• 한국정밀공학회지
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• 제13권9호
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• pp.156-164
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• 1996

Tool interference is one of the most critical problems in machining die cavities and punches. When machining concave or convex regions of cavities with large radius tool in rough cutting, the tool easily overcuts or undercuts the portions of the surface, which result in machining inaccuracy. So the generation of interference-free tool path must be required for more efficient rough cutting. In this paper, we present a method for modeling die cavities which consist of simple surface or analytic compoyund surfaces and present an algorithm for checking and removing the tool interference occurred in machining the die cavities. Using these algorithms, we can represent a die cavity, and check the interfer- ence regions, and then remove these interferences. Especially we focus on the side interference in the sides of analytic elements and base surface boundary.

• 천문학회보
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• 제39권1호
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• pp.46.1-46.1
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• 2014

In understanding "cooling flow" problem and the galaxy-SMBH co-evolution, AGN feedback is considered as one of the most important phenomena. Among various AGN feedback phenomena, X-ray cavities are particularly useful for studying AGN feedback over 10 kpc scales, as the origin of X-ray cavities is believed to be related to radio jet from AGN. For a comprehensive study of X-ray cavities, we collect all available diffuse X-ray data of galaxies in various galaxy environments, ranging from field galaxies to galaxy clusters, using the Chandra X-ray data archive. As a result we build up a sample of 87 targets showing enough X-ray photons to perform the analysis. Using modeling and unsharp masking techniques, we detected X-ray cavities and measured their physical properties (i.e., cavity size) for the 49 targets. Here, we present X-ray cavity properties and discuss environmental effects.

• 한국소음진동공학회논문집
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• 제22권8호
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• pp.742-747
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• 2012

A modified NDIF method using a sub-domain approach is introduced to extract highly accurate eigenvalues of two-dimensional, arbitrarily shaped acoustic cavities. The NDIF method, which was developed by the authors for the eigen-mode analysis of arbitrarily shaped acoustic cavities, has the feature that it yields highly accurate eigenvalues compared with other analytical methods or numerical methods(FEM and BEM). However, the NDIF method has the weak point that it can be applicable for only convex cavities. It was revealed that the solution of the NDIF method is very inaccurate or is not suitable for concave cavities. To overcome the weak point, the paper proposes the sub-domain method of dividing a concave domain into several convex domains. Finally, the validity of the proposed method is verified in two case studies, which indicate that eigenvalues obtained by the proposed method are more accurate compared to the exact method, the NDIF method, or FEM(ANSYS).

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.281-287
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• 2003

A Natural cavities were found at shallow depth during construction of a huge bridge in Moon-Kyung, Korea. The distribution patterns of cavities in the Moon-Kyung limestone were investigated carefully with a supplementary field job such as a structural geological survey, a geophysical survey, and a rock mechanical test in laboratory or field. A structural geological mapping produced a detail geological map on this area. It suggested that there were three faults in this area, and these faults had an influence on the mechanism of natural cavities. Among many kinds of geophysical surveys, an electrical resistivity prospecting was applied firstly on the specific area that was selected by results from the geological survey. Many evidences for cavities were disclosed from this geophysical data. Therefore, a seismic tomography was tested on the target area, which was focused by results from the electrical resistivity prospecting and was believed to have several large cavities. A distinct element numerical simulation using the UDEC was followed on the target area after completing all of field surveys. Data from field tests were directly dumped or extrapolated to numerical simulations as input data. It was verified from numerical analysis that several natural cavities underneath the foundation of the bridge should be reinforced. Based on the project result, finally, most of foundations for the bridge were re-examined and the cement grouting reinforcement was constructed on several foundations among them.

• 전기학회논문지
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• 제65권8호
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• pp.1424-1429
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• 2016

Segmentation is one of the first steps in most diagnosis systems for characterization of dental caries in an early stage. The purpose of automatic dental cavity detection system is helping dentist to make more precise diagnosis. We proposed the semi-automatic method for the segmentation of dental caries on digital x-ray images. Based on a manually and roughly selected ROI (Region of Interest), it calculated the contour for the dental cavity. A snake algorithm which is one of active contour models repetitively refined the initial contour and self-examination and correction on the segmentation result. Seven phantom tooth from incisor to molar were made for the evaluation of the developed algorithm. They contained a different form of cavities and each phantom tooth has two dental cavities. From 14 dental cavities, twelve cavities were accurately detected including small cavities. And two cavities were segmented partly. It demonstrates the practical feasibility of the dental lesion detection using Computer-aided Detection (CADe).

• 한국산림과학회지
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• 제101권2호
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• pp.324-332
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• 2012

이 연구는 시설양묘과정에서 요구되는 활엽수 수종별 적정 용기의 용적 및 생육밀도를 구명하고자 수행하였다. 용기 20혈(150본/$m^2$-400 mL), 24혈(200본/$m^2$-320 mL), 35혈(260본/$m^2$-240 mL)에서 거제수나무, 백합나무, 물푸레나무, 들메나무, 느티나무 및 참느릅나무 6 수종의 근원경, 간장, 물질생산량, 묘목품질지수 및 뿌리밀도를 조사 분석하였다. 용기에 따른 근원경, 간장, 물질생산량, 묘목품질지수 및 뿌리밀도는 6 수종 모두 용기 용적이 크고, 생육밀도가 낮은 20혈 용기에서 가장 높았다. 그러나 물푸레나무는 20혈과 24혈, 느티나무는 24혈과 35혈, 거제수나무는 세 용기 모두에서 유의적 차이는 없었다. 느티나무를 제외한 실험 대상 5 수종 모두 근원경, 간장, 물질생산량이 용기 용적과는 정의 상관관계, 생육밀도와는 부의 상관관계를 보였다. 이 결과를 바탕으로 양묘 단계에서 백합나무, 들메나무, 참느릅나무는 20혈, 물푸레나무는 20혈 또는 24혈, 느티나무는 24혈 또는 35혈, 거제수나무는 35혈의 용기가 적정 용기 크기로 판단된다. 수종별 적정 용기의 사용은 우량 묘목 생산이 가능하면서 경제적으로도 비용을 절감시킬 것으로 기대된다.

• Restorative Dentistry and Endodontics
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• 제15권1호
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• pp.107-119
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• 1990

The purpose of this study was to evaluate the marginal adaptability of the amalgam restorations in applying the cavity varnish (Copalite$^{(R)}$) and dentin bonding agent (Scotchbond 2$^{(R)}$) under the scanning electron microscope. For this study, eighteen sound extracted human molars were selected. Class I cavities in 12 teeth and class V cavities in 6 teeth were prepared using an air turbine with No. 701 tungsten carbide bur and finished using a low speed handpiece with No. 557 fissure bur. The prepared specimens were then divided into three groups including 4 class I cavities and 2 class V cavities in each group and restored as follows ; Group I. All the prepared cavities were restored with amalgam only (Control). Group II. Two layers of Copalite$^{(R)}$ cavity varnish were applied to the cavities with a gentle stream of air after each application and cavities were restored with amalgam. Group III. The enamel cavity margins were etched with 37% phosphoric acid gel for 60 sec., rinsed for 30 sec. and dried. One layer of visible lightcured Scotchbond Dental Adhesive$^{(R)}$ was applied and immediately cured for 20 seconds with visible light-cure unit and cavities were restored with amalgam. All the specimens were cut at the neck of the teeth and the occlusal halves of specimens were sectioned buccolingually in the longitudinal axis centering the amalgam restorations, using the disk. The cut specimens were ground with sandpapers (400, 600, 800, 1000 grit), and cleaned for 5 minutes in the ultrasonic cleaner (Brason Co. U.S.A.). In the cut surfaces, the amalgam - tooth interfaces were examined under the scanning electron microscope (JSM, 35C type, JEOL). The obtained results were as follows ; 1. The amalgam-tooth interfaces were reduced more significantly in the Copalite$^{(R)}$ and Scotchbond 2$^{(R)}$ application group than in the control group. 2. In the class I cavities, the Scotchbond 2$^{(R)}$ application group showed the findings similar to the Copalite$^{(R)}$ application group in the cavity floor, and the marginal adaptability was better in the side wall than in the cavity floor. 3. In the class I cavities, the Scotchbond 2$^{(R)}$ application group showed better marginal adaptability in the occlusal margin than in the gingival margin. 4. The marginal adaptability was in the order of the Scothbond 2$^{(R)}$ application group, the Copalite$^{(R)}$ application group and the control group.

• 지질공학
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• 제18권1호
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• pp.7-16
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• 2008

석회암지역은 외부의 압력에 의한 파쇄대와 용해성공동 등과 같은 지질학적인 결함을 대부분 갖고 있다. 특히, 장대교량을 건설할 경우 지질학적인 결함을 갖고 있는 석회암공동의 처리는 꼭 필요하다. 석회암 공동에서 기초의 침하량을 줄이고 지반을 보강하기 위한 대책공법으로 고압분사주입공법이 많이 활용되고 있다. 그러나 고압분사주입공법은 석회암공동에 대한 보강공법으로 활용되어 왔으나 연구실적과 기술적인 자료의 축적이 부족한 편이다. 그러므로 본 논문은 고압분사주입공법에 의하여 보강된 석회암공동 구간에 대하여 강도특성과 변형특성에 대한 연구결과를 제시하였다. 그리고 하중전이시험이 수반된 정재하시험에 의하여 지지력특성도 논의하였다.

• 대한기계학회논문집B
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• 제34권8호
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• pp.749-754
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• 2010

비강의 3 가지 생리학적 주요기능은 공기조절, filtering, 후각기능이다. 비강 내 공기유동특성에 대한 지식은 비강 호흡의 생,병리학적 측면을 기반으로 한다. 본 연구실에서는 정상 및 변형된 비강 모델 내 유동에 관하여 일정유량 및 주기유동 하에서 다양한 PIV 실험들을 진행해 왔다. 비대칭 비강을 가진 환자들 중에 일부는 고통을 느끼거나 불편함을 호소하는 반면 그렇지 않은 환자들도 있다. 이 원인을 밝히기 위하여 비중격이 휘어진 비대칭 모델에 대하여 PIV 및 수치해석적인 연구를 진행하였다. 이를 위하여 이비인후과 의사로부터 모델에 관한 CT 데이터를 제공받아 PIV 및 수치해석을 통해 호기 및 흡기시의 RMS 값 및 속도 분포를 얻었다. 모델에 따라 좌우 유량이 크게 다른 것을 확인할 수 있었고 이것이 고통을 느끼는 원인중에 하나가 될 수 있다.

• 대한금속재료학회지
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• 제49권12호
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• pp.924-929
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• 2011

It is well known that grain boundary cavitation is the main failure mechanism in austenitic stainless steel under tensile hold creep-fatigue interaction conditions. The cavities are nucleated at the grain boundary during cyclic loading and grow to become grain boundary cracks. The attenuation of ultrasound depends on scattering and absorption in polycrystalline materials. Scattering occurs when a propagation wave encounters microstructural discontinuities, such as internal voids or cavities. Since the density of the creep-fatigue cavities increases with the fatigue cycles, the attenuation of ultrasound will also be increased with the fatigue cycles and this attenuation can be detected nondestructively. In this study, it is found that individual grain boundary cavities are formed and grow up to about 100 cycles and then, these cavities coalesce to become cracks. The measured ultrasonic attenuation increased with the cycles up to cycle 100, where it reached a maximum value and then decreased with further cycles. These experimental measurements strongly indicate that the open pores of cavities contribute to the attenuation of ultrasonic waves. However, when the cavities develop, at the grain boundary cracks whose crack surfaces are in contact with each other, there is no longer any open space and the ultrasonic wave may propagate across the cracks. Therefore, the attenuation of ultrasonic waves will be decreased. This phenomenon of maximum attenuation is very important to judge the stage of grain boundary crack development, which is the indication of the dangerous stage of the structures.