• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.7
• /
• pp.761-768
• /
• 2011

The large surface micro machining system includes the equipments and processes for manufacturing the ultra precision micro patterned products with large surface through the mechanical machining. Recent major issue on the micro machining technology may be the development of optical parts for the back light unit of display which has the largest market. This special issue makes up with three parts; the large surface micro machining system and machine, machining process and forming process. In this paper, the state-of-the-art and core technology of large surface micro machining system is introduced with focus on the manufacturing technology for the back light unit of LCD TV. Then, some research results on the development of a roll die lathe is introduced which involves the concept of machine design, improvement of thermal characteristics in the spindle system, improvement of relative parallelism and straightness between spindle system and long stroke feed table, machining of micro pitch patterns. Finally, the direct forming process is introduced as the future work in the large surface micro machining field.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.14 no.4
• /
• pp.8-13
• /
• 2015

In this study, we fabricated and characterized a nanostructured surface based on a plastic injection molding with a local mold heating (LMH) system. A metal mold core with a closed packed nano convex array (CVA) was achieved by integrated engineering procedures: (1) master template fabrication by anodic aluminum oxidation (AAO), (2) nickel electroforming (NE) process, and (3) post-processing by precision machining. The nickel mold core was utilized to replicate a surface with a closed packed nano concave-array (CCA) based on injection molding using cyclic olefin copolymer (COC) as a plastic material. In particular, an LMH system was introduced to enhance transcription quality of the nano structures by delaying solidification of molten polymer near the surface of the mold core.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.97-100
• /
• 1997

In order to predict the moldability of a injection molded part, a simulation of filling is needed. Especially when short shot is predicted by CAE simulation in the filling stage, there are mainly three ways to solve the problem. Modification of gate and runner, replacement of plastic resin, and adjustment of process conditions are the main ways. Among them, adjustment of process conditions is the most economic way in the cost and time since the mold doesn\\`t need t be modified at all. But it is difficult to adjust the process conditions appropriately in no times since it requires an empirical knowledge of injection molding. In this paper, a fuzzy neural network(FNN) based upon injection molding process is proposed to evaluate moldability in filling stage and also to solve the problem in case of short shot. An adequate mold temperature is generated through the fuzzy neural network where fill time and melt temperature are taken into considerations because process conditions affect each other.

• Polymer(Korea)
• /
• v.30 no.5
• /
• pp.402-406
• /
• 2006

New antibacterial Polyurethane foams for car seat with Urushiol extracted from a natural lacquer were prepared. Influences of antibacterial agent's concentration on the reactivity with isocyanate and the mechanical properties of foams were investigated. It was observed that the urethane formation reaction was delayed a little when the amount of Urushiol was increased. However, the foams made using Urushiol showed similar property to the neat polyurethane foam. In terms of antibacterial property, the foams prepared with Urushiol showed better performance than the neat polyurethane foam.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.3 no.3
• /
• pp.501-507
• /
• 1999

At the mobile unit for adaptation the propagation environment, it is necessity to adapt very fast the weight coefficient vector of adaptive array antenna In this paper, for the BPSK and BFSK signals with S/I=2, S/N=10 subband adaptive array signal processing method to the linear array antenna using the LMS & the Kalman filter algorithm is proposed. For the 4 elements equidistance linear array antenna systems LMS and Kalman algorithms with subband adaptive instruction principles using the subband signal processing method are adopted and the computer simulation results to the constant amplitude envelope signals such as BPSK or BFSK can be seen that the convergence characteristics of directional patterns and the signal following characteristics are more fast and stable.

• Journal of the Korean Society for Precision Engineering
• /
• v.21 no.11
• /
• pp.61-68
• /
• 2004

Recently, there has been an increasing demand for computer-vision based inspection and/or measurement system as a part of factory automation equipment. Existing manual inspection method can inspect only specific samples and has low measuring accuracy as well as it increases working time. Thus, in order to improve the objectivity and reproducibility, computer-aided analysis method is needed. In this paper, front and side profile inspection and/or data transfer system are developed using computer-vision during the inspection process on three kinds of pipes coming from a forming line. Straight line and circle are extracted from profiles obtained from vision using Laplace operator. To reduce inspection time, Hough Transform is used with clustering method for straight line detection and the center points and diameters of inner and outer circle are found to determine eccentricity and whether good or bad. Also, an inspection system has been built that each pipe's data and images of good/bad test are stored as files and transferred to the server so that the center can manage them.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2016.10a
• /
• pp.913-914
• /
• 2016

This paper analyzes the impact of the satellite TWTA non-linearity charateristics for shared band transmission technology to improve spectral efficiency in satellite communication system. In shared band transmission technology for star network, a hub and terminals use same frequency band. In order to receive terminals's signal a hub have to remove the its own DVB-S2 carrier. In this paper the non-linearity impact of satellite TWTA is analyzed for self-interference cancellation.

• Design & Manufacturing
• /
• v.15 no.1
• /
• pp.1-7
• /
• 2021

The position of the gate is one of the important factors for optimal injection molding. This is because inappropriate gate positions cannot fill the cavity uniformly, which can lead to defects such as contraction. In this study, CAE was performed on hot runner injection molding of the washing machine base and plasticity was compared by changing gate position from existing gate position. A total of two alternatives have been applied to compare the plasticity of the washing machine base according to its optimal gate position. The gate position of the improved molds and the gate position of the current mold is analyzed by injection molding analysis. The results of the fill time, the pressure at V/P switchover, clamping force, and deflection were compared. In washing machine base injection molding, the deflection was reduced by about 3.76% in the improved mold 2. In improved mold 1, the fill time during injection molding was reduced by 3.32% to enable uniform charging, and the clamping force was reduced by 31.24%. We have confirmed that the position of the gate can change the charging pressure and the clamping force and affect the quality and cost savings of the molded product.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.25 no.3
• /
• pp.275-284
• /
• 2022

Linear Shaped Charge(LSC) is widely used as a separation system in the field of weapon system. However, there are some disadvantages that are charging lots of explosives due to lack of uniformity and having difficulties of the design of liner and explosives because of manufacturing process. In order to solve these problems, Precision Linear Shaped Charge(PLSC) that can design a liner independently and charge explosives uniformly has been developed. In this study, PLSC was designed to have a proper liner shape and amount of explosives, and the penetration test of PLSC with different stand-off distance from liner to target was conducted. On the basis of the penetration test results of PLSC, the numerical analysis method using AUTODYN was established and verified. The penetrative mechanism and characteristics of PLSC with targets of different materials was analyzed from experimental and numerical results.

• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.183-186
• /
• 2004

본 논문에서는 수중 초음파 통신용 QPSK 버스트 수신기를 DSP시스템을 이용하여 구현하기위한 시스템 설계에 대하여 논한다. 본 논문에서 고려하는 시스템은 25kHz의 반송주파수를 사용하고, 심벌율은 5kHz이며, 데이터 전송율은 10,000bps이다. 송신기에서 심벌정보를 전송하기 위해 펄스성형필터를 거친 신호를 디지털 믹서기를 이용하여 디지털 영역에서 반송주파수 대역으로 신호를 변조한 후 200kHz로 샘플링하는 D/A변환기를 이용하여 전송 아날로그 신호를 생성한다. 수신기에서는 수신 신호를 디지털로 처리하기 위하여 100kHz로 free running하는 A/D 변환기를 이용하여 수신 데이터를 얻는다. 수신기에서는 32심벌 길이의 프리앰블을 이용하여 프레임 동기를 찾음과 동시에 개략적인 심벌시간 동기와 위상편이를 추정한다. 추정한 위상편이값은 2차 PLL (phase-looked loop)의 초기값으로 사용하여 위상 추적을 수행하는 전송 시스템이다. 또한, 된 논문에서는 실해역 전송 시험 테이터를 통하여 조류의 변화에 의해 발생하는 Doppler 편이를 보상하기 위하여 PLL이 필수적으로 필요함을 보인다.