• Title/Summary/Keyword: CR

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Comparative studies on microstructure and mechanical properties of CrN, Cr-C-N and Cr-Mo-N coatings (CrN, Cr-C-N, Cr-Mo-N 박막의 미세구조와 기계적 성질에 관한 연구)

  • Lee, Jeong-Du;Lee, Gwang-Ho
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2009.05a
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    • pp.184-185
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    • 2009
  • 하이브리드 코팅 시스템을 이용하여 CrN 을 기초로 3성분계 코팅을 합성한다. 이번 연구는 C를 첨가한 음이온 고용경화와 Mo를 첨가한 양이온 고용경화의 영향이 미세구조와 기계적 성질에 미치는 영향을 알아보는 것이다. Cr-C-N 과 Cr-Mo-N 코팅은 23, 43GPa의 최대 경도 값을 가진다. 이 경도강화는 고용강화로 설명할 수 있다.

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CR beaconing method in Indoor CR Network for Coexistence with WLAN system (Indoor CR 네트워크에서의 WLAN 과 공존하는 CR beaconing 방법)

  • Kim, Hyun-Ju;Yoo, Sang-Jo
    • Proceedings of the Korea Information Processing Society Conference
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    • 2007.05a
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    • pp.1306-1309
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    • 2007
  • 본 논문에서는 indoor 환경에서 CR 네트워크를 이용하기 위한 방안으로 CR-Wi-Fi device 시스템을 제안했으며 IU 을 보호하는 방법으로 CR beaconing 을 제안했다. IU 가 출현하면 UHF, VHF band 와 ISM band 로 동시에 이를 알리고 CR 네트워크가 간섭을 주는 경우 사용 중이던 채널 사용을 중지 혹은 이동하도록 명령해야 한다. 본 논문에서는 CR beaconing 방식을 제안하여 보다 효과적인 IU 보호 및 복구를 수행하도록 하였다.

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Magnetic properties of $\textrm{SiO}_2$/CoNiCr/Cr thin films ($\textrm{SiO}_2$/CoNiCr/Cr 합금 박막의 자기적 성질)

  • Kim, Taek-Su;Kim, Jong-O;Seo, Gyeong-Su
    • Korean Journal of Materials Research
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    • v.7 no.1
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    • pp.69-75
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    • 1997
  • Thin films of $Si0_2(1000{\AA})/CoNiCr(400{\AA})/Cr$ were fabricated as a function of Cr thickness by KF magnetron sputtering. The saturation magnetization, coercive force and squareness with annealing temperature for these films were investigated. The values of saturation magnetization of $SiO_2/CoNiCr/Cr$ thin films decreased as the thickness of Cr underlayer increased, whereas coercive force increased as the thickness of Cr underlayer increased. The value of Ms was 600 emu/cc and the maximum value of Hc was 550 Oe. Especially, the value of saturation magnetization was rapidly decreased $SiO_2/CoNiCr/Cr(1700{\AA})$ thin films as the annealing temperature increased And the coercive force increased as the annealing temperature increased When annealing temperature was $650^{\circ}C$, the Ms was reduced to 90 % of the as-deposited film. And the Hc was showed maximum 1600 Oe. It was thought that Cr diffusion into CoNiCr layer reduced the magnetic moment of CoKiCr layer. In addition. Hc might he increased due to grain growth perpendicular to the film plane.

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Biosorption of Pb and Cr by using Sargassum sagamianum (비틀대모자반, Sargassum sagamianum을 이용한 Pb 및 Cr 생체흡착 및 회수)

  • SUH Kuen-Hack;AHN Kab-Hwan;LEE Hack-Sung;LEE Hwae-Geon;CHO Jin-Koo;HONG Yong-Ki
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.32 no.4
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    • pp.399-403
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    • 1999
  • Biosorption of Pb and Cr to Sargassum sagamianum was evaluated in the various conditions. An adsorption equilibrium was reached in about 15 min. for Pb and Cr. The uptake capacity was 224.5 mg Pb/g biomass and 77.5 mg Cr/g biomass, respectively. The adsorption parameters for Pb and Cr were determined according to Langmuir and Freundlich model. Biosorption of Pb and Cr was increased with an increase in pH value. Pb and Cr adsorbed by S. sagamianum could be recovered by desorption process with 0.1M HCl, 0.1M $HNO_3$ and 0.1M EDTA and the efficiency of Pb desorption was above $90\%$, whereas the efficiency of Cr desorption was below $51\%$.

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WLAN CR Coexistence Beacon Protocol for Cognitive Radio-Based WLAN Network (무선인지 기술을 이용한 차세대 WLAN 네트워크에서의 WLAN CR 공존 비콘 프로토콜)

  • Kim, Hyun-Ju;Yoo, Sang-Jo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.12B
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    • pp.790-799
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    • 2007
  • In this paper, we propose WLAN CR coexistence beacon protocol for thenext WLAN network. This method can provide WLAN with high-speed data rate in new WLAN architecture and network platform based on cognitive radio technology. WLAN CR devices that enter the CR network can know UHF channels by listening CR beacon including the coexistence parameter set and start using CR channel fast. During handover of WLAN device in UHF spectrums, WLAN device that lost their channel can change available channel by obtaining the current CR channel information from the CR beacon. In advance relaying coexistence parameter set to entire CR system, WLAN CR system can prepare own candidate channel set that is different with other CR system. In CR beacon and relay delay, we show the results that WLAN CR coexistence beacon protocol supports spectrum handover efficiently and decreases the probability of collision in candidate channel set.

A manufacturing process and characteristic observation of alloy blocks for dental CAD/CAM system (치과 CAD/CAM 가공용 합금블럭 제조 및 특성 관찰)

  • Kim, Chi-young
    • Journal of Technologic Dentistry
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    • v.40 no.3
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    • pp.125-131
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    • 2018
  • Purpose: Automatic dental prosthesis manufacturing process was accelerated by the spread of dental CAD / CAM system. The CAD / CAM system with milling alloys were needed supplement. So, sintered alloy blocks were introduced. In this study, we want to study sintered alloy block. And to evaluate the alloy block manufacture and alloy properties. Methods: The alloy powders were prepared by high pressure water dispersion method. The sintered alloy blocks were prepared by low temperature pressing method. Their components observation were EDX, and the alloy structure was observed by XRD. Results: Co-Cr alloy powders were observed to have a circle shape with an average diameter of about $100{\mu}m$ and a Ni-Cr alloy powder had a circle shape with an average diameter of about $50{\mu}m$. The Co-Cr alloy block is composed of Co (34.62 wt%), Cr (17.33 wt%), Mo (2.98 wt%), Si (0.36 wt%) and C (44.17 wt%). The Ni-Cr alloy powder was composed of Ni (40.29 wt%), Cr (19.37 wt%), Mo (3.53 wt%), Si (0.52 wt%) and C (33.18 wt%). The peak of the Co and CoCr peaks were observed in the CoCr alloy body by the means of XRD study. Cr2Ni3 of the peak was observed in the Ni-Cr alloy material. Conclusion : As a result, the following conclusions were obtained. 1. Prepared by high-pressure water-law Co-Cr alloy powder has an average diameter $100{\mu}m$, Ni-Cr alloy powder was found to have the form of sphere having an average diameter $50{\mu}m$. 2. Co-Cr alloy and Ni-Cr alloy block produced by low-temperature processing showed a certain ratio. 3. In the XRD study, Co phase appeared in Co-Cr alloy block after sintering. and Cr2Ni3 phase appeared in Ni-Cr alloy block after sintering.

Composition and Microstructure of Electroplated Zinc-Chromium Alloy according to Electrolysis Conditions (전해조건에 따른 아연-크롬합금 도금층의 조성 및 조직특성)

  • 안덕수;김대영;예길촌
    • Journal of the Korean institute of surface engineering
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    • v.35 no.4
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    • pp.232-240
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    • 2002
  • The composition and the microstructure of the Zn-Cr alloys electroplated in chloride bath with EDTA were studied according to electrolysis conditions. The cathode current efficiency decreased with increasing both Cr/(Cr+Zn) ratio and current density. The Cr content of the alloy deposits increased with Cr/(Cr+Zn) ratio and current density The phase structure of Zn-Cr alloy deposits changed from η-Zn through η-Zn+${\gamma}$'-ZnCr to ${\gamma}$'-ZnCr with increasing Cr content of alloys. The surface morphology of Zn-Cr alloy deposits changed from fine needle shaped crystallites through the mixed structure of needle-shaped and granular one to the colony structure with fine granular crystallites according to the change of phase structure

Interfacial diffusion in Fe/Cr magnetic multilayers studied by synchrotron x-ray techniques (다층형 Fe/Cr 자성박막에서 계면확산의 방사광 x-선 연구)

  • Cho, Tae-Sik;Jeong, Ji-Wook
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2003.05a
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    • pp.84-87
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    • 2003
  • The interfacial diffusion in Fe/Cr/MgO(001) multilayers has been studied using synchrotron x-ray techniques, such as x-ray reflectivity, extended x-ray absorption fine structures (EXAFS), and anomalous x-ray scattering (AXS). The results of x-ray reflectivity indicated that the interfacial roughness of Fe/Cr multilayers with Cr-$4{\AA}$-thick was larger than that with Cr-$4{\AA}$-thick. The results of EXAFS indicated that the Fe element dominantly diffuse into the stable Cr layers at the Fe/Cr interface. The AXS was certified the existence of the interdiffused Fe element in the Cr layers. Our study revealed that the rough interface of the Fe/Cr multilayers was caused by the interfacia diffusion of Fe element into the Cr layers.

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Effects of Cr Interlayer on Adhesion Properties between Cr-Al-Si-N Coatings and SUS 304 Substrate (Cr Interlayer 삽입에 따른 Cr-Al-Si-N 코팅과 SUS 304 기판의 밀착 특성 연구)

  • Choi, Kwang-Su;Hong, Yeong-Su;Kim, Kwang-Ho
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2009.10a
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    • pp.165-166
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    • 2009
  • 이 연구에서는 SUS304 기판과 Cr-Al-Si-N 코팅사이의 밀착특성을 향상시키기 위하여 하이브리드 증착법으로 Cr Interlayer를 기판위에 증착시킨 후 Cr-Al-Si-N 코팅을 증착하였다. 그리고 Ball-on-disk 마모테스트와 스크래치 테스트를 통해 밀착력, 파괴기구, 그리고 마찰거동 등을 살펴보았다. Cr-Al-Si-N 코팅에 60nm 두께의 Cr Interlayer 삽입되었을 때는 기판에 Cr-Al-Si-N 코팅만 증착되었을 때의 밀착력(${\sim}30N$) 보다 더 우수한 ${\sim}50N$의 밀착력을 나타내었고 내마모성 또한 향상되었다. 밀착력 증가는 Cr Interlayer 삽입에 따른 SUS304 기판과 Cr-Al-Si-N 코팅사이의 전단응력 감소에 기인한 것으로 사료된다.

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