• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2001.10a
• /
• pp.216-219
• /
• 2001

The production of fine wire through multi-pass wet wire drawing process would be impossible with no backtension at inlet of dies. Backtension is affected by many process parameters, such as dies reduction, coiling number of wire at capstan, machine constant, slip between wire and capstan, characteristic of lubricant and so on. Up to date, dies design and dies pass schedule of multi-pass wet wire drawing process have performed by trial and error of expert in the Industrial field without consideration of quantitative relation among process variables. Thus study investigates the multi-pass wet wire drawing process considering the relation among process variables, such as dies reduction, coiling number of wire at capstan, machine constant, slip between wire and capstan, etc. And analysis program which can analyze many important process values(drawing force, backtension force, slip rate, slip velocity rate, etc) for die design and dies pass schedule of multi-pass wet wire drawing process was developed.

• Journal of Korean Neurosurgical Society
• /
• v.51 no.3
• /
• pp.155-159
• /
• 2012

The treatment of bilateral vertebral artery dissecting aneurysms (VADAs) presenting with subarachnoid hemorrhage (SAH) is still challenging. The authors report a rare case of bilateral VADA treated with coil trapping of ruptured VADA and covered stents implantation after multiple unsuccessful stent assisted coiling of the contralateral unruptured VADA. A 44-year-old woman was admitted to our hospital because of severe headache and sudden stuporous consciousness. Brain CT showed thick SAH and intraventricular hemorrhage. Cerebral angiography demonstrated bilateral VADA. Based on the SAH pattern and aneurysm configurations, the right VADA was considered ruptured. This was trapped with endovascular coils without difficulty. One month later, the contralateral unruptured VADA was protected using a stent-within-a-stent technique, but marked enlargement of the left VADA was detected by 8-months follow-up angiography. Subsequently two times coil packing for pseudosacs resulted in near complete occlusion of left VADA. However, it continued to grow. Covered stents graft below the posterior inferior cerebellar artery (PICA) origin and a coronary stent implantation across the origin of the PICA resulted in near complete obliteration of the VADA. Covered stent graft can be used as a last therapeutic option for the management of VADA, which requires absolute preservation of VA flow.

• Journal of Korean Neurosurgical Society
• /
• v.49 no.2
• /
• pp.134-138
• /
• 2011

Pediatric patients with dissecting aneurysms usually present with ischemia rather than bleeding. We report a case of a 15-year-old boy with a dissecting aneurysm of the posterior cerebral artery (PCA) presenting with hemorrhage. He was first treated with stent-assisted coil embolization, in an attempt to avoid trapping of the PCA and preserve the perforators. After the procedure, he recovered well from general anesthesia, but rebleeding occurred from the same lesion 6 hours after the procedure, therefore endovascular segmental occlusion of the parent artery was performed secondarily. Apparently, a reconstructive method of stent-assisted coiling is worth trying to preserve the parent vessel and perforators, but it is not always efficient and durable for dissecting aneurysms.

• Journal of the Korean earth science society
• /
• v.25 no.8
• /
• pp.799-811
• /
• 2004

In this one species of planktonic foraminifers, Neogloboquadrina pachyderma, which has been collected from the sediments cores in the northeast Pacific ODP sites, was computerized through using digitalized images. The foraminiferal communities were analyzed, and the coiling direction of the N. pachyderma was determined by using computer progamming technology. In this way by appling algorithm-based method of reading, the tasks of sorting and analyzing the foraminiferal indiniduals and communities can be performad and high speed on a very large amount of specimens collected. It is found that the study had 90% accordance with the result of stereoscopic observation. This result suggested that digital image analysis could be successfully adopted in the field of micropaleontology.

• Journal of the Korean Society of Visualization
• /
• v.2 no.2
• /
• pp.52-57
• /
• 2004

The development and interaction of vortices over a delta wing with leading edge extension (LEX) was investigated through off-surface flow visualization using micro water droplets and a laser beam sheet. Angles of attack of $20^{\circ}$ and 24$^{\circ}$ were tested at sideslip angles of $0^{\circ}$, $-5^{\circ}$, and $-10^{\circ}$ The flow Reynolds number based on the main-wing root chord was $1.82{\times}10^{5}$. The wing vortex and the LEX vortex coiled around each other while maintaining comparable strength and identity at a zero sideslip. The increase of angle of attack intensified the coiling and shifted the cores of the wing and LEX vortices inboard and upward. By sideslip, the coiling, the merging and the diffusion of the wing and LEX vortices were increased on the windward side, whereas they were delayed significantly on the leeward side. The present study confirmed that the sideslip angle had a profound effect on the vortex structure and interaction of a delta wing with LEX, which characterized the vortex-induced aerodynamic load.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.08a
• /
• pp.390-398
• /
• 1999

The thermomechanical control process(in hot rolling strip mill) was employed to produce 2.25Cr-1Mo steel, which is to be construction material for the steam generator for power plant. Although the Conventional processes has been the primary means of producing the 2.25Cr-1Mo steel, an alternative method was used to meet the specification of ASTM heat treatment for A387-22-Classl using autotempering after coiling in hot rolling strip mill. The microstructures, tensile properties at various temperatures, and creep-rupture properties have been investigated to compare the properties with those of materials produced by the conventional process and to certify the application of the thermomechanical control process to an actual process of manufacturing 2.25-Cr-1Mo steel, this in turn, will reduce the cost of the process. About 14 to 34% glanular bainite (remainder proetectoid ferrite) formed in a coil, and this variety of volume fraction stems from the different cooling rates, which varies with position of the coil after coiling. Tensile testing from room temperature to 700$^{\circ}C$ indicated that strength increases with test temperature showing peaks at around 600$^{\circ}C$. Creep-rupture properties have been being investigated at the temperature of 500$^{\circ}C$ with 27.5, 32kg/$\textrm{mm}^2$ loads and have showed no rupture for over 1000 hours.

• Journal of Korean Neurosurgical Society
• /
• v.50 no.1
• /
• pp.45-47
• /
• 2011

Abnormal contrast enhancement on brain computed tomography (CT) scan after diagnostic or interventional angiography is not rare, and has known to be induced by temporary blood-brain barrier (BBB) disruption from contrast media. Furthermore, it has been regarded as clinically subtle, but reported to have no symptom or mild transient symptoms. However, we recently experienced two cases of serious BBB disruption during the acute period after coiling of an unruptured intracranial aneurysm. One patient presented with an unruptured paraclinoid internal carotid artery (ICA) aneurysm on the right and the other with an unruptured right supraclinoid ICA aneurysm. Both patients showed similar findings on immediate postembolization CT scan and clinical courses after coiling. Typical radiological, clinical characteristics of BBB disruption were described. In addition, the role of immediate postembolization CT scan are also discussed.

• Transactions of Materials Processing
• /
• v.20 no.6
• /
• pp.450-455
• /
• 2011

This paper presents an inverse design methodology for the cross section geometry of mold spring with a rectangular cross section as the starting material for a coiling process. The cross-sections of mold springs are universally rectangular, as the parallel sides minimize the possibility of failure under high service loads. Pre-coiled wires are initially designed to have a trapezoidal cross section, which becomes a rectangle by the coiling process. This study demonstrates a numerical exercise to predict changes in the sectional geometry in spring manufacture and to obtain the initial cross section which becomes the exact rectangle desired from the manufacturing process. Finite element analysis was carried out to calculate the sectional changes for various mold springs. Geometrical parameters were the widths at inner and outer radii, the inner and the outer corner radii, and the height. A partial least square regression analysis was carried out to find the main contributing factors for deciding initial design values. The height and the width mainly affected various initial parameters. The initial width at the inner radius was mostly affected by various specification parameters.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2011.04a
• /
• pp.574-578
• /
• 2011

본 논문에서는 해저케이블 부두 하역용 장비인 코일링 암(coiling arm)에 대한 구조설계 및 해석을 수행하였다. 본 연구에서는 구조설계를 위해 3차원 CAD프로그램을 이용하여 모델링하였고 구조해석 프로그램을 이용하여 유한요소법에 기초한 전산해석 기법으로 해석을 수행하였다. 코일링 암의 목적에 맞추어 케이블을 케이블 탱크에 가이드 할 수 있도록 베어링 및 롤러를 설계하여 메인 암이 회전하고 케이블 가이드가 이동할 수 있도록 하였고, 기존의 외국 모델에서 사용하던 와이어 및 모터 시스템을 이용한 케이블 가이드 작동방식을 유압 시스템을 이용한 작동방식으로 변경하여 설계 및 제작이 쉽고 사용자가 직관적으로 작동할 수 있도록 설계하였다. 자중 및 케이블 하중에 대한 응력 해석을 수행하였고, 유압시스템에 의한 파손 가능성을 고려하였다. 케이블 가이드에 이동 및 지면 경사도에 따른 전복해석을 수행하였으며, 설치 장소를 고려한 풍하중 효과도 추가로 고려하였다. 본 연구를 통해 코일링 암의 작동방식을 개선하였으며 설계 및 해석 방법을 확립과 더불어 국내 최초로 실제 코일링 암을 제작 및 설치하였다.

• Journal of Cerebrovascular and Endovascular Neurosurgery
• /
• v.20 no.4
• /
• pp.235-240
• /
• 2018

The safety and feasibility of simple coil embolization and stent deployment for the treatment of posterior inferior cerebellar artery (PICA) aneurysms, as well as their radiologic and clinical results, have not been adequately understood. Especially, if dissecting aneurysm of proximal PICA is associated with small caliber PICA and stenosis of ipsilateral vertebral artery orifice (VAO), endovascular coiling with saving of PICA is not always easy. This 64-year-old man presented with subarachnoid hemorrhage due to a ruptured dissecting aneurysm of left proximal PICA. The aneurysm was irregularly fusiform in nature with a shallow PICA orifice (1.4 mm) and narrow caliber (0.9-1.5 mm). Moreover, the ipsilateral VAO showed severe stenosis (1.8 mm). We performed bifemoral puncture and chose additional route from right vertebral artery to left vertebrobasilar junction for retrograde approach and deployment of LVIS Jr. intraluminal support at proximal PICA. And then, the antegrade approach and coiling of aneurysm was done. Despite of transient thrombus of PICA, the aneurysm was successfully secured with preservation of whole PICA course. For preservation of narrow PICA with ipsilateral VAO stenosis, the contralateral approach and deployment of LVIS Jr. intraluminal support may be considered.