• Korean Journal of Soil Science and Fertilizer
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• v.22 no.1
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• pp.6-11
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• 1989

This investigation was conducted to get basic informations on land consolidation works and soil management for arable land. The characteristics of geometrical features of mapping units in the detailed soil maps of Korea were measured from 70 soil series (565 soil phases) by using a picture analysis system. The results obtained were as follows: 1. The mean values of the mapping units in extent, periphery, diameter of long axis and short axis, roundness and number of acute angles were 22.0ha, 2.267m, 911m, 0.104, and 3.5, respectively. It was suggested that "Simplicity Index of Mapping Unit", $=\frac{Extent\;in\;ara}{Length\;of\;boundary\;periphery\;in\;meter}{\times}\frac{1}{number\;of\;acute\;angle}$ be valuable to judge the complexity degrees of mapping units. 2. The size of mapping unit among physiographyic position was shown in order of Alluvial plains > Fluviomarine plains > Terraces > Hills > Fans > Mt. foot slopes > Valleys, and the simplicity index of mapping units also showed similar order of the extent. 3. The size and the simplicity index of the soils developed on plains with silty textured imperfectly drained were higher than the soils developed on sloped land with loamy textured. As the slopes getting steeper or relatively better in soil drainage, the size and the simplicity index became smaller. 4. The relationship between the simplicity index and the size of the farm unit divides by the land consolidation works was positively correlated. And it was concluded that the parcelling of the farm unit divides by the planning of land consolidation should be based on the soil boundaries of the detailed soil maps for mechanized or collaborated farming.

• Journal of the Korean Chemical Society
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• v.38 no.11
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• pp.827-832
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• 1994

The crystal structure of bis(N-methylphenazinium) bis(oxalato)palladate(II) has been determined by X-ray crystallography. Crystal data: ((C_{13}H_{11}N_2)_2[Pd(C_2O_4)_2]) $M_w$ = 672.93, Triclinic, Space Group P1 (No = 2), a = 7.616(8), b = 9.842(3), c = $20.335(7)\AA$, $\alpha$ = 103.53(3), $\beta$ = 90.00(5), $\gamma$ = $112.38(5)^{\circ}$, Z = 2, $V = 1363(2){\AA}^3\;D_c = 1.639\;gcm^{-3},\;{\mu} = 7.3\;cm^{-1},\;F(000) = 680.0$. The intensity data were collected with $Mo-K\alpha$ radiation (${\lambda}$= 0.7107\;\AA)$ on an automatic four-circle diffractometer with a graphite monochromater. The structure was solved by Patterson method and refined by full matrix least-square methods using Killean & Lawrence weights. The final R and S values were $R = 0.069,\;R_w = 0.050,\;R_{all} = 0.069$ and S = 5.45 for 3120 observed reflections. Both cation and anion complexes are essentially planar and have dihedral angles of 6.3(6) and $57.06(6)^{\circ}$ between their planes. The planar complex anions are sandwiched between slightly bent cations. The interplanar separations of two triads are 3.328 and 3.463 $\AA$, respectively. The triads are stacked along b-axis, but their orientations are different based on dihedral angle $59.08(9)^{\circ}$ of two complex anions.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.3
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• pp.251-257
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• 2017

Purpose: The purpose of this study was to evaluate whether the internal abutment length affected screw stability in an internal connection implant. Materials and methods: Twenty long internal connection implants (Replus system, $4.7{\times}11.5mm$) were selected for this investigation. Abutments were assigned to four groups depending on the length of the internal connection (abutments with internal lengths of 1, 2, 3, and 4 mm, respectively). Each implant fixture specimen was embedded in resin medium and connected to an abutment with an abutment screw. A load of 100 N, applied at an angle of $30^{\circ}$ to the long axis of the implant, was repeated for $1.0{\times}10^6$ cycles. Reverse torque values (RTV) were recorded before and after loading, and the change in RTV was calculated. Data were analyzed with the Kruskal-Wallis test. Results: The change in RTV was not significantly different among the groups (P>.05). Screw loosening and fractures were not observed in any groups, and joint stability was maintained. Conclusion: The internal length of the abutment may not significantly affect the degree of screw loosening.

• The korean journal of orthodontics
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• v.33 no.2 s.97
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• pp.73-84
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• 2003

This study was performed to find out how much projection errors in the cephalometric measurements were made by vertical head rotation in taking posteroanterior cephalograms. 25 adults without any apparent facial asymmetry or severe sagittal skeletal discrepancy were selected and the posteroanterior cephalograms were taken with the head rotated $5^{\circ},\;10^{\circ}$ superior and inferior each to the reference $position(0^{\circ})$. The 7 height, 5 width and 6 angular measurements were taken at each 5 positions. Through the statistical analysis of all measurements taken at each rotated position, folowing results were obtained.1. The projection errors of height measurements were remarkably target than those of width or angular measure nents. f. Among the height measurements, the farther to the rotation axis the measurements were, the larger the projection errors were. 3. Among the width measurements, mandibular width and mandibular width of mandibular first molars showed significant differences between the values taken at each rotated position, while nasal width, maxillary width and intermolar width of maxillary first molars did not. 4. Among the angular measurements, the angle between horizontal reference line and the line that is connected to crista galli and antegonion or maxillare showed significant differences between the values taken at each rotated Position. The above results suggest that it is needed to the effort to keep constant head position for taking the useful posteroanterior cephalogra, because projection errors are caused by vertical head rotation.

• The Journal of Korean Academy of Prosthodontics
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• v.33 no.2
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• pp.177-197
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• 1995

The endodontically treated tooth is generally restored with post & core, owing to the brittleness and the loss of large amount of tooth structure. Although there have been lots of studies about the endodontically treated teeth, the three-dimensional quantitative studies about the strees distribution of them are in rare cases. In this study, it was assumed that the coronal portion of the upper incisou had severely damaged. After the root canal therapy it was post cored, and restored with PFM crown, for this experiment nine types of model were constructed : 1); long, 2); medium, 3); short gold post for the roots supported with a narmal alveolar bone, 4); long, 5); medium, 6); short gold post for the roots supported with an alveolar bone resorbed to its 1/3 of root length, 7); long, 8); medium, 9); short base metal post for the roots supported with an alveolar bone resorbed to its 1/3 of root length. Force was applied from two directions. One was functional maximum bite force(300N) applied to the spot just lingual to the incisal edge with the angle of 45 degrees to the long axis of the tooth, and the other one was horizontal force(300N) applied to the labial surface. The results analyzed with three-dimensional finite element method were as follows : 1. Stress was concentrated on the middle portion of the labial side dentin of the root and the lingual portion of the apical dentin of the root. Stress in the post showed maximum value at 2 mm above the post apex. 2. In case of the long post and base metal post, strees was concentrated on the apex of the root and the post. 3. In case of the longer post, the displacement on the post-cement interface was lessened. The gold post was more displaceable than the base metal post. 4. In case of the alveolar bone resorption, stress concentrated on the root and the post and displacement on the post-cement interface were increased.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.3
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• pp.287-295
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• 2002

Statement of Problem. Endodontically treated teeth frequently required posts and cores to provide retention and resistance form for crowns. In spite of excellent mechanical properties of metal post and core, its metallic color can be detected through all ceramic restorations occasionally. To solve esthetic problems of metal post and core zirconia post system has been introduced recently. Purpose. The purpose of this study was to examine the fracture strength and mode of resin root analogs restored with zirconia, gold and titanium posts with resin, ceramic and metal cores after cementation with metal crowns. Materials and methods. To avoid the morphological variations of natural teeth, 40 root analogs were fabricated with composite resin. Forty resin root analogs were randomly assigned to four groups according to post and core materials: Group A: cast gold post and core and complete cast crowns, as control. Group B: titanium posts (Parapost, Coltent/Whaledent Inc., NJ, USA) and composite resin cores. Group C: zirconia posts (Cosmopost, Ivoclar AG, Schaan/Liechtenstein) and composite resin cores Group D: zirconia posts and heat-pressed ceramic cores (IPS Empress Cosmo Ingots, Ivoclar AG) After thermocycling ($5^{\circ}C{\sim}55^{\circ}C$, 30 sec.), cyclic loading was applied at 3mm below the incisal edge on the palatal surfaces at an angle of 135 degree to the long axis (2Hz, 50N, 50000cycles). Fracture strength was measured by universal testing machine (Instron, High Wycombe, UK) and fracture pattern of restored resin root analogs was also evaluated. Results and conclusion. Within the limitations of this study following results were drawn. 1. Resin root analogs restored with zirconia posts and composite resins demonstrated lowest fracture strength among tested groups. 2. There was no significant difference in the fracture strength between zirconia posts and heat pressed glass ceramic cores and cast gold posts and cores 3. The fracture strength of resin root analogs restored with titanium posts and composite resin cores was lower than that of gold posts and cores. 4. The deep oblique fracture lines were dominantly observed in root analogs restored with cast gold post and core and zirconia post and heat-pressed ceramic core groups.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.5
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• pp.582-595
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• 2003

Statement of problem : Most posts are metallic, but in response to the need for a post that possesses optical properties compatible with an all-ceramic crown. an esthetic post has been developed. Although there have been many studies about the esthetic post materials, 3-dimensional finite element studies about the stress distribution of them are in rare. Purpose : The purpose of this study is to investigate comparatively the distribution of stresses of the restored, endodontically treated maxillary incisors with the esthetic post materials and the displacement on the cement layer on simulated occlusal loading by using a 3-dimensional finite element analysis model. Material and method : Four 3-dimensional finite element models were constructed in a view of a maxillary central incisor, a post, a core, and the supporting tissues to investigate the stresses in various esthetic posts and cores and the displacement on the cement layer (Model 1 ; Cast gold post and core, Model 2 ; Glass fiber post with composite core, Model 3 ; Zirconia post with composite core. Model 4 ; Zirconia post with ceramic core). Force of 300N was applied to the incisal edge and the cingulum (centric stop point) with the angle of 135-degree to the long axis of the tooth. Results : 1. The stresses and displacement on the incisal edge were higher than on the cingulum 2. The stresses in dentin were the highest in Model 2 (Glass fiber post with composite core), and the second was Model 3, the third Model 1, and the lowest Model 4. 3. The stresses in post and core were the highest in Model 4 (Zirconia post with ceramic core), and the second was Model 1, the third Model 3, and the lowest Model 2. 4. The displacement on the cement layer was the highest in Model 2 (Glass fiber post with composite core), and the second was Model 3, the third Model 1, and the lowest Model 4. Conclusion : When a functional maximum bite force was applied, the distribution of stresses or the esthetic post and core materials and the displacement on the cement layer were a little different. It seems that restoring extensively damaged incisors with esthetic post and core materials would be decided according to the remaining tooth structure.

• The Journal of Korean Academy of Prosthodontics
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• v.55 no.2
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• pp.151-155
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• 2017

Purpose: The aim of this study was to evaluate screw removal torque of the two-piece zirconia abutment with the novel titanium component compared to the conventional one-piece titanium abutment in the internal connection implant before and after dynamic cyclic loading. Materials and methods: Two types of the abutment assemblies with internal connection were prepared and divided into the groups; titanium abutment-titanium abutment screw assemblies as control, and zirconia abutment-titanium socket-titanium abutment screw assemblies as experimental group. A total of 12 abutments and implants were used of six assemblies each group. Each assembly was tightened to 30 Ncm. A cyclic load of 300 N at an angle of 30 degrees in reference to the loading axis was applied until one million cycles or failure. The removal torque values (RTVs) of the abutment screws were measured with a digital torque gauge before and after cyclic loading. The RTVs of the pre load and post load were analyzed with t-test, and P-values < .05 were considered statistically significant. Results: The assemblies of both groups survived all after the dynamic cyclic loading test without screw loosening. The statistically significant differences were found between the mean RTVs before and after the cyclic loading in both groups (P < .05). The RTV differences for the control and the experimental group were $-7.25{\pm}1.50Ncm$ and $-7.33{\pm}0.93Ncm$, respectively. Statistical analysis revealed that the RTV differences in both groups were not significantly different from each other (P > .05). Conclusion: Within the limitation of this study, the two-piece zirconia abutment with the titanium component did not show a significant RTV difference of the abutment screw compared to the titanium abutment after dynamic cyclic loading.

• The korean journal of orthodontics
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• v.36 no.5
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• pp.369-379
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• 2006

Objective: The purpose of this study was to find changes in the occlusal plane related to different vertical facial patterns and suggest treatment goals and conduct possible treatment mechanisms. Methods: 60 adult patients (28 males, 32 females) who had been diagnosed as Class 1 skeletal malocclusion and treated without extraction were selected. Patients were divided into three groups; short face type (group 1), average face type (group 2) and long face type (group 3), using the data on normal occlusion of Korean adults. Results: The results were achieved by analyzing cephalometric tracings of each group at pre-treatment, end-treatment and post-treatment (about 1 year recall check). The inclination of the occlusion plane tends to gradually increase as the face becomes longer In group 1, COP-X, FOP-X, L6/L1, MP-L6 were significantly decreased, and L1-FOP was significantly increased during the retention period (T3-T2). Group 2 showed no significant change, In group 3, FOP-X was significantly increased during the retention period (T3-T2). During the retention period, FOP-X showed significant change among each group, especially between group 1 and group 3. Conclusion: These results suggest that changes of occlusal plane inclination according to facial vertical pattern need to be considered during the retention period for intrusion, extrusion, and incisor overbite.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.81-98
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• 2003

The purpose of this study is to closely examine kinematic characteristics by jump phase of Li Xiaopeng motion in horse vaulting and provide the training data. In doing so, as a result of analyzing kinematic variables through 3-dimensional cinematographic using the high-speed video camera to Li Xiaopeng motion first performed at the men's vault competition at the 14th Busan Asian Games, the following conclusion was obtained. 1. It was indicated that at the post-flight, the increase of flight time and height and twisting rotational velocity has a decisive effect on the increase of twist displacement. And Li Xiaopeng motion showed longer flight time and higher flight height than Ropez motion with the same twist displacement of entire movement. Also the rotational displacement of the trunk at peak of COG was much short of $360^{\circ}$(one rotation) but twist displacement showed $606^{\circ}$. Likewise, Li Xiaopeng motion was indicated to concentrate on twist movement in the early flight. 2. It was indicated that at the landing, Li Xiaopeng motion gets the hip to move back, the trunk to stand up and the horizontal velocity of COG to slow down. This is thought to be the performance of sufficient landing, resulting from large security of rotational displacement of airborne and twist displacement. 3. It was indicated that at the board contact, Li Xiaopeng motion made a rapid rotation uprighting the trunk to recover slowing velocity caused by jumping with the horse in the back, and has already twisted the trunk nearly close to $40^{\circ}$ at board contact. Under the premise that elasticity is generated without the change of the feet contacting the board, it will give an aid to the rotation and twist of pre-flight. Thus, in the round-oH phase, the tap of waist according to the fraction and extension of hip joint and arm push is thought to be very important. 4. It was indicated that at the pre-flight, Li Xiaopeng motion showed bigger movement than the techniques of precedented studies rushing to the horse, and overcomes the concern of relatively low power of jump through the rapid rotation of the trunk. Li Xiaopeng motion secured much twist distance, increased rotational distance with the trunk bent forward, resulting in the effect of rushing to the horse. 5. At horse contact, Li Xiaopeng motion makes a short-time contact, and maintains horse take-off angle close to vertical, contributing to the increase of post-flight time and height. This is thought to be resulted from rapid move toward movement direction along with the rotational velocity of trunk rapidly earned prior to horse contact, and little shave of rotation axis according to twist motion because of effective twist in the same direction.