• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.124-124
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• 2004

최근 MEMS공학의 발전으로 미소 가공물과 그 미소 가공물을 가공하는 공작기계의 발전이 두드러지고 있다. 마이크로 성형기는 이러한 미소 가공물을 만드는 공작기계들 중의 하나이다. 마이크로 성형기(micro former)는 마이크로 홀(micro holl)을 만드는 성형기로써 크랭크 축의 회전에 의한 펀치의 직선 운동으로 마이크로 홀을 뚫는 성형기이다. 마이크로 홀을 성형할 때에는 상하, 좌우의 미세한 변위가 생길 수 있다.(중략)

• Composites Research
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• v.35 no.3
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• pp.147-152
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• 2022

Low-temperature characteristics according to internal temperature conditions during rotational molding of Type 4 pressure vessel liners were studied in this paper. Since rotational molding has a sensitive effect on the formability of the liner depending on the temperature conditions, the temperature conditions for the polyamide used should be accurately set. The structural changes of polyamide as the liner material was analyzed the surface by atomic force microscope (AFM), and the crystallinity measured with a differential scanning calorimeter (DSC) is used to evaluate the change of the mechanical strength value at low temperature. In addition, the formability of the liner was confirmed by observation of the yellow index inside the liner. As a result, as the melting range of the internal temperature becomes wider, the yellow index shows a lower value, and the elongation and impact characteristics at low temperatures are improved. It was also confirmed that the structure of the polyamide was uniform and the crystallinity was high by AFM and DSC. These experimental results contribute to the improvement of characteristics at low temperatures due to changes in temperature conditions during rotational molding.

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.243-244
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• 2007

본 연구에서는 성형용 코어 가공에서 초경합금(WC, Co 0.5%)의 초정밀 가공특성을 파악하기 위하여 다이아몬드 휠의 메시, 주축 회전속도, 터빈 회전속도, 이송속도 및 연삭깊이에 따른 표면거칠기를 측정하여 최적연삭조건을 규명하였다. 규명된 최적연삭가공조건을 활용하여 페러렐 연삭법으로 초정밀 연삭가공을 수행하였다. 연삭가공은 초정밀가공기(ASP01, Nachi-Fujikoshi Co., Japan)를 사용하였다. 최종 정삭가공을 수행한 비구면 성형용 코어의 형상측정결과 형상정도(PV; ${\varphi}$ 3.0mm) 0.15${\mu}m$(비구면), 0.10${\mu}m$(평면)으로 3M급 이상의 고화질 카메라폰에 채용되고 있는 비구면 Glass렌즈 양산용 성형용 코어 규격에 만족한 결과로서 본 연구에 수행된 초정밀 가공조건 및 측정방법이 매우 유효함을 알 수 있었다. 형상정도(PV) 및 표면조도(Ra) 측정은 초정밀 자유곡면 측정기(UA3P, Panasonic Co., Japan)와 3차원 표면조도 측정기(NewView5000, Zygo Co., USA)를 각각 사용하였다. 초정밀 가공된 성형용 코어면에 이온증착법을 활용하여 DLC 코팅을 수행하였다. 코팅 전후의 성형용코어를 활용하여 Glass소재(K-BK7, Sumita Co., Japan)를 최적의 성형조건(성형온도, 압력, 냉각속도)으로 성형하였다. DLC 코팅과 성형은 DLC 코팅기(NC400, Nanotech Co., Japan)와 Glass렌즈 성형기(Nano Press-S, Sumitomo Co., Japan)을 각각 사용하였다. Fig. 1은 초정밀 연삭가공, DLC 코팅막 구조, 코팅된 성형용 코어, 그리고, 성형된 비구면Glass렌즈를 각각 나타낸다.

• Restorative Dentistry and Endodontics
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• v.31 no.3
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• pp.179-185
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• 2006

This study was conducted to evaluate canal configuration after shaping by $ProTaper^{TM}$ with various rotational speed in J-shaped simulated resin canals. Forty simulated root canals were divided into 4 groups, and instrumented using by $ProTaper^{TM}$ at the rotational speed of 250, 300, 350 and 400 rpm. Pre-instrumented and post-instrumented images were taken by a scanner and those were superimposed. Outer canal width, inner canal width, total canal width, and amount of transportation from original axis were measured at 1, 2, 3, 4, 5, 6, 7 and 8 mm from apex. Instrumentation time, instrument deformation and fracture were recorded. Data were analyzed by means of one-way ANOVA followed by Scheffe's test. The results were as follows 1. Regardless of rotational speed, at the $1{\sim}2mm$ from the apex, axis of canal was transported to outer side of a curvature, and at 3~6 mm from the apex, to inner side of a curvature. Amounts of transportation from original axis were not sienifcantly different among experimental groups except at 5 and 6 mm from the apex. 2. Instrumentation time of 350 and 400 rpm was significantly less than that of 250 and 300 rpm (p<0.01). In conclusion the rotational speed of $ProTaper^{TM}$ files in the range of $250{\sim}400rpm$ does not affect the change of canal configuration, and high rotational speed reduces the instrumentation time. However appearance of separation and distortion of Ni-Ti rotary files can occur in high rotational speed.

• Journal of Korean Society of Steel Construction
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• v.14 no.5 s.60
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• pp.657-664
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• 2002

This paper described the ultimate strength and deformation limit of the new uniplanar T-joints in cold-formed square hollow sections. In the configuration of the new T-joint, only a branch member is orientated to a chord member at 45 degrees in the plane of the truss. This study focused on the branch-rotated T-joints that were governed by chord flange failure in previous studies. Test results of the T-joint in cold-formed square hollow sections revealed a deformation limit of 3%B for $16.7{\leq}2{\gamma}(=B/T){\leq}33.3$ and $0.27{\leq}{\beta}(=b1/B){\leq}0.6$. The existing strength formulae for traditional T-joint were determined and a new yield-line model for the branch-rotated T-joint proposed. Finally, the strength formula on the yield-line analysis was compared with test results and the application range of the proposed formula recommended.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.3
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• pp.181-186
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• 2017

Single point incremental forming (SPIF) is a sheet-forming technique. It is a die-less sheet metal manufacturing process for rapid prototyping and small batch production. The Critical parameters in the forming process include tool diameter, step depth, feed rate, spindle speed, etc. In this study, these parameters and the die shape corresponding to the Varying Wall Angle Conical Frustum(VWACF) model were used for forming 0.8mm in thick Al5052-O sheets. The Taguchi method of Experiments of Design (DOE) and Grey relational optimization were used to determine the optimum parameters in SPIF. A response study was performed on formability, spring back, and thickness reduction. The research shows that the optimum combination of these parameters that yield best performance of SPIF is as follows: tool diameter, 6mm; spin speed, 60rpm; step depth, 0.3mm; and feed rate, 500mm/min.

• Clinics in Shoulder and Elbow
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• v.12 no.1
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• pp.7-13
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• 2009

Purpose: To evaluate the clinical and radiological results of arthroscopic tuberoplasty for irreparable massive rotator cuff tears. Materials and Methods: Eleven patients underwent arthroscopic tuberoplasty for irreparable massive rotator cuff tears between December 2004 and April 2007. The mean follow-up period was 17.3 months, and the average age at the time of surgery was 61.7-year-old. Five cases underwent arthroscopic tuberoplasty and 6 cases had arthroscopic subacromial decompression and tuberoplasty, simultaneously. Results: The average Constant score improved from 61.8 to 86.9 and the average UCLA score changed from 14.8 to 31.8 with 6 excellent, 3 good and 2 poor results (p=0.003). The active forward flexion improved from $111.8^{\circ}$ to $154.1^{\circ}$(p=0.011). The acromiohumeral interval increased from 3.94 mm preoperatively to 4.22 mm postoperatively (p=0.12). In the poor UCLA score group, the acromiohumeral interval changed from 1.67 mm preoperatively to 0.94 mm postoperatively. Conclusion: Arthroscopic tuberoplasty may be a second option to relieve the pain of irreparable massive rotator cuff tears and improve the range of motion. However, good results could not be expected if the acromiohumeral interval is < 2 mm preoperatively and decreased postoperatively.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.560-567
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• 2020

Incremental Sheet Forming (ISF) is a unique sheet-forming technique. The process is a die-less sheet metal manufacturing process for rapid prototyping and small batch production. In the forming process, the critical parameters affecting the formability of sheet materials are the tool diameter, step depth, feed rate, spindle speed, etc. This study examined the effects of these parameters on the formability in the forming of the varying wall angle conical frustum model for a pure Al3004 sheet with 1mm in thickness. Using Minitab software based on Back Propagation Neural Network (BPNN) and Genetic Algorithm (GA), a second order mathematical prediction model was established to predict and optimize the wall angle. The results showed that the maximum forming angle was 87.071° and the best combination of these parameters to give the best performance of the experiment is as follows: tool diameter of 6mm, spindle speed of 180rpm, step depth of 0.4mm, and feed rate of 772mm/min.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.433-438
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• 2011

A machine that makes paper cups has many parts, including a barrel cam, an index, and a turret. When the barrel cam, which is the main operating part of the machine, rotates, it pushes the roller fixed on the index, and paper cups are formed as the turret connected to the index rotates. Therefore, the performance of the machine is affected by the barrel cam. In this study, the program for designing barrel cam, which creates the profile of the cam is developed using MATLAB. This profile is used to develop a 3D CAD model by using a 3D CAD program. Dynamic models containing the barrel cam are created on the basis of the profile and 3D laser scan of the barrel cam. Further, the rotation angle of the index in the machine is measured using a high-speed camera. The rotation angles of the dynamics models are compared to verify the effectiveness of the program.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1834-1839
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• 2003

Temperature and velocity distributions of hot air flows in rotational molding machines with two different shapes and structures of oven and inlet were investigated by using FLUENT, a commercial computational fluid dynamics code. The shape and structure of oven and inlet in current rotational molding machine were improved. Two different sizes of mold inside each oven were considered in the analysis. Temperature and velocity distributions of hot air flows in two different rotational molding machines were compared to each other. In order to reduce cycle time and improve product quality in current rotational molding machine, the improved shape and structure of oven and inlet were proposed.