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151.
152.
Sun-Yuan Hsieh 《The Journal of supercomputing》2007,39(1):39-57
A graph is distance-hereditary if the distance stays the same between any of two vertices in every connected induced subgraph containing both. Two well-known
classes of graphs, trees and cographs, both belong to distance-hereditary graphs. In this paper, we first show that the perfect
domination problem can be solved in sequential linear-time on distance-hereditary graphs. By sketching some regular property
of the problem, we also show that it can be easily parallelized on distance-hereditary graphs. 相似文献
153.
Wenying Wei Zhen Wang Yanhua Yin Jinyu Han Wen Xu 《Korean Journal of Chemical Engineering》2008,25(3):562-567
Composition Group Vector Space (CGVS) method for estimating melting and boiling point T
m
, T
b
of organic compound has been proposed, and the principle of this method has been elucidated. The models for estimating T
m
, T
b
have been established and the numerical values of relative parameters have been presented. The average percentage deviations
of T
m
, T
b
estimation are 7.53 and 1.58, respectively, which show that the present method demonstrates significant improvement in applicability
to predict the above properties, compared to conventional group methods. 相似文献
154.
155.
156.
Sangho Kim Young-Roc Im Sunghak Lee Hu-Chul Lee Sung-Joon Kim Jun Hwa Hong 《Metallurgical and Materials Transactions A》2004,35(7):2027-2037
This study is concerned with the effects of alloying elements on fracture toughness in the transition temperature region of
base metals and heat-affected zones (HAZs) of Mn-Mo-Ni low-alloy steels. Three kinds of steels whose compositions were varied
from the composition specification of SA 508 steel (grade 3) were fabricated by vacuum-induction melting and heat treatment,
and their fracture toughness was examined using an ASTM E1921 standard test method. In the steels that have decreased C and
increased Mo and Ni content, the number of fine M2C carbides was greatly increased and the number of coarse M3C carbides was decreased, thereby leading to the simultaneous improvement of tensile properties and fracture toughness. Brittle
martensite-austenite (M-A) constituents were also formed in these steels during cooling, but did not deteriorate fracture
toughness because they were decomposed to ferrite and fine carbides after tempering. Their simulated HAZs also had sufficient
impact toughness after postweld heat treatment. These findings indicated that the reduction in C content to inhibit the formation
of coarse cementite and to improve toughness and the increase in Mo and Ni to prevent the reduction in hardenability and to
precipitate fine M2C carbides were useful ways to improve simultaneously the tensile and fracture properties of the HAZs as well as the base
metals. 相似文献
157.
This article proposes an approach for investigating the exponential stability of a nonlinear
interval dynamical system with the nonlinearity of a quadratic type on the basis of the Lyapunov’s direct method. It also
constructs an inner estimate of the attraction domain to the origin for the system under consideration. 相似文献
158.
Stock market forecasting has been a challenging financial research topic for decades. In the literature, there are numerous
results based on point methods. However, poor forecasting quality has been a continuous problem. Motivated by the fact that
financial data varies within intervals, we apply interval methods on a well known stock pricing model [3] to predict stock
market variability as intervals. Empirical results obtained with a few different approaches in this paper consistently suggest
that interval forecasts have better overall quality than traditional point forecasts. 相似文献
159.
G. Heiberg Ch -A. Gandin H. Goerner L. Arnberg 《Metallurgical and Materials Transactions A》2004,35(9):2981-2991
Hypoeutectic aluminum silicon alloys without and with additions of magnesium, copper, iron, and strontium have been cast in
a mold, giving directional solidification from a chill. Detailed temperature measurements have been carried out. Solidification
modeling based on front tracking of the microstructure growth fronts allowed identification of the time and temperature at
which the dendrite tips and the first eutectic pass the thermocouples. The undercooling, growth rate, and thermal gradients
at the dendritic and eutectic growth fronts were derived. The effect of varying thermal parameters and alloy compositions
on the microstructure was investigated. Compared to the binary alloy, a coarser eutectic was observed in the alloys with magnesium,
iron, and/or copper. The coarsening is explained as a result of the transition from a eutectic forming at one specific temperature,
to a eutectic forming over a temperature range. The former is likely to grow as a plane front, whereas the latter is likely
to form an interdendritic eutectic mushy zone. 相似文献
160.
Summary Well-defined water-soluble poly(styrenesulfonate)-b-poly(ethylene glycol)-b- poly(styrenesulfonate) (PSS-b-PEG-b-PSS) triblock
copolymers with narrow molecular weight distribution (1.29 < Mw/Mn < 1.36) were synthesized in aqueous solution at 70 oC via reversible addition-fragmentation chain transfer (RAFT) polymerization. The complex formed by the PSS-b-PEG-b-PSS triblock
copolymer coordinated with aluminum ion was investigated with turbidimetry, dynamic light scattering (DSL), zeta-potential,
and transmission electron microscopy (TEM). The aggregation formation was based on the neutralization of the SO3- groups in the PSS blocks with Al3+ ions. The appearance, size and stability of the PSS-b-PEG-b-PSS/Al3+ aggregates were controlled by varying the PSS block length and degree of neutralization (DN). At DN = 0.33, where the PSS-b-PEG-b-PSS
copolymer was completely neutralized with Al3+, the aggregate size increased with increasing PSS block length. The transition from the shrinking coil of small size to the
interchain aggregates of large size was found at DN of about 0.33. 相似文献