• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.6
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• pp.41-49
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• 2016

To evaluate lubrication properties by surface roughness under boundary and mixed lubrication, a new approach is suggested by both asperity flow and contact with stochastic characteristics. Many researchers already have studied the effect of surface roughness on flow. But, it has become important to research of the phenomenon of asperities contact in surfaces because the growth of asperities contact area under heavy load conditions. In this paper, flow factors in the average flow model derived by Patir and Cheng were used, and a multi-asperity contact model was included to calculate lubrication properties of a surface with a randomly generated rough surface. A numerical analysis using the average Reynolds equation with both the average flow model and the asperity contact model was conducted, and the results were compared with those from previous research. The results showed that the influence of asperities on lubrication and the friction coefficient changed rapidly on application of contact model.

• Research in Plant Disease
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• v.26 no.1
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• pp.53-56
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• 2020

Red spots symptoms were observed on the leaves of Rumex japonicus Houtt. in Goesan, Korea, in May 2019. Diseased leaf showing red spot and white-colored sori were found behind of diseased leaves. Aeciospores were confirmed and observed using a stereomicroscope, light microscope, and scanning electron microscope. They were globose or ovoid and measured 19.0-24.4×19.0-24.5 ㎛, with verrucae ornamentation. For the phylogenetic analysis, partial of large subunit rDNA region and cytochrome c oxidase subunit III were sequenced. As a result, the isolated fungus species showed high similarities with Puccinia prizeliana. Based on the previous report, morphological characters, phylogenetic analysis, it was confirmed as Puccinia phragmitis which have not been reported in Korea, and we firstly report this fungal agent on R. japonicus as P. phragmitis in Korea.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.4
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• pp.39-46
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• 2018

Two surfaces that have relative motion show different characteristics according to surface roughness or surface patterns in all lubrication areas. For two rough surfaces with mixed lubrication, this paper proposes a new approach that includes the contact characteristics of the surfaces and a probabilistic method for a numerical analysis of lubrication. As the contact area of the two surfaces changes according to the loading conditions, asperity contact is very important. An average flow model developed by Patir-Cheng is central to the study of lubrication for rough surfaces. This average flow model also refers to a multi-asperity contact model for deriving a modified Reynolds equation and calculating the lubricant characteristics of a bearing surface with random roughness during fluid flow. Based on the average flow model, this paper carried out a numerical analysis of lubrication using a contact model by considering a load change made by the actual contact of asperities between two surfaces. Lubrication properties show different characteristics according to the surface patterns. This study modeled various geometric surface patterns and calculated the characteristics of lubrication.

• Korean Journal of Plant Resources
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• v.33 no.2
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• pp.116-129
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• 2020

The genus Sedum comprises about 400 taxa with worldwide distribution, and about 20 taxa of the genus Phedimus distributed from Asia to Europe. According to some taxonomists, Phedimus and Sedum are two separate genera of the family Crassulaceae; however, in Korea Phedimus has been treated as a subgenus Aizoon within the genus Sedum. This ambiguous taxonomic treatment of the genus Phedimus needs further confirmation. In the study, we investigated morphological characteristics such as the whole plant height, leaf morphology, and seed coat features of these two genera. We believe that these characters are very important to distinguish Phedimus and Sedum. The result indicated that the seed surface pattern was the most useful diagnostic character. The Sedum had a hexagonal pattern with a single nipple protrusion, whereas the Phedimus had a rectangular pattern with papilla on both ends. The results of this study strongly support the separation of Phedimus from Sedum and thus Phedimus need to be treated as an independent genus.

• Applied Microscopy
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• v.37 no.2
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• pp.53-63
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• 2007

The culticular substructure of the venom apparatus in the orb-web spider Araneus ventricosus are studied with scanning electron microscopy. The apparatus is composed of chelicera and paired venom glands in the cephalothorax. Each chelicera consists of a basal segment and a movable fang that articulates with each other. The chelicera of this spider is labidognathous form that moves at right angles to the body axis, and has two segments similar to that of a folding jackknife. Each cylindrical fang has a specialized hinge joint which articulate with the cheliceral groove which contains numerous small protrusions. In addition, each side of cheliceral groove is covered with a total of 7 cuticular teeth in two rows which composed of 4 promarginal and 3 retromarginal teeth. It has been also observed that a single venom pore is always located toward the direction of retromarginal teeth, and surface cuticular pits are distributed on the cuticular depressive area of cheliceral groove.

• Journal of Plant Biology
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• v.37 no.2
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• pp.183-193
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• 1994

인삼(Panax ginseng C.A. Meyer)의 뇌두 캘러스로부터 분리한 원형질체와 배양된 원형질체의 미세구조 변화와 원형질막 표면을 투과 및 주사전자현미경으로 조사하였다. 분리 직후의 원형질체에서는 캘러스세포에서보다 작은 액포들이 많이 형성되어 있었다. 또한 활면소포체의 수가 증가하였으며 이들은 원형질막과 평행으로 배열하였다. 활면소포체는 가끔 세포질을 둘러싸서 세포질분리체(cytosegresome)를 형성하였고, 이 구조는 세포질을 분해시킨 후 액포로 변화하기도 하였다. 배양된 원형질체에서는 분리 직후의 원형질체와 비교하여 조면소포체, 딕티오좀, 리보좀, 미토콘드리아, proplastid 및 액포 등의 수가 현저하게 증가하였다. 딕티오좀으로부터 많은 소낭들이 형성되었고 이들은 세포질 전반에 걸쳐 존재하였다. 때로는 소낭들이 원형질막 바깥으로 돌출되어 돌기를 형성하기도 하였다. 배양된 원형질체의 표면에는 섬유소로 구성되어 있을 것으로 추정되는 섬유상 구조들이 형성되어 있었다.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.10
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• pp.53-60
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• 2001

Surface roughness plays a significant role in friction, wear, and lubrication in machine components. Most engineering surfaces have the nongaussian height distribution. So, in this study, contact simulations are conducted for not only gaussian surfaces but also nongaussian surfaces. Nongaussian rough surface considering the kurtosis is generated numerically And the effects of kurtosis on real contact area fraction, average gap, and mean asperity contact pressure are studied. It will be shown that the real contact area fraction and the mean asperity contact pressure are sensitive to the characteristics of surface geometry according to kurtosis.

• Information Display
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• v.10 no.1
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• pp.15-21
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• 2009

다중 도메인 수직배향 LCD는 러빙 공정을 필요치 않는 다는 장점에서 출발해 현재 액정 TV 시장에서 주를 이루고 있다. 하지만 현재 사용화 되고 있는 제품들이 투과율, 응답속도, 명암대비율 등 성능부분의 개선이 필요하고 공정 측면에서 돌기를 사용하거나 상판 패턴을 필요로 하는데 이러한 공정을 제거하면서도 성능이 우수한 새로운 형태의 수직배향 LCD가 최근 대두되고 있다. 기 발표된 기술들을 정리해 보면 신기술에서는 액정에 UV curing이 가능한 모노머를 소량 도핑 한 후 적절한 셀 구조를 형성해 전압 인가시 중간에 액정 배열에 충돌이 있더라도 최종적으로 안정한 배열을 갖게 만든 다음 UV조사를 통해 양 기판 표면에 모노머가 고분자화되면서 액정 배향 방향과 프리틸트각을 갖게 하도록 만든다. 이러한 신개념의 수직배향 LCD는 종래 LCD에 비해 전기광학 특성이 우수해지고 제조공정도 단순해져 향후 수직배향 LCD의 주를 이룰 것으로 예상된다. 더불어 수직배향 기술은 해마다 새로운 진화를 하고 있으며 앞으로 더 진화를 할 것으로 예상되어 이 부분에 대한 적극적인 연구 지원이 필요하다.

• Korean Journal of Plant Taxonomy
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• v.31 no.4
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• pp.343-358
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• 2001

We have examined the pedicel pubescence and other major morphological characters of 11 putative hybrid populations of Aconitum subgn. Aconitum at Mt. Sobaek to understand their origin. These populations show very complicated patterns of variation in pedicel pubescence ; they contain individuals having pedicels (1) completely glabrous, (2) with few micropapillate curved hairs near the receptacle, (3) moderately pubescent with micropapillate curved hairs from middle to upper portion, (4) sparsely pubescent with a mixture of micropapillate curved hairs and smooth-surfaced spreading glandular hairs near the receptacle, and (5) moderately pubescent with both types of hairs but from middle to upper portion. All five types of individuals co-occur in most populations with varying proportions. These results, in conjunction with evidence from the analysis of other major morphological characters, suggest that the populations at Mt. Sobaek were derived from the multiple hybridization events involving A. kusnezoffii, A. japonicum subsup. napiforme, and A. jaluense subsp. jaluense. In addition, the absence of "typical" forms of these putative parental taxa in Mt. Sobaek area suggests that repeated introgression has probably occurred in these populations.

• Korean Journal of Plant Resources
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• v.16 no.1
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• pp.89-98
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• 2003

Pollens of six taxa in the genus Atractytis L. confused with Atractylodes DC. were investigated by the light and the scanning electron microscope. Pollen grains of six taxa in this genus were monads, 46.5-66.7$\mu\textrm{m}$ in length of polar axis, 43.6-60.47$\mu\textrm{m}$ in equatorial width. Aperture was tri-colporate, 19.6-29.1 $\mu\textrm{m}$ in colpus length,7.3-11.0$\mu\textrm{m}$ in colpus width and 6.4-10.6$\mu\textrm{m}$ in porus diameter. The exine was composed of three layers(foot layer, columellne, tectum), and 5.2-8.3 $\mu\textrm{m}$ in thickness. The surface sculpturing pattern was echinate, the spines were 1.4-5.8$\mu\textrm{m}$ in length and 6-33 per 20$\mu\textrm{m}$$^2$ in distribution numbers over the surface. Atractylis L. was not distinguished from Atractylodes DC. by pollen morphology, especially the pollens of Atractylis arabica, A. aristata, A. carduus, A. microcephala were very similar to that of Atractylodes. But its taxonomic significance was different, the taxa of Atractylodes DC. were divided into 2 types by only pollen size, but the treated taxa in this study were divided into various types by pollen size, shape of equatorial view, surface sculpturing and spine size. The characteristics of spine size and shape of equatorial view in A. cancellata and A. prolifera were very useful for consideration of evolutionary trends in this genus.