• Proceedings of the KWS Conference
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• 대한용접접합학회 2003년도 춘계학술발표대회 개요집
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• pp.87-89
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• 2003

The yield strengths of austenitic stainless steel have been approximately doubled by increasing the nitrogen content. But, the increasing the nitrogen cause of increase the pressure of metal vapor inside the keyhole in electron beam welding. During welding, eruptions of keyhole often occur that cause excessive spatter, concavity, and porocity in the weld zone. Additionally the fast evaporation of nitrogen content cause of decrease the strength of weld zone. Therefore in this paper, we investigated of the weldability of electron beam welding and the change of chemical content after welding for strengthened austenitic stainless steel, measured the deformation scale of both of electron beam and narrow gap TIG and the spike fluctuation in the root.

• Journal of the Korea Safety Management & Science
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• 제15권1호
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• pp.101-108
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• 2013

Industrial disaster caused the deaths of 2,114, construction workers among them was the highest of 621 deaths. In the construction industry, has established a number of safety alternatives to prevent accidents. But until now, the cause of the accident has stopped being superficial analysis, awareness on the root cause of the acciden did not reflect. In this study, we analyze the characteristics and causes in G contractors' safety accidents. And innovation strategy, organization-wide safety management system and detailed tasks to derive essentially was to prevent the occurrence of large construction companies. A lot of business for accident prevention effect was transient and formal, to reflect a management style and organizational culture, and try to prevent construction accidents. we will strive to prevent the disaster from the construction site through the improvement of these.

• Oral Biology Research
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• 제42권4호
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• pp.241-247
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• 2018

Toothache is one of the most common discomforts experienced by patients in dental clinic. If clinical and radiographic examinations do not reveal any pathologic findings, we can suspect nonodontogenic toothache. Nonodontogenic toothache can be caused by a variety of causes such as muscle disorders, sinus and nasal mucosal problems, neuropathic pain, neurovascular pain, psychogenic problems, and cardiogenic disease. A thorough history and clinical examination should be performed to confirm the cause of the pain, and more accurate diagnosis can be established through local anesthetic injection. If the nonodontogenic toothache is misdiagnosed, unnecessary dental treatment such as root canal treatment, periodontal treatment, and extraction can be performed, and the patient's pain is not alleviated through such treatment. Therefore, the cause of toothache must be diagnosed correctly before dental treatment is performed, and clinicians should be fully aware of the diseases that may cause these symptoms.

• Journal of Periodontal and Implant Science
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• 제29권3호
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• pp.577-594
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• 1999

The major cause of periodontal disease is microorganism in the dental plaque. Gingival sulcular fluid, which is exudate released from the tissue near crevicular epithelium is related with inflammation. The purpose of this study was to evaluate the argon laser efficiency between the clinical index and onset of collagenase of gingival sulcular fluid. Material divided 16 patients into 4 groups. The first control was without treatmemt. The second was with just treatment of argon laser, The third was treated by scaling and root planning and the fourth was treated with both scailing and root planning and argon laser. The level of periocheck test, the index of bleeding, and the depth of periodontal pocket were evaluated from for 128 teeth of 64 anterior teeth and 64 posterior teeth. The results were as follows ; 1. In the score of periocheck test, root planing group(group 3) was significantly reduced more than the group without treatment(group 1) and the argon laser treatment(group 2) for results of 3 days and 7 days. But root planing plus argon laser treatment(group 4) in the 7days after experiment, was significantly reduced than no treatment(group 1) and root planing treatment(group 3)(P<0.05), in the 3 days after experiment, was significantly reduced than root planing(group3)(P<0.05). The score of periocheck test to the root planning group(group 3) were significantly reduced between days1, day3 and day7(P<0.05). Root planning plus argon laser group(group 4) were significantly reduced to 1 or 7days and 3 or 7days(P<0.05). The argon laser group(group 2) didn't show any changes. 2. In the case of sulcus bleeding index, the root planning group(group 3) and root planning plus argon laser group(group 4) were reduced more than without treatment group(group 1)(P<0.05) and sulcus bleeding index in the root planning group(group 3) were reduced more than the argon laser group(group 2)(P<0.05). 3. There wasn't any changes of pocket depth between the control and the experiment group as with experiment periods also.

• Journal of the korean academy of Pediatric Dentistry
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• 제38권3호
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• pp.229-236
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• 2011

ProRoot MTA(Dentsply Tulsa, U.S.A) which has similar component with Portland cement has setting expansion character and long setting time. Excessive expansion can cause fracture at the apical portion of the root and decreasing of volume stability. And the long setting time makes additional visits for crown restoration and slow setting process of this material can change physical properties itself. In this study, among requirements of root canal filling material(KS P ISO 6876) which is revised at 2008, we investigated the setting time and setting expansion. Objects are recently developed OrthoMTA(BioMTA, Korea), conventional ProRoot white MTA(Dentsply Tulsa, U.S.A) and White portland cement(Union, Korea). The results in setting expansion, OrthoMTA was $0.08{\pm}0.02%$, ProRoot white MTA and White portland cement were each $0.28{\pm}0.06$, $0.80{\pm}0.25%$(p<0.05). The results in setting time, OrthoMTA, ProRoot white MTA, White portland cement were each $307.78{\pm}3.83$ min, $150.44{\pm}2.35$ min, $235.33{\pm}9.07$ min(p<0.05).

• Korean Journal of Medicinal Crop Science
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• 제26권5호
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• pp.345-353
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• 2018

Background: Some phenolics detected in the soil may inhibit the seed germination and seedling growth of ginseng (Panax ginseng). This study investigated the effect of irrigation and ginseng root residue addition on the soil microbial community and root rot disease in 2-year-old ginseng. Methods and Results: Each $20{\ell}$ pot was filled with soil infected with ginseng root rot pathogens, and irrigated daily with $2{\ell}$ of water for one month. After the irrigation treatment, ginseng fine root powder was mixed with the irrigated soil at a rate of 20 g per pot. In descending order, ${NO_3}^-$, electric conductivity (EC), exchangeable Na (Ex. Na) and K (Ex. K) decreased due to irrigation. In descending order, ${NO_3}^-$, EC, Ex. K, and available $P_2O_5$ increased with the additon of ginseng powder to the soil. The abundance of Trichoderma crassum decreased with irrigation, but increased again with the incorporation of ginseng powder. The abundance of Haematonectria haematococca increased with irrigation, but decreased with the incorporation of ginseng powder. The abundance of Cylindrocarpon spp. and Fusarium spp., which cause ginseng root rot, increased with the incorporation of ginseng powder. The abundance of Arthrobacter oryzae and Streptomyces lavendulae increased with irrigation. The abundance of Streptomyces lavendulae decreased, and that of Arthrobacter spp. increased, with the incorporation of ginseng powder. Aerial growth of ginseng was promoted by irrigation, and ginseng root rot increased with the incorporation of ginseng powder. Conclusions: Ginseng root residues in the soil affected soil nutrients and microorganisms, and promoted ginseng root rot, but did not affect the aerial growth of ginseng.

• Journal of Ginseng Research
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• 제44권3호
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• pp.506-518
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• 2020

Background: Red-skin root of Asian ginseng (Panax ginseng) significantly reduces the quality and limits the production of ginseng in China. The disease has long been thought to be a noninfectious physiological disease, except one report that proved it was an infectious disease. However, the causal agents have not been successfully determined. In the present study, we were to reveal the pathogens that cause red-skin disease. Methods: Ginseng roots with red-skin root symptoms were collected from commercial fields in Northeast China. Fungi were isolated from the lesion and identified based on morphological characters along with multilocus sequence analyses on internal transcription spacer, β-tubulin (tub2), histone H3 (his3), and translation elongation factor 1α (tef-1α). Pathogens were confirmed by inoculating the isolates in ginseng roots. Results: A total of 230 isolates were obtained from 209 disease samples. These isolates were classified into 12 species, including Dactylonectria sp., D. hordeicola, Fusarium acuminatum, F. avenaceum, F. solani, F. torulosum, Ilyonectria mors-panacis, I. robusta, Rhexocercosporidium panacis, and three novel species I. changbaiensis, I. communis, and I. qitaiheensis. Among them, I. communis, I. robusta, and F. solani had the highest isolation frequencies, being 36.1%, 20.9%, and 23.9%, respectively. All these species isolated were pathogenic to ginseng roots and caused red-skin root disease under appropriate condition. Conclusion: Fungal complex is the causal agent of red-skin root in P. ginseng.

• The korean journal of orthodontics
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• 제21권1호
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• pp.77-96
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• 1991

Many studies has been conducted concerning prevention of unnecessary complications such as root resorption during orthodontic too th movement under various mechanical forces. Nowadays, the cause of the root resorption is not thought to be confined only to mechanical forces. But the factor that affects bone metabolism are thought to be major one of the predisposing factors. The light microscope and scanning electron microscope were used to the effects of 60 gm, and 100 gm of tipping force on root resorption of cats, which were treated with Etidronate disodium. The results were as follows: 1. In the 60gm control group, hyalinization on the compression site of periodontal ligament appeared after first week and second week. In the 60gm experimental group, it appeared after first week with low frequency. In the 100gm control group it appeared with high frequency by first and second week while in 100gm experimental group, it appeared with low frequency. 2 In the 100gm control group, resorption of the cementum and the alveolar bone rapidly increased after second week. In the 60gm experimental group, resorption or formation of alveolar bone and cementum didn't appear all through the experimental period. 3. In the 100gm control group, formation of cementum and alveolar bone appeared after first week while in the 100gm experimental group, formation of cementum and alveolar bone appeared after second week and fourth week respectively. In the 60gm control group, formation of the cementum didn't appear all through the experimental period. 4. In the control group, the root resolution of 100gm group was higher than that of 60gm group after second week, while in experimental group, root resorption didn't appear regardless of the forces.

• Microbiology and Biotechnology Letters
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• 제41권1호
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• pp.70-78
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• 2013

Rhizoctonia solani and Fusarium oxysporum cause yield losses in numerous economically important crops. To develop a bio-control agent, cell free extracellular compounds (ECs) of 5 bacterial strains Burkholdria sp. L1, Pseudomonas sp. L4, Pseudomonas chlororaphis VN391, Bacillus subtilis VN21 and Enterobacter sp. VN99 from Vietnamese fields, which reduced levels of R. solani root rot in lettuces and F. oxysporum root rot in tomatoes, were investigated. In a growth chamber, ECs of all antagonists markedly enhanced the biomass of lettuces (10 to 14.1%) and tomatoes (11.38 to 13.88%). In greenhouses, the disease's severity on both crops treated with ECs of the antagonists was reduced significantly and biomass losses in the plants decreased markedly. The reduction level of R. solani root rot in lettuces was 75, 66.7, 50, and 16.7% by ECs of strains L1, L4, VN21 and VN391, respectively. The biomass of lettuces increased markedly by 29.13%, 21.67%, and 23.4% by ECs of strains L1, L4 and VN21, respectively. Similarly, the reduction levels of F. oxysporum root rot in tomatoes was 76.3, 75, 41.7 and 25% by ECs of strain L1, L4, VN21 and VN391, respectively, and the biomass was significantly enhanced by 14.42, 12.7 and 13%, respectively. The ECs of strain L1 exhibited the most effective bio-control agents to suppress R. solani and F. oxysporum.

• Proceedings of the Ginseng society Conference
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• 고려인삼학회 1978년도 학술대회지
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• pp.67-74
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• 1978

The phenomenon of 'soil sickness' is one of the most important limiting factors for ginseng(Panax ginseng) production in Korea. The principal cause is known to be due to the root rots caused by Cylindrocarpon destructans and Fusarium solani. Attempts were made to control the root rots with non-polluting cultural methods or soil amendments. Among the nine soil amendments tested, crab shell, cow bone and pig feces were selected for further testing. Each of the three amendments increased the populations or various actinomycetes in the range of 10-25 times over that of non-amended soil, whereas the population of C. destructans was reduced to about $50-70\%$ as compared with the control. Five isolates of Streptomyces with clear zones on chitin-agar medium were selected and then tested for their antagonistic effects on C. destructans. When anyone of the five isolates of Streptomyces and C. destructans was grown together in a modified peptone broth, growth of the latter was highly inhibited. When three levels of crab shell, cow bone, or pig feces were used to amend potted soil infested with C. destruetans, the root rot ratings of ginseng seedlings were reduced to less than one half in all the treatments as compared to the control. In another similar experiment, crab shell and cow bone amendments resulted in almost complete control of the seedling root rots in soil infested with C. destructans or F. solani. In conclusion, biological control with soil amendments of ginseng root rots caused by C. destructans and F. solani was successful. Further basic studies should be pursued using soil amendments for better control. In addition, field experiments are needed to complement the soil amendment control measures in an integrated pest control program.