• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.678-681
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• 2009

사출성형은 열가소성수지의 가공법으로써 정밀도나 고품질의 제품을 효과적으로 생산하는데 널리 이용되며 플라스틱은 현재 광범위하게 사용되고 있는 공업재료 중의 하나이다. 과거에는 플라스틱을 일회용품 및 외장재로 사용하였다. 그러나 산업기술이 발전하며 플라스틱은 금속을 대체 할 수 있는 재료로서 사용할 수 있다는 인식의 변화로 점차 기계요소용 재료로 사용되고 있으며 기계요소용 재료로 사용됨에 따라 플라스틱 제품이 정밀한 부품으로 사용되기 위해서는 금형의 가공뿐만 아니라 사출성형 시 용융수지가 금형의 각 캐비티에 균형적으로 충전되는것이 요구된다. 이러한 요구조건을 만족하기 위해서는 각 캐비티의 가공치수는 매우 높은 정밀도를 유지해야 하며, 각 캐비티에서의 충전과 냉각도 동일한 상태를 유지해야 한다. 충전 불균형은 성형품의 품질에 큰 저해 요인으로서 플라스틱 제품의 치수성, 밀도, 외관품질, 강도 등에 불균일한 결과를 가져오는 요인으로 지적되고 있다. 실제로 충전 불균형은 충전 단계에서 런너 내에서 발생하는 불균일한 전단분포에 기인하여 발생되므로 점도변화에 영향을 주는 수지의 물성, 런너의 배열과 같은 외부 요인과 사출압력, 사출속도, 수지온도, 금형온도와 같은 성형공정 조건에 의한 요인에 의한 충전 불균형의 양상이 달라지게 된다. 본 연구는 다수 캐비티 금형에서 충전 불균형 현상에 대한 원인을 검토하고 실제로 사출성형을 실시하기 전 사출성형해석 소프트웨어를 이용하여 시뮬레이션을 하여 다수 캐비티에 대한 충전 패턴을 미리 예측하여 보았다.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.413-416
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• 2011

Flip top cap은 경량성, 가공성, 내식성 우수하여 최근에 생활 용기 뚜껑으로 많이 활용되고 있다. Flip top cap은 사출성형에 의해 제작 되며 사출성형 과정에서 힌지부분에 웰드라인(Weldline)이 형성되어 기계적 강도가 떨어지게 된다. Flip top cap은 생활용기에 사용되며 실제생활에서 많은 작동을 요구하기 때문에 힌지부분의 웰드라인은 제품불량에 큰 원인이 된다. 또한 Flip top cap은 생산성을 높이기 위해 멀티캐비티(Multi-cavity) 사출방식을 선호한다. 멀티캐비티 방식은 높은 사출압력을 요구하기 때문에 사출품의 불량과 사출기에 많은 부하가 예상된다. 본 연구에서는 게이트 위치를 조정함으로써 사출품 힌지부분에서 발생할 수 있는 웰드라인을 품질에 영향이 없는 곳으로 이동시키고 최적의 사출 압력을 찾기 위한 유동해석을 통해 최적의 사출조건을 도출함으로써 Flip top cap의 기계적 품질과 제품생산성 향상을 위한 연구가 수행되었다.

• Journal of Korean Neurosurgical Society
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• v.47 no.3
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• pp.228-231
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• 2010

Posttraumatic syringomyelia may result from a variety of inherent conditions and traumatic events, or from some combination of these. Many hypotheses have arisen to explain this complex disorder, but no consensus has emerged. A 28-year-old man presented with progressive lower extremity weakness, spasticity, and decreased sensation below the T4 dermatome five years after an initial trauma. Magnetic resonance imaging (MRI) revealed a large, multi-septate syrinx cavity extending from C5 to L1, with a retropulsed bony fragment of L2. We performed an L2 corpectomy, L1-L3 interbody fusion using a mesh cage and screw fixation, and a wide decompression and release of the ventral portion of the spinal cord with an operating microscope. The patient showed complete resolution of his neurological symptoms, including the bilateral leg weakness and dysesthesia. Postoperative MRI confirmed the collapse of the syrinx and restoration of subarachnoid cerebrospinal fluid (CSF) flow. These findings indicate a good correlation between syrinx collapse and symptomatic improvement. This case showed that syringomyelia may develop through obstruction of the subarachnoid CSF space by a bony fracture and kyphotic deformity. Ventral decompression of the obstructed subarachnoid space, with restoration of spinal alignment, effectively treated the spinal canal encroachment and post-traumatic syringomyelia.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.6
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• pp.753-765
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• 2003

A finite element code for the numerical solution of the Navier-Stokes equation is parallelized by vertex-oriented domain decomposition. To accelerate the convergence of iterative solvers like conjugate gradient method, parallel block ILU, iterative block ILU, and distributed ILU methods are tested as parallel preconditioners. The effectiveness of the algorithms has been investigated when P1P1 finite element discretization is used for the parallel solution of the Navier-Stokes equation. Two-dimensional and three-dimensional Laplace equations are calculated to estimate the speedup of the preconditioners. Calculation domain is partitioned by one- and multi-dimensional partitioning methods in structured grid and by METIS library in unstructured grid. For the domain-decomposed parallel computation of the Navier-Stokes equation, we have solved three-dimensional lid-driven cavity and natural convection problems in a cube as benchmark problems using a parallelized fractional 4-step finite element method. The speedup for each parallel preconditioning method is to be compared using upto 64 processors.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.6
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• pp.847-851
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• 2010

It was attempted to develop an auto part by over molding injection mold that produces precision products in high productivity with use of an eco-friendly TPE substitute material for NBR. NBR is currently used in motor gear cover, one of the key parts in motor module for auto doors. Gear cover is composed of plastics and rubber mostly today, which requires a two (2) step process for production using two presses of different types. A hot press is used at this time for forming the rubber, which has drawback of requiring a rather long forming time of 400 seconds for one forming process. Even though this difficulty is overcome by reducing production time through employment of multi-cavity molds, time for forming process must be shortened for improvement of the productivity eventually, and the existing method of insert injection for products that have been formed with plastic material must be outgrown. In this point of view, over molding injection using TPE has a big advantage. Forming time is shortened to 54 seconds, and working the two (2) processes in series by one (1) press could solve the durability problem caused by deflection of the plastics, not to mention shortening the process time. Enhancement of productivity by almost 80% and improvement in the accuracy of the product could thus be achieved.

• Journal of Korean Neurosurgical Society
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• v.44 no.3
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• pp.170-173
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• 2008

Ventriculoperitoneal (VP) shunt is commonly and effectively used to treat hydrocephalus. Intracardiac migration of the shunt catheter is a rare complication. A 68-year-old woman underwent ventriculoperitoneal shunting for hydrocephalus secondary to subarachnoid hemorrhage due to anterior communicating artery aneurysm rupture. Two weeks after the shunt surgery, she had suffered from the abdominal pain. Plain chest x-rays, computed tomography, and echocardiography revealed the distal catheter which was in the right ventricle of the heart. We tried to remove the catheter through the internal jugular vein by fluoroscopic guidance. But, the distal catheter was kinked and knotted; therefore, we failed to withdraw the catheter. After then, we punctured the right femoral vein and pulled down the multi-knotted shunt catheter to the femoral vein using the snare catheter. Finally, we removed the knotted distal catheter via the femoral vein and a new distal catheter was placed into the peritoneal cavity. We report a case in which the distal catheter of the VP shunt migrated into the heart via the internal jugular vein. We emphasize the importance of careful and proper placement of the distal catheter during the tunneling procedure to prevent life-threatening complications.

• Journal of Korean Medical classics
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• v.36 no.1
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• pp.17-32
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• 2023

Objectives : This paper investigates the background, meaning and origin of the descriptions of the Heart such as 'seven orifices', 'sanmao', 'saw-toothed four layered lines' that are unique to the diagram in the Donguibogam. Methods : First the Heart diagram of the Donguibogam was compared with other Zhangfu diagrams of the past. Materials related to unique features in the descriptions of the Heart in the Donguibogam were collected, against which descriptive features were analyzed. Results : Of the many unique features, the descriptive basis of the 'seven orifices' could be found in the Qixingban[七星板] as a physical entity reflecting basic anatomical knowledge. The 'sanmao', which is compared to the Santaixing[三台星], could be understood as a non-physical entity whose descriptive basis could be found in the Xinxuetu of the Xinching. It could be assumed that the 'saw-toothed four layered lines' are likened to the multi-layered petals or calyx of a lotus flower bud to describe the Pericardium, or to the multiple walls of a mountain fortress surrounding a palace to describe the Danzhong, which is the chest cavity. These features could be understood as results of spiritualism influence. Conclusions : It could be concluded that Heo Jun, in his attempt to describe the Heart in more detail than previous diagrams of the Zangfu, referenced popular texts and images based on anatomical knowledge of previous texts, added varied descriptions resulting in a new diagram with a completely different origin.

• Korean Journal of Heritage: History & Science
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• v.45 no.1
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• pp.86-101
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• 2012

The constituting rocks of Multi-storied Round shape stone Pagoda of Unjusa Temple are lithic tuff and rhyolite tuff breaccia which show green or grey and also rock fragment with poor roundness are present in the structure. lithic tuff is composed of feldspar and quartz which are glassy texture and cryptocrystalline and also micro crystalline are scattered. phenocryst quartz and feldspar in the substrate composed of feldspar and opaque minerals are found in rhyolite tuff breaccia. dust, exfoliation, cavity, fracture and crack are observed in all the stone of the pagoda and the result of Infrared Thermography shows partial inter cavities have developed severely which may cause further exfoliation. In addition, a great deal of various grey, green, and yellow brown lichen as well as bryophyte are present at the upper part of eastern and western roof stone located above the third floor. Discolors remarkably shown at stereobate and roof stone are identified as inorganic pollutants such as manganese oxide, iron oxide and iron hydroxide. The stone of the pagoda of the Chemical Index of Alteration (CIA) and the Weathering Potential Index (WPI) are 55.69 and 1.12 respectively and this corresponds to a highly weathered stage. The measured values, average ultrasonic velocity 2,892m/s, coefficient of weathering 0.4k and compressive strength $1,096kg/cm^3$, suggest that the rock strength and durability are weakened.

• Journal of Korean society of Dental Hygiene
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• v.4 no.2
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• pp.277-291
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• 2004

The purpose of this study is to analyze the dental hygienists' overall performance in operative restoration and the clinical performance in operative restoration according to dental hygienists' career and to provide basic data for establishing the appropriate range of dental hygienists' work. Subjects of this study are 339 dental hygienists working at dental clinic and hospital nationwide, selected by their working place, career, type of clinic, and location of clinical institution. The distribution of people who responded to the survey shows that 81 belong to beginner level(less than 2 years since entering clinic), 115 intermediate level(2 to 3 years since entering clinic), 81 higher level(4 to 5 years since entering clinic) and 62 advanced level(more than 6 years since their entering clinic). In terms of the types of clinical institution, 178 belong to dental clinics and 161 belong to dental hospitals. The survey used in this study are focused on perception about clinical performance in operative dentistry and adequacy of the work. Operative dentistry consists of operative restoration and endodontic therapy. The operative restoration consists of 15 categories such as patient welcoming, examination and diagnosis, planning of treatment, anesthesia, control of moisture, cavity preparation, pulp protection, matrix band application, amalgam filling, resin filling, glass ionomer cement filling, abrasive strip removal, rubber dam removal, bite check and polishing, patient education, and arrangement. The reliability was Cronbach's Alpha .9453. SPSS 10.0 for Windows was used to analyze the responses. One way ANOVA was utilized to verify the differences in the dental hygienists' job performance in operative restoration and their job performance according to career. When significant difference was found. Duncan multi comparison post hoc was done. To sum up the results of this study, patient welcoming look the first place in the operative restoration. It was followed by patient education, examination and diagnosis, introducing treatment plan, resin filling, glass ionomer cement filling, amalgam filling, bite check and polishing, anesthesia, pulp protection, control of moisture, abrasive strip removal, cavity preparation, matrix band application, rubber dam removal, and anesthesia. In terms of the clinical performance by career, there were significant differences in 19 activities such as medical eraluation, oral examination, patient charting, intra oral readio graphs, firm developing fixing mounting, curing light gun, education of attention content after operation. Based on the results of this study, the specific range of operative restoration for dental hygienists should be focused on providing basic data for dentists' diagnosis, alleviation of fear and aching accompanied by injection and anesthesia, data providing for dentists' decision of anesthesia degree, and maximization of control of moisture.

• The Korean Journal of Rheology
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• v.10 no.4
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• pp.217-226
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• 1998

The anisotropy caused by the fiber orientation, which is inevitably generated by the flow during injection molding of short fiber reinforced polymers, greatly influences dimensional accuracy, mechanical properties, and other quality of the final product. Since the filling stage of the injection molding process plays a vital role in determining fiber orientation, an accurate analysis of flow field for the filling stage is needed. Unbalanced filling occurs when a complex or a multi-cavity mold is used leading to development of regions where the fiber suspension is under compression. It is impossible to make an accurate calculation of the flow field during filling with the analysis assuming incompressible fluid. A mold with four cavities with different filling times was produced to compare the numerical analysis results with the experimental data. There was a good agreement between the experimental and theoretical results when the compressibility of the polymer melt was considered for the numerical simulation. The fiber orientation states for compressible and incompressible fluids were also compared qualitatively as well as quantitatively in this study.