• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.7-12
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• 2008

A hot stamping technology of vehicle door impact beam made of thin sheet steel has been developed, with the aim of ensuring occupant safety in a side collision. This technology has been implemented to increase the strength of vehicle body parts and to reduce not only the weight of door impact beam but also the number of work processes. Mechanical tests were performed to obtain material properties of hot-stamped specimen and those were used as input data in stamping and structural simulation for optimal design of door impact beam. Strength of hot-stamped door impact beam increased to the value 102% higher than that of conventional pipe-shaped door impact beam and structural simulation showed that hot-stamped door impact beam achieved 28% weight reduction.

• KIEE International Transactions on Electrophysics and Applications
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• 제5C권1호
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• pp.18-22
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• 2005

We developed a new systematic calibration procedure and applied it to the calibration of the diffusivity, segregation and TED model of the indium impurity. The TED of the indium impurity was studied under 4 different experimental conditions. Although the indium proved to be susceptible to the TED, the RTA was effective in suppressing the TED effect and in maintaining a steep retrograde profile. Just as in the case of boron, indium demonstrated significant oxidation-enhanced diffusion in silicon and its segregation coefficients at the Si/SiO₂ interface were significantly below 1. In contrast, the segregation coefficient of indium decreased as the temperature increased. The accuracy of the proposed technique has been validated by SIMS data and 0.13-㎛ device characteristics such as Vth and Idsat with errors less than 5% between simulation and experiment.

• Journal of Welding and Joining
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• 제19권1호
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• pp.75-81
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• 2001

The metallurgical study of microconstituents in transient liquid phase bonded joints of Ni-base single crystal superalloys, CMSX-2 and CMSX-4 was investigated employing MBF-80 insert metal. TLP bonding of specimens was carried out at 1,373~1,523K for 0~19.6ks in vacuum. Three types of microconstituents ; needle-like constituent, dot-like constituent and abnormal shape constituent were formed in the bonded interlayer during TLP bonding operation. All these microconstituents were identified as boride. Microconstituents contain a large percentage of Cr in the early stage of bonding. As increasing the holding time, the amount of Cr was decreased and the amount of W, Co and Re were increased. From the analysis results of electron diffraction pattern by TEM, composition of elements in microconstituents were into MBlongrightarrowM$_{5}$B$_3$longrightarrowM$_2$B type with the increased in holding time. It can be explained by the fact that the relative amount of boron in microconstituents was decreased when the holding time was increased.d.

• 소성∙가공
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• 제24권1호
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• pp.13-19
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• 2015

For an accurate analysis of hot stamping, a coupled simulation with different aspects of the process(i.e. mechanical, thermal, and phase transformation) is needed. However, coupled simulations are time consuming and costly. Therefore, the current study proposes a simplified method focused on the forming for the hot stamping simulation of a coupled torsion beam axle (CTBA) tubular beam. In this simplified method, non-isothermal conditions were assumed and only conduction was considered, since it represents the majority of the heat transfer during hot stamping. In addition, temperature and strain rate effects were also included. Moreover, an isothermal simulation was conducted and compared with a non-isothermal simulation. Finally, the simulations were verified by experiments. In conclusion, the proposed method is shown to be effective for the development of tube-type parts, and it effectively predicts the deformation of the tubular beam during hot stamping.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.473-474
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• 2006

Boron Phosphide films were deposited on (111) Si substrate at $650^{\circ}C$, by the reaction of B2H6 with PH3 using APCVD. N2 was carried out as carrier gas. The optimal gas rates were $20\;m{\ell}/min$ for B2H6, $60\;m{\ell}/min$ for PH3 and $1\;{\ell}/min$ for N2. After as grown the films were insitu annealed for 1hour in N2 ambient at $550^{\circ}C$ and measured. The measurement of AFM shows that the RMS is $29.626{\AA}$ for the reaction temperature at $650^{\circ}C$. The measurement of XRD shows that the films have the orientation of (101). Also, the measurement of AES is shown that the films have B13P2 stoichiometry.

• Bulletin of the Korean Chemical Society
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• 제19권5호
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• pp.501-503
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• 1998

In this work, we applied the 1D $11^B$ nutation NMR method for the analysis of the local structural environments in powdered borosilicates $(SiO_2-B_2O_3)$. Spin dynamics during a rf irradiation for spin I=3/2 was analytically calculated with a density ma trix formalism. Spectral simulation programs were written in MATLAB on a PC. Two borosilicates prepared by the sol-gel process at different stabilization temperature were used for the 1D $11^B$ nutation NMR experiment. The $11^B$ NMR parameters, quadrupole coupling constants $(e^2qQ/h)$ and asymmetry parameters (η), for each borosilicate were extracted from the nonlinear least-squares fitting. The effects of heat treatments on the local structures of boron sites in borosilicates were discussed.

• Bulletin of the Korean Chemical Society
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• 제19권5호
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• pp.519-524
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• 1998

In this work, we applied the 1D 11B nutation NMR method for the analysis of the local structural environments in powdered borosilicates (SiO2-B2O3). Spin dynamics during a rf irradiation for spin I=3/2 was analytically calculated with a density matrix formalism. Spectral simulation programs were written in MATLAB on a PC. Two borosilicates prepared by the sol-gel process at different stabilization temperature were used for the 1D 11B nutation NMR experiment. The 11B NMR parameters, quadrupole coupling constants (e2qQ/h) and asymmetry parameters (η), for each borosilicate were extracted from the nonlinear least-squares fitting. The effects of heat treatments on the local structures of boron sites in borosilicates were discussed.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 추계 학술논문 발표대회
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• pp.79-80
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• 2019

This study was intended to examine the possibility of reducing hydration heat by FA substitution and combination of slag (CGS) from coal gasification power generation (IGCC) with mixed aggregate for concrete. The analysis results showed good results if liquidity increases as the ratio of CGS increases, air volume decreases, and compressive strength is mixed up to 25% in the residual aggregate. The results showed that the heat of hydration was reduced compared to plain due to the boron content of CGS as the CGS substitution rate increased, but it was larger due to the combination with FA substitution. It was found that the heat of hydration was reduced.

• Nuclear Engineering and Technology
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• 제53권5호
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• pp.1642-1651
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• 2021

In this study, isophtalic neopentyl glycol polyester (NPG-PES) based composites with different loading ratios of pure tungsten metal (W), tungsten (VI) oxide (WO₃), tungsten boron (WB) and tungsten carbide (WC) composites were prepared as alternative shielding materials for ionizing electromagnetic radiation (IEMR) shielding. Structural characterizations of the composites were done. Gamma spectrometric analysis of composites for 80-2000 keV energy range was performed and their usability as IEMR shielding was discussed. As a result, the produced composites showed a shielding performance of 60-100% of the lead (the most widely used IEMR shielding material) depending on the reinforcement material, reinforcement loading rate and experimental conditions. Thus, it was reported that produced composites could be an alternative to lead shieldings that have several disadvantages as toxic properties, difficulty of processing and inelasticity.

• Nuclear Engineering and Technology
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• 제52권12호
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• pp.2743-2759
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• 2020

A detailed computational fluid dynamics (CFD) simulation analysis model was developed using ANSYS CFX 16.1 and analyzed to simulate the basic design and internal flow characteristics of a 180 MW small modular reactor (SMR) with a natural circulation flow system. To analyze the natural circulation phenomena without a pump for the initial flow generation inside the reactor, the flow characteristics were evaluated for each output assuming various initial powers relative to the critical condition. The eddy phenomenon and the flow imbalance phenomenon at each output were confirmed, and a flow leveling structure under the core was proposed for an optimization of the internal natural circulation flow. In the steady-state analysis, the temperature distribution and heat transfer speed at each position considering an increase in the output power of the core were calculated, and the conceptual design of the SMR had a sufficient thermal margin (31.4 K). A transient model with the output ranging from 0% to 100% was analyzed, and the obtained values were close to the T_hot and T_cold temperature difference value estimated in the conceptual design of the SMR. The K-factor was calculated from the flow analysis data of the CFX model and applied to an analysis model in RELAP5/MOD3.3, the optimal analysis system code for nuclear power plants. The CFX analysis results and RELAP analysis results were evaluated in terms of the internal flow characteristics per core output. The two codes, which model the same nuclear power plant, have different flow analysis schemes but can be used complementarily. In particular, it will be useful to carry out detailed studies of the timing of the steam generator intervention when an SMR is activated. The thermal and hydraulic characteristics of the models that applied porous media to the core & steam generators and the models that embodied the entire detail shape were compared and analyzed. Although there were differences in the ability to analyze detailed flow characteristics at some low powers, it was confirmed that there was no significant difference in the thermal hydraulic characteristics' analysis of the SMR system's conceptual design.