• Bulletin of the Korean Chemical Society
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• v.10 no.2
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• pp.151-154
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• 1989

4-Methoxy-4-methylcyclohexa-2,5-dienone 1 in aqueous sulfuric acid underwent the normal dienone-phenol rearrangement with methyl group migration. The fact that methyl is migrating group and methoxy is remaining group can be rationalized by the stabilization of positive charge at C-4 during the transition state. Methoxy methyl dienone 1 $((H_0)_{1/2} = - 4.6)$ is less basic than 4,4-dimethylcyclohexa-2,5-dienone whose half protonation acidity is reported as - 3.15 or - 3.66. This basicity difference comes from the unstabilization of the protonated methoxy methyl dienone 1 due to the electron withdrawing inductive effect of a methoxy group.

• Bulletin of the Korean Chemical Society
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• v.16 no.2
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• pp.153-157
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• 1995

Calix[6]arenes are selectively dialkylated at the lower rim and further functionalized by the aminomethylation and Claisen Rearrangement reactions. Dialkylation was conducted by the reaction of calix[6]arene and alkyl halides such as benzyl bromide, allyl bromide, ethyl bromoacetate, propyl bromide, and methyl iodide under the carefully controlled reaction conditions. Aminomethylation was carried out with the treatment of disubstituted calix[6]arene and secondary amine in the presence of formaldehyde. Claisen rearrangement reaction of the O-diallylcalix[6]arene produced the p-diallylcalix[6]arene.

• Bulletin of the Korean Mathematical Society
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• v.10 no.1
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• pp.1-6
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• 1973

• Journal of the Korean Chemical Society
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• v.27 no.1
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• pp.38-45
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• 1983

Aziridine derivatives were utilized for the formation of aziridine N-oxides at low temperature, which were subject to easy decomposition and/or rearrangement like the protonated aziridines at room temperature. t-Butyl nitroso compound formed by the decomposition of N-oxide is easily characterized by its blue color and it is the major product in case that no branched alkyl groups are substituted on the carbon atoms of the aziridine ring and the stationary groups on the nitrogen are inert to rearrange the oxide such as the t-butyl group. The oxidative rearrangement products, however, are mainly formed when the substituents are methyl or ethyl group on the carbon atoms. It is interesting to see that the sigmatropic rearrangement of 2-ethyl aziridine gave only cis olefinic compound selectively in case that t-butyl group was substituted on the nitrogen, whereas N-hydroxy aziridine compounds were formed exclusively when t-butyl group was replaced with ethyl group.

• Applied Chemistry for Engineering
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• v.7 no.1
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• pp.51-58
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• 1996

The rearrangement of [(ethoxycarbonyl)phenylaminomethyl]phenylcarbamic acid ethyl esters(N-benzyl compounds) to methylenediphenyldiurethanes(MDU) in sulfuric acid, sulfuric acid-absolute ethanol solvent system, and sulfuric acid-nitrobenzene solvent system, and boron trifluoride at $90^{\circ}C$ was studied. The production of MDU was the highest in sulfuric acid-nitrobenzene system giving 64% MDU yield, of which 58% was 4,4'-MDU. The simultaneous condensation of EPC and formaldehyde and rearrangement to MDU were studied in the presence of different amounts of sulfuric acid, trifluoroacetic acid, and boron trifluoride at $70^{\circ}C$. Though 17mmol of sulfuric acid with 30mmol of EPC produced the highest MDU, the MDU yield was much lower than that from separate condensation and rearrangement reaction.

• Journal of KIISE
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• v.43 no.10
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• pp.1131-1143
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• 2016

How can we effectively compress big graphs composed of billions of edges? By concentrating non-zeros in the adjacency matrix through vertex rearrangement, we can compress big graphs more efficiently. Also, we can boost the performance of several graph mining algorithms such as PageRank. SlashBurn is a state-of-the-art vertex rearrangement method. It processes real-world graphs effectively by utilizing the power-law characteristic of the real-world networks. However, the original SlashBurn algorithm displays a noticeable slowdown for large-scale graphs, and cannot be used at all when graphs are too large to fit in a single machine since it is designed to run on a single machine. In this paper, we propose a distributed SlashBurn algorithm to overcome these limitations. Distributed SlashBurn processes big graphs much faster than the original SlashBurn algorithm does. In addition, it scales up well by performing the large-scale vertex rearrangement process in a distributed fashion. In our experiments using real-world big graphs, the proposed distributed SlashBurn algorithm was found to run more than 45 times faster than the single machine counterpart, and process graphs that are 16 times bigger compared to the original method.

• Journal of the Korean Chemical Society
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• v.32 no.4
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• pp.301-310
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• 1988

Reaction rates for mononuclear heterocyclic rearrangement of N-(5-phenyl-1,2,4-oxadiazol-3-yl)-N'-arylformamidines into 3-acylamino-1-aryl-1,2,4-triazoles were determined spectrophotometrically in dioxane/water (50 : 50, v/v). There are two different reaction paths according to pH. One is pH-independent path, the other is pH-dependent one. In pH-independent path, the result of substituent effect by IYT equation show that N-H bond breaking as well as new N-N bond formation controls the reaction rate. In pH-dependent path, concave-upward Hammett plot was observed. It can be concluded that new N-N bond formation is more advanced than N-H bond breaking in transition state for electron-donating substituents, but N-H bond breaking is more advanced than new N-N bond formation for electron-withdrawing substituents.

• Polymer(Korea)
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• v.33 no.2
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• pp.183-188
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• 2009

Structural rearrangements of uni-axially deformed polyethylenes containing 1-octene comonomer and HDPE upon heating were investigated by time-resolved small and wide angle X-ray scattering techniques. During heating, structural changes including crystal transformation and lamellar rearrangement noted were very different depending on the comonomer contents. At low comonomer content below 2 wt%, inverse martensitic transformation of crystal lattice from monoclinic to orthorhombic cell and the rearrangement of broken lamellar units into more ordered and perfect lamellar stacks were noted with the temperature increase. At high contents above 9.5 wt%, however, polyethylene copolymers showed neither the crystal transformation nor lamellar rearrangement that can be attributed to low crystallinity and high content of branch units.

• Journal of Mechanical Science and Technology
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• v.19 no.2
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• pp.549-557
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• 2005

The requirements of multi-resolution models of feature-based solids, which represent an object at many levels of feature detail, are increasing for engineering purposes, such as analysis, network-based collaborative design, virtual prototyping and manufacturing. To provide multi-resolution models for various applications, it is essential to generate adequate solid models at varying levels of detail (LOD) after feature rearrangement, based on the LOD criteria. However, the non-commutative property of the union and subtraction Boolean operations is a severe obstacle to arbitrary feature rearrangement. To solve this problem we propose history-based Boolean operations that satisfy the commutative law between union and subtraction operations by considering the history of the Boolean operations. Because these operations guarantee the same resulting shape as the original and reasonable shapes at the intermediate LODs for an arbitrary rearrangement of its features, various LOD criteria can be applied for multi-resolution modeling in different applications.

• Journal of the Korean Ceramic Society
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• v.34 no.8
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• pp.877-885
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• 1997

The dependence of strength, crack growth, fracture mode and degree of domain rearrangement of PZT ceramics on poling strength were studied. The PZT [(Pb0.94Sr0.06)(Zr0.46Ti0.54)O3+Nb(trace)] specimens were poled at 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 kv/mm, and the strength of the specimens was measured by 3 point flexure system. The bending strength of the specimen decreased in different modes according to the bending directions; xz, zx and yz plane direction with x axis of the poling direction in Cartesian coordinate system. The strength differences between the directions increased as the poling strength increased. The fracture mode transferred to intergranular fracture mode from transgranular one as the poling strength increased. The mechanical breakdown occurred when the poling strength higher than 3 kV/mm was applied to the specimen. It was observed that the crack length increased in the normal direction to the poling direction, however, decreased in the parallel direction to the poling direction when the poled PZT specimen was indented by the Vickers indenter. However, the crack produced by indentation continuously was continuously increased little by little after indentation on the specimen. The domain rearrangement occurred as the poling strength increased and the domains were rearranged more effectively when the electric field was continuously increased little by little.