• Structural Engineering and Mechanics
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• 제57권5호
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• pp.809-821
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• 2016

Concentric-tube continuum robots have formed an active field of research in robotics because of their manipulative exquisiteness essential to facilitate delicate surgical procedures. A set of concentric tubes with designed initial curvatures comprises a robot whose workspace can be controlled by relative translations and rotations of the tubes. Kinematic models have been widely used to predict the movement of the robot, but they are incapable of describing its time-dependent hysteretic behaviors accurately particularly when snapping occurs. To overcome this limitation, here we present a finite element modeling approach to investigating the dynamics of concentric-tube continuum robots. In our model, each tube is discretized using MITC shell elements and its transient responses are computed implicitly using the Bathe time integration method. Inter-tube contacts, the key actuation mechanism of this robot, are modeled using the constraint function method with contact damping to capture the hysteresis in robot trajectories. Performance of the proposed method is demonstrated by analyzing three specifications of two-tube robots including the one exhibiting snapping phenomena while the method can be applied to multiple-tube robots as well.

• Animal Systematics, Evolution and Diversity
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• 제25권2호
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• pp.197-199
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• 2009

The alpheid shrimps collected from Jejudo Island turned out to be a species belonging to the genus Prionalpheus which is an unreported genus from Korean waters. In this paper, Prionalpheus sulu is reported for the first time from Korean waters with description and illustration.

• Animal cells and systems
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• 제7권1호
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• pp.15-24
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• 2003

Early zoeas of snapping shrimps Alpheus lobidens De Haan,1850 and A. sudara Banner and Banner, 1966 are described and illustrated in detail, based on laboratory-reared materials. A provisional key to the known first alpheid zoeas from Korean coast is provided.

• 전산구조공학
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• 제8권2호
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• pp.153-161
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• 1995

세계적으로 대공간 구조물의 건설은 점점 늘어나고 있으며, 이러한 증가 추세와 함께 붕괴 사고 또한 점차 늘어나고 있다. 보다 안전하고 경제적인 구조물의 구축을 위해서는 사고 및 붕괴의 원인이 정확히 규명되어야 한다. 따라서 이러한 규명을 위하여 대공간 구조물의 붕괴 메커니즘의 정확한 규명이 필요하며, 많은 연구자들에 의한 연구가 보고되고 있다. Step 하중 하에서의 동적 파괴 메커니즘은 비교적 많은 연구가 진행되어 왔으나, 주기성을 가진 동적 외력에 의한 파괴 메커니즘에 관한 연구는 거의 없는 실정이며, Step 하중하에서의 메커니즘과는 매우 다르리라 예상된다. 본 연구는 주기성을 가진 동적 외력에 의한 얕은 EP 쉘(Elliptic Paraboloidal Shell)의 동적 불안정 현상을 Fourier 스펙트럼을 이용하여 분석한다. 즉 1 자유도의 얕은 EP 쉘의 동적 좌굴 현상과 파라메트릭 공진 현상과의 상호 작용을 파악하기 위하여 비선형 응답의 연속 스펙트럼(runing spectrum)을 이용한다. 연구 결과, 동적 불안정 현상은 외력의 성질에 따라 크게 다른 메커니즘을 나타내는 것을 알 수 있다.

• 한국공간구조학회논문집
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• 제20권4호
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• pp.149-158
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• 2020

The governing equation for a dome-type shallow spatial truss subjected to a transverse load is expressed in the form of the Duffing equation, and it can be derived by considering geometrical non-linearity. When this model under constant load exceeds the critical level, unstable behavior is appeared. This phenomenon changes sensitively as the number of free-nodes increases or depends on the imperfection of the system. When the load is a periodic function, more complex behavior and low critical levels can be expected. Thus, the dynamic unstable behavior and the change in the critical point of the 3-free-nodes space truss system were analyzed in this work. The 4-th order Runge-Kutta method was used in the system analysis, while the change in the frequency domain was analyzed through FFT. The sinusoidal wave and the beating wave were utilized as the periodic load function. This unstable situation was observed by the case when all nodes had same load vector as well as by the case that the load vector had slight difference. The results showed the critical buckling level of the periodic load was lower than that of the constant load. The value is greatly influenced by the period of the load, while a lower critical point was observed when it was closer to the natural frequency in the case of a linear system. The beating wave, which is attributed to the interference of the two frequencies, exhibits slightly more behavior than the sinusoidal wave. And the changing of critical level could be observed even with slight changes in the load vector.

• 대한견주관절학회:학술대회논문집
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• 대한견주관절학회 2008년도 제16차 학술대회
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• pp.171-171
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• 2008

발음성 삼두근 증후군은 주관절을 굴곡하거나 신전할 때 삼두근 말단부 일부와 척골 신경이 내상과 전방으로 탈구되는 드문 질환이다. 이학적 검사 만으로는 다른 질환으로 오진되는 경우가 많아 정확한 진단이 필수적이며 확진을 위하여는 척골 신경 및 삼두근의 비정상적인 움직임을 관찰할 수 있는 영상 검사가 필요하다. 초음파 검사는 자기 공명 영상 촬영 등 다른 검사에 비해 간편하고 효과적으로 연부 조직의 동적 검사를 시행할 수 있는 장점이 있다. 저자들은 발음성 삼두근 증후군 환자를 동적 초음파 검사를 사용하여 진단하고 척골 신경 전방 전위술 및 삼두근 내두의 이전술을 시행하여 치유하였기에 문헌 고찰과 함께 초음파 검사의 유용성을 보고하고자 한다.

• 한국해양공학회지
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• 제20권6호
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• pp.75-81
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• 2006

In this study, the dynamic response of the umbilical cable in a deep-water unmanned underwater vehicle system was analyzed. In order to analyze the forces acting on the cable, the launcher and umbilical cable were modeled by the simple 1-D mass-spring system. Damping and dynamic analysis was carried out by a direct time integration scheme using the $Newmark-{\beta}$ method with inverse iteration procedure, considering the nonlinear drag forces acting on the launcher. The obtained results of the present study can be used for the design of connecting the structure of the launcher and cable of the UUV system.

• 한국작물학회지
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• 제46권5호
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• pp.367-374
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• 2001

End-use properties of six Korean waxy wheat lines and their parental plants were evaluated in this study. Korean waxy wheat lines showed unsuitable characteristics for end products, such as sticky crumb of bread, sticky cooked wet and dry noodles and small cookie diameter. Korean waxy wheat lines produced lower loaf volume and less desirable crumb grain structure of bread, and lower chewiness of cooked wet and dry noodles than their parental plants even though Korean waxy wheats were much higher in protein content and SDS-sedimentation volume than their parental plants. We observed adverse effects of high flour protein content in Korean waxy wheat lines, such as smaller cookie diameter and harder snapping force than those produced from their parental plants.

• 대한기계학회논문집A
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• 제31권5호
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• pp.617-624
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• 2007

This paper presents a novel quadstable monolithic mechanism (QsMM) which provides four stable equilibrium positions within its operation range. The quadstable mechanism has been realized from the use of both X- and Y-directional bistable structures which use curved snapping beams. A millimeter-scale brass mechanism was fabricated by ultra-precision milling to test the quadstability and the displacement-load behavior, and the prototype clearly demonstrated four distinct stable positions in its millimeter-scale planar operation. We discuss the design concept, finite element simulation for static and transient responses, fabrication by ultra-precision milling, and experimental measurement of the proposed quadstable mechanism.

• Fisheries and Aquatic Sciences
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• 제10권1호
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• pp.37-42
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• 2007

The snapping shrimp Alpheus bisincisus is redescribed on the basis of nine specimens collected in southern Korea. This species is readily distinguished from the other reported species of the Edwardsii group of Alpheus from Korea (A. heeia, A. hoplocheles, A. japonicus, A. lobidens, A. malabaricus, A. pacificus, A. richardsoni, and A. sudara) by having the rostrum and rostral triangle on the carapace flattened dorsally and sharply demarked, and by the presence of overhanging orbitorostral grooves.