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排序方式: 共有119条查询结果,搜索用时 250 毫秒
81.
Jae Ryong Kweon 《Journal of Differential Equations》2007,235(1):166-198
We are concerned with singularities and regularities of solutions for the Navier-Stokes system of incompressible flows on a polygonal domain with a concave vertex. We subtract the corner singularities by the Stokes operator from the solution velocity and pressure functions of the system. It is shown that the stress intensity factors are functions of time variable, belong to a fractional Sobolev space on the time interval and can be expressed in terms of given data. An increased regularity for the remainder is obtained. 相似文献
82.
Mi-Seon Shin Young-Jin Kang Hyun-A Chung Jung-Won Park Deok-Heon Kweon Woo Song Lee Yong-Jin Yoon Sung-Kyu Kim 《Journal of heterocyclic chemistry》1999,36(5):1135-1142
Some novel 3-halo-6-(4-substituted-phenoxy)pyridazines and 3,6-di-(4-substituted-phenoxy)pyridazines were synthesized from 3,6-dichloropyridazine or 3,6-diiodopyridazine. 3,6-Diiodopyridazine was prepared from 3,6-dichloropyridazine using hydriodic acid/iodine monochloride. 相似文献
83.
Jung‐Won Park Deok‐Heon Kweon Young‐Jin Kang Woo Song Lee Su‐Dong Cho Yong‐Jin Yoon 《Journal of heterocyclic chemistry》2000,37(1):5-10
This paper presents the synthesis of some novel acyclonucleosides involving pyrrolo[2,3‐c]pyridazine and 4‐hydroxybutyl side chain. 相似文献
84.
85.
Structural and magnetic properties of silicon/aluminum-added and -free FeCoNi magnetic alloy nanofibers with nanogranular
phases prepared by electrospinning and subsequent annealing of the PVP-blended ternary metal precursors in hydrogen atmosphere
were investigated. The FeCoNi magnetic alloy nanofibers with evenly distributed nanocrystalline phases were formed, which
are identified as γ-Fe1−x
Ni
x
binary phase with face-centered cubic structure and α-CoFe phase with body-centered cubic structure. At elevated temperature,
the α → γ structural martensitic transformation in the FeCoNi ternary alloys occurred due to the inhomogeneities in composition
of the matrix during annealing of the alloy with metastable α-phase. In the Si/Al-added FeCoNi nanofibers, more than two phases
with complicated-boundaries of the grains in and/or outside the nanofibers were formed as crystalline phases and amorphous
phase. The amorphous phase consisted of Si and/or Al acted as an inhibitor diminishing α → γ transformation as well as an
interparticle insulation layer. At low annealing temperature of 450 °C, the Si/Al-added nanofiber mainly consisted of metastable
α-phase with a low-crystallinity surface structure and very small diameter of 13 nm was formed and showed an unexpectedly
high coercivity, which attributed to the surface effects and/or high surface/volume ratio. 相似文献
86.
Jae Ryong Kweon 《Numerical Methods for Partial Differential Equations》2004,20(3):412-431
A linearized compressible viscous Stokes system is considered. The a posteriori error estimates are defined and compared with the true error. They are shown to be globally upper and locally lower bounds for the true error of the finite element solution. Some numerical examples are given, showing an efficiency of the estimator. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 20: 412–431, 2004. 相似文献
87.
Jong-Woo Sun Sang-Hyo Kweon Tae-Geun Seong Jin-Seong Kim Byoung-Jik Jeong Sahn Nahm 《Current Applied Physics》2013,13(1):148-151
The leakage current density of a 1.0 mol% TiO2-doped Bi5Nb3O15 (TB5N3) film was high, and the breakdown electric field was low. This could be attributed to the presence of intrinsic oxygen vacancies and free electrons. The electrical properties of the TB5N3 film improved upon the addition of MnO2 because of the formation of extrinsic oxygen vacancies, which caused the number of intrinsic oxygen vacancies to decrease in order to maintain the equilibrium concentration of oxygen vacancies in the film. However, the electric properties degraded when the MnO2 content exceeded 15.0 mol% because of the formation of interstitial oxygen ions and holes. The dielectric constant (?r) of the TB5N3 film slightly decreased upon the addition of a small amount of MnO2. The TB5N3 film with 15.0 mol% MnO2, which exhibited a small leakage current density of 2.5 × 10?11 A/cm2 at 0.15 MV/cm and a high breakdown electric field of 0.47 MV/cm, still maintained a large ?r of 118 with a small loss tangent of 2.0% at 100.0 kHz. 相似文献
88.
An evolution compressible Stokes system is studied in a bounded cylindrical region . The initial datum of pressure is assumed to have a jump at a specified curve C0 in Ω. As predicted by the Rankine-Hugoniot conditions, the pressure and velocity derivatives have jump discontinuities along the characteristic plane of the curve C0 directed by an ambient velocity vector. An explicit formula for the jump discontinuity is presented. The jump decays exponentially in time, more rapidly for smaller viscosities. Under suitable conditions of the data, a regularity of the solution is established in a compact subregion of Q away from the jump plane. 相似文献
89.
Jung‐Ohk Kweon Yong‐Kuen Lee Si‐Tae Noh 《Journal of polymer science. Part A, Polymer chemistry》2001,39(23):4129-4138
Poly(N‐substituted urethane)s with an alkyl or ligo(ethylene oxide) monomethyl ether side chain were synthesized by the reaction operating in the following two‐step process: first, by metalation of the starting polymer with potassium tertiary butoxide (t‐BuOK) and then by treatment of the obtained urethane polyanion with tosylate in dimethyl sulfoxide. The thermal properties of poly(ethylene oxide) poly(N‐substituted urethane) (N‐sub PEOPU) were investigated in view of the N‐substitution degree and properties of the substituent. The chemical structures were characterized by Fourier transform infrared, 1H NMR, and 13C NMR spectroscopies. DSC and thermogravimetric analysis (TGA) were used to investigate the thermal properties of N‐sub PEOPUs. As the degree of N‐methylation increased, the glass‐transition temperature (Tg) of the N‐sub PEOPUs linearly decreased from 6 to ?29 °C, and the weight‐loss temperature of 5% (T) from TGA in air increased from 278 to 360 °C. In the fully N‐substituted PEOPUs, the behavior of the thermal decomposition of the PEOPU that was processed in two stages was changed to one‐step decomposition in the temperature range of 360–440 °C. The Tg was shifted to a lower temperature with an increasing length of the substituent in N‐sub PEOPU. Improvement of the thermal stability by N‐substitution was more significant in N‐alkyl PEOPU than in N‐ethoxylate PEOPU. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4129–4138, 2001 相似文献
90.
Influence of Extracellular Polymeric Substances on Membrane Fouling and Cleaning in a Submerged Membrane Bioreactor 总被引:2,自引:0,他引:2
Chackrit Nuengjamnong Ji Hyang Kweon Jinwoo Cho Kyu-Hong Ahn Chongrak Polprasert 《Colloid Journal》2005,67(3):351-356
There is little information available on the correlation between the concentration of extracellular polymeric substances (EPS) and membrane fouling as well as cleaning efficiency. In this study, two lab-scale flat submerged membrane bioreactors (SMBRs) at sludge retention times (SRTs) of 25 and 250 days were operated at a constant permeate flux (12.5 l m−2 h−1). Samples of activated sludge were tested to quantify the concentration of extractable EPS using cation exchange resin. Batch filtration tests were also performed to determine the specific cake resistances and the flux recoveries. The extractable EPS and protein concentrations were relatively low at the prolonged SRT, leading to cake layers easily removable by the physical manual cleaning or the de-ionized water backwashing and the chemical cleaning with sodium hypochlorite methods. The extent of flux recoveries (both in SMBRs and batch filtration tests) and macroscopic as well as microscopic images indicated that the chemical cleaning could enhance the effectiveness of cleaning. The membrane fouling and cleaning mechanisms were also discussed.__________From Kolloidnyi Zhurnal, Vol. 67, No. 3, 2005, pp. 392–397.Original English Text Copyright © 2005 by Chackrit Nuengjamnong, Ji Hyang Kweon, Jinwoo Cho, Kyu-Hong Ahn, Chongrak Polprasert.This article was submitted by the authors in English. 相似文献