• The korean journal of orthodontics
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• v.29 no.2 s.73
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• pp.165-181
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• 1999

Treatment mechanics should be individualized to be suitable for each patient's personal teeth and anatomic environment to get a best treatment result with the least harmful effects to teeth and surrounding tissues. Especially, the change of biomechanical reaction associated with that of the centers of resistance of teeth should be considered when crown-to-root ratio changed due to problematic root resorption and/or periodontal disease during adult orthodontic treatment. At the present study, in order to investigate patterns of initial displacements of anterior teeth under certain orthodontic force when crown-to-root ratio changed in not only normal periodontal condition but also abnormal periodontal and/or teeth condition, the changes of the centers of resistance for maxillary and mandibular 6 anterior teeth as a segment were studied using the laser reflection technique, the lever & pulley force applicator and the photodetector with these quantified variables reducing alveolar bone 2mm by 2mm for each of maxillary 6 anterior teeth until the total amount of 8mm and root 2mm by 2mm for each of mandibular 6 anterior ones until the total amount of 6mm. The results were as follows: 1. Under unreduced condition, the center of resistance during initial displacement of maxillary 6 anterior teeth was located at the point of about $42.4\%$ apically from cemento-enamel junction(CEJ) of the averaged tooth of them and kept shifting to about $76.7\%$ with alveolar bone reduction. 2. The distance from the averaged alveolar crest level of maxillary 6 anterior teeth to the center of resistance for the averaged tooth of them kept decreasing with alveolar bone reduction, but the ratio to length of the averaged root embedded in the alveolar bone was stable at around $33\%$ regardless of that. 3. Under unreduced condition, the center of resistance during initial displacement of mandibular 6 anterior teeth was located at the Point of about $43\%$ apically from CEJ of the averaged tooth of them and this ratio kept increasing to about $54\%$ with root reduction. But the distance from CEJ to the center of resistance decreased from around 5.3mm to around 3.3mm, that is to say, the center of resistance kept shifting toward CEJ with the shortening of root length. 4. A unit reduction of alveolar bone had greater effects on the change of the centers of resistance than that of root did during initial Phase of each reduction. But both of them had similar effects at the middle region of whole length of the averaged root.

• The korean journal of orthodontics
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• v.29 no.5 s.76
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• pp.627-635
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• 1999

Soft tissue changes that occurred between presurgery to 5-years post-surgery in 49 orthognathic surgery patients whose maxillae were moved upward by Le Fort I osteotomy were examined by lateral cephalometric film. The objective of this paper was to document soft tissue changes at long-term follow-up after superior repositioning of the maxilla and to relate soft tissue and hard tissue changes in this group. The results were as follows. 1. On average, soft tissue landmarks in the nose and the upper lip were not changed statistically significantly except superior movement of superior labial sulcus and forward movement of pronasale between presurgery and 5 years postsurgery. 2. Upward and forward movement of the lower lip were found at 5 years postsurgery in comparison with presurgery and genioplasty added this effects. 3. Upper lip length and vertical dimension of upper vermilion didn't show any significant changes, but increase of lower lip length and decrease of vertical dimension of lower vermilion were statistically significant between presurgery and 5 years post-surgery. 4. The decrease of upper incisor exposure and interlabial distance from presurgery to 1 year were continued from 1 year to 5 years and the amount of the decrease was more than that of vertical movement of the maxilla by surgery. 5. Long term changes in soft tissue landmarks from 1 to 5 years postsurgery exceeded hard tissue changes, meaning soft tissue moved down more than skeletal changes.

• Journal of Korean Society of Transportation
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• v.20 no.2
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• pp.105-115
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• 2002

For many rears, traffic accident statistics are the most direct measure of safety for a signalized intersection. However it takes more than 2 or 3 yearn to collect certain accident data for adequate sample sizes. And the accident data itself is unreliable because of the difference between accident data recorded and accident that is actually occurred. Therefore, it is rather difficult to evaluate safety for a intersection by using accident data. For these reasons, traffic conflict technique(TCT) was developed as a buick and accurate counter-measure of safety for a intersection. However, the collected conflict data is not always reliable because there is absence of clear criteria for conflict. This study developed objective and accurate conflict criteria, which is shown below based on traffic engineering theory. Frist, the rear-end conflict is regarded, when the following vehicle takes evasive maneuver against the first vehicle within a certain distance, according to car-following theory. Second, lane-change conflict is regarded when the following vehicle takes evasive maneuver against first vehicle which is changing its lane within the minimum stopping distance of the following vehicle. Third, cross and opposing-left turn conflicts are regarded when the vehicle which receives green sign takes evasive maneuver against the vehicle which lost its right-of-way crossing a intersection. As a result of correlation analysis between conflict and accident, it is verified that the suggested conflict criteria in this study ave applicable. And it is proven that estimating safety evaluation for a intersection with conflict data is possible, according to the regression analysis preformed between accident and conflict, EPDO accident and conflict. Adopting the conflict criteria suggested in this study would be both quick and accurate method for diagnosing safety and operational deficiencies and for evaluation improvements at intersections. Further research is required to refine the suggested conflict criteria to extend its application. In addition, it is necessary to develope other types of conflict criteria, not included in this study, in later study.

• Journal of the Korean Geographical Society
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• v.40 no.2 s.107
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• pp.221-241
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• 2005

Land Use and Land Cover Changes (LUCC) occur over a wide range of space and time scales, and involve complex natural, socio-economic, and institutional processes. Therefore, modelling and predicting LUCC demands an understanding of how various measured properties behave when considered at different scales. Understanding spatial and temporal variability of driving forces and constraints on LUCC is central to understanding the scaling issues. This paper aims to 1) assess the heterogeneity of land cover change processes over the landscape in northern Ghana, where intensification of agricultural activities has been the dominant land cover change process during the past 15 years, 2) characterise dominant land cover change mechanisms for various spatial scales, and 3) identify the optimal spatial scale for LUCC modelling in a savanna landscape. A multivariate statistical method was first applied to identify land cover change intensity (LCCI), using four time-sequenced NDVI images derived from LANDSAT scenes. Three proxy land use change predictors: distance from roads, distance from surface water bodies, and a terrain characterisation index, were regressed against the LCCI using a multi-scale hierarchical adaptive model to identify scale dependency and spatial heterogeneity of LUCC processes. High spatial associations between the LCCI and land use change predictors were mostly limited to moving windows smaller than 10$\times$10km. With increasing window size, LUCC processes within the window tend to be too diverse to establish clear trends, because changes in one part of the window are compensated elsewhere. This results in a reduced correlation between LCCI and land use change predictors at a coarser spatial extent. The spatial coverage of 5-l0km is incidentally equivalent to a village or community area in the study region. In order to reduce spatial variability of land use change processes for regional or national level LUCC modelling, we suggest that the village level is the optimal spatial investigation unit in this savanna landscape.

• Korean Journal of Environment and Ecology
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• v.29 no.5
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• pp.703-709
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• 2015

A breeding pair of the Black-faced Spoonbill Platalea minor was firstly recorded on Chilsando Islands, Younggwang, Jeollanamdo Province in 1991. Since the mid 2000s, breeding population on the breeding sites has gradually increased. This study was conducted to identify breeding status and nest site characteristics of the species from May to August, 2013 on Chilsando Islands. We recorded number of nests, length and width of the nest base, slope around the nests, nest materials, distances from the nearest nest, presence of nest cover and nesting area. In 2013 breeding season, 25 of 49 nests produced at least one successful fledging. A total of 55 youngs were successfully fledged and number of fledging per nest was 2.20 individuals. Nesting area was $77.8m^2$ and $93.4m^2$ for Sansando and Yuksando Islet, respectively. Soil and soil mixed with tree root were preferred for substrate of nest base over rock and Brassica napus was dominantly selected as nest materials by Black-faced Spoonbills. Nest characteristics of 22 nests in Sasando and Yuksando Islet varied $49.59{\pm}6.53cm$(mean${\pm}$SD) for length of nest base, $41.00{\pm}5.82cm$ for width of nest base, $20.85{\pm}9.96^{\circ}$ for slope above the nest, $34.09{\pm}17.75^{\circ}$ for slope below the nest and $130.82{\pm}84.17cm$ for distances from the nearest nest. Fifteen pairs (68.2%) occupied where nest cover existed. Nest cover were located in front of the nest for 5 pairs, back of the nest for 9 pairs and both front and back of the nest for 1 pair.

• Journal of Radiation Protection and Research
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• v.14 no.1
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• pp.24-33
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• 1989

The peripheral dose, defined as the dose outside therapeutic photon fields, was estimated for 6MV X-ray linear accelerator. The measurements were performed using silicon diode detectors controlled by automatic controlled water phantom. The effects of field size, collimator position, presence or absence of wedge filter, and wedge angle were analyzed. The results were as follows 1. The peripheral dose decreases as the distance from field margin increases and it is more than 2.4% of central axis maximum dose even at 15cm distance from field margin. 2. Maximum build-up of peripheral dose is at 2-3 mm from the water surface and drops to a minimum at 1.5cm depth and then the dose increase again. 3. The peripheral dose increases as the field size. increases. At the short distance from field margin, the difference of peripheral dose between 5 $\times\;5cm^2$ and 20 $\times\;20cm^2$ field size reaches more than 2 fold. 4. The peripheral dose is higher along the upper collimator than along the lower collimator. The differences is less than 1%. 5. The presence of wedge filter increases peripheral dose. And the peripheral dose is higher along the blade side of wedge filter than along the ridge side. The difference is about 3% at 5cm distance from the field margin for 15 $\times\;15cm^2$ field size and 60$^{\circ}$ wedge filter. 6. The Peripheral dose of wedge filter increases as the wedge filter angle increases and the increasing ratio is about 2 fold in 60$^{\circ}$wedge filter compared with open field.

• Journal of the Korean Chemical Society
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• v.40 no.7
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• pp.474-482
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• 1996

Two crystal structures of the vacuum dehydrated $Ag^+$-exchanged zeolite X have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at 21(1)$^{\circ}C$ (a=24.922(1)${\AA}$ and a=24.901(1)${\AA}$, respectively). Each crystal was ion exchanged in flowing streams of aqueous $AgNO_3$ for three days. The first crystal was dehydrated at 300$^{\circ}C$ and $2{\times}10^{-6$torr for two days. The second crystal was similarly dehydrated at 350$^{\circ}C$. Their structures were refined to the final error indices, $R_1=0.095\;and\;R_2=0.092$ with 227 reflections, and $R_1=0.096\;and\;R_2=0.087$ with 334 reflections, respectively, for which I > 3${\sigma}$(I). In the first crystal, Ag species are found at five different crystallographic sites: sixteen $Ag^+$ ions fill the site I, the center of the double 6-ring, thirty-two Ag0 atoms fill the I' site in the sodalite cavities opposite double six-rings, seventeen $Ag^+$ ions lie at the 32-fold site II' inside the sodalite cavity at the single six-oxygen ring in the supercage, fifteen Ag+ ions lie at the 32-fold site II, in the supercage, and the remaining twelve $Ag^+$ ions lie at site III' in the supercage at a little off two-fold axes. In the second crystal, all Ag species are located similarly as crystal 1; 16 at site I, 28 at site I', 16 at site II, 16 at site II', 6 at site III and 6 at site III'. Total 88 silver species were found per unit cell. The remaining four Ag atoms were migrated out of the zeolite framework to form small silver crystallites on the surface of the zeolite single crystal. In the first structure, the numbers of Ag atoms per unit cell are approximately 32.0 and these may form tetrahedral $Ag_4$ clusters at the centers of the sodalite cavities. The probable four-atom cluster is stabilized by coordination to two $Ag^+$ ions. The Ag-Ag distance in the cluster, ca. 3.05 ${\AA}$, is a little longer than 2.89 ${\AA}$, Ag-Ag distance in silver metal. At least two six-ring $Ag^+$ ions on sodalite cavity (site II') must necessarily approach this cluster and this cluster may be viewed as a distorted octahedral silver cluster, (Ag6)2+.

• Journal of the Korean Chemical Society
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• v.37 no.3
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• pp.344-350
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• 1993

25,26,27,28-Tetraacetoxycalix[4]arene·monohydrate is orthorhombic, space group Pbca with a = 14.979(4), b = 15.154(4), c = 27.890(3) ${\AA}$, Z = 8, V = 6330.6 ${\AA}^{-3}$, D$_c$ = 1.28 $g{\cdot}cm^{-3}$, (Mo K${\alpha}$) = 0.71069 ${\AA}$, ${\mu}$ = 0.86 cm$^{-1}$, F(000) = 2600, and R = 0.069 for 3376 unique observed reflections with I > 1.0 ${\sigma}$(I). The structure was solved by direct methods and refined by cascade diagonal least-squares refinement. All the C-H bond lengths(= 0.96 ${\AA}$), the methyl groups and the methylene groups are fixed and refined as the rigid groups with ideal geometry. The macrocycle exists in the 1,3 alternate conformation (by Conforth) making the angles of 110.7, 684, 113.7 and 68.8$^{\circ}$ between the benzene rings and the methylenic mean plane, and four each acetoxy groups are twisted away from their own benzene rings with the angles of 68.2, 97.6, 78.9 and 71.3$^{\circ}$, respectively. The relative dihedral angles between two opposite side of the benzene rings are 135.6$^{\circ}$ for the rings (1) and (3) and 135.2$^{\circ}$ for (2) and (4). A water molecule which has nearly the same height of the methylenic plane of the macrocycle in the c-axis, is located within the distances of 2.942(5) ${\AA}$ from the O(8) atom of the carbonyl group and 2.901 ${\AA}$ from, another O(2)(1/2-x, -1/2＋y, z). The shortest contact between the molecule is 3.193 ${\AA}$ from the O(4) to the C(3)(1/2＋x, 1/2-y,-z).

• Journal of the Korean Geotechnical Society
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• v.33 no.11
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• pp.21-34
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• 2017

The ground penetrating radar (GPR) signal can be measured with different amplitudes according to the directivity, so the directivity of the antenna should be considered. The objective of this study is to investigate the directivity of antenna by analyzing the reflection characteristics of electromagnetic waves radiated from the antenna, and to evaluate effective range of angle that can inspect an abnormal area according to the directivity of antenna. For the measurement of the directivity, a circular metal bar is used as reflector and the signals are measured by changing the angle and the distance between reflector and antenna in the E- and H-plane. The boundary distance between the near field and the far field is determined by analyzing the amplitudes of reflected signals, and two points with different distances from each of near and far fields are designated to analyze radiation patterns in near and far fields. As a result of radiation pattern measurement, in the near field, minor lobes are observed at angle section at more than $50^{\circ}$ in both E- and H-plane. Therefore, antenna has the directivity for the direction of main lobe and minor lobes in near field. In the far field, antenna has the directivity for a single direction of main lobe because minor lobes are not observed. The amplitude of the signal reflected from the near field is unstable, but it can be distinguished from noise. Therefore, in the near field, the ground anomaly can be detected with high reliability. On the other hand, the amplitude of the signal reflected from the far field is stable, but it is hard to distinguish between reflected signal and noise because of the excessive loss of electromagnetic wave. The analyses of directivity in the near and the far fields performed in this study may be effectively used to improve the reliability of the analyses of abnormal area.

• Journal of Korean Society of Forest Science
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• v.90 no.1
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• pp.43-54
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• 2001

Genetic differentiation of populations is resulted from the environmental and the genetic effects, and the interactions between them. Whereas, the major factors influencing to the genetic differentiation within populations are the gene flow induced by seed or pollen dispersial, the microsite heterogeneity, and the density-dependent distribution of individuals. For the purpose of studying spatial genetic structure and the distribution pattern of Korean pines(Pinus koraiensis), we set up one $100{\times}100m$ plot at a Korean pine stand in Quercus mongolica community on Mt. Jumbong in Korea. To estimate the coefficient of spatial autocorrelation as Moran's index and an analogue, simple block distance, isozyme markers were analyzed in 325 Korean pines. For 11 polymorphic loci observed in 9 enzyme systems, the average percentage of polymorphic loci, the observed and expected heterozygocity were 72.2% 0.200, and 0.251, respectively. It was revealed the excess of homozygotes was observed in the plot, which suggests that here may be more number of consanguineous trees than expected. On the basis of isozyme genotypes observed in this study, 325 trees were classified into 147 groups in which the maximum number of trees for one group was 34. From the distance class of 24-32m, the genetic heterogeneity began to increase. The variation of simple block distance against the growth performance by tree height and diameter also showed the same trend at 24~32m class. According to high fixation index(F=0.204), the spatial genetic structure within a stand, the analysis of the growth performance, and the distribution patterns of identical genotypes, we inferred that the genetic structure of a Korean pine stand in Mt. Jumbong has been maintained rather density-dependent mechanism than the gene flow, such as the pollen dispersial or the heavy input of seeds following the forest gaps. The genetic patchy size was determined between 24~32m, which suggests that the selection of individuals for the ex situ conservation of Korean pine in Mt. Jumbong may be desirable to be made with the spatial distance over 37 meters between trees.