• Restorative Dentistry and Endodontics
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• v.47 no.4
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• pp.39.1-39.12
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• 2022

Objectives: This study investigated the prevalence and characteristics of external cervical resorption (ECR) regarding sex, age, tooth, stages of progression, and portal of entry, using cone-beam computed tomography (CBCT) scans. Materials and Methods: CBCT scans of 1,313 patients from a Brazilian subpopulation comprising 883 female and 430 male patients (mean age, 55.2 years), acquired using a PreXion 3D CBCT unit, were evaluated. All permanent teeth included in the scans were evaluated for the presence of ECR according to the 3-dimensional classification and the portal of entry. The association between the presence of ECR and the factors studied was assessed using the χ² test. Intra-observer agreement was analyzed with the kappa test (α = 0.05). Results: In total, 6,240 teeth were analyzed, of which 84 (1.35%) were affected by ECR. A significant association was found between the presence of ECR and sex, with a higher prevalence in male patients (p = 0.002). The most frequently affected teeth were the mandibular and maxillary central incisors. The most common height was the mid-third of the root. For the portal of entry, 44% of cases were on the proximal surfaces, 40.5% on the lingual/palatal surface and 15.5% on the buccal surface. Intra-observer agreement was excellent. Conclusions: The prevalence of ECR was 1.35%, with a higher prevalence in male patients and a wide age distribution. The mandibular and maxillary central incisors were the most commonly affected teeth, and cases of ECR most frequently showed a height into the mid-third of the root and proximal entry.

• Tunnel and Underground Space
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• v.23 no.3
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• pp.180-191
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• 2013

The purpose of this research was to find an optimal quarrying for marble by analyzing the applicability and the work efficiency of a chain saw machine newly introduced in the underground Baekwoon mine. From the test results of the physical properties of Baekwoon marble, which affects the efficiency of rock cutting, it was found to have similar physical characteristics as the ones which are now being produced in the other areas in Korea. And especially it shows isotropic property, which can be thought to be advantageous as a dimensional stone. To check the long-term quality of the marble as a stone material, several tests such as corrosion resistance test and abrasion test were carried out. It was found to be vulnerable to acid rain with decrease of weight and seismic wave velocity after applying artificial rain at pH 5.6 for 50 times. The percentage of wear from abrasion test was 22.67%. The working time and cutting speed of the chain saw machine were recorded and analyzed during the test-run at the quarry. The overall work cycle was assorted into 9 unit operations and the operating time per each unit was drawn. The operating times for the two cutting patterns, which could be possibly applicable to the work site, were compared. The results indicated that the pattern B, that the cutting sequence was set to minimize the movement of the machine, showed 6% less working hours than the pattern A, which first cuts the outer boundary. With cutting pattern analysis, the ore body in the Baekwoon mine was 3 dimensionally modeled and a quarrying plan considering the existing conditions of the marble was suggested.

• Investigative Magnetic Resonance Imaging
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• v.18 no.1
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• pp.17-24
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• 2014

Purpose : To determine whether high-resolution contrast-enhanced three dimensional imaging with spoiled gradient-recalled sequence (HR-CE 3D-SPGR) plays a meaningful role in the assessment of intracranial vertebral artery (ICVA) and posterior inferior cerebellar artery (PICA) in lateral medullary infarction (LMI). Materials and Methods: Twenty-five patients confirmed with LMI were retrospectively enrolled with approval by the IRB of our institute, and 3T MRI with HR-CE 3D-SPGR and contrast-enhanced magnetic resonance angiography (CE-MRA) were performed. Two radiologists who were blinded to clinical information and other brain MR images including diffusion weighted image independently evaluated arterial lesions in ICVA and PICA. The demographic characteristics, the area of LMI and cerebellar involvement were analyzed and compared between patients with arterial lesion in ICVA only and patients with arterial lesions in both ICVA and PICA on HR-CE 3D-SPGR. Results: Twenty-two of twenty-five LMI patients had arterial lesions in ICVA or PICA on HR-CE 3D SPGR. However twelve arterial lesions in PICA were not shown on CE-MRA. Concurrent cerebellar involvement appeared more in LMI patients with arterial lesion in ICVA and PICA than those with arterial lesion in ICVA alone (p = 0.069). Conclusion: HR-CE 3D-SPGR can help evaluate arterial lesions in ICVA and PICA for LMI patients.

• Korean Chemical Engineering Research
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• v.47 no.6
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• pp.720-726
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• 2009

Hydrodynamic similarity was investigated in pressurized three-phase slurry bubble columns by selecting the bubble holdup and pressure drop as objective functions, for the effective design and scale-up of it. In addition, effects of operating variables on the bubble holdup with variation of column diameter were also analyzed. Gas velocity($U_G$), viscosity(${\mu}_{SL,eff}$) and surface tension(${\rho}_{SL}$) of slurry phase, density difference between the slurry and gas phases(${\rho}_{SL}-{\rho}_G$) depending on the operating pressure, pressure drop per unit length(${\Delta}P/L$), column diameter(D) and gravitational acceleration(g) were chosen as governing parameters in determining the bubble holdup and pressure drop in the column. From the dimensional analysis, four kinds of dimensionless groups were derived from the 7 parameters and 4 fundamental dimensions. Effects of dimensionless groups such as Reynolds, Froude and Weber numbers on the bubble holdup in the column were discussed. The pressure drop and bubble holdup could be predicted from the correlation of dimensionless groups effectively, which could be used as useful information for the design and scale-up of pressurized slurry bubble columns.

• Journal of Radiation Protection and Research
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• v.32 no.3
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• pp.105-110
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• 2007

Purpose : In spite of recent remarkable improvement of diagnostic imaging modalities such as CT, MRI, and PET and radiation therapy planing systems, ICR plan of uterine cervix cancer, based on recommendation of ICRU38(2D film-based) such as Point A, is still used widely. A 3-dimensional ICR plan based on CT image provides dose-volume histogram(DVH) information of the tumor and normal tissue. In this study, we compared tumor-dose, rectal-dose and bladder-dose through an analysis of DVH between CTV plan and ICRU38 plan based on CT image. Method and Material : We analyzed 11 patients with a cervix cancer who received the ICR of Ir-192 HDR. After 40Gy of external beam radiation therapy, ICR plan was established using PLATO(Nucletron) v.14.2 planing system. CT scan was done to all the patients using CT-simulator(Ultra Z, Philips). We contoured CTV, rectum and bladder on the CT image and established CTV plan which delivers the 100% dose to CTV and ICRU plan which delivers the 100% dose to the point A. Result : The volume$(average{\pm}SD)$ of CTV, rectum and bladder in all of 11 patients is $21.8{\pm}6.6cm^3,\;60.9{\pm}25.0cm^3,\;111.6{\pm}40.1cm^3$ respectively. The volume covered by 100% isodose curve is $126.7{\pm}18.9cm^3$ in ICRU plan and $98.2{\pm}74.5cm^3$ in CTV plan(p=0.0001), respectively. In (On) ICRU planning, $22.0cm^3$ of CTV volume was not covered by 100% isodose curve in one patient whose residual tumor size is greater than 4cm, while more than 100% dose was irradiated unnecessarily to the normal organ of $62.2{\pm}4.8cm^3$ other than the tumor in the remaining 10 patients with a residual tumor less than 4cm in size. Bladder dose recommended by ICRU 38 was $90.1{\pm}21.3%$ and $68.7{\pm}26.6%$ in ICRU plan and in CTV plan respectively(p=0.001) while rectal dose recommended by ICRU 38 was $86.4{\pm}18.3%$ and $76.9{\pm}15.6%$ in ICRU plan and in CTV plan, respectively(p=0.08). Bladder and rectum maximum dose was $137.2{\pm}50.1%,\;101.1{\pm}41.8%$ in ICRU plan and $107.6{\pm}47.9%,\;86.9{\pm}30.8%$ in CTV plan, respectively. Therefore, the radiation dose to normal organ was lower in CTV plan than in ICRU plan. But the normal tissue dose was remarkably higher than a recommended dose in CTV plan in one patient whose residual tumor size was greater than 4cm. The volume of rectum receiving more than 80% isodose (V80rec) was $1.8{\pm}2.4cm^3$ in ICRU plan and $0.7{\pm}1.0cm^3$ in CTV plan(p=0.02). The volume of bladder receiving more than 80% isodose(V80bla) was $12.2{\pm}8.9cm^3$ in ICRU plan and $3.5{\pm}4.1cm^3$ in CTV plan(p=0.005). According to these parameters, CTV plan could also save more normal tissue compared to ICRU38 plan. Conclusion : An unnecessary excessive radiation dose is irradiated to normal tissues within 100% isodose area in the traditional ICRU plan in case of a small size of cervix cancer, but if we use CTV plan based on CT image, the normal tissue dose could be reduced remarkably without a compromise of tumor dose. However, in a large tumor case, we need more research on an effective 3D-planing to reduce the normal tissue dose.

• The Journal of Korean Academy of Prosthodontics
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• v.57 no.3
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• pp.203-210
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• 2019

Purpose: The purpose of this study was to verify the effect of the abutment superimposition process on the final virtual model in the scanning process of single and 3-units bridge model using a dental model scanner. Materials and methods: A gypsum model for single and 3-unit bridges was manufactured for evaluating. And working casts with removable dies were made using Pindex system. A dental model scanner (3Shape E1 scanner) was used to obtain CAD reference model (CRM) and CAD test model (CTM). The CRM was scanned without removing after dividing the abutments in the working cast. Then, CTM was scanned with separated from the divided abutments and superimposed on the CRM (n=20). Finally, three-dimensional analysis software (Geomagic control X) was used to analyze the root mean square (RMS) and Mann-Whitney U test was used for statistical analysis (${\alpha}=.05$). Results: The RMS mean abutment for single full crown preparation was $10.93{\mu}m$ and the RMS average abutment for 3 unit bridge preparation was $6.9{\mu}m$. The RMS mean of the two groups showed statistically significant differences (P<.001). In addition, errors of positive and negative of two groups averaged $9.83{\mu}m$, $-6.79{\mu}m$ and 3-units bridge abutment $6.22{\mu}m$, $-3.3{\mu}m$, respectively. The mean values of the errors of positive and negative of two groups were all statistically significantly lower in 3-unit bridge abutments (P<.001). Conclusion: Although the number of abutments increased during the scan process of the working cast with removable dies, the error due to the superimposition of abutments did not increase. There was also a significantly higher error in single abutments, but within the range of clinically acceptable scan accuracy.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.569-578
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• 2004

The purpose of this study was to clarify the palatal arch length, width and height in the primary and permanent dentition. Samples were consisted of normal occlusions both in the primary dentition(50 males and 50 females) and in the permanent dentition(50 males and 50 females). With their upper plaster casts were used and through 3-dimensional laser scanning(3D Scanner, DS4060, LDI, U.S.A.), cloud data, polygonization, section curve and loft surface, fit and horizontal plane were based to measure the palatal arch length, width and height(Surfacer 10.0, Imageware, U.S.A.). T-tests were applied for the statistical analyze of the data. The results were as follows : 1. In the measurement values, the values of the male were higher than those of the female except primary anterior palatal height. There were not only statistically significant differences in anterior palatal width(p<0.05) and posterior palatal width(p<0.01) in primary dentition but palatal width(p<0.05), anterior palatal length(p<0.01), middle and posterior palatal length(p<0.05) in permanent dentition between male and female. 2. In the indices of palate, there were statistically significant differences in height-length index(p<0.05) and width-length index(p<0.01) between male and female in primary dentition. In permanent dentition, there was statistically difference between male and female. 3. In the measurement values, posterior palatal width was increased most greatly. Posterior palatal height, anterior palatal width and anterior palatal length were followed by descending order. On the other hand, anterior palatal height and posterior palatal length were decreased. 4. In the indices of palate, the height-length index, the width-length index and posterior height-width index were increased, but the others were decreased.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.49-63
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• 1989

Wave drift forces which are small in magnitudes compared to the first order wave exciting forces can cause very large motion of a vessel in waves. In this paper a theoretical and experimental analysis is made of the mean and slowly varying wave dirft forces on the semi-submersible platform. Theoretical calculations are performed by using near field method with three dimensional diffraction theory and model tests are carried out in regular and irregular waves with a 1/60 semi model. Test results are compared with theoretical calculations and the mooring spring effects in the test are discussed.

• Plant Biotechnology Reports
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• v.4 no.3
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• pp.201-211
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• 2010

We present a highly effective T-DNA inserted gene screening method as part of a reverse genetics model system using the Chinese cabbage (Brassica rapa L. spp. pekinensis). Three-step two-dimensional (2D) matrix strategies are potentially accurate and useful for the identification of specific T-DNA inserted mutants from a large population. To construct our Chinese cabbage model, we utilized a forward genetics screening approach for the abnormal phenotypes that were obtained from transgenic plants of Brassica rapa generated with Agrobacteria tumefaciens containing the pRCV2 vector. From one transgenic plant with an abnormal phenotype, we observed that the st1 gene (which is related to senescence-associated process proteins) contained a T-DNA fragment, and that its expression level was decreased. This T-DNA insert was then used as a control to construct an effective screening pool. As a result, the optimum template concentration was found to be 0.1-1 ng in our PCR strategy. For other conditions, positive changes to the Gibbs free energy prevented the formation of oligo dimers and hairpin loop structures, and autosegment extension gave better results for long fragment amplification. Using this effective reverse genetics screening method, only 23 PCR reactions were necessary to select a target gene from a pool of 100 individual DNAs. Finally, we also confirmed that the sequence we obtained from the above method was identical to the flanking sequence isolated by rescue cloning.

• Journal of dental hygiene science
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• v.14 no.4
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• pp.455-460
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• 2014

This study compared the surface roughness and surface characteristics between a type IV stone and scannable stone. Materials used were a type IV stone, two different kind of scannable stone. Ten specimens per experimental group were prepared according to manufacturer's direction. Surface roughness of specimen was measured using profilometer. The measurement was based on the standard of Japanese Industrial Standards 1994. The mean and standard deviations of each reference point were analyzed using one-way ANOVA and Scheff$\acute{e}$ post hoc test. The program used to handle statistical analysis was SPSS 20.0 and the significance level was set at 0.05. The difference of surface roughness was statistically significant in order of Scannable Stone $10.07{\pm}0.02{\mu}m$, Scannable Stone $20.08{\pm}0.03{\mu}m$, Type IV $0.10{\pm}0.04{\mu}m$. These results will have to be confirmed in further clinical application researches.