• 한국정밀공학회지
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• 제9권4호
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• pp.36-43
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• 1992

This paper presents a hierarchical real-time operation control and monitoring scheme of the FMS/CIM center which has been implemented at the Automation and Systems Research Institute of Seoul National University. The hierarchical structure of the whole scheme consists of three lavers. The upper layer is in charge of on-line scheduling, computer network control, shop-floor monitoring and command generation for AGV dispatching, machining, assembly, inspection, set-up, etc. The middle layer has six modules, which are installed in the FMS host computer with the upper layer and run on the multi-tasking basis. Each module is connected to one of six cell controllers distributed in the FMS model plant and transfers operation command down to each cell controller through the Ethernet/TCP-IP local area network. The lower layer is comprised of six cell control software modules for machining cell, assembly cell, inspection cell, set-up stations. AS/RS and AGV. Each cell controller reports the status of the manufacturing facilites to the middle layer as well as ecxecuting the appropriate sequence control of the manufacturing processes.

• 한국분말재료학회지
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• 제4권3호
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• pp.196-204
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• 1997

Joining of AIN ceramics to W and Cu by active-metal brazing method was tried with use of (Ag-Cu)-Ti alloy as insert-metal. Joints were produced under various conditions of temperature, holding time and Ti-content in (Ag-Cu) alloy Reaction and microstructural development in bonded interface were investigated through observation and analysis by SEM/EDS, EPMA and XRD. Joint strengths were measured by shear test. Bonded interface consists of two layers: an insert-metal layer of eutectic Ag- and Cu-rich phases and a reaction layer of TiN. Thickness of reaction layer increases with bonding temperature, holding time and Ti-content of insert-metal. It was confirmed that the growth of reaction layer is a diffusion-controlled process. Activation energy for this process was 260 KJ/mol which is lower than that for N diffusion in TiN. Maximum shear strength of 108 MPa and 72 MPa were obtained for AIN/W and AIN/Cu joints, respectively. Relationship between processing variables, joint strength and thickness of reaction layer was also explained.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권9호
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• pp.2213-2231
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• 2013

Compressed sensing is a novel technology used in the field of wireless communication and sensor networks for channel estimation, signal detection, data gathering, network monitoring, and other applications. It plays a significant role in highly secure, real-time, well organized, and cost-effective data communication in smart-grid (SG) systems, which consist of multi-tier network standards that make it challenging to synchronize in power management communication. In this paper, we present a multi-layer communication model for SG systems and propose compressed-sensing based data transmission at every layer of the SG system to improve data transmission performance. Our approach is to utilize the compressed-sensing procedure at every layer in a controlled manner. Simulation results demonstrate that the proposed monitoring devices need less transmission power than conventional systems. Additionally, secure, reliable, and real-time data transmission is possible with the compressed-sensing technique.

• 한국표면공학회지
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• 제22권1호
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• pp.26-42
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• 1989

It has between investigated that the optimum spaying conditions, such as, spraying distance, fusing temperature and fusing time, ect, in a Ni-cr base self fluxing alloy sprayed on the mild steel substrate by oxygen-acetylenc flame spraying. Sprayed specimens on various conditions were fuused in a vacuum furnace and the results were as follows. The optimum spraying condition for excellent coating layer are obtained under spraying distances, fusing temperature and fusing and time ; 180~240mm,1050~110$0^{\circ}C$and 15~30min, respectively. The adhesive strength and surface hurface hardness of the as sprayed specimens were very low by mechanical bonding becaus of the diffusion layer during process. The carbides and borides and formed in the sprayed coating layer and densification of the layer was resulted from the elimination of pores and oxides. The hardness of sprayed coating layer, particularly in the high temperature, was superior to ordinary tool steels.

• 전자공학회논문지D
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• 제34D권6호
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• pp.43-49
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• 1997

Tungsten poycide has studied gate oxide reliability and dielectric strength charactristics as the composition of gate electrode which applied submicron on CMOS and MOS device for optimizing gate electrode resistivity. The gate oxide reliability has been tested using the TDDB(time dependent dielectric breakdwon) and SCTDDB (stepped current TDDB) and corelation between polysilicon and WSi$_{2}$ layer. iN the case of high intrinsic reliability and good breakdown chracteristics on polysilicon, confirmed that tungsten polycide layer is a better reliabilify properities than polysilicon layer. Also, hole trap is detected on the polysilicon structure meanwhile electron trap is detected on polycide structure. In the case of electron trap, the WSi$_{2}$ layer is larger interface trap genration than polysilicon on large POCL$_{3}$ doping time and high POCL$_{3}$ doping temperature condition. WSi$_{2}$ layer's leakage current is less than 1 order and dielectric strength is a larger than 2MV/cm.

• 한국표면공학회지
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• 제31권5호
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• pp.266-277
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• 1998

The effects of $H_2S$ gas ratio, temperature and time on the case depth, hardness, and sulfide and nitride formation on the surface of sulfnitrided SCM440 steel have been studied by micro-pulse plasma technique. The thickness of compound layer of sulfide and nitride increased with the increase of time, temperautre and $H_2S$ gas ratio. But surface hardness decreased with the increase of soft sulfide layer because the hard nitride layer formed beneath the sulfide. The thickness of sulfide layer was about 10$\mu\textrm{m}$ abpve 0.0088% of $H_2S$ gas. The highest surface hardness of the compound layer was Hv835 at $530^{\circ}C$, 1hr and 0.06% of $H_2S$ gas. X-ray diffraction indicated that the surface products were $Fe_{1_x}S$, $Fe_{2.5}N$ and $Fe_4N$. It was confirmed by EPMA that sulfide only existed in the surface.

• 대한수학회지
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• 제60권2호
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• pp.465-477
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• 2023

In this study, we consider a heat equation with a variable-coefficient linear forcing term and a time-periodic boundary condition. Under some decay and smoothness assumptions on the coefficient, we establish the existence and uniqueness of a time-periodic solution satisfying the boundary condition. Furthermore, possible connections to the closed boundary layer equations were discussed. The difficulty with a perturbed leading order coefficient is demonstrated by a simple example.

• 한국재료학회지
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• 제28권4호
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• pp.201-207
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• 2018

Infrared(IR) heating has many advantages, such as energy efficiency, reduced heating time, cleanliness, equipment compactness, high drying rate and easy automation. These features of IR heating provide widely industrial applications, such as surface heat treatment in semiconductor fabrication, thermoforming of polymers, drying and disinfection of food products, heating to metal forging, and drying of wet materials. In this study, the characteristics of a protected gold mirror were examined by spectrophotometer and the lifetime of the coating layers were evaluated by a cross-cutting method and salt spray test. The effects of manufacturing conditions on the protected gold mirror were seen and remedies for these effects were noted in order to improve the properties of the protected gold mirror in the drying process. The reflectance and lifetime of the protected gold mirror was influenced by manufacturing conditions, such as surface roughness and forming conditions of the anti-oxide layer, the adhesion layer, the reflecting layer and the protection layer. The results of this study showed that the protected gold mirror manufactured using a buffing method for pre-treatment resulted in the most effective reflectance. In addition, $Al_2O_3$ coating on an Al substrate as an anti-oxide layer was more effective than the anodizing process in the test of reflectance. Furthermore, the protected gold mirror manufactured by layers forming of various materials resulted in the most effective reflectance and lifetime when coated with $Al_2O_3$ as the anti-oxide layer, coated Cr as the adhesion layer, and coated $MgF_2$ as the protection layer.

• 전기전자학회논문지
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• 제22권2호
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• pp.302-308
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• 2018

다층 박막 스퍼터링(Multi-Layer Sputtering)은 상이한 물질을 원하는 두께의 박막을 다층(Multi-Layer) 으로 형성함을 목적으로 한다. 다층 박막 증착 공정은 공정 시간이 비교적 많은 비중을 차지하는데, 그 주요 원인은 공정 시간에 비해 증착하고자하는 기판의 이동 시간과 챔버를 고진공 상태로 만드는 시간이 많이 소요되기 때문이다. 반도체나 디스플레이 산업은 하나의 챔버에서 단일 물질을 스퍼터링하고 기판이 다관절 로봇을 통해 다른 챔버로 이동하여 다른 물질을 스퍼터링하는 공정이 대부분인데, 이는 필연적으로 공정 설비 내에 여러 개의 챔버와 진공펌프, 다관절 로봇이 필요하다. 이러한 문제점을 해결하기 위해 본 논문에서는 단일 진공 챔버 내에서 서로 상이한 물질을 증착하는 다층박막 스퍼터링 장치에 대한 제어시스템을 제안하고 TFT 공정에서 적용한다. 제어시스템의 제작과 실험을 통해 유효성을 입증한다.

• 방송공학회논문지
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• 제13권4호
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• pp.452-462
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• 2008

본 논문에서는 디지털 라디오와 지상파 Digital Multimedia Broadcasting (DMB)에서 사용되는 MUSICAM 이라 불리는 MPEG-1/2 Layer-II 와 MPEG-4 ER-BSAC 디코더를 330 MHz 클럭수를 가지고 동작하는 고정 소수점 digital signal processor (DSP) TMS320C64x+ 상에 실시간 구현한다. 오디오 디코더의 실시간 구현하기 위해, 다음과 같은 여러 단계의 최적화를 수행한다. 첫 째, 메모리 공유, 데이터 타입 재설정 및 루프의 unrolling 과정을 통해, C 코드 레벨에서 최적화를 수행한다. 다음으로, 비트스트림 분석의 재구성, 합성 필터의 변경 및 합성 필터의 윈도우 계수의 재배열을 통해 알고리즘 레벨에서 최적화를 수행한다. 또한, MPEG-1/2 Layer-II 디코더의 합성필터 모듈을 linear assembly program 레벨로 치환한다. Linear assembly program 레벨로 치환하는 이유는 MPEG-1/2 Layer-II 디코더에서 합성 필터 모듈이 가장 많은 계산량을 차지하기 때문이다. 구현된 오디오 디코더의 성능 평가를 위해, 복호화 처리시간의 비율을 측정하고, 최적화된 MPEG 디코더와 레퍼런스 MPEG 디코더로 처리된 오디오 신호 사이의 root mean square (RMS)를 계산한다. 최적화 실시간 구현 결과, MPEG-1/2 Layer-II 와 MPEG-4 ER-BSAC 디코더는 TMS320C64x+가 동작하는 최대 클럭 수의 3%와 11%의 사용으로 각각 동작하며, 오디오 디코더의 품질은 MPEG standard에 정의된 -77.01 dB의 조건을 모두 만족함을 확인할 수 있었다.