• The korean journal of orthodontics
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• v.15 no.2
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• pp.291-301
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• 1985

Fifty subjects who were to be treated with fixed orhodontic appliances by light wire edgewise technique were selected. Bands with different marginal depth were made in first molar and direct bonding brackets were bonded in second premolar. For determining the effects of fixed orthodontic appliance on the gingival tissue, the changes of clinical crown length, periodontal pocket depth, gingival sulcus fluid were checked. The results were as follows: 1. Gingival condition was deteriorated after wearing the fixed orthodontic appliance, and the deteriorative rate was decreased gradually. 2. The greatest gingival change was occurred in the maxillary first molar among the experimental teeth. 3. The gingival change of maxillary teeth was greater than that of mandibular teeth. $(p\leq0.01)$ 4. The greater gingival change was occurred around subgingivally located band than around supragingivally located band. 5. Comparing the gingival changes of banded teeth with them of bonded teeth, the gingival tissue was more effected by oral hygiene than by type of appliances. 6. In the quantitive changes of gingival crevicular fluid, there was no exact relationship with gingival inflammation.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.168-172
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• 2009

Shihmen reservoir was started in May 1963. The main purposes of Shihmen reservoir are for agriculture, power supply, flood control and tourism. Shihme Asn dam is an earth dam. Its crown height is 133m above mean sea level, with length 360 m, watershed 763.4 km², and maximum volume 309 million cms. Turbidity in Shihmen dam was severely affected by typhoons Aere (2004) and Masa (2005). Increased deposition after Aere was 28 million cms. Turbidity at Shihmen Canal Inlet is 3000 NTU (Nephelometry Turbidity Unit). Sediment sluicing strategies for downstream channel are demanded. Therefore, diversionary sediment preventing channel is planned in the upstream of Shihmen reservoir. Finally, turbid flow in tunnel channel is bypassed and diverted its flow down to downstream.

• Applied Chemistry for Engineering
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• v.4 no.4
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• pp.715-720
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• 1993

Diphenylmethane (pKa=33.4), which is difficult to be oxidized in normal oxidation conditions, was oxidized to produce benzophenone at ambient temperature and atmospheric pressure by using phase transfer catalysts and solid potassium tert-butoxide as base. Quaternary salt such as benzyltriethylammonium chloride, tetrabutyl ammonium bisulfate, tetrabutylphosponium chloride, are ineffective catalysts for this reaction, but 18-crown-6 and polyethylene glycols showed catalytic activity. The conversion of diphenylmethane was increased with increasing chain length of PEG molecules when they are used as phase transfer catalysts both in equal molar and equal weight basis. The conversion of diphenylmethane was increased with the agitation speed, and aprotic solvent like DMF showed higher reaction rate compared with benzene.

• Journal of Environmental Science International
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• v.25 no.2
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• pp.289-294
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• 2016

In this study, we examined the impact of transplant timing of mother plants for seedling strawberry on growth and development of daughter plants and field stage. The leaf growth of treated mother plants and crown thickness were low when transplant was performed on April $10^{th}$. Based on the results collected until July $13^{th}$, the numbers of daughter plants with more than two leaves were 20.6 and 19.5 for March $10^{th}$ and March $25^{th}$, and these values decreased by April $10^{th}$ and April $25^{th}$ showing values of 15.1 and 11.8, respectively. After seedling growth was complete, leaf area and fresh weight of the saplings were remarkably low beginning from the transplant on April $10^{th}$. Crown thickness of saplings was generally lower when transplant timing was late. After 45 days of transplant leaf length and width were noticeably lower than the transplant on April $10^{th}$ and $25^{th}$. First cluster was 100% for both the March $10^{th}$ and $25^{th}$ transplant, followed April 10th and $25^{th}$ with values of 66% and 43%. The results revealed that transplant on March $10^{th}$ and $25^{th}$ had a greater positive impact on the growth and development of the strawberry cultivar 'Seolhyang'. A supplementary study will have to be conducted to determine the relationship between the harvest period of the first cluster and the yield of marketable strawberries depending on the transplanting time of mother plants.

• The Journal of Advanced Prosthodontics
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• v.8 no.2
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• pp.150-157
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• 2016

PURPOSE. The modified lateral-screw-retained implant prosthesis (LSP) is designed to combine the advantages of screw- and cement-retained implant prostheses. This retrospective study evaluated the mechanical and biological complication rates of implant-supported single crowns (ISSCs) inserted with the modified LSP in the posterior region, and determined how these complication rates are affected by clinical factors. MATERIALS AND METHODS. Mechanical complications (i.e., lateral screw loosening [LSL], abutment screw loosening, lateral screw fracture, and ceramic fracture) and biological complications (i.e., peri-implant mucositis [PM] and peri-implantitis) were identified from the patients' treatment records, clinical photographs, periapical radiographs, panoramic radiographs, and clinical indices. The correlations between complication rates and the following clinical factors were determined: gender, age, position in the jaw, placement location, functional duration, clinical crown-to-implant length ratio, crown height space, and the use of a submerged or nonsubmerged placement procedure. RESULTS. Mechanical and biological complications were present in 25 of 73 ISSCs with the modified LSP. LSL (n=11) and PM (n=11) were the most common complications. The incidence of mechanical complications was significantly related to gender (P=.018). The other clinical factors were not significantly associated with mechanical and biological complication rates. CONCLUSION. Within the limitations of this study, the incidence of mechanical and biological complications in the posterior region was similar for both modified LSP and conventional implant prosthetic systems. In addition, the modified LSP is amenable to maintenance care, which facilitates the prevention and treatment of mechanical and biological complications.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.47 no.5
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• pp.356-360
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• 2002

The seedlings of yacon (Polymnia sonchifolia Poeppig ＆ Endlicher), which were cuttings, plug seedling (PS), crown bud before sprouting (CBBS), crown bud after sprouting (CBAS), and divided seedling after budding (DSAB) were planted at 70$\times$50 cm planting distance on ridge; that was interow spacingintrarow spacing, and about 28,500$\pm$71 plants/ha. CBBS didn't need work and equipment to raise seedlings. PS and DSAB grew taller to 140.5 and 143.3cm, respectively, than others at 150 days after planting. In the changes of plant height, PS and DSAB showed taller than others during growth period, cuttings, CBBS, and CBAS grew rapidly in middle growth stage. Excepting main stem and petiole length, other characters were significant for seedling. Fresh weights were different among seedlings. Even though the yield of plants grown from CBAS and CBBS were lower with 34.7 and 36.4 ton/ha, respectively, than 3.6 ton/ha of DSAB; its yield index were over 95%, hence, those of plants grown from cutting and PS were lower with 73 and 87%, respectively. The ratio of tuberous roots over 200g to total tuberous roots per plant was the highest from DSAB. Most of tuberous roots were under 200g per tuberous root from cuttings. CBBS, CBAS, and DSAB are suitable to use seedlings for high yield of yacono. Yacon plant by DSAB much produced tuberous root of over 200g.

• Structural Engineering and Mechanics
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• v.74 no.4
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• pp.567-576
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• 2020

Considerable controversy surrounds the choice of the best abutment type for implant prosthetics. The two most common structures are hex and non-hex abutments. The non-hex abutment typically furnishes a larger contact area between itself and the implant than that provided by a hex structure. However, when a hex abutment is loaded, the position of its contact area may be deeper than that of a non-hex abutment. Hence, the purpose of this study is to determine the different biomechanical behaviors of an internal bone-level implant based on the abutment type-hex or non-hex-and clinical crown length under static and cyclic loadings using finite element analysis (FEA). The hex structure was found to increase the implant and abutment stability more than the nonhex structure among several criteria. The use of the hex structure resulted in a smaller volume of bone tissues being at risk of hypertrophy and fatigue failure. It also reduced micromovement (separation) between the implant components, which is significantly related to the pumping effect and possible inflammation. Both static and fatigue analyses, used to examine short- and long-term stability, demonstrated the advantages of the hex abutment over the non-hex type for the stability of the implant components. Moreover, although its impact was not as significant as that of the abutment type, a large crown-implant ratio (CIR) increased bone strain and stress in the implant components, particularly under oblique loading.

• The korean journal of orthodontics
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• v.45 no.4
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• pp.190-197
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• 2015

Objective: The aim of the study was to analyze the prevalence and distribution of ectopic eruption of the permanent maxillary first molar (EEM) in individuals scheduled for orthodontic treatment and to investigate the association of EEM with dental characteristics, maxillary skeletal features, crowding, and other dental anomalies. Methods: A total of 1,317 individuals were included and randomly divided into two groups. The first 265 subjects were included as controls, while the remaining 1,052 subjects included the sample from which the final experimental EEM group was derived. The mesiodistal (M-D) crown width of the deciduous maxillary second molar and permanent maxillary first molar, maxillary arch length (A-PML), maxillomandibular transverse skeletal relationships (anterior and posterior transverse interarch discrepancies, ATID and PTID), maxillary and mandibular tooth crowding, and the presence of dental anomalies were recorded for each subject, and the statistical significance of differences in these parameters between the EEM and control groups was determined using independent sample t -tests. Chi-square tests were used to compare the prevalence of other dental anomalies between the two groups. Results: The prevalence of maxillary EEM was 2.5%. The M-D crown widths, ATID and PTID, and tooth crowding were significantly greater, while A-PML was significantly smaller, in the EEM group than in the control group. Only two subjects showed an association between EEM and maxillary lateral incisor anomalies, which included agenesis in one and microdontia in the other. Conclusions: EEM may be a risk factor for maxillary arch constriction and severe tooth crowding.

• The korean journal of orthodontics
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• v.44 no.6
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• pp.294-303
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• 2014

Objective: The purpose of this study was to examine whether orthodontic treatment experience affects the individual's perception of smile esthetics and to evaluate differences among orthodontically treated laypersons, non-treated laypersons, and dentists by using computerized image alterations. Methods: A photograph of a woman's smile was digitally altered using a software image editing program. The alterations involved gingival margin height, crown width and length, incisal plane canting, and dental midline of the maxillary anterior teeth. Three groups of raters (orthodontically treated laypersons, non-treated laypersons, and dentists) evaluated the original and altered images using a visual analog scale. Results: The threshold for detecting changes in maxillary central incisor gingival margin height among laypersons was 1.5 mm; the threshold of dentists, who were more perceptive, was 1.0 mm. For maxillary lateral incisor crown width and height, the threshold of all three groups was 3.0 mm. Canting of the incisal plane was perceived when the canting was 3.0 mm among non-treated laypersons, 2.0 mm among treated laypersons, and 1.0 mm among dentists. Non-treated laypersons could not perceive dental midline shifts; however, treated laypersons and dentists perceived them when the shift was ${\geq}3.0mm$. Conclusions: Laypersons with and without orthodontic treatment experience and dentists have different perceptions of smile esthetics. Orthodontically treated laypersons were more critical than non-treated laypersons regarding incisal plane canting and dental midline shifts. Based on these findings, it is suggested that orthodontic treatment experience improved the esthetic perceptions of laypersons.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.26-33
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• 1996

This study is related to the investigation of the characteristics of phase transfer catalysts on the addition reaction of carbon dioxide and phenyl glycidyl ether(PGE). Quaternary ammonium salts showed a good conversion of PGE at l atm of $CO_2$. Among the quaternary ammonium salts tested, the ones with higher alkyl chain length and with more hydrophilic counter anion showed higher catalytic activity. Polyethylene glycol and crown ether were also effective catalysts when they are used with NaI. High pressure of $CO_2$increased the conversion of PGE by increasing solubility of $CO_2$in NMP. A mechanism of the reaction involving the role of phase transfer catalyst was also proposed.