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排序方式: 共有1488条查询结果,搜索用时 15 毫秒
101.
Sang H. Shim Junkeol Choi Seungcheol Lee Jay H. Lee 《American Institute of Chemical Engineers》2023,69(4):e18036
A statistical modeling procedure is established for carbocation polymerization with the characteristics of living with chain transfer. A single state model is suggested for cases of narrow molecular weight distribution, whereas a multi-state model is claimed for cases of broad distribution. In the multi-state case, it is demonstrated how the overall kinetics can be derived using the expectations and variances of the kinetic parameters rather than those of individual states, thereby simplifying the modeling step. Although the expectation and variance do not follow the relationship of the Arrhenius equation, a procedure is given for how to account for temperature dependence. The proposed statistical method minimizes the number of parameters to identify and therefore is expected to help establish a model with fewer experiments. The whole procedure is demonstrated through an experimental study of isobutylene polymerization. 相似文献
102.
Heon Jun Jeong Wanhyuk Chang Beum Geun Seo Yun Sung Choi Keun Hee Kim Dong Hwan Kim Joon Hyung Shim 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(22):2208149
This study reports the performance and durability of a protonic ceramic fuel cells (PCFCs) in an ammonia fuel injection environment. The low ammonia decomposition rate in PCFCs with lower operating temperatures is improved relative to that of solid oxide fuel cells by treatment with a catalyst. By treating the anode of the PCFCs with a palladium (Pd) catalyst at 500 °C under ammonia fuel injection, the performance (peak power density of 340 mW cm−2 at 500 °C) is approximately two-fold higher than that of the bare sample not treated with Pd. Pd catalysts are deposited through an atomic layer deposition post-treatment process on the anode surface, in which nickel oxide (NiO) and BaZr0.2Ce0.6Y0.1Yb0.1O3–δ (BZCYYb) are mixed, and Pd can penetrate the anode surface and porous interior. Impedance analysis confirmed that Pd increased the current collection and significantly reduced the polarization resistance, particularly in the low-temperature region (≈500 °C), thereby improving the performance. Furthermore, stability tests showed that superior durability is achieved compared with that of the bare sample. Based on these results, the method presented herein is expected to represent a promising solution for securing high-performance and stable PCFCs based on ammonia injection. 相似文献
103.
Piao H.-G. Shim J.-H. Djuhana D. Lee S.-H. Jun S.-H. Heo C.-M. Oh S.-K. Yu S.-C. Kim D.-H. 《IEEE transactions on magnetics》2010,46(2):224-227
104.
Do-Sik Shim Jong-Youn Son Eun-Mi Lee Gyeong-Yun Baek 《International Journal of Material Forming》2017,10(4):581-596
This paper focuses on the corrugated thin-walled sheet metal in the roll bending process. The main defect that appears in corrugated panels subjected to high amounts of bending deformation is a wavy edge. Edge defects are caused by excessive longitudinal stress and strain near the edge of the plate, and local edge buckling may occur when some critical value of the bending radius is exceeded. This paper proposes two different approaches to avoid a wavy edge for a formed panel: excessive stress on the edge region is restrained by controlling the length of the cross-sectional end of the corrugated panel while considering the stress distribution, and the bending radius in each forming step is determined by considering the strain limit at which the initial edge waviness occurs to avoid excessive compression at particular steps. The experimental and numerical results indicated that the two proposed design strategies can minimize wavy edges in the formed shape. 相似文献
105.
Ik Seon Kwon Tekalign Terfa Debela In Hye Kwak Yun Chang Park Jaemin Seo Ju Yong Shim Seung Jo Yoo Jin‐Gyu Kim Jeunghee Park Hong Seok Kang 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(13)
2D MoS2 nanostructures have recently attracted considerable attention because of their outstanding electrocatalytic properties. The synthesis of unique Co–Ru–MoS2 hybrid nanosheets with excellent catalytic activity toward overall water splitting in alkaline solution is reported. 1T′ phase MoS2 nanosheets are doped homogeneously with Co atoms and decorated with Ru nanoparticles. The catalytic performance of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is characterized by low overpotentials of 52 and 308 mV at 10 mA cm?2 and Tafel slopes of 55 and 50 mV decade?1 in 1.0 m KOH, respectively. Analysis of X‐ray photoelectron and absorption spectra of the catalysts show that the MoS2 well retained its metallic 1T′ phase, which guarantees good electrical conductivity during the reaction. The Gibbs free energy calculation for the reaction pathway in alkaline electrolyte confirms that the Ru nanoparticles on the Co‐doped MoS2 greatly enhance the HER activity. Water adsorption and dissociation take place favorably on the Ru, and the doped Co further catalyzes HER by making the reaction intermediates more favorable. The high OER performance is attributed to the catalytically active RuO2 nanoparticles that are produced via oxidation of Ru nanoparticles. 相似文献
106.
Focused ion beam (FIB) milling is the typical method used to fabricate micropillars to study small-scale plasticity and size effects in uniaxial compression. However, FIB milling can introduce defects into the milled pillars. To investigate the effects of FIB damage on mechanical behavior, we tested Mo-alloy micropillars that were FIB milled following directional solidification, and compared their compressive response to pillars that were not FIB milled. We also FIB milled at glancing incidence a Mo-alloy single-crystal surface, and compared its nanoindentation response to an electropolished surface of the same crystal. Implications for the interpretation of data obtained from FIB-milled micropillars are discussed. 相似文献
107.
Seung-Wook Lee Daeyun Shim Yeon-Jae Jung Dong-Yun Lee Chang-Hyun Kim Wonchan Kim 《Electronics letters》1999,35(12):952-953
An output buffer is described which employs built-in load monitoring in order to bound the transition time over a wide range of load conditions. The adaptive control of driving current enables the switching-noise to be kept to a minimum value. The experimental chip, which was designed to bound the fall time within 6 ns for loading capacitance up to 100 pF, revealed a reduced switching-noise level, 15-35% of a conventional buffer 相似文献
108.
Ku-ho Chung Jong-in Shim 《Quantum Electronics, IEEE Journal of》1999,35(5):730-736
In a conventional polarization-insensitive multiquantum-well electroabsorption modulator, it is normal to apply tensile and compressive strain on the well and the barrier, respectively. But the main disadvantages of such a structure are a low conduction band offset (0.04-0.06 eV), a high heavy-hole band offset (0.20-0.24 eV), and a relatively large well thickness (110-120 Å). We propose a new method of overcoming these disadvantages by placing a tensile strain on both the well and the barrier and compensating for them with a compressive strained intrinsic layer 相似文献
109.
This article is the first of a four-part series by the authors that treats various aspects of digital signal processing applied to partial discharge detection. It is shown that manufacturers and users of high-voltage apparatus are interested in on-site, off-line and on-line analysis of partial discharge to identify and locate defects in insulation systems 相似文献
110.
Herein, uniformly silica coated carbon nanotubes (CNTs) were fabricated by step reactions with minimized damage of CNTs during oxidation process. First, hydroxyl groups were generated on the surface of CNTs using KMnO4 in conjunction with tetrapropyl ammonium bromide (TPABr) as a phase transfer catalyst, followed by the grafting of a vinyl group carrying silane coupling agent, methacryloxypropyl trimethoxy silane (MPTMS). Utilizing terminal vinyl groups in in-situ solution polymerization, poly(4-vinylpyrridine) (P4VP) brush was grown from the CNTs which promotes the acid–base interaction between CNTs and tetraethylorthosilicate (TEOS). By means of well-known ammonia catalyzed sol–gel reaction of TEOS in the presence of P4VP-functionalized CNTs, uniformly silica-coated CNTs were obtained. The thickness of the silica layer could be readily controlled by the amounts of reactants. After calcination of silica-coated CNTs, only outer silica remained which resulted in silica nanotubes. 相似文献