oral health. In the event of the workers with dental caries, the greatest group that numbered 708(75.5%) found themselves to have one or more carious tooth(teeth). The disparity between them was statistically significant (p < 0.001). 5. As for connections between dietary habits and dental caries, those who had dental caries (2.29) showed a greater preference for snack than the others who hadn't (2.21). The preference for snack made a bigger statistically significant difference to dental caries than the other dietary habits (p < 0.05).

• Journal of dental hygiene science
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• v.7 no.3
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• pp.187-191
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• 2007

In this study a research was conducted with 108 adolescents sent to three reformatories in D city to investigate their recognition of oral health so that they could assess their knowledge of oral health and improve oral health through correct oral health education. For this purpose, after the primary survey from June 13 to 28, 2006, oral health education was implemented through audio-vidual teaching aids and tooth-brushing training using one toothbrush per person, followed by the secondary survey using the same questionnaire. The research obtained the following results. 1. As for recognition of the concept of dental caries, the answer that it was a disease developing on teeth increased from 75.0% before oral health education to 82.4% after the education, which showed statistically significant differences (p < 0.001). 2. As for recognition of a preventive agent for dental caries, the answer that it was fluorine increased from 34.3% before oral health education to 75.0% after the education, which showed statistically significant differences (p < 0.001). 3. As for recognition of a good tooth-brushing method, the answer that it was a rotating method increased from 21.3% before oral health education to 95.4% after the education. 4. As for recognition of the amount of time for tooth-brushing, the answer that it was three minutes increased from 58.3% before oral health education to 88.9% after the education, which showed statistically significant differences (p < 0.001). 5. As for recognition of effects of smoking on oral health, the answer that it was bad increased from 65.7% before oral health education to 93.5% after the education. 6. As for recognition after oral health education for improving oral health, "completely agree" (78.7%) comprised the largest percentage (p < 0.001) for "teeth are important for health"; "completely agree" (76.9%) comprised the largest percentage (p < 0.001) for "correct tooth-brushing serves to prevent an oral disease"; "completely agree" (37.0%) comprised the largest percentage (p < 0.001) for "scaling is necessary to prevent a gingival disease"; "completely agree" (77.8%) comprised the largest percentage (p < 0.001) for "non-smoking is good for dental health"; "completely agree" (62.0%) comprised the largest percentage (p < 0.001) for "a seasonal medical check-up should be taken by all means".

• Journal of dental hygiene science
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• v.15 no.6
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• pp.703-711
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• 2015

The high dental treatment cost has been considered as one of the major reasons for inappropriate dental treatment in Korea. The aim of this study was to investigate the opinions of expansion of National Health Insurance (NHI) in dental treatment fields not covered with NHI and buying private dental insurance. This survey was carried out targeting 266 adults from their 30s to 50s with convenience sampling. The higher orders in stress of dental treatment cost were orthodontic treatment, dental implant, prosthodontic treatment, and caries treatment not covered with NHI. The higher orders in needs of expansion of NHI were caries treatment not covered with NHI, prosthodontic treatment, and orthodontic treatment. The agreement percentages with age restriction in NHI were scaling 57.1%, denture 23.3%, implant 14.3%, respectively. The subjective oral health had impact on the stress of dental treamtent cost and expansion on NHI. Although only 8.3% subjects had private dental insurance, 68.4% of the subjects had positive opinions buying private dental insurance. The correlation coefficients between stress of dental treatment cost and buying private dental insurance were implant 0.408, caries treatment not covered with NHI 0.404, denture 0.394, crown and bridge 0.375, and orthodontic treatment 0.313. Expansion of NHI in dental treatment and development of private dental insurance was suggested to treat dental disease in appropriate time.

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

• Proceedings of the Plant Resources Society of Korea Conference
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• 2002.11a
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• pp.29-30
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• 2002

The goal of this research was to develop the effectiveness of in vitro culture method for A. formosanus and study the environment in vitro conditions affecting on growth. The first series of experiments were examined to investigate the response of three different basal media, MS (Murashige and Skoog, 1962), Knudson (KC; Knudson, 1946) and modified hyponex on growth and multiplication during in vitro culture. Multiple shoot proliferation was induced in shoot tip explants on Hyponex (H3) media supplemented with BA (1 mg1$\^$-1/) or TDZ (1-2 mg1$\^$-1/). Addition of activated charcoal (1%) to the TDZ containing medium promoted rapid shoot tip proliferation (11.1 shoots per explant) but the same medium had an opposite effect resulting in poor proliferation in the nodal explants. However, the regenerated shoots had slow growth rate and failed to elongate. This problem was overcome by transferring the shoot clumps to a hormone free H3 media supplemented with 2% sucrose and 0.5% activated charcoal. Using bioreactor culture for scaling up was also shown the best way for multiple shoot induction and growth of this plant. The second series of experiments was studied to investigate the effect of physical environment factors on growth of in vitro plantlets. The Anoectochilus formosanus plantlets were cultured under different air exchange rate (0.1, 0.9, 1.2h$\^$-1/), without sucrose or supplement 20g.1$\^$-1/ (photoautotrophic or photomixotrophic, respectively), and different photosynthesis photon flux (40, 80, 120 ,${\mu}$mol.m$^2$.s$\^$-1/- PPF). Under non-enrichment CO$_2$ treatment, slow growth was observed in photoautotrophical condition as compared with photomixotrophical condition on shoot height, fresh weigh and dry weight parameters; High air exchange (1.2.h-l) was found to be inadequate for plant growth in photomixotrophical condition. On the contrary, under CO$_2$, enrichment treatment, the plant growth parameters were sharply (visibly) improved on photoautotrophic treatments, especially on the treatment with air exchange rate of 0.9.h-1. The growth of plant in photoautotrophic condition was not inferior compared with photomixotrophic, and the best growth of plantlet was observed in treatment with low air exchange rate (0.9.h-1). Raising the PPF level from 80 to 120${\mu}$mol.m$\^$-2/.s$\^$-1/ decreased the plant height, particularly at 120${\mu}$mol.m$\^$-2/.s$\^$-1/ in photoautotrophic condition, fresh weight and dry weight declined noticeably. At the PPF of 120${\mu}$mol.m$\^$-2/,s$\^$-1/, chlorophyll contents lowed compared to those grown under low PPF but time courses of net photosynthesis rate was decreased noticeably. Light quality mainly affected morphological variables, changes of light quality also positively affected biomass production via changes in leaf area, stem elongation, chlorophyll content. Plant biomass was reduced when A. formosanus were grown under red LEDs in the absence of blue wavelengths compare to plants grown under supplemental blue light or under fluorescent light. Stem elongation was observed under red and blue light in the present experiment. Smaller leaf area has found under blue light than with other lighting treatments. Chlorophyll degradation was more pronounced in red and blue light compared with white light or red plus blue light which consequent affected the photosynthetic capacity of the plant. The third series of experiment were studied to investigate the effect of physical environment factors on growth of ex vitro plants including photosynthesis photon flux (PPF), light quality, growing substrates, electrical conductivity (EC) and humidity conditions. In the present experiments, response of plant on PPF and light quality was similar in vitro plants under photosynthesis photon flux 40${\mu}$mol.m,$\^$-2/.s$\^$-1/ and white light or blue plus red lights were the best growth. Substrates testing results were indicated cocopeat or peat moss were good substrates for A. formosanus growth under the greenhouse conditions. In case of A. formosanus plants, EC is generally maintained in the range 0.7 to 1.5 dS.m-1 was shown best results in growth of this plant. Keeping high humidity over 70% under low radiation enhanced growth rate and mass production.