• Title/Summary/Keyword: 비금속관

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Characteristic Changes in Ground-Penetrating Radar Responses from Dielectric-Filled Nonmetallic Pipes Buried in Inhomogeneous Ground (비균일 지하에 묻혀있는 유전체 충진 비금속관에 의한 지표투과레이다 응답의 특성 변화)

  • Hyun, Seung-Yeup
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.30 no.5
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    • pp.399-406
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    • 2019
  • The variation of ground-penetrating radar(GPR) signal characteristics from dielectric-filled nonmetallic pipes buried in inhomogeneous ground are compared through a numerical simulation. The relative permittivity distribution of the ground is generated by using the continuous random media(CRM) technique. As a function of the relative permittivity of the material filling the nonmetallic pipe buried in the ground media, GPR signals are simulated by using the finite-difference time-domain(FDTD) method. We show that, unlike the case for homogeneous ground, the distortion characteristics of the reflected waves caused by the front convex surface and the rear concave surface of the pipe buried in inhomogeneous ground are different depending on the permittivity contrast between the inside and outside of the pipe.

Numerical Simulation of Ground-Penetrating Radar Signals for Detection of Metal Pipes Buried in Inhomogeneous Grounds (비균일 지하에 매설된 금속관 탐지를 위한 지하탐사레이다 신호의 수치 모의계산)

  • Hyun, Seung-Yeup
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.29 no.1
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    • pp.61-67
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    • 2018
  • The effects of subsurface inhomogeneities on the detection of buried metal pipes in ground-penetrating radar(GPR) signals are investigated numerically. To model the electrical properties of the subsurface inhomogeneities, the continuous random media(CRM) generation technique is introduced. For the electromagnetic simulation of GPR signals, the finite-difference time-domain(FDTD) method is implemented. As a function of the standard deviation and the correlation length of the relative permittivity distribution for a randomly inhomogeneous ground, the GPR signals of the buried metal pipes are compared using numerical simulations. As the subsurface inhomogeneities increase, the GPR signals of the buried pipes are distorted because of the effect of the subsurface clutter.

Comparative Evaluation of the Survival Rates of Zirconia Crown and Stainless Steel Crown for Proximal Caries in Primary Molars: a Retrospective Study (유구치 인접면 우식증 수복 시 지르코니아 전장관과 기성금속관의 생존율 비교 평가: 후향적 연구)

  • Gahui Jeong;Nanyoung Lee;Hyewon Shin;Suhyun Park;Myeongkwan Jih
    • Journal of the korean academy of Pediatric Dentistry
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    • v.50 no.3
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    • pp.307-317
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    • 2023
  • Due to increasing demand for aesthetics, zirconia crowns have become a popular choice for treating primary molars. However, there is limited literature available comparing the survival rates of zirconia crowns with those of other restorative materials. The objective of this study was to compare the 36-month survival rates of zirconia crowns and stainless steel crowns for proximal caries, as well as to analyze failure types associated with each crown type. Electronic medical records and radiographs of 1,061 primary molars from 498 patients treated with 2 types of prefabricated crowns at Chosun University Dental Hospital and 2 private dental clinics between 2017 and 2019 were collected and analyzed. The survival rate of zirconia crowns was found to be lower compared to that of stainless steel crowns. Regarding the groups without pulp treatment, the survival rate of stainless steel crowns was significantly higher than that of zirconia crowns. However, in the groups that received pulp therapy, no significant difference in the survival rates was observed between the two preformed crowns. Notably, abnormal root resorption or periapical lesions were identified as the primary cause of restorative failure in stainless steel crowns, whereas loss of restoration was the predominant cause in zirconia crowns. This study holds valuable implications for clinicians when selecting preformed crowns for primary molars.

A Morphometric Study of the Stainless Steel Permanent Molar Crown with Three-Dimensional Scanner (3차원 스캐너를 이용한 대구치용 기성금속관의 형태에 관한 계측학적 연구)

  • Shin, Jonghyun;Lee, Hyeongjik;Jeong, Taesung;Kim, Shin;Kim, Jiyeon
    • Korean Journal of Dental Materials
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    • v.45 no.4
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    • pp.287-300
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    • 2018
  • The aim of this study was to compare the morphological characteristics of two types of stainless steel permanent molar crowns using three-dimensional scanners and the morphological changes of these crowns after crimping. Two types of stainless steel permanent molar crowns, PO-96 and PERMACROWN were scanned using three-dimensional scanner. Crown size, crown index (ratio of buccolingual diameter to mesiodistal diameter at height of contour), cervical convergency of crown were measured. Stainless steel crowns were crimped and re-scanned with three-dimensional scanner. Morphological changes of stainless steel permanent molar crowns were analyzed. As for the crown index, maxillary PERMACROWN was larger buccolingually and smaller mesiodistally than maxillary PO-96 and mandibular PERMACROWN was smaller buccolingually and larger mesiodistally than mandibular PO-96. Maxillary PO-96 was more convergent to cervical mesiodistally than maxillary PERMACROWN and mandibular PO-96 was more convergent to the cervical mesiodistally, buccolingually than mandibular PERMACROWN. Both types of stainless steel permanent molar crowns showed reduction of cervical circumference after crimping. Two products were morphologically different in crown size, shape and cervical convergence. Although both types of stainless steel permanent molar crowns are pre-contoured type, additional crimping is needed to achieve better marginal adaptation.

GPR Exploration of Non-metallic Water Pipes Linked with Network RTK (네트워크 RTK와 연계한 비금속 상수관의 GPR 탐사)

  • Lee, Keun-Wang;Park, Joon-Kyu
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.22 no.2
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    • pp.296-301
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    • 2021
  • GPR is used for non-destructive investigations, ground investigations, and underground facilities exploration at construction sites. In this study, the applicability to GPR exploration of water pipes linked to Network RTK was presented. Data on the water supply pipes in the study site were acquired using GPR, and the location and depth of buried water pipes could be measured. The accuracy was evaluated from the GNSS observation performance and showed a deviation of -0.16m ~ 0.15m. This satisfied the equipment performance of the public survey work regulation, suggesting that the exploration of water pipes using GPR is possible. Because GPR does not require grounding installation, as in conventional metal pipe detectors, it will increase the efficiency of work for underground facility exploration. Exploration using GPR can acquire the location and depth of metallic and non-metallic underground facilities, so it can be utilized in the construction of a GIS system. If a comparison of the exploration characteristics is carried out, it will be possible to present various uses of underground facility exploration using GPR.

A Study of Margin Fitness in Metal-bond Porcelain Crown II (도재용착주조관 변연의 적합성에 관한 연구 II)

  • Lee, In-Kyu
    • Journal of Technologic Dentistry
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    • v.5 no.1
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    • pp.27-30
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    • 1983
  • This study was undertaken to know the difference that margin fittness in metal bond porcelain crown. When we use porcelain precious metal and non-precious metal as porcelain-fused metal, the results were as following. 1. The precious metal was showed best result in margin fittness and shade. 2. The non-precious metals were showed good results, especially Gemini II was excellent, but that was not good than precious metal. 3. 10k. gold plating on non-precious metal cap showed same result as nonprecious metal in margin fittness, and not good in shade. 4. When we use the non-precious metals at upper part of crown, and using precious metal in 2mm cervical portion, the margin fittness were very good, and the results same as full veneer precious metal.

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A Study on the Burst Pressure of Composite Motor Case due to the Change of Metal Boss PDR Design (금속 보스 압력분포비 설계 변경에 따른 복합재 연소관 파열압력에 관한 연구)

  • Kim, Namjo;Jeong, Seungmin;Yun, Kyeongsoo;Chung, Sangki;Hwang, Taekyung
    • Journal of the Korean Society of Propulsion Engineers
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    • v.23 no.4
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    • pp.21-27
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    • 2019
  • Composite motor cases fabricated by the filament winding method are structurally weak in the dome when they are required to withstand the internal pressure of the combustion gas. In this study, a finite element analysis is conducted to compare the burst pressure of a composite dome according to the variation of the pressure distribution ratio(PDR). The performance of the composite motor case was compared quantitatively by calculating the stress on the inner and outer dome surfaces and metal boss volume. As a result, the critical point of the failure mode was observed at a PDR between 2.5 and 3.0. A design at a PDR of 2.5­-3.5 can reduce the weight of metal boss without fluctuation in the burst pressure of the combustion motor case. Moreover as the design reference value changes according to the dome shape and opening size, further analysis and testing are necessary.

Dental implant bottom-up cost analysis (치과 임플란트 상향식(bottom-up) 원가산정)

  • Kim, Min-Young;Choi, Ha-Na;Shin, Ho-Sung
    • The Journal of Korean Academy of Prosthodontics
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    • v.52 no.1
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    • pp.18-26
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    • 2014
  • Purpose: The purpose of this study was to estimate the cost of dental implant using the bottom-up approach with the current data from dental clinics. Materials and methods: In this study, direct and indirect costs required for each treatment were calculated using the bottom-up approach. In the bottom-up costing, the average monthly total cost of dental clinic includes labor and material costs, administrative expenses, medical malpractice costs, and opportunity costs of invested capital. For the dental implant cost components, those include direct costs (labor costs, laboratory costs, material costs, depreciation or other operating costs), indirect costs (administrative costs), and the opportunity costs of investment for dental clinic. Results: Dental implant costs of metal crown, porcelain crown and over-denture were 1,449,000 won, 1,583,000 won, and 2,471,000 won respectively. The proportion of cost components was as follows. The labor cost were 50%, and material, administrative and other cost were 33%, 15% and 2%, respectively. For direct, indirect and investment cost, the ratio were 83%, 15% and 2%, respectively. Conclusion: The labor costs were evaluated to comprise largest proportion (about 50%, 730,000 won). Dental implant cost using Bottom-up costing was 1,450,000 won for metal crown and 1,580,000 won for porcelain crown.

A MORPHOMETRIC STUDY OF THE MAXILLARY PRIMARY FIRST MOLARS USING THREE-DIMENSIONAL SCANNER (3차원 스캐너를 이용한 상악 제1유구치 치관의 크기와 형태에 관한 연구)

  • Lee, Jong-Beom;Kim, Chong-Chul;Hahn, Se-Hyun;Lee, Sang-Hoon
    • Journal of the korean academy of Pediatric Dentistry
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    • v.33 no.4
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    • pp.643-652
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    • 2006
  • The purpose of this study was to elucidate the size and morphologic characteristics of maxillary primary first molars in Korean children using three-dimensional laser scanner and compare three-dimensional image with preformed stainless steel crown. Scanned three-dimensional images of dental cast taken from 132 children(male 62, female 70) by three-dimensional laser scanner(Breuckmann opto-Top HE100, INUS, Korea) were used. Mesiodistal diameter, buccolingual diameter, occlusogingival height and crown shape of each image were calculated by Rapidform 2004 program(INUS, Korea). The values were statistically compared by independent samples t-test with 95% of significant level. The results were as follows : 1. No significant difference in crown size was found between left and right maxillay primary first molar(p>0.05). 2, Significant difference in mesiodistal diameter, buccolingual diameter, buccal occlusogingival height was found between male and female (p<0.05), and crown size of male was bigger than that of female. 3. Average image of maxillay primary first molar was shaped three-dimensionally and measured. In comparison with 3M stainless steel crown, this image was similar with No.4 or No.5 SS crown in male, No.4 in female. In comparison with ILSUNG SS crown, this image was similar with No.5 in male, No.4 in female. 4 Mesiolingual line angle area, distolingual line angle area and buccogingival ridge were more obvious in average image than 3M stainless steel crown. ILSUNG SS crown was more square and had longer mesiodistal diameter than average 3D image.

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Prediction Model on Electrical Conductivity of High Density Metallic Plasma (고밀도 금속 플라즈마 전기전도도 예측모델)

  • Kyoungjin Kim
    • Journal of the Korean Society of Propulsion Engineers
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    • v.26 no.6
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    • pp.1-9
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    • 2022
  • This study introduces the calculation model of ionization composition and electrical conductivity for metallic plasma for practical application to modeling and simulation of modern electrical detonators. The present model includes the correction for non-ideality of dense plasma conditions which are expected in electrical explosion of bridge in detonators. The computational results for copper plasma show favorable agreement with experimental data for a wide range of plasma temperature and high density conditions and the model is proper for detonator modeling with good prediction accuracy.