• Journal of the Korean institute of surface engineering
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• v.40 no.6
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• pp.279-282
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• 2007

Cr-Mo-Si-C-N coatings were deposited on steel and Si wafer by a hybrid system of AIP and sputtering techniques using Cr, Mo and Si target in $Ar/N_2/CH_4$ gaseous mixture. Instrumental analyses of XRD and XPS revealed that the Cr-Mo-Si-C-N coatings must be a composite consisting of fine(Cr, Mo and Si)(C and N) crystallites and amorphous $Si_3N_4$ and SiC. The hardness value of Cr-Mo-Si-C-N coatings significantly increased from 41 GPa of Cr-Mo-C-N coatings to about 53 GPa with Si content of 9.3 at.% due to the refinement of (Cr, Mo and Si)(C and N) crystallites and the composite microstructure characteristics. A systematic investigation of the microstructures and mechanical properties of Cr-Mo-Si-C-N coatings prepared with various Si contents is reported in this paper.

• IEIE Transactions on Smart Processing and Computing
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• v.3 no.5
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• pp.285-297
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• 2014

This paper presents the results of an investigation into bi-directional communication in spectrum sharing-based cognitive radio (Bi-CR) systems. A Bi-CR system can increase the spectral efficiency significantly by sharing the spectrum and through the bi-directional use of spatial resources for two-way communication. On the other hand, the primary user experiences more interference from the secondary users in a Bi-CR system. Satisfying the interference constraint by simply reducing the transmission power results in performance degradation for secondary users. In addition, secondary users also experience self-interference from echo channels due to full duplexing. These imperfections may weaken the potential benefits of the Bi-CR system. Therefore, a new way to overcome these defects in the Bi-CR system is needed. To address this need, this paper proposes some novel power allocation schemes for the Bi-CR system. This contribution is based on two major analytic environments, i.e., noise-limited and interference-limited environments, for providing useful analysis. This paper first proposes an optimal power allocation (OPA) scheme in a noise-limited environment and then analyzes the achievable sum rates. This OPA scheme has an effect in the noise-limited environment. In addition, a power allocation scheme for the Bi-CR system in an interference-limited environment was also investigated. The numerical results showed that the proposed schemes can achieve the full duplexing gain available from the bi-directional use of spatial resources.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.231-236
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• 2001

A newly developed Advanced Indentation System (AIS), which is a portable and nondestructive system for evaluating tensile properties, was used to measure mechanical behavior of materials used under high temperature and pressure conditions. This test measures indentation load-depth curve during indentation and analyzes the mechanical properties related to deformation and fracture. Aging effects of Cr-Mo and Cr-Mo-V steel at high temperature were simulated. Tensile properties including yield strength and tensile strength at various temperature are obtained from the test. For all test materials and conditions, the AIS-derived results were in good agreement with those from conventional standard test method. Examples of the test results ate given and potential applications of the AIS to assess the integrity of aging structures are briefly discussed.

• Journal of the Korean Mathematical Society
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• v.39 no.1
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• pp.91-102
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• 2002

Let M and N be CR manifolds with nondegenerate Levi forms of hypersurface type of dimension 2m ＋ 1 and 2n ＋ 1, respectively, where 1 $\leq$ m $\leq$ n. Let f : M longrightarrow N be a CR mapping. Under a generic assumption we construct a complete system of finite order for the infinitesimal deformations of f. In particular, we prove the space of infinitesimal deformations of f forms a finite dimensional Lie algebra.

• Investigative Magnetic Resonance Imaging
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• v.8 no.2
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• pp.86-93
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• 2004

Purpose: We evaluated $^1H$ MR spectroscopy improves the preoperative diagnosis of diffuse infiltrative type of primary central nervous system lymphomas. Materials and methods: After review of conventional MR images and medical records, we retrospectively reviewed proton MR spectra in seven patients with primary central nervous system lymphoma diagnosed by means of biopsy. Relative ratio of choline (Cho), N-acetylaspartate (NAA), and lipid-lactate (Lip-Lac) to creatine (Cr) were measured for quantitative analysis. Results: The average ratio of Cho/Cr was $1.80{\pm}0.95$, NAA/Cr was $1.34{\pm}0.41$, and Lip-Lac/Cr was $1.12{\pm}0.16$. All cases of lymphomas showed increased Lip-Lac peak. Two case of mass forming lymphoma showed decreased NAA/Cr significantly, whereas five cases of lymphoma without mass formation showed preserved NAA/Cr. Conclusion : We thought the presence of Lip-Lac peak without significant reduction of NAA on the MR spectroscopy was helpful for diagnosis of diffuse infiltrative type of central nervous system lymphoma.

• Journal of the Korean institute of surface engineering
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• v.43 no.5
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• pp.238-242
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• 2010

In the present work, the influence of oxide on the Cr-Si-N coatings was investigated for the Cr-Si-O-N coatings on AISI 304 and Si wafer deposited by hybrid system, which combines the DC magnetron sputtering technique and arc ion plating (AIP) using Cr and Si target in an $Ar/N_2/O_2$ gaseous mixture. As the O content in the Cr-Si-N coatings increased, the diffraction patterns of the Cr-Si-O-N coatings showed CrN and $Cr_2O_3$ phases. However, as the O content increased to 28.8 at.%, diffraction peak of $Cr_2O_3$ was disappeared in the Cr-Si-O-N coating. The $d_{200}$ value was decreased with increasing of O content. The average grain size increased from about 40 nm to 65 nm as the O content increased. The maximum micro-hardness of the Cr-Si-O-N coating was obtained 4507 Hk at the O content of 24.8 at.%. The average friction coefficient of the Cr-Si-O-N coatings was gradually decreased by increasing the O content and the average friction coefficient decreased from 0.37 to 0.25 by increasing the O content. These results indicated that amorphous phase was increased in the Cr-Si-O-N coatings by increasing of O content.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3691-3695
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• 2012

Photocatalytic reduction of hexavalent chromium (Cr(VI)) in ferric-tartrate system under irradiation of visible light was investigated. Effects of light resources, initial pH value and initial concentration of various reactants on Cr(VI) photocatalytic reduction were studied. Photoreaction kinetics was discussed and a possible photochemical pathway was proposed. The results indicate that Fe(III)-tartrate system is able to rapidly and effectively photocatalytically reduce Cr(VI) utilizing visible light. Initial pH variations resulte in the concentration changes of Fe(III)-tartrate complex in this system, and pH at 3.0 is optimal for Cr(VI) photocatalytic reduction. Efficiency of Cr(VI) photocatalytic reduction increases with increasing initial concentrations of Cr(VI), Fe(III) and tartrate. Kinetics analysis indicates that initial Fe(III) concentration affects Cr(VI) photoreduction most significantly.

• Journal of the Korean institute of surface engineering
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• v.29 no.5
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• pp.386-392
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• 1996

The epitaxial TM/bcc-Cr(001) (TM=Fe, Co, Ni) multilayers have been prepared using MBE. The crystal structure, interlayer exchange coupling and magnetoresistance of those multilayers have been discussed. The structure of Fe, Co and Ni grown on bcc-Cr(001) exhibited bcc(001), distorted hcp(1120) and fcc(110), respectively. In Fe/Cr multilayes, an oscillatory exchange coupling has been observed, but not observed in Ni/Cr system, which may come from the large mixing at interfaces. Large MR ratio (116%, 4.2K) has been obtained in Fe/Cr system, but only 2% in Co/Cr system. This difference can be understood from the view point of the relative potential geight for down spin electrons between TM and Cr.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.208-211
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• 2000

We prepared Co-Cr-Ta and Co-Cr-Ta/Ti thin film for perpendicular magnetic recording media by facing targets sputtering system (FTS system). Ti underlayer effects on crystallographic and magnetic characteristics of Co-Cr-Ta perpendicular magnetic recording media have been investigated. Crystallgraphic and magnetic characteristic of prepared thin films were evaluated by x-ray diffractometry(XRD), vibrating sample magnetometer(VSM) and kerr hysteresis loop measurement. The coercivity and anisotropy field increase by introduced Ti underlayer when substrate temperature is higher than 150$^{\circ}C$. The c-axis dispersion angle and grain size of Co-Cr-Ta/Ti thin film is decrease than Co-Cr-Ta when substrate temperature is higher than 100$^{\circ}C$. Consequently, the use of a Ti underlayer highly orientated can be improved crystallographic and magnetic characteristics of Co-Cr -Ta perpendicular media layer.

• Nuclear Engineering and Technology
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• v.55 no.12
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• pp.4491-4503
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• 2023

This study aimed to verify and validate the transient simulation capability of the hybrid code system RAST-F for fast reactor analysis. For this purpose, control rod (CR) drop experiments involving eight separate CRs and six CR groups in the China Experimental Fast Reactor (CEFR) start-up tests were utilized to simulate the CR drop transient. The RAST-F numerical solution, including the neutron population, time-dependent reactivity, and CR worth, was compared against the measurement values obtained from two out-of-core detectors. Moreover, the time-dependent reactivity and CR worth from RAST-F were verified against the results obtained by the Monte Carlo code Serpent using continuous energy nuclear data. A code-to-code comparison between Serpent and RAST-F showed good agreement in terms of time-dependent reactivity and CR worth. The discrepancy was less than 160 pcm for reactivity and less than 110 pcm for CR worth. RAST-F solution was almost identical to the measurement data in terms of neutron population and reactivity. All the calculated CR worth results agreed with experimental results within two standard deviations of experimental uncertainty for all CRs and CR groups. This work demonstrates that the RAST-F code system can be a potential tool for analyzing time-dependent phenomena in fast reactors.