• 한국시뮬레이션학회논문지
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• 제32권3호
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• pp.1-8
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• 2023

영상레이더(SAR)에서 인공표적에 대한 모델링은 주로 3차원 CAD(Computer Aided Design) 모델의 면(face) 및 모서리(edge)에서 반사되는 레이더 신호를 광선추적(ray-tracing) 방식으로 시뮬레이션하고 있고, 지구 표면의 클러터(clutter)에 대한 모델링은 영상레이더 이미지 자체에 대한 통계학적(statistical) 분석을 통해 분포(distribution) 특성이 유사한 종류들을 구분하는 방식을 사용하고 있다. 본 논문에서는 지상의 인공표적 및 지표면의 배경 클러터를 3차원 점구름(point cloud) 산란점(scatterer point) 모델로 만들고 두 개의 모델이 통합된 상황에서 계산적(computational)인 신호처리 과정을 통해 영상 레이더 이미지를 생성하였으며, 이것을 실제 차량탑재형 영상레이더 시스템의 스트립맵(stripmap) 이미지 생성 결과 및 전자기적(EM) 모델링 또는 통계학적 분포 모델을 사용하여 분석한 결과와 유사한 지 비교해 보았다. 모델링 대상은 지상의 인공표적인 교량(다리)을 선정 했는데, 그 이유는 교량의 경유 주변에 수면과 지면이 같이 존재하는 특성이 있고 또한 군사용 및 민간용 활용에서 모두 관심이 많은 표적이기 때문이다.

• 대한치과보철학회지
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• 제61권3호
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• pp.215-226
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• 2023

전치부의 심한 교모는 측방운동 중 구치부를 교모로부터 보호하는 전방유도의 상실을 촉진하며, 구치부의 상실은 교합의 부조화 및 수직고경의 감소를 초래한다. 또한 다수의 치아상실과 치아 마모로 인해 교합이 붕괴된 환자 치료시에는 정확한 임상 및 방사선 검사, 진단용 왁스업을 이용하여 수직고경 상실에 대한 여부를 파악하는 것이 중요하다. 본 증례의 환자는 44세 여성환자로 이갈이와 이악물기 습관으로 전체적인 치아 마모 및 구치부 상실로 저작기능 및 발음, 심미적 불편감을 호소하였으며, 보철적 치료를 통해 저작기능 회복 및 심미적 안모 개선을 주소로 내원하였다. 과도한 치아 마모와 상, 하악 구치부의 결손으로 감소한 수직교합고경 및 전치부의 심한 수직피개를 보였다. 모형 분석과 진단납형을 통해 수직고경 증가를 결정하였으며, 고정성 보철물로 전악수복을 계획하였다. 안정된 치료위로의 적응을 위해 CAD (Computer aided design)소프트웨어로 디자인한 3D(3-Dimensional) 프린팅 교합안정장치를 이용하여 단계적으로 수직고경에 대한 적응도를 확인하였으며, 이 후 임시치아로 수복하여 4개월의 적응기간 후 전체 치열은 금속도재관 및 임플란트로 수복하여 심미적 및 기능적으로 만족스러운 결과를 얻었기에 이를 보고하고자 한다.

• 한국정밀공학회지
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• 제19권1호
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• pp.107-118
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• 2002

This paper deals with an automated computer-aided process planning and die design system by which designer can determine operation sequences even if they have a little experience in process planning and die design of quasi-axisymmetric cold forging product by cold former working. The approach to the system is based on knowledge-based rules and a process knowledge base consisting of design rules is built. Knowledge for the system is formulated from plasticity theories, empirical results and the empirical knowledge of field experts. Programs for the system have been written in AutoLISP for the AutoCAD using a personal computer. An attempt is made to link programs incorporating a number of expert design rules with the process variables obtained by commercial FEM softwares, DEFORM and ANSYS, to form a useful package. The system is composed of three main modules and five sub-modules. The process planning and die design module considers several factors, such as the complexities of preform geometry, punch and die profiles, specifications of available cold farmer, and the availability of standard parts. As the system using 2D geometry recognition is integrated with the technology of process planning, die design, and CAE analysis, the standardization of die parts for wheel bolt requiring cold forging process is possible. The developed system makes it possible to design and manufacture quasi-axisymmetric cold forging product more efficiently.

• 한국정밀공학회지
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• 제20권4호
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• pp.29-38
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• 2003

This paper deals with an automated computer-aided process planning and die design system with which designer can determine operation sequences even after only a little experience in process planning and die design of multi former-bolt products by multi-stage former working. The approach is based on knowledge-based rules, and a process knowledge base consisting of design rules is built. Knowledge fur the system is formulated from plasticity theories, empirical results and the empirical knowledge of field experts. Programs for the system have been written in AutoLISP for AutoCAD with a personal computer. An attempt is made to link programs incorporating a number of expert design rules with the process variables obtained by commercial FEM softwares, DEFORM and ANSYS, to form a useful package. The system is composed of four main modules. The process planning and die design module considers several factors, such as the complexities of preform geometry, punch and die profiles, specifications of available multi former, and the availability of standard parts. It can provide a flexible process based on either the reduction in the number of forming sequences by combining the possible two processes in sequence, or the reduction of deviation of the distribution and the level of the required forming loads by controlling the forming ratios. The system uses 2D geometry recognition and is integrated with the technology of process planning, die design, and CAE analysis. The standardization of die parts for multi former-bolt products requiring a cold forging process is described. The system developed makes it possible to design and manufacture multi former-bolt products more efficiently.

• The Journal of Advanced Prosthodontics
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• 제5권1호
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• pp.21-28
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• 2013

PURPOSE. This study examined the effects of the abutment types and dynamic loading on the stability of implant prostheses with three types of implant abutments prepared using different fabrication methods by measuring removal torque both before and after dynamic loading. MATERIALS AND METHODS. Three groups of abutments were produced using different types of fabrication methods; stock abutment, gold cast abutment, and CAD/CAM custom abutment. A customized jig was fabricated to apply the load at $30^{\circ}$ to the long axis. The implant fixtures were fixed to the jig, and connected to the abutments with a 30 Ncm tightening torque. A sine curved dynamic load was applied for $10^5$ cycles between 25 and 250 N at 14 Hz. Removal torque before loading and after loading were evaluated. The SPSS was used for statistical analysis of the results. A Kruskal-Wallis test was performed to compare screw loosening between the abutment systems. A Wilcoxon signed-rank test was performed to compare screw loosening between before and after loading in each group (${\alpha}$=0.05). RESULTS. Removal torque value before loading and after loading was the highest in stock abutment, which was then followed by gold cast abutment and CAD/CAM custom abutment, but there were no significant differences. CONCLUSION. The abutment types did not have a significant influence on short term screw loosening. On the other hand, after $10^5$ cycles dynamic loading, CAD/CAM custom abutment affected the initial screw loosening, but stock abutment and gold cast abutment did not.

• 대한치과보철학회지
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• 제54권3호
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• pp.291-297
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• 2016

쉐그렌 증후군($Sj{\ddot{o}}gren^{\prime}s$ syndrome)을 가진 환자들은 구강건조증으로 인하여 치질이 연화되어 마모와 변색을 가지는 경우가 빈번하다. 전치부가 심하게 마모된 경우 전방유도의 상실 및 교합의 부조화, 보철수복을 위한 공간의 부족 등의 문제가 발생할 수 있는데, twin-stage method를 이용하여 수복시 전방유도와 측방유도를 통해 구치부 이개량을 확보하여 중심위와 편심위에서 모두 이상적인 교합을 형성할 수 있다. 본 증례는 쉐그렌 증후군으로 인하여 상, 하악 전치부의 심한 변색과 마모를 가진 환자에게 twin-stage method를 이용하여, 수복하였기에 보고하는 바이다.

• 대한치과보철학회지
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• 제56권2호
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• pp.166-172
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• 2018

상악 전치부 치료 시에는 다양한 구도 속에서 체계적인 진단을 통해 적절한 형태와 배열, 색조를 가지는 수복물을 제작하여 심미적으로 환자가 만족할 수 있는 결과를 이끌어내야 한다. 이를 위해 치아 구도, 치은구도, 안면구도, 치아-안면 구도의 4가지 구도 속에서 조화를 이루는 진단 및 치료계획이 필요하다. 심미적인 욕구가 강한 경우, 주관적인 환자의 심미안을 만족시키면서 기능적인 부분을 확인하기 위해, 적절한 임시 수복물을 제작하여 기능적, 심미적 측면의 평가가 필요하다. 최종 보철물 제작에 이중 스캔을 이용하여 임시 수복물의 정보를 반영할 수 있다. 본 증례는 상악 전치부가 비심미적인 환자에서, 체계적인 심미 분석 하에 임시 수복물을 제작하고 기능적, 심미적 측면을 평가 및 수정하여, 이중 스캔을 통해 임시수복물의 정보를 최종 수복물에 반영 후 최종 수복한 증례이다.

• The Journal of Advanced Prosthodontics
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• 제10권4호
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• pp.328-334
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• 2018

PURPOSE. To evaluate the reproducibility of scan-based abutments using a blue light model scanner. MATERIALS AND METHODS. A wax cast abutment die was fabricated, and a silicone impression was prepared using a silicone material. Nine study dies were constructed using the prepared duplicable silicone, and the first was used as a reference. These dies were classified into three groups and scanned using a blue light model scanner. The first three-dimensional (3D) data set was obtained by scanning eight dies separately in the first group. The second 3D data set was acquired when four dies were placed together in the scanner and scanned twice in the second group. Finally, the third 3D data set was obtained when eight dies were placed together in the scanner and scanned once. These data were then used to define the data value using third-dimension software. All the data were then analyzed using the non-parametric Kruskal-Wallis H test (${\alpha}=.05$) and the post-hoc Mann-Whitney U-test with Bonferroni's correction (${\alpha}=.017$). RESULTS. The means and standard deviations of the eight dies together were larger than those of the four dies together and of the individual die. Moreover, significant differences were observed among the three groups (P<.05). CONCLUSION. With larger numbers of abutments scanned together, the scan becomes more inaccurate and loses reproducibility. Therefore, scans of smaller numbers of abutments are recommended to ensure better results.

• The Journal of Advanced Prosthodontics
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• 제8권4호
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• pp.275-284
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• 2016

PURPOSE. The aim of this study was to evaluate the influence of different surface treatment methods on the microtensile bond strength of resin cement to resin nanoceramic (RNC). MATERIALS AND METHODS. RNC onlays (Lava Ultimate) (n=30) were treated using air abrasion with and without a universal adhesive, or HF etching followed by a universal adhesive with and without a silane coupling agent, or tribological silica coating with and without a universal adhesive, and divided into 6 groups. Onlays were luted with resin cement to dentin surfaces. A microtensile bond strength test was performed and evaluated by one-way ANOVA and Tukey HSD test (${\alpha}$=.05). A nanoscratch test, field emission scanning electron microscopy, and energy dispersive X-ray spectroscopy were used for micromorphologic analysis (${\alpha}$=.05). The roughness and elemental proportion were evaluated by Kruskal-Wallis test and Mann-Whitney U test. RESULTS. Tribological silica coating showed the highest roughness, followed by air abrasion and HF etching. After HF etching, the RNC surface presented a decrease in oxygen, silicon, and zirconium ratio with increasing carbon ratio. Air abrasion with universal adhesive showed the highest bond strength followed by tribological silica coating with universal adhesive. HF etching with universal adhesive showed the lowest bond strength. CONCLUSION. An improved understanding of the effect of surface treatment of RNC could enhance the durability of resin bonding when used for indirect restorations. When using RNC for restoration, effective and systemic surface roughening methods and an appropriate adhesive are required.

• 대한치과보철학회지
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• 제59권4호
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• pp.469-477
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• 2021

상악 전치부 임플란트의 성공적인 수복을 위해서는 pink esthetics와 white esthetics가 모두 충족되어야 한다. Pink esthetics 부분의 경우 적절한 임시보철물의 역할이 중요하고, white esthetics 부분의 경우에는 최종 보철물의 색상과 형태가 중요하다. 다층 지르코니아는 기존의 단일구조 지르코니아에 비해 절단 부위의 투명도가 높기 때문에 추가적인 도재 축성 없이 자연스러운 보철물 제작이 가능하다. 따라서 본 증례에서는 상악 전치를 상실한 환자에서 적절한 임시보철물을 통해 기능과 심미성을 충분히 회복한 후 다층 지르코니아를 통해 white esthetics를 달성하였다.