• 제어로봇시스템학회논문지
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• 제14권11호
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• pp.1146-1154
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• 2008

This paper presents a method for the acceleration analysis of multi-legged walking robots in consideration of the frictional ground contact. This method is based on both unified dynamic equation for finding the acceleration of a robot's body and constraint equation for satisfying no-slip condition. After the dynamic equation representing relationship between actuator torques and body acceleration, is derived from the force and acceleration relationship between foot and body's gravity center, the constraint equation is formulated to reconfigure the maximum torque boundaries satisfying no-slip condition from given original actuator torque boundaries. From application of the reconfigured torques to the dynamic equation, interested acceleration boundaries are obtained. The approach based on above two equations, is adapted to the changes of degree-of-freedoms of legs as well as friction of ground. And the method provides the maximum translational and rotational acceleration boundaries of body's center that are achievable in every direction without occurring slipping at the contact points or saturating all actuators. Given the torque limits in infinite normsense, the resultant accelerations are derived as a polytope. From the proposed method, we obtained achievable acceleration boundaries of 4-legged and 6-legged walking robot system successfully.

• 한국재료학회지
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• 제26권1호
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• pp.13-16
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• 2016

Morphology and formation processes of lamellar grain boundaries in titanium rich binary TiAl intermetallics were studied. TiAl alloys containing aluminum content of 44 to 48 at.% were induction-heated to 1723 K followed by helium-gas-quenching at various temperatures. For the Ti-44%Al, few lamellae were observed in samples quenched from higher than 1473 K. Although small peaks of beta phase were detected using X-ray diffraction, only the ordered hexagonal phase (${\alpha}_2$) with clear APB contrast was observed in TEM observation. For the Ti-48 at.%Al alloy, almost no lamellar structure, and straight grain boundaries were observed in samples quenched from higher than 1623 K. The formation of lamellae along grain boundaries was observed in the sample quenched from 1573 K. The fully lamellar microstructures with serrated boundaries were observed in samples quenched from lower than 1473 K. It was found that the formation of ${\gamma}$ platelets took place at higher temperatures in Ti-48 at.%Al than in Ti-44 at.%Al. Although the size of the serration is different, serrated lamellar grain boundaries could be obtained for all alloy compositions employed. The serration appeared to be due to the grain boundary migration induced by precipitation and growth of ${\gamma}$. Differences in transformation characteristics with aluminum content are discussed.

• 한국공작기계학회논문집
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• 제18권2호
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• pp.144-153
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• 2009

It is widely known that no-slip assumptions are often violated on regular basis in micrometer- or nanometer-scale fluid flow. In the case of cavity-filling process of nanoimprint lithography(NIL), slip phenomena take place naturally at the solid-to-liquid boundaries, that is, at the mold-to-polymer or polymer-to-substrate boundaries. If the slip or partial slip phenomena are promoted at the boundaries, the processing time of NIL, especially of thermal-NIL which consumes more tact time than that of UV-NIL, can be significantly improved. In this paper it is aimed to elucidate how the cavity-filling process of NIL can be influenced by the slip phenomena at boundaries and to what degree those phenomena increase the process rate. To do so, computational fluid dynamics(CFD) analysis of cavity filling process has been carried out. Also, the effect of mold pattern shape and initial thickness of polymer resist were considered in the analysis, as well.

• 아태비즈니스연구
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• 제12권3호
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• pp.87-99
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• 2021

Purpose - In this study, I attempt to clarify three theories of firm boundaries (vertical integration): the principal-agent theory, transaction cost theory, and property rights theory. Although these theories have been widely cited and much discussed, it has been found that understanding the commonalities and distinctions of these seemingly familiar theories is difficult. Design/methodology/approach - I present the three theories about the decisions that firms make concerning their boundaries. Then, I compare elemental versions of the theories of the firm. Findings - Comparing the ingredients of the elemental property rights and principal-agent theories shows that they provide a unified account of the costs and benefits of vertical integration. However, the property rights theory in no sense formalizes the transaction cost theory. Research implications or Originality - Clarifying the three theories of the firm can help to construct empirical models and interpret its results.

• 분석과학
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• 제5권1호
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• pp.121-126
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• 1992

GaAs ${\Sigma}=19$, [110] tilt grain boundary의 구조를 투과전자현미경을 이용하여 연구하였다. Higher-Order Laue-Zone(HOLZ) 빔들과 {200} 빔과의 dynamical coupling 결과를 검토하여 입계 양쪽 각각의 입자(grain) 내 Ga-As의 상대적 위치(방향성)를 결정하였으며, 두 입자 사이에는 inversion symmetry가 결합되지 않은 ${\Sigma}=19$ coincidence에 해당하는 교차각이 있었다. 계면은 $\{331\}_A/\{331\}_B$, [110] 결정면을 따라서 발생하는 경향이 강함을 관측했다. 이 facet에서의 원자구조 및 격자이동 등을 고분해 투과전자현미경을 이용하여 밝혔다. 5-, 7-, 그리고 6-member ring의 조합으로 되어 있는 단위를 계면원자구조 model로 제시했다.

• 한국재료학회지
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• 제14권1호
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• pp.35-40
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• 2004

In this study, dissolution characteristics of four types of commercial calcium phosphate ceramics were investigated in distilled water with respect to chemical composition and microstructure. For all samples, no significant damage was observed after 3 days of immersion. Following the 7 days of immersion, surface dissolution of the ceramics containing a crystalline phase susceptible to water such as TCP, even pure hydroxyapatite, was initiated at grain boundaries and the dissolution was extended interior to the material along the grain boundaries. In the considerably dissolved area, there was grain separation followed by the formation of 20 $\mu\textrm{m}$ of cavities. In at least one case, the residual pores on the surface appeared to initiate dissolution. In a dissolved area, a crack during the fracture propagates along the grain boundaries resulting in intergranular fracture, while transgranular fracture occurs in a dense area without significant dissolution.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.246-251
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• 1998

This paper proposes a new building segmentation method from 1m resolution imagery using an Active Contour Model, known as "Balloons". The original balloons, which was designed by Cohen(Cohen, 1991) to extract features from medical images, are modified for building segmentation. The proposed method consists of two phases. Firstly, building boundaries are extracted by balloons with a given position on buildings from an operator. Since balloons actively adjust their shapes according to the boundaries, there is no more shape limitations on detecting buildings. Secondly, buildings are segmented by connecting the corners detected from the building boundaries, because most buildings, which are man-made objects, are effectively described by polygons. The test results show that most buildings are segmented efficiently and easily. The proposed method is new and timely as 1m resolution spaceborne imagery will be available in the very near future. The proposed method can be used fur operational building segmentation from such imagery.

• 웰빙융합연구
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• 제2권1호
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• pp.35-39
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• 2019

This paper presents two social and academic studies on the boundary between cultural production and consumption. The first line of the study on cultural omnivore analyzes the choice of heterogeneous audiences in the face of various cultural offerings. The second line is a study of market categories, which analyzes the responses of peer audiences to objects with different levels of category code compliance. As such, this paper developed a heterogeneous audience model to evaluate objects of different types. This allows us to consider two dimensions of cultural preference: diversity and orientation of selection. To this end, this paper proposes a new analytical frame work to map consumption behavior on these two dimensions. The results suggest that one type of target that values diversity and transformation is particularly resistant to those that span boundaries. We test this argument in the analysis of two large data sets on film and restaurant reviews. Overall, our findings can extend beyond cultural consumption. Outline variability of contextual individuals or individuals in the same situation can cross cultural boundaries even if they are not intentionally pursuing such hybridism.

• Asian Pacific Journal of Cancer Prevention
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• 제15권23호
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• pp.10509-10512
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• 2015

Objective: To investigate the differential features of CT images in children with neuroblastomas (N) and ganglioneuroblastomas (G). Materials and Methods: Clinical data of 12 children in group G and 15 in group N undergoing CT examination and definitely diagnosed by pathology were retrospectively analyzed. The focal conditions were observed and compared in the two groups, including location, size, boundaries, morphology, enhanced degree and mode, abdominal vascular involvement, presence or absence of spanning the midline, infiltration of peripheral organs, angiography manifestations in tumors or surroundings, presence or absence of calcification and vascular tumor emboli as well as metastases of distal organs and lymph nodes. Results: In group N, the incidence of tumors in the adrenal area was conspicuously higher than in group G (P<0.05), while that of tumors with regular morphology and clear boundaries was significantly lower than in group G (P<0.01); Angiography manifestation rate and incidences of vascular embedding, lymph node metastasis, infiltration and organic metastasis in group N were all markedly higher than in group G (P<0.05). There was no statistical significance between the two groups in terms of focal size, presence or absence of calcification and spanning the midline, and enhanced degree and mode, as well as vascular tumor emboli (P>0.05). Conclusions: Mostly located in adrenal areas and with vascular embedding as a primary manifestation, the neuroblastoma extremely readily metastases to lymph nodes and other organs as well as infiltrating local tissues, with dilation on angiography frequent in or around the tumors. With vascular displacement as a primary manifestation, ganglioneuroblastoma has a regular morphology and clear boundaries.

• Ocean and Polar Research
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• 제29권1호
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• pp.55-67
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• 2007

A reference to natural prolongation appeared for the first time in the North Sea Judgement. Although it was not suggested that the concept of natural prolongation would automatically allow for the fixing of a continental shelf boundary, that concept encouraged States to request international tribunals to determine continental shelf boundaries on the basis of the geological and geomorphological features of the seabed. In the Libya v. Malta Case, however, the rejection of geological and geomorphological factors was total. Especially, Natural prolongation was the then checkmated as a relevant fact in delimitation between coasts situated less than 400 nm. apart. There can be no doubt that, in several disputed cases, prominent geomorphological variations are simply ignored ; nevertheless, there are also a few agreements where geological and geomorphological characteristics come into play and, to a certain extent, affect maritime boundaries. Physical characteristics of sea-bed are generally given serious consideration in the boundary delimitation such as the final negotiated boundary of the Australia-Indonesia Continental Shelf boundary Agreement(Timor and Arafura seas) which follows the continental slope bordering the Timor Trench.