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191.
Sang Yong Shin Hackcheol Lee Seung Youb Han Chang-Hyo Seo Kayoung Choi Sunghak Lee Nack J. Kim Jai-Hyun Kwak Kwang-Geun Chin 《Metallurgical and Materials Transactions A》2010,41(1):138-148
An investigation was conducted into the correlation of microstructure and the cracking phenomenon that often occurred in hot-rolled
lightweight steel plates. Two kinds of steels were fabricated with varying Mn and Al contents, and their microstructures,
tensile properties, and high-temperature transformation behavior were investigated. In the two steels, banded structures containing
ferrite grains and κ-carbides were well developed along the rolling direction. Detailed microstructural analyses showed that cracks initiated
at film-type κ-carbides continuously formed interfaces between bands, while the band populated with κ-carbides did not play an important role in initiating cracks. Thus, the formation of band structures and film-type interfacial
κ-carbides must be minimized to prevent the cracking. The decreased content of hardenability elements, including aluminum,
higher finish-rolling temperature, reduced central segregation during the slabmaking process, and decreased material variation
during hot rolling, were suggested as practical methods for preventing the cracking. 相似文献
192.
In this study, we have attempted to describe the phenomenon of vacancy formation in various types of diamonds (natural type
IaAB, synthetic type Ib, synthetic type IIa, and type IaABC suspected of having been pretreated with an unknown method) using
electron beam irradiation. After the electron beam irradiation, vacancies were formed in the natural type IaAB and synthetic
type IIa diamonds, whereas vacancies were not formed in the synthetic type Ib and pre-treated type IaABC diamonds. From these
results, we suggest a model of vacancy creation by electron beam irradiation in various types of diamonds. The irradiation
was performed with electron dose densities of 1–6×1017/cm2 at 10 MeV, and with a heat treatment of two hours at a temperature of 900 °C. Electron beam-irradiated and heat-treated samples
were analyzed using UV-Vis-NIR, FT-IR, and PL spectroscopy. 相似文献
193.
H.S. Yoon J.H. Seo J.H. Kim 《International Journal of Heat and Mass Transfer》2010,53(21-22):4525-4535
The present study numerically investigates two-dimensional laminar force convection heat transfer past two rotating circular cylinders in a side-by-side arrangement at a various range of absolute rotational speeds (|α| ? 2) for four different gap spacings (g1) of 3, 1.5, 0.7 and 0.2 at Reynolds number of 100, and a fixed Prandtl numbers of 0.7 (air). As |α| increases, the thermal field became stabilized and eventually steady beyond the critical rotational speed depending on the gap spacing. In general, as |α| increases, because the vertical motion of flow in the region of gap is strongly inhibited, the inner isotherms are early merged and shorter than the outer isotherms in the free-stream sides elongating further downstream. As |α| increases, because the rotating fluid near the cylinders surrounded much space where the steady conduction mode is predominant to the heat transfer, the behavior of the time- and surface-averaged Nusselt number has the decaying pattern with increasing |α| for all gap spacings considered in this study. 相似文献
194.
Jungyol Jo Hyoshik Choi Junho Yun Haemi Kim Ogweon Seo Byeonggon Lee 《Thin solid films》2009,517(23):6337-1923
We developed a new method to realize enhancement-mode zinc oxide (ZnO) thin-film transistors (TFT) by metalorganic chemical vapor deposition (MOCVD). We used growth interruptions during MOCVD to encourage complete oxidation of deposited ZnO film, where diethylzinc and oxygen were used as sources. With this method, turn-off characteristics were significantly improved, and threshold voltage was shifted to positive voltages. ZnO TFTs grown at 450 °C showed 107 on/off ratio with 18 cm2/V s mobility, and + 5 V threshold voltage. Our data support that the surface layer is also important in determining ZnO TFT characteristics. 相似文献
195.
This study was designed to compare the effectiveness and applicability of the Petrifilm plate method with the Association of Official Analytical Chemists' (AOAC) standard aerobic count method and violet red bile agar method for meat products. The comparison was carried out using 303 meat samples collected from various retailers: 110 pork samples, 87 chicken samples, and 107 beef samples. In the comparison of the correlation coefficient (R) between the conventional method and the Petrifilm plate method by a linear regression analysis, the correlation coefficient in total microorganisms was 0.99, 0.95, and 0.94 in pork, beef, and chicken samples, respectively. The correlation coefficient in coliform count was 0.83, 0.96, and 0.81 in pork, beef, and chicken samples, respectively. Based on the high correlation in the total microorganism count, it might be possible to replace the conventional methods with the Petrifilm plate method. For coliform counts, the Petrifilm plate method also showed a generally high correlation coefficient, except for pork samples, which are more subject to contamination. The Petrifilm plate method was simpler and less time-consuming in sample preparation and, in procedures, faster than the conventional method. These results suggested that the 3M Petrifilm plate method could replace the conventional methods in the analysis of microorganism contamination measurement in meat products. 相似文献
196.
The inward approach in the design of control systems is introduced. This approach differs from the root-locus and the Bode-plot methods in that it involves first searching for an overall transfer function to meet design specifications and then computing the required compensator. The method is simple and straightforward and can easily be carried out with the aid of a digital computer simulator program 相似文献
197.
Sang-Yong Kim Sung-Woo Park Yong-Jin Seo 《Journal of Materials Science: Materials in Electronics》2002,13(12):693-696
As the integrated circuit device size shrinks to smaller dimensions, a chemical mechanical polishing (CMP) process was required for the global planarization of inter-metal dielectric (IMD) layer free of defects. However, as the IMD layer gets thinner, micro-scratches are becoming a major concern. Micro-scratches are generated by agglomerated slurry, solidified and attached slurry in the pipe-lines of the slurry supply system. In order to prevent the agglomerated slurry particles from slurry inflow, we installed a 0.5-m point-of-use (POU) filter, which is a depth-type filter and has 80% filtering efficiency for the 1.0-m size particles. Also, a high-spray bar of de-ionized water with high pressure was installed in the CMP equipment. In this paper, we studied the relationship between defect generation and pad counts to understand the exact efficiency of the slurry filter, and to determine the appropriate pad usage. Our experimental results showed that it is impossible to prevent defect-causing particles completely through the depth-type filter. Thus, we suggest that it is necessary to optimize the slurry flow rate and to install a high-spray bar of de-ionized water (DIW) with high pressure, in order to overcome weak points of the POU depth-type filter. 相似文献
198.
In this work, to study the characteristics of carbon fiber-reinforced composites with different fiber cross-section types, such as round, C, and hollow-shape, the thermal conductivity and mechanical properties were investigated and compared. The thermal conductivity was measured by means of steady-state method to the parallel and perpendicular direction of reinforcing fibers. The mechanical properties were evaluated by a variety of test methods i.e., flexural, interlaminar shear strength, and impact strength. As a result, it was found that the thermal conductivity was greatly depended on the cross-section type of the reinforcing fibers, as well as, the reinforcing orientation. Especially, the anisotropy factor (k
///k
) and the thermal diffusivity factor (///) of C and hollow-type carbon fiber-reinforced composites showed about two times higher values than those of round-type one. Also, the mechanical results showed that C and hollow-type carbon fibers-reinforced composites had higher values than those of round-type one in all mechanical tested. These results were probably due to the basic properties of non-circular (C and hollow-type) carbon fiber which can improve interfacial binding forces and widen interfacial contact area between reinforcement and matrix, resulting in effectively transferring the applied stress. 相似文献
199.
Won-Gap Seo Hiroyuki Matsuura Fumitaka Tsukihashi 《Metallurgical and Materials Transactions B》2006,37(2):239-251
Recently, molecular dynamics (MD) simulation has been widely employed as a very useful method for the calculation of various
physicochemical properties in the molten slags and fluxes. In this study, MD simulation has been applied to calculate the
structural, transport, and thermodynamic properties for the FeCl2, PbCl2, and ZnCl2 systems using the Born—Mayer—Huggins type pairwise potential with partial ionic charges. The interatomic potential parameters
were determined by fitting the physicochemical properties of iron chloride, lead chloride, and zinc chloride systems with
experimentally measured results. The calculated structural, transport, and thermodynamic properties of pure FeCl2, PbCl2, and ZnCl2 showed the same tendency with observed results. Especially, the calculated structural properties of molten ZnCl2 and FeCl2 show the possibility of formation of polymeric network structures based on the ionic complexes of ZnCl
4
2−
, ZnCl
3
−
, FeCl
4
2−
, and FeCl
3
−
, and these calculations have successfully reproduced the measured results. The enthalpy, entropy, and Gibbs energy of mixing
for the PbCl2-ZnCl2, FeCl2-PbCl2, and FeCl2-ZnCl2 systems were calculated based on the thermodynamic and structural parameters of each binary system obtained from MD simulation.
The phase diagrams of the PbCl2-ZnCl2, FeCl2-PbCl2, and FeCl2-ZnCl2 systems estimated by using the calculated Gibbs energy of mixing reproduced the experimentally measured ones reasonably well. 相似文献
200.
Jaewon Seo Dohyoung Chung Chan Gook Park Jang Gyu Lee 《Automatic Control, IEEE Transactions on》2005,50(7):1039-1043
Controllability and observability of discrete linear time-varying systems with norm-bounded parameter uncertainties are analyzed in this note. Like in the continuous case, we propose the sufficient conditions, which ensure controllability and observability of the uncertain system. The proposed conditions allow the evaluation of controllability and observability of the uncertain system without knowledge of specific values of uncertainties. 相似文献