• 한국결정성장학회지
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• 제14권4호
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• pp.174-186
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• 2004

Striations are growth-induced inhomogeneities which hamper the applications of solid-solution crystals and of doped crystals in numerous technologies. Thus the optimized performance of solid solutions often can not be exploited. The inhomogeneity problem can be solved in specific cases by achieving a distribution coefficient one in growth from melts and from solutions. Macrostep-induced striations can be suppressed by controlling the growth mode, by achieving growth on facets thereby preventing step bunching. Thermal striations are commonly assumed to be caused by convective instabilities so that reduced convection by microgravity or by damping magnetic fields was and is widely attempted to reduce such inhomogeneities. Here it will be shown that temperature fluctuations at the growth interface cause striations, and that hydrodynamic fluctuations in a quasi-isothermal growth system do not cause striations. The theoretically derived conditions were experimentally established and allowed the growth of striation-free crystals of $KTa_{1-x}Nb_xO_3$"KTN" solid solutions. Hydrodynamic variations from the accelerated crucible rotation technique ACRT did not cause striations as long as the temperature was controlled within $0.03^{\circ}$ at $1200^{\circ}C$ growth temperature. Alternative approaches to solve or reduce the segregation and striation problems in growth from melts and from solutions are discussed as well.

• 한국주조공학회지
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• 제17권2호
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• pp.145-150
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• 1997

The striations parallel to the casting direction are the characteristic defects occurring during the unidirectional solidification of nonferrous metals such as pure Al and Sn. It has been known that the defects affect the recrystallization temperature as well as the mechanical and electrical properties of Al. However, it has not been still known about the effect of casting factors such as the casting speed, rod diameter of cast metals, and alloying elements on the occurrence of striations. In the present study, these casting factors affecting the occurrence of striation were investigated by adopting the quantitative examination of striations. Also, the relation between striation defects and feathery grain, which are very similar to the striation defects, was studied.

• Animal Systematics, Evolution and Diversity
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• 제32권1호
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• pp.55-59
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• 2016

Two species of the genus Parthenocodrus Pschorn-Walcher, 1958 (Hymenoptera: Proctotrupidae) are reported: P. elongatus from Japan and South Korea and P. puncticauda from South Korea. Parthenocodrus elongatus is easily distinguished by having posterior surface of propodeum without transverse carinae and ovipositor sheath with distinct longitudinal striations. Parthenocodrus puncticauda is easily distinguished by having posterior surface of propodeum with transverse carinae and ovipositor sheath without distinct longitudinal striations. This genus is also newly recorded in each country. Redescriptions and photographs of the diagnostic characters are provided. All specimens for this study are deposited in the Yeungnam University (YNU), Gyeongsan-si, South Korea.

• 대한기계학회논문집A
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• 제27권12호
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• pp.2055-2060
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• 2003

Striation is a typical pattern observed on the fatigue fracture surface and the spacing is known to correspond to a macroscopic fatigue crack growth rate, and many models for the predict in the formation of such striation have been proposed. However, these theories and methods can't be applied under random loading spectrum. In this study, the fatigue tests were carried out on aluminum alloy under random loading spectrum. The fatigue fracture surfaces were observed in the scanning electron microscope (SEM) and great quantities of SEM micrographs were synthesized and saved in computer system. The space and morphology of several large-scale striations, which are expected to from at the relatively greater load range in loading block, were observed. The crack length for each loading blocks was decided in consideration of regularity and repetition of those striations. It is shown that the applicability of fractographic methods on the fatigue fracture surface under random loading spectrum.

• 대한치과의사협회지
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• 제12권12호
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• pp.913-918
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• 1974

The authors have observed clinically and histopathologically on two cases of rhabdomyosarcomas occurred in the oral cavity. The results were as follow: 1. A case of adult pleomorphic rhabdomyosarcoma, involving the right mandibular third molar area of 52 year old male, revealed pathological fracture of the right mandibular angle area. Microscopically, sections of this tumor showed cross striations by staining of phosphotungstic acid hematoxylin. 2. A case of embryonal alveolar rhabdomyosarcoma, involving the right buccal area of one year and ten months old female, revealed severe bone destruction on the right mandibular body area. Microscopically, sections of this tumor did not show cross striations.

• 한국초전도ㆍ저온공학회논문지
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• 제15권2호
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• pp.44-47
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• 2013

Large AC loss from the second generation (2G) high temperature superconducting (HTS) wires has been one of the major bottlenecks in power applications with HTS materials. Moreover, the large power applications also require the large current capacity from the HTS wires, which makes them produce larger AC losses. In order to reduce the AC loss from the HTS conductors with large current capacity, an HTS compact cable with some striations on the superconducting layers has been proposed. In this paper, we prepared some sample HTS compact conductors with striations, and measured their magnetization loss from the external magnetic field. We also made some slits on the superconducting layer of the HTS wire by laser cutting to reduce the aspect ratio of the superconducting layers. It would make the low eddy current loss and magnetic decoupling. Finally, the magnetization losses of the sample HTS compact conductors were measured and analyzed.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.153-158
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• 2000

Atomic Force Microscope (AFM) was used to study cross sectional profiles and dimensions of fatigue striations in 2017-T351 aluminum alloy. Their widths (SW) and heights $(SH,\;SH_h)$ were measured from the cross sectional Profiles of three-dimension AFM images. The following results that will be helpful to understand the fatigue crack growth mechanism were obtained. (1) Coincidence of the crack growth rate with the striation width was found down to the growth rate of $10^{-5}$ mm/cycle. (2) The relation of $SH={\alpha}(SW)^{1.2}$ was obtained. (3) The ratio of the striation height to its width SH/SW and did not depend on the stress intensity factor range ${\Delta}K$ and the stress ratio R. From these results, the applicability of the AFM to nano-fractography is discussed.

• Parasites, Hosts and Diseases
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• 제27권3호
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• pp.217-224
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• 1989

눈에 이물감, 결막 자극 증상, 소양감 등을 호소하며 서울 지역 안과의원을 내원한 2명의 환자로부터 백색 실 모양의 선충 자충 4마리, 웅충 1마리 및 유충 여러 마리를 얻었다. 충체들을 통상적인 방법으로 처리하여 주사 전자현미경으로 표피 미세구조를 관찰하였다. 웅충의 경우, 체장은 11.00mm, 체폭은 0.18mm, 교미침의 길이는 0.70mm, 식도의 길이는 0.35mm이었다. 자충의 경우 체장은 13.50∼18.00mm, 체폭은 0.20∼0.30mm, 앞 끝에서 vaginal opening까지 0.27mm, 식도 의 길이는 0.41∼0.80mm, 뒤 끝에서 항문까지는 0.062mm이었다. 특징적으로 체표에 가로 주름이 있었는데 전단에서는 주름의 간격이 좁고 몸통 부위에서 그 수는 점차적으로 감소하며 표피가 일어나 나풀거리는 형태를 나타내는데 주름의 수는 단위 mm당 250∼650개의 범위이었다. 위 측정 결과를 통해 본 충을 동양안충(Thelazia callipaeda)으로 동정하였다. 본 충의 전체 모양은 구부와 미부에서 가늘고 몸통 중앙부위는 점점 굵어지는 형태였고 웅충의 경우 미부가 꼬여 있었다. 자충에서는 구부에 6각형 구조로 배열된 6개의 끈 모양의 각질 구조와 그 측면으로 화학적 자극 수용체인 amphid, 몸통 부위에 옆줄과 vaginal opening, 미부에서 또다른 자극 수용체인 1쌍의 phasmid와 anus의 미세구조를 관찰할 수 있었다. 웅충에서는 두부에 끈 모양의 각질 구조 이외에 1쌍의 papillae와 미부에서는 우벼내어진 형태의 구조물을 확인하였으며 교미침과 caudal papillae는 웅충이 1마리이고 그 말단이 꼬여 있어 확인이 어려웠다. 자충의 자궁에서 얻은 유충은 얇은 막에 싸여 있었고 이 막을 벗어야만 특징적인 가로 주름을 볼 수 있었다. 본 연구의 Thelazia callipaeda는 우리 나라에서 보고된 것 중 18번 및 19번째 인체 감염의 예이다.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2004년도 춘계총회 및 연구발표회 초록집
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• pp.43.4-43.4
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• 2004

• 대한기계학회논문집A
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• 제24권4호
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• pp.955-962
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• 2000

Scanning Probe Microscope (SPM) such as Scanning Tunneling Microscope (STM) and Atomic Force Microscope (AFM) was shown to be the powerful tool for nano-scale characterization of a fracture surface . AFM was used to study cross sectional profiles and dimensions of fatigue striations in 2017-T351 aluminum alloy. Their widths (SW) and heights (SH) were measured from the cross sectional profiles of three-dimension AFM images. The following results that will be helpful to understand the fatigue crack growth mechanism were obtained. (1) Coincidence of the crack growth rate with the striation width was found down to the growth rate of 10-5 mm/cycle. (2) The relation of SH=0.085(SW)1.2 was obtained. (3) The ratio of the striation height to its width SH/SW did not depend on the stress intensity factor range K and the stress ratio R. (4) Not only the SW but also the SH changed linearly with the crack tip opening displacement (CTOD) when plotted in log-log scale. From these results, the applicability of the AFM to nano-fractography is discussed.