• 구강회복응용과학지
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• 제17권4호
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• pp.245-256
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• 2001

The purpose of this study is to analyze the mechanical stress and displacement on the jaws during the simulated bilateral clenching task on the three-dimensional finite element model of the dentated skull with unilateral molar loss. For this study, the computed tomography(G.E.8800 Quick, USA) was used to scan the total length of human skull in the frontal plane at 2.0mm intervals. The fully assembled finite element model consists of the articular disc, maxilla, mandible, teeth, periodontal ligament and cranium. The FE model was used to simulate the bilateral clenching in intercuspal position. The loading condition was the force of the masseter muscle exerted on the mandible as reported by Korioth et al. degrees of freedom of the zygomatic region where the masseter muscle is attached were fixed as restraints. In order to reflect the actual action of the muscles force, the displacement of the region was attached where the muscle is connected to the temporal bone and restraint conditions were given values identical to values at the attachment region of the masticatory muscle but with the opposite direction of the reaction from when the muscle force is acted on the mandible. Although the mandible generally has higher displacement and von Mises stress than the maxilla, its mandibular corpus on the molar-loss side has a higher stress and displacement than the molar-presence side. Because the displacement and von Mises Stress was the highest on the lateral surface of mandibular corpus with molar loss, the stress level of the condyle on the molar-loss side is greater than that of the molar-presence side, which in turn caused the symphysis of the mandible to bend. In conclusion, the unilateral posterior bite collapse with molar loss under para-functional activities such as bruxism and clenching can affect the stress concentration on the condyle and mandibular corpus. It is therefore necessary to consider the biomechanical function of dento-skeleton under masticatory force while designing the occlusal scheme of restoration on alveolar bone with the posterior collapse.

• 정보과학회 논문지
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• 제43권11호
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• pp.1233-1244
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• 2016

저전력, 저품질의 네트워크 환경인 LLNs(Low power and Lossy Networks) IoT 네크워크 환경에서는 IETF에서 제안한 IPv6 라우팅 프로토콜인 RPL이 대표적으로 사용된다. RPL은 루프가 존재하지 않는 방향성 비순환 그래프(Directed Acyclic Graph)를 생성하는 것을 목표로 하며, 이를 위해 loop avoidance, loop detection 메커니즘과 문제 발생 시 복구를 위한 DIO Poisoning 메커니즘을 정의하고 있다. 하지만, 기존의 DIO Poisoning은 루프 발생 노드에서 일어난 poisoning이 해당 노드의 서브트리로 전파되어 복구 시간과 컨트롤 메시지가 증가하는 문제점을 가지고 있다. 본 논문에서는 RPL 기반 IoT 무선 네트워크에서 루프 복구 과정 시 서브 트리의 라우팅 오버헤드가 추가로 발생할 수 있는 현상을 보완한 효율적인 경로 복구 기법을 제안한다. 개선된 RPL 루프 복구 과정에서는 기존 선호 부모로 선택될 수 없던 경로를 활용하여 빠르게 복구함으로써 새로운 경로설정을 위한 컨트롤 패킷 트래픽과 경로 복구 시간을 줄인다. 시뮬레이션을 사용하여 제안한 프로토콜이 기존 프로토콜에 비해 복구 시간 단축과 컨트롤 패킷의 감소를 통한 복구 성능을 향상시킬 수 있음을 알 수 있었다.

• 한국동물학회지
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• 제8권2호
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• pp.89-127
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• 1965

1. This report is on the outcome of observation made up the breeding process of Narcissus flycatcher, Muscicapa narcissina zanthopygia, using 15 ness-boxes at Seoul and Kwang Nung Experimental forest in 1964, and the relevant feeding habit was studied by the collar method of wrapping the necks of thenestlings for 50-60 minutes or more in some cases from 1963 to 1964. 2. The Narcissus flycatcheris a common summer resident throughout Korea arriving at the end of April. The earliest data of arrival of this species in Seoul, is April 26, 1964. They migrate southward from the later part of September to early part of October. 3. In a week after their arrival , they start to build nest after a brief courtship. Male and female prepare their nest ina nestboxes in 4 or 5 days. Nests are usually found in the moss, which provide definite frame-work. The inner side of the nest is usually composed of roots of Gramineae or leaves of pine, oak or other broad leave tree. 4. The laying period is generally from the later part of April to the middle of June : and the number of eggs laid is from 3 to 8 , therefore 5 in average : eggs are pink with traces of milky yellow blending of light auburn and orange red spots and chicken-egg-like in shape. 5.The incubation takes place for 7-12 days from the middle part of May to the middle of June, in the order of male and female . The hatching rate tends to increase in proportion to clutch size. 6. The feeding period usually lasts 15 days in average from the early part of June to the middle of July and the feeding urge tends to increase in proportion to brood size. 7. The animals invading into their nest-boxes are red ants, chipmunks, bees , barkbeetles and philippine red-tailed shirkes, etc. 8. On the basis of analysis covering 714 birds in 31 nests, the food they consumed during the nesting period of nestlings were mostly of animal matters composing of : insect larvae form-39. 88% insect adult form 36.26%, insect pupae-0.19%, spider-17.75% and other animal matters 5.92% , Besides a small amount of plant pieces were found . As to the insect larvae, Lepidoptera was the largest in the content followed by Hymenoptera , Orthoptera and Coleoptera. As to the insect adult, Diptera was the largest in the content followed by Coleoptera, and Hymenoptera. In view of forest protection, noxious insect was of 69.38%, useful insect 4.39%, and spider 17.75%. 9. The rich assortment of its food, the ability of acquiring various insect (adults as well as larvae), its destruction of great numbers of harmful insects , and its quick assimilation artificial nesting with the nest-boxes of 2.5-3cm entrance hole employed, allow us to conclude that the flycatcher may be successfully employed in the elimination of fores pests. The above results are only that part obtained near Seoul in the middle of Korea, however, if we would extend the scheme to other broad areas using similar techniques, the nest-boxes could not only be well used by the birds, but also it would help to prevent the increase of harmful. insects.

• 한국환경복원기술학회지
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• 제1권1호
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• pp.28-44
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• 1998

This study was conducted to suggest the ecological restoration strategies for the disturbed landscapes by theoretical study. Especially, it is aimed to suggest three objectives for restoration by using native plants ; (1) prevention or reduction of wind and water erosion, (2) provision of food and cover for variety of animal species, (3) improvement of the visual or aesthetic quality of disturbed sites. The main results were summarized as follows. 1. Cooperation between restoration ecologists and restoration practitioners is needed to delineate a scientific approach to restoration ; (1) Being aware of published literature that describes similar work and/or establish general principles. (2) Preparedness to carry out proper experiments to test ideas. (3) Preparedness to monitor fundamental parameters in a restoration scheme. (4) Providing information about the behavior of species. (5) Publish results. 2. There are three models of succession in theories of plant succession. The tolerance and facilitation models were recommended to ecological restoration. The inhibition model applies in most secondary succession, but the actual species which are introduced first may inhibit the germination and growth of slower-growing species, or they may prevent the growth of other species whose propagules arrive later. 3. The objectives of erosion control, wildlife habitat provision, and visual quality improvement are not mutually exclusive. However, many revegetation practices in the past have emphasized one of these aspects at the expense of the others. 4. A native plant community can be the model of ecological restoration. By stylization/abstraction of native plant community, trying to learn the most essential characteristics of community types - environmental factors ; dominant, prevalent, and "visual essence" species composition - in order to use such information in restoration. 5. After developing mass/spaces plan, match plant communities to the mass/space plan. In utilizing community grouping, there needs aesthetic ability to understand design elements. 6. Several hydrophytes such as Pennisetum saccharifluous, Themeda triandra, Cirsium pendulum show relatively good germination rates. In case of mesophytes and xerophytes, Arundinella hina, Artemisia princeps, Oenothera odorata and legumes seem to have quick-germinating abilities at barren sites. Pinus thunbergii, Rhus chinensis, Evodia daniellii, Alnus firma and Albizzia julibrissin can be considered as "late succession" woody plants because they show low germinating rates and slow growing habitat. 7. The seeds used for restoration should be collected within a certain radius of where it will be planted. Consideration in genetic issues in the collection and use of germplasm can increase the odds for successful restoration efforts. 8. The useful model in the "drift" pattern occurs so abundantly in naturally evolving landscapes. As one species diminishes in density, a second or third species are increased. Thus, dynamic interactions between species are created. Careful using of "drift phenomenon" in planting was recommended. 9. Virtually no stand of vegetation today is immune from the introduction and/or spreading of exotic species. Therefore, the perpetuation of a restored sites requires conscious monitoring and management. Thus, management would be the most important process in ecological restoration. 10. In order to keep the sites "natural", alternative management strategies would be applied in management ; Atenative management strategies are decelerating successional process, accelerating successional processes or modifying species composition. As management tools, mechanical, chemical, biological or environmental factor manipulation, e.g., fire could be used.

• 지구물리와물리탐사
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• 제8권1호
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• pp.50-58
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• 2005

하저지반은 단층대의 분포가능성이 매우 높으나 수층으로 인해 지표지질조사가 불가능하여 단층대를 파악하기가 쉽지 않다. 하상 전기비저항 탐사는 하저지반에 대한 연속적인 영상을 제공하여 주므로 단층이나 연약대의 위치를 파악하는데 매우 효과적인 탐사법이다. 하저터널의 설계에서는 단층대의 위치뿐만 아니라 단층대의 주향방향이 매우 중요한 요소이다. 단층대의 주향방향을 파악하는 방법으로는 격자형의 측선에 대한 광대역 조사가 매우 효과적이다. 하지만. 종래의 하상 전기비저항 탐사는 케이블을 하저에 설치하여야 하므로 광대역 조사에 적합하지 않다. 이에 이 연구에서는 소형보트에 스트리머 케이블을 설치하여 신속하게 광대역의 하저지반을 영상화하는 스트리머 전기비저항 탐사의 적용성에 대해 고찰하였다. 스트리머 전기비저항 탐사에 의한 단층대의 분해능을 고찰하기 위하여, 수직단층이 수층 하부의 퇴적층에 피복되어 있는 모형을 설정하여 수치모형실험을 수행하였다. 전극의 설치위치와 수심의 변화에 따른 수직단층의 분해능에 대해 살펴보았으며, 그 결과 수층의 두께가 전극간격의 2 배 이내인 경우에는 전극을 수층 표면에 설치하는 방식으로도 단층을 영상화할 수 있음을 보였다. 또한, 스트리머 전기비저항 탐사에 적합한 4 가지의 전극배열법을 설정하여 신호대 잡음비와 수직 단층의 분해능을 비교 검토하였다. 수치모형실험을 기초로 하여 한국 서울에 위치한 한강의 하저터널 예정부지에서 하상 전기비저항 탐사를 수행하였다. 하저터널 예정노선에서는 고분해능의 영상이 요구되므로 하저에 전극을 설치하여 자료를 획득하였으며, 2차원 역산을 적용하여 강 양단에서 단층대로 추정되는 3개의 저비저항 이상대를 탐지하였다. 저비저항 이상대의 윈인을 규명하기 위하여 시추조사를 수행하였으며, 그 결과 수 m 이상의 폭을 가지는 다수의 단층이 관측되었다. 단층대의 주향방향을 탐지하기 위하여 확인된 저비저항 이상대를 중심으로 격자형의 측선을 설정하여 스트리머 전기비저항 탐사를 수행하였다. 이를 통해 하저에 케이블을 설치하는 방식에 비해 매우 신속하고 경제적으로 하저에 분포하는 이상대의 분포범위와 발달방향을 규명할 수 있었다.