• 한국정밀공학회지
• /
• 제12권12호
• /
• pp.130-138
• /
• 1995

Machined graphite/epoxy surfaces were studied by using SEM (Scanning Electron Microscopy), surface profilometry and its analysis to determine suitable surface describing parameters for machined unidirectional and multidirectional laminate composite. The surface roughness and profile are found to be highly depdndent on the fiber layup direction and the measurement direction. It was possible to machine 90 .deg. and -45 .deg. plies due to the adjacent plies, which were holding those plies. It was found that the microgeometrical variations in terms of roughness parameters $R_{a}$ without $D_{y}$(Maximum Damage Depth) region and $D_{y}$are better descriptors of the machined laminate composite surface than commonly used roughness parameters $R_{a}$and $R_{max}$ The characteristics of surface profiles in laminate composite are well represented in CPD (Cumulative Probability Distribution) plot and PPD (Percentage Probability Density) plot. Edge-trimmed multidirectional laminate surfaces are Gaussian and random for profiles measured along the tool movement direction, they are periodic and non-Gaussian in the direction perpendicular to the tool movement.t.ent.t.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2010년도 추계학술대회 논문집
• /
• pp.319-320
• /
• 2010

• 대한치과보철학회지
• /
• 제50권1호
• /
• pp.61-66
• /
• 2012

연구 목적: 이 연구는 Br${\aa}$nemark 임플란트의 후향적인 연구를 통해 machined 임플란트 의 15년, TiUnite$^{TM}$ 임플란트의 5년 누적 생존율을 구하여 비교하고, 위험 요소와의 상관관계를 밝히고자 하였다. 연구 재료 및 방법: 본 연구는 1993년부터 2008년까지 고려대 구로병원 임플란트클리닉에서 임플란트 치료를 받은 환자를 대상으로 하여, 환자의 임상기록을 토대로 조사하였고, 임플란트 일차수술 후 즉시 부하를 가한 경우와 임플란트 보철물이 다른 임플란트 시스템과 결합한 경우는 제외하였다. 15년 간 총 155명의 환자에게 541개의 Br${\aa}$nemark 임플란트 중, 264개의 machined 임플란트와 277개의 TiUnite$^{TM}$ 임플란트를 식립하였고, 임플란트 수술 및 보철수복 술식은 Adell 등이 제안한 방법에 따랐다. 6개월에서 1년 간격으로 Follow-up을 위한 재내원 기간 동안 임플란트에 대한 임상검사를 실시하였다. 본 연구의 관찰 기간은 1차 수술일로부터 2008년 12월 이내의 최종 내원일까지였고, 임상검사시 동요도, 타진, screw loosening, 그리고 환자의 불편감 등을 관찰하고, Zarb와 Albreksson에 의한 임플란트 생존 범주를 근거로 누적생존률을 평가하였다. 임플란트 누적생존율(CSR)이 Kaplan Meier estimate를 이용하여 얻었으며, 각각의 위험요소가 누적생존율에 미치는 영향을 Cox proportional hazards regression을 이용하여 분석하였다(${\alpha}$=.05). 결과: 전체 Br${\aa}$nemark 임플란트의 15년 누적생존율은 86.07%이었고, machined 임플란트의 경우 15년 누적생존율은 82.89%, 5년 누적생존율은 89.21%였으나 Tiunite$^{TM}$ 임플란트의 5년 누적생존율은 98.74%로 machined surface가 Tiunite$^{TM}$ 임플란트에 비해 실패율이 4.6배 정도 더 높았다. 전신질환을 가진 환자의 경우 실패율이 32% 더 증가하였고, 상악동 거상술 또는 골이식을 동반한 수술 등 부가적인 수술을 받은 경우 임플란트 실패율이 40% 더 증가하여 위험 요소와 임플란트의 생존율은 상관 관계가 있었다. Kennedy 분류에 따른 부분 무치악부의 위치에 따라 임플란트 실패율이 통계적으로 유의하게 달랐으며, 소구치와 구치부가구치부가 전치부에 비해 임플란트 실패율이 높게 나타났다. 결론: Br${\aa}$nemark machined 임플란트와 TiUnite$^{TM}$ 임플란트는 모두 우수한 임상적 결과를 보였으나, TiUnite$^{TM}$ 임플란트가 더 성공적이었으며, 임플란트의 누적 생존율은 위험요소와 연관성이 있었다.

• 대한치과보철학회지
• /
• 제47권1호
• /
• pp.12-20
• /
• 2009

연구목적: 임플란트가 식립되어질 때 매식체는 조직액과 접촉하게 된다. 임플란트의 조직액 흡착은 표면처리에 따라 다양하게 나타난다. 이 때 임플란트 시편의 표면 거칠기와 젖음성과의 상관관계를 분석하고자 하였다. 연구재료 및 방법: 표면 거칠기와 젖음성의 상관관계를 측정하기 위해 네 종류의 임플란트 시편을 각각 5종류 만들었다. 각각의 그룹은 그룹 A: Machined Surface, 그룹 B: Anodized surface, 그룹 C: RBM (HA blasting) surface, 그룹 D: CMP (calcium methaphosphate) coating surface이다. 연구결과: 1. 표면의 거칠기는 RBM, CMP, Anodized, Machined 그룹 순서로 거칠었다. RBM과 CMP는 통계적으로 유의차가 없었다 (P<.05). 2. 젖음성은 Anodized, RBM, CMP, Machined 그룹 순서로 높았다. CMP와 Machined는 통계적으로 유의차가 없었다 (P<.05). 3. 표면 거칠기와 젖음성과의 상관관계는 없었다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• 제32권6호
• /
• pp.514-523
• /
• 2006

The purpose of the present study was to evaluate the effects of several implant surface treatments to the bone formation, by placing Machined implants, 75${\mu}m$ Calcium phosphate-blasted implants and $Al_2O_3$-blasted and acid-etched implants in rabbit tibia through histomorphometric study. Two animals of each group were sacrificed at 2, 4, 8 weeks. The specimens containing the implants were dehydrated and embedded into hard methylmethacrylate plastic. Thereafter, the sections were ground to 50${\mu}m$. The specimens were stained with Villanueva bone stain for a light microscopic study. The results were as follows; 1. When the surface roughness of three different implants was measured by Surfcorder, the Ra of the Machined group, the RBM group and the SLA group was 0.16${\mu}m$, 0.44${\mu}m$, and 1.08${\mu}m$. 2. When examining the surfaces of the implants in the scanning microscope, Machined implant has the smooth surface with a few scratches, RBM implant has the rough surface with curled ridges and valleys, and SLA implant has the rough surface structures such as sharp protruding parts and micropits measuring 1-2${\mu}m$ in diameter. 3. After 2 weeks of implantation, the percentage of bone-to-implant contact of the Machined group, the RBM group and the SLA group was 26.86%, 35.40% and 45.99%. However, its differences between each group decreased during the healing periods. 4. After 2 weeks of implantation, the percentage of bone area inside the threads of the Machined group, the RBM group and the SLA group were 21.55%, 30.43% and 41.18%. However, its difference of bone area between machined group and surface treatment groups was maintained but the difference within the surface treatment groups decreased during the healing periods. In summary, the amount of bone formation in RBM and SLA group was greater than Machined group in early healing stage. These results suggest that RBM and SLA implants can reduce the healing period for osseointegration and may be suitable for early function.

• 대한치과교정학회지
• /
• 제42권1호
• /
• pp.4-10
• /
• 2012

Objective: To determine the effect of surface anodization on the interfacial strength between an orthodontic microimplant (MI) and the rabbit tibial bone, particularly in the initial phase aft er placement. Methods: A total of 36 MIs were driven into the tibias of 3 mature rabbits by using the self-drilling method and then removed aft er 6 weeks. Half the MIs were as-machined (n = 18; machined group), while the remaining had anodized surfaces (n = 18; anodized group). The peak insertion torque (PIT) and the peak removal torque (PRT) values were measured for the 2 groups of MIs. These values were then used to calculate the interfacial shear strength between the MI and cortical bone. Results: There were no statistical differences in terms of PIT between the 2 groups. However, mean PRT was significantly greater for the anodized implants ($3.79{\pm}1.39$ Ncm) than for the machined ones ($2.05{\pm}1.07$ Ncm) (p < 0.01). The interfacial strengths, converted from PRT, were calculated at 10.6 MPa and 5.74 MPa for the anodized and machined group implants, respectively. Conclusions: Anodization of orthodontic MIs may enhance their early-phase retention capability, thereby ensuring a more reliable source of absolute anchorage.

• 대한치과보철학회지
• /
• 제42권3호
• /
• pp.261-266
• /
• 2004

Statement of problem. The effects of surface roughness have not or insufficiently been analyzed on earlier events such as cell adhesion though cell behavior most germane to implant performance is cell adhesion. Purpose. The purpose of this study was to evaluate cell adhesion of osteoblast-like cells (MG63) onto three types of titanium disks with varying roughness using the Elisa assay. Materials and methods. Representative disks from each group (SLA, HA, machined) were subjected to surface analysis and surface roughness was measured by the optical interferometer (Accura 2000, Intekplus Co., Seoul, Korea). Following this, MG63 cells were cultured on the titanium disks and released. Cell adhesion measurements using the Elisa assay were performed specifically at three points: after 24, 48, and 72 hours of culture. Results. Among the 3 types of surface analyzed, the SLA surface was the roughest with a Ra value of $1.114{\mu}m$ followed by HA coated surface and machined surface, consecutively. The optical density values for the SLA surface group was significantly higher than that of the machined and HA coated surface groups following 24 and 48 hours of culture. The cell culture on HA coated surface showed significantly higher values compared to the machined surface following 24, 48 and 72 hours of culture. Conclusion. The results suggest that surface treatment of titanium surfaces enhanced cell adhesion of human osteoblast-like cells (MG63).

• Journal of Advanced Marine Engineering and Technology
• /
• 제39권5호
• /
• pp.522-526
• /
• 2015

Generally, underwater unmanned vehicle have adopted an inertial navigation system (INS), dead reckoning (DR), acoustic navigation and geophysical navigation techniques as the navigation method because GPS does not work in deep underwater environment. Even if the tactical inertial sensor can provide very detail measurement during long operation time, it is not suitable to use the tactical inertial sensor for small size and low cost UUV because the tactical inertial sensor is expensive and large. One alternative to INS is attitude heading reference system (AHRS) with the micro-machined electro mechanical system (MEMS) inertial sensor because of MEMS inertial sensor's small size and low power requirement. A cost effective and small size attitude heading reference system (AHRS) which incorporates measurements from 3-axis micro-machined electro mechanical system (MEMS) gyroscopes, accelerometers, and 3-axis magnetometers has been developed to provide a complete attitude solution for UUV. The AHRS based MEMS overcome many problems that have inhibited the adoption of inertial system for small UUV such as cost, size and power consumption. Several evaluation experiments were carried out for the validation of the developed AHRS's function and these experiments results are presented. Experiments results prove the fact that the developed MEMS AHRS satisfied the required specification.

• 한국생산제조학회지
• /
• 제9권3호
• /
• pp.55-61
• /
• 2000

In this paper we have discussed on the characteristics and modeling of machined geometry which was established for the case of round shape machining also the effects of externally machined profile are analyzed and its modeling realia-bility was verified by the experiments of roundness testing especially in lathe operation. In this study we established a harmonic geometric model with the parameter harmonic function. In general we can calculate the theoretical roundness profile with an arbitrary multilobe parameter. But in real experiments only 2-5 lobe profile was frequently measured, The most frequently measured ones are 3 and 5 lobe profile in experiments. With these results we can predict that these results may be applied to round shape machining such as turning drilling boring ball screw and cylindrical grinding operation in bearing and shaft making operation with the same method. in this study simulation and experimental work were performed to show the profile behaviors. we can apply these new modeling methods in real process for the predic-tion of part profile behaviors machined such as in round shape machining operation.

• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
• /
• pp.659-664
• /
• 2000

In this paper, We have discussed on the modeling of machined outer geometry which was established for the case of round shape machining, also the effects of externally machined profile are analyzed and its modeling realiability was verified by the experiments of roundness testing, especially in lathe operation. In this study, we established harmonic geometric model with the parameter harmonic function. In general, we can calculate the theoretical roundness profile with arbitrary multilobe parameter. But in real experiments, only 2-5 lobe profile was frequently measured. the most frequently ones are 3 and 5 lobe profile in experiments. With this results, we can predict that these results may be applies to round shape machining such as turning, drilling, boring, ball screw and cylindrical grinding operation in bearing and shaft making operation with the same method. In this study, simulation and experimental work were performed to show the profile behaviors. we can apply these new modeling method in real process for the prediction of part profile behaviors machined such as in round shape machining operation.